WO2008090190A1 - Verfahren zur herstellung von acrylsäure - Google Patents
Verfahren zur herstellung von acrylsäure Download PDFInfo
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- WO2008090190A1 WO2008090190A1 PCT/EP2008/050785 EP2008050785W WO2008090190A1 WO 2008090190 A1 WO2008090190 A1 WO 2008090190A1 EP 2008050785 W EP2008050785 W EP 2008050785W WO 2008090190 A1 WO2008090190 A1 WO 2008090190A1
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- acrylic acid
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- weight
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- water
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C57/00—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms
- C07C57/02—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms with only carbon-to-carbon double bonds as unsaturation
- C07C57/03—Monocarboxylic acids
- C07C57/04—Acrylic acid; Methacrylic acid
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
- C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/48—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
Definitions
- the present invention relates to a process for the preparation of acrylic acid in which by heterogeneously catalyzed gas phase partial oxidation of at least one C3 precursor of acrylic acid with molecular oxygen to solid state catalysts at elevated temperature produces an acrylic acid, water vapor and minor components containing product gas mixture, the temperature of acrylic acid, water vapor and secondary components containing product gas mixture optionally reduced by direct and / or indirect cooling, and the acrylic acid, water vapor and secondary components containing product gas mixture then passes into a equipped with separating internals condensation column, within the condensation column can rise in itself and fractionating fraction condenses as well as a first and, above the feed of the product gas mixture in the condensation column located, side draw a water and Maukompo nents total depleted (depleted) containing crude acrylic acid as the target product and a second, above the first side draw, liquid phase withdrawal (preferably a side draw) still acrylic acid and minor components containing acidic water and at the top of the condensation column a deeper (at lower temperature (relative to atmospheric
- Acrylic acid is a significant intermediate which is used, for example, in the preparation of polymer dispersions (if appropriate also in the form of their esters with alkanols) and of water-based superabsorbent polymers.
- Acrylic acid is inter alia by heterogeneously catalyzed gas phase partial oxidation of C3 precursors (of C3 precursor compounds) of acrylic acid (this term is intended to summarize in particular those chemical compounds which are formally obtainable by reduction of acrylic acid, known C3 precursor of acrylic acid for example, propane, propene, acrolein, propionaldehyde and propionic acid, but the term should also include precursor compounds of the aforementioned compounds, such as glycerol (starting from glycerol, acrylic acid can be generated, for example, by heterogeneously catalyzed oxidative dehydration in the gas phase; see. z.
- glycerol starting from glycerol, acrylic acid can be generated, for example, by heterogeneously catalyzed oxidative dehydration in the gas phase; see. z.
- EP-A 1 710 227, WO 06/1 14506 and WO 06/092272 with molecular oxygen available in the solid state state catalysts at elevated temperature
- the said starting gases usually with inert gases such.
- inert gases such as nitrogen, CO2, saturated hydrocarbons and / or steam, in admixture with molecular oxygen at elevated temperatures and optionally elevated pressure over (eg. Transition metal) mixed oxide catalysts passed and oxidatively in an acrylic acid, water and undesired by-products such.
- the heterogeneously catalyzed gas-phase partial oxidation with molecular oxygen is at least partially an oxidative dehydrogenation.
- DE-A 199 24 533, DE-A 199 24 532, WO 01/77056, DE-A 101 56 016, DE-A 102 43 625, DE-A 102 23 058, DE-A 102 35 847, WO 2004/035514, WO 00/53560 and DE-A 103 32 758 are known as described in the beginning for the production of acrylic acid, in which a basic separation of a crude acrylic acid by fractional condensation of the product gas mixture of the heterogeneously catalyzed gas phase partial oxidation is carried out.
- crude acrylic acid or crude acrylic acid expresses the fact that the acrylic acid withdrawn via the first side draw is not a pure product but a mixture which, in addition to acrylic acid (usually> 50 or> 60% by weight) , usually> 70 or> 80 wt .-%, often> 90 wt .-% and often> 95 wt .-% or more of the total weight) nor water and secondary components such.
- the total content of water and secondary components, based on the content of acrylic acid, in the crude acrylic acid is lower than in the product gas mixture of the gas phase partial oxidation, which is why it is also said that the crude acrylic acid contains these components in a fully enriched form (individual components however, may be relatively enriched in crude acrylic acid).
- the purity of the crude acrylic acid thus separated is already sufficient for the intended use of the acrylic acid (for example, for the purpose of esterifying it, or for the purpose of building up by radical polymerisation). obtainable polymers).
- the separated crude acrylic acid is subjected to at least one further thermal separation process in order to obtain from the crude acrylic acid a purer acrylic acid (which has a higher acrylic acid content in comparison with the crude acrylic acid in percent by weight) acrylic acid required for the respective intended use Purity has.
- Thermal separation processes are understood to mean those in which a physically at least two-phase system is generated with supply or with removal of (usually thermal) energy, whereby due to the temperature and molar mass gradient existing between the phases, it becomes a heat and moisture Mass transfer occurs, which ultimately causes the desired separation, and the extraction.
- thermal separation processes are carried out in separating columns containing separating internals, in which the abovementioned at least two material phases are generally conducted in countercurrent to one another.
- one of the two material phases is gaseous (it is usually conducted in a separation column as an ascending phase) and the other liquid (it is usually performed in a separation column as a descending phase).
- the at least two material phases can also be liquid (for example in the case of extraction) or solid and liquid (for example in the case of crystallization), or solid and gaseous (for example in the case of adsorption) ,
- thermal separation processes in which one of the at least two material phases is liquid and gaseous, and thus a natural element of the term "thermal separation process" used in this document, are the rectification (an ascending vapor phase is in countercurrent in the separation column the desorption (the reversal process for absorption; the gas dissolved in a liquid phase becomes liquid by lowering the pressure above the liquid phase, increasing the temperature of the liquid phase, and / or passing a gas phase through the liquid phase If the passage of a gas phase is involved, the desorption is also referred to as stripping.) But also the absorption (as a rule, a gas ascending in a separating column is passed countercurrently to at least one absorbent which descends in the separating column in liquid form ) and the fractional condensation of a gas mixture (gas / liquid phase example) are part of the term thermal separation process.
- a particularly favorable thermal separation process for the further purification of crude acrylic acid is the crystallisative further purification (the crystallization).
- the gas phase partial oxidation of at least one C3 precursor of the acrylic acid is the additional accumulation of acidic water which is still containing acrylic acid and secondary components (also referred to simply as "sour water”.)
- the term "acidic water” initially expresses that the acidic acid in the Re - gel> 50 wt .-%, often> 60 wt .-%, often> 70 wt .-% and often> 80 wt .-% of water (it is usually both water of reaction, as well as to dilution water (water vapor) used as inert diluent gas in the course of the gas phase partial oxidation)).
- B. contains propionic acid, acetic acid and formic acid and acrylic acid, and thus has a pH of ⁇ 7 (the total content of the non-acrylic acid secondary component carboxylic acids is usually, based on the weight of the acid water, at values ⁇ 10 wt .-%, partially at values ⁇ 5% by weight).
- the acrylic acid content of the sour water will be 4 or 5 to 15, often about 10 wt .-%.
- a disadvantage of the method recommended in the cited prior art for the basic separation of acrylic acid from the product gas mixture of the heterogeneously catalyzed gas phase partial oxidation is that it supplies the acid water not containing acrylic acid which is not recycled into the rectification column in its entirety to combustion (cf. -A 102 43 625, WO 2004/035514 and DE-A 103 32 758).
- the object of the present invention in view of the prior art described, has been to provide an improved process for the production of acrylic acid which is particularly distinguished by ensuring an increased yield of acrylic acid without appreciably affecting the purity thereof ,
- a method for the production of acrylic acid which comprises by heterogeneously catalyzed gas phase partial oxidation of at least one C3 precursor (a C3 precursor compound) of the acrylic acid with molecular oxygen to solid state catalysts at elevated temperature, an acrylic acid, water vapor and minor components containing Product gas mixture produced, the temperature of the acrylic acid, water vapor and secondary components containing product gas mixture optionally reduced by direct (by direct contact with a cooling liquid) and / or indirect cooling, and the acrylic acid, water vapor and secondary components containing product gas mixture then in a equipped with separating elements condensation column conducts, within the Condensation column can rise in itself and thereby fractionally condensed and via a first, located above the feed of the product gas mixture in the condensation column, side draw a water and minor components Entreichert containing crude acrylic acid as the target product and a second, located above the first side draw, liquid phase withdrawal (all statements in this document are valid in particular in the case of such a sour water side draw) still containing acrylic acid and
- At least 25% by weight, more preferably at least 50% by weight, even better at least 75% by weight and preferably the total amount of acid water not recirculated to the condensation column is extruded and further treated according to the invention.
- a mixer eg a stirred tank or a static mixer
- a separator eg a settling tank
- Suitable stirrers are in principle all common stirrers. Examples include disc stirrer, impeller stirrer, crossbar stirrer, lattice stirrer, blade stirrer, anchor stirrer, paddle stirrer, propeller stirrer, helical stirrer and multistage stirrer. Pulse countercurrent stirrer.
- the stirrers can also be multi-stage, that is, a plurality of stirrers are mounted on a common axis one above the other. Preferably, a two-stage impeller agitator is used.
- all common containers come into consideration as settling tanks.
- a recumbent container is used.
- Such an extraction unit can be operated continuously or discontinuously, wherein discontinuing the settling tank can be omitted and the phase separation is carried out in the stirred tank.
- the separation of the feed into a heavy and light phase can be improved by installations transverse to the flow direction in the settling tank.
- all common fixtures into consideration, such as perforated plates, plates, packings and / or beds.
- the residence time in the settling tank is typically 0.05 to 2 hours.
- mixer-separator units in succession, this is called a cascade.
- the units can be switched both in the counter, as well as in the DC or cross current.
- the extraction to be carried out according to the invention will be carried out in an extraction column containing separating internals.
- the specific heavier phase enters the top and the specific lighter phase at the bottom of the column.
- both phases move in countercurrent.
- the same extraction columns the columns for a countercurrent distillation (rectification).
- extraction columns suitable for the extraction process according to the invention can be of a type known per se and have the customary internals.
- Possible column types are both extraction columns with and without energy input into consideration.
- Extraction columns containing internals in the form of packages (in particular structured or ordered) and / or beds can be operated both with and without energy input.
- the beds those having rings, coils, calipers, Raschig, Intos or Pall rings, Barrel or Intalox saddles, Top-Pak etc. are preferred.
- packages are z. B. packs of Julius Montz GmbH in D-40705 Hilden, such.
- the pack Montz-Pak B1-350 Preferably, perforated structured packings of stainless steel sheets are used. Packing columns with ordered packs are known in the art and z.
- the Karr column works similarly, except that the liquid is not pulsed here, but the sieve trays are moved up and down.
