Method for obtaining heteroatom-containing monomers during the pyrolysis of polymer-containing starting materials

Abstract

The invention relates to a method for obtaining heteroatom-containing monomers during the pyrolysis of polymer-containing starting materials, the method comprising: providing a starting material (30) which comprises at least one heteroatom-containing polymer, introducing the starting material into a pyrolysis reactor (16), pyrolysing the starting material (30) in the pyrolysis reactor (16), wherein at least the heteroatom-containing polymer is pyrolytically cleaved, and wherein a product gas is obtained which comprises heteroatom-containing monomers (M), spray cooling the product gas, wherein the product gas already comprises a polar solvent prior to spray cooling, and / or wherein a polar solvent is added to the product gas during spray cooling, wherein a multi-phase product liquid (32) is obtained as a result of the spray cooling and comprises a polar liquid phase (34) and a non-polar liquid phase (36), wherein the heteroatom-containing monomer (M) and the polar solvent are enriched in the polar liquid phase, and separating the polar liquid phase (34) from the non-polar liquid phase (36).

Description

[0001] Title: Method for obtaining heteroatom-containing

[0002] Monomers during the pyrolysis of polymer-containing starting materials

[0003] Description

[0004] The present invention relates to a process for obtaining heteroatom-containing monomers during the pyrolysis of polymer-containing starting materials.

[0005] Plastic waste is often incinerated or processed through pyrolysis. The pyrolysis oil obtained through this process can be used as a feedstock in the chemical industry.

[0006] Plastics can be reused in plastic synthesis. This closes a material cycle and reduces the overall demand for fossil crude oil. However, the production of pyrolysis oil from plastic waste is only conditionally economical when using known pyrolysis processes, as the pyrolysis oils have to be reintroduced very early in the value chain in the refining and steam cracking processes, and the valuable monomers contained in the pyrolysis oil are destroyed.

[0007] The invention addresses the problem of increasing the economic efficiency of the pyrolysis of plastics.

[0008] This problem is solved according to the invention by a method having the features of claim 1.

[0009] According to the invention, a starting material for pyrolysis is provided. The starting material comprises at least one heteroatom-containing polymer, such as polyamide, polyamide 6, polyamide 6.6, polyamide 6.12, polyamide 6T.6, polyethylene terephthalate, or polyurethane. The heteroatom-containing polymer can be the only polymer contained in the starting material. However, the starting material can also comprise at least one other polymer, for example, at least one other heteroatom-containing polymer and / or at least one heteroatom-free polymer.

[0010] The starting material is introduced into a pyrolysis reactor and pyrolyzed. At least the heteroatom-containing polymer is pyrolytically cleaved, yielding a product gas containing heteroatom-containing monomers. These heteroatom-containing monomers are cleavage products of the heteroatom-containing polymer formed during pyrolysis. Depending on the heteroatom-containing polymer used, different heteroatom-containing monomers are obtained. For example, caprolactam, aminocaproic acid, terephthalic acid, 1,6-hexamethylenediamine, adipic acid (1,6-hexanedioic acid), and 1,12-dodecanedioic acid are obtained as heteroatom-containing monomers.

[0011] The resulting product gas is spray-cooled in the presence of at least one polar solvent. The at least one polar solvent may already be present in the product gas before spray cooling. Alternatively or additionally, at least one polar solvent may be added to the product gas during spray cooling. By spray-cooling the product gas in the presence of the at least one polar solvent, a multiphase product liquid is obtained, particularly through condensation of condensable components of the product gas. The multiphase product liquid comprises at least one polar liquid phase and at least one nonpolar liquid phase. The heteroatom-containing monomers and the at least one polar solvent are enriched in the polar liquid phase. The nonpolar liquid phase forms the actual pyrolysis oil and is hereinafter also referred to as pyrolysis oil. For example, the nonpolar liquid phase contains...Nonpolar, especially heteroatom-free, fission products of the starting material are concentrated. Preferably, the product liquid is collected in a receiving vessel. A separatory funnel, a container with a partition, and / or other apparatus can be used as a receiving vessel.

