Field of the invention

The invention relates to a process for producing fully or partially isomerized hydrocarbons from mixed plastic using a thermocatalytic process. The invention also relates to the use of such isomerized hydrocarbons as raw materials in the polymer industry.

Background

Production of short hydrocarbon fragments from organic compounds is well known to a person skilled in the art. Methods utilized in such processes are, for example, pyrolysis, depolymerization, hydrolysis and the use of supercritical water. The reaction products obtained using conventional methods have not been suitable for use as raw materials in the polymer industry, whereby the main raw material for polymer industry still has been crude oil and its derivatives. When using conventional methods, there has been a need to separate different types of plastics from each other prior to processing the feedstock to new raw materials. Thus, there is still a need for an improved process enabling the utilization of waste plastics as raw material in the polymer industry, as this would greatly decrease the demand for fossilbased raw materials and thereby reduce the carbon footprint of the end products.

Prior Art

Some prior art publications relating to the field of plastic recycling and pyrolysis are presented below:

US 10233395 B2 relates to a process for converting mixed waste plastic into valuable petrochemicals.

Wei, T.-T. et al., Chemical recycling of post-consumer polymer waste over fluidizing cracking catalysts for producing chemicals and hydrocarbon fuels, published in Resources, Conservation and Recycling (2010), Vol. 54, pp. 952-961, discloses pyrolysis of a mixture of polymer waste over various catalysts using a laboratory fluidized- bed reactor operating isothermally at ambient pressure. US 2018371327 Al relates to a process for converting waste plastic into gases, liquid fuels and waxes by catalytic cracking.

Cocchi, M. et al., Catalytic Pyrolysis of a Residual Plastic Waste Using Zeolites Produced by Coal Fly Ash, Catalysts (2Q2Q), Vol. 10, No. 1113 discusses pyrolysis of plastic film residue of a plastic waste recycling process, and the effect of low-cost catalysts on yields and quality of pyrolysis oils.

Mark, L. 0. et al, The Use of Heterogeneous Catalysis in the Chemical Valorization of Plastic Waste, ChemSusChem (2020), Vol 13, pp. 5808-5836 relates to recycling of plastic solid waste.

Miandad, R. et al., Catalytic pyrolysis of plastic waste: A review, Process Safety and Environmental Protection (2016), Vol. 102, pp. 822-838 discusses the progress and challenges of the catalytic pyrolysis of plastic waste.

Martin, A. J. et al., Catalytic processing of plastic waste on the rise, Chem (2021), Vol. 7, pp. 1487-1533 is a review on catalytic transformation of different types of plastics.

Palos, R. et al., Waste Refinery: The Valorization of Waste Plastics and End-of-Life Tires in Refinery Units. A Review, Energy Fuels (2 2 }, Vol. 35, pp. 3529-3557 collects a range of initiatives and results that expose the potential of the refineries to be converted into waste refineries.

Fadillah, G. et al., Recent Progress in Low-Cost Catalysts for Pyrolysis of Plastic Waste to Fuels, Catalysts {2Q2 ), Vol. 11, No. 837 discusses catalytic and thermal decomposition of plastic waste to fuels over low-cost catalysts.

Kasar, P. et al., Thermal and catalytic decomposition of waste plastics and its coprocessing with petroleum residue through pyrolysis process, Journal of Cleaner Production (2020), Vol. 265, No. 121639 is a literature review on cracking of plastics waste and it's co-processing with petroleum residues and other heavy oil, the types of reactors and the catalyst employed in the process. Summary of invention

The present invention relates to a process for producing fully or partially isomerized hydrocarbons from mixed plastic using a thermocatalytic process. In the method, a mixture of plastics is subjected to a thermolysis process in at least one reactor at a temperature ranging from 150 to 950 °C in a substantially oxygen free environment in the presence of at least one catalyst functioning as a pyrolysis catalyst, as well as a further catalyst functioning as an isomerization catalyst.

