Process for the recovery of dimethyl ether from a degradation of a cryptic amine resin catalyzed by ammonium

Abstract

The present application belongs to the field of resin solid waste recycling and resource utilization, and particularly relates to a method for recovering dimethyl ether by catalytic degradation of melamine resin with ammonium. The present application aims to selectively break specific chemical bonds in melamine resin by using an efficient catalyst system, retain ether bonds as dimethyl ether, and obtain by-product cyanuric acid, so as to realize efficient recovery of melamine resin. The present application solves the problems of poor selectivity of chemical bond catalytic degradation, complex product composition, low added value, easy generation of highly toxic hydrocyanic acid, and difficulty in retaining valuable chemical functional groups of C-O-C in the chemical treatment method. The catalyst-solvent system is directly used for reaction, and high added value dimethyl ether and cyanuric acid are finally obtained through subsequent treatment.

Description

Technical Field

[0001] This invention belongs to the field of resin solid waste recycling and resource utilization, specifically relating to a method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation. Background Technology

[0002] Melamine resin, also known as melamine-formaldehyde resin (MF), is a low-density, high-density resin produced by microwave polymerization of melamine and formaldehyde. It possesses excellent flame retardancy, heat insulation, sound absorption, and is easy to process, making it a widely used lightweight flame-retardant material in aerospace, rail transportation, and interior decoration. Melamine resin also boasts excellent thermal insulation, flame retardancy, corrosion resistance, and ductility, and in recent years has been widely used in household cleaning, audio equipment, and fire-resistant materials. With the rapid development of the construction industry, MF consumption is growing at an alarming rate. Due to the high chemical stability of melamine resin products, they are not easily degraded by light, microorganisms, or water in the environment, which not only encroaches on human living space but may also cause soil or groundwater pollution.

[0003] Currently, the main methods for treating waste melamine resin are landfill incineration and high-temperature pyrolysis. Landfill incineration, which involves directly burying waste melamine resin in the soil or burning it in the open air, poses a serious threat to the soil environment. The combustion releases toxic gases, causing environmental pollution, and yields no economically valuable products. High-temperature pyrolysis primarily involves treating waste melamine resin at high temperatures. The high temperature non-selectively breaks the chemical bonds in the resin, allowing for the recovery of the corresponding components. This method is convenient to implement and has a simple process. However, the catalytic degradation of chemical bonds has poor selectivity, the products are complex in composition, have low added value, and are inconvenient for reuse. Furthermore, melamine resin easily generates highly toxic substances such as hydrogen cyanide at high temperatures, which greatly limits the application of this method.

[0004] Existing research has mainly focused on the recovery and acquisition of diaminomethyl ether (Methanamine, C2H8N2O). Methanamine is mainly used in organic synthesis to introduce aminomethyl groups onto aromatic rings, serving as an intermediate for the drugs cyclophosphamide, octaazine dipropyl ether, and diphosphatidylcholine.

[0005] However, during the degradation of melamine resin, the ether bonds between the six-membered rings are also destroyed. If, under appropriate reaction conditions, only the sp... 2 If the C-NH2 bond is selectively opened, melamine resin can be catalytically degraded into diaminomethyl ether, cyanuric acid monoamide, and cyanuric acid diamide, but no related research has been reported. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to selectively break specific chemical bonds in melamine resin using a highly efficient catalytic system, retaining the ether bond as diaminomethyl ether (NH2-CH2-O-CH2-NH2), while simultaneously obtaining the byproduct cyanuric acid. This achieves efficient recovery of melamine resin and provides a method for recovering diaminomethyl ether from melamine resin through ammonium catalytic degradation.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation includes the following steps:

[0009] (1) The waste melamine resin is immersed in the catalyst-solvent liquid phase system for reaction;

[0010] (2) After the reaction is complete, the filter residue and filtrate are separated and recovered separately;

[0011] (3) Add dilute sulfuric acid to the filter residue for hot hydrolysis to obtain cyanuric acid as a byproduct, and then add alkali to neutralize and precipitate cyanuric acid;

[0012] (4) Extract, distill, dry and dehydrate the filtrate to obtain diamine methyl ether.

[0013] Further, the catalyst mentioned in step (1) is any one or more of the following ammonium catalysts: NH4HCO3, CH3COONH4, (NH4)2CO3, NH3·H2O, NH4Cl, (NH4)3PO4 and HCOONH4.

