CN118308597B - Method for recovering palladium from palladium-containing polyketone - Google Patents

Abstract

The invention belongs to the field of noble metal recovery, and particularly relates to a method for recovering palladium from palladium-containing polyketone. The method of the invention comprises the following steps: 1) Dissolving palladium-containing polyketone in zinc chloride solution to obtain solution I; 2) Adding p-benzoquinone into the solution I in the step 1) to obtain a solution II; 3) Heating and stirring the solution II in the step 2), and heating to a temperature higher than the temperature required by the polymerization reaction; adding palladium adsorbent, filtering to obtain filtrate and palladium-enriched solid; 4) Washing the filtrate in step 3), and recovering polyketone in the filtrate. The method has simple process, and can recover most of palladium remained on the polyketone, and the content of the palladium remained on the polyketone after recovery treatment is less than or equal to 0.6ppm.

Description

A method for recovering palladium from palladium-containing polyketone

Technical Field

The invention belongs to the field of precious metal recovery and relates to a method for recovering palladium from palladium-containing polyketone.

Background Art

Polyketone is a high molecular weight linear alternating polymer composed of carbon monoxide and olefins. Among them, commonly used olefin raw materials include ethylene and C3~C8 olefins. Due to the high molecular weight linear alternating structure of carbon monoxide and ethylene, polyketone materials have excellent chemical resistance, wear resistance, hydrolysis resistance, heat resistance, low temperature resistance, high barrier performance and meet the requirements of low VOC at the same time. It is a green and environmentally friendly material with diversified performance. Polyketone has a wide range of uses. It can be used to manufacture high-quality, high-strength, high-temperature resistant parts, seals and composite materials, etc., and can be applied to automobiles, electronics, aerospace and other fields. At the same time, due to its low cytotoxicity and good biocompatibility, polyketone can also be used in biomedical fields, such as drug delivery systems and tissue engineering. Moreover, polyketone also has controllable degradability, and has broad development prospects in terms of resource conservation and environmental friendliness.

In the early days, the catalytic systems of polyketones can be divided into nickel, cobalt, and palladium catalysts (patent CN86105214A). However, the palladium catalyst system is truly used for industrial production. Compared with nickel and cobalt, the use of palladium as a catalyst can greatly improve the space-time yield of polyketones, and its reaction conditions are relatively mild. According to Mechanistic aspects of metal-catalyzed alternating copolymerization of olefins with carbon monoxide (Acc. Chem. Res. 1993, 26, 6, 303–310, doi: 10.1021/ar00030a002), the production of polyketones is usually prepared by catalytic polymerization in methanol slurry, starting from a 1:1 gas mixture of carbon monoxide and ethylene, at moderate temperature (25±100℃) and certain pressure conditions. The catalytic system usually contains a bisphosphine ligand (such as 1,3-bis(diphenylphosphino)propane), a salt of Pd(II) (such as Pd(OAc) ₂ ) and trifluoroacetic acid.

However, despite the relatively high time-space yield, a considerable amount of palladium will remain on the polyketone. This brings two problems: 1) The loss of precious metal palladium increases the production cost. 2) The residual palladium reduces the stability of polyketone, making it easier to discolor and decompose under heating conditions. Since polyketone itself has a high melting point, the residual palladium is extremely unfavorable for subsequent injection molding processing. According to Efficient palladium catalysts for the copolymerization of carbon monoxide with olefins to produce perfectly alternating polyketones (Journal of Organometallic Chemistry Volume 417, Issues 1–2, doi: 10.1016/0022-328X(91)80176-K). Compared with Pd(0), Pd(II) has a greater damage to the thermal stability of polyketone.

