Process for preparing a high-activity supported cobalt-based catalyst

Abstract

The application discloses a kind of high-activity supported cobalt-based catalyst's production process in thermal catalytic technical field, comprising the following:1) precipitation reaction: in hydrothermal precipitation reactor, in 0~0.08mol / L cobalt nitrate and 0~0.008mol / L manganese nitrate aqueous solution Add hexadecyl trimethyl ammonium bromide aqueous solution and urea, and urea and cobalt cation precipitate to generate cobalt hydroxide;2) solid-liquid separation: in solid-liquid separation equipment, the material obtained in the above step is carried out solid-liquid separation, and the solid-phase material obtained by solid-liquid separation is a cobalt hydroxide crude product, and a cobalt carbonate product is obtained after further impurity removal treatment;3) heat treatment: in heat treatment reaction equipment, the cobalt carbonate product obtained in the above step is heat treated to obtain a product with manganese oxide supported on tricobalt tetroxide, the application realizes the complete catalytic oxidation of carbon monoxide at room temperature, thereby reducing carbon monoxide emission, and realizing energy saving and emission reduction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of thermal catalytic technology, in particular to a cobalt-based catalyst manufacturing process. BACKGROUND

[0002] With the progress of society and the improvement of living standards, people are facing new crises and challenges while obtaining rich material resources. The popularity of a large number of motor vehicles makes people's daily travel more convenient, but also directly leads to the rapid increase of motor vehicle ownership, so the exhaust emission problem and purification treatment problem of motor vehicles need to be solved. The pollutants in automobile exhaust mainly include carbon monoxide (CO), hydrocarbons, sulfur oxides, nitrogen oxides, and suspended solid particles. About 40-80% of automobile exhaust emissions are released during the cold start process, and during the cold start process of the automobile engine, CO and hydrocarbons are discharged into the atmosphere without treatment. At present, air pollution problems are attracting more and more attention, and CO is one of the three major air pollutants in the world, which is colorless and odorless and kills people invisibly. CO has strong toxicity, and CO has strong binding force with hemoglobin in human blood, making it difficult for oxygen to combine with hemoglobin, ultimately leading to brain hypoxia and poisoning. When the volume content of CO in the air reaches 0.01-0.12%, people will have symptoms such as headache, nausea, and coma, and when the content reaches 0.16-0.60%, the higher the concentration of CO, the greater the possibility of death in a short time. In order to solve the problem of CO gas emission, the most widely used technology at present is thermal catalytic technology, that is, using a catalyst to convert toxic CO gas into non-toxic carbon dioxide (CO2) at a certain temperature before emission. The addition of the catalyst reduces the activation energy of the catalytic oxidation reaction, thereby increasing the reaction rate, reducing the reaction conversion temperature, and saving unnecessary energy consumption.

[0003] In cobalt-based catalysts, compared with CoO with rock salt structure and Co2O3 with hexagonal structure, cobalt trioxide with spinel structure is widely used in environmental catalysis. This is because Co(II) and Co(III) exist in cobalt trioxide, Co(II) is located in the spinel tetrahedral site, and Co(III) is located in the spinel octahedral site, which makes it subject to the interaction between the two valence ions when participating in some redox reactions, thereby showing excellent catalytic oxidation activity. However, in the presence of water in the reaction, the activity of cobalt trioxide will be greatly affected, and the reaction active site will be blocked, resulting in catalyst deactivation. In addition, the loading of metal doping will affect the electronic structure, redox ability and defect of cobalt oxide to some extent, which will change the activity of the catalyst. More importantly, low-temperature catalytic CO oxidation technology not only has great significance in human health and environmental protection such as automobile exhaust treatment, but also has wide and important practical application value in the purification of gas flow in petrochemical industry, the reforming process of catalysts in hydrocarbon processing, the development of proton fuel cells, CO gas sensor purifier and other fields. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a manufacturing process of a high-activity supported cobalt-based catalyst, which realizes complete catalytic oxidation of carbon monoxide at room temperature, thereby reducing carbon monoxide emissions and achieving energy saving and emission reduction.

