Removal of silicon from depolymerized oils

Abstract

The present invention relates to an improved process for removing silicon from a depolymerized oil, and more particularly to a process for producing a pyrolytic oil, the process comprising the steps of adding alumina in particulate form to waste plastic containing silicone to form a mixture, feeding the mixture to a pyrolysis reactor, in one embodiment, a method for producing an oil product includes heating a mixture in a reactor, pyrolyzing the mixture in the reactor, recovering at least a pyrolysis gas and a solid residue from the reactor, and condensing the pyrolysis gas to provide an oil product wherein the solid residue comprises alumina that reacts with silicon.

Description

Technical Field

[0001] The present invention relates to an improved method for removing silicon from depolymerized oil, more particularly to in-situ reduction of silicon content during pyrolysis of waste plastics and to the use of aluminum oxide for in-situ reduction of silicon content during pyrolysis of waste plastics. Background Art

[0002] Purification methods of liquefied waste plastic (LWP), also known as depolymerized oil, have been studied for many years to obtain a more valuable (pure) substance.

[0003] LWP is usually produced by pyrolysis or hydrothermal liquefaction (HTL) of waste plastics. Depending on the source of the waste plastics, LWP has different levels of impurities.

[0004] Feedstock for chemical recycling of plastics usually contains mixed plastic waste, which can originate, for example, from plastics collected separately from households (from which the cleaner plastic fraction has been taken for mechanical recycling) or from plastics separated from municipal solid waste (MSW). However, even sorting wastes with close to 100% plastic content is not economically feasible. Therefore, the waste plastic material used to produce LWP (waste plastic feed) usually also contains materials other than plastics. These other materials (including biomass) can also be a source of impurities that end up in LWP.

[0005] In particular, consumer waste including discarded packaging often contains components other than hydrocarbons. Silicon is one of the common non-hydrocarbon elements in plastic waste, from various sources, such as silicone. Therefore, plastic waste subjected to chemical recycling often encounters large amounts of silicon impurities. Other typical impurity components are chlorine, nitrogen, sulfur and oxygen.

[0006] Whether LWP undergoes only ordinary refining processing (e.g. fractionation) or is forwarded to subsequent petrochemical conversion processes, the LWP feed needs to meet the impurity levels of these processes to avoid facility damage, such as catalyst poisoning. In this regard, silicon impurities may cause catalyst deactivation, such as in the hydroprocessing step, and therefore technologies for reducing the silicon content in LWP have been studied.

[0007] WO 2021 / 80899 A1 discloses passing LWP (ie depolymerized oil) through an absorbent at a temperature of 80° C. to 360° C. in the presence of hydrogen.

[0008] However, further improvements are still needed with respect to removing silicon from LWP products. Summary of the invention

[0009] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a method for reducing the silicon content in LWP obtained by a pyrolysis method.

[0010] The present invention is based on the finding that by using aluminum oxide as a reactant, the silicon content in LWP can already be reduced in situ during the pyrolysis process. That is, in addition to the prior art, no special steps need to be provided to remove silicon from the already produced LWP. Instead, the silicon content in LWP is already reduced in the pyrolysis step.

[0011] The problem of the invention is solved by the subject matter stated in the independent claims. Further advantageous developments are stated in the dependent claims.

[0012] Briefly, the present invention relates to one or more of the following:

[0013] 1. A method for producing pyrolysis oil, the method comprising the following steps:

[0014] Alumina in granular form is added to waste plastic containing silicone to form a mixture,

[0015] feeding the mixture into a pyrolysis reactor,

[0016] pyrolyzing the mixture in the reactor,

[0017] At least one pyrolysis gas and solid residue are recovered from the reactor, and the pyrolysis gas is condensed to obtain an oil product, wherein

[0018] The solid residue comprises alumina reacted with silicon.

[0019] 2. The method according to item 1, wherein the amount of aluminum oxide added is 0.2 to 40.0 wt.-%, 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.-%.

[0020] 3. The method according to item 1 or 2, wherein the adding of alumina to form the mixture is carried out at an elevated temperature.

[0021] 4. The method according to any of the preceding items, wherein the adding of alumina to form a mixture is carried out at a temperature in the range of 50°C to 280°C, preferably in the range of 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.

[0022] 5. The method according to any preceding item, wherein said adding alumina to form a mixture comprises melting said waste plastic.

[0023] 6. The method according to any preceding item, wherein said adding of aluminium oxide to form a mixture comprises melting said waste plastic, and the addition of aluminium oxide is carried out before and / or during and / or after melting the waste plastic, preferably at least before melting.

[0024] 7. The method according to any of the preceding items, wherein the waste plastics mainly contain thermoplastic compounds.

[0025] 8. The method according to any preceding item, wherein said adding of alumina to form a mixture is performed in an extruder, preferably in a melt extruder.

[0026] 9. The method according to any preceding item, wherein said adding of the aluminium oxide to form a mixture is performed by blending the aluminium oxide with waste plastic, preferably solid waste plastic, without external heating.

[0027] 10. The method according to any preceding item, wherein the average particle size of the aluminum oxide is in the range of 50 nm to 10 mm, preferably in the range of 10 μm to 2.0 mm, in the range of 50 μm to 1.8 mm or in the range of 100 μm to 1.5 mm.

[0028] 11. The method according to any preceding item, wherein the alumina is activated alumina.

[0029] 12. The method according to any preceding item, wherein the alumina has an open pore structure.

[0030] 13. The method according to any of the preceding items, wherein the pore size of the aluminum oxide is in the range of 30 angstroms to 10,000 angstroms, preferably 40 angstroms to 1,000 angstroms, 50 angstroms to 500 angstroms, 55 angstroms to 300 angstroms, or 60 angstroms to 200 angstroms.

[0031] 14. The method according to any of the preceding items, wherein the BET specific surface area of ​​the aluminum oxide is between 50 m 2 / g to 500m 2 / g, preferably greater than 50 m 2 / g, greater than 100 m 2 / g, or 150 m 2 / g or higher, for example, between 150 and 300 m 2 / g range.

[0032] 15. The method according to any preceding item, further comprising post-processing the oil product recovered from the pyrolysis reactor.

[0033] 16. The method according to item 15, wherein the post-treatment comprises heat-treating the oil product with an aqueous solution of an alkaline substance, preferably an aqueous solution of a metal hydroxide, more preferably an aqueous solution of sodium hydroxide, followed by phase separation (liquid-liquid separation) to provide a further purified oil product.

