Study On Performance Of Catalytic Dehydrogenation At Low Temperature With Loaded Palladium Based Catalysts

In recent years chlor-alkali industry is developing so fast that the output of chlorine could reach25million tons per year in China. However, it would also produce large amount of hydrogen-containing exhaust chlorine using traditional electrolysis method. The constitution of exhaust chlorine is much complicated and it seriously pollutes the environment. Tradition treatment crafts with exhaust chlorine has the disadvantages of complication and could not exhaustively solve the problem of explosion. Safety removal of hydrogen from exhaust chlorine has become a major issue. If the method was proper, we will get purer chlorine for industrial production so that the economic value could improve.In this experiment, two kinds of loaded palladium based catalysts were studied. Hydrogen-oxygen and hydrogen-chlorine reaction occurred during the dehydrogenation. The catalysts were prepared by impregnation method, using SiO2and γ-Al2O3as carriers and palladium dichloride solution as source of palladium. The performance of catalytic dehydrogenation was carried on a self-made continuously flowing fixed-bed reactor and the catalysts were characterized by XRD, FTIR, XPS and N2-adsorption. Optimal metal loading amount, hydrogen reduction temperature, calcination temperature reacting temperature, space velocity and the lifespan of the catalysts were studied in this paper. Through this experiment, there were following conclusions:1. Both Pd/SiO2and Pd/AlO2showed high hydrogen conversion rate and selectivity of hydrogen reacts with hydrogen and oxygen. Under the same conditions, Pd/SiO2had a better performance of catalytic dehydrogenation than that of Pd/Al2O3.2. Suitable hydrogen reduction temperature and calcination temperature were needed during the preparation of loaded palladium based catalysts.Under450℃calcination temperature,250℃reduction temperature, the overall hydrogen conversion rate and selectivity of oxygen-hydrogen reaction of Pd/SiO2could respectively reached98.79%and0.8288; Under500℃calcination temperature,250℃reduction temperature, the overall hydrogen conversion rate and selectivity of oxygen-hydrogen reaction of Pd/Al2O3could respectively reached99.99%and0.7919.3. The higher temperature and lower space velocity, the better performance of the catalysts. Under100℃reaction temperature,4×104h-1space velocity, the overall hydrogen conversion rate of Pd/SiO2and Pd/Al2O3could respectively reached80.02%and97.38%, the selectivity could reach0.8001and0.7919.4. As the Pd/SiO2and Pd/Al2O3catalysts were characterized by XRD, FIRT, XPS and nitrogen adsorption showed after a continuous twelve-hour dehydrogenation reaction:the palladium on the surface of the catalysts still remained zero valence and well-distributed; the structures of Pd/SiO2and Pd/Al2O3catalysts whose surface areas change little are stable; and they can be used for chlorine exhaust catalytic dehydrogenation.