Process for treating pyrolysis oil

Abstract

A method of maintaining the stability of a pyrolysis oil: removing oxygen from the pyrolysis oil, and / or preventing or reducing the condition in which oxygen is in contact with the pyrolysis oil. The method includes removing oxygen from the pyrolysis oil by a physical process.

Description

[0001] Related Applications Cross-Referenced

[0002] This application claims the priority benefit of European Patent Application No. 22216309.9, filed on December 23, 2022, the entire content of which is incorporated herein by reference. Technical Field

[0003] The present invention generally relates to the treatment of pyrolysis oil. More specifically, the present invention relates to maintaining the stability and quality of pyrolysis oil by reducing the amount of oxygen in contact with the pyrolysis oil. Background Art

[0004] The chemical recycling of mixed plastic waste has emerged as an important alternative feedstock for the production of olefins and aromatics. However, pyrolysis oil is very unstable and it quickly forms gum during transportation or storage. It has been found that typical antioxidants (which are considered effective in stabilizing pyrolysis oil) are not very effective. As a result of the instability of pyrolysis oil and the lack of effective antioxidants to maintain its stability, the longer pyrolysis oil is stored, the lower its quality as a feedstock. Summary of the Invention

[0005] The instability of pyrolysis oil is at least partially due to the compounds in pyrolysis oil being prone to react with each other or with other materials. For example, oxygen or nitrogen compounds present in pyrolysis oil from the chemical recycling process and / or oxygen or nitrogen compounds in contact with pyrolysis oil during storage and / or transportation can cause chemical reactions to form other compounds, and thereby reduce the quality of pyrolysis oil as a feedstock. The inventors of the present invention have discovered a method for maintaining the stability of pyrolysis oil by removing oxygen from pyrolysis oil and / or preventing or reducing the contact of oxygen with pyrolysis oil.

[0006] Embodiments of the present invention include a method for maintaining the stability and / or improving the quality of pyrolysis oil. The method includes removing oxygen from pyrolysis oil by a physical process. In this method, the physical process can involve passing an inert gas over the pyrolysis oil to remove oxygen from the pyrolysis oil or placing the pyrolysis oil under vacuum.

[0007] Embodiments of the present invention include a method for maintaining the stability and / or quality of pyrolysis oil. The method includes providing a tank for storing pyrolysis oil. The method further includes removing oxygen from the tank. Still further, the method includes flowing pyrolysis oil into the tank and storing the pyrolysis oil in the tank.

[0008] Embodiments of the present invention include a method for maintaining the stability and / or quality of pyrolysis oil. The method includes storing pyrolysis oil in a tank and removing oxygen from the headspace of the tank.

[0009] The following includes definitions of different terms and phrases used throughout this specification.

[0010] As understood by those skilled in the art, the term "about" or "approximately" is defined as being close to. In a non-limiting embodiment, the term is defined as being within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0011] In the present invention, "X, Y, and / or Z" can be interpreted as only X, only Y, only Z, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, XZ, YZ).

[0012] The terms "wt%", "vol%", or "mol%" refer to the weight, volume, or mole percentage of a component, respectively, based on the total weight, total volume, or total moles of the material containing the component. In a non-limiting example, 10 moles of a component in 100 moles of material is 10 mol% of that component.

[0013] The term "substantially" and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0014] When used in the claims and / or the specification, the terms "inhibit" or "reduce" or "prevent" or "avoid" or any variations of these terms include any measurable reduction or complete inhibition to achieve the desired result.

[0015] As used in the specification and / or claims, "effective" means sufficient to achieve the desired, intended, or targeted result.

[0016] When used in the claims or the specification in conjunction with the terms "comprising", "including", "containing", or "having", the wording "a" or "an" can mean "one", but it is also consistent with the meanings of "one or more", "at least one", and "one or more than one".

[0017] The wording "comprising", "having", "including", or "containing" is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.

[0018] The methods of the present invention can "comprise / include" the specific ingredients, components, compositions, etc. disclosed throughout the specification, "consist essentially of", or "consist of".

[0019] As used in the specification and / or claims, the term "substantial" means greater than any one of 50 wt%, 50 mol%, and 50 vol%. For example, "substantial" can include 50.1 wt% - 100 wt% and all values and ranges therebetween, 50.1 mol% - 100 mol% and all values and ranges therebetween, or 50.1 vol% - 100 vol% and all values and ranges therebetween.

