Kinetics Of The Heterogeneous Catalytic Synthesis Of Oleic Acid Cyclic Carbonate

Vegetable oil cyclocarbonates are catalyzed by carbon dioxide and epoxy vegetable oil and can be used as precursors to polycarbonate and polyurethane.This approach is considered to be an eco-friendly approach that not only contributes to the high-value use of vegetable oils and carbon dioxide,but also contributes to the mitigation of greenhouse effects.At present,the preparation method of cyclocarbonates mainly focuses on homogeneous catalytic synthesis.There are some problems such as product purification,catalyst separation and low recycling.In comparison,heterogeneous catalysts have the advantages of recyclable recycling and high catalytic activity,and have attracted the attention of researchers.Soybean oil,cottonseed oil,castor oil and so on are the main vegetable oils used to synthesize cyclocarbonate.As an industrial chemical raw material,oleic acid is abundant in its source.The synthesis of cyclocarbonates with oleic acid can reduce the use of edible oil source and realize the high value of waste oil.In this paper,the kinetics of heterogeneous catalytic synthesis of oleic acid cyclocarbonates is studied in order to provide theoretical and technical support for the synthesis and high value utilization of oleic acid cyclocarbonates.The main studies are as follows:（1）Synthesis and characterization of heterogeneous catalyst（HBim Cl-Nb Cl₅/HCMC）:Firstly,the preparation process of carboxymethyl cellulose was optimized by studying different conditions of hydrochloric acid addition,volume fraction of isopropanol and stirring time.Secondly,the ionic liquid was loaded onto carboxymethyl cellulose,and the structure of the process products was characterized to evaluate the final prepared heterogeneous catalyst.The preparation effect of the final heterogeneous catalyst was evaluated.According to the results of the carboxyl group content,the highest conversion of carboxyl groups was obtained when the addition of hydrochloric acid was 3.4%,the volume fraction of isopropanol was 75%,and the stirring time was 3 h.The results of the infrared spectroscopy characterization showed that the conversion product of sodium carboxymethyl cellulose,with a vibrational peak at 1739 cm^-1,indicated the conversion of sodium carboxymethyl cellulose into carboxymethyl cellulose.The structure of HBim Cl ionic liquid was confirmed by the NMR analysis of the ionic liquid.On this basis,it was further combined with scanning electron microscopy to confirm that the ionic liquid was successfully loaded onto carboxymethyl cellulose.（2）Analytical study of the structure and physicochemical properties of the process products of oleic acid cyclic carbonate synthesis:The infrared spectral characterization of methyl oleate,epoxidized oleic acid methyl ester and oleic acid cyclic carbonate resulted in the appearance of vibrational peaks of ester groups at 1738 cm^-1 and stretching vibrational peaks of epoxy groups at 815 cm^-1 and 950 cm^-1,as well as the appearance of cyclic The characteristic peak of carbonate ester at 1800 cm^-1 indicates the change of groups in the process products.The density,refractive index,viscosity and specific heat capacity values of the process products were measured,and the results showed that the density and refractive index showed a linear decrease with increasing temperature;the logarithm of viscosity showed a linear relationship with 1/RT,in which the viscosity of oleic acid cyclic carbonate was much larger than that of methyl oleate and epoxidized oleic acid methyl ester,which was caused by the conversion of the epoxy group into the cyclic carbonate group.The specific heat capacity value,which is relatively stable at a certain temperature,but the specific heat capacity value of cyclic carbonate oleate is larger than that of methyl oleate and methyl oleate epoxide,so more heat is required per unit temperature change for cyclic carbonate oleate,while the corresponding specific heat capacity value is closely related to thermodynamic studies.Based on this,changes in the structure of the process products can be predicted later based on the changes in the physicochemical properties of the substance.（3）Analysis and simulation of the gas-liquid mass transfer process in the catalytic synthesis of cyclic carbonate oleate:The gas-liquid mass transfer process was studied by different temperatures,pressures and composition of the oil phase during the synthesis of cyclic carbonate oleate.It was concluded that the solubility of carbon dioxide in the liquid phase decreases with increasing temperature and increases with increasing pressure.The dissolution of carbon dioxide in oleic acid cyclic carbonate is exothermic by combining Henry’s law with the van’t Hoff’s law equation.Meanwhile,the software was also used to model the gas-liquid mass transfer process,and the mass transfer coefficients of methyl oleate,methyl oleate epoxide and cyclic carbonate oleate were estimated,and the standard error of the estimated coefficients was within 7%,indicating the reliability of the model.（4）Kinetics and simulation of the catalytic synthesis of oleic acid cyclic carbonate:Kinetic study of the synthesis of oleic acid cyclic carbonate from methyl oleate by epoxidation at different temperatures,pressures,catalyst loadings and concentrations of epoxy groups.The results showed that when the temperature was 443.15 K,the pressure was3 MPa,the catalyst load was 0.042 g/m L,and the concentration of epoxy group was 2.88mol/L,the conversion rate of epoxy group was the highest.Combined with the study of mass transfer process,the kinetic process model was established.The model shows that the experimental values fit well with the simulated ones,and the kinetic constants are evaluated by nonlinear regression analysis.In this study,the gas-liquid mass transfer process of carbon dioxide within the methyl oleate system and the kinetics of the cyclic carbonation reaction of the epoxidized methyl oleate catalyzed by the heterogeneous catalyst HBim Cl-Nb Cl₅/HCMC were investigated to establish a model based on gas-liquid mass transfer and reaction kinetics,and the results of the study can provide theoretical basis and technical support for the synthesis of cyclic carbonate of oleic acid and lay the foundation for future industrial applications.