Co3O4-H-X type catalyst for catalytic combustion of low-concentration methane as well as preparation method and application of Co3O4-H-X type catalyst
By preparing the Co3O4-H-X catalyst, the cobalt oxide catalyst has been solved, and the problem of low activity and poor high temperature stability in methane catalytic oxidation is achieved, and a highly efficient low-concentration methane catalytic combustion effect is achieved.
Patent Information
- Application Number
- CN202510325086.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2025-07-04
AI Technical Summary
The existing cobalt oxide catalysts have low activity in methane catalytic oxidation, poor high temperature stability and easy sintering, which limits their application.
AB2O4 spinel Co3O4 was synthesized by sol-gel method, Srx-Co3O4 was added to form Srx-Co3O4 and pickled, and Sr atoms on the surface were etched off to prepare Co3O4-H-X catalyst.
The Co2+/Co3+ ratio was improved, the reactive oxygen vacancies and redox properties were increased, the catalyst reached 50% conversion at 323°C, and 90% conversion at 435°C, and showed excellent stability and difficulty in sintering at high temperatures.
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Figure CN120243024A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of methane catalytic materials, and in particular, to a Co3O4-H-X type catalyst for low-concentration methane catalytic combustion, a preparation method thereof, and an application thereof. Background Art
[0002] Methane is the main component of natural gas and accounts for a relatively large proportion among greenhouse gases. It is considered to be the second largest greenhouse gas after CO2, and its greenhouse effect is more than 20 times that of CO2. The C-H bond of methane is very stable and is usually difficult to activate. Direct combustion requires a very high temperature and is prone to generating secondary pollutants such as NOx. Catalytic combustion has the characteristics of low operating temperature, high utilization rate, and easy utilization of reaction heat, and is a more effective method. The use of this technology requires the development of catalysts with high catalytic activity, stability, and low cost.
[0003] Currently, methane combustion catalysts mainly include noble metal catalysts, hexaaluminate catalysts, perovskite-type catalysts, and metal oxide catalysts. Noble metal catalysts have good low-temperature catalytic activity and anti-sintering ability. However, the high price and easy deactivation of the active components limit their development. Perovskite-type catalysts have good thermal stability and low cost, but their natural surface is preferentially occupied by A-site cations without catalytic activity, which limits the active sites and their catalytic activity needs to be further improved. Hexaaluminate-type catalysts have excellent stability at high temperatures and still have a large specific surface area after high-temperature treatment, but there is still a large room for improvement in their catalytic activity. Metal oxide catalysts have low cost, are widely available, and have high catalytic activity under specific conditions, so they have good application scenarios in the catalytic oxidation of methane.
[0004] Due to the variable oxidation state of metallic cobalt and its excellent lattice oxygen storage capacity, cobalt oxides have attracted a great deal of attention in the research of methane catalytic oxidation. In cobalt oxides, cobalt tetroxide has a small particle size and high cobalt oxide activity, which are all beneficial to methane catalytic oxidation. At present, cobalt oxides still have the defects of poor oxidation activity of methane catalysts, instability at high temperatures, and easy sintering at high temperatures, and further improvement is needed. Summary of the Invention
[0005] In order to solve the problems existing in the prior art that cobalt oxides used in methane catalysts have low activity, poor high-temperature stability, and easy sintering, the present invention provides a Co3O4-H-X type catalyst for low-concentration methane catalytic combustion, a preparation method thereof, and an application thereof.
[0006] To achieve the above technical solution, the present invention provides a preparation method of a Co3O4-H-X type catalyst for low-concentration methane catalytic combustion. The steps are as follows: First, use the sol-gel method to synthesize the AB2O4 type spinel Co3O4, and add SrCO3 to the system for preparing Co3O4 to form Sr x -Co3O4, and then perform pickling on Sr x -Co3O4 to etch away the Sr atoms on the surface to obtain the Co3O4-H-X catalyst.
[0007] Further, the preparation process of Co3O4 is as follows: Disperse EDTA in water, add NH3·H2O to dissolve it, and then add CA to make it uniformly mixed; Disperse Co(NO3)2·6H2O in an aqueous solution to obtain a salt solution, and then slowly add the salt solution drop by drop to the mixed solution of EDTA and CA. Adjust the pH value with ammonia water. After heating and stirring to form a gel-like substance, dry it to obtain the Co3O4 precursor. Place the Co3O4 precursor in a muffle furnace for roasting, and grind it after taking it out to obtain Co3O4.
