Porous ionic liquid based on micro-mesoporous MOF as well as preparation method and application of porous ionic liquid

Abstract

The invention belongs to the technical field of fuel oil desulfurization, and discloses a porous ionic liquid based on micro-mesoporous MOF and a preparation method and application thereof.The porous ionic liquid based on the micro-mesoporous MOF is constructed by using the micro-mesoporous MOF MOF-808 and ionic liquid [P6, 6, 6, 14] [NTF2] as raw materials, the preparation process is simple, convenient, rapid, green and environmentally friendly, and the porous ionic liquid has excellent stability and catalytic performance and is suitable for industrial production. Efficient removal of thiophene sulfides in fuel oil can be realized under mild conditions, and the catalyst can be used as an excellent oxidative desulfurization catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel desulfurization, and relates to a porous ionic liquid based on micro-mesoporous MOF and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of industry has led to an increasing demand for fuel oil. However, SO2 x It will cause environmental disasters such as acid rain, posing a threat to human health and property. Fuel desulfurization has become an urgent problem to be solved. Hydrodesulfurization technology is a traditional desulfurization method. Hydrodesulfurization can effectively remove sulfides such as mercaptans, but the removal efficiency of poorly soluble aromatic sulfides (such as dibenzothiophene and its derivatives) is low, and harsh reaction conditions are required, including high temperature, high pressure and high energy consumption. In order to overcome these limitations of hydrodesulfurization, people have developed several non-dehydrogenation desulfurization technologies, such as adsorption desulfurization, biological desulfurization, extractive desulfurization (EDS) and oxidative desulfurization (ODS). In addition, new desulfurization technologies have been developed based on oxidative desulfurization, among which extractive coupled catalytic oxidative desulfurization (ECODS) has attracted much attention due to its advantages of low cost, simple operation and efficient removal of thiophene sulfides under mild conditions.

[0003] Metal-organic frameworks (MOFs) are a new type of porous solid material composed of metal atoms as central atoms and organic compounds as ligands. They have the advantages of high porosity, high specific surface area and adjustable structure.

[0004] Porous ionic liquids are new liquids with permanent pores. Ionic liquids have attracted widespread attention due to their excellent physicochemical properties (such as good chemical stability and adjustable structure) and are considered to be a good substitute for traditional volatile organic solvents. Due to the size matching principle of solvent molecules and pore size in porous ionic liquids, most porous ionic liquids are currently microporous. Although micropores are conducive to the stability of porous ionic liquids, the microporous structure creates mass transfer barriers for macromolecular reactants, making it difficult to fully utilize the catalytic reaction active sites in MOF. Although mesoporous materials have enhanced mass transfer performance, they have poor stability. Therefore, using micro-mesoporous MOF-808 as a porous solid material and ionic liquids as steric hindered solvents, the micro-mesoporous MOF-based porous ionic liquids constructed have both the catalytic performance and permanent pores of MOF-808 and the efficient mass transfer and extraction performance of ionic liquids, and show excellent stability. There are literatures showing that micro-mesoporous MOF-based porous ionic liquids have been used to study gas absorption, but they are rarely reported in the field of catalysis, especially in the field of desulfurization. Therefore, it is necessary to provide a new technical solution to overcome the above defects. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems and provide a porous ionic liquid based on micro-mesoporous MOF and its preparation method and application. The ionic liquid is used as a steric solvent and MOF-808 is used as a porous solid material. It has the advantages of both, has good stability and high catalytic activity, and can be used for fuel desulfurization.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a porous ionic liquid based on micro-mesoporous MOF, comprising the following steps:

[0008] (1) Synthesis of metal organic framework MOF-808 with catalytic properties;

[0009] ZrOCl 2 8H 2 O and trimesic acid are dissolved in a mixed solution of DMF / FA, stirred at room temperature for 1-2 hours; transferred to a high-pressure reactor, reacted in an oven at 100-120°C for 24-48 hours; cooled to room temperature, washed by centrifugation to obtain a white solid, and vacuum dried to obtain the porous material MOF-808;

[0010] (2) Add the MOF-808 obtained in step (1) to the ionic liquid [P 6,6,6,14 ][NTF 2 ], a porous ionic liquid MOF-808-PILs based on micromesoporous MOF was constructed through reaction.

