CN116422343A

CN116422343A - Double-atom catalyst for removing smoke pollutants, preparation method thereof, layered combination catalyst combination and application

Info

Publication number: CN116422343A
Application number: CN202310381745.6A
Authority: CN
Inventors: 韩小金; 赵文平; 黄张根; 侯亚芹; 曾泽泉
Original assignee: Shanxi Institute of Coal Chemistry of CAS
Current assignee: Shanxi Institute of Coal Chemistry of CAS
Priority date: 2023-04-11
Filing date: 2023-04-11
Publication date: 2023-07-14
Anticipated expiration: 2043-04-11
Also published as: CN116422343B

Abstract

The invention provides a diatomic catalyst for removing smoke pollutants, a preparation method thereof, a layered combination catalyst combination and application thereof, and relates to the field of catalysts. The diatomic catalyst comprises a catalyst carrier, a first metal and a second metal supported on the catalyst carrier; the first metal comprises at least one of Pd, pt, rh, au and the second metal comprises at least one of Ag, cu, mn, ce, cr. The preparation method comprises the following steps: the raw materials including the salt of the first metal and the salt of the second metal are formulated into a mixed metal salt solution, and then the mixed metal salt solution is supported on a catalyst support, calcined in the presence of a reducing agent, or calcined without using a reducing agent and then reduced in a reducing atmosphere. The diatomic catalyst for removing the smoke pollutant has high utilization rate of active components, can form stable diatomic active centers and has good catalytic efficiency.

Description

Double-atom catalyst for removing smoke pollutants, preparation method thereof, layered combination catalyst combination and application

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to a diatomic catalyst for removing smoke pollutants, a preparation method thereof, a layered combination catalyst combination and application.

Background

The sintering flue gas and the coke oven flue gas generated in the production process of steel and coke bring great atmospheric pollution. The flue gas contains a large amount of nitrogen oxides (NOx), carbon monoxide (CO), a small amount of low-carbon hydrocarbon, chlorine-containing aromatic hydrocarbon and other pollutants. Nitrogen oxides are important factors responsible for ozone depletion, photochemical smog and acid rain. The emission reduction of nitrogen oxides is particularly valued by the state and has greatly progressed, and medium-low temperature SCR method nitrogen oxides are often used in industrial flue gas. Substances such as CO, hydrocarbons and the like contained in the flue gas cannot be removed. The problem of CO emission and hydrocarbon and other VOCs emission in the centralized area of steel coking production is serious. In particular, the heat generated by oxidation of CO, hydrocarbons and the like can be further beneficial to denitration.

An atomic dispersion catalyst is a hotspot in the field of heterogeneous catalysis. The double monoatomic catalyst has two sets of monoatomic structures, different monoatomic structures can play different functions in the catalytic reaction, and the synergistic effect of the two can not only improve the utilization rate of atoms to the greatest extent, but also improve the catalytic selectivity.

For the co-removal of nitrogen oxides and carbon monoxide as well as lower hydrocarbons, there is also a need to develop a suitable catalyst to efficiently solve this problem.

Furthermore, loading new active sites on the catalyst is a convenient method, but these highly oxidative active sites will be NH ₃ Rapid oxidation, leading to NH ₃ The SCR reaction cannot proceed and the denitration reaction is inhibited. Introducing NH with high concentration ₃ Can lead to increased operating costs and NH ₃ Competing with CO for oxidation sites also results in a reduction in CO oxidation rate.

Therefore, it is important to further solve the above problems.

In view of this, the present invention has been made.

Disclosure of Invention

The invention aims to provide a diatomic catalyst for removing smoke pollutants, a preparation method thereof, and a layered combination catalyst combination and application thereof, so as to solve the problems.

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

a diatomic catalyst for flue gas pollutant removal, comprising a catalyst carrier and a first metal and a second metal supported on the catalyst carrier;

the first metal comprises at least one of Pd, pt, rh, au and the second metal comprises at least one of Ag, cu, mn, ce, cr.

Preferably, the first metal accounts for 0.01% -0.1% of the total mass of the diatomic catalyst, and the second metal accounts for 0.01% -2% of the total mass of the diatomic catalyst.

The first metal is typically a noble metal for cost and dispersibility considerations; the second metal can adjust the dispersibility of the first metal, improve the sinterability, have a synergistic effect, and can be used in an appropriately increased amount.

