Patent TW-I308146-B (TW)
Title: Process for isolating vinyl acetate
Inventor: STAMM JOHANN
IPC: C07C67/54
Filed: 2006-08-03
Granted: 2009-04-01
Abstract: The separation of vinyl acetate from a gas mixture, comprises feeding the mixture left from a reaction zone into a first distillation column, cooling down (-20 to + 50[deg]C) the mixture discharged at the column head to form a first condensate separated into water phase (42) and first organic phase (44), and removing the water phase. The gas mixture from the zone is cooled down in a counter-current heat exchanger (9) with a colder cycle gas to 115-150[deg]C. The first organic phase as feedback is totally/partly fed back to the column head. The separation of vinyl acetate from a gas mixture, comprises feeding the mixture left from a reaction zone into a first distillation column, cooling down (-20 to + 50[deg]C) the mixture discharged at the column head to form a first condensate separated into water phase (42) and first organic phase (44), and removing the water phase. The gas mixture from the zone is cooled down in a counter-current heat exchanger (9) with a colder cycle gas to 115-150[deg]C. The first organic phase as feedback is totally or partly fed back to the column head, and a part of the organic phase not used as feedback is removed. The gas mixture is formed in a gas phase during a reaction of ethylene with acetic acid and oxygen at a catalyst containing palladium or palladium compounds. A gas containing non-condensed vinyl acetate is washed in a washing column with aqueous acetic acid (90%) to obtain the acid containing the vinyl acetate at a sump. The sump product containing vinyl acetate, ethyl acetate, acetic acid and water, is supplied to a collecting tank (14), and a liquid is primarily relaxed at 0.1-0.15 MPa to from a gas. The relaxed liquid is supplied to a second distillation column to remove a side stream containing ethyl acetate from an enrichment zone above the sump of the column. The removed side stream is totally or partly used for the gas washing in the washing column. A head vapor removed from the side stream is cooled down to form second condensate separated into water and second organic phases, and the water phase is removed. A part of the second organic phase is fed back to the head of the second distillation column, and the non-fed back second organic phase is removed. A part of the acetic acid solution containing the vinyl acetate is cooled through a pumping (15) in a closed cycle and the cooled solution is fed back to the sump of the washing column. The uncooled solution is heated at 60-100[deg]C and the heated solution is delivered to 5 t>h to 10 t>h column plates of the first distillation column bottom. The sump discharge of the first distillation column exhibits a temperature of 80-150[deg]C. The first non-fed back organic phase is secondarily relaxed at 0.1- 0.15 MPa in relaxation container (56) to from a gas combined with the gas from the primary relaxation. The head vapor of the second distillation contains acetic acid and ethyl acetate. The secondarily relaxed organic phase is combined with the second fed-back organic phase in a phase separator containing ethyl acetate. A part of the non-fed back second organic phase removed is directed into a third distillation column (48). A head product of the third distillation column is cooled down to form low boiling fraction and water. A sump product of the third distillation column is directed into a fourth distillation column to remove the pure vinyl acetate at the fourth distillation column head.