A catalyst for catalyzing the oxidation of NO by hydrogen peroxide and a preparation method thereof

Abstract

The present invention belongs to the technical field of flue gas denitration, and specifically relates to a catalyst for catalytic oxidation of NO by hydrogen peroxide and a preparation method thereof. According to the structural characteristics of foamed concrete, such as light weight, porous structure and certain mechanical strength, and the fact that most of the oxidation method flue gas denitration catalysts are in powder form and cannot be directly filled, or have a large mass transfer resistance during filling, the two are combined, and the characteristics of waste foamed concrete are fully utilized. On the one hand, it provides a resource utilization way for waste foamed concrete; on the other hand, it provides a loose and porous carrier for the powdered iron-based catalyst, making it possible to realize the industrialization of the oxidation method for flue gas denitration. The present invention is simple and easy to operate, has strong practicability, and has remarkable social, environmental and economic benefits, and is easy to be popularized and applied industrially.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas denitrification, and specifically to a catalyst for catalytic oxidation of NO by hydrogen peroxide and a preparation method thereof. Background Art

[0002] Foamed concrete is a new type of lightweight thermal insulation material, which is mainly filled in non-load-bearing walls of buildings and has the functions of being light in weight, easy to install, heat-insulating and sound-absorbing. After a building is demolished, the waste foamed concrete blocks are generally disposed of by burying or stacking, which occupies a large area and wastes resources. There is an urgent need for a method for recycling waste foamed concrete. Scholars have done a lot of research on the resource utilization of waste foamed concrete.

[0003] Chinese patent application with publication number CN118254277A discloses a raw material mixing device and method for producing low-carbon concrete from waste aerated blocks. The process mainly produces waste aerated blocks into building aggregates. The waste aerated blocks are first crushed by a conical plate, and then further crushed by crushing rollers. Finally, the waste foamed concrete is reused in the form of building aggregates. The recycling idea of this process for foamed concrete is relatively simple, and the influence of the recycled foamed concrete on the performance of the cementitious material needs to be further explored.

[0004] Chinese patent application with publication number CN106396733A discloses a thermal insulation material prepared from nano-modified waste foamed concrete and a preparation method thereof. The thermal insulation material prepared from nano-modified waste foamed concrete includes the following raw materials by mass percentage: 25-50% of fly ash, 10-30% of 425 cement, 25-50% of waste foamed concrete powder, 0.9-2% of foaming agent, 0.7-1% of nano-modifying agent, 1-2% of sodium borate, and 0.9-4% of naphthalene sulfonic acid formaldehyde high polymer. This process adds waste foamed concrete as a filler to the preparation of existing thermal insulation materials. This process has a large amount of cement used and a large amount of additives used, and the product preparation cost is relatively high.

[0005] Chinese patent application with publication number CN110981538A discloses a method for preparing sound insulation materials from waste foamed concrete. The method uses a surfactant to reactivate the waste foam concrete to improve the internal foam structure, increases the iron content therein by using an additive for deposition, and then calcines it to destroy the internal foam structure and increase the pore structure. At the same time, the polymer is modified by using a mixed monomer to enhance the water resistance. Finally, it is mixed with an acid solution, and the formed ions are adsorbed on the particle surface under the action of the polymer, improving the sound blocking and sound insulation effects of the pores and forming a rich microporous structure to improve the sound insulation effect. This process increases the added value of waste foamed concrete, but the preparation method is relatively complex and it is difficult to realize industrial production.

[0006] In summary, the current recycling process of waste foam concrete mainly uses it as a filler or utilizes its complex porous structure for recycling, without maximizing the utilization of the structural characteristics of foam concrete. Currently common oxidation flue gas denitration catalysts (such as α-Fe2O3, nZVI, Fe3O4, Fe2(MoO4)3, and Fe2(SO4)3, etc.) have high NO removal capabilities, but they are mainly in powder form, and the mass transfer resistance is relatively large when they are filled into the reactor. It is necessary to study a carrier to load them. Waste foam concrete has the characteristics of light weight, porosity, and high water absorption, and theoretically can be used as the carrier of the above iron-based catalysts. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention uses waste foam concrete loaded with iron-based catalysts for oxidation flue gas denitration according to the characteristics of foam concrete, and provides a low-cost and high-value utilization approach for waste foam concrete.

[0008] According to one aspect of the present invention, the present invention provides the following technical solutions:

[0009] A preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide, comprising the following steps:

[0010] S1. Crush and screen the waste foam concrete, and then soak it in a slurry containing an iron-based catalyst;

[0011] S2. Perform centrifugation and drying treatments to obtain porous foam concrete particles rich in iron-based catalysts, which are used as catalysts for catalyzing the oxidation of NO by hydrogen peroxide.

[0012] As a preferred scheme of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the density of the waste foam concrete < 600 kg / m 3 .

[0013] As a preferred scheme of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the crushing is one or several of jaw crushing, cone crushing, and impact crushing.

[0014] As a preferred scheme of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the 0.5 - 3 cm fine particles of foam concrete after screening are soaked in the slurry containing an iron-based catalyst and used as the carrier of the iron-based catalyst.

