WO2024057098A1

WO2024057098A1 - Method to produce an oil from olefin-based resins by pyrolysis

Info

Publication number: WO2024057098A1
Application number: PCT/IB2023/020058
Authority: WO
Inventors: Ana Paula De Azeredo; Regina FUNCK NONEMACHER; Ana Paula RODRIGUES CAMILO
Original assignee: Braskem S.A.
Priority date: 2022-09-16
Filing date: 2023-09-15
Publication date: 2024-03-21

Abstract

Provided is a method for producing an oil comprising feeding an olefin-based resin in a pyrolysis reactor, converting the olefin-based resin into oil, and recovering the produced oil wherein the olefin-based resin is a low molecular weight (LMW) olefin-based resin. The LMW olefin-based resin comprises a molecular weight of less than 50,000 g/mol, preferably less than 40,000 g/mol measured according to ISO 16014-4. In certain embodiments, the method further comprises the steps of feeding a higher molecular weight (HMW) olefin-based resin into an extruder, cracking the HMW olefin-based resin to produce a LMW olefin-based resin. Also provided are an oil produced according to the method and a use of the oil for as a feedstock for production of olefin-based resins.

Description

METHOD TO PRODUCE AN OIL FROM OLEFIN-BASED RESINS BY PYROLYSIS

BACKGROUND

[0001] Polyolefins such as polyethylene (PE) and polypropylene (PP) may be used to manufacture a varied range of articles, including films, molded products, foams, and the like. Polyolefins may have characteristics such as high processability, low production cost, flexibility, low density, and recyclability. While plastics such as polyethylene and polypropylene have many beneficial uses, there is a need for their correct disposal after use, or even their reuse or recycling so as to minimize the environmental impact of plastic wastes.

[0002] Mechanical recycling techniques are being widely used due to their simplicity and relative low cost. Those techniques preserve the molecular structure of polymers. They usually comprise process steps such as sorting, shredding, washing, melting, etc. Although simple, mechanical recycling techniques present some limitations. The separation of different types of polymers and contaminants is a great challenge, especially when dealing with poor quality waste sources.

[0003] On the other hand, advanced recycling techniques are being considered as a promising alternative. The goal of those techniques is converting plastic waste into oil and building blocks (e.g., monomers) that would be ultimately feed back into the plastic production.

[0004] An example of advanced recycling is pyrolysis. Pyrolysis is a thermochemical treatment wherein a material (e.g., plastic) is exposed to high temperature in the absence of oxygen. This process results in thermal decomposition of the material which forms new molecules. As an example, US10131847B2 discloses a process to convert waste plastics material to fuel by using pyrolysis.

[0005] Thermal cracking processes such as pyrolysis present several limitations regarding the heat distribution. To produce products with a consistent quality, it is important that the same heat is applied to the plastic. However, considering heating conductivity and low IR absorption of plastics, radiant heat and convection are not good ways to heat plastics in a pyrolysis reactor. The most efficient way of heating plastics is by contact heating, which means that the superficial area and the physical characteristics of the plastics (particle size, for example) and reactor design are very important to assure pyrolysis efficiency. While a lot of new technologies are being developed for chemical recycling of plastics, some reactors can be considered not efficient and obsolete, and it can be very slow and expensive to make changes to an operating reactor.

SUMMARY

[0006] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0007] In one aspect, embodiments disclosed herein are related to a method for producing an oil comprising:

- feeding an olefin-based resin into a pyrolysis reactor,

- converting the olefin-based resin into oil, and

- recovering the produced oil, wherein the olefin-based resin is a low molecular weight (LMW) olefin-based resin.

[0008] In another aspect, embodiments disclosed herein relate to an oil produced according to said method.

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 shows a schematic representation of a pyrolysis unit.

[0010] FIG. 2 shows the molecular weight distribution of samples Wax C, Wax G, LLDPE 1, and LLDPE 2.

