Nanostructured large-pore zeolite: The enhanced accessibility of active sites and its effect on the catalytic performance

Zeolites Y, ZSM-5, beta, mordenite and LTL were converted into hierarchical meso-microporous catalysts applying the surfactant templating strategy and the resulting materials were utilised as catalysts for esterification and aldol condensation reactions for the production of the second generation biofuels and platform chemicals from biomass derived molecules. The relationship between the catalytic performance and the accessibility of active sites in zeolites was examined using FTIR spectroscopy of adsorbed pyridine, 2,4,6-trimethylpyridine and 1,3,5-triisopropylbenzene. It was found that the esterification of oleic acid can be enhanced by the presence of strong acid sites in zeolites and their improved accessibility. In the aldol condensation reaction, furfural conversion over hierarchical catalysts also increased as compared to the parent zeolites. However, K-forms of the studied zeolites exhibited a higher conversion and selectivity toward the desired reaction products in comparison with their H-forms. Overall, mesostructured zeolites demonstrated an improved catalytic performance as a result of increasing accessibility of the zeolite active sites.