Method for separating w / o emulsions

Abstract

The invention relates to a method for separating a W / O emulsion comprising an aqueous phase dispersed in an organic phase, the method having the steps of: (A) providing the W / O emulsion, (B) breaking the W / O emulsion by applying an electric field which is built up by an assembly of non-insulated electrodes and in which an alternating voltage having an effective value of 25 V to 400 V and a frequency ranging from 0.1 Hz to 25 Hz is applied, the organic phase and the aqueous phase being unmixed, and (C) carrying out a phase separation in which the organic phase and the aqueous phase are separated from one another.

Description

[0001] 2024PF30100 - Abroad

[0002] - 1 -

[0003] METHOD FOR SEPARING W / O EMULSIONS

[0004] The present invention relates to a method for separating a W / O emulsion comprising an aqueous phase dispersed in an organic phase, the method comprising the steps of: (A) providing the W / O emulsion, (B) breaking up the W / O emulsion by applying an electric field generated by an arrangement of non-insulated electrodes and in which an alternating voltage with an RMS value of 25 V to 400 V and with a frequency in the range of 0.1 Hz to 25 Hz is applied, whereby the organic phase and the aqueous phase separate, and (C) performing a phase separation in which the organic and the aqueous phase are separated from each other.

[0005] In many industrial processes, the separation of two-phase systems into an aqueous and an organic phase plays a significant role, particularly in the context of aqueous-organic liquid-liquid extractions. Such extractions are common in the processing of chemical raw materials, for example, to extract an organic target product from a predominantly aqueous phase or to wash an organic target product with an aqueous washing liquid.

[0006] In industrial practice, extractions are usually carried out in so-called M / xer-Setter apparatus. These are combinations of a residence time apparatus in which the aqueous and organic phases are mixed (for example, a stirred tank or, in continuous processes, often a static mixer), followed by a phase separation apparatus in which, ideally, the two phases spontaneously separate and recombine within a timeframe acceptable for industrial processes. Depending on various factors, such as the input mixing energy or the presence of impurities that can act as emulsifiers, the mixing of the two phases in the first step can sometimes be "too thorough," resulting in a temporally stable emulsion that either does not separate spontaneously into its phases at all or at least not within an acceptable timeframe. The occasional occurrence of a so-called...The layer of detritus between the organic and aqueous phases, which can make a clean phase separation very difficult or impossible, falls into this category, because such a layer of detritus is nothing other than a temporally stable emulsion.

[0007] Phase separation problems due to emulsion formation are known, for example, from the production of aromatic nitro compounds by nitration of the corresponding aromatics with nitric acid in the presence of sulfuric acid. Problems can arise there as early as the separation of the crude product into crude nitroaromatics and the excipient. Against this background, EP 0004 278 A2 describes a process for electrophoretic refraction 2024PF30100 - Foreign

[0008] - 2 - of electrically conductive emulsions, characterized in that, in the case of emulsions with an electrical conductivity of greater than 2000 p Q, one can -1The conductivity is increased by increasing the degree of dispersion to values ​​in the range of approximately 0.1 to approximately 2000 pQ. -1The emulsion is set and then breaks down upon passing through a DC voltage field of approximately 100 to 1000 volts. The subsequent washings of the crude nitroaromatics are also critical in this context, especially the final so-called "neutral wash" with water. Against this background, EP 1 816 117 Al describes a continuous process for the work-up of crude nitrobenzene, in which the crude nitrobenzene is washed successively in an acidic, an alkaline, and a neutral wash. In the neutral wash, the organic phase containing nitrobenzene is mixed with water to form a dispersion, which is then broken down in an electrophoresis unit, followed by the separation of the aqueous and organic phases.In the electrophoresis unit, the dispersion passes through a DC voltage field of preferably 100 to 500 volts, particularly preferably 200 to 400 volts, and most preferably 220 to 300 volts. The current is preferably 0.05 to 3 amperes and particularly preferably 0.1 to 1 ampere. The application of the described process avoids the use of demulsifiers (chemical separation aids) in the nitrobenzene scrubbing process, which is also known.

[0009] WO 2015 / 173161 Al describes the application of an electrocoalescing device in the processing of dinitrotoluene. A direct current voltage of 50 volts to 1000 volts is used, to which the starting dinitrotoluene material is exposed in a cell with an electrode spacing of 1 mm to 100 mm for a period of 0.01 seconds to 100 seconds.

[0010] US Patent 4,391,698 describes a device for the electrostatic breaking of emulsions containing solids. The device includes a flexible electrode, contains electrolytes, and has a pumping tube for solids. Emulsions are broken by passing an electric current through the electrolyte at frequencies of approximately 60 Hz. Application examples include highly aqueous liquid membrane emulsions, emulsions from sludge from oil tankers and refineries, and oil emulsions containing conductive catalyst particles.

