Method for treating chlorine-containing plastic oil

Abstract

The invention relates to the field of recycling of waste plastic oil, and discloses a method for treating chlorine-containing plastic oil. The method comprises the following steps: contacting chlorine-containing plastic oil with sodium methoxide and H2O2 for a first reaction, then contacting the obtained reaction product with water and a demulsifier for mixing, and then carrying out first oil-water separation on the obtained mixture to obtain an oil phase; and in the presence of a palladium-carbon catalyst, contacting the oil phase with a hydrogen donor and alkali liquor, blowing H2 to carry out a second reaction, and then carrying out second oil-water separation on the obtained reaction product. According to the method for treating the chlorine-containing plastic oil, the dechlorination effect can be guaranteed, on one hand, the problem of high cost of catalytic hydrodechlorination is solved, on the other hand, the operation safety is improved, additional high-temperature and high-pressure hydrogenation devices and dechlorination devices are not needed, and under the preferable condition, low-temperature and low-pressure operation is adopted, so that the reaction conditions are milder.

Description

Technical Field

[0001] The invention relates to the field of recycling of waste plastic oil, and in particular to a method for treating chlorine-containing plastic oil. Background Art

[0003] Common waste plastics include: polyethylene terephthalate (PET), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), polycarbonate (PC), polylactic acid (PA), nylon (Nylon), fiberglass reinforced plastics (FRP), and polylactic acid film (BOPLA).

[0004] Waste plastics can be converted into recycled oil under high temperature or catalyst, called plastic oil or waste plastic oil. Plastic oil can be used as fuel or chemical raw material, or it can be converted into high value-added products such as diesel, low-carbon olefins and high-octane gasoline under appropriate process conditions. Preparing plastic oil from waste plastics and then using plastic oil as raw material to make high value-added products can achieve chemical recycling of waste plastics. It is a promising technology that has received widespread attention at home and abroad.

[0005] The methods for cracking and oiling waste plastics include: thermal cracking, catalytic cracking, thermal cracking-catalytic modification, catalytic cracking-catalytic modification, etc. The catalysts used include solid acid catalysts, alkali metal catalysts (such as CaO, BaO, Al2O3), molecular sieves (ZSM-5), etc.

[0006] Due to the large variety of waste plastics and the large number of additives contained in waste plastics, the impurity content in plastic oil is generally high, and the main impurities include chlorine and metals.

[0007] The chlorine in plastic oil will have a relatively large impact on subsequent processing. The chlorine in plastic oil mainly comes from HCl released by the decomposition of PVC. It has been reported in the literature that PVC begins to dechlorinate at 200°C and completes dechlorination before 350°C. HCl can add to other olefins or alkyne compounds produced by cracking to form chlorinated alkanes or chlorinated olefin compounds. HCl can react with PET decomposition products to form chlorinated ester compounds. Chlorinated hydrocarbon compounds and ester compounds will release HCl again during the processing of plastic oil, causing corrosion and salt formation of equipment. Therefore, the technology of many plastic oil companies has strict requirements on the content of PVC and PET in waste plastic raw materials. However, due to the wide source of waste plastics and the difficulty of sorting, the actual prepared plastic oil still has the problem of excessive chlorine content. For example, the chlorine content of plastic oil produced by some companies is 0.25%-0.48%, which has a great impact on subsequent processing, resulting in equipment corrosion and catalyst poisoning when processing plastic oil.

[0008] At present, the main methods for removing organic chlorine include catalytic hydrogenation, advanced oxidation, metal reduction, nucleophilic substitution, electrochemical dechlorination and biological dechlorination, etc. Among these methods, the catalytic hydrogenation method has the highest dechlorination efficiency (greater than 90%), while the other methods have a relatively low chlorine removal rate (less than 40%).

[0009] The catalytic hydrogenation method is that hydrogen and organic chloride generate HCl and corresponding hydrocarbons on the surface of the catalyst. CN104492480A and CN111171865A disclose catalytic hydrodechlorination methods, but the reaction temperature in the existing methods is greater than 300°C, the reaction pressure is greater than 2.5MPa, and high-temperature and high-pressure equipment is required, and the equipment investment and operating costs are relatively high. In addition, the HCl produced by catalytic hydrodechlorination will cause equipment corrosion, seriously affecting operational safety.

