Aluminum hydroxide suspension, preparation

Oral 350, 420, 500, 600, 650, 750, 1000, 1250 mg chewable tablets 1250 mg/5 ml suspension Combination aluminum hydroxide and magnesium hydroxide preparations (Maalox, Mylanta, Gaviscon, Gelusil, others) Oral 400 to 800 mg combined hydroxides per tablet, capsule, or 5 ml suspension... 

If a carrier is to be incorporated in the final catalyst, the original precipitation is usually carried out in the presence of a suspension of the finely divided support or, alternatively, a compound or suspension, which will eventually be converted to the support, may initially be present in solution. Thus, a soluble aluminum salt may be converted to aluminum hydroxide during precipitation and ultimately to alumina. Alternatively, a supported nickel catalyst could be prepared from a solution of nickel nitrate, containing a suspension of alumina, by precipitation of a nickel hydroxide with ammonia. 

Hydroxide suspensions of mullite with partially stabilized zirconia were prepared from metal alkoxide starting materials. Zirconium isoamyloxide and yttrium isopropoxide were mixed in the proper proportions for the partially stabilized zirconia. Aluminum isopropoxide and silicon ethoxide were added in the proper proportions for mullite. These solutions were refluxed for 4 to 8 h and then hydrolyzed to a pH of 0.5 using HNO3. The solutions were then neutralized to a pH of 8 using NH4OH. The resulting suspensions then contained the proper amount of each component as a hydroxide to form the mullite partially-stabilized zirconia matrix materials. With MgO as a stabilizer, procedures were identical to the above, except that MgO ethoxide was used instead of yttrium isopropoxide. Batch sizes were 25 to 100 g of final material. 

The aluminum oxide layer was applied to the inner walls of the glass capillary from an aqueous dispersion in the form of aluminum hydroxide and converted In situ into aluminum oxide by heat treatment. By varying heat treatment and by blocking unwanted activities with potassium chloride, adjustment to the desired separation characteristics can be achieved [55]. To prepare the coating suspension, aluminum oxide (particles <2 urn) obtained by calcination of hydroxide is heated for 24 h at 300 °C. 20 g of the alumina is mixed with 70 ml of 5% (w/w) Baymal solution (colloidal aluminum hydroxide) and with 0.3 ml of acetic acid (>96%) and stirred for about 10 min in an ultrasonic bath. Subsequently the mixture is filtered through a wire sieve of 300 mesh and allowed to stand for 24 h for aging. The suspension thus prepared shows thixotropic behavior. 

The magnesia and alumina suspension is prepared by treatment of an aqueous solution, containing aluminum and magnesium salt in the desired proportion, with sodium hydroxide. The coprecipitated aluminum and magnesium hydroxides are collected by filtration, washed free of soluble salts, and stabilized by the addition of a suitable hexatol. 

The Raney nickel reagent is prepared by addition of 9.5 g. of sodium hydroxide pellets over 8-10 minutes to a stirred suspension of 7.8 g of nickel-aluminum alloy (50% Ni, 50% A1 powder, purchased from Merck-Schuchardt) in 120 ml. of distilled water contained in a 250-ml. beaker. Fifteen minutes after the addition is completed, the beaker is immersed into a 70° water bath for 20 minutes. The water is decanted, and the catalyst is washed sequentially with two 20-ml. portions of distilled water and two 20-ml. portions of methanol. 

N-4 Raney Ni.58 In a 10-ml conical flask are placed 0.5 g of Raney Ni-Al alloy powder (40% Ni) and 1 g of the bayerite prepared by the procedure described below. To this 10 ml of distilled water is added and stirred well at 40°C. Then 0.03 ml of 20% sodium hydroxide solution is added and the mixture stirred for 30 min at the same temperature, in which a violent reaction almost subsides. A further 0.3 ml of 20% sodium hydroxide solution is added and the mixture stirred for 1 h at 40°C. Then the upper layer is decanted carefully to avoid leakage of the catalyst. The catalyst is washed 3 times with each 10 ml of distilled water and 3 times with the same volume of methanol or ethanol. A specimen of the catalyst thus prepared contains 0.192 g of nickel, 0.050 g of aluminum, and 0.036 g of acid-insoluble materials. The bayerite suspensions are combined and acidified with a dilute hydrochloric acid, and then warmed to 50-60°C, when the gray color of the bayerite turns almost white. The bayerite is collected, washed well with water, and then dried in vacuo over silica gel. The bayerite thus recovered amounts to 1.4-1.6 g and can be reused for the preparation of a new catalyst. 

Aluminum (400 g) is melted and heated to 1200°. Cubes of nickel (300 g) are added to the melt all at once (cubic nickel is more suitable than compact, mechanically worked metal for preparation of the alloys). The nickel dissolves in a lively reaction, the temperature rising to about 1500°. After cooling, the alloy is broken and powdered. The alloy (250 g) is added in small portions to an ice-cold, approximately 25% sodium hydroxide solution (100 ml), whereupon decomposition sets in exothermally with lively evolution of hydrogen (foaming and spitting). When all the alloy has been added, the temperature is raised to 90-100° and kept there until evolution of hydrogen ceases. The metal is allowed to settle and is then decanted, and the treatment with alkali is repeated twice (11 of fresh solution each time). After decantation of the last alkali the precipitated nickel is washed with water by suspension, settling, and decantation until the wash-water reacts neutral to phenolphthalein. The water is then replaced by alcohol. The catalyst is stored under alcohol in bottles. 

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