CoO / SiO2 photo-thermal catalyst as well as preparation method and application thereof
CoO/SiO2 photothermal catalyst was prepared by one-step method, and the photothermal synergistic effect was used to solve the problems of high cost and poor stability of existing catalysts, and the efficient preparation of high-activity and high selectivity CO2 methanation reaction was achieved, and the rate and selectivity of CH4 were significantly improved.
Patent Information
- Application Number
- CN202510428148.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-08-01
AI Technical Summary
The existing photothermal catalytic CO2 methanation catalysts have problems such as high cost, poor activity stability, low selectivity and easy carbon deposition poisoning, making it difficult to efficiently prepare highly active and highly selective CoO/SiO2 photothermal catalysts.
The CoO/SiO2 photothermal catalyst was prepared by a one-step method. The cobalt silicate precursor was converted into CoO/SiO2 through hydrothermal reaction and photothermal activation. The CO2 methanation reaction was carried out by photothermal synergistic reaction, and the CO2 conversion to CH4 was directly carried out in the photothermal catalytic device.
The structural stability and high activity of the catalyst were achieved, the CH4 generation rate was 43 mmol/g/hour, and the selectivity was 90%, which avoided carbon deposits and poisoning, and simplified the preparation process.
Smart Images
Figure CN120394014A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalytic materials, and particularly relates to a CoO / SiO2 photothermal catalyst, a preparation method thereof, and an application thereof. Background Art
[0002] Under the severe situation of global warming, the excessive emission of CO2 has caused a serious greenhouse effect, having many adverse effects on the ecological environment and human life. Catalytically converting CO2 into fuels and chemicals is not only a potential means to alleviate the greenhouse effect, but also a key path to realizing the carbon resource cycle.
[0003] The photothermal catalytic CO2 hydrogenation technology uses solar energy to drive the reaction and conversion of CO2 and H2, with both green pollution-free and sustainability. At present, the photothermal catalytic CO2 hydrogenation faces two major problems: low energy conversion efficiency and poor product selectivity. CO2 is a stable linear molecule, and the dissociation energy of its carbon-oxygen double bond (C=O) is as high as 750 KJ / mol, which is difficult to be activated. Moreover, this reaction involves a complex multi-proton-electron coupling process, and multiple C1 intermediates compete to generate at the catalytic sites, making it difficult to control the product selectivity. The common products include CO, CH3OH, CH4, and higher hydrocarbon compounds. Kinetically, the two-electron transfer products (such as CO and CH3OH) are easier to generate than the eight-electron transfer product CH4, resulting in a low selectivity of CH4. CH4 is a key component of natural gas and is widely used in fields such as heating, cooking, and power generation. Producing CH4 from CO2 through the methanation reaction helps to promote the development of a circular carbon economy and achieve the closure of the carbon cycle. However, it is challenging to prepare a practical catalyst with high activity and high selectivity for the photothermal catalytic CO2 methanation reaction.
[0004] Common photocatalytic CO₂ methanation catalysts include noble metal catalysts (such as Pt, Pd, etc.), nickel-based catalysts, cobalt-based catalysts and other supported catalysts. Although noble metal catalysts have extremely high activity stability, their large-scale application is greatly limited due to their high cost. For nickel-based and cobalt-based catalysts, the active component metals Ni and Co are usually loaded on carriers such as alumina, silica, titanium dioxide, molecular sieves (such as ZSM-5, etc.), carbon nanotubes (CNTs), etc. The active components are effectively dispersed by the carriers to improve the activity of the catalysts. Although different carriers can regulate the performance of supported catalysts, the interaction between the carrier and the metal component is relatively complex. If the interaction is too strong, it may limit the adsorption and activation ability of the metal active sites to reactants; if the interaction is too weak, the active components are likely to fall off from the carrier surface, resulting in poor catalyst stability. And in the actual preparation process, it is difficult to precisely control the strength of this interaction, which is not conducive to the precise regulation of catalyst performance. In addition, cobalt-based and nickel-based supported catalysts also have problems such as easy carbon deposition, limited anti-sintering ability, sulfur poisoning, and low selectivity. Summary of the Invention
[0005] Aiming at the problems existing in the above background technology, the purpose of the present invention is to provide a CoO / SiO₂ photocatalyst and its preparation method and application, to obtain a catalyst with stable structure and excellent catalytic activity in the photocatalytic reaction, and to improve the yield of photocatalytic CO₂ methanation and the selectivity of CH₄.
