Editing Propionic acid (section)

===Chemical===
In industry, propionic acid is mainly produced by the [[Carbonylation#Reppe chemistry|hydrocarboxylation]] of [[ethylene]] using [[nickel carbonyl]] as the catalyst:<ref name=Ullmann>{{Ullmann |year=2018 |first1=Ulf-Rainer |last1=Samel |first2=Walter |last2=Kohler |first3=Armin Otto |last3=Gamer |first4=Ullrich |last4=Keuser |first5=Shang-Tian |last5=Yang |first6=Ying |last6=Jin |first7=Meng |last7=Lin |first8=Zhongqiang |last8=Wang |first9=Joaquim Henrique |last9=Teles |title=Propionic Acid and Derivatives |doi=10.1002/14356007.a22_223.pub4}}</ref>

:[[File:Industrial synthesis of propionic acid (hydrocarboxylation process).svg|450px|class=skin-invert-image|Hydrocarboxylation of ethene with carbon monoxide and water to form propionic acid in the presence of nickel tetracarbonyl as catalyst]]

It is also produced by the aerobic [[oxidation]] of [[propionaldehyde]].  In the presence of [[cobalt]] or [[manganese]] salts (manganese propionate is most commonly used), this reaction proceeds rapidly at temperatures as mild as 40–50&nbsp;°C:

:[[File:Industrial synthesis of propionic acid (oxidation process).svg|450px|class=skin-invert-image|Liquid-phase oxidation of propionaldehyde with atmospheric oxygen to form propionic acid in the presence of manganese(II)-propionate as catalyst]]

Large amounts of propionic acid were once produced as a byproduct of acetic acid manufacture. At the current time, the world's largest producer of propionic acid is [[BASF]], with approximately 150 kt/a production capacity.