Method and apparatus for refining waste plastic pyrolysis oil

Abstract

The present disclosure provides a method for refining waste plastic pyrolysis oil, comprising: a first step of mixing a desalted solution containing a polar aprotic solvent and water with waste plastic pyrolysis oil to form a mixed oil; a second step of allowing the mixed oil from the first step to stand and separating the lower desalted solution to obtain a pretreated waste plastic pyrolysis oil; a third step of hydrotreating the pretreated waste plastic pyrolysis oil from the second step at a first temperature under a hydrotreating catalyst to perform a dechlorination reaction; and a fourth step of hydrotreating the product of the third step at a second temperature under a hydrotreating catalyst to perform a denitrification reaction.

Description

[Technical field]

[0001] The present disclosure relates to a method and an apparatus for refining waste plastic pyrolysis oil. [Background technology]

[0002] Waste plastics are manufactured using petroleum as a raw material, and have a low recycling rate, so most of them are disposed of as garbage. Such waste takes a long time to decompose in natural conditions, so it pollutes the soil and causes serious environmental pollution. One method for recycling waste plastics is to pyrolyze them and convert them into usable fractions, which are called waste plastic pyrolysis oil.

[0003] However, pyrolysis oil obtained by pyrolyzing waste plastics contains higher amounts of impurities such as chlorine, nitrogen, and metals than fractions produced from crude oil using conventional methods. As a result, it cannot be immediately used as a high-value-added fuel such as gasoline or diesel oil, and must go through a refinery process.

[0004] Conventionally, a refinery process has been carried out by hydrogenating waste plastic pyrolysis oil in the presence of a hydrogenation catalyst to remove chlorine, nitrogen and other metal impurities. However, due to the characteristics of waste plastic pyrolysis oil containing high impurities, hydrogenation must be carried out under excessive conditions, and in particular, when hydrogenation is carried out at 450°C or higher, problems such as catalyst inactivation and a decrease in reaction yield due to the occurrence of side reactions such as cracking are encountered. In addition, the high content of chlorine impurities contained in the waste plastic pyrolysis oil produces an excessive amount of HCl, which causes problems such as equipment corrosion, reaction abnormalities and deterioration of product properties. In particular, the HCl reacts with nitrogen compounds to produce ammonium salts (NH4Cl), which not only corrodes the reactor and reduces its durability, but also causes various process problems such as the generation of differential pressure and a decrease in process efficiency.

[0005] In order to reduce the chlorine content in the pyrolysis oil to a level that can be introduced into the refinery process, pretreatment such as a washing process or a water treatment process is carried out, but this has the limitation that it only mainly removes inorganic chlorine from the pyrolysis oil and does not remove organic chlorine. As an example of another pretreatment process, a process is carried out in which impurities such as chlorine, nitrogen, and sulfur are removed through a neutralization process using base substances such as KOH and NaOH, but this neutralization removal process induces corrosion of equipment, causing problems such as reaction abnormalities and reduced process efficiency, and has the limitation that it is difficult to reduce the chlorine content to a level that can be introduced into the refinery process because the chlorine removal efficiency is not high.

[0006] Therefore, there is a need for a method and apparatus for refining waste plastic pyrolysis oil, which can minimize problems such as generation of differential pressure, equipment corrosion, reaction abnormalities, and deterioration of product properties in the refinery process of waste plastic pyrolysis oil containing a high chlorine content. Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure aims to provide a method and apparatus for refining waste plastic pyrolysis oil that can stably perform the refining process for a long period of time by minimizing the production of ammonium salts (NH4Cl) in the refining process through coordination of the pretreatment process and hydrotreatment process of the waste plastic pyrolysis oil.

[0008] Another object of the present disclosure is to provide a refining method and apparatus capable of obtaining waste plastic pyrolysis oil from waste plastic pyrolysis oil in a high yield with very low impurity contents such as chlorine, nitrogen, metals, and the like, and very low olefin contents, without any change in molecular weight distribution. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present disclosure provides a method for refining waste plastic pyrolysis oil, comprising: a first step of mixing a desalted solution containing a polar aprotic solvent and water with waste plastic pyrolysis oil to form a mixed oil; a second step of allowing the mixed oil of the first step to stand and separating the lower desalted solution to obtain a pretreated waste plastic pyrolysis oil; a third step of hydrotreating the pretreated waste plastic pyrolysis oil of the second step at a first temperature under a hydrotreating catalyst to perform a dechlorination reaction; and a fourth step of hydrotreating the product of the third step at a second temperature under a hydrotreating catalyst to perform a denitrification reaction.

[0010] In one embodiment, the first step may involve stirring the desalted solution and the waste plastic pyrolysis oil at a temperature of 60 to 300°C.

[0011] In one embodiment, the polar aprotic solvent can have a dielectric constant of 20 or greater and a density of 0.9 g / cc or greater.

[0012] In one embodiment, the polar aprotic solvent can include dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

[0013] In one embodiment, the density difference between the desalted solution and the waste plastic pyrolysis oil may be 0.3 g / cc or more.

[0014] In one embodiment, the desalted solution may be contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the waste plastic pyrolysis oil.

[0015] In one embodiment, the weight ratio of the polar aprotic solvent and water can be from 50:50 to 95:5.

[0016] In one embodiment, the method may further comprise a fifth step of separating the polar aprotic solvent from the desalted solution recovered in the second step and re-supplying it to the first step.

[0017] In one embodiment, the fifth step can include a fifth step of distilling the desalted solution to separate water and recover a residual solution, a fifth step of filtering the residual solution to separate chlorine-containing salts from the residual solution and recover a polar aprotic solvent, and a fifth step of resupplying the recovered polar aprotic solvent to the polar aprotic solvent of the first step.

