Novel preparation method for supported metal catalysts with high resistance to sintering

1.提出了一种新型的油包水微乳液法制备负载型金属催化剂的新方法--微乳化法。在这种方法中，Rh粒子部分嵌入到SiO_2载体中，因为SiO_2载体是在反胶束中合成之前在Rh前驱体粒子周围的TEOS水解形成的。本文研究了不同制备方法(ME法、溶胶-凝胶法和浸渍法制备)制备的Pt/Al_2O_3催化剂中铂的烧结行为。与IMP法制备的催化剂相比，ME法和Sol-Gel法制备的Pt/Al_2O_3催化剂具有更高的抗烧结性，这是因为载体中嵌入了铂颗粒。此外，在156 Mpa压力下压制催化剂可提高催化剂的抗铂颗粒烧结性。在空气流量为70 0℃、时间为12h的耐久试验中，采用微乳液加压制备的催化剂，压制的ME催化剂比溶胶凝胶法和浸渍法制备的催化剂具有更强的抗铂颗粒烧结的能力。压片式ME催化剂在NO-CO反应中表现出较高的活性，并保持了较高的活性。在特定的微乳液体系中，我们成功地合成了包覆在纳米级SiO_2层上的Rh纳米粒子。比较了包覆SiO_2的Rh催化剂与ME法、Sol-Gel法和IMP法制备的催化剂的热稳定性和CO-CO反应活性。在SiO_2包覆的Rh催化剂中，所有的Rh颗粒都被SiO_2层覆盖，即使在900℃的热处理12h后，Rh颗粒仍然很小，这表明SiO_2包覆的Rh催化剂中的Rh粒子的迁移受到SiO_2层的抑制，因此具有最高的抗烧结性。结果表明，该催化剂在900℃、12h的热处理条件下具有最高的CO还原NO活性。

1. We have developed a novel preparation method for supported metal catalysts using water-in-oil microemulsion, an ME method. In this method, Rh particles are partially embedded in SiO_2 supports because the SiO_2 supports are formed by hydrolysis of TEOS around the Rh precursor particle before being synthesized in the reverse micelle. In this work, sintering behaviors of Pt particles were investigated in Pt/Al2O3 catalysts prepared by different preparation method (ME, sol-gel and impregnation method (IMP). Pt/Al2O3 catalysts prepared by ME and sol-gel method possessed high resistance to sintering compared with the catalyst prepared by IMP method, because Pt particles were embedded in the support. Furthermore, resistance to the sintering of Pt particles was improved by pressing the catalysts at 156 MPa. For the endurance test under air flow at 700 ℃ for 12 h, the catalyst prepared using microemulsion and then pressed, the pressed ME catalyst, had greater resistance to sintering of Pt particles than the sol-gel and impregnation catalysts. The pressed ME catalyst exhibited higher activity in NO-CO reaction and maintain the high activity.2. We successfully synthesized Rh nanoparticles wholly coated by a nanometer-scale SiO2 layer ring a specific microemulsion system. The thermal stability and the catalytic activity of CO-CO reaction of SiO2-coated Rh catalyst were compared with those of the catalysts prepared by ME, sol-gel and IMP methods. In the SiO2-coated Rh catalyst, all the Rh particles were covered by the SIO2 layer and remained small even after the thermal treatment at 900 ℃ for 12 h. It is concluded that migration of Rh particles of the SiO2-coated Rh catalyst was restrained by the SiO2 layer, resulting in the highest resistance to sintering. As a result, this catalyst had the highest activity in NO reduction by CO after thermal treatment at 900 ℃ for 12 h.