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对比研究了二甲醚在氢型丝光沸石和吡啶修饰的氢型丝光沸石上的二甲醚羰基化反应.结果表明,吡啶预吸附大大提高了二甲醚羰基化反应的稳定性,并且在473K反应48h能够保持约30%的乙酸甲酯收率.原位红外光谱和NH3程序升温脱附研究发现,吡啶吸附在12元环内,而8元环内的酸性位基本不受干扰.129Xe核磁共振研究表明,未经修饰的丝光沸石反应后孔道严重堵塞,而吡啶修饰的分子筛反应后孔道基本不变.因此,12元环内酸性位是积炭失活位,吡啶吸附抑制了12元环内积炭的生成,二甲醚羰基化反应能够在8元环内活性位上顺利进行.
The dimethyl carbonylation of dimethyl ether on hydrogen-type mordenite and pyridine-modified hydrogen-type mordenite was compared.The results showed that the pre-adsorption of pyridine greatly enhanced the stability of dimethyl carbonylation reaction, and at 473K The yield of methyl acetate was maintained at about 30% after 48h reaction.Isothermal adsorption of NH3 in situ and in the NH3 temperature range showed that pyridine was adsorbed in the 12-membered ring, while the acidic sites in the 8-membered ring were not disturbed. Resonance studies showed that the pores of the modified mordenite were blocked severely, whereas the pyridine-modified molecular sieve reaction did not change significantly after the reaction of the mordenite.Therefore, the acid sites in the 12-membered ring are the inactivation sites for carbon deposition and the pyridine adsorption inhibits the 12-membered ring Within the formation of coke, DME carbonylation reaction can be carried out in 8 yuan ring active position smoothly.