[0018] In one embodiment, the first temperature may be from 100 to 300°C, and the second temperature may be from 300 to 450°C.

[0019] In one embodiment, the hydrotreating catalyst in the third and fourth steps may be a catalyst in which an active metal including any one or more selected from molybdenum, nickel, cobalt, and tungsten is supported on a support.

[0020] In one embodiment, during the third and fourth steps of hydrotreating, the reaction pressure may be less than 100 bar.

[0021] In one embodiment, during the hydrotreatment in the third and fourth steps, the ratio of liquid hourly space velocity (LHSV) may be 1:0.1 to 1:0.8.

[0022] In one embodiment, between the third step and the fourth step, a step of mixing the product of the third step with a desalting solution containing a polar aprotic solvent and water to perform a desalting process may be further included.

[0023] The present disclosure also provides a purification device for waste plastic pyrolysis oil, comprising a first reactor into which a desalted solution containing a polar aprotic solvent and water and waste plastic pyrolysis oil are flowed and a pretreatment process is carried out, a second reactor into which products and hydrogen gas from the first reactor are flowed and hydrotreated at a first temperature in the presence of a hydrotreatment catalyst and a dechlorination reaction is carried out, and a third reactor into which products and hydrogen gas from the second reactor are flowed and hydrotreated at a second temperature in the presence of a hydrotreatment catalyst and a denitrification reaction is carried out.

[0024] In one embodiment, the first reactor can be a batch reactor.

[0025] In one embodiment, the second and third reactors can be fixed bed reactors.

[0026] In one embodiment, the system includes a recovery tank for recovering the desalted solution discharged from the first reactor, the recovery tank including a distillation zone and a filtration zone, and may further include a recycle line for resupplying the polar aprotic solvent separated from the recovery tank to the first reactor. Effect of the Invention

[0027] The method and apparatus for refining waste plastic pyrolysis oil disclosed herein enables the refining process to be carried out stably for a long period of time by suppressing or minimizing the production of ammonium salts (NH4Cl) when linking the pretreatment process of waste plastic pyrolysis oil with the hydrotreatment process, which is the refinery process.

[0028] The method and apparatus for refining waste plastic pyrolysis oil disclosed herein can effectively reduce both organic chlorine and inorganic chlorine remaining in waste plastic pyrolysis oil at the same time.

[0029] The method and apparatus for refining waste plastic pyrolysis oil disclosed herein has the advantage of being able to stably carry out the refining process for a long period of time by suppressing or minimizing the production of ammonium salts (NH4Cl) by performing the hydrogenation treatment process in two stages at different temperatures.

[0030] The refining method and refining apparatus for waste plastic pyrolysis oil disclosed herein can provide waste plastic pyrolysis oil with very low impurity contents such as chlorine, nitrogen, metals, etc. and olefin contents, and in high yields without any change in molecular weight distribution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Unless otherwise defined, the technical and scientific terms used in this specification have the meanings that are commonly understood by those having ordinary knowledge in the technical field to which the present invention belongs, and in the following description and the attached drawings, descriptions of known functions and configurations that may obscure the gist of the present disclosure will be omitted.

[0032] As used herein, the singular forms of the terms "a," "an," and "the" can be construed as including the plural forms as well, unless otherwise indicated.

[0033] Numerical ranges used herein include lower and upper limits, all values ​​within the range, increments logically derived from the form and width of the ranges defined, all values ​​contained therein, and all possible combinations of upper and lower limits of numerical ranges defined in different forms from each other. Unless otherwise specified in the present specification, values ​​outside the numerical ranges that may occur due to experimental error or rounding of values ​​are also included in the defined numerical ranges.

[0034] As referred to in this specification, "comprising" is an open-ended term having the same meaning as terms such as "comprising," "containing," "having," "characterized," and the like, and does not exclude further unrecited elements, materials, or steps.

[0035] In this specification, the unit of % used without special mention means % by weight unless otherwise defined.

[0036] The ppm unit used in this specification without any special mention means ppm by mass unless otherwise defined.

[0037] Unless otherwise specified, the boiling point used in this specification means the boiling point at 1 atmosphere and 25°C.

[0038] Density as used herein, unless otherwise specified, means density at 1 atmosphere and 25°C.

[0039] Pyrolysis oil obtained by pyrolyzing waste plastics contains higher amounts of impurities such as chlorine, nitrogen, and metals than fractions produced from crude oil using conventional methods. As such, it cannot be immediately used as high-value-added fuels such as gasoline and diesel oil and must go through a refinery process.

[0040] In the refinery process, waste plastic pyrolysis oil is hydrotreated in the presence of a hydrogenation catalyst to convert chlorine into HCl and remove it, but waste plastic pyrolysis oil contains a high content of chlorine, and an excessive amount of HCl is generated during hydrotreatment, which causes problems such as equipment corrosion, reaction abnormalities, and deterioration of product properties. In addition, during the refinery process, the HCl reacts with nitrogen compounds to generate ammonium salts (NH4Cl), which not only corrodes the reactor and reduces its durability, but also causes various process problems such as the generation of differential pressure and reduced process efficiency.

[0041] Therefore, the present disclosure provides a method for refining waste plastic pyrolysis oil, comprising: a first step of mixing a desalted solution containing a polar aprotic solvent and water with waste plastic pyrolysis oil to form a mixed oil; a second step of allowing the mixed oil of the first step to stand and separating the lower desalted solution to obtain pretreated waste plastic pyrolysis oil; a third step of hydrotreating the pretreated waste plastic pyrolysis oil of the second step at a first temperature under a hydrotreating catalyst to perform a dechlorination reaction; and a fourth step of hydrotreating the product of the third step at a second temperature under a hydrotreating catalyst to perform a denitrification reaction.

