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 manufacturing method thereof, and applications.

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 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 among them, the most effective is the catalytic oxidation method. On the catalyst, H2O chemisorption is stronger than CO2 chemisorption, and there is a synergistic effect on the adsorption of CO2 and H2O, 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 is reduced. In addition, other trace gases present in 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 manufacturing method thereof, and applications in order to solve the above problems. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention employs the following technical solutions.

[0007] A water-resistant low-temperature CO oxidation catalyst, wherein the catalyst has a core-shell structure in which a polymetallic oxide active component is coated with SiO2, and the active component comprises at least two metal oxides such as Cu, Co, Mn, Ce, Pt, Ag, Pd, and Ir.

[0008] The crystalline form of the active ingredient may be selected to include one or more of the following: spinel crystalline form, perovskite crystalline form, or hydrotalcite-like crystalline form.

[0009] A method for producing the water-resistant low-temperature CO oxidation catalyst, comprising the steps of first producing a catalyst precursor having a core-shell structure in which the active component is coated with SiO2, and then hydrophobically modifying the SiO2 shell layer of the precursor to obtain the catalyst.

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

[0011] Optionally, the hydrophobic modification includes dispersing the precursor in n-hexane, adding chlorotrimethylsilane, sonicating, then centrifuging, washing, and drying. The duration of the ultrasonic treatment is 1 to 5 hours. The aforementioned drying process is carried out at a temperature of 60-100°C for 9-13 hours.

[0012] Selectively, 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] The preparation of the precursor may optionally include first coating by atomization, and then hydrolysis. The atomizing coating includes atomizing an ethyl silicate ethanol solution to form an atomizing belt, and flowing the active ingredient airflow onto the atomizing belt to achieve coating of the active ingredient with ethyl silicate atomized particles. The hydrolysis includes hydrolyzing the product obtained by the atomizing coating by placing it in an alkaline solution, followed by sequential centrifugation, filtration, and dehydration.

[0014] Using an atomization-hydrolysis method, a core-shell structure is formed by coating a polymetallic oxide active component with a porous silica shell layer. The catalytic active component acts as a condensation nucleus, and the liquid condenses into a spherical shape under the action of molecular tension, thereby improving the performance of the manufactured catalyst.

[0015] The production of the precursor can be further, a. The mass fraction of the ethyl silicate ethanol solution is 10-55%, and the thickness of the SiO2 shell layer can be adjusted by changing the concentration of ethyl orthosilicate. Reducing the thickness of the shell layer creates conditions favorable for carrying out the catalytic oxidation process. b. The alkaline solution includes conditions such as aqueous ammonia solution and / or sodium hydroxide solution, c. The ammonia aqueous solution has a mass fraction of 5-15% and a temperature of 50-70°C, d. The sodium hydroxide solution is provided under the conditions of having a concentration of 0 to 0.01 mol / L and a temperature of 15 to 35°C. e. The condition that the hydrolysis time is 3 to 5 hours, f. The dehydration process satisfies one or more of the following conditions: a temperature of 40-60°C and a duration of 8-14 hours.

[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 elemental 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 of 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 the conventional catalyst in humid air decreases, 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 explain the specific embodiments of the present invention or the technical solutions in the prior art, the drawings necessary for describing the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only a 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] It is a schematic diagram of the apparatus and procedure for manufacturing the precursor used in Example 1. [Figure 2] It is a TEM diagram of the water-resistant low-temperature CO oxidation catalyst manufactured in Example 1. [Figure 3] It is a TEM diagram of the water-resistant low-temperature CO oxidation catalyst manufactured in Example 5.

Embodiments for Carrying out the Invention

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are only a 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 belong to 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 component was manufactured. 2.416 g of Cu(NO3)2·3H2O, 1.458 g of Co(NO3)2·6H2O, and 2.632 g of Mn(NO3)2(aq)(50 wt%) were weighed out and placed in a beaker. Deionized water was added and the mixture was stirred at 25°C for 15 minutes until homogeneous. Subsequently, ammonium bicarbonate solution was added and the mixture was stirred for 60 minutes until precipitation was complete. After standing for 6 hours, the mixture was washed with distilled water and centrifuged. The mixture was then dried overnight in an 80°C oven. The resulting product was then placed in a tube furnace and calcined under an air atmosphere at a rate of 3°C / min until it reached 500°C for 3 hours to obtain the active ingredient.

