Abstract
Gold catalysts were prepared by deposition precipitation, chemical vapor deposition and ion-exchange methods. The samples were characterized by AA, XRPD, TG/DTA, TPR, TEM and BET. Titanium hydroxy were prepared by hydrolyzation of titanium iso-propoxide. After calcined in air, it converted into titanium oxide. The crystalline phase of titanium oxide were changed from amorphouse (TC ≤ 200 ℃) to anatase (600 ℃ ≥ TC > 200 ℃) with the heating. It converted to rutile phase (TC > 600 ℃) at higher temperature and gradually sintered to large particles. Small gold particles can prepared by deposition precipitation method with adjusting the pH value of supports. Au/Y-zeolite prepared by ion-exchange method can form small gold particles, because the limitations of pore size. Samples prepared by deposition precipitation and ion exchange methods were poisoned by the contamination of chloride. Chloride can be eliminated from reducing with hydrogen or sodium borohydride. In the samples prepared by chemical vapor deposition method, organic gold adsorbed on supports decomposed into small particles at 300 ℃. With the existing of these small particles ( ~ 2 nm), these catalysts have higher oxidative activity of CO then the samples prepared by deposition precipitation and ion exchange methods. The activity of gold catalysts was in relation to the gold particle size and the type of supports. And the gold particle size was the major factor influences the activity. Titanium oxide have vacancy sites to adsorb oxygen, so it’s a better support for oxidation of CO than aluminum oxide.