Preparation Of Porous Ceramics Using Industrial Residues Of Aluminium Formation Product Factory And Properties Investigation On The Rare Earth Catalysts

Porous ceramics are widely used in automobile exhaust purifications, catalyst supports, sound-deadening insulation and furnace insulation materials. Cordierite ceramics have wonderful effects as a catalyst carrier and the high temperature flue gas filters because of great surface area, low thermal expansion coefficient, good thermal shock resistance and low cost, which other materials can not be replaced. Rare earth oxides have aroused widespread concern for their excellent comprehensive properties and good catalytic ability.In this research, plate-shaped cordierite was successfully synthesized by aluminium industrial residues with talcum powder and kaolin. The preparation process, microstructure and thermal expansion coefficient of the compounds were systematically investigated by thermogravimetric differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, hermal expansion coefficient instrument etc.The Al₂O₃ content of the burn aluminium industrial residues is over 90%, which can completely replace industrial alumina as the main raw material of cordierite. The theoretical composition of cordierite cordierite is not the best formula of synthesis. It is benefit to fabricate cordierite when the contents of Al₂O₃ and MgO are higher than the theoretical compositions, and the SiO2 content is below the theoretical composition. Sintering temperature can significantly affect the synthesis of cordierite, crystal structure, thermal expansion coefficient and other properties. The pure sheet cordierite was obtained at thermal expansion coefficient of 1.82×10-6℃-1 when the sintering temperature was 1380℃.Holding time significantly affected the crystal growth and the degree of reaction. When the holding time was 4 h, the prepared cordierites were uniform size and the thermal expansion coefficient was 1.73×10-6℃-1. Cordierite clinker as a nucleating agent can significantly promote the formation and development of cordierite and as well as help to reduce the thermal expansion coefficient of cordierite, which can solve the difficult problem of cordierite nucleation in a certain extent.Porous cordierite honeycomb ceramic supports were prepared by extrusion technology using self-made sheet cordierite powder as main raw material and water-soluble polymers as additives for the first time. The preparation process, microstructure, phase composition, cell density, thermal expansion coefficient and thermal shock resistance of the samples were systematically investigated.The sheet cordierite powder as raw material and extrusion methods are conducive to cordierite crystal oriented arrangement, which due to the anisotropy of thermal expansion coefficient vector, lower thermal expansion coefficient, and high thermal shock resistance. With water-soluble adhesive binder to instead of tung oil can improve the lubricity and plastic of the mud significantly, and prevent the generation of harmful emissions during the process. In this study, the obtained cordierite honeycomb ceramic supports with mainly of sheet structure show a certain alignment along the wall. The carrier thermal expansion coefficient, cell density and wall thickness are 8.565×10-6℃-1 (30-800℃), 90.6 holes/cm2, 0.16 mm, respectively.The porous mullite fiber ceramics were used as catalytic supports for the first time. Supported La_1-xSr_xCoO_3-δ and La_1-xSr)xCo_0.9Pd_0.1O3-δ (x=0.2, 0.4, 0.6, and 0.8) perovskite-type oxide catalysts were prepared by vacuum impregnation method. The phase composition, microstructure and catalytic properties of the catalysts were systematically investigated by thermogravimetric differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, specific surface area analyzer and flue gas analyzing apparatus etc. The affect of the element substituent on the catalytic activity was discussed deeply, and the catalytic properties of the catalyst on NO + CO gas were assessed.The catalyst particles can bind with the porous mullite fiber ceramics and disperse uniformly on the surface of the supports. SrCO3 phase was not found in porous mullite fiber ceramic supported La_1-xSr_xCoO_3-δ catalysts, which indicated that the supports depressed the growth of SrCO3 phase. La(OH)3 peaks were not observed in supported La_1-xSr)xCo_0.9Pd_0.1O3-δ perovsite-type catalysts, which showed that Pd-doped perovskite oxide catalysts was helpful to inhibit the growth of La(OH)3 crystal phase. The Sr-doping to the La-position is benefit to increase the oxygen vacancies of the perovsite-type catalysts.The investigation of catalytic activity showed that La_1-xSr_xCoO_3-δ and La_1-xSr)xCo_0.9Pd_0.1O3-δ perovskite-type catalysts supported on porous mullite fiber ceramics exhibited significant catalytic redox activity. The catalytic activity of La-Sr-Co-O catalysts was improved notably due to the Pd doping. For all supported La_1-xSr_xCoO_3-δ perovskite-type catalysts, supported La0.6Sr0.4CoO3-δcatalysts showed the highest CO integral oxidizability, while supported La_0.4Sr_0.6CoO_3-δ perovskite-type catalysts exhibited the highest NO integral reducibility. And supported La_0.8Sr_0.2CoO_3-δ perovskite-type catalysts presented the best redox activity of the unit surface area. The integral redox of supported La_0.6Sr_0.4Co_0.9Pd_0.1O3-δ perovskite-type catalysts for CO+NO was higher than the rest of supported La_1-xSr)xCo_0.9Pd_0.1O3-δ perovskite-type oxide catalysts. Supported La_0.4Sr_0.6Co_0.9Pd_0.1O3-δ perovskite-type catalysts showed the highest CO oxidizability of unit surface area among supported La_1-xSr)xCo_0.9Pd_0.1O3-δ perovskite-type catalysts. Meanwhile the best dramatic effect by catalytic temperature was observed on supported La_0.4Sr_0.6Co_0.9Pd_0.1O3-δ perovskite-type catalyst.