Aluminum compounds reactions

Aqueous solutions of caustic soda aie highly alkaline. Hence caustic soda is ptimatily used in neutralization reactions to form sodium salts (79). Sodium hydroxide reacts with amphotoric metals (Al, Zn, Sn) and their oxides to form complex anions such as AlO, ZnO. SnO ", and (or H2O with oxides). Reaction of AI2O2 with NaOH is the primary step during the extraction of alumina from bauxite (see Aluminum compounds) ... 

Organochromium Catalysts. Several commercially important catalysts utilize organ ochromium compounds. Some of them are prepared by supporting bis(triphenylsilyl)chromate on siUca or siUca-alumina in a hydrocarbon slurry followed by a treatment with alkyl aluminum compounds (41). Other catalysts are based on bis(cyclopentadienyl)chromium deposited on siUca (42). The reactions between the hydroxyl groups in siUca and the chromium compounds leave various chromium species chemically linked to the siUca surface. The productivity of supported organochromium catalysts is also high, around 8—10 kg PE/g catalyst (800—1000 kg PE/g Cr). 

Chromium Oxide-Based Catalysts. Chromium oxide-based catalysts were originally developed by Phillips Petroleum Company for the manufacture of HDPE resins subsequendy, they have been modified for ethylene—a-olefin copolymerisation reactions (10). These catalysts use a mixed sihca—titania support containing from 2 to 20 wt % of Ti. After the deposition of chromium species onto the support, the catalyst is first oxidised by an oxygen—air mixture and then reduced at increased temperatures with carbon monoxide. The catalyst systems used for ethylene copolymerisation consist of sohd catalysts and co-catalysts, ie, triaLkylboron or trialkyl aluminum compounds. Ethylene—a-olefin copolymers produced with these catalysts have very broad molecular weight distributions, characterised by M.Jin the 12—35 and MER in the 80—200 range. 

Dicyclopentadiene is also polymerized with tungsten-based catalysts. Because the polymerization reaction produces heavily cross-Unked resins, the polymers are manufactured in a reaction injection mol ding (RIM) process, in which all catalyst components and resin modifiers are slurried in two batches of the monomer. The first batch contains the catalyst (a mixture of WCl and WOCl, nonylphenol, acetylacetone, additives, and fillers the second batch contains the co-catalyst (a combination of an alkyl aluminum compound and a Lewis base such as ether), antioxidants, and elastomeric fillers (qv) for better moldabihty (50). Mixing two Uquids in a mold results in a rapid polymerization reaction. Its rate is controlled by the ratio between the co-catalyst and the Lewis base. Depending on the catalyst composition, solidification time of the reaction mixture can vary from two seconds to an hour. Similar catalyst systems are used for polymerization of norbomene and for norbomene copolymerization with ethyhdenenorbomene. 

Organoaluminum Compounds. Apphcation of aluminum compounds in organic chemistry came of age in the 1950s when the direct synthesis of trialkylalurninum compounds, particularly triethylalurninum and triisobutylalurninum from metallic aluminum, hydrogen, and the olefins ethylene and isobutylene, made available economic organoalurninum raw materials for a wide variety of chemical reactions (see a-BONDED alkyls and aryls). 

Gel-Based Activated Aluminas. Alumina gels can be formed by wet chemical reaction of soluble aluminum compounds. An example is rapid mixing of aluminum sulfate [17927-65-0], Al2(S0 2 XH20, and sodium aluminate [1302-42-7], NaA102, solutions to form pseudoboehmite and a... 

Calcium Aluminate Cements. Low purity calcium aluminate [12042-78-3] cements are obtained by sintering or fusing bauxite and lime in a rotary or shaft kiln. A high purity calcium aluminate cement, 2CaO 5AI2O2, capable of withstanding service temperatures of 1750°C can be prepared by the reaction of high purity lime with calcined or hydrated alumina (see Aluminum compounds). 

Aluminum alkyls react by the Ziegler reaction with the least substituted double bond to give the tricitroneUyl aluminum compound. Oxidation of the iatermediate compound then produces the tricitroneUyl aluminate, which is easily hydroly2ed with water to give citroneUol (112,113). If the citroneUene is opticaUy active, opticaUy active citroneUol can be obtained (114). The (—)-citroneUol is a more valuable fragrance compound than the ( )-citroneUol. 

A disaccharide is added to a pyridine SO3 complex solution, which is prepared by reacting 5 to 6 times the molar amount of liquid SO3 as much as that of disaccharide with 5 to 10 times the amount of pyridine as that of the disaccharide at 0°C to 5°C, for sulfation at 50°C to 70°C for 3 to 7 hours. After the completion of sulfation, the greater part of pyridine Is removed by decantation. The obtained solution exhibits an acidity that is so strong that it is improper to apply the reaction with aluminum ion and, therefore, sodium hydroxide is added for neutralization. After the remaining pyridine is removed by concentration, 100 unit volumes of water per unit volume of the residue is added thereto. To the solution is then added aluminum ion solution mainly containing aluminum dihydroxychloride, the pH of which is 1.0 to 1.2, in such an amount that the aluminum ion Is present in an amount of 4 to 6 molar parts of the amount of disaccharide to provide a pH of 4 to 4.5. The mixture is reacted under stirring at room temperature and the formed disaccharide poly sulfate-aluminum compound is allowed to precipitate. After filtration, the residue is washed with water and dried. 

