Catalyst for catalyzing hydrogen peroxide to oxidize NO and preparation method thereof

Abstract

The invention belongs to the technical field of flue gas denitration, and particularly relates to a catalyst for catalyzing hydrogen peroxide to oxidize NO and a preparation method thereof, according to the structural characteristics of light weight, porosity and certain mechanical strength of foam concrete and the characteristics that most of oxidation-process flue gas denitration catalysts are powdery and cannot be directly filled, or the filling mass transfer resistance is relatively large. The two are combined, and the characteristics of the waste foam concrete are fully utilized. On one hand, a recycling way is provided for the waste foam concrete; on the other hand, a loose and porous carrier is provided for the powdery iron-based catalyst, and the possibility is provided for realizing the industrialization of flue gas denitration by an oxidation method. The method is simple and easy to operate, high in practicability, remarkable in social benefit, environmental protection benefit and economic benefit and easy to industrially popularize and apply.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas denitration, and in particular to a catalyst for catalyzing the oxidation of NO by hydrogen peroxide and a preparation method thereof. Background Art

[0002] Foam concrete is a new type of lightweight thermal insulation material, which is mainly used to fill non-pressure-bearing walls of buildings. It is light and easy to install, and has the functions of thermal insulation and sound absorption. After the demolition of buildings, the discarded foam concrete blocks are generally buried or piled up, which occupies a large area and wastes resources. There is an urgent need for a method to recycle the discarded foam concrete. Scholars have done a lot of research on the resource utilization of discarded foam concrete.

[0003] A 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, first crushes the waste aerated blocks by cone plates, and further crushes the waste aerated blocks by crushing rollers. Finally, the waste foamed concrete is reused in the form of building aggregates. The process has a relatively simple idea for recycling foamed concrete, and the influence of the reused foamed concrete on the performance of cementitious materials needs to be further explored.

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

[0005] The Chinese patent application with publication number CN110981538A discloses a method for preparing sound insulation materials from waste foam concrete, which uses surfactants to reactivate waste foam mixed concrete to improve the internal foam structure, uses additives to increase the iron content, deposits, and then calcines to destroy the internal foam structure and increase the pore structure. At the same time, the polymer is modified by mixed monomers to enhance water resistance, and finally mixed with an acid solution. The formed ions are adsorbed on the particle surface under the action of the polymer, which improves the sound resistance and sound insulation effect of the pores, forms a rich microporous structure, and improves the sound insulation effect. This process increases the added value of waste foam concrete, but the preparation method is relatively complicated and difficult to achieve industrial production.

[0006] In summary, the current recycling process of waste foam concrete mainly uses it as a filler or recycles it using its complex porous structure, which does not maximize the structural characteristics of foam concrete. The common oxidation flue gas denitrification catalysts (α-Fe2O3, nZVI, Fe3O4, Fe2(MoO4)3 and Fe2(SO4)3, etc.) have high NO removal capacity, but they are mainly in powder form, and the mass transfer resistance is large when filling them 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 can theoretically be used as a carrier for the above iron-based catalysts. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention uses the loaded iron-based catalyst of foam concrete for oxidation flue gas denitrification according to the characteristics of foam concrete, and provides a low-cost and high-value utilization method for waste foam concrete.

[0008] According to one aspect of the present invention, the present invention provides the following technical solution: A method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide comprises the following steps: S1, crushing and screening the waste foam concrete and then immersing it in a slurry containing an iron-based catalyst; 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.

[0009] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in step S1, the density of the waste foam concrete is less than 600 kg / m 3 .

[0010] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, wherein: in the step S1, the crushing is one or more of jaw crushing, cone crushing, and impact crushing.

[0011] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, in the step S1, the sieved 0.5-3 cm foam concrete fine particles are immersed in a slurry containing an iron-based catalyst as a carrier of the iron-based catalyst.