[0011] FIG. 3 shows the viscosity profile at 140°C for samples Wax C, Wax G, LLDPE 1, and LLDPE 2.

[0012] FIG. 4 shows TGA analysis (T onset) for samples Wax C, Wax G, LLDPE 1, and LLDPE 2. [0013] FIG. 5 shows condensable yields for samples Wax C, Wax G, LLDPE 1, and LLDPE 2 in a pyrolysis trial at 450°C, 30 minutes.

[0014] FIG. 6 shows condensable yields for samples Wax C, Wax G, LLDPE 1, and LLDPE 2 in a pyrolysis trial at 450°C, 45 minutes.

[0015] FIG. 7 shows the molecular weight distribution graph for samples PCR 1, Wax 2, Wax 3-2, and Wax 8.

[0016] FIG. 8 shows viscosity profile at 140°C for samples PCR 1, Wax 2, Wax 3-2, and Wax 8.

[0017] FIG. 9 shows TGA analysis (T onset) for samples PCR 1, Wax 2, Wax 3-2, and Wax 8.

[0018] FIG. 10 shows condensable yields for samples PCR 1, Wax 2, Wax 3-2, and Wax 8 in a pyrolysis trial at 450°C, 30 minutes.

[0019] FIG. 11 shows condensable yields for samples PCR 1, Wax 2, Wax 3-2, and Wax 8 in a pyrolysis trial at 450°C, 15 minutes.

[0020] FIG. 12 shows condensable yields for samples PCR 1, Wax 2, and Wax 8 in a pyrolysis trial at 450°C, 45 minutes.

[0021] FIG. 13 shows a schematic representation of the extruder working at 250 °C and feeding a chemical reactor.

[0022] FIG. 14 shows a schematic representation of the extruder working at 450 °C and feeding a chemical reactor.

[0023] FIG. 15 shows the energetic demand for samples of different molecular weight.

DETAILED DESCRIPTION

[0024] Embodiments disclosed herein generally relate to a method of producing an oil by feeding a low molecular weight (LMW) olefin-based resin into a pyrolysis reactor, converting the LMW olefin-based resin into an oil, and recovering said oil. According to the present disclosure, it was surprisingly found that feeding a pyrolysis reactor with low molecular weight olefin-based resins increases the process efficiency and reduces energy consumption.

[0025] Specifically, embodiments of the present disclosure may improve heat transfer and increase the efficiency of advanced chemical recycling processes. As described herein, the process of the present disclosure melts and cracks the polymer before it is introduced into the reactor. The polymer is introduced through an extruder, and thus the polymer enters into the thermal reactor already melted and with a very low viscosity, which significantly increases the heat transfer. Besides increasing the heat transfer efficiency, the low viscosity also facilitates polymer transportation and homogeneity inside the reactor.

[0026] In some embodiments, the method for producing an oil in the present invention comprises the following steps:

- feeding an olefin-based resin into a pyrolysis reactor,

- converting the olefin-based resin into an oil, and

[0027] In the present invention, the term “pyrolysis” refers to a thermal degradation treatment wherein the polymeric chains of the resin are broken to form smaller molecules by heat and under an environment substantially free of oxygen.

[0028] In some embodiments, LMW olefin-based resin has a molecular weight of less than 50,000 g/mol, preferably less than 40,000 g/mol, measured by high temperature gel permeation chromatography (GPC) according to ISO 16014-4.

[0029] In accordance with one or more embodiments, the feeding step may occur by means of an extruder, preferably a twin-screw extruder.

[0030] In one or more embodiments, the LMW olefin-based resin is fed into the reactor in a molten state. Therefore, the LMW olefin-based resin may be fed above its melting temperature. In a preferred embodiment, the LMW olefin-based resin is maintained and fed in a temperature close to the reactor temperature, preferably equal to or greater than 300°C, preferably greater than 400 °C, more preferably greater than 450°C. In some embodiments, the LMW olefin-based resin is molten and fed (e.g. by using an extruder) in an environment substantially free of oxygen. [0031] In one or more embodiments, the conversion step occurs in a reactor selected from a batch reactor, semi-batch reactor, or a two-stage pyrolysis system.

