METHOD FOR MONITORING CONTROL PARAMETERS OF SUBSTANTIALLY PLASTIC MATERIALS AND ASSOCIATED APPARATUS AND PYROLYSIS PROCESS USING THE METHOD - Patent application

Abstract

This invention relates to the treatment of plastic materials that are subjected to a chemical recycling process in order to convert substantially plastic materials that would otherwise be disposed of as waste into valuable materials. In particular, the present invention involves the following steps: a) A substantial plastic material, at least partially in a molten state, is supplied to the pyrolysis reactor; b) The substantial plastic material supplied to the pyrolysis reactor is subjected to at least one analytical measurement "Ax" in in-line mode; c) Determine the value of at least one "Px" property of the substantial plastic material by the at least one analytical measurement "Ax"; d) Based on the value of this at least one "Px" characteristic, set at least one "Ox" parameter of the pyrolysis process; The system includes, and is characterized in that at least one analytical measurement "Ax" provides or consists of a measurement of the light reflectance spectrum of a substantial plastic material. This relates to a thermal decomposition process for substantially plastic materials to obtain liquid hydrocarbons at least 25°C.

Description

[Technical field]

[0001] The present invention relates to the treatment of plastic materials subjected to chemical recycling processes in order to obtain value from substantially plastic materials which would otherwise be disposed of as waste.

[0002] In particular, the present invention relates to a method for monitoring a control parameter of a substantially plastic material, an associated apparatus and a pyrolysis process of a substantially plastic material using said method.

[0003] Advantageously, the invention is applicable for processing plastic material that has been substantially pre-processed in a sorting plant where several types of plastic material are identified and separated as individual polymers.

[0004] In this way, the fraction that can be recovered as a single typology of polymer can be reused as such (by so-called "mechanical" or "physical" recycling) and only the part that cannot be recovered as a single polymer is subjected to pyrolysis. After pyrolysis, hydrocarbon products are produced and further processing, such as steam cracking, produces monomers that can be polymerized to form new plastics. This closes the plastic cycle and realizes the so-called "closed loop recycling".

[0005] Recovery of the above essentially plastic materials, and in particular recovery of the residues after sorting, is particularly difficult because what can be recovered as single polymers (e.g., polyethylene and polyethylene terephthalate) has already been sorted and the residues are very diverse, including non-plastic materials that are difficult to recover.

[0006] Through the methods, devices and processes described in this invention, which teach an innovative way of analyzing said essentially plastic material, which is itself very heterogeneous, and carrying out its pyrolysis according to the results of the analysis carried out, it is possible to close the plastic cycle efficiently (thus recovering said residues by "chemical" methods). [Background technology]

[0007] There are numerous papers and patent applications relating to the pyrolysis process of plastic materials, but only a few disclose measurement systems for the processed raw materials.

[0008] EP3405297 discloses a method and an apparatus for classifying tires based on their silicon content (<15% or >15% by weight silicon). The silicon content is measured by sensors based on electrical resistivity, X-ray fluorescence, near infrared (NIR) absorption and laser induced plasma spectroscopy (LIPS). A method for selective pyrolysis of tires with high silicon content to obtain a char residue with high silica content is also disclosed.

[0009] WO2012172527 discloses a method for the continuous recycling and conversion of plastics into liquid fuels. The method comprises feeding plastics to a rotating tank, which continuously removes non-gaseous products, facilitating the transport of the resulting products to an end by angular motion. One method described comprises the preventive separation of unwanted plastic materials, i.e. materials containing "heteroatoms". According to a further method, said separation is carried out by a NIR system capable of distinguishing different plastic materials containing heteroatoms based on their NIR spectra, separating said fractions with the aid of an ejector gas.

[0010] In the prior art, the NIR spectrum is analyzed with a spectrometer in transmission or transmittance mode.

[0011] In transmission spectroscopy, the radiation analyzed by the spectrometer is that portion of the incident radiation that is transmitted through the sample, i.e., that is not absorbed or reflected by the sample.

[0012] In transmission spectroscopy, the radiation analyzed by the spectrometer is that portion of the incident radiation that has passed through the sample and is reflected beyond the sample by a special reflective screen placed in the measurement cavity along the path of the radiation; the radiation reflected from the screen passes through the sample a second time before reaching the spectrometer.

[0013] There are also several patents and scientific papers on pyrolysis processes carried out at pressures other than atmospheric pressure.

[0014] EP2348254 describes a "zero-emission" pyrolysis process carried out at 10-15 bar and simultaneously supplying a flow of pure oxygen.

[0015] ES2389799 discloses a process for the production of diesel fuel (C13-C40), which envisages a two-stage process under pressure (1-15 bar). The first stage is thermal, the second catalytic, carried out in the presence of hydrogen. The input materials are preferably of polyolefin origin. They may contain polystyrene, but preferably contain less than 10% of other plastics such as PVC or PET.

[0016] There are also several inventions that disclose pyrolysis under reduced pressure (sub-atmospheric pressure), such as WO2013187788, WO0231082, and EP2184334.

[0017] From the analysis of the known art, it is clear that the measurements of the properties of the plastic material fed to the pyrolysis plant are carried out exclusively for the selection of the feed power to the pyrolysis reactor or for classifying the products obtained. In particular, the analyses carried out are not used for the control of the pyrolysis process. Also, there are some pyrolysis processes carried out at lower or higher pressures than atmospheric pressure. However, there are no generalized teachings that allow to establish whether it is advantageous to manage the pyrolysis process of complex polymer mixtures at atmospheric pressure, at a pressure below atmospheric pressure (reduced pressure) or at overpressure (i.e. at a pressure higher than atmospheric pressure). The available information is often very diverse, sometimes contradictory and sometimes gives completely different indications. Moreover, no information is specified in any document on how to set the process parameters, such as the operating pressure of the pyrolysis system, depending on the quality of the polymer fed. In no case is the composition of the fed material constant, and in no case is it known how changes in the composition are managed and what effect they have on the process and on the products obtained.

[0018] The substantially plastic material remaining after the selection and extraction of a single polymer is, by its very nature, highly diverse in composition, consisting of multiple types of plastic and non-plastic materials.

[0019] Moreover, the pyrolysis process requires a pre-sorting of the plastics fed to it in order to reduce the amount of difficult-to-process plastics (PVC, PET, cellulose, polystyrene, etc.) and non-plastic materials, in favor of polyolefins (especially polyethylene and polypropylene) instead. However, most of the polyolefins contained in substantial plastic materials are generally separated in the sorting process and then recycled as is, without pyrolysis. There is therefore an interest in pyrolytically processing the remaining fraction after sorting, which contains, in addition to polyolefins, a significant amount of other plastics and smaller amounts of non-plastic materials.

[0020] Further problems associated with these spectroscopic modes relate to the fact that substantially plastic materials are often diverse in composition and also contain non-plastic materials such as carbon black and graphite, which, even in small amounts, obscure the transmitted radiation and thus make the spectrum difficult to read. Moreover, substantially plastic materials can partially decompose and thus become partially opaque, especially in the presence of large amounts of oxygen. Moreover, polymeric compounds are generally incompatible. Thus, the polymer melts thus produced are generally opaque and inhomogeneous.

[0021] Furthermore, assessment of the composition of such substantially plastic materials (i.e., with respect to particulates received from a supplier) is imprecise because it is not homogenous (each individual particle is typically a different material). Furthermore, the analysis is dependent on uncontrollable variables such as the size and aspect ratio of the particulate matter. Assessment of the composition of substantially plastic materials already in a melt-mixed state could address these criticalities, but is generally difficult with spectroscopic techniques known in the art for the reasons discussed above.

[0022] Additionally, it would be desirable to have a method for quickly determining at least those compositional features that have the greatest impact on the pyrolysis process, so that there is little latency between feeding the substantially plastic material to the pyrolysis reactor and process changes such as temperature, pressure or residence time, etc. Indeed, typically the residence time of such material in the molten state before being fed to the pyrolysis reactor is very short.

[0023] For the above reasons, there is a need to identify processes and associated equipment that can overcome the limitations of the known art. Summary of the Invention [Problem to be solved by the invention]

[0024] The applicant has surprisingly discovered a process for the pyrolysis of substantially plastic materials in order to obtain hydrocarbons which are in the liquid phase at least at 25° C. by subjecting the substantially plastic materials, which are of variable composition and optionally contain large amounts of components which are normally considered to be objectionable, to a specific pyrolysis process. [Means for solving the problem]

[0025] This process consists of the following steps: a) providing a substantially plastic material in an at least partially molten state to a pyrolysis reactor; b) subjecting said substantially plastic material in a molten state fed to a pyrolysis reactor to at least one analytical measurement "Ax" in an in-line mode; c) determining the value of at least one property "Px" of said substantially plastic material by said at least one analytical measurement "Ax"; d) setting at least one pyrolysis process parameter “Ox” based on the value of said at least one characteristic “Px”; Including, Said at least one analytical measurement "Ax" is characterized in that it provides or consists of a measurement of the optical reflectance spectrum of a substantially plastic material at least partially in a molten state.

[0026] In one embodiment, this step comprises the steps of: e) repeatedly performing steps b), c) and d); Also includes. Effect of the Invention

[0027] A first advantage of the process disclosed in this invention is that it is capable of processing substantially plastic materials of very diverse compositions without the need to stop the process when the type of substantially plastic material fed is changed.

[0028] A further advantage of the process disclosed in this invention is that, by incorporating a pre-sorting step, plastics can be recycled an indefinite number of times ("closed-loop recycling"); i.e., the material can be used and regenerated many times without losing its properties during recycling.

[0029] One of the further advantages of the process disclosed in this invention is that it is capable of processing vinyl polymers (polyethylene and polypropylene), polyvinyl aromatic polymers such as polystyrene (PS) and its alloys, non-vinyl polymers such as polyethylene terephthalate (PET), as well as oxygen-rich polymers such as cellulose and PET itself, without any process problems such as fouling or occlusions, with a high quality of said hydrocarbons in liquid phase at 25°C.

[0030] An additional advantage of the process disclosed in this invention is that it can process essentially plastic materials that contain large amounts of components that are normally considered objectionable, such as paper and cardboard (cellulose) and polymers containing chlorinated or brominated compounds, e.g. polyvinyl chloride (PVC) and halogenated flame retardants.

[0031] An additional advantage of the process disclosed in this invention is that it can process substantially plastic materials of variable composition without fouling or occlusion.

[0032] A further advantage of the process disclosed in this invention is that it allows the processing of substantially plastic material consisting of residues that could not be separated and recycled by selective processes typically applied to plastic waste.

[0033] A further advantage of the process disclosed in the present invention is that it allows the production of high quality pyrolysis oil in terms of the resulting composition, even if the substantially plastic material being treated has a non-constant composition, while maintaining a substantially high quality of the resulting hydrocarbons that are in the liquid phase at 25° C.

[0034] One advantage of the apparatus disclosed in this invention is that it can be operated continuously and for extended periods of time without the need for interruptions for maintenance and cleaning.

[0035] A further advantage of the disclosed apparatus is that encumbrances of the probe and detection system within the cavity are minimized, especially in the way these elements are arranged within a single integrated device, which reduces the pressure loss experienced by the substantially plastic material within the measurement cavity and reduces fouling of the same.

[0036] A further advantage of the process and apparatus disclosed in this invention is that the measurements are performed in-line (also known as in-situ).

[0037] In fact, on-line measuring systems are known in the art, in which the samples to be analyzed are taken, either continuously or discontinuously, from the main process flow. Said transport from the process line to the measuring instrument takes place through a transport line. The problem of fouling of the sampling window remains, since the polymerization mixture must in any case pass through a measuring cell (outside the line dedicated to the pyrolysis process and connected via a transport line) which has exactly the same problems as the measuring cavity of an immersion probe. Moreover, in many cases, during the transfer of the sample of the practical plastic material to be analyzed from the reactor to the measuring instrument, structural changes in the sample itself can occur, which can also have a significant influence on the measurement result of the evaluated "Px" property (for example, unmixing, decomposition, gas evolution can occur). Moreover, on-line measurements suffer from measurement delays that are often difficult to quantify, since the material removed from the main flow at a certain moment is measured by a measuring instrument placed downstream of said transport line only after a time equal to the residence time of the material in said transport line.

[0038] The method for measuring the property "Px" proposed in the present invention is instead performed in-line, i.e. the measurement is performed essentially in the same flow of plastic material fed to the pyrolysis reactor or without the need for a transfer line for the material to be analysed.

[0039] A further advantage of the process disclosed in the present invention is that the waiting time between the analytical measurement "Ax" and the setting of the process parameter "Ox" is less than 1 hour, preferably less than 10 minutes, and more preferably between 1 and 60 seconds.

[0040] Considering that the time required for the substantially plastic material thus analyzed to enter the reactor is typically more than 1 second, ensuring the above waiting time suggests that adjustments to the "Ox" process parameter, if necessary, can be made in a time not exceeding 10 minutes, preferably within 59 seconds.