- the pulsed sieve tray column is preferred.
- the continuous phase passes from one floor to the next floor via downcomers and only the disperse phase is forced through the holes in the perforated trays due to the density difference (the designations used in this document for mass transfer trays are based on those of DE -A 103 32 758).
- the theoretical soil (or theoretical separation stage) is to be understood generally in this document as meaning the room unit of a separating column containing separation-active internals used for a thermal separation process, which causes a material enrichment in accordance with the thermodynamic equilibrium. That is, the concept of theoretical soil is applicable both to extraction columns with mass transfer trays, and to extraction columns with packing and / or packing.
- the specifically heavier of the two phases will be suitably applied in terms of application technology by means of a distributor at the top of the column, distributed as uniformly as possible over the cross section.
- the specific lighter phase is also useful in terms of application technology via a distributor into the bottom of the column. Accordingly, the lighter phase rises in the column and the heavy phase sinks down. If the lighter of the two phases is dispersed, ie if it is in the form of droplets, then the phase separation takes place in the top of the column; in the opposite case, in which the heavier phase is dispersed, the phase separation takes place in the bottom of the column.
- Cheap drop sizes in both cases have a diameter (a
- Longest extent in the range of 1 to 10 mm, preferably in the range of 2 to 5 mm.
- the extractant will have a higher boiling point than acrylic acid (in each case based on atmospheric pressure), since this usually facilitates the subsequent separation of the acrylic acid from the organic extract.
- the organic solvent to be used as extractant has a viscosity appreciably higher than that of water.
- the organic extractant entering into the extraction column is in the form of a disperse phase and the acid water is a continuous phase (this necessitates, for example, an accelerated mass transfer between the two phases and ultimately allows shorter columns with the same separation result
- a continuous aqueous phase wets better extraction columns made of stainless steel and their internals, moreover, a transport of the substance to be extracted from the continuous phase into the disperse phase leads to a stabilization of the latter (lower tendency to coalescence)).
- an organic extractant having a higher mass density than the mass density of the acid water this means that the extractant is added and dispersed at the top of the column and the resulting extractant drops in the column fall down.
- the extractant when using an extractant having a lower mass density than the mass density of sour water, the extractant is dispersed in the bottom of the column and the resulting extractant drops rise in the column.
- the undivided continuous phase should wet the selected internals well, since otherwise the droplets of the dispersed phase usually creep along the internals.
- the organic extractant is in this case by means of tubes arranged over the cross-section of the column and extending over the respective cross-sectional length of the normally circular-cylindrical extraction column, which generally have circular passage openings (bores) (which normally have an identical cross-section; give up. If the organic extractant is added at the top of the column, the circular passages point downwards, when the extractant is discharged at the bottom of the column.
- the diameter (the longitudinal expansion) of the aforementioned passage openings will be usually 1 mm to 10 mm, preferably 3 mm to 6 mm and often 2 to 5 mm.
- the extractant is in a simple manner in the distribution pipes on and out of the passages flow out again.
- stirred columns or centrifugal extractors can also be used for the acid water extraction to be carried out according to the invention.
- Stirred columns improve the contact of both phases. All stirrers of the column suitably sit on a common shaft in terms of application technology.
- the column tube is expediently equipped with stator rings on the walls.
- the shaft which is usually arranged in the middle, typically carries stirrers in such a way that in each case see two stator rings rotating a stirrer.
- the rotating disc contactor (RDC) column the asymmetric rotating disc (ARD) column
- BRAhni column Kerhni stirred column
- QVF stirred cell extractor the QVF stirred cell extractor.
- Centrifugal extractors use the centrifugal force to mix and separate the two countercurrent phases.
- the centrifugal force provides good raffinate / extract separation even if both phases tend to form a stable emulsion. Examples include the apparatus Podbielnak extractor or the Westfalia separator.
- the extraction unit for the process according to the invention is preferably made of the material 1.4571. This also applies to the other devices that can be used for the separation of the acrylic acid from the product gas mixture of the heterogeneously catalyzed gas phase partial oxidation.
- the driving force for the separation of extract and raffinate is the difference in the mass density (g / cm 3 ) between the two phases.
- a high mass density difference between the two liquid phases facilitates phase separation and reduces emulsion formation.
- organic solvents are therefore advantageously used whose mass density in kg / m 3 differs from the mass density of water (also in kg / m 3 ) by> 25 kg / m 3 , preferably by> 50 kg / m 3 (based on the pressure used in the extraction and the temperature used in the extraction).
- the aforementioned mass density difference will be ⁇ 250 kg / m 3 , generally ⁇ 150 kg / m 3 .
- the dynamic viscosity of the organic extractant under the extraction conditions is ⁇ 100 mPas, preferably ⁇ 50 mPas. In general, however, the aforementioned dynamic viscosity will be> 1 rnPa -s. Dynamic viscosities in the range from 2 to 10 mPa-s are particularly favorable according to the invention.
- suitable extraction agents for the acid water extraction include organic liquids are those whose boiling point at atmospheric pressure (1 atm) above 150 or above 160 0 C in the light of what has been said. Examples include middle oil fractions from the Paraffugillation, diphenyl ether, diphenyl, or mixtures of the aforementioned liquids, such as. B. a mixture of 70 to 75 wt .-% diphenyl ether and 25 to 30 wt .-% diphenyl.
- organic solvents for acid water extraction according to the invention are the esters of aliphatic or aromatic mono- or dicarboxylic acids (especially when both carboxyl groups have been esterified), whose alcoholic component has 1 to 8 carbon atoms and their carboxylic acid component has 5 to 20 carbon atoms contains.
- the alcoholic component preferably has only two or only one hydroxyl group before the esterification.
- the alcoholic component is particularly preferably monohydric (an OH group) or divalent (two OH groups) alkanols.
- the number of carbon atoms of the alcoholic component (especially in the case of monohydric or dihydric alkanols) is from 1 to 6, more preferably from 1 to 4 and most preferably 1 or 2.
- the aliphatic or aromatic mono- or Dicarboxylic acids advantageously contain 5 to 15 C atoms, preferably 5 to 10 C atoms and particularly preferably 6 to 8 C atoms (especially in the case of a respective esterification (also in the diester case) with 1 to 4 or with 1 or 2 C. Atoms having alkanols).
- Dicarboxylic acids are preferred over monocarboxylic acids as the acid component of the relevant esters (especially when both carboxyl groups are esterified).
- Phthalic acid, isophthalic acid and terephthalic acid and adipic acid are very particularly preferred acid components of the relevant esters according to the invention. The latter is especially true in the case of dialkyl esters (C 1 to C 1 alkyl, advantageously C 1 to C 6 alkyl, very particularly advantageously C 1 to C 4 alkyl and even better d or C 2 alkyl).
- D. h. Most favorable for the inventive method extractants are methylphthalate the di-, diethyl terephthalate, the (z. B. A Palatinol ® from BASF Aktiengesellschaft), the dimethyl isophthalate, diethyl isophthalate the that of dimethyl terephthalate, the diethyl, dimethyl adipate and diethyl adipate.
- esters are the triesters of phosphoric acid, such as. For example, tributyl phosphate or tricresyl phosphate. Suitable cresyl radicals are both ortho-cresyl, meta-cresyl and para-cresyl.
- the extractants used for the acid water extraction according to the invention are esters of acrylic acid and branched or linear monohydric C 1 - to C 12 -alkanols (for example 2-propylheptyl acrylate or 2-ethylhexyl acrylate) and mono- and diesters of maleic acid and monohydric C 4 - to Alkanols into consideration.
- the acid water to be extracted will contain acetic acid in addition to acrylic acid and water as further constituent (usually in wt .-% based on the total amount of Sau wasser the third largest component).
- the acid water can be up to 10 wt .-%, or up to 5 wt .-% (often 2 to 8 wt .-%) or more of acetic acid.
- the sour water contains about 2 times the weight fraction of acrylic acid, based on the weight fraction of acetic acid.
- the extractant does not react with water under the extraction conditions and has only a low solubility in water. So z.
- the diethyl phthalate particularly stable to hydrolysis.
- Another advantage of the Phthalcicrediethylesters is be at atmospheric pressure (1 atm) comparatively high boiling point, according to the invention advantageous to use extraction agent (organic solvent)> 200 0 C, more preferably is> 225 ° C and even better> 250 0 C.
- the acid water falls in accordance with the invention to be carried out fractional condensation of Artsgasge- premixture at a temperature of 50 to 80 0 C, preferably 60 to 70 ° C at. That is, at this temperature, it is normally withdrawn via the second liquid phase draw (preferably a side draw) (the lower the temperature, the lower the need for the polymerization inhibitor, and in favorable cases, the separate addition of such to the sour water, extractant, is not required , Raffinate and / or extract). From an application point of view, therefore, the extraction in this temperature range will be carried out. D.
- the acidic water substantially at its aforementioned temperature in the extraction unit preferably an extraction column (particularly preferably a packed column, advantageously Montz-Pak B1-350) lead.
- the feed from below into the extraction column and from above the specific heavier extractant (with advantage diethyl phthalate) is abandoned.
- the temperature of the charged extractant will not be very different from that of the supplied sour water.
- the amount of this temperature difference is> 0 ° C and ⁇ 20 0 C, preferably> 0 ° C and ⁇ 15 ° C and often> 0 0 C and ⁇ 10 0 C.
- the pressure of the condensing column removed acid water is at the Outlet according to the invention typically> 1 to 1, 5 bar, often 2 bar.
- the withdrawn sour water is fed by means of a pump into the extraction column.
- the delivery pressure can z. B. 2 to 6 bar.
- the working pressure in the extraction column is selected according to the invention so that it requires no additional pump to promote the organic extract in the first stripping. In principle, however, the extraction of acid water can also be carried out at higher or lower temperatures and at higher or lower pressures.
- the supply of the sour water can in principle take place directly via a corresponding feed nozzle.
- the sour water can also be supplied via a feed tube (diameter of the passage openings lying at typically 5 to 10 mm) which has one (or more) passage openings in its wall.
- the extraction column is suitably made in terms of application technology made of stainless steel. Typical wall thicknesses are 5 to 20 mm. Outwardly, the extraction column is normally thermally isolated in a conventional manner.
- the ratio V of the amounts of organic extractant fed to the extraction column (E, in kg / h) and acidic water (S, in kg / h), d. h., E: S, in the process according to the invention may be 0.05 to 20, preferably 0.1 to 10, more preferably 0.8 to 1, 2 and particularly preferably 1: 1.
- the sour water (leached, depleted) leached out with acrylic acid is normally sent for disposal (eg burned or transported to the sewage treatment plant). It leaves the extraction column according to the invention typically at its head (as a raffinate), while the organic, acrylic acid-containing extract leaves the extraction column typically below.
- the separation of the acrylic acid from the organic extract whose extraction temperature from the extraction column substantially corresponds to the feed temperature of the acid water into the extraction column, can in principle be carried out using different thermal separation processes or also using combinations of such thermal separation processes.