[0042] The waste plastic pyrolysis oil pretreated with the polar aprotic solvent and the desalted solution containing water has a reduced content of organic chlorine and inorganic chlorine, and when the pretreated pyrolysis oil is introduced as a raw material for the hydrotreating process, which is a refinery process, the generation of ammonium salt (NH4Cl) during the hydrotreating process can be minimized to prevent clogging of the reactor, and the refining process can be stably performed for a long period of time. In addition, the hydrotreating process can be performed under milder conditions, which can prevent a decrease in reaction yield caused by performing hydrotreating under excessive conditions in the past, and can both minimize impurities in the waste plastic pyrolysis oil (refined oil) and improve the reaction yield. In addition, the refining method including the first to fourth steps is performed continuously, in which the impurity content of the waste plastic pyrolysis oil is primarily reduced in the first and second pretreatment steps, the third step of hydrogenation is performed at a first temperature to mainly remove chlorine, and the fourth step of hydrogenation is performed at a second temperature to mainly remove nitrogen. By removing chlorine and nitrogen in separate steps, the effect of inhibiting the generation of ammonium salts (NH4Cl) can be maximized, and high-quality waste plastic pyrolysis oil with chlorine and nitrogen minimized to a few ppm level can be obtained.

[0043] In particular, the waste plastic pyrolysis oil may be a mixture of hydrocarbon fractions produced by high-temperature pyrolysis of waste plastic, where the waste plastic may include solid or liquid wastes related to synthetic polymer compounds, such as waste synthetic resin, waste synthetic fiber, waste synthetic rubber, and waste vinyl.

[0044] The hydrocarbon fraction mixture present in the waste plastic pyrolysis oil may include H-naphtha (up to C8, bp<150°C):Kero (C9-C17, bp150-265°C), LGO (C18-C20, bp265-340°C) and VGO / AR (C21, bp>340°C) in a weight ratio of 10:90-40:60 or a weight ratio of 20:80-30:70, but this is presented as an example, and the composition of the waste plastic pyrolysis oil is not necessarily limited thereto, and may be present in various amounts within the range of 100% by weight of the above composition.

[0045] The waste plastic pyrolysis oil may contain various impurities in addition to the hydrocarbon fraction. For example, it may contain impurities such as chlorine compounds, nitrogen compounds, and metal compounds, and specifically, it may contain 300 ppm or more of nitrogen, 30 ppm or more of chlorine, 20 vol. % or more of olefins, and 1 vol. % or more of conjugated diolefins.

[0046] Among the impurities, with regard to chlorine compounds, the content of chlorine compounds in the waste plastic pyrolysis oil can be 100 ppm or more, specifically 300 ppm or more, and the upper limit of the content of the chlorine compounds is not particularly limited, but can be, for example, 1000 ppm or less, specifically 800 ppm or less.

[0047] The chlorine compound may include both organic chlorine and inorganic chlorine. The weight ratio of organic chlorine and inorganic chlorine contained in the chlorine compound may be 50:50 to 90:10, specifically 55:45 to 80:20, but this is merely an example and the weight ratio is not necessarily limited thereto, and may be in various ranges depending on the composition of the waste plastic.

[0048] The pretreatment process for reducing impurities in the waste plastic pyrolysis oil can be carried out by a first step of mixing the waste plastic pyrolysis oil with a desalted solution containing a polar aprotic solvent and water to form a mixed oil, and a second step of leaving the mixed oil of the first step to stand and separating the lower desalted solution to obtain a pretreated waste plastic pyrolysis oil. By using a co-solvent containing a polar aprotic solvent and water as the desalted solution, organic chlorine and inorganic chlorine can be removed simultaneously. In detail, the polar aprotic solvent can effectively capture organic chlorine because it is easy to stir and remove organic polar substances, and water can effectively capture inorganic chlorine because it has a high selectivity for inorganic chlorine such as HCl. By using the desalted solution, organic chlorine and inorganic chlorine can be effectively removed simultaneously in a single step process.

[0049] In one embodiment, the first step may involve stirring the desalted solution and the waste plastic pyrolysis oil at a temperature of 60 to 300°C. Since the waste plastic pyrolysis oil exists in a solid state at room temperature, the waste plastic pyrolysis oil and the desalted solution can be easily mixed in the above temperature range, and the chlorine compounds released from the waste plastic pyrolysis oil can be effectively prevented from recombining with olefins. The higher the temperature, the more improved the chlorine reduction activity can be, but considering the inactivation of the catalyst and the occurrence of side reactions such as cracking, it is preferable to carry out the stirring at a temperature of 300°C or less. Specifically, the temperature may be 60 to 270°C, more specifically, 80 to 250°C.

[0050] The stirring can be carried out under normal pressure conditions at a stirring speed of 50 to 5000 rpm for 2 to 6 hours. The stirring conditions can be appropriately changed to a level that allows easy mixing of the desalted solution and the waste plastic pyrolysis oil, and specifically, the stirring can be carried out at 100 to 4000 rpm for 3 to 5 hours, but is not necessarily limited thereto.

[0051] The mixed oil of the first step is allowed to stand, and the desalted solution in the lower layer is separated to obtain pretreated waste plastic pyrolysis oil in the second step, thereby obtaining waste plastic pyrolysis oil from which organic chlorine and inorganic chlorine have been removed. In particular, when the stirring process is completed, layer separation of the pyrolysis oil and the desalted solution begins, and the mixed oil can be allowed to stand for a predetermined time for complete layer separation. The standing time can be 0.3 to 12 hours, and specifically, 1 hour to 10 hours. After standing, the desalted solution containing organic chlorine and inorganic chlorine separated in the lower layer is separated and removed to obtain pretreated waste plastic pyrolysis oil.

