Preparation of reverse catalyst and application of reverse catalyst in catalysis of polymer degradation

Abstract

The invention discloses preparation of a reversed-phase catalyst and application of the reversed-phase catalyst in catalyzing degradation of a polymer. According to the catalyst, nano metal oxide RO is used as a loading phase to be uniformly loaded on carrier metal R ', a nano oxide / metal reverse phase interface structure is formed and recorded as ROx / R', and x represents the molar ratio of R 'to R; the catalyst disclosed by the invention can enhance adsorption of C-O bonds in polymer molecules by utilizing strong interface electron interaction between RO and R ', so that cracking of the C-O bonds in the polymer molecules is promoted, and a high-selectivity polymer monomer is obtained. The reverse catalyst provided by the invention can effectively improve the polymer degradation rate and selectivity, solves the technical problems of low conversion efficiency, high cost and difficult catalyst recycling in oxygen-containing plastic degradation in the prior art, and realizes high efficiency, high selectivity, low cost and low energy consumption of polyester and polyether plastic degradation.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer degradation, and in particular relates to a reverse ROx / R' catalyst and application of the catalyst in catalyzing polymer degradation. Background Art

[0002] Plastics are convenient, durable, cheap, and easy to process, and are widely used in various fields of the national economy. At present, about 80% of waste plastics are landfilled in the natural environment. Plastics will exist in the natural environment for a long time, which not only interferes with the growth of animals and plants, but also seriously threatens human food safety. In 2020, my country's plastic product output was about 76.03 million tons, and the apparent consumption was about 130 million tons. It is estimated that by 2025, the plastic waste generated in my country will exceed 17 million tons, becoming the world's largest producer of plastic waste. The traditional strategies to solve the problem of plastic pollution mainly include: designing degradable plastics or recyclable plastics; developing plastic recycling technologies, including mechanical recycling, chemical recycling and incineration. However, these strategies face many economic and technical challenges (high cost, low benefits, low efficiency, and secondary pollution). Compared with traditional mechanical recycling and chemical recycling technologies, the technology of upgrading and recycling waste plastics into high-quality chemicals, fuels or functional materials can help improve the economic value of products, reduce resource and energy consumption and secondary pollution in the conversion process, and is expected to become a key strategy to solve waste plastic pollution. Therefore, it is of great research significance to develop chemical upgrading and recycling technology for waste plastics and convert them into high-quality chemicals, fuels or functional materials. PET is one of the five most widely used engineering plastics, with an annual waste volume of up to 8 million tons. PET monomers are polymerized into macromolecules with CO bonds. Upgrading PET waste requires selective breaking of CO bonds to obtain corresponding monomer chemicals. However, the current catalytic system for hydrogenolysis of PET is still in the initial stage of research, and there are still problems such as harsh reaction conditions, difficult selectivity control, and easy deactivation of catalysts. In summary, the key to opening up the route for upgrading PET waste to prepare chemicals is to develop a low-cost, stable and highly selective CO bond hydrogenolysis catalyst. Summary of the invention

[0003] The main purpose of the present invention is to provide a cheap reverse phase ROx / R' catalyst and the application of the catalyst in catalyzing polymer degradation. The reverse phase ROx / R' catalyst of the present invention exhibits higher activity and selectivity than traditional catalysts when catalyzing polymer degradation, especially being able to obtain polymer monomers with high selectivity.

[0004] The reverse phase catalyst uses nano metal oxide RO as a supporting phase uniformly supported on a carrier metal R' to form a nano oxide / metal reverse phase interface structure, which is recorded as ROx / R', where x represents the molar ratio of R' to R; wherein the nano metal oxide RO is a lanthanide metal oxide, and the carrier metal R' is one of nickel, copper or cobalt.

[0005] In the catalyst, the molar ratio of R' to R is preferably 5-320:1.

