Catalyst for synergistically controlling nox and cvocs, and method of making and using same

Abstract

The application discloses a catalyst for synergistically controlling NOx and CVOCs, a preparation method of the catalyst and application of the catalyst in synergistically catalytically purifying NOx and CVOCs in industrial flue gas. The catalyst comprises a carrier and an active component. The carrier is mesoporous titanium phosphate, and the active component is vanadium, tungsten and ruthenium. The catalyst can synergistically remove NOx and CVOCs, has high thermal stability and strong sulfur resistance, and can greatly inhibit the generation of more toxic polychlorinated by-products of CVOCs in the catalytic combustion process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atmospheric environmental protection, and in particular to a catalyst for synergistically controlling NOx and CVOCs, a preparation method and application thereof. BACKGROUND

[0002] The flue gas of waste incineration, steel sintering and non-ferrous smelting contains a large amount of pollutants such as nitrogen oxides (NOx) and chlorine-containing volatile organic compounds (CVOCs). Among them, NOx can cause environmental problems such as acid rain, photochemical smog, and ozone layer destruction, which seriously harm human health and the ecological environment. CVOCs have the characteristics of strong toxicity, difficult degradation, and high stability, and when discharged into the atmosphere, they can cause persistent pollution. CVOCs also have strong carcinogenic, teratogenic, and mutagenic effects, which are very harmful to human health.

[0003] The ammonia selective reduction method (NH3-SCR) is the most mature technology for purifying NOx in flue gas at present, and is widely used in coal-fired power plant flue gas emission and motor vehicle exhaust emission. At present, such catalysts mainly use anatase TiO2 as a carrier and V2O5 modified with MoO3 or WO3 as an active component. The treatment methods for CVOCs include direct combustion method, adsorption method, absorption method, photocatalytic method, catalytic hydrogenation dechlorination method, and catalytic combustion method. Among them, the catalytic combustion method has the advantages of low operating energy consumption, wide treatment concentration, high removal efficiency, and high product selectivity, and is considered to be the most effective method for treating CVOCs.

[0004] CVOCs can easily generate more toxic polychlorinated by-products under the conditions of flue gas after incineration (containing Cu, Fe and other components in fly ash), and even generate dioxins which are extremely toxic and very stable. The "Standard for Pollution Control on Incineration of Municipal Waste" (GB 18485-2014) stipulates that the dioxin content of treated flue gas should be controlled at 0.1 ng TEQ·m -3 Therefore, it is necessary to control the generation of polychlorinated by-products while eliminating CVOCs.

[0005] Chinese Patent No. CN 107376895B discloses a preparation method and application of a clover-shaped catalyst for synergistically controlling nitrogen oxides and chlorine-containing volatile organic compounds. The catalyst uses organic vanadium as a vanadium precursor and titanium white or titanium tungsten powder as a carrier. The catalyst with a clover structure is prepared by mechanical ball milling and then extrusion molding. The catalyst has little modification compared with commercial vanadium-based catalysts, but can achieve high deNOx rate and CVOCs removal efficiency, and has high mechanical strength and wear resistance.

[0006] A Chinese patent with publication number CN 116272953 A discloses a NOx and CVOCs cooperative removal catalyst and preparation and application thereof. Any crystal form of TiO2 which is not modified or modified by doping with at least one of non-metal elements (N, P) is used as a carrier. After sufficient stirring of metal soluble salts (at least one of Sb, V, Fe, Pt, Pd), a clear solution is obtained. The carrier powder is placed in the clear solution, and after stirring, drying and calcination, the catalyst is obtained. The catalyst has high CVOCs and NOx removal activity and CO2 selectivity, a wide active temperature window, and good SO2 poisoning resistance.

[0007] Although the catalysts involved in the above patent documents exhibit certain activity, their efficiency in cooperative removal of NOx and CVOCs, especially the catalytic activity of CVOCs, cannot be said to be satisfactory, and their thermal stability and sulfur resistance need to be improved. SUMMARY

[0008] The present application provides a catalyst for cooperative control of NOx and CVOCs and its preparation method and application. The catalyst can cooperatively remove NOx and CVOCs, and also has high thermal stability, strong sulfur resistance, and can significantly inhibit the generation of more toxic polychlorinated by-products during catalytic combustion of CVOCs.

