A PROCESS FOR PYROLYZING A POLYOLEFIN RECOVERED FROM A SOLID MATERIAL COMPRISING SAID POLYOLEFIN

Description

The present invention relates to a process for pyrolyzing a polyolefin recovered from a solid material M containing said polyolefin and a production unit for carrying out said process. The present invention further relates to a pyrolysis oil obtainable or obtained by the aforementioned process as well as the use of said oil.

Polyolefin, such as polyethylene (PE) and polypropylene (PP), can be found in numerous materials, such as packaging and plastics from automotive. Thus, its consumption represents a significant percentage of the global CO₂ emissions. Thus, there is a need to recycle polyolefin from such materials. Polyolefin can be chemically recycled by pyrolysis. However, when the waste streams contain a low fraction of polyolefins, non-olefinic plastics form less liquid product of lower quality. Therefore, the product yields of the by-products (light gases and solid residues) are increased. Furthermore, these by-products also have a lower quality, e.g. the light gases might consist of CO, CO₂, methane, ethane, which are contaminated with undesired components such as acidic gases like HCl, NOx, HCN, and so forth and/or the solid residue can contain substantial amounts of rare earth metals, PAH, and so on. Hence the solid residue, has to be landfilled or incinerated. The obtained pyrolysis oil from such materials usually becomes richer and richer in oxygen and/or nitrogen due to the presence of polyamide, polyurethane, polyester, polyether, which leads to increased effort in purification after pyrolysis. These heteroatoms have to be removed in a laborious manner by hydrogenation reactions in the hydrotreatment. Pre-hydrogenation may even be necessary to deplete dienes, styrene and chlorine before any hydrotreatment may be possible. Furthermore, in case of the presence of silicone in the waste streams, it is known that siloxanes formed during pyrolysis interfere with the hydrotreatment and are also undesirable in the steam cracker or in the partial oxidation (POX). For example, US 2019/0322832 A1 relates to methods for recovering polymers and hydrocarbons mixtures from sorted waste feedstock or mixtures of waste. The methods therein rely on an extraction process which uses a non-polar solvent for extracting polymers from polymer blends followed by reversal of the solvent polarity by adding the non-polar solvated extract to a more polar solvent in order to precipitate the product. However, there is still a need to provide an improved process for recycling polyolefin contained in a solid material, such as waste plastic material.

Surprisingly, it was found that the process of the present invention exhibits better yield and is more cost effective. Indeed, the process of the present invention permits to simplify the overall polyolefin recycling process which permits to reduce costs. Hence, using a method of pyrolyzing a polyolefin recovered from a solid material comprising said polyolefin according to the present invention permits to reduce the CO₂ footprint.

Therefore, the present invention relates to a process for pyrolyzing a polyolefin recovered from a solid material M containing said polyolefin, the process comprising

• • (i) providing a liquid stream S_P containing a polyolefin dissolved in a non-polar solvent, comprising:
    • (i.1) providing the solid material M containing the polyolefin;
    • (i.2) providing a liquid stream S_LS comprising a non-polar solvent, wherein from 80 to 100 weight-% of S_LS consist of the non-polar solvent and wherein S_LS has a temperature T_SLS<T_ES, T_ES being the ebullition temperature of the non-polar solvent;
    • (i.3) bringing into contact the solid material M provided according to (i.1) and the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent;
  • (ii) feeding the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent provided according to (i) into a solid-liquid separation unit SLU, obtaining a liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent;
  • (iii) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation conditions, obtaining a solid mixture comprising the precipitated polyolefin P_P;
  • (iv) subjecting the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii) to pyrolysis conditions into a pyrolysis reactor R_P, obtaining a pyrolysis oil O_P.

One of the advantages of the present process is that hydrogenation of the obtained pyrolysis oil is not necessary or the effort for hydrogenation is reduced due to the lower concentration of atoms other than carbon or hydrogen. Further, no pre-treatment prior to pyrolysis of the polyolefin is necessarily required, such as thermal treatment to remove PVC, additional washing steps or pre-pyrolysis. Also due to the lower amount of gas and the reduced amount of components such as NOx, sulfuric components, halogenated component (HCl, HBr, halogenated hydrocarbons, cyanic acid, CO, CO₂) the treatment of the gaseous phase before release to the environment is reduced. Thus, the process according to the present invention is more efficient as it simplifies the recycling of polyolefin and is more cost effective compared to known processes.

As mentioned above, the process for pyrolyzing a polyolefin recovered from a solid material M containing said polyolefin according to the present invention comprises

• • (i) providing a liquid stream S_P containing a polyolefin dissolved in a non-polar solvent, comprising:
    • (i.1) providing the solid material M containing the polyolefin;
    • (i.2) providing a liquid stream S_LS comprising a non-polar solvent, wherein from 80 to 100 weight-% of S_LS consist of the non-polar solvent and wherein S_LS has a temperature T_SLS<T_ES, T_ES being the ebullition temperature of the non-polar solvent;
    • (i.3) bringing into contact the solid material M provided according to (i.1) and the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent;
  • (ii) feeding the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent provided according to (i) into a solid-liquid separation unit SLU, obtaining a liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent;
  • (iii) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation conditions, obtaining a solid mixture comprising the precipitated polyolefin P_P;
  • (iv) subjecting the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii) to pyrolysis conditions into a pyrolysis reactor R_P, obtaining a pyrolysis oil O_P.

Preferably, the polyolefin is selected from the group consisting of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene-1 (PB-1), ethylene-octene copolymers, stereo-block PP, olefin block copolymers, propylene-butane copolymers, polyisobutylene (PIB), ethylene propylene rubber (EPR), ethylene propylene diene monomer (M-class) rubber (EPDM rubber), and a mixture of two or more thereof, more preferably selected from the group consisting of polyethylene, polypropylene, and a mixture of polyethylene and polypropylene.

In the context of the present invention, the polyolefin can preferably be a mixture of the same polyolefin, namely a mixture of PE or PP, or a mixture of two or more different polyolefins, such as a mixture of PE and PP.

Preferably, providing the solid material M containing the polyolefin according to (i.1) comprises

• • shredding the solid material M containing the polyolefin in a shredding unit US1.

Preferably from 90 to 100 weight-%, more preferably from 95 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, of S_LS provided in (i.2) consist of the non-polar solvent. In other words, the liquid stream S_LS provided in (i.2) preferably consists essentially of, more preferably consists of, the non-polar solvent.

Preferably, the non-polar solvent is selected from the group consisting of xylene, toluene, n-heptane, pentyl acetate, n-amyl acetate, isobutyl acetate, n-propyl propanoate, n-butyl propanoate, heptan-2-one, methyl-cyclohexane, cyclohexane, and a mixture of two or more thereof, more preferably is selected from the group consisting of xylene, toluene, pentyl acetate, cyclohexane, and a mixture of two or more thereof, more preferably is xylene.

Preferably (i) comprises providing a liquid stream S_P containing a polyolefin dissolved in one non-polar solvent.

It is preferred that the non-polar solvent is a single solvent selected from the group consisting of xylene, toluene, n-heptane, pentyl acetate, n-amyl acetate, isobutyl acetate, n-propyl propanoate, n-butyl propanoate, heptan-2-one, methyl-cyclohexane, and cyclohexane, more preferably the non-polar solvent is a single solvent selected from the group consisting of xylene, toluene, pentyl acetate, and cyclohexane, more preferably the non-polar solvent is xylene.

The present invention offers several improvements over systems like those described in US2019/0322832 A1. More specifically, the present process has an improved polymer extraction and isolation method by using a non-polar solvent, preferably at elevated temperatures, to extract the desired polymers which are then precipitating, for example by cooling, the desired polyolefin from supersaturated solutions of a single solvent. Without wanted to be bound to any theory, this approach permits to simplify the overall process including the recycling of solvent as well as the equipment needed for carrying out the process on large continuous scale while reducing the energy expenditure compared to the prior art.

In the context of the present invention, the term “xylene” refers to all isomers and mixtures thereof of xylene, preferably refers to a mixture of ortho-xylene, meta-xylene and para-xylene isomers.

