Bjørnar Arstad

• Strassheim, Dennis; Benz, Michael; Kauffmann, Florian; Arstad, Bjørnar; Estes, Deven P. & Dyballa, Michael Martin (2026). Properties and acidity of gallium ZSM-5 zeolites synthesized by galliation, impregnation, or direct synthesis. Materials Chemistry Frontiers. doi: 10.1039/d6qm00687f. Fulltekst i vitenarkiv
• Kidibule, Peter Elias; Klau, Leesa Jane; Costa, Thales; Aachmann, Finn Lillelund; Ringel, Marion & Melcher, Felix [Vis alle 11 forfattere av denne artikkelen] (2026). Biocatalytic Upcycling of Aspergillus niger Biomass with Proteases and Glucanases to Produce Chitin. ACS Sustainable Chemistry and Engineering. 14(29), s. 13124–13135. doi: 10.1021/acssuschemeng.6c02866. Fulltekst i vitenarkiv Vis sammendrag

  The large-scale production of citric acid using Aspergillus niger generates substantial quantities of fungal biomass, which remains an underutilized resource. In this study, we developed a tailored enzyme-based strategy to valorize A. niger biomass by selectively extracting chitin, while generating glucose-rich hydrolyzates suitable for fermentation. Comprehensive screening of 16 commercial proteases and glucanases led to the identification of optimal enzyme combinations and process conditions. At a 30 L scale, this process yielded a chitin-rich fraction representing 27% of the initial biomass. The extracted chitin was characterized using X-ray diffraction and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy, revealing high crystallinity and purity. The chitin content of the chitin-rich fraction was quantified using newly established NMR calibration curves based on distinct carbon signals associated with the acetamido group (C-2, CH3, and C═O) and estimated to be on the order of 74%. The chitin-rich fraction was subsequently converted into chitosan with a degree of deacetylation of ∼55% (45% yield on a dry matter basis) and colloidal chitin (60% yield on a dry matter basis), with product properties similar to those of corresponding products derived from crustacean chitin. This study demonstrates the feasibility of enzyme-only extraction of fungal chitin and provides a scalable, sustainable approach for converting fungal biomass into high-value bioproducts.

• Pupo, Rafael Cortez Sgroi; Garetto, Beatrice; Rasheed, Mouhammad Abu; Cao, Ning; Arstad, Bjørnar & Pourpoint, Frédérique [Vis alle 12 forfattere av denne artikkelen] (2025). C-H Activation with Cu(I) MOFs: The Pertinence of Natural-Like Active Centres and Their Facile Modification. Topics in catalysis. ISSN 1022-5528. 68(20), s. 2375–2392. doi: 10.1007/s11244-025-02218-5. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The easy modulation of the first and second ligand spheres of the redox active centres in heterogenised enzyme-inspired catalysts is highly desirable for speeding up de-novo design and optimisation. In this study, we employ metal-organic framework (MOF) hosts, capable of emulating enzyme-like heterogenised Cu(I) active sites to study their catalytic performance. By leveraging on a post-synthetic modification (PSM) strategy, we modified the microenvironment around copper centres within the selected UiO-67 MOFs, thereby mimicking functionalities typical of enzymatic systems. In order to assess the feasibility of a facile modulation of the microenvironment around the active centre without recourse to organic chemistry approaches, our strategy also involved the incorporation of secondary guest molecules into the MOF matrix, such as phenol and propionamide. Through a thorough combined theoretical-experimental study, we demonstrate that the selected propionamide molecule coordinates to the redox-active cuprous centre, whereas phenol does not get adsorbed into the matrix. The synthesised materials were tested for a C–H activation reaction using cyclohexene as a model substrate and tert-butyl hydroperoxide ( t BuOOH) as oxidant, under aerobic conditions. The cuprous ions coordinated to the enzyme-like motifs showed catalytic activity for cyclohexene oxidation, and in addition, showed better performance compared with its cupric counterpart. The catalytic performance of the materials modulated with propionamide however was not significantly different from the parent catalyst, on account of the swift removal of the secondary guest molecule under reaction conditions.

• Karl, Christian W.; Bernat, Szymon Czeslaw; Arstad, Bjørnar; Kubowicz, Stephan; Persson, Anna-Maria Märta Ruth & Stenerud, Gaute [Vis alle 11 forfattere av denne artikkelen] (2025). Degradation Behavior of Biodegradable and Conventional Polymers for Gill Nets, Exposed to Accelerated Aging. ACS Applied Polymer Materials. 7(5), s. 2830–2840. doi: 10.1021/acsapm.4c03333. Fulltekst i vitenarkiv Vis sammendrag

  Replacing nondegradable plastics in fishing gear with abrasion-resistant biodegradable polymers is expected to reduce marine pollution caused by seabed contact and to lower the environmental impact of abandoned, lost, or otherwise discarded fishing gear (ALDFG). The chemical and physical properties, as well as the tribological behavior of conventional polyamide (PA6) and biodegradable poly butylene succinate-co-adipate-co-terephthalate (PBSAT) monofilaments for a commonly used fishing gear (gill nets), treated under accelerated aging simulating outdoor conditions, have been studied. A plethora of different methods have been used to investigate the degradation mechanism, including scanning electron microscopy, optical microscopy, 3D imaging and wear measurements, nanoindentation, mechanical and tribological testing, ATR-FTIR analyses (including micro-ATR-FTIR microscopy), and 1H NMR spectroscopy. FTIR data indicate alterations in the outermost monofilament layer, and NMR analysis corroborates that the aging effects initially take place at the surface. PA6 showed signs of chain cleavage, while PBSAT did not show any sign of degradation, indicating hydrolysis to small, dissolved molecules during aging. The findings revealed that for both PA6 and PBSAT, the process of aging exerts a small influence on the tensile modulus. After a thousand hours of aging, an increase in the tensile modulus was observed, amounting to 21% and 5%, respectively, for PA6 and PBSAT. However, a pronounced impact on the elongation at break was detected. The elongation at break diminished by approximately 67% and 91% for PA6 and PBSAT, respectively. Tribological testing of the monofilaments shows higher wear and abrasion of the PBSAT monofilament under dry conditions compared to PA6. Nevertheless, under conditions of lubrication by seawater, the wear and friction force exerted by PBSAT and PA6 were found to be comparable. This study demonstrates that biodegradable PBSAT materials can replace nondegradable PA6 in gill nets.

• Seremak, Agnieszka Patrycja; Berdiell, Izar Capel; Arstad, Bjørnar; Fjermestad, Torstein & Svelle, Stian (2025). Investigating the Flexibility of H-ZSM-5 Zeolite Upon Adsorption of Coke Precursors: A Theoretical and Experimental Approach. Journal of Physical Chemistry C. ISSN 1932-7447. 129(2), s. 1183–1197. doi: 10.1021/acs.jpcc.4c07349. Fulltekst i vitenarkiv Vis sammendrag

  The flexibility of the H-ZSM-5 zeolite upon adsorption of selected coke precursors was investigated using both theoretical and experimental approaches. Four structural models with varying active site locations were analyzed through density functional theory (DFT) simulations to determine their responses to different types and quantities of aromatic molecules. Complementary experimental analysis was performed, allowing for a direct comparison with the theoretical findings, using thermogravimetric analysis (TGA), nitrogen adsorption (N2 adsorption), solid-state NMR, and X-ray diffraction (XRD). By employing proposed flexibility descriptors, significant structural changes in the MFI-type zeolite framework were identified, particularly in the unit cell parameters and the morphology of the straight channels. These changes were driven by electrostatic repulsion between adsorbates and by electrostatic attraction between adsorbates and the zeolite framework. The observed structural changes depended on both the active site location and the size and number of coke precursors. Consistent trends in structural flexibility were observed in both experimental and theoretical studies, primarily driven by variations in organic species loading. Our findings show the critical importance of active site location in influencing the magnitude of framework flexibility, which, in turn, affects the stabilization and accommodation of different coke precursors within the zeolite structure.

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2025). Unique Na5−xSbSe Phase Enables High-Rate Performance of Sb2Se3 Anodes in Na-Ion Batteries. Advanced Energy Materials. ISSN 1614-6832. 15(31), s. 1–16. doi: 10.1002/aenm.202501433. Fulltekst i vitenarkiv Vis sammendrag

  Na-ion batteries (NIBs) need new anode materials to improve energy density. Metal chalcogenides, such as Sb2Se3, represent a promising alternative to commonly used hard carbon materials, demonstrating high-rate performance up to 5 A g−1 with minimal capacity losses. However, Sb2Se3 is believed to operate under the conversion/alloying mechanism, typically linked with large structural transformations and volumetric changes—quite contrary to its performance. Herein, by combining multiple operando techniques and atomistic simulations, a new fully sodiated phase, Na5−xSbSe, is unambiguously revealed as the origin of the high-rate performance of Sb2Se3. Na5−xSbSe is stable within 0.01–0.80 V versus Na/Na+ and crystallizes in I4/mmm. The remarkable structural flexibility of Na5SbSe to changes in Na-content allows the anode to be (de)sodiated with minimal volumetric changes (≈3.4%). This unique “breathing effect” is intimately linked to high inherent vacancy concentration, disordered, and structurally flexible anion sublattice, providing a stable framework for fast Na diffusion, contributing to the fast-charging properties of Sb2Se3. The study showcases the power of operando methods for discovering new phases that are hidden in the mechanistic paths of well-studied reactions and underlines the intertwined nature of various characterization methods assisted by atomistic insights for a comprehensive understanding of complex (de)sodiation mechanisms.

• Hempel, Frida Sveen; Sławiński, Wojciech A.; Arstad, Bjørnar & Fjellvåg, Helmer (2024). Superstructure of Locally Disordered Na2Zn2TeO6. Chemistry of Materials. ISSN 0897-4756. 36(22), s. 11084–1109. doi: 10.1021/acs.chemmater.4c01953. Fulltekst i vitenarkiv Vis sammendrag

  This work expands on the superstructure in the layered oxide Na2Zn2TeO6 (NZTO). The diffractogram contains weak peaks that are not fitted by the average structure but are found to belong to a 2 × 2 × 3 commensurate modulation of the structure. The modulated structure was found by randomizing the starting points to ensure that the global minima are identified. The resulting superstructure is then used to generate a starting structure for reversed Monte Carlo (RMC) fitting of the total scattering data. We identify two structural features that are preserved through both fittings. One is that two of the Zn/Te columns in the layer direction have a significantly higher degree of disorder, with the exchange of Zn and Te. The second feature is that one of the crystallographic Na sites (2a) was found to be empty. The Na atoms are located midway between crystallographic 2a and 6g sites, which surrounds half of the 2a sites. This type of off-centering is found both in the modulated structure and in the corresponding structure preserved through RMC modeling. The results are discussed in relation to variable-temperature solid-state NMR data measured between 100 and 293 K. We suggest that the phenomenon is a feature of a dynamic situation and an important clue to progress the understanding of ion dynamics in more detail.

• Wagaarachchige, Jayangi Dinesha; Idris, Zulkifli; Arstad, Bjørnar; Halstensen, Maths & Jens, Klaus-Joachim (2024). Low-Viscosity Nonaqueous Sulfolane-Amine-Methanol Solvent Blend for Reversible CO2 Capture: Part II. Blend Optimization, Water Effect, and Speciation. Journal of Chemical and Engineering Data. ISSN 0021-9568. 69(9), s. 3063–3074. doi: 10.1021/acs.jced.4c00175. Fulltekst i vitenarkiv Vis sammendrag

  This work is part II of the investigation of a low viscosity, low regeneration energy nonaqueous CO2 capture solvent blend consisting of readily available chemicals diisopropylamine (DPA)–methanol–sulfolane and featuring the monomethyl carbonate anion (MMC) as a CO2 absorption specie. The region of practical solvent composition, high CO2 capacity, low regeneration energy, and avoidance of solvent solidification at a CO2 capture condition is identified by the design of experiment methodology combined with solvent attenuated total reflectance–Fourier transform infrared and nuclear magnetic resonance monitoring and speciation analysis. Flue gas contains water vapor; hence, solvent water stability is important. The limit of solvent blend water content is determined to be 5 wt % because of MMC decomposition to DPA-bicarbonate and -carbamate.

