EP3274319A1 - Procédé de préparation de 1,3-butadiène à partir de n-butènes par déshydrogénation oxydative - Google Patents

Procédé de préparation de 1,3-butadiène à partir de n-butènes par déshydrogénation oxydative

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Publication number
EP3274319A1
EP3274319A1 EP16709473.9A EP16709473A EP3274319A1 EP 3274319 A1 EP3274319 A1 EP 3274319A1 EP 16709473 A EP16709473 A EP 16709473A EP 3274319 A1 EP3274319 A1 EP 3274319A1
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EP
European Patent Office
Prior art keywords
stream
gas stream
absorbent
column
butenes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP16709473.9A
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German (de)
English (en)
Inventor
Jan Pablo Josch
Stephan DEUBLEIN
Regina Benfer
Friedemann GAITZSCH
Hendrik Reyneke
Christine TOEGEL
Ulrike Wenning
Anton Wellenhofer
Heinz Boelt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Linde GmbH
Original Assignee
BASF SE
Linde GmbH
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Filing date
Publication date
Application filed by BASF SE, Linde GmbH filed Critical BASF SE
Publication of EP3274319A1 publication Critical patent/EP3274319A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/42—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor
    • C07C5/48—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by dehydrogenation with a hydrogen acceptor with oxygen as an acceptor
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C11/00—Aliphatic unsaturated hydrocarbons
    • C07C11/12—Alkadienes
    • C07C11/16—Alkadienes with four carbon atoms
    • C07C11/167—1, 3-Butadiene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/005—Processes comprising at least two steps in series
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/04—Purification; Separation; Use of additives by distillation
    • C07C7/05—Purification; Separation; Use of additives by distillation with the aid of auxiliary compounds
    • C07C7/08—Purification; Separation; Use of additives by distillation with the aid of auxiliary compounds by extractive distillation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/09—Purification; Separation; Use of additives by fractional condensation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids

Definitions

  • the invention relates to a process for the preparation of 1, 3-butadiene from n-butenes by oxidative dehydrogenation (ODH).
  • ODH oxidative dehydrogenation
  • Butadiene (1,3-butadiene) is an important basic chemical and is used, for example, for the preparation of synthetic rubbers (butadiene homopolymers, styrene-butadiene rubber or nitrile rubber) or for the preparation of thermoplastic terpolymers (acrylonitrile-butadiene-styrene -Copolymers) used. Butadiene is further converted to sulfolane, chloroprene and 1, 4-hexamethylenediamine (over 1, 4-dichlorobutene and adiponitrile). By dimerization of butadiene it is also possible to produce vinylcyclohexene, which can be dehydrogenated to styrene.
  • Butadiene can be prepared by thermal cracking (steam cracking) of saturated hydrocarbons, usually starting from naphtha as the raw material. Steam cracking of naphtha produces a hydrocarbon mixture of methane, ethane, ethene, acetylene, propane, propene, propyne, allenes, butanes, butenes, butadiene, butynes, methylalls, Cs and higher hydrocarbons.
  • Butadiene can also be obtained by oxidative dehydrogenation of n-butenes (1-butene and / or 2-butene) in the presence of molecular oxygen.
  • oxidative dehydrogenation oxydehydrogenation, ODH
  • any n-butenes containing mixture can be used.
  • a fraction containing n-butenes (1-butene and / or 2-butene) as a main component and obtained from the C 4 fraction of a naphtha cracker by separating butadiene and isobutene can be used.
  • reaction gas mixtures which comprise 1-butene, cis-2-butene, trans-2-butene or mixtures thereof and which have been obtained by dimerization of ethylene can also be used as the feed gas stream.
  • n-butenes containing gas mixtures obtained by catalytic fluid cracking (FCC) can be used as the feed gas stream.
  • FCC catalytic fluid cracking
  • the reaction gas mixture usually contains inert components. Inert components here mean that they are converted under the reaction conditions of the ODH to less than 90%. Inert components are, for example, water vapor and nitrogen, but also, for example, alkanes, such as methane.
  • the molar ratio of the inert component to molecular oxygen is usually higher than that in air, especially to prevent the risk of explosions.
  • This can be done, for example, by using air as the oxygen-containing gas and using molecular Nitrogen is diluted.
  • air as the oxygen-containing gas
  • molecular Nitrogen is diluted.
  • this can be done by using a molecular oxygen-depleted air (lean air) as the oxygen-containing gas.
  • lean air molecular oxygen-depleted air
  • this can be done by diluting air with lean air.
  • US 2012 / 0130137A1 describes such a process using catalysts containing oxides of molybdenum, bismuth and, as a rule, other metals.
  • a critical minimum oxygen partial pressure in the gas atmosphere is required in order to avoid too extensive a reduction and thus a loss of performance of the catalysts.
  • ODH reactor oxydehydrogenation reactor
  • an oxygen content of 2.5 to 8 vol .-% is described in the starting gas.
  • the N2 / 02 ratio in the reaction gas mixture is adjusted to the desired value by diluting air as the oxygen-containing gas with nitrogen gas.
  • JP 201 1 -006381 A of Mitsubishi addresses the risk of peroxide formation in the working up part of a process for the preparation of conjugated alkadienes.
  • the solution describes the addition of polymerization inhibitors to the absorption solutions for the process gases and the adjustment of a maximum peroxide content of 100 ppm by weight by heating the absorption solutions.
  • no information is given on the prevention or control of peroxides in upstream process steps.
  • the cooling step of the ODH reactor discharge with a water quench can be seen critically. Formed organic peroxides are hardly soluble in water so that they can deposit and accumulate in solid or liquid form in the apparatus instead of being discharged with the aqueous purge stream of the quencher.
  • the temperature of the water quench is not so high that it can be assumed that the peroxides formed are sufficiently high and steady.
  • high-boiling minor components such as maleic anhydride, phthalic anhydride, benzaldehyde, benzoic acid, ethylbenzene, styrene, fluorenone, anthraquinone and others can be formed.
  • Such deposits can lead to blockages and a pressure drop increase in the reactor or behind the reactor in the field of workup and thus interfere with a regulated operation.
  • Deposits of said high-boiling secondary components may also impair the function of heat exchangers or damage moving apparatus such as compressors. Water-volatile compounds such as fluorenone can penetrate through a quench apparatus operated with water and precipitate in the gas discharge lines behind it. Thus, in principle there is also the risk that solid deposits in downstream equipment parts, such as compressors, get there and cause damage.
  • US 2012 / 0130137A1 also refers to the problem of high-boiling by-products.
  • phthalic anhydride, anthraquinone and fluorenone are mentioned, which are typically present in concentrations of 0.001 to 0.10 vol .-% in the product gas.
  • a cooling liquid usually first 5 to 100 ° C.
  • cooling liquids are called water or aqueous alkali solutions.
