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SAPO-11晶化液中预置HZSM-5合成了HZSM-5(核)/SAPO-11(壳)复合分子筛。以复合分子筛为载体负载10%Cr_2O_3,研究了其孔分布、酸性质及其对液化石油气(LPG)转化制乙烯和丙烯反应的催化性能。结果表明,复合分子筛由HZSM-5表面包覆不同厚度的SAPO-11微晶组成,随着晶化时间延长,复合分子筛壳层厚度增加。复合分子筛负载Cr_2O_3催化剂的介孔率先增加后降低;弱酸量先增加后降低,强酸强度增加,强酸量先降低后增加,强酸密度减小。复合分子筛载体在LPG选择转化反应中催化性能优于单个分子筛和机械混合分子筛,其中,晶化12 h合成样品负载Cr_2O_3用于LPG转化反应对原料总转化率和乙烯+丙烯选择性最高,分别为42.63%和65.89%,CH_4和C_(5+)选择性分别为6.32%和15.48%。通过控制晶化时间可调变壳层厚度、复合分子筛介孔率以及酸性质,改善产物分布。
HZSM-5 (core) / SAPO-11 (shell) composite molecular sieve was synthesized by presetting HZSM-5 in SAPO-11 crystallization solution. The composite zeolite was loaded with 10% Cr 2 O 3 as carrier, and its pore distribution, acid property and its catalytic performance for the conversion of liquefied petroleum gas (LPG) to ethylene and propylene were studied. The results show that composite zeolite is composed of HZSM-5 coated with different thickness of SAPO-11 crystallites. With the prolongation of crystallization time, the thickness of composite molecular sieve shell increases. The mesoporosity of Cr 2 O 3 supported composite zeolite firstly increased and then decreased. The amount of weak acid firstly increased and then decreased, the intensity of strong acid increased, the amount of strong acid decreased firstly and then decreased, and the density of strong acid decreased. The catalytic performance of composite zeolite supports was better than that of single molecular sieves and mechanical mixed molecular sieves in the selective conversion of LPG. Among them, Cr 2 O 3 was the most efficient catalyst for LPG conversion and the highest selectivity of ethylene and propylene for 12 h crystallization 42.63% and 65.89%, respectively. The selectivity of CH_4 and C_ (5+) were 6.32% and 15.48% respectively. By controlling the crystallization time adjustable shell thickness, composite molecular sieve mesoporosity and acid nature, to improve product distribution.