GB999630A - Removal of maleic anhydride from a maleic anhydride-containing gas - Google Patents

Abstract

The maleic anhydride content of a gas containing 15 p.p.m. by volume to 5 molar per cent maleic anhydride is reduced by contacting the gas in a scrubbing zone with water or aqueous maleic acid solution to absorb maleic anhydride from the gas, the maleic acid solution containing maleic acid in an amount less than the saturation concentration by at least 5% by weight at the initial contacting temperature of the liquid, withdrawing scrubbing liquid from the scrubbing zone, recycling at least part of the withdrawn scrubbing liquid to the scrubbing zone after any necessary dilution to reduce the maleic acid content of the solution below the above-mentioned value, and withdrawing a gas containing less than 15 p.p.m. by volume of maleic anhydride from the scrubbing zone, in which process the scrubbing liquid temperature is maintained at a temperature at least 10 DEG C. below the adiabatic equilibrium temperature of the gas throughout the scrubbing zone. The adiabatic equilibrium temperature is determined experimentally. As described, reactor gas obtained from a maleic anhydride reactor is fed through heated tubing into a Venturi scrubber wherein said reactor gas contacts water or aqueous maleic acid. The scrubbing medium containing maleic anhydride is then recirculated through the scrubber, the concentration of said scrubbing liquid being maintained by periodically draining a portion and adding fresh water. In a preferred embodiment, reactor gas is first partially condensed in order to remove a portion of the contained maleic anhydride. Any gas liquid contacting device, e.g. bubble cap columns, sieve tray columns or packed columns, may be used instead of the Venturi scrubber. The feed gas temperature may be in the range 15-300 DEG C. and pressure atmospheric-500 p.s.i.g. The volume ratio of gas to scrubbing medium is in the range 1-400 volumes of gas per volume of scrubbing medium.