Direct transformation of cellulose into methyl and ethyl glucosides in methanol and ethanol media catalyzed by heteropolyacids

The alcoholysis of cellulose in methanol and ethanol media has been studied in the presence of various kinds of acid catalysts. Keggin-type tungstosilicious and tungstophosphoric acids (H4SiW12O40 and H3PW12O40) were found to be highly efficient for the alcoholysis of cellulose. Methyl and ethyl glucosides (both containing α and β isomers) could be obtained in methanol and ethanol with yields as high as 57% and 63%, respectively. The ratio of α and β isomers was ∼1.4–1.6 in both methyl or ethyl glucosides, suggesting the intermolecular transformations between α and β isomers. Our comparative studies show that the alcoholysis of cellulose in methanol or ethanol proceeds more efficiently than the hydrolysis of cellulose in water medium. Glucose yields of only about 5–10% were obtained in water in the presence of an acid catalyst under similar reaction conditions.