[0010] Although CN1800310A and CN1095388A disclose a catalytic reforming regeneration gas dechlorinating agent and a preparation method thereof, the dechlorinating agent contains the following chemical raw materials in mass percentage: Ca(OH)2 or CaO 30%-60%, MgCO3 or MgO 20%-30%, K2CO3 or KOH 10%-15%; porous zeolite or silica-alumina clay 5%-15%, aluminum colloid powder or silica sol 5%-15%, and the sum of the raw materials is 100%. However, adding the dechlorinating agent during the catalytic hydrogenation dechlorination process still cannot guarantee 100% removal of the generated HCl, and therefore the operation safety cannot be guaranteed.

[0011] Although the catalytic hydrogenation method can remove organic chlorine compounds with high efficiency, on the one hand, the equipment investment and operating costs are high, and on the other hand, it cannot solve the safety problems caused by HCl corrosion under high temperature and high pressure. Summary of the invention

[0012] The purpose of the present invention is to overcome the problems of the existing organic chlorine removal method that the dechlorination effect needs to be improved, an additional hydrogenation device and a dechlorination device are required, the cost is high and the safety is poor.

[0013] In order to achieve the above object, the present invention provides a method for treating chlorine-containing plastic oil, the method comprising the following steps:

[0014] (1) contacting the chlorine-containing plastic oil with sodium methoxide and H2O2 to carry out a first reaction, then contacting the obtained reaction product with water and a demulsifier to mix them, and then performing a first oil-water separation on the obtained mixture to obtain an oil phase;

[0015] (2) In the presence of a palladium-carbon catalyst, the oil phase is contacted with a hydrogen donor and an alkaline solution, and H2 is blown into the mixture to carry out a second reaction, and then the obtained reaction product is subjected to a second oil-water separation.

[0016] Through the above technical scheme, the method provided by the present invention treats chlorine-containing plastic oil, which can solve the problem of high cost of catalytic hydrogenation dechlorination while ensuring the dechlorination effect, and improve the safety of operation on the other hand, without the need for additional hydrogenation equipment and dechlorination equipment, and in a preferred case, adopts low temperature and low pressure operation, and the reaction conditions are milder. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] In the present invention, unless otherwise specified, the room temperature refers to 25±2°C.

[0019] In the present invention, unless otherwise stated, the pressures described are gauge pressures.

[0020] In the present invention, unless otherwise specified, normal pressure refers to 0.1013 MPa.

[0021] As mentioned above, the present invention provides a method for treating chlorine-containing plastic oil, the method comprising the following steps:

[0022] (1) contacting the chlorine-containing plastic oil with sodium methoxide and H2O2 to carry out a first reaction, then contacting the obtained reaction product with water and a demulsifier to mix them, and then performing a first oil-water separation on the obtained mixture to obtain an oil phase;

[0023] (2) In the presence of a palladium-carbon catalyst, the oil phase is contacted with a hydrogen donor and an alkaline solution, and H2 is blown into the mixture to carry out a second reaction, and then the obtained reaction product is subjected to a second oil-water separation.

[0024] According to some embodiments of the present invention, preferably, in step (1), the sodium methoxide is provided in the form of a sodium methoxide methanol solution. Preferably, in the sodium methoxide methanol solution, the mass ratio of sodium methoxide to methanol is 0.5-1.5:1, preferably 0.8-1.2:1.

[0025] According to some embodiments of the present invention, preferably, in step (1), the mass ratio of the sodium methoxide to the H2O2 is 1-10:1, preferably 2.5-5:1.

[0026] According to some embodiments of the present invention, preferably, in step (1), the mass ratio of the chlorine-containing plastic oil to the sodium methoxide is 100:0.1-15, preferably 100:2.5-10.

[0027] According to some embodiments of the present invention, preferably, in step (1), the conditions of the first reaction include: reaction temperature of 70-120°C, preferably 80-110°C; reaction time of 1-5h, preferably 1-3h.

[0028] According to some embodiments of the present invention, preferably, in step (1), after the first reaction, the obtained reaction product is first cooled, and then contacted with water and a demulsifier for the mixing.

[0029] According to some embodiments of the present invention, preferably, in step (1), the mass ratio of the water to the chlorine-containing plastic oil is 1-2:1, preferably 1-1.5:1.