[0026] In S2, a precursor was prepared. The active ingredient obtained in S1 was dispersed in ethanol by ultrasound, ethyl orthosilicate (TEOS) was added, and the mixture was stirred at 450 rpm for 4 hours. A small amount of aqueous ammonia (25-28%, AR) and water were then added. The mixture was stirred again at 450 rpm for 4 hours, washed with ethanol, and then dried at 100°C for 11 hours to obtain A@SiO2. A@SiO2 was preheated in a vacuum oven at 150°C for 11 hours and then cooled to 30°C in the vacuum oven.

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

[0028] Performance test: The obtained catalyst was placed in a fixed-bed reactor. The experimental conditions were 4000 ppm CO, 200 ppm NO, 16% O2, and 10% H2O, with N2 as the carrier gas. The reaction temperatures were 130°C, 180°C, 210°C, and 250°C, respectively. The reaction pressure was atmospheric pressure, and the evaluated space velocity was 60000 gscm. ―3 That was the case.

[0029] (Example 1) A water-resistant low-temperature CO oxidation catalyst is produced according to the method provided in the present invention, and the specific steps are as follows:

[0030] In S1, the active ingredient was produced. 2.416 g of Cu(NO3)2·3H2O and 3.579 g of Mn(NO3)2(aq)(50 wt%) were weighed out and placed in a beaker. Deionized water was added and the mixture was stirred at 25°C for 15 minutes until homogeneous. Subsequently, ammonium bicarbonate solution was added and the mixture was stirred for 60 minutes until precipitation was complete. After standing for 6 hours, the mixture was washed with distilled water and centrifuged. The mixture was then dried overnight in an 80°C oven. The resulting product was then placed in a tube furnace and calcined under an air atmosphere at a rate of 3°C / min until it reached 500°C for 3 hours to obtain the active ingredient.

[0031] In S2, the precursor was produced. Using the apparatus shown in Figure 1, a 20% ethyl ethanol silicate solution is fed into the high-pressure pump 1 and pressurized, then passed through the atomizing orifice 2 to the atomizing chamber 3 to form an atomizing belt. The active ingredient obtained in S1 was dispersed into the atomization chamber 3 by the airflow pump 4. At this time, the ethyl silicate mist particles in the atomization chamber 3 coated the active ingredient, and then the ethyl silicate mist particles gradually grew larger with the active ingredient as a core. Under the action of gravity, they entered the collector 5 and underwent hydrolysis. The collector 5 contained an aqueous ammonia solution with a concentration of 10% at 60°C, and the ethyl silicate was hydrolyzed in the aqueous ammonia solution, forming a porous silica shell layer. After hydrolysis was carried out for 4 hours, the product was centrifuged, collected, and dried in a vacuum oven at 50°C for 12 hours to obtain the precursor.

[0032] In S3, the material was hydrophobically modified. The precursor obtained in S2 was dispersed in n-hexane, and chlorotrimethylsilane was added so that 1g of precursor corresponded to 1ml of chlorotrimethylsilane. After sonication at 25°C for 3 hours, the mixture 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, with a silica shell layer thickness of 9nm.

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

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

[0035] (Example 2) The constituent metal elements and amounts of the active ingredients in S1 are 2.416 g of Cu(NO3)2·3H2O, 2.037 g of Co(NO3)2·6H2O, and 1.302 g of Ce(NO3)3·6H2O, and the calcination temperature is 550°C. The concentration of the ethyl silicate ethanol solution in S2 is 10%, which is different from Example 1.

[0036] (Example 3) The constituent metal elements and dosages of the active ingredients in S1 are 3.81 g of Ce(NO3)3·6H2O, 1.569 g of Mn(NO3)2(aq) (50 wt%), and 0.0482 g of Pt(NO3)2, and the concentration of the ethyl silicate ethanol solution used in S2 is 35%, which is different from Example 1.

[0037] The silica shell layer thickness 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 ingredients in S1 are 3.81 g of Ce(NO3)3·6H2O, 2.416 g of Cu(NO3)2·3H2O, and 0.0482 g of Pt(NO3)2, and the concentration of the ethyl silicate ethanol solution used in S2 is 55%, which is different from Example 1.

[0039] (Example 5) The constituent metal elements and dosages of the active ingredients in S1 are 3.579 g of Mn(NO3)2(aq) (50 wt%), 2.9103 g of Co(NO3)2·6H2O, and 0.1152 g of Pd(NO3)2(aq) (15 wt%), and the concentration of the ethyl silicate ethanol solution used in S2 is 10%, which is different from Example 1.