[0006] The preparation method of the reverse phase catalyst comprises the following steps: dripping an aqueous solution of a carrier metal R' precursor and a nano metal oxide RO precursor into a precipitant solution under vigorous stirring, stirring and mixing the mixture evenly, sealing the mixture in a hydrothermal kettle, heating the mixture to 100-200° C., and performing a hydrothermal reaction for 12-48 hours; filtering, washing, and drying the mixture after the reaction is completed; then calcining the dried sample at 300-600° C. for 2-8 hours in an air atmosphere, and reducing the calcined sample at 250-550° C. for 2-6 hours in a hydrogen atmosphere to obtain a reverse phase catalyst ROx / R'.

[0007] The carrier metal R' precursor is selected from one or two of chlorides, sulfates, nitrates, acetates and hydrates of nickel, copper and cobalt, and the nano metal oxide RO precursor is selected from one or two of chlorides, sulfates, nitrates, acetates and hydrates of lanthanide metals. The precipitant solution is one or more aqueous solutions of oxalic acid, sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, potassium carbonate, urea, potassium bicarbonate, ammonium carbonate, tetramethylammonium hydroxide and ammonia water.

[0008] The reverse phase catalyst is used in catalyzing polymer degradation.

[0009] The polymer is one of polyethylene glycol (PEG), polyethylene terephthalate (PET), and poly(bisphenol A-co-epichlorohydrin) glycidyl terminated (PBAE).

[0010] The polymer degradation reaction is carried out in an intermittent reactor. 2 The pressure is 1-5 MPa, the reaction temperature is 120-200° C., the reaction system is a solvent-free system or a solvent system, and the solvent is one of methanol, ethanol, isopropanol, and tetrahydrofuran.

[0011] The reverse phase catalyst ROx / R' of the present invention has the characteristics of selectively breaking carbon-oxygen bonds and selectively hydrogenating. It can utilize the strong interfacial electronic interaction between RO and R' to enhance the adsorption of ether oxygen adsorbed on the electron-rich interface near the oxygen vacancy, promote the cleavage of the CO bond in the polymer molecule, and obtain highly selective polymer monomers.

[0012] The present invention has the following advantages over the prior art: 1. The present invention forms a strong interfacial electronic interaction by constructing an inverse interface structure between nano-metal oxide RO and carrier metal R', thereby solving the problems of poor polymer monomer selectivity and unstable catalyst in the prior art; 2. The present invention achieves efficient degradation of polymers under relatively mild and environmentally friendly conditions, providing useful guidance for solving waste plastic pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The inverse CeO prepared in Example 1 of the present invention 2 SEM photograph of the Ni / Ni catalyst.

[0014] Figure 2 The inverse CeO prepared in Example 1 of the present invention 2 / Ni catalyst XRD pattern.

[0015] Figure 3 The inverse CeO prepared in Example 1 of the present invention 2 XPS photograph of / Ni catalyst. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below through specific examples, but the protection scope of the present invention is not limited to these examples. The experimental methods used in the examples are conventional methods unless otherwise specified; the materials, reagents, etc. used in the examples, unless otherwise specified, can be obtained from commercial channels.

[0017] Example 1 Reverse CeO 2 Preparation of Ni / Ni catalyst (Ni to Ce molar ratio of 80): 23.2 g Ni(NO 3 ) 2 6H 2 O aqueous solution and 0.43 g Ce(NO 3 ) 3 6H 2 O aqueous solution was added dropwise to the oxalic acid aqueous solution and stirred for 1 h. The mixed solution was placed in a hydrothermal kettle and hydrothermaled at 140 °C for 24 h. After filtering, washing with water, and drying, it was calcined at 400 °C in air for 3 h, and then reduced at 350 °C in hydrogen for 3 h to obtain reverse CeO 2 / Ni catalyst.

[0018] The catalyst was characterized and the results are shown in Figure 1 , Figure 2 and Figure 3 . Figure 1 The results showed that CeO 2The particle size is 2~3nm, evenly distributed on the Ni carrier, with a dispersion of 85%; Figure 2 The XRD results showed only nickel diffraction peaks, but no CeO 2 The diffraction peaks of CeO 2 The particles are evenly dispersed and have a small particle size; Figure 3 The results show that nickel is mainly present in the zero-valent form, while cerium coexists in the trivalent and tetravalent forms.

