Method for dechlorination of waste plastic pyrolysis oil

Abstract

This invention discloses a method for dechlorinating waste plastic pyrolysis oil, comprising the following steps: S1, after removing mechanical impurities from the waste plastic pyrolysis oil, washing with water to remove inorganic chlorides, then separating the oil phase by oil-water separation, and drying the resulting oil phase to obtain primary dechlorinated waste plastic pyrolysis oil; S2, mixing the primary dechlorinated waste plastic pyrolysis oil with hydrogen and then feeding it into a pre-hydrogenation reactor, where, under the action of a pre-hydrogenation catalyst, the dienes in the primary dechlorinated waste plastic pyrolysis oil are converted into monoolefins to obtain pre-hydrogenated waste plastic pyrolysis oil; S3, fractionating the pre-hydrogenated waste plastic pyrolysis oil into light distillate oil, medium distillate oil, and heavy distillate oil; S4, reacting the light distillate oil with hydrogen under the action of a hydrodechlorination catalyst to remove organic chlorides, and separating the reaction product by gas-liquid separation to obtain hydrodechlorinated pyrolysis oil; S5, contacting the medium distillate oil with an adsorbent to obtain adsorbed dechlorinated pyrolysis oil. This invention's method has a high chloride removal rate and produces high-quality products.

Description

Technical Field

[0001] This invention belongs to the field of waste plastic chemical recycling technology, specifically relating to a method for dechlorination of waste plastic pyrolysis oil. Background Technology

[0002] Since the beginning of the 20th century, the production and application of plastics have developed extremely rapidly. The main types include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), acrylonitrile-butadiene-styrene polymer (ABS), nylon (PA), and polylactic acid (PLA). In 2021, my country's output of plastic products was approximately 8 × 10⁻⁶. 7 t, the usage is approximately 9.088 × 10 7 The generation of waste plastics is increasing in tandem with the amount of plastic used. Improper disposal of waste plastics will cause them to gradually accumulate in the environment, forming "white pollution." It is estimated that by 2050, the global accumulation of waste plastics in the environment will reach 1.20 × 10⁻⁶ tons. 10 Promoting the recycling and reuse of waste plastics, transforming low-value waste plastics into valuable resources such as pyrolysis oil, and obtaining economically efficient products while completely achieving the harmlessness and reduction of waste plastics is an important part of the chemical cycle of waste plastics and helps to promote the achievement of carbon neutrality goals. For polyolefin waste plastics, mainly PP and PE, domestic and foreign companies usually use pyrolysis to convert them into pyrolysis oil, which is used as a raw material for refining and chemical enterprises to produce low-carbon olefins and other chemicals. However, waste plastics have complex compositions, and existing sorting technologies have low precision, making it impossible to completely remove chlorine-containing plastics such as PVC from waste plastics. In addition, the widespread use of halogenated plastic additives results in generally poor properties of plastic pyrolysis oil, with impurity content far exceeding that of crude oil and its distillate oils, making it unsuitable as a raw material for refining and chemical enterprises. Among them, chlorine mainly exists in the form of organic chlorine, which can easily cause catalyst poisoning and equipment corrosion in existing refining and chemical units. Therefore, the removal of chlorine from waste plastic pyrolysis oil is particularly critical. The pyrolysis products of mixed waste plastics containing PVC are mostly olefins, aromatics, and paraffin compounds with carbon numbers concentrated in C1-C4, C5-C17, and C11-C28. Chlorides are mostly concentrated in light oils and gases, while pyrolysis products also contain a certain amount of sulfides, which restricts the use of precious metal catalysts with high dechlorination efficiency. Among existing oil dechlorination technologies, the adsorption method is simple, but due to the high chlorine content in the pyrolysis oil, the adsorbent is easily saturated and difficult to regenerate, and frequent replacement increases dechlorination costs. The hydrotreating method has a higher dechlorination efficiency, but impurities such as metals, sulfur, and nitrogen compete with chlorides on the catalyst surface, which is not conducive to chloride removal. In addition, the waste plastic pyrolysis oil has a high degree of unsaturation, and the large amount of dienes in the pyrolysis oil can easily cause severe coking in equipment such as heating furnaces and heat exchangers, and greatly affect the activity and lifespan of the catalyst.