[0012] The process also includes separating the polar liquid phase from the nonpolar liquid phase. Typically, the density of the polar liquid phase is higher than that of the nonpolar liquid phase. Consequently, a gravity-based separation can be performed. For example, if a separating funnel is used as a collection vessel, the polar and nonpolar liquid phases can be drained from the funnel sequentially.

[0013] The inventors have recognized that the claimed method enables the effective separation of heteroatom-containing monomers from other decomposition products. Spray cooling in the presence of the polar solvent triggers the formation of the two separate liquid phases, with the heteroatom-containing monomers preferentially accumulating in the polar liquid phase. This process is promoted by a large phase interface in the spray cooler. The heteroatom-containing monomers are particularly valuable starting materials. Because the heteroatom-containing monomers are separated from the pyrolysis oil, the monomers are not destroyed along with the pyrolysis oil. Instead, the monomers can be reintegrated further downstream in the value chain.By enriching the heteroatom-containing monomers in the polar liquid phase and subsequently separating the liquid phases from each other, the economic efficiency of pyrolysis can be increased. In other words, the claimed process yields a pyrolysis oil and, separately, the heteroatom-containing monomers, and not just a pyrolysis oil.

[0014] Within the scope of this disclosure, heteroatoms are atoms that are not carbon or hydrogen. Preferably, the heteroatom-containing polymer has oxygen atoms and / or nitrogen atoms as heteroatoms. Within the scope of this disclosure, a polar solvent is a solvent that has a permittivity of at least 15 at 25 °C. Preferably, a polar solvent is used that has a permittivity of at least 20 at 25 °C.

[0015] After spray cooling, the heteroatom-containing monomers are enriched in the polar liquid phase. This means that the majority of the heteroatom-containing monomers are present in the polar liquid phase. This does not preclude the presence of heteroatom-containing monomers in the nonpolar liquid phase as well, albeit at a lower concentration. Preferably, the mass concentration of heteroatom-containing monomers in the polar liquid phase is at least 10 times greater than the mass concentration of heteroatom-containing monomers in the nonpolar liquid phase.

[0016] Depending on the starting material used, a polar liquid phase with a different composition can be obtained. Preferably, the mass concentration of heteroatom-containing monomers in the polar liquid phase is between 10 wt% and 90 wt%, more preferably between 30 wt% and 60 wt%. The mass concentration of the polar solvent, e.g., water, can be, for example, between 5 wt% and 80 wt%. The mass concentration of other compounds, in particular soluble or bound aromatics, specifically ethylbenzene and / or styrene and / or benzene and / or toluene, short-chain alcohols, organic acids, and nitriles, specifically benzonitrile, hexanitrile, and pentamitrile,

[0017] The concentration of 2,4-hexadieneitrile, cyclopentanecarbonitrile, is preferably at most 20 wt%, particularly preferably at most 10 wt%. In some preferred embodiments, the polar solvent is selected from the group consisting of: water, organic acids, in particular formic acid, propionic acid, butyric acid or oxalic acid, alcohols, in particular isopropanol, ethanol or 1,4-butanediol, aldehydes, in particular formaldehyde, and ketones, in particular acetone.

[0018] In some preferred embodiments, the starting material comprises, as a heteroatom-containing polymer, at least one polyester, in particular polyethylene terephthalate, at least one polyamide, in particular polyamide 6 and / or polycaprolactam and / or polyamide 6, 12 and / or polyamide 12, and / or at least one polyurethane. The starting material may also comprise several different heteroatom-containing polymers.

[0019] In addition to the at least one heteroatom-containing polymer, the starting material may also contain at least one heteroatom-free polymer. In some preferred embodiments, the starting material comprises at least one polyolefin, in particular polyethylene and / or polypropylene. The breakdown products of this polymer obtained during pyrolysis typically pass from the product gas into the nonpolar liquid phase, i.e., into the pyrolysis oil.

[0020] In some preferred embodiments, the starting material comprises a multilayer material having different polymer layers, in particular a multilayer film. Pyrolysis of such a multilayer material is typically hardly economical.

