Promotional effect of Ti on catalytic performance of Cs/Ti-SiO2 for conversion of methyl propionate and formaldehyde to methyl methacrylate

Synthesis of methyl methacrylate (MMA) by aldol condensation of methyl propionate (MP) with formaldehyde (FA) has received researchers' attention in recent years. Herein, a kind of acid-base bi-functional Cs/Ti-SiO2 was developed for the conversion of MP and FA to MMA. A series of Cs/Ti-SiO2 samples with different acid-base properties were prepared by changing the loading amount of Cs and Ti elements and characterized using XRD, BET, FT-IR, DR UV-vis, SEM, TEM, XPS, CO2/NH3-TPD, O2-TPO, py-IR, and TGA. The introduction of Ti species could significantly regulate the acidity and affect the surface structure of catalyst, facilitating the acti-vation of reactants and aldol reaction effectively. The relationship between the acid-base properties and catalytic activity was correlated, which revealed the crucial role of weak and medium acid sites in this transformative process. The production of MMA was optimized by using response surface methodology (RSM) based on the Box-Behnken design (BBD) approach. As a result, 62.8 % yield of MMA with selectivity of 75.6 % could be achieved at optimal reaction conditions. The catalyst would suffer deactivation from carbon deposition, which could be easily regenerated by simple thermal treatment without any decrease in initial activity during 600 h time-on -stream. Kinetic studies unraveled the activation energy of aldol condensation was 112.2 kJ/mol.