Method for recycling waste printed circuit board through in-situ pyrolysis-ectopic catalysis

Abstract

The invention belongs to the technical field of waste printed circuit board recycling, and particularly discloses a method for recycling a waste printed circuit board through in-situ pyrolysis-ectopic catalysis. The method comprises the following steps: removing components from the waste printed circuit board to prepare waste printed circuit board resin powder; mixing the waste printed circuit board resin powder with iron oxide to obtain a resin mixture; placing the resin mixture in a first pyrolyzing furnace, and pyrolyzing; and finally, introducing the pyrolyzed product into a second pyrolyzing furnace filled with a catalyst, carrying out a thermocatalytic reaction, and cooling to obtain the recycled pyrolytic oil. According to the recycling process, the combustion heat value of the waste printed circuit board resin powder pyrolytic oil is increased, heavy components in the pyrolytic oil are reduced, and therefore the purpose of recycling the high-heat-value light oil is achieved; the calorific value of the pyrolytic oil exceeds 30 MJ / kg, and the content of light components reaches 50% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of waste printed circuit board recycling, and particularly relates to a method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis. Background Art

[0002] With the rapid development of electronic technology, the amount of waste printed circuit boards (WPCB) has increased dramatically, and its treatment and recycling have become an environmental problem that needs to be solved urgently. Waste WPCB is mainly composed of resin, metal and glass fiber, among which the resin part accounts for a considerable proportion, and most of them are polymer materials such as epoxy resin, which have high calorific value and potential recycling value. However, traditional treatment methods such as incineration and landfill not only waste resources seriously, but also easily cause environmental pollution.

[0003] In recent years, pyrolysis technology has attracted much attention due to its ability to efficiently convert organic waste into energy products. For the resin powder in waste WPCB, in-situ pyrolysis technology can be used to crack it into gas, liquid and solid products at high temperature in an oxygen-free or low-oxygen environment. Among them, the liquid product is mainly light oil, which has a high calorific value and utilization value. However, the light oil obtained directly by pyrolysis often contains more heavy components and impurities, and needs further treatment to improve the quality.

[0004] Therefore, it is urgent to develop a new method for recycling waste printed circuit boards to increase the combustion calorific value of the recycled products and reduce the content of heavy components. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis, which can effectively improve the combustion calorific value of the recycled pyrolysis oil, reduce the content of heavy components in the pyrolysis oil, and make the recycled pyrolysis oil lighter.

[0006] The inventive concept of the present invention is: the pyrolysis oil of waste circuit board resin powder has two major technical problems: low combustion calorific value and high content of heavy components, which are not conducive to its resource recycling. The present invention uses iron oxide (such as Fe3O4, Fe2O3 or FeO) and modified 4A molecular sieve to react with hydrogen bromide in pyrolysis oil, and effectively fix it in the solid phase product; at the same time, small molecular bromine-containing organic matter such as alkyl bromide can be catalytically decomposed and debrominated by modified 4A molecular sieve, thereby reducing its volatilization; and the modified 4A molecular sieve has a large specific surface area, which can provide more effective sites to contact with macromolecular organic matter, thereby promoting the conversion of macromolecular organic matter into small molecular organic matter, reducing the content of heavy components in pyrolysis oil, and making the recovered pyrolysis oil lighter. In addition, the present invention adopts an in-situ pyrolysis-ex situ catalytic process, which is beneficial to improve the combustion calorific value of pyrolysis oil and reduce the heavy components in pyrolysis oil compared to the direct pyrolysis catalytic process, thereby achieving the purpose of recovering high calorific value light oil, and the use of ex situ catalytic method can also effectively recover the used catalyst for regeneration and reuse.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a method for recycling waste printed circuit boards, comprising the following steps:

[0008] (1) removing components from waste printed circuit boards to prepare waste printed circuit board resin powder;

[0009] (2) mixing the waste printed circuit board resin powder with iron oxide to obtain a resin mixture; and then placing the resin mixture in a first pyrolysis furnace for pyrolysis;

[0010] (3) The pyrolysis product of step (2) is introduced into a second pyrolysis furnace containing a catalyst to undergo a thermal catalytic reaction, and then cooled to obtain recovered pyrolysis oil.

[0011] In some embodiments of the present invention, in step (1), after removing components from the waste printed circuit boards, the waste printed circuit boards are crushed and sorted to recover the rare and precious metals therein; and then the remaining components are dehydrated and dried to obtain the waste printed circuit board resin powder.