Preferably the process for pyrolyzing a polyolefin recovered from a solid material M containing said polyolefin according to the present invention comprises

• • (i) providing a liquid stream S_P containing a polyolefin dissolved in a non-polar solvent, comprising:
    • (i.1) providing the solid material M containing the polyolefin;
    • (i.2) providing a liquid stream S_LS comprising a non-polar solvent, wherein from 80 to 100 weight-% of S_LS consist of the non-polar solvent and wherein S_LS has a temperature T_SLS<T_ES, T_ES being the ebullition temperature of the non-polar solvent;
    • (i.3) bringing into contact the solid material M provided according to (i.1) and the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent;
  • (ii) feeding the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent provided according to (i) into a solid-liquid separation unit SLU, obtaining a liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent;
  • (iii) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation conditions, obtaining a solid mixture comprising the precipitated polyolefin P_P;
  • (iv) subjecting the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii) to pyrolysis conditions into a pyrolysis reactor R_P, obtaining a pyrolysis oil O_P;
    wherein the non-polar solvent is selected from the group consisting of xylene, toluene, n-heptane, pentyl acetate, n-amyl acetate, isobutyl acetate, n-propyl propanoate, n-butyl propanoate, heptan-2-one, methyl-cyclohexane and cyclohexane.

Preferably, the non-polar solvent has a Hansen solubility parameter δ_H in the range of from 0 to 10 MPa^1/2, more preferably in the range of from 0 to 8 MPa^1/2, more preferably in the range of from 0 to 7 MPa^1/2.

In the context of the present invention, the Hansen solubility parameter δ_H is a known parameter which characterizes the solubility of a compound. δ_H relates to the energy from hydrogen bonds between molecules. For numerous compounds, such as xylene, toluene and cyclohexane, the Hansen parameter δ_H can be found in standard chemical books. The Hansen solubility parameters δ_H mentioned in the present invention refers to values tabulated in: Hansen, C. M., Hansen Solubility Parameters—A user's handbook, 2. Edition, CRC Press, Boca Raton, USA, 2007.

It is preferred that according to (i), no solvent other than the non-polar solvent is involved in the dissolution.

Preferably, the solid material M provided according to (i.1) comprises, more preferably consists of waste material, wherein said waste material more preferably comprises plastic waste material.

In the context of the present invention, the terms “plastic waste material” or “mixed plastic waste material” refers to plastic waste material containing different kinds of plastic objects. Often plastic is sorted before it is used for treatment/recycling, such as the plastic waste material can be only plastic bags or plastic foils to be treated or recycled. This can be done upfront by different companies. However, in the context of the present invention, there is no such presorting requirement, the mixed plastic waste material or plastic waste material is municipal plastic waste material as obtained from households, such as a mixture of plastic bags, plastic packaging, plastic tubes, etc. According to the present invention, a good quality oil can be directly formed from these plastic waste materials.

Preferably, from 5 to 99 weight-%, more preferably from 20 to 98.5 weight-%, more preferably from 30 to 98 weight-%, more preferably from 40 to 98 weight-%, of M consist of the polyolefin.

Preferably, the solid material M comprises, in addition to the polyolefin, one or more of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethane (PU), paper, aluminum, and polyamide.

Preferably, the solid material M has a Cl content of at most 25000 mg/kg, more preferably in the range of from 1500 to 15000 mg/kg, more preferably in the range of from 1500 to 12000 mg/kg based on the weight in kg of the solid material M, the Cl content being determined as described in Analytics 3.

Preferably, the solid material M has a N content of at most 5 weight-%, more preferably in the range of from 0.55 to 3 weight-%, based on the weight of the solid material M, the N content being determined as described in Analytics 3.

Preferably, the solid material M has a O content of at most 20 weight-%, more preferably in the range of from 4 to 15 weight-%, based on the weight of the solid material M, the O content being determined as described in Analytics 3.

Preferably, the solid material M has a S content of at most 1000 wppm, more preferably in the range of from 0 to 800 wppm, more preferably in the range of from 0 to 500 wppm, based on the weight of the solid material M, the S content being determined as described in Analytics 3.

Preferably, the solid material M has a Si content in the range of from 300 to 15000 wppm, more preferably in the range of from 300 to 14500 wppm, based on the weight of the solid material M, the Si content being determined as described in Analytics 3.

Preferably, T_SLS is in the range of from 55 to 150° C., more preferably in the range of from 60 to 140° C.

Preferably, T_D is in the range of from 55 to 150° C., more preferably in the range of from 60 to 140° C.

Preferably, p_D is in the range of from 800 to 200 000 hPa, more preferably in the range of from 800 to 10000 hPa.

The present invention offers several improvements over systems like those described in US2019/0322832 A1. More specifically, the present inventive process has an improved polymer extraction and isolation method by using a non-polar solvent at elevated temperatures, i.e. preferably from 55 to 150° C., to extract the desired polymers which are then obtained by precipitating (for example by cooling) the desired polyolefins from supersaturated solutions of the single non-polar solvent. This approach simplifies the overall process including the recycling of solvents as well as the equipment needed for carrying out the process on large continuous scale while reducing the energy expenditure compared to the process known in the art.

Preferably, prior to (i.3), the solid material M containing the polyolefin is fed into the reactor unit R_D via gravity or pneumatic transport.

Preferably, in the reactor unit R_D, the weight ratio of the solid material M relative to the non-polar solvent is in the range of from 1:1 to 1:20, more preferably in the range of from 1:3 to 1:15, more preferably in the range of from 1:4 to 1:12.

Preferably, (i.3) comprises bringing into contact and mixing, more preferably stirring, the solid material M provided according to (i.1) with the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent.

Preferably, the reactor unit R_D comprises z chemical reactors R_D, i=1 . . . z, wherein z is in the range of from 1 to 5, more preferably in the range of from 1 to 3.

Preferably when z>1, at least 2 reactors R_Di are arranged in parallel, more preferably z reactors R_Di are arranged in parallel.

Preferably, the temperature T_Di in the z reactor(s) R_Di is maintained by heating the z reactor(s) R_Di content, more preferably by passing a heating medium through a heating jacket of R_Di.

It is also conceivable that the reactors R_Di are heated directly using a heater beneath said reactors for example.

Preferably, the process further comprises, prior to (ii), maintaining the temperature TS, of the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent obtained according to (i.3) such that 50° C.<T_SP<T_ES.

Preferably, the temperature TS, is essentially maintained, more preferably maintained, via one or more heated tubes used for transferring the liquid stream S_P into SLU.

Preferably, the solid-liquid separation unit SLU is a filtration unit F1, more preferably a stirred pressure filter, the filtration unit F1 more preferably has a mesh size in the range of from 1 to 100 micrometers, more preferably in the range of from 1 to 20 micrometers.

The solid-liquid separation can alternatively be done by sedimentation or centrifugation (see Handbuch der mechanischen Fest-Flüssig-Trennung Taschenbuch—29 Apr. 2004 von Klaus Luckert (Herausgeber)).

Preferably, the filtration unit F1 comprises a filter for blocking the solid contaminants and a receiving vessel for the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent; wherein the solid contaminants comprises one or more of a polymer other than polyolefin, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethane (PU), and polyamide (PA).

Preferably, the filtration unit F1 is operated under a pressure p_F, with p_F Z 1 bar(abs), more preferably p_F is in the range of from 1 to 30 bar(abs), more preferably in the range of from 1 to 10 bar(abs), more preferably in the range of from 1 to 6 bar(abs).

It is more preferred that, when the non-polar solvent is xylene, p_F is in the range of from 2 to 4 bar(abs), more preferably 2.5 to 3.5 bar(abs) and that TS, is in the range of from 110 to 130° C.

Preferably, (iii) comprises

• • (iii.1) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation at a temperature T_SLS and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a solid mixture comprising the precipitated polyolefin P_P.

More preferably, (iii.1) comprises cooling the liquid stream S_SLU, comprising the polyolefin dissolved in the non-polar solvent, for precipitation at a temperature T_SLS and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a stream P comprising the polyolefin precipitated in the non-polar solvent.

Preferably, T_P<T_D−5° C., more preferably T_P≤T_D−10° C., more preferably T_P≤T_D−30° C., more preferably T_P<T_D−30° C.

Preferably, cooling according to (iii.1) comprises

• • (iii.1.a) passing a cooling medium into a cooling jacket of the receiving vessel of the filtration unit containing S_SLU; or
  • (iii.1.b) letting the liquid stream S_SLU stand into the receiving vessel of the filtration unit.

Preferably, the cooling rate is in the range of from 2 to 200 K/h, more preferably in the range of from 3 to 150 K/h, more preferably 20 to 120 K/h.

