Sulfur tolerant ammonia selective catalytic oxidation catalysts suitable for ammonia slip control and preparation and use thereof

Abstract

The application discloses a sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for escape ammonia control and a preparation method and application thereof. The catalyst has a core-shell structure with a chromium-cerium composite oxide as a core and cerium phosphate as a shell. The preparation method comprises the following steps: firstly, preparing the chromium-cerium composite oxide core by using a coprecipitation method; and then mixing the core with a small amount of CePO4 crystal seeds and growing the CePO4 shell by using a hydrothermal method. The catalyst has excellent characteristics such as a wide temperature window, high activity, high water-sulfur stability and the like, can realize low-cost removal of escape ammonia in an SCR section, and overcomes the problems of poor temperature window matching and poor water-sulfur stability of a current NH3-SCO catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ammonia escape control in denitration process, and particularly relates to a sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for escape ammonia control and a preparation method and application thereof. BACKGROUND

[0002] As a control index of atmospheric pollutants, ammonia (NH3) is an important precursor of haze formation, which can cause serious impact on ecological environment and human health. In addition to industrial production process, livestock and agricultural fertilization, one of the main sources of ammonia emission is the ammonia escape that occurs when ammonia is used as a reducing agent in the industrial flue gas denitration process (ammonia selective catalytic reduction, NH3-SCR). In order to overcome the influence of complex working conditions, variable flue gas nitrogen oxide (NO x ) content, poor ammonia nitrogen mixing effect, etc. in the actual industrial environment on the SCR denitration effect, more than stoichiometric ratio of NH3 is injected into the SCR device, and the unreacted NH3 forms an escape phenomenon, which can cause problems such as blockage of the downstream air preheater and formation of secondary inorganic aerosols.

[0003] Compared with technologies such as absorption method, adsorption method and biological treatment method that need additional structures, the catalytic technology of installing an NH3-SCO (ammonia selective catalytic oxidation) catalyst bed at the end of the SCR device to selectively oxidize the escaped ammonia into nitrogen (N2) has a significant advantage. Common NH3-SCO catalysts mainly include noble metal, transition metal and molecular sieve catalysts, which are significantly different and have different characteristics. The noble metal-based catalyst has the problems of narrow temperature window, poor N2 selectivity and high cost, which limits its practical application in industrial flue gas treatment; the Cu-based catalyst is the most widely studied among transition metal-based catalysts, but the problem of sulfur dioxide (SO2) stress in flue gas has not been overcome; the supported molecular sieve-based catalyst shows excellent activity due to its good structural characteristics, and has good water and sulfur tolerance stability, but its poor high-temperature stability and high catalyst cost limit its industrial application in flue gas treatment.

[0004] The Chinese patent document with publication number CN114042452A discloses a preparation method of an ammonia oxidation catalyst for diesel vehicle exhaust, which uses reducible P25 type titanium dioxide as a carrier, silver as an active component, and adopts an atomic layer deposition method to cover a nano-oxide film. Although the catalyst has excellent low-temperature catalytic activity (T 100 as low as 200℃), the preparation process is complex and the high Ag content increases the industrial application cost of the catalyst.

[0005] The Chinese patent document with publication number CN114904570A discloses a preparation method of a double-layer catalyst, which includes a uniformly distributed carrier composed of cordierite; a catalyst bottom layer composed of an aluminum oxide / cerium-zirconium powder / molecular sieve and other metal oxides with the addition of Pt noble metal; and a catalyst surface layer loaded with Cu and using SSZ-13 as a molecular sieve. However, the N2 selectivity is poor, and the influence of SO2 components in flue gas is not considered.

[0006] The Chinese patent document with publication number CN114405541A discloses a preparation method of a catalyst for selective oxidation of NH3, which uses a metal alkoxide to modify a CuO / CeO2 / ZrO2 composite metal catalyst to obtain an NH3-SCO catalyst with high catalytic activity and thermal stability. However, the influence of H2O and SO2 components in flue gas on the catalyst is not considered.

[0007] Although the above-mentioned documents provide some help for the development of ammonia escape control catalysts, there are still shortcomings such as mismatched temperature window, high preparation cost, poor water and sulfur stability, and the like, which hinder the industrial application of NH3-SCO catalysts in flue gas treatment.