[0021] However, by selectively separating the heteroatom-containing monomers, economic efficiency can be effectively increased.

[0022] In some preferred embodiments, it is provided that the mass fraction of biomass in the starting material is at most 30% by mass, preferably at most 10% by mass, and particularly preferably at most 5% by mass.

[0023] In some preferred embodiments, it is provided that the mass fraction of non-convertible inert substances in the starting material is less than 5 wt%, preferably less than 1 wt%.

[0024] The residence time of the starting material in the pyrolysis reactor is preferably between 0.1 h and 24 h, particularly preferably between 0.5 h and 20 h. Such a residence time allows for effective pyrolysis of the pyrolyzable components of the starting material.

[0025] Preferably, a catalyst is added to the starting material. The mass fraction of the catalyst, based on the total mass of the starting material, is preferably between 1 wt% and 8 wt%, preferably about 2 wt%. Preferably, a zeolite based on SiCy / AAO and / or a layered silicate is used as the catalyst.

[0026] In some preferred embodiments, the starting material is pyrolyzed at a pyrolysis temperature of at least 280 °C. This allows for effective pyrolysis of the pyrolyzable components of the starting material. Preferably, the starting material is pyrolyzed at a pyrolysis temperature of at least

[0027] 280 °C and at most 450 °C pyrolyzed, preferably at a pyrolysis temperature of at least 360 °C and at most 400 °C, particularly preferably at a pyrolysis temperature of about 380 °C.

[0028] Preferably, the pyrolysis reactor has at least one reaction mixer, in particular a turbine, which is designed to mix and pump the starting material in the pyrolysis reactor.

[0029] The pyrolysis temperature can be achieved in various ways. For example, the pyrolysis reactor may have an electric heating device, a microwave-based heating device, and / or an inductive heating device. Preferably, the feedstock is heated by the aforementioned reaction mixer being configured as a friction mixer, in particular as a friction turbine. The friction mixer can also be the sole heating device. Alternatively, the feedstock can be heated in the pyrolysis reactor by a thermal oil circuit.

[0030] The pyrolysis reactor can have a single-stage or a multi-stage reactor system.

[0031] In some preferred embodiments, at least one polar solvent, in particular water, is contained in the product gas, wherein the mass fraction of polar solvent in the product gas before spray cooling is at least 0.1 wt%, preferably at least 0.5 wt%, particularly preferably at least 0.5 wt% and at most 10 wt%. A product gas that already contains a polar solvent is one way to ensure the required presence of polar solvent during spray cooling.

[0032] In some preferred embodiments, the starting material contains at least one polar solvent, particularly if the starting material is aqueous. For example, the starting material may contain residual moisture. Preferably, the mass fraction of polar solvent, especially water, in the starting material is at least 0.1 wt% and at most 15 wt%, more preferably at least 0.1 wt% and at most 5 wt%, and most preferably at least 0.1 wt% and at most 2 wt%. In some preferred embodiments, at least one polar solvent, especially water, is added to the starting material in the pyrolysis reactor. In some embodiments, the starting material releases at least one polar solvent, especially water, upon pyrolytic cleavage.These preferred measures can yield a product gas that contains at least one polar solvent.

[0033] It is preferred that the residence time of the heteroatom-containing monomers in the product gas be as short as possible. This prevents undesired repolymerization of the heteroatom-containing monomers in the product gas. Preferably, the time period, which starts with the generation of the product gas in the pyrolysis reactor and ends with spray cooling of the generated product gas, is at most 30 seconds, preferably at most 15 seconds, and particularly preferably at most 10 seconds. Preferably, the product gas is removed from the pyrolysis reactor by a vacuum generation device and / or by the pressure generated during the pyrolysis itself and fed to the spray cooler.

[0034] Preferably, the product gas is spray-cooled in a spray cooler. The spray cooler can be single-stage or multi-stage.

[0035] Preferably, spray cooling of the product gas comprises spraying a cooling liquid into the product gas.

