Process for preparing low molecular weight aromatic compounds such as benzene, toluene, and xylene (BTX) from plastics

Abstract

To provide a novel process for preparing low molecular weight aromatic compounds such as benzene, toluene, and xylene (BTX) from plastics.SOLUTION: There is provided a thermo-catalytic pyrolysis process for preparing aromatic compounds from a feed stream comprising plastic, including the steps of: a) subjecting a feed stream comprising a plastic to a pyrolysis treatment at a pyrolysis temperature in the range of 600 to 1000°C to produce pyrolysis vapors; b) optionally cooling the pyrolysis vapors to a temperature that is below the pyrolysis temperature; c) contacting the vaporous phase with an aromatization catalyst at an aromatization temperature in the range of 450 to 700°C, which is at least 50°C lower than the pyrolysis temperature, in a catalytic conversion step to yield a conversion product comprising aromatic compounds; and d) optionally recovering the aromatic compounds from the conversion product.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a novel method for preparing low molecular weight monocyclic aromatic compounds, such as benzene, toluene, and xylene (BTX), from plastics. These compounds are important starting materials for bulk chemicals such as ethylbenzene, cumene, cyclohexane, adipic acid (from benzene), toluene diisocyanate, benzaldehyde and benzoic acid (from toluene), and terephthalic acid (from p-xylene). [Background technology]

[0002] Currently, the above-mentioned aromatic compounds are mainly produced in the refining process of fossil resources. Common methods include steam cracking, steam reforming, catalytic cracking, and catalytic reforming. Alternatively, biomass, waste, or a combination thereof is used for the preparation. Mixed waste plastics are considered to be an interesting alternative raw material for this purpose. Several routes have been proposed that can convert biomass or waste plastic materials into aromatic compounds by chemical synthesis and / or thermochemical conversion. However, only a few technologies have been scaled up to pilot scale or beyond.

[0003] Thermal conversion of plastics to aromatics is a promising technology to reduce plastic waste and generate bulk chemicals, especially in the case of mixed and / or contaminated plastics that cannot be easily recycled. Currently, these streams are incinerated and in some cases used to convert plastics into alternative fuels, but conversion into chemical building blocks for the chemical industry would greatly valorize these waste streams.

[0004] Various articles and patents describe the (catalytic) pyrolysis of plastics, mixed plastic waste, plastics mixed with biomass and their mixtures to alternative fuels and bulk chemicals. Five types of conversion can be distinguished: 1. Non-catalytic pyrolysis: The non-catalytic (non-catalytic) pyrolysis of a material at elevated temperatures in an inert atmosphere. Pyrolysis involves a change in chemical composition and is irreversible. 2. In situ catalytic pyrolysis: pyrolysis in the direct presence of a catalyst, as described above. The catalyst may alter the required pyrolysis temperature, the product composition, or both. 3. Ex situ catalytic pyrolysis: pyrolysis as described above, except that the vapors from the pyrolysis reaction are catalytically reformed (upgraded) in a section distinct from the pyrolysis section. 4. Integrated Cascading Catalytic Pyrolysis (ICCP): A combination of 2 and 3 above, i.e. catalytic pyrolysis, typically using a cracking catalyst, followed by steam reforming (upgrading) using a second catalyst. 5.2-step non-integrated process: Pyrolysis with or without the aid of a cracking catalyst, followed by condensation and further followed by catalytic conversion of at least the liquid fraction.

[0005] Lopez et al. (Renewable and Sustainable Energy Reviews, 73(2017), pp. 346-368) review the literature on the thermal conversion of plastics to fuels and chemicals. Miandad et al. (Process Safety and Environmental Protection, 102(2016), pp. 822-838) review the literature on catalytic pyrolysis of plastic waste.

[0006] Various studies have been directed towards the production of BTX from waste plastics by thermal or catalytic pyrolysis, choosing the operating conditions such as temperature, heating rate, residence time, catalyst, etc. See, for example, Bagri and Williams (Journal of Analytical and Applied Pyrolysis, 63, 1(2002), pp. 29-41). They studied the temperature effect in an ex situ catalytic pyrolysis process of polyethylene. Pyrolysis was carried out at 500°C, and the pyrolysis gas was sent to a second reactor containing a catalyst bed at temperatures ranging from 400 to 600°C. It was found that the aromatics content increased with increasing temperature of the catalytic conversion.

[0007] Takuma et al. studied the catalytic cracking of polyolefins to produce aromatic hydrocarbons using H-gallosilicate catalysts at temperatures between 375 and 550 °C. It was found that the yield of BTX was temperature dependent, with a BTX yield of 60.5% being obtained at 525 °C. However, the H-gallosilicate catalyst cannot be prepared in an economically feasible manner, so this process does not allow for industrial-scale application. In any case, the overall conclusion in the Lopez et al. publication is that the reported BTX yields using industrially scalable methods are low, typically less than 20%. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Application Publication No. 2017 / 0247617 [Patent Document 2] US Patent Application Publication No. 2009 / 0170739 [Non-patent literature]

[0009] [Non-Patent Document 1] Lopez et al., Renewable and Sustainable Energy Reviews, 73(2017), pp. 346-368 [Non-Patent Document 2] Miandad et al., Process Safety and Environmental Protection, 102(2016), pp. 822-838 [Non-Patent Document 3] Bagri and Williams, Journal of Analytical and Applied Pyrolysis, 63, 1(2002), pp. 29-41 Summary of the Invention [Problem to be solved by the invention]

[0010] Accordingly, the inventors aimed to improve the yield of low molecular weight aromatics, particularly monocyclic aromatics, such as BTX, from feed streams comprising plastics in processes that allow for scale-up to commercial production of BTX, particularly processes that involve the use of catalysts that are commercially available or can be made commercially available. [Means for solving the problem]

[0011] Surprisingly, it has been observed that if the pyrolysis temperature in the ex situ pyrolysis of plastics is significantly higher than conventional pyrolysis temperatures, i.e., in the range of 600-1000°C, and then the pyrolysis vapors are cooled and subjected to a catalytic aromatization step at a temperature in the range of 450-700°C, provided that the aromatization temperature is significantly lower than the pyrolysis temperature, then unprecedented high yields of BTX can be obtained. For example, pyrolysis of a feed stream containing (mixed) plastics at 800°C followed by catalytic aromatization at 550°C resulted in a product stream containing more than 40 wt% BTX. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Accordingly, the present invention provides an ex situ catalytic pyrolysis, or ICCP, process for preparing low molecular weight monocyclic aromatic compounds from a feed stream comprising plastics, the process comprising the steps of: a) subjecting a plastic-containing feed stream to a pyrolysis temperature (T pyr ) to generate pyrolysis vapor; b) optionally cooling said pyrolysis vapors to a temperature below said pyrolysis temperature; and c) In the catalytic conversion step, the (cooled) pyrolysis steam obtained in a) or b) is heated to an aromatization temperature (T arom ) with an aromatization catalyst at T arom is T pyr at least 50° C. lower than the reaction temperature to produce a conversion product comprising low molecular weight aromatic compounds; d) Optionally, recovering low molecular weight monocyclic aromatic compounds from the above conversion products.

