75-20-7 calcium carbide

Calcium carbide can produce acetylene, a feedstock for methyl acrylate, a monomer for the production of ACM specialty elastomer. 

Calcium carbide produces acetylene, which has been dimerized into chloroprene monomer (by an older process) to produce polychloroprene rubber through polymerization. However, this synthesis route is quite minor today. 

Calcium carbide is a feedstock for producing acetylene-phenol tackifying resin. Calcium carbide is a feedstock to make 1,4-butanediol for curing polyurethane elastomers. 

Calcium carbide is the feedstock to make acetylene black (filler) for rubber. 

ASTM C911 (formerly ASTM C433) specifies the required quality of quick- and hydrated lime for chemical uses including the production of hypochlorite bleach. High purity products are required with high available lime contents, low levels of sludge-forming impurities and a low iron oxide content (iron oxide is understood to catalyse the decomposition of calcium hypochlorite) [31.1]. 

Technical grade calcium carbide is produced by reacting quicklime with carbonaceous matter at 1800 to 2100 °C. 

Typically 950 kg of lime and 550 kg of coke or anthracite are used to produce a tonne of 300 litre calcium carbide, consisting of about 80 % of CaC2 and 13 % of unreacted CaO. 

The most widely used process employs a short electrothermal furnace. Electrical energy is supplied via electrodes, which causes the lime and carbon to react, forming molten calcium carbide, which then acts as a reaction medium. An alternative process uses a shaft furnace, which is charged with a mixture of lime and coke/anthracite [31.4]. The temperatures required for the reaction to proceed are generated by the partial combustion of the carbonaceous matter in oxygen, or oxygen-enriched air. The residual carbonaceous matter then reacts with the lime to produce calcium carbide. 

Most of the quicklime used is in the size range 6 to 50 mm to provide the necessary voidage for the gases produced in the reaction to escape. However, modern electrothermal furnaces have hollow electrodes through which fine material (less than 6 mm) can be blown. This enables less expensive fine fractions of coke and quicklime (including any recycled lime) to be introduced. Up to 25 % of the charge to the furnace may be added in this way. 

CaC2 manufacture only is of minor importance (supplanted by petrochemical feedstocks) 

Economic Importance The production of calcium carbide in Western Europe in 1993 was ca. 500 10- t/a, in the USA 220 10 t/a, in Eastern Europe including Russia 887 10 t/a and in Japan 245 10 t/a. The demand for calcium carbide has been almost constant although declining slightly over the last 20 years, due to the decreasing importance of ethyne in organic chemistry (replacement by e.g. ethene) and stagnation in the utilization of calcium cyanamide as a fertilizer. The worldwide production, which in the mid-1960 s was still 10 10 t/a, had dropped to 6 10 t/a by the mid-1970 s and is currently about 2 10 t/a. 

Manufacture Calcium carbide is manufactured by reacting highly purified calcium oxide with coke in an electrical arc reduction furnace at 2000 to 2200°C  

CaC2 manufacture is very energy intensive very pure starting materials are required 

The ca. 80% carbide produced, the rest being mainly calcium oxide, is formed as a liquid and is removed as blocks. Crucial in the economics of calcium carbide production is, in addition to the price of the raw materials, the electricity price, because the process is very energy intensive, 2.8 to 3.1 MWh being required per t. Calcium carbide furnaces with power demands up to 70 MW generally have to be operated with three-phase current and utilize Soderberg hollow carbon electrodes dipped deeply into the reaction mixture. 

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The original method for the manufacture of ethyne, the action of water on calcium carbide, is still of very great importance, but newer methods include the pyrolysis of the lower paraffins in the presence of steam, the partial oxidation of natural gas (methane) and the cracking of hydrocarbons in an electric arc. 

Acetylene can be readily obtained by the action of water on calcium carbide since, however, commercial calcium carbide contains traces of calcium... 

Drying agents may be divided broadly into (a) those which combine with water reversibly and (6) tho.se which react chemically with water by a non-revcrsible process giving rise to a new water-free compound. Sodium, calcium carbide and phosphorus peiitoxide belong to the latter class and wih be discussed in Section 11,39. 

Acetylene was discovered m 1836 by Edmund Davy and characterized by the French chemist P E M Berthelot m 1862 It did not command much attention until its large scale preparation from calcium carbide m the last decade of the nineteenth century stim ulated interest m industrial applications In the first stage of that synthesis limestone and coke a material rich m elemental carbon obtained from coal are heated m an electric furnace to form calcium carbide... 

Calcium carbide is the calcium salt of the doubly negative carbide ion (C=C ) Car bide ion is strongly basic and reacts with water to form acetylene... 

Use curved arrows to show how calcium carbide reacts with water... 

Calcium carbide Moisture, selenium, silver nitrate, sodium peroxide, tin(II) chloride, potassium hydroxide plus chlorine, HCl gas, magnesium... 

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