CN119278247A

CN119278247A - Removal of Silicon from Depolymerized Oil

Info

Publication number: CN119278247A
Application number: CN202380046525.6A
Authority: CN
Inventors: 基莫·哈卡拉; 瓦莱里娅·莫雷柳斯; 维尔·帕西卡利奥; 穆罕默德·萨德·库雷希
Original assignee: Neste Oyj
Current assignee: Neste Oyj
Priority date: 2022-07-12
Filing date: 2023-06-09
Publication date: 2025-01-07
Also published as: WO2024013424A1; AU2023308404A1; KR20250024081A

Abstract

The present invention relates to an improved process for removing silicon from depolymerized oil, and more particularly to a process for producing pyrolysis oil comprising the steps of adding alumina in particulate form to waste plastics containing silicone to form a mixture, feeding the mixture to a pyrolysis reactor, pyrolyzing the mixture in the reactor, recovering from the reactor at least pyrolysis gas and solid residues, and condensing the pyrolysis gas to provide an oil product, wherein the solid residues comprise alumina reacted with silicon.

Description

Silicon removal from depolymerized oils

Technical Field

The present invention relates to an improved process for removing silicon from depolymerized oils, more particularly to in situ reduction of silicon content during pyrolysis of waste plastics and to the use of alumina for in situ reduction of silicon content during pyrolysis of waste plastics.

Background

Methods for purifying Liquefied Waste Plastics (LWP), which may also be referred to as depolymerized oils, have been studied for many years to obtain more valuable (pure) materials.

LWP is typically produced by pyrolysis or hydrothermal liquefaction (HTL) of waste plastics. LWP has different levels of impurities depending on the source of the waste plastic.

The feed for chemical recovery of plastics typically contains mixed plastic waste, which may originate, for example, from plastics collected separately from the home (from which cleaner plastic fractions have been removed for mechanical recovery) or from plastics separated from Municipal Solid Waste (MSW). However, even sorting waste close to 100% plastic content is not economically viable. Therefore, the waste plastic material (waste plastic feed) used for producing LWP generally contains materials other than plastic. These other materials (including biomass) may also be sources of impurities that ultimately enter LWP.

In particular, consumer waste, including waste packaging, typically comprises a composition other than hydrocarbons. Silicon is one of the non-hydrocarbon elements commonly found in plastic waste and is of various sources, such as silicone. As a result, chemically recovered plastic waste often encounters significant amounts of silicon impurities. Other typical impurity components are chlorine, nitrogen, sulfur and oxygen.

Whether LWP is subjected to only ordinary refining processes (e.g., fractional distillation) or is forwarded to subsequent petrochemical conversion processes, LWP feeds need 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, for example in a hydrotreating step, and thus techniques for reducing the silicon content in LWP have been studied.

WO2021/80899A1 discloses passing LWP (i.e. depolymerized oil) through an absorbent in the presence of hydrogen at a temperature of 80 to 360 ℃.

However, there remains a need for further improvements in relation to the removal of silicon from LWP products.

Disclosure of Invention

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

The present invention is based on the discovery that by using alumina as a reactant, the silicon content in LWP can already be reduced in situ during pyrolysis. That is, no special steps need to be provided to remove silicon from the produced LWP outside of the prior art. Instead, the silicon content in the LWP has been reduced during the pyrolysis step.

The problem of the invention is solved by the subject matter set forth in the independent claims. Further advantageous developments are set forth in the dependent claims.

Briefly, the present invention is directed to one or more of the following:

1. a method of producing pyrolysis oil, the method comprising the steps of:

Alumina in particulate form is added to waste plastics containing silicone to form a mixture,

Feeding the mixture to a pyrolysis reactor,

Pyrolyzing the mixture in the reactor,

Recovering at least one pyrolysis gas and solid residue from the reactor and condensing the pyrolysis gas to obtain an oil product, wherein

The solid residue comprises alumina after reaction with silicon.

2. The method of item 1, wherein the alumina 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 of clause 1 or 2, wherein the adding alumina to form the mixture is performed at an elevated temperature.

4. The method of any preceding item, wherein the adding alumina to form the mixture is performed at a temperature in the range of 50 ℃ to 280 ℃, preferably at a temperature in the range of 60 ℃ to 270 ℃, 80 ℃ to 260 ℃, 100 ℃ to 250 ℃, 110 ℃ to 250 ℃, 120 ℃ to 250 ℃, 130 ℃ to 240 ℃, 140 ℃ to 230 ℃, or 150 ℃ to 220 ℃.

5. The method of any preceding item, wherein the adding alumina to form a mixture comprises melting the waste plastic.

6. The method of any preceding item, wherein the adding alumina to form a mixture comprises melting the waste plastic, and the adding of alumina occurs before and/or during and/or after melting the waste plastic, preferably at least before melting.

7. The method of any preceding item, wherein the waste plastic comprises predominantly thermoplastic compounds.

8. The method according to any preceding item, wherein the adding alumina to form the mixture is performed in an extruder, preferably in a melt extruder.

9. The method of any preceding item, wherein the adding alumina to form the mixture is performed by blending alumina with waste plastic (preferably solid waste plastic) without external heating.

