A cobalt-based catalyst and its preparation method and application

Abstract

The present invention relates to the technical field of catalyst preparation, and discloses a cobalt-based catalyst, a preparation method thereof, and an application thereof. The cobalt-based catalyst contains 40-60 wt% of cobalt and 0.5-5 wt% of magnesium; the oxygen vacancy content of the cobalt-based catalyst is 15-60%, and the specific surface area is 50-200 m 2 The cobalt-based catalyst provided by the present invention has a high CO removal rate, a low removal temperature, and low energy consumption. The preparation method of the cobalt-based catalyst provided by the present invention is simple, environmentally friendly, highly controllable, suitable for industrial large-scale production, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a cobalt-based catalyst and a preparation method and application thereof. Background Art

[0002] Many industrial processes generate CO2-rich gases, such as coal-to-gasification and coke oven, blast furnace, and converter gases from steel production. These gases contain high CO concentrations (>5 vol%), and direct emission results in significant resource waste and severe environmental pollution. Therefore, CO2 is typically purified, separated, and refined using methods such as cryogenic separation, solvent recovery, and solid adsorption separation. The purified gases have a very low CO content, allowing them to meet emission standards.

[0003] However, some other processes generate low CO concentrations in tail gas (<5000ppm), such as the desorption gas from low-temperature methanol scrubbers used to remove acid gases from coal gasification plants. Recovering this type of tail gas is costly, and to meet emission requirements, CO removal is typically achieved through adsorption, photocatalysis, low-temperature plasma conversion, and combustion. Among these, catalytic oxidation, which incorporates a high-efficiency catalyst into the combustion process to reduce the combustion temperature, has attracted widespread attention due to its simplicity and high removal efficiency.

[0004] Common precious metal catalysts are widely used for CO exhaust removal, but inexpensive non-precious metal-based catalysts can greatly reduce costs for this reaction and are therefore more attractive.

[0005] For example, CN109621972A provides a method using CuMnO x In the method of eliminating CO by catalyst, CO begins to be oxidized into CO2 at 30°C and is completely oxidized into CO2 at 108-115°C. The temperature at which 50% of CO is oxidized is 65-70°C. However, the preparation method still requires the addition of ammonium oxalate as a precipitant, and the process is complicated.

[0006] CN113145164A discloses a method for preparing a Cu@HS hollow molecular sieve for CO removal. The method uses a Silicalite solid molecular sieve to prepare a Cu-Silicalite solid molecular sieve. The sieve is then mixed with deionized water using TPAOH. The solution is then added dropwise to the impregnated Cu-Silicalite sample under reduced pressure and filtration. The Cu@HS hollow molecular sieve removes 100% CO from refinery catalytic cracking flue gas. However, due to the need to synthesize the molecular sieve, the preparation process produces organic wastewater that pollutes the environment, and the molecular sieve preparation process is difficult to scale up.

[0007] CN115430431A discloses a Mn-doped Co-based catalyst, its preparation method, and application. This prior art involves adding cobalt and manganese salts in appropriate proportions to a magnesium oxide solution, stirring for 1-2 hours to obtain a precipitate, which is then washed to a pH of 6.5-7.5. The precipitate is then dried at 60-80°C for 10-15 hours, then heated to 500-600°C at a rate of 1-5°C / min, and calcined at 500-600°C for 1-3 hours to obtain a Mn-doped Co-based catalyst. The porous nanosheet catalyst prepared by this prior art increases the contact area between soot and the catalyst, effectively utilizing the active area of ​​the catalyst. However, the preparation process still requires the addition of a precipitant to adjust the pH, making it difficult to operate and hindering large-scale application. Summary of the Invention

[0008] The purpose of the present invention is to provide a cobalt-based catalyst with high CO removal rate, high catalyst conversion rate and suitable for low-concentration CO removal system.

[0009] In order to achieve the above object, the first aspect of the present invention provides a cobalt-based catalyst, which contains 40-60wt% of cobalt and 0.5-5wt% of magnesium; the oxygen vacancy content of the cobalt-based catalyst is 15-60%, and the specific surface area is 50-200m 2 / g.

