Method for dechlorinating waste plastic pyrolysis oil

Abstract

The invention discloses a waste plastic pyrolysis oil dechlorination method, which comprises: S1, removing mechanical impurities in waste plastic pyrolysis oil, washing to remove inorganic chloride, carrying out oil-water separation, and drying the obtained oil phase to obtain primary dechlorinated waste plastic pyrolysis oil; s2, mixing the primary dechlorinated waste plastic pyrolysis oil with hydrogen, feeding the mixture into a pre-hydrogenation reactor, and converting alkadiene in the primary dechlorinated waste plastic pyrolysis oil into monoolefine under the action of a pre-hydrogenation catalyst 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, the light distillate oil reacts with hydrogen under the action of a hydrodechlorination catalyst to remove organic chlorides, and a reaction product is subjected to gas-liquid separation to obtain hydrodechlorinated pyrolysis oil; and S5, contacting the medium distillate oil with an adsorbent to obtain adsorption dechlorinated pyrolysis oil. The method is high in chlorine removal rate and good in product quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical recycling of waste plastics, and particularly relates to a method for dechlorinating waste plastic pyrolysis oil. Background Art

[0002] Since the early 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 copolymer (ABS), nylon (PA), polylactic acid (PLA), etc. In 2021, the output of plastic products in China was approximately 8×10 7 t, and the usage was approximately 9.088×10 7 t, and the generation amount of waste plastics has increased synchronously with the plastic usage. Improper disposal methods of waste plastics will cause them to gradually accumulate in the environment and form "white pollution". It is estimated that the cumulative waste plastics in the global environment will reach 1.20×10 10 t by 2050. Promoting the recycling technology of waste plastics and converting low-value waste plastics into valuable resources such as pyrolysis oil, while completely realizing the harmlessness and reduction of waste plastics and obtaining products with higher economic benefits, is an important part of the chemical cycle of waste plastics and helps to promote the realization of the carbon neutrality goal. For polyolefin waste plastics mainly composed of PP and PE, domestic and foreign enterprises usually use pyrolysis to convert them into pyrolysis oil, and the pyrolysis oil is used as a raw material for refining enterprises to produce chemical products such as low-carbon olefins. However, the composition of waste plastics is complex, and the existing sorting technology has low accuracy, unable to completely remove chlorine-containing plastics such as PVC in waste plastics. Coupled with the widespread use of halogen-containing plastic additives, the properties of plastic pyrolysis oil are generally poor, and the impurity content is much higher than that of crude oil and its fractionated oils, and it cannot be directly used as a raw material for refining enterprises. Among them, chlorine mainly exists in the form of organic chlorine, which is easy to cause poisoning of the catalysts of existing refining devices and device corrosion. Therefore, the removal of chlorine in waste plastic pyrolysis oil is particularly critical. The pyrolysis products of PVC-containing mixed waste plastics 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 oil and gas, and the pyrolysis products also contain a certain amount of sulfides, which restricts the use of noble metal catalysts with higher dechlorination efficiency. In the existing oil dechlorination technology, the adsorption method has a simple process, but due to the high chlorine content in pyrolysis oil, the adsorbent is extremely easy to reach saturation and difficult to regenerate, and frequent replacement will increase the dechlorination cost; the hydrodechlorination method has a higher dechlorination efficiency, but there are competitive reactions between metals, sulfur, nitrogen and other impurities and chlorides on the catalyst surface, which is not conducive to the removal of chlorides. In addition, the degree of unsaturation of waste plastic pyrolysis oil is relatively high, and a large amount of dienes in pyrolysis oil are likely to cause serious coking of equipment such as heating furnaces and heat exchangers, and greatly affect the use activity and service life of the catalyst.

