A dual channel showerhead comprising a first plurality of channels formed in the back surface of the showerhead and extending from a first end to a second end, a second plurality of channels formed through the thickness of the showerhead and extending from a first end to a second end, a first end plenum in fluid connection with the second plurality of channels at the first end and a second end plenum in fluid connection with the second plurality of channels at the second end. Processing chambers including the dual channel showerhead and a blocker ring separating the edge ring from the pumping ring are also discussed.

Disclosed is an alumina slurry substantially including alpha-alumina particles and water, wherein the alpha-alumina particles satisfy all particle diameter distribution conditions (a) to (d) mentioned below, the alpha-alumina particles have an alumina purity of 90% by weight or more, the content of alumina in the slurry is 20% by weight or more and 50% by weight or less, and the slurry has a viscosity of 0.5 Pa.Math.s or more and 15 Pa.Math.s or less: condition (a): the average particle diameter is 1 m or less, condition (b): particles having a particle diameter of less than 0.2 m account for 7% by weight or less, condition (c): particles having a particle diameter of more than 1.5 m account for 15% by weight or less, and condition (d): one or more frequency maximums exist in a particle diameter range of 0.1 m or more and less than 0.5 m.

An alumina powder containing a hydroxycarboxylic acid and an alkaline component contains amorphous alumina, pseudoboehmite, or boehmite, and satisfies all of (1) to (4). (1) A colloidal dispersion A with 2.5% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and distilled water is free from precipitate, and has a light transmittance of at least 80% measured at a wavelength of 500 nm and an optical path length of 10 mm. (2) A colloidal dispersion B with 15% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and distilled water is free from precipitate. (3) The dispersions A and B have a pH in a range of 5 to 8. (4) A colloidal dispersion C with 2.5% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and methanol is free from precipitate, and has a light transmittance of at least 80% measured under the above condition.

The present disclosure relates to an alumina having a surface area in the range of 330-400 m.sup.2/g, a pore volume in the range of 1.2-1.7 cc/g, and an average pore diameter in the range of 125-160 . The present disclosure also relates to alumina extrudates having a diameter in the range of 1 mm to 3 mm, a surface area in the range of 300-360 m.sup.2/g, a pore volume in the range of 0.8-1.3 cc/g and pore diameter in the range of 90-130 with a crushing strength in the range of 1-2.5 daN/mm. Further, the present disclosure relates to a process for the preparation of alumina and alumina extrudates. The alumina extrudates can be used as a support for catalyst preparation or as a catalyst or adsorbent in various processes. The process of the present disclosure enhances metal loading capacity, has better metal dispersion, and exhibit delay in deactivation of the catalyst due to mouth pore plugging.

Described herein are stable aqueous dispersions of alumina; methods of decreasing the viscosity of an alumina slurry; methods of decreasing the D50 of an alumina slurry; and methods of decreasing the level of hard packing in an alumina slurry, where the slurry comprises alumina feed material, water, and a dispersant agent.

A method of making an alumina including providing an alumina slurry, aging the slurry, adding a tricarboxylic acid to the aged alumina slurry, further aging the slurry, and spray drying, the method being characterized by the addition of a dicarboxylic acid either at the same time as the tricarboxylic acid, or after the second aging and before the spray drying. The resulting alumina is dispersible at a pH greater than 9.5 above 95% and has a viscosity below 0.4 Pa.Math.S for 10 wt % sols.

A dual channel showerhead comprising a first plurality of channels formed in the back surface of the showerhead and extending from a first end to a second end, a second plurality of channels formed through the thickness of the showerhead and extending from a first end to a second end, a first end plenum in fluid connection with the second plurality of channels at the first end and a second end plenum in fluid connection with the second plurality of channels at the second end. Processing chambers including the dual channel showerhead and a blocker ring separating the edge ring from the pumping ring are also discussed.

An alumina powder containing a hydroxycarboxylic acid and an alkaline component contains amorphous alumina, pseudoboehmite, or boehmite, and satisfies all of (1) to (4). (1) A colloidal dispersion A with 2.5% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and distilled water is free from precipitate, and has a light transmittance of at least 80% measured at a wavelength of 500 nm and an optical path length of 10 mm. (2) A colloidal dispersion B with 15% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and distilled water is free from precipitate. (3) The dispersions A and B have a pH in a range of 5 to 8. (4) A colloidal dispersion C with 2.5% by mass of Al.sub.2O.sub.3 consisting of the alumina powder and methanol is free from precipitate, and has a light transmittance of at least 80% measured under the above condition.

A method of making an alumina including providing an alumina slurry, aging the slurry, adding a tricarboxylic acid to the aged alumina slurry, further aging the slurry, and spray drying, the method being characterized by the addition of a dicarboxylic acid either at the same time as the tricarboxylic acid, or after the second aging and before the spray drying. The resulting alumina is dispersible at a pH greater than 9.5 above 95% and has a viscosity below 0.4 Pa.Math.S for 10 wt % sols.

A method of making an alumina including providing an alumina slurry, aging the slurry, adding a tricarboxylic acid to the aged alumina slurry, further aging the slurry, and spray drying, the method being characterized by the addition of a dicarboxylic acid either at the same time as the tricarboxylic acid, or after the second aging and before the spray drying. The resulting alumina is dispersible at a pH greater than 9.5 above 95% and has a viscosity below 0.4 Pa.Math.S for 10 wt % sols.