添加氯离子对Ni/CeO_2催化剂CO选择甲烷化反应催化性能的促进

Effect of Chlorine Doped in Ni/CeO_2 Catalyst on Selective Methanation of CO in H_2-Rich Gas

采用浸渍方法制备NiO(Clx)/CeO_2系列样品,经还原后得到Ni(Clx)/CeO_2催化剂,用于富氢气体中CO的选择甲烷化反应,考察Cl/Ce原子比(x)对CO选择甲烷化反应活性的影响.结果表明,添加氯离子能够显著抑制CO_2甲烷化反应,因而可使富氢气体中CO浓度降至10-5以下并且CO甲烷化反应选择性不低于50%,满足质子交换膜燃料电池对燃料的要求.通过CO和CO_2吸附实验、程序升温还原(TPR)测定以及物相组成和晶粒尺寸分析,揭示添加氯离子的作用.

A series of 20%NiO（Clx）/CeO2 samples with feed atomic ratio of C1/Ce at x=0.0- 0.30 were prepared by impregnation method and used to selective methanation of CO in H2-rich gas （CO-SMET） after reduction. It is found that chlorine doped suppressed CO2 conversion greatly. And CO concentration was thus decreased to below 10^-5 over 20% Ni（Cl02）/CeO2 catalyst with CO methanation reaction selectivity not less than 50% in a wide reaction temperature range of 220 - 240 ℃, meeting the requirement for fuel of proton exchange membrane fuel cell （PEMFC）. In order to reveal effect of chlorine doping, measurements of X- ray diffraction （XRD）, temperature programmed reduction （TPR） and adsorption isotherms of CO and CO2 were conducted. Phase composition of the samples and crystallite size of CeO2 were estimated by the Rietveld method. Thickness of crystallites of NiO or Ni was estimated by the Scherrer equation.