[0003] Patent CN101899321B discloses a chlorine removal and transfer agent for crude oil and its preparation method. Aiming at the problem of removing organic chlorine in crude oil, a chlorine transfer agent and its preparation method are provided. The chlorine transfer agent is composed of 25 - 40 parts of N,N-dimethylpropylenediamine, 10 - 30 parts of hexadecylamine polyoxyethylene polyoxypropylene ether, 10 - 20 parts of modified β-hydroxyethyltrimethylammonium hydroxide, and 10 - 55 parts of decanol, and can effectively remove the organic chlorine in crude oil that cannot be removed by electro-desalting. This technical solution aims at the problem that only inorganic chlorine can be removed during the electro-desalting process of crude oil, while organic chlorine cannot be removed. Instead, a chlorine transfer agent is used to convert organic chlorine into inorganic chlorine and then transfer it into water, and then the chlorine is removed by combining with the electro-desalting and dehydration process of crude oil. However, the use of amine-containing polyethers will increase the oxygen and nitrogen content in the oil, increasing the process burden of subsequent deoxygenation and denitrification; the chlorine element content in waste plastic pyrolysis oil is much higher than that in crude oil, and the types of chlorides are more complex. This technology is not fully applicable to waste plastic pyrolysis oil, and the dechlorination effect is limited; the price of this phase transfer agent is expensive.

[0004] Patent CN111171865B discloses a method for dechlorinating waste plastic pyrolysis oil. Aiming at the problems of complex dechlorination process and high cost of noble metal catalysts for waste plastic oil, a hydrodechlorination method is provided, which specifically includes: a) reacting waste plastic pyrolysis oil with hydrogen under the action of a hydrocatalyst, and obtaining a hydrogenated product oil after oil-gas separation; b) mixing the hydrogenated product oil obtained in step a) with an adsorbent and performing an adsorption treatment to obtain an oil product after chlorine removal by adsorption; the adsorbent is prepared by compounding activated alumina and a metal element-modified molecular sieve with a mass ratio of 1:(1 - 2). In this technical solution, waste plastic pyrolysis oil first undergoes a hydrotreating reaction over a non-noble metal-supported alumina-based hydrocatalyst to remove impurities such as sulfur, nitrogen, and chlorine, and then the adsorbent is used to achieve deep dechlorination of the whole fraction oil. However, since chlorides are mainly concentrated in the light components, the competitive adsorption of macromolecular hydrocarbons and sulfur and nitrogen compounds in the whole fraction pyrolysis oil and their steric hindrance effects will affect the dechlorination efficiency of the hydrocatalyst, and impurities such as metals and dienes in the pyrolysis oil are likely to cause catalyst poisoning and coking. The dechlorination effect of this method will be restricted during long-term operation.

[0005] Patent CN116426308A discloses a method and device system for producing steam cracking feedstock oil and nano-carbon materials from waste plastics. Aiming at the problems of high content of unsaturated components in liquid hydrocarbons and low utilization efficiency of waste plastic cracking oil, a method for producing steam cracking feedstock oil for ethylene plants from waste plastics is provided. Specifically, it includes: thermally cracking waste plastics to obtain hydrocarbon cracking oil and gas, then separating the hydrocarbon cracking oil and gas into liquid and gas phases to obtain crude cracking oil and cracking gas, further performing decarbonization treatment on the cracking gas to obtain nano-carbon materials, and sequentially subjecting the crude cracking oil to hydrocracking and fractionation to obtain steam cracking feedstock oil for ethylene plants; this technical solution does not remove impurities from waste plastic cracking oil, and problems such as catalyst poisoning, coking, and equipment corrosion are likely to occur during the hydrocracking process.

[0006] Patent CN112547093B discloses a hydrodechlorination catalyst, its preparation method and application. Aiming at the problems of poor conversion rate and selectivity of the hydrodechlorination catalyst, a hydrodechlorination catalyst and its preparation method are provided. Specifically, the catalyst uses activated carbon as a carrier, the content of active metal components is 0.5 - 3%, including Pd and Cu, and the promoter is 0.2 - 2%, including Zn. The prepared catalyst has high activity for the hydrodechlorination reaction of 1,1,2-trichloro-1,2,2-trifluoroethane to produce chlorotrifluoroethylene; in this technical solution, the catalyst is a Pd-based noble metal catalyst, with a high cost, and waste plastic cracking oil also contains impurities such as sulfur, nitrogen, and silicon, which are extremely likely to cause poisoning and deactivation of the noble metal Pd-based catalyst. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for dechlorinating waste plastic cracking oil. The waste plastic cracking oil obtained by the method of the present invention has a high chlorine removal rate, good product quality, and effectively avoids the deficiencies of easy coking, fast catalyst deactivation, and high dechlorination cost during the direct hydrodechlorination reaction of waste plastic cracking oil.

