Study On Decomposition Of Ionic Liquid-Ethylene Carbonate System And Abso Rption And Inhibition Of Decomposition Products

The massive emission of CO₂ is the main culprit of global warming,and how to convert carbon dioxide into value-added chemicals is a hot issue of research at present.Currently,there are few reactions in which carbon dioxide can be successfully applied industrially,among which the synthesis of cyclic carbonate by carbon dioxide and epoxide is considered as one of the most promising reactions for industrial application due to its high atomic utilization and compliance with green chemical routes,the key to the industrial application of this reaction is the long cycle use of efficient and stable catalysts.In this paper,in view of the problems of yield decline,ethylene carbonate decomposition and long-term instability of the catalyst in the separation process of the homogeneous ionic liquid catalyst-ethylene carbonate system,the stability of ethylene carbonate and ionic liquid was studied,focusing on the decomposition of ethylene carbonate,the decomposition of ionic liquid and the inhibition conversion of catalyst system decomposition were studied,which provided data reference for the design of industrial application process of ionic liquid.The main results are as follows:1.For the decomposition of ethylene carbonate in the experimental process will produce CO₂ and ethylene oxide and the emission of CO₂ in the experimental process,the exhaust gas absorbers were studied.Ethylene oxide absorption was selected from ethylene carbonate as the absorber,while CO₂ absorption was selected from alcohol-amine solution polyethylene glycol 200（PEG）and 1,3-propanediamine（PDA）,and the density and viscosity of the solution system were measured,and the strongest binding force of both was determined at a molar ratio of 1:1 in combination with infrared spectral characterization（FT-IR）and DFT simulation calculations,which can achieve a good solid amine.2.The stability of ethylene carbonate was studied under simulated industrial CO₂bubbling conditions.The decomposition products of ethylene carbonate were determined to be CO₂ and ethylene oxide by gas chromatography-mass spectrometry.The effects of reaction time,reaction temperature,catalyst content and catalyst type on the decomposition of ethylene carbonate were investigated respectively.For the same time,temperature and mass fraction,the decomposition of vinyl carbonate was prompted by imidazole-based ionic liquids more than quaternary amines and quaternary phosphoniums.This data provides a data reference for the reaction conditions such as residence time,separation temperature and catalyst content during separation for homogeneous catalysts.3.The stability of the ionic liquid in the experiment was studied,and the reaction liquid system was characterized by ESI mass spectrometry and analyzed by gas chromatography-mass spectrometry,it was found that the cationic structure of imidazole ionic liquids was decomposed,and quaternary amines and quaternary phosphonium ionic liquids were stable under the reaction conditions,but six types of ionic liquid anions were lost to generate bromine ethanol,and the content of bromine ethanol generated by imidazole was greater than that of quaternary amines.which corresponds to the decomposition of cations,and for the mechanism of bromine ethanol generation may be due to the presence of hydrogen ions,therefore,the study of alkaline substances to inhibit the conversion of bromine ethanol generation was studied,and the inhibition of conversion of imidazole and potassium hydroxide is more effective.