Hydrolysis method of waste nylon 6 fishing net

Abstract

The invention provides a hydrolysis method of a waste nylon 6 fishing net. The hydrolysis method comprises the following steps: step 1, screening the waste nylon 6 fishing net, cleaning, removing impurities, disinfecting and crushing; step 2, pretreating diatomite; step 3, adding pretreated diatomite, solid acid and deionized water into a reaction kettle, stirring at 50 DEG C for 5 hours, and removing moisture to obtain a solid acid catalyst; 4, adding the solid acid catalyst, the cleaned waste nylon 6 fishing net and deionized water into a reaction kettle, controlling the temperature and time for reaction, and filtering while hot to obtain a liquid-phase product; 5, neutralizing, decolorizing and extracting the liquid-phase product to obtain a caprolactam monomer; and 6, carrying out polymerization reaction on the obtained caprolactam monomer to generate regenerated polyamide for chinlon spinning. According to the method provided by the invention, the solid acid catalyst is easily separated from reactants, the catalytic efficiency is high, the corrosion to equipment can be reduced, and the method is more environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of polymers, and in particular to a technology for hydrolyzing waste nylon 6 fishing nets. Background Art

[0002] Due to the excellent properties of polymer materials, such as versatility, low cost, light weight, durability, corrosion resistance, etc., the use of polymer materials in many application fields has grown exponentially in the past few decades, resulting in a large amount of plastic waste accumulated in natural environments such as beaches or oceans. Since they are not easily degraded under normal environmental conditions, a large amount of plastic waste poses a huge risk to the entire ecosystem. Recycling is an important option to reduce plastic waste. The main component of most fishing nets is nylon 6. Common methods for depolymerizing and recycling waste nylon 6 fishing nets include pyrolysis, hydrolysis, alcoholysis, aminolysis, ionic liquid method, supercritical method, etc. Among the many methods, hydrolysis is the most practical and convenient recycling method.

[0003] Existing hydrolysis technology can realize the hydrolysis and recovery of waste nylon 6 fishing nets at a certain temperature and pressure by high temperature and high pressure or by adding a liquid acid catalyst. For example, Chinese invention patent CN102503890A discloses a method for recovering ε-caprolactam by hydrolyzing waste nylon 6 using acidic ionic liquid, which comprises: (a) dissolving waste nylon 6 at 100-180°C under anhydrous conditions; (b) using the same acidic ionic liquid to catalyze the hydrolysis of waste nylon 6 under water as the medium, thereby obtaining a crude hydrolysis product. The method provided in the document is simple in process and has few by-products, but the acidic ionic liquid catalyst used is easy to corrode equipment and cause environmental pollution. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for hydrolyzing waste nylon 6 fishing nets which can reduce corrosion to equipment.

[0005] The present invention is achieved by: a method for hydrolyzing waste nylon 6 fishing nets, comprising the following steps:

[0006] Step 1: Screening, cleaning, removing impurities, disinfecting and crushing the waste nylon 6 fishing nets to obtain cleaned waste nylon 6 fishing nets;

[0007] Step 2: pre-treating the diatomite by soaking it in nitric acid, adjusting it to neutral, and calcining it at high temperature;

[0008] Step 3: Add pretreated diatomaceous earth, solid acid and deionized water into a reaction kettle, stir at 50° C. for 5 h to remove water and obtain a solid acid catalyst;

[0009] Step 4: adding the solid acid catalyst, the washed waste nylon 6 fishing net, and deionized water into a reaction kettle, controlling the temperature and time for reaction, and filtering while hot to obtain a liquid product;

[0010] Step 5: neutralizing, decolorizing and extracting the liquid product to obtain caprolactam monomer;

[0011] Step six: The obtained caprolactam monomer is polymerized to generate regenerated polyamide for nylon spinning.

[0012] Furthermore, in the step of cleaning and removing impurities from the waste nylon 6 fishing net in step 1, deionized water and ethanol are used for soaking and cleaning three times respectively.

[0013] Furthermore, the step 2 is specifically as follows: pouring the diatomaceous earth into a nitric acid solution, allowing the nitric acid solution to immerse the diatomaceous earth, placing it in a 25°C water bath and stirring for 2 hours, filtering, and then washing with distilled water until the filtrate is neutral; then placing the diatomaceous earth in a 400°C muffle furnace and drying it for 2.5 hours to obtain diatomaceous earth that has been acid-treated and calcined.

[0014] Furthermore, in the step three, the mass ratio of the pretreated diatomaceous earth, heteropoly acid and deionized water is 3:1:6.

[0015] Furthermore, in the step 4, the ratio of deionized water to washed waste nylon 6 fishing net is 10:1, and the solid acid catalyst is filtered while hot at a temperature below 100°C.

[0016] Furthermore, the component ratio of the washed waste nylon 6 fishing net, the solid acid catalyst, the catalyst carrier and the deionized water is as follows: 8-10: 2-3: 7-8: 80-100;

[0017] The solid acid in the solid acid catalyst is phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid;

[0018] The catalyst carrier uses pretreated diatomaceous earth.

