Carbides, reactions

At about the same time that the Birkeland-Eyde process was developed, the Frank-Caro cyanamide process was commercialized (14). In this process limestone is heated to produce lime, which then reacts with carbon in a highly energy-demanding reaction to give calcium carbide. Reaction with N2 gives calcium cyanamide [150-62-7] which hydrolyzes to ammonia and calcium carbonate (see Cyanamides). 

In the same way, if the gas pressure increases, the nitrogen concentration is not modified but the carbon concentration increases (mainly in the graphite or free form). This can suggest that the nitridation reaction is slower than the carbidation reaction. This assumption is experimentally confirmed by reaction of metal foils in a furnace. At similar reaction temperatures and times, the thickness of metal which has reacted is much greater with carbon than with nitrogen. 

Reaction (a) is measurable at about 275°C. The rate of decomposition of Hagg carbide, reaction (b), depends upon the amount of carbidic carbon present. For a completely carbided synthetic-ammonia-type catalyst the reaction, which proceeds approximately according to Equation (2),... 

The expression stoichiometric quantities of reactants means molar amounts of the reactants numerically equal to their stoichiometric coefficients. For the calcium carbide reaction, stoichiometric quantities of the reactants in the SI system of units would be I mol of CaC (s) and 2 mol of H20(1). If stoichiometric quantities of the reactants are fed and the reaction proceeds to completion, both reactants would be completely consumed and stoichiometric quantities of the products would be formed. (Convince yourself.)... 

In the original work methane was used as the gaseous carbon source. It will now be shown that using ethane as the carbon source results in the formation of metal carbides with higher surface areas than those produced by TPR with methane. Further, the use of ethane allows the carbiding reaction to proceed in a topotactic manner and provides a potential method for synthesising a variety of carbide phases. 

Chromium carbenes can also be prepared by the so-called Semmelhack-Hegedus route. Chromium hexacarbonyl is first reduced to a nucleophilic pentacarbonyl dichromate dianion 23 with sodium naphthalenide or potassium carbide. Reaction of this dianion species with an acid chloride gives a metal alkoxide that can be quenched with an electrophile to provide the desired chromate ester 24. Alternatively, the dianion can be added to an amide carbonyl to give a tetrahedral intermediated which collapses to the chromate amide 25 on treatment with trimethylsilyl chloride. 

Acetylene manufactured from hydrocarbon feedstock is inherently free from phosphine, arsine, and hydrogen sulfide. However, phosphine, arsine, and hydrogen sulfide levels in acetylene produced from a water/calcium carbide reaction are not routinely checked by the acetylene producer (due to the noncritical nature of the use—welding and cutting). These purity levels traditionally have been based on the calcium carbide producers raw material information. 

Obermayer D, Gutmann B, Kappe CO. Microwave chemistry in silicon carbide reaction vials separating thermal from non-thermal effects. Angew. Chem. Int. Ed. 2009 48 8321-8324. 

Calcium carbide Reactions in fused salts with chlorosilanes... 

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