A catalyst for catalytic degradation of N-VOCs to produce ammonia and SCR denitration, and a preparation method and application thereof

Abstract

The application discloses a catalyst for N-VOCs catalytic degradation ammonia and SCR denitration, and a preparation method and application thereof, and belongs to the technical field of environmental catalysis. The application provides a core-shell structure bifunctional catalyst, the inner core of which is a spherical defective titanium dioxide loaded with silver, and the shell is an anatase titanium dioxide coating layer loaded with vanadium pentoxide and tungsten trioxide. The catalyst realizes the partition design of active components: the silver in the catalyst is used as the active center for N-VOCs catalytic degradation, the vanadium pentoxide outside is used as the main active component for NH3-SCR, and the tungsten trioxide is used as an additive. The catalyst physically separates the N-VOCs degradation ammonia region and the NH3-SCR reaction region, not only avoids the competitive adsorption of different atmospheres on the catalyst surface, but also realizes the efficient synergistic removal of N-VOCs and NO x by in-situ conversion of ammonia from the degradation product to the denitration reactant.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis technology, and in particular to a catalyst for the catalytic degradation of N-VOCs to produce ammonia in conjunction with SCR denitrification, its preparation method, and its application. Background Technology

[0002] Nitrogen-containing volatile organic compounds (N-VOCs) and nitrogen oxides (NOx) x VOCs (volatile organic compounds) are major air pollutants emitted during industrial production and pose significant risks to the human respiratory and immune systems. Compared to ordinary VOCs, N-VOCs are more toxic and more difficult to treat; current technologies primarily convert them into N2 or NO. x This method cannot achieve nitrogen resource recovery and is prone to secondary pollution, presenting significant drawbacks. Currently, industrial NO removal... x The most mature technology is ammonia selective catalytic reduction (NH3-SCR) denitrification technology. This technology requires an additional ammonia source as a reducing agent, but the storage and transportation of externally supplied ammonia sources poses safety hazards due to leakage, increases process operating costs, and is prone to ammonia escape causing secondary pollution, thus limiting its widespread application. To address these shortcomings of existing technologies, research is needed on developing technologies that can synergistically treat N-VOCs and NO. x The technology has become a current research focus. Based on this, a synergistic SCR denitrification technology for N-VOCs catalytic degradation to ammonia production is proposed. This technology can directionally convert the nitrogen-containing groups of N-VOCs into NH3 during degradation, directly using it as a reducing agent for SCR denitrification. This achieves "dual treatment from a single source" and nitrogen resource recovery, avoiding the drawbacks of external ammonia supply. It aligns with the trend of green and energy-saving development, possesses industrial application value and environmental benefits, and has become a research hotspot in related fields.

[0003] CN120939954A discloses a honeycomb non-precious metal catalyst for treating nitrogen-containing volatile organic compounds and its application. The catalyst is prepared by milling a support component, a crosslinking agent, rare earth oxides, and water into a coating slurry, followed by vacuum coating, drying, impregnation with a metal nitrate solution, aging, drying, and calcination. This honeycomb non-precious metal catalyst can achieve highly efficient catalytic oxidation of nitrogen-containing VOCs and reduce NO. x Secondary pollution. However, the conversion efficiency of this catalyst for some nitrogen-containing VOCs at low temperatures still needs to be improved, and its resistance to sulfur, water, and other poisoning under complex flue gas conditions has not been investigated.

[0004] CN109289911B discloses a catalyst and method for treating nitrogen-containing volatile organic pollutants. It prepares a supported catalyst or a hydrotalcite-derived composite oxide catalyst as a selective oxidation-catalytic-reduction bifunctional material. An integrated device allows the nitrogen-containing organic waste gas to react with the preheated catalyst. The concentration of nitrogen oxides in the exhaust gas determines whether a reducing gas is introduced for further reaction, thereby achieving the degradation of nitrogen-containing organic pollutants and NO reduction. x The emissions meet the standards. However, the complete conversion temperature of this catalytic system for some nitrogen-containing organic pollutants is too high, and the catalytic stability under conditions of high space velocity and complex nitrogen-containing organic waste gas still needs to be improved.

[0005] In summary, this study addresses the existing technologies for the catalytic degradation of N-VOCs and their interaction with NO. x The shortcomings in synergistic removal necessitate the development of a method that can efficiently catalyze the degradation of N-VOCs and convert them into NH3 as a reducing agent for SCR denitrification, thereby achieving the removal of N-VOCs and NO. x High-performance catalysts for synergistic removal. Summary of the Invention

[0006] The purpose of this invention is to provide a catalyst for the catalytic degradation of N-VOCs to ammonia production, synergistic SCR denitrification, and its preparation method and application, thereby solving the aforementioned problems in the background art. This invention provides a core-shell bifunctional catalyst, with a core of silver-loaded spherical defective titanium dioxide and an outer shell of anatase titanium dioxide coated with vanadium pentoxide and tungsten trioxide. This catalyst achieves a partitioned design of the active components: silver inside the catalyst serves as the active center for N-VOCs catalytic degradation, vanadium pentoxide on the outside serves as the main active component for NH3-SCR, and tungsten trioxide serves as a promoter.