[0019] The present invention has the following advantages: using phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid as a solid acid catalyst, it is easy to separate from the reactants, has high catalytic efficiency, can reduce corrosion to equipment, and is more environmentally friendly. DETAILED DESCRIPTION

[0020] The embodiment of the present application provides a method for hydrolyzing waste nylon 6 fishing nets.

[0021] The technical solution in the embodiment of the present application has the following general idea:

[0022] Embodiment 1:

[0023] This embodiment provides a method for hydrolyzing waste nylon 6 fishing nets, comprising the following components in percentage by weight:

[0024] 8 parts of washed nylon 6 waste fishing nets, 2 parts of solid acid, 8 parts of diatomaceous earth, and 80 parts of water; the solid acid is selected from phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid; the catalyst carrier is diatomaceous earth treated with acid and calcined.

[0025] The specific steps are as follows:

[0026] Step 1: 8 parts of waste nylon 6 fishing nets are screened, cleaned, disinfected and crushed to obtain 8 parts of cleaned waste nylon 6 fishing nets; wherein, the cleaning and impurity removal step uses deionized water and ethanol to soak and clean for 3 times respectively.

[0027] Step 2: Pour 8 parts of diatomaceous earth into nitric acid solution, immerse 8 parts of diatomaceous earth in the nitric acid solution, put it into a 25°C water bath and stir for 2 hours, filter it, and then wash it with distilled water until the filtrate is neutral; then put the diatomaceous earth into a 400°C muffle furnace and bake it for 2.5 hours to obtain 8 parts of pretreated diatomaceous earth.

[0028] Step 3: Add 30g of solid acid (phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid), 10g of diatomaceous earth carrier and 60ml of deionized water into a reactor, stir at 50°C for 5h to remove water to obtain a solid acid catalyst; wherein the mass ratio of diatomaceous earth, heteropoly acid and deionized water is 3:1:6.

[0029] Step 4: Add solid acid catalyst, 8 parts of washed waste nylon 6 fishing nets, and 80 parts of deionized water into the reactor, control the temperature to 200°C for 5 hours, and filter while hot to obtain a liquid product when the temperature is below 100°C. The filtered solid catalyst can be dried and reused for the next hydrolysis. The ratio of washed waste nylon 6 fishing nets to deionized water is 1:10.

[0030] Step 5: neutralize, decolorize and extract the liquid product to obtain caprolactam monomer.

[0031] Step 6: The obtained caprolactam monomer is polymerized to generate regenerated polyamide for nylon spinning.

[0032] Embodiment 2:

[0033] This embodiment provides a method for hydrolyzing waste nylon 6 fishing nets, comprising the following components in percentage by weight:

[0034] 10 parts of washed nylon 6 waste fishing nets, 3 parts of solid acid, 7 parts of diatomaceous earth, and 100 parts of water; the solid acid is selected from phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid; the catalyst carrier is diatomaceous earth treated with acid and calcined.

[0035] The specific steps are as follows:

[0036] Step 1: Screen, clean, remove impurities, disinfect and crush 10 parts of waste nylon 6 fishing nets to obtain 10 parts of cleaned waste nylon 6 fishing nets; wherein, the cleaning and removing impurities step uses deionized water and ethanol to soak and clean for 3 times respectively.

[0037] Step 2: Pour 7 parts of diatomaceous earth into nitric acid solution, immerse 7 parts of diatomaceous earth in the nitric acid solution, put it into a 25°C water bath and stir for 2 hours, filter it, and then wash it with distilled water until the filtrate is neutral; then put the diatomaceous earth into a 400°C muffle furnace and bake it for 2.5 hours to obtain 7 parts of pretreated diatomaceous earth.

[0038] Step 3: Add 45g of solid acid (phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid), 15g of diatomaceous earth carrier and 90ml of deionized water into a reactor, stir at 50°C for 5h to remove moisture to obtain a solid acid catalyst; wherein the mass ratio of diatomaceous earth, heteropoly acid and deionized water is 3:1:6.

[0039] Step 4: Add solid acid catalyst, 10 parts of washed waste nylon 6 fishing nets, and 100 parts of deionized water into the reactor, control the temperature to 200°C for 6 hours, and filter while hot to obtain a liquid product when the temperature is below 100°C. The filtered solid catalyst can be dried and reused for the next hydrolysis. The ratio of washed waste nylon 6 fishing nets to deionized water is 1:10.

[0040] Step 5: neutralize, decolorize and extract the liquid product to obtain caprolactam monomer.

[0041] Step 6: The obtained caprolactam monomer is polymerized to generate regenerated polyamide for nylon spinning.

