Photocatalytic modification of hydrocarbons and catalysts therefor

Abstract

A method for photocatalytic dehydrogenation of light hydrocarbons using a metal oxide catalyst is disclosed. In a preferred embodiment, the metal oxide catalyst is a substituted lanthanum manganese oxide perovskite (LaMn 0.9 Cu 0.1 (O3, etc.) The light source used in the reaction is 2 W cm -1 The above strength is also disclosed. A method for preparing copper-substituted lanthanum manganese oxide perovskite, which is used as a photocatalyst for dehydrogenation reactions, is also disclosed.

Description

[Technical Field]

[0001] The present invention relates to a method for synthesizing unsaturated hydrocarbons and hydrogen by photocatalytic non-oxidation conversion of light hydrocarbons. In this method, the light hydrocarbons may be mixed with a diluent such as nitrogen (N2) or argon (Ar), and the light hydrocarbons are introduced into a photocatalytic reactor where the gas is exposed to a light source. The light source may be an LED light source, which is applied to produce unsaturated hydrocarbons and hydrogen. The catalyst may be selected to improve the performance of the photocatalyst, the conversion of the light hydrocarbons, and the selectivity of the photocatalytic conversion of the light hydrocarbons. [Background technology]

[0002] Natural gas, primarily composed of methane, ethane, propane, butane, and pentane, along with carbon dioxide, nitrogen, trace amounts of water, and oxygen, is one of the most abundant fossil fuels currently available on Earth. In addition to its use as a fuel, natural gas is a vital source of these light alkenes, which can be processed to produce a variety of chemical products, including unsaturated hydrocarbons. Alkanes can be processed via thermally powered catalytic dehydrogenation into alkenes and hydrogen, either by carbon dioxide catalytic dry reforming to syngas, carbon monoxide, and hydrogen, or by steam reforming with water vapor to syngas. However, these processes typically require extreme temperatures, usually achieved by burning fossil fuels, resulting in significant greenhouse gas emissions.

[0003] The direct conversion of methane under mild reaction conditions to produce carbon and hydrogen requires high energy (434 kJ mol) mainly to break the CH bond. -1Therefore, it is the "holy grail" of chemistry.

[0004] Ethane (C2H6) has a high molar hydrogen content (75 mol%). In particular, the CH bond in ethane is an optimal alternative hydrogen source for ethane and is therefore more easily broken than the -H bond in methane in industrial hydrogen synthesis methods. However, this reaction typically requires temperatures of several hundred Celsius to overcome the high activation barrier of the CH bond using conventional thermal catalytic methods.

[0005] Conventional methods for producing ethylene from light hydrocarbons, particularly methane and ethane, typically involve steam cracking. This method or process is widely used in the petrochemical industry due to its efficiency in breaking down larger hydrocarbon molecules into smaller ones, including ethylene, which is an important building block for various chemical products and plastics. In this method or process, a mixture of hydrocarbons such as ethane and steam is fed into a cracking furnace, which is then rapidly heated to a high temperature, typically between 750°C and 950°C. At high temperatures, larger molecules (ethane) are broken down (cracked) into smaller molecules, primarily ethylene (C2H4) and hydrogen (H2). The ratio of steam to hydrocarbons is carefully controlled to optimize the reaction and prevent cooking.

[0006] Oxidative dehydrogenation (ODH) with oxygen exhibits good thermodynamics and coking resistance, but its ethylene selectivity can be hindered by the over-oxidation of ethane to carbon monoxide and carbon dioxide. In contrast to oxidative dehydrogenation, non-oxidative dehydrogenation (EDH) can produce C2H4 and H2 in a single step and offers the highest carbon utilization among conversion processes. Unfortunately, this process still relies on fossils and consumes a lot of energy, requiring temperatures of 550-700°C due to the endothermic reaction (ΔH = 412 kJ / mol) associated with the activation of strong CH bonds in ethane.

[0007] Ethylene is widely used in the chemical industry. Its global production (over 150 million tons in 2016) surpasses that of any other organic compound. Most of this production is used to create polyethylene, a widely used plastic containing polymer chains of ethylene units of various chain lengths. Polythene production emits greenhouse gases, including methane from feedstock production and carbon dioxide from any unsustainable energy used. [Overview of the project]