[0010] The second aspect of the present invention provides a method for preparing the cobalt-based catalyst described in the first aspect, comprising the following steps:

[0011] (1) In the presence of water, magnesium hydroxide nanosheets are mixed with a cobalt salt precursor to obtain a mixture I containing cobalt hydroxide nanosheets; the second mixing time is 2-30 hours; the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:0.5-3, calculated as metal elements; the average thickness of the magnesium hydroxide nanosheets is 1-10 nm, and the specific surface area is 100-500 m 2 / g;

[0012] (2) drying the mixture I to obtain a mixture II;

[0013] (3) subjecting the mixture II to a second calcination treatment to obtain the cobalt-based catalyst; the conditions of the second calcination treatment include: a temperature of 200-800°C, a heating rate of 2-20°C / min, and a time of 2-4 hours.

[0014] The third aspect of the present invention provides a cobalt-based catalyst prepared by the method described in the second aspect.

[0015] The fourth aspect of the present invention provides use of the cobalt-based catalyst described in the first or third aspect in treating CO-containing gas.

[0016] This invention addresses the efficient removal of CO tail gas from petrochemical production processes and provides a non-precious metal catalyst with a simple and controllable preparation process. It also invents a template ion exchange, precipitant-free method for preparing the catalyst, which regulates the number of oxygen vacancies on the catalyst surface, promoting the dispersion of active metals and the exposure of active metal sites. Furthermore, the optimal calcination temperature is adjusted to control the particle size of the catalyst particles, efficiently constructing catalytically active sites on the catalyst surface. The method provided by the invention enables the active metal precursor and support to fully fuse and transform each other, creating more doped oxygen vacancies for adsorbing and activating CO, thereby improving the catalyst's catalytic performance.

[0017] This invention uses an ion exchange method, using an ultrathin magnesium hydroxide precursor as a template. By leveraging solubility product differences, ultrathin cobalt hydroxide nanosheets are formed in situ, and then calcined to produce a cobalt-based catalyst. By regulating the salt solution concentration and calcination temperature, surface defects are efficiently created on the catalyst, promoting substrate adsorption and activation. This results in high catalytic oxidation efficiency, low removal temperatures, and reduced energy consumption.

[0018] Compared with the prior art, the preparation method of the cobalt-based catalyst provided by the present invention has a simple process, is green and environmentally friendly, has strong controllability, is more suitable for industrial large-scale production, and has good application prospects.

[0019] The co-precipitation method used in existing technologies to prepare cobalt-based catalysts requires the addition of a precipitant and strict pH control, making the process complex. The technical solution provided by the present invention enables the controllable preparation of cobalt-based catalysts, resulting in catalysts with smaller active component particle sizes, high catalytic activity, and a long catalyst life. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a transmission electron microscope image of magnesium hydroxide nanosheets in Example 1;

[0021] Figure 2 This is a transmission electron microscope image of magnesium hydroxide nanosheets in Example 1;

[0022] Figure 3 This is a transmission electron microscope image of cobalt hydroxide nanosheets in Example 1;

[0023] Figure 4 is a transmission electron microscope image of the cobalt-based catalyst in Example 1;

[0024] Figure 5 This is the X-ray diffraction (XRD) pattern of the cobalt-based catalyst of Example 1. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] As mentioned above, the first aspect of the present invention provides a cobalt-based catalyst, which contains 40-60wt% cobalt and 0.5-5wt% magnesium; the oxygen vacancy content of the cobalt-based catalyst is 15-60%, and the specific surface area is 50-200m 2 / g.

[0027] Preferably, the cobalt-based catalyst contains 50-60 wt% of cobalt and 0.5-2 wt% of magnesium.

[0028] Preferably, the cobalt-based catalyst has an oxygen vacancy content of 20-60% and a specific surface area of ​​50-200 m 2 / g.

[0029] In the present invention, the cobalt element and the magnesium element are both present in the cobalt-based catalyst in the form of oxides.