[0011] The article "Power consumption measurements for AC and pulsed DC for electrostatic coalescence of water-in-oil emulsions" by C.-M. Lee, GW Sams, and JP Wagner in Journal of Electrostatics 2001, 53, 1-24 describes a study on the coalescence of a defined emulsion (16.7 vol% water and 83.3 vol% Isopar M) by reverse osmosis under the influence of DC and pulsed AC voltage at frequencies from 60 to 600 Hz. 2024PF30100 - Foreign

[0012] - 3 -

[0013] The article "Oil-in-water and water-in-oil emulsions formation and demulsification" by AM Sousa, MJ Pereira and HA Matos in Journal of Petroleum Science and Engineering 2022, 210, 110041 deals with emulsion formation and demulsification in the oil industry.

[0014] EP 2 512 615 Bl describes a method and apparatus for treating contaminated drilling mud containing oil-in-water (O / W) emulsions. In an O / W emulsion, the organic phase is the dispersed phase and the aqueous phase is the dispersion medium. The method involves depositing the drilling mud in a sludge mixing / storage tank of a sludge decomposition apparatus and homogenizing the sludge while it is crushed to obtain an optimal particle size. The emulsion component of the sludge is decomposed by applying a DC or AC voltage, and the resulting phases are separated. A practical method for separating water-in-oil (W / O) emulsions is not described.

[0015] EP 1 652 835 Al describes the avoidance of a layer of sludge in the processing of crude di- and polyamines of the diphenylmethane series by limiting the content of divalent and higher-valent metal ions.

[0016] WO 2020 / 260387 Al describes the occurrence of an emulsion during the work-up of a polyurethane alcoholylysis product. The emulsion forms after water washing of a polyol-containing solvent phase and is broken down again by extraction with further organic solvent.

[0017] There are therefore a number of technical application areas where emulsion formation can be a problem. The described solutions range from the use of direct current or high-frequency alternating current, to controlling the chemical composition or using chemical demulsifiers, to carrying out additional extraction steps. None of these approaches is without drawbacks, whether regarding the quality of emulsion breaking or the economic viability of the process.

[0018] There was therefore a need for further improvements in the field of emulsion breaking. In particular, it would be desirable to be able to break frequently occurring W / O (water-in-oil) emulsions in a simple, cost-effective and reliable way.

[0019] Taking this need into account, the invention provides the following:

[0020] A process for separating (at least) a W / O emulsion (a “water-in-oil” emulsion) comprising an aqueous phase dispersed in an organic phase, the process comprising the steps: 2024PF30100 - Foreign

[0021] - 4 -

[0022] (A) Providing the (at least one) W / O emulsion,

[0023] (B) Breaking down the (at least one) W / O emulsion by applying an electric field, which is generated by an arrangement of non-insulated electrodes and in which an alternating voltage with an RMS value of 25 V to 400 V and with a frequency in the range of 0.1 Hz to 25 Hz, preferably up to 20 Hz, particularly preferably up to 15 Hz, very preferably up to 5.0 Hz and extremely, very preferably up to 1.0 Hz is applied, wherein the organic phase and the aqueous phase separate, and

[0024] (C) Performing a phase separation in which the organic and aqueous phases are separated from each other.

[0025] Completely unexpectedly, it was found that the above-mentioned goals can be achieved, or at least approached, by using a low-frequency alternating voltage.

[0026] The attached illustrations show:

[0027] FIG. 1 a side view of a preferred embodiment of a device suitable for carrying out step (B); and

[0028] FIG. 2 shows a graphical representation of the influence of an electric field on the separation time of the product of a dinitrotoluene wash.

[0029] Glossary

[0030] In the terminology of the present invention, a W / O emulsion is understood to be a temporally stable dispersion of an aqueous liquid phase (dispersed phase) in an organic liquid phase (dispersion medium). "Temperaturely stable" means that, at the temperature at which the phase separation according to step (C) is to take place, the dispersion does not separate sufficiently in time, without the application of an electric field, to allow the aqueous and organic phases to be separated from each other. If the phase separation is carried out continuously, this means that the time required for the dispersion to separate exceeds the residence time of the dispersion provided in the device (phase separation apparatus) used for step (C).When phase separation is carried out discontinuously, this means that the demixing of the dispersion takes 20 minutes or more, preferably 30 minutes or more, particularly preferably 60 minutes or more, and most preferably 120 minutes or more. 2024PF30100 - Foreign.

[0031] - 5 -

[0032] Polyurethanes within the meaning of the present invention are the polyaddition products obtained by reacting polyhydric isocyanates (the isocyanate component of polyurethane production) with polyols (the polyol component of polyurethane production). Polyurethanes generally contain, in addition to the known polyurethane base structure, other structures, for example, urea, isocyanurate, allophanate, and biuret structural units. The presence of such structures, deviating from the pure polyurethane base structure, alongside polyurethane structures is not outside the scope of the present invention. Polyurethanes within the meaning of the present invention are preferably polyurethane foams obtained by reacting polyhydric isocyanates with polyols in the presence of a blowing agent.

