A sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal and its preparation method

Abstract

The present invention discloses a sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal and its preparation method, which uses cerium, niobium, and platinum composite oxides as core active components, tin and ruthenium composite oxides as outer surface active components, ascorbic acid as a reducing agent and stabilizer, and polyvinyl pyrrolidone as a morphology guiding agent. The sea urchin-shaped rare earth-based catalyst is obtained through two-step hydrothermal synthesis, washing, and drying. The catalyst is in the shape of a sea urchin and can achieve NO removal under low temperature conditions. x , VOCs synergistic catalytic removal, strong resistance to water, sulfur and chlorine poisoning, which is beneficial to simplify the treatment process of industrial tail gas purification, improve the purification efficiency of the reactor and reduce the cost of flue gas treatment.

Description

Technical Field

[0001] The invention relates to a sea urchin-shaped rare earth-based catalyst for simultaneous denitration and removal of VOCs and a preparation method thereof, and belongs to the field of industrial flue gas purification. Background Art

[0002] NO x It is one of the main sources of air pollution and has great harm to human health and the ecological environment. The composition of industrial flue gas is complex, including dust, heavy metals, SO x 、NO x As well as VOCs, they have become important factors restricting the green development of the industry. In recent years, due to the wide variety of VOCs and their volatility, many VOCs have high photochemical reactivity and are easily precursors of ozone and fine particulate matter in the atmosphere. Therefore, the reduction of VOCs has also become an important issue in the current environmental air pollution control. At present, the control of these pollutants generally adopts a separate removal method, which results in a large area of ​​factory flue gas treatment equipment and high treatment costs. Therefore, research and development of a method that can convert NO x The catalyst that can remove VOCs and VOCs at the same time can greatly save equipment and operating costs and has great market prospects.

[0003] Among existing denitrification patents, patent CN202110271099.9 uses anatase nano-titanium dioxide as a carrier, surface-loaded with vanadium pentoxide as the active component, molybdenum trioxide or tungsten trioxide as a co-catalyst, and modified metal elements such as tin or cerium. A plate-type low-temperature SCR denitrification catalyst is obtained through an impregnation process involving mixing, impregnation, extrusion granulation, coating, and calcination. The catalyst exhibits a denitrification activity of 80-99% within the temperature range of 100-420°C. Patent CN202010759686.8 pre-treats the carrier zeolite molecular sieve through dehydration and alkali treatment to produce a defective molecular sieve. The catalyst is then placed in an aqueous solution containing a copper salt and a silicon source, impregnated, filtered, dried, and calcined to produce a denitrification catalyst. This catalyst exhibits excellent NH3-SCR denitrification performance at high temperatures. The catalyst described in patent CN202210549148.5 is a cerium-based denitrification catalyst with honeycomb stone as the carrier. After being injected into the flue gas of the waste incineration furnace at 850-1050°C, it can continue to play a denitrification role during the subsequent full cooling process of the flue gas, and has particularly good low-temperature activity. Patent CN201410419979.6 uses ceramic glass fiber to produce a catalyst substrate, and obtains a catalyst through impregnation and drying. The catalyst has better corrosion resistance and flue gas impact resistance than traditional honeycomb catalysts. However, industrial flue gas currently presents the characteristics of multiple pollutants. A simple denitrification catalyst is difficult to meet the process requirements for the coordinated removal of multiple pollutants in flue gas under complex working conditions, resulting in a long flue gas purification process and high flue gas purification costs. At the same time, the flue gas temperature in the non-electric industry is low, and conventional vanadium-titanium system denitrification catalysts are difficult to meet the requirements of NO under low temperature conditions.x The need for high-efficiency removal.

[0004] Among the existing denitrification and VOCs removal catalyst patents, the catalyst described in patent CN202210744878.0 includes TiO2, Ce2S3, V2O5 and MoO3, and the preparation method includes: mixing, molding, drying and roasting; the catalyst has the dual functions of denitrification and VOCs removal, and can achieve NO x The conversion rate is ≥80%, and the VOCs catalytic oxidation conversion rate is ≥70%. CN202210744878.0 Patent CN202210452380.7 uses an adaptive reaction method to obtain VOCs and NO in medium and low temperature flue gas. x The composite manganese oxide catalyst for simultaneous removal shows excellent VOCs and NO removal under medium and low temperature flue gas conditions. x Synchronous removal performance. The catalysts obtained by the current conventional catalyst preparation methods (co-precipitation, impregnation, and distributed precipitation) usually do not have a special morphology. As a result, under complex flue gas conditions (high water content, VOCs content, and low temperature), the catalysts show insufficient synergistic removal activity on the one hand, and are prone to poisoning and deactivation on the other hand, which seriously affects the catalyst market application.

