EP4669723A1

EP4669723A1 - METHOD FOR REMOVAL OF CONTAMINANTS FROM PLASTIC WASTE OIL

Info

Publication number: EP4669723A1
Application number: EP24704490.2A
Authority: EP
Inventors: Jean-Paul Andre Marie Joseph Ghislain LANGE; Guus VAN ROSSUM; Timothé Johannes OLTHOF; Kai Jürgen FISCHER; Hendrik Stichter; Jose Atilio Quevedo Enriquez; Matthieu Simon Henri Fleys
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2023-02-21
Filing date: 2024-02-14
Publication date: 2025-12-31
Also published as: CN120641528A; WO2024175435A1

Abstract

A process for the removal of contaminant from a contaminated liquid waste plastics oil, said process comprising: (i) contacting the contaminated liquid waste plastics oil having an initial contaminant content with a washing stream having a pH of greater than, the washing stream comprising a washing solvent, a phase transfer catalyst, and optionally a reducing agent; (ii) mixing the contaminated liquid waste plastics oil with the washing stream to produce a reaction mixture; (iii) settling the reaction mixture into at least a hydrocarbon phase having a final contaminant content that is less than the initial contaminant content, and an aqueous phase containing at least one reaction product of the contaminant and the washing stream, and (iv) separating the hydrocarbon phase from the aqueous phase.

Description

PROCESS FOR REMOVING CONTAMINANTS FROM WASTE PLASTICS

OIL

FIELD OF THE INVENTION

[0001] The present invention is directed to a process for removing contaminants from a waste plastics oil stream.

BACKGROUND OF THE INVENTION

[0002] Waste plastics oils are oils which are produced from waste plastics material. As well as containing desirable hydrocarbons typically with a high content of paraffins (> 30%), waste plastics oils may also contain undesirable contaminants such as heteroatom-containing compounds, for example organic halides and siloxanes.

[0003] Waste plastics oils are useful feedstocks and can be fed to a steam cracker or a catalytic cracker for the production of useful and high-value chemicals such as olefins, including ethylene and propylene which are monomers which can be used in making new plastics. However, before being subjected to cracking processes, contaminants present in the waste plastics oils must be dealt with in order to prevent problems resulting from fouling and corrosion of process equipment, or poisoning of downstream units, for example through catalyst deactivation. Examples of contaminants which may need to be removed from waste plastics oils before being fed to a cracker include heteroatoms and heteroatom-containing compounds such as metals, organic acids, organic halides, phenols and substituted phenols, caprolactam and siloxanes.

[0004] Hydrotreating is seen as a standard solution for the removal of heteroatom containing organic compounds, such as organic chlorides, from a waste plastics oil stream. An alternative method makes use of washing followed by extraction to remove contaminants from the oil. However, there are problems associated with these known methods of removing contaminants from waste plastics oil streams. Hydrotreating requires a hydrogen supply which can be expensive. Further, reactors are required containing catalysts and/or adsorbents which are prone to deactivation or saturation depending on contaminant levels leading to high operating costs. These reactors operate at high temperature and pressure leading to high investment costs as well. Further, extraction methods typically involve a washing step and an extraction step using toxic extraction solvents, typically requiring energy intensive purification step(s) and may generate a significant waste oil effluent stream enriched in contaminants.

[0005] Organic chlorides, such as tetrachloromethane, trichloromethane (chloroform) and dichloromethane, are particularly problematic contaminants in chemical processing plants as their presence during chemical processing results in the production of hydrochloric acid. Hydrochloric acid attacks metal resulting in corrosion of equipment with the associated risk of leaks and other safety incidents. Further processing of contaminated waste plastics oil can be inefficient and challenging in terms of logistics and storage if contamination levels are substantially above desirable or allowable limits.

[0006] Silicon-containing compounds, such as siloxanes are also particularly problematic when present as contaminants in waste plastics oil, especially if not removed before subjecting the waste plastics oil to cracking processes. Siloxanes can cause fouling of process equipment and catalyst poisoning downstream in the steam cracker.

[0007] Oxygenates such as organic acids, phenol/substituted phenols, caprolactams, and the like, can cause fouling or corrosion of process equipment and catalyst poisoning downstream in the steam cracker.

