Tetragonal lanthanum oxycarbonate, catalyst and preparation method and application of tetragonal lanthanum oxycarbonate
By developing a tetragonal phase lanthanum oxide carbonate catalyst, the problems of difficult separation and recycling of existing homogeneous catalysts have been solved, and efficient catalysts of CO2 hydrogenation reaction have been achieved, reducing costs and improving the feasibility of industrial applications.
Patent Information
- Application Number
- CN202510297202.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-13
- Publication Date
- 2025-06-20
AI Technical Summary
Existing homogeneous catalysts are difficult to separate and recover in CO2 hydrogenation reaction. The raw materials of precious metal catalysts are expensive, the monomers of metal complex catalysts are highly toxic, and the catalyst synthesis route is complex, making it difficult to meet the needs of efficient CO2 catalysis and industrial applications.
A tetragonal phase lanthanum oxide carbonate (t-La2O2CO3) catalyst was developed, and the gel was formed by heating and stirring raw materials such as acetic acid, lanthanum nitrate hexahydrate and citric acid, and annealing was prepared under the grinding of polyethyleneimine. The metal-supported catalyst was further prepared by dropping addition and annealing of metal acid solution to achieve the separation and recovery of the catalyst.
The catalyst has a large specific surface area and oxygen vacancies, which enhances the activation ability of CO2, and is easily separated and recovered through simple physical methods, reducing catalyst losses and costs, improving the feasibility of industrial application of CO2 hydrogenation reactions, and achieving selective switching between CO and methanol.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of catalysts, and particularly to a tetragonal lanthanum oxycarbonate, a catalyst, and a preparation method and application thereof. Background Art
[0002] With the rapid development of the global economy, the social demand for energy is increasing day by day. The use of a large amount of fossil fuels has led to a continuous increase in the concentration of CO2 in the atmosphere. At the beginning of 2024, the CO2 concentration has reached 420.95 ppm, triggering a serious environmental crisis. Therefore, realizing the efficient catalytic conversion of CO2 has become the top priority for alleviating environmental pressure. The hydrogenation of CO2 to produce CO, also known as the reverse water gas shift reaction (RWGS), is one of the most important branches of the CO2 hydrogenation reaction. The CO product can be used as a raw material for the Fischer-Tropsch reaction (F-T) to synthesize a series of high-value-added chemical products, such as synthetic oil, olefins, etc. Since the C=O bond energy in the CO2 molecule is as high as 799 kJ mol -1 , it is difficult to activate the CO2 molecule in the reaction. Therefore, traditional catalytic processes often require a large amount of energy input, such as electric energy, heat energy, etc., which is not conducive to meeting the requirements of energy conservation and emission reduction. Therefore, researchers are committed to developing efficient catalytic systems to achieve the purpose of reducing the activation energy barrier, improving the reaction activity and economy.
[0003] To solve the above problems, some researchers have proposed that metal complex catalysts and noble metal (such as Rh, Pd, Pt) catalysts have high catalytic activity and excellent selectivity in the carbon dioxide hydrogenation reaction. However, such catalysts usually have expensive raw materials, toxic coordination monomers, and complex synthesis routes, and are not suitable for large-scale industrial applications; traditional homogeneous catalysts, such as ionic liquid materials, although showing certain activity, have problems of difficult separation and recovery in the CO2 hydrogenation reaction, which not only increases the cost but also seriously affects the reuse efficiency of the catalyst, and does not meet the high-efficiency and green requirements of the CO2 hydrogenation reaction industry. Therefore, developing a heterogeneous catalyst to improve the catalytic activity of CO2 in the hydrogenation reaction and reduce the production cost lays a foundation for realizing the efficient catalysis of CO2 and promoting green and sustainable development. Summary of the Invention
[0004] To solve the problems of difficult separation and recovery of existing homogeneous catalysts in the CO2 hydrogenation reaction, as well as expensive raw materials of noble metal catalysts, large toxicity of metal complex catalyst monomers, and complex catalyst synthesis routes, etc., the present invention proposes a tetragonal lanthanum oxycarbonate, a catalyst, and a preparation method and application thereof. The technical solution of the present invention is as follows:
[0005] A preparation method of a tetragonal lanthanum oxycarbonate, comprising the following preparation steps:
[0006] Put acetic acid, lanthanum nitrate hexahydrate, and citric acid in a beaker, heat and stir them. Take out the obtained gel to a mortar, add polyethyleneimine and grind it. Anneal the ground sample to prepare tetragonal lanthanum oxycarbonate;
[0007] Further, the heating temperature is 50 °C;
[0008] Further, the stirring time is 1 h;
[0009] Further, the grinding time is 10 min;
[0010] Further, the annealing temperature is 550 °C, the annealing time is 2 h, and the annealing heating rate is 10 °C / min.
