Effect of La₂O₃ addition on the catalytic performance of Rh/SiO₂ for CO hydrogenation

SiO₂ and La₂O₃-SiO₂ were synthesized via sol-gel method and used as support to prepared Rh-La or Rh doped catalysts by iso-volumic impregnation. Effects of doping mode of La on the catalytic performance of Rh/SiO₂ for CO hydrogenation are investigated detailedly. The results reveal that the addition of La can improve the dispersion of Rh and increase Rh⁺ centers, which can effectively inhibit the formation of CO₂ and improve the selectivity of oxygenates. Furthermore, the doping mode of La can affect the interaction between La and Rh. A strong La-Rh interaction is achieved over the 2Rh-5La₂O₃/SiO₂ catalyst prepared by co-impregnation of Rh and La with SiO₂ support. The strong interaction between La and Rh can efficiently weaken the Rh-CO bonds and enhance the CO insertion reaction in the reaction process, which makes the product dominated by C₂₊ oxygenates. The 2Rh/5La₂O₃-SiO₂ catalyst prepared via La₂O₃-SiO₂ composite support exhibits a weak La-Rh interaction, and methanol, ethanol and other low-carbon alcohols are obtained as the main products.