CN111420660A

CN111420660A - Precious metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas and preparation method and application thereof

Info

Publication number: CN111420660A
Application number: CN202010204553.4A
Authority: CN
Inventors: 胡芸; 肖高飞; 杜玥莹; 张益兰; 郭梓洋; 李剑晗; 程源璟; 熊涛; 叶代启; 付名利
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2020-03-21
Filing date: 2020-03-21
Publication date: 2020-07-17

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

Precious metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas and preparation method and application thereof

Technical Field

The invention belongs to the technical field of environment functional materials, and particularly relates to a preparation method of a noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas, and application of the noble metal composite vanadium-titanium catalyst in coal-fired flue gas and high SO ₂High NOx, high NH ₃The catalytic oxidation of organic matters in the waste gas and the like.

Background

The coal burning process of power plants, coking plants and the like can discharge pollutants with complex types and large total amount, including dust, NOx and SO ₂Etc. and the process also includes the steps of Producing organic pollutants, the harmfulness of which is likewise not negligible. Organic matters in the coal-fired flue gas have the characteristics of complex components, low concentration, high toxicity and the like, can cause the generation of ozone and PM2.5, and poses great threats to human health and environment. Selective catalytic reduction (NH) ₃-SCR) is a widely used technology for controlling NOx emissions from coal-fired power plants, but also from power plants, coking plants, steel and waste incineration industries. Will V ₂O₅Supported on TiO ₂The catalyst prepared in the above has excellent surface acidity and NOx reducibility. In addition, commercial catalysts for catalytic combustion are supported noble or transition metal catalysts that can oxidize organics to less harmful products at relatively low temperatures, with good reducibility and oxygen vacancies, however, SO in flue gas ₂、NO、NH₃The content is very high, the treatment atmosphere is complex, and the catalyst is easy to be poisoned and inactivated, so that the organic pollutants in the coal-fired flue gas can not be treated by the conventional commercial catalytic oxidation catalyst directly. Meanwhile, the concentration of VOCs generated in the coal burning process is low, a set of control technology and device is separately established, and the technical and economic benefits are low. The method for simultaneously controlling VOCs in a Selective Catalytic Reduction (SCR) device of nitrogen oxides by adopting a cooperative control method is easy to implement and has good technical economy. Catalytic combustion and NH ₃Similar characterization of SCR catalysts suggests that novel high SO tolerance catalysts may be developed ₂High NOx, high NH ₃The organic exhaust gas purifying catalyst of (1).

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

Disclosure of Invention

The invention aims to provide a method for purifying coal-fired flue gas and high SO ₂High NOx, high NH ₃Noble metal composite vanadium-titanium of organic waste gas in waste gas Simple preparation method of catalyst, and application of catalyst in purifying coal-fired flue gas and high SO ₂High NOx, high NH ₃Organic waste gas in the waste gas and the like in the atmospheric environmental pollution treatment.

The purpose of the invention is realized by the following technical scheme:

an in-situ photoreduction process for preparing the noble metal-vanadium-titanium composite catalyst used to purify the organic waste gas in fume generated by burning coal features that chloroplatinic acid and methanol are added to deionized water to remove nitrogen, xenon lamp (Perfectlight, P L S-SXE300/300UV) is used as light source, and the active components noble metal and the assistants (V, W, Mo and Ti) are loaded on TiO ₂Finally, centrifugally washing to obtain the noble metal composite catalyst.

A one-step dipping process for preparing the noble metal-vanadium-titanium composite catalyst used to purify the organic waste gas in fuel coal features that the ammonium metavanadate, tungstate or molybdate is added to deionized water without nitrogen, oxalic acid is then added, chloroplatinic acid and methanol are then added, and TiO is loaded ₂To obtain NO for purifying coal-fired flue gas _XAnd the noble metal is compounded with vanadium-titanium catalyst for organic waste gas.

A two-step dipping process for preparing the noble metal-vanadium-titanium composite catalyst used to purify the organic waste gas in coal-burning fume includes such steps as adding oxalic acid to ammonium metavanadate or ammonium molybdate, loading it on TiO ₂Preparing the vanadium-titanium catalyst; then adding chloroplatinic acid into the deionized water from which the nitrogen is removed, and performing secondary impregnation to obtain the catalyst for purifying NO in the coal-fired flue gas _XAnd the noble metal is compounded with vanadium-titanium catalyst for organic waste gas.