[0007] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of the present invention is to provide a catalyst for the catalytic degradation of N-VOCs to produce ammonia and synergistic SCR denitrification, wherein the core layer of the catalyst is spherical defect titanium dioxide supported on silver, and the shell layer is a titanium dioxide coating layer; The catalyst has an external active component supported on its shell; the external active component includes vanadium pentoxide and tungsten trioxide.

[0008] Preferably, the proportion of silver in the catalyst is 1-2 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 40-50 wt%. The titanium dioxide coating layer accounts for 45-55 wt% of the catalyst; the vanadium pentoxide accounts for 1-5 wt% of the catalyst; and the tungsten trioxide accounts for 5-10 wt% of the catalyst.

[0009] The second technical solution of the present invention provides a method for preparing the above-mentioned catalyst for catalytic degradation of N-VOCs to produce ammonia and synergistic SCR denitrification, comprising the following steps: (1) The titanium precursor and silicon precursor are mixed with a mixed solvent to carry out a sol-gel reaction, and then a first calcination is carried out to obtain titanium silicon powder; (2) Add the titanium silicon powder to an alkaline solution and perform alkaline etching to obtain spherical defect titanium dioxide. Mix it with the silver precursor in the first solvent and perform a deposition reaction. Then perform a second calcination to obtain silver titanium powder. (3) The silver titanium powder and titanium precursor are added to ethanol for coating reaction, and then calcined for the third time to obtain titanium-coated silver titanium powder. (4) The titanium-coated silver-titanium powder, vanadium precursor and tungsten precursor are mixed in the first solvent to carry out the active component loading reaction, and then calcined for the fourth time to obtain the catalyst.

[0010] Preferably, in step (1): the titanium precursor is tetrabutyl titanate; the volume ratio of the titanium precursor to the mixed solvent is 8:200; The silicon precursor is tetraethyl silicate; the volume ratio of the silicon precursor to the mixed solvent is (0.5-2):200; The sol-gel reaction time was 2 hours. The first calcination temperature is 400-900℃, and the time is 3-6 hours.

[0011] Preferably, in step (2): the alkaline solution is a NaOH solution with a concentration of 1-3 mol / L; The mass-to-volume ratio of the titanium silicon powder to the alkaline solution is (4-6) g: 100 mL; The alkaline etching temperature is 60-80℃, and the time is 18-24h.

[0012] Preferably, in step (3): the silver precursor is silver nitrate; the deposition reaction temperature is 60-80℃ and the time is 0.5-2h; The second calcination temperature is 200-500℃, and the time is 3-6 hours.

[0013] Preferably, in step (3): the coating reaction is carried out at a temperature of 70°C for 2 hours; The third calcination is carried out at a temperature of 400-900℃ for 3-6 hours.

[0014] Preferably, in step (4): the vanadium precursor is ammonium metavanadate; the tungsten precursor is ammonium metatungstate; The loading reaction of the active component is carried out at a temperature of 60-80℃ for a time of 0.5-2 hours. The fourth calcination is carried out at a temperature of 400-900℃ for 3-6 hours.

[0015] The third technical solution of the present invention provides an application of the above-mentioned catalyst in the field of N-VOCs catalytic degradation to ammonia production and synergistic SCR denitrification.

[0016] The fourth technical solution of the present invention provides a method for N-VOCs catalytic degradation to produce ammonia in conjunction with SCR denitrification, wherein the above-mentioned catalyst is used as a catalytic component in the reaction process.

[0017] The beneficial technical effects of the present invention are as follows: This invention provides a core-shell bifunctional catalyst, with a core of silver-loaded spherical defect titanium dioxide and an outer shell of anatase titanium dioxide coated with vanadium pentoxide and tungsten trioxide. Based on the reaction characteristics of N-VOCs catalytic degradation to ammonia production and NH3-SCR denitrification, this catalyst achieves a partitioned design of active components: silver inside the catalyst serves as the active center for N-VOCs catalytic degradation, vanadium pentoxide on the outer shell serves as the main active component for NH3-SCR, and tungsten trioxide serves as an auxiliary agent.

[0018] Compared to traditional bifunctional catalysts, this core-shell structure achieves effective separation of catalytic active sites, physically separating the ammonia-producing region from the NH3-SCR reaction region. This not only avoids competitive adsorption of different atmospheres on the catalyst surface but also establishes a spatial relay mechanism between the two reactions through the in-situ conversion of ammonia from degradation products to denitrification reactants, thereby realizing the reaction between N-VOCs and NO. x Highly efficient and coordinated removal.

[0019] Since the reducing agent required for the SCR denitrification process comes directly from the ammonia generated by the catalytic degradation of N-VOCs, this design avoids the storage and transportation risks associated with external ammonia sources, effectively prevents secondary pollution caused by ammonia escape, and significantly improves the economy and safety of the process. The catalyst was synthesized via sol-gel and impregnation methods, and the resulting product exhibits distinct structural characteristics and excellent synergistic catalytic performance and selectivity in the intermediate temperature reaction range. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0021] Figure 1 This is a SEM image of the catalyst provided in Example 1 of the present invention; Figure 2 The XRD patterns of the catalysts provided in Example 1 and Comparative Examples 1-4 of this invention; Figure 3 Raman diagrams of the catalysts provided in Example 1 and Comparative Examples 1-4 of this invention; Figure 4 The NH3-TPD diagrams are for the catalysts provided in Example 1 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0023] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0025] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0026] This invention provides a catalyst for the catalytic degradation of N-VOCs to produce ammonia in conjunction with SCR denitrification, wherein the core layer of the catalyst is spherical defect titanium dioxide (silver titanium powder) supported on silver, and the shell layer is a titanium dioxide coating layer; The catalyst has an external active component supported on its shell; the external active component includes vanadium pentoxide and tungsten trioxide.

