A photocatalyst for methane conversion induced by defect-state layered ferrous titanate, its preparation method and its application

Abstract

This invention relates to a photocatalyst, preparation method, and application of defect-state layered ferrous titanate-induced methane conversion, belonging to the field of methane catalytic conversion technology. First, ferrous titanate nanoparticles are prepared using a sol-gel technique. Then, layered ferrous titanate nanosheet catalysts are synthesized using an alkaline etching hydrothermal method. The layered ferrous titanate nanosheet catalysts are uniformly dispersed in a solvent and then spin-coated onto a glass fiber membrane. Activation is performed at <1 Pa and 473–573 K to obtain a catalyst with a uniform and smooth surface. The catalyst is then placed in a quartz reactor to remove impurities adsorbed on the catalyst surface. After cooling to room temperature, the catalyst can be used for photocatalytic oxygen-free dehydrogenation coupling reaction of methane at lower temperatures (273–353 K) and lower pressures (10–1000 mbar). The design, construction, and modification of the nanocatalyst in this invention enable efficient methane activation under mild conditions, while reducing energy consumption and environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of methane catalytic conversion technology, specifically relating to a photocatalyst for methane conversion induced by defect-state layered ferrous titanate, its preparation method, and its application in the photocatalytic dehydrogenation of methane molecules to produce ethane and hydrogen. Background Technology

[0002] Since the mid-20th century, with advancements in oil exploration and extraction techniques, the chemical industry, using petroleum as a raw material, has flourished at an unprecedented pace. Petroleum is a non-renewable resource with finite reserves, and with its increasing scarcity, the search for and development of alternative energy sources has become urgent. Among numerous alternatives, natural gas holds great promise due to its many unique properties. Natural gas reserves are vast, and it is a major component of resources such as coalbed methane, biogas, shale gas, and methane hydrate, playing an irreplaceable energy role in human society. In 2021, natural gas accounted for 24.4% of global energy production. Over the past 20 years, global natural gas production has increased from 2,523.9 billion cubic meters to 4,036.9 billion cubic meters, a growth of approximately 60%. Compared to oil and coal, natural gas releases significantly less sulfur oxides and nitrogen oxides during combustion, while also having a higher calorific value, thus being considered the cleanest fossil fuel.

[0003] Globally, the development of chemical synthesis using natural gas as a feedstock has become a prominent research hotspot. It is foreseeable that in the near future, the chemical industry will enter an era of rapid development centered on natural gas. With the continuous increase in proven natural gas reserves, methane, as the main component of natural gas (wt>80%), has the highest H / C ratio among hydrocarbons and is an important raw material for the production of hydrogen and multi-carbon products, not just as a fuel, which has attracted widespread attention. This shift provides an opportunity to reduce the current heavy dependence of the chemical industry on increasingly depleted crude oil.

[0004] Catalytic methane conversion is an important method for transforming methane into valuable chemicals. However, the methane molecule is composed of four identical CH bonds linked by sp... 3 The hybridization results in a structure with tetrahedral symmetry, where the bond energy of the CH bonds reaches as high as 435 kJ·mol⁻¹. -1 Furthermore, the molecule contains neither π bonds nor non-bonded electron pairs, lacking functional groups conducive to bond breaking, making nucleophilic or electrophilic reactions difficult. Methane has a low polarizability (2.84 × 10⁻⁶). -40 C 2 m 2 J -1The harsh conditions that cause methane to be difficult to polarize under normal local electric fields mean that methane conversion often requires stringent reaction conditions to activate methane, leading to energy consumption, catalyst deactivation, and side reactions. For example, Ni-Mo nanocatalysts on single-crystal MgO are used for thermocatalytic dry reforming of methane, but uncontrollable agglomeration of Ni-Mo nanocatalysts occurs at 800℃. Furthermore, large-scale industrial applications have been achieved through steam methane reforming, with the resulting syngas subsequently used extensively for the synthesis of methanol, light olefins, and liquid hydrocarbons. However, this conversion route relies on high temperatures and pressures, increasing process complexity and energy consumption. Direct methane conversion under mild conditions has become an ideal goal for researchers.