[0032] In one or more embodiments, the conversion step occurs at a temperature ranging from 400 to 600°C, and a residence time from 15 min to 2 h, and in an environment substantially free of oxygen. In some embodiments, the converting step occurs in the presence of a catalyst.

[0033] In some preferred embodiments, the method further comprises a cracking step (that may be also referred as pre-treatment or pre-cracking step) wherein a higher molecular (HMW) olefin-based resin is melted and cracked to produce the LMW olefin-based resin that is fed into the reactor. Thus, in one or more embodiments, the cracking step may occur before or during the feeding step.

[0034] In one or more embodiments, the cracking step occurs by means of an extruder.

[0035] In one or more embodiments, the cracking step occurs in an extruder that is directly connected to the reactor. Therefore, the LMW olefin-based resin may be directly fed into the reactor.

[0036] In some preferred embodiments, the extruder used in the cracking step is a twin- screw extruder.

[0037] In one or more embodiments, the molecular weight of the HMW olefin-based resin is reduced by at least 4 times (i.e. “4x”) in the cracking step.

[0038] In one or more embodiments, the cracking step may be performed above the onset degradation temperature, optionally in the presence of a visbreaking agent. The “onset degradation temperature” is the temperature wherein the polymer chains of the resin start to breakdown. This “onset degradation temperature” may be determined by thermogravimetric analysis (TGA), according to ASTM El 131 standard method.

[0039] In some alternative embodiments, the cracking step is performed at a temperature above the melting temperature and below the onset degradation temperature of the HMW olefin-based resin and in the presence of a visbreaking agent.