[0011] A kind of tetragonal lanthanum oxycarbonate is prepared by the above method.
[0012] A preparation method of a catalyst, the catalyst uses the above-mentioned tetragonal lanthanum oxycarbonate as a carrier, and the preparation method includes the following preparation steps: wet the tetragonal lanthanum oxycarbonate with water, drop a metal acid solution onto it, evaporate the solvent, and then anneal it to prepare a metal-loaded tetragonal lanthanum oxycarbonate catalyst;
[0013] Further, the metal acid solution includes chloroplatinic acid solution and copper nitrate solution;
[0014] Further, the temperature for evaporating the solvent is 80 °C;
[0015] Further, the annealing temperature is 300 °C, the annealing time is 2 h, and the annealing heating rate is 10 °C / min.
[0016] A catalyst is prepared by the above method.
[0017] A catalyst is applied to the catalytic reaction of CO2 hydrogenation.
[0018] Compared with the prior art, the present invention solves the problems of difficult separation and recovery of existing homogeneous catalysts in the CO2 hydrogenation reaction, as well as problems such as expensive raw materials of noble metal catalysts, high toxicity of metal complex catalyst monomers, and complex catalyst synthesis routes. The specific beneficial effects are as follows:
[0019] 1. Development of tetragonal phase catalyst support: The tetragonal phase catalyst support t-La2O2CO3 provided by the present invention has a large specific surface area and oxygen vacancies, which can provide more active sites for CO2 adsorption and enhance the activation ability of CO2. Moreover, through strong metal-support interaction, a metal-loaded t-La2O2CO3 catalyst is prepared, reducing metal loss and improving the catalyst life. In addition, the catalyst can be easily separated and recovered by simple physical methods (such as filtration and sedimentation), without complex solvent extraction or chemical precipitation, realizing recycling, reducing catalyst loss and cost, and reducing solvent pollution, thus improving the industrial application feasibility of the CO2 hydrogenation reaction.
[0020] 2. Realize the selective switching between CO and methanol: The Cu / t-La2O2CO3 and Pt / t-La2O2CO3 catalysts are prepared from lanthanum nitrate and platinum nitrate as raw materials in the present invention. The raw materials used are widely sourced and inexpensive, making up for the defects of traditional metal complex catalysts with complex structures and expensive precursors, as well as noble metal catalysts with large usage amounts and high costs. At the same time, in the CO2 hydrogenation reaction, for the Pt / t-La2O2CO3 catalyst, at 380 °C, the conversion rate of CO2 can reach 24.1%, and the CO selectivity is greater than 99%. For the Cu / t-La2O2CO3 catalyst, the conversion rate of CO2 can reach 5%, and the methanol selectivity can reach 99% at the collection temperature of 200 °C. Therefore, while ensuring excellent catalytic performance, the present invention can realize the selective switching between CO and methanol by adjusting the components of the active centers, providing new research ideas and industrial application potential for the efficient conversion of CO2.
[0021] 3. Simple preparation process: In the present invention, the metal sites in the acidic metal precursor solution are anchored on the surface of the t-La2O2CO3 catalyst support by annealing. The preparation method is simple, fast, and time-consuming, enabling mass production and industrial application, and having high potential industrial application value in the field of energy catalysis. Description of the Drawings
[0022] Figure 1 is the preparation flow chart of the Pt / t-La2O2CO3 catalyst;
[0023] Figure 2 is the X-ray diffraction pattern of the Pt / t-La2O2CO3 catalyst;
[0024] Figure 3 is the transmission electron microscope image of the Pt / t-La2O2CO3 catalyst at different magnification ratios;
[0025] Figure 4 is the RWGS catalytic property diagram of the Pt / t-La2O2CO3 catalyst at different collection temperatures;
[0026] Figure 5 Properties diagram of methanol production from CO2 hydrogenation over Cu / t-La2O2CO3 catalyst. Detailed implementation mode
[0027] To make the technical solution of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the specification of the present invention. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as a limitation of the present invention.
[0028] Example 1.
[0029] Put 1 mL of acetic acid, 2.1 g of La(NO3)3·6H2O and 0.262 g of citric acid in a beaker, heat and stir at 50 °C for 1 h, take out the obtained gel to a mortar, add polyethyleneimine (PEI) and grind for 10 min; anneal the ground sample in an air atmosphere, the annealing temperature is 550 °C, the annealing time is 2 h, and the heating rate is 10 °C / min to prepare tetragonal La2O2CO3 (t-La2O2CO3).
