Process for recycling plastics material

Abstract

The present invention relates to a process for recycling plas- tics material (1) comprising nitrile-containing polymers, pref- erably acrylonitrile butadiene styrene (ABS) and / or styrene ac- rylonitrile (SAN), the process comprising: - processing a pyrolysis feed (8) comprising the plastics ma- terial (1) comprising nitrile-containing polymers in a py- rolysis reactor (9) to generate a pyrolysis product (10) comprising nitriles; - hydrotreating at least a portion of the pyrolysis product (10) in a hydrotreatment unit (17), whereby at least a por- tion of the nitriles are converted into non-nitrile con- taining compounds and NH3; - withdrawing an aqueous phase (18) from the hydrotreated py- rolysis product (19), wherein the aqueous phase (18) com- prises at least a portion of the generated NH3.

Description

[0001] Process for recycling plastics material

[0002] The present invention relates to a process for recycling plastics material comprising nitrile-containing polymers such as acrylonitrile butadiene styrene (ABS ) and / or styrene acrylonitrile ( SAN) .

[0003] ABS and SAN are polymers extensively utili zed across various industries due to their advantageous properties , including impact resistance , toughness , and chemical stability . These materials are commonly employed in the automotive and electronics sectors , as well as in consumer goods that require durable materials , such as children ' s toys . Their widespread application contributes to a signi ficant presence of ABS and SAN in both industrial and post-consumer waste streams . Also , other types of nitrile-containing polymers such as polyacrylonitrile ( PAN) , poly (methyl methacrylate ) ( PMMA) and nitrile rubber (NBR) are widely used and found in waste streams .

[0004] The recycling of plastics materials , particularly those containing nitrile-containing polymers such as ABS and SAN, presents a series of challenges . While pure ABS or SAN waste is typically sorted and recycled through mechanical processes , mixed waste streams - especially those involving multi-layer structures , glued components , or other complex assemblies - often pose signi ficant di f ficulties . These mixed waste streams are generally unsuitable for mechanical recycling due to contamination, degradation, or other quality issues . As a result , they are frequently incinerated .

[0005] Incineration of waste containing nitrile-containing polymers such as ABS and SAN causes signi ficant environmental problems . It not only results in the release of carbon dioxide ( CO2 ) but also generates nitrogen oxides (N0x) due to the presence of nitrile groups in the polymer structure . This contributes to a substantial environmental footprint and underscores the need for alternative recycling methods that can ef fectively handle these types of waste streams .

[0006] Chemical recycling, speci fically pyrolysis , has emerged as a promising alternative to incineration . Pyrolysis involves the thermal decomposition of plastics at high temperatures , typically between 400 and 600 ° C, to produce hydrocarbon products commonly referred to as "pyrolysis oils" , " synthetic crude oils" or " syncrudes" . These pyrolysis oils have a range of potential applications , including the use as alternative fuels or as feedstock for the production of new chemicals and materials . However, the presence of nitrile groups in polymers such as ABS and SAN complicates this process , as the pyrolysis of these polymers generates nitrile-containing by-products . These by-products can be detrimental to downstream refinery units such as fluid catalytic cracking ( FCC ) or other cracker units . Thus , plastics materials comprising high amounts of nitrile-containing polymers such as ABS or SAN have traditionally not been regarded as feedstocks suitable for chemical recycling .

[0007] For this reason, conventional plastics pyrolysis processes often speci fy low tolerances for the content of nitrile-containing polymers such as ABS and SAN in the feedstock . This necessitates extensive pre-sorting of materials to exclude or minimi ze the presence of these polymers , or alternatively, requires elaborate post-treatment of the pyrolysis products . However, this leads to less flexible , less ef ficient and less economical processes .

[0008] In light of these challenges , there is a clear need for new and improved processes for recycling plastics material containing nitrile-containing polymers such as ABS and / or SAN, in particular processes that address at least some of the limitations of the prior art and that enable the ef fective handling of such materials in an economically viable manner . It is an obj ect of the present invention to provide such processes .

[0009] Therefore , the present invention provides a process for recycling plastics material comprising nitrile-containing polymers , preferably ABS and / or SAN, the process comprising :

[0010] - processing a pyrolysis feed comprising the plastics material comprising nitrile-containing polymers in a pyrolysis reactor to generate a pyrolysis product comprising nitriles ;

[0011] - hydrotreating at least a portion of the pyrolysis product in a hydrotreatment unit , whereby at least a portion of the nitriles are converted into non-nitrile containing compounds and NH3;

[0012] - withdrawing an aqueous phase from the hydrotreated pyrolysis product , wherein the aqueous phase comprises at least a portion of the generated NH3.

[0013] The present invention provides a highly ef ficient process for recycling plastics material containing nitrile-containing polymers such as ABS and / or SAN . Conventional methods for the chemical recycling of plastics materials have often avoided the inclusion of such polymers in pyrolysis feeds due to concerns about their complex degradation products . As observed by the inventors , pyrolysis of such nitrile-containing polymers yields signi ficant amounts of nitriles derived from the acrylonitrile moiety of the polymers . These nitriles can be detrimental for downstream processing in refinery units such as fluid catalytic cracking ( FCC ) or other cracker units .

[0014] Surprisingly, the inventors found that hydrotreating is remarkably ef fective in converting these nitrile-containing pyrolysis oils into valuable products . This process ef fectively trans forms the nitriles into ammonia (NH3) and non-nitrile containing compounds , particularly saturated hydrocarbons . The inventors further found that signi ficant amounts of NH3can be recovered from an aqueous phase generated in the hydrotreatment process . NH3is a crucial chemical building block that typically requires energy-intensive production methods . The co-production of NH3in the inventive process therefore signi ficantly enhances its economic viability and reduces reliance on conventional , energy-consuming ammonia synthesis . Moreover, the produced NH3can even be recycled and directly used in the process itsel f , as will be described in more detail below, further enhancing the ef ficiency of the overall process .

