Improved method for depolymerization of polyethylene terephthalate.

Abstract

The present invention relates to a process for the depolymerization of polyethylene terephthalate (= "PET"), in which PET is reacted with an electrolytically generated alkali metal glycolate, in particular sodium glycolate or potassium glycolate, to obtain a mixture M1 containing bis-2-hydroxyethyl terephthalate (= "BHET"). The process according to the invention is characterized in that BHET makes up a particularly high proportion of the cleavage products in the mixture M1. As a result, the process according to the invention provides a high yield of BHET, which can be used directly for the production of recycled PET. The present invention therefore also relates to a process for the regeneration of PET, in which the BHET obtained in the depolymerization of PET, if appropriate after further purification from M1, is repolymerized to produce PET.

Description

[Technical field]

[0001] The present invention relates to a method for the depolymerization of polyethylene terephthalate (=“PET”), which comprises reacting PET with an electrolytically generated alkali metal glycolate, in particular sodium glycolate or potassium glycolate, to produce a mixture M containing bis-2-hydroxyethyl terephthalate (=“BHET”; CAS number: 959-26-2). 1 This relates to a method for obtaining

[0002] The process according to the invention is characterized in that BHET is a mixture M 1 As a result, the process according to the invention provides a high yield of BHET, which can be used directly in the production of recycled PET.

[0003] Therefore, the present invention is a method for regenerating PET, which comprises the steps of: 1 and a process for repolymerizing the resulting PET after further purification.

[0004] 2. Background of the Invention Polyethylene terephthalate (PET) is one of the most important plastics used in textile fibers, as films and as a material for plastic bottles. In 2007 alone, the amount used in plastic bottles was about 10 7 (W. Casey, Polyethylenterephthalate, RD-16-03258 (2009) in F. Buckler, B. Dill, G. Eisenbrand, F. Faupel, B. Fugmann, T. Gamse, R. Matissek, G. Pohnert, A. Ruehling, S. Schmidt, G. Sprenger, ROEMPP [Online], Stuttgart, Georg Thieme Verlag, January 2022).

[0005] PET is one of the biggest environmental problems of our time due to its durability and the amount of waste it generates. The solution to this problem lies in avoiding PET or recycling it efficiently.

[0006] Several methods for cleaving PET have been proposed in the prior art.

[0007] GB 784,248 describes the methanolysis of PET.

[0008] Methods for depolymerizing PET by hydrolysis are described in JP 2000-309663, U.S. Pat. No. 4,355,175, and T. Yoshioka, N. Okayama, A. Okuwaki, Ind. Eng. Chem. Res. 1998, 37, 336-340.

[0009] The reaction of PET with glycols is described in EP 0 723 951, U.S. Pat. No. 3,222,299, WO 2020 / 002999, SR Shukla, AM Harad, Journal of Applied Polymer Science 2005, 97, 513-517 (hereinafter "Shukla & Harad") and NDP Ingale, SR Shukla, European Polymer Journal 2008, 44, 4151-4156.

[0010] Shukla & Harad report that bis-2-hydroxyethyl terephthalate (= "BHET") is produced during the glycolysis of PET. This cleavage product can also be used as a reactant for the production of new PET.

[0011] Therefore, there is growing interest in methods for depolymerizing PET that will yield the highest possible proportion of BHET among the cleavage products.

[0012] The object of the present invention is to provide such a method.

[0013] Brief description of the invention Surprisingly, a method has now been found which solves the problem according to the invention.

[0014] The present invention relates to a method for depolymerizing polyethylene terephthalate (PET), comprising the steps of: (a)M A Glycol solution of glycolate L 1 <21> Electrolysis cell E <1> In the process, A is an alkali metal cation, in particular selected from lithium, potassium, sodium, preferably selected from potassium, sodium, very preferably sodium, and said electrolytic cell E <1> is the following: - at least one supply Z KA <110> and at least one discharge section A KA <111> and the anode electrode E A <113> Interior space with KA <112> At least one anode chamber K A <11> and, - at least one supply Z KK <120> and at least one discharge section A KK <121> and the cathode electrode E K <123> Interior space with KK <122> At least one cathode chamber K K <12> and Equipped with and optionally, at least one supply Z KM <130> and at least one discharge section A KM <131> and Inner Space A KM <132> At least one intermediate chamber K M <13> Equipped with In this case, I KA <112> and I KM <132> is the diffusion barrier D <14> They are separated from each other by AKM <131> is the connection part V AM <15> Powered by Z KA <110> Since it is connected to AM <15> Liquid by I KM <132> From I KA <112> It can be passed through Where: - Electrolytic Cell E <1> is the intermediate chamber K M <13> If you do not have I KA <112> and I KK <122> Partition wall W <16> They are separated from each other by - Electrolytic Cell E <1> At least one intermediate chamber K M <13> If it has I KK <122> and I KM <132> Partition wall W <16> They are separated from each other by Partition wall W <16> is the surface KK <163> Surface S with KK <161> and surface S KK <161> and the opposite surface O A / MK <164> Surface S with A / MK <162> and a partition wall W <16> Partition wall W <16> Alkaline cation conductive solid electrolyte ceramic F A <18> Surface O KK <163> Through the surface S KK <161> Inner Space I KK <122> At least one alkali cation conductive solid electrolyte ceramic F is placed in direct contact with the A <18> Contains Again here, - Electrolytic Cell E <1> is the intermediate chamber K M <13> If not equipped with a partition wall W <16> Alkaline cation conductive solid electrolyte ceramic F A <18> is the surface A / MK <164> Through the surface S A / MK <162> Inner Space I KA <112> I have direct contact with - Electrolytic Cell E <1> At least one intermediate chamber K M <13> If equipped with a partition wall W <16> Alkaline cation conductive solid electrolyte ceramic F A <18> is the surface A / MK <164> Through the surface S A / MK <162> Inner Space I KM <132> I have direct contact with (α) Electrolytic cell E <1> is the intermediate chamber K M <13> If no electrolytic cell E <1> The process comprises the steps (α1), (α2), and (α3) proceeding simultaneously as follows: (α1) Solution L containing glycol 2 <22> I KK <122> The process of passing (α2)M A A neutral or alkaline aqueous solution of salt S containing as a cation L 3 <23> I KA <112> The process of passing (α3)E A <113> and E K <123> applying a voltage between or (β) Electrolytic cell E <1> At least one intermediate chamber K M <13> If equipped with electrolytic cell E <1> The method comprises the steps of (β1), (β2), and (β3) proceeding simultaneously as follows: (β1) Solution L containing glycol 2 <22> I KK <122> The process of passing (β2)M A A neutral or alkaline aqueous solution of salt S containing as a cation L 3 <23> I KM <132> , then V AM <15> , then I KA <112> The process of passing (β3)E A <113> and E K <123> applying a voltage between Implemented the following: This allows discharge section A KK<121> Solution L 1 <21> is obtained, where L 1 <21> M in A The concentration of glycolate is L 2 <22> Higher than the middle, This causes discharge section A KA <111> Aqueous solution of S in L 4 <24> is obtained, where L 4 <24> The concentration of S in L 3 <23> lower than medium; (b) Solution L 1 <21> with PET to give a mixture M containing bis-2-hydroxyethyl terephthalate (=“BHET”). 1 and generating The present invention relates to a method comprising the steps of:

[0015] In a further aspect, the present invention relates to a method for the regeneration of PET, comprising, in step (ζ), polymerizing BHET obtained by the depolymerization method according to the present invention to produce PET.

[0016] PET was dissolved in the solution L obtained by the electrolytic method according to the present invention. 1 <21> It has surprisingly been found that reacting with a glycol in the corresponding alkali metal hydroxide gives a higher percentage of BHET than the conventional method of obtaining an alkaline alkali metal glycolate solution by mixing the glycol in the corresponding alkali metal hydroxide. [Brief description of the drawings]

[0017] [Figure 1A] Electrolysis cell E according to the invention <1> Sodium glycolate solution in L1 <21> FIG. [Figure 1B] Intermediate chamber KM <13> Electrolysis cell E equipped with <1> FIG. 2 illustrates a further embodiment of the method according to the invention using [Figure 2A] Preferred Partition Wall W <16> FIG. [Figure 2B] Preferred Partition Wall W <16> FIG. [Figure 3A] FIG. 2C is a detail highlighted by the dashed circle in FIGS. 2A and 2B. [Figure 3B] FIG. 2 shows a further embodiment of a preferred partition wall W. [Figure 3C] FIG. 2 shows a further embodiment of a preferred partition wall W. [Figure 4A] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 4B] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 4C] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 4D] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 5A] Electrolysis cell E in a preferred embodiment of the method according to the invention <1> FIG. [Figure 5B] Electrolysis cell E in a preferred embodiment of the method according to the invention <1> FIG. [Figure 6A] Electrolysis Cell E <1> FIG. 2 illustrates a method according to the present invention using [Figure 6B] Electrolysis Cell E <1> FIG. 2 illustrates a further embodiment of the method according to the invention using [Figure 7A] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 7B] Preferred Partition Wall W <16> FIG. 13 shows a further embodiment of the [Figure 8] FIG. 1 shows a comparison of the BHET ("1"), 2-hydroxyethyl terephthalate ("MHET"; "2") and terephthalate ("TS"; "3") contents upon depolymerization using sodium glycolate obtained by the method according to the invention and by a conventional method.

[0018] drawing Drawings 1A and 1B Drawing 1A (= "FIG. 1A") shows an electrolysis cell E according to the invention. <1> Sodium glycolate solution in 1 L 1 <21> The manufacturing method of the electrolysis cell E <1> is the cathode chamber K K <12> and anode chamber K A <11> It is equipped with:

[0019] Cathode Chamber K K <12> is the internal space I KK <122> Cathode electrode E K <123> and Supply Section Z KK <120> and discharge section A KK <121> It is equipped with:

[0020] Anode Chamber K A <11> is the internal space I KA <112> Anode electrode E A <113> and Supply Section Z KA <110> and discharge section A KA <111> It is equipped with:

[0021] These two chambers K A <11> and K. K <12> E is a two-chamber cell <1> Outer wall W A <80> It is bordered by the Inner Space I KK <122> In addition, NaSICON solid electrolyte ceramic F, which is selectively permeable to sodium ions, A <18> Partition wall W made of plates <16> By Inner Space I KA <112> It is divided into two parts: NaSICON solid electrolyte ceramic F A <18> E is a two-chamber cell <1> The partition wall extends over the entire depth and height of the KK <161> and S A / MK <162> and its surface O KK <163> and O A / MK <164> is the internal space I KK <122> Or I KA <112> is in contact with.

[0022] Sodium chloride solution at pH 10.5 L 3 <23> is the supply section Z KA <110> Through the gravity of the inner space I KA <112> will be given to.

[0023] Supply section Z KK <120> 1% by weight of sodium glycolate in glycol solution L 2 <22> is the inner space I KK <122> will be sent.

[0024] Here, the cathode electrode and the anode electrode E K <123> and anode electrode E A <113> A voltage is applied between the inner space I KK <122> Electrolyte L 2 <22> The glycol in the amine is reduced to glycolate and H 2 is generated (HOCH 2 CH 2 OH+e - →HOCH 2 CH 2 O - +1 / 2H 2 ;In addition to this, HOCH 2 CH 2 O - +e - → - OCH 2 CH 2 O - +1 / 2H 2 ) where sodium ions are in the inner space I KA <112> NaSICON Solid Electrolyte Ceramic F A <18> Through the interior space I KK <122> Overall, this results in an internal space I KK <122> The sodium glycolate concentration in the outlet A increases, KK <121> Glycol solution of sodium glycolate obtained by 1 <21> The sodium glycolate concentration of L 2<22> The amount of sodium glycolate in glycol is increased by about 20% by weight compared to that in the case of

[0025] interior space I KA <112> In the case of chlorine, the oxidation of chloride ions to molecular chlorine occurs (Cl - →1 / 2Cl 2 +e - ). Discharge part A KA <111> Well then, L 3 <23> Aqueous solution L with reduced NaCl content compared to 4 <24> Chlorine gas Cl is obtained. 2 is Cl in water. 2 +H 2 The reaction O → HOCl + HCl forms hypochlorous acid and hydrochloric acid, which react with additional water molecules in an acidic manner. This acidity is generated by the NaSICON solid electrolyte ceramic F A <18> Damage to the equipment.

[0026] Drawing 1B (= “FIG. 1B”) shows the intermediate chamber K M <13> Electrolysis cell E equipped with <1> Thus, this three-chamber cell E <1> is the cathode chamber K K <12> and anode chamber K A <11> and an intermediate chamber K M <13> It is equipped with:

[0027] Cathode Chamber K K <12> is the internal space I KK <122> Cathode electrode E K <123> and Supply Section Z KK <120> and discharge section A KK <121> It is equipped with:

[0028] Anode Chamber K A <11> is the internal space I KA <112> Anode electrode E A <113> and Supply Section Z KA <110> and discharge section A KA <111> It is equipped with:

[0029] Intermediate chamber K M <13> is the internal space I KM <132> and Supply Section Z KM <130> and discharge section A KM <131> It is equipped with:

[0030] interior space I KA <112> is the connection part V AM <15> Through the interior space I KM <132> is connected to

[0031] These three chambers are called three-chamber cell E <1> Outer wall W A <80> The intermediate chamber K is M <13> Inner Space I KM <132> In addition, NaSICON solid electrolyte ceramic F, which is selectively permeable to sodium ions, A <18> Partition wall W made of plates <16> Cathode chamber K K <12> Inner Space I KK <122> It is divided into two parts: NaSICON solid electrolyte ceramic F A <18> Three-chamber cell E <1> The partition wall extends over the entire depth and height of the KK <161> and S A / MK <162> and its surface O KK <163> and O A / MK <164> is the internal space I KK <122> Or I KM <132> is in contact with.

[0032] Intermediate chamber K M <13> Inner Space I KM <132> In this case, the diffusion barrier D <14> Anode chamber K A <11> Inner Space I KA <112> It is divided into two parts: NaSICON solid electrolyte ceramic F A<18> and diffusion barrier D <14> Three-chamber cell E <1> The diffusion barrier D extends over the entire depth and height of the <14> is a cation exchange membrane (sulfonated PTFE).