[0008] This invention provides a method for inducing a catalytic reaction using solar energy, enabling the direct conversion of ethane or natural gas into ethylene and hydrogen. Unlike thermochemically driven catalytic processes that operate in the electronic ground state, photochemically usable catalytic processes operate in the excited state and benefit from the chemical potential provided by photogenerated electron-hole pairs. In addition, the electron-hole non-radiative relaxation process allows for localized heating via phonon confinement, bringing photothermal advantages to all photochemical processes. Another approach of this invention involves using artificial lighting, which may be driven by sunlight or renewable energy, to induce similar reactions and produce a variety of similar alkenes, carbon monoxide, and hydrogen products. Compared to conventional thermal methods, using artificial light emitted from solar or renewable energy breaks the limits of thermodynamics, allowing for reactions under milder conditions to induce the dehydrogenation of natural gas while simultaneously reducing greenhouse gas emissions. Due to its various advantages, including low cost, environmental friendliness, good structural stability, and tunable activity, the lanthanum manganese oxide-based perovskite of the present invention may be used to achieve efficient photocatalytic dehydrogenation of ethane and natural gas.

[0009] In one embodiment of the present invention, when an alkane such as ethane is photocatalytically modified to an alkene, a series of Cu(II)-substituted lanthanum manganese oxides (LaMn) prepared by a hydrothermal method are used. 1-x Cu xO3 is used as a catalyst. Substitution of the Mn(IV) moiety in LaMnO3 with Cu(II) creates more Mn(III) moieties that form oxygen vacancies and surface hydroxyl groups. This oxygen non-stoichiometry gives rise to the redox-active Lewis acid Mn(IV) / Mn(III) and Lewis base O(-II),OH(-I) moieties, resulting in the formation of surface frustrated Lewis pairs (SFLPs) used for photocatalytic CH activation of ethane.

[0010] LaMn 1-x Cu x Including O3, these photocatalytic SFLP catalysts further improve the activity of ethane to ethylene and hydrogen conversion, enabling a novel approach to non-oxidative conversion of ethane photocatalytic SFLPs.

[0011] In the catalyst preparation process, a hydrothermal method is used, which is based on the synthesis of a non-stoichiometric ratio of oxygen that yields the redox-active Lewis acid Mn(IV) / Mn(III) and the Lewis base O(-II),OH(-I) moiety. The Lewis acid Mn(IV) / Mn(III) and the Lewis base O(-II),OH(-I) moiety are essential for the formation of SFLP. The catalyst prepared by the method of the present invention may be used to carry out a photocatalytic reaction for the dehydrogenation of ethane or natural gas. [Brief explanation of the drawing]

[0012] The drawings below are merely illustrative of specific embodiments of the disclosure and should not be considered as limitations on its scope. They may be used to understand the processes disclosed herein and the results of experimental studies described later.

[0013] [Figure 1]Figure 1 shows the powder X-ray diffraction (PXRD) patterns of LaMnO3 and LaMn0.9Cu0.1O3. [Figure 2] Figure 2 shows the X-ray photoelectron spectroscopy (XPS) spectra of (a) Mn 2p and O 1s for LaMnO3 and LaMn0.9Cu0.1O3 samples. [Figure 3] Figure 3 shows the Raman results for LaMnO3 and LaMn0.9Cu0.1O3. [Figure 4] Figure 4 shows the results of Fourier Transform Infrared Spectroscopy (FT-IR) for LaMnO3 and LaMn0.9Cu0.1O3. [Figure 5] Figure 5 illustrates the photocatalytic ethylene production activity of LaMnO3, LaMn0.9Cu0.1O3, and Cu@LaMnO3 samples under atmospheric pressure in a Herrick cell reactor. [Figure 6] Figure 6 shows (a) the GC-MS analysis of the entire spectrum, (b) the GC-MS analysis of the 13CO2 and (c) the 13C2H4 products after the photocatalytic ethane dehydrogenation reaction from 13C2H6, and (c) the GC-MS analysis of 13C2H6. [Figure 7] Figure 7 illustrates the effect of ethane concentration on LaMn0.9Cu0.1O3 and photocatalytic performance. [Figure 8] Figure 8 illustrates the photocatalytic performance of LaMnO3 and LaMn0.9Cu0.1O3 for ethane dehydrogenation under different light intensities, as well as the corresponding surface temperatures measured by an infrared (IR) camera. [Figure 9] Figure 9 shows the C2O4 production rates using LaMnO3 and LaMn0.9Cu0.1O3 under thermal conditions. [Figure 10]Figure 10 shows the Arrhenius plots for the photocatalytic and thermocatalytic ethane dehydrogenation reactions of LaMnO3 and LaMn0.9Cu0.1O3. [Figure 11] Figure 11 shows the stability test results for each catalyst in the catalyst regeneration experiment. [Figure 12] Figure 12 shows the C2H6-TPRS results for C2H6, C2H4, CO, CO2, and H2 obtained by adsorbing C2H6. [Figure 13] Figure 13 shows the X-ray diffraction patterns of used LaMnO3 and LaMn0.9Cu0.1O3 after 10 test runs of the photocatalytic reaction shown in Figure 11. [Figure 14] Figure 14 shows the XPS results for (a) Mn 2p and (b) O 1s 2p for used LaMnO3 and LaMn0.9Cu0.1O3 samples in graphical format. [Figure 15] Figure 15 shows the results of in-situ DRIFT spectroscopy studies of the time evolution of the photocatalytic ethane dehydrogenation reaction in LaMnO3. [Figure 16] Figure 16 shows the results of in-situ DRIFT spectroscopy studies of the time evolution of the photocatalytic ethane dehydrogenation reaction in LaMn0.9Cu0.1O3. [Figure 17] Figure 17 shows the ex situ solid-state 1H NMR spectra of LaMnO3 and LaMn0.9Cu0.1O3 after photocatalytic and thermocatalytic reactions with ethane. [Modes for carrying out the invention]

