Understanding the Deactivation Phenomena of Small-Pore Mo/H-SSZ-13 during Methane Dehydroaromatisation.
Understanding the Deactivation Phenomena of Small-Pore Mo/H-SSZ-13 during Methane Dehydroaromatisation.
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DOI：
10.3390/molecules25215048
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发表时间：
2020-10-30
期刊：
影响因子：
--
通讯作者：
Beale AM
中科院分区：
文献类型：
--
作者：
Agote-Arán M;Kroner AB;Wragg DS;Sławiński WA;Briceno M;Islam HU;Sazanovich IV;Rivas ME;Smith AWJ;Collier P;Lezcano-González I;Beale AM
小孔沸石在许多催化反应中显示出巨大的潜力。虽然含钼中孔沸石已被广泛研究用于甲烷脱氢芳构化（MDA），但由于催化剂的快速失活，小孔载体的使用引起的关注有限。该工作通过原位X射线吸收光谱（XAS）、原位同步加速器粉末衍射（SPD）和电子显微镜研究了小孔Mo/H-SSZ-13在催化剂制备和反应过程中的结构；然后将结果与中孔Mo/H-ZSM-5进行比较。而SPD表明，在催化剂制备过程中，部分MoOx锚定在孔内，Mo分散和随后的离子交换在小孔催化剂中效果较差，导致介孔和Al2(MOO4)3颗粒的形成。与Mo/H-ZSM-5不同，Mo/H-SSZ-13中的部分Mo物种在MDA过程中完全还原为Mo0，而废催化剂的表征表明所形成的碳沉积物的性质也存在差异。因此，不同的Mo形态和小孔沸石的低性能可归因于煅烧过程中中孔的形成以及与分散良好的Mo-oxo位点的无效离子交换。这些结果为优化合成路线以探索小孔拓扑的潜力开辟了空间。
Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoOx anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al2(MOO4)3 particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo0 during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies.
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影响因子：
3.7
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