[0013] The ex-situ catalytic pyrolysis process of the present invention has not been disclosed or suggested in the art. The "optimum" pyrolysis temperature (T pyr ) is generally considered to be around 500 °C. At this temperature, the highest yield of condensable liquid (oil) is obtained. Lower T pyr results in more coke production, while higher T pyr produces more gas. Therefore, the T that produced the highest oil yield pyr In general, 500 °C is also the optimal T for ex-situ catalytic pyrolysis of plastics research. pyrTherefore, studies aimed at optimizing the yield of a particular product of interest, e.g., BTX, usually focus on the second stage, where catalytic conversion occurs. In fact, the aromatization temperature T arom The effect of changing the temperature has been the subject of various studies. For example, Bagri et al. conducted pyrolysis of plastics at 550°C and taught that increasing the temperature of catalytic aromatization from 400°C to 600°C can increase the formation of BTX. There is no mention of changing (increasing) the pyrolysis temperature. Furthermore, for practical reasons, T pyr and T arom A process where T is the same is often used in ex situ pyrolysis. arom is the estimated optimal T pyr Since it is within the range of T pyr There was no motivation in the art to separately investigate the effect of varying

[0014] US Patent Application Publication No. 2017 / 0247617 discloses a two-step ICCP process for producing BTX from a biomass feed stream, which may contain (waste) plastics, comprising: pyr and T arom The paper teaches a broad range of 300 to 1000 °C for both T arom T within the range currently claimed, which is at least 50° C. higher than pyr No mention is made of selecting a T. Rather, in line with the commonly held view in the art, all of the examples are carried out within the conventional range of 500-550° C., and T pyr and T arom are (almost) the same (540 / 550°C and 500 / 500°C).

[0015] US 2009 / 0170739 discloses a process for preparing a pour point depressing lubricant base oil component, which comprises pyrolysis of waste plastics. Pyrolysis is carried out at a temperature in the range of 450-700°C with a pyrolysis residence time of 3-60 minutes to produce a pyrolysis stream which is then contacted with an isomerization dewaxing catalyst, typically at a temperature of about 200°C to about 475°C. In contrast to the present invention, US 2009 / 0170739 does not use an aromatization catalyst and does not produce conversion products containing low molecular weight monocyclic aromatic compounds.

[0016] In one embodiment of the present invention, T pyr The temperature ranges from 700 to 1000° C., preferably from 700 to 950° C. For example, the pyrolysis is carried out at 720, 740, 750, 760, 780, 800, 825, 850, 875, 900, 925, 950, 975, or 1000° C. pyr is in the range of 750 to 950°C, for example, 800 to 950°C, 850 to 950°C, 750 to 900°C, 750 to 875°C, 750 to 850°C, 750 to 825°C, or 750 to 800°C.

[0017] The pyrolysis reaction according to the present invention is typically a fast process with a residence time of only a few minutes, e.g., 3 minutes or less. In one embodiment, the residence time in the pyrolysis reactor ranges from 0.1 seconds to 3 minutes, preferably 1 second to 2 minutes, e.g., 1, 3, 5, 7, 10, 15, 20, 25, 30, 45, 60, 80, 90, or 100 seconds. The relatively high T pyr The pyrolysis reaction in produces pyrolysis vapors containing low molecular weight alkanes and alkenes, which are then converted to T with the aid of an aromatization catalyst. arom to low molecular weight monocyclic aromatic compounds, particularly benzene, toluene, and / or xylenes.

[0018] Typically, the aromatization reaction according to the present invention is also a fast process with residence times of only a few minutes, for example 3 minutes or less. In one embodiment, the residence time in the aromatization zone ranges from 0.1 seconds to 3 minutes, preferably 0.5 seconds to 2 minutes, more preferably less than 30 seconds. Exemplary residence times are 1, 3, 5, 7, 10, 15, 20, 25, 30, 45, 60, 80, 90, 100, or 120 seconds.

[0019] According to the present invention, T arom is T pyr At least 50°C lower than the temperature at which the temperature is reached and within the range of 450 to 700°C. For example, T arom is lowered by at least 80° C., preferably at least 100° C., more preferably at least 150° C. For example, it is lowered by at least 80, 100, 150, 200, 225, 250, 275, 300, or 350° C. pyr and T arom The maximum difference between (ΔT pyr- T arom ) can vary, but is typically up to about 250°C.

[0020] However, it is interesting to note that the proportion of xylene in the BTX conversion product obtained from, for example, a polypropylene stream, increases with increasing ΔT pyr -T arom is found to be optimal when the temperature is at least 50° C., but not more than about 200° C. Xylenes are typically the most desired compounds contained in BTX products. Thus, in one embodiment, the present invention provides a two-step thermos-catalytic pyrolysis process for the preparation of low molecular weight monocyclic aromatic compounds, particularly xylenes, from a feed stream comprising plastic, preferably polypropylene, which process comprises the steps of: a) subjecting a plastics-containing feed stream to a pyrolysis treatment at a pyrolysis temperature in the range of 600-1000°C, preferably for a duration of 2 minutes or less, to produce pyrolysis vapors containing low molecular weight alkanes and alkenes; b) Optionally, actively cooling the pyrolysis vapors to a temperature below the pyrolysis temperature; and c) in a catalytic conversion step, contacting the pyrolysis vapor phase with an aromatization catalyst at an aromatization temperature in the range of 450-700°C, preferably 500-650°C, which aromatization temperature is 50-200°C, preferably 50-150°C, lower than the pyrolysis temperature, to produce a conversion product comprising low molecular weight (monocyclic) aromatic compounds; and d) Optionally, recovering said low molecular weight monocyclic aromatic compounds, preferably xylenes, from said conversion products.