[0036] Preferably, the cooling liquid has a cooling temperature of at most 100 °C when sprayed into the product gas. This achieves effective cooling of the product gas and consequently effective condensation of condensable components from the product gas. Preferably, the cooling temperature is at least 30 °C and at most 100 °C, more preferably at least 70 °C and at most 85 °C, and particularly preferably about 77 °C.

[0037] In some preferred embodiments, it is provided that the cooling liquid is at least partially formed by the nonpolar liquid phase.

[0038] In some preferred embodiments, the cooling liquid is provided for to be at least partially composed of a polar solvent, in particular water. This is another way in which the presence of a polar solvent can be achieved in spray cooling. A cooling liquid containing a polar solvent also has the advantage that the residual proportion of heteroatom-containing monomers in the nonpolar liquid phase can be reduced. The heteroatom-containing monomers are essentially washed out of the nonpolar liquid phase. In particular, water is used as the cooling liquid.

[0039] Preferably, the mass fraction of polar solvent in the cooling liquid is between 0.1% by mass and 10% by mass.

[0040] There are several ways in which the presence of a polar solvent can be achieved during spray cooling of the product gas. The polar solvent may already be contained in the product gas. Alternatively or additionally, the polar solvent may be contained in the sprayed cooling liquid.

[0041] The cooling liquid can be a liquid mixture comprising a nonpolar liquid phase and a polar liquid phase containing a polar solvent, in particular water.

[0042] In some preferred embodiments, it is provided that the heteroatom-containing monomers are isolated from the separated polar liquid phase. This can be achieved by various measures, in particular by crystallization processes and / or by chromatography processes and / or by extraction processes and / or by distillation and / or by rectification and / or by thermal separation processes, preferably under suppression.

[0043] In some preferred embodiments, the separated polar liquid phase is intensively perfused and mixed with water to such an extent that an upper nonpolar phase and a lower polar phase containing the heteroatom-containing monomers are formed, and the lower polar phase is separated from the upper nonpolar phase. The addition of water to the polar liquid phase allows aromatic components contained in the polar liquid phase to be separated. These aromatic components accumulate in the upper nonpolar phase.

[0044] The invention will be explained in more detail below with reference to the drawings. The only drawing shown is...

[0045] Figure shows a plant for the pyrolysis of polymer-containing starting materials.

[0046] The figure shows a schematic representation of plant 10 for the pyrolysis of polymer-containing starting materials.

[0047] Plant 10 can pyrolyze polymer-containing feedstocks 30 (mixed plastics or sorted or defined production waste and / or mixed waste and / or alternative fuels).

[0048] In the following, it is assumed that a starting material 30 is used which has at least one heteroatom-containing polymer, for example at least one polyester, at least one polyurethane and / or at least one polyamide. Preferably, the mass fraction of heteroatom-containing polymer in the starting material 30 is between 5 wt% and 60 wt%, more preferably between 10 wt% and 50 wt%, and more preferably between 15 wt% and 30 wt%. Preferably, the starting material 30 comprises a different

[0049] Multilayer material comprising polymer layers.

[0050] The plant 10 comprises a pyrolysis unit 12. The pyrolysis unit 12 comprises at least one pyrolysis reactor 16. The introduction of the starting material 30 into the pyrolysis reactor 16 is simplified in the figure by an arrow 31, but can be carried out according to the process steps explained below.

[0051] The starting material 30 is usually initially in the form of pressed bales or, in small quantities, as coarse granules or already shredded. This starting material typically undergoes preparation before processing in plant 10.

[0052] The polymer-containing starting material 30 is typically initially wet. For example, the mass fraction of water in the starting material 30 is between 5 wt% and 25 wt%. Other polar solvents besides water may also be present in the starting material 30. In addition, inert substances (mineral and metal) and biomass may be present.

[0053] The starting material 30 is shredded in a shredding system before pyrolysis, e.g., into particles ranging in size from 5 mm to 60 mm, preferably approximately 30 mm. The shredded particles can then pass through several separation stages in a conveyor system, such as magnetic separators, static non-ferrous separators, air classifiers, and others. This removes some of the loose inert substances from the starting material 30 beforehand. However, inert substances that are adhered to or embedded within the starting material 30 (composite material) cannot be separated using this method.

