Method for preparing acetone through photo-thermal catalysis of methane conversion
By designing coupling reaction sites and photothermal coupling reactions on the catalyst, and utilizing nano-semiconductors and supported metals, we achieved efficient activation of methane and selective generation of acetone at low temperatures. This solved the problem of converting methane into high-value products under mild conditions and improved the light energy utilization efficiency of the catalyst and the selectivity of liquid products.
Patent Information
- Application Number
- CN202511555214.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-29
- Publication Date
- 2026-01-16
AI Technical Summary
Existing technologies struggle to efficiently activate methane under mild conditions, converting it into high-value C2+ oxygen-containing compounds such as acetic acid, ethanol, and acetone, and also suffer from the problem of over-oxidation.
By designing coupling reaction sites on the catalyst and utilizing light and heat to drive the reaction, and by using nano-semiconductor carriers and loaded metals to promote the separation of photogenerated electrons and holes, and by using water as an oxidant to avoid over-oxidation, high-value liquid oxygen-containing products such as acetone are generated.
The catalyst efficiently activates methane at low temperatures, selectively generating acetone while avoiding the formation of excessive oxidation products such as CO2, thus improving the light energy utilization efficiency of the catalyst and the selectivity of liquid products.
Smart Images
Figure CN121342637A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methane conversion, and more particularly to a method for photothermal catalytic conversion of methane to acetone. Background Technology
[0002] Methane (CH4), widely stored in natural gas, shale gas, coalbed methane, combustible ice, and biogas, is an abundant and inexpensive fossil fuel. However, the methane molecule has a symmetrical structure and high CH bond energy, resulting in high stability. Therefore, efficient utilization of abundant methane resources is a crucial research direction. Currently, industrially, methane is mainly converted into syngas through steam reforming, and then into other chemicals. This reaction is carried out at high temperatures (700~1100℃), consuming a large amount of energy, requiring sophisticated equipment, and generating significant amounts of CO2, leading to substantial production costs and environmental pressures. Achieving direct conversion of methane into high-value chemicals under milder conditions is more energy-efficient and environmentally friendly, but it also presents greater challenges. Due to the high stability of the methane molecule, it is difficult to activate under mild conditions, resulting in low conversion rates. Therefore, designing and synthesizing catalysts for the efficient conversion of methane into high-value products at low temperatures is of paramount importance for the rational utilization of fossil fuels and for energy conservation and emission reduction.
[0003] In recent years, photocatalysis technology has gained attention in the field of low-temperature selective oxidation of methane. Currently, the main products of photocatalytic methane conversion are low-carbon oxygen-containing compounds (methanol, formaldehyde, etc.) and low-carbon alkanes (ethane, propane), producing C64O3. 2+ Reports on higher-value chemicals such as liquid oxygen-containing compounds, acetic acid, ethanol, and acetone are limited, mainly because carbon-carbon coupling reactions are difficult to occur and the products are unstable and easily over-oxidized. Therefore, the design and controllable synthesis of supported semiconductor photocatalysts with carbon-carbon coupling active sites to achieve low-temperature selective oxidation of methane to prepare high-value-added C... 2+ Oxygen-containing compounds are of great significance. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned problems in the prior art and provide a photothermal catalytic method for the conversion of methane into acetone, aiming to achieve efficient activation of methane under mild conditions. By designing coupling reaction sites on the catalyst, active intermediates generated during the reaction are precisely captured and coupled through a designated reaction pathway to generate acetone. The reaction is driven by both light and heat, achieving efficient activation of methane under mild conditions, thereby generating high-value liquid oxygen-containing products such as acetone with high activity and selectivity. Water is used as the oxidant to avoid over-oxidation. The catalyst prepared in this invention uses nano-semiconductors as a support. By rationally designing the energy band positions of the semiconductor, photogenerated holes possess sufficient oxidizing power to activate methane. By loading metal, the absorption of the catalyst under ultraviolet-visible light is enhanced, promoting the separation of photogenerated electrons and holes on the semiconductor and improving the catalyst's efficiency in utilizing light energy. The catalyst preparation method of this invention provides guiding principles for designing catalysts for the direct conversion of methane under mild conditions. Simultaneously, it provides the possibility of a process route for the one-step conversion of methane into high-value products at low temperatures, which has practical guiding significance.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for photothermal catalytic conversion of methane to acetone includes the following steps: adding a catalyst, water, and a reaction gas containing methane gas to a reactor, wherein the catalyst is composed of an active metal component supported on a nano-semiconductor carrier; and carrying out the reaction under coupled conditions of light irradiation and heating at 25~150℃ to generate a liquid product containing acetone.