[0030] According to some embodiments of the present invention, preferably, in step (1), the demulsifier is at least one of fatty alcohol polyoxypropylene polyoxyethylene ether, polyol polyoxypropylene polyoxyethylene ether, polyethylene polyamine polyoxypropylene polyoxyethylene ether, alkylphenol polyoxypropylene polyoxyethylene ether and alkylphenol amine polyoxypropylene polyoxyethylene ether.

[0031] According to some embodiments of the present invention, preferably, in step (1), the amount of the demulsifier used is 50-200 μg, preferably 100-150 μg, relative to 1 g of the chlorine-containing plastic oil.

[0032] According to some embodiments of the present invention, preferably, in step (1), the first oil-water separation method is centrifugal separation, and the conditions of the centrifugal separation include: a centrifugal speed of 1500-2000 rpm and a centrifugal time of 5-20 min.

[0033] According to some embodiments of the present invention, preferably, in step (2), the content of Pd in ​​the palladium-carbon catalyst is 5-20 wt%, preferably 7-15 wt%.

[0034] According to some embodiments of the present invention, preferably, in step (2), the method for preparing the palladium-carbon catalyst comprises: contacting the activated carbon with an aqueous solution of palladium chloride salt for impregnation, and then contacting the obtained impregnation product with KBH4 for reduction.

[0035] Preferably, before the impregnation, the activated carbon is first subjected to an acidification treatment. The acidification treatment comprises: mixing the activated carbon with an HNO3 aqueous solution.

[0036] Preferably, the method further comprises: washing the product obtained by the acidification treatment with deionized water until it is neutral, and drying the washed product to remove residual moisture. The washing and drying operations and conditions can be carried out with reference to the prior art and are not particularly limited.

[0037] According to some embodiments of the present invention, preferably, the conditions of the acidification treatment include: a temperature of 30-50° C. and a time of 1-5 h.

[0038] According to some embodiments of the present invention, preferably, the immersion conditions include: a temperature of 40-60° C. and a time of 1-2 h.

[0039] According to some embodiments of the present invention, preferably, the obtained impregnation product is first cooled to room temperature and then contacted with KBH4. Preferably, the contacting method includes: placing the cooled impregnation product in an ice water bath, adding KBH4 aqueous solution dropwise while stirring, controlling the dropping speed to maintain the system temperature at the reduction temperature, and adding until no bubbles are generated.

[0040] According to some embodiments of the present invention, preferably, the reduction temperature is 0°C±1°C.

[0041] According to some embodiments of the present invention, preferably, after the reduction is completed, the obtained reduction product is filtered, washed and dried in sequence. The operations and conditions of filtering, washing and drying can be carried out with reference to the prior art and there is no particular limitation on this.

[0042] According to some embodiments of the present invention, preferably, in step (2), the mass ratio of the oil phase to the palladium-carbon catalyst is 120:1-2.

[0043] According to some embodiments of the present invention, preferably, in step (2), the hydrogen donor is at least one of formates, phosphites, hydrazine, alcohols and metal hydrides.

[0044] According to some embodiments of the present invention, preferably, in step (2), the mass ratio of the oil phase to the hydrogen donor is 120:0.1-5, preferably 120:0.2-2.

[0045] According to some embodiments of the present invention, preferably, in step (2), the alkali solution is a NaOH aqueous solution, and the concentration of the alkali solution is 0.1-2 wt%, preferably 0.2-1 wt%.

[0046] According to some embodiments of the present invention, preferably, in step (2), the mass ratio of the oil phase to the alkali solution is 1:0.5-1.5.

[0047] According to some embodiments of the present invention, in step (2), H2 is bubbled in during the reaction, preferably, the flow rate of H2 bubbles is 5-15 mL / min.

[0048] According to some embodiments of the present invention, preferably, in step (2), the conditions of the second reaction include: reaction temperature of 70-150°C, preferably 70-130°C; reaction time of 0.5-5h, preferably 1-3h; reaction pressure less than 1MPa, preferably normal pressure-0.8MPa.

[0049] According to some embodiments of the present invention, preferably, the chlorine content of the chlorine-containing plastic oil is 200-4000 μg / g.

[0050] The present invention will be described in detail below through examples.