[0008] To achieve the above purpose, the present invention provides a method for dechlorinating waste plastic cracking oil, including the following steps:

[0009] S1, after removing mechanical impurities from waste plastic cracking oil, washing with water to remove inorganic chlorides, and then performing oil-water separation, the obtained oil phase is dried to obtain primary dechlorinated waste plastic cracking oil;

[0010] S2, mixing the primary dechlorinated waste plastic cracking oil with hydrogen and then entering a pre-hydrogenation reactor. Under the action of a pre-hydrogenation catalyst, converting dienes in the primary dechlorinated waste plastic cracking oil into monoolefins to obtain pre-hydrogenated waste plastic cracking oil;

[0011] S3, fractionating the pre-hydrogenated waste plastic cracking oil into light fraction oil, middle fraction oil, and heavy fraction oil;

[0012] S4. React the light distillate oil with hydrogen under the action of a hydrodechlorination catalyst to remove organic chlorides, and separate the reaction products by gas-liquid separation to obtain hydrodechlorination cracked oil;

[0013] S5. Contact the middle distillate oil with an adsorbent to obtain adsorption dechlorination cracked oil.

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

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

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

[0017] In the method for dechlorinating waste plastic cracked oil according to the present invention, the mass content of alumina in the pre-hydrogenation catalyst is 50% - 80%, and the content of one or more oxides of Co, Mo, Ni, and W is 20% - 50%.

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

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

[0020] In the method for dechlorinating waste plastic cracked oil according to the present invention, the molecular sieve is one or more of modified Y molecular sieve, modified ZSM-5 molecular sieve, and modified 13X molecular sieve. The modification in the present invention is acid modification or hydrothermal modification, etc., which are all common modification methods in the technical field of hydrodechlorination catalysts. The present invention does not make specific limitations, and those skilled in the art can select according to actual situations.

[0021] In the method for dechlorinating waste plastic cracked oil according to the present invention, the mass composition of the hydrodechlorination catalyst is: 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] In the method for dechlorinating waste plastic cracked oil according to the present invention, the Na2O content in the molecular sieve is less than 0.5%.

[0023] For the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the hydrodechlorination reaction conditions in step S4 are as follows: the reaction temperature is 200 - 350 °C, the hydrogen partial pressure is 3.5 - 6 MPa, the volume space velocity is 0.5 - 2 h -1 , and the hydrogen-oil volume ratio is 300 - 700:1.

[0024] For the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the adsorbent includes a carrier composed of one or more of modified 13X molecular sieve, NaY molecular sieve, alumina, and activated carbon, and a metal oxide supported on the carrier. The modification in the present invention is acid modification or hydrothermal modification, etc., which are all common modification methods in the technical field of adsorption dechlorination catalysts. The present invention does not make specific limitations, and those skilled in the art can select according to actual situations.

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

[0026] For the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the mass content of the carrier in the adsorbent is 65 - 90%, and the mass content of the metal oxide is 10 - 35%.

[0027] For the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the reaction temperature in step S4 is 50 - 200 °C, the volume space velocity is 0.5 - 1.5 h -1 , and the reaction pressure is 0.1 - 0.8 MPa.

[0028] For the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the cut-off point between the light distillate oil and the middle distillate oil in step S3 is 180 - 230 °C, and the cut-off point between the middle distillate oil and the heavy distillate oil is 270 - 360 °C.

[0029] In the method for dechlorination of waste plastic pyrolysis oil according to the present invention, the heavy distillate oil obtained in step S3 can be used as a feedstock for refinery hydrocracking, catalytic cracking, or delayed coking; the hydrodechlorination pyrolysis oil obtained can be used as a feedstock for steam cracking to produce ethylene or reforming to produce aromatics; the adsorption dechlorination pyrolysis oil obtained can be used as a feedstock for diesel hydrofining or wax oil hydrofining.