[0007] In this invention, the reaction pressure is 0.1~5MPa, the reaction time is 1~10h, and the illumination uses a xenon lamp as the light source with an illumination intensity of 100~650mW / cm².
[0008] In the reactor, the mass-to-volume ratio of catalyst to water is 1g:100~5000mL.
[0009] The reactant gas is a mixture of CH4 and Ar, with a volume ratio of CH4 to Ar of 1:0.05~20.
[0010] The nano-semiconductor carrier is selected from one or more of In2O3, GaN, Cu2O, CdS, CeO2, MoS2, WO3, TiO2, g-C3N4, and ZnO; the active metal component is one or more combinations of Zr, Cr, Cu, Pd, Au, Rh, Co, Pt, Ru, Fe, Re, and In.
[0011] The catalyst has an active metal component loading of 0.5% to 2%.
[0012] The catalyst is prepared by a method comprising the following steps:
[0013] 1) The nano-semiconductor carrier was ultrasonically dispersed in water, and an active metal precursor and methanol were added to the resulting dispersion to obtain a mixture;
[0014] 2) Under stirring conditions, the mixture obtained in step 1) was subjected to light treatment. After the reaction was completed, solid-liquid separation, washing and drying were performed to obtain an intermediate.
[0015] 3) The intermediate obtained in step 2) is heat-treated under a reducing atmosphere to obtain the catalyst.
[0016] In step 1), the mass-to-volume ratio of the nano-semiconductor carrier to water and methanol is 1g:30~1000mL:5~200mL.
[0017] In step 2), a xenon lamp is used for illumination, with an illumination intensity of 600~1000mW / cm², an illumination time of 0.5~3h, and a stirring speed of 300~600rpm.
[0018] In step 3), the heat treatment is carried out in a mixed atmosphere of H2 / Ar with a volume fraction of 5% at a temperature of 200~500℃ for 1~5h.
[0019] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:
[0020] 1. The catalyst prepared in this invention can efficiently and selectively oxidize methane and water to acetone directly under ultraviolet-visible light. Compared with existing reaction systems, the photothermal catalytic conversion of methane to acetone is achieved using water as a mild oxidant, with the remaining liquid products being acetic acid and methanol. Using water as the oxidant avoids the generation of over-oxidation products such as CO2 and HCOOH, significantly improving the selectivity of the liquid oxygen-containing products.
[0021] 2. The catalyst preparation method of this invention is simple, using photodeposition to prepare a supported catalyst. The supported catalyst prepared by this invention, by loading metal, enhances the catalyst's absorption under ultraviolet-visible light, promotes the separation of photogenerated electrons and holes on the semiconductor, and improves the catalyst's efficiency in utilizing light energy. Attached Figure Description
[0022] Figure 1 The images show the XRD characterization patterns of the catalysts prepared in Examples 1-3.
[0023] Figure 2 The UV-Vis-NIRDRS characterization diagrams are of the catalysts prepared in Examples 1-3.
[0024] Figure 3This is a schematic diagram of the reaction mechanism of the present invention. Detailed Implementation
[0025] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0026] Example 1
[0027] In this embodiment, a TiO2-P25 catalyst co-supported with metal Rh and metal Pd is used.
[0028] 0.15 g of TiO2-P25 was added to 80 mL of water and ultrasonically dispersed. Then, a certain amount of 10.36 mg / mL PdCl2 hydrochloric acid (20%) solution and 9.84 mg / mL RhCl3•3H2O aqueous solution were added, ensuring that the mass fraction of Rh and Pd relative to TiO2 was 1%. The mixture was magnetically stirred at 500 rpm for 1.5 h. Afterward, 15 mL of methanol was added, and the reaction was irradiated under a 300 W xenon lamp for 1 h at a light intensity of 835 mW / cm². 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven, dried at 80℃ for 20h, and reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst, denoted as RhPd / TiO2.
[0029] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0030] Example 2
[0031] In this embodiment, a TiO2-P25 catalyst supported on metal Pd is used.
[0032] 0.15 g of TiO2-P25 was added to 80 mL of water and ultrasonically dispersed to ensure complete and uniform dispersion of TiO2-P25 in the aqueous solution. A certain amount of 10.36 mg / mL PdCl2 hydrochloric acid (20%) solution was added to achieve a Pd mass fraction of 2% relative to TiO2. The mixture was magnetically stirred at 500 rpm for 1.5 h. Then, 15 mL of methanol was added, and the reaction was irradiated under a 300 W xenon lamp for 1 h at a light intensity of 835 mW / cm². 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven, dried at 80℃ for 20h, and reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst, denoted as Pd / TiO2.