[0005] Photocatalysis is a promising alternative that uses photons to drive chemical reactions, primarily at room temperature. Compared to thermocatalysis, photocatalysis generates high-energy charge carriers in methane conversion, pre-activating methane and lowering the activation energy. This pre-activation process even allows thermodynamically unfavorable reactions to occur at room temperature, overcoming the limitations of traditional thermocatalysis. The mechanism of photocatalytic methane conversion is as follows: the excited state (photogenerated electron-hole separation) entered by the photocatalyst material after absorbing photons interacts with the charge transfer between adsorbed methane molecules, causing the methane molecule to lose or gain an electron, thus entering a higher-energy excited state and inducing further reactions. Compared to traditional thermocatalysis, photocatalysis starts from the high-energy methane excited state, enabling many conversion processes that cannot occur spontaneously under traditional ground-state conditions (such as the oxygen-free dehydrogenation coupling reaction of methane) or lowering the temperature required for catalytic reactions (such as the oxygen-free aromatization reaction of methane). Wang et al. published a paper entitled "Photo-induced non-oxidative coupling of methane in stable solid solutions" in Angew. Chem. Int. Ed. (2021, Vol. 38, pp. 20760-20764); and a paper entitled "Preparation of stepped CeO2 nanoislands for efficient photocatalytic methane coupling" in ACS Catal. (2023, Vol. 17, pp. 11666-11674). In their research, they found that coordination unsaturation, variable valence state of the central metal, semiconductor polarity, acid-base surface, and structural defects are important influencing factors of methane photocatalytic conversion. Based on these findings, catalysts can be scientifically and rationally designed to achieve efficient photocatalytic dehydrogenation coupling of methane. Summary of the Invention

[0006] The purpose of this invention is to provide a photocatalyst for methane conversion induced by defect-state layered ferrous titanate, its preparation method, and its application in the photo-driven dehydrogenation coupling reaction of methane molecules at room temperature.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The preparation method of the defect-state layered ferrous titanate photocatalyst of the present invention comprises the following steps:

[0009] (1) Ferrous titanate nanoparticles (FeTiO) 3-x Preparation of FeTiO3 nanoparticles (FeTiO3-NP): The raw materials are titanium and iron precursors. FeTiO3 nanoparticles are prepared using sol-gel technology. First, a certain amount of titanium precursor is added to 10 mL of solvent and magnetically stirred for 10–15 min to form solution A. A certain amount of iron precursor is weighed and dissolved in 10 mL of solvent and stirred for 10–15 min to form solution B. Solution B is slowly added to solution A to maintain a 1:1 molar ratio of Fe ions to Ti ions, followed by vigorous stirring for 50–70 min to ensure homogeneity. A precipitant is then slowly added dropwise to the mixed solution until a gel is formed. The gel is allowed to stand overnight for aging, and then dried in an oven at 333–373 K to obtain an orange-red iron-titanium bimetallic oxide precursor. Finally, the precursor is dried in a reducing atmosphere (5% vol H2, 95% vol H2). Ferrous titanate nanoparticles were obtained by heating the solution in Ar at a rate of 1.5–3.0 K / min to 773–1173 K and holding it for 1.5–3.0 h. The nanoparticles were then washed with deionized water and dried in an oven at 333–373 K.

[0010] The precursor of titanium is one of tetrabutyl titanate, titanium tetrafluoride, titanium trichloride, titanium acetylacetonate, and titanium tetraisopropoxide; the precursor of iron is one of ferric nitrate, ferric chloride, and ferric sulfate; the precipitant is ammonia; and the solvent is one of anhydrous methanol, anhydrous ethanol, anhydrous ethylene glycol, and ethylene glycol monomethyl ether.

