Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
  • C10G1/10—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal from rubber or rubber waste
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
  • C10G1/002—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal in combination with oil conversion- or refining processes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
  • C10G1/08—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal with moving catalysts

Definitions

• the present invention relates to an improved method of removing silicon from depolymerized oil, more specifically to in-situ reduction of silicon content during pyrolysis of waste plastic and to a use of alumina for in-situ reduction of silicon content during pyrolysis of waste plastic.
• LWP liquefied waste plastics
• LWP is typically produced by pyrolysis or hydrothermal liquefaction (HTL) of waste plastics. Depending on the source of the waste plastics, LWP has variable levels of impurities.
• HTL hydrothermal liquefaction
• the feed for chemical recycling of plastics usually comprises mixed plastics waste which can originate for example from separately collected plastics from households from which the cleaner plastics fractions have been taken out for mechanical recycling, or from plastics separated from municipal solid waste (MSW).
• MSW municipal solid waste
• sorting the waste even close to 100% plastics content is not economically feasible.
• the waste plastic material (waste plastic feed) for producing LWP usually contains also materials other than plastics. These other materials, including biomass, are also possible sources of impurities which end up in the LWP.
• consumer waste including waste packaging often comprise compositions other than hydrocarbons.
• Silicon is one common nonhydrocarbon element in plastic waste coming from various sources, such as silicones. Therefore, plastic waste that is being subjected to chemical recycling often encounters high amounts of silicon impurities.
• Other typical impurity components are chlorine, nitrogen, sulphur, and oxygen.
• the LWP feed needs to meet the impurity levels for these processes so as to avoid deterioration of the facility, such as catalyst poisoning.
• silicon impurities may cause catalyst deactivation e.g. in hydrotreatment steps and thus techniques for reducing the silicon content in LWP have been studied.
• WO2021/80899 A1 discloses passing LWP (i.e. depolymerized oil) over an absorbent in the presence of hydrogen at temperatures of 80°C to 360°C.
• LWP i.e. depolymerized oil
• the present invention was made in view of the above-mentioned problems and it is an object of the present invention to provide a method of reducing the content of silicon in LWP obtained by a pyrolysis process.
• the present invention is based on the finding that the content of silicon in LWP can be reduced in-situ already during pyrolysis by employing alumina as a reactant. That is, other than in the prior art, it is not necessary to provide a dedicated step of removing silicon from already-produced LWP. Rather, the amount of silicon in the LWP is reduced already in the pyrolysis step.
• the present invention relates to one or more of the following items:
• the present invention relates to relates to an improved method of reducing silicon content in depolymerized oil.
• the content of silicon impurities should be reduced before the LWP is subjected to further processing.
• the present invention focusses on a method of in-situ removal of silicon during the pyrolysis step (i.e. during depolymerisation of waste plastic).
• the present invention specifically relates to a method making use of alumina in the form of granules (also referred to as granulated alumina or alumina granules) which is added to the waste plastic before pyrolysis and which reacts with the silicon compounds produced from organic silicon in the waste plastic during pyrolysis so that the silicon which has undergone reaction with the alumina ends up in the solid residue of the pyrolysis reaction whereas the gas product (gas effluent) is minimized in silicon content and this gas product is then condensed to provide a depolymerized oil (liquefied waste plastic; LWP).
• liquefied waste plastics means a product effluent from pyrolysis process comprising at least depolymerising waste plastics.
• LWP is thus a material which is obtainable by depolymerizing waste plastics.
• LWP may also be referred to as polymer waste-based oil or as depolymerized oil.
• waste plastics may be derived from any source, such as (recycled or collected) consumer plastics, (recycled or collected) industrial plastics or (recycled or collected) end-life-tires (ELT).
• waste plastics refers to an organic polymer material which is no longer fit for its use or which has been disposed of for any other reason. Waste plastics may more specifically refer to end-life tires, collected consumer plastics (consumer plastics referring to any organic polymer material in consumer goods, even if not having "plastic” properties as such), collected industrial polymer waste.
• waste plastics or "polymer” in general does not encompass purely inorganic materials (which are otherwise sometimes referred to as inorganic polymers). Polymers in the waste plastics may be of natural and/or synthetic origin and may be based on renewable and/or fossil raw material.