Alternatively, (iii) comprises

• • (iii.1′) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation by contacting SLU with a polar solvent, obtaining a stream P comprising the polyolefin precipitated in the polar solvent and the non-polar solvent.

Preferably, contacting SLU with a polar solvent is performed at a temperature in the range of from 10 to 120° C., more preferably in the range of from 20 to 60° C.

Preferably, contacting SLU with a polar solvent is performed at a pressure in the range of from 0 to 10 bar(abs), more preferably in the range of from 0.5 to 2 bar(abs).

Preferably, the polar solvent is selected from the group consisting of water, ethanol, methanol, propanol, butanol, acetone, dimethylsulfoxide, acetonitrile, dimethylformamide, ethylacetate, sulfolane, dichloromethane, tetrahydrofurane, and a mixture of two or more thereof, more preferably selected from the group consisting of water, acetone, ethanol, methanol and a mixture of two or more thereof.

Preferably, the polar solvent has an Hansen solubility parameter δ_H of more than 5 MPa^1/2, preferably in the range of from 6 to 50 MPa^1/2, more preferably in the range of from 10 to 30 MPa^1/2.

Preferably, (iii) comprises

• • (iii.1) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a solid mixture comprising the precipitated polyolefin P_P, more preferably cooling the liquid stream S_SLU, comprising the polyolefin dissolved in the non-polar solvent, for precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a stream P comprising the polyolefin precipitated in the non-polar solvent; or
  • (iii.1′) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation by contacting SLU with a polar solvent, obtaining a stream P comprising the polyolefin precipitated in the polar solvent and the non-polar solvent;
  • (iii.2) passing the stream P obtained according to (iii.1), or (iii.1′), more preferably
  • (iii.1), into a filtration unit F2, obtaining the solid mixture comprising the precipitated polyolefin P_P separated from the non-polar solvent and the polar solvent when applicable;
  • (iii.3) optionally washing the solid mixture comprising the precipitated polyolefin obtained according to (iii.2), more preferably the solid mixture is washed with one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone and water;
  • (iii.4) optionally drying the solid mixture comprising the washed precipitated polyolefin obtained according to (iii.3).

Preferably, (iii) further comprises

• • (iii.5) recycling at least a part of the non-polar solvent obtained according to (iii.2) as a component of the liquid stream S_LS in (i.2);
  • wherein more preferably (iii.5) comprises
  • (iii.5.1) passing the at least a part of the non-polar solvent obtained according to (iii.2) in a distillation unit D, obtaining a purified non-polar solvent;
  • (iii.5.1) adding the purified non-polar solvent obtained according to (iii.5.1) into the liquid stream S_LS in (i.2).

Preferably, the distillation unit D is heated by a heating source, more preferably steam. Such heating source preferably is generated from the recycled gas stream obtained after pyrolysis.

Preferably, if (iii.1′) is performed, (iii.5) further comprises recycling the polar solvent more preferably in (iii.1′). Recycling the polar solvent more preferably comprises

• • (iii.5.3) passing the at least a part of the polar solvent obtained according to (iii.2) in a distillation unit D′, obtaining a purified polar solvent;
  • (iii.5.4) adding the purified polar solvent obtained according to (iii.5.3) in (iii.1′).

It is also conceivable to recycle both solvents, namely the polar solvent and the non-polar solvent by fractional distillation using the same column.

Preferably, the precipitated polyolefins are in the form of flakes, the flakes having an average size in the range of from 0.05 to 10 cm, more preferably in the range of from 0.1 to 5 cm, more preferably in the range of from 0.1 to 2 cm, the flake average size being determined as defined in Reference Example 1.

Preferably, the precipitated polyolefin has a Cl content of at most 600 mg/kg, more preferably in the range of from 0 to 5000 mg/kg, more preferably in the range of from 0 to 2000 mg/kg based on the weight in kg of the precipitated polyolefin, the Cl content being determined as described in Analytics 3.2.

Preferably, the precipitated polyolefin has a N content of at most 2 weight-%, more preferably of at most 1 weight-%, more preferably of at most 0.5 weight-%, based on the weight of the precipitated polyolefin, the N content being determined as described in Analytics 3.2.

Preferably, the precipitated polyolefin has a O content of at most 2 weight-%, more preferably of at most 1 weight-%, more preferably of at most 0.5 weight-%, based on the weight of the precipitated polyolefin, the O content being determined as described in Analytics 3.2.

Preferably, the precipitated polyolefin has a S content of at most 1000 wppm, more preferably in the range of from 0 to 800 wppm, more preferably in the range of from 0 to 500 wppm, based on the weight of the precipitated polyolefin, the S content being determined as described in Analytics 3.2.

Preferably, the precipitated polyolefin has a Si content of at most 300 wppm, more preferably in the range of from 0 to 200 wppm, more preferably in the range of from 0 to 100 wppm, more preferably in the range of from 0 to 70 wppm, based on the weight of the precipitated polyolefin, the Si content being determined as described in Analytics 3.2.

Optionally, (iii) further comprises

• • (iii.6) comminuting the dried solid mixture comprising the precipitated polyolefin obtained according to (iii.4) into flakes in a comminuting unit US2, the flakes having an average size in the range of from 0.05 to 10 cm, more preferably in the range of from 0.1 to 5 cm, more preferably in the range of from 0.1 to 2 cm, the flake average size being determined as defined in Reference Example 1.

Preferably, the flakes obtained according to (iii.6) have an average thickness in the range of from 0.01 to 5 cm, more preferably in the range of from 0.1 to 2 cm. FIG. 2 shows the flakes of the precipitated polyolefins.

Preferably, the solid mixture obtained according to (iii) comprises the precipitated olefin in an amount in the range of from 90 to 100 weight-%, more preferably in the range of from 95 to 100 weight-%, based on the weight of the solid mixture.

Preferably according to (iii), no solvent other than the non-polar solvent is involved in the precipitation conditions.

Preferably the polarity of the non-polar solvent according to (iii) is not changed by addition of a solvent with increased polarity relative to the polarity of the non-polar solvent.

Preferably, (iv) comprises

• • (iv.1) feeding the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii), more preferably according to (iii.2), optionally according to (iii.4), optionally according to (iii.6), into a pyrolysis reactor R_P;
  • (iv.2) heating the polyolefin precipitated into the pyrolysis reactor R_P to a temperature in the range of from 350 to 900° C., more preferably in the range of from 400 to 550° C., and a pressure in the range of from 0.5 to 2 bar(abs), more preferably in the range of from 0.9 to 1.5 bar(abs);
  • (iv.3) removing a gas stream V from the top of R_P and subjecting V to condensation conditions in a gas-liquid separation unit LGU, obtaining a pyrolysis oil O_P.

Preferably, feeding the precipitated polyolefin obtained according to (iii), preferably according to (iii.2), optionally according to (iii.4), optionally according to (iii.6), is performed via a dosing unit, the dosing unit being more preferably one or more of a screw, an extruder and a rotary valve.

It is also conceivable that the precipitated polyolefin is fed via pneumatic conveyor or liquid injector into the pyrolysis reactor R_P.

Further, (iv.1) may further comprise

• • pre-heating the solid mixture comprising the precipitated polyolefin, more preferably in an extruder by internal friction or by a heat exchanger. Preferably, the heat exchanger uses electricity of the combustion energy from the pyrolysis gas or other heat sources.

It is conceivable that prior to the pyrolysis according to (iv), the solid mixture comprising the precipitated polyolefin may be subjected to a pre-pyrolysis at a temperature in the range of from 220 to 360° C. Such pyrolysis at low temperature permits to pyrolysed PVC if present in the solid mixture. However, in the context of the present invention, such step can be avoided in view of the particular process steps (i) to (iii) prior to (iv) of the process according to the present invention.

Preferably, the pyrolysis reactor R_P is selected from the group consisting of a fluidized bed, a moving bed, an entrained flow, an auger, a screw reactor, an extruder, a stirred tank reactor and a rotary kiln, more preferably a fluidized bed. Preferably the fluidized bed is bubbling, turbulent, fast or circulating.

Preferably, the pyrolysis is performed in the pyrolysis reactor R_P under an atmosphere exempt of oxygen.

Preferably, the pyrolysis is performed by thermal cracking (absence of catalyst) or catalytic cracking, more preferably thermal cracking.

It is noted that such catalyst are used to influence the properties of the pyrolysis products as known by the skilled person.

Preferably the pyrolysis according to (iv) is not a hydrothermal treatment.