[0011] (2) Layered ferrous titanate nanosheets (Fe l-x TiO 3-x Preparation of ferrous titanate (Fe2N) catalyst: Layered ferrous titanate nanosheets were synthesized by alkaline etching hydrothermal method; 50-200 mg of ferrous titanate nanoparticles obtained in step (1) were dispersed in 30-50 mL of 10-20 M alkaline solution to form a suspension, and ultrasonically stirred for 0.5-2.0 h; then the suspension was transferred to a 50-100 mL Teflon-lined reactor and hydrothermally reacted at 393-493 K for 2-36 h; after cooling to room temperature, the product was centrifuged and washed repeatedly with distilled water until the pH of the filtrate was 7; finally, it was dried in a vacuum drying oven to obtain layered ferrous titanate nanosheets (Fe2N). l- x TiO 3-x -NS) catalyst, namely the defect-state layered ferrous titanate-induced methane conversion photocatalyst;

[0012] The alkaline solution is either sodium hydroxide or potassium hydroxide.

[0013] (3) Photocatalytic methane conversion: Layered ferrous titanate nanosheets (Fe) are reacted with solvents (anhydrous ethanol, acetone, deionized water, etc.) to form methane. l-x TiO 3-x The -NS) catalyst was uniformly dispersed at a concentration of 1–5 mg / mL and then spin-coated onto a glass fiber membrane. The solvent was evaporated at 333–363 K for 10–30 min, resulting in a catalyst with a uniform and smooth surface. The obtained catalyst was placed in a quartz reactor and activated under vacuum (<1 Pa) at 473–573 K for 1.5–3.0 h to remove impurities adsorbed on the catalyst surface. After cooling to room temperature, the catalyst was used for the photocatalytic oxygen-free dehydrogenation coupling reaction of methane at lower temperatures (273–353 K) and lower pressures (10–1000 mbar) (methane was the only reactant). The process involves highly selective dehydrogenation coupling of defect-state layered ferrous titanate to produce ethane and propane under catalysis. The main reaction is 2CH4 → C2H6 + H2; the side reaction is 3CH4 → C3H8 + 2H2. The catalyst is not consumed during the catalytic reaction and can be recycled multiple times. The photocatalytic light source wavelength range is 200–780 nm, and the photocatalytic time is 5–600 min. During the photocatalytic reaction, the temperature is controlled by a constant-temperature reaction bath. After the reaction, 1 mL of the post-reaction gas is extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction is determined by gas chromatography (GC). The results are then analyzed using a standard curve. Figure 6 (a) Calculate the hydrogen production rate; extract 1 mL of the gas after reaction using a gas-tight needle, and determine the peak areas of various hydrocarbons in the quartz reactor after reaction using GC, and analyze the results using a standard curve ( Figure 6 (cd) Calculate the formation rates of ethane and the byproduct propane. The calculation formula is as follows:

[0014]

[0015] *Generation rate unit: μmol·g -1 ·h -1 Molar quantity is in μmol, catalyst mass is in g, and reaction time is in h.

[0016] This invention relates to the construction of a defect-state catalyst based on layered ferrous titanate for the oxygen-free dehydrogenation coupling reaction of methane. Photo-driven activation of methane is a green, environmentally friendly, inexpensive, and convenient method. The design and construction of nanocatalysts, along with catalyst modification, enable efficient methane activation under mild conditions, while reducing energy consumption and environmental pollution. Attached Figure Description

[0017] Figure 1 : The synthesized ferrous titanate nanoparticles (FeTiO₂) 3-x -NP) and ferrous titanate nanosheets (Fe l-x TiO 3-xThe XRD pattern of ferrous titanate (NS) and the comparison with the standard PDF card of ferrous titanate indicate that the synthesized product is pure ferrous titanate. (Corresponding to Example 4)

[0018] Figure 2 (a) Ferrous titanate nanoparticles (FeTiO2) synthesized in this invention 3-x Transmission electron microscopy (TEM) images of ferrous titanate (-NP) and high-resolution transmission electron microscopy (HR-TEM) images, scale bar 2 nm, show that ferrous titanate mainly exposes two crystal planes, with a {012} lattice spacing of [missing information]. The lattice spacing of {104} is (b) Ferrous titanate nanoparticles (FeTiO) 3-x The X-ray energy dispersive spectroscopy (EDX) pattern of ferrous titanate nanoparticles (NP) shows that Fe, Ti, and O elements are uniformly distributed in the sample. (c) Particle size distribution of ferrous titanate nanoparticles: the sample particle size is mainly between 20 and 60 nm, with a large proportion at 40 nm. (Corresponding to Example 4)

