Acetylenes natural

Benzene Petroleum, coal tar, trimerization of acetylene, natural products, etc. Colourless liquid, b.p.80°C m.p.5.5°C. stable. Has relatively pleasant odour, (carcinogenic). Industrially a very important compound). 

Keywords compression chemical reactor, methane pyrolysis, acetylene, natural gas conversion, hydraulic ram. 

It is clear that these gases have widely varying compositions according to the processes used, but refinery gas is distinguished from natural gases by the presence of hydrogen, mono- and diolefins, and even acetylenes. 

The first breakthrough came m 1911 when Richard Willstatter prepared cyclooc tatetraene by a lengthy degradation of pseudopelletienne a natural product obtained from the bark of the pomegranate tree Today cyclooctatetraene is prepared from acetylene m a reaction catalyzed by nickel cyanide... 

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... 

Although the rapid cost increases and shortages of petroleum-based feedstocks forecast a decade ago have yet to materialize, shift to natural gas or coal may become necessary in the new century. Under such conditions, it is possible that acrylate manufacture via acetylene, as described above, could again become attractive. It appears that condensation of formaldehyde with acetic acid might be preferred. A coal gasification complex readily provides all of the necessary intermediates for manufacture of acrylates (92). 

R. J. Tedeschi, Acetylene Based Chemicals from Coal and Other Natural Resources, Marcel Dekker, Inc., New York, 1982. 

The two synthetic steroidal estrogens which have attained the greatest degree of therapeutic use are ethinyl estradiol [57-63-6] (EE) (5) and its 3-methyl ether, mestranol [72-33-3]((5). In contrast to the naturally occurring estrone derivatives, these acetylenic analogues are orally active and are the main estrogenic components of combination oral contraceptives (see Contraceptives) and certain estrogen replacement products. 

Aliphatic Chemicals. The primary aliphatic hydrocarbons used in chemical manufacture are ethylene (qv), propjiene (qv), butadiene (qv), acetylene, and / -paraffins (see Hydrocarbons, acetylene). In order to be useflil as an intermediate, a hydrocarbon must have some reactivity. In practice, this means that those paraffins lighter than hexane have Httle use as intermediates. Table 5 gives 1991 production and sales from petroleum and natural gas. Information on uses of the C —C saturated hydrocarbons are available in the Hterature (see Hydrocarbons, C —C ). 

Purification of Carbide Acetylene. The purity of carbide acetylene depends largely on the quaUty of carbide employed and, to a much lesser degree, on the type of generator and its operation. Carbide quahty in turn is affected by the impurities in the raw materials used in carbide production, specifically, the purity of the metallurgical coke and the limestone from which the lime is produced. The nature and amounts of impurities in carbide acetylene are shown in Table 4. 

Although acetylene production in Japan and Eastern Europe is stiU based on the calcium carbide process, the large producers in the United States and Western Europe now rely on hydrocarbons as the feedstock. Now more than 80% of the acetylene produced in the United States and Western Europe is derived from hydrocarbons, mainly natural gas or as a coproduct in the production of ethylene. In Russia about 40% of the acetylene produced is from natural gas. 

Hydrocarbon, typically natural gas, is fed into the reactor to intersect with an electric arc stmck between a graphite cathode and a metal (copper) anode. The arc temperatures are in the vicinity of 20,000 K inducing a net reaction temperature of about 1500°C. Residence time is a few milliseconds before the reaction temperature is drastically reduced by quenching with water. Just under 11 kWh of energy is required per kg of acetylene produced. Low reactor pressure favors acetylene yield and the geometry of the anode tube affects the stabiUty of the arc. The maximum theoretical concentration of acetylene in the cracked gas is 25% (75% hydrogen). The optimum obtained under laboratory conditions was 18.5 vol % with an energy expenditure of 13.5 kWh/kg (4). 

In 1991, U.S. plant capacity for producing acetylene was estimated at 176, 000 t/yr. Of this capacity, 66% was based on natural gas, 19% on calcium carbide, and 15% on ethylene coproduct processing. Plants currendy producing acetylene in the United States are Hsted in Table 13. 

