Aluminum removal from

Fig. 1. Flow diagram for aluminothermic process showiag alternative methods of aluminum removal from alloy regulus.

An opposing effect is possible under the severe conditions of a single extraction with HC1 some of the aluminum removed from the crystal structure may not be transported out of the catalyst particle. The resulting amorphous alumina, (after subsequent calcining) remaining in the particle would cause some reduction in effective diffusivity. Such amorphous alumina has been suggested by others (17,18). 

In contrast, Kim et al. (13) found that the amount of aluminum removed from the zeolite lattice during ion-exchange with solutions of metal chlorides was directly related to the pH of the solution and that the presence of the metal cation played no part in the dealumination. Our work more closely mirrors that of Bailar and coworkers (14-16) who found that solutions of CrCl3 under reflux conditions could dealuminate a variety of zeolites to a much greater extent than the pH of the CrCl3 solutions would predict. To explain their results, they proposed that the chromium cations could complex with hydrolyzed aluminum ions in the zeolite through the formation of "ol bridges" which then diffused out of the zeolite. Therefore,... 

Y-zeolite (Si02/Al203 framework = 59), in which the aluminum removed from the framework remains in the zeolite as extra framework aluminum (total SiCyA Oj = 5.2) (Bezman, 1991). By electron microscopy, the crystal sizes were found to be of the order of 1... 

Aluminum-27 NMR spectra show that after crystallization, all the TOA-containing zeolites exhibit a well resolved resonance at <50 ppm, corresponding to framework Al(IV) atoms. However, following NH.- exchange and calcination in air at 500°C, a new band appears at abdut 0 ppm due to Al(VI) resulting from aluminum removed from the crystal lattice. In general, calculated Si/Al ratio from silicon-29 NMR data are in reasonable agreement with chemical analysis results. Thus, all the aluminum atoms in these siliceous mordenite and Al-rich pentasils are believed to be in tetrahedral coordination and incorporated into the zeolite lattice. 

Fig. 2. Stoichiometry of aluminum removal from Na-Y by H4/EDTA. FW formula weight, NaA102(Si02)y [24]...

The rate (kinetics) and the completeness (fraction dissolved) of oxide fuel dissolution is an inverse function of fuel bum-up (16—18). This phenomenon becomes a significant concern in the dissolution of high bum-up MO fuels (19). The insoluble soHds are removed from the dissolver solution by either filtration or centrifugation prior to solvent extraction. Both financial considerations and the need for safeguards make accounting for the fissile content of the insoluble soHds an important challenge for the commercial reprocessor. If hydrofluoric acid is required to assist in the dissolution, the excess fluoride ion must be complexed with aluminum nitrate to minimize corrosion to the stainless steel used throughout the facility. Also, uranium fluoride complexes are inextractable and formation of them needs to be prevented. 

The fifth component is the stmcture, a material selected for weak absorption for neutrons, and having adequate strength and resistance to corrosion. In thermal reactors, uranium oxide pellets are held and supported by metal tubes, called the cladding. The cladding is composed of zirconium, in the form of an alloy called Zircaloy. Some early reactors used aluminum fast reactors use stainless steel. Additional hardware is required to hold the bundles of fuel rods within a fuel assembly and to support the assembhes that are inserted and removed from the reactor core. Stainless steel is commonly used for such hardware. If the reactor is operated at high temperature and pressure, a thick-walled steel reactor vessel is needed. 

Molten aluminum is removed from the cells by siphoning, generally daily, into a cmcible. Normally the metal is 99.6—99.9% pure. The principal impurities are Ee, Si, Ti, V, and Mn, and come largely from the anode, but also from the alumina. 

Aluminum sulfate is a starting material in the manufacture of many other aluminum compounds. Aluminum sulfate from clay could potentially provide local sourcing of raw materials for aluminum production. Processes have been studied (24) and the relative economics of using clay versus bauxite have been reviewed (25). It is, however, difficult to remove impurities economically by precipitation, and purification of aluminum sulfate by crystallization is not practiced commercially because the resulting crystals are soft, microscopic, and difficult to wash effectively on a production scale (26—28). 

Ethyltoluene is manufactured by aluminum chloride-cataly2ed alkylation similar to that used for ethylbenzene production. All three isomers are formed. A typical analysis of the reactor effluent is shown in Table 9. After the unconverted toluene and light by-products are removed, the mixture of ethyltoluene isomers and polyethyltoluenes is fractionated to recover the meta and para isomers (bp 161.3 and 162.0°C, respectively) as the overhead product, which typically contains 0.2% or less ortho isomer (bp 165.1°C). This isomer separation is difficult but essential because (9-ethyltoluene undergoes ring closure to form indan and indene in the subsequent dehydrogenation process. These compounds are even more difficult to remove from vinyltoluene, and their presence in the monomer results in inferior polymers. The o-ethyltoluene and polyethyltoluenes are recovered and recycled to the reactor for isomerization and transalkylation to produce more ethyltoluenes. Fina uses a zeoHte-catalyzed vapor-phase alkylation process to produce ethyltoluenes. 

Dichloroethane is produced commercially from hydrogen chloride and vinyl chloride at 20—55°C ia the presence of an aluminum, ferric, or 2iac chloride catalyst (8,9). Selectivity is nearly stoichiometric to 1,1-dichloroethane. Small amounts of 1,1,3-tfichlorobutane may be produced. Unreacted vinyl chloride and HCl exit the top of the reactor, and can be recycled or sent to vent recovery systems. The reactor product contains the Lewis acid catalyst and must be separated before distillation. Spent catalyst may be removed from the reaction mixture by contacting with a hydrocarbon or paraffin oil, which precipitates the metal chloride catalyst iato the oil (10). Other iaert Hquids such as sdoxanes and perfluorohydrocarbons have also been used (11). 

An aluminum alloy cooling water conduit section was removed from a machine that made polyethylene sheeting. A large hole had formed just below a in. (1.9 cm) cooling water orifice. The designed orifice is shown in Fig. 8.11, with the elliptically shaped corroded hole just below. 

The excess lithium aluminum hydride and the metallic complexes are decomposed by the careful addition of 82 ml. of distilled water, from a dropping funnel, to the well-stirred mixture. The reaction mixture is stirred for an additional 30 minutes, filtered with suction, and the solid is washed with several 100-ml. portions of ether. After the ether is removed from the filtrates, the residual oil is distilled under reduced pressure. The yield of laurylmethylamine, a colorless liquid boiling at 110-115°/1.2-1.5 mm., is 121-142 g. (81-95%) (Note 6). 

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