[0052] In one embodiment, the polar aprotic solvent may have a dielectric constant of 20 or more and a density of 0.9 g / cc or more. When the dielectric constant is 20 or more, ionic compounds can be effectively separated, which is preferable, and when the density is 0.9 g / cc or more, the residual rate of the polar aprotic solvent in the waste plastic pyrolysis oil is low, which is preferable, and layer separation of the desalted solution can be easily performed. Specifically, the dielectric constant may be 25 or more (more specifically, 25 to 70), and the density may be 0.95 g / cc or more (more specifically, 1 to 2 g / cc).

[0053] The polar aprotic solvent may have a boiling point of 100° C. or higher. Since the polar aprotic solvent must be mixed with the waste plastic pyrolysis oil in a liquid state, it is advantageous to use a polar aprotic solvent with a boiling point of 100° C. or higher, taking into consideration the (mixing) temperature conditions of the first step. Specifically, the boiling point may be 120° C. or higher, and more specifically, may be 150° C. or higher and 300° C. or lower.

[0054] In one embodiment, the polar aprotic solvent may be dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, ethyl acetate, tetrahydrofuran (THF) or acetone. In consideration of the dielectric constant, density and boiling point characteristics, and in consideration of the efficiency of reducing chlorine from waste plastic pyrolysis oil and the efficiency of layer separation, dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) is preferred.

[0055] In one embodiment, the density difference between the desalted solution and the waste plastic pyrolysis oil may be 0.3 g / cc or more. When the density difference is 0.3 g / cc or more, it is preferable because layer separation from the pyrolysis oil can be easily performed after the second step (standing) treatment. Specifically, the density difference may be 0.4 g / cc or more, more specifically, 0.5 to 2 g / cc.

[0056] In one embodiment, the desalting solution may be contained in an amount of 5 to 20 parts by weight per 100 parts by weight of the waste plastic pyrolysis oil. When the amount of the desalting solution is satisfied, organic chlorine and inorganic chlorine in the waste plastic pyrolysis oil can be effectively captured. Specifically, the desalting solution may be contained in an amount of 5 to 20 parts by weight, more specifically, 5 to 15 parts by weight per 100 parts by weight of the pyrolysis oil.

[0057] In one embodiment, the weight ratio of the polar aprotic solvent and water may be 50:50 to 95:5. When the weight ratio is satisfied, the layer separation recovery rate can be excellent, and the problem of impurity generation due to mixing with the pyrolysis oil can be minimized. Specifically, the weight ratio may be 60:40 to 90:10, more specifically, 65:35 to 85:15.

[0058] In one embodiment, the method may further include a fifth step of separating the polar aprotic solvent from the desalted solution recovered in the second step and resupplying it to the first step. Specifically, the desalted solution recovered in the second step contains a polar aprotic solvent containing organic chlorine and water containing inorganic chlorine. By separating and recovering the polar aprotic solvent from the desalted solution and resupplying it to the first step, the amount of polar aprotic solvent used separately can be reduced, process efficiency can be improved, and the cost of disposing of and treating by-products in the purification process can be reduced, thereby improving economic efficiency.

[0059] In one embodiment, the fifth step can include a fifth step of distilling the desalted solution to separate water and recover a residual solution, a fifth step of filtering the residual solution to separate chlorine-containing salts from the residual solution and recover a polar aprotic solvent, and a fifth step of resupplying the recovered polar aprotic solvent to the polar aprotic solvent of the first step.

[0060] In detail, the 5-1 step is a step of distilling the desalted solution, and the desalted solution may contain a polar aprotic solvent containing organic chlorine and water containing inorganic chlorine. Water can be removed by discharging it from the desalted solution through distillation using the boiling point difference between water and the polar aprotic solvent, and as an example, the distillation can be performed at normal pressure and at a temperature of 100 to 120°C. The residual solution can be recovered by discharging water with water vapor through the distillation process.

[0061] The 5-2 step is a step of filtering the residual solution, and salts containing chlorine can be separated from the residual solution. Since chlorine and other impurities exist in the form of solid salts in the solution, the solution can be filtered to separate the solid salts from the residual solution. The residual solution from which the solid salts have been removed contains a polar aprotic solvent, and may contain traces of residual salts such as chlorine. In order to remove the traces of residual salts, an additional distillation step can be performed. In order to prevent operational abnormalities due to traces of residual salts such as chlorine, the chlorine content in the polar aprotic solvent of the residual solution is preferably 5% by weight or less, and specifically, the chlorine content may be 1% by weight or less.

[0062] The 5-3 step is a step of re-supplying the recovered polar aprotic solvent to the polar aprotic solvent of the first step. By recovering the polar aprotic solvent from the 5-1 to 5-3 steps and re-supplying it to the polar aprotic solvent of the first step, the amount of polar aprotic solvent separately added can be reduced, improving the process efficiency, and the cost of disposing of and treating the by-products of the purification step can be reduced, improving the economic efficiency.

[0063] The pretreated waste plastic pyrolysis oil is hydrotreated at a first temperature in the presence of a hydrotreatment catalyst to carry out a dechlorination reaction in a third step, and the product of the third step is hydrotreated at a second temperature in the presence of a hydrotreatment catalyst to carry out a denitrification reaction in a fourth step, thereby obtaining waste plastic pyrolysis oil (refined oil) with minimized impurities such as chlorine and nitrogen.