[0034] 17. The method according to item 16, wherein the aqueous solution comprises at least 50 wt.-% water, preferably at least 70 wt.-% water, more preferably at least 85 wt.-% water, at least 90 wt.-% water or at least 95 wt.-% water.

[0035] 18. The method according to item 16 or 17, wherein the aqueous solution comprises at least 0.3 wt.-% alkaline substance, more preferably at least 0.5 wt.-%, at least 1.0 wt.-% or at least 1.5 wt.-% alkaline substance, for example 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.-% to 6.0 wt.-%, or 1.5 wt.-% to 4.0 wt.-%.

[0036] 19. The method according to any of items 16 to 18, wherein the aqueous solution comprises at least 0.5 wt.-%, preferably at least 1.0 wt.-% or at least 1.5 wt.-% of metal hydroxide or alkali metal hydroxide, for example 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.-% to 6.0 wt.-%, or 1.5 wt.-% to 4.0 wt.-%.

[0037] 20. The method according to any one of items 16 to 19, wherein the heat treatment is carried out at a temperature of 150°C or higher, preferably at a temperature of 190°C or higher.

[0038] 21. The method according to any one of items 16 to 20, wherein the heat treatment is carried out at a temperature of 200°C or higher (eg, 210°C or higher, 220°C or higher, 240°C or higher or 260°C or higher).

[0039] 22. The method according to any one of items 16 to 21, wherein the heat treatment is 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).

[0040] 23. The method according to any one of items 16 to 22, wherein the heat treatment is 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).

[0041] 24. The method according to any one of items 15 to 23, wherein post-processing comprises hydrotreating the oil product to provide a hydrotreated oil product.

[0042] 25. The method according to any preceding item, wherein the pyrolysis is performed in two or more steps.

[0043] 26. The method according to item 25, wherein the first pyrolysis step is carried out in the absence of a pyrolysis catalyst and at least one of the subsequent pyrolysis steps is carried out in the presence of a pyrolysis catalyst.

[0044] 27. The method according to any of the preceding items, wherein a Group II metal oxide or a Group II metal hydroxide (Group II metal oxide / hydroxide) is further added in the step of adding alumina to form a mixture and / or directly to the pyrolysis reactor.

[0045] 28. The method according to claim 27, wherein the Group II metal is magnesium or calcium.

[0046] 29. The method according to item 27 or 28, wherein the Group II metal oxide / hydroxide is at least one selected from calcium oxide and calcium hydroxide.

[0047] 30. The method according to any one of items 27 to 29, wherein the Group II metal oxide / hydroxide is added in an amount ranging from 0.2 to 40.0 wt.-%, preferably in an amount ranging from 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.-%, 5.0 to 10.0 wt.-%, or 5.5 to 9.0 wt.-%.

[0048] 31. A method according to any preceding item, wherein the amount of alumina added is such that the silicon content (by weight) in the oil product recovered from the pyrolysis reactor is reduced by at least 15% compared to the silicon content in the oil product recovered from the pyrolysis reactor when no alumina is added.

[0049] 32. The method according to any of the preceding items, wherein the alumina is acidic alumina or basic alumina, preferably acidic alumina.

[0050] 33. The method according to any preceding item, wherein the pyrolysis is carried out at a temperature in the range of 250°C to 850°C.

[0051] 34. The method according to any preceding item, further comprising heating the organosilicon-containing waste plastic and / or the mixture to an elevated temperature and devolatilizing at least part of the organosilicon compound contained therein.

[0052] 35. The method according to item 34, wherein the temperature is 175°C or higher, preferably 180°C or higher, 185°C or higher, 190°C or higher, 200°C or higher, or 210°C or higher.

[0053] 36. The method according to item 34 or 35, wherein the temperature is 280°C or lower, preferably 270°C or lower, 265°C or lower, 260°C or lower, 255°C or lower, or 250°C or lower.

[0054] 37. The method according to any one of items 34 to 36, wherein the temperature is in the range of 175°C to 280°C, for example 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 200°C to 255°C, or 210°C to 250°C.

[0055] 38. The process according to any one of items 34 to 37, wherein the devolatilization is performed before, during and / or after the addition of alumina.

[0056] 39. The method according to any one of items 34 to 38, wherein the devolatilization is performed at least in the step of adding alumina to form a mixture.

[0057] 40. The method according to any one of items 34 to 39, wherein the devolatilization is performed at least in the step of adding alumina to form a mixture.

[0058] 41. The process according to any one of items 34 to 40, wherein the devolatilization is carried out in an extruder.

[0059] 42. The process according to any one of items 34 to 41, wherein the devolatilization is carried out in a melt extruder.

[0060] 43. A method according to item 41 or 42, wherein the extruder has a gas exhaust port.

[0061] 44. The method according to any preceding item, wherein the alumina is acidic alumina.

[0062] 45. The method according to any preceding item, wherein the amount of aluminum oxide added is 0.2 to 12.0 wt.-%, preferably 0.5 to 10.0 wt.-%, 1.0 to 10.0 wt.-%, 1.5 to 10.0 wt.-%, 2.0 to 10.0 wt.-%, 2.5 to 10.0 wt.-%, 3.0 to 10.0 wt.-%, 4.0 to 10.0 wt.-%, 5.0 to 10.0 wt.-%, 5.5 to 10.0 wt.-%, or 6.0 to 10.0 wt.-%.

[0063] 46. ​​A method according to any preceding item, wherein the adding of alumina to form a mixture is carried out at a temperature in the range of 150°C to 280°C, preferably in the range of 160°C to 280°C, 170°C to 280°C, 175°C to 280°C, 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 2000°C to 255°C, or 210°C to 250°C.

[0064] 47. Use of aluminum oxide in granular form for in-situ reduction of the content of organosilicon during pyrolysis of waste plastics.

[0065] 48. The use described in item 47 is used in the waste plastic pyrolysis process (method) defined in any one of items 1 to 46.

[0066] 49. A method for producing pyrolysis oil according to item 47 or 48, the method comprising the following steps:

[0067] Alumina in granular form is added to waste plastic containing silicone to form a mixture,

[0068] feeding the mixture into a pyrolysis reactor,

[0069] pyrolyzing the mixture in the reactor,

[0070] At least pyrolysis gas and solid residue are recovered from the reactor, and the pyrolysis gas is condensed to provide an oil product, wherein

[0071] The solid residue comprises alumina reacted with silicon.