[0008] It would be highly desirable to provide alternative effective processes for removing chemical contaminants, particularly oxygenates, nitrogen compounds, organic halides and siloxanes from waste plastics oils. It would be even more preferable if such a process could be carried out without the addition of complicated apparatus and infrastructure. It would also be preferable to provide a process for removing contaminants which does not involve the need for hydrogen which is required in hydrotreating. It would also be preferably to provide a process which does not involve toxic extraction solvents and which is simpler than a process which involves a washing step followed by an extraction step. It would also be preferable to provide a process which is less energy intensive than hydrotreating and extraction methods. Further, it would be preferable to provide a process which has high hydrocarbon recovery.

SUMMARY OF THE INVENTION

[0009] According to the present invention, there is provided a process for the removal of contaminant from a contaminated liquid plastics waste oil, said process comprising:

(i) contacting the contaminated liquid plastics waste oil having an initial contaminant content with a washing stream having a pH of greater than 10, the washing stream comprising a washing solvent, a phase transfer catalyst, and optionally a reducing agent;

(ii) mixing the contaminated liquid plastics waste oil with the washing stream to produce a reaction mixture;

(iii) settling the reaction mixture into at least a hydrocarbon phase having a final contaminant content that is less than the initial contaminant content, and an aqueous phase containing at least one reaction product of the contaminant and the washing stream, and

(iv) separating the hydrocarbon phase from the aqueous phase.

[00010] It has been found that the process of the present invention provides an efficient and effective way of removing undesirable contaminants such as organic acids, phenols, substituted phenols, caprolactams, organic halides and siloxanes from a contaminated liquid plastics waste oil, without the problems associated with known processes mentioned above. Once such contaminants have been removed, the resulting decontaminated liquid plastics waste oil can be more readily subjected to processes such as steam cracking and catalytic cracking without negative side effects associated with the contaminants.

DETAILED DESCRIPTION OF THE INVENTION

[00011] While the process of the present invention and the stream(s) used in said process are described in terms of “comprising”, “containing” or “including” one or more various described steps and components, respectively, they can also “consist essentially of” or “consist of’ said one or more various described steps and components, respectively.

[00012] In the context of the present invention, in a case where a stream or a phase comprises two or more components, these components are to be selected in an overall amount not to exceed 100%.

[00013] Further, where upper and lower limits are quoted for a property, then a range of values defined by a combination of any of the upper limits with any of the lower limits is also implied.

[00014] Surprisingly, it has been found that contaminants such as organic acids, organic halides, phenols, substituted phenols, caprolactams and siloxanes can be removed from contaminated waste plastics oil by contacting the contaminated waste plastics oil with a washing stream having a pH of greater than 10, wherein the washing stream comprises a washing solvent, a phase transfer catalyst, and optionally a reducing agent. The contaminated waste plastics oil is mixed with the washing stream to produce a reaction mixture. The reaction mixture is then settled into a hydrocarbon phase and an aqueous phase. The hydrocarbon phase has a final concentration of contaminant, such as organic acids, phenols, substituted phenols, caprolactams, organic halide or siloxane, that is less than the initial contaminant content of the contaminated waste plastics oil. The aqueous phase comprises at least one reaction product of the contaminant and the washing stream. The hydrocarbon phase and the aqueous phase can then be separated.

[00015] The hydrocarbon phase may then be subjected to further processing such as catalytic cracking, steam cracking, gasification, and the like. Alternatively, the hydrocarbon phase can be subjected to further treatment before being fed to a catalytic cracker, steam cracker or a gasifier, such as solvent extraction, hydrotreatment, adsorption and the like. [00016] The present invention also relates to a process for steam cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises the hydrocarbon phase produced by the process of the present invention. Further, the present invention relates to a process for catalytic cracking a hydrocarbon feed, wherein the hydrocarbon feed comprises the hydrocarbon phase produced by the process of the present invention.

[00017] Further, the present invention also relates to a process for steam cracking a hydrocarbon feed, comprising the following steps: (a) producing a hydrocarbon phase by the process of the present invention and (b) steam cracking a hydrocarbon feed comprising at least part of the hydrocarbon phase produced in step (a). Still further, the present invention relates to a process for catalytic cracking a hydrocarbon feed, comprising the following steps: (a) producing a hydrocarbon phase by the process of the present invention and (b) catalytic cracking a hydrocarbon feed comprising at least part of the hydrocarbon phase produced in step (a).

[00018] The aqueous phase may be disposed of in an effluent treating process known to those skilled in the art.