[0008] Further, the subscript x in Sr x -Co3O4 is determined according to the molar ratio of Sr:Co; the molar ratio is 0.05 - 0.15.
[0009] Further, the acid solution used for pickling Sr x -Co3O4 is dilute nitric acid. The concentration of the acid solution is 0.5 - 1.5 mol·L-1, and the pickling time is 1 - 7 hours.
[0010] Further, adjust the pH value to the range of 7 ± 0.5 with ammonia water.
[0011] Further, the stoichiometric ratio of CA, EDTA and metal ions is 2:1:1.
[0012] Further, use a blast drying oven to dry the gel-like mixed solution. The drying temperature is 200 °C and the drying time is 5 hours.
[0013] Further, the roasting temperature is 600 °C and the heat preservation time is 5 hours.
[0014] Further, a Co3O4-H-X type catalyst for low-concentration methane catalytic combustion, which is prepared by the preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion described in any one of claims 1 to 8.
[0015] Further, an application of the Co3O4-H-X type catalyst, using the Co3O4-H-X type catalyst in the process of catalytic combustion of methane with a concentration lower than 1%.
[0016] In summary, the present invention has the following beneficial effects compared with the prior art:
[0017] (1) The Co3O4-H catalyst obtained by the method of etching and removing surface Sr in the spinel structure in the present invention has a higher Co 2+ / Co 3+ ratio, more active oxygen vacancies, better high-temperature stability, less sintering tendency at high temperatures, and better redox performance.
[0018] (2) This catalyst is a non-noble metal catalyst with good catalytic effect on methane, reaching a 50% conversion rate at 323 °C and a 90% conversion rate at 435 °C, and showing excellent stability under high-temperature conditions. It is a low-concentration methane catalytic combustion material with excellent performance and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:
[0020] Figure 1 is the X-ray powder diffraction pattern of Co3O4 in Example 1 of the present invention and Co3O4-SA in Comparative Example 1;
[0021] Figure 2 is the X-ray powder diffraction pattern of the Sr x -Co3O4 catalyst prepared in Example 2 of the present invention;
[0022] Figure 3 is the X-ray powder diffraction pattern of Co3O4-H-X in Example 3 of the present invention;
[0023] Figure 4 is the field emission scanning electron microscope images of Examples 1-3 and Comparative Example 1 of the present invention;
[0024] Figure 5 is the X-ray photoelectron spectroscopy spectra of Co3O4 in Example 1, Sr 0.1 -Co3O4 in Example 2, Co3O4-H-1 in Example 3, and Co3O4-SA in Comparative Example 1 of the present invention;
[0025] Figure 6 is the methane catalytic conversion rate graph of the catalysts prepared in Examples 1-3 and Comparative Example 1 of the present invention;
[0026] Figure 7It is the test result of the methane catalytic combustion stability of the Co3O4-H-1 type catalyst prepared in Example 3 of the present invention. Detailed implementation manners
[0027] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.
[0028] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise clearly specified in the context, the singular form can also include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.
[0029] See Figures 1 to 7 As shown, the present invention provides a preparation method for a Co3O4-H-X type catalyst for the catalytic combustion of low-concentration methane. The steps are as follows: First, the AB2O4 type spinel Co3O4 is synthesized by the sol-gel method. A certain molar amount of SrCO3 is added to the system for preparing Co3O4 to form Sr x -Co3O4, and then Sr x -Co3O4 is pickled to etch away the Sr atoms on the surface to obtain the Co3O4-H-X catalyst.
[0030] In the production process of this catalyst, the Sr atoms loaded on the surface of Co3O4 are etched away to obtain the Co3O4-H-X catalyst, which has a higher Co 2+ / Co 3+ ratio, more active oxygen vacancies and better redox performance, and the catalyst also exhibits very excellent high-temperature stability and high-temperature non-sintering property.
[0031] As a preference, the preparation process of Co3O4 is as follows: EDTA is dispersed in water, NH3·H2O is added to dissolve it, and then CA is added to mix them evenly; Co(NO3)2·6H2O is mixed and dispersed in an aqueous solution to obtain a salt solution, and then the salt solution is slowly added dropwise to the mixed solution of EDTA and CA. The pH value is adjusted with ammonia water. After heating and stirring to form a gel-like substance, it is dried to obtain the Co3O4 precursor. The Co3O4 precursor is placed in a muffle furnace for roasting, and after taking out, it is ground to obtain Co3O4.
