Methanol is a small and versatile molecule which can be converted to a myriad of different hydrocarbons by means of the MTG process. Under optimal conditions a high octane clean gasoline is produced. Since methanol is easily produced from natural gas, biomass or coal, the MTG process offers an important alternative route for fuel supply to the existing transportation market.
At present, the world is dependent on oil for production of both fuels and raw materials for plastics. Gasoline production by the MTG process was started at industrial scale during the oil crisis in the 1980s, but the subsequent drop in oil price led to shut down of the Gasoline production part of the plants. Today's economy, however, shows renewed interest and boost in the industrial sector for this process.
The catalysts: Zeolites
Different intermediates fit into the different zeolites, determining the product distribution.
Zeolites are the catalysts used in the MTG-process. Zeolites are microporous crystalline structures with TO4 (T is an element that can have four bonds) units as building blocks. These solid particles look like powders or pellets to our eyes, but at the molecular level they can be considered 3-dimensional labyrinths. Each crystal contains cavities and channels which the reactant methanol can diffuse into, and inside these channels the reaction occurs. The resulting product depends on the type of zeolite we use as well as reaction conditions. For gasoline production the product molecules must be allowed to diffuse trough channels consisting of at least 10 T-atoms.
At inGAP we study the mechanisms of the MTG reaction down to the molecular level in order to understand how to tune processes into producing only the products we desire. As the reaction mechanisms involved are highly complex, a range of advanced techniques have to be utilized in combination with each other. This requires a research group mastering a wide range of disciplines within chemistry. The diversity of experience and specialties found within the inGAP center ensures that the group remains world-leading in studies of this highly complex and important reaction.
Detailed insight gives new posibilities
Our researchers have been able to determine the presence of two different mechanisms in the MTG process: an aromatic based cycle and an alkene based cycle. The aromatic cycle requires more space for the reaction to proceed than the alkene based cycle. This insight enabled the prediction that low-aromatic gasoline may be produced in a zeolite with just enough space for gasoline production, but small enough to repress the aromatic cycle. Our detailed insight provided us the opportunity for rational design of a new process making the desired low-aromatic gasoline product.