CN111420660A - A noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas and its preparation method and application - Google Patents

Abstract

The invention discloses a noble metal composite vanadium-titanium for purifying coal-fired organic waste gas A catalyst and a preparation method and application of an integral catalyst thereof. The noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas is prepared by the invention. The method overcomes the defects of narrow temperature window, low activity and CO of the prior commercial vanadium-titanium catalyst and commercial noble metal catalyst to organic waste gas in high-sulfur, high-nitrogen and high-ammonia flue gas _xLow selectivity, low oxidation efficiency and poor stability, and has excellent oxidation performance on organic waste gas in high-sulfur, high-nitrogen and high-ammonia flue gas. The prepared catalyst can be widely applied to the fields of atmospheric pollution control such as purification of organic waste gas in high-sulfur, high-nitrogen and high-ammonia flue gas.

Description

A noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas and its preparation method and application

technical field

The invention belongs to the technical field of environmental functional materials, and in particular relates to a preparation method of a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas and its use in coal-fired flue gas and high SO ₂ , high NOx and high NH ₃ Application in atmospheric pollution control such as catalytic oxidation of organic matter in exhaust gas.

Background technique

Coal-burning processes such as power plants and coking plants emit complex types and large amounts of pollutants, including conventional pollutants such as dust, NOx, and SO _2. At the same time, organic pollutants are also generated in the process, and their harmfulness cannot be ignored. The organic matter in coal-fired flue gas has the characteristics of complex composition, low concentration and high toxicity, which can lead to the production of ozone and PM2.5, and pose a major threat to human health and the environment. Selective Catalytic Reduction (NH ₃ -SCR) is a widely used technology to control NOx emissions from coal-fired power plants, as well as from power plants, coking plants, steel and waste incineration industries. _The catalyst prepared by loading _V2O5 on _TiO2 has excellent surface acidity and NOx reduction. In addition, commercial catalysts for catalytic combustion are supported noble metal or transition metal catalysts, which can oxidize organics to less harmful products at relatively low temperatures, which have good reducibility and oxygen vacancies, however SO2 in _flue gas , NO, NH ₃ content is high, the treatment atmosphere is complex, and the catalyst is easily poisoned and deactivated, so it is impossible to directly use the existing commercial catalytic oxidation catalyst to treat organic pollutants in coal-fired flue gas. At the same time, the concentration of VOCs produced in the coal combustion process is relatively low, and a separate set of control technology and devices is established, resulting in low technical and economic benefits. Using a coordinated control approach, the simultaneous control of VOCs in a selective catalytic reduction (SCR) device for nitrogen oxides is easy to implement and has good technical economy. The similar characteristics of catalytic combustion and NH ₃ -SCR catalysts suggest that new organic exhaust gas purification catalysts with high SO ₂ resistance, high NOx and high NH ₃ resistance can be developed.

In view of this, according to the characteristics of coal-fired flue gas, the present invention develops a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas. The catalyst has a wide temperature window and high CO in coal-fired flue gas. _x selectivity and stability. The invention provides a new idea and direction for the preparation of the purification material of the organic waste gas in coal-fired flue gas and high SO ₂ , high NOx and high NH ₃ waste gas.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple preparation method of a noble metal composite vanadium-titanium catalyst for purifying coal-fired flue gas and organic waste gas in high SO ₂ , high NOx and high NH ₃ waste gas, which is applied to purifying coal-fired flue gas and High SO ₂ , high NOx, high NH ₃ waste gas in organic waste gas and other atmospheric pollution control.

The object of the present invention is achieved through the following technical solutions:

An in-situ photoreduction preparation method of a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas, characterized in that, in deionized water from which nitrogen is removed, chloroplatinic acid and methanol are added, and a xenon lamp (Perfectlight, PLS-SXE300/300UV) as a light source, irradiated under continuous stirring, the active component precious metals and additives such as vanadium, tungsten, molybdenum, and titanium were loaded on _TiO2 , and finally the precious metal composite catalyst was obtained by centrifugal washing.

A one-step impregnation method for preparing a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal combustion, characterized in that, in deionized water from which nitrogen is removed, ammonium metavanadate, ammonium tungstate or ammonium molybdate are added with oxalic acid Then, chloroplatinic acid and methanol are added and loaded on TiO ₂ to obtain a noble metal composite vanadium-titanium catalyst for purifying NO _X and organic waste gas in coal-fired flue gas.

A two-step impregnation method for preparing a noble metal composite vanadium-titanium catalyst used for purifying organic waste gas in coal-fired flue gas, characterized in that, firstly, ammonium metavanadate or ammonium molybdate, after adding oxalic acid, is loaded on TiO ₂ , The vanadium-titanium catalyst is prepared; then chloroplatinic acid is added to the deionized water from which nitrogen is removed, and the second impregnation obtains a noble metal composite vanadium-titanium catalyst for purifying _NOx and organic waste gas in coal-fired flue gas.