[0014] The present invention provides an improved method for synthesizing unsaturated hydrocarbons and hydrogen by dehydrogenation of light hydrocarbons, including natural gas and its component gases. This method includes the preparation and use of photocatalytic materials to provide photocatalytic reforming of light hydrocarbons at lower temperatures and with lower power consumption than conventional reforming methods.

[0015] The process or method of the present invention includes a method for manufacturing and using a copper-substituted lanthanum manganese oxide-based catalyst to improve the conversion rate of light hydrocarbons.

[0016] Embodiments of the present invention also include a dehydrogenation process or method for one or more light hydrocarbons. The process or method includes introducing the light hydrocarbon into a reactor; and exposing the light hydrocarbon in the reactor to a light source having an intensity of at least about 2 W cm -1 and performing dehydrogenation in the presence of a catalyst that is a metal oxide.

[0017] The dehydrogenation of the light hydrocarbon dissociates at least one such light hydrocarbon into separable gaseous hydrogen and one or more alkene co-products.

[0018] In one embodiment of the present invention, the metal oxide is used as a catalyst in a dehydrogenation process or method for one or more light hydrocarbons or a mixture of light hydrocarbons such as natural gas. The process or method includes introducing the light hydrocarbon or the mixture of light hydrocarbons into a reactor in which the metal oxide is present; and bringing one or more of the light hydrocarbons into intimate contact with the metal oxide while exposing the metal oxide in the reactor to a light source having an intensity of at least about 2 W cm -1 The intensity may be from about 2 W cm [[ID=2(0]] -1 to about 10 cm -1 and still be acceptable.

[0019] In one embodiment of the present invention, the metal oxide is a stoichiometric (ABO3) perovskite or a non-stoichiometric (ABO 3-x ) perovskite, or other stoichiometric or non-stoichiometric metal oxide MO n It may also be. The metal oxide ABO3 or ABO 3-xThis may be a redox-active perovskite; or a version thereof doped with isomorphic substitution at the A and / or B sites of the perovskite, or a version modified with single metal atoms or dual-site single atoms supported by the perovskite. The redox-active perovskite ABO3 or ABO 3-x The dopant in this may consist of periodic table elements exemplified by isomorphic substitutions of transition metals such as Cu, Fe, Ni, Co, In, Al, and Sn at its B site.

[0020] In one embodiment of the present invention, the metal oxide is a copper-substituted lanthanum manganese oxide perovskite. In one embodiment of the present invention, the copper-substituted lanthanum manganese oxide perovskite is of the formula LaMn 1-x Cu x This is a Cu(II)-substituted lanthanum manganese oxide represented by O3. In the above formula, x may range from 0.01 to about 0.5. In one embodiment of the present invention, the copper-substituted lanthanum manganese oxide perovskite is LaMn 0.9 Cu 0.1 It is O3.

[0021] In various embodiments of the present invention, the light hydrocarbon may be a single light hydrocarbon or a mixture of light hydrocarbons selected from the group consisting of methane, ethane, propane, butane, and methylcyclohexane.

[0022] In a preferred embodiment of the present invention, the light hydrocarbon is ethane.

[0023] In another preferred embodiment of the present invention, the light hydrocarbon is natural gas.

[0024] In another embodiment, the present invention provides a process or method for preparing a copper-substituted lanthanum-manganese oxide perovskite used as a catalyst in the dehydrogenation of one or more light hydrocarbons, comprising: mixing stoichiometric amounts of lanthanum nitrate, manganese t, and copper nitrate to form a mixed salt solution; suspending the resulting salt in a solution by adding a base; heating the resulting suspension at about 180°C for about 12 hours, followed by cooling the solution to room temperature; isolating the resulting copper-substituted lanthanum-manganese oxide perovskite precursor by centrifugation and washing; and calcining the dried precursor.