[0015] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the iron-based catalyst is one or more of Fe2O3, Fe2(MoO4)3, nZVI(FeO), Fe2(SO4)3, La 1-x Ca x FeO3, α-FeOOH, Fe 2.5 Ti 0.5 O4, and one or more of the steel slag flue gas desulfurization slurry.

[0016] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the solid content of the slurry containing the iron-based catalyst > 5 wt%.

[0017] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the soaking time is 30 - 360 min.

[0018] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the soaking is carried out under centrifugation conditions, and the centrifugation speed is 200 - 1000 r / min.

[0019] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S2, the liquid on the surface of the foamed concrete is removed by centrifugation, and the centrifugation speed is 200 - 1000 r / min.

[0020] As a preferred embodiment of the preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S2, the drying is direct drying, spray drying or freeze drying.

[0021] According to another aspect of the present invention, the present invention provides the following technical solution:

[0022] A catalyst for catalyzing the oxidation of NO by hydrogen peroxide, which is prepared by the above preparation method.

[0023] As a preferred embodiment of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: the catalyst is foamed concrete particles loaded with an iron-based catalyst.

[0024] According to another aspect of the present invention, the present invention provides the following technical solution:

[0025] A method for treating flue gas containing NO, wherein the reaction gas is treated with the above catalyst.

[0026] As a preferred embodiment of the method for treating NO-containing flue gas according to the present invention, wherein: the reaction gas is a mixed gas of vaporized hydrogen peroxide and NO-containing flue gas; the NO-containing flue gas is one or more of waste heat flue gas from coal-fired power plants, waste heat flue gas from lime kilns, sintering flue gas from steel mills, waste heat flue gas from chemical plants, and waste heat flue gas from cement plants.

[0027] As a preferred embodiment of the method for treating NO-containing flue gas according to the present invention, wherein: the temperature of the treatment is 150~350 °C.

[0028] The beneficial effects of the present invention are as follows:

[0029] The present invention provides a catalyst for catalyzing the oxidation of NO by hydrogen peroxide and a preparation method thereof. According to the structural characteristics of lightweight, porous, and having certain mechanical strength of foam concrete, and the characteristics that most of the oxidation method flue gas denitration catalysts are powdery and cannot be directly filled, or the mass transfer resistance during filling is relatively large, the two are combined and the characteristics of waste foam concrete are fully utilized. On the one hand, it provides a resource utilization way for waste foam concrete; on the other hand, it provides a porous carrier for the powdery iron-based catalyst, making it possible to realize the industrialization of the oxidation method for flue gas denitration. The present invention is simple and easy to operate, has strong practicability, significant social, environmental, and economic benefits, and is easy to be popularized and applied industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0031] Figure 1 It is a schematic flow chart of the preparation method of the catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention.

[0032] The realization of the object, functional characteristics, and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] Such as Figure 1As shown in the figure, the present invention provides a preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide, comprising the following steps:

[0035] S1. Crush and screen the waste foam concrete, and then soak it in a slurry containing an iron-based catalyst;

[0036] S2. Perform centrifugation and drying to obtain foam concrete particles rich in porous iron-based catalysts, which are used as catalysts for catalyzing the oxidation of NO by hydrogen peroxide.

[0037] According to the characteristics of foam concrete, the present invention loads an iron-based catalyst on it for flue gas denitrification by the oxidation method, and provides a low-cost and high-value utilization way for waste foam concrete.

[0038] The technical solution of the present invention will be further described below with specific embodiments.

[0039] Example 1

[0040] A preparation method of a catalyst for catalyzing the oxidation of NO by hydrogen peroxide, comprising the following steps:

[0041] S1. Crush and screen the waste foam concrete with a density of 573 kg / m 3 ³, and soak the screened fine foam concrete particles with a size of 0.5 - 3 cm in a slurry containing an iron-based catalyst; the slurry containing an iron-based catalyst is the steel slag flue gas desulfurization tail liquid with a solid content of 10%, and soak it for 100 min under the condition of a centrifugal speed of 500 r / min;

[0042] S2. Perform centrifugation and drying, centrifuge and dehydrate at 200 r / min, and then dry in an oven at 105 °C to obtain foam concrete particles rich in porous iron-based catalysts, which are used as catalysts for catalyzing the oxidation of NO by hydrogen peroxide.

[0043] Example 2

[0044] The difference from Example 1 is that the density of the waste foam concrete is 358 kg / m 3 .

[0045] Example 3

[0046] The difference from Example 1 is that the density of the waste foam concrete is 232 kg / m 3 .

[0047] Example 4

[0048] The difference from Example 1 is that the slurry containing an iron-based catalyst is the Fe2(MoO4)3 slurry with a solid content of 10%.

[0049] Example 5

[0050] The difference from Example 1 is that the slurry containing the iron-based catalyst is an α-FeOOH slurry with a solid content of 10%.

[0051] Example 6

[0052] The difference from Example 1 is that the slurry containing the iron-based catalyst is the steel slag flue gas desulfurization tail liquid with a solid content of 20%.