The specific steps of the above method are as follows:

(1) Dissolution of precious metal precursors:

Precious metal precursors are added to deionized water from which nitrogen has been removed, and continuous constant temperature and strong stirring is continued after ultrasonication to prepare a precursor solution; the precious metal precursors include chloroplatinic acid, platinum chloride or palladium chloride;

( ₂ ) Preparation of TiO2:

Mix ethanol and ammonia water to obtain solution A, mix tetrabutyl titanate and ethanol to obtain solution B, and ultrasonically stir solution A and solution B at room temperature for 10-30 min at the same time, and then add solution B dropwise to solution A, The solution C was obtained, ultrasonically stirred at room temperature and then transferred to the inner liner of the polytetrafluoroethylene reaction kettle. Finally, the inner liner of the polytetrafluoroethylene reaction kettle was put into the autoclave, hydrothermally reacted, and after natural cooling, the precipitate was utilized. After centrifugal washing with ethanol, vacuum drying and grinding, anatase TiO ₂ nanoparticles are obtained; the volume of ethanol in the solution A is 30-50 mL; the volume of ammonia water in the solution A is 1-3 mL; the titanic acid in the solution B The volume of tetrabutyl ester is 3-8 mL; the volume of ethanol in the solution B is 10-30 mL;

(3) preparation of vanadium-titanium catalyst:

Add ammonium metavanadate, ammonium tungstate or ammonium molybdate to deionized water and mix thoroughly. After ultrasonication, place it in a collector-type constant temperature magnetic stirrer to fully stir at a constant temperature to dissolve it. Add oxalic acid precursor under stirring. Continue constant constant vigorous stirring to prepare a mixed precursor solution; take out the TiO ₂ as the catalyst carrier after drying in a vacuum drying oven, and cool it to room temperature for later use; the mass of the TiO ₂ is 1-5 g; add the above-mentioned TiO 2 under stirring The TiO ₂ of the dried carrier is continuously stirred at constant temperature until it evaporates to dryness, and after drying, grinding and calcining in a vacuum drying box, a vanadium-titanium catalyst powder catalyst is obtained, which is used for later use.

(4) Preparation of noble metal composite vanadium-titanium catalyst by in-situ photoreduction:

Add the dried vanadium-titanium catalyst nanoparticles in deionized water with nitrogen removed, continue stirring at constant temperature after ultrasonication, add dropwise a certain amount of chloroplatinic acid and methanol, use a xenon lamp as a light source, and irradiate for several hours under continuous stirring to obtain a reduction After the catalyst, the reduced catalyst is centrifugally washed, dried and ground in a vacuum drying oven to obtain a precious metal composite catalyst;

(5) One-step impregnation method to prepare noble metal composite vanadium-titanium catalyst:

Add ammonium metavanadate, ammonium tungstate or ammonium molybdate to deionized water and mix thoroughly. After ultrasonication, place it in a collector-type constant temperature magnetic stirrer to fully stir at a constant temperature to dissolve it. Add oxalic acid precursor under stirring. Continue to stir vigorously at constant temperature to prepare a mixed precursor solution; take out the TiO ₂ as the catalyst carrier after drying in a vacuum drying oven, and cool it to room temperature for later use; add the TiO ₂ of the dried carrier under stirring, and then add Add chloroplatinic acid and methanol, continue stirring at a constant temperature until it evaporates to dryness, dry in a vacuum drying oven, grind, and then calcinate in a horse-boiler furnace to obtain a vanadium-titanium catalyst powder catalyst, which is pressed under the set pressure of the tablet machine. Sieve to get 40-60 mesh catalyst.

(6) two-step impregnation method to prepare noble metal composite vanadium-titanium catalyst:

Add the dried vanadium-titanium catalyst nanoparticles in deionized water with nitrogen removed, continue to stir at constant temperature after ultrasonication, add dropwise a certain amount of chloroplatinic acid and methanol, continue to stir at constant constant temperature and vigorously until evaporated to dryness, and then dried in a vacuum drying oven. Grinding, and then calcining in a horse-boiling furnace to obtain a vanadium-titanium catalyst powder catalyst, the powder catalyst is pressed into tablets under the set pressure of a tableting machine, and sieved to obtain a catalyst of 40-60 meshes.

(7) Preparation of noble metal composite vanadium-titanium monolithic catalyst:

The cordierite honeycomb ceramics were cut into sample blocks with a diameter of 25 mm and a height of 8 mm. After ultrasonic treatment, it is dried and calcined to remove various adsorbed impurities. Boiling with nitric acid for a period of time, then washing with distilled water until the pH of the washing solution is neutral. The residual liquid was blown off with an air compressor, and the carrier was dried and calcined to remove impurities adsorbed on the catalyst surface and modify the surface morphology of the catalyst; a certain amount of precious metal precursors, ammonium metavanadate and ammonium tungstate were dissolved in 60 mL at 60 °C After fully stirring and dissolving in deionized water, a certain amount of _TiO2 powder and silica sol were added to the above solution so that the molar ratio of silicon and titanium was 2:8. A certain amount of HCl was added to adjust the pH to about 4, and a stable slurry was formed after stirring. The cordierite sample block was immersed in the above slurry for ultrasonic loading, and then the residual suspension was purged with air to form a uniform film on the surface of the substrate and dried. The above impregnation process is then repeated until the desired loading is reached. Finally, the sample block was calcined in a muffle furnace to obtain a monolithic catalyst.

In step (1), the concentrations of chloroplatinic acid, platinum chloride and palladium chloride are 1-10 mg/L.

In the above method, in step (2), the hydrothermal reaction temperature is 90-180°C, the hydrothermal reaction pressure is 0.1-0.4MPa, and the reaction time is 12-24h; the vacuum drying temperature is 100-150°C, Drying time is 12-24h.

In the above method, in step (3), the added amount of vanadium accounts for 1% to 5% of the mass of the catalyst; the added amount of the tungsten accounts for 1% to 10% of the mass of the vanadium-titanium catalyst powder catalyst; The added amount accounts for 1%-10% of the mass of the vanadium-titanium catalyst powder catalyst; the volume of the deionized water is 10-50 mL; and the added amount of the oxalic acid is 0.5-2.5 g.