[0005] Therefore, the design of simultaneous denitrification and deVOCs catalysts should first adopt reasonable means to construct catalysts with special morphology, so as to achieve the goal of synergistic and efficient removal of multiple pollutants under complex flue gas conditions and reduce investment and operating costs. Summary of the Invention

[0006] The purpose of the present invention is to address the current status and problems of existing industrial flue gas denitrification, deVOCs removal processes and catalysts, and to propose a rare earth-based catalyst for simultaneous denitrification and deVOCs removal with a special sea urchin-like morphology. Another purpose of the present invention is to provide a method for preparing the above-mentioned sea urchin-shaped rare earth-based catalyst.

[0007] The technical solution of the present invention is as follows: the present invention realizes that the first hydrothermal reaction of precursor solutions of different active components is carried out in different regions at a relatively low hydrothermal temperature through the isolation effect of an H-type electrolytic cell and a PE film, so that the active components on one side form a spherical core and the active components on the other side form a specific nanoneedle morphology, thereby increasing the specific surface area of ​​the composite oxide and exposing more reactive sites; the hydrothermal temperature is increased to carry out the second hydrothermal reaction, the PE film is decomposed under high temperature conditions, the solutions on both sides are mixed, and the nanoneedle active components are anchored to the spherical core during the hydrothermal reaction to form a sea urchin-shaped catalyst; the synergistic effect of the cerium (Ce), niobium (Nb), and platinum (Pt) composite oxide in the catalyst is utilized to inhibit catalyst surface agglomeration, increase the specific surface area of ​​the catalyst core, enhance the anchoring effect of the nanoneedles on the catalyst core surface, and greatly improve the low-temperature catalytic performance of the catalyst; ruthenium (Ru) and tin (Sn) increase the adsorbed oxygen concentration on the catalyst surface, significantly improving the catalytic oxidation efficiency of VOCs, and can also act as sacrificial agents to protect the rare earth main active components, enhance the catalyst's anti-poisoning effect, and ensure the overall catalytic activity and long service life of the catalyst.

[0008] A sea urchin-shaped rare earth-based catalyst for simultaneous denitrification and VOCs removal has a cerium, niobium, and platinum composite oxide as an inner core active component, a tin and ruthenium composite oxide as an outer surface active component, ascorbic acid as a reducing agent and stabilizer, and polyvinyl pyrrolidone as a morphology directing agent. The catalyst is obtained through a two-step hydrothermal synthesis, washing, and drying.

[0009] In the technical solution of the present invention, the mass ratio of cerium oxide: niobium oxide: platinum oxide: tin oxide: ruthenium oxide in the catalyst is (5.4-10): (1.5-4): (0.01-0.05): (2-4): (0.01-0.03).

[0010] A method for preparing the above-mentioned sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal is as follows:

[0011] (1) Preparation of active component precursor solution

[0012] Cerium salt, niobium salt, and platinum salt are added to deionized water and stirred evenly to obtain active component precursor solution A. Tin salt and ruthenium salt are added to deionized water and stirred evenly to obtain active component precursor solution B. Active component precursor solutions A and B are then poured into both sides of an H-type electrolytic cell, with the middle of the electrolytic cell separated by a PE film. The H-type electrolytic cell is then moved as a whole into a hydrothermal reactor.

[0013] (2) Hydrothermal synthesis of catalyst core and nanoneedles

[0014] Ascorbic acid is added to the active component precursor solution A obtained in step (1), and polyvinyl pyrrolidone is added to the active component precursor solution B obtained in step (1). Deionized water is added between the inner tank of the hydrothermal reactor and the H-type electrolytic cell to perform the first hydrothermal reaction to synthesize the catalyst core and the outer surface nanoneedles;

[0015] (3) Hydrothermal synthesis of sea urchin-shaped catalysts

[0016] After the first hydrothermal reaction of step (2) is completed, the reaction temperature is increased to carry out the second hydrothermal reaction. After the reaction is completed, the mixture is cooled to room temperature, washed with deionized water until neutral, and then dried to obtain a sea urchin-shaped catalyst.

