High-temperature reaction of kaolin with sulfuric acid

A new procedure is described in which kaolin and a small amount; of concentrated sulfuric acid are heated in a furnace at temperatures between 150 and 1000 degreesC. Parameters studied were reaction temperature and time, proton to alumina molar ratio, calcination temperature and time, and amount of water in the reaction medium. Al yield grew sharply until reaching a maximum at a reaction temperature of 700degreesC and decreasing sharply beyond this temperature. Ti reaction yield values were lower than the Al reaction yield, showing a maximum at 200 degreesC and decreasing steadily as the reaction temperature was increased. Fe reaction yield showed a maximum in the same range of reaction temperature as Al. Previous calcination of kaolin produced only slight increases in reaction yields. Brunauer-Emmett-Teller (BET) surface area tests indicated an increase of the BET surface area for short reaction times, reaching values above 100 m(2)/g. Products of the reaction were mostly Al-2(SO4)(3).