[0064] As described above, by introducing waste plastic pyrolysis oil pretreated with a desalted solution containing a polar aprotic solvent and water as the raw material for the hydrotreating process in the third step, it is possible to prevent reactor blockage by minimizing the generation and accumulation of ammonium salts (NH4Cl), improve operational stability, and operate the refinery stably for a long period of time. In addition, by carrying out the hydrotreating process under mild conditions, it is possible to obtain waste plastic pyrolysis oil (refined oil) in high yield without catalyst inactivation or change or decrease in molecular weight distribution. In addition to the above effects, by first removing chlorine in the third step and then mainly removing nitrogen in the fourth step, it is possible to maximize the effect of minimizing the generation and accumulation of ammonium salts (NH4Cl) in the reactor, and further improve operational stability.

[0065] The third and fourth steps of hydrotreating may be carried out continuously, and the second temperature may be higher than the first temperature. The types of components removed during the third and fourth steps of hydrotreating may be determined according to the reaction temperature, and the third step of hydrotreating may be carried out at a first temperature to mainly remove chlorine, and the fourth step of hydrotreating may be carried out at a second temperature higher than the first temperature to mainly remove nitrogen.

[0066] In detail, the hydrotreating in the third step is carried out at a first temperature, and chlorine can be mainly removed from the waste plastic pyrolysis oil, and some olefins and metal impurities can also be removed. A hydrogenation reaction of the waste plastic pyrolysis oil occurs in the presence of the hydrotreating catalyst, and most of the chlorine is removed from the waste plastic pyrolysis oil to produce hydrogen chloride. In addition, some of the olefins are removed from the waste plastic pyrolysis oil, and other metal impurities are removed. A fluid containing the hydrotreated hydrocarbon fraction, hydrogen chloride, and unreacted hydrogen is produced.

[0067] The fourth step of hydrogenation treatment is carried out at a second temperature, and a waste plastic pyrolysis oil (refined oil) from which nitrogen has been removed from the fluid can be produced. At the second temperature, impurities including nitrogen, oxygen, sulfur, etc. can be all removed from the fluid along with hydrogen chloride and unreacted hydrogen gas, and a mixed gas containing hydrogen chloride, ammonia, water vapor, hydrogen sulfide, etc. can be produced. The mixed gas is discharged and removed, and the waste plastic pyrolysis oil (refined oil) can be separated into gas and liquid and recovered.

[0068] In one embodiment, the first temperature may be 100 to 300°C, and the second temperature may be 300 to 450°C. In the first temperature range, chlorine can be intensively removed during hydrotreating, and olefins and other metal impurities can also be effectively removed. In the second temperature range, nitrogen can be intensively removed, and other impurities such as chlorine, sulfur, and oxygen can also be removed. The first temperature may be 120 to 250°C, more specifically 150 to 230°C, and the second temperature may be 350 to 420°C, more specifically 370 to 400°C. The difference between the first temperature and the second temperature may be 50 to 350°C, more specifically 50 to 280°C, more specifically 50 to 200°C, but this is merely an example and is not necessarily limited thereto.

[0069] By introducing the waste plastic pyrolysis oil pretreated with the desalted solution as the raw material for the hydrotreating process, the hydrotreating process is carried out under a somewhat mild temperature condition that satisfies the range of the first and second temperatures, so that the waste plastic pyrolysis oil (refined oil) can be obtained in a high yield without yield loss due to catalyst inactivation and changes or decreases in molecular weight distribution. Specifically, the waste plastic pyrolysis oil (refined oil) can be obtained in a yield of 90% or more, and more specifically, the yield can be 95% or more.

[0070] In one embodiment, the hydrotreating catalyst in the third and fourth steps may be a catalyst in which an active metal containing any one or more selected from molybdenum, nickel, cobalt, and tungsten is supported on a support. The hydrotreating catalyst is a catalyst in which a dechlorination reaction or a denitrification reaction is carried out as a main reaction depending on the above-mentioned conditions such as temperature, and may contain an active metal having hydrotreating catalytic ability, and may be a catalyst in which an active metal is supported on a support. The active metal may include any one or more selected from molybdenum, nickel, cobalt, and tungsten having hydrotreating catalytic ability. The support may be any one having durability capable of supporting an active metal, and may include, for example, any one or more selected from metals containing any one or more selected from silicon, alumina, zircon, titanium, and the like; oxides of the metals; and carbon-based materials containing any one or more selected from carbon black, activated carbon, graphene, carbon nanotubes, graphite, and the like; and the like. As a specific example, the hydrotreating catalyst may be a catalyst in which active metals including 0.1-10 wt % of nickel and 0.1-30 wt % of molybdenum are supported on an alumina support, but this is merely an example and is not necessarily limited thereto.

[0071] In one embodiment, the reaction pressure during the hydrogenation treatment of the third and fourth steps can be less than 100 bar. Under high pressure conditions of 100 bar or more, there is a problem that the production of ammonium salts (NH4Cl) is promoted, and under too low pressure conditions, there is a problem that impurities containing chlorine and nitrogen cannot be effectively removed. Specifically, the reaction pressure can be 30 bar to 90 bar, more specifically, 50 bar to 80 bar.

[0072] In one embodiment, the ratio of liquid hourly space velocity (LHSV) during the hydrotreating in the third and fourth steps may be 1:0.1 to 1:0.8. When the ratio satisfies the above range, impurities can be removed more effectively during the hydrotreating in the third and fourth steps, the activity of the hydrotreating catalyst can be maintained at a high activity for a long period of time, and the process efficiency can be improved.

