CN108554398B

CN108554398B - Preparation method and application of a wide temperature window denitration catalyst

Info

Publication number: CN108554398B
Application number: CN201810549720.1A
Authority: CN
Inventors: 谢峻林; 公丕军; 何峰; 李凤祥; 方德; 齐凯
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2018-05-31
Filing date: 2018-05-31
Publication date: 2021-04-20
Anticipated expiration: 2038-05-31
Also published as: CN108554398A

Abstract

The invention belongs to the technical field of catalysts, and in particular relates to a preparation method and catalytic application of a wide temperature window and low toxicity denitration catalyst. The catalyst is composed of three components, CeO ₂ , ZrO ₂ and TiO ₂ , in the form of composite oxides; the Ce:Zr:Ti molar ratio is 0.1-0.5:1:1. The invention adopts the cerium-zirconium-titanium catalyst synthesized by the glucose hydrothermal method, and cleverly uses the polyhydroxy chelation effect of glucose to form coordination bonds to bond around the cerium-zirconium-titanium particles, and then under high temperature conditions, the glucose wrapped around the catalyst generates Carbonization burns off, resulting in more oxygen vacancies and defects on the surface of the catalyst; the CeO ₂ -ZrO ₂ -TiO ₂ catalyst synthesized by this method has a high space velocity of 30000h ^-1 and a wide temperature of 200 ℃ ~ 400 ℃ has good catalytic reduction The NO _X performance and activity are all above 80%, and the activity is close to 100% at 280-340°C. It shows that the catalyst has a wider temperature window and wider applicability.

Description

Preparation method and application of wide-temperature-window denitration catalyst

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a preparation method and application of a wide-temperature-window denitration catalyst.

Background

Nitrogen oxides (NOx) are the main pollutants causing air pollution, and the most serious of the pollutants are NO and NO₂And N₂And O, three nitrogen oxides. Nitrogen oxides can cause acid rain, which can cause burns to ecological trees and crops, reduce yield, and corrode buildings and reduce their useful life. In addition, nitrogen oxides cause photochemical pollution, which has great influence on human health,for example, inhalation of NO can cause poisoning of the human body and, in severe cases, can cause life risks.

Selective catalytic reduction of ammonia (NH)₃SCR) technology is the most effective method for treating nitrogen oxide hazards and is most widely used. The core of the SCR catalytic technology is a denitration catalyst, and the most widely applied denitration catalyst in the current market is vanadium tungsten titanium (V)₂O₅-WO₃/TiO₂) A catalyst. However, the vanadium-tungsten-titanium catalyst has the defects of narrow temperature window, poor environmental adaptability and the like, and the waste vanadium-tungsten-titanium catalyst brings great harm to the environment. Therefore, the country has made strict regulations on the purchase and use of vanadium tungsten titanium catalysts, and has actively advocated the development and use of non-vanadium titanium catalysts that are highly efficient and low in toxicity. Therefore, the catalyst with high efficiency, low toxicity and wide temperature window has wide market application prospect.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a preparation method and application of a denitration catalyst with a wide temperature window.

In order to achieve the purpose, the invention adopts the technical scheme that:

a denitration catalyst with wide temperature window is prepared from CeO₂、ZrO₂And TiO₂The three components are formed in a composite oxide form; the molar ratio of Ce to Zr to Ti is 0.1-0.5: 1: 1.

A preparation method of a wide temperature window denitration catalyst comprises the following steps:

(1) dissolving soluble zirconium salt, soluble titanium salt and soluble cerium salt in deionized water to obtain a solution A; dissolving glucose in deionized water to obtain a solution B; stirring and mixing the solution A and the solution B uniformly to obtain a solution C

(2) Dropwise adding an ammonia water solution into the solution C while stirring until the pH is controlled to be 10 to obtain a mixed emulsion D; transferring the mixed emulsion D to a reaction kettle for hydrothermal treatment reaction, and cooling to room temperature after the reaction is finished;

(3) and (3) carrying out suction filtration on the precipitate, taking a filter cake, washing and drying the filter cake, then placing the filter cake in a muffle furnace for high-temperature calcination, cooling to room temperature after the calcination is finished, and fully grinding the obtained product to obtain the denitration catalyst with the wide temperature window.