10. The method according to any preceding item, wherein the alumina has an average particle size in the range of 50nm to 10mm, 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.

11. The method of any preceding item, wherein the alumina is activated alumina.

12. The method of any preceding item, wherein the alumina has an open pore structure.

13. A method according to any preceding item wherein the pore size of the alumina is in the range 30 to 10000 angstroms, preferably 40 to 1000 angstroms, 50 to 500 angstroms, 55 to 300 angstroms, or 60 to 200 angstroms.

14. A method according to any preceding item, wherein the alumina has a BET specific surface area in the range 50 m ²/g to 500 m ²/g, preferably greater than 50 m ²/g, greater than 100m ²/g, or 150 m ²/g or higher, for example in the range 150 to 300 m ²/g.

15. The method of any preceding item, further comprising post-treating the oil product recovered from the pyrolysis reactor.

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.

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.

18. The method according to item 16 or 17, wherein the aqueous solution comprises at least 0.3 wt% alkaline material, more preferably at least 0.5 wt%, at least 1.0 wt% or at least 1.5 wt% alkaline material, e.g. 0.5 wt to 10.0 wt%, 1.0 wt to 6.0 wt%, or 1.5 wt to 4.0 wt%.

19. The method according to any one 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%.

20. The method according to any one of items 16 to 19, wherein the heat treatment is performed at a temperature of 150 ℃ or more, preferably 190 ℃ or more.

21. The method according to any one of clauses 16 to 20, wherein the heat treatment is performed at a temperature of 200 ℃ or more (e.g., 210 ℃ or more, 220 ℃ or more, 240 ℃ or more, or 260 ℃ or more).

22. The method according to any one of items 16 to 21, wherein the heat treatment is performed at a temperature of 450 ℃ or less (preferably 400 ℃ or less, 350 ℃ or less, 320 ℃ or less, or 300 ℃ or less).

23. The method according to any one of clauses 16 to 22, wherein the heat treatment is performed at a temperature in the range of 200 ℃ to 350 ℃ (preferably 220 ℃ to 330 ℃, 240 ℃ to 320 ℃, or 260 ℃ to 300 ℃).

24. The method of any of clauses 15 to 23, wherein post-treating comprises hydrotreating the oil product to provide a hydrotreated oil product.

25. The method of any preceding item, wherein the pyrolyzing is performed in two or more steps.

26. The method of clause 25, 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.

27. A method according to any preceding item, wherein a group II metal oxide or group II metal hydroxide (group II metal oxide/hydroxide) is further added during the step of adding alumina to form the mixture and/or directly to the pyrolysis reactor.

28. The method of clause 27, wherein the group II metal is magnesium or calcium.

29. The method according to clause 27 or 28, wherein the group II metal oxide/hydroxide is at least one selected from the group consisting of calcium oxide and calcium hydroxide.

30. The method according to any one of clauses 27 to 29, wherein the group II metal oxide/hydroxide is added in an amount in the range of 0.2 to 40.0 wt ], preferably in an amount 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%.

31. The method of any preceding item, wherein the alumina is added in an amount such 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 without the alumina added.

32. A method according to any preceding item wherein the alumina is an acidic alumina or a basic alumina, preferably an acidic alumina.

33. The method of any preceding item, wherein the pyrolyzing is performed at a temperature in the range of 250 ℃ to 850 ℃.

34. The method of any preceding item, further comprising heating the silicone-containing waste plastic and/or the mixture to an elevated temperature and devolatilizing at least a portion of the silicone compound contained therein.

35. The method of clause 34, wherein the temperature is 175 ℃ or higher, preferably 180 ℃ or higher, 185 ℃ or higher, 190 ℃ or higher, 200 ℃ or higher, or 210 ℃ or higher.

36. The method of clauses 34 or 35, wherein the temperature is 280 ℃ or less, preferably 270 ℃ or less, 265 ℃ or less, 260 ℃ or less, 255 ℃ or less, or 250 ℃ or less.

37. The method according to any one of clauses 34 to 36, wherein the temperature is in the range of 175 ℃ to 280 ℃, such as 180 ℃ to 270 ℃, 185 ℃ to 265 ℃, 190 ℃ to 260 ℃, 200 ℃ to 255 ℃, or 210 ℃ to 250 ℃.

38. The method according to any one of clauses 34 to 37, wherein the devolatilizing is performed before, while and/or after the addition of alumina.

39. A method as set forth in any one of items 34 to 38 wherein the devolatilizing is performed at least in the step of adding alumina to form the mixture.

40. The method of any of clauses 34 to 39, wherein the devolatilizing is performed at least in the step of adding aluminum oxide to form the mixture.

41. The method according to any one of items 34 to 40, wherein the devolatilizing is performed in an extruder.

42. The method according to any one of items 34 to 41, wherein the devolatilizing is performed in a melt extruder.

43. The method of clause 41 or 42, wherein the extruder has a gas vent.

44. The method of any preceding item, wherein the alumina is an acidic alumina.

45. The method according to any preceding item, wherein the alumina is added in an amount of 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%.

