Preparation method of nickel-iron bimetallic debromination agent and method for in-situ debromination of bromine-containing plastics

Abstract

The present application belongs to the harmless treatment of waste and debromination agent technical field, disclose a kind of nickel-iron bimetallic debromination agent preparation method and its in-situ debromination method to bromine-containing plastics, with ferrous salt and nickel salt preparation nickel-iron bimetallic debromination agent, bromine-containing plastics in electronic waste and debromination agent are co-pyrolysis, in-situ catalytic method is used to convert organic bromine in bromine-containing plastics into inorganic bromine and is fixed in pyrolysis residue, to realize the efficient debromination of bromine-containing plastics pyrolysis oil gas;Nickel-iron bimetallic debromination agent prepared by the present application has abundant iron, nickel interface, can promote the transfer of electrons in debromination reaction, can remove organic bromine and inorganic bromine in bromine-containing plastics simultaneously, with high removal efficiency, and debromination agent is resistant to high temperature;Debromination agent preparation process is simple, energy consumption is low, easy to recycle.

Description

Technical fields:

[0001] This invention belongs to the field of waste harmless treatment and debromination agent technology, and specifically relates to a debromination method for bromine-containing plastics in electronic waste. It utilizes a nickel-iron bimetallic debromination agent to remove bromine from the plastics with a high removal rate. Background technology:

[0002] Traditional treatment methods for bromine-containing plastics in electronic waste, such as incineration and landfill, not only waste land resources and cause environmental pollution, but also lead to resource waste. Currently, pyrolysis is one of the most promising methods for treating electronic waste. However, due to the presence of bromine-containing plastics in electronic waste, the pyrolysis oil and gas produced after pyrolysis contain numerous bromides and have a complex composition, making their high-value utilization very difficult. Chinese Patent CN105713641A discloses an apparatus and method for preparing pyrolysis oil by catalytic debromination of bromine-based flame-retardant waste plastics. The apparatus includes a feeder, a fluidized bed reactor, a condenser, a separator, a primary oil storage tank, a reaction vessel, a secondary oil storage tank, and a tail gas processor. The fluidized bed reactor is used to heat the bromine-based flame-retardant waste plastics to be treated, causing them to undergo a pyrolysis reaction to obtain primary pyrolysis oil. The reaction vessel is used to catalytically debrominate the primary pyrolysis oil to obtain secondary pyrolysis oil.

[0003] Currently, existing technologies are not ideal for removing bromine from bromine-containing plastics, and it is necessary to find a new method to simultaneously remove organic and inorganic bromine from plastics. Summary of the Invention:

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a highly efficient bimetallic in-situ debromination method for bromine-containing plastics in electronic waste. This method addresses the issue that HBr and Br2 generated after the pyrolysis of bromine-containing plastics in electronic waste enter the pyrolysis oil and gas, making them unusable directly. A novel nickel-iron-based bimetallic debromination agent is prepared, and the bromine-containing plastics in the electronic waste are co-pyrolyzed with the debromination agent. An in-situ catalytic method is used to convert the organic bromine in the bromine-containing plastics into inorganic bromine, which is then fixed in the pyrolysis residue, thereby achieving highly efficient debromination of the pyrolysis oil and gas containing bromine-containing plastics.

[0005] To achieve the above objectives, this invention provides a method for preparing a nickel-iron-based bimetallic debrominating agent. Ferrous salt is dissolved in deionized water at a solid-liquid mass ratio of 1:5–20. The solution is stirred under constant temperature water bath at 60°C with inert gas. A reducing agent solution is added to the ferrous salt aqueous solution at a molar ratio of ferrous salt to reducing agent of 2:1–5, and the treatment time is 5–60 min. Then, nickel salt is added to the solution at a molar ratio of ferrous salt to nickel salt of 1–10:1, and the treatment time is 30–120 min. After filtration, washing, and drying, the nickel-iron bimetallic debrominating agent is obtained.