[0032] Example 1: For the preparation of Co3O4, in the actual operation of the present invention, 5.8448 g of EDTA was dispersed in water, NH3·H2O was added to dissolve it, and then 8.4056 g of CA was added to make it evenly mixed; 2.9103 g of Co(NO3)2·6H2O was dispersed in an aqueous solution to obtain a salt solution, and then the salt solution was slowly added dropwise to the mixed solution of EDTA and CA, and the pH value was adjusted to about 7 with NH3·H2O. After heating and stirring for a period of time, a gel-like substance was formed, and it was dried in a forced-air drying oven at 200 °C for 5 h to obtain a Co3O4 precursor, and the Co3O4 precursor was calcined in a muffle furnace at different temperatures for 4 hours.
[0033] As a preference, Sr x The subscript x in -Co3O4 is determined according to the molar ratio of Sr:Co; the molar ratio is 0.05 - 0.15.
[0034] Example 2: For the preparation of Sr x -Co3O4, in the actual operation of the present invention, a certain molar amount of SrCO3 was weighed and added to the system for preparing Co3O4. According to the molar ratio of Sr:Co, the obtained samples were respectively named Sr 0.05 -Co3O4, Sr 0.1 -Co3O4, Sr 0.15 -Co3O4.
[0035] As a preference, the acid solution used for pickling Sr x -Co3O4 is dilute nitric acid, the concentration of the acid solution is 0.5 - 1.5 mol·L-1, and the pickling time is 1 - 7 hours.
[0036] Example 3: For the pickling process of Sr x -Co3O4, in the actual operation of the present invention, a 0.5 mol / L HNO3 solution was prepared. After weighing a certain amount of Sr 0.1 -Co3O4 obtained in Example 2 and adding it to the HNO3 solution, it was reacted in a magnetic stirrer for 30 min. After the reaction, it was washed with deionized water and absolute ethanol, and after drying, it was named Co3O4-H-X.
[0037] As a preference, the stoichiometric ratio of CA, EDTA and metal ions is 2:1:1.
[0038] As a preference, the pH value is adjusted to the range of 7 ± 0.5 with ammonia water.
[0039] As a preference, the gel-like mixed solution is dried in a forced-air drying oven, the drying temperature is 200 °C, and the drying time is 5 hours.
[0040] As a preference, the calcination temperature is 600 °C and the heat preservation time is 5 hours.
[0041] The second aspect of the present invention provides an application of a Co3O4-H-X type catalyst. The Co3O4-H-X type catalyst is used as a catalyst in the catalytic combustion of low-concentration methane, where the volume concentration of methane is 1%. The Co3O4-H type catalyst reaches a 50% conversion rate at 323 °C, a 90% conversion rate at 435 °C, and exhibits excellent stability and anti-sintering properties under high-temperature conditions.
[0042] Comparative Example 1:
[0043] A preparation method of a Co3O4-SA type catalyst for the catalytic combustion of low-concentration methane includes the following steps:
[0044] Add equimolar amounts of La(NO3)3·6H2O and Co(NO3)2·6H2O to distilled water, stir to completely dissolve them, then add citric acid and ethylenediaminetetraacetic acid to the mixed solution, and evaporate the solution at 80 °C under continuous stirring until a gel is formed. The obtained gel is dried in an oven at 200 °C for 5 h, and then calcined in a muffle furnace at 700 °C for 5 h to obtain LaCoO3 material.
[0045] Prepare a 3 mol·L -1 NaOH solution, add the prepared LaCoO3 to the solution, and mix well using a magnetic stirrer. Transfer the solution to a 100 mL reaction kettle lined with polytetrafluoroethylene, place the reaction kettle in a forced-air drying oven, and heat-treat it at 200 °C for 2 h. After completion, wash the sample with deionized water and absolute ethanol, dry the obtained product and transfer it to a ceramic boat, and calcine it in a muffle furnace at 600 °C for 1 h. The obtained product is named Co3O4-SA.
