CN113426472B - Cobalt-based catalyst and CO 2 Method for preparing CO by catalytic hydrogenation - Google Patents

Cobalt-based catalyst and CO 2 Method for preparing CO by catalytic hydrogenation Download PDF

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CN113426472B
CN113426472B CN202010207829.4A CN202010207829A CN113426472B CN 113426472 B CN113426472 B CN 113426472B CN 202010207829 A CN202010207829 A CN 202010207829A CN 113426472 B CN113426472 B CN 113426472B
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CN113426472A (en
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张斌
梁浩杰
覃勇
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Shanxi Institute of Coal Chemistry of CAS
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Abstract

The invention belongs to the technical field of catalytic conversion of carbon dioxide, and particularly relates to a cobalt-based catalyst and CO adopting the cobalt-based catalyst 2 A method for preparing CO by catalytic hydrogenation. The cobalt-based catalyst comprises an SBA-15 substrate and a cobalt active center loaded on the SBA-15 substrate, wherein the cobalt active center is obtained by reducing a cobalt oxide deposition layer loaded on the SBA-15 substrate, and the cobalt oxide deposition layer is formed in an atomic layer deposition mode. The cobalt-based catalyst has better catalytic activity and stability. When the cobalt-based catalyst of the present invention is used for catalyzing CO 2 And the catalyst has better selectivity and stability when being used for preparing CO by hydrogenation.

Description

Cobalt-based catalyst and CO 2 Method for preparing CO by catalytic hydrogenation
Technical Field
The invention belongs to the technical field of catalytic conversion of carbon dioxide, and particularly relates to a cobalt-based catalyst and CO adopting the cobalt-based catalyst 2 Application in the aspect of preparing CO by catalytic hydrogenation.
Background
Introducing CO 2 Conversion to other chemicals, especially CO 2 Is CO is 2 An important way for resource utilization and emission reduction is to relieve the environmental pressure caused by emission of the organic waste and provide various chemicals with economic value such as carbon monoxide, methanol, formic acid, dimethyl ether, ethanol, olefin and the like. However, CO 2 Strong inertia and difficult activation. In CO 2 The selection of the catalyst in the conversion process of (2) is very critical.
CO 2 The synthesis of carbon monoxide (CO) by catalytic hydrogenation is a rational route for its utilization. CO is the main component of synthesis gas, is not only an important raw material of coal chemical industry, but also participates in the synthesis of various chemical industries to produce various chemicals. Currently, researchers have tried to develop various heterogeneous catalysts for CO over the years 2 And (4) hydrogenation to prepare CO. There are many catalysts such as Pd/ZnO, PtCo/CeO 2 、Ru/CeO 2 And the like. However, the product is usually a mixture of CO, methanol and methane, the selectivity to CO is low and CO is low 2 The activity was also low. Limited by thermodynamics, CO 2 Hydro-synthesisCO generally needs higher reaction temperature, a noble metal catalyst is often used as a main catalyst or an auxiliary agent, and the CO selectivity and stability of the catalyst are lower.
The Co-based catalyst is a hydrogenation catalyst commonly used in industry, shows excellent performance in Fischer-Tropsch synthesis, but has good performance in CO 2 The main product in hydrogenation is CH 4 And C2, C3 and other light alkanes have great limitation in direct utilization and secondary utilization. In addition, the Co also has the problems of phase change, migration, loss and the like in the high-temperature reaction process, and the selectivity of the CO is difficult to control.
Disclosure of Invention
The invention aims to provide a cobalt-based catalyst which has better catalytic activity and stability.
The invention also aims to provide CO adopting the cobalt-based catalyst 2 The method for preparing CO by catalytic hydrogenation has high CO selectivity.
In order to achieve the purpose, the invention adopts the technical scheme that:
a cobalt-based catalyst consists of an SBA-15 substrate and cobalt active centers loaded on the SBA-15 substrate, wherein the cobalt active centers are obtained by reducing a cobalt oxide deposition layer loaded on the SBA-15 substrate, and the cobalt oxide deposition layer is formed in an atomic layer deposition mode.
The atomic layer deposition technology is a preparation technology capable of realizing accurate atomic-level control of deposits, and deposits are generated through monolayer chemical adsorption and reaction on the surface of a substrate. The invention utilizes the atomic layer deposition technology to deposit cobalt oxide (CoO) on the surface of an SBA-15 substrate x ) Depositing a layer and then reducing the cobalt active center in the obtained cobalt-based catalyst and SiO on the surface of SBA-15 2 The binding force between the two is stronger, and the stability of the cobalt-based catalyst is improved. And formed by atomic layer deposition of CoO x After reduction, a cobalt active center is formed in situ, and the cobalt active center has high dispersion unicity, so that the cobalt-based catalyst has better catalytic activity.