[0003] Patent CN101899321B discloses a chlorine removal and transfer agent and its preparation method for crude oil. Addressing the problem of removing organochlorine from crude oil, it provides a chlorine transfer agent and its preparation method. The chlorine transfer agent is prepared from 25-40 parts of N,N-dimethylpropylenediamine, 10-30 parts of hexadecylamine polyoxyethylene polyoxypropylene ether, 10-20 parts of modified β-hydroxyethyltrimethylamine hydroxide, and 10-55 parts of decanol. It can effectively remove organochlorine from crude oil that cannot be removed by electro-desalting. This technical solution addresses the issue that crude oil electrochemical desalting processes can only remove inorganic chlorine but not organic chlorine. It employs a chlorine transfer agent to convert organic chlorine into inorganic chlorine, which is then transferred to the water. This is combined with the crude oil electrochemical desalting and dehydration process to remove chlorine. However, the use of amine-containing polyethers increases the oxygen and nitrogen content in the oil, increasing the burden on subsequent deoxygenation and denitrification processes. Furthermore, the chlorine content in waste plastic pyrolysis oil is much higher than in crude oil, and the types of chlorides are more complex. This technology is not entirely suitable for waste plastic pyrolysis oil, and its dechlorination effect is limited. Additionally, this phase transfer agent is expensive.

[0004] Patent CN111171865B discloses a dechlorination method for waste plastic pyrolysis oil. Addressing the issues of complex dechlorination processes and high costs of precious metal catalysts for waste plastic oil, it provides a hydrodechlorination method, specifically including: a) reacting the waste plastic pyrolysis oil with hydrogen under the action of a hydrodechlorination catalyst, and obtaining a hydrodechlorinated product oil after oil-gas separation; b) mixing the hydrodechlorinated product oil obtained in step a) with an adsorbent for adsorption treatment to obtain an adsorbed dechlorinated oil product; the adsorbent is composed of activated alumina and metal element-modified molecular sieves in a mass ratio of 1:(1-2). In this technical solution, waste plastic pyrolysis oil is first hydrogenated to remove impurities such as sulfur, nitrogen, and chlorine through a non-precious metal-loaded alumina-based hydrogenation catalyst. Then, it is dechlorinated through an adsorbent to achieve deep dechlorination of the entire distillate. However, since chlorides are mainly concentrated in the light components, the competitive adsorption of large molecular hydrocarbons and sulfur and nitrogen compounds in the whole distillate pyrolysis oil, as well as their steric hindrance effect, will affect the dechlorination efficiency of the hydrogenation catalyst. Furthermore, impurities such as metals and dienes in the pyrolysis oil can easily cause catalyst poisoning and coking. Therefore, the dechlorination effect of this method will be limited during long-term operation.

[0005] Patent CN116426308A discloses a method and apparatus system for producing steam cracking feedstock oil and nano-carbon materials from waste plastics in an ethylene production plant. Addressing the problem of high unsaturated hydrocarbon content and low utilization efficiency in waste plastic cracking oil, this method specifically includes: thermally cracking waste plastics to obtain hydrocarbon cracking oil and gas; then performing gas-liquid separation on the hydrocarbon cracking oil and gas to obtain crude cracking oil and cracking gas; further, decarbonizing the cracking gas to obtain nano-carbon materials; and then sequentially subjecting the crude cracking oil to hydrocracking and fractionation to obtain the steam cracking feedstock oil for the ethylene plant. However, this technical solution does not remove impurities from the waste plastic cracking oil, and the hydrocracking process is prone to catalyst poisoning, coking, and equipment corrosion.

[0006] Patent CN112547093B discloses a hydrodechlorination catalyst, its preparation method, and its application. Addressing the issues of poor conversion and selectivity in hydrodechlorination catalysts, it provides a hydrodechlorination catalyst and its preparation method. Specifically, the catalyst uses activated carbon as a support, with an active metal component content of 0.5-3%, including Pd and Cu, and an auxiliary agent of 0.2-2%, including Zn. The resulting catalyst exhibits high activity for the hydrodechlorination of trifluorotrichloroethane to trifluorochloroethylene. However, this technical solution uses a Pd-based noble metal catalyst, which is costly. Furthermore, waste plastic pyrolysis oil contains impurities such as sulfur, nitrogen, and silicon, which can easily lead to poisoning and deactivation of the noble metal Pd-based catalyst. Summary of the Invention

[0007] The purpose of this invention is to provide a method for dechlorinating waste plastic pyrolysis oil. The method of this invention has a high chlorine removal rate and good product quality, and effectively avoids the shortcomings of direct hydrodechlorination of waste plastic pyrolysis oil, such as easy coking, rapid catalyst deactivation, and high dechlorination cost.