[0025] Embodiments of the present invention may be understood by reviewing the following examples, when they include the steps described below. a. Prepare and characterize the catalyst to be used; b. To evaluate the production of ethylene from ethane using such prepared catalyst; c. Confirm that the ethylene and hydrogen produced by the photocatalytic process (or method) of the present invention were formed from ethane raw materials; d. Experimentally investigate the effect of ethane concentration on the rate and degree of conversion; e. To evaluate the effects of light intensity and temperature on the rate and degree of conversion; f. Evaluate the stability and regeneration of the catalyst used; g. To confirm the photochemical activity versus photothermal activity of the process or method of the present invention; h. To confirm the applicability of the catalyst and process or method of the present invention to the reforming of mixtures of light hydrocarbons such as natural gas.

[0026] [Example 1] Preparation of catalyst All chemical products used in the preparation of the catalyst were analytical grade and were used without further purification. Briefly, stoichiometric amounts of lanthanum nitrate (La(NO3)3·6H2O), manganese nitrate (Mn(NO3)3·4H2O), and copper nitrate (Cu(NO3)2·H2O) were dissolved in 25 mL of deionized water and stirred for 30 minutes to form a mixed salt solution. Then, 1 mL of KOH (10 M) was slowly added to the solution under continuous stirring. After aging for 30 minutes, the resulting suspension was transferred to a 30 mL stainless steel Teflon-coated autoclave and heated at 180°C for 12 hours, after which it was cooled to room temperature. The resulting product was recovered after centrifugation, washed several times with deionized water, and finally dried at 60°C. The dried precursor was calcined in air at 250°C for 2.5 hours and then at 850°C for 6 hours.

[0027] A sample of Cu-loaded LaMnO3 (referred to as Cu@LaMnO3 in this book) is created by combining Cu(NO3)2·H2O with LaMnO3. 0.9 Cu 0.1 The solution was prepared by mixing in a stoichiometric ratio corresponding to the amount of copper in the O3 sample, and stirred in water in a glass beaker for 12 hours. After drying the solution, the powder was collected and introduced into a tube furnace, where it was heated to 160°C for 2 hours under air. This sample was used to confirm the importance of Cu substitution in the perovskite lattice.

[0028] Transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images of LaMnO3 showed that LaMnO3 consists of highly aggregated and partially sintered nanoparticles having a size in the range of 50-200 nm and perovskite (110) planes with a spacing of 0.275 nm (Figure 1b).

[0029] Energy-dispersive fluorescence X-ray (EDX) elemental mapping images of the prepared catalyst samples confirmed the presence of a uniform distribution of La and Mn in the perovskite lattice.

[0030] The catalyst sample was imaged using a transmission electron microscope (TEM) with a FEI TALOS-200X TEM operated at an accelerating voltage of 300 kV. (LaMn) 0.9 Cu 0.1 TEM and HRTEM results for O3 showed a slight increase in lattice spacing (0.280 nm), indicating a slight expansion of the perovskite lattice as expected for substitutions of larger Cu(II) (0.073 nm) and smaller Mn(III) ions (0.064 nm) or Mn(IV) ions (0.060 nm) in the lattice.

[0031] Powder X-ray diffraction (PXRD) studies of catalyst samples were performed using a Bruker D2-PHASER X-ray diffractometer with 30kV Cu Kα radiation. As shown in Figure 1, the LaMnO3 catalyst and LaMn 0.9 Cu 0.1 Powder X-ray diffraction (PXRD) patterns of the O3 catalyst confirmed the rhombohedral perovskite crystalline phase of the prepared sample. A monotonic shift of the diffraction peak was observed at a smaller angle, indicating that the Cu-substituted sample was successfully prepared.

[0032] LaMn 0.9 Cu 0.1The Cu content of the O3 samples was measured. The results are shown in Table 1, demonstrating a very consistent stoichiometric ratio of Cu addition during synthesis. The relative molar ratio of La to (Mn+Cu) was approximately 0.7:1. (LaMnO3 and LaMn) 0.9 Cu 0.1 The Brunauer-Emmett-Teller (BET) surface area of ​​O3 was detected and recorded using accelerated surface area measurement and a pore distribution analyzer with N2 adsorption analysis (Micromeritics, ASAP 2020, USA). The results are summarized in Table 2. LaMnO3 and LaMn 0.9 Cu 0.1 For O3, the surface areas are 18.6 m² and 21.3 m², respectively. 2 / g is LaMn 0.9 Cu 0.1 An increase in the surface area of ​​O3 is shown.

[0033] [Table 1]

[0034] [Table 2]

[0035] LaMnO3 and LaMn 0.9 Cu 0.1 To investigate the physicochemical properties of O3, X-ray photoelectron spectroscopy (XPS) was performed using a PerkinElmer Phi 5500 ESCA spectrometer, as shown in Figure 2, to clarify the elemental chemical state. From the Mn 2p spectrum, two peaks belonging to Mn(III) and Mn(IV) can be obtained by deconvolution. Mn(III) (641.4 and 653.0 eV in LaMnO3; LaMn 0.9 Cu 0.1 In O3, 641.5 and 653.1 eV; Mn(IV)(LaMnO3, 643.1 and 654.4 eV; LaMn0.9 Cu 0.1 LaMn (643.6 and 654.6 eV in O3) 0.9 Cu 0.1 The slight shift to the higher bond energy of O3 may be due to the higher electronegativity of Cu. In addition, in the case of Cu(II) substitution, the Mn(IV) / Mn(III) intensity ratio is reduced.

[0036] The Raman spectra of each prepared catalyst were collected using a Bruker SENTERRA Raman microscope with a red laser (532 nm) at 1 mW. The results are shown in Figure 3. Jahn-Teller, LaMn related to MnO6 strain 0.9 Cu 0.1 The Raman mode in O3 also strengthened, which is consistent with the decrease in the Mn(IV) / Mn(III) ratio shown in the XPS results.

[0037] To explain in more detail, the O 1s spectrum of LaMnO3 is shown in Figure 2b, which shows surface hydroxyl groups (OH) and oxygen vacancies (O) at 533.5, 531.6, and 529.2 eV, respectively. V ) and lattice oxygen (O latt This shows a peak caused by LaMn. 0.9 Cu 0.1 The peak intensities of O3 at 533.3 and 531.9 eV are stronger than those of LaMnO3, indicating more OH and O V The part is LaMn 0.9 Cu 0.1 Its presence in O3 was noteworthy.

[0038] Fourier transform infrared spectroscopy (FT-IR) was used to further confirm the presence of OH groups. The results are shown in Figure 4. From these results, 3606 cm⁻¹ was obtained. -1 The peak shown indicates that more OH is present in LaMn 0.9 Cu 0.1 This indicates that it is formed from O3.

[0039] The analytical results collected from this study indicate that by controlling the Cu(II) substitution in LaMnO3, it is possible to adjust the sites of the Mn(III,IV) Lewis acid and the O(-II) and OH(-I) Lewis bases within the perovskite lattice. This control enables rational and systematic control of the physicochemical properties of the perovskite lattice. These results also suggest that LaMn 0.9 Cu 0.1 We demonstrated that O3 exhibits higher Lewis acidity and Lewis basicity. Furthermore, Lewis acidity and Lewis basicity provide a basis for regulating the photoactivity and redox activity of SFLP in the dehydrogenation of ethane to ethylene.

[0040] [Example 2] Production of ethylene by photocatalytic ethane dehydrogenation LaMnO3 and LaMn 0.9 Cu 0.1 The photocatalytic dehydrogenation of ethane (O3) was investigated using a laboratory-scale flow-type reactor. This reactor consisted of a stainless steel reactor body with one or more quartz glass windows surrounding it, and valves controlling the inflow of gas into and outflow of the reactor body. The quartz glass windows of the reactor allowed light from LEDs, simulated sunlight, and other sources to illuminate the LaMnO3 and LaMnO3 inside the reactor. 0.9 Cu 0.1 This allowed for irradiation of the O3 surface and the promotion of a photocatalytic ethane dehydrogenation reaction. A combination of four LED lights (ultraviolet (UV), blue, green, and red) was used as the light source for the reaction. The light intensity was changed by manually adjusting the power to the LED lights. An Omega temperature controller was attached to a heating cartridge inserted into a copper block, along with a thermocouple inserted into the catalyst bed to measure and control the catalyst temperature. A reaction gas consisting of 9.1 vol% C2H6 and 90.9% balanced Ar was added at a rate of 2.2 mL·min. -1The total flow rate was introduced into the reactor. At that time, the WHSV value measured by two mass flow controllers (Alicat MC-2SCCM-D / 5M) was 5.0h -1 The surface area of ​​the irradiated sample was 0.785 cm². 2 The results were as follows: A new sample was used for each test condition. The ethylene concentration in the exhaust gas was periodically collected and analyzed using a thermal conductivity detector (TCD) with Ar as the carrier gas.