• the liquefaction process (pyrolysis) is carried out at elevated temperature, and preferably under non-oxidative conditions.
• the liquefaction process may be carried out at elevated pressure.
• the liquefaction process may be carried out in the presence of a catalyst.
• the liquefaction process provides a gas effluent and a solid residue, wherein the gas effluent is condensed to yield an oil product.
• the oil product may be employed as the pyrolysis oil (LWP; i.e. as the product of the process) as such or may be subjected to fractionation (or separation) to provide a fraction (or separated liquid) and may also be subjected to other work-up, in particular to further purification.
• fractionation refers to fractional distillation and/or fractional evaporation.
• typical oil products from the pyrolysis processes comprise gaseous (NTP) hydrocarbons, and hydrocarbons that are waxy or solid at NTP but become liquids upon heating, for example upon heating to 80°C.
• depolymerizing waste plastic means decomposing or degrading the polymer backbones of the waste plastic by pyrolysis to the extent yielding polymer and/or oligomer species of smaller molecular weight compared to the starting waste plastic, but still comprising at least liquid (NTP) hydrocarbons.
• Depolymerizing waste plastics may also involve cleavage of covalently bound heteroatoms such as O, S, and N from optionally present heteroatom-containing compounds.
• the waste plastics, or each waste plastics species in mixed waste plastics, to be subjected to pyrolysis is usually in solid state, typically having a melting point in the range of 100°C or more as measured by DSC as described by Larsen et al. ("Determining the PE fraction in recycled PP", Polymer testing, vol. 96, April 2021, 107058 ).
• the waste plastics, or each waste plastics species may be melted before and/or during the depolymerisation.
• Solid waste plastics may contain various further components such as additives, reinforcing materials, etc., including fillers, pigments, printing inks, flame retardants, stabilizers, antioxidants, plasticizers, lubricants, labels, metals, paper, cardboard, cellulosic fibres, fibre-glass, even sand or other dirt. Some of the further components may be removed, if so desired, from the solid waste plastics, from melted waste plastic, and/or from liquefied waste plastic using commonly known methods.
• the (solid) waste plastics to be subjected to the pyrolysis has an oxygen content of 15 wt.-% or less, preferably 10 wt.-% or less, more preferably 5 wt.-% or less, of the total weight of the (solid) waste plastics.
• the oxygen content may be 0 wt.-% and may preferably be in the range of 0 wt.-% to 15 wt.-% or 0 wt.-% to 10 wt.%.
• Oxygen content in wt.-% can be determined by difference using the formula 100 wt.-% - (CHN content + ash content), wherein CHN content refers to combined content of carbon, hydrogen and nitrogen, as determined in accordance with ASTM D5291, and ash content refers to ash content as determined in accordance with ASTM D482/EN15403.
• the term "granules” or “ in granulated form” encompasses all kinds of powders, grains, agglomerates and the like and is not limited to a specific shape.
• pyrolysis reactor refers to the pyrolysis zone of an apparatus carrying out a pyrolysis reaction. That is, the “ pyrolysis reactor” is the place where the actual pyrolysis reaction takes place.
• the term "solid residue" means a material which is not transferred to the gas phase in the course of the pyrolysis reaction. Usually, such a solid residue contains tar and inorganic impurities which are not evaporated.
• the solid residue comprises the alumina reacted with silicon. This means that the alumina has a higher Si content than at the time of addition (i.e. a higher Si content than the granulated alumina).
• the reaction may comprise or be a physical reaction (e.g. adsorption) and/or a chemical reaction.
• Si is chemically reacted with the alumina, preferably bonded to the alumina surface (accessible surface, including permeating into the open pores).
• organic silicon in waste plastic is in the form of polysiloxanes, which form volatile oligosiloxanes during pyrolysis and are thus transferred to the oil product.
• Inorganic silicon e.g. in the form of silica, on the other hand, is not reactive (and not volatile) under pyrolysis conditions and thus ends up in the solid residue in any case.
• the method of the present invention is characterized by mixing granulated alumina with waste plastic and subjecting this mixture to pyrolysis in a pyrolysis reactor so that silicon in the waste plastic reacts with the alumina and is transferred to the solid residue.