  • the product discharge gas of the oxidative dehydrogenation is first adjusted to a temperature between 300 and 221 ° C and then further cooled to a temperature between 99 and 21 ° C.
  • heat exchangers are used, but also a part of the high boilers from the product gas could fail in these heat exchangers.
  • suitable solvents are aromatic hydrocarbons such as toluene or xylene or an alkaline aqueous solvent such as, for example, the aqueous solution of sodium hydroxide.
  • JP201 1 - 001341 A describes a structure with two heat exchangers arranged in parallel, each of which is operated or purged alternately (so-called A / B mode of operation).
  • JP 2010-90083 A describes a process for the oxidative dehydrogenation of n-butenes to butadiene, in which the product gas of the oxidative dehydrogenation is cooled and dehydrated. Butadiene and unreacted butenes and butane are then absorbed in a solvent from the feed gas stream containing C 4 -hydrocarbons. The residual gas not absorbed by the solvent is then disposed of by incineration. When a solvent such as low boiling point toluene is used as the absorbent, it is recovered from the residual gas stream by absorption in a high boiling point solvent such as decane to avoid solvent losses.
  • the residual gas which is not absorbed by the solvent and which is largely freed from the C4 hydrocarbons can also be recycled as recycle gas into the oxydehydrogenation.
  • JP 2012-072086 A describes that, as the oxygen-containing gas, a gas in which the hydrocarbons such as butadiene, n-butene, n-butane and isobutane have been separated from the product gas mixture can be recycled to the oxydehydrogenation.
  • the document makes no statements as to how such a recycle gas stream is recovered and what impurities are contained therein.
  • JP 2012-240963 describes a process for Butadienher ein, wherein the C 4 -Kohlen- hydrogen-containing product gas stream from the dehydrogenation in a first absorption stage with a first adsorbent for C 4 hydrocarbons is brought into contact.
  • the gas stream freed from C 4 hydrocarbons is then contacted with a second liquid absorbent in a second absorption stage to reduce the content of vaporous first absorbent in the gas stream.
  • the second absorbent has a higher boiling point than the first absorbent.
  • the first absorbent is for example toluene, the second absorbent another hydrocarbon with a higher boiling point.
  • the disadvantage is that for regeneration, the first and second absorbent must be separated from each other.
  • the object of the present invention is to provide a method which remedies the abovementioned disadvantages of known methods.
  • a method should be provided in which deposits are avoided by high-boiling organic secondary constituents in the ODH downstream equipment.
  • a method is to be provided in which the possible accumulation of organic peroxides is avoided.
  • the determination of the volume fraction of the aromatic hydrocarbon solvent and the other gas components is carried out by gas chromatography.
  • the calibration of the aromatic hydrocarbon solvent, for example of mesitylene takes place here by means of an external standard.
  • a gasifiable solvent such as m-xylene
  • mesitylene in a certain molar ratio in a solvent such as Example acetone
  • the gas sample with a known volume fraction of the gasifiable solvent is fed to the GC via a test loop.
  • the defined volume sample loop is operated at constant pressure and temperature, whereupon an external factor can be determined from the areas of the reference substance and, for example, mesitylene. This can then be set in relation to the mesitylene.
  • the other components are similarly calibrated singly or in mixtures. All components are treated like ideal gases. This also applies to the analysis of gas flows in the ODH process.
  • the amount of aromatic hydrocarbon solvent in the reaction gas mixture depends on the proportion of the aromatic hydrocarbon solvent in the recycle gas and the proportion of the recycle gas in the reaction gas mixture.
  • the content of aromatic hydrocarbon solvent in the circulating gas stream a2 is limited to less than 1% by volume by the absorbent A1 contained in the gas stream d2) in vapor form or in the form of fine droplets in an absorbent stream A2 is absorbed.
  • A2 may contain an absorption agent different from A1 or else the appropriate absorption medium.
  • the current A2 may have a lower temperature than the gas flow d2. If the absorbent contained in stream A2 and the absorbent contained in stream A1 are the same, the temperature of stream A2 is even below the temperature of stream d2 to reduce the content of aromatic hydrocarbon in stream d2.
  • this further absorbent stream A2 in the column K2 is limited to a maximum of 80, preferably to a maximum of 50 wt .-%, it is avoided that the solubility of the absorbent A2 for organic peroxides (primarily butadiene peroxide) is reduced so far that a separate phase of organic peroxides can form.
  • organic peroxides primarily butadiene peroxide
  • the formation of a peroxide phase is safety-critical and should be avoided at all costs.
  • the water content of the further absorbent stream A2 is limited to a maximum of 80% by weight, preferably to a maximum of 50% by weight.
  • an organic solvent is preferably used. These generally have a much higher solubility for the high-boiling by-products found in the downstream of the ODH reactor parts to deposits and blockages can lead to as water or alkaline-aqueous solutions.
  • Preferred organic solvents used as cooling agents are aromatic hydrocarbons, particular preference is given to toluene, o-xylene, m-xylene, p-xylene, mesitylene, all possible constitutional isomers of mono-, di- and triethylbenzene and all possible constitutional isomers of mono-, di-, and triisopropylbenzene or mixtures thereof.
  • aromatic hydrocarbons having a boiling point at 1013.25 hPa of more than 120 ° C. or mixtures thereof.
  • mesitylene is especially preferred.
  • the absorbent used in the separation step Da) is an aromatic hydrocarbon solvent.
  • aromatic hydrocarbons having a boiling point at 1013.25 hPa of more than 120.degree. Particularly preferred is mesitylene.
  • the same aromatic hydrocarbon solvent is used as in the preceding cooling step Ca) when an organic solvent is used in the cooling step Ca).
  • non-condensable and low-boiling gas constituents comprising water vapor, oxygen, low-boiling hydrocarbons, optionally carbon oxides and optionally inert gases are obtained as gas stream d2. At least part of this gas stream d2 is recycled as circulating gas stream a2 into the oxidative dehydrogenation (step B)).
  • the content of aromatic hydrocarbon solvent in the cycle gas stream a2 is less than 1% by volume.
  • the content of aromatic hydrocarbon solvent A1 in the circulating gas stream a2 is limited to less than 1% by volume in that the gas stream d2 leaving the separation stage Da) is brought into contact in a further column K2 with a liquid absorbent A2 for the aromatic hydrocarbon solvent A1 ,
  • the absorbent A2 used in this further column K2 must be miscible with the aromatic hydrocarbon solvent A1 from the absorption column K1 of the separation stage Da) and may optionally also be the same solvent.