In the above method, in steps (4) to (6), the volume of the deionized water is 10-50 mL, the ultrasonic time is 5-10 min, and the platinum mass fraction after the dropwise addition of chloroplatinic acid is 0.1 wt % to 1 wt % , the methanol volume fraction after the dropwise addition of methanol is 10%-25%, the xenon light intensity is 100-400mW/cm ² , the irradiation time is 1-12h, and the rotational speed of the centrifugal washing centrifuge is 5000-10000r/min , the centrifugation time is 3 to 6 min/time, and the washing times are 3 to 5 times.

In the above method, in steps (3), (5), (6) and (7), the drying temperature is 100-150°C, and the drying time is 12-24h; the calcination temperature is 250-550°C, The calcination time is 3～6h, and the heating rate is 1～5℃/min; the specific method of the calcination is as follows: the temperature rise program is to first raise the temperature from room temperature to 250～350℃ at a rate of 2～5℃/min, and at 250～350℃ 350℃ constant temperature for 60~120min, then rise to 350~550℃ at a rate of 2~5℃/min, constant temperature for 3~6h, and finally drop to room temperature at a rate of 1~10℃/min. The pressure of the tablet press is 5-15MpA, and the stabilization time is 1-5min.

In the above method, in step (7), the content of precious metals in the slurry is 0.1wt% to 1wt%, the catalyst slurry loading is 20 to 40wt.% of the mass of the substrate, and the added amount of vanadium accounts for the mass of the monolithic catalyst The added amount of tungsten accounts for 1% to 10% of the mass of the monolithic catalyst; the added amount of the molybdenum accounts for 1% to 10% of the mass of the monolithic catalyst.

A noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas is used in the field of air pollution control for catalytic oxidation of coal-fired flue gas and organic waste gas containing sulfur, nitrogen and ammonia.

The present invention utilizes active component noble metal and auxiliary agents such as vanadium, tungsten, molybdenum, titanium and the like to be supported on TiO ₂ to prepare a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas. The catalyst has a large specific surface area, high activity, wide temperature window, and has high oxidation performance in the treatment of coal-fired flue gas and atmospheric environmental pollution such as sulfur-, nitrogen-, and ammonia-containing organic compounds.

Compared with the prior art, the present invention has the following advantages:

(1) The preparation method adopted in the present invention is simple and feasible, the active components can be regulated in a wide range, the content of precious metals is low, and the precious metals can be well dispersed on the carrier.

(2) For the first time in the present invention, noble metals and additives such as vanadium, tungsten, molybdenum, and titanium are loaded on _TiO2 for the purification of organic waste gas in coal-fired flue gas, and it has a wide temperature window and excellent performance in coal-fired flue gas. activity and high CO _x selectivity. The catalyst can be widely used in the treatment of atmospheric environmental pollution such as coal-fired flue gas and organic waste gas with high sulfur, high nitrogen, and high ammonia.

Description of drawings

Fig. 1A is a graph showing the activity evaluation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for catalytic oxidative degradation of toluene;

Figure 1B is a graph showing the COx selectivity evaluation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for the catalytic oxidation of toluene

Fig. 1C is a graph showing the activity evaluation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalysts prepared by in-situ photoreduction method, one-step impregnation method and two-step impregnation method for catalytic oxidative degradation of toluene;

2A is a graph showing the activity evaluation of the 0.25%wtPt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention for catalytic oxidation of toluene under simulated coal-fired flue gas conditions.

Fig. 2B is a graph showing the COx selectivity evaluation of the catalytic oxidation of toluene under the simulated coal-fired flue gas condition with the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention.

Fig. 3A is a graph showing the stability evaluation of the activity of the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention for catalytic oxidation of toluene for 24 hours under simulated coal-fired flue gas conditions.

3B is a 24h stability evaluation diagram of the selectivity of the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention for catalytic oxidation of toluene under simulated coal-fired flue gas conditions.

3C is a graph showing the 24h activity stability evaluation of the oxidation rate calculated by total hydrocarbons for the catalytic oxidation of toluene under simulated coal-fired flue gas conditions with the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention.

4A is a graph showing the stability evaluation of the activity of the 0.1 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention for catalytic oxidation of toluene under simulated coal-fired flue gas conditions for 24 hours.

4B is a 24h stability evaluation diagram of the selectivity of the 0.1 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention for catalytic oxidation of toluene under simulated coal-fired flue gas conditions.

Figure 4C is a graph showing the 24h activity stability evaluation of the oxidation rate calculated by total hydrocarbons for the catalytic oxidation of toluene in the 0.1wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst of the present invention under simulated coal-fired flue gas conditions.

Detailed ways

The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. For process parameters that are not particularly noted, reference may be made to conventional techniques.

Example 1

Preparation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst by in situ photoreduction:

(1) Dissolution of precious metal precursors:

Add 1 g of chloroplatinic acid to 250 mL of deionized water with nitrogen removed, and continue to stir vigorously at constant temperature after ultrasonication to prepare a precursor solution;

(2) Preparation of V ₂ O ₅ -WO ₃ -TiO ₂ :

Mix 40 mL of ethanol and 2 mL of ammonia to obtain solution A, and mix 50 mL of tetrabutyl titanate and 10 mL of ethanol to obtain solution B. Solution A and solution B are stirred at room temperature for 20 min at the same time, and then solution B is added dropwise to solution A. , get solution C, stir at room temperature for 30min and transfer it to the inner liner of the PTFE reaction kettle. Finally, put the inner liner of the PTFE reaction kettle into the high pressure reaction kettle, hydrothermally react at 150 ℃ for 12h, and after natural cooling , the precipitate was centrifuged and washed 3 times with ethanol at 6500 r/min, transferred to a vacuum drying oven at 105 °C for 12 h, and after grinding, anatase TiO ₂ nanoparticles were obtained;

0.0458g of V precursor ammonium metavanadate and 0.1654g of W precursor ammonium tungstate were added to 20mL of deionized water and mixed thoroughly, and then placed in a collector-type constant temperature magnetic stirrer under constant temperature stirring for 30min to dissolve. Add 0.8 g of oxalic acid precursor under stirring, and continue stirring at constant temperature after sonication for 60 min to prepare a mixed precursor solution; TiO ₂ as a catalyst carrier is dried in a vacuum drying box and taken out, cooled to room temperature for use; the TiO ₂ mass is 2g.