Alternatively, the proportion of the first metal to the total mass of the diatomic catalyst may be any value between 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1% or 0.01% -0.1%, and the proportion of the second metal to the total mass of the diatomic catalyst may be any value between 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or 0.01% -2%.

Preferably, the loading concentration of the first metal and the second metal on different sites of the catalyst carrier is the same or distributed in a gradient.

When uniformly distributed catalyst is used, the catalyst usage amount is not more than 1/4 of the total usage amount. Particularly, when heterogeneous catalysts are adopted (gradient distribution is adopted), the existing denitration catalyst can be conveniently replaced, and simultaneous removal and use of multiple pollutants are realized.

Preferably, the catalyst support is selected from the group consisting of finished catalysts or catalyst supports that are not loaded with active metals;

the catalyst carrier is honeycomb, plate-shaped or corrugated.

Preferably, the combination of the first metal and the second metal is any one of pd+cu, pd+ag, pt+mn, rh+ce, au+cr, pd+cu+mn, and pt+ag.

The application also provides a preparation method of the diatomic catalyst for removing the smoke pollutant, which comprises the following steps:

preparing a raw material including a salt of the first metal and a salt of the second metal into a mixed metal salt solution, and then supporting the mixed metal salt solution on the catalyst support, calcining in the presence of a reducing agent, or calcining without using a reducing agent and then reducing in a reducing atmosphere.

Preferably, the method of loading comprises a dipping or electrostatic spraying method;

when the electrostatic spraying method is used for carrying out the loading, the salt of the first metal and the salt of the second metal are uniformly or gradient distributed on the catalyst carrier by adjusting the voltage and the gas carrying capacity. Compared with the conventional dipping means, the dispersibility can be further improved by adopting an electrostatic spraying mode. Meanwhile, the functions of gravity, carried gas and the like are considered, and the gradient distribution can avoid NH consumption caused by oxidation of the inlet end ₃ 。

Preferably, the preparation method satisfies one or more of the following conditions:

a. the time of the impregnation is 6-12h, and the impregnation further comprises drying after the completion of the impregnation;

b. the calcining temperature is 480-500 ℃ and the calcining time is 4-8h;

c. the reducing atmosphere includes an atmosphere containing hydrogen;

d. the reducing agent comprises sodium citrate which is added into the mixed salt solution when in use;

e. the reduction temperature is 480-500 ℃ and the time is 1-3h.

The application also provides a layered combination catalyst combination, which comprises the diatomic catalyst and NH for removing the smoke pollutant in a layered arrangement ₃ -an SCR catalyst.

The application also provides application of the layered combination catalyst combination, and particularly can be applied to oxidation of CO and low-carbon hydrocarbon and removal of nitrogen oxides.

The invention has the beneficial effects that:

according to the diatomic catalyst for removing the smoke pollutants, the first metal and the second metal are loaded on the catalyst carrier, so that the utilization rate of active components is high, stable diatomic active centers can be formed, the preparation method is simple, the cost is low, and the catalytic efficiency is good.

The diatomic catalyst carries out catalytic oxidation on carbon monoxide and low-carbon hydrocarbon, the carbon monoxide conversion rate under the condition of 130 ℃ is more than 95%, and the NO conversion rate under the condition of 180 ℃ is more than 90%.

The layered combination catalyst provided by the invention combines the diatomic catalyst for removing the smoke pollutants with the NH3-SCR catalyst, so that the ammonia oxidation problem can be effectively relieved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a diatomic catalyst for flue gas pollutant removal prepared by an electrostatic spraying method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of layered combination of a diatomic catalyst and an NH3-SCR catalyst for flue gas pollutant removal according to an embodiment of the present invention;

reference numerals:

1-a high voltage electrostatic generator; 2-coaxial atomizing nozzles; 3-a catalyst support; 4-mixing the salt solution; 5-high pressure pump; 6-carrying gas; 7-a first sampling point; 8-a second sampling point; 9-a third sampling point; 10-a heat exchanger; 11-hot blast stove; 12-an ammonia spraying system; 13-denitration catalyst bed; 14-a bed of a terminal denitration catalyst; 15-gradient distribution improvement of denitration catalyst; 16-a homogeneous phase improved denitration catalyst; 17-a commercially available denitration catalyst.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