The method comprises the following specific steps:

(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 the ethanol and the ammonia water, and then mixing, Obtaining 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, ultrasonically stirring at room temperature, transferring the solution C into a polytetrafluoroethylene reaction kettle liner, finally placing the polytetrafluoroethylene reaction kettle liner into a high-pressure reaction kettle, carrying out hydrothermal reaction, naturally cooling, centrifugally washing a precipitate with ethanol, carrying out vacuum drying, and grinding to obtain anatase TiO ₂the 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, and the volume of ethanol in the solution B is 10-30 m L;

(3) Preparation of vanadium-titanium catalyst:

Adding ammonium metavanadate and ammonium tungstate or ammonium molybdate into deionized water for full mixing, placing the mixture into a heat collection type constant-temperature magnetic stirrer after ultrasonic treatment, fully stirring at constant temperature to dissolve the mixture, adding an oxalic acid precursor under the stirring state, and continuously stirring strongly at constant temperature after ultrasonic treatment to prepare a mixed precursor solution; TiO to be used as catalyst carrier ₂Drying in a vacuum drying oven, taking out, and cooling to room temperature for later use; the TiO is ₂The mass is 1-5 g; adding the dried TiO carrier into the mixture under stirring ₂And continuously stirring strongly at constant temperature until the mixture is evaporated to dryness, and drying, grinding and calcining the mixture in a vacuum drying oven to obtain the vanadium-titanium catalyst powder catalyst for later use.

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

Adding the dried vanadium-titanium catalyst nanoparticles into deionized water from which nitrogen is removed, carrying out ultrasonic treatment, then continuing constant-temperature strong stirring, dropwise adding a certain amount of chloroplatinic acid and methanol, using a xenon lamp as a light source, and irradiating for a plurality of hours under continuous stirring 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 catalyst by a one-step impregnation method:

Adding ammonium metavanadate and ammonium tungstate or ammonium molybdate into deionized water for full mixing, placing the mixture into a heat collection type constant-temperature magnetic stirrer after ultrasonic treatment, fully stirring at constant temperature to dissolve the mixture, adding an oxalic acid precursor under the stirring state, and continuously stirring strongly at constant temperature after ultrasonic treatment to prepare a mixed precursor solution; TiO to be used as catalyst carrier ₂Drying in a vacuum drying oven, taking out, and cooling to room temperature for later use; adding the dried TiO carrier into the mixture under stirring ₂Then adding chloroplatinic acid and methanol, continuously stirring at constant temperature and strong force until the mixture is evaporated to dryness, drying and grinding the mixture by a vacuum drying box, calcining the mixture by a muffle furnace to obtain the vanadium-titanium catalyst powder catalyst, tabletting the powder catalyst under the set pressure of a tabletting machine, and sieving the tableted powder catalyst to obtain the catalyst with the granularity of 40-60 meshes.

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

Adding the dried vanadium-titanium catalyst nano particles into deionized water without nitrogen, carrying out ultrasonic treatment, then continuing constant-temperature strong stirring, dropwise adding a certain amount of chloroplatinic acid and methanol, continuing constant-temperature strong stirring 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 a set pressure of a tabletting machine, and sieving to obtain the catalyst with the particle size of 40-60 meshes.

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

cutting cordierite honeycomb ceramic into sample blocks with the diameter of 25mm and the height of 8mm, drying and calcining after ultrasonic treatment to remove various adsorbed impurities, boiling for a period of time by using nitric acid, washing by using distilled water until the pH value of a washing solution is neutral, blowing off residual liquid by using an air compressor, drying and calcining a carrier to remove the impurities adsorbed on the surface of the catalyst and improve the surface appearance of the catalyst, dissolving a certain amount of precious metal precursor, ammonium metavanadate and ammonium tungstate in 60m L deionized water at 60 ℃, fully stirring and dissolving, and then dissolving a certain amount of TiO ₂The powder and silica sol were added to the above solution so that the molar ratio of silicon to titanium was 2: 8. Adding a certain amount of HCl to adjust the pH value to about 4, and stirring to form stable slurry. Dipping a cordierite sample block into the slurry and performing ultrasonic treatment Loading, blowing air to remove the residual suspension to form uniform film on the surface of substrate, and drying. The impregnation process is then repeated until the desired loading is achieved. And finally, calcining the sample block in a muffle furnace to obtain the monolithic catalyst.