[0027] Preferably, the proportion of silver in the catalyst is 1-2 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 40-50 wt%. The titanium dioxide coating layer accounts for 45-55 wt% of the catalyst; the vanadium pentoxide accounts for 1-5 wt% of the catalyst; and the tungsten trioxide accounts for 5-10 wt% of the catalyst.

[0028] The core-shell structured catalyst provided by this invention uses silver as the main active component for the catalytic degradation of N-VOCs, which is confined within the catalyst by an anatase titanium dioxide shell (titanium dioxide coating). Vanadium pentoxide and tungsten trioxide are loaded on the outside of the anatase titanium dioxide shell as the main active components for selective catalytic resorption (SCR). Compared with conventional catalysts, this invention places the active sites for N-VOCs catalytic degradation inside the catalyst and the SCR active sites outside the catalyst, separating the ammonia-producing region of N-VOCs catalytic degradation from the ammonia-consuming region of the SCR reaction. This prevents competitive adsorption between different gas components, thereby effectively improving the catalyst's removal efficiency for the synergistic reaction of the two pollutants.

[0029] The present invention also provides a method for preparing the above-mentioned catalyst for N-VOCs catalytic degradation to ammonia production and synergistic SCR denitrification, comprising the following steps: (1) The titanium precursor, silicon precursor, alkali, binder and mixed solvent are mixed and the sol-gel reaction is carried out under stirring conditions. After centrifugation, washing and evaporation, the mixture is dried and then calcined for the first time to obtain titanium silicon powder. (2) Add the titanium silicon powder described in step (1) to an alkaline solution, perform alkaline etching under water bath stirring conditions, centrifuge, wash and evaporate to dry, obtain spherical defect titanium dioxide, disperse it in the first solvent to obtain a dispersion turbidity; (3) Add the silver precursor to the first solvent to obtain a silver solution. Add the silver solution to the dispersion turbidity in step (2). After the deposition reaction is carried out under water bath heating conditions, centrifugation, washing, evaporation drying and second calcination are carried out in sequence to obtain silver titanium powder. (4) Add the silver titanium powder, binder and titanium precursor mentioned in step (3) to ethanol, carry out the coating reaction under water bath heating conditions, and then perform centrifugation, washing, evaporation drying and third calcination in sequence to obtain titanium-coated silver titanium powder. (5) Disperse the titanium-coated silver-titanium powder described in step (4) in the first solvent to obtain a dispersion; dissolve the vanadium precursor and co-solvent in the first solvent to obtain a vanadium precursor solution; dissolve the tungsten precursor in the first solvent to obtain a tungsten precursor solution; mix the vanadium precursor solution, the tungsten precursor solution and the dispersion, and carry out the active component loading reaction under water bath stirring conditions, and then perform centrifugation, washing and fourth calcination in sequence to obtain the catalyst for N-VOCs catalytic degradation to produce ammonia and synergistic SCR denitrification.

[0030] This invention prepares silver-loaded spherical defect titanium dioxide through sol-gel method, etching method and deposition reaction, and then coats the surface of the silver-loaded spherical defect titanium dioxide (silver titanium powder) with titanium precursor using hydrothermal method to form the core and shell structure of the core-shell catalyst; then, by impregnating the outside of the shell with vanadium and tungsten active components, a bifunctional catalyst with a core-shell structure is obtained.

[0031] Preferably, the titanium precursor is tetrabutyl titanate; the volume ratio of the titanium precursor to the mixed solvent is 8:200.

[0032] Preferably, the silicon precursor is tetraethyl silicate; the volume ratio of the silicon precursor to the mixed solvent is (0.5-2):200, for example, it can be 0.5mL:200mL, 1mL:200mL, 1.5mL:200mL or 2mL:200mL, and is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] The purpose of mixing and stirring the titanium precursor and silicon precursor in this invention is to ensure that the titanium precursor and silicon precursor are fully mixed and form a spherical carrier through the sol-gel method.

[0034] Preferably, the alkaline agent in step (1) includes any one or a combination of at least two of sodium hydroxide, ammonia, or urea; The adhesive includes hydroxypropyl cellulose; The mixed solvent contains ethanol and acetonitrile; The volume ratio of ethanol to acetonitrile is 3:1; The first calcination temperature is 400-900℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0035] Preferably, the volume ratio of the titanium precursor to the silicon precursor is 4-10:1, and more preferably 8:1.

[0036] Preferably, the first calcination time in step (1) is 3-6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] The first calcination in this invention promotes the transformation of amorphous titanium-silicon precursors into crystalline forms, thereby improving the stability of the internal structure of the carrier.

[0038] Preferably, the alkaline solution in step (2) is a NaOH solution with a concentration of 1-3 mol / L, such as 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 3 mol / L, but not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 2 mol / L being the preferred value.