[0015] The inclusion of ABS / SAN in plastics pyrolysis processes has been mentioned in the prior art , e . g . , in WO 2023 / 041680 Al . However, it was not expected that hydrotreatment would be ef fective in this context - WO 2023 / 041680 Al describes elaborate post-treatments of generated pyrolysis oil and explicitly states that it is preferred that the process disclosed therein does not comprise a hydrotreating step . In addition, it was generally not expected that conventional plastics pyrolysis processes would be able to tolerate high amounts of ABS / SAN, without being detrimental to the process . Finally, the surprising finding that NH3can be obtained as a valuable co-product signi ficantly increases the ef ficiency and economic viability of the process compared to conventional processes .

[0016] The aqueous phase comprising at least a portion of the generated NH3is preferably formed during the hydrotreating, preferably through the addition of process water . In a preferred embodiment , an aqueous solution is added to the hydrotreated pyrolysis product , resulting in the formation of the aqueous phase comprising at least a portion of the generated NH3. Additionally, water may also be produced as a result of the conversion of organic oxygen compounds in the hydrotreatment unit .

[0017] Thus , the hydrotreating preferably results in the formation of an aqueous phase and an organic phase . The aqueous phase comprises at least a portion of the NH3generated by the conversion of nitriles into non-nitrile containing compounds . Preferably, the aqueous phase comprises the maj ority, more preferred at least 60 wt% , more preferred at least 70 wt% , more preferred at least 80 wt% , more preferred at least 90 wt% , more preferred at least 95 wt% , more preferred substantially all of the generated

[0018] NH3. The organic phase preferably comprises at least a portion of the non-nitrile containing compounds generated by the conversion of nitriles , preferably the maj ority, more preferred at least 60 wt% , more preferred at least 70 wt% , more preferred at least

[0019] 80 wt% , more preferred at least 90 wt% , more preferred at least

[0020] 95 wt% , more preferred substantially all of the generated non- nitrile containing compounds .

[0021] The skilled person is familiar with how to withdraw an aqueous phase from the hydrotreated pyrolysis product , as aqueous phases are also commonly removed in conventional hydrotreatment units , where such aqueous phases are typically considered wastewater . Additionally, the skilled person is familiar with the removal of NH3from wastewater, typically referred to as ammonia stripping .

[0022] In a preferred embodiment , at least a portion of the NH3is separated from the aqueous phase . Preferably, the maj ority, more preferred at least 60 wt% , more preferred at least 70 wt% , more preferred at least 80 wt% , more preferred at least 90 wt% , more preferred at least 95 wt% , more preferred substantially all of the NH3generated by the conversion of nitriles in the hydrotreatment unit is separated from the aqueous phase . The NH3may be separated from the aqueous phase using any method known in the art , preferably using a stripper, especially a gas stripper . Preferably, substantially pure NH3is obtained . Thus , preferably, a stream consisting essentially of NH3is separated from the aqueous phase .

[0023] In a preferred embodiment , the at least a portion of the NH3that is generated by the conversion of nitriles in the hydrotreatment unit is recycled and reused in the inventive process . This leads to a highly ef ficient process , since rather than relying on external NH3that needs to be produced by costly and energy-intensive processes , the process can use its own coproduced NH3. Preferably, the maj ority, more preferred at least

[0024] 60 wt% , more preferred at least 70 wt% , more preferred at least

[0025] 80 wt% , more preferred at least 90 wt% , more preferred at least

[0026] 95 wt% , more preferred substantially all of the NH3generated by the conversion of nitriles in the hydrotreatment unit is recycled and reused in the inventive process .

[0027] More speci fically, it is preferred that at least a portion of the NH3is separated from the aqueous phase and added to the pyrolysis feed and / or to the pyrolysis product . Preferably, the NH3is added to the pyrolysis feed upstream of the pyrolysis reactor and / or added to the pyrolysis product downstream of the pyrolysis reactor . Preferably, the maj ority, more preferred at least 60 wt% , more preferred at least 70 wt% , more preferred at least 80 wt% , more preferred at least 90 wt% , more preferred at least 95 wt% , more preferred substantially all of the NH3that is separated from the aqueous phase is added to the pyrolysis feed and / or to the pyrolysis product .

[0028] Adding NH3to the pyrolysis feed and / or to the pyrolysis product has a number of advantages . First , NH3can trap HC1 formed in various parts of the plant , protecting against corrosion . Additionally, adding NH3can reduce the amount of organically bound halogen in the pyrolysis oil obtained from the process .

[0029] Halogens pose signi ficant problems in plastics pyrolysis processes . Plastic mixtures often contain halogenated polymers , for example polyvinyl chloride ( PVC ) , polytetrafluoroethylene ( PTFE ) or even halogenated flame retardants . Such feedstock components can lead to the formation of HC1 or HBr during the process , which can cause harmful corrosion of refinery equipment . Such corrosion can be prevented by addition of NH3, which e . g . can neutrali ze HC1 by forming the salt NH4+ Cl“ . In addition, halogenated feedstock components can lead to the presence of organic halogen compounds in pyrolysis products , which can signi ficantly reduce the product quality . This problem is addressed, e . g . , in WO 2023 / 067035 Al , which teaches the addition of a nitrogen compound to a gaseous hydrocarbon stream, whereby organically bound halogen present in the hydrocarbon stream is converted into halide ions through nucleophilic substitution reactions .

[0030] In the context of the inventive process , both of these functions can be ful filled by the NH3generated by the conversion of nitriles in the hydrotreatment unit . When said NH3is added to the pyrolysis feed and / or to the pyrolysis product , it can on the one hand neutrali ze HC1 or HBr by forming the respective salts , and on the other hand remove organically bound halogens through nucleophilic substitution reactions cleaving the carbonhalogen bond .

