Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/58—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D11/00—Solvent extraction
  • B01D11/04—Solvent extraction of solutions which are liquid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D11/00—Solvent extraction
  • B01D11/04—Solvent extraction of solutions which are liquid
  • B01D11/0426—Counter-current multistage extraction towers in a vertical or sloping position
  • B01D11/043—Counter-current multistage extraction towers in a vertical or sloping position with stationary contacting elements, sieve plates or loose contacting elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J4/00—Feed or outlet devices; Feed or outlet control devices
  • B01J4/001—Feed or outlet devices as such, e.g. feeding tubes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds

Definitions

• the present invention relates to a liquid-liquid extraction process, as well as the use of this process in the context of the production of acrylic esters, and especially of methyl acrylate and ethyl acrylate.
• FR 2509294, US 5,435,892 and FR 2884514 provide examples of such processes for producing acrylic esters.
• the invention firstly relates to a liquid-liquid extraction process, comprising:
• the main inlet liquid flow and the liquid washing flow have a difference in density of less than or equal to 50 kg / m 3 and an interfacial tension of less than or equal to 3 dyn / cm;
• the extraction step is carried out in a packed contactor with a mass ratio at the inlet of the washing liquid stream / main liquid flow ranging from 0.3 to 0.5.
• the main liquid input stream is an organic stream and the liquid wash stream is an aqueous stream;
• the compound of interest is an acrylic ester, more particularly preferably methyl acrylate and / or ethyl acrylate; and the excess compound is an alcohol, preferably methanol and / or ethanol.
• the main inlet liquid stream contains from 0.5 to 30% of excess compound, preferably from 1 to 20% and more particularly from 2 to 10%; and / or the main liquid flow outlet contains less than 2000 ppm of excess compound, preferably less than 1000 ppm, and more particularly less than 750 ppm or less than 500 ppm.
• S represents the interfacial tension between the main inlet liquid flow and the washing liquid flow, expressed in N / m, and ⁇ representing the difference in density between the main inlet liquid flow and the washing liquid flow, expressed in kg / m 3 , where gc is the conversion of the gravitational constant (kg.m / Ns 2 ) and g the gravitational constant (9.83 m / s 2 ).
• the specific surface of the packing (loose or structured) of the contactor is greater than or equal to 200 m 2 / m 3 .
• the invention also relates to an acrylic ester production process comprising:
• the liquid-liquid extraction of the acrylic ester stream by an aqueous stream making it possible to collect a stream of purified acrylic ester, the liquid-liquid extraction being carried out according to the process described above, in which the liquid flow main input is the acrylic ester stream, the liquid wash stream is the aqueous stream, the main liquid output stream is the purified acrylic ester stream, the compound of interest is the acrylic ester, and the Excess compound is alcohol.
• the purified acrylic ester stream is further subjected to one or more distillation steps to remove additional organic compounds.
• the process comprises a decanting step at the outlet of the reactor, making it possible to collect an aqueous phase in addition to the acrylic ester stream, the aqueous phase being distilled to recover on the one hand an alcohol-rich fraction which is recycled to the reactor, and on the other hand a water-rich fraction which is used as a washing liquid stream in the liquid-liquid extraction step.
• the method comprises collecting an aqueous stream enriched in alcohol at the end of the liquid-liquid extraction step and combining it with the aqueous phase from the reactor.
• the subject of the invention is also an acrylic ester production plant comprising:
• a liquid-liquid extraction unit comprising a packed contactor, fed by the acrylic ester collection line as well as by a washing liquid flow supply line;
• the washing liquid flow expressed in kg / m 3
• gc being the conversion factor of the gravitational constant (kg.m / Ns 2 ) and g the gravitational constant (9.83 m / s 2 ).
• the purified acrylic ester collection line feeds one or more distillation units.
• the installation comprises:
• a hydroalcoholic distillation unit supplied by the aqueous phase collection line and optionally furthermore by an alcohol-enriched aqueous stream collection line from the liquid-liquid extraction unit, the flow supply line; washing liquid being connected at the outlet of the hydroalcoholic distillation unit;
• an alcohol-rich fraction collection line connected at the outlet of the hydroalcoholic distillation unit and supplying the reactor.
• the alcohol supply line is a methanol feed line or an ethanol feed line.
• the present invention overcomes the disadvantages of the state of the art. More particularly, it provides a means for recovering unreacted alcohol at the outlet of a more efficient acrylic ester production reactor.
• the inventors have in fact discovered that, when the liquid flows in contact in a liquid-liquid extraction unit have a small difference in density and a low interfacial tension, the use of such a packed contactor is more advantageous than that of a conventional contactor with mechanical agitation, in that it offers higher productivity (with similar extraction performance) - it being specified that other types of contactors, such as centrifugal contactors for example, have the disadvantage of being more complex and therefore more expensive.
• Liquid streams having the aforementioned properties present a particular difficulty of treatment because the separation tends to be inefficient, due to a relatively high droplet size (greater than 0.6 mm). In particular, there has been a tendency for clogging in mechanically agitated contactors, except for using low flow rates.