[0021] In one embodiment, T in the process provided herein arom The T is in the range of 450 to 650° C. For example, the aromatization is carried out at 450, 480, 500, 525, 550, 575, 600, 625, 650, 675, or 700. arom The ranges include 450 to 650°C, 500 to 700°C, 450 to 600°C, 550 to 650°C, 500 to 600°C, 450 to 550°C, 500 to 550°C, 550 to 600°C, 600 to 700°C, and 550 to 700°C. arom is 450 to 550°C, for example, 500 to 550°C.

[0022] In particular, in addition to the BTX yield and xylene yield, T arom Keeping T sufficiently low has additional technical advantages, especially when the aromatization catalyst is a zeolite catalyst. Zeolite catalysts tend to be damaged and therefore deactivated at high temperatures. Thus, the process using the temperature conditions of the present invention is beneficial to catalyst life and process economics. Furthermore, T arom The process of the present invention, which allows for high BTX yields while keeping the temperature relatively low, i.e., up to 600° C., allows for the use of lower quality steel. This has a significant impact on the capital cost of the equipment and therefore the economics of the process.

[0023] As will be appreciated by those skilled in the art, T pyr Any exemplary and preferred temperature values ​​or ranges of T arom Any of the examples and preferred temperature values ​​or ranges may be combined.

[0024] In certain aspects, the present invention provides an ex situ catalytic pyrolysis process for preparing low molecular weight monocyclic aromatic compounds from a feed stream comprising plastics, the method comprising the steps of: a) subjecting a plastic-containing feed stream to a temperature T pyr subjecting the mixture to a pyrolysis process at 200° C. to generate pyrolysis vapor; b) Optionally, in some cases, the pyrolysis vapor is treated with T pyr cooling to a lower temperature; c) The (cooled) pyrolysis vapor obtained in a) or b) is heated to a temperature T in the range of 500 to 600 ° C. in a catalytic conversion step. arom with an aromatization catalyst at to produce conversion products comprising low molecular weight monocyclic aromatic compounds.

[0025] The method of the present invention allows the production of valuable chemicals from waste plastics, such as post-consumer waste plastics, off-spec plastics, industrial scrap plastics, etc. The waste plastics can be single plastics or, preferably, mixed waste plastics. The feed stream may contain heteroatoms, such as oxygen, sulfur, nitrogen, as well as halogens, such as chlorine and bromine. In particular, for (mixed) plastics that do not contain aromatic moieties in the polymer backbone (polyethylene, polypropylene, etc.), the effect of increasing the temperature in the first pyrolysis step significantly increased the yield of BTX. The method of the present invention is capable of converting the plastic feed stream into a conversion product that contains a significant proportion of low molecular weight aromatics, preferably benzene, toluene, and xylene (BTX). For example, a conversion product containing at least 25% by weight, preferably at least 30% by weight, more preferably at least 35% by weight of BTX can be obtained.

[0026] The feed stream may comprise synthetic or semi-synthetic polymers or mixtures thereof, including polyolefins, aromatic polymers, fiber reinforced composites, multilayer plastics, mixed plastics waste polyamides, and / or recycled waste, or may comprise liquid streams derived from pyrolysis of any of the above-listed materials. The feed stream may be pretreated, for example, feed pretreatment may consist of liquefying, solvating, or slurrying the feed stream. In some embodiments, the feed stream may also comprise other organic material streams, such as biomass or pyrolysis oils.

[0027] Plastics are mainly composed of a specific polymer, and plastics are generally named by this specific polymer. Preferably, plastics contain more than 25% by weight of the specific polymer, preferably more than 40% by weight, more preferably more than 50% by weight of the specific polymer of its total weight. Other components in plastics are, for example, additives, such as fillers, reinforcing agents, processing aids, plasticizers, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, inks, antioxidants, etc. Generally, plastics contain more than one additive. Plastics suitable for the method of the present invention are, for example, polyolefins and polystyrene, polypropylene, and polystyrene. Here, the feed stream comprises or consists of one or more of polypropylene (PP), polyethylene (PE), including high density polyethylene (HDPE) and low density polyethylene (LDPE), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polystyrene (PS), MPB, and styrofoam FB, and any mixtures thereof. Also included are mixed plastics composed primarily of polyolefins and polystyrene. The polymers may be in the form of composite materials, such as metallized plastic bags (MPB), fiber reinforced polymers, multi-layer plastics, hybrid materials, or others.

[0028] The pyrolysis process of step a) can be carried out using an inert heat transfer medium, a cracking catalyst, an acid scavenging material, or a combination thereof. In one embodiment, the pyrolysis process step a) is carried out in the presence of a cracking catalyst to produce a vapor fraction and a coked cracking catalyst, which is then separated from the coked cracking catalyst before contacting the vapor phase with the aromatization catalyst. Preferably, the coked cracking catalyst is regenerated by contacting the coked cracking catalyst with oxygen to produce a regenerated cracking catalyst. More preferably, the regenerated cracking catalyst is recycled to the pyrolysis process of step a).

[0029] Suitable cracking catalysts positively affect the thermal cracking of the feedstock, thereby increasing the amount of steam formed and / or altering the composition of the vapor phase so that a higher yield of aromatics is formed. Such inert materials include, for example, but are not limited to, various types of sand, pumice, and silicon carbide.

[0030] The decomposition catalyst (cracking catalyst) is preferably selected from acidic or alkaline inorganic materials and combinations thereof. Alkaline refractory oxides include magnesium oxide, calcium oxide, chromium oxide, and combinations thereof, which therefore constitute suitable cracking catalysts. Suitable acidic refractory oxides include silica-alumina, zeolites, alumina, silica, or combinations thereof, red mud, Co / Al2O3, Mn / Al2O3, kaolin, hydrocalcite, etc. In some embodiments, the catalyst may include metals and / or metal oxides. Suitable metals and / or oxides include, for example, nickel, platinum, vanadium, palladium, manganese, cobalt, zinc, copper, chromium, gallium, sodium, bismuth, tungsten, zirconium, and / or any oxide thereof, among others.

[0031] The heat transfer medium / cracking catalyst (decomposition catalyst) may also include compounds capable of removing acid compounds such as hydrochloric acid from the PVC, such as iron chloride, calcium carbonate, calcium oxide, calcium hydroxide, and crushed oyster shells, as well as other alkaline components.

[0032] Since in the process of the invention step c) is carried out at a lower temperature than step a), it is inherent that the pyrolysis vapors obtained in step a) are passively cooled in step c), however, it is preferred to carry out an active cooling step b) before sending the pyrolysis vapors to the catalytic conversion step.

