Methanol dynamics in different CHA-type zeolite catalysts

The increasing demand for fuel and bulk chemicals across the globe and the need to reduce carbon emissions has prompted significant research into more sustainable, and economical, feedstocks to crude oil such as biomass and syngas derived methanol both of which could be used in methanol-to-hydrocarbons (MTH) processes.
CHA-type zeolites, specifically H-SAPO-34, have shown promise for use in the methanol-to-olefins (MTO) reaction and will play a key role in future fuel and chemicals production.
Despite the important commercial application of zeolites in the methanol-to-olefins (MTO) process, the exact mechanisms are very complex and still debated. The initial step involves the diffusion of methanol to the active site and interaction with Brønsted acidic sites. The rate at which these molecules diffuse through the CHA framework is of great importance to the catalytic process, and the effect that catalyst structure and composition has on such behaviour is of significant interest. The aim of this work is to measure the self-diffusivities/rotational rates and decipher any diffusion mechanisms (such as jump diffusion) of methanol within different CHA-type zeolite catalysts using QENS. The Si/Al (dictating the concentration of Bronsted acidic active sites) will be varied, in order to quantify and hindrances to diffusion or rotation in the catalyst. Such an understanding of the dynamical behaviour will be of crucial importance to the design and optimisation of future MTO catalysts.