[0033] In the embodiment according to FIG. 1B, the connection V AM <15> is the electrolytic cell E <1> The connection part V is formed, in particular, by a pipe or hose, the material of which can be selected from rubber, metal or plastic. AM <15> This allows the liquid to flow into the intermediate chamber K M <13> Inner Space I KM <132> Three-chamber cell E <1> Outer wall W A <80> The external anode chamber K A <11> Inner Space I KA <112> Connection V AM <15> is the intermediate chamber K M <13> At the bottom of the electrolytic cell E <1> Outer wall W A <80> Discharge section A that penetrates KM <131> and anode chamber K A <11> At the bottom of the electrolytic cell E <1> Outer wall W A <80> Supply section Z passing through KA <110> Connect with.

[0034] Sodium chloride solution at pH 10.5 L 3 <23> is the supply section Z KM <130> In the same direction as gravity through the middle chamber K M <13> Inner Space I KM <132> The joint V AM <15> By the intermediate chamber K M <13> Inner Space I KM <132> Anode chamber K A <11> Inner Space I KA <112> Sodium chloride solution L 3 <23> This connection V AM <15> Through the interior space I KM <132> From Interior Space IKM <112> will be sent.

[0035] Supply section Z KK <120> Through about 1% by weight of sodium glycolate in glycol solution L 2 <22> is the inner space I KK <122> will be sent.

[0036] Here, the cathode electrode and the anode electrode E K <123> and anode electrode E A <113> A voltage is applied between the inner space I KK <122> Electrolyte L 2 <22> The glycol in the amine is reduced to glycolate and H 2 is generated (HOCH 2 CH 2 OH+e - →HOCH 2 CH 2 O - +1 / 2H 2 ;In addition to this, HOCH 2 CH 2 O - +e - → - OCH 2 CH 2 O - +1 / 2H 2 ) where sodium ions are in the middle chamber K M <103> Inner Space I KM <132> NaSICON Solid Electrolyte Ceramic F A <18> Through the interior space I KK <122> Overall, this results in an internal space I KK <122> The sodium glycolate concentration in the outlet A increases, KK <121> Glycol solution of sodium glycolate obtained by 1 <21> The sodium glycolate concentration in L 2 <22> The sodium glycolate in the glycol is increased to about 20% by weight compared to 10% by weight.

[0037] interior space I KA <112> In the case of chlorine, the oxidation of chloride ions to molecular chlorine occurs (Cl - →1 / 2Cl 2 +e - ). Discharge part A KA <111> Well then, L 3 <23> Aqueous solution L with reduced NaCl content compared to 4 <24> Chlorine gas Cl is obtained. 2 is Cl in water. 2 +H 2 The reaction O → HOCl + HCl forms hypochlorous acid and hydrochloric acid, which react with additional water molecules in an acidic manner. This acidity is generated by the NaSICON solid electrolyte ceramic F A <18> However, the arrangement of the three-chamber cell allows the anode chamber K A <11> Therefore, the electrolytic cell E <1> In NaSICON solid electrolyte ceramic F A <18> This significantly extends its useful life.

[0038] Drawings 2A and 2B Drawing 2A (= "FIG. 2A") shows a preferred partition wall W <16> This shows that two NaSICON solid electrolyte ceramics F A <18> and F B <19> These are the partition elements T <17> and are fixed to each other without gaps. <17> has a rectangular parallelepiped geometric shape, with F on its opposite faces. A <18> and F B <19> are fixed without gaps (for example with adhesive).

[0039] surface O KK <163> Surface S with KK <161> is a surface O that exists in the image plane and is not visible in FIG. 2A. A / MK <164> Surface S with A / MK <162> exists deep inside the image plane.

[0040] Drawing 2B (= "FIG. 2B") shows a preferred partition wall W <16> 1 shows another embodiment of the present invention, which is a ceramic solid electrolyte battery comprising four NaSICON solid electrolyte ceramics F A <18> , F B <19> , F C <28> , F D <29> These are the partition elements T <17> and are fixed to each other without gaps. <17> has a cross shape and F on its opposing surfaces A <18> , F B <19> , F C <28> and F D <29> is glued in place.

[0041] surface O KK <163> Surface S with KK <161> is a surface O that exists in the image plane and is not visible in FIG. 2B. A / MK <164> Surface S with A / MK <162> exists deep inside the image plane.

[0042] Drawings 3A~3C FIG. 3A (= "FIG. 3A") shows a detail highlighted by a dashed circle in FIGS. 2A and 2B. As described, each solid electrolyte ceramic F A <18> and F B <19> The separation element T can be attached, for example, by adhesive. <17> is fixed at.

[0043] Drawing 3B (= "FIG. 3B") illustrates a further embodiment of a preferred partition wall W. Here, the partition element T <17> has two concave recesses (grooves), and two solid electrolyte ceramics F A <18> and F B <19> For this purpose, a solid electrolyte ceramic F A <18> and F B <19> The shape of the edge of the sealing Di <40> is used, which is attached, for example by means of an adhesive, to the separation element T <17> and each solid electrolyte ceramic FA <18> Or F B <19> Here, the partition element T <17> is two or more parts <171> and <172> These can be fixed to each other as shown by the dashed lines in FIG. 3B. A <18> Or F B <19> Due to the appropriate geometry and adaptation of the edge shape of the solid electrolyte ceramic F A <18> Or F B <19> Both parts <171> and <172> This allows the separation element T <17> / Ceramic F A <18> Or F B <19> The stability of the connection and the partition wall W <16> The airtightness of the container is further improved.

[0044] Drawing 3C (= "FIG. 3C") illustrates a further embodiment of a preferred partition wall W. This is made up of two solid electrolyte ceramics F A <18> and F B <19> Partition element T into which <17> 3B, except that the depression (groove) is tapered rather than concave.

[0045] Drawings 4A~4D Drawings 4A (= "FIG. 4A") to 4D show a preferred partition wall W <16> 1 shows a further embodiment of the

[0046] Partition wall W shown in drawing 4A <16> is the frame element R <20> The partition wall W shown in FIG. 2A, except that it also includes <16> This is the same as the partition wall W <16> O KK <163> and O A / MK <164> Completely covers all surfaces except for frame element R <20> is the partition element T <17> It is not finished as a single piece.

[0047] Drawing 4B (= "FIG. 4B") shows a preferred partition wall W <16> This shows a further embodiment of the partition wall W <16> Two frame elements R bounding the upper and lower surfaces of <20> 4B is the same as the embodiment shown in FIG. 4A, except that it includes:

[0048] Drawing 4C (= "FIG. 4C") shows a preferred partition wall W <16> A further embodiment of the partition wall W shown in FIG. <16> is the frame element R <20> The partition wall W shown in FIG. 2B, except that it also includes <16> This is the same as the partition wall W <16> O KK <163> and O A / MK <164> Completely covers all surfaces except for frame element R <20> is the partition element T <17> It is not finished as a single piece.

[0049] Drawing 4D (= "FIG. 4D") shows a preferred partition wall W <16> This shows a further embodiment of the partition wall W <16> Two frame elements R bounding the upper and lower surfaces of <20> 4C, except that it includes:

[0050] Drawings 5A and 5B Drawing 5A (= "FIG. 5A") shows an electrolysis cell E in a preferred embodiment of the method according to the invention. <1> This is the same as the electrolysis cell shown in FIG. 1A, but with the addition of a partition wall W <16> By this, the cathode chamber K K <12> Inner Space I KK <122> and anode chamber K A <11> Inner Space I KA <112> This partition is shown in Figures 2A and 2B.

[0051] Drawing 5B (= "FIG. 5B") shows an electrolysis cell E in a preferred embodiment of the method according to the invention. <1> This is the same as the electrolysis cell shown in FIG. 1A, but with the addition of a partition wall W <16> By this, the cathode chamber K K <12> Inner Space I KK<122> and anode chamber K A <11> Inner Space I KA <112> The difference is that the partition wall W <16> is shown in Figs. 4A to 4D. <20> is the exterior wall W A <80> Since it forms part of the partition wall W <16> The solid electrolyte ceramic contained in the partition wall W <16> If it is part of the partition wall W <16> The solid electrolyte ceramic is protected from the pressure that would otherwise act through the electrolytic cell E because it is not partially covered by the outer wall. <1> Inner Space I KK <122> and I KA <112> is used to separate.

[0052] Drawings 6A and 6B Drawing 6A (="FIG. 6A") is the same as that shown in FIG. 1B, except that the intermediate chamber K M <13> Inner Space I KM <132> From anode chamber K A <11> Inner Space I KA <112> Hookup V AM <15> is the diffusion barrier D <14> Electrolytic cell E differs in that it is formed by multiple perforations in <1> These perforations are subsequently formed into a diffusion barrier D <14> It is also possible to punch out the material into a single layer or (e.g. in the case of textile fabrics such as filter cloths or metal meshes) to create a diffusion barrier D <14> The manufacturing process already provides a diffusion barrier <14> In this embodiment, all of these perforations are located in the connection V <15> Through this, the electrolyte is introduced into the internal space I KM <132> From Interior Space I KA <112> can be sent to.

[0053] Drawing 6B (= "FIG. 6B") shows an electrolytic cell E <1> This shows a further embodiment of the method according to the invention using the electrolysis cell E <1> Same as above, except for the intermediate chamber K M <13> Inner Space I KM<132> From anode chamber K A <11> Inner Space I KA <112> Hookup V AM <15> However, the diffusion barrier D <14> and exterior wall W A <80> This gap is formed by a gap between the normally dense diffusion barrier D <14> , the diffusion barrier D <14> By intermediate chamber K M <13> Inner Space I KM <132> The anode chamber K A <11> Inner Space I KA <112> The gap is not partitioned into two parts, but the connection part V AM< 15> Electrolytic cell as maintained as E <1> The support may be provided by being disposed within the support.

[0054] Drawings 7A and 7B Drawing 7A (= "FIG. 7A") shows a preferred partition wall W <16> This shows a further embodiment of the present invention, which is a ceramic solid electrolyte with four NaSICON solid electrolytes. A <18> , F B <19> , F C <28> and F D <29> These are two halves <171> and <172> Partition element T containing <17> They are separated from each other by a partition wall W <16> is the frame element R <20> which also consists of two halves <201> and <202> It consists of:

[0055] Partition wall W <16> consists of two foldable parts, the separating element T <17> Half of <171> is the frame element R <20> Half of <201> Combined with the partition element T <17> Half of <172> is the frame element R <20> Half of <202> These two parts are optionally joined together by a hinge. <50> They can be connected together through the hinges and locked in the folded position. <60> can be locked via

[0056] Between these halves are four NaSICON solid electrolyte ceramic F A <18> , FB <19> , F C <28> and F D <29> are sandwiched together, and at that time, sealing Di <40> A ring that functions as a

[0057] On the left side of Drawing 7A is the partition wall W. <16> Surface of KK <163> Surface S with KK <161> The front view of the sealing Di <40> The ring that serves as the partition wall W is shown in dashed outline. <16> A side view of the above is shown.

[0058] Drawing 7B (= "FIG. 7B") shows a preferred partition wall W <16> This shows a further embodiment of the NaSICON solid electrolyte ceramic F A <18> , F B <19> , F C <28> , F D <29> , F E <30> , F F <31> , F G <32> , F H <33> , F I <34> 7B is the same as the embodiment shown in FIG. 7A, except that it includes:

[0059] Drawing 8 FIG. 8 (="FIG. 8") shows a comparison of the BHET ("1"), 2-hydroxyethyl terephthalate ("MHET"; "2") and terephthalate ("TS"; "3") contents upon depolymerization using sodium glycolate obtained by the method according to the invention and by a conventional method.

[0060] The bars with thin hatching " / / / / / / / / " indicate the respective contents of BHET, MHET and TS in the reactor effluent during the depolymerization of PET according to example E1 according to the invention, where the sodium glycolate used for the depolymerization was obtained by electrolysis.

[0061] The black bars show the BHET, MHET and TS contents in the reactor effluent during the depolymerization of PET according to comparative example V1, in which only glycol was used during the depolymerization.

[0062] The bars with bold hatching " / / / / / " indicate the BHET, MHET and TS contents in the reactor effluent during the depolymerization of PET according to comparative example V2, where the sodium glycolate used for the depolymerization was obtained by mixing NaOH and glycol in the reactor.

[0063] Detailed Description of the Invention It has now surprisingly been found that the glycolysis of PET proceeds particularly efficiently with alkali metal glycolates obtained by electrolysis, in particular sodium or potassium glycolate. It has been determined that the process according to the invention gives a higher proportion of BHET in the cleavage products compared to the prior art processes which use glycolates obtained by dissolving the corresponding alkali metal hydroxides in glycol.

[0064] 1. Step (a): Electrolysis of glycol and M A Glycolate and solution L 1 Get The glycols and M used in the process according to the invention A Glycolate and solution L 1 According to the invention, the electrolytic cell E <1> It is obtained by electrolysis in

[0065] "Glycol" means, for the purposes of this invention, a glycol having the formula HO-CH 2 -CH 2 It is understood to be 1,2-ethylenediol having the —OH group (CAS number 107-21-1).

[0066] "M A "Glycolate" means, for the purposes of the present invention, a glycol and M A It is understood to be a salt of "M A The term "glycolate" includes A O-CH2 -CH 2 -OH and M A O-CH 2 -CH 2 -OM A At least one of, preferably at least M A O-CH 2 -CH 2 -OH, very preferably M A O-CH 2 -CH 2 -OH and M A O-CH 2 -CH 2 -OM A is included.

[0067] M A is an alkali metal cation, in particular selected from lithium, sodium, potassium, preferably selected from sodium, potassium. Very preferably, the alkali metal cation is sodium.

[0068] 1.1 Electrolytic cell E M used in step (b) of the process according to the invention A Glycol solution of glycolate L 1 <21> is produced in the electrolytic cell E in step (a) of the method according to the invention.