[0009] The technical solution of the present application is as follows:

[0010] A catalyst for cooperative control of NOx and CVOCs, comprising a carrier and an active component, wherein the carrier is mesoporous titanium phosphate, and the active component is vanadium, tungsten and ruthenium.

[0011] Due to the strong acidity of the titanium phosphate surface, the acidic sites on the carrier can inhibit the formation of chlorine free radicals during the catalytic combustion of CVOCs, thereby reducing the generation of polychlorinated by-products. On the other hand, the acidic sites on the surface of the titanium phosphate carrier can significantly inhibit the adsorption of SO2 on the surface of the catalyst, slow down the generation of corresponding sulfates or sulfides by the carrier and active elements, and improve the sulfur resistance of the catalyst.

[0012] The catalyst of the present application has strong CVOCs catalytic activity, which can efficiently degrade dioxins generated in the front-end flue gas and significantly reduce the harm of the exhaust gas to the environment.

[0013] In addition, due to the strong thermal stability of titanium phosphate, even if the temperature of the catalyst bed rises sharply to above 650℃ during actual reaction, the catalyst will not sinter, so the catalyst of the present application exhibits strong thermal stability.

[0014] VW(Mo) / Ti is a traditional catalyst for NOx removal in NH3-SCR, but its insufficient oxidizing power results in low catalytic combustion activity for CVOCs. In this invention, the addition of Ru significantly enhances the catalyst's oxidizing power, thus exhibiting high activity for CVOCs. Furthermore, Ru promotes the removal of Cl adsorbed on the active sites of the catalyst as Cl2 during the catalytic combustion of CVOCs, and also inhibits the formation of polychlorinated byproducts.

[0015] Preferably, based on the elemental mass of vanadium, tungsten, and ruthenium, the catalyst contains 0.1–2 wt% vanadium, 0.5–10 wt% tungsten, and 0.1–1.0 wt% ruthenium.

[0016] More preferably, based on the elemental mass of vanadium, tungsten, and ruthenium, the catalyst contains 0.8–1.2 wt% vanadium, 5–7 wt% tungsten, and 0.5–0.8 wt% ruthenium.

[0017] This invention also provides a method for preparing a catalyst that synergistically controls NOx and CVOCs, comprising the following steps:

[0018] (1) Mesoporous titanium phosphate carriers were prepared by hydrothermal method;

[0019] (2) The active components were loaded onto the mesoporous titanium phosphate support by the equal volume impregnation method.

[0020] Preferably, step (1) includes: adding titanium precursor and phosphorus precursor to water, stirring evenly, and then carrying out a hydrothermal reaction at 150-200℃; and obtaining mesoporous titanium phosphate support by filtration, washing, drying, and calcination.

[0021] Preferably, in step (1), the drying temperature is 80-100℃ and the drying time is 5-10h; the calcination temperature is 450-550℃ and the calcination time is 3-5h.

[0022] The titanium precursor is at least one of titanium chloride, titanium sulfate, and tetrabutyl titanate; preferably titanium sulfate.

[0023] When mesoporous titanium phosphate support is prepared using titanium sulfate as a titanium precursor, the resulting catalyst exhibits good catalytic activity, thermal stability, and catalytic selectivity. The prepared catalyst maintains a NO conversion rate of over 90% within the temperature range of 200℃ to 375℃, demonstrating efficient NO removal over a wide temperature range.

[0024] The phosphorus precursor is at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and trimethyl phosphate; preferably, it is ammonium dihydrogen phosphate.

[0025] Preferably, the molar ratio of titanium precursor to phosphorus precursor is 1:1 to 5; more preferably, it is 1:2 to 3.

[0026] The active components vanadium, tungsten, and ruthenium were loaded onto the titanium phosphate support by an equal-volume impregnation method.

[0027] Preferably, step (2) includes: dissolving soluble salts of vanadium, tungsten, and ruthenium and ascorbic acid in deionized water to form an active component solution; adding the active component solution dropwise onto a mesoporous titanium phosphate support while stirring; and obtaining a catalyst that synergistically controls NOx and CVOCs after drying and calcination.

[0028] Preferably, the soluble salts of vanadium, tungsten, and ruthenium are ammonium metavanadate, ammonium metatungstate, and ruthenium nitrate, respectively.

