A method of producing a hydrophobic porous alumina by: i) providing a slurry comprising an alumina compound, the slurry having a pH equal to or greater than 7; ii) adding an organic composition comprising carboxylic acids with alkyl hydrocarbon chains having a carbon length less than 14 to the slurry to form an acidic modified slurry; the acidic modified slurry having a pH of between 3 and less than 7; iii) hydrothermally aging the acidic modified slurry to form a hydrothermally aged slurry; and iv) drying the hydrothermally aged slurry.

A system and method of combusting aluminium comprising i) feeding aluminium wire to a substantially oxygen-free furnace comprising a. a first low-temperature section in communication with b. a second high-temperature section ii) forming aluminium particles with an average particle size ranging from 1 m to 200 m from said aluminium wire in said first section iii) feeding water and/or steam to said first and/or second section to provide an oxidizer for oxidizing said aluminium particles in the second section iv) conveying aluminium particles from the first section to the second section v) oxidizing said aluminium particles in the presence of steam in said second section.

A system and method of combusting aluminium comprising i) feeding aluminium wire to a substantially oxygen-free furnace comprising a. a first low-temperature section in communication with b. a second high-temperature section ii) forming aluminium particles with an average particle size ranging from 1 m to 200 m from said aluminium wire in said first section iii) feeding water and/or steam to said first and/or second section to provide an oxidizer for oxidizing said aluminium particles in the second section iv) conveying aluminium particles from the first section to the second section v) oxidizing said aluminium particles in the presence of steam in said second section.

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.

-Alumina in the related art has an average particle diameter of 2 to 20 m, and it can be said that the -alumina does not necessarily a large particle diameter. As a result, with respect to the molded product obtained from a resin composition including the -alumina in the related art as a filler, high heat dissipation characteristics are not obtained, in some cases. An object of the present invention is to provide means of producing -alumina having a large particle diameter according to a flux method. There is provided a method of producing -alumina particles including molybdenum which have an average particle diameter of greater than 20 m, and the production method includes a step of firing an aluminum compound in the presence of a molybdenum compound and a potassium compound.

-Alumina in the related art has an average particle diameter of 2 to 20 m, and it can be said that the -alumina does not necessarily a large particle diameter. As a result, with respect to the molded product obtained from a resin composition including the -alumina in the related art as a filler, high heat dissipation characteristics are not obtained, in some cases. An object of the present invention is to provide means of producing -alumina having a large particle diameter according to a flux method. There is provided a method of producing -alumina particles including molybdenum which have an average particle diameter of greater than 20 m, and the production method includes a step of firing an aluminum compound in the presence of a molybdenum compound and a potassium compound.

96 parts by mass of a -alumina powder, 4 parts by mass of a an AlF.sub.3 powder, and 0.17 parts by mass of an -alumina powder as a seed crystal were mixed by a pot mill. The purities of each raw material were evaluated, and it was found that the mass ratio of each impurity element other than Al, O, F, H, C, and S was 10 ppm or less. In a high-purity alumina-made sagger having a purity of 99.9 percent by mass, 300 g of the obtained mixed powder was received, and after a high-purity alumina-made lid having a purity of 99.9 percent by mass was placed on the sagger, a heat treatment was perforated at 900 C. for 3 hours in an electric furnace in an air flow atmosphere, so that an alumina powder was obtained. The value of AlF.sub.3 mass/container volume was 0.016 g/cm.sup.3.

96 parts by mass of a -alumina powder, 4 parts by mass of a an AlF.sub.3 powder, and 0.17 parts by mass of an -alumina powder as a seed crystal were mixed by a pot mill. The purities of each raw material were evaluated, and it was found that the mass ratio of each impurity element other than Al, O, F, H, C, and S was 10 ppm or less. In a high-purity alumina-made sagger having a purity of 99.9 percent by mass, 300 g of the obtained mixed powder was received, and after a high-purity alumina-made lid having a purity of 99.9 percent by mass was placed on the sagger, a heat treatment was perforated at 900 C. for 3 hours in an electric furnace in an air flow atmosphere, so that an alumina powder was obtained. The value of AlF.sub.3 mass/container volume was 0.016 g/cm.sup.3.

Core-shell particles may be based on red lead coated with pyrogenically produced titanium dioxide and/or a pyrogenically produced aluminum oxide, and a process may prepare such core-shell particles which may be used in lead-acid batteries. The red lead may include PbO.sub.2 in a range of from 25 to 32 wt. %.

An alumina having a multimodal particle size distribution wherein at least one of the particle sizes giving local maximum values in the particle size distribution is less than 10 m, and wherein the alumina comprises 1 to 5 wt % of at least one of La and Ba.