Ni/CeO2-Al2O3催化剂上CH4-CO2转化积炭性能的研究

采用脉冲微量反应技术研究了添加n型半导体氧化物CeO₂对Ni基催化剂上CH₄积炭/CO₂消炭性能的影响,用TPR,XPS和氢吸附技术对催化剂进行了表征.结果表明,活性金属原子Ni与半导体氧化物CeO₂之间存在金属-半导体相互作用(MScI),CeO₂的添加提高了活性原子Ni⁰的d电子密度,在一定程度上抑制了CH₄分子中C-Hσ电子向d轨道的迁移,降低了CH₄裂解积炭活性;可加强Ni⁰原子d轨道向CO₂空反键π轨道的电子迁移,促进CO₂分子的活化,提高CO₂的消炭活性,使Ni/CeO₂-Al₂O₃催化剂具有较强的抗积炭性能.

Studies on Property of Carbon Deposition on Ni/CeO2-Al2O3 Catalyst for CH4-CO2 Reforming Reaction

The influence of the addition of n-type semiconductor oxide CeO₂ to Ni-based catalyst on carbon deposition from CH₄ and carbon elimination by CO₂ was studied by using a pulse microreaction technique. The catalysts were characterized by TPR, XPS and hydrogen chemisorption. It was found that there was an interaction between active metal Ni and semiconductor oxide CeO₂. The XPS data indicated that the addition of CeO₂ could increase the d-electron density of active atom Ni, which would inhibit the migration of C-H σ-electron from CH₄ molecule to d-orbital of Ni atom, therefore, the carbon deposition activity of CH₄ decreases. Meanwhile, the migration of d-electron from Ni atom to empty antibond π-orbital of CO₂ could be strengthened due to the addition of n-type semiconductor CeO₂, thereby, carbon elimination activity of CO₂ increases. As a result, the Ni/CeO₂-Al₂O ₃ catalyst has an excellent resistance to carbon deposition. In addition, the influence of the synergetic effect between SMSI and MScI on the resistance to carbon deposition of the catalysts calcined at various temperatures was investigated. It was discovered that, only in the presence of relatively weak metal-support interaction, it could exhibit the metal-semiconductor interaction(MScI).