ZSM-5/MOR复合分子筛催化剂对混合C_4烃转化反应的催化性能

Catalytic Performance of ZSM-5/MOR Composite Zeolite Catalyst for Conversion of Mixed C_4 Hydrocarbons

以ZSM-5/丝光沸石(MOR)复合分子筛为催化剂,对混合C4烃的催化转化反应进行了评价,并采用程序升温脱附和原位红外光谱技术对ZSM-5/MOR的酸性进行了表征.结果表明,与ZSM-5相比,MOR具有很低的催化活性,但ZSM-5/MOR复合分子筛具有较高的催化活性,随着ZSM-5/MOR复合分子筛中ZSM-5含量的增加,C4烃转化率稍有升高;在C4烃转化率大致相同的情况下,乙烯和丙烯的总选择性比较接近,但苯和甲苯的总收率却快速升高.随着ZSM-5/MOR复合分子筛中ZSM-5含量的增加,弱酸和中强酸的酸量逐渐减少,强酸的酸量有所增加.由于ZSM-5/MOR复合分子筛中MOR对ZSM-5起到分散作用而产生更多的L酸中心,且此L酸中心处于分子筛的外表面而具有较高的能量,导致苯和甲苯的总收率升高.

The catalytic performance of a ZSM-5/mordenite （ZSM-5/MOR） composite zeolite catalyst for the conversion of mixed C4 hydrocarbons was investigated. The acidic properties of the ZSM-5/MOR zeolite catalyst were characterized by means of temperature-programmed desorption and in situ infrared spectroscopy. The re- sults indicated that, compared with the ZSM-5 zeolite, the ZSM-5/MOR composite zeolite had much higher catalytic activity, but MOR had much lower catalytic activity. The conversion of mixed C4 hydrocarbons slightly increased with the increase of the ZSM-5 content in ZSM-5/MOR composite zeolite. At the similar conversion of mixed （24 hydrocarbons, the total selectivity for ethylene and propylene was very similar. However, the total yield of benzene and toluene rapidly increased with the increase of the ZSM-5 content in the ZSM-5/MOR composite zeolite. The amount of weak acid and medium strength acid gradually decreased with increasing ZSM-5 content in the ZSM-5/MOR composite zeolite, while the amount of strong acid increased. The conversion of mixed C4 hydrocarbons over ZSM-5/MOR composite zeolites was closely related to its acidic properties. The increase in the amount of L acid sites was due to the formation of more L acid sites, which was caused by the dispersion of ZSM-5 zeolite in the presence of MOR. Moreover, the L acid centers on the ZSM-5/MOR composite zeolite surface possessed higher energy than that in toluene was related to the L acid centers. the bulk of composite zeolite. The formation of benzene and