The catalytic performance of the cobalt-based catalyst is further optimized by adjusting the content of Co element, and the preferable mass percentage of Co element in the cobalt-based catalyst is 2-30%.
The reduction conditions for reducing the cobalt oxide deposition layer can be adjusted according to the existing method for reducing the cobalt oxide into the cobalt simple substance. Preferably, the temperature during reduction is 250 to 450 ℃. The type of the reducing gas used in the reduction, the flow rate of the reducing gas and the reduction time can be adjusted according to the actual situation, and the cobalt oxide is reduced fully. Further preferably, the reducing gas used is a hydrogen-argon mixture or pure hydrogen. When the reducing gas is hydrogen-argon mixed gas, the volume percentage of the hydrogen is 10-30%. More preferably, the reduction time is 3-5 h.
Reduction equipment which can be used for reducing the cobalt oxide layer includes a tube furnace, a fixed bed reactor, and the like. When the reaction equipment is a fixed bed reactor, the specific parameters of the reduction are as follows: the temperature is 250-450 ℃, the pressure is 0.1-0.3 MPa, and 1g CoO passes through every 1h x The flow rate of the reducing gas of the SBA-15 is 12000-60000 mL. Wherein CoO x The term SBA-15 is the general name of SBA-15 and the cobalt oxide deposition layer formed by surface deposition.
The cobalt in the cobalt active center exists in a 2-valent cobalt one valence state or coexists in three valence states of 2-valent cobalt, 3-valent cobalt and 0-valent cobalt. Atomic layer deposition formed CoO x Cobalt in the deposition layer exists in the form of oxides such as cobalt dioxide and cobaltosic oxide, the reduced cobalt exists in a single atomic state or cluster form, and corresponding cobalt is coordinated with silicon dioxide in the SBA-15 matrix to form a Co (I) -O-Si and Co (III) -O-Si chemical bond or the atomic cobalt forms a Co nano cluster, so that cobalt active centers in different valence states are formed. Different cobalt active centers have different catalytic activities and can meet the requirements of hydrogenation reduction of various substances. When the cobalt-based catalyst of the present invention is used for catalyzing CO 2 In the hydrogenation reduction, the cobalt in the 2-valent state is favorable for the generation of CO, and the cobalt in the 3-valent state and the cobalt in the 0-valent state are favorable for CH 4 And (4) generating.
In the cobalt-based catalyst, the method for forming the cobalt oxide layer by adopting the atomic layer deposition mode specifically comprises the following steps of:
(1) in an atomic layer deposition vacuum reaction cavity, a Co precursor is pulsed on the surface of an SBA-15 matrix, then, the gas is held, so that the Co precursor is adsorbed on the surface of the SBA-15 matrix, and then, air is pumped to remove the Co precursor which is not adsorbed;
(2) the pulse oxidant is then blocked to enable the oxidant to react with the Co precursor adsorbed on the surface of SBA-15 in the step (1), and then air is extracted to remove the unreacted oxidant;
(3) and (3) sequentially repeating the step (1) and the step (2), namely forming a cobalt oxide deposition layer on the surface of the SBA-15.
The deposition effect is optimized by adjusting deposition parameters, preferably, when the atomic layer deposition is carried out in the step (1) and the step (2), the temperature is 200-300 ℃, the pressure is 10-200 Pa, and the volume ratio of the carrier gas to the atomic layer deposition vacuum reaction cavity is 1: (5 to 50) min -1 . The carrier gas flow is fixed during deposition. The Co precursor is cobaltocene or bis (N, N-diisopropylacetamidinyl) cobalt, and the oxidant is ozone, oxygen or water vapor.
During atomic layer deposition, the pulse time, the gas holding time and the gas pumping time in the step (1) and the step (2) can be adjusted according to the prior art and the actual situation. Preferably, in the step (1), the pulse time is 4-6 s, the air blocking time is 30-50 s, and the air extraction time is 50-70 s; in the step (2), the pulse time is 0.5-100 s, the breath holding time is 40-200 s, and the air extraction time is 60-300 s.
And (4) during atomic layer deposition, adjusting the mass of the Co element by adjusting the cycle number, wherein the repetition number in the step (3) is 50-1000.