[0072] 50. The use according to any one of items 47 to 49, wherein the addition amount of the aluminum oxide is 0.2 to 40.0 wt.-%, 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.-%.

[0073] 51. The use according to any one of items 47 to 50, wherein said adding of alumina to form a mixture is carried out at elevated temperature.

[0074] 52. The use according to any one of items 47 to 51, wherein the adding of alumina to form a mixture is carried out at a temperature in the range of 50°C to 280°C, preferably in the range of 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.

[0075] 53. The use according to any one of items 47 to 52, wherein said adding of alumina to form a mixture comprises melting said waste plastic.

[0076] 54. The use according to any one of items 47 to 53, wherein the adding of aluminum oxide to form a mixture comprises melting the waste plastic, and the addition of aluminum oxide is carried out before and / or during and / or after melting the waste plastic, preferably at least before melting.

[0077] 55. The use according to any one of items 47 to 54, wherein the waste plastics mainly contain thermoplastic compounds.

[0078] 56. The use according to any one of items 47 to 55, wherein the adding of alumina to form a mixture is carried out in an extruder, preferably in a melt extruder.

[0079] 57. The use according to any one of items 47 to 56, wherein the adding of the aluminum oxide to form the mixture is carried out by blending the aluminum oxide with waste plastic, preferably solid waste plastic, without external heating.

[0080] 58. The use according to any one of items 47 to 57, wherein the average particle size of the aluminum oxide is in the range of 50 nm to 10 mm.

[0081] 59. The use according to any one of items 47 to 58, wherein the average particle size of the aluminum oxide is in the range of 10 μm to 2.0 mm, preferably in the range of 50 μm to 1.8 mm or in the range of 100 μm to 1.5 mm.

[0082] 60. The use according to any one of items 47 to 58, wherein the aluminum oxide has an open-pore structure.

[0083] 61. The use according to any one of items 47 to 60, wherein alumina is added to the waste plastic before the pyrolysis reaction (before the waste plastic enters the pyrolysis reactor).

[0084] 62. The use according to any one of items 47 to 61, wherein the pore size of the aluminum oxide is in the range of 30 angstroms to 10,000 angstroms, preferably 40 angstroms to 1,000 angstroms, 50 angstroms to 500 angstroms, 55 angstroms to 300 angstroms, or 60 angstroms to 200 angstroms.

[0085] 63. The use according to any one of items 47 to 62, wherein the BET specific surface area of ​​the aluminum oxide is 50 m 2 / g to 500 m 2 / g, preferably higher than 50 m 2 / g, higher than 100 m 2 / g, or 150 m 2 / g or higher, for example, between 100 and 300 m 2 / g or in the range of 150 to 300 m 2 / g range.

[0086] 64. The use according to any one of items 47 to 63, wherein the pyrolysis is carried out in two or more steps.

[0087] 65. The use according to any one of items 47 to 64, wherein the first pyrolysis step is carried out in the absence of a pyrolysis catalyst and at least one of the subsequent pyrolysis steps is carried out in the presence of a pyrolysis catalyst.

[0088] 66. The use according to any one of items 47 to 65, wherein a Group II metal oxide or a Group II metal hydroxide (Group II metal oxide / hydroxide) is also added to the pyrolysis reactor.

[0089] 67. The method according to item 66, wherein the Group II metal is magnesium or calcium.

[0090] 68. The method according to item 65 or 66, wherein the Group II metal oxide / hydroxide is at least one selected from calcium oxide and calcium hydroxide.

[0091] 69. The method according to any one of items 65 to 68, wherein the added amount of the Group II metal oxide / hydroxide is in the range of 0.2 to 40.0 wt.-%, preferably in the range of 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.-%, 5.0 to 10.0 wt.-%, or 5.5 to 9.0 wt.-%.

[0092] 70. The use according to any one of items 47 to 69, wherein the amount of aluminum oxide added is such that the silicon content (by weight) in the oil product recovered from the pyrolysis reactor is reduced by at least 15% compared to the silicon content in the oil product recovered from the pyrolysis reactor when no aluminum oxide is added.

[0093] 71. The use according to any one of items 47 to 70, wherein the alumina is acidic alumina or basic alumina, preferably acidic alumina.

[0094] 72. The use according to any one of items 47 to 71, wherein the alumina is activated alumina.

[0095] 73. The use according to any one of items 47 to 72, wherein the pyrolysis is carried out at a temperature in the range of 250°C to 850°C.

[0096] 74. The use according to any one of items 47 to 73, further comprising heating the silicone-containing waste plastic and / or the mixture to an elevated temperature and devolatilizing at least part of the organosilicon compound contained therein.

[0097] 75. The use according to item 74, wherein the temperature is 175°C or higher, preferably 180°C or higher, 185°C or higher, 190°C or higher, 200°C or higher, or 210°C or higher.

[0098] 76. The use according to item 74 or 75, wherein the temperature is 280°C or lower, preferably 270°C or lower, 265°C or lower, 260°C or lower, 255°C or lower, or 250°C or lower.

[0099] 77. The use according to any one of items 74 to 76, wherein the temperature is in the range of 175°C to 280°C, for example 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 200°C to 255°C, or 210°C to 250°C.

[0100] 78. The use according to any one of items 74 to 77, wherein the devolatilization is carried out before, during and / or after the addition of alumina.

[0101] 79. The use according to any one of items 74 to 78, wherein the devolatilization is carried out at least in the step of adding alumina to form a mixture.

[0102] 80. The use according to any one of items 74 to 79, wherein the devolatilization is carried out at least in the step of adding alumina to form a mixture.

[0103] 81. The use according to any one of items 74 to 80, wherein the devolatilization is carried out in an extruder.

[0104] 82. The use according to any one of items 74 to 81, wherein the devolatilization is carried out in a melt extruder.

[0105] 83. The use according to item 81 or 82, wherein the extruder has a gas discharge port.

[0106] 84. The use according to any one of items 47 to 83, wherein the alumina is acidic alumina.