[0017] In the technical solution of the present invention: the cerium salt described in step (1) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the niobium salt is niobium oxalate or niobium chloride; the platinum salt is chloroplatinic acid; the tin salt is anhydrous stannous chloride; and the ruthenium salt is anhydrous ruthenium trichloride.

[0018] In the technical solution of the present invention: the mass ratio of ascorbic acid described in step (2) to active component precursor solution A is (0.15-0.4): (8-12).

[0019] In the technical solution of the present invention: the mass ratio of the polyvinyl pyrrolidone described in step (2) to the active component precursor solution B is (0.02-0.05): (5-10).

[0020] In the technical solution of the present invention: the first hydrothermal reaction temperature in step (2) is 80-90° C., and the reaction time is 2-4 h.

[0021] In the technical solution of the present invention: the second hydrothermal reaction temperature in step (3) is 180-200° C., and the reaction time is 4-8 hours.

[0022] In the technical solution of the present invention: the drying temperature in step (3) is 80-100° C., and the drying time is 2-4 hours.

[0023] In the technical solution of the present invention: the application of the catalyst in the field of industrial flue gas purification.

[0024] The experimental conditions and results for evaluating the catalyst activity of the present invention are as follows: 1 mL of a 40-60 mesh catalyst was poured into a quartz tube with an inner diameter of 8 mm, secured with quartz wool and wire mesh, and placed in a tube furnace. The actual temperature of the catalytic reaction was adjusted by controlling the heating temperature of the tube furnace. Ethylbenzene was used as a representative VOC. Laboratory gas was used to simulate flue gas. The inlet components were: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. The NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and the ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. After 25 minutes at 140°C, the NO removal efficiency was 100%, and the ethylbenzene removal efficiency was over 90%.

[0025] Beneficial effects of the present invention:

[0026] In view of the high concentration of pollutants (NO x , VOCs, etc.) purification generally adopts a separate removal method, which leads to problems such as large floor space occupied by factory flue gas treatment equipment and high management costs. The catalytic active components of existing denitrification and VOCs removal catalysts are unevenly dispersed on the carrier, and water molecules, sulfur dioxide and reaction intermediates are difficult to desorb, resulting in poor resistance to water and sulfur poisoning of the synergistic removal catalyst at low temperatures. Therefore, the present invention innovatively develops a catalyst that can remove NO x The sea urchin-shaped rare earth-based catalyst can remove NO and VOCs simultaneously, so that the flue gas can be removed by the catalyst. x , and VOCs are removed simultaneously.

[0027] The main basis is:

[0028] Cerium (Ce) has a unique 4f electron layer structure. When its oxide is used in combination, it has a significant synergistic effect and can greatly improve the low-temperature catalytic performance of the catalyst. The addition of niobium (Nb) is beneficial to inhibiting the agglomeration of the catalyst surface, increasing the specific surface area of ​​the catalyst core, and enhancing the anchoring effect of the nanoneedles on the surface of the catalyst core. Platinum (Pt) and ruthenium (Ru) have high catalytic activity, ensuring the overall catalytic activity of the catalyst. Tin (Sn) oxide increases the concentration of oxygen adsorbed on the catalyst surface, significantly improving the catalytic oxidation efficiency of VOCs, and can also act as a sacrificial agent to protect the main active components of rare earth and enhance the anti-poisoning effect of the catalyst. Ascorbic acid acts as a reducing agent and stabilizer. On the one hand, it acts as a reducing agent to ensure the Ce on the catalyst surface. 3+The relative content of ions is high. On the other hand, it is added to the solution as a stabilizer to make the solution acidic. The Sn element will produce hydroxide precipitation under alkaline conditions, thus ensuring the effective addition of the catalytic component Sn in the catalyst; polyvinyl pyrrolidone is used as a morphology guide to guide the active components to form nano-needle morphology under hydrothermal conditions, exposing more reactive sites, enhancing the adsorption effect of pollutants, accelerating the desorption of intermediate products and SO2, H2O, protecting the active components in the catalyst core, and improving the catalytic performance and service life of the catalyst. The successful application of the present invention can achieve NO x , and VOCs are removed synergistically, bringing excellent economic, environmental and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the following examples, but the scope of protection of the present invention is not limited thereto: Example 1