The embodiment provides a diatomic catalyst for removing smoke pollutants, which is prepared by the following steps:

respectively preparing copper nitrate solid and palladium nitrate solid into aqueous solutions, adding deionized water, uniformly mixing, and adding crushed commercial iron-based denitration catalyst, wherein the substances and proportions of the substances are as follows: pd: iron-based catalyst = 0.1%:0.1%:99.8% (mass percent, all relevant proportions of the examples of the application are not mass percent). After 8 hours of sealed impregnation, the mixture is dried for 3 hours at 120 ℃, heated to 500 ℃ at 3 ℃/min under air atmosphere and calcined for 6 hours, and 1% hydrogen is introduced at 480 ℃ for reduction for 2 hours.

The testing method comprises the following steps:

1mL of the powder catalyst was placed in a fixed bed reactor with an inner diameter of 6mm to perform an activity evaluation test under the following conditions: 16% oxygen, 10% water, 0.4% CO, 200ppm NO, 200-800ppm ammonia, 0-50ppm ethylene, 0-200ppm propane, 0-30ppm dichloromethane, and a reaction space velocity (GHSV) of 10000h ^-1 The reaction temperature is 120-300 ℃.

The test was performed according to the test method described above. Adding NH ₃ At 200ppm, the CO oxidation rate at 130 ℃ is 35.0%, and the NO conversion rate is 11.8%; adding NH ₃ At 800ppm, the CO oxidation rate at 210℃was 92.8%, the NO conversion was 96.7%, and at the same time, the conversion was 35% when 200ppm propane was fed.

Example 2

Other conditions of the preparation method are the same as those of the example 1, and the composition and the proportion of the inactive components are Ag: pd: manganese-based catalyst = 0.9%:0.1%:99.0%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 210℃was 94.6% and the NO conversion was 89.9%.

Example 3

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Pt: mn: vanadium-based catalyst = 0.1%:0.1%:99.8%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 210℃was 88.6% and the NO conversion was 93.2%.

Example 4

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Rh: ce: vanadium-based catalyst = 0.05%:0.1%:99.85%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 240℃was 81.8% and the NO conversion was 86.2%.

Example 5

Other conditions of the preparation method are the same as those of the example 1, and the composition and the proportion of the inactive components are as follows: cr: vanadium-based catalyst = 0.05%:0.2%:99.75%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 210℃was 74.8% and the NO conversion was 66.8%.

Example 6

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Pt: ag: manganese-based catalyst = 0.05%:1.0%:98.95%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 180℃was 99.1% and the NO conversion was 83.1%.

Example 7

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Pd: cu: mn: iron-based catalyst = 0.1%:0.05%:0.05%:98.95%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 210℃was 93.5% and the NO conversion was 88.7%.

Example 8

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Pt: cr: manganese-based catalyst = 0.1%:0.2%:98.7%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 240 ℃ is 99.8%, and the NO conversion rate is 91.2%; at the same time, 200ppm of methylene chloride was introduced, with a conversion of 49.2%.

Example 9

Other conditions of the preparation method are the same as in example 1, and the composition and the proportion of the inactive components are Pd: ag: iron-based catalyst calcined precursor = 0.01%:2.0%:98.95%.

The test was performed according to the test method of example 1. Adding NH ₃ At 800ppm, the CO oxidation rate at 150℃was 98.8% and the NO conversion was 95.2%.

Example 10

The preparation method was otherwise the same as in example 1 except that the support was 15cm x 100cm honeycomb iron-based catalyst.

The catalyst was cut to the desired size and tested according to the following test method:

taking 5cm x 5cm square catalyst to be vertically placed, wherein the height is 100cm, placing the catalyst in a fixed bed reactor to perform activity evaluation test experiments, and the experimental conditions are as follows: 16% of oxygen, 10% of water, 0.4% of carbon monoxide, 200ppm of nitric oxide, 200-800ppm of ammonia, 0-50ppm of ethylene, 0-100ppm of propane, 0-30ppm of methylene dichloride, 3000h-1 of reaction space velocity (GHSV) and 120-300 ℃.

Adding NH ₃ At 200ppm, the CO oxidation rate at 130 ℃ is 46%, and the NO conversion rate is 14.9%; adding NH ₃ At 800ppm, the CO oxidation rate at 210 ℃ is 83.3% and the NO conversion rate is 74.7%; at the same time, 200ppm of propane was fed in, with a conversion of 43.1%.