[0033] In the terminology of the present invention, the term polyols encompasses all polyols known to those skilled in the art in connection with polyurethane chemistry, such as, in particular, polyether polyols, polyester polyols, polyether ester polyols, and polyether carbonate polyols. The expression "a polyol" naturally also includes embodiments in which two or more different polyols are used in the production of a polyurethane. Therefore, when, for example, "a polyether polyol" (or "a polyester polyol," etc.) is mentioned below, this terminology naturally also includes embodiments in which two or more different polyether polyols (or two or more different polyester polyols, etc.) are used in the production of a polyurethane. The entirety of all polyols used in the production of a polyurethane is referred to as the polyol component (of the polyurethane product). The polyol component comprises at least one polyol.Polyols that are relatively unreactive can be recovered (essentially) chemically unchanged. This applies particularly to polyether polyols. In the case of polyols with chemically relatively reactive groups in the polymer chain, such as polyester polyols, the polyols originally used in polyurethane production cannot usually be recovered as such. However, their underlying alcohol monomers (e.g., 1,6-hexanediol) can be recovered and are then considered the recovered polyols. In addition, the acid component used in the production of a polyester polyol (e.g., adipic acid) can also be recovered.

[0034] In the terminology of the present invention, the term isocyanate encompasses all isocyanates known to those skilled in the art in connection with polyurethane chemistry. The expression "one isocyanate" naturally also includes embodiments in which two or more different isocyanates (e.g., mixtures of MDI and TDI) are used in the manufacture of a polyurethane, unless otherwise expressly stated, for example by the formulation "exactly one isocyanate". The totality of all isocyanates used in the manufacture of a polyurethane is referred to as 2024PF30100 - Foreign

[0035] - 6 - referred to as the isocyanate component (of the polyurethane). The isocyanate component contains at least one isocyanate.

[0036] An amine corresponding to an isocyanate is that amine by whose phosgenation the isocyanate can be obtained according to R-NH2 + COCI2 —> RN=C=O + 2 HCl.

[0037] In the context of the present invention, an organic chemolysis reagent means an organic compound that has functional groups which can react with urethane bonds by cleaving them, in particular alcohol and amine groups.

[0038] When the present invention refers to a device / assembly (e.g., in expressions such as "a reactor," etc.), this also includes embodiments in which several devices / assemblies of the aforementioned type are connected in series or in parallel (the example expression is thus to be read as "at least one reactor"), unless expressly stated otherwise (e.g., by the phrase "exactly one"). The same applies to substances (see the above explanations regarding polyols and isocyanates; the same naturally applies to expressions such as "a carbamate" or "a urea").

[0039] The term distillation, as used in the context of the present invention, also includes rectification.

[0040] The following is a brief summary of various possible embodiments of the invention:

[0041] In a first embodiment of the invention, which can be combined with all other embodiments, the non-insulated electrodes are plate electrodes or ring electrodes, preferably plate electrodes.

[0042] In a second embodiment of the invention, which can be combined with all other embodiments, the non-insulated electrodes are arranged horizontally (i.e. parallel to the phase boundary formed in step (B)).

[0043] In a third embodiment of the invention, which can be combined with all other embodiments, the non-insulated electrodes are arranged at a distance from one another in the range of 5 mm to 1000 mm, preferably from 5 mm to 500 mm, particularly preferably from 5 mm to 250 mm, most preferably from 5 mm to 100 mm, and most preferably from 5 mm to 50 mm. 2024PF30100 - Abroad

[0044] - 7 - In a fourth embodiment of the invention, which can be combined with all other embodiments, an electric field strength of 0.1 V / m to 150 V / m prevails between each pair of the non-insulated electrodes.

[0045] In a fifth embodiment of the invention, which can be combined with all other embodiments, the (at least one) W / O emulsion is exposed to the alternating voltage for a period of 1 second to 6000 seconds, preferably 5 seconds to 500 seconds, particularly preferably 10 seconds to 180 seconds.

[0046] In a sixth embodiment of the invention, which can be combined with all other embodiments, a temperature in the range of 25 °C to 115 °C is maintained in step (B).

[0047] In a seventh embodiment of the invention, which can be combined with all other embodiments, the (at least one) W / O emulsion is provided in step (A) as part of a continuous process.

[0048] In an eighth embodiment of the invention, which can be combined with all other embodiments and is preferably a special embodiment of the seventh embodiment, the (at least one) W / O emulsion flows continuously through the electric field in step (B).

[0049] In a ninth embodiment of the invention, which can be combined with all other embodiments, in particular with the eighth embodiment in conjunction with the second embodiment, the (at least one) emulsion provided in step (A) is introduced into a phase separation vessel in which the arrangement of non-insulated electrodes is located, wherein the non-insulated electrodes are arranged in the phase separation vessel such that, after complete separation of the aqueous and organic phases, a first part of the arrangement of non-insulated electrodes is located in the aqueous phase and a second part of the arrangement of non-insulated electrodes is located in the organic phase, wherein the breaking of the emulsion is monitored by (periodic or continuous, preferably continuous) measurement of a current flow between the non-insulated electrodes.wherein the alternating voltage is maintained at least in the first part of the arrangement of non-insulated electrodes as long as no current flow is measured there.