[0107] 85. The use according to any one of items 47 to 84, wherein the addition amount of the aluminum oxide is 0.2 to 12.0 wt.-%, preferably 0.5 to 10.0 wt.-%, 1.0 to 10.0 wt.-%, 1.5 to 10.0 wt.-%, 2.0 to 10.0 wt.-%, 2.5 to 10.0 wt.-%, 3.0 to 10.0 wt.-%, 4.0 to 10.0 wt.-%, 5.0 to 10.0 wt.-%, 5.5 to 10.0 wt.-%, or 6.0 to 10.0 wt.-%.

[0108] 86. The use according to any one of items 47 to 85, wherein the adding of alumina to form a mixture is carried out at a temperature in the range of 150°C to 280°C, preferably at a temperature in the range of 160°C to 280°C, 170°C to 280°C, 175°C to 280°C, 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 2000°C to 255°C, or 210°C to 250°C. DETAILED DESCRIPTION

[0109] The present invention relates to an improved process for reducing the silicon content in depolymerized oils.

[0110] Before further processing of LWP, the content of silicon impurities should be reduced. The present invention focuses on a method for removing silicon in situ during the pyrolysis step (i.e., during the depolymerization of waste plastics). The present invention specifically relates to a method using alumina in particle form (also known as granular alumina or alumina particles) which is added to the waste plastics before pyrolysis and reacts with silicon compounds produced by organosilicon in the waste plastics during the pyrolysis, so that the silicon reacted with the alumina ends up in the solid residue of the pyrolysis reaction, while the gaseous products (gas effluent) in the silicon content are minimized, and the gaseous products are then condensed to provide depolymerized oil (liquefied waste plastics; LWP).

[0111] In the context of the present invention, liquefied waste plastic (LWP) refers to the product effluent from the pyrolysis process, which contains at least depolymerized waste plastic. Thus, LWP is a material obtainable by depolymerization of waste plastic. LWP may also be referred to as polymer waste base oil or depolymerized oil.

[0112] Waste plastics may come from any source, such as (recycled or collected) consumer plastics, (recycled or collected) industrial plastics or (recycled or collected) end-of-life tyres (ELTs). In particular, the term waste plastics refers to organic polymeric materials that are no longer suitable for their purpose or are discarded for other reasons. Waste plastics may more specifically refer to scrap tyres, collected consumer plastics (consumer plastics refers to any organic polymeric material in consumer products, even if it does not have the characteristics of "plastic" itself), collected industrial polymer waste. In the sense of the present invention, the term waste plastics or "polymers" generally does not cover purely inorganic materials (which are sometimes referred to as inorganic polymers). The polymers in the waste plastics may be natural and / or synthetic and may be based on renewable and / or fossil raw materials.

[0113] The liquefaction process (pyrolysis) is carried out at high temperature and preferably under non-oxidizing conditions. The liquefaction process can be carried out under high pressure. The liquefaction process can be carried out in the presence of a catalyst. The liquefaction process provides a gaseous effluent and a solid residue, wherein the gaseous effluent is condensed to produce an oil product. The oil product can be used as pyrolysis oil (LWP; i.e. as a product of the process) as it is, or can be fractionated (or separated) to provide fractions (or separated liquids), and can also be subjected to other treatments, in particular further purification. In this context, fractionation refers to fractional distillation and / or fractional evaporation.

[0114] In addition to liquid (NTP) hydrocarbons, i.e. hydrocarbons that are liquid at normal temperature and pressure (NTP; 20 °C, 101.325 kPa absolute), typical oil products from pyrolysis processes include gaseous (NTP) hydrocarbons and hydrocarbons that are waxy or solid at NTP but become liquid when heated, e.g. to 80 °C.

[0115] In the context of the present disclosure, waste plastic depolymerization means decomposing or degrading the polymer backbone of waste plastic by pyrolysis to produce polymer and / or oligomeric species of smaller molecular weight than the starting waste plastic, but still containing at least liquid (NTP) hydrocarbons. Waste plastic depolymerization may also involve cleavage of covalently bound heteroatoms, such as O, S and N, from optionally present heteroatom-containing compounds.

[0116] Initially, the waste plastic or each waste plastic species in the mixed waste plastic to be pyrolyzed is usually in a solid state, with a melting point measured by DSC usually in the range of 100°C or higher, as described by Larsen et al. (“Determining the PE fraction in recycled PP”, Polymer testing, vol. 96, April 2021, 107058). However, the waste plastic or each waste plastic species may be melted before and / or during depolymerization.

[0117] Solid waste plastics may contain various additional components, such as additives, reinforcing materials, etc., including fillers, pigments, printing inks, flame retardants, stabilizers, antioxidants, plasticizers, lubricants, labels, metals, paper, cardboard, cellulose fibers, glass fibers, and even sand or other dirt. If necessary, some of the additional components can be removed from solid waste plastics, molten waste plastics and / or liquefied waste plastics using commonly known methods.

[0118] Preferably, the oxygen content of the (solid) waste plastic to be pyrolyzed is 15 wt.-% or less, preferably 10 wt.-% or less, more preferably 5 wt.-% or less, based on the total weight of the (solid) waste plastic. 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.-%. The oxygen content (expressed in wt.-%) may be determined by using the difference of the formula 100 wt.-% - (CHN content + ash content), wherein the CHN content refers to the total content of carbon, hydrogen and nitrogen determined according to ASTM D5291, and the ash content refers to the ash content determined according to ASTM D482 / EN15403.

[0119] In the present disclosure, when a standard is cited, unless otherwise indicated, the latest revised version available on January 31, 2022 shall be referred to. In addition, all embodiments of the present invention (e.g., all preferred values ​​and / or ranges within the embodiments) can be combined with each other to obtain new (preferred) embodiments, unless explicitly stated otherwise or unless such combination leads to a contradiction.

[0120] In the present invention, the term "granules" or "granular form" encompasses all types of powders, pellets, agglomerates, etc., and is not limited to a specific shape.

[0121] The term "pyrolysis reactor" refers to the pyrolysis zone of a device where the pyrolysis reaction is carried out. That is, the "pyrolysis reactor" is where the actual pyrolysis reaction occurs.