[0033] In one embodiment, the pyrolysis step a) and the catalytic conversion step c) are carried out in two different reactors. However, it is also included to use a single reactor that contains different reactor zones, each of which operates at a different temperature and has a different (catalytic) bed. See, for example, US Patent Application Publication No. 2013 / 261355.

[0034] The pyrolysis process of step a) can be carried out in a variety of reactors, including, but not limited to, rotary kilns, continuous stirred tank reactors (CSTRs), fixed bed reactors, moving bed reactors, auger reactors, screw conveyor reactors, entrained flow reactors, rotating cone reactors, fluidized bed reactors, spouted bed reactors, and circulating fluidized bed reactors.

[0035] Reactors that allow for relatively short contact times and vigorous mixing of the components of the feed stream are most preferred. This is the case for fluidized bed reactors, and these reactors are particularly preferred. However, when the particle size of the feedstock does not allow for short contact times, such as in the case of composite waste materials, reactors that allow for longer reaction times may be preferred.

[0036] The pyrolysis reactor may include a heat transfer medium. In one embodiment, the pyrolysis reactor includes a material capable of removing acid compounds such as hydrochloric acid, such as iron chloride, calcium carbonate, calcium oxide, calcium hydroxide, and crushed oyster shells, and other alkaline components.

[0037] The stream containing the pyrolysis products may be subjected to a separation step to remove non-vapor components. Separation of the vapor fraction from the non-vapor coke fraction may be carried out in a separation system by any known method for separating vapors from solids and / or liquids. The vapors may be subjected to a cooling system to reduce the temperature of the vapors. The cooling system may be, for example, non-insulated piping, an air-cooled heat exchanger, or a liquid-cooled heat exchanger. The vapor fraction thus obtained is then used for conversion to aromatic compounds.

[0038] In some embodiments, the pyrolysis reactor includes a system for treating non-vaporous materials. Treatment can include coke removal by oxidation, removal of particles of a particular size, removal of particles of a particular density, removal of aerosols, or combinations thereof. If the material includes a catalyst, treatment can include regeneration or reactivation of the catalyst.

[0039] The vapour fraction obtained by pyrolysis according to the invention is highly suitable for conversion to aromatics, since it tends to contain saturated and unsaturated (low molecular weight) hydrocarbons which are easily converted to aromatics in step c) of the process of the invention using appropriate conditions. Step c) is a step of subjecting the (cooled) pyrolysis steam obtained in step a) or b) to an aromatization temperature (T) in the range of 450 to 700 °C in a catalytic conversion step. arom ) (where T arom is T pyrwith an aromatisation catalyst at temperatures at least 50°C below 200°C to produce conversion products containing aromatic compounds. At these temperatures, aromatisation tends to increase and the formation of low molecular weight monocyclic aromatic compounds from the vapour phase is optimal. The pressure is suitably in the range of 1 to 4 bar.

[0040] As in the case of the pyrolysis process of step a), the conversion process of step c) of the present invention can also be carried out in various reactors. The aromatization process of step c) is suitably carried out in a fixed bed, a moving bed or a fluidized bed. These two reactors can be integrated, but do not have to be.

[0041] The aromatization catalyst may comprise one or more of a zeolitic catalyst, a non-zeolitic catalyst, a metal catalyst, and / or a metal oxide catalyst. In a particular aspect, the aromatization catalyst is a zeolitic catalyst, suitably selected from aluminosilicates, SAPO, silicates, and combinations thereof. It has been discovered that the aromatization catalyst is preferably acidic. The acidity may be influenced by the structure of the aluminosilicate and also by the ratio between the silicate and aluminate moieties in the aluminosilicate. The acidity is achieved, for example, by ion-exchanging the aromatization catalyst with an ammonium salt and subsequently calcining it. For N-containing feedstocks, a basic catalyst may be preferred. Suitable silica-alumina ratios include those in the range of 5 to 100, preferably 10 to 80, more preferably 20 to 60. Another characteristic that may play a role in the performance of the catalyst is the pore size. It has been discovered that particularly good results are obtained when the pore size of the aromatization catalyst is in the range of 4.5 to 6.5 Å, preferably in the range of 5 to 6 Å.

[0042] The zeolite catalyst is preferably selected from the group consisting of (S)AlPO-31, EU-1, ferrierite, IM-5, MCM-22, modernite, SSZ-20, SSZ-23, SSZ-55, SUZ-4, TNU-9, zeolite A, zeolite beta, zeolite X, zeolite Y, ZSM-11, ZSM-23, ZSM-35, ZSM-5, ZSM-57, and combinations thereof, and may also be treated, exchanged, or impregnated with a metal to improve aromatics yield. In a particular aspect, the aromatization catalyst is ZSM-5. The metal may be selected from nickel, platinum, vanadium, palladium, manganese, cobalt, zinc, copper, chromium, gallium, sodium, bismuth, tungsten, zirconium, indium, tin, thallium, lead, molybdenum, and / or any of their oxides, among others.

[0043] The zeolite may be contained in an amorphous binder. Thus, the catalyst may suitably contain an amorphous binder in addition to the zeolite. The amorphous binder provides the strength, density, shape to the resulting particles and provides the catalyst particles with a specific particle size. Thus, the amorphous binder may suitably be selected from inorganic refractory oxides, in particular alumina, silica, silica-alumina, titania, zirconia, clays, layered mixed metal oxides, phosphates, sulfonates, and mixtures thereof.

[0044] When a binder is used, the amount of binder in such a combination may vary within a wide range. Suitably, the amount of amorphous binder in the zeolite second catalyst ranges from 30 to 80% by weight, preferably from 40 to 70% by weight, based on the weight of the zeolite and amorphous binder. Such a ratio not only provides the particles with satisfactory mechanical strength, but also provides a synergistic effect of increased aromatics yield compared to the proportionally expected yield in the case of silica-alumina. In the process according to the invention, the aromatization catalyst can be regenerated by contacting the coked catalyst with oxygen to produce a regenerated aromatization catalyst.

[0045] Suitably, the process is carried out as a continuous process. Thus, step c) of the process can be carried out in a fixed bed. The vapour fraction can then pass through the fixed bed in an upward flow (upflow) or downward flow (downflow) direction. However, gradual deactivation can occur in such fixed beds, as the conversion to aromatics can result in some coke deposition on the catalyst. It is therefore preferred to carry out the conversion process in a configuration of two or more fixed bed reactors in a swing mode, or in a moving bed reactor or a fluidised bed reactor. In a fluidised bed, the catalyst can be continuously added and passed through a fluidised passage to the outlet, while being surrounded by vapours. The vapours initially consist of vapours from the vapour fraction, but over time are converted into an aromatisation product stream consisting mainly of aromatics, small hydrocarbons, other gases, coke and catalyst.