46. The method of any preceding item, wherein the adding alumina to form the mixture is performed at a temperature in the range of 150 ℃ to 280 ℃, preferably at a temperature in the range of 160 ℃ to 280 ℃, 170 ℃ to 280 ℃, 175 ℃ to 280 ℃, 180 ℃ to 270 ℃, 185 ℃ to 265 ℃, 190 ℃ to 260 ℃, 2000 ℃ to 255 ℃, or 210 ℃ to 250 ℃.

47. Use of alumina in particulate form for in situ reduction of the silicone content in a waste plastics pyrolysis process.

48. The use according to item 47 for a waste plastic pyrolysis process (method) as defined in any one of items 1 to 46.

49. A method for producing pyrolysis oil according to the use of item 47 or 48, the method comprising the steps of:

Feeding the mixture to 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 comprises alumina reacted with silicon.

50. The use according to any one of clauses 47 to 49, wherein the alumina 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%.

51. The use according to any one of clauses 47 to 50, wherein the adding alumina to form the mixture is performed at an elevated temperature.

52. The use according to any one of clauses 47 to 51, wherein the adding alumina to form the mixture is performed at a temperature in the range of 50 ℃ to 280 ℃, preferably at a temperature in the range of 60 ℃ to 270 ℃, 80 ℃ to 260 ℃, 100 ℃ to 250 ℃, 110 ℃ to 250 ℃, 120 ℃ to 250 ℃, 130 ℃ to 240 ℃, 140 ℃ to 230 ℃, or 150 ℃ to 220 ℃.

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

54. The use according to any one of items 47 to 53, wherein the adding of alumina to form a mixture comprises melting the waste plastics and the adding of alumina is performed before and/or during and/or after melting the waste plastics, preferably at least before melting.

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

56. The use according to any one of clauses 47 to 55, wherein the adding alumina to form the mixture is performed in an extruder, preferably in a melt extruder.

57. The use according to any one of clauses 47 to 56, wherein the adding alumina to form a mixture is performed by blending alumina with waste plastic (preferably solid waste plastic), without external heating.

58. The use according to any one of clauses 47 to 57, wherein the alumina has an average particle size in the range of 50 nm to 10mm.

59. The use according to any one of clauses 47 to 58, wherein the alumina has an average particle size 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.

60. The use according to any one of clauses 47 to 58, wherein the alumina has an open pore structure.

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

62. The use according to any one of clauses 47 to 61, wherein the pore size of the alumina is in the range of 30 to 10000 angstroms, preferably 40 to 1000 angstroms, 50 to 500 angstroms, 55 to 300 angstroms, or 60 to 200 angstroms.

63. The use according to any one of clauses 47 to 62, wherein the alumina has a BET specific surface area in the range of 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 higher, for example in the range of 100 to 300 m ²/g or in the range of 150 to 300 m ²/g.

64. The use according to any one of clauses 47 to 63, wherein the pyrolysis is performed in two or more steps.

65. The use according to any one of clauses 47 to 64, 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.

66. The use according to any one of clauses 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.

67. The method of clause 66, wherein the group II metal is magnesium or calcium.

68. A method according to clause 65 or 66, wherein the group II metal oxide/hydroxide is at least one selected from the group consisting of calcium oxide and calcium hydroxide.

69. The method according to any one of clauses 65 to 68, wherein the group II metal oxide/hydroxide is added in an amount 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%.

70. The use according to any one of clauses 47 to 69, 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 without the alumina added.

71. The use according to any one of clauses 47 to 70, wherein the alumina is an acidic alumina or a basic alumina, preferably an acidic alumina.

72. The use according to any one of clauses 47 to 71, wherein the alumina is activated alumina.

73. The use according to any one of clauses 47 to 72, wherein the pyrolysis is carried out at a temperature in the range of 250 ℃ to 850 ℃.

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

75. The use according to item 74, wherein the temperature is 175 ℃ or higher, preferably 180 ℃ or higher, 185 ℃ or higher, 190 ℃ or higher, 200 ℃ or higher, or 210 ℃ or higher.

76. The use according to clause 74 or 75, wherein the temperature is 280 ℃ or less, preferably 270 ℃ or less, 265 ℃ or less, 260 ℃ or less, 255 ℃ or less, or 250 ℃ or less.

77. The use according to any one of clauses 74 to 76, wherein the temperature is in the range of 175 ℃ to 280 ℃, such as 180 ℃ to 270 ℃, 185 ℃ to 265 ℃, 190 ℃ to 260 ℃, 200 ℃ to 255 ℃, or 210 ℃ to 250 ℃.

78. The use according to any one of clauses 74 to 77, wherein the devolatilization is performed before, while and/or after the addition of alumina.

79. The use according to any one of clauses 74 to 78, wherein the devolatilizing is performed at least in the step of adding aluminum oxide to form the mixture.

80. The use according to any of clauses 74 to 79, wherein the devolatilizing is performed at least in the step of adding aluminum oxide to form the mixture.

81. The use according to any one of items 74 to 80, wherein the devolatilization is performed in an extruder.

82. The use according to any one of items 74 to 81, wherein the devolatilization is performed in a melt extruder.

83. The use according to clause 81 or 82, wherein the extruder has a gas discharge port.

84. The use according to any one of clauses 47 to 83, wherein the alumina is an acidic alumina.

85. The use according to any one of clauses 47 to 84, wherein the alumina is added in an amount of 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%.