  • the water content of the absorption medium A2 in the further column K2 is limited to a maximum of 80% by weight, preferably at most 50% by weight. This can be done by (i) continuously withdrawing a portion of the aqueous absorbent A2 from the further column K2 and replacing it with fresh, not or not so strongly hydrous absorbent A2; or
  • the water-containing absorbent is separated in a phase separator into an absorbent phase and a water phase, the water phase is separated off and the absorbent phase is applied again to the further column K2;
  • the phase separator may be a separate phase separator or integrated into the column bottom of the further column K2;
  • the absorption column K1 used in the absorption step Da) or the further column K2 used after the absorption step Da) has one or more devices, for example a demister or droplet separator, which entrain the liquid components from the absorption column K1 or K1 reduce the further column K2 into the gas stream d2.
  • a demister or droplet separator which entrain the liquid components from the absorption column K1 or K1 reduce the further column K2 into the gas stream d2.
  • demisters or mist eliminators are understood to mean devices for separating the finest liquid droplets from gases, vapors or mists, generally aerosols. In columns, the liquid entrainment can be reduced by demisters or droplet separators.
  • Demisters or droplet separators may, for example, consist of wire mesh packings, lamella separators or fillings of fillers with a large internal surface area.
  • steels, chromium-nickel steels, aluminum, copper, nickel, polypropylene, polytetrafluoroethylene and the like are used as materials. The degree of separation decreases with decreasing droplet diameters.
  • Demisters can be counted among the coalescence separators. Demisters are described inter alia in applications US 3,890,123 and US 4,141,706 and the references cited therein.
  • the demister or mist eliminator can be located either within the absorption column or the absorption columns, or downstream of it.
  • the content of the circulating gas stream a2 of aromatic hydrocarbon solvent is preferably less than 0.5% by volume, more preferably less than 0.2% by volume, in particular less than 0.1% by volume.
  • the process according to the invention preferably also comprises the following further process steps: E) separation of the C4 product stream d1 by extractive distillation with a butadiene-selective solvent into a butadiene and the stream e1 containing the selective solvent and a stream e2 containing n-butenes;
  • the stage Ca), at least one cooling stage can be connected upstream, in which the product gas stream b is cooled by indirect cooling in a heat exchanger.
  • the stage Ca) can be carried out in several stages in stages Ca1) to Can), preferably in two stages in two stages Ca1) and Ca2). In this case, particularly preferably at least part of the coolant is supplied after passing through the second stage Ca2) as cooling agent of the first stage Ca1).
  • the stage Cb) generally comprises at least one compression stage Cba) and at least one cooling stage Cbb).
  • the compressed in the compression stage Cba) gas is brought into contact with a cooling agent.
  • the cooling agent of the cooling step Cbb) contains the same organic solvent used as the cooling agent in step Ca) when an organic solvent is used in the cooling step Ca).
  • at least part of this cooling agent is fed after passing through the at least one cooling stage Cbb) as cooling agent of stage Ca).
  • the cooling stage Cbb) may consist of heat exchangers.
  • the stage Cb) comprises a plurality of compression stages Cba1) to Cban) and cooling stages Cbb1) to Cbbn), for example four compression stages Cba1) to Cba4) and four cooling stages Cbb1) to Cbb4).
  • Step Da) preferably comprises the steps Daa) to Dac):
  • feed gas stream a1 it is possible to use pure n-butenes (1-butene and / or cis-2-butene and / or trans-2-butene), but also gas mixtures containing butenes.
  • a gas mixture can be obtained, for example, by non-oxidative dehydrogenation of n-butane. It it is also possible to use a fraction which contains n-butenes as the main constituent and was obtained from the C 4 fraction of naphtha cracking by removal of butadiene and isobutene.
  • gas mixtures comprising pure 1-butene, cis-2-butene, trans-2-butene or mixtures thereof, obtained by dimerization of ethylene, can also be used as the feed gas stream.
  • feed gas stream n-butenes containing gas mixtures can be used, which were obtained by fluid catalytic cracking (FCC).
  • the feed gas stream containing n-butenes is obtained by non-oxidative dehydrogenation of n-butane.
  • a non-oxidative catalytic dehydrogenation with the oxidative dehydrogenation of the n-butenes formed, a high yield of butadiene, based on n-butane used, can be obtained.
  • a gas mixture is obtained which, in addition to butadiene 1-butene, 2-butene and unconverted n-butane, contains minor constituents.
  • Common secondary constituents are hydrogen, water vapor, nitrogen, CO and CO2, methane, ethane, ethene, propane and propene.
  • the composition of the gas mixture leaving the first dehydration zone can vary greatly depending on the mode of operation of the dehydrogenation.
  • the product gas mixture has a comparatively high content of water vapor and carbon oxides.
  • the product gas mixture of the non-oxidative dehydrogenation has a comparatively high content of hydrogen.
  • step B) the reaction gas mixture containing the n-butenes containing feed gas stream a1, an oxygen-containing gas, an oxygen-containing cycle gas stream a2 and optionally other components in at least one dehydrogenation zone (the ODH reactor) is fed and the butenes contained in the gas mixture in the presence an oxydehydrogenation catalyst oxidatively dehydrogenated to butadiene.
  • Catalysts suitable for oxydehydrogenation are generally based on a Mo-Bi-O-containing multimetal oxide system, which generally additionally contains iron.
  • the catalyst system contains other additional components, such as potassium, cesium, magnesium, zirconium, chromium, nickel, cobalt, cadmium, tin, lead, germanium, lanthanum, manganese, tungsten, phosphorus, cerium, aluminum or silicon.
  • Iron-containing ferrites have also been proposed as catalysts.
  • the multimetal oxide contains cobalt and / or nickel. In a further preferred embodiment, the multimetal oxide contains chromium. In a further preferred embodiment, the multimetal oxide contains manganese.
  • Mo-Bi-Fe-O-containing multimetal oxides are Mo-Bi-Fe-Cr-O or Mo-Bi-Fe-Zr-O-containing multimetal oxides.
  • Preferred systems are described, for example, in US 4,547,615 (Moi2BiFeo, iNi 8 ZrCr 3 Ko, 20x and Moi2BiFeo, iNi 8 AICr 3 Ko, 20x), US 4,424,141
  • X 1 Si, Mn and / or Al
  • X 2 Li, Na, K, Cs and / or Rb,
  • the molecular oxygen-containing gas generally contains more than 10% by volume, preferably more than 15% by volume, and more preferably more than 20% by volume of molecular oxygen. It is preferably air.
  • the upper limit of the content of molecular oxygen is generally 50% by volume or less, preferably 30% by volume or less, and more preferably 25% by volume or less.
  • any inert gases may be contained in the molecular oxygen-containing gas. Possible inert gases include nitrogen, argon, neon, helium, CO, CO2 and water.
  • the amount of inert gases for nitrogen is generally 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. In the case of components other than nitrogen, it is generally 10% by volume or less, preferably 1% by volume or less.
  • a gas mixture which has a molar oxygen: n-butenes ratio of at least 0.5. Preference is given to operating at an oxygen: n-butenes ratio of 0.55 to 10.
