Preparation method of vinyl acetate by ethylene process and device thereof

Patent metadata

Field	Value
Publication number	US-12049442-B2
Application number	US-202318235136-A
Country	US
Kind code	B2
Filing date	Aug 17, 2023
Priority date	Nov 16, 2022
Publication date	Jul 30, 2024
Grant date	Jul 30, 2024

Abstract

The present disclosure relates to a process and a device for producing vinyl acetate by an ethylene process. By additionally arranging an ethylene recovery membrane assembly in a vinyl acetate synthesis section, the content of inert components such as nitrogen in a circulating system is controlled, ethylene gas is recovered from non-condensable gas, and a recovery rate of the ethylene reaches 58% or above. By adding sideline extraction at a refined VAC tower in a vinyl acetate refining section, a vinyl acetate product with purity higher than 99.98% is obtained, a mass fraction of acetic acid is less than or equal to 20 ppm, a mass fraction of acetaldehyde is less than or equal to 20 ppm, and a mass fraction of water is less than or equal to 100 ppm. In synthesis and refining processes of the vinyl acetate, a cooling method is adopted.

First claim

What is claimed is:

1. A preparation method of vinyl acetate, comprising:
(a) a step of feeding non-condensable gas of an absorption tower gas-liquid separation tank into an ethylene recovery membrane assembly, and recovering ethylene from the non-condensable gas through membrane separation; the ethylene recovery membrane assembly ( 110 ) comprises an aggregator and membrane equipment; the ethylene recovery membrane assembly ( 110 ) is used for controlling the content of inert components including nitrogen in the circulating system and recovering ethylene gas from the non-condensable gas, so as to reduce losses caused by the fact that raw material ethylene is directly fed to be incinerated in the non-condensable gas; the aggregator in the membrane assembly has two effects that firstly, gas flows from bottom to top, and a demister in the aggregator can prevent water in the stream from flowing into the membrane equipment; secondly, electric trace heating is arranged on a pipeline led out of the aggregator for heating, so that gas enters the membrane equipment after being overheated by 3-5° C., thereby preventing condensation caused by the fact that saturated gas directly makes contact with the membrane equipment;
(b) a step of feeding vinyl acetate containing a polymerization inhibitor and high-boiling-point impurities into a refined VAC tower, and drawing from a side of the refined VAC tower, to obtain a high-purity VAC product; and
(c) a step of allowing overhead vapour of an acetic acid tower and overhead vapour of a crude VAC tower to enter a distillation phase splitting tank after passing through an overhead condenser and a condensate cooler adopting circulating water series cooling and a tail gas condenser for cooling with chilled water respectively.

2. The preparation method of vinyl acetate according to claim 1 , wherein in the step (a), the ethylene recovery membrane assembly ( 110 ) is additionally arranged between an absorption tower gas-liquid separation tank ( 107 ) and a flare.

3. The preparation method of vinyl acetate according to claim 1 , wherein in the step (b), a side-draw stream is additionally added at third to seventh theoretical plates on an upper portion of the refined VAC tower.

4. The preparation method of vinyl acetate according to claim 1 , wherein in the step (c), original respective and independent cooling of the overhead condenser and the condensate cooler is improved into a cooling method for cooling with the circulating water in series respectively on a top of the acetic acid tower ( 204 ) and a top of the crude VAC tower ( 210 ).

5. The preparation method of vinyl acetate according to claim 1 , wherein refined gas from a synthesis and refining system is fed at bottoms of the acetic acid tower ( 204 ) and an aldehydo-ester concentrating tower ( 221 ); one part of tower bottoms of the acetic acid tower ( 204 ) is fed to a synthesis section, and the other part thereof and the refined gas from the synthesis and refining system return to a lower portion of the acetic acid tower ( 204 ) after passing through an acetic tower reboiler ( 205 ); and one part of tower bottoms of the aldehydo-ester concentrating tower ( 221 ) and distillate of an extractive distillation tower phase splitting tank ( 237 ) return to a top of the crude VAC tower ( 210 ), and the other part thereof and the refined gas from the synthesis and refining system return to a lower portion of the aldehydo-ester concentrating tower ( 221 ) after passing through an aldehydo-ester concentrating tower reboiler ( 223 ).