86. The use according to any one of clauses 47 to 85, wherein the adding alumina to form the mixture is performed at a temperature in the range of 150 to 280 ℃, preferably at a temperature in the range of 160 to 280 ℃, 170 to 280 ℃, 175 to 280 ℃, 180 to 270 ℃, 185 to 265 ℃, 190 to 260 ℃, 2000 to 255 ℃, or 210 to 250 ℃.

Detailed Description

The present invention relates to an improved process for reducing the silicon content of depolymerized oils.

The silicon impurity content should be reduced before the LWP is further processed. The present invention focuses on a method for in situ removal of silicon in a pyrolysis step (i.e., during depolymerization of waste plastics). The invention relates in particular to a process utilizing alumina in particulate form (also referred to as particulate alumina or alumina particles) which is added to waste plastics prior to pyrolysis and reacts during pyrolysis with organosilicon compounds produced from the waste plastics such that the silicon reacted with the alumina ends up in the solid residue of the pyrolysis reaction while minimizing gaseous products (gaseous effluent) in the silicon content which are then condensed to provide depolymerized oil (liquefied waste plastics; LWP).

In the context of the present invention, liquefied Waste Plastics (LWP) refers to the product effluent from the pyrolysis process, which comprises at least depolymerized waste plastics. Therefore, LWP is a material obtainable by depolymerizing waste plastics. LWP may also be referred to as a polymer waste base oil or depolymerized oil.

The waste plastic may come from any source, such as consumer plastic (recycled or collected), industrial plastic (recycled or collected) or scrap tires (ELT). In particular, the term waste plastic refers to organic polymeric materials that are no longer suitable for their use or are discarded for other reasons. Waste plastics may more particularly refer to scrap tires, collected consumer plastics (consumer plastics refer to any organic polymeric material in consumer goods, even if not having the characteristics of "plastic" itself), collected industrial polymeric waste. In the sense of the present invention, the term waste plastics or "polymers" does not generally cover pure inorganic materials (which are sometimes referred to as inorganic polymers). The polymers in the waste plastic may be natural and/or synthetic and may be based on renewable and/or fossil raw materials.

The liquefaction process (pyrolysis) is carried out at high temperature and preferably under non-oxidizing conditions. The liquefaction process may be carried out at elevated pressure. The liquefaction process may be performed 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 may be used as such as pyrolysis oil (LWP; i.e. as a product of the process), or may be fractionated (or separated) to provide fractions (or separated liquids), and may also be subjected to other treatments, in particular further purification. In this context, fractional distillation (fractionation) refers to fractional distillation (fractional distillation) and/or fractional evaporation (fractional evaporation).

In addition to liquid (NTP) hydrocarbons (i.e., hydrocarbons that are liquid at normal temperature and pressure (NTP; 20 ℃,101.325 kPa a. Absolute), typical oil products from pyrolysis processes also include gaseous (NTP) hydrocarbons, as well as hydrocarbons that are waxy or solid at NTP but become liquid when heated (e.g., to 80 ℃).

In the context of the present disclosure, waste plastic depolymerization means decomposition or degradation of the polymer backbone of the waste plastic by pyrolysis to produce polymer and/or oligomer species of lower molecular weight than the starting waste plastic, but still comprising at least liquid (NTP) hydrocarbons. Depolymerization of waste plastics may also involve cleavage of covalently bound heteroatoms, such as O, S and N, from optionally present heteroatom-containing compounds.

Initially, each of the waste plastics or mixed waste plastics to be pyrolysed is typically in the solid state, with a melting point typically in the range of 100 ℃ or higher as measured by DSC, as described in Larsen et al ("DETERMINING THE PE fraction IN RECYCLED PP", polymer testing, vol. 96, 2021, month 4, 107058). However, the or each waste plastic material may be melted before and/or during depolymerization.

The solid waste plastic 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 desired, some of the additional components may be removed from the solid waste plastic, molten waste plastic, and/or liquefied waste plastic using generally known methods.

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, by 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%o- (CHN content + ash content), where CHN content refers to the total content of carbon, hydrogen and nitrogen determined according to ASTM D5291 and ash content refers to the ash content determined according to ASTM D482/EN 15403.

In this disclosure, when referring to a standard, unless otherwise indicated, the latest revision available on day 31, month 2022 should be referred to. Furthermore, all embodiments of the invention (e.g., all preferred values and/or ranges within an embodiment) can be combined with each other to arrive at a new (preferred) embodiment unless specifically indicated otherwise or unless such combination would result in a conflict.

In the present invention, the term "particle" or "particle form" encompasses all types of powders, granules, agglomerates, etc., and is not limited to a particular shape.

The term "pyrolysis reactor" refers to the pyrolysis zone of the apparatus in which the pyrolysis reaction is carried out. That is, a "pyrolysis reactor" is where the actual pyrolysis reaction occurs.

