Wang Junwen, Gao Xiaofeng, Chen Guoliang, Ding Chuanmin
College of Chemistry & Chemical Engineering, Taiyuan University of Technology Taiyuan 030024 P. R. China
School of Chemistry and Chemical Engineering, Liaocheng University Liaocheng 252000 P. R. China.
RSC Adv. 2019 Sep 10;9(49):28451-28459. doi: 10.1039/c9ra05513d. eCollection 2019 Sep 9.
For an industrial-scale catalytic process with a fixed or packed bed reactor, powder catalysts are not suitable because they may block the reaction pipe and increase the pressure of the reactor. Therefore, catalyst molding is essential for the industrial application of a catalyst. During the catalyst molding, binders are employed as indispensable additives that can achieve the mechanical strength requirements for industrial applications. However, the addition of binders may cover the activity sites of the catalyst and suppress the mass transfer of the reactants and products. So, traditional processes of catalyst molding significantly affect the catalytic performance. In this study, we proposed a vapor-phase-treatment to synthesize a pure shaped ZSM-5 zeolite with the re-crystallization of the binder incorporated silica sol and aluminum nitrate, which were converted into a part of ZSM-5 on a commercial H-ZSM-5 zeolite substrate. Subsequently, the shaped ZSM-5 catalyst was evaluated using the catalytic conversion of methanol to an aromatic (MTA reaction). The results showed that compared to the EPHZ catalyst, the SPHZ catalyst exhibited a long lifetime with a relatively high shape selectivity for methanol and aromatics. To rationalize these results and establish a structure-activity relationship, the zeolite catalysts were thoroughly characterized by XRD, NH-TPD, FT-IR, N adsorption, TG, SEM, TEM, ICP and Al MAS-NMR. The results demonstrated that an interesting intra-particle pore structure was formed within the monoliths of the SPHZ catalyst. Moreover, the superior catalytic performance obtained for SPHZ may have also been due to the broad acid strength distribution and the conversion of the silicon aluminum adhesive agent to zeolite crystals.
对于使用固定床或填充床反应器的工业规模催化过程，粉末催化剂不合适，因为它们可能会堵塞反应管并增加反应器压力。因此，催化剂成型对于催化剂的工业应用至关重要。在催化剂成型过程中，粘结剂作为不可或缺的添加剂使用，可满足工业应用的机械强度要求。然而，粘结剂的添加可能会覆盖催化剂的活性位点并抑制反应物和产物的传质。所以，传统的催化剂成型工艺会显著影响催化性能。在本研究中，我们提出了一种气相处理方法，通过粘结剂结合的硅溶胶和硝酸铝的重结晶来合成纯成型ZSM-5沸石，它们在商业H-ZSM-5沸石载体上转化为ZSM-5的一部分。随后，使用甲醇催化转化为芳烃（MTA反应）对成型ZSM-5催化剂进行了评估。结果表明，与EPHZ催化剂相比，SPHZ催化剂具有较长的寿命，对甲醇和芳烃具有相对较高的形状选择性。为了合理解释这些结果并建立结构-活性关系，通过XRD、NH-TPD、FT-IR、N吸附、TG、SEM、TEM、ICP和Al MAS-NMR对沸石催化剂进行了全面表征。结果表明，在SPHZ催化剂的整体结构中形成了有趣的颗粒内孔结构。此外，SPHZ获得的优异催化性能可能还归因于宽泛的酸强度分布以及硅铝粘合剂向沸石晶体的转化。