[0039] The purpose of adding an alkaline solution in this invention is to etch away the silicon dioxide composite in the carrier by alkaline etching, forming a titanium dioxide carrier with defect sites, thereby improving the role of the active component in the reaction.

[0040] Preferably, the mass-volume ratio of the titanium silicon powder to the alkaline solution in step (2) is (4-6) g:100 mL, for example, it can be 4 g:100 mL, 4.5 g:100 mL, 5 g:100 mL, 5.5 g:100 mL or 6 g:100 mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the alkaline etching temperature in step (2) is 60-80℃, the time is 18-24h, and the stirring speed is 50-80r / min; The evaporation and drying temperature is 80-110℃.

[0042] Preferably, the temperature of the deposition reaction in step (3) is 60-80℃, for example, it can be 60℃, 64℃, 68℃, 72℃, 76℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the deposition reaction time in step (3) is 0.5-2h, for example, it can be 0.5h, 0.75h, 1h, 1.25h, 1.5h, 1.75h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] In this invention, the deposition reaction serves to ensure that the silver precursor is uniformly and fully dispersed on the surface of the titanium dioxide powder. Therefore, it is necessary to control the heating temperature and time within a reasonable range.

[0045] Preferably, the evaporation and drying temperature in step (3) is 80-110℃ and the time is 12-24h; the silver precursor is silver nitrate.

[0046] Preferably, the second calcination temperature in step (3) is 200-500℃, for example, it can be 200℃, 300℃, 400℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the second calcination time in step (3) is 3-6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] The second calcination in this invention serves to convert the silver nitrate impregnated on the surface of the support into active silver species, thereby improving the dispersibility of the catalyst.

[0049] Preferably, the mass-volume ratio of silver titanium powder to ethanol in step (4) is (4-6) g:250 mL, for example, it can be 4 g:100 mL, 4.5 g:100 mL, 5 g:100 mL, 5.5 g:100 mL or 6 g:100 mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 5 g:100 mL.

[0050] Preferably, the adhesive in step (4) is hydroxypropyl cellulose; the detergent used for washing includes deionized water and ethanol.

[0051] Preferably, the temperature of the third calcination in step (4) is 400-900℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] Preferably, the third calcination time in step (4) is 3-6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] The third calcination in this invention serves to remove organic residues and volatile components from the outer shell, thereby improving the stability of the internal structure of the carrier.

[0054] Preferably, the mass-to-volume ratio of the titanium-coated silver-titanium powder to the first solvent in step (5) is (4-6) g:250 mL, for example, it can be 4 g:100 mL, 4.5 g:100 mL, 5 g:100 mL, 5.5 g:100 mL or 6 g:100 mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] In step (5), the vanadium precursor is ammonium metavanadate; the tungsten precursor is ammonium metatungstate; the co-solvent is oxalic acid dihydrate; and the molar ratio of the co-solvent to the vanadium precursor is (0.5-2):1. The mass-to-volume ratio of vanadium precursor to the first solvent in the vanadium precursor solution is (0.1-0.6) g: 100 mL; The mass-to-volume ratio of tungsten precursor to the first solvent in the tungsten precursor solution is (0.5-1) g: 100 mL; The loading reaction of the active component is carried out at a temperature of 60-80℃ for 0.5-2 hours and at a rotation speed of 50-80 r / min.

[0056] Preferably, the fourth calcination temperature in step (5) is 400-900℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Preferably, the fourth calcination time in step (5) is 3-6 hours, for example, it can be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] The fourth calcination in this invention serves to convert the metal salt on the surface of titanium dioxide into the corresponding oxide, thereby improving the catalyst activity or stability.

[0059] The present invention also provides an application of the above-mentioned catalyst for N-VOCs catalytic degradation of ammonia production and SCR denitrification in the field of N-VOCs catalytic degradation of ammonia production and SCR denitrification.

[0060] Preferably, the first solvent is water.

[0061] The present invention also provides a method for N-VOCs catalytic degradation to produce ammonia in conjunction with SCR denitrification, wherein the above-mentioned catalyst is used as a catalytic component in the reaction process.

[0062] Preferably, the reaction temperature is 80-400℃, for example, it can be 80℃, 100℃, 200℃, 300℃ or 400℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] The catalyst provided by this invention can achieve the catalytic degradation of N-VOCs to generate ammonia, and use the generated ammonia as a reducing agent to participate in the SCR denitrification reaction, exhibiting high N-VOCs conversion rate and N2 selectivity.

[0064] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0065] Example 1 A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is spherical defect titanium dioxide loaded with silver, and the shell layer is a titanium dioxide coating layer; vanadium pentoxide and tungsten trioxide are loaded on the outer side of the catalyst.

[0066] The proportion of silver in the catalyst is 1 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 44 wt%. The titanium dioxide coating accounts for 47 wt% of the catalyst; vanadium pentoxide accounts for 3 wt% of the catalyst; and tungsten trioxide accounts for 5 wt% of the catalyst.

