In order to explore the feasibility of one-pot preparation of methyl levulinate (MLA)from biomass catalyzed by dilute sulfuric acid in near-critical methanol,the kinetics of MLA production were investigated at initial glucose concentration of 10—30 mg·ml-1,temperature range from 160 ℃ to 190 ℃,and sulfuric acid concentration between 0.01—0.06 mol·L-1.The results show that reaction temperature has a significant effect on the selectivity of MLA and higher yield of MLA is obtained at higher temperature.With the first-order kinetic equations,the activation energies evaluated are 107.5 kJ·mol-1 and 68.4 kJ·mol-1,and the reaction orders to H+ concentration are 0.981 and 0.953 for main and side alcoholysis reactions of glucose,respectively.The paper demonstrates that the one-pot process is promising for MLA production catalyzed by dilute sulfuric acid in near-critical methanol.
The decomposition kinetics of glucose and 5-hydroxymethylfurfural catalyzed by copper chloride were measured in small volume high-pressure vessel batch reactors,at various temperatures from 423.15 K to 463.15 K and catalyst concentration from 0 to 0.08 mol·L-1.The results showed that their conversion went up with the increase of reaction temperature and catalyst concentration,resulting in higher yield of levulinic acid.By comparing the correlation coefficients,it was confirmed that both glucose and 5-hydroxymethylfurfural decomposition are first order reaction.By using first order kinetics equation,the activation energies of desired and undesired reaction were estimated,134.65 kJ·mol-1 and 144.1 kJ·mol-1 for glucose decomposition,131.97 kJ·mol-1 and 135.18 kJ·mol-1 for 5-hydroxymethylfurfural decomposition,respectively.This work would provide important basic data not only for the exploration of reaction mechanism of glucose decomposition,but also for the development of high activity and high selectivity catalyst.
