Study On The Synthesis Of Ethyl Methyl Carbonate Catalyzed By New Carbon Supported Metal Oxides

Recently,the electronic products such as mobile phones and computers develop rapidly to meet the requirement of society.Meanwhile,electrical motorcycle and cars are also promoted due to the environmental issues and shortage of oil resources.Lithium batteries are bound to become a sunrise industry.As the main component of electrolyte,the demand for ethyl methyl carbonate?EMC?is further pushed forward.Hence,it is of great practical significance to explore an efficient method for the synthesis of EMC.In this study,suitable and efficient catalysts were prepared and selected for the reaction between methyl carbonate?DMC?and ethyl carbonate?DEC?as well as methyl carbonate and ethanol?EtOH?.Catalysts ZnO/NC and ZnO/NC-M were prepared derived from ZIF-8 materials with the addition of methanol and ammonia respectively and used for the synthesis of EMC in two reaction systems.The above were different in morphology,particle size and pore structure.Single weak base sites were provided by ZnO according to the CO₂-TPD analysis.The results showed that ZnO/NC was more suitable for the reaction between DMC and DEC with the EMC yield of 29.50%,while ZnO/NC-M showed better activity in the reaction between DMC and EtOH with the EMC yield of17.15%.A series of Zn-Co-M materials varying the Co to Zn molar ratio?0.25,0.5,0.75,1?were prepared with the addition of methanol and used for the synthesis of EMC in two reaction systems.ZnO crystal structure was formed in ZnCo_0.25/NC-M and ZnCo_0.5/NC-M catalysts.The morphology was well preserved and the mesopore percentage was higher in those catalysts with lower Co to Zn molar ratio.It had been proved that the corporation of cobalt updated the basic sites.As the cobalt content increased,the alkalinity of catalysts became stronger.The results showed that ZnCo_0.25/NC-M possessed the best catalytic performance in the reaction between DMC and EtOH due to the formation of ZnO and suitable alkaline sites.The yield of EMC reached up to 33.42%,but only 16.24%in the reaction between DMC and DEC.A series of Zn-Co materials were prepared with the addition of ammonia and used for the synthesis of EMC in two reaction systems.The Co to Zn molar ratio?0.6,0.8,1,1.2,1.4?and calcination temperature?550°C,600°C,650°C,700°C?were varied respectively.The characteristic peak of zinc oxide appeared on XRD patterns when the temperature was 600°C with appropriate Co to Zn molar ratio?0.8¹.2?.It can be deduced that the formation of ZnO crystalline structure and the interaction between zinc and cobalt providing weak basic sites and strong basic sites respectively in different samples,significantly affected their catalytic performance.The ZnCo/NC-600 catalyst with strongest base sites activated the reaction between DMC and DEC most effectively,in which superior yield of product EMC can be gained around 51.50%.But it showed unsatisfactory activity in the reaction between DMC and EtOH with highest EMC yield only reaching 2.02%.Finally,the reaction conditions of DMC and DEC transesterification over catalyst ZnCo/NC-600 were optimized.The optimum reaction conditions were obtained as follows:reaction time 7 h,temperature 100°C,1 wt%catalyst amount.With the DMC to DEC molar ratio controlled of 5:1,the EMC yield could reach up to81.56%.