[0067] The specific preparation method is as follows: (1) The alkali (ammonia water, 1.6 mL) and hydroxypropyl cellulose (0.2 g) were injected into a mixed solvent (ethanol and acetonitrile in a volume ratio of 3:1), and then mixed with tetrabutyl titanate and tetraethyl silicate (the volume ratio of tetrabutyl titanate and tetraethyl silicate was 8:1, and the volume ratio of tetrabutyl titanate to the mixed solvent was 8:200). The mixture was stirred and subjected to a sol-gel reaction (2 h). After centrifugation, washing, evaporation and drying were performed, and then the mixture was calcined for the first time (calcined at 500 °C for 4 h) to obtain titanium silicon powder. (2) Add the titanium silicon powder from step (1) to a 2 mol / L NaOH solution (the mass-volume ratio of titanium silicon powder to NaOH solution is 5 g: 200 mL), perform alkaline etching under water bath stirring conditions (temperature is 70 °C, time is 20 h, stirring speed is 70 r / min), centrifuge, wash and evaporate to dry, and obtain spherical defect titanium dioxide. Disperse it in water at a mass-volume ratio of 5 g: 100 mL to obtain a dispersion turbidity. (3) Add silver nitrate to water to obtain silver nitrate solution, add it to the dispersion turbidity in step (2), carry out deposition reaction under water bath heating conditions (heat at 60℃ for 1h), and then centrifuge, wash, evaporate and dry and second calcination (calcination at 200℃ for 4h) to obtain the core silver titanium powder of the core-shell catalyst. (4) The silver titanium powder, hydroxypropyl cellulose (addition amount is 0.2g) and titanium precursor from step (3) are added to ethanol (the mass-volume ratio of silver titanium powder to ethanol is 5g:250mL), and the coating reaction is carried out under water bath heating conditions (heating at 70℃ for 2h). Then, centrifugation, washing, evaporation drying and third calcination (calcination at 500℃ for 4h) are carried out in sequence to obtain titanium-coated silver titanium powder. (5) Disperse the titanium-coated silver-titanium powder from step (4) in water at a mass-volume ratio of 5g:200mL to obtain a dispersion; dissolve ammonium metavanadate and oxalic acid dihydrate in water at a molar ratio of 1:1 (mass-volume ratio of ammonium metavanadate to water is 0.38g:100mL) to obtain a vanadium precursor solution; mix ammonium metatungstate and water at a mass-volume ratio of 0.54g:100mL to obtain a tungsten precursor solution; mix the vanadium precursor solution, the tungsten precursor solution and the dispersion, and carry out the active component loading reaction under water bath stirring conditions (heating at 60℃ for 1h), followed by centrifugation, washing and fourth calcination (calcination at 500℃ for 4h) to obtain the core-shell bifunctional catalyst (denoted as 3V5W-Ag-Ti@Ti).

[0068] SEM image of the core-shell bifunctional catalyst of Example 1 is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 2 As shown in the figure; it can be seen from the figure that the titanium dioxide in the product has anatase crystal phase, and the (1 0 1) crystal plane has high crystallinity; the Raman diagram of the catalyst prepared in this example is shown in the figure. Figure 3 As shown, Figure 3 The peak positions marked by the three dashed lines (406, 526, 645 cm) -1 ( ) represents the typical Raman activity mode of anatase TiO2; the NH3-TPD diagram is shown below. Figure 4 As shown, the low-temperature desorption peak position of the core-shell bifunctional catalyst provided in this embodiment is significantly lower than that of other samples, proving that it is more conducive to the adsorption and activation of N-VOCs molecules (test conditions: 200 mg catalyst, drying temperature 500℃, gas NH3 / He, gas flow rate 30-50 mL / min).

[0069] Example 2 A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is spherical defect titanium dioxide loaded with silver, and the shell layer is a titanium dioxide coating layer; vanadium pentoxide and tungsten trioxide are loaded on the outer side of the catalyst.

[0070] The proportion of silver in the catalyst is 1 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 44 wt%. The titanium dioxide coating accounts for 47 wt% of the catalyst; vanadium pentoxide accounts for 3 wt% of the catalyst; and tungsten trioxide accounts for 5 wt% of the catalyst.

[0071] For specific preparation steps, please refer to Example 1.

[0072] Example 3 The only difference from Example 1 is that the volume ratio of tetrabutyl titanate to tetraethyl silicate is changed from 8:1 to 4:1.

[0073] Example 4 The only difference from Example 1 is that the volume ratio of tetrabutyl titanate to tetraethyl silicate is changed from 8:1 to 10:1.

[0074] Comparative Example 1 (Tungsten omitted) A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is spherical defect titanium dioxide loaded with silver, and the shell layer is a titanium dioxide coating layer; vanadium pentoxide is loaded on the outer side of the catalyst.

[0075] The proportion of silver in the catalyst is 1 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 44 wt%. The titanium dioxide coating accounts for 52 wt% of the catalyst; vanadium pentoxide accounts for 3 wt% of the catalyst.

[0076] The preparation method of the catalyst in this comparative example differs from that in Example 1 only in that step (5) is modified to the following form: The titanium-coated silver-titanium powder from step (4) was dispersed in water at a mass-volume ratio of 5g:200mL to obtain a dispersion. Ammonium metavanadate and oxalic acid dihydrate with a molar ratio of 1:1 were dissolved in water (the mass-volume ratio of ammonium metavanadate and water was 0.38g:100mL) to obtain a vanadium precursor solution. The vanadium precursor solution and the dispersion were mixed, and the active component loading reaction was carried out under water bath stirring conditions (heated at 60℃ for 1h). Then, the mixture was centrifuged, washed, and calcined for the fourth time (calcined at 500℃ for 4h). The resulting catalyst was denoted as 3V-Ag-Ti@Ti.

