Method for producing vinyl acetate
AssigneeWacker Chemie AG
InventorsWillibald Dafinger, Brigitte Patsch, Guenther Rudolf
Life of this patent
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Abstract
Fouling of the acetic acid saturator by recycle gas in the continuous gas phase process for manufacture of vinyl acetate is reduced by adding an N-oxyl fouling inhibitor to the saturator and/or at one or more other addition sites in the process, in amounts such that the concentration of N-oxyl compound which accumulates in the saturator bottoms is from 10 to 100 ppm. The amount of N-oxyl compound in the saturator is preferably from 10-50 ppm. The reduction in fouling is evidenced by lessening the lowering of the heat transfer coefficient of the saturator over time.
Claims5
A process for producing vinyl acetate in a heterogeneously catalyzed, continuous gas phase process via reaction of ethylene with acetic acid and oxygen in a fixed bed tubular reactor and workup of the product gas stream, wherein a cycle gas mixture consisting predominantly of ethylene, carbon dioxide, ethane, nitrogen and oxygen is circulated, and the cycle gas is admixed with the reactants acetic acid, ethylene and oxygen upstream of the fixed bed tubular reactor and is brought to reaction temperature by means of heat exchangers operated with heating steam, and wherein the enrichment of the cycle gas with acetic acid is effected in an acetic acid saturator containing bottoms, the improvement comprising:
- adding one or more N-oxyl compounds containing at least one N-oxyl radical group —N—O., selected from the group consisting of 2,2,6,6-tetramethylpiperidinyloxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl, 4-oxo-2,2,6,6-tetramethylpiperidinyloxyl and 4-ethanoyloxy-2,2,6,6-tetramethylpiperidinyloxyl, to the acetic acid saturator in an amount such that the concentration of the N-oxyl compound in the bottoms of the acetic acid saturator is 10 to 100 ppm by weight, based on the weight of the bottoms of the acetic acid saturator.
Dependencies are inferred from the claim text.