[0019] Figure 3 (a) Ferrous titanate nanosheets (Fe l-x TiO 3-x Scanning electron microscope (SEM) images (NS) and high-resolution transmission electron microscope (HRTEM) images show that the sample is mainly composed of layered sheets with interlayer spacing of [missing information]. The main exposed crystal planes are the {012} crystal planes, with a spacing of [missing information]. (b) Ferrous titanate nanosheets (Fe l-x TiO 3-x The X-ray energy dispersive spectroscopy (EDX) pattern of -NS shows that Fe, Ti, and O elements are uniformly distributed. (Corresponding to Example 4)

[0020] Figure 4 : Ferrous titanate nanosheets (Fe l-x TiO 3-x The room-temperature electron paramagnetic resonance (EPR) spectrum of the catalyst (-NS) is shown. The bottom curve represents the EPR spectrum measured under dark conditions, the middle curve represents the EPR spectrum measured after photoexcitation, and the top curve represents the EPR spectrum measured after photoexcitation of the sample followed by the reaction with methane. It can be seen that photoexcitation can generate strong Fe... 3+ The signal weakens after methane is introduced, indicating that it has participated in the methane reaction. (Corresponding to Example 4)

[0021] Figure 5 : Ferrous titanate nanosheets (Fe l-x TiO 3-xThe low-temperature electron paramagnetic resonance (EPR) spectrum of the catalyst (-NS) is shown. The bottom curve represents the spectrum measured under dark conditions, the middle curve represents the spectrum measured after photoexcitation, and the top curve represents the spectrum of the photoexcited sample reacting with methane. It can be seen that photoexcitation generates an enhanced oxygen hole signal and produces Ti. 3+ The signal weakens after methane is introduced, indicating that it has participated in the reaction with methane.

[0022] Corresponding Example 4

[0023] Figure 6 (a) is the standard curve for determining different amounts of hydrogen using GC;

[0024] The curve equation is y = 1.42x, where y represents the peak area of ​​hydrogen gas as measured by GC, and x represents the amount of hydrogen gas introduced, in μmol. This standard curve uses five different amounts of hydrogen gas, introduced into a 90mL sealed quartz reactor, with 1mL of gas extracted sequentially using a gas-tight needle and injected into the chromatograph to measure the corresponding peak area, thus obtaining a standard curve of hydrogen peak area versus hydrogen concentration.

[0025] Figure 6 (b) is a standard curve for determining different amounts of methane using GC;

[0026] The curve equation is y = 1.51x, where y represents the peak area of ​​methane as measured by GC, and x represents the amount of methane introduced, in μmol. This standard curve uses five different amounts of methane gas, introduced into a 90mL closed quartz reactor. 1mL of gas was sequentially extracted using a gas-tight needle and injected into the chromatograph to measure the corresponding peak area, thus obtaining a standard curve of methane peak area versus methane concentration. This standard curve primarily calculates the consumption of methane in the reaction and verifies the carbon balance in the reaction.

[0027] Figure 6 (c) is a standard curve for determining different amounts of ethane using GC;

[0028] The curve equation is y = 2.82x, where y represents the peak area of ​​ethane as measured by GC, and x represents the amount of ethane introduced, in μmol. This standard curve uses five different amounts of ethane gas, introduced into a 90mL sealed quartz reactor. 1mL of gas is extracted sequentially using a gas-tight needle and injected into the chromatograph to measure the corresponding peak area, thus obtaining the standard curve of ethane peak area versus ethane concentration.

[0029] Figure 6 (d) is the standard curve for determining different amounts of propane using GC.