[0069] The electrolytic cell E comprises at least one anode chamber K A and at least one cathode chamber K K and optionally at least one intermediate chamber K M This includes two or more anode chambers K A and / or cathode chamber K K and / or intermediate chamber K M Also included is an electrolysis cell E comprising: a chamber connected in a modular manner. Electrolysis cells with these chambers are described, for example, in DR 258143 A1 and US 2006 / 0226022 A1.

[0070] The electrolysis cell E, in a preferred embodiment of the present invention, is provided with an anode chamber K A and cathode chamber K K and an intermediate chamber K optionally present therebetween M It is equipped with:

[0071] The electrolytic cell E is usually A It is equipped with the exterior wall W A is in particular made of a material selected from the group consisting of steel, preferably rubberized steel, plastic, in particular Telene® (thermosetting polydicyclopentadiene), PVC (polyvinyl chloride), PVC-C (post-chlorinated polyvinyl chloride), PVDF (polyvinylidene fluoride). A may in particular be perforated for supply and discharge. In that case, W A At least one anode chamber K A and at least one cathode chamber K K and, in an embodiment in which the electrolytic cell E comprises such a chamber, at least one intermediate chamber K M And there exists.

[0072] 1.1.1 Cathode chamber K K At least one cathode chamber K K At least one supply Z KK and at least one discharge section A KK and the cathode electrode E K Interior space with KK It is equipped with:

[0073] Electrolysis cell E is in the intermediate chamber K M If the anode chamber K is not equipped with A Inner Space I KA The cathode chamber K is separated by a partition wall W. K Inner Space I KK The electrolytic cell E is separated from at least one intermediate chamber K M If equipped with a cathode chamber K K Inner Space I KKThe intermediate chamber K is separated by a partition wall W. M Inner Space I KM It is separated into two sections:

[0074] The partition wall W and its arrangement within the electrolytic cell E will be described later (section 1.1.4).

[0075] 1.1.1.1 Cathode electrode E K Cathode Chamber K K In this case, the cathode electrode E K Interior space with KK Such a cathode electrode E K Suitable electrodes include any electrode known to the skilled artisan that is stable under the conditions of step (a) of the method according to the invention. Such electrodes are in particular described in paragraph

[0025] of WO 2014 / 008410 or in paragraph

[0030] of DE 10360758 A1. This electrode E K can be selected from the group consisting of a mesh wool, a three-dimensional matrix structure or a "sphere". The cathode electrode E K In particular, E comprises a material selected from the group consisting of steel, nickel, copper, platinum, platinized metals, palladium, palladium on carbon, titanium, and more preferably comprises a material selected from the group consisting of steel and nickel. K comprises steel, even more preferably VA steel (=stainless steel).

[0076] Intermediate chamber K M In an embodiment of the electrolysis cell E comprising an intermediate chamber K M Anode chamber K A and cathode chamber K K It exists between.

[0077] 1.1.1.2 Supply section Z KK and discharge section A KK Cathode Chamber K K also includes at least one supply Z KK and at least one discharge section A KKThis allows, for example, the solution L 2 A liquid such as K Inner Space I KK For example, solution L 1 Here, it is possible to remove liquid such as KK and discharge section A KK The liquid is in the cathode chamber K K Inner Space I KK When flowing through the cathode electrode E K In contact with the cathode chamber K K This means that when carrying out step (a) of the method according to the invention, A A solution of glycols containing glycolates L 2 Cathode chamber K K Inner Space I KK When passing through discharge section A KK Solution L 1 This is a prerequisite for obtaining

[0078] Supply section Z KK and discharge section A KK can be installed in the electrolysis cell E in a manner known to those skilled in the art, for example by holes in the outer wall and corresponding connectors (valves), which allow easy supply or discharge of liquid.

[0079] 1.1.2 Anode chamber K A At least one anode chamber K A At least one supply Z KA and at least one discharge section A KA and the anode electrode E A Interior space with KA It is equipped with:

[0080] Electrolysis cell E is in the intermediate chamber K M If equipped with an anode chamber K A Inner Space I KA is separated from the intermediate chamber K by a diffusion barrier W. M Inner Space IKM It is separated into two sections:

[0081] Electrolysis cell E is in the intermediate chamber K M If the anode chamber K does not have an internal space I KA The cathode chamber K is separated by a partition wall W. K Inner Space I KK It is separated into two sections:

[0082] 1.1.2.1 Anode electrode E A Anode Chamber K A In this case, the anode electrode E A Interior space with KA Such an anode electrode E A Suitable electrodes include any electrode known to the skilled artisan that is stable under the conditions of step (a) of the method according to the invention. Such electrodes are in particular described in paragraph

[0024] of WO 2014 / 008410 or in paragraph

[0031] of DE 10360758 A1. This electrode E A The anode electrode E may consist of one layer or of several flat layers parallel to one another, each of which may be perforated or elongated. A In particular, the anode electrode E comprises a material selected from the group consisting of ruthenium oxide, iridium oxide, nickel, cobalt, nickel tungstate, nickel titanate and, in particular, precious metals such as platinum, which is supported on a support such as titanium or Kovar® (an iron / nickel / cobalt alloy, the individual proportions of which are preferably as follows: 54% by weight iron, 29% by weight nickel, 17% by weight cobalt). Other possible anode materials are, in particular, stainless steel, lead, graphite, tungsten carbide and titanium diboride. Preferably, the anode electrode E A The titanium anode coated with ruthenium oxide / iridium oxide (RuO 2 +IrO 2 / Ti).

[0083] 1.1.2.2 Supply section Z KA and discharge section A KA Anode Chamber K A is the supply section Z KA and discharge section A KA This also provides a solution L 3 A liquid like this is placed in the anode chamber K A Inner Space I KA For example, solution L 4 Here, it is possible to remove liquid such as KA and discharge section A KA The liquid is in the anode chamber K A Inner Space I KA When flowing through the anode electrode E A In contact with the anode chamber K A This means that when carrying out step (a) of the method according to the invention, the solution L of salt S is 3 Anode chamber K A Inner Space I KA When passing through discharge section A KA Solution L 4 This is a prerequisite for obtaining

[0084] Supply section Z KA and discharge section A KA can be installed in the electrolytic cell E by a method known to those skilled in the art, for example by holes in the outer wall and corresponding connectors (valves), which facilitate the supply or discharge of liquid. M In a particular embodiment, the supply Z KA can also be present inside the electrolysis cell, for example as perforations in the diffusion barrier D.

[0085] 1.1.3 Optional intermediate chamber K M The electrolytic cell E used in step (a) of the method according to the invention may optionally have at least one intermediate chamber K M This optional intermediate chamber K M is the cathode chamber K K and anode chamber K AThe intermediate chamber K exists between M At least one supply Z KM and at least one discharge section A KM and Inner Space I KM It is equipped with:

[0086] Electrolysis cell E is in the intermediate chamber K M If equipped with an anode chamber K A Inner Space I KA is separated from the intermediate chamber K by a diffusion barrier W. M Inner Space I KM It is divided into two sections: A KM Then, the connection part V AM Powered by Z KA Since it is connected to AM Liquid by I KM From I KA can be passed through.

[0087] 1.1.3.1 Diffusion Barrier D Optional intermediate chamber K M Inner Space I KM is separated from the anode chamber K by a diffusion barrier D. A Inner Space I KA The cathode chamber K is separated by a partition wall W. K Inner Space I KK It is separated into two sections:

[0088] The diffusion barrier D is stable under the conditions of step (a) of the method according to the invention and has a structure suitable for the anode chamber K A Inner Space I KA from the liquid present in any intermediate chamber K M Inner Space I KM Any material that blocks or retards the transfer of protons to the substrate can be used.

[0089] In particular, an ion-nonspecific partition or a membrane permeable to specific ions is used as the diffusion barrier D. Preferably, the diffusion barrier D is an ion-nonspecific partition.

[0090] The material of the non-ion-specific partition is in particular selected from the group consisting of fabrics, in particular textile fabrics or metal meshes, glass, in particular sintered glass or glass frit, ceramics, in particular ceramic frits, membrane diaphragms, particularly preferably textile fabrics or metal meshes, particularly preferably textile fabrics. The textile fabric preferably comprises a plastic, more preferably a plastic selected from PVC, PVC-C, polyvinyl ether ("PVE"), polytetrafluoroethylene ("PTFE").

[0091] If the diffusion barrier D is a "membrane permeable to specific ions", this means according to the invention that the respective membrane prefers the diffusion of a specific ion through it over the diffusion of another ion through it. In particular, this means a membrane that prefers the diffusion of an ion of a specific charge type through it over the diffusion of an ion of the opposite charge through it. Even more preferably, the membrane permeable to specific ions further prefers the diffusion of a specific ion of one charge type through it over the diffusion of another ion of the same charge type through it.

[0092] If the diffusion barrier D is a "membrane permeable to specific ions", the diffusion barrier D is in particular an anion-conducting or cation-conducting membrane.

[0093] An anion-conducting membrane is according to the invention a membrane that selectively conducts anions, preferably a specific anion, in other words, it prefers the diffusion of anions through it over the diffusion of cations, particularly protons, through it, and even more preferably it also prefers the diffusion of a specific anion through it over the diffusion of another anion through it.

[0094] A cation-conducting membrane is according to the invention a membrane that selectively conducts cations, preferably selectively for a particular cation, in other words, a cation-conducting membrane preferentially conducts the diffusion of a cation through the membrane over the diffusion of anions through the membrane, and even more preferably, a cation-conducting membrane further preferentially conducts the diffusion of a particular cation through the membrane over the diffusion of another cation through the membrane, and even more preferably, a cation-conducting membrane further preferentially conducts the diffusion of a cation other than the proton through the membrane, and even more preferably, the sodium cation through the membrane over the diffusion of the proton through the membrane.

[0095] "Preference for the diffusion of a particular ion X over another ion Y" refers in particular to the diffusion coefficient (units m 2 / s) is 10 times, preferably 100 times, more preferably 1000 times higher than the diffusion coefficient of ion type Y in the membrane.

[0096] If the diffusion barrier D is a membrane that is permeable to specific ions, then the anode chamber K A From intermediate chamber K M This is preferably an anion conducting membrane since it is particularly good at preventing the diffusion of protons into the anion conducting membrane.

[0097] In particular, anion-conducting membranes are used that are selective for the anions contained in the salt S. Such membranes are known and available to those skilled in the art. According to the invention, the salt S is M A as a cation.

[0098] The salt S is preferably M A of the formula (I) are preferably halides, sulfates, sulfites, nitrates, bicarbonates or carbonates, and even more preferably halides.

[0099] The halides are fluoride, chloride, bromide and iodide. Highly preferred halides are chlorides.

[0100] Preferably, as anion conducting membrane a membrane selective for halides, preferably chloride, is used.

[0101] Anion-conducting membranes are described, for example, in MA Hickner, AMHerring, EB Coughlin, Journal of Polymer Science, Part B: Polymer Physics 2013, 51, 1727-1735, CGArges, V. Ramani, PNPintauro, Electrochemical Society Interface 2010, 19, 31-35, WO 2007 / 048712, and Volkmar M. Schmidt, textbook Elektrochemische Verfahrenstechnik: Grundlagen, Reaktionstechnik, Prozessoptimierung, 1st edition (October 8, 2003), p. 181.

[0102] Thus, even more preferably, as anion conducting membranes, organic polymers are used which are in particular chosen from polyethylene, polybenzimidazole, polyetherketone, polystyrene, polypropylene or fluorinated membranes such as polyperfluoroethylene, preferably polystyrene, which organic polymers are selected from -NH 3 + , -NRH 2 + , -NR 3 + , =NR + ;-PR 3 + (wherein R is preferably an alkyl group having 1 to 20 carbon atoms) or another cationic group. Preferably, the organic polymer has a covalently attached functional group selected from -NH 3 + , -NRH 2 + , -NR 3 + More preferably, selected from -NH 3 + , -NR 3+ and even more preferably selected from -NR 3 + having a covalently attached functional group selected from

[0103] In the case where the diffusion barrier D is a cation-conducting membrane, this is especially the case for M A , i.e. a membrane selective for the cations contained in the salt S. Still more preferably, the diffusion barrier D is an alkali cation-conducting membrane, still more preferably a potassium and / or sodium ion-conducting membrane, very preferably a sodium ion-conducting membrane.

[0104] Cation-conducting membranes are described, for example, in the textbook Elektrochemische Verfahrenstechnik: Grundlagen, Reaktionstechnik, Prozessoptimierung, 1st edition (October 8, 2003), p. 181, by Volkmar M. Schmidt.

[0105] Thus, even more preferably, as cation-conducting membranes, organic polymers are used, in particular selected from fluorinated membranes such as polyethylene, polybenzimidazole, polyetherketone, polystyrene, polypropylene or polyperfluoroethylene, preferably polystyrene, polyperfluoroethylene, which organic polymers are selected from -SO 3 - , -COO - , -PO 3 2- , -PO 2 H - , preferably -SO 3 - (described in DE 102010062804 A1, U.S. Pat. No. 4,831,146).

[0106] This may be, for example, sulfonated polyperfluoroethylene (Nafion® with CAS number: 31175-20-9). These are known to the skilled artisan, for example from WO 2008 / 076327, US 2010 / 0044242, US 2016 / 0204459, and can be purchased under the trade names Nafion®, Aciplex® F, Flemion®, Neosepta®, Ultrex®, PC-SK®. Neosepta® membranes are described, for example, in SAMareev, D.Yu.Butylskii, ND Pismenskaya, C. Larchet, L.Dammak, VV Nikonenko, Journal of Membrane Science 2018, 563, 768-776.

[0107] If a cation-conducting membrane is used as the diffusion barrier D, this can be, for example, a polymer functionalized with sulfonic acid groups, in particular a polymer of the formula P NAFION wherein n and m are each independently 1 to 10. 6 is an integer of 10 to 10 5 and even more preferably an integer of 10 2 ~10 4 is an integer.