[0031] In a preferred embodiment , at least a portion of the NH3generated by the conversion of nitriles is added to the pyrolysis feed upstream of the pyrolysis reactor . This can be particularly advantageous , as in this case NH3is present in the pyrolysis reactor at the time when cracking reactions take place and potentially problematic compounds are formed . Alternatively, or in addition, at least a portion of the NH3generated by the conversion of nitriles is added to the pyrolysis product downstream of the pyrolysis reactor . This can also be advantageous , since in this case the NH3may be speci fically targeted towards harmful compounds present after pyrolysis , without already being used up during the pyrolysis process .

[0032] In a preferred embodiment , the plastics material comprises organically bound halogen . Preferably, at least a portion of said organically bound halogen reacts with the NH3added to the pyrolysis feed and / or to the pyrolysis product and is converted into halide ions . In preferred embodiments, the organically bound halogen is selected from organically bound fluorine, chlorine, bromine, iodine, or mixtures thereof; more preferred, chlorine, bromine, iodine, or mixtures thereof; more preferred, chlorine.

[0033] The plastics material preferably contains at least 1 ppm, preferably at least 10 ppm, even more preferred at least 100 ppm, even more preferred at least 1,000 ppm, even more preferred at least 2,000 ppm, even more preferred at least 5,000 ppm, even more preferred at least 10,000 ppm, even more preferred at least 15, 000 ppm of organically bound halogen, in particular organically bound chlorine. The plastics material preferably contains from 1 ppm to 70,000 ppm, preferably from 10 ppm to 65,000 ppm, more preferred from 100 ppm to 60,000 ppm, even more preferred from 1,000 ppm to 50,000 ppm, even more preferred from 2,000 ppm to 40,000 ppm, even more preferred from 5,000 ppm to 30,000 ppm, even more preferred from 10,000 to 20,000 ppm of organically bound halogen, in particular organically bound chlorine.

[0034] In connection with the inventive method, the plastics material preferably contains halocarbon compounds, preferably selected from haloalkanes, haloalkenes, aromatic halocarbons and / or mixtures thereof. It is particularly preferred, if the plastics material contains halogenated polymers, in particular PVC and / or PTFE.

[0035] PVC poses significant challenges for the chemical recycling of plastics material. During the pyrolysis process, some of the carbon-chlorine bonds can be cleaved by B-elimination, which can lead to the formation of HC1, but these reactions are generally not complete and chlorine-containing alkenes can also be found in the products. In order to keep the content of organically bound chlorine in the pyrolysis oil low, conventional pyrolysis processes often limit the proportion of PVC in the starting material to lower values. The chlorine-containing alkenes, which are formed as PVC degradation products in the pyrolysis process, can be converted particularly effectively in substitution reactions with NH3. As a result, the inventive process is particularly well suited for recycling plastics material containing high amounts of PVC. This applies, for instance, to plastic mixtures from the recycling of electronic waste, which typically contain high proportions of organochlorine and organobromine, in particular PVC from cables, but also flame retardants such as hexabromocyclododecane (HBCD) , or chlorinated paraffins.

[0036] In a preferred embodiment, the plastics material therefore comprises PVC, preferably at least 0.001 wt%, more preferred at least 0.01 wt%, more preferred at least 0.1 wt%, even more preferred at least 0.2 wt%, even more preferred at least 0.3 wt%, even more preferred at least 0.4 wt%, even more preferred at least 0.5 wt%, even more preferred at least 0.6 wt%, even more preferred at least 0.7 wt%, even more preferred at least 0.8 wt%, even more preferred at least 0.9 wt%, even more preferred at least 1 wt% PVC. The plastics material preferably contains from 0.001 to 10 wt%, preferably from 0.01 to 8 wt%, more preferred from 0.1 to 7.0 wt%, even more preferred from 0.2 to 6.5 wt%, even more preferred from 0.3 to 6.0 wt%, even more preferred from 0.4 to 5.5 wt%, even more preferred from 0.5 to 5.0 wt% of PVC.

[0037] Another source of organic halogen compounds that can cause problems in refining processes are halogen-containing flame retardants. For example, waste plastics and other plastic mixtures often contain considerable amounts of such flame retardants, which are subsequently found as organic halogen compounds in the pyrolysis oils obtained from the plastic mixtures. Bromine-containing flame retardants, for example decabromodiphenyl ether (DecaBDE) , which is added inter alia in considerable amounts to polyamides and polyolefins, or tetrabromobisphenol A (TBBPA) , which is added inter alia to polyesters, or hexabromocyclododecane (HBCD) , which is used, for example, in insulation foams, e.g. EPS (expanded polystyrene) and XPS (extruded polystyrene) , are particularly widespread in this context. The inventive method has also proven to be particularly suitable for removing organically bound halogen from halogen-containing flame retardants, in particular organically bound bromine. In a further preferred embodiment, the plastics material therefore comprises halogen-containing, preferably bromine-containing flame retardants, preferably polybrominated diphenyl ethers and / or polybrominated biphenyls, more preferred decabromodiphenyl ether (DecaBDE) , tetrabromobisphenol A (TBBPA) and / or hexabromocyclododecane (HBCD) . It is particularly preferred, if the plastics material contains at least 1 ppm, preferably at least 10 ppm, even more preferred at least 50 ppm, even more preferred at least 200 ppm, even more preferred at least 1,000 ppm of organically bound bromine, preferably in the form of bromine-containing flame retardants.

[0038] In a preferred embodiment, the pyrolysis product is in gaseous form when it is brought in contact with the NH3. As described in WO 2023 / 067035 Al, this can further enhance the efficiency of nucleophilic substitution reactions for removing organically bound halogen. Carrying out the substitution reactions in the gas phase has the advantage, on the one hand, that the hydrocarbon stream is mixed particularly well with the NH3and, on the other hand, that the substitution reactions take place particularly efficiently and a short reaction time is made possible.