[0122] The term "solid residue" refers to the material that is not transferred to the gas phase during the pyrolysis reaction. Typically, such solid residue contains unevaporated tar and inorganic impurities. In the present invention, the solid residue comprises alumina reacted with silicon. This means that the alumina has a higher Si content than when added (i.e., a higher Si content than granular alumina). The reaction may comprise or be a physical reaction (e.g., adsorption) and / or a chemical reaction. Preferably, Si reacts chemically with alumina, preferably binding to the surface of alumina (accessible surface, including penetration into open pores). Although the mechanism is not fully understood, it is speculated that when Si is added to the pyrolysis reactor, it reacts primarily with alumina on its surface to form a layered structure, and it is speculated that the layered structure is formed by a Si-Al-oxide type material.

[0123] It is assumed that most of the organosilicon in waste plastics is in the form of polysiloxanes, which form volatile oligosiloxanes during the pyrolysis process and are thus transferred to the oil product. On the other hand, inorganic silicon (e.g. silicon dioxide) is not reactive (and non-volatile) under the pyrolysis conditions and therefore ends up in the solid residue in any case.

[0124] The method of the present invention is characterized in that granular aluminum oxide is mixed with waste plastics and then the mixture is pyrolyzed in a pyrolysis reactor so that silicon in the waste plastics reacts with the aluminum oxide and is transferred to the solid residue.

[0125] Specifically, the present invention relates to a method for producing pyrolysis oil, comprising the steps of adding alumina in particulate form to waste plastic containing silicone to form a mixture, feeding the mixture into a pyrolysis reactor, pyrolyzing the mixture in the reactor, recovering at least pyrolysis gas and solid residue from the reactor, and condensing the pyrolysis gas to provide an oil product, wherein the solid residue contains alumina reacted with silicon.

[0126] Thus, the mixture is prepared before entering the pyrolysis reactor (i.e., the pyrolysis reaction zone). For example, the mixture can be prepared in advance or in a feeding device (e.g., an extruder). The step of adding alumina to form the mixture can also be referred to as a mixing step.

[0127] The amount of aluminum oxide added is preferably 0.2 wt.-% to 40.0 wt.-% (relative to 100 wt.-% of the 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 inventors have found that, considering the balance between silicon removal efficiency and alumina utilization efficiency, adding alumina in an amount of 0.2 to 12.0 wt.-% (within this range) (e.g., 0.5 to 10.0 wt.-%, 1.0 to 10.0 wt.-%, 1.5 to 10.0 wt.-%, 2.0 to 10.0 wt.-%, 2.5 to 10.0 wt.-%, 3.0 to 10.0 wt.-%, 4.0 to 10.0 wt.-%, 5.0 to 10.0 wt.-%, 5.5 to 10.0 wt.-%, or 6.0 to 10.0 wt.-%) is particularly advantageous. The term "relative to 100 wt.-% of pyrolysis feed" refers to the total amount of waste plastic (including all impurities and contaminants, such as biomass), alumina and other feeds (but excluding pyrolysis catalyst (if present)). That is, as noted above, waste plastics can come from municipal waste and can include some biomass even after sorting.

[0128] The step of adding alumina to form a mixture (ie the mixing step) may be carried out at an elevated temperature. In this regard, "elevated temperature" refers to applying external heating to the mixing device (such that the components to be mixed are heated).

[0129] For example, the mixing step can be carried out at a temperature in the range of 50°C to 280°C, preferably at a temperature in the range of 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. By adopting an elevated temperature in the mixing step, processing can be facilitated and a more uniform mixture can be prepared. In some embodiments, it may be beneficial to limit the temperature in the mixing step to 180°C or less (e.g., in the range of 50°C to 180°C) to minimize the generation of hydrochloric acid in the mixing stage. In the context of the present invention, the "temperature" at which the mixing step is carried out refers to the temperature of the mixed material (rather than the temperature of the heating medium).

[0130] In particular, the addition of aluminum oxide to form a mixture may comprise (at least partially) melting the waste plastic. When the waste plastic is melted, a more homogeneous mixture may be prepared. In addition, the melted material further facilitates its handling. The addition of aluminum oxide may be carried out before and / or during and / or after melting the waste plastic, but preferably at least before melting.

[0131] Melting the waste plastic (at least partially) requires the presence of a thermoplastic compound. Therefore, the waste plastic in the present invention preferably mainly contains thermoplastic compounds. The term "mainly 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 by thermoplastic compounds based on the waste plastic as a whole.

[0132] In one embodiment, the mixing step is carried out in an extruder, preferably in a melt extruder. Since an extruder is usually used as a feeding device to feed the waste plastics to the pyrolysis reactor, the addition of aluminum oxide can be easily achieved at this stage while achieving uniform mixing. In particular, the use of a melt extruder can homogenize the mixture of aluminum oxide and waste plastics and thereby improve the pyrolysis process. In addition, the melt-extruded material can be more easily handled, such as directly fed to the pyrolysis reactor or pelletized and fed to the pyrolysis reactor.

[0133] Alternatively or additionally, the mixing step may be performed without external heating, for example at room temperature. In this case, processing is facilitated since there is no need to pay attention to high temperatures and / or cooling effects during the mixing step.

[0134] In another embodiment, in addition to using additives to remove silicon before the pyrolysis step, the present invention can also utilize a devolatilization step to further remove the silicon component contained in the waste plastic. It has been unexpectedly found that by heating the waste plastic containing silicone (before, during and / or after the addition of alumina) to a certain temperature before pyrolysis (i.e., before the mixture is fed to the pyrolysis reactor), the amount of silicon-containing compounds in the oil product (i.e., obtained by condensation of the pyrolysis gas) can be further reduced. Although the reason for this effect is not entirely clear, it is speculated that heating removes part of the organosilicon compounds (most of which are believed to be siloxane compounds) into the gas phase. Based on this understanding, this heating stage can also be referred to as a "degassing" or "devolatilization" stage. Therefore, it is preferred that the heating temperature is high enough to fully convert the organosilicon compounds contained in the waste plastic (or, as the case may be, in the mixture) to degas. Specifically, the temperature is preferably 175°C or higher, such as 180°C or higher, 185°C or higher, 190°C or higher. The temperature may in particular be 200°C or higher, or 210°C or higher. The temperature should also not be too low to avoid (or minimize) product losses. Suitable temperature ranges are 175°C to 280°C, such as 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 200°C to 255°C, or 210°C to 250°C.