  • the input gas stream with oxygen or at least one oxygen-containing gas, such as air, and optionally additional inert gas or steam can be mixed.
  • the resulting oxygen-containing gas mixture is then fed to the oxydehydrogenation.
  • inert gases such as nitrogen and also water (as water vapor) may be contained together in the reaction gas mixture. Nitrogen can be used to adjust the oxygen concentration and prevent the formation of an explosive gas mixture, the same applies to water vapor. Steam also serves to control the coking of the catalyst and to dissipate the heat of reaction.
  • the reaction temperature of the oxydehydrogenation is generally controlled by a heat exchange medium located around the reaction tubes.
  • liquid heat exchange agents e.g. Melting of salts such as potassium nitrate, potassium nitrite, sodium nitrite and / or sodium nitrate and melting of metals such as sodium, mercury and alloys of various metals into consideration. But ionic liquids or heat transfer oils are used.
  • the temperature of the heat exchange medium is between 220 to 490 ° C and preferably between 300 to 450 ° C and more preferably between 350 and 420 ° C.
  • the temperature in certain sections of the interior of the reactor during the reaction may be higher than that of the heat exchange medium and a so-called hotspot is formed.
  • the location and height of the hotspot is determined by the reaction conditions, but it may also be regulated by the dilution ratio of the catalyst layer or the flow rate of mixed gas.
  • the difference between hotspot temperature and the temperature of the heat exchange medium is generally between 1 to 150 ° C, preferably between 10 to 100 ° C and more preferably between 20 to 80 ° C.
  • the temperature at the end of the catalyst bed is generally between 0 to 100 ° C, preferably between 0.1 to 50 ° C, more preferably between 1 to 25 ° C above the temperature of the heat exchange medium.
  • the oxydehydrogenation can be carried out in all fixed-bed reactors known from the prior art, such as, for example, in a hearth furnace, in a fixed-bed or shell-and-tube reactor or in a plate heat exchanger reactor.
  • a tube bundle reactor is preferred.
  • the oxidative dehydrogenation is carried out in fixed bed tubular reactors or fixed bed bundle bundle reactors.
  • the reaction tubes are (as well as the other elements of the tube bundle reactor) usually made of steel.
  • the wall thickness of the reaction tubes is typically 1 to 3 mm. Their inner diameter is usually (uniformly) at 10 to 50 mm or 15 to 40 mm, often 20 to 30 mm.
  • the submerged in the tube bundle reactor The number of reaction tubes usually amounts to at least 1000, or 3000, or 5000, preferably to at least 10,000. Frequently, the number of reactor tubes accommodated in the tube bundle reactor is 15,000 to 30,000 or up to 40,000 or up to 50,000.
  • the length The reaction tubes usually extend to a few meters, typical is a reaction tube length in the range of 1 to 8 m, often 2 to 7 m, often 2.5 to 6 m.
  • the catalyst layer configured in the ODH reactor may consist of a single layer or of two or more layers. These layers may be pure catalyst or diluted with a material that does not react with the feed gas stream or components from the product gas of the reaction. Furthermore, the catalyst layers can consist of solid material or supported shell catalysts.
  • the product gas stream leaving the oxidative dehydrogenation generally contains unreacted 1-butene and 2-butene, oxygen and water vapor.
  • the product gas stream leaving the oxidative dehydrogenation generally contains unreacted 1-butene and 2-butene, oxygen and water vapor.
  • it furthermore generally contains carbon monoxide, carbon dioxide, inert gases (mainly nitrogen), low-boiling hydrocarbons such as methane, ethane, ethene, propane and propene, butane and isobutane, optionally hydrogen and optionally oxygen-containing hydrocarbons, so-called oxygenates.
  • Oxygenates may be, for example, formaldehyde, furan, acetic acid, maleic anhydride, formic acid, methacrolein, methacrylic acid, crotonaldehyde, crotonic acid, propionic acid, acrylic acid, methyl vinyl ketone, styrene, benzaldehyde, benzoic acid, phthalic anhydride, fluorenone, anthraquinone and butyraldehyde.
  • the product gas stream at the reactor exit is characterized by a temperature near the temperature at the end of the catalyst bed.
  • the product gas stream is then brought to a temperature of 150 to 400 ° C, preferably 160 to 300 ° C, more preferably 170 to 250 ° C. It is possible to isolate the line through which the product gas stream flows to maintain the temperature in the desired range, or to use a heat exchanger. This heat exchanger system is arbitrary as long as the temperature of the product gas can be maintained at the desired level with this system.
  • heat exchangers there can be mentioned spiral heat exchangers, plate heat exchangers, double tube heat exchangers, multi-tube heat exchangers, boiler spiral heat exchangers, shell-shell heat exchangers, liquid-liquid contact heat exchangers, air heat exchangers, direct contact heat exchangers and finned tube heat exchangers. Because, while the temperature of the product gas is adjusted to the desired temperature, a portion of the high-boiling by-products contained in the product gas may precipitate, therefore, the heat exchanger system should preferably have two or more heat exchangers.
  • the two or more intended heat exchangers may be arranged in parallel.
  • the product gas is supplied to one or more, but not all, heat exchangers, which are replaced after a certain period of operation of other heat exchangers. In this method, the cooling can be continued, recovered a portion of the heat of reaction and parallel to the in one of the heat exchangers deposited high-boiling by-products are removed.
  • a solvent may be used so long as it is capable of dissolving the high-boiling by-products.
  • aromatic hydrocarbon solvents such as toluene and xylenes
  • alkaline aqueous solvents such as the aqueous solution of sodium hydroxide.
  • This stage is also referred to below as quench.
  • This quench can consist of only one stage or of several stages.
  • the cooling can be effected by contacting with a coolant, preferably an organic solvent.
  • the cooling medium used are organic solvents, preferably aromatic hydrocarbons, particularly preferably toluene, o-xylene, m-xylene, p-xylene, mesitylene, all possible constitutional isomers of mono-, di- and triethylbenzene and all possible constitutional isomers of mono-, di- and triisopropylbenzene or mixtures thereof.
  • aromatic hydrocarbons having a boiling point at 1013.25 hPa of above 120 ° C or mixtures thereof.
  • the stage Ca comprises two cooling stages Ca1) and Ca2), in which the product gas stream b is brought into contact with the organic solvent.
  • the product gas depending on the presence and temperature level of a heat exchanger before the quench, a temperature of 100 to 440 ° C.
  • the product gas is brought into contact with the cooling medium in the 1st quench stage.
  • the cooling medium can be introduced through a nozzle in order to achieve the most efficient possible mixing with the product gas.
  • internals such as, for example, additional nozzles, can be introduced into the quenching stage and pass through the product gas and the cooling medium together.
