Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
  • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
  • C07C67/05—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation

Definitions

• the invention relates to processes for the preparation of vinyl acetate in a heterogeneously catalyzed, continuous gas phase process by reacting ethylene with acetic acid and oxygen using the process heat released thereby.
• exothermic reaction generally at a pressure of 5 to 15 bar and a temperature of 120 ° C to 200 ° C in a fixed bed tubular reactor or fluidized bed reactor according to the following general formula converted to vinyl acetate:
• the light emerging from the reactor product mixture contains, besides vinyl acetate unreacted substantially starting materials, water as ⁇ as inerts and by-products such as carbon dioxide, acetaldehyde, Methyl acetate and ethyl acetate.
• Inerts are essentially nitrogen, argon, methane and ethane and are introduced into the process as impurities in the reactants.
• Water also arises from the side reaction of ethylene and oxygen to carbon dioxide. In particular, the separation of water and ethyl acetate require a lot of energy.
• the reaction conditions in the reactor are controlled by means of boiling water cooling to temperatures of 120 ° C to 200 ° C and pressures of 5 to 15 bar.
• the water of the boiling water cooling is converted into steam, the so-called domestic steam, which usually has a temperature of 120 ° C to 170 ° C at a pressure of 2 to 8 bar.
• Portions of the generated steam are used frequently fig ⁇ for heating individual process steps of the vinyl acetate production, such as for the heating of individual distillation columns for the separation of the product mixture.
• a problem here is that the steam thus obtained has a relatively low temperature and pressure level and therefore can be used without heating or compression only for heating part of the process steps of the known method for vinyl acetate production, such as for controlling the temperature of the dewatering, the ethyl acetate or low-boiling column or else the wastewater treatment, the residue workup, the cycle gas heater or the acetic acid evaporator or heater.
• the process gas heater or the acetic acid evaporator or heater To operate these parts of the system, however, not the total amount of the resulting intrinsic ⁇ steam is required, so that a part of the internal steam unge ⁇ uses remains.
• a heating steam was required so far, which usually has a temperature of up to 250 ° C and thus has a higher temperature level than the known art from known vinyl acetate manufacturing process available steam, and therefore external sources had to be served.
• the non-recyclable in the preparation of vinyl acetate content of the generated steam has been condensed usually resulting in full ⁇ constant energy loss, or delivered as part of a nationwide Maschinenver- to other companies. However, this is associated with an organizational and equipment expense or lack of demand in many cases not possible.
• the use of self-steam for the heating of product pipes or buildings is subject to seasonal fluctuations and is therefore not suitable for a permanent full utilization of the internal steam.
• DE-A 102005054411 recommends compressing the internal steam by means of steam jet vapor compressors using external high-pressure steam. In many cases, this requires considerable amounts of valuable high-pressure steam, so that more steam is generated in this way than can ultimately be utilized in the vinyl acetate production process and, consequently, there continues to be a problem of steam transport. In addition, the compaction is associated with technical effort and makes the process control complex when starting up the system. Against this background, the object is to provide process for the preparation of vinyl acetate ⁇ position available in which the natural vapor formed in this process from the removal of the reaction energy can be recovered as completely as possible in selbigem Vi ⁇ acetate manufacturing process consisted.
• the object is achieved, surprisingly, that too ⁇ least an azeotrope and / or at least a purifying distillation column contained and packing at least a portion of the resulting in vinyl acetate production process egg gendampfes for the power supply in a thus equipped Aze ⁇ otropkolonne and / or purifying distillation column WUR recycled ⁇ de.
• Particularly surprising here was that despite these measures ⁇ the desired separation efficiency was achieved and any Impurities occurred in any appreciable or only to the usual extent.
• the invention relates to processes for the preparation of vinyl acetate by means of heterogeneously catalyzed, continuous gas phase reaction of ethylene, acetic acid and oxygen in a reactor, wherein thereby liberated process heat is removed by heat exchange of water from the reactor and thereby self-vapor is formed, and
• At least one azeotrope and / or at least a pure distillation column contains packings and the generated steam is utilized to ⁇ least partially Lonnen for supplying power in one or more so equipped Azeotropkolonnen and / or Reindestillationsko-.
