Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/72—Treatment of water, waste water, or sewage by oxidation
  • C02F1/722—Oxidation by peroxides
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/048—Purification of waste water by evaporation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/30—Organic compounds
  • C02F2101/34—Organic compounds containing oxygen
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
  • C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

• the present invention relates to a process for treating wastewater containing formaldehyde.
• the invention relates to a process for treating liquid effluents resulting from the manufacture of acrylic acid, aimed at eliminating the formaldehyde present in these effluents.
• the invention also relates to the use of the purified aqueous solution thus obtained for treatment before discharge into the natural environment.
• the invention also aims at recycling the effluent freed from the majority of formaldehyde in a process for producing acrylic acid by catalytic oxidation of propylene and / or propane.
• the processes for making acrylic acid from propylene and / or propane generate formaldehyde as a by-product of the catalytic oxidation reaction.
• these processes produce a large amount of water (at least one mole of water per mole of propylene converted).
• Formaldehyde is a slight impurity (gas at room temperature) which is very soluble in water forming a hydrate making it difficult to separate from its aqueous solutions.
• the wastewater streams generated during the acrylic acid recovery and purification steps generally contain formaldehyde as the majority organic impurity.
• Formaldehyde levels and emissions are subject to strict regulations. Installations operating with formaldehyde must comply with emission regulations which limit the concentration of formaldehyde in waste gases and also in aqueous discharges.
• the concentration of propylene in the mixture feeding the reactor is usually between 5% and 15% by volume.
• Dilution is usually provided by nitrogen, accompanying the air introduced as a source of oxygen and water vapor, which is also necessary to limit the formation of carbon oxides by combustion and ensure good desorption of the reactive species. on the catalyst.
• an economical process for the production of acrylic acid consists in using part of the wastewater from the workshop, after vaporization, as a diluent. gaseous propylene and / or propane. This makes it possible to use the water generated by this reaction (generating one mole of water per mole of converted propylene) and thus avoid the need for additional water of external origin.
• the step of vaporization of the water containing this impurity in order to obtain water vapor intended for the dilution of the propylene most of the formaldehyde is entrained with the water supplied to the oxidation reactor. propylene.
• formaldehyde is a poison for reactions to manufacture acrylic acid and the acrolein intermediate by catalytic oxidation of propylene and / or propane.
• formaldehyde present in the overhead stream of the steam generators and recycled as feed to the reactors can cause a loss of acrylic acid yield, due to the deactivation of the catalysts.
• Pretreatment methods using chemical treatments by addition of third compounds can be implemented, consisting in forming adducts with formaldehyde which are more easily separable from the aqueous medium, by distillation or by absorption on resins.
• the invention provides a process for removing formaldehyde in wastewater from the manufacture of acrylic acid from propylene and / or propane, said process being based on the oxidation of formaldehyde in the process. 'using hydrogen peroxide, in the absence of catalyst.
• the invention relates firstly to a process for removing formaldehyde in wastewater from the manufacture of acrylic acid or acrolein, said process being implemented in an installation comprising a reaction section and a vaporization section. , said method comprising the following steps: i. treating the waste water with hydrogen peroxide in the reaction section, ii. transferring the treated wastewater to the spray section, and iii. carrying out a partial vaporization of the treated wastewater, generating an overhead flow and a bottom flow, the top and bottom flows each having a formaldehyde concentration of less than 1% by weight.
• the waste water to be treated contains from 0.5 to 5%, preferably from 0.5 to 2.5% by weight of formaldehyde.
• the molar ratio between hydrogen peroxide and formaldehyde varies from 0.1 / I to 3/1.
• the hydrogen peroxide is introduced into the reaction section in aqueous form.
• the invention also aims to provide a process for the synthesis of acrylic acid by catalytic oxidation of propylene and / or propane, in which the aqueous phase containing formaldehyde is treated with hydrogen peroxide, making it possible to obtain, of a on the one hand, a gaseous aqueous flow, which will be recycled to the propylene and / or propane oxidation stage, and on the other hand, a liquid aqueous flow free of most of the formaldehyde, which thus becomes suitable for being discharged in the natural environment, after treatment intended to eliminate other organic products.
• the present invention overcomes the drawbacks of the state of the art. More particularly, it provides a simple, economical and efficient treatment method for removing formaldehyde in wastewater from an acrylic acid manufacturing process. In addition, this method makes it possible to avoid the loss of yield of the reactions of oxidation of propylene and / or propane by recycling stream concentrated in formaldehyde.
• the method according to the invention can also be used to reduce the concentration of formaldehyde in wastewater from the manufacture of (meth) acrylic monomers containing this impurity which are intended to be treated before discharge into the external environment, for example by biological treatment or incineration. .
