Iron based desulfurization catalyst
Iron based desulfurization catalyst
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Iron based desulfurization catalyst - Names and Identifiers
Iron based desulfurization catalyst - Technical background
With the development of the global economy, the consumption of gasoline is increasing. The combustion of organic sulfur in gasoline directly leads to an increase in sulfur dioxide emissions and endangers public health. Traditional hydrodesulfurization mainly removes organic sulfur such as mercaptan and thioether, but it is difficult to remove stubborn organic sulfur such as benzothiophene and dibenzothiophene. The recently developed oxidative desulfurization can be used as a beneficial supplement to hydrodesulfurization, which can have higher catalytic activity at normal pressure and lower temperature.
The steps of oxidative desulfurization are:(1) Use oxidants and catalysts to oxidize dibenzothiophene, so that dibenzothiophene, which is similar to light alkanes, becomes dibenzothiophene sulfone with greater polarity;(2) Through polar solvents, such as N,N-dimethylformamide, acetonitrile, etc., the more polar dibenzothisulfone is extracted to reduce the organic sulfur content in gasoline.
Heteropoly acids have good activity for oxidative desulfurization in homogeneous reactions due to their adjustable redox potential, but their characteristics of difficult recovery and the need for surfactants have caused an increase in cost. In addition, if used as a heterogeneous catalyst, its specific surface area is very low, resulting in low catalytic activity. At present, in order to solve the above problems, people mainly use silica, cerium dioxide, activated carbon, molecular sieve and other supported heteropoly acids to form composite materials as catalysts for oxidative desulfurization. However, the use of these carriers will have some defects, such as low loading of heteropoly acids, easy shedding, uneven distribution, etc. It is very important to choose a suitable carrier that can overcome the above shortcomings. This can not only improve the activity of the catalyst, but also increase the number of cycles of the catalyst. The metal organic framework material has the advantages of large specific surface area, high porosity, adjustable pore size, easy post-modification, etc., and can be used as a very good carrier. Although some studies have discussed that phosphotungstic acid is loaded in metal organic framework (MIL-101(Cr)) for oxidative desulfurization, it is easy to fall off because the diameter of phosphotungstic acid (~ 1.2nm) is smaller than the diameter of metal organic framework window (~ 1.6nm).
Last Update：2024-01-02 23:10:35
Iron based desulfurization catalyst - Technology realization elements
In order to overcome the defects of the prior art, the invention provides a preparation method and application of oxidation desulfurization catalyst with high catalytic activity, high stability, multiple recycling and easy recovery
The object of the invention can be achieved by the following technical scheme:
The preparation method of supported iron-based metal organic framework oxidation desulfurization catalyst is synthesized by in-situ hydrothermal method with phosphotungstic acid as the center PTA@MIL-100 (FE), where PTA is phosphotungstic acid, mil-100 (FE) is iron-based metal organic skeleton, PTA@MIL-100 (FE) is a supported iron-based metal organic framework heterogeneous oxidation desulfurization catalyst, and the specific steps are as follows:
(1) Catalyst PTA@MIL-100 Preparation of (FE): evenly mix iron powder, pyromellitic acid, hydrofluoric acid, nitric acid, phosphotungstic acid and deionized water, place them in a polytetrafluoroethylene hydrothermal reactor, and react at a constant temperature of 150 ~ 170 ℃ for 10 ~ 30h. After filtering to obtain orange solid products, wash them with deionized water and ethanol for several times, and finally dry them in a drying oven at 50 ~ 100 ℃ overnight. The molar ratio of iron powder, pyromellitic acid, hydrofluoric acid, nitric acid and deionized water is 1:0.66:2:0.6:325; The molar ratio of iron powder to phosphotungstic acid is 1:0 ~ 1:0.25
(2) Preparation of blank catalyst mil-100 (FE): evenly mix iron powder, pyromellitic acid, hydrofluoric acid, nitric acid and deionized water, place them in a polytetrafluoroethylene hydrothermal reactor, and react at a constant temperature of 150 ~ 170 ℃ for 10 ~ 30h. After filtering to obtain orange solid products, wash them with deionized water and ethanol for several times, and finally dry them in a drying oven at 50 ~ 100 ℃ overnight. The molar ratio of iron powder, pyromellitic acid, hydrofluoric acid, nitric acid and deionized water is 1:0.66:2:0.6:325