Therefore, how to remove the palladium remaining in the polyketone and recycle it is a key technology in the polyketone production process. One solution is to dissolve the polyketone in a specific solvent and then capture it using a compound that is affinity for Pd(II). Patent US4870156A, in one embodiment, introduces a method of dissolving polyketone particles using hexafluoroisopropanol, followed by capturing palladium using sodium diethyldithiocarbamate, thereby reducing the palladium content in the polyketone from 2230 ppm to less than 100 ppm. However, hexafluoroisopropanol is expensive, highly toxic and has a low boiling point, so its industrial application value is low. US5362850A uses ethylene to treat the reacted polyketone, and in one embodiment, it reduces the palladium content from about 500 ppm to 50 ppm. Patent CN1008102B introduces a method of using a bidentate phosphine ligand as a palladium capture agent. For each gram of palladium, 1 to 3 grams of 1,3-bis-(diphenylphosphino)propane or 2-methyl-2-(diphenylphosphinomethyl)-1,3-bis-(diphenylphosphino)propane is used and added to the kettle after the reaction. Since the amount of ligand is greatly excessive relative to palladium, the palladium remaining on the polyketone can be captured by the ligand in the solution. Through this method, the residual palladium content on the polyketone is reduced from 95ppm to 37ppm. Patent CN1018734B uses a similar method. In one embodiment, it uses triphenylphosphine as a capture agent to reduce the palladium content of the polyketone from 50ppm to 10ppm. Patent EP0285218A2, in one embodiment, uses a bidentate phosphine ligand as a capture agent while raising the capture temperature to a temperature higher than the polymerization reaction temperature, so that the residual palladium content on the polyketone is reduced to 5ppm. Patent GB2247890A introduces a method for oxidizing and capturing Pd(0) using nitrosyl fluoroborate. Under reflux, this reduced the palladium content remaining on the polyketone to 5 ppm.

However, the common problem of the above methods is that although up to 97% of the palladium on the polyketone has been removed, there is still at least 4 ppm of palladium remaining. This is still extremely disadvantageous for the production cost and subsequent processing of the polyketone. For example, in terms of production cost, for a polyketone plant with an annual output of 50,000 tons, the palladium content of 4 ppm on the polyketone corresponds to a palladium loss of 300 kg, which is equivalent to a cost of 60 million yuan based on 200 yuan/gram of palladium.

Summary of the invention

The present invention is made to solve the above-mentioned problem, and aims to provide a method for recovering palladium from palladium-containing polyketone, by which the loss of precious metal palladium can be reduced; and the residual palladium is prevented from affecting the stability of polyketone and being unfavorable for subsequent injection molding processing.

The present invention provides a method for recovering palladium from a palladium-containing polyketone, the method comprising the following steps:

1) dissolving the palladium-containing polyketone in a zinc chloride solution to obtain a solution I;

2) adding p-benzoquinone to the solution I in step 1) to obtain a solution II;

3) heating and stirring the solution II in step 2) to a temperature higher than the temperature required for the polymerization reaction; then adding a palladium adsorbent, filtering to obtain a filtrate and a solid enriched with palladium;

4) washing the filtrate in step 3) to recover the polyketone in the filtrate;

The mass concentration of the zinc chloride solution is 85-90wt%.

The present invention has the following beneficial effects:

By using a method for recovering palladium from palladium-containing polyketone provided by the present invention, most of the palladium remaining on the palladium-containing polyketone can be recovered, and the palladium content in the polyketone after recovery treatment is ≤0.6ppm.

DETAILED DESCRIPTION

Hereinafter, a specific disclosed embodiment of a method for recovering palladium from a palladium-containing polyketone is described in detail.

The present invention adopts a specific method to recover palladium from palladium-containing polyketone, specifically: dissolving the palladium-containing polyketone in a zinc chloride solution, adding p-benzoquinone and heating to a temperature greater than the temperature required for the polymerization reaction, then adding a palladium adsorbent for adsorption, obtaining a filtrate and a solid enriched in palladium; washing the filtrate, and recovering the polyketone in the filtrate. The method has a simple process, and after the recovery treatment, most of the palladium on the palladium-containing polyketone is recovered, and the palladium content in the polyketone is ≤0.6ppm. The operation is simple, safe, and efficient, and has a wide range of application prospects. On this basis, the present invention is completed.

The present invention provides a method for recovering palladium from a palladium-containing polyketone, the method comprising the following steps:

1) dissolving the palladium-containing polyketone in a zinc chloride solution to obtain a solution I;

2) adding p-benzoquinone to the solution I in step 1) to obtain a solution II;

3) heating and stirring the solution II in step 2) to a temperature higher than the temperature required for the polymerization reaction; then adding a palladium adsorbent, filtering to obtain a filtrate and a solid enriched with palladium;

4) washing the filtrate in step 3) to recover the polyketone in the filtrate;

The mass concentration of the zinc chloride solution in the present invention is 85-90wt%, which can be selected as 85-87wt%, 87-88wt% or 88-90wt%.