Example 11

Respectively preparing copper nitrate solid, palladium nitrate and sodium citrate solid into aqueous solutions, adding deionized water, and uniformly mixing, wherein the substances and proportions are as follows: pd: sodium citrate = 1:1:5.

the preparation was carried out using the apparatus shown in fig. 1, and specifically as follows:

the high-voltage electrostatic generator 1 is respectively connected with the coaxial atomizing nozzle 2 and the catalyst carrier 3, the catalyst carrier 3 adopts a honeycomb iron-based catalyst with the diameter of 5cm and the diameter of 100cm, the mixed salt solution 4 is adsorbed on the catalyst carrier 3 after being atomized under the action of the high-pressure pump 5, the concentration of the solution and the total solution amount are controlled, the electrostatic voltage is 20KV, the carrying gas 6 is air, the gas amount is 1L/min, and the content of active components in each sampling point is ensured to be as high as Cu: pd: carrier = 0.1%:0.1%: near 99.8%. Drying at room temperature for 24 hours, heating to 500 ℃ at 3 ℃/min under air atmosphere, and calcining for 6 hours.

The catalyst was cut to the desired size and tested according to the test method provided in example 10. Adding NH ₃ At 200ppm, the CO oxidation rate at 130 ℃ is 52%, and the NO conversion rate is 15.5%; adding NH ₃ At 800ppm, the CO oxidation rate at 210 ℃ is 85.9%, and the NO conversion rate is 81.8%; at the same time, 200ppm of propane was fed in, with a conversion of 44.2%.

Example 12

Other conditions of the preparation method were the same as in example 11. The catalyst was cut to the desired size, a 50cm high inlet end catalyst was used as the honeycomb manganese-based catalyst, and a 50cm high outlet end catalyst was prepared and tested according to the test method provided in example 10. Adding NH ₃ At 350ppm, the CO oxidation rate at 210 ℃ is 83.9%, and the NO conversion rate is 80.8%; at the same time, 200ppm of propane was fed in, with a conversion of 40.6%.

Example 13

Respectively preparing copper nitrate, palladium nitrate and sodium citrate solid into aqueous solutions, adding deionized water, and uniformly mixing, wherein the substance types and proportions of the copper nitrate, the palladium nitrate and the sodium citrate solid are as follows: pd: sodium citrate = 1:1:5. the high-voltage electrostatic generator 1 is respectively connected with the coaxial atomizing nozzle 2 and the catalyst carrier 3, the catalyst carrier 3 adopts a honeycomb vanadium-based catalyst with the thickness of 5cm and the thickness of 100cm, the electrostatic voltage is 16KV, the carrier gas 6 is air, and the gas quantity is 0.5L/min. The mixed salt solution 4 is atomized by a high-pressure pump 5 and then adsorbed on a catalyst carrier 3, the concentration of the solution and the total solution amount are controlled, active components of all sampling points are taken, a first sampling point 7 is 25cm away from an atomization adsorption inlet, and Cu: pd: carrier = 0.2%:0.2%:99.6%, second sampling point 8 at 50cm from atomization adsorption inlet, cu: pd: carrier = 0.09%:0.09%:99.82%, third sampling point 9 at 75cm from the atomization adsorption inlet, cu: pd: carrier = 0.02%:0.02%: 99.96%. Drying at room temperature for 24 hours, heating to 500 ℃ at 3 ℃/min under air atmosphere, and calcining for 6 hours. The catalyst was cut to the desired size and tested according to the test method provided in example 10, with the end with the higher concentration of the components placed on the outlet side. Adding NH ₃ At 300ppm, the CO oxidation rate at 240 ℃ is 98.3%, and the NO conversion rate is 92.8%; at the same time, when 200ppm of propane is introduced, the conversion rate is 53.6%; at the same time, when 100ppm of ethylene is introduced, the conversion rate is 41.0 percent; at the same time, 50ppm of methylene chloride was introduced, the conversion was 35.6%.

Example 1 and example 10 both show that the catalyst pair NH ₃ Has higher oxidation performance, which affects NH ₃ NO reaction proceeds and high NH ₃ Oxidation of (2) can also inhibit the progress of CO oxidation.