[0030] Preferably, the average particle diameter of the cobalt-based catalyst is 1-20 nm, preferably 1-10 nm.

[0031] The cobalt-based catalyst provided by the present invention has a highly efficient catalytic effect on raw gas with a CO concentration of ≤5v%, a reaction mass space velocity of 60,000 mL / g / h, a CO conversion rate of ≥1% above 50°C, a CO conversion rate of ≥99% above 230°C, stability of ≥300h, and can ensure that the residual CO volume concentration in the raw gas after the reaction is ≤50ppm.

[0032] As mentioned above, the second aspect of the present invention provides a method for preparing the cobalt-based catalyst described in the first aspect, comprising the following steps:

[0033] (1) In the presence of water, magnesium hydroxide nanosheets are mixed with a cobalt salt precursor to obtain a mixture I containing cobalt hydroxide nanosheets; the second mixing time is 2-30 hours; the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:0.5-3, calculated as metal elements; the average thickness of the magnesium hydroxide nanosheets is 1-10 nm, and the specific surface area is 100-500 m 2 / g;

[0034] (2) drying the mixture I to obtain a mixture II;

[0035] (3) subjecting the mixture II to a second calcination treatment to obtain the cobalt-based catalyst; the conditions of the second calcination treatment include: a temperature of 200-800°C, a heating rate of 2-20°C / min, and a time of 2-4 hours.

[0036] pass Figure 1 and Figure 2 The transmission electron micrograph of the magnesium hydroxide nanosheets shown shows that the magnesium hydroxide nanosheets described herein exhibit irregular flakes. The inventors discovered that using magnesium hydroxide nanosheets of this size as a template, combined with the other technical features of the present invention, yields a cobalt-based catalyst with superior catalytic performance.

[0037] Preferably, the method further comprises: first mixing the magnesium oxide particles with water to obtain magnesium hydroxide nanosheets; the conditions for the first mixing include: a stirring rate of 70-150 rpm, a temperature of 18-40° C., and a time of 10 min to 24 h.

[0038] Preferably, the amount of the magnesium oxide particles used is such that the initial concentration of magnesium in the reaction system formed by the first mixing is 1.0-1.5 mol / L.

[0039] Preferably, the magnesium oxide particles are obtained by subjecting a magnesium precursor to a first calcination treatment; and the average particle diameter of the magnesium oxide particles is 5-30 nm.

[0040] According to a preferred embodiment, the conditions of the first calcination treatment include: a temperature of 600-1000° C., a heating rate of 2-20° C. / min, a time of 2-4 hours, and an air flow rate of 10-100 mL / min.

[0041] Preferably, the magnesium precursor is selected from at least one of light magnesium oxide, basic magnesium carbonate, and magnesium chloride hexahydrate.

[0042] According to a preferred embodiment, the magnesium precursor is basic magnesium carbonate and / or magnesium chloride hexahydrate, and the second mixing time in step (1) is 2-5 hours. The inventors of the present invention have found in their research that using basic magnesium carbonate and / or magnesium chloride hexahydrate as the magnesium precursor can significantly shorten the reaction time of the second mixing and improve the production efficiency of the cobalt-based catalyst.

[0043] According to another preferred embodiment, the magnesium precursor is light magnesium oxide, and the second mixing time in step (1) is 20-30 hours. The inventors of the present invention have found in their research that the cobalt-based catalyst prepared using light magnesium oxide as a magnesium precursor has better catalytic performance.

[0044] In the present invention, after the solid-liquid mixture containing magnesium hydroxide nanosheets is obtained through the first mixing, the cobalt salt precursor can be directly introduced into the mixture for the second mixing. Alternatively, the solid-liquid mixture containing magnesium hydroxide nanosheets can be sequentially washed, filtered, dried, and the like to obtain the magnesium hydroxide nanosheets, which are then used to participate in the second mixing. The present invention will not be further described herein, and those skilled in the art should not be construed as limiting the present invention.

