Investigation On Reaction Behavior Of Glucose's Hydrolysis Over Environmentally Friendly Catalysts

Levulinic acid (LA), which can be prepared from biomass, is an important chemical raw material with various applications in the industry. As a result, LA can become a new platform chemical. But the traditional preparation processes of LA from biomass using liquid acid catalysts such as hydrochloric acid and sulfuric acid. Since these liquid acids are corrosive and produce a large amount of waste, it is desirable for the solid acid catalysts to replace the liquid ones which can develop environmentally benign process.The hydrolysis of glucose to LA in water over green catalysts instead of liquid acid has been studied. Based on the selection of the catalysts, we further study on the influence of the parameters, such as the structure, pore size, acid characterization, the ratio of SiO₂ to Al₂O₃ and stability of the ZRP-5 on the LA yield. The kinetics of hydrolysis of glucose over ZRP-5 has also been studied.The hydrolysis of glucose in water over four different catalysts respectively has been studied. These catalysts are two ZRP-5 molecular-sieving catalysts, named catalyst 1 and catalyst 2, and Formic acid, and water. There are other side reactions besides the main reaction which is hydrolysis of glucose to the main product, levulinic acid (LA). The side products are 5-hydroxymethylfurfural(HMF), fructose, lactic acid, formic acid, furfural, and so on. A lot of humin was formed. It is easy for hydrolysis of glucose to HMF, but it is relatively hard for the further hydrolysis HMF to LA .The two ZRP-5 molecular-sieving catalysts have better selectivity to LA.We further study on the structure, pore size, acid characterization, the ratio of SiO₂ to Al₂O₃ and stability of the ZRP-5 to observe how these parameters influence the LA yield. The reason of the better selectivity to LA over the ZRP-5 molecular-sieving catalysts is that the ZRP-5 has the abundant mesopore to achieve shape selective. The smaller value of SiO₂/Al₂O₃, the higher LA yield. But LA yield is not high when the value of SiO₂/Al₂O₃ is too low. The recovered ZRP-5 is dealuminiation, but still has the order framework and lots of acid sites .The selectivity to LA yield is lower, however it is still well over the recovered ZRP-5.The kinetics of hydrolysis of glucose in water over two catalysts respectively has been studied under four different temperatures. The hydrolysis reaction of glucose is of an order 1. The hydrolysis of glucose apparent activation energy over ZRP-5 with SiO2/Al2O3 20-25 is 99.24kJ/mol, over ZRP-5 with SiO2/Al2O3 30 is 109.0 kJ/mol. The hydrolysis of HMF to LA is also of an order 1. The hydrolysis HMF to LA apparent activation energy over ZRP-5 with SiO2/Al2O3 20-25 is 43.94kJ/mol, over ZRP-5 with SiO2/Al2O3 30 is 31.58kJ/mol. ZRP-5 catalysts can reduce the hydrolysis HMF to LA apparent activation energy to increase the reaction rate and LA yield.ZRP-5 molecular-sieving shows good catalytic character and stabilization. It has further exploitation value and widely application.