[0011] In step (1), ZrOCl 2 8H 2 The molar ratio of O to trimesic acid is 1:1; in the mixed solution of DMF / FA, the volume ratio of DMF to FA is 1:1.

[0012] In step (2), MOF-808 and [P 6,6,6,14 The dosage ratio of ][NTF] is 0.025-0.04g:0.5g;

[0013] In step (2), the reaction is stirred at room temperature for 6-12 hours.

[0014] In the porous ionic liquid MOF-808-PILs prepared according to the above preparation method, the mass fraction of MOF-808 is 5-8%.

[0015] In addition, the present invention also provides a specific method for applying MOF-808-PILs to fuel desulfurization, comprising the following steps: mixing a certain amount of MOF-808-PILs and model oil under constant temperature conditions for extraction reaction, and then adding 30wt% H2 O 2 The oxidation reaction is carried out, and after the reaction is completed, the oil phase is allowed to stand and separated, and the upper oil phase obtained is the desulfurized oil product.

[0016] The model oil contains one or more aromatic sulfides, wherein the sulfur content is 500 mg / kg;

[0017] Preferably, in the step, the ratio of MOF-808-PILs to model oil is 0.5 g:5 mL;

[0018] Preferably, the oxygen-sulfur ratio in the step is 2-7;

[0019] Preferably, the reaction temperature is 30-70° C., the stirring speed is 600 rpm, the extraction reaction time is 15 min; and the oxidation reaction time is 90 min.

[0020] The organic sulfide contained in the model oil is one or more of dibenzothiophene, 4-methylbenzothiophene and 4,6-dimethyldibenzothiophene.

[0021] Compared with the prior art, the present invention exhibits the following excellent effects:

[0022] (1) The MOF-808-PILs prepared by the present invention has the advantages of good stability and excellent catalytic performance, and has no effect on the human body and the environment, and is an environmentally friendly material.

[0023] (2) The preparation method adopted by the present invention has mild reaction conditions, is pollution-free, simple to operate, and does not require pressurized equipment, thus meeting environmental protection requirements.

[0024] (3) The MOF-808-PILs of the present invention have good stability and can achieve efficient desulfurization of fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0026] Figure 1 A schematic diagram of the synthesis of a porous ionic liquid based on micro-mesoporous MOF provided by the present invention;

[0027] Figure 2 A stability state diagram of a porous ionic liquid based on micro-mesoporous MOF provided by the present invention;

[0028] Figure 3 A nitrogen adsorption-desorption curve and pore size distribution diagram of a porous ionic liquid based on micro-mesoporous MOF provided by the present invention;

[0029] Figure 4 An infrared spectrum of a porous ionic liquid based on micro-mesoporous MOF provided by the present invention;

[0030] Figure 5 A gas absorption diagram of a porous ionic liquid based on micro-mesoporous MOF provided by the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, a clear and complete description will be given below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments.

[0032] The following is the preparation of the fuel used in the examples:

[0033] Dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were dissolved in n-octane, with tetradecane as an internal standard substance, and transferred to a volumetric flask for use. The sulfur content in the model oils prepared with DBT, 4-MDBT and 4,6-DMDBT was 500 mg / kg.

[0034] The preparation method of porous ionic liquid based on micro-mesoporous MOF provided by the present invention has mild reaction conditions and simple operation. The synthesis schematic diagram is as follows Figure 1 shown.

[0035] Example 1

[0036] A method for preparing a porous ionic liquid based on micro-mesoporous MOF, comprising the following steps:

[0037] (1) Preparation of metal organic framework, namely MOF-808.

[0038] 1.5 mmol ZrOCl 2 8H 2 O and 1.5 mmol of trimesic acid were dissolved in a DMF / FA (30 mL / 30 mL) mixed solution and stirred at room temperature for 1 h; transferred to a high-pressure reactor and reacted in an oven at 100°C for 48 h; cooled to room temperature and washed by centrifugation to obtain a white solid; the white solid was vacuum dried to obtain the porous material MOF-808.

[0039] (2) Preparation of MOF-808 (5%)-PILs:

[0040] Weigh 0.025g MOF-808 and add it to 0.5g [P 6,6,6,14 ][NTF 2 ] and stirred at room temperature for 12 h to obtain MOF-808(5%)-PILs.

