Study On Preparation Of Catalyst Carrier Material

The carrier materials of catalysts in automobile exhaust catalyst control technology must meet the requirements of good high temperature stability and large specific surface area. Currently γ-Al₂O₃ is the most widely used catalyst carrier, however, the thermal stability of which is so poor that the phase transformation and sintering are easy to occur under high temperature environment. The specific surface area of the carrier decreases significantly and the catalytic purification efficiency plummeted as a result. Therefore, research on new catalyst carrier materials with high temperature stability and large specific surface area is of great significance to improve the efficiency of automobile catalytic purification.This paper did detailed research on the preparation of several kinds of carrier material with high temperature resistance and large specific surface area. The experiment chose silicate clay minerals of sepiolite as raw material in that it has a larger specific surface area. Then modified it with acid. And the preparation of ZrO2/sepiolite compound carrier material was also studied. The experiment used aluminum nitrate and ethyl orthosilicate as raw material, and prepared aluminium silicon oxide composite material through hydrolysis-coprecipitation method. The analysis of different samples is studied through specific surface area and pore size analysis, X-ray diffraction spectrum, scanning electron microscope（SEM）, thermogravimetric analysis, etc. Details of the research content and innovative results are listed as follows:The meerschaum was acid modified by HCl, and the influences of HCl concentration, acidification time and calcination temperature on the specific surface area（SSA）, high temperature stability, microstructure and phase composition of meerschaum were studied. It turned out that, with the increase of HCl concentration, the SSA of meerschaum would increase before its reduction, and the thermal stability would increase gradually; While as acidification time prolonged, both SSA and thermal stability would increase and then decrease. The SSA of meerschaum reached up to maximum value of 140.183m2/g after modified by 1mol/L HCl for 18h; The SSA of meerschaum decreased with the increasing of calcination temperature, after calcinated at 1000 oC, the SSA of meerschaum was reduced to only 16.149m2/g.The ZrO2/meerschaum composite catalyst supported materials was prepared by precipitation-loading method, the influences of the dosage of different zirconium salt, ZrO2 and lanthanum oxide on the composite materials’ SSA and thermal stability was researched. The results indicated that samples prepared by using ZrOCl2 as the zirconium source got spherical shape with high SSA and good thermal stability. The SSA of composite catalyst supported materials increased substantially with adding 5wt.% lanthanum oxide. After calcinated at 600 oC, the composite material’s SSA decreased with the increasing dosage of ZrO2; After calcinated at 1000 oC, the SSA firstly increased and then decreased as the dosage of ZrO2 increased. The composite materials achieved best thermal stability when the mass ration of Zr O2 to meerschaum was 2:1, the samples’ SSA was 144.097m2/g after calcinated at 600 oC, and could still reach 51.088m2/g after calcinated at 1000 oC.Hydrolysis precipitation method was used to fabricate aluminium silicon oxide catalyst supported materials, in order to establish the best preparation process, the effects of pH, concentration of aluminium nitrate solution and the dosage of PEG-4000 on the hydrolyzation of TEOS was studied by orthogonal test. The SSA of aluminium silicon oxide catalyst supported materials fabricated by hydrolysis precipitation with optimum conditions could reach up to 333.911m2/g, after calcination ageing at 1000 oC, the specific surface area could still reach 199.871m2/g, which means that the loss rate of SSA after ageing was 40.2%.The effects of different doped rare earth ion and the ratio of Al₂O₃/SiO2（mass ratio）on the SSA and thermal stability of aluminium silicon oxide catalyst supported materials fabricated by hydrolysis precipitation was studied. The results showed that the SSA was increased by doping rare earth, the greatest benefits on increasing SSA was obtained by doping Ce, which could reach 485.681m2/g after calcinated at 500 oC, and after calcination degradation at 1000 oC, it could still reach 278.668m2/g, the loss rate of SSA was 42.6%. In the composite materials system, with the increasing of Al₂O₃ content,, the SSA firstly increased and then decreased. When Al₂O₃/SiO2 was 3:1（mass ratio）, the specific surface area both reached the maximum value before and after calcination, which was 492.745m2/g and 314.855m2/g respectively, indicated that the loss rate of SSA after degradation was only 36.1%.