[0077] Comparative Example 2 (vanadium omitted) A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is a spherical defect titanium dioxide loaded with silver, and the shell layer is a titanium dioxide coating layer; tungsten trioxide is loaded on the outer side of the catalyst.

[0078] The proportion of silver in the catalyst is 1 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 44 wt%. The titanium dioxide coating accounts for 50 wt% of the catalyst; the tungsten trioxide accounts for 5 wt% of the catalyst.

[0079] The preparation method of the catalyst in this comparative example differs from that in Example 1 only in that step (5) is modified to the following form: The titanium-coated silver-titanium powder from step (4) was dispersed in water at a mass-volume ratio of 5g:200mL to obtain a dispersion. Ammonium metatungstate and water were mixed at a mass-volume ratio of 0.54g:100mL to obtain a tungsten precursor solution. The tungsten precursor solution and the dispersion were mixed and subjected to an active component loading reaction under water bath stirring (heated at 60℃ for 1h). The mixture was then centrifuged, washed, and subjected to a fourth calcination (calcined at 500℃ for 4h). The resulting catalyst was denoted as 5W-Ag-Ti@Ti.

[0080] The XRD pattern of the catalyst provided in this comparative example is as follows: Figure 2 As shown in the figure, the crystal phase of titanium dioxide is anatase, and the (1 0 1) crystal plane has a high degree of crystallinity; the Raman diagram of the core-shell bifunctional catalyst is shown in the figure. Figure 3 As shown, Figure 3 The peak positions marked by the three dashed lines (406, 526, 645 cm) -1 ( ) represents the typical Raman activity mode of anatase TiO2; the NH3-TPD diagram is shown below. Figure 4 As shown in the figure, the low-temperature desorption of NH3 by the catalyst in this comparative example is significantly reduced compared to Example 1, and the number of NH3 adsorption sites is greatly reduced.

[0081] Comparative Example 3 (Silver omitted) A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is spherical defect titanium dioxide loaded with silver, and the shell layer is a titanium dioxide coating layer; vanadium pentoxide and tungsten trioxide are loaded on the outer side of the catalyst.

[0082] Of these, titanium dioxide with spherical defects accounted for 45 wt% of the catalyst; The titanium dioxide coating accounts for 47 wt% of the catalyst; vanadium pentoxide accounts for 3 wt% of the catalyst; and tungsten trioxide accounts for 5 wt% of the catalyst.

[0083] The only difference between the preparation method of the catalyst in this comparative example and that in Example 1 is that the silver titanium powder added in step (4) is replaced with an equal mass of spherical defect titanium dioxide prepared in step (2), and the subsequent processing is carried out in the same manner; the resulting catalyst is denoted as 3V5W-Ti@Ti.

[0084] The XRD pattern of the catalyst provided in this comparative example is as follows: Figure 2 As shown in the figure, the crystal phase of titanium dioxide is anatase, and the (1 0 1) crystal plane has a high degree of crystallinity; the Raman diagram of the core-shell bifunctional catalyst is shown in the figure. Figure 3 As shown, Figure 3 The peak positions marked by the three dashed lines (406, 526, 645 cm) -1 ( ) represents the typical Raman activity mode of anatase TiO2; the NH3-TPD diagram is shown below. Figure 4 As shown in the figure, compared with the product of Comparative Example 3, the catalyst of Example 1 of the present invention significantly weakens the strength of the weak acid sites due to the introduction of silver, which is beneficial to the adsorption and activation of reactants such as N-VOCs.

[0085] Comparative Example 4 (non-core-shell bifunctional structure, containing only a core layer) The silver-titanium powder prepared in Example 1 was used directly as the final product, denoted as Ag-Ti.

[0086] The XRD pattern of the comparative Ag-Ti is as follows: Figure 2 As shown in the figure, the titanium dioxide crystal phase is anatase, and the (1 0 1) crystal plane has a high degree of crystallinity; the Raman diagram is as follows. Figure 3 As shown, the peak positions marked by the three dashed lines are 406, 526, and 645 cm. -1 ( ) represents the typical Raman activity mode of anatase TiO2; the NH3-TPD diagram is shown below. Figure 4 As shown in the figure, the amount of NH3 desorption in the mid-to-low temperature range of Ag-Ti is significantly reduced, and the number of NH3 adsorption sites is greatly reduced.

[0087] Comparative Example 5 (Ag, V, and W active components are all loaded into the shell layer) A core-shell bifunctional catalyst is disclosed, wherein the core layer of the catalyst is spherical defect titanium dioxide and the shell layer is a titanium dioxide coating layer; vanadium pentoxide, tungsten trioxide and silver are supported on the outer side of the catalyst.

[0088] Of these, titanium dioxide with spherical defects accounted for 45 wt% of the catalyst; The titanium dioxide coating in the catalyst accounts for 55 wt%; vanadium pentoxide accounts for 3 wt%; tungsten trioxide accounts for 5 wt%; and silver accounts for 1 wt%.

