Preparation method and application of layered double hydroxide hybrid nickel-cobalt metal organic framework
By preparing layered double hydroxide hybrid nickel-cobalt metal-organic framework catalysts, the problem of low deoxygenation and bond-breaking efficiency of microalgal oils was solved, achieving efficient conversion of algal oils into biofuels and improving product selectivity and safety.
Patent Information
- Application Number
- CN202510845466.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, fatty acid methyl esters obtained from microalgal oil transesterification have high oxygen content and long carbon chains, resulting in low energy density and poor low-temperature performance. Traditional nickel-based metal-organic frameworks tend to stack, making it difficult for active sites to contact with macromolecular algal oil, thus limiting the deoxygenation and bond-breaking reactions of algal oil.
A layered double hydroxide hybrid nickel-cobalt metal-organic framework catalyst was used. By preparing a porous flower-like structure, the coordinated cobalt ions were transformed into active elemental cobalt, forming Lewis acid sites. The catalytic reaction was carried out using a CO2 atmosphere instead of a H2 atmosphere.
It improves the efficiency of algal oil deoxygenation and bond breaking, increases the selectivity of hydrocarbons by more than 10% and the selectivity of cycloalkanes by 6%, reduces reaction risk and cost, and enhances catalytic performance.
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Figure CN120900712A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of microalgae biofuel production, and particularly relates to a preparation method of layered double hydroxide hybrid nickel-cobalt metal organic framework and application of the layered double hydroxide hybrid nickel-cobalt metal organic framework as a catalyst in catalyzing algal oil deoxygenation and bond breaking to produce biofuel. BACKGROUND
[0002] Algal oil biofuel production technology as a new biofuel production technology has attracted extensive attention in recent years. Algae have rich biological diversity, high photosynthetic efficiency and rich oil content. In addition, microalgae have strong environmental adaptability and can grow rapidly in fresh water, waste water, sea water and other water bodies, and can also survive in extreme conditions such as high temperature. In addition, microalgae can be cultivated in marginal lands such as saline-alkali land, tidal flat and desert, without occupying arable land resources. Moreover, the oil production rate of microalgae is significantly higher than that of other biological energy sources. In the process of metabolism, the key precursors of biofuel generated by microalgae can also derive a variety of high-value chemicals, and a full-component high-value utilization system of algae can be constructed.
[0003] A main reason for limiting the industrial application of microalgae biofuel production is that the fatty acid methyl ester obtained by transesterification of microalgae oil has high oxygen content and long carbon chain, resulting in low energy density and poor low-temperature performance. How to quickly realize the deoxygenation and bond breaking reaction of microalgae oil has become a key problem for promoting the large-scale application of microalgae oil in biofuel production. At present, a variety of catalysts have been studied in the field of biofuel to realize the deoxygenation and bond breaking of biofuel precursors.
[0004] The deoxygenation of biological oil under high temperature conditions is mainly completed on the metal active site, and the nickel metal ranks second after the noble metal in the catalytic activity sequence. The metal organic framework catalyst contains metal and acid sites at the same time, the metal sites are highly dispersed, and the amount of metal required in the synthesis process can be effectively reduced, and a high catalytic activity can be maintained. However, the traditional nickel-based metal organic framework is prone to stacking, which limits the contact between the internal active sites and the macromolecular algal oil. The highly dispersed metal active sites can be efficiently obtained by material hybridization. Although the traditional molecular sieve can effectively disperse the active sites, the supported metal active sites are prone to uneven loading and active site agglomeration, which limits the catalytic performance to some extent.
[0005] Therefore, the present application proposes a new scheme, which applies the hybrid metal organic framework catalyst to large-scale algal oil fuel production. SUMMARY
[0006] The technical problem to be solved by the present application is to overcome the deficiencies in the prior art, and to provide a preparation method of layered double hydroxide hybrid nickel-cobalt metal organic framework and application thereof.
