Study On Preparation Of Ionic Liquid Supported Materials And Catalytic Synthesis Of Carbonate

Carbonate is a series of versatility,low toxicity and even non-toxic chemicals.Among them,ethyl methyl carbonate（EMC）is a widely used asymmetric linear carbonate due to its special organic chemical properties,and is mainly used as a solvent for lithium battery electrolyte.At present,the industry mainly uses dimethyl carbonate（DMC）and ethanol（EtOH）as raw materials,and strongly basic homogeneous sodium methoxide（CH₃ONa）as a catalyst to catalyze the synthesis of EMC.However,CH₃ONa is easily deactivated,cannot be recycled,and produces a large amount of strong alkaline solid waste,which does not conform to the concept of green chemistry.Ionic liquids（ILs）are gradually favored by the majority of researchers for their green environmental protection,designable structure,non-volatile and high catalytic activity,but homogeneous ionic liquids cannot replace sodium methoxide and can be used alone for EMC synthesis because of distillation separation During the process of dimethyl carbonate（DMC）and EMC,the ionic liquid will continue to catalyze the EMC disproportionation reaction,resulting in low EMC yield and poor quality.The immobilization methods of immobilized ionic liquid catalysts for the synthesis of carbonates were summarized,and the immobilization methods of ionic liquids were named according to the nature of the interaction between the ionic liquid and the carrier:physical adsorption,Coordination bonding,ester-forming bonding,silane coupling bonding,carbon-nitrogen bonding,and double bond or functional group self-polymerization,reviewed and compared the catalytic performance and catalytic performance of catalysts prepared by various supported methods in the synthesis of carbonates.Advantages and disadvantages,it is concluded that the bonding method immobilized ionic liquid catalyst has obvious advantages in the process of carbonate synthesis,and pointed out the technical problems to be solved urgently by immobilized ionic liquid and the future development direction.A series of heterogeneous catalysts were prepared using different immobilization methods,and their activity was tested using the transesterification reaction of DMC and EtOH to synthesize EMC.The embedding method with better activity was screened out and the step-by-step embedding method was investigated.The effect of adding acid solutions of different concentrations during the catalyst process on the catalytic performance.The smaller concentration of catalyst 0.5S-[Emim]-Im12 has better activity.The molar ratio of raw materials is 1:1,the reaction temperature is 81℃,and the space velocity is 1 h^-1,the weight of the catalyst is 4 g,the DMC conversion rate and the EMC yield under the reaction conditions of 3 h are 50.73%and 40.78%,respectively;using the alkalinity of the laboratory-made highly active ionic liquid to promote the hydrolysis of ethyl orthosilicate For one-step embedding,the solid catalyst synthesized by this method has a larger specific surface area than the catalyst with additional alkali to promote the hydrolysis of the silicon source,and the strong alkaline ionic liquid is not only an efficient catalytic active center,but also promotes the hydrolysis of ethyl orthosilicate.An integrated porous solid base catalyst is formed.This not only avoids the participation of pollutants and simplifies the separation process of the catalyst,but also prevents the ionic liquid from falling off more effectively,avoids insufficient contact between the active center and the raw material due to the mass transfer effect of the carrier material,thereby ensuring the catalytic performance of the catalyst.Finally,the catalyst was optimized at the preparation level,and the optimal preparation conditions were determined as follows:the hydrolysis temperature and aging temperature are both 60℃,the aging time is 12 h,the embedding volume is 12 g,and the DMC conversion rate reaches 48.96%under the same reaction conditions.And it has strong stability without deactivation after running for more than 2500 min.Combining N₂-adsorption/desorption,Fourier infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）and other characterization attempts to explain the mechanism of action between[Emim]Im and the Si-O-Si-O structure of the carrier and the structural community formed from the microstructure.