Ketonization of xylose over CeO2 to produce mono-functional ketones

Ketonization of biomass-derived oxygenates provides an efficient way for bio-oil upgrading. However, little information on the ketonization of oxygen-rich sugars has been reported, leaving the deep deoxygenation of biomass an unsolved challenge. To address the problem, this paper investigated the catalytic pyrolysis of xylose over nano-CeO2 using an analytical pyrolyzer. Results showed that upon the addition of CeO2, multi-functional oxygenated compounds from xylose pyrolysis were majorly reformed to mono-functional ketonic products, resulting in a 5-fold increase in peak area of ketones. Among them, acetone and 2-butanone presented the highest selectivity of 51% with the CeO2 to xylose ratio of 10:1 at the temperature of 600 °C. Meanwhile, the short-chain oxygenates, i.e. C2-C3 aldehydes and alcohols, had been converted into C3-C5 ketones, indicating an outstanding ability of chain-increasing over CeO2. Both the catalyst dosage and the pyrolysis temperature play a vital role during the ketonization process. The reaction mechanism was proposed according to the experimental results, in which three major reaction pathways were analyzed. This study demonstrates that ketonization of biomass-derived sugars is a promising method for oxygen removal and carbon chain increase, thus improving the bio-oil quality.