CN104209116A - Vanadium-series middle-temperature and high-temperature SCR catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a vanadium-series middle-temperature and high-temperature catalyst. The catalyst takes a titanium zirconium oxide as a carrier, takes an oxide of vanadium as an active component and takes an oxide of tungsten as a cocatalyst, wherein the mol ratio of titanium to zirconium in the catalyst is 1 to 1; the mass of the oxide of the tungsten accounts for 6%-12% of the total mass of the oxide of tungsten and the titanium zirconium oxide; and the mass of the oxide of the vanadium accounts for 1% of the total mass of the catalyst. The invention further provides a preparation method of the catalyst; tungsten trioxide is added so that the heat stability and the reduction capability of V2O5 are enhanced; the pore diameter and the pore volume of the catalyst are increased; and the staying time of NH3 on the surface of the catalyst is prolonged and the amount of br.nsted acid on the surface of the catalyst is increased, so that the denitration efficiency of the catalyst is improved.

Description

A kind of medium and high temperature SCR catalyst of vanadium system and preparation method thereof

technical field

The invention belongs to the technical field of flue gas denitrification in thermal power plants, and in particular relates to a preparation method of a vanadium-based medium-high temperature SCR catalyst.

Background technique

Selective Catalytic Reduction (SCR) is currently the most widely used denitration technology with the highest treatment efficiency. There are many types of catalysts used for SCR denitration reaction, V ₂ O ₅ /WO ₃ (MoO ₃ )/TiO ₂ (Anatase type) series catalysts have become the most widely used SCR industrial catalysts due to their advantages of high denitrification efficiency, high temperature resistance, high activity and good anti-poisoning performance. However, the required temperature is relatively high, which is generally required to be controlled at 573-673K. The higher flue gas temperature is due to problems such as sintering of the catalyst, which all lead to the deactivation of the catalyst.

It is generally believed that V ₂ O ₅ has a good performance in catalytic reduction of NO, WO ₃ as an auxiliary agent plays a certain role in stabilizing the catalyst structure and changing the catalyst texture, and TiO ₂ has good sulfur tolerance. TiO ₂ is chosen as the carrier because TiO ₂ is only weakly and reversibly sulfided under the action of SO ₂ and oxygen. In addition, TiO ₂ also has a good electronic interaction with V ₂ O ₅ , which makes the catalyst have good activity. Relevant studies have shown that on the surface _of new catalysts, the V ₂ O ₅ on _the surface of the catalyst is mainly in a monolayer and aggregated state. _{The 2} O ₅ gradually increased, and after aging for 24 hours, the dispersed V ₂ O ₅ basically disappeared, and the crystalline V ₂ O ₅ directly led to the oxidation of NH ₃ , resulting in a decrease in the conversion rate of NO. At the same time, it is worth noting that V ₂ O ₅ /TiO ₂ (anatase) is a rather unstable system, and TiO ₂ (anatase) is a metastable crystal in titanium oxide with a small specific surface area , the surface is easy to shrink when heated, and it is easy to transform into rutile with relatively stable thermodynamic state under certain temperature and pressure conditions, and the addition of WO ₃ helps to prevent the transformation of anatase form, stabilize the crystal structure, and increase the crystal phase transition temperature , and WO ₃ can also inhibit the formation of V ₂ O ₅ crystalline species. Therefore, it is often used as a WO ₃ co-catalyst to improve the thermal stability of the catalyst.

Contents of the invention

The technical problem to be solved by the present invention is to provide a vanadium-based medium-high temperature SCR catalyst. The vanadium-based medium-high temperature SCR catalyst not only has strong high-temperature catalytic activity, but also has a wide temperature window and strong sintering resistance.

Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned vanadium-based medium-high temperature SCR catalyst.

In order to solve the above-mentioned technical problems, the present invention provides a vanadium-based medium-high temperature SCR catalyst, which uses titanium-zirconium oxide as a carrier, vanadium oxide as an active component, and tungsten oxide as a cocatalyst, wherein the In the catalyst, the molar ratio of titanium element and zirconium element is 1:1, and the quality of the oxide of tungsten accounts for 6% to 12% of the total mass of the oxide of tungsten and titanium zirconium oxide; The mass accounts for 1% of the mass of the total catalyst.

