Pd／CeO_2－γ－Al_2O_3上表面氧物种脱附及其对甲醇氧化活性的影响

Desorption of Surface Oxygen on Pd/CeO_2-γ-Al_2O_3 and Its Influence on the Catalytic Performance

采用ＴＰＳＲ－ＭＳ及ＴＰＤ－ＭＳ技术研究了Ｐｄ／ＣｅＯ２－γＡｌ２Ｏ３体系催化剂上表面氧物种脱附－恢复和甲醇表面反应性能，并以甲醇氧化反应为探针考察了催化剂在不同气氛下的氧化活性．结果表明，ＣｅＯ２对γ－Ａｌ２Ｏ３载体的改性，有利于钯催化剂上表面氧物种的脱附和氧化再恢复，从而促进Ｐｄ／ＣｅＯ２－γ－Ａｌ２Ｏ３催化剂对甲醇的完全氧化．甲醇在催化剂表面的程脱过程中均产生选择性氧化产物甲醛、甲酸、ＣＯ和ＣＯ２，ＣｅＯ２的存在有利于甲醇的脱附及深度氧化，选择性氧化产物的脱附量明显减少，并发现ＣＯ２的脱附量及峰温次序与对甲醇的氧化活性一致．

In this paper,the desorption and surface reaction properties of CH3OH,the desorption and reproduction properties of surface oxygen over Pd/CeO2-γ-Al2O3,Pd/Al2O3 and CeO2-Al2O3 were investigated by means of TPSR-MS and TPD-MS.The oxidation activity of CH3OH on these catalysts was studied under different concentrations of oxygen.The results showed that CH2O,HCOOH and CO were generated in CH3OH-TPSR of the catalysts.The desorption and complete oxidation of CH3OH over Pd/Al2O3 were promoted in the case of adding CeO2,and the desorption amount of these associated by-products decreased evidently. It was found that the catalytic activities well agreed with the desorbed amount of CO2 and the order of peak temperature.The results of O2-TPD showed that CeO2 can promote the desorption and reproduction of the surface absorbed oxygen over Pd/Al2O3,and evidently increases the amount of surface oxygen.these results were closely relative to their activities.