In the above scheme, the soluble zirconium salt in step (1) is Zr (NO)₃)₄·5H₂O, the soluble titanium salt is TiOSO_4，The soluble cerium salt is Ce (NO)₃)₃·6H₂O。

In the scheme, the concentration of the solution A in the step (1) is 0.1-0.5 mol/L.

In the scheme, the molar ratio of Ce, Zr and Ti in the step (1) is 0.1-0.5: 1: 1.

In the scheme, the molar weight of the glucose in the step (1) is 1-3 times of the total molar weight of Ce, Zr and Ti.

In the scheme, the concentration of the ammonia water solution in the step (2) is 1-2 mol/L.

In the scheme, the temperature of the hydrothermal treatment in the step (2) is 120-200 ℃, and the time is 12-36 h.

In the above scheme, the high-temperature calcination process in step (3) is as follows: firstly, the temperature is rapidly raised to 110 ℃ at the speed of 20 ℃/min, then the temperature is slowly raised to 500 ℃ at the speed of 5 ℃/min, and the mixture is roasted for 3h at 500 ℃.

The preferable molar ratio of Ce, Zr and Ti in the preparation process of the catalyst is 0.1-0.5: 1:1, when the molar ratio of Ce is less than 0.1, the activity of the catalyst is poor, and when the molar ratio of Ce is more than 0.5, the cost is increased; when the molar ratio of Zr to Ti is not 1:1, the specific surface area of the catalyst is lowered, which is disadvantageous for the catalytic process.

The optimal hydrothermal treatment temperature in the preparation process of the catalyst is 140-180 ℃, and the time is 18-24 h. If the hydrothermal temperature is lower than 140 ℃, the hydrothermal reaction of the catalyst is incomplete, and the yield of the cerium-zirconium-titanium oxide is low; if the hydrothermal temperature is higher than 180 ℃, the crystallization tendency of the catalyst is serious, and the activity of the catalyst is influenced, so that the temperature of 140-180 ℃ is more reasonable hydrothermal treatment temperature. Meanwhile, within the temperature of 140-180 ℃, the hydrothermal treatment time is less than 18h, which can cause incomplete reaction of the catalyst, while the treatment time is more than 24h, which can cause excessive consumption of energy. Therefore, the reasonable hydrothermal treatment time is 12-36 h.

The application of the wide temperature window denitration catalyst in the flue gas denitration process comprises the following steps:

(1) the flue gas analyzer is started to preheat and zero, and N is used₂The air tightness test is carried out for the balance gas, and N is kept in the experimental process₂The balance gas is unchanged;

(2) weighing the denitration catalyst and pressing the denitration catalyst into tablets before testing the selective catalytic reduction activity;

(3) before the SCR activity test, gradually raising the temperature to the reaction temperature of the catalyst;

(4) in the SCR activity test, introducing reaction mixed gas, respectively keeping the temperature of 80-420 ℃ for about 30min, and monitoring the numerical value on line when the gas is stable;

(5) under the action of a catalyst with wide temperature window and high activity, NO and a reducing agent NH₃Reacting to produce harmless N₂And H₂O, and discharging into the atmosphere through a pipeline; the gas inlet and outlet of the whole system is monitored on line through a gas analyzer, and the denitration rate is obtained through calculation.

In the above scheme, the reaction conditions of step (5) are as follows: [ NO ]]＝720ppm,[NH₃]＝800ppm,[O₂]＝3vol％，N₂As balance gas, the space velocity is 30,000h^-1。

The invention has the following beneficial effects: the cerium-zirconium-titanium (Ce, Zr and Ti) composite catalyst synthesized by adopting a glucose hydrothermal method skillfully utilizes the polyhydroxy chelation of glucose to form coordinate bonds to be combined around cerium-zirconium-titanium particles, so that the uniformity and the dispersibility of the catalyst particles are improved; then under the condition of high temperature, the glucose wrapped around the catalyst is carbonized and lost, so that more oxygen vacancies and defects are generated on the surface of the catalyst; the catalyst prepared by the method has higher specific surface area and more surface acid sites, is beneficial to the adsorption and reaction of reaction gas molecules, has high efficiency and low toxicity, and does not contain V₂O₅And the like harmful to the environment; said catalyst is notThe denitration catalyst exists in a single oxide form, but exists in a solid solution form, and the solid solution has a better denitration rate compared with a single oxide; the denitration rate is more than 80% in a wide temperature window range of 200-400 ℃, and the activity of 280-340 ℃ is close to 100%, which shows that the denitration catalyst has a wider temperature window and wider applicability.

