Patent ID: 6040460
Filing Date: 2000-03-21
Classification: C07C

Abstract:
A process for the production of maleic anhydride by the oxidation of n-butane with molecular oxygen or a molecular oxygen containing gas in the vapor phase at a temperature of about 300.degree. C. to 550.degree. C. in the presence of a suitable phosphorous-vanadium mixed oxide catalyst, with or without modifying components, comprising the steps of:a) Preparing a reaction mixture comprising oxygen, butane, carbon dioxide and a recycle gaseous stream, wherein the oxygen concentration in the reaction mixture ranges from 5 to 16% by volume, the butane concentration in the reaction mixture ranges from 2 to 20% by volume, the carbon dioxide concentration in the reaction mixture does not exceed 60% by volume and is in a molar ratio to carbon monoxide of at least 1.5 to 1.0,b) Feeding the reaction mixture to an inlet of an oxidation reactor operating at an inlet pressure in the range of 2.03 to 6.03 bar where a suitable V.P.O. catalyst causes a portion of the butane to react to produce maleic anhydride,c) Cooling the reaction gases comprising oxygen, non-converted butane, organic by-products, carbon dioxide, carbon monoxide, water steam and maleic anhydride produced,d) Recovering the maleic anhydride by absorption in a solvent in a maleic anhydride absorber, operating the absorption at an outlet pressure ranging from 1.21 to 4.5 bar, to form a stream comprising recovered maleic anhydride and a stream comprising recycling exhaust gases,e) Water scrubbing the recycling exhaust gases after removal of maleic anhydride, so as to eliminate all organics present, except butane,f) Compressing the recycling exhaust gases after the water scrubbing to the pressure of reaction,g) Separating the compressed recycling exhaust gases to form a first fraction and a second fraction, purging said first fraction of the compressed recycling exhaust gases to avoid accumulation of inerts and of carbon oxides, said recycle gaseous stream comprising said second fraction, and optionallyh) Washing said purge of the compressed recycling exhaust gases with the solvent referred to at step d), to remove by absorption a large fraction of the butane contained in said purge gas stream, the absorbed butane being then desorbed in the maleic anhydride absorber and recovered in the recycling exhaust gases after the removal of maleic anhydride in the maleic anhydride absorber.