[0007] To solve the above technical problems, the solution of the present application is:
[0008] A preparation method of layered double hydroxide hybrid nickel-cobalt metal organic framework is provided, comprising:
[0009] (1) Dissolve nickel nitrate hexahydrate Ni(NO3)2·6H2O and cobalt nitrate hexahydrate Co(NO3)2·6H2O in a N,N-dimethylformamide DMF-deionized water-ethanol mixed solution, then add trimesic acid and triethylamine, and react under ultrasonic conditions; after the reaction is completed, separate the solid and dry it to obtain a bimetallic organic framework NiCo-BTC;
[0010] (2) Dissolve the NiCo-BTC in a methanol solution containing cobalt nitrate hexahydrate Co(NO3)2·6H2O, and stir to dissolve; then add a methanol solution containing 2-methylimidazole 2-MIM, stir uniformly, and then place it at room temperature for 11-13 h to react; after the reaction is completed, separate the solid and dry it to obtain a metal organic framework ZIF-67@BTC carrying ZIF-67, that is, a ZIF framework is carried on the basis of the NiCo-BTC framework;
[0011] (3) Dissolve the ZIF-67@BTC and nickel nitrate hexahydrate Ni(NO3)2·6H2O in ethanol, stir uniformly, and then transfer it to a hydrothermal reaction kettle, and hydrothermally react at 75-82℃ for 5-7 h; after the reaction is completed, separate the solid and dry it to obtain a layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst LDH@BTC.
[0012] As a preferred scheme of the present application, in the N,N-dimethylformamide DMF-deionized water-ethanol mixed solution of step (1), the volume ratio of the three solvents is 300-330:18-21:18-21.
[0013] As a preferred scheme of the present application, in step (1), the addition ratio of nickel nitrate hexahydrate, cobalt nitrate hexahydrate, trimesic acid, and triethylamine is 1-1.1 g:1-1.1 g:1.56-1.58 g:7-9 mL.
[0014] As a preferred scheme of the present application, in step (1), the reaction time under ultrasonic conditions is 7-9 h.
[0015] As a preferred scheme of the present application, in step (2), the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate, and 2-methylimidazole 2-MIM is 23-25:15-16:17-18.
[0016] As a preferred scheme of the present application, in step (3), the mass ratio of ZIF-67@BTC to nickel nitrate hexahydrate is 0.55-0.57:1.9-2.2.
[0017] As a preferred scheme of the present application, the separated solid after the reaction in each step is dried, specifically: the reaction product is poured into a centrifuge bottle, centrifuged at a speed of 8000-10000 rpm for 5-10 min to separate the solid precipitate from the supernatant; the separated solid is placed in a blast drying oven, and the drying temperature is 50-70 DEG C.
[0018] The present application further provides a method for preparing biofuel by catalyzing deoxygenation and bond breaking of algal oil using the catalyst LDH@BTC prepared by the aforementioned method, comprising: adding algal oil and catalyst LDH@BTC into a reaction kettle, sealing the reaction kettle after uniform stirring; then introducing pure CO2 gas until the pressure is 1-4 MPa, and reacting at 410-430 DEG C for 6-9 h; after natural cooling to room temperature, the gas is discharged, and the reaction product is centrifuged, and the obtained liquid phase product is a hydrocarbon corresponding to the typical components of biodiesel.
[0019] As a preferred scheme of the present application, the mass ratio of algal oil to catalyst LDH@BTC is 3-5:0.04-0.2.
[0020] As a preferred scheme of the present application, the algal oil is any one of the following: methyl stearate or methyl palmitate.
[0021] Invention principle description:
[0022] The present application adds a bifunctional catalyst in the process of converting algal oil into biofuel, thereby improving the deoxygenation and bond breaking efficiency; the metal acidic bifunctional catalyst is treated by hybridizing nickel-cobalt metal organic framework with layered double hydroxide, in which the stacked layered structure is changed into a porous flower-like structure, and the coordinated cobalt ions are changed into active elemental cobalt, so that more metal center atoms produce unsaturated coordination, and there are more empty orbitals, thereby forming Lewis acid sites to promote the carbon-carbon bond breaking of long carbon chains in catalytic algal oil to generate short carbon chain products. Specifically as follows:
[0023] 1. The application utilizes the precursor solution of nickel nitrate hexahydrate Ni(NO3)2·6H2O, cobalt nitrate hexahydrate Co(NO3)2·6H2O and trimesic acid to prepare a bimetallic organic framework catalyst NiCo-BTC through ultrasonic treatment, and the role of triethylamine is to regulate the grain size and morphology. Then, the methanol solution containing NiCo-BTC, cobalt nitrate hexahydrate and 2-methyl imidazole is treated by static precipitation to prepare ZIF-67@BTC, and then the ZIF-67@BTC is reacted with the nickel nitrate hexahydrate solution through hydrothermal reaction to prepare a composite catalyst LDH@BTC. The test shows that the composite catalyst LDH@BTC is a layered double hydroxide hybrid nickel-cobalt metal organic framework, and has a porous flower-like structure at a micro level. By converting the coordinated cobalt ions into active elemental cobalt, more metal center atoms generate unsaturated coordination, and there are more empty orbitals, so that Lewis acid sites are formed to promote the catalytic algal oil deoxygenation and bond breaking to generate short carbon chain products. Therefore, the layered double hydroxide composite catalyst prepared by the application has dispersed metal active sites and acidic active sites, and can be applied to various catalytic application scenarios.
[0024] 2. In the prior art, when the active sites of the metal organic framework are dispersed by various methods, the generated pore structure is usually single (mostly concentrated in 2-10 nm), and the intention is to obtain dispersed active sites by material loading, so as to enhance the contact between the algal oil and the active sites and improve the catalytic performance. However, the pore size generated by the regular loading material is concentrated, which leads to the failure of the active sites to achieve the purpose of large pore transportation and small pore reaction.
[0025] The application generates a porous flower-like structure through the layered double hydroxide hybrid metal organic framework, can form a hierarchical pore structure, and ensures that the catalytic work is more efficient.
[0026] 3. In the catalytic conversion of algal oil to bio-jet fuel, the application selects CO2 atmosphere instead of the commonly used H2 atmosphere, which not only reduces the danger of the high-temperature reaction, but also reduces the transportation cost and storage cost of the reaction atmosphere. Under the CO2 atmosphere, the conversion rate and product selectivity of the layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst in the catalytic deoxygenation and bond breaking of algal oil to produce jet fuel can both maintain a high level.
[0027] Compared with the prior art, the application has the following beneficial effects:
[0028] 1. The application prepares a hybrid catalyst through the layered double hydroxide hybrid metal organic framework, has a porous flower-like structure, converts the coordinated cobalt ions into active elemental cobalt, makes more metal center atoms generate unsaturated coordination, and there are more empty orbitals, so that Lewis acid sites are formed to promote the catalytic algal oil deoxygenation and bond breaking to generate short carbon chain products.
[0029] 2. This invention disperses active sites through the sheet-like structure of layered double hydroxides, which can form a layered porous structure, improve the utilization rate of the original active sites, and ensure more efficient catalytic work.
[0030] 3. Through extensive experiments and production practice, the method of this invention has been verified to increase the hydrocarbon selectivity of algal deoxygenation and bond breaking biofuel production by more than 10%, while increasing the cycloalkanes selectivity by 6%. Therefore, this invention not only proposes a new method for material preparation and application, but also promotes the development of the algal oil conversion fuel industry. Attached Figure Description
[0031] Figure 1 High-resolution transmission electron microscopy images of three different metal skeletons.
[0032] Figure 2 for Figure 1 X-ray diffraction (XRD) spectra of various metal-organic frameworks.
[0033] Figure 3 for Figure 1 Pore size distribution of various metal-organic frameworks.
[0034] Figure 4 for Figure 1 Infrared spectrum of LDH@BTC, a metal-organic framework.
[0035] Figure 5 For Figure 1 High-resolution XPS spectra of Ni 2p and Co 2p orbitals in various metal-organic frameworks
[0036] Figure 6 This is a comparison of conversion efficiency and product selectivity in the methyl stearate conversion experiment.
[0037] Figure 7 This study compares the conversion efficiency and product selectivity of methyl stearate conversion experiments at different temperatures. Detailed Implementation
[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:
[0039] 1. Overview of the implementation scheme of the present invention
[0040] The application is to improve the deoxygenation and bond breaking efficiency by adding a bifunctional catalyst in the process of converting algal oil into biofuel; the metal acid bifunctional catalyst adopts a layered double hydroxide hybrid metal organic framework, in the bifunctional catalyst, the stacked layered structure is changed into a porous flower-shaped structure, and the coordinated cobalt ions are changed into active elemental cobalt, so that more metal center atoms produce unsaturated coordination, more empty orbitals exist, thereby forming Lewis acid sites to promote the carbon-carbon bond breaking of catalytic algal oil long carbon chain to generate short carbon chain products.
[0041] Firstly, the application provides a preparation method of a layered double hydroxide hybrid nickel-cobalt metal organic framework, comprising:
[0042] (1) Dissolve nickel nitrate hexahydrate Ni(NO3)2·6H2O and cobalt nitrate hexahydrate Co(NO3)2·6H2O in a N,N-dimethylformamide DMF-deionized water-ethanol mixed solution, then add trimesic acid and triethylamine, and react under ultrasonic conditions for 7-9 h; after the reaction is completed, separate the solid and dry it to obtain a bimetallic organic framework NiCo-BTC;
[0043] As an optional example, in the N,N-dimethylformamide DMF-deionized water-ethanol mixed solution, the volume ratio of the three solvents is 300-330:18-21:18-21. The addition ratio of nickel nitrate hexahydrate, cobalt nitrate hexahydrate, trimesic acid and triethylamine is 1-1.1 g:1-1.1 g:1.56-1.58 g:7-9 mL.
[0044] (2) Dissolve NiCo-BTC in a methanol solution containing cobalt nitrate hexahydrate Co(NO3)2·6H2O, and stir to dissolve; then add a 2-methylimidazole 2-MIM-containing methanol solution, stir uniformly, and then place at room temperature for 11-13 h to react; in the reaction system, the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate and 2-methylimidazole 2-MIM is 23-25:15-16:17-18. After the reaction is completed, separate the solid and dry it to obtain a metal organic framework ZIF-67@BTC carrying ZIF-67, that is, a ZIF framework is carried on the basis of the NiCo-BTC framework;
[0045] (3) Dissolve ZIF-67@BTC and nickel nitrate hexahydrate Ni(NO3)2·6H2O in ethanol at a mass ratio of 0.55-0.57:1.9-2.2, stir uniformly, and then transfer to a hydrothermal reaction kettle, and hydrothermally react at 75-82℃ for 5-7 h; after the reaction is completed, separate the solid and dry it to obtain a layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst LDH@BTC.
[0046] As an optional example, the separation and drying treatment after the reaction in each step ends, specifically refers to: pouring the reaction product into a centrifuge bottle, centrifugal treatment at a speed of 8000-10000 rpm for 5-10 min, separating the solid precipitate from the supernatant; the separated solid is placed in a blast drying oven, and the drying temperature is 50-70℃.
[0047] Secondly, the application also provides a method for applying the catalyst LDH@BTC to catalyze the preparation of biofuel by deoxygenating and breaking the bond of algal oil, which comprises: adding algal oil and catalyst LDH@BTC into a reaction kettle according to a mass ratio of 3-5:0.04-0.2, sealing the reaction kettle after uniform stirring; then introducing pure CO2 gas until the pressure is 1-4 MPa, and reacting at 410-430℃ for 6-9 h; after natural cooling to room temperature after the reaction ends, the gas is exhausted, and the reaction product is centrifuged and separated, and the obtained liquid phase product is a hydrocarbon corresponding to the typical component of biodiesel.
[0048] As an optional example, the algal oil is any one of the following: methyl stearate or methyl palmitate.
[0049] 2、The embodiment and the comparative example
[0050] Example 1
[0051] (1) 1g of nickel nitrate hexahydrate Ni(NO3)2·6H2O and 1.1g of cobalt nitrate hexahydrate Co(NO3)2·6H2O were dissolved in a mixed solution of 300mL of N,N-dimethylformamide DMF, 21mL of deionized water and 21mL of ethanol. Then 1.58g of trimesic acid and 7mL of triethylamine were added. Ultrasonic treatment for 7h in a reagent bottle, the mixed product after reaction was poured into a centrifuge bottle, centrifugal treatment at a speed of 8000rpm for 5min, separating the solid precipitate from the supernatant. The separated solid was placed in a blast drying oven, and dried at 70℃, to obtain a bimetallic organic framework catalyst NiCo-BTC.
[0052] (2) NiCo-BTC (concentration after dissolution: 15 mg / mL) was dissolved in a methanol solution containing 24 mg / mL of cobalt nitrate hexahydrate Co(NO3)2·6H2O and stirred, and then poured into a methanol solution containing 52 mg / mL of 2-methylimidazole 2-MIM, so that the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate, and 2-methylimidazole 2-MIM in the reaction solution was 23:16:17. After being placed at room temperature for 12 h, the reaction was completed, and the ZIF-67@BTC was obtained by centrifugal drying according to the operation in step (1). Then, 0.55 g of the ZIF-67@BTC and 2.2 g of nickel nitrate hexahydrate Ni(NO3)2·6H2O were dissolved in ethanol and stirred. Subsequently, it was transferred to a hydrothermal reaction kettle and reacted at 75 °C for 7 h. After the reaction was completed, the layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst LDH@BTC was obtained by centrifugal drying according to the operation in step (1).
[0053] (3) Methyl stearate with a mass ratio of 5:0.2 was added to the reaction kettle together with the layered double hydroxide composite catalyst LDH@BTC as a catalyst, and stirred uniformly; the reaction kettle was sealed, and pure CO2 gas was introduced until the pressure was 1 MPa; the reaction was carried out at 410 °C for 9 h, and after cooling was completed, the gas in the kettle was slowly exhausted, and the mixture of the liquid phase product and the catalyst was taken out of the reaction kettle and placed in a centrifugal tube after the reaction kettle was opened. The liquid phase product corresponding to the typical components of biodiesel was obtained after high-speed centrifugal filtration separation.
[0054] Example 2
[0055] (1) 1.09 g of nickel nitrate hexahydrate Ni(NO3)2·6H2O and 1 g of cobalt nitrate hexahydrate Co(NO3)2·6H2O were dissolved in a mixed solution of 320 mL of N,N-dimethylformamide DMF, 20 mL of deionized water, and 20 mL of ethanol. Then, 1.56 g of trimesic acid and 9 mL of triethylamine were added. It was transferred to a reagent bottle and ultrasonically treated for 8 h. The mixed product after the reaction was poured into a centrifugal bottle and centrifuged at a speed of 10,000 rpm for 8 min to separate the solid precipitate from the supernatant. The separated solid was placed in a blast drying oven and dried at 60 °C to obtain a bimetallic organic framework catalyst NiCo-BTC.
[0056] (2) NiCo-BTC (concentration after dissolution: 16 mg / mL) was dissolved in a methanol solution containing 25 mg / mL of cobalt nitrate hexahydrate Co(NO3)2·6H2O and stirred, and then poured into a methanol solution containing 52.6 mg / mL of 2-methylimidazole 2-MIM, so that the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate, and 2-methylimidazole 2-MIM in the reaction solution was 24:15.5:17.4. After being placed at room temperature for 11 h, the reaction was completed, and the ZIF-67@BTC was obtained by centrifugal drying according to the operation in step (1). 0.56 g of the ZIF-67@BTC was stirred with 2.0 g of nickel nitrate hexahydrate Ni(NO3)2·6H2O dissolved in ethanol. Subsequently, it was transferred to a hydrothermal reaction kettle, and hydrothermal reaction was carried out at 80°C for 6 h. After the reaction was completed, the LDH@BTC layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst was obtained by centrifugal drying according to the operation in step (1).
[0057] (3) Methyl stearate with a mass ratio of 4:0.16 was added to the reaction kettle together with the layered double hydroxide composite catalyst LDH@BTC as a catalyst, and stirred uniformly; the reaction kettle was sealed, and pure CO2 gas was introduced until the pressure was 2 MPa; reaction was carried out at 420°C for 8 h, and after cooling was completed, the gas in the kettle was slowly exhausted, and the mixture of the liquid phase product and the catalyst was taken out of the reaction kettle and placed in a centrifugal tube after the reaction kettle was opened. The liquid phase product, which is a typical component of hydrocarbons corresponding to biodiesel, was obtained after high-speed centrifugal filtration separation.
[0058] Example 3
[0059] (1) 1.1 g of nickel nitrate hexahydrate Ni(NO3)2·6H2O and 1.09 g of cobalt nitrate hexahydrate Co(NO3)2·6H2O were dissolved in a mixed solution of 330 mL of N,N-dimethylformamide DMF, 18 mL of deionized water, and 18 mL of ethanol. Then, 1.5665 g of trimesic acid and 8 mL of triethylamine were added. After being transferred to a reagent bottle and ultrasonically treated for 9 h, the mixed product after the reaction was poured into a centrifugal bottle and centrifuged at a speed of 9000 rpm for 10 min to separate the solid precipitate from the supernatant. The separated solid was placed in a blast drying oven and dried at 50°C to obtain a bimetallic organic framework catalyst NiCo-BTC.
[0060] (2) NiCo-BTC (concentration after dissolution: 15.4 mg / mL) was dissolved in a methanol solution containing 23 mg / mL of cobalt nitrate hexahydrate Co (NO3) 2·6H2O and stirred, and then poured into a methanol solution containing 53 mg / mL of 2-methylimidazole 2-MIM, so that the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate, and 2-methylimidazole 2-MIM in the reaction solution was 25:15:18. After being placed at room temperature for 13 h, the reaction was completed, and the ZIF-67@BTC was obtained by centrifugal drying according to the operation in step (1). Then, 0.57 g of the ZIF-67@BTC and 1.9 g of nickel nitrate hexahydrate Ni (NO3) 2·6H2O were dissolved in ethanol and stirred. Subsequently, the mixture was transferred to a hydrothermal reaction kettle, and hydrothermal reaction was performed at 82°C for 5 h. After the reaction was completed, the LDH@BTC layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst was obtained by centrifugal drying according to the operation in step (1).
[0061] (3) Methyl palmitate with a mass ratio of 3:0.04 was added to the reaction kettle together with the layered double hydroxide composite catalyst LDH@BTC as a catalyst, and the mixture was stirred uniformly. The reaction kettle was sealed, and pure CO2 gas was introduced until the pressure was 4 MPa. Reaction was performed at 430°C for 6 h. After cooling was completed, the gas in the kettle was slowly exhausted, and the mixture of the liquid phase product and the catalyst was taken out of the reaction kettle using a dropper and placed in a centrifuge tube. After high-speed centrifugal filtration separation, the liquid phase product, which was a hydrocarbon corresponding to a typical component of biodiesel, was obtained.
[0062] Comparative Example 1
[0063] The catalyst NiCo-BTC was synthesized by the ultrasonic method in Reference Example 1, and the ultrasonic time was 8 h.
[0064] 4 g of methyl stearate and 0.16 g of NiCo-BTC were weighed and added to a high-temperature and high-pressure reaction kettle, and the mixture was stirred uniformly. Then, the kettle body and the kettle cover with a pressure gauge were fastened with bolts and gaskets. High-purity CO2 was connected to 2 MPa, and reaction was performed for 8 h after the reaction temperature was reached. After natural cooling to room temperature, the gas in the kettle was slowly exhausted, and the mixture of the liquid phase product and the catalyst was taken out of the reaction kettle using a dropper and placed in a centrifuge tube. After high-speed centrifugal filtration separation, the liquid phase product was obtained.
[0065] Comparative Example 2
[0066] The catalyst NiCo-BTC was synthesized by the ultrasonic method in Reference Example 1, and the ultrasonic time was 6 h.
[0067] Weigh 4g of methyl stearate and 0.16g of NiCo-BTC, and add them together to a high-temperature, high-pressure reactor, stirring until the mixture is homogeneous. Then, tighten the reactor body and the lid equipped with a pressure gauge using bolts and gaskets. Connect high-purity CO2 to 2MPa, and react for 8 hours after reaching the reaction temperature, allowing it to cool naturally to room temperature. After cooling, slowly purge the gas from the reactor, open the reactor, and use a dropper to remove the mixture of liquid product and catalyst into a centrifuge tube. Separate the liquid product by high-speed centrifugation and filtration.
[0068] Comparative Example 3
[0069] Referring to the operation steps and experimental parameters in step (2) of Example 1, the difference is that the bimetallic organic framework NiCo-BTC is not added in this scheme, as detailed below:
[0070] A methanol solution containing cobalt nitrate hexahydrate Co(NO3)2·6H2O was poured into a methanol solution containing 2-methylimidazolium 2-MIM, and the reaction was allowed to proceed at room temperature. After the reaction was completed, the solid was separated and dried to obtain the ZIF-67 metal-organic framework. The ZIF-67 framework was then dissolved in ethanol with nickel nitrate hexahydrate Ni(NO3)2·6H2O and stirred. The mixture was then transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction was completed, the catalyst NiCo-LDH was obtained by centrifugation and drying.
[0071] Weigh 4g of methyl stearate and 0.16g of NiCo-LDH, and add them together to a high-temperature, high-pressure reactor, stirring until the mixture is homogeneous. Then, tighten the reactor body and the lid equipped with a pressure gauge using bolts and gaskets. Connect high-purity CO2 to 2MPa, and react for 8 hours after reaching the reaction temperature, allowing it to cool naturally to room temperature. After cooling, slowly purge the gas from the reactor, open the reactor, and use a dropper to remove the mixture of liquid product and catalyst into a centrifuge tube. Separate the liquid product by high-speed centrifugation and filtration.
