A copper-based MOF material, a preparation method and application thereof

Abstract

The application discloses a copper-based MOF material and a preparation method and application thereof. The method comprises the following steps: adding an organic ligand solution into a metal salt solution, adding tetrafluoroboric acid, uniformly mixing and reacting to obtain the copper-based MOF material; the organic ligand comprises camphoric acid, amino pyrazine and triethylenediamine; and the metal salt is copper salt. The copper-based MOF material can be synthesized under normal pressure, the synthesis steps are simple, the raw material cost is low, the preparation method has scalability, and the copper-based MOF material is favorable for industrial practical application. The prepared material can screen double-branched chain hexane isomers (22DMB) in a one-step method, can be applied to hexane isomer separation, can be used as a gasoline additive to improve the octane number of gasoline, and thus improves the oil product quality.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of metal organic framework materials, and specifically relates to a copper-based MOF material and a preparation method and application thereof. Background Art

[0002] Hexane plays a crucial role in petrochemicals and is a major component of gasoline. There are five hexane isomers, each with a significant variability in octane rating. As the degree of hexane branching increases, it acquires a higher research octane number (RON). The doubly branched isomer, 2,2-dimethylbutane (22DMB), possesses the highest octane number and can be used as a gasoline additive to enhance gasoline quality. To improve gasoline octane rating, the industry requires isomerization to convert n-hexane (nHex, RONs = 30) into monobranched isomers, such as 2-methylpentane and 3-methylpentane (2MP / 3MP). However, because the conversion rate of the isomerization reaction is limited by thermodynamic equilibrium, a significant proportion of the low-octane nHex isomer remains unreacted after the isomerization reaction. In the UOP isomerization process (TIP) in the United States, nHex, MP, and DMB account for 11.1%, 46.9%, and 42% of the isomerization products, respectively. Therefore, further purification of these products is necessary to improve the octane number of gasoline. Efficient and energy-saving separation of hexane isomers has become a key factor in producing high-octane gasoline. Traditional separation methods (such as distillation) often suffer from high energy consumption, low efficiency, and high investment when separating isomers with similar structures, boiling points, and polarizabilities. Low-energy, high-efficiency adsorption separation methods, however, show greater application prospects and potential. Adsorption separation using 5A zeolite molecular sieve is used industrially as an adsorbent for hexane isomer separation to remove n-hexane isomers. However, to improve gasoline quality, separation of single and double branches is essential. However, 5A zeolite molecular sieve cannot separate single and double branches, and its adsorption capacity for n-hexane is low, necessitating the search for higher-quality adsorbents.

[0003] Metal-organic frameworks (MOFs) are porous materials self-assembled from inorganic metal ions and organic ligands. Due to the high porosity, large specific surface area, and adjustable pore size of MOFs, it is possible to design MOFs that can accommodate single-chain and straight-chain hexane isomers and exclude double-chain hexane isomers. Currently, the main mechanisms for MOFs to separate hexane isomers are (1) thermodynamic equilibrium separation (2) kinetic separation (3) size screening. Due to the large difference in molecular size between straight-chain and branched hexane isomers, most of the MOF materials reported so far for size-screening hexane isomers focus on the separation of straight-chain and branched hexane isomers, while separating double-chain hexane isomers using a one-step method remains a major challenge. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention adopts a mixed ligand strategy to prepare a new type of copper-based MOF material, accurately controls the pore size of the material, and realizes the next step of eliminating dibranched hexane isomers under mild conditions.

[0005] The objects of the present invention are achieved through the following technologies.

[0006] A method for preparing a copper-based MOF material comprises the following steps:

[0007] The organic ligand solution is added to the metal salt solution, and tetrafluoroboric acid is added, and the mixture is mixed evenly to react to obtain a copper-based MOF material;

[0008] The organic ligand comprises camphoric acid, aminopyrazine and triethylenediamine; and the metal salt is copper salt.

[0009] Preferably, the molar ratio of the copper salt, camphoric acid, and (aminopyrazine / triethylenediamine) is 1-3:1-3:1-3, and more preferably 2:1:2.

[0010] Preferably, the molar ratio of aminopyrazine to triethylenediamine is 1:1 to 1:5, more preferably 1:1 to 1:3, and most preferably 1:3.

[0011] Preferably, the solvent in the organic ligand solution is a mixed solvent of deionized water and methanol; the solvent in the metal salt solution is N,N-dimethylformamide (DMF); and the metal salt is anhydrous copper acetate.

[0012] Further preferably, the volume ratio of N,N-dimethylformamide (DMF), methanol and deionized water is 1:1:1-3:2:2, and further preferably 3:2:2.

