Acetylene, C
2
H
2
, is a highly reactive, commercially important hydrocarbon. Its reactivity is related to its triple bond between carbon atoms and, as a consequence, its high positive free energy of formation. Because of its explosive nature, long distance shipping or pressurized storage is not recommended. Thus acetylene is generally used as it is produced without shipping or storage.
Commercially, acetylene is used primarily as a raw material for the synthesis of a variety of organic chemicals. In the United States, this accounts for about 80% of acetylene usage, with the balance being used for metal welding and cutting. Worldwide acetylene production peaked in the mid‐1960s, after which it declined dramatically as processes were developed to substitute lower cost olefins and paraffins for the acetylene feedstock. Production levels reached a minimum in the early 1980s and since have been growing at a rate of about 2–4% per year, mainly in response to the growth of 1,4‐butanediol production.
Although acetylene production in Japan, China, and Eastern Europe is still based on the calcium carbide process, the large producers in the United States, Western Europe, and Russia now rely principally on the partial oxidation of natural gas. However, much of the incremental growth in production is based on producing acetylene as a coproduct of ethylene in the steam cracking process. As a coproduct, acetylene is much less costly than as produced from partial oxidation or calcium carbide.