A trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst, its preparation method and application

Abstract

The present invention discloses a trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst, its preparation method and application. ZrCl4, Ce(NO3)2·6H2O and terephthalic acid are dissolved in N,N-dimethylformamide. After the obtained mixed solution is stirred at room temperature, trifluoroacetic acid is added. After continuous stirring, it is transferred into a polytetrafluoroethylene reaction kettle for hydrothermal reaction. After the trifluoroacetic acid-modified MOF material UIO-66(Zr, Ce) is mixed with deionized water, chloroplatinic acid solution is added. After stirring at room temperature, it is placed in a muffle furnace for high-temperature calcination to obtain the Pt / UIO-66(Zr, Ce) catalyst. The Pt / UIO-66(Zr:Ce = 5) catalyst provided by the present invention selects 150 # solvent oil as a representative of VOCs, and finally realizes low-temperature and high-efficiency catalytic oxidation of low-concentration VOCs without by-products, which has great value for practical applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of a trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst. Background Art

[0002] At present, volatile organic pollutants (VOCs) have become an important factor affecting people's quality of life. In 2020, the VOCs treatment plan issued by the Ministry of Ecology and Environment pointed out that it is necessary to comprehensively strengthen the control of VOCs substances with strong photoreaction activity. The harmfulness of volatile organic compounds can be roughly divided into the toxicity to organisms caused by direct exposure, the destruction of the stratospheric ozone layer, global warming, and the destruction of vegetation and production facilities such as acid rain generated by photoreaction. Among many VOCs treatment technologies, catalytic oxidation technology is a feasible, effective and promising technology. It has the advantages of high conversion efficiency, low operating temperature, and low heat energy use, and is very useful for environmental protection and rational utilization of energy. Metal-organic framework materials have excellent framework structures, and their large specific surface area and porous characteristics make them popular materials in the field of catalysts. Summary of the Invention

[0003] Based on the above situation, the purpose of the present invention is to provide a preparation method and application of a trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst. The trifluoroacetic acid-modified Pt / UIO-66(Zr:Ce = 5) catalyst provided by the present invention selects 150 # solvent oil (the main component is mesitylene) as a representative of VOCs, and finally realizes low-temperature and high-efficiency catalytic oxidation of low-concentration VOCs without by-products, which has great value for practical applications.

[0004] The technical solution adopted by the present invention is as follows: A trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst, the carrier is a MOF material UIO-66(Zr, Ce) with a trifluoroacetic acid-modified zirconium-cerium molar ratio of 5:1, and the loaded substance is platinum.

[0005] A preparation method of a trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst includes the following steps:

[0006] 1) Take an appropriate amount of ZrCl 4 , Ce(NO 3 ) 2 ·6H 2O and terephthalic acid are dissolved in N,N-dimethylformamide to form a mixed solution; after the obtained mixed solution is stirred at room temperature for 30 min, trifluoroacetic acid is added, and after continuing to stir at room temperature for 30 min, it is transferred into a reaction kettle with a polytetrafluoroethylene lining for hydrothermal reaction. The obtained product is centrifuged, washed, and dried to obtain a trifluoroacetic acid-modified MOF material UIO-66(Zr, Ce).

[0007] 2) After mixing the trifluoroacetic acid-modified MOF material UIO-66(Zr, Ce) obtained in step 1) with deionized water, chloroplatinic acid solution is added, and it is stirred at room temperature for 10 h, centrifuged, and dried. The obtained product is placed in a muffle furnace for high-temperature calcination to obtain a trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst.

[0008] Furthermore, in step 1), in terms of molar ratio, ZrCl 4 :Ce(NO 3 ) 2 ·6H 2 O:terephthalic acid = 5:1:5.

[0009] Furthermore, in step 1), in terms of molar ratio, terephthalic acid:trifluoroacetic acid = 1:2 - 20.

[0010] Furthermore, in step 1), the hydrothermal reaction is carried out at 120 °C for 24 h.

[0011] Furthermore, in step 2), the concentration of the chloroplatinic acid solution is 10 mg / mL, and the solid-liquid ratio of the trifluoroacetic acid-modified MOF material UIO-66(Zr, Ce) to the chloroplatinic acid solution is 1 g:2.5 mL.

[0012] Furthermore, in step 2), the high-temperature calcination is carried out at 350 °C for 4 h.

[0013] The application of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst provided by the present invention in catalytic combustion of solvent oil.

[0014] Furthermore, the method is as follows: the solvent oil is subjected to catalytic combustion in a fixed-bed tubular reactor, the reaction temperature range is 100 - 280 °C, and the reaction time is 3 - 5 h; in the fixed-bed tubular reactor, a fixed-bed catalyst is made of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst.