[0041] (3) Extraction coupled catalytic oxidation desulfurization:

[0042] Accurately weigh 0.5 g of the prepared MOF-808 (5%)-PILs into a reaction bottle, add 5 mL of DBT model oil, mix and stir, and react at a constant temperature of 60 ° C. After 15 minutes, add 30 wt% H 2 O 2 The reaction was continued for 90 minutes. After the reaction was completed, the upper oil phase was separated and the residual DBT content was detected by gas chromatography. The desulfurization rate was calculated to be 88.4%.

[0043] Example 2

[0044] (1) The steps for preparing the metal organic framework MOF-808 are the same as those in Example 1;

[0045] (2) Preparation of MOF-808 (6%)-[BDIM] [NTF 2 ]:

[0046] Weigh 0.03g MOF-808 and add it to 0.5g [P 6,6,6,14 ][NTF 2 ] and stirred at room temperature for 12 h to obtain MOF-808(6%)-[BDIM][NTF 2 ].

[0047] (3) Extraction coupled catalytic oxidation desulfurization:

[0048] Accurately weigh 0.5 g of the prepared MOF-808 (6%)-PILs into a reaction bottle, add 5 mL of model oil and stir, and react in a constant temperature water bath at different temperatures (30 ° C, 40 ° C, 50 ° C, 60 ° C, 70 ° C). After 15 min, add 30 wt% H 2 O 2 The reaction was continued for 90 minutes. After the reaction was completed, the upper oil phase was separated and the residual DBT content was detected by gas chromatography. The desulfurization rates were calculated to be 44.6%, 64.3%, 87.2%, 99.8% and 96.1, respectively.

[0049] Example 3

[0050] (1) The steps for preparing the metal organic framework MOF-808 are the same as those in Example 1;

[0051] (2) Preparation of MOF-808 (7%)-PILs

[0052] Weigh 0.035g MOF-808 and add it to 0.5g [P 6,6,6,14 ][NTF2 ] and stirred at room temperature for 12 h to obtain MOF-808(7%)-PILs.

[0053] (3) Extraction coupled catalytic oxidation desulfurization:

[0054] Accurately weigh 1g of the prepared MOF-808 (7%)-PILs into a reaction bottle, and then add 5mL of DBT, 4-MDBT, and 4,6-MDBT model oils, respectively, and mix and stir. The reaction was carried out at a constant temperature of 60°C. After 15 minutes, 30wt% H 2 O 2 The reaction was continued for 90 minutes. After the reaction was completed, the upper oil phase was separated and the residual sulfur content was detected by gas chromatography. The desulfurization rates were calculated to be 99.8%, 78.2% and 49.9%, respectively.

[0055] Next, the product of this embodiment is tested as follows:

[0056] like Figure 2 As shown, the porous ionic liquid based on micro-mesoporous MOF prepared in this embodiment has a certain fluidity. After standing for three months, no sedimentation was found, showing excellent stability.

[0057] Figure 3 The nitrogen adsorption-desorption curve and pore size distribution of MOF-808 show that the pore size distribution of MOF-808 is between 0.9nm and 2.7nm, and the specific surface area is 2321m 2 / g indicates that MOF-808 has both microporous and mesoporous structures.

[0058] Figure 4 For MOF-808, [P 6,6,6,14 ][NTF 2 ] and the infrared spectra of MOF-808-PILs. It can be seen that the vibration peaks of Zr-O bond and -COOH were detected in MOF-808-PILs, indicating that MOF was uniformly dispersed in the ionic liquid and the porous ionic liquid was successfully synthesized.

[0059] Figure 5 For [P 6,6,6,14 ][NTF 2 ] and CO of MOF-808-PILs 2 Absorption diagram, the absorption capacity of micro-mesoporous MOF-808-PILs is higher than that of pure ionic liquids [P 6,6,6,14 ][NTF 2 ] has a stronger absorption capacity, indicating that the pore structure of MOF-808 is retained and can accommodate more guest molecules.

[0060] Example 4

[0061] (1) The steps for preparing the metal organic framework MOF-808 are the same as those in Example 1;

[0062] (2) Preparation of MOF-808 (8%)-PILs

[0063] Weigh 0.04g Mo-MOF and add it to 0.5g [P 6,6,6,14 ][NTF 2 ] and stirred at room temperature for 12 h to obtain MOF-808(8%)-PILs.