Within the process of the invention, biomass derived ash is functioning as pyrolysis catalyst and the at least one further catalyst, being an isomerization catalyst, includes at least one of Na, Ni, Mo, Zr, Al, Mg, zeolite, silicates, or a metal catalyst, possibly in the form of metal oxide, metal salt or metal complex. In an embodiment of the invention, said isomerization catalyst is a metal catalyst including any of Cu, Ni, Co, Zn, Ag, Al, K, Na, Zr, Ca, Ba, Pt, Pd, V, Rh, Mg, Mn, Mo and Ti, or a combination thereof.

In an embodiment of the invention, said at least one catalyst is natural biomass derived ash in combination with any of the following: fossil fuel derived ash, including fly ash; metal powders; inorganic metal salts and oxides, such as metal chlorides, kaolin, clay, montmorillonite, zeolite, bentonite and sand; organic metal salts, e.g., acetates and citrates; carbonaceous catalyst components; organic and inorganic alkalis and bases, such as tert-butyl amine compounds, for example, TBAB, TBAH; geopolymers; diatomaceous earth, and waste or residue derived minerals and mixtures. At least one further catalyst, in addition to biomass derived ash, is functioning as an isomerization catalyst. The isomerization catalyst may include at least one compound selected from Na, Ni, Mo, Zr, Al, Mg, Zn, Ti, zeolite and silicates. Said isomerization catalyst may also be another metal catalyst, metal oxide, metal salt or a metal complex. It was found to be especially preferred to use at least two different catalysts, such that one is biomass derived ash in combination with at least one isomerization catalyst as mentioned above.

The mixed plastic feed may also be blended with liquid oil, biomass, or fossil oils, or any combinations thereof, preferably prior to or during the pyrolysis step. The plastic mixture may be melted using an extruder, preferably a single or twin-screw extruder. The oxygen and air content of the raw material entering the reactor may be reduced by compacting the plastics mixture using a hydraulic press with air outlet.

In one preferred embodiment, coking is inhibited by adding sulfur containing additives, such as DMDS and DMS, phosphorus containing compounds, such as organophosphates and organophosphites, silicon containing compounds, cerium oxide or alumina, or any combination thereof into the blend.

An isomerized oil containing more than 70 % saturated and unsaturated hydrocarbons, with or without a nitrogen content varying between 0.01 ppm and 10000 ppm, may be produced in the above process. The isomerized oil produced in the process may be filtered using any of the following: metallic or ceramic sieves, reverse osmosis, minerals, such as bentonite, clay, kaolinite, zeolite, montmorillonite, attapulgite, sepiolite, activated or non-activated aluminum oxide, activated carbon, biomass, diatomaceous earth, fly ash, ash or aluminosilicates, or any combination thereof.

In one preferred embodiment, the isomerized oil is treated with hydrogen at a temperature range of 300-400 °C in the presence of catalysts such as Ni and/or Co and/or Mo based catalyst, with or without a catalyst carrier, such as a refractory metal oxide, to reduce oxygenates and olefin content.

The isomerized oil produced using the method of the invention may be distilled to produce a series of fractions, preferably at least four hydrocarbon fractions. Such fractions are preferably a gas fraction containing, in any ratio, methane, ethane, ethylene, propane, propylene, butane, isobutane, butylene, isobutylene; a naphthalike liquid fraction having a molecular weight approximately between 70-150; a heavier diesel/gasoil type fraction, and heavy fuel oil type fraction.

In one preferred embodiment excess heat originating from any part of the process may be used to preheat and dry the plastic feed and/or to preheat the oil or biomass feed. In a further preferred embodiment, the isomerized hydrocarbons obtained in the process as described above are used as raw material in the polymer industry.

Drawings

Figure 1: Flowchart presenting the main steps of the process of the invention.

Detailed description of the invention

The present inventors surprisingly discovered that with the process according to the disclosed claims, it is possible to use recycled plastic, and especially mixed plastic as raw material for products that may be utilized in the polymer industry. The inventors also discovered that the invention enables good controllability of the process, as it is possible to produce hydrocarbon products in a very selective manner, for example, by the choice of catalysts and by adjusting the reaction pressure and/or temperature. The process of the invention also decreases the energy demand, as it is possible to use lower temperatures and pressures than in the current state of the art. In this way, the overall efficiency of the process can be substantially improved.