• the process according to the invention does not generate new products or solids.
• the reaction can be carried out in a small reaction volume which thus allows continuous treatment in a tubular reactor of the static mixer type, which reduces the investment costs compared with a conventional reactor.
• Figure 1 shows the diagram of an acrylic acid production plant implementing the method of the invention according to one embodiment.
• Figure 2 shows the diagram of a variant of the installation for the production of acrylic acid implementing the method of the invention according to another embodiment.
• the invention relates to a process for removing formaldehyde in the wastewater originating from the manufacture of acrylic acid or acrolein, said process being implemented in an installation comprising a reaction section and a section. vaporization, said process comprising the following steps: i. treating the waste water with hydrogen peroxide in the reaction section, ii. transferring the treated wastewater to the spray section, and iii. carrying out a partial vaporization of the treated wastewater, generating an overhead flow and a bottom flow, the top and bottom flows each having a formaldehyde concentration of less than 1% by weight.
• said method comprises the following characters, if necessary combined.
• the manufacture of acrylic acid or acrolein is carried out by catalytic oxidation of propylene and / or propane.
• the waste water to be treated contains from 0.5 to 5%, preferably from 0.5 to 2.5% by weight of formaldehyde.
• said waste water comprises a mixture of acrylic acid, acetic acid, maleic acid and formic acid and has a pH of 1 to 3.
• the molar ratio between hydrogen peroxide and formaldehyde varies from 0.1 / 1 to 3/1, preferably from 0.3 / 1 to 1/1.
• the hydrogen peroxide is introduced into the reaction section in aqueous form.
• the solution used has a concentration of 20% to 70% by mass of hydrogen peroxide, preferably 30% to 70%.
• Step i) can be carried out in batch or continuous mode.
• the treatment of the wastewater with hydrogen peroxide in the reaction section takes place in a continuous mode.
• Step i) can be carried out under an absolute pressure of between 900 Pa and 1300 Pa.
• the treatment of the waste water with hydrogen peroxide in the reaction section takes place under an absolute pressure of 900 Pa. at 1100 Pa.
• the reaction temperature during step i) can vary from 20 to 110 ° C.
• the oxidation reaction takes place at a temperature above 60 ° C, in particular between 75 and 105 ° C.
• the flow of wastewater originating from the acrylic acid manufacturing process generally obtained at the bottom of a distillation column, therefore at high temperature, does not require substantial prior cooling before reaction, namely not a decrease. temperature greater than 10 ° C.
• the contact of the oxygenated water with the waste water to be treated can vary between 2 minutes and 2 hours, and preferably it is between 2 and 10 minutes.
• the reaction section can be carried out in one or more stirred reactors in series.
• Any type of reactor making it possible to ensure good contact between the aqueous flow to be treated and the hydrogen peroxide reagent can be used, for example a reactor equipped with a stirrer or with recirculation via a pump.
• the reactor may be a tubular reactor of the static mixer type, or a heat exchanger in which the medium flows in a turbulent manner, also providing slight cooling, or a combination of these types of reactors.
• Waste water treated with hydrogen peroxide is sent after this time to the vaporization section.
• the vaporization rate in step iii) is from 30% to 95%, preferably from 50% to 90%.
• Step iii) can be carried out under atmospheric pressure or overpressure.
• the water vapor produced is intended to be recycled as feed for the reaction section, which comprises two reaction zones in series (oxidation of propylene to acrolein, then of acrolein to acrylic acid). Since the solid catalysts contained in these two reaction zones create an additive pressure drop, the gaseous reactants must feed the first reaction zone under sufficient pressure.
• the partial vaporization of the treated wastewater takes place under a pressure slightly higher than that of the reagents supplying the first reaction zone, namely an absolute pressure between 2000 and 2700 Pa.
• the vaporization can be carried out at a lower pressure, for example at an absolute pressure between atmospheric pressure and 1300 Pa, and the water vapor is then compressed to reach an absolute pressure between 2000 and 2700 Pa.
• This vaporization step can be carried out in any type of equipment known to those skilled in the art generating water vapor from a liquid aqueous stream.
• the steam generator could consist of a capacity equipped with recirculation of the liquid through an external heat exchanger circulated by a heat transfer fluid (water vapor or thermal oil), or more simply of an exchanger. heat with a tube bundle arranged inside an envelope, circulated by a heat transfer fluid.
• Vaporization equipment can also be provided with internal separation elements, such as trays or packing. The residence time in the vaporization equipment does not significantly impact the performance of the process.
• step iii) an overhead stream and a foot stream are obtained, the head and foot streams each having a formaldehyde concentration of less than 1% by weight.
