Study On Microwave-assisted Catalytic Dehydration Of Glycerol To Acrolein

Biodiesel is a type of green and renewable energy.Glycerol is the main by-product of biodiesel production process,and the efficient utilization of glycerol can reduce the cost of biodiesel production.Glycerol can be used as the raw material to produce many important value-added chemicals,among which the preparation of acrolein is a prospective route.However,catalyst deactivation is an issue encountered by most studies on glycerol dehydration for acrolein production.In order to solve this problem,most researchers focused on the improvement of catalyst and reaction process,while few studies on device improvement were reported.In this paper,microwave device was used in glycerol dehydration to prepare acrolein,with the aim of improving the catalyst stability throuth uinform heating of microwave.Silicon carbide is good microwave absorbent,which has large heat capacity and high thermal conductivity.WO₃/ZrO₂ has good thermal stability and catalytic effect on glycerol dehydration for acrolein preparation.SiC and WO₃/ZrO₂were combined in this study to prepare WO₃-ZrO₂@SiC which was used as the microwave absorbing catalyst in glycerol dehydration process.Microwave assisted glycerol dehydration for acrolein production was investigated in this paper.The effects of reaction temperature,space velocities under different glycerol concentrations,and WO₃ loading on glycerol conversion and acrolein selectivity were examined in an“integrated”device of microwave assisted vaporization and reaction.Results showed that the optimal reaction conditions were reaction temperature of 300?,concentration of glycerol aqueous solution of 20wt%,and mass space velocity of glycerol of 0.2 h^-1.The glycerol conversion and acrolein selectivity reached 97%and 52%,respectively under the optimal conditions.To further increase the acrolein yield,the process of glycerol dehydration was improved.The catalyst preparation method was optimized,and the vaporization approach of glycerol aqueous solution was improved.The glycerol dehydration process was then changed to be a“two-step process”of electric heating vaporization coupled with microwave reaction The effects of reaction conditions and catalyst preparation method on glycerol dehydration were investigated.The results showed that the dispersant type and ZrO₂ coating quantity during the catalyst preparation had great influence on the reaction results.The best results were obtained when sodium metasilicate was used as the dispersant and the ZrO₂ coating quantity was 37.5 wt%.Both glycerol conversion and acrolein selectivity were higher than those from the above“integrated”device.The glycerol conversion was almost 100%,and the acrolein selectivity reached 65%under the optimal conditions.