[0040] When present, the visbreaking agents may be free radical generators selected from peroxides, nitroxides, and combinations thereof. The peroxides may be selected from 3 -hydroxy- 1,1 -dimethylbutyl peroxyneodecanoate, a-cumyl peroxyneodecanoate, 2-hydroxy- 1,1 -dimethylbutyl peroxyneoheptanoate a-cumyl peroxyneoheptanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneodecanoate, di(2- ethylhexyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, di(sec -butyl) peroxydicarbonate, t-butyl peroxyneoheptanoate, t-amyl peroxypivalate, t-butyl peroxypivalate, diisononanoyl peroxide, didodecanoyl peroxide, 3 -hydroxy- 1,1- dimethylbutylperoxy-2-ethylhexanoate, didecanoyl peroxide, 2,2'- azobis(isobutyronitrile), di(3 -carboxypropionyl) peroxide, 2,5-dimethyl-2,5-di(2- ethylhexanoylperoxy)hexane, dibenzoyl peroxide, t-amylperoxy 2-ethylhexanoate, t- butylperoxy 2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy-(cis-3- carboxy)propenoate, 1 , 1 -di(t-amylperoxy)cyclohexane, 1 , 1 -di(t-butylperoxy)-3 ,3 ,5- trimethylcyclohexane, l,l-di(t-butylperoxy) cyclohexane, OO-t-amyl O-(2- ethylhexyl) monoperoxycarbonate, OO-t-butyl O-isopropyl monoperoxycarbonate, OO-t-butyl O-(2-ethylhexyl) monoperoxycarbonate, polyether tetrakis(t- butylperoxycarbonate), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-amyl peroxyacetate, t-amyl peroxybenzoate, t-butyl peroxyisononanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, di-t-butyl diperoxyphthalate, 2.2-di(t- butylperoxy )butane, 2,2-di(t-amylperoxy)propane, n-butyl 4,4-di(t- butylperoxy)valerate, ethyl 3,3-di(t-amylperoxy)butyrate, ethyl 3.3-di(t- butylperoxy)butyrate, dicumyl peroxide, a,a'-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, di(t-amyl) peroxide, t-butyl a-cumyl peroxide, di(t-butyl) peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, dicetil peroxi-dicarbonato, 3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxonane, tertbutylperoxy 2-ethylhexyl carbonate, tert-butyl-peroxide n-butyl fumarate(benzoate), dimyristoyl peroxydiicarbonate, 3,3,5,7,7-pentamethyl-l,2,4-trioxepane, tert-butyl hydroperoxide, bis(4-t-butylcyclohexyl) peroxydicarbonate, and 1, 2, 4, 5,7,8- hexoxonane, 3,6,9-trimethyl-3,6,9-tris(ethyl and propyl derivatives). The nitroxides may be selected from nitroxide compound, such as 2,2,5,5-tetramethyl-l- pyrrolidinyloxy, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidinyloxy, 2,2,6,6-tetramethyl- 1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-l-piperidinyloxy, 4-methoxy- 2,2,6,6-tetramethyl-l-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-l-piperidinyloxy, bis-(l-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)sebacate, 2,2,6,6-tetramethyl-4- hydroxypiperidine-l-oxyl)monophosphonate, N-tert-butyl-l-diethylphosphono-2,2- dimethyl propyl nitroxide, N-tert-butyl-l-dibenzylphosphono-2,2-dimethylpropyl nitroxide, N-tert-butyl-l-di(2,2,2-trifluoroethyl)phosphono-2,2dimethylpropyl nitroxide, N-tert-butyl-(l-diethylphosphono)-2-methyl-propyl nitroxide, N-(l- methylethyl)- 1 -cyclohexyl- 1 -(diethylphosphono) nitroxide, N-( 1 -phenylbenzyl)-( 1 - diethylphosphono)-l -methyl ethylnitroxide, N-phenyl-l-diethylphosphono-2,2- dimethyl propyl nitroxide, N-phenyl-l-diethylphosphono-l-methyl ethyl nitroxide, N-(l-phenyl 2-methyl propyl)- 1 -diethylphosphono- 1 -methyl ethyl nitroxide, N-tert- butyl-l-phenyl-2-methyl propyl nitroxide, and N-tert-butyl-l-(2-naphthyl)-2-methyl propyl nitroxide, or a mixture thereof.

[0041] In one or more embodiments, a pro-degradant is further added in the cracking step. The pro-degradant may be selected from the group consisting of zinc stearate, tin stearate, iron (II) stearate, iron (III) stearate, cobalt stearate, manganese stearate, and any combinations thereof.

[0042] The cracking step may be performed for a residence time of less than 2 min, preferably less than 90 s, most preferably less than 70 s.

[0043] In one or more embodiments, the cracking step may be performed as disclosed in patent applications US20220153976A1 and US20220153883A1, which are herein incorporated by reference in their entirety.

[0044] In some embodiments, the HMW olefin-based resin has an initial molecular weight Mw of 50,000 g/mol up to 1,000,000 g/mol, preferably 50,000 g/mol up to 500,000 g/mol measured according to ISO 16014-4.

[0045] The methods of the present disclosure are particularly useful in the recycling field. Therefore, in a preferred embodiment the olefin-based resins (LMW and/or HMW) are selected from plastic waste (also known as recycled resins or plastics). Preferably, the olefin-based resins are selected from post-consumer resins, postindustrial resins, resin scraps, and combinations thereof. The olefin-based resins may also be produced from petrochemical sources, biobased sources, or combinations thereof.

[0046] In one or more embodiments, olefin-based resins are selected from resins comprising more than 50% of olefin monomers, preferably selected from ethylene, olefins comprising from 3 to 10 carbon atoms, and combinations thereof. [0047] In one or more embodiments, the method of the present disclosure comprises a further step of purifying the oil recovered from the reactor.

[0048] In one or more embodiments, the method of the present disclosure comprises the following steps:

- feeding an HMW olefin-based resin into an extruder,

- cracking the HMW olefin-based resin to produce a LMW olefin-based resin,

- feeding the LMW olefin-based resin into a pyrolysis reactor,

- converting the LMW olefin-based resin into an oil, and

- recovering the produced oil, wherein the HMW olefin-based resin is preferably a plastic waste.