Specifically, the titanium-zirconium oxide is TiO ₂ -ZrO ₂ , the vanadium oxide is V ₂ O ₅ , and the tungsten oxide is WO ₃ .

The present invention also proposes a preparation method for the above-mentioned vanadium-based medium-temperature SCR catalyst, comprising the following steps:

(1) Preparation of TiO ₂ -ZrO ₂ carrier: The TiO ₂ -ZrO ₂ carrier was prepared by co-precipitation method, dried and then calcined for later use, wherein _the molar ratio of TiO ₂ and ZrO ₂ in the TiO ₂ -ZrO 2 carrier was 1:1;

(2) Preparation of WO ₃ /TiO ₂ -ZrO ₂ catalyst: Take the TiO ₂ -ZrO ₂ carrier prepared in step (1) and add it to the oxalic acid solution of ammonium tungstate, and stir in an oil bath at 30-40°C for 2-3 hours , heated up to 80-90°C and continued stirring and impregnating for 4-5 hours, evaporated to dryness with water, then dried, ground, and calcined to obtain WO ₃ /TiO ₂ -ZrO ₂ catalyst, oxalic acid only played a role in promoting ammonium tungstate For the effect of dissolution, 5g of oxalic acid is sufficient for a load of no more than 2g each time, and the subsequent oil bath will decompose excess oxalic acid into CO ₂ and H ₂ O. The mass ratio of ammonium tungstate to TiO ₂ -ZrO ₂ support is 6.97%-13.54%, so that the mass of tungsten oxide accounts for 6-12% of the total mass of tungsten oxide and TiO ₂ -ZrO ₂ support;

(3) Preparation of 1% V ₂ O ₅ -WO ₃ /TiO ₂ -ZrO ₂ catalyst: Add WO ₃ /TiO ₂ -ZrO ₂ prepared in step (2) to the oxalic acid solution, and then continue to add ammonium metavanadate , stirred in an oil bath at 30-40°C for 2-3 hours, raised the temperature to 80-90°C and continued stirring and impregnating for _{4-5 hours} . ₃ /TiO ₂ -ZrO ₂ catalyst, oxalic acid only plays a role in promoting the dissolution of ammonium metavanadate, 5g of oxalic acid is sufficient for the load of no more than 2g each time, and the subsequent oil bath will remove the excess Oxalic acid decomposes into _CO2 and _H2O . Wherein, the mass ratio of ammonium metavanadate to WO ₃ /TiO ₂ -ZrO ₂ catalyst is 1.29%, so that the mass of V ₂ O ₅ in the catalyst accounts for V ₂ O ₅ -WO ₃ /TiO ₂ -ZrO ₂ catalyst 1% of the total mass.

Specifically, the step of co-precipitation in step (1) is: under the conditions of ice-water bath and magnetic stirring, TiCl ₄ is added dropwise at a rate of 0.8-1 ml/min while stirring, and at the same time Add ammonia water dropwise to the reactor at a rate of 3-5ml/min until the pH of the solution measured by the pH test paper is 9-10, then let it stand in the dark for 12-14 hours, and then pour off the supernatant to obtain a precipitate. The precipitate was washed with deionized water, and filtered under reduced pressure, and the washing was repeated until no ^Cl- was detected in the filtrate to obtain a TiO ₂ -ZrO ₂ precipitate. In the solution of TiCl ₄ and zirconium oxychloride octahydrate, dropwise add ammoniacal liquor (NH ₃ content is 25%～28%) to adjust the pH value to 9～10, when dripping ammoniacal liquor with rubber head dropper, TiCl ₄ and A white milky precipitate will be produced in the solution of zirconium oxychloride octahydrate. When dropping the next drop of ammonia water, observe the dripping position of the previous drop of ammonia water in the solution. The position of the next drop of ammonia water dripping should be staggered from the previous drop. Precipitation can be formed at different positions in the solution; during the dripping of ammonia water, the solution in the large beaker should be dipped continuously with a glass rod, and the pH value of the solution should be measured with pH test paper until it is 9-10, at this time, stop adding ammonia water. A white milky precipitate was obtained, which was allowed to stand for 12 to 14 hours, washed and filtered with suction. Specifically, wash with deionized water, collect the waste liquid that has been washed and precipitated, put the waste liquid in a beaker, use 0.1mol/L silver nitrate solution to check whether there are chloride ions in the waste liquid, if there are chloride ions, continue Wash until there is no chloride ion in the silver nitrate test waste liquid. The purpose of this method is to prevent the symbiosis of chloride ions in the raw material TiCl ₄ and zirconium oxychloride octahydrate to form metal complexes containing chloride ions in the precipitation, which will affect the precipitation. quality.

