MODIFICATION OF THE CATALYTIC SYSTEM IN AN INDUSTRIAL PROCESS FOR MAKING ACETIC AND/OR METHYL ACETATE ACID

摘要

The invention concerns a method for continuous production of acetic and/or methyl acetate acid, characterised in that, it is based on a known continuous industrial process, called initial process, of carbonylation of methanol or a methanol derivative capable of being subjected to carbonylation, such as dimethylether, methyl halides or methyl acetate, in homogeneous liquid phase and under carbon monoxide pressure, in the presence of a catalytic system comprising a homogeneous catalyst based in rhodium and a halogenated promoter, and in the presence of a water concentration in the reaction medium higher than 14 %; the method consists, during the continuous operation of the installation, in carrying out a gradual modification of the composition of said homogeneous catalyst by adding from time to time, an iridium compound. Said method enables both to modify the composition of the catalytic system to shift from a rhodium-based homogeneous catalyst on its own to a catalyst based on rhodium and iridium, or even on iridium alone, without stopping the installation and to reduce the water content of the reaction medium once the iridium has been added.