Pd/HZSM-5催化剂异构化反应特性的研究

Study on Isomerization of Pd/HZSM-5 Catalysts

为了筛选适用于异构化 /吸附分离工艺的催化剂 ,考虑到ZSM -5分子筛对直链烷烃的择形催化作用 ,以其为载体 ,采用离子交换法对其改性 ,并负载了不同含量的贵金属Pd。在此基础上 ,利用微反 -色谱系统考察了不同Pd负载量、氢压和反应温度对HZSM -5催化剂异构化活性的影响以及Pd对该类催化剂异构化选择性和稳定性的影响。结果发现 ,HZSM -5催化剂负载Pd后可以有效地提高反应的稳定性及异构化选择性 ;金属分散度的提高有利于改善催化剂的异构化选择性 ;反应温度过高将导致金属的加氢裂化活性增强 ,使异构化选择性下降 ,因此以中温 2 50℃为好 ;在中温下操作时 ,为保证一定的异构化活性 ,氢压不宜太大 ,应控制在 1 .5MPa左右。

In order to select appropriate catalyst for the isomerization/adsorptive separation technology ,based on the isomerization and shape selectivity of the ZSM-5 molecular sieves catalyst to paraffin hydrocarbons, ZSM-5 is taken for carrier and ion exchange is used to change its performances by loading various content of noble metal Pd.The effects of some factors,including the Pd loading, metal dispersion, hydrogen pressure and temperature, on the isomerization activity, selectivity and stability are studied on Microreactor-Chromatograph system. The results show that the isomerization selectivity and stability can be improved effectively when the Pd is loaded on HZSM-5 zeolites. The better metal dispersion, the better isomeration selectivity is the isomerization selectivity will reduce with the temperature being too high. The effects of the hydrogen pressure and temperature were also investigated. The condition of reacting under 1.5 MPa and 250 ℃ are preferred.