Preparation Of High Purity Pseudo-boehmite By Hydrolysis Of Aluminium Isopropanol

Pseudo-boehmite has large specific surface area,good adhesion,large pore volume,which can be used as catalyst and catalyst carrier,adsorbent,fine abrasive and so on.In the preparation process of pseudo-boehmite,isopropyl alcohol aluminum hydrolyzing method is environmentally friendly,the product of pseudo-boehmite has high purity,good performance,and is adopted by some high-purity alumina production enterprises in China.In practical production,there are some problems such as poor peptizing properties of pseudo-boehmite and low recovery of isopropanol.In order to solve the above problems,this project explored the influence of preparation conditions in one-step hydrolysis and two-step hydrolysis on the carbon content,crystal phase and dispersion index of hydrolysate under the condition of low water-aluminum ratio hydrolysis,so as to improve the recovery rate of isopropyl alcohol and realize recycling.The hydration operation is carried out to further improve the peptizing properties of the product.Finally,the two hydrolysis methods were compared to explore a better process for industrial production.（1）Preparation of pseudo-boehmite by one-step hydrolysis.Under the condition of a small amount of water,the effects of preparation factors on the properties of the product were investigated.During the hydrolysis of aluminum isopropyl alcohol,the carbon content of the product was affected by the change of preparation conditions,and the water consumption was the most obvious.With the increase of water dosage,the crystallinity of the product increased,and the dispersion index increased from 2.3%to more than 95%.Prolonging hydrolysis time was beneficial to the growth of grain size and the improvement of dispersion index（increased from 35.4%to over 65%）.The dispersion index of the product increased with the dripping time,but the dripping time had no effect on the crystallinity of the product.Drying temperature and drying time had little effect on crystallinity and dispersion index.（2）Preparation of pseudo-boehmite by two-step hydrolysis.Two-step hydrolysis method was adopted to explore the influence of hydrolysis time and dripping time on the peptizing properties of the product.Regardless of changing hydrolysis parameters in the first step or in the second step,the dispersion index of the product would increase gradually with the extension of hydrolysis time and dripping time（The dispersion index of the optimal product was 74.67%）.During the two hydrolysis processes,when the hydrolysis time was investigated,the effect of the second hydrolysis process on the crystallinity and peptizing properties of the product was more obvious,while the effect of the first hydrolysis process on the peptizing properties of the product was more obvious when the dripping time factor was investigated.Hydrolysis time can change the crystallinity of the product,but dripping time has no effect on crystallinity.（3）High peptizing properties pseudo-boehmite was prepared by hydration.The hydration process was carried out to explore the effects of agitation state,hydration temperature and hydration time on the properties of the hydration product.It is concluded that hydration process can effectively improve the peptizing properties of the product,and hydration temperature has the most obvious effect on the peptizing properties of the product.With the increase of hydration temperature,the gelatinization time of the product was rapidly shortened,the specific surface area of theγ-Al₂O₃ decreased rapidly（when the hydration temperature was 130℃,the specific surface area was lower than 200 m²/g）,and the crystallinity of the product was significantly enhanced.With the extension of hydration time,the crystallinity of the product increases,the gelatinization time and the specific surface area of theγ-Al₂O₃ decreased.The static state is more conducive to crystallization and the gelatinization time of the product is shorter than that of the product in the stirred state.（4）Comparison between one-step hydrolysis method and two-step hydrolysis method.The product and equipment cost of the two hydrolysis methods were compared.In terms of product properties,the crystallinity and peptizing properties of the hydration products obtained by the two hydrolysis methods are excellent,and the peptizing properties of the products is close to the level of SB powder.In terms of equipment cost,taking the annual output of 1000 tons of high-purity pseudo-boehmite as an example,the equipment cost of one-step hydrolysis method（7.4 million yuan）is far less than that of two-step hydrolysis method（13.3 million yuan）.By comprehensive comparison,there is little difference in the properties of the products obtained by the two hydrolysis methods.One-step hydrolysis method has lower equipment cost and more advantages in production.