Preparation Of Porous Solid Acid And Base Catalysts For Green Synthesis Of Ethyl Methyl Carbonate

As one of eco-friendly asymmetric carbonate,Ethyl methyl carbonate（EMC）is widely used as an intermediate in organic synthesis because there are methyl,ethyl,carbonyl,methoxy,ethoxy in the EMC molecular.In addition,due to its small viscosity,high dielectric constant and large solubility of lithium salts,EMC is an ideal electrolyte in lithium batteries and has a broad application prospect.The traditional synthesis method of ethyl methyl carbonate by using phosgene had been abandoned due to the high toxicity of the raw material and strong corrosion of the by-product.Oxidative carbonylation has not been industrialized due to the rigorous reaction conditions and low selectivity of target products.Transesterification is the principal method of synthesis of EMC at present.In this thesis,the porous basic material and porous acid-basic materials were prepared,and their catalytic performances in the transesterification reaction between dimethyl carbonate（DMC）and diethyl carbonate（DEC）were investigated in detail.（1）The hard template of deposited carbon was in situ generated by pyrolysis of different organic compounds in an inert atmosphere.Meanwhile,Mg O formed by the thermal decomposition of the magnesium resource attached to the carbon deposition template,and then the porous structure was fabricated after removing the carbon template.The samples were characterized by XRD,TG,N₂ adsorption-desorption,FT-IR,SEM,CO₂-TPD and other technologies,and their catalytic performance was also evaluated in the transesterification reaction.The obtained results show that the M-46G-9P-500 sample,which was prepared with46%glucose and 9%PEG20000 as composite organic carbon source via a two-step calcination at 500℃displays the highest catalytic activity.This may be attributed to the two aspects as following:the large amount of medium basic sites acting as active catalytic sites;the larger specific surface area and pore size,which facilitates the diffusion of the substrates and products.The prepared catalyst displayed a good stability and no significant decrease was observed after 3 times recycles.（2）The acid-base bifunctional materials of MA-MCM-41 and MZA-MCM-41 were successfully synthesized by doping Mg,Al or Mg,Al,Zn into the framework of MCM-41molecular sieve materials with the hydrothermal method.The catalytic performance of the transesterification between DMC and DEC was investigated.The results indicated that metal heteroatoms had been successfully doped into the mesoporous silica framework,and the metal-doped framework mesoporous materials MA-MCM-41 and MZA-MCM-41 possess the hexagonal mesoporous structure,and the bonds of Si-O-Mg,Si-O-Al and Si-O-Zn were formed through the doping of the heteroatoms into the MCM-41 framework.In addition,the results of reactions showed that the catalytic activity of the ternary hybrid sample MZA-MCM-41 was higher than that of the binary hybrid sample MA-MCM-41.Moreover,the ratio of three components also has an evident effect on its catalytic performance,the sample with the ratio of Mg/Zn/Al=0.4/1.6/1 gave the highest activity and a better stability,and the catalytic activity did not decrease significantly after 3 times recycles.