• Karl, Christian W.; Arstad, Bjørnar; Shamsuyeva, Madina; Lecinski, Jacek; Olafsen, Kjell & Larsen, Åge Gellein [Vis alle 9 forfattere av denne artikkelen] (2024). Upgrading and Enhancement of Recycled Polyethylene Terephthalate with Chain Extenders: In-Depth Material Characterization. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 63(28), s. 12277–12287. doi: 10.1021/acs.iecr.4c00018. Fulltekst i vitenarkiv Vis sammendrag

  Chemical chain extenders (CEs) can be used to restore the properties of recycled low-molecular-weight polyethylene terephthalate (PET). The aim of this work is to investigate the influence of the type and concentration of the CEs Joncryl and pyromellitic dianhydride (PMDA) on the viscosity and other rheological properties with a unique combination of different methods based on industrial samples originating from recycled PET bottles and trays. The resulting chain-extended thermoplastics were characterized by a combination of differential scanning calorimetry, viscometry, cone plate rheometry, pyrolysis-gas chromatography-mass spectroscopy, optical photo-thermal infrared spectroscopy, 13 C solid-state-and 1 H NMR liquid spectroscopy, and size exclusion chromatography. For a recycled PET mixture containing bottle and tray materials, our investigations have shown that a significantly better effect for chain elongation can be achieved with Joncryl compared to PMDA. This can presumably be attributed to water molecules formed during the use of PMDA, which accelerate the degradation of PET. The storage modulus values are therefore significantly higher for the samples with Joncryl compared to PMDA. The results of this study show that chain extension with Joncryl proceeds better compared to the reaction with PMDA.

• Krishnamurthy, Shreenath; Roelant, Raf; Blom, Richard; Arstad, Bjørnar; Li, Zuoan & Rombouts, Marleen [Vis alle 9 forfattere av denne artikkelen] (2024). Scaling up 3D printed hybrid sorbents towards (cost) effective post-combustion CO2 capture: A multiscale study. International Journal of Greenhouse Gas Control. ISSN 1750-5836. 132. doi: 10.1016/j.ijggc.2024.104069. Fulltekst i vitenarkiv Vis sammendrag

  A 3D-printed sorbent containing polyethylene-imine and multi-walled carbon nanotubes (PEI-MWCNT) was studied for post-combustion carbon capture. In this work, the adsorbent was printed on a kg scale and characterized for CO2 adsorption through lab experiments. A 6-step VSA process was simulated using the lab data to capture CO2 from a representative 800 MW power plant. The adsorbent captured >70 % of the CO2 and 95 % CO2 purity was achieved. The levelized cost of electricity (LCOE) was 130.2 $/MWh and the costs of CO2 captured and avoided were 80 and 100.12 $/tonne. However, a zeolite 13X-activated carbon (13X-AC) monolith achieved a lower LCOE of 118.1 $/MWh, with the captured and avoided costs being 63 and 78.4 $/tonne, respectively. The LCOE value for the 13X-AC monolith was 5.1 % lower than a reference-packed bed system with Zeolite 13X pellets. The corresponding cost values were lower by 9.1 % and 13.9 %, respectively for the costs of CO2 captured and avoided. The lab experiments on the PEI-MWCNT sorbent revealed that further work is necessary to improve the thermal stability and stability with long-term storage of the precursor paste

• Gaukås, Nikolai Helth; Sunde, Tor Olav Løveng; Arstad, Bjørnar; Reksten, Anita; Stefan, Elena & Thøgersen, Annett [Vis alle 9 forfattere av denne artikkelen] (2024). Effects of Different Doping Strategies on Cubic Li7La3Zr2O12 Solid-State Li-Ion Battery Electrolytes. ACS Applied Energy Materials. 7(24), s. 12141–12154. doi: 10.1021/acsaem.4c02708. Fulltekst i vitenarkiv Vis sammendrag

  Solid-state Li-ion conductors based on cubic Li7La3Zr2O12 (LLZO) garnets have received much attention in recent years as potential next-generation battery electrolytes, enabling safer and more energy-dense Li-ion batteries. Aliovalent doping of the LLZO structure is usually necessary to stabilize the cubic garnet phase and increase the ionic conductivity by increasing the concentration of Li vacancies. Here, we report on the synthesis, characterization, and testing of Li7−3xAlxLa3Zr2O12 ceramics with different amounts of Al doping (x = 0.20−0.40). Phase-pure LLZO with a cubic crystal structure was prepared by an aqueous synthesis route, and dense (>93%) ceramic samples were fabricated by conventional sintering at 1200 °C. By analyzing the composition, microstructure, and electrochemical performance, we found that the optimal Al content in LLZO is x = 0.2, the lowest content needed to stabilize the cubic structure in our series. For the composition with x = 0.2, we found a Li-ion conductivity at room temperature of 3.7 × 10−4 S cm−1 and an activation energy of Ea = 0.3 eV. At a higher doping concentration, the conductivity decreases, and the activation energy increases; for x ≥ 0.35, secondary Al-rich phases appear. These results indicate an inverse relationship between Li-ion conductivity and Al doping, where the optimal amount of doping is the minimum amount necessary to stabilize the cubic LLZO phase. Additionally, we present an analysis of the available literature on chemical modification of LLZO to compare how different doping strategies affect Li conductivity. Based on our literature review, Ga and Ta doping gives the highest conductivities (≤2 × 10−3 S cm−1). The literature analysis also supports our findings that the primary objective of the dopant is to stabilize the cubic structure rather than create Li vacancies.

• Hempel, Frida Sveen; Martineau-Corcos, Charlotte; Bianchini, Federico; Fjellvåg, Helmer & Arstad, Bjørnar (2023). Dynamics of Interlayer Na-Ions in Ga-Substituted Na2Zn2TeO6 (NZTO) Studied by Variable-Temperature Solid-State 23Na NMR Spectroscopy and DFT Modeling. ACS Physical Chemistry Au. 3(4), s. 320–405. doi: 10.1021/acsphyschemau.3c00012. Fulltekst i vitenarkiv Vis sammendrag

  Local Na-coordination and dynamics of Na2–xZn2–xGaxTeO6; x = 0.00 (NZTO), 0.05, 0.10, 0.15, 0.20, were studied by variable-temperature, 23Na NMR methods and DFT AIMD simulations. Structure and dynamics were probed by NMR in the temperature ranges of 100–293 K in a magnetic field of 18.8 T and from 293 up to 500 K in a magnetic field of 11.7 T. Line shapes and T1 relaxation constants were analyzed. At 100 K, the otherwise dynamic Na-ions are frozen out on the NMR time scale, and a local structure characterization was performed for Na-ions at three interlayer sites. On increasing the temperature, complex peak shape coalescences occurred, and at 293 K, the Na NMR spectra showed some averaging due to Na-ion dynamics. A further increase to 500 K did not reveal any new peak shape variations until the highest temperatures, where an apparent peak splitting was observed, similar to what was observed in the 18.8 T experiments at lower temperatures. A three-site exchange model coupled with reduced quadrupolar couplings due to dynamics appear to explain these peak shape observations. The Ga substitution increases the Na-jumping rate, as proved by relaxation measurements and by a decrease in temperature for peak coalescence. The estimated activation energy for Na dynamics in the NZTO sample, from relaxation measurements, corresponds well to results from DFT AIMD simulations. Upon Ga substitution, measured activation energies are reduced, which is supported, in part, by DFT calculations. Addressing the correlated motion of Na-ions appears important for solid-state ion conductors since benefits can be gained from the decrease in activation energy upon Ga substitution, for example.

• Tolchard, Julian R; Vullum, Per Erik; Arstad, Bjørnar & Wagner, Nils Peter (2023). New insights into orthophosphoric acid assisted rapid aqueous processing of NMC622 cathodes. RSC Sustainability. 1(2), s. 378–387. doi: 10.1039/D3SU00031A. Fulltekst i vitenarkiv Vis sammendrag

  The use of orthophosphoric acid to stabilize aqueous processing of high nickel NMC622 electrodes was assessed under rapid processing conditions, in which the active material powder was in suspension for less than 1 hour. It was found, as previously reported, that corrosion of the aluminum current-collector was suppressed, and capacity retention greatly improved relative to aqueous-processed material without orthophosphoric acid addition. The rapid processing conditions led to incomplete reaction of the orthophosphoric acid with the surface of the electrode active material however, with concomitant formation of orthophosphate precipitates upon drying. Reaction of these with organic carbonate electrolytes resulted in rapid cell death typically occurring between 50 and 100 cycles, characterized by formation of a thick degradation film on the NMC622 cathode. Washing with ethanol was found to remove the components responsible for the degradation process, yielding an electrode that demonstrated almost 400 cycles with 78% capacity retention. It is concluded that whilst the addition of orthophosphoric acid aids aqueous processing of NMC materials, close attention must be paid to the quantities and reaction times used.

• Prodinger, Sebastian; Berdiell, Izar Capel; Cordero-Lanzac, Tomas; Bygdnes, Odd Reidar; Solemsli, Bjørn Gading & Kvande, Karoline [Vis alle 10 forfattere av denne artikkelen] (2023). Cation-induced speciation of port-size during mordenite zeolite synthesis. Journal of Materials Chemistry A. ISSN 2050-7488. 11(40), s. 21884–21894. doi: 10.1039/d3ta03444e. Fulltekst i vitenarkiv Vis sammendrag

  Mordenite (MOR) zeolite, an important industrial catalyst exists in two, isostructural variants defined by their port-size, small and large-port. Here we show for the first time how a systematic, single-parameter variation influences the synthesis out-come on the final MOR material leading to distinctly different catalysts. The cation identity has a direct impact on the synthesis mechanism with potassium cations generating the more constrained, small-port MOR variant compared to the large-port obtained with sodium cations. This was expressed by different degrees of accessibility ascertained with a combination of toluene breakthrough and temperature programmed desorption (TPD), propylamine TPD, as well as sterically sensitive isobutane conversion. Rietveld refinement of the X-ray diffractograms elucidated the preferential siting of the smaller sodium cations in the constricted 8-ring, from which differences in Al distribution follow. Note, there are no organic structure directing agents utilized in this synthesis pointing at the important role of inorganic structure directing agents (ISDA).

• Kommedal, Eirik; Angeltveit, Camilla Fløien; Klau, Leesa Jane; Ayuso-Fernandez, Ivan; Arstad, Bjørnar & Antonsen, Simen [Vis alle 13 forfattere av denne artikkelen] (2023). Visible light-exposed lignin facilitates cellulose solubilization by lytic polysaccharide monooxygenases. Nature Communications. 14(1). doi: 10.1038/s41467-023-36660-4. Fulltekst i vitenarkiv Vis sammendrag

  Lytic polysaccharide monooxygenases (LPMOs) catalyze oxidative cleavage of crystalline polysaccharides such as cellulose and are crucial for the conversion of plant biomass in Nature and in industrial applications. Sunlight promotes microbial conversion of plant litter; this effect has been attributed to photochemical degradation of lignin, a major redox-active component of secondary plant cell walls that limits enzyme access to the cell wall carbohydrates. Here, we show that exposing lignin to visible light facilitates cellulose solubilization by promoting formation of H2O2 that fuels LPMO catalysis. Light-driven H2O2 formation is accompanied by oxidation of ring-conjugated olefins in the lignin, while LPMO-catalyzed oxidation of phenolic hydroxyls leads to the required priming reduction of the enzyme. The discovery that light-driven abiotic reactions in Nature can fuel H2O2-dependent redox enzymes involved in deconstructing lignocellulose may offer opportunities for bioprocessing and provides an enzymatic explanation for the known effect of visible light on biomass conversion.

