Ni/CeO_2-Al_2O_3催化剂上CH_4-CO_2转化积炭性能的研究

Studies on Property of Carbon Deposition on Ni/CeO_2-Al_2O_3 Catalyst for CH_4-CO_2 Reforming Reaction

采用脉冲微量反应技术研究了添加 n型半导体氧化物 Ce O2 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Ce O2 之间存在金属 -半导体相互作用 ( MSc I) ,Ce O2 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/Ce O2 -Al2 O3 催化剂具有较强的抗积炭性能 .

The influence of the addition of n-type semiconductor oxide CeO 2 to Ni-based catalyst on carbon deposition from CH 4 and carbon elimination by CO 2 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 CeO 2. The XPS data indicated that the addition of CeO 2 could increase the d-electron density of active atom Ni, which would inhibit the migration of C-H σ-electron from CH 4 molecule to d-orbital of Ni atom, therefore, the carbon deposition activity of CH 4 decreases. Meanwhile, the migration of d-electron from Ni atom to empty antibond π-orbital of CO 2 could be strengthened due to the addition of n-type semiconductor CeO 2, thereby, carbon elimination activity of CO 2 increases. As a result, the Ni/CeO 2-Al 2O 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).