Monsanto Company

Jerry L Price

Earle C Makin

Yu Wen Wei

Lloyd S Eubanks

There is provided an improved continuous homogeneous catalytic carbonylation process wherein a mixed gas stream is removed from the carbonylation reactor, condensable liquids separated from said gas stream and said gas stream vented, the improvement comprising contacting said gas stream with a plurality of hollow fiber membranes selectively permeable to hydrogen under conditions substantially non-degrading of the membranes to generate a non-permeated gas stream of higher carbon monoxide content and recycling said non-permeated gas stream to the carbonylation process reactor. There is also provided for the recovery and recycle to the process of carbonylation products such as acetic or propionic acids by adsorption and removal from a solid adsorbent or absorption in a liquid absorbent.

Carbonylation process

An improved process for the simultaneous and continuous production of acetic and propionic acids in a single reactor wherein the rate of propionic acid production is enhanced over that which prevails when this acid is produced separately in the same reactor under the same conditions, said rate enhancement being achieved by the introduction of methanol at a critical rate.

Coproduction of acetic and propionic acids

A method is provided for the removal of contaminating alkanes from the vaporized carbonylation products of a process wherein carboxylic acids are produced by the reaction in the liquid phase of an alcohol or an ester, halide or ether derivative of said alcohol with carbon monoxide in the presence of a catalyst system containing a rhodium or iridium component and an iodine or bromine component. The method involves distillation of the alkane-containing vaporized carbonylation products, phase separation of the overhead from said distillation, further distillation of a slipstream of the resulting heavy phase using carbon monoxide as stripping gas and removal of the alkanes as the bottoms stream from the latter distillation.

Purification of carbonylation products

Acetic acid containing very minor amounts of iodine, either as I.sup.-, free iodine, or alkyl iodide, or all of these, is purified by fractionation in a single column with an acid product containing 20 parts or less of iodine per billion parts of acid (ppb) being withdrawn as a liquid sidedraw from said column. Generally, more than one column is required for obtaining an acid product of such extremely high purity. The process is particularly applicable for purification of acetic acid made by the carbonylation of methanol using a catalyst system formed on the mixing of a rhodium or iridium component and an iodine component notably hydrogen iodide or an alkyl iodide such as methyl iodide.

Purification of acetic acid streams by distillation

A method is provided for removal of excess water which tends to build up in recycle streams and reduces the rate of pure acid production during operation of a distillation system for purification of crude acetic acid containing water and methyl iodide. The crude acid is introduced into the upper half of a distillation zone. The methyl iodide, a major proportion of water and an equivalent amount of acid are removed overhead from the zone. A minor proportion of the water containing a small amount of acetic acid is removed as a liquid sidedraw at a point near the top of the distillation zone. A product acid stream essentially dry and substantially free of methyl iodide is removed from the bottom of the distillation zone. The overhead stream can be stored, disposed of or preferably recycled to the acid-producing step. The liquid water sidedraw may either be discarded or subjected to rectification for recovery of acid values.

Growing community of inventors

Texas City, TX, United States of America

Jerry L Price