• the temperature in the reactor can be adjusted in a conventional manner by a boiling water cooling. As is known, water evaporates and a so-called internal vapor (ED) is formed. This allows the process heat, ie in the course of chemical reactions in the reactor liberated heat, also called reaction energy, are discharged from the reactor.
• ED internal vapor
• the internal vapor has a temperature of preferably 120 ° C to 170 ° C, and more preferably 140 ° C to 160 ° C.
• the pressure of the egg ⁇ gendampfs is preferably from 2 to 8 bar and particularly before Trains t ⁇ 3.5 to 5.5 bar.
• the self-vapor has the pressure level of the so-called medium-pressure steam and thus a lower
• relative pressure specifications indicate the pressure difference relative to the respective ambient pressure.
• the remaining portion of the internal steam is generally utilized for plant parts whose energy supply is operated with low-pressure steam or medium-pressure steam, in particular the dewatering column, the
• the total amount of released of vinyl acetate in a process for the preparation ⁇ position-generated steam is recovered in demsel ⁇ ben method.
• the amount of process heat also depends on the ethylene selectivity.
• the ethylene selectivity characterizes the selectivity of the conversion of ethylene to vinyl acetate in the reactor at the respective time during the execution of the process and is calculated as the molar ratio of the respective time in the
• Reactor formed vinyl acetate based on vinyl acetate and Koh ⁇ lendioxid.
• the ethylene selectivity depends on the990 to 96%.
• the forms in the reactor is heat-specific process corresponding spre ⁇ accordingly usually 0.907 to 0.660 MWh per ton of produced vinyl acetate.
• the invention is characterized in that at least one azeotrope and / or at least a purifying distillation column packing maintains ⁇ ent.
• filler the usual in chemical process technology filler can be used.
• the filler bodies are based on metallic or ceramic materials or on plastic. Preference is given to metallic materials.
• metallic materials are iron, such as steel, in particular stainless steel, copper, brass, aluminum, nickel, Monel metals or titanium.
• ceramic materials are oxides of the main group metals or semimetals, for example boron, aluminum or silicon, in particular borosilicate glasses or aluminum silicate glasses.
• plastics are polyolefins, halogen-substituted polyolefins, polyethersulfones, polyphenylene sulfides or polyaryletherketones.
• the fillers can be in a variety of forms, such as in hollow cylinder shape, also called rings, saddle or Ku ⁇ gel shape. Preference is given to Pall rings, Berl saddles, Hiflow rings, Intalox saddles, hedgehogs or in particular Raschig super-rings.
• the packing has one or more diameters of preferably 5 to 100 mm, more preferably 10 to 80 mm, and most preferably 25 to 50 mm.
• the fillers have a specific Surface of preferably 80 to 350 m 2 / m 3 and particularly preferably ⁇ from 100 to 250 m 2 / m 3 .
• the specific surface area it pays off ⁇ this case by multiplying the surface of Ma terials ⁇ from which a packing element is shaped, relative to the quantity of this filler body, in a cubic meter of the bed.
• the packing can be used as a package or preferably as a bulk ⁇ tion.
• a bed is known to a plurality of packing elements in loose and disorderly layering on supporting elements, such as perforated support grates or Other pe ⁇ ge support plates or grids. If several support elements are used, several layers of packing can be installed (laminations).
• Packages have a regularly shaped structure, such as fabric or sheet metal packings, in particular thin, corrugated or perforated plates or nets, in ⁇ example of metal, plastic, glass or ceramic. The per ⁇ stays awhile process gas flows as usual through the fill or packing.
• the packings have a specific surface area of preferably 100 to 750 m 2 / m 3 and more preferably from 150 to 350 m 2 / m 3 . The specific surface is calculated here from the surface of the material from which the package is formed, based on one cubic meter of the package.
