沉淀方法对Ru/CeO_2氨合成催化剂催化性能的影响

Effect of Precipitation Methods on Catalytic Activity of Ru/CeO_2 Catalyst for Ammonia Synthesis

采用沉淀法制备了Ru/CeO2氨合成催化剂,并运用N2物理吸附、X射线衍射、X射线荧光光谱、CO吸附和H2程序升温还原等技术对其进行了表征,考察了沉淀时反应液的并流、反加、正加以及沉积-沉淀对所制备的Ru/CeO2催化剂氨合成性能的影响.结果表明,不同制备方法所得到的催化剂,其氯残留量和载体的还原性能都存在明显的差别,最终影响了催化剂的氨合成活性,其中采用正加法制备的催化剂上氯残留量少,载体易还原,因而催化活性最高,在10MPa,10000h-1,450oC反应时,NH3浓度达到11.9%.

The Ru/CeO2 catalyst was prepared by precipitation methods, including normal precipitation, reverse precipitation, parallel flow precipitation, and deposition-precipitation. The obtained catalysts were characterized by N2 adsorption-desorption, X-ray diffraction, H2 temperature-programmed reduction, CO chemisorption, and X-ray fluorescence spectroscopy. The results showed that the ammonia synthesis activity of the Ru/CeO2 catalyst prepared by normal precipitation was 11.9% at 10 MPa, 10000 h^-1, and 450 ℃, which was higher than those obtained by other methods. The residual chloride content in this catalyst was much lower and its cerium was easier to be reduced. Thus the activity of the catalyst prepared using normal precipitation was high.