[0008] Therefore, it is of great significance to develop a new NH3-SCO catalyst that can be used for ammonia escape control in the process of flue gas SCR denitrification, has a wide temperature window, high activity, high water and sulfur stability, and relatively low preparation cost, and has wide application prospects. SUMMARY

[0009] In view of the above technical problems and the deficiencies in the field, the present application provides a sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for ammonia escape control, which has a wide temperature window, high activity, high water and sulfur stability, and the like, and can achieve low-cost removal of ammonia escaping from the SCR section, overcoming the problems of poor temperature window matching and poor water and sulfur stability of current NH3-SCO catalysts.

[0010] A sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for ammonia escape control has a core-shell structure with chromium-cerium composite oxide as the core and cerium phosphate (CePO4) as the shell.

[0011] The chromium-cerium composite oxide is chromium oxide loaded on a cerium oxide carrier, and the molar ratio of chromium to cerium is 1:3-10, for example, 1:5, 1:10, and the like.

[0012] The present application adopts a core-shell structure to solve the above technical problems, and the chromium-cerium composite oxide inner core with strong redox performance is wrapped in the CePO4 shell. The chromium-cerium composite oxide inner core is a good oxidation catalyst, and through the high oxygen-carrying capacity of Ce oxide and the strong electron transfer capacity of Cr oxide, the two can cooperate to quickly realize the dehydrogenation oxidation of NH3. Under the combined action of the sulfur resistance of Cr element, the sulfur affinity of Ce element and the strong mutual interaction of the metal in the chromium-cerium composite oxide inner core, SO2 in the flue gas will be preferentially captured at the interface of the CeO2 carrier adjacent to the Cr site to form a special steric hindrance, which not only inhibits the further accumulation of surface sulfate species, but also protects the highly dispersed Cr sites on the surface of CeO2. Adjusting the chromium-cerium molar ratio of the chromium-cerium composite oxide can adjust the strong mutual interaction between the metals, change the uniformity of the surface Cr element distribution, and strengthen the steric hindrance effect, thereby affecting the surface redox performance and sulfur resistance performance.

[0013] In the process of using the catalyst for NH3-SCO, the shell CePO4 can not only participate in the internal SCR process to improve the NH3-SCO performance, but also further strengthen the SO2 resistance of the chromium-cerium composite oxide inner core. The oxidation product NO x The SCR reaction with the adsorbed NH3 inhibits the problem of excessive oxidation of NH3 caused by the strong oxidation of the inner core, high temperature conditions and other factors, thereby widening the reaction temperature window and improving the nitrogen selectivity. At the same time, the shell CePO4 has strong acidity and special electronic structure, which can limit the diffusion of SO2 to the inner core, delay the sulfation speed of the inner core catalyst, and further improve the sulfur resistance of the catalyst. Therefore, the catalyst can overcome the interference of SO2 in the actual industrial flue gas.

[0014] The molar ratio of cerium element in the chromium-cerium composite oxide to the cerium phosphate can be 2:1-4, for example, it can be 1:1, 1:2, 2:1, etc.

[0015] The present application also provides a preparation method of the sulfur-tolerant ammonia selective catalytic oxidation catalyst, comprising the following steps:

[0016] (1) adjusting the pH of the mixed solution of chromium nitrate and cerium nitrate to 8-11 (for example, it can be 8-10, 9-11, etc.), separating the obtained precipitate, washing, drying and calcining to obtain the chromium-cerium composite oxide;

[0017] (2) preparing a mixed solution of H3PO4 and cerium nitrate with a molar ratio of 1:1, adjusting the pH to 9-11, and keeping sufficient stirring during the preparation process to form a uniform gel; then adding the chromium-cerium composite oxide obtained in step (1), and after sufficient stirring, drying and calcining to obtain the chromium-cerium composite oxide loaded with CePO4 crystal seeds;

[0018] (3) preparing a mixed solution of pyrophosphoric acid and cerium nitrate with a molar ratio of 1:1, adding ammonia water drop by drop until the mixed solution is clear; then adding the chromium-cerium composite oxide loaded with CePO4 seed crystals obtained in step (2) and adding urea and / or tetrapropylammonium hydroxide (TPAH) to form a slurry, and after hydrothermal reaction, the obtained solid is washed, dried and calcined to obtain the sulfur-tolerant ammonia selective catalytic oxidation catalyst.