[0005] The purpose of the present application is achieved by a manufacturing process of a high-activity supported cobalt-based catalyst, comprising the following steps:

[0006] Step 1) precipitation reaction: in a hydrothermal precipitation reactor, 0-0.08 mol / L cobalt nitrate and 0-0.008 mol / L manganese nitrate aqueous solution are added with cetyltrimethylammonium bromide aqueous solution and urea, and urea reacts with cobalt cations to form cobalt hydroxide by precipitation;

[0007] Step 2) solid-liquid separation: in a solid-liquid separation device, the material obtained in the previous step is subjected to solid-liquid separation, and the solid material obtained by solid-liquid separation is a cobalt hydroxide crude product, which is further treated to obtain a cobalt carbonate product;

[0008] Step 3) heat treatment: in a heat treatment reaction device, the cobalt carbonate product obtained in the previous step is subjected to heat treatment to obtain a product of manganese oxide loaded on cobalt trioxide.

[0009] Further, in the precipitation reaction of step 1), the molar ratio of urea to cobalt cations is (0-0.017):(0-0.08), and the operating temperature is 25°C.

[0010] Furthermore, the concentration of the urea aqueous solution in step 1) is 0~0.28 mol / L, and the operating temperature is 25℃.

[0011] Furthermore, the concentration of the hexadecyltrimethylammonium bromide aqueous solution in step 1) is 0~0.13 mol / L, and the operating temperature is 25℃.

[0012] Furthermore, in the hydrothermal precipitation reaction described in step 1), the hydrothermal temperature is 160℃~180℃ and the hydrothermal time is 2h~5h.

[0013] Furthermore, the separation method in step 2) is vacuum filtration, with a drying temperature of 80°C and a drying time of 12 hours.

[0014] Furthermore, in step 2) of the solid-liquid separation process, the solid-liquid separation device is any one of a pressure filter, a centrifugal filter, a leaf filter, a pipeline filter, and a vacuum filter.

[0015] Furthermore, in step 3), the heat treatment temperature is 150℃~550℃ and the heat treatment time is 3h.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention employs a hydrothermal precipitation method to obtain manganese-doped nanowires stacked into spherical cobalt tetroxide, thereby achieving complete low-temperature carbon monoxide conversion. By adding manganese, this invention increases oxygen adsorption on the surface of the cobalt-based catalyst, promotes carbon monoxide adsorption, enhances the activity of the cobalt-based catalyst, achieves complete carbon monoxide conversion at room temperature, and reduces direct carbon monoxide emissions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 The present invention includes three different morphologies of stacked spheres: (a) nanowire stacked spheres; (b) nanosheet stacked spheres; and (c) cubic stacked spheres.

[0020] Figure 2 The following are XPS spectra of the catalyst samples of this invention: (a) is the Co 2p XPS spectrum, and (b) is the O 1s XPS spectrum. Detailed Implementation

[0021] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0022] The test materials used in the embodiments of the present application are commercially available, unless otherwise specified. In the embodiments of the present application, the catalyst evaluation, conversion rate and selectivity calculation methods are as follows:

[0023] In the experiment, the CO probe reaction was carried out in a CO catalytic oxidation micro fixed bed evaluation device. In the constant temperature zone of the reaction tube, quartz wool was used as the reaction bed support, 50 mg of the sample and 50 mg of quartz sand were accurately weighed, mixed uniformly and then filled in the reaction tube. Before the reaction started, the catalyst was pretreated first, and the sample surface impurities were removed by blowing at 180 ℃ for 120 min under high-purity N2 atmosphere to promote the generation of oxygen vacancies on the catalyst surface. After the pretreatment was completed, the reactor temperature was reduced to room temperature, and then the test was started. The test reaction gas was CO mixed gas (V CO :V O2 :V N2 =1.6:21.4:77.0), the inlet gas flow rate was 30 mL / min, the reactor was controlled at the reaction temperature for 30 min, and then the sampling was started. Each temperature point was sampled for 5 times, and the average value was finally taken. The reacted gas was introduced into the HF-900 gas chromatograph (GC) for online analysis and processing. The gas chromatograph filling column was a 5A molecular sieve filling column (Φ4 mm×2 mm stainless steel column), and the chromatographic analysis conditions were as follows: column temperature 45 ℃, vaporization temperature 100 ℃, TCD thermal conductivity detector temperature 100 ℃, and bridge flow 100 mA. The conversion rate of CO was calculated according to the formula:

[0024]

[0025] X CO(%) —CO conversion rate; (CO) in —Initial CO concentration; (CO) out —CO concentration after reaction.

