Controllable synthesis of gallium-containing MFI zeolite for bifunctionally catalyzing methanol aromatization
Controllable synthesis of gallium-containing MFI zeolite for bifunctionally catalyzing methanol aromatization
复制标题
DOI：
10.1016/j.micromeso.2023.112877
复制
发表时间：
2023-10
影响因子：
5.2
通讯作者：
Jian Song;Qing Miao;Yunpeng Lv;Zhipeng Wang;Yu Li;Liyan Wang;Mei Dong;Pengfei Wang;
中科院分区：
文献类型：
--
作者：
Jian Song;Qing Miao;Yunpeng Lv;Zhipeng Wang;Yu Li;Liyan Wang;Mei Dong;Pengfei Wang;
以胶态silicalite-1为晶种，水热合成了晶粒大小可控的Ga-MFI分子筛，并评价了其对甲醇制芳烃（MTA）反应的催化性能。结果表明，随着晶种加入量的增加，制得的Ga-MFI分子筛晶粒变小。小尺寸的短孔道Ga-MFI分子筛由于更有利于芳烃产物的向外扩散，因此具有更好的抗结焦性能，从而延长了催化剂的使用寿命。此外，通过浸渍镓物种到Ga-MFI沸石中可以进一步提高稳定性，但略微牺牲其芳烃选择性。Ga在沸石中不同位置的存在形式对MTA起着不同的作用。四面体骨架Ga 3+的弱本征质子酸性抑制了氢转移反应生成低碳烷烃，而非骨架Ga物种特别是纳米Ga 2 O 3促进了脱氢环化反应。强布朗斯特酸和弱刘易斯酸中心之间的协同作用有助于优异的芳烃产率。
Ga-MFI zeolites with controllable crystal sizes were hydrothermally synthesized by using colloidal silicalite-1 as seed crystals and their catalytic performances for methanol-to-aromatics (MTA) were evaluated. It was found that the crystal size of as-made Ga-MFI zeolite became small with the adding amounts of seed crystals. Small-sized Ga-MFI zeolite with short channels shows much better coking-resistance and thus longer catalytic lifetime owning to its more favorable outward diffusion of aromatic products. In addition, the stability could be further improved by impregnating gallium species into Ga-MFI zeolite, but which slightly sacrificed its aromatic selectivity. The Ga species with different locations in zeolite play distinct roles in MTA. The weak intrinsic protonic acidity from tetrahedral framework Ga3+could suppress hydrogen transfer reactions for light alkane formation while non-framework gallium species especially Ga2O3nanoparticles promoted the dehydrocyclization process. The synergy between the strong Brønsted and weak Lewis acid sites contributes to the excellent aromatic yield.