[0014] Further, the solvent in step (1) is water or a mixture of water and an organic reagent, wherein the organic reagent is any one or more of methanol, ethanol, n-propanol, isopropanol, tetrahydrofuran, DMSO, dioxane, DMF, γ-butyrolactone, γ-valerolactone or acetone; the volume ratio of water to organic solvent is 1:0 to 10.

[0015] Further, in step (1), the mass ratio of the catalyst to the waste melamine resin is 1:0.05 to 5; and the mass ratio of the solvent to the waste melamine resin is 1 to 100:1.

[0016] Further, the reaction conditions described in step (1) are a reaction temperature of 100 to 300°C and a reaction time of 120 min to 36 h.

[0017] Furthermore, in step (3), the temperature for co-hydrolysis with dilute sulfuric acid is 50-150°C, and the concentration of dilute sulfuric acid is 5-20%.

[0018] Furthermore, the alkali mentioned in step (3) is sodium hydroxide.

[0019] Further, the extraction distillation described in step (3) is as follows: when only aqueous solution is involved in catalytic degradation, diamine methyl ether is extracted with ethyl acetate, that is, the aqueous phase system is recycled, and diamine methyl ether is obtained by distillation of the ethyl acetate phase; when the organic solvent-water mixed solution is involved in catalytic degradation, petroleum ether is added to the system until the organic solvent-water mixed solution is phase-separated, the lower aqueous phase is recycled, and the upper organic phase is obtained by distillation.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention achieves the catalytic degradation of waste melamine resin. Selecting a suitable catalyst-solvent system facilitates the entry of the catalyst and solvent into the melamine resin, making it easier to contact its reactive sites, thereby improving the efficiency of catalytic degradation.

[0022] 2. Compared with previous chemical degradation, the present invention achieves catalytic degradation of melamine resin under mild conditions, retains the ether bond portion in the resin, and can recover diaminomethyl ether.

[0023] 3. This invention solves the problems of poor selectivity of chemical bond catalytic degradation, complex product composition, low added value, easy generation of highly toxic hydrogen cyanide, and difficulty in retaining valuable chemical functional groups of COC in chemical treatment methods. It directly adopts a catalyst-solvent system reaction, and after subsequent treatment, finally obtains high-value-added diamine methyl ether and the by-product cyanuric acid. Attached Figure Description

[0024] Figure 1 The diaminomethyl ether and cyanuric acid monoamide and cyanuric acid diamide of Example 1 of this invention 13 CNMR spectrum.

[0025] Figure 2 The NMR spectra of diamine methyl ether, cyanuric acid monoamide, and cyanuric acid diamide in Example 1 of this invention are shown. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0027] Example 1

[0028] (1) Immerse 1g of waste melamine resin in the NH3HCO3-water reaction system (the mass ratio of NH3HCO3 to melamine resin is 1:5; the mass ratio of water to melamine resin is 10:1), and react at 100℃ for 36h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0029] (2) After the reaction is completed, filter the residue and hydrolyze it with a 15% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Add sodium hydroxide to neutralize the cyanuric acid.

[0030] (3) Extract the filtrate with ethyl acetate, i.e., recycle the aqueous phase system, distill the ethyl acetate phase, and then vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0031] This example yielded 0.10 g of diaminomethyl ether and 0.80 g of cyanuric acid as a byproduct; cyanuric acid monoamide, cyanuric acid diamide, and diaminomethyl ether were also obtained. 13 CNMR spectrum as shown Figure 1 As shown, chemical shifts at 167.3 ppm and 171.2 ppm correspond to carbons within the cyanuric acid ring, chemical shift at 72.7 ppm corresponds to carbons on the diaminomethyl ether, and other peaks correspond to the solvent.

[0032] The NMR hydrogen spectrum is as follows: Figure 2 As shown, the chemical shift at 8.68 ppm corresponds to the hydrogen in the cyanuric acid ring, the chemical shift at 4.92 ppm corresponds to the hydrogen on the diamine methyl ether, and the other peaks correspond to the solvent.

