Macro-Kinetics And Regeneration For Catalytic Production Of Methyl Methacrylate By Cs/SiO₂

Methyl methacrylate（MMA）is an important organic chemical raw material with an expanding market demand.Catalytic condensation between methyl propionate and formaldehyde（aldol reaction）offers a potential route to produce MMA,and the key problem to be solved is the development of highly efficient catalyst for the Aldol reaction.Alkaline catalysts modified by Cs have many shortcomings,such as low conversion and selectivity,high loading of active components,and serious carbon deposition in the aldol reaction.For this purpose,the preparation process of Cs/SiO₂ catalysts was improved,and the reaction macro-kinetics were preliminarily explored under optimized conditions.Besides,the lifespan of Cs/SiO₂,deactivation,and regeneration were briefly discussed in terms of characterization results.The main results and conclusions of the thesis are listed below.（1）The silicon source has great influence on the crystalline phase,basicity,and other physicochemical properties of Cs/SiO₂catalysts.Ammonium-stabilized silica sol proved to be the best method to prepare Cs/SiO₂catalysts.Addition of Zr and CTAB surfactant increased the specific surface area of Cs/SiO₂,but had little effect on the activity of the catalyst.Results showed that 10 wt%Cs/SiO₂ catalyst exhibited the best performance in the aldol reaction between methyl propionate and formaldehyde.（2）The macro-kinetics for the Cs/SiO₂-catalyzed condensation between methyl propionate and formaldehyde was investigated in a fixed-bed reactor,contributing to an apparent rate equation and the related kinetic parameters.The conversion of methyl propionate increased with enhancing temperature,decreasing space velocity,and the increasing mass ratio of aldehyde to ester.The single-pass conversion of methyl propionate was as high as 46.26%under the selected reaction conditions.（3）The activity of Cs/SiO₂ started to decline after reaction for 12 h,which was probably caused by the deposition of organic matter on the catalyst surface.The deactivated catalyst after reaction for 200 h was regenerated by calcination,giving similar conversion of methyl propionate to the fresh one,in spite of the slight leaching of Cs and expanding pores in silica.