Temporal Analysis of Products (TAP)

Principles of operation

TAP is a time-resolved technique for precise kinetic characterization of gas-solid reactions in catalysis, adsorption, and other applications. Unlike in conventional kinetic devices (e.g. well-mixed or tubular flow reactors), gas transport in the TAP reactor occurs via Knudsen diffusion – a special transport regime whereby molecules collide with the reactor walls and catalytic surfaces, but not with each other. Knudsen diffusion is advantageous as a transport regime for kinetic characterization because it is very well-defined, i.e. the transport rate of each gas is uniquely defined by its molecular mass, the temperature, and the geometry of the reactor packing. Gas-phase reactions which may interfere with the gas-solid interactions of interest are completely eliminated under TAP conditions. Importantly, both model and realistic high-surface area materials can be studied using TAP.


In the beginning of a typical TAP pulse-response experiment, a small amount (10-9 mol/pulse) of gas mixture with known composition is rapidly injected into an evacuated (10-7 torr background) microreactor with a catalytic sample. After traversing the reactor space by Knudsen diffusion, the unreacted and newly formed molecules escape into the adjacent vacuum chamber where they are quantitatively detected by a calibrated mass spectrometer. The millisecond time resolution of these kinetic data provides unique insight into the inner workings of gas-solid reactions. Our TAP instrument is equipped with both Quadrupole (QMS) and Time-of-Flight (ToF) detectors for enhanced mass-and time-resolution. Pretreatments and kinetic measurements under atmospheric pressure flow conditions are also possible within the same instrument, and rapid switching between flow and pulsing modes enables complex experimental design.

Current projects

  • Diffusion characterization in microporous and hierarchically porous materials (zeolites, zeotypes, MOFs);
  • Intrinsic kinetics of olefin methylation and other steps of the Methanol-To-Hydrocarbons (MTH) chemistry in zeolites;
  • CO2 reduction by non-stoichiometric ceria and mixed oxides, generation and stability of oxygen vacancies in metal oxide
  • Tandem spectro-kinetic (TAP-XPS) investigations of reaction mechanisms on complex metal oxides that are derived from Metal-Organic Frameworks (MOFs);


PI: Unni Olsbye, Instrument curator: Evgeniy Redekop, Users: Emil Sebastian Gutterød, Sajjad Ahmadigoltapeh Technical specialists: Tomas Mikoviny, Sharmala Aravinthan, Simen Kristiansen, Terje GrønåsBehzad Foroughinejad


John Gleaves (WUSTL, Mithra Tech.), John Gleaves Jr. (Mithra Tech.), Gregory Yablonsky (SLU), Rebecca Fushimi (INL), Yves Schuurman (CNRS Lyon), Guy B. Marin (LCT@UGENT), Vladimir Galvita (LCT@UGENT), Denis Constales (UGENT), Renato Feres (WUSTL), Alexandru Botan (DTU, Energy), Anders Hafreager (UiO, Physics), Benoit Cordonnier (UiO, Geosciences), Knut Erling Moen (SINTEF), Bob Madix (Harvard University), Cynthia Friend (Harvard University), Gabor Somorjai (UC Berkeley, LBNL), Samuli Urpelainen (MAX-IV, Lund University, Sweden), Niclas Johansson (MAX-IV, Lund University, Sweden)

Global TAP community

TAP-team at UiO is proud to be part of a larger international TAP community.

References and links

TAP on Wikipedia

Mithra Technologies