[0039] In a preferred embodiment, the temperature of the gaseous pyrolysis product when brought into contact with the NH3is at least 150 °C, preferably at least 200 °C, more preferred at least 250 °C, even more preferred at least 300 °C, even more preferred at least 350 °C. Preferably, the temperature is between 150 °C and 550 °C, preferably between 200 °C and 500 °C, more preferred between 200 °C and 480 °C, even more preferred between 250 °C and 460 °C, even more preferred between 300 °C and 450 °C. The addition of the NH3into such a hot gaseous stream enables particularly good mixing, since the NH3composition evaporates more quickly when brought into contact and thus mixes better with the pyrolysis product stream. This in turn leads to a more efficient course of the substitution reactions and thus to a more efficient removal of organically bound halogen .

[0040] It has also proven advantageous if the temperature of a gaseous mixture formed by the addition of NH3to the gaseous pyrolysis product is at least 150 °C, preferably at least 200 °C, more preferred at least 250 °C, even more preferred at least 300 °C, even more preferred at least 350 °C. Preferably, the temperature is between 150 °C and 550 °C, preferably between 200 °C and 500 °C, more preferred between 200 °C and 480 °C, even more preferred between 250 °C and 460 °C, even more preferred between 300 °C and 450 °C. A high temperature of the gaseous mixture favors the course of nucleophilic substitution reactions. This has proven to be particularly advantageous in the removal of organic chlorine compounds as they are less reactive than organic bromine or iodine compounds .

[0041] In the method according to the invention, the NH3can be added to the pyrolysis feed and / or the pyrolysis product in essentially pure form, i.e. a composition consisting essentially of the NH3can be added. However, it can also be advantageous if the NH3is added to the pyrolysis feed and / or the pyrolysis product as part of an aqueous composition. This is particularly preferred when the NH3is added to the pyrolysis product when the pyrolysis product is in a gaseous form, in particular having a temperature as specified above. In this case, an even more efficient removal of organically bound halogen can be achieved. In the opinion of the inventors, without being bound to a theory, this is due, on the one hand, to the fact that the presence of water can promote nucleophilic substitution reactions and, on the other hand, to the fact that the water can evaporate rapidly when brought into contact with the gaseous pyrolysis product and lead to a better mixing of hydrocarbon stream and NH3.

[0042] In this context, it has proven particularly favorable if the concentration of NH3in the aqueous composition is between 5 and 80 wt%, preferably between 7 and 70 wt%, even more preferred between 10 and 50 wt%. A concentration in this range enables an efficient course of the substitution reactions.

[0043] The mass ratio between the pyrolysis feed and the added NH3and / or between the pyrolysis product and the added NH3is preferably at least 5:1, preferably at least 10:1, even more preferred at least 20:1, even more preferred at least 50:1, even more preferred at least 100:1, even more preferred at least 150:1. Preferably, the mass ratio is between 5:1 and 250:1, preferably between 10:1 and 200:1, even more preferred between 20:1 and 150:1, even more preferred between 40:1 and 100:1. It has been found that with such a mass ratio, there is a sufficient amount of NH3to ensure an efficient course of the substitution reactions, but at the same time the pyrolysis feed and / or the pyrolysis product is not diluted too much, so that the method can nevertheless be carried out particularly economically.

[0044] The plastics material used in the inventive process comprises nitrile-containing polymers. The nitrile-containing polymers are preferably selected from ABS, SAN, PAN, PMMA, NBR, and mixtures thereof. ABS and / or SAN are particularly preferred.

[0045] In addition, the plastics material may further comprise other types of plastics and mixtures thereof, preferably selected from polyethylene (PE) , polypropylene (PP) , polystyrene (PS) , polyvinyl chloride (PVC) , polyethylene terephthalate (PET) and / or polyamide (PA) . Preferably, the plastics material is plastic waste, especially pre-consumer, post-consumer and / or post-industrial plastics.

[0046] Preferably, the plastics material comprises at least 1 wt% nitrile-containing polymers, more preferred at least 2 wt%, more preferred at least 5 wt%, more preferred at least 10 wt%, more preferred at least 15 wt%, more preferred at least 20 wt%, more preferred at least 25 wt%. Preferably, the plastics material comprises between 1 wt% and 90 wt% nitrile-containing polymers, more preferred between 2 wt% and 75 wt%, more preferred between 5 wt% and 60 wt%, more preferred between 10 wt% and 50 wt%, more preferred between 15 wt% and 45 wt%, more preferred between 20 wt% and 40 wt%, more preferred between 25 wt% and 35 wt%.

[0047] Preferably, the plastics material comprises at least 1 wt% ABS and / or SAN, more preferred at least 2 wt%, more preferred at least 5 wt%, more preferred at least 10 wt%, more preferred at least 15 wt%, more preferred at least 20 wt%, more preferred at least 25 wt%. Preferably, the plastics material comprises between 1 wt% and 90 wt% ABS and / or SAN, more preferred between 2 wt% and 75 wt%, more preferred between 5 wt% and 60 wt%, more preferred between 10 wt% and 50 wt%, more preferred between 15 wt% and 45 wt%, more preferred between 20 wt% and 40 wt%, more preferred between 25 wt% and 35 wt%. In these embodiments, the phrase "comprises ... wt% ABS and / or SAN" is preferably understood as the sum of ABS and SAN making up the indicated wt% of the plastics material.

[0048] Moreover, the indicated values are also preferred for ABS and SAN, each individually. Thus, preferably, the plastics material comprises at least 1 wt% ABS, more preferred at least 2 wt%, more preferred at least 5 wt%, more preferred at least 10 wt%, more preferred at least 15 wt%, more preferred at least 20 wt%, more preferred at least 25 wt%. Preferably, the plastics material comprises between 1 wt% and 90 wt% ABS , more preferred between 2 wt% and 75 wt% , more preferred between 5 wt% and 60 wt% , more preferred between 10 wt% and 50 wt% , more preferred between 15 wt% and 45 wt% , more preferred between 20 wt% and 40 wt% , more preferred between 25 wt% and 35 wt% . Alternatively, or in addition, the plastics material preferably comprises at least 1 wt% SAN, more preferred at least 2 wt% , more preferred at least 5 wt% , more preferred at least 10 wt% , more preferred at least 15 wt% , more preferred at least 20 wt% , more preferred at least 25 wt% . Preferably, the plastics material comprises between 1 wt% and 90 wt% ABS , more preferred between 2 wt% and 75 wt% , more preferred between 5 wt% and 60 wt% , more preferred between 10 wt% and 50 wt% , more preferred between 15 wt% and 45 wt% , more preferred between 20 wt% and 40 wt% , more preferred between 25 wt% and 35 wt% .