Add the TiO ₂ of the above dried carrier under stirring, continue to stir vigorously at a constant temperature for 90 min to evaporate to dryness, then dry in a vacuum drying oven, grind, and then increase from room temperature to 350 ° C at a rate of 5 ° C/min, and at 350 ° C The temperature was kept constant for 60 minutes, then raised to 450°C at a rate of 5°C/min, kept at a constant temperature for 4 hours, and finally lowered to room temperature at a rate of 10°C/min to obtain a V ₂ O ₅ -WO ₃ /TiO ₂ powder catalyst. The V ₂ O ₅ -WO ₃ -TiO ₂ powder catalyst was dried in a vacuum drying oven at 120° C. and taken out, and cooled to room temperature for use. The V ₂ O ₅ -WO ₃ -TiO ₂ was dried in a vacuum drying oven and taken out, and cooled to room temperature for use; the V ₂ O ₅ -WO ₃ -TiO ₂ had a mass of 1 g.

(3) In situ photoreduction synthesis of Pt/V ₂ O ₅ -WO ₃ -TiO ₂ :

Add 1 g of V ₂ O ₅ -WO ₃ -TiO ₂ of the dried carrier to 40 mL of deionized water with nitrogen removed, continue to stir vigorously at constant temperature, add 1.33 mL of 1.87 mg/mL platinum precursor solution dropwise, and continue to add 10 mL of methanol, A xenon lamp (Perfectlight, PLS-SXE300/300UV) was used as the light source, the light intensity was 350 mW/cm ₂ , and the light was irradiated under continuous stirring for 10 h.

(4) Post-treatment of Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst:

The precipitate was centrifuged at 10,000 r/min, transferred to a vacuum drying oven at 120°C for 12 hours, and ground to obtain a Pt/V ₂ O ₅ -WO ₃ -TiO ₂ powder catalyst; the Pt/V ₂ O ₅ -WO ₃ - TiO ₂ powder catalyst is pressed into tablet under 10Mpa of tableting machine and sieved to obtain 40-60 mesh catalyst.

Example 2

Preparation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst by one dip method:

Mix 40 mL of ethanol and 2 mL of ammonia to obtain solution A, and mix 50 mL of tetrabutyl titanate and 10 mL of ethanol to obtain solution B. Solution A and solution B are stirred at room temperature for 20 min at the same time, and then solution B is added dropwise to solution A. , get solution C, stir at room temperature for 30min and transfer it to the inner liner of the PTFE reaction kettle. Finally, put the inner liner of the PTFE reaction kettle into the high pressure reaction kettle, hydrothermally react at 150 ℃ for 12h, and after natural cooling , the precipitate was centrifuged and washed 3 times with ethanol at 6500 r/min, transferred to a vacuum drying oven at 105 °C for 12 h, and after grinding, anatase TiO ₂ nanoparticles were obtained;

Mix 0.0458 g of V precursor ammonium metavanadate, 0.1654 g of W precursor ammonium tungstate with 20 mL of deionized water, and place them in a collector-type constant temperature magnetic stirrer at 70 °C and a stirring rate of 450 r/min. Fully stir for 30min to dissolve, add 2g of the above prepared anatase _TiO2 nanoparticles under stirring, add to 20mL of deionized water and mix thoroughly, and place in a collector-type constant temperature magnetic stirrer to fully stir for 30min at a constant temperature to dissolve , add 0.8g oxalic acid precursor under stirring, continue to stir at constant temperature after sonicating for 60min, prepare a mixed precursor solution, add 4mg/mL platinum precursor solution dropwise to make the Pt content 0.25%, continue to add 10mL methanol, Continue constant constant stirring and stirring until evaporated to dryness, transfer to a blast drying oven at 105 °C for 12 h, and after grinding, place it in a muffle furnace for high temperature calcination. 300°C, kept at 300°C for 1 h, then heated from 300°C to 450°C at a rate of 3°C/min, kept at 450°C for 4h, and finally lowered to room temperature at a rate of 2°C/min to obtain Pt/V ₂ O ₅ -WO ₃ -TiO ₂ material. The Pt/V ₂ O ₅ -WO ₃ -TiO ₂ powder catalyst was pressed into a tablet under 10Mpa of a tableting machine and sieved to obtain a catalyst of 40-60 meshes.

Example 3

Preparation of 0.25 wt% PtPt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst by double impregnation method:

(1) Dissolution of precious metal precursors:

Add 1 g of chloroplatinic acid to 250 mL of deionized water with nitrogen removed, and continue to stir vigorously at constant temperature after ultrasonication to prepare a precursor solution;

(2) Preparation of V ₂ O ₅ -WO ₃ -TiO ₂ :

Mix 40 mL of ethanol and 2 mL of ammonia to obtain solution A, and mix 50 mL of tetrabutyl titanate and 10 mL of ethanol to obtain solution B. Solution A and solution B are stirred at room temperature for 20 min at the same time, and then solution B is added dropwise to solution A. , get solution C, stir at room temperature for 30min and transfer it to the inner liner of the PTFE reaction kettle. Finally, put the inner liner of the PTFE reaction kettle into the high pressure reaction kettle, hydrothermally react at 150 ℃ for 12h, and after natural cooling , the precipitate was centrifuged and washed 3 times with ethanol at 6500 r/min, transferred to a vacuum drying oven at 105 °C for 12 h, and after grinding, anatase TiO ₂ nanoparticles were obtained;

0.0458g of V precursor ammonium metavanadate and 0.1654g of W precursor ammonium tungstate were added to 20mL of deionized water and mixed thoroughly, and then placed in a collector-type constant temperature magnetic stirrer under constant temperature stirring for 30min to dissolve. Add 0.8 g of oxalic acid precursor under stirring, and continue stirring at constant temperature after sonication for 60 min to prepare a mixed precursor solution; TiO ₂ as a catalyst carrier is dried in a vacuum drying box and taken out, cooled to room temperature for use; the TiO ₂ mass is 2g.