  • the coolant inlet into the quench is designed to minimize clogging due to deposits in the area of the coolant inlet.
  • the product gas in the first quenching stage is cooled to 5 to 180 ° C, preferably to 30 to 130 ° C and even more preferably to 60 to 1 10 ° C.
  • the temperature of the coolant medium at the inlet may generally be 25 to 200 ° C, preferably 40 to 120 ° C, particularly preferably 50 to 90 ° C.
  • the pressure in the first quenching stage is not particularly limited, but is generally 0.01 to 4 bar (g), preferably 0.1 to 2 bar (g) and more preferably 0.2 to 1 bar (g).
  • the quenching stage is designed as a cooling tower.
  • the cooling medium used in the cooling tower is often used in a circulating manner.
  • the recycle flow of the cooling medium in liters per hour, based on the mass flow of butadiene in grams per hour, can generally 0.0001 to 5 l / g, preferably 0.001 to 1 l / g and more preferably 0.002 to 0.2 l / g be.
  • the temperature of the cooling medium in the bottom can generally be 27 to 210 ° C, preferably 45 to 130 ° C, particularly preferably 55 to 95 ° C. Since the loading of the cooling medium with secondary components increases over time, a portion of the loaded cooling medium can be withdrawn from the circulation as a purge stream and the circulation volume can be kept constant by adding unzula- denem cooling medium. The ratio of effluent amount and added amount depends on the vapor load of the product gas and the product gas temperature at the end of the first quench stage.
  • condensation of water may occur in the first quenching stage.
  • an additional aqueous phase may form, which may additionally contain water-soluble secondary components. This can then be subtracted in the bottom of the quenching stage. Preference is given to an operation in which no aqueous phase is formed in the first quench stage.
  • the cooled and possibly depleted in secondary components product gas stream can now be fed to a second quenching stage. In this he can now be brought into contact again with a cooling medium.
  • cooling media are organic solvents, preferably aromatic hydrocarbons, particularly preferably toluene, o-xylene, m-xylene, p-xylene, mesitylene, all possible constitutional isomers of mono-, di- and triethylbenzene and all possible constitutional isomers of mono-, di-, and triisopropylbenzene or mixtures thereof. Also preferred are aromatic hydrocarbons having a boiling point at 1013.25 hPa of above 120 ° C or mixtures thereof.
  • the product gas is cooled to 5 to 100 ° C, preferably 15 to 85 ° C and even more preferably 30 to 70 ° C, to the gas exit of the second quench stage.
  • the coolant can be supplied in countercurrent to the product gas.
  • the temperature of the coolant medium at the coolant inlet may be 5 to 100 ° C, preferably 15 to 85 ° C, particularly preferably 30 to 70 ° C.
  • the pressure in the second quenching stage is not particularly limited, but is generally 0.01 to 4 bar (g), preferably 0.1 to 2 bar (g), and more preferably 0.2 to 1 bar (g).
  • the second quenching stage is preferably designed as a cooling tower.
  • the cooling medium used in the cooling tower is often used in a circulating manner.
  • the circulation stream of the cooling medium in liters per hour can generally be from 0.0001 to 5 l / g, preferably from 0.3001 to 1 l / g and particularly preferably from 0.002 to 0, 2 l / g.
  • condensation of water may occur in the second quench stage.
  • an additional aqueous phase may form, which may additionally contain water-soluble secondary components. This can then be subtracted in the bottom of the quenching stage.
  • the temperature of the cooling medium in the bottom can generally be from 20 to 210 ° C., preferably from 35 to 120 ° C., particularly preferably from 45 to 85 ° C. Since the loading of the cooling medium with secondary components increases over time, part of the loaded cooling medium can be used as purge stream are withdrawn from circulation, and the circulating amount to be kept constant by adding unladen cooling medium.
  • built-in components can be present in the second quenching stage.
  • Such internals include, for example, bell, centrifugal and / or sieve trays, columns with structured packings, eg sheet metal packings having a specific surface area of 100 to 1000 m 2 / m 3 such as Mellapak® 250 Y, and packed columns.
  • the coolant circulations of the two quench stages can be both separated from each other and connected to each other.
  • the power can be supplied to the power or replace it.
  • the desired temperature of the circulating streams can be adjusted by means of suitable heat exchangers.
  • the cooling stage Ca) is carried out in two stages, with the second-stage coolant Ca 2) loaded with secondary components being led into the first stage Ca1).
  • the coolant removed from the second stage Ca2) contains fewer secondary components than the coolant removed from the first stage Ca1).
  • suitable structural measures such as the installation of a demister, can be taken.
  • high-boiling substances which are not separated from the product gas in the quench, can be removed from the product gas by further structural measures, such as further gas scrubbing.
  • Such high boiling components include, for example, methyl vinyl ketone, methyl ethyl ketone, crotonaldehyde, acrylic acid, propionic acid, maleic anhydride, ethylbenzene, styrene, furanone, benzoic acid, benzaldehyde, fluorenone and anthraquinone.
  • this gas stream may contain formaldehyde, methacrolein and / or furan.
  • the gas stream b 'from the cooling step Ca which is depleted in high-boiling secondary components, is cooled in step Cb) in at least one compression stage Cba) and preferably in at least one cooling stage Cbb).
  • the product gas stream from the quench is compressed in at least one compression stage and subsequently further cooled in the cooling apparatus, wherein at least one condensate stream containing water is formed. If a coolant other than water is used in the quench, the coolant used in the quench can continue to condense and optionally form a separate phase.
  • the compression and cooling of the gas stream can take place in one or more stages (n-stage). Generally, a total pressure is compressed in the range of 1.0 to 4.0 bar (absolute) to a pressure in the range of 3.5 to 20 bar (absolute).
  • a cooling stage follows, in which the gas stream is cooled to a temperature in the range of 15 to 60 ° C.
  • the cooling is preferably carried out by contacting with an organic solvent as a cooling agent.
  • heat exchangers can also be used.
  • the condensate stream can therefore also comprise a plurality of streams in the case of multistage compression.
  • the condensate stream consists to a large extent of water (aqueous phase) and optionally the refrigerant used in the quench (organic phase). Both streams (aqueous and organic phase) may also contain minor components such as low boilers, C4 hydrocarbons, oxygenates and carbon oxides.
  • the condensed quench coolant can be cooled in a heat exchanger and recycled as coolant into the apparatus. Since the loading of this cooling medium with minor components increases over time, a portion of the loaded cooling medium can be withdrawn from circulation and the circulating amount of the cooling medium can be kept constant by adding uncharged coolant.
  • the coolant, which is added as a cooling medium thus also preferably consists of the aromatic hydrocarbon solvent used as quench coolant.
  • the condensate stream can be returned to the recycle stream of the quench.
  • the C4 components absorbed in the condensate stream can be reintroduced into the gas stream and thus the yield can be increased.
