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摘要
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 (similar to 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 degrees C and 6 MPa H-2. 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 C-6 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 C-C 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 C-C 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 C-C bond cleavage on the basic sites.
- 出版日期2014-7
- 单位北京大学