Drawings

FIG. 1 shows CeO prepared by the present invention₂-ZrO₂-TiO₂The catalytic activity of the catalyst is compared with that of other catalysts.

FIG. 2 shows 0.3CeO prepared in example 3 of the present invention₂-ZrO₂-TiO₂SEM image of catalyst.

FIG. 3 shows CeO prepared in examples 1 and 3 of the present invention₂-ZrO₂-TiO₂XPS spectra of the catalyst.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.

The following examples are not specifically described, and the purity of the reagent used is 99.9% chemical reagent.

In the practice of the present invention, the reaction conditions for the SCR activity test are as follows: [ NO ]]＝720ppm,[NH₃]＝800ppm,[O₂]＝3vol％，N₂As balance gas, the space velocity is 30,000h^-1. In addition, the temperature points between 200 ℃ and 400 ℃ are respectively kept for about 30min, and the numerical value is monitored on line when the gas is stable. The influent and effluent gases were both detected by a gas analyzer (Gasboard-3800P), NO_XIs determined by the formula ([ NO ]]_in－[NO]_out)/[NO]_inAnd calculating to characterize the activity of the catalyst.

Example 1

A denitration catalyst with a wide temperature window is prepared by mixing three components of Ce, Zr and Ti according to a molar ratio of 0.1:1:1, and is prepared by the following method: 1) firstly, 4.2932g of zirconium nitrate pentahydrate, 1.9595g of titanyl sulfate and 0.4312g of cerous nitrate hexahydrate are weighed, mixed and dissolved in 250mL of deionized water, and stirred by a magnetic stirrer for 2-3 hours until the solution becomes clear from turbidity, so as to obtain a mixed solution A; 2) the dosage of the glucose is 2.5 times of the total molar ratio of Ce, Zr and Ti, 10.4039g of glucose is weighed and dissolved in 100mL of deionized water to obtain liquid B; mixing the solution B with a clear solution mixed solution A containing cerium, zirconium and titanium to obtain a mixed solution C, and continuously stirring for 30 min; 3) preparing 1mol/L ammonia water solution, dropwise adding the 1mol/L ammonia water solution into the mixed solution C, controlling the pH value to be 10 to obtain emulsion D, transferring the emulsion into a 150mL reaction kettle, and carrying out hydrothermal treatment at 160 ℃ for 24 hours; 4) cooling to room temperature, carrying out suction filtration on the precipitate through a circulating water type vacuum pump, carrying out ultrasonic dispersion on the obtained filter cake through an ultrasonic disperser, and then continuing suction filtration, repeating the steps, and carrying out suction filtration for 2-3 times; dispersing with absolute ethyl alcohol, and performing suction filtration for 1-2 times; the obtained precipitate is dried for 12h at 110 ℃, and the dried substance is calcined in a muffle furnace at high temperature: firstly, rapidly heating to 110 ℃ at a speed of 20 ℃/min, then slowly heating to 500 ℃ at a speed of 5 ℃/min, and roasting for 3h at 500 ℃; 5) grinding the product obtained by calcination to finally obtain the cerium-zirconium-titanium catalyst with high efficiency, low toxicity and wide temperature window.

The cerium-zirconium-titanium catalyst prepared in the embodiment is subjected to a simulated flue gas denitration test in a reactor, and the result shows that: when the NO concentration is 720ppm, NH₃/NO＝1.1、O₂The content is 3 percent and 30000h^-1When the air velocity ratio is high, the denitration rate is more than 80% in a wide temperature window range of 240-380 ℃, and the activity is more than 90% at 280-320 ℃.