• Wang, Zichun; Arstad, Bjørnar; Wang, Leizhi; Ling, Huajuan; Shi, Jeffrey & Stampfl, Catherine [Vis alle 8 forfattere av denne artikkelen] (2022). Bio-oil upgrading via ketonization of carboxylic acids on Na promoted Ca/AlOx catalysts. Carbon Neutralization. ISSN 2769-3333. doi: 10.1002/cnl2.4. Fulltekst i vitenarkiv
• Hempel, Frida Sveen; Bianchini, Federico; Arstad, Bjørnar & Fjellvåg, Helmer (2022). Effects of Ga Substitution on the Local Structure of Na2Zn2TeO6. Inorganic Chemistry. ISSN 0020-1669. 61(33), s. 13067–13076. doi: 10.1021/acs.inorgchem.2c01431. Fulltekst i vitenarkiv Vis sammendrag

  In the work presented here, we prepared Ga-substituted NZTO (Na2–xZn2–xGaxTeO6, x = 0.00, 0.05, 0.10, 0.15, 0.20) layered materials with a soft chemical, citric acid-based synthesis method and characterized these by means of X-ray diffraction (XRD), 23Na and 125Te NMR, and by density functional theory (DFT) modeling. The influence of randomly distributed Ga cations on the 125Te NMR spectra confirms the successful synthesis. With DFT-based linear response computations, we show that the local distribution of Na ions in the two neighboring interlayers influences the 125Te chemical shift, consistent with observations. DFT modeling suggests that some of the Na sites are rarely occupied in pure NZTO but become favorable upon Ga substitution. There are clear indications that Ga substitution gives an uneven distribution of Na ions in neighboring interlayers and that the Na structure in one layer affects the adjacent layers.

• Prodinger, Sebastian; Kvande, Karoline; Arstad, Bjørnar; Borfecchia, Elisa; Beato, Pablo & Svelle, Stian (2022). Synthesis-Structure-Activity Relationship in Cu-MOR for Partial Methane Oxidation: Al Siting via Inorganic Structure-Directing Agents. ACS Catalysis. 12(4), s. 2166–2177. doi: 10.1021/acscatal.1c05091. Fulltekst i vitenarkiv Vis sammendrag

  In the pursuit of controlling the propensity of Cu-mordenite (MOR) for the selective oxidation of CH4, we take a closer look at intrinsic zeolite parameters. Via synthesis design, we vary the relative proportion of Al situated near the 8-rings and 12-rings of MOR zeolite. This is accomplished using different Al sources impacting the local degree of silica dissolution and zeolite formation as evidenced by crystallization times and morphological differences. Interrogating the crystalline system with steric probe molecules in conjunction with spectroscopic techniques such as 1H magic angle spinning (MAS) NMR, infrared spectroscopy, as well as temperature-programmed desorption confirms discrete changes of the Al within the unit cell. The subsequent copper exchange allows for the generation of Cu-MOR materials of different inclinations for the activation of methane in the stepwise formation of MeOH. Here, an increasing degree of acid sites in more easily accessible locations (e.g., 12-ring) correlates with increasing maximum productivity toward MeOH at moderate exchange degrees. X-ray absorption spectroscopy supports this notion, finding a higher concentration of self-reduction-resistant framework-associated Cu2+ species, previously established as the active sites in the selective oxidation of CH4.

• Hansen, Line Degn; Østensen, Martin; Arstad, Bjørnar; Tschentscher, Roman; Eijsink, Vincent & Horn, Svein Jarle [Vis alle 7 forfattere av denne artikkelen] (2022). 2-Naphthol Impregnation Prior to Steam Explosion Promotes LPMO-Assisted Enzymatic Saccharification of Spruce and Yields High-Purity Lignin. ACS Sustainable Chemistry and Engineering. 10(16), s. 5233–5242. doi: 10.1021/acssuschemeng.2c00286. Fulltekst i vitenarkiv Vis sammendrag

  The recent discovery that impregnation with a carbocation scavenger may improve the enzymatic saccharification of steam-exploded softwood has brought a softwood-based biorefinery closer to reality. However, the nature of the impregnation effect remains unresolved, and its impact on process efficiency and product quality in high-dry matter reactions remains underexplored. Here, we show that 2-naphthol impregnation enables the complete saccharification of spruce cellulose by lytic polysaccharide monooxygenase (LPMO)-containing Cellic CTec2, but not by an LPMO-poor cellulase cocktail (Celluclast), in 10% dry matter reactions with an industrially feasible enzyme dose and reaction time. Importantly, we show that this remarkably high saccharification yield correlates with increased LPMO activity, which is due to the impact of 2-naphthol on the ability of lignin to drive the LPMO reaction. These findings show that impregnation improves saccharification not only by reducing cellulase adsorption and inactivation but also by boosting oxidative cellulose depolymerization by LPMOs. Pyrolysis of the lignin-rich saccharification residues revealed that 2-naphthol impregnation had little effect on lignin-derived components in the resulting bio-oil, which, due to the efficient saccharification, showed reduced levels of carbohydrate-derived components that reduce oil storage stability. These results bring closer the prospect of a spruce-based biorefinery that combines biochemical and thermochemical conversion routes.

• Wagaarachchige, Jayangi Dinesha; Idris, Zulkifli; Arstad, Bjørnar; Kummamuru, Nithin Bharadwaj; Sætre, Kai Arne & Halstensen, Maths [Vis alle 7 forfattere av denne artikkelen] (2022). Low-Viscosity Nonaqueous Sulfolane-Amine-Methanol Solvent Blend for Reversible CO2 Capture. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 61(17), s. 5942–5951. doi: 10.1021/acs.iecr.1c04946. Fulltekst i vitenarkiv Vis sammendrag

  In this work, the absorption–desorption performance of CO2 in six new solvent blends of amine (diisopropylamine (DPA), 2-amino-2-methyl-1-propanol (AMP), methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), and ethanolamine (MEA)), sulfolane, and methanol has been monitored using ATR-FTIR spectroscopy. Additionally, NMR-based species confirmation and solvent viscosity analysis were done for DPA solvent samples. The identified CO2 capture products are monomethyl carbonate (MMC), carbamate, carbonate, and bicarbonate anions in different ratios. The DPA solvent formed MMC entirely with 0.88 molCO2/molamine capture capacity, 0.48 molCO2/molamine cyclic capacity, and 3.28 mPa·s CO2-loaded solvent viscosity. MEA, DEA, DIPA, and MDEA were shown to produce a low or a negligible amount of MMC while AMP occupied an intermediate position.

• Li, Zheng; Benz, Michael; Rieg, Carolin; Dittmann, Daniel; Beurer, Ann-Katrin & Haussermann, Dorothea [Vis alle 8 forfattere av denne artikkelen] (2021). The alumination mechanism of porous silica materials and properties of derived ion exchangers and acid catalysts. Materials Chemistry Frontiers. 5(11), s. 4254–4271. doi: 10.1039/d1qm00282a. Fulltekst i vitenarkiv Vis sammendrag

  We herein investigate the alumination mechanism of siliceous micro- and mesoporous materials (SBA-15, SBA-16, and dealuminated Y-zeolite) with NaAlO2 to synthesize new ion exchangers and acid catalysts. We show that in aqueous alkaline solution, the materials’ surface is partially dissolved to form Si(OH)x groups (x = 1, 2, 3) that react with tetrahedral aluminum sites. The amount of introduced aluminum depends on the aqueous treatment temperature, pore diameters and structure of siliceous parents. The incorporation works best for hexagonal SBA-15 mesopores at the cost of micropores. Zeolite Y micropores remain accessible upon alumination. All Na-forms can quantitatively be ion exchanged. They are thus potential carriers for catalytically active metal ions. The presence of different Al(OH) groups is proven by 1H{27Al} TRAPDOR. The 27Al MQMAS NMR spectra indicate the formation of octahedral and pentahedral aluminum upon transformation into H-forms. On [Al]SBA-15 up to 18% of ion exchange sites can be transformed into Brønsted acid sites. The acid properties were investigated using the probe molecules NH3, acetonitrile-d3, and TMPO. On mesoporous SBA-15 and SBA-16, Brønsted acid sites show a flexible coordination between Si(OH) and tetrahedral aluminum. The sites are weak and form exclusively in the presence of a strong base or counter ion. Zeolite acid site strength was found for re-aluminated Y. TMPO loading combined with 27Al and 31P MAS NMR spectroscopy indicates the presence of Lewis acidic framework aluminum and the presence of several distinct Brønsted and Lewis acid sites on H-forms.

• Hill, Adam R.; Cubillas, Pablo; Gebbie-Rayet, James T.; Trueman, Mollie; Bruyn, Nathan de & Harthi, Zulaikha al [Vis alle 14 forfattere av denne artikkelen] (2021). CrystalGrower: a generic computer program for Monte Carlo modelling of crystal growth. Chemical Science. ISSN 2041-6520. 12(3), s. 1126–1146. doi: 10.1039/d0sc05017b. Fulltekst i vitenarkiv Vis sammendrag

  A Monte Carlo crystal growth simulation tool, CrystalGrower, is described which is able to simultaneously model both the crystal habit and nanoscopic surface topography of any crystal structure under conditions of variable supersaturation or at equilibrium. This tool has been developed in order to permit the rapid simulation of crystal surface maps generated by scanning probe microscopies in combination with overall crystal habit. As the simulation is based upon a coarse graining at the nanoscopic level features such as crystal rounding at low supersaturation or undersaturation conditions are also faithfully reproduced. CrystalGrower permits the incorporation of screw dislocations with arbitrary Burgers vectors and also the investigation of internal point defects in crystals. The effect of growth modifiers can be addressed by selective poisoning of specific growth sites. The tool is designed for those interested in understanding and controlling the outcome of crystal growth through a deeper comprehension of the key controlling experimental parameters.

• Arstad, Bjørnar; Blom, Richard; Håkonsen, Silje Fosse; Pierchala, Joanna; Cobden, Paul & Lundvall, Fredrik [Vis alle 10 forfattere av denne artikkelen] (2020). Synthesis and Evaluation of K-Promoted Co3-xMgxAl-Oxides as Solid CO2 Sorbents in the Sorption-Enhanced Water−Gas Shift (SEWGS) Reaction. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 59(40), s. 17837–17844. doi: 10.1021/acs.iecr.0c02322. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen is essential in a variety of large-scale chemical processes. As a carbon-free energy carrier, hydrogen has a potential for wide use within power production and transportation. However, most of the recent production methods involve the release of CO2 as a by-product. Hence, decarbonization of hydrogen production is one step to reduce CO2 emission into the Earth’s atmosphere. Several process schemes have been suggested for low-carbon emission production of hydrogen. In this work, we show how to improve solid sorbents for the sorption-enhanced water–gas shift (SEWGS) process, which is a process that exploits a solid sorbent in the water–gas shift reactor to capture CO2 in situ and drive the process toward an improved hydrogen yield. We report herein a series of CoxMg3-xAl materials based on hydrotalcites, promoted with various loadings of K. The materials have been characterized by BET, XRD, and NMR and tested for their CO2 adsorption performance in three adsorption–desorption cycles in a lab-scale fixed-bed reactor (20–22 bar, CO2 + steam as reactant gas, and isothermal conditions at 375 and 400 °C). The most promising material was subjected to a long-term test (120 adsorption–desorption cycles at similar conditions). This test indicates that a K-promoted Co1.5Mg1.5Al (22 wt % of added K2CO2 to the oxide) material has a higher cyclic capacity for CO2 than standard reference cases. We have estimated that the volumetric capacity (in mol/L unit) of this sorbent will be 23–26% higher than a standard reference material at 400 °C and 30–39% higher at 375 °C. This would, in fixed-bed columns, lead to significant reduction in the needed column volumes in the final process and reduce costs.

