A method for producing boehmite under atmospheric pressure may include producing a sodium aluminate solution by dissolving sodium aluminate in water. The method may further include producing an aluminum hydroxide gel by mixing a hydrochloric acid solution with the sodium aluminate solution. The method may further include producing an aluminum chloride solution by mixing a hydrochloric acid solution with the aluminum hydroxide gel. The method may further include producing saturated aluminum chloride solution by heating the aluminum chloride solution. The method may further include producing a boehmite gel by mixing an ammonia solution with the saturated aluminum chloride solution and heating the boehmite gel to produce boehmite.

A method for producing boehmite under atmospheric pressure may include producing a sodium aluminate solution by dissolving sodium aluminate in water. The method may further include producing an aluminum hydroxide gel by mixing a hydrochloric acid solution with the sodium aluminate solution. The method may further include producing an aluminum chloride solution by mixing a hydrochloric acid solution with the aluminum hydroxide gel. The method may further include producing saturated aluminum chloride solution by heating the aluminum chloride solution. The method may further include producing a boehmite gel by mixing an ammonia solution with the saturated aluminum chloride solution and heating the boehmite gel to produce boehmite.

The present invention relates to a process for the preparation of particulate alumina, the process comprising (i) preparing a mixture comprising water and one or more sources of alumina; (ii) spraying the mixture for forming droplets; (iii) heating the droplets in a non-polar organic solvent system to a specific temperature, to obtain precursor particles; (iv) heating the precursor particles in an aqueous solution to a specific temperature, wherein the pH of said aqueous solution is adjusted to a value in the range of from 12 to 14. Further, the present invention relates to a particulate alumina as obtained and/or obtainable by said process. Yet further, the present invention relates to a particulate alumina having a side crushing strength in the range of from 9 to 25 N/mm and a packed apparent bulk density in the range of from 0.45 to 0.55 g/cm.sup.3 and use thereof.

The present invention relates to a process for the preparation of particulate alumina, the process comprising (i) preparing a mixture comprising water and one or more sources of alumina; (ii) spraying the mixture for forming droplets; (iii) heating the droplets in a non-polar organic solvent system to a specific temperature, to obtain precursor particles; (iv) heating the precursor particles in an aqueous solution to a specific temperature, wherein the pH of said aqueous solution is adjusted to a value in the range of from 12 to 14. Further, the present invention relates to a particulate alumina as obtained and/or obtainable by said process. Yet further, the present invention relates to a particulate alumina having a side crushing strength in the range of from 9 to 25 N/mm and a packed apparent bulk density in the range of from 0.45 to 0.55 g/cm.sup.3 and use thereof.

A pseudo-boehmite has a dry basis content of 55-85 wt % and contains a phosphoric acid ester group. The sodium oxide content is not greater than 0.5 wt %, and the phosphorus content (in terms of phosphorus pentoxide) is 1.2-5.7 wt %, relative to 100 wt % of the total weight of the pseudo-boehmite. The pseudo-boehmite has a low sodium content.

A pseudo-boehmite has a dry basis content of 55-85 wt % and contains a phosphoric acid ester group. The sodium oxide content is not greater than 0.5 wt %, and the phosphorus content (in terms of phosphorus pentoxide) is 1.2-5.7 wt %, relative to 100 wt % of the total weight of the pseudo-boehmite. The pseudo-boehmite has a low sodium content.

A method of manufacturing a nanocomposite may include combining a magnesium salt, an aluminum salt, and a ferric salt in stoichiometric proportions within 5 mol. % in an aqueous solvent including menthol or dextrose, to obtain a first mixture, heating the first mixture to remove at least 99.5 wt. % of the aqueous solvent to obtain a first solid, grinding the first solid into a first powder, calcining the first powder at a temperature of about 600 C. to 800 C. for a time of about 2 to 4 hours to obtain a second solid, grinding the second solid and urea, in an amount sufficient to form the nanocomposite, into a second powder, heating the second powder at a temperature of about 550 C. to 650 C. for a time of about 15 minutes to 1.5 hours to obtain the nanocomposite.

A method of manufacturing a nanocomposite may include combining a magnesium salt, an aluminum salt, and a ferric salt in stoichiometric proportions within 5 mol. % in an aqueous solvent including menthol or dextrose, to obtain a first mixture, heating the first mixture to remove at least 99.5 wt. % of the aqueous solvent to obtain a first solid, grinding the first solid into a first powder, calcining the first powder at a temperature of about 600 C. to 800 C. for a time of about 2 to 4 hours to obtain a second solid, grinding the second solid and urea, in an amount sufficient to form the nanocomposite, into a second powder, heating the second powder at a temperature of about 550 C. to 650 C. for a time of about 15 minutes to 1.5 hours to obtain the nanocomposite.

The alumina powder contains: a first alumina particle having an average particle diameter of 0.1 m or more and less than 1 m; a second alumina particle having an average particle diameter of 1 m or more and less than 10 m; and a third alumina particle having an average particle diameter of 10 m or more and 100 m or less, wherein each of the average particle diameters is a particle diameter measured using laser light diffraction scattering particle size distribution analyzer, average sphericity of first alumina particle having projected area equivalent circle diameter of 0.1 m or more and 1 m or less as determined by microscopy is 0.80 or more and 0.98 or less, a specific surface area of first alumina particle is 1.9 m.sup.2/g or more and 20.0 m.sup.2/g or less, and content ratio of an crystal phase is 80% by mass or more.

The present invention provides a coating agent including -alumina particles having a polyhedral crystal structure and having an average particle size (D50) of 100-900 nm. The -alumina particles are produced in such a way that pseudo-boehmite is mixed with a fluoride-based mineralizer and ultrapure water and pulverized to obtain a powder which is then fired and grown into a polyhedral shape. The polyhedral alumina particles make surface contact and are coated on the surface of a porous polymer substrate, and empty space induced by the interstitial volume between particles is formed larger than that of spherical particles, thereby being capable of achieving excellent air permeability while effectively suppressing thermal contraction of the porous polymer substrate. In addition, due to a nano-level particle size, excellent dispersibility and the formation of a thin coating layer can be achieved.