The term "solid residue" refers to a substance that is not transferred to the gas phase during the pyrolysis reaction. Typically, such solid residues contain non-evaporated tars 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 the particulate alumina). The reaction may comprise or be a physical reaction (e.g., adsorption) and/or a chemical reaction. Preferably, the Si chemically reacts with the alumina, preferably binding to the alumina surface (accessible surface, including penetration into open pores). While the mechanism is not completely understood, it is presumed that when Si is added to the pyrolysis reactor, it reacts mainly with alumina at the surface thereof to form a layered structure, and that the layered structure is formed of si—al-oxide type materials.

It is speculated that most of the silicone in the waste plastic is in the form of polysiloxanes, which form volatile oligosiloxanes during pyrolysis and thus transfer into the oil product. On the other hand, inorganic silicon (e.g., silica) is not reactive (and does not volatilize) under pyrolysis conditions and therefore, in any case, eventually goes into the solid residue.

The method according to the invention is characterized in that granular aluminium oxide is mixed with waste plastics, and the mixture is then pyrolysed in a pyrolysis reactor, so that silicon in the waste plastics reacts with the aluminium oxide and is transferred to the solid residue.

In particular, the invention relates to a process for producing pyrolysis oil comprising the steps of adding alumina in particulate form to waste plastics containing silicone to form a mixture, feeding the mixture to a pyrolysis reactor, pyrolysing the mixture in the reactor, recovering at least pyrolysis gas and solid residues from the reactor, and condensing the pyrolysis gas to provide an oil product, wherein the solid residues comprise alumina reacted with the silicone.

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

The amount of alumina added is preferably 0.2 wt to 40.0 wt% (relative to 100 wt%) and 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 found that in view of the balance of silicon removal efficiency and alumina utilization efficiency, it is particularly advantageous to add 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%). The term "pyrolysis feed relative to 100 wt. -%" refers to the total amount of waste plastics (including all impurities and contaminants, such as biomass), alumina and other feeds (but not pyrolysis catalyst (if present)). That is, as noted above, waste plastic may come from municipal waste and may include some biomass even after sorting.

The step of adding alumina to form a mixture (i.e., the mixing step) may be performed at an elevated temperature. In this respect, "elevated temperature" means that external heating is applied to the mixing device (such that the components to be mixed are heated).

For example, the mixing step may be performed at a temperature in the range of 50 ℃ to 280 ℃, preferably at a temperature in the range of 60 ℃ to 270 ℃, 80 ℃ to 260 ℃,100 ℃ to 250 ℃, 110 ℃ to 250 ℃, 120 ℃ to 250 ℃,130 ℃ to 240 ℃, 140 ℃ to 230 ℃, or 150 ℃ to 220 ℃. By employing elevated temperatures during the mixing step, processing may be facilitated and a more uniform mixture may be prepared. In some embodiments, it may be beneficial to limit the temperature in the mixing step to 180 ℃ or less (e.g., in the range of 50 ℃ to 180 ℃) to minimize the production of hydrochloric acid during the mixing stage. In the context of the present invention, the "temperature" at which the mixing step is performed refers to the temperature of the mixture (rather than the temperature of the heating medium).

In particular, the addition of alumina to form a mixture may comprise (at least partially) melting waste plastics. When the waste plastics are melted, a more uniform mixture can be prepared. In addition, the molten material further facilitates its handling. 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.

Melting the waste plastic (at least in part) requires the presence of a thermoplastic compound. Therefore, the waste plastics in the present invention preferably mainly contain thermoplastic compounds. The term "predominantly comprises" 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 from thermoplastic compounds based on the waste plastic as a whole.

In one embodiment, the mixing step is performed in an extruder, preferably a melt extruder. Since an extruder is generally used as a feeding device to supply waste plastics to the pyrolysis reactor, alumina addition can be easily achieved at this stage while achieving uniform mixing. In particular, the use of a melt extruder can homogenize the mixture of alumina and waste plastic and thereby improve the pyrolysis process. In addition, the melt extruded material may be easier to handle, such as being fed directly to the pyrolysis reactor or being pelletized and fed into the pyrolysis reactor.

Alternatively or additionally, the mixing step may be performed without external heating, for example at room temperature. In this case, the handling is facilitated since no attention is paid to the high temperature and/or cooling effect in the mixing step.

In another embodiment, the present invention may utilize a devolatilization step to further remove silicon components contained in the waste plastic in addition to using additives to remove the silicon tung prior to the pyrolysis step. It has been unexpectedly discovered that by heating the silicone-containing waste plastic (before, during and/or after the addition of alumina) to a temperature prior to pyrolysis (i.e., prior to feeding the mixture to the pyrolysis reactor), the amount of silicon-containing compounds in the oil product (i.e., resulting from pyrolysis gas condensation) can be further reduced. Although the reason for this effect is not completely clear, it is speculated that heating will remove part of the organosilicon compound (most of which is considered to be the siloxane compound) into the gas phase. Based on this understanding, this heating stage may also be referred to as a "degassing" or "devolatilization" stage. Therefore, it is preferable that the heating temperature is high enough to sufficiently convert the organosilicon compound contained in the waste plastic (in the mixture as the case may be) to degas. In particular, the temperature is preferably 175 ℃ or higher, for example 180 ℃ or higher, 185 ℃ or higher, 190 ℃ or higher. The temperature may in particular be 200 ℃ or more, or 210 ℃ or more. The temperature should also not be too low to avoid (or minimize) product loss. Suitable temperature ranges are 175 ℃ to 280 ℃, e.g., 180 ℃ to 270 ℃, 185 ℃ to 265 ℃, 190 ℃ to 260 ℃, 200 ℃ to 255 ℃, or 210 ℃ to 250 ℃.