[0019] In the preparation method of the present application, first, a chromium-cerium composite oxide inner core is prepared by a coprecipitation method, and then the inner core is mixed with a small amount of CePO4 seed crystals and a CePO4 shell is grown by a hydrothermal method. When NH3 is adsorbed on the surface of the catalyst, the CePO4 on the shell can well adsorb NH3 as a solid acid, and the chromium-cerium composite oxide inner core has high catalytic oxidation performance to oxidize NH3 to N2 and NO x , and the excessive NO x migrates to the shell CePO4 and reacts with the surface adsorbed NH3 to generate N2 by internal NH3-SCR reaction, completing the overall SCO reaction process and ensuring high nitrogen selectivity, avoiding excessive oxidation of NH3 and secondary production of nitrogen oxides. At the same time, the combination of sulfur-hating and sulfur-loving metal oxides in the inner core structure can resist the poisoning effect of SO2, and the shell of CePO4 also has good SO2 resistance. Therefore, the catalyst with this structure can achieve high NH3 conversion rate while effectively avoiding excessive oxidation of NH3 at high temperature, and the catalyst material has good sulfur resistance, which is an excellent catalyst with wide temperature window, high activity, and high water and sulfur stability.

[0020] In step (1), ammonia water can be used to adjust the pH.

[0021] In step (1), the calcination temperature can be 450-550℃, and the time can be 4-6h.

[0022] In step (2), ammonia water can be used to adjust the pH.

[0023] In step (2), the calcination temperature can be 350-450℃, and the time can be 3-5h.

[0024] In step (2), the mass percentage of CePO4 seed crystals in the chromium-cerium composite oxide loaded with CePO4 seed crystals can be 5%-10%.

[0025] In step (3), the molar ratio of urea and / or tetrapropylammonium hydroxide to cerium nitrate can be 2-10:1.

[0026] In step (3), the temperature of the hydrothermal reaction can be 150-200 DEG C, and the time can be 8-24h.

[0027] In step (3), the temperature of the calcination can be 450-550 DEG C, and the time can be 4-6h.

[0028] The application further provides application of the sulfur-tolerant ammonia selective catalytic oxidation catalyst in ammonia selective catalytic oxidation.

[0029] The sulfur-tolerant ammonia selective catalytic oxidation catalyst can be used for selective catalytic oxidation of escaped ammonia after ammonia selective catalytic reduction denitration.

[0030] As a general inventive concept, the application further provides an ammonia selective catalytic oxidation method, which uses the sulfur-tolerant ammonia selective catalytic oxidation catalyst to selectively catalyze and oxidize ammonia.

[0031] The temperature of selective catalytic oxidation of ammonia by the sulfur-tolerant ammonia selective catalytic oxidation catalyst can be 200-450 DEG C.

[0032] The ammonia selective catalytic oxidation method can contain sulfur dioxide in the reaction system.

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] 1) The core-shell structure catalyst prepared by the application can realize efficient removal of escaped NH3 in a wide temperature window, can effectively avoid the problem of excessive oxidation of NH3, and can improve the N2 selectivity of the reaction.

[0035] 2) The catalyst prepared by the application has certain sulfur resistance in the core and shell structure, improves the sulfur resistance stability of the catalyst, and can meet the complex working conditions under actual conditions.

[0036] 3) The application uses transition metals and rare earth metals as precursors to realize efficient removal of NH3 under SO2 stress on the catalyst, and reduces the cost of removing pollutants. DETAILED DESCRIPTION

[0037] The application will be further described below in combination with specific examples. It should be understood that the examples are only used to illustrate the application and not used to limit the scope of the application.

[0038] Example 1

[0039] Catalyst preparation:

[0040] (1) The chromium-cerium composite metal oxide was prepared by precipitation method. Different amounts of Cr and Ce metal element precursors were weighed, the element molar ratio of Cr:Ce was controlled to be 1:10, mixed with 100 mL deionized water, stirred on a rotor stirrer until uniformly dispersed, and then concentrated ammonia was added dropwise to adjust the pH of the mixed solution to 10. The precipitate was washed, filtered, dried, and calcined at 500°C for 5h to obtain the composite metal oxide catalyst core. The amounts of each component added are as follows: 0.01 mol of Cr salt Cr(NO3)3·9H2O, and 0.1 mol of Ce salt Ce(NO3)3·6H2O.

