High-efficient Catalytic Synthesis Of Glycerol Carbonate From Glycerol By Heterogeneous Solid Base Catalysts

CaO was used as a catalyst for the synthesis of glycerol carbonate via transesterification from glycerol and dimethyl carbonate.A series of co-solvents were applied to improve glycerol carbonate production,the use of co-solvent gave significant positive effect on the yield of glycerol carbonate.The effects of the catalyst preparation conditions and reactions condition on the performances of CaO in the transesterification were investigated in the presence of ethanol.The results showed that the catalyst activity of CaO was greatly influenced by the calcination temperatures,and the catalyst possesses a good activity when it was calcined at 800?.A desired glycerol carbonate yield of 87.02%was obtained at a relative short reaction time?1 h?by using the following reaction conditions:glycerol/dimethyl carbonate of 1:3,catalyst amount of 5%?referring to weight of glycerol?,and reaction temperature at 65?.The characterization results of CO₂-TPD suggested that the basicity of CaO highly depended on calcination temperature,the CaO catalytic activity was affected by their total basicity rather than by their BET surface area.To achieve high efficient transesterification reactions of glycerol with dimethyl carbonate,it is necessary to develop a cheap highly activity and easily prepared solid base catalyst.Various heterogeneous LiCl/CaO catalysts with different LiCl loadings are prepared by impregnation method and employed in the synthesis of glycerol carbonate from glycerol and dimethyl carbonate were compared.LiCl/CaO exhibited high catalytic activity,89.45%of glycerol carbonate yield can be obtained under same reaction conditions,which is higher than that of unmodified CaO.Combined XRD and CO₂-TPD characterization results together,it is found that the catalytic activity of the catalysts highly depended on the formation of CaClOH and LiOH species with moderate basic sites.Glycerol carbonate was synthesized by transesterification of glycerol with dimethyl carbonate using different mixed oxide base catalysts.A series of mixed oxide base catalysts were prepared by using co-precipitation method and calcining at different temperatures.Among the prepared catalysts,MgO-CaO showed the best catalytic ability and glycerol carbonate yield of78.78%were obtained under the optimum reaction conditions,which is much lower than that of commercial CaO.The characterization results of CO₂-TPD revealed that the type of precipitant agents and salts main affected catalyst basic during the preparation step.Aimed to obtain the catalysts with high specific surface area,nono solid base catalysts was prepared by sol-gel and co-precipitation method and used for synthesis of glycerol carbonate via transesterififation from glycerol and dimethyl carbonate.It was found that the nano CaO and nano MgO-CaO were high efficient heterogeneous,the yield of glycerol carbonate reached94.56%and 90.18%,respectively.The BET and CO₂-TPD were used for characterization of the catalyst and showed the the BET surface area and pore size structure significantly increase all kinds of nano catalysts either nano oxide or mixed oxide while the catalytic activity was main affected by their basicity.Commercial CaO was modified by with different modifying agents bonding on its surface chemically and the catalytic performance for transesterification of glycerol and dimethyl carbonate to glycerol carbonate production has been investigated.It was found that the reaction efficiency has been greatly improved by aromatic modified CaO whie reduced by ester-based modified CaO compared to commercial CaO under the same reaction conditions.Catalyst BET,XRD and CO₂-TPD characterization showed,it can be seen that the surface morphology have been changed significantly after modification without obvious change of the BET surface area,crystal structure and basicity.In conclusion,the catalytic activity of the catalysts was attributed to its surface morphology.