• Packings are preferably located in the reinforcement section of the azeotrope column. Packings are preferably in egg ⁇ nem area above the feed point.
• the feed point is the point of the azeotrope column at which the mixture to be separated is introduced into the azeotrope column.
• the fillers are preferably located directly above the feed point or above the tenth tray, from the feed point of the
• the filling bodies are located in front ⁇ preferably above the uppermost tray of the azeotrope.
• the uppermost soil is the soil closest to the top of the azeotrope column.
• Azeotrope column is preferably from 30 to 80, particularly ⁇ vorzugt be 30 to 70 and most preferably 40 to 60.
• the gust ⁇ are preferably mounted between the bottom of the azeotrope column up to the point of the azeotrope, at the Swamp from considered the first packing are introduced.
• the floors are thus preferably below the filling ⁇ body. Above the packing so preferably no floors are attached.
• the pressure at the top of the azeotrope column (top pressure) is preferably more than 600 to 1500 mbar, preferably 800 to 1000 mbar, more preferably 800 to 950 mbar and most preferably 850 to 935 mbar.
• the pressure at the bottom of the azeotrope column is preferably more than 600 to 1500 mbar, preferably 800 to 1000 mbar, more preferably 800 to 950 mbar and most preferably 850 to 935 mbar.
• (Sumpfdruck) is preferably 650 to 2500 mbar, more preferably 1000 to 2000 mbar, more preferably 1000 to 1200 mbar, most preferably 1050 to 1150 mbar.
• the difference between the bottom pressure and the top pressure is preferably 50 to 1000 mbar, more preferably 100 to 300 mbar and most preferably 125 to 250 mbar.
• the temperature at the bottom of the azeotrope column (bottom temperature) is preferably 100 to 130 ° C and particularly preferably 110 to 125 ° C.
• Gas stream or liquid to which heat is transferred from the intrinsic vapor is preferably from 5 to 25 ° C, more preferably from 10 to 25 ° C, even more preferably from 15 to 25 ° C, and most preferably from 15 to 20 ° C.
• the transfer of energy, in particular heat, from the intrinsic ⁇ steam in the azeotrope can be done in different ways, for example using one or more heat exchangers.
• the conventional heat exchangers can be used, such as, for example, plate heat exchangers, tubular heat exchangers, U-tube heat exchangers, jacket tube heat exchangers, heating coils or countercurrent layer heat exchangers.
• a liquid ⁇ speed is taken from the bottom of the azeotrope, which is then transferred heat by means of one or more heat exchangers.
• the liquid thus heated, if appropriate in the form of a liquid-vapor mixture, is preferably recycled to the bottom of the azeotrope column.
• partially external steam in particular ⁇ medium-pressure steam or high-pressure steam
• partially self-steam can be used as steam.
• the withdrawn liquid is in this case heated to a temperature of preferably 110 to 140 ° C and particularly preferably 130 to 140 ° C.
• one or more, preferably an intermediate, evaporator may also be connected to the azeotrope column. It can be used, the usual intermediate evaporator.
• Intermediate evaporators are preferably operated with internal steam and optionally additionally external steam, more preferably exclusively with internal steam.
• Intermediate evaporators are preferably connected to the stripping section of the azeotropic column, ie preferably below the feed, and more preferably below the withdrawal of ethyl acetate. Most preferred is to connect intermediate evaporators between bottom 5 and 20, more preferably between bottom 7 to 15 and most preferably between bottom 8 and 12, depending on the bottom of the azeotrope column counted. Liquid is withdrawn from the azeotropic column at one or more of the abovementioned sites and fed to intermediate evaporators. In intermediate evaporators the removed azeotrope the liquid is heated by means of one or more bathtau ⁇ shear.
• the thus heated liquid optionally in the form of a liquid-vapor mixture, as ⁇ returned to the azeotrope, preferably at the same point or the same zone at which the liquid was removed from the azeotrope.
• the operating temperature of the intermediate evaporator is to preferably from 5 to 15 ° C, particular ⁇ DERS preferably 7 to 10 ° C lower than the bottom temperature.