[0041] (2) Different amounts of H3PO4 and Ce(NO3)3·6H2O with the same molar ratio were weighed to prepare a mixed solution, and concentrated ammonia was added dropwise to adjust the pH of the mixed solution to 10. During the preparation process, sufficient stirring was maintained to form a uniform gel. Then the chromium-cerium composite metal oxide core obtained in step (1) was added, and after sufficient stirring, drying and calcination at 400°C, a chromium-cerium metal oxide core loaded with a small amount of CePO4 crystal seeds was obtained. Among them, the amounts of H3PO4 and Ce(NO3)3·6H2O in the mixed solution were controlled so that the mass percentage of the crystal seeds (calculated as CePO4) in the obtained chromium-cerium metal oxide core loaded with a small amount of CePO4 crystal seeds was 5%.

[0042] (3) The cerium nitrate solution of the same concentration was added dropwise into the pyrophosphoric acid solution to ensure that the element molar ratio of Ce to P was 1:1. Concentrated ammonia was added dropwise until the mixed solution was clear. Then the chromium-cerium metal oxide core loaded with a small amount of CePO4 crystal seeds obtained in step (2) was added, and urea was added to form a slurry. Among them, 2 mol of urea was added per mol of cerium nitrate. Then the mixture was stirred for 1h, and then hydrothermal treatment was carried out at 180°C for 12h. The obtained sample was washed, vacuum dried, and calcined at 500°C for 5h to obtain the Cr-CeO x @CePO4 catalyst. Among them, the molar ratio of Ce element in the core to CePO4 in the shell of the whole core-shell catalyst was 1:2.

[0043] Example 2

[0044] The difference from Example 1 is only that the molar ratio of Ce element in the core to CePO4 in the shell of the whole core-shell catalyst is 1:1, and the rest is the same.

[0045] Example 3

[0046] The difference from Example 1 is only that the molar ratio of Ce element in the core to CePO4 in the shell of the whole core-shell catalyst is 2:1, and the rest is the same.

[0047] Example 4

[0048] The difference from Example 1 is only that the amount of Cr salt is increased in step (1) without changing the amount of Ce salt, and the element molar ratio of Cr:Ce is controlled to be 1:5, and the rest is the same.

[0049] Example 5

[0050] The difference from Example 2 is only that the amount of Cr salt is increased in step (1) without changing the amount of Ce salt, and the element molar ratio of Cr:Ce is controlled to be 1:5, and the rest is the same.

[0051] Example 6

[0052] The difference from Example 3 is only that the amount of Cr salt is increased in step (1) without changing the amount of Ce salt, and the element molar ratio of Cr:Ce is controlled to be 1:5, and the rest is the same.

[0053] Comparative Example 1

[0054] The preparation method of Example 1 is adopted, and only the catalyst core obtained in step (1) is obtained.

[0055] Comparative Example 2

[0056] The preparation method of Example 2 is adopted, wherein no metal Cr is added in step (1), and the rest of the steps are the same to obtain the catalyst. Among them, the molar ratio of CeO2 in the core to CePO4 in the shell of the whole core-shell catalyst is 1:1.

[0057] Comparative Example 3

[0058] The preparation method of Example 5 is adopted, wherein the calcination temperature of step (1) and step (3) is increased to 650°C, and the rest of the steps are the same to obtain the catalyst.

[0059] Comparative Example 4

[0060] The preparation method of Example 2 is adopted, wherein the amount of Ce salt is not changed, and the amount of Cr salt is reduced, and the element molar ratio of Cr:Ce is controlled to be 1:20, and the rest is the same.

[0061] Comparative Example 5

[0062] The preparation method of Example 2 is adopted, wherein the amount of Ce salt is not changed, and the amount of Cr salt is increased, and the element molar ratio of Cr:Ce is controlled to be 1:1, and the rest is the same.