[0049] It has been found that by performing pyrolysis using a LMW olefin-based resin as feedstock, the condensables (also referred as liquid or oil) yield of the pyrolysis reaction is increased. It was observed that in the presently disclosed method, the condensables yield in the converting step is at least 10% higher in comparison to the condensables yield when feeding HMW into the pyrolysis reactor.

[0050] The oil obtained according to the present disclosure may be further used in polymerization processes to produce new resins.

Examples

Measurement methods description

GPC

[0051] The molecular weight of samples was measured according to ISO 16014-4 using high-temperature GPC experiments carried out in a gel permeation chromatograph coupled with an infrared detector IR6 from Polymer Char. A set of 4 columns (mixed bed, 13 pm, from Tosoh) at a temperature of 140°C is used. The conditions of the experiments are concentration of 1 mg/mL, flow rate of 1 mL/min, dissolution temperature and time of 160°C and 30 min, respectively, and an injection volume of 200 pL. The solvent used is ODCB (1,2-dichlorobenzene) stabilized with 100 ppm of BHT (butylated hidroxy toluene). Prior to the analyses, samples were dissolved for 60 min and filtered in an external filtration system (EFS, Polymer Char). TGA

[0052] The thermogravimetric analysis of samples was measured according to the ASTM El 131, Compositional Analysis by Thermogravimetry.

[0053] The analysis was performed using a TA Instruments Model Q500 with a temperature ramp rate of 20 °C/min from room temperature to 800 °C in a nitrogen atmosphere. 10 mg of sample are used for each analysis.

Rheometry

[0054] Rheological measurements were performed in flow regime at 140°C, using 25 mm cone and plate geometry, with a shear rate varying from 0.1 up to 1000 s’¹. A soaking time of 60s was used.

Density

[0055] All density data was obtained following ASTM D792.

Melt flow index (MFI)

[0056] All MFI data was obtained according to ASTM D1238. For PE samples, the conditions used were 190°C and 2.16kg.

Description of the pyrolysis methodology

[0057] The experiments were conducted in a pyrolysis unit, as shown in Figure 1.

[0058] A fixed amount of 7 g of sample (polymer or wax) was degraded at a preselected temperature and time. The reaction system comprised a quartz reactor 101 (internal diameter of 3 cm and height of 60 cm) and a fixed bed 102, which was aligned in series with the exhaust line 103 of the pyrolysis reactor. The reactors were located inside two independent cylindrical electrical furnaces (furnace A 104 and furnace B 105), used to control the reaction temperature, and were isolated with glass wool. Two thermocouples (“A" 106 and “B" 107) were attached to the furnaces and used to provide temperature readings to the controller 108. A third thermocouple (“C" 109) was connected to a datalogger (USB-501-TC-ECD Series) and placed inside the melting pot 110 to record the heating profile with sampling interval of 10 seconds. A heating coil 111 surrounded the quartz reactor and was used to preheat the nitrogen stream 112, used to maintain the reaction environment free of oxygen and to drag the generated gases. The nitrogen gas flow was kept constant in all trials (80 mL/min).

[0059] A cylindrical quartz melting pot (internal diameter of 2 cm and height of 12 cm) was used to place the polymer material inside the pyrolytic reactor. Before the start of the reaction, the melting pot was suspended by a wire 113 above the furnace; after reaching the desired temperature, the melting pot was placed into the reactor to initiate the pyrolysis reaction. The generated products were condensed with help of an electrostatic precipitator condenser 114 after flowing through the catalyst bed and the liquid fraction was stored in a glass flask 115. A tedlar bag 116 for collecting gas may be fluidly connected to the flask.

[0060] The final gas, liquid, and solid mass fractions were quantified through mass balance. Also, note that, experimentally, the gas fraction is obtained by mass difference.