[0046] Test Example:
[0047] (1) Perform XRD tests on Examples 1-3 and Comparative Example 1
[0048] Figure 1 The X-ray powder diffraction patterns of the catalysts prepared for Example 1 and Comparative Example 1. From Figure 1It can be seen that the LaCoO3 prepared by the sol-gel method exhibits a good perovskite diffraction structure, corresponding to PDF#48-0123 on the standard card. After hydrothermal treatment of LaCoO3 with NaOH solution, the original perovskite structure is destroyed, and the LaCoO3 phase transforms to generate La(OH)3 and CoOOH respectively. After the generated sample is calcined again and then treated with dilute nitric acid solution, a pure Co3O4 phase is obtained, which is named Co3O4-SA and corresponds well to PDF#43-1003 on the standard card without other impurities. Similarly, Co3O4 material is synthesized by the sol-gel method, and it can be seen from the XRD pattern of the sample that it corresponds well to the standard card.
[0049] Figure 2 X-ray powder diffraction pattern of the catalyst prepared in Example 2. From Figure 2 It can be seen that after doping Co3O4 with Sr element, the diffraction peaks of the spinel structure tend to broaden and the intensity weakens, indicating that Sr element doping may inhibit the crystal growth of Co3O4. Sr 0.1 -Co3O4 shows a peak of SrCO3 at 25.2°, which may be due to the fact that after doping with Sr element, the ionic radius of Sr 3+ is larger than that of Co 2+ and Co 3+ in the original Co3O4 structure, resulting in that Sr atoms are not effectively doped into the lattice of Co3O4 but are loaded on the surface of Co3O4, and the melting point of SrCO3 is as high as 1500 °C and can stably exist under the calcination condition of 600 °C without decomposition.
[0050] Figure 3 X-ray powder diffraction pattern of the catalyst prepared in Example 3. Sr 0.1 -Co3O4 was treated with dilute nitric acid solutions of different concentrations. From Figure 3 it can be seen that only the diffraction peaks of Co3O4 are present in the Co3O4-H-1 and Co3O4-H-2 samples, and the peak of SrCO3 disappears, indicating that the nitric acid treatment has an impact on the material surface.
[0051] (2) SEM tests were carried out on Co3O4, Sr x -Co3O4 and Co3O4-H-X in Examples 1-3 and Co3O4-SA in Comparative Example 1.
[0052] As Figure 4It can be seen that LaCoO3 exhibits a relatively dense surface with a small number of pores, while Co3O4-SA obtained by etching LaCoO3 shows a broken layered structure with serrated edges, indicating that the original perovskite structure has been destroyed and the morphology of the sample has changed significantly. Co3O4 prepared by sol-gel shows a spongy morphology with loose and porous texture. After adding Sr element to the system, it can be seen that Sr element is evenly distributed on the surface of the sample, and the morphology of Sr x -Co3O4 has changed, with more gully-like gaps, a slightly rough surface, and more small particles loaded on the surface. After further acid treatment, the surface gaps of the sample are more abundant and more small pore channels appear.
[0053] (3) Perform XPS tests on Examples 1-3 and Comparative Example 1
[0054] Figure 5 Among them are the X-ray photoelectron spectroscopy spectra of the Co 2P orbitals of Co3O4, Sr x -Co3O4, Co3O4-H-1 and Co3O4-SA type catalysts. It can be seen from Figure 5 that the phase has a higher Co 2+ / Co 3+ ratio, and the richer Co 2+ species means the generation of more lattice defects, which is beneficial to enhancing the redox ability of the catalyst and improving the catalytic activity.
[0055] (3) Test the methane catalytic combustion conversion rates of the catalysts prepared in Examples 1-3 and Comparative Example 1 at different temperatures.
[0056] The test process is as follows: The catalytic activity of methane is carried out in a quartz reactor with a diameter of 8 mm. Specifically, the catalyst and quartz sand are granulated (40-60 mesh) respectively. After mixing 0.2 g of the catalyst and 0.4 g of quartz sand, they are placed in the middle of the reactor, and the samples are fixed with quartz wool at both ends. Subsequently, 1 Vol.% CH4 and 99 Vol.% air are passed through a mass flow meter and mixed evenly, and the total gas flow rate is controlled at 100 ml·min -1 , corresponding to a reaction space velocity of 30000 ml·g -1 h -1 . After passing the mixed gas from the upper end of the reactor, before the catalytic reaction, the catalyst is activated with the reaction gas at 200 °C for 30 minutes. Then, the temperature is programmed from 200 °C to 700 °C at a heating rate of 10 °C / min, and the tail gas signal under different temperature conditions is detected by a gas detector at the lower end of the reactor. Collect the activity data and measure one temperature point every 50 °C.