  • Suitable compressors are, for example
  • Turbo rotary piston and reciprocating compressors.
  • the compressors can be driven, for example, with an electric motor, an expander or a gas or steam turbine.
  • Typical compression ratios (outlet pressure: inlet pressure) per compressor stage are between 1, 5 and 3.0, depending on the design.
  • the cooling of the compressed gas is carried out with organic solvent purged heat exchangers or organic quench, which may be designed, for example, as a tube bundle, spiral or plate heat exchanger.
  • coolant cooling water or heat transfer oils are used in the heat exchangers.
  • air cooling is preferably used using blowers.
  • the butadiene, n-butenes, oxygen, low-boiling hydrocarbons (methane, ethane, ethene, propane, propene, n-butane, isobutane), water vapor, optionally carbon oxides and optionally inert gases and optionally traces of minor components containing gas stream c2 is used as the output stream the further processing supplied.
  • a step Da) are non-condensable and low-boiling gas components comprising water vapor, oxygen, low-boiling hydrocarbons (methane, ethane, ethene, propane, propene), carbon oxides and inert gases in an absorption column K1 from the process gas stream c2 by absorption of C4 hydrocarbons separated in a hydrocarbon aromatic solvent as a high-boiling absorbent A1 and subsequent desorption of the C4 hydrocarbons.
  • the step Da) comprises the steps Daa) to Dac):
  • the gas stream c2 is brought into contact with the absorbent A1 and the C 4 hydrocarbons are absorbed in the absorbent A1, whereby an absorbent A1 'laden with C 4 hydrocarbons and a gas stream d 2 containing the other gas constituents are obtained which is at least partially recycled as a recycle gas stream in the oxidative dehydrogenation.
  • the C 4 -hydrocarbons are released from the loaded absorbent A1 'again.
  • organic solvents preferably aromatic hydrocarbons, particularly preferably toluene, o-xylene, m-xylene, p-xylene, mesitylene, all possible constitutional isomers of mono-, di- and triethylbenzene and all possible constitutional isomers of mono-, Di- and triisopropylbenzene or mixtures thereof.
  • aromatic hydrocarbons having a boiling point at 1013.25 hPa of above 120 ° C or mixtures thereof. More specifically, in the separation step Da), the same aromatic hydrocarbon solvent is used as in the preceding cooling step Ca) when an organic solvent is used in the cooling step Ca).
  • Preferred absorbents are solvents which have a solubility for organic peroxides of at least 1000 ppm (mg active oxygen / kg solvent). In a preferred embodiment, A1 mesitylene is used as the absorption medium.
  • the absorption stage can be carried out in any suitable absorption column known to the person skilled in the art. Absorption can be accomplished by simply passing the product gas stream through the absorbent. But it can also be done in columns or in rotational absorbers. It can be used in DC, countercurrent or crosscurrent gear- be processed. Preferably, the absorption is carried out in countercurrent. Suitable absorption columns are, for example, tray columns with bell, centrifugal and / or sieve trays, columns with structured packings, for example sheet metal packings with a specific surface area of 100 to 1000 m 2 / m 3 such as Mellapak® 250 Y, and packed columns. Rice and spray towers, graphite block absorbers, surface absorbers such as thick-film and thin-layer absorbers, as well as rotary columns, rags, cross-flow scrubbers and rotary scrubbers are also suitable.
  • the absorption column K1 is a tray column with bells, centrifugal and / or sieve bottom or a column with structured packing or a packed column, more preferably a column with structured packings. This generally has 10 to 40 theoretical plates.
  • the absorption column K1 is generally operated at a pressure of 5 to 15 bar, preferably 8 to 12 bar.
  • the temperature of the absorbent A1 added to the column K1 is generally from 5 to 50 ° C, preferably from 20 to 40 ° C.
  • the absorption column K1 is supplied in the lower region of the butadiene, n-butenes and the gas stream c2 containing the low-boiling and non-condensable gas constituents. In the upper part of the absorption column, the absorbent is applied.
  • a gas stream d2 is withdrawn, which is essentially water vapor, oxygen, low-boiling hydrocarbons (methane, ethane, ethene, propane, propene), the aromatic hydrocarbon solvent, optionally C4-hydrocarbons (butane, butenes, butadiene) , optionally inert gases and optionally containing carbon oxides.
  • This stream is brought according to the invention in the further column K2 with a liquid absorbent A2 for the aromatic hydrocarbon solvent in contact and then at least partially supplied as a circulating gas stream a2 the ODH reactor.
  • the inlet flow of the ODH reactor can be adjusted to the desired C4 hydrocarbon content.
  • the purge gas stream may be subjected to thermal or catalytic afterburning. In particular, it can be thermally utilized in a power plant.
  • the recycle stream is 10 to 70% by volume, preferably 30 to 60% by volume, based on the sum of all material streams fed into the oxidative dehydrogenation B).
  • the content of aromatic hydrocarbon solvent in the circulating gas stream a2 is limited to less than 1% by volume by passing the gas stream d2 leaving the separation stage Da) in contact with a liquid absorbent A2 for the aromatic hydrocarbon solvent in a further column K2 , wherein the water content of the absorbent A2 in the further column K2 is limited to a maximum of 50 wt .-%.
  • This can be done by (i) continuously withdrawing a portion of the aqueous absorbent A2 from the further column K2 and replacing it with fresh, not or not so strongly hydrous absorbent A2; or
  • the water-containing absorbent is separated in a phase separator into an absorbent phase and a water phase, the water phase is separated off and the absorbent phase is applied again to the further column;
  • the phase separator may be a separate phase separator or integrated into the column bottom of the further column;
  • Suitable absorbents are organic solvents, preferably aromatic hydrocarbons, particularly preferably toluene, o-xylene, m-xylene, p-xylene, mesitylene, all possible constitution isomers of mono-, di- and triethylbenzene and all possible constitution isomers of mono-, di- and Triisopropylbenzene or mixtures thereof.
  • Preferred absorbents are solvents which have a solubility for organic peroxides of at least 1000 ppm (mg active oxygen / kg solvent).
  • mesitylene is used as absorption medium A2.
  • the same aromatic hydrocarbon solvent is used in the further column K2 as the absorbent A2, which is also used in the absorption column K1 as the absorbent A1.
  • absorption column K2 for example, tray columns with bells, centrifugal and / or sieve plates, columns with structured packings, for example sheet metal packings having a specific surface area of 100 to 1000 m 2 / m 3, such as Mellapak® 250 Y, and packed columns are suitable. These generally have 1 to 15 theoretical plates.
  • the further column K2 is generally operated at a pressure of 5 to 15 bar, preferably 8 to 12 bar.
  • the temperature of the absorbent A2 added to the column K2 is generally from 0 to 30 ° C, preferably 5 to 15 ° C.
