Graphite reaction with alkali metals

Graphite reacts with alkali metals - potassium, cesium and rubidium - to form lamellar compounds with different stoichiometries. The most widely known intercalate is the potassium-graphite which has the stoichiometry of CgK. In this intercalate the space between the graphite layers is occupied by K atoms. CgK functions as a reducing agent in various reactions such as reduction of double bonds in a,fl-unsaturated ketones [19], carboxylic acids and Schiff bases alkylation of nitriles [20], esters and imines [21] reductive cleavage of carbon-sulfur bonds in vinylic and allylic sulfones [22]. The detailed reaction mechanism of CgK is not known, and the special properties which are ascribed to the intercalate come either from the equilibrium between K+/K [23], or topochemical observations (the layer structure) [24]. 

Alkali-metal graphites are extremely reactive in air and may explode with water. In general, reactivity decreases with ease of ionization of M in the sequence Li > Na > K > Rb > Cs. Under controlled conditions H2O or ROH produce only H2, MOH and graphite, unlike the alkali-metal carbides M2C2 (p. 297) which produce hydrocarbons such as acetylene. In an important new reaction CgK has been found to react smoothly with transition metal salts in tetrahydrofuran at room temperature to give the corresponding transition metal lamellar compounds ... 

The reaction with 4-nitrophenol and pentafluorophenol in the presence of KF-18-crown-6 has been investigated. Pentafluorophenoxide anion was found to be a better leaving group [82JFC(20)439]. Alkali metal fluorides on graphite can act as catalysts for nucleophilic substitution of pentafluor-opyridine [90JFC(46)57]. 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

Intercalation of some guest species, such as alkali metals, can simply be performed via a chemical reaction of a gaseous reactant with graphite. 

Catalysts and reaction conditions used are generally similar to those used for olefin isomerization. Catalysts reported are sodium-organosodium catalysts prepared in situ by reaction of a promoter such as o-chloro-toluene or anthracene with sodium 19-24), alkali metal hydrides 20,21), alkali metals 22), benzylsodium 26), and potassium-graphite 26). These catalysts are strong bases that can react with alkylaromatics to replace a benzylic hydrogen [Reaction (2)]. 

GICs have been first discovered from the reaction of graphite with sulfuric acid more than 150 years ago.30 In the long history of GICs research, a huge number of compounds have been yielded with a large variety of donors and acceptors, in which alkali metals, alkaline earth metals, transition metal chlorides, acids, and halogens are involved as typical intercalates. 

The reaction of various carbonaceous materials with steam to yield CO, CO2, and H2 has been intensively studied. Of special interest has been the catalysis of this reaction by various alkali metal containing compounds, most notably potassium carbonate (32-37). Various mechanisms have been proposed, some including alkali metal atoms (37) or even graphite intercalation compounds (38) as intermediates. 

Review of Process Alternatives, Superior Graphite began in 1968 to investigate possible alternatives for desulfurization of petroleum cokes. The methods considered included various chemical treatments and direct thermal purification processes. The chemical treatment methods included hydrodesulfurization and reactions with various alkali metal compounds. Fine grinding of the coke appeared to be required and reaction conditions generally involved high pressure. 

Besides Urushibara Ni and Ni boride catalysts, various finely divided nickel particles have been prepared by reaction of nickel salts with other reducing agents, such as sodium phosphinate 20,85 alkali metal/liquid NH3 21 NaH-f-AmOH (designated Nic) 22,86Na, Mg, and Zn in THF or Mg in EtOH 24 or C8K(potassium graphite)/THF-HMPTA (designated Ni-Grl) 23,87 Some of these have been reported to compare with Raney Ni or Ni borides in their activity and/or selectivity. 

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