A sulfur-tolerant ultra-low temperature nitrogen oxide reduction catalyst

Abstract

The application belongs to the technical field of catalysts, and discloses a sulfur-tolerant ultra-low-temperature nitrogen oxide reduction catalyst. A preparation method of the catalyst comprises the following steps: adding TiOSO4 into deionized water, a nitric acid solution, polystyrene microspheres, and adjusting pH to obtain a second suspension; filtering and drying the second suspension to obtain dried precipitate; placing the dried precipitate in a nitrogen atmosphere for calcination treatment to obtain a macroporous TiO2 carrier; adding the macroporous TiO2 carrier into deionized water, adding tin tetrachloride and ferrous sulfate to obtain a first suspension; adding ammonia water into the first suspension, adjusting the pH value of the first suspension, filtering, and drying to obtain dried precipitate; and calcining the dried precipitate to obtain the final catalyst. The catalyst prepared by the application can effectively improve the catalytic efficiency of the catalyst in an ultra-low-temperature environment and can maintain stability during long-term operation.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a nitrogen oxide reduction catalyst, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NOx) contained in flue gas X Nitrogen oxides (NOx), including NO, NO2, and N2O, are the main substances that form acid rain and are also a major factor in the formation of regional PM2.5 and smog. Nitrogen oxides pose a serious threat to the ecological environment and sustainable economic development; therefore, the continuous reduction of nitrogen oxide pollutants is imperative. Selective catalytic reduction (SCR) is widely used due to its simple structure and high catalytic efficiency. However, commonly used vanadium-based nitrogen oxide reduction catalysts have disadvantages such as high reduction reaction temperatures, easy vanadium loss, and the potential for secondary pollution. Meanwhile, non-vanadium-based medium- and low-temperature nitrogen oxide reduction catalysts are limited in practical applications due to their poor sulfur resistance.

[0003] The flue gas temperature in non-power industries is usually below 300℃, and the flue gas temperature in kilns that have completed desulfurization and dust removal is even below 200℃. However, most nitrogen oxide reduction catalysts have the disadvantages of low nitrogen oxide reduction efficiency and poor sulfur resistance under low temperature (<180℃) conditions.

[0004] Therefore, research on nitrogen oxide reduction catalysts has practical application value and environmental protection significance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a sulfur-resistant ultra-low temperature nitrogen oxide reduction catalyst. Research has found that by increasing the pore size of the support, constructing a special acid structure on the catalyst surface, and introducing tin dioxide (SnO2) oxide into the catalyst as an active component, the catalytic efficiency of the catalyst under ultra-low temperature conditions can be effectively improved, and its stability can be maintained during long-term operation.

[0006] On one hand, the present invention relates to a method for preparing a nitrogen oxide reduction catalyst, which includes: adding macroporous TiO2 to deionized water, adding tin tetrachloride and ferrous sulfate to obtain a first suspension;

[0007] Ammonia water was added to the first suspension, the pH value was adjusted, and the solution was filtered, dried, and then calcined to obtain the nitrogen oxide reduction catalyst.

[0008] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the preparation method of the macroporous TiO2 includes: adding TiOSO4 to deionized water, adding nitric acid solution dropwise, adding polystyrene microspheres, stirring evenly, adding ammonia water, and adjusting the pH to obtain a second suspension;

[0009] After filtering and drying, the second suspension is placed in a nitrogen atmosphere for calcination.

[0010] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the pH range of the first suspension is adjusted to 8-9.

[0011] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the pH range of the second suspension obtained by adjusting the pH is 6 to 7.

[0012] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the drying conditions are 120°C for 18 hours.

[0013] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the calcination treatment is carried out by heating to 450°C in a nitrogen atmosphere at a heating rate of 6°C / min and then holding at that temperature for 6 hours.

[0014] Furthermore, in the preparation method of the nitrogen oxide reduction catalyst provided by the present invention, the addition ratio of macroporous TiO2, tin tetrachloride and ferrous sulfate is as follows: 0.69-2.09g of SnCl4·5H2O and 0.6-1.2g of FeSO4 are added to every 15g of macroporous TiO2.

[0015] On the other hand, the present invention relates to a nitrogen oxide reduction catalyst, which is prepared by the above-described method for preparing nitrogen oxide reduction catalysts.