[0041] The significant problems exemplified above with respect to the technique have so far prevented proper exploitation of the potential of spectroscopy in monitoring the properties of substantial plastic materials in pyrolysis plants, especially when information must be obtained from these with reduced waiting times or reduced time delays between the determination of the property in question and the processing of the same sample in pyrolysis.

[0042] Thus, in current practice, pyrolysis is usually carried out under constant conditions and therefore independent of the substantially plastic material supplied. Sometimes, empirically, experience is gained regarding optimal processing conditions as a function of the type of substantially plastic material. For example, the substantially plastic material supplied by a given supplier is assumed to be of constant composition, and therefore, over time, empirical process recipes (temperatures, residence times, flow rates, etc.) optimized for the substantially plastic material are developed from a particular supplier.

[0043] It would probably be possible to carry out off-line measurements by taking spot samples of the actual plastic material, analyzing them in a laboratory with a spectrometer, and adapting the process recipe according to accumulated experience. However, this approach has a crucial disadvantage: the turnaround time of laboratory analysis is necessarily not very short, and the information obtained in the laboratory can only be used after the pyrolysis process has been started.

[0044] Furthermore, in this mode, the substantially plastic material analyzed may only be a sample: Given the high variability and uncontrollability of the composition of the substantially plastic materials being processed, the sample analysis may not be representative of the substantially plastic material actually being processed; therefore, the process conditions determined may be erroneous.

[0045] The object of the present invention is therefore to overcome or at least mitigate the above highlighted drawbacks of the state of the art, in particular by providing a process for the pyrolysis of substantially plastic materials, which makes it possible to maintain a high quality constancy of said hydrocarbons in liquid phase at 25° C. obtained by said pyrolysis process, even when the substantially plastic material fed to said pyrolysis process is not constant.

[0046] The advantages achieved and disclosed herein utilizing reflectance spectroscopy in accordance with the present invention are believed to be even more surprising when one considers that the intensity of emitted light reflected by the polymerization mixture that can be collected by the probe (and subsequently processed by a detection system) is significantly lower than that which can be collected with a transmittance or transflectance measurement probe.

[0047] The invention also relates to a mixture comprising hydrocarbons in an amount of more than 90% by weight relative to the total weight of the mixture and tetrahydrofuran in an amount between 0.01% by weight and 0.25% by weight, and to the use of said mixture for feeding a cracking plant.

[0048] A further aspect of the invention is a method for determining the value of said at least one property "Px" of said substantially plastic material, which method can be used to carry out steps b) and c) of said pyrolysis process.

[0049] The method for determining the value of at least one property "Px" of the substantially plastic material comprises the following steps: (i) calculating, for each of said at least one property "Px", a calibration curve "Cx" correlating the reflectance spectrum with said property "Px" for sample materials having known values ​​of the property "Px"; (ii) performing at least one measurement of the reflectance spectrum of said substantially plastic material; (iii) determining a value of said at least one property “Px” of said substantially plastic material from said at least one calibration curve “Cx”; wherein, under reflectance spectrum measurement conditions, at least 60% by weight, preferably 70% to 99% by weight, and more preferably 80% to 94% by weight of the substantially plastic material is in a molten state relative to the total weight of the substantially plastic material.

[0050] Preferably, said substantially plastic material under measurement conditions has a temperature comprised between 140 and 300°C, more preferably between 160 and 260°C.

[0051] Preferably, the substantially plastic material under measurement conditions has a pressure of 2 bara or more, more preferably 3 to 300 bara.

[0052] According to a preferred method, called "multiple correlation", there are at least two "Px" characteristics. According to a further preferred modality, called "double correlation", there are two "Px" characteristics.

[0053] According to this preferred embodiment having a double correlation, preferably the "Px" properties are the hydrogen index on carbon (H / C index) and the carbon index.

[0054] Preferably, the reflectance spectrum of the substantially plastic material obtained in step ii) is in the range of 4000 to 12000 cm -1 More preferably, the wavelength is in the range of 4500 to 10000 cm. -1 , and more preferably 5000 to 9000 cm -1 is included in the range.

[0055] Preferably, the "Cx" calibration curve is obtained by applying a multivariate regression method. Preferably, said multivariate regression method is multiple linear regression (MLR), regression by principal component analysis (PCR), or regression by partial least squares (PLS). More preferably, the multivariate regression is partial least squares (PLS) regression.

[0056] Furthermore, the present invention also relates to an apparatus for determining the value of at least one property "Px" of a substantially plastic material in an at least partially molten state, said device comprising: 1) a cavity through which the substantially plastic material can slide, the cavity having an inlet and an outlet for the substantially plastic material in an at least partially molten state; 2) at least one probe capable of emitting light within said cavity; 3) at least one detection system optically coupled to the probe for detecting reflected light and determining an analytical measurement "Ax"; 4) at least one temperature reading sensor connected to said cavity; 5) optionally a system for determining said at least one property "Px" of said at least partially molten substantially plastic material by correlating said at least one analytical measurement "Ax" with a calibration curve "Cx" obtained from sample material having known values ​​of property "Px"; Here, the cavity can withstand a pressure of at least 50 bar, preferably 80 to 300 bar. Includes.

[0057] Preferably, the temperature reading sensor is positioned so that the minimum distance between the area where the temperature is read and the area where the reflectance spectrum is measured is 100 mm or less, preferably 30 mm or less, more preferably 3 mm or less.

[0058] The temperature reading zone is the surface on which the temperature sensor detects the temperature. In the case of devices such as thermocouples and thermistors, where the temperature detected is the temperature at their end, said area therefore corresponds to the surface of said end.

[0059] Preferably, the at least one detection system optically coupled to the probe is positioned such that the minimum distance between the light emission zone of the probe and the detection zone of the light emission is 50 mm or less, preferably 15 mm or less, more preferably 3 mm or less.

[0060] Preferably, the probe has a wavelength of at least 4000 to 12000 cm -1 , more preferably 4500 to 10000 cm -1 , and more preferably 5000 to 9000 cm -1 The light can be emitted having a wave number in the range

[0061] Preferably, the "Px" property is the hydrogen to carbon index (H / C index) and / or the carbon index.

[0062] According to one preferred method, said cavity is constituted by at least a portion of the cylinder of an extruder, which can be used to melt at least a portion of the material and selectively remove gaseous compounds.

[0063] According to an alternative method, said cavity is the cavity of a conveyor screw connected to the inlet of the substantially plastic material in the pyrolysis reactor.

[0064] According to an alternative method, the cavity is a portion of a pipe connected to the inlet of the substantially plastic material in the pyrolysis reactor.

[0065] According to an alternative method, the cavity is inside the inlet of the pyrolysis reactor.

[0066] According to an alternative method, the apparatus for determining the value of at least one property "Px" of a substantially plastic material also comprises a window made of a material substantially transparent in the wavenumber range of the detection system optically coupled to the probe, interposed between the probe and the cavity and / or between the optically coupled detection system and the cavity.

[0067] In this alternative embodiment, the window allows for a physical separation of the substantially plastic material to be analyzed from the probe and / or detection system, thus making it possible to use a probe and / or detection system that does not necessarily have to ensure hermeticity and resistance to the high pressures and temperatures typical of substantially plastic materials in a molten or semi-molten state.

[0068] definition In the present specification, ranges of values ​​(eg, ranges of pressure, temperature, amount, etc.) are intended to be inclusive of the limits unless otherwise specified.

[0069] In the present specification, unless otherwise specified, percentages are to be understood as % by weight (i.e. % by mass). The symbol "%" means percent and always denotes weight (mass).

[0070] In the specification of the present invention, the term "comprise" also includes the meaning of "consist of" or "consist in", as a specific limiting case.

[0071] In the present specification, the terms "essentially consists of" or "essentially consists in" mean that a composition or formulation (A) necessarily contains the recited ingredients, and (B) is open to unrecited ingredients that do not materially affect the basic and novel characteristics of the composition.

[0072] For the purposes of this invention, a material is in the "molten state" at a given temperature if, rather than in the solid state, its melt flow rate (MFR), measured in accordance with ISO 1133-1:2011, is greater than 2 g for 10 minutes under a weight of 10 kg at the given temperature.

[0073] Therefore, in the present specification, the "molten state" also includes the liquid state.

[0074] In the present specification, the term "meltable substance" means that said substance can be brought into a molten state at a temperature below 300° C. For example, a meltable substance is a substance that is already liquid at room temperature, such as water, or a substance that is solid at room temperature, such as most thermoplastic polymers. For example, inorganic salts and inorganic carbon compounds, such as carbon black, coke, graphite, or polymers, such as polyetheretherketone (PEEK), are not meltable substances.

[0075] In the present specification, the substantially plastic material is "at least partially in a molten state" means that the material is at least 60% by weight, preferably 70% to 99% by weight, and more preferably 80% to 94% by weight, of the total weight of the substantially plastic material.

[0076] In the present specification, the term "sample spectrum" refers to a spectrum obtained on a sample material.

[0077] In the present specification, unless otherwise specified, maintaining a parameter (e.g. pressure) within a prescribed range means actively manipulating this parameter to be within the range, e.g. by checking that a measured value is within the prescribed range, and / or regulating the parameter by a feedback regulation system in which the value of this parameter is set within the prescribed range. Preferably, keeping a parameter (e.g. pressure) at a set value or within a prescribed range means setting this parameter to a value within the prescribed range in a feedback control system in order to ensure that the parameter is within the set value or within the prescribed range.

[0078] In the present specification, unless otherwise specified, a hydrocarbon which is in a liquid phase at 25° C. means a hydrocarbon mixture which is in a liquid phase at 25° C. and atmospheric pressure.

[0079] In the context of the present invention, pyrolysis oil means a pyrolysis product in the liquid state at 25° C. and atmospheric pressure.

[0080] In the context of this invention, "pyrolysis vapors" means products produced during the pyrolysis process that are in a gaseous state within the pyrolysis reactor, i.e., products that are in a gaseous state under the temperature, pressure and composition conditions of pyrolysis.

[0081] In the context of the present invention, "pyrolysis residue" means the products which are in the liquid, solid or liquid and solid state in the pyrolysis reactor, i.e. the products which are in the liquid and / or solid state under the temperature, pressure and composition conditions of pyrolysis.

[0082] In the present specification, unless otherwise specified, a value of a parameter that is at most equal to a value X means that the parameter is equal to or less than X, and a value of a parameter that is at least equal to a value X means that the parameter is equal to or greater than X.

[0083] In the present specification, unless otherwise specified, the yield in the production of a product means the weight percentage of that product relative to the total products produced.

[0084] Unless otherwise specified, in this document "part" and "parts" mean part by weight and parts by weight respectively, where weight means mass, i.e. kg in SI units. [Brief description of the drawings]

[0085] [Figure 1] FIG. 1 shows a cavity through which a substantially plastic material flows, including an integrated device including a probe capable of emitting light, a detection system optically coupled to said probe, and a thermocouple for detecting the temperature of the substantially plastic material illuminated with said light; [Diagram 2] FIG. 2 illustrates one example embodiment of the integrated withdraw device; [Diagram 3] Figure 3 shows the predictive ability of the calibration curves "Cx" corresponding to the characteristic "Px" of the carbon index and H / C index in the PLS (Partial Least Squares) regression: - the horizontal axis shows the number of principal components used (NC), - the vertical axis shows the root mean square error in cross validation (RMSECV); the measurement units correspond to the characteristic "Px" (H / C index is 100 for polyethylene / polypropylene); [Figure 4] Figure 4 shows the predictive ability of the "Cx" calibration curves corresponding to the "Px" H / C index characteristics (H / C index) for the 51 sample materials investigated; there are almost overlapping points, so that in the figure there appear to be fewer than 51 points, the horizontal axis shows the "true" H / C values, i.e. the values ​​determined by the primary analysis, and the vertical axis shows the H / C values ​​calculated with the corresponding calibration curve "Cx"; [Diagram 5] Figure 5 shows the predictive ability of the calibration curve “Cx” corresponding to the carbon index characteristic “Px” for the 51 sample materials investigated; [Figure 6] Figure 6 shows the absorption spectra of sample material M48 at various temperatures, with the horizontal axis being wavenumber (cm-1) and the vertical axis being absorbance; [Figure 7] FIG. 7 shows diagrammatically a device according to the invention for the pyrolysis of substantially plastic materials to obtain hydrocarbons which are in the liquid phase at least at 25° C.; [Figure 8] FIG. 8 illustrates one embodiment of a split range control mode in accordance with the present invention; [Figure 9] FIG. 9 shows temperature vs. time for the two temperature profiles T1 and T2 used in the example pyrolysis process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0086] Detailed Description of the Invention The present invention relates primarily to a process for the pyrolysis of substantially plastic materials to obtain hydrocarbons that are in a liquid phase at least at 25° C., comprising the following steps: a) providing a substantially plastic material in an at least partially molten state to a pyrolysis reactor; b) subjecting said substantially plastic material fed to the pyrolysis reactor to at least one analytical measurement "Ax" in in-line mode; c) determining the value of at least one property "Px" of said substantially plastic material by said at least one analytical measurement "Ax"; d) setting at least one “Ox” parameter of the pyrolysis process based on the value of said at least one “Px” characteristic; Including, The analytical measurement "Ax" is characterized in that it provides or consists of a measurement of the light reflectance spectrum of the substantially plastic material.

