Method for improving the stability and activity of a catalyst system used in the preparation of acetic acid and methyl acetate by ensuring a sufficient presence of formylated compounds at the flash separation stage

摘要

The method is applicable to an iridium-based catalyst system used in the continuous preparation of acetic acid and/or methyl acetate obtained by carbonylation of methanol and isomerization of methyl formate. A process for improving the stability and/or avoid deactivation of a catalyst used in the preparation of acetic acid is claimed, the preparation being effected in the following stages. The first stage(reaction stage) is effected in the presence of carbon monoxide and a catalytic system comprising a halogenated promoter and an iridium-based compound involving an isomerisation reaction of methyl formate ; in the next stage(flash stage), the liquid phase from the first stage is subjected to a flash separation at a lower pressure, whereby the vapor fraction obtained is processed for recovery of acetic acid and the remaining liquid fraction(containing the catalyst) is recycled. A proportion of at least 1% wt. of the liquid fraction consists of formic acid and methyl formate(preferably 1 - 50% and more preferably 1 - 30%). An Independent claim is also included for the process of manufacture of acetic acid and/or methyl acetate using the technique as above.