[0019] Example 2 Reverse La 2 O 3 Preparation of Co / Co (Co to La molar ratio of 320) catalyst: 23.2 g Co(NO 32 6H 2 O aqueous solution and 0.11 g La(NO 3 ) 3 6H 2 O aqueous solution was added dropwise to the urea aqueous solution and stirred for 1 hour. The mixed solution was placed in a hydrothermal kettle and hydrothermalized at 110℃ for 24 hours. After filtering, washing, and drying, it was calcined at 500℃ in air for 5 hours, and then reduced at 400℃ in hydrogen for 3 hours to obtain reverse La 2 O 3 / Co catalyst.

[0020] Example 3 Reverse La 2 O 3 Preparation of Cu / Cu (Cu to La molar ratio of 10) catalyst: 19.3 g Cu(NO 3 ) 2 6H 2 O aqueous solution and 3.44 g La(NO 3 ) 3 6H 2 O aqueous solution was added dropwise to the sodium hydroxide aqueous solution, and stirring was continued for 1 hour. The mixed solution was placed in a hydrothermal kettle, hydrothermal at 140°C for 24 hours, filtered, washed with water, dried, calcined in air at 400°C for 3 hours, and then reduced in hydrogen at 300°C for 3 hours to obtain reverse La 2 O 3 / Cu catalyst.

[0021] Example 4 The reverse CeO prepared in Example 1 2 / Ni catalyst (Ni to Ce molar ratio of 80) is used to catalyze the degradation reaction of PEG. The specific degradation reaction method is as follows: 0.4 g of catalyst and 0.5 g of PEG were added to a 100 mL stainless steel reactor, tetrahydrofuran was used as solvent, the reactor was closed, the gas in the reactor was replaced with hydrogen five times, 4 MPa of hydrogen was filled at room temperature before the reaction, the reactor was heated to 160°C, the reaction was started, and after 20 hours of reaction, the reactor was placed in an ice water bath to cool, the hydrogen was vented, and the liquid was analyzed in a gas chromatograph after centrifugal separation. The results are shown in Table 1.

[0022] Example 5 The reverse CeO prepared in Example 1 2 / Ni catalyst (Ni to Ce molar ratio is 80) is used to catalyze the degradation reaction of PET. The specific degradation reaction method is as follows: 0.4 g of catalyst and 0.5 g of PET (PET is white granules with a viscosity of 0.82 dL / g) were added to a 100 mL stainless steel reactor, the reactor was closed, and the gas in the reactor was replaced with hydrogen five times. 4 MPa of hydrogen was filled at room temperature before the reaction, and the reactor was heated to 170°C to start the reaction. After 10 hours of reaction, the reactor was placed in an ice water bath to cool, the hydrogen was vented, and the liquid was analyzed in a gas chromatograph after centrifugal separation. The results are shown in Table 1.

[0023] Example 6 The reverse CeO prepared in Example 1 2 / Ni catalyst (Ni to Ce molar ratio of 80) is used to catalyze the PBAE degradation reaction. The specific degradation reaction method is as follows: 0.4g catalyst and 0.5g PBAE (molecular weight about 1075) were added to a 100mL stainless steel reactor, methanol was used as solvent, the reactor was closed, and the gas in the reactor was replaced with hydrogen five times. 4MPa hydrogen was filled at room temperature before the reaction, and the reactor was heated to 170°C to start the reaction. After 10 hours of reaction, the reactor was placed in an ice water bath to cool, the hydrogen was vented, and the liquid was analyzed in a gas chromatograph after centrifugal separation. The results are shown in Table 1.

[0024] Table 1 Reverse CeO 2 Results of using -x / Ni catalyst for polymer degradation reaction .

[0025] Comparative Example 1 Traditional Ni / CeO 2 Preparation of catalyst Ni:Ce molar ratio of 1:9.5: 1.53 g Ni(NO 3 ) 2 6H 2 O aqueous solution and 21.7 g Ce(NO 3 ) 3 6H 2O aqueous solution was added dropwise to the oxalic acid aqueous solution and stirred for 1 hour. The mixed solution was placed in a hydrothermal kettle and hydrothermaled at 140°C for 24 hours. After filtering, washing, and drying, it was calcined at 400°C in air for 3 hours, and then reduced at 350°C in hydrogen for 3 hours to obtain the conventional Ni / CeO 2 Catalyst. (Ni to Ce molar ratio is 1:9.5) Comparative Example 2 The conventional Ni / CeO prepared in Comparative Example 1 2 The catalyst was used to catalyze the degradation reaction of PEG, and the specific method of hydrogenation reaction was the same as that of Example 4. The results are shown in Table 2.