[0046] Thus, the aromatization product stream will not be entirely composed of aromatic compounds. It will contain gaseous compounds such as carbon dioxide, carbon monoxide, hydrogen, water, low molecular weight alkanes, and also valuable by-products such as olefins and oxygenates. It may be desirable to recover the olefins separately from the (low molecular weight) aromatic compounds. Therefore, the conversion product is preferably fractionated to produce the aromatic compounds as a separate fraction or separate fractions, optionally one or more olefin fractions, and a residue. To this end, the vapor fraction can be sent to a cooling system, for example a heat exchanger such as a condenser, to produce a liquid stream and a vapor stream.

[0047] Due to the known relatively high vapor pressure of compounds such as benzene, it is expected that the vapor stream will contain significant amounts of BTX. A suitable method for recovering aromatics from a liquid stream consists of passing the conversion product through an extraction column where light (i.e., low molecular weight) aromatics, primarily BTX, are extracted from the liquid stream to produce a BTX-enriched liquid stream and a BTX-lean liquid stream.

[0048] In one embodiment, the method of the present invention may also include recovering aromatic compounds from a vapor stream containing aromatic compounds such as the conversion product, the method comprising contacting the vapor stream with a liquid hydrocarbon to obtain a hydrocarbon phase containing aromatic compounds and an oxygenate phase, and separating the hydrocarbon phase from the oxygenate phase. The oxygenate phase may only be present if the plastic contains oxygen atoms and / or if water is present in the material. The aromatic compounds may be suitably recovered from the hydrocarbon phase by any known method, including distillation or fractionation. The liquid hydrocarbon may be aliphatic, cycloaliphatic, aromatic, fatty acid ester, or a combination thereof. When aromatic hydrocarbons are used as liquid hydrocarbons, there is an advantage that no external products need to be used in the process. The aromatic hydrocarbons used for this purpose may be products from the catalytic pyrolysis process step a). In other words, the fraction of aromatic compounds separated from the conversion product may be used to further extract aromatic compounds from the conversion product.

[0049] A further embodiment of the present invention relates to a process for preparing aromatic compounds from a feed stream comprising plastics, the process comprising the steps of: a) subjecting a feed stream comprising plastics or a mixture of plastics to the process disclosed above to obtain a conversion product comprising aromatic compounds; b) recovering aromatic compounds from said conversion product; c) separating by distillation a higher molecular weight fraction comprising polycyclic aromatic hydrocarbons (PAHs) from a lower molecular weight fraction comprising benzene, toluene, and xylenes (BTX); d) optionally reducing said higher molecular weight fraction to obtain a reduced fraction comprising polycyclic aliphatics (PCA); and e) subjecting the higher molecular weight fraction obtained in step c), the reduced fraction obtained in step d), or a mixture thereof, to a process to obtain lower molecular weight aromatics (BTX).

[0050] Typically, step a) involves pyrolysis of the plastic feedstock at high temperatures in the range of 700-950°C, preferably in the range of 750-850°C, using an inexpensive cracking catalyst, followed by subjecting the resulting vapor to an ex situ catalytic aromatization step. In one embodiment, step a) involves adding at least one further reactant to the feed stream, the reactant being selected from the group consisting of olefins, alcohols, aldehydes, ketones, acids, and combinations thereof. For example, the further reactant comprises from 1 to 6 carbon atoms, preferably in this case the further reactant is selected from the group consisting of ethene, propene, butene, isobutene, pentene, hexene, methanol, ethanol, propanol, isopropanol, hexanol, formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, formic acid, and acetic acid.

[0051] In one embodiment, step d) comprises catalytic hydrogenation, preferably using a catalyst selected from the group consisting of Ru / C, Ni / C, Pd / C, Pt / C, MoS2, WS2, Co-Mo-S / Al2O3, Ni-WS / Al2O3, Co-Mo / Al2O3, or a homogeneous catalyst, such as Wilkinson's catalyst and Crabtree's catalyst. Said catalytic hydrogenation is suitably carried out without the addition of a solvent.

[0052] Step e) advantageously comprises mixing the higher molecular weight fraction obtained in step c) or the reduced fraction obtained in step d) with the plastics feed stream and subjecting the resulting mixture to pyrolysis or gasification.

[0053] FIG. 1 is a schematic diagram of the main steps of the ex situ thermal catalytic pyrolysis process according to the present invention. The plastic-containing feed stream 45 enters the pyrolysis reactor 10 where it is heated to a high temperature (T between 600-1000° C. pyr) to produce pyrolysis vapors 61 containing hydrocarbons and other gas components, such as carbon dioxide, carbon monoxide, and hydrogen, as well as ash, inorganic materials, and coke. The pyrolysis vapors 61 are separated from the coke fraction in a separation system 11, which may contain a heat transfer medium therein, to produce a vapor fraction 62 containing hydrocarbons, water, and other gas components. The vapor fraction 62 is cooled in a cooling system 12 to produce a pyrolysis vapor 61 containing hydrocarbons, water, and other gas components, such as carbon dioxide, carbon monoxide, and hydrogen, as well as a pyrolysis vapor 62 containing inorganic materials and coke. The pyrolysis vapor 61 is separated from the coke fraction in a separation system 11, which may contain a heat transfer medium therein, to produce a vapor fraction 62 containing hydrocarbons, water, and other gas components. The vapor fraction 62 is cooled in a cooling system 12 to produce a pyrolysis vapor 61 containing hydrocarbons, water, and other gas components, such as carbon dioxide, carbon monoxide, and hydrogen, as well as a pyrolysis vapor 62 containing inorganic materials and coke ...1 containing inorganic materials and coke. The vapor fraction 62 is cooled in a cooling system 12 to produce a pyrolysis vapor 61 pyr The vapor phase 63 is actively cooled to a lower temperature to obtain a vapor phase fraction 63. The cooling system may consist of a heat exchanger. The vapor phase 63 is fed into the aromatization reactor 20 where it is contacted with a catalyst and cooled to a T in the range of 450-700° C. arom (wherein the aromatization temperature is at least 50° C. below the pyrolysis temperature) to produce an aromatics conversion stream 64 comprising aromatics, particularly the low molecular weight aromatic BTX.