Add the TiO ₂ of the above dried carrier under stirring, continue to stir vigorously at a constant temperature for 90 min to evaporate to dryness, then dry in a vacuum drying oven, grind, and then increase from room temperature to 350 ° C at a rate of 5 ° C/min, and at 350 ° C The temperature was kept constant for 60 minutes, then raised to 450°C at a rate of 5°C/min, kept at a constant temperature for 4 hours, and finally lowered to room temperature at a rate of 10°C/min to obtain a V ₂ O ₅ -WO ₃ /TiO ₂ powder catalyst. The V ₂ O ₅ -WO ₃ -TiO ₂ powder catalyst was dried in a vacuum drying oven at 120° C. and taken out, and cooled to room temperature for use.

(3) Synthesis of Pt/V ₂ O ₅ -WO ₃ -TiO ₂ :

Add 1 g of Pt/V ₂ O ₅ -WO ₃ -TiO ₂ of the above dried carrier to 40 mL of deionized water with nitrogen removed, continue to stir vigorously at constant temperature, continue to stir and stir at constant constant temperature until evaporated to dryness, and transfer to 105°C for blast drying It was dried in the oven for 12 hours, and after grinding, it was calcined at high temperature in a muffle furnace. The temperature was increased from 300 °C to 450 °C at a min rate, kept at 450 °C for 4 h, and finally decreased to room temperature at a rate of 2 °C/min to obtain a Pt/V ₂ O ₅ -WO ₃ -TiO ₂ material. The Pt/V ₂ O ₅ -WO ₃ -TiO ₂ powder catalyst was pressed into a tablet under 10Mpa of a tableting machine and sieved to obtain a catalyst of 40-60 meshes.

Example 4

Preparation of Pt/V ₂ O ₅ -WO ₃ -TiO ₂ Monolithic Catalyst

The cordierite honeycomb ceramics were cut into sample blocks with a diameter of 20 mm and a height of 40 mm, dried and calcined after ultrasonic treatment to remove various adsorbed impurities, boiled with nitric acid for 20 min, and then washed with distilled water until the pH of the washing solution was neutral. ;Use an air compressor to blow off the residual liquid, dry and calcine the carrier, first rise from room temperature to 350°C at a rate of 5°C/min, keep the temperature at 350°C for 60 minutes, and then rise to 450°C at a rate of 5°C/min , kept at a constant temperature for 4 h, and finally lowered to room temperature at a rate of 10 °C/min to remove impurities adsorbed on the catalyst surface and modify the surface morphology of the catalyst; the noble metal precursor, ammonium metavanadate and ammonium tungstate were dissolved in 60 mL of deionized water at 60 °C. , after fully stirring and dissolving, adding _TiO2 powder to the above solution, adding HCl to adjust the pH to about 4, and forming a stable slurry after stirring, the mass fraction of platinum in the slurry is 0.1wt%, and the volume fraction of methanol is 10%, The addition amount of vanadium accounts for 1% of the slurry, and the addition amount of tungsten accounts for 6% of the slurry mass. The cordierite sample block is immersed in the above-mentioned slurry and ultrasonically loaded, and then the residual suspension is purged with air to form a uniform film on the surface of the substrate, and then dried; then repeat the above-mentioned dipping process until reaching the ideal load, and the load is 25% of the mass of the substrate. %; finally, the sample block is calcined in a muffle furnace. The calcination method is to first increase from room temperature to 350 ℃ at a rate of 5 ℃/min, maintain a constant temperature at 350 ℃ for 60 min, and then increase to 450 ℃ at a rate of 5 ℃/min. , constant temperature for 4h, and finally lowered to room temperature at a rate of 10°C/min to obtain a monolithic catalyst.

Example 5

Evaluation of catalytic oxidation activity of organic waste gas in coal-fired flue gas: Toluene (C ₇ H ₈ ) was used as a probe molecule to explore the catalytic oxidation activity of the catalyst to toluene at different temperatures. The degradation reaction of catalytic oxidation of toluene was carried out in a self-made fixed-bed reactor. The test conditions were as follows: the concentration of toluene was 50 ppm, the amount of catalyst was 100 mg, the reaction temperature was 150 ℃ ~ 390 ℃, the reaction flow rate was 200 mL/min, and the space velocity was 120000 h ^{- 1.} The reaction atmosphere is simulated coal-fired flue gas, in which the concentration of NH ₃ is 1000ppm, the concentration of NO is 1000ppm, the concentration of NH ₃ is 1000ppm, 5vol% O ₂ , and N ₂ are equilibrium gases; use a flame with hydrogen ion (FID) detection The gas chromatograph of the reactor and the nickel reformer was used to detect the concentration values of toluene, CO and CO ₂ .