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

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

in the method, 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.

in the method, in the steps (4) to (6), the volume of the deionized water is 10-50 m L, the ultrasonic time is 5-10 min, the mass fraction of platinum is 0.1 wt% -1 wt% after the chloroplatinic acid is dripped, the volume fraction of methanol is 10% -25% after the methanol is dripped, and the light intensity of the xenon lamp is 100-400mW/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 method, 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 raising procedure comprises the steps of raising the temperature from room temperature to 250-350 ℃ at the speed of 2-5 ℃/min, keeping the temperature at 250-350 ℃ for 60-120 min, raising the temperature to 350-550 ℃ at the speed of 2-5 ℃/min, keeping the temperature for 3-6 h, and finally lowering the temperature to 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.

In the method, in the step (7), the content of the noble metal in the slurry is 0.1-1 wt%, the loading capacity 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.

A noble metal composite vanadium-titanium catalyst for purifying organic waste gas in coal-fired flue gas 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.

The invention utilizes the active components of noble metal and auxiliary agents of vanadium, tungsten, molybdenum, titanium and the like to load TiO ₂And finally, preparing the noble metal composite vanadium-titanium catalyst for purifying the organic waste gas in the coal-fired flue gas. The catalyst has large specific surface area, high activity and wide temperature window, and has high oxidation performance in treating the atmospheric environmental pollution such as coal-fired flue gas and sulfur-containing, nitrogen-containing and ammonia-containing organic matters.

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

(1) The preparation method adopted by the invention is simple and feasible, the active components can be regulated and controlled in a larger range, the content of the noble metal is low, and the noble metal can be well dispersed on the carrier.

(2) The invention firstly loads noble metal and auxiliary agents such as vanadium, tungsten, molybdenum, titanium and the like on TiO ₂The catalyst is used for purifying organic waste gas in coal-fired flue gas, and has wider temperature window, excellent activity and high CO in the coal-fired flue gas _xAnd (4) selectivity. The catalyst can be widely applied to the treatment of the atmospheric environmental pollution such as coal-fired flue gas, organic waste gas in high sulfur, high nitrogen and high ammonia.

Drawings

FIG. 1A is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂An activity evaluation chart of the catalyst for catalytic oxidative degradation of toluene;

FIG. 1B is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂COx selectivity evaluation chart of catalyst for catalytic oxidation of toluene

FIG. 1C shows the in-situ photo-reduction method, one-step dipping method and two-step dipping method 0.25wt％Pt/V₂O₅-WO₃-TiO₂An activity evaluation chart of the catalyst for catalytic oxidative degradation of toluene;

FIG. 2A is a 0.25% wtPT/V of the present invention ₂O₅-WO₃-TiO₂The activity evaluation chart of the catalyst for catalytic oxidation of toluene under the condition of simulating coal-fired flue gas.

FIG. 2B is a 0.25 wt% Pt/V embodiment of the present invention ₂O₅-WO₃-TiO₂The COx selectivity evaluation chart of the catalyst for catalytic oxidation of toluene under the condition of simulating coal-fired flue gas.

FIG. 3A is a 0.25 wt% Pt/V embodiment of the present invention ₂O₅-WO₃-TiO₂The activity of the catalyst for catalytic oxidation of toluene under the simulated coal-fired flue gas condition is 24h stability evaluation chart.

FIG. 3B is a 0.25 wt% Pt/V embodiment of the invention ₂O₅-WO₃-TiO₂A 24-hour stability evaluation chart of the selectivity of the catalyst for catalytic oxidation of toluene under the condition of simulating coal-fired flue gas.

FIG. 3C is a 0.25 wt% Pt/V embodiment of the present invention ₂O₅-WO₃-TiO₂An activity stability evaluation chart of the catalyst for toluene catalytic oxidation under simulated coal-fired flue gas conditions, wherein the oxidation rate is calculated by total hydrocarbon and is 24 h.

FIG. 4A is a 0.1 wt% Pt/V embodiment of the invention ₂O₅-WO₃-TiO₂The activity of the catalyst for catalytic oxidation of toluene under the simulated coal-fired flue gas condition is 24h stability evaluation chart.

FIG. 4B is a 0.1 wt% Pt/V embodiment of the invention ₂O₅-WO₃-TiO₂A 24-hour stability evaluation chart of the selectivity of the catalyst for catalytic oxidation of toluene under the condition of simulating coal-fired flue gas.