Acid rain adversely affects trees as well (Figure A). It appears that the damage is largely due to the leaching of metal cations from the soil. In particular, H+ ions in acid rain can react with insoluble aluminum compounds in the soil, bringing Al3+ ions into solution. The following reaction is typical ... 

Nickel(O) reacts with the olefin to form a nickel(0)-olefin complex, which can also coordinate the alkyl aluminum compound via a multicenter bond between the nickel, the aluminum and the a carbon atom of the trialkylaluminum. In a concerted reaction the aluminum and the hydride are transferred to the olefin. In this mechanistic hypothesis the nickel thus mostly serves as a template to bring the olefin and the aluminum compound into close proximity. No free Al-H or Ni-H species is ever formed in the course of the reaction. The adduct of an amine-stabihzed dimethylaluminum hydride and (cyclododecatriene)nickel, whose structure was determined by X-ray crystallography, was considered to serve as a model for this type of mechanism since it shows the hydride bridging the aluminum and alkene-coordinated nickel center [31]. 

A gel of diesel or crude oil can be produced using a phosphate diester or an aluminum compound with phosphate diester [740]. The metal phosphate diester may be prepared by reacting a triester with phosphorous pentoxide to produce a polyphosphate, which is then reacted with an alcohol (usually hexanol) to produce a phosphate diester [870]. The latter diester is then added to the organic liquid along with a nonaqueous source of aluminum, such as aluminum isopropoxide (aluminum-triisopropylate) in diesel oil, to produce the metal phosphate diester. The conditions in the previous reaction steps are controlled to provide a gel with good viscosity versus temperature and time characteristics. All the reagents are substantially free of water and will not affect the pH. 

The structure of dimethylberyllium is similar to that of trimethylaluminum except for the fact that the beryllium compound forms chains, whereas the aluminum compound forms dimers. Dimethylberyllium has the structure shown in Figure 12.3. The bridges involve an orbital on the methyl groups overlapping an orbital (probably best regarded as sp3) on the beryllium atoms to give two-electron three-center bonds. Note, however, that the bond angle Be-C-Be is unusually small. Because beryllium is a Lewis acid, the polymeric [Be(CH3)2] is separated when a Lewis base is added and adducts form. For example, with phosphine the reaction is... 

In the low-temperature reaction of 1 with dimethylaluminum chloride insertion into the Al-Cl bond was expected. Instead, insertion into a Al-C bond took place, as concluded from the reaction products. After the insertion process, a reductive elimination step led to the formation of the known aluminum compound 3937 and of an undefined polymer of the composition (Me5C5SiMe)ra.30 This surprising result has initiated further... 

The pathways in the reaction of 1 with certain halogenoboron and -aluminum compounds are much more complicated than those described in the last chapter. Here, addition and insertion reactions take place in combination with multistep rearrangement and elimination processes. Some reactions are still not fully understood concerning the mechanistic details, but plausible reaction sequences have been suggested. 

Reaction conditions toluene 50 ml, butadiene 70 ml, Co(acac)3 1 mmole, aluminum compound 8 mmoles, ethylene 50 kg/cm2. c HD = Hexadiene. 

Aluminum compounds. See also Bauxite(s) chemical reactions, 2 348-349 commercially significant, 2 356-359 in paper manufacture, 78 111 prepolymerized, 77 626 survey, 2 344-360... 

The patent literature contains several references to the use of sulfoxide complexes, usually generated in situ, as catalyst precursors in oligomerization and polymerization reactions. Thus, a system based upon bis(acrylonitrile)nickel(0> with added Me2SO or EtgSO is an effective cyclotrimerization catalyst for the conversion of butadiene to cyclo-1,5,-9-dodecatriene (44). A similar system based on titanium has also been reported (407). Nickel(II) sulfoxide complexes, again generated in situ, have been patented as catalyst precursors for the dimerization of pro-pene (151) and the higher olefins (152) in the presence of added alkyl aluminum compounds. 

When the process of chain growth is satisfactorily completed, separation of the three hydrocarbon chains that are connected to the aluminum atom is accomplished by a displacement reaction. The chain-laden aluminum compound (called trialkyl aluminum compounds) is subjected to still higher temperatures and pressure. This causes an ethylene molecule to displace the long linear carbon chain. As the separation is made, triethyl aluminum is reformed, making a recyclable root for another go-around. 

Prepared from bauxite, kaolin or aluminum compounds on reaction with H2SO4. The insoluble silicic acid is filtered out the hydrate salt forms on crystallization. 

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