• Pappas, Dimitrios; Kvande, Karoline; Kalyva, Maria Evangelou; Dyballa, Michael Martin; Lomachenko, Kirill A. & Arstad, Bjørnar [Vis alle 11 forfattere av denne artikkelen] (2020). Influence of Cu-speciation in mordenite on direct methane to methanol conversion: Multi-Technique characterization and comparison with NH3 selective catalytic reduction of NOx. Catalysis Today. ISSN 0920-5861. 369, s. 1–7. doi: 10.1016/j.cattod.2020.06.050. Fulltekst i vitenarkiv Vis sammendrag

  The direct conversion of methane to methanol has the potential of substantially reducing methane emissions and flaring, as such a process might provide an alternative for remote natural gas locations. In this report, we investigate the performance of a range of Cu-exchanged mordenite zeolites as active materials for such a reaction, employing a stepwise protocol comprising activation in oxygen, methane loading, and methanol extraction with steam. We employ in situ HERFD XANES, FT-IR spectroscopy with CO as probe molecule, and XPS to investigate the Cu species in the zeolites during the process. The activity of the materials is investigated both for methane to methanol conversion and NH3 Selective Catalytic Reduction of NOx. It is demonstrated that, despite the fact that the same zeolite materials are active both for NH3-SCR and direct methane to methanol conversion, the active site requirements for these two reactions are different.

• Kvande, Karoline; Pappas, Dimitrios; Dyballa, Michael Martin; Buono, Carlo; Signorile, Matteo & Borfecchia, Elisa [Vis alle 13 forfattere av denne artikkelen] (2020). Comparing the Nature of Active Sites in Cu-loaded SAPO-34 and SSZ-13 for the Direct Conversion of Methane to Methanol. Catalysts. 10(191). doi: 10.3390/catal10020191. Fulltekst i vitenarkiv Vis sammendrag

  On our route towards a more sustainable future, the use of stranded and underutilized natural gas to produce chemicals would be a great aid in mitigating climate change, due to the reduced CO2 emissions in comparison to using petroleum. In this study, we investigate the performance of Cu-exchanged SSZ-13 and SAPO-34 microporous materials in the stepwise, direct conversion of methane to methanol. With the use of X-ray absorption spectroscopy, infrared (in combination with CO adsorption) and Raman spectroscopy, we compared the structure–activity relationships for the two materials. We found that SSZ-13 performed significantly better than SAPO-34 at the standard conditions. From CH4-TPR, it is evident that SAPO-34 requires a higher temperature for CH4 oxidation, and by changing the CH4 loading temperature from 200 to 300 ◦C, the yield (µmol/g) of SAPO-34 was increased tenfold. As observed from spectroscopy, both three- and four-fold coordinated Cu-species were formed after O2-activation; among them, the active species for methane activation. The Cu speciation in SAPO-34 is distinct from that in SSZ-13. These deviations can be attributed to several factors, including the different framework polarities, and the amount and distribution of ion exchange sites.

• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Thorshaug, Knut; Lind, Anna Maria; Vajeeston, Ponniah & Dovgaliuk, Iurii [Vis alle 9 forfattere av denne artikkelen] (2020). Factors Determining Microporous Material Stability in Water: The Curious Case of SAPO-37. Chemistry of Materials. ISSN 0897-4756. 32(4), s. 1495–1505. doi: 10.1021/acs.chemmater.9b04510. Fulltekst i vitenarkiv Vis sammendrag

  Silicoaluminophosphates (SAPOs) are a special class of zeolites that, due to their acidic and shape-selective properties, play a major role in ion exchange and separation processes and in crude oil cracking. SAPO-37 has the faujasite (FAU) topology same as zeolites X and Y, which are involved in more than 40% of the total crude oil conversion worldwide. A critical parameter that promotes detrimental structural transformations in SAPOs during real-life applications is the presence of humidity. In this study, we employ a multidisciplinary approach combining in situ synchrotron radiation powder X-ray diffraction (SR-PXRD), water adsorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and density functional theory (DFT) calculations to describe the mechanism and reveal the reasons why SAPO-37 collapses upon contact with humidity below 345 K. SR-PXRD revealed that the sodalite (SOD) cages (subunits of the FAU structure) have the strongest affinity to water during hydration below 345 K. Furthermore, below 345 K, the faujasite framework takes up an order of magnitude more water molecules than at temperatures above 345 K. DRIFTS confirmed the presence of Si−OH and P−OH surface structural defects that act as hydration centers, accelerating the loss of a long-range order. Finally, DFT calculations showed that the enthalpy of water adsorption in the sodalite cage and the faujasite supercage is −212 and −13 kJ/mol, respectively. The results presented in this work are highly topical for understanding the effect of water on the frameworks of the SAPO microporous catalysts family. The notorious instability of SAPO-37 is the result of the accumulative contribution of topological, physical, and chemical effects, leading to an array of rapidly evolving cascading effects. Our work shows how advancements in SR-PXRD methodology and hardware give new insight into highly dynamic features previously difficult to observe. In addition, this work introduces the conceptual insight that nonhomogeneous sorption of molecular species will induce dynamic features with dramatic consequences at both molecular and atomic levels. This is a highly impactful factor opening research paths for further work within catalysis, porous material design and chemistry, and sorption reactions and processes.

• Gawel, Bartlomiej; Ulvensøen, Anna; Lukaszuk, Katarzyna Anna; Arstad, Bjørnar; Muggerud, Astrid Marie Flattum & Erbe, Andreas (2020). Structural evolution of water and hydroxyl groups during thermal, mechanical and chemical treatment of high purity natural quartz. RSC Advances. 48(48), s. 29018–29030. doi: 10.1039/d0ra05798c. Fulltekst i vitenarkiv Vis sammendrag

  Fused silica crucibles are commonly used in the fabrication process of solar grade silicon ingots. These crucibles are manufactured from high purity natural quartz sand and as a consequence, their properties are influenced by the presence of water and hydroxyls in the raw quartz. In this work, diffuse reflectance IR, 1H magic angle spinning NMR, and Raman spectroscopy were used to investigate the influence of thermal treatment on water and hydroxyl groups in high purity natural quartz sand. Most of the water in dry sand is present in the form of closed inclusions within the quartz grains which were detected in Raman imaging studies, even after thermally treating the samples at 600 °C. Only after heating to 900 °C did this water completely vanish, most likely as a result of rupturing of the inclusions. However, newly formed OH groups, identified as isolated and hydrogen bound OH were observed as products of the reaction between water and quartz. Similarly, liquid water was observed in NMR spectra even after treatment at 600 °C while at temperatures >900 °C, only non-interacting silanol groups were present. The comparison of the temperature dependence of the IR and NMR spectra also yields insight into the assignment of the OH stretching mode region of the IR spectrum in this system. The intensity of water related bands decreases while the intensity of OH bands first increases and then decreases with increasing temperature. The band intensity of Al-rich defects as well as the characteristic feature at 3200 cm−1 does not follow the temperature dependence of typical water peaks. It is also shown that leaching the quartz sand in HF solution helps to remove water from inclusions, likely by forming pathways for fluid flow inside the quartz grains. Milling of the samples caused formation of an additional type of hydroxyl group, possibly due to partial amorphisation of the surfaces of the quartz grains surface during the process. The results improve the basis for a knowledge-based processes development for the processing of high purity natural quartz.

• Dyballa, Michael Martin; Thorshaug, Knut; Pappas, Dimitrios; Borfecchia, Elisa; Kvande, Karoline & Bordiga, Silvia [Vis alle 12 forfattere av denne artikkelen] (2019). Zeolite surface methoxy groups as key intermediates in the stepwise conversion of methane to methanol. ChemCatChem. ISSN 1867-3880. 11(20), s. 5022–5026. doi: 10.1002/cctc.201901315. Fulltekst i vitenarkiv Vis sammendrag

  This contribution clarifies the overoxidation-preventing key step in the methane-to-methanol (MTM) conversion over copper mordenite zeolites. We followed the methane-to-methanol conversion over copper mordenite zeolites by NMR spectroscopy supported by DRIFTS to show that surface methoxy groups (SMGs) located at zeolite Brønsted sites are the key intermediates. The SMGs with chemical shift of 59 ppm are identical to those formed on a copper-free reference zeolite after reaction with methanol and react with water, methanol, or carbon monoxide to yield methanol, dimethyl ether, and acetate. This reactivity corroborates the location of SMGs at Brønsted sites. We find no evidence for stable SMGs directly at copper sites and explain mechanistically why H-form mordenites outperform their Na-form analogues. This finding is of interest for any future process that tries to trap the intermediate methane oxidation product towards methanol.

• Pappas, Dimitrios; Borfecchia, Elisa; Lomachenko, Kirill A.; Lazzarini, Andrea; Gutterød, Emil Sebastian & Dyballa, Michael Martin [Vis alle 14 forfattere av denne artikkelen] (2019). Cu-Exchanged Ferrierite Zeolite for the Direct CH4 to CH3OH Conversion: Insights on Cu Speciation from X-Ray Absorption Spectroscopy. Topics in catalysis. ISSN 1022-5528. 62(7-11). doi: 10.1007/s11244-019-01160-7. Fulltekst i vitenarkiv Vis sammendrag

  The direct stepwise transformation of CH4 to CH3OH over Cu-exchanged zeolites has been an intensively researched reaction as it can provide a solution for the utilization of this abundant feedstock. Up to date a commercial process is far from realization, which is why an understanding of the Cu speciation in zeolites as a function of reaction conditions as well as the development of a mechanistic view of the reaction are necessary to further advance the field. Herein we study Cu-exchanged ferrierite zeolite for the direct CH4 to CH3OH conversion by utilizing X-ray absorption spectroscopy (XAS), in order to assess the local structure and electronic properties of Cu through the reaction. A Cu-FER sample with a Cu/Al = 0.20 and Si/Al = 11 was subjected to three reaction cycles yielding ultimately 96 µmol CH3OH/gzeolite . Normalized to the Cu loading, this accounts for 0.33 mol CH3OH /molCu, making the sample comparable to very active Cu-MOR materials reported in the literature. During O2 activation, a transient self-reduction regime of CuII to CuI ions was identified; eventually leading to mostly framework interacting CuII species. CH4 loading leads to a reduction of these CuII containing species; which are finally partially reoxidized during H2O-assisted CH3OH extraction. The speciation after CH4 activation as well as H2O-assisted CH3OH extraction was assessed via linear combination fitting analysis of the XAS data.

• Dyballa, Michael Martin; Pappas, Dimitrios; Kvande, Karoline; Borfecchia, Elisa; Arstad, Bjørnar & Beato, Pablo [Vis alle 8 forfattere av denne artikkelen] (2019). On how copper mordenite properties govern the framework stability and activity in the methane-to-methanol conversion. ACS Catalysis. 9(1), s. 365–375. doi: 10.1021/acscatal.8b04437. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2019). Characterization and evaluation of synthetic Dawsonites as CO2 sorbents. Fuel. ISSN 0016-2361. 236, s. 747–754. doi: 10.1016/j.fuel.2018.09.057. Fulltekst i vitenarkiv Vis sammendrag

  The sorbent enhanced water-gas shift (SEWGS) process has great potential for CO2 capture and is thereby a realistic alternative to conventional post-combustion capture by gas emission scrubbing. Nevertheless, better performing materials are required to make SEWGS competitive against state-of-the-art scrubbing technologies. Dawsonite, NaAl(OH)2CO3, has a high carbonate content and forms in situ during CO2 capture on alkali metal promoted alumina, thereby showing potential in variable temperature capture processes. For the isothermal SEWGS process the performance in pressure swing absorption is essential. We evaluate here synthetic Dawsonites [MAl(OH)2CO3, M = K, Na] as CO2 sorbents for the SEWGS process based on data from in situ X-ray diffraction, combined thermogravimetric analysis and mass spectrometry, magic-angle spinning nuclear magnetic resonance spectroscopy, as well as high pressure fixed bed reactor tests at isothermal conditions. The results show that synthetic Dawsonites are promising sorbents for the SEWGS process, however, with moderate cyclic CO2 capacities (∼0.3–0.7 mmol CO2/g sorbent) in comparison to alkali-metal promoted hydrotalcites. On the other hand, the materials exhibit relatively fast sorption rates at low temperatures (280–310 °C), favoring the water-gas shift reaction in the SEWGS process.

