Application Of The Solid Base Catalyst In The Synthesis Of Glycerol Carbonate

Glycerol carbonate（GC）is a very important cyclic carbonate which can be widely used in the production of cosmetics,electrolytes,coatings,polyurethanes and oil additives.The preparation of GC by transesterification using glycerol is a common method.Glycerol is the by-product obtained during biodiesel production.The transesterification method is usually applied in the mild reaction conditions,which can effectively utilize glycerol to promote the development of the biodiesel industry.Therefore,this method had received more and more attention.However,this method had two problems.On the one hand,when GC was prepared using a homogeneous catalyst such as sodium hydroxide and potassium carbonate,although the catalytic efficiency of them was high,the catalyst was not easy to separate,which made the post-treatimen process complicated.This is a shortcoming in the industrial production of GC.On the other hand,when some heterogeneous catalysts such as metal oxides composite were used,the reaction time was long,which was a disadvantageous for improving production efficiency.Therefore,it is necessary to develop heterogeneous catalysts with high catalytic activity and good separation ability.In response to these problems,this paper first developed a high performance heterogeneous catalyst to study the effect of catalyst preparation conditions on the structure and catalytic performance of the catalyst.Secondly,the application of microwave in the preparation of GC was explored to determine the effect of microwave condition on the reaction.The main research contents of the thesis include:A series of heterogeneous catalysts based on industrial water glass（WG）were prepared and the performance of these catalysts was investigated.Firstly,five WG catalysts with different modulus were prepared and used to synthesize GC by the transesterification reaction between glycerol and dimethyl carbonate（DMC）.Then,the structure and properties of these catalysts were investigated by XRD,BET,FT-IR,FE-SEM.WG-2.0 was chosen as the optimal catalyst in the synthesis of GC.The high glycerol conversion of 96.3%and GC yield of 94.1%could be achieved under the optimum reaction conditions:DMC to glycerol mole ratio of 4:1,reaction temperature of 75℃,reaction time of 90min,and WG-2.0 catalyst amount of 4wt.%.Moreover,WG-2.0 also exhibited excellent stability with the glycerol conversion decreasing less than 3%even after five times reuse.The application of microwave method in the GC synthesis was studied.GC was synthesized by transesterification using a microwave synthesis method in a sealed reaction system using Na₂SiO₃ as the catalyst.It was found that the microwave-assisted reaction modes,namely,the temperature constant mode（TCM）and the power constant mode（PCM）,greatly influenced the reaction.When the reaction was conducted in TCM,with a catalyst amount of5wt.%,DMC-to-glycerol molar ratio of 4:1,reaction temperature of 95℃,and reaction time of15min,the glycerol conversion and the GC yield reached 96.7%and 94.3%,respectively.Similar glycerol conversion and GC yield were also obtained in PCM with 1wt.%catalyst,4:1molar ratio of DMC to glycerol at 175W in fifty seconds.Compared to traditional heating reactions,TCM and PCM greatly recdued the concumption of energy and reation time.Compared to TCM,PCM provided a more efficient way to synthesize GC.These investigations indicated that the microwave-assisted reaction not only benefit the energy efficiency but also make the industrialization of the transesterification of glycerol with DMC more feasible and economical.