[0026] Comparative Example 3 The conventional Ni / CeO prepared in Comparative Example 1 2 The catalyst was used to catalyze the degradation reaction of PET, and the specific method of hydrogenation reaction was the same as that of Example 5. The results are shown in Table 2.

[0027] Comparative Example 4 The conventional Ni / CeO prepared in Comparative Example 1 2 The catalyst was used to catalyze the degradation reaction of PBAE, and the specific method of hydrogenation reaction was the same as that of Example 6. The results are shown in Table 2.

[0028] Table 2 Ni / CeO 2 The results of the catalyst used in polymer degradation reactions From the comparison between Tables 1 and 2, it can be seen that the performance of the reverse catalyst is much higher than that of the traditional catalyst. The reason is that the strong interfacial electronic interaction between the metal oxide and the metal of the reverse catalyst enhances the adsorption of CO bonds in the polymer molecules, thereby promoting the cleavage of CO bonds in the polymer molecules and improving the catalytic performance of the catalyst.

Claims

1. A reverse phase catalyst, characterized in that Nano-metal oxide RO is used as a loading phase and is uniformly loaded on a carrier metal R' to form a nano-oxide / metal reverse interface structure, which is recorded as ROx / R', where x represents the molar ratio of R' to R; wherein the nano-metal oxide RO is a lanthanide metal oxide, and the carrier metal R' is one of nickel, copper or cobalt.

2. A reverse phase catalyst as claimed in claim 1, characterized in that: The molar ratio of R' to R is 5-320:

1.

3. A method for preparing a reverse phase catalyst as claimed in claim 1, characterized in that: Under vigorous stirring, an aqueous solution of a carrier metal R' precursor and a nano-metal oxide RO precursor is dropped into a precipitant solution, stirred and mixed evenly, and then the mixture is sealed in a hydrothermal kettle and heated to 100-200°C for a hydrothermal reaction for 12-48 hours. After the reaction is completed, the mixture is filtered, washed, and dried; then the dried sample is calcined at 300-600°C in an air atmosphere for 2-8 hours, and the calcined sample is placed in a hydrogen atmosphere for reduction at 250-550°C for 2-6 hours to obtain a reverse catalyst ROx / R'.

4. The method for preparing a reverse phase catalyst as claimed in claim 3, characterized in that: The carrier metal R' precursor is selected from one or two of chlorides, sulfates, nitrates, acetates and hydrates of nickel, copper and cobalt, and the nano metal oxide RO precursor is selected from one or two of chlorides, sulfates, nitrates, acetates and hydrates of lanthanide metals.

5. The method for preparing a reverse phase catalyst as claimed in claim 3, characterized in that: The precipitant solution is an aqueous solution of one or more of oxalic acid, sodium carbonate, urea, sodium bicarbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, potassium bicarbonate, ammonium carbonate, tetramethylammonium hydroxide, and ammonia water.

6. Use of the reverse phase catalyst as claimed in claim 1 in catalyzing polymer degradation.

7. The use of the reverse phase catalyst in catalyzing polymer degradation as claimed in claim 6, characterized in that: The polymer is one of polyethylene glycol, polyethylene terephthalate or poly(bisphenol A-co-epichlorohydrin) glycidyl terminated.

8. The use of the reverse phase catalyst in catalyzing polymer degradation as claimed in claim 7, characterized in that: The polymer degradation reaction is carried out in an intermittent reactor, the H2 pressure is 1-5 MPa, the reaction temperature is 120-200°C, the reaction time is 10-20 hours, the reaction system is a solvent-free system or a solvent system, and the solvent is one of methanol, ethanol, isopropanol and tetrahydrofuran.

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