Development Of Ru/C Catalysts For Hydrogenation Of Glucose To Sorbitol

The RuCl₃ hydrate was selected as the precursor and the activatedcarbon was selected as the carrier in preparation of high active Ru/Ccatalysts for the hydrogenation of glucose to sorbitol bydeposition-precipitation with urea. The effect of pretreatment of theactivated carbon, and the reduction and calcinations process on thecatalysts was studied. High performance liquid chromatography wasused to quantitate the glucose concentration during the reaction. The firstorder rate constants calculated on changes of glucose concentration withtime was adopted for comparison of the activity of catalysts made indifferent ways.Firstly, the preparation method of activated carbon supported Rucatalysts for glucose hydrogenation to sorbitol was modified. Thetreatment temperature, treatment time, H₂O₂ concentration and the pH ofthe solution were researched. H₂O₂ treatment of the activated carbon wasoptimized via the orthogonal experimental method, which found theresult that the pretreatment on the carrier had a huge effect on thecatalytic activities and the best catalytic activity is more than three timeshigher than the worst catalytic activity. The importance of the factors is:pH of the solution > treatment temperature > time > H₂O₂ concentration,and the optimal conditions are: acidic 5M H₂O₂ solution stirs for 6hr at50℃.In order to improve the catalytic activity, the influences of reductionand calcination on catalyst properties were revealed. The catalystsreduced directly after drying has demonstrated twice higher activity thanthose reduced after first calcined. Characterizations by BET, SEM, TEMhave illustrated that removal of calcination can make Ru crystallinesmaller and it indirectly testified that the preparation withoutcalcinations is beneficial to catalysts. Catalyst prepared in optimalmethod is 20% higher than commercial Ru/C. Finally, preparation of activated carbon onγ-Al₂O₃ substrate wasprobed by screening of the carbon source, the carbonation and activationmethod were also studied. Catalysts with relatively low activities weremade on these composite activated carbon, which nevertheless paved away for development of Ru/C monolithic catalysts.