Example 2

A denitration catalyst with a wide temperature window is prepared by mixing three components of Ce, Zr and Ti according to a molar ratio of 0.2:1:1, and is prepared by the following method: 1) firstly, 4.2932g of zirconium nitrate pentahydrate, 1.9595g of titanyl sulfate and 0.8682g of cerous nitrate hexahydrate are weighed, mixed and dissolved in 250mL of deionized water, and stirred by a magnetic stirrer for 2-3 hours until the solution becomes clear from turbidity, so as to obtain a mixed solution A; 2) the dosage of the glucose is 2.5 times of the total molar ratio of Ce, Zr and Ti, 10.4039g of glucose is weighed and dissolved in 100mL of deionized water to obtain liquid B; mixing the solution B with a clear solution mixed solution A containing cerium, zirconium and titanium to obtain a mixed solution C, and continuously stirring for 30 min; 3) preparing 1mol/L ammonia water solution, dropwise adding the 1mol/L ammonia water solution into the mixed solution C, controlling the pH value to be 10 to obtain emulsion D, transferring the emulsion into a 150mL reaction kettle, and carrying out hydrothermal treatment at 160 ℃ for 24 hours; 4) cooling to room temperature, carrying out suction filtration on the precipitate through a circulating water type vacuum pump, carrying out ultrasonic dispersion on the obtained filter cake through an ultrasonic disperser, and then continuing suction filtration, repeating the steps, and carrying out suction filtration for 2-3 times; dispersing with absolute ethyl alcohol, and performing suction filtration for 1-2 times; the obtained precipitate is dried for 12h at 110 ℃, and the dried substance is calcined in a muffle furnace at high temperature: firstly, rapidly heating to 110 ℃ at a speed of 20 ℃/min, then slowly heating to 500 ℃ at a speed of 5 ℃/min, and roasting for 3h at 500 ℃; 5) grinding the product obtained by calcination to finally obtain the cerium-zirconium-titanium catalyst with high efficiency, low toxicity and wide temperature window.

The catalyst prepared in the embodiment is subjected to a simulated flue gas denitration test in a reactor, and the result shows that: when the NO concentration is 720ppm, NH₃/NO＝1.1、O₂The content is 3 percent and 30000h^-1When the air velocity ratio is high, the denitration rate is more than 80% within a wide temperature window range of 220-380 ℃, and the activity is more than 90% at 280-340 ℃.

Example 3

A denitration catalyst with a wide temperature window is prepared by mixing three components of Ce, Zr and Ti according to a molar ratio of 0.3:1:1, and is prepared by the following method: 1) firstly, 4.2932g of zirconium nitrate pentahydrate, 1.9595g of titanyl sulfate and 1.3024g of cerous nitrate hexahydrate are weighed, mixed and dissolved in 250mL of deionized water, and stirred by a magnetic stirrer for 2-3 hours until the solution becomes clear from turbidity, so as to obtain a mixed solution A; 2) the dosage of the glucose is 2.5 times of the total molar ratio of Ce, Zr and Ti, 11.3948g of glucose is weighed and dissolved in 100mL of deionized water to obtain liquid B; mixing the solution B with a clear solution mixed solution A containing cerium, zirconium and titanium to obtain a mixed solution C, and continuously stirring for 30 min; 3) preparing 1mol/L ammonia water solution, dropwise adding the 1mol/L ammonia water solution into the mixed solution C, controlling the pH value to be 10 to obtain emulsion D, transferring the emulsion into a 150mL reaction kettle, and carrying out hydrothermal treatment at 160 ℃ for 24 hours; 4) cooling to room temperature, carrying out suction filtration on the precipitate through a circulating water type vacuum pump, carrying out ultrasonic dispersion on the obtained filter cake through an ultrasonic disperser, and then continuing suction filtration, repeating the steps, and carrying out suction filtration for 2-3 times; dispersing with absolute ethyl alcohol, and performing suction filtration for 1-2 times; the obtained precipitate is dried for 12h at 110 ℃, and the dried substance is calcined in a muffle furnace at high temperature: firstly, rapidly heating to 110 ℃ at a speed of 20 ℃/min, then slowly heating to 500 ℃ at a speed of 5 ℃/min, and roasting for 3h at 500 ℃; 5) grinding the product obtained by calcination to finally obtain the cerium-zirconium-titanium catalyst with high efficiency, low toxicity and wide temperature window.