• the overhead stream has a formaldehyde mass concentration of less than 0.6%.
• the foot flow has a formaldehyde mass concentration of less than 0.3%.
• the foot stream contains less than 1% or even less than 0.3% by weight of formaldehyde, resulting in a decrease in the concentration of formaldehyde between the feed stream and the foot stream of about 80%. This makes it suitable for being subjected to biological treatment or by incineration, before being released into the natural environment.
• the process according to the invention does not generate new products or solids.
• the invention also relates to a process for the synthesis of acrylic acid by catalytic oxidation of propylene and / or propane, said process comprising the oxidation treatment of an aqueous phase containing formaldehyde, with hydrogen peroxide, in a section of reaction, transferring the mixture thus formed into a vaporization section so as to obtain, at the head, an aqueous gaseous stream having a formaldehyde concentration of less than 1% by weight, which is recycled to the propylene oxidation step and / or propane, and at the bottom, a liquid aqueous stream having a formaldehyde concentration of less than 1% by weight, or even less than 0.3% by weight.
• said liquid aqueous stream is discharged into the natural environment, after a biological treatment or by incineration.
• the process for removing formaldehyde in the wastewater from the manufacture of acrylic acid does not use a catalyst.
• this process was applied to wastewater from the manufacture of acrylic acid, in the presence of iron (II) ions, it was found that the concentration of formaldehyde in the overhead stream remains very high (greater than 1% by weight) (Comparative Example 12).
• the method according to the invention is implemented using an installation shown in Figures 1 and 2.
• an acrylic acid production plant comprises a first reactor 1 supplied with a mixture (1) of propylene and / or propane and oxygen in which a mixture rich in acrolein is produced, and sent in a second reactor 2 where the selective oxidation of acrolein to acrylic acid is carried out.
• the gas mixture (2) resulting from the second stage consists, apart from acrylic acid, of unconverted compounds resulting from the reagents involved or of impurities generated during at least one of the 2 reaction stages, to know : - light compounds that are incondensable under the temperature and pressure conditions usually used, namely essentially: propylene, propane, nitrogen, unconverted oxygen, carbon monoxide and carbon dioxide formed in small quantities by ultimate oxidation;
• - condensable light compounds ie essentially: water, light aldehydes such as unconverted acrolein, formaldehyde and acetaldehyde, formic acid, acetic acid, propionic acid;
• the complexity of the gas mixture (2) obtained in this process requires carrying out a series of operations to recover the acrylic acid contained in this gaseous effluent and transform it into a grade of acrylic acid compatible with its end use.
• the gas mixture (2) is sent to an absorption column 3 where acrylic acid and other oxidation products are condensed by absorption with water, a flow (4) of incondensable compounds being eliminated.
• the liquid stream (3) leaving the absorption column 3 is subjected to a dehydration step which is carried out in the presence of a solvent (7) for acrylic acid immiscible with water in a unit 4.
• the dehydration step is carried out by liquid-liquid extraction of acrylic acid in the presence of the solvent (7) in a liquid extraction column 4, generating a bottom flow ( 5) containing water and impurities including formaldehyde, and an overhead flow (14) rich in acrylic acid in a solvent medium.
• solvents which can be used there may be mentioned, for example, ethyl acrylate or isopropyl acetate.
• the stream (14) is then subjected to a distillation 8 to recover the solvent (16) which is recycled via the flow (6) in the extraction column 4, the stream (15) at the bottom being subjected to a purification section (not described in FIG. 1) with a view to obtaining technical grade acrylic acid, after removal of light impurities and heavy impurities.
• the aqueous stream (5) containing a small amount of dissolved solvent is advantageously sent to a solvent recovery step by distillation in a column 5; the solvent is recovered at the top (8) and recycled into the stream (6) feeding unit 4, and an aqueous phase containing most of the formaldehyde is obtained at the bottom (9).
• the method according to the invention consists in treating the aqueous phase (9) by adding hydrogen peroxide in a reaction section 6 and sending the mixture thus formed (11) into a vaporization section 7, so as to obtain at the top a gaseous aqueous stream (13) containing little formaldehyde, which is recycled to the propylene and / or propane oxidation reaction step, and at the bottom a liquid aqueous stream (17) also stripped of most of the formaldehyde.
• the stream (17) is then treated so as to remove most of the organic products it contains, before discharge into the natural environment, for example by incineration or by biological treatment.
• the dehydration step is carried out by azeotropic distillation with a solvent (7) in a distillation column 4, generating a two-phase medium (6) at the top of the column: an organic phase (16). ) essentially consisting of the solvent, which is recycled under reflux in column 4, and an aqueous phase (5) containing impurities including formaldehyde.
