Natural or produced alumina monohydrate and alumina trihydrate have the characteristics of small pore volume, small specific surface area, and low activity. They cannot be used as desiccants, adsorbents, catalysts and catalyst carriers. Therefore, it is necessary to process alumina monohydrate or alumina trihydrate into pseudo-boehmite. The product has the characteristics of high specific surface area, large pore volume, large pore size, and high activity. It is suitable for petrochemical, fertilizer, exhaust gas and other fields as a desiccant, adsorbent, catalyst and catalyst carrier.
One is to prepare pseudo-boehmite by carbonization. The carbonization method to prepare the product is based on the sintering method for preparing alumina. Take NaAlO2 solution and CO2, the central product in the production process, as the response material. The process is simple, the cost is the lowest, there is basically no waste discharge, and the environmental pollution is small. This is a competitive advantage and a way out. The quality of the product prepared by the carbonization method is related to the production conditions such as the concentration of the material, the gelation temperature, the pH value, the aging temperature and time, and the drying temperature of the wet cake. The defects of the carbonization method to produce the product are that the product contains impurities, the purity is not high, and the sodium washing water consumption is large.
The second is the alkaline method to produce the product. In order to get used to the replacement of catalysts in chemical fertilizer plants, the research and development and production of fertilizer catalysts have been handled. The technical indicators of the alumina carrier are: the apparent density is 0.5～0.65 kg/L, the mass fraction of alumina is 94%～95.5%, the mass fraction of sodium oxide is 0.01%～0.03%, the specific surface area is 175-250M2/g, The pore volume is about 0.50ML/g, and the pore diameter is 3-6nm. The pore diameter of the product is 0.7-1ml/g, the pore diameter is scattered in 10-50nm, and the most suitable pore size is 40nm. It is a high-quality product with a wide range of uses.
The third is the acid method to produce the product. The depositing agent ammonia (or sodium hydroxide, sodium carbonate, etc.) is added to the aluminum trichloride (or aluminum sulfate) solution, and then the product is obtained through deposition, filtration, scrubbing and drying. The effects of neutralization temperature, pH value, repertoire concentration and aging conditions on the pore structure were discussed. This method has the advantages of large pore volume, large specific surface area, and high cost.
The fourth is the production of pseudo-boehmite by the double aluminum method. The so-called "double aluminum method" is that aluminum sulfate and sodium metaaluminate react in parallel to prepare the product.
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