[0050] In a tenth embodiment of the invention, which can be combined with all other embodiments, step (C) is carried out continuously.

[0051] In an eleventh embodiment of the invention, which can be combined with all other embodiments, step (A) comprises: 2024PF30100 - Abroad

[0052] - 8 -

[0053] (I) a new manufacture (of at least) of a chemical product, or

[0054] (II) a (chemical and / or thermal) cleavage of a polymeric organic compound for the recovery of (at least) one chemical product, wherein a crude product is formed and this is further processed, optionally comprising (at least) one extraction, to obtain the (at least one) chemical product, wherein the W / O emulsion is the crude product or a process product obtained in the (at least) one extraction.

[0055] In a twelfth embodiment of the invention, which is a particular embodiment of the eleventh embodiment, (I) is comprised, wherein the (at least one) chemical product is an organic nitro compound, wherein the crude product is obtained by reacting (at least) a nitridable organic compound with nitric acid in the presence of sulfuric acid and contains sulfuric acid and the organic nitro compound, wherein the (at least one) extraction is carried out and comprises a (one- or multi-stage) washing process.

[0056] In a thirteenth embodiment of the invention, which is a particular embodiment of the twelfth embodiment, the (single- or multi-stage) washing process comprises a first wash with water or a (diluted) aqueous acid, a second wash with an aqueous base solution and a third wash with water (each of these washes may itself be single- or multi-stage).

[0057] In a fourteenth embodiment of the invention, which is a special embodiment of the twelfth and thirteenth embodiments, the nitrifiable organic compound is benzene and the organic nitro compound is mononitrobenzene.

[0058] In a fifteenth embodiment of the invention, which is a further special embodiment of the twelfth and thirteenth embodiments, the nitrifiable organic compound is toluene and the organic nitro compound is mononitrotoluene.

[0059] In a sixteenth embodiment of the invention, which is a further particular embodiment of the twelfth and thirteenth embodiments, the nitrifiable organic compound is toluene and the organic nitro compound is dinitrotoluene, wherein the nitration is carried out as (direct) dinitration without isolation of mononitrotoluene.

[0060] In a seventeenth embodiment of the invention, which is a further particular embodiment of the twelfth and thirteenth embodiments, the process comprises the nitration of toluene as a first nitrifiable organic compound to obtain mononitrotoluene as a first chemical product, which is then nitrated as a second nitrifiable organic compound to dinitrotoluene as a second chemical product. 2024PF30100 - Foreign

[0061] - 9 - further nitration, whereby the (one- or multi-stage) washing process is applied only to the dinitrotoluene.

[0062] In an eighteenth embodiment of the invention, which is a further particular embodiment of the eleventh embodiment, (II) is comprised, wherein the polymeric organic compound is a polyurethane based on an isocyanate component and a polyol component, wherein the crude product is obtained by reacting the polyurethane with water and optionally an organic chemolysis reagent and

[0063] (i) comprising (at least) one polyol of the polyol component and (ii) comprising (at least) one amine corresponding to an isocyanate of the isocyanate component, and wherein the further processing comprises a work-up of the crude product separating the (at least one) polyol as a first chemical product and the (at least one) amine as a second chemical product.

[0064] In a nineteenth embodiment of the invention, which is a further particular embodiment of the eleventh embodiment, (II) is comprised, wherein the polymeric organic compound is a polyurethane based on an isocyanate component and a polyol component, wherein the crude product is obtained by reacting the polyurethane with an organic chemolysis reagent (without the presence of substantial amounts of water) and (i) (at least) a polyol of the polyol component and

[0065] (ii) comprising (at least) one carbamate and / or (at least) one urea of ​​an isocyanate of the isocyanate component, wherein further processing comprises work-up of the crude product by separating the (at least one) polyol as a first chemical product and the (at least one) carbamate and / or urea as a second chemical product.

[0066] In a twentieth embodiment of the invention, which is a particular embodiment of the nineteenth embodiment, the further processing further comprises the reaction of the second chemical product with water and / or hydrogen to form (at least) one amine as a third chemical product, wherein the (at least one) amine is an amine corresponding to an isocyanate of the isocyanate component.

[0067] In a twenty-first embodiment of the invention, which is a particular embodiment of the eighteenth to twentieth embodiments, the (at least one) extraction is included and is carried out to separate the first and second chemical products.

[0068] The embodiments and further possible configurations of the invention briefly described above are explained in more detail below. All previously described embodiments and the further configurations of the 2024PF30100 - Abroad described below are

[0069] - 10 -

[0070] Unless the context clearly indicates otherwise to a person skilled in the art, or unless something else is expressly stated, inventions can be combined with each other and in any way.