[0054] The wet starting material 30, as already mentioned, can be dried to a desired residual moisture content in a dryer, usually a screw dryer, a belt dryer, or a drum dryer. A certain residual moisture content is advantageous for the pyrolysis process, which will be explained in more detail below. The temperature in the dryer should not be so high that the starting material 30 becomes too soft and sticks together.

[0055] It is energetically advantageous to feed the still hot starting material 30 (approx. 60–150 °C after drying) into the pyrolysis reactor 16, for example, by means of a conveying device (not shown) that conveys the starting material 30 into the pyrolysis reactor 16. There are two preferred variants in this regard.

[0056] The first variant is a simple screw conveyor system with a screw break in which safety devices (valves that close immediately in an emergency; with nitrogen cover) are installed. The outlet of the screw conveyor system in the pyrolysis reactor 16 is located below the liquid level in the pyrolysis reactor 16. The feed material 30 typically enters the pyrolysis reactor 16 in solid form and only absorbs heat there until it reaches its melting point. With this feed variant, the heat input into the pyrolysis reactor 16 is greater than in the next variant.

[0057] The second variant involves feeding the material through an extruder system in which the starting material 30 is already heated to its melting temperature. The extruder outlet in the pyrolysis reactor 16 is located below the liquid level in the pyrolysis reactor 16. Preferably, an extruder with multiple temperature zones and at least one or more degassing outlets is used. The starting material 30 is then forcibly conveyed into the pyrolysis reactor 16 in a single-phase state, particularly as a liquid, paste, or viscous substance, or in a two-phase state, particularly as a vapor / liquid mixture.

[0058] The different types of plastics in the starting material 30 have different decomposition temperatures and require varying amounts of depolymerization energy due to their bonding structure. The pyrolysis reactor 16 is preferably operated at 360 °C to 420 °C. This ensures the effective pyrolysis of the pyrolyzable components of the starting material 30. Pyrolysis of the heteroatom-containing polymer yields heteroatom-containing, polar monomers M. Pyrolysis of polyolefins, on the other hand, yields nonpolar decomposition products.

[0059] The pyrolysis unit 12 also comprises at least one reaction mixer 14, in particular a reaction turbine 14. The reaction mixer 14 is arranged in a circulation line which is fluidically connected at the inlet side to a vertically lower section of the pyrolysis reactor 16 and at the outlet side to a vertically upper section of the pyrolysis reactor 16. The reaction mixer 14 is designed to circulate a material arranged in the pyrolysis reactor 16. In this embodiment, the reaction mixer 14 is designed as a friction mixer 14, in particular as a friction turbine 14. A friction mixer has a poor efficiency due to friction, so the friction mixer heats the feed material 30. Thus, in this embodiment, the reaction mixer 14 acts as a heating and pumping device for the pyrolysis unit 12. Alternatively or additionally, another type of heating system may be present.

[0060] In this process, the starting material 30 is introduced into an upper section of the pyrolysis reactor 16 via the reaction mixer 14. The pumped-over starting material 30, heated by the reaction mixer 14, expands upon entering the upper section of the pyrolysis reactor 16. The fission products obtained by the pyrolysis, in particular the heteroatom-containing monomers M, evaporate and are withdrawn from the pyrolysis reactor 16 as product gas by means of a vacuum generation device 22 (slight vacuum).

[0061] The system 10 also includes a spray cooler 18, which is located downstream of the pyrolysis reactor 16. The spray cooler 18 comprises a spray chamber 20, into which the product gas is fed by the vacuum generation device 22. At least one spray nozzle is configured to spray a cooling liquid into the spray chamber 20. A collection vessel 24 with a partition is located downstream of the spray chamber 20.

[0062] Alternatively or additionally, the starting material 30 can also be circulated in the pyrolysis reactor 16. This stimulates mixing and, especially when fed according to the first variant, the supplied starting material 30 is distributed more evenly in the pyrolysis vessel 16. As an additional effect, the mixing further enhances the direct outgassing via the surface of the pyrolysis mixture.