[0033] Example 2

[0034] (1) Immerse 1g of waste melamine resin in a (NH4)2CO3-water and tetrahydrofuran reaction system (the mass ratio of (NH4)2CO3 to melamine resin is 1:0.05; the mass ratio of solvent to melamine resin is 100:1; the volume ratio of water to tetrahydrofuran in the solvent is 1:5), and react at 300℃ for 120min in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0035] (2) After the reaction is completed, filter the residue and hydrolyze it with a 15% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Add sodium hydroxide to neutralize the cyanuric acid.

[0036] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0037] In this example, 0.12 g of diamine methyl ether and 0.82 g of cyanuric acid as a byproduct were obtained.

[0038] Example 3

[0039] (1) Immerse 1g of waste melamine resin in the HCOONH4-water and acetone reaction system (the mass ratio of HCOONH4 to melamine resin is 1:1; the mass ratio of solvent to melamine resin is 80:1; the volume ratio of water to acetone in the solvent is 1:6), and react at 180°C for 20h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0040] (2) After the reaction is complete, filter the residue and hydrolyze it with a 5% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Neutralize with sodium hydroxide to obtain cyanuric acid.

[0041] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0042] In this example, 0.11 g of diamine methyl ether and 0.85 g of cyanuric acid as a byproduct were obtained.

[0043] Example 4

[0044] (1) Immerse 1g of waste melamine resin in a (NH4)3PO4-water and ethanol reaction system (the mass ratio of (NH4)3PO4 to melamine resin is 1:3; the mass ratio of solvent to melamine resin is 50:1; the volume ratio of water to ethanol in the solvent is 1:3), and react at 200℃ for 19h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0045] (2) After the reaction is complete, filter the residue and hydrolyze it with a 20% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Neutralize with sodium hydroxide to obtain cyanuric acid.

[0046] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0047] In this example, 0.05 g of diamine methyl ether and 0.65 g of cyanuric acid as a byproduct were obtained.

[0048] Example 5

[0049] (1) Immerse 1g of waste melamine resin in the CH3COONH4-water and isopropanol reaction system (the mass ratio of CH3COONH4 to melamine resin is 1:2; the mass ratio of solvent to melamine resin is 80:1; the volume ratio of water to ethanol in the solvent is 1:1), and react at 220℃ for 14h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0050] (2) After the reaction is completed, filter the residue and hydrolyze it with a 15% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Add sodium hydroxide to neutralize the cyanuric acid.

[0051] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0052] In this example, 0.09 g of diamine methyl ether and 0.70 g of cyanuric acid as a byproduct were obtained.

[0053] Example 6

[0054] (1) Immerse 1g of waste melamine resin in an NH3·H2O and methanol reaction system (the mass ratio of NH3·H2O to melamine resin is 1:4, the mass ratio of H2O to NH3 is 3:1; the mass ratio of solvent to melamine resin is 30:1, and the volume ratio of water to methanol in the solvent is 1:5), and react at 180°C for 24h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0055] (2) After the reaction is complete, filter the residue and hydrolyze it with a 10% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Neutralize with sodium hydroxide to obtain cyanuric acid.

[0056] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0057] In this example, 0.12 g of diamine methyl ether and 0.73 g of cyanuric acid as a byproduct were obtained.

[0058] Example 7

[0059] (1) Immerse 1g of waste melamine resin in the CH3COONH4-water and DMF reaction system (the mass ratio of CH3COONH4 to melamine resin is 1:3; the mass ratio of solvent to melamine resin is 10:1; the volume ratio of water to DMF in the solvent is 1:7), and react at 140℃ for 30h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0060] (2) After the reaction is completed, filter the residue and hydrolyze it with a 15% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Add sodium hydroxide to neutralize the cyanuric acid.

[0061] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0062] In this example, 0.10 g of diamine methyl ether and 0.79 g of cyanuric acid as a byproduct were obtained.

[0063] Example 8

[0064] (1) Immerse 1g of waste melamine resin in the NH4Cl-water and dioxane reaction system (the mass ratio of NH4Cl to melamine resin is 1:1; the mass ratio of solvent to melamine resin is 70:1; the volume ratio of water to dioxane in the solvent is 1:10), and react at 160℃ for 27h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0065] (2) After the reaction is complete, filter the residue and hydrolyze it with a 10% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Neutralize with sodium hydroxide to obtain cyanuric acid.

[0066] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0067] In this example, 0.08 g of diamine methyl ether and 0.54 g of cyanuric acid as a byproduct were obtained.

