Cs/SiO2 catalysts with different Cs contents are prepared via the impregnation method,and characterized by means of XRD,nitrogen physical adsorption,CO2-TPD and NH3-TPD.The reaction conditions for the Cs/SiO2-catalyzed condensation between methyl propionate and formaldehyde to methyl methacrylate(MMA)are optimized in a fixed-bed reactor,and the reaction kinetics is also briefly explored.It is proved that the Cs/SiO2 catalyst with a Cs content of 10 wt%is the optimal for the condensation,over which the conversion of methyl propionate reaches 46.3%and the selectivity of MMA reaches nearly 100%under the optimized conditions as follows:the reaction temperature is 370℃,n(MP)/n(HCHO)= 1/1,and WHSV=1.2 h-1.It is shown from additional kinetic analysis that the apparent activation energy for the reaction is 39.1 kJ·mol-1,close to the theoretical value.
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