METHOD FOR IMPROVING THE STABILITY AND/OR AVOIDING DEACTIVATION OF A CATALYST WHEN MAKING AN ACETIC ACID AND/OR METHYL ACETATE

摘要

The invention concerns a method for improving the stability and/or avoiding deactivation of a catalyst in processes for making acetic acid and/or methyl acetate which consists in: in a first so-called reaction step, carrying out, in liquid phase, in the presence of carbon monoxide and a catalytic system comprising at least a halogenated promoter and at least a catalytic compound based on iridium, at least an isomerisation reaction of methyl formate; and in a second so-called flash step, evaporating partly the reaction medium derived from the first step in a separator called flash separator. The invention is characterised in that it consists in maintaining in the non-evaporated liquid fraction derived from said flash separator a global formic acid and methyl formate content at least equal to 1 wt. % of said liquid fraction, preferably ranging between 1 and 50 wt. %, more preferably between 1 and 30 wt. % relative to said liquid fraction. The invention also concerns a complete method for making acetic acid and/or methyl acetate integrating said improvement. The invention enables to prepare acetic acid and/or methyl acetate with increased stability of the catalytic system, even in the presence of particular low water contents and particularly low pressure levels in carbon monoxide in the reaction zone and is particularly applicable to processes for preparing acetic acid and/or methyl acetate wherein the first step further comprises carbonylation reaction of methanol.