Direct conversion of cellulose into acetol on bimetallic Ni-SnOx/Al2O3 catalysts

•High acetol yields from cellulose, and also from glucose and fructose were obtained.•The mechanism of cellulose conversion to acetol on bimetallic Ni-SnOx/Al2O3 catalysts was studied.•SnOx facilitated the isomerizaiton of glucose to fructose and its subsequent CC bond cleavage.•The hydrogenation activity of the Ni-SnOx/Al2O3 catalysts depends on the Sn/Ni ratio.

The direct conversion of cellulose into acetol was studied on SnOx-modified Ni/Al2O3 catalysts with different Sn/Ni atomic ratios in the range of 0–2.0. The selectivity to acetol strongly depended on the Sn/Ni ratios, which reached the highest value of 53.9% at the ratio of 0.5, compared at similar cellulose conversions (∼20%). On Ni-SnOx/Al2O3 (Sn/Ni = 0.5), cellulose, glucose and fructose converted to acetol in high yields of approximately 35%, 53% and 73%, respectively, at 210 °C and 6 MPa H2. The effects of the Sn/Ni ratios on the acetol selectivity appear to be related to their effects on the hydrogenation activity of the Ni-SnOx/Al2O3 catalysts that decreased with increase of the Sn/Ni ratios, and to the relative rate between the hydrogenation of C6 sugar intermediates (e.g. glucose and fructose) and their degradation intermediates (e.g. glyceraldeyde and dihydroxyacetone) involved in the cellulose reaction on the Ni particles and the isomerization of glucose to fructose and their CC bond cleavage by retro-aldol condensation on the SnOx domains. Comparison of SnOx with CeOx, ZnOx and AlOx supported on Al2O3 with different basicity suggested that the larger concentration of stronger basic sites on SnOx facilitated the isomerizaiton of glucose to fructose and its subsequent CC bond cleavage. These results and their understanding provide guidance for improving the acetol production from cellulose by tuning the catalytic functions required for the involved reactions of hydrogenation on the metal surfaces, and isomerization and CC bond cleavage on the basic sites.

Graphical abstractCellulose directly converted to acetol on bimetallic Ni-SnOx/Al2O3 catalysts with a high efficiency.Figure optionsDownload full-size imageDownload high-quality image (118 K)Download as PowerPoint slide