Preparation method and application of bimetallic modified catalyst based on waste circuit board

Abstract

The invention belongs to the technical field of catalysts, and provides a preparation method and application of a bimetallic modified catalyst based on a waste circuit board. After a waste circuit board material is pretreated, a bimetallic modification system is formed by metal Co and metal Mn, Zn, Fe and Ni to modify the waste circuit board material; when the obtained bimetallic modified catalyst is applied to pyrolysis of waste circuit boards, the bromide content in pyrolysis oil can be remarkably reduced. The waste circuit board material is adopted as a raw material, the waste circuit board is converted into the bimetallic modified catalyst with high catalytic activity, the bimetallic modified catalyst is applied to catalytic pyrolysis of the waste circuit board, harmless treatment of the waste circuit board and effective recycling of resources are effectively achieved, and the method is particularly suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing a bimetallic modified catalyst based on waste circuit boards and its application. Background Technology

[0002] With advancements in technology and improvements in production levels, the replacement cycle of electronic products has shortened, leading to a rapid increase in the quantity of waste circuit boards. Waste circuit boards are mainly composed of glass fiber reinforced resin and various metals, making them a typical type of electronic waste. Improper disposal can result in resource waste and, due to the presence of harmful components such as cadmium and brominated flame retardants, pose a serious threat to the ecological environment and human health.

[0003] Currently, the main methods for recycling and disposing of waste circuit boards include traditional methods such as direct landfill, incineration, and wet treatment. However, these methods easily generate particulate matter and volatile toxic substances during the process, which can easily cause secondary pollution of the atmosphere, water bodies, or soil. Therefore, there is an urgent need for a treatment method that can achieve both harmless disposal and efficient resource recovery of waste circuit boards.

[0004] Pyrolysis decomposes organic matter in waste circuit boards, recovering combustible fuels, gases, and metals. Unlike incineration, pyrolysis is performed under anaerobic conditions, significantly reducing the formation of organic pollutants such as dioxins and furans, and producing less waste gas, thus minimizing environmental pollution. The main pyrolysis products include pyrolysis oil, pyrolysis gas, and solid residue. The pyrolysis oil can be used as fuel or chemical feedstock, achieving resource recycling. The solid residue primarily consists of metals, glass fibers, and coke. However, directly pyrolyzing waste circuit boards results in a high bromide content in the pyrolysis oil, severely impacting its subsequent utilization value.

[0005] Therefore, developing a catalytic technology that can achieve efficient debromination and improve the quality of pyrolysis oil during pyrolysis is of great significance for promoting the practical application of pyrolysis processes and the recycling of electronic waste resources. Summary of the Invention

[0006] In a first aspect, the present invention provides a method for preparing a bimetallic modified catalyst based on waste circuit boards, comprising the following steps:

[0007] S1. The waste circuit board material is mixed with phosphoric acid solution, stirred and dried to obtain pretreated waste circuit board material; the mass-to-volume ratio of the waste circuit board material to the phosphoric acid solution is (30-50)g:(300-500)mL; the mass fraction of phosphoric acid in the phosphoric acid solution is 5-15%.

[0008] S2. Disperse the pretreated waste circuit board material into water, add metal A and metal B, perform ultrasonic-assisted stirring, and dry to obtain activated waste circuit board material.

[0009] S3. Under the protection of inert gas, the activated waste circuit board material is calcined to obtain the bimetallic modified catalyst.

[0010] The metal A includes Co; the metal B includes at least one of Mn, Zn, Fe and Ni.

[0011] The inventors discovered that by using the bimetallic system of this invention to modify waste circuit board materials, a specific bimetallic combination can effectively regulate the electronic structure of the catalyst and synergistically construct bifunctional active sites. Through the interaction of electron transfer and charge transfer, the debromination reaction is promoted, significantly reducing the content of bromine-containing compounds in pyrolysis oil and effectively improving the quality of pyrolysis oil.

