Efficient Conversion Of Corn Starch Into Methyl Levulinate Catalyzed By Aluminum Salts

Methyl levulinate (MLA) is an important organic chemical,which is considered as a promising platform compound. It can be considered as fuel additive and food additives.It is widely used in medicine, paint, spices, plasticizer and other areas of chemical industry. In this investigation, environmentally green reaction was developed to convert starch to methyl levulinate in the presence of catalyst in methanol.Acidic metal salts catalysts were tested for the conversion of corn starch to methyl levulinate. Aluminum salts (aluminum sulfate) were found to give relatively higher methyl levulinate yield. Based on the investigation, several ionic liquids were tested as co-catalysts of aluminum sulfate to catalyze the topic reaction. It was found that 1,3-dimethylimidazole hydrogen sulfate ([DMIM]HS04) is a good co-catalyst of the aluminum salt. At optimum reaction conditions (150℃,3h), methyl levulinate yield of 49.0% was obtained in the presence of aluminum sulfate catalyst. Adding [DMIM]HSO4 into the aluminum salt (Al2(SO4)3·18H2O) catalysts improves the methyl levulinate yield.A series of aluminum salts with different anions, such as (Al(CH3SO3)3, Al(C6H5SO3)3, Al(CH3C6H4SO3)3 and Al(C12H25C6H4SO3)， and aluminum salt-[DMIM]HSO4 were tested as the catalysts to conversion corn starch to methyl levulinate in the methanol. Reaction parameters temperature, reaction time, catalyst amount, ionic liquid amount, and methanol amount were optimized with regarding to methyl levulinate yield. The investigation shows that 1,3-dimethylimidazolium hydrogen sulfate has significant improvement effect on the catalytic activities of Al(CH3SO3)3 and Al(C6H5SO3)3 catalysts. They can significantly improve the yield of methyl levulinate. A yield of 57.1% could be obtained at 150℃ within 3h of reaction when the ratio of corn:Al (CH3SO3)3:[DMIM]HSO4:methanol equal to 0.8:0.7:0.3:6. Methyl levulinate yield of 58.0% could be obtained at 170℃ within 3h of reaction at the ratio of corn:Al(C6H5SO3)3:[DMIM]HSO4:methanol= 0.8:0.5: 0.3:7. When Al(CH3C6H5SO3)3 only was used, the highest yield of methyl levulinate was 53.1%.