If the repetition time is not more than 100 times, the cobalt of the cobalt active center in the cobalt-based catalyst exists in a valence state of 2-valent cobalt; if the repetition number is not less than 300 times, the cobalt in the cobalt-based catalyst active center exists in three valence states of 2-valent cobalt, 3-valent cobalt and 0-valent cobalt. When the cobalt-based catalyst of the present invention is used for catalyzing CO 2 In the hydrogenation reduction, the cobalt in the 2-valent state is favorable for the generation of CO, and the cobalt in the 3-valent state and the cobalt in the 0-valent state are favorable for CH 4 And (4) generating.
CO of the invention 2 Catalytic hydrogenation processThe technical scheme of the CO method is as follows:
CO (carbon monoxide) 2 The method for preparing CO by catalytic hydrogenation comprises the following steps: the raw material gas reacts under the action of the cobalt-based catalyst to generate CO and CH 4 。
CO pairs Using the cobalt-based catalyst of the invention 2 The selectivity of CO is higher by carrying out catalytic hydrogenation; and the cobalt-based catalyst has good stability, the CO selectivity is still in a high state after the continuous operation for 500 hours, and the catalyst is suitable for the requirement of industrial production. Wherein the raw material gas contains CO 2 And hydrogen gas.
Preferably, the temperature during the reaction is 200-600 ℃, the pressure is 0.1-5.0 MPa, and the flow of the raw material gas passing through 1g of the cobalt-based catalyst in every 1h is 12000-25000 mL. Further preferably, the feed gas contains CO 2 And hydrogen in a volume ratio of 1: 1.
Catalysis of CO Using the Process of the invention 2 When the CO is prepared by hydrogenation, the used equipment can be a fixed bed reactor or a fluidized bed reactor.
Drawings
FIG. 1 shows CO in example 12 of the present invention 2 Conversion of (a) and selectivity of CO versus run time;
FIG. 2 is a TEM image of a cobalt-based catalyst in examples 1, 2 and 6 to 9 of the present invention;
FIG. 3 shows XPS spectra of cobalt-based catalysts of examples 1, 2, 6, 7 of the present invention.
Detailed Description
The invention is further described below with reference to the following description of embodiments and the accompanying drawings.
Cobalt-based catalyst examples
Example 1
The cobalt-based catalyst of the embodiment has a mass percentage of Co element of 2.6%, and is composed of an SBA-15 substrate and a cobalt active center loaded on the surface of the SBA substrate, wherein the cobalt active center is divalent cobalt.
The preparation method of the cobalt-based catalyst of the embodiment comprises the following steps:
(1) mixing SBA-15 matrixUniformly dispersing in an ethanol solution to obtain a suspension with the concentration of 0.01 g/mL; uniformly coating the suspension on the surface of a glass sheet, airing, placing the glass sheet into an atomic deposition vacuum reaction cavity, wherein the temperature of the reaction cavity is 250 ℃, the pressure of the reaction cavity is 90Pa, and the volume ratio of a carrier gas to the vacuum reaction cavity is 1/6min -1 Filling carrier gas, wherein the flow of the carrier gas is fixed in the deposition process;
(2) firstly, pulsing Co precursor cobaltocene on the surface of an SBA-15 substrate, then holding the gas, so that the Co precursor is adsorbed on the surface of the SBA-15 substrate, then performing air extraction to remove the Co precursor which is not adsorbed, wherein the pulse time is 5s, the holding time is 40s, and the air extraction time is 60 s;
(3) then, pulsing ozone and holding the gas, enabling an oxidant and the Co precursor adsorbed on the surface of the SBA-15 in the step (2) to be extracted to remove unreacted ozone, wherein the pulse time is 0.5s, the holding time is 50s, and the extraction time is 60 s;
(4) repeating the steps (2) and (3) in sequence, and repeating the steps for 50 times to obtain the CoO x /SBA-15；
(5) CoO (sodium hypochlorite) x The method comprises the following steps of scraping from a glass sheet, tabletting and granulating, screening 50mg of particles with 20-40 meshes, diluting to 1g by quartz sand, filling the particles into a fixed bed reactor (phi 10 is multiplied by 500mm), and then carrying out reduction treatment, wherein the conditions during the reduction treatment are as follows: keeping the temperature at 450 ℃ and 0.1MPa for 5h, wherein the flow of reducing gas passing through 1g of CoOx/SBA-15 in every 1h is 24000mL, and pure hydrogen is adopted as the reducing gas.
