Decomposition Kinetics Of Glucose Catalyzed By Metal Chlorides In High Temperature Liquid Water

Diminishing fossil fuel reserves indicates that alternative sources of energy and chemicals are needed in the future.Abundant biomass resources are a promising alternative for the sustainable supply of fuel and valuable chemicals.With small volume high-pressure vessel batch reactors,glucose and 5-hydroxymethylfurfural decomposition kinetics in high temperature liquid water catalyzed with metal chlorides were determined at 180℃.13 types of metal chlorides were selected.A series of first-order reactions with the consideration of parallel by-reactions were used to fit the kinetic data.The results show that the catalytic effects of different metal chlorides on glucose and 5-hydroxymethylfurfural decomposition were totally different.Iron(Ⅲ),nickel and zinc chlorides could greatly accelerate the decomposition rate of glucose,while the decomposition rate of 5-hydroxymethylfurfural was highly improved by adding copper chloride and iron(Ⅲ) chloride.The catalytic effects of transition metal chlorides on glucose and 5-hydroxymethylfurfural decomposition were much better than alkaline metal chlorides and alkaline earth metal chlorides.As to the metal elements in fourth cyclic,the results show that the rate constants of glucose decomposition were increased with the increase of atomic weight except copper chloride.In addition,the lower the pKa value of different metal ions, the stronger the catalytic effects on glucose and 5-hydroxymethylfurfural decomposition.Based on the above research,copper chloride was chosen as catalyst.With small volume high-pressure vessel batch reactors,the decomposition kinetics of glucose and 5-hydroxymethylfurfural catalyzed by copper chloride were determined for temperature from 423.15K to 463.15K and copper chloride concentration from 0 to 0.08M.The results showed that glucose and 5-hydroxymethylfurfural decomposition were enhanced with the increase of reaction temperature and copper chloride concentration,resulting in higher yield of levulinic acid.By comparing the correlation coefficients correlating with different reaction orders,it was confirmed that both glucose and 5-hydroxymethylfurfural decomposition are the first order reaction.With the first order kinetics equation,the evaluated activation energies of desired and undesired reaction of glucose decomposition were 134.65kJ.mol^-1 and 144.1kJ.mol^-1.And,the evaluated activation energies of main and side reaction of 5-hydroxymethylfurfural decomposition were 131.97kJ.mol^-1 and 135.18kJ.mol^-1, respectively.With small volume high-pressure vessel batch reactors,effects of different anions on glucose and 5-hydroxymethylfurfural decomposition were preliminarily explored.9 types of potassium salts were chosen as catalysts.The results indicate that the catalytic effects of different anions on glucose and 5-hydroxymethylfurfural decomposition were different, potassium dihydrogen phosphate and potassium sulphate could highly improve the decomposition of glucose and 5-hydroxymethylfurfural.Meanwhile,it was found that the value of pH could affect the mechanism of glucose decomposition.This work not only obtained some general rules on effects of metal chlorides on glucose and 5-hydroxymethylfurfural decomposition,but also systematically determined the kinetics of glucose and 5-HMF decomposition catalyzed by copper chloride,what is more,effects of different anions on glucose and 5-hydroxymethylfurfural decomposition were preliminarily explored,these will provide important basic data for efficient utilization and catalytic hydrolysis reaction of biomass.