[0089] The difference between the preparation method of the catalyst in this comparative example and that in Example 1 is that the addition of silver nitrate solution in step (3) is omitted, and the vanadium precursor solution and tungsten precursor solution in step (5) are first mixed with silver nitrate solution, and then the subsequent processing is carried out in the same way; the resulting catalyst is denoted as 3V5WAg / Ti@Ti.

[0090] Comparative Example 6 (Ag, V, and W active components are all loaded into the core) A core-shell bifunctional catalyst, wherein the core layer of the catalyst is spherical defect titanium dioxide supported on V, W and Ag, and the shell layer is a titanium dioxide coating layer; Of these, titanium dioxide with spherical defects accounted for 45 wt% of the catalyst; The titanium dioxide coating in the catalyst accounts for 55 wt%; vanadium pentoxide accounts for 3 wt%; tungsten trioxide accounts for 5 wt%; and silver accounts for 1 wt%.

[0091] The difference between the preparation method of the catalyst in this comparative example and that in Example 1 is that the addition of vanadium precursor solution and tungsten precursor solution in step (5) is omitted, and the silver nitrate solution in step (3) is first mixed with vanadium precursor solution and tungsten precursor solution, and then the subsequent processing is carried out in the same manner; the resulting catalyst is denoted as 3V5WAg-Ti@Ti.

[0092] The XRD pattern of the catalyst provided in this comparative example is as follows: Figure 2 As shown in the figure, the crystal phase of titanium dioxide is anatase, and the (1 0 1) crystal plane has a high degree of crystallinity; the Raman diagram of the core-shell bifunctional catalyst is shown in the figure. Figure 3 As shown, Figure 3 The peak positions marked by the three dashed lines (406, 526, 645 cm) -1 ( ) represents the typical Raman activity mode of anatase TiO2; the NH3-TPD diagram is shown below. Figure 4 As shown in the figure, compared with the product of Comparative Example 3, the catalyst of Example 1 of the present invention significantly weakens the strength of the weak acid sites due to the introduction of silver, which is beneficial to the adsorption and activation of reactants such as N-VOCs.

[0093] Effect verification The catalytic performance of the catalysts provided in Examples 1-4 and Comparative Examples 1-4 was tested under the following conditions: flue gas composition: [MEA] = 200 ppm, [NO] = 200 ppm, [O2] = 16 vol%, N2 as carrier gas, catalyst dosage 200 mg; reactor temperature 80-400℃, flue gas flow rate 100 mL / min. The results of the maximum conversion rate of MEA and the reaction temperature at which the maximum conversion rate is reached in the catalytic degradation of N-VOCs are shown in Table 1. The results of the maximum conversion rate of NO and the reaction temperature at which the maximum conversion rate is reached in the catalytic SCR reaction are shown in Table 2.

[0094] Table 1 Table 2 As can be seen from Tables 1 and 2, the core-shell bifunctional catalysts provided in the various embodiments of the present invention have excellent catalytic degradation of N-VOCs and synergistic SCR denitrification performance.

[0095] The product of Example 1 achieved a 100% conversion rate of N-VOCs at 250°C and a 100% NO removal efficiency at 280°C. The comparison between Example 1 and Example 2 suggests that a lower silver loading will lead to an increase in the reaction temperature required for the complete degradation of N-VOCs, which in turn leads to a decrease in ammonia production at the same temperature, resulting in low efficiency of the SCR denitrification reaction. The comparison between Example 1 and Example 3 suggests that if the titanium-silicon ratio is too high, etching can easily cause the TiO2 framework to become too thin or collapse locally, resulting in poor structural stability and reduced catalytic performance. The comparison between Example 1 and Example 4 shows that it is difficult to form an ideal loose porous structure and abundant defect sites after etching, which is not conducive to the adsorption and activation of N-VOCs and subsequent reactions. The comparison between Example 1 and Comparative Example 2 suggests that the vanadium pentoxide loaded on the outer shell is the main active component catalyst of NH3-SCR, and the lack of vanadium pentoxide will significantly increase the complete conversion temperature of pollutants. The comparison between Example 1 and Comparative Example 3 suggests that the complete conversion temperature of N-VOCs is significantly increased when silver is missing, and silver is the main active component in the catalyst for the catalytic degradation of N-VOCs. The comparison between Example 1 and Comparative Example 4 suggests that although the encapsulated catalyst (Example 1) has a certain impact on the catalytic degradation of N-VOCs, the anatase titanium dioxide shell in the catalyst defined in this invention can effectively separate the N-VOCs catalytic degradation reaction region and the SCR denitrification reaction region of the catalyst, preventing competitive adsorption between different gas components and thus improving the performance of the catalyst.

[0096] A comparison between Example 1 and Comparative Example 5 suggests that when Ag, V, and W active components are all loaded in the catalyst shell, their overall impact on the catalytic degradation process of N-VOCs is relatively small, and the Ag component on the shell surface is beneficial to promoting the catalytic conversion of N-VOCs to some extent. However, in this structure, NH3 generated from N-VOCs degradation is difficult to adsorb and subsequently react with the vanadium-tungsten active sites in a timely and effective manner, thus limiting the NO conversion efficiency. In contrast, the catalyst defined in this invention, by setting an anatase TiO2 shell, achieves a reasonable separation between the N-VOCs catalytic degradation reaction region and the SCR denitration reaction region. This not only helps to reduce the competitive adsorption and mutual interference of different reactive gas components at the active sites, but also optimizes the transfer and utilization of intermediate products, thereby improving the overall synergistic catalytic performance of the catalyst.