[0087] In accordance with the present invention, a sample of a substantially plastic material is illuminated by a suitable light source and the reflectance spectrum of the substantially plastic material exposed to the light source is obtained by a device called a spectrometer.

[0088] Preferably, the spectrometer is a spectrophotometer, ie it comprises a system for quantitatively measuring light intensity.

[0089] There is no particular limitation on the type of spectrometer. For example, a spectrometer equipped with a prism or grating monochromator, or a Fourier transform spectrometer known as FTIR, can be used.

[0090] The monochromator may advantageously comprise an array of photodiodes ("photodiode array" or PDA, otherwise known as "diode array"). Such spectrometers are also known by the terms "DAS" (diode array spectrometer) or "PDAS" (photo diode array spectrometer). Alternatively, a sensor and a corresponding CCD (charged-coupled device) spectrometer may be used.

[0091] A sample of the substantially plastic material to be measured is illuminated with broad spectrum light, ie light that includes all frequencies within the range of wavenumbers to be measured.

[0092] The spectrum is preferably in the visible range, i.e. from 12000 to 25000 cm -1 , near infrared (NIR), i.e. 4000-12000 cm -1 , and / or mid-infrared (MIR), i.e., 400-4000 cm -1 More preferably, the spectrum is in the range of 4000 to 12000 cm -1 , and more preferably 4500 to 10000 cm -1 and even more preferably 5000 to 9000 cm -1 It is.

[0093] Light reflected by the substantially plastic material sample is collected by a detection system optically coupled to the probe emitting light source.

[0094] By a system optically coupled to the probe that emits the light source is meant a detection system positioned to receive light emitted by the light source and reflected by the sample.

[0095] For example, the probe and the detection system can be configured with optical fibers and joined into a single integrated device, as shown in FIG.

[0096] FIG. 2 illustrates the following embodiment: -integrated extractable device (13); -Body (14) of the device (13); -windows(15); - an optical fiber (21) constituting a probe capable of emitting light, located in the center and connected to a light source (1) (not shown in FIG. 2, only in FIG. 1); an optical fiber (22) (not shown in FIG. 2, but only in FIG. 1) constituting a detection system optically coupled to said probe (21) and connected to a spectral analyzer (2); A thermocouple (23) (not shown in FIG. 2, only in FIG. 1), which is placed in close proximity to the luminescent probe (21) and connected to a temperature reader (3).

[0097] The probe fibers and the detection system fibers are closely aligned and the substantially plastic material is in contact with the window, ensuring that the emitted light illuminates the substantially plastic material and that reflected light reaches the detection system.

[0098] According to an alternative embodiment of the invention, the optical fiber of the light-emitting probe is arranged externally to the optical fiber of the detection system optically coupled to said probe. Still referring to Figure 2, in this mode, the optical fiber (22) is the light-emitting probe and the optical fiber (21) is the detection system probe optically coupled to said probe.

[0099] The sampling window (15) is made of a material that is substantially transparent to optical radiation in the wavenumber range of the spectrum to be analyzed, and may be made of, for example, quartz, sapphire, potassium bromide, or zinc selenide.

[0100] FIG. 1 instead shows a cavity through which a substantially plastic material flows, including an integrated device including a probe capable of emitting light, a detection system optically coupled to said probe, and a thermocouple for detecting the temperature of the substantially plastic material illuminated by said light, and represents: - a hollow body (17) in which said substantially plastic material slides; - an inlet (11) and an outlet (12) for said substantially plastic material, the sliding direction of the substantially plastic material being indicated by arrows; -below: o a body (14) rigidly connected to said hollow body (17) by threading; o A window made of a material that is substantially transparent in the wavenumber range of the spectrum (15); o a central cavity (16) in which are located optical fibers for emitting and detecting light and a thermocouple for reading the temperature of the illuminated substantially plastic material; an integrated withdrawable device (13); - A light source (1), a spectrum analyzer (2) and a temperature reader (3) connected to said integrated extractable device (13).

[0101] Therefore, when an integrated device is used that includes both the light-emitting probe and the optically coupled detection system, it is advantageous for the device to be positioned substantially perpendicular to the direction of movement of the substantially plastic material (as shown in FIG. 1), i.e. with the light-emitting and light-receiving optical fibers substantially perpendicular to the direction of movement.

[0102] Even when an integrated device is used, it is advantageous for said device to protrude no more than 3cm, preferably no more than 1cm, more preferably no more than 0.5cm into said cavity through which the substantial plastic material flows.

[0103] However, it is not excluded that the integrated device can be inserted into the cavity (17) in other configurations as well, for example, the integrated device can be inserted substantially towards the direction of plastic material flow, rather than perpendicular to the direction of flow.

[0104] Advantageously, the apparatus for measuring at least one "Px" property of a substantially plastic material can be used continuously and for extended periods of time. Thus, the preferred method of the present invention is a continuous or semi-batch (semi-continuous) pyrolysis process of a substantially plastic material.

[0105] In order to apply the method according to the invention to the control of pyrolysis of a substantially plastic material, at least one calibration curve "Cx" is required, which is able to correlate the reflectance spectrum of the substantially plastic material fed to the pyrolysis reactor with the value of at least one parameter "Px" of said substantially plastic material.

[0106] Preferably, said at least one property "Px" of said substantially plastic material is the hydrogen / carbon ratio (ie, H / C index) and / or the carbon index ("CI" or "carbon index").

[0107] The carbon index and hydrogen / carbon ratio (H / C index) are calculated using the following formula:

number

number

[0108] The calibration curve can be prepared by a method known to those skilled in the art. The calibration curve can be obtained by a univariate regression method. Preferably, the calibration curve can be obtained by a multivariate regression method.

[0109] To obtain a calibration curve, for example, a plurality of substantially plastic materials (hereinafter referred to as "sample materials") can be prepared, each of which is subjected to at least one primary analysis capable of determining the value of at least one of the above-mentioned "Px" characteristics.

[0110] Therefore, according to one embodiment of the pyrolysis process for a substantially plastic material of the present invention, the determination of the value of at least one property "Px" of said substantially plastic material is performed by correlation of said analytical measurement "Ax" with analytical measurements obtained by obtaining a plurality of model absorbances of plastic materials having known values ​​of said at least one property "Px".

[0111] For example, where the "Px" properties are H / C index (H / C ratio) and carbon index (CI or "carbon index"), it is sufficient to analytically determine the total amounts of elements present in the substantially plastic material. Thus, the H / C index is conveniently calculated from the ratio of the amount of hydrogen to the amount of carbon, and the carbon index is conveniently calculated from the ratio of the amount of carbon to the total weight.

[0112] For this purpose, it is possible to use, for example, an elemental analyzer which performs complete combustion of a sample followed by analysis of the product gases by gas chromatography, thermal conductivity, infrared spectroscopy, or a combination of these techniques.

[0113] In general, the more sample spectra used to generate the "Cx" calibration curve, the more accurate the determination of the associated "Px" parameter.

[0114] According to the invention, the number of sample materials used for the definition of the calibration curve is at least equal to 5, more preferably at least equal to 10. In a particularly preferred embodiment, the number of sample materials is between 10 and 50.

[0115] Advantageously, the sample material may be prepared by making a mixture of a substantially plastic material having a known property "Px".

[0116] For example, the sample material may be a blend of polymers including polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polyethylene terephthalate, and cellulose in various ratios. For example, the H / C index and carbon index values ​​of the polymers are known or, in any case, are easily determined by the techniques described above. As a result, the H / C index and carbon index can be calculated for the blend according to the given formulas.

[0117] Alternatively, the sample material may be different samples of substantially plastic material obtained from recycling of plastic material. Advantageously, it may be desirable to use substantially plastic material of different origins and / or different manufacturers.

[0118] According to the invention, it is particularly preferred to start from a substantially plastic material obtained from the recycling of plastic materials and to produce a sample material to which is added a measured amount of other polymeric and / or non-polymeric substances, the property "Px" being known, such as the H / C index or carbon index value.

[0119] Advantageously, these polymers may be those already mentioned, namely polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polyethylene terephthalate and cellulose, and the non-polymeric materials may be, for example, wood, carbon black, graphite, calcium carbonate, talc.

[0120] The spectrum of a sample material containing at least 50% by weight of meltable material can be obtained by measuring the absorption of reflected light after the same material has been brought to an at least partially molten state.

[0121] Furthermore, the temperature in the measurement conditions is preferably 140 to 300° C., more preferably 160 to 260° C., and the pressure in the measurement conditions is preferably 2 bara or more, more preferably 3 to 300 bara.

[0122] In fact, such temperature and pressure conditions have been found to be conducive to obtaining highly reproducible spectra. For example, at low pressure conditions, such as below atmospheric pressure, the presence of gaseous substances has been observed. This can lead to spurious spectra, especially if gas is generated in the measurement zone (e.g., pressure drops due to pressure drops).

[0123] To obtain the spectra for constructing the calibration curve, these sample materials are preferably processed so that the spectra are read on the same equipment and under similar process conditions as those used in the process of the present invention.

[0124] It is also advantageous to provide more than one sample spectrum for each sample material.More preferably, it is advantageous to create multiple sample spectra for each sample material and under different process conditions.In particular, it is preferred to create multiple sample spectra for the same sample material at different temperatures, pressures and sample material flow rates.

[0125] In fact, the spectrum can vary greatly depending on the variables mentioned above (temperature, flow rate, pressure), especially the temperature. In the following, these variables that affect the spectrum obtained will be called "accessory variables".

[0126] If the variations in these adjunct variables are not taken into account, they can affect the quality of the calibration curves generated from these spectra.

[0127] However, applicants have found that it is possible to obtain an excellent calibration curve by implicitly or explicitly taking into account the above-mentioned additional variables, as described below.

[0128] There is no particular limitation on the spectrometer that can be used. Preferably, the spectrometer is a spectrophotometer. More preferably, the spectrophotometer is a Fourier transform (FTIR) or diode series or dispersive spectrophotometer.

[0129] In either case, the spectrum is typically obtained in digital form. In particular, a digital spectrum typically is obtained that includes spectral values ​​for discrete numerical wavenumbers, also called channels. Advantageously, in the case of a diode-based spectrophotometer, the channels can correspond to individual diodes.

[0130] Advantageously, the optical radiation reflected by the sample and analyzed and collected by the detection system is expressed as a function of the number d waves of the incident radiation (usually in cm -1 The light may be treated in the form of a reflectance spectrum (R) or preferably absorbance (A) as a function of wavelength (usually expressed in nm) or reflectance (R) as a function of wavelength (usually expressed in nm). The absorbance (A) is calculated from the measured reflectance (R) based on the relationship A=log(1 / R), where "log" is the natural logarithm.

[0131] The calibration and measurement spectra, once acquired, may be pre-processed in a manner known in the art, for example to correct for any spectral distortions due to baseline shifts.

[0132] To determine a given calibration curve "Cx", the calibration curve spectrum and the property "Px" values ​​(already determined or known for the sample material as explained above) are analyzed by applying univariate linear regression and / or multivariate known statistical-mathematical techniques or machine learning (ML) models, typically such as artificial neural networks (ANN), genetic algorithms (GA), fuzzy logic, particle swarm optimization (PSO) and combinations thereof.

[0133] Preferably, the multivariate linear regression method is selected from the multiple linear regression (MLR) method, the partial least squares (PLS) method, the principal component regression (PCR) method, and combinations thereof.

[0134] According to one embodiment, the calibration curve resulting from application of the aforementioned multivariate regression method may be a linear combination of absorbances or other quantities derived therefrom.

[0135] Thus, according to this embodiment, for each sample spectrum, the following equation (hereinafter referred to as the "linear regression equation") is calculated:

number

[0136] Therefore, there are N+1 unknowns (k i coefficients), there are M equations (one for each sample spectrum being evaluated).

[0137] If the number of sample spectra, M, is greater than N+1, and there are no linearly dependent sample spectra (i.e., linear combinations of two or more other spectra), then mathematically, k i It is possible to regress a system of M equations to obtain the values ​​of the coefficients. This is the multiple linear regression (MLR) method.

[0138] However, in practice many unknowns are not linearly independent, so it is desirable to reduce the number of unknowns N+1. For example, the signal associated with the absorption of the double bond of the carbon atom of ethylene has various upper harmonics ("overtones"), so the presence of this double bond increases the absorbance signal in various channels.

[0139] Therefore, according to a preferred embodiment of the present invention, the number of unknowns can be reduced by using multivariate analysis.