[0063] Application Example 1

[0064] The catalysts prepared in Examples 1-6 and Comparative Examples 1-2 are subjected to selective catalytic oxidation test of NH3 to explore the best component ratio. Specifically as follows:

[0065] Activity experiments were conducted in a fixed-bed reactor with a catalyst loading of 1.0 mL and a particle size of 40-60 mesh. Initial gas volume concentrations were: [NH3] = 50 ppm, [O2] = 5 vol%, [H2O] = 5 vol%, N2 as carrier gas, and GHSV (gas space velocity) = 100,000 mL·g -1 ·h -1 The test reaction temperatures were 200°C, 250°C, 300°C, 350°C, 400°C, and 450°C. The NH3 conversion data after 1 hour of reaction are detailed in Table 1. Furthermore, NH3 should ideally be selectively oxidized to N2 and H2O. Therefore, N2 selectivity is also an important factor in evaluating catalyst performance. This experiment further examined N2 selectivity in the activity experiment, and the data are detailed in Table 2.

[0066] The results are expressed in terms of NH3 conversion and N2 selectivity, which are calculated as follows:

[0067]

[0068]

[0069] The test data are detailed in Table 1 and Table 2.

[0070] Table 1 Catalytic oxidation efficiency of catalyst for NH3 / %

[0071]

[0072] Table 2 N2 selectivity of catalysts for NH3 oxidation / %

[0073]

[0074] From the results in Tables 1 and 2, it can be seen that the core of the core-shell structure catalyst of the present invention has a strong deoxidation and oxidation ability for NH3, while the outer shell CePO4 enhances NH3 adsorption, participates in the internal SCR process, regulates over-oxidation, and improves the N2 selectivity of the NH3-SCO process.

[0075] The preferred catalyst in the present invention is Example 5, which has the advantages of a wide temperature window, high activity, and good N2 selectivity.

[0076] According to the comparative example 1, the strong oxidation of the catalyst core leads to the non-selective catalytic oxidation of NH3, and the N2 selectivity is extremely poor. The comparison of the example 3 and the comparative example 1 shows that the wrapping of cerium phosphate has almost no effect on the ammonia oxidation activity of the catalyst at low temperature (250℃), but can significantly improve the nitrogen selectivity. The comparison of the example 5 and the comparative example 3 shows that the excessively high calcination temperature seriously damages the structure of the catalyst and affects the catalytic performance. The catalytic performance of the comparative example 2, the comparative example 4 and the comparative example 5 shows that the Cr species as the main active site participates in the NH3-SCO oxidation process, but the Cr / Ce ratio affects the catalytic performance. The Cr / Ce ratio of the chromium-cerium composite oxide is greatly reduced, which leads to the decline of the oxidation performance of the catalyst, and further makes the temperature window of the NH3-SCO activity of the catalyst greatly delayed; when the Cr content in the chromium-cerium composite oxide is too high, although the NH3 conversion rate is relatively higher, the N2 selectivity is too low to affect the actual application.

[0077] Application Example 2

[0078] Stability test of the catalyst for catalytic oxidation of NH3.

[0079] The following experiments were carried out on a fixed bed reactor, and the catalyst loading was 1.0 mL, and the particle size was 40-60 mesh. The initial gas volume concentration was: [NH3] = 50 ppm, [O2] = 5 vol%, [H2O] = 5 vol%, [SO2] = 300 ppm, N2 was the carrier gas, GHSV (gas space velocity) = 100000 mL·g -1 ·h -1 The test reaction temperature was 350℃, and the test data are shown in Table 3.

[0080] Table 3: NH3 catalytic oxidation efficiency of the catalyst under the condition of sulfur passing / % (test temperature is 350℃)

[0081]

[0082] As shown in Table 3, the catalyst of the example of the application can stably realize NH3 oxidation under the influence of the SO2 component in the flue gas, and the NH3 conversion rate is almost not affected. The catalyst of the application has good sulfur resistance and can be stably operated for a long time.

[0083] The preferred catalyst in the application is the example 5, which can maintain more than 95% of the NH3 conversion rate in the flue gas atmosphere of 300 ppm SO2, and has certain potential for industrial application.

[0084] According to the comparative example 1, the inner core itself has strong oxidation ability, but poor SO2 stability, and the comparison with example 3 further illustrates the protective effect of CePO4. The comparison of example 5 and comparative example 3 illustrates that the excessive calcination temperature destroys the inner core and shell structure, affects the interaction between Cr and Ce in the inner core and the wrapping effect of CePO4, and further leads to the decline of SO2 stability. The comparison of the catalytic performance of comparative example 2, comparative example 4 and comparative example 5 not only reflects the influence of Cr species content on NH3-SCO activity, but also further confirms the influence of the molar ratio of Cr / Ce in the inner core on the interface effect, steric hindrance effect, active species dispersion and strong intermetallic interaction of the catalyst, and further affects the overall ammonia oxidation activity, nitrogen selectivity and sulfur resistance of the catalyst.