• the present invention relates to a method of producing a pyrolysis oil, said method comprising the steps of adding alumina in the form of granules to organic silicon-containing waste plastic to form a mixture, feeding said mixture to a pyrolysis reactor, pyrolysing said mixture in said reactor, recovering at least a pyrolysis gas and a solid residue from said reactor, and condensing the pyrolysis gas to provide an oil product, wherein the solid residue comprises the alumina reacted with silicon.
• the mixture is thus prepared before the mixture enters the pyrolysis reactor (i.e. the pyrolysis reaction zone).
• the mixture may be prepared in advance or in a feed unit, such as an extruder.
• the step of adding alumina to form a mixture may also be referred to as mixing step
• the alumina is preferably added in an amount of 0.2 wt.-% to 40.0 wt.-% (relative to 100 wt.-% of pyrolysis feed), more preferably 0.5 to 35.0 wt.-%, 1.0 to 30.0 wt.-%, 1.5 to 25.0 wt.-%, 2.0 to 20.0 wt.-%, 2.5 to 15.0 wt.-%, 3.0 to 13.0 wt.-%, 4.0 to 12.0 wt.-%. 5.0 to 11.0 wt.-%, 5.5 to 10.0 wt.-%, or 6.0 to 9.0 wt.-%.
• the term " relative to 100 wt.-% of pyrolysis feed” refers to the summed amount of waste plastic (including all impurities and contaminations such as biomass), alumina and other feeds (but excluding pyrolysis catalyst if present). That is, as pointed out above, the waste plastic may be derived from municipal waste and may include some biomass even after sorting.
• the step of adding alumina to form a mixture may be carried out at elevated temperature.
• elevated temperature means that external heating is applied to the mixing device (such that the components to be mixed are heated).
• the mixing step may be carried out at a temperature in the range of from 50°C to 280°C, preferably in the range of from 60°C to 270°C, 80°C to 260°C, 100°C to 250°C, 110°C to 250°C, 120°C to 250°C, 130°C to 240°C, 140°C to 230°C, or 150°C to 220°C.
• elevated temperature in the mixing step, the processing can be facilitated and a more intimate mixture can be prepared.
• the "temperatur" at which the mixing step is carried out refers to the temperature of the mixed materials (not to the temperature of the heating medium).
• said adding alumina to form a mixture may comprises (at least partially) melting the waste plastic.
• a more intimate mixture can be prepared.
• a melted material further facilitates handling thereof.
• the addition of alumina may be carried out before and/or during and/or after melting the waste plastic, but is preferably carried out at least before melting.
• the waste plastic in the present invention preferably predominantly contains thermoplastic compounds.
• the term " predominantly contains " thermoplastic compounds means that at least 50 wt.-% (preferably at least 60 wt.-%, at least 70 wt.-%, at least 80 wt.- %, at least 90 wt.-%) of the waste plastic is formed of thermoplastic compounds based on the waste plastic as a whole.
• the mixing step is carried out in an extruder, preferably in a melt extruder. Since an extruder is often used as a feed unit to supply waste plastic to a pyrolysis reactor, the addition of alumina at this stage can be easily achieved while at the same time achieving intimate mixing.
• the mixing step may be carried out without external heating, such as at room temperature. In this case, handling is facilitated since it is not necessary to take care of high temperatures and/or cooling effects in the mixing step.
• Pyrolysis may be carried out as a batch or continuous method, preferably a continuous method.
• the alumina (alumina granules) preferably has an average particle size in the range of from 50 nm to 10 mm, preferably in the range of from 10 ⁇ m to 2.0 mm, in the range from 50 ⁇ m to 1.8 mm or in the range from 100 ⁇ m to 1.5 mm.
• Average particle sizes can be measured for example by laser diffraction (ISO 13320) or by optical or electron microscopy (ISO13322) methods.
• Specific surface areas and pore sizes (pore diameters) of alumina can be determined by gas adsorption measurements, e.g. based on ISO 9277 or ISO 15901-2.
• the particle size refers to the size of the agglomerate rather than to the primary particle size.
• the alumina (alumina granules) may for example have a porosity in the range of 20-85%.
• the alumina preferably has an open pore structure.
• the inventors found that the silicon mainly reacts with the alumina surface and therefore an open pore structure (having a high accessible alumina surface) is preferable.
• the alumina has pore sizes in the range of from 30 ⁇ to 10000 ⁇ , preferably from 40 ⁇ to 1000 ⁇ , from 50 ⁇ to 500 ⁇ , from 55 ⁇ to 300 ⁇ , or from 60 ⁇ to 200 ⁇ .