[0015] Furthermore, the diameter of the fixed-bed tubular reactor Set the gas flow rate to 0.15 L / min.

[0016] Furthermore, the solvent oil is aromatic solvent oil.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst prepared by the present invention has good catalytic activity for catalytic cracking of 150 # solvent oil, and the reaction only produces CO 2 and water, without generating other by-products.

[0019] 2. The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst prepared by the present invention has good stability, and the conversion rate does not change significantly within 30 h.

[0020] 3. The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst prepared by the present invention shows a rod-like structure and has a larger specific surface area after being tested by transmission electron microscopy. Description of the Drawings

[0021] Figure 1 is the transmission electron microscopy image of the Pt / UIO-66(Zr, Ce)-2.5F catalyst.

[0022] Figure 2 is the XRD pattern of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst.

[0023] Figure 3 is the infrared spectrum of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst.

[0024] Figure 4 is the catalytic activity diagram of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst for catalytic cracking of 150 # solvent oil.

[0025] Figure 5 is the stability test diagram of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst. Detailed Embodiments

[0026] Example 1 Preparation method of trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst (I) is as follows:

[0027] 1) Take ZrCl 4 (1.165 g, 0.005 mol), Ce(NO 3 ) 2 ·6H 2O (0.4342 g, 0.001 mol) and terephthalic acid (0.8307 g, 0.005 mol) were dissolved in 60 mL of N,N-dimethylformamide to form a mixed solution. After stirring the obtained mixed solution at room temperature for 30 min, trifluoroacetic acid (1, 2.5, 5, 7.5 mL) was added respectively. After continuing to stir at room temperature for 30 min, it was transferred into a reaction kettle lined with polytetrafluoroethylene. The reaction kettle was placed in an oven at 120 °C for hydrothermal reaction for 24 h. After the reaction kettle was cooled, the product obtained in the reaction kettle was centrifuged (10000 r / 5 min), and then washed twice with DMF and twice with ethanol in sequence, and dried overnight in an oven at 60 °C to obtain white powders, which were trifluoroacetic acid-modified UIO-66(Zr, Ce) with the molar ratios of terephthalic acid to trifluoroacetic acid being 1:2, 1:6, 1:12 and 1:20 respectively.

[0028] 2) After mixing the trifluoroacetic acid-modified UIO-66(Zr, Ce) with different molar ratios obtained in step 1) and 20 mL of deionized water, 2.5 mL of chloroplatinic acid solution with a concentration of 10 mg / mL was added, and stirred at room temperature for 10 h, centrifuged (12000 r / 5 min), and dried overnight in an oven at 60 °C to obtain yellow powders. The obtained yellow powders were placed in a muffle furnace and calcined at 350 °C for 4 h to obtain trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalysts with different molar ratios respectively. They were labeled as Pt / UIO-66(Zr, Ce)-1F, Pt / UIO-66(Zr, Ce)-2.5F, Pt / UIO-66(Zr, Ce)-5F, Pt / UIO-66(Zr, Ce)-7.5F.

[0029] (II) Characterization

[0030] A little of the prepared Pt / UIO-66(Zr, Ce)-2.5F catalyst was dispersed in ethanol and ultrasonicated for 30 min. The dispersed sample was dropped on a copper grid for transmission electron microscopy test, and the test results are as Figure 1 . From Figure 1 it can be seen that obvious rod-like structures can be clearly seen.

[0031] The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst was ground and subjected to XRD test, and the test results are as Figure 2 shown. The reflections of all catalysts at 2θ = 30.3°, 35.14°, 50.48° and 60.2° correspond to the (111), (200), (220) and (311) planes of the cubic ZrO 2 structure [JCPDS CAS No. 27-0997]. Among them, the Pt / UIO-66(Zr, Ce)-1F catalyst also has characteristic peaks of metal-organic framework. No obvious PtOx Characteristic peaks, which may be due to the uniform Pt loading.

[0032] The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst and potassium bromide were ground in a certain proportion and subjected to infrared spectroscopy tests. The test results are as Figure 3 shown. As the amount of trifluoroacetic acid increases, the characteristic peaks of the UIO-66 framework structure of the catalyst gradually disappear, and the characteristic peak of the catalyst at 550 cm -1 also gradually disappears. This characteristic peak is attributed to the asymmetric stretching vibration peak of Zr-(OC). It is possible that trifluoroacetic acid modification replaces part of terephthalic acid, causing defect sites. The increase in defect sites is beneficial to the enhancement of catalytic activity. And as the amount of trifluoroacetic acid increases, only a band remains at 670 - 910 cm -1 which is attributed to the bending vibration of the benzene ring. In addition, no new peaks are added to the infrared spectrum of the Pt-loaded catalyst, which further indicates the uniform Pt loading.

