Abstract: The effects of various atmospheres (oxidative，reducing and inert atmosphere） pretreatment on the catalytic activity of Pd/γ-Al2O3 catalyst in benzene degradation were studied in this paper. The property of the catalyst was characterized by X-ray photoelectron spectroscopy (XPS)，X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis，and a possible influence mechanism of reducing，oxidative，and inert atmosphere pretreatment on the catalytic activity of Pd/γ-Al2O3 catalyst was proposed. The experimental results revealed that the pretreatment with reducing and inert atmosphere has a significant positive effect on the catalytic activity in benzene oxidation at a certain temperature. Crystal structure of Pd active species is another important factor to affect the catalytic activity besides chemical state. The pretreatment of inert atmosphere led to the change of crystal structure，with crystalline PdO transformed to amorphous state，and this change in crystal structure is beneficial for enhancing the catalytic activity.

Key words: Pd/γ-Al2O3, benzene, catalytic degradation, chemical state, crystal structure

摘要： 研究了不同气氛（惰性、还原性及氧化性气氛）预处理对Pd/γ-Al2O3催化降解苯的影响，采用XPS、XRD和TEM等分析手段对预处理前后的催化剂进行了表征，探索了预处理方式对催化剂活性的影响机制。研究结果表明，预处理方式对于催化剂活性的影响显著，还原性及惰性气氛预处理均可以明显提高催化剂的活性；除Pd活性组分的化学态以外，晶体结构是影响催化剂活性的另一个重要因素，惰性气氛预处理过程中活性组分PdO由结晶态向无定形态转变，这种晶体结构的转变有利于Pd/γ-Al2O3催化降解苯性能的提高。

关键词: Pd/γ-Al2O3, 苯, 催化降解, 化学态, 晶体结构