[0108] [ka]

[0109] 1.1.3.2 Supply section Z KM and discharge section A KM Optional intermediate chamber K M is the supply section Z KM and discharge section A KM This also provides a solution L 3 A liquid such as M Inner Space IKM For example, solution L 3 A liquid like this is placed in the anode chamber K A Inner Space I KA It will be possible to move it to another location.

[0110] Supply section Z KM and discharge section A KM can be installed in the electrolysis cell E by a method known to those skilled in the art, for example by holes in the outer wall and corresponding connectors (valves), which facilitate the supply or discharge of liquid. KM can also be present inside the electrolysis cell, for example as perforations in the diffusion barrier D.

[0111] 1.1.3.3 Connection V AM In the electrolytic cell E used in step (a) of the method according to the invention, the outlet A KM is the connection part V AM Liquid by I KM From I KA The connection part V AM Powered by Z KA is connected to

[0112] Connection V AM may be formed inside the electrolytic cell E and / or outside the electrolytic cell E, preferably inside the electrolytic cell.

[0113] 1) The connection part V AM is formed inside the electrolytic cell E, the connection V AM is preferably formed by at least one perforation of the diffusion barrier D. This embodiment is particularly preferred if a non-ion-specific partition wall is used as the diffusion barrier D, in particular a metal mesh or a textile woven fabric, which acts as the diffusion barrier D and which, due to the nature of the web, already has perforations or gaps, which are formed at the connection V AM It functions as:

[0114] 2) The embodiment described below is particularly preferred when a membrane permeable to certain ions is used as the diffusion barrier D: In this embodiment, the connection V AM is formed outside the electrolytic cell E, whereby the connection V AM preferably extends outside the electrolysis cell E KM and Z KA This is in particular formed by the connection of the intermediate chamber K M Inner Space I KM From exterior wall W A through, preferably, the intermediate chamber K M Discharge section A at the bottom KM is formed, and more preferably still, the supply Z KM is the intermediate chamber K M On the top surface of the anode chamber K A Inner Space I KA Supply to Z KA But the exterior wall W A through, preferably, the anode chamber K A and these are connected by a line, for example a pipe or hose, preferably made of a material selected from rubber and plastic. In that case, the discharge section A KA More preferably, the anode chamber K A is formed on the upper surface of the

[0115] "Intermediate chamber K M Discharge section A at the bottom KM " refers to solution L 3 is in the same direction as gravity in the middle chamber K M From the outlet A KM is installed in electrolytic cell E.

[0116] "Anode Chamber K A The bottom supply section Z KA " refers to solution L 3 against gravity in the anode chamber K A Supply section Z KA is installed in electrolytic cell E.

[0117] "Intermediate chamber K M Supply section Z on the top of KM " refers to solution L 3 is in the same direction as gravity in the middle chamber K M Supply section Z KM is installed in electrolytic cell E.

[0118] "Anode Chamber K A Discharge section A on the top of KA " refers to solution L 4 against gravity in the anode chamber K A From the outlet A KA is installed in electrolytic cell E.

[0119] Here, in this embodiment, the discharge section A KM is the intermediate chamber K M The bottom outer wall W A The supply section Z is formed by KA Anode chamber K A The bottom outer wall W A This arrangement is particularly advantageous and therefore preferred when the anode chamber K A The gas formed in L 4 Together with the anode chamber K A In this embodiment, it is particularly easy to drain the liquid from the liquid source and then separate it further. Figure 1B shows such an embodiment.

[0120] As shown in particular in FIG. 1B, the connection part V AM is formed outside the electrolytic cell E, especially Z KM and A KM is the intermediate chamber K M Outer wall W A are placed on the opposite sides of KM is at the bottom of electrolytic cell E, and A KM is placed on the top surface of the electrolytic cell E, or vice versa), and Z KA and A KA Anode chamber K A Outer wall W A (i.e., ZKA is at the bottom of electrolytic cell E, and A KA is placed on top of the electrolytic cell E, or vice versa). This geometry allows 3 There are two chambers K M and K. A In this case, Z KA and Z KM may be formed on the same surface of the electrolytic cell E, in which case A KM and A KA are also automatically formed on the same surface of the electrolytic cell E. Alternatively, as in the embodiment shown in FIG. 1B, Z KA and Z KM may be formed on the opposing surface of the electrolytic cell E, in which case A KM and A KA is also automatically formed on the opposing surface of the electrolytic cell E.

[0121] 3) The connection part V AM is formed inside the electrolytic cell E, this is particularly the case when one face ("face A") of the electrolytic cell E (which may be the top or bottom face of the electrolytic cell E, preferably the top face as shown in FIG. 6B) is connected to the supply Z KM and discharge section A KA and the diffusion barrier D extends from this face ("face A") into the electrolysis cell E, but does not reach completely to the opposite face ("face B") of face A of the electrolysis cell E (which is then the bottom or the top face of the electrolysis cell E), which can be ensured in this case by covering more than 50% of the height of the three-chamber cell E, more preferably 60% to 99% of the height of the three-chamber cell E, even more preferably 70% to 95% of the height of the three-chamber cell E, even more preferably 80% to 90% of the height of the three-chamber cell E, and still more preferably 85% of the height of the three-chamber cell E. Since the diffusion barrier D does not contact face B of the three-chamber cell E, the diffusion barrier D and the outer wall W of face B of the three-chamber cell E are not in contact with each other. A In this case, a gap occurs between the connection part V AM This geometric shape allows L 3 There are two chambers K M and K. AIt will flow completely through.

[0122] According to these embodiments, the aqueous salt solution L 3 is the anode electrode E A This best ensures that the acid is formed by flowing around the acid-sensitive solid electrolyte before contacting the electrolyte.

[0123] According to the present invention, the "bottom of the electrolytic cell E" refers to the surface of the electrolytic cell E that is exposed to the solution (e.g., the bottom of the electrolytic cell E in FIG. 1B). KM L in 3 ) exits the electrolytic cell E in the same direction as gravity, or the surface of the electrolytic cell E on which the solution (e.g., Z in Figs. 1A, 1B, 6A and 6B) KK L in 2 , and Z in Drawings 1A and 1B KA L in 3 ) is the surface on which the water is fed into the electrolytic cell E against gravity.

[0124] According to the present invention, the "upper surface of the electrolytic cell E" refers to the surface of the electrolytic cell E that is exposed to the solution (e.g., the A of FIG. 1A, FIG. 1B, FIG. 6A, and FIG. 6B). KA L in 4 and A KK L in 1 ) exits the electrolytic cell E against gravity, or the surface of the electrolytic cell E where the solution (e.g., Z in Fig. 1B, Fig. 6A and Fig. 6B) KM L in 3 ) is the surface that is fed into the electrolytic cell E in the same direction as gravity.

[0125] 1.1.3.4 Intermediate chamber K M Further embodiments of the present invention In a preferred embodiment of the electrolysis cell E, the interior space I KM also has at least one additional feature selected from the following: 1) Electrolyte L 3 internal structures installed to create turbulence in the 2) Stirring device; 3) Additional inert gas (e.g., nitrogen or a noble gas) can be introduced through an additional supply at the bottom of the intermediate chamber and an additional exhaust at the top of the intermediate chamber. If the salt S is a carbonate or bicarbonate, then CO 2 Gases such as I are discharged through this additional exhaust section. KM can be discharged from

[0126] These additional preferred embodiments 1), 2) and 3) provide KM When the electrolyte L 3 This creates vortices and turbulence in the intermediate chamber, which further prevents the formation of a pH gradient in the intermediate chamber and, as a result, prevents damage to the AFK due to a too low pH. This increases the service life of the AFK.

[0127] 1.1.4 Partition wall W The electrolytic cell E used in step (a) of the method according to the invention is equipped with a partition wall W. The partition wall W is provided with at least one alkali cation-conducting solid electrolyte ceramic F A In a preferred embodiment, the partition wall W comprises an alkali cation-conducting solid electrolyte ceramic F A It consists of:

[0128] In an alternative preferred embodiment of the present invention, the partition wall W is made of at least two alkali cation conductive solid electrolyte ceramics (hereinafter, "alkali cation conductive solid electrolyte ceramics" will be abbreviated as "AFK") F, which are optionally separated from each other by partition elements T. A and F B Includes.

[0129] The partition wall W has two opposing faces S KK and S A / MK That is, the surface S A / MK is the surface S KK (and vice versa). Two faces S KK and S A / MK in particular include planes that are substantially parallel to one another.

[0130] The geometric shape of the partition wall W is not otherwise further limited and can in particular be adapted to the cross-section of the electrolysis cell E in which it is used. For example, it can have the geometric shape of a rectangular parallelepiped and thus a rectangular cross-section, or the geometric shape of a truncated cone or cylinder and thus a circular cross-section.

[0131] Optionally, the partition W can also have a rectangular parallelepiped geometry with rounded corners and / or bulges, which in turn can have holes. In that case, the partition W has bulges ("rabbit ears") that can also fasten the partition W to the electrolysis cell and / or fasten frame parts of the partition W to each other.

[0132] Face S of partition wall W KK is the surface KK and the surface S of the partition wall W A / MK is the surface A / MK has.

[0133] The "partition" feature means that the partition W is liquid-tight. Thus, an aqueous solution, an alcohol solution, alcohol or water can penetrate the surface S KK From surface S A / MK There is no gap where the electrolyte can flow to or from the electrolyte. This means that the partition wall W is made of at least two alkali cation conductive solid electrolyte ceramics F A and F B and optionally a partition element T, A and F B and at least one optionally present partition element T are connected to one another without gaps.

[0134] The partition wall W which can be used in the electrolysis cell E according to step (a) of the method according to the invention also includes embodiments in which the partition wall W comprises three or more AFKs, for example 4 or 9 or 12 AFKs, where the AFKs are either immediately adjacent to one another or separated from one another by partition elements T.

[0135] However, if the AFKs are directly adjacent to each other, the aqueous liquid or water or glycol or glycol solution may KK From surface S A / MK It is necessary to precisely match each adjacent AFK in order to exclude the formation of gaps between them that could allow for flow to the other AFK. Therefore, if a partition wall W contains two or more AFKs, it is advantageous and preferable that within the partition wall W, all AFKs contained in the partition wall W are separated from each other by at least one separation element T, i.e., no AFK is directly connected to another AFK, i.e., without a separation element T between them.

[0136] Partition W is further divided into F, an AFK contained in partition W. A However, the surface O KK Not only through the surface A / MK The partition wall W is characterized by being directly accessible through at least two AFKs F A , F B In an embodiment including the above, all AFKs included in the partition wall W are located on the surface O KK Not only through the surface A / MK It is preferable that the contact is directly accessible via the

[0137] "Directly accessible" means that the AFK included in the partition wall W is directly accessible from the surface O KK and O A / MK At least a part of the AFK is formed by the surface of the AFK included in the partition wall W, that is, the AFK included in the partition wall W is formed by two surfaces O KK and O A / MK Since the two surfaces O of the partition wall W are directly accessible at KK and O A / MK This means that the material can be wetted with, for example, an aqueous solution, a glycol solution, glycol, or water.

[0138] Regarding the placement of AFKs at partition W, this means that for all AFKs contained in partition W, KK Surface of KK From surface S A / MK Surface ofA / MK This means that there is a path that goes completely through each AFK.

[0139] If the partition wall W comprises at least one partition element T, typically the at least one partition element T also has a surface O KK Not only through at least a portion of the surface O A / MK It is also possible to directly contact the substrate through at least a portion of the substrate.

[0140] "Directly accessible" means that the surface O of at least one partition element T, which is optionally provided on the partition wall W, KK and O A / MK is formed by the surface of the partition element T, i.e., the partition element T is formed by two surfaces O KK and O A / MK Since the two surfaces O of the separation element T are directly accessible at KK and O A / MK This means that the material can be wetted with, for example, an aqueous solution, an alcoholic solution, alcohol or water.

[0141] Regarding the arrangement of any partition element T in the partition wall W, this is especially true for the partition element T optionally provided in the partition wall W, the surface S KK Surface of KK From surface S A / MK Surface of A / MK This means that there exists a path through the partition element T and possibly through the ceiling Di but not through AFK.

[0142] In a preferred embodiment of the partition wall W, the surface O A / MK At least 50%, more preferably at least 60%, even more preferably at least 70%, even more preferably at least 85% of the AFKs are formed by the AFKs contained in the partition wall W.

[0143] In a preferred embodiment of the partition wall W, the surface O KKAt least 50%, more preferably at least 60%, even more preferably at least 70%, even more preferably at least 85% of the AFKs are formed by the AFKs contained in the partition wall W.

[0144] In an embodiment in which the partition wall W has two or more AFKs, the surface O KK In particular, 50% to 99%, more preferably at least 60% to 96%, even more preferably at least 70% to 92%, even more preferably at least 85% to 90% of the surface O is formed by the AFK contained in the partition wall W, and even more preferably, the surface O KK The remainder of the surface O is formed by the partition element T and, optionally, the frame element R. At the same time, in the embodiment in which the partition wall W has two or more AFKs, the surface O A / MK In particular, 50% to 99%, more preferably at least 60% to 96%, even more preferably at least 70% to 92%, even more preferably at least 85% to 90% of the surface O is formed by the AFK contained in the partition wall W, and even more preferably, the surface O A / MK The remainder is formed by a partition element T and optionally a frame element R.

[0145] In a preferred embodiment, the partition wall W <16> Alkaline cation conductive solid electrolyte ceramic F A and optionally a frame element R. Even more preferably, the partition wall W <16> Alkaline cation conductive solid electrolyte ceramic F A It consists of:

[0146] In another preferred embodiment, the partition wall W has at least four AFKs F A , F B , F C and F D In this case, the partition W preferably includes exactly four AFKs F A , F B , F C and F D Includes.

[0147] In a further preferred embodiment, the partition wall W has at least 9 AFKs F A , F B , F C , F D , F E , F F , F G , F H and F I In this case, the partition W preferably includes exactly 9 AFKs F A , F B , F C , F D , F E , F F , F G , F H and F I Includes.