The method of the present invention enables the reduction of the pour point of the thermolysis oils, i.e., pyrolysis oils, by producing an isomerized oil with lower pour point and/or cloud point than achieved using conventional methods. This is important with respect to the feasibility of using plastic waste in a circular economy, as the possibility to produce product fractions that can be utilized in the polymer industry reduces the carbon footprint and is crucial in order the reduce the use of crude oil as raw material. By the method of the present invention, it is possible to exploit the plastics already in use and to re-circulate plastic materials for as long as possible. All kinds of waste plastics, such as plastics from household waste or the industry, are suitable as raw material for the process.

In the method of the present invention, plastics may be used as the only raw material, and also in the combination with liquid oils and/or biomass. From a sustainability perspective, such liquid oils are preferably not originating from crude oil. One benefit with the method of the present invention is that different types of plastics do not need to be separated before entering the thermocatalytic process, as it is possible to use an unsorted or partially sorted plastic mix as feedstock. It may, however, be beneficial to separate or otherwise avoid certain types of plastics in the mix, the decomposition products of which either may act as catalyst poisons or may be damaging to the apparatus. Examples of such plastics are polyethylene terephthalate (PET), due to high oxygen content, and polyvinyl chloride (PVC), due to corrosive nature of fragments. The selectivity of the process can be obtained by gradually adding different catalysts and by adjusting the temperature and pressure of the process. The selectivity is based, among others, on different plastics having different properties, e.g., depolymerization and vaporization properties, which can be used in the process for the selective production of the monomers and other short hydrocarbon fragments.

The present invention relates to a process for producing fully or partially isomerized hydrocarbons from mixed plastic in a thermocatalytic process. In said process, a mixture of plastics is subjected to a thermolysis process in at least one reactor at a temperature range from 150 to 950 °C in a substantially oxygen free environment in the presence of a combination of catalysts, wherein at least one catalyst functions as pyrolysis catalyst and at least one further catalyst functions as isomerization catalyst. The combination of catalysts may be a combination of catalysts or catalytic agents added simultaneously, or two or more catalysts or catalytic agents added at different stages of the process. One of the catalysts is natural biomass derived ash, functioning as pyrolysis catalyst, and the at least one further catalyst is an isomerization catalyst including at least one of Na, Ni, Mo, Zr, Al, Mg, zeolite, silicates or a metal catalyst, possibly in the form of metal oxide, metal salt or metal complex. In one embodiment, the isomerization catalyst is a metal catalyst including any of the following or a combination thereof: Cu, Ni, Co, Zn, Ag, Al, K, Na, Zr, Ca, Ba, Pt, Pd, V, Rh, Mg, Mn, Mo and Ti. Such a metal catalyst may be in the form of, for example, metals, oxides, salts hydroxides or complexes.

An isomerized oil is obtained in the process of the invention, the isomerized oil being a pyrolysis oil containing partially or fully isomerized hydrocarbons. The isomerized oil has substantially lower pour point and cloud point compared to pyrolysis or thermolysis oils produced using conventional methods. The isomerized oil produced in accordance with the present invention may have a pour point of around 0°C and higher, while pyrolysis oils produced using conventional methods have a pour point of approximately 20 °C and higher, the lower pour point indicating a higher degree of isomerization.

The process of the invention is carried out using a suitable catalyst, or combination of catalysts. When two or more catalysts are used, these may be added simultaneously or at different stages of the process.

In the present invention, the catalyst may comprise any of the following or a mixture or mixtures of any of the following, in any given ratio:

* natural biomass derived ash,

* fossil fuel derived ash, including fly ash,

* metal powders, e.g., copper,

* inorganic metal salts and oxides, such as, kaolinite, clay, montmorillonite, zeolite, silicates, bentonite, sand etc.,

- Metal catalysts in the form of, for example, metals, oxides, salts, hydroxides or complexes, preferably including any of the following or a combination thereof: Cu, Ni, Co, Zn, Ag, Al, K, Na, Zr, Ca, Ba, Pt, Pd, V, Rh, Mg, Mn, Mo and Ti,

* organic metal salts, e.g., acetates, citrates etc.,

* carbonaceous catalyst components, such as:

- graphite and oxides,

- graphene and/or carbon nano tubes, and blends,

- activated carbon,

- coke or char,

* organic and inorganic alkalis and bases, such as tert-butyl amine compounds, for example, TBAB, TBAH,

* geopolymers,

* diatomaceous earth,

* waste or residue derived minerals or mixtures.

