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56 Acetylene

formaldehyde to yield butyne-1,4-diol and propargyl lene burned in the presence of oxygen provided a very hot
alcohol. flame, useful in the joining of metals. The welding indus-
Surfynols Acetylenic hydroxyl compounds used as high- try today still uses significant amounts of acetylene in spite
speed, low-foam wetting–dispersing agents and as of the availability of less expensive fuels such as propane.
agricultural adjuvants and formulation aids. Initially, acetylene was handled in industry as the undi-
Trofimov reaction Formation of substituted pyrroles luted liquefied gas below its critical temperature of 36 C
◦
and N-vinylpyrroles by reaction of acetylene with at a pressure greater than 600 psig. This appeared to be
ketoximes. a safe procedure until a series of industrial explosions
Vinylation Reaction of acetylene with alcohols or pyrol- in the early 1900s eliminated the practice. Today acety-
lidone to form vinyl ethers and vinylpyrrolidone. lene is shipped in cylinders under pressure that contain a
mixture of diatomaceous earth or asbestos, acetone, and
stabilizers. Another safe method of transport is via granu-
ACETYLENE CHEMISTRY is the chemistry of the lar calcium carbide in sealed containers, free of water. The
carbon–carbon triple bond ( C C ). This functionality large-volume use of acetylene for the manufacture of com-
defines the unique chemistry of this reactive group, in ad- modity chemicals has led to the building of plants, either
dition to its diverse and important applications. The high petrochemical or calcium carbide, “across the fence” from
electron density of the triple bond with its circular, sym- acetylene producers. Today the factors leading to acety-
metrical π field makes acetylene and its derivatives reac- lene hazards are well understood and have been well doc-
tive and useful intermediates for synthesizing a wide va- umented. Acetylene now poses a minimum risk in well-
riety of organic compounds. These organic products find operated processes and plants.
wide use in the synthesis of flavors and fragrances, vita-
mins A, E, and K, β-carotene, pesticides, surfactants, cor-
rosion inhibitors, and specially intermediates. This article II. ACETYLENE AND COMMODITY
describes the technology and applications of acetylene, CHEMICALS
acetylenic compounds, and the chemicals derived from
them. From1965to1970morethan1billionpoundsofacetylene
In the mid-1960s more than 1 billion pounds of were used annually to manufacture a variety of chemi-
acetylene were used annually for the production of cals. Welding applications constituted ∼10% of this to-
large-volume (commodity) chemicals. Since then, acety- tal. After 1970, the use of acetylene for the manufac-
lene has been gradually supplanted by less expensive ture of commodity chemicals began to decline markedly,
olefin feedstocks. However, acetylene is still used in and by 1979–1983 only 269 million pounds were em-
multimillion-pound levels to produce Reppe chemicals ployed. Less expensive petrochemical raw materials such
(butynediol, propargyl alcohol, butanediol, butyrolactone, as ethylene, propylene, butadiene, amylenes, and methane
N-methylpyrrolidone, polyvinylpyrrolidone, and vinyl were replacing acetylene. Table I summarizes chemicals
ether copolymers) and specialty acetylenic chemicals and manufactured mainly from actylene before 1965, types of
their derivatives. Large volumes of butanediol are used in processes, and replacement raw materials. The principal
the manufacture of engineering plastics such as polybuty- use of the monomers listed in the table was in diverse
lene terephthalate. Other significant uses for acetylene in polymer applications spanning plastics, latex emulsions,
specialty areas include acetylene black, vitamins A and E, rubbers, and resins. Chlorinated solvents were important
flavor–fragrance (F & F) compounds, corrosion inhibitors, in vapor degreasing, but their use in more recent years
acetylenic surfactants, and pesticides. Acetylenic chemi- has been gradually limited as a result of toxicity and air
cals, polymers, and derivatives of potential value in re- pollution.
search and commerce are also discussed. Some special The applications of the polymer products derived from
aspects of acetylene chemistry research in Russia are also theabovemonomersarenotwithinthescopeofthisarticle.
summarized.

III. PRODUCTION OF ACETYLENE AND
I. INTRODUCTION COMMODITY CHEMICALS

Acetylene has always been an important raw material for The following tabulation shows the gradual decline in U.S.
making chemical products. In the early years of its history acetylene production from its high point of 1.23 billion
(circa 1890–1900) it was used extensively as an illuminant pounds in 1965 to ∼269 million pounds in 1979. In 1965
for trains and city streets. It was soon realized that acety- bulk acetylene was valued at 7–12c //lb, while ethylene was