Y型分子筛酸性和孔结构对其催化异丁烷/丁烯烷基化反应性能的影响

Impact of Acidity and Pore Structure of Y-Type Zeolites on Isobutane/Butene Alkylation Reaction

通过3种后处理方法对工业NaY分子筛进行改性,得到具有不同酸性和孔结构的Y型分子筛Y-1、Y-2、Y-3。采用X射线衍射(XRD)、氨气程序升温脱附(NH_(3)-TPD)、N_(2)吸附-脱附、吡啶吸附红外(Py-IR)等手段表征分子筛的物化性质,并研究了其催化异丁烷/丁烯烷基化反应的性能。结果表明:Y-1和Y-3均为微孔分子筛,Y-2存在较多介孔,Y-1和Y-2总酸量均远大于Y-3;在80℃、1 MPa、异丁烷/丁烯摩尔比37.81、质量空速1.04 h^(-1)、30 min的条件下,Y-1、Y-2、Y-3作用下的目标产物C8收率分别为74.07%、19.28%、5.47%。对于孔结构相似的Y型分子筛,总酸量的提高有利于目标产物的生成;但对于总酸量接近的Y型分子筛,含有较多介孔且外比表面积较大的分子筛不利于反应物分子的择形,目标产物的收率较低。相对于孔性质,分子筛酸中心的调控是影响该反应产物分布的关键因素。

Three Y-type zeolites,Y-1,Y-2 and Y-3,with different acidity and pore structures were obtained by modifying the industrial NaY zeolite with three different post-processing methods.The physicochemical properties of the zeolites were characterized by X-ray diffraction(XRD),ammonia temperature programmed desorption(NH_(3)-TPD),N_(2)adsorption-desorption and Py-IR,and the catalytic performance of these zeolites for isobutene/butane alkylation reaction were studied.The results show that Y-1 and Y-3 are microporous zeolites while Y-2 has more mesopores,and the total acid amount of Y-1 and Y-2 was much higher than that of Y-3.When the temperature is 80℃,the pressure is 1 MPa,the isobutane/butene molar ratio is 37.81,the molar hourly space velocity(MHSV)is 1.04 h^(-1) and the raction time is 30 min,the yields of the target product C_(8) under the action of Y-1,Y-2 and Y-3 are 74.07%,19.28%and 5.47%,respectively.For Y-type zeolites with similar pore structure,the increase of total acid content is conducive to producing the target product.However,when the Y-type zeolites are similar in total acid content,those with more mesopores and larger external specific surface area are detrimental to the shape selectivity of reactant molecules,and the yield of the target product is low.By comparison with the pore properties,the regulation of acid center in zeolites is the key factor affecting the distribution of reaction products.