Example 2
The cobalt-based catalyst of this example contains 5.4% by mass of Co, and is composed of an SBA-15 substrate and a cobalt active center supported on the surface of the SBA substrate, where the cobalt active center is divalent cobalt. The cobalt-based catalyst of this example was prepared in essentially the same manner as in example 1, except that: the number of repetitions of step (4) in example 2 was 100.
Examples 3 to 5
In examples 3 to 5, the cobalt-based catalysts each include 5.4% by mass of Co, which are composed of an SBA-15 substrate and cobalt active centers supported on the surface of the SBA substrate, wherein the cobalt active centers are divalent cobalt. The cobalt-based catalysts of examples 3-5 were prepared in essentially the same manner as in example 2, except that: the temperature at the time of reduction in step (5) in example 3 was 150 ℃; the temperature at the time of reduction in step (5) in example 4 was 250 ℃; the temperature at the time of reduction in step (5) in example 5 was 350 ℃.
Example 6
The cobalt-based catalyst of the embodiment has a mass percentage of Co element of 11.8%, and is composed of an SBA-15 substrate and a cobalt active center loaded on the surface of the SBA substrate, wherein three valence states of divalent cobalt, trivalent cobalt and 0-valent cobalt coexist in the cobalt active center. The cobalt-based catalyst of this example was prepared in substantially the same manner as in example 1, except that the repetition of step (4) was repeated 300 times.
Example 7
The cobalt-based catalyst of the embodiment has a mass percentage of Co element of 20.6%, and is composed of an SBA-15 substrate and a cobalt active center loaded on the surface of the SBA substrate, wherein the cobalt active center is formed by coexistence of three valence states of medium divalent cobalt, trivalent cobalt and 0-valent cobalt. The cobalt-based catalyst of this example was prepared in substantially the same manner as in example 1 except that the repetition of step (4) was 500 times.
Example 8
The cobalt-based catalyst of the embodiment has a mass percentage of Co element of 24.6%, and is composed of an SBA-15 substrate and a cobalt active center loaded on the surface of the SBA substrate, wherein the cobalt active center is in a valence state of divalent cobalt, trivalent cobalt and 0-valent cobalt. The cobalt-based catalyst of this example was prepared in substantially the same manner as in example 1, except that the repetition of step (4) was repeated 700 times.
Example 9
The cobalt-based catalyst of the embodiment has a mass percentage of Co element of 28.3%, and is composed of an SBA-15 substrate and a cobalt active center loaded on the surface of the SBA substrate, wherein the cobalt active center is in the coexistence of three valence states of divalent cobalt, trivalent cobalt and 0-valent cobalt. The cobalt-based catalyst of this example was prepared by substantially the same method as in example 1, except that the repetition of step (4) was repeated 1000 times.
The above cobalt-based catalystIn the example of (1) is on a CoO x Reduction of SBA-15 to facilitate subsequent catalysis of CO 2 The hydrogenation reaction is carried out by using a fixed bed reactor as reduction equipment. In other embodiments of the cobalt-based catalyst preparation process, the reduction apparatus used in the reduction is a tube furnace.
Two, CO 2 Examples of the Process for the production of CO by catalytic hydrogenation
Examples 10 to 34
Examples 10 to 34 Co-based catalysts of examples 1 to 9 were subjected to CO treatment at different temperatures 2 The catalytic hydrogenation reaction comprises the following specific test methods: after the cobalt-based catalyst is reduced, the temperature is increased or reduced from the reduction temperature to the reaction temperature, then the feed gas is introduced, wherein the feed gas is CO 2 、H 2 And argon (H in the gas mixture) 2 /CO 2 and/Ar (v/v/v) ═ 9:9:2, the flow rate of feed gas passing 1g of CoOx/SBA per 1h was 18000mL, and the pressure in the fixed-bed reactor was 2 MPa. Testing CO at different run times during run 2 Conversion of (3), CO and the other reaction product CH 4 Selectivity of (2).
