Modification of the catalytic system in an industrial process for making acetic and/or methyl acetate acid

Abstract

The invention relates to a continuous process for the manufacture of acetic acid and/or methyl acetate, characterized in that, during the continuous operation of the installation for a continuous industrial process, called the initial process, for the carbonylation of methanol or a carbonylatable derivative of methanol such as dimethyl ether, methyl halides or methyl acetate, in the homogeneous liquid phase and under carbon monoxide pressure, in the presence of a catalyst system comprising a rhodium-based homogeneous catalyst and a halogenated promoter, and in the presence of a concentration of water greater than or equal to 14% in the reaction medium, the composition of said homogeneous catalyst is modified gradually by adding an iridium compound over time. This process makes it possible on the one hand to modify the composition of the catalyst system so as to change from a homogeneous catalyst based on rhodium alone to a catalyst based on rhodium and iridium, or even iridium alone, without stopping the installation, and on the other hand to reduce the water content of the reaction medium once the iridium additions have been effected.