Direct Preparation Of Alumina From Bauxite Ores As A Catalyst Support

Activated alumina is widely used as catalysts or catalyst supports in the petrochemical industry for its favorable properties, such as high surface area, controllable pore structure, and tunable surface chemistry. Currently, activated alumina is prepared as a derivative of aluminum production industry, which makes the process complicated and high cost. Therefore, it is of great significance to develop a novel process to prepare activated alumina as catalyst support or catalyst for chemical industry.In this thesis, we proposed a novel process, which is simple and low-cost, to prepare activated alumina through aluminum sulfate method with leaching liquid of diasporic bauxite as aluminum source. The work included focused on the evaluation of bauxites from different regions, optimization of leaching process of bauxite, parametric study on the precipitation of aluminum sulfate and bauxite leaching liquid. The results were as follows:(1) Bauxites from different regions had been evaluated with techniques such as XRD. TGA and XRF. It was found that1#bauxite from Henan had the highest Al/Si ratio (A/S) and maximum aluminum content and was the best raw resources for the direct preparation of activated alumina.1#Henan bauxite was suitable for producing leach liquid in this new route.(2) The leaching of1bauxite in hot concentrated NaOH solution was carried out in a group autoclave, aiming to determining the optimum leaching condition. The alumina leaching ratio reached93.11%under the following optimum conditions:leaching time of1h, leaching temperature of260℃, bath molar ratio of Na20to Al2O3of1.55, the caustic concentration of260gNa2O/L and mass ratio of CaO to bauxite of9%.(3) Parametric study on the precipitation of Al2(SO4)3and NaAlO2indicated that the neutralization pH and temperature were the most important factors to affect the alumina property. The pore structure and surface chemistry of alumina could be tailored by properly controlling the preparation parameters to meet different requirements.(4) Activated alumina with good thermal stability and low acidity has been directly prepared from domestic bauxite using this new process, with specific surface area of328m2/g and pore volume of0.72cm3/g.