In the method for recovering palladium from palladium-containing polyketone provided by the present invention, step 1) is to dissolve the palladium-containing polyketone in a zinc chloride solution to obtain a solution I. Specifically:

In step 1) of the present invention, the mass volume ratio of the palladium-containing polyketone and the zinc chloride solution is equal to 10g: (70-120) mL, which can be selected as 10g: (70-100) mL, 10g: (100-120) mL, 10g: (70-80) mL, 10g: (80-90) mL, 10g: (90-100) mL, 10g: (100-110) mL or 10g: (110-120) mL, etc. The present invention finds that the use of the above mass volume ratio helps to fully dissolve the palladium-containing polyketone and recover palladium. If a smaller volume of zinc chloride solution is used, it is easy to cause the palladium-containing polyketone to still not dissolve sufficiently even in a heated state, thereby reducing the recovery rate of palladium. If a larger volume of zinc chloride solution is used, unnecessary raw material loss is caused and the load of the waste liquid treatment process is increased.

In step 1) of the present invention, the polyketone in the palladium-containing polyketone is a high molecular weight linear alternating polyketone composed of carbon monoxide and olefins.

In the method for recovering palladium from palladium-containing polyketone provided by the present invention, step 2) is to add p-benzoquinone to the solution I in step 1) to obtain solution II.

The mass ratio of the palladium-containing polyketone in step 1) of the present invention to the p-benzoquinone in step 2) is 1: (0.01-0.04), which may be 1: (0.01-0.02), 1: (0.02-0.04), 1: (0.02-0.03) or 1: (0.03-0.04), etc. This mass ratio range helps to oxidize palladium into stable palladium oxide, preventing it from being reduced in subsequent steps.

In the method for recovering palladium from palladium-containing polyketone provided by the present invention, step 3) is to heat and stir the solution II in step 2) to a temperature greater than the temperature required for the polymerization reaction; then add a palladium adsorbent, and filter to obtain a filtrate and a solid enriched in palladium. Specifically: the solution II in step 2) is heated to a temperature greater than the temperature required for the polymerization reaction, and then the palladium adsorbent is added after stirring, the temperature is lowered, the stirring is continued, and then the filtrate and the solid enriched in palladium are obtained.

In step 3) of the present invention, the heating temperature is 120°C.

In step 3) of the present invention, the stirring time is 1 hour.

In step 1) of the present invention, the mass ratio of the palladium-containing polyketone to the palladium adsorbent in step 3) is 2: 1. Within this mass ratio range, it can be ensured that the palladium adsorbent in the system has sufficient adsorption capacity.

In step 3) of the present invention, the cooling temperature is 55-60°C, and can be 55-58°C or 58-60°C.

In step 3) of the present invention, the palladium adsorbent is selected from one or more of activated carbon, cation exchange resin or anion exchange resin, preferably anion exchange resin.

In the method for recovering palladium from palladium-containing polyketone provided by the present invention, step 4) is to wash the filtrate in step 3) and recover the polyketone in the filtrate. Specifically: the filtrate in step 3) is cooled to room temperature and the polyketone is precipitated, and the polyketone is washed with water to remove residual zinc chloride and dried. The palladium content in the polyketone is detected by ICP-MS.

In step 4) of the present invention, the filtrate is cooled to room temperature to precipitate polyketone.

In step 4) of the present invention, the palladium content of the polyketone is ≤0.6ppm, which can be selected from 0~0.1ppm, 0.1~0.5ppm, 0.5~0.6ppm, etc.

The beneficial effects of the present invention are further illustrated below in conjunction with embodiments.

In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with examples. However, it should be understood that the examples of the present invention are only for explaining the present invention, not for limiting the present invention, and the examples of the present invention are not limited to the examples given in the specification. The specific experimental conditions or operating conditions not specified in the examples are made under conventional conditions, or are made under the conditions recommended by the material supplier.

