METHOD FOR PROCESSING LIQUEFIED WASTE POLYMERS

Abstract

The present disclosure relates to methods for processing liquefied waste polymers (LWP) containing diolefins. The LWP feed is supplied to steam stripper A to provide a distillate containing diolefins and naphtha, and a distillate bottom. The distillate is subjected to hydrotreatment B to produce a diolefin depleted distillate which is separated by distillation C to give rise to one or more fractions comprising at least a naphtha fraction, an optional middle fraction and a bottom fraction. Hydroprocessing D of the naphtha fraction gives rise to hydrogenated naphtha which is suitable as a feed for a steam cracker E. Since the distillation bottom, bottom fraction and the middle distillate are predominantly free from diolefins, they can be mixed with crude oil and processed further in oil refinery.

Claims

1.-19. (canceled)

20. A method for processing liquefied waste plastic (LWP), the method comprising the following steps: a) providing an LWP stream containing diolefins and naphtha; b) subjecting the LWP stream to a steam stripper to obtain a distillate containing diolefins and naphtha, and a distillate bottom; c) subjecting the distillate to hydrotreatment reaction conditions in a presence of hydrogen and one or more hydrotreatment catalysts to produce diolefin depleted distillate, wherein the hydrotreatment reaction conditions include temperature 120-210° C., pressure 1-50 barg, and LHSV 1-5 h-1, an/or 4-4.5 h-1, and the one or more hydrotreatment catalysts are selected from CoMo and NiMo; and d) separating the diolefin depleted distillate to, one or more fractions including: at least a naphtha fraction with a boiling Point below 180° C. at atmospheric pressure, an optional middle fraction with a boiling Point between 180° C. and 360° C. at atmospheric pressure; and a bottom fraction.

21. The method according to claim 20, comprising: e) subjecting the naphtha fraction of step d) to hydroprocessing reaction conditions in a presence of hydrogen and one or more hydroprocessing catalysts to produce hydrogenated naphtha.

22. The method according to claim 21, wherein the hydroprocessing reaction conditions of step e) comprise: temperature 280-350° C. and pressure 20-100 barg, and/or 20-50 barg.

23. The method according to claim 22, wherein the hydrotreatment reaction conditions comprise; LHSV 1-5 h.sup.−1, and hydrogen/hydrocarbon ratio 100-900 Nm.sup.3/m.sup.3.

24. The method according to claim 21, wherein the one or more hydroprocessing catalysts are selected from CoMo and NiMo.

25. The method according to claim 21, comprising: feeding the hydrogenated naphtha to a steam cracker.

26. The method according to claim 20, comprising: admixing the bottom fraction of step d) and crude oil to form an admixture.

27. The method according to claim 26, comprising: feeding the admixture to a crude oil distillation unit.

28. The method according to claim 20, wherein the one or more fractions of step d) comprise a middle fraction with a boiling Point between 180° C. and 360° C. at atmospheric pressure.

29. The method according to claim 28, comprising: feeding the middle fraction to a crude oil distillation unit.

30. The method according to claim 20, wherein the LWP is selected from waste plastic pyrolysis oil and hydrothermally liquefied waste plastic oil or mixtures thereof.

31. The method according to claim 20, wherein the LWP comprises: waste plastic pyrolysis oil.

32. The method according to claim 21, comprising: feeding the hydrogenated naphtha to a steam cracker.

33. The method according to claim 20, comprising: feeding a mixture of crude oil and the bottom fraction of step d) to an oil refinery feed.

34. The method according to claim 20, comprising: feeding a mixture of crude oil and the middle fraction of step d) to an oil refinery.

35. The method according to claim 20, comprising: feeding a mixture of crude oil and distillation bottom of step b) to an oil refinery.

Description

BRIEF DESCRIPTION OF FIGURES

[0033] The exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below with reference to the accompanying figure, which shows an exemplary non-limiting flow chart for processing liquefied waste polymers 10 comprising diolefins.

DESCRIPTION

[0034] The present invention concerns a method for processing liquefied waste polymers (LWP) such as waste plastic pyrolysis oil. The principle of the method is shown in FIG. 1. Accordingly, an LWP stream 10 comprising diolefins is fed to a stream stripper vessel A wherein a distillate 20 and a distillate bottom 30 are separated. The distillate comprises diolefins and naphtha while the metallic impurities remain predominantly in the distillate bottom. The distillate is fed to a hydrotreatment unit B to produce diolefin depleted distillate 40. When the hydrotreatment reaction is performed in mild, preferably in liquid phase conditions, in the presence of hydrogen and one or more hydrotreatment catalysts known in the art, predominantly only the diolefins present in the LWP are reduced. Exemplary hydrotreatment reaction conditions for selective reduction of diolefins comprise temperature 120-210° C. and pressure 1-50 barg. An exemplary pressure is 28.5 barg. Liquid hourly space velocity (LHSV) is typically 1-5 h.sup.−1, preferably 4-4.5 h.sup.−1. An exemplary hydrogen/hydrocarbon ratio is 15 N m.sup.3/m.sup.3. Exemplary hydrotreatment catalysts include NiMo and CoMo, preferably on a support. An exemplary hydrotreatment catalyst is NiMo/Al.sub.2O.sub.3. Another exemplary hydrotreatment catalyst is CoMo/Al.sub.2O.sub.3.

[0035] The diolefin depleted distillate comprising naphtha is fed to a separation unit such as a distillation unit C, wherein one or more fractions comprising at least a naphtha fraction 50 boiling below 180° C. at atmospheric pressure and bottom fraction 70 are separated. According to one embodiment the distillation produces a naphtha fraction 50 boiling below 180° C. at atmospheric pressure and a bottom fraction 70 comprising material boiling above 180° C. at atmospheric pressure.

