Patent ID: 7294741

Claim:
A process for the production of acrylic acid (AA) comprising the steps: (a) subjecting a first gas mixture comprising propylene, oxygen, an inert gas, and steam to a first catalytic oxidation reaction stage thereby converting the propylene in the presence of a catalyst mainly into acrolein being contained in a second gas mixture from said first catalytic oxidation reaction, (b) subjecting said a second gas mixture from the first catalytic oxidation reaction stage to a second catalytic oxidation reaction stage thereby converting the acrolein in the presence of a catalyst mainly into AA, being contained in a product gas, (c) subjecting said product gas to a quench tower, wherein said AA is recovered as an aqueous solution comprising AA being contained in the process water, wherein a process vent gas is obtained at the top of said quench tower, and wherein the process vent gas is treated in a subsequent thermal or catalytic combustion unit, and (d) separating said process water in a subsequent separation unit and process water is fed back into said quench tower so that most parts of the process water vaporized is mixed with the process vent gas leaving the quench tower on top and is treated together with the process vent gas in the thermal or catalytic combustion unit, wherein said first gas mixture has a steam/propylene ratio of greater than about 0.3 and less than about 2; and the amount of said process water is less or equal to the amount of water in said aqueous solution withdrawn from the quench tower; and wherein said treatment in said thermal or catalytic combustion unit yields a combusted process vent gas and at least a part of said combusted process vent gas is recycled to said first catalytic oxidation reaction stage.