[0051] In the following examples and comparative examples, unless otherwise specified, all raw materials used are commercially available.

[0052] Activated carbon was purchased from Sinopharm Group, 80-100 mesh;

[0053] PdCl2 solution was purchased from Suzhou Jinwo Chemical Co., Ltd., Pd ≥ 59.5wt%;

[0054] Demulsifier, purchased from Beijing Linhua Water Stabilizer Factory, model RP-2;

[0055] 98wt% hydrazine hydrate, Inokane reagent;

[0056] The properties of chlorine-containing plastic oil are shown in Table 1, and the composition of its chlorine-containing compounds is shown in Table 2:

[0057] Table 1

[0058] project Crude Oil A Crude oil B <![CDATA[Density (20 °C) / (kg / m 3 )]]> 863.4 811.2 Oxygen mass fraction / % 3.4 3.68 Fe / (μg / g) 9.3 20 Ca / (μg / g) 0.2 ＜0.1 Na / (μg / g) ＜0.1 1 <![CDATA[Total chlorine (calculated as Cl - ) / wt%]]> 0.17 0.37 Total acid value / (mgKOH / g) 20.11 11

[0059] Table 2

[0060]

[0061] The following preparation examples are used to illustrate the palladium-carbon catalyst provided by the present invention and its preparation method

[0062] Preparation Example 1

[0063] (1) 2 g of activated carbon is contacted with a 1 wt % HNO3 aqueous solution for acidification, and the acidification product is washed with deionized water until it is neutral, and the washed product is dried to obtain an activated carbon carrier; wherein: the acidification conditions are: temperature 40°C, time 4h; drying temperature 100°C;

[0064] (2) 2 g of the above-mentioned activated carbon support was mixed with 14 mL of PdCl2 solution (Pd mass concentration 25 mg / mL) for impregnation, and then the obtained impregnation product was allowed to stand and cool to room temperature, and then contacted with KBH4 (which was provided in the form of KBH4 aqueous solution with a concentration of 2 mol / L) for reduction; wherein:

[0065] The immersion conditions were: temperature 50°C, time 2 h;

[0066] The contact method is as follows: the impregnation product after cooling is placed in an ice water bath, and the KBH4 aqueous solution is added dropwise while stirring, the dropping speed is controlled so that the system temperature is maintained at about 0°C, and the addition is continued until no bubbles are generated;

[0067] After the reduction was completed, the obtained reduction product was filtered, and then washed once with distilled water and anhydrous ethanol respectively, and then the washed product was dried in vacuum for 24 hours to obtain a Pd / C catalyst with a Pd content of 15 wt%.

[0068] Preparation Example 2

[0069] The method of Preparation Example 1 is followed, except that in step (2), the Pd mass concentration of the PdCl2 solution is 12.5 mg / mL, and a Pd / C catalyst with a Pd content of 7 wt% is obtained.

[0070] The following examples are used to illustrate the method for treating chlorine-containing plastic oil provided by the present invention.

[0071] Example 1

[0072] (1) 100 g of chlorine-containing plastic oil is contacted with 2.5 g of sodium methoxide (the mass ratio of chlorine-containing plastic oil to sodium methoxide is 100:2.5) (provided in the form of sodium methoxide methanol solution with a concentration of 50 wt%) and 0.5 g of H2O2 (provided in the form of a 30 wt% aqueous solution) to carry out a first reaction (the mass ratio of sodium methoxide to H2O2 is 5:1), then the obtained reaction product is contacted with water and a demulsifier to mix, and then the obtained mixture is subjected to a first oil-water separation to obtain an oil phase; wherein:

[0073] The chlorine-containing plastic oil is raw material oil A; the water is deionized water; the demulsifier is RP-2 demulsifier;

[0074] The conditions of the first reaction were: reaction temperature of 100°C and reaction time of 3 h;

[0075] After the first reaction, the obtained reaction product is first cooled to 90°C, and then contacted with water and a demulsifier for mixing;

[0076] The mass ratio of water to chlorinated plastic oil is 1:1;

[0077] Relative to 1g of chlorine-containing plastic oil, the dosage of demulsifier is 150μg;

[0078] The mixing time is 0.5h; the first oil-water separation method is centrifugal separation, and the conditions for centrifugal separation are: centrifugal speed is 1700rpm, and the centrifugal time is 10min;