[0054] FIG. 2 shows a schematic diagram of a catalytic pyrolysis process according to one embodiment of the present invention. The plastic-containing feed stream 41 may optionally be subjected to a drying system 02 to reduce its moisture content. A moisture fraction 51 is removed, resulting in a dried feed stream 42. The feed stream 41 or the dried feed stream 42 may or may not be subjected to a chopping and / or grinding system 03, resulting in a chopped feed stream 43. The feed stream 41, the dried feed stream 42, or the chopped feed stream 43 may or may not be subjected to a material forming system 04, such as chopping, grinding, pelletizing, sieving, and other suitable methods, resulting in a shaped feed stream 44. The feed stream 41, the dried feed stream 42, the chopped feed stream 43, or the shaped feed stream 44 are provided to a feed system 05. The feed system can consist of a feed screw, a cooled feed screw, several feed screws with or without cooling, an extruder, or any feed system suitable for processing the feed stream 41, the dried feed stream 42, the chopped feed stream 43, or the shaped feed stream 44. The feed stream 45 enters the pyrolysis reactor 10 where it is heated to a high temperature (T between 600-1000° C.). pyr ) to produce pyrolysis vapors 61 containing hydrocarbons (mainly low molecular weight alkanes / alkenes), other gas components such as carbon dioxide, carbon monoxide, and hydrogen, as well as ash, inorganic materials, and coke. The pyrolysis vapors 61 are separated from the coke fraction in a separation system 11, which may include a heat transfer medium therein, to produce a vapor fraction 62 containing hydrocarbons, water, and other gas components. The solid fraction 52 may be removed, cooled, and stored. The solid-gas separation system 11 may consist of one or more cyclones, filters, or a combination thereof. The vapor fraction 62 is separated from the coke fraction in a cooling system 12, which may optionally be used. pyr It is actively cooled to a lower temperature to produce a vapor phase fraction 63. The cooling system may consist of a heat exchanger. The heat transfer medium may be air, steam, or a liquid.

[0055] In some embodiments, reactor 10 is a fluidized bed or circulating fluidized bed or moving bed or equivalent type reactor that uses some kind of media in the bed. Optionally, stream 46 may consist of coked bed material and coke particles. Optionally, stream 47 may consist of virgin, decoked, or regenerated bed material. In some embodiments, stream 46 is oxygenated in system 13 to produce decoked and regenerated bed material. System 13 may produce heat, which can be utilized.

[0056] The vapor phase 63 is fed into the aromatization reactor 20 where it is contacted with a catalyst and heated to a temperature within the range of T arom (the aromatization temperature is at least 50° C. below the pyrolysis temperature) to produce an aromatic conversion stream 64 comprising low molecular weight monocyclic aromatic compounds.

[0057] The aromatics converted stream 64 exiting the conversion reactor 20 can be used as is, or aromatics can be recovered from the converted stream using, for example, a separate solid gas separation system 21, a condenser 31, one or more scrubbers 32, and a separation system 33.

[0058] 2, aromatics conversion stream 64, consisting primarily of aromatics, small hydrocarbons, other gases, coke, and catalyst products 64, may be subjected to separation step 21. Non-vapor stream 53, consisting of catalyst and other solids, is separated from vapor aromatics conversion stream 64 in separator 21. Stream 53 may be sent to regenerator 22 where it may be suitably contacted with an oxygen-containing gas to remove coke deposited on the catalyst. The catalyst thus regenerated may be recycled, typically continuously, to conversion reactor 20 as stream 56. In some embodiments, catalyst is continuously removed from reactor 20 as stream 55 without the need for a separator. Separation of the vapor fraction from the non-vapor coke fraction in separation system 21 may be performed by any known method for separating vapors from solids and / or liquids.

[0059] The vaporous aromatic conversion product 65 does not consist solely of aromatic compounds. It includes gaseous compounds such as carbon dioxide, carbon monoxide, hydrogen, water, low molecular weight alkanes, and further valuable by-products such as olefins. It may be desirable to recover the olefins separately from the aromatic compounds. Thus, the aromatic conversion product 65 may be subjected to fractionation, which may result in low molecular weight monocyclic aromatic compounds as a separate fraction(s), possibly one or more olefin fractions, and a residue. Thus, the vaporous fraction 65 is subsequently sent to a cooling system 31 to produce a liquid stream 70 and a fluid stream 66. The cooling system 31 may consist of a heat exchanger, such as a condenser.

[0060] The liquid stream 70 is directed to an oil-water separator 35 for separating the organic liquid 71 from the aqueous layer 54 if water is present in the liquid stream. Such an oil-water separator may consist of, for example, a decanter, a hydrocyclone, or a centrifugal liquid-liquid separator. Oxygen-containing compounds, including water, that may be formed during the process, may be separated from the mixture of conversion products and liquid hydrocarbons. In this way, aromatic hydrocarbons are recovered together with the liquid hydrocarbons. After separating the liquid hydrocarbon phase containing low MW aromatic compounds from the phase containing oxygen-containing compounds, including water, the liquid hydrocarbon stream 71 is suitably fractionated (distilled) in section 33 to obtain low molecular weight monocyclic aromatic compounds.

[0061] The distillation system 33 produces a top fraction 72 consisting of benzene, toluene, xylenes, and other light aromatics and hydrocarbons. In some embodiments, the distillation system 33 is equipped as a fractional distillation, producing benzene, toluene, and xylenes as separate fractions. It is feasible to recover the various low molecular weight single ring aromatics separately. Alternatively, it is feasible to recover all aromatics in one fraction. The desired level of fractionation can be employed according to the needs and applications of the aromatics.

[0062] The BTX lean bottoms fraction 73 is composed primarily of heavy aromatics and substituted polycyclic aromatic hydrocarbons. The product stream 73 can be used as a fuel or for further downstream processing. A portion of the bottoms stream from 33 can be used as a recycle stream to increase the BTX yield or as a scrubbing liquor. To do so, it is separated as stream 74a and sent to heat exchanger 34 where it is cooled to make it more effective in the extraction system 32.