[0045] The magnesium hydroxide nanosheets obtained in the present invention may also contain unreacted magnesium oxide particles. When participating in the second mixing in step (1), the unreacted magnesium oxide particles in the magnesium hydroxide nanosheets can continue to react to obtain magnesium hydroxide nanosheets. At the same time, the magnesium hydroxide nanosheets are used as templates and the difference in solubility product is utilized to in-situ form the cobalt hydroxide nanosheets through an ion exchange method.

[0046] pass Figure 3 It can be seen from the transmission electron microscope image of the cobalt hydroxide nanosheet shown in that the cobalt hydroxide nanosheet of the present invention is in an irregular sheet shape.

[0047] Preferably, in step (1), the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1-2.

[0048] Preferably, in step (1), the amount of the cobalt salt precursor used is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.1-2 mol / L, more preferably 0.4-0.8 mol / L. The inventors have found that under this more preferred condition, the cobalt-based catalyst obtained by the present invention has a higher CO removal rate and catalyst conversion rate.

[0049] Preferably, in step (1), the cobalt salt precursor is selected from at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate.

[0050] More preferably, in step (1), the cobalt salt precursor is cobalt nitrate hexahydrate. The inventors of the present invention have found in their research that, compared with other water-soluble cobalt salts, the cobalt-based catalyst prepared by selecting cobalt nitrate hexahydrate as the cobalt salt precursor has better catalytic activity and higher CO conversion rate.

[0051] Preferably, in step (1), the second mixing conditions include: a stirring rate of 70-150 rpm, a temperature of 18-40° C., and a time of 2-30 h.

[0052] Preferably, in step (2), the drying treatment temperature is 20-50°C, preferably 20-30°C, and the drying time is 20-26 hours.

[0053] According to a preferred embodiment, in step (3), the conditions for the second calcination treatment include: a temperature of 200-400°C, a heating rate of 2-10°C / min, a time of 2-3 hours, and an air flow rate of 10-100 mL / min. The inventors of the present invention have found that under these preferred second calcination treatment conditions, the cobalt-based catalyst provided by the present invention has a higher CO removal rate and catalyst conversion rate, and has better catalytic performance.

[0054] As mentioned above, the third aspect of the present invention provides a cobalt-based catalyst prepared by the method described in the second aspect.

[0055] from Figure 4 It can be seen from the transmission electron microscope image of the cobalt-based catalyst that the cobalt-based catalyst particles provided by the present invention have a small and uniform particle size and a higher specific surface area.

[0056] Figure 5 is the XRD pattern of the cobalt-based catalyst, where 2-theta is the angle of 2θ at which the X-ray diffractometer scans the entire diffraction area, which exists as the angle change and the horizontal coordinate of the X-ray diffraction spectrum. Figure 5 It can be seen from the XRD pattern that the cobalt-based catalyst provided by the present invention exhibits an obvious diffraction peak of Co3O4.

[0057] Since the magnesium content in the cobalt-based catalyst of the present invention does not reach the detection limit of XRD, the present invention uses inductively coupled plasma technology (ICP) to detect the magnesium content in the cobalt-based catalyst.

[0058] As mentioned above, the fourth aspect of the present invention provides the use of the cobalt-based catalyst described in the first or third aspect in the treatment of CO-containing gas.

[0059] Preferably, the concentration of CO in the CO-containing gas is ≤5v%.

[0060] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0061] In the following examples, the specific surface areas of magnesium hydroxide nanosheets and cobalt-based catalysts were determined using nitrogen adsorption-desorption.

[0062] In the following examples, an XPS ray photoelectron spectrometer (manufacturer: Thermo Fisher Scientific, model: Thermo Kalpha) was used to measure the oxygen vacancy content of the cobalt-based catalyst.