[0040] The silica shell layer thickness of the water-resistant low-temperature CO oxidation catalyst obtained in this embodiment is 6 nm, and its TEM diagram is 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, the thickness of the shell layer is adjustable, it is hydrophobic, and it is advantageous for CO to enter the catalyst and undergo the oxidation reaction, thereby improving the CO oxidation efficiency.

[0043] The catalyst manufacturing method provided in the examples of the present invention is the same as that of Comparative Example 1 in terms of the active ingredients and modification method, except for the different core-shell layer thicknesses 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 incorporation of reaction molecules such as CO and O2 and for catalytic reactions, and the conversion rate of 95% can be reduced from 250°C in the conventional manufacturing method to 180°C or lower.

[0044] (Example 6) The constituent metal elements and dosages of the active ingredient in S1 are 3.579 g Mn(NO3)2(aq) (50 wt%) and 0.1152 g C 12 H 18 Ir3O 13 The difference from Example 1 is that the solution is .C2H3O2.3(H2O), and the concentration of the ethyl silicate ethanol solution used in S2 is 15%.

[0045] Performance test: The obtained catalyst was placed in a fixed-bed reactor. The experimental conditions were 4000 ppm CO, 200 ppm NO, 5% O2, 10% H2O, with N2 as the carrier gas and an evaluation space velocity of 30000 gscm. ―3 The reaction pressure was atmospheric pressure. The reaction temperatures were 130°C, 180°C, 210°C, and 250°C, respectively, and the denitrification rates were 22.2%, 24.6%, 41.8%, and 66.4%, respectively.

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

[0047] The technical features of the above embodiments can be combined in any way, and for the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, it should be noted that these combinations of technical features should be considered to fall within the scope described herein, as long as they are consistent. The above embodiments are merely examples of some embodiments of the present application, and although the descriptions are specific and detailed, they cannot be understood as limiting the scope of the invention patent. Furthermore, those skilled in the art can make some modifications and improvements without departing from the concept of the present application, and all of these fall within the scope of protection of the present application. Therefore, the scope of protection of the patent of the present application should be in accordance with the attached claims. [Explanation of symbols]

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

Claims

1. First, the active ingredient is SiO ２ A catalyst precursor with a core-shell structure coated with is manufactured, and then the SiO of the precursor is processed. ２ The process includes the step of hydrophobically modifying the shell layer to obtain a water-resistant low-temperature CO oxidation catalyst. The hydrophobic modification includes dispersing the precursor in n-hexane, adding chlorotrimethylsilane, sonicating, then centrifuging, washing, and drying. The duration of the ultrasonic treatment is 1 to 5 hours. The drying process described above is carried out at a temperature of 60 to 100°C for a duration of 9 to 13 hours. 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. The production of the aforementioned precursor includes first coating by atomization, and then hydrolysis. The atomizing coating includes atomizing an ethyl ethanol orthosilicate solution to form an atomizing belt, and flowing the active ingredient airflow onto the atomizing belt to achieve coating of the active ingredient with ethyl orthosilicate atomized particles. The hydrolysis includes hydrolyzing the product obtained by the atomizing coating by placing it in an alkaline solution, followed by sequentially performing centrifugation, filtration, and dehydration. The mass fraction of the ethyl ethanol orthosilicate solution is 10 to 55%. The aforementioned water-resistant low-temperature CO oxidation catalyst uses a polymetallic oxide active component in SiO ２ It has a core-shell structure coated with [a certain material], and the active component contains at least two of the metal oxides of Cu, Co, Mn, Ce, Pt, Pd, and Ir, thereby improving the oxidation efficiency of CO up to 210°C. The crystalline form of the active ingredient includes one or more of the following: spinel crystalline form, perovskite crystalline form, and hydrotalcite crystalline form. A method for producing a water-resistant low-temperature CO oxidation catalyst, characterized by the following:

2. The production of the aforementioned precursor further involves a. The alkaline solution includes conditions such as aqueous ammonia solution and / or sodium hydroxide solution, b. The ammonia aqueous solution has a mass fraction of 5 to 15% and a temperature of 50 to 70°C, c. The sodium hydroxide solution is provided under the conditions of having a concentration of 0 to 0.01 mol / L and a temperature of 15 to 35°C, d. The condition that the hydrolysis time is 3 to 5 hours, e. The dehydration satisfies one or more of the following conditions: a temperature of 40 to 60°C and a duration of 8 to 14 hours. The manufacturing method according to claim 1, characterized in that it

3. The water-resistant low-temperature CO oxidation catalyst is a CO-SCR catalyst, The manufacturing method according to claim 1 or 2, characterized in that it is a method of production according to claim 1 or 2.

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