[0012] In some embodiments of the present invention, the iron oxide includes at least one of Fe3O4, Fe2O3, and FeO; preferably Fe3O4.

[0013] In some embodiments of the present invention, the mass ratio of the waste printed circuit board resin powder to the iron oxide is 1:(0.2-1.5); preferably, the mass ratio of the waste printed circuit board resin powder to the iron oxide is 1:(0.5-1.0).

[0014] In some embodiments of the present invention, the catalyst is a modified 4A molecular sieve, and the preparation steps of the iron-modified 4A molecular sieve include: immersing the 4A molecular sieve in a ferric chloride solution, mixing; filtering, solidifying, and calcining to obtain the catalyst.

[0015] In some embodiments of the present invention, the concentration of the ferric chloride solution is 0.01-0.2 mol / L.

[0016] In some embodiments of the present invention, the curing temperature is 70-80°C.

[0017] In some embodiments of the present invention, the curing time is 45-20 hours.

[0018] In some embodiments of the present invention, the calcination temperature is 450-550°C.

[0019] In some embodiments of the present invention, the calcination time is 3-5 hours.

[0020] In some embodiments of the present invention, the mass ratio of the waste printed circuit board resin powder to the catalyst is 1:0.4-0.6.

[0021] In some embodiments of the present invention, in step (2), the temperature regime of the first pyrolysis furnace is: heating to 500-600°C at a heating rate of 5-15°C / min and keeping the temperature for 1-3 hours.

[0022] In some embodiments of the present invention, in step (3), the temperature regime of the second pyrolysis furnace is: heating to 500-600°C at a heating rate of 5-15°C / min and keeping the temperature for 1-2 hours.

[0023] In some embodiments of the present invention, the first pyrolysis furnace and the second pyrolysis furnace are both in a vacuum state, and the vacuum degree is 0.7-1 MPa.

[0024] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0025] (1) In the process of recovery, the present invention utilizes iron oxide (such as Fe3O4, Fe2O3 or FeO) and modified 4A molecular sieve to react with hydrogen bromide in pyrolysis oil, thereby effectively fixing it in the solid phase product; at the same time, small molecular bromine-containing organic matter such as alkyl bromide can be catalytically decomposed and debrominated by the modified 4A molecular sieve, thereby reducing its volatility; and the modified 4A molecular sieve has a large specific surface area, which can provide more effective sites for contact with large molecular organic matter, thereby promoting the conversion of large molecular organic matter into small molecular organic matter, reducing the content of heavy components in pyrolysis oil, and making the recovered pyrolysis oil lighter.

[0026] (2) The present invention adopts an in-situ pyrolysis-ex situ catalytic process, which is beneficial to improving the combustion calorific value of pyrolysis oil and reducing the heavy components in the pyrolysis oil compared to the direct pyrolysis catalytic process, thereby achieving the purpose of recovering high calorific value light oil; and the introduction of ex situ catalytic technology can deeply treat the light oil produced by pyrolysis, which is beneficial to remove impurities and crack heavy components, thereby obtaining a high calorific value and high quality light oil product; achieving a pyrolysis oil calorific value of more than 30MJ / kg and a light component content of more than 50%.

[0027] (3) The in-situ pyrolysis-ex-situ catalytic recovery method for waste printed circuit boards of the present invention not only realizes the efficient recovery and resource utilization of resin powder in waste printed circuit boards, thereby reducing environmental pollution; but also can effectively recover the used catalyst, regenerate and reuse it, thus having significant economic and environmental benefits. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the examples, so that the technical personnel of the relevant technical field can understand the present invention. It is necessary to point out here that the examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The non-essential improvements and adjustments made to the present invention by the skilled person in the relevant field according to the above invention content should still belong to the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0029] Example 1

[0030] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0031] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0032] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0033] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0034] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.5;

[0035] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping the temperature for 60 minutes; the temperature regime of the second pyrolysis furnace is the same as that of the first pyrolysis furnace, and the vacuum degrees in the first pyrolysis furnace and the second pyrolysis furnace are both 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for a thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0036] Example 2

[0037] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0038] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0039] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0040] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:1, and then placing the mixture in a first pyrolysis furnace;

[0041] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.5;

[0042] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes; the temperature regime of the second pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace is 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0043] Example 3

[0044] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0045] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.05 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0046] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0047] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0048] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.5;