[0063] Example 1

[0064] (1) The magnesium precursor was first calcined at 750°C for 2 h at an air flow rate of 30 mL / min and a heating rate of 5°C / min to obtain magnesium oxide particles (with an average particle diameter of 20 nm). The magnesium oxide particles were first mixed with water at 80 rpm and 25°C for 24 h, and then washed, filtered, and dried to obtain magnesium hydroxide nanosheets (with an average thickness of 3 nm and a specific surface area of ​​250 m 2 / g);

[0065] The magnesium precursor is basic magnesium carbonate; the amount of magnesium oxide particles used is 0.0125 mol, and the amount of magnesium oxide particles used is such that the initial concentration of magnesium in the first mixed system is 1.25 mol / L;

[0066] (2) in the presence of water, mixing all the magnesium hydroxide nanosheets obtained in step (1) with the cobalt salt precursor at 100 rpm and 25° C. for a second time for 3 h to obtain a mixture I containing cobalt hydroxide nanosheets;

[0067] The cobalt salt precursor is cobalt nitrate hexahydrate, and the amount used is 0.0125 mol. The amount of the cobalt salt precursor is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.5 mol / L (the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1, calculated as the metal element);

[0068] (3) Drying the mixture I at 25°C for 24 hours to obtain a mixture II;

[0069] (4) The mixture II was subjected to a second calcination treatment at 300° C. for 2 h at an air flow rate of 50 mL / min and a heating rate of 3° C. / min to obtain a cobalt-based catalyst.

[0070] Example 2

[0071] (1) The magnesium precursor was first calcined at 750°C for 2 h at an air flow rate of 50 mL / min and a heating rate of 3°C / min to obtain magnesium oxide particles (with an average particle diameter of 25 nm). The magnesium oxide particles were first mixed with water at 120 rpm and 25°C for 24 h, and then washed, filtered, and dried to obtain magnesium hydroxide nanosheets (with an average thickness of 2 nm and a specific surface area of ​​170 m 2 / g);

[0072] The magnesium precursor is light magnesium oxide; the amount of magnesium oxide particles used is 0.0125 mol, and the amount of magnesium oxide particles used is such that the initial concentration of magnesium in the first mixed system is 1.25 mol / L;

[0073] (2) in the presence of water, mixing all the magnesium hydroxide nanosheets obtained in step (1) with the cobalt salt precursor at 80 rpm and 25° C. for a second time for 24 h to obtain a mixture I containing cobalt hydroxide nanosheets;

[0074] The cobalt salt precursor is cobalt nitrate hexahydrate, and the amount used is 0.0125 mol. The amount of the cobalt salt precursor is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.5 mol / L (the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1, calculated as the metal element);

[0075] (3) Drying the mixture I at 25°C for 24 hours to obtain a mixture II;

[0076] (4) The mixture II was subjected to a second calcination treatment at 200° C. for 3 h at an air flow rate of 30 mL / min and a heating rate of 7° C. / min to obtain a cobalt-based catalyst.

[0077] Example 3

[0078] (1) The magnesium precursor was first calcined at 750°C for 2 h at an air flow rate of 30 mL / min and a heating rate of 5°C / min to obtain magnesium oxide particles (with an average particle diameter of 25 nm). The magnesium oxide particles were first mixed with water at 75 rpm and 28°C for 24 h, and then washed, filtered, and dried to obtain magnesium hydroxide nanosheets (with an average thickness of 3 nm and a specific surface area of ​​250 m 2 / g);

[0079] The magnesium precursor is magnesium chloride hexahydrate; the amount of magnesium oxide particles used is 0.0125 mol, and the amount of magnesium oxide particles used is such that the initial concentration of magnesium in the system formed by the first mixing is 1.25 mol / L;

[0080] (2) in the presence of water, mixing all the magnesium hydroxide nanosheets obtained in step (1) with the cobalt salt precursor at 100 rpm and 28° C. for a second time for 3 h to obtain a mixture I containing cobalt hydroxide nanosheets;

[0081] The cobalt salt precursor is cobalt chloride hexahydrate, and the amount used is 0.0125 mol. The amount of the cobalt salt precursor is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.5 mol / L (the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1, calculated as the metal element);

[0082] (3) Drying the mixture I at 28°C for 24 hours to obtain a mixture II;

[0083] (4) The mixture II was subjected to a second calcination treatment at 400° C. for 2 h at an air flow rate of 50 mL / min and a heating rate of 3° C. / min to obtain a cobalt-based catalyst.