[0026] Example 1

[0027] In a 100 mL beaker, Co(N03)2*6H20 1.46 g, Mn(N03)2*xH20 0.1 g were dissolved in 60 mL deionized water, and stirred for 30 min. To the above solution, CTAB 0.0175 g, CO(NH2)21 g were added, and stirred for 30 min. The solution was put into a high-pressure reactor, and heated at 160 °C for 2 h. After the hydrothermal reaction, the temperature was allowed to decrease to room temperature. The obtained dark red precursor was washed with 400 mL deionized water, and filtered. The precursor was dried at 80 °C for 12 h. After drying, the solid was placed in a crucible furnace, and heated to 250 °C at a rate of 2 °C / min under air atmosphere, and calcined for 3 h to obtain a supported cobalt-based catalyst.

[0028] Example 2

[0029] In a 100 mL beaker, (CH3COO)2Co*4H20 1.25 g, Mn(N03)2*xH20 0.1 g were dissolved in 60 mL ethylene glycol, and stirred for 30 min. To the above solution, CTAB 2.916 g, CH3COONa 2.45 g were added, and stirred for 30 min. The solution was put into a high-pressure reactor, and heated at 180 °C for 12 h. After the hydrothermal reaction, the temperature was allowed to decrease to room temperature. The obtained precursor was washed with 400 mL deionized water, and filtered. The precursor was dried at 80 °C for 12 h. After drying, the solid was placed in a crucible furnace, and heated to 250 °C at a rate of 2 °C / min under air atmosphere, and calcined for 3 h to obtain a supported cobalt-based catalyst.

[0030] Example 3

[0031] In a 100 mL beaker, (CH3COO)2Co*4H20 1.25 g, Mn(N03)2*xH20 0.1 g were dissolved in 60 mL ethylene glycol, and stirred for 30 min. To the above solution, CO(NH2)21 g was added, and stirred for 30 min. The solution was put into a high-pressure reactor, and heated at 180 °C for 12 h. After the hydrothermal reaction, the temperature was allowed to decrease to room temperature. The obtained precursor was washed with 400 mL deionized water, and filtered. The precursor was dried at 80 °C for 12 h. After drying, the solid was placed in a crucible furnace, and heated to 250 °C at a rate of 2 °C / min under air atmosphere, and calcined for 3 h to obtain a supported cobalt-based catalyst.

[0032] Examples 4-10

[0033] Table 1 Influence of different preparation processes on the performance of carbon monoxide catalytic oxidation

[0034]

[0035] From Table 1, Example 1 is a nanowire accumulation ball, Example 2 is a nanosheet accumulation ball, and Example 3 is a cubic accumulation ball, as shown in Figure 1 The three similar morphologies, the same metal addition amount, and the prepared cobalt-based catalysts are compared, and the nanowire accumulation ball with 10% manganese metal addition has the best performance and can be completely converted at room temperature. The specific surface area of the nanowire accumulation ball catalyst is larger than that of the other two morphologies, thereby exposing more defects and being beneficial to the participation of high-activity oxygen in the carbon monoxide oxidation reaction. As can be seen from Table 1, Examples 1 and 4-7, when the manganese addition amount is different, the performance of the catalysts is different. Too low manganese content will lead to incomplete electron transfer between Mn-Co species; when the manganese content is too high, the manganese species will accumulate and aggregate on the surface of the nanowire accumulation ball, thereby blocking the pores and reducing the performance.