• the invention makes it possible to use a smaller and less expensive contactor in order to achieve the desired productivity and the desired specifications for the residual alcohol content in the product stream.
• Figure 1 schematically shows an acrylic ester production plant according to one embodiment of the invention.
• FIG. 2 illustrates an exemplary packed contactor that can be used in the context of the invention.
• the drawing on the left is a sectional view of the contactor in a vertical plane.
• the drawings on the right are detailed views of the device (cut in a vertical plane at the top and in a horizontal plane at the bottom).
• liquid-liquid extraction process of the invention is described with reference to a process for producing acrylic ester.
• an acrylic ester production plant comprises a reactor 4.
• the reactor 4 is fed by an acrylic acid supply line 2, an alcohol supply line 3 and a catalyst supply line 1.
• the alcohol is methanol.
• the alcohol is ethanol.
• a mixture of methanol and ethanol is also possible.
• the catalyst can be used for example sulfuric acid, or an organic sulfonic acid, such as methanesulfonic acid, para-toluene sulfonic acid, benzene sulfonic acid, dodecyl sulfonic acid, or their mixtures.
• the heavy products are eliminated via a heavy product bleeding collection 5.
• an acrylic ester stream is recovered at the outlet of the reactor 4 via an acrylic ester collection line 8; and on the other hand an aqueous phase (also containing a portion of the unreacted alcohol) via an aqueous phase collection line 6.
• the acrylic ester stream comprises acrylic ester as "compound of interest” (within the meaning of the invention), as well as by-products, contaminants and unreacted reagents, and in particular the alcohol compound mentioned herein. above, which constitutes the "excess compound” within the meaning of the invention.
• the acrylic ester (compound of interest) is preferably methyl acrylate and / or ethyl acrylate.
• the unreacted alcohol (excess compound) is preferably methanol and / or ethanol.
• the acrylic ester stream may comprise, for example, from 50 to 98% of acrylic ester, preferably from 70 to 97%, and more particularly from 80 to 95%.
• This same acrylic ester stream may comprise, for example, from 0.5 to 30% unreacted alcohol, preferably from 1 to 20%, more particularly from 2 to 10%.
• the acrylic ester stream described above constitutes the "main liquid flow input" within the meaning of the invention.
• the aqueous phase collection line 6 feeds a hydroalcoholic distillation unit 7.
• This hydroalcoholic distillation unit 7 makes it possible to recover the unreacted alcohol, and to recycle it to the reactor 4 via an alcohol-rich fraction collection line 12.
• the remainder of the aqueous phase (water-rich fraction) is recovered at the bottom of the hydroalcoholic distillation unit 7 in order to be used as a washing liquid stream (within the meaning of the invention), via a line called a pipe supply of liquid washing flux 1 1. It should be noted that the totality of this flux is not necessarily used as a washing liquid flow, a part being able to be eliminated, as shown in the diagram by the vertical arrow.
• the washing liquid flow supply pipe 1 1 and the acrylic ester collecting pipe 8 both feed a liquid-liquid extraction unit 9, in which a liquid-liquid extraction is carried out between the two flows, allowing transferring the excess compound (unreacted alcohol) from the acrylic ester stream to the liquid wash stream.
• the liquid-liquid extraction unit is operated with a mass ratio at the inlet of the washing liquid stream / main liquid stream ranging from 0.3 to 0.5. Indeed, it has been shown that below a weight ratio of 0.3, the excess compound still remained at a high content in the main liquid flow output.
• the residual alcohol in the purified acrylic ester output stream is greater than 3000 ppm, which is not compatible with the uses the use of a ratio greater than 0.5 implies the implementation of a large volume of washing liquid and the use of a larger extraction column to obtain the same extraction efficiency, which is not economically advantageous.
• This liquid-liquid extraction unit 9 is described in more detail below.
• a purified acrylic ester collection line 13 in order to recover the flow of acrylic ester depleted in alcohol
• a pipe for collecting an alcohol-enriched aqueous stream in order to recover the alcohol-enriched wash liquid stream
• the alcohol-enriched aqueous flow collection line 10 returns to the hydroalcoholic distillation unit 7: the alcohol enriched wash stream is thus combined with the aqueous phase from the reactor, to recover and recycle the alcohol. that it contains.
• the purified acrylic ester collection line 13 feeds successive distillation units 14, 15, which make it possible to eliminate other undesirable compounds and to recover the acrylic ester in its final form via a final product collection line.
• One or more recycle lines 17 may be provided to return a portion of the stream to the reactor 4, fed by the purified acrylic ester collection line 13 and / or the successive distillation units 14, 15.
• the residual content of alcohol in the stream recovered in the purified acrylic ester line 13 is preferably less than or equal to 2000 ppm or 1000 ppm, for example less than or equal to 750 or 500 ppm.
• the invention provides for the use of a packed contactor for the liquid-liquid extraction unit 9 above.
• the liquid-liquid extraction unit 9 consists of a single-packed contactor, or of a plurality of packed contactors arranged in series or in parallel.
• the liquid-liquid extraction unit 9 additionally comprises a contactor of another type, for example a contactor with mechanical stirring.
• additional means for removing the excess compound are associated with the liquid-liquid extraction unit (for example a distillation unit).