FIG. 4C is a 0.1 wt% Pt/V embodiment of the invention ₂O₅-WO₃-TiO₂An activity stability evaluation chart of the catalyst for toluene catalytic oxidation under simulated coal-fired flue gas conditions, wherein the oxidation rate is calculated by total hydrocarbon and is 24 h.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto, and may be carried out with reference to conventional techniques for process parameters not particularly noted.

Example 1

In-situ photoreduction method for preparing 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂Catalyst:

(1) Dissolving a noble metal precursor:

adding 1g of chloroplatinic acid into 250m L deionized water from which nitrogen is removed, carrying out ultrasonic treatment, and then continuously carrying out constant-temperature strong stirring to prepare a precursor solution;

(2)V₂O₅-WO₃-TiO₂The preparation of (1):

mixing 40m L ethanol and 2m L ammonia water to obtain a solution A, mixing 50m L tetrabutyl titanate and 10m L ethanol to obtain a solution B, simultaneously stirring the solution A and the solution B at room temperature for 20min, then dropwise adding the solution B into the solution A to obtain a solution C, stirring at room temperature for 30min, transferring the solution C into a polytetrafluoroethylene reaction kettle liner, finally placing the polytetrafluoroethylene reaction kettle liner into a high-pressure reaction kettle, carrying out hydrothermal reaction at 150 ℃ for 12h, naturally cooling, centrifugally washing the precipitate for 3 times by using ethanol at 6500r/min, transferring the precipitate into a vacuum drying oven at 105 ℃ for drying for 12h, and grinding to obtain anatase TiO ₂A nanoparticle;

adding 0.0458g of ammonium metavanadate as a V precursor and 0.1654g of ammonium tungstate as a W precursor into 20m L of deionized water, fully mixing, placing in a heat collection type constant-temperature magnetic stirrer, fully stirring at constant temperature for 30min to dissolve, adding 0.8g of oxalic acid precursor under stirring, carrying out ultrasonic treatment for 60min, continuing to stir at constant temperature and strongly to prepare a mixed precursor solution, and adding TiO as a catalyst carrier ₂Drying in a vacuum drying oven, taking out, and cooling to room temperature for later use; the TiO is ₂The mass was 2 g.

Adding the dried TiO carrier into the mixture under stirring ₂Continuously stirring for 90min at constant temperature to dry, drying in vacuum drying oven, grinding, heating from room temperature to 350 deg.C at 5 deg.C/min, holding at 350 deg.C for 60min, heating to 450 deg.C at 5 deg.C/min, holding for 4h, and cooling to 10 deg.C/min At room temperature to obtain V ₂O₅-WO₃/TiO₂A powder catalyst. Will V ₂O₅-WO₃-TiO₂The powder catalyst is dried in a vacuum drying oven at 120 ℃, taken out and cooled to room temperature for later use. Will V ₂O₅-WO₃-TiO₂Drying in a vacuum drying oven, taking out, and cooling to room temperature for later use; the V is ₂O₅-WO₃-TiO₂The mass was 1 g.

(3)Pt/V₂O₅-WO₃-TiO₂The in-situ photoreduction synthesis:

V of the above dried carrier 1g was added to 40m L deionized water to remove nitrogen ₂O₅-WO₃-TiO₂continuously stirring strongly at constant temperature, dropwise adding 1.33ml of 1.87mg/ml platinum precursor solution, continuously adding 10m L methanol, using xenon lamp (Perfectlight, PL S-SXE300/300UV) as light source, and light intensity of 350mW/cm ₂Irradiation was continued for 10h with stirring.

(4)Pt/V₂O₅-WO₃-TiO₂And (3) post-treatment of the catalyst:

Centrifuging the precipitate at 10000r/min, transferring to a vacuum drying oven at 120 ℃ for drying for 12h, and grinding to obtain Pt/V ₂O₅-WO₃-TiO₂A powdered catalyst; mixing Pt with V ₂O₅-WO₃-TiO₂And tabletting the powder catalyst under 10Mpa of a tabletting machine, and sieving to obtain the 40-60-mesh catalyst.

