A process for the preparation of acetic acid product comprising, in a first catalytic step, conversion of a hydrogen and carbon monoxide containing synthesis gas to obtain a liquid process stream comprising methanol and, in a second catalytic step, carbonylation of the process stream with carbon monoxide to a product stream being rich in the acetic acid product in presence of catalytic effective amounts of a metal compound selected from Group VIII of the Periodic Table promoted with a halide compound, the improvement comprising the further steps of: (i) withdrawing from the carbonylation step a vent gas stream comprising carbon monoxide and residual amounts of acetic acid and halide compound; (ii) separating the vent gas stream into a liquid fraction containing a part of the residual amounts of acetic acid and part of the halide compound and a gaseous fraction with the carbon monoxide and remaining amounts of acetic acid and halide compound; (iii) recycling the liquid fraction to the carbonylation step; (iv) subjecting the gaseous fraction to liquid absorption to remove the acetic acid and halide compound in the gaseous fraction to obtain a carbon monoxide rich recycle stream; and (v) introducing the carbon monoxide rich recycle stream into the synthesis gas conversion step.