General Acid-Type Catalysis in the Dehydrative Aromatization of Furans to Aromatics in H-[Al]-BEA, H-[Fe]-BEA, H-[Ga]-BEA, and H-[B]-BEA Zeolites

Abstract

Al, Ga, Fe, and B metal substituents have been examined for their ability to change the Bronsted acid strength of BEA zeolite and inhibit undesired hydrolysis in the production of aromatics from furan, 2-methylfuran, and 2,5-dimethylfuran. We employed electronic structure calculations to examine this series of furans in H-[Al]-, H-[Fe]-, H-[Ga]-, and H-[B]-BEA zeolites. These calculations were used to parametrize a microkinetic model to make direct comparisons to experiments run with furan and DMF in the weakest and strongest acid zeolites, H-[B]-BEA and H-[Al]-BEA, respectively. Electronic structure calculations revealed that the Diels–Alder reaction remains unaffected by changes to the Bronsted acid strength of the zeolite, whereas the dehydration and hydrolysis reactions are affected in a fashion reminiscent of general acid catalysis. Interestingly, despite its significantly lower acid strength, H-[B]-BEA was experimentally shown to have an activity similar to that of H-[Al]-BEA for the production of b...