• one or more intermediate evaporators and additionally one or more heat exchangers can be connected to the azeotropic column. In such a procedure, the heat exchangers can be operated, for example, partly with internal steam and partly, preferably exclusively with external steam, in particular medium-pressure steam or high-pressure steam.
• heat exchangers are preferably connected to the bottom of the azeotrope column.
• the bottom of the azeotrope column is heated by means of a heat exchanger to a temperature of preferably from 110 to 150.degree. C., more preferably from 125 to 140.degree. C., and most preferably from 130 to 135.degree.
• azeotrope column a mixture containing essentially acetic acid, ethyl acetate, water and vinyl acetate is usually distilled. Vinyl acetate and water are generally distilled off as an azeotrope and removed at the top or in the region of the head of the azeotrope column.
• the feed to the azeotrope column preferably contains 25 to 50% by weight of vinyl acetate, 5 to 15% by weight of water, 0 to 1% by weight of ethyl acetate and 40 to 70% by weight of acetic acid.
• In the bottom of the aze ⁇ otropkolonne is preferably a mixture containing water and acetic acid with a content of acetic acid of preferably 90 to 99 wt .-% before.
• the header of the azeotrope column a mixture is discharged before ⁇ preferably containing 90 to 95 wt .-% Vi ⁇ acetate and 5 to 10 wt .-%, particularly 5 to 8 wt .-% water.
• Ethyl acetate is preferably taken off as a side draw.
• the side draw is preferably in Ab ⁇ drive part of the azeotrope.
• the side draw contains before ⁇ preferably 0 to 1 wt .-% ethyl acetate, particularly preferably 0.1 to 0.3 wt .-% ethyl acetate.
• the data in wt .-% relate on the total weight of the mixture or feed or side draw.
• the azeotrope may be used at different points in the process upstream located, as will be described hereinafter by way of example ⁇ .
• the product mixture leaving the reactor contains we ⁇ sentlichen vinyl acetate, ethylene, acetic acid, water, oxygen, carbon dioxide and inerts such as nitrogen, argon, methane or ethane and by-products such as carbon dioxide, acetaldehyde, methyl acetate and ethyl acetate.
• Acetic acid and other condensable reaction products are typically condensed (Kon ⁇ condensate) from the product mixture.
• the remaining gas phase is optionally washed in ei ⁇ ner scrubber stage with acetic acid (cycle gas scrubbing).
• the gas phase thus washed can be returned to the reactor and the washing solution thereby obtained can be introduced, for example, into an azeotrope column.
• Vinyl acetate can be separated from the condensate and possibly from the wash solution, the wash cycle gas powered by heating steam distillation ⁇ steps of acetic acid, water, and other impurities.
• the distillation units usually include several columns, such as a Entwêt ⁇ approximately kolonne an azeotrope, a Vorentskyss mecanicsko ⁇ lonne or pure vinyl acetate.
• Individual columns Kgs ⁇ NEN be arranged in different variants of the method in a different order, as explained below.
• the condensate recovered from the product mixture can be given, for example, directly into a Azeotropko ⁇ lonne.
• the overhead vapor of the azeotrope column can be cooled and subjected to phase separation, forming a water phase and an organic phase.
• Water phase can be deducted.
• the vinyl acetate-containing, organic phase may optionally be partially recycled to the top of the azeotrope and all or part placed in a dewatering column or collected in a Sammelbe ⁇ container.
• the liquid from the Sam ⁇ mel matterser can then be further purified in a dewatering column, or in a further column.
• the bottom of the dewatering column can finally be converted into a pure vinyl acetate column, from which pure vinyl acetate is obtained overhead.
• the product mixture is fed directly into a predewatering, from the distilled overhead water, vinyl acetate and optionally further condensate ⁇ matable portions and are subsequently condensed.
• the vinyl acetate thus obtained organic phase containing the responsible personnel who can be omitted.