[0049] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes; the temperature regime of the second pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace is 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0050] Example 4

[0051] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0052] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0053] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0054] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0055] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.7;

[0056] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes; the temperature regime of the second pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 60 minutes, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace is 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0057] Example 5

[0058] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0059] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in a 70°C oven for 20 hours, and then calcined at a high temperature in a muffle furnace at 400°C for 3 hours to obtain a modified Fe / 4A molecular sieve;

[0060] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0061] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0062] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.5;

[0063] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 550°C at a heating rate of 10°C / min and keeping warm for 110 minutes; the temperature regime of the second pyrolysis furnace is: heating to 600°C at a heating rate of 10°C / min and keeping warm for 60 minutes, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace are both 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0064] Example 6

[0065] A method for recycling waste printed circuit boards by in-situ pyrolysis-ex-situ catalysis comprises the following steps:

[0066] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0067] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0068] (3) mixing the waste printed circuit board resin powder obtained in step (2) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0069] (4) placing the modified Fe / 4A molecular sieve obtained in step (1) in a second pyrolysis furnace, wherein the mass ratio of the waste printed circuit board resin powder to the modified Fe / 4A molecular sieve is 1:0.5;

[0070] (5) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping warm for 120 minutes; the temperature regime of the second pyrolysis furnace is: heating to 600°C at a heating rate of 10°C / min and keeping warm for 60 minutes, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace are both 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is passed into the second pyrolysis furnace for a thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0071] Comparative Example 1

[0072] A method for recycling waste printed circuit boards comprises the following steps:

[0073] (1) After removing components from waste printed circuit boards, crushing and sorting are performed to recover rare and precious metals therein; and then the remaining components are dehydrated and dried to obtain waste printed circuit board resin powder;

[0074] (2) placing the waste printed circuit board resin powder obtained in step (1) in a pyrolysis furnace, wherein the temperature of the pyrolysis furnace is: heating to 500° C. at a heating rate of 10° C. / min and keeping the temperature for 60 min; the vacuum degree in the pyrolysis furnace is 0.7-1 MPa; after pyrolysis cooling, collecting the pyrolysis oil.

[0075] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, no Fe3O4 and modified Fe / 4A molecular sieve were added during the pyrolysis process.

[0076] Comparative Example 2

[0077] A method for recycling waste printed circuit boards comprises the following steps:

[0078] (1) After removing components from waste printed circuit boards, crushing and sorting are performed to recover rare and precious metals therein; and then the remaining components are dehydrated and dried to obtain waste printed circuit board resin powder;

[0079] (2) mixing the waste printed circuit board resin powder obtained in step (1) and Fe3O4 in a mass ratio of 1:0.7, and then placing the mixture in a first pyrolysis furnace;

[0080] (3) placing 4A molecular sieve in a second pyrolysis furnace, wherein the mass ratio of waste printed circuit board resin powder to 4A molecular sieve is 1:0.5;

[0081] (4) The first pyrolysis furnace and the second pyrolysis furnace are started simultaneously, wherein the temperature regime of the first pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min and keeping the temperature for 60 minutes; the temperature regime of the second pyrolysis furnace is the same as that of the first pyrolysis furnace, and the vacuum degree in the first pyrolysis furnace and the second pyrolysis furnace is 0.7-1MPa; the pyrolysis product of the first pyrolysis furnace is introduced into the second pyrolysis furnace for a thermal catalytic reaction, and after cooling, the pyrolysis oil is collected.

[0082] The difference between Comparative Example 2 and Example 1 is that the 4A molecular sieve in Comparative Example 2 is not modified.

[0083] Comparative Example 3

[0084] A method for recycling waste printed circuit boards comprises the following steps:

[0085] (1) The modified Fe / 4A molecular sieve was prepared by an impregnation and calcination method, i.e., the 4A molecular sieve was immersed in a 0.1 mol / L ferric chloride solution and shaken at 25°C for 24 hours; after filtration, it was cured in an oven at 80°C for 12 hours, and then calcined in a muffle furnace at 500°C for 4 hours to obtain a modified Fe / 4A molecular sieve;

[0086] (2) After removing components from the waste printed circuit boards, crushing and sorting them to recover the rare and precious metals therein; then dehydrating and drying the remaining components to obtain waste printed circuit board resin powder;

[0087] (3) mixing the waste printed circuit board resin powder obtained in step (2), the modified Fe / 4A molecular sieve obtained in step (1) and Fe3O4 in a mass ratio of 1::0.5:0.7, and then placing the mixture in a pyrolysis furnace;

[0088] (4) Starting the pyrolysis furnace, the temperature regime of the pyrolysis furnace is: heating to 500°C at a heating rate of 10°C / min, and keeping the temperature for 60 minutes; after the pyrolysis is cooled, the pyrolysis oil is collected.