[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions: A preparation method of a CoO / SiO₂ photocatalyst, comprising the following steps: S1. Dissolve tetraethyl orthosilicate (TEOS) in ethanol and stir, add ammonia water (NH₃·H₂O) thereto, after stirring for several hours, wash and dry the precipitate; S2. Disperse the dried solid in deionized water, then add cobalt chloride (CoCl₂·6H₂O) and ammonia water (NH₃·H₂O), stir and mix evenly, and then carry out a hydrothermal reaction. After the reaction is completed, wash, filter and dry the precipitate to obtain a cobalt silicate (Co₂SiO₄) sample; S3. Place the obtained cobalt silicate (Co₂SiO₄) sample in a photocatalytic device, and carry out an activation reaction at a reaction temperature of 30 - 300 °C to obtain a CoO / SiO₂ photocatalyst.
[0007] Further, in step S2, the conditions of the hydrothermal reaction are: reaction temperature: 100 - 200 °C, reaction time: 5 - 24 hours. The preferred reaction temperature is 120 °C and the reaction time is 20 hours.
[0008] Further, in step S3, the conditions for the activation reaction are as follows: a continuously flowing CO2 / H2 mixed gas stream, 1 - 1.2 atmospheres, xenon lamp illumination with 6 - 15 sun energies, and a reaction time of 1 - 12 hours.
[0009] Further, the flow rate ratio of the CO2 / H2 mixed gas stream is 1:3.
[0010] The present invention further provides a CoO / SiO2 photo - thermal catalyst obtained by the above - mentioned preparation method.
[0011] The present invention further provides the application of the CoO / SiO2 photo - thermal catalyst in the production of CH4 by CO2 methanation reaction. The method for catalyzing the CO2 methanation reaction to produce CH4 is as follows: after the cobalt silicate (Co2SiO4) sample is subjected to an activation reaction in a photo - thermal catalytic device to obtain a CoO / SiO2 photo - thermal catalyst, without taking out the CoO / SiO2 photo - thermal catalyst, the CO2 methanation reaction to produce CH4 is directly carried out in the photo - thermal reaction device.
[0012] Compared with the disadvantages and deficiencies of the prior art, the present invention has the following beneficial effects: (1) The CoO / SiO2 photo - thermal catalyst prepared by the present invention has a simple composition, consisting of only three elements: Si, Co, and O. The raw materials are cheap and easily available, and the synthesis process is convenient and easy to operate. (2) In the application of photo - thermal catalytic CO2 methanation to produce CH4, only the synthesized cobalt silicate precursor needs to be loaded into the photo - thermal catalytic device. The production of CH4 from the cobalt silicate precursor can be completed through a two - step photo - thermal catalytic process, and the method is simple.
[0013] (3) CoO / SiO2 exhibits excellent photo - thermal catalytic activity. Under the reaction conditions of 300 °C, the rate of CH4 generation is 43 mmol / g / h, and the selectivity reaches 90%, showing excellent product generation rate and selectivity.
