Water-resistant low-temperature CO oxidation catalyst, its manufacturing method, and applications

Abstract

The present invention provides a water-resistant low-temperature CO oxidation catalyst, a manufacturing method thereof, and an application, belonging to the field of exhaust gas treatment technology. The present invention provides a water-resistant low-temperature CO oxidation catalyst, wherein the catalyst has a core-shell structure coated with a multi-metal oxide active component, and the active component contains at least two of metal oxides such as u, Co, Mn, Ce, Pt, Ag, Pd, Ir, etc. 2 The manufacturing method of the water-resistant low-temperature CO oxidation catalyst first manufactures a catalyst precursor with a core-shell structure coated with the active component by SiO 2 , and then includes the step of hydrophobically modifying the SiO 2 shell layer of the precursor to obtain. The present invention further provides an application of the manufacturing method and applies it to the manufacture of a CO-SCR catalyst. The catalyst provided by the present invention has a controllable thickness of its silica shell layer, high water resistance, and high catalytic activity. Its manufacturing method has a simple process, controllable conditions, low cost, easy industrialization popularization and use, and can be used for the manufacture of multiple types of catalysts.

Description

Technical Field

[0001] The present invention belongs to the field of exhaust gas treatment technology, and particularly relates to a water-resistant low-temperature CO oxidation catalyst, a method for manufacturing the same, and an application thereof.

Background Art

[0002] China's steel production accounts for more than 50% of the world's total steel production. However, steel production in China mainly follows a long process, with many steps, high energy consumption, many types of pollution, and a large total emissions. Therefore, steel enterprises have become a major industry for air pollution. Among them, in the sintering process, a large amount of CO, an air pollutant harmful to human health and the natural environment, is generated, and the emission volume is huge. Therefore, its treatment work has already become a key issue of concern to the steel industry. Currently, there are multiple methods for removing CO from sintering flue gas, and the most effective among them is the catalytic oxidation method. On the catalyst, H 2 O chemisorption is stronger than CO 2 chemisorption, and there is a synergistic effect on the adsorption of CO 2 and H 2 O, and the co-adsorption is enhanced. From research, it has been found that water molecules are adsorbed on oxygen vacancies, inhibiting the generation of active oxygen, thereby reducing the CO oxidation reaction activity of the catalyst in humid air. In the atmosphere under actual reaction conditions, a large amount of water vapor often exists, and in most cases, the catalyst activity is severely suppressed and the catalyst efficiency decreases. In addition, other trace gases present in the flue gas also affect the catalyst performance.

[0003] In view of the above problems, it is further necessary to develop a highly efficient catalyst to solve this problem.

[0004] In view of this, the present invention is particularly proposed.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to provide a water-resistant low-temperature CO oxidation catalyst, a method for manufacturing the same, and an application thereof in order to solve the above problems.

Means for Solving the Problems

[0006] In order to achieve the above object, the present invention adopts the following technical solutions.

[0007] A water-resistant low-temperature CO oxidation catalyst, wherein the catalyst has a core-shell structure coated with SiO 2 and the active component contains at least two of metal oxides such as Cu, Co, Mn, Ce, Pt, Ag, Pd, and Ir.

[0008] Optionally, the crystal form of the active component includes any one or more of spinel crystal form, perovskite crystal form, and hydrotalcite-like crystal form.

[0009] A method for manufacturing the water-resistant low-temperature CO oxidation catalyst, first, manufacturing a catalyst precursor having a core-shell structure coated with SiO 2 for the active component, and then hydrophobically modifying the SiO 2 shell layer of the precursor, including the step of obtaining.

[0010] Optionally, the manufacturing of the precursor includes dissolving the active component and ethyl orthosilicate in ethanol, then adding an aqueous ammonia solution, stirring, washing, and then drying.

[0011] Optionally, the hydrophobic modification includes dispersing the precursor in n-hexane, adding chlorotrimethylsilane, performing ultrasonic treatment, then centrifuging, washing, and drying. The time of the ultrasonic treatment is 1 to 5 h. The drying is at a temperature of 60 to 100 °C and a time of 9 to 13 h.

[0012] Optionally, the ratio of the mass of the precursor to the volume of the chlorotrimethylsilane is 1:0.5 to 2, where the unit of mass is g and the unit of volume is ml.

[0013] Optionally, the production of the precursor includes first coating by atomization and then hydrolysis. The atomization coating includes atomizing an ethyl silicate ethanol solution to form an atomization belt, and flowing the active ingredient air flow into the atomization belt to achieve coating of the active ingredient with ethyl silicate droplets. The hydrolysis includes putting the product obtained by the atomization coating into an alkaline solution for hydrolysis, and then sequentially performing centrifugation, filtration and dehydration.

[0014] Using the atomization-hydrolysis method, a core-shell structure in which a polymetallic oxide active ingredient is coated with a porous silica shell layer is formed. The catalytic active ingredient becomes the condensation nucleus, and the liquid condenses into a spherical shape under the action of molecular tension, whereby the performance of the produced catalyst is more excellent.

[0015] Optionally, the production of the precursor further includes a. The mass fraction of the ethyl silicate ethanol solution is 10 to 55%, and by changing the concentration of orthoethyl silicate, the thickness of the SiO 2 shell layer can be adjusted. Reducing the thickness of the shell layer is advantageous for the implementation of the catalytic oxidation process, and b. The alkaline solution includes an aqueous ammonia solution and / or a sodium hydroxide solution. c. The aqueous ammonia solution has a mass fraction of 5 to 15% and a temperature of 50 to 70 °C. d. The sodium hydroxide solution has a concentration of 0 to 0.01 Mol / L and a temperature of 15 to 35 °C. e. The hydrolysis time is 3 to 5 h. f. The dehydration satisfies one or more of the conditions that the temperature is 40 to 60 °C and the time is 8 to 14 h.

[0016] The thickness of the porous silica shell layer has an important influence on the activity and hydrophobicity of the catalyst. When the thickness is large, due to the hydrophobic groups on the surface, it is difficult for water to enter the core of the catalyst, but it also becomes difficult for reaction molecules to enter. In the present invention, by adjusting the reaction parameters, the thickness of the porous silica shell layer can be flexibly adjusted. In particular, by adjusting the concentration of ethyl silicate ethanol, the thickness of the porous shell layer can be effectively adjusted between 5 and 50 nm. The method is simple and feasible, and the adjustment effect is good. The present invention further provides an application of the manufacturing method, and the method is applied to the manufacture of a CO-SCR catalyst.

[0017] Optionally, the constituent metal elements of the active component used in the manufacture of the CO-SCR catalyst are Ir and Mn, and the element dosage ratio of Ir to Mn is 0.5 to 1.5:100.

Advantages of the Invention

[0018] The beneficial effects of the present invention are as follows.

[0019] The water-resistant low-temperature CO oxidation catalyst provided by the present invention has a silica shell layer structure and a core of a metal oxide active component, has high water resistance and high catalyst activity. Through experimental verification, under the water-containing condition at 180 °C, the conversion rate of carbon monoxide can reach 100%.

[0020] The present invention first coats the active substance, and then hydrophobically modifies the outer surface of the shell layer to form a core-shell structured catalyst, thereby realizing excellent water resistance performance on the premise of having high catalyst activity, solving the problem that the CO oxidation reaction activity of conventional catalysts decreases in humid air, improving the use efficiency of the catalyst, and enriching its application scenarios.

[0021] The manufacturing method provided by the present invention can manufacture a water-resistant low-temperature CO oxidation catalyst with excellent performance. In addition, by selecting the active component and dosage, a denitration catalyst can also be manufactured, and its applications are wide.

Brief Description of the Drawings

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings that need to be used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only part of the embodiments of the present invention, and those skilled in the art can also obtain other drawings based on these drawings without creative labor.

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, hereinafter, while referring to the drawings of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor shall fall within the protection scope of the present invention.

[0024] (Comparative Example 1) A core-shell type CO oxidation catalyst was manufactured using a common method, and the specific steps are as follows.