[0016] On the other hand, the present invention relates to the application of the above-mentioned method for preparing nitrogen oxide reduction catalysts in improving the catalytic efficiency of nitrogen oxide reduction.

[0017] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects or advantages:

[0018] (1) The catalyst of this invention uses macroporous TiO2 as a support. The primary factor limiting the application of ultra-low temperature nitrogen oxide reduction is that under ultra-low temperature conditions, sulfur reacts with ammonia to form ammonium bisulfate, which is adsorbed on the catalyst surface, thus causing catalyst deactivation. This invention improves the pore size of the support through directional synthesis, reducing the capillary aggregation phenomenon of ammonium bisulfate. At the same time, by constructing a special surface acid structure of the catalyst, the formation of ammonium bisulfate is reduced, the deposition of ammonium bisulfate in the catalyst channels is inhibited, and the sulfur resistance stability of the catalyst under ultra-low temperature conditions is improved.

[0019] (2) The catalyst of this invention uses a metal FeSO4-SnO2 system supported on TiO2 as the active component. SnO2 oxide is introduced into the catalyst to act as the active component. This oxide has active surface oxygen, which can effectively activate the adsorbed ammonia molecules and significantly improve the activity of the catalyst under ultra-low temperature conditions. The special structure and acidic sites of the FeSO4-SnO2 system give it significant performance advantages over traditional vanadium oxide nitrogen oxide reduction catalysts under ultra-low temperature nitrogen oxide reduction conditions, which can meet the needs of ultra-low temperature industrial flue gas treatment.

[0020] (3) The raw material cost of the present invention is lower than that of traditional vanadium-titanium catalysts.

[0021] (4) Existing ultra-low temperature nitrogen oxide reduction catalysts are mainly manganese-based, and the active components are easily sulfated. The oxide active components of the present invention are not easily sulfated at low temperatures. After long-term sulfur tolerance, no significant changes were found in the microstructure of the catalyst in the sample of the present invention, which explains why the catalyst can maintain stability during long-term operation.

[0022] (5) The preparation and application methods of the catalyst of the present invention are simple and do not require modification of existing equipment, which is conducive to industrial promotion. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a comparison of Example 2, which uses macroporous TiO2 as a carrier, and the synthesis of a conventional titanium carrier, with pore size distribution diagrams.

[0025] Figure 2 This is a microstructure diagram of the nitrogen oxide reduction catalyst of the present invention. Figure 2 a is the SEM image before the long-cycle reaction; Figure 2 b is a SEM image of the sulfur resistance test of the nitrogen oxide reduction catalyst of the present invention after 200h reaction;

[0026] Figure 3 The graph shows the sulfur resistance stability of Example 2 and Comparative Example 2. Detailed Implementation

[0027] Example 1:

[0028] This embodiment provides a nitrogen oxide reduction catalyst and its preparation method.

[0029] Add 50g TiOSO4 to deionized water, add 30% nitric acid solution dropwise, and after it is fully dissolved, add polystyrene microspheres (XFB25 Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), stir evenly to obtain a second suspension, add 26% ammonia water to adjust the pH value of the second suspension to 8, filter to obtain precipitate;

[0030] The obtained precipitate was dried at 120℃ for 18 hours.

[0031] The dried precipitate was placed in a tube furnace and nitrogen gas was introduced. The temperature was increased to 450°C at a rate of 6°C / min and then held for 6 hours for calcination to obtain macroporous TiO2 support.

[0032] Take 15g of macroporous TiO2 and add it to deionized water. After stirring evenly, add 0.69g of SnCl4·5H2O and 0.9g of FeSO4 to obtain the first suspension. Then add ammonia water with a mass concentration of 26% to adjust the pH value of the first suspension to 6. Filter to obtain the precipitate and dry it.

[0033] The dried precipitate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min, and then held at that temperature for 6 hours for calcination to obtain the final catalyst.

[0034] The obtained catalyst was subjected to an atmosphere containing 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, and 20 ppm SO2 at a space velocity of 80,000 h⁻¹. -1 Under the specified conditions, the reduction efficiency of nitrogen oxides is 60% at 140℃, 69% at 160℃, and 90% at 180℃.

[0035] Example 2:

[0036] This embodiment provides a nitrogen oxide reduction catalyst and its preparation method.

