GB805110A - Process for the oxidation of paraffins - Google Patents

Abstract

A C4-8 paraffin hydrocarbon is oxidized in the liquid phase at elevated temperatures and pressures with a gas consisting of or comprising molecular oxygen, to produce aliphatic carboxylic acids of 1-4 carbon atoms, the primary oxidation product is distilled to separate as light ends the materials boiling in the presence of water below 99 DEG C., the oxidation waste gases are contacted, preferably at the reaction pressure, at a temperature not above - 1 DEG C. with the light ends whereby organic materials are condensed from the waste gases, and the light ends and condensed material are oxidized in the liquid phase at elevated temperatures and pressures with a gas consisting of or comprising molecular oxygen to produce additional quantities of aliphatic C1-4 carboxylic acids, e.g. by recycling. In a preferred embodiment the oxidation waste gases are cooled to about 30 DEG C. to condense out part of the volatile organic material, before being contacted with the light ends. Such contact is preferably made at - 1 DEG to - 50 DEG C., more preferably at - 10 DEG to - 40 DEG C. The light ends may also be cooled before contact with the waste gases. In the preferred method the waste gases after contact with the light ends are expanded adiabatically to furnish part of the cooling necessary. In a variation the waste gases are cooled in the presence of light ends containing in solution filtered oxidation products of boiling-point above about 140 DEG C. (the filter residue comprising largely succinic acid), the organic material being recycled to the oxidation stage. Preferred hydrocarbon starting materials have a boiling range not exceeding about 100 DEG C. In an example related to the diagram of the apparatus (not shown) a feed of boiling range of approximately 30-70 DEG C. is oxidized with air at 175 DEG C. and 630 lb. per square inch. Specification 743,990 is referred to.