[0030] Advantages of the present invention:

[0031] Under the action of the pre-hydrogenation catalyst, the diolefins in the oil react with hydrogen to be converted into monoolefins, reducing the content of diolefins in the waste plastic pyrolysis oil, effectively avoiding the condensation of diolefins, reducing the generation of carbon deposition, being beneficial to reducing the coverage of the active sites of the catalyst by carbon deposition during hydrodechlorination, prolonging the service life of the hydrodechlorination catalyst, and also being beneficial to reducing the coking rate of the heating furnace and heat exchanger.

[0032] Since the organic chlorine in waste plastic pyrolysis oil is mainly concentrated in the fractions with a boiling point below 230°C, the organic chlorine content in the heavy fractions above 350°C is very low, while metal impurities such as iron and calcium are mainly enriched in the heavy fractions. In addition, the contents of impurities such as sulfur and nitrogen in the middle and heavy fractions are also higher than those in the light fractions. If the whole-fraction waste plastic pyrolysis oil is directly subjected to hydrodechlorination, the macromolecular hydrocarbons and sulfur and nitrogen compounds in the middle and heavy fractions will compete for adsorption with small-molecule chlorides, affecting the removal effect of organic chlorine. At the same time, the polycyclic aromatic hydrocarbons and metal impurities in the heavy fractions are likely to cover or poison the active sites of the hydrodechlorination catalyst, reducing the catalyst activity. Before the removal of organic chlorine, the waste plastic pyrolysis oil is fractionated into light, middle, and heavy fraction oils in the present invention. For the light fraction with a high organic chlorine content, a hydrodechlorination method is adopted. For the middle fraction oil with a relatively low organic chlorine content, an adsorption dechlorination method is adopted. For the heavy fraction oil with an extremely low organic chlorine content, which meets the feed requirements of the heavy oil processing unit, it is directly blended without dechlorination. Therefore, the application of the technical solution of the present invention can, on the one hand, avoid the influence of the middle and heavy fraction oil molecules on the catalyst activity and service life during the hydrodechlorination of the whole fraction, and on the other hand, only perform hydrodechlorination on the light fraction and adopt an adsorption dechlorination method for the middle fraction oil with a relatively low organic chlorine content, which can improve the overall removal efficiency of organic chlorine and reduce the operation cost. Specific Embodiments

[0033] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

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

[0035] After filtering the waste plastic pyrolysis oil raw material to remove mechanical impurities, wash it with water to remove inorganic chlorides in the oil product, then perform oil-water separation in a separation tank, and subject the separated oil product to adsorption drying treatment in a drying tower to obtain primary dechlorinated waste plastic pyrolysis oil; react the obtained primary dechlorinated waste plastic pyrolysis oil with hydrogen under the action of a pre-hydrogenation catalyst, and fractionate the product into light fraction oil, middle fraction oil and heavy fraction oil; then react the obtained light fraction oil with hydrogen under the action of a hydrodechlorination catalyst to obtain hydrodechlorinated fraction oil; contact and react the obtained middle fraction oil with an adsorbent to obtain adsorption dechlorinated fraction oil. The properties of the primary dechlorinated waste plastic pyrolysis oil are shown in Table 1, and the properties of the light, middle and heavy fraction oils after pre-hydrogenation are shown in Tables 2, 3 and 4 respectively, the properties of the hydrodechlorinated fraction oil are shown in Table 5, and the properties of the adsorption dechlorinated fraction oil are shown in Table 6. In the examples, the preparation of various catalysts is the conventional supported catalyst preparation method, that is, after the carrier is formed, the corresponding metal salt solution is impregnated on the carrier to obtain it.

[0036] Table 1 Properties of pyrolysis oil raw material, primary dechlorinated pyrolysis oil and pre-hydrogenated pyrolysis oil

[0037]

[0038] Example 1:

[0039] Composition of pre-hydrogenation catalyst: 80% alumina, 15% nickel oxide, 5% molybdenum oxide.

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

[0041] Cut-off point of light and middle fraction oils is 185 °C, cut-off point of middle and heavy fraction oils is 280 °C.

[0042] Mass composition of hydrodechlorination catalyst: 48% alumina, 28% phosphorus-modified alumina, 4% hydrothermally modified ZSM-5 molecular sieve (containing 0.4% Na2O), 4.5% cobalt oxide, 15.5% molybdenum oxide.

