Lithium aluminate carbonate

An emerging electrochemical appHcation of lithium compounds is in molten carbonate fuel ceUs (qv) for high efficiency, low poUuting electrical power generation. The electrolyte for these fuel ceUs is a potassium carbonate—hthium carbonate eutectic contained within a lithium aluminate matrix. The cathode is a Hthiated metal oxide such as lithium nickel oxide. 

Molten Carbonate Fuel Cell The electrolyte in the MCFC is a mixture of lithium/potassium or lithium/sodium carbonates, retained in a ceramic matrix of lithium aluminate. The carbonate salts melt at about 773 K (932°F), allowing the cell to be operated in the 873 to 973 K (1112 to 1292°F) range. Platinum is no longer needed as an electrocatalyst because the reactions are fast at these temperatures. The anode in MCFCs is porous nickel metal with a few percent of chromium or aluminum to improve the mechanical properties. The cathode material is hthium-doped nickel oxide. 

To prolong the life of MCFC, the amount of electrolyte in the matrix must be maintained at an appropriate level over long-term operation. The growth of particles of L1A102 as an electrolyte retention material in molten carbonates leads to a decrease in the electrolyte retention ability. These phenomena result in a decrease of the fuel cell performance. It was found that zirconia powder added to lithium aluminate keeps the electrolyte retention ability constant for over 7000 hr in Li/Na carbonates and pCOx = 0.1. ... 

Kinoshita, K. Sim, K.W. Kucera, H. Synthesis of fine particle size lithium aluminate for application in molten carbonate fuel cells. Mater. Res. Bull. 1979, 14 (10), 1357-1368. 

Singh, R.N. Fracture strength of a porous lithium aluminate structure for application in molten carbonate fuel cells. Proc. Ceram. Sci. Eng. 1981, 1 (7-8)(B), 500-507. 

Singh, R.N. Dusek, J.T. Sim, J.W. Fabrication and properties of a porous lithium aluminate electrolyte retainer for molten carbonate fuel cells. Am. Ceram. Soc. Bull. 1981, 60 (6), 629-635. 

Sim, J.W. Singh, R.N. Kinoshita, K. Testing of sintered lithium aluminate structures in molten carbonate fuel cells. J. Electrochem. Soc. 1980, 127 (8), 1766-1768. 

Alvani, C. Roncari, E. Preparation and characterization of y-lithium aluminate tiles for molten carbonate fuel cells. High Temp.-High Pressures 1988, 20 (3), 247-250. 

Lithium aluminates are also important in the development of molten carbonate fuel cells (MCFC) [82, 83], In these fuel cells, a molten carbonate salt mixture is used as an electrolyte. These fuel cells operate through an anode reaction, which is a reaction between carbonate ions and hydrogen. A cathode reaction combines oxygen, C02, and electrons from the cathode to produce carbonate ions, which enter the electrolyte. These cells operate at temperatures of 650°C and the electrolyte, which is usually lithium and potassium carbonate, is suspended in an inert matrix, which is usually a lithium aluminate. 

V.S. Batra, et al., Development of alpha lithium aluminate matrix for molten carbonate fuel cell. 

The MCFC anode is made of porous nickel with 2-10% chromium or aluminium to improve the creep resistance. The state-of-the-art cathode is made of in-situ oxidised and lithiated nickel oxide. Both electrodes are partially filled with carbonate in order to obtain optimal 3-phase contact. The matrix is a porous lithium aluminate tile, which is completely filled with the carbonate mixture. The individual cells are separated by a metallic separator plate. 

Thermodynamic calculations [12] show that aluminium oxide/lithium aluminate is stable at much more cathodic potentials than -1100mV.Therefore it seems likely that the oxidation reactions proceed at all potentials in the carbonate stability range. Thus some oxide will probably be formed before the polarisation measurements are started when the electrode is dipped into the molten carbonate. The constant current from -1000 mV to —800 mV reflects some further but limited growth of the oxide layer, which reaches a thickness of 1 pm after 24 hours (see Fig. 2). The crystallite size of the oxide also increases with exposition time especially during the first few hours. After about 4 hours the morphology hardly changes anymore. 

The working temperature of molten carbonate fuel cells is around 600-650°C. Mixed carbonate melts containing 62-70 mol% of lithium carbonate and 30-38 mol% of potassium carbonate, with compositions close to the eutectic point, are used in molten carbonate fuel cells as an electrolyte. Sometimes, sodium carbonate and other salts are added to the melts. This liquid melt is immobilized in the pores of a ceramic fine-pore matrix, made of sintered magnesium oxide or lithium aluminate powders. 