• Langseth, Eirin; Swang, Ole; Arstad, Bjørnar; Lind, Anna Maria; Cavka, Jasmina Hafizovic & Jensen, Tomas Lunde [Vis alle 10 forfattere av denne artikkelen] (2019). Synthesis and characterization of Al@MOF materials. Materials Chemistry and Physics. ISSN 0254-0584. doi: 10.1016/j.matchemphys.2019.01.009. Fulltekst i vitenarkiv Vis sammendrag

  The potential impregnation of Al(0) nanoparticles in the pores of three different metal-organic frameworks (MOFs), MIL-53-Al, HKUST-1, and UiO-67, was investigated through the suspension of the MOFs in AlH3•NMe2Et (1), followed by filtration, toluene wash, and heating to 150 °C under vacuum. Calculations based on the ratios of molecular and pore volumes provided idealized, benchmark impregnation capacities. Three successive impregnation cycles were performed to provide maximum incorporation of Al in the pores, and the materials were characterized after each impregnation cycle by ICP elemental analysis, BET surfacearea, and pore volume measurements. For MIL-53-Al, about half of the calculated amount of Al was incorporated into the MIL-53 pore structure, and PXRD data indicated a loss of crystallinity after the third incorporation cycle. Little Al incorporation was observed with HKUST-1, and the large decrease in surface area and pore volume, without significant change in the PXRD pattern, is attributed to pore blockage. Reaction of a large excess of 1 with UiO-67 was highly exothermic and evolved gas, likely from reaction with the μ3-OH groups in the UiO-67 structure. The resulting material was amorphous apart from metallic Al(0) crystals approximately 30 nm in size and larger than the UiO-67 pores, as determined by PXRD and 27Al MAS NMR spectroscopy. This material exhibited no apparent reaction with air or water and exposure to air gave little change in the 27Al MAS NMR spectrum. The Al(0) crystals thus appear to be protected from oxidation, presumably by the remaining UiO-67 framework.

• Pappas, Dimitrios; Martini, Andrea; Dyballa, Michael Martin; Kvande, Karoline; Teketel, Shewangizaw & Lomachenko, Kirill A. [Vis alle 16 forfattere av denne artikkelen] (2018). The nuclearity of the active site for methane to methanol conversion in Cu-mordenite: a quantitative assessment. Journal of the American Chemical Society. ISSN 0002-7863. 140(45), s. 15270–15278. doi: 10.1021/jacs.8b08071. Fulltekst i vitenarkiv
• Dyballa, Michael Martin; Pappas, Dimitrios; Borfecchia, Elisa; Beato, Pablo; Olsbye, Unni & Lillerud, Karl Petter [Vis alle 8 forfattere av denne artikkelen] (2018). Tuning the material and catalytic properties of SUZ-4 zeolites for the conversion of methanol or methane. Microporous and Mesoporous Materials. ISSN 1387-1811. 265, s. 112–122. doi: 10.1016/j.micromeso.2018.02.004. Fulltekst i vitenarkiv Vis sammendrag

  This work describes the synthesis and investigation of improved SUZ-4 catalysts (SZR framework) and their application in methanol-to-olefins and methane-to-methanol conversion. We report boron containing, dealuminated and desilicated SUZ-4 catalysts. Ammonia and pyridine probe molecules enabled the assignment of acid site densities to the 10-MR and 8-MR pores, respectively. The difference in between the theoretically expected and the for the probes accessible acid site density is a good descriptor for the accessibility of pores and acid sites. The access to the 8-MR SUZ-4 pores is sterically hindered by counter ions as well as extra framework aluminum (EFAl) species that account for up to 15% of the aluminum. Dealumination and desilication were successfully applied to optimize the diffusion properties and resulted in outstandingly high BET surface area, nSi/nAl-ratios and potassium exchange degrees. The improved accessibility led to an up to 2-fold increased MTO conversion capacity of the catalysts. Cu-exchanged SUZ-4 was applied in the selective oxidation of methane to methanol. By operando X-ray absorption spectroscopy (XAS) we showed that CuII ions are mainly coordinated in 2Al sites of 6-MR motifs and inhibited for redox-reactions.

• Lind, Anna Maria; Thorshaug, Knut; Andreassen, Kari Anne; Blom, Richard & Arstad, Bjørnar (2018). The Role of Water during CO2 Adsorption by Ca-Based Sorbents at High Temperature. Industrial & Engineering Chemistry Research. ISSN 0888-5885. 57(8), s. 2829–2837. doi: 10.1021/acs.iecr.7b04052. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Checchia, Stefano; Lind, Anna Maria; Wragg, David & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2018). In Situ Flow MAS NMR Spectroscopy and Synchrotron PDF Analyses of the Local Response of the Brønsted Acidic Site in SAPO-34 during Hydration at Elevated Temperatures. ChemPhysChem. ISSN 1439-4235. 19(4), s. 519–528. doi: 10.1002/cphc.201700973. Fulltekst i vitenarkiv
• Pappas, Dimitrios; Borfecchia, Elisa; Dyballa, Michael Martin; Lomachenko, Kirill A.; Martini, Andrea & Berlier, Gloria [Vis alle 12 forfattere av denne artikkelen] (2018). Understanding and optimizing the performance of Cu‐FER for the direct CH4 to CH3OH conversion. ChemCatChem. ISSN 1867-3880. 11(1), s. 621–627. doi: 10.1002/cctc.201801542. Fulltekst i vitenarkiv
• Anderson, Michael W; Gebbie-Rayet, James T.; Hill, Adam R.; Farida, Nani; Attfield, Martin P. & Cubillas, Pablo [Vis alle 11 forfattere av denne artikkelen] (2017). Predicting crystal growth via a unified kinetic three-dimensional partition model. Nature. ISSN 0028-0836. 544(7651), s. 456–459. doi: 10.1038/nature21684. Fulltekst i vitenarkiv Vis sammendrag

  Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system9,10,11. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal–organic frameworks, calcite, urea and L-cystine.

• Arstad, Bjørnar; Blom, Richard; Didriksen, Terje; Frøseth, Morten; Heyn, Richard H. & Øien-Ødegaard, Sigurd (2017). NMR spectroscopic investigations into the mechanism of absorption and desorption of CO2 by (tris-pyridyl)amine Zn complexes. Journal of CO2 Utilization. ISSN 2212-9820. 19, s. 58–67. doi: 10.1016/j.jcou.2017.02.007. Fulltekst i vitenarkiv Vis sammendrag

  The Zn complex [(NN3)Zn(OH)]2(NO3)2 (1(NO3)2, NN3 = tris(2-pyridylmethyl)amine) reacts with atmospheric CO2 to form a zinc carbonate species {[(NN3)Zn]3CO3}(NO3)4 (2(NO3)4), isolable as a crystalline product from organic solvents. The aqueous chemistry of the CO2 absorption and desorption processes for 1(NO3)2 and the presumed end-point of the reaction, 2(NO3)4, was unknown and hence investigated by NMR spectroscopy. Carboxylation of aqueous solutions of both 1(NO3)2 and 2(NO3)4 form products that can best be described as mixtures of monomeric [(NN3)ZnCO3H]+ and dimeric {[(NN3) Zn]2CO3}2+, which are in a dynamic equilibrium on the NMR time-scale. No evidence for the involvement of 2(NO3)4 in the carboxylation-decarboxylation processes is observed. Rather, the data suggest that 2 (NO3)4 provides [(NN3)Zn(OH2)]2+ that does not participate in the CO2 chemistry upon warming. A mechanism that is supported by NMR experiments and that accounts for the formation of [(NN3) ZnCO3H]+ and {[(NN3)Zn]2CO3}2+ from both ends of the reaction manifold is proposed.

• Wang, Xuehang; Mehandzhiyski, Aleksandar Yordanov; Arstad, Bjørnar; Aken, Katherine L. Van; S., Mathis Tyler & Gallegos, Alejandro [Vis alle 14 forfattere av denne artikkelen] (2017). Selective Charging Behavior in an Ionic Mixture Electrolyte- Supercapacitor System for Higher Energy and Power. Journal of the American Chemical Society. ISSN 0002-7863. 139(51), s. 18681–18687. doi: 10.1021/jacs.7b10693. Fulltekst i vitenarkiv Vis sammendrag

  Ion–ion interactions in supercapacitor (SC) electrolytes are considered to have significant influence over the charging process and therefore the overall performance of the SC system. Current strategies used to weaken ionic interactions can enhance the power of SCs, but consequently, the energy density will decrease due to the increased distance between adjacent electrolyte ions at the electrode surface. Herein, we report on the simultaneous enhancement of the power and energy densities of a SC using an ionic mixture electrolyte with different types of ionic interactions. Two types of cations with stronger ionic interactions can be packed in a denser arrangement in mesopores to increase the capacitance, whereas only cations with weaker ionic interactions are allowed to enter micropores without sacrificing the power density. This unique selective charging behavior in different confined porous structure was investigated by solid-state nuclear magnetic resonance experiments and further confirmed theoretically by both density functional theory and molecular dynamics simulations. Our results offer a distinct insight into pairing ionic mixture electrolytes with materials with confined porous characteristics and further propose that it is possible to control the charging process resulting in comprehensive enhancements in SC performance.

• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Chernyshov, Dmitry & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2017). SAPO-37 microporous catalysts: revealing the structural transformations during template removal. Catalysis, Structure & Reactivity. 3(1-2), s. 79–88. doi: 10.1080/2055074X.2016.1262569. Fulltekst i vitenarkiv Vis sammendrag

  We have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This expansion seems to be related with residual coke from template combustion. We could differentiate between the thermal response of oxygen and T-atoms. The T–O–T angle between two double 6-rings and a neighboring T–O–T linkage shared by SOD and FAU had different response to the thermal events. We were able to monitor the changes in the positions of oxygen and T-atoms during the removal of TPA+ and TMA+. Large changes to the framework structure at the point of template removal may have a significant effect on the long-term stability of the material in its activated form.

• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Thermogravimetric Analysis – A Viable Method for Screening Novel Materials for the Sorbent Enhanced Water-gas Shift Process. Energy Procedia. 114, s. 2294–2303. doi: 10.1016/j.egypro.2017.03.1372. Fulltekst i vitenarkiv Vis sammendrag

  Pre-combustion CO2 capture technologies are becoming viable alternatives to more conventional post-combustion capture by gas emissions scrubbing. The sorbent enhanced water-gas shift (SEWGS) process is a promising future technology for CO2 capture. However, the process needs better performing materials than those available today to be competitive against state-of-the-art scrubbing technologies. Layered double hydroxides (LDH) are a promising class of materials to improve the performance of the SEWGS process. These materials have a general formula of M2+1-xM3+x(OH)2(An-)x/n·mH2O, and can be tuned by substituting the metal species, changing the M2+/M3+ ratio, adjusting the synthesis parameters to influence morphology or by adding so-called promotors to improve performance. To aid an ongoing systematic study looking at several of these parameters we have developed a simple yet efficient way of screening materials for further in-depth studies. The method is highly suitable for a typical laboratory setting, and is based on thermogravimetric analysis combined with cyclic exposure to selected gases. In this article we present the results of applying the method to a selection of benchmark materials.