[0012] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in step S1, the iron-based catalyst is Fe2O3, Fe2(MoO4)3, nZVI(FeO), Fe2(SO4)3, La 1-xCa x FeO3, α-FeOOH, Fe 2.5 Ti 0.5 O4 and one or more of steel slag flue gas desulfurization slurry.

[0013] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, wherein: in the step S1, the solid content of the slurry containing the iron-based catalyst is >5wt%.

[0014] As a preferred embodiment of the method for preparing 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 to 360 minutes.

[0015] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to the present invention, wherein: in the step S1, the immersion is carried out under centrifugal conditions, and the centrifugal speed is 200-1000 r / min.

[0016] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, wherein: in the step S2, liquid on the surface of the foamed concrete is removed by centrifugation, and the centrifugal speed is 200-1000 r / min.

[0017] As a preferred embodiment of the method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, wherein: in the step S2, the drying is direct drying, spray drying or freeze drying.

[0018] According to another aspect of the present invention, the present invention provides the following technical solution: A catalyst for catalyzing the oxidation of NO by hydrogen peroxide is prepared by the above preparation method.

[0019] As a preferred embodiment of the catalyst for catalyzing the oxidation of NO by hydrogen peroxide described in the present invention, the catalyst is foamed concrete particles loaded with an iron-based catalyst.

[0020] According to another aspect of the present invention, the present invention provides the following technical solution: A method for treating flue gas containing NO, using the above catalyst to treat the reaction gas.

[0021] As a preferred embodiment of the method for treating NOx-containing flue gas described in the present invention, the reaction gas is a mixed gas of gasified hydrogen peroxide and NOx-containing flue gas; the NOx-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 plants, waste heat flue gas from chemical plants, and waste heat flue gas from cement plants.

[0022] As a preferred embodiment of the method for treating NO-containing flue gas of the present invention, the treatment temperature is 150-350°C.

[0023] The beneficial effects of the present invention are as follows: The present invention proposes a catalyst for catalyzing the oxidation of NO by hydrogen peroxide and a preparation method thereof. Based on the structural characteristics of foamed concrete, which is light, porous, and has a certain mechanical strength, and the characteristics that the catalyst for flue gas denitration by oxidation is mostly in powder form and cannot be directly filled, or the filling mass transfer resistance is large, the two are combined and the characteristics of waste foamed concrete are fully utilized. On the one hand, it provides a resource recovery path for waste foamed concrete; on the other hand, it provides a loose and porous carrier for powdered iron-based catalysts, making it possible to realize the industrialization of flue gas denitration by oxidation. The present invention is simple and easy to operate, has strong practicality, and has significant social, environmental and economic benefits, and is easy to promote and apply industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 The present invention is a schematic flow chart of a method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide.

[0026] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, the present invention provides a method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide, comprising the following steps: S1, crushing and screening the waste foam concrete and then immersing it in a slurry containing an iron-based catalyst; 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.

[0029] According to the characteristics of foamed concrete, the invention uses the loaded iron-based catalyst for oxidation flue gas denitration, and provides a low-cost and high-value utilization approach for waste foamed concrete.

[0030] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0031] Example 1 A method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide comprises the following steps: S1, density 573kg / m 3 The waste foam concrete is crushed and screened, and the 0.5-3 cm foam concrete fine particles after screening are soaked in the slurry containing iron-based catalyst; the slurry containing iron-based catalyst is steel slag flue gas desulfurization tail liquid with a solid content of 10%, and is soaked for 100 minutes under the condition of a centrifugal speed of 500r / min; S2. Perform centrifugal and drying treatments, centrifuge and dehydrate at 200 r / min, and then dry in an oven at 105° C. 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.

[0032] Example 2 The difference from Example 1 is that the density of the waste foam concrete is 358 kg / m 3 .

[0033] Example 3 The difference from Example 1 is that the density of the waste foam concrete is 232 kg / m 3 .

[0034] Example 4 The difference from Example 1 is that the slurry containing the iron-based catalyst is a Fe2(MoO4)3 slurry with a solid content of 10%.