[0089] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not adopt an ex situ catalytic process.

[0090] Performance Testing

[0091] 1. Calorific value

[0092] The pyrolysis oil collected from Examples 1-6 and Comparative Examples 1-3 was measured using an oxygen bomb combustion method. The results are shown in Table 1.

[0093] Table 1: Pyrolysis oil calorific value table

[0094]

[0095] 2. Pyrolysis oil components and ingredients

[0096] The composition and components of the pyrolysis oil collected in Examples 1-6 and Comparative Examples 1-3 were determined using a gas chromatography-mass spectrometer. The results are shown in Table 2 and Table 3, respectively.

[0097] Table 2: Pyrolysis oil component content

[0098]

[0099]

[0100] Table 3: Composition of pyrolysis oil

[0101]

[0102] As shown in Tables 1-3, the calorific value of the pyrolysis oil recovered in Examples 1-6 is higher than 30MJ / kg, and can even reach 33.09MJ / kg; and the content of light components is more than 50%. Compared with Example 1, Comparative Examples 1-3 are not added with Fe3O4 and modified Fe / 4A molecular sieve, 4A molecular sieve is not modified, and ex situ catalytic process is not used in the pyrolysis process. The calorific value of the recovered pyrolysis oil is not only lower than that of Example 1, but also the content of heavy components (such as bisphenol A) is much higher than that of Example 1.

[0103] For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, without having to go through creative labor. Therefore, simple improvements made to the present invention by those skilled in the art based on the disclosure of the present invention should be within the protection scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should belong to the protection scope of the present invention.

Claims

1. A method for recycling waste printed circuit boards, characterized in that: The following steps are involved: (1) removing components from waste printed circuit boards to prepare waste printed circuit board resin powder; (2) mixing the waste printed circuit board resin powder with iron oxide to obtain a resin mixture; and then placing the resin mixture in a first pyrolysis furnace for pyrolysis; (3) The product obtained by pyrolysis in step (2) is introduced into a second pyrolysis furnace containing a catalyst to undergo a thermal catalytic reaction, and then cooled to obtain the recovered pyrolysis oil of the waste printed circuit boards.

2. The method for recycling waste printed circuit boards according to claim 1, characterized in that: The iron oxide includes at least one of Fe3O4, Fe2O3, and FeO.

3. The method for recycling waste printed circuit boards according to claim 1 or 2, characterized in that: The mass ratio of the waste printed circuit board resin powder to the iron oxide is 1:(0.2-1.5).

4. The method for recycling waste printed circuit boards according to claim 1, characterized in that: The catalyst is a modified 4A molecular sieve, and the preparation steps of the modified 4A molecular sieve include: immersing the 4A molecular sieve in a ferric chloride solution, mixing; filtering, solidifying, and calcining to obtain the catalyst.

5. The method for recycling waste printed circuit boards according to claim 4, characterized in that: The concentration of the ferric chloride solution is 0.01-0.2 mol / L.

6. The method for recycling waste printed circuit boards according to claim 4, characterized in that: The curing temperature is 70-80°C; and / or, the curing time is 45-20 hours; and / or, the calcining temperature is 450-550°C; and / or, the calcining time is 3-5 hours.

7. The method for recycling waste printed circuit boards according to claim 1, characterized in that: The mass ratio of the waste printed circuit board resin powder to the catalyst is 1:(0.4-0.6).

8. The method for recycling waste printed circuit boards according to claim 1, characterized in that: In step (2), the temperature regime of the first pyrolysis furnace is: heating to 500-600°C at a heating rate of 5-15°C / min and keeping the temperature for 1-3 hours.

9. The method for recycling waste printed circuit boards according to claim 1, characterized in that: In step (3), the temperature regime of the second pyrolysis furnace is: heating to 500-600°C at a heating rate of 5-15°C / min and keeping warm for 1-2 hours.

10. The method for recycling waste printed circuit boards according to claim 1, characterized in that: The vacuum degrees in the first pyrolysis furnace and the second pyrolysis furnace are both 0.7-1 MPa.

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