• the alumina preferably has a BET specific surface area in the range of from in the range of from 50 m 2 /g to 500 m 2 /g, preferably above 50 m 2 /g, above 100 m 2 /g, or 150 m 2 /g or more, such as in the range of from 150 to 300 m 2 /g.
• the method of the present invention may further comprise post-processing the oil product recovered from the pyrolysis reactor.
• the oil product produced by the method of the present invention may be sufficiently pure to be added to the value chain (such as being used in a crude oil refinery process), it is preferable to post-process the oil product to improve its purity or usability.
• the post-processing thus may in particular comprise purification process(es), such as fractionation or extraction, and/or upgrading process(es), such as hydrotreatment. Nevertheless, any known petrochemical process may be used for post-processing and, in particular, the oil product may be used as a co-feed in a petrochemical process.
• the post-processing comprises subjecting the oil product to heat treatment with an aqueous solution of a basic substance, preferably an aqueous solution of a metal hydroxide, more preferably of sodium hydroxide, followed by liquid-liquid separation to provide an oil product which was further purified.
• aqueous solution preferably comprises at least 50 wt.- % water, more preferably at least 70 wt.-% water, more preferably at least 85 wt.-% water, at least 90 wt.-% water or at least 95 wt.-% water.
• the aqueous solution preferably comprises at least 0.3 wt.-% of the basic substance, more preferably at least 0.5 wt.-%, at least 1.0 wt.-%, or at least 1.5 wt.-% of the basic substance, such as 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.- % to 6.0 wt.-%, or 1.5 wt.-% to 4.0 wt.-%.
• the aqueous solution comprises at least 0.5 wt.-%, preferably at least 1.0 wt.-%, or at least 1.5 wt.-% of a metal hydroxide or of an alkali metal hydroxide, such as from 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.-% to 6.0 wt.-%, or 1.5 wt.-% to 4.0 wt.-%.
• the heat treatment may be carried out at a temperature of 150°C or more, preferably 190°C or more, or 200°C or more, such as 210°C or more, 220°C or more, 240°C or more or 260°C or more.
• the heat treatment is preferably carried out at a temperature of 450°C or less, preferably 400°C or less, 350°C or less, 320°C or less, or 300°C or less.
• the heat treatment may be carried out at a temperature in the range of 200°C to 350°C, preferably 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C.
• the post-processing may comprise hydrotreating the oil product to provide a hydrotreated oil product.
• Hydrotreatment may in particular be used for removal of heteroatoms and/or for olefin saturation.
• Hydrotreatment is particularly favourable in the present invention because organic silicon may act as a catalyst deactivator.
• the method of the present invention can protect the hydrotreatment catalyst from being deteriorated and increase its service life.
• the pyrolysis step in the method of the present invention can be further implemented with a second step (as a two-step process).
• the two steps can vary in reactor types also with reaction temperatures.
• the first step is to perform cracking with solid residue removed in the first reactor.
• the second step is then to treat the pyrolysis gas by contacting it with catalyst to selective crack long (carbon) chains.
• a product stream e.g. oil or gas
• a product stream e.g. oil or gas
• the first step may be a step of cracking the waste plastic into (long chain) compounds whereas the second step mainly serves to crack (long chain) compounds of the already-cracked material.
• the product distribution is improved.
• the viscosity of the oil product is reduced, thus facilitating handling and storage.
• the cracking in the second step is preferably a selective cracking step. It is therefore preferable that the second pyrolysis step (and even more preferably subsequent pyrolysis step(s)) be carried out in the presence of a catalyst.
• a catalyst is not as beneficial and thus may preferably be omitted. Accordingly, it is preferable that the first pyrolysis step be carried out in the absence of a pyrolysis catalyst and at least one of the subsequent pyrolysis step(s) be carried out in the presence of a pyrolysis catalyst. It is particularly preferable that at least the last pyrolysis step be carried out in the presence of a catalyst.
• a solid catalyst is preferred, such as an acidic solid catalyst, for example an acidic FCC catalyst, an acidic zeolite catalyst or an acidic silica-alumina catalyst, such as ZSM-5 or H-ultrastable Y-zeolite.