[0085] Furthermore, it is to be understood that various alterations and modifications can be made to the application herein disclosed in the above description without departing from the scope of the application as defined in the appended claims.

Claims

1. Use of a sulfur-tolerant ammonia selective catalytic oxidation catalyst suitable for ammonia slip control in the selective catalytic oxidation of ammonia, characterized in that, The sulfur-tolerant ammonia selective catalytic oxidation catalyst has a core-shell structure with a chromium-cerium composite oxide as a core and cerium phosphate as a shell. The chromium-cerium composite oxide is chromium oxide supported on a cerium oxide carrier, and the molar ratio of chromium elements to cerium elements is 1:3-10. The molar ratio of cerium elements in the chromium-cerium composite oxide to the cerium phosphate is 2:1-4.

2. Use according to claim 1, characterized in that, The preparation method of the sulfur-tolerant ammonia selective catalytic oxidation catalyst comprises the following steps: (1) adjusting the pH of a mixed solution of chromium nitrate and cerium nitrate to 8-11, separating the obtained precipitate, washing, drying, and calcining to obtain a chromium-cerium composite oxide; (2) preparing a mixed solution of H3PO4 and cerium nitrate with a molar ratio of 1:1, adjusting the pH to 9-11, and keeping sufficient stirring during the preparation process to form a uniform gel; then adding the chromium-cerium composite oxide obtained in step (1), and after sufficient stirring, drying and calcining to obtain a chromium-cerium composite oxide loaded with CePO4 seeds; (3) preparing a mixed solution of pyrophosphoric acid and cerium nitrate with a molar ratio of 1:1, adding ammonia water drop by drop until the mixed solution is clear; then adding the chromium-cerium composite oxide loaded with CePO4 seeds obtained in step (2), and adding urea and / or tetrapropylammonium hydroxide to form a slurry, and after hydrothermal reaction, the obtained solid is washed, dried, and calcined to obtain the sulfur-tolerant ammonia selective catalytic oxidation catalyst.

3. Use according to claim 2, characterized in that, In step (1): The pH is adjusted with ammonia water; The calcination temperature is 450-550°C, and the time is 4-6 h.

4. Use according to claim 2, characterized in that, In step (2): The pH is adjusted with ammonia water; The calcination temperature is 350-450°C, and the time is 3-5 h; The mass percentage of the CePO4 seeds in the chromium-cerium composite oxide loaded with CePO4 seeds is 5%-10%.

5. Use according to claim 2, characterized in that, In step (3): The molar ratio of urea and / or tetrapropylammonium hydroxide to cerium nitrate is 2-10:1; The hydrothermal reaction temperature is 150-200°C, and the time is 8-24 h; The calcination temperature is 450-550°C, and the time is 4-6 h.

6. The use according to claim 1, characterized in that, The sulfur-tolerant ammonia selective catalytic oxidation catalyst is used for selective catalytic oxidation of escaped ammonia after the ammonia selective catalytic reduction denitration engineering.

7. A method for the selective catalytic oxidation of ammonia, characterized in that The sulfur-tolerant ammonia selective catalytic oxidation catalyst is used for selective catalytic oxidation of ammonia suitable for escaped ammonia control; the sulfur-tolerant ammonia selective catalytic oxidation catalyst has a core-shell structure with a chromium-cerium composite oxide as a core and cerium phosphate as a shell; the chromium-cerium composite oxide is chromium oxide supported on a cerium oxide carrier, and the molar ratio of chromium elements to cerium elements is 1:3-10; the molar ratio of cerium elements in the chromium-cerium composite oxide to the cerium phosphate is 2:1-4; The temperature for selective catalytic oxidation of ammonia by the sulfur-tolerant ammonia selective catalytic oxidation catalyst is 200-450°C.

8. The method of selective catalytic oxidation of ammonia according to claim 7, characterized in that, The reaction system contains sulfur dioxide.

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