Heating and degassing (devolatilization) may suitably be carried out in a process in which the addition of alumina may be carried out, since together they may produce a synergistic effect with the use of high temperatures during the homogenization of the waste plastics. In this case, the alumina addition (mixing) temperature preferably corresponds to the heating (devolatilization) temperature described above. Nevertheless, heating (devolatilization) may also be performed as a dedicated stage (step) before and/or after the alumina addition/mixing (in addition to or instead of during the alumina addition/mixing).

Pyrolysis may be carried out as a batch process or a continuous process, with a continuous process being preferred.

The average particle diameter of the alumina (alumina 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 may be measured, for example, by laser diffraction (ISO 13320) or by optical or electron microscopy (ISO 13322) methods. The specific surface area and pore size (pore diameter) of the alumina can be determined by gas adsorption measurements, for example based on ISO 9277 or ISO 15901-2. In the case of agglomerates, particle size refers to the size of the agglomerates, rather than the primary particle size. The porosity of the alumina (alumina particles) may be in the range of, for example, 20-85%.

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

The BET specific surface area of the alumina (alumina particles) is preferably in the range of 50m ²/g to 500m ²/g, preferably above 50m ²/g, above 100m ²/g, or 150 m ²/g or higher, for example in the range of 100 to 300m ²/g, 150 to 300m ²/g.

The process of the present invention may further comprise post-treating the oil product recovered from the pyrolysis reactor. Although the oil product produced by the method of the present invention may be sufficiently pure to be added to a value chain (e.g., for use in a crude oil refining process), it is preferred that the oil product be post-treated to increase its purity or availability. Thus, the post-treatment may particularly comprise a purification process (e.g. fractionation or extraction) and/or an upgrading process (e.g. hydrotreating). Nevertheless, any known petrochemical process can be used for the post-treatment, and in particular, the oil product can be used as co-feed in the petrochemical process.

In one embodiment, 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 liquid-liquid separation to provide a further purified oil product. Such a treatment is suitable for further removing impurities, in particular chlorine-containing impurities, from the oil product in a very efficient 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 a 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 performed at a temperature of 150 ℃ or more (preferably 190 ℃ or more, or 200 ℃ or more, for example 210 ℃ or more, 220 ℃ or more, 240 ℃ or more, or 260 ℃ or more). In order to keep the heating power within usual limits and avoid excessive side reactions, the heat treatment is preferably performed at a temperature of 450 ℃ or less (preferably 400 ℃ or less, 350 ℃ or less, 320 ℃ or less, or 300 ℃ or less). In particular, the heat treatment may be performed at a temperature in the range of 200 ℃ to 350 ℃ (preferably 220 ℃ to 330 ℃, 240 ℃ to 320 ℃, or 260 ℃ to 300 ℃).

The post-treatment may comprise hydrotreating the oil product to provide a hydrotreated oil product. Hydroprocessing is particularly useful for heteroatom removal and/or for olefin saturation. The hydrogenation treatment is particularly advantageous in the present invention because the silicone can act as a catalyst deactivator. Thus, the process of the present invention can protect the hydrotreating catalyst from degradation and extend its useful life.

The pyrolysis step in the process of the present invention may be further carried out by a second step (as a two-step process). In this embodiment, both the reactor type and the reaction temperature of both steps may be varied. Typically, the first step is to carry out the cleavage with the solid residue removed in the first reactor. The second step is then to treat the pyrolysis gas by contacting it with a catalyst to selectively cleave the long (carbon) chains. For example, a mixture of waste plastics and alumina is fed to the first step and solid residues are removed from the first step while the product stream (e.g. oil or gas) is sent to the second (and optionally subsequent) step. The first step may be a step of cracking the waste plastic into (long chain) compounds, while the second step is mainly used for cracking the (long chain) compounds of the cracked material. By adopting the two-step process, the product distribution is improved. In particular, the viscosity of the oil product is reduced, thereby facilitating handling and storage.

The cleavage in the second step is preferably a selective cleavage step. Thus, it is preferred that the second pyrolysis step (and even more preferred the subsequent pyrolysis step) is performed in the presence of a catalyst. In the first pyrolysis step, the catalyst is less beneficial and is therefore preferably omitted. Thus, it is preferred that 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. It is particularly preferred that at least the final pyrolysis step is carried out in the presence of a catalyst. Preference is given to solid catalysts, for example acidic FCC catalysts, acidic zeolite catalysts or acidic silica-alumina catalysts, for example ZSM-5 or H-ultrastable Y-zeolite.

In order to further improve the product distribution (in particular to reduce the chlorine content in the oil product), it is preferred that wherein a group II metal oxide or group II metal hydroxide (hereinafter sometimes collectively referred to as group II metal oxide/hydroxide) is further added during the step of adding alumina to form the mixture and/or directly to the pyrolysis reactor. The group II metal oxide/hydroxide is suitable for reducing chlorine impurities during pyrolysis (in situ), and the inventors have also found that the additional presence of the group II metal oxide/hydroxide further reduces the silicon content of the oil product. In view of the efficiency of the procedure, it is preferred to add the alumina and the group II metal oxide/hydroxide in the same step, which may be simultaneous and/or sequential, for example, by adding the alumina first and then the group II metal oxide/hydroxide.