  • the temperature of the absorbent A2 charged to the column K2 is generally 1 to 50, preferably 20 to 30 ° C lower than the temperature of the absorbent A1 applied to the column K1.
  • part of the water-containing absorption medium A2 from the further column K2 is continuously withdrawn and replaced by fresh, not or not so strongly hydrous absorbent A2.
  • the part of the water-containing absorbent stream A2 which is withdrawn and is not fed back to the column K2 is 0.1 to 10% of the total stream of the absorbent A2.
  • the withdrawn stream is optionally passed to column K1 or solvent regeneration.
  • the water-containing absorbent is separated in a phase separator into an absorbent phase and a water phase, the water phase is separated off and the absorbent phase is again applied to the further column K2.
  • the phase separator may be a separate phase separator or integrated into the column bottom of the further column K2.
  • part of the water-containing absorption medium from the column K2 is fed into the absorption column K1. If there are two separate columns, a part of the bottom effluent from the column K2 is fed into the column K1. However, it can also run over an overflow part of the stream from column K2 in the column K1, while the rest of the stream is withdrawn and added back to the top of the column K2, wherein the column K2 and the column K1 column sections of a single combined column are. In one embodiment, this combined column contains a chimney tray between the column sections K1 and K2. In general, the part of the aqueous absorption medium A2, which is led into the absorption column K1 and is not applied again to the column K2, amounts to 0.1 to 10% of the total flow of the absorbent stream A2.
  • the absorbent dissolved oxygen can be discharged in a further column K3 by flushing with a gas.
  • the remaining oxygen content is preferably so small that the stream d1 leaving the desorption column and containing butane, butenes and butadiene only contains a maximum of 100 ppm of oxygen.
  • the stripping out of the oxygen in step Dab) can be carried out in any suitable column known to the person skilled in the art.
  • the stripping can be carried out by simply passing non-condensable gases, preferably inert gases such as nitrogen, through the loaded absorption solution. With stripped C4 hydrocarbons are washed in the upper part of the absorption column back into the absorption solution by the gas stream is passed back into this absorption column. This can be done both by a piping of the stripping column and a direct assembly of the stripping column below the absorber column. Since the pressure in the stripping column part and the absorption column part is the same according to the invention, this direct coupling can take place.
  • Suitable spiked columns are e.g. Tray columns with
  • the laden with C4 hydrocarbons, largely freed from water absorbent stream AT can be heated in a heat exchanger and then passed into a desorption.
  • the desorption step De) is carried out by relaxation and / or heating of the loaded absorbent.
  • a preferred process variant is the use of a reboiler in the bottom of the desorption column.
  • the absorbent A1 regenerated in the desorption stage can be cooled in a heat exchanger and returned to the absorption stage.
  • Low boilers in the process gas stream such as ethane or propane, as well as high-boiling components, such as benzaldehyde, maleic anhydride and phthalic anhydride, can accumulate in the circulation stream.
  • a purge can be deducted. This can be separated in a distillation column according to the prior art in low boilers, regenerated absorbent and high boiler.
  • the C4 product gas stream d1 consisting essentially of n-butane, n-butenes and butadiene generally contains from 20 to 80% by volume of butadiene, from 0 to 80% by volume of n-butane, from 0 to 10% by volume 1 - Butene, and 0 to 50% by volume of 2-butenes, the total amount being 100% by volume. Furthermore, small amounts of iso-butane may be included.
  • a portion of the condensed head effluent of the desorption column, mainly containing C 4 hydrocarbons, is returned to the top of the column to increase the separation efficiency of the column.
  • the liquid or gaseous C4 product streams leaving the condenser can subsequently be separated by extractive distillation in step E) with a butadiene-selective solvent into a butadiene and the material stream containing the selective solvent and a stream containing n-butenes.
  • the extractive distillation may, for example, as described in "petroleum and coal - natural gas - petrochemistry", Volume 34 (8), pages 343 to 346 or “Ullmann's Encyclopedia of Industrial Chemistry", Volume 9, 4th edition 1975, pages 1 to 18, be performed.
  • the C4 product gas stream with an extractant preferably an N-methylpyrrolidone
  • the extraction zone is generally designed in the form of a wash column which contains trays, fillers or packages as internals. This generally has 30 to 70 theoretical plates, so that a sufficiently good release effect is achieved.
  • the wash column has a backwash zone in the column head. This backwash zone is used to recover the extractant contained in the gas phase by means of a liquid hydrocarbon reflux, to which the top fraction is condensed beforehand.
  • the mass ratio extractant to C4 product gas stream in the feed of the extraction zone is generally from 10: 1 to 20: 1.
  • the extractive distillation is preferably carried out at a bottom temperature in the range from 100 to 250 ° C., in particular at a temperature in the range from 110 to 210 ° C., a top temperature in the range from 10 to 100 ° C., in particular in the range from 20 to 70 ° C. ° C and one Pressure in the range of 1 to 15 bar, in particular operated in the range of 3 to 8 bar.
  • the extractive distillation column preferably has from 5 to 70 theoretical plates.
  • Suitable extractants are butyrolactone, nitriles such as acetonitrile, propionitrile, methoxypropionitrile, ketones such as acetone, furfural, N-alkyl-substituted lower aliphatic acid amides such as dimethylformamide, diethylformamide, dimethylacetamide, diethylacetamide, N-formylmorpholine, N-alkyl-substituted cyclic acid amides (lactams) such as N Alkylpyrrolidones, especially N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • alkyl-substituted lower aliphatic acid amides or N-alkyl substituted cyclic acid amides are used.
  • Particularly advantageous are dimethylformamide, acetonitrile, furfural and in particular NMP.
  • mixtures of these extractants with each other e.g. NMP and acetonitrile, mixtures of these extractants with cosolvents and / or tert-butyl ether, e.g. Methyl tert-butyl ether, ethyl tert-butyl ether, propyl tert-butyl ether, n- or iso-butyl tert-butyl ether
  • NMP preferably in aqueous solution, preferably with 0 to 20 wt .-% water, particularly preferably with 7 to 10 wt .-% water, in particular with 8.3 wt .-% water.
  • the overhead product stream of the extractive distillation column contains essentially butane and butenes and in small amounts of butadiene and is taken off in gaseous or liquid form.
  • the stream consisting essentially of n-butane and 2-butene contains up to 100% by volume of n-butane, 0 to 50% by volume of 2-butene and 0 to 3% by volume of further constituents, such as isobutane, isobutene , Propane, propene and Cs + hydrocarbons.
  • the stream consisting essentially of n-butane and 2-butene can be supplied wholly or partly to the C 4 feed of the ODH reactor.
  • this recycle stream can be catalytically isomerized prior to being fed to the ODH reactor. As a result, the isomer distribution can be adjusted in accordance with the isomer distribution present in the thermodynamic equilibrium.