[0008] To achieve the above objectives, the present invention provides a method for dechlorinating waste plastic pyrolysis oil, comprising the following steps:

[0009] S1, after removing mechanical impurities from the waste plastic pyrolysis oil, it is washed with water to remove inorganic chlorides, and then separated by oil and water. The resulting oil phase is dried to obtain first-grade dechlorinated waste plastic pyrolysis oil.

[0010] S2, after mixing the primary dechlorinated waste plastic pyrolysis oil with hydrogen, enters the pre-hydrogenation reactor. Under the action of the pre-hydrogenation catalyst, the dienes in the primary dechlorinated waste plastic pyrolysis oil are converted into monoolefins to obtain pre-hydrogenated waste plastic pyrolysis oil.

[0011] S3, the pre-hydrogenated waste plastic pyrolysis oil is fractionated into light distillate oil, medium distillate oil and heavy distillate oil;

[0012] S4 involves reacting light distillate oil with hydrogen under the action of a hydrodechlorination catalyst to remove organochlorides, and the reaction product is separated by gas-liquid separation to obtain hydrodechlorinated cracked oil.

[0013] S5, medium-grade distillate oil is contacted with an adsorbent to obtain adsorbed dechlorination cracked oil.

[0014] The method for dechlorinating waste plastic pyrolysis oil according to the present invention wherein the total chlorine content of the waste plastic pyrolysis oil is not less than 300 ppm.

[0015] The method for dechlorinating waste plastic pyrolysis oil according to the present invention wherein the inorganic chlorine content in the primary dechlorinated waste plastic pyrolysis oil is not greater than 5 ppm, preferably not greater than 1 ppm, and the water content is not greater than 500 ppm, preferably not greater than 300 ppm.

[0016] The method for dechlorinating waste plastic pyrolysis oil according to the present invention comprises a pre-hydrogenation catalyst composed of alumina and one or more oxides of Co, Mo, Ni, and W.

[0017] The method for dechlorinating waste plastic pyrolysis oil according to the present invention comprises a pre-hydrogenation catalyst with an alumina content of 50% to 80% by mass and a content of one or more oxides of Co, Mo, Ni, and W of 20% to 50%.

[0018] The method for dechlorination of waste plastic pyrolysis oil according to the present invention, wherein the reaction temperature of the pre-hydrogenation reaction in step S2 is 135-200°C, the hydrogen partial pressure is 2-5 MPa, and the volume hourly space velocity is 2-5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 50–500:1.

[0019] The method for dechlorinating waste plastic pyrolysis oil according to the present invention includes alumina, magnesium or phosphorus modified alumina, molecular sieve, nickel oxide or cobalt oxide, molybdenum oxide or tungsten oxide as the hydrodechlorination catalyst.

[0020] The method for dechlorinating waste plastic pyrolysis oil according to the present invention uses one or more of modified Y molecular sieve, modified ZSM-5 molecular sieve, and modified 13X molecular sieve. The modification described in this invention is acid modification or hydrothermal modification, etc., which are commonly used modification methods in the field of hydrodechlorination catalyst technology. This invention does not impose specific limitations, and those skilled in the art can choose according to the actual situation.

[0021] The method for dechlorinating waste plastic pyrolysis oil according to the present invention comprises the following mass composition of the hydrodechlorination catalyst: 40-60% alumina, 10-30% magnesium or phosphorus modified alumina, 0.5-8% molecular sieve, 2-5% nickel oxide or cobalt oxide, and 10-20% molybdenum oxide or tungsten oxide.

[0022] The method for dechlorinating waste plastic pyrolysis oil according to the present invention wherein the Na2O content in the molecular sieve is less than 0.5%.

[0023] The dechlorination method for waste plastic pyrolysis oil described in this invention includes the following hydrodechlorination reaction conditions in step S4: reaction temperature 200–350°C, hydrogen partial pressure 3.5–6 MPa, and volume hourly space velocity 0.5–2 h⁻¹. -1 The hydrogen-to-oil volume ratio is 300–700:1.