[0053] Example 7

[0054] The difference from Example 1 is that the slurry containing the iron-based catalyst is the steel slag flue gas desulfurization tail liquid with a solid content of 30%.

[0055] Example 8

[0056] The difference from Example 1 is that the slurry containing the iron-based catalyst is the steel slag flue gas desulfurization tail liquid with a solid content of 10%; after centrifugal dehydration, it is soaked in the steel slag flue gas desulfurization tail liquid with a solid content of 10% again.

[0057] Example 9

[0058] The difference from Example 1 is that spray drying is used for drying.

[0059] Comparative Example 1

[0060] Take the foamed concrete particles obtained by sieving in Example 1 without performing other operations.

[0061] Comparative Example 2

[0062] Take the foamed concrete particles obtained by sieving in Example 2 without performing other operations.

[0063] Comparative Example 3

[0064] Take the foamed concrete particles obtained by sieving in Example 3 without performing other operations.

[0065] Comparative Example 4

[0066] Take the iron-based catalyst obtained by drying the steel slag flue gas desulfurization tail liquid used in Example 1 without performing other operations.

[0067] Comparative Example 5

[0068] Take the Fe2(MoO4)3 powder iron-based catalyst in Example 4 without performing other operations.

[0069] Comparative Example 6

[0070] Take the α-FeOOH powder iron-based catalyst in Example 5 without performing other operations.

[0071] Performance test:

[0072] The catalysts obtained in Examples 1-9 and Comparative Examples 1-6 were tested for their performance in catalyzing the oxidation of NO by hydrogen peroxide. The test method is as follows:

[0073] The test was carried out in a fixed-bed reactor. The simulated flue gas was preheated and then mixed with vaporized hydrogen peroxide and introduced into the reactor. The reaction temperature was 200 °C, the total gas flow rate of the reaction gas was 1 L / min, and the empty tower velocity of the reaction was 40000 h -1 ;

[0074] The composition of the simulated flue gas was NO: 1000 ppm, O2: 10%. N2 was the balance gas;

[0075] The hydrogen peroxide was vaporized through a bypass and then mixed with the simulated flue gas. The vaporization temperature of the hydrogen peroxide was 200 °C.

[0076] The test results of the catalysts prepared in Examples 1-9 and Comparative Examples 1-6 for catalyzing the oxidation of NO by hydrogen peroxide are shown in the following table.

[0077]

[0078] As can be seen from the above table, in the method described in the embodiments of the present invention, the iron-based catalyst is loaded onto the waste foam concrete, and the catalytic activity of the catalyst for catalyzing the oxidation of NO by hydrogen peroxide is significantly better than that of the catalysts prepared by the methods described in Comparative Examples 1-6. For the catalyst prepared by the method described in the embodiments of the present invention, the NO conversion rate ≥ 90%. The present invention makes full use of the characteristics of the waste foam concrete, such as being porous, light in weight, and having a certain mechanical strength, and loading the iron-based catalyst on it improves the catalytic performance of the iron-based catalyst and reduces the mass transfer resistance during the filling process of the powdery catalyst. This preparation process is simple, has a low preparation cost, and is green and environmentally friendly, providing the possibility for the industrialization of oxidative flue gas denitrification.

[0079] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural transformations made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a catalyst for catalyzing the oxidation of NO with hydrogen peroxide, characterized in that: The steps include: S1. The waste foamed concrete is crushed and screened, and the screened foamed concrete fine particles of 0.5-3 cm are immersed in a slurry containing an iron-based catalyst; the solid content of the slurry containing the iron-based catalyst is greater than 5wt%; and the immersion time is 30-360 min; S2. Perform centrifugation and drying to obtain porous foamed concrete particles rich in iron-based catalysts, which are used as catalysts for catalyzing the oxidation of NO by hydrogen peroxide.

2. The method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 1, characterized in that: In step S1, the density of the waste foam concrete is less than 600 kg / m 3 .

3. The method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 1, characterized in that: In step S1, the iron-based catalyst is Fe2O3, Fe2(MoO4)3, nZVI, Fe2(SO4)3, La 1-x Ca x FeO3, α-FeOOH, Fe 2.5 Ti 0.5 O4 and one or more of steel slag flue gas desulfurization slurry.

4. The method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 1, characterized in that: In step S2, the centrifugal speed is 200-1000 r / min.

5. A catalyst for catalyzing the oxidation of NO by hydrogen peroxide, characterized in that: The preparation method is described in any one of claims 1 to 4.

6. The catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 5, characterized in that: The catalyst is foamed concrete particles loaded with an iron-based catalyst.

7. A method for treating NO-containing flue gas, characterized in that: The reaction gas is treated using the catalyst for catalyzing the oxidation of NO by hydrogen peroxide as described in any one of claims 5-6.

8. The method for treating NO-containing flue gas according to claim 7, characterized in that: The reaction gas is a mixed gas of gasified hydrogen peroxide and NO-containing flue gas; the treatment temperature is 150-350°C.

Images