[0135] Heating and degassing (devolatilization) can be appropriately performed during the process in which the aluminum oxide addition can be performed, because together they can produce a synergistic effect with the use of high temperatures during the homogenization of waste plastics. In this case, the aluminum oxide addition (mixing) temperature preferably corresponds to the above-mentioned heating (devolatilization) temperature. Nevertheless, heating (devolatilization) can also be performed as a dedicated stage (step) before and / or after the aluminum oxide addition / mixing (in addition to or instead of the aluminum oxide addition / mixing period).

[0136] The pyrolysis can be carried out as a batch process or a continuous process, with a continuous process being preferred.

[0137] The average particle size of the aluminum oxide (aluminum oxide particles) is preferably in the range of 50 nm to 10 mm, preferably in the range of 10 μm to 2.0 mm, in the range of 50 μm to 1.8 mm or in the range of 100 μm to 1.5 mm. The average particle size can be measured, for example, by laser diffraction (ISO 13320) or by optical or electron microscopy (ISO13322) methods. The specific surface area and pore size (pore diameter) of aluminum oxide can be determined by gas adsorption measurements, for example based on ISO 9277 or ISO 15901-2. In the case of agglomerates, the particle size refers to the size of the agglomerates, not the primary particle size. The porosity of the aluminum oxide (aluminum oxide particles) can be in the range of, for example, 20-85%.

[0138] Alumina (alumina particles) preferably have an open pore structure. The inventors have found that silicon reacts primarily with the surface of the alumina, so an open pore structure (with a highly accessible alumina surface) is preferred. Preferably, the alumina has a pore size in the range of 30 Å to 10000 Å, preferably 40 Å to 1000 Å, 50 Å to 500 Å, 55 Å to 300 Å, or 60 Å to 200 Å.

[0139] The BET specific surface area of ​​alumina (alumina particles) is preferably 50 m 2 / g to 500 m 2 / g, preferably higher than 50 m 2 / g, higher than 100 m 2 / g, or 150 m 2 / g or higher, for example, between 100 and 300 m 2 / g, 150 to 300 m 2 / g range.

[0140] The method of the present invention may further include post-processing the oil product recovered from the pyrolysis reactor. Although the oil product produced by the method of the present invention can be pure enough to add to the value chain (e.g., for crude oil refining process), it is preferred that the oil product is post-processed to improve its purity or availability. Therefore, post-processing can especially comprise purification process (e.g., fractionation or extraction) and / or upgrading process (e.g., hydrotreating). Nevertheless, any known petrochemical process can be used for post-processing, and in particular, the oil product can be used as a co-feed in the petrochemical process.

[0141] In one embodiment, post-treatment comprises heat treatment of the oil product with an aqueous solution of an alkaline substance (preferably an aqueous solution of a metal hydroxide, more preferably an aqueous solution of sodium hydroxide), followed by liquid-liquid separation to provide a further purified oil product. Such treatment is suitable for further removing impurities, particularly chlorine-containing impurities, from the oil product in a very effective manner. The 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.-% alkaline substance, more preferably at least 0.5 wt.-%, at least 1.0 wt.-% or at least 1.5 wt.-% alkaline substance, for example 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.-% to 6.0 wt.-%, or 1.5 wt.-% to 4.0 wt.-%. For example, the aqueous solution comprises at least 0.5 wt.-%, preferably at least 1.0 wt.-% or at least 1.5 wt.-% of metal hydroxide or alkali metal hydroxide, for example 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, for example 210°C or more, 220°C or more, 240°C or more or 260°C or more). In order to keep the heating intensity within the usual limits and avoid excessive side reactions, 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). In particular, the heat treatment may be performed at a temperature ranging from 200°C to 350°C (preferably 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C).

[0142] Post-treatment can include hydrotreating the oil product to provide a hydrotreated oil product. Hydrotreating can be particularly useful for removing heteroatoms and / or for olefin saturation. Hydrotreating is particularly advantageous in the present invention because organosilicon can serve as a catalyst deactivator. Therefore, the method of the present invention can protect the hydrotreating catalyst from degradation and extend its service life.

[0143] The pyrolysis step in the method of the present invention can be further implemented (as a two-step process) by a second step. In this embodiment, the reactor type and reaction temperature of the two steps can be varied. Typically, the first step is to crack the solid residue removed in the first reactor. Then, the second step is to treat the pyrolysis gas by contacting the pyrolysis gas with a catalyst to selectively crack long (carbon) chains. For example, a mixture of waste plastics and aluminum oxide is fed to the first step, and the solid residue is removed from the first step, while the product stream (such as oil or gas) is sent to the second (and optional subsequent) step. The first step can be a step of cracking the waste plastic into (long-chain) compounds, while the second step is mainly used to crack the (long-chain) compounds of the cracked material. With this two-step process, the product distribution is improved. In particular, the viscosity of the oil product is reduced, which is conducive to handling and storage.

[0144] The cracking in the second step is preferably a selective cracking step. Therefore, it is preferred that the second pyrolysis step (and even more preferably the subsequent pyrolysis steps) is carried out in the presence of a catalyst. In the first pyrolysis step, the catalyst is not so beneficial and is therefore preferably omitted. Therefore, it is preferred that the first pyrolysis step is carried out in the absence of a pyrolysis catalyst and at least one of the subsequent pyrolysis steps is carried out in the presence of a pyrolysis catalyst. It is particularly preferred that at least the last pyrolysis step is carried out in the presence of a catalyst. Preferably a solid catalyst, such as an acidic solid catalyst, such as an acidic FCC catalyst, an acidic zeolite catalyst or an acidic silica-alumina catalyst, such as ZSM-5 or H-ultra-stable Y-zeolite.

[0145] In order to further improve the product distribution (especially to reduce the chlorine content in the oil product), it is preferred that a Group II metal oxide or a Group II metal hydroxide (hereinafter sometimes collectively referred to as Group II metal oxide / hydroxide) is further added in the step of adding alumina to form a mixture and / or directly to the pyrolysis reactor. Group II metal oxide / hydroxide is suitable for reducing chlorine impurities (in situ) during pyrolysis, and the inventors have also found that the additional presence of Group II metal oxide / hydroxide further reduces the silicon content of the oil product. Considering the efficiency of the procedure, it is preferred to add alumina and Group II metal oxide / hydroxide in the same step, which can be added simultaneously and / or successively, for example, first adding alumina and then adding Group II metal oxide / hydroxide.