(3) Preparation of blank catalyst zif-8: mix zinc nitrate hexahydrate and methanol evenly and put them in flat bottom flask a, then mix 2-methylimidazole and methanol evenly and put them in flat bottom flask B, finally, pour the solution in flask B into flask A and mix evenly. The mixed solution was reacted at room temperature for 10 ~ 30h, centrifuged to obtain white powder, washed with methanol for many times, and finally dried in an oven overnight. The molar ratio of zinc nitrate hexahydrate, 2-methylimidazole and methanol is 1:4:506
(4) Blank catalyst PTA@ZIF-8 Preparation of: mix zinc nitrate hexahydrate, phosphotungstic acid and methanol evenly and put them in flat bottom flask a, then mix 2-methylimidazole and methanol evenly and put them in flat bottom flask B, finally, pour the solution in flask B into flask A and mix evenly. The mixed solution was reacted at room temperature for 10 ~ 30h, centrifuged to obtain white powder, washed with methanol for many times, and finally dried in an oven overnight. The molar ratio of zinc nitrate hexahydrate, 2-methylimidazole and methanol is 1:4:506; The molar ratio of zinc nitrate hexahydrate to phosphotungstic acid is 1:0 ~ 1:0.1
In the invention, steps (1) and (2) are uniformly mixed by ultrasonic treatment for 10 ~ 30min
In the invention, the catalysts prepared by the method are used for extraction catalytic oxidation desulfurization
In the invention, the extraction catalytic oxidation desulfurization step is: add the model oil and polar solvent into the reaction tube at the same time. Because the density of the model oil is less than that of the polar solvent, the model oil is in the upper layer, the polar solvent is in the lower layer, and some organic stubborn sulfur, such as dibenzothiophene, will enter the polar solvent and be oxidized by the catalyst to dibenzothiophene sulfone, reducing the concentration of Dibenzothiophene in the polar phase, Further strengthen the flow of Dibenzothiophene to the polar phase, and finally reduce the concentration of organic stubborn sulfur in the model oil
In the invention, the preparation method of the model oil used is:
(5) A certain amount of Dibenzothiophene and internal standard were added to 1000ml n-heptane to prepare a model oil with a concentration of 1000mass ppm
(6) Add a certain amount of benzothiophene and internal standard into 1000ml n-heptane to prepare a model oil with a concentration of 1000mass ppm
(7) Add a certain amount of 4,6-dimethyldibenzothiophene and internal standard into 1000ml n-heptane to prepare a model oil with a concentration of 1000mass ppm
In the invention, the internal standard used in steps (5), (6) and (7) is n-dodecane
In the invention, the conversion rate of organic sulfur and the residual sulfur content in the model oil are determined by GC and GC-MS
The invention studies the catalyst load, catalyst type, catalyst quality, catalytic reaction temperature, hydrogen peroxide / organic sulfur molar ratio, catalytic reaction time, catalyst circularity and catalytic substrate
The catalyst in the invention carries out oxidative desulfurization research on gasoline
Compared with the prior art, the invention has the following advantages:
1. Because the invention adopts the hydrothermal in-situ growth route, phosphotungstic acid larger than the cage hole window of the metal organic framework exists in the molecular state and is well dispersed in the cage hole of the metal organic framework material
2. After loading phosphotungstic acid, the metal organic framework material still has a large specific surface area, which is conducive to the mass transfer of reaction substrates and products
3. The metal organic framework material with large specific surface area can pre adsorb the reaction substrate well, and cooperate with phosphotungstic acid, the active center of high concentration reaction, so as to improve the catalytic activity of the catalyst
4. Because the molecular diameter (~ 1.2nm) of phosphotungstic acid is larger than the window diameter (~ 0.86nm) of the cage hole of iron-based metal organic framework, it is difficult to fall off, easy to recover and reuse
5. The catalyst in the invention can efficiently remove a variety of stubborn organic sulfur and achieve ultra deep desulfurization effect
6. The ligand used in the invention is pyromellitic acid, which is a simple organic small molecule with low price; Other raw materials used in the invention, such as iron powder and phosphotungstic acid, are commercially available and cheap
7. The synthesis process of the invention is simple, has strong operability, and has broad application prospects
Description of drawings
Figure 1 shows mil-100 (FE) and PTA@MIL-100 Field emission scanning electron microscope of (FE). Where (a) mil-100 (FE), (b) PTA@MIL-100 (Fe)-7％，(c) PTA@MIL-100 (Fe)-16％，(d) PTA@MIL-100 (Fe)-35％。
Figure 2 shows the sample prepared in example 1 PTA@MIL-100 (FE) transmission electron microscope, using HAADF technology PTA@MIL-100 (FE) -16% carry out element surface scanning, and the detected elements are Fe, P and W
