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本文考察烷烃(正已烷烃,正庚烷,液体石蜡)在HZSM—5和稀土金属La,Ce:Th改性ZSM—5分子筛上的催化裂解行为,结果有:(1)较高的反应温度(范围:370—430℃)有利于烷烃在分子筛表面强酸中心和碱中心协同作用下,形成正碳离子,而提高烷烃的裂解转化率;(2)较低反应物进料空速,可以增大炕烃在催化剂表面的接触时间,其裂解产物(尤其是气相产物)含量增多,在相同条件下稀土金属改性的ZSM—5催化剂其裂解活性低些,这正支持了烷烃在分子筛强酸中心上裂解的机理;(3)以稀土改性ZSM—5分子筛为催化剂的裂解的烷烃油相产物中芳烃含量有较明显降低;(4)稀土改性ZSM—5分子筛具有较少的积碳现象。
The catalytic cracking behavior of alkanes (n-hexane, n-heptane and liquid paraffin) on HZSM-5 and rare earth La, Ce: Th modified ZSM-5 zeolites was investigated. The results are as follows: (Range: 370-430 ° C) favors alkanes to form positive carbon ions under the synergistic action of strong acid sites and base centers on the surface of the molecular sieve, thereby increasing the cracking conversion of alkanes; (2) lower reactant feed space velocity, which can be increased The contact time of the kang hydrocarbon at the surface of the catalyst increased the content of the cracking product (especially the gas phase product), and the cracking activity of the rare earth metal-modified ZSM-5 catalyst under the same conditions was lower, which supported the alkane hydrolysis in the zeolitic strong acid center (3) the content of aromatics in the cracked alkane oil product with rare earth-modified ZSM-5 zeolite as a catalyst is significantly reduced; (4) the rare earth-modified ZSM-5 zeolite has less carbon deposition .