[0024] The method for dechlorinating waste plastic pyrolysis oil according to the present invention comprises an adsorbent consisting of a support composed of one or more of modified 13X molecular sieve, NaY molecular sieve, alumina, and activated carbon, as well as a metal oxide supported on the support. The modification described in this invention is acid modification or hydrothermal modification, etc., both of which are commonly used modification methods in the field of adsorption dechlorination catalyst technology. This invention does not impose specific limitations, and those skilled in the art can choose according to the actual situation.

[0025] The method for dechlorinating waste plastic pyrolysis oil according to the present invention includes, in the case of, one or more of the following metal oxides in the adsorbent: copper oxide, ferric oxide, magnesium oxide, nickel oxide, cobalt oxide, and zinc oxide.

[0026] The method for dechlorinating waste plastic pyrolysis oil according to the present invention comprises an adsorbent with a carrier mass content of 65-90% and a metal oxide mass content of 10-35%.

[0027] The method for dechlorinating waste plastic pyrolysis oil according to the present invention has a reaction temperature of 50–200°C and a volume hourly space velocity of 0.5–1.5 h⁻¹ in step S4. -1 The reaction pressure is 0.1–0.8 MPa.

[0028] In the dechlorination method for waste plastic pyrolysis oil described in this invention, the cutoff point between light distillate oil and medium distillate oil in step S3 is 180-230°C, and the cutoff point between medium distillate oil and heavy distillate oil is 270-360°C.

[0029] In the method for dechlorinating waste plastic pyrolysis oil of the present invention, the heavy distillate oil obtained in step S3 can be used as feedstock for hydrocracking, catalytic cracking or delayed coking in refineries; the hydrodechlorinated pyrolysis oil obtained can be used as feedstock for steam cracking to produce ethylene or reforming to produce aromatics; and the adsorption dechlorinated pyrolysis oil obtained can be used as feedstock for diesel hydrorefining or wax oil hydrorefining.

[0030] Beneficial effects of this invention:

[0031] Under the action of the pre-hydrogenation catalyst, the dienes in the oil react with hydrogen to convert into monoolefins, which reduces the diene content in waste plastic pyrolysis oil. This can effectively prevent diene condensation, reduce carbon deposit formation, and help reduce the coverage of active sites of the catalyst by carbon deposits during hydrodechlorination, thus extending the service life of the hydrodechlorination catalyst. It also helps to reduce the coking rate of the heating furnace and heat exchanger.

[0032] Because organochlorines in waste plastic pyrolysis oil are mainly concentrated in the fractions below 230°C, while the heavy fractions above 350°C contain very little organochlorine, and metallic impurities such as iron and calcium are mainly enriched in the heavy fractions. Furthermore, the content of impurities such as sulfur and nitrogen in the medium and heavy fractions is also higher than in the light fractions. If the entire fraction of waste plastic pyrolysis oil is directly subjected to hydrodechlorination, the large molecular hydrocarbons and sulfur and nitrogen compounds in the medium and heavy fractions will compete with small molecular chlorides for adsorption, affecting the removal efficiency of organochlorines. At the same time, polycyclic aromatic hydrocarbons and metallic impurities in the heavy fraction can easily cover or poison the active sites of the hydrodechlorination catalyst, reducing catalyst activity. This invention fractionates waste plastic pyrolysis oil into light, medium, and heavy distillate oils before organochlorine removal. For the light distillate oil with high organochlorine content, hydrodechlorination is used; for the medium distillate oil with low organochlorine content, adsorption dechlorination is used; and for the heavy distillate oil with extremely low organochlorine content, meeting the feed requirements of the heavy oil processing unit, it can be directly blended without dechlorination. Therefore, the application of this invention avoids the influence of medium and heavy distillate oil molecules on catalyst activity and lifespan during hydrodechlorination of the entire distillate. Furthermore, by only hydrodechlorinating the light distillate and using adsorption dechlorination for the relatively low-organochlorine medium distillate oil, the overall organochlorine removal efficiency is improved while reducing operating costs. Detailed Implementation

[0033] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0034] The methods for dechlorinating waste plastic pyrolysis oil in the various embodiments of this invention are as follows:

[0035] After filtering to remove mechanical impurities, the waste plastic pyrolysis oil feedstock is washed with water to remove inorganic chlorides. It then undergoes oil-water separation in a separator, followed by adsorption drying in a drying tower to obtain primary dechlorinated waste plastic pyrolysis oil. This primary dechlorinated waste plastic pyrolysis oil is then reacted with hydrogen in the presence of a pre-hydrogenation catalyst, resulting in fractionation into light, medium, and heavy distillate oils. The light distillate oil is then reacted with hydrogen in the presence of a hydrodechlorination catalyst to obtain hydrodechlorinated distillate oil. The medium distillate oil is then reacted with an adsorbent to obtain adsorbed dechlorinated distillate oil. The properties of the primary dechlorinated waste plastic pyrolysis oil are shown in Table 1. The properties of the pre-hydrogenated light, medium, and heavy distillate oils are shown in Tables 2, 3, and 4. The properties of the hydrodechlorinated distillate oil are shown in Table 5. The properties of the adsorbed dechlorinated distillate oil are shown in Table 6. In the examples, all catalysts were prepared using conventional supported catalyst preparation methods, i.e., after forming a support, the corresponding metal salt solution was impregnated onto the support.

[0036] Table 1 Properties of cracked oil feedstock, primary dechlorinated cracked oil, and pre-hydrogenated cracked oil

[0037]

[0038] Example 1:

[0039] The pre-hydrogenation catalyst composition is: 80% alumina, 15% nickel oxide, and 5% molybdenum oxide.

[0040] Pre-hydrogenation reaction process conditions: reaction temperature 140℃, hydrogen partial pressure 2.5MPa, volume hourly space velocity 2.1h. -1 The hydrogen-to-oil ratio is 50:1 (V:V).

[0041] The cut-off point for light and medium distillate oils is 185℃, while the cut-off point for medium and heavy distillate oils is 280℃.

[0042] The hydrodechlorination catalyst has the following composition by mass: 48% alumina, 28% phosphorus-modified alumina, 4% hydrothermally modified ZSM-5 molecular sieve (containing 0.4% Na2O), 4.5% cobalt oxide, and 15.5% molybdenum oxide.

[0043] Hydrodechlorination reaction process conditions: reaction temperature 240℃, hydrogen partial pressure 3.6MPa, volume hourly space velocity 0.6h⁻¹ -1 The hydrogen-to-oil ratio is 300:1 (V:V).

[0044] The mass composition of the adsorption dechlorination catalyst is: 65% acid-modified 13X molecular sieve, 20% zinc oxide, 10% magnesium oxide, and 5% ferric oxide.

[0045] The adsorption dechlorination reaction process conditions are: reaction temperature 60℃, volume hourly space velocity 0.6 h⁻¹. -1 The reaction pressure is 0.7 MPa.

[0046] Example 2:

[0047] The pre-hydrogenation catalyst composition is: 65% aluminum oxide, 15% nickel oxide, 10% cobalt oxide, and 10% molybdenum oxide.

[0048] Pre-hydrogenation reaction process conditions: reaction temperature 180℃, hydrogen partial pressure 4.5MPa, volume hourly space velocity 2.5h⁻¹ -1 The hydrogen-to-oil ratio is 480:1 (V:V).

[0049] The cut-off point for light and medium distillate oils is 210℃, while the cut-off point for medium and heavy distillate oils is 320℃.

[0050] The hydrodechlorination catalyst has the following composition by mass: 50% alumina, 25% magnesium-modified alumina, 2% acid-modified Y molecular sieve (containing 0.3% Na2O), 5% cobalt oxide, and 18% tungsten oxide.

[0051] Hydrodechlorination reaction process conditions: reaction temperature 285℃, hydrogen partial pressure 5MPa, volume hourly space velocity 1.0h⁻¹. -1 The hydrogen-to-oil ratio is 600:1 (V:V).

[0052] The mass composition of the adsorption dechlorination catalyst is: 28% NaY molecular sieve, 60% activated carbon, and 12% copper oxide.

[0053] The adsorption dechlorination reaction process conditions are: reaction temperature 150℃, volume hourly space velocity 0.8 h⁻¹. -1 The reaction pressure is 0.5 MPa.

[0054] Example 3:

[0055] The pre-hydrogenation catalyst composition is: 50% alumina, 25% nickel oxide, and 25% tungsten oxide.

