CO和H_2与Ni基催化剂的相互作用研究  

On the Interaction of CO and H2 with Ni-based Catalyst

作　　者：胡常伟[1] 陈耀强[1] 李平[1] 明虹[1] 陈豫[1] 田安民[1] 李荣勇[1] 

机构地区：[1]四川大学化学系,成都中医药大学

出　　处：《分子催化》1995年第6期435-444,共10页Journal of Molecular Catalysis(China)

摘　　要：用活性测试和程序升温动态红外光谱方法研究了ＣＯ和Ｈ_２在Ｎｉ／Ａｌ_２Ｏ_３催化剂上的行为，并用量子化学从头算方法进行了模拟表征。结果表明，在较低温度下，ＣＯ在Ｎｉ／Ａｌ_２_Ｏ３上的线式吸附态与桥式吸附态相比，桥式对ＣＯ压力更敏感，而线式则对温度更敏感，桥式吸附的ＣＯ在４７３Ｋ附近发生歧化反应，而线式则要在５２３Ｋ以上才发生歧化。线式吸附的ＣＯ在４１０Ｋ附近就开始与Ｈ_２反应生成ＣＨ_４，而桥式则要在４２３Ｋ以上才能发生反应。ＣＯ先于Ｈ_２吸附及与Ｈ_２共吸附的动态红外光谱发现，两条件下均发生２０６０ｃｍ￣（－１）和１９００ｃｍ￣（－１）附近两谱带强度在４２３到５２３Ｋ之间随温度变化而同步变化，并伴以频率向低波数移动。量子化学从头算模拟研究表明，两谱带强度的这一同步变化可能是镍羰基氢化物的生成引起的，计算预测，１Ｈ镍羰基氢化物为直线结构，２Ｈ镍羰基氢化物为Ｃ_（２ｖ）。结构。在ＣＯ加Ｈ_２生成ＣＨ_４过程中，可能经历了镍羰基氢化物的步骤。The interaction of CO and H2 with Ni/Al_2O_3 is studied by CO methanation activity measurement and in situ TP-IR method. Ab initio calculation is also carried out to simulate the surface species.It is found that the linear-CO adspecies is more sensitive to temperature whereas the bridge-CO adspecics is more sensitive to CO pressure at low temperature.The bridge-CO adspecies starts to disproportionate at lower temperature(473 K) than the linear one(>523 K).The linear-CO adspecies starts to react with hydrogen to form CH_4 at lower temperature(about 410 K) than the bridge-CO adspecies(about 423 K) .The methanation of CO occurs at much lower temperature than that for the disproportionation of CO to occur.The concomitant variation of the IR bands near 2060 cm￣(-1) and 1900 cm￣(-1) when CO and H_2 co-exist indicates the formation of certain H containing species in the interaction of CO and H_2 over Ni/Al_2O_3.Ab initio investigation predicts that nickel carbonyl hydride species containing 1 H has a linear structure while that containing 2 H has a C_(2V) symmetric structure.The vibratonal frequencies of the calculated species are in the range of those experimentally assigned to linear and bridge CO adspecies. It is possible that nickel carbonyl hydride species are intermediates in the methanation of CO over Ni/Al_2O3 catalyst.

关 键 词：一氧化碳 镍 羰基 氢化物 甲烷化 催化剂 

分 类 号：O643.36[理学—物理化学]