In examples 10 to 13, the cobalt-based catalyst of example 1 was subjected to CO treatment at different reaction temperatures 2 Carrying out catalytic hydrogenation reaction; example 14 Co-based catalyst of example 2 was subjected to CO at 230 deg.C 2 Examples 15 to 16 were catalytic hydrogenation reactions, in which the cobalt-based catalysts of examples 3 to 5 were subjected to CO at 260 ℃ respectively 2 Carrying out catalytic hydrogenation reaction; examples 17 to 18 were conducted by subjecting the cobalt-based catalyst of example 2 to CO treatment at different reaction temperatures 2 Carrying out catalytic hydrogenation reaction; examples 19 to 22 were conducted by subjecting the cobalt-based catalyst of example 6 to CO reaction at different reaction temperatures 2 Carrying out catalytic hydrogenation reaction; examples 23 to 26 were conducted by subjecting the cobalt-based catalyst of example 7 to CO at different reaction temperatures 2 Carrying out catalytic hydrogenation reaction; examples 27 to 33 were conducted by subjecting the cobalt-based catalyst obtained in example 8 to CO reaction at different reaction temperatures 2 Carrying out catalytic hydrogenation reaction; example 34 cobalt-based catalyst prepared in example 9 was heated at 260 deg.CCO is carried out at moderate temperature 2 And (3) catalytic hydrogenation reaction.
Reaction temperatures and CO at various times in examples 10 to 34 2 Conversion of (3), CO and the other reaction product CH 4 The results of the selectivity test are shown in table 1.
TABLE 1 results of testing catalytic performance of catalysts under different reaction conditions
Figure BDA0002421763120000061
Figure BDA0002421763120000071
CO Selectivity and CO over 500h of run in example 12 2 The conversion was counted and the results are shown in FIG. 1.
The results in table 1 and figure 1 show that: CO pairs Using the cobalt-based catalyst of the invention 2 The products of hydrogenation catalysis are CO and CH 4 。
From examples 14 to 17, it can be seen that the reduction temperature is set to CO 2 Has the effect that the proportion of metallic cobalt increases, the thermodynamically favourable methane selectivity increases and, with increasing reduction temperature, the CO increases 2 Increase in the conversion of (b).
For cobalt-based catalysts of different cobalt contents, CO increases with reaction temperature 2 The conversion of (a) tends to increase. For cobalt-based catalysts with different cobalt contents, CO and CH at the same reaction temperature 4 The selectivity of (a) is different: when the content of the cobalt element is not high and 5.4 percent (namely the cycle number is not higher than 100), the selectivity of the CO is higher than that of the CH 4 The selectivity of (a); when the content of cobalt element is not less than 11.8% (i.e. the number of cycles is not less than 300), CH 4 The selectivity of (a) is higher than that of CO. It is shown that the catalytic activity of the cobalt active centers in different valence states is different, and that bivalent cobalt favors CO 2 CO is generated in the hydrogenation reaction; trivalent cobalt is easily reduced into metal cobalt to generate methane, divalent cobalt is favorable for generating CO, and goldThe catalytic performance of cobalt is much higher than that of bivalent cobalt and is beneficial to the generation of methane, so that the main product of the reaction is changed into methane along with the increase of the cycle number.
As can be seen from fig. 1, the cobalt-based catalyst of the present invention has better stability even though the cobalt element content is small.
CO of the invention 2 In other embodiments of the method for producing CO by catalytic hydrogenation, other conditions such as reaction pressure may be adjusted within the following ranges: the pressure is 0.1-5.0 MPa, and the flow of the raw material gas passing through 1g of the cobalt-based catalyst in every 1h is 12000-25000 mL.
In conclusion, the cobalt-based catalyst of the invention is used in CO 2 The catalyst has better catalytic activity and stability in hydrogenation reduction reaction. And the reduction degree of Co is changed and the valence state of Co is regulated by regulating and controlling the cycle number during depositing the cobalt oxide and the reduction condition during reduction treatment, so that CO and CH can be realized 4 Selective regulation of (2).
Third, test example section
Test example 1
TEM tests were performed on the cobalt-based catalysts of examples 1, 2 and 6-9, and the results are shown in FIG. 2. In FIG. 2, 50Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 1, 100Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 2, 300Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 6, 500Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 7, 700Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 8, and 1000Co/SBA-15 is a TEM image of the cobalt-based catalyst in example 9.
According to TEM test results, CoO x When the circulation frequency is less, the cobalt precursor can enter the pore channel of the SBA-15 so as to realize the deposition of cobalt in the pore channel, and after 500 circulations, the cobalt precursor is difficult to enter the pore channel of the SBA-15 and mainly grows outside the pore channel.
Test example 2
The cobalt-based catalysts of examples 1, 2, 6 and 7 were subjected to XPS test, and the spectra of cobalt element were as shown in fig. 3. In FIG. 3, 50Co is a spectrum of the cobalt element of the cobalt-based catalyst of example 1; 100Co is the spectrogram of the cobalt element of the cobalt-based catalyst in the example 2; 300Co is the spectrogram of the cobalt element of the cobalt-based catalyst of the example 6; 500Co is the spectrum of the cobalt element of the cobalt based catalyst of example 7.