Preferably, the stirring speed of magnetic stirring or mechanical stirring in the above steps is 20-30 r/s.

Preferably, the drying conditions in steps (1), (2) and (3) are drying at 100-120° C. for 11-13 hours.

The calcination conditions in steps (1), (2) and (3) are calcination at 400-500°C for 3-4 hours, and the calcination temperature in the whole preparation process cannot be higher than 500°C. When the calcination temperature is higher than 500°C, titanium dioxide begins to Anatase crystal form changes to rutile crystal form, which is unfavorable for the reaction. Preferably, the calcination condition is 450° C. for 4 hours.

In order to further improve the performance of the catalyst, it is characterized in that, in step (2) and step (3), after the TiO ₂ -ZrO ₂ carrier and WO ₃ /TiO ₂ -ZrO ₂ catalyst are ground through a 60-mesh sieve, and then Soluble in deionized water or ammonium tungstate in oxalic acid solution.

The present invention further proposes the application of the vanadium-based supported medium-temperature SCR catalyst in medium-high temperature SCR denitrification.

Preferably, the temperature range of the medium temperature is 300-400°C.

Beneficial effects: Compared with the prior art, the vanadium-based medium-high temperature SCR denitration catalyst of the present invention enhances the thermal stability and reduction ability of V ₂ O ₅ by adding WO ₃ , increases the pore diameter and pore volume of the catalyst, and enhances the The residence time of NH ₃ on the catalyst surface and the acid content, thereby improving the denitrification efficiency of the catalyst.

Description of drawings

Fig. 1 is a comparison chart of the denitrification performance of the series catalysts of the present invention;

The anti-sulfur performance figure of series catalyst of the present invention of Fig. 2;

The NH ₃ -TPD spectrogram of series catalyst of the present invention of Fig. 3;

The FT-IR spectrogram of series catalyst of the present invention of Fig. 4;

Fig. 5 is an XRD pattern of a series of catalysts of the present invention.

Detailed ways

The present invention can be better understood from the following examples. However, those skilled in the art will readily understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims .

Example 1:

(1) TiO ₂ -ZrO ₂ solid solution (titanium zirconium solid solution, Ti-Zr) was synthesized by co-precipitation method.

Using titanium tetrachloride (TiCl ₄ , density 1.726g/ml) and zirconium oxychloride octahydrate (ZrOCl ₂ 8H ₂ O) as raw materials, first add 200ml of deionized water to a 2L beaker in a fume hood, and place a 2L large Move the beaker into ice water, insert a magnetic stirrer into the large beaker, start stirring, and the stirring speed is 20-30r/s. Dissolve 31.7346g of zirconium oxychloride octahydrate in a 25ml beaker on the test bench outside the fume hood, and transfer the solution into a 2L beaker, then add 10.8ml of titanium tetrachloride solution drop by drop while stirring , Each drop is separated by 10s to ensure that the titanium tetrachloride solution can be completely hydrolyzed in the solution of zirconium oxychloride octahydrate. Then dropwise add ammoniacal liquor (NH _content is 25%～28%) to adjust the pH value of the solution in the beaker to 9～10, in the process of dropping, the dripping positions of the front and back two drops of ammoniacal liquor in the large beaker solution should be staggered, Add drop by drop until a white milky precipitate occurs in the solution. During this process, continuously dip a glass rod into the solution in the beaker and measure the pH value of the solution with pH test paper. When the pH value is 9-10, stop the dropwise addition. Let the precipitate stand for 12 hours, wash with deionized water, suction filter, and dry in an oven at 110°C for 12h, take the dried solid, crush and sieve, take the 60-mesh solid after sieving, and calcinate in a muffle furnace at 450°C After 3 hours, a titanium-zirconium solid solution (TiO ₂ -ZrO ₂ , n(Ti)/n(Zr)=1, n being the number of moles) was obtained. The characterization results of the titanium-zirconium solid solution are shown in Figure 4.