[00019] The process of the present invention is suitable for the removal of a wide variety of contaminants, including heteroatoms, or heteroatom containing compounds. As used herein, the term ‘heteroatom’ refers to any atom which is not carbon or hydrogen. Examples of contaminants present in a waste plastics oil stream include organic halides such as organic chlorides, bromides and fluorides, nitrogen, oxygen, sulphur, metals such as aluminium, calcium, chromium, copper, iron, potassium, magnesium, sodium, nickel, phosphorus, silicon, and zinc, organic acids, phenols, substituted phenols, caprolactams and siloxanes, and mixtures thereof.

[00020] The process of the present invention is particularly advantageous for the removal of organic halides, organic acids, phenols, substituted phenols, caprolactams and siloxanes from a liquid waste plastics oil.

[00021] Organic chlorides include, but are not limited to, chloroform, carbon tetrachloride, tetrachloroethylene, vinyl chloride, chlorobenzene, chloroprene, propylene dichloride, dichloromethane and trichloroethylene. Organic chlorides are not tolerated in chemical processes at very high levels.

[00022] Examples of siloxane contaminants include cyclic siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane, hexadecamethylcyclooctosiloxane, octadecamethylcyclononasiloxane, cyclodecasiloxane and eicosamethylsiloxane, and mixtures thereof.

[00023] When the contaminant is organic chloride, the initial organic chlorides content expressed in ppmw Cl in the contaminated waste plastics oil before the process of the present invention can be greater than 0 ppmw or greater than 10 ppmw, or at least 20 ppmw, or at least 50 ppmw, or at least 100 ppmw, and may be at most 5000 ppmw, or at most 3000 ppmw, based on the overall weight of the contaminated waste plastics oils. The final organic chloride content expressed in ppmw Cl in the hydrocarbon phase is preferably no more than 200 ppmw, or no more than 100 ppmw, or no more than 25 ppmw, or no more than 10 ppmw, preferably no more than 5ppmw based on the overall weight of the hydrocarbon phase. In a preferred embodiment herein, the final organic chloride expressed in ppmw Cl content is 30% less, more preferably 50% less, even more preferably 70% less than the initial organic chloride content expressed in ppmw Cl.

[00024] When the contaminant is siloxane, the initial siloxane content expressed in ppmw Si in the contaminated waste plastics oil before the process of the present invention can be greater than 0 ppmw or greater than 10 ppmw, or at least 20 ppmw, or at least 50 ppmw, or at least 100 ppmw, and may be at most 5000 ppmw, or at most 3000 ppmw, based on the overall weight of the contaminated waste plastics oils. The final siloxane content expressed in ppmw Si in the hydrocarbon phase is preferably no more than 200 ppmw, or no more than 100 ppmw, or no more than 25 ppmw, or no more than 10 ppmw, preferably no more than 5 ppmw based on the overall weight of the hydrocarbon phase. In a preferred embodiment herein, the final siloxane content expressed in ppmw Si is 30% less, more preferably 50% less, even more preferably 70% less than the initial siloxane content expressed in ppmw Si. [00025] The contaminated waste plastics oil may be any waste plastics oil that has not yet been subjected to further processing. The contaminated waste plastics oil is typically produced by liquefaction, pyrolysis, thermal cracking, hydrothermal treatment or catalytic cracking, among others, of a waste plastics material. A preferred method of producing the contaminated waste plastics oil is via pyrolysis or liquefaction of a waste plastics material, preferably in a waste plastics liquid plant (WPLP). In liquefaction the product remains in liquid form (at elevated pressure), whereas in pyrolysis gas and vapours are formed which upon condensation form the liquid plastics pyrolysis oil. The waste plastics used in a waste plastics liquid plant are typically polyolefins and polystyrenes. PET and PVC can also be used in a WPLP but these typically include high levels of contaminants such as chlorides and oxygenates. The contaminated waste plastics oil typically has a boiling range from light naphtha to heavy diesel (around 450 up to 650°C final boiling point).

[00026] The washing stream comprises a washing solvent, a phase transfer catalyst, and optionally a reducing agent. Importantly, the washing stream has a pH of greater than 10, preferably greater than 11, more preferably greater than 12, even more preferably greater than 13, or greater than 14.

[00027] In a preferred embodiment, the washing solvent is an aqueous solution of an alkali metal salt or an alkaline earth metal salt. Examples of suitable alkali metal or alkaline earth metal salts are lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, and mixtures thereof. In a preferred embodiment, the washing solvent is a caustic solution, i.e. NaOH-based.

