The invention provides highly reactive nano-sized alumina particle compositions, including alumina compositions with a BET surface areas on the order of 2000 m.sup.2/g. Also disclosed are impregnated alumina supports comprising materials that are metal oxides or carbonates. Methods for the synthesis and fabrication of these compositions are provided, along methods for the use of these compositions as sorbents.

A boehmite structure includes a plurality of boehmite particles where adjacent boehmite particles are bonded to each other. The boehmite structure has a porosity of 30% or less. A method of producing a boehmite structure includes obtaining a mixture by mixing hydraulic alumina with a solvent including water, and pressurizing and heating the mixture under a condition of a pressure of 10 to 600 MPa and a temperature of 50 to 300° C.

Disclosed is alumina having a water desorption index H (=(V.sub.d0.5-V.sub.a0.5)÷V.sub.a0.9) of 0.15 or less in a water adsorption/desorption isotherm at 25° C., where V.sub.d0.5 represents a water adsorption amount [mg/g] per 1 g of alumina in the desorption isotherm at a relative water vapor pressure of 0.5, V.sub.a0.5 represents a water adsorption amount [mg/g] per 1 g of alumina in the adsorption isotherm at a relative water vapor pressure of 0.5, and V.sub.a0.9 represents a water adsorption amount [mg/g] per 1 g of alumina in the adsorption isotherm at a relative water vapor pressure of 0.9.

The present invention refers to a process for the preparation of a high surface area nanoparticulate alpha alumina.

The present invention refers to a process for the preparation of a high surface area nanoparticulate alpha alumina.

An object of the present invention is to provide an alumina used for a slurry for reducing unevenness in a surface of a porous membrane. The present invention is an α-alumina wherein a crystallite size obtained by a Rietveld analysis is not greater than 95 nm, and a lattice strain obtained by the Rietveld analysis is not greater than 0.0020. A BET specific surface area by a nitrogen adsorption method of the α-alumina is preferably not greater than 10 m.sup.2/g. A particle diameter D50 equivalent to 50% cumulative percentage by volume of the α-alumina is also preferably not greater than 2 μm.

The present invention relates to an alpha alumina having a high purity, a high density and a low surface area and particularly, to a method to produce such an alpha alumina as well as to the use of the alpha alumina in sapphire production or the production of composite and ceramic bodies.

A process of forming a sintered article includes heating a green portion of a tape of polycrystalline ceramic and/or minerals in organic binder at a binder removal zone to a temperature sufficient to pyrolyze the binder; horizontally conveying the portion of tape with organic binder removed from the binder removal zone to a sintering zone; and sintering polycrystalline ceramic and/or minerals of the portion of tape at the sintering zone, wherein the tape simultaneously extends through the removal and sintering zones.

The present disclosure is directed to an alpha alumina powder having a specific surface area, a specific crystallite size, and a specific particle size distribution for use in abrasive polishes, and method of making such powder. The method of making the alpha alumina powder can include calcining an aluminum oxide precursor powder at a temperature of 800-1500° C. and milling the calcined powder to the specific particle size distribution. The alpha alumina powder disclosed herein can quickly enable high removal rate with undiminished aesthetic quality when used in abrasive polishes.

An alumina exhibiting a structure with a porosity such that the volume of the pores having a diameter of between 70 and 2000 Å is between 0.15 and 0.50 ml/g, and comprising at least one alkali metal (M), such that the content by weight of alkali metal, expressed as M.sub.2O, is between 400 and 1500 ppm, with respect to the total weight of the alumina, and a process for the transformation of a feedstock comprising at least one alcohol into an olefinic effluent, said process comprising a stage of dehydration of said alcohol in the presence of the alumina according to the present invention, having an acidity and a structure with a porosity which are optimal.