(2) Ammonium tungstate is loaded and calcined to obtain a WO ₃ /TiO ₂ -ZrO ₂ (W/Ti-Zr) catalyst.

Get three parts of the titanium-zirconium solid solution prepared by step (1), each part of 5g, get three 25ml beakers, add 10ml deionized water, 5g oxalic acid respectively in the three beakers (oxalic acid only plays the role of promoting the dissolution of ammonium tungstate, The subsequent oil bath will decompose oxalic acid into CO ₂ and H ₂ O), then add 5g of titanium-zirconium solid solution, and then take 0.349g, 0.541g, and 0.745g of ammonium tungstate, respectively, and add them to three beakers. No. ①②③, 80°C oil bath, stir and evaporate to dryness, take out the evaporated solid, dry in an oven at 110°C for 12 hours, crush and sieve, take the 60-mesh solid after sieving; calcinate in a muffle furnace at 450°C for 3 hours, Obtained: 6% W/Ti-Zr (6% WO ₃ /TiO ₂ -ZrO ₂ ), 9% W/Ti-Zr (9% WO ₃ /TiO ₂ -ZrO ₂ ), 12% W/Ti-Zr ( 12% WO ₃ /TiO ₂ -ZrO ₂ ) (6%, 9%, and 12% respectively represent the proportion of WO ₃ in the prepared WO ₃ /TiO ₂ -ZrO ₂ catalyst of the WO ₃ /TiO ₂ -ZrO ₂ catalyst 6%, 9% and 12% by weight).

(3) Ammonium metavanadate is loaded and calcined to obtain 1% V ₂ O ₅ -(X%)WO ₃ /TiO ₂ -ZrO ₂ (abbreviated as VX%W/Ti-Zr or V-(X%)W/ Ti-Zr) catalyst. Wherein, X% means that the mass ratio of WO ₃ to tungsten oxide to WO ₃ /TiO ₂ -ZrO ₂ carrier is X%.

Get respectively 3 grams of three kinds of W/Ti-Zr catalysts that step (2) makes, get three 25ml beakers, add 10ml deionized water in each beaker, add 5g oxalic acid (oxalic acid only plays a role in promoting metavanadate The purpose of ammonium dissolution, even if it is added more, the excess oxalic acid will be decomposed into _CO2 and _H2O ) in the oil bath process, then add 3gW/Ti-Zr catalyst, get 0.0389g ammonium metavanadate respectively, And add to three beakers respectively, 80 ℃ oil bath, evaporate, take the solid after the oil bath, dry in the oven at 110 ℃ for 12 hours, crush and sieve, take the 60 mesh solid after sieving; calcined at 450 ℃ for 3 hours in the muffle furnace , namely: 1%V ₂ O ₅ -6%WO ₃ /TiO ₂ -ZrO ₂ (1%V-6%W/Ti-Zr), 1%V ₂ O ₅ -9%WO ₃ /TiO ₂ - ZrO ₂ (1%V-9%W/Ti-Zr) and 1%V ₂ O ₅ -12%WO ₃ /TiO ₂ -ZrO ₂ (1%V-12%W/Ti-Zr), wherein, 1 % represents the percentage of V ₂ O ₅ accounting for the total weight of V ₂ O ₅ -WO ₃ /TiO ₂ -ZrO ₂ catalyst is 1%; 6%, 9% and 12% respectively represent WO ₃ accounting for WO ₃ /TiO ₂ -ZrO ₂ The weight percent of the catalyst is 6%, 9% and 12%.

Example 21 Characterization of V ₂ O ₅ -(X%) WO ₃ /TiO ₂ -ZrO ₂ catalyst.

