Aluminum hydroxide heating

Kaolin3 Talcb Heat treatment Aluminum hydroxide ... 

Aluminum Oxide (Alumina, oAlumina, Corundum, Alandum). A1203, mw 101.96, v hard white cryst powd, mp 2045°, bp 2980°, d 3.965g/cc. Insol in w, v si sol in aq alkaline solns. Found in nature as a mineral such as bauxite. Lab prepn is by heating aluminum hydroxide to above 1100°. 

Oil and hydrocarbon leaks that return with the condensate coat heat-exchange surfaces and cause FW system fouling and deposit binding. These materials must be removed or they will reenter the boiler to produce nonwettable boiler surfaces, and create serious problems. Oil in condensate should be removed by the use of an inline pre-coat filter. The pre-coating should be either aluminum hydroxide ox ferric hydroxide becaue both these hydrous oxide gels have an affinity for oil. 

Aluminum is the most abundant metallic element in the Earth s crust and, after oxygen and silicon, the third most abundant element (see Fig. 14.1). However, the aluminum content in most minerals is low, and the commercial source of aluminum, bauxite, is a hydrated, impure oxide, Al203-xH20, where x can range from 1 to 3. Bauxite ore, which is red from the iron oxides that it contains (Fig. 14.23), is processed to obtain alumina, A1203, in the Bayer process. In this process, the ore is first treated with aqueous sodium hydroxide, which dissolves the amphoteric alumina as the aluminate ion, Al(OH)4 (aq). Carbon dioxide is then bubbled through the solution to remove OH ions as HCO and to convert some of the aluminate ions into aluminum hydroxide, which precipitates. The aluminum hydroxide is removed and dehydrated to the oxide by heating to 1200°C. 

A Typical Lithium Aluminum Hydride Reduction. JACS, 72, 2781 (1950). To a well stirred mixture of 53 g lithium aluminum hydride (LAH) and 2500 ml of dry ether is added 55 g of 4-hydroxy-3-methoxy-B-nitrostyrene (or equimolar ratio of nitropropene or analog) in 150 ml of dry ether over an hour and 20 min. Stir and reflux for about 9 hours, taking care to exclude all moisture. Cool and add 3000 ml of ice cold 1.5 N sulfuric acid dropwise with good stirring (the acid addition can be speeded up after about half of it has been added). The water layer is separated and its pH adjusted to 6 with solid lithium carbonate. This solution is heated to boiling and the aluminum hydroxide that precipitates is filtered off The hot filtrate is mixed with a solution of 70 g of picric acid in the minimum amount of hot ethanol that it takes to dissolve the picric. Let stand for 4 hours, filter and recrystallize from water. 

Chlorides Aluminum chloride AlClj 6H20. white crystals, soluble, by reaction of aluminum hydroxide and HC1. and then crystallizing anhydrous aluminum chloride A1C1-, white powder, fumes in air, formed by reaction of dry aluminum oxide plus carbon heated with chlorine in a furnace, used as a reagent in petroleum refining and other organic reactions. 

Hydroxide Aluminum hydroxide Al(OH>3, white gelatinous precipitate, by reaction of soluble, aluminum salt solution and an alkali hydroxide, carbonate or sulfide (sodium aluminate is formed with excess NaOH but no reaction with excess NH4OH). upon heating aluminum hydroxide the residue formed is aluminum oxide. Used as intermediate substance in transforming bauxite into pure aluminum oxide. 

Oxide Aluminum oxide, alumina AI1O3, white solid, insoluble, melting point 2020 C. formed by heating aluminum hydroxide to decomposition when bauxite is fused in the electric furnace and then cooled, there results a very hard glass ( alundum ), used as an abrasive (hardness 9 Mohs scale) and heat refractory material. Aluminum oxide is the only oxide that reacts both 111 H20 medium and at fusion temperature, 10 form salts with both acids and alkalis. 

Like the hydroxides of the Rare earth, scandium hydroxide, Sc(OH)3, is precipitated by addition of alkalies to solutions of scandium salts however, the latter is precipitated at pH 4.9, while the former require pH 6.3 or more, a property which is utilized in one method of separation. Upon heating the hydroxide (or certain oxyatid salts), scandium oxide. Sc>C>3 is produced. Scandium hydroxide is less acidic than aluminum hydroxide, requiring boiling KOH solution to form the complex potassium compound, K2[Sc(OH)5 H 0] 3H 0. 

The aluminum hydroxide is removed and dehydrated to the oxide by heating to 1200°C ... 

Subsequent heating converts the aluminum hydroxide to alumina. 

The reactant concentrations of 48 g of sodium aluminate and 105 g of lactose are equivalent to a mol ratio of two mols of aluminate to one mol of lactose. The mixture was then heated to 50°C and 100 ml aliquots were removed at periodic intervals to determine the level of conversion. The reaction was terminated after three hours by adding sufficient 30% HCI to lower the pH to 4.2. The pH was then raised to neutrality, i.e., 6.5 to 7.0, with ammonium hydroxide so as to completely precipitate insoluble aluminum hydroxide. The precipitate was then removed by vacuum filtration and the filtrate was analyzed for the presence of ketose sugar by chromatographic analysis. The chromatographic analysis of the filtrate confirmed that the main component of the filtrate was lactulose and not the monosaccharide ketose sugar, fructose. 

In the process to produce alumina (Fig. 1), bauxite is crushed and wet ground to 100-mesh, dissolved under pressure and heated in digesters with concentrated spent caustic soda solution from a previous cycle and sufficient lime and soda ash. Sodium aluminate is formed, and the dissolved silica is precipitated as sodium aluminum silicate. The undissolved residue (red mud) is separated from the alumina solution by filtration and washing and sent to recovery. Thickeners and Kelly or drum filters are used. The filtered solution of sodium aluminate is hydrolyzed to precipitate aluminum hydroxide by cooling. The precipitate is filtered from the liquor, washed, and heated to 980°C in a rotary kiln to calcine the aluminum hydroxide. 

Although, the decomposition of aluminum hydroxide to oxide is usually written as one step, it can proceed through an intermediate mono-hydroxide [boehmite, A10(0H)], which often has a much higher stability than the hydroxide, decomposing at about 450°C and, if present, can reduce fire-retardant effectiveness. In addition, several so-called transition aluminas are formed upon heating of hydroxides, depending on the applied temperature.31 Boehmite formation can occur when the... 

Experimental conditions temperature 525°C hydrogen pressure 1.5 atm I g catalyst. The a-A Oj was prepared by heating aluminum hydroxide to 1200°C specific area 40 m2/g. 

Figure 7. Sequence of phases formed after thermal treatment of aluminum hydroxides and aluminum oxide hydroxides. Pathway (a) is favored by pressures exceeding 1 bar, moist air, heating rates higher than IK min-1 and particle sizes higher than 100 fim. Pathway (b) is favored by pressures of 1 bar, dry air, heating rates below 1 Kmin-1 and particle sizes below 10 pm.

As in the previous procedures, to prepare aluminum oxide, all you need to do is place the dried mass of hydrated aluminum hydroxides (prepared in step 1) into a crucible and then heat at 600 to 800 Celsius using a typical Bunsen burner for about 3 to 4 hours. During the heating process, water is volatized and removed, and the hydrate aluminum hydroxides are dehydrated forming a white powder. After the roasting process, the aluminum oxide is cooled, and then stored in any suitable container. This aluminum oxide is well suitable for use as a filtering aid, and for use in silica gel columns for filtration purification. 

This acid-phosphate is formed when a mixmre of aluminum hydroxide and phosphoric acid solution is heated between 100 and 120°C. The reaction is represented as... 

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