[0049] The inventive process has been found to be particularly well suited for recycling polyolefin ( PO) -based plastics material comprising ABS and / or SAN . Thus , it is particularly preferred that the plastics material comprises PO, preferably selected from PE and / or PP . Preferably, the plastics material comprises at least 5 wt% PO, more preferred at least 10 wt% , more preferred at least 20 wt% , more preferred at least 30 wt% , more preferred at least 40 wt% , more preferred at least 50 wt% . Preferably, the plastics material comprises between 5 wt% and 95 wt% PO, more preferred between 10 wt% and 90 wt% , more preferred between 20 wt% and 80 wt% , more preferred between 30 wt% and 70 wt% , more preferred between 40 wt% and 60 wt% .

[0050] In a preferred embodiment of the inventive process , the plastics material is heated to form a plastic melt , wherein the pyrolysis feed comprises the plastic melt . Preferably, the plastics material is heated in a mixer, especially in an extruder . This allows the subsequent pyrolysis to be carried out more energy-ef f iciently and in a shorter amount of time . In the mixer, especially the extruder, the plastics material can preferably also be degassed . This allows producing a uni form mass without gas inclusions , ensuring that a homogeneous pyrolysis product can be obtained through the subsequent pyrolysis .

[0051] Preferably, the plastics material is heated to a temperature of at least 80 °C to form the plastic melt, preferably at least 100 °C. Preferably, the plastics material is heated to a temperature between 80 °C and 450 °C, more preferred between 100 °C and 350 °C. Preferably, the plastics material is heated to the said temperature at a pressure of 10 to 30 bar, preferably 15 to 25 bar.

[0052] In a preferred embodiment of the inventive process, the pyrolysis feed further comprises an external solvent. Pyrolysis processes involving the addition of external solvents have been previously described, e.g. in WO 2012 / 149590 Al. The addition of an external solvent to the pyrolysis feed comprising the plastic melt allows reducing the viscosity of the pyrolsis feed supplied to the pyrolysis reactor relative to the viscosity of the plastic melt. In this way, the mobility of polymer chains at a given temperature can be increased, which can result in an improved heat transfer into the plastics material within the pyrolysis reactor. Moreover, the reduction in viscosity allows achieving a smaller temperature gradient drop across the crosssection of the pyrolysis reactor, thereby reducing the risk of overheating the plastics material near the reactor wall as well as the risk of coking.

[0053] Suitable types of external solvents are described, e.g., in WO 2012 / 149590 Al. Preferably, the external solvent is a hydrocarbon oil having a boiling range with an initial boiling point of at least 150 °C, preferably at least 300 °C, and / or with a final boiling point of at most 850 °C, preferably at most 600 °C.

[0054] In a preferred embodiment, the inventive process comprises the step of mixing the plastic melt with a diluent stream to form the pyrolysis feed, wherein the diluent stream preferably comprises the external solvent. As described in more detail below, diluent stream may further comprise a recycling stream.

[0055] At the timepoint when the diluent stream is added to the plastic melt, the plastic melt preferably has a temperature of at least 80 °C, preferably at least 120 °C, more preferred at least 150 °C, more preferred at least 200 °C. Preferably, the plastic melt has a temperature between 80 °C and 450 °C, preferably between 120 °C and 450 °C, more preferred between 150 °C and 400 °C, more preferred between 200 °C and 350 °C. Alternatively or in addition, the diluent stream can preferably be heated to a temperature of at least 80°C, preferably at least 120°C, more preferred at least 150 °C, more preferred at least 200 °C before being added to the plastic melt. Preferably the diluent stream has a temperature between 80 °C and 450 °C, preferably between 120 °C and 450 °C, more preferred between 150 °C and 400 °C, more preferred between 200 °C and 350 °C. By increasing the temperature of the plastic melt and / or the diluent stream, the mixing can proceed more quickly and efficiently. This can also allow the subsequent pyrolysis to be carried out more efficiently.

[0056] In a preferred embodiment, the plastics material is depolymerized in the pyrolysis reactor at a temperature of at least 360 °C. However, even higher temperatures may be preferred to allow for more efficient and / or faster depolymerization. Thus, it is preferred if the plastics material is depolymerized at a temperature of at least 370 °C, more preferred at least 380 °C, more preferred at least 390 °C, more preferred at least 400

[0057] °C, more preferred at least 410 °C, more preferred at least 420

[0058] °C, more preferred at least 430 °C, more preferred at least 440

[0059] °C. Preferably the plastics material is depolymerized at a temperature between 360 °C and 510 °C, more preferred between 380 °C and 505 °C, more preferred between 400 °C and 500 °C, more preferred between 440 °C and 480 °C.

[0060] The depolymerization of the plastics material may be by thermal cracking, without the addition of a catalyst, and / or by catalytic cracking. Thermal cracking is preferred. The depolymerization can be carried out under a substantially oxygen-free atmosphere, particularly under an inert atmosphere, such as under nitrogen. By limiting or excluding oxygen, complete combustion can be prevented more effectively.

[0061] In a preferred embodiment of the inventive process, the pyrolysis product is separated into a heavy product and a light product, wherein at least a portion of the light product is hydrotreated in the hydrotreatment unit. Thus, in this case, the "at least a portion of the pyrolysis product" that is hydrotreated in the hydrotreatment unit is at least a portion of the light product. Additionally, in this case, it is preferred that in the embodiment, in which the NH3generated by the conversion of nitriles in the hydrotreatment unit is added to the pyrolysis product, said NH3is added to the light product. Moreover, as laid out in more detail below, the light product can undergo further processing steps before hydrotreatment, such as washing steps, distillation, etc.

