Catalytic Conversion of Glucose to Levulinic Acid over Temperature-Responsive Al-Doped Silicotungstic Acid Catalyst

Abstract

Converting renewable biomass into liquid fuels and value-added chemicals has emerged as a pivotal technology, driving the transformation of the energy landscape. Efficiently transforming the cellulose components of biomass into the crucial liquid fuel precursor levulinic acid holds profound significance. The principal objective of this study is to fabricate a temperature-responsive catalyst based on Al-doped silicotungstic acid, which is intended for converting glucose into levulinic acid. By exploiting the interaction between choline chloride and silicotungstic acid, which exhibits a notable capacity for high proton migration, we successfully synthesized a stable acid catalyst with responsive properties to temperature changes. Through precise adjustments of Al 3+ concentration, we engineered a collection of Lewis/Brønsted composite catalysts capable of responding to temperature variations. A comprehensive analysis of the catalyst's structure and acidity was conducted using various techniques including FTIR, XRD, TEM, and Py-IR. These methods revealed crucial insights into the crystalline architecture, surface morphology, and distribution of acidic domains, providing a solid foundation for a deeper understanding of the catalytic reaction mechanism. Through the meticulous optimization of key reaction parameters, including Al 3+ loading, solvent composition, reaction temperature, and reaction duration, the ChAl 2/3 HSiW 12 O 40 catalyst achieved its pinnacle of efficiency at 150 °C over an 8 h period. This resulted in the remarkable outcome of complete glucose conversion, yielding an impressive 62.01% of levulinic acid. Additionally, an evaluation of the catalyst's recyclability was carried out, demonstrating its commendable hydrothermal stability and ability for repetitive usage without any reduction in catalytic efficiency.