The catalytic epimerization of sugars over immobilized heptamolybdate: comparison of resins, layered double hydroxides and mesoporous silica as support

摘要

The synthesis and characterization of heptamolybdate exchanged on quaternary ammonia modified SBA-15 type mesoporous silica is described. Its activity and stability in the epimerization of D-glucose to D-mannose is investigated, and compared with those obtained with the corresponding silica gel supported catalyst (commercial Bondesil sax), commercial resins and ZnAl layered double hydroxide. The epimerization occurs highly selectively to the C-2 epimer D-mannose in case of the heptamolybdate modified SBA-15 catalyst without any loss of metal in the reaction mixture. When performed in methanol, the heterogeneous epimerization proceeds at comparable rates than the homogeneous system.