[0013] Preferably, the molar ratio of the added amount of tetrafluoroboric acid to the metal salt is in the range of 5 to 25:1.

[0014] Preferably, the amount of tetrafluoroboric acid added is 1 to 7 mL, more preferably 5 mL.

[0015] Preferably, the reaction temperature is 70-100° C., more preferably 85° C.; the reaction time is 24-72 h, more preferably 48 h.

[0016] Preferably, after the reaction, the obtained product is filtered, dried, and activated with methanol to obtain a copper-based MOF material; during the methanol activation, the material is immersed in methanol for 24 to 72 hours, and the methanol is replaced every 6 to 36 hours.

[0017] Preferably, the drying temperature is 50 to 80° C., more preferably 60° C., and the drying time is 6 to 12 hours.

[0018] A copper-based MOF material prepared by any of the preparation methods described above.

[0019] The application of the copper-based MOF material described above in the adsorption separation of hexane isomers.

[0020] Preferably, the temperature of the adsorption separation is 298.15-363.15K, more preferably 303.15K.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) The synthesis conditions of the Cu-MOF material prepared by the present invention are mild (normal pressure synthesis), the synthesis process is green and environmentally friendly, and the energy consumption and raw material usage costs are low.

[0023] (2) The Cu-MOF synthesis method developed in the present invention is scalable and has a good foundation for large-scale industrial production.

[0024] (3) The single-component adsorption isotherm of the Cu-MOF material prepared in the present invention at 303.15 K shows that the double-branched isomers of hexane are completely excluded, thereby separating the high-octane hexane isomers, which has great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Wide-angle X-ray diffraction patterns of the Cu-MOF materials prepared in Examples 1-4 of the present invention.

[0026] Figure 2 These are scanning electron microscope images of the Cu-MOF materials prepared in Examples 3 and 4 of the present invention.

[0027] Figure 3 This is a thermogravimetric curve of the Cu-MOF material prepared in Example 4 of the present invention.

[0028] Figure 4 This is an adsorption isotherm curve of hexane isomers adsorbed by the Cu-MOF prepared in Example 1 of the present invention at 303.15K.

[0029] Figure 5 This is an adsorption isotherm curve of the Cu-MOF prepared in Example 2 of the present invention adsorbing hexane isomers at 303.15K.

[0030] Figure 6 This is an adsorption isotherm curve of hexane isomers adsorbed by the Cu-MOF prepared in Example 3 of the present invention at 303.15K.

[0031] Figure 7This is an adsorption isotherm curve of the Cu-MOF prepared in Example 4 of the present invention adsorbing hexane isomers at 303.15K.

[0032] Figure 8 This is an adsorption isotherm curve of hexane isomers adsorbed by Cu-MOF prepared in Comparative Example 1 of the present invention at 303.15K.

[0033] Figure 9 This is an adsorption isotherm curve of hexane isomers adsorbed by Cu-MOF prepared in Comparative Example 2 of the present invention at 303.15K. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection claimed by the present invention is not limited to the scope described in the embodiments.

[0035] Example 1

[0036] 0.3633 g of Cu(OAC)2 was dissolved in 30 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute to obtain a green transparent solution A; 0.224 g of camphoric acid, 0.1122 g of triethylenediamine and 0.095 g of aminopyrazine were dissolved in deionized water and methanol (40 mL, 1:1) and sonicated for 1 minute to obtain a brown transparent solution B; solution B was poured into solution A and sonicated to obtain a mixed solution C, and 5 mL of HBF4 was added to the mixed solution C to obtain a mixed solution D; the mixed solution D was transferred to a polytetrafluoroethylene liner and allowed to stand at 85°C for 48 hours and then filtered. The resulting product was washed with deionized water and methanol, purified with methanol for 48 hours, filtered, and vacuum dried at 60°C for 8 hours to obtain a Cu-MOF material, marked as sample A1.

[0037] Example 2

[0038] 0.3633 g of Cu(OAC)2 was dissolved in 30 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute to obtain a green transparent solution A; 0.224 g of camphoric acid, 0.149 g of triethylenediamine and 0.063 g of aminopyrazine were dissolved in deionized water and methanol (40 mL, 1:1) and sonicated for 1 minute to obtain a brown transparent solution B; solution B was poured into solution A and sonicated to obtain a mixed solution C, and 5 mL of HBF4 was added to the mixed solution C to obtain a mixed solution D; the mixed solution D was transferred to a polytetrafluoroethylene liner and allowed to stand at 85°C for 48 hours and then filtered. The resulting product was washed with deionized water and methanol, purified with methanol for 48 hours, filtered, and vacuum dried at 60°C for 8 hours to obtain a Cu-MOF material, marked as sample A2.

