Method of preparing unsaturated esters by oxidation of olefins

Claim 1

THE OXIDATION OF AN OLEFIN HAVING 2 TO ABOUT 5 CARBONS TO AN UNSATURATED ESTER OF AN ALKANOIC ACID HAVING 2 TO ABOUT 10 CARBON THAT COMPRISES CONTACTING, IN A REACTION ZONE, SAID OLEFIN WITH OXYGEN IN THE PRESENCE OF A SUBSTANTIALLY ANHYDROUS ORGANIC REACTION MEDIUM COMPRISING SAID ALKANOIC ACID AND (1) BETWEEN ABOUT 0.04 AND ABOUT 2.0 WEIGHT PERCENT OF A PLATINUM GROUP METAL, (2) BETWEEN ABOUT 0.05 AND ABOUT 5.0 WEIGHT PERCENT OF A HALOGEN CONTAINING COMPOUND SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE CONTAINING COMPOUNDS, (3) BETWEEN ABOUT 0.1 AND ABOUT 10 WEIGHT PERCENT OF AN ALKALI METAL SALT OF SAID ALKANOIC ACID, (4) BETWEEN ABOUT 0.1 AND ABOUT 5.0 WEIGHT PERCENT OF A SOLUBLE SALT OF A MULTIVALENT METAL HAVING AN OXIDATION POTENTIAL MORE POSITIVE THAN THE PLATINUM GROUP METAL IN THE SOLUTION; SAID CONTACTING BEING AT A TEMPERATURE BETWEEN ABOUT 30* AND ABOUT 300* CENTIGRADE AND A PRESSURE BETWEEN ABOUT 1 AND 100 ATMOSPHERES, SUFFICIENT TO MAINTAIN LIQUID PHASE CONDITIONS AND WHEREIN THE RELATIVE FEED RATES OF SAID OLEFIN AND SAID OXYGEN ARE CONTROLLED TO MAINTAIN THE OXYGEN CONTENT OF THE GAS PHASE OF SAID REACTION ZONE LESS THAN 1 VOLUME PERCENT SO AS TO OBTAIN A CRUDE REACTION PRODUCT CONTAINING SAID UNSATURATED ESTER, WITHDRAWING A LIQUID EFFLUENT FROM SAID REACTION ZONE, CONTAINING PLATINUM GROUP METAL AND MULTIVALENT METAL IN A REDUCED STATE, DISTILLING SAID LIQUID EFFLUENT TO RECOVER SAID UNSATURATED ESTER FROM A LIQUID RESIDUE CONTAINING SAID PLATINUM GROUP METAL AND MULTIVALENT METAL, RETURNING SAID RESIDUE TO SAID REATION ZONE, AND PREVENTING THE PRECIPITATION OF SAID MULTIVALENT METAL AS A INSOLUBLE SALT DURING SAID OXIDATION AND DISTILLATION BY MAINTAIN THE ATOMIC RATIO OF HALOGEN TO SAID MULTIVALENT METAL GREATER THAN ABOUT 6.5:1 IN SAID REACTION MEDIUM.