The application of neutron scattering to investigate hydrocarbon conversion over zeolite catalysts

The use of acid zeolites as catalysts for the conversion of hydrocarbons is widespread due to their ability to catalyse both bond-breaking and formation reactions and their shape selectivity. This selectivity arises from steric interactions with the pore structure which increase the stability of some intermediates and reactions, favouring given products. In this way, yields of highvalue products can be increased by use of the correct zeolite structure, such as H-ZSM-5 which optimises the production and utilisation of light olefins. The ways in which olefins interact with, and diffuse through, zeolite frameworks are therefore matters of considerable academic and industrial interest due to the possibility of providing targets for the development of improved catalysts. Neutron scattering methods are a family of related techniques which are uniquely suited to studying hydrocarbon catalysis in zeolites due to factors arising from the properties of the neutron and how scattering events occur at a sub-atomic level. This thesis enumerates these advantages and seeks to apply them to model compound systems for olefin conversion reactions of industrial interest in a commercial H-ZSM-5 powder-form zeolite. Studies are made of how C3 and C8 hydrocarbons react with and diffuse through the zeolite at low temperatures, and the effect of catalyst aging on these processes. The work is then extended to higher temperature studies of olefin isomerisation and cracking reactions under realistic conditions, and the examination of the diffusion of other small-molecule hydrocarbons in zeolites. The results demonstrate the ability of neutron techniques to complement techniques more conventionally used for catalytic reaction studies and to provide new insights into catalytic processes.