6. The preparation method of vinyl acetate according to claim 1 , wherein the preparation method is realized by a device comprising an ethylene recovery membrane assembly ( 110 ); and the ethylene recovery membrane assembly ( 110 ) comprises an aggregator and membrane equipment; a stream at an overhead outlet of an absorption tower gas-liquid separation tank ( 107 ) is divided into two streams connected with an inlet of the ethylene recovery membrane assembly ( 110 ) and a cooling side inlet of a refined gas heat exchanger ( 109 ) respectively; and an outlet of the ethylene recovery membrane assembly ( 110 ) is connected with a flare inlet and an inlet of a gas recovery compressor ( 112 ), respectively; wherein an overhead outlet of a refined VAC tower ( 211 ) is connected with a cooling side inlet of a refined VAC tower condenser ( 214 ), and a cooling side outlet of the refined VAC tower condenser ( 214 ) is connected with a cooling side inlet of a refined VAC tower condensate cooler ( 218 ); a cooling side outlet of the refined VAC tower condensate cooler ( 218 ) is connected with a refined VAC tower reflux tank ( 219 ); circulating water enters from a heating side inlet of the refined VAC tower condensate cooler ( 218 ), a heating side outlet of the refined VAC tower condensate cooler ( 218 ) is connected with a heating side inlet of the refined VAC tower condenser ( 214 ), and the circulating water exits from a heating side outlet of the refined VAC tower condenser ( 214 ); a side outlet of the refined VAC tower ( 211 ) is connected with a cooling side inlet of a VAC product condenser ( 215 ), and a cooling side outlet of the VAC product condenser ( 215 ) is connected with a VAC product tank; chilled water enters from a heating side inlet of the VAC product condenser ( 215 ), and exits from a heating side outlet of the VAC product condenser ( 215 ); and a tower kettle outlet of the refined VAC tower ( 211 ) is connected with an upper end inlet of the acetic acid tower ( 204 );
wherein an overhead outlet of an acetic acid tower ( 204 ) is connected with a cooling side inlet of an acetic acid tower condenser ( 206 ), and a cooling side outlet of the acetic acid tower condenser ( 206 ) is connected with a cooling side inlet of an acetic acid condenser cooler ( 208 ) and a cooling side inlet of an acetic acid tower tail gas condenser ( 209 ); a cooling side outlet of the acetic acid tower tail gas condenser ( 209 ) is connected with an inlet of a gas recovery compressor ( 112 ) and an inlet of an acetic acid tower distillation phase splitting tank ( 207 ); a cooling side outlet of the acetic acid tower condensate cooler ( 208 ) is connected with the inlet of the acetic acid tower distillation phase splitting tank ( 207 ); a circulating water inlet is connected with a heating side inlet of the acetic acid condenser cooler ( 208 ), a heating side outlet of the acetic acid condenser cooler ( 208 ) is connected with a heating side inlet of the acetic acid tower condenser ( 206 ), and a heating side outlet of the acetic acid tower condenser ( 206 ) is connected with a circulating water outlet; and a chilled water inlet is connected with a heating side inlet of the acetic acid tower tail gas condenser ( 209 ), and a heating side outlet of the acetic acid tower tail gas condenser ( 209 ) is connected with a chilled water outlet;
wherein an overhead outlet of a crude VAC tower ( 210 ) and an overhead outlet of a dehydrating tower ( 232 ) are both connected with a cooling side inlet of a crude VAC tower condenser ( 213 ), and a cooling side outlet of the crude VAC tower condenser ( 213 ) is connected with a cooling side inlet of a crude VAC tower condensate cooler ( 217 ) and a cooling side inlet of a crude VAC tower tail gas condenser ( 220 ); a cooling side outlet of the crude VAC tower tail gas condenser ( 220 ) is connected with an inlet of a gas recovery compressor ( 112 ) and an inlet of a crude VAC tower distillation phase splitting tank ( 216 ); a cooling side outlet of the crude VAC tower condensate cooler ( 217 ) is connected with the inlet of the crude VAC tower distillation phase splitting tank ( 216 ); a chilled water inlet is connected with a heating side inlet of the crude VAC tower tail gas condenser ( 220 ), a

Assignees

• Univ Tianjin

Inventors

• Zhang Minhua
• Gong Hao
• Dong He
• Geng Zhongfeng
• Yu Yingzhe

Classifications

• B01J19/0013

  Controlling the temperature of the process · CPC title

• B01D2311/25

  Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed · CPC title

• B01D53/22

  by diffusion (manufacturing semi-permeable membranes B01D67/00; form, structure or properties of semi-permeable membranes B01D69/00; material for semi-permeable membranes B01D71/00) · CPC title

• C07C7/12

  by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers · CPC title

• C07C67/54

  by distillation · CPC title