[0063] In the spray chamber 20, a cooling liquid 40 is sprayed into the product gas. The spray cooler 18 can be single-stage or multi-stage. Normally, a single-stage spray cooler 18 is used (cooling liquid 40 has the same inlet temperature throughout), in which the cooling liquid 40 is sprayed at one or more levels or heights. The spray chamber 20 typically consists of a vertically arranged cylindrical section through which the product gas flows from bottom to top. The cold cooling liquid 40 is sprayed through nozzles at multiple levels, and the condensable and possibly also the soluble fission products are removed from the product gas.

[0064] The cooling liquid 40 preferably has a cooling temperature of at least 30 °C and at most 100 °C when sprayed into the product gas. The spray cooler 18 enables rapid and effective condensation of condensable components from the hot product gas.

[0065] The condensed or dissolved components of the product gas collect in the receiving vessel 24. In particular, because the spray cooling takes place in the presence of a polar solvent, in this example water (the polar solvent can, for example, be contained in the product gas and / or introduced by the cooling liquid 40), a multiphase product liquid 32 is obtained in the receiving vessel 24. The multiphase product liquid 32 has at least one polar liquid phase 34 and at least one nonpolar liquid phase 36, which is also referred to below as pyrolysis oil 36.

[0066] The heteroatom-containing monomers M are enriched in the polar liquid phase 34. In addition, the polar solvent present is also typically enriched in the polar liquid phase 34.

[0067] The nonpolar liquid phase 36 contains an enrichment of nonpolar decomposition products, e.g., decomposition products of the polyolefins of the starting material 30. The nonpolar liquid phase 36 is the actual pyrolysis oil.

[0068] The collection container 24 is followed by a collection container 26 for the polar liquid phase 34 and a collection container 28 for the nonpolar liquid phase 36.

[0069] Various liquids can be used as the cooling liquid 40. Preferably, a cooling liquid 40 is used that is at least partially formed by cooled nonpolar liquid phase 36, i.e., by the pyrolysis oil. A cooling liquid 40 that is at least partially formed by a polar solvent can also be used.

[0070] The polar liquid phase 34 can be further processed by mixing and / or diluting it with a polar solvent 44. This results in the formation of an upper nonpolar phase and a lower polar phase. Aromatic components accumulate in the upper nonpolar phase. The lower polar phase contains the monomers M. Examples:

[0071] Input composition:

[0072] Initial composition:

[0073] In Example 1, the starting material 30 was a multilayer film with the following composition: 74 wt% polyethylene; 19 wt% polyamide; approximately 3 wt% polyethylene terephthalate; < 0.5 wt% other solid components; water (residual moisture) 4 wt%. The throughput, i.e., the feed rate of the starting material 30 to the pyrolysis reactor 16, was 100 kg / h. The starting material 30 was pyrolyzed at a pyrolysis temperature of 380 °C. The temperature of the cooling liquid 40 was 75 °C. The nonpolar liquid phase 36 (i.e., the pyrolysis oil) was used as the cooling liquid 40. The cooling liquid 40 was sprayed via three nozzle levels. The amount of cooling liquid 40 was evenly distributed across the three nozzle levels.

[0074] A multiphase product liquid 32 was obtained with a nonpolar liquid phase 36 and a polar liquid phase 34.

[0075] The mass fraction of caprolactam in the nonpolar liquid phase 36 was approximately 1.5 wt%. The mass fraction of caprolactam in the polar liquid phase 34 was approximately 81 wt%. In addition, the polar liquid phase 34 contained approximately 4 wt% aminocaproic acid and approximately 5 wt% aromatic compounds, some containing nitrogen, and water.

[0076] It has proven particularly advantageous to use modified cooling liquids 40 in the process. In the processing of mixed plastics, especially multilayer films, a large number of polymers containing heteroatoms are found. Due to the lower bond energies at the heteroatom incorporation sites, these polymers break down more quickly or easily, forming polar functional groups. These compounds can then be readily separated from the product gas using a polar cooling liquid 40, e.g., water, processed return water, or a specific model mixture (water with small amounts of lower alcohols or acids). The use of different cooling liquids 40 can also improve the specification of the nonpolar liquid phase 36, i.e., the pyrolysis oil. Because the heteroatomic functional groups are enriched in the polar liquid phase 34, significantly less oxygen and nitrogen are found in the pyrolysis oil.

