Methane–propane coaromatization (MPCA) upgrades two abundant and inexpensive light alkanes into value-added aromatic products. While Ga-loaded MFI zeolites represent by far the most promising catalysts for MPCA reaction, they often contain a sizable portion of Ga species at the external surface of zeolites, which are remote from the Brønsted acid sites (BAS) within MFI pores and thus inefficient for MPCA. Here, we show that Ga can be introduced into MFI pores at fairly high loadings via a simple cocrystallization approach, yielding catalysts possessing well-dispersed Ga sites predominantly residing inside the pores and framework. Adjacency between Ga and BAS within the constraints of MFI channels makes these (Ga, Al)-H-MFI catalysts more active toward methane and propane activation and more selective toward aromatics compared to the Ga/MFI counterparts prepared by impregnation that inevitably leaves a large fraction of Ga at the external surface (i.e., without confinement and few adjacent BAS). Further, the effects of the Si/Al ratio on MPCA performance have been investigated for (Ga, Al)-H-MFI catalysts. Due to the multifold roles of BAS in the overall reaction sequence, an increased BAS concentration generally results in higher propane conversion and productivity of aromatics together with lower net methane conversion and severer coking.

中文翻译：

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具有高度分散的 Ga位点和近端质子位点的 （Ga， Al）-H-MFI 催化剂可实现甲烷-丙烷共芳构化


甲烷-丙烷共芳构化 （MPCA） 将两种丰富且廉价的轻质烷烃升级为增值芳烃产品。虽然负载 Ga的 MFI 分子筛是迄今为止最有前途的 MPCA 反应催化剂，但它们通常在分子筛的外表面包含相当大一部分 Ga 物质，这些物质远离 MFI 孔内的 Brønsted 酸位 （BAS），因此对 MPCA 效率低下。在这里，我们表明可以通过简单的共结晶方法以相当高的负载量将 Ga 引入 MFI 孔中，从而产生具有主要位于孔和框架内的分散良好的 Ga 位点的催化剂。在 MFI 通道的约束下，Ga 和 BAS 之间的邻接使得这些 （Ga， Al）-H-MFI 催化剂对甲烷和丙烷活化更具活性，与通过浸渍制备的 Ga/MFI 对应物相比，对芳烃更具选择性，而浸渍制备的 Ga/MFI 对应物不可避免地在外表面留下大量 Ga（即，没有限制且几乎没有相邻的 BAS）。此外，还研究了 （Ga， Al）-H-MFI 催化剂的 Si/Al 比对 MPCA 性能的影响。由于 BAS 在整个反应序列中具有多重作用，因此 BAS 浓度的增加通常会导致更高的丙烷转化率和芳烃的生产率，同时降低净甲烷转化率和更严重的焦化。