[0140] According to a first method, data relating to the absorption of a sample spectrum is subjected to a Principal Component Analysis (PCA), preferably 5 to 15 principal components are extracted, more preferably 8 to 11 principal components are extracted.

[0141] The model is given by the linear regression equation defined above, where A ji " represents the value (score) of principal component "i" for sample spectrum "j". This method of applying PCA is called Principal Component Regression (PCR).

[0142] According to a further preferred embodiment of the present invention, data on the absorbance of the sample spectrum and the parameter P xj The data are subjected to partial least squares regression ("partial least squares" or "PLS").

[0143] The regression parameter P xj By using the information of xj It becomes possible to determine the principal components that are best able to describe the variability of

[0144] For PCR, preferably 5 to 15 principal components are extracted by this method, more preferably 8 to 11 principal components are extracted.

[0145] The model is given by the linear regression equation defined above, where A ji " represents the value ("score") of principal component "i" for sample spectrum "j", in this case obtained by PLS.

[0146] As indicated above, applicants have determined that adjunct variables have a significant effect on the calculated regression coefficients.

[0147] Figure 6 shows the spectra obtained for the same sample measured at different temperatures. It is clear that there is a large effect of temperature. For example, note that the distance between the minimum and maximum of absorbance tends to decrease as temperature increases, although the composition of the spectrum is not easily decipherable.

[0148] Despite this effect on the spectra, applicants have discovered that multivariate regression methods such as PCR and / or PLS described above can implicitly remove the effect of temperature if multiple sample spectra are performed for each sample material by varying the variables to cover the interval that may be found in the pyrolysis process of the present invention when measuring the absorption spectrum. In other words, regression on a small number of principal components as described above can be performed with the parameter P xj One can choose a combination of absorbances of several channels that can maximize the response on , thus limiting the effect of temperature, which instead appears as residual noise. This is an implicit mode that mitigates the effect of temperature mentioned above.

[0149] Alternatively, according to a more preferred embodiment, called the explicit modality, it is also possible to take adjunct variables into account explicitly.

[0150] According to this aspect, the linear regression equation is as follows:

number

[0151] Therefore, the model requires an additional unknown NVA. As with the implicit embodiment disclosed above, it is preferred to apply Principal Component (PCR) regression analysis, more preferably Partial Least Squares Regression (PLS).

[0152] Preferably, according to both the explicit and implicit aspects, the number of process conditions applied to the same sample material by varying at least one auxiliary variable is at least 8, preferably between 12 and 100.

[0153] It is advantageous to generate more than one sample spectrum under the same process conditions (ie, the ancillary variables, such as temperature and flow rate, are substantially constant).

[0154] Preferably, according to both the explicit and implicit aspects, the number of sample spectra performed under the same process conditions is at least 4, preferably 8-20.

[0155] The "Cx" calibration curve obtained from multivariate regression analysis (e.g., MLR, PCR or PLS) is then validated using a series of spectra prepared in the same manner as the sample spectra used to determine "Cx", i.e., spectra generated on a substantially plastic material with a known property "Px" or determinable by primary analysis, as exemplified above.

[0156] Surprisingly, a so-called "rotational" mode was discovered that allows obtaining particularly useful calibration curves for predicting the "Px" control parameters, in particular the carbon index and the H / C index.

[0157] According to this method: A) Split the sample spectra so that 1-40% (by number), preferably 10-30% of the spectra are used for validation and the rest for calibration; B) performing a multivariate regression, preferably PLS or PCR, on the spectra selected for calibration and performing validation on the spectra selected for validation, and calculating the mean squared error of the "Px" feature; C) Re-subdivide the sample spectra so that 1%-40% (by number), preferably 8%-25% of the spectra are used for validation and the remaining spectra are used for calibration; D) Repeat the multivariate regression with newly selected spectra for calibration and the validation with newly selected spectra for validation; E) Calculate a new loading matrix, where each element of the matrix corresponds to the average of the corresponding elements of the single load matrices obtained in steps B) and D).

[0158] Once validated, the calibration curves can be used to calculate the values ​​of control parameters "Px", such as H / C index or carbon index, by applying them to the in-line acquired spectra. If multivariate regression methods are used, it is possible to calculate, from the discrete values ​​of absorbance, the values ​​(scores) of the same principal components of PCA and / or PLS previously identified during the determination of the "Cx" calibration curve (i.e. using the same loading matrix).

[0159] During the production stage (i.e. the pyrolysis process according to the invention), the spectrum analyzer may be advantageously connected to a control system, such as a computer, a computing server, a distributed control system (DCS), a programmable logic controller (PLC) or a "field programmable gate array" (FPGA).

[0160] Spectral analyzers can perform spectral measurements in a very short time, usually less than a minute. The calculation of said at least one parameter Px from said at least one calibration curve Cx is also very fast and generally consists of a relatively small number of algebraic operations (for an electronic computer). Control systems can also be very fast. Thus, the entire sequence (from the "Ax" analysis to the calculation of the "Ox" process parameter) can be performed in a very short time, less than a minute or even a few seconds.

[0161] According to the present invention, it is preferable to repeat spectrum acquisition at a high frequency, preferably at least 10 times per hour, more preferably at least 30 times per hour, even more preferably 60 to 3600 times per hour, and even more preferably 120 to 900 times per hour.

[0162] According to the invention, it is preferred to acquire a series of spectra in order to calculate an average parameter Px which is passed to the process controller for the calculation of the process parameter "Ox". It has been found that in this way it is possible to take into account better the presence of any material that is not in the molten state in the hollow duct in which the spectral measurements are carried out.

[0163] Preferably, the substantially plastic material is a composition of various plastics, more preferably including at least polymers with a high H / C index, such as polyethylene, polypropylene, polyamide, polymethyl methacrylate, and polymers with a low H / C index, such as polystyrene, polycarbonate, polyethylene terephthalate.

[0164] Alternatively or in combination, the various plastic compositions include high carbon index polymers such as polyethylene (including LDPE, LLDPE, HDPE), polypropylene, polystyrene, elastomers, and low carbon index polymers such as polyamide, polymethyl methacrylate, polyethylene terephthalate, polyvinyl chloride, cellulose, etc.

[0165] Preferably, said substantially plastic material is characterized by an H / C index at least equal to 70, preferably between 80 and 98, more preferably between 85 and 96. Preferably, said substantially plastic material is characterized by a carbon index at least equal to 55, preferably between 65 and 95, more preferably between 75 and 90.

[0166] In certain embodiments, the substantially plastic material comprises at least one non-plastic material in an amount comprised between 0.01% and 10%, or between 0.05% and 7.5%, or between 0.2% and 5% by weight based on the weight of the substantially plastic material. The non-plastic material may comprise at least one of paper, cardboard, wood, compost (as defined by IUPAC in "Terminology for biorelated polymers and applications (IUPAC Recommendations 2012)", Pure Appl. Chem., Vol. 84, No. 2, pp. 377-410, 2012, DOI 10.1351 / PAC-REC-10-12-04), metallic materials such as aluminum and iron, and / or inert materials.

[0167] Optionally, the substantially plastic material may include an inorganic filler such as silica, titanium dioxide, talc, coke, graphite, carbon black, calcium carbonate, etc. In certain embodiments, the filler may be present in an amount of 0.01-10%, preferably 0.1-5%, based on the total weight of the substantially plastic material. In certain embodiments, the substantially plastic material has a final inorganic residue (ash) of at least 0.01%, preferably 0.1%-20%, more preferably 0.4%-12%, and even more preferably 1.1%-7%, based on the weight of the substantially plastic material, as measured according to the methods described herein.

[0168] Optionally, the substantially plastic material may contain brominated and chlorinated additives used to make the plastic material fireproof or in any case impart flame retardant properties. Examples of such additives are hexabromocyclododecane, decabromodiphenyl oxide, polybrominated diphenyl ethers, and brominated polymers such as brominated styrene-butadiene copolymers or brominated polystyrene.

[0169] Optionally, the substantially plastic material may include non-halogenated additives, such as phosphorus or nitrogen compounds, that are used to render the plastic material fire resistant or flame retardant.

[0170] Where the substantially plastic material comprises one or more of the above materials or substances, the pyrolysis process according to the present invention is not adversely affected.

[0171] "Non-constant composition" means that the composition varies between different production batches. Separately or in combination, within the same batch, the composition is not constant because of compositional variations, for example due to stratification of the material. Indeed, stratification may occur during transportation, which generally determines an increased concentration of heavier and / or smaller or powdery plastics at the bottom and an increased concentration of lighter and / or larger plastics at the top.

[0172] Apart from that, the substantially plastic materials are not uniform in composition because they are supplied by different manufacturers or suppliers, each of which may have different production specifications and / or different production processes, resulting in different products.

[0173] Preferably, the substantially plastic material is also recycled.

[0174] Preferably, the substantially plastics material also comprises from 0.01% to 10% by weight of a halogenated component, based on the weight of the substantially plastics material.

[0175] Preferably, said substantially plastic material is obtained by a process of selection (sorting) of plastic materials. More preferably, said substantially plastic material is the residual substantially plastic material, i.e. the fraction of substantially plastics remaining after recovery of some plastics, i.e. after selective extraction of some plastics from the substantially plastic material fed to the selection process. Selective extraction consists of the extraction of a substantially homogeneous material of a particular plastic (i.e. as monoplastic). Usually, in the sorting process, it is possible to extract a substantially pure plastic stream of polyethylene, polypropylene and polyethylene terephthalate components (i.e. as monoplastic). In this preferred selection, the substantially residual plastic material is therefore the material resulting after extraction of said substantially pure plastics. This fraction is known in Italy under the term "Plas Compound" or "Plasmix" and is defined as "a set of heterogeneous plastics contained in post-consumer packaging and not recovered as individual polymers" (Art. 1, Draft Law, Chamber Law No. 4502 of 18 May 2017).

[0176] This substantially plastic material may be further selected to eliminate non-recyclable materials or may be used as such. In particular, according to a preferred method, said substantially plastic material, possibly resulting from a plastic material selection (sorting) process as defined above, is pre-treated before being used in the pyrolysis step of the present invention.

[0177] This pretreatment preferably includes washing to remove at least a portion of the organic matter.

[0178] Preferably, said pretreatment also includes, alternatively or in combination, the removal of non-organic solid particulates such as ferrous materials and crushed stone.

[0179] Hydrocarbons obtained by pyrolysis that are liquid at 25°C are also called pyrolysis oils.

[0180] A preferred method of the process of the present invention According to a preferred method, said luminescent probe comprises one or more optical fibres. According to a further preferred method, said detection system optically coupled to said probe also comprises one or more optical fibres.

[0181] According to a preferred method, the luminescent probe and the detection system optically coupled to the probe are integrated into a single device having both functions.

[0182] According to a further preferred method, in said integrated device, both said luminescent probe and said detection system optically coupled to said probe are constituted by optical fibres.

[0183] In this mode, the optical fibers associated with the light-emitting probes are preferably positioned at the center of the integrated device, while the optical fibers associated with the detection system optically coupled to the probes are preferably positioned around the periphery, equally spaced along a circle passing through the center.

[0184] According to one embodiment, the device for measuring at least one property "Px" of a substantially plastic material also comprises means for measuring the temperature of the substantially plastic material.

[0185] The means for measuring the temperature may be any means known in the art, such as a thermocouple, thermal resistance ("PT100" or "PT1000"), or an infrared meter.

[0186] Advantageously, the minimum distance between the temperature reading area and the area where the reflectance spectrum is measured is less than 100 mm, preferably less than 30 mm, and even more preferably less than 3 mm.

[0187] Preferably, the means for measuring temperature is a thermocouple, and said integrated device comprising said light emitting probe and said detection system optically coupled to said probe further comprises said thermocouple.

[0188] Indeed, it has been found that the absorption spectrum detected by the detection system optically coupled to the probe for detecting reflected light depends on the temperature of the actual plastic material illuminated by the light, and that the reproducibility of the measurements is better if temperature measurement is integrated into the device.

[0189] Preferably, the substantially plastic material fed to the reactor in step a) is at least partially brought to a molten state by heating in a preheating device, which may be a single screw extruder, a twin screw extruder or an auger, which may comprise a degassing device to vent water vapour and other evolved gases, in particular hydrogen chloride (HCl).

[0190] For this purpose, it may be advantageous to supply the preheating device with additives capable of promoting the generation of hydrochloric acid or salifying it in addition to the substantially plastic material. Such additives preferably consist of elements of groups IA and IIA. More preferably, they are oxides, hydroxides, carbonates, silicates and aluminosilicates of groups IA and IIA. More preferably, they are calcium oxide, calcium hydroxide, calcium carbonate, sodium oxide, sodium hydroxide, sodium carbonate, potassium oxide, potassium hydroxide, potassium carbonate or sodium aluminosilicate.