[0036] According another embodiment the distillation produces a naphtha fraction 50 boiling below 180° C. at atmospheric pressure, and a middle distillate 60 boiling between 180° C. and 360° C. at atmospheric pressure. According to this embodiment the bottom fraction 70 comprises material boiling above 360° C. at atmospheric pressure.

[0037] According to one embodiment the distillation is performed at atmospheric pressure. According to another embodiment the distillation is performed at reduced pressure. According to still another embodiment the distillation is performed at excess pressure.

[0038] According to a preferable embodiment the naphtha fraction 50 is fed to a hydroprocessing unit D. The hydroprocessing is performed preferably with NiMo- and CoMo-type catalysts which remove remaining heteroatoms such as chlorine, oxygen, sulphur, and nitrogen in the naphtha fraction and simultaneously carries out hydrogenation of olefins and aromatics present therein. The hydroprocessing of naphtha is performed typically in gas phase in elevated temperature and pressure in the presence of hydrogen. Exemplary hydroprocessing reaction conditions comprise temperature 280-350° C. and pressure 20-100 barg preferably 20-50 barg. LHSV is typically 1-5 h.sup.−1, and hydrogen/hydrocarbon ratio 100-900 Nm.sup.3/m.sup.3 such as 360 Nm.sup.3/m.sup.3. Exemplary non-limiting hydroprocessing catalysts are CoMo/Al.sub.2O.sub.3 and NiMo/Al.sub.2O.sub.3. The product is a hydrogenated naphtha fraction 80.

[0039] It is known that steam crackers have specifications for olefinic, aromatic and heteroatom content of the feed. Accordingly, the hydrogenated naphtha fraction 80 is suitable as a feed of steam cracker E.

[0040] LWPs can be co-processed with crude oil in an oil refinery. However, as the products from crude oil distillation units are typically directed to units that are not designed for olefinic feeds, the absence of olefinic components, and in particular diolefins, would be beneficial. The aforementioned limitation is particularly relevant in the context of naphtha hydroprocessing units which are designed for the processing of straight run naphtha. Such units typically operate in gas phase, and the overall exotherm, i.e., temperature increase which occurs inside the reactor due to heat released by the chemical reactions, is limited. Adding an olefinic feed to such a reactor can result in a substantial increase in the overall exotherm, which may in turn shorten the lifetime of the hydroprocessing catalyst. Thus, removing the naphtha fraction from LWP prior to co-processing at the refinery is beneficial also from the refinery perspective. Co-processing of the heavier LWP fractions at the refinery is less problematic compared to the naphtha fraction, as hydroprocessing units which designed for middle distillates and e.g., heavy gas oil or vacuum gas oil are otherwise also used for processing thermally cracked feeds from e.g., visbreaking or delayed coking units.

[0041] According to a particular embodiment the bottom fraction 70 is admixed with crude oil 90 e.g., in a mixing unit F to form an admixture 100 which is then fed to a crude oil distillation unit G wherein the admixture is separated to one or more distilled streams 110, 120.

[0042] According to another embodiment the middle fraction 60 is admixed with crude oil 90 e.g., in a mixing unit H to form an admixture which is then fed to a crude oil distillation unit I wherein the admixture is separated to one or more distilled streams 140, 150.

[0043] According to another embodiment the distillation bottom 30 is admixed with crude oil 90 e.g., in a mixing unit J to form an admixture 160 which is then fed to a crude oil distillation unit H wherein the admixture is separated to one or more distilled streams 170, 180.

[0044] According to another embodiment the present invention concerns use of hydrogenated naphtha produced from LWP comprising diolefins as a steam cracker feed. The steam cracker feed is produced by a method comprising the following steps: [0045] a) providing an LWP stream comprising diolefins and naphtha, [0046] b) subjecting the LWP stream to a steam stripper to obtain a distillate comprising diolefins and naphtha, and a distillate bottom, [0047] c) subjecting the distillate to hydrotreatment reaction conditions in the presence of hydrogen and one or more hydrotreatment catalysts to produce diolefin depleted distillate and [0048] d) separating the diolefin depleted distillate to [0049] one or fractions comprising at least a naphtha fraction boiling below 180° C. at atmospheric pressure, and optional middle fraction boiling between 180° C. and 360° C. at atmospheric pressure and [0050] bottom fraction, and [0051] e) subjecting the naphtha fraction to hydroprocessing reaction conditions in the presence of hydrogen and one or more hydroprocessing catalysts.

[0052] The method of the present invention is suitable for processing different type of liquefied waste polymers and their mixtures such as waste plastic pyrolysis oils (WPPO) and hydrothermally liquefied waste plastic oils. According to one embodiment the liquefied waste polymers comprises WPPO. According to another embodiment the liquefied waste polymers comprises hydrothermally liquefied waste plastic oils.

[0053] The use of a steam stripper in the method of processing LWPs has the following advantages [0054] fouling caused by the diolefins in the column is reduced. [0055] the steam stripping accumulates the majority of metals present in the LWP to the distillation bottom, thus creating a low metal content in the naphtha. This in turn, protects the diolefin removal catalyst and prolong its lifetime. [0056] Since the distillate bottom of step b) as well as the bottom fraction and the optional middle fraction of step d) are predominantly free from diolefins, they can be mixed with crude oil and used as feeds in oil refinery.

[0057] The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims.