Ru-based catalyst as well as preparation method and application thereof
By preparing a Ru1/Co3O4-Ov catalyst rich in oxygen vacancies, the problem of poor pre-depolymerization and catalytic effect of existing catalysts during PET hydrogenolysis was solved, and efficient hydrogenolysis of PET and high yield of light aromatics were achieved. Production.
Patent Information
- Application Number
- CN202411454261.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-01-21
AI Technical Summary
The existing catalysts need to be pre-depolymerized and catalytic in the hydrogenolysis process of PET, and electron polarization effects are difficult to occur at the active sites, resulting in weak substrate adsorption capacity.
The preparation method of the RU base catalyst is used to burn the cobalt oxide carrier by burning cobalt salt, and then reacts with the salt salt solution and dry the vacuum. Finally, it is restored in the restoring atmosphere to form an oxygen-rich RU1/Co3O4-OV catalyst.
This catalyst is produced by the RU-O-CO active site and a large amount of oxygen space to produce electronic polarization effects, increasing the substrate adsorption energy, and can complete the hydrogenation of PET under the content of lower active metal RU to simplify the process process. Shorten the reaction time and achieve high -end light -yield light aromatics production.
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Figure CN119327482A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a Ru-based catalyst and a preparation method and application thereof. Background Art
[0002] Polyethylene terephthalate (PET) is a linear thermoplastic polymer composed of repeating units of terephthalic acid and ethylene glycol monomers with a wide range of uses. Mass-produced plastics can degrade in strength when exposed to sunlight for a long time, causing the plastic to break into particles known to be up to millimeters or microns in size. These microplastics not only have ecological impacts on marine and freshwater environments, but also have important impacts on human health through oral inhalation, ingestion or skin absorption of nanoplastic products. In view of this, there is increasing interest in developing strategies to recycle PET plastics, such as mechanical extrusion, enzymatic decomposition, and thermochemical treatment, but these schemes are usually only able to recover PET in the form of monomers (terephthalic acid or terephthalate), and the high melting points of these monomers make the purification process difficult.
[0003] As a complementary method to chemical or mechanical recycling, the method of upgrading PET to light aromatic products by heterogeneous catalysis has the advantages of high atom economy and low waste generation. However, this method usually requires a two-step conversion process of cascade hydrolysis or methanol decomposition and hydrogenolysis. Due to the kinetic limitations of PET hydrolysis or alcoholysis, it still takes a long reaction time to fully hydrogenolyze it to light aromatics. If the acid / base active sites that increase the solvent depolymerization rate are combined with the metal sites required for the hydrogenolysis of PET monomers, the catalyst preparation will be complicated. In addition, in the hydrogenolysis of PET, zero-valent metal nanoparticles are usually used as the active component of the catalyst. However, it is difficult for the active site to undergo electronic polarization effect, resulting in a weak adsorption capacity of the catalyst to the substrate. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a Ru-based catalyst and a preparation method and application thereof, so as to solve the technical problems that the existing catalyst needs to pre-depolymerize PET and has poor catalytic effect.
[0005] To achieve the above object, the technical solution adopted by the present invention is: to provide a method for preparing a Ru-based catalyst, comprising the following steps:
[0006] S1. calcining the cobalt salt at 350-450°C for 2-4h to obtain a cobalt oxide carrier; the cobalt salt decomposes under heat to form cobalt oxide, which decomposes and releases water and carbon dioxide after calcination in the air to generate low-valent cobalt oxide, which then combines with oxygen in the air to undergo a phase change and finally form cobalt tetroxide;
[0007] S2. Disperse the cobalt oxide carrier in water, then add the ruthenium salt solution to react for 8-12 hours, and then vacuum dry to obtain a dry product (Ru1 / Co3O4); the ratio of the cobalt oxide carrier to the ruthenium salt solution is 180-220 mg: 3-5 mL; since the oxygen atoms in the metal oxide (cobalt oxide) are electronegative, this allows it to adsorb a certain amount of Ru 3+ Or Ru 2+ ions to form a relatively stable coordination structure, and Ru1 / Co3O4 can be obtained after drying;
[0008] S3, placing the dried product in a reducing atmosphere, reducing it at 50-200°C for 1.5-2.5h, to obtain a Ru1 / Co3O4-Ov catalyst rich in oxygen vacancies, wherein Ov represents oxygen vacancies; affected by the low-temperature reducibility of Co3O4, in a reducing atmosphere, the oxygen in Ru1 / Co3O4 will combine with hydrogen to generate water, and when a certain amount of oxygen combines with hydrogen, cobalt tetraoxide will gradually convert into cobalt monoxide until it is reduced to elemental cobalt. The present invention controls the reduction temperature, reduces part of the oxygen when cobalt tetraoxide does not transform into cobalt oxide crystal form, and forms a Ru1 / Co3O4-Ov catalyst rich in oxygen vacancies.
[0009] On the basis of the above technical solution, the present invention can also be improved as follows:
[0010] Furthermore, the cobalt salt is cobalt acetate, cobalt carbonate or cobalt nitrate.
[0011] Furthermore, the cobalt oxide carrier is cobalt tetraoxide (Co3O4-Ov) and / or cobalt monoxide (CoO-Ov).
[0012] Furthermore, the ruthenium salt solution is a ruthenium dichloride or ruthenium trichloride solution with a concentration of 0.5-1.5 mg / mL.
[0013] Furthermore, the vacuum drying temperature is 50-70°C and the time is 10-14h.
[0014] Furthermore, the gas used in the reducing atmosphere is hydrogen.
[0015] The invention also discloses a Ru1 / Co3O4-Ov catalyst prepared by the preparation method.
[0016] Furthermore, the loading amount of Ru in the Ru1 / Co3O4-Ov catalyst is 0.2-3wt%.
[0017] The invention also discloses the application of Ru1 / Co3O4-Ov catalyst in the degradation and recovery of polyethylene terephthalate.
[0018] Furthermore, the application includes the following steps: dispersing Ru1 / Co3O4-Ov catalyst and polyethylene terephthalate (PET) in an organic solvent in a mass ratio of 4-6:11-13, then heating to 100-400°C in a reducing atmosphere at 0.1-6MPa, and stirring the reaction for 20-300 minutes to obtain a light aromatic product.
[0019] In the main process of PET hydrogenolysis, the CO bond in PET is broken first, until terephthalaldehyde and ethylene glycol are generated, and then ethylene glycol undergoes hydrogenation cracking reaction to generate methane and water, while terephthalaldehyde undergoes hydrogenation deoxygenation reaction to generate p-xylene; however, during the whole reaction process, the oligomers generated by PET hydrogenolysis may undergo decarboxylation reaction to generate a small amount of toluene and benzene. Single atom Ru will strongly adsorb oxygen atoms in PET and activate CO bonds, and then the oxygen atoms next to Ru on the catalyst will adsorb H atoms, causing them to attack the C atoms on the CO bond, thus causing the CO bond to break.
[0020] Furthermore, the organic solvent is an aromatic hydrocarbon or a linear alkane.
[0021] Furthermore, the mass ratio of Ru atoms to polyethylene terephthalate in the Ru1 / Co3O4-Ov catalyst is 1-20:1000.
[0022] Furthermore, the light aromatics product is a mixture of benzene, toluene and xylene.
[0023] The beneficial effects of the present invention are:
[0024] 1. The catalyst prepared by the present invention contains Ru-O-Co active sites, and produces an electronic polarization effect under the condition of the presence of a large number of oxygen vacancies, thereby causing the electrons of atomic-level Ru to transfer to oxygen atoms, thereby increasing the substrate adsorption energy, and can complete the hydrogenolysis of PET at a lower active metal Ru content.
[0025] 2. The present invention utilizes an atomic-level Ru-based catalyst to directly hydrogenolyze PET into corresponding monomers, thereby avoiding the step of pre-depolymerizing PET when methanol or water is used as a solvent, simplifying the process flow and shortening the reaction time.
[0026] 3. The catalyst prepared by the present invention can mainly complete the cleavage of the CO bond specified by PET, and can achieve high-yield production of light aromatic compounds.
[0027] 4. The Ru-based catalyst prepared by the present invention is a heterogeneous catalyst and has magnetism. The recovery process is simple and can be recycled more than 8 times, which significantly reduces the use cost of the catalyst. The production process is simple, practical, and easy to promote industrialization. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1The electron paramagnetic resonance characterization diagram of oxygen vacancies in Ru1 / Co3O4 and Ru1 / Co3O4-Ov catalysts;
[0029] Figure 2 This is the effect of catalyst cycle number on the yield of light aromatics converted by Co3O4-Ov catalyst. DETAILED DESCRIPTION
[0030] The specific embodiments of the present invention are described below to facilitate the understanding of the present invention by those skilled in the art. If the specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.
[0031] Example 1
[0032] A method for preparing a Ru-based catalyst comprises the following steps:
[0033] S1. Calcine 1g of cobalt carbonate at 350℃ for 4h. The intermediate (CoO x ) Under the action of oxygen, a cobalt oxide carrier is finally obtained;
[0034] S2, dispersing 180 mg of the cobalt oxide carrier in 20 mL of water, then adding 3 mL of a 1.5 mg / mL ruthenium trichloride solution to react for 8 h, then centrifuging, and vacuum drying the centrifuged product at 70° C. for 10 h to obtain a dried product;
[0035] S3. The dried product was placed in a hydrogen atmosphere and reduced at 50°C for 2.5 hours to obtain a Ru1 / Co3O4-Ov catalyst with a Ru loading of 0.2 wt%.
[0036] The application of Ru1 / Co3O4-Ov catalyst in the degradation and recovery of polyethylene terephthalate includes the following steps: 40 mg of Ru1 / Co3O4-Ov catalyst and 110 mg of polyethylene terephthalate (PET) are dispersed in 3 mL of n-dodecane, followed by charging 0.1 MPa of hydrogen, raising the temperature of the reaction system to 400°C, stirring the reaction for 20 minutes, and finally using gas chromatography to analyze the product content. According to calculations, the yield of light aromatics is 90%, of which the yields of 1,4-dimethylbenzene, toluene and benzene are 81%, 8% and 1% respectively.
[0037] Example 2
[0038] A method for preparing a Ru-based catalyst comprises the following steps:
[0039] S1. Calcine 1g of cobalt nitrate at 450℃ for 2h. The intermediate (CoO x ) Under the action of oxygen, a cobalt oxide carrier is finally obtained;
[0040] S2, dispersing 220 mg of the cobalt oxide carrier in 20 mL of water, then adding 5 mL of a 0.5 mg / mL ruthenium trichloride solution to react for 12 h, then centrifuging, and vacuum drying the centrifuged product at 50° C. for 14 h to obtain a dried product;
[0041] S3. The dried product was placed in a hydrogen atmosphere and reduced at 200°C for 1.5 hours to obtain a Ru1 / Co3O4-Ov catalyst with a Ru loading of 3 wt%.
[0042] The application of Ru1 / Co3O4-Ov catalyst in the degradation and recovery of polyethylene terephthalate includes the following steps: dispersing 60 mg of Ru1 / Co3O4-Ov catalyst and 130 mg of polyethylene terephthalate (PET) in 3 mL of n-dodecane, then charging 6 MPa of hydrogen, raising the temperature of the reaction system to 100 ° C, stirring the reaction for 300 minutes, and finally using gas chromatography to analyze the product content. According to calculations, the yield of light aromatics is 93%, of which the yields of 1,4-dimethylbenzene, toluene and benzene are 74%, 15% and 4% respectively.
[0043] Example 3
[0044] A method for preparing a Ru-based catalyst comprises the following steps:
[0045] S1. Calcine 1g of cobalt acetate at 400℃ for 3h. Cobalt acetate decomposes at high temperature to generate an intermediate (CoO x ) Under the action of oxygen, a cobalt oxide carrier is finally obtained;
[0046] S2, dispersing 200 mg of the cobalt oxide carrier in 20 mL of water, then adding 4 mL of a 1 mg / mL ruthenium trichloride solution to react for 10 h, then centrifuging, and placing the centrifuged product under vacuum drying at 60° C. for 12 h to obtain a dried product;
[0047] S3. The dried product was placed in a hydrogen atmosphere and reduced at 130°C for 2 hours to obtain a Ru1 / Co3O4-Ov catalyst with a Ru loading of 1 wt%.
[0048] The application of Ru1 / Co3O4-Ov catalyst in the degradation and recovery of polyethylene terephthalate includes the following steps: 50 mg of Ru1 / Co3O4-Ov catalyst and 120 mg of polyethylene terephthalate (PET) are dispersed in 3 mL of n-dodecane, followed by charging with 1 MPa of hydrogen, raising the temperature of the reaction system to 250°C, stirring the reaction for 120 minutes, and finally using gas chromatography to analyze the product content. According to calculations, the yield of light aromatics is 99%, of which the yields of 1,4-dimethylbenzene, toluene and benzene are 86%, 11% and 2% respectively.
[0049] Comparative Example 1
[0050] The difference between this comparative example and Example 3 is that the calcination atmosphere in step S1 is replaced by nitrogen instead of air, and the remaining components and preparation process are the same as those in Example 3 to obtain Ru1 / CoO x catalyst.
[0051] Ru1 / CoO x The catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. According to calculation, the yield of light aromatics was 19%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 17%, 2% and 0% respectively.
[0052] Comparative Example 2
[0053] The difference between this comparative example and Example 3 is that the reducing atmosphere in step S3 is replaced by nitrogen instead of hydrogen, and the remaining components and preparation process are the same as those in Example 3 to obtain a Ru1 / Co3O4 catalyst.
[0054] The Ru1 / Co3O4 catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. It was calculated that the yield of light aromatics was 69%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 63%, 5% and 1% respectively.
[0055] Comparative Example 3
[0056] The difference between this comparative example and Example 3 is that the reducing atmosphere in step S3 is replaced by air instead of hydrogen, and the remaining components and preparation process are the same as those in Example 3 to obtain a Ru1 / Co3O4 catalyst.
[0057] The Ru1 / Co3O4 catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. It was calculated that the yield of light aromatics was 75%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 67%, 7% and 1% respectively.
[0058] Comparative Example 4
[0059] The difference between this comparative example and Example 3 is that the calcination atmosphere in step S1 is replaced by nitrogen from air, and the reducing atmosphere in step S3 is replaced by air from hydrogen. The remaining components and preparation process are the same as those in Example 3. x catalyst.
[0060] Ru1 / CoO x The catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. According to calculation, the yield of light aromatics was 59%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 41%, 7% and 1% respectively.
[0061] Comparative Example 5
[0062] The difference between this comparative example and Example 3 is that the reduction temperature of step S3 is adjusted to 300° C., and the remaining components and preparation process are the same as those of Example 3 to obtain a Ru1 / Co3O4 catalyst.
[0063] The Ru1 / Co3O4 catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. It was calculated that the yield of light aromatics was 5%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 5%, 0% and 0% respectively.
[0064] Comparative Example 6
[0065] The difference between this comparative example and Example 3 is that the reduction temperature of step S3 is adjusted to 600°C, and the remaining components and preparation process are the same as those of Example 3 to obtain Ru1 / CoO x catalyst.
[0066] Ru1 / CoO x The catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. According to calculation, the yield of light aromatics was 5%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 1%, 0% and 0% respectively.
[0067] Comparative Example 7
[0068] The difference between this comparative example and Example 3 is that S2 is specifically as follows: 200 mg of cobalt oxide carrier is dispersed in 20 mL of water, followed by adding 4 mL of 1 mg / mL ruthenium trichloride solution, and then adjusting the pH value of the reaction system to 10 with ammonia water to precipitate Ru to form aggregated Ru nanoparticles, followed by reacting for 10 hours and then centrifuging, and the centrifuged product is placed at 60°C and vacuum dried for 12 hours to obtain a dry product; the remaining components and preparation process are the same as in Example 3 to obtain a Ru / Co3O4 catalyst.
[0069] The Ru / Co3O4 catalyst was used to degrade and recover polyethylene terephthalate, and the specific steps were the same as those in Example 3. Finally, the product content was analyzed by gas chromatography. According to calculation, the yield of light aromatics was 5%, of which the yields of 1,4-dimethylbenzene, toluene and benzene were 6%, 0% and 0% respectively.