- a suitable separation variant is the crystallisative separation. All crystallization processes which are recommended in DE-A 19838845 and in DE-A 10 2005 015 637 come into consideration.
- the advantage of the crystallative separation is that crystallization, unlike other thermal separation processes, is a sharp separation process. In other words, the composition of the acrylic acid crystals which form is largely independent (in the ideal case, there is complete independence) of the composition of the liquid phase, the liquid extract.
- a fuzzy thermal separation process is one in which the composition of the phase comprising the target product enriched in the application of the separation process is markedly dependent on the composition of the mixture to be separated.
- thermodynamic theory in thermodynamic theory a one-time equilibrium sufficient to obtain the pure target product, while it requires in fuzzy separation a repeated successive adjustment of the thermodynamic equilibrium.
- Crystallization processes which are particularly suitable according to the invention for the purpose of separating acrylic acid from the extract are suspension crystallization and layer crystallization.
- the desorption unit used is usually a column with separation-active internals. In principle, all known separating internals come into consideration as such column internals. These include, in particular, soils, packings and / or fillings.
- mass transfer trays sieve trays e.g., B.
- Forced sieve or dual-flow trays are bubble-cap trays, (dual-flow trays), valve trays and / or Thormann trays (or Thormann ® -floors) are preferred.
- the random packings are those comprising rings, coils, saddles , Raschig, Intos or PaII rings, Barrel or Intalox saddles, Top-Pak etc. or braids are preferred, very particular preference is given to dual-flow trays and / or Thormann trays
- Thormann floors are the single-flow Thormann floors preferred.
- the dual-flow trays are most preferably used in the lower section of the desorption unit and the Thormann trays in the upper section of the desorption unit.
- 5 to 10 theoretical plates in the desorption unit are sufficient.
- the desorption can be effected solely by lowering the pressure.
- the partial pressure of the to be desorbed acrylic acid is prepared by diluting with a non-condensable under the desorption conditions (preferably the boiling point of the stripping gas at 1 atm of at least 50 0 C below the boiling point of water) and (as against chemical change) substantially inert gas lowered. D.
- the driving force behind this process is that the vapor pressure of the acrylic acid to be removed from the extract is greater than its partial pressure in the gas itself, so that the acrylic acid is transferred from the extract to the gas.
- the extract for the purpose of stripping against the flow direction of the stripping gas (ie, in countercurrent) out. That is, the extract is advantageously applied at the top of the stripping column and the stripping gas is passed down into the stripping column.
- residual gas mixture has the advantage that on the one hand no additional stripping gas has to be provided (which would later have to be additionally disposed of) and on the other hand a stripping gas is used which does not affect the entire removal process of the acrylic acid from the product gas mixture the partial oxidation contains foreign components.
- residual gas consists predominantly of the inert diluent gases used for the partial oxidation of the C3 precursor of acrylic acid (essentially unchanged chemically in the partial oxidation) and of steam formed as by-product during the partial oxidation and optionally added as diluent gas and undesirable full oxidation as a side reaction formed carbon oxides (often also a residual gas mixture composition having partial amount of the residual gas is recycled as diluent gas in the partial oxidation, this should be referred to in this document as partial tialoxid Vietnamese Vietnamese gas or cycle gas).
- the inert diluent gases used in the partial oxidation eg N 2, CO 2, H 2 O and / or saturated hydrocarbons, etc.
- the hole diameter (the diameter of the passage openings in the trays) is generally 8 to 50 mm, preferably 10 to 35 mm. Preferably, the hole diameter increases from top to bottom.
- the floor spacing (usually the floors are arranged equidistantly) is often 300 to 800 mm, often 400 to 600 mm and often 500 mm.
- the desorption unit is usually made of austenitic steel, preferably of the material 1.4571 (according to DIN EN 10020).
- the column feed to extract to be stripped takes place in the upper region of the desorption unit, preferably on its upper (theoretical) bottom.
- the extract is previously heated (typically at temperatures of 80 to 120 0 C, often about 10O 0 C).
- internal and / or external indirect heat exchangers of conventional design eg Robert evaporator, forced circulation tube bundle heat exchangers, forced circulation tube bundle expansion heat exchangers, plate heat exchangers, etc. cf., for example, EP-A 854 129) and / or double wall heating (as heat carrier is advantageously used with the waste heat of the partial oxidation of water vapor used) is advantageously fed to the bottom of the stripping column (the desorption column) additional heat.
- External circulation evaporator with natural or forced circulation.
- Outer circulation evaporators with forced circulation are particularly preferably used.
- the use of multiple evaporators, connected in series or in parallel, is possible (typical bottom temperatures are 145 to 165 0 C, often at about 155 0 C).
- non-condensable and inert stripping gas is advantageously introduced directly into the bottom of the desorption.
- the feed from the external heat exchanger (in which previously removed bottoms liquid the required heat is supplied) is advantageously carried out on one of the lower (theoretical) column trays (preferably in the area of the theoretical trays 2 to 4 from below) or below.
- the resulting in the column bottom of the desorption column, acrylic acid substantially free extractant is advantageously recycled to the head of the acid water extraction.
- Extractant stream are normally additionally discharged from 0.01 to 1 wt .-% of the bottoms of the stripping column (purge stream) (behind the aforementioned water cooling is usually a corresponding stream of fresh extractant in the extractant recycle stream supplemented).
- This purge stream can be disposed of (eg burned together with residual gas) or worked up by rectification and transferred to fresh extractant.
- the stripping gas is preferably performed at a temperature in the stripping column, which largely corresponds to at least that of the bottom liquid in the stripping column (normally the two temperatures are not more than 30 0 C, preferably not more than 20 0 C apart). If residual gas is used as the stripping gas, it may, for. B.
- this compression can be carried out together with recycle gas to a pressure which is suitable also for the recirculation of residual gas into the C3 precursor partial oxidation (usually with the aid of a radial compressor).
- the aforementioned pressure is 2 to 4 bar, often 2.5 to 3.5 bar (at a residual gas pressure of typically> 1 and ⁇ 1, 5 bar).
- the amount of stripping gas required for free-stripping the acrylic acid is typically 1.5 to 2.5 Nm 3 of stripping gas.
- Typical loadings of the stripping gas with acrylic acid are (at the top of the stripping column) 2 to 6 wt .-%.
- the heat input into the bottom of the stripping column can be reduced as the amount of stripping gas used increases.
- the advantage of separating off the acrylic acid from the extract by stripping with a stripping gas which is usually not condensable under the desorption conditions and is due, inter alia, to the fact that it is a particularly efficient and, at the same time, low-energy removal method.
- crystallisative or rectificative separation from the extract has the advantage that it does not produce additional, acrylic acid in increased concentration, having liquid phase, which requires the expense of an additional pronounced polymerization inhibition.
- the stripping gas charged with acrylic acid in particular when residual gas was used for stripping, can be recirculated as such into the condensation column (which is used for the fractional condensation of the product gas mixture of the partial oxidation).
- the condensation column which is used for the fractional condensation of the product gas mixture of the partial oxidation.
- such a recirculation takes place below the first side draw in the condensation column.
- one will make the return directly into the bottom space of the condensation column. In principle, it can take place directly in the bottoms liquid.
- the present application therefore comprises in particular such a process according to the invention which is characterized in that at least one partial amount (advantageously a partial amount of at least 25% by weight, more preferably at least 50% by weight, preferably at least 75% by weight) is used. , or the total amount) of acidic water not recycled into the condensation column in this acrylic acid by extraction with an organic solvent to form an acrylic acid-containing organic extract from the acidic water into the organic acid. see solvent absorbs, subsequently separating the acrylic acid from the organic extract by stripping with a stripping gas and recycled the stripping gas loaded with acrylic acid in the condensation column.
- the recycling of the acrylic acid contained in the loaded stripping gas into the condensation column could also be carried out in a condensed out form. However, this condensed acrylic acid could also be combined with the crude acrylic acid taken from the condensation column for further purification thereof.
- the stripping gas charged with acrylic acid (or at least a subset thereof) is very particularly advantageously used to likewise strip off acrylic acid still present in a second stripping column in the bottoms liquid withdrawn from the condensation column (and only then into the Condensate return) before the bottoms liquid is sent for disposal.
- the loaded stripping gas of this second stripping is still subjected to a (countercurrent) rectification, as already described in WO 2004/035514 and in DE-A 103 32 758 (but with the direct use of residual gas as stripping gas) only then returned to the condensation column).
- the bottom space in the condensation column used in the process according to the invention is the space below the lowest separating internals (eg trays, packings and random packings, which are the countercurrent interface between those in the separation column increase guided phases) within the condensation column.
- the so-called bottoms liquid collects, which in particular comprises those components whose boiling point at normal pressure (1 atm) is above the boiling point of acrylic acid.
- acrylic acid boiling by-products such as maleic anhydride, minor components such as phenothiazine, which are added as polymerization inhibitors, but also secondary products which form in the course of the fractional condensation of the product gas stream of the Partialoxidati- on from the components thereof only.
- secondary products include, in particular, free-radical polymers of acrylic acid which form undesirably in spite of the polymerization inhibition.
- higher molecular compounds fertilize that form by condensation reactions of different components of the product gas mixture of the partial oxidation.
- the bottom liquid of the condensation column also contains by-products which boil only slightly higher than acrylic acid at atmospheric pressure (eg benzaldehyde, furfurals and maleic anhydride), it is advantageous to store the stripping gas of this second stripping (before, for example, its recirculation into the Condensation column) additionally subject to a (countercurrent) rectification (ie, a countercurrent of reflux liquid) (expediently in the same column), resulting in an improved purity of the loaded with acrylic acid second stripping gas.
- a (countercurrent) rectification ie, a countercurrent of reflux liquid
- the recycling of the first laden stripping gas and / or the second laden stripping gas into the condensation column does not necessarily have to be effected directly.
- the first loaded stripping gas and / or the second loaded stripping gas can also be at least partially or completely mixed with the product gas mixture and the resulting gas mixture fed into the condensation column.
- the combination can be carried out before, during and / or after an optionally be carried out direct and / or indirect cooling of the product gas mixture of the gas phase partial oxidation.
- the stripping gas loaded with acrylic acid from the extract stripping is called “first laden gas” and the (preferably rectified) stripping gas from the (condensation column) bottom stripping charged with acrylic acid is called “second laden gas” (correspondingly) the extract stripping is referred to as “first stripping” and the sump stripping is termed “second stripping”, etc.).
- first laden gas the stripping gas loaded with acrylic acid from the extract stripping
- second laden gas the (preferably rectified) stripping gas from the (condensation column) bottom stripping charged with acrylic acid
- second stripping the extract stripping
- the first loaded gas leaves the extract stripping at a pressure of 1, 5 to 3.5 bar, often 2 to 3 bar, z. B. 2.5 bar. Its temperature is usually about 10 0 C below the temperature at which the extract is applied to the first stripping. Typical temperatures of the first laden gas are 65 to 95 0 C, often 75 to 95 0 C, or 85 0 C.
