Synthesis of Nano EU-1 Zeolite and Its Catalytic Performance in Toluene Methylation
TONG Weiyi
State Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208, China
摘要 采用溴化六甲双铵（HMBr2）和质量分数25%的氢氧化六甲双铵[HM(OH)2]水溶液作为复合模板剂，水热合成得到高结晶度的纳米EU-1分子筛。通过X射线衍射（XRD）、固态27Al核磁共振（27Al MAS NMR）、扫描电子显微镜（SEM）、N2吸附/脱附和NH3程序升温脱附（NH3-TPD）对样品进行了表征，结果表明：与单一HMBr2模板剂相比，复合模板剂协同作用合成得到的EU-1分子筛骨架结晶性更好；不同于常规梭子状聚集体，所得产品形貌呈现高度均匀分散的纳米块并自组装盘状交错，具有更大的微孔比表面积；同时，该样品的中强酸活性位更多。相比商业ZSM-5分子筛，该纳米EU-1分子筛在催化甲苯与甲醇的烷基化反应中，甲苯转化率及产物二甲苯收率均出现明显提升，同时二甲苯选择性维持较高水平。研究表明，甲苯甲基化的反应性能受到分子筛晶体孔结构和酸分布的双重影响，EU-1分子筛是理想的甲苯甲基化反应催化材料。
Abstract：Nano EU-1 molecular-sieve/zeolite with high crystallinity was successfully synthesized by using hexamethyldiammonium bromide (HMBr2) and hexamethyldiammonium hydroxide [HM(OH)2] aqueous solution with mass fraction of 25% as mixed organic structure-directing agents (OSDAs/templates). The samples were characterized by X-ray diffraction (XRD), 27Al MAS nuclear magnetic resonance (27Al MAS NMR), scanning electron microscopy (SEM), N2 adsorption-desorption and NH3 temperature programmed desorption (NH3-TPD). The results showed that the crystallinity of EU-1 zeolites synthesized by the synergistic action of the mixed OSDAs was better than that by the only HMBr2 template. Different from the conventional shuttle like aggregates, the morphology of the obtained EU-1 zeolites (S1) presented highly uniformly dispersed nano-blocks and self-assembled plate-like morphology, with a larger microporous specific surface area. Above these, there were more medium/strong acid sites in these EU-1 samples. The conversion of toluene and the yield of xylene were significantly improved in the alkylation of toluene and methanol catalyzed by the as-synthesized EU-1 zeolites, and maintain a high selectivity of xylene products at the same time, compared with the commercial ZSM-5 zeolite. All these results showed that the reaction performance of toluene methylation was affected both by the pore-structure and acid-distribution of zeolites. Hence, EU-1 zeolite would be an ideal catalytic material for toluene methylation.
TONG Weiyi. Synthesis of Nano EU-1 Zeolite and Its Catalytic Performance in Toluene Methylation [J]. Chemical Reaction Engineering and Technology, 2022, 38(1): 48-55.