The amount of catalyst used may be in the range of 0.001-10 w-% of the total composition. Preferable ranges are from 0.001 wt-% up to 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 wt-%, or from 0.01 wt-% up to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 wt-%, or from 0.1 wt-% up to 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 wt- % of the total composition.

It may be beneficial to use different catalysts for the thermolysis and for the isomerization. The thermolysis process may be catalyzed using any pyrolysis catalyst known in the art. Especially preferable is use of natural biomass derived ash as pyrolysis catalyst, preferably in combination with a further catalyst selected from fossil fuel derived ash, including fly ash; metal powders; inorganic metal salts and oxides, such as metal chlorides, kaolin, clay, montmorillonite, zeolite, bentonite and sand; organic metal salts, e.g., acetates and citrates; carbonaceous catalyst components; organic and inorganic alkalis and bases, such as tert-butyl amine compounds, for example, TBAB, TBAH; geopolymers; diatomaceous earth, and waste or residue derived minerals and mixtures. It is preferable to use at least one isomerization catalyst in the process, preferably a metal catalyst, possibly in the form of a metal oxide, metal salt or metal complex, or any combination thereof. Suitable isomerization catalysts may include, for example, Na, Ni, Mo, Zr, Al, Mg, zeolite, or silicates. Other suitable isomerization catalysts are Ti and Zn. Especially preferable is the use of both at least one pyrolysis catalyst as well as at least one isomerization catalyst. In one preferred embodiment of the invention, liquid oil, biomass or fossil oils, or any combination thereof is added to the mixture of plastics as raw material in the ther- mocata lytic process.

The mixture of plastics, or any reaction product thereof, may be brought into contact with the catalysts at different stages of the process. The catalysts may be premixed into the feed or added later in the process, for example directly into the at least one reactor, such as a fluidized bed reactor or fixed bed reactor. When the at least one catalyst is premixed into the feed, it may be premixed into any part of it, such as the mixed plastic, liquid oil and/or biomass feed. The addition of the catalyst in the reactor is an especially beneficial approach when it comes to the pyrolysis catalyst. Another alternative is incorporation of the catalysts into structural parts of the reactor, such as the sieve of a fixed bed reactor or any contact surfaces. Having the catalyst incorporated into structural parts of the reactor is an especially preferable approach for isomerization catalysts. The reaction product obtained in the thermolysis process may, for example, be contacted with isomerization catalysts present on 1-10 static fixed beds after the pyrolysis reactor.

The mix of plastics is melted in a reactor, prior to entering a reactor and/or in a feeding apparatus. Especially preferred is use of an extruder, such as a single or twin-screw extruder, to melt the plastics mixture entering the reactor. The feedstock, which contains the plastics mixture, is preferably compacted using a hydraulic press with air outlet to reduce the oxygen and air content in the raw material before entering the reactor. When liquid oil and/or biomass is blended into the mixture of plastics, the weight ratio of plastics to the total content of liquid oil and/or biomass may vary greatly, preferably being from 100:1 to 1:100, or more preferably from 10:1 to 1: 10.

Within this application is by the term "liquid oil" meant any liquid oil of natural, processed, or synthetic origin. Such oils may be natural oils or products derived from natural oils, for example, natural origin triglycerides, fatty acids or organic or inorganic esters or salts of fatty acids, or tall oil derivatives, including tall oil pitch and rosins. The liquid oil may also be a recycled or pyrolyzed oil, fossil oil, or a product derived from crude oil, such as, VGO (vacuum gas oil). From a sustainability perspective, it is, however, preferable that the oil is not derived from crude oil.

Within this application is by the term "biomass" meant an organic material of any origin biomass, such as wood, lignin, forest and agricultural residues, organic waste or other solid carbon-containing biomass, natural oils, algae oils, microbial oils, natural resins and rosins, algae or other aquatic or marine biomass, or other organic material even if derived synthetically from carbon dioxide.