The catalyst prepared in the embodiment is subjected to a simulated flue gas denitration test in a reactor, and the result shows that: when the NO concentration is 720ppm, NH₃/NO＝1.1、O₂The content is 3 percent and 30000h^-1When the air velocity ratio is high, the denitration rate is more than 80% within a wide temperature window range of 200-400 ℃, and the activity is more than 95% at 240-360 ℃. As can be seen, the catalyst prepared by the embodiment has a wide reaction temperature window and an excellent NOx removal rate in a low temperature range.

Example 4

A denitration catalyst with a wide temperature window is prepared by mixing three components of Ce, Zr and Ti according to a molar ratio of 0.4:1:1, and is prepared by the following method: 1) firstly, 4.2932g of zirconium nitrate pentahydrate, 1.9595g of titanyl sulfate and 1.7365g of cerous nitrate hexahydrate are weighed, mixed and dissolved in 250mL of deionized water, and stirred by a magnetic stirrer for 2-3 hours until the solution becomes clear from turbidity, so as to obtain a mixed solution A; 2) the dosage of the glucose is 2.5 times of the total molar ratio of Ce, Zr and Ti, 11.3948g of glucose is weighed and dissolved in 100mL of deionized water to obtain liquid B; mixing the solution B with a clear solution mixed solution A containing cerium, zirconium and titanium to obtain a mixed solution C, and continuously stirring for 30 min; 3) preparing 1mol/L ammonia water solution, dropwise adding the 1mol/L ammonia water solution into the mixed solution C, controlling the pH value to be 10 to obtain emulsion D, transferring the emulsion into a 150mL reaction kettle, and carrying out hydrothermal treatment at 160 ℃ for 24 hours; 4) cooling to room temperature, carrying out suction filtration on the precipitate through a circulating water type vacuum pump, carrying out ultrasonic dispersion on the obtained filter cake through an ultrasonic disperser, and then continuing suction filtration, repeating the steps, and carrying out suction filtration for 2-3 times; dispersing with absolute ethyl alcohol, and performing suction filtration for 1-2 times; the obtained precipitate is dried for 12h at 110 ℃, and the dried substance is calcined in a muffle furnace at high temperature: firstly, rapidly heating to 110 ℃ at a speed of 20 ℃/min, then slowly heating to 500 ℃ at a speed of 5 ℃/min, and roasting for 3h at 500 ℃; 5) grinding the product obtained by calcination to finally obtain the cerium-zirconium-titanium catalyst with high efficiency, low toxicity and wide temperature window.

The CeO prepared by the invention₂-ZrO₂-TiO₂The catalytic activity of the catalyst was compared with that of the other catalysts, and the results are shown in FIG. 1, which shows that: pure CeO₂The catalytic activity is poor, the maximum catalytic activity is only 40 percent, and the binary CeO₂-ZrO₂And ZrO₂-TiO₂The catalyst activity was also poor, although CeO₂-TiO₂The catalyst has certain activity, but the temperature window is narrow, and the highest activity is only 80 percent. The CeO prepared by the invention₂-ZrO₂-TiO₂The catalyst has a denitration rate of more than 80% in a wide temperature window range of 220-380 ℃, and the activity of more than 90% in a temperature range of 280-340 ℃, which shows that the catalyst has better catalytic activity and a wide temperature window.

The BET characterization of the denitration catalyst prepared in example 3 of the present invention was carried out, and the results are shown in Table 1, wherein Table 1 shows that the catalyst prepared in example 3 of the present invention has a specific surface area of 205m²(ii)/g, higher specific surface area than other catalysts; the scanning electron microscope picture of the method is shown in figure 2, and figure 2 shows that the dispersing effect of the active ingredients of the catalyst is better. FIG. 3 shows the preparation of CeO according to examples 1 and 3₂-ZrO₂-TiO₂XPS spectrum of the catalyst, XPS analysis showing the lattice oxygen O of the catalyst_βIs high in ratio of O_β/(O_α+O_β) 0.29, indicating that the catalyst has stronger oxygen storage capacity and more surface active oxygen O_αThe catalyst is shown to have more oxygen vacancies and defects, which all contribute to catalyst productionHigh catalytic activity.