[0025] In S1, the active components were manufactured. Cu(NO 3 ) 2 ·3H 2 O of 2.416 g, Co(NO 3 ) 2 ·6H 2 O of 1.458 g, Mn(NO 3 ) 2Weighed 2.632 g of (aq) (50 wt%), placed it in a beaker, added deionized water, stirred at 25 °C for 15 min until uniformly mixed, then added ammonium bicarbonate solution, continued stirring for 60 min until precipitation was complete, then allowed to stand for 6 h, washed with distilled water and centrifuged, dried overnight in an oven at 80 °C, and then placed the obtained product in a tube furnace and heated at 3 °C / min to 500 °C in an air atmosphere and calcined for 3 h to obtain the active ingredient.

[0026] In S2, the precursor was prepared. The active ingredient obtained in S1 was dispersed in ethanol by ultrasonic waves, tetraethyl orthosilicate (TEOS) was added, and stirred at 450 rpm for 4 h. Then, a little ammonia water (25 - 28%, AR) and water were added. The mixture was stirred again at 450 rpm for 4 h, washed with ethanol, and then dried at 100 °C for 11 h to obtain A@SiO 2 A@SiO 2 was preheated in a vacuum oven at 150 °C for 11 h and cooled to 30 °C in the vacuum oven.

[0027] In S3, it was hydrophobically modified. The precursor obtained in S2 was dispersed in n - hexane, chlorotrimethylsilane was added such that 1 g of the precursor corresponded to 1 ml of chlorotrimethylsilane, then ultrasonicated at 25 °C for 3 h and centrifuged, the product was washed with n - hexane, and dried in a vacuum oven at 80 °C for 11 h to obtain a core - shell type CO oxidation catalyst obtained by a general method, and the thickness of the silica shell layer was 120 nm.

[0028] Performance test: The obtained catalyst was placed in a fixed - bed reactor. The experimental conditions were 4000 ppm CO, 200 ppm NO, 16% O 2 , 10% H 2 O, the carrier gas was N 2 , the reaction temperatures were 130 °C, 180 °C, 210 °C, and 250 °C respectively, the reaction pressure was atmospheric pressure, and the evaluation space velocity was 60000 gscm ―3 .

[0029] (Example 1) A water-resistant low-temperature CO oxidation catalyst was produced according to the method provided by the present invention. The specific steps are as follows.

[0030] In S1, the active component was produced. Cu(NO 3 ) 2 ·3H 2 O of 2.416 g and Mn(NO 3 ) 2 (aq) (50 wt%) of 3.579 g were weighed and placed in a beaker. Deionized water was added, and the mixture was stirred at 25 °C for 15 min until uniformly mixed. Subsequently, an ammonium bicarbonate solution was added, and stirring was continued for 60 min until precipitation was complete. Subsequently, it was left standing for 6 h, washed with distilled water and centrifuged, then dried overnight in an oven at 80 °C. Subsequently, the obtained product was placed in a tube furnace and heated at 3 °C / min to 500 °C in an air atmosphere and calcined for 3 h to obtain the active component.

[0031] In S2, the precursor was produced. Using the apparatus shown in Figure 1, a 20% ethyl silicate ethanol solution was pumped into high-pressure pump 1 and pressurized, then entered the atomization chamber 3 through the atomization orifice 2 to form an atomization belt. The active component obtained in S1 was dispersed and fed into the atomization chamber 3 by an air flow pump 4. At this time, after the ethyl silicate mist particles in the atomization chamber 3 coated the active component, the ethyl silicate mist particles gradually grew with the active component as the core and entered the collector 5 under the action of gravity for hydrolysis. There was an aqueous ammonia solution with a concentration of 10% at 60 °C in the collector 5, and ethyl silicate was hydrolyzed in the aqueous ammonia solution to form a porous silica shell layer. After hydrolysis was carried out for 4 h, centrifugation was performed, and the product was collected and placed in a vacuum oven at 50 °C and dried for 12 h to obtain the precursor.

[0032] In S3, it was hydrophobically modified. The precursor obtained in S2 was dispersed in n - hexane, and chlorotrimethylsilane was added such that the precursor per gram corresponded to 1 ml of chlorotrimethylsilane. Then, after ultrasonic treatment at 25 °C for 3 hours, it was centrifuged, the product was washed with n - hexane, and dried in a vacuum oven at 80 °C for 11 hours to obtain a water - resistant low - temperature CO oxidation catalyst, and the thickness of the silica shell layer was 9 nm.

[0033] The TEM image of the water - resistant low - temperature CO oxidation catalyst obtained in Example 1 is as shown in Figure 2. As can be seen from Figure 2, the core - shell catalyst can be effectively synthesized using the method provided in the present invention.

[0034] The conditions for the performance test are the same as those in Comparative Example 1.

[0035] (Example 2) The constituent metal elements and dosages of the active components in S1 were 2.416 g of Cu(NO 3 ) 2 ·3H 2 O, 2.037 g of Co(NO 3 ) 2 ·6H 2 O, 1.302 g of Ce(NO 3 ) 3 ·6H 2 O, and the calcination temperature was 550 °C. The difference from Example 1 was that the concentration of the ethyl silicate ethanol solution in S2 was 10%.

[0036] (Example 3) The constituent metal elements and dosages of the active components in S1 were 3.81 g of Ce(NO 3 ) 3 ·6H 2 O, 1.569 g of Mn(NO 3 ) 2 (aq)(50 wt%), 0.0482 g of Pt(NO 3 ) 2 The difference from Example 1 was that the concentration of the ethyl silicate ethanol solution used in S2 was 35%.

[0037] The thickness of the silica shell layer of the water-resistant low-temperature CO oxidation catalyst obtained in this example was 11 nm.

[0038] (Example 4) The constituent metal elements and dosages of the active components in S1 were 3.81 g of Ce(NO 3 ) 3 ·6H 2 O, 2.416 g of Cu(NO 3 ) 2 ·3H 2 O, 0.0482 g of Pt(NO 3 ) 2 This is different from Example 1 in that the concentration of the ethyl silicate ethanol solution used in S2 was 55%.

[0039] (Example 5) The constituent metal elements and dosages of the active components in S1 were 3.579 g of Mn(NO 3 ) 2 (aq)(50 wt%), 2.9103 g of Co(NO 3 ) 2 ·6H 2 O, 0.1152 g of Pd(NO 3 ) 2 (aq)(15 wt%). This is different from Example 1 in that the concentration of the ethyl silicate ethanol solution used in S2 was 10%.

[0040] The thickness of the silica shell layer of the water-resistant low-temperature CO oxidation catalyst obtained in this example was 6 nm, and its TEM image was as shown in Figure 3.

[0041]

Table 1

[0042] As can be seen from Figures 2 and 3, the water-resistant low-temperature CO oxidation catalyst produced by the method provided in the present invention has a distinct core-shell structure, and the thickness of the shell layer can be adjusted. It has hydrophobicity, which is advantageous for CO to enter the catalyst interior for oxidation reaction, improving the oxidation efficiency of CO.

[0043] The catalyst manufacturing method provided in the embodiments of the present invention is the same as that of Comparative Example 1 in terms of the active ingredient and the modification method, except for the thickness of different core-shell layers due to different core-shell manufacturing methods. As can be seen from the performance results, the thin core-shell layer provided in the present invention is advantageous for the uptake of reaction molecules such as CO, O 2 etc. and the catalytic reaction, and the conversion rate of 95% can be reduced from 250 °C to 180 °C or lower for the conventional manufacturing method.

[0044] (Example 6) The constituent metal elements and dosages of the active ingredient in S1 are 3.579 g of Mn(NO 3 ) 2 (aq)(50 wt%), 0.1152 g of C 12 H 18 Ir 3 O 13 .C 2 H 3 O 2 .3(H 2 O), and the concentration of the ethyl silicate ethanol solution used in S2 is 15%, which is different from Example 1.

[0045] Performance test: The obtained catalyst was placed in a fixed-bed reactor. The experimental conditions were 4000 ppm CO, 200 ppm NO, 5% O 2 , 10% H 2 O, the carrier gas was N 2 , the evaluation space velocity was 30000 gscm ―3 , and the reaction pressure was normal pressure. The reaction temperatures were 130 °C, 180 °C, 210 °C, and 250 °C respectively, and the denitration rates were 22.2%, 24.6%, 41.8%, and 66.4% respectively.