[0071] In step (A) of the process according to the invention, the W / O emulsion to be separated is provided. This includes both cases in which a dispersion of an aqueous liquid phase in an organic liquid phase regularly forms in a difficult-to-separate form (i.e., as an emulsion within the meaning of the present invention) and cases in which this only occurs temporarily. An example of the latter could be the start-up process of a continuously operated extraction system. During start-up phases, when not all process flows have yet reached the flow rates intended for standard operation and are subject to constant changes (a so-called non-steady-state condition exists), challenges can arise that are no longer a problem in later operation. Thus, emulsion formation can also be limited to specific operating conditions such as start-up in certain cases.Another example of emulsion formation occurring only temporarily is a disruption in the regular operating process, which results in the increased formation of byproducts that act as emulsifiers. In such a case, the problem of emulsion formation only occurs as long as the operational disruption persists. As long as the operational disruption is not of a nature that would necessitate shutting down the plant anyway, phase separation or extraction can continue in such a case by applying the method according to the invention.

[0072] In general, the inventive method is not limited to specific technical fields of application. Rather, in principle, W / O emulsions from a wide variety of technical applications can be broken down using the inventive method.

[0073] Possible applications of the process according to the invention relate to both (I) the production of new chemical products and (II) the recycling of used materials to obtain chemical products, in particular the recycling of polymeric organic compounds. The recycling of polymeric organic compounds comprises their chemical and / or thermal decomposition, optionally supported by the use of catalysts, to obtain chemical products such as the underlying monomers or reaction products thereof. In both the case of production and recycling, a crude product is formed, which is subjected to further processing, optionally including extraction, to obtain the desired chemical product. The W / O emulsion to be separated can be the crude product itself and / or a component obtained during extraction.

[0074] - 11 - the resulting process product. It is therefore possible that steps (A) to (C) are repeated several times, for example during the separation of the crude product into two phases and again in a subsequent extraction.

[0075] An example of the synthesis of a new chemical product in which the process according to the invention can be applied is the nitration of organic compounds to the corresponding nitro compounds, in particular mono- or dinitrated aromatics. In such a case, the chemical product is an organic nitro compound. The crude product is obtained by reacting a nitridable organic compound with nitric acid in the presence of sulfuric acid and contains sulfuric acid and the organic nitro compound. The work-up of the crude product comprises phase separation and a one- or multi-stage washing process (extraction with aqueous washing liquids). Emulsion formation can occur both in the crude product itself and in the subsequent extraction. An example of the latter is emulsion formation in the so-called neutral wash.Neutral washing is the final stage of a typically three-stage washing sequence comprising a first wash with water or a (diluted) aqueous acid (so-called "acidic wash" to remove residual acid), a second wash with an aqueous base solution (so-called "alkaline wash" to neutralize acidic byproducts), and a third wash with water (so-called "neutral wash"). Phase separation occurs after each wash, and the resulting organic phase is fed into the next washing step. "Three-stage" refers to the three types of washing ("acidic," "alkaline," and "neutral") and does not preclude each of these stages from being further subdivided, meaning the total number of stages could be greater than three.

[0076] In a preferred embodiment, the nitrifiable organic compound is benzene and the organic nitro compound is mononitrobenzene.

[0077] In another preferred embodiment, the nitrifiable organic compound is toluene and the organic nitro compound is mononitrotoluene.

[0078] In yet another preferred embodiment, the nitrifiable organic compound is toluene and the organic nitro compound is dinitrotoluene, wherein the nitration is carried out as (direct) dinitration without isolation of mononitrotoluene (one-step process). However, in the case of dinitrotoluene as the target product of the new synthesis, it is particularly preferred to carry out the nitration in two steps. In this case, step (A) comprises the nitration of toluene as a first nitrifiable compound to obtain mononitrotoluene as a first chemical product, which is further nitrated as a second nitrifiable compound to dinitrotoluene as a second chemical product, wherein the (one- or multi-step) washing process is applied only to the dinitrotoluene. 2024PF30100 - Foreign

[0079] - 12 -

[0080] All these nitriding processes are well known from the state of the art and therefore do not require further explanation here.

[0081] An example of the recycling of polymeric organic compounds is the recycling of polyurethanes, i.e., the polymeric organic compound is a polyurethane based on an isocyanate component and a polyol component.

[0082] In this embodiment, the crude product is obtained by reacting the polyurethane with water and optionally an organic chemolysis reagent. In this process, the crude product contains (i) a polyol of the polyol component and (ii) an amine corresponding to an isocyanate of the isocyanate component. Further processing of the crude product includes work-up to separate the polyol as a first chemical product and the amine as a second chemical product. An optional organic chemolysis reagent may include, in particular, a chemolysis alcohol, a chemolysis amine, and / or a chemolysis amino alcohol (hydroalcohollysis or aminohydrolysis). Reacting the polyurethane with water alone, without the use of an organic chemolysis reagent, is a hydrolysis reaction.