• solvents which can be used there may be mentioned, for example, methyl isobutyl ketone (MIBK) or toluene.
• the stream (15) is subjected to a purification section (not described in FIG. 2) with a view to obtaining technical grade acrylic acid, after removal of light impurities and heavy impurities.
• the flow (9) of wastewater supplying the vaporizer contains 2.2% formaldehyde and the vaporization rate of this mixture is 75%.
• aqueous mixture representative of the flow of wastewater from the workshop consisting of 2.31% formaldehyde, 0.6% acrylic acid, 2.3% acetic acid, 0.21% maleic acid, 0.26% formic acid, the remainder being water.
• This mixture is vaporized under atmospheric pressure in a rotary evaporator. After having vaporized 75% of this mixture, an overhead flow is obtained containing 2.55% of formaldehyde, the rest of the unvaporized formaldehyde representing a concentration of 1.55% by foot. Examples 2 to 10
• An aqueous mixture representative of the flow of wastewater from the workshop is prepared, consisting of formaldehyde in a concentration of between 1% and 2.3%, as well as 0.6% of acrylic acid, 2.3% of acetic acid, 0.2% maleic acid, 0.25% formic acid, the remainder being water.
• This mixture is introduced by a pump into a stirred glass reactor, along with a 39% aqueous solution of hydrogen peroxide, introduced by a second pump.
• the stirred reactor has a double wall circulated by a thermal fluid at controlled temperature.
• the flow rate of the mixture of the two streams is controlled so as to ensure a residence time in the reactor of 5 min to 60 min.
• the initial temperature in the reactor is between 20 ° C and 80 ° C.
• the reaction mixture is collected and a quantity of 150 g to 200 g of this mixture is subjected to vaporization under atmospheric pressure in a laboratory rotary evaporator.
• the vaporization rate (mass ratio of distillate flow to feed flow) is between 69% and 78%.
• Table 1 below indicates the operating conditions of the tests and analyzes of the flows obtained. No significant increase in temperature was observed during the course of these tests. In all the cases tested, the reaction mixture remained clear, without precipitation of solid. Likewise, at the end of the vaporization step, no solid precipitation is observed.
• the process according to the invention makes it possible to eliminate most of the formaldehyde present in the wastewater, by generating by vaporization a flow of which the concentration of this impurity is very markedly reduced, without generating any solid deposit or new product.
• the very fast processing kinetics allow the reaction to be carried out in continuous mode with a very short residence time, thus reducing the reaction volume required.
• the reactor can be a simple tubular mixing reactor, for example of the static mixer type, thus limiting the investment costs.
• the treatment can be carried out on a hot wastewater stream coming from a column bottom, without having to resort to prior cooling.
• the same aqueous mixture representative of the workshop wastewater stream is prepared, in which the formaldehyde concentration is 2.3%. 11.4% iron (II) sulfate monohydrate is dissolved in this mixture and the mixture is then introduced into the stirred reactor described above, at a flow rate of 235 g / h, at the same time as an aqueous solution of hydrogen peroxide. to 39.
• the molar ratio of hydrogen peroxide relative to the formaldehyde initially present is 1.2 / 1
• that of iron (II) sulfate relative to hydrogen peroxide is 0.4 / 1.
• the residence time in the reactor is 60 min.
• the initial reaction temperature is 22 ° C.
• the temperature of the reaction mixture reaches 60 ° C., and a yellowish solid deposit accumulates on the wall of the reactor.
• the reaction mixture is filtered, and a quantity of 203 g of this mixture is subjected to vaporization under atmospheric pressure in a laboratory rotary evaporator.
• the vaporization rate (mass ratio of distillate flow to feed flow) targeted is 70%.
• the concentration of formaldehyde in the distilled stream is 1.57%.

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• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment Of Water By Oxidation Or Reduction (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Removal Of Specific Substances (AREA)

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• 2019
  • 2019-08-28 FR FR1909477A patent/FR3100243B1/fr active Active
• 2020
  • 2020-08-18 BR BR112022001878A patent/BR112022001878A2/pt unknown
  • 2020-08-18 KR KR1020227009932A patent/KR20220052985A/ko active Search and Examination
  • 2020-08-18 WO PCT/FR2020/051477 patent/WO2021038159A1/fr unknown
  • 2020-08-18 US US17/633,994 patent/US20220267179A1/en active Pending
  • 2020-08-18 EP EP20775372.4A patent/EP4021856A1/de active Pending
  • 2020-08-18 CN CN202080059336.9A patent/CN114269697A/zh active Pending
  • 2020-08-18 JP JP2022513287A patent/JP2022546973A/ja active Pending

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