[0014] (4) In the preparation of the CoO / SiO2 photo - thermal catalyst, the in - situ construction of the catalyst is realized by using the photo - thermal catalytic CO2 reaction conditions, which saves time and effort. Moreover, the catalyst obtained under these conditions has a stable structure, does not suffer from carbon deposition, poisoning, deactivation, etc., is easy to control, and has high activity and selectivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 is the XRD pattern of the Co2SiO4 sample provided in Example 1 of the present invention and the products prepared at different photo - thermal catalytic reaction temperatures; Figure 2 is the TEM image (a and b), HRTEM image (c), and elemental distribution image (d) of the product prepared by the Co2SiO4 sample provided in Example 1 of the present invention under photo - thermal catalytic reaction at 300 °C; Figure 3 These are the XPS spectra of the products prepared by the Co2SiO4 samples provided in Example 1 of the present invention through photothermal catalytic reactions at 100°C and 300°C respectively. In the figures, (a) represents Co 2p; (b) represents O 1s; (c) represents Si 2p; Figure 4 These are the result graphs of the CoO / SiO2 photothermal catalyst provided in Example 2 of the present invention for the production of CH4 through the CO2 methanation reaction at different reaction temperatures; Figure 5 These are the result graphs of the CoO / SiO2 photothermal catalyst provided in Example 2 of the present invention for the photothermal catalytic hydrogenation reaction of CO2 for 22 hours at 300°C. Detailed implementation manners
[0016] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment
[0017] The preparation method of the CoO / SiO2 photothermal catalyst is as follows: S1. Dissolve 2 mL of TEOS in ethanol and stir. Add 5 mL of NH3·H2O thereto. After stirring for 4 hours, wash and dry the precipitate; S2. Disperse the dried solid in 15 mL of deionized water, then add 1.25 mmol of CoCl2·6H2O and 6 mL of NH3·H2O. After stirring and mixing evenly, perform a hydrothermal reaction. Reaction temperature: 120°C, reaction time: 20 hours. After the reaction ends, wash, filter and dry the precipitate to obtain a Co2SiO4 sample; S3. Place the obtained Co2SiO4 sample in a photothermal catalytic device and react for 1 hour under the conditions of a reaction temperature of 30 - 300°C, a flow rate ratio of the CO2 / H2 mixed gas stream of 1:3 (the flow rates of CO2 and H2 are 2 mL / min and 6 mL / min respectively), 1 atmospheric pressure, and xenon lamp illumination with 6 sun energies to obtain a CoO / SiO2 sample.
[0018] Product characterization test: 1. Perform XRD tests on the Co2SiO4 sample obtained in step S2 and the products prepared at different reaction temperatures after placing this sample in a photothermal catalytic device. The results are as Figure 1 shown. It can be seen that for the Co2SiO4 sample obtained in step S2, its diffraction peaks ( Figure 1The diffraction peaks of the (middle-bottom curve) are exactly corresponding to those of the Co2SiO4 reference material, indicating that the synthesized material under this condition is Co2SiO4. After the Co2SiO4 reacts under the condition of photothermal CO2 hydrogenation, when the reaction temperature is between 30 - 100 °C, the obtained sample still maintains the structure of Co2SiO4; when the reaction temperature rises to 125 - 300 °C, the obtained sample shows the diffraction peaks of CoO, and at the same time, a diffraction envelope of amorphous SiO2 appears in the range of 20 - 30 0 proving that it is transformed into CoO / SiO2 after photothermal catalysis.
[0019] 2. TEM and HRTEM tests were carried out on the products prepared by the photothermal catalytic reaction of the Co2SiO4 sample at 300 °C. The TEM results are as shown in Figure 2 Figures a and b, and the HRTEM results are as shown in Figure 2 Figure c. It can be seen that the prepared products are crystalline, spherical aggregates, and the diameter of the aggregated nanospheres is about 60 - 150 nm, and there are a large number of pores inside the nanospheres. The element distribution map obtained by TEM is as shown in Figure 2 Figure d, indicating that the finally prepared product is composed of three elements: Si, O, and Co, further verifying the conclusion that the final product is a CoO / SiO2 composite material.