[0072] 3. Product testing and results analysis
[0073] from Figure 1 and Figure 2 The high-resolution transmission electron microscopy (TEM) images and X-ray diffraction (XRD) spectra show that this invention successfully prepared a porous spherical structure formed by a combination of NiCo-BTC ultrathin sheets. The hybrid nanosheets were successfully prepared, and the doping did not change the original NiCo-BTC structure. Figure 3 The pore size distribution of the layered double hydroxide composite catalyst LDH@BTC shows that the pores of LDH@BTC in Example 2 are uniformly distributed in the range of 2–50 nm, exhibiting a regular and distinct layered pore structure. Figure 4 The infrared spectrum of the layered double hydroxide composite catalyst LDH@BTC shows that the peaks at 1618 and 1380 cm⁻¹ are... -1The peaks at 1690-1730 cm-1 are due to the asymmetric and symmetric stretching modes of -COO- in the BTC ligand, indicating that the Ni 2+ atoms in the NiCo-BTC catalyst are successfully coordinated with the BTC ligand, and there are no peaks related to -COOH groups in the range of 1690-1730 cm -1 , further indicating that the BTC is deprotonated when it reacts with metal ions. The stretching vibration of Co-O or Ni-O groups causes peaks at 660 cm -1 (symmetric stretching) and 1107 cm -1 (asymmetric stretching). From Figure 5 The high-resolution XPS spectra of the Ni 2p and Co 2p orbits of the layered double hydroxide composite catalyst LDH@BTC show that a peak corresponding to zerovalent cobalt appears near 755.88 eV, and the Ni atoms in the LDH@BTC catalyst are combined with cobalt atoms, and the introduction of NiCo-BTC is conducive to the reduction of Co.
[0074] Figures 6-7 The algal oil conversion analysis data of the examples and comparative examples are shown in Table 1.
[0075] In order to compare the effects of different catalysts on the conversion efficiency and product selectivity of algal oil for preparing bio-jet fuel, the three catalysts prepared in Examples 1-3 were further used for methyl stearate conversion experiments. Figure 6 The conversion differences of the catalysts prepared in Examples and Comparative Examples 1, 3 for algal oil are shown in Table 2. As can be seen from the table, Comparative Example 1 uses a non-hybridized NiCo-BTC catalyst, and Comparative Example 3 uses a NiCo-LDH catalyst, and the conversion rates of methyl stearate are 90.73% and 95.71%, respectively, and the selectivities are 64.29% and 71.23%, respectively. The selectivities of the catalysts prepared in the three examples for target hydrocarbons are better than those of the catalysts of Comparative Examples 1 and 3; among them, the catalyst of Example 3 can increase the conversion rate and the selectivity of target hydrocarbons to 96.4% and 83.95%, respectively, showing the best catalytic effect, which is significantly higher than that of the catalysts of Examples 1 and 2. This is because the Ni 2+ in the NiCo-BTC catalyst of Comparative Example 1 is coordinated with a large number of carboxylic acid anions, and the catalyst presents a layer-by-layer stacking structure, resulting in poor contact of the active sites with the reactants and poor bond breaking ability. In the catalysts of the present application, more Co sites are reduced to nanoparticles, and the metal center atoms have more empty orbits, producing unsaturated coordination to form Lewis acid sites, which have stronger deoxygenation ability and Lewis acid sites.
[0076] Figure 7The conversion efficiency and product selectivity of the conversion experiment of methyl stearate in Comparative Example 3 and the examples of different reaction temperatures are compared. The LDH@BTC is selected to catalyze methyl stearate in each example. When the catalytic reaction temperature is 410℃, the conversion rate of LDH@BTC catalysis is 98.77%, and the selectivity is 77.76. When the reaction temperature is 420℃, the reaction reaches the best state, and the conversion rate and total selectivity are 96.56% and 81.38%, respectively. When the reaction temperature is 430℃, the conversion rate and total selectivity are 96% and 80.41%, respectively. It can be seen that the conversion rate and total selectivity of each example are higher than those of Comparative Example 1. Considering that the total selectivity and naphthene selectivity of LDH@BTC are high, the energy density and sealing performance are also high, so it is selected as the best catalyst.
[0077] From the data comparison in the chart, it can be seen that in the present application, the layered double hydroxide composite catalyst LDH@BTC is prepared by the layered double hydroxide hybrid metal organic framework. The catalyst has a porous flower-like structure, which not only converts the coordinated cobalt ions into active elemental cobalt, but also makes more metal center atoms produce unsaturated coordination, and also disperses the active sites through the sheet structure of the layered double hydroxide, which can form a hierarchical pore structure, improve the utilization rate of the original active sites, and ensure that the catalytic work is more efficient. Compared with the catalyst in the comparative example, the application of the method of the present application can increase the product hydrocarbon selectivity of the algal deoxygenation and bond breaking to produce biofuel by more than 10%, and the naphthene selectivity is increased by 6%.