- the second stripping (including the rectification of the stripping gas) are basically all columns with separating internals into consideration, with possible installations z.
- packs packing and / or floors are.
- rotary columns which spray the return liquid in drops.
- the second stripping column used is preferably one which only has bottoms and / or packs.
- soils dual-flow trays are advantageously used, and with particular advantage the stripping column contains exclusively dual-flow trays as separating internals.
- each dual-flow tray can be flush with the walls of the second stripping column. But he can also be connected via webs with these. As the load of the second stripping column decreases, dual-flow trays run dry, in contrast to hydraulically sealed cross-flow trays.
- the dual-flow bottom stripping column which can be used for the second stripping can contain up to 60 dual-flow trays.
- these have an opening ratio (the ratio D: U, formed from the area fraction of the soil, which is permeable to the cleavage gas (D) and the total area of the soil (U)) of 10 to 20%, preferably from 10 to 15% up.
- the passage points of the dual-flow trays are preferably circular holes with a uniform inside diameter of the circle diameter.
- the latter is suitably 10 to 30 mm.
- the circular holes above the individual dual-flow trays are preferably evenly arranged in a strict triangular division (see DE-A 102 30 219).
- the punching burr of the through-openings punched out in the dual-flow trays in the second stripping column preferably points downwards.
- the dual-flow trays are arranged equidistantly in the second stripping column.
- the ground clearance is 300 mm to 500 mm. Also favorable according to the invention is a ground clearance of 400 mm.
- the feed of the bottom liquid to be stripped (it may have previously been used for the direct cooling of the product gas mixture of the partial oxidation and / or supplemented by the high boiler fraction taken off in the lower region of the condensation column) to the fourth to tenth dual-flow tray of the second stripping column (counted from below).
- the bottom temperature in the second stripping column is advantageously maintained at 150 to 190 0 C, preferably at 160 to 180 0 C.
- the working pressure in the second stripping column will normally be> 1 to 3 bar, often 1.5 to 2.5 bar.
- the energy input required in the second stripping column is advantageously fed by means of an external forced-circulation tube bundle expansion evaporator, fed to the bottom liquid withdrawn from the second stripping column for the purpose of overheating, and subsequently returned to the second stripping column superheated (see DE-A 103 32 758).
- an external forced-circulation tube bundle expansion evaporator fed to the bottom liquid withdrawn from the second stripping column for the purpose of overheating, and subsequently returned to the second stripping column superheated (see DE-A 103 32 758).
- a pure forced circulation evaporator or a natural circulation evaporator, z As a Robert evaporator, are used, which can also be integrated into the second stripping.
- the second stripping column itself (as well as the condensation column and the first stripping column) is suitably thermally insulated from the environment in terms of application technology.
- the generation of the return liquid can be done by direct and / or indirect cooling.
- the method of direct cooling is advantageously used.
- the gas passing through the last (theoretical) tray is fed to a quenching device, which, for. B. via a chimney tray of the separating internals of the second stripping column separated into the second stripping integrated (can be placed on the separating effective part) may be.
- the quench device can also be spatially outsourced from the second stripping column. Any such device known in the art (e.g., spray scrubbers, venturi scrubbers, bubble columns or other sprinkler-type apparatus) may be used as such a quench apparatus, preferably using Venturi scrubbers or spray coolers.
- a DC device eg one with baffle plate nozzle
- indirect cooling of the quench liquid it is usually passed through an (indirect) heat exchanger or heat exchanger.
- all common heat exchangers or heat exchangers are suitable.
- Suitable cooling media are air in the corresponding air cooler and cooling liquids, in particular water (eg surface water), in the other cooling devices.
- quench liquid 0 a portion of the condensate formed during quenching is used as the quench liquid (hereinafter also referred to as "quench liquid 0") .
- the other portion of the condensate formed during quenching is essentially recycled to the top (theoretical) tray of the second stripping column a small portion of the condensate can also be branched off at this point and fed to and combined with the bottoms liquid taken from the condensation column, a portion of the resultant mixture being able to still be used later in this document.
- leading quench liquid 1 are used; another part of this mixture forms the feed to the second stripping column and the remaining (comparatively small) residual amount of this mixture is combined with the remaining portion of the condensate and forms in this union then partly the remindlaufmud- speed on the top (theoretical) bottom of the second stripping column and the other part the quench liquid 0).
- the temperature of the quench liquid is 0 immediately before its use for quenching about 40 0 C, whereas the reflux liquid is recycled in typical manner with about 80 0 C.
- the mass ratio of recirculated return liquid to the second stripping column supplied bottoms (and optionally high boilers) liquid is typically> 2. Often it is 2 to 10 and preferably 4 to 8.
- the second stripping column (like all other apparatuses in which liquid phases having appreciable acrylic acid contents are conducted) must be operated in a polymerization-inhibited manner.
- polymerization inhibitors in principle all known in the art polymerization inhibitors can be used for this purpose.
- Examples include as such phenothiazine (PTZ) and p-methoxyphenol (MEHQ). Often these two are used in combination. Conveniently, they are added dissolved in a pure acrylic acid. MEHQ is preferably added as a melt.
- PTZ phenothiazine
- MEHQ p-methoxyphenol
- the polymerization inhibition of the quench circle 0 and the second stripping column can be accomplished by adding a subset of the polymerization-inhibited, polymerization-inhibited, d. h., containing polymerization inhibitor bottoms liquid (and optionally high boiler fraction) is added.
- the quench liquid contains 0 such. B. 0.01 to 0.1 wt .-% MEHQ and 0.01 to 0.5 wt .-% PTZ.
- the molecular oxygen usually still present in the first loaded gas (which acts as stripping gas for the second stripping column) further promotes the polymerization inhibition.
- a subset of the sump liquid arising in the bottom of the second stripping column is continuously discharged and disposed of.
- an organic solvent for.
- methanol the highly volatile residue is kept fluid when needed.
- other hydrophilic organic liquids such as ethanol or in WO 2004/035514 Recommended (or mixtures of such liquids) are used.
- Ausschleusestrom at about 10 or 20 to 30 wt .-%. From an application point of view, the outflow stream from the forced circulation expansion steamer, which supplies the second stripping column with energy, overheated leaving stream branched off. He is degassed and z. B. diluted with methanol z. B. the residue combustion supplied.
- the second charged gas leaving the quench circle 0 (typical temperatures 70 ° C. to 90 ° C.) can now be recirculated as such to the condensation column (it should be noted that in the second stripping column 1 kg was fed from the condensation column
- Bottom liquid typically 1 to 10 Nm 3 of first charged gas can be used as stripping gas, usually the liquid in the bottom of the second stripping column is in the boiling state).
- acrylic acid content is typically 15 to 20% by weight.
- the recycling of the acrylic acid contained therein into the condensation column could also take place in a condensed out form.
- such an acrylic acid condensate can also be combined with the crude acrylic acid taken from the condensation column for further purification thereof.
- the return of the second laden gas in the condensation column is preferably carried out below the first side draw (in principle, it can also in the direct cooling circuit of the product gas mixture of the gas phase partial oxidation into it).
- This recirculation can be immersed in the bottoms liquid as well as above the liquid level of the bottom liquid and below the first (theoretical) bottom of the condensation column.
- the bottom space of the condensation column contains a mist eliminator (for example a centrifugal droplet separator) in order to ensure entrainment of sump liquid drops by ascending flow
- the sump space can be separated by a first chimney tray from the lowermost separating insert.
- the residence time of the bottoms liquid fed to the second stripping column from the condensation column (optionally including removed high-boiling fraction) in the second stripping apparatus should usually be 0.5 to 4 hours (for a high-boiling-ether component finally discharged).
- WO 2004/035514 recommends.
- the bottom of the second stripping column can also aids such Komad ® 313 the MOL (Hungary) and / or dispersing agents (for. Example those of EP-A 1062197 and / or US-A 3,271, 296) such.
- tertiary amines for example trimethylamine, triethylamine, N, N, N'-tetramethyl-1,6-hexanediamine and pentamethyldiethylenetriamine
- the additional amounts may be from 0.1 to 10% by weight, based on the bottom of the second stripping column. Since these are already advantageously high-boiling substances or these additives form with acrylic acid, they are not stripped off.
- the advantage of the described procedures according to the invention is u. a. in that they allow an increase in the yield of acrylic acid without substantially reducing the purity of the crude acrylic acid removed via the first side draw. This applies not least to the stripping variant described, even if residual gas from the condensation column is used for the purpose of stripping as described.
- the purity of both the first and the second laden gas with respect to secondary components which interfere with subsequent use of the acrylic acid is so good that (of the respective total or partial) also only from a subset of the first and / or second loaded gas) the acrylic acid contained therein also directly from the gas phase of the first or second loaded gas out into the aqueous solution of a metal hydroxide (eg an alkali metal hydroxide and / or alkaline earth metal hydroxide, eg NaOH, KOH, Ca (OH) 2 and / or Mg (OH) 2) was added (z. B.
- a metal hydroxide eg an alkali metal hydroxide and / or alkaline earth metal hydroxide, eg NaOH, KOH, Ca (OH) 2 and / or Mg (OH) 2
- aqueous sodium hydroxide solution for example, resulting aqueous solution of sodium acrylate z.
- B. directly for the production of water superabsorb Schlierenden polymers by appropriate radical polymerization (see also WO 2003/014172) can be used.
- the acrylic acid-containing product gas mixture of a heterogeneously catalyzed gas phase partial oxidation of C3 precursors of acrylic acid with molecular oxygen to catalysts in the solid state z Typically, the following contents (especially when used as C3 precursor propylene) have:
- propylene 0 to 1 wt .-% of propylene, and the remainder essentially ent-nerte gases such.
- nitrogen carbon monoxide, carbon dioxide, methane and / or propane.
- the product gas mixture based on the acrylic acid present, usually contains> 0.005 mol%, frequently> 0.03 mol%, of furfurals. As a rule, however, the furfural content obtained in this way is ⁇ 3 mol%.
- the gas phase partial oxidation itself can be carried out as described in the prior art. Starting from propylene, the gas phase partial oxidation z. B. in two successive oxidation stages are carried out, as described in EP-A 700 714 and in EP-A 700 893. Of course, however, the gas phase partial oxidations cited in DE-A 197 40 253 and in DE-A 197 40 252 may also be used.
- the propylene-gas phase partial oxidation is preferably carried out as described in DE-A 101 48 566.
- a propylene source to polymer grade propylene or chemical grade propylene according to DE-A 102 32 748 can be used.
- the C3 precursor used is propane, the partial oxidation can be carried out as described in DE-A 102 45 585.
