Tin-Functionalized Wood Biochar as a Sustainable Solid Catalyst for Glucose Isomerization in Biorefinery

Abstract

This study tailored a novel engineered biochar as a solid catalyst for glucose isomerization by pyrolyzing Sn-functionalized wood waste under varying hypothesis-driven selected conditions (i.e., 650, 750, and 850 degrees C in N-2 and CO2 atmosphere). The results showed that properties of biochar support (e.g., porosity and acid/base property) and chemical speciation of Sn were highly related to their catalytic performance. Variations in pyrolysis temperature and feed gas modified the porous structure and surface functionality of biochar as well as the valence state of doped Sn on the biochar. For the N-2 biochars, higher pyrolysis temperature enhanced the fructose yield yet had trivial effect on the selectivity, where 12.1 mol % fructose can be obtained at 150 degrees C and 20 min using biochar produced at 850 degrees C. This was plausibly attributed to the increased fraction of amorphous Sn structures and metallic Sn that were more reactive than its oxide form. At the pyrolysis temperature of 750 degrees C, the use of CO2 increased the surface area by 40%, enlarged the pore volume from 0.062 to 0.107 cm(3) and enriched the amorphous Sn structures compared to those for N-2 biochar. This probably accounted for the better catalytic performance of CO2 biochar than that of N-2 biochar (similar to 50% and 100% enhancement in fructose yield and selectivity, respectively). The Sn-biochar catalysts may have promoted glucose isomerization via both the Lewis acid and Bronsted base pathways. This study paves a new way to design biochar as a sustainable and low-cost solid catalyst for biorefinery applications.