[0083] In another embodiment, the crude product is obtained by reacting the polyurethane with an organic chemolysis reagent (without the presence of substantial amounts of water) and comprises (i) (at least) a polyol of the polyol component and (ii) a carbamate and / or a urea of ​​an isocyanate of the isocyanate component. The organic chemolysis reagents are preferably those mentioned above; thus, the reaction is either alcoholysis or aminolysis. Further processing of the crude product then comprises working it up to separate the polyol as a first chemical product and the carbamate and / or urea as a second chemical product. The second chemical product thus obtained is further preferably reacted with water and / or hydrogen to give an amine (corresponding to an isocyanate of the isocyanate component) as a third chemical product.

[0084] The separation of the first and second chemical products is preferably carried out by extraction in any case.

[0085] All these recycling processes are well known from the state of the art and therefore do not require further explanation here.

[0086] Emulsions within the meaning of the present invention can occur both during the separation of the originally obtained crude product and during subsequent extractive processing steps. An example of the former is the so-called split-phase glycolysis, a reaction of a polyurethane with an alcohol using the 2024PF30100 - Abroad

[0087] - 13 - the intended goal of spontaneous separation of the crude product into a non-polar polyol phase and a polar, aqueous carbamate phase (even without targeted water addition, such recycling processes in industrial practice are never completely anhydrous, which is why carbamate phases generally contain water and consequently also small amounts of amines). An example of the latter is the emulsion formation already mentioned in the process according to WO 2020 / 260387 Al.

[0088] In a preferred embodiment, the W / O emulsion is provided in step (A) as part of a continuous process. This is particularly the case with the nitriding processes mentioned above as examples, which are usually carried out continuously on an industrial scale.

[0089] In step (B) of the process according to the invention, the W / O emulsion provided in step (A) is broken down, causing the aqueous and organic phases to separate. According to the invention, the W / O emulsion is broken down by applying an electric field generated by an arrangement of non-insulated electrodes (hereinafter also referred to as: electrode arrangement) in which an alternating voltage with an RMS value of 25 V to 400 V and a frequency in the range of 0.1 Hz to 25 Hz, preferably up to 20 Hz, particularly preferably up to 15 Hz, very preferably up to 5.0 Hz, and most preferably up to 1.0 Hz is applied. Plate electrodes or ring electrodes are particularly suitable as non-insulated electrodes, preferably plate electrodes. Suitable electrode materials include, in particular, stainless steels, tantalum, and precious metals such as platinum.

[0090] The size of the electrodes depends on the size of the container in which step (B) is performed, as well as on the magnitude of the applied voltage. The higher the voltage, the smaller the electrode plates can be, since the field lines of the electric field also extend into the vicinity of the electrode plates, and this is more pronounced with increasing voltage. Preferably, the area of ​​a plate electrode or the circular area enclosed by a ring electrode should cover at least 20% of the cross-sectional area of ​​the container available at its position for step (B). In a preferred embodiment, the electrode arrangement is located in a phase separation apparatus in which step (C) is also performed. It is further preferred that the non-insulated electrodes are arranged horizontally (i.e., parallel to the phase boundary formed in step (B)).

[0091] In particular, the non-insulated electrodes are arranged at a distance from each other in the range of 5 mm to 1000 mm, preferably from 5 mm to 500 mm, particularly preferably from 5 mm to 250 mm, very preferably from 5 mm to 100 mm, and extremely, very preferably from 5 mm to 50 mm. The total number of electrodes is preferably adapted to the size of the container used. Between each pair of 2024PF30100 - Abroad

[0092] - 14 - an electric field strength of 0.1 V / m to 150 V / m is preferably set for the non-insulated electrodes.

[0093] The water-in-oil emulsion to be broken is preferably exposed to alternating current for a period of 1 second to 6000 seconds, particularly preferably 5 seconds to 500 seconds, and most preferably 10 seconds to 180 seconds. Breaking the emulsion preferably takes place at temperatures between 25 °C and 115 °C. A higher temperature may be advantageous due to the associated reduction in viscosity. The temperature to be selected also depends on the application. For applications such as the nitriding process mentioned above, a temperature of 5 °C to 105 °C is preferably selected for step (B). For applications such as the polyurethane recycling process mentioned above, a temperature of 5 °C to 105 °C is also preferably selected for step (B).

[0094] In one embodiment, step (B) is performed continuously, meaning the W / O emulsion to be broken down flows continuously through the electric field. Batch processing is, of course, also possible. Which variant is more suitable depends in particular on the quantity of W / O emulsion produced. If the W / O emulsion is produced as part of a continuous process (for example, in continuous nitration), it is advantageous to also perform step (B) continuously.

[0095] FIG. 1 shows a preferred embodiment of a device suitable for carrying out step (B) in a side view. Shown is a substantially cylindrical, horizontally arranged phase separation apparatus (100) with a feed line (1) for the mixture to be separated, which is at least partially a water-in-oil emulsion, a discharge (2) for the heavy phase, and a discharge (3) for the light phase. The phase separation apparatus is operated continuously. The light phase flows over an overflow weir (4) and is thus separated from the heavy phase. An electrode arrangement (5) is provided in the area to the left of the overflow weir (4), here comprising eight non-insulated plate electrodes (5-1, 5-2, ..., 5-8).The plate electrodes are arranged horizontally, i.e., parallel to the phase interface that forms during operation of the phase separation apparatus, and extend over most of the available area of ​​the container (both longitudinally and – not visible in FIG. 1 – transversely). The electrode arrangement (5) is connected to an AC voltage source (6).

