Hβ／MCM-41复合分子筛催化剂上苯甲醚与乙酸酐酰化反应研究

Acylation of anisole with acetic anhydride over Hβ/MCM-41 composite molecular sieves

以β沸石为硅源,制备了不同硅铝比的Hβ/MCM-41复合分子筛,考察了该复合分子筛对苯甲醚与乙酸酐酰化反应的催化效果,并与介孔MCM-41、微孔Hβ分子筛的催化效果进行了比较,研究了分子筛硅铝比、酸性及孔道结构对酰化反应催化性能的影响。结果表明,对于苯甲醚和乙酸酐酰化反应,Hβ/MCM-41复合分子筛具有较好的催化稳定性,反应过程中的积炭量较少,积炭的碳氢比较低。该复合分子筛不仅具有微孔沸石的强酸性,而且具有较大孔径的介孔,产物分子能及时从孔道中扩散出来,催化活性位不易中毒失活。

Hβ/MCM-41 composite molecular sieves with different Si/Al ratios were synthesized by using β zeolites as the silica-alumina source of mesoporous phases. The catalytic performance of the as-synthesized composite molecular sieves in the acylation of anisole with acetic anhydride was evaluated and compared with that of mesoporous MCM-41 and microporous Hβ zeolites. The composite molecular sieve exhibits much higher stability than MCM-41 and Hβ. UV-Vis spectra and elementary analysis of the spent catalysts suggested that with the composite Hβ/MCM-41 as catalyst, the amounts of coke deposited during the reaction and C/H tool ratio of the deposited coke was much lower than that with Hβ as catalyst. The composite Hβ/MCM-41 is provided with both the strong acidity of microporous Hβ and the large pore of mesoporous MCM-41 ; the large pores in Hβ/MCM-41 facilitated the evacuation of heavier products from active sites of the molecular sieve and therefore preserve its catalytic activity provided by the strong acidity.