Bridging the "pressure gap" towards high pressures - Elastic neutron scattering for in-situ investigation of catalysts under industrial conditions

Catalyst characterization is usually performed in the pressure range from UHV to ambient depending on the methods used. Linear extrapolation of the catalytic properties over these several orders of magnitude in pressure is often not possible (“pressure gap”), which makes in-situ characterization necessary. Typically, only little information is available about structural dynamics of catalysts at pressures above atmospheric pressure, i.e. in the range, which is important for many industrial processes. Neutron diffraction is uniquely suitable to close this gap, because thick metallic walls of tubular reactors are almost transparent for neutrons. Thus, such conventional reactors, which allow application of elevated pressures, can be used for characterization of the catalyst bed without the necessity of special beam transparent windows. Using neutrons, information on the crystalline phases present, the crystal structure, structural disorder, crystalline domain size and shape, lattice strain and defect structure of the working catalyst are available from diffraction experiments