[0096] The non-insulated electrodes (5-1, 5-2, ... 5-8) extend almost to the height of the overflow weir (4), so that after the two phases have separated, electrodes are present in each phase. This is generally preferred and allows monitoring of the 2024PF30100 - Abroad

[0097] - 15 -

[0098] Breaking the emulsion by (periodic or continuous, preferably continuous) measurement of a current flow between the non-insulated electrodes: As long as the entire space to the left of the overflow weir (4) is filled with emulsion, no (significant) current flow will be detectable. As soon as the phases separate and an aqueous phase forms, a current flow will be detected abruptly in this phase, or there will be a sudden, sharp increase in the current flow, while this will not be the case in the developing organic phase and the disappearing emulsion phase. Electrodes between which such a current flow is detected are preferably switched off.If all electrodes in the aqueous phase are affected by the current flow (which is easy to determine because the phase boundary is either already known or can be easily determined, for example, using sight glasses), the alternating voltage can be completely switched off. Such a situation can occur, for example, if emulsion formation is limited to certain operating conditions, such as start-up.

[0099] In step (C) of the process according to the invention, the phases separated in step (B) are separated from each other. For this purpose, all devices known in the prior art for liquid-liquid phase separation can be used.

[0100] 2024PF30100 - Abroad

[0101] - 16 -

[0102] Example 1: Application of the process according to the invention to the neutral washing of a process for the production of dinitrotoluene

[0103] Dinitrotoluene was produced in a two-stage isothermal process by nitrating toluene in a first stage and nitrating the mononitrotoluene formed in a second stage. A sulfuric acid / nitric acid mixture was used for each nitration step. The crude product from the second stage was separated into an aqueous acid phase and an organic dinitrotoluene phase. The dinitrotoluene phase underwent a three-stage washing process (acidic, alkaline, and neutral – see also the explanations above in the description), with the final neutral washing stage itself comprising two washing steps. During this second neutral washing step, the influence of an applied voltage on the phase separation time was investigated for the use of direct current (DC – comparison) and alternating current (AC – according to the invention) at a frequency of 1.0 Hz.The separation time of the present W / O emulsion without the application of a voltage was 2320 s (mean of three trials). The results are shown in FIG. 2. The separation time in seconds is plotted on the ordinate axis and the voltage in volts (RMS value for AC voltage) on the abscissa axis. As can be seen, applying a low-frequency AC voltage results in a significant reduction in the phase separation time, a greater reduction than applying a DC voltage. When using a high-frequency AC voltage of 50 Hz (not shown in FIG. 2), no reduction in the separation time was observed; however, with further increases in frequency, an increase in the stability of the washing emulsion was even observed.

[0104] Example 2 (comparison): Attempted separation of an O / W emulsion

[0105] With the exception of the following difference, dinitrotoluene was produced and processed as described in Example 1. Unlike Example 1, four times the volume of wash water, based on DNT, was used in the second washing step of the neutral wash. This high water-to-oil ratio reflects an atypical plant condition, which can result in a stable oil-in-water (O / W) emulsion, as was the case here. The influence of an applied voltage on the phase separation time of this O / W emulsion was investigated, analogous to Example 1, using both direct current (DC) and alternating current (AC) at a frequency of 1.0 Hz. The separation time without applying a voltage was up to 3 days (mean of three trials). However, varying the voltage as performed in Example 1 showed no effect on the stability of the O / W emulsion. Even varying the voltage to a certain level (2024PF30100 - Abroad)

[0106] - 17 -

[0107] An alternating voltage range of up to 200 Hz did not produce a significant effect. A significant acceleration of the phase separation of the O / W emulsion was not achieved.

[0108] Example 3: Application of the inventive method in the reprocessing of a polyurethane recycling process

[0109] 4,000 kg of a polyurethane foam based on toluene diisocyanate (TDI) and polyether polyols were reacted with 4,000 kg of diethylene glycol in the presence of 40.0 g of sodium carbonate for 3 h at 180 °C. 207 g of water were added to the resulting reaction mixture, and the reaction was continued for a further 3 h at 180 °C. Water, diethylene glycol, and the toluenediamine (TDA) formed were largely distilled off the resulting product mixture under vacuum. After filtration to remove solids, the resulting filtered crude polyether polyol fraction was extracted with dichloromethane (DCM), water, and hydrochloric acid at 30 °C for further purification, in particular to remove residual TDA (determined by amine number determination). The hydrochloric acid was added in such a quantity as to ensure a TDA protonation level of approximately 98%.The following mass ratio of filtered crude polyether polyol fraction to DCM to water (excluding the water contained in the hydrochloric acid) was maintained: 1 : 0.5 : 0.5.

