纳米金催化剂低温催化氧化甲醛和一氧化碳的研究

Catalytic oxidation of HCHO and CO at low temperature by nanosized gold catalysts

采用均相沉积沉淀法制备了Au/CeO2催化剂,考察了不同焙烧条件对金催化剂催化HCHO和CO氧化两个反应的活性变化规律,并对活性机理进行了研究。实验结果显示,该催化剂具有优异的低温催化HCHO和CO氧化的活性。其中经500℃焙烧的催化剂在50℃、体积空速为5000h-1下可以实现甲醛的完全催化氧化;经300℃焙烧的催化剂在0℃、体积空速为450000h-1下可以实现对CO70%的转化。发射扫描透射电镜、X射线粉末衍射的表征结果显示:对于催化CO氧化来说,粒径越小活性越高,而对于催化HCHO氧化来说,则呈高斯曲线型,粒径较低时,粒径的大小和活性是呈正比的。X射线光电子能谱表征结果显示:催化CO氧化体系中,Auδ+和Au0共同作为活性组分,而催化HCHO氧化体系中,则是Au0为主要的活性组分。

A series of 4.85% Au/CeO2 catalysts were prepared by homogeneous deposition-precipitation and shown to possess very high activity in the catalytic oxidation of both HCHO and CO. Complete conversion of HCHO was obtained at 50℃ using a catalyst calcined at 500℃, and 70 % conversion of CO was obtained at 0 ℃ using a catalyst calcined at 300℃. STEM, XRD and XPS were used to investigate the differences between the system for the catalytic oxidation of HCHO system and that for the catalytic oxidation of CO in terms of the particle size effects and the oxidation states of the active gold species. Two conclusions were obtained： （1） For the CO oxidation system, the activity increased with decreasing gold particle size, whereas for the HCHO oxidation system, the activity at first increased and then decreased when the gold particle size was increased. （2） The oxidation states of the active gold species in the two systems were also found to be different. In the CO oxidation system, the active species involved both Au^δ＋ and Au^0 together, whereas for the HCHO oxidation system, Au^0 was shown to be the main active species.