1. Welding
Due to the high flame temperature,
the industrial gases sector provides 20% or more of the acetylene used in
oxyacetylene gas welding and cutting. Acetylene burns with oxygen to produce a
flame that is over 3,600 K (3,330 °C; 6,020 °F) and 11.8 kJ/g of energy is
released. The hottest burning common fuel gas is oxyacetylene.
After cyanogen at 4,798 K (4,525
°C; 8,177 °F) and dicyanoacetylene at 5,260 K (4,990 °C; 9,010 °F), acetylene
is the third-hottest natural chemical flame. In earlier decades, oxy-acetylene
welding was a widely used welding technique. Oxy-fuel welding is all but
obsolete for many applications due to the advancement and benefits of arc-based
welding methods. Welding acetylene usage has decreased considerably.
Contrarily, oxy-acetylene welding equipment is quite adaptable because it lends
itself easily to brazing, braze-welding, metal heating (for annealing or
tempering, bending or forming), the loosening of corroded nuts and bolts, and
other applications. This is not just because the torch is preferred for some
types of iron or steel welding (as in some artistic applications).
In manholes and in some aerial
sites, Bell Canada cable maintenance employees still utilize portable
acetylene-fueled torch kits as a soldering tool to seal lead sleeve splices. In
locations without easy access to electricity, oxyacetylene welding may also be
employed. Many metal fabrication shops employ oxygen acetylene cutting. Since
acetylene explodes when exposed to shockwaves above 15 psi (100 kPa), such as
those created by flashbacks, the working pressures used for welding and cutting
must be controlled by a regulator.
2. Portable lighting
The early 20th century saw
significant acetylene commercialization due to the powerful, bright light
produced by acetylene combustion and the widespread use of carbide lamps.
Common usage included headlamps for cars and mining equipment, as well as
coastal lighthouses and street lights. Since direct combustion presents a fire
risk in the majority of these applications, acetylene has been replaced, first
by incandescent lighting and then, decades later, by low-power/high-lumen LEDs.
However, there is still a small
amount of demand for acetylene lamps in distant or inaccessible regions as well
as in nations with a shoddy or unreliable central electric infrastructure.
3. Plastics and acrylic acid derivatives
A number of polyethylene polymers
can use acetylene as a feedstock since it can be semihydrogenated to ethylene.
The production of derivatives of acrylic acid is another important use of acetylene,
particularly in China. Products including acrylic fibers, glasses, paints,
resins, and polymers are created from these derivatives.
Due to costs and environmental
concerns, the usage of acetylene as a chemical feedstock decreased by 70% from
1965 to 2007 outside of China.
4. Niche applications
Mikhail Kucherov, a Russian
chemist, first documented the conversion of acetylene to acetaldehyde in 1881
utilizing catalysts like mercury(II) bromide. This reaction was carried out on
an industrial scale prior to the invention of the Wacker process.
Films made of polyacetylene are
created when acetylene is polymerized using Ziegler-Natta catalysts. One of the
first organic semiconductors was polyacetylene, a chain of CH centers with
alternate single and double bonds. It forms a highly electrically conductive
substance when it reacts with iodine. Despite the fact that these materials are
useless, their findings paved the way for the creation of organic
semiconductors, as Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa
were honored with the Nobel Prize in Chemistry in 2000.
Pure acetylene was tested as an
inhalation anesthetic in the 1920s.
When a piece of steel is too large
to fit inside a furnace, acetylene is occasionally used to carburize (i.e.,
harden) the steel.
In radiocarbon dating, acetylene
is utilized to volatilize carbon. In a tiny, specialized research furnace,
lithium metal is used to convert the carbonaceous material in an archeological
sample to create lithium carbide (also known as lithium acetylide). The
isotopic ratio of carbon-14 to carbon-12 can then be determined by reacting the
carbide with water as usual to produce acetylene gas, which can then be fed
into a mass spectrometer.
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