[0041] As shown in Figure 5, Cu(II) substitution strongly affected photocatalytic activity. The generation rate and selectivity of C2H4 are as follows: LaMn 0.9 Cu 0.1 O3(1106.5 μmol·g -1 ·h -1 ;91.0%)>LaMnO3(227.5 μmol·g -1 ·h -1 52.3%. The activity result was LaMn 0.9 Cu 0.1 Regarding O3, the production rate of C2H4 increased 4.86 times compared to LaMnO3. 0.9 Cu 0.1 LaMnO3 (represented as Cu@LaMnO3), which was formed by the same copper addition as O3, was also examined as a control sample, and the effect of introducing Cu into the catalyst lattice using different preparation methods on ethane dehydrogenation was investigated. As a result, Cu@LaMnO3 showed higher C2H4 activity (324.6 μmol·g) than LaMnO3. -1 ·h -1 ) showed. However, the activity of Cu@LaMnO3 was LaMn 0.9 Cu 0.1 The activity remained significantly lower than that exhibited by O3, demonstrating the importance of isomorphic Cu(II) substitution in photocatalytic ethane dehydrogenation.

[0042] [Example 3] For confirming photocatalytic ethane dehydrogenation 13 C is used LaMn 0.9 Cu 0.1 The performance of photocatalytic ethane dehydrogenation to ethylene in LaMnCuO3 was excellent among the reported photocatalysts. Using 13 C2H6 as a raw material, an isotope-labeling test was conducted, and the products were analyzed by gas chromatography-mass spectrometry (GC-MS). The test was carried out at atmospheric pressure in a batch reactor with a total volume of 20 mL. A gas mixture composed of 0.2 sccm of 13 C2H6 and 2 sccm of Ar was introduced into a reactor with an irradiated sample surface area of 0.785 cm 2 . The intensity of white light was simulated using an LED at 4.8 W cm -2 . A new sample was used for each test condition. As shown in Fig. 6, 13 C2H4 and 13 CO2 fragmentation patterns confirmed that these products were 13 derived from C2H6.

[0043] [Example 4] Influence of ethane concentration LaMn 0.9 Cu 0.1 The influence of the C2H6 supply concentration (vol%) on photocatalytic ethane dehydrogenation to ethylene in LaMnCuO3 was measured by changing the C2H6 supply concentration from 9.1 to 33.3 vol% (balanced with Ar) while maintaining the weight hourly space velocity (WHSV) at 5.0 h -1 in a helical cell reactor operated at a total flow rate of 2.2 mL·min -1 . The results are shown in Fig. 7. The total gas flow rate was set to 2.2 sccm by changing the ratio of ethane and Ar. The intensity of the pseudo-white LED light used (LED simulated white light intensity) was 4.8 W cm -2 . A new sample was used for each test condition.

[0044] The increase in the C2H6 supply concentration resulted in an increase in the C2H4 production rate, and it was clear that the C2H6 conversion subsequently decreased. Therefore, an ethane concentration of 9.1 vol% was used in the subsequent photocatalytic ethane conversion activity test.

[0045] [Example 5] Influence of Light Intensity and Temperature To distinguish the photothermal contribution and the photochemical contribution to the dehydrogenation of ethane, the degree and ratio of photocatalytic ethane conversion were measured under different light intensities. The intensities of the pseudo-white LED light used were 2.7, 3.2, 3.6, 4.0, 4.5, and 4.8 W cm -2 respectively. The total gas flow rate was set to 2.2 sccm (0.2 sccm of ethane: 2 sccm of Ar) for the irradiated sample surface area of 0.785 cm 2 . A new sample was used for each test condition. The temperature generated on the sample surface under the reaction gas was measured in a photoreactor with a CaF2 window using an infrared camera.

[0046] The thermocatalytic reaction was carried out at temperatures of 500, 550, 600, 650, and 700 °C using a flow-type reactor.

[0047] As shown in Fig. 8, as the light intensity increased, the C2H4 production rate in LaMnO3 and LaMn 0.9 Cu 0.1 O3 improved. As shown on the right axis of Fig. 8, the surface temperatures of LaMnO3 and LaMn 0.9 Cu 0.1 O3 were measured using an infrared camera at various light intensities. The surface temperatures of LaMnO3 and LaMn 0.9 Cu 0.1 O3 were similar and were found to increase linearly from 330 and 331 °C to 447 and 452 °C, respectively, for 2.68 W cm -2 to 4.80 W cm -2 . From the results in Fig. 8, LaMnO3 and LaMn 0.9 Cu 0.1O3 exhibits similar surface temperatures, and regarding the photochemical contribution to the photocatalytic reaction, Cu(II) substitution is more effective than LaMnO3 and LaMn 0.9 Cu 0.1 It was found that the effect on photothermal conversion capacity was minimal among the O3 groups.