[0006] The preferred solid-liquid mass ratio is 1:10-20; the molar ratio of ferrous salt to reducing agent is 2:3-5, and the treatment time is 30-60 min; the molar ratio of ferrous salt to nickel salt is 1-5:1, and the treatment time is 30-60 min.

[0007] The ferrous salt described in this invention is ferrous sulfate or ferrous nitrate, the reducing agent is sodium borohydride or potassium borohydride, and the nickel salt is nickel sulfate or nickel nitrate.

[0008] Furthermore, the washing process includes three steps: washing with distilled water, washing with anhydrous ethanol, and washing with distilled water again.

[0009] This invention also provides an in-situ debromination method for bromine-containing plastics in electronic waste using the aforementioned nickel-iron-based bimetallic debromination agent, comprising the following steps:

[0010] The nickel-iron-based bimetallic debrominating agent is mixed evenly with bromine-containing plastics and then subjected to co-thermal debromination under an argon atmosphere. This process converts the organic bromine in the bromine-containing plastics into inorganic bromine, which is then fixed in the pyrolysis residue, thereby achieving efficient debromination of the pyrolysis oil and pyrolysis gas from the bromine-containing plastics.

[0011] Furthermore, the bromine in the bromine-containing plastic exists in the form of organic bromine, inorganic bromine, or combinations thereof.

[0012] Furthermore, the mass ratio of the bromine-containing waste plastic to the debrominating agent is 1:1 to 10; preferably, the mass ratio is 1:5 to 10.

[0013] In the co-pyrolysis debromination process described in this invention, the co-pyrolysis temperature is 400–1000℃, the heating rate is 1–20℃ / min, the processing time is 1–8h, and the Ar flow rate is 10–100ml / min; preferably, the co-pyrolysis temperature is 500–800℃, the heating rate is 2–15℃ / min, the processing time is 1–7h, and the argon flow rate is 15–90ml / min.

[0014] Furthermore, in the pyrolysis oil and gas and pyrolysis residue, the yield of pyrolysis oil is 5-10%, the yield of pyrolysis gas is 20-25%, and the yield of pyrolysis residue is 60-75%.

[0015] Furthermore, the removal rates of HBr and Br2 in the pyrolysis oil and pyrolysis gas are 95%–100%, and the removal rate of organic bromine is 90%–100%. The debrominated pyrolysis oil and gas can be applied in the fields of resin materials, graphite carbon materials, and superhydrophobic film materials.

[0016] This invention employs a bimetallic compound for in-situ, efficient removal of bromine-containing plastics from electronic waste. First, a nickel-iron bimetallic debrominating agent is prepared. The bromine-containing plastics from the electronic waste are then uniformly mixed with the nickel-iron bimetallic debrominating agent and subjected to co-pyrolysis under an inert atmosphere. During co-pyrolysis, the nickel-iron bimetallic debrominating agent promotes the breaking of C-Br bonds. The resulting bromine free radicals combine with hydrogen free radicals to generate HBr, or two bromine free radicals combine to generate Br2, thus converting organic bromine into inorganic bromine. The generated HBr and Br2 then react with the nickel-iron bimetallic debrominating agent to generate solid-phase NiBr2 and FeBr3, which are fixed in the pyrolysis residue. This removes bromine-containing substances from the pyrolysis oil and gas, simplifies the composition of the pyrolysis oil and gas, and allows it to be directly utilized as a chemical raw material or fuel.

[0017] Compared with existing technologies, the nickel-iron bimetallic debrominator prepared by this invention has abundant iron and nickel interfaces, which can promote electron transfer in the debromination reaction. It can simultaneously remove organic and inorganic bromine from bromine-containing plastics (solids), with high removal efficiency and high temperature resistance. The iron and nickel in the nickel-iron bimetallic debrominator have a synergistic debromination effect, and the debromination effect is greater than that of iron debrominator, nickel debrominator, and a mixture of the two. The debrominator preparation process of this invention is simple, energy-efficient, and easy to recycle, making it suitable for large-scale promotion. Attached image description:

[0018] Figure 1 The XRD pattern of the nickel-iron bimetallic debrominator prepared in Example 1 of this invention.