[0073] The waste plastic pyrolysis oil (refined oil) finally obtained by the above-mentioned method for refining waste plastic pyrolysis oil can be a high-quality pyrolysis oil with extremely low impurity content. Specifically, the impurity content contained in the obtained waste plastic pyrolysis oil (refined oil) can be 10 ppm (weight) or less of chlorine, 30 ppm (weight) or less of nitrogen, 10 ppm (weight) or less of sulfur, 10 ppm (weight) or less of other metal components, 0.1 wt% or less of oxygen, 10 vol% or less of olefin, and 0.2 vol% or less of conjugated diolefin.

[0074] In one embodiment, the method may further include a step of mixing the product of the third step with a desalted solution containing a polar aprotic solvent and water between the third step and the fourth step to perform a desalting process. The desalted solution of the present disclosure has both organic chlorine and inorganic chlorine removal capabilities, and the efficiency of the purification process can be further improved by adding the desalted solution between the third and fourth steps of the hydrotreating process to further remove chlorine. After adding the desalted solution to the fluid hydrotreated by the third step, the desalted process can be performed in the same manner as the first and second steps described above.

[0075] The present disclosure also provides a purification device for waste plastic pyrolysis oil, comprising: a first reactor into which a desalted solution containing a polar aprotic solvent and water and waste plastic pyrolysis oil are flowed in and a pretreatment process is carried out; a second reactor into which products and hydrogen gas from the first reactor are flowed in and hydrotreated at a first temperature in the presence of a hydrotreatment catalyst to carry out a dechlorination reaction; and a third reactor into which products and hydrogen gas from the second reactor are flowed in and hydrotreated at a second temperature in the presence of a hydrotreatment catalyst to carry out a denitrification reaction.

[0076] The reactors are connected to each other by pipes, and reaction products may flow from each reactor through the pipes.

[0077] In one embodiment, the first reactor may be a batch reactor. The first reactor may be any type of batch reactor capable of stirring and temperature control. The first reactor may be provided with an agitator for stirring the desalted solution and the waste plastic pyrolysis oil. The agitator may have a stirring capacity of 50 to 5000 rpm.

[0078] The first reactor may have an outlet at the bottom. When the stirring process of the desalted solution and the waste plastic pyrolysis oil is completed, layer separation begins due to density difference, and the mixed oil may be left to stand for a predetermined time for complete layer separation. The layer-separated desalted solution is separated and discharged through the outlet located at the bottom of the first reactor, and the pretreated waste plastic pyrolysis oil may be introduced into the second reactor through a pipe.

[0079] The outlet of the first reactor may further include a density profiler, and by detecting the density, the pyrolysis oil layer can be prevented from being removed together with the desalted solution when the desalted solution is removed.

[0080] In one embodiment, the second and third reactors can be fixed bed reactors. Fixed bed reactors have the advantage of high productivity and can be operated in a continuous mode.

[0081] The second reactor has a reaction zone equipped with a hydrotreating catalyst. The pretreated waste plastic pyrolysis oil and hydrogen gas are introduced from the first reactor into the reaction zone and hydrotreated at a first temperature, so that chlorine can be mainly removed from the waste plastic pyrolysis oil, and some olefins and metal impurities can also be removed.

[0082] The second reactor may not have a separate gas outlet, and thus the dechlorinated fraction, hydrogen chloride, and unreacted hydrogen-containing fluid produced by the second reactor may be directly fed into the third reactor.

[0083] The third reactor includes a reaction zone containing a hydrotreating catalyst, into which the fluid and hydrogen gas from the second reactor are introduced and hydrotreated at a second temperature to remove impurities from the fluid.

[0084] The third reactor may have a gas outlet at the top of the third reaction region for discharging the mixed gas, and a fraction outlet at the bottom of the third reaction region for discharging the waste plastic pyrolysis oil (refined oil) from which impurities have been removed. The mixed gas is discharged through the gas outlet, and the waste plastic pyrolysis oil (refined oil) from which impurities have been removed can finally be obtained through the fraction outlet located at the bottom.

[0085] In one embodiment, the system includes a recovery tank for recovering the desalted solution discharged from the first reactor, the recovery tank including a distillation zone and a filtration zone, and may further include a recycle line for re-supplying the polar aprotic solvent separated from the recovery tank to the first reactor.

[0086] The recovery tank may include a distillation region and a filtration region, and the recovery tank may include a gas outlet in the distillation region. Water may be distilled from the desalted solution through the gas outlet and discharged in the form of water vapor, and the remaining solution may be flowed into the filtration region. The filtration region may include a filtration membrane, and solid salts contained in the fraction may be removed through the filtration membrane, and trace amounts of remaining salts may be removed by an additional distillation process.

[0087] That is, the chlorine-containing salts are filtered from the remaining solution through the filtration region, and the polar aprotic solvent is recovered. The polar aprotic solvent can be re-supplied to the first reactor through a recirculation line located at the bottom of the recovery tank.

[0088] For matters not further described regarding the refining apparatus for waste plastic pyrolysis oil, please refer to the contents described in the above-mentioned method for refining waste plastic pyrolysis oil.

[0089] Hereinafter, the present disclosure will be described in detail with reference to examples. However, these are intended to provide a more detailed explanation, and the scope of the invention is not limited to the following examples.

[0090] Example 1 Waste plastic was pyrolyzed to prepare 500 g of pyrolysis oil feedstock.

[0091] The total chlorine, organic chlorine and inorganic chlorine contents (ppm) in the waste plastic pyrolysis oil were measured by ICP and XRF analysis, and the total chlorine content was confirmed to be 860 ppm, the organic chlorine content was 596 ppm and the inorganic chlorine content was 264 ppm.

[0092] As the desalted solution, 100 g of desalted solution was prepared by mixing 80 g of dimethyl sulfoxide (DMSO) and 20 g of water.