Example 11 shows that the catalyst subjected to the atomization adsorption is better than the impregnation method compared with example 10, which may result from a more uniform distribution of the catalyst active components.

Example 12 As compared with example 11, it can be seen that the combined use of the catalysts greatly reduces NH of the process described in example 11 under similar conditions of CO oxidation, NO reduction, etc ₃ Consumption.

Example 14

The embodiment provides a layered combination catalyst, which comprises a diatomic catalyst for removing smoke pollutants and NH ₃ -an SCR catalyst.

The catalyst may be any of the above examples 1 to 13 with NH ₃ SCR catalyst layering is used in combination.

As shown in fig. 2, the usage method may be as follows:

after the heat of the flue gas is primarily recovered through the heat exchanger 10, the flue gas is heated through the hot blast stove 11, is mixed with ammonia gas sprayed by the ammonia spraying system 12, enters the denitration catalyst bed 13 for denitration reaction, and is discharged cleanly after the heat is recovered through the heat exchanger 10. The catalyst in the tail end denitration catalyst bed 14 is changed into the gradient distribution improved denitration catalyst 15 (the diatomic catalyst for removing the smoke pollutants provided by the application), wherein the catalyst with the low load concentration is placed in the upward direction, carbon monoxide and/or low carbon hydrocarbon in the smoke can be oxidized at the same time of denitration, and the oxidation heat release can replace the supplementary heat of the hot blast stove 11 or reduce the load thereof, so that the energy consumption is reduced. When the homogeneous phase improved denitration catalyst 16 is adopted, the original commercial denitration catalyst 17 can be adopted in the upper half layer of the catalyst in the tail end denitration catalyst bed 14, and the homogeneous phase improved denitration catalyst 16 is adopted in the lower half layer, so that the problem of ammonia oxidation can be partially relieved, but the oxidation rate of carbon oxide and/or low-carbon hydrocarbon is slightly reduced.

Note that the technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be regarded as the scope of the description. The foregoing examples represent only a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims

1. A diatomic catalyst for flue gas pollutant removal, comprising a catalyst carrier and a first metal and a second metal supported on the catalyst carrier;

2. The diatomic catalyst for flue gas pollutant removal according to claim 1, characterized in that the first metal represents 0.01% -0.1% of the total mass of the diatomic catalyst and the second metal represents 0.01% -2% of the total mass of the diatomic catalyst.

3. The diatomic catalyst for flue gas pollutant removal according to claim 1, characterized in that the loading concentration of the first metal and the second metal on different sites of the catalyst carrier is the same or distributed in a gradient.

4. The diatomic catalyst for flue gas pollutant removal according to claim 1, characterized in that the catalyst carrier is selected from the group consisting of finished catalysts or catalyst carriers that are not loaded with active metals;

the catalyst carrier is honeycomb, plate-shaped or corrugated.

5. The diatomic catalyst for flue gas pollutant removal according to any of claims 1 to 4, characterized in that the combination of the first metal and the second metal is any of pd+cu, pd+ag, pt+mn, rh+ce, au+cr, pd+cu+mn and pt+ag.

6. A method of preparing a diatomic catalyst for flue gas pollutant removal as recited in any one of claims 1 to 5, comprising:

7. The method for preparing a diatomic catalyst for flue gas contaminant removal according to claim 6, wherein the method of loading comprises a dipping or electrostatic spraying method;

when the electrostatic spraying method is used for carrying out the loading, the salt of the first metal and the salt of the second metal are uniformly or gradient distributed on the catalyst carrier by adjusting the voltage and the gas carrying capacity.

8. The method for preparing a diatomic catalyst for flue gas pollutant removal according to claim 6, wherein one or more of the following conditions are satisfied:

b. the calcining temperature is 480-500 ℃ and the calcining time is 4-8h;

c. the reducing atmosphere includes an atmosphere containing hydrogen;

e. the reduction temperature is 480-500 ℃ and the time is 1-3h.

9. A layered combination of catalysts comprising a layered diatomic catalyst for flue gas pollutant removal according to any of claims 1 to 5 and NH ₃ -an SCR catalyst.

10. Use of a layered combination of catalysts according to claim 9 for the oxidation of CO, lower hydrocarbons and removal of nitrogen oxides.