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 Brønsted 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 Brønsted 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 both benzene and p-xylene from furan and 2,5-dimethylfuran, respectively. Analysis with the microkinetic model revealed that, even with this weaker heterogeneous acid site, the dehydration reaction is sufficiently catalyzed, activating the aromatic production pathway. The use of a weaker, heterogeneous Brønsted-acidic zeolite did not have a significant effect on the product selectivity, however, indicating that the same reaction pathways are active with both catalysts.

WITHDRAWN: The Catalytic Pyrolysis Mechanism of Cellulose On ZSM-5: Based On Py-GC/MS And Density Functional Theory

“…Since the addition reaction is bimolecular, the transition state C_TS 9 with a roof-shaped spatial geometry is formed during the addition process. A double bond forms, so active-H cannot participate in the reaction, but active H affects the electronic structure around the reactant and can also reduce the energy required for the reaction to a certain extent, which is consistent with the report by Patet et al Patet et al 2017 . The third step is that active-H promotes the breaking of the ether bond and the free water molecules in the reaction process, and the oxygen on the ring form a hydrogen bond, preparing for the water addition reaction in the fourth step.…”

“…To study the Diels-Alder cycloaddition reaction of furan and ethylene on the Brønsted-acidic molecular sieve, Patet et al used electronic structure calculations and microscopic kinetic models, and the subsequent dehydration reaction of furan and ethylene Patet et al 2017 . The electronic structure calculation showed that the acid strength of the Brønsted-acidic zeolite changes with the changes of Al, Ga, Fe, and B metal substituents.…”

Aqueous‐Phase Transformation of Glucose into Hydroxymethylfurfural and Levulinic Acid by Combining Homogeneous and Heterogeneous Catalysis

“…[43] Reaction system Reactions were carried out in a0.5 Lstirred batch autoclave reactor (Autoclave Engineers EZE seal) with ab ackpressure regulator and a PID temperature controller.I natypical experiment, 0.175 Lo fa n aqueous solution of d-(À)-glucose (5.83 g) and b-zeolite (0.466 g) were used. 99.5 %) and sodium hydrogen carbonate (!…”

On the Acid Sites of Phosphorous Modified Zeosils

“…19,20 While this assumption holds true for bridging hydroxyls in aluminosilicates, 29 challenges associated with extending it to weak acids have been previously illustrated on [B]-substituted zeolites. 30,31 Gorte and co-workers have shown that in the course of a TPD, isopropylamine can desorb without reacting on the weakly Brønsted acidic centers of [B]-substituted MFI, leading to the undercounting of available BAS. 31 On weaker BAS where the barrier to molecular desorption is reduced, the assumption of negligible rates of molecular desorption may not hold true.…”