[0012] Pretreatment of waste circuit board materials with phosphoric acid solution allows the solution to penetrate the organic resin, promoting intermolecular dehydration and cross-linking. It also selectively corrodes some hydrocarbons and releases gases, resulting in a porous structure within the material. Furthermore, this pretreatment introduces numerous phosphorus- and oxygen-containing functional groups onto the surface of the waste circuit board materials. These functional groups provide acidic catalytic active sites, facilitating the breaking of C-Br bonds; and provide metal anchoring sites, preventing metal migration and agglomeration into large particles during high-temperature calcination. This achieves high metal dispersion, forming small and uniform metal particles on the material surface, significantly improving catalyst performance. However, the inventors discovered that the mass-to-volume ratio of waste circuit board materials to phosphoric acid solution needs to be controlled within a certain range. Insufficient phosphoric acid may lead to a decrease in the number of catalytic sites, affecting the subsequent bimetallic loading effect, and also cause the metal to easily agglomerate into large particles within the catalyst, failing to achieve highly uniform dispersion and significantly reducing catalytic performance. Excessive phosphoric acid content can lead to over-etching of waste circuit board materials, damaging the existing pore structure and hindering bimetallic loading. When the phosphoric acid content is controlled within a reasonable range, it effectively etches and activates the waste circuit board materials, forming a suitable pore structure. If the pore size is too small, reactant molecules may be unable to enter the pores, preventing effective reaction between the active sites and reactants. Alternatively, after reactants enter the pores, product molecules may struggle to diffuse out, leading to carbon buildup and pore blockage. Conversely, excessively large pore sizes can decrease the catalyst's specific surface area, reducing the number of active sites and lowering catalytic activity.

[0013] In some embodiments, metal A and metal B are added in the form of metal salts.

[0014] In some embodiments, the amounts of metal A and metal B added are calculated based on the carbon production of the waste circuit board material. The carbon production amount mentioned in this invention refers to the mass of coke generated when the organic matter in the waste circuit board material is carbonized during pyrolysis under anaerobic or oxygen-deficient conditions. In some embodiments, the pyrolysis conditions are: catalytic pyrolysis for 30 minutes at a heating rate of 10°C / min to 600°C under an inert gas N2 atmosphere. In some embodiments, the waste circuit board material used in this invention has been pre-processed using physical recycling processes such as crushing, pulverizing, and sorting to remove components, metals, and glass fibers from the surface of the waste circuit board. In some embodiments, the waste circuit board material used in this invention is purchased from Henan Ruiside Energy Environmental Protection Technology Co., Ltd., and the waste circuit board material has been pre-processed using physical recycling processes to remove components, metals, and glass fibers from the surface of the waste circuit board. In some embodiments, 40g of the waste circuit board material is heated to 600°C at a heating rate of 10°C / min under a N2 atmosphere and catalytically pyrolyzed for 30min. The carbon yield of the waste circuit board material is calculated by weighing the waste circuit board material before pyrolysis and the waste circuit board material after pyrolysis. The mass of the 40g waste circuit board material after pyrolysis is 13g, and the carbon yield (%) = (13g / 40g) × 100% = 32.5%.

[0015] In some implementations, the amount of metal A added is 1-10 wt%, and the amount of metal B added is 1-10 wt%, based on the amount of carbon produced from the waste circuit board material.

[0016] In some implementations, based on the amount of carbon produced from the waste circuit board material, the amount of metal A added is 4-6 wt%, and the amount of metal B added is 4-6 wt%.

[0017] In some implementations, metal A is Co and metal B is Mn.

[0018] In some implementations, in step S2, the ultrasonic-assisted stirring process is carried out in a water bath with an ultrasonic power of 300-500W, an ultrasonic frequency of 40-50kHz, a water bath temperature of 60-70℃, a stirring speed of 500-700r / min, and a stirring time of 2-4h.

[0019] In some implementations, in step S3, the calcination treatment is carried out at a temperature of 500-700°C for a time of 30-90 minutes.

[0020] In a second aspect, the present invention provides a bimetallic modified catalyst based on waste circuit boards, which is prepared by the above method.

[0021] In a third aspect, the present invention provides the application of the above-mentioned bimetallic modified catalyst in the catalytic pyrolysis of waste circuit boards.

[0022] In some implementations, the catalytic pyrolysis time is 20-40 min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Using Co metal and Mn, Zn, Fe and Ni metals to form a bimetallic modification system can significantly reduce the bromide content in pyrolysis oil;

[0025] (2) The catalyst prepared by the process of phosphoric acid pretreatment and ultrasonic-assisted loading is particularly suitable for reducing the bromide content in pyrolysis oil and improving the quality of pyrolysis oil.

