C₄ to C₈ hydrocarbons are the favored feedstocks for the manufacture of acetic acid by oxidative degradation. They can be separated into the following groups and process modifications:
1. n- (Hoechst Celanese, Hüls, UCC)
2. n-Butenes (Bayer, with sec-butyl acetate as intermediate; Hüls directly)
3. Light gasoline (BP, British Distillers)

To 1:

In 1982, about 31% of the acetic acid capacity in the USA was still based on the liquid-phase oxidation of n-butane as practiced by UCC and Celanese. The UCC plant has been shut down, and following an accident the Hoechst Celanese plant resumed operation in 1989. In 1991, their production of ca. 230000 tonnes accounted for about 14% of the total acetic acid production in the USA. Formerly, the UCC plant in Texas produced about 225000 tonnes acetic acid, 36000 tonnes methyl ethyl ketone, 23 000 tonnes formic acid, and 18 000 tonnes propionic acid annually by the uncatalyzed oxidation of n-butane with oxygen in a bubble column at 15-20 bar and 180°C using the liquid oxidation products as reaction medium. More extensive oxidative degradation was controlled by limiting the conversion to 10-20%.

The Celanese LPO process (Liquid-Phase Oxidation) operates at 175°C and 54 bar with Co acetate as catalyst. After separating the acetic acid, part of the byproduct mixture is recycled to the process and oxidized either to acetic acid or completely. This simplifies the product workup. In addition to acetic acid, , acetone, methyl ethyl ketone, ethyl acetate, formic acid, propionic acid, butyric acid, and methanol are isolated. On demand, amounts of methyl ethyl ketone up to 17% of the plant capacity can be manufactured, though at the cost of acetic acid production.

From 1965 to 1984, a plant in The Netherlands with an acetic acid capacity of 130000 tonnes per year (after several expansions) used the Celanese LPO process.

For several years, Huls also carried out n-butane oxidation - without a catalyst - in a commercial plant with a capacity of 20000 tonnes per year. The oxidation took place at 60-80 bar and 170-200°C with air or O₂ enriched air (ca. 30% O₂) in a liquid phase consisting of crude acetic acid. n-Butane conversion was limited to about 2% to prevent secondary reactions. The main product was in fact acetic acid (about 60% selectivity), but numerous byproducts such as acetone, methyl ethyl ketone, methyl and ethyl acetate, and smaller amounts of formic and propionic acid, were also formed. Processing required a multistep distillation unit with, for example, 14 columns at normal pressure and others at reduced or excess pressure.

To 2:

Hüls developed yet another acetic acid process based on the oxidation of n-butenes. This was operated for a long time in a pilot plant, though an industrial-scale unit was never built. In this method, butene is oxidized at slight excess pressure at 200 °C in a liquid phase consisting essentially of crude acetic acid. and tin vanadate are employed as catalysts. For various reasons, including the extremely narrow explosion limits, this oxidation takes place in the presence of a large amount of steam. The very dilute acetic acid produced must be concentrated to a crude acid consisting of 95% acetic acid, which requires a great deal of energy. The crude acid selectivity reaches 73% at 75% butene conversion.

Bayer uses a different two-stage process for its liquid-phase oxidation of n-butenes to acetic acid. After removing butadiene and isobutene from the C₄ cracking fraction, a mixture of 1 -butene and cis- and trans-2-butene remains. This is converted into 2-acetoxybutane, i. e., sec-butyl acetate:

Theadditionof aceticacidtakesplaceat 100- 120 °C and 15-25 bar over acidic ion-exchange resins with sulfonic acid groups. Due to the simultaneous isomerization of the n-butenes, only 2-acetoxybutane is formed. In the second stage, this is oxidized with air to acetic acid in a noncatalytic liquid-phase reaction at 200 °C and 60 bar:

After working up the reaction mixture by an azeotropic and a normal distillation, a portion of the acetic acid is recycled to the sec-butyl acetate manufacture.

To 3:

A process for the oxidation of crude oil distillates in the boiling range 15 - 95 °C (roughly corresponding to a light gasoline in the C₄ - C₈ region) was developed by British distillers in England. The uncatalyzed air oxidation is done in the liquid phase in a stainless steel reactor at 160-200°C and 40-50 bar, and proceeds by a free-radical mechanism. The product from the oxdiation is separated by a two-stage distillation into starting material, more volatile byproducts, and an aqueous acid mixture. The acids and a small amount of water are first extracted from the mixture with a low boiling solvent such as isoamyl acetate. The organic phase is then separated into its individual components by distillation. Besides acetic acid, formic acid, propionic acid, and small amounts of succinic acid are formed. Enough acetone is produced to warrant its isolation. All byproducts contribute to the profitability of the process. Depending on the process conditions, 0.35 to 0.75 tonnes of byproducts can be obtained per tonne of acetic acid.

BP developed the Distillers process further and brought it to maturity, particularly in England. In 1996 the capacity there was 220 000 tonnes per year acetic acid and about 18 000 tonnes per year propionic acid. This is the last plant using the BP process.