[0191] The preheating temperature may be 120 to 430° C., preferably 150 to 320° C., more preferably 180 to 220° C. The residence time in the preheating device is preferably less than 10 minutes, more preferably less than 2 minutes, particularly preferably less than 1 minute.

[0192] Thus, according to a preferred method of the process of the invention, said substantially plastic material, at least in part in a molten state, is obtained by means of a preheating device, preferably an auger or an extruder.

[0193] The above process for the pyrolysis of substantially plastic materials to obtain hydrocarbons which are in the liquid phase at least at 25° C. can be carried out in both batch, continuous and semi-continuous modes.

[0194] In the latter mode, the substantially plastic material is continuously charged and the evolved steam is continuously extracted, but any solid residue is retained within the pyrolysis reactor. When the amount of solid residue within the reactor exceeds a certain threshold, or at preset time intervals, e.g., every 2-10 days, the material contained within the reactor is removed, followed by the removal of said solid residue.

[0195] Preferably, the reactor is operated in a continuous or semi-continuous mode, more preferably in a semi-continuous mode.

[0196] The pyrolysis process of the present invention is not limited to any particular type of reactor.

[0197] In particular, horizontal or vertical, stirred or unstirred reactors, rotating reactors (kiln reactors) or screw reactors may be used.

[0198] Among continuously stirred reactors (CSTRs), fully packed reactors can be used, as well as reactors with separate phases, including gas phase and possibly other phases such as liquid and resulting solids (char), or reactors with a free surface.

[0199] Preferably the reactor is a stirred reactor having a free surface.

[0200] According to one preferred method, the pyrolysis vapors produced by the pyrolysis reactor are then passed through at least one condensation separator to recover hydrocarbons that are in the liquid phase at least at 25°C (as defined in the present invention).

[0201] By condensation separator (separator by condensation) is meant any device that can receive a fluid in a gaseous state and remove sufficient heat from that fluid to produce at least a portion of the fluid in a liquid state.

[0202] An example of a device is a condenser that includes a coil through which a heat carrier fluid flows that can remove heat from the gaseous fluid being treated.

[0203] Other methods of removing heat can also be used, for example, alternatively or in combination, the condensation separator can be equipped with a jacket through which the above-mentioned heat transfer fluid flows, through which heat can be removed.

[0204] Advantageously, a flooding condenser can also be used, partially flooded by the liquid phase produced, whose condensing power is adjusted by varying the height of said liquid phase, since only the non-flooded coils can absorb calories from the vapors being condensed, thus effectively adjusting the power of the capacitor.

[0205] Alternatively, the condensing separator may consist of a distillation column, in which case the condensing fluid originates in a column condenser and flows back into the column by gravity or a pump, condensing the vapor therein.

[0206] The use of a distillation column type condensation separator also results in a better fractionation of the incoming vapors, i.e., between the condensed high-boiling components and the low-boiling components that remain in the vapor phase. This is because each equilibrium step allows the enrichment of the liquid phase with the heavier components and the vapor phase with the lighter components. In addition, the condensate that falls into the column scrubs the vapors in the distillation column. This ensures that any solid particles present in the incoming vapor are retained and ultimately recovered in the liquid phase.

[0207] Any technique known in the art may be used to maintain the pressure in the pyrolysis reactor at the specified value.

[0208] According to a first method, the pressure can be maintained at a specified value by regulating the heat extracted from a condensation separator located downstream of the reactor and in fluid connection with it.

[0209] According to a second method, the pressure can be regulated by means of a controllable pressure drop device placed downstream of the pyrolysis reactor and / or downstream of said at least one condensation separator.

[0210] The controllable pressure drop device may preferably be of concentrated pressure drop type, such as for example a lamination valve, or a distributed pressure drop (tube with variable cross section) or pneumatic device (such as for example a hydraulic seal).

[0211] Non-condensable gases, including auxiliary gases that may be used for pressurization, may be routed to a thermal oxidation system before being released to the atmosphere.

[0212] Advantageously, the two control systems (power regulation of the separator by condensation and regulation with a controllable pressure drop device) can be combined together.

[0213] The pressure in the reactor is preferably kept within the range of atmospheric pressure to 13 bara. More preferably, the pressure is kept within the range of 1.1 to 8 bara. Even more preferably, the pressure is kept within the range of 1.5 to 6 bara. Most preferably, the pressure is kept within the range of 1.1 to 4 bar, or 2.5 to 4 bar.

[0214] The pressure in the reactor can be measured according to any method known in the art. For example, a pressure transducer installed in the reactor can be used. Alternatively, according to a preferred method in case an inert gas such as nitrogen is used for the initial pressurization of the reactor, a pressure sensor can be advantageously placed inside the injection duct of said inert gas, more preferably towards the direction of entry into the reactor.

[0215] Advantageously, the determination of the value of a property "Px" of said substantially plastic material by means of said at least one analytical measurement "Ax" is used to set at least one parameter "Ox" of the pyrolysis process.

[0216] The at least one parameter "Ox" is preferably at least one of the following parameters: pressure of the pyrolysis reactor, temperature of the pyrolysis reactor, residence time of the substantially plastic material in the pyrolysis reactor, flow rate of the substantially plastic material in the pyrolysis reactor, and combinations of the above parameters.

[0217] A setting (a "set point") of the at least one "Ox" parameter is calculated based on determining a value of the at least one "Px" characteristic.

[0218] Said calculation may advantageously be a simple formula. If there is more than one at least one characteristic "Px", said formula for the calculation of at least one parameter "Ox" may advantageously include more than one characteristic "Px".

[0219] The regulation of the "Ox" process parameter can be performed by any means known in the art, for example by a controller capable of reading said "Ox" value, comparing it with a setpoint and acting on at least one parameter of at least one plant element (such as those already disclosed above) in order to nullify the difference between said two values. For this purpose, any process controller can be used, such as a PID controller with fuzzy logic, particle swarm optimization (PSO) or neural networks, or a combination of these, for example an integrated PID and fuzzy logic controller.

[0220] Preferably, said regulation is performed with a PID algorithm (proportional, integral, derivative) of position (Position PID) or velocity (Velocity PID) type.

[0221] Preferably, the liquid product at 25°C condensed with said pyrolysis vapours obtained according to the invention (i.e. pyrolysis oil) has a C5-C12 fraction at least equal to 35% and at the same time a C21-and-higher fraction (hereinafter referred to as "C21+") at most equal to 3.5%.

[0222] Preferably, the pyrolysis oil obtained from the process of the present invention is a mixture containing more than 90% by weight of hydrocarbons relative to the total weight of the mixture.

[0223] Preferably, the yield of C5-C12 obtained according to the present invention is at least 30% and the yield of the C21 and above fraction is at most 3%.

[0224] The applicant of the present invention has found it advantageous to define an Overall Index (hereinafter also called "OI", short for "Overall Index"), which is the Carbon Index (CI) multiplied by the H / C Index (as defined in the present invention) divided by 10000:

number

[0225] According to a preferred method of the invention, the "Ox" parameter is determined by a formula which is a function of the Overall Index (OI).

[0226] According to a particularly preferred method of the invention, the "Ox" parameter is the pyrolysis pressure, also called "Ox", which is set to a pressure at least equal to a threshold pressure PS if the result of the overall index is 0.7 or more, and to a pressure lower than said threshold pressure if the "overall index" OI is less than 0.7. Preferably, said threshold pressure PS is at least 1.5 bara, more preferably 2-2.9 bara, in particular 2.5 bara. In general, the best results can be obtained in this mode.

[0227] Indeed, by applying this criterion in Examples 1 to 11 of the present invention, a C5-C12 yield of at least 30% was obtained, with a simultaneous yield of the C21 and above fraction (C21+) equal to at most 3%.

[0228] Example of an apparatus for the procedure of the invention FIG. 7 shows a schematic diagram of an example of an apparatus for the process of the invention, comprising: - a reactor (70) for the pyrolysis of a substantially plastic material (54) producing pyrolysis vapors (52) and a solid residue (53), optionally receiving an auxiliary gaseous fluid (51) to facilitate maintaining the pressure within the reactor; a second reactor (71) for thermal or thermo-catalytic treatment of the pyrolysis vapors (52) exiting the pyrolysis reactor (70); - a first pressure control device (72), e.g. a valve, acting in feedback on the pressure value (80) measured in the pyrolysis reactor (70); - a first condenser (73) from which the condensate (60) is partially returned (55) to the pyrolysis reactor (70); - a second condenser (74) that receives the vapor (57) from the first condenser (73) and produces a second condensate (61) and vapor (58); a third condenser (75) that receives the vapor (58) from the second condenser (74) and produces a third condensate (62) and a non-condensed vapor or residual gas (59); a second device for feedback control of the pressure (76) relative to the pressure value (80) measured in the pyrolysis reactor (70), for example a valve restricting the passage of the residual gas leaving the condenser (59) before sending the residual gas (56) to a receiving unit; Shows.

[0229] Examples of pressure control according to the present invention FIG. 8 shows some examples of embodiments of pressure control according to the invention, showing a flooding type condensate separator (75) with a level sensor (LT) and a level adjustment system by adjusting the opening valve (78) of the condensate outlet (62).

[0230] The pyrolysis reactor (70) receives at its inlet the substantially plastic material (54) and optionally an auxiliary gaseous fluid (51) and produces a solid residue (53) and pyrolysis vapors that are directed to at least one condensation separator (75). An optional control valve (72) receives the pyrolysis vapors from the pyrolysis reactor (70) and directs them to the condensation separator (75). The opening control is provided by a signal (85).

[0231] The condensate separator (75) of FIG. 8 is a flooded condenser: the condensate floods the lower part of the condenser and condensation is achieved by passing a heat transfer fluid, which is cooler than the pyrolysis vapors, through a jacket or coil arranged such that the part of the jacket in contact with the vapor to be condensed varies depending on the level of the condensate (e.g. by applying a jacket to the side walls of the condenser).

[0232] An optional regulating valve (76) regulates the pressure by restricting the passage of the residual gas (59) before it is sent to the receiving unit (56).

[0233] The control valve (78) is optional and regulates the outflow of condensate (62) and therefore the flooding level of the flood condenser (75).

[0234] An optional regulating valve (77) regulates the flow rate of the auxiliary gaseous fluid entering the pyrolysis reactor (70).

[0235] The level controller (LIC) reads the flooded condenser (75) level signal (83) measured by the level sensor (LT) and feedback adjusts the opening of the valve (78) to ensure that the level (83) corresponds to the setpoint indication (86) received from the PIC controller. Note that the setpoint indication (86) is equal to 0 at 100% level (i.e., maximum flooding = minimum condensing power) and equal to 100 at 0% level (i.e., empty condenser = maximum condensing power).

[0236] The opening instruction (87) sent to the valve (76) is 0 if the valve is closed and 100 if the valve is fully open.

[0237] Since valve (77) must open to increase pressure in reactor (80) and close to decrease pressure, the position command (84) sent to valve (77) instead operates in reverse mode.

[0238] The pressure signal of the pyrolysis reactor (80) can be the result of processing multiple pressure transducers, as described below; and can be detected near the outlet to the pyrolysis reactor on the clean fluid sent to the pyrolysis reactor so that the transducer membranes are kept clean, as shown in the figure, where the pressure signal is input to the conduit sending the auxiliary gaseous fluid (51) to the pyrolysis reactor.

[0239] The pressure set point (PS) of the pyrolysis reactor can be local, for example by setting a value on the plant's control panel, or can be given manually, for example by setting a value on the plant's control panel, or can be set from an external setting signal.

[0240] The external signal may be a calculated set point (81) based on one or more parameters read on the substantially plastic material arriving at the pyrolysis reactor (54). For example, the pressure set point may be a formula whose variables are the H / C index and the carbon index of the substantially plastic material as measured by an analyzer either in line or off line (AT INPUT).

[0241] A pressure control device (PIC) reads said pressure signal (80), compares it with a set point (PS) and acts on one of the regulating devices (84, 85, 86, 87) individually or in combination, for example using a PID algorithm (Proportional, Integral, Derivative) in feedback, to minimize the error between the read signal (80) and the set point (PS). An example of said combined embodiment is obtained by using regulating devices (86) and (87) in a split range mode.

[0242] Gas chromatographic analysis of pyrolysis oil samples. The pyrolysis oil samples were characterized by gas chromatographic analysis. Qualitative identification of compounds was preliminarily performed by coupled gas chromatography-mass spectrometry (GC-MS) method, and quantitative identification of compounds was performed by gas chromatography with flame ionization detector (GC-FID).

[0243] The following are the instrumental parameters adopted for the GC-FID analysis: - GC: Agilent HP 7890 B equipped with MPS Gerstel autosampler -Column: HP-PONA Agilent Technologies J&W - 50m - 0.2mm - 0.5μm, -Carrier (H2): 1.1mL / min constant flow -Injector: 320℃, 255:1 split, 3mm liner with glass wool (Ultra Inert) -Detector: 360℃ -Oven: Column temperature program: 20°C 5 min, 2°C / min to 70°C 5 min, 160°C 5 min at 2°C / min, 320°C 30 min at 2°C / min (run time: 195 min).