• a wherein a Group II metal oxide or Group II metal hydroxide in the following sometimes collectively referred to as Group II metal oxide/hydroxide
• a Group II metal oxide/hydroxide is suited to reduce chlorine impurities during pyrolysis (in situ) and the inventors furthermore found that the additional presence of a Group II metal oxide/hydroxide further reduces the silicon content of the oil product.
• the alumina and the Group II metal oxide/hydroxide be added in the same step, be it simultaneously and/or one after another, such as first adding the alumina and then adding the Group II metal oxide/hydroxide.
• the Group II metal of the Group II metal oxide/hydroxide is preferably at least one selected from the group consisting of calcium and magnesium. Specifically, the Group II metal oxide/hydroxide is preferably at least one selected from the group consisting of calcium oxide and calcium hydroxide.
• the Group II metal oxide/hydroxide is preferably added in an amount in the range of 0.2 wt.-% to 40.0 wt.-%, more preferably in an amount in the range of 0.5 wt.-% to 35.0 wt.-%, 1.0 wt.-% to 30.0 wt.-%, 1.5 wt.-% to 25.0 wt.- %, 2.0 wt.-% to 20.0 wt.-%, 2.5 wt.-% to 15.0 wt.-%, 3.0 wt.-% to 13.0 wt.-%, 4.0 wt.-%to 12.0 wt.-%, 5.0 wt.-% to 11.0 wt.-%, 5.0 wt.-% to 10.0 wt.-%, or 5.5 wt.-% to 9.0 wt.-%.
• the amount of Group II metal oxide/hydroxide is calculated in terms of Group II metal oxide. That is, if a Group II metal hydroxide (e.g. Ca(OH) 2 ) is added, a Group II metal oxide (e.g. CaO) equivalent amount is calculated assuming that all Group II metal-containing compounds are present as Group II metal oxide (e.g. CaO), i.e. using the content of Group II metal (e.g. Ca) as a basis.
• a Group II metal hydroxide e.g. Ca(OH) 2
• a Group II metal oxide (e.g. CaO) equivalent amount is calculated assuming that all Group II metal-containing compounds are present as Group II metal oxide (e.g. CaO), i.e. using the content of Group II metal (e.g. Ca) as a basis.
• the alumina is preferably added in such an amount that the silicon content (by weight) in the oil product recovered from the pyrolysis reactor is reduced by at least 15% as compared to the silicon content in the oil product recovered from the pyrolysis reactor when no alumina is added.
• the amount of silicon may be determined based on ASTM D5185.
• the oil product refers to the oil product directly after pyrolysis (i.e. condensed product) from which only gaseous (NTP) products are removed and no further work-up or post-processing is applied.
• NTP gaseous
• the term "when no alumina is added” means that the reaction is carried out under the same conditions but without addition of alumina. Adjusting the Si content reduction may preferably be achieved by means of a feedback control or feed-forward control, e.g. feed-forward control using tabulated values for known waste plastic compositions.
• the alumina may be acidic, neutral or basic alumina, and is preferably neutral or acidic alumina, more preferably acidic alumina.
• Alumina is called acidic, when it gives a pH (of the water) below 6 when placed in water.
• Alumina is called basic, it gives a pH (of the water) above 8 when placed in water.
• Alumina is called neutral, when the pH of the water between is 6 and 8. It is assumed that acidic and/or neutral alumina more easily forms chemical bonds with Si and thus results in better Si removal efficiency.
• the alumina is preferably activated alumina, more preferably acidic activated alumina.
• Activated alumina is a highly porous form of aluminium oxide which is used in chemistry for example as drying agent. Its surface area is high, typically above 100 m 2 /g, often even exceeding 200 m 2 /g.
• Activated alumina may be produced by dehydroxylating aluminium hydroxide such that a highly porous material is formed.
• the activated alumina may have an open pore structure, in particular tunnel-like pores.
• Activated alumina may comprise or consist of gamma alumina ( ⁇ -Al 2 O 3 ) .
• the temperature in the pyrolysis step is not particularly limited and a conventional range may be employed. In a case where multiple pyrolysis steps are employed, the temperature is preferably adjusted to the presence or absence of a catalyst.