(1) BET characterization results

The specific surface area BET of the catalyst was measured by ASAP 2020, a fully automatic gas adsorption system from McMurray, USA. The sample was pretreated under vacuum at 200 °C for 2 h, and measured at -196 °C with _N2 adsorbate.

Table 1 Specific surface area of 1%V ₂ O ₅ -(X%)WO ₃ /TiO ₂ -ZrO ₂ series catalysts

It can be seen from Table 1 that with the increase of _WO3 loading, the specific surface area of the catalyst gradually decreases, which may be because the loaded blocked the pores of the catalyst, so that the specific surface area of the catalyst decreases with the increase of _WO3 loading . It can also be seen from Table 1 that the cumulative pore volume and average pore diameter of the catalyst reached the maximum when the _WO3 loading was 9%. On the one hand, because the catalytic reaction of the catalyst is carried out in the pores on the surface of the catalyst, the nitrogen oxides in the flue gas are first adsorbed on the surface of the catalyst before they can react; on the other hand, the denitrification efficiency of the catalyst is not only compared with the catalyst. The surface area is related, because the specific surface area is measured with nitrogen, which reflects the total specific surface area of the catalyst, and does not reflect the active specific surface area of the catalyst surface; although when the WO ₃ loading is 9%, the specific surface area of the catalyst is not the largest However, since the increase of catalyst pore size and pore volume is beneficial to the catalytic reaction of the catalyst, this shows that for VX%W/Ti-Zr series catalysts, the pore volume of the catalyst plays an important role in the denitrification reaction , which is in good agreement with the denitrification efficiency of the catalyst in the performance test.

(2) NH ₃ -TPD analysis

For NH ₃ -TPD analysis, the automatic temperature-programmed chemical adsorption instrument (FINESORB-3010) of Zhejiang Fantai Instrument Co., Ltd. was used. The pretreatment temperature was 150°C, the heating rate was 10°C/min, the desorption temperature was 25°C-800°C, and nitrogen was purged for 10 minutes. , the data were detected by TCD thermal conductivity detector. Fig. 3 is the NH ₃ -TPD figure of V ₂ O ₅ (1%)-WO ₃ (X%)/TiO ₂ -ZrO ₂ series catalysts, and table 2 is V ₂ O ₅ (1%)-WO ₃ (X%) )/TiO ₂ -ZrO ₂ series catalysts NH ₃ adsorption capacity and desorption temperature. The result shows: the comparative result of three kinds of catalysts shows: three kinds of catalysts all have a desorption peak at 100 ℃～160 ℃, promptly prove that three kinds of catalyzers all have weak acid center (100 ℃～160 ℃), table 2 shows: V ₂ O ₅ -9%WO ₃ /TiO ₂ -ZrO ₂ has the smallest amount of acid, but the activation energy required for its desorption is higher (that is, the desorption temperature is higher). Compared with the other two catalysts, the adsorption on the catalyst The NH ₃ on the surface is not easy to desorb, which enhances the residence time of NH ₃ on the catalyst surface and promotes the removal of NO _X . Comparing V ₂ O ₅ -6%WO ₃ /TiO ₂ -ZrO ₂ and V ₂ O ₅ -12%WO ₃ /TiO ₂ -ZrO ₂ catalysts, under the same desorption activation energy, NH ₃ in The residence time on the surface of the catalyst is the same. At this time, the catalyst with more ammonia adsorbed on the surface has higher denitrification efficiency, which corresponds to the results of the catalyst activity test; while the V ₂ O ₅ /TiO ₂ -ZrO ₂ catalyst exhibits In addition to higher acid content and desorption temperature, its efficiency is the lowest, which may be caused by the lack of WO ₃ and the poor thermal stability of V ₂ O ₅ in the V ₂ O ₅ /TiO ₂ -ZrO ₂ catalyst, which It is also consistent with the performance test of the catalyst.