[0062] The pyrolysis product may be separated into the heavy product and the light product using any suitable method known to the skilled person. For instance, it may be separated in a separation vessel, preferably wherein the separation vessel is a liquid-gas separation vessel, especially a cyclone. A particularly suitable type of separation vessel is disclosed in WO 2023 / 036751 Al.

[0063] Preferably, the light product has a boiling range with an FBP (final boiling point) below 250 °C, more preferred below 230 °C, more preferred below 210 °C. However, it is also preferred that the FBP is not too low, as this may reduce the amount of the final hydrocarbon product obtained through the process. Therefore, the light product preferably has a boiling range with a FBP above 150 °C, more preferred above 170 °C, more preferred above 190 °C. It is particularly preferred, if the light product has a boiling range with a FBP between 150 and 250 °C, more preferred between 170 and 230 °C, more preferred between 190 and 210 °C.

[0064] The heavy product preferably has a boiling range with an IBP (initial boiling point) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the IBP is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C. Similarly, it is preferred that the heavy product has a boiling range with an T10 (temperature at 10% volume distilled) of at most 250 °C, more preferred at most 230 °C, more preferred at most 210 °C. Preferably, the T10 is between 150 °C and 250 °C, more preferred between 170 °C and 230 °C, more preferred between 190 °C and 210 °C.

[0065] In a preferred embodiment, the inventive process further comprises the step of withdrawing a recycling stream from the pyrolysis product and including at least a portion of said recycling stream in the pyrolysis feed . In this way, the recycling stream can ful fil a similar function as the external solvent described above , thereby reducing the consumption of external solvent . When the pyrolysis product is separated into a heavy product and a light product , as described above , it is preferred that the recycling stream is withdrawn from the heavy product .

[0066] Thus , preferably, the pyrolysis feed comprises the external solvent and the recycling stream, in addition to the plastics material , particularly in addition to the plastic melt . In a preferred embodiment , the external solvent is mixed with the recycling stream to form a diluent stream, wherein said diluent stream is added to the plastic melt . In this embodiment , therefore , the pyrolysis feed preferably comprises the diluent stream in addition to the plastic melt .

[0067] In a preferred embodiment , the at least a portion of the pyrolysis product is washed with an aqueous washing solution before it is hydrotreated . This advantageously allows removing contaminants before hydrotreatment . Moreover, in the embodiments , in which NH3is added to the pyrolysis feed and / or the pyrolysis product , such a washing step allows removing halide ions that may have been trapped in the form of salts such as NH4+ Cl- . Due to their water solubility, halide ions or salts formed therefrom can pass into the water phase and be separated . The washing can for instance be carried out in a mechanical mixer, in a static mixer and / or in a mixer-settler . Mixer-settlers have proven to be particularly suitable in this context , since the mixing of the oil phase and aqueous washing solution as well as the subsequent settling process for segregating the phases and separating the puri fied oil phase can take place in a continuous process . In this context , it is particularly preferred i f the aqueous washing solution is a basic aqueous washing solution, preferably wherein the pH value of the aqueous washing solution is at least 7 . 5 , preferably at least 8 , even more preferred at least 9 , even more preferred at least 10 , even more preferred at least 12 .

[0068] In a further embodiment , the at least a portion of the pyrolysis product undergoes distillation before it is hydrotreated . This also allows removing salts such as NH4+ Cl“ and other impurities. Independently therefrom or in addition, the at least a portion of the pyrolysis product may undergo further treatment steps before hydrotreatment, such as using guard beds or adsorbers .

[0069] For the purposes of the inventive process, any suitable type of hydrotreatment unit that the skilled person is familiar with may be used. However, it is particularly preferred that the hydrotreatment unit comprises a non-acidic catalyst. It was found that acidic catalysts can be partially deactivated by neutralization with NH3formed through the conversion of nitriles in the hydrotreatment unit, leading to shorter catalyst lifetimes and decreasing the efficiency of the overall process. Thus, it is preferred if a non-acidic catalyst is used in the hydrotreatment unit. Preferably, the hydrotreament unit does not comprise any acidic catalysts.

[0070] The skilled person is familiar with suitable non-acidic catalysts. Preferably, the term "non-acidic catalyst" is understood as any catalyst that does not exhibit significant Bronsted or Lewis acidity under the operating conditions in the hydrotreatment unit. Preferably, the non-acidic catalyst comprises active metals selected from cobalt, nickel, molybdenum, tungsten, or combinations thereof. Preferably, the non-acidic catalyst comprises a non-acidic support material, e.g., silica, titania, or zirconia. Preferably, the non-acidic catalyst is selected from a cobalt-molybdenum (Co / Mo) catalyst, a nickel-molybdenum (Ni / Mo) catalyst, a nickel-tungsten (Ni / W) catalyst, a cobalt-tungsten (Co / W) catalyst, a nickel- molybdenum-tungsten (Ni / Mo / W) catalyst, or a cobalt-nickel- molybdenum catalyst (Co / Ni / Mo) .

[0071] Unless specified otherwise, all parameters as used herein correspond to parameters at IUPAC SATP-conditions („Standard Ambient Temperature and Pressure") , in particular a temperature of 25 °C and a pressure of 101.300 Pa.

[0072] Percentages (indicated as "wt%" and the like) as used herein correspond to weight per weight (w / w) unless specified otherwise. Similarly, ratios used herein correspond to weight ratios (w / w) unless specified otherwise.

[0073] References to percentages of a given component in any composition refer to the weight percent relative to the total weight of the respective composition unless specified otherwise. Thus, when it is specified that a certain composition comprises X wt% compound A, this means that compound A constitutes X wt% of said composition, i.e., that said composition contains X wt% compound A based on the total weight of said composition. For instance, if it is stated that "the plastics material comprises at least 1 wt% ABS", this means that ABS constitutes at least 1 wt% of the plastics material.

