Preparation Of Catalyst With Modified Red Mud As Carrier And Its Catalytic Properties For CO Oxidation

Red mud produced as by product from the production of aluminum oxide is a kind of solid waste. It was reported that more than ten million tons red mud is discharged from the alumina factories annually in China. The output of red mud in China has reached about 10% all over the world. Large amount of red mud was exposed to atmosphere, which not only occupy much land but also cause pollution of the environment and groundwater. The reutilization rate of red mud is about 15%~20% at present. Therefore, how to eliminate the pollution and utilize the red mud to change the residue into raw material have become a social focus and an interesting research subject for many investigators.CO is a well-known typical flammable and toxic pollutant. The burning of fossil fuel, developing of chemical industry and application of motor vehicles will all dispose large amount of CO. At the same time, CO oxidation is an important model reaction for catalyst study. The elimination of CO at low-temperature has important applications in many areas, which is also a valueable subject that much attention has been paid by many researchers.Noble metal catalysts, whose main active component is Au, Pt, Pd, Ru and so on, are used mostly in the area of CO low-temperature catalytic oxidation. This kind of catalyst shows higher catalytic activity at low temperature, anti-poisoning ability and water resistance. However the inadequate reserves and expensive price are limiting factors for wide using. Copper has been considered having great application prospect due to its abundant reserves, low cost and high catalytic activity on CO oxidation.Red mud has high surface area and good stability at high temperature. In this paper, different kinds of catalysts, copper oxide, cerium oxide and copper oxide-cerium oxide loaded on the red mud and modified red mud, were respectively prepared and the catalytic activity for the CO oxidation reaction has been examined.The main contents of this thesis are listed as follows:1. The main chemical composition of red mud employed was determined by various ordinary chemical analyses, and it is characterized by TG-DTA, XRD, FT-IR, BET, SEM, HRTEM, etc. The red mud contains large amount of SiO2, Fe2O3, Al2O3 and a certain amount of silicate minerals. Some R2O(Na++K+) were found whose content is about 6%. Meanwhile, quartz, hydrated aluminum silicate, goethite, hematite,β-dicalcium silicate (β-C2S), as well as small amounts of calcite, forms the main constituent of the red mud.2. We used the atmospheric pressure de-alkalization method to remove alkali existing in the red mud. The rate of de-alkalization is up to 52.11% under the conditions that the de-alkalization dosage is 8%; de-alkali time is 2.0 h and de-alkali temperature is 70℃.3. Different kinds of catalysts loaded CuO, CeO2, CuO-CeO2 were prepared by precipitation method. The influence of different load amount and the ratio of copper to cerium on catalytic properties of CO oxidation were studied. The prepared samples were characterized by SEM, XRD and HRTEM. It shows that the optimum load amount of CuO is 8(wt)% and the conversion of CO achieved up to 100% at 200℃.4. Catalysts were prepared using de-alkalized red mud as support. The influences of different load amount of CuO on catalytic properties were studied. It indicates that the optimum load amount of CuO is 8(wt)% and the prepared samples were characterized by SEM and XRD.5. Catalysts loaded 8(wt)% CuO using three different acid-modified red mud as support were prepared. Catalytic properties test was carried out and it indicated that the increasing of support's specific surface area can not improve catalyst's activity.6. The influence of alkali metal modification of red mud on catalytic properties was studied. The 100 h continuous test and repeated heating and cooling test on catalyst which use red mud as support loaded 8(wt)% CuO were carried out. The results showed that alkali metal is good for improving catalyst's property and the catalyst (red mud loaded 8(wt)% CuO) has continuous high catalytic activity and stability for CO oxidation, the catalyst of this kind is promising of research and application.