Example 2

Preparation of 0.25 wt% Pt/V by one-time dipping method ₂O₅-WO₃-TiO₂Catalyst:

mixing 40m L ethanol and 2m L ammonia water to obtain a solution A, mixing 50m L tetrabutyl titanate and 10m L ethanol to obtain a solution B, simultaneously stirring the solution A and the solution B at room temperature for 20min, then dropwise adding the solution B into the solution A to obtain a solution C, stirring at room temperature for 30min, transferring the solution C into a polytetrafluoroethylene reaction kettle liner, finally placing the polytetrafluoroethylene reaction kettle liner into a high-pressure reaction kettle, carrying out hydrothermal reaction at 150 ℃ for 12h, naturally cooling, and then precipitating Centrifuging and washing the precipitate with ethanol at 6500r/min for 3 times, transferring to a vacuum drying oven at 105 deg.C, drying for 12 hr, and grinding to obtain anatase TiO ₂A nanoparticle;

fully mixing 0.0458g of ammonium metavanadate as a V precursor, 0.1654g of ammonium tungstate as a W precursor and 20m L of deionized water, placing the mixture in a heat collection type constant-temperature magnetic stirrer, fully stirring the mixture for 30min at the temperature of 70 ℃ and the stirring speed of 450r/min to dissolve the mixture, and adding the prepared anatase TiO in a stirring state ₂2g of nano particles are added into 20m L deionized water to be fully mixed, the mixture is placed in a heat collection type constant temperature magnetic stirrer to be fully stirred at constant temperature for 30min to be dissolved, 0.8g of oxalic acid precursor is added under the stirring state, constant temperature strong stirring is continued after ultrasonic treatment for 60min to prepare a mixed precursor solution, 4mg/m L of platinum precursor solution is dropwise added to ensure that the content of Pt is 0.25%, 10m L of methanol is continuously added, constant temperature strong stirring and stirring are continued until the mixture is dried, the mixture is transferred to a 105 ℃ blast drying box to be dried for 12h, the mixture is ground and then placed in a muffle furnace to be calcined at high temperature, the temperature rising procedure is that the temperature is firstly raised from room temperature to 300 ℃ at the speed of 4.5 ℃/min, the temperature is kept at 300 ℃ for 1h, then the temperature is raised from 300 ℃ to 450 ℃ at the speed of 3 ℃/min, the temperature is kept at the constant temperature of ₂O₅-WO₃-TiO₂A material. Mixing Pt with V ₂O₅-WO₃-TiO₂And (3) pressing the powder catalyst into tablets under 10Mpa of a tablet press, and sieving to obtain the catalyst with 40-60 meshes.

Example 3

Preparation of 0.25 wt% PtPt/V by two-time immersion method ₂O₅-WO₃-TiO₂Catalyst:

(1) Dissolving a noble metal precursor:

(2)V₂O₅-WO₃-TiO₂The preparation of (1):

mixing 40m L ethanol and 2m L ammonia water to obtain solution A, mixing 50m L tetrabutyl titanate and 10m L ethanol to obtain solution B, mixing solution A and solution B Stirring the solution B at room temperature for 20min, dropwise adding the solution B into the solution A to obtain a solution C, stirring at room temperature for 30min, transferring to a polytetrafluoroethylene reaction kettle liner, putting the polytetrafluoroethylene reaction kettle liner into a high-pressure reaction kettle, carrying out hydrothermal reaction at 150 ℃ for 12h, naturally cooling, centrifugally washing the precipitate with ethanol at 6500r/min for 3 times, transferring to a 105 ℃ vacuum drying oven for drying for 12h, and grinding to obtain anatase TiO ₂A nanoparticle;

Adding the dried TiO carrier into the mixture under stirring ₂Continuously stirring strongly at constant temperature for 90min until the mixture is evaporated to dryness, drying and grinding the mixture in a vacuum drying oven, firstly heating the mixture from room temperature to 350 ℃ at the speed of 5 ℃/min, keeping the temperature at 350 ℃ for 60min, then heating the mixture to 450 ℃ at the speed of 5 ℃/min, keeping the temperature for 4h, and finally cooling the mixture to room temperature at the speed of 10 ℃/min to obtain V ₂O₅-WO₃/TiO₂A powder catalyst. Will V ₂O₅-WO₃-TiO₂The powder catalyst is dried in a vacuum drying oven at 120 ℃, taken out and cooled to room temperature for later use.