[0031] 1. Catalyst Preparation

[0032] (1) Preparation of active component precursor solution

[0033] 13.6234 g of cerium nitrate hexahydrate, 7.1082 g of niobium oxalate, and 0.0252 g of chloroplatinic acid were weighed, added to 83.0269 g of deionized water, and stirred evenly to obtain an active component precursor solution A; 2.1750 g of anhydrous stannous chloride and 0.0156 g of ruthenium trichloride were weighed, added to 17.5250 g of deionized water, and stirred evenly to obtain an active component precursor solution B; the active component precursor solutions A and B were then poured into both sides of an H-type electrolytic cell, respectively, and the middle isolation part of the electrolytic cell was separated by a PE film. The H-type electrolytic cell was then moved as a whole into a 500 ml hydrothermal reactor; the mass ratio of niobium oxide: platinum oxide: tin oxide: ruthenium oxide was 5.4:1.5:0.01:2:0.01.

[0034] (2) Hydrothermal synthesis of catalyst core and nanoneedles

[0035] 1.9459 g of ascorbic acid was weighed and added to the active component precursor solution A obtained in step (1), and 0.0789 g of polyvinyl pyrrolidone was weighed and added to the active component precursor solution B obtained in step (1). At the same time, an appropriate amount of deionized water was added between the inner tank of the hydrothermal reactor and the H-type electrolytic cell. The mixture was hydrothermally heated at 80° C. for 2 h. In the first step, the catalyst core and the outer surface nanoneedles were hydrothermally synthesized; wherein the mass ratio of ascorbic acid: active component precursor solution A was 0.15:8, and the mass ratio of polyvinyl pyrrolidone: active component precursor solution B was 0.02:5.

[0036] (3) Hydrothermal synthesis of sea urchin-shaped catalysts

[0037] After the first hydrothermal reaction of step (2) is completed, the hydrothermal reaction temperature is increased to 180°C and the hydrothermal reaction is carried out for 4 hours. After the second hydrothermal reaction is completed, the mixture is cooled to room temperature, the mixture is taken out and washed with deionized water until neutral, and then dried at 80°C for 2 hours to obtain a sea urchin-shaped catalyst.

[0038] 2. Activity Test Results

[0039] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0040] Example 2

[0041] 1. Catalyst Preparation

[0042] (1) Preparation of active component precursor solution

[0043] 25.2285 g of cerium nitrate hexahydrate, 18.9550 g of niobium oxalate, and 0.1258 g of chloroplatinic acid were weighed and added to 221.5469 g of deionized water, and stirred evenly to obtain an active component precursor solution A; 4.3500 g of anhydrous stannous chloride and 0.0468 g of ruthenium trichloride were weighed and added to 43.9684 g of deionized water, and stirred evenly to obtain an active component precursor solution B; the active component precursor solutions A and B were then poured into both sides of an H-type electrolytic cell, respectively, and the middle isolation part of the electrolytic cell was separated by a PE film. The H-type electrolytic cell was then moved as a whole into a 500 ml hydrothermal reactor; the mass ratio of niobium oxide: platinum oxide: tin oxide: ruthenium oxide was 10:4:0.05:4:0.03.

[0044] (2) Hydrothermal synthesis of catalyst core and nanoneedles

[0045] 8.8619 g of ascorbic acid was weighed and added to the active component precursor solution A obtained in step (1), and 0.2418 g of polyvinyl pyrrolidone was weighed and added to the active component precursor solution B obtained in step (1). At the same time, an appropriate amount of deionized water was added between the inner tank of the hydrothermal reactor and the H-type electrolytic cell. The mixture was hydrothermally heated at 90 ° C for 4 h. The catalyst core and the outer surface nanoneedles were hydrothermally synthesized in the first step; wherein the mass ratio of ascorbic acid: active component precursor solution A was 0.4:12, and the mass ratio of polyvinyl pyrrolidone: active component precursor solution B was 0.05:10.

