Method for modifying catalyst performance during the gas phase synthesis of vinyl acetate
AssigneeE. I. Du Pont de Nemours and Company
InventorWilliam Douglas Provine
Life of this patent
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Abstract
An improved method for synthesizing vinyl acetate by the gas phase reaction of acetic acid with ethylene in the presence of oxygen. At least two catalyst modifiers are used, each causing a different level of catalyst activity. The relative mounts of the catalyst modifiers are used to fine tune the productivity of the catalyst.
Claims21
In a gas phase reaction of ethylene with acetic acid in the presence of oxygen and catalyzed by a charge of a metal catalyst, the metal catalyst being degraded over time due to the reaction, a method for improving the performance of the catalyst charge, the improvement comprising:
- (a) adding an excess amount of catalyst to the catalyst charge so that the total amount of catalyst would exceed the design limits of the process, if the process were initially run at maximum achievable catalyst activity;
- (b) adding a primary catalyst modifier to the feed stream or imbibing the primary catalyst modifier onto at least a portion of the catalyst or a catalyst support, wherein the primary catalyst modifier changes the productivity of the catalyst;
- (c) adding a secondary catalyst modifier to the feed stream, the secondary catalyst modifier being different from the primary catalyst modifier, wherein the secondary catalyst modifier increases the productivity of the catalyst, and wherein the catalyst activity due to the secondary catalyst modifier divided by the catalyst activity due to the primary catalyst modifier is greater than 1;
- (d) initially running the process at less than maximum achievable catalyst activity;
- and
- (e) continuously or discontinuously altering the relative amounts of the primary catalyst modifier and secondary catalyst modifier, so that as the catalyst degrades during the reaction process, at least a portion of the remaining non-degraded catalyst is caused to continuously or discontinuously increase in productivity.
In a gas phase reaction of ethylene with acetic acid in the presence of oxygen and catalyzed by a charge of a metal catalyst, the metal catalyst being degraded over time due to the reaction, a method for improving the efficacy of the catalyst charge, the improvement comprising:
- (a) adding a primary catalyst modifier to the feed stream or imbibing the primary catalyst modifier onto at least a portion of the catalyst or a catalyst support, wherein the primary catalyst modifier increases the productivity of the catalyst;
- (b) adding a secondary catalyst modifier to the feed stream, the secondary catalyst modifier being different from the primary catalyst modifier, wherein the secondary catalyst modifier increases the productivity of the catalyst, and wherein the catalyst activity due to the secondary catalyst modifier divided by the catalyst activity due to the primary catalyst modifier is greater than 1;
- and
- (c) continuously or discontinuously altering the relative amounts of the primary catalyst modifier and secondary catalyst modifier, so that as the catalyst degrades during the reaction process, at least a portion of the remaining non-degraded catalyst is caused to continuously or discontinuously increase in productivity,
- wherein the primary catalyst modifier and the secondary catalyst modifier are members of the group consisting of:
- oxo acids of boron, carbon, silicon, phosphorus, arsenic, antimony, sulfur or nitrogen, or a salt or acid salt derivative thereof;
- at least when primary catalyst modifier and the secondary catalyst modifier are initially added to the process.
Dependencies are inferred from the claim text.