[0064] (3) Extraction coupled catalytic oxidation desulfurization:

[0065] Accurately weigh 0.5 g of the prepared MOF-808 (8%)-PILs into a reaction bottle, add 5 mL of model oil and stir, and react at a constant temperature of 60 ° C. After 15 min, add 30 wt% H 2 O 2 The reaction was continued for 90 minutes. After the reaction was completed, the residual sulfur content was detected by gas chromatography and dried at 80°C to completely remove the model oil. This cycle was repeated 11 times.

[0066] Comparative Example:

[0067] Take MOF-808(7%)-PILs as an example.

[0068] Accurately weigh 0.025g MOF-808, 0.5g [P 6,6,6,14 ][NTF 2 ] and 0.5 g MOF-808 (7%)-PILs were added to the reaction bottle, and 5 mL of DBT model oil was added and stirred. The reaction was carried out at a constant temperature of 60 ° C. After 15 min, 30 wt% H 2 O 2 The reaction was continued for 90 minutes. After the reaction was completed, the upper oil phase was separated and the residual sulfur content was detected by gas chromatography. The desulfurization rate was calculated. The desulfurization rate dropped to only 90% for the 11th time.

[0069] The calculation formula for the desulfurization rate in the above-mentioned Examples 1 to 4 and the comparative example is as follows:

[0070]

[0071] It can be seen from the experimental data obtained from the above examples and comparative examples that the porous ionic liquid based on micro-mesoporous MOF provided by the present invention has excellent stability and excellent desulfurization performance.

[0072] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

Claims

1. A method for preparing a porous ionic liquid based on micro-mesoporous MOF, characterized in that: The steps include: (1) Synthesis of metal organic framework MOF-808 with catalytic properties; Dissolve ZrOCl2·8H2O and trimesic acid in a DMF / FA mixed solution in proportion, stir at room temperature, transfer to a high-pressure reactor, heat in an oven for reaction, cool to room temperature, wash by centrifugation to obtain a white solid, and dry in vacuum to obtain the porous material MOF-808; (2) Add the MOF-808 obtained in step (1) to the ionic liquid [P 6,6,6,14 ][NTF2], a porous ionic liquid MOF-808-PILs based on micro-mesoporous MOF was constructed through reaction.

2. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of ZrOCl2·8H2O to trimesic acid is 1:1; in the DMF / FA mixed solution, the volume ratio of DMF to FA is 1:1; the stirring time at room temperature is 1-2 hours; the reaction temperature in the oven is 100-120°C, and the reaction time is 24-48 hours.

3. The preparation method according to claim 1, characterized in that: In step (2), MOF-808 and [P 6,6,6,14 The dosage ratio of ][NTF] is 0.025-0.04g:0.5g.

4. The preparation method according to claim 1, characterized in that: In step (2), the reaction is stirred at room temperature for 6-12 hours.

5. A porous ionic liquid based on micro-mesoporous MOF, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 4, wherein the mass fraction of MOF-808 is 5-8%.

6. Use of the porous ionic liquid based on micro-mesoporous MOF according to claim 5 for fuel desulfurization.

7. The use according to claim 6, characterized in that The steps are: MOF-808-PILs and model oil are mixed and stirred at a constant temperature to perform an extraction reaction, and then 30wt% H2O2 is added at an oxygen-sulfur ratio of 2-7 for an oxidation reaction. After the reaction is completed, the mixture is allowed to stand and separated, and the upper oil phase obtained is the desulfurized oil product.

8. The use according to claim 7, characterized in that The model oil contains one or more aromatic sulfides, wherein the sulfur content is 500 mg / kg; the usage ratio of MOF-808-PILs to the model oil is 0.5 g:5 mL.

9. The use according to claim 8, characterized in that The organic sulfide contained in the model oil is one or more of dibenzothiophene, 4-methylbenzothiophene and 4,6-dimethyldibenzothiophene.

10. The use according to claim 7, characterized in that The reaction temperature is 30-70°C, the stirring speed is 600 rpm; the extraction reaction time is 15 minutes; and the oxidation reaction time is 90 minutes.

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