[0029] Furthermore, in the active component solution, the concentrations of ammonium metavanadate, ammonium metatungstate, and ruthenium nitrate are 5-10 g / L, 60-80 g / L, and 50-70 g / L, respectively.

[0030] Furthermore, the volume-to-mass ratio of the active component solution to the mesoporous titanium phosphate support is 1 mL:(1-3) g.

[0031] Ascorbic acid acts as a competitive adsorbent during the impregnation process, enhancing the dispersion of active components vanadium, tungsten, and ruthenium on the support surface, thereby improving catalyst activity. The molar ratio of ascorbic acid to the total amount of vanadium, tungsten, and ruthenium ions is 0.5–1.5:1; preferably 0.7–1.2:1.

[0032] Preferably, in step (2), the drying temperature is 100-120℃ and the drying time is 5-10h; the calcination temperature is 400-450℃ and the calcination time is 3-5h.

[0033] This invention also provides the application of catalysts for synergistic control of NOx and CVOCs in the synergistic catalytic purification of NOx and CVOCs in industrial flue gas.

[0034] The industrial flue gas mentioned above originates from waste incineration, steel sintering, or non-ferrous smelting waste gas.

[0035] Preferably, the active temperature range of the catalyst for synergistic catalytic purification of NOx and CVOCs is 275-325℃.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The catalyst of the present invention exhibits high activity, high thermal stability and high sulfur resistance in the synergistic purification of NOx and CVOCs, and can significantly inhibit the formation of more toxic polychlorinated byproducts.

[0038] (2) The preparation method of the catalyst of the present invention is simple, easy to produce on a large scale, and has certain practical application prospects. Attached Figure Description

[0039] Figure 1 The graph shows the catalytic activity data of the catalysts prepared in Examples 1-4 and Comparative Example 1 for NO.

[0040] Figure 2 The graph shows the catalytic activity data of the catalysts prepared in Examples 1-4 and Comparative Example 1 for chlorobenzene.

[0041] Figure 3 The graph shows the thermal stability data of the catalysts prepared in Example 4 and Comparative Example 1;

[0042] Figure 4 The graph shows the stability data of the catalysts prepared in Example 4 and Comparative Example 1. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0044] Example 1

[0045] 3.29 g of titanium chloride was dissolved in 300 ml of deionized water. 6.90 g of ammonium dihydrogen phosphate was added to the solution, and the mixture was stirred for 60 min. The solution was then transferred to a crystallization vessel and crystallized at 180 °C for 4 h. After filtration, washing, drying at 100 °C for 5 h, and calcination at 450 °C for 4 h, the supported titanium phosphate was obtained.

[0046] Weigh 0.021 g ammonium metavanadate, 0.184 g ammonium metatungstate, 0.139 g ruthenium nitrate solution (Ru content 18%), and 0.246 g ascorbic acid, and dissolve them in 2.5 ml of deionized water to form an impregnation liquid. Weigh 5 g of the above titanium phosphate support, and add the impregnation liquid dropwise onto the support while stirring. After drying at 100 °C for 6 h, calcine at 450 °C for 4 h to obtain the catalyst.

[0047] Example 2

[0048] Weigh 0.021 g ammonium metavanadate, 0.184 g ammonium metatungstate, 0.278 g ruthenium nitrate solution (18%), and 0.246 g ascorbic acid, and dissolve them in 2.5 ml of deionized water to form an impregnation liquid. Weigh 5 g of the titanium phosphate support prepared in Example 1 using titanium chloride as a precursor, and add the impregnation liquid dropwise onto the support while stirring. After drying at 100 °C for 6 h, calcination at 450 °C for 4 h yields the catalyst.

[0049] Example 3

[0050] 4.16 g of titanium sulfate was dissolved in 300 ml of deionized water. 6.90 g of ammonium dihydrogen phosphate was added to the solution, and the mixture was stirred for 60 min. The solution was then transferred to a crystallization vessel and crystallized at 180 °C for 4 h. After filtration, washing, drying at 100 °C for 5 h, and calcination at 450 °C for 4 h, the supported titanium phosphate was obtained.