(3)Pt/V₂O₅-WO₃-TiO₂The synthesis of (2):

1g of the above dried support in Pt/V was added to 40m L deionized water with nitrogen removed ₂O₅-WO₃-TiO₂Continuously stirring strongly at constant temperature, stirring strongly at constant temperature until the mixture is evaporated to dryness, transferring the mixture to a 105 ℃ forced air drying oven for drying for 12h, grinding the mixture, putting the mixture into a muffle furnace for high-temperature calcination, and heating the mixture to 300 ℃ at a speed of 4.5 ℃/min, keeping the temperature of the mixture at 300 ℃ for 1h, and then heating the mixture from 300 ℃ at a speed of 3 ℃/min Heating to 450 deg.C, maintaining at 450 deg.C for 4h, and cooling to room temperature at a rate of 2 deg.C/min to obtain Pt/V ₂O₅-WO₃-TiO₂A material. Mixing Pt with V ₂O₅-WO₃-TiO₂And (3) pressing the powder catalyst into tablets under 10Mpa of a tablet press, and sieving to obtain the catalyst with 40-60 meshes.

Example 4

Pt/V₂O₅-WO₃-TiO₂Monolithic catalyst preparation

cutting cordierite honeycomb ceramic into sample blocks with the diameter of 20mm and the height of 40mm, drying and calcining after ultrasonic treatment to remove various adsorbed impurities, boiling for 20min by nitric acid, washing by distilled water until the pH value of a washing solution is neutral, blowing off residual liquid by an air compressor, drying and calcining a carrier, raising the temperature from room temperature to 350 ℃ at the speed of 5 ℃/min, keeping the temperature at 350 ℃ for 60min, raising the temperature to 450 ℃ at the speed of 5 ℃/min, keeping the temperature for 4h, finally lowering the temperature to room temperature at the speed of 10 ℃/min to remove the impurities adsorbed on the surface of the catalyst and improve the surface appearance of the catalyst, dissolving a precious metal precursor, ammonium metavanadate and ammonium tungstate in 60m L deionized water at the temperature of 60 ℃, fully stirring and dissolving, and then dissolving TiO m L ₂Adding the powder into the solution, adding HCl to adjust the pH value to be about 4, and stirring to form stable slurry, wherein the mass fraction of platinum in the slurry is 0.1 wt%, 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. Dipping a cordierite sample block into the 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 impregnation process until the ideal load is reached, wherein the load is 25% of the mass of the matrix; and finally calcining the sample block in a muffle furnace, wherein the calcining method comprises the steps of firstly heating from room temperature to 350 ℃ at the speed of 5 ℃/min, keeping the temperature at 350 ℃ for 60min, then heating to 450 ℃ at the speed of 5 ℃/min, keeping the temperature for 4h, and finally cooling to room temperature at the speed of 10 ℃/min to obtain the monolithic catalyst.

Example 5

Evaluating the catalytic oxidation activity of the organic waste gas in the coal-fired flue gas: with toluene (C) ₇H₈) As a probe the degradation reaction of the catalytic oxidation toluene is carried out on a self-made fixed bed reactor under the test conditions that the concentration of the toluene is 50ppm, the dosage of the catalyst is 100mg, the reaction temperature is 150-390 ℃, the reaction flow rate is 200m L/min, and the space velocity is 120000h ^-1The reaction atmosphere is simulated coal-fired flue gas, wherein NH ₃Concentration 1000ppm, NO concentration 1000ppm, NH ₃Concentration of 1000ppm, 5 vol% O ₂，N₂Is a balance gas; detecting toluene, CO and CO by gas chromatograph with hydrogen ion Flame (FID) detector and nickel converter ₂The concentration value of (c).

FIG. 1A is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂The activity evaluation chart of the catalyst for the catalytic oxidative degradation of toluene is shown in FIG. 1B, which is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂COx selectivity evaluation chart of catalyst for catalytic oxidation of toluene, and FIG. 1C shows 0.25 wt% Pt/V prepared by different methods ₂O₅-WO₃-TiO₂The activity evaluation chart of the catalyst for toluene catalytic oxidative degradation. The results show that the commercial VWT catalyst catalyzes the oxidation of toluene to T ₉₀331 ℃ C, T for catalytic oxidation of toluene by commercial noble metal catalyst ₉₀T for catalytic oxidation of toluene at 271 ℃ with a commercial transition metal catalyst ₉₀At 370 ℃ 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂Catalyst T for catalytic oxidation of p-toluene ₉₀The temperature was 181 ℃. The results illustrate that 0.25 wt% Pt/V is prepared according to the invention ₂O₅-WO₃-TiO₂The catalyst has wider activity temperature window and more excellent CO compared with commercial catalyst _xAnd (4) selectivity.