[0077] Example 2 - Pyrolysis oil and possible improvements

[0078] The basic data are analogous to Example 1. However, approximately 20 liters of water 42 are additionally mixed into the uppermost nozzle level of the spray cooler 18. This results in the formation of the multiphase product liquid 32 during spray drying, and the caprolactam is essentially washed out of the pyrolysis oil, i.e., from the nonpolar liquid phase 36. The oxygen content of the pyrolysis oil is almost halved, and the nitrogen content decreases by approximately one-third.

[0079] In addition, in example 2 the starting material 30 was partially dried beforehand, thereby reducing the proportion of water in the starting material to 1% by mass.

[0080] Comparative example

[0081] In the comparative example, a dry, almost pure PE to PA6 mixture in a ratio of approximately 4:1 was used as the starting material 30 (approximately 80:20). The throughput was also approximately 100 kg / h. The starting material 30 was pyrolyzed at a pyrolysis temperature of 380 °C. The temperature of the cooling liquid 40 was 70 °C. The nonpolar liquid phase 36 (i.e., the pyrolysis oil) was used as the cooling liquid 40. The cooling liquid 40 was sprayed via three nozzle levels. The quantity of cooling liquid 40 was evenly distributed across the three nozzle levels.

[0082] Due to the a) absence of polar solvent in the pyrolysis gas, b) the dryness of the material 30 and c) the non-addition of a polar solvent in the spray cooler 18, no polar liquid phase could form, which is why a single-phase product liquid 32 was obtained.

[0083] The presence of only one phase was confirmed by measuring the dielectric constant of the product liquid 32. No change in the dielectric constant was measured that could indicate two separate phases.

[0084] No polar byproduct was found in container 26 and the caprolactam remained in the single-phase

[0085] Product liquid 32, which in this case forms the pyrolysis oil, is dissolved at approximately 15% by mass.

[0086] This is also evident from the calorific value, which, due to the high content of caprolactam, is significantly lower at 44.1 than in examples 1 and 2, where the calorific value is over 45.5 MJ / kg.

Claims

Patent claims 1. A process for obtaining heteroatom-containing monomers by the pyrolysis of polymer-containing starting materials, the process comprising: providing a starting material (30) comprising at least one heteroatom-containing polymer, introducing the starting material (30) into a pyrolysis reactor (16), pyrolyzing the starting material (30) in the pyrolysis reactor (16), wherein at least the heteroatom-containing polymer is pyrolytically cleaved, and wherein a product gas is obtained comprising heteroatom-containing monomers (M), in particular caprolactam and / or aminocaproic acid and / or terephthalic acid, spray-cooling the product gas, i. wherein the product gas already comprises at least one polar solvent before spray-cooling, and / or wherein at least one polar solvent is added to the product gas during spray-cooling, ii.wherein a multiphase product liquid (32) is obtained by spray cooling, comprising a polar liquid phase (34) and a nonpolar liquid phase (36), and wherein the heteroatom-containing monomers (M) and the polar solvent are enriched in the polar liquid phase (34), and separation of the polar liquid phase (34) from the nonpolar liquid phase (36).

2. The method according to claim 1, characterized in that the polar solvent is selected from the group consisting of: water, organic acids, in particular formic acid, propionic acid, butyric acid or oxalic acid, alcohols, in particular isopropanol, ethanol or 1,4-butanediol, aldehydes, in particular formaldehyde, and ketones, in particular acetone.

3. Method according to one of the preceding claims, characterized in that the starting material (30) comprises as a heteroatom-containing polymer at least one polyester, in particular polyethylene terephthalate, at least one polyurethane, and / or at least one polyamide, in particular polyamide 6 and / or polycaprolactam and / or polyamide 6.12 and / or polyamide 12.