Optionally, according to (iv) the pyrolysis reactor R_P contains trace amounts of water, wherein preferably trace amounts of water is less than 2 wt. % water calculated on the basis of the total weight of the precipitated polyolefin P_P, more preferably less than 1 wt. % water, more preferably less than 0.1 wt. % water.

Preferably the pyrolysis reactor R_P is free of water.

The precipitated polyolefins obtained according to (iii) of the present process are advantageously pyrolyzed under thermal conditions in absence of water at pressures close to atmospheric pressure. The present inventive process does not require either water or hydrothermal reactors which greatly reduces the equipment cost and complexity since hydrothermal conditions are well known to be corrosive. Furthermore, hydrothermal conditions are also not as easily implemented under continuous processes which are often necessary on large scale. Finally, by avoiding a hydrothermal treatment as in US2019/0322832 A1, further water treatment steps and equipment to remove contaminants are not necessary. Further, non-desirable side products such as coke that builds up in the hydrothermal reactors is also reduced with the process of the present invention.

Preferably, in the pyrolysis reactor R_P the solid mixture comprising the precipitated polyolefin is mixed with one or more of CaO, Ca(OH)₂ and CaCO₃.

Such additives permit to react with formed HCl and thus remove impurities such as chlorine from PVC.

In addition or as an alternative, it is conceivable that the gas stream V exiting the pyrolysis reactor is passed through a catalyst bed or an adsorption bed, in order to reduce the concentration of impurities and atoms other than C and H.

Preferably, in (iv.3) after removing V from R_P and prior to subjecting V to condensation conditions in LGU, the gas stream V is passed through a filtration unit, more preferably a filter, or a cyclone.

Such filtration unit or cyclone permits to remove dust particles from the gas stream V before condensation. In addition to such removal of dust, a catalyst bed or an adsorption bed can be used upstream thereof or downstream thereof to reduce the concentration of impurities and atoms other than C and H.

Preferably, according to (iv.3) V is subjected to a condensation step in LGU at a temperature in the range of from 0 to 80° C.; wherein more preferably LGU is a condenser, a scrubber or a quench.

Preferably, the gas stream V in (iv.3) is subjected to a first condensation step at a temperature in the range of from 50 to 150° C. and to a second condensation step at a temperature in the range of from 35 to 0° C., obtaining the pyrolysis oil O_P; each of the first and second condensation steps more preferably being performed in a separate condenser or quench. Alternatively, the gas stream V in (iv.3) is preferably subjected to only one condensation step at a temperature in the range of from 0 to 80° C.

The non-condensable “permanent” gases G exiting LGU can be used to generate process heat/electricity by burning in a gas burner, gas motor or combined heat and power plant. The flue gases of this combustion might need to be cleaned according to emission laws to remove dust, ashes and other components.

The solid residues SR from the pyrolysis can be disposed or treated further to recover valuable substances such as fibers, metals, carbon black depending on the specific properties and composition of the solid material M.

Preferably, the process further comprises

• • (v) passing the pyrolysis oil O_P obtained according to (iv), more preferably (iv.3), as a stream S_O, into a purification unit PU, obtaining a purified pyrolysis oil O_PP.

Preferably, the purification unit PU comprises one or more of a filter, a centrifuge, a decanter, and a decanter centrifuge, more preferably one or more of a filter, a centrifuge and a decanter.

The pyrolysis oil obtained according to (iv), more preferably (iv.3), can be filtered including the possible use of a filter agent to remove solids. Alternatively, said pyrolysis oil can be centrifuged to remove solids.

Further, in the purification unit PU, water residue can be removed from the pyrolysis oil by decanting or centrifugation. Furthermore, the pH can be adjusted to a pH value of at most 3 or, alternatively, a pH value of at least 8, preferably at least 9. Preferably, the adjustment is performed by the addition of an acid or a base such as an alkali metal hydroxide, for example sodium hydroxide (NaOH), potassium hydroxide (KOH), alkaline earth metal hydroxide, for example calcium hydroxide (Ca(OH)₂, NH₃, or mixtures thereof sulfuric acid (H₂SO₄), nitric acid (HNO₃) or phosphoric acid (H₃PO₄).

Preferably, (v) comprises

• • (v.1) passing the stream S_O into a filter, obtaining a liquid phase comprising a filtered pyrolysis oil and further obtaining a solid phase made of impurities;
  • (v.2) introducing the liquid phase comprising the filtered pyrolysis oil into a decanter or a centrifuge for water removal, obtaining a pyrolysis oil having a water content of at most 0.3 weight-%, more preferably of at most 0.1 weight-%, more preferably at most 0.01 weight-%, more preferably of 0 weight-%, based on the pyrolysis oil weight; and further obtaining water;
  • (v.3) optionally adjusting the pH of the pyrolysis oil obtained according to (v.2) such that the pH be of at most 3 or of at least 8;
  • (v.4) introducing the pyrolysis oil obtained according to (v.2), or optionally according to
  • (v.3), into a distillation column, obtaining a purified pyrolysis oil.

Preferably, (v) further comprises

• • (v.5) subjecting the purified pyrolysis oil obtained according to (v.4) to hydrotreatment conditions into a reactor, obtaining a purified pyrolysis oil O_PP.

The pyrolysis oil is preferably further treated to remove halogens, for example by hydrotreatment. Defined in the context of the present invention and as known in the art, a hydrotreatment (or hydroprocessing) is a catalytic reductive process for upgrading hydrocarbons. The objective of the hydrotreatment being to add hydrogen while simultaneously removing undesired heteroatoms such as but not limited to N, P, O, S, Si, F, Cl, Br, I, present in the pyrolysis oil and to reduce the amount of double bonds and if necessary aromatics. Such treatments are well known in the art and disclosed in “CHAPTER TWO—Distillate Hydrotreating”, Refinery Refining Processes Handbook, 2003, Pages 29-61. The hydrotreatment can be followed by a hydrocracking step. Further, it is conceivable that after the hydrotreatment/hydrocracking, the pyrolysis oil is further distillated to separate the oil in different fractions.

Preferably the process is a continuous process or a semi-continuous process, preferably the process is a continuous process.

The present invention further relates to a production unit for carrying out the process of the present invention, the production unit comprising

• • a reactor unit R_D;
  • a means for introducing a solid material M containing the polyolefin into R_D;
  • a means for introducing a liquid stream S_LS comprising a non-polar solvent, wherein from 80 to 100 weight-% of S_LS consist of the non-polar solvent and wherein S_LS has a temperature T_SLS<T_ES, T_ES being the ebullition temperature of the non-polar solvent, into R_D;
  • a means for removing a liquid stream S_P comprising the dissolved polyolefin from R_D;
  • a solid-liquid separation unit SLU;
  • a means for introducing the liquid stream S_P in SLU;
  • a pyrolysis reactor R_P;
  • a precipitation means for obtaining a solid mixture comprising the precipitated polyolefin P_P;
  • a means for introducing the solid mixture comprising the precipitated polyolefin P_P into R_P.

Preferably, the production unit of the present invention further comprises the units and elements listed in the foregoing in order to carry out the process according to the present invention. Preferably, the production unit further comprises one or more of a shredding unit US1, a comminuting unit US2, a distillation column D, a gas-liquid separation unit LGU and a purification unit PU, wherein said units are as defined herein in the context of the inventive process.

The present invention further relates to a pyrolysis oil obtainable or obtained by a process according to the present invention.

Preferably, the pyrolysis oil has a C content of at least 80 weight-%, more preferably in the range of from 82 to 87 weight-%, more preferably in the range of from 82 to 86 weight-%, based on the weight of the pyrolysis oil, the C content being determined as described in Analytics 3.

Preferably, the pyrolysis oil has a N content of at most 0.5 weight-%, more preferably of at most 0.3 weight-%, more preferably at most 0.1 weight-%, based on the weight of the pyrolysis oil, the N content being determined as described in Analytics 3.2. More preferably, the pyrolysis oil has a N content of at most 500 wppm, more preferably of at most 100 wppm, the N content being determined as described in Analytics 3.2.

Preferably, the pyrolysis oil has a O content of at most 2 weight-%, more preferably of at most 1 weight-%, more preferably of at most 0.5 weight-%, more preferably of at most 0.3 weight-%, based on the weight of the pyrolysis oil, the O content being determined as described in Analytics 3.2.

Preferably, the pyrolysis oil has a S content of at most 50 wppm, more preferably in the range of from 0 to 30 wppm, more preferably in the range of from 0 to 20 wppm, based on the weight of the pyrolysis oil, the S content being determined as described in Analytics 3.2.