After being melted, the plastics mixture, possibly blended with liquid oil and/or biomass, is then subjected into a pyrolysis process, i.e., a thermolysis process, as both terms herein are interpreted as interchangeable. The pyrolysis is conducted in at least one reactor at a temperature ranging from 150 to 700 °C in a substantially oxygen free/anaerobic environment. The temperature range is varied depending on the raw material, the wanted product outcome and the catalysts used. The temperature range may also be chosen within the above range, such that the temperature is, for example, from 150, 175, 200, 250 or 300 °C up to 300, 350, 400, 450, 500, 550, 600, 650, 700, 850, 900, 950 °C. The temperature range may also be from 150 or 175 °C up to 200 or 250 °C. The pyrolysis and the isomerization may take place at different temperatures, for example, such that a slightly higher temperature is utilized in the pyrolysis step than in the isomerization step. The temperatures may, as a non-limiting example, be from 400 °C and above in the thermolysis step, while the isomerization takes place at approximately 350 °C. Noteworthy is, that these temperatures may vary greatly depending on, for example, the catalysts used and the plastic mixture.

Since coking is not desired to occur in the thermocatalytic process, it may be inhibited by addition of any of the following substances, or any combination thereof:

* sulphur containing additives, such as, DMDS and DMS,

* phosphorus containing compounds, e.g., organophosphates and organophos- phites,

* silicon containing compounds,

* cerium oxide and/or alumina.

In a preferred embodiment, the pyrolysis product is transferred to filtration via a pipe or vessel containing fixed-bed metallic catalysts such as Ni, Mo or Al or Pt or Zr or Ti based to promote isomerization of the hydrocarbons produced. This tube or vessel is heated, or heat is maintained, to obtain a reaction temperature required for a certain catalyst. The temperature may, for example, be between 300-400 °C for optimal isomerization with Mo, and 100-200 °C for optimal isomerization with Zr and Pt catalysts. The reaction time is preferably up to two hours for Ni, Mo and Ti catalysts, while the reaction time is longer, preferably up to 9 hours, with Zr and Pt to allow enough contact time between the hydrocarbons and the catalyst.

In one embodiment of the invention the pyrolysis product is filtered using any of the following, without being limited thereto, metallic or ceramic sieves, reverse osmosis, minerals such as bentonite, clay, kaolinite, zeolite, montmorillonite, attapulgite, sepiolite, activated or non-activated aluminum oxide, activated carbon, biomass, diatomaceous earth, fly ash, ash or aluminosilicates, or used minerals or mixtures from any process. In the process according to the invention it is important to eliminate oxygen content from the products as well as possible. Therefore, after the filtration, the isomerization oil is preferably treated with hydrogen at 300-400 °C in the presence of catalysts, e.g., Ni and/or Co and/or Mo based catalysts, with or without a catalyst carrier such as a refractory metal oxide, to reduce oxygenates and also olefin content.

In another embodiment of the invention, the isomerized oil is distilled to produce a series of hydrocarbon fractions. Any number of fractions may be produced, although it is preferred to separate at least four hydrocarbon fractions, such as a gas fraction containing, in any ratio, methane, ethane, ethylene, propane, propylene, butane, isobutane, butylene or isobutylene; a naphtha-like liquid with molecular weight approximately between 70 and 150 g/mol; a heavier diesel/gasoil type fraction; and a heavy fuel oil type fraction.

An isomerized oil is obtained as a product of the above-mentioned process. The isomerized oil preferably containing more than 70% saturated and unsaturated hydrocarbons with or without a nitrogen content, which may vary from 0.01 ppm up to 1000 ppm or 10000 ppm.

As a side product of the process according to the invention a char can be produced from plastics and biomass.

Excess heat originating from any part of the process may be used to preheat and dry the plastic feed and/or to preheat the liquid oil or biomass feed. Although this kind of waste heat cannot be utilized in combustion processes, for example, it could be recovered and used as auxiliary heat in any process in which the raw material needs to be heated in the process itself. Such processes are, for example, processes for plastic processing, such as extrusion and/or injection-molding. In this way the temperature of the raw material feed can be raised to reduce energy required in the heating process.