In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices/apparatuses mentioned in the present invention does not exclude the existence of other devices/apparatuses before or after the combination device/apparatus or the insertion of other devices/apparatuses between these explicitly mentioned two devices/apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

In the following examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

Unless otherwise specified, the purity of each product in each embodiment of the present invention exceeds 98%.

Comparative Example 1

The synthesis of polyketone will refer to one of the embodiments in patent CN116535441B. In a 250 ml high-pressure reactor, 200 ml of methanol and 1.2 ml of palladium-containing catalyst (containing 0.597 mg of palladium) were added. The reactor was replaced with nitrogen 5 times, then the temperature was raised to 90°C, and a mixture of carbon monoxide and ethylene (volume molar ratio 1:1) was introduced to make the pressure in the reactor reach 53 bar, and the reaction lasted for 7 hours. Finally, the reaction was terminated by cooling and depressurizing, and a methanol slurry containing polyketone was collected. The slurry was centrifuged, washed and filtered with 200 ml of hot methanol, and dried to obtain 72.2 g of polyketone, in which the palladium content was 6 ppm as detected by ICP-MS, corresponding to 72.6% of palladium remaining on the polyketone.

Comparative Example 2

This comparative example will compare the method of CN1008102B. In a 250 ml high-pressure reactor, 200 ml of methanol and 1.2 ml of palladium-containing catalyst (containing 0.597 mg of palladium) were added. The reactor was replaced with nitrogen 5 times, then the temperature was raised to 90°C, and a mixture of carbon monoxide and ethylene (volume molar ratio 1:1) was introduced to make the pressure in the reactor reach 53 bar, and the reaction lasted for 7 hours. Then, 1 mg of 2-methyl-2-(diphenylphosphinomethyl)-1,3-bis-(diphenylphosphino)propane in 10 ml of methanol solution was added to terminate the reaction. Finally, the reaction was terminated by cooling and depressurizing, and a methanol slurry containing polyketone was collected. The slurry was centrifuged and washed and filtered with 200 ml of hot methanol, and dried to obtain 70.8 g of polyketone, in which the palladium content was 3.9 ppm as detected by ICP-MS, corresponding to 46.3% of palladium remaining on the polyketone.

Comparative Example 3

This comparative example will compare the method of patent EP0285218A2. In a 250 ml high-pressure reactor, 200 ml of methanol and 1.2 ml of palladium-containing catalyst (containing 0.597 mg of palladium) were added. The reactor was replaced with nitrogen 5 times, then the temperature was raised to 90°C, and a mixture of carbon monoxide and ethylene (volume molar ratio 1:1) was introduced to make the pressure in the reactor reach 53 bar, and the reaction lasted for 7 hours. Then, 1 mg of 2-methyl-2-(diphenylphosphinomethyl)-1,3-bis-(diphenylphosphino)propane in 10 ml of methanol solution was added to terminate the reaction, and the temperature of the reactor was raised to 120°C for 2 hours. Finally, the reaction was terminated by cooling and depressurizing, and a methanol slurry containing polyketone was collected. The slurry was centrifuged, washed and filtered with 200 ml of hot methanol, and dried to obtain 71.5 g of polyketone, in which the palladium content was 3.2 ppm as detected by ICP-MS, corresponding to 38.3% of palladium remaining on the polyketone.

Comparative Example 4

This comparative example will compare the effect of the implementation without step 2. In a 250 ml high-pressure reactor, 200 ml of methanol and 1.2 ml of palladium-containing catalyst (containing 0.597 mg of palladium) were added. The reactor was replaced with nitrogen 5 times, then the temperature was raised to 90°C, and a mixture of carbon monoxide and ethylene (volume molar ratio 1:1) was introduced to make the pressure in the reactor reach 53 bar, and the reaction lasted for 7 hours. Finally, the reaction was terminated by cooling and depressurizing, and a methanol slurry containing polyketone was collected. The slurry was centrifuged, washed and filtered with 200 ml of hot methanol, and dried to obtain 71.4 g of polyketone.