[0046] As can be seen from Example 6, a CO-SCR catalyst with excellent denitration performance is manufactured by the manufacturing method provided in the present invention.

[0047] Each of the technical features of the above embodiments can be arbitrarily combined. For the sake of brevity, not all possible combinations of all the technical features in the above embodiments are described. However, it should be noted that as long as these combinations of technical features are not contradictory, they should be considered to be within the scope described in this specification. The above embodiments only show some embodiments of the present application, and their descriptions are specific and detailed, but they cannot be understood as limiting the scope of the invention patent. Those skilled in the art can make some modifications and improvements on the premise of not departing from the concept of the present application, and all of these belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be in accordance with the scope of the appended patent claims.

Explanation of Signs

[0048] 1... High-pressure pump 2... Atomization orifice 3... Atomization chamber 4... Airflow pump 5... Collector.

Claims

1. The multimetal oxide active ingredient is SiO ２ The active component has a core-shell structure coated with at least two of the metal oxides of Cu, Co, Mn, Ce, Pt, Ag, Pd, and Ir; A water-resistant low-temperature CO oxidation catalyst.

2. The crystalline form of the active ingredient includes any one or more of a spinel crystalline form, a perovskite crystalline form, and a hydrotalcite crystalline form; The catalyst according to claim 1 .

3. A method for producing the water-resistant low-temperature CO oxidation catalyst according to any one of claims 1 to 2, comprising the steps of: first, converting the active component into SiO ２ A catalyst precursor having a core-shell structure is prepared by coating the catalyst precursor with SiO. ２ hydrophobically modifying the shell layer to obtain The present invention relates to a method for producing a water-resistant low-temperature CO oxidation catalyst.

4. The preparation of the precursor includes dissolving the active ingredient and ethyl orthosilicate in ethanol, then adding aqueous ammonia, stirring, washing, and drying. The method according to claim 3 .

5. The hydrophobic modification includes dispersing the precursor in n-hexane, adding chlorotrimethylsilane, sonicating, centrifuging, washing, and drying; The ultrasonic treatment time is 1 to 5 h, The drying is performed at a temperature of 60 to 100° C. for 9 to 13 hours. The method according to claim 3 .

6. The ratio of the mass of the precursor to the volume of the chlorotrimethylsilane is 1:0.5-2, where the unit of mass is g and the unit of volume is ml; The method according to claim 5 .

7. The preparation of said precursor comprises a first coating by atomization and then hydrolysis; The atomization coating includes atomizing an ethyl silicate ethanol solution to form an atomization belt, and flowing the active ingredient airflow into the atomization belt to achieve coating of the active ingredient with ethyl silicate mist particles; The hydrolysis step includes hydrolyzing the product obtained by the spray coating in an alkaline solution, followed by centrifuging, filtering and dehydrating the product in sequence. The method according to claim 3 .

8. The preparation of the precursor further comprises: a. The mass fraction of the ethyl silicate ethanol solution is 10 to 55%; b. The alkaline solution contains an aqueous ammonia solution and / or a sodium hydroxide solution; c. The ammonia aqueous solution has a mass fraction of 5 to 15% and a temperature of 50 to 70° C.; d. The sodium hydroxide solution has a concentration of 0 to 0.01 Mol / L and a temperature of 15 to 35° C.; e. The hydrolysis time is 3 to 5 hours; f. The dehydration satisfies one or more of the following conditions: temperature is 40 to 60° C., and time is 8 to 14 hours; The method according to claim 7 .

9. Application of the method according to any one of claims 3 to 8, wherein the method is applied to the production of a CO-SCR catalyst.

2. Application of the manufacturing method characterized in that

10. The constituent metal elements of the active component used in the production of the CO-SCR catalyst are Ir and Mn, The element dosage ratio of Ir to Mn is 0.5-1.5:100; 10. The application according to claim 9 .

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