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.

D. T. Tilin and co-workers, "Production of Acetylene by Electrocracking of Natural Gas ia a Coaxial Reactor," translated from J. Jippl. Chem. ULLR 42(3), 648 (1969). 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Calcium Carbide. Until the 1940s, calcium carbide, which is made by interacting quicklime and coke in an electric furnace, was the only source of acetylene. Although much more acetylene is now derived from natural gas, calcium carbide is stiH being produced, using 0.9—1.0 t of quicklime to make 11 of carbide... 

This excess hydrogen is normally carried forward to be compressed into the synthesis loop, from which it is ultimately purged as fuel. Addition of by-product CO2 where available may be advantageous in that it serves to adjust the reformed gas to a more stoichiometric composition gas for methanol production, which results in a decrease in natural gas consumption (8). Carbon-rich off-gases from other sources, such as acetylene units, can also be used to provide supplemental synthesis gas. Alternatively, the hydrogen-rich purge gas can be an attractive feedstock for ammonia production (9). 

Partial oxidation of natural gas or a fuel oil using oxygen may be used to form acetylene, ethylene (qv) and propylene (qv). The ethylene in turn may be partially oxidi2ed to form ethylene oxide (qv) via advantages (/) and (5). A few of the other chemicals produced using oxygen because of advantages (/) and (5) are vinyl acetate, vinyl chloride, perchloroethylene, acetaldehyde (qv), formaldehyde (qv), phthaHc anhydride, phenol (qv), alcohols, nitric acid (qv), and acryhc acid. 

When natural gas is used as a feedstock to produce thermal blacks, the reaction is endothermic. In order to maintain the reaction, the reactor has to be kept at about 1300°C. When acetylene is used as the feedstock to produce acetylene blacks, the reaction is exothermic, and the reaction can be mn at a temperature between 800 and 1000°C. 

Subsequent dehydrohalogenation afforded exclusively the desired (Z)-olefin of the PGI2 methyl ester. Conversion to the sodium salt was achieved by treatment with sodium hydroxide. The sodium salt is crystalline and, when protected from atmospheric moisture and carbon dioxide, is indefinitely stable. A variation of this synthesis started with a C-5 acetylenic PGF derivative and used a mercury salt cataly2ed cyclization reaction (219). Although natural PGI has not been identified, the syntheses of both (6R)- and (65)-PGl2, [62777-90-6] and [62770-60-7], respectively, have been described, as has that of PGI3 (104,216). 

The largest use of NMP is in extraction of aromatics from lube oils. In this appHcation, it has been replacing phenol and, to some extent, furfural. Other petrochemical uses involve separation and recovery of aromatics from mixed feedstocks recovery and purification of acetylenes, olefins, and diolefins removal of sulfur compounds from natural and refinery gases and dehydration of natural gas. 

A number of processes have been used to produce carbon black including the oil-furnace, impingement (channel), lampblack, and the thermal decomposition of natural gas and acetjiene (3). These processes produce different grades of carbon and are referred to by the process by which they are made, eg, oil-furnace black, lampblack, thermal black, acetylene black, and channel-type impingement black. A small amount of by-product carbon from the manufacture of synthesis gas from Hquid hydrocarbons has found appHcations in electrically conductive compositions. The different grades from the various processes have certain unique characteristics, but it is now possible to produce reasonable approximations of most of these grades by the od-fumace process. Since over 95% of the total output of carbon black is produced by the od-fumace process, this article emphasizes this process. 

Acetic acid (qv) can be produced synthetically (methanol carbonylation, acetaldehyde oxidation, butane/naphtha oxidation) or from natural sources (5). Oxygen is added to propylene to make acrolein, which is further oxidized to acryHc acid (see Acrylic acid and derivatives). An alternative method adds carbon monoxide and/or water to acetylene (6). Benzoic acid (qv) is made by oxidizing toluene in the presence of a cobalt catalyst (7). 

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