[0033] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0034] Example 3
[0035] In this embodiment, a TiO2-P25 catalyst supported on metal Rh is used.
[0036] 0.15 g TiO2-P25 was added to 80 mL of water and ultrasonically dispersed to ensure complete and uniform dispersion of TiO2-P25 in the aqueous solution. A certain amount of 9.84 mg / mL RhCl3•3H2O aqueous solution was added to achieve a Rh mass fraction of 2% relative to TiO2. The mixture was magnetically stirred at 500 rpm for 1.5 h. Then, 15 mL of methanol was added, and the reaction was irradiated under a 300 W xenon lamp for 1 h at a light intensity of 835 mW / cm². 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven, dried at 80℃ for 20h, and reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst, denoted as Rh / TiO2.
[0037] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0038] Comparative Example 1
[0039] In this comparative example, a TiO2-P25 catalyst co-supported with metal Pd and metal Rh was used.
[0040] The comparative catalyst was prepared using the catalyst preparation method described in Example 1.
[0041] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%), 1 bar of oxygen (high-purity gas, volume fraction >99.999%), and 4 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0042] Comparative Example 2
[0043] In this comparative example, a TiO2-P25 catalyst co-supported with metal Pd and metal Rh was used.
[0044] The comparative catalyst was prepared using the catalyst preparation method described in Example 1.
[0045] 25 mg of the catalyst prepared above was placed in a reactor with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reactor was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the reactor. The reaction system was maintained at 25°C, and the reactor was irradiated from the top with a 300 W xenon lamp at a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0046] Comparative Example 3
[0047] In this comparative example, a CeO2 catalyst co-supported with metal Pd and metal Rh was used.
[0048] 0.15 g of CeO2 was added to 80 mL of water and ultrasonically dispersed. Then, a certain amount of 10.36 mg / mL PdCl2 hydrochloric acid (20%) solution and 9.84 mg / mL RhCl3•3H2O aqueous solution were added, ensuring that the mass fraction of Rh and Pd relative to CeO2 was 1%. The mixture was magnetically stirred at 500 rpm for 1.5 h. Afterward, 15 mL of methanol was added, and the mixture was irradiated under a 300 W xenon lamp for 1 h at a light intensity of 835 mW / cm². 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven and dried at 80℃ for 20h. Then, it was reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst.
[0049] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0050] Comparative Example 4
[0051] In this comparative example, a SiO2 catalyst co-supported with metal Pd and metal Rh was used.
[0052] 0.15 g SiO2 was added to 80 mL of water and ultrasonically dispersed. Then, a certain amount of 10.36 mg / mL PdCl2 hydrochloric acid (20%) solution and 9.84 mg / mL RhCl3•3H2O aqueous solution were added, ensuring that the mass fraction of Rh and Pd relative to SiO2 was 1%. The mixture was magnetically stirred at 500 rpm for 1.5 h. Afterward, 15 mL of methanol was added, and the mixture was irradiated under a 300 W xenon lamp for 1 h at a light intensity of 835 mW / cm². 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven and dried at 80℃ for 20h. Then, it was reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst.
[0053] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0054] Comparative Example 5
[0055] In this comparative example, a TiO2-P25 catalyst supported on metal Os was used.
[0056] 0.15 g TiO2-P25 was added to 80 mL of water and ultrasonically dispersed. Then, 9.35 mg / mL of OsCl3•3H2O aqueous solution was added to achieve a 2% mass fraction of Os relative to TiO2. The mixture was magnetically stirred at 500 rpm for 1.5 h. Afterward, 15 mL of methanol was added, and the reaction was irradiated under a 300 W xenon lamp at an intensity of 835 mW / cm² for 1 h. 2 After the reaction was completed, the precipitate was collected by centrifugation, washed 4-7 times with deionized water, placed in a vacuum drying oven and dried at 80℃ for 20h. Then, it was reduced with H2 (15mL / min) at 300℃ (heating rate of 5℃ / min) for 3h to obtain the supported photocatalyst.
[0057] 25 mg of the catalyst prepared above was placed in a reaction vessel with a quartz glass window on the top. 40 mL of H₂O was added, and the mixture was stirred to disperse the catalyst. The reaction vessel was then sealed, and 25 bar of methane (high-purity gas, volume fraction >99.999%) and 5 bar of argon (high-purity gas, volume fraction >99.999%) were introduced into the vessel. The reaction system was heated to 60 °C, and a 300 W xenon lamp was used to irradiate the reaction vessel from the top, with a light intensity of 200 mW / cm². 2 The reaction time was 5 hours. After the reaction was completed, the liquid products were detected using 500 MHz liquid NMR.