[0146] The Group II metal in the Group II metal oxide / hydroxide is preferably at least one selected from calcium and magnesium. Specifically, the Group II metal oxide / hydroxide is preferably at least one selected from calcium oxide and calcium hydroxide. The amount of Group II metal oxide / hydroxide added is preferably in the range of 0.2 wt.-% to 40.0 wt.-%, more preferably 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 as Group II metal oxide. That is, if a Group II metal hydroxide (e.g., Ca(OH)2) is added, it is assumed that all Group II metal-containing compounds are in the form of Group II metal oxides (e.g., CaO), that is, the Group II metal (e.g., Ca) content is used as the basis to calculate the Group II metal oxide (e.g., CaO) equivalent.

[0147] The amount of aluminum oxide added is preferably such that the silicon content (by weight) in the oil product recovered from the pyrolysis reactor is reduced by at least 15% compared to the silicon content in the oil product recovered from the pyrolysis reactor when aluminum oxide is not added. The amount of silicon can be determined based on ASTM D5185. In this regard, the oil product refers to the oil product immediately after pyrolysis (i.e., the condensed product), from which only gaseous (NTP) products are removed, and no further processing or post-treatment is required. In addition, the term "without the addition of aluminum oxide" refers to reacting under the same conditions but without the addition of aluminum oxide. Adjusting the reduction in Si content can preferably be achieved by feedback control or feedforward control, such as feedforward control using a tabulated value for a known waste plastic composition.

[0148] Alumina can be acidic alumina, neutral alumina or alkaline alumina, preferably neutral alumina or acidic alumina, more preferably acidic alumina. When placed in water with a tendency to reach pH 6 or lower (e.g., lower than 6), the alumina is of acidic type. When placed in water with a tendency to reach pH 8 or higher (e.g., higher than 8) (of water), the alumina is of alkaline type. When the pH of water tends to be 6 to 8, the alumina is called neutral. It has been demonstrated that alumina can be of acidic, neutral and alkaline types, and each type can provide the chemical adsorption capacity of alumina to Si, thereby showing Si removal efficiency. However, the inventors unexpectedly found that the acidic type of alumina showed an improved silicon removal efficiency relative to alkaline and neutral alumina, so the acidic type is most preferred. Without being bound by any particular theory, the active sites provided by alumina can be further optimized by pH to provide appropriate conditions for the chemical adsorption interaction between alumina and silicon, thereby exerting the expected silicon removal function.

[0149] Furthermore, in order to improve reactivity, the alumina is preferably activated alumina, more preferably acid activated alumina. Activated alumina is a highly porous form of alumina used as a desiccant in the chemical field, etc. Its surface area is high, usually above 100 m 2 / g, often even exceeding 200 m 2 / g. Activated alumina can be produced by dehydroxylating aluminum hydroxide to form a highly porous material. Activated alumina can have an open pore structure, particularly tunnel-like pores. Activated alumina can contain or consist of gamma alumina (γ-Al2O3).

[0150] The temperature in the pyrolysis step is not particularly limited, and a conventional range may be employed. In the case where multiple pyrolysis steps are employed, the temperature is preferably adjusted according to the presence or absence of a catalyst.

[0151] The heated non-catalytic pyrolysis preferably uses a temperature in the range of 300° C. to 850° C., for example 400° C. to 800° C. The process is usually carried out at atmospheric pressure, usually under non-oxidizing conditions (especially in the absence of air). Non-oxidizing conditions can be achieved, for example, by purging the liquefaction equipment with an inert gas (e.g., nitrogen).

[0152] The heated catalytic pyrolysis preferably uses a temperature in the range of 250° C. to 500° C., for example 300° C. to 450° C. The process is usually carried out at atmospheric pressure, usually under non-oxidizing conditions (especially in the absence of air). The process usually uses a solid catalyst, preferably an acidic solid catalyst, such as an acidic FCC catalyst, an acidic zeolite catalyst or an acidic silica-alumina catalyst, such as ZSM-5 or H-ultrastable Y-zeolite, to name a few. Non-oxidizing conditions can be achieved, for example, by purging the liquefaction equipment with an inert gas (e.g. nitrogen).

[0153] The waste plastics may be mixed waste plastics or sorted waste plastics. Since the present invention is particularly suitable for highly contaminated waste plastics, the reliance on the quality of the sorted waste plastics can be reduced and thus the sorted waste plastics of lower quality can be used. Waste plastics (especially unprocessed mixed waste plastics) may contain a large amount of silicon from various sources. The silicon content of the waste plastics may be, for example, in the range of 300 to 50,000 ppm, such as 300 to 20,000 ppm or 500 to 10,000 ppm. Any conventional method may be used to determine the silicon content, such as ICP-MS (inductively coupled plasma mass spectrometry) or XRF (X-ray fluorescence).

[0154] The invention further relates to the use of aluminum oxide particles for in-situ reduction of the organosilicon content during the pyrolysis of waste plastics. In this regard, in-situ reduction means that the organosilicon substances (which may be initially present or generated during the pyrolysis reaction) are removed, accumulated in the solid residue and reduced in content in the product stream (gas / oil product) when pyrolysis is carried out. In this use, aluminum oxide is preferably added before starting the pyrolysis reaction (for example before feeding the waste plastics into the reaction zone). The embodiments described for the method of the invention can be applied similarly to the method of the invention.

[0155] The present invention provides a pyrolysis oil with reduced organosilicon content and an efficient method for achieving the same.

[0156] Example

[0157] Hereinafter, the present invention is illustrated by non-limiting examples. However, it should be understood that the examples represent preferred embodiments of the present invention, and in particular the numerical values ​​and ranges described in the examples can be combined with other ranges and values ​​disclosed in the specification to obtain the scope of the present invention.

[0158] Comparative Example 1

[0159] Sorted waste plastics (industrial grade DKR310, commonly used in Germany) were used for pyrolysis, to which 1 wt.-% PVC (relative to the final waste plastic mixture) was added and further 0.5 wt.-% PDMS (polydimethylsiloxane; 0.5 wt.-%) was added to simulate silicone-containing waste plastic materials with high silicone content.

[0160] Pyrolysis was carried out at a temperature of 380°C (pyrolysis temperature in the reactor) without a catalyst. The generated gases were condensed and collected to provide an oil product. The oil product was analyzed. The Si content in the oil was analyzed based on ASTM D5185, and the procedure was adjusted as needed to measure the pyrolysis oil. The results are shown in Table 1.