[0020] Other objects, features, and advantages of the present invention will become apparent from the following drawings, detailed description, and examples. However, it should be understood that the drawings, detailed description, and examples, although indicating specific embodiments of the present invention, are given by way of illustration only and are not meant to be limiting. Additionally, it will be appreciated that changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any other embodiment. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0022] Figure 1A and Figure 1B shows a system for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention;

[0023] Figure 2 shows a method for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention;

[0024] Figure 3 shows a method for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention;

[0025] Figure 4 shows a method for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention;

[0026] Figure 5A 、 Figure 5B and Figure 5C shows the results of experiments for showing how certain factors affect gum formation; and

[0027] Figure 6 shows the results of experiments for showing how certain factors affect the formation of gum. DETAILED DESCRIPTION

[0028] After pyrolysis oil is formed by chemical recycling of mixed plastic waste, the pyrolysis oil is prone to deterioration due to the presence of oxygen in the pyrolysis oil or contact of oxygen with the pyrolysis oil. Oxygen reacts with specific components of the pyrolysis oil to form gums. The gums reduce the quality of the pyrolysis oil and cause product loss due to significant deposition during transportation or storage of the pyrolysis oil. Accordingly, embodiments of the present invention relate to purging the pyrolysis oil vapor phase or bulk with nitrogen or any other inert gas to remove oxygen from the pyrolysis oil itself and / or from tanks storing or intended to store the pyrolysis oil.

[0029] Figure 1A System 10A for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention is shown. Figure 1B System 10B for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention is shown. Figure 2 Method 20 for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention is shown. Figure 3 Method 30 for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention is shown. Figure 4 Method 40 for maintaining the stability and / or quality of pyrolysis oil according to an embodiment of the present invention is shown. In an embodiment of the present invention, method 20 can be implemented by system 10A. In an embodiment of the present invention, method 30 can be implemented by system 10B. In an embodiment of the present invention, method 40 can be implemented by system 10B.

[0030] System for maintaining the stability and / or quality of pyrolysis oil

[0031] According to an embodiment of the present invention, system 10A includes tank 101, which is adapted to store pyrolysis oil 100. In an embodiment of the present invention, system 10A includes compressor 103 for flowing inert gas 102 through tank 101 and thus through pyrolysis oil 100 (when stored in tank 101), wherein inert gas 102 and oxygen leave tank 101 as effluent 104.

[0032] According to an embodiment of the present invention, system 10B includes a tank 101 adapted to store pyrolysis oil 100. In an embodiment of the present invention, system 10B includes a compressor 106 for removing gas (such as air and / or oxygen) from the tank 101 or the headspace 105 of the tank 101. According to an embodiment of the present invention, in the absence of any or a large amount of oxygen in the tank 101 or the headspace 105, the pyrolysis oil 100 can be stored in the tank 101 away from oxygen or with minimal contact with oxygen. In an embodiment of the present invention, system 10B includes a pump 107 for pumping the pyrolysis oil 100 into the tank 101. According to an embodiment of the present invention, system 10B includes a compressor 103 for flowing an inert gas 102 through the tank 101 and thus through the pyrolysis oil 100 (when stored in the tank 101), wherein the inert gas 102 and oxygen leave the tank 101 as an effluent 104 or are removed by the compressor 106.

[0033] Method for maintaining pyrolysis oil stability and / or quality

[0034] According to an embodiment of the present invention, method 20 implemented using system 10A includes, at block 200, storing pyrolysis oil 100 in a tank 101. In an embodiment of the present invention, block 201 of method 20 includes flowing an inert gas 102 through the pyrolysis oil 100 under compression by a compressor 103 (as Figure 1A shown) to remove oxygen from the pyrolysis oil 100. According to an embodiment of the present invention, the removal of oxygen is carried out by a physical process that takes effect by flowing the inert gas 102 through the pyrolysis oil 100. In an embodiment of the present invention, the inert gas 102 comprises any one of the following: nitrogen, helium, argon, neon, carbon dioxide, and any combination thereof. According to an embodiment of the present invention, when the inert gas 102 flows through the pyrolysis oil 100, the temperature of the pyrolysis oil 100 is at a temperature of 20°C - 70°C, including 20 - 25°C, 25 - 30°C, 30 - 35°C, 35 - 40°C, 40 - 45°C, 45 - 50°C, 50 - 55°C, 55 - 60°C, 60 - 65°C, and 65 - 70°C. According to an embodiment of the present invention, method 20 includes block 202, which involves allowing the effluent 104 (containing oxygen and an inert gas (such as nitrogen)) to flow out of the tank 101.