[0148] In a further preferred embodiment, the partition wall W has at least 12 AFKs F A , F B , F C , F D , F E , F F , F G , F H , F I , F J , F K and F L In this case, the partition W preferably has exactly 12 AFKs F A , F B , F C , F D , F E , F F , F G , F H , F I , F J , F K and F L Includes.

[0149] Arranging at least two AFKs next to each other within the partition W has the advantage that, compared to arranging only one AFK, there are more directions in which the AFKs can expand during temperature fluctuations that occur during operation of the electrolysis cell. The NaSICON plates acting as partitions are confined within the electrolysis cell by the outer wall of the electrolysis cell or by the solid plastic frame. Therefore, mechanical stresses occurring within the NaSICON during expansion cannot escape, which could lead to fracture of the ceramic.

[0150] In contrast, the individual AFKs inside the partition wall W are preferably adjacent to the partition element T, which has two advantageous effects, both of which increase the long-term stability of the AFKs: - each AFK provides at least one further degree of freedom, i.e. an expandable dimension: in addition to the expansion in the z-direction (i.e. across the thickness of the ceramic plate at right angles to the plane of the partition wall W), expansion in the x-direction and / or y-direction, i.e. horizontally and vertically in the plane of the partition wall W, is now also possible. This direction of expansion is not given, or at least severely limited, if the AFK spans the cross-section of the electrolytic cell, for example as a solid plate, and is adjacent to a solid wall of the electrolytic cell; - Compared to a partition of the same size consisting of only one AFK, the stress generated within the small AFK is smaller in absolute value as it is divided into several smaller AFKs, and can be dissipated more quickly, so the stress does not build up so rapidly that it breaks the AFK.

[0151] This significantly reduces the tendency for the "split" AFK in the partition wall W to break, compared to when plates are used.

[0152] 1.1.4.1 Alkaline cation conductive solid electrolyte ceramic "AFK" Alkaline cation conductive solid electrolyte ceramic F contained in partition wall W A , F B As the surface S, a cation, particularly an alkali cation, and even more preferably a sodium cation, is preferably used. A / MK From surface S KKAny solid electrolyte that can be transported to a suitable temperature range is suitable. Such solid electrolytes are known to the person skilled in the art and are described, for example, in DE 102015013155 A1, WO 2012 / 048032 A1, paragraphs

[0035] ,

[0039] ,

[0040] , US 2010 / 0044242 A1, paragraphs

[0040] ,

[0041] , and DE 10360758 A1, paragraphs

[0014] to

[0025] . They are commercially available under the names NaSICON, LiSICON, KSICON. Sodium ion-conducting solid electrolytes are preferred, which even more preferably have the NaSICON structure. NaSICON structures that can be used according to the invention are further described, for example, in N. Anantharamulu, K. Koteswara Rao, G. Rambabu, B. Vijaya Kumar, Velchuri Radha, M. Vithal, J Mater Sci 2011, 46, 2821-2837.

[0153] In a preferred embodiment of the partition wall W, the alkali cation conductive solid electrolyte ceramic contained in the partition wall W, in particular AFK, is A are, independently of one another, of the formula M I 1+2w+x-y+z M II w M III x Zr IV 2-w-x-y M V y (SiO 4 ) z (PO 4 ) 3-z It has the NaSICON structure.

[0154] Here, M I is Na + , Li + Preferably, Na + It is.

[0155] Here, M II is a divalent metal cation, preferably Mg 2+, Ca 2+ , Sr 2+ , B.A. 2+ , Co 2+ , Ni 2+ More preferably, Co 2+ , Ni 2+ is selected from.

[0156] Here, M III is a trivalent metal cation, preferably Al 3+ , Ga 3+ , Sc 3+ , La 3+ , Y 3+ , Gd 3+ , Sm 3+ , Lu 3+ , Fe 3+ , Cr 3+ More preferably, Sc 3+ , La 3+ , Y 3+ , Gd 3+ , Sm 3+ Particularly preferably, Sc 3+ , Y 3+ , La 3+ is selected from.

[0157] Here, M V is a pentavalent metal cation, preferably V 5+ , Nb 5+ , Ta 5+ is selected from.

[0158] The Roman alphabet suffixes I, II, III, IV, and V indicate the oxidation states in which the respective metal cations exist.

[0159] w, x, y, z are real numbers with 0≦x<2, 0≦y<2, 0≦w<2, 0≦z<3, where w, x, y, z are selected such that 1+2w+x-y+z≧0 and 2-wxy≧0.

[0160] Here, the NaSICON structure is still more preferably according to the invention of the formula Na (1+v) Zr 2 S v P(3-v) O 12 where v is a real number and 0≦v≦3. Highly preferably, v=2.4.

[0161] Partition W is at least 2 AFK F A , F B In a preferred embodiment of the partition wall W including the AFKs, all of the AFKs included in the partition wall W have the same structure.

[0162] 1.1.4.2 Partition element T Partition W is at least 2 AFK F A , F B In the embodiment of the partition wall W according to the invention, which comprises at least two alkali cation-conducting solid electrolyte ceramics F, the partition wall W preferably comprises one partition element T. In that case, the partition element T comprises at least two alkali cation-conducting solid electrolyte ceramics F, which are included in the partition wall W according to the invention. A and F B That is, the partition element T is composed of at least two alkali cation conductive solid electrolyte ceramics F contained in a partition wall W. A and F B is placed between.

[0163] Any object is suitable as the partition element T, which is preferably provided in the partition wall W, by means of which the respective AFKs can be arranged separated from one another. In this case, the AFKs are connected to the partition element T without gaps, so as not to impair the function of the partition wall, which is intended to separate the cathode chamber from the adjacent intermediate or anode chamber in a liquid-tight manner in the electrolysis cell E.

[0164] The shape of the partition element T can be selected by a person skilled in the art depending on the number of AFKs that the partition wall W contains in a preferred embodiment.

[0165] If the partition wall W comprises, for example, two or three AFKs, these can each be separated by webs arranged as partition elements T between the AFKs.

[0166] If the partition wall W contains four or more AFKs, these can be separated by partition elements T having the shape of a cross or a grid.

[0167] Partition W is at least 2 AFK F A , F B In an embodiment of the partition wall W according to the present invention comprising at least four AFKs, it is particularly preferred that the partition wall W comprises at least four AFKs, in which case it is even more preferred that the partition element T is cross- or lattice-shaped, since in this case it is ensured that the AFK has full availability of all three dimensions for thermal expansion / contraction.

[0168] In this case, the partition element T can consist of one piece. The AFKs are then fixed tightly to the partition element T, for example by means known to the person skilled in the art, for example by means of adhesives, preferably epoxy resins, phenolic resins being used. Alternatively or additionally, the partition element T can also be designed in such a way that the respective AFKs can be snapped or clamped into the partition element. This can be done as soon as possible during the production of the partition wall W.

[0169] In the preferred embodiment in which the partition wall W comprises a partition element, this in particular comprises a seal Di between the partition element T and the AFK (FIGS. 3B, 3C). This ensures particularly well that the partition wall W is liquid-tight. The seal Di can be selected by the skilled person for the respective AFK or for the respective partition element T.

[0170] The sealing Di in particular comprises a material selected from the group consisting of elastomers, adhesives, preferably elastomers.

[0171] Suitable elastomers are in particular rubbers, preferably ethylene propylene diene rubbers ("EPDM"), fluoropolymer rubbers ("FPM"), perfluoropolymer rubbers ("FFPM"), acrylonitrile butadiene rubbers ("NBR").

[0172] In a further preferred embodiment, the partition element T is made up of at least two parts T 1 and T 2 These can be fixed together and therefore AFK can be sandwiched between them.

[0173] In this embodiment, it is particularly preferred to further install a sealing Di between the partition element T and the AFK in order to ensure liquid-tightness.

[0174] The partition element T preferably comprises a material selected from the group consisting of plastic, glass, wood. The partition element T is particularly preferably made of plastic. Even more preferably, the plastic is selected from the group consisting of polypropylene, polystyrene, polyvinyl chloride, post-chlorinated polyvinyl chloride ("PVC-C").

[0175] 1.1.4.3 Frame element R In a further preferred embodiment, the partition wall W also comprises a frame element R. The frame element R differs from the partition element T in that it is not arranged between the alkali cation-conducting solid electrolyte ceramics contained in the partition wall W, i.e. does not separate them from one another. The frame element R is in particular arranged on the surface O KK and O A / MK This means in particular that: the frame element R defines the surface O at least partially, preferably completely. KK and O A / MK at least partially, and preferably completely, surrounds

[0176] In this case, the frame element R is KK and OA / MK Preferably, the frame element R is formed as part of the surface O. KK and O A / MK is formed as part of

[0177] The frame element R is especially KK and O A / MK The surface of the substrate 10 may be directly accessible via a surface 12 or not, preferably directly accessible.

[0178] "Not directly accessible" refers to a frame element R that is optionally provided on the partition wall W, and the frame element R is in contact with the surface S of the partition wall W. KK and S A / MK In this case, in particular, the frame element R is formed only as a part of the surface of the partition wall W other than the surface S. KK and S A / MK It forms at least 1%, more preferably at least 25%, more preferably at least 50%, and even more preferably 100% of the surface of the face other than the face.

[0179] "Directly accessible" means that the surface O of the frame element R, which is optionally provided on the partition wall W, KK and O A / MK A part of the frame element R is formed by the surface of the frame element R, that is, the frame element R provided in the partition wall W has two surfaces O KK and O A / MK The two surfaces O of the frame element R are directly accessible at KK and O A / MK This means that the material can be wetted with, for example, an aqueous solution, an alcoholic solution, alcohol or water.

[0180] Regarding the arrangement of the frame element R in the partition wall W, this is KK Surface of KK From surface S A / MK Surface of A / MK,means that there exists a path that goes completely through frame element R.

[0181] This includes the following embodiments: - Surface O KK and O A / MK a part of the edge of which is formed by a frame element R (as shown in Fig. 4B, Fig. 4D); - Surface O KK and O A / MK the edge of which is completely formed by the frame element R (as shown in Drawings 4A, 4C, 7A and 7B); Here, the frame element R is further connected to the surface S of the partition wall W. KK and S A / MK In particular, the frame element R may be formed as at least a part of the surface of the partition wall W other than the surface S. KK and S A / MK It forms at least 1%, more preferably at least 25%, more preferably at least 50%, and even more preferably 100% of the surface of the face other than the face.

[0182] In FIG. 4B and FIG. 4D, for example, the frame element R is located on the surface S of the partition wall W. KK and S A / MK 10. An embodiment is shown in which the axial direction of the slab forms part of the surface of a plane other than the axial direction.

[0183] In FIG. 4A and FIG. 4C, for example, the frame element R is located on the surface S of the partition wall W. KK and S A / MK An embodiment is shown in which the surface of the other side is completely formed.

[0184] The frame element R is in particular manufactured from a material selected from the group consisting of plastic, glass and wood. The frame element R is particularly preferably made of plastic.

[0185] Even more preferably, the plastic is selected from the group consisting of polypropylene, polystyrene, polyvinyl chloride, PVC-C.

[0186] In a further preferred embodiment, when the partition wall W comprises a partition element T and a frame element R, the frame element R and the partition element T are manufactured from the same material, even more preferably both made of plastic, even more preferably this plastic being selected from polypropylene, polystyrene, polyvinyl chloride, PVC-C.

[0187] In this case, the frame element R can consist of one piece. The AFKs are then fixed tightly to the frame element R, for example by means known to the person skilled in the art, for example by means of adhesives, with epoxy resins and phenolic resins being particularly suitable. Alternatively or additionally, the frame element R can also be designed in such a way that the respective AFK can be snapped or clamped into the frame element R.

[0188] This means that the partition W has at least two AFK F A and F B In the preferred embodiment comprising an AFK and at least one partition element T and a frame element R, this also means that the AFK and the at least one partition element T and the frame element R are connected to each other without any gaps.

[0189] In that case, glycol, glycol solution, aqueous solution or water is therefore present on the surface S between the partition element T and the frame element R and the AFK contained in the partition wall W. KK From surface S A / MK There are no gaps that could allow flow into or out of the water.

[0190] In addition, in particular, the partition W has at least two AFKs F A , F Band a frame element R and at least one partition element T, where the frame element R and the at least one partition element T are at least partially formed integrally with one another, the frame element R can consist of two parts, which are fixed to one another and in that case sandwich the AFK between them. In that case, for example, the partition wall W can have a hinge by which the two parts of the frame element R can be folded open and closed. In that case, the partition wall W can further have a lock by which the two parts of the frame element R can be locked in the closed state (Drawing 7A).

[0191] In the closed state, the AFK and, if this is not yet integrally formed with the frame element R, the separation element T, can then be sandwiched between two parts of the frame element R. In this embodiment, in that case, further seals can be provided between the separation element T and the AFK or between the frame element R and the AFK in order to ensure liquid-tightness.

[0192] In a preferred embodiment, the partition wall W has at least two AFKs F A , F B and a frame element R and at least one partition element T, at least part of the partition element T is formed integrally with at least part of the frame element R. This means in particular that at least part of the partition element T is integrated into the frame element R.

[0193] In this case, preferably, at least one partition element T and the frame element R are integral.

[0194] This embodiment of the frame element R has the advantage that the frame element R can function as part of the outer wall when assembling the electrolysis cell E. This part of the partition wall W separates the respective interior spaces I KK , I KA Or I KMSince this part does not come into contact with the solution in the A Furthermore, since the portion sandwiched between the outer wall of the partition wall W and the portion forming a part of it are exposed to pressure, the brittle solid electrolyte ceramic F A is not suitable. Instead, a less crack-resistant and less expensive material is selected for the frame R.

[0195] 1.1.4.4 Manufacturing of Partition Wall W The partition wall W can be manufactured by methods known to those skilled in the art.

[0196] As the partition wall W, F, which is AFK in one embodiment of the method according to the invention, A can be utilized which can be cut or shaped by methods known to those skilled in the art.

[0197] If the partition wall W comprises a frame element R or at least one partition element T, the AFK contained in the partition wall, possibly together with a sealing, can be placed in a mold and the partition element can be cast onto liquid plastic and then solidified (injection molding process), which upon solidification surrounds the AFK.

