Showing papers on "Pseudoboehmite published in 1971"

Conditions for the Formation of Bayerite and Gibbsite

Abstract: Aluminium hydroxide gels have been prepared by the hydrolysis of amalgamated aluminium in water and by precipitation from aluminium salt solutions with an anion exchange resin in the hydroxyl form. The products crystallizing from such gels have been examined by electron microscopy and by X-ray and electron diffraction. Bayerite crystallizes as cone or pyramid-shaped particles and gibbsite as hexagonal plates or prisms. Two types of gel are postulated. The first type, pseudoboehmite, predominates in the absence of acids, is uncharged and rapidly crystallizes to bayerite; the second type, pregibbsite gel, occurs in carboxylic acid solutions, is positively charged and, in the absence of inorganic anions, crystallizes slowly to gibbsite.

Agglomerating partially dehydrated gel-derived pseudoboehmitic alumina to form strong porous spheres

Abstract: Gel-derived crystalline alumina containing at least 40 percent pseudoboehmite and having low cationic and anionic impurity levels is partially dehyrated to an LOI of 22-34 percent, ground to at least 85 percent minus 325 mesh, shaped into spheres by conventional agglomerating devices while adding sufficient water to rise the total water content to 52-65 percent These shaped spheres, without any ageing treatment, are then heated to a temperature in the range of 350 DEG -650 DEG C for a time necessary to produce the desired strength The resultant spheres are strong and have a high total porosity, at least 20 percent of which consists of pores in the 120-800 A size range They are useful as desiccants, active alumina and catalyst supports