[0093] 500g of waste plastic pyrolysis oil and 100g of the desalted solution were put into the first reactor and stirred to produce a mixed oil. Specifically, the mixture was stirred at 80°C and 500 rpm for 3 hours, and after stirring was completed, the mixture was left to stand for 3 hours while maintaining the temperature. Then, only the desalted solution separated in the lower layer of the mixed oil was separated and discharged through the outlet located at the bottom of the reactor to obtain a pretreated waste plastic pyrolysis oil.

[0094] The pretreated waste plastic pyrolysis oil was introduced into the second reactor and then hydrotreated. In detail, the second reactor was equipped with hydrotreatment catalysts NiMo / r-Al2O3 and CoMo / r-Al2O3, and the pretreated waste plastic pyrolysis oil and hydrogen gas were introduced into the second reactor and hydrotreated at 250°C, 80 bar, H2 / Oil ratio 840, and LHSV 0.4h. -1 The mixture was subjected to hydrotreatment under the following conditions.

[0095] The fluid hydrotreated in the second reactor was introduced into the third reactor and hydrotreated. Specifically, the third reactor was equipped with the same hydrotreatment catalyst as the second reactor, and the fluid and hydrogen gas were respectively introduced into the third reactor, and the conditions were 370°C, 85 bar, H2 / Oil ratio 840, and LHSV 0.7h. -1 The mixture was subjected to hydrotreatment under the following conditions.

[0096] A mixed gas containing ammonia, hydrogen chloride, water, hydrogen sulfide, hydrogen, etc. generated during the hydrotreating process was discharged through the gas outlet located at the top of the third reactor, and finally, waste plastic pyrolysis oil (refined oil) from which impurities had been removed was collected through the distillate outlet located at the bottom.

[0097] Example 2 In Example 1, 80 g of dimethylformamide (DMF) and 20 g of water were used as the desalting solution, and the temperature condition of the first reactor was set to 120°C. Except for this, the same process as in Example 1 was carried out to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0098] Example 3 In Example 1, the purification process was carried out using 70 g of DMSO and 30 g of water as the desalted solution, but the same process as in Example 1 was carried out to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0099] Example 4 In Example 1, the purification process was carried out in the same manner as in Example 1, except that the second reactor was operated at 160°C and 85 bar, and the third reactor was operated at 320°C and 90 bar, to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0100] Example 5 The same process as in Example 1 was carried out, except that the purification process was carried out using 80 g of tetrahydrofuran (THF) and 20 g of water instead of DMSO in the desalted solution, to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0101] Example 6 In Example 1, the purification process was carried out using 30 g of DMSO and 70 g of water, which were the desalted solution, in the same manner as in Example 1, and waste plastic pyrolysis oil (refined oil) from which impurities had been removed was recovered.

[0102] Comparative Example 1 In Example 1, the first reactor was omitted in the refining process, and the waste plastic pyrolysis oil was directly fed into the second reactor to perform the refining process. The same process was carried out as in Example 1, and waste plastic pyrolysis oil (refined oil) from which impurities had been removed was recovered.

[0103] Comparative Example 2 In Example 1, the purification process was carried out using only 100 g of DMSO as the desalting solution, but the same process as in Example 1 was carried out to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0104] Comparative Example 3 In Example 1, the purification process was carried out using only 100 g of water as the desalted solution, but the same process as in Example 1 was carried out to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0105] Comparative Example 4 In Example 1, the purification process was carried out under the same reaction conditions in the second reactor as in the third reactor, but the same process was carried out as in Example 1 to recover waste plastic pyrolysis oil (refined oil) from which impurities had been removed.

[0106] How to measure results Chlorine Content The total chlorine, organic chlorine and inorganic chlorine contents (ppm) in the obtained waste plastic pyrolysis oil were measured by ICP and XRF analysis.

[0107] Maximum operating time The maximum operation time was measured until the pressure drop (delta P) due to the ammonium salt (NH4Cl) produced during the hydrotreating process reached 7 bar.

[0108] [Table 1]

[0109] evaluation In the case of Example 1, Example 3, and Example 4, it can be confirmed that the organic chlorine content is effectively reduced to 150 ppm or less and the inorganic chlorine content is 80 ppm or less by pretreating the waste plastic pyrolysis oil in the first reactor with a polar aprotic solvent DMSO (dielectric constant 47 and density 1.1) and a desalted solution containing water. In addition, in Example 2, it can be confirmed that the organic chlorine content in the pyrolysis oil pretreated in the first reactor using DMF (dielectric constant 38 and density 0.94) as a polar aprotic solvent is effectively reduced to 150 ppm and the inorganic chlorine content is effectively reduced to 80 ppm or less. As a result, it can be confirmed that the hydrotreatment process, which is a continuous process, can be stably performed for a long period of time of 15 days or more, and that the organic chlorine in the finally obtained pyrolysis oil (refined oil) is reduced to a few ppm level.

[0110] In particular, referring to Example 4, it can be confirmed that since the organic chlorine and inorganic chlorine contents are reduced by pretreating the pyrolysis oil in reactor 1, the impurity content in the finally obtained pyrolysis oil (refined oil) can be effectively reduced to the level of several ppm even when the hydrotreating process is performed under somewhat milder conditions (second reactor 160°C, third reactor 320°C).