The present invention further relates to the use of the pyrolysis oil according to the present invention as a naphtha substitute in steam crackers or in the production of synthesis gas.

The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as “The process of any one of embodiments 1 to 4”, every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to “The process of any one of embodiments 1, 2, 3 and 4”. Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

• • 1. A process for pyrolyzing a polyolefin recovered from a solid material M containing said polyolefin, the process comprising
    • (i) providing a liquid stream S_P containing a polyolefin dissolved in a non-polar solvent, comprising:
      • (i.1) providing the solid material M containing the polyolefin;
      • (i.2) providing a liquid stream S_LS comprising a non-polar solvent, wherein from 80 to 100 weight-% of S_LS consist of the non-polar solvent and wherein S_LS has a temperature T_SLS<T_ES, T_ES being the ebullition temperature of the non-polar solvent;
      • (i.3) bringing into contact the solid material M provided according to (i.1) and the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent;
    • (ii) feeding the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent provided according to (i) into a solid-liquid separation unit SLU, obtaining a liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent;
    • (iii) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation conditions, obtaining a solid mixture comprising the precipitated polyolefin P_P;
    • (iv) subjecting the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii) to pyrolysis conditions into a pyrolysis reactor R_P, obtaining a pyrolysis oil O_P.
  • 2. The process of embodiment 1, wherein the polyolefin is selected from the group consisting of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polybutene-1 (PB-1), ethylene-octene copolymers, stereo-block PP, olefin block copolymers, propylene-butane copolymers, polyisobutylene (PIB), ethylene propylene rubber (EPR), ethylene propylene diene monomer (M-class) rubber (EPDM rubber), and a mixture of two or more thereof, preferably selected from the group consisting of polyethylene, polypropylene, and a mixture of polyethylene and polypropylene.
  • 3. The process of embodiment 1 or 2, wherein providing the solid material M containing the polyolefin according to (i.1) comprises
    • shredding the solid material M containing the polyolefin in a shredding unit US1.
  • 4. The process of any one of embodiments 1 to 3, wherein from 90 to 100 weight-%, preferably from 95 to 100 weight-%, preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, of S_LS provided in (i.2) consist of the non-polar solvent.
  • 5. The process of any one of embodiments 1 to 4, wherein the non-polar solvent is selected from the group consisting of xylene, toluene, n-heptane, pentyl acetate, n-amyl acetate, isobutyl acetate, n-propyl propanoate, n-butyl propanoate, heptan-2-one, methyl-cyclohexane, cyclohexane, and a mixture of two or more thereof, preferably is selected from the group consisting of xylene, toluene, pentyl acetate, cyclohexane, and a mixture of two or more thereof, more preferably is selected from the group consisting of xylene, toluene, pentyl acetate and cyclohexane, more preferably is xylene.
  • 6. The process of any one of embodiments 1 to 5, wherein the non-polar solvent has an Hansen solubility parameter δ_H in the range of from 0 to 10 MPa^1/2, preferably in the range of from 0 to 8 MPa^1/2, more preferably in the range of from 0 to 7 MPa^1/2.
  • 7. The process of any one of embodiments 1 to 6, wherein the solid material M provided according to (i.1) comprises, more preferably consists of waste material, wherein said waste material more preferably comprises plastic waste material.
  • 8. The process of any one of embodiments 1 to 7, wherein the solid material M comprises, in addition to the polyolefin, one or more of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethane (PU), paper, aluminum, and polyamide.
  • 9. The process of any one of embodiments 1 to 8, wherein T_SLS is in the range of from 55 to 150° C., preferably in the range of from 60 to 140° C.
  • 10. The process of any one of embodiments 1 to 9, wherein T_D is in the range of from 55 to 150° C., preferably in the range of from 60 to 140° C.
  • 11. The process of any one of embodiments 1 to 10, wherein p_D is in the range of from 800 to 200 000 hPa, preferably in the range of from 800 to 10000 hPa.
  • 12. The process of any one of embodiments 1 to 11, wherein prior to (i.3), the solid material M containing the polyolefin is fed into the reactor unit R_D via gravity or pneumatic transport.
  • 13. The process of any one of embodiments 1 to 12, wherein, in the reactor unit R_D, the weight ratio of the solid material M relative to the non-polar solvent is in the range of from 1:1 to 1:20, preferably in the range of from 1:3 to 1:15, more preferably in the range of from 1:4 to 1:12.
  • 14. The process of any one of embodiments 1 to 13, wherein (i.3) comprises bringing into contact and mixing, preferably stirring, the solid material M provided according to (i.1) with the liquid stream S_LS provided according to (i.2) in a reactor unit R_D at a temperature T_D and a pressure p_D, with T_D<T_ES, obtaining a liquid stream S_P containing the polyolefin dissolved in the non-polar solvent.
  • 15. The process of any one of embodiments 1 to 14, wherein the reactor unit R_D comprises z chemical reactors R_Di, i=1 . . . z, wherein z is in the range of from 1 to 5, preferably in the range of from 1 to 3;
    • wherein, preferably when z>1, at least 2 reactors R_Di are arranged in parallel, more preferably z reactors R_Di are arranged in parallel.
  • 16. The process of embodiment 15, wherein the temperature T_Di in the z reactor(s) R_Di is maintained by heating the z reactor(s) R_Di content, preferably by passing a heating medium through a heating jacket of R_Di.
  • 17. The process of any one of embodiments 1 to 16, comprising, prior to (ii), maintaining the temperature T_SP of the liquid stream S_P containing the polyolefin dissolved in the non-polar solvent obtained according to (i.3) such that 50° C. <T_SP<T_ES.
  • 18. The process of any one of embodiments 1 to 17, wherein the solid-liquid separation unit SLU is a filtration unit F1, preferably a stirred pressure filter, the filtration unit F1 preferably has a mesh size in the range of from 1 to 100 micrometers, more preferably in the range of from 1 to 20 micrometers.
  • 19. The process of embodiment 18, wherein the filtration unit F1 comprises a filter for blocking the solid contaminants and a receiving vessel for the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent;
    • wherein the solid contaminants are one or more of a polymer other than polyolefin, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethane (PU), and polyamide (PA).
  • 20. The process of embodiment 18 or 19, wherein the filtration unit F1 is operated under a pressure p_F, with p_F Z 1 bar(abs), preferably p_F is in the range of from 1 to 30 bar(abs), more preferably in the range of from 1 to 10 bar(abs), more preferably in the range of from 1 to 6 bar(abs).
  • 21. The process of any one of embodiments 1 to 20, wherein (iii) comprises
    • (iii.1) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a solid mixture comprising the precipitated polyolefin P_P.
  • 22. The process of embodiment 21, wherein (iii.1) comprises cooling the liquid stream S_SLU, comprising the polyolefin dissolved in the non-polar solvent, for precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a stream P comprising the polyolefin precipitated in the non-polar solvent.
  • 23. The process of embodiment 21 or 22, wherein T_P<T_D−5° C., preferably T_P≤T_D−10° C., more preferably T_P≤T_D−30° C., more preferably T_P<T_D−30° C.
  • 24. The process of embodiment 22 or 23, wherein cooling according to (iii.1) comprises
    • (iii.1.a) passing a cooling medium into a cooling jacket of the receiving vessel of the filtration unit containing S_SLU; or
    • (iii.1.b) letting the liquid stream S_SLU stand into the receiving vessel of the filtration unit.
  • 25. The process of any one of embodiments 22 to 24, wherein the cooling rate is in the range of from 2 to 200 K/h, preferably in the range of from 3 to 150 K/h, more preferably 20 to 120 K/h.
  • 26. The process of any one of embodiments 1 to 20, wherein (iii) comprises
    • (iii.1′) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation by contacting SLU with a polar solvent, obtaining a stream P comprising the polyolefin precipitated in the polar solvent and the non-polar solvent.
  • 27. The process of any one of embodiments 1 to 26, wherein (iii) comprises
    • (iii.1) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a solid mixture comprising the precipitated polyolefin P_P, preferably cooling the liquid stream S_SLU, comprising the polyolefin dissolved in the non-polar solvent, for precipitation at a temperature T_P and a pressure p_P, with T_P<T_D and T_P<100° C., obtaining a stream P comprising the polyolefin precipitated in the non-polar solvent; or