[00028] A phase transfer catalyst (PTC) is a catalyst that facilitates migration of a reactant from one phase to another phase where reaction occurs. Suitable phase transfer agents include quaternary ammonium salt compounds, quaternary phosphonium salt compounds, crown ethers, cryptands, polyethylene glycols, and mixtures thereof. Preferably, the phase transfer agent is selected from quaternary ammonium salts, quaternary phosphonium salts and mixtures thereof. Examples of suitable quaternary ammonium salts and quaternary phosphonium ammonium salts include methyltributyl-ammonium chloride , benzyltriethyl ammonium hydroxide, tetrabutyl ammonium hydroxide, tetrabutylsulfuric acid ammonium hydroxide, tetrapentyl ammonium hydroxide, tetrahexyl ammonium hydroxide, trioctylpropyl ammonium hydroxide, decyltripropyl ammonium hydroxide, decyltributyl ammonium hydroxide, dodecyltrimethyl ammonium hydroxide, tetradecyltrimethyl ammonium hydroxide, pentadecyltrimethyl ammonium hydroxide, cetyltrimethylammonium hydroxide, hexaalkyl phosphonium bromide, ethyltriphenyl phosphonium bromide, and mixtures thereof. Examples of suitable crown ethers include 15-crown-5-ether, 18-crown-6 ether, dibenzo-18 crown-6 ether, and mixtures thereof.

[00029] In a preferred embodiment herein, the phase transfer agent is methyltributyl- ammonium chloride or methyltributyl-ammonium hydroxide.

[00030] The phase transfer agent is preferably present in an amount from 0.01 wt% to 1 wt%, more preferably from 0.1 wt% to 0.5 wt%, by weight of the washing stream.

[00031] Suitable reducing agents, when present, include metals such as potassium, calcium, barium, sodium and magnesium and compounds which contain a hydride ion such as alkali metal hydrides (such as NaH, LiH), alkaline earth metal hydrides (such as Cafh). and salts of boron-group hydrides (such as sodium borohydride, lithium borohydride or sodium or lithium salts of aluminium hydrides, gallium hydrides, indium hydrides, thallium hydrides).

[00032] Preferably, the boron-group hydride is boron hydride or aluminium hydride, more preferably boron hydride. Preferably, the salt of the boron-group hydride is an alkali metal salt, wherein the alkali metal may be any one of lithium, sodium, potassium, rubidium, and cesium, more preferably any one of lithium, sodium and potassium, most preferably sodium. Examples of suitable salts of a boron-group hydride include sodium boron hydride, lithium aluminium hydride, and diisobutyl aluminium hydride. Most preferably, the salt is sodium boron hydride (NaBEE).

[00033] When the contaminant for removal is an organic halide, the reducing agent such as sodium borohydride, is preferably selected to be capable of reacting with the organic halide contaminant to form hydrohalic acid and a hydrocarbon.

[00034] Preferably, an excess amount of the reducing agent is used in the present invention. Preferably, the amount of the reducing agent is in the range of from 1 to 5 times, more preferably 1.1 to 3 times, the stoichiometric amount required for reacting with the contaminant compound, e.g. organic halide, in the liquid waste plastics oil. [00035] In a preferred embodiment herein, the washing stream is prepared using an aqueous solution of caustic, phase transfer agent, and optionally an alkali metal salt of a boron-group hydrides. Additional water may also be added to the washing stream, the contaminated waste plastics oil and/or while the washing stream is being contacted and./or mixed with the contaminated waste plastics oil.

[00036] The washing stream may be contacted with the contaminated waste plastics oil in several ways, including, adding the washing stream to a tank or vessel of the contaminated waste plastics oil.

[00037] In one embodiment of the present invention, the contaminated waste plastics oil and the washing stream are contacted at a temperature in the range from 25°C to 100°C, preferably from 30°C to 70°C, more preferably from 40°C to 60°C. This may be achieved by using a cold washing stream having a temperature in the range from 25°C to 100°C, preferably from 30°C to 70°C, more preferably from 40°C to 60°C.

[00038] In another embodiment of the present invention, the contaminated waste plastics oil and the washing stream are contacted at a hot temperature in the range from greater than 100°C to 250°C, preferably from 150°C to 250°C, more preferably from 150°C to 200°C. This may be achieved by using a hot washing stream having a temperature in the range from greater than 100°C to 250°C, preferably from 150°C to 250°C, more preferably from 150°C to 200°C. A hot washing stream is particularly useful for removal of organic chlorides from the waste plastics oil and further improves siloxane removal as well.