Calculating the content of cobalt in each valence state according to XPS and the content of Co element, and calculating the binding energy (Co) of Co species in different valence states before calculation 2+ 2d1/2 and 2d3/2 of (B) are 797.50eV and 781.70eV, respectively, and Co3 + 2d1/2 and 2d3/2 of 795.74eV and 780.13eV, respectively, and 2d1/2 and 2d3/2 of Co0 of 794.05eV and 778.5eV, respectively), and then the relative content of each valence Co was calculated from the peak area, the calculation results being shown in Table 2.
Table 2 cobalt active center statistics
Figure BDA0002421763120000081
The XPS result further shows that the valence state of cobalt in the cobalt active center is changed along with the content of cobalt in the cobalt-based catalyst. At low cycles (<100), the Co atoms form strongly interacting Co-O-Si chemical bonds with the support, are difficult to reduce, and can remain divalent. At high cycles, Co atoms mainly aggregate into a cobalt oxide film, have a weak interaction with the support, are easily oxidized into trivalent during production, and the weakly interacting Co is easily reduced into metallic Co in a reducing atmosphere.

Claims (9)

1. A cobalt-based catalyst, which is characterized by consisting of an SBA-15 substrate and cobalt active centers supported on the SBA-15 substrate, wherein the cobalt active centers are obtained by reducing a cobalt oxide deposition layer supported on the SBA-15 substrate, and the cobalt oxide deposition layer is formed by atomic layer deposition; the mass percentage of Co element in the cobalt-based catalyst is 2.6-5.4%; or the Co element in the cobalt-based catalyst accounts for 24.6 percent by mass, and CO accounts for 2 The reaction temperature is 400-600 ℃ when the CO is prepared by catalytic hydrogenation.
2. The cobalt-based catalyst according to claim 1, wherein the temperature at the time of reduction is 250 to 450 ℃.
3. The cobalt-based catalyst according to claim 1, wherein cobalt in the cobalt active center is present in a valence state of 2-valent cobalt or in a coexistence of three valence states of 2-valent cobalt, 3-valent cobalt and 0-valent cobalt.
4. A cobalt-based catalyst according to any one of claims 1 to 3, wherein the cobalt oxide deposition layer is formed by atomic layer deposition and comprises the following steps:
(1) in an atomic layer deposition vacuum reaction cavity, a Co precursor is pulsed on the surface of an SBA-15 matrix, then, the gas is held, so that the Co precursor is adsorbed on the surface of the SBA-15 matrix, and then, air is pumped to remove the Co precursor which is not adsorbed;
(2) the pulse oxidant is then held in the atmosphere, so that the oxidant reacts with the Co precursor adsorbed on the surface of SBA-15 in the step (1), and then the unreacted oxidant is removed by pumping;
(3) and (3) sequentially repeating the step (1) and the step (2), namely forming a cobalt oxide deposition layer on the surface of the SBA-15.
5. The cobalt-based catalyst according to claim 4, wherein the atomic layer deposition in the step (1) and the step (2) is carried out at a temperature of 200-300 ℃ and a pressure of 10-200 Pa, and a volume ratio of a carrier gas to an atomic layer deposition vacuum reaction chamber is 1: (5 to 50) min -1 。
6. A cobalt-based catalyst according to claim 4, wherein the number of repetitions in step (3) is 50 to 1000.
7. The cobalt-based catalyst according to claim 6, wherein the repetition number is not more than 100 times, and cobalt of the cobalt active center in the cobalt-based catalyst exists in a valence state of 2-valent cobalt; the repeating times are not less than 300 times, and the cobalt in the cobalt-based catalyst exists in the form of three valence states of 2-valent cobalt, 3-valent cobalt and 0-valent cobalt.
8. CO (carbon monoxide) 2 The method for preparing CO by catalytic hydrogenation is characterized by comprising the following steps: reacting raw material gas under the action of a cobalt-based catalyst as claimed in any one of claims 1 to 7 to generate CO and CH 4 。
9. CO according to claim 8 2 The method for preparing CO through catalytic hydrogenation is characterized in that the temperature is 200-600 ℃, the pressure is 0.1-5.0 MPa, and the flow of feed gas passing through 1g of cobalt-based catalyst in every 1 hour is 12000-25000 mL.
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