Rh Supported on LaPO4/SiO2 Nanocomposites as Thermally Stable Catalysts for TWC Applications

Abstract

Hydrothermally synthesized LaPO4/SiO2 nanocomposites were investigated as thermally stable support materials for Rh catalysts. The nanocomposites were composed of macroporous SiO2 and highly dispersed columnar LaPO4 crystallites of approximately 20 nm in thickness and 100 nm in length, the surface of which anchored Rh nanoparticles via Rh–O–P interfacial bonding. The microstructure was useful to prevent agglomeration and sintering of LaPO4 during high-temperature thermal aging under both oxidizing and reducing atmospheres. The Rh catalyst supported on the LaPO4/SiO2 composite exhibited higher catalytic activities for simulated NO–CO–C3H6–O2 reactions over a wide Rh loading range (0.01–0.4 wt%), compared to those of Rh catalysts supported on the individual components (LaPO4 and SiO2), and on ZrO2, which is widely used as a support for Rh in commercial three-way catalysts. Enhanced catalytic activities for elementary CO–O2, CO–H2O, and CO–NO reactions were achieved while maintaining the activity toward C3H6 as an advanced feature of phosphate supports.