[0056] Pre-hydrogenation reaction process conditions: reaction temperature 160℃, hydrogen partial pressure 3.0 MPa, volume hourly space velocity 4.5 h⁻¹ -1 The hydrogen-to-oil ratio is 300:1 (V:V).

[0057] The cut-off point for light and medium distillate oils is 225℃, while the cut-off point for medium and heavy distillate oils is 350℃.

[0058] The hydrodechlorination catalyst has the following composition by mass: 42% alumina, 30% phosphorus-modified alumina, 8% hydrothermally modified 13X molecular sieve (containing 0.4% Na2O), 5% nickel oxide, and 15% tungsten oxide.

[0059] Hydrodechlorination reaction process conditions: reaction temperature 330℃, hydrogen partial pressure 5.8MPa, volume hourly space velocity 1.5h⁻¹ -1 The hydrogen-to-oil ratio is 650:1 (V:V).

[0060] The adsorption dechlorination catalyst has the following composition by mass: 90% alumina, 5% nickel oxide, and 5% cobalt oxide.

[0061] The adsorption dechlorination reaction conditions are: reaction temperature 200℃, volume hourly space velocity 1.2 h⁻¹. -1 The reaction pressure is 0.3 MPa.

[0062] Comparative Example 1:

[0063] Waste plastic pyrolysis oil raw material, the same as in the example, was subjected to the same water washing, separation, and drying process as in the example to obtain waste plastic pyrolysis oil with inorganic chlorine removed; without pre-hydrogenation and fractionation, the waste plastic pyrolysis oil with inorganic chlorine removed was directly subjected to hydrodechlorination, the same hydrodechlorination process as in Example 1, to obtain waste plastic pyrolysis oil with organic chlorine removed, the properties of which are shown in Table 5.

[0064] Comparative Example 2:

[0065] Waste plastic pyrolysis oil raw material, the same as in the example, was subjected to the same water washing, separation, and drying process as in the example to obtain waste plastic pyrolysis oil with inorganic chlorine removed; without pre-hydrogenation and fractionation, the waste plastic pyrolysis oil with inorganic chlorine removed was directly subjected to adsorption dechlorination, the same adsorption dechlorination process as in Example 1, to obtain waste plastic pyrolysis oil with organic chlorine removed, the properties of which are shown in Table 5.

[0066] Comparative Example 3:

[0067] Waste plastic pyrolysis oil raw material, the same as in Example 1, was subjected to the same water washing, separation, and drying process as in Example 1 to obtain waste plastic pyrolysis oil with inorganic chlorine removed. The obtained waste plastic pyrolysis oil was pre-hydrogenated under the same conditions as in Example 1, and then directly subjected to hydrodechlorination without fractionation. The hydrodechlorination process was the same as in Example 1 to obtain waste plastic pyrolysis oil with organic chlorine removed. The properties are shown in Table 5.

[0068] Comparative Example 4:

[0069] Waste plastic pyrolysis oil feedstock, the same as in Example 1, was subjected to the same washing, separation, and drying processes as in Example 1 to obtain waste plastic pyrolysis oil with inorganic chlorine removed. The obtained waste plastic pyrolysis oil was directly fractionated without pre-hydrogenation, and the fractionation conditions were the same as in Example 1. The light fraction was subjected to hydrodechlorination, and the middle fraction was subjected to adsorption dechlorination. The hydrodechlorination and adsorption dechlorination conditions were exactly the same as in Example 1, and hydrodechlorinated pyrolysis oil and adsorption dechlorinated pyrolysis oil were obtained respectively. The properties are shown in Table 7.

[0070] Table 2 Properties of light distillate oils in the embodiments of the present invention

[0071] Item Example 1 Example 2 Example 3 Total chlorine, mg / kg 2295 2020 1423 Sulfur, mg / kg 988 1024 1371 Nitrogen, mg / kg 2180 2372 2425 Metals, mg / kg 12 14 22

[0072] Table 3 Properties of medium-quality distillate oils in the embodiments of the present invention

[0073]

[0074]

[0075] Table 4 Properties of Heavy Distillate Oils in the Embodiments of the Invention

[0076] Item Example 1 Example 2 Example 3 Total chlorine, mg / kg 8 6 5 Sulfur, mg / kg 2690 2807 2933 Nitrogen, mg / kg 7894 9549 11069 Metals, mg / kg 660 879 1081