• Pappas, Dimitrios; Borfecchia, Elisa; Dyballa, Michael Martin; Pankin, Ilia A.; Lomachenko, Kirill A. & Martini, Andrea [Vis alle 16 forfattere av denne artikkelen] (2017). Methane to methanol: structure-activity relationships for Cu-CHA. Journal of the American Chemical Society. ISSN 0002-7863. 139(42), s. 14961–14975. doi: 10.1021/jacs.7b06472. Fulltekst i vitenarkiv Vis sammendrag

  Cu-exchanged zeolites possess active sites that are able to cleave the C–H bond of methane at temperatures ≤200 °C, enabling its selective partial oxidation to methanol. Herein we explore this process over Cu-SSZ-13 materials. We combine activity tests and X-ray absorption spectroscopy (XAS) to thoroughly investigate the influence of reaction parameters and material elemental composition on the productivity and Cu speciation during the key process steps. We find that the CuII moieties responsible for the conversion are formed in the presence of O2 and that high temperature together with prolonged activation time increases the population of such active sites. We evidence a linear correlation between the reducibility of the materials and their methanol productivity. By optimizing the process conditions and material composition, we are able to reach a methanol productivity as high as 0.2 mol CH3OH/mol Cu (125 μmol/g), the highest value reported to date for Cu-SSZ-13. Our results clearly demonstrate that high populations of 2Al Z2CuII sites in 6r, favored at low values of both Si:Al and Cu:Al ratios, inhibit the material performance by being inactive for the conversion. Z[CuIIOH] complexes, although shown to be inactive, are identified as the precursors to the methane-converting active sites. By critical examination of the reported catalytic and spectroscopic evidence, we propose different possible routes for active-site formation.

• Mudu, Federica; Olsbye, Unni; Arstad, Bjørnar; Diplas, Spyridon; Li, Yanjun & Fjellvåg, Helmer (2016). Aluminium substituted lanthanum based perovskite type oxides, non-stoichiometry and performance in methane partial oxidation by framework oxygen. Applied Catalysis A : General. ISSN 0926-860X. 523, s. 171–181. doi: 10.1016/j.apcata.2016.05.013. Fulltekst i vitenarkiv Vis sammendrag

  A series of Rh-promoted La0.75Sr0.25(Fe0.80Co0.20)(1-x)AlxO3-δ (x = 0, 0.10, 0.25, 0.40, 0.60) samples were investigated as oxygen reservoirs for the conversion of CH4 to syngas at 873 K and 1 atm. Neutron powder diffraction studies revealed a decreasing rhombohedral distortion on increasing Al-content. XPS and TEM were employed to investigate surface chemistry and morphology of the Al = 0.25 sample. The influence of Al-substitution on the redox properties was studied by flowing titration whereas catalytic properties were studied by means of transient pulses of CH4 and O2, as well of 13CH4 and CO. The products (CO, H2, CO2 and H2O) of the reaction between CH4 and the studied oxides were successfully tuned by tailoring the redox properties of the reducible oxides through the Al-substitution.

• Arstad, Bjørnar; Lind, Anna Maria; Cavka, Jasmina Hafizovic; Thorshaug, Knut; Akporiaye, Duncan & Wragg, David [Vis alle 9 forfattere av denne artikkelen] (2016). Structural changes in SAPO-34 due to hydrothermal treatment. A NMR, XRD, and DRIFTS study. Microporous and Mesoporous Materials. ISSN 1387-1811. 225, s. 421–431. doi: 10.1016/j.micromeso.2016.01.024. Fulltekst i vitenarkiv Vis sammendrag

  When SAPO-34 is used as an industrial MTO catalyst, structural transformations leading to permanent deactivation are inevitable. The performance loss is linked principally to a redistribution of Si in the material, leading to the formation of Si-islands/aggregates with a concomitant loss of Brønsted acidic sites and catalytic activity. In this work we have studied transformations taking place in a SAPO-34 sample after hydrothermal treatment by studying two samples with different levels of Si; 7 atomic % and 13 atomic % Si T-atoms, corresponding to about one and two Si per CHA cage respectively. The 13% Si sample contains significant amount of silicon islands in its as-synthesized form, while the 7% Si sample does not. The 7% Si sample was steamed for a week at 700 °C and a partial pressure of steam of 0.7 atm. The changes were analysed in the context of Si-island formation, and compared with the 13% Si sample. The results clearly illustrated existence of two distinct types of local aggregation of silicon: Silicon islands produced during synthesis and aggregate silicon reminiscent of silicon islands induced by hydrothermal treatment. The materials were synthesized with full 29Si isotopic enrichment and allowed us, for the first time, to characterise the multiplicity of silicon species in great detail by 29Si solid state NMR.

• Stewart, Joseph A.; Drexel, Roland; Arstad, Bjørnar; Reubsaet, Erik; Weckhuysen, Bert M. & Bruijnincx, Pieter C.A. (2016). Homogeneous and Heterogenised Masked N-Heterocyclic Carbenes for Bio-based Cyclic Carbonate Synthesis. Green Chemistry. ISSN 1463-9262. 18(6), s. 1605–1618. doi: 10.1039/c5gc02046h. Fulltekst i vitenarkiv Vis sammendrag

  Multifunctional) cyclic carbonates are generating much interest, with bio-based bis-cyclic compounds attracting attention from the polymer sector as potential renewable monomers for systems such as non-isocyanate polyurethanes. Here, the efficient synthesis of one such substrate, diglycerol dicarbonate, utilising CO2-masked N-heterocyclic carbene (NHC) organocatalysts is demonstrated. The 1,3-dialkylimidazole-2-carboxylate pre-catalyst, which can be produced both in and ex situ, yields the desired cyclic product, expressing full conversion within 3 h when using the ex situ synthesised pre-catalyst with 5 mol% loading, but can also operate with 1 mol% loading efficiently. Substituted derivatives of the imidazole-based organocatalyst have also been investigated to gauge the sensitivity of the system. A number of bio-based diols are also investigated, with 1,2-, 2,3- and 1,3-diols yielding five- and six-membered cyclic products, respectively; 1,3-diols are significantly more reluctant to cyclisation, yielding both 1- and 3-monocarbonates, dicarbonates and the cyclic products. A more in depth study was also carried out on glycerol as a substrate, both in its pure a crude form, providing insight into how impurities impact on the activity of the carbene catalyst. Through 13C-labelled reagent experiments, a mechanism is proposed for the conversion of diols to their cyclic carbonate analogues. Finally, the organocatalyst was immobilized on siliceous mesostructured cellular foam (MCF). Using an alternative activation procedure, a supported, masked NHC catalyst is achieved and characterised with DRIFTS, TGA and 13C solid-state NMR. This heterogenised catalyst can be easily recovered and reused up to three times expressing its original activity if properly regenerated by a simple ion exchange procedure. Of important note, this system can also successfully convert crude glycerol with high selectivity observed for the cyclic product.

• Saldan, Ivan; Frommen, Christoph; Llamas-Jansa, Isabel; Kalantzopoulos, Georgios N.; Hino, Satoshi & Arstad, Bjørnar [Vis alle 12 forfattere av denne artikkelen] (2015). Hydrogen storage properties of γ–Mg(BH4)2 modified by MoO3 and TiO2. International Journal of Hydrogen Energy. ISSN 0360-3199. 40(36), s. 12286–12293. doi: 10.1016/j.ijhydene.2015.07.082. Fulltekst i vitenarkiv Vis sammendrag

  The reversible hydrogen desorption–absorption of γ–Mg(BH4)2 ball milled with MoO3 and TiO2 has been investigated. No mechanochemical interaction between γ–Mg(BH4)2 and TiO2 was observed while for the 1:1 M ratio with MoO3, MoB2 was formed. There was little difference in the properties of γ–Mg(BH4)2 and γ–Mg(BH4)2 ball–milled with 0.02 mol percent TiO2 and MoO3. However, mixing in the same ratio γ–Mg(BH4)2 with TiO2 and MoO3 that had previously been subjected to high energy milling provided significant effects. For these materials, the DSC peaks appeared broader and were shifted to slightly lower temperatures, while the TPD peaks were decreased by ca. 20 °C, as compared to the pure γ–Mg(BH4)2. Faster hydrogen desorption kinetics was observed for the γ–Mg(BH4)2–MoO3 mixture. The reversible hydrogen storage capacity of γ–Mg(BH4)2–TiO2 at 271 °C was found to be 2.4 wt% H2 in the first cycle.

• Sprung, Christoph; Kechagiopoulos, Panagiotis N.; Thybaut, Joris W.; Arstad, Bjørnar; Olsbye, Unni & Marin, Guy B. (2015). Microkinetic evaluation of normal and inverse kinetic isotope effects during methane steam reforming to synthesis gas over a Ni/NiAl2O4 model catalyst. Applied Catalysis A : General. ISSN 0926-860X. 492, s. 231–242. doi: 10.1016/j.apcata.2014.10.062. Fulltekst i vitenarkiv Vis sammendrag

  A microkinetic model was developed and applied to simulate an extensive experimental dataset on methane steam reforming. The data set consisted of 537 data points, and was collected over a Ni/NiAl2O4 catalyst at 843, 858, and 873 K in a wide steam-to-carbon ratio range between 0.2 and 7.1. A microkinetic engine modeling tool was applied for the construction and parameter estimation of an elementary step network consisting of 12 reversible reactions. Specific reaction pathways were implemented for the formation of CO and CO2, respectively. The model qualitatively if not quantitatively explains inverse and normal isotope effects experimentally observed at low and high S/C ratios, respectively, and is thermodynamically consistent. A combination of the approach to partial equilibrium (i.e. whether the elementary step proceeds forward or backward) and net rate (i.e. the difference between forward and backward reaction rate) provides novel insight into the oxidation mechanism of CHx and CHxO surface species.

• Neyertz, Sylvie; Brown, David; Pilz, Monika; Rival, Nicolas; Arstad, Bjørnar & Männle, Ferdinand [Vis alle 7 forfattere av denne artikkelen] (2015). The stability of amino-functionalized polyhedral oligomeric silsesquioxanes in water. Journal of Physical Chemistry B. ISSN 1520-6106. 119(21), s. 6433–6447. doi: 10.1021/acs.jpcb.5b01955. Fulltekst i vitenarkiv Vis sammendrag

  Octa(aminopropylsilsesquioxane) Si8O12[(CH2)3NH2]8 is a very important precursor for many other hybrid organic/inorganic polyhedral oligomeric silsesquioxanes (POSS) because of the reactivity of its primary amine groups. Unfortunately, it is unstable in water, which can lead to the cleavage of its siloxane cage. In the present work, such a degradation was confirmed using solid-state 29Si NMR spectroscopy, and the molecular features at the basis of this instability were studied using molecular dynamics simulations (MD). It was also investigated whether replacing the primary amine end groups by secondary amines or by amides with long aliphatic chains could lead to an improvement in the water stability of the Si/O framework. In the pure bulk models, all POSS interdigitate with their pendant organic arms intertwined. Upon insertion of isolated molecules into water, the dimensions of the primary amine POSS remain close to those of the bulk, while the secondary amine and the amide POSS favor conformations that optimize the intramolecular chain–chain interactions. When there are several POSS molecules in water, they cluster with each other through both intra- and intermolecular chain–chain interactions. This tendency for the organic chains to intertwine whenever possible provides some protection to the siloxane cages from water, but also leaves some of the siloxane O exposed. As such, the latter are accessible to form transient hydrogen bonds with the water molecules, which could be a precursor step to hydrolysis and thus cage breakage. In the molecular models, a better protection was obtained in the amide POSS for two reasons: its chains tended to wrap efficiently around its cage, and its ketone O kept water from getting close to the siloxanes. The molecular modeling characterizations were found to agree very well with experimental evidence.