[0037] Add 50g TiOSO4 to deionized water, add 30% nitric acid solution dropwise, and after it is fully dissolved, add polystyrene microspheres (XFB25 Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), stir evenly to obtain a second suspension, add 26% ammonia water to adjust the pH value of the second suspension to 8, filter to obtain precipitate;

[0038] The obtained precipitate was dried at 120℃ for 18 hours.

[0039] The dried precipitate was placed in a tube furnace and nitrogen gas was introduced. The temperature was increased to 450°C at a rate of 6°C / min and then held for 6 hours for calcination to obtain macroporous TiO2 support.

[0040] Take 15g of macroporous TiO2 and add it to deionized water. After stirring evenly, add 1.39g of SnCl4·5H2O and 0.9g of FeSO4 to obtain the first suspension. Then add ammonia water with a mass concentration of 26% to adjust the pH value of the first suspension to 7. Filter to obtain the precipitate and dry it.

[0041] The dried precipitate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min, and then held at that temperature for 6 hours for calcination to obtain the final catalyst.

[0042] The obtained catalyst was subjected to an atmosphere containing 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, and 20 ppm SO2 at a space velocity of 80,000 h⁻¹. -1 Under these conditions, the reduction efficiency of nitrogen oxides is 65% at 140℃, 72% at 160℃, and 94% at 180℃.

[0043] Example 3

[0044] This embodiment provides a nitrogen oxide reduction catalyst and its preparation method.

[0045] Add 50g TiOSO4 to deionized water, add 30% nitric acid solution dropwise, and after it is fully dissolved, add polystyrene microspheres (XFB25 Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), stir evenly to obtain a second suspension, add 26% ammonia water to adjust the pH value of the second suspension to 9, filter to obtain precipitate;

[0046] The obtained precipitate was dried at 120℃ for 18 hours.

[0047] The dried precipitate was placed in a tube furnace and nitrogen gas was introduced. The temperature was increased to 450°C at a rate of 6°C / min and then held for 6 hours for calcination to obtain macroporous TiO2 support.

[0048] Take 15g of macroporous TiO2 and add it to deionized water. After stirring evenly, add 2.09g of SnCl4·5H2O and 0.9g of FeSO4 to obtain the first suspension. Then add ammonia water with a mass concentration of 26% to adjust the pH value of the first suspension to 6. Filter to obtain the precipitate and dry it.

[0049] The dried precipitate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min, and then held at that temperature for 6 hours for calcination to obtain the final catalyst.

[0050] The obtained catalyst was subjected to an atmosphere containing 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, and 20 ppm SO2 at a space velocity of 80,000 h⁻¹. -1 Under the specified conditions, the reduction efficiency of nitrogen oxides is 63% at 140℃, 70% at 160℃, and 93% at 180℃.

[0051] Example 4:

[0052] This embodiment provides a nitrogen oxide reduction catalyst and its preparation method.

[0053] Add 50g TiOSO4 to deionized water, add 30% nitric acid solution dropwise, and after it is fully dissolved, add polystyrene microspheres (XFB25 Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), stir evenly to obtain a second suspension, add 26% ammonia water to adjust the pH value of the second suspension to 9, filter to obtain precipitate;

[0054] The obtained precipitate was dried at 120℃ for 18 hours.

[0055] The dried precipitate was placed in a tube furnace and nitrogen gas was introduced. The temperature was increased to 450°C at a rate of 6°C / min and then held for 6 hours for calcination to obtain macroporous TiO2 support.

[0056] Take 15g of macroporous TiO2 and add it to deionized water. After stirring evenly, add 1.39g of SnCl4·5H2O and 0.6g of FeSO4 to obtain the first suspension. Then add ammonia water with a mass concentration of 26% to adjust the pH value of the first suspension to 7. Filter to obtain the precipitate and dry it.

[0057] The dried precipitate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min, and then held at that temperature for 6 hours for calcination to obtain the final catalyst.

[0058] The obtained catalyst was subjected to an atmosphere containing 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, and 20 ppm SO2 at a space velocity of 80,000 h⁻¹. -1 Under these conditions, the reduction efficiency of nitrogen oxides is 58% at 140℃, 65% at 160℃, and 93% at 180℃.

[0059] Example 5:

[0060] This embodiment provides a nitrogen oxide reduction catalyst and its preparation method.