[0048] The photochemical contribution in the photocatalytic ethane dehydrogenation reaction was further confirmed by measuring the photocatalytic ethane conversion activity under dark conditions, i.e., without LED lighting, but within a temperature range encompassing the temperature reached when LED lighting is used, as shown in Figure 9. (LaMnO3 and LaMn) 0.9 Cu 0.1 For both O3s, C2H4 was not produced below 452°C, and the C2H4 production rate increased rapidly only above 600°C. Compared to LaMnO3, LaMn 0.9 Cu 0.1 The difference in the increase in ethylene production rates during the thermal and photocatalytic reactions of O3 demonstrates that, in addition to the photothermal role played by LED lighting, it also contributes photochemically to the dehydrogenation of ethane.

[0049] As shown in Figure 10, the activation energy (E) under photochemical reaction conditions a The following was calculated using the Arrhenius equation: LaMnO3 and LaMn 0.9 Cu 0.1 Regarding O3, E for the conversion of ethane to ethylene. a The calculated values ​​are 90.94 and 94.62 kJ·mol for the photocatalyst, respectively. -1 Then, with thermal catalyst, 169.57 and 171.54 kJ·mol were obtained. -1 The more drastic decrease in activation energy under illumination (light) highlights the advantages of photocatalytic dehydrogenation of ethane compared to thermal (heating) processes.

[0050] [Example 6] Evaluation of catalyst stability LaMnO3 and LaMn across multiple photodehydrogenation and regeneration cycles 0.9 Cu 0.1The durability of the O3 catalyst was investigated. Stability tests were performed for five cycles. After each dehydrogenation reaction, the spent catalyst was subjected to a simulated white LED light intensity of 4.8 W cm outdoors. -2 The surface residue was removed by irradiating the catalyst with the same LED light used in the photocatalytic ethane conversion reaction for 20 minutes. The results are shown in Figure 11. From these results, it can be seen that both catalysts were gradually deactivated over time, but most importantly, these catalysts can be regenerated by oxidation with ambient air.

[0051] [Example 7] Investigation of the ethane dehydrogenation reaction pathway We conducted a C2H6 temperature-programmed surface reaction (TPSR) experiment to gain a deeper understanding of the ethane dehydrogenation pathway under thermal (heating) conditions. This experiment was performed with a 50 mg sample loading. Initially, the reaction temperature was set to 200°C for 10 minutes, using He(30 mL·min). -1 The gas was then purged using ). Next, the gas flow rate was set to He (30 mL·min). -1 Switch to 5% C2H6 in the state shown, and set the temperature to 10℃·min. -1 The temperature was increased from 200°C to 700°C at a certain rate, and the output gas was detected by online QMS (Bruker, MATRIX-MG(HR)-01).

[0052] As shown in Figure 12a, LaMn 0.9 Cu 0.1 More CO and CO2 were observed with LaMnO3 than with O3. Surprisingly, with LaMnO3, H2O and H2 were produced at 350 and 600°C, but with LaMnO3... 0.9 Cu 0.1 In the case of O3, a relatively high temperature is required for H2O release (500°C), and a relatively low temperature is required for H2 release (570°C). In the latter case, it was shown that H2 is easily formed (C2H6 → C2H4 + H2).

[0053] [Example 8] Evaluation of structural changes in catalysts Used LaMnO3 and LaMn 0.9 Cu 0.1 To investigate the structural changes in O3 samples, PXRD tests were performed on used samples. As can be seen from the results in Figure 13, used LaMnO3 and LaMn 0.9 Cu 0.1 O3 did not show any change in its current external structure, and the bulk perovskite structure was shown to be stable after the photocatalytic ethane dehydrogenation reaction.

[0054] [Example 9] Experiment with spent catalyst X-ray photoelectron spectroscopy (XPS) analysis of spent catalyst samples was performed using a PerkinElmer Phi 5500 ESCA spectrometer. The used LaMnO3 and LaMn after the photocatalytic reaction were analyzed. 0.9 Cu 0.1 The XPS spectrum of O3 is shown in Figure 14. The results in Figure 14 show that LaMnO3 has a larger O latt This shows a decrease in [something]. Furthermore, the Mn(IV) / Mn(III) ratio increased significantly in LaMnO3, but LaMn 0.9 Cu 0.1 In O3, the larger O of LaMnO3 latt This was not the case due to the loss of [unclear]. In relation to the catalytic activity results (Figure 5), these results indicate that the Mn(III) / Mn(IV) ratio plays a crucial role in the conversion of ethane to ethylene.

