Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D301/00—Preparation of oxiranes
  • C07D301/32—Separation; Purification
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S203/00—Distillation: processes, separatory
  • Y10S203/20—Power plant

Definitions

• the invention relates to methods and a device for pure ethylene oxide distillation.
• Pure ethylene oxide is a product manufactured in annual tonnages of several million tons worldwide.
• the final process step in the production of pure ethylene oxide is pure distillation.
• ethylene oxide is obtained from an aqueous solution.
• aldehydes in particular formaldehyde and acetaldehyde, which are present in the feed, do not get into the pure product.
• formaldehyde has to be separated off from ethylene oxide during the pure distillation are high demands on product purity (frequently below 10 ppm total aldehyde) and the introduction of new catalysts which lead to higher concentrations of formaldehyde in the feed.
• GB-B 1, 180.822 discloses a process for separating formaldehyde from an aqueous mixture containing ethylene oxide.
• the degree of purity of the pure ethylene oxide obtained in the purification distillation essentially depends on the amount of fresh water used as washing water in this process. In order to achieve low formaldehyde contents in the pure oxide, large wash water flows must be used, which increases the wastewater load. The procedure is therefore unfavorable.
• EP-B 0 322 323 discloses a process for separating aldehyde impurities from crude ethylene oxide by distillation, in which the crude ethylene oxide is introduced from above into a column with 50 theoretical stages at the level of the 30th stage.
• the ethylene oxide is obtained as a top product with a content of about 0.0015 to 0.0020% by weight of aldehyde impurities.
• the liquid stream emerging at the bottom of the column has the water and ethylene oxide present in the crude ethylene oxide in 0.15 to 3 times the amount by weight of the water - the bottom is therefore not free of ethylene oxide, which is disadvantageous in terms of process technology, since in this case the pure distillation is only can be operated economically in connection with a glycol plant.
• the high ethylene oxide content in the bottom also means that only small temperature differences between the top and bottom occur in the column used in the known process for the pure distillation of ethylene oxide.
• the disadvantages of this process are the high expenditure on equipment, the increase in the amount of ethylene oxide, which is problematic in terms of safety, in the column and the fact that crude oxide is only partially converted into pure oxide (contaminated top product).
• the object of the invention is therefore to provide a process which is simple to carry out and at the same time makes it possible to produce a product in the pure distillation of ethylene oxide which is largely free of formaldehyde.
• largely free means, for example, that starting from a content of approximately 50 ppm or more in the feed, the purified ethylene oxide obtained contains only approximately 4 ppm or less formaldehyde.
• the process should also meet high safety requirements. Furthermore, it is said to lead to a highly formaldehyde-free ethylene oxide without washing steps with large amounts of waste water.
• the object is achieved according to the invention by a process for pure ethylene oxide distillation, which comprises the step that an aqueous mixture comprising ethylene oxide, formaldehyde and at least 5% by weight of water is introduced via an inlet into a distillation device comprising at least one distillation column, the introduction being carried out at a height above the bottom of at least 8, preferably 12 to 56 theoretical stages, the ethylene oxide removed at the top and a mixture being obtained in the bottom which is less than 5% by weight, preferably less than 0.05 Wt .-% contains ethylene oxide.
• a device for carrying out the process according to the invention, comprising a distillation column with an inlet (1) at a height above the bottom (4) of at least 8 theoretical stages or in the case of a bottom column of at least 12 plates above the bottom ( 4), a top hood (3), optionally a side hood (5), as well as flame-retardant packs and optionally an intermediate evaporator between the inlet (1) and the sump (4).
• a process for pure ethylene oxide distillation comprises the step that an aqueous mixture containing ethylene oxide, formaldehyde and at least 5% by weight of water, is introduced via a feed into a distillation device comprising at least one packing or packed column with a specific mass transfer area A, the introduction at a height above the bottom of at least x min (in m), which is given for a specific mass transfer area A (in m 2 / m 3 ) from the equation
• the ethylene oxide is taken off at the top and a mixture is obtained in the bottom which contains less than 5% by weight, preferably less than 0.05% by weight, of ethylene oxide.
• a process for pure ethylene oxide distillation comprises the step that an aqueous mixture containing ethylene oxide, formaldehyde and at least 5% by weight of water is introduced via an inlet into a distillation device comprising at least one tray column , wherein the introduction takes place at a height above the bottom of at least 12, preferably 16 to 84 trays, the ethylene oxide is taken off at the top and a mixture is obtained in the bottom which is less than 5% by weight, preferably less than 0.05% by weight .
• a process for pure ethylene oxide distillation comprises the step that an aqueous mixture containing ethylene oxide, formaldehyde and at least 5% by weight of water is introduced via an inlet into a distillation device comprising at least one tray column , wherein the introduction takes place at a height above the bottom of at least 12, preferably 16 to 84 trays, the ethylene oxide is taken off at the top and a mixture is obtained in the bottom which is less than 5% by weight, preferably less than 0.05% by weight .