Take 10g of the above polyketone, dissolve it in 70ml of 85% zinc chloride solution at 80℃, and stir for 1 hour. Add 5g of activated carbon (produced by Shanghai Activated Carbon Factory) to the solution, lower the temperature to 60℃ and continue stirring for 1 hour, then filter out the activated carbon solid containing palladium. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove the residual zinc chloride and dried. The palladium content of the polyketone is 2.9ppm by ICP-MS, corresponding to 34.8% of palladium remaining on the polyketone.

Comparative Example 5

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 120ml of 30% zinc bromide solution, and add 0.1g of p-benzoquinone. Then, raise the temperature to 120°C and stir for 1 hour. Add 5g of activated carbon (produced by Shanghai Activated Carbon Factory) to the solution, lower the temperature to 60°C and continue stirring for 1 hour, then filter out the activated carbon solid containing palladium. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc bromide and dried. The palladium content of the polyketone is 1.7ppm as detected by ICP-MS, corresponding to 20.4% of palladium remaining on the polyketone.

Example 1

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 70ml of 85% zinc chloride solution at 80°C, and add 0.1g of p-benzoquinone. Then, raise the temperature to 120°C and stir for 1 hour. Add 5g of Amberlyst® 15 cation exchange resin to the solution, lower the temperature to 60°C and continue stirring for 1 hour, then filter out the palladium-containing resin solid. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc chloride and dried. The palladium content of the polyketone is 0.6ppm by ICP-MS, corresponding to 7.2% of palladium remaining on the polyketone.

Example 2

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 70ml of 85% zinc chloride solution at 80°C, and add 0.2g of p-benzoquinone. Then, raise the temperature to 120°C and stir for 1 hour. Add 5g of Amberlite IRA900Cl anion exchange resin to the solution, lower the temperature to 60°C and continue stirring for 1 hour, then filter out the palladium-containing resin solid. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc chloride and dried. The palladium content of the polyketone is 0.1ppm by ICP-MS, corresponding to 1.2% of palladium remaining on the polyketone.

Comparative Example 6

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 120ml of 30% zinc bromide solution, and add 0.4g of p-benzoquinone. Then, raise the temperature to 110°C and stir for 1 hour. Add 5g of Amberlyst® 15 cation exchange resin to the solution, lower the temperature to 60°C and continue stirring for 1 hour, then filter out the palladium-containing resin solid. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc bromide and dried. The palladium content of the polyketone is 2.0ppm by ICP-MS, corresponding to 24% of palladium remaining on the polyketone.

Examples 3-5 used similar conditions to Example 2, except that different contents of p-benzoquinone and different concentrations of zinc chloride solutions were used.

Zinc chloride mass concentration (wt%) p-Benzoquinone (g) Palladium content (ppm) Example 3 85 0.1 0.2 Example 4 90 0.4 <0.1 Example 5 90 0.2 0.1

Comparative Examples 7-9 used similar conditions to Example 2, except that acetonitrile was used as a solvent or nitrosotetrafluoroborate was used as an oxidant.

Solution Oxidants Palladium content (ppm) Comparative Example 7 85% Zinc Chloride Nitroso tetrafluoroborate 3.2 Comparative Example 8 Acetonitrile p-Benzoquinone 3.7 Comparative Example 9 Acetonitrile Nitroso tetrafluoroborate 4.2

Example 6

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 120ml of 85% zinc chloride solution, and add 0.2g of p-benzoquinone. Then, raise the temperature to 120℃ and stir for 1 hour. Add 5g of Amberlite IRA900Cl anion exchange resin to the solution, lower the temperature to 60℃ and continue stirring for 1 hour, then filter out the palladium-containing resin solid. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc chloride and dried. The palladium content of the polyketone is 0.1ppm by ICP-MS, corresponding to 1.2% of palladium remaining on the polyketone.

Comparative Example 10

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 70ml of 85% zinc chloride solution at 80°C, and add 0.2g of hydrogen peroxide. Then, raise the temperature to 120°C and stir for 1 hour. Add 5g of Amberlite IRA900Cl anion exchange resin to the solution, lower the temperature to 60°C and continue stirring for 1 hour, then filter out the palladium-containing resin solid. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500ml of water to remove residual zinc chloride and dried. The palladium content of the polyketone is 2.2ppm as detected by ICP-MS, corresponding to 26.4% of palladium remaining on the polyketone.