[0074] As used herein, the phrase "at least a portion of" or similar phrases refer to any subset of a specified material, component, or stream, which may include part or all of the specified entity. This definition is intended to encompass not only partial quantities but also the entirety of the material, component, or stream in question. Consequently, whenever "at least a portion of" a stream or other entity is mentioned, it is also preferred to use the entire stream or entity. For instance, when it is mentioned that the least a portion of the pyrolysis product is hydrotreated in a hydrotreatment unit, it is also preferred that the pyrolysis product (as a whole) is hydrotreated.

[0075] Pressures given in "bar" indicate absolute pressures ("bara") , unless specified otherwise.

[0076] Quantities given in "ppm" refer to parts per million on a weight basis (ppmw) , unless indicated otherwise. Thus, 1 ppm as used herein corresponds to 0.0001 wt%.

[0077] Boiling ranges mentioned herein are preferably determined according to ISO 3924:2019, in particular, Procedure A or Procedure B as defined in said standard, or ASTM D86-23ae; preferably ASTM D86-23ae.

[0078] As used herein, the term "nitrile" refers to any chemical compound comprising a cyano functional group (-C=N) attached to a carbon atom. The term "nitrile-containing polymers" refers to polymers that include one or more cyano functional group (-C=N) within their molecular structure. The term "non-nitrile containing compounds" refers to compounds not comprising such a -C=N functional group. They can also be referred to as "non-nitrile compounds" or "nitrile-free compounds". Preferably, the non-nitrile containing compounds described herein are hydrocarbons, preferably saturated hydrocarbons , especially paraf finic hydrocarbons .

[0079] As used herein, "organically bound halogen" preferably means halogens which are present in chemical compounds bound to carbon, i . e . , wherein a halogen atom is bound to a carbon atom . Preferably, the content of organically bound halogen is determined according to DIN EN 14077 : 2004- 03 . Alternatively, the content of organically bound halogen can also be determined according to DIN EN 14582 : 2016- 12 . In connection with the invention, the standard ASTM D7359 : 2014 07 01 is also suitable for the determination of organically bound halogen, in particular organically bound fluorine and / or chlorine .

[0080] Figure 1 shows a process flow diagram of a first embodiment of the process for depolymeri zing plastics material .

[0081] Figure 2 shows a process flow diagram of a further embodiment of the process for depolymeri zing plastics material .

[0082] In the embodiment shown in Figure 1 , plastics material 1 comprising ABS and / or SAN is supplied to an extruder 2 , in which the plastics material is compacted, molten and / or degassed . The resulting plastic melt 3 is mixed with a diluent stream 4 , which comprises an external solvent 5 , preferably a heavy oil , and a recycling stream 6 comprising a fraction of depolymeri zed plastics material . The plastic melt 3 is mixed with the diluent stream 4 in a static mixer 7 to form a pyrolysis feed 8 . The pyrolysis feed 8 is processed in a pyrolysis reactor 9 at a temperature between 360 ° C and 510 ° C, whereby the plastics material 1 contained in the pyrolysis feed 8 is depolymeri zed through thermal cracking, yielding a pyrolysis product 10 . The pyrolysis product 10 comprises nitrile compounds derived from the acrylonitrile moieties of the ABS and SAN contained in the plastics material 1 . Next , the pyrolysis product 10 is conveyed to a separation vessel 11 , wherein the pyrolysis product 10 is separated into a heavy product 12 and a light product 13 . At least a part of the heavy product 12 is withdrawn as the recycle stream 6 , which is recycled and added to the plastic melt 3 as part of the diluent stream 4 . The light product 13 is obtained from the separation vessel 11 in gaseous form and conveyed to a fractionation column 14 , through which a gas stream 15 is removed from the light product 13 . Subsequently, the condensed light product 16 is conveyed to a hydrotreatment unit 17 , wherein it is hydrotreated . During hydrotreating, at least a portion of the nitriles contained in the condensed light product 16 are converted into non-nitrile containing compounds and NH3. Moreover, an aqueous phase 18 containing the maj ority of generated NH3and an organic phase containing the maj ority of the generated non-nitrile containing compounds are formed . The aqueous phase 18 is removed, and the organic phase is recovered as hydrotreated pyrolysis product 19 , which is the primary product of the process , and which can be used for a variety of downstream applications such as alternative fuels or the production of new chemicals and materials . The aqueous phase 18 is conveyed to a stripper 20 to recover an NH3stream 21 comprising the NH3generated by the conversion of the nitriles in the hydrotreatment unit 17 as a secondary product of the process . The remaining part of the aqueous phase 18 may be discarded as wastewater stream 22 .

[0083] The process shown in Figure 2 comprises all features of the process shown in Figure 1 . In addition, portions of the NH3recovered as NH3stream 21 are added to the pyrolysis feed 8 as well as to the light product 13 . The NH3added to the pyrolysis feed 8 and the light product 13 allows neutrali zing HC1 or HBr formed during the process by forming the respective salts NH4+ Cl“ and NH4+ Br~ . Additionally, the NH3can eliminate organically bound halogens deriving from polymers such as PVC through nucleophilic substitution reactions . In the embodiment shown in Figure 2 , the condensed light product 16 , which comprises halide ions formed as products of these nucleophilic substitution reactions as well as the above-mentioned ammonium salts , is conveyed to a mixer settler 23 , wherein it is washed with an aqueous washing solution 24 . The condensed light product 16 is mixed with the aqueous washing solution 24 in a mixing zone of the mixer-settler 23 , whereby halide ions and ammonium salts pass into the aqueous phase . Subsequently, the puri fied oil phase is segregated from the aqueous phase in a settling zone of the mixer-settler 23 . The aqueous phase is removed as wastewater stream 25 , containing the halide ions and ammonium salts , and the oil phase is obtained as the washed light product 26 . The washed light product 26 is then hydrotreated in the hydrotreatment unit 17, as described above.