[0244] Samples are analyzed as such by imputing arbitrary response factors equal to 1 for all compounds; resulting concentrations are normalized to 100%.

[0245] Gas chromatographic analysis of wax samples. Wax refers to the bottom fraction after ultracentrifugation of the pyrolysis oil, as described below, which is analyzed by various methods that allow the identification of high molecular weight compounds.

[0246] In fact, these compounds may not be eluted and analyzed in the gas chromatographic analysis.

[0247] Prior to taking samples for GPC analysis, pyrolysis oil in a Schott bottle was heated to 50°C and the contents homogenized (precipitation and / or stratification of waxy compounds may be observed at room temperature or in the cooled state). A few milligrams of sample in 1,2,4-trichlorobenzene (Baker) was mixed with 10 μL of n-heptane (internal marker) and dissolved by heating (dissolved at 150°C for 1 h) to obtain a concentration of approximately 1.8 mg / mL.

[0248] The analyses were carried out on the following chromatographic equipment: -High temperature GPC-IR polymer characterization - Three TSK gel HT2 columns (13 μm) and a bench with a precolumn - A high temperature infrared detector IR5 that provides an absorbance signal proportional to the amount of methyl and methylene groups.

[0249] The experimental conditions employed were as follows: -Eluent: 1, 2, 4 TCB stabilized with BHT -Flow: 1mL / min -Temperature: Pump 25℃, injector 150℃, column 150℃, detector 150℃ -Injection volume: 200 microliters -Internal standard: n-heptane

[0250] Gas chromatographic analysis of pyrolysis gases. Pyrolysis gas effluent samples were sampled in 500 mL Swagelok cylinders, DOT type (i.e., regulated by the U.S. Department of Transportation-DOT), made of 304L stainless steel with an inner PTFE coating to render the inner surface inert. The instrument used was an Agilent 490μ GC with three modules in parallel, each module determining only a specific class of compounds. In particular: - Module 1: 10m MS 5Å with heated injector and backflush - Module 2: 10m PPQ with unheated injector - Module 3: 10m CpSil-5CB with heated injector.

[0251] Below are the device parameters adopted for the various modules: -Module 1: Injector temperature: 110°C, Backflush: 30 s, Injection time: 100 ms, Column temperature: 45°C, Carrier gas pressure: 80 kPa, Carrier gas: Argon (required for hydrogen analysis). Module 2: injection time: 15 ms, column temperature: 70°C, carrier gas pressure: 180 kPa, carrier gas: helium. - Module 3: injector temperature: 110 °C, injection time: 20 ms, column temperature: 70 °C, carrier gas pressure: 230 kPa, carrier gas: helium: 70 °C, carrier gas pressure: 230 kPa, carrier gas: helium.

[0252] Each module analyzes only a few specific compounds: -Module 1: Hydrogen, Oxygen, Nitrogen, Methane, CO. -Module 2: CO2, ethylene, ethane, propylene, propane, propadiene, propyne, i-butane, i-butene, 1-butene, 1,3-butadiene, n-butane, trans-2-butene, cis-2-butene. - Module 3: 1-butene-3-yno, 1,2-butadiene, i-pentane, 1,4-pentadiene, 1-pentene, n-pentane, 2-methyl-2-butene, 1,3-pentadiene, cyclopentene, n-hexane, methyl-1,3-cyclopentadiene, benzene, 3-ethylcyclopentene, methylcyclohexane, toluene, ethylbenzene, xylene.

[0253] Quantification is performed by means of an external standard calibration line consisting of two calibration cylinders of the following composition: -Tank 1: Pentene-2(trans)=0.1%mol; Pentene-2(cis)=0.1%mol; Pentene-1=0.1%mol; Pentane-n=0.25%mol; Methyl-2-butene-2=0.2%mol; Iso-pentane=0.5%mol; Hexane-n=0.1%mol; Propylene=20%mol; Propane=0.5%mol; Propadiene=0.5%mol; Methane=20%mol; Iso-butene=1%mol; Iso-butane=0.5%mol; Hydrogen=15%mol; Ethylene=30%mol; Ethane=3%mol; Carbon monoxide=1%mol; Carbon dioxide=0.5%mol; Butene-1=1%mol; Butene-2(trans)=0.5%mol; Butene-2(cis)=0.5%mol; Butane-n=0.5%mol; Butadiene-1.3=1.5% mol; Acetylene=0.5% mol; Complement to 100%: Nitrogen. Cylinder volume [liters]: 40; Filling pressure [bar]: 6.29; Cylinder type: Aluminum.

[0254] -Tank 2: Benzene = 0.0302%mol; Toluene = 0.0323%mol; Methylcyclohexane = 0.0674%mol; Styrene = 0.0334%mol; Ethylbenzene = 0.0339%mol; Complement to 100%: Helium. Cylinder volume [liters]: 5; Filling pressure [bar]: 13.9; Cylinder type: Aluminum.

[0255] The following compounds were not present in the calibration cylinders, therefore calibration curves of similar enough compounds with very similar response factors (the difference in this case is negligible) were used: [Table 1]

[0256] Methods for Thermogravimetric Analysis (TGA) of Solid Residues (Chars) TGA analysis was performed on a TA Instrument model Q500 instrument. Temperature calibration was performed using the Curie points of Alumel and Nickel samples, and weight calibration was performed using certified weights supplied by TA Instruments with the analyzer. Samples weighed out at 20-30 mg on a stainless steel sample holder were placed on the platinum crucible of the TGA analyzer along with the sample holder. The use of the stainless steel sample holder facilitates separation and recovery of the final residue (ash) while preserving the integrity of the platinum crucible. Samples are analyzed in three steps: - First step (pyrolysis under nitrogen atmosphere): Starting from an initial temperature of 40°C, the sample is heated at a controlled rate (v=10°C / min) up to 800°C. - Second step (cooling under nitrogen atmosphere): starting from an initial temperature of 800°C, cooling at a controlled rate (v=20°C / min) to 400°C. - Third step (thermal oxidation under air atmosphere): Starting from 400 °C, the sample obtained from pyrolysis (first step) is heated at a controlled rate (v = 20 °C / min) up to 850 °C.

[0257] Integration was performed using Universal software (TA Instrument) and the results were as follows: - Step 1: The temperature corresponding to the maximum peak of the derivative of the weight loss versus temperature and the residue at 800°C are determined, and then the weight loss at various temperatures is measured. - STEP 3: After determining the temperature corresponding to the maximum peak of the derivative of the weight loss with respect to temperature and the residue at 850°C, the weight loss at various temperatures is measured. In STEP 3, the weight loss corresponds to one or more carbon species with different allotropic states or grain sizes.

[0258] Some illustrative, but non-limiting examples of the present invention are given below.

[0259] Working Example raw materials It was deemed appropriate to use samples of both substantially recycled plastic material and virgin raw materials (i.e. synthetic, not recycled). The substantially recycled plastic material used is Plasmix, which is a heterogeneous collection of plastics contained after consumer packaging and which were not recovered as individual polymers in the pre-treatment plants of the plastics recycling plants. In particular, four Plasmix samples with different H / C and carbon indices were selected.

[0260] Virgin feedstocks with known and constant composition were also used to facilitate experimental reproducibility.Furthermore, recycled and virgin feedstocks were combined to increase the range of H / C ratios and carbon indices used, broadening the base of polymer blends evaluated.

[0261] The virgin materials used were as follows: [Table 2]

[0262] The polyethylene granules were mixed with 5.7% HDPE Eraclene® BC82, 34.3% LLDPE Flexirene® CL10 and 60% Riblene® FC20, therefore this mixture is the "PE" material used later.

[0263] The table below shows the atomic composition (weight percent) of the materials used.

[0264] [Table 3]

[0265] The following compounds were prepared using the virgin raw materials (parts by weight) listed: [Table 4]

[0266] Based on the carbon and hydrogen atom contents of the raw materials used (shown in the previous table), the carbon index and hydrogen / carbon ratio (H / C index) were calculated according to the formulas shown above.

[0267] Thus, the following H / C index and Carbon index values ​​can be calculated for the five PAT1, PAT2, PAT3, PAT4 and PAT5 compounds used: [Table 5]

[0268] The above H / C ratios and carbon indices were also calculated for the Plasmix recycled plastics B01, B02, B03 and B04 used in the experiment: [Table 6]

[0269] Analyzing the two tables, it can be seen that PAT1 and PAT2 are compounds characterized by high H / C index, PAT3 and PAT4 by low H / C index, PAT1 and PAT3 have high carbon index (both 86), and PAT2 and PAT4 have low carbon index (both 76).

[0270] In this way, the behavior of the pyrolyzed material can be analyzed with respect to two variables: H / C index and carbon index.

[0271] In addition, two of the recycled materials (B01, B02) are characterized by a high H / C index, while the other two (B01, B03) are characterized by a high carbon index.

[0272] The PAT5 compound is the average composition of the previous four compounds (PAT1, PAT2, PAT3 and PAT4) and was used for model and experimental validation.

[0273] Compounds used for calibration and validation The following table shows the compositions of the compounds prepared and used to generate and verify the calibration curve.

[0274] In the table, the "Compound" column indicates the compound name and "Bas" indicates the base used. The percentages are calculated only on the base weight used, not on the total weight of the compound. For example, "M03" compound is made of B01+4%LDPE, i.e. a compound containing 100 parts B01 and 4 parts LDPE.

[0275] [Table 7] [Table 8]

[0276] The equipment and process conditions used to determine the calibration curve and subsequently used to feed the pyrolysis reactor The device of the present disclosure consists of a ZSK 26 co-rotating twin screw extruder with a ratio of the length L of the screw to the diameter D equal to L / D=32. The extruder is equipped with: - Feeding section with a hopper and a screw profile with conveying elements; - Melting and mixing section, where kneading and mixing elements are used, plus left profile elements to ensure filling; - degassing section for suctioning the evolved gases, where the pressure of the polymer melt is reduced by reducing the diameter of the screw core, an opening is made in the cylinder connected to a vacuum pump; -Pressure section with increased screw core diameter.

[0277] The extruder is equipped with a heating and cooling control system to regulate the temperature of the barrel in each section of the extruder.

[0278] The extruder outlet is connected to a hollow duct of the type shown in Figure 1, to which an integrated device is connected, containing both the light emission probe and the optically coupled detection system described above. The integrated device used for this purpose is a titanium reflection probe with sapphire windows and optical fibres (seven 400 micrometres and seven 600 micrometres), both for the light emission probe (centre) and for the optically coupled detection system (periphery). The integrated device is a 12800-4000 cm-spectral range detector with an InGaAs detector. -1 , with a resolution of 2cm -1 The spectrometer used was a Bruker Matrix-F, connected to a Fourier transform spectrometer (FTIR) with an industrial PC and Modbus interface for communication with the distributed control system (DCS) of the pyrolysis plant.

[0279] The hollow duct also includes a temperature transducer for measuring the temperature of the substantially plastic material, extending into the interior of the duct across approximately one-third of the inside diameter of the duct, and a pressure transducer.

[0280] The outlet of the hollow conduit is connected to an orifice intended to ensure that the required pressure is maintained within the hollow conduit.

[0281] The extruder is fed into a hopper by three gravimetric feeders.

[0282] During the tests carried out to generate the calibration curve, and in those instances where the compound is fed in batches, the melt of the substantially plastic material is passed through a die, then through a water and granulate bath, whereas in the continuous pyrolysis tests, the melt of the substantially plastic material is fed into a pyrolysis reactor.

[0283] The extruder screw speed was kept high enough to ensure that the extruder hopper remained empty.

[0284] Tests for creating a calibration curve For each sample material, tests were carried out at four different temperatures (170, 190, 210 and 230 °C, reduced compared to the intervals used in the spectra shown in Figure 6) and three different flow rates (corresponding to the average velocity in the duct, calculated as the volumetric flow rate relative to the area of ​​the hollow duct, equal to 1, 1.5 and 2 mm / s). The pressure measured in the hollow duct near the measurement point of the spectrum varied depending on the test and the sample material, but was always between 5 and 200 bara.

[0285] Additionally, 10 spectra were acquired for each condition, for a total of 120 spectra for each sample material.

[0286] Determination of "Cx" calibration curve The calibration curve was determined according to the "rolling" mode described above, selecting seven sample materials for verification and 51-7=44 sample materials as calibration samples for multivariate regression. In the second round, seven other sample materials (different from the first round) were selected for verification, and the remaining samples were selected as calibration samples for multivariate regression. This was done in a total of six laps. The seventh and final round was also done in a similar manner, except that the remaining 51-7×6=9 sample materials not yet used for verification were used for verification, and the remaining 42 were calibration samples for multivariate regression.

[0287] Therefore, we used the implicit mode in which process variables such as temperature, pressure, and speed act implicitly in the model rather than as additional parameters.