Fig. 1A is a graph showing the activity evaluation of 0.25 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for the catalytic oxidative degradation of toluene, and Fig. 1B is a 0.25 wt % Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for p-toluene The evaluation diagram of COx selectivity of catalytic oxidation, Fig. 1C is the evaluation diagram of the activity evaluation of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalysts prepared by different methods for catalytic oxidative degradation of toluene. The results show that the T90 of the commercial VWT catalyst for the catalytic oxidation of _toluene is 331 °C, the T90 of the commercial noble metal catalyst for the catalytic oxidation of toluene is 271 °C, and the T90 of the commercial transition metal catalyst for the catalytic oxidation of _toluene is 370 °C, _0.25wt % Pt The T ₉₀ of the /V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for the catalytic oxidation of toluene was 181°C. This result indicates that the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst prepared by the present invention has a wider active temperature window and better CO _x selectivity than commercial catalysts.

Fig. 2A is a graph showing the activity evaluation of 0.25 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for catalytic oxidative degradation of toluene in coal-fired flue gas, and Fig. 2B is a graph showing 0.25 wt % Pt/V ₂ O ₅ -WO ₃ -The evaluation chart of CO _x selectivity of TiO ₂ catalyst for catalytic oxidation of toluene in coal-fired flue gas. The test conditions are: toluene concentration of 50 ppm, catalyst dosage of 100 mg, reaction temperature of 350 ° C, reaction flow rate of 200 mL/min, empty air The speed is 120000h ^-1 , and the reaction atmosphere is simulated coal-fired flue gas, in which the concentration of NH ₃ is 1000ppm, the concentration of NO is 1000ppm, the concentration of SO ₂ is 1000ppm, 5vol% O ₂ , and N ₂ are equilibrium gases; (FID) detector and gas chromatograph of nickel reformer to detect the concentration values of toluene and _COx . The experimental results show that the catalytic oxidation removal rate of toluene at 350 ℃ for commercial precious metal catalysts is 12.3% for CO _x selectivity, and the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for toluene catalytic oxidation removal at 350 ℃ The rate is 99%, and the CO _x selectivity reaches 99%. This result shows that the 0.25W%/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst prepared by the present invention has better activity stability and oxidation efficiency than commercial catalysts.

The above results fully demonstrate that the 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst exhibits excellent catalytic oxidation activity and CO _x selectivity.

Example 6

Evaluation of catalytic oxidation stability of organic waste gas in coal-fired flue gas: exploring the performance of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ and 0.1wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalysts Catalytic oxidation stability of toluene. The degradation reaction of catalytic oxidation of toluene was carried out in a self-made reactor. The test conditions were as follows: the concentration of toluene was 50 ppm, the amount of catalyst was 100 mg, the reaction temperature was 350 °C, the reaction flow rate was 200 mL/min, the space velocity was 120000 h ^-1 , and the reaction atmosphere was Simulated coal-fired flue gas with NH ₃ concentration of 500ppm, NO concentration of 500ppm, SO ₂ concentration of 1000ppm, 5vol% O ₂ , and N ₂ as equilibrium gases; using a hydrogen ion flame (FID) detector and a nickel reformer A gas chromatograph was used to detect the concentrations of toluene and COx. Figure 3A shows the 24 h removal rate of 0.25 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for the catalytic oxidative degradation of toluene, and Figure 3B shows the 0.25 wt % Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for 24h COx selectivity of toluene catalytic oxidation, Figure 3C is the oxidation efficiency of 0.25 wt% Pt/ _{V2O5 -} WO3 _{- TiO2} catalyst for toluene catalytic oxidation for 24h in terms of total hydrocarbons. Figure 4A shows the 24h removal rate of 0.1 wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for catalytic oxidative degradation of toluene, and Figure 4B shows 0.1 wt % Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for toluene 24h COx selectivity of catalytic oxidation, Figure 4C is the oxidation efficiency of 0.1 W% wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ catalyst for 24 h of total hydrocarbons for the catalytic oxidation of toluene. The experimental results show that after 24h reaction, the removal rate of 0.25wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ and 0.1wt% Pt/V ₂ O ₅ -WO ₃ -TiO ₂ pairs both reached 99%, with the total removal rate of 99%. The oxidation efficiency of hydrocarbon meter reaches 99%, and the COx selectivity reaches 99%.

The above embodiments are only used to illustrate the technical solutions of the present invention rather than strict conditions. Those of ordinary skill in the art should understand that the details or forms can be adjusted without departing from the spirit and scope of the present invention as defined in the claims. It makes various changes.

Claims (10)

1. A process for preparing the noble metal-vanadium-titanium composite catalyst used to purify the organic waste gas in the fume of coal-burning includes such steps as adding noble metal and methanol to the deionized water without nitrogen, stirring while loading the noble metal and assistant as active components to TiO ₂Finally, centrifugally washing to obtain the noble metal composite vanadium-titanium catalyst; the auxiliary agent comprises vanadium, tungsten or molybdenum and titanium; the noble metal comprises platinum, palladium or rhodium;

The addition amount between the noble metal and the auxiliary agent meets the following requirements: the addition amount of the noble metal is 0.1-1 wt%, the addition amount of vanadium is 1-5 wt%, the addition amount of molybdenum is 1-10 wt%, and the addition amount of tungsten is 1-10 wt%.

2. The method of claim 1 The preparation method is characterized in that ammonium metavanadate, ammonium tungstate or ammonium molybdate is added into deionized water without nitrogen, oxalic acid is added, chloroplatinic acid and methanol are added, and the loaded TiO is used as a carrier ₂To obtain NO for purifying coal-fired flue gas _XAnd the noble metal is compounded with vanadium-titanium catalyst for organic waste gas.

