Catalytic Conversion Of Cellulose To Methyl Lactate And Methyl Levulinate By Paired Metal Chlorides

In recent years, using renewable resources to replace limited fossil resources is urgent desired. Cellulose, in particular, the inedible lignocellulose is the most abundant renewable biomass resources. Nowadays, the methods of converting cellulose to fuel or other valuable chemicals by means of chemical or biological approaches are extensively studied. In our work, a new simple method is designed to convert cellulose into methyl lactate and methyl levulinate.In the investigation, various catalysts including most of the metal chlorides, metallic tin and other tin compounds to directly alcoholyze cellulose to methyl lactate and methyl levulinate in methanol were tested.The tin chloride(Ⅱ) was found to be the best single component catalyst, which gave the highest methyl lactate yield. It was therefore selected as the major catalyst component, and in combination with the second catalyst component, such as ionic liquids, ammonium chloride and other metal chloride, the catalytic performances were examined. The high yield of methyl lactate showed that SnCl2·2H2O/ZnCl2 had the best catalytic activity. The influences of reaction temperature, reaction time, the amount of catalyst, and other factors on the yield of methyl lactate and methyl levulinate were also systematically studied. Under the optimal condition:m(SnCl2·2H2O):m(ZnCl2):m(cellulose):m(methanol) is 3:1:4:200, the yield of methyl lactate and methyl levulinate was 31.1% and 13.3%, respectively at 190℃ for 7h.SnCl2·2H2O/ZnCl2 catalyst was employed in the conversion of bagasse into methyl lactate and methyl levulinate in methanol. Some factors, such as reaction temperature, reaction time, the amount of catalyst, and feed ratio were investigated in detail. Methyl lactate, methyl levulinate, methyl acetate yields of 22.8%,4.4%,4.9%, separately, were obtained after a reaction of 6 hours, at 190℃, with the mass ratio of SnCl2·2H2O to ZnCl2 to bagasse to methanol is 1:2:6:120.Finally, the catalytic performances of metal chlorides in conversion of monosaccharides, disaccharides, and polysaccharides to methyl lactate were compared and discussed. It was concluded that relatively weaker Lewis acid catalysts are more suitable for glucose and sucrose conversions, while stronger Lewis acid catalysts are prefered to convert polysaccharides.