[00039] Advantageously, the contaminated waste plastics oil may be contacted with the washing stream by injecting the washing stream during a tank-to-tank transfer or by injecting the washing stream into the contaminated waste plastics oil while loading into a vessel. In this way, there is mixing of the contaminated waste plastics oil and the washing stream during the contacting step.

[00040] The reactive mixture can be processed in different types of processing units such as a column-type with random or structured packing; trays or other contacting internals, a staged mixer/settler type with a conventional line-up or in a column, a line-up with multiple mixer stages, either in separate vessels, a single compartmentalised vessel or in a column, a static mixer followed by a settler or a combination of process units. In the mixing step it is important to provide sufficient power input to maintain sufficient kLa, where kLa is the mass transfer coefficient given in sec . A suitable mechanical stirring device includes static mixer, stirred vessel, a high shear rotating mixer or other mixing device with rotating parts, a continuously stirred tank reactor (CSTR), a plug flow reactor (PFR), and the like. For the mixing and settling steps, a mixer/settler arranagement can be used. For a mixer/settler arrangement, it is important to achieve an efficient and stable emulsion in the mixer and a relatively quick de-emulsification in the settler. A PFR or countercurrent (plug) flow of washing stream and waste plastics oil may be preferable over a CSTR type flow pattern in order to ensure the washing stream and waste plastics oil reach maximum removal efficiency. Alternatively, the mixing may be carried out by removing a portion of the contents of the vessel at one point of a vessel or tank; circulating the portion via external piping; and returning it to the vessel or tank at a different point. Alternatively, the mixing may be carried out via a contacting column or a fiber film contactor.

[00041] The residence time that the waste plastics oil is in contact with the washing stream is in the order or several minutes to several hours. It is important for the plastics waste oil and the washing stream to be well dispersed and this will determine how long to carry out the mixing.

[00042] After mixing, the reaction mixture, comprising the contaminated waste plastics oil, the washing stream and any reaction products of the washing stream and the contaminated waste plastics oil are allowed to settle. Reaction of the contaminants with the washing stream may continue until the aqueous phase and the hydrocarbon phase settle into two substantially distinct phases. However, the reaction rate will diminish over time during settling.

[00043] After settling, the hydrocarbon phase is separated from the aqueous phase. This may be done in a number of ways known to those skilled in the art, for example, without limitation, by draining the aqueous phase from the bottom of a tank or vessel and/or withdrawing the hydrocarbon phase from the top of a tank or vessel. Decanters and centrifuges, among others, may be used in the separation step.

[00044] The aqueous phase (e.g. containing used washing stream) may be recycled back to upstream of the mixing step (ii).

[00045] Optionally, following separation of the hydrocarbon phase from the aqueous phase, the hydrocarbon phase may be subjected to a further washing step with water and/or a further extraction step using an extraction solvent, in order to remove any remaining contaminants. An example of a suitable extraction solvent for this purpose is N-methyl-2- pyrrolidone (NMP), but other solvents can also be used including diols, triols, diketones, glycolethers, amides, DMSO, NFM and furfuryl. Further details on such an extraction step, including suitable extraction solvents can be found in WO2018/104443, incorporated herein by reference in its entirety.

[00046] The hydrocarbon phase can be rinsed with water or an aqueous solution to remove traces of the washing stream which could entrain contaminants.

EXAMPLES

Example 1 (Cold caustic experiment)

Shake tube in lab test: impact of PTC addition (PTC = phase transfer catalyst)

Tests were done in shake tubes at different residence time (mixing time) to assess the effect of temperature, residence time and addition of PTC, methyltributyl-ammonium chloride (MTBAC) on the efficiency removal of Si-compounds. The results are shown in Table 1 and Table 2 at two different residence times, i.e. 2 min and 5 min. The tests were done with a volumetric ratio between Oil and Solvent [water] of 2:1 and at atmospheric pressure. The tests were done with commercial plastics pyrolysis oil samples. The pH of the (washing) solvent (water) was 14.

Table 1: Laboratory test in shake tubes to assess impact of temperature, residence time and addition of PTC on Si removal (at a residence time of 2 minutes): Table 2: Laboratory test in shake tubes to assess impact of temperature, residence time and addition of PTC on Si removal (at a residence time of 5 minutes):

From the results in Tables 1 and 2, it can be seen that PTC addition enhances Si-removal from plastic oil in the low temperature range tested, i.e. at 26°C and 40°C.