[0043] Hydrodechlorination reaction process conditions: reaction temperature 240 °C, hydrogen partial pressure 3.6 MPa, volume space velocity 0.6 h -1 , hydrogen-oil ratio 300:1 (V:V).

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

[0045] Adsorption dechlorination reaction process conditions are: reaction temperature 60 °C, volume space velocity 0.6 h -1 , reaction pressure 0.7 MPa.

[0046] Example 2:

[0047] The composition of the pre-hydrogenation catalyst: 65% alumina, 15% nickel oxide, 10% cobalt oxide, 10% molybdenum oxide.

[0048] The process conditions for the pre-hydrogenation reaction: reaction temperature 180 °C, hydrogen partial pressure 4.5 MPa, volume space velocity 2.5 h -1 , hydrogen-oil ratio 480:1 (V:V).

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

[0050] The mass composition of the hydrodechlorination catalyst is: 50% alumina, 25% magnesium-modified alumina, 2% acid-modified Y zeolite (containing 0.3% Na2O), 5% cobalt oxide, 18% tungsten oxide.

[0051] The process conditions for the hydrodechlorination reaction: reaction temperature 285 °C, hydrogen partial pressure 5 MPa, volume space velocity 1.0 h -1 , hydrogen-oil ratio 600:1 (V:V).

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

[0053] The process conditions for the adsorption dechlorination reaction are: reaction temperature 150 °C, volume space velocity 0.8 h -1 , reaction pressure 0.5 MPa.

[0054] Example 3:

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

[0056] The process conditions for the pre-hydrogenation reaction: reaction temperature 160 °C, hydrogen partial pressure 3.0 MPa, volume space velocity 4.5 h -1 , hydrogen-oil ratio 300:1 (V:V).

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

[0058] The mass composition of the hydrodechlorination catalyst is: 42% alumina, 30% phosphorus-modified alumina, 8% hydrothermally modified 13X zeolite (containing 0.4% Na2O), 5% nickel oxide, 15% tungsten oxide.

[0059] The process conditions for the hydrodechlorination reaction: reaction temperature 330 °C, hydrogen partial pressure 5.8 MPa, volume space velocity 1.5 h -1 , hydrogen-oil ratio 650:1 (V:V).

[0060] The mass composition of the adsorption dechlorination catalyst is as follows: 90% alumina, 5% nickel oxide, and 5% cobalt oxide.

[0061] The process conditions for the adsorption dechlorination reaction are as follows: reaction temperature 200 °C, volume space velocity 1.2 h -1 , and reaction pressure 0.3 MPa.

[0062] Comparative Example 1:

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

[0064] Comparative Example 2:

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

[0066] Comparative Example 3:

[0067] The waste plastic pyrolysis oil raw material identical to that in the example was subjected to the same water washing, separation, and drying processes as in the example 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 without fractionation, directly subjected to hydrodechlorination, and the hydrodechlorination process was the same as in Example 1 to obtain waste plastic pyrolysis oil with organic chlorine removed, and its properties are shown in Table 5.

[0068] Comparative Example 4:

[0069] The waste plastic pyrolysis oil raw material identical to that in the example was subjected to the same water washing, separation, and drying processes as in the example to obtain waste plastic pyrolysis oil with inorganic chlorine removed; the obtained waste plastic pyrolysis oil was not pre-hydrogenated and directly fractionated under the same conditions as in Example 1. The light components were subjected to hydrodechlorination, and the middle distillates were 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, and their properties are shown in Table 7.

[0070] Table 2 Properties of light distillate oil in the examples of the present invention

[0071] Project 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 Metal, mg / kg 12 14 22

[0072] Table 3 Properties of middle distillate oil in the examples of the present invention

[0073]

[0074]

[0075] Table 4 Properties of heavy distillate oil in the examples of the present invention

[0076] Project 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 Metal, mg / kg 660 879 1081

[0077] Table 5 Properties of hydrodechlorinated oils in the examples and comparative examples of the present invention

[0078]

[0079] Table 6 Properties of adsorptive dechlorinated oils in the examples and comparative examples of the present invention (organic chlorine results)

[0080]

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

[0082]

