| 摘要 |
A process for the recovery of maleic anhydride contained as a by-product in a phthalic anhydride gaseous reactor effluent is described. This process consists of gas scrubbing in order to obtain an aqueous solution of the maleic acid and the other organic substances contained in the gas, including phthalic acid, concentration of this solution as maleic acid to a concentration of 25-35 % by weight by addition of a return stream to the solution and removal of the phthalic acid by crystallisation. The resultant solution, rich in maleic acid and depleted in phthalic acid, is then partially fed back into the gas scrubbing step (in order to promote the solubility of the phthalic acid and to enrich the solution of maleic acid thus obtained) and partially submitted to a treatment to recover the maleic anhydride by dehydration by means of azeotropic distillation with ortho-xylene. The resultant crude maleic anhydride is then purified by rectification in plate-type columns. An apparatus for the recovery of maleic anhydride is also described which includes a gas scrubbing section, a maleic acid dehydration section and a maleic anhydride purification section. <IMAGE> |