[0084] Example 4

[0085] This embodiment is carried out using a process similar to that of Example 1, except that in step (2), the amount of the cobalt salt precursor used in this embodiment is such that the initial concentration of the cobalt element in the reaction system formed by the second mixture is 0.2 mol / L, and the type and amount of the cobalt salt precursor remain unchanged;

[0086] A cobalt-based catalyst was prepared.

[0087] Example 5

[0088] This embodiment adopts a process similar to that of embodiment 1, except that in step (4), the temperature of the second calcination treatment adopted in this embodiment is adjusted from 300°C to 500°C, and the other conditions remain unchanged;

[0089] A cobalt-based catalyst was prepared.

[0090] Example 6

[0091] This embodiment adopts a process similar to that of embodiment 2, except that this embodiment does not perform the first roasting treatment, and directly uses light magnesium oxide to participate in the first mixing. Specifically:

[0092] (1) Light magnesium oxide and water were first mixed at 75 rpm and 25 ° C for 24 h, and then washed, filtered, dried, and other steps to obtain magnesium hydroxide nanosheets (average thickness of 2 nm, specific surface area of ​​225 m 2 / g);

[0093] The amount of light magnesium oxide used is 0.0125 mol, and the initial concentration of light magnesium oxide in the first mixed system is 1.25 mol / L;

[0094] (2) in the presence of water, mixing all the magnesium hydroxide nanosheets obtained in step (1) with the cobalt salt precursor at 100 rpm and 25° C. for a second time for 24 h to obtain a mixture I containing cobalt hydroxide nanosheets;

[0095] The cobalt salt precursor is cobalt nitrate hexahydrate, and the amount used is 0.0125 mol. The amount of the cobalt salt precursor is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.5 mol / L (the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1, calculated as the metal element);

[0096] (3) Drying the mixture I at 25°C for 24 hours to obtain a mixture II;

[0097] (4) The mixture II was subjected to a second calcination treatment at 200° C. for 3 h at an air flow rate of 50 mL / min and a heating rate of 3° C. / min to obtain a cobalt-based catalyst.

[0098] Example 7

[0099] This embodiment adopts a process similar to that of embodiment 1, except that in step (3), the drying temperature is adjusted from 25°C to 60°C, and the other conditions remain unchanged;

[0100] A cobalt-based catalyst was prepared.

[0101] Example 8

[0102] This example is carried out using a process similar to that of Example 1, except that in step (2), the cobalt salt precursor, cobalt nitrate hexahydrate, is replaced with cobalt acetate tetrahydrate; specifically:

[0103] Step (2): In the presence of water, all the magnesium hydroxide nanosheets obtained in step (1) are mixed with the cobalt salt precursor at 100 rpm and 25° C. for a second time for 3 hours to obtain a mixture I containing cobalt hydroxide nanosheets;

[0104] The cobalt salt precursor is cobalt acetate tetrahydrate, and the amount used is 0.0125 mol. The amount of the cobalt salt precursor is such that in the reaction system formed by the second mixture, the initial concentration of the cobalt element is 0.1 mol / L (in terms of metal elements, the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:1).

[0105] The rest remained unchanged to prepare a cobalt-based catalyst.

[0106] Comparative Example 1

[0107] This comparative example was carried out using a process similar to that of Example 1, except that in step (4), the temperature of the second calcination treatment was adjusted from 300°C to 900°C, and the other conditions remained unchanged;

[0108] A cobalt-based catalyst was prepared.

[0109] Comparative Example 2

[0110] Preparation of Co3O4 catalyst by coprecipitation method

[0111] 8.58g of magnesium acetate tetrahydrate and 4.24g of anhydrous sodium carbonate were dissolved in 400ml and 100ml of deionized water, respectively, to form an aqueous solution with a concentration ratio of 1:4. The sodium carbonate solution was then poured into the magnesium acetate solution and mixed and stirred for 10 minutes to obtain a magnesium hydroxide precipitate. The magnesium hydroxide precipitate was centrifuged once, and then water was added twice and ethanol was added once and then centrifuged and washed again to a pH of 7. Finally, it was dried at 60°C for 12h and heated to 500°C at a heating rate of 2°C / min; calcined at 500°C for 2h to form magnesium oxide.