[0070] Yield of light aromatics Y i The calculation formula is as follows:
[0071] Y i =m i / m(rational) i ×100%;
[0072] Among them, m i is the mass of light aromatics, g; m (rational) i is the mass of light aromatics that can be produced theoretically, g.
[0073] Experimental Example 1
[0074] The catalysts prepared in Example 3 (Ru1 / Co3O4-Ov) and Comparative Example 3 (Ru1 / Co3O4) were characterized in terms of structure. The specific steps were as follows: grinding the sample to be tested into powder, placing the powder sample into a quartz tube, and sealing and evacuating the tube. Using standard substances (such as Mn 2+ ) to calibrate the instrument. Ensure that the magnetic field strength and microwave frequency are accurate. Place the sealed quartz tube sample into the EPR chamber. Start scanning and record the EPR spectrum. Measure the spectral line intensity and g factor in the spectrum.
[0075] The results are as follows Figure 1 As shown in the figure, it can be seen that the spectral line intensity of Ru1 / Co3O4-Ov is more than twice that of Ru1 / Co3O4, proving that there are abundant oxygen vacancies in Ru1 / Co3O4-Ov.
[0076] Experimental Example 2
[0077] The Ru1 / Co3O4-Ov catalyst prepared in Example 3 was used to degrade and recover polyethylene terephthalate. After each reaction was completed, the catalyst was separated from the liquid product using a magnet, and the catalyst was washed with cyclohexane and then vacuum dried at 60° C. The dried catalyst was repeatedly used in the reaction of degrading and recovering polyethylene terephthalate to examine the stability of the catalyst.
[0078] The results are as follows Figure 2 As shown in the figure, it can be seen that after the catalyst was used 8 times, the total yield of light aromatics in the product still remained above 92%, indicating that Ru1 / Co3O4-Ov has good stability.
Claims
1. A method for preparing a Ru-based catalyst, characterized in that: The following steps are involved: S1. calcining the cobalt salt at 350-450° C. for 2-4 hours to obtain a cobalt oxide carrier; S2, dispersing the cobalt oxide carrier in water, then adding a ruthenium salt solution to react for 8-12 hours, and then vacuum drying to obtain a dry product; the ratio of the cobalt oxide carrier to the ruthenium salt solution is 180-220 mg: 3-5 mL; S3. Place the dried product in a reducing atmosphere and reduce it at 50-200° C. for 1.5-2.5 h to obtain a Ru1 / Co3O4-Ov catalyst rich in oxygen vacancies.
2. The method for preparing a Ru-based catalyst according to claim 1, characterized in that: The cobalt salt is cobalt acetate, cobalt carbonate or cobalt nitrate.
3. The method for preparing a Ru-based catalyst according to claim 1, characterized in that: The cobalt oxide carrier is cobalt tetroxide and / or cobalt monoxide.
4. The method for preparing a Ru-based catalyst according to claim 1, characterized in that: The ruthenium salt solution is a ruthenium dichloride or ruthenium trichloride solution with a concentration of 0.5-1.5 mg / mL.
5. The method for preparing a Ru-based catalyst according to claim 1, characterized in that: The vacuum drying is carried out at a temperature of 50-70°C and for a time of 10-14 hours.
6. The method for preparing a Ru-based catalyst according to claim 1, characterized in that: The gas used in the reducing atmosphere is hydrogen.
7. A Ru1 / Co3O4-Ov catalyst, characterized in that: The Ru1 / Co3O4-Ov catalyst is prepared by the preparation method described in any one of claims 1-6.
8. The Ru1 / Co3O4-Ov catalyst according to claim 7, characterized in that The loading amount of Ru in the Ru1 / Co3O4-Ov catalyst is 0.2-3wt%.
9. Use of the Ru1 / Co3O4-Ov catalyst according to claim 7 or 8 in the degradation and recovery of polyethylene terephthalate.
10. The use according to claim 9, characterized in that: The following steps are involved: The Ru1 / Co3O4-Ov catalyst and polyethylene terephthalate are dispersed in an organic solvent in a mass ratio of 4-6:11-13, and then heated to 100-400°C in a reducing atmosphere at 0.1-6MPa, and stirred for reaction for 20-300 minutes to obtain a light aromatic hydrocarbon product.