[0161] Example 1

[0162] Comparative Example 1 was repeated under the same conditions, except that 20 wt.-% of activated acidic alumina powder (BET SSA 155 m 2 / g, pore size 58 Å, average particle size 150 mesh, corresponding to 105 μm) (to obtain a mixture containing 20 wt.-% alumina and 80 wt.-% mixed waste plastics). The oil product was analyzed. The results are shown in Table 1.

[0163] Comparative Example 2

[0164] Comparative Example 1 was repeated under the same conditions, except that DKR350 (industrial grade) was used to sort the waste plastic (originally with high Si content) and no PVC or PDMS was added. The oil product was analyzed. The results are shown in Table 1.

[0165] Examples 2 to 4

[0166] Comparative Example 2 was repeated under the same conditions, except that different amounts of alumina as detailed in Example 1 were added. Specifically, 3 wt.-% (Example 2) and 7 wt.-% (Example 3) were added in a twin screw melt extruder at a temperature of 165°C. In Example 4, 7 wt.-% of alumina was added and further 6.7 wt.-% of CaO was added. The oil product was analyzed. The results are shown in Table 1.

[0167] Table 1

[0168]

[0169] The results show that a significant reduction in the Si content in the oil product can be achieved by simply adding alumina to the pyrolysis raw materials.

[0170] Examples 5 to 8

[0171] Example 3 (addition of 7 wt.-% alumina) was repeated under the same conditions, except that a different type of alumina was used.

[0172] In Example 5, activated acidic alumina (pH of stirred aqueous dispersion: 4.5 ± 0.5; 150 mesh powder, specific surface area 155 m 2 / g, pore size 58 Å). In Example 6, activated basic alumina (pH of stirred aqueous dispersion: 9.5±0.5; 150 mesh powder, specific surface area 205 m 2 / g, pore size 58 Å). In Example 7, activated neutral alumina (pH of stirred aqueous dispersion: 7.0±0.5; 40-160 μm powder, specific surface area 205 m 2 / g, pore diameter 58 Å).

[0173] Example 8 was carried out at pilot plant scale under the conditions of Example 5 (acidic alumina) (Examples 5 to 7 were carried out at laboratory scale).

[0174] The silicon content in the resulting oil product was measured and is shown in Table 2 below. In addition, Figure 1 A graphical representation of the results of Comparative Example 2 (no alumina) and Examples 2, 5-7 and 8 (each containing 7 wt.-% alumina) is provided.

[0175] Table 2

[0176]

[0177] Experiments 1 to 3

[0178] In order to quantify the effect of heating (and devolatilization) of waste plastics on silicon removal, experimental tests were performed without the addition of aluminum oxide. Thus, the possible effect of the reaction of the mixed aluminum oxide at high temperatures during heating was excluded for better comparability.

[0179] The experiments were conducted using the same mixed waste plastic raw material (DSD 350), which was subjected to melt extrusion at different temperatures and then to laboratory-scale pyrolysis under the same conditions. The results are shown in Table 3 below. Experiment 1 was performed twice and the resulting silicon content was averaged. Experiments 2 and 3 were performed only once. It can be confirmed that high temperature heating (and devolatilization) before pyrolysis can significantly reduce the silicon content in the resulting oil product.

[0180] Table 3

[0181]

Claims

1. A method for producing pyrolysis oil, the method comprising the following steps: adding alumina in granular form to waste plastic containing silicone to form a mixture; feeding the mixture into a pyrolysis reactor; pyrolyzing the mixture in the reactor; At least pyrolysis gas and solid residue are recovered from the reactor, and the pyrolysis gas is condensed to provide an oil product, wherein The solid residue comprises the alumina reacted with silicon.

2. The method according to claim 1, wherein: The aluminum oxide is added in an amount of 0.2 to 40.0 wt.-%, 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.-%.

3. The method according to claim 1 or 2, wherein: The adding of alumina to form a mixture is carried out at a temperature in the range of 50°C to 280°C, preferably in the range of 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.

4. A method according to any one of the preceding claims, wherein: The adding of aluminum oxide to form a mixture includes melting the waste plastic.

5. A method according to any one of the preceding claims, wherein: The addition of alumina to form a mixture is carried out in an extruder, preferably a melt extruder.

6. A method according to any one of the preceding claims, wherein: The aluminum oxide has an open-pore structure.

7. A method according to any one of the preceding claims, wherein: The BET specific surface area of ​​the alumina is 50 m 2 / g to 500 m 2 / g, preferably higher than 50 m 2 / g, higher than 100 m 2 / g, or 150 m 2 / g or higher, for example, between 100 and 300 m 2 / g or in the range of 150 to 300 m 2 / g range.

8. A method according to any one of the preceding claims, wherein: The pyrolysis is performed in two or more steps.

9. The method according to claim 24, wherein: The first pyrolysis step is performed in the absence of a pyrolysis catalyst and at least one of the subsequent pyrolysis steps is performed in the presence of a pyrolysis catalyst.

10. A method according to any one of the preceding claims, wherein: A Group II metal oxide or Group II metal hydroxide (Group II metal oxide / hydroxide), preferably magnesium or calcium, is added during the step of adding alumina to form a mixture and / or directly to the pyrolysis reactor.

11. The method according to claim 10, wherein: The Group II metal oxide / hydroxide is at least one selected from the group consisting of calcium oxide and calcium hydroxide.

12. The method according to claim 10 or 11, wherein: The addition amount of the Group II metal oxide / hydroxide is in the range of 0.2 to 40.0 wt.-%, preferably in the range of 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.-%, 5.0 to 10.0 wt.-%, or 5.5 to 9.0 wt.-%.

13. The method according to any of the preceding claims, further comprising heating the waste plastic containing silicone and / or the mixture to an elevated temperature and devolatilizing at least part of the organosilicon compound contained therein before feeding the mixture to the pyrolysis reactor, wherein the heating is carried out at a temperature in the range of 175°C to 280°C, for example 180°C to 270°C, 185°C to 265°C, 190°C to 260°C, 200°C to 255°C, or 210°C to 250°C.

14. A method according to any one of the preceding claims, wherein: The alumina is acidic alumina, preferably activated acidic alumina.

15. Use of aluminum oxide in granular form for in-situ reduction of the organosilicon content during the pyrolysis of waste plastics.

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