Halloysite Nanotube Supported Ru Nanocatalysts Synthesized by the Inclusion of Preformed Ru Nanoparticles for Preferential Oxidation of CO in H2-Rich Atmosphere

Abstract

The small-sized and well-dispersed Ru nanocatalysts supported on halloysite nanotubes (HNTs) were synthesized by the inclusion of preformed Ru nanoparticles onto HNTs (Ru NPs/HNTs) and employed for the preferential oxidation of CO in H2-rich atmosphere (PROX). Polyol reduction was adopted to prepare Ru nanoparticles, and the synthesis conditions affected the morphology of the resulting nanoparticles. The catalysis results show that the Ru NPs/HNTs present significantly higher CO conversion and CO2 selectivity than the catalyst prepared by traditional wet impregnation. RuCl3 is a better Ru precursor than Ru(acac)3 for synthesizing Ru nanoparticles with higher catalytic reactivity. The catalytic performance of Ru NPs/HNTs can be further enhanced by the reduction pretreatment due to the removal of polyvinylpyrrolidone (PVP) capping on the surface of Ru nanoparticles, and this enhancement is more significant with reduction at 400 °C than at 200 °C. Finally, the characterizations on the used catalysts indicate that the morphology of Ru nanoparticles is maintained after PROX reaction; slight growth of particle size is observed with 200 °C reduction pretreatment, yet Ru nanoparticles lose their original size and shape with 400 °C reduction.