3. The method according to claim 1, wherein the ammonium metavanadate or ammonium molybdate is first supported on TiO after oxalic acid is added ₂Preparing the vanadium-titanium catalyst; and then adding chloroplatinic acid into the deionized water from which the nitrogen is removed, and performing secondary impregnation to obtain the noble metal composite vanadium-titanium catalyst for purifying the organic waste gas in the coal-fired flue gas.

4. The preparation method of the cordierite honeycomb ceramic material according to claim 1, wherein the cordierite honeycomb ceramic material is firstly subjected to ultrasonic treatment for 20-90 min before being loaded, then dried at the temperature of 100-120 ℃ for 3-9 h, and then transferred to a muffle furnace to be calcined at the temperature of 400-600 ℃ for 3-6 h so as to remove various adsorbed impurities; dissolving a noble metal precursor, ammonium metavanadate and ammonium tungstate in deionized water, fully stirring and dissolving, and then, dissolving TiO ₂Adding powder and silica sol into the solution, adding HCl to adjust the pH value to 3-5, stirring to form stable slurry, dipping a cordierite sample block into the slurry, carrying out ultrasonic loading on the slurry for 5-30 min, then blowing the residual suspension, forming a uniform film on the surface of a substrate, and drying at the temperature of 100-150 ℃ for 3-6 h; then repeating the impregnation process until the loading capacity is 20% -50%; and finally, calcining the sample block in a muffle furnace at 400-600 ℃ for 3-6 h to obtain the nano-porous ceramic material.

5. The preparation method of the noble metal composite catalyst for purifying coal-fired organic exhaust gas according to claim 1, characterized by comprising the steps of:

(1) Dissolving a noble metal precursor:

Adding a noble metal precursor into the deionized water from which the nitrogen is removed, carrying out ultrasonic treatment, and then continuously carrying out constant-temperature strong stirring to prepare a precursor solution; the noble metal precursor comprises chloroplatinic acid, platinum chloride or palladium chloride;

(2)TiO₂The preparation of (1):

mixing ethanol and ammonia water to obtain a solution A, mixing tetrabutyl titanate and ethanol to obtain a solution B, ultrasonically stirring the solution A and the solution B at room temperature for 10-30 min, dropwise adding the solution B into the solution A to obtain a solution C, wherein the volume of ethanol in the solution A is 30-50 m L, the volume of ammonia water in the solution A is 1-3 m L, the volume of tetrabutyl titanate in the solution B is 3-8 m L, the volume of ethanol in the solution B is 10-30 m L, ultrasonically stirring at room temperature, transferring the solution B into a polytetrafluoroethylene reaction kettle inner container, finally placing the polytetrafluoroethylene reaction kettle inner container into a high-pressure reaction kettle, carrying out hydrothermal reaction, naturally cooling, centrifugally washing precipitates with ethanol, carrying out vacuum drying, and grinding to obtain anatase TiO ₂A nanoparticle;

(3) Preparation of vanadium-titanium catalyst:

Adding an ammonium salt auxiliary agent into deionized water, fully mixing, performing ultrasonic treatment, placing the mixture into a heat collection type constant-temperature magnetic stirrer, fully stirring at constant temperature to dissolve the mixture, adding an oxalic acid precursor under a stirring state, performing ultrasonic treatment, and continuously performing constant-temperature strong stirring to prepare a mixed precursor solution; the anatase TiO obtained in the step (2) as a catalyst carrier ₂Drying the nano particles in a vacuum drying oven, taking out the nano particles, and cooling the nano particles to room temperature for later use; the TiO is ₂The mass is 1-10 g; adding the dried TiO carrier into the mixture under stirring ₂Continuously stirring strongly at constant temperature until the mixture is evaporated to dryness, drying in a vacuum drying oven, grinding and calcining to obtain a vanadium-titanium catalyst powder catalyst for later use; the ammonium salt auxiliary agent is ammonium tungstate or ammonium molybdate;

(4) Preparing a noble metal composite vanadium-titanium powder catalyst by in-situ photoreduction:

Adding the dried vanadium-titanium catalyst nano particles obtained in the step (3) into deionized water without nitrogen, continuing to stir at constant temperature and strong force after ultrasonic treatment, dropwise adding a noble metal precursor in the step (1), finally enabling the loading amount of platinum on the catalyst to be 0.1-1 wt%, dropwise adding methanol to enable the volume fraction of the methanol in the solution to be 10-25%, and continuously stirring and irradiating for hours by using a xenon lamp as a light source to obtain a reduced catalyst; centrifugally washing the reduced catalyst, drying the catalyst in a vacuum drying oven, and grinding the catalyst to obtain a noble metal composite catalyst; tabletting the powder catalyst under the set pressure of a tabletting machine, and sieving to obtain the catalyst with 40-60 meshes;

(5) Preparing a noble metal composite vanadium-titanium powder catalyst by a one-step impregnation method:

Adding an ammonium salt auxiliary agent into deionized water, fully mixing, performing ultrasonic treatment, placing the mixture into a heat collection type constant-temperature magnetic stirrer, fully stirring at constant temperature to dissolve the mixture, adding an oxalic acid precursor under a stirring state, performing ultrasonic treatment, and continuously performing constant-temperature strong stirring to prepare a mixed precursor solution; the anatase TiO obtained in the step (2) as a catalyst carrier ₂Drying the nano particles in a vacuum drying oven, taking out the nano particles, and cooling the nano particles to room temperature for later use; adding the dried TiO carrier into the mixture under stirring ₂Then, dropwise adding the noble metal precursor in the step (1), finally enabling the loading capacity of platinum on the catalyst to be 0.1-1 wt%, dropwise adding methanol to enable the volume fraction of the methanol in the solution to be 10-25%, continuously stirring at constant temperature and strong force until the mixture is evaporated to dryness, drying and grinding the mixture in a vacuum drying box, calcining the mixture in a muffle furnace to obtain a vanadium-titanium catalyst powder catalyst, tabletting the powder catalyst under the set pressure of a tabletting machine, and sieving to obtain a 40-60-mesh catalyst; the ammonium salt auxiliary agent is ammonium tungstate or ammonium molybdate;