Example 2 (hot caustic experiment)

Tests with caustic at elevated temperature were carried out in a dedicated unit, consisting of four high temperature shaking autoclaves made of Hastelloy. The reactor temperature was set at 140°C, a heating oil bath was used as a medium of heat exchange. Pressure was set high enough to prevent evaporisation of hydrocarbons, typically below 30 bar and the residence time was set at 4 hours. All the tests were done with commercial pyrolised plastic feedstock samples. After the caustic exposure at elevated temperature, the oil fraction was separated and it was water-washed (2 volumes of water and 1 volume of oil) three times at room temperature. The pH of the (washing) solvent (water) was 14.

The results are summarized in Table 3 below.

Table 3, Effect of PTC and/or reducing agent additions on the removal of Cl and Si compounds contained in plastic oil at 140°C

Test 1 can be seen as a benchmark since no PTC (phase transfer catalyst) and no reducing agent was added. The results show that, at high temperature such as 140°C and under tested reaction conditions, the effect of adding a reducing agent (Test 3) or a PTC (Test 2) can essentially be seen on Si removal, as shown in Tests 2 and 3. Furthermore, in Test 4, where both the reducing agent and the PTC were added, all silicon-containing compounds were removed from the pyrolyzed oil. Still further, the additives (reducing agent and PTC) had no or little impact on Cl-compound removal (all Tests 2, 3 and 4), when compared to Test 1.

Overall, the results show that a high reactor temperature combined with the addition of PTC and/or a reducing agent can drastically improve the removal of silicon-containing compounds contained in the pyrolyzed oil.

It was observed that the addition of PTC increases the oil recovery by a few percentages. In our tests, it was found that the oil recovery could be increased from 90 to 93 %. The setling behavior was also improved by PTC addition which likely will increase the separation efficiency in the setler.

Claims

C L A I M S

1. A process for the removal of contaminant from a contaminated liquid waste plastics oil, said process comprising:

(i) contacting the contaminated liquid waste plastics oil having an initial contaminant content with a washing stream having a pH of greater than 10, the washing stream comprising a washing solvent, a phase transfer catalyst, and optionally a reducing agent;

(ii) mixing the contaminated liquid waste plastics oil with the washing stream to produce a reaction mixture;

(iv) separating the hydrocarbon phase from the aqueous phase.

2. The process according to Claim 1 wherein the temperature of the washing stream is from 25°C to 100°C.

3. The process according to Claim 1 wherein the temperature of the washing stream is from greater than 100°C to 250°C.

4. The process according to any of Claims 1 to 3, wherein the washing stream has a pH of above 13.

5. The process according to any of Claims 1 to 4 wherein the contaminants are heteroatoms or heteroatom-containing compounds.

6. The process according to any of Claims 1 to 5 wherein the contaminants are selected from organic acids, organic halides, phenols, substituted phenols, caprolactams, siloxanes, and mixtures thereof.

7. The process according to any of Claims 1 to 6 wherein the washing solvent is an aqueous solution of an alkali metal salt or an alkaline earth metal salt.

8. The process according to any of Claims 1 to 7 wherein the washing solvent is an aqueous caustic solution.

9. The process according to any of Claims 1 to 8 wherein the phase transfer catalyst is selected from quaternary ammonium salt compounds, quaternary phosphonium salt compounds, crown ethers, cryptands, polyethylene glycols, and mixtures thereof.

10. The process according to any of Claims 1 to 9 wherein the phase transfer catalyst is a quaternary ammonium salt.

11. The process according to any of Claims 1 to 10 wherein the reducing agent is selected from alkali metals, alkaline earth metals, alkali metal hydride salts, alkaline earth metal hydrides and salts of boron-group hydrides, and mixtures thereof.

12. The process according to any of Claims 1 to 11 wherein the liquid waste plastics oil is produced by liquefaction, pyrolysis, thermal cracking, hydrothermal treatment or catalytic cracking of a waste plastics material.

13. A process for steam cracking a hydrocarbon feed, comprising the following steps: (a) producing a hydrocarbon phase by the process of any one of Claims 1 to 12 and (b) steam cracking a hydrocarbon feed comprising at least part of the hydrocarbon phase produced in step (a).

14. A process for catalytic cracking a hydrocarbon feed, comprising the following steps: (a) producing a hydrocarbon phase by the process of any one of Claims 1 to 12 and (b) catalytic cracking a hydrocarbon feed comprising at least part of the hydrocarbon phase produced in step (a).