[0058] Table 1
[0059]
[0060] Under the above reaction conditions, the photothermal methane conversion test results of the examples and comparative examples are shown in Table 1. The results in Table 1 indicate that using a suitable semiconductor catalyst is key to generating photocatalytic methane conversion activity. Using a suitable supported metal helps to improve methane conversion activity and acetone selectivity. Among them, the Rh and Pd co-supported TiO2-P25 photocatalyst synthesized in Example 1 exhibited the highest methane conversion activity and acetone selectivity under the stated reaction conditions, producing 279 μmol of acetone per gram of catalyst after 5 hours of reaction, with an acetone selectivity of 74.5%.
[0061] Figure 1 The XRD patterns of the catalysts synthesized in Examples 1-3 are shown. In the figures, the XRD diffraction peak positions of the three catalysts are consistent with those of TiO2-P25. No diffraction peaks of noble metals and their oxides were observed, indicating that the noble metals are highly dispersed on the support and have not agglomerated, effectively improving the utilization efficiency of the noble metals. Besides the catalyst structure, the introduction of noble metals also alters the light absorption activity of the catalysts. The UV-Vis diffuse reflectance spectra of the catalysts synthesized in Examples 1-3 and TiO2-P25 are also shown. Figure 2 As can be seen, the catalyst loaded with noble metals exhibits significantly enhanced light absorption activity in the visible light region. The TiO2-P25 photocatalyst co-supported with Rh and Pd synthesized in Example 1 has the highest visible light absorption activity, and the absorption edge position shows a significant red shift, indicating that its band gap is narrowed and it can be excited by light with longer wavelengths and weaker energy.
[0062] like Figure 3 As shown, this invention innovatively uses water as an oxidant, avoiding further interaction between the oxidant and the products, significantly improving the over-oxidation phenomenon present in existing studies. No over-oxidation products (CO2, HCOOH, etc.) were detected, improving the selectivity of oxygen-containing liquid products. Simultaneously, the combination of photocatalysis and thermocatalysis solves the problem of low methane conversion activity under pure photocatalytic conditions, promoting carbon-carbon coupling reactions and improving the selectivity of multi-carbon liquid products. This invention converts methane into high-value-added products, significantly improving the utilization value of methane and providing valuable reference for the efficient utilization of methane resources.
Claims
1. A method for the photo-thermal catalytic conversion of methane to acetone, characterized in that, The method comprises the following steps: adding a catalyst, water and a reaction gas containing methane into a reactor, wherein the catalyst is composed of an active metal component supported on a nano semiconductor carrier; and performing a reaction under the coupling of light and heating at 25-150 DEG C to generate a liquid product containing acetone.
2. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein: The nano semiconductor carrier is selected from one or more of In2O3, GaN, Cu2O, CdS, CeO2, MoS2, WO3, TiO2, g-C3N4 and ZnO; and the active metal component is one or more of Zr, Cr, Cu, Pd, Au, Rh, Co, Pt, Ru, Fe, Re and In.
3. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein: The loading amount of the active metal component in the catalyst is 0.5-2%.
4. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein: The reaction pressure is 0.1-5 MPa, the reaction time is 1-10 h, the light source is a xenon lamp, and the light intensity is 100-650 mW / cm2.
5. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein: In the reactor, the mass / volume ratio of the catalyst to water is 1 g:100-5000 mL.
6. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein: The reaction gas is a mixture of CH4 and Ar, and the volume ratio of CH4 to Ar is 1:0.05-20.
7. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 1, wherein, The catalyst is prepared by a method comprising the following steps: 1) dispersing the nano semiconductor carrier in water, adding an active metal precursor and methanol to the obtained dispersion to obtain a mixture; 2) performing light treatment on the mixture obtained in step 1) under stirring, performing solid-liquid separation, washing and drying after the reaction is completed to obtain an intermediate; 3) performing heat treatment on the intermediate obtained in step 2) in a reducing atmosphere to obtain the catalyst.
8. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 7, wherein: In step 1), the mass / volume ratio of the nano semiconductor carrier to water and methanol is 1 g:30-1000 mL:5-200 mL.
9. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 7, wherein: In step 2), the light treatment is performed by using a xenon lamp, the light intensity is 600-1000 mW / cm2, the light treatment time is 0.5-3 h, and the stirring speed is 300-600 rpm.
10. A method of photo-thermal catalytic conversion of methane to acetone as claimed in claim 7 wherein: In step 3), the heat treatment is performed in a 5% H2 / Ar mixed gas atmosphere, the heat treatment temperature is 200-500 DEG C, and the time is 1-5 h.