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 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 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 5.5.5 to 3563 to 9.26%. 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 exist in the form of a group II metal oxide (e.g., caO), i.e., the group II metal oxide (e.g., caO) equivalent is calculated using the content of the group II metal (e.g., ca) as a basis.

The amount of alumina 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 without the addition of alumina. The amount of silicon may be determined based on ASTM D5185. In this respect, an oil product refers to an oil product immediately after pyrolysis (i.e., a condensed product) from which only gaseous (NTP) products are removed and no further processing or post-treatment need be applied. Furthermore, the term "when alumina is not added" means that the reaction is performed under the same conditions but alumina is not added. The adjustment of the Si content reduction may preferably be achieved by feedback control or feedforward control, for example using a tabulated value for known waste plastic compositions.

The alumina may be acidic alumina, neutral alumina or basic alumina, preferably neutral alumina or acidic alumina, more preferably acidic alumina. Alumina is of the acidic type when placed in water has a tendency to reach a pH (of the water) of 6 or less (e.g., below 6). Alumina is of alkaline type when placed in water has a tendency to reach a pH (of the water) of 8 or higher (e.g. above 8). Alumina is said to be neutral when it tends to reach a pH of 6 to 8 for water. It has been demonstrated that alumina can be of the acidic, neutral and basic types, and each type provides the chemisorption of Si to the alumina, thus exhibiting Si removal efficiency. However, the inventors have unexpectedly found that the acidic type of alumina exhibits improved silicon removal efficiency relative to basic and neutral alumina, and thus the acidic type is most preferred. Without being bound by any particular theory, the active sites provided by alumina may be further optimized by pH to provide appropriate conditions for chemisorption interactions between alumina and silicon to perform the intended silicon removal function.

In order to improve the reactivity, the alumina is preferably activated alumina, and more preferably acidic activated alumina. Activated alumina is a highly porous form of alumina that is used in the chemical arts as a desiccant, etc. Its surface area is high, typically above 100m ²/g, often even exceeding 200m ²/g. Activated alumina can be produced by dehydroxylation of aluminum hydroxide to form highly porous materials. The activated alumina may have an open cell structure, in particular tunnel-like pores. The activated alumina may comprise or consist of gamma alumina (gamma-Al ₂O₃).

The temperature in the pyrolysis step is not particularly limited, and a conventional range may be employed. In the case of using a plurality of pyrolysis steps, it is preferable to adjust the temperature according to the presence or absence of a catalyst.

The heated non-catalytic pyrolysis preferably employs a temperature in the range of 300 ℃ to 850 ℃, for example 400 ℃ to 800 ℃. The process is typically carried out at atmospheric pressure, typically under non-oxidising conditions (especially in the absence of air). The non-oxidizing conditions may be achieved, for example, by purging the liquefaction plant with an inert gas (e.g., nitrogen).

The heated catalytic pyrolysis preferably employs a temperature in the range of 250 ℃ to 500 ℃, for example 300 ℃ to 450 ℃. The process is typically carried out at atmospheric pressure, typically under non-oxidising conditions (especially in the absence of air). The process typically employs 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. The non-oxidizing conditions may be achieved, for example, by purging the liquefaction plant with an inert gas (e.g., nitrogen).

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 dependence 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, particularly raw mixed waste plastics, may contain significant amounts of silicon from various sources. The waste plastic may have a silicon content in the range of 300 to 50000 ppm, such as 300 to 20000 ppm or 500 to 10000 ppm, for example. The silicon content may be determined by any conventional method, such as ICP-MS (inductively coupled plasma mass spectrometry) or XRF (X-ray fluorescence).

The invention further relates to the use of alumina particles for in situ reduction of the organosilicon content during pyrolysis of waste plastics. In this regard, in situ reduction means that the organosilicon material (which may be initially present or generated during the pyrolysis reaction) is removed, accumulates in the solid residue and reduces the content in the product stream (gas/oil product) as the pyrolysis proceeds. In such applications, it is preferred to add the alumina prior to the initiation of the pyrolysis reaction (e.g., prior to feeding the waste plastic to the reaction zone). The embodiments set forth for the method of the present invention are similarly applicable to the method of the present invention.

The invention provides a pyrolysis oil with reduced organosilicon content and a high-efficiency method for realizing the pyrolysis oil.

Examples

Hereinafter, the present invention is illustrated by way of non-limiting examples. It is to be understood, however, that the examples represent preferred embodiments of the invention, and that the numerical values and ranges recited in the examples, in particular, can be combined with other ranges and values disclosed in the specification to arrive at a range embodying the invention.

Comparative example 1

Pyrolysis was performed using a sorted waste plastic (technical grade DKR310, commonly used in germany), to which 1 wt.+ -. PVC (relative to the final waste plastic mixture) was added and further 0.5.+ -. 0.5 wt.+ -. PDMS (polydimethylsiloxane; 0.5 wt.%) was added to simulate a silicone-containing waste plastic material with a high silicone content.