[0198] Alternatively, the partition element T is cast separately (or partially) and then fixed (eg glued) tightly to at least two AFKs.

[0199] 1.1.4.5 Arrangement of Partition Wall W in Electrolysis Cell E 1) Alkaline cation conductive solid electrolyte ceramic F contained in the partition wall W A Surface O KK Through the surface S KK Inner Space I KK A partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0200] Partition W is at least 2 AFK F A , F Band at least one partition element T and optionally a frame element R, the partition wall W is provided with an alkali cation-conducting solid electrolyte ceramic F A and F B but preferably the partition element T also has a surface O KK Through the surface S KK Inner Space I KK A partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0201] This is the inner space I KK Surface S KK Solution L 2 In that case, when the tank is completely filled with solution L 2 Surface O KK The alkali cation conductive solid electrolyte ceramic F contained in at least the partition wall W is A When the ions (e.g., alkali metal ions such as sodium and lithium) come into contact with F A From solution L 2 This means that a partition wall W is arranged in the electrolysis cell E so that

[0202] Partition W is at least 2 AFK F A , F B and at least one partition element T and optionally a frame element R, this defines an internal space I KK Surface S KK Solution L 2 In that case, when the tank is completely filled with solution L 2 Surface O KK At least two alkali cation conductive solid electrolyte ceramics F included in the partition wall W through A and F B ions (e.g. alkali metal ions such as sodium and lithium) in the F, and preferably also in the partition element T. A and F B From solution L 2 This means that the partition wall W is disposed within the electrolytic cell E so as to be in contact with the

[0203] 2) Furthermore, the electrolytic cell E is connected to the intermediate chamber K M In the embodiment not including the above, the alkali cation-conducting solid electrolyte ceramic F included in the partition wall W is A Surface O A / MK Through the surface S A / MK Inner Space I KA A partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0204] Partition W is at least 2 AFK F A , F B and at least one partition element T and optionally a frame element R, and the electrolysis cell E is provided with an intermediate chamber K M In the absence of such a structure, this is because the alkali cation-conductive solid electrolyte ceramic contained in the partition wall W, and preferably also the partition element T, is provided with a surface O A / MK Through the surface S A / MK Inner Space I KA This means that the partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0205] This means that the electrolytic cell E is M In an embodiment not including the anode chamber K, the partition wall W A Inner Space I KA It borders on the

[0206] In that case, in these embodiments, the internal space I KA Surface S A / MK Solution L 3 In that case, when the tank is completely filled with solution L 3 Surface O A / MK The alkali cation conductive solid electrolyte ceramic F contained in at least the partition wall W is A When the solution comes into contact with the metal, ions (e.g., alkali metal ions such as sodium and lithium) are dissolved in the solution L 4 F who is AFK from A A partition wall W is disposed within the electrolysis cell E to allow access to the

[0207] Partition W is at least 2 AFK F A , F B and at least one partition element T and optionally a frame element R, this defines an internal space I KA Surface S A / MK Solution L 3 In that case, when the tank is completely filled with solution L 3 Surface O A / MK At least two alkali cation conductive solid electrolyte ceramics F included in the partition wall W through A and F B Ions (e.g. alkali metal ions such as sodium and lithium) are introduced into the solution L, and preferably into the partition element T as well. 3 F who is AFK from A and F B This means that the partition wall W is disposed within the electrolytic cell E so as to be in contact with the

[0208] 3) Furthermore, the electrolytic cell E is provided with at least one intermediate chamber K M In the case where the partition wall W is provided with the alkali cation conductive solid electrolyte ceramic F A Surface O A / MK Through the surface S A / MK Inner Space I KM A partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0209] Partition W is at least 2 AFK F A , F B and at least one partition element T and optionally a frame element R, and the electrolytic cell E has at least one intermediate chamber K M In the case where the partition wall W is provided with a surface O, this is because the alkali cation conductive solid electrolyte ceramic contained in the partition wall W, and preferably also the partition element T, A / MK Through the surface S A / MK Inner Space I KM This means that the partition wall W is disposed within the electrolytic cell E so as to be in direct contact with the

[0210] This means that the electrolytic cell E is connected to at least one intermediate chamber K M In the embodiment, the partition wall W is provided with an intermediate chamber K M Inner Space I KM It borders on the

[0211] In that case, in these embodiments, the internal space I KM Surface S A / MK Solution L 3 In that case, when the tank is completely filled with solution L 3 Surface O A / MK The alkali cation conductive solid electrolyte ceramic F contained in at least the partition wall W is A When the solution comes into contact with the metal, ions (e.g., alkali metal ions such as sodium and lithium) are dissolved in the solution L 3 F who is AFK from A A partition wall W is disposed within the electrolysis cell E to allow access to the

[0212] Partition W is at least 2 AFK F A , F B and at least one partition element T and optionally a frame element R, this defines an internal space I KM Surface S A / MK Solution L 3 In that case, when the tank is completely filled with solution L 3 Surface O A / MK At least two alkali cation conductive solid electrolyte ceramics F included in the partition wall W through A and F B Ions (e.g. alkali metal ions such as sodium and lithium) are introduced into the solution L, and preferably into the partition element T as well. 3 F who is AFK from A and F B This means that the partition wall W is disposed within the electrolytic cell E so as to be in contact with the

[0213] In a preferred embodiment of the electrolysis cell E, the surface O formed by AFK KKat least 50%, in particular at least 70%, preferably at least 90%, very preferably 100% of the part of the inner space I KK Contact with.

[0214] In a preferred embodiment of the electrolysis cell E without an intermediate chamber, the surface O formed by the AFK A / MK at least 50%, in particular at least 70%, preferably at least 90%, very preferably 100% of the part of the inner space I KA Contact with.

[0215] In a preferred embodiment of the electrolytic cell E with at least one intermediate chamber, the surface O formed by the AFK A / MK at least 50%, in particular at least 70%, preferably at least 90%, very preferably 100% of the part of the inner space I KM Contact with.

[0216] 1.2 Step (a) of the method according to the invention Step (a) of the method according to the invention comprises A Glycol solution of glycolate L 1 In the case of the production of A is an alkali metal cation. The process is carried out in an electrolytic cell E.

[0217] Preferably, M A Li + , K + , Na + More preferably, K + , Na + Highly preferably, M A =Na + It is.

[0218] 1.2.1 Intermediate chamber K M The method according to the invention in an electrolysis cell E not equipped with Electrolysis cell E is in the intermediate chamber K M If the above-mentioned step is not provided, steps (α1), (α2), and (α3) are carried out simultaneously.

[0219] 1.2.1.1 Process (α1) In step (α1), a glycol-containing, preferably an alkali metal glycolate M A Solution L containing glycolate and glycol 2 I KK Pass through.

[0220] solution L 2 is preferably free of water. "Free of water" means, according to the invention, that the solution L 2 weight of glycol in L of solution 2 This means that the weight of water in (mass ratio) is ≦1:10, more preferably ≦1:20, even more preferably ≦1:100, even more preferably ≦0.5:100, even more preferably ≦1:1000, even more preferably ≦1:10000.

[0221] solution L 2 M A If glycolate is included, solution L 2 M in A The mass proportion of glycolate based on the total solution L is in particular >0 to 30% by weight, preferably 0.1 to 20% by weight, more preferably still 0.2 to 10% by weight, more preferably still 0.5 to 5% by weight, very preferably 0.7 to 2% by weight and most preferably 1% by weight.

[0222] solution L 2 M A If glycolate is included, solution L 2 Among them, M A The mass ratio of glycolate to glycol is in the range of 1:1000 to 1:5, more preferably in the range of 1:250 to 3:20, even more preferably in the range of 1:120 to 1:8, and even more preferably 1:100.

[0223] 1.2.1.2 Process (α2) In step (α2), M A A neutral or alkaline aqueous solution of salt S containing as a cation L 3 I KA Pass through.

[0224] The salt S is preferably M A of the formula (I) are preferably halides, sulfates, sulfites, nitrates, bicarbonates or carbonates, and even more preferably halides.

[0225] The halides are fluoride, chloride, bromide and iodide. Highly preferred halides are chlorides.

[0226] Here, the aqueous solution L 3 The pH of the solution is ≧7.0, preferably in the range of 7 to 12, more preferably in the range of 8 to 11, even more preferably 10 to 11, and very preferably 10.5.

[0227] Here, solution L 3 of salt S in solution L 3 The mass proportion in relation to the total is preferably in the range of >0-20% by weight, preferably 1-20% by weight, more preferably 5-20% by weight, even more preferably 10-20% by weight, very preferably 20% by weight.

[0228] 1.2.1.3 Process (α3) In step (α3), E A and E K A voltage is applied between

[0229] This results in current transport from the charge source to the anode, charge transport via the ions to the cathode, and finally current transport back to the charge source. Charge sources are known to those skilled in the art and are typically rectifiers, which convert alternating current to direct current, which can be used to generate a desired voltage via a voltage converter.

[0230] This in turn results in the following: Discharge part A KK Solution L 1 is obtained, where L 1 M in A The concentration of glycolate is L 2 Higher than medium, Discharge part A KAAqueous solution of S in L 4 is obtained, where L 4 The concentration of S in L 3 Lower than medium.

[0231] In particular, in step (α3) of the method according to the invention, the current density (=I KA The ratio of the current flowing through the electrolytic cell to the area of ​​the solid electrolyte in contact with the anolyte present in the cell is 10 to 8000 A / m 2 More preferably, it is in the range of 100 to 2000 A / m 2 and more preferably 300 to 800 A / m 2 and even more preferably in the range of 494 A / m 2 A voltage is applied to the anode chamber K such that a current flows such that A Inner Space I KA The area of ​​the solid electrolyte in contact with the anolyte present in the electrolyte is typically in the range of 0.00001 to 10 m 2 , preferably 0.0001 to 2.5 m 2 , more preferably 0.0002 to 0.15 m 2 , and even more preferably 2.83 cm 2 It is.

[0232] It will be appreciated that step (α3) of the method according to the invention is carried out in the anode chamber K A Inner Space I KA At least partially in L 3 is loaded into the cathode chamber K K Inner Space I KK At least partially in L 2 By charging L 3 and L 2 is implemented when both of them contact the AFK contained in the partition W and, in particular, when the partition W is provided with a partition element T, also contact the partition element T.

[0233] In step (α3), A and E K The fact that charge transport occurs between I KK and I KAAt the same time, L 2 Or L 3 is inserted, the more the circuit is closed, the more the electrode E K Or E A L 2 Or L 3 It means to be covered by.

[0234] This is especially true for L 3 The liquid flow is I KA And L 2 The liquid flow is I KK Continuously passing through L 3 The liquid flow at electrode E A Covering L 2 The liquid flow at electrode E K is at least partially, preferably completely, covered.

[0235] In a further preferred embodiment, the method according to the invention is carried out continuously, i.e. steps (α1) and (α2) are carried out continuously, with the voltage being applied according to step (α3).

[0236] After carrying out step (α3), discharge section A KK Solution L 1 is obtained, where L 1 M in A The concentration of glycolate is L 2 Higher than medium. L 2 But already M A If it contains glycolate, L 1 M in A The glycolate concentration is L 2 Among them, the height is preferably 1.01 to 200.2 times, more preferably 5.04 to 100.8 times, even more preferably 10.077 to 50.4 times, and even more preferably 18.077 to 20.08 times, and very preferably L 2 20.00 times higher in the L 1 Medium and L 2 M in A The mass proportion of glycolate is in the range from 0.1 to 50% by weight, even more preferably from 1 to 20% by weight.

[0237] Discharge part A KA Aqueous solution of S in L 4 is obtained, where L 4 The concentration of S in L 3 Lower than medium.

[0238] Aqueous solution L 3 Cation M in A The concentration of the aqueous solution L is preferably in the range of 0.5 to 5 mol / l, and more preferably 1 mol / l. 4 Cation M in A The concentration of is preferably in the aqueous solution L used in each case. 3 This is 0.5 mol / l lower than the concentration of

[0239] In particular, steps (α1) to (α3) of the method according to the invention are carried out at a temperature between 20° C. and 110° C., preferably between 50° C. and 105° C., more preferably between 80° C. and 99° C., even more preferably between 90° C. and 95° C., and at a pressure between 0.5 bar and 1.5 bar, preferably between 0.9 bar and 1.1 bar, more preferably at 1.0 bar.

[0240] When steps (α1) to (α3) of the method according to the present invention are carried out, I KK Hydrogen is typically generated within the KK Through solution L 1 The hydrogen and the solution L can be discharged from the cell together. 1 The mixture with can then be separated by methods known to those skilled in the art in certain embodiments of the invention. KA In the case where the alkali metal compounds used are halides, especially chlorides, chlorine or other halogen gases may be generated, which are discharged into the exhaust section A. KK Through solution L 4 Additionally, oxygen and / or carbon dioxide may be generated and may be exhausted as well. Chlorine, oxygen and / or CO 2 and solution L 4The mixture of solution L and solution L may then be separated by methods known to those skilled in the art in certain embodiments of the present invention. 4 from chlorine, oxygen and / or CO 2 After separation of the gases, they can be separated from each other by methods known to those skilled in the art.

[0241] 1.2.2 Intermediate chamber K M The method according to the invention in an electrolysis cell E comprising The electrolytic cell E is provided with at least one intermediate chamber K M In the case where the method includes the steps (β1), (β2), and (β3), which proceed simultaneously, are carried out.

[0242] The electrolytic cell E is provided with at least one intermediate chamber K M In the case where the method includes the steps (β1), (β2), and (β3), it is preferable to carry out the steps (β1), (β2), and (β3) simultaneously.

[0243] 1.2.2.1 Process (β1) In step (β1), a glycol-containing, preferably an alkali metal glycolate M A Solution L containing glycolate and glycol 2 I KK Pass through.

[0244] solution L 2 is preferably free of water. "Free of water" means, according to the invention, that the solution L 2 weight of glycol in L of solution 2 This means that the weight of water in (mass ratio) is ≦1:10, more preferably ≦1:20, even more preferably ≦1:100, even more preferably ≦0.5:100.

