Insights into the size and structural effects of zeolitic supports on gaseous toluene oxidation over MnOx/HZSM-5 catalysts
Insights into the size and structural effects of zeolitic supports on gaseous toluene oxidation over MnOx/HZSM-5 catalysts
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深入了解沸石载体的尺寸和结构对 MnOx/HZSM-5 催化剂气态甲苯氧化的影响
DOI：
10.1016/j.apsusc.2019.04.201
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发表时间：
2019
影响因子：
6.7
通讯作者：
Li Xuebing
中科院分区：
文献类型：
--
作者：
Zhang Chuanhui;Wang Chao;Huang He;Zeng Kai;Wang Zhong;Jia Hong peng;Li Xuebing
分别合成了具有微纳晶和空心结构的HZSM-5分子筛，制备了MnOx/HZSM-5负载型催化剂，并通过大量的表征和实验评价，研究了分子筛载体的大小和结构对MnOx/HZSM-5催化剂的理化性能和甲苯氧化性能的影响。得益于纳米级空心HZSM-5（即H-Z5）沸石的高表面积和分层孔隙率，所得到的mnox催化剂（即MnOx/H-Z5）具有良好的表面分散性，同时大大增强了其低温还原性，表面氧迁移率和更丰富的表面Mn4+阳离子。这些理化特性的优越性与MnOx/H-Z5对甲苯的最佳催化活性和良好的催化耐久性有关。焦炭分析结果表明，MnOx/H-Z5具有较高的抗焦炭能力，这是由于沸石表面高度分散的MnOx纳米颗粒有效地促进了甲苯和其他有机物的氧化破坏。基于原位DRIFTS实验结果，提出了一种可能的反应机理，确定了苯甲醛、苯甲酸和环酸酐等关键中间体及其转化途径。mnox纳米颗粒气相氧活化产生的表面活性氧在空气环境下将焦炭前驱体氧化消除为二氧化碳和水的过程中起着至关重要的作用。
HZSM-5 zeolites with micro/nano crystallites and hollow structure were respectively synthesized for the preparation of supported MnOxcatalysts, and the size and structural effects of zeolitic supports on both the physicochemical properties and toluene oxidation performances of MnOx/HZSM-5 catalysts were extensively investigated by numerous characterizations and experimental evaluation. Beneficially from the higher surface area and hierarchical porosity of nanoscale hollow HZSM-5 (namely as H-Z5) zeolite, good surface dispersion of MnOxnanoparticles was acquired over the resultant supported MnOxcatalyst (namely as MnOx/H-Z5), simultaneously achieving great enhancement of its low-temperature reducibility, surface oxygen mobility and more plentiful surface Mn4+cations. The superiority in these physicochemical characteristics was reasonably correlated with the optimum catalytic activity and good catalytic durability for toluene oxidation over MnOx/H-Z5. The results of coke analysis indicated that MnOx/H-Z5 exhibited relatively higher coke-resistant ability since the highly dispersed MnOxnanoparticles on zeolite surface effectively promoted the oxidative destruction of toluene and other organics species. A possible reaction mechanism was proposed based on the in situ DRIFTS results, where the key reaction intermediates including benzaldehyde, benzoic acid and cyclic anhydride and the relevant conversion pathways were determined. The surface active oxygen originating from gas-phase oxygen activation by MnOxnanoparticles played a crucial role in the oxidative elimination of coke precursors into carbon dioxide and water under air atmosphere.