Table 2 Surface acid content and desorption temperature of V ₂ O ₅ (1%)-WO ₃ (X%)/TiO ₂ -ZrO ₂ series catalysts

sample Surface acid content (ml/g) Desorption temperature (°C) V-6%W/Ti-Zr 30.7344 111 V-9%W/Ti-Zr 23.6610 127 V-12%W/Ti-Zr 37.2289 111 V/Ti-Zr 45.3169 151

(3) FT-IR analysis

The FT-IR analysis adopts the American Nicholas 6700 Fourier Transform Infrared Analyzer, the pretreatment temperature is 400°C, the heating rate is 10°C/min, the adsorption temperature is 25°C (normal temperature adsorption), the adsorption time is 1h, and the nitrogen is purged for 15min. DTGS detector and record the reaction data. Fig. 4 is the FT-IR spectrum of (1%) V ₂ O ₅ -(X%) WO ₃ /TiO ₂ -ZrO ₂ series catalysts. The results show that: it can be seen that after NH ₃ is adsorbed on the acidic catalyst surface, both the adsorption peak of NH ₃ at the Lewis acid center and the adsorption peak of NH ₃ at the acidic center appear. The adsorption peaks of the acid centers, the adsorption peaks of the two catalysts are roughly the same. After NH ₃ is adsorbed on V ₂ O ₅ /TiO ₂ -ZrO ₂ at 25°C, weaker absorption peaks appear at 1454 and 1168 cm-1, and the peak at 1168 cm ^-1 is attributed to the NH in NH ₃ adsorbed by the Lewis acid center The degenerate stretching vibration of the bond, the absorption peak at 1454cm ^-1 is the catalyst surface The deformation vibration of the NH bond in the adsorbed _NH4 ⁺ of the acid center, the absorption peak at 1680cm ^-1 belongs to Symmetrical stretching vibrations of NH bonds in _NH4 ⁺ adsorbed on acid centers. For the modified WO ₃ modified V ₂ O ₅ /TiO ₂ -ZrO ₂ catalyst, the position of the absorption peak on the FT-IR spectrum is mostly the same as that before the modification, but with the increase of the content, The intensity of the absorption peak at 1454cm ^-1 is significantly enhanced, and the active sites for NH ₃ adsorption are significantly increased, while the intensity of the absorption peak _at 1168cm ^-1 has not changed much, so it can be preliminarily speculated that the catalyst modified by WO ₃ The adsorption active sites increase, and the NH ₃ adsorption capacity increases, among which Acid sites play a major role, which has a _strong The acidity is consistent, and it can be seen from the denitrification rate diagram that The increase of acid sites is beneficial to the improvement of denitrification efficiency (when the weight percentage of WO ₃ in the WO ₃ /TiO ₂ -ZrO ₂ catalyst is 6%-12%).

(4) X-ray diffraction analysis

Adopt XRD-2 type X-ray diffraction analyzer, tube voltage 35kV, tube current 20mA, step size 0.02°/s, X-ray wavelength 1.5406A, Cu target, 2θ/θ coupling continuous scanning, scanning angle is 10°～ 70°, the catalyst sample needs to be fully ground before testing, take an appropriate amount of powder and fill it on a glass carrier and flatten it. The thickness of the sample powder is about 1mm. Figure 5 shows: the diffraction peaks of ZrO ₂ and ZrTiO ₄ are obvious, this is because the thermal stability of ZrO ₂ and ZrTiO ₄ is better with the increase of WO ₃ loading; with the increase of WO ₃ loading, V ₂ O The diffraction peaks of ₅ are not obvious, and the height and area of the diffraction peaks do not change much, which indicates that the addition of WO ₃ increases the crystal phase transformation temperature of V ₂ O ₅ , that is, V ₂ O ₅ is in an amorphous form, and increases the catalyst The number of acid centers on the surface reduces the sintering temperature of V ₂ O ₅ and enhances the thermal stability of V ₂ O ₅ , thereby improving the thermal stability of the catalyst and promoting the improvement of catalyst efficiency.

(5) Catalyst denitrification reaction

Test Conditions:

The catalyst is subjected to a denitrification test under fixed bed simulated flue gas conditions: take the modified denitrification catalyst and place it in the isothermal zone of the reaction tube. Carry out selective catalytic reduction denitrification reaction.