TABLE 1 denitration catalyst BET characterization results

Sample (I)	Specific surface area (m)²/g)
		ZrO₂-TiO₂	156
CeO₂	71
		CeO₂-TiO₂	122
CeO₂-ZrO₂	78
		0.3Ce-Zr-Ti	205

It is apparent that the above embodiments are only examples for clearly illustrating and do not limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are therefore intended to be included within the scope of the invention as claimed.

Claims

1. a preparation method of wide temperature window denitration catalyst, is characterized in that, comprises the steps:

(1) Dissolve soluble zirconium salt, soluble titanium salt and soluble cerium salt in deionized water to obtain solution A; dissolve glucose in deionized water to obtain solution B; stir and mix solution A and solution B to obtain solution C ; the soluble zirconium salt is Zr(NO ₃ ) ₄ ·5H ₂ O, the soluble titanium salt is TiOSO ₄ , and the soluble cerium salt is Ce(NO ₃ ) ₃ ·6H ₂ O; the wide temperature window denitration The catalyst is composed of three components, CeO ₂ , ZrO ₂ and TiO ₂ in the form of solid solution; the molar ratio of Ce:Zr:Ti is 0.1-0.5:1:1, and the molar amount of glucose is Ce, Zr and Ti 1~3 times of the total molar amount;

(2) adding the ammonia solution dropwise to the solution C, stirring while adding dropwise, until the pH of the solution is controlled at 10 to obtain the mixed emulsion D; the mixed emulsion D is transferred to the reactor for hydrothermal treatment, After the reaction, cooled to room temperature;

(3) Filter the precipitate with suction, take the filter cake, wash and dry the filter cake, then calcinate at high temperature in a muffle furnace, cool down to room temperature after calcination, and fully grind the obtained calcined product to obtain a wide temperature window for denitration catalyst.

2 . The preparation method according to claim 1 , wherein the concentration of the solution A in step (1) is 0.1-0.5 mol/L. 3 .

3 . The preparation method according to claim 1 , wherein the concentration of the aqueous ammonia solution in step (2) is 1 mol/L to 2 mol/L. 4 .

4 . The preparation method according to claim 1 , wherein the temperature of the hydrothermal treatment in step (2) is 120°C to 200°C, and the time is 12h to 36h. 5 .

5 . The preparation method according to claim 1 , wherein the high-temperature calcination process in step (3) is: firstly, the temperature is rapidly raised to 110° C. at 20° C./min, and then the temperature is raised at a slow rate of 5° C./min. 6 . , heated to 500 ℃, and calcined at 500 ℃ for 3h.

6. The wide temperature window denitration catalyst obtained by any one of the preparation methods of claims 1-5 is characterized in that: the denitration catalyst is composed of three components, CeO ₂ , ZrO ₂ and TiO ₂ in the form of solid solution; the The molar ratio of Ce:Zr:Ti is 0.1~0.5:1:1.

7. The application of the wide temperature window denitration catalyst obtained by the preparation method of the wide temperature window denitration catalyst according to claim 1 in the flue gas denitration process.

8. The application according to claim 7, wherein the application specifically comprises the following steps:

(1) The flue gas analyzer is preheated and zeroed, and the air tightness test is carried out with N ₂ as the balance gas, and the N ₂ balance gas is kept unchanged during the experiment;

(2) Before the selective catalytic reduction activity test, weigh the denitration catalyst and press it into tablets;

(3) Before the SCR activity test, gradually raise the temperature to the reaction temperature of the catalyst;

(4) In the SCR activity test, the reaction mixture gas was introduced, and the temperature was kept between 80 °C and 420 °C for 30 minutes. After the gas was stable, the value was monitored online;

(5) Under the action of a wide temperature window and high activity catalyst, NO reacts with the reducing agent NH ₃ to generate harmless N ₂ and H ₂ O, which are discharged into the atmosphere through pipes; the gas in and out of the whole system is analyzed by a gas analyzer. Online monitoring, denitrification rate is obtained by calculation.