Pyrolysis Example

[0061] The main objective is to evaluate the influence of different feedstock sources and how they can affect pyrolysis conditions and products.

[0062] The following samples were evaluated:

[0063] LLDPE 1 is a commercial resin from Braskem produced using metallocene catalyst, MFI 190°C/2.16kg is 25g/10 min (ASTM D1238), density 0.910g/cm³ (ASTM D792).

[0064] LLDPE 2 is a commercial resin from Braskem, produced using metallocene catalyst, MFI 190°C/2.16kg is lg/10 min (ASTM D1238), density 0.917g/cm³ (ASTM D792).

[0065] WAX C is a commercial linear polyethylene wax with very low molecular weight.

[0066] Wax G is a commercial resin Braskem polyethylene-based wax produced with green ethylene.

[0067] Table 1 lists Mw values for samples of HMW (LLDPE 1 1 and LLDPE2) and LMW (Wax C and Wax G). Figure 2 shows the molecular weight distribution, where it is observed that the samples presented in this example have a significant difference in the Mw that reflects in the difference in viscosity of more than 5 orders of magnitude, measured at 140°C (Figure 3).

Table 1. Molecular weight (Mw) information for samples of HMW (LLDPE 1 and LLDPE2) and LMW (Wax C and Wax G)

[0068] Comparing low and high molecular weight samples, different energy gains in the pyrolysis process are observed, such as a reduction of temperature or time in the reactor.

[0069] TGA analysis is usually used to correlate pyrolysis results because it can simulate, on a small scale, a proof of concept for the thermal behavior of polymers.

[0070] TGA analysis comparing the samples of this example indicates the influence of molar mass on thermal behavior, as is shown in Figure 4. It is shown that the T onset (temperature of the beginning of degradation) is lower for samples with LMW and higher for samples of HMW.

[0071] The different pyrolysis products are described as liquid (or condensable or oil), gas (or volatile), and solid residue. The best result is to obtain a higher concentration of liquid, and consequently, less solid residue in the reactor.

[0072] Four samples of different molar masses were tested at three different temperatures and at three residence times. The yields obtained were compared:

At 450° C, 30 min, it was possible to identify significant differences between the samples as shown in Figure 5; thus, proving the direct influence of the molar mass on the liquid yields (approximately 50%);

At all temperatures and residence times tested is possible to see the effect of molecular weight (Figure 6). PCR Example

[0073] In this example the same thermal treatment procedure described for the former example was done for 4 samples. In this case the samples are PCR (post-consumer resin). Sample PCR1 is a Braskem PCR sample, with MFI ranging from 0.10 up to 0.90 g/lOmin and density ranging from 0.910 up to 0.915g/cm³, its main component being LLDPE. Sample PCR 1 (HMW) was pre-cracked in an extruder at temperature around 450°C for 60 s and fed to a pyrolysis reactor in the following different ways:

1) in the presence of a peroxide. The resulting LMW product is Wax 3-2.

2) Mixed with 10% wt. of polypropylene (PP) PCR and the resulted LMW sample is Wax 8. PP PCR is a post-consumer PP composed of a mixture of PP heterophasic copolymer and LLDPE, with MFI of 14g/ 10 min;

3) Only PCR 1 was added to the extruder and the resulting LMW is Wax 2.

[0074] The molecular weight distribution graph of the referenced samples is shown in Figure 7, where it is possible to observe that, besides the Mw difference (shown in Table 2) between PCR1 and Waxes, it is also possible to observe a narrowing of the MWD.

Table 2. Molecular weight (Mw) information for samples of HMW (PCR 1) and LMW (Wax 2, Wax 3-2 and Wax 8)

[0075] The Mw of cracked samples is around 10 times lower than the original sample. The influence of this difference in the viscosity can be seen in Figure 8, where it is shown that PCR 1 has a viscosity of more than 2 orders of magnitude higher than the generated waxes.