[0112] Take 0.04g of magnesium oxide and dissolve it in deionized water and add 20mL of 0.05mol / L cobalt nitrate solution, stir for 1.5h, then filter (or centrifuge) and wash with water and ethanol again to make its pH 7, then dry at 60℃ for 12h, and heat to 500℃ at a heating rate of 2℃ / min, calcine at 500℃ for 2h to finally obtain Co3O4 catalyst.

[0113] The composition and parameter characteristics of the cobalt-based catalysts prepared in each example are shown in Table 1.

[0114] Table 1

[0115]

[0116] Test Example 1

[0117] The catalytic CO reaction was tested on a fixed bed. The specific test process is as follows:

[0118] 0.7 g of the cobalt-based catalyst of the present invention was used to carry out a CO catalytic oxidation reaction on a micro-fixed bed evaluation device-gas chromatography online analysis integrated system. The cobalt-based catalyst tablets were sieved, and catalyst particles (0.4-0.85 mm) were selected and loaded into a stainless steel reaction tube with a quartz liner. The reaction was switched to the desired reaction temperature, and a mixed raw gas of CO and air was introduced for reaction. The CO concentration in the raw gas was 5% by volume, and the mass space velocity was 60,000 mL / g / h. The reaction temperature was controlled by increasing the temperature. During the reaction, each temperature point was stabilized for 30 minutes, and then chromatographic sampling was performed for online analysis.

[0119] The cobalt-based catalyst provided by the present invention has a high catalytic effect on feed gas with a CO concentration of ≤5% by volume. The reaction mass space velocity is 60,000 mL / g / h, and the CO conversion rate is ≥1% at temperatures above 50°C, and ≥99% at temperatures above 230°C. The data shown in Table 2 illustrate the catalytic effect of the cobalt-based catalyst prepared in Example 2.

[0120] CO conversion rate (%) = (volume flow rate of CO in the raw gas - volume flow rate of CO in the tail gas after reaction) / volume flow rate of CO in the raw gas × 100%

[0121] Table 2

[0122] Temperature (℃) CO conversion rate (%) 50 1.2 100 21.3 125 54.0 150 98.6 175 100 200 100

[0123] It can be seen from the data in Table 2 that the catalyst prepared by this method has very good low-temperature activity.

[0124] Test Example 2

[0125] The cobalt-based catalysts prepared in the examples and comparative examples were used to carry out CO catalytic oxidation reaction. The specific test process is as follows:

[0126] 0.35g of the cobalt-based catalyst prepared in each example was taken to carry out CO catalytic oxidation reaction, which was carried out on a micro-fixed bed evaluation device gas chromatography online analysis integrated system device. The cobalt-based catalyst tablets were sieved, and catalyst particles (0.4-0.85mm) were selected and loaded into a stainless steel reaction tube with a quartz liner. The reaction was switched to the required reaction temperature, and CO and air mixed raw gas were introduced separately for reaction. The CO concentration in the raw gas was 5v%, the reaction mass space velocity was 60000mL / g / h, and the reaction temperature was controlled by heating. During the reaction, after each temperature point was stable for 30min, chromatographic sampling was performed for online analysis.

[0127] CO conversion rate (%) = (volume flow rate of CO in the raw gas - volume flow rate of CO in the tail gas after reaction) / volume flow rate of CO in the raw gas × 100%

[0128] The cobalt-based catalysts prepared in each embodiment and comparative example were used to carry out CO catalytic oxidation reaction, and the T 50 and T 90 Value, T 50 、T 90 They represent the temperature corresponding to a CO conversion rate of 50% and the temperature corresponding to a CO conversion rate of 90%, respectively.

[0129] The results are shown in Table 3.