[0051] Weigh 0.021 g ammonium metavanadate, 0.184 g ammonium metatungstate, 0.139 g ruthenium nitrate solution (18%), and 0.246 g ascorbic acid, and dissolve them in 2.5 ml of deionized water to form an impregnation liquid. Weigh 5 g of the above titanium phosphate support into the solution, and add the impregnation liquid dropwise onto the support while stirring. After drying at 100 °C for 6 h, calcine at 450 °C for 4 h to obtain the catalyst.

[0052] Example 4

[0053] Weigh 0.021 g ammonium metavanadate, 0.184 g ammonium metatungstate, 0.278 g ruthenium nitrate solution (18%), and 0.246 g ascorbic acid, and dissolve them in 2.5 ml of deionized water to form an impregnation liquid. Weigh 5 g of the titanium phosphate support prepared in Example 3 using titanium sulfate as a precursor, and add the impregnation liquid dropwise onto the support while stirring. After drying at 100 °C for 6 h, calcinate at 450 °C for 4 h to obtain the catalyst.

[0054] Comparative Example 1

[0055] Weigh 0.021 g ammonium metavanadate, 0.184 g ammonium metatungstate, 0.139 g ruthenium nitrate solution (18%), and 0.246 g ascorbic acid, and dissolve them in 2.5 ml of deionized water to form an impregnation liquid. Weigh 5 g anatase, and add the impregnation liquid dropwise onto the anatase support while stirring. After drying at 100 °C for 6 h, calcine at 450 °C for 4 h to obtain the catalyst.

[0056] Catalyst activity evaluation

[0057] 200 mg of the catalysts prepared in Examples 1, 2, 3, 4 and Comparative Example 1 were weighed and placed into a fixed-bed reactor. The following gases were introduced: NO concentration of 600 ppm, NH3 concentration of 600 ppm, chlorobenzene concentration of 100 ppm, O2 volume concentration of 5%, and the remainder being nitrogen. The total gas flow rate was 133.3 ml / min.

[0058] Chlorobenzene, CO, and CO2 were tested using gas chromatography. The concentrations of NOx, NO, NO2, and O2 were tested using an infrared flue gas analyzer. The conversion rates of the corresponding substances were calculated based on the changes in net outlet concentration. The temperature was increased from 150℃ to 400℃, and the outlet concentration was measured every 25℃, with each temperature test point held for 30 minutes.

[0059] The formula for calculating the conversion rate of NO or chlorobenzene is:

[0060] The results of the catalyst activity evaluation for NO are shown in the figure. Figure 1 .

[0061] from Figure 1 It can be observed that the NO conversion activity of the catalysts prepared using titanium sulfate as a precursor (Examples 3 and 4) is superior to that of the catalysts prepared using titanium chloride as a precursor (Examples 1 and 2). Furthermore, the NO activity of the catalysts using titanium phosphate as a support and titanium sulfate as a precursor is also significantly higher than that of the catalysts using titanium oxide as a support. The catalyst prepared in Example 4 maintains a NO conversion rate of over 95% within the temperature range of 200℃ to 375℃, demonstrating efficient NO removal over a wide temperature range. The catalytic activity evaluation results for chlorobenzene are shown in [the table below]. Figure 2 .

[0062] from Figure 2 It can be found that the catalysts with titanium phosphate as the support and titanium sulfate as the precursor (Examples 3 and 4) exhibit significantly higher chlorobenzene catalytic activity than the catalysts with titanium oxide as the support (Comparative Example 1). The catalysts with titanium phosphate as the support and titanium sulfate as the precursor (Examples 3 and 4) can achieve more than 98% chlorobenzene degradation at temperatures above 300°C.

[0063] Catalyst thermal stability evaluation

[0064] The catalysts prepared in Example 4 and Comparative Example 1 were respectively placed in a muffle furnace and treated at 700°C for 4 hours, and their activity was then tested. The performance of the catalysts was evaluated under the same conditions. The evaluation results are shown below. Figure 3 .

[0065] from Figure 3 It can be observed that after aging at 700°C, the catalytic activity of the titanium phosphate catalyst (Example 4) using titanium sulfate as a precursor remained essentially unchanged, while the catalytic activity of Comparative Example 1 showed a significant decrease. This indicates that the catalyst involved in this invention has strong thermal stability.