[0076] TGA analysis comparing the samples of this example indicates the influence of molar mass on thermal behavior, as is shown in Figure 9. It is shown that the T onset (temperature of the beginning of degradation) is lower for samples with LMW and higher for samples of HMW and it is even possible to see differences among the LMW samples.

[0077] From low and high molecular weight samples, different energy gains in the pyrolysis process are observed, such as a reduction of temperature or time in the reactor.

[0078] Four samples of different molar masses were tested at three different temperatures and at three residence times. The yields obtained were compared:

At 450° C, 30 min of residence time, it was possible to identify significant differences between the samples as shown in Figure 10; thus, proving the direct influence of the molar mass on the liquid yields (approximately 40%);

At all temperatures and times tested it is possible to see the effect of molecular weight: Waxes 2, 3-2 and 8 have a better liquid yield than PCR1 (Figure 11 and Figure 12).

Energetic Benefit Example

Extruder Energy

[0079] In order to quantify the energy spent to melt and crack the polymer in the extruder, the equations used are described in Table 3 and Equation 1. This calculation method is according to literature references: 2010 - Rauwendaal, C. - How to Get Peak Performance & Efficiency Out of Your Extrusion Line, Part I; 2014 - Abeykoon et al - Process efficiency in polymer extrusion: Correlation between the energy demand and melt thermal stability; 2014 - Abeykoon et al - Investigation of the process energy demand in polymer extrusion: A brief review and an experimental study; 2021 - Abeykoon et al - Energy efficiency in extrusion-related polymer processing: A review of state of the art and potential efficiency improvements.

Table 3. Equations for calculation of different kinds of heat during extrusion processes

Equation 1

Chemical Recycling Reactor Energy

[0080] In order to quantify the energy spent to melt and crack the polymer in the thermal degradation reactor, the equations used are described in Table 4 and Equation 2. This calculation method is according to the following literature reference: Szostak, Elzbieta, et al. "Characteristics of plastic waste processing in the modern recycling plant operating in Poland." Energies 14.1 (2021): 35.

Table 4. Equations for calculation of different kinds of heat during thermal degradation in the chemical recycling reactor

Heat loss through insulation (Qj) ~10% Heat loss due to gas carrier (Q._fg) ~40%

Chemical Recycling Reactor

[0081] The chemical recycling reactor is fed with the polymer at room temperature (around 25°C). The starting polymer has a molecular weight of around 200,000 g/mol. In the chemical recycling reactor, the polymer is heated from 25°C up to 500°C. In the reactor the polymer is cracked until C25 - C35.

Table 5. Energy spent to heat samples, considering two different MW.

Extruder operating at 250°C + Chemical Recycling Reactor

[0082] As represented in Figure 13, the chemical recycling reactor is fed by an extruder operating at 250°C. The polymer is heated from room temperature (around 25°C) up to 250°C. The starting polymer has a molecular weight of around 200,000 g/mol. The molecular weight does not change in the extruder. In the chemical recycling reactor, the polymer is heated from 250°C up to 500°C. In the reactor the polymer is cracked until C25 - C35, or less.

Extruder operating at 450°C + Chemical Recycling Reactor

[0083] According to the present disclosure, the chemical recycling reactor is fed by an extruder operating at 450°C. The polymer is heated from room temperature (around 25°C) up to 450°C, in less than 2 minutes (Figure 14). The starting polymer has a molecular weight of around 200,000 g/mol and breaks down during the extrusion, in a cracking reaction, ending the extrusion process and entering the chemical recycling reactor with a molecular weight of around 10,000 g/mol. In the reactor, the polymer is cracked until C25 - C35, or less.

Table 6. Energy spent to heat and crack samples in the extruder and reactor, considering two different MW.

[0084] Considering the performance of the high amount of condensables as demonstrated in the previous example, the chemical recycling reactor can operate at 450°C, consuming even less energy.