[0019] Figure 2 This is a schematic diagram showing the test results of the removal rates of HBr and Br2 from pyrolysis oil and gas of bromine-containing waste plastics using the nickel-iron bimetallic debrominating agent, iron debrominating agent, and nickel debrominating agent of Example 3 of the present invention.

[0020] Figure 3 This is a schematic diagram showing the test results of the removal rate of organic bromine from the pyrolysis oil and gas of bromine-containing waste plastics using the nickel-iron bimetallic debrominating agent, iron debrominating agent, and nickel debrominating agent of Example 3 of the present invention. Detailed implementation method:

[0021] The technical solution of the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents and instruments used are commercially available conventional products.

[0022] Example 1:

[0023] This embodiment relates to a highly efficient bimetallic in-situ debromination method for bromine-containing plastics in electronic waste, comprising the following steps:

[0024] (1) Preparation of nickel-iron bimetallic debromination agent:

[0025] First, 5.56 g of FeSO4·7H2O was dissolved in 100 mL of deionized water. Inert gas was passed through the ferric sulfate aqueous solution at 60 °C, and the mixture was stirred for 30 min. Then, 0.5 g of sodium borohydride was added to the solution, and the mixture was stirred for 30 min. After that, 2.5 g of NiSO4·5H2O was added, and the reaction time was 30 min. The mixture was then filtered, and after filtration, it was washed with deionized water, anhydrous ethanol, and deionized water again before drying to obtain the nickel-iron bimetallic debromination agent.

[0026] (2) Co-pyrolysis debromination: The bromine-containing waste plastics in electronic waste are crushed to a particle size of less than 5.0 mm using a pulverizer, and mixed evenly with the nickel-iron bimetallic debromination agent prepared in step (1) at a mass ratio of 1:5. The mixture is placed in a pyrolysis furnace, and the temperature is raised to 600 °C at a rate of 10 °C / min with an argon (Ar) flow rate of 10 ml / min for co-pyrolysis. The co-pyrolysis time is 2 h. The pyrolysis oil, pyrolysis gas and pyrolysis residue are collected after pyrolysis. The yield of pyrolysis oil is 5%, the yield of pyrolysis gas is 20%, and the yield of pyrolysis residue is 75%.

[0027] The total bromine content in pyrolysis oil and pyrolysis gas was determined by oxygen bomb combustion-ion chromatography; the HBr and Br2 contents in pyrolysis oil and pyrolysis gas were determined by ion chromatography; therefore, the organic bromine content in pyrolysis oil and pyrolysis gas is the total bromine content minus the HBr and Br2 contents.

[0028] This embodiment simultaneously detects the amounts of HBr, Br2, and organic bromine in the pyrolysis oil and pyrolysis gas collected after the pyrolysis of bromine-containing waste plastics in electronic waste without the addition of a debromination agent, and calculates the bromine removal rate when using the debromination agent of this embodiment.

[0029] Using the debrominating agent of this embodiment, the total removal rate of HBr and Br2 in pyrolysis oil and pyrolysis gas is 98%, and the removal rate of organic bromine is 100%.

[0030] Example 2:

[0031] This embodiment relates to a highly efficient bimetallic in-situ debromination method for bromine-containing plastics in electronic waste, comprising the following steps:

[0032] (1) Preparation of nickel-iron bimetallic debromination agent:

[0033] Using bromine-containing waste plastics from electronic waste as raw material, firstly, 5.56g of ferrous sulfate (FeSO4·7H2O) was weighed and dissolved in 80mL of deionized water. Inert gas was passed through the ferrous sulfate solution at 60℃ and the mixture was stirred for 50min. Then, 1g of sodium borohydride was added to the solution and stirred for 30min. After that, 2g of nickel sulfate (NiSO4·5H2O) was added and the reaction time was 30min. After filtration, the mixture was washed with deionized water, anhydrous ethanol, and deionized water, and then dried to obtain a nickel-iron bimetallic debromination agent.

