The hydrodemethylation reaction of 3,4‐xylenol on micro/mesoporous catalysts with active component TiO₂ was studied. TiO₂/YM‐m and TiO₂/YM‐c micro/mesoporous materials were, respectively, derived by loading TiO₂ with the composition and mechanical mixing of Al‐MCM‐41 and HY zeolite. The effect of the bifunctional catalysts on the catalytic performance of hydroxymethylation of xylenol before and after the introduction of Al‐MCM‐41 into HY was investigated in this study. Compared with TiO₂/Y catalyst, TiO₂/MCM‐41, TiO₂/YM‐m, and TiO₂/YM‐c have higher selective dealkylation products, especially the selectivity of cresol. This is attributed to the addition of Al‐MCM‐41 mesoporous molecular sieve to eliminate diffusion limitation. Compared with TiO₂/YM‐m catalyst, the TiO₂/YM‐c composite with Al‐MCM‐41 coated structure grown on the surface of HY crystals has better catalytic conversion activity and ability to inhibit secondary reactions. This is because of the existence of the special “coating” of HY zeolite, which eliminates the diffusion limitation and prevents the product and the reaction intermediate from entering the micropores for multiple reactions, thereby reducing the occurrence of side reactions. Meanwhile, TiO₂/YM‐c catalyst has the best demethylation performance under the optimal reaction conditions, the conversion of 3,4‐xylenol, the selectivity to phenol, and m‐cresol were 52.15%, 62.17%, and 36.32%, respectively. And the TiO₂/YM‐c catalyst has good stability within 80 h of reaction.

中文翻译：

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微/中量含TiO2的双功能催化剂上的二甲苯酚羟甲基化：Y沸石与MCM-41结合的影响

研究了3,4-二甲苯酚在具有活性成分TiO _2的微/介孔催化剂上的加氢脱甲基反应。TiO ₂ / YM‐m和TiO ₂ / YM‐c微/介孔材料分别是通过向TiO _2中加入Al‐MCM‐41和HY沸石的成分并进行机械混合而得到的。在这项研究中研究了双功能催化剂对Al-MCM-41引入HY之前和之后对二甲苯酚羟甲基化催化性能的影响。与TiO ₂ / Y催化剂相比，TiO ₂ / MCM‐41，TiO ₂ / YM‐m和TiO ₂/ YM-c具有更高的选择性脱烷基产物，尤其是甲酚的选择性。这归因于添加了Al-MCM-41中孔分子筛以消除扩散限制。与TiO ₂ / YM-m催化剂相比，在HY晶体表面生长有Al-MCM-41涂层结构的TiO ₂ / YM-c复合材料具有更好的催化转化活性和抑制二次反应的能力。这是因为存在HY沸石的特殊“涂层”，它消除了扩散限制，并防止产物和反应中间体进入微孔进行多次反应，从而减少了副反应的发生。同时，TiO ₂/ YM-c催化剂在最佳反应条件下具有最佳的脱甲基性能，3,4-二甲苯酚的转化率，对苯酚的选择性和间甲酚的选择性分别为52.15％，62.17％和36.32％。TiO ₂ / YM-c催化剂在反应80小时内具有良好的稳定性。