Preparation of Anodised Aluminium Catalysts by an Electrolysis Supporting Method for VOC Catalytic Combustion

Abstract

Catalytic combustion of volatile organic compounds (VOCs) benefits from a low oxidation temperature due to less energy consumption. It is widely applied in industry. A novel technique of Pt/Al₂O₃/Al catalyst preparation is presented in this paper. Al₂O₃ film was formed on an Al plate by anodic oxidation in 4% oxalic acid solution at 50 A·m^–2 current density. After anodic oxidation, Pt was supported on the oxidized plate utilizing an electrolysis supporting method with an alternating current in an aqueous solution of chloroplatinic acid hexahydrate under both high and low voltages. Catalytic activity was evaluated by both toluene and benzene combustion. Dispersion of platinum in developed catalysts was about 20%, measured by CO pulse adsorption.
In the activity test, toluene or benzene was mixed with air and then toluene–air and benzene–air mixtures combusted on the developed catalysts. It is shown that a catalyst prepared under a high voltage has a higher reaction rate than that one prepared under low voltage. This may be explained by that large platinum particles were formed on the film by high voltage. In the running time of 140 hours duration, there exists an induction process of about 10 hours for fresh catalysts, in which, the conversion of toluene was promoted by up to about 8%, and with no obvious change in the reactions that follow. Experimental results indicated that electrolysis impregnation can be regarded as a short-time supporting method for preparing catalyst.