[0026] (3) This invention uses waste circuit board material as raw material to transform waste circuit board into a bimetallic modified catalyst with high catalytic activity and apply it to the catalytic pyrolysis of waste circuit board, effectively realizing the harmless treatment of waste circuit board and the effective recycling of resources, which is particularly suitable for industrial production. Detailed Implementation

[0027] The following detailed embodiments further illustrate the content of the present invention. These embodiments do not constitute a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention. The raw materials, reagents, or devices used in the embodiments are all available from conventional commercial sources or can be obtained through existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0028] The waste circuit board materials used in the examples and comparative examples were from Henan Ruiside Energy Environmental Protection Technology Co., Ltd. The waste circuit board materials had undergone physical recycling processes such as crushing, pulverizing, and sorting to remove components, metals, and glass fibers from their surfaces. The calculation of the residual carbon rate of the waste circuit board materials: 40g of waste circuit board material was catalytically pyrolyzed at 600℃ for 30min under a N2 atmosphere at a heating rate of 10℃ / min. The carbon yield was calculated by weighing the waste circuit board material before and after pyrolysis. Carbon yield (%) = (mass of waste circuit board material after pyrolysis / initial mass of waste circuit board material) × 100%. Since the mass of 40g of waste circuit board material after pyrolysis was 13g, the carbon yield (%) = (13g / 40g) × 100% = 32.5%.

[0029] Example 1

[0030] A method for preparing a bimetallic modified catalyst based on waste circuit boards includes the following steps:

[0031] S1. Grind 40g of waste circuit board material into powder with a particle size of 100 mesh, then mix it with 400mL of H3PO4 solution (the mass fraction of phosphoric acid in the H3PO4 solution is 11%), put it in an electromagnetic stirrer, stir at 600r / min for 12h, then wash it with deionized water until it is close to neutral, and dry it in a drying oven at 105℃ for 24h to obtain pretreated waste circuit board material; wherein, the carbon yield of 40g of waste circuit board material is 40g×32.5%=13g.

[0032] S2. Disperse the pretreated waste circuit board material in 60mL of distilled water, add 3.21g Co(NO3)2·6H2O and 2.97g Mn(NO3)2·4H2O, place in an electromagnetic stirrer, heat in a water bath at 60℃, stir at 600r / min, and treat with ultrasonic assistance for 3h. The ultrasonic assistance parameters are: ultrasonic power of 300W and ultrasonic frequency of 50kHz. Then dry in a drying oven at 105℃ to remove moisture. The 3.21g Co(NO3)2·6H2O means it contains 0.65g of Co element. Based on the carbon production of 40g of waste circuit board material, the amount of Co element added is (0.65g / 13g)×100wt%=5wt%; 2.97g Mn(NO3)2·4H2O means that it contains 0.65g of Mn element. That is, based on the carbon production of 40g of waste circuit board material, the amount of Mn element added is (0.65g / 13g)×100wt%=5wt%.

[0033] S3. Calcination at 600℃ under N2 atmosphere for 1 hour yields the bimetallic modified catalyst.

[0034] Example 2

[0035] The only difference from Example 1 is that in step S2, 3.21g Co(NO3)2·6H2O and 2.96g Zn(NO3)2·6H2O are added. That is, based on the carbon production of 40g waste circuit board material, the amount of Co added is 5wt% and the amount of Zn added is 5wt%. The rest of the steps are exactly the same as in Example 1.

[0036] Example 3

[0037] The only difference from Example 1 is that in step S2, 3.21g of Co(NO3)2·6H2O and 3.37g of Fe(NO3)2·6H2O are added. That is, based on the carbon production of 40g of waste circuit board material, the amount of Co added is 5wt% and the amount of Fe added is 5wt%. The rest of the steps are exactly the same as in Example 1.

[0038] Example 4

[0039] The only difference from Example 1 is that in step S2, 3.21g Co(NO3)2·6H2O and 3.22g Ni(NO3)2·6H2O are added. That is, based on the carbon production of 40g waste circuit board material, the amount of Co added is 5wt% and the amount of Ni added is 5wt%. The rest of the steps are exactly the same as in Example 1.