[0245] solution L 2 M A If glycolate is included, solution L 2 M in A Glycolate, solution L 2The proportion by weight relative to the total is in particular >0 to 30% by weight, preferably 0.1 to 20% by weight, more preferably still 0.2 to 10% by weight, more preferably still 0.5 to 5% by weight, very preferably 0.7 to 2% by weight and most preferably 1% by weight.

[0246] solution L 2 M A If glycolate is included, solution L 2 Among them, M A The mass ratio of glycolate to glycol is in the range of 1:1000 to 1:5, more preferably in the range of 1:250 to 3:20, even more preferably in the range of 1:120 to 1:8, and even more preferably 1:100.

[0247] 1.2.2.2 Process (β2) In step (β2), M A A neutral or alkaline aqueous solution of salt S containing as a cation L 3 I KM Then through V AM via I KA Pass through.

[0248] The salt S is preferably M A of the formula (I) are preferably halides, sulfates, sulfites, nitrates, bicarbonates or carbonates, and even more preferably halides.

[0249] The halides are fluoride, chloride, bromide and iodide. Highly preferred halides are chlorides.

[0250] Here, the aqueous solution L 3 The pH of the solution is ≧7.0, preferably in the range of 7 to 12, more preferably in the range of 8 to 11, even more preferably 10 to 11, and very preferably 10.5.

[0251] Here, solution L 3 of salt S in solution L 3The mass proportion in relation to the total is preferably in the range of >0-20% by weight, preferably 1-20% by weight, more preferably 5-20% by weight, even more preferably 10-20% by weight, very preferably 20% by weight.

[0252] 1.2.2.3 Process (β3) In step (β3), E A and E K A voltage is applied between

[0253] This results in current transport from the charge source to the anode, charge transport via the ions to the cathode, and finally current transport back to the charge source. Charge sources are known to those skilled in the art and are typically rectifiers, which convert alternating current to direct current, which can be used to generate a desired voltage via a voltage converter.

[0254] This in turn results in the following: Discharge part A KK Solution L 1 is obtained, where L 1 M in A The concentration of glycolate is L 2 Higher than medium, Discharge part A KA Aqueous solution of S in L 4 is obtained, where L 4 The concentration of S in L 3 Lower than medium.

[0255] In particular, in step (β3) of the method according to the invention, the current density (=I KM The ratio of the current flowing through the electrolytic cell to the area of ​​the solid electrolyte in contact with the anolyte present in the cell is 10 to 8000 A / m 2 More preferably, it is in the range of 100 to 2000 A / m 2 and more preferably 300 to 800 A / m 2 and even more preferably in the range of 494 A / m 2 A voltage is applied to the intermediate chamber K such that a current flows such that MThe area of ​​the solid electrolyte in contact with the anolyte in the electrolyte is 0.00001 to 10 m 2 , preferably 0.0001 to 2.5 m 2 , more preferably 0.0002 to 0.15 m 2 , and even more preferably 2.83 cm 2 It is.

[0256] Of course, step (β3) of the method according to the invention involves the steps of both chambers K M and K. A Inner Space I KA and I KM At least partially in L 3 is inserted into the inner space I KK At least partially in L 2 By charging L 3 and L 2 are in contact with the solid electrolyte contained in the partition W and, in particular, also with the partition element T if the partition W comprises the partition element T.

[0257] In step (β3), A and E K The fact that charge transport occurs between I KK , I KM and I KA At the same time, L 2 Or L 3 is inserted, the more the circuit is closed, the more the electrode E K Or E A L 2 Or L 3 It means to be covered by.

[0258] This is especially true for L 3 The liquid flow is I KM , V AM and I KA And L 2 The liquid flow is I KK Continuously passing through L 3 The liquid flow at electrode E A Covering L 2 The liquid flow at electrode E K is at least partially, preferably completely, covered.

[0259] In a further preferred embodiment, the method according to the invention is carried out continuously, i.e. steps (β1) and (β2) are carried out continuously, with the voltage being applied according to step (β3).

[0260] After carrying out step (β3), discharge section A KK Solution L 1 is obtained, where L 1 M in A The concentration of glycolate is L 2 Higher than medium. L 2 But already M A If it contains glycolate, L 1 M in A The glycolate concentration is L 2 Among them, the height is preferably 1.01 to 200.2 times, more preferably 5.04 to 100.80 times, even more preferably 10.077 to 50.40 times, and even more preferably 18.077 to 20.08 times, and very preferably L 2 20.00 times higher in the L 1 Medium and L 2 M in A The mass proportion of glycolate is in the range from 0.1 to 50% by weight, even more preferably from 1 to 20% by weight.

[0261] Discharge part A KA Aqueous solution of S in L 4 is obtained, where L 4 The concentration of S in L 3 Lower than medium.

[0262] Aqueous solution L 3 Cation M in A The concentration of the aqueous solution L is preferably in the range of 0.5 to 5 mol / l, and more preferably 1 mol / l. 4 Cation M in A The concentration of is preferably in the aqueous solution L used in each case. 3 This is 0.5 mol / l lower than the concentration of

[0263] In particular, steps (β1) to (β3) of the method according to the invention are carried out at a temperature between 20° C. and 110° C., preferably between 50° C. and 105° C., more preferably between 80° C. and 99° C., even more preferably between 90° C. and 95° C., and at a pressure between 0.5 bar and 1.5 bar, preferably between 0.9 bar and 1.1 bar, more preferably at 1.0 bar.

[0264] When steps (β1) to (β3) of the method according to the present invention are carried out, the cathode chamber I KK Hydrogen is typically generated within the KK Through solution L 1 The hydrogen and the solution L can be discharged from the cell together. 1 The mixture with can then be separated by methods known to those skilled in the art in certain embodiments of the invention. KA In the case where the alkali metal compounds used are halides, especially chlorides, chlorine or other halogen gases may be generated, which are discharged into the exhaust section A. KK Through solution L 4 Additionally, oxygen and / or carbon dioxide may be generated and may be exhausted as well. Chlorine, oxygen and / or CO 2 and solution L 4 The mixture of solution L and solution L may then be separated by methods known to those skilled in the art in certain embodiments of the present invention. 4 from chlorine, oxygen and / or CO 2 After separation of the gases, they can be separated from each other by methods known to those skilled in the art.

[0265] 1.2.2.4 Additional benefits of steps (β1) to (β3) These implementations of steps (β1) to (β3) result in yet further surprising advantages that were not anticipated in the light of the prior art. By steps (β1) to (β3) of the method according to the invention, the acid-labile solid electrolyte is protected from corrosion without the need to sacrifice the alcoholate solution from the cathode chamber as a buffer as in the prior art. Thus, the method according to the invention is more efficient than the procedure described in WO 2008 / 076327, in which the overall conversion is reduced due to the use of product solution in the intermediate chamber.

[0266] 2. Step (b): PET and solution L 1 <21> Reaction with In step (b) of the process according to the invention, the glycol obtained in step (a) is reacted with M A Glycolate and solution L 1 <21> was reacted with PET to obtain a mixture M containing BHET. 1 Generate.

[0267] 2.1 PET starting material As PET used in step (b) of the process according to the invention, any PET that needs to be depolymerized can be used. Typically, such PET arises as waste, in particular in households, industries or agriculture.

[0268] In one embodiment of the process according to the invention, the PET to be depolymerized according to the invention is mixed with other plastics, in particular at least one plastic selected from polyethylene ("PE"), polyvinyl chloride ("PVC"). This is typical when PET is depolymerized from plastic waste in the process according to the invention. In this embodiment, the PET is at least partially separated from other plastics, preferably by sorting, before being subjected to step (b) of the process according to the invention.

[0269] In one embodiment of the method according to the invention, the PET is subjected to at least one pretreatment step.

[0270] Such a pretreatment step is described, for example, in DE 100 32 899 C1.

[0271] According to the invention, the PET is subjected to at least one pretreatment step selected from a chemical pretreatment step, a shredding step, before being used in step (b).

[0272] If the PET is mixed with other plastics, the PET is preferably subjected to at least one pre-treatment step selected from at least partial separation from other plastics, preferably by sorting, a chemical pre-treatment step, a shredding step, before being used in step (b).

[0273] If the PET is mixed with other plastics, the PET is more preferably first at least partially separated from the other plastics, then chemically pre-treated at least once, and finally shredded.

[0274] The chemical pretreatment step is in particular a washing step. Such a washing step has the advantage that before step (b) is carried out, impurities possibly present are removed, in particular food residues, cosmetic residues and / or bodily secretions (e.g. blood, semen, feces). Such impurities may reduce the efficiency of the reaction in step (b) and / or impair the purity of the BHET obtained.

[0275] In the chemical pretreatment step, especially in the washing step, the waste is heated, especially in the washing liquid, at a temperature between 30°C and 99°C, preferably between 50°C and 90°C, even more preferably between 70°C and 85°C.

[0276] Typical washing solutions are well known to those skilled in the art and are preferably selected from the following: - an aqueous solution of a surfactant, preferably a non-ionic surfactant; - An aqueous solution of an alkali metal hydroxide or an alkaline earth metal hydroxide, preferably an aqueous NaOH solution.

[0277] The treatment time of the chemical pretreatment step, in particular the washing step, is in this case in particular from 1 min to 12 h, preferably from 10 min to 6 h, more preferably from 30 min to 2 h, even more preferably from 45 min to 90 min, very preferably 60 min.

[0278] After treatment of the PET by the chemical pretreatment steps, in particular the washing steps, the aqueous solution is separated, for example by filtration, and the washed PET is preferably washed at least once with water to remove residues of the washing liquid.

[0279] The PET waste thus obtained is then dried, in particular in a drying cabinet, the temperature used for drying being in this case in particular in the range from 30 to 120°C, preferably from 50 to 100°C, more preferably from 60 to 90°C, very preferably 80°C.

[0280] The shredding step has the advantage that the surface area of ​​the PET available for reaction in step (b) is increased, thereby increasing the reaction rate of the reaction in step (b). Shredding can be carried out in equipment known to those skilled in the art, such as a shredder or cutting mill.

[0281] In a further embodiment of the process according to the invention, the PET is bleached or targeted colored before being subjected to step (b), which can be carried out using methods known to the skilled artisan, for example bleaching with hydrogen peroxide or coloring with dyes.

[0282] 2.2 Reaction conditions PET, glycol and M A Glycolate and solution L 1 <21> Mixture M by reaction with 1 The formation of can then be carried out under conditions well known to those skilled in the art.

[0283] Preferably, the reaction of step (b) is carried out at a time t band for a period of time until at least P=10%, preferably at least P=20%, more preferably at least P=25%, more preferably at least P=30%, more preferably at least P=40%, more preferably at least P=50%, more preferably at least P=60%, more preferably at least P=70%, more preferably at least P=80%, more preferably at least P=90%, more preferably at least P=95%, and even more preferably at least P=99% of the PET used in step (b) has reacted, at a time t b This will be carried out until

[0284] This percentage P is calculated according to the following formula: P = (n TS +n MHET +n BHET ) / n PET where n PET is the amount of repeating units of the following structure (≡) in the PET used in step (b): [ka]

[0285] n TS is the time from the start of step (b) to time t b is the amount of TS formed up to that point.

[0286] n MHET is the time from the start of step (b) to time t b is the amount of MHET substance formed up to that point.

[0287] n BHET is the time from the start of step (b) to time t b is the amount of BHET material formed up to that point.

[0288] The structures of the compounds BHET, MHET, and TS are as follows: [ka]

[0289] "MHET" also encompasses the corresponding carboxylates of the structures shown.

[0290] "TS" also encompasses the corresponding mono- and dicarboxylates of the structures shown.

[0291] The reaction of step (b) is in this case especially carried out at a temperature of at least 100°C, preferably at a temperature in the range of ≧100°C to ≦197°C, more preferably at a temperature in the range of ≧130°C to ≦197°C, more preferably at a temperature in the range of ≧150°C to ≦197°C, more preferably at a temperature in the range of ≧175°C to ≦197°C.

[0292] The reaction of step (b) is preferably carried out at the boiling temperature of the glycol. Even more preferably, the glycol is refluxed in this case, i.e. the glycol is evaporated from the reaction, condensed and then returned to the reaction again. This reflux can be set up using means well known to those skilled in the art, for example in a distillation apparatus.

[0293] The ratio of the total weight of PET used in the method to the mass of A The total weight of glycolates is in particular in the range from 0.1 to 100% by weight, preferably in the range from 0.5 to 80% by weight, more preferably in the range from 1.0 to 50% by weight, more preferably in the range from 1.5 to 25% by weight, more preferably in the range from 2.0 to 10% by weight, more preferably in the range from 2.5 to 6.0% by weight, particularly preferably in the range from 3.5 to 5.0% by weight and very preferably 3.9% by weight.

[0294] This reaction can be carried out using equipment familiar to those skilled in the art.

[0295] After completion of step (b) of the method according to the invention, the amount of substance of BHET (n BHET ) and the sum of the amount of substance of MHET and the amount of substance of TS (n MHET +n TS) in a molar ratio η in the range of 1:1 to 1000:1, preferably 2:1 to 500:100, more preferably 4:1 to 300:1, even more preferably 10:1 to 100:1, even more preferably 13:1 to 60:1, even more preferably 13:1 to 24:1. 1 is obtained.

[0296] η=n BHET / (n MHET +n TS ) 2.3 Preferred step (c) In a preferred further step (c), BHET is reacted with M 1 This is still more preferably carried out by crystallization and / or distillation. Still more preferably, BHET is at least partially separated from M in step (c). 1 It is filtered off and then crystallized.

[0297] 3. How to recycle PET In the process according to the invention, the mixture M 1 The BHET obtained during is preferably polymerized in step (ζ) in a process for the reproduction of polyethylene terephthalate to produce PET.