• packed contactor an apparatus comprising an enclosure in which two liquids are brought into contact, the enclosure comprising a lining.
• packing is meant a solid structure capable of increasing the contact area between the two liquids.
• the packed contactor is a static contactor, that is to say devoid of mechanical stirring means (such as blades, turbines, etc.) in the aforementioned enclosure.
• mechanical stirring means such as blades, turbines, etc.
• a heavy phase supply line 21 and a light phase supply line 22 are connected at the inlet of the column 20, respectively at the head and at the bottom of the latter.
• a light phase collection line 23 and a heavy phase collection line 24 are connected at the outlet of the column 20, respectively at the head and at the bottom of the latter.
• Column 20 contains a packing 25 which rests on a tray 29 in the form of a grid.
• a delivery system 26 is provided at the level of the arrival of the light-phase supply line 22.
• This distribution system 26 comprises, for example, a set of nozzles, in order to make it possible to generate light-phase drops in the phase heavy. It is disposed below the plate 29 and can pass therethrough. Above the packing 25, a settling zone 27 is formed, allowing the separation of the heavy phase and the light phase.
• the flow rates are adjusted so that the interface between the phases is located between the heavy phase supply line 21 and the light phase collection line 23 (placed above the preceding one).
• the light phase is the main liquid stream (acrylic ester stream), and the heavy phase is the washing liquid stream (of aqueous nature).
• the heavy phase is the continuous phase, in which are dispersed light phase drops at the level of the packing 25.
• the extraction temperature is preferably 20 to 50 ° C.
• the mass ratio at the input of heavy phase / light phase is preferably 0.3 to 0.5.
• the packing may be loose packing or structured packing or possibly a combination of both, preferably loose packing.
• a loose packing is composed of packed pore-shaped articles, the packing elements, which may for example have a substantially cylindrical outer shape.
• Structured packing is composed of a single porous three-dimensional structure, or in the form of blocks arranged one above the other and / or next to each other.
• the lining may be made of a ceramic material, or metal or glass, or possibly plastic.
• the preferred material is stainless steel.
• the outer diameter of the packing elements is preferably 5 to 50 mm. Generally speaking, this outer diameter is selected at or above the critical diameter d c presented in Perry's Chemical Engineers' Handbook 7th edition, authors and RHPerry DWGreen, chapter 15- Liquid-Liquid Extraction operations and equipment).
• the size of the drops formed and therefore the exchange area are virtually independent of the choice of packing.
• the diameter of the packing elements is less than one tenth of the diameter of the extraction column to reduce fouling of the column.
• the packing elements may be for example Raschig rings, Pall rings, Saddle rings, Berl saddles or Intalox saddles. Alternatively, beads could also be used.
• the specific surface of the packing elements is greater than or equal to 200 m 2 / m 3 .
• structured packing When structured packing is used, it is advantageously chosen so that it has a surface / volume ratio of at least 200 m 2 / m 3 , for example at least 250 m 2 / m 3 , or at least 500 m 2 / m 3 .
• Possible commercially available structured packings are Suizer BX packing at 250 m 2 / m 3 and Mellapack 750Y, also from Suizer, at 750 m 2 / m 3 .
• a 180 mm diameter column with an active height of 4 to 5 m is used.
• the packing consists of Pall rings with a diameter of 16 mm and a specific surface area of 205 m 2 / m 3 .
• the decanter at the head has a diameter of 150 mm, and a zone of tranquilization is provided in foot.
• the flow to be treated (organic flow) is taken from a methyl acrylate production facility. It contains 91.0% methyl acrylate and 5.03% methanol. The main other compounds detected in the stream are methyl acetate (1.94%) and acrylic acid (0.21%).
• the wash stream is an aqueous phase containing 0.1% methanol.
• the difference in density between the column head product and that of the foot is in this case 30 kg / m 3 .
• the densities of the products are measured at 20 ° C using a volumetric flask and confirmed with the simulation software ASPEN.
• the interfacial tension is 3 dyn / cm. It is measured at 20 ° C thanks to an IT concept drop tensiometer equipped with a computer, an EXMIRE type syringe pump, a camera and a glass tub, all coupled to a HAAKE thermostated bath. .
• the contactor with mechanical stirring makes it possible to obtain a desired residual methanol content (generally less than 1000 ppm).
• the system has a tendency to become engorged (letter E in the table) when the specific flow rate is around 18 m 3 / m 2 / h.
• the engorgement corresponds to an organic phase which stagnates, preventing any movement in the column and therefore any separation.
• the packed contactor also offers suitable separation performance, while allowing a specific flow of 1.5 to 2 times greater than that achievable with the mechanical stirring column.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Extraction Or Liquid Replacement (AREA)

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• 2013
  • 2013-09-23 FR FR1359110A patent/FR3010998B1/fr active Active
• 2014
  • 2014-08-26 EP EP14786981.2A patent/EP3049168B1/fr active Active
  • 2014-08-26 WO PCT/FR2014/052124 patent/WO2015040298A2/fr not_active Ceased
  • 2014-08-26 JP JP2016543440A patent/JP6529977B2/ja active Active
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