T> acetylene

Japan and China. During the 1980s, acetylene demand in Japan suffered a significant decline. Chemical use declined from over 100,000 to 42,000 t, acetylene black production declined from 20,000 to less than 10,000 t, and industrial use went from 42,000 to 30,000 t. Thus, based on 1990 estimates, Japan has an excess capacity for acetylene production with capabiUties for 247, 000 t/yr and a demand of only 82,000 t. 

Oxides of Nitrogen See Nitrogen oxide Dienes, etc. t Acetylene, 0686 t 1,3-Butadiyne, 1385... 

Tautomerization Between T) -Acetylene and Vinylidene on Transition Metal Centers... 

Masuda, T., Acetylene Polymerization , in Catalysis in Precision Polymerisation, John Wiley Sons, Chichester-New York, 1997, pp. 67-97. 

Method Refer- Fulminic acid t acetylene Fulminic acid i-ethylene Nitrone +ethylene... 

C6H404)t Acetylene dicarboxylic acid dimethyl ester 600 g, 238... 

Besides the T-cyclopropanes, T-butenes and T-pentenes, several highly unsaturated tritium-labeled products, including acetylene, allene, propyne and 1,3-butadiene were observed in the hot T reaction with EC and DMC. Except for T-acetylene, whose yield is about 10 % of the substituted parent molecule, the yields of the other products are very low. 

X—22M propane -o— cy do pentane - —cycle pentene -X- i-pentane -o— n-pentane - — dienes -t—acetylenes -ni— pentenes methyl butenes... 

Masuda, T. Acetylene polymerization. In Catalysis in Precision Polymerization, Kobayashi, S., Ed. WUey Chichester, 1997 pp 67-97. 

To prepare pure acetylene, assemble the apparatus shown in Fig. 57. F is a wide-necked 300 ml. bolt-head flask, to which is fitted a double-surface reflux water-condenser C and the dropping-funnel D. From the top of C, a delivery-tube leads down to the pneumatic trough T, where the gas can be collected in jars in the usual way. (Alternatively, use the apparatus shown in Fig. 23(A),... 

The high acidity of superacids makes them extremely effective pro-tonating agents and catalysts. They also can activate a wide variety of extremely weakly basic compounds (nucleophiles) that previously could not be considered reactive in any practical way. Superacids such as fluoroantimonic or magic acid are capable of protonating not only TT-donor systems (aromatics, olefins, and acetylenes) but also what are called (T-donors, such as saturated hydrocarbons, including methane (CH4), the simplest parent saturated hydrocarbon. 

T.F. Rutledge, "Acetylenes and Allenes", Reinhold Book Corporation, New York, Amsterdam, London, (1969). 

Terminal alkyne anions are popular reagents for the acyl anion synthons (RCHjCO"). If this nucleophile is added to aldehydes or ketones, the triple bond remains. This can be con verted to an alkynemercury(II) complex with mercuric salts and is hydrated with water or acids to form ketones (M.M.T. Khan, 1974). The more substituted carbon atom of the al-kynes is converted preferentially into a carbonyl group. Highly substituted a-hydroxyketones are available by this method (J.A. Katzenellenbogen, 1973). Acetylene itself can react with two molecules of an aldehyde or a ketone (V. jager, 1977). Hydration then leads to 1,4-dihydroxy-2-butanones. The 1,4-diols tend to condense to tetrahydrofuran derivatives in the presence of acids. 

FIGURE 9 2 The carbon atoms of acetylene are con nected by a cr + tt + tt triple bond (a) Both carbon atoms are sp hybridized and each IS bonded to a hydrogen by a (T bond The two tt bonds are perpendicular to each other and are shown sepa rately in (b) and (c)... 

Acetylene (HC=CH) belongs to the point group whose character table is given in Table A.37 in Appendix A, and its vibrations are illustrated in Figure 6.20. Since V3 is a vibration and T T ) = 2"+, the 3q transition is allowed and the transition moment is polarized along the z axis. Similarly, since Vj is a vibration, the 5q transition is allowed with the transition moment in the xy plane. 