[0066] Catalyst selectivity study

[0067] The catalysts from Example 4 and Comparative Example 1 were reacted continuously under the same conditions for 50 hours. The tail gas was then passed into pesticide residue-grade toluene for continuous absorption reaction for 50 hours. Samples were sent to a third-party testing institution for analysis of the dioxin content in the toluene absorption solution. The analytical results are shown in Table 1.

[0068] Table 1. Dioxin content in exhaust gas

[0069] Dioxin content (ng I-TEQ Nm -3 )]]> Example 4 0.0142 Comparative Example 1 0.0638

[0070] As can be seen from Table 1, the catalyst involved in this invention can significantly inhibit the formation of polychlorinated byproducts.

[0071] Catalyst stability study

[0072] 200 mg of the catalysts prepared in Example 4 and Comparative Example 1 were weighed and placed into fixed-bed reactors respectively. The following gases were introduced: NO concentration 600 ppm, NH3 concentration 600 ppm, chlorobenzene concentration 100 ppm, SO2 concentration 35 ppm, water vapor volume concentration 5%, O2 volume concentration 5%, and the remainder nitrogen. The total gas flow rate was 133.3 ml / min. The reaction was carried out continuously at 300 °C for 100 h. The conversion rate of the corresponding substances was calculated based on the change in net outlet concentration. The evaluation results are shown below. Figure 4 .

[0073] from Figure 4 It can be observed that within the 100-hour reaction time, the catalyst activity of Example 4 remained essentially unchanged, while the catalyst activity of Comparative Example 1 gradually decreased. This indicates that the catalyst involved in this invention possesses strong sulfur resistance stability.

[0074] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A catalyst for the synergistic control of NOx and CVOCs, characterized in that, The catalyst comprises a carrier and an active component, the carrier is mesoporous titanium phosphate, and the active component is vanadium, tungsten and ruthenium; the catalyst contains 0.1-2 wt% of vanadium, 0.5-10 wt% of tungsten and 0.1-1.0 wt% of ruthenium in terms of the element mass of vanadium, tungsten and ruthenium. The preparation method of the mesoporous titanium phosphate comprises the following steps: adding a titanium precursor and a phosphorus precursor into water, stirring uniformly, and then performing hydrothermal reaction at 150-200 DEG C; and filtering, washing, drying and calcining to obtain the mesoporous titanium phosphate carrier; the titanium precursor is at least one of titanium chloride, titanium sulfate and butyl titanate; and the phosphorus precursor is at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and trimethyl phosphate.

2. The catalyst for the synergic control of NOx and CVOCs according to claim 1, characterized in that, The catalyst contains 0.8-1.2 wt% of vanadium, 5-7 wt% of tungsten and 0.5-0.8 wt% of ruthenium in terms of the element mass of vanadium, tungsten and ruthenium.

3. A method of producing the catalyst for the synergistic control of NOx and CVOCs according to claim 1 or 2, characterized by, The method comprises the following steps: (1) preparing the mesoporous titanium phosphate carrier by using a hydrothermal method, which comprises the following steps: adding a titanium precursor and a phosphorus precursor into water, stirring uniformly, and then performing hydrothermal reaction at 150-200 DEG C; and filtering, washing, drying and calcining to obtain the mesoporous titanium phosphate carrier; the titanium precursor is at least one of titanium chloride, titanium sulfate and butyl titanate; and the phosphorus precursor is at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate and trimethyl phosphate; (2) loading the active component onto the mesoporous titanium phosphate carrier by using an equal-volume impregnation method.

4. The production method according to claim 3, characterized by, The drying temperature is 80-100 DEG C, and the drying time is 5-10 h; the calcining temperature is 450-550 DEG C, and the calcining time is 3-5 h.

5. The preparation method according to claim 3, characterized in that, The step (2) comprises the following steps: dissolving soluble salts of vanadium, tungsten and ruthenium and ascorbic acid in deionized water to form an active component solution, adding the active component solution drop by drop onto the mesoporous titanium phosphate carrier while stirring, and then drying and calcining to obtain the catalyst for synergistically controlling NOx and CVOCs.

6. The production method according to claim 5, wherein The molar ratio of ascorbic acid to the total amount of vanadium, tungsten and ruthenium metal ions is 0.5-1.5:

1.

7. The catalyst for synergistically controlling NOx and CVOCs according to claim 1 or 2 is applied to synergistically catalytically purifying NOx and CVOCs in industrial flue gas.

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