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Applications of Acetylene

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.