[0079] (2) in the presence of a palladium-carbon catalyst, 12 g of the oil phase is contacted with a hydrogen donor and an alkali solution to carry out a second reaction, and then the obtained reaction product is subjected to a second oil-water separation to obtain a treated plastic oil; wherein:

[0080] The palladium carbon catalyst is the Pd / C catalyst obtained in Preparation Example 1;

[0081] The mass ratio of the oil phase to the palladium carbon catalyst is 120:1;

[0082] The hydrogen donor is N2H4 (provided in the form of 98 wt% hydrazine hydrate);

[0083] The mass ratio of the oil phase to the hydrogen donor is 120:1;

[0084] The alkali solution is a NaOH aqueous solution (concentration is 0.24wt%);

[0085] The mass ratio of the oil phase to the alkali solution is 1:1;

[0086] The conditions of the second reaction were: reaction temperature of 70°C, reaction time of 1 h, and reaction pressure of normal pressure; H2 bubbles were continuously introduced during the reaction at a flow rate of 10 mL / min;

[0087] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0088] Example 2

[0089] The method of Example 1 is different from that of Example 1:

[0090] In step (1), the mass ratio of sodium methoxide to H2O2 is 2.5:1, the ratio of chlorine-containing plastic oil to sodium methoxide is 100:2.5; the rest are the same, and an oil phase is obtained;

[0091] In step (2), the reaction temperature of the second reaction is 80° C., the mass ratio of the oil phase to the palladium carbon catalyst is 120:1; the rest are the same, and the treated plastic oil is obtained;

[0092] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0093] Example 3

[0094] The method of Example 1 is different from that of Example 1:

[0095] In step (1), the mass ratio of sodium methoxide to H2O2 is 5:1, the mass ratio of chlorine-containing plastic oil to sodium methoxide is 100:5, and the rest are the same, to obtain an oil phase;

[0096] In step (2), the reaction temperature of the second reaction is 90° C., the mass ratio of the oil phase to the palladium carbon catalyst is 120:1; the rest are the same, and the treated plastic oil is obtained;

[0097] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0098] Example 4

[0099] The method of Example 1 is different from that of Example 1:

[0100] In step (1), the mass ratio of sodium methoxide to H2O2 is 2.5:1; the mass ratio of chlorine-containing plastic oil to sodium methoxide is 100:5; and the rest are the same to obtain an oil phase;

[0101] In step (2), the reaction temperature of the second reaction is 70° C., the mass ratio of the oil phase to the palladium carbon catalyst is 120:2; the rest are the same, and the treated plastic oil is obtained;

[0102] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0103] Example 5

[0104] The method of Example 1 is different from that of Example 1:

[0105] In step (1), the mass ratio of sodium methoxide to H2O2 is 5:1; the mass ratio of chlorine-containing plastic oil to sodium methoxide is 100:10; and the rest are the same to obtain an oil phase;

[0106] In step (2), the reaction temperature of the second reaction is 80° C., the mass ratio of the oil phase to the palladium carbon catalyst is 120:2; the rest are the same, and the treated plastic oil is obtained;

[0107] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0108] Example 6

[0109] The method of Example 1 is different from that of Example 1:

[0110] In step (1), the mass ratio of sodium methoxide to H2O2 is 2.5:1; the mass ratio of chlorine-containing plastic oil to sodium methoxide is 100:10; and the rest are the same to obtain an oil phase;

[0111] In step (2), the reaction temperature of the second reaction is 90° C., the mass ratio of the oil phase to the palladium carbon catalyst is 120:2; the rest are the same, and the treated plastic oil is obtained;

[0112] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0113] Example 7

[0114] The method of Example 1 is followed, except that in step (2), the palladium carbon catalyst is the Pd / C catalyst obtained in Preparation Example 2, and the rest are the same;

[0115] The total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively. The results are shown in Table 3.

[0116] Example 8

[0117] The method of Example 1 is followed, except that the chlorine-containing plastic oil is raw oil B, and the rest are the same; the total chlorine content of the obtained oil phase and the treated plastic oil is analyzed respectively, and the results are shown in Table 3.

[0118] Comparative Example 1

[0119] The method of Example 1 was followed, except that sodium methoxide was replaced by NaOH, and the rest was the same; the total chlorine content of the obtained oil phase and the treated plastic oil was analyzed respectively, and the results are shown in Table 3.