[0046] (3) Hydrothermal synthesis of sea urchin-shaped catalysts

[0047] After the first hydrothermal reaction of step (2) is completed, the hydrothermal reaction temperature is increased to 200° C. and the hydrothermal reaction is carried out for 8 hours. After the second hydrothermal reaction is completed, the mixture is cooled to room temperature, the mixture is taken out and washed with deionized water until neutral, and then dried at 100° C. for 4 hours to obtain a sea urchin-shaped catalyst.

[0048] 2. Activity Test Results

[0049] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0050] Example 3

[0051] 1. Catalyst Preparation

[0052] (1) Preparation of active component precursor solution

[0053] 17.3177 g of cerium chloride heptahydrate, 4.7590 g of niobium chloride, and 0.0755 g of chloroplatinic acid were weighed and added to 99.6851 g of deionized water, and stirred evenly to obtain an active component precursor solution A; 3.2626 g of anhydrous stannous chloride and 0.0312 g of ruthenium trichloride were weighed and added to 29.6436 g of deionized water, and stirred evenly to obtain an active component precursor solution B; the active component precursor solutions A and B were then poured into both sides of an H-type electrolytic cell, respectively, and the middle isolation part of the electrolytic cell was separated by a PE film. The H-type electrolytic cell was then moved as a whole into a 500 ml hydrothermal reactor; the mass ratio of niobium oxide: platinum oxide: tin oxide: ruthenium oxide was 8:2:0.03:3:0.02.

[0054] (2) Hydrothermal synthesis of catalyst core and nanoneedles

[0055] 3.6551 g of ascorbic acid was weighed and added to the active component precursor solution A obtained in step (1), and 0.1647 g of polyvinyl pyrrolidone was weighed and added to the active component precursor solution B obtained in step (1). At the same time, an appropriate amount of deionized water was added between the inner tank of the hydrothermal reactor and the H-type electrolytic cell. The mixture was hydrothermally heated at 90°C for 3 hours. The catalyst core and the outer surface nanoneedles were hydrothermally synthesized in the first step; wherein the mass ratio of ascorbic acid: active component precursor solution A was 0.3:10, and the mass ratio of polyvinyl pyrrolidone: active component precursor solution B was 0.04:8.

[0056] (3) Hydrothermal synthesis of sea urchin-shaped catalysts

[0057] After the first hydrothermal reaction of step (2) is completed, the hydrothermal reaction temperature is increased to 200° C. and the hydrothermal reaction is carried out for 4 hours. After the second hydrothermal reaction is completed, the mixture is cooled to room temperature, the mixture is taken out and washed with deionized water until neutral, and then dried at 100° C. for 2 hours to obtain a sea urchin-shaped catalyst.

[0058] 2. Activity Test Results

[0059] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0060] Comparative Example 1

[0061] 1. Catalyst Preparation

[0062] During the catalyst preparation process, the cerium salt, the precursor of the active component, was not added, and the other steps were the same as in Example 1.

[0063] 2. Activity Test Results

[0064] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0065] 3. Contrast effect

[0066] Compared with Example 1, the cerium salt, the precursor of the active component, was not added during the catalyst preparation process, and the synergistic effect of the composite oxide was significantly weakened, resulting in a significant decrease in catalyst activity.

[0067] Comparative Example 2

[0068] 1. Catalyst Preparation

[0069] The catalyst preparation process does not use a PE film to isolate the active component precursor solution, and the rest is the same as in Example 2.

[0070] 2. Activity Test Results

[0071] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0072] 3. Contrast effect

[0073] Compared with Example 2, the catalyst preparation process does not use PE film to separate the active component precursor solution. The active component precursor solution undergoes hydrothermal reaction under direct mixing conditions, and the special sea urchin-like morphology in which the outer surface nanoneedles are anchored on the inner core surface is not formed, resulting in a significant decrease in catalyst activity.

[0074] Comparative Example 3

[0075] 1. Catalyst Preparation

[0076] No polyvinyl pyrrolidone was added during the catalyst molding process, and the other steps were the same as in Example 3.

