Acetic Acid Synthesis via Butane or Naphtha Oxidation

Acetic Acid Synthesis via Butane or Naphtha Oxidation 

The oxidation of butane or naphtha is also used for the commercial production of acetic acid. The relevant processes were developed in the 1950s and 1960s, when increasing refinery capadties led to attractive prices for light hydrocarbon cuts. Not all mixtures of hydrocarbons are good feedstock for this process. The desirable ratio of methyl to methylene groups is 1 1 and the alkene content must be very low. 

Two main feedstocks have been established for the commercial production of acetic acid, butane in the United States and Canada (e.g., Celanese) and light naphtha (called primary flash distillate) in the United Kingdom (e.g., BP). 

The oxidation of hydrocarbons follows a radical chain reaction. Hydroperoxide radicals are formed and these radicals react to give various oxygenated products [for the detailed mechanism see Cheung, Tanke, and Torrence (2000)]. The oxidation of hydrocarbons can be non-catalytic. For catalytic processes metal ions, for example, Mn, Co, Ni, and Cr, are used as catalysts. 

In the Celanese-LPO-process (liquid-phase oxidation) the catalytic oxidation of n-butane with cobalt acetate takes place at 175 °C and 54 bar. Many by-products are formed in this process (main by-product methyl ethyl ketone other by-products butanoic acid, propionic acid, formic acid, acetaldehyde, acetone, ethyl acetate, and methanol). These by-products are recycled to the reactor where they convert into acetic acid again or oxidize totally. 

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