关键词: 甲基丙烯酸甲酯, 羟醛缩合, 酸碱催化剂, 技术经济性

Abstract:

SiO₂ supported cesium catalyst was prepared and its performance in the aldol condensation of formaldehyde and methyl propionate was studied in a fixed-bed reactor. X-ray diffraction, field emission scanning electron microscopy, X-ray fluorescence spectroscopy and thermal analysis were used to determine the composition and structure changes of the catalyst. The conversion of methyl propionate of 13%~15%, that of formaldehyde of 60%~65%, and the selectivity to MMA based on methyl propionate of 93%~95% were achieved. During the reaction, the crystal structure and morphology of the catalyst did not change significantly with insignificant aggregation and loss of the active component Cs and the amount of carbon deposition increased. After in-situ regeneration by carbon burning, the catalytic activity was restored, and the initial activity was even higher than that of the fresh catalyst. With the progress of the reaction, formaldehyde and methyl propionate conversions approached the average level before regeneration. For a long-term run for about 1700h, the MMA selectivity based on methyl propionate maintained at 93%~95%. Technical and economic analysis showed that the new coal-based MMA synthesis route with the core step of aldol condensation is safer, more environmentally friendly, more economical and more efficient than the traditional routes of acetone cyanohydrin and isobutylene oxidation, and hence is quite suitable for using in China, which has rich coal, lean oil, and little gas in resource structure. The route fits the national coal chemical policy, which not only can break through the patent blockade of C2 and C4 routes so as to change the existing technology pattern of the MMA industry, but also can provide an important way for coal chemical companies to enter the MMA synthesis technology field to enrich the coal chemical product chain by consuming the excess production capacities of formaldehyde, acetic acid and a large amount of low-value by-product methyl acetate.

Key words: methyl methacrylate(MMA), aldol condensation, acid-base catalyst, techno-economics