[0077] 2. Activity Test Results

[0078] 1 mL of a 40-60 mesh catalyst was poured into an 8 mm inner diameter quartz tube, secured with quartz wool and wire mesh. The tube was then placed in a tube furnace, and the actual catalytic reaction temperature was adjusted by controlling the furnace's heating temperature. Ethylbenzene was used as a representative VOC. Laboratory flue gas was used to simulate the inlet composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), ethylbenzene (500 ppm), and the remainder was N2. The total gas flow rate was 500 mL / min. NO concentration was measured using a Laoying 3021 portable carbon emission monitor, and ethylbenzene concentration was measured using a Trace 1300ISQ 7000 gas chromatograph-mass spectrometer. The NO removal efficiency and ethylbenzene removal efficiency after 25 minutes at a temperature of 140-200°C are shown in Tables 1-2.

[0079] 3. Contrast effect

[0080] Compared with Example 3, polyvinyl pyrrolidone was not added as a morphology directing agent during the catalyst preparation process, and outer surface nanoneedles with high specific surface area and strong anti-poisoning ability were not produced, resulting in a significant decrease in catalyst activity.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

Claims

1. A sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal, characterized by: The composite oxides of cerium, niobium and platinum are used as the core active components, the composite oxides of tin and ruthenium are used as the outer surface active components, ascorbic acid is used as the reducing agent and stabilizer, and polyvinyl pyrrolidone is used as the morphology directing agent. The product is obtained through a two-step hydrothermal synthesis, washing and drying. The preparation method of the catalyst is as follows: (1) Preparation of active component precursor solution Cerium salt, niobium salt, and platinum salt are added to deionized water and stirred evenly to obtain active component precursor solution A. Tin salt and ruthenium salt are added to deionized water and stirred evenly to obtain active component precursor solution B. Active component precursor solutions A and B are then poured into both sides of an H-type electrolytic cell, with the middle of the electrolytic cell separated by a PE film. The H-type electrolytic cell is then moved as a whole into a hydrothermal reactor. (2) Hydrothermal synthesis of catalyst core and nanoneedles Ascorbic acid is added to the active component precursor solution A obtained in step (1), and polyvinyl pyrrolidone is added to the active component precursor solution B obtained in step (1). Deionized water is added between the inner tank of the hydrothermal reactor and the H-type electrolytic cell to perform the first hydrothermal reaction to synthesize the catalyst core and the outer surface nanoneedles; the first hydrothermal reaction temperature in step (2) is 80-90 ° C, and the reaction time is 2-4 h; (3) Overall hydrothermal synthesis of sea urchin-shaped catalysts After the first hydrothermal reaction in step (2) is completed, the reaction temperature is increased to carry out the second hydrothermal reaction. After the reaction is completed, the mixture is cooled to room temperature, and the mixture is taken out and washed with deionized water until it is neutral, and then dried to obtain a sea urchin-shaped catalyst. The temperature of the second hydrothermal reaction in step (3) is 180~200℃, and the reaction time is 4~8h.

2. The sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal according to claim 1, characterized in that: The mass ratio of cerium oxide: niobium oxide: platinum oxide: tin oxide: ruthenium oxide in the catalyst is (5.4~10): (1.5~4): (0.01~0.05): (2~4): (0.01~0.03).

3. The sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal according to claim 1, characterized in that: The cerium salt described in step (1) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the niobium salt is niobium oxalate or niobium chloride; the platinum salt is chloroplatinic acid; the tin salt is anhydrous stannous chloride; and the ruthenium salt is anhydrous ruthenium trichloride.

4. The sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal according to claim 1, characterized in that: The mass ratio of ascorbic acid to active component precursor solution A described in step (2) is (0.15~0.4):(8~12).

5. The sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal according to claim 1, characterized in that: The mass ratio of polyvinyl pyrrolidone to active component precursor solution B in step (2) is (0.02~0.05):(5~10).

6. The sea urchin-shaped rare earth-based catalyst for simultaneous denitration and VOCs removal according to claim 3, characterized in that: The drying temperature in step (3) is 80-100°C, and the drying time is 2-4 hours.

7. Use of the catalyst according to claim 1 in the field of industrial flue gas purification.

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