Studies On Catalytic Hydrogenation Of Ethylene Carbonate To Methanol And Ethylene Glycol

Reducing CO₂ emission and effective utilization of CO₂ have become a hot spot reasearch.It is a very important chemical process to convert CO₂ to methanol（ME）.ME is an important organic chemical raw material,which can be used to produce a series of chemical products or directly used as a fuel.Although ME can be produced via direct hydrogenation of carbon dioxide,but it usually requires harsh conditions to obtain high activity and selectivity.Meanwhile,the synthesis of cyclic carbonate from CO₂ and epoxide is one of the most effective routes.It is reported that the conversion and selectivity of ethylene carbonate synthesized from CO₂ and ethylene oxide are very high.Then,ME and ethylene glycol（EG）can be obtained by hydrogenation of ethylene carbonate（EC）.However,at present,the research on ethylene carbonate hydrogenation is still not extensive and the results are not satisfactory yet.Therefore,in this thesis,the hydrogenation of EC to methanol（ME）and ethylene glycol（EG）is selected as a model reaction mainly with Cu-based catalysts modified by different transition-metal as additives.The binary or ternary Cu-based catalysts were prepared using a deposition-precipitation method.The Cu particle size was controlled through modulation of the relative content of additives and active components,calcination temperature for catalyst precursors and other variables in the preparation process.It was found that with the molar ratio of each component was n（Cu）:n（Mg）:n（Zr）=8:1:0.47,the Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst furnished high selectivity to ME and EG together whith excellent conversion of EC.Then,the Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst was used as the standard catalyst for the further optimization of the reaction parameters for the hydrogenation of EC.Under the optimized conditions including 1 g Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst precursor after calcined at 450 ^oC,reduction at 350 ^oC,reaction at 180 ^oC,hydrogen flow rate of 60mL/min,liquid flow rate（a weight ratio of EC of 10 wt.%dissolved in 1,4-dioxane）of0.02 mL/min,hydrogen pressure of 4 MPa,with a boron oxide loading of 0.5 wt.%,the conversion of EC and the selectivity of EG are over 99%and the selectivity to ME is over 85%.Moreover,the lifetime of the Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst was also investigated.After 208 h test,the catalyst performance was very stable and no deactivation was observed.In addition,the Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst was applied to the hydrogenation of acetates to the relevant alcohols ethanol.The results demonstrated that the Cu₈-Mg₁-Zr_0.47/SiO₂ catalyst was also active and selective for the hydrogenation of acetates to the related alcohols.Finally,we tried to apply the cobalt-based catalyst for the hydrogenation of EC,however,no satisfactory results have been obtained with the Co-based catalysts until now.