ZSM-5/ZSM-57复合分子筛催化剂上混合C_4烃的催化转化反应

Catalytic Conversion of Mixed C_4 Hydrocarbons over ZSM-5/ZSM-57 Composite Zeolite Catalyst

以ZSM-5/ZSM-57复合分子筛为催化剂,考察了其对混合C4烃催化转化的反应性能.采用氨程序升温脱附(NH3-TPD)和吡啶吸附傅立叶变换红外(FT-IR)光谱技术表征复合分子筛的酸性质.结果表明,当复合分子筛中ZSM-5的含量较低时,比ZSM-5具有更高的催化活性及乙烯和丙烯选择性,这是因为此时复合分子筛酸强度较高、酸量较多,且小孔ZSM-57有利于乙烯和丙烯的择形反应.而当复合分子筛中ZSM-5的含量较高时,具有较高的苯和甲苯选择性,其原因可能是其孔结构及共晶生长时的结构匹配性对芳构化反应有利.

The catalytic performance of a ZSM-5/ZSM-57 composite zeolite catalyst for the conversion of mixed C4 hydrocarbons was investigated. The acidic properties of the ZSM-5/ZSM-57 composite zeolite catalyst were characterized by means of ammonia temperature-programmed desorption （NH3-TPD） and pyridine adsorption Fourier transform infrared （FT-IR） spectroscopy. Results indicated that compared with ZSM-5 zeolite, the ZSM-5/ZSM-57 composite zeolite with lower ZSM-5 content showed higher catalytic activity and higher selectivity for ethylene and propylene because of its enhanced acidic strength and increased acid amount. ZSM-57 has small pores in the composite zeolite and this is beneficial in the shape-selective reaction of ethylene and propylene. On the contrary, the ZSM-5/ ZSM-57 composite zeolite with higher ZSM-5 content exhibited higher selectivity for benzene and toluene. This probably results from the pore structure and the structure matching property of the ZSM-5/ZSM-57 composite zeolite, which favors the aromatization of mixed Ca hydrocarbons.