Cai Lihua, Han Shanlei, Xu Wenlong, Chen Si, Shi Xianxian, Lu Junling
Key Laboratory of Precision and Intelligent Chemistry, School of Chemistry and Materials Science, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), University of Science and Technology of China, Hefei, 230026, China.
Angew Chem Int Ed Engl. 2024 Jul 8;63(28):e202404398. doi: 10.1002/anie.202404398. Epub 2024 Jun 11.
Catalyst deactivation by sintering and coking is a long-standing issue in metal-catalyzed harsh high-temperature hydrocarbon reactions. Ultrathin oxide coatings of metal nanocatalysts have recently appeared attractive to address this issue, while the porosity of the overlayer is difficult to control to preserve the accessibility of embedded metal nanoparticles, thus often leading to a large decrease in activity. Here, we report that a nanometer-thick alumina coating of MgAlO-supported metal catalysts followed by high-temperature reduction can transform a nonporous amorphous alumina overlayer into a porous MgAlO crystalline spinel structure with a pore size of 2-3 nm and weakened acidity. The high porosity stems from the restrained Mg migration from the MgAlO support to the alumina overlayer through solid-state reactions at high temperatures. The resulting Ni/MgAlO and Pt/MgAlO catalysts with a porous crystalline MgAlO overlayer achieved remarkably high stability while preserving much higher activity than the corresponding alumina-coated Ni and Pt catalysts on MgO and AlO supports in the reactions of dry reforming of methane and propane dehydrogenation, respectively.
在金属催化的苛刻高温烃类反应中，烧结和积炭导致的催化剂失活是一个长期存在的问题。金属纳米催化剂的超薄氧化物涂层最近在解决这个问题方面显得很有吸引力，然而，覆盖层的孔隙率很难控制以保持嵌入的金属纳米颗粒的可及性，因此常常导致活性大幅下降。在此，我们报道，对MgAlO负载的金属催化剂进行纳米厚的氧化铝涂层处理，然后进行高温还原，可以将无孔的非晶态氧化铝覆盖层转变为孔径为2 - 3纳米且酸度减弱的多孔MgAlO晶体尖晶石结构。高孔隙率源于高温下通过固态反应抑制了Mg从MgAlO载体迁移到氧化铝覆盖层。在甲烷干重整和丙烷脱氢反应中，所得具有多孔晶体MgAlO覆盖层的Ni/MgAlO和Pt/MgAlO催化剂分别比在MgO和AlO载体上相应的氧化铝涂层Ni和Pt催化剂具有更高的活性，同时实现了显著的高稳定性。