[0110] The following table contains the results of experiments on the separation of the washing emulsion into an aqueous phase (containing TDA hydrochloride) and an organic phase (containing DCM and polyether polyols) under different conditions:

[0111] [a] Effective value.

[0112] [b] After three days the experiment was aborted; a complete separation of the phases had not yet been observed at that time.

Claims

2024PF30100 - Abroad - 18 - 1. A method for separating a W / O emulsion comprising an aqueous phase dispersed in an organic phase, the method comprising the steps: (A) Providing the W / O emulsion, (B) Breaking the W / O emulsion by applying an electric field generated by an arrangement of non-insulated electrodes and carrying an alternating voltage with an RMS value of 25 V to 400 V and a frequency in the range of 0.1 Hz to 25 Hz, whereby the organic phase and the aqueous phase separate, and (C) Performing a phase separation in which the organic and aqueous phases are separated from each other.

2. The method of claim 1, wherein the non-insulated electrodes are plate electrodes or ring electrodes.

3. Method according to claim 1 or 2, wherein the non-insulated electrodes are arranged at a distance from each other in the range of 5 mm to 1000 mm.

4. Method according to one of claims 1 to 3, wherein an electric field strength of 0.1 V / m to 150 V / m prevails between each pair of the non-insulated electrodes.

5. Method according to any one of claims 1 to 4, wherein the W / O emulsion is exposed to alternating voltage for a period of 1 second to 6000 seconds.

6. Method according to any one of claims 1 to 5, wherein the W / O emulsion is provided in step (A) as part of a continuous process.

7. Method according to any one of claims 1 to 6, wherein the W / O emulsion in step (B) continuously flows through the electric field.

8. A method according to any one of claims 1 to 7, wherein the emulsion provided in step (A) is introduced into a phase separation vessel containing an arrangement of non-insulated electrodes, the non-insulated electrodes being arranged in the phase separation vessel such that, after complete separation of the aqueous and organic phases, a first part of the arrangement of non-insulated electrodes is located in the aqueous phase and a second part of the arrangement of non-insulated electrodes is located in the organic phase, the breaking of the emulsion being monitored by measuring a current flow between the non-insulated electrodes. 2024PF30100 - Abroad - 19 - wherein the alternating voltage is maintained at least in the first part of the arrangement of non-insulated electrodes as long as no current flow is measured there.

9. Method according to any one of claims 1 to 8, wherein step (C) is carried out continuously.

10. Method according to any one of claims 1 to 9, wherein step (A) comprises: (I) a new production of a chemical product, or (II) a cleavage of a polymeric organic compound for the production of a chemical product, wherein a crude product is formed and this is further processed, optionally comprising extraction, to obtain the chemical product, wherein the W / O emulsion is the crude product or a process product obtained in the extraction.

11. The method of claim 10, comprising (I), wherein the chemical product is an organic nitro compound, wherein the crude product is obtained by reacting a nitridable organic compound with nitric acid in the presence of sulfuric acid and contains sulfuric acid and the organic nitro compound, wherein the extraction is carried out and comprises a washing process.

12. The method of claim 11, wherein the nitrifiable organic compound is benzene and the organic nitro compound is mononitrobenzene; or wherein the nitrifiable organic compound is toluene and the organic nitro compound is mononitrotoluene; or wherein the nitrifiable organic compound is toluene and the organic nitro compound is dinitrotoluene, wherein the nitration is carried out as a dinitration without isolation of mononitrotoluene; or comprising the nitration of toluene as a first nitrifiable organic compound to obtain mononitrotoluene as a first chemical product, which is reacted as a second nitrifiable organic compound to form dinitrotoluene 2024PF30100 - Abroad - 20 - is further nitrated as a second chemical product, whereby the washing process is applied only to the dinitrotoluene.

13. The method of claim 10, comprising (II), wherein the polymeric organic compound is a polyurethane based on an isocyanate component and a polyol component, wherein the crude product is obtained by reacting the polyurethane with water and optionally an organic chemolysis reagent, and comprising (i) a polyol of the polyol component and (ii) an amine corresponding to an isocyanate of the isocyanate component, and wherein the further processing comprises working up the crude product by separating the polyol as a first chemical product and the amine as a second chemical product.

14. The method of claim 10, comprising (II), wherein the polymeric organic compound is a polyurethane based on an isocyanate component and a polyol component, wherein the crude product is obtained by reacting the polyurethane with an organic chemolysis reagent and comprising (i) a polyol of the polyol component and (ii) a carbamate and / or a urea of ​​an isocyanate of the isocyanate component, wherein the further processing comprises working up the crude product by separating the polyol as a first chemical product and the carbamate and / or urea as a second chemical product.

15. The method of claim 14, wherein the further processing further comprises the reaction of the second chemical product with water and / or hydrogen to form an amine as a third chemical product, wherein the amine is an amine corresponding to an isocyanate of the isocyanate component.

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