[0030] The curve equation is y = 6.88x, where y represents the peak area of ​​propane as measured by GC, and x represents the amount of propane introduced, in μmol. This standard curve uses five different amounts of propane gas, introduced into a 90mL closed quartz reactor, with 1mL of gas extracted sequentially using a gas-tight needle and injected into the chromatograph to measure the corresponding peak area, thus obtaining a standard curve of propane peak area versus propane concentration.

[0031] Figure 7 Photocatalytic performance graphs of different catalysts: The horizontal axis represents different catalysts, and the vertical axis represents the product formation rate. Ferrous titanate nanoparticles (FeTiO₂) 3-x -NP), ferrous titanate nanosheets (Fe l-x TiO 3-x The figure includes ferrous titanate nanosheets (FeNS), commercially available ferrous titanate (c-FeTiO3, Aladdin), and commercially available ferrous titanate (c-FeTiO3, Aladdin). Each catalyst corresponds to two columns. The solid column on the left corresponds to the left ordinate, representing the formation rate of the products (ethane, propane); the lined column on the right corresponds to the right ordinate, representing the formation rate of the product hydrogen. This figure illustrates the effect of ferrous titanate nanosheets (FeNS, Aladdin). l-x TiO 3-x -NS) has the highest ethane formation rate. (See Example 4.)

[0032] Figure 8 (a) The reaction rates of methane dehydrogenation coupling catalyzed by samples treated with hydrothermal alkaline etching at different temperatures, corresponding to Examples 1-6. The horizontal axis represents the catalysts treated at different hydrothermal temperatures, and the vertical axis represents the product formation rate. Each catalyst corresponds to two columns; the left column corresponds to the formation rates of ethane and propane, and the right column corresponds to the hydrogen production rate. The figure shows that the sample treated with hydrothermal etching at 453K has the highest production rate, and the product formation rate is not significantly different from the hydrogen production rate (2CH4→C2H6+H2). (b) The reaction rates of methane dehydrogenation coupling catalyzed by samples treated with hydrothermal etching at 453K for different times, corresponding to Examples 7-11. The horizontal axis represents the catalysts treated with hydrothermal etching for different times, and the vertical axis represents the product formation rate. Each catalyst corresponds to two columns; the left column corresponds to the formation rates of ethane and propane, and the right column corresponds to the hydrogen production rate. The figure shows that the sample treated for 12 hours has the highest production rate. This figure illustrates the effect of ferrous titanate nanoparticles (FeTiO2). 3-x Ferrous titanate nanosheets (Fe) were obtained by treating Fe at 453K for 12 h. l-x TiO 3-x -NS) has the highest ethane production rate.

[0033] Figure 9 : Ferrous titanate nanosheets (Fe l-x TiO 3-xCyclic stability graph of the catalytic methane dehydrogenation coupling reaction (NS), corresponding to Example 12. The horizontal axis represents the number of cycles, the left vertical axis represents the rate of product formation, and the right vertical axis represents the selectivity of ethane in the products. Each cycle corresponds to one column and one point; the column represents the rate of product (ethane, propane) formation, and the point represents the selectivity of ethane in the products. This graph illustrates Fe l-x TiO 3-x -NS catalysts have good cycle stability and can be reused multiple times. After 23 cycles of 46 hours each, they can still maintain the catalytic effect of the first cycle. Detailed Implementation

[0034] Example 1: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in photocatalytic oxygen-free coupling reaction of methane.

[0035] (1) Ferrous titanate nanoparticles (FeTiO) 3-x Preparation of FeTiO3 nanoparticles (Fe(NO3)3·9H2O), tetrabutyl titanate, anhydrous ethanol, and ammonia were prepared using sol-gel technology. First, 5 mL of tetrabutyl titanate (TBT) was added to 10 mL of anhydrous ethanol and stirred for 10 min on a magnetic stirrer to form solution A. Then, 5.94 g of Fe(NO3)3·9H2O was dissolved in 10 mL of anhydrous ethanol and stirred for 10 min to form solution B. Solution B was slowly added to solution A, with a Fe ion to Ti ion molar ratio of 1:1, and then stirred vigorously for 1 h to ensure homogeneity. Ammonia was then slowly added dropwise to the mixture until a gel was formed. The gel was allowed to stand overnight for aging and then dried in a 353 K oven to obtain an orange-red iron-titanium bimetallic oxide precursor. Then, the temperature was increased to 773 K at a rate of 2 K / min in a reducing atmosphere (5% vol H2, 95% vol Ar) and held for 2 h to obtain ferrous titanate nanoparticles (2.43 g). Afterwards, the nanoparticles were washed with deionized water and dried in an oven at 353 K.

