流化床CH_4部分氧化-CO_2重整Ni/CeO_2-SiO_2催化剂的研究

采用在载体中添加CeO2的方法对Ni/SiO2催化剂进行改性,得到Ni/CeO2-SiO2催化剂,考察了CeO2改性对Ni/SiO2催化剂在流化床中CH4部分氧化-CO2重整制合成气反应活性的影响,利用X射线衍射考察了Ni/CeO2-SiO2催化剂的物相结构变化,用氢程序升温还原、质谱示踪CH4/CO2-程序升温表面反应技术对Ni/CeO2-SiO2催化剂的氧化还原性能进行了研究,并与其催化活性进行关联。实验结果表明,CeO2改性促进了Ni物种在载体表面的分散和NiO物种的还原,在流化床反应器中不同的反应气氛下Ni的价态迅速转换,因此Ni/CeO2-SiO2催化剂的活性与稳定性提高。其中Ni和Ce质量分数均为5%的5Ni/5CeO2-SiO2催化剂的活性和稳定性最好,在反应温度750℃时,CH4的转化率达到87%,接近热力学平衡值,在15h内5Ni/5CeO2-SiO2催化剂的活性未下降。

Ni/SiO2-CeO2 Catalyst for Partial Oxidation of CH4 and Reforming of CO2 in a Fluidized Bed

Partial oxidation of methane and reforming of CO2 were investigated in a fluidized bed reactor over Ni/SiO2 catalyst modified by adding CeO2 in SiO2 support. The Ni/CeO2-SiO2 catalyst were characterized by means of XRD, H2-TPR and CH4/CO2-temperature programmed surface reaction(TPSR)-MS. Addition of CeO2 in SiO2 support can not only promote dispersion of nickel species but also reduction of NiO species. Due to rapid transformation of valence state of nickel species under different reaction atmospheres in fluidized bed, activity and stability of the catalyst are improved. At 750 ℃, conversions of CH4 over 5Ni/5CeO2-SiO2 catalyst(the mass fractions of Ni and Ce are all 5%)can reach 87%,which approaches thermodynamic equilibrium. The activity of catalyst can maintain for 15 h. The high activity and stability of catalyst may possibly attribute to interaction between Ni species and CeO2- SiO2 support.