[0042] Embodiment three:

[0043] This embodiment provides a method for hydrolyzing waste nylon 6 fishing nets, comprising the following components in percentage by weight:

[0044] 10 parts of washed nylon 6 waste fishing nets, 2 parts of solid acid, 8 parts of diatomaceous earth, and 100 parts of water; the solid acid is selected from phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid; the catalyst carrier is diatomaceous earth treated with acid and calcined.

[0045] The specific steps are as follows:

[0046] Step 1: Screen, clean, remove impurities, disinfect and crush 10 parts of waste nylon 6 fishing nets to obtain 10 parts of cleaned waste nylon 6 fishing nets; wherein, the cleaning and removing impurities step uses deionized water and ethanol to soak and clean for 3 times respectively.

[0047] Step 2: Pour 8 parts of diatomaceous earth into nitric acid solution, immerse 8 parts of diatomaceous earth in the nitric acid solution, put it into a 25°C water bath and stir for 2 hours, filter it, and then wash it with distilled water until the filtrate is neutral; then put the diatomaceous earth into a 400°C muffle furnace and bake it for 2.5 hours to obtain 7 parts of pretreated diatomaceous earth.

[0048] Step 3: Add 30g of solid acid (phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid), 10g of diatomaceous earth carrier and 60ml of deionized water into a reactor, stir at 50°C for 5h to remove water to obtain a solid acid catalyst; wherein the mass ratio of diatomaceous earth, heteropoly acid and deionized water is 3:1:6.

[0049] Step 4: Add solid acid catalyst, 10 parts of washed waste nylon 6 fishing nets, and 100 parts of deionized water into the reactor, control the temperature to 250°C for 5 hours, and filter while hot to obtain a liquid product when the temperature is below 100°C. The filtered solid catalyst can be dried and reused for the next hydrolysis. The ratio of washed waste nylon 6 fishing nets to deionized water is 1:10.

[0050] Step 5: neutralize, decolorize and extract the liquid product to obtain caprolactam monomer.

[0051] Step 6: The obtained caprolactam monomer is polymerized to generate regenerated polyamide for nylon spinning.

[0052] By using the method provided by the present invention, a carrier-loaded solid superacid is used to hydrolyze nylon 6 fishing nets, phosphotungstic heteropolyacid or phosphomolybdic heteropolyacid is easily separated from the reactants, the catalytic efficiency is high, corrosion to equipment can be reduced, and the environment is more environmentally friendly.

[0053] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for hydrolyzing waste nylon 6 fishing nets, characterized in that: The following steps are involved: Step 1: Screening, cleaning, removing impurities, disinfecting and crushing the waste nylon 6 fishing nets to obtain cleaned waste nylon 6 fishing nets; Step 2: pre-treating the diatomite by soaking it in nitric acid, adjusting it to neutral, and calcining it at high temperature; Step 3: Add pretreated diatomaceous earth, solid acid and deionized water into a reaction kettle, stir at 50° C. for 5 h to remove water and obtain a solid acid catalyst; Step 4: adding the solid acid catalyst, the washed waste nylon 6 fishing net, and deionized water into a reaction kettle, controlling the temperature and time for reaction, and filtering while hot to obtain a liquid product; Step 5: neutralizing, decolorizing and extracting the liquid product to obtain caprolactam monomer; Step six: The obtained caprolactam monomer is polymerized to generate regenerated polyamide for nylon spinning.

2. The method for hydrolyzing waste nylon 6 fishing nets according to claim 1, characterized in that: In the step 1, the waste nylon 6 fishing net is cleaned and impurity-removed by soaking and cleaning with deionized water and ethanol for 3 times respectively.

3. The method for hydrolyzing waste nylon 6 fishing nets according to claim 1, characterized in that: The step 2 is specifically as follows: pouring the diatomaceous earth into a nitric acid solution, allowing the nitric acid solution to immerse the diatomaceous earth, placing it in a 25° C. water bath and stirring for 2 hours, filtering it with suction, and then washing it with distilled water until the filtrate is neutral; then placing the diatomaceous earth in a 400° C. muffle furnace and drying it for 2.5 hours to obtain the diatomaceous earth after acid treatment and calcination.

4. The method for hydrolyzing waste nylon 6 fishing nets according to claim 1, characterized in that: The mass ratio of the pretreated diatomaceous earth, heteropoly acid and deionized water in step three is 3:1:

6.

5. According to claim 1, there is a method for hydrolyzing waste nylon 6 fishing nets, characterized in that: In the step 4, the ratio of deionized water to washed waste nylon 6 fishing net is 10:1, and the solid acid catalyst is filtered while hot at a temperature below 100°C.

6. The method for hydrolyzing waste nylon 6 fishing nets according to claim 1, characterized in that: The composition ratio of the washed waste nylon 6 fishing net, the solid acid catalyst, the catalyst carrier and the deionized water is as follows: 8-10: 2-3: 7-8: 80-100; The solid acid in the solid acid catalyst is phosphotungstic heteropoly acid or phosphomolybdic heteropoly acid; The catalyst carrier uses pretreated diatomaceous earth.