| With the rapid development of the times and the improvement of people's quality of life,a series of pollution problems have been brought along,such as underground drinking water and air pollution,which are closely related to people's lives.Nowadays,in solving these two thomy problems,the wastewater treatment is currrently mainly based on physical adsorption and chemical deposition,The sources of air pollution are mainly automobile exhaust and industrial exhaust gas.The method of chemical catalytic conversion or absorption is often adopted for the treatment of exhaust gas.Because mesoporous?-Al2O3 has a high specific surface area and can survive in harsh environments,it is often used as an adsorbent or catalyst carrier for wastewater treatment and industrial exhaust gas or automotive exhaust.?-alumina is insoluble in water and can be dissolved into strong acid or alkali,but it is unstable at high temperaturs,and when the temperature rises to 1200oC,it is transformed into stable?-alumina.Industrial?-alumina is usually a colorless or slightly pinkish cylindrical particle with good pressure resistance.Because of its high hardness and dimensional stability,nano-alumina is easy to disperse in solvent water and does not need to be added with dispersant.It can be stirred in propylene glycol,solvent ethanol,propanol,isopropanol ethylene glycol monobutyl ether,acetone,butanone,benzene,and xylene.Therefore,in order to prepare nano-sized?-Al2O3 powders and improve the high-temperature stability of?-Al2O3 and increase its pore size,the research focus of this paper is mainly focused on the following aspects.1.Preparation of?-Al2O3 precursors?ie,boehmite powder?by hydrothermal method using several common aluminum salts?AlCl3·6H2O,KAl?SO4?2·12H2O,Al?NO3?3·9H2O,Al2?SO4?3·18H2O?as aluminum sources,then the precursor powder is calcined at different temperatures to prepare?-Al2O3 powder.To explore the temperature range for the synthesis of?-alumina and the collapse of?-alumina structures into?-alumina under conditions that can be achieved in the laboratory.At the same time,the effects of four common alumina sources on the structure and microscopic morphology of alumina were also studied.2.After studying the effects of several common aluminum salts on the structure and microstructure of alumina,an aluminum salt was selected as the aluminum source.Preparation of wet sols by sol-gel method,then dry for a while at a certain temperature to produce a white transparent xerogel.Finally calcined xerogel at a certain temperature obtains boron-doped?-Al2O3 powder.After investigating the causes of high temperature stability and high specific surface area of?-Al2O3,the material structure was doped and modified to improve its high temperature stability and specific surface.And the doped and modified?-Al2O3 was characterized.3.The materials prepared in study 1 and the modified materials prepared in study 2are calcined at high temperatures and resulted in structure failure,conversion to stable?-alumina,and investigation of the temperature range for conversion to stable phase.Analyze the changes in the hige temperature stability and specific surface area of the material before and after conversion to a stable phase. |
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