• the product mixture can be passed from the reactor into a pre-dewatering column.
• the bottom product of Vorent ⁇ ->ssansskolonne can be introduced into the azeotrope ⁇ to.
• From the predewatering water and vinyl acetate and other volatile constituents can be abdestil ⁇ lines, a portion of which after condensation and phase separation into an organic phase and a water phase are separated meet ⁇ overhead.
• the acetate thus obtained containing ⁇ or ganic phase can be wholly or partly recycled to the column approximately Vorentwêt- or partially introduced in a Azeotropko ⁇ lonne or dehydration column.
• the uncondensed components of the head product of the column approximately Vorentwässe ⁇ are placed in a powered with acetic acid Waschko ⁇ lonne (recycle gas scrubber) and washed.
• the Sumpfpro- domestic product of the recycle gas scrubber is also conducted in the above Aze ⁇ otropkolonne.
• Pure vinyl acetate can be obtained as a side draw from the dewatering column.
• the bottoms of the dewatering column can be further purified in a pure vinyl acetate column.
• pure vinyl acetate can also be obtained as the top product of the pure vinyl acetate column.
• an overall is generally mixed distilled comprising vinyl acetate, water, acetic acid and ethyl acetate, which, in particular, tends in the rectifying section of the azeotrope to phase separation.
• a phase separation in a distillation plant counteracts a material separation by means of distillation, in the present case in particular the separation of ethyl acetate.
• the azeotrope was finally fitted in the art of ⁇ with separating floors. Separators are also less susceptible to contamination that occurs during continuous operation of a Vinylacetather einsstrom and can accumulate over time.
• the reaction of ethylene with acetic acid, and oxygen in the Re ⁇ actuator was carried out in a conventional manner.
• the reactor was operated at an inlet pressure of 10.8 bar abs and a reaction temperature of 160 to 175 ° C.
• the selectivity was 92%, the internal steam temperature 145 ° C, the internal steam pressure 4 bar and the specific internal steam generation 1.45 to self-vapor per ton of vinyl acetate formed.
• the workup of the product mixture was carried out as described in the example of DE-Al 3422575.
• the azeotrope column accordingly contained no fillers.
• the azeotropic distillation was carried out under atmospheric pressure, the bottom temperature of the azeotrope had a temperature of 136 ° C.
• the aze ⁇ otropkolonne were supplied 0.43 tons of heating steam per ton of vinyl acetate.
• the heating steam had a pressure of 6 bar abs and came from the factory network. 35% of the internal steam, ie 0.5 tons of internal steam per tonne of vinyl acetate produced, could not be used in the vinyl acetate production plant.
• 0.92 tonnes of external, ie non-vinyl acetate production, medium pressure steam per tonne of vinyl acetate formed was used.
• the workup of the product mixture was carried out as described in the example of DE-Al 102010001097.
• the azeotrope column contained trays but no packing.
• the azeotropic distillation was carried out under atmospheric pressure, the bottom temperature of the azeotrope had a temperature of 136 ° C.
• the azeotrope column was fed with 0.8 tons of heating steam per ton of vinyl acetate.
• the heating steam had a pressure of 6 bar abs and came from the factory network. 45% of its own vapor, ie 0.65 tone ⁇ NEN-generated steam per ton of produced vinyl acetate, could not be used in the plant for vinyl acetate production.
• During the plant 1.05 tons of external, ie not derived from the Vinylacetather einsclar medium pressure steam per ton of vinyl acetate formed were used.

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• 2013
  • 2013-03-27 DE DE102013205492.0A patent/DE102013205492A1/de not_active Withdrawn
• 2014
  • 2014-03-26 EP EP14714653.4A patent/EP2978737A2/de not_active Withdrawn
  • 2014-03-26 CN CN201480018620.6A patent/CN105102416A/zh active Pending
  • 2014-03-26 WO PCT/EP2014/056067 patent/WO2014154751A2/de active Application Filing
  • 2014-03-26 US US14/780,364 patent/US20160046557A1/en not_active Abandoned

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