Co-templated synthesis of zeolites for applications in adsorption and catalysis

Zeolites are microporous aluminosilicates with applications in gas adsorption and catalysis, prepared hydrothermally using inorganic or organic cations to direct or template the framework crystallisation.

This project aims to develop co-templating routes in which inorganic and organic cations are used together to prepare zeolites with new structures or compositions. The work will include the characterisation of a series of flexible (RHO-type) zeolites, prepared using different metal and tetraethylammonium cations that show highly selective gas adsorption. Using the principles derived from this, other zeolite syntheses will then be devised using combinations of cations and other small organics to give small pore low Si/Al zeolites valuable in gas separations, including merlinoite and phillipsite.

The structures will be measured in situ during gas separations. Elliott Bruce, as the best MChem student graduating this year, is uniquely placed to perform these complex analyses. Existing in situ synchrotron X-ray powder diffraction data is available on the complex RHO family structures ZSM-25 and PST-20 with and without adsorbed carbon dioxide and initial structural studies will involve their refinement using the TOPAS program, required for such complex structures. This will enable the determination of cation locations and so help understand, in combination with computational studies, their selective adsorption behaviour for a range of industrially relevant separations. Additionally, further X-ray and neutron diffraction data will be collected on zeolite Rho itself, for mixed cation systems that have been found to be of interest for industrial separations with a collaborating industrial company.

Further, co-templating routes to zeolites with high Si/Al required for stable auto-exhaust catalysts will be devised. Several promising materials have been prepared using highly expensive organic templates. Here, the aim is to use combinations of inorganic and less-expensive organic templates to make such catalysts more accessible, making use of computational modelling for template design. This is of great interest to Johnson Matthey, so the project will be conducted in collaboration with them, giving Elliott insight into industrial catalytic chemistry and access to their extensive facilities at Billingham.