Abstract:
Low density alumina spheres of improved strength at high temperature are prepared by commingling an acidic alumina sol and an aqueous rare earth metal salt solution with an ammonia precursor at below gelation temperature and dispersing the mixture as droplets in a hot oil bath. The hydrogel spheres which form are aged, washed and dried, and calcined. Low density alumina spheres are useful as a catalyst or as a catalyst support, particularly in the conversion of hot exhaust gases from an internal combustion engine.
Abstract:
SPHERICAL ALUMINUM OXIDE GELS ARE MADE BY FEEDING DROPS OF A COAGULABLE AQUEOUS SLURRY OF HYDROUS ALUMINA INTO A COLUMN OF A WATER-IMMISCIBLE LIQUID, E.G., MINERAL OIL, WHICH CAN BE MAINTAINED AT CLOSE TO AMBIENT TEMPERATURE. THE HYDROUS ALUMINA IS PREPARED BY HYDROLYSIS OF FINELY DIVIDED ALUMINUM HAVING A SURFACE AREA OF ABOUT 75,000 TO 1,000,000 SQUARE MILLIMETERS PER GRAM, AND THE HYDROLYSIS MEDIUM IS ACIDIC FROM THE PRESENCE OF A NONOXIDIZING ACID FOR INSTANCE, FORMIC ACID. THE HYDROUS ALUMINA FEED HAS A RATIO OF ALUMINA MONOHYDRATE TO AMOR-
PHOUS HYDROUS ALUMINA OF AT LEAST 0.5/1 AND THE ALUMINA MONOHYDRATE HAS A CRYSTALLINE SIZE OF LESS THAN 65 A. AMMONIA CAN BE ADDED TO THE COLUMN TO AID THE COAGULATION. OTHER SOLIDS, FOR INSTANCE, CALCINED ALUMINA, ALUMINA TRIHYDRATE, SILICA OR CARBON CAN BE INCORPORATED IN THE AQUEOUS SLURRY AS CAN ALUMINUM OXYUCHLORIDE. DRYING AND CALCINATION OF THE COAGULATED HYDROUS ALUMINA PROVIDES ADSORPTIVE SOLIDS WITH ADVANTAGEOUS CHARACTERISTIC WHEN USED, FOR INSTANCE, AS CATALYST COMPONENTS.
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*-650*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.
Abstract:
Porous catalyst bodies are produced from a thermally stable inorganic carrier material by introducing a suspension of the said carrier material into a liquid immiscible with the suspension medium and heated above the boiling point of the said medium. After evaporation of the suspension medium to an essential extent, the porous catalyst bodies formed are separated from the liquid and subsequently heated to an elevated temperature to improve the strength caracteristics thereof.
Abstract:
Silica particles, e.g., in bead form, are prepared from an alkali-metal (preferably sodium) silicate in an aqueous-organic reaction medium at ambient (preferably) or higher temperature and at a pH within the range of from 4.5 to 10. The organic (preferably recoverable organic) medium is critical and has a specifically defined bead-making capability. It provides a dispersed phase in which a silica ''''hydrosol'''' derived from an alkali-metal silicate is soluble and wherein it can polymerize to yield gelled particles of silica. Examples of operative organic media are n-hexylamine, 2ethylhexylamine, 2-methyl-5-ethylpyridine, n-hexyl Carbitol and n-hexyl Cellosolve. Organic media found to be inoperative are 2methyl-1-pentanol, 1-hexanol, 5-ethylbutanol and n-butanol. Descriptions are given of the two different types of silica products that are obtained; also, details of operating conditions and factors that influence the type of silica particles that result. The silica products are useful as, for example, catalysts and catalyst supports, and in other applications wherein silica in particulate form is employed.
Abstract:
A GERMANIUM COMPONENT IS UNIFORMLY DISPERSED THROUGHTOUT AN ALUMINA CARRIER MATERIAL BY THE STEPS OF: FIRST, UNIFORMLY DISTRIBUTING FINELY DIVIDED GERMANIUM DIOXIDE PARTICLES THROUGHTOUT AN ALUMINUM HYDROXYL HALIDE SOL TO FORM AN INTIMATE MIXTRUE THEREOF; SECOND, GELLING THE RESULTING MIXTURE TO OBTAIN A HYDROGEL; AND, FINALLY, TREATING AND CALCININING THE RESULTING HYDROGEL TO PRODUCE A SOLID COMPOSITE HAVING A GERMANIUM COMPONENT UNIFORMLY DISPERSED THEREIN. KEY FEATURE OF THIS METHOD INVOLVES THE PREPARATION OF THE CATALYST FROM AN ALUMINUM HYDROXYL HALIDE SOL TO WHICH FINELY DIVIDED PARTICLES OF GERMANIUM DIOXIDE ARE ADDED, THEREBY ACHIEVING UNIFORM DISPERSION OF THE GERMANIUM COMPONENT IN THE ALUMINA CARRIER MATERIAL AND ALSO CAUSING SOME BENEFICICAL INTERACTION BETWEEN THE SOL AND THE GERMANIUM DIOXIDE PARTICLES. RESULTING COMPOSITE IS TYPICALLY COMBINED WITH A PLATINUM GROUP COMPONENT AND UTILIZED TO ACCELERATE A WIDE VARIETY OF REACTIONS IN PROCESSES SUCH AS HYDROCRACKING, REFORMING, ISOMERIZATION, ETC.