[0083] Of course, the present invention may also have many other 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 dechlorination of waste plastic pyrolysis oil, characterized in that, it comprises the following steps: S1, after removing mechanical impurities from the waste plastic pyrolysis oil, washing with water to remove inorganic chlorides, and then performing oil-water separation, the obtained oil phase is dried to obtain primary dechlorinated waste plastic pyrolysis oil; S2, mixing the primary dechlorinated waste plastic pyrolysis oil with hydrogen and then entering a pre-hydrogenation reactor, and under the action of a pre-hydrogenation catalyst, converting dienes in the primary dechlorinated waste plastic pyrolysis oil into mono-olefins to obtain pre-hydrogenated waste plastic pyrolysis oil; S3, fractionating the pre-hydrogenated waste plastic pyrolysis oil into light fraction oil, middle fraction oil and heavy fraction oil; S4, reacting the light fraction oil with hydrogen under the action of a hydrodechlorination catalyst to remove organic chlorides, and the reaction product is subjected to gas-liquid separation to obtain hydrodechlorinated pyrolysis oil; S5, contacting the middle fraction oil with an adsorbent to obtain adsorption dechlorinated pyrolysis oil.

2. The method for dechlorination of 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 dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, the inorganic chlorine content in the primary dechlorinated waste plastic pyrolysis oil is not more than 5 ppm, preferably not more than 1 ppm, and the water content is not more than 500 ppm, preferably not more than 300 ppm.

4. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, the pre-hydrogenation catalyst is composed of alumina and one or more oxides of Co, Mo, Ni, and W.

5. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, the mass content of alumina in the pre-hydrogenation catalyst is 50% - 80%, and the content of one or more oxides of Co, Mo, Ni, and W is 20% - 50%.

6. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, In step S2, the reaction temperature of the pre-hydrogenation reaction is 135 to 200 °C, the hydrogen partial pressure is 2 to 5 MPa, the volume hourly space velocity is 2 to 5 h -1 , and the hydrogen-oil volume ratio is 50 to 500:

1.

7. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, the hydrodechlorination catalyst comprises alumina, magnesium or phosphorus modified alumina, molecular sieve, nickel oxide or cobalt oxide, molybdenum oxide or tungsten oxide.

8. The method for dechlorination of waste plastic pyrolysis oil according to claim 7, 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.

9. The method for dechlorination of waste plastic pyrolysis oil according to claim 7, characterized in that, the mass composition of the hydrodechlorination catalyst is: 40 - 60% alumina, 10 - 30% magnesium or phosphorus modified alumina, 0.5 - 8% molecular sieve, 2 - 5% nickel oxide or cobalt oxide, 10 - 20% molybdenum oxide or tungsten oxide.

10. The method for dechlorination of waste plastic pyrolysis oil according to claim 7, characterized in that, the Na2O content in the molecular sieve is less than 0.5%.

11. The method for dechlorination of waste plastic pyrolysis oil according to claim 7, characterized in that, The hydrodechlorination reaction conditions in step S4 are as follows: reaction temperature is 200 - 350 °C, hydrogen partial pressure is 3.5 - 6 MPa, volumetric space velocity is 0.5 - 2 h -1 , and hydrogen - to - oil volume ratio is 300 - 700:

1.

12. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that, The adsorbent includes a carrier composed of one or more of modified 13X molecular sieve, NaY molecular sieve, alumina, and activated carbon, and a metal oxide supported on the carrier.

13. The method for dechlorination of waste plastic pyrolysis oil according to claim 12, characterized in that the metal oxide in the adsorbent includes one or more of copper oxide, ferric oxide, magnesium oxide, nickel oxide, cobalt oxide, and zinc oxide.

14. The method for dechlorination of waste plastic pyrolysis oil according to claim 12, characterized in that the mass content of the carrier in the adsorbent is 65-90%, and the mass content of the metal oxide is 10-35%.

15. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that The reaction temperature in step S4 is 50 to 200 °C, the volume space velocity is 0.5 to 1.5 h -1 , and the reaction pressure is 0.1 to 0.8 MPa.

16. The method for dechlorination of waste plastic pyrolysis oil according to claim 1, characterized in that in step S3, the cut-off point between the light fraction oil and the middle fraction oil is 180-230 °C, and the cut-off point between the middle fraction oil and the heavy fraction oil is 270-360 °C.

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