Pyrolysis was performed at a temperature of 380 ℃ without catalyst (pyrolysis temperature within the reactor). The generated gas is 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, with procedures adjusted as necessary to measure pyrolysis oil. The results are shown in Table 1.

Example 1

Comparative example 1 was repeated under the same conditions, except that 20 wt% of active acidic alumina powder (BET SSA 155 m ²/g, pore size 58 a, average particle size 150 mesh, corresponding to 105 μm) was further added by mixing without external heating (to obtain a mixture containing 20 wt% alumina and 80 wt% of mixed waste plastic). The oil product was analyzed. The results are shown in Table 1.

Comparative example 2

Comparative example 1 was repeated under the same conditions except that DKR350 (technical grade) was used to sort waste plastics (originally having a high Si content) without adding PVC or PDMS. The oil product was analyzed. The results are shown in Table 1.

Examples 2 to 4

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 ℃. In example 4, 7 wt% of alumina was added and 6.7 wt% of CaO was further added. The oil product was analyzed. The results are shown in Table 1.

TABLE 1

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

Examples 5 to 8

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

In example 5, an active acidic alumina (pH of the stirred aqueous dispersion: 4.5.+ -. 0.5;150 mesh powder, specific surface area 155 m ²/g, pore size 58A) was used. In example 6, activated basic alumina (pH of the stirred aqueous dispersion: 9.5.+ -. 0.5;150 mesh powder, specific surface area 205 m ²/g, pore size 58A) was used. In example 7, activated neutral alumina (pH of the stirred aqueous dispersion: 7.0.+ -. 0.5;40-160 μm powder, specific surface area 205 m ²/g, pore size 58A) was used.

Example 8 was performed on a pilot plant scale under the conditions of example 5 (acidic alumina) (examples 5 to 7 were performed on a laboratory scale).

The silicon content in the resulting oil product was measured and is shown in table 2 below. Furthermore, fig. 1 provides a graphical representation of the results of comparative example 2 (no alumina) and examples 2, 5-7 and 8 (each containing 7 wt% alumina).

TABLE 2

Experiments 1 to 3

To quantify the effect of heating (and devolatilization) the waste plastic on silicon removal, experimental tests were performed without the addition of alumina. Thus, to obtain better comparability, the possible effect of reacting with the mixed alumina at high temperature during heating is excluded.

The experiments were performed using the same mixed waste plastic raw material (DSD 350) which was subjected to melt extrusion at different temperatures, followed by 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 has been demonstrated that high temperature heating (and devolatilization) prior to pyrolysis can significantly reduce the silicon content of the resulting oil product.

TABLE 3 Table 3

Claims

1. A method of producing pyrolysis oil, the method comprising the steps of:

adding alumina in particulate form to waste plastics containing silicone to form a mixture;

feeding the mixture to a pyrolysis reactor;

Pyrolyzing the mixture in the reactor;

The solid residue comprises the alumina reacted with silicon.

2. The method of claim 1, wherein the alumina 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 of claim 1 or 2, wherein the adding alumina to form the mixture is performed at a temperature in the range of 50 ℃ to 280 ℃, preferably in the range of 60 ℃ to 270 ℃, 80 ℃ to 260 ℃, 100 ℃ to 250 ℃, 110 ℃ to 250 ℃, 120 ℃ to 250 ℃, 130 ℃ to 240 ℃, 140 ℃ to 230 ℃, or 150 ℃ to 220 ℃.

4. The method of any of the preceding claims, wherein the adding alumina to form a mixture comprises melting the waste plastic.

5. A method according to any one of the preceding claims, wherein the adding of alumina to form a mixture is performed in an extruder, preferably a melt extruder.

6. The method of any of the preceding claims, wherein the alumina has an open cell structure.

7. The method according to any of the preceding claims, wherein the BET specific surface area of the alumina is in the range of 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, such as in the range of 100 to 300 m ²/g or in the range of 150 to 300 m ²/g.

8. The method of any of the preceding claims, wherein the pyrolyzing is performed in two or more steps.

9. The method of 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 process according to any one of the preceding claims, wherein a group II metal oxide or group II metal hydroxide (group II metal oxide/hydroxide), wherein the group II metal is preferably magnesium or calcium, is added in the step of adding alumina to form a mixture and/or directly into the pyrolysis reactor.

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

12. The process according to claim 10 or 11, wherein the group II metal oxide/hydroxide is added in an amount 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 of any of the preceding claims, further comprising heating the silicone-containing waste plastic and/or the mixture to an elevated temperature and devolatilizing at least a portion of the silicone compound contained therein prior to feeding the mixture to the pyrolysis reactor, wherein the heating is performed at a temperature in the range of 175 ℃ to 280 ℃, such as 180 ℃ to 270 ℃, 185 ℃ to 265 ℃, 190 ℃ to 260 ℃, 200 ℃ to 255 ℃, or 210 ℃ to 250 ℃.

14. A method according to any one of the preceding claims, wherein the alumina is an acidic alumina, preferably an active acidic alumina.

15. Use of alumina in particulate form for reducing the organosilicon content in situ during pyrolysis of waste plastics.