    • (iii.1′) subjecting the liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent obtained according to (ii) to precipitation by contacting SLU with a polar solvent, obtaining a stream P comprising the polyolefin precipitated in the polar solvent and the non-polar solvent;
    • (iii.2) passing the stream P obtained according to (iii.1), or (iii.1′), preferably
    • (iii.1), into a filtration unit F2, obtaining the solid mixture comprising the precipitated polyolefin P_P separated from the non-polar solvent and the polar solvent when applicable;
    • (iii.3) optionally washing the solid mixture comprising the precipitated polyolefin obtained according to (iii.2), preferably the solid mixture is washed with one or more of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone and water;
    • (iii.4) optionally drying the solid mixture comprising the washed precipitated polyolefin obtained according to (iii.3).
  • 28. The process of embodiment 27, wherein (iii) further comprises
    • (iii.5) recycling at least a part of the non-polar solvent obtained according to (iii.2) as a component of the liquid stream S_LS in (i.2);
    • wherein preferably (iii.5) comprises
    • (iii.5.1) passing the at least a part of the non-polar solvent obtained according to (iii.2) in a distillation unit D, obtaining a purified non-polar solvent;
    • (iii.5.1) adding the purified non-polar solvent obtained according to (iii.5.1) into the liquid stream S_LS in (i.2).
  • 29. The process of any one of embodiments 1 to 28, wherein (iii) further comprises
    • (iii.6) comminuting the dried solid mixture comprising the precipitated polyolefin obtained according to (iii.4) into flakes in a comminuting unit US2, the flakes having an average size in the range of from 0.05 to 10 cm, preferably in the range of from 0.1 to 5 cm, more preferably in the range of from 0.1 to 1 cm, the flake average size being determined as defined in Reference Example 1.
  • 30. The process of any one of embodiments 1 to 29, wherein the solid mixture obtained according to (iii) comprises the precipitated olefin in an amount in the range of from 90 to 100 weight-%, preferably in the range of from 95 to 100 weight-%, based on the weight of the solid mixture.
  • 31. The process of any one of embodiments 1 to 30, wherein (iv) comprises
    • (iv.1) feeding the solid mixture comprising the precipitated polyolefin P_P obtained according to (iii), preferably according to (iii.2), optionally according to (iii.4), into a pyrolysis reactor R_P;
    • (iv.2) heating the polyolefin precipitated into the pyrolysis reactor R_P to a temperature in the range of from 350 to 900° C., preferably in the range of from 400 to 550° C., and a pressure in the range of from 0.5 to 2 bar(abs), preferably in the range of from 0.9 to 1.5 bar(abs);
    • (iv.3) removing a gas stream V from the top of R_P and subjecting V to condensation conditions in a gas-liquid separation unit LGU, obtaining a pyrolysis oil O_p.
  • 32. The process of embodiment 31, wherein feeding the precipitated polyolefin obtained according to (iii), preferably according to (iii.2), optionally according to (iii.4), is performed via a dosing unit, the dosing unit being preferably one or more of a screw, an extruder and a rotary valve.
  • 33. The process of embodiment 31 or 32, wherein (iv.1) further comprises pre-heating the solid mixture comprising the precipitated polyolefin, preferably in an extruder by internal friction or by a heat exchanger.
  • 34. The process of any one of embodiments 29 to 32, wherein the pyrolysis reactor R_P is selected from the group consisting of a fluidized bed, a moving bed, an entrained flow, an auger, a screw reactor, an extruder, a stirred tank reactor and a rotary kiln, more preferably a fluidized bed.
  • 35. The process of any one of embodiments 1 to 33, wherein the pyrolysis is performed in the pyrolysis reactor R_P under an atmosphere exempt of oxygen.
  • 36. The process of any one of embodiments 1 to 34, wherein the pyrolysis is performed by thermal cracking or catalytic cracking, preferably thermal cracking.
  • 37. The process of any one of embodiments 30 to 36, as far as if dependent on embodiment 35 or 36, said embodiment are dependent on embodiment 30, wherein in (iv.3) after removing V from R_P and prior to subjecting V to condensation conditions in LGU, V is passed through a filtration unit, preferably a filter, or a cyclone.
  • 38. The process of any one of embodiments 30 to 37, as far as if dependent on embodiment 35 or 36, said embodiment are dependent on embodiment 30, wherein according to (iv.3) V is subjected to a condensation step in LGU at a temperature in the range of from 0 to 80° C.; wherein preferably LGU is a condenser, a scrubber or a quench.
  • 39. The process of any one of embodiments 1 to 38, further comprises
    • (v) passing the pyrolysis oil O_P, obtained according to (iv), preferably (iv.3), as a stream S_O, into a purification unit PU, obtaining a purified pyrolysis oil O_PP.
  • 40. The process of embodiment 39, wherein the purification unit PU comprises one or more of a filter, a centrifuge, a decanter, and a decanter centrifuge, preferably one or more of a filter, a centrifuge and a decanter.
  • 41. The process of embodiment 39 or 40, wherein (v) comprises
    • (v.1) passing the stream S_O into a filter, obtaining a liquid phase comprising a filtered pyrolysis oil and further obtaining a solid phase made of impurities;
    • (v.2) introducing the liquid phase comprising the filtered pyrolysis oil into a decanter or a centrifuge for water removal, obtaining a pyrolysis oil having a water content of at most 3000 wppm, preferably of at most 1000 ppm, more preferably at most 100 wppm, more preferably 0 wppm, and further obtaining water;
    • (v.3) optionally adjusting the pH of the pyrolysis oil obtained according to (v.2) such that the pH be of at most 3 or at least 8;
    • (v.4) introducing the pyrolysis oil obtained according to (v.2), or optionally according to (v.3), into a distillation column, obtaining a purified pyrolysis oil.
  • 42. The process of embodiment 41, wherein (v) further comprises
    • (v.5) subjecting the purified pyrolysis oil obtained according to (v.4) to hydrotreatment conditions into a reactor, obtaining a purified pyrolysis oil O_PP.
  • 43. The process of any one of embodiments 1 to 42, wherein the process is a continuous process or a semi-continuous process, preferably the process is a continuous process.
  • 44. The process of any one of embodiments 1 to 43, wherein according to (iii), no further solvent other than the non-polar solvent is involved in the precipitation conditions.
  • 45. The process of any one of embodiments 1 to 44, wherein the polarity of the non-polar solvent according to (iii) is not changed by addition of a solvent with increased polarity relative to the polarity of the non-polar solvent.
  • 46. The process of any one of embodiments 1 to 45, wherein according to (iv), the pyrolysis conditions do not include a hydrothermal treatment.
  • 47. A pyrolysis oil obtainable or obtained by a process according to any one of embodiments 1 to 46.
  • 48. The pyrolysis oil of embodiment 47, having a C content of at least 80 weight-%, preferably in the range of from 82 to 87 weight-%, more preferably in the range of from 82 to 86 weight-%, based on the weight of the pyrolysis oil, the C content being determined as described in Analytics 3.2.
  • 49. The pyrolysis oil of embodiment 47 or 48, having a N content of at most 0.5 weight-%, more preferably of at most 0.3 weight-%, more preferably at most 0.1 weight-%, based on the weight of the pyrolysis oil, the N content being determined as described in Analytics 3.2;
  • wherein more preferably the pyrolysis oil has a N content of at most 500 wppm, more preferably of at most 100 wppm, the N content being determined as described in Analytics 3.2.
  • 50. The pyrolysis oil of any one of embodiments 47 to 49, having a O content of at most 2 weight-%, preferably of at most 1 weight-%, more preferably of at most 0.5 weight-%, more preferably of at most 0.3 weight-%, based on the weight of the pyrolysis oil, the O content being determined as described in Analytics 3.2.
  • 51. The pyrolysis oil of any one of embodiments 47 to 50, having a S content of at most 50 wppm, preferably in the range of from 0 to 30 wppm, more preferably in the range of from 0 to 20 wppm, based on the weight of the pyrolysis oil, the S content being determined as described in Analytics 3.2.
  • 52. Use of the pyrolysis oil according to any one of embodiments 47 to 51 as a naphtha substitute in steam crackers or in the production of synthesis gas.

The term “bar” as used in the context of the present invention refers to “bar(abs)”.

In the context of the present invention, a term “X is one or more of A, B and C”, wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10° C., 20° C., and 30° C. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. “X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.

The term “non-polar solvent” used in the present invention refers to a solvent that dissolves non-polar compounds, has a low dielectric constant, has non-polar bond. For example, the non-polar solvents can be as described in the foregoing.

