Soot Catalytic Purification

The cooking oil fume pollution has been becoming a serious problem, with the appearance of more and more big restaurants in cities of China. According to corresponding researches there are many noxious and harmful components in oil fume, some of which are carcinogens and may cause mutations. As a result, the exclusion of oil smoke affects the life of urban residents greatly, and the complaints on this issue account for 40% of the total on environment discontentment. Recently, the government has enacted relevant laws, forcing the owner of restaurants to purify it.Though several methods on disposal technology of oil fume have been developed at home and abroad, such as filtration process, electrostatic process and wet process, practical and effective technology is still needed. This dissertation explores a new disposal process of cooking fume, which is able to convert all of cooking oil fume pollution (oil drop, gas pollutant molecules) completely into water and CO2 in the presence of catalysts of noble metals supported on alumina-honeycomb ceramic.Due to the extreme complexity of oil fume compositions, the first crucial task for this research is to develop a suitable evaluation system for purification efficiency of catalysts. Through many trials, a scientific and accurate method was set up in our lab. First, compressed air flow going through the cooking oil was used to produce oil fume, and oil fume with the same flow rate and similar composition to the real situation was obtained. Second, the method of absorbingoil fume by the tube filled with CCU solvent was developed, which was practical and gained high absorbing efficiency. Third, IR method was used to measure the concentration of the solution, and a new calculation method for the treatment of IR-Data was developed.Catalytic complete oxidation technology and precious metal catalysts were used in this research. Catalysts were prepared by the following procedure. First, layer of A12O3 was painted on the inner pore surface of ceramic honeycomb carrier. Second, a solution of palladium and platinum salts was used for impregnation to obtain a catalyst with suitable loading of noble metals. In this step, the congruent volume impregnation method was used.The single component Pd and Pt catalysts with various loading of noble metal were prepared and examined at 250, 300 and 360. The results show that the loading of 0.1% was the best for both Pd and Pt catalysts; At lower temperarure(250-300), the performance of Pt catalyst was better than Pd catalyst, while at higher temperature(300-360) Pd was the better. The purification efficiency of 0.1%Pd/ y -A12O3 catalyst was 93.1% at 360 (Csmokeis 142mg/m3)The dual-components Pd-Pt catalysts with various ratios of noble metals were prepared and examined at 250, 275 and 300. The results show that the SMSI between Pd and Pt improved the purification performances of dual-components catalysts, which behaved with much higher conversion of oil fume than single component catalysts. When Pt/ (Pd+Pt) ratio is 3/4, the catalyst showed the best efficiency. The most suitable calcination temperature for catalyst preparation is 500.Catalysts with CeO2 addition were prepared and tested, which showed much better performance for oil fume purification than the corresponding unchanged ones. The data show that 2%(wt) was better than 1% as the CeO2 addition amount; As for the addition way, impregnating Ce(NO3)3 was better than mixing CeO2 with A12O3.The catalysts were studied by means of TPR, TPD and XRD technique. The result shows that reduction temperature of Pd single component catalyst, 138 , was higher than those reported. There was no TPR peak on the curve of 0.1% Pt catalyst. On the other hand, several peaks appeared on the H2-TPR curve of dual components catalyst, and the O2-TPD area of dual components catalysts was much bigger than that of single ones. This difference indicates that the co-existence of Pd and Pt brought about new active centers on the catalyst surface and improved the attribute of surface oxygen.