Use steel cylinders to simulate flue gas composition Flue gas includes NO, O ₂ , N ₂ , NH ₃ , the flue gas composition is volume fraction Φ(NO)=Φ(NH3)=0.08%, Φ(0 ₂ )=5 %, with _N2 as the balance gas. The space velocity is =3.0×10 ⁴ h ^-1 , and the total flue gas flow rate is 100ml/min. The gas in each pipeline passes through the mass flowmeter (all flowmeters are calibrated by the soap foam flowmeter) and enters the gas mixer to mix and balance before entering the reactor. The concentrations of NO, NO ₂ and O ₂ were measured by German Testo 330-2LL flue gas analyzer. Based on this, the NO removal efficiency was calculated. In order to ensure the stability and accuracy of the data, each working condition should be stable for at least 30 minutes.

Test Results:

The vanadium-based medium-high temperature catalyst provided by the invention adopts a co-precipitation method to prepare a carrier and an impregnation method to load active substances. Figure 1 shows that the denitrification efficiencies of the three catalysts all showed a trend of increasing first and then decreasing, and the denitrification efficiency of the catalysts reached the maximum at 300°C, especially V ₂ O ₅ (1%)-WO ₃ (9%)/ TiO ₂ -ZrO ₂ , within the range of 300°C-400°C, the NO removal efficiency reaches an average value of more than 91%, and the temperature window is wide, and the stability is high, which may be because the content of WO ₃ is 9%. , the addition of WO ₃ increases the crystallization temperature of V ₂ O ₅ , makes it amorphous, and enhances the thermal stability of V ₂ O ₅ , and the denitrification efficiency of the catalyst is the highest compared with the same series of catalysts.

(6) The sulfur resistance performance test of the catalyst.

Test Conditions:

The denitrification test of the catalyst is carried out under the fixed bed simulated flue gas conditions: the modified denitrification catalyst is taken and placed in the isothermal zone of the reaction tube, the flue gas enters the reaction tube, and the selective catalytic reduction denitrification is carried out by the catalyst in the reaction tube reaction.

Use steel cylinders to simulate flue gas composition. Flue gas includes NO, O ₂ , N ₂ , and NH ₃ . The flue gas composition is volume fraction Φ(NO)=Φ(NH ₃ )=0.08%, Φ(O ₂ )= 5%, Φ(SO ₂ )=1% (about 150ppm), with N ₂ as the balance gas. The space velocity is =3.0×10 ⁴ h ^-1 , the total flue gas flow rate is 100ml/min, and the test temperature is 300°C. The gas in each pipeline passes through the mass flowmeter (all flowmeters are calibrated by the soap foam flowmeter) and enters the gas mixer to mix and balance before entering the reactor. The German Testo 330-2LL flue gas analyzer is used to measure the concentration of NO and NO ₂ . In order to ensure the stability and accuracy of the data, each working condition is stable for at least 30 minutes. Brief introduction of reaction steps: No SO ₂ flow in the first 160 minutes, one sample is taken every 40 minutes, and 5 samples are collected from 0 minute; 5 samples are also collected when SO ₂ is passed in the middle 160-360 minutes; 360-560 mm stop the flow of SO _2. Also collect 5 samples; measure the NOx content in each sample, calculate the denitrification efficiency, and then draw a graph, as shown in Figure 2:

The experimental results show that: V ₂ O ₅ (1%)-WO ₃ (9%)/TiO ₂ -ZrO ₂ and V ₂ O ₅ (1%)-WO ₃ (12%)/TiO ₂ -ZrO ₂ The catalyst has good sulfur resistance performance at 300°C. At the same time, for V ₂ O ₅ (1%)-WO ₃ (12%)/TiO ₂ -ZrO ₂ , the performance of the catalyst will be slightly reduced when the SO ₂ is stopped. The improvement was increased from 92% to 94%, which may be because when the SO ₂ was 150ppm, the Zr(SO ₄ ) ₂ species generated on the catalyst surface enhanced the acidity of the catalyst surface, and the test results also showed that when WO ₃ was in WO ₃ When the content of /TiO ₂ -ZrO ₂ is 9% and 12%, the thermal stability of the catalyst is obviously enhanced, making ZrO ₂ in an amorphous state, so ZrO ₂ can react with SO ₂ to form Zr(SO ₄ ) ₂ , In turn, the sulfur resistance performance of the catalyst is enhanced.