[0068] Example 9

[0069] (1) Immerse 1g of waste melamine resin in the HCOONH4-water and γ-butyrolactone reaction system (the mass ratio of HCOONH4 to melamine resin is 1:1; the mass ratio of solvent to melamine resin is 50:1; the volume ratio of water to γ-butyrolactone in the solvent is 1:5), and react at 260℃ for 8h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0070] (2) After the reaction is completed, filter the residue and hydrolyze it with a 15% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Add sodium hydroxide to neutralize the cyanuric acid.

[0071] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0072] In this example, 0.10 g of diamine methyl ether and 0.82 g of cyanuric acid as a byproduct were obtained.

[0073] Example 10

[0074] (1) Immerse 1g of waste melamine resin in a (NH4)2CO3-water and DMSO reaction system (the mass ratio of (NH4)2CO3 to melamine resin is 1:0.05; the mass ratio of solvent to melamine resin is 80:1; the volume ratio of water to DMSO in the solvent is 1:9), and react at 280℃ for 5h in a closed pressure vessel to allow the waste melamine resin material to react fully.

[0075] (2) After the reaction is complete, filter the residue and hydrolyze it with a 20% sulfuric acid aqueous solution at 120°C to generate cyanuric acid. Neutralize with sodium hydroxide to obtain cyanuric acid.

[0076] (3) Add petroleum ether to the filtrate until the organic solvent-water mixture is separated into phases. Recycle the lower aqueous phase and distill the upper organic phase. Then, vacuum dry to remove trace amounts of water to obtain diamine methyl ether.

[0077] In this example, 0.12 g of diamine methyl ether and 0.83 g of cyanuric acid as a byproduct were obtained.

[0078] The organic solvent in each of the above embodiments can also be replaced with n-propanol or γ-valerol.

[0079] The embodiments described above are merely specific examples of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation, characterized in that, The specific steps are as follows: (1) The waste melamine resin is immersed in the catalyst-solvent liquid phase system for reaction; (2) After the reaction is complete, the filter residue and filtrate are separated and recovered separately; (3) Add dilute sulfuric acid to the filter residue for hot hydrolysis to obtain cyanuric acid as a byproduct, and then add alkali to neutralize and precipitate cyanuric acid; (4) Extract the filtrate by distillation, drying and dehydration to obtain diaminomethyl ether NH2-CH2-O-CH2-NH2; The catalyst in step (1) is any one or more of the following ammonium catalysts: NH4HCO3, CH3COONH4, NH3•H2O, NH4Cl, (NH4)3PO4 and HCOONH4; The reaction conditions in step (1) are a reaction temperature of 100~300℃ and a reaction time of 120min~36h; The solvent in step (1) is water or a mixture of water and organic reagent; In step (4), the extraction distillation is performed by using ethyl acetate to extract diamine methyl ether when only aqueous solution is involved in the catalytic degradation, i.e., recycling the aqueous phase system and distilling the ethyl acetate phase to obtain diamine methyl ether; when the organic solvent-water mixed solution is involved in the catalytic degradation, petroleum ether is added to the system until the organic solvent-water mixed solution separates into phases, the lower aqueous phase is recycled, and the upper organic phase is distilled to obtain diamine methyl ether.

2. The method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation according to claim 1, characterized in that, The solvent mentioned in step (1) is water or a mixture of water and organic reagent, wherein the organic reagent is any one or more of methanol, ethanol, n-propanol, isopropanol, tetrahydrofuran, DMSO, dioxane, DMF, γ-butyrolactone, γ-valerolactone or acetone; the volume ratio of water to organic solvent is 1:0~10.

3. The method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation according to claim 1, characterized in that, The mass ratio of the catalyst to the waste melamine resin in step (1) is 1:0.05~5; the mass ratio of the solvent to the waste melamine resin is 1~100:

1.

4. The method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation according to claim 1, characterized in that, The temperature for adding dilute sulfuric acid for co-hydrolysis in step (3) is 50~150℃, and the concentration of dilute sulfuric acid is 5-20%.

5. The method for recovering diamine methyl ether from melamine resin by ammonium catalytic degradation according to claim 1, characterized in that, The alkali mentioned in step (3) is sodium hydroxide.

Images