Molten carbonate fuel cells operate at temperatures around 650 °C and are tolerant to unlimited amounts of carbon monoxide. In most instances mixtures of lithium carbonate and potassium carbonate act as the electrolyte. The electrolyte is suspended in an insulating and chemically inert lithium aluminate ceramic. Nickel or nickel-chromium alloys serve as the anode catalysts, while nickel oxide is used as the cathode catalysts. 

Molten carbonate fuel cells (MCFC) are composed of a porous nickel-based anode, a porous nickel oxide-based cathode and molten carbonate salts as electrolyte within a porous lithium aluminate matrix. Molten carbonate fuel cells with internal reforming can be fed directly with light hydrocarbons rich gas such as... 

In vacuum thermochemical reduction process, aluminum and silicon are suitable reduction agents [5, 6]. Vacuum aluminothermic reduction lithium is from a US patent about aluminum reduction of lithium oxide. Aluminum reduction of spodumene has been reported by Stauffer [7]. Lithium is difficultly reduced if not adding calcium oxide into spodumene. When the mass ratio of calcium oxide and spodumene is 3 2, the maximum productivity was 92.2% under the conditions of 1050 1150"C for 2 hours. Fedorov and Shamrai used aluminum to reduce lithium aluminate, and pointed out that the lithium productivity could reach 95% when the reduction temperature was 1200 C and the system pressure was below 0.0013 Pa [4]. The previous researches were focused on the production of lithium. But the recovery of reduction residue was not investigated. In present work, a novel vacuum aluminofliermic reduction lithium process is developed which used lithium carbonate, alumina and calcium oxide as raw materials. The products were metal lithium and high-whiteness aluminum hydroxide. 

L. Zhou, H. Lin, and B. Yi, Sintering Behavior of Porous a-Lithium Aluminate Matrices in Molten Carbonate Fuel CeUs at High Temperature, J. Power Sources, Vol. 164, pp. 24-32,2007. 

The Li-SOCl2 battery consists of a lithium-metal foil anode, a porous carbon cathode, a porous non-woven glass or polymeric separator between them, and an electrolyte containing thionyl chloride and a soluble salt, usually lithium tetrachloro-aluminate. Thionyl chloride serves as both the cathode active material and the elec-... 

High-alumina cement is a rapid-hardening cement made from bauxite and limestone. It is comparatively resistant to chemical attack. Milling retards the setting of aluminous cement [1582]. On the other hand, setting accelerators such as lithium carbonate increase their effect by this treatment. 

The reaction of complex hydrides with carbonyl compounds can be exemplified by the reduction of an aldehyde with lithium aluminum hydride. The reduction is assumed to involve a hydride transfer from a nucleophile -tetrahydroaluminate ion onto the carbonyl carbon as a place of the lowest electron density. The alkoxide ion thus generated complexes the remaining aluminum hydride and forms an alkoxytrihydroaluminate ion. This intermediate reacts with a second molecule of the aldehyde and forms a dialkoxy-dihydroaluminate ion which reacts with the third molecule of the aldehyde and forms a trialkoxyhydroaluminate ion. Finally the fourth molecule of the aldehyde converts the aluminate to the ultimate stage of tetraalkoxyaluminate ion that on contact with water liberates four molecules of an alcohol, aluminum hydroxide and lithium hydroxide. Four molecules of water are needed to hydrolyze the tetraalkoxyaluminate. The individual intermediates really exist and can also be prepared by a reaction of lithium aluminum hydride... 

Heteroaromatics are subdivided, according to the electron influence of the heteroatom, into w-electron-deficient compounds and compounds with an excess of it electrons on the ring carbon atoms. The typical ff-electron-delicient compound pyridine has so far been made to react only in one case the reaction of lithium tetrakis(A-dihydropyridyl)-aluminate (LDPA) [112-114), obtainable from pyridine and lithium aluminum hydride, with trifluoromethanesulfenyl chloride in an excess of pyridine affords 3-trifluoromethylmercaptopyridine in low yield (13%) (60). This reaction probably occurs through sulfenylation of the l,2-dihydrop5T idyl moiety of the LDPA with the formation of a 2,5-... 

The silyl halides can now" be prepared in high purity and high yield by the facile hydrogen halide cleavage of the carbon-silicon bond in arylsilanes. " No catalyst is required, and the use of the hazardous intermediate reagent, silane, is avoided. Bromosilane is prepared by the reaction of hydrogen bromide and phenylsilane. The latter is obtained by lithium hydro-aluminate reduction of the commercially available phenyltri-chlorosilane. lodosilane can be prepared in a similar fashion however, mixtures of iodosilane and benzene are difficult to separate. The preferred alternative procedure described below utilizes an isomeric mixture of 2-, 3-, and 4-chlorophenylsilanes as the intermediate. This intermediate is obtained by the chlorination of phenyltrichlorosilane, and is then reduced to the hydride. 

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