[0040] Example 5

[0041] The only difference from Example 1 is that in step S2, 1.28g Co(NO3)2·6H2O and 4.75g Mn(NO3)2·4H2O are added. That is, based on the carbon production of 40g waste circuit board material, the amount of Co added is 2wt% and the amount of Mn added is 8wt%. The rest of the steps are exactly the same as in Example 1.

[0042] Example 6

[0043] The only difference from Example 1 is that in step S2, 2.57g Co(NO3)2·6H2O and 3.57g Mn(NO3)2·4H2O are added. That is, based on the carbon production of 40g of waste circuit board material, the amount of Co added is 4wt% and the amount of Mn added is 6wt%. The rest of the steps are exactly the same as in Example 1.

[0044] Example 7

[0045] The only difference from Example 1 is that in step S2, 3.85g of Co(NO3)2·6H2O and 2.38g of Mn(NO3)2·4H2O are added. That is, based on the carbon production of 40g of waste circuit board material, the amount of Co added is 6wt% and the amount of Mn added is 4wt%. The rest of the steps are exactly the same as in Example 1.

[0046] Example 8

[0047] The only difference from Example 1 is that in step S2, 5.14g of Co(NO3)2·6H2O and 1.19g of Mn(NO3)2·4H2O are added. That is, based on the carbon production of 40g of waste circuit board material, the amount of Co added is 8wt% and the amount of Mn added is 2wt%. The rest of the steps are exactly the same as in Example 1.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that only deionized water is used to pretreat the waste circuit board material, and no metal activation is added. The specific steps are as follows:

[0050] S1. Grind 40g of waste circuit board material into powder with a particle size of 100 mesh, then mix it with 400mL of deionized water, put it into an electromagnetic stirrer, stir at a speed of 600r / min for 12h, then wash it with deionized water until it is close to neutral, and dry it in a drying oven at a temperature of 105℃ for 24h to obtain pretreated waste circuit board material.

[0051] S2. Disperse the pretreated waste circuit board material in 60mL of distilled water, place it in an electromagnetic stirrer and heat it in a water bath at 60℃. Stir at 600r / min and treat with ultrasonic assistance for 3h. The ultrasonic assistance parameters are: ultrasonic power of 300W and ultrasonic frequency of 50kHz. Then dry it in a drying oven at 105℃ to remove moisture.

[0052] S3. Calcination at 600℃ under N2 atmosphere for 1 hour yields the modified catalyst.

[0053] Comparative Example 2

[0054] The only difference from Example 1 is that in step S1, 40g of waste circuit board material is ground into powder with a particle size of 100 mesh, and then mixed with 100mL of H3PO4 solution (the mass fraction of phosphoric acid in the H3PO4 solution is 11%). The remaining steps are exactly the same as in Example 1.

[0055] Comparative Example 3

[0056] The only difference from Example 1 is that in step S1, 40g of waste circuit board material is ground into powder with a particle size of 100 mesh and then mixed with 800mL of H3PO4 solution (the mass fraction of phosphoric acid in the H3PO4 solution is 11%). The remaining steps are exactly the same as in Example 1.

[0057] Comparative Example 4

[0058] The only difference from Example 1 is that in step S2, 6.42g of Co(NO3)2·6H2O is added, that is, based on the carbon production of 40g of waste circuit board material, the amount of Co element added is 10wt%. The rest of the steps are exactly the same as in Example 1.

[0059] Comparative Example 5

[0060] The only difference from Example 1 is that in step S2, 5.94g of Mn(NO3)2·4H2O is added, that is, based on the carbon production of 40g of waste circuit board material, the amount of Mn added is 10wt%. The rest of the steps are exactly the same as in Example 1.

[0061] Comparative Example 6

[0062] The only difference from Example 1 is that in step S2, 5.91g of Zn(NO3)2·6H2O is added, that is, based on the carbon production of 40g of waste circuit board material, the amount of Zn added is 10wt%. The rest of the steps are exactly the same as in Example 1.

[0063] Comparative Example 7

[0064] The only difference from Example 1 is that in step S2, 6.73g of Fe(NO3)2·6H2O is added, that is, based on the carbon production of 40g of waste circuit board material, the amount of Fe added is 10wt%. The rest of the steps are exactly the same as in Example 1.

