采用沉淀法制备了 ZrO2载体,进一步采用浸渍法制备了不同 Ni负载量的 Ni/ZrO2催化剂.通过 XRD、N2物理吸附、H2-TPR和H2-TPD等表征手段对Ni/ZrO2催化剂的物理结构和化学特性进行了研究,探讨了活性金属Ni物种的状态,并计算了Ni粒子的大小.随着Ni负载量的增加,Ni/ZrO2催化剂的比表面积逐渐减小,金属Ni的分散度逐渐减小,Ni粒子尺寸逐渐增大,低温H2脱附峰所占比例逐渐增大.当Ni负载量为10.2%(质量分数)时,Ni/ZrO2催化剂上ZrO2晶粒的平均尺寸和Ni粒子的尺寸大小均接近30nm.进一步考察了Ni/ZrO2催化剂在甲烷分步水蒸气重整反应中的催化性能.结果表明,Ni负载量在一定范围内的Ni/ZrO2催化剂对于甲烷分步水蒸气重整反应具有良好的催化性能,Ni负载量过高或过低均不利于甲烷的转化.当Ni负载量为10.2%时,载体ZrO2粒子和金属Ni粒子尺寸匹配,Ni/ZrO2催化剂表现出最佳的甲烷转化活性和稳定性.%A series of Ni/ZrO2catalysts with different amount of nickel loadings were prepared via impregnation method using zirconium dioxide as the carrier,while zirconium dioxide was firstly obtained through precipitation from zirconium salts and calcination treatment. X-ray diffraction (XRD),nitrogen physical adsorption,hydrogen temperature programmed reduction (H2-TPR),and hydrogen temperature programmed desorption(H2-TPD)techniques were utilized to analyze the physical and chemical properties of the prepared catalysts. The possible status of the active nickel species were investigated and the diameters of nickel and nickel oxide aggregates were calculated. With the increase of the loading amount of nickel,both the BET area of the Ni/ZrO2catalysts and the dispersion degree of nickel decreased,while the diameter of the nickel aggregates and the portion of the desorption area in the H2-TPD curves increased. When the loading amount of nickel was around 10.2%,the diameter of the nickel aggregates and that of zirconia dioxide crystals were close to 30nm. The performance of Ni/ZrO2catalysts was further investigated based on the reaction of stepwise steam reforming of methane. The results indicated that the Ni/ZrO2catalysts could exhibit excellent performance only when the amount of nickel loading was in some range. Both insufficient and excess amount of nickel loadings would lower the catalytic conversion of methane. When the loading amount of nickel was around 10.2%,the catalyst showed the best performance in that the zirconium dioxide particles had similar size to that of the nickel species.
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