Oxidation of ethylene to vinyl esters by a platinum group metal catalyst in the presence of a halogen compound, a heavy metal salt, molecular oxygen and a vanadium compound

Claim 1

IN THE OXIDATION OF ETHYLENE TO VINYL ACETATE WHEREIN ETHYLENE AND OXYGEN ARE CONTACTED WITH A SUBSTANTIALLY ANHYDROUS REACTION MEDIUM COMPRISING ACETIC ACID, AN ACETATE SELECTED FROM THE CLASS OF ALKALI METAL AND ALKALINE EARTH METAL ACETATES, A HALOGEN COMPOUND SELECTED FROM THE CLASS OF BROMINE AND CHLORINE COMPOUNDS, CATALYTIC AMOUNTS OF A MEMBER SELECTED FROM THE CLASS CONSISTING OF A PLATINUM GROUP METAL AND HALIDE SALTS THEREOF AND A SALT OF A MULTIVALENT HEAVY METAL HAVING A MORE POSITIVE OXIDATION POTENTIAL IN SAID REACTION MEDIUM THAN SAID PLATINUM GROUP METAL AND WHEREIN OXALIC ACID IS PRODUCED AS A BYPRODUCT OF THE OXIDATION AND PRECIPITATES SAID MULTIVALENT METAL AS AN INSOLUBLE OXALATE, THE IMPROVED METHOD FOR PREVENTING THE PRECIPITATION OF SAID MULTIVALENT METAL AND THEREBY MAINTAINING THE CATALYTIC ACTIVITY OF THE REACTION MEDIUM THAT COMPRISES THE DESTRUCTIVE OXIDATION OF THE OXALIC ACID BYPRODUCT OF SAID OXIDATION BY THE CONTACTING OF AT LEAST A PORTION OF THE REACTION MEDIUM WITH CATALYTIC AMOUNTS OF FROM 0.05 TO 0.5 WEIGHT PERCENT OF A VANADIUM COMPOUND AND OXYGEN AT A TEMPERATURE FROM ABOUT 30* TO 300*C. AND A PRESSURE FROM 5 TO 100 ATMOSPHERES, SUFFICIENT TO MAINTAIN LIQUID PHASE CONDITION.