[0065] Comparative Example 8

[0066] The only difference from Example 1 is that in step S2, 6.44g of Ni(NO3)2·6H2O is added, that is, based on the carbon production of 40g of waste circuit board material, the amount of Ni added is 10wt%. The rest of the steps are exactly the same as in Example 1.

[0067] The specific surface area, pore size, and pore volume of the catalysts prepared in the examples and comparative examples were tested, and the results are shown in Table 1.

[0068] Table 1

[0069]

[0070]

[0071] The catalysts prepared in the examples and comparative examples were used for the pyrolysis of waste circuit boards: A non-in-situ pyrolysis method was adopted. The catalyst and waste circuit boards were placed in two separate reactors. 1g of waste circuit board and 2g of catalyst were taken and heated at a rate of 10℃ / min under a N2 atmosphere until catalytic pyrolysis occurred at 600℃ for 30min. The oil produced during pyrolysis was collected, cooled, and separated to obtain waste circuit board pyrolysis oil. The distribution of the pyrolysis products was analyzed by gas chromatography-mass spectrometry (GC-MS). The percentage content of the pyrolysis products was calculated using the formula: w = peak area of ​​the target product / total peak area of ​​the bio-oil × 100%. The results are shown in Table 2.

[0072] Table 2

[0073] Group Bromine-containing compounds (%) Group Bromine-containing compounds (%) Example 1 0.4 Comparative Example 1 17.12 Example 2 2.65 Comparative Example 2 6.00 Example 3 3.33 Comparative Example 3 6.15 Example 4 4.22 Comparative Example 4 7.34 Example 5 5.33 Comparative Example 5 8.76 Example 6 1.57 Comparative Example 6 9.66 Example 7 1.15 Comparative Example 7 10.25 Example 8 4.64 Comparative Example 8 9.92

[0074] The results show that, compared with a single metal system, the bimetallic modification system provided by this invention can significantly reduce the bromide content in pyrolysis oil.

[0075] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a bimetallic modified catalyst based on waste circuit boards, characterized in that, Includes the following steps: S1. The waste circuit board material is mixed with phosphoric acid solution, stirred and dried to obtain pretreated waste circuit board material; the mass-to-volume ratio of the waste circuit board material to the phosphoric acid solution is (30-50)g:(300-500)mL; the mass fraction of phosphoric acid in the phosphoric acid solution is 5-15%. S2. Disperse the pretreated waste circuit board material into water, add metal A and metal B, perform ultrasonic-assisted stirring, and dry to obtain activated waste circuit board material. S3. Under the protection of inert gas, the activated waste circuit board material is calcined to obtain the bimetallic modified catalyst. The metal A includes Co; the metal B includes at least one of Mn, Zn, Fe and Ni.

2. The preparation method according to claim 1, characterized in that, Metal A and metal B are added in the form of metal salts.

3. The preparation method according to claim 1, characterized in that, The amount of metal A and metal B added is calculated based on the carbon production of the waste circuit board material; the carbon production is the mass of coke generated when the organic matter in the waste circuit board material is carbonized under anaerobic or oxygen-deficient conditions.

4. The preparation method according to claim 3, characterized in that, Based on the amount of carbon produced from waste circuit board materials, the amount of metal A added is 1-10 wt%, and the amount of metal B added is 1-10 wt%.

5. The preparation method according to claim 3, characterized in that, Based on the carbon production of waste circuit board materials, the amount of metal A added is 4-6 wt%, and the amount of metal B added is 4-6 wt%.

6. The preparation method according to claim 1, characterized in that, Metal A is Co, and metal B is Mn.

7. The preparation method according to claim 1, characterized in that, In step S2, the ultrasonic-assisted stirring process is carried out in a water bath with an ultrasonic power of 300-500W, an ultrasonic frequency of 40-50kHz, a water bath temperature of 60-70℃, a stirring speed of 500-700r / min, and a stirring time of 2-4h.

8. The preparation method according to claim 1, characterized in that, In step S3, the calcination treatment is carried out at a temperature of 500-700℃ for 30-90 minutes.

9. A bimetallic modified catalyst based on waste circuit boards, characterized in that, Prepared by the method described in any one of claims 1-8.

10. The application of the bimetallic modified catalyst as described in claim 9 in the catalytic pyrolysis of waste circuit boards.

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