[0034] (2) Co-pyrolysis debromination: The bromine-containing waste plastics in electronic waste are mixed with nickel-iron bimetallic debrominating agent at a mass ratio of 1:7. The mixture is then heated to 800℃ at a flow rate of 10ml / min and co-pyrolyzed for 2h. The pyrolysis oil, pyrolysis gas and pyrolysis residue are collected, the bromine content is detected and the bromine removal rate is calculated.

[0035] In this embodiment, the yield of pyrolysis oil is 10%, the yield of pyrolysis gas is 20%, and the yield of pyrolysis residue is 70%. The total removal rate of HBr and Br2 in pyrolysis oil and pyrolysis gas is 95%, and the removal rate of organic bromine is 98%.

[0036] Example 3

[0037] This embodiment relates to a highly efficient bimetallic in-situ debromination method for bromine-containing plastics in electronic waste, comprising the following steps:

[0038] (1) Preparation of nickel-iron bimetallic debromination agent:

[0039] Using bromine-containing waste plastics from electronic waste as raw material, firstly, 5.56 g of FeSO4·7H2O was dissolved in 80 mL of deionized water. An inert gas was passed through the ferrous sulfate aqueous solution at 60℃ and the mixture was stirred for 30 min. Then, 0.6 g of sodium borohydride was added to the solution, and stirring was continued for 30 min. Afterward, 2.5 g of NiSO4·5H2O was added, and the reaction time was 30 min. The mixture was filtered, washed successively with deionized water, anhydrous ethanol, and then with deionized water, and finally dried to obtain a nickel-iron bimetallic debromination agent.

[0040] (2) Co-pyrolysis debromination: Bromine-containing waste plastics in electronic waste are mixed with nickel-iron bimetallic debrominating agent at mass ratios of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 and 1:8 respectively. The mixture is then heated to 600℃ at a flow rate of 10 ml / min and co-pyrolyzed for 2 hours. The pyrolysis oil, pyrolysis gas and pyrolysis residue are collected and the bromine removal rate is tested.

[0041] Specifically, when the mass ratio of bromine-containing waste plastic to nickel-iron bimetallic debrominating agent is 1:6, the yield of pyrolysis oil is 8%, the yield of pyrolysis gas is 22%, and the yield of pyrolysis residue is 70%. Figure 2 and Figure 3 It can be seen that the removal rates of HBr and Br2 in pyrolysis oil and gas are 98%, and the removal rate of organic bromine is 99%.

[0042] In this embodiment, iron-based debromination agent, nickel-based debromination agent, and a mixture of both (iron-based and nickel-based debromination agent mixed in a 1:1 mass ratio) were used as comparative debromination agents. The same co-thermal debromination method was employed to debrominate bromine-containing waste plastics from the same electronic waste. Pyrolysis oil, pyrolysis gas, and pyrolysis residue were collected, and the bromine removal rate was measured. The results are as follows: Figure 2 and Figure 3 As shown.

[0043] The preparation method of the iron debromination agent is as follows: First, weigh 5.56g of FeSO4·7H2O and dissolve it in 60mL of deionized water. Inert gas is introduced into a constant temperature water bath at 60℃ and the mixture is stirred for 30min. Then, 0.6g of sodium borohydride is added to the solution and stirred continuously for 30min. After filtration, the solution is washed with deionized water, anhydrous ethanol, and deionized water, and then dried to obtain the iron debromination agent.

[0044] The preparation method of the nickel debromination agent is as follows: First, 5.56g of NiSO4·5H2O is weighed and dissolved in 60mL of deionized water. Inert gas is introduced into a constant temperature water bath at 60℃ and stirred for 30min. Then, 0.6g of sodium borohydride is added to the solution and stirred continuously for 30min. After filtration, the solution is washed with deionized water, anhydrous ethanol, and deionized water, and then dried to obtain the nickel debromination agent.