[0036] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 393 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0037] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 150.45 μmol·g. -1 ·h -1 The hydrogen production rate is 183.80 μmol·g. -1 ·h -1 The propane formation rate is 7.43 μmol·g -1 ·h -1 .

[0038] Example 2: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in photocatalytic oxygen-free coupling reaction of methane.

[0039] (1) Same as step (1) in Example 1;

[0040] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 413 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0041] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 235.97 μmol·g. -1 ·h -1 The hydrogen production rate is 261.51 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 11.68 μmol·g. -1 ·h -1 .

[0042] Example 3: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in the photocatalytic oxygen-free coupling reaction of methane.

[0043] (1) Same as step (1) in Example 1;

[0044] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 433 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0045] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 246.38 μmol·g. -1 ·h -1 The hydrogen production rate is 272.65 μmol·g. -1 ·h -1 The propane formation rate is 12.21 μmol·g. -1 ·h -1 .

[0046] Example 4: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in photocatalytic oxygen-free coupling reaction of methane.

[0047] (1) Same as step (1) in Example 1;

[0048] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0049] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 301.15 μmol·g⁻¹. -1 ·h -1 The hydrogen production rate is 334.48 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 13.26 μmol·g. -1 ·h -1 .

[0050] Example 5: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in the photocatalytic oxygen-free coupling reaction of methane.

[0051] (1) Same as step (1) in Example 1;

[0052] (2) 10 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 473 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0053] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 183.42 μmol·g⁻¹. -1 ·h -1 The hydrogen production rate is 194.80 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 5.31 μmol·g. -1 ·h -1 .

[0054] Example 6: Preparation method of ferrous titanate nanoparticles treated with different hydrothermal temperatures and their application in the photocatalytic oxygen-free coupling reaction of methane.

[0055] (1) Same as step (1) in Example 1;

[0056] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 493 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0057] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 153.67 μmol·g. -1 ·h -1 The hydrogen production rate is 168.23 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 6.37 μmol·g. -1 ·h -1 .

[0058] Example 7: Preparation method of ferrous titanate nanoparticles with different hydrothermal treatment times and their application in photocatalytic oxygen-free coupling reaction of methane.

[0059] (1) Same as step (1) in Example 1;

[0060] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 2 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0061] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 195.32 μmol·g⁻¹. -1 ·h -1 The hydrogen production rate is 242.84 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 7.43 μmol·g -1 ·h -1 .

[0062] Example 8: Preparation method of ferrous titanate nanoparticles with different hydrothermal treatment times and their application in photocatalytic oxygen-free coupling reaction of methane.

[0063] (1) Same as step (1) in Example 1;

[0064] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 4 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0065] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 210.68 μmol·g. -1 ·h -1 The hydrogen production rate is 266.88 μmol·g. -1 ·h -1 The propane formation rate is 7.43 μmol·g -1 ·h -1 .

[0066] Example 9: Preparation method of ferrous titanate nanoparticles with different hydrothermal treatment times and their application in photocatalytic oxygen-free coupling reaction of methane.

[0067] (1) Same as step (1) in Example 1;

[0068] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 8 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0069] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 257.28 μmol·g. -1 ·h -1 The hydrogen production rate is 301.42 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 11.15 μmol·g. -1 ·h -1 .

[0070] Example 10: Preparation method of ferrous titanate nanoparticles with different hydrothermal treatment times and their application in photocatalytic oxygen-free coupling reaction of methane.

[0071] (1) Same as step (1) in Example 1;

[0072] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 24 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0073] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 241.42 μmol·g⁻¹. -1 ·h -1 The hydrogen production rate is 266.15 μmol·g. -1 ·h -1 The propane formation rate is 10.08 μmol·g. -1 ·h -1 .