[0020] 3. XPS tests were carried out on the products prepared by the photothermal catalytic reaction of the Co2SiO4 sample at 100 °C and 300 °C respectively. The results are as shown in Figure 3 Figure, indicating that the sample after the reaction at 100 °C contains the characteristic peaks of Co 2+ and Co 3+ , while the sample after the reaction at 300 °C only has the characteristic peak of Co 2+ ; the chemical environments around the oxygen atoms and silicon atoms in the two samples are basically the same, both composed of Si-O-Si, Si-O-Co, and Co-O-Co. Example
[0021] When using the CoO / SiO2 photothermal catalyst prepared in Example 1 to produce CH4 by CO2 methanation reaction, the prepared Co2SiO4 sample was placed in a photothermal catalytic device, first activated at 300 °C to obtain the CoO / SiO2 photothermal catalyst, and then without taking out the CoO / SiO2 photothermal catalyst, directly carried out the CO2 methanation reaction to produce CH4 in the photothermal reaction device. The performance tests of the thermal catalytic and photothermal catalytic CO2 hydrogenation reactions were carried out in the temperature range of 30 - 300 °C respectively. The results are as shown in Figure 4 Figure, indicating that the sample is not conducive to the formation of CH4 under the conditions of pure thermal catalysis and photothermal catalysis at lower temperatures. Only under the photothermal synergy in the high-temperature region is the formation of CH4 more obvious. Under the photothermal synergy at 300 °C, the formation rate of CH4 can reach 42.5 mmol g-1 h -1 , this performance far exceeds that of the vast majority of catalysts reported currently.
[0022] The performance of the CoO / SiO2 photothermal catalyst in the photothermal catalytic hydrogenation of CO2 at 300 °C for 22 hours is as Figure 5 shown. It can be seen from the figure that when the reaction temperature is 300 °C, the catalyst exhibits good photothermal catalytic stability, and the average formation rates of CH4 and CO are stably at 43 mmol·g⁻¹·h⁻¹ and 4.5 mmol·g - ¹·h - ¹, and the selectivity of the main product CH4 is about 95.3%.
[0023] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A preparation method of CoO / SiO2 photothermal catalyst, characterized in that It includes the following steps: S1. Dissolve TEOS in ethanol and stir. Add NH3·H2O thereto. After stirring for several hours, wash and dry the precipitate; S2. Disperse the dried solid in deionized water, then add CoCl2·6H2O and NH3·H2O, stir and mix evenly, and then carry out a hydrothermal reaction. After the reaction is completed, wash, filter and dry the precipitate to obtain a Co2SiO4 sample; S3. Place the obtained Co2SiO4 sample in a photothermal catalytic device, activate the reaction at a reaction temperature of 30 - 300 °C to obtain a CoO / SiO2 photothermal catalyst.
2. The preparation method of the CoO / SiO2 photothermal catalyst according to claim 1, wherein In step S2, the conditions of the hydrothermal reaction are: reaction temperature: 100 - 200 °C, reaction time: 5 - 24 hours.
3. The preparation method of the CoO / SiO2 photothermal catalyst according to claim 2, wherein, The conditions of the hydrothermal reaction are: reaction temperature: 120 °C, reaction time: 20 hours.
4. The preparation method of the CoO / SiO2 photothermal catalyst according to claim 1, characterized in that, In step S3, the conditions of the activation reaction are: a continuously flowing CO2 / H2 mixed gas stream, 1 - 1.2 atmospheres, xenon lamp illumination with 6 - 15 sun energies, and react for 1 - 12 hours.
5. The preparation method of the CoO / SiO2 photothermal catalyst according to claim 4, characterized in that, The flow rate ratio of the CO2 / H2 mixed gas stream is 1:
3.
6. A CoO / SiO2 photothermal catalyst prepared by the preparation method according to any one of claims 1 - 5.
7. An application of the CoO / SiO2 photothermal catalyst according to claim 6 in the production of CH4 by CO2 methanation reaction.
8. The application according to claim 7, wherein The method for producing CH4 by CO2 methanation reaction is: after the Co2SiO4 sample is activated in a photothermal catalytic device to obtain a CoO / SiO2 photothermal catalyst, without taking out the CoO / SiO2 photothermal catalyst, directly carry out the CO2 methanation reaction in the photothermal reaction device to produce CH4.