[0063] Due to the known relatively high vapor pressure of compounds such as benzene, the fluid stream 66 produced in the cooling system 31 may contain a significant amount of BTX. A suitable method for recovering aromatic compounds from the fluid stream 66 consists of passing the conversion products through an extraction column. For example, the cooled liquid hydrocarbons 74b are sprayed into the product stream 66 in the extraction system 32, thereby cooling the conversion products and providing a solvent for the aromatic compounds. In the extraction system 32, the low molecular weight aromatic compounds, mainly BTX, are extracted from the fluid stream 66 to produce a BTX-rich liquid stream 75 and a BTX-lean fluid stream 67. The BTX-rich liquid stream 75 is mixed with the liquid hydrocarbon stream 71 and directed to the distillation system 33.

[0064] Stream 67 may be sent to fluid processing section 36. In some embodiments, one or more additional gas-liquid extraction systems may be present between system 32 and system 36 to recover more aromatics, water-soluble compounds, or other compounds. The additional gas-liquid extraction systems may be equipped with their own strippers.

[0065] The process of the present invention can also include recycling of the gas by feeding it into the pyrolysis reactor 10. The resulting gas can be used to aid in feeding the plastic into the reactor, as a carrier gas for a fluidized bed, or for other purposes for which a process gas can be used. The gas formed can also be used to increase the liquid yield in the overall process. In the fluid processing section 36, one or more common treatments of the fluid stream 67 can be applied, including fractionation to produce light olefins, splitting the stream into a gas recycle stream 68 and a product gas stream 69a, preheating the recycle gas, etc.

[0066] Preferably, fluid processing section 36 also produces an olefin fraction 69b. The residue may be combusted to produce energy for heating the various feed streams and intermediate products. At least a portion of the olefin fraction(s) may be recycled to the conversion process with stream 68. It is also possible to recycle at least a portion of the olefin fraction(s) to the thermal cracking process. Thus, at least a portion of the olefin fraction is suitably recycled to the conversion process, the thermal cracking process, or both.

[0067] Another preferred method for increasing the yield of low molecular weight aromatic compounds consists in adding an additional reactant to reactor 10 or reactor 20. Such additional reactant may be suitably selected from the group consisting of olefins, alcohols, aldehydes, ketones, acids, and combinations thereof. The additional reactant preferably has an effective hydrogen index (EHI) greater than that of the primary feedstock. Examples of suitable additional reactants include hydrogen, butane, isobutene, pentene, and hexene, methanol, ethanol, propanol or isopropanol, and hexanol, formaldehyde, and acetaldehyde, acetone, methyl ethyl ketone, formic acid, acetic acid, polycyclic aliphatics, and partially reduced polycyclic aromatics.

[0068] The aromatic compounds recovered as products of the process can be used in conventional applications, including as fuels (gasoline, diesel, etc.), as well as precursors for polymers and chemical intermediates. The polycyclic aromatic hydrocarbon fraction 73 obtained after distillation of BTX can then be (re)used (recycled) in a pyrolysis process, thereby obtaining a mixture of BTX and higher aromatics (see WO 2017 / 222380).

[0069] For example, the method of the present invention includes the steps of separating a high MW fraction 73 comprising polycyclic aromatic hydrocarbons (PAHs) from a low MW fraction 72 comprising benzene, toluene, and xylenes (BTX) by distillation, reducing at least a portion of said high MW fraction to obtain a reduced fraction comprising polycyclic aliphatics (PCAs); and subjecting the resulting high MW fraction, reduced fraction, or a mixture thereof, to a process to obtain low MW aromatics (BTX).

[0070] In one embodiment, the above mentioned high molecular weight fraction (partially or fully reduced or not reduced) is fed together with plastics or their mixtures, thereby resulting in a significantly higher yield of BTX. BTX can be easily distilled and the remaining higher aromatic fraction can be utilized again for pyrolysis or can be first reduced to aliphatic / aromatic fractions and reused in the pyrolysis process. Repeating the above procedure results in a high conversion rate of plastics to BTX.

[0071] As used herein, singular words (such as "a", "an" and "the" in foreign language specifications) are intended to include the plural, unless the context clearly indicates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprise" and / or "comprising" specify the presence of the stated feature but do not exclude the presence or addition of one or more other features. [Brief description of the drawings]

[0072] [Figure 1] FIG. 1 shows a schematic diagram of a catalytic pyrolysis process according to the present invention. [Diagram 2] FIG. 2 shows a schematic diagram of a catalytic pyrolysis process according to one embodiment of the present invention. [Diagram 3]Figure 3 shows the effect of Tpyr (500, 700, or 800 °C) on the ex situ pyrolysis of the plastics high density polyethylene (HDPE), polypropylene (PP), polybutylene terephthalate / polyethylene terephthalate (PBT-PET) blends, acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polyethylene-polypropylene blends (PP-PE blends), and multi-layer plastic bags (MPB). [Figure 4] FIG. 4 shows the effect of Tpyr (600, 650, 700, 750, 800, 850, or 900°C) on the pyrolysis of the plastic polypropylene, where Tarom is constant at 550°C, in ex situ pyrolysis. [Diagram 5] FIG. 5 shows the effect of differences in Tpyr (600, 650, 700, 750, 800, 850, or 900° C.) and Tarom (450, 500, 550, 600, 650, 700° C.) on the yield of xylenes. EXAMPLES

[0073] Experimental Section

[0074] Materials and Methods The experiments were carried out in a Frontier Lab tandem μ-reactor (Rx-3050TR) equipped with a single shot sampler (PY1-1040). The temperatures of both the reactor and the interface were controlled separately to allow different reaction conditions for the pyrolysis (first reactor) and aromatization unit (second reactor). A carrier gas inlet was connected to the top of the first reactor to provide a flow of carrier gas through the reactor and into the GC-MS. The whole system was connected by a docking station on top of the GC-MS and by an injection needle through a rubber septum.

[0075] Before the experiment, approximately 80 mg of H-ZSM-5(23) catalyst (size 212-425 μm) was placed in the quartz liner inside the second reactor. The system was then pressurized to 150 kPa with an inert carrier gas (helium) to check for leaks. After the leak check, the pressure was returned to 50 kPa using a helium flow rate of 50 mL / min, and the system was heated to the desired T. pyr and T arom was heated to .

[0076] In experiment A: Reactor 1 (T pyr ): 500℃, 700℃, or 800℃, Reactor 2 (T arom ): 550℃, and both interfaces: 300℃. In experiment B: Reactor 1 (T pyr ): 600, 650, 700, 750, 800, 850, or 900 °C, Reactor 2 (T arom ): 550℃, and both interfaces: 300℃. In experiment C: Reactor 1 (T pyr ): 600, 650, 700, 750, 800, 850, or 900 °C, Reactor 2 (T arom ): 450, 500, 550, 600, 650, 700℃, and both interfaces: 300℃.