Ethylene. During Wodd War 11 the Germans manufactured more than 60,000 t/yr of ethylene [74-85-1], by hydrogenation of acetylene,... 

Calcium carbide has been used in steel production to lower sulfur emissions when coke with high sulfur content is used. The principal use of carbide remains hydrolysis for acetylene (C2H2) production. Acetylene is widely used as a welding gas, and is also a versatile intermediate for the synthesis of many organic chemicals. Approximately 450,000 t of acetylene were used aimuaHy in the early 1960s for the production of such chemicals as acrylonitrile, acrylates, chlorinated solvents, chloroprene, vinyl acetate, and vinyl chloride. Since then, petroleum-derived olefins have replaced acetylene in these uses. 

Electric Discharge Processes. The synthetic mbber plant built by the 1. G. Farbenindustrie during World War 11 at Hbls, contained the first successful commercial instaUation for the electric arc cracking of lower hydrocarbons to acetylene. The plant, with a capacity of 200 t/d, was put into operation in August 1940. 

The composition of the cracked gas with methane and naphtha and the plant feed and energy requirements are given in Table 9. The overall yield of acetylene based on methane is about 24% (14). A single burner with methane produces 25 t/d and with naphtha or LPG produces 30 t/d. The acetylene is purified by means of /V-methy1pyrro1idinone. 

Worldwide, approximately 180, 000 t/yr acetylene product is recovered as a by-product within olefin plants. This source of acetylene is expected to increase as plant capacity and furnace temperature increase. The recovery may include compression and transfer of the acetylene product via pipelines directly to the downstream consumer. 

Acetylene black is prepared by the partial combustion of acetylene and has specialty uses in batteries. Only about 3500 t/yr are produced in the United States. 

Most by-product acetylene from ethylene production is hydrogenated to ethylene in the course of separation and purification of ethylene. In this process, however, acetylene can be recovered economically by solvent absorption instead of hydrogenation. Commercial recovery processes based on acetone, dimetbylform amide, or /V-metby1pyrro1idinone have a long history of successfiil operation. The difficulty in using this relatively low cost acetylene is that each 450, 000 t/yr world-scale ethylene plant only produces from 7000 9000 t/yr of acetylene. This is a small volume for an economically scaled derivatives unit. 

In the United States, the acetylene production exceeded 450, 000 t/yr between 1963 and 1970, but then declined until it hit a minimum production level below 150, 000 t/yr in 1982. Of this production, about 40,000 t were dedicated to industrial use, ie, welding, etc. Thus only slightly more than 100,000 t were produced for the chemical process industry. Figure 14 illustrates the 17-year decline in acetylene production and indicates the reduced derivative demand to which the accumulated decline is attributed (37). 

Fig. 14. Acetylene for chemical us in the United States (37). Courtesy of Chem Systems. Total consumption for specified years in 10 t as follows 1965,...

In 1984, acetylene production received a significant influx with the increase of capacity at the Borden Co. plant in Geismar, Louisiana. This influx provided an additional 33,000 t/yr, which were absorbed by the vinyl chloride monomer (VCM) and acetylenic chemicals market. Acetylene demand has... 

The U.S. Department of Commerce estimates total production of about 163,000 t in 1990. Other estimates based on demand data indicate that it was as high as 175,000 t. With demand and supply in balance, it is estimated that in 1997 the demand will be 185,000 t. The distribution in product demand is projected to be the following 1,4-butanediol and other acetylenic chemicals (45%), vinyl chloride monomer (45%), acetylene black (5%), and industrial use (5%). 

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. 

Western Europe. Acetylene demand in Western Europe exceeds by far that of any other geographical region. Prior to the unification of Germany in 1990, acetylene consumption in Western Europe was estimated to be 430, 000 t/yr with the addition of 280,000 t of consumption attributed to the former German Democratic RepubHc, total consumption increased to 710,000 t. 

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