Meso-Zr-Al-beta zeolite as a robust catalyst for cascade reactions in biomass valorization

Abstract

Hierarchical Meso-Zr-Al-beta zeolites are successfully prepared through a multiple-step post-synthesis strategy composed of controlled dealumination, desilicication and metal incorporation. The presence of both Brønsted and Lewis acid sites with a certain extent of strength in Meso-Zr-Al-beta is demonstrated by NH3-TPD and FTIR spectroscopy with pyridine adsorption/desorption. The creation of mesopores via desilicication through alkaline treatment is confirmed by N2 adsorption/desorption isotherms. Meso-Zr-Al-beta, with Brønsted acid sites, Lewis acid sites and mesopores, is applied as a zeolite catalyst for the cascade conversion of biomass platform molecule furfural to γ-valerolactone. Owing to the presence of multiple functional sites and their mutual compatibility, remarkable activity for γ-valerolactone production and catalyst recyclability could be achieved with a single Meso-Zr-Al-beta, which appears to be a better catalyst than the commonly-employed combination catalyst systems. The multifunctional Meso-Zr-Al-beta zeolite is also applied as a promising catalyst in other cascade reactions in biomass valorization, i.e. glucose conversion to 5-hydromethylfurfural and trioses conversion to ethyl lactate. Similar zeolite catalysts containing multiple functional sites could be prepared via similar routes, and the number of acid sites and their strength can be adjusted to some extent to derive an optimized catalyst by changing the preparation parameters.