[0288] Multivariate regression with partial least squares (PLS) was applied.

[0289] The final calibration curve uses a load value given by the average value of the loads specified according to the rotational modes above.

[0290] Choosing the number of components The number of PLS ​​components used in the model was evaluated.

[0291] A small number of components reduces the accuracy of the model, while too many components creates the risk of overfitting, reducing the model's extrapolation and interpolation capabilities.

[0292] Figure 3 shows the results, showing that the mean squared error in the prediction drops to very low values ​​already when using the first five components (NC=5).

[0293] We chose to use the calibration curve containing the first 11 components (NC = 11) considering that for NC = 11, the prediction error was very close to the minimum.

[0294] Prediction accuracy of "Cx" calibration curve Figures 4 and 5 show the H / C index and carbon index calculated using the calibration curves, respectively, compared to the "true" H / C values, i.e., values ​​determined based on primary analysis. The predictive capabilities of the method disclosed in this invention, and the remarkable accuracy of said predictions, are evident from these figures.

[0295] Pyrolysis apparatus used in the pyrolysis examples (Apparatus 1) The pyrolysis apparatus used in the pyrolysis examples of the present invention consisted of: - a thermostatic reactor equipped with flanges for the material input, a dip tube for the inlet of an inert gas (nitrogen), a nozzle connectable to an extruder for inputting the substantially plastic material, a nozzle for discharging steam and a nozzle for each thermocouple for measuring the temperature and the measured pressure, and two nozzles for level measurement; - the stirring system of the reactor, equipped with an anchor-type agitator with a breakwater and a low rotation speed (tip speed of about 0.1 m / s); - A flow rate meter equipped with a fine adjustment valve for regulating the inert gas flow rate into the reactor; - a pressure transducer installed at the head of the reactor and a local pressure gauge reading the pressure of the gas in the reactor; - 3 thermocouples for measuring the actual temperature placed at the bottom of the reactor; - A reactor temperature regulation system that reads the temperature value of one of three thermocouples and feeds it back to a thermostat system, where its control parameters are properly calibrated to ensure high thermal stability (low temperature fluctuations at 5°C); -Level indicator using a differential pressure sensor that reads the static pressure head in the reactor (the difference between the pressure at the head and bottom of the reactor); - a condenser for condensing the vapours leaving the reactor, kept at -10°C by a refrigerant flowing through a temperature-controlled refrigeration unit; - a valve interposed between the reactor and the condenser for regulating the flow of gas leaving the reactor; - A reactor pressure regulation system that reads the pressure value of said pressure transducer and feeds it back to said control valve to ensure high pressure stability (pressure oscillations less than 50mBar). an expansion flask, gas-tightly connected to the upper outlet of the condenser and designed to recover the non-condensed gaseous fraction; a receiving vessel, hermetically connected to the lower output of said condenser and having a vent connected to the upper output of said condenser, and designed to collect the condensed liquid fraction; -Valve to shut off the incoming nitrogen; - a valve that blocks the liquid product leaving the condenser before the gas-tight connection with the receiving vessel; - a valve blocking the gaseous products leaving the condenser before the gas-tight connection with the expansion flask; - an apparatus for feeding a substantially plastic material, at least partially in a molten state, to a pyrolysis reactor, comprising a system for measuring and analyzing the spectrum of said plastic material; a gravimetric feeder for feeding the granulated polymer mixture into the hopper of said twin-screw extruder and for feeding the granulated polymer mixture into a reactor;

[0296] Preparation of granulated polymer blends Compounds (PAT1, PAT2, PAT3, PAT4, PAT5) were prepared according to the provided composition tables. For example, the following materials: 42 parts of Riblene® FC20 from Versalis, a type low-density polyethylene (LDPE); 24 parts of Flexirene® CL10 from Versalis, a type linear low density polyethylene (LLDPE); - 4 parts of Eraclene® BC82 from Versalis, type high density polyethylene (HDPE) 30 parts of ISPLEN® PP040 from Repsol, of the polypropylene (PP) type, A "PAT1" compound was prepared containing:

[0297] The compounds thus prepared were melted at 250°C in a Coperion ZSK26 twin screw extruder, mixed using mixing elements in the extruder screw and passed through a die. The total residence time in the extruder was less than 1 minute. The polymer mixture thus obtained was cooled in a liquid bath and granulated into granules with a diameter and length of about 3 mm. In this way, granular polymer compounds PAT1, PAT2, PAT3, PAT4 and PAT5 were produced.

[0298] Pyrolysis Examples 1 to 8 (Comparative and Inventive) Examples 1-8 were prepared using granular polymer at the pressures shown in the table below: [Table 9]

[0299] The reactor of "Apparatus 1" described above was loaded with the above granular polymer mixture at room temperature until it reached 1 / 3 of the geometric volume of the reactor. The nozzle through which the molten polymer could enter from the extruder was not used and was plugged.

[0300] The valve regulating the flow rate of gas exiting the reactor was manually set to full open.

[0301] Thereafter, the fine adjustment valve of the flow rate meter was fully opened and nitrogen was injected from below through the dip tube.

[0302] Thereafter, the gas contained in the reactor was removed over a period of 24 hours to ensure the removal of oxygen.

[0303] The valves for the gas and liquid product outlets from the condenser were then closed. Immediately afterwards, the nitrogen supply was interrupted. An expansion flask was then connected to collect the evolved gas and a receiving vessel was then connected to collect the evolved liquid.

[0304] The valves for the gas and liquid product outlets from the condenser were then reopened.

[0305] The valve regulating the flow rate of gas exiting the reactor was set to autoregulate to a value selected for the test (in this example, 0 barg = 1 bara).

[0306] Nitrogen was then injected from below through the dip tube at a low flow rate selected so that the amount of nitrogen recovered in the expansion flask before replacement did not exceed 30% of the maximum volume of the flask.

[0307] Hereinafter, the above-described mode for realizing the first to eighth embodiments will be defined as "setup A1."

[0308] The reactor temperature control system was turned on and the following program was set: 1. Initial heating ramp is 4 degrees per minute until 380°C is reached; 2. Maintain 380℃ for 3 hours; 3. The second heating rate is 2 degrees per minute until it reaches 430°C; 4. Maintain 430℃ for 3 hours; 5. The third heating rate is 2 degrees per minute until 480°C is reached; 6. Maintain 480℃ for 3 hours; 7. Turn off the heat.

[0309] Hereinafter, the above temperature versus time profile will be referred to as the "T1 profile."

[0310] cleaning Twelve hours after the end of the program, the reactor temperature was verified to be below 60° C., the nitrogen supply was interrupted, the valves to shut off the liquid and gaseous products leaving the condenser were closed, and the reactor flange was opened.

[0311] The inside of the reactor was thoroughly cleaned to remove all dirt and deposits from parts that come into contact with the liquids and gases generated inside the reactor.

[0312] analysis The bottom of the reactor was then completely cleared of solid material and weighed, and the liquid receiver and expansion flask were removed.

[0313] The liquid contained in the liquid receiving vessel was weighed and ultracentrifuged (ThermoScientific Ultracentrifuge Model Sorvall Evolution RC) at 25000 RPM for 45 minutes.

[0314] After ultracentrifugation, the fraction remaining at the bottom (hereinafter referred to as the wax fraction) and the supernatant (hereinafter referred to as the oil fraction) were separated and weighed.

[0315] The oil percentage was calculated by dividing the weight of the resulting oil fraction by the weight of the material initially charged to the reactor.

[0316] The wax percentage was calculated by dividing the weight of the resulting wax fraction by the weight of the materials initially charged to the reactor.

[0317] The percentage of carbon residue (char) was calculated by dividing the weight of the resulting solid fraction by the weight of the material initially charged to the reactor.

[0318] The mass of gas evolved was calculated as the difference between the weight of the material initially charged to the reactor and the sum of the weights of the wax fraction, carbon residue (char) and oil. The gas fraction produced was calculated by dividing the mass of the gaseous fraction thus calculated by the weight of the material initially charged to the reactor.

[0319] The obtained fractions were analyzed by the above-mentioned method, and approximately 130 compounds were identified.

[0320] For each of these compounds, the atomic mass fraction was calculated from the number of atoms of each element and the atomic weight of each atom.

[0321] "C5-C12 yield" means the sum of the masses of compounds having 5 to 12 carbon atoms (inclusive) in the evaporated pyrolysis product relative to the total mass fed. Similarly, "C21+ yield" means the sum of the masses of compounds having at least 21 carbon atoms in the evaporated pyrolysis product relative to the total mass fed.

[0322] "C5-C12 fraction" refers to the sum of the masses of compounds having 5 to 12 carbon atoms (inclusive) contained in the product relative to the total mass of the product. Similarly, "C21+ fraction" refers to the sum of the masses of compounds having at least 21 carbon atoms contained in the product relative to the total mass of the product.

[0323] Thus, vaporized pyrolysis products means the sum of the gas, oil and wax fractions, and does not include residual solids (char).

[0324] For this purpose, gas chromatographic analyses were carried out separately for the gas, oil and wax fractions, and the yield of a given compound "C" was then calculated according to the following formula:

number

number

[0325] The following table summarizes the pyrolysis conditions for the patent examples and comparative examples 1-8: [Table 10]

[0326] Examples of pyrolysis from 9 to 11 Examples 9, 10 and 11 were carried out under the same setup and temperature profile conditions (setup A1 and temperature profile T1) as in Examples 1 to 8. The pressure was 3 bara. In practice, the aim was to evaluate the reproducibility, i.e. the reliability, of the results obtained, and it was decided to repeat the center point three times, as is often done in design of experiments (DOE).

[0327] The compound used for all three examples was PAT5, which has the average composition of compounds PAT1, PAT2, PAT3 and PAT4 as previously reported. The blends were extruded to form granular polymers similar to Examples 1-8.

[0328] Pyrolysis Examples 12-13 (Comparative and Inventive) The examples according to the invention and comparative examples 1 and 2 (PAT1 polymer blend, pyrolysis pressures 1 and 5 bara) were repeated using the different thermal profiles described here.

[0329] The following program was set on the reactor temperature control system: 1. Heat at 4°C per minute until it reaches 430°C; 2. Maintain 430℃ for 6 hours; 3. Turn off the heat.

[0330] Therefore, the difference from the previous examples is that the pyrolysis treatment time was shortened from 9 hours to 6 hours (plus the temperature rise time), and the temperature in the intermediate stage was set to 430° C. as the treatment temperature.

[0331] The modified temperature profile is hereafter referred to as "Profile T2". The graph in Figure 9 illustrates the difference. Examples 12 and 13 were carried out using the PAT1 polymer blend. The set pressure was atmospheric in Example 12 and 5 bar in Example 13.

[0332] Example 14 This example concerns a pyrolysis plant operated in semi-continuous mode and follows the "A2" set-up detailed below: The nozzle of "Apparatus 1" through which the polymer could enter from the extruder was opened and connected to the device for feeding the substantially plastic material, at least partially in a molten state, to the pyrolysis reactor described above. The PAT2 granular polymer blend was not initially charged to the reactor, as was done in the previous examples 1-13. Instead, the PAT2 granular polymer blend was fed to the hopper of a gravimetric feeder feeding the extruder. The speed of the extruder screw was adjusted so that the extruder hopper was empty ("empty screw"). The flow rate of the gravimetric feeder was adjusted so that the reactor level, maintained at 430°C, was 40% of the total reactor volume. The volumetric flow rate of the polymer leaving the extruder was calculated by dividing the mass flow rate set on the dispenser by the density of the molten polymer. Before starting the feeding of the substantially plastic material, the atmosphere of the pyrolysis reactor was filled by introducing nitrogen as an inert gas, as was done in the previous examples. The valves regulating the flow of gas leaving the reactor were set to automatic adjustment to the value selected for the test, as was already done in the previous examples. The reaction and regulation were allowed to stabilize for 6 hours, during which the nitrogen inlet was closed. After the stabilization period, the residence time was measured and calculated by dividing the flow rate by the density of the substantially plastic material fed in the molten state and the volume used in the reactor (40% of the total, as mentioned above), and was equal to about 6.3 hours. Unlike the batch-type examples, the tests were carried out in succession without opening the reactor between one and the next, so that it is not possible to evaluate the mass of the solid residue until the end of the test. The mass of the non-condensed vapors was therefore evaluated based on the volume of the expansion flask and the density of the gas calculated based on the compositional analysis of the gas present therein. The mass of the residual solids in the reactor was then calculated by the difference between the mass of the substantially plastic material fed and the sum of the mass of the recovered pyrolysis oil and the mass of the gas, and was thus evaluated as follows:

number

[0333] Example 14 was carried out using the "PAT2" compound as the substantially plastic material at the pressures shown in the table for an additional 2 hours after the initial stabilization period (with the same compound), with pyrolysis products collected as in the previous examples.