[0035] Example 5 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%.

[0036] Example 6 The difference from Example 1 is that the slurry containing the iron-based catalyst is steel slag flue gas desulfurization tail liquid with a solid content of 20%.

[0037] Example 7 The difference from Example 1 is that the slurry containing the iron-based catalyst is steel slag flue gas desulfurization tail liquid with a solid content of 30%.

[0038] Example 8 The difference from Example 1 is that the slurry containing the iron-based catalyst is steel slag flue gas desulfurization tail liquid with a solid content of 10%; after centrifugal dehydration, it is immersed in 10% steel slag flue gas desulfurization tail liquid again.

[0039] Example 9 The difference from Example 1 is that the drying is carried out by spray drying.

[0040] Comparative Example 1 The foamed concrete particles obtained by screening in Example 1 were taken without performing other operations.

[0041] Comparative Example 2 The foamed concrete particles obtained by screening in Example 2 were taken without performing other operations.

[0042] Comparative Example 3 The foamed concrete particles obtained by screening in Example 3 were taken without performing other operations.

[0043] Comparative Example 4 The iron-based catalyst obtained by drying the steel slag flue gas desulfurization tail liquid used in Example 1 was taken without performing other operations.

[0044] Comparative Example 5 Take the Fe2(MoO4)3 powder iron-based catalyst in Example 4 without performing other operations.

[0045] Comparative Example 6 The α-FeOOH powder iron-based catalyst in Example 5 was taken without performing other operations.

[0046] Performance Test: The catalysts obtained in Examples 1-9 and Comparative Examples 1-6 were tested for their performance in catalyzing the oxidation of NO with hydrogen peroxide, and the test method was as follows: The test was conducted in a fixed bed reactor, where the simulated flue gas was preheated and mixed with gasified hydrogen peroxide before being introduced into the reactor; the reaction temperature was 200°C, the total flow rate of the reaction gas was 1L / min, and the superficial velocity of the reaction was 40000h -1 ; The composition of the simulated flue gas is NO: 1000ppm, O2: 10%. N2 is the balance gas; The hydrogen peroxide is gasified through a bypass and then mixed with the simulated flue gas; the gasification temperature of the hydrogen peroxide is 200°C.

[0047] The performance test results of the catalysts prepared in Examples 1-9 and Comparative Examples 1-6 for catalytic oxidation of NO with hydrogen peroxide are shown in the following table.

[0048] As can be seen from the above table, the method described in the embodiment of the present invention loads the iron-based catalyst 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 the catalyst prepared by the method described in Comparative Examples 1-6. The catalyst prepared by the method described in the embodiment of the present invention has a NO conversion rate of ≥90%. The present invention makes full use of the characteristics of waste foam concrete that is porous, light, and has a certain mechanical strength, and uses it as an iron-based catalyst to improve the catalytic performance of the iron-based catalyst and reduce the mass transfer resistance during the filling process of the powdered catalyst. The preparation process is simple, the preparation cost is low, and it is green and environmentally friendly, which provides the possibility of realizing the industrialization of flue gas denitrification by oxidation.

[0049] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied 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, crushing and screening the waste foam concrete and then immersing it in a slurry containing an iron-based catalyst; 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 the step S1, the sieved foamed concrete fine particles of 0.5-3 cm are immersed in a slurry containing an iron-based catalyst.

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 S1, the iron-based catalyst is 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 steel slag flue gas desulfurization slurry.

5. The method for preparing a catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 1, characterized in that: In the step S1, the solid content of the slurry containing the iron-based catalyst is >5wt%; and the soaking time is 30-360min.

6. 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.

7. 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 6.

8. The catalyst for catalyzing the oxidation of NO by hydrogen peroxide according to claim 7, characterized in that: The catalyst is foamed concrete particles loaded with an iron-based catalyst.

9. 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 7 to 8.

10. The method for treating NO-containing flue gas according to claim 9, 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