• the raw ethylene oxide supplied contains ethylene oxide, formaldehyde and at least 5% by weight, preferably 20 to 60% by weight, of water.
• the process is carried out in such a way that the bottom mixture contains less than 100 ppm of ethylene oxide.
• parts by weight are always meant.
• the bottom temperature in the column is far above the temperature at the top of the column, where pure ethylene oxide is located.
• the swamp there is then above of the swamp a - spatially narrow - area in which the temperature changes greatly.
• the process according to the invention is characterized in that the feed to the purifying distillation takes place clearly above the temperature jump above the bottom in the column.
• the crude ethylene oxide is introduced at a height of at least 8, preferably 12 to 56 theoretical stages, or of at least 12, preferably 18 to 84 trays above the bottom.
• the introduction of the crude ethylene oxide takes place in a minimum height x min determined by the above equation depending on the specific mass transfer area ; the aqueous mixture is preferably introduced via the feed at a height of 1.5 ⁇ M ⁇ n to 7 ⁇ M ⁇ n .
• the equation gives, for example, a specific one
• Mass transfer area of 250 m 2 / m 3 a minimum height of 4 m, preferably an introduction height of 6 to 28 m.
• a specific mass transfer area of 500 m / m there is a minimum inlet height of 2.5 m, a preferred inlet height of 3.75 m to 17.5 m.
• the introduction of the crude ethylene oxide can also take place via several feed lines.
• the bottom of the plurality of supply lines is preferably located at the distance from the sump according to the invention mentioned above.
• the process can also be carried out in such a way that more than one column is used.
• the minimum distance according to the invention is preferably maintained between the point or points of supply of the crude ethylene oxide and the sump.
• the formaldehyde In the incoming aqueous mixture, the formaldehyde is predominantly in the form of methylene glycol, which is formed in an equilibrium reaction with water.
• Distillation device at a certain - as defined above - (minimum) distance from the bottom, the zone between the inlet and the bottom of the column according to the invention is so long that monomeric formaldehyde, which is in the bottom due to the high temperatures due to the high temperature at the bottom Side of the monomeric formaldehyde equilibrium is released, is absorbed again by the feed stream running in countercurrent.
• residues of formaldehyde which, despite the measure described above, get into the rectifying section of the column are washed out by feeding a small stream of water into the rectifying section of the column; i.e. that at a level of at least 1 theoretical stage or tray, preferably 3 to 20 theoretical stages or trays, above the feed of the aqueous mixture containing ethylene oxide, formaldehyde and the minimum amount of water mentioned, in addition a further mixture, mainly containing water or essentially water alone, is introduced via a supply line. Sufficient supply values of about 0.02 are sufficient for the ratio of water to mass ascending gas flow.
• the monomeric formaldehyde released in the bottom is preferably still absorbed in the stripping section of the purifying distillation by the above-mentioned water-containing feed stream. Residues of monomeric formaldehyde that get into the booster section are thus washed out by the make-up water.
• FIG. 1 shows a preferred embodiment of the for performing the er ⁇
• the process is carried out in a single column.
• the minimum distance according to the invention - as stated above - is maintained between the point at which the feed (1) of the crude ethylene oxide, which contains water, acetaldehyde and formaldehyde, and the bottom (4) of water, acetaldehyde and formaldehyde.
• the further aqueous mixture preferably water, which is used to absorb residues of monomeric formaldehyde, is fed in at the point marked (2).
• the product - the ethylene pure oxide - is withdrawn via head (3).
• a largely formaldehyde-free product is drawn off at the top of the column.
• a side draw (5) is located between the feed (1) and the bottom draw (4), via which a stream of ethylene oxide, water, acetaldehyde and formaldehyde is drawn which is enriched in acetaldehyde compared to the feed.
• an intermediate evaporator is provided between the feed (1) and the bottom draw (4), into which heat is introduced at a lower temperature than in the bottom evaporator.
• flame-retardant packings such as are described, for example, in WO 97/19069, are used to achieve the separation effect in the column or at the inlets and / or fume cupboards.
• Typical values for the concentration of formaldehyde in the product are below 1 to 2 ppm. example
• the method according to the invention was checked by an operational test in an ethylene oxide plant [location: Ludwigshafen]. A formaldehyde concentration in the top product of 2 ppm was achieved with formaldehyde concentrations in the feed of approximately 170 ppm.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Epoxy Compounds (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1997
  • 1997-01-31 DE DE19703627A patent/DE19703627A1/de not_active Withdrawn
• 1998
  • 1998-01-26 MY MYPI98000370A patent/MY132756A/en unknown
  • 1998-01-27 AR ARP980100353A patent/AR010400A1/es unknown
  • 1998-01-29 JP JP53253098A patent/JP2001509171A/ja active Pending
  • 1998-01-29 CA CA002278574A patent/CA2278574A1/en not_active Abandoned
  • 1998-01-29 ID IDW990760A patent/ID22856A/id unknown
  • 1998-01-29 KR KR1019997006877A patent/KR20000070629A/ko not_active Application Discontinuation
  • 1998-01-29 CN CNB988038730A patent/CN1290837C/zh not_active Expired - Lifetime
  • 1998-01-29 EP EP98908014A patent/EP0963373A1/de not_active Withdrawn
  • 1998-01-29 US US09/341,921 patent/US6833057B1/en not_active Expired - Lifetime
  • 1998-01-29 WO PCT/EP1998/000480 patent/WO1998033785A1/de not_active Application Discontinuation
  • 1998-02-10 SA SA98180836A patent/SA98180836B1/ar unknown

Non-Patent Citations (1)

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