[0084] Example 1: Co-production of pyrolysis oil and NH3 from ABS- / SAN- containing plastics material .

[0085] In order to test the co-production of pyrolysis oil and NH3from ABS- and SAN-containing plastics material, experiments were carried out using a process essentially as shown in Figure 1. As starting material, PO-based waste plastics material comprising 30 wt% ABS or SAN was used. This plastics material was depolymerized in a pyrolysis reactor, a light product having a boiling range with a final boiling point of 400 °C to 470 °C was separated from the pyrolysis product, washed, and used in hydrotreating test runs.

[0086] An analysis of the washed pyrolysis oil prior to hydrotreating in the hydrotreatment unit gave the following results:

[0087] - Bromine Number [g / lOOg] : 33.3

[0088] - C [%] : 84.8

[0089] - H [%] : 14.2

[0090] - N [ppm] : 2936

[0091] - Cl [ppm] : 12

[0092] - P [ppm] : 2.8

[0093] - S [ppm] : 49

[0094] The bromine number of 33.3 g / lOOg indicates a significant amount of unsaturated hydrocarbons in the pyrolysis oil. The nitrogen content of nearly 3,000 ppm further demonstrates the high concentration of nitrile compounds, resulting from the large amount of ABS in the plastic material.

[0095] For each hydrotreating experiment, 50 L of this pyrolysis oil were hydrotreated using H2pressures of 45 bar or 51 bar, Co / Mo or Ni / Mo catalysts, and a temperature of 364 °C. The recovered hydrotreated pyrolysis oil was separated into a light fraction (IBP to 180 °C) and a heavy fraction (180 °C to 415 °C) and the bromine numbers and nitrogen (N) -contents of each fraction were analyzed. The following results were obtained:

[0096] The obtained bromine numbers show that the unsaturated hydrocarbons contained in the pyrolysis oil were fully saturated . In addition, nitrile compounds were fully converted to NH3, as demonstrated by the reduction of N-content from the washed pyrolysis oil ( approximately 3 , 000 ppm) to the hydrotreated fractions (< 15 ppm) , from which the NH3containing water phase had been removed . The small remaining N-contents observed in the hydrotreated fractions were due to other N-containing compounds such as N-heterocycles .

[0097] In addition, the following yields of NH3relative to the amounts of ABS / SAN contained in the starting material were calculated :

[0098] - ABS : 5- 6 . 6 wt%

[0099] SAN : 5- 8 . 9 wt% This means that for each kg of ABS contained in the plastics material used to produce the pyrolysis oil, between 0.05 kg and 0.066 kg of NH3could be obtained, whereas for each kg of SAN between 0.05 kg and 0.089 kg of NH3could be obtained.

Claims

24Claims :

1. A process for recycling plastics material (1) comprising ni- trile-containing polymers, preferably acrylonitrile butadiene styrene (ABS) and / or styrene acrylonitrile (SAN) , the process comprising :- processing a pyrolysis feed (8) comprising the plastics material (1) comprising nitrile-containing polymers in a pyrolysis reactor (9) to generate a pyrolysis product (10) comprising nitriles;- hydrotreating at least a portion of the pyrolysis product (10) in a hydrotreatment unit (17) , whereby at least a portion of the nitriles are converted into non-nitrile containing compounds and NH3; withdrawing an aqueous phase (18) from the hydrotreated pyrolysis product (19) , wherein the aqueous phase (18) comprises at least a portion of the generated NH3.

2. The process according to claim 1, wherein at least a portion of the NH3is separated from the aqueous phase (18) , preferably by using a stripper (20) .

3. The process according to any one of claims 1 to 2, wherein at least a portion of the NH3is separated from the aqueous phase (18) and added to the pyrolysis feed (8) and / or to the pyrolysis product (10) .

4. The process according to claim 3, wherein the plastics material (1) further comprises organically bound halogen, wherein at least a portion of said organically bound halogen reacts with the NH3added to the pyrolysis feed (8) and / or to the pyrolysis product (10) and is converted into halide ions.

5. The process according to any one of claims 1 to 4, wherein the plastics material (1) comprises at least 1 wt% ABS and / orSAN, preferably at least 25 wt%.

6. The process according to any one of claims 1 to 5, wherein the plastics material (1) comprises between 1 wt% and 90 wt% ABS and / or SAN, preferably between 25 wt% and 35 wt%.

7. The process according to any one of claims 1 to 6, wherein the plastics material (1) comprises at least 5 wt%, preferably at least 50 wt% polyolefins (PO) , preferably selected from polyethylene (PE) and / or polypropylene (PP) .

8. The process according to any one of claims 1 to 7, wherein the plastics material (1) comprises polyvinyl chloride (PVC) , preferably at least 0.1 wt% PVC.

9. The process according to any one of claims 1 to 8, wherein the plastics material (1) is heated to form a plastic melt (3) , wherein the pyrolysis feed (8) comprises the plastic melt (3) .

10. The process according to any one of claims 1 to 9, wherein the pyrolysis feed (8) further comprises an external solvent11. The process according to any one of claims 1 to 10, wherein the plastics material (1) is depolymerized in the pyrolysis reactor (9) at a temperature of at least 360 °C.

12. The process according to any one of claims 1 to 11, wherein the pyrolysis product (10) is separated into a heavy product (12) and a light product (13) , wherein at least a portion of the light product (13) is hydrotreated in the hydrotreatment unit (17) .

13. The process according to any one of claims 1 to 12, furthercomprising the step of withdrawing a recycling stream (6) from the pyrolysis product (10) and including at least a portion of said recycling stream (6) in the pyrolysis feed (8) .

14. The process according to any one of claims 1 to 13, wherein the at least a portion of the pyrolysis product (10) is washed with an aqueous washing solution (24) before it is hydrotreated.

15. The process according to any one of claims 1 to 14, wherein the hydrotreatment unit (17) comprises a non-acidic catalyst.

Images