[0111] Meanwhile, in the case of Example 5, by using THF (dielectric constant 7.5, density 0.89) as the polar aprotic solvent in the first reactor, the organic chlorine content in the pretreated pyrolysis oil was 279 ppm, and the inorganic chlorine content was 85 ppm, indicating that the chlorine removal effect was somewhat reduced. In the case of Example 6, when the desalting solution contained more water than the polar aprotic solvent DMSO, the organic chlorine content in the pretreated pyrolysis oil was 321 ppm, and the inorganic chlorine content was 35 ppm, indicating that the organic chlorine removal effect was somewhat reduced. Since the chlorine content in the pyrolysis oil increased, it was confirmed that the maximum operating time of the hydrotreatment process, which is a continuous process, was shortened to less than 9 days, and the organic chlorine content in the finally obtained pyrolysis oil (refined oil) was also somewhat high at the 10 ppm level.

[0112] In Comparative Example 1, it was confirmed that when the pretreatment process using the first reactor was not performed, the maximum operating time of the hydrotreatment process was significantly shortened to less than 5 days, and the organic chlorine content in the finally obtained pyrolysis oil (refined oil) was also high at the 20 ppm level.

[0113] In Comparative Example 2, it was confirmed that the inorganic chlorine reduction efficiency was decreased when DMSO was used alone as the desalting solution, and in Comparative Example 3, it was confirmed that the organic chlorine reduction efficiency was decreased when water was used alone as the desalting solution, and therefore the maximum operation time of the hydrotreating process was significantly shortened to 7 days or less. In particular, in Comparative Example 3, it was confirmed that the organic chlorine content in the finally obtained pyrolysis oil (refined oil) was also high at the 20 ppm level.

[0114] In Comparative Example 4, the hydrotreating of the pretreated waste plastic pyrolysis oil was carried out only under conditions of 370°C and 85 atm in both the second and third reactors, and it was confirmed that the generation of ammonium salt (NH4Cl) increased and the maximum operating time was significantly shortened to less than 5 days.

[0115] Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples, and may be implemented in various different forms, and a person having ordinary skill in the art to which the present invention belongs can understand that the present invention may be implemented in other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the above-described examples are illustrative in all respects and are not limiting.

Claims

1. A first step of mixing a desalted solution containing a polar aprotic solvent and water with waste plastic pyrolysis oil to form a mixed oil; A second step of allowing the mixed oil from the first step to stand and separating the desalted solution in the lower stage to obtain a pretreated waste plastic pyrolysis oil; A third step of hydrotreating the pretreated waste plastic pyrolysis oil in the second step at a first temperature under a hydrotreating catalyst to carry out a dechlorination reaction; A fourth step of hydrotreating the product of the third step in the presence of a hydrotreating catalyst at a second temperature to carry out a denitrification reaction.

2. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the first step comprises stirring the desalted solution and the waste plastic pyrolysis oil at a temperature of 60 to 300°C.

3. The method for refining waste plastic pyrolysis oil according to claim 1 , wherein the polar aprotic solvent has a dielectric constant of 20 or more and a density of 0.9 g / cc or more.

4. The method for purifying waste plastic pyrolysis oil according to claim 1, wherein the polar aprotic solvent comprises dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

5. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the density difference between the desalted solution and the waste plastic pyrolysis oil is 0.3 g / cc or more.

6. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the desalted solution is contained in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the waste plastic pyrolysis oil.

7. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the weight ratio of the polar aprotic solvent and water is 50:50 to 95:

5.

8. The method for refining waste plastic pyrolysis oil according to claim 1, further comprising a fifth step of separating a polar aprotic solvent from the desalted solution recovered in the second step and resupplying the polar aprotic solvent to the first step.

9. The fifth step includes a fifth step of distilling the desalted solution to separate water and recovering a residual solution, a fifth step of filtering the residual solution to separate chlorine-containing salts from the residual solution and recovering a polar aprotic solvent, and a fifth step of resupplying the recovered polar aprotic solvent to the polar aprotic solvent of the first step. The method for refining waste plastic pyrolysis oil according to claim 8.

10. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the first temperature is 100 to 300°C and the second temperature is 300 to 450°C.

11. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the hydrotreating catalyst in the third and fourth steps is a catalyst in which an active metal containing one or more selected from molybdenum, nickel, cobalt and tungsten is supported on a support.

12. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the reaction pressure during the third and fourth steps of hydrotreatment is less than 100 bar.

13. The method for refining waste plastic pyrolysis oil according to claim 1, wherein the ratio of liquid hourly space velocity (LHSV) during the hydrotreatment in the third and fourth steps is 1:0.1 to 1:0.

8.

14. 2. The method for refining waste plastic pyrolysis oil according to claim 1, further comprising the step of mixing the product of the third step with a desalted solution containing a polar aprotic solvent and water between the third step and the fourth step, and carrying out a desalting process.

15. A first reactor into which a desalted solution containing a polar aprotic solvent and water and waste plastic pyrolysis oil are introduced and a pretreatment process is performed; a second reactor into which the product and hydrogen gas from the first reactor are flowed and hydrotreated at a first temperature in the presence of a hydrotreatment catalyst to carry out a dechlorination reaction; and a third reactor into which the product and hydrogen gas from the second reactor are flowed and hydrotreated at a second temperature in the presence of a hydrotreatment catalyst, and a denitrification reaction is carried out.

16. The purification apparatus for waste plastic pyrolysis oil according to claim 15, wherein the first reactor is a batch reactor.

17. The purification apparatus for waste plastic pyrolysis oil according to claim 15, wherein the second reactor and the third reactor are fixed bed reactors.

18. 16. The waste plastic pyrolysis oil purification apparatus according to claim 15, further comprising a recovery tank for recovering the desalted solution discharged from the first reactor, the recovery tank including a distillation area and a filtration area, and further comprising a recirculation line for re-supplying the polar aprotic solvent separated from the recovery tank to the first reactor.

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