- gas phase partial oxidation can also be carried out as described in US 2006/0161019, WO 2006/092410, WO 2006/002703, WO 2006/002713, WO 2005/1 13127, DE-A 10 2004 021 763, EP-A 1 61 1 076, WO 2005/108342,
- the temperature of the gas phase partial oxidation leaving product gas mixture is 150 to 350 0 C, often 200 to 300 0 C, sometimes up to 500 0 C.
- the hot product gas mixture is then cooled in a quenching device 1 by direct cooling usually to a temperature of 100 to 180 0 C, before it, in terms of application advantageous together with the used quench liquid 1, for the purpose of fractional condensation preferably in the lower section (Preferably, the lowest, eg., The bottom space) of a separating internals containing condensation column is passed.
- condensation column internals in particular trays, packings and / or random packings. From the bottoms, bubble-cap trays, sieve trays, valve trays and / or dual-flow trays are preferred.
- the total number of trays is 20 to 100, often 20 to 80, and preferably 50 to 80.
- the condensation column is one which contains from bottom to top, first dual-flow trays and subsequently hydraulically substitutedich- ended crossflow trays (z. B. Thormann ® -floors) as separating internals, as the DE-A 102 43 625, DE-A 199 24 532 and DE-A 102 43 625 recommend.
- the number of dual-flow trays can be 5 to 60, often 25 to 45, and the number of hydraulically sealed crossflow trays also 5 to 60, often 30 to 50.
- Sauerbergbil- Phys (acrylic acid content of the reflux liquid from bottom to top considered usually ⁇ 15 wt .-%, or partially ⁇ _ 10 wt .-%) come as separating internals preferably valve trays into consideration, as it DE-A 199 24 532 and DE-A 102 43 625 describe.
- the quench liquid 1 For indirect cooling or heating of the quench liquid 1, it is preferably, but not necessarily, passed through a heat exchanger or heat exchanger, in particular during startup.
- a heat exchanger or heat exchanger In this regard, all common heat exchangers or heat exchangers are suitable. Preferred are shell-and-tube heat exchangers, plate heat exchangers and air coolers. Suitable cooling media are air in the corresponding air cooler and cooling liquids, in particular water, in the other cooling devices.
- quench liquid 1 z. B. from the bottom of the condensation column sump liquid withdrawn (optionally combined with led out of the quench O 0 condensate), or via a located near the side sump high pressure fraction or a mixture of such bottoms liquid and Schwersie- derfr forcing (especially if the sump space and the Optionally, only the portion of the quench liquid 1 removed from the bottom of the condensation column is passed over the above-mentioned heat exchanger Quench device 1 usually useful 90 0 C to 120 0 C.
- the discharge point for the quenched (or otherwise cooled or otherwise not cooled) product gas mixture of the catalytic gas phase partial oxidation (according to the invention as described preferably in admixture with Quenchlotkeit used for direct cooling 1) in the condensation column is advantageously in the bottom space of this column, with Advantage contains a Zentrifugaltropfenab- integrated and is usually separated by a first chimney tray from the lowest separating effective insert (in terms of application suitably passes in this case via a connecting line or overflow continuously high boiler fraction in the bottom of the condensation column).
- this is the first dual-flow tray of a first series of suitably equidistantly arranged, dual-flow trays.
- the chimney tray acts as a collection tray from which condensate (high boiler fraction) is continuously withdrawn and fed as part of the quench liquid 1 into the quench apparatus 1 or into the sump space.
- the first series of dual-flow trays is completed by a second chimney tray. From this second collecting tray crude acrylic acid is continuously withdrawn in the first side draw as medium boiler fraction, preferably a Purity of> 90 and> 95 wt .-%.
- this crude acrylic acid it is expedient to feed this crude acrylic acid to further distillation (rectification) and / or crystallization purification steps and at least some of the bottom liquids and / or mother liquors obtained in the course of this distillation (rectification) and / or crystallization below the first side draw, but above the first side draw Trap bottom in the condensation column.
- this recycling is carried out integrated with heat. That is to say, cold mother liquor to be recycled is passed through one or more indirect heat exchangers connected in series (for example spiral heat exchangers) in order to cool the crude acrylic acid which is to be further purified by crystallization and removed in the heat exchanger on the opposite side. At the same time this causes heating of the mother liquor.
- two series-connected plate heat exchangers are used for this purpose.
- the crude acrylic acid withdrawn (as the medium boiler fraction) will be subjected to crystallization for further purification.
- the crystallization process to be used is subject to no restriction in principle.
- the crystallization can be carried out continuously or batchwise, in one stage or in several stages to any degree of purity.
- water can be advantageously added to the crude acrylic acid to be purified by crystallization before crystallization (as a rule, it contains up to 20% by weight or up to 10% by weight, usually up to 10% by weight, based on the amount of acrylic acid present to 5% by weight of water).
- a water addition can be omitted, since the aldehydes are able to take over the function of the water in this case.
- the water is added in the form of sour water in a particularly advantageous manner. This leads to an increase in the yield of pure acrylic acid.
- esterification-compliant eg for the production of n-butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate and ethyl acrylate
- acrylic acid pure -> 98 wt .-%
- this crystallization stage is carried out as suspension crystallization, as described in column 10 of DE-A 199 24 532 or in example 1 of DE-A 102 23 058 (for example in a cooling disk crystallizer as in WO 2006/111565 described).
- the resulting in the suspension crystallization acrylic acid crystals have a cubic to cuboid appearance.
- the thickness D of the crystals is usually in the range of 20 to 600 ⁇ m, often 50 to 300 ⁇ m.
- the length L of the crystals is usually in the range of 50 to 1500 ⁇ m, often 200 to 800 ⁇ m.
- the separation of the suspension crystals from the remaining mother liquor can take place in the case of acrylic acid suitable for esterification on a centrifuge (for example a 2-stage or 3-stage pusher centrifuge), the separated crystals being advantageously deposited on the centrifuge by means of melted pure crystals getting washed. Separating the suspension crystal lisate from the remaining mother liquor by means of a wash column, for.
- a centrifuge for example a 2-stage or 3-stage pusher centrifuge
- a melt wash column eg., Such as according to WO 01/77056, or DE-A 101 56 016, or DE-A 102 23 058, or as in WO 2006/1 11565, WO 04/35514, WO 03/41833, WO 02/09839, WO 03/41832, DE-A 100 36 881, WO 02/55469 and WO 03/78378
- a single crystallization stage superabsorbent acrylic acid purity> 99.7 or> 99.9 wt .-%), ie, acrylic acid, which is suitable for the production of water superabsorbent or other polyacrylates, can be achieved.
- the total amount of the separated mother liquor is expediently returned to the condensation column.
- the crystallization can also be carried out as a fractional falling film crystallization, as recommended by EP-A 616 998.
- This can e.g. two, three or more (e.g., 2 to 4) purification steps include (in this case, suitable falling-film crystallizers may contain, for example, 1000 to 1400 crystallization tubes of 10 to 15 m in length and 50 to 100 mm in outer diameter).
- the separated in a higher purification stage mother liquor can be recycled to one of the previous purification stages.
- the mother liquor separated in the first purification stage is advantageously completely recycled to the condensation column.
- the mother liquors of the individual purification stages can also be recycled in their total amount into the condensation column.
- the pure product of the penultimate purification stage can be supplied completely or only partially to the last purification stage. If only a part of the feed is to mix the remaining amount usually with the pure product of the last cleaning stage to then consumption-friendly end product.
- the dual-flow tray located below the catch tray associated therewith.
- this base will also be fed into the mother liquor to be recycled to the condensation column.
- the mother liquor is usually heat-integrated, as already described, to a temperature which corresponds approximately to the withdrawal temperature of the crude acrylic acid.
- Another subset of the crude acrylic acid removed via the first side draw is advantageously heated by 10 to 15 ° C. by indirect heat exchange and recycled to the condensation column above the removal point, preferably immediately below the first subsequent dual-flow tray. This measure has a favorable effect on the acetic acid content of the withdrawn crude acrylic acid.
- a second series of expediently equidistant dual-flow trays follows, which is then separated from hydraulically sealed cross-flow mass transfer trays (eg Thormann trays or modified Thormann trays according to DE-A 102 43 625) ), which are expediently also arranged equidistantly, are replaced.
- the uppermost dual-flow tray may be equipped as a distributor tray. That is, he has z. B. overflow troughs with serrated overflow.
- the first of the Thormann bottoms from below is appropriately in terms of application technology such that the liquid draining from the bottom takes place via six drainage tubes designed as tubes. These tubes are hydraulically sealed against the headspace of the underlying dual-flow tray.
- the weir height of the six drainpipe decreases expediently in terms of application technology in the direction of flow of the crossflow faucet.
- the drainpipes are preferably uniformly distributed in the second half, more preferably in the last third of the bottom cross-section (opposite the inlet on the bottom).
- the hydraulic sealing takes place in a cup with an inclined overflow weir (45 ° C).
- the cross-flow mass transfer trays are closed with a third chimney tray (catch bottom).
- valve trays Above the third catch tray are, preferably double-flow, valve trays.
- the principle of valve trays and valve trays which can be used according to the invention can be found, for example, in Technical Progress Reports, Volume 61, Basics of Dimensioning of Column Trays, pp. 96 to 138. They are essentially characterized by the fact that over a wide load range they are one of the traversing steams respective load appropriate flow opening available.
- Ballast floors are preferably used according to the invention. That is, in the openings of the floor there are cages with openings closed by weights. Particularly preferred according to the invention are VV12 valves from the company Stahl, DE, Viernheim. In the valve floor space condenses essentially water and more volatile than water volatile components.
- the condensate obtained is sour water.
- the sour water is continuously removed in a second side draw.
- a portion of the withdrawn sour water is recycled to the top of the cross-flow mass transfer trays into the condensation column.
- Another part of the withdrawn sour water is cooled by indirect heat exchange and, appropriately split, also recycled to the condensation column.
- a cooled subset is in this case on the uppermost valve bottom (with a temperature of 15 to 25, preferably 20 to 25 0 C) and the other cooled subset to a between the third catch bottom and the uppermost valve bottom approximately centrally located valve bottom in the condensation column recycled (with a temperature of 20 to 35, preferably 25 to 30 0 C). From the remaining amount of acid removed, the amount of acrylic acid contained can be separated according to the invention.
- Part of the cooling (which may be accomplished via one or more indirect heat exchangers in series) is accomplished by passing the appropriate portion of sour water through the evaporator of the C3 precursor (e.g., the propylene evaporator) to remove liquid-stored C3 precursors, e.g. Propylene, for the heterogeneously catalyzed gas phase oxidation in the gas phase to convert.
- the C3 precursor e.g., the propylene evaporator
- liquid-stored C3 precursors e.g. Propylene
- the volatile than water volatile components are withdrawn in gaseous form at the top of the condensation column as the residual gas (or residual gas mixture) and normally returned at least partially as a diluent gas (recycle gas) in the gas phase partial oxidation.
- the residual gas mixture is previously overheated by indirect heat exchange.
- the non-recirculated part of the residual gas mixture is normally supplied to the combustion.
- Part of the (preferably compressed) residual gas mixture is, as already described, advantageously used as stripping gas for the separation of acrylic acid from the extract and from the bottom liquid of the condensation column.
- the gas phase partial oxidation is carried out with an excess of molecular oxygen, so that the residual gas mixture and thus the first and the second stripping gas contain molecular oxygen, if residual gas mixture is used as such stripping gas.
- the acrylic acid used here is preferably a pure acrylic acid, as is produced in the further purification of the withdrawn crude acrylic acid.
- the pure acrylic acid produced in the context of the further purification by crystallization can be used. This solution is also useful for Pure product stabilization used.
- the sour water formation z. B. also be practiced behind a first condensation column (see, DE-A 102 35 847).
- a first condensation column see, DE-A 102 35 847.
- the sour water formation z. B. also be practiced behind a first condensation column (see, DE-A 102 35 847).
- from the then at the top of the first condensation column Textilsiedergasstrom expediently by direct cooling in a free internals (this can be integrated for the purpose of sour water formation in the condensation column, then such an internals free quenching z B. separated via a chimney tray from the top separating components within the condensation column) or internals containing downstream space (second column) by means of a quench liquid 2 essentially water condense.
- the condensate obtained is again the sour water.
- a portion of the acid water will then be recirculated in a meaningful way to increase the separation efficiency at the top of the first condensation column in selbige.
- Another portion of the sour water is indirectly cooled in an external heat exchanger and used as the quench liquid 2 and from the remaining amount of acid water, the acrylic acid can be extracted according to the invention again.
- Volatile constituents of the low-boiler stream in turn, form residual gas which is normally at least partially recycled as recycle gas into the gas-phase partial oxidation or used as stripping gas.
- the dual-flow trays expediently extend approximately up to the cross section in the condensation column from which the acrylic acid contents of the reflux liquid toward the top of the column are ⁇ 90% by weight, based on the Weight of the return liquid.
- the number of dual-flow trays is, as already stated, for the described preferred variant of the fractional condensation usually 25 to 45. Their opening ratio is suitably 12 to 25%.
- the dual-flow trays preferably have circular holes with a uniform circular diameter. The latter is suitably 10 to 20 mm. If necessary, the hole diameter in the condensation column can be tapered or enlarged from top to bottom and / or the number of holes can be reduced or increased (eg the hole diameter can be uniformly 14 mm and the opening ratio from top to bottom 17.4%). increase to 18.3%). However, the number of holes can also be constant across all dual-flow trays.
- the circular holes above the individual dual-flow trays are preferably uniformly arranged in a strict triangular division. orders (see DE-A 102 30 219).
- the punching burr of the passage openings punched out in the dual-flow trays in the condensation column preferably points downwards (unwanted polymerisation is thereby reduced).
- the number of hydraulically sealed cross-flow mass transfer trays following the dual-flow trays in the condensation column of the invention which is preferred according to the invention will, as already mentioned, generally be from 30 to 50.
- Their opening ratio is expediently 5 to 25%, preferably 10 to 20% (the opening ratio generally represents the percentage of the passage cross sections on the total cross section; it is quite generally expedient in the aforementioned range for the crossflow mass transfer trays which are preferably to be used).
- Single-flow cross-flow mass transfer trays are preferably used according to the invention.
- the number of hydraulically sealed crossflow trays for the preferred variant of the fractionating product gas mixture condensation is such that it corresponds to about 10 to 30, often 25 theoretical plates.
- Both the hydraulically sealed cross-flow trays and possibly also used valve trays have at least one downcomer. You can both both single-flow and multi-flood, z. B. be designed double-ended. They can have more than one downcomer even with a single-flow design. As a rule, the inlet shafts of the valve bottoms are also hydraulically sealed.
- the polymerization inhibition of the quench system 1 for the product gas mixture of the partial gas phase oxidation can be achieved both by polymerization inhibitors contained in the bottoms used for quenching (from the condensation column) and by polymerization inhibitors contained in the high boiler fraction (from the condensation column) used for quenching.
- Product gas mixture obtained by (preferably two-stage) heterogeneous partial oxidation of propylene to acrylic acid.
- the preferred one described above Variant of the method according to the invention in no way limits the general feasibility.
- both the first stripping gas and the second stripping gas advantageously contain molecular oxygen.
- the condensation column is optionally supplied with a liquid (different from the return liquid) absorption medium via a feed point located between its first side draw and its second side draw, its boiling temperature Ts at a pressure of 1 atm greater than or equal to Boiling temperature Tw of water at a pressure of 1 atm.
- a liquid different from the return liquid
- Ts Boiling temperature
- z. B. as described in EP-A 1 818 324.
- absorbents come z. B. higher boiling organic liquids into consideration.
- those organic liquids are those which are recommended in DE-A 103 36 386 and the cited in this document prior art as an absorbent.
- the absorbents recommended in EP-A 1 818 324 can also be used at this point.
- high-boiling (inert) liquid hydrophobic organic liquids are suitable as such absorbents, as are listed in EP-A 722 926, DE-A 44 36 243 and DE-A 103 36 386 (eg dimethyphthalate, diethyl phthalate and / or diphyl). These are z. B. liquids whose boiling point at atmospheric pressure (1 atm) is above the boiling point of acrylic acid and which consist of at least 70 wt .-% of such molecules, which are not polar outward
- absorbents include exemplified as Diphyl ® designated mixtures of diphenyl ether (70 to 75 wt .-%) and biphenyl (25 to 30% by weight) as well as the mixture of a mixture of 70 to 75 wt .-% of diphenyl ether and 25 to 30 wt .-% diphenyl and, based on this mixture, 0.1 to 25 wt .-% dimethyl phthalate.
- absorbents and aqueous liquids can be used.
- aqueous liquids are those which are recommended in EP-A 1 818 324.
- water belongs to these absorbents.
- the aqueous phase remaining in the extraction of acid water to be carried out according to the invention can also be used as such an aqueous absorption medium.
- the abovementioned addition of absorbent will have the purpose of deliberately increasing the proportion of certain secondary components contained in the crude acrylic acid led out of the condensation column via the first side draw reduce. It is therefore advantageous if the absorbent used itself contains these secondary components at most in a very small proportion by weight (preferably not at all).
- an aqueous absorbent it is e.g. B. favorable if its individual minor component weight portions are smaller than the respective corresponding of the sour water.
- aqueous absorbents eg of water
- aqueous absorbents eg of water
- a mixture of an aqueous and an organic liquid can also be used as such an absorbent.
- such a mixture can also be multiphase.
- the absorbent can advantageously be guided at the same height into the condensation column as the reflux liquid. Both can also be performed in a mixture in the condensation column.
- the temperature of the absorbent may vary over a wide range as it is fed to the condensation column. It can be both above and below the temperature of the return liquid. Often, the temperature of the absorbent in the interval ⁇ 20 0 C to the temperature of the reflux liquid manufacturers to be. Preferably, the temperature of the reflux liquid and the absorbent are the same.
- the crude acrylic acid removed via the first side draw contains parts of the absorbent used, they are generally separated off from the latter by the crystallization-type further purification of the crude acrylic acid described in this document. Otherwise, a co-used absorbent normally accumulates in the bottoms liquid discharged from the condensation column and can be reused as an absorbent after separation thereof in the manner described above.
- the mass flow of an absorbent conducted into the condensation column is 0 to 30%.
- the crystalline further purification of crude acrylic acid described in this document can also be applied to a crude acrylic acid obtainable according to the procedure described in DE-A 103 36 386 (in particular such a further purification according to claims 16 to 20) the present document).
- a further purification by crystallization can also be applied to any mixture of the two abovementioned types of crude acrylic acid. From such a procedure you will z. B. then make use of when the separation process of the invention and a separation process according to DE-A 103 36 386 are operated in parallel to separate acrylic acid from product gas mixtures of (optionally operated in parallel) heterogeneously catalyzed partial gas phase oxidation of C3 precursors of acrylic acid.
- the removal from the storage tank can be done continuously or clocked for this purpose. Normally, it is made in such a manner that the resulting crystallizate is in conformity with the specification (the crystallization design capacity is usually above the design capacity of crude acrylic acid preparation, but for a short time crystallization can be further purified above the crystallization design capacity).
- the present invention particularly includes the following embodiments:
- a process for the preparation of acrylic acid which comprises by heterogeneously catalyzed gas phase partial oxidation of at least one C3 precursor of acrylic acid with molecular oxygen in the solid state Catalyst at elevated temperature produces an acrylic acid, water vapor and secondary components containing product gas mixture, the temperature of the acrylic acid, water vapor and minor components containing product gas mixture optionally reduced by direct and / or indirect cooling, and the acrylic acid, water vapor and secondary components containing product gas mixture then in a equipped with separating internals Condensation column passes within the condensation column can rise in itself and thereby fractionally condensed and on a first, above the feed point of the product gas mixture in the Kondensations- onskolonne, side draw a water and minor components entreichert containing crude acrylic acid as the target product and a second, above the first side draw, liquid phase withdrawal (preferably a side draw) still acrylic acid and secondary components containing acidic water and the Kop f of the condensation column a lower than water-boiling secondary components containing residual
- a process according to embodiment 1 or 2 characterized in that in at least 25 wt .-% of not recycled to the condensation column acidic water contained in this acrylic acid by extraction with an organic solvent to form an acrylic acid-containing organic extract in the organic solvent receives, subsequently the acrylic acid from the organic extract using at least one separating off the thermal separation process and recirculating the acrylic acid separated from the extract either into the condensation column or feeding it to the crude acrylic acid for further purification and / or into the aqueous solution of a metal hydroxide.
- organic solvent contains at least one diester of an aliphatic or aromatic dicarboxylic acid containing 5 to 20 C atoms and an alcohol having 1 to 8 C atoms.
- a method characterized in that one separates the acrylic acid from the organic extract by stripping with a first stripping gas and used thereby resulting charged with acrylic acid first stripping gas as a second stripping gas thereto in order to freeze acrylic acid still contained in bottoms liquid discharged from the condensation column and to recycle the second stripping gas charged with acrylic acid into the condensation column and / or to take up the acrylic acid contained in the second stripping gas in the aqueous solution of a metal hydroxide.
- Absorbent is supplied whose boiling temperature Ts at a pressure of 1 atm greater than or equal to the boiling temperature Tw of water at a pressure of 1 atm.
- reaction gas mixture to be supplied to each of the three tandem reactor reactor lines is in each case a mixture of cycle gas and chemical grade propylene, to which primary air is subsequently added.
- the mix is accomplished by a static mixer.
- the product gas mixture (177184 kg / h) is operated in a co-current
- Spray cooler (quench 1) by direct cooling to a temperature of 107.3 0 C. cooled.
- the liquid (quench liquid 1) to be used for the direct cooling of the product gas mixture is a partial amount of a mixture 1 of bottoms liquid taken from the bottom of the condensation column described below and a small amount (251 kg / h) of taken from the quench circle 0 Condensate.
- the spray cooler of Quenchnikes 1 for direct cooling of the product gas mixture is fed with the aforementioned temperature only an amount of 458 m 3 / h. 3137 kg / h are fed as feed to the second stripping column and 1 195 kg / h are fed to the quench circuit 0 in order to inhibit the quench liquid 0 and the reflux liquid to be led to the uppermost tray of the second stripping column against undesired polymerization.
- the resulting from the direct cooling mixture of cooled to 107.3 0 C product gas mixture and non-evaporated quench liquid 1 is fed as such in the bottom of the condensation column.
- the pressure in the sump space and in the quench 1 is 1, 50 bar.
- the internal diameter of the condensation column is 6.5 m in the area of the Thormann trays and 6.0 m otherwise.
- the second stripping column contains 50 dual-flow trays as separating internals.
- the second stripping column is thermally insulated from the environment.
- the inner diameter of the second stripping column is uniformly 2.4 m across all dual-flow trays.
- the dual-flow trays are arranged equidistantly (400 mm) in the second stripping column. Their opening ratio is uniformly 12%.
- the feed of the 3137 kg / h of the mixture 1 takes place with a temperature of 105.2 0 C on the eighth dual-flow soil (from below).
- the energy is supplied to the second stripping column by means of an external forced three-flow tube bundle expansion evaporator (see Basic Operations Chemical Process Engineering, 4th Edition, Steinkopff Verlag Dresden, 1974, p 434).
- This 271650 kg / h are fed to from the bottom of the second stripping column with a temperature of 151, 7 0 C and a pressure of 1, 655 bar withdrawn bottoms liquid, which has the following contents:
- first laden gas 17424 kg / h from the first stripping column, which has the following contents:
- the mixture has the following contents:
- a Zentrifugaltropfenabscheider is integrated, which prevents drops of the bottoms liquid are entrained from the sump space upwards.
- the bottom space of the condensation column is at a column height (like all heights from the bottom of the sump) of 7.80 m through a first collecting bottom (collecting bottom, chimney trays with 16 equally distributed roofed chimneys, chimney diameter: 600 mm, chimney height : 1 m) completed.
- the collecting base is double-walled with a 2 ° drop inwards and with a central extraction cup and drainage nozzle (DN ⁇ 200).
- the free gas cross section is about 30%.
- the high boiler fraction has the following contents at a temperature of 99.8 ° C and a pressure of about 1, 50 bar:
- the bottom temperature is 104.9 0 C and the bottom pressure (at the liquid level) is 1, 51 bar.
- the first of the first 15 dual-flow trays is located 2.0 m above the first trapping floor. These dual-flow trays (number of holes uniformly 33678) are equidistant with a ground clearance of 380 mm.
- the passage openings consist of circular openings of the uniform diameter of 14 mm, wherein the punching burr in the separation column points downwards.
- the arrangement of the centers of the passage circles follows a strict triangular division. The nearest distance between two circle centers is 24.5 mm.
- the fifteenth dual-flow floor acts as a distributor floor.
- the column wall between the second collecting tray and the fifteenth dual-flow tray contains two plug-in tubes (DN ⁇ 150) with 45 outlet holes (diameter: 15 mm) per plug-in tube.
- the first series of dual-flow trays is equipped with a second collecting bottom (collecting bottom, chimney floor with 16 evenly distributed roofed fireplaces, chimney height approx.1, 70 m, central extractor with drain (DN ⁇ 250), free gas cross-section of ⁇ 30 %), which is located 1, 50 m above the last dual-flow floor.
- a second collecting bottom collecting bottom, chimney floor with 16 evenly distributed roofed fireplaces, chimney height approx.1, 70 m, central extractor with drain (DN ⁇ 250), free gas cross-section of ⁇ 30 %), which is located 1, 50 m above the last dual-flow floor.
- the sour water has the following contents:
- the respective cooling medium is passed in countercurrent to the crystallizing mixture through the respective crystallizer from the cooling disk to the next to the cooling disk, which is at an equidistant distance of 30 + 1 cm in a row That is, the respective cooling medium is divided in the form of two parallel streams over the cooling plates of the respective crystallizer out the numerically straight cooling plates, the other current passes through the numerically odd cooling plates (numbering of the cooling disks in the flow direction starting with 1).
- the respective cooling medium is divided in the form of two parallel streams over the cooling
- Coolant quantity amounts to a total of 180-220 t / h (metric tons) per crystallizer, ie, per stream 90-1 10 t / h.
- the pressure loss per cooling disk is 60 to 100 mbar.
- the inlet temperature of the cooling medium (the brine) is +2.5 to +3 0 C.
- the outlet temperature is 2.5 0 C higher.
- the wall thickness of the cooling surfaces made of stainless steel is 4 mm.
- the heat transfer coefficient is on the side at about 1500 to 2500 W / (m 2 »K).
- the heat transfer coefficients are usually 380 to 420 W / (m 2 »K).
- the specific cooling capacity is 1, 5 + 0.2 kW / m 2 cooling surface.
- the dehydrated crude acrylic acid is continuously fed from back to front through the respective crystallizer (pumped or overflow controlled).
- the single-phase, drained crude acrylic acid thickened (residence time 2.5 h) to a two-phase, acrylic acid crystals as solid phase-containing suspension of a temperature of 7 to 8.5 ° C and a solids content at the outlet of about 25 wt .-%.
- the mass density of the suspension is usually 11 10 to 11 15 kg / m 3 .
- the speed of the wiper is 5 to 6 revolutions per minute.
- a hollow profile eg, in the simplest embodiment, a pipe
- a second heat carrier eg likewise water / glycol mixture
- the wipers are preferably segmented in the radial direction (4 segments). The specific contact pressure of the wiper is in the installed state perpendicular to the cooling surface at 3 to 5 N per cm active wiper edge length.
- the shaft drives paddles (expediently two each in symmetrical arrangement between two cooling disks and before the first and last cooling disks), which effect an improved mixing.
- the suspension In the conveying direction of the suspension rear part of the respective crystallizer (preferably behind the last cooling disk), the suspension is attached via a connected pipe (expediently immersed; alternatively, the suspension can flow via an overflow weir into a stirred collecting tank, from which the washing columns are fed) to hydraulic melt wash columns, as described in EP-A 1 272 453, EP-A 1 448 283, WO 03/041833, EP-A 1 305 097,
- the washing column diameter is 1.4 m.
- the control flow pump is also designed as a centrifugal pump with control valve.
- the control flow amount used to control a wash column is 5 to 60 t / h, usually 8 to 30 t / h. In some cases, it is possible to operate the respective scrubbing column without control flow if the amount of liquid supplied with the suspension is already sufficient for the transport of the crystal bed.
- Typical ratios of effective transport pressure difference to effective wash pressure difference are 1, 1 to 3, usually 1, 2 to 1, 8.
- the blade speed is usually at values of 5 to 10 per minute.
- the temperature in the melt circuit is normally 13 to 16 ° C.
- the detection of the filtration front is carried out according to DE-A 10 2005 018 702 via two pressure loss measurements taken over a ratio of different bed lengths.
- the wash front is controlled by means of temperature measurement in the crystal bed.
- the overall height of the crystal bed is due to regulation at 250 to 1500 mm, usually at 600 to 1 100 mm.
- the wash front is typically 100 to 200 mm above the knife.
- a centrifugal pump with istseiti- ger flushing of the shaft seal is (mechanical seal; performed twice, with 15 - (30 0 C chilled barrier medium water / glycol mixture)) or a magnetically coupled pump with increased sliding bearing flushing.
- the circulation rate in the respective melt circuit is 10 to 15 m 3 / h per ton with the knife removed purified crystallization sat.
- the melt cycle is stabilized column-specifically with 200 to 300 ppm by weight of MEHQ, or with 40 to 70 ppm by weight of MEHQ, or with 100 to 300 ppm by weight of PTZ.
- the crystals separated on the 2nd or 3rd stage of the centrifuge are washed with 0.15 to 0.3 kg of washing liquid per kg of crystallizate.
- Temperature of the washing liquid is 15 to 30 0 C, preferably at 20 to 30 0 C.
- the solids discharge shaft of the centrifuge is rinsed with tempered to 15 to 30 0 C rinsing liquid. Rinsing and washing liquids are preferably melted, separated off via the centrifuge and washed crystals. To avoid deposits and
- Encrustations it is expedient to temper the centrifuge housing, the suspension feed tube and the Waschillonkeitszu Foodrohr to a temperature> 15 0 C and ⁇ 40 0 C.
- the product space of the centrifuge is expediently rendered inert with nitrogen or with a mixture of air and nitrogen.
- the shaft seal is flushed with gas (eg nitrogen or a mixture of air and nitrogen) or with water.
- the separated in the wash columns mother liquor is first moved into a heatable collection container and from there into a tank. From this, it is (as already mentioned) thermally integrated heated to 90 0 C and in an amount of 72716 kg / h together with 18474 kg / h at the second collecting bottom removed crude acrylic acid on the fifteenth dual-flow tray of the condensation column ( counted from below).
- the composition of this recycled mother liquor is as follows:
- the bottom one of the Thormann trays is one in which the liquid draining from the bottom is drained through six downcomers formed as tubes. These tubes are hydraulically sealed against the headspace of the underlying dual-flow tray.
- the weir height of the six drainpipes decreases in the flow direction of the cross flow meter.
- the hydraulic seal has idle openings with baffle plate.
- the drain pipes are evenly distributed in the last third of the floor cross-section (opposite the inlet on the floor). The hydraulic sealing takes place in a cup with an inclined overflow weir (45 °).
- the Thormann trays are designed such that in each case an opposite flow direction of the liquid is generated by the arrangement of the driving slots in the hoods of the Thormannn-bottoms in successive transverse flow direction troughs.
- the opening ratio of Thormann floors is 14%.
- the ratio of chimney area to slot exit area is 0.8.
- the chimney height and the height of the drain weir are 40 mm.
- the ground clearance of the bell (distance between lower edge of slot and bottom) is 10 mm.
- the slot height is 15 mm.
- the angle between flared slot and longitudinal edge of the hood is 30 degrees.
- the length of the longitudinal edge of the hood is a maximum of 800 mm. In the edge region of the column, the hood length is reduced to up to 200 mm for reasons of adaptation to the roundness of the column.
- the distance between two cross-directional hoods is 66 mm.
- the drainage area of the downcomer is 1, 5% related to the cross-sectional area of the floor.
- the width between the two lower longitudinal edges of a hood is 64 mm.