Comparative Example 11

Take 10g of the polyketone obtained by polymerization in Comparative Example 4, dissolve it in 120 ml of 30% zinc chloride solution at 80°C, and add 0.2 g of hydrogen peroxide. Subsequently, the temperature is raised to 120°C and stirred for 1 hour. 5g of Amberlite IRA900Cl anion exchange resin is added to the solution, and the temperature is lowered to 60°C and stirred for 1 hour, and then the palladium-containing resin solid is filtered out. The remaining solution is cooled to room temperature and polyketone is precipitated. The polyketone is washed with 500 ml of water to remove residual zinc chloride and dried. The palladium content of the polyketone is 3.5ppm as detected by ICP-MS, corresponding to 42.0% of palladium remaining on the polyketone.

Combined with Comparative Examples 1-4 and Comparative Examples 6-11, although the residual amount of palladium on polyketone can be reduced by different methods. However, the palladium content of polyketone is above 2.0ppm. In Examples 1-6, the method of dissolving the palladium-containing polyketone in a zinc chloride solution, adding p-benzoquinone, raising the temperature to exceed the polymerization reaction temperature and then adding a palladium adsorbent has a better effect on reducing the residual content of palladium in polyketone, and the residual palladium content on the polyketone can be made ≤ 0.6ppm. In particular, in Example 4, the palladium-containing polyketone is dissolved in a zinc chloride solution, p-benzoquinone is added as an oxidant, and the temperature is raised to 120°C and then an anion exchange resin is added as a palladium adsorbent. This method is the most excellent for recovering palladium on polyketone, and the palladium content remaining on the polyketone can be reduced to less than 0.1ppm, corresponding to less than 1.2% of palladium remaining on the polyketone, and an unexpected technical effect has been achieved.

The above embodiments are preferred cases of the present invention and are not intended to limit the protection scope of the present invention. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims (10)

1. A method for recovering palladium from a palladium-containing polyketone, said method comprising the steps of:

1) Dissolving palladium-containing polyketone in zinc chloride solution to obtain solution I;

2) Adding p-benzoquinone into the solution I in the step 1) to obtain a solution II;

3) Heating and stirring the solution II in the step 2), and heating to a temperature higher than the temperature required by the polymerization reaction; adding palladium adsorbent, filtering to obtain filtrate and palladium-enriched solid;

4) Washing the filtrate in the step 3), and recovering polyketone in the filtrate;

the mass concentration of the zinc chloride solution is 85-90wt%.

2. The method for recovering palladium from a palladium-containing polyketone according to claim 1, wherein in the step 1), the polyketone in the palladium-containing polyketone is a high molecular weight linear alternating polyketone composed of carbon monoxide and an olefin.

3. The method of recovering palladium from a palladium-containing polyketone according to claim 1, wherein the mass to volume ratio of the palladium-containing polyketone to the zinc chloride solution is equal to 10g: (70-120) mL.

4. The method for recovering palladium from a palladium-containing polyketone according to claim 1, wherein the mass ratio of the palladium-containing polyketone in step 1) to the p-benzoquinone in step 2) is 1: (0.01 to 0.04).

5. A method for recovering palladium from a palladium-containing polyketone according to claim 1 wherein the temperature of said heating in step 3) is 120 ℃.

6. The method for recovering palladium on a palladium-containing polyketone according to claim 5, wherein said stirring in step 3) is carried out for a period of 1 hour.

7. The method of recovering palladium from a palladium-containing polyketone according to claim 1, further comprising any one or more of the following conditions:

a1 The mass ratio of polyketone in step 1) to palladium adsorbent in step 3) is 2:1, a step of;

a2 The palladium adsorbent in step 3) is selected from one or more of activated carbon, cation exchange resin or anion exchange resin.

8. The method of recovering palladium on a palladium-containing polyketone according to claim 7 wherein said palladium adsorbent in step 3) is an anion exchange resin.

9. The method for recovering palladium from a palladium-containing polyketone according to claim 1, wherein said filtrate in step 4) is cooled to room temperature to precipitate a polyketone.

10. The method for recovering palladium from a palladium-containing polyketone according to claim 1, wherein the palladium content in said polyketone in step 4) is not more than 0.6ppm.