[0039] Example 3

[0040] Cu(OAC)2(0.3633 g) was dissolved in 30 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute to give a green transparent solution A; camphoric acid (0.224 g) and triethylenediamine (0.1602 g) and aminopyrazine (0.0543 g) were dissolved in deionized water and methanol (40 mL, 1 : 1) and sonicated for 1 minute to give a brown transparent solution B; solution B was poured into solution A and sonicated to give a mixed solution C; mixed solution C was added to 5 mL of HBF4to give a mixed solution D; mixed solution D was transferred to a polytetrafluoroethylene liner and left to stand at 85 °C for 48 h before being suction filtered; the resulting product was washed with deionized water, methanol, then purified with methanol for 48 h, suction filtered, and vacuum dried at 60 °C for 8 h to give a Cu-MOF material, labelled as sample A3.

[0041] Example 4

[0042] Cu(OAC)2(0.3633 g) was dissolved in 30 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute to give a green transparent solution A; camphoric acid (0.224 g) and triethylenediamine (0.1683 g) and aminopyrazine (0.047 g) were dissolved in deionized water and methanol (40 mL, 1 : 1) and sonicated for 1 minute to give a brown transparent solution B; solution B was poured into solution A and sonicated to give a mixed solution C; mixed solution C was added to 5 mL of HBF4to give a mixed solution D; mixed solution D was transferred to a polytetrafluoroethylene liner and left to stand at 85 °C for 48 h before being suction filtered; the resulting product was washed with deionized water, methanol, then purified with methanol for 48 h, suction filtered, and vacuum dried at 60 °C for 8 h to give a Cu-MOF material, labelled as sample A4.

[0043] Comparative Example 1

[0044] Cu(OAC)2(0.3633 g) was dissolved in 30 mL of N,N-dimethylformamide (DMF) and sonicated for 1 minute to give a green transparent solution A; camphoric acid (0.224 g) and triethylenediamine (0.1902 g) and aminopyrazine (0.0543 g) were dissolved in deionized water and methanol (40 mL, 1 : 1) and sonicated for 1 minute to give a brown transparent solution B; solution B was poured into solution A and sonicated to give a mixed solution C; mixed solution C was added to 5 mL of HBF4to give a mixed solution D; mixed solution D was transferred to a polytetrafluoroethylene liner and left to stand at 85 °C for 48 h before being suction filtered; the resulting product was washed with deionized water, methanol, then purified with methanol for 48 h, suction filtered, and vacuum dried at 60 °C for 8 h to give a Cu-Cam-Apyz material, labelled as sample A5.

[0045] The materials were tested for hexane isomer vapour adsorption performance at 303.15 K and the adsorption isotherms are shown in Figure 1. Figure 8The adsorption amounts of the material for nHex, 3MP and 22DMB are 1.45 mmol, 2.19 mmol and 0.51 mmol respectively. It can be seen from the results that the material pores can accommodate three hexane isomers, and the double branched chain isomer 22DMB cannot be well excluded from the pores, the selectivity is not high, and the separation effect is not as good as that of the A1 of the embodiment.

[0046] Comparative Example 2

[0047] 0.3633 g of Cu(OAC)2 was dissolved in 30 mL of N,N-dimethylformamide (DMF) to obtain a green transparent solution A by ultrasonic treatment for 1 minute; 0.224 g of camphoric acid and 0.2243 g of triethylenediamine were dissolved in deionized water and methanol (40 mL, 1:1) to obtain a brown transparent solution B by ultrasonic treatment for 1 minute; solution B was poured into solution A to obtain a mixed solution C by ultrasonic treatment, and mixed solution C was added to 5 mL of HBF4 to obtain a mixed solution D; mixed solution D was transferred into a polytetrafluoroethylene liner, and after standing at 85°C for 48 h, it was suction filtered, and the obtained product was washed with deionized water and methanol, and then purified by methanol for 48 h, suction filtered, and vacuum dried at 60°C for 8 h to obtain a Cu-Cam-Ted material, which was marked as sample A6.

[0048] The material was subjected to hexane isomer vapor adsorption performance test at 303.15 K, and the adsorption isotherm is shown in Figure 9 The adsorption amount of the material for nHex is 0.43 mmol / g, and the adsorption amount for 3MP and 22DMB is almost 0. This is because the pore size of the material can only accommodate the straight chain isomer nHex, and the branched chain isomers with larger molecular sizes cannot enter the pores, so they are excluded from the pores. However, this material cannot separate the double branched chain isomers, and the adsorption amount is also very low, and the separation effect is not as good as that of the A1 of the embodiment.

[0049] The Cu-MOF material prepared according to the embodiment was analyzed, and the analysis results are shown in the accompanying drawings.

