Font Size: a A A

Preparation Of Ceria-zirconia Solid Solution By Complexometry And Its Application In Formaldehyde Cleaning

Posted on:2016-11-22Degree:MasterType:Thesis
Country:ChinaCandidate:C ZhaoFull Text:PDF
GTID:2191330479494039Subject:Materials science
Abstract/Summary:PDF Full Text Request
The development of the urbanization has brought us air pollution as well as the convenience. The indoor volatile organic compounds especially formaldehyde and the haze which mainly comes from the vehicular exhaust have made people troubled. Ce O2-based materials are commonly used in automobile exhaust three-way catalytics and attract extensive attention of scholars all over the world, due to their good behavior of oxygen storage and release. But there was not enough rearch about their applying in formaldehyde cleaning covered. The various methods in the preparation of ceria-zirconia solid solution have advantages and disadvantages. For example, precipitation is easy to operating but the performance of the powder is not good enough. The shortcomings of the hydrothermal method are existed in low yield, bad stability and difficult for industrial preparation. While Complexometry is easier for industrial preparation and the powders can be fine with larger surface area, better stability and better oxygen storage behavior. Based on the above, this thesis studied the influence of various parameters in the preparation of ceria-zirconia solid solution in complexometry. That will provide some guidance for the preparation of high-performance ceria-zirconia solid solutions. We also used that ceria-zirconia solid solution complexd with activated carbon/Mn O composite to improve formaldehyde absorbtion.The effect of the concent of Zr4+, the alcohol proportion in solvent system,complexing agents and surfactants was detailed studied in this paper. Found that when the concent of Zr4+ is 25%, the solid solution has good stability with the average grain size smaller than 20 nm; when the alcohol/watter proportion is 5:5 in solvent system, the solid solutions get excellent performance with the specific surface area reaching 41.88 m2/g.Further rearch was did to find the effect of different complexing agents and surfactants on the morphology and properties of ceria-zirconia solid solution. We found that different shaped solid solutions were prepared with different structured complexing agents. Rose, plate, porous network like of Ce0.77Zr0.23O2 solid solutions were prepared by the complexed-precipitation method using different complexing agents(oxalic acid, glutamic acid, citric acid, malic acid and tartaric acid). For the rose like of Ce0.77Zr0.23O2 solid solution powders preparated with the oxalic acid, the average grain size increased rapidly with the thermal treatment temperature, and the phase segregation happened, the thermal stability became bad. For rice grain like of Ce0.77Zr0.23O2 solid solution powders preparated with tartaric acid, the specific surface area reaching 53.89 m2/g, and the average grain size was even smaller than 20 nm after 2 h of thermal treatment at 900 ℃, and the oxygen storage capacity was also excellent. What’s more, adding the anionic surfactant PAA can effectively reduce the original particle size of the ceria-zirconia solid solutions, forming a finer grid structured particles, and which has a specific surface area as big as 66.52 m2/g and an excellent oxygen storage capacity than ceria-zirconia solid solutions adding other surfactants. After 900 ℃ heated for 2 h, the average grain size was also less than 10 nm, and the H2 reduction amount reached to 15.43 cm3/g(STP), which was 1.5-2.5 times higher than ceria-zirconia solid solutions by adding other surfactants.The activated carbon/Mn O-Ce0.77Zr0.23O2 composite was prepared by physical mixing and dipping precursor solution. The composite made by dipping precursor solution has a persistent effect on formaldehyde clearing. and after 24 hours formaldehyde absorption, It hadn’t reached absorbtion equilibrium. When Ce0.77Zr0.23O2 capacity is 3 wt%, the cerium zirconium solid solution dispersed well on activated carbon and contacted well with the activated carbon and Mn O. This composite has the best absorption in 24 hours up to 6.52 mg/g, which is more than 62% increase than carbon/Mn O composite. What’s more the mechanism of activated carbon/Mn O-Ce0.77Zr0.23O2 composite in formaldehyde cleaning is as follow: As a carrier, activated carbon provides large amounts of pores and huge surface area. Mn O and Ce0.77Zr0.23O2 are loaded on the activated carbon surface and the wall of the pores. Formaldehyde molecules are physically adsorbed on the surface of activated carbon within the capillary capillary force, and then activated at chemisorption of Ce0.77Zr0.23O2 and Mn O. Finally they react with active oxygen and become CO2 and H2 O. Ce0.77Zr0.23O2 provide a steady flow of surface active oxygen to Mn O, and they play a role of synergistic effect in the catalytic reaction to improve the efficiency of formaldehyde cleaning.
Keywords/Search Tags:Ceria-Zirconia Solid Solution, Three-Way Catalytic, Complexing Reaction, Formaldehyde Cleaning
PDF Full Text Request
Related items