Hydrolysis of aluminum

Aluminum chloride hydroxide [1327-41 -9] also called polyaluminum chloride or PAG, is made by partial hydrolysis of aluminum chloride to form a mixture of polymeric species. It is more expensive than alum on a weight basis, but has advantages over alum such as not lowering the pH as much and better cost-effectiveness in some appHcations. Residual aluminum in the water is said to be lower and performance in cold water is better (6,7). It is sold as a solution (see Aluminum compounds, polyaluminum cm ORiDEs). 

Commercial grades of socbum aluminate contain both waters of hycbation and excess socbum hycboxide. In solution, a high pH retards the reversion of socbum aluminate to insoluble aluminum hycboxide. The chemical identity of the soluble species in socbum aluminate solutions has been the focus of much work (1). Solutions of sodium aluminate appear to be totaby ionic. The aluminate ion is monovalent and the predominant species present is deterrnined by the Na20 concentration. The tetrahydroxyaluminate ion [14485-39-3], Al(OH) 4, exists in lower concentrations of caustic dehydration of Al(OH) 4, to the aluminate ion [20653-98-9], A10 2) is postulated at concentrations of Na20 above 25%. The formation of polymeric aluminate ions similar to the positively charged polymeric ions formed by hydrolysis of aluminum at low pH does not seem to occur. Al(OH) 4 has been identified as the predominant ion in dilute aluminate solutions (2). 

Hydrolysis of aluminum alkoxides is also used commercially to produce precursor gels. This approach avoids the introduction of undesirable anions or cations so that the need for extensive washing is reduced. Although gels having surface area over 800 m /g can be produced by this approach, the commercial products are mosdy pseudoboehmite powders in the 200 —300 m /g range (28). The forming processes already described are used to convert these powders into activated alumina shapes. 

Fig. 8. Gelation behavior of alumina sols prepared from hydrolysis of aluminum isopropoxide at ( ) 90°C and (-) room temperature (49).

In preparing the membrane, a clear sol was obtained by the addition of acid into the aluminum sec-butoxide sol to peptise the sol and obtain a stable colloid solution. Aluminum monohydroxides formed by the hydrolysis of aluminum alkoxides, which are peptisable to a clear sol. Peptisation was performed by the addition of acid and heat treatment for a sufficient time. It was found that stable sols cannot be obtained when the concentration of the peptisation acid is too low. The critical range for inorganic acids such as nitric, hydrochloric and perchloric acids is 0.03-0.1 mole/mole of hydroxide. In this study, nitric acid was used as the peptising agent. The resulting sols are poured into Petri dishes and dried in an oven at a controlled drying rate to obtain a gel layer. The molar ratio of zirconia salt... 

A common reaction for the deposition of alumina is the hydrolysis of aluminum trichloride ... 

May, H., 1992, The hydrolysis of aluminum, conflicting models and the interpretation of aluminum geochemistry. In Y. K. Kharaka and A. S. Maest (eds.), Water-Rock Interaction. Balkema, Rotterdam, pp. 13-21. 

The controlled hydrolysis of aluminum alkyl and aryl compounds yields oligomeric species of the formula (RA10) . They are called alumoxanes. Alkyl substituted alu-... 

The reactions of gibbsite (y-Al(OH)3) with liX salts (X = e.g. Cl, Br, I, NO3, 5CO3, ISO4) in aqueous media to yield the LDHs [IiAl2(OH)6]X-mH20 (liAl-X) are rare examples of reactions in which both cations and anions are similarly intercalated into the host lattice. Although other routes are available to synthesise this family of LDHs, including hydrolysis of aluminum... 

Pure alumina catalyst prepared either by hydrolysis of aluminum isopropoxide or by precipitation of aluminum nitrate with ammonia, and calcined at 600-800°, contains intrinsic acidic and basic sites, which participate in the dehydration of alcohols. The acidic sites are not of equal strength and the relatively strong sites can be neutralized by incorporating as little as 0.1 % by weight of sodium or potassium ions or by passing ammonia or organic bases, such as pyridine or piperidine, over the alumina. 

Alumina (A1203) powders can be prepared from aluminum ethoxide by the sol-gel method. Write a balanced equation for the hydrolysis of aluminum ethoxide. 

First investigations of hydrolysis of aluminum alkoxides were performed in the 1950s and 1960s [1252, 285]. Stolarek [1536] studied hydrolysis reactions with the aim of the preparation of aluminum oxide as a carrier for catalysts. 

The final step is hydrolysis of aluminum alkoxides to free the product alcohols. 

Why does the hydrolysis of aluminum nitride take place in NaOH solution but not in pure water (See Experiment 9, Chapter II, p. 69.)... 

Reference books tell us that aluminum carbonate has never been prepared. In this experiment we brought together the ions of aluminum carbonate and the result showed that this salt cannot exist in solution. The reaction might be described as the hydrolysis of aluminum carbonate ... 

Bis methylgermyl] Tellurium5 0.36 g (1.62 mmol) of bis[methylgermyl]carbodiimide are condensed into a 150 m/, greaseless vessel. The vessel is cooled to — 196°, excess hydrogen telluride, prepared by acidic hydrolysis of aluminum telluride, is condensed into the vessel, and the mixture is carefully warmed to 20° (the mixture is cooled if the reaction becomes too vigorous). After 1 h the reaction mixture is fractionated under reduced pressure using cold traps to collect the product yield 0.31 g (62%). 

A third, very important source of aluminum oxide hydoxides is the hydrolysis of aluminum alcoholates. Due to the high purity of the alcoholate, almost no impurities, except for carbon residues at low concentrations, are present in the product ... 

Alkylaluminoxanes, or alkylalumoxanes as they are often called, contain at least one oxide bridge between two or more aluminum centers that contain an organic substituent. Alkylaluminoxanes are most commonly obtained by partial hydrolysis of aluminum triaUcyls under controlled conditions, but many other preparative routes have been described in the literature and in patents. The structures and compositions of most alkylaluminoxanes are the subject of much debate. Often referred to as black box materials, proposed stmctures previously focused on cyclic or polymeric structures as described in an excellent review by Pasynkiewicz. New structural models for aUcylaluminoxane have emerged over the past 15 years. 

Scheme 2 Proposed reaction scheme for hydrolysis of aluminum trialkyls...

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