In the context of the present invention, it is noted that the terms “gas stream” and “gaseous stream” can be used interchangeably, both terms means that the stream is in gas phase.

The present invention is further illustrated by the following example.

EXAMPLES

Analytics

1 Determination of the Particle Size Distribution of the Flakes

The particle size distribution of the polyolefin flakes after solvolysis has be obtained via static image analysis from FIG. 2 (optical granulometry technique). Therefore, the particles have been dispersed as much as possible and a background with a big contrast to the individual particles has been used. The projection area of the individual particles has been measured with an automatic image analyzing tool (imageJ). From the projected areas of the individual particles, the diameter of the sphere that has the same surface area as the individual particles were calculated:

D = 4 ⁢ A π 2 ,

• • where
  • D: diameter of representative sphere
  • A: projected surface area of particle

From the obtained particle sizes the number and volume-based distributions have been calculated.

The average article size (volume-based: index 3) x₃ has been calculated by:

x _ 3 = ∑ i = 1 n x _ i · Δ ⁢ Q 3 , i ,

• • where
  • x_i is the arithmetic average particle size in a discrete particle size interval x_i and x_i+1
  • ΔQ_3,i is the amount of particle in the discrete particle size interval (from cumulative particle size distribution).

2 NMR

The contents of polyolefin in the samples were determined by quantitative 1H-NMR spectroscopy. All NMR spectra were recorded at T=298.2 K on a Bruker Avance 111 400 spectrometer operating at 400.33 MHz for 1H. The spectrometer was equipped with a 5 mm z-gradient broadband observe smartprobe. Chemical shifts were referenced to tetramethylsilane (TMS, δ (TMS)=0 ppm). 1H 1D spectra were recorded under quantitative conditions using the zg30 pulse program with a sampling of 128 k data points, the 5 relaxation delay D1 was chosen as 40 seconds for the solvent chloroform-d1 (CDCl3) or 120 seconds for the solvent sulfuric acid-d2 (D2SO4). 8 transients were summed up per spectrum. For processing in Bruker TopSpin 4.0.9 software, 64 k data points were used, an exponential window function with a line broadening of 0.3 Hz was applied. Automatic baseline correction with a polynomial of 5 was performed, phase correction and integration was performed manually by the user.

3 Elemental Analysis

3.1 Analysis of Mixed Municipal Solid Plastic Waste (MMSPW)

	Chlorine:	DIN EN 15408: 2011 May
	Nitrogen:	DIN EN 15407: 2011 May
	Sulphure:	DIN EN 15408: 2011 May
	Oxygen:	DIN EN ISO 16993: 2016 November
	Ash content:	DIN EN 15403: 2011 May
	Silicon:	DIN EN ISO 11885 (E22): 2009 September

3.2 Elemental Analysis of Oil Sample/Polyolefin Sample

C, H, N (Combustion) Analysis:

The sample (1-10 mg) was combusted in a helium/oxygen atmosphere and the formed NOx was subsequently reduced to N₂. After separation of the combustion gases, nitrogen was determined as N₂, carbon as CO₂ and hydrogen as H₂O. The detection and quantification was done via thermal conductivity. Analyzer: Elementar, model Vario EL Cube

N (Chemiluminescence) Analysis: (Typically for Concentration Below 0.5 g/100 g)

The sample (1-10 mg or 10-30 μl) was combusted in oxygen with argon as carrier gas at about 1000° C. Dilution of the sample could be used to extend the linear dynamic range of the method. The combustion gases (NO) reacts with ozone to form exited species. The light emitted during the relaxation was detected. Analyzer: TE Instruments, e.g. model TN/TS

O Analysis:

The sample (1-10 mg) was pyrolysed/reduced in a forming gas atmosphere on a soot contact, the oxygen was converted hereby to carbon monoxide (CO). The carbon monoxide was detected and quantified via IR spectrometry. Analyzer: Elementar, model rapid OXY cube

S Analysis:

The sample (1-10 mg) was weighed into a tin capsule and placed into the analyser. The sample was combusted catalytically in an argon/oxygen atmosphere and the sulphur was converted hereby to a mixture of SO₂ and SO₃. The formed SO₃ was subsequently reduced to SO₂ with copper granules. After drying and separation of the combustion gases, sulphur was detected and quantified as SO₂ via IR spectrometry. Analyser: Elementar, Unicube

S (COUS) Analysis: (Typically for Concentration Below, 05 g/100 g)

The sample (1-10 mg) was combusted in oxygen with argon as carrier gas at ca. 1000° C. The combustion gases (SO₂) are transferred into the coulometric cell for detection. (Alternatively UV-Fluorescence can be used for detection after combustion.)

Analyzer: TE Instruments, e.g. model TX/TS (coulometry) (or TN/TS (UV-Fluorescence))

Cl (Rohr and COCL) Analysis:

Chlorine Calculated from Sum Chlorine-Bromine-Iodine (Coulometry) (Typically for Concentration Below 0.5 g/100 g)

The sample (1-10 mg) was combusted in oxygen with nitrogen as carrier gas at about 1000° C. The resulting hydrochloric acid in the form of gas is cleaned from by-products of the combustion (e.g. water) in concentrated sulfuric acid and then transferred into the coulometric cell for detection. The method does not distinguish between halides, therefore, the result is presented as a sum parameter (chlorine, bromine, iodine) calculated with the molar mass of chlorine. Analyzer: TE Instruments, model TX/TS

Si Analysis:

An aliquot of 0.3-0.4 g of sample was weighed into a Pt-crucible and calcinated in a muffle furnace at 600° C. Afterwards, a mix of 0.4 g K₂CO₃—Na₂CO₃ and 0.1 g Na₂B₄O₇ was added to the crucible, which was then loaded into an automated digestion system: The crucible is heated by induction to ca. 930° C. while rotated to promote sample dissolution in the flux mixture. After fusion, the digested contents of the crucible are dissolved in diluted HCl, the volume is corrected to 50 mL and the solution is analyzed for Si via ICP-OES. The spectrometer is calibrated with matrix adapted standards. Two aliquots are prepared in parallel and averaged for the final result. A blank subtraction is made, with the blank sample being prepared in an analogous manner.

Example 1 Lab Scale Experiments

60 g of mixed municipal solid plastic waste, the composition of plastic waste is listed in Table 1 below, were mixed with 300 g of xylene, the weight ratio of plastic waste relative to xylene was thus of 1:5. The obtained mixture was stirred at 60 UPM in a glass vessel with nitrogen blanketing and further was heated up to 100° C. The stirring was continued for one hour. Then, hot filtration at 100° C. of the mixture was performed, with a nitrogen pressure of 3 bar(abs). On the filter the other polymers and contaminants were separated from the mixture. When cooling down xylene in the vessel beneath the filter, the polyolefins started to precipitate at 70° C. They were then filtered and dried. 22 g of polyolefins, namely a mixture of polyethylene (PE) (86% by weight) and polypropylene (PP), (16% by weight), were obtained. The proportions of PE and PP before drying were determined by NMR analysis as defined under Analytics 2 above (NMR: 82% PE, 13% PP, 5% Xylene)

TABLE 1A
Mixed municipal solid plastic waste (MMSPW)

	Composition calculated	kg	Weight.-%

	PE Film	159.85	37
	PE Rigid	13.91	3.2
	PP Film	61.41	14.2
	PP Rigid	37.39	8.7
	PE-PP Film	6.69	1.5
	PE-PET Film	1.77	0.4
	Other multilayer film	14.91	3.5
	PE-PA Film	2.95	0.77
	Tetra	1.24	0.3
	PU Foam	0.76	0.2
	Pater and Cardboard	1.35	0.3
	PVC	9.19	2.1
	Black fraction (not sorted plastic)	44.01	10.2
	Rest	76.56	17.7
	Sum	432	100

TABLE 1B
Elemental analysis of MMSPW & the
obtained polyolefin (PO), dry basis

	Cl	N	O	S	Ash	Si
	(mg/kg)	(ppm)	(wt.-%)	(ppm)	(wt.-%)	(ppm)

MMSPW	10790	0.59	12.0	862	6.3	9839.8
PO	1400	<0.5	<0.5	<500	n.d.	55

Already feedstock composition for the pyrolysis reactor shows significant reduction of Cl, O, Si and Ash (as indicated by Si). Factor of reduction for Cl of 7.7; for O of >24 and for Si of 180. Therefore, there is a significant reduction of heteroatom containing plastics (such as PET, PA, etc.) in the obtained precipitated polyolefin.

