Production of maleic anhydride

Claim 1

A METHOD OF PRODUCING MALEIC ANHYDRIDE WHICH COMPRISES FEEDING MALEIC ACID INTO AN INTERMEDIATE LEVEL OF A FRACTIONATING COLUMN AND PASSING IT DOWNWARDLY THROUGH A DEHYDRATION ZONE THEREIN IN ADMIXTURE WITH LIQUID MALEIC ANHYDRIDE AND IN COUNTER-CURRENT CONTACT WITH A RISING STREAM OF MALEIC ANHYDRIDE VAPOR AND THEREBY HEATING THE MIXTURE TO 190*-220*C. AND RAPIDLY FORMING SUPERHEATED STEAM AND MALEIC ANHYDRIDE THEREFROM, PASSING DOWNWARDLY THROUGH A SEPARATION ZONE IN THE COLUMN ABOVE SAID DEHYDRATION ZONE A FEED OF AN ORGANIC WATER-IMMISCIBLE MALEIC ANHYDRIDE SOLVENT HAVING A BOILING POINT LOWER THAN THAT OF MALEIC ANHYDRIDE BUT HIGHER THAN THAT OF WATER, PASSING UPWARDLY FROM THE DEHYDRATION ZONE INTO SAID SEPARATION ZONE BOTH THE SUPERHEATED STEAM AND SUFFICIENT MALEIC ANHYDRIDE VAPOR TO VAPORIZE THE FEED OF ORGANIC MALEIC ANHYDRIDE SOLVENT AND FRACTIONATING THE RESULTING MIXTURE IN SAID ZONE INTO AN OVERHEAD FRACTION OF SAID SOLVENT AND A BOTTOM FRACTION OF SUBSTANTIALLY SOLVENT-FREE LIQUID MALEIC ANHYDRIDE, RETURNING SAID BOTTOM FRACTION TO THE DEHYDRATION ZONE AND MIXING IT WITH THE MALEIC ACID FEED THEREIN, WITHDRAWING PRODUCT MALEIC ANHYDRIDE FROM THE BOTTOM OF SAID DEHYDRATION ZONE, WITHDRAWING AND CONDENSING VAPORS OF SAID ORGANIC SOLVENT FROM THE TOP OF THE COLUMN AND RETURNING SAID SOLVENT TO THE SEPARATION ZONE THEREIN.

Claim 2

A METHOD OF PRODUCING MALEIC ANHYDRIDE WHICH COMPRISES FEEDING MALEIC ACID INTO AN INTERMEDIATE LEVEL OF A FRACTIONATING COLUMN AND PASSING IT DOWNWARDLY THROUGH A DEHYDRATION ZONE THEREIN IN ADMIXTURE WITH LIQUID MALEIC ANHYDRIDE AND IN COUNTER-CURRENT CONTACT WITH A RISING STREAM OF MALEIC ANHYDRIDE VAPOR AND THEREBY HEATING THE MIXTURE TO 190*-220*C. AND RAPIDLY FORMING SUPERHEATED STEAM AND MALEIC ANHYDRIDE THEREFROM, PASSING DOWNWARDLY THROUGH A SEPARATION ZONE IN THE COLUMN ABOVE SAID DEHYDRATION ZONE A FEED OF AN ORGANIC WATER-IMMISCIBLE MALEIC ANHYDRIDE SOLVENT HAVING A BOILING POINT LOWER THAN THAT OF MALEIC ANHYDRIDE BUT HIGHER THAN THAT OF WATER, PASSING UPWARDLY FROM THE DEHYDRATION ZONE INTO SAID SEPARATION ZONE BOTH THE SUPERHEATED STEAM AND SUFFICIENT MALEIC ANHYDRIDE VAPOR TO VAPORIZE THE FEED OF ORGANIC MALEIC ANHYDRIDE SOLVENT AND FRACTIONATING THE RESULTING MIXTURE IN SAID ZONE INTO AN OVERHEAD FRACTION OF SAID SOLVENT AND A BOTTOM FRACTION OF SUBSTANTIALLY SOLVENT-FREE LIQUID MALEIC ANHYDRIDE, RETURNING SAID BOTTOM FRACTION TO THE DEHYDRATION ZONE AND MIXING IT WITH THE MALEIC ACID FEED THEREIN, WITHDRAWING PRODUCT MALEIC ANHYDRIDE FROM THE BOTTOM OF SAID DEHYDRATION ZONE, WITHDRAWING AND CONDENSING VAPORS OF SAID ORGANIC SOLVENT FROM THE TOP OF THE COLUMN AND RETURNING SAID SOLVENT TO THE SEPARATION ZONE THEREIN.