4. Method according to one of the preceding claims, characterized in that the starting material (30) comprises at least one polyolefin, in particular polyethylene and / or polypropylene.

5. Method according to one of the preceding claims, characterized in that the starting material (30) comprises a multilayer material having different polymer layers, in particular a multilayer film.

6. Method according to one of the preceding claims, characterized in that the mass fraction of biomass in the starting material (30) is at most 30% by mass, preferably at most 10% by mass, particularly preferably at most 5% by mass.

7. A method according to one of the preceding claims, characterized in that the mass fraction of non-convertible inert materials in the starting material (30) is at most 5% by mass, preferably at most 1% by mass. Mass % .

8. Method according to one of the preceding claims, characterized in that the residence time of the starting material (30) in the pyrolysis reactor (16) is between 0.1 h and 24 h, preferably between 0.5 h and 20 h .

9. Method according to one of the preceding claims, characterized in that a catalyst is added to the starting material (30), in particular a zeolite catalyst based on SiCy / A^Oa and / or a layer silicate catalyst.

10. Method according to one of the preceding claims, characterized in that the starting material (30) is pyrolyzed at a pyrolysis temperature of at least 280 °C, preferably at a pyrolysis temperature of at least 280 °C and at most 450 °C, preferably at a pyrolysis temperature of at least 360 °C and at most 400 °C, particularly preferably at a pyrolysis temperature of about 380 °C.

11. Method according to one of the preceding claims, characterized in that the at least one polar solvent is contained in the product gas, wherein the mass fraction of polar solvent in the product gas before spray cooling is at least 0.1 wt%, preferably at least 0.5 wt%, particularly preferably at least 0.5 wt% and at most 5 wt%.

12. A method according to any of the preceding claims, characterized in that the at least one polar solvent is contained in the starting material (30), in particular wherein the mass fraction of polar solvent in the starting material (30) is at least 0.1 wt% and at most 15 wt%, preferably at least 0.1 wt% and at most 5 wt%, particularly preferably at most 0.1 wt% and at most 2 wt%, in particular wherein the starting material (30) has residual moisture, and / or that the starting material (30) releases at least one polar solvent, in particular water, upon pyrolytic cleavage, and / or that at least one polar solvent is added to the starting material (30) in the pyrolysis reactor (16).

13. Method according to one of the preceding claims, characterized in that the time period, which begins with the formation of the product gas in the pyrolysis reactor (16) and ends with spray cooling of the product gas formed, is at most 30 seconds, preferably at most 15 seconds, particularly preferably at most 10 seconds.

14. Method according to one of the preceding claims, characterized in that the product gas is spray-cooled in a single-stage or multi-stage spray cooler (18).

15. Method according to one of the preceding claims, characterized in that the spray cooling of the Product gas includes the injection of a cooling liquid (40) into the product gas.

16. Method according to the preceding claim, characterized in that the cooling liquid (40) has a cooling temperature of at most 100 °C when sprayed, preferably a cooling temperature of at least 30 °C and at most 100 °C, preferably a cooling temperature of at least 70 °C and at most 85 °C, particularly preferably a cooling temperature of about 77 °C.

17. Method according to one of claims 15 and 16, characterized in that the cooling liquid (40) is formed at least partially by the nonpolar liquid phase (36).

18. Method according to one of claims 15 to 17, characterized in that the cooling liquid (40) is formed at least partially by a polar solvent, in particular wherein water is used as the cooling liquid (40).

19. Method according to the preceding claim, characterized in that a mass fraction of polar solvent in the cooling liquid (40) is between 0.1 wt% and 10 wt%.

20. Method according to one of the preceding claims, characterized in that the heteroatom-containing monomers (M) are obtained from the separated polar liquid phase (34) be isolated.

21. Method according to one of the preceding claims, characterized in that the separated polar liquid phase (34) is reacted with a polar solvent. ( 44 ) is mixed and / or diluted so that an upper nonpolar phase and a lower polar phase containing the heteroatom-containing monomers (M) are formed, and the lower polar phase is separated from the upper nonpolar phase.

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