[0097] A comparison between Example 1 and Comparative Example 6 suggests that when all active components are loaded into the catalyst core, the N-VOCs generate ammonia, making it difficult for NO to contact within the core. This leads to direct oxidation within the core, resulting in byproduct formation and reduced NH3 utilization. In contrast, the catalyst defined in this invention, by constructing an anatase TiO2 shell, achieves a reasonable spatial separation between the N-VOCs catalytic degradation region and the SCR denitrification region. This reduces the likelihood of deep oxidation of intermediate products within the core and promotes the migration of generated NH3 to the outer vanadium-tungsten active sites, enabling it to participate in the SCR reaction. This reduces side reactions, improves NO conversion, and enhances the overall synergistic catalytic performance of the catalyst.

[0098] This invention prepares a heterogeneous dual-effect core-shell catalyst through a multi-step reaction process including sol-gel and impregnation methods. The core is a defective titanium dioxide shell with silver-loaded active components for highly efficient catalytic degradation of N-VOCs, while the outer shell is anatase titanium dioxide with SCR denitrification function, supporting vanadium and tungsten active components. Furthermore, the prepared catalyst achieves the denitrification of N-VOCs and NO... x The synergistic removal of ammonia has good catalytic performance, requires no external ammonia source, and has greater resource value.

[0099] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A catalyst for catalytic degradation of N-VOCs to ammonia production and synergistic SCR denitrification, characterized in that, The core layer of the catalyst is silver-loaded spherical defect titanium dioxide, and the shell layer is a titanium dioxide coating layer. The catalyst has an external active component supported on its shell; the external active component includes vanadium pentoxide and tungsten trioxide.

2. The catalyst for N-VOCs catalytic degradation to ammonia production and synergistic SCR denitrification according to claim 1, characterized in that, The proportion of silver in the catalyst is 1-2 wt%; the proportion of spherical defect titanium dioxide in the catalyst is 40-50 wt%. The titanium dioxide coating layer accounts for 45-55 wt% of the catalyst; the vanadium pentoxide accounts for 1-5 wt% of the catalyst; and the tungsten trioxide accounts for 5-10 wt% of the catalyst.

3. A method for preparing the catalyst according to any one of claims 1-2 for catalytic degradation of N-VOCs to ammonia production and synergistic SCR denitrification, characterized in that, Includes the following steps: (1) The titanium precursor and silicon precursor are mixed with a mixed solvent to carry out a sol-gel reaction, and then a first calcination is carried out to obtain titanium silicon powder; (2) Add the titanium silicon powder to an alkaline solution and perform alkaline etching to obtain spherical defect titanium dioxide. Mix it with the silver precursor in the first solvent and perform a deposition reaction. Then perform a second calcination to obtain silver titanium powder. (3) The silver titanium powder and titanium precursor are added to ethanol for coating reaction, and then calcined for the third time to obtain titanium-coated silver titanium powder. (4) The titanium-coated silver-titanium powder, vanadium precursor and tungsten precursor are mixed in the first solvent to carry out the active component loading reaction, and then calcined for the fourth time to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that, In step (1): the titanium precursor is tetrabutyl titanate; the volume ratio of the titanium precursor to the mixed solvent is 8:200; The silicon precursor is tetraethyl silicate; the volume ratio of the silicon precursor to the mixed solvent is (0.5-2):200; The sol-gel reaction time was 2 hours. The first calcination temperature is 400-900℃, and the time is 3-6 hours.

5. The preparation method according to claim 3, characterized in that, In step (2): the alkaline solution is a NaOH solution with a concentration of 1-3 mol / L; The mass-to-volume ratio of the titanium silicon powder to the alkaline solution is (4-6) g: 100 mL; The alkaline etching temperature is 60-80℃, and the time is 18-24h.

6. The preparation method according to claim 3, characterized in that, In step (3): the silver precursor is silver nitrate; the deposition reaction temperature is 60-80℃ and the time is 0.5-2h; The second calcination temperature is 200-500℃, and the time is 3-6 hours.

7. The preparation method according to claim 3, characterized in that, In step (3): the coating reaction is carried out at a temperature of 70°C for 2 hours; The third calcination is carried out at a temperature of 400-900℃ for 3-6 hours.

8. The preparation method according to claim 3, characterized in that, In step (4): the vanadium precursor is ammonium metavanadate; the tungsten precursor is ammonium metatungstate; The loading reaction of the active component is carried out at a temperature of 60-80℃ for a time of 0.5-2 hours. The fourth calcination is carried out at a temperature of 400-900℃ for 3-6 hours.

9. The application of the catalyst according to any one of claims 1-2 in the field of N-VOCs catalytic degradation to ammonia production and synergistic SCR denitrification.

10. A method for N-VOCs catalytic degradation to ammonia production and synergistic SCR denitrification, characterized in that, The catalyst described in any one of claims 1-2 is used as a catalytic component during the reaction.

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