[0298] This polymerization is known to those skilled in the art as "polycondensation" and is described, for example, in EP 0 723 951 A1 and in the book "Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters. Edited by J. Scheirs and TELong, 2003, John Wiley & Sons, Ltd ISBN: 0-471-49856-4" by Th. Rieckmann and S. Voelker, Chapter 2 "Poly(Ethylen Terephthalate) Polymerization - Mechanism, Catalysis, Kinetics, Mass Transfer and Reactor Design", page 92.

[0299] In particular, for this purpose, BHET is polymerized in step (ζ) in the presence of a catalyst to give PET again, which catalyst is in particular an antimony compound, preferably Sb 2 O 3 The catalyst is selected from the group consisting of:

[0300] Preferably, the polymerization of BHET to PET in step (ζ) is carried out at at least the boiling temperature of the glycol, in particular, glycol is removed from the reaction mixture during the polymerization in step (ζ) to shift the reaction equilibrium towards the polymer PET.

[0301] More preferably, the polymerization of BHET to PET in step (ζ) is carried out at the boiling temperature of the glycol. Even more preferably, glycol is subsequently removed from the reaction mixture during the polymerization in step (ζ) to shift the reaction equilibrium towards the polymer PET.

[0302] This is in particular achieved by distillation at a pressure <1 bar, preferably 0.1 mbar, at the simultaneous boiling temperatures of the glycols at the respective pressures.

[0303] Working Example 1. Example E1 according to the invention: 1.1 Production of glycol solution of sodium glycolate by electrolysis 1.1.1 Test Setup The electrolytic production of sodium glycolate was carried out in a three-chamber electrolytic cell.

[0304] The intermediate chamber was separated from the anode chamber by a filter cloth and from the cathode chamber by a 15 x 15 cm Nasicon ceramic.

[0305] The anode was a DSA anode [dimensionally stable anode]; a titanium anode coated with ruthenium oxide / iridium oxide (RuO 2 +IrO 2 / Ti)] was used, and the cathode was made of VA steel (VA stands for "stainless steel").

[0306] A Gamry Reference 3000 (AE) potentiostat and a Reference 30K Booster were used as the voltage source.

[0307] The cathode chamber of the electrolysis cell was connected to a 250 ml heated double-jacketed vessel equipped with a magnetic stirrer, from which the electrolyte could be pumped via a peristaltic pump to the conductivity measuring point and then via a 100 ml glass heat exchanger to the cathode chamber of the electrolysis cell, from where the catholyte could be pumped back into the double-jacketed vessel again, thus circulating the catholyte.

[0308] The electrolyte temperature on the cathode side could be measured or set by a thermostat equipped with a PT100 sensor (a platinum sensor with a nominal resistance of 100 Ω at a temperature of 0° C.) and a heat exchanger.

[0309] The intermediate chamber of the electrolysis cell was connected to a storage vessel from which the electrolyte could be pumped by a peristaltic pump into the intermediate chamber, then through a filter cloth to the anode chamber, and from there through a pH measuring point to a collection vessel.

[0310] The electrolyte temperature on the anode side could be measured or set by a thermostat or a heat exchanger equipped with a PT100 sensor. No anolyte was circulated.

[0311] 1.1.2 Testing: The thermostat on the cathode side was set to 90° C. and started. 650 g of 1% by weight sodium glycolate solution was poured into a heated double-jacketed vessel and the peristaltic pump was started (flow rate 1000 ml / h), which pumped the sodium glycolate solution into the cathode chamber of the electrolysis cell via the conductivity measuring point and a further heat exchanger. The glycolate then flowed from the cathode chamber back into the double jacket. The glycolate and the chamber were thus thermostated at 90° C. The thermostat on the NaCl side was set to 105° C. and the peristaltic pump for the NaCl brine was started (flow rate 4000 ml / h). 20% by weight NaCl brine with a pH of 11 from the storage vessel was pumped into the intermediate chamber of the electrolysis cell via a heat exchanger. From there this NaCl brine flowed through a filter cloth into the anode chamber and then out of the cell into the pH measuring point before flowing into a collection vessel. The NaCl brine was not circulated. Once the cathode chamber was heated to 90°C and the temperature on the anode side at the pH measurement point was 80°C, the current of the electrolysis cell was switched on. To do so, the potentiostat was switched to galvanostatic mode. The current was fixed at 10 amps and the voltage was adjusted accordingly. Then the conductivity measurement of the glycolate and the pH measurement of the NaCl brine were recorded.

[0312] The current, voltage, glycolate temperature, glycolate conductivity, brine pH, and brine temperature were recorded every 20 seconds. The evolved hydrogen and evolved chlorine were absorbed. The chlorine was neutralized with NaOH in a gas washing bottle.

[0313] The electrolysis was carried out for 4 hours, after which the power was turned off and the cell was allowed to completely drain.

[0314] The concentration of the sodium glycolate solution was about 20% by weight.

[0315] 1.2 Depolymerization of PET using glycol solution of electrolytically obtained sodium glycolate In the process according to the invention, 100 g of PET were charged into an autoclave together with 800 g of ethylene glycol. The solution was then heated to 150° C. with stirring. As soon as a temperature of 150° C. was reached, 19.5 g (corresponding to 0.046 mol) of a 20% by weight solution of sodium glycolate obtained by electrolysis in ethylene glycol were added. The reaction was carried out for 5 hours and the reactor discharge was examined after cooling. The conversions of the obtained BHET (1) and mono 2-hydroxyethyl terephthalic acid ("MHET") (2) and terephthalic acid ("TS") (3) are shown in FIG. 8 (measured by gas chromatography; % conversion with respect to the repeating unit of the structure (≡) of the PET used; thin hatching " / / / / ").

[0316] 2. Comparative Example V1: In a comparative test, 100 g of PET was charged into an autoclave with 800 g of ethylene glycol. The solution was then heated to 150° C. with stirring. The reaction was carried out for 5 hours and the reactor discharge was examined after cooling. The resulting conversions of BHET (1) and MHET (2) and TS (3) are shown in Figure 8. [ka]

[0317] 3. Comparative Example V2: In a comparative test, 100 g of PET are charged into an autoclave together with 800 g of ethylene glycol. The solution is then heated to 150° C. with stirring. As soon as a temperature of 150° C. is reached, 3.7 g of a 50% by weight aqueous NaOH solution (corresponding to 0.046 mol) are added. The reaction is carried out for 5 hours and the reactor discharge is examined after cooling. The resulting conversions of BHET (1) and MHET (2) as well as TS (3) are shown in FIG. 8 (bold hatching: “ / / / / ”).

[0318] 4. Results Comparing the contents of BHET, MHET and TS in the depolymerized products of Example E1 according to the invention and Comparative Examples V1 and V2 (see FIG. 8), it can be seen that the depolymerization with the glycol solution of sodium glycolate obtained by electrolysis gives a higher percentage of BHET, which is advantageous since it means that more products are obtained that can be directly converted into new PET products by polycondensation.

[0319] 6. Reference symbols in the drawings [Table 1-1] [Table 1-2]

Claims

1. 1. A method for depolymerizing polyethylene terephthalate (PET), comprising: (a) M Ａ Glycol solution of glycolate L １ <21> in an electrolytic cell E<1>, wherein M Ａ is an alkali metal cation, and the electrolytic cell E<1> is: at least one supply Z ＫＡ <110> and at least one discharge section A ＫＡ <111> and the anode electrode E Ａ Inner space I with <113> ＫＡ At least one anode chamber K equipped with <112> Ａ <11> and at least one supply Z ＫＫ <120> and at least one discharge section A ＫＫ <121> and the cathode electrode E Ｋ Inner space I with <123> ＫＫ At least one cathode chamber K equipped with <122> Ｋ <12> and Equipped with and optionally, at least one supply Z ＫＭ <130> and at least one discharge section A ＫＭ <131> and Inner Space I ＫＭ <132> and at least one intermediate chamber K Ｍ <13> is provided, In this case, I ＫＡ <112> and I ＫＭ <132> are separated from each other by a diffusion barrier D<14>, and A ＫＭ <131> is the connecting part V ＡＭ <15> by the supply section Z ＫＡ <110>, the connection part V ＡＭ <15> to make the liquid I ＫＭ <132> to I ＫＡ <112> can be passed through, where: - the electrolysis cell E<1> is in the intermediate chamber K Ｍ If <13> is not provided, I ＫＡ <112> and I ＫＫ <122> are separated from each other by a partition wall W<16>, said electrolysis cell E<1> has at least one intermediate chamber K Ｍ If <13> is provided, I ＫＫ <122> and I ＫＭ <132> are separated from each other by a partition wall W<16>, The partition wall W<16> has a surface O ＫＫ Surface S having <163> ＫＫ <161> and the surface S ＫＫ Surface O opposite to <161> Ａ／ＭＫ Surface S with <164> Ａ／ＭＫ <162>, and the partition wall W<16> has an alkali cation conductive solid electrolyte ceramic F contained in the partition wall W<16>. Ａ <18> is the surface O ＫＫ <163> through the surface S ＫＫ <161> and the internal space I ＫＫ At least one alkali cation conductive solid electrolyte ceramic F is in direct contact with <122>. Ａ <18> is included, Also here, - the electrolysis cell E<1> is in the intermediate chamber K Ｍ When the partition wall W<13> is not provided, the alkali cation conductive solid electrolyte ceramic F included in the partition wall W<16> Ａ <18> is the surface O Ａ／ＭＫ <164> through the surface S Ａ／ＭＫ <162> in the internal space I ＫＡ I have direct contact with <112>, said electrolysis cell E<1> has at least one intermediate chamber K Ｍ When the partition wall W<16> is provided with the alkali cation conductive solid electrolyte ceramic F Ａ <18> is the surface O Ａ／ＭＫ <164> through the surface S Ａ／ＭＫ <162> in the internal space I ＫＭ I have direct contact with <132>, (α) The electrolytic cell E<1> is in the intermediate chamber K Ｍ When the electrolytic cell E<1> is not provided with <13>, the following steps (α1), (α2), and (α3) are carried out simultaneously in the electrolytic cell E<1>: (α1) Solution L containing glycol ２ <22> I ＫＫ <122> passing the (α2)M Ａ A neutral or alkaline aqueous solution L of a salt S containing as a cation ３ <23> I ＫＡ <112> passing the (α3)E Ａ <113> and E Ｋ A step of applying a voltage between <123> or (β) the electrolytic cell E<1> has at least one intermediate chamber K Ｍ When the electrolytic cell E<1> is provided with <13>, the following steps (β1), (β2), and (β3) are carried out simultaneously in the electrolytic cell E<1>: (β1) Solution L containing glycol ２ <22> I ＫＫ <122> passing the (β2)M Ａ A neutral or alkaline aqueous solution L of a salt S containing as a cation ３ <23> I ＫＭ <132>, then V ＡＭ <15> then I ＫＡ <112> passing the (β3)E Ａ <113> and E Ｋ A step of applying a voltage between <123> and As a result, the discharge section A ＫＫ <121> in the solution L １ <21> is obtained, where L １ <21>M in Ａ The concentration of glycolate is L ２ <22> Higher than the middle, As a result, the discharge section A ＫＡ <111> S aqueous solution L ４ <24> is obtained, where L ４ The concentration of S in <24> is L ３ <23> A step of making the temperature lower than the medium temperature; (b) the solution L １ <21> is reacted with PET to obtain a mixture M containing bis-2-hydroxyethyl terephthalate BHET. １ and generating A method comprising:

2. The alkali cation conductive solid electrolyte ceramic F Ａ <18> is a compound represented by the formula M Ｉ １＋２ｗ＋ｘ－ｙ＋ｚ M ＩＩ ｗ M ＩＩＩ ｘ Zr ＩＶ ２－ｗ－ｘ－ｙ M Ｖ ｙ (SiO ４ ) ｚ (P.O. ４ ) ３－ｚ having the structure Here, M Ｉ is Na ＋ , Li ＋ is selected from M ＩＩ is a divalent metal cation, M ＩＩＩ is a trivalent metal cation, M Ｖ is a pentavalent metal cation, The Roman alphabet suffixes I, II, III, IV, and V indicate the oxidation number in which the respective metal cation exists; 2. The method of claim 1, wherein w, x, y, and z are real numbers such that 0≦x<2, 0≦y<2, 0≦w<2, and 0≦z<3, and where w, x, y, and z are selected such that 1+2w+x−y+z≧0 and 2−w−x−y≧0.

3. The electrolysis cell E<1> is located in the intermediate chamber K Ｍ The method according to claim 1 or 2, wherein <13> is not provided.

4. The electrolysis cell E<1> has at least one intermediate chamber K Ｍ The method according to claim 1 or 2, further comprising: <13>.

5. M Ａ 3. The method of claim 1, wherein is selected from the group consisting of potassium and sodium.

6. 3. The process of claim 1 or 2, wherein step (b) is carried out for a time until at least P=10% of the PET used in step (b) has reacted.

7. 3. The process of claim 1 or 2, wherein step (b) is carried out at the boiling temperature of the glycol.

8. The ratio of the M used in step (b) to the total weight of the PET used in step (b) Ａ A quantity of solution L such that the total weight of glycolate is in the range of 0.1 to 100% by weight １ The method according to claim 1 or 2, wherein <21> is used in step (b).

9. In a further step (c), BHET is reacted with M １ 3. The method of claim 1, wherein the at least partially separates the

10. M in step (c) １ 10. The process of claim 9, wherein at least partial separation of BHET from the ester is carried out by crystallization and / or distillation.

11. 3. The method of claim 1 or 2, wherein the PET is subjected to at least one pretreatment step selected from a chemical pretreatment step, a shredding step, before being used in step (b).

12. A method for regenerating polyethylene terephthalate, comprising obtaining BHET by the method of claim 1 and polymerizing the BHET thus obtained in step (ζ) to produce PET.

13. 13. The method of claim 12, wherein the polymerization of BHET to form PET in step (ζ) is carried out at a temperature of at least the boiling temperature of the glycol.

14. 14. The process according to claim 12 or 13, wherein the polymerization in step (ζ) is carried out in the presence of a catalyst.

15. 15. The method of claim 14, wherein the catalyst is selected from the group consisting of antimony compounds.

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