[0061] Add 50g TiOSO4 to deionized water, add 30% nitric acid solution dropwise, and after it is fully dissolved, add polystyrene microspheres (XFB25 Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), stir evenly to obtain a second suspension, add 26% ammonia water to adjust the pH value of the second suspension to 9, filter to obtain precipitate;

[0062] The obtained precipitate was dried at 120℃ for 18 hours.

[0063] The dried precipitate was placed in a tube furnace and nitrogen gas was introduced. The temperature was increased to 450°C at a rate of 6°C / min and then held for 6 hours for calcination to obtain macroporous TiO2 support.

[0064] Take 15g of macroporous TiO2 and add it to deionized water. After stirring evenly, add 1.39g of SnCl4·5H2O and 1.2g of FeSO4 to obtain the first suspension. Then add ammonia water with a mass concentration of 26% to adjust the pH value of the first suspension to 6. Filter to obtain the precipitate and dry it.

[0065] The dried precipitate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min, and then held at that temperature for 6 hours for calcination to obtain the final catalyst.

[0066] The obtained catalyst was subjected to an atmosphere containing 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, and 20 ppm SO2 at a space velocity of 80,000 h⁻¹. -1 Under these conditions, the reduction efficiency of nitrogen oxides is 61% at 140℃, 68% at 160℃, and 96% at 180℃.

[0067] Comparative Example 1:

[0068] The difference between this comparative example and Example 1 is that a commercially available low-temperature V-based catalyst (Anhui Yuanchen Environmental Protection Technology Co., Ltd., using titanium-tungsten powder as a carrier, with a vanadium content of 4% as the active component) was used for nitrogen oxide reduction efficiency testing. The reaction conditions were 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, 20 ppm SO2, and a space velocity of 80,000 h⁻¹. -1 Under the specified conditions, the reduction efficiency of nitrogen oxides was 36% at 140°C, 42% at 160°C, and 75% at 180°C. Commercial catalysts showed lower reduction efficiencies of nitrogen oxides under the same experimental or operating conditions compared to Example 1.

[0069] Comparative Example 2:

[0070] The difference between this comparative example and Example 2 is that a common titanium dioxide catalyst was used as the support. The reduction efficiency of the obtained catalyst was tested under nitrogen oxide conditions: 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, 20 ppm SO2, and a space velocity of 80,000 h⁻¹. -1 Under the specified conditions, the reduction efficiency of nitrogen oxides was 63% at 140℃, 70% at 160℃, and 92% at 180℃. Comparing with Example 2, it can be seen that the activity of Comparative Example 2 is comparable to that of Example 2; however, with increasing time, the NO conversion rate of the catalyst obtained in Comparative Example 2 gradually decreases, indicating that its sulfur resistance stability is significantly lower than that of Example 2. Figure 3 ).

[0071] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for preparing a nitrogen oxide reduction catalyst, characterized in that, include: Macroporous TiO2 was added to deionized water, followed by the addition of tin tetrachloride and ferrous sulfate to obtain the first suspension. Ammonia water was added to the first suspension, the pH value was adjusted to 8-9, and then the solution was filtered, dried, and calcined to obtain the nitrogen oxide reduction catalyst. The preparation method of the macroporous TiO2 includes: adding TiOSO4 to deionized water, adding nitric acid solution dropwise, adding polystyrene microspheres, stirring evenly, adding ammonia water, adjusting the pH to 6-7 to obtain a second suspension; After filtering and drying, the second suspension was placed in a nitrogen atmosphere for calcination. The addition ratio of macroporous TiO2, tin tetrachloride and ferrous sulfate is as follows: 0.69~2.09g of SnCl4·5H2O and 0.6~1.2g of FeSO4 are added to every 15g of macroporous TiO2.

2. The method for preparing the nitrogen oxide reduction catalyst according to claim 1, characterized in that, The drying conditions were all 120℃ for 18 hours.

3. The method for preparing the nitrogen oxide reduction catalyst according to claim 1, characterized in that, In the roasting process, the temperature is raised to 450°C at a heating rate of 6°C / min in a nitrogen atmosphere and then held for 6 hours.

4. A nitrogen oxide reduction catalyst, characterized in that, It is prepared by the method of any one of claims 1 to 3 for the preparation of nitrogen oxide reduction catalyst.

5. The application of the nitrogen oxide reduction catalyst according to claim 4 in improving the catalytic efficiency of nitrogen oxide reduction.

Images