[0035] According to an embodiment of the present invention, method 30 implemented using system 10B includes, at block 300, providing a tank 101 for storing pyrolysis oil. In an embodiment of the present invention, block 301 of method 30 includes removing from the tank 101 (as Figure 1BRemove gas (such as air and / or oxygen) from the one shown in the figure. According to an embodiment of the present invention, at block 301, removing gas (such as air and / or oxygen) may involve extracting gas (or at least some of it) with compressor 106 and / or flowing inert gas 102 into tank 101. According to an embodiment of the present invention, at block 302, pump 107 pumps pyrolysis oil 100 into tank 101 to occupy all or some of the space in tank 101, thereby forming a headspace 105. In the case where pyrolysis oil 100 occupies all or most of tank 101 and / or the inert gas mainly or completely occupies headspace 105, the amount of oxygen in contact with the pyrolysis oil is minimal (or there is no oxygen), so oxygen is not sufficient to destabilize pyrolysis oil 100 and deteriorate its quality. According to an embodiment of the present invention, as a result of method 30, the oxygen concentration in tank 101 is reduced to 0.01% - 1%.

[0036] In an embodiment of the present invention, before or after implementing method 30 to remove oxygen from tank 101, method 20 may be implemented to remove oxygen from pyrolysis oil 100.

[0037] According to an embodiment of the present invention, method 40 implemented using system 10B includes, at block 400, storing pyrolysis oil 100 in tank 101. Block 401 of method 40 includes compressor 106 removing gas (such as air and / or oxygen) from the headspace 105 of tank 101. In the case where there is no or a significant amount of oxygen in headspace 105, pyrolysis oil 100 is not prone to instability and quality deterioration.

[0038] In an embodiment of the present invention, before or after implementing method 40 to remove oxygen from the headspace 105 of tank 101, method 20 may be implemented to remove oxygen from pyrolysis oil 100.

[0039] Although embodiments of the present invention have been described with reference to the blocks of Figure 2 、 Figure 3 and Figure 4 , it should be understood that the operation of the present invention is not limited to the specific blocks shown in Figure 2 、 Figure 3 and Figure 4 and / or the specific order of the blocks. Therefore, embodiments of the present invention may use various blocks in an order different from that of Figure 2 、 Figure 3 and Figure 4 to provide the functions described herein.

[0040] The systems and methods described herein may also include different devices not shown that are known to those skilled in the art of chemical processing. For example, some controllers, pipes, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, etc. may not be shown.

[0041] As part of the disclosure of the present invention, specific embodiments are included below. The embodiments are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art will readily recognize that parameters can be changed or modified to produce substantially the same results.

[0042] Embodiment

[0043] Aging study of pyrolysis oil samples

[0044] Six liters of pyrolysis oil samples were collected in bottles pre-filled with nitrogen. Some samples were purged with nitrogen.

[0045] Density

[0046] The density of the samples was measured at time 0 (i.e., after sample preparation was completed). The data shown in Table 1 indicate that the purging step increased the density of the pyrolysis oil. This is because volatile components were to some extent stripped from the samples during purging.

[0047] Table 1: Densities of pure and purged samples

[0048] Measurement 1 Measurement 2 Measurement 3 Average Standard Deviation Density of pure sample at 0 day [g / ml] 0.79057 0.79063 0.79061 0.79060 0.00003 Density of purged sample at 0 day [g / ml] 0.79220 0.79208 0.79215 0.79214 0.00006

[0049] Gum kinetics formation

[0050] Sixteen vials were prepared to track gum kinetics formation. Eight vials were purged with nitrogen, and another eight vials were not purged. The goal was to measure the amount of gum formed after 10, 20, and 60 days. The pure samples were poured from the received Schott bottles into the vials without treatment. The purged samples were purged with nitrogen for 5 minutes. Then the vials were sealed and parafilm was used. At each data point time, the supernatant of the vials was emptied. The vials were placed in a fume hood to dry overnight. The next day, 10 mL of tetrahydrofuran (THF) was added to the vials to dissolve the gum formed during aging. Then the THF was poured into a pre-weighed alumina dish. The THF was evaporated overnight in a fume hood. Finally, the dish was placed in a vacuum oven at 40 °C to completely remove the volatiles. Then the amount of gum formed during aging under each condition was defined by weighing the dried alumina dish.

[0051] Then the weight of the gum was fitted in JMP (statistical software) to study the effects of the following factors: glass type (amber, clear), aging time (8, 15, 26, and 48 days), treatment type (pure and purged).

[0052] Figure 5A 、 Figure 5B and Figure 5C showed that aging time and treatment had a significant effect on the amount of gum formed (P < 0.05).

[0053] Figure 6 It shows that the amount of gum increases with the increase of aging time, and the amount of gum in the pure sample is higher. The factor "glass type" is marginally significant, and the p-value is 0.052.

[0054] Based on this specific aging study, it can be concluded that when the sample is not purged with nitrogen, it is favorable for gum formation. Light also seems to increase the rate of gum formation.

