沉淀剂对Ru/MgO-CeO2氨合成催化剂催化性能的影响

以K<,2>RuO<,4>为钌前驱体,通过共沉淀法制备了Ru/MgO-CeO<,2>氨合成催化剂.考察了5种不同沉淀剂对Ru/MgO-CeO<,2>催化剂的结构和性能的影响,并运用X射线衍射(XRD)、CO吸附、N<,2>物理吸附和H<,2>程序升温还原(H<,2>-TPR)等技术对催化剂进行了表征,讨论了沉淀剂对氨合...

Effects of precipitants on catalytic activity of Ru/MgO-CeO2 for ammonia synthesis

Ru/MgO-CeO2 catalysts for ammonia synthesis were prepared by co-precipitation method using five precipitants, NH4 HCO3, （ NH4 ）2 CO3, KOH, KHCO3 and K2 CO3. The influence of different precipitants on the structure and properties of Ru/MgO-CeO2 catalysts was investigated. The catalysts were characterized by X-ray diffraction （XRD）, CO chemisorption, temperature-programmed reduction of hydrogen （H2-TPR）. The results indicated that Ru/MgO-CeO2 catalysts using NH4HCO3 and （NH4）2CO3 as the precipitants and K2 RuO4 as the precursor exhibited high activity for ammonia synthesis under the reaction condition of 450 ℃, 10 MPa and 10 000 h -1 ,and the catalyst using NH4HCO3 as the precipitants had the highest activity; without the addition of the assistant, ammonia concentration in outlet was 15.91%. Ru/MgO-CeO2 catalysts using KHCO3, K2CO3 and KOH as the precipitants possessed relatively lower activity of ammonia synthesis. The high catalytic activity of Ru/MgO-CeO2 catalysts at low temperature for ammonia synthesis was attributed to higher dispersion of ruthenium particles and larger BET surface area of the catalysts, and easier reduction of surface oxygen of MgO-CeO2 support and ruthenium.