Jia Yanming, Shi Qinghua, Wang Junwen, Ding Chuanmin, Zhang Kan
Department of Chemistry, Taiyuan Normal University PO Box 030619 Jinzhong China
College of Chemistry and Chemical Engineering, Taiyuan University of Technology Taiyuan 030024 China.
RSC Adv. 2020 Aug 10;10(50):29618-29626. doi: 10.1039/d0ra06040b.
Hierarchical nano-ZSM-5 zeolites (Z5-) with different grain sizes were synthesized by varying amounts of 3-glycidoxypropyltrimethoxysilane (KH-560) in the hydrothermal synthesis strategy. Moreover, the conventional ZSM-5zeolite(Z5), which was prepared without KH-560, was used as the reference sample. The crystalline phases, morphologies, porous characteristics, Si/Al molar ratios and acidic properties of all fresh catalysts were characterized using the X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), N adsorption-desorption, inductively coupled plasma atomic emission spectroscopy (ICP) and temperature programmed desorption of ammonia (NH-TPD) techniques. Results show that the grain size and strong acid amount of zeolite decreased with the increasing amount of KH-560. The micropore surface areas and the corresponding volume of Z5- changed less compared with Z5. Consequently, the high shape-selectivity of zeolite was preserved well under the addition of KH-560. However, the mesopore surface areas and the corresponding volume increased significantly with the increasing amount of KH-560. Benefiting from the abundant hierarchical structure, the Z5- catalysts exhibited a larger coke capacity than the Z5 catalyst. The coke depositions of all the deactivated catalysts were characterized by the thermogravimetric technique (TG), and the results are indicative of the decreased average rate of coke deposition with an increasing amount of KH-560, which could result from the gradually reduced strong acid amount and the nano-sized crystallites. The catalytic performance of methanol-to-aromatics (MTA) indicates that the Z5-0.12 catalyst exhibited higher catalytic activity and selectivity of BTX as the reaction was prolonged, which could result from the synergistic effect among the proper strong acid amount, the smaller zeolite grain size, and the abundant hierarchical structure.
通过在水热合成策略中改变3-缩水甘油氧基丙基三甲氧基硅烷（KH-560）的用量，合成了具有不同晶粒尺寸的分级纳米ZSM-5沸石（Z5-）。此外，将未使用KH-560制备的传统ZSM-5沸石（Z5）用作参考样品。使用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、扫描电子显微镜（SEM）、N吸附-脱附、电感耦合等离子体原子发射光谱（ICP）和氨程序升温脱附（NH-TPD）技术对所有新鲜催化剂的晶相、形貌、多孔特性、Si/Al摩尔比和酸性进行了表征。结果表明，随着KH-560用量的增加，沸石的晶粒尺寸和强酸量减小。与Z5相比，Z5-的微孔表面积和相应体积变化较小。因此，在添加KH-560的情况下，沸石的高形状选择性得到了很好的保留。然而，随着KH-560用量的增加，中孔表面积和相应体积显著增加。得益于丰富的分级结构，Z5-催化剂表现出比Z5催化剂更大的积炭容量。通过热重技术（TG）对所有失活催化剂的积炭进行了表征，结果表明随着KH-560用量的增加，积炭平均速率降低，这可能是由于强酸量逐渐减少和纳米尺寸微晶所致。甲醇制芳烃（MTA）的催化性能表明，随着反应时间的延长，Z5-0.12催化剂表现出更高的催化活性和对BTX的选择性，这可能是由于适当的强酸量、较小的沸石晶粒尺寸和丰富的分级结构之间的协同作用。
