One-Pot Conversion of Furfural to Gamma-Valerolactone over Zr-SBA-15: Cooperation of Lewis and Bronsted Acidic Sites

A series of bifunctional Zr-SBA-15_x of varying molar Si/Zr ratio x (15-730) with isolated Lewis and Bronsted acid sites were prepared by an in situ synthesis procedure and applied to the one-pot conversion of furfural (FUR) to gamma-valerolactone (GVL). These catalysts were detailed and characterized by XRF, XRD, N-2 physisorption, FTIR, SEM, TEM, NH3-TPD, and pyridine-DRIFT techniques. On all these Zr-SBA-15_x catalysts, the conversion of FUR was higher than 99%, while the GVL selectivity first increased and then decreased with decreasing x. A Zr-SBA-15_25 was identified as the best-performing catalyst, offering a 93.3% selectivity of GVL under optimized reaction conditions. The effects of reaction temperature, time, and solvent on catalytic performance were also investigated. Correlating the catalyst performance with the Bronsted acid site (BAS)/Lewis acid site (LAS) ratio uncovers that the balance between the LAS and the BAS would be the key to the higher catalytic performance. The possible reaction mechanism for the cascade conversion of FUR to GVL was proposed. Moreover, basic (lutidine and pyridine) additives were added, respectively, to the reaction solution to investigate their effects on catalytic performance, which provide a piece of evidence in support of the cooperative LAS-BAS bifunctional catalytic mechanism.

Automated summary

A series of bifunctional Zr-SBA-15_x catalysts with isolated Lewis and Bronsted acid sites were prepared and applied to the one-pot conversion of furfural to gamma-valerolactone. The best-performing catalyst was identified as Zr-SBA-15_25, offering a 93.3% selectivity of GVL under optimized reaction conditions. The balance between the Lewis acid sites and the Bronsted acid sites was found to be the key to higher catalytic performance.