US Patent 7256308 Process for the production of acetic acid

A process for the production of acetic acid by carbonylating methanol and/or a reactive derivative thereof in a carbonylation reactor in a liquid reaction composition comprising an iridium carbonylation catalyst, methyl iodide, methyl acetate, water, acetic acid and at least one promoter selected from the group consisting of ruthenium, rhenium and osmium, characterized in that there is also present in the reaction composition a bis-phosphonate compound having the formula (I): wherein R1, R2, R3, R4 are independently hydrogen or an organic functional group; Y is an optionally substituted C1-C10 alkylene or C6-C10 aryl group.