Acetylene from calcium carbide

Acetylene from calcium carbide can be advantageous in that calcium carbide may be shipped to the point of acetylene usage and acetylene generated on the spot. This avoids the necessity for low pressure, low pressure-drop gaseous acetylene pipelines, or high pressure cylinders for shipping acetylene. 

Carbide lime is a waste lime hydrate by-product from the generation of acetylene from calcium carbide and may occur as a wet sludge or dry powder of widely varying purity and particle size. It is gray and has the pungent odor associated with acetylene (see Hydrocarbons, acetylene). 

The acetylide ion, C/, is isoelectronic with N2, CO, and CN. The reaction producing acetylene from calcium carbide can be shown as... 

Although a great variety of chlorinated hydrocarbons of the lower carbon numbers had been well known and produced in small quantities for many years, the large scale manufacture and use of such compounds other than chloroform and carbon tetrachloride is a fairly recent development. And although synthesis, particularly of the two-carbon derivatives, has in great measure depended on acetylene from calcium carbide, more and more reliance has been placed on petroleum raw materials in this field in the last few years. 

Major producers manufacture acetylene by either the partial oxidation of natural gas or as a coproduct of the thermal cracking of ethylene minor producers manufacture acetylene from calcium carbide. About 80% of production is used as a closed system intermediate in the manufacture of acetylene black as well as acetylenic and vinyl derivatives used in a variety of applications such as the manufacture of plastics. The remaining 20% is used primarily in oxyacetylene torches for welding and metal cutting. Although acetylene was used as an anesthetic in the early 1900s, this use has fallen into disfavor due to the explosive properties of acetylene. 

Preparation of acetylene from calcium carbide in the laboratory gives a product that is difficult to purify. The literature485 should be consulted for methods of purifying this material. 

Figure 5.3 illustrates a process to manufacture acetylene from calcium carbide. The carbide is introduced by a screw conveyor into a perforated horizontal cylinder housed in a concentric envelope. Water is sprayed inside the internal shell. The acetylene formed passes upstream through the screw conveyor to a scrubbing tower, where, a new water spray carries off most, of the solids conveyed by the gas. The residual lime and carbide impurities are removed by a screw conveyor to a sludge receiver. The acetylene is cooled to — 10°C to condense most of the water. It is then purified by contact with dilute sulfuric acid in a liquid liquid absorber, and then with sodium hypochlorite prepared by the action of chlorine on caustic soda, to. remove impurities. The acetylene is then cooled to 0°C for the more complete separation of moisture. The final product nevertheless still contains 0.4 per cent by weight of water, which is suitable for most uses. More intensive dehydratation can be achieved by passage over silicagel. 

The manufacture of acetylene from calcium carbide is marked by the need to handle large amounts of solids. In fact although the yield of the hydrolysis reaction is practically quantitative, the manufacture of 11 of acetylene requires 3.11 of carbide with a purity of 80 per cent weight... 

In Germany during World War II, acetylene (from calcium carbide) was selectively hydrogenated to ethylene (5,000 tons per month capacity), using a palladium catalyst on silica gel. The catalyst required periodic... 

Kirkpatrick, D.M. 1976. Acetylene from calcium carbide is an alternate feedstock route. OiZGa 774 133-134. 

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... 

Historically, the use of acetylene as raw material for chemical synthesis has depended strongly upon the avadabihty of alternative raw materials. The United States, which until recendy appeared to have limitless stocks of hydrocarbon feeds, has never depended upon acetylene to the same extent as Germany, which had more limited access to hydrocarbons (1). During Wodd War 1 the first manufacture of a synthetic mbber was undertaken ia Germany to replace imported natural mbber, which was no longer accessible. Acetylene derived from calcium carbide was used for preparation of... 

Table 14 Hsts the acetylene-producing plants in Western Europe as of 1991. Of the 782,000 t of aimual capacity, 48% is produced from natural gas, 46% from calcium carbide, 4% from naphtha, and 2% as ethylene coproduct.

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

Ethylene is produced in quantity using acetylene or propylene as feedstock to make a large number of products (Figure 7.2-3) such as acetaldehyde, acrylonitrile, acetic acid, and acetic anhydride. These are made generally from acetylene which is made from calcium carbide. 

Although the current source of acetylene is petroleum, it can be manufactured from calcium carbide, a product of the reachon of limestone and coke (carbon). During World War II, Germany, having a shortage of petroleum, used the latter technology to develop a chemical industry based on acetylene. 

Example describes the synthesis of acetylene (C2 H2) from calcium carbide (CaC2). Modem industrial production of acetylene is based on a reaction of methane (CH4) under carefully controlled conditions. At temperatures greater than 1600 K, two methane molecules rearrange to give three molecules of hydrogen and... 

See also Acetoacetyl-CoA in citric acid cycle, 6 633 Acetyl cyclohexanesulfonyl peroxide (ACSP), 74 282 78 478 Acetylene(s), 7 177-227, 227-228 25 633 addition of hydrogen chloride to, 73 821 from calcium carbide, 4 532, 548 carbometalation of, 25 117 as catalyst poison, 5 257t chemicals derived from, 7 227-265 decomposition of, 70 614 Diels-Alder adduct from cyclopentadiene, 8 222t direct polymerization, 7 514 economic aspects of, 7 216-217 explosive behavior of, 7 181-187 as fuel, 7 221-222 health and safety factors related to, 7 219... 

Mercuric oxide (5 g.) is dissolved for the most part in a still warm mixture of 110 c.c. of water and 50 c.c. of concentrated sulphuric acid. The mixture is brought into a large hydrogenation flask (Fig. 58, p. 377) and shaken for some time with acetylene prepared from calcium carbide, purified with acid solutions of dichromate and copper nitrate, and collected over saturated sodium chloride solution in a glass gas-holder (capacity 10-15 litres). Before shaking is begun the air present must be displaced by the hydrocarbon. 

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

If the acetylene is produced from calcium carbide, pproximately 178 lb. of calcium carbide and 100 lb. of /ater are theoretically required to produce 1000 cubic set of hydrogen at 40° F. and 30 inches barometer, /hile, at the same time, 39 lb. of carbon in the form of amp-black is produced. 

The decomposition of acetylene may be obtained by leating thus, if acetylene derived from calcium carbide >r some other source is passed through a tube heated to bout 500° C. it decomposes, in accordance with the ollowing equation, with the evolution of heat —... 

Problem 8.11 Industrially, acetylene is made from calcium carbide, CaC, + 2HjO- HC CH + Ca(OH),. 

A competing process produces vinyl chloride from acetylene, which also can be derived from petroleum feed stocks but is usually made from calcium carbide. It has been estimated (17) that 45% of current production of vinyl chloride is from ethylene, the remainder from acetylene. 

It is scarcely necessary to remove the flask for weighing until near the end of the experiment, since the volume of acetylene is known and practically complete absorption takes place. If a tank of compressed gas is not available, the acetylene may be prepared from calcium carbide by the usual laboratory methods.1... 

Acetylene prepared from calcium carbide and purified by passing (1) through copper sulphate solution, and (2) through a tower packed... 

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