Vinyl acetate oxygen removal from

Fresh ethylene and recycled gas are compressed to 150 p.s.i.g. and pumped into the reactor where the reaction is carried out at 120°-130°C. The latter contains a suspension of catalyst and promoters suspended in acetic acid. Recovered acetic acid and fresh acid and oxygen are pumped into the reactor. A supply of HCl (not shown) is also necessary. Excess ethylene, containing vinyl acetate, acetaldehyde, and a small amount of H2O and acetic acid, is expanded to ca. 50 p.s.i.g. by flash distillation. At this point, acetaldehyde is separated from vinyl acetate. The bottoms from the acetaldehyde still will contain all the vinyl acetate together with HgO and acetic add. Vinyl acetate is separated from the HtO by a decanter and distilled to remove HiO and light ends. Subsequently, the bottom from this distillation is submitted to a final distillation to give pure vinyl acetate. Acetic add is recovered by distillation. 

Step 1. For this process we must be able to set the production rate of vinyl acetate while minimizing yield losses to carbon dioxide. During the lifetime of the catalyst charge, catalyst activity decreases and the control system must operate under these different conditions. To maintain safe operating conditions, the oxygen concentration in the gas loop must remain outside the explosivity region for ethylene. The azeotropic distillation column must produce an overhead product with essentially no acetic acid and a bottoms product with no vinyl acetate. The absorber must recover essentially all of the vinyl acetate, water, and acetic acid from the gas recycle loop to prevent yield losses in the CCf removal system and purge,... 

Fresh acetic acid and a liquid acetic acid recycle stream are fed into a vaporizer along with a gas recycle stream and fresh ethylene feed. Oxygen is added after the vaporizer, and reactions occur in a gas-phase reactor. Reactor effluent is cooled and fed into a separator. Vapor from the separator is compressed and fed into an absorber to recover vinyl acetate. Recycle acetic acid is used as lean oil in the absorber. Exit gas from the absorber is sent to a CO2 removal unit, which produces a CO2 purge stream and gas recycle. Another purge stream is used to remove the small amount of ethane that is in the fresh ethylene makeup feed. 

An azeotropic mixture of methyl acetate and methanol is a common coproduct from the manufacture of poly(vinyl alcohol) from poly(vinyl acetate) in the presence of methanol and sodium methoxide. The polymerization of vinyl acetate in this azeotropic solution, with the total removal of oxygen from the system, and using conventional free radical initiators is said to afford high-molecular weight poly(vinyl acetate) [106]. 

For example, compositions of 10 ml of a 3.75 gm per 100 ml aqueous solution of sodium dioctylsulfosuccinate (Aerosol OT or Manoxol OT) and 1.25 ml of vinyl acetate with small additions of sodium dihydrogen phosphate, after exclusion of oxygen by at least four degassings, were sealed in glass ampoules. The samples were exposed, at 15°C, to a Co source (100 curie). Conversion was nearly 75% after 30 min. Polymers of MW as high as 10 were formed. The polymers contained trapped free radicals capable of initiating graft polymerization with methyl methacrylate after removal from the radiation source [185]. 

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