• Thermal non-catalytic pyrolysis preferably employs a temperature in the range from 300°C to 850°C, such as from 400°C to 800°C. This process is typically conducted at atmospheric pressure, usually under non-oxidative conditions, especially in the absence of air. The non-oxidative conditions may be achieved for example by purging the liquefaction equipment with an inert gas such as nitrogen.
• Thermal catalytic pyrolysis preferably employs a temperature in the range from 250°C to 500°C, such as from 300°C to 450°C.
• This process is typically conducted at atmospheric pressure, usually under non-oxidative conditions, especially in the absence of air.
• the process typically employs a solid catalyst, preferably an acidic solid catalyst, for example an acidic FCC catalyst, an acidic zeolite catalyst or an acidic silica-alumina catalyst, such as ZSM-5 or H-ultrastable Y-zeolite, just to name a few.
• the non-oxidative conditions may be achieved for example by purging the liquefaction equipment with an inert gas such as nitrogen.
• the waste plastic may be mixed waste plastic or sorted waste plastic. Since the present invention is particularly suited for highly contaminated waste plastic, it is possible to reduce the reliance on the quality of sorted waste plastic and thus sorted waste plastic of lower quality may be used.
• Waste plastic, in particular non-processed mixed waste plastic may contain high amounts of silicon from various sources.
• the waste plastic may for example have a silicon content in the range of from 300 to 50000 ppm, such as from 300 to 20000 ppm or from 500 to 10000 ppm.
• the silicon content may be determined with any conventional method, such as ICP-MS (Inductively coupled plasma mass spectrometry) or XRF (X-ray fluorescence).
• the present invention further relates to a use of alumina granules for in-situ reduction of the amount of organic silicon in a waste plastic pyrolysis process.
• in-situ reduction means that the organic silicon species (which may be originally present or generated in the course of the pyrolysis reaction) are removed, accumulate in a solid residue and are reduced in content in the product stream (gas/oil product) while carrying out the pyrolysis.
• the alumina is preferably added before starting the pyrolysis reaction (e.g. before feeding the waste plastic to the reaction zone).
• the embodiments set forth for the method of the present invention may be similarly applied to the process of the present invention.
• the present invention provides a pyrolysis oil having reduced organic silicon content and an efficient method for achieving this.
• Pyrolysis was carried out using sorted waste plastic (industry grade DKR310, commonly used in Germany) to which 1 wt.-% PVC (relative to final waste plastic mixture) was added and to which 0.5 wt.-% PDMS (polydimethylsiloxane; 0.5 wt.-%) was further added to mimic an organic silicon-containing waste plastic material having a high organic silicon content.
• the pyrolysis was carried out without catalyst at a temperature (pyrolysis temperature inside the reactor) of 380°C. Generated gases were condensed and collected to provide an oil product. The oil product was analysed. Si content in the oil was analysed based on ASTM D5185, with the procedure adjusted as necessary for measurement of pyrolysis oil. Results are shown in Table 1.
• Comparative Example 1 was repeated under the same conditions, except that 20 wt.-% activated acidic alumina powder (BET SSA 155 m 2 /g, pore size 58 ⁇ , average particle size 150 mesh, corresponding to 105 ⁇ m) was further added (to give a mixture containing 20 wt.-% alumina and 80 wt.-% mixed waste plastic) by mixing without external heating. The oil product was analysed. Results are shown in Table 1.
• Comparative Example 1 was repeated under the same conditions, except that DKR350 (industry grade) sorted waste plastic (originally having a high Si content) was used without addition of PVC or PDMS. The oil product was analysed. Results are shown in Table 1
• Comparative Example 2 was repeated under the same conditions, except that varying amounts of the alumina specified in Example 1 alumina were added. Specifically, 3 wt.-% (Example 2) and 7 wt.-% (Example 3) were added in a double screw melt extruder at a temperature of 165°C. In Example 4, 7 wt.- % alumina was added and 6.7 wt.-% CaO were further added. The oil products were analysed. Results are shown in Table 1. Table 1 C.Ex. 1 Ex. 1 C.Ex. 2 Ex. 2 Ex. 3 Ex. 4 alumina addition 0 20% 0 3% 7% 7% (+CaO) Si content in oil [ppm] 2000 440 490 430 260 220 Si content reduction - 78% - 12% 47% 55%

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• 2022
  • 2022-07-12 EP EP22184304.8A patent/EP4306621A1/fr active Pending

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