Abstract:

ZSM-5/EU-1 co-crystalline zeolites were designed by two-stage synthesis technique with surfactants of diquaternary ammonium and hexamethonium bromide, that both surfactants displayed similar structure-directing effect. By adjusting pre-crystallization process, crystal coexistence of two zeolites was achieved and various ZSM-5/EU-1 co-crystalline zeolites were prepared with controllable phase proportions. Study on gel composition at each stage showed that gel composition at the first stage, especially the template concentration, had pronounced effect on phase proportions for the resulting ZSM-5/EU-1 co-crystalline zeolites. Compared to the mechanical mixture and pure-phase counterpart, ZSM-5/EU-1 co-crystalline zeolites had the largest BET surface area and the highest pore volume, especially for external surface area and mesopore volume. In catalytic cracking n-hexane reaction, ZSM-5/EU-1 co-crystalline zeolite with 39% EU-1 phase content exhibited the most excellent stability of reaction activity and the highest selectivity to light olefins, in particular propylene. At reaction time of 120 min, ZSM-5/EU-1 of 39% EU-1 had the selectivity of light olefins 10.7 percentage points higher than the mechanical mixture of 39% EU-1 and pure ZSM-5 zeolite, the propylene selectivity 8.5 and 9.1 percentage points as well as the P/E ratio 0.42 and 0.46 higher than the mechanical mixture of 39% EU-1 and pure ZSM-5 zeolite, respectively.

Key words: molecular sieves, alkane, catalysis, ZSM-5/EU-1 co-crystalline zeolite, controllable synthesis, catalytic cracking, light olefins

摘要：

采用双模板剂两步晶化法设计合成了ZSM-5/EU-1共生分子筛，通过调整预晶化过程，实现了两种分子筛的共生和晶相比例的可控调变。研究两段凝胶组成的影响发现，第一段凝胶组成，尤其是模板剂浓度对所得共生样品晶相比例具有较大影响。与机械混合和纯相样品相比，ZSM-5/EU-1共生分子筛表现出最大的BET表面积和孔体积尤其是外表面积和介孔体积。而且EU-1相含量为39%的ZSM-5/EU-1共生分子筛在正己烷催化裂解制低碳烯烃反应中表现出比机械混合样品和ZSM-5分子筛更高的反应活性稳定性和低碳烯烃选择性，尤其是丙烯选择性。在反应120 min时，该共生分子筛上低碳烯烃选择性比相同EU-1相含量机械混合样品和ZSM-5分子筛均高出约10.7个百分点，丙烯选择性分别高出8.5和9.1个百分点，P/E比分别高出0.42和0.46。

关键词: 分子筛, 烷烃, 催化(作用), ZSM-5/EU-1共生分子筛, 可控合成, 催化裂解, 低碳烯烃