The obtained polyolefins flakes were fed into a pyrolysis tank reactor R_P (1). The average particle size of the flakes was of 15.9 mm. Some of the flakes had to be cut to be fed into the reactor. For the pyrolysis experiments, a bench scale pyrolysis system was used. A flow scheme of the system is shown in FIG. 5. The pyrolysis system consists of the tank reactor (1) of about 0.14 L volume, an electrically heated oven (5), two condensers (7) and (8) and two washing bottles (10) & (11). As a first step the reactor (1) was filled with the weighed obtained precipitated polyolefins. Then a pressure-test was carried out to ensure that the system is air-tight. Furthermore, the plant volume is flushed before and during the experiments with nitrogen (3) to ensure an oxygen-free atmosphere in the setup. The oven (5) was pre-heated to 570° C. After the pressure-test and inertization the oven (5) was elevated to enclose the reactor (1). Subsequently the reactor (1) was heated up to reaction temperature of 550° C. (1.1 bar(abs)). The reaction temperature was measured via a NiCrNi-thermocouple (4). The reaction temperature was reached after about 15 min, which corresponds to an average heating rate of about 35 K/min. The effluent pyrolysis vapors and gases coming from the reactor (1) flow through a heated pipe (6) to prevent condensation before the cold traps (7) & (8). The pyrolysis gas streams V are condensed in the two cold traps (7) & (8), obtaining the pyrolysis product oil O_P. The temperature of the first cold trap (7) was adjusted via a heating plate (9) to 45° C., while the temperature of the second cold trap (8) was adjusted via a cooling bath with ice water (10) to about 0° C. The non-condensable gases were cleaned in two washing bottles (11) with NaOH & (12) with distilled water. The off-gas (13) was vented into the air-discharge vent of the digestorium. 30 min after the reaction temperature of 550° C. was reached the pyrolysis was complete and the oven heating (5) was turned off.

The obtained pyrolysis oil was analyzed, the results are depicted in Tables 2 and 3.

Comparative Example 1

Mixed municipal solid plastic waste, with a composition as listed in Table 1, was fed into a pyrolysis tank reactor (1), however no dissolution/precipitation according to the present invention was performed prior to the pyrolysis. Otherwise, the pyrolysis experiments and conditions were the same for both Example 1 and this Comparative Example 1.

The obtained pyrolysis oil was analyzed, the results are depicted in Tables 2 and 3.

Reference Example 1

LDPE (low density polyethylene) was fed into a pyrolysis tank reactor (1), however no dissolution/precipitation according to the present invention was performed prior to the pyrolysis. Otherwise, the pyrolysis experiments and conditions were the same for all Example 1, Comparative Example 1 and Reference Example 1.

The obtained pyrolysis oil was analyzed, the results are depicted in Table 2.

TABLE 2
Pyrolysis yield

	Ref. Ex. 1	Ex. 1	Comp. Ex. 1
	(wt.-%)	(wt.-%)	(wt.-%)

	Oil	82.7	82.4	66.6
	Char	0.3	0.7	14.7
	Rest (Gas, . . .)	16.9	16.9	18.7

As shown in Table 2, the pyrolysis yield with the process according to the present invention is very similar to the yield obtained after pyrolysis of LDPE (virgin plastic) which demonstrates that the process of the present invention permits to obtain yields with mixed municipal plastic waste which are as high as for virgin polyolefinic plastics. Further, the comparison of Ex. 1 and Comp. Ex. 1 shows that the particular pre-treatment disclosed in the present invention permits to greatly improve the oil yield, namely from 66.6 to 82.4 wt.-%, and greatly reduce the impurities, from 14.7 wt.-% char to only 0.7 weight-%.

TABLE 3
Elemental analysis of the obtained pyrolysis oils

		C	H		Nb	O
	Cl	(wt.-	(wt.-	Na	(wt.-	(wt.-	S
	(mg/kg)	%)	%)	(ppm)	%)	%)	(ppm)

Ex. 1	160.0	85.6	14.0	75	—	<0.5	19.0
Comp.	6333.3	80.4	13.0	n.d.	0.5	4.7	153.3
Ex. 1
aChemiluminescence method;
bCombustion method

As is shown in Table 3, the pyrolysis oil obtained according to the process of the present invention has lower Cl content, namely about 39.6 times lower than with Comp. Ex. 1, as well as lower N, O and S contents, for example the N & S contents were reduced by a factor of 66 & 8, respectively.

Therefore, it has been clearly demonstrated that the process according to present invention exhibits better pyrolysis oil yield and is more cost effective as the further treatments of the oils can be greatly reduced. The improved reduction of char compared to the prior art is of great importance in term of CO₂ footprint (reduce the need to use landfill/incinerators).

Thus, the process of the present invention permits to simplify the overall polyolefin recycling process which permits to also reduce costs. Hence, using a method of pyrolyzing a polyolefin recovered from a solid material comprising said polyolefin according to the present invention permits to reduce the CO₂ footprint.

DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit R_D, a shredding unit US1, a solid-liquid separation unit SLU comprising a filter F1, a pyrolysis reactor RP, a filter F2, a liquid-gas separation unit LGU and optionally a distillation unit D, a washing and drying unit W/D and a purification unit U. The solid material M, e.g. plastic waste, comprising the polyolefin, preferably PP and PE, is fed into a shredding unit US1. The flakes/pieces of M obtained from US are fed into the reactor unit R_D. A liquid stream S_LS containing a non-polar solvent is also fed into the reactor unit R_D for dissolving the solid material M at a temperature T_D and a pressure p_D, with T_D<T_ES, T_ES being the ebullition temperature of the non-polar solvent of S_LS as detailed in the foregoing. A liquid stream S_P is removed from the bottom of R_D, S_P comprising the polyolefin dissolved in the non-polar solvent. The liquid stream S_P is fed into the solid-liquid separation unit SLU obtaining a liquid stream S_SLU comprising the polyolefin dissolved in the non-polar solvent. The liquid stream S_Lu is subjected to precipitation, preferably by cooling the temperature of the solvent in SLU as detailed in the foregoing. The liquid stream P exiting SLU and comprising the precipitated polyolefin P_P and the non-polar solvent is fed into a filter F2, P_P is blocked on F2 and the non-polar solvent S_NP passes through. The solid waste w1 is removed from F1, w1 comprising among other non-dissolved polyolefins and contaminants such as those listed in the foregoing. The precipitated polyolefin P_P is then fed into the pyrolysis reactor R_P, after having optionally been washed and dried in W/D. Prior to pyrolysis, P_P can be comminuted in US2 not shown in FIG. 1. The precipitated polyolefins P_P (flakes) are subjected to pyrolysis as detailed in the foregoing, obtaining at the top of the reactor a gas stream V comprising hydrocarbons and at the bottom of the reactor solid residues SR. The stream V is fed into the liquid-gas separation unit LGU, obtaining a liquid stream of pyrolysis oil O_P and a gas stream G of non-condensable pyrolysis gases. The pyrolysis oil O_P is optionally further purified in the purification unit PU to obtain a purified pyrolysis oil O_PP.

FIG. 2 shows a picture of the flakes of the precipitated polyolefins (inventive process).

FIG. 3 shows a picture of the solid material comprising the mixed municipal solid plastic waste obtained after the shredding unit US1 (starting material for the process of Example 1 and of Comparative Example 1). Scale: cm.

FIG. 4 shows the particle size distribution of the flakes of precipitated polyolefin obtained according to (iii) to be pyrolyzed according to (iv). The average particle size of the flakes was 15.9 mm.

FIG. 5 is a schematic drawing of the pyrolysis setup used for Example 1, Comparative Example 1 and Reference Example 1—1. Reactor; 2. Plastic feedstock; 3. Nitrogen (inertization & flushing of reactor); 4. Thermocouple; 5. electrically heated oven; 6. heated pipe; 7. 1st cold trap; 8. 2nd cold trap; 9. heating plate; 10. cooling bath; 11. washing bottle (NaOH); 12. washing bottle (distilled water); 13. off-gas.

CITED LITERATURE

• Hansen, C. M., Hansen Solubility Parameters—A user's handbook, 2. Edition, CRC Press, Boca Raton, USA, 2007
• CHAPTER TWO—Distillate Hydrotreating, Refinery Refining Processes Handbook, 2003, Pages 29-61
• US2019/0322832 A1