[0033] Example 2 Application of trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst in catalytic combustion of low-concentration 150 # solvent oil

[0034] The catalytic combustion reaction of solvent oil was carried out in a fixed-bed tubular reactor. In this example, 150 # aromatic solvent oil was taken as an example for illustration.

[0035] 1) Accurately weigh 0.2 g of the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst and place it in the straight glass tube of the fixed-bed tubular reactor Inside, quartz wool was attached to both ends of the catalyst to prevent the catalyst powder from entering the pipeline with the gas flow.

[0036] 2) Air was blown to mix 150 # aromatic solvent oil and enter the tubular reactor equipped with the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst. The inlet flow rate was controlled within 0.15 L / min. Before the reaction started, a handheld VOCs detector was used to detect the inlet VOCs concentration, and the inlet VOCs concentration was controlled at about 130 ppm. After the inlet concentration was stable, the catalytic combustion reaction was carried out at 100 - 280 °C for 3 - 5 h. When the detection temperature point was reached, it was stabilized for 10 min and then the outlet gas concentration was detected.

[0037] 3) Calculate the catalytic efficiency using the CO 2 and VOCs concentrations detected at the outlet.

[0038]

[0039] In the formula, C150#溶剂油,in is the concentration of solvent naphtha in the inlet gas at 150 # ;

[0040] C 150#溶剂油,out is the concentration of solvent naphtha in the outlet gas at 150 # .

[0041] Figure 4 is the catalytic oxidation activity diagram of 150 solvent naphtha by the trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst, among which the catalytic activity of Pt / UIO-66(Zr, Ce)-5F is the best. #

[0042] Taking the Pt / UIO-66(Zr, Ce)-5F catalyst with the best effect for the stability test, the results are as Figure 5 shown. It can be seen that during the 30-hour activity test continuously carried out at 198 °C, the conversion rate is always around 90%. The trifluoroacetic acid-modified Pt / UIO-66(Zr, Ce) catalyst has good stability.

Claims

1. A trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst, characterized in that, for the trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst, the carrier is a MOF material UIO-66(Zr, Ce) modified by trifluoroacetic acid with a molar ratio of zirconium to cerium of 5:1, and the loaded substance is platinum; The preparation method of the trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst comprises the following steps: 1) Take an appropriate amount of ZrCl 4 , Ce(NO 3 ) 3 ·6H 2 O and terephthalic acid are dissolved in N,N-dimethylformamide to form a mixed solution; after stirring the obtained mixed solution at room temperature for 30 min, according to the molar ratio, terephthalic acid:trifluoroacetic acid = 1:2 - 20, trifluoroacetic acid is added, and after continuing to stir at room temperature for 30 min, it is transferred into a reaction kettle with a polytetrafluoroethylene liner for hydrothermal reaction. The obtained product is centrifuged, washed, and dried to obtain a trifluoroacetic acid-modified MOF material UIO-66(Zr, Ce); 2) Take the trifluoroacetic acid modified MOF material UIO-66(Zr, Ce) obtained in step 1), mix it with deionized water, add chloroplatinic acid solution, stir at room temperature for 10 h, centrifuge, dry, put the obtained product into a muffle furnace, and calcine at 350 °C for 4 h to obtain the trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst.

2. The trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst according to claim 1, characterized in that, In step 1), by molar ratio, ZrCl 4 : Ce(NO 3 ) 3 ·6H 2 O: terephthalic acid = 5:1:

5.

3. The trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst according to claim 1, characterized in that, In step 1), the hydrothermal reaction is carried out at 120 °C for 24 h.

4. The trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst according to claim 1, characterized in that, In step 2), the concentration of the chloroplatinic acid solution is 10 mg / mL, and the solid-liquid ratio of the trifluoroacetic acid modified MOF material UIO-66(Zr, Ce) to the chloroplatinic acid solution is 1 g:2.5 mL.

5. Application of the trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst according to claim 1 in catalytic combustion of solvent oil.

6. The application according to claim 5, characterized in that, The method is as follows: The solvent oil is catalytically combusted in a fixed bed tubular reactor, the reaction temperature range is 100 - 280 °C, and the reaction time is 3 - 5 h; In the fixed bed tubular reactor, a fixed bed catalyst is made of the trifluoroacetic acid modified Pt / UIO-66(Zr, Ce) catalyst.

7. The application according to claim 6, characterized in that, The diameter of the fixed bed tubular reactor φ = 2.2 cm, the gas flow rate is set to 0.15 L / min, and the solvent oil is aromatic solvent oil.

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