• Smith, Rachel L.; Slawinski, Wojciech Andrzej; Lind, Anna Maria; Wragg, David; Cavka, Jasmina Hafizovic & Arstad, Bjørnar [Vis alle 10 forfattere av denne artikkelen] (2015). Nanoporous Intergrowths: How Crystal Growth Dictates Phase Composition and Hierarchical Structure in the CHA/AEI System. Chemistry of Materials. ISSN 0897-4756. 27(12), s. 4205–4215. doi: 10.1021/cm504284x. Fulltekst i vitenarkiv Vis sammendrag

  Some of the most important nanoporous materials that are used for industrial applications are formed as intergrowths between structurally related phases. Further, the specific properties and functions are often strongly related to the nature of these intergrowths. By their nature such structures are notoriously difficult to characterize in detail and thereby formulate a structure/property relationship. We approach the problem of the industrially relevant CHA/AEI intergrowth system by getting insight into not only the structure of the materials but also the crystal-growth mechanism and show that the former is crucially dependent upon the latter. Through a detailed X-ray diffraction analysis with optimization of the CHA/AEI layer stacking sequence, it is shown that up to three distinct components are present. These consist of the two end member structures intimately cocrystallizing with an intergrowth structure. The intergrowth composition is further corroborated by nuclear magnetic resonance and unit cell measurements. The mechanism by which these complex intergrowth structures form is revealed by atomic force microscopy that shows there are at least two competing mechanisms of growth at the surface: layer-by-layer and spiral. This has profound consequences on the resulting intergrowth materials, as intergrowth formation is not permitted in spiral growth. The competition from the lower energy spiral growth at screw dislocations does not allow intergrowth formation and consequently results in blocks of pure-phase AEI or CHA. Owing to this competitive growth nature, the different possibilities furnish the material with its higher level hierarchical structure.

• Smith, Rachel; Svelle, Stian; Campo, Pablo Del; Fuglerud, Terje; Arstad, Bjørnar & Lind, Anna Maria [Vis alle 10 forfattere av denne artikkelen] (2015). CHA/AEI intergrowth materials as catalysts for the Methanol-to-Olefins process. Applied Catalysis A : General. ISSN 0926-860X. 505, s. 1–7. doi: 10.1016/j.apcata.2015.06.027. Fulltekst i vitenarkiv Vis sammendrag

  A series of SAPO-34/SAPO-18 intergrowth materials were prepared with a range of silicon content from 0.5 to 7.0%, where low levels of silicon resulted in SAPO-18 and higher levels resulted in CHA/AEI intergrowths. These materials were tested for their performance in the Methanol-to-Olefins reaction. The acidity of the catalysts was related to their silicon content, where a higher level of silicon gave a greater acid site density. The catalytic activity increased with increasing acid site density. There was consequently a higher level of heavy hydrocarbons in the catalysts at the end of the reaction in the materials with higher silicon content. The selectivity as a function of overall time on stream was similar for all catalysts, but at a given level of conversion, the C2/C3 ratio was lower for the materials with higher AEI content. Catalysts with a higher ratio of AEI cages had a higher selectivity to C3 and C4 products than the other catalysts, due to the larger size of the internal AEI cage. The C2/C3 ratio showed a strong correlation to the cage shape, making catalysts with high AEI content suitable where higher propylene ratios are desired.

• Sjåstad, Anja Olafsen; Andersen, Niels Højmark; Vajeeston, Ponniah; Karthikeyan, Jayakumar; Arstad, Bjørnar & Karlsson, Arne [Vis alle 7 forfattere av denne artikkelen] (2015). On the Thermal Stability and Structures of Layered Double Hydroxides Mg1-xAlx(OH)2(NO3)x·mH2O (0.18 ≤ x ≤ 0.38). European Journal of Inorganic Chemistry (EurJIC). ISSN 1434-1948. 2015(10), s. 1775–1788. doi: 10.1002/ejic.201403232. Fulltekst i vitenarkiv Vis sammendrag

  Nitrate-based layered double hydroxides, Mg1–xAlx(OH)2(NO3)x·mH2O, have been investigated to settle issues relating to stability towards humidity, dehydration and staging, nitrate group orientation, Al migration and crystal structure. Raman and IR spectroscopy together with modelling methods proved that flat-lying water and nitrate become tilted towards [001] at higher nitrate concentrations, accompanied by expansion along the c-axis. The distribution of the molecular tilts is greatest for x = 0.25, which explains the extraordinary broad diffraction peaks. The unit cell volume was modified for all samples when subjected to moist air, most strongly for x = 0.25. On heating, in situ synchrotron diffraction data showed continuous changes along the c-axis during dehydration of samples with x = 0.20 and 0.33. For x = 0.25, an intermediate phase appeared. Dehydroxylation was initiated at the OH groups bonded to the cations MgAl2, Mg2Al and Mg3 (in said order), whereas complete nitrate loss occurred at higher temperatures for higher Al contents. Some aluminium simultaneously moved to tetrahedral sites, which, according to 1H–27Al CP NMR spectroscopy, lack protons in their near neighbourhood. In contrast, octahedral aluminium remains surrounded by protons during decomposition. For the metastable oxide product, neutron diffraction indicated that 2/3 of aluminium reside in tetrahedral interstices. This oxide is defective, probably mimicking wüstite rather than a regular rock salt structure.

• Boström, Zebastian Cal Markus; Arstad, Bjørnar & Lillerud, Karl Petter (2014). Preparation of high silica chabazite with controllable particle size. Microporous and Mesoporous Materials. ISSN 1387-1811. 195, s. 294–302. doi: 10.1016/j.micromeso.2014.03.030. Fulltekst i vitenarkiv Vis sammendrag

  In this work synthesis procedures for controlling particle size distributions of high silica chabazite (Si/Al = 100) zeolites between 0.3 and 4.5 μm is described. The chabzite zeolite crystallization and crystal growth have been monitored using XRD, SEM and DLS. Hydrothermal treatment parameters such as time, temperature and agitation and gel composition parameters such as amounts of water and structure directing agent (SDA) have been correlated with chabazite zeolite crystal size, crystal shape, synthesis yield and crystallinity. From this data a chabazite zeolite formation and crystal growth mechanism based on experimental studies and previous studies has been proposed. It was also found that large aggregates formed in the chabazite zeolite gel before any hydrothermal treatment (1 μm large when using zeolite gel with composition 1Al2O3:100SiO2:60TMAdaOH:3100H2O). The size controlling parameter and size controlling synthesis step of the chabazite zeolite (below 1 μm) has been identified as the primary fractal aggregation of the silicium/aluminium/SDA species.

Se alle arbeider i NVA

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2026). Hidden Na5SbSe Unlocks Sb2Se3 Anodes for Na-Ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Antimony selenide (Sb2Se3) is a promising alternative to commonly used NIB anodes, storing 12 Na+ per formula unit, to achieve a capacity of 670 mAh g-1. The (de)sodiation mechanism is very complex: the material progresses through multiple phases when interacting with Na+, including intercalation, con-version, and alloying reactions. These multiple chemical transformations may kinetically limit the material at high rates, however, Sb2Se3 can deliver almost 150 mAh g-1 at 5000 mA g-1. Understanding this unusual behavior is important not only to rationalize the electrochemical performance, but also for the design of other materials capable of working at high (dis)charge rates. Meanwhile, subtle phase transitions or transformations of active battery materials can be traced in operando X-ray diffraction (XRD), which enables the extraction of real-time information about potentially hidden mechanistic pathways, including the discovery of new materials. In this study, Na5SbSe was discovered as the main sodiated product of Sb2Se3 anodes. Na5SbSe is predominantly composed of Na-ions and has a highly flexible composition (breathing effect) that unlocks the exceptional high rate performance of Sb2Se3 anodes

• Skurtveit, Amalie; Jr, Andrew Pastusic; Brennhagen, Anders; Maddar, Faduma M.; Mohn, Chris Erik & Karmakar, Abhoy [Vis alle 13 forfattere av denne artikkelen] (2026). Material's Discovery via Synchrotron Operando XRD and XAS: the Case of Sb2Se3 Anodes for Na-Ion Batteries. Fulltekst i vitenarkiv Vis sammendrag

  Antimony selenide (Sb2Se3) is a promising alternative to commonly used NIB anodes, storing 12 Na+ per formula unit, to achieve a capacity of 670 mAh g-1. The (de)sodiation mechanism is very complex: the material progresses through multiple phases when interacting with Na+, including intercalation, con-version, and alloying reactions. These multiple chemical transformations may kinetically limit the material at high rates, however, Sb2Se3 can deliver almost 150 mAh g-1 at 5000 mA g-1. Understanding this unusual behavior is important not only to rationalize the electrochemical performance, but also for the design of other materials capable of working at high (dis)charge rates. Meanwhile, subtle phase transitions or transformations of active battery materials can be traced in operando X-ray diffraction (XRD), which enables the extraction of real-time information about potentially hidden mechanistic pathways, including the discovery of new materials. In this study, operando XRD and X-ray absorption spectroscopy (XAS) were employed to unravel the mysteries of the (de)sodiation mechanism of Sb2Se3 anodes. Complete elucidation of the reaction pathway was further enabled by solid-state NMR, ex situ work, and ab initio simulations.

