A process for the preparation of an alumina in the form of beads with a sulphur content in the range 0.001% to 1% by weight and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads is described, said beads being prepared by shaping an alumina gel having a high dispersibility by drop coagulation. The alumina gel is itself prepared using a specific precipitation preparation process in order to obtain at least 40% by weight of alumina with respect to the total quantity of alumina formed at the end of the gel preparation process right from the first precipitation step, the quantity of alumina formed at the end of the first precipitation step possibly even reaching 100%. The invention also concerns the use of alumina beads as a catalyst support in a catalytic reforming process.

A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

A process of making a silica-alumina composition having improved properties is provided. The process includes (a) mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound and an acid, while maintaining a pH of the mixed solution in a range of 1 to 3, and obtaining an acidified silica-alumina sol; (b) adding an aqueous solution of a base precipitating agent to the acidified silica-alumina sol to a final pH in a range of 5 to 8, and co-precipitating a silica-alumina slurry, wherein the base precipitating agent is selected from ammonium carbonate, ammonium bicarbonate, and any combination thereof; (c) optionally, hydrothermally aging the silica-alumina slurry to form a hydrothermally aged silica-alumina slurry; and (d) recovering a precipitate solid from the silica-alumina slurry or the hydrothermally aged silica-alumina slurry, wherein the precipitate solid comprises the silica-alumina composition.

A process of making a silica-alumina composition having improved properties is provided. The process includes (a) mixing an aqueous solution of a silicon compound and an aqueous solution of an aluminum compound and an acid, while maintaining a pH of the mixed solution in a range of 1 to 3, and obtaining an acidified silica-alumina sol; (b) adding an aqueous solution of a base precipitating agent to the acidified silica-alumina sol to a final pH in a range of 5 to 8, and co-precipitating a silica-alumina slurry, wherein the base precipitating agent is selected from ammonium carbonate, ammonium bicarbonate, and any combination thereof; (c) optionally, hydrothermally aging the silica-alumina slurry to form a hydrothermally aged silica-alumina slurry; and (d) recovering a precipitate solid from the silica-alumina slurry or the hydrothermally aged silica-alumina slurry, wherein the precipitate solid comprises the silica-alumina composition.

Disclosed herein is a method of producing alumina trihydrate crystals from an alumina trihydrate recovery process stream wherein an aqueous emulsion comprising an alkyl or alkenyl succinic anhydride is added to the alumina trihydrate recovery process stream, wherein the aqueous emulsion is substantially free of mineral oils. The method provides a decrease in percentage of alumina trihydrate crystals having a volume average diameter of less than about 45 micrometers compared to the percentage of alumina trihydrate crystals produced in the absence of the aqueous emulsion of an alkyl or alkenyl succinic anhydride.

Disclosed herein is a method of producing alumina trihydrate crystals from an alumina trihydrate recovery process stream wherein an aqueous emulsion comprising an alkyl or alkenyl succinic anhydride is added to the alumina trihydrate recovery process stream, wherein the aqueous emulsion is substantially free of mineral oils. The method provides a decrease in percentage of alumina trihydrate crystals having a volume average diameter of less than about 45 micrometers compared to the percentage of alumina trihydrate crystals produced in the absence of the aqueous emulsion of an alkyl or alkenyl succinic anhydride.

Disclosed herein is a method of producing alumina trihydrate crystals from an alumina trihydrate recovery process stream wherein an aqueous emulsion comprising an alkyl or alkenyl succinic anhydride is added to the alumina trihydrate recovery process stream, wherein the aqueous emulsion is substantially free of mineral oils. The method provides a decrease in percentage of alumina trihydrate crystals having a volume average diameter of less than about 45 micrometers compared to the percentage of alumina trihydrate crystals produced in the absence of the aqueous emulsion of an alkyl or alkenyl succinic anhydride.

Disclosed herein is a method of producing alumina trihydrate crystals from an alumina trihydrate recovery process stream wherein an aqueous emulsion comprising an alkyl or alkenyl succinic anhydride is added to the alumina trihydrate recovery process stream, wherein the aqueous emulsion is substantially free of mineral oils. The method provides a decrease in percentage of alumina trihydrate crystals having a volume average diameter of less than about 45 micrometers compared to the percentage of alumina trihydrate crystals produced in the absence of the aqueous emulsion of an alkyl or alkenyl succinic anhydride.

A sintered compact has a first material, a second material, and a third material. The first material is cubic boron nitride. The second material is a compound including zirconium. The third material is an aluminum oxide and the aluminum oxide includes a fine-particle aluminum oxide. The sintered compact has a first region in which not less than 5 volume % and not more than 50 volume % of the fine-particle aluminum oxide is dispersed in the second material. On arbitrary straight lines in the first region, an average value of continuous distances occupied by the fine-particle aluminum oxide is not more than 0.08 m and a standard deviation of the continuous distances occupied by the fine-particle aluminum oxide is not more than 0.1 m.