[0334] result The following table shows the C5-C12 yield, the C21+ yield and the achieved overall quality of the product ("+" if C5-C12 yield ≥ 30% and C21+ ≤ 3%) as a function of the H / C index, the carbon index and the overall index OI (given by the product of the H / C index divided by the carbon index by 10000): [Table 11] [Table 12]

[0335] Discussion of results One of the aims of the present invention is to solve the significant problems associated with the pyrolysis of substantially plastic materials of widely differing composition while maintaining high quality of the pyrolysis products.

[0336] Therefore, PAT1, PAT2, PAT3 and PAT4 compounds were selected to evaluate the optimal pyrolysis conditions when the incoming raw materials underwent significant changes: - PAT1 is made exclusively of vinyl polymers (polythene and polypropylene); -PAT2 contains a large amount of cellulose (20.2%) -PAT3 contains a large amount of polystyrene (27%) -PAT4 has a high content of polyethylene terephthalate (PET) (26.5%).

[0337] The experiments carried out show that for every available raw material composition, there are no optimal process conditions with respect to the above objectives of the present invention.

[0338] It is clear that pyrolysis at pressures higher than atmospheric pressure is highly advantageous, especially when the H / C and carbon indices are high: in Example 2 carried out at 5 bara, the yield of C5-C12 almost doubled, and the yield of the undesirable C21 and higher fractions (C21+) also dropped sharply from 3.7% to 0.24%, compared to Example 1 (comparative example) carried out at atmospheric pressure.

[0339] Comparative Examples 3 and 4 according to the invention show the effect of pressure when using a feedstock with a similar H / C index as Examples 1 and 2, but with a reduced carbon index (from 86 to 76). Also in this case, there is a significant, even diminished, advantage to pyrolysis at high pressure (C5-C12 yield goes from 34% to 49%, while C21+ yield drops from 22.3% to 2.1%).

[0340] Comparative Examples 5 and 6 according to the invention show the effect of pressure when using a feedstock with a carbon index substantially equal to that of Examples 1 and 2 (86 in both cases) but with a significantly reduced H / C index (from 100 to 83). Also in this case, there is a significant, even diminished, advantage to carrying out pyrolysis at high pressure (C5-C12 yield goes from 47% to 58%, while C21+ yield drops from 3.8% to 0.7%).

[0341] Comparative Examples 7 and 8 according to the invention show the effect of pressure when using a feedstock with a carbon index substantially equal to the low value used in Examples 3 and 4 (77, very close to the value of 76 in Examples 3 and 4) and a H / C index substantially equal to the low value used in Examples 5 and 6 (both 83). Surprisingly, in this case there was no advantage to increasing the pyrolysis pressure: in fact the C5-C12 yield remained substantially constant (if not decreased from 33% to 32%). However, the large increase in the C21+ yield from 2.9% to more than 10% is very significant. It is therefore clear that some feedstock mixtures are advantageous to operate at high pressure, while others are advantageous not to operate at high pressure.

[0342] Furthermore, with regard to the preferred objective of obtaining a C5-C12 yield of at least 30%, and even more preferably at least 40%, with a simultaneous C21 or higher yield (C21+) of at most 3%, it is clear that the use of a high pressure system makes it possible to achieve this objective only under certain conditions (PAT1, PAT2, PAT3), while under other conditions (PAT4) it is advantageous to keep the system at low pressure.

[0343] This evidence, discovered for the first time by the applicant, gives rise to the opportunity to adapt the process conditions depending on the composition of the substantially plastic material fed. As previously mentioned, since this compound can vary during the process (especially when carried out in semi-continuous or continuous mode), the process of the invention advantageously allows to adjust the pressure during the pyrolysis stage, thus maximizing the results even if the raw materials entering the pyrolysis vary; preferably, the process of the invention also allows, by varying the pyrolysis pressure, to achieve the preferred objective of obtaining a C5-C12 yield of at least 30%, more preferably at least 40%, and at the same time a C21+ yield (C21+) equal to at most 3%.

[0344] It should be noted that, in comparison with the more preferred mode of carrying out the thermal cracking process at a pressure at least equal to the threshold pressure PS when the overall index, equal to the CI index multiplied by the H / C index divided by 10,000, is equal to or greater than 0.7, and at a pressure lower than said threshold pressure PS when the overall index is less than 0.7, the use of this criterion makes it possible to produce a product which maximizes the C5 fraction minus C12 and minimizes the C21+ yield over time, especially at the above pressure values ​​of 2.0 to 2.9 bara.

[0345] Indeed, application of this criterion in the examples of patents 1 to 11 resulted in a C5-C12 yield of at least 30%, while at the same time a C21 or higher (C21+) yield of at most 3% was obtained.

[0346] Furthermore, the C21+ fraction in the obtained pyrolysis oil was not more than 3.5%, and the C5-C12 fraction in the pyrolysis oil was at least 35%.

[0347] The process of the present invention has proven to be highly reproducible, as shown in Examples 9-11.

[0348] Examples 12 and 13 also show that different thermal profiles can be used to obtain similar results, which may be consistent with the teachings of the present invention.

[0349] Surprisingly, the process of the present invention allows the pyrolysis of substantially plastic materials, including those with very low polymer / carbon content, carbon index even lower than 80, and high oxygen content, particularly substantially plastics containing more than 20% cellulose, with high yields of C5-C12 and low yields of C21 and higher fractions, both in batch mode (Example 4) and semi-continuously (Example 14), without showing any control or fouling problems.< / frac> < / frac>

Claims

1. 1. A process for the pyrolysis of substantially plastic materials to obtain hydrocarbons that are in a liquid phase at least at 25° C., comprising the steps of: a) providing a substantially plastic material in an at least partially molten state to a pyrolysis reactor; b) subjecting said at least partially molten substantially plastic material fed to the pyrolysis reactor to at least one analytical measurement "Ax" in in-line mode; c) determining the value of at least one property "Px" of said substantially plastic material by correlation of said at least one analytical measurement "Ax" with at least one calibration curve "Cx" obtained from sample materials having known values ​​of property "Px"; d) setting at least one "Ox" parameter of a pyrolysis process based on the value of said at least one "Px" characteristic; Including, said at least one analytical measurement "Ax" provides or consists of a measurement of the optical reflectance spectrum of a substantially plastic material at least partially in a molten state; and The at least one property "Px" of the substantially plastic material is an H / C index and / or a carbon index, and the carbon index and hydrogen / carbon ratio (H / C index) satisfy the following formula: [Equation 1] wherein the atomic weight is the atomic weight present in substantially the entire plastic material. A pyrolysis process, characterized in that the temperature is calculated according to

2. 2. The pyrolysis process of substantially plastic materials according to claim 1, wherein the waiting time between said at least one analytical measurement "Ax" and the setting of at least one parameter "Ox" of said pyrolysis process is equal to or less than 1 hour, or equal to or less than 10 minutes, or between 1 and 60 seconds.

3. 2. The process for pyrolysis of a substantially plastic material of claim 1, wherein said determining the value of at least one property "Px" of said substantially plastic material is performed by correlation of said analytical measurement "Ax" with an analytical measurement obtained by obtaining a plurality of model absorbances of plastic materials having known values ​​of said at least one property "Px".

4. 2. The process for the pyrolysis of substantially plastic materials of claim 1, wherein at least one parameter "Ox" of the pyrolysis process is selected from the pressure of the pyrolysis reactor, the temperature of the pyrolysis reactor, the flow rate of the substantially plastic material fed to the pyrolysis reactor, the residence time of the substantially plastic material in the pyrolysis reactor, and combinations of said parameters.

5. 5. The pyrolysis process of substantially plastic materials according to claim 4, wherein at least one parameter "Ox" of the pyrolysis process is the pressure of the pyrolysis reactor.

6. At least one parameter "Ox" of the pyrolysis process is expressed by the following formula: [Equation 2] where C.I. is the carbon index and H / C idx is the H / C index.

4. The process of claim 3, wherein the thermal decomposition of substantially plastic materials is determined by a formula which is a function of an overall index (O.I.) defined as:

7. 7. A process for the pyrolysis of substantially plastic materials according to claim 6, wherein the pressure is set to at least a threshold pressure PS if the "Overall Index" (O.I.) is 0.7 or greater, and wherein the pressure is set below the threshold pressure PS if the "Overall Index" (O.I.) is less than 0.7, wherein preferably the threshold pressure PS is at least 1.5 bar, more preferably 2-2.9 bara, in particular 2.5 bara.

8. 1. A method for determining the value of at least one property "Px" of a substantially plastic material, comprising the steps of: i) calculating, for each of said at least one property "Px", a calibration curve "Cx" correlating reflectance spectra with said property "Px" for sample materials having known values ​​of said property "Px"; ii) performing at least one measurement "Ax" of the reflectance spectrum of said substantially plastic material; iii) determining the value of said at least one property "Px" of said substantially plastic material by correlation of said at least one measurement "Ax" with said at least one calibration curve "Cx"; Including, The substantially plastic material is in a molten state at least 60 wt %, or 70 wt % to 99 wt %, or 80 wt % to 94 wt %, based on the total weight of the substantially plastic material, under reflectance spectrum measurement conditions; and The at least one property "Px" of the substantially plastic material is an H / C index and / or a carbon index, and the carbon index and hydrogen / carbon ratio (H / C index) satisfy the following formula: [Equation 3] wherein the atomic weight is the atomic weight present in substantially the entire plastic material. The method is characterized in that the calculation is performed according to the following formula:

9. 9. A method for determining the value of at least one property "Px" according to claim 8, wherein the substantially plastic material has a temperature of 140°C to 300°C, or 160°C to 260°C under the conditions for measuring the reflectance spectrum.

10. 9. A method for determining the value of at least one property "Px" according to claim 8, wherein the substantially plastic material has a pressure of 2 bar or more, or 3 to 300 bara, under the conditions for measuring the reflectance spectrum.

11. 9. The method for determining the value of at least one characteristic "Px" according to claim 8, wherein the at least one characteristic "Px" is at least two.

12. The reflectance spectrum of the substantially plastic material obtained in step ii) is －１ , 4500~10000cm －１ , or 5000 to 9000 cm －１ 9. The method of claim 8, wherein the value of at least one characteristic "Px" is in the range:

13. 9. A method for determining the value of at least one property "Px" according to claim 8, wherein the calibration curve "Cx" is obtained by applying a multivariate regression method.

14. 14. The method for determining the value of at least one property "Px" according to claim 13, wherein the multivariate regression is selected from the group consisting of multiple linear regression (MLR), regression by principal component analysis (PCR), and regression by partial least squares (PLS).

15. 15. The method of claim 14, wherein the multivariate regression is a principal component analysis (PCR) regression or a partial least squares (PLS) regression.

16. 16. The method for determining the value of at least one property "Px" according to claim 15, wherein the calibration curve "Cx" is calculated based on a first principal component comprising 5 to 15 principal components, or a first principal component comprising 8 to 11 principal components.

17. 16. A method for determining the value of at least one property "Px" according to claim 15, wherein the calibration curve "Cx" is obtained by performing measurements at various temperature conditions of the sample material.

18. 17. The method of determining the value of at least one property "Px" as claimed in claim 16, wherein said calibration curve "Cx" also includes the temperature of the sample material as a variable.

19. The at least one property "Px" of the substantially plastic material is an H / C index and / or a carbon index, wherein the carbon index and hydrogen / carbon ratio (H / C index) satisfy the following formula: [Equation 4] wherein the atomic weight is the atomic weight present in substantially the entire plastic material.

1. An apparatus for determining the value of at least one property "Px" of a substantially plastic material in an at least partially molten state, the value being calculated according to: 1) a cavity through which the substantially plastic material can slide, the cavity having an inlet and an outlet for the substantially plastic material in at least a portion of a molten state; 2) at least one probe capable of emitting light within said cavity; 3) at least one detection system optically coupled to said probe for detecting reflected light and determining at least one analytical measurement "Ax"; 4) at least one temperature reading sensor connected to said cavity; 5) a system for determining said at least one property "Px" of said at least partially molten substantially plastic material by correlating said at least one analytical measurement "Ax" with at least one calibration curve "Cx" obtained from sample materials having known values ​​of property "Px"; wherein the cavity is capable of withstanding a pressure of at least 50 bara, or from 80 to 300 bara.

20. 20. An apparatus for determining the value of at least one property "Px" as claimed in claim 19, wherein the temperature reading sensor is positioned such that the minimum distance between the temperature reading area and the area where the reflectance spectrum is measured is 100 mm or less, or 30 mm or less, or 3 mm or less.

21. 20. An apparatus for determining the value of at least one property "Px" as described in claim 19, wherein the at least one detection system optically coupled to the probe is positioned so that the minimum distance between the light emission zone of the probe and the detection zone of the light emission is 50 mm or less, or 15 mm or less, or 3 mm or less.

22. 20. The apparatus for determining the value of at least one property "Px" according to claim 19, wherein the cavity is a portion of an extruder cylinder, a portion of a conveyor screw, or a section of pipe connected to a pyrolysis reactor.

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