Claims (10)

1. high temperature SCR catalyst in a vanadium system, it is characterized in that, described catalyst is taking titanium Zirconium oxide as carrier, taking the oxide of vanadium as active component, taking the oxide of tungsten as co-catalyst, wherein, in described catalyst, the mol ratio of titanium elements and zr element is 1: 1, and the quality of the oxide of described tungsten accounts for 6～12% of the oxide of tungsten and the gross mass of titanium Zirconium oxide; The quality of the oxide of vanadium account for total catalyst quality 1%.

2. high temperature SCR catalyst in vanadium according to claim 1 system, is characterized in that, described titanium Zirconium oxide is TiO ₂-ZrO ₂, the oxide of described vanadium is V ₂o ₅, the oxide of described tungsten is WO ₃.

3. the preparation method of high temperature SCR catalyst in vanadium claimed in claim 1 system, is characterized in that, comprises the steps:

(1) TiO ₂-ZrO ₂the preparation of carrier: utilize coprecipitation to prepare TiO ₂-ZrO ₂carrier, then for subsequent use after drying, grinding, calcining successively;

(2) WO ₃/ TiO ₂-ZrO ₂the preparation of catalyst: get TiO prepared by step (1) _2-zrO ₂carrier joins in the oxalic acid solution of ammonium tungstate, under 30～40 DEG C of oil baths, stirs 2～3h, is warming up to 80～90 DEG C and continuation stirring dipping 4～5h, after band moisture evaporate to dryness, then after drying, grinding, calcining, obtains WO successively ₃/ TiO ₂-ZrO ₂catalyst;

(3) 1%V ₂o ₅-WO ₃/ TiO ₂-ZrO ₂the preparation of catalyst: WO prepared by step (2) ₃/ TiO ₂-ZrO ₂catalyst joins in oxalic acid solution, then adds ammonium metavanadate, under 30～40 DEG C of oil baths, stirs 2～3h, is warming up to 80～90 DEG C and continuation stirring dipping 4～5h, after moisture evaporate to dryness, obtains V successively after drying, grinding, calcining ₂o ₅-WO ₃/ TiO ₂-ZrO ₂catalyst.

4. preparation method according to claim 3, it is characterized in that, in step (1), the step of co-precipitation is: under the condition of ice-water bath, magnetic agitation, in the aqueous solution of eight water zirconium oxychlorides, drip TiCl while stirring with the speed of 0.8～1ml/min ₄drip ammoniacal liquor to reactor with the speed of 3～5ml/min simultaneously, be 9～10 until pH test paper records the pH of solution, then under dark condition, leaving standstill 12～14h hypsokinesis goes supernatant liquor to be precipitated, wash described precipitation by deionized water, and decompress filter, repeated washing is until the Cl that in filtrate, inspection does not measure ^-till, obtain TiO ₂-ZrO ₂precipitation.

5. according to the preparation method described in claim 3 or 4, it is characterized in that, described magnetic agitation or churned mechanically mixing speed are 20～30r/s.

6. preparation method according to claim 3, is characterized in that, the drying condition in step (1), (2) and (3) is 100～120 DEG C of dry 11～13h.

7. preparation method according to claim 3, is characterized in that, the calcination condition in step (1), (2) and (3) is to calcine 3～4h at 400～500 DEG C.

8. preparation method according to claim 3, is characterized in that, in step (2) and step (3), and described TiO ₂-ZrO ₂carrier and WO ₃/ TiO ₂-ZrO ₂catalyst ground after 60 mesh sieves, and then be dissolved in deionized water or the oxalic acid solution of ammonium tungstate in.

9. the application of the system supported Medium temperature SCR catalyst of vanadium claimed in claim 1 in middle high temperature SCR denitration.

10. application according to claim 9, is characterized in that, the temperature range of described middle high temperature is 300～400 DEG C.