[0030] Example 2.
[0031] Put 250 mg of t-La2O2CO3 in a beaker, moisten t-La2O2CO3 with 20 mL of water, continue to add 47 μL of 0.05 mol / L chloroplatinic acid solution, evaporate the solvent at 80 °C, and anneal the obtained sample in 10% H2 / Ar, the annealing temperature is 300 °C, the annealing time is 2 h, and the heating rate is 10 °C / min to prepare Pt / t-La2O2CO3 catalyst.
[0032] As Figure 1 is the preparation flow chart of Pt / t-La2O2CO3 catalyst; as Figure 2 is the X-ray diffraction pattern of Pt / t-La2O2CO3 catalyst. It can be seen from the figure that obvious diffraction peaks are shown between 2θ of 10° and 80°, the peak shape is sharp and the intensity is high, indicating that the grain size is large and the crystallinity is good; the peak position matches the standard card highly, indicating that t-La2O2CO3 is the main crystal phase in the catalyst material; as Figure 3 is the transmission electron microscope image (TEM) of Pt / t-La2O2CO3 catalyst at different magnification ratios. It can be seen from the figure that the Pt / t-La2O2CO3 catalyst under low magnification TEM (left figure) is a porous network structure, proving its large specific surface area; high magnification TEM (right figure) further reveals that the particle size of Pt / t-La2O2CO3 catalyst is between 5 and 20 nm, showing a high degree of crystallinity and uniform distribution.
[0033] Pt / t-La2O2CO3 Catalyst for the Reverse Water-Gas Shift Reaction (RWGS):
[0034] 100 mg of the Pt / t-La2O2CO3 catalyst was placed in a 40-cm-long quartz tube reactor, which was filled with quartz wool at both the top and bottom. The reaction gas composition was 24% CO2 / 72% H2 / 4% Ar. The heating rate was 10 °C / min, and the collection temperatures were 200, 250, 300, 350, 380, and 400 °C. The reaction pressure was atmospheric pressure. The products were analyzed by gas chromatography. When the collection temperature was 380 °C, the CO2 conversion rate of the Pt / t-La2O2CO3 catalyst was 21%, and the selectivity was greater than 99%. As Figure 4 Figure Figure 4 shows the RWGS catalytic properties of the Pt / t-La2O2CO3 catalyst at different collection temperatures. It can be seen from the figure that as the collection temperature increases, the CO2 conversion rate of the Pt / t-La2O2CO3 catalyst shows an upward trend, and its gas selectivity remains almost unchanged. This is because as the temperature increases, the reaction activation energy is reduced, and the kinetic processes of CO2 adsorption and H2 dissociation are accelerated, thus increasing the CO2 conversion rate. In addition, the RWGS reaction is more selective at high temperatures, while side reactions such as methanation are usually more likely to occur at lower temperatures. Therefore, as the temperature increases, the CO2 conversion rate increases, while the gas selectivity remains unchanged.
[0035] Example 3.
[0036] The difference between this invention and Example 2 is that 100 μL of 0.05 mol / L chloroplatinic acid solution was added, and the rest of the experimental steps and conditions were the same as those in Example 2, and the Pt / t-La2O2CO3 catalyst was prepared.
[0037] In the RWGS reaction, when the collection temperature was 380 °C, the CO2 conversion rate of the Pt / t-La2O2CO3 catalyst was 22.3%, and the selectivity was greater than 99%.
[0038] Example 4.
[0039] The difference between this invention and Example 2 is that 200 μL of 0.05 mol / L chloroplatinic acid solution was added, and the rest of the experimental steps and conditions were the same as those in Example 2, and the Pt / t-La2O2CO3 catalyst was prepared.
[0040] In the RWGS reaction, when the collection temperature was 380 °C, the CO2 conversion rate of the Pt / t-La2O2CO3 catalyst was 23.4%, and the selectivity was greater than 99%.
[0041] Example 5.
[0042] The difference between the present invention and Example 2 lies in that 500 μL of 0.05 mol / L chloroplatinic acid solution is added, and the remaining experimental steps and conditions are the same as those in Example 2, to prepare the Pt / t-La2O2CO3 catalyst.
[0043] In the RWGS reaction, when the collection temperature is 380 °C, the CO2 conversion rate is 24.1%, and the selectivity is greater than 99%.