[0050] (I) X-ray powder diffraction analysis of Cu-MOF

[0051] The crystal structure of samples A1, A2, A3 and A4 synthesized in Examples 1, 2, 3 and 4 of the application was characterized by using a D8-ADCANCE type X-ray polycrystalline diffractometer (Bruker, Germany). It can be seen from Figure 1 that the characteristic diffraction peaks of the samples prepared in Examples 1, 2, 3 and 4 are obvious, and are consistent with the simulated XRD diffraction peaks; when the ligand ratio is changed, samples A1, A2, A3 and A4 have similar and identical XRD spectra, and the diffraction peak position does not change significantly, indicating that the Cu-MOF material can be synthesized by using the synthesis conditions of Examples 1, 2, 3 and 4.

[0052] (2) Scanning electron microscopy images of Cu-MOF materials

[0053] The morphology of the samples prepared in Example 3 and Example 4 was characterized using a JSM-6330F scanning electron microscope (JEOL Electronics Co., Ltd., Japan). Figure 2 It shows that the samples obtained under the synthesis conditions of changing the ligand ratio in Example 3 and Example 4 all have three-dimensional stacked uneven blocks.

[0054] (2) Thermogravimetric analysis of Cu-MOF materials

[0055] The thermal stability of the sample prepared in Example 4 was tested by a thermal gravity analyzer TGA55 at a heating rate of 5°C / min under N2 atmosphere. Figure 3 It shows that the synthesized sample can maintain structural integrity below 300℃ and has good thermal stability.

[0056] (III) Performance analysis of Cu-MOF materials for adsorption and separation of hexane isomers

[0057] The single component hexane isomer vapor adsorption isotherms of the prepared samples A1, A2, A3 and A4 were measured at 303.15K. Figure 4-7 It can be seen that as the ratio of triethylenediamine to aminopyrazine ligands increases, the pores of the material gradually shrink, the adsorption capacity gradually decreases, the double-branched isomers are gradually excluded, and the selectivity of nHex / 22DMB and 3MP / 22DMB also gradually increases. When the ratio of triethylenediamine to aminopyrazine is 3:1, the selectivity reaches the highest, such as Figure 7 As shown in the figure, the A4 sample completely excludes the double-branched isomer (22DMB) at 303.15k, and the adsorption amount of nHex is as high as 1.34mmol / g, the adsorption amount of 3MP is 1.28mmol / g, and the adsorption amount of the double-branched isomer (22DMB) is only 0.062mmol / g, which is almost close to 0, indicating that the pore environment of the material can well accommodate linear and single-branched isomers and exclude the double-branched isomers from the pores, thereby achieving the separation effect of screening the double-branched hexane isomers.

[0058] The above embodiments are ideal implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based MOF material, characterized in that: The process includes the following steps: The organic ligand solution is added to the metal salt solution, and tetrafluoroboric acid is added, and the mixture is mixed evenly to react to obtain a copper-based MOF material; The organic ligand includes camphoric acid, aminopyrazine and triethylenediamine; the metal salt is a copper salt; The molar ratio of the aminopyrazine to triethylenediamine is 1:1 to 1:

5.

2. The method for preparing a copper-based MOF material according to claim 1, wherein The molar ratio of the copper salt, camphoric acid, and (aminopyrazine / triethylenediamine) is 1-3:1-3:1-3.

3. The method for preparing a copper-based MOF material according to claim 1, wherein The molar ratio of the aminopyrazine to triethylenediamine is 1:1 to 1:

3.

4. The method for preparing a copper-based MOF material according to claim 1, wherein The solvent in the organic ligand solution is a mixed solvent of deionized water and methanol; the solvent in the metal salt solution is N,N-dimethylformamide; and the metal salt is anhydrous copper acetate.

5. The method for preparing a copper-based MOF material according to claim 1, wherein The molar ratio of the added amount of tetrafluoroboric acid to the metal salt is in the range of 5 to 25:

1.

6. The method for preparing a copper-based MOF material according to claim 1, wherein: The reaction temperature is 70-100°C; the reaction time is 24-72 h.

7. The method for preparing a copper-based MOF material according to claim 1, wherein: After the reaction, the obtained product is filtered, dried, and activated with methanol to obtain a copper-based MOF material; the methanol activation is performed by immersing the material in methanol for 24 to 72 hours, with the methanol being replaced every 6 to 36 hours.

8. A copper-based MOF material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the copper-based MOF material according to claim 8 in the adsorption separation of hexane isomers.

10. Use of a copper-based MOF material according to claim 9 in the adsorption separation of hexane isomers, characterized in that: The temperature of the adsorption separation is 298.15-363.15 K.

Images