Selective oxidation of cellulose into formic acid over heteropolyacid-based temperature responsive catalysts

Abstract

Formic acid (FA) is one of the most promising vectors for sustainable hydrogen energy and it can be synthesized from renewable biomass resources. In this work, a range of heteropolyacid derived temperature-responsive catalysts (ChnH4-nPMo11VO40, n=1–3) were prepared by modifying H3PMo12O40 heteropolyacid with an oxidation site V5+ and temperature-responsive monomer choline chloride (Ch+), and used for the cascade conversion of biomass derived cellulose into FA via hydrolysis-oxidation in water. The ChH3PMo11VO40 with a Ch/H ratio of 1/3 exhibited an outstanding catalytic performance to give a 49.5% yield of FA at 165 °C after 3 h reaction time. Catalytic activity of ChnH4-nPMo11VO40 was found to be related to its amount of H+ and V5+, while the recyclable ability of ChnH4-nPMo11VO40 was found to be related to its amount of Ch+. The as-prepared catalyst could be perfectly recycled with a single decrease the temperature of reaction systems, and be reused four times with limit loss in catalytic activity. The developed temperature-responsive catalysts have both advantages of homogeneous catalyst and heterogeneous catalyst, which should have potential application in other reactions of lignocellulosic biomass valorization.