[0074] Example 11: Preparation method of ferrous titanate nanoparticles with different hydrothermal treatment times and their application in photocatalytic oxygen-free coupling reaction of methane.

[0075] (1) Same as step (1) in Example 1;

[0076] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 36 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0077] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 178.96 μmol·g. -1 ·h -1 The hydrogen production rate is 186.24 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 7.43 μmol·g -1 ·h -1 .

[0078] Example 12: Preparation method of hydrothermally treated ferrous titanate nanoparticles and their application in photocatalytic oxygen-free coupling reaction of methane.

[0079] (1) Same as step (1) in Example 1;

[0080] (2) 100 mg of ferrous titanate nanoparticles were dispersed in 30 mL of 10 M NaOH solution to form a suspension. After ultrasonic treatment and stirring for 1 hour, the suspension was transferred to a 50 mL Teflon-lined reactor and reacted at 453 K for 12 hours. After cooling to room temperature, the product was centrifuged and washed several times with distilled water until the pH of the filtrate was 7. Then, it was dried in a vacuum drying oven to obtain 100 mg of sample.

[0081] (3) Weigh 10 mg of catalyst into a 10 mL beaker, disperse it evenly with 5 mL of deionized water, and then spin-coat it onto a glass fiber membrane (Shanghai Xingya Purification Materials Factory). Dry it under an infrared lamp for 30 min to obtain a catalyst with a uniform and smooth surface. Place the catalyst into a self-made intermittent quartz reactor, place the reactor in an electric furnace, connect it to a vacuum system to evacuate to (<1 Pa), and then heat it to 573 K at 10 K / min for 2 h to remove water and other gases adsorbed on the catalyst surface. After cooling to room temperature, inject 0.05 MPa of high-purity methane gas (99.999%) into the quartz reactor, and then transfer the reactor to a reaction bath with a constant temperature of 293 K. Use a 300 W xenon lamp (wavelength range 200-780 nm, Zhongjiao Jinyuan CEL-HXUV300) to perform photocatalytic oxygen-free coupling of methane to ethane and hydrogen. The illumination time is 2 h. After the reaction is completed, use gas chromatography to quantitatively analyze the reaction products. 1 mL of the gas after the reaction was extracted using a gas-tight needle, and the peak area of ​​hydrogen in the quartz reactor after the reaction was determined by GC. The result was then analyzed using a standard curve. Figure 6 (a) The molar amount of hydrogen produced can be read directly. The hydrogen production rate is obtained by dividing the molar amount of hydrogen produced by the catalytic reaction time and the catalyst mass. 1 mL of the gas after the reaction is extracted with a gas-tight needle, and the peak areas of methane and other hydrocarbons in the quartz reactor after the reaction are determined by GC. The peak areas are then analyzed using a standard curve. Figure 6 (cd) Calculate the molar amounts of ethane and propane produced. The calculation shows that the ethane production rate can reach 301.15 μmol·g⁻¹. -1 ·h -1 The hydrogen production rate is 334.48 μmol·g⁻¹. -1 ·h -1 The propane formation rate is 13.26 μmol·g. -1 ·h -1 .

[0082] The quartz reactor containing the catalyst was then re-evacuated to remove adsorption. High-purity methane gas at 0.05 MPa was then introduced into the reactor, which was then placed in a water bath and irradiated with an Xe lamp for 2 hours. The reaction products were then analyzed by chromatography. This process was repeated 23 times, and no significant decrease in activity was observed.

[0083] The above facts demonstrate that defect-layered ferrous titanate nanosheets possess good photocatalytic activity, can efficiently catalyze the dehydrogenation coupling of methane at room temperature, and exhibit good cyclic stability and selectivity, allowing for repeated use.