Figure 3 shows mil-100 (FE) and PTA@MIL-100 Powder XRD diffraction pattern of (FE)
Figure 4 shows mil-100 (FE) and PTA@MIL-100 Fourier transform infrared spectroscopy of (FE)
Figure 5 shows the sample prepared in example 1 PTA@MIL-100 XRD diffraction patterns of (FE) -16% and its recycled powder
Figure 6 shows the sample prepared in example 1 PTA@MIL-100 Fourier transform infrared spectroscopy of (FE) -16% and its cycle
Figure 7 shows mil-100 (FE) and PTA@MIL-100 Nitrogen adsorption isotherm of (FE)
Figure 8 shows mil-100 (FE) and PTA@MIL-100 (FE) pore size distribution calculated by NLDFT model
Figure 9 shows zif-8 and PTA@ZIF-8 Field emission scanning electron microscope. Where (a) zif-8, (b) PTA@ZIF-8 。
Figure 10 shows zif-8 and PTA@ZIF-8 Powder XRD diffraction pattern
Figure 11 shows zif-8 and PTA@ZIF-8 Nitrogen adsorption isotherm
Figure 12 shows zif-8 and PTA@ZIF-8 The aperture distribution map calculated by NLDFT model
Specific implementation mode
The invention will be described in detail below in combination with the accompanying drawings and specific embodiments
Example 1:
(1) PTA@MIL-100 Preparation of (FE)
Hydrothermal method, taking iron powder (0.45g), pyromellitic acid (1.13g), hydrofluoric acid (0.71ml, 22.5m), nitric acid (0.32ml, 15m), phosphotungstic acid (1.44g, 2.88g, 5.76g) and deionized water (47ml) as raw materials, ultrasonic treatment for 20min to get a mixed solution, and keep it in an oven at 160 ℃ for 24h. The orange solid obtained is washed three times with water and ethanol, and dried overnight at 70 ℃ PTA@MIL-100 (Fe)-7％， PTA@MIL-100 (Fe)-16％， PTA@MIL-100 (Fe)-35％。 Among them, 7%, 16% and 35% are the percentage of phosphotungstic acid in the total mass of the catalyst, respectively
(2) Preparation of blank material mil-100 (FE)
By hydrothermal method, taking iron powder (0.45g), pyromellitic acid (1.13g), hydrofluoric acid (0.71ml, 22.5m), nitric acid (0.32ml, 15m) and deionized water (47ml) as raw materials, the mixed solution was obtained by ultrasonic treatment for 20min, and was kept in an oven at 160 ℃ for 24h. The orange solid obtained was washed three times by water and ethanol, and dried in an oven at 70 ℃ overnight to obtain mil-100 (FE)
(3) Preparation of blank catalyst zif-8
Mix zinc nitrate hexahydrate (734mg) and methanol (25ml) evenly and put them into flat bottom flask A. then mix 2-methylimidazole (810mg) and methanol (25ml) evenly and put them into flat bottom flask B. finally, pour the solution in flask B into flask A and mix evenly. The mixed solution reacted at room temperature for 24h, centrifuged to obtain white powder, washed with methanol for many times, and finally dried in an oven at 70 ℃ overnight
(4) Blank catalyst PTA@ZIF-8 Preparation of
First mix zinc nitrate hexahydrate (734mg) and methanol (25ml) evenly and put them into flat bottom flask a, then mix 2-methylimidazole (810mg) and methanol (25ml) evenly and put them into flat bottom flask B, then mix 288mg phosphotungstic acid and 5ml water evenly and put them into flat bottom flask C, then pour the solution of bottle C into bottle a and mix them evenly, and finally pour the solution of bottle B into bottle a and mix them evenly. The mixed solution reacted at room temperature for 24h, centrifuged to obtain white powder, washed with methanol for many times, and finally dried in an oven at 70 ℃ overnight
Field emission scanning electron microscopy was used to PTA@MIL-100 (FE) morphology was characterized, indicating that the morphology changed little after loading. The element surface scanning of transmission electron microscope shows that phosphotungstic acid is evenly distributed in the pores of iron-based metal organic framework materials. Powder XRD and IR spectra showed that the crystal skeleton remained unchanged after loading, and the heteropoly acid was highly dispersed. Through powder XRD and IR characterization of the recycled materials, the reason why the catalyst remains active after recycling is revealed. The nitrogen adsorption isotherm and pore size analysis show that the catalyst has a large specific surface area and porosity, and has a more appropriate pore size and window diameter. In addition, blank materials zif-8 and PTA@ZIF-8 Scanning electron microscopy, powder XRD, infrared spectroscopy and nitrogen adsorption were characterized. However, because the window diameter of zif-8 is too small, the reaction substrate cannot enter and can only react on the surface, so the apparent activity of the reaction is very low
Example 2:
PTA@MIL-100 Evaluation of Extraction Catalytic Oxidation Desulfurization Performance of (FE) catalyst:
(1) Dibenzothiophene was selected as the probe molecule to study the performance of the prepared catalyst. Take 2ml of Dibenzothiophene / n-heptane mixed solution with sulfur content of 1000mass ppm and put it into the reaction tube, then add 2ml of acetonitrile, and then add 15mg of catalyst mil-100 (FE) PTA@MIL-100 (Fe)-7％、 PTA@MIL-100 (FE) -16% or PTA@MIL-100 (Fe)-35％。 Add 10μ After L of hydrogen peroxide, put it into an air bath reaction mold at 80 ℃ to start the reaction, and react for 1H. After catalysis, the catalytic activities of the four catalysts were 0%, 32%, 70% and 28% respectively. It shows that when the load of phosphotungstic acid is low, the catalytic activity increases with the increase of the load of phosphotungstic acid, while when the load of catalyst is too high, the catalytic activity decreases
(2) Select PTA@MIL-100 The effect of the quality of (FE) -16% catalyst on its catalytic activity was studied. According to the conditions in step (1), the mass of the catalyst is 5, 15, 30 and 50mg respectively, and its catalytic activity is 55%, 70%, 75% and 76% respectively. While maintaining high catalytic activity and high economic efficiency, we chose 30mg catalyst for subsequent catalytic conditions
(3) Effect of reaction temperature on catalytic activity. Under the condition of keeping the conditions of step (2) unchanged, we use 50, 60, 70, 80, 90 and 100 degrees Celsius as the reaction temperature, and their catalytic activities are 10%, 66%, 85%, 76%, 70% and 65% respectively. We chose 70 ℃ as the reaction temperature of the next step
(4) Effect of molar ratio of hydrogen peroxide to organic sulfur (o/s) on catalytic activity. Keep the reaction conditions of step (3) unchanged, change the amount of hydrogen peroxide, and the amount of hydrogen peroxide used is 5, 10, 15, 20, 30, 40, 50 mu respectively; 50. That is, the o/s ratio is 1, 2, 3, 4, 6, 8 and 10, and its activity is 40%, 85%, 95%, 99%, 90%, 85% and 80% respectively. Therefore, the o/s ratio of 4 is taken as the reaction condition
(5) Effect of reaction time on catalytic activity. Keep the conditions in step (4) unchanged, change the reaction time to 5, 10, 15, 20, 30, 40, 50, 60 and 120min respectively, and the corresponding catalytic activity is 3%, 20%, 39%, 60%, 71%, 88%, 94%, 99% and 100% respectively
(6) Cyclic experiment. After the reaction, the catalyst was washed with ethyl acetate for five times and dried to make the next round of reaction. Under the optimal conditions, the catalytic activity remained unchanged after five rounds of reaction
(7) Extended substrate. Under the optimal conditions, 1000mass ppm benzothiophene and 4,6-dimethyldibenzothiophene were catalyzed to desulfurization, but the reaction time was extended to 24h, and the catalytic activity was 60% and 90% respectively
Example 3:
PTA@ZIF-8 Evaluation of Extraction Catalytic Oxidation Desulfurization Performance of catalyst:
(1) Using the optimal conditions in example 2, that is, the reaction conditions are: the temperature is 70 ℃, the o/s is 4, the reaction time is 1H, and the mass of the catalyst is 23mg (the amount of phosphotungstic acid, the active component, and PTA@MIL-100 (FE) -16% same). The activity of the catalyst is 13%
(2) Extended substrate. Under the optimal conditions, 1000mass ppm benzothiophene and 4,6-dimethyldibenzothiophene were catalyzed to desulfurization, but the reaction time was extended to 24h, and the catalytic activity was 10% and 23% respectively
Example 4:
Evaluation of Extraction Catalytic Oxidation Desulfurization Performance of zif-8 catalyst:
Using the optimal conditions in example 2, that is, the reaction conditions are: the temperature is 70 ℃, the o/s is 4, the reaction time is 1H, and the mass of the catalyst is 23mg. The activity of catalyst is 0
Example 5:
Will be the best PTA@MIL-100 (FE) -16% catalyst is used for desulfurization test of 473mass ppm gasoline
Take 2ml of 473mass ppm gasoline with sulfur content and put it into the reaction tube, then add 2ml of acetonitrile and 30mg of catalyst PTA@MIL-100 (Fe)-16％。 Join 20μ After L of hydrogen peroxide, put it into the air bath reaction mold at 70 ℃ to start the reaction, and react for 24h. Because the density of gasoline is higher than that of acetonitrile, it is in the lower layer. After the reaction, take out the upper gasoline, move it into another reaction tube, and add 2ml acetonitrile. The catalyst is activated by ethyl acetate and dried, and then add the reaction. Before the reaction, add 20 mu; L hydrogen peroxide, react again for 24h. After the first round of catalysis, 85% of organic sulfur will be removed, and after the second round of catalysis, 92% of organic sulfur will be removed
The description of the above embodiments is convenient for ordinary technicians in the technical field to understand and apply the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described here to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein. According to the invention, the improvements and modifications made by those skilled in the art should be within the protection scope of the invention
Last Update：2023-08-17 01:00:06
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