[0044] The following table shows the catalytic properties of the Pt / t-La2O2CO3 catalysts with different Pt addition amounts prepared in Examples 2-5. At a reaction temperature of 380 °C, as the Pt content increases, the CO2 conversion rate of the Pt / t-La2O2CO3 catalyst gradually increases, and the selectivity is maintained at a level of >99%. This is because the increase in Pt content increases the number of active sites, enhances the electronic effect, and improves the synergistic effect with the carrier, thus facilitating the adsorption, activation, and reaction of CO2, increasing the CO2 conversion rate, and ensuring high CO selectivity.
[0045]
[0046] Example 6.
[0047] The difference between the present invention and Example 2 lies in that the chloroplatinic acid solution is replaced with 400 μL of 0.1 mol / L copper nitrate solution, and the remaining experimental steps and conditions are the same as those in Example 2, to prepare the Cu / t-La2O2CO3 catalyst.
[0048] In the RWGS reaction, the reaction condition pressure is 3 MPa, and the collection temperatures are 200, 220, 240, 260, 280, and 300 °C respectively, and the other conditions are the same as those in Example 2.
[0049] As Figure 5 It is the property diagram of CO2 hydrogenation to methanol of the Cu / t-La2O2CO3 catalyst. It can be seen from the figure that as the temperature increases, the conversion rate of CO2 of the Cu / t-La2O2CO3 catalyst gradually increases, but its methanol selectivity shows a decreasing trend. This is mainly because at a higher temperature, the surface activity of the Cu / t-La2O2CO3 catalyst changes, which may promote the partial decomposition of La2O2CO3, exposing more oxygen vacancies. This helps the activation of CO2 and increases the reaction rate. At the same time, the exposure degree of Cu active sites may increase, thus enhancing the dissociation ability of H2, accelerating the CO2 hydrogenation reaction. However, the further reduction or excessive sintering of Cu will also enhance the side reactions, affecting the interfacial synergistic effect between Cu and La2O2CO3, reducing the active sites for direct hydrogenation of CO2 to methanol, and promoting the formation of CO, resulting in a decrease in methanol selectivity.
[0050] The t-La2O2CO3 provided by the present invention has a large specific surface area and oxygen vacancies, which can enhance the activation ability of CO2. Cu / t-La2O2CO3 and Pt / t-La2O2CO3 catalysts are prepared through strong metal-support interaction. The raw materials used are widely sourced, low in cost, and the preparation process is simple and fast. After the reaction, the catalyst can be easily separated and recovered. At the same time, the Cu / t-La2O2CO3 and Pt / t-La2O2CO3 catalysts have excellent catalytic performance, and the selectivity between CO and methanol can be switched by adjusting the components of the active center, providing new research ideas and industrial application potential for the efficient conversion of CO2.
[0051] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
[0052] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for preparing tetragonal lanthanum oxycarbonate, characterized in that: The method comprises the following preparation steps: Acetic acid, lanthanum nitrate hexahydrate and citric acid are placed in a beaker, heated and stirred, the obtained gel is taken out to a mortar, polyethyleneimine is added thereto and ground, and the ground sample is annealed to prepare a tetragonal lanthanum carbonate.
2. The method for preparing tetragonal lanthanum oxycarbonate according to claim 1, characterized in that: The heating temperature is 50°C.
3. The method for preparing tetragonal lanthanum oxycarbonate according to claim 1, characterized in that: The stirring time is 1 h.
4. The method for preparing tetragonal lanthanum oxycarbonate according to claim 1, characterized in that: The grinding time is 10 min.
5. The method for preparing tetragonal lanthanum oxycarbonate according to claim 1, characterized in that: The annealing temperature is 550° C., the annealing time is 2 h, and the annealing heating rate is 10° C. / min.
6. A tetragonal lanthanum carbonate, characterized in that: Prepared by the method according to any one of claims 1 to 5.
7. A method for preparing a catalyst, characterized in that: The catalyst uses the tetragonal lanthanum carbonate oxide described in claim 6 as a carrier, and the preparation method comprises the following preparation steps: soaking the tetragonal lanthanum carbonate oxide with water, adding a metal acid solution dropwise thereto, evaporating the solvent, and then annealing to prepare a metal-loaded tetragonal lanthanum carbonate oxide catalyst.
8. The method for preparing the catalyst according to claim 7, characterized in that: The metal acid solution is a chloroplatinic acid solution or a copper nitrate solution; the temperature of the evaporated solvent is 80° C.; the annealing temperature is 300° C., the annealing time is 2 hours, and the annealing heating rate is 10° C. / min.
9. A catalyst, characterized in that Prepared by the method described in claim 7 or 8.
10. Use of the catalyst according to claim 9, characterized in that: Applied in CO2 hydrogenation catalytic reaction.