Table 7. Energy spent to heat and crack samples in the extruder and reactor, considering two different MW

[0085] Considering the calculations discussed above, it is possible to save around 30% of energy when an extruder operating at 450°C is feeding inline the thermal degradation reactor and the entering material (LMW) is cracked during the extrusion, reaching a low viscosity characteristic that improves the heating transfer.

Energetic benefit Example 2

[0086] A potentiometer was used to measure the energy needed to heat samples of different molecular weight from 200°C up to 450°C. The results are listed in Figure 15 and it is possible to see that the energy required to heat samples of LMW is at least 40% lower than the HMW.

Claims

1. A method for producing an oil comprising:

- feeding an olefin-based resin into a pyrolysis reactor,

- converting the olefin-based resin into oil, and

2. The method according to claim 1 wherein the feeding step occurs by means of an extruder, preferably a twin-screw extruder.

3. The method according to claims 1 or 2 wherein the LMW olefin-based is fed in a molten state.

4. The method according to any of claims 1 to 3 wherein the LMW olefin-based is fed at a temperature of equal to or above 300°C, preferably above 400 °C, more preferably above 450°C.

5. The method according to any of claims 1 to 4 wherein the pyrolysis reactor is selected from a batch reactor, semi-batch reactor, or two-stage pyrolysis system.

6. The method according to any of claims 1 to 5 wherein the converting step occurs at a temperature ranging from 400 to 600°C, a residence time from 15 min to 2 h, and in an environment substantially free of oxygen.

7. The method according to any of claims 1 to 6 wherein the converting step occurs in the presence of a catalyst.

8. The method according to any of claims 1 to 7 comprising a further step of cracking a higher molecular (HMW) olefin-based resin to produce the LMW olefin-based resin wherein the cracking may occur before or during the feeding step.

9. The method according to claim 8 wherein in the cracking step the molecular weight of the HMW olefin-based resin is reduced by at least 4 times.

10. The method according to claims 8 or 9 wherein the cracking step occurs in an extruder.

11. The method according to and of claims 8 to 10 wherein the LMW olefin-based resin is directly fed into the reactor.

12. The method according to any of claims 8 to 11 wherein the cracking step is performed above the onset degradation temperature, optionally in the presence of a visbreaking agent.

13. The method according to any of claims 8 to 11, wherein the cracking step is performed in a temperature above the melting temperature and below the onset degradation temperature of the HMW olefin-based resin and in the presence of a visbreaking agent.

14. The method according to any of claims 8 to 13 wherein the cracking step is performed at a residence time of less than 2 min, preferably less than 90 s, most preferably less than 70 s.

15. The method according to any of claims 8 to 14 wherein the condensables yield in the converting step is at least 10% higher in comparison to the condensables yield when feeding HMW into the pyrolysis reactor.

16. The method according to any of claims 8 to 15 wherein the HMW olefin-based resin has an initial molecular weight Mw of 50,000 g/mol to 1,000,000 g/mol, preferably 50,000 g/mol to 500,000 g/mol measured according to ISO 16014-4.

17. The method according to any of claims 1 to 16 wherein the LMW olefin-based resin is a plastic waste, preferably a post-consumed resin, post-industrial resin, or scrap source.

18. The method according to any of claims 1 to 16 wherein the LMW olefin-based resin is from petrochemical or biobased source.

19. The method according to any of claims 1 to 18 wherein the LMW olefin-based resin comprises olefin monomers selected from ethylene, olefins comprising 3 to 10 carbon atoms, and combinations thereof.

20. The method according to any of claims 1 to 19 wherein the LMW olefin-based resin comprises a molecular weight of less than 50,000 g/mol, preferably less than 40,000 g/mol measured according to ISO 16014-4.

21. The method according to any of claims 1 to 20 comprising a further step of purifying the oil recovered from the reactor.

22. An oil obtained according to the process of any of claims 1 to 21.

23. Use of the oil according to claim 22 as a feedstock for production of olefin- based resins.