(6) Preparing a noble metal composite vanadium-titanium powder catalyst by a two-step impregnation method:

Adding the dried vanadium-titanium catalyst nano particles obtained in the step (3) into deionized water without nitrogen, continuously stirring at constant temperature and strong force after ultrasonic treatment, dropwise adding a noble metal precursor in the step (1), finally enabling the loading amount of platinum on the catalyst to be 0.1-1 wt%, dropwise adding methanol to enable the volume fraction of the methanol in the solution to be 10-25%, continuously stirring at constant temperature and strong force until the methanol is evaporated to dryness, drying and grinding the catalyst in a vacuum drying box, calcining the catalyst in a muffle furnace to obtain a vanadium-titanium catalyst powder catalyst, tabletting the powder catalyst under a set pressure of a tabletting machine, and sieving to obtain a catalyst with 40-60 meshes;

(7) Preparing a noble metal composite vanadium-titanium monolithic catalyst:

Cutting cordierite honeycomb ceramic into sample blocks with the diameters of 25-100 mm and the heights of 8-100 mm, drying and calcining after ultrasonic treatment to remove various adsorbed impurities, boiling for 10-30 min by using nitric acid, and then washing by using distilled water until the pH value of a washing liquid is neutral; blowing off residual liquid by using an air compressor, drying and calcining the carrier to remove impurities adsorbed on the surface of the catalyst and modify the surface appearance of the catalyst;

dissolving a noble metal precursor, ammonium metavanadate and ammonium tungstate in 60m L deionized water at 60 ℃, fully stirring and dissolving, and then, obtaining anatase TiO obtained in the step (2) ₂adding nanoparticles into the solution (or directly dissolving the (4), (5) and (6) powder catalysts in 60m L deionized water at 60 ℃), adding HCl to adjust the pH to about 4, and stirring to form stable catalyst slurry;

Dipping a cordierite sample block into the catalyst slurry for ultrasonic loading, then blowing the residual suspension liquid by using air to form a uniform film on the surface of the substrate, and drying; then repeating the above impregnation process until the desired loading is reached; and finally, calcining the sample block in a muffle furnace to obtain the monolithic catalyst.

6. the preparation method of the noble metal composite vanadium-titanium catalyst according to claim 5, wherein in the step (1), the concentrations of chloroplatinic acid, platinum chloride and palladium chloride are 1-10 mg/L, and in the step (2), the hydrothermal reaction temperature is 90-180 ℃, the hydrothermal reaction pressure is 0.1-0.4 MPa, the reaction time is 12-24 h, the vacuum drying temperature is 100-150 ℃, and the drying time is 12-24 h;

in the step (3), the addition amount of vanadium accounts for 1-5% of the mass of the catalyst, the addition amount of tungsten accounts for 1-10% of the mass of the vanadium-titanium catalyst powder catalyst, the addition amount of molybdenum accounts for 1-10% of the mass of the vanadium-titanium catalyst powder catalyst, the volume of deionized water is 10-50 m L, and the addition amount of oxalic acid is 0.5-2.5 g.

7. The method for preparing the noble metal composite vanadium-titanium catalyst according to claim 5, which is characterized in that characterized in that in the steps (4) to (6), the volume of the deionized water is 10 to 50m L, the ultrasonic time is 5 to 10min, the mass fraction of platinum is 0.1wt percent to 1wt percent after the chloroplatinic acid is dripped, the volume fraction of methanol is 10 to 25 percent after the methanol is dripped, and the light intensity of the xenon lamp is 100 to 400mW/cm ²The irradiation time is 1-12 h, the rotating speed of the centrifugal washing centrifuge is 5000-10000 r/min, the centrifugation time is 3-6 min/time, and the washing times are 3-5 times;

In the steps (3), (5), (6) and (7), the drying temperature is 100-150 ℃, and the drying time is 12-24 hours; the calcination temperature is 250-550 ℃, the calcination time is 3-6 h, and the heating rate is 1-5 ℃/min; the specific calcining method comprises the following steps: the temperature rise procedure is that the temperature is raised from the room temperature to 250-350 ℃ at the speed of 2-5 ℃/min, the temperature is kept constant at 250-350 ℃ for 60-120 min, then the temperature is raised to 350-550 ℃ at the speed of 2-5 ℃/min, the temperature is kept constant for 3-6 h, and finally the temperature is lowered to the room temperature at the speed of 1-10 ℃/min; the pressure of the tablet press is 5-15 MpA, and the stabilization time is 1-5 min.

8. The preparation method of the noble metal composite catalyst according to claim 5, wherein in the step (7), the content of the noble metal in the slurry is 0.1-1 wt%, the loading of the catalyst slurry is 20-40 wt% of the mass of the substrate, and the addition amount of the vanadium accounts for 1-5 wt% of the mass of the monolithic catalyst; the addition amount of the tungsten accounts for 1-10% of the mass of the monolithic catalyst; the addition amount of the molybdenum accounts for 1-10% of the mass of the monolithic catalyst.

9. The noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas is prepared by the preparation method of any one of claims 1 to 8.

10. The noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas, according to claim 9, is applied to the field of air pollution control of catalytic oxidation of coal-fired flue gas and organic waste gas containing sulfur, nitrogen and ammonia.

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