部分NH_4^+交换对FER分子筛催化正丁烯骨架异构反应性能的影响

Effect of Partial NH_4^+ Exchange on n-Butene Skeletal Isomerization Catalytic Performance of FER Zeolites

采用部分NH4+交换法制备了一系列不同NH4+交换度的FER分子筛(记为HF-x,x为FER分子筛的NH4+交换度),采用XRD、N2吸附-脱附、XRF、吡啶吸附IR、NH3-TPD等方法对其进行表征。以含丁烯-1体积分数为10%的丁烯-1/N2为原料,在温度350℃、常压和空速4.0h-1的条件下,考察了NH4+交换度对FER分子筛催化正丁烯骨架异构反应性能的影响。结果表明,随NH4+交换度的增加,初始正丁烯转化率升高,而异丁烯选择性降低。当交换度为45时,初始异丁烯产率最高。除FER分子筛特殊的二维孔道系统外,中强/强酸中心比例是影响初始阶段异丁烯形成的重要因素。

A series of FER zeolites with different NH＋4 exchange levels （denoted as HF-x and x standed for the NH＋4 exchange level） were prepared by partial NH＋4 exchange method, and characterized by XRD, N2 adsorption-desorption, XRF, pyridine-adsorbed IR and NH3-TPD. The catalytic performance of HF-x in the skeletal isomerization of n-butene into isobutene was tested in a fixed-bed mini-reactor, operating at 350℃, atmospheric pressure and MHSV of 4 h-1 , with a mixture of 10% butene-1 and 90% N2 as a model reactant. With the NH＋ exchange level of HF-x increasing, the initial n-butene conversion of n-butene skeletal isomerization over HF-x increased, while the isobutene selectivity decreased. The initial isobutene yield of n-butene skeletal isomerization reached its maximum value over HF-45 （The NH4＋ exchange level of 45）. Except for the two-dimensional pore system of FER, the proper proportion of the medium and strong acid sites played an important role in the production of isobutene isomerized from n-butene at the initial stage of the reaction.