多级孔道ZSM-5分子筛催化正庚烷裂解制烯烃性能

Catalytic Performance of n-Heptane Cracking to Light Olefins over Hierarchical ZSM-5 Zeolites

石脑油裂解制烯烃分子筛催化剂的性能同时受到酸性和扩散性质的影响,调变二者可以提升催化剂稳定性和烯烃选择性。采用溶剂挥发自组装方法制备了Si/Al物质的量比分别为30和50的多级孔道ZSM-5分子筛,经P和La修饰后,以正庚烷裂解作为探针反应,考察了多级孔道分子筛的催化性能,并与普通微孔分子筛进行了比较。结果表明:在正庚烷裂解制烯烃反应中,制得的纳米组装多级孔结构分子筛表现出更高的催化稳定性,双烯收率和丙烯选择性更高。Si/Al比的提高以及分子筛的多级孔道结构,有利于单分子裂解反应的发生,也有利于抑制氢转移等副反应的发生,从而降低了烯烃的损失。

Catalytic performance of zeolites in naphtha cracking to olefins was influenced by both acidity and diffusion properties of catalysts,which could be optimized to enhanced catalyst stability and promoted light olefin selectivity.The hierarchical ZSM-5 zeolites with Si/Al(molar ratio)of 30 and 50 were prepared by the solvent evaporation induced self-assembly method.The modified ZSM-5 zeolites by P and La were evaluated as n-heptane catalytic cracking catalyst,and compared with conventional ZSM-5.The results demonstrated a high catalytic stability of the prepared nano assembled multi-stage porous zeolite in n-heptane cracking reaction to olefins,and light olefin(ethylene and propylene,in particular propylene)selectivity,with respect to microporous control samples.The increase of Si/Al ratio and the hierarchical porosity of zeolites were conducive to the occurrence of mono-molecule cracking reaction and also inhibit the occurrence of side reactions such as hydrogen transfer,so as to reduce the loss of olefins.