[0045] When iron is used as the debrominating agent, the yield of pyrolysis oil is 10%, the yield of pyrolysis gas is 20%, and the yield of pyrolysis residue is 70%. Figure 2 and Figure 3 It can be seen that the removal rates of HBr and Br2 in pyrolysis oil and gas are 60%, and the removal rate of organic bromine is 50%.

[0046] When nickel is used as the debrominating agent, the yield of pyrolysis oil is 10%, the yield of pyrolysis gas is 20%, and the yield of pyrolysis residue is 70%. Figure 2 and Figure 3 It can be seen that the removal rates of HBr and Br2 in pyrolysis oil and gas are 50%, and the removal rate of organic bromine is 40%.

[0047] When iron and nickel debrominating agents are mixed at a mass ratio of 1:1 as the debrominating agent, the yield of pyrolysis oil is 10%, the yield of pyrolysis gas is 20%, and the yield of pyrolysis residue is 70%. The removal rates of HBr and Br2 in the pyrolysis oil and gas are 70%, and the removal rate of organic bromine is 70%.

[0048] In summary, the removal rates of HBr, Br2, and organic bromine by the nickel-iron bimetallic debrominator in this embodiment are higher than those of the iron debrominator and nickel debrominator, indicating that the iron and nickel in the nickel-iron bimetallic debrominator have a synergistic debrominating effect, and the debrominating effect is greater than that of the iron debrominator, the nickel debrominator, and a mixture of the two.

Claims

1. A method for in-situ debromination of bromine-containing plastics in electronic waste using a nickel-iron-based bimetallic debrominating agent, characterized in that, Nickel-iron-based bimetallic debrominating agent is mixed evenly with bromine-containing plastics and debrominated by co-heating under an argon atmosphere; the organic bromine in the bromine-containing plastics is converted into inorganic bromine and fixed in the pyrolysis residue, thereby achieving efficient debromination of bromine-containing plastic pyrolysis oil and pyrolysis gas; The preparation method of the nickel-iron-based bimetallic debrominating agent is as follows: ferrous salt is dissolved in deionized water, an inert gas is passed through and stirred, a reducing agent solution is added to the ferrous salt aqueous solution, then nickel salt is added to the solution, and after filtration, washing and drying, the nickel-iron bimetallic debrominating agent is obtained.

2. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The mass ratio of ferrous salt to deionized water is 1:5~20; the molar ratio of ferrous salt to reducing agent is 2:1~5, and the treatment time after adding the reducing agent solution to the ferrous salt aqueous solution is 5~60 min; the molar ratio of ferrous salt to nickel salt is 1~10:1, and the treatment time after adding the nickel salt to the solution is 30~120 min.

3. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debromination agent according to claim 1, characterized in that, The ferrous salt is ferrous sulfate or ferrous nitrate, the reducing agent is sodium borohydride or potassium borohydride, and the nickel salt is nickel sulfate or nickel nitrate.

4. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The washing process includes three steps: washing with distilled water, washing with anhydrous ethanol, and washing with distilled water again.

5. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The bromine in the bromine-containing plastic exists in the form of organic bromine, inorganic bromine, and combinations thereof.

6. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The mass ratio of the bromine-containing plastic to the debrominating agent is 1:1~10.

7. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The mass ratio of the bromine-containing plastic to the debrominating agent is 1:5~10.

8. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, During the co-thermal debromination process, the co-thermal temperature is 400~1000℃, the heating rate is 1~20℃ / min, the treatment time is 1~8h, and the Ar flow rate is 10~100ml / min.

9. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The co-pyrolysis temperature is 500~800℃, the heating rate is 2~15℃ / min, the treatment time is 1~7h, and the argon flow rate is 15~90ml / min.

10. The in-situ debromination method for bromine-containing plastics in electronic waste using the nickel-iron-based bimetallic debrominating agent according to claim 1, characterized in that, The removal rates of HBr and Br2 in the pyrolysis oil and pyrolysis gas are 95%~100%, and the removal rate of organic bromine is 90%~100%.

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