A General Strategy for Efficient Upgrading of Biomass-Derived Rice Husk Vinegar with ZrO₂ Supported HSiW Catalyst: Extractive Coupling Esterification

Abstract

Rice husk vinegar, a byproduct of biomass pyrolysis, can be refined to increase its value and reduce harmful emissions. This study synthesized a range of HSiW solid acid catalysts supported by ZrO 2 using impregnation and investigated the esterification of rice husk vinegar, a biomass pyrolysis liquid rich in acetic acid. The catalytic esterification experiment was performed on an extraction coupling esterification reaction device to enrich acetic acid and improve conversion. The physicochemical characterization of catalysts verified their improved catalytic performance with an increased calcined temperature, as it amplifies the Brønsted/Lewis ratio. Esterification results indicated that the 30-HZ (300) catalyst underwent a conversion of 94.02%, at the temperature of 130 °C, alcohol-to-liquid ratio of 0.5, catalyst dose of 3 wt %, and reaction period of 4 h. The catalyst retained 91% of its conversion at the fifth cycle. The catalyst facilitated the conversion of most short-chain organic acids to esters, some oxidation of n-butanol and ketones, and the etherification of n-butanol. These results are beneficial for the high-value transformation and application of rice husk vinegar and future research on biomass pyrolytic liquids.