[0077] Table 5 Properties of Hydrodechlorinated Oils in Embodiments and Comparative Examples of the Invention

[0078]

[0079] Table 6. Properties of adsorbed and dechlorinated oil in the embodiments and comparative examples of the present invention (organochlorine results)

[0080]

[0081] Table 7 Properties of dechlorinated oils in embodiments and comparative examples of the present invention (organochlorine results)

[0082]

[0083] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for dechlorinating waste plastic pyrolysis oil, characterized in that, Includes the following steps: S1, after removing mechanical impurities from the waste plastic pyrolysis oil, it is washed with water to remove inorganic chlorides, and then separated by oil and water. The resulting oil phase is dried to obtain first-grade dechlorinated waste plastic pyrolysis oil. S2, after mixing the primary dechlorinated waste plastic pyrolysis oil with hydrogen, enters the pre-hydrogenation reactor. Under the action of the pre-hydrogenation catalyst, the dienes in the primary dechlorinated waste plastic pyrolysis oil are converted into monoolefins to obtain pre-hydrogenated waste plastic pyrolysis oil. S3, the pre-hydrogenated waste plastic pyrolysis oil is fractionated into light distillate oil, medium distillate oil and heavy distillate oil; S4 involves reacting light distillate oil with hydrogen under the action of a hydrodechlorination catalyst to remove organochlorides, and the reaction product is separated by gas-liquid separation to obtain hydrodechlorinated cracked oil. S5, medium distillate oil is contacted with an adsorbent to obtain adsorbed dechlorination cracked oil; The pre-hydrogenation catalyst is composed of alumina and one or more oxides of Co, Mo, Ni, and W; The pre-hydrogenation catalyst contains 50% to 80% alumina by mass and 20% to 50% one or more oxides of Co, Mo, Ni, and W. The pre-hydrogenation reaction in step S2 is carried out at a temperature of 135–200 °C, a hydrogen partial pressure of 2–5 MPa, and a volume hourly space velocity of 2–5 h⁻¹. -1 The hydrogen-to-oil volume ratio is 50-500:

1. The hydrodechlorination catalyst has the following mass composition: 40-60% alumina, 10-30% magnesium or phosphorus modified alumina, 0.5-8% molecular sieve, 2-5% nickel oxide or cobalt oxide, and 10-20% molybdenum oxide or tungsten oxide. The hydrodechlorination reaction conditions in step S4 are: reaction temperature 200~350℃, hydrogen partial pressure 3.5~6MPa, and volume hourly space velocity 0.5~2h. -1 The hydrogen-to-oil volume ratio is 300-700:

1.

2. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The total chlorine content of the waste plastic pyrolysis oil is not less than 300 ppm.

3. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The inorganic chlorine content in the primary dechlorinated waste plastic pyrolysis oil is no more than 5 ppm, and the water content is no more than 500 ppm.

4. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The inorganic chlorine content in the primary dechlorinated waste plastic pyrolysis oil is no more than 1 ppm, and the water content is no more than 300 ppm.

5. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The molecular sieve is one or more of modified Y molecular sieve, modified ZSM-5 molecular sieve, and modified 13X molecular sieve.

6. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The Na2O content in the molecular sieve is less than 0.5%.

7. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The adsorbent comprises a support consisting of one or more of modified 13X molecular sieve, NaY molecular sieve, alumina and activated carbon, and a metal oxide supported on the support.

8. The method for dechlorinating waste plastic pyrolysis oil according to claim 7, characterized in that, The metal oxides in the adsorbent include one or more of copper oxide, ferric oxide, magnesium oxide, nickel oxide, cobalt oxide, and zinc oxide.

9. The method for dechlorinating waste plastic pyrolysis oil according to claim 7, characterized in that, The adsorbent contains 65-90% carrier by mass and 10-35% metal oxide by mass.

10. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, The reaction temperature in step S5 is 50~200℃, and the volume hourly space velocity is 0.5~1.5h. -1 The reaction pressure is 0.1~0.8MPa.

11. The method for dechlorinating waste plastic pyrolysis oil according to claim 1, characterized in that, In step S3, the cutoff point between light distillate oil and medium distillate oil is 180~230℃, and the cutoff point between medium distillate oil and heavy distillate oil is 270~360℃.

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