A mechanism study on the efficient conversion of cellulose to acetol over Sn–Co catalysts with low Sn content

Efficient conversion of renewable cellulose to high value-added C3 chemicals is a great challenge in the field of biomass valorization. In this work, we found that the combination of Co and Sn could significantly improve the efficiency of cellulose conversion to acetol. 54.4% yield of acetol and 66.6% total yield of C3 products were obtained when using 2%Sn–10%Co/SiO2 (2 wt% Sn content) as a catalyst. However, using the same Sn content of 2%Sn–10%Ni/SiO2, no acetol and only 7.1% yield of C3 products were produced. By studying the effects of different Sn and Co concentrations on cellulose conversion, it was found that the Sn species play an important role in catalyzing glucose conversion to C3 intermediates, while Co mainly played a role in hydrogenation, the same as Ni. The study demonstrated that Sn–Co/SiO2 with low Sn content can convert glucose to C3 intermediates more efficiently than the Sn–Ni/SiO2 catalyst. Moreover, Sn–Co/SiO2 could effectively convert C3 intermediates to acetol at a high temperature which is essential for acetol production from cellulose; but under the same conditions, the Sn–Ni/SiO2 catalyst tended to catalyze the polymerization of C3 intermediates. A series of characterization methods including AAS, TEM, HRTEM, EDS, XRD, ex situ XPS, in situ XPS, and CO2-TPD found that the combination of Sn and Co could significantly increase the noninteger valent SnOx species in the catalyst. These species increased the basicity of the catalyst and were beneficial in catalyzing the isomerization of glucose and the retro-aldol condensation of fructose.