- the separation column begins to conically constrict again. 700 mm above the uppermost Thormann bottom, this constriction is completed and the inside diameter of the column has shrunk back to 6.00 m.
- the sour water has, as already mentioned, the following contents:
- 6010 kg / h of the withdrawn sour water are supplied to the purpose of the still to be carried out according to the invention extraction of the extraction column.
- the pressure at the top of the column is 1.17 bar.
- the residual gas is heated to 38 0 C and then 110880 kg / h of this residual gas are compressed via a cycle gas compressor to a pressure of 2.9 bar, the temperature rises to about 160 0 C. 94553 kg / h of the compressed residual gas are recycled as recycle gas in the gas phase partial oxidation. 16327 kg / h of the compressed residual gas are fed to the first stripping column for the purpose of stripping the extract from the extraction of acid water and 59241 kg / h of the residual gas are sent for combustion.
- the extraction column for the extraction of acid water contains, as separating internals fitted flush with the edge, punched structured packings (height of a packing element: 200 mm) of stainless steel plates (material 1.4571) of the Montz-Pak B1-350 type having an overall active height of 10 m, which are arranged one above the other.
- the inner diameter of the extraction column is uniform across all packages 800 mm. Its height is 14 m.
- Palatinol® ® A is used as extracting agents.
- Bottom and top vessel of the column are expanded in diameter to 1100 mm in order to improve the phase separation in the bottom and to reduce the entrainment of extractant in the top of the column.
- a bed of plastic filling bodies eg polyethylene or Teflon
- coalescing aid in the head of the column is introduced as coalescing aid in the head of the column.
- the recycled extractant has the following contents:
- the specific mass of the sour water is 967.5 kg / m 3 .
- the extractant is also given through appropriate openings (holes of diameter 4 mm) having manifolds.
- the sour water forms the continuous phase and the extractant forms the droplet-shaped dispersed phase (droplet diameter lying in the range of 2 to 5 mm), which descends in the aqueous phase.
- the total amount of the extract is fed to the top of the first stripping column.
- the extract is heated by indirect heat exchange in a Platten Knoxaus- exchanger to 95 0 C.
- the heat transfer medium used is 5987 kg / h of bottoms liquid withdrawn from the first stripping column.
- the first stripping column contains 5 dual-flow trays and 15 Thormann trays as separating internals. Like the extraction column, the first stripping column is thermally insulated from the environment.
- the inner diameter of the first stripping column is uniform over all soils, 1.5 m. Its height is 14.5 m.
- the lowest 5 trays are designed as dual-flow trays and are arranged in the first stripping column equidistant (500 mm). Their opening ratio is uniformly 18%.
- the hole diameter of the dual-flow trays is uniformly 14 mm (hole arrangement corresponding to strict threefold division).
- Above the uppermost dual-flow tray are 15 single-flow Thormann trays arranged equidistantly (500 mm distance).
- the Thormann trays are designed such that in each case an opposite flow direction of the liquid is generated by the arrangement of the driving slots in the hoods of the Thormannn-bottoms in successive transverse flow direction troughs.
- the opening ratio (on the cross-section related gas passage area) is 14%.
- Residual gas (pressure ⁇ 2.9 bar, temperature - 160 0 C) led into the first stripping column, where it rises in countercurrent to the running in the stripping column extract.
- the temperature in the bottom of the first stripping column is approximately 155 0 C.
- 4931 1 kg / h bottoms liquid is removed from the bottom of the first stripping column continuously.
- 5987 kg / h of the withdrawn from the first stripping column bottom liquid be two-stage indirect heat exchange (the first stage in a heat integrated Plattenmaschiner- mestander against extract) at 50 0 C cooled and recycled to the head of the extraction column.
- 43324 kg / h from the first stripping column bottom liquid of removed are heated in an external Zwangsumlaufrohrbün- delentêtmentsverdampfer to 160 0 C and recycled to the bottom of the first stripping column.
- the extraction column and the first stripping column omitted.
- the appropriate amount of compressed residual gas is used for stripping the bottoms liquid withdrawn from the condensation column.
- the stream of crude acrylic acid taken off via the first side draw is 87307 kg / h and contains 96.863% by weight of acrylic acid.
- the amount of pure acrylic acid to be supplied to the storage tank is 16994 kg / h. Their purity is 99.736 wt .-% acrylic acid.
- the non-inhibited acid water had the following contents: 2.36% by weight of formaldehyde,
- the aqueous raffinate introduced at the top of the column still contained 0.8% by weight of acrylic acid and 2.9% by weight of acetic acid.
- the content of acrylic acid in the sour water could thus be depleted (based on the original weight content) by 93.3% by weight and that of acetic acid by 41% by weight.
- 0.2% by weight of diethyl phthalate was dissolved in the raffinate.
- the effluent at the top of the extraction column aqueous raffinate still contained 0.2 wt .-% acrylic acid and 2.4 wt .-% acetic acid.
- the content of acrylic acid in the sowing water could thus (relative to the original weight content) to
- Example 1 The procedure is as in Example 1. In addition to the reflux liquid (sour water), 1000 kg / h of water (additional absorbent) are fed into the condensation column together with the same and at the same temperature. The furfural content of the crude acrylic acid discharged from the second collecting tray as the first side draw from the condensation column thereby falls from 0.1642% by weight (value in Example 1) to 0.1225% by weight.
- Example 1 The procedure is as in Example 1. In addition to the return liquid (sour water), 5000 kg / h of water and water are used together with the same and at the same temperature. (additional absorbent) into the condensation column. The furfural content of the crude acrylic acid taken out of the condensation column as the first side draw from the second collecting tray drops thereby from 0.1642% by weight (value in Example 1) to 0.1125% by weight.
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Abstract
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Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
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KR1020097017686A KR101463278B1 (ko) | 2007-01-26 | 2008-01-24 | 아크릴산의 제조 방법 |
BRPI0806767-8A BRPI0806767A2 (pt) | 2007-01-26 | 2008-01-24 | processo para preparar ácido acrìlico |
CN2008800032325A CN101589015B (zh) | 2007-01-26 | 2008-01-24 | 生产丙烯酸的方法 |
RU2009132005/04A RU2472768C2 (ru) | 2007-01-26 | 2008-01-24 | Способ получения акриловой кислоты |
JP2009546752A JP5489726B2 (ja) | 2007-01-26 | 2008-01-24 | アクリル酸の製造方法 |
EP08708128.7A EP2114852B1 (de) | 2007-01-26 | 2008-01-24 | Verfahren zur herstellung von acrylsäure |
ZA2009/05851A ZA200905851B (en) | 2007-01-26 | 2009-08-24 | Method for the production of acrylic acid |
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US88677107P | 2007-01-26 | 2007-01-26 | |
US60/886,771 | 2007-01-26 | ||
DE102007004960.0 | 2007-01-26 | ||
DE102007004960A DE102007004960A1 (de) | 2007-01-26 | 2007-01-26 | Verfahren zur Herstellung von Acrylsäure |
US98861907P | 2007-11-16 | 2007-11-16 | |
US60/988,619 | 2007-11-16 | ||
DE102007055086.5 | 2007-11-16 | ||
DE102007055086A DE102007055086A1 (de) | 2007-11-16 | 2007-11-16 | Verfahren zur Herstellung von Acrylsäure |
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US (1) | US7566804B2 (de) |
EP (1) | EP2114852B1 (de) |
KR (1) | KR101463278B1 (de) |
BR (1) | BRPI0806767A2 (de) |
MY (1) | MY144918A (de) |
WO (1) | WO2008090190A1 (de) |
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JP2009286776A (ja) * | 2008-05-30 | 2009-12-10 | Rohm & Haas Co | 水性(メタ)アクリル酸の製造方法 |
DE102009027401A1 (de) | 2009-07-01 | 2010-02-18 | Basf Se | Verfahren der Abtrennung von Acrylsäure aus dem Produktgasgemisch einer heterogen katalysierten partiellen Gasphasenoxidation wenigstens einer C3-Vorläuferverbindung |
DE102008041573A1 (de) | 2008-08-26 | 2010-03-04 | Basf Se | Verfahren zur Auftrennung von in einem Produktgasgemisch einer partiellen heterogen katalysierten Gasphasenoxidation einer C3-Vorläuferverbindung der Acrylsäure als Hauptbestandteil enhaltener Acrylsäure und als Nebenprodukt enthaltenem Glyoxal |
DE102008054587A1 (de) | 2008-12-12 | 2010-06-17 | Basf Se | Verfahren zur Rückspaltung von in einer Flüssigkeit F enthaltenen Michael-Addukten, die bei der Herstellung von Acrylsäure oder deren Ester gebildet wurde |
DE102009045767A1 (de) | 2009-10-16 | 2010-08-12 | Basf Se | Verfahren der Inbetriebnahme eines Trennverfahrens zur reinigenden Abtrennung von Acrylsäurekristallen aus einer Suspension S ihrer Kristalle in Mutterlauge |
DE102010030279A1 (de) | 2010-06-18 | 2010-10-28 | Basf Se | Verfahren der Inbetriebnahme eines Trennverfahrens zur reinigenden Abtrennung von Acrylsäurekristallen aus einer Suspension S ihrer Kristalle in Mutterlauge |
DE102010001228A1 (de) | 2010-01-26 | 2011-02-17 | Basf Se | Verfahren der Abtrennung von Acrylsäure aus dem Produktgasgemisch einer heterogen katalysierten partiellen Gasphasenoxidation wenigstens einer C3-Vorläuferverbindung |
WO2011000808A3 (de) * | 2009-07-01 | 2011-03-10 | Basf Se | Verfahren der abtrennung von acrylsäure aus dem produktgasgemisch einer heterogen katalysierten partiellen gasphasenoxidation wenigstens einer c3-vorläuferverbindung |
WO2011045356A1 (de) | 2009-10-16 | 2011-04-21 | Basf Se | Verfahren der inbetriebnahme eines trennverfahrens zur reinigenden abtrennung von acrylsäurekristallen aus einer suspension s ihrer kristalle in mutterlauge |
DE102010042216A1 (de) | 2010-10-08 | 2011-06-09 | Basf Se | Verfahren zur Hemmung der unerwünschten radikalischen Polymerisation von in einer flüssigen Phase P befindlicher Acrylsäure |
JP2012502893A (ja) * | 2008-09-16 | 2012-02-02 | アルケマ フランス | グリセリンから生物起源のポリマーグレートのアクリル酸を製造する方法 |
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Also Published As
Publication number | Publication date |
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US20080183014A1 (en) | 2008-07-31 |
KR20090108099A (ko) | 2009-10-14 |
KR101463278B1 (ko) | 2014-11-18 |
EP2114852A1 (de) | 2009-11-11 |
EP2114852B1 (de) | 2015-09-23 |
MY144918A (en) | 2011-11-30 |
US7566804B2 (en) | 2009-07-28 |
BRPI0806767A2 (pt) | 2011-09-13 |
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