Synthesis gas, or syngas, is a mixture of carbon monoxide and hydrogen which is an intermediate of great value in the production of fuels and chemicals. It can be used in the creation of synthetic natural gas, ammonia, methanol and petroleum via the Fischer-Tropsch process. There are a number of methods of synthesis gas production, which are suited to different conditions and starting materials.
Three methods are commonly used to make syngas from methane, all of which use catalysts to decrease the energy needed to maintain the reaction. Partial oxidation of methane reacts methane with oxygen to create the carbon monoxide and hydrogen. The other routes to syngas from methane are known as reforming reactions and come in two forms.
Dry reforming reacts carbon dioxide with methane to form carbon monoxide and hydrogen, whereas steam reforming uses water vapour to create the same gases, but in different proportions. Catalysts containing nickel are used to increase the rate of the reaction, making the production of syngas cheaper.
Catalysts speed up the reaction, without being consumed. Over time however, the catalyst becomes less effective, as unwanted reactions occur. When running a commercial plant, minimising side reactions is an important consideration. A major cause of catalyst deactivation in reforming catalysts is coking. Carbon is deposited on the surface of the catalyst, which limits its contact with the reactants. Research is continuing into producing catalysts which resist coking, and understanding the form of carbon produced is fundamental to this.
The project is a collaborative partnership between the University of Glasgow, the University of Keele, the ISIS neutron scattering facility at the Rutherford Appleton Laboratory and the EPSRC, using primarily vibrational spectroscopy to investigate why a series of methane reforming catalysts exhibit favourable catalytic performance. Combining conventional catalytic measurements with infrared spectroscopy, Raman scattering and inelastic neutron scattering, the aim is to evaluate the deactivation characteristics of a number of candidate methane reforming catalysts.
Infrared spectroscopy (diffuse reflectance and transmission) can define the surface morphology and surface acidity of the supported metal catalysts. The Raman spectrum is diagnostic in characterising the chemical form and composition of the catalyst hydrocarbonaceous overlayer. Samples exhibiting contrasting reaction profiles will be selected for examination by inelastic neutron scattering (INS) at the ISIS Facility. INS has considerable potential for characterising heterogeneous catalysis and is additionally amenable to simulation via computational studies. The linkage of infrared, Raman and INS in this way is a truly novel approach to define the various stages of the deactivation process. This information will be shared with the catalytic chemists at Keele, who will use the information gleaned from the Glasgow-based experiments to refine their preparative procedures. This multi-strand approach will lead to improvements in catalytic performance and the development of reaction schemes that describe the multivariate nature of this economically important reaction.