Gamma alumina is made by dehydration of aluminum hydroxide at a low temperature of 140-150 ° C. It is also called activated alumina and aluminum glue in industry. Oxygen ions in its structure are approximately tightly packed in the center of the cubic face, and AL3 + is irregularly distributed in the octahedral and tetrahedral voids surrounded by oxygen ions. Gamma-type alumina is insoluble in water and can be dissolved in strong acid or alkali solutions. It is fully converted into alpha-type alumina when heated to 1200 ° C. Gamma-type alumina is a porous substance with an internal surface area of hundreds of square meters per gram and strong adsorption capacity. Industrial products are often colorless or slightly pink cylindrical particles with good pressure resistance. In petroleum refining and petrochemical industry, it is a commonly used adsorbent, catalyst and catalyst carrier; in industry, it is a deacidifier for transformer oil and turbine oil, and it is also used for color layer analysis; in the laboratory, it is a neutral strong desiccant, whose drying capacity is no less than phosphorus pentoxide, and it can be regenerated and reused after heating below 175 ° C for 6-8H.