[0055] [Example 10] Evaluation of DRIFT-interface chemistry We used in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to investigate the changes in the interfacial chemistry of the catalyst during the photocatalytic conversion from ethane to ethylene. DRIFT spectra were collected using a Thermo Scientific iS50 series FT-IR spectrometer equipped with Harrick's Playing Mantis® DRIFT accessory. Each spectrum was scanned at 4 cm intervals using an average of 32 scans. -1 The data was recorded at the specified resolution. Powder samples were placed in the holder without packing or dilution. The background IR spectrum was collected after purging for 2 hours in the presence of He at 300°C. Next, for the ethane adsorption test, C2H6 / Ar (1:3; 5 sccm of ethane and 15 sccm of He, respectively) was flowed at 30°C for 30 minutes. The ethane dehydrogenation test was performed at 300°C at 2.1 W cm². -2 The procedure was performed under white LED light at the specified intensity. Figure 15 shows the in-situ drift results of LaMnO3 under illumination (light) conditions; no signals other than the ethane peak were observed.

[0056] Figure 16 shows LaMn 0.9 Cu 0.1 This shows the results of in-situ drift of O3, but LaMn 0.9 Cu 0.1 O3 exhibited a series of fingerprint signature peaks, the intensity of which gradually increased with exposure time. (1845 cm) -1 The peaks at 3730 and 3700 cm² indicated fingerprint diagnosis of magnesium hydride Mn-H surface species. -1 The vibration of OH at 1976 cm indicated the formation of Mn-OH and protonated Mn2OH species. -1The peak at 2984 cm⁻¹ was due to the vibration of the C=C bond, which indicates ethylene formation. This corresponds to C₂H₄. -1 This was confirmed by the peak that appeared. The above results indicate that C2H6 undergoes a heterolytic dissociative pathway involving Lewis acids Mn(III,IV) and Lewis bases O(-II),OH(-I)SFLP.

[0057] [Example 11] Confirmation of photochemical activity solid 1 Using 1H NMR spectroscopy, we obtained supporting information regarding the photochemical roles derived from the thermal decomposition (T) and photodecomposition (L) ethane dehydrogenation reactions. 1 The 1H solid-state NMR spectrum was obtained at a rotation speed of 11 kHz. Using adamantane as a reference, the NMR spectrum was calibrated by optimizing the parameters: pulse width (pwX90) = 3.5 microseconds, number of scans = 1, delay time = 10 seconds. 1 For the H solid-state NMR, samples were treated with ethane under light (illumination) or heat (heating) (600°C) and then tested immediately. The results are shown in Figure 17. L and T are samples exposed to ethane under light and heat (600°C) reaction conditions. A new chemical shift related to Mn-H appeared around -3.14 ppm relative to the adamantane reference material after the heat reaction. 1 A positive 1H NMR peak was observed, ranging from -3.14 to -2.37 ppm. 1 As can be seen from the chemical shift of the 1H NMR spectrum, the Mn-H bond was extended under illumination (light) by modified Lewis acidity. 1 Observations from 1H NMR showed that photochemical action elongates and weakens the Mn-H bond, promoting the breakdown of the CH bond. These results indicate the photochemical contribution of the catalyst in the photocatalytic ethane dehydrogenation reaction, in addition to the photothermal contribution due to the heat of the light source.

[0058] [Example 12] Direct dehydrogenation of natural gas using photocatalysis Photocatalytic dehydrogenation of natural gas to ethylene or syngas was carried out under ambient conditions using the same flow reactor used for photocatalytic ethane dehydrogenation. A xenon lamp was applied as the light source, with a light intensity of 8.64 W cm². -2 The settings were adjusted. The natural gas flow rate was set to 2 sccm. The corresponding WHSV value was set to 8.6 h -1 The reactants and products were detected using a gas chromatograph (GC-2014, Shimadzu Corporation) equipped with both a thermal conductivity detector (TCD) and flame ionization detectors (FID).

[0059] LaMnO3 and LaMn for natural gas dehydrogenation reaction 0.9 Cu 0.1 O3 catalyst was used. Figure 18 shows LaMnO3 and LaMn 0.9 Cu 0.1 It exhibits photocatalytic activity for the direct dehydrogenation of natural gas by O3. In particular, LaMn 0.9 Cu 0.1 The C2H4 production rate of O3 is 673 μmol·g -1 ·h -1 Therefore, the C2H4 production rate of LaMnO3 is (402 μmol·g). -1 ·h -