沉淀剂对Ru/MgO-CeO_2氨合成催化剂催化性能的影响  

Effects of precipitants on catalytic activity of Ru/MgO-CeO_2 for ammonia synthesis

作　　者：王国华[1] 王秀云[1] 张留明[1] 王榕[1] 林建新[1] 魏可镁[1] 

机构地区：[1]福州大学化肥催化剂国家工程研究中心,福建福州350002

出　　处：《工业催化》2011年第4期69-73,共5页Industrial Catalysis

基　　金：国家自然科学基金(20576021);国家科技支撑计划(2007BAE08B02)

摘　　要：以K_2RuO_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成催化剂结构和性能的影响。结果表明,在450℃、10 MPa和10 000 h^(-1)条件下,以NH_4HCO_3和(NH_4)_2CO_3为沉淀剂制备的催化剂活性较好,其中,以NH_4HCO_3最好,在无添加助剂的情况下,出口氨浓度为15.91%,而采用KHCO_3、K_2CO_3和KOH为沉淀剂制备的Ru/MgO-CeO_2催化剂氨合成活性相对较低。Ru/MgO-CeO_2催化剂较好的氨合成性能归因于较高的钌分散度和较大的催化剂比表面积,以及较易的钌和载体MgO-CeO_2表面氧的还原程度。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.

关 键 词：催化剂工程 Ru/MgO-CeO_2氨合成催化剂 沉淀剂 共沉淀法 

分 类 号：TQ113.266[化学工程—无机化工]