Claims

1. A method for preparing a defect-state layered ferrous titanate photocatalyst, comprising the following steps: (1) Preparation of ferrous titanate nanoparticles: First, a certain amount of titanium precursor was added to the solvent and magnetically stirred for 10-15 min to form solution A; a certain amount of iron precursor was weighed and dissolved in the solvent and stirred for 10-15 min to form solution B; solution B was slowly added to solution A so that the molar ratio of Fe ions to Ti ions was 1:1, and then the mixture was stirred vigorously for 50-70 min to make it uniform; then a precipitant was slowly added dropwise to the mixed solution until a gel was formed. The gel was allowed to stand overnight for aging, and then dried in an oven at 333-373 K to obtain an orange-red iron-titanium bimetallic oxide precursor; finally, the precursor was heated to 773-1173 K in a reducing atmosphere at 1.5-3.0 K / min and held for 1.5-3.0 h to obtain ferrous titanate nanoparticles, which were then washed with deionized water and dried in an oven at 333-373 K. (2) Preparation of layered ferrous titanate nanosheet catalyst: 50-200 mg of ferrous titanate nanoparticles obtained in step (1) were dispersed in 30-50 mL of 10-20 M alkaline solution to form a suspension, and ultrasonically stirred for 0.5-2.0 h; then the suspension was transferred to a reaction vessel and hydrothermally reacted at 393-493 K for 2-36 h; after cooling to room temperature, the product was centrifuged and washed repeatedly with distilled water until the pH of the filtrate was 7; finally, it was dried in a vacuum drying oven to obtain the layered ferrous titanate nanosheet catalyst, namely the defective layered ferrous titanate photocatalyst.

2. The method for preparing a defect-state layered ferrous titanate photocatalyst as described in claim 1, characterized in that: In step (1), the precursor of titanium is one of tetrabutyl titanate, titanium tetrafluoride, titanium trichloride, titanium acetylacetonate, and titanium tetraisopropoxide; the precursor of iron is one of ferric nitrate, ferric chloride, and ferric sulfate; the precipitant is ammonia; and the solvent is one of anhydrous methanol, anhydrous ethanol, anhydrous ethylene glycol, and ethylene glycol monomethyl ether.

3. The method for preparing a defect-state layered ferrous titanate photocatalyst as described in claim 1, characterized in that: The reducing atmosphere in step (1) is a mixture of 5% vol H2 and 95% vol Ar.

4. The method for preparing a defect-state layered ferrous titanate photocatalyst as described in claim 1, characterized in that: In step (2), the alkaline solution is either sodium hydroxide or potassium hydroxide.

5. A defect-state layered ferrous titanate photocatalyst, characterized in that: It is prepared by the method described in any one of claims 1 to 4.

6. The application of the defect-state layered ferrous titanate photocatalyst of claim 5 in the photocatalytic dehydrogenation of methane molecules to produce ethane and hydrogen.

7. The application of the defect-state layered ferrous titanate photocatalyst as described in claim 6 in the photocatalytic dehydrogenation of methane molecules to produce ethane and hydrogen, characterized in that: The layered ferrous titanate nanosheet catalyst was uniformly dispersed in a solvent at a concentration of 1–5 mg / mL, and then spin-coated onto a glass fiber membrane. The solvent was evaporated at 333–363 K for 10–30 min, resulting in a catalyst with a uniform and smooth surface. The obtained catalyst was placed in a quartz reactor and activated at <1 Pa and 473–573 K for 1.5–3.0 h to remove impurities adsorbed on the catalyst surface. After cooling to room temperature, the catalyst was used for the photocatalytic oxygen-free dehydrogenation coupling reaction of methane at 273–353 K and 10–1000 mbar.

8. The application of the defect-state layered ferrous titanate photocatalyst as described in claim 7 in the photocatalytic dehydrogenation of methane molecules to produce ethane and hydrogen, characterized in that: The wavelength range of the photocatalytic light source is 200–780 nm, and the photocatalytic time is 5–600 min. During the photocatalytic reaction, the temperature is controlled by a constant temperature reaction bath.

9. The application of the defect-state layered ferrous titanate photocatalyst as described in claim 7 in the photocatalytic dehydrogenation of methane molecules to produce ethane and hydrogen, characterized in that: The solvent is anhydrous ethanol, acetone or deionized water.

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