• Heyn, Richard Hamilton; Håkonsen, Silje Fosse; Frøseth, Morten; Arstad, Bjørnar; Didriksen, Terje & Swang, Ole [Vis alle 7 forfattere av denne artikkelen] (2025). Gas phase hydroformylation with the post-modified Metal-Organic Framework NU-1000. Fulltekst i vitenarkiv
• Arstad, Bjørnar (2025). A step further in understanding Na dynamics in Na2Zn2TeO6 by synchrotron XRD, total scattering and solid-state NMR analyses. Fulltekst i vitenarkiv
• Yang, Juan; Lind, Anna Maria; Didriksen, Terje; Grandcolas, Mathieu; Arstad, Bjørnar & Carvalho, Patricia Almeida [Vis alle 12 forfattere av denne artikkelen] (2023). Synthesis and characterization of multifunctional nanoparticles for potential theranostic applications. Fulltekst i vitenarkiv
• Yang, Juan; Lind, Anna Maria; Didriksen, Terje; Grandcolas, Mathieu; Arstad, Bjørnar & Szczepanowicz, Krzysztof [Vis alle 9 forfattere av denne artikkelen] (2022). Synthesis of Ceo2/Gd engineered Nanoparticles as Theranostic Nanocarriers. Fulltekst i vitenarkiv
• Hansen, Line Degn; Østensen, Martin; Arstad, Bjørnar; Tschentscher, Roman; Eijsink, Vincent & Horn, Svein Jarle [Vis alle 7 forfattere av denne artikkelen] (2022). 2-Naphthol impregnation prior to steam explosion promotes LPMO-assisted enzymatic saccharification of spruce and yields high-purity lignin. Fulltekst i vitenarkiv
• Hansen, Line Degn; Østensen, Martin; Arstad, Bjørnar; Tschentscher, Roman; Eijsink, Vincent & Horn, Svein Jarle [Vis alle 7 forfattere av denne artikkelen] (2021). An example of combining biochemical and thermocatalytic conversion technologies. Fulltekst i vitenarkiv
• Mondino, Giorgia; Nord, Lars O.; Grande, Carlos Adolfo; Arstad, Bjørnar; Plassen, Martin & Håkonsen, Silje Fosse [Vis alle 7 forfattere av denne artikkelen] (2021). Initial operation of a continuous lab-scale MBTSA pilot using activated carbon adsorbent. Fulltekst i vitenarkiv
• Wagner, Nils Peter; Pollen, Harald Norrud; Svensson, Ann Mari; Tolchard, Julian R; Dahl, Paul Inge & Vullum, Per Erik [Vis alle 7 forfattere av denne artikkelen] (2021). Advancing Lithium Batteries:An Interdisciplinary Approach. Fulltekst i vitenarkiv
• Hempel, Frida Sveen; Arstad, Bjørnar & Fjellvåg, Helmer (2020). Layered hexagonal materials - Differences in ionic conductivity for solid-state electrolyte. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Dyballa, Michael Martin; Thorshaug, Knut; Pappas, Dimitrios K; Borfecchia, Elisa & Kvande, Karoline [Vis alle 12 forfattere av denne artikkelen] (2020). Solid State NMR studies of the stepwise transformation of methane to methanol over Cu-Zeolites. Fulltekst i vitenarkiv
• Blom, Richard; Borras, Adolfo B.; Chan, Fang-Yue; Houlle, Matthieu; Eqtesadi, Siamak & Motealleh, Azadeh [Vis alle 9 forfattere av denne artikkelen] (2019). CO2 capture using PEI adsorbents supported by carbon nano-structures. Fulltekst i vitenarkiv
• Dyballa, Michael Martin; Pappas, Dimitrios; Borfecchia, Elisa; Kvande, Karoline; Bordiga, Silvia & Berlier, Gloria [Vis alle 11 forfattere av denne artikkelen] (2019). Cu-MOR applied in the stepwise methane-to-methanol conversion. Fulltekst i vitenarkiv
• Hempel, Frida Sveen; Arstad, Bjørnar; Fjellvåg, Helmer & Li, Xinyu (2019). Na-dynamics in Na2Zn2TeO6, a possible solid-state electrolyte. Fulltekst i vitenarkiv
• Lind, Anna Maria; Sluijter, Soraya N; Arstad, Bjørnar; Krishnamurthy, Shreenath; Grande, Carlos Adolfo & Cobden, Paul D. [Vis alle 8 forfattere av denne artikkelen] (2019). Development of 3D printed amine grafted silica adsorbents for CO2 capture – adsorbent preparation, performance and potential applications. Fulltekst i vitenarkiv
• Mondino, Giorgia; Nord, Lars O.; Grande, Carlos Adolfo; Spjelkavik, Aud I.; Didriksen, Terje & Stensrød, Ruth Elisabeth [Vis alle 11 forfattere av denne artikkelen] (2019). Moving bed temperature swing adsorption (MBTSA) technology for post-combustion CO2 capture. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Broge, Nils Lau Nyborg; Søndergaard-Pedersen, Frederik M; Lind, Anna Maria & Arstad, Bjørnar [Vis alle 9 forfattere av denne artikkelen] (2018). Real-Time Evolution of SAPO Catalysts' Local Coordination during Hydrothermal Treatment. Fulltekst i vitenarkiv
• Arstad, Bjørnar (2018). Catalyst Material science:in situ flow mas nmr spectroscopy and synchrotron pair distribution function analyses of the local response of the Brønsted acidic site in the sapo-34 solid catalyst during hydration at elevated temperatures. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Håkonsen, Silje Fosse; Lind, Anna Maria; Mondino, Giorgia; Didriksen, Terje & Karimov, Fuad [Vis alle 9 forfattere av denne artikkelen] (2018). Design, construction, adsorbents and evaluation of a moving bed temperature swing adsorption (MBTSA) pilot reactor for post combustion CO2 capture. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Thermogravimetric analysis – a viable method for screening materials for the SEWGS process. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Dawsonite as sorbent for the SEWGS process. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Blom, Richard; Håkonsen, Silje Fosse; Pierchala, Joanna; Lundvall, Fredrik & Kalantzopoulos, Georgios N. [Vis alle 8 forfattere av denne artikkelen] (2017). Preparation and evaluation of new sorbent materials for the Sorption Enhanced Water-Gas Shift (SEWGS) reaction. Fulltekst i vitenarkiv
• Pappas, Dimitrios; Borfecchia, Elisa; Dyballa, Michael Martin; Pankin, Ilia; Lomachenko, Kirill A. & Berlier, Gloria [Vis alle 12 forfattere av denne artikkelen] (2017). Key Reaction Steps in the Partial Oxidation of Methane to Methanol over Cu-SSZ-13. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Hill, Adam; Lind, Anna Maria; Arstad, Bjørnar & Attfield, Martin P. [Vis alle 9 forfattere av denne artikkelen] (2017). CATalyst transformations and LIFEtime by in-situ techniques and modelling (CATLIFE). Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Chernyshov, Dmitry & Wragg, David [Vis alle 7 forfattere av denne artikkelen] (2017). High time-resolution in-situ methods for tracking structural transformations in SAPO materials. Fulltekst i vitenarkiv
• Dyballa, Michael Martin; Arstad, Bjørnar; Pappas, Dimitrios; Svelle, Stian; Olsbye, Unni & Beato, Pablo [Vis alle 8 forfattere av denne artikkelen] (2017). On the preparation of Cu-containing Zeolites - How to avoid comparing Apples to Oranges. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2017). Finding new materials for the SEWGS process. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Lind, Anna Maria; Arstad, Bjørnar; Wragg, David & Fjellvåg, Helmer (2017). Sub-unit cell structural transformations during template-removal and hydration of SAPO-37 microporous catalysts. Fulltekst i vitenarkiv
• Pappas, Dimitrios; Borfecchia, Elisa; Dyballa, Michael Martin; Pankin, Ilia A.; Lomachenko, Kirill A. & Martini, Andrea [Vis alle 16 forfattere av denne artikkelen] (2017). XAS reveals structure-activity relationships for the Methane-to-Methanol conversion over Cu-zeolites. ESRF Highlights of the Year. s. 49–51. Fulltekst i vitenarkiv
• Olsbye, Unni; Mudu, Federica; Palcheva, Radostina Dimitrova; Arstad, Bjørnar; Diplas, Spyros & Li, Yanjun [Vis alle 9 forfattere av denne artikkelen] (2016). On the performance of aluminium or gallium substituted lanthanum based perovskite type oxides in methane partial oxidation by framework oxygen. Fulltekst i vitenarkiv
• Lundvall, Fredrik; Kalantzopoulos, Georgios N.; Wragg, David; Arstad, Bjørnar; Blom, Richard & Sjåstad, Anja Olafsen [Vis alle 7 forfattere av denne artikkelen] (2016). Thermogravimetric analysis – a viable method for screening materials for the SEWGS process. Fulltekst i vitenarkiv
• Rørvik, Per Martin; Arstad, Bjørnar; Jørgensen, Sissel; Stub, Sindre Østby; Norby, Truls & Hansen, Eddy Walther (2016). 1H-NMR and Resistance Study of Surface-Adsorbed Water in Porous YSZ. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Lind, Anna Maria; Thorshaug, Knut; Cavka, Jasmina Hafizovic; Akporiaye, Duncan & Kalantzopoulos, Georgios N. [Vis alle 11 forfattere av denne artikkelen] (2016). Structural changes in the methanol-to-olefin (MTO) catalyst SAPO-34 after/during hydrothermal treatment. Fulltekst i vitenarkiv
• perinu, c; Jinadasa, Wathsala; Arstad, Bjørnar; Bouzga, Aud Mjærum & Jens, Klaus-Joachim (2016). Applications of NMR in the Field of CO2 capture by solvents. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Lind, Anna Maria; Akporiaye, Duncan; Fuglerud, Terje; Grønvold, Arne & Kalantzopoulos, Georgios N. [Vis alle 9 forfattere av denne artikkelen] (2016). Characterization and studies of Si and Brønsted site developments in SAPO-18 and SAPO-34 during and after hydrothermal treatments. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Lind, Anna Maria; Cavka, Jasmina Hafizovic; Akporiaye, Duncan; Kalantzopoulos, Georgios N. & Lundvall, Fredrik [Vis alle 10 forfattere av denne artikkelen] (2016). Characterization of catalytic sites in microporous materials using solid-state NMR. An ex-situ and in-situ high temperature flow study. Fulltekst i vitenarkiv
• Arstad, Bjørnar (2016). Applications of NMR in the studies of CO2 capture solvents. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Hill, Adam; Lind, Anna Maria; Wragg, David & Arstad, Bjørnar [Vis alle 9 forfattere av denne artikkelen] (2016). Structural Characterization and Long-term Performance Understanding of SAPO Industrial Catalyst Materials. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Blom, Richard; Lind, Anna Maria; Thorshaug, Knut & Andreassen, Kari Anne (2015). in-situ DRIFTS and in-situ XRD studies of CaO and calcined dolomite during CO2 adsorption-desorption reactions. Fulltekst i vitenarkiv
• Arstad, Bjørnar; Lind, Anna Maria; Thorshaug, Knut; Cavka, Jasmina Hafizovic; Akporiaye, Duncan & Kalantzopoulos, Georgios N. [Vis alle 11 forfattere av denne artikkelen] (2015). Studies of SAPO-34 during and after hydrothermal treatment. Fulltekst i vitenarkiv
• Langseth, Eirin; Heyn, Richard H; Cavka, Jasmina Hafizovic; Swang, Ole; Arstad, Bjørnar & Unneberg, Erik [Vis alle 9 forfattere av denne artikkelen] (2015). Loading metal-organic frameworks with aluminium. Fulltekst i vitenarkiv Vis sammendrag

  We here demonstrate impregnation of metallic Al in MOFs; the highest loading was seen for UiO-67. The samples were analysed by TGA, ICP, DSC, BET and solid state NMR. ICP shows that the samples contain Al. 27Al NMR of Al@UiO-67 confirms that Al is present in metallic form. Surface area and pore volume decreases substantially after impregnation with alane which is to be expected if there is Al in the pores of the framework.

• Heyn, Richard H.; Aronu, Ugochukwu Edwin; Hoff, Karl Anders; Didriksen, Terje; Arstad, Bjørnar & Blom, Richard (2015). Use of a Zn organometallic complex for CO2 capture. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Wragg, David; Lind, Anna Maria; Arstad, Bjørnar & Fjellvåg, Helmer (2015). Structural Characterization of SAPO-37 Zeolites in RECX lab and SNBL. Fulltekst i vitenarkiv
• Kalantzopoulos, Georgios N.; Lundvall, Fredrik; Slawinski, Wojciech Andrzej; Lind, Anna Maria; Wragg, David & Arstad, Bjørnar [Vis alle 7 forfattere av denne artikkelen] (2015). Structural Characterization and Hydrothermal Stability of SAPO-34 and SAPO-37 Catalyst Materials. Fulltekst i vitenarkiv
• Perinu, Cristina; Arachchige, Gumunu L. Samarakoon; Arstad, Bjørnar & Jens, Klaus-Joachim (2014). Application of 15N-NMR spectroscopy to analysis of amine based CO2 capture solvents. Fulltekst i vitenarkiv
• Sannes, Johnny Andreas; Olsbye, Unni; Kalantzopoulos, Georgios N. & Arstad, Bjørnar (2020). CO2 adsorption and characterization of tailor-made metal-organic frameworks. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  In this work, the 𝐶𝑂2adsorption capacityof chemically interesting metal-organic frameworks (MOFs) have been investigated. The MOFs have been characterized using standard inorganic/organic characterization tools such as pXRD, TGA, liquidand solid state NMR, SEM-EDS, static anddynamic gas adsorption.Potentially strong adsorption sites on the Pt–Zr interface was investigated by the use of TAP. The isosteric heat of adsorption have been estimated for UiO –67 as a function of pretreatment.A comparison of the isosteric heat of adsorption determined by the use of static and dynamic gas adsorption studies have been made.A two-step adsorption mechanismin the N2adsorption isotherm was observed for UiO –67 in the low pressure regime (𝑝𝑝0<0.005). The observed adsorption isothermshow resemblance to that of MOF –808, however occurring at a much lower pressure.UiO –67 and UiO –67 type MOFs have been investigated by the use of ss –NMR. A major effort was made towards the assignment of the peaks in therecorded1H and 13C spectrum of UiO –67. The work was leading to the hopeful elucidation of adsorption sites and adsorption orientations, however due to time constraint only the groundworkhave been performed.

Se alle arbeider i NVA