[0120] Table 3

[0121]

[0122]

[0123] It can be seen from the above results that the method provided by the present invention for treating chlorine-containing plastic oil has a good dechlorination effect, does not require additional hydrogenation equipment and dechlorination equipment, and has low cost.

[0124] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for treating chlorine-containing plastic oil, characterized in that: The method comprises the following steps: (1) contacting the chlorine-containing plastic oil with sodium methoxide and H2O2 to carry out a first reaction, then contacting the obtained reaction product with water and a demulsifier to mix them, and then performing a first oil-water separation on the obtained mixture to obtain an oil phase; (2) In the presence of a palladium-carbon catalyst, the oil phase is contacted with a hydrogen donor and an alkaline solution, and H2 is blown into the mixture to carry out a second reaction, and then the obtained reaction product is subjected to a second oil-water separation.

2. The method according to claim 1, wherein: In step (1), the sodium methoxide is provided in the form of a sodium methoxide methanol solution; in the sodium methoxide methanol solution, the mass ratio of sodium methoxide to methanol is 0.5-1.5:1, preferably 0.8-1.2:1; Preferably, in step (1), the mass ratio of the sodium methoxide to the H2O2 is 1-10:1, preferably 2.5-5:1; Preferably, in step (1), the mass ratio of the chlorine-containing plastic oil to the sodium methoxide is 100:0.1-15, preferably 100:2.5-10.

3. The method according to claim 1 or 2, wherein: In step (1), the conditions of the first reaction include: reaction temperature of 70-120° C., preferably 80-110° C.; reaction time of 1-5 h, preferably 1-3 h.

4. The method according to any one of claims 1 to 3, wherein: In step (1), the mass ratio of the water to the chlorine-containing plastic oil is 1-2:1, preferably 1-1.5:1; Preferably, the demulsifier is at least one of fatty alcohol polyoxypropylene polyoxyethylene ether, polyol polyoxypropylene polyoxyethylene ether, polyethylene polyamine polyoxypropylene polyoxyethylene ether, alkylphenol polyoxypropylene polyoxyethylene ether and alkylphenol amine polyoxypropylene polyoxyethylene ether; Preferably, the amount of the demulsifier used is 50-200 μg, preferably 100-150 μg, relative to 1 g of the chlorine-containing plastic oil.

5. The method according to any one of claims 1 to 4, wherein: In step (2), the content of Pd in ​​the palladium-carbon catalyst is 5-20wt%, preferably 7-15wt%; Preferably, the preparation method of the palladium-carbon catalyst comprises: contacting the activated carbon with a palladium chloride salt aqueous solution for impregnation, and then contacting the obtained impregnation product with KBH4 for reduction; Preferably, before the impregnation, the activated carbon is first subjected to an acidification treatment.

6. The method according to claim 5, wherein: The conditions of the acidification treatment include: temperature of 30-50°C and time of 1-5h; Preferably, the immersion conditions include: temperature of 40-60°C and time of 1-2h; Preferably, the reduction temperature is 0°C±1°C.

7. The method according to any one of claims 1 to 6, wherein: In step (2), the mass ratio of the oil phase to the palladium carbon catalyst is 120:1-2; Preferably, in step (2), the hydrogen donor is at least one of formates, phosphites, hydrazine, alcohols and metal hydrides; Preferably, in step (2), the mass ratio of the oil phase to the hydrogen donor is 120:0.1-5, preferably 120:0.2-2.

8. The method according to any one of claims 1 to 7, wherein: In step (2), the alkali solution is a NaOH aqueous solution, and the concentration of the alkali solution is 0.1-2wt%, preferably 0.2-1wt%; Preferably, in step (2), the mass ratio of the oil phase to the alkali solution is 1:0.5-1.

5.

9. The method according to any one of claims 1 to 8, wherein: In step (2), the conditions of the second reaction include: reaction temperature of 70-150°C, preferably 70-130°C; reaction time of 0.5-5h, preferably 1-3h; reaction pressure less than 1MPa, preferably normal pressure-0.8MPa.

10. The method according to any one of claims 1 to 9, wherein: The chlorine content of the chlorine-containing plastic oil is 200-4000 μg / g.

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