[0057] The test results are shown in Figure 6 , fromFigure 6 It can be seen that the Co3O4-H-1 type catalysts prepared in Examples 1-3 all have relatively high conversion rates, reaching a 50% conversion rate at 323 °C and a 90% conversion rate at 435 °C. Compared with Comparative Example 1, the Examples achieved a substantial increase in the conversion rate at a lower temperature. In Comparative Example 1, the conversion rate reached 10% at 355 °C and 50% at 452 °C, and the conversion rate was obviously lower than that of the Examples under the same conditions.
[0058] (4) Stability test of the Co3O4-H-1 type catalyst prepared in Example 3
[0059] The test process is as follows: When conducting the catalyst stability test, after starting to heat up, the reaction temperature is controlled at 500 °C, and the reaction space velocity is stabilized at 30000 ml·g -1 h -1 , and a mixed gas is introduced to test the change in the catalytic activity of the sample within 100 h.
[0060] The test results are shown in Figure 7 , and it can be seen from Figure 7 that the conversion rate of the Co3O4-H-1 type catalyst prepared in Example 3 at 500 °C did not decrease significantly with the increase of time. Among them, the conversion rate was 96% when the catalyst was used for 20 h and 94% when used for 100 h, and the conversion rate did not decrease significantly, indicating that the catalyst prepared by the present invention exhibits excellent stability under high-temperature conditions.
[0061] Therefore, the present invention adopts a Co3O4-H-1 type catalyst for low-concentration methane catalytic combustion and its preparation method with the above structure. By etching and removing the A-site cations in the perovskite structure, the Co3O4-H-1 catalyst is obtained, which has a higher Co 2+ / Co 3+ ratio, more active oxygen vacancies and more excellent redox performance, reaching a 90% conversion rate at 435 °C, and the catalyst also exhibits very excellent high-temperature stability. It is an excellent low-concentration methane catalytic combustion material with broad application prospects.
[0062] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A preparation method of Co3O4-H-X type catalyst for low-concentration methane catalytic combustion, characterized in that, First, the AB2O4-type spinel Co3O4 was synthesized by the sol-gel method. SrCO3 was added to the system for preparing Co3O4 to form Sr x -Co3O4. Then, Sr x -Co3O4 was pickled to etch away the Sr atoms on the surface, and the Co3O4-H-X catalyst was obtained.
2. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 1, characterized in that, The preparation process of Co3O4 is as follows: Disperse EDTA in water, add NH3·H2O to dissolve it, and then add CA to make it evenly mixed; Disperse Co(NO3)2·6H2O in an aqueous solution to obtain a salt solution, and then slowly add the salt solution drop by drop to the mixed solution of EDTA and CA. Adjust the pH value with ammonia water. After heating and stirring to form a gel-like substance, dry it to obtain a Co3O4 precursor. Place the Co3O4 precursor in a muffle furnace for roasting, and grind it after taking it out to obtain Co3O4.
3. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 1, characterized in that, Sr x The subscript x in Sr-Co3O4 is determined according to the molar ratio of Sr:Co; the molar ratio is 0.05 - 0.
15.
4. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 1, characterized in that, For Sr x The acid solution used for pickling Sr-Co3O4 is dilute nitric acid, the concentration of the acid solution is 0.5 - 1.5 mol·L-1, and the pickling time is 1 - 7 hours.
5. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 2, characterized in that, Adjust the pH value to the range of 7±0.5 with ammonia water.
6. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 2, characterized in that, The stoichiometric ratio of CA, EDTA and metal ions is 2:1:
1.
7. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 2, characterized in that, Use a forced-air drying oven to dry the gel-like mixed solution. The drying temperature is 200°C and the drying time is 5 hours.
8. The preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion according to claim 2, characterized in that, The roasting temperature is 600°C and the heat preservation time is 5 hours.
9. A Co3O4-H-X type catalyst for low-concentration methane catalytic combustion, characterized in that, This catalyst is prepared by the preparation method of the Co3O4-H-X type catalyst for low-concentration methane catalytic combustion described in any one of claims 1 to 8.
10. Use of the Co3O4-H-X type catalyst according to claim 9, characterized in that, Use the Co3O4-H-X type catalyst in the catalytic combustion process of methane with a concentration lower than 1%.