[0036] Figure 2 As can be seen from -a, the addition of Mn species makes the Co 2p orbital of the series of catalysts shift to the high binding energy direction, indicating that the electron density of the surface Co species decreases, which indicates that there is a strong interaction between Mn-Co species. As can be seen from Table 2, the introduction of Mn species makes the Co 3+ content increase, which further indicates that the doping of manganese species will reduce the electron density of the surface cobalt species.

[0037] Table 2 XPS fitting data results of samples

[0038] Sample name Co 3+ / (Co 2+ +Co 3+ ) a (%)]]> O ads / (O latt +O ads ) a (%)]]> Co3O4-C 53.77 21.61 10MnCo 55.23 26.68

[0039] Figure 2 As can be seen from -b, the introduction of Mn species makes the O 1s of the catalyst shift to the low binding energy direction, which may be due to the increased mobility of O ads and the increased electron density. From the XPS fitting results in Table 2, the 10MnCo catalyst has more surface active oxygen content and Co 3+ content, and in combination with its excellent performance in catalyzing CO oxidation, a large amount of O ads and Co 3+ play an important role in the process of catalyzing CO oxidation.

[0040] As can be seen from the comparison of Examples 1 and 8-11, appropriate calcination temperature is beneficial to the formation of more surface adsorbed oxygen vacancies, which is beneficial to the participation of high-activity oxygen in the reaction.

[0041] The present application is not limited to the above examples, and any technical solution formed by equivalent replacement or equivalent replacement belongs to the scope of the application. In addition to the above examples, there are many embodiments of the present application, and any technical solution formed by equivalent or equivalent replacement is within the scope of protection of the present application.

[0042] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. Use of a highly active supported cobalt-based catalyst in the catalytic oxidation of carbon monoxide, characterized in that, The method comprises the following steps: Step 1) precipitation reaction: in a hydrothermal precipitation reactor, an aqueous solution of cobalt nitrate with a concentration of 0.08 mol / L and an aqueous solution of manganese nitrate with a concentration of 0.008 mol / L are added with an aqueous solution of cetyltrimethylammonium bromide with a concentration of 0.13 mol / L and an aqueous solution of urea with a concentration of 0.28 mol / L at an operating temperature of 25 DEG C; the urea reacts with cobalt cations to form cobalt hydroxide; the operating temperature of the aqueous solution of cetyltrimethylammonium bromide is 25 DEG C; the operating temperature of the aqueous solution of urea is 25 DEG C; Step 2) solid-liquid separation: in a solid-liquid separation device, the material obtained in the previous step is subjected to solid-liquid separation, and the solid material obtained by the solid-liquid separation is a crude cobalt hydroxide product, which is further treated to obtain a cobalt carbonate product; Step 3) heat treatment: in a heat treatment reactor, the cobalt carbonate product obtained in the previous step is subjected to heat treatment to obtain a product of manganese oxide supported on cobalt oxide; in the heat treatment process, the heat treatment temperature is 250 DEG C to 550 DEG C, and the heat treatment time is 3 h; the cobalt-based catalyst has a morphology of nanowire accumulation spheres.

2. Use of a highly active supported cobalt-based catalyst according to claim 1 in the catalytic oxidation of carbon monoxide, characterized in that: In the precipitation reaction of step 1), the molar ratio of urea to cobalt cations is 0.017:0.08, and the operating temperature is 25 DEG C.

3. Use of a highly active supported cobalt-based catalyst according to claim 1 or 2 for the catalytic oxidation of carbon monoxide, characterized in that: In the hydrothermal precipitation reaction of step 1), the hydrothermal temperature is 160 DEG C to 180 DEG C, and the hydrothermal time is 2 h to 5 h.

4. Use of a highly active supported cobalt-based catalyst according to claim 1 or 2 for the catalytic oxidation of carbon monoxide, characterized in that: In step 2), the separation method is suction filtration, and the drying temperature is 80 DEG C, and the drying time is 12 h.

5. Use of a highly active supported cobalt-based catalyst according to claim 1 or 2 for the catalytic oxidation of carbon monoxide, characterized in that: In the solid-liquid separation process of step 2), the solid-liquid separation device is any one of a filter press device, a centrifugal filter device, a vane filter device, a pipe device, and a vacuum suction filter device.

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