[0077] The residence time in each reactor was as follows: Reactor 1 was estimated to be less than 3 seconds and Reactor 2 was estimated to be 0.09 seconds.

[0078] A thin stainless steel cup was filled with a feed stream containing various types of plastics and attached to a sample injector suspended slightly above the first reactor. The system was closed and flushed with helium gas for 3 min. After flushing, the cup was dropped into the first reactor to start the pyrolysis reaction. The vapor products passed through a ZSM-5(23) catalyst bed before entering the GC-MS.

[0079] The total BTX yield (as well as the contributions of the individual compounds benzene, toluene, m-, p-xylene, and o-xylene) obtained in experiment A is shown in Figure 3 as an average of two measurements and expressed in mass % based on the organic fraction present in the plastic. It clearly shows that by increasing the temperature of pyrolysis from the conventional 500°C to higher temperatures, e.g. 700 or 800°C, the yield of BTX increases significantly.

[0080] The total BTX yield (as well as the contribution of the individual compounds benzene, toluene, and m-, p-, o-xylene) obtained in experiment B is shown in Figure 4, expressed in mass % (wt%) based on the organic fraction present in the plastic. It clearly shows that the yields of BTX, benzene, and toluene increase significantly by increasing the pyrolysis temperature from the conventional 600 °C to higher temperatures, e.g., 900 °C. It also shows that the yield of xylenes initially increases when increasing the pyrolysis temperature from 600 to 700 °C, but decreases with increasing pyrolysis temperature above 800 °C.

[0081] Figure 4 shows the T arom While keeping constant at 550℃, T pyr It is shown that the yields of BTX, benzene, toluene, and xylenes increase significantly as T increases. pyr indicates that the temperature should not be higher than 800°C.

[0082] The total yields of m-, p-, and o-xylenes (xylenes) obtained in experiment C are shown in Figure 5 and are expressed as mass % (wt%) based on the organic fraction present in the plastic. pyr and T arom It is clearly shown that the yield of xylenes increases by increasing the temperature difference between

[0083] Figure 5 shows the yield of xylene from the catalytic pyrolysis of polypropylene as a function of T1 (T pyr )-T2(T arom) (the difference between T1 and T2), where T1 is in the range of 600-900 °C and T2 is in the range of 450-700 °C. The data are for a ΔT pyr T arom It has been shown that the ΔT pyr T arom Further increases in xylene yields lead to even higher xylene yields, after which a flattening of the curve is observed.

Claims

1. A two-stage thermal-catalytic pyrolysis process for preparing low molecular weight monocyclic aromatic compounds from a feed stream comprising plastics, comprising the steps of: a) subjecting a plastic-containing feed stream to a pyrolysis temperature (T ｐｙｒ ) subjecting the mixture to a pyrolysis process to generate pyrolysis vapors; b) optionally actively cooling the pyrolysis vapors to a temperature below the pyrolysis temperature; and c) In the catalytic conversion step, the pyrolysis steam is subjected to an aromatization temperature (T ａｒｏｍ with an aromatization catalyst at a temperature of at least 50° C. below the pyrolysis temperature to produce conversion products comprising low molecular weight aromatic compounds; and d) optionally recovering low molecular weight monocyclic aromatic compounds from said conversion products; The process includes:

2. T ｐｙｒ The process according to claim 1, wherein the heating temperature is in the range of 650 to 950°C, preferably in the range of 700 to 850°C.

3. 3. The process according to claim 1 or 2, wherein in step a) the residence time in the pyrolysis reactor is less than 2 minutes, preferably less than 1 minute, more preferably less than 30 seconds.

4. T ａｒｏｍ The process according to any one of claims 1 to 3, wherein the heating temperature is in the range of 500 to 700°C, preferably 500 to 650°C, more preferably 500 to 600°C.

5. T ａｒｏｍ T ｐｙｒ The process according to any one of claims 1 to 4, wherein the temperature is at least 80°C lower, preferably at least 100°C lower.

6. T ａｒｏｍ T ｐｙｒ The process according to any one of claims 1 to 5, wherein the temperature is at most 200°C lower, preferably at most 175°C lower than

7. T ｐｙｒ is in the range of 650 to 850°C, and T ａｒｏｍ The process of any one of claims 1 to 6, wherein the temperature is in the range of 500 to 600°C.

8. 8. The process according to any one of claims 1 to 7, wherein in step c) the residence time in the aromatisation reactor is less than 2 minutes, preferably less than 1 minute, more preferably less than 30 seconds.

9. 9. The process of any one of claims 1 to 8, wherein step d) comprises recovering benzene, toluene, and xylenes (BTX) from the conversion product.

10. The process according to any one of claims 1 to 9, wherein the pyrolysis step a) and the catalytic conversion step c) are carried out in two different reactors.

11. 11. The process of any one of claims 1 to 10, wherein the aromatization catalyst is selected from the group consisting of ZSM-5, ZSM-11, ZSM-35, ZSM-23, ferrierite, zeolite beta, zeolite Y, zeolite X, mordenite, zeolite A, IM-5, SSZ-20, SSZ-55, MCM-22, TNU-9, metal treated, exchanged or impregnated catalysts, and combinations thereof.

12. 12. The process of any one of claims 1 to 11, wherein the feed stream comprises synthetic or semi-synthetic polymers or mixtures thereof including polyolefins, aromatic polymers, fibre reinforced composites, multi-layer plastics, mixed plastics waste polyamides and / or recycled waste, or liquid streams derived by pyrolysis of any of the aforementioned materials.

13. 13. The process of any one of claims 1 to 12, wherein the feed stream comprises or consists of one or more of polypropylene (PP), polyethylene (PE), polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polystyrene (PS), and polyamide (PA).

14. The process according to any one of claims 1 to 13, wherein step b) comprises cooling the pyrolysis vapours with the aid of a heat exchanger.

15. The process according to any one of claims 1 to 14, wherein step c) is carried out in a vapour upgrading reactor comprising a heat carrier.

16. 16. The process according to any one of claims 1 to 15, wherein the pyrolysis treatment in step a) is carried out in the presence of a cracking catalyst to produce pyrolysis vapours and coked cracking catalyst, and then separating the pyrolysis vapours from the coked cracking catalyst.

17. 17. The process of claim 16, wherein the cracking catalyst is selected from the group consisting of acidic or alkaline inorganic materials, and amorphous or crystalline silica-alumina containing materials.

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