[0130] Table 3

[0131] <![CDATA[T 50 (℃)]]> <![CDATA[T 90 (℃)]]> Example 1 122 141 Example 2 120 138 Example 3 151 162 Example 4 125 150 Example 5 160 181 Example 6 135 156 Example 7 125 150 Example 8 150 171 Comparative Example 1 197 293 Comparative Example 2 191 218

[0132] It can be seen from the data in Table 3 that when the cobalt-based catalyst obtained by the technical solution provided by the present invention is used for CO catalytic oxidation, T 50 and T 90 The value is lower, and the temperature of the second calcination has a significant effect on the performance of the cobalt-based catalyst. A lower calcination temperature is conducive to the synthesis of catalysts with smaller particle size and significantly better catalytic performance.

[0133] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-based catalyst, characterized in that: The following steps are involved: (1) In the presence of water, magnesium hydroxide nanosheets are mixed with a cobalt salt precursor to obtain a mixture I containing cobalt hydroxide nanosheets; the second mixing time is 2-30 hours; the molar ratio of the cobalt element in the cobalt salt precursor to the magnesium element in the magnesium hydroxide nanosheets is 1:0.5-3, calculated as metal elements; the average thickness of the magnesium hydroxide nanosheets is 1-10 nm, and the specific surface area is 100-500 m 2 / g; (2) drying the mixture I to obtain a mixture II; (3) subjecting the mixture II to a second calcination treatment to obtain the cobalt-based catalyst; The conditions of the second calcination treatment include: temperature of 200-800°C, heating rate of 2-20°C / min, and time of 2-4h; The cobalt-based catalyst contains 40-60 wt% of cobalt and 0.5-5 wt% of magnesium; The cobalt-based catalyst has an oxygen vacancy content of 15-60% and a specific surface area of ​​50-200 m 2 / g.

2. The method according to claim 1, wherein The average particle diameter of the cobalt-based catalyst is 1-20 nm.

3. The method according to claim 1 or 2, wherein: The method further comprises: first mixing magnesium oxide particles with water to obtain magnesium hydroxide nanosheets; the conditions for the first mixing include: a stirring rate of 70-150 rpm, a temperature of 18-40° C., and a time of 10 minutes to 24 hours.

4. The method according to claim 3, wherein: The magnesium oxide particles are obtained by subjecting a magnesium precursor to a first calcination treatment; the average particle diameter of the magnesium oxide particles is 5-30 nm.

5. The method according to claim 4, wherein The conditions of the first calcination treatment include: temperature of 600-1000° C., heating rate of 2-20° C. / min, time of 2-4 hours, and air flow rate of 10-100 mL / min.

6. The method according to claim 4 or 5, wherein: The magnesium precursor is selected from at least one of light magnesium oxide, basic magnesium carbonate, and magnesium chloride hexahydrate.

7. The method according to claim 1 or 2, wherein: In step (1), the amount of the cobalt salt precursor used is such that the initial concentration of the cobalt element in the reaction system formed by the second mixing is 0.1-2 mol / L.

8. The method according to claim 1 or 2, wherein: In step (1), the cobalt salt precursor is selected from at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate.

9. The method according to claim 8, wherein The cobalt salt precursor is cobalt nitrate hexahydrate.

10. The method according to claim 1 or 2, wherein: In step (1), the second mixing conditions include: a stirring rate of 70-150 rpm, a temperature of 18-40° C., and a time of 2-30 h.

11. The method according to claim 1 or 2, wherein: In step (2), the drying temperature is 20-50°C and the drying time is 20-26 hours.

12. The method according to claim 1 or 2, wherein: In step (3), the conditions of the second calcination treatment include: temperature of 200-400°C, heating rate of 2-10°C / min, time of 2-3h, and air flow rate of 10-100mL / min.

13. A cobalt-based catalyst prepared by the method according to any one of claims 1 to 12.

14. Use of the cobalt-based catalyst according to claim 13 in treating CO-containing gas.

15. The use according to claim 14, wherein: The concentration of CO in the CO-containing gas is ≤5v%.

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