FIG. 2A is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂The activity evaluation chart of the catalyst in catalytic oxidative degradation of toluene in coal-fired flue gas is shown in FIG. 2B, which is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂CO catalytically oxidized by toluene in coal-fired flue gas by catalyst _xSelectivity evaluation chart, test conditions are as follows: toluene concentration 50ppm and catalyst amount 100mg, the reaction temperature is 350 ℃, the reaction flow rate is 200m L/min, and the space velocity is 120000h ^-1The reaction atmosphere is simulated coal-fired flue gas, wherein NH ₃Concentration of 1000ppm, NO concentration of 1000ppm, SO ₂Concentration of 1000ppm, 5 vol% O ₂，N₂Is a balance gas; detecting toluene and CO using a gas chromatograph with a hydrogen ion Flame (FID) detector and a nickel reformer _xThe concentration value of (c). The experimental result shows that the commercial noble metal catalyst has the removal rate of the catalytic oxidation of the toluene at 350 ℃, and CO _xThe selectivity was 12.3%, 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂The removal rate of the catalyst at 350 ℃ for the catalytic oxidation of toluene is 99 percent, and CO is _xThe selectivity reaches 99 percent. The results illustrate that 0.25W%/V was prepared according to the invention ₂O₅-WO₃-TiO₂The catalyst has better activity stability and oxidation efficiency than commercial catalysts.

The above results fully illustrate that 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂The catalyst shows excellent catalytic oxidation activity and CO _xAnd (4) selectivity.

Example 6

Evaluation of catalytic oxidation stability of organic waste gas in coal-fired flue gas: exploration of 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂And 0.1 wt% Pt/V ₂O₅-WO₃-TiO₂the catalytic oxidation stability of the catalyst on the toluene and the degradation reaction of the catalytic oxidation toluene are carried out on a self-made reactor under the test conditions that the concentration of the toluene is 50ppm, the dosage of the catalyst is 100mg, the reaction temperature is 350 ℃, the reaction flow rate is 200m L/min, and the space velocity is 120000h ^-1The reaction atmosphere is simulated coal-fired flue gas, wherein NH ₃Concentration 500ppm, NO concentration 500ppm, SO ₂Concentration of 1000ppm, 5 vol% O ₂，N₂Is a balance gas; the concentration values of toluene and COx were measured using a gas chromatograph with a hydrogen ion Flame (FID) detector and a nickel reformer. FIG. 3A is 0.25 wt% Pt/V ₂O₅-WO₃-TiO₂The removal rate of catalyst p-toluene for 24 h in catalytic oxidative degradation is 0.25w in FIG. 3B t％Pt/V₂O₅-WO₃-TiO₂The 24h COx selectivity of the catalyst for catalytic oxidation of toluene is 0.25 wt% Pt/V in FIG. 3C ₂O₅-WO₃-TiO₂The oxidation efficiency of the catalyst for toluene catalytic oxidation is 24h based on total hydrocarbon. FIG. 4A is 0.1 wt% Pt/V ₂O₅-WO₃-TiO₂The 24-hour removal rate of the catalyst for the catalytic oxidative degradation of toluene is shown in FIG. 4B as 0.1 wt% Pt/V ₂O₅-WO₃-TiO₂Catalyst 24h COx selectivity to toluene catalytic oxidation, 0.1W% wt% Pt/V in FIG. 4C ₂O₅-WO₃-TiO₂The oxidation efficiency of the catalyst for toluene catalytic oxidation is 24h based on total hydrocarbon. The experimental result shows that after 24 hours of reaction, 0.25 wt% of Pt/V ₂O₅-WO₃-TiO₂And 0.1 wt% Pt/V ₂O₅-WO₃-TiO₂The removal rate of the catalyst reaches 99 percent, the oxidation efficiency based on the total hydrocarbon reaches 99 percent, and the selectivity of the COx reaches 99 percent.

The above examples are merely illustrative of the technical solutions of the present invention and not restrictive, and it will be understood by those of ordinary skill in the art that various changes in the details or forms thereof may be made without departing from the spirit and scope of the present invention as defined by the claims.

Claims

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:

(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.