  • the stream comprising butadiene and the selective solvent is fractionated by distillation into a stream consisting essentially of the selective solvent and a stream comprising butadiene.
  • the stream obtained at the bottom of the extractive distillation column generally contains the extractant, water, butadiene and, in minor proportions, butenes and butane and is fed to a distillation column. In this can be obtained overhead or as a side take butadiene.
  • an extractant and optionally water-containing material flow is obtained, wherein the composition of the extractant and water-containing material stream corresponds to the composition as it is added to the extraction.
  • the extractant and water-containing stream is preferably returned to the extractive distillation. If the butadiene is recovered via a side draw, the extraction solution thus withdrawn is transferred to a desorption zone, wherein the butadiene is desorbed again from the extraction solution and washed back.
  • the desorption zone can be embodied, for example, in the form of a wash column which has 2 to 30, preferably 5 to 20 theoretical stages and optionally a backwashing zone with, for example, 4 theoretical stages.
  • This backwash zone is used to recover the extractant contained in the gas phase by means of a liquid hydrocarbon reflux, to which the top fraction is condensed beforehand.
  • trays or packing are provided.
  • the distillation is preferably carried out at a bottom temperature in the range from 100 to 300 ° C., in particular in the range from 150 to 200 ° C. and a top temperature in the range from 0 to 70 ° C., in particular in the range from 10 to 50 ° C.
  • the pressure in the distillation column is preferably in the range of 1 to 10 bar. In general, a reduced pressure and / or elevated temperature prevails in the desorption zone relative to the extraction zone.
  • the product stream obtained at the top of the column generally contains 90 to 100% by volume of butadiene, 0 to 10% by volume of 2-butene and 0 to 10% by volume of n-butane and isobutane.
  • a further distillation according to the prior art can be carried out.
  • FIG. 1 A variant of the method according to the invention is shown in FIG.
  • the process gas mixture leaving the compressor enters the latter at 64 ° C. and the composition shown in Table 1 as stream 1 at the 30th stage of the absorption column 22 comprising 60 stages.
  • the top pressure of the column is 10 bar absolute.
  • the column contains bubble trays.
  • the process gas stream flows in countercurrent to the unloaded absorbent stream 10 fed from above, consisting mainly of mesitylene saturated with water.
  • the absorbent preferably absorbs the C 4 - hydrocarbons and small amounts of non-condensable gases.
  • the ratio between the mass of the absorbent stream 10 and the process gas stream 1 is 2.2: 1.
  • the non-condensable gases leave the absorption column mainly as stream 3 above the top of the column at a temperature of 35 ° C and the composition shown in Table 1.
  • this is passed into a further absorber column 25 and further cooled in contact with the stream 17.
  • the resulting exhaust gas flow 20 then has only 80 mol. Ppm of mesitylene.
  • Nitrogen flow 2 desorbs oxygen from the absorbent stream loaded with C 4 hydrocarbons.
  • the largely deoxygenated, with C 4 -Kohlen- hydrogens laden absorbent stream 4 is heated in the heat exchanger 28 and passed as stream 7 in the desorber 26.
  • the C 4 -hydrocarbons are removed from the absorbent stream by the stripping steam stream 6 and leave the column 26 as stream 13. This is partially condensed in the condenser 29, the gas stream 15 remaining. Part of the condensate is recycled as stream 16 to the desorber column 26, while stream 14 is the C 4 product stream.
  • non-condensable gas e.g., nitrogen, methane or like gases

Abstract

La présente invention concerne un procédé de préparation de butadiène à partir de n-butènes, comprenant les étapes consistant à : A) produire un flux de gaz d'alimentation a1 contenant des n-butènes ; B) introduire le flux de gaz d'alimentation a1 contenant des n-butènes, un gaz contenant de l'oxygène et un flux de gaz de recyclage a2 contenant de l'oxygène dans au moins une zone de déshydrogénation oxydative et effectuer une déshydrogénation oxydative des n-butènes en butadiène, un flux de gaz produit b contenant du butadiène, des n-butènes n'ayant pas réagi, de la vapeur d'eau, de l'oxygène, des hydrocarbures à bas point d'ébullition, des composants secondaires à point d'ébullition élevé, éventuellement des oxydes de carbone et éventuellement des gaz inertes étant obtenu ; Ca) refroidir le flux de gaz produit b et éventuellement séparer au moins partiellement les composants secondaires et la vapeur d'eau, un flux de gaz produit b' étant obtenu, Cb) comprimer et refroidir le flux de gaz produit b' dans au moins un étage de compression et de refroidissement, au moins une flux de condensat aqueux c1 et un flux de gaz c2 contenant du butadiène, des n-butènes, de la vapeur d'eau, de l'oxygène, des hydrocarbures à bas point d'ébullition, éventuellement des oxydes de carbone et éventuellement des gaz inertes étant obtenu ; Da) absorber les hydrocarbures C4 contenant du butadiène et des n-butènes dans un solvant d'hydrocarbure aromatique en tant que flux d'absorbant A1 dans une colonne d'absorption K1 et séparer du flux de gaz c2 les constituants gazeux non condensables et à bas point d'ébullition, contenant de la vapeur d'eau, de l'oxygène, des hydrocarbures à bas point d'ébullition, éventuellement des oxydes de carbone, le solvant d'hydrocarbure aromatique et éventuellement des gaz inertes, sous la forme d'un flux de gaz d2, un flux d'absorbant A1' chargé en hydrocarbures C4 et le flux de gaz d2 étant obtenus, puis effectuer la désorption des hydrocarbures C4 du flux d'absorbant A1' chargé, un flux de gaz produit C4 d1 étant obtenu, Db) réintroduire au moins partiellement le flux de gaz d2 en tant que flux de gaz de recyclage a2 dans la zone de déshydrogénation oxydative. Le procédé selon l'invention est caractérisé en ce que la teneur en solvant d'hydrocarbure aromatique dans le flux de gaz de recyclage a2 est limitée à moins de 1% en volume par le fait que le flux de gaz d2 à l'issue de l'étape de séparation Da) est mis en contact dans une autre colonne K2 avec un flux d'absorbant A2 liquide, au moins partiellement recyclé, pour le solvant d'hydrocarbure aromatique A1, et la teneur en eau du solvant d'absorption liquide A2 dans la colonne K2 est limitée à 80 % en poids au maximum.
EP16709473.9A 2015-03-26 2016-03-14 Procédé de préparation de 1,3-butadiène à partir de n-butènes par déshydrogénation oxydative Withdrawn EP3274319A1 (fr)

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US10647639B2 (en) 2016-02-04 2020-05-12 Basf Se Method for preparing 1,3-butadiene from N-butenes by oxidative dehydrogeneation
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CN107428636A (zh) 2017-12-01
US20180072638A1 (en) 2018-03-15

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