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

1. 本文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方法——ME法。在此方法中，Rh颗粒部分嵌入SiO_2载体中，因为SiO_2载体是在Rh前驱体颗粒周围通过TEOS水解形成的，然后在反胶团中合成。本文研究了Pt颗粒在不同制备方法（ME法、溶胶-凝胶法和浸渍法）制备的Pt/Al2O3催化剂中的烧结行为。与IMP法制备的Pt/Al2O3催化剂相比，ME法制备的Pt/Al2O3催化剂具有较高的抗烧结性能，因为Pt颗粒嵌入在载体中。此外，在156 MPa的压力下，催化剂的抗烧结性能得到了提高。在700℃空气流动下12 h的耐久性试验中，用微乳液制备的经压制的ME催化剂比溶胶-凝胶和浸渍催化剂具有更大的抗Pt颗粒烧结性能。压制后的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。我们成功地在特定的微乳液体系中合成了完全包被纳米级SiO2层的Rh纳米颗粒。比较了sio2包覆Rh催化剂与ME法、溶胶-凝胶法和IMP法制备的催化剂的热稳定性和CO-CO反应的催化活性。在SIO2包覆的Rh催化剂中，所有的Rh颗粒都被SIO2层覆盖，即使在900℃热处理12 h后仍保持较小的体积。由此可见，SIO2层抑制了SIO2包覆的Rh催化剂中Rh颗粒的迁移，使其具有最高的抗烧结性能。结果表明，该催化剂在900℃热处理12 h后，CO还原NO的活性最高。

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.