[0055] In the context of the present invention, at least the following 14 embodiments are described. Embodiment 1 is a method for maintaining the stability and / or quality of pyrolysis oil. The method includes removing oxygen from the pyrolysis oil by a physical process. Embodiment 2 is the method of Embodiment 1, wherein the physical process includes passing an inert gas over the pyrolysis oil. Embodiment 3 is the method of Embodiment 2, wherein the inert gas comprises: nitrogen, helium, argon, neon, carbon dioxide, or a combination thereof. Embodiment 4 is the method of any one of Embodiments 1-4, wherein the temperature of the pyrolysis oil is 20°C - 70°C.

[0056] Embodiment 5 is a method for maintaining the stability and / or quality of pyrolysis oil. The method includes providing a tank for storing the pyrolysis oil. The method further includes removing oxygen from the tank. The method also further includes flowing the pyrolysis oil into the tank and storing the pyrolysis oil in the tank. Embodiment 6 is the method of Embodiment 5, wherein removing oxygen from the tank includes displacing with an inert gas and / or pumping with a compressor. Embodiment 7 is the method of any one of Embodiments 5 or 6, wherein the oxygen concentration in the tank is reduced to 0.01% - 1%. Embodiment 8 is the method of any one of Embodiments 5-7, which further includes passing an inert gas over the pyrolysis oil to remove oxygen from the pyrolysis oil. Embodiment 9 is the method of Embodiment 8, wherein the inert gas comprises: nitrogen, helium, argon, neon, carbon dioxide, or a combination thereof. Embodiment 10 is the method of any one of Embodiments 8 or 9, wherein the temperature of the pyrolysis oil is 20°C - 70°C.

[0057] Embodiment 11 is a method for maintaining the stability and / or quality of pyrolysis oil. The method includes storing the pyrolysis oil in a tank. The method further includes removing oxygen from the headspace of the tank. Embodiment 12 is the method of Embodiment 11, wherein removing oxygen from the headspace of the tank includes pumping with a compressor. Embodiment 13 is the method of any one of Embodiments 11 or 12, wherein the oxygen concentration in the tank is reduced to 0.01% - 1%. Embodiment 14 is the method of any one of Embodiments 11-13, which further includes passing an inert gas over the pyrolysis oil to remove oxygen from the pyrolysis oil.

[0058] The systems and methods described herein may also include various devices not shown that are known to those skilled in the art of chemical processing. For example, some controllers, pipes, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, etc. may not be shown. Unless explicitly excluded, all of the embodiments described above and herein may be combined in any manner.

[0059] Although the embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the embodiments defined by the appended claims. In addition, the scope of the present application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, devices, methods, and steps described in the specification. As will be readily understood by those skilled in the art from the foregoing disclosure, such processes, machines, manufactures, compositions of matter, devices, methods, or steps, whether currently existing or developed in the future, that perform substantially the same function or achieve substantially the same result as the corresponding technical solutions described herein can be used. Accordingly, the appended claims are intended to cover such processes, machines, manufactures, compositions of matter, devices, methods, or steps within their scope.

Claims

1. A method for maintaining the stability and / or quality of pyrolysis oil, the method comprising: Removing oxygen from the pyrolysis oil by a physical process.

2. The method according to claim 1, wherein the physical process comprises: Passing an inert gas through the pyrolysis oil.

3. The method according to claim 2, wherein the inert gas comprises: nitrogen, helium, argon, neon, carbon dioxide, or a combination thereof.

4. The method according to any one of claims 1-3, wherein the temperature of the pyrolysis oil is 20°C - 70°C.

5. A method for maintaining the stability and / or quality of pyrolysis oil, the method comprising: Providing a tank for storing pyrolysis oil; Removing oxygen from the tank; Flowing the pyrolysis oil into the tank; and Storing the pyrolysis oil in the tank.

6. The method according to claim 5, wherein removing oxygen from the tank comprises displacing with an inert gas and / or pumping with a compressor.

7. The method according to any one of claims 5-6, wherein the oxygen concentration in the tank is reduced to 0.01% - 1%.

8. The method according to any one of claims 5-7, further comprising: Passing an inert gas through the pyrolysis oil to remove oxygen from the pyrolysis oil.

9. The method according to claim 8, wherein the inert gas comprises: nitrogen, helium, argon, neon, carbon dioxide, or a combination thereof.

10. The method according to any one of claims 8-9, wherein the temperature of the pyrolysis oil is 20°C - 70°C.

11. A method for maintaining the stability and / or quality of pyrolysis oil, the method comprising: Storing the pyrolysis oil in a tank; and Removing oxygen from the headspace of the tank.

12. The method according to claim 11, wherein removing oxygen from the headspace of the tank comprises pumping with a compressor.

13. The method according to any one of claims 11-12, wherein the oxygen concentration in the tank is reduced to 0.01% - 1%.

14. The method according to any one of claims 11-13, further comprising: Passing an inert gas through the pyrolysis oil to remove oxygen from the pyrolysis oil.

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