[0078] In addition, the applicant uses the catalyst LDH@BTC for the experiment of preparing biofuel by deoxygenation and bond breaking of methyl palmitate, and the results show that it has similar improvement effect as methyl stearate. Therefore, the present application has the advantages of dispersing catalyst active sites, constructing regular pores, and improving the conversion rate of algal oil and product selectivity, and can be applied to the scene of large-scale conversion of algal oil to produce fuel.
[0079] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or modifications within the scope of the claims, which does not affect the essential content of the present application.
Claims
1. A method for preparing a layered double hydroxide hybrid nickel cobalt metal-organic framework, characterized in that, The method comprises the following steps: (1) dissolving nickel nitrate hexahydrate Ni(NO3)2·6H2O and cobalt nitrate hexahydrate Co(NO3)2·6H2O in a mixed solution of N,N-dimethylformamide (DMF), deionized water and ethanol, then adding trimesic acid and triethylamine, and reacting under ultrasonic conditions; after the reaction is completed, the solid is separated and dried to obtain a bimetallic organic framework NiCo-BTC; (2) dissolving the NiCo-BTC in a methanol solution containing cobalt nitrate hexahydrate Co(NO3)2·6H2O, stirring to dissolve; then adding a methanol solution containing 2-methylimidazole 2-MIM, stirring uniformly, and then reacting at room temperature for 11-13 hours; after the reaction is completed, the solid is separated and dried to obtain a metal organic framework ZIF-67@BTC carrying ZIF-67, that is, a ZIF framework is carried on the basis of the NiCo-BTC framework; (3) dissolving the ZIF-67@BTC and nickel nitrate hexahydrate Ni(NO3)2·6H2O in ethanol, stirring uniformly, then transferring to a hydrothermal reaction kettle, and hydrothermally reacting at 75-82°C for 5-7 hours; after the reaction is completed, the solid is separated and dried to obtain a layered double hydroxide hybrid nickel-cobalt metal organic framework catalyst LDH@BTC.
2. The method of claim 1, wherein, In the N,N-dimethylformamide (DMF)-deionized water-ethanol mixed solution of step (1), the volume ratio of the three solvents is 300-330:18-21:18-21.
3. The method of claim 1, wherein, In step (1), the addition ratio of nickel nitrate hexahydrate, cobalt nitrate hexahydrate, trimesic acid and triethylamine is 1-1.1g:1-1.1g:1.56-1.58g:7-9mL.
4. The method of claim 1, wherein, In step (1), the reaction time under ultrasonic conditions is 7-9 hours.
5. The method of claim 1, wherein, In step (2), the mass ratio of NiCo-BTC, cobalt nitrate hexahydrate and 2-methylimidazole 2-MIM is 23-25:15-16:17-18.
6. The method of claim 1, wherein, In step (3), the mass ratio of ZIF-67@BTC and nickel nitrate hexahydrate is 0.55-0.57:1.9-2.
2.
7. The method of claim 1, wherein, After the reaction in each step is completed, the solid is separated and dried, which specifically refers to: pouring the reaction product into a centrifugal bottle, centrifuging at a speed of 8000-10000 rpm for 5-10 minutes to separate the solid precipitate from the supernatant; and placing the separated solid into a blast drying oven, and drying at a temperature of 50-70°C.
8. The method for preparing bio-fuel by catalyzing deoxygenation and breaking bond of algal oil using the catalyst LDH@BTC prepared by the method of any one of claims 1 to 7, characterized in that, The method comprises the following steps: adding algal oil and the catalyst LDH@BTC into a reaction kettle, stirring uniformly, then sealing the reaction kettle; then introducing pure CO2 gas until the pressure is 1-4 MPa, and reacting at 410-430°C for 6-9 hours; after the reaction is completed, the gas is exhausted after natural cooling to room temperature, and the reaction product is centrifugally separated, and the obtained liquid phase product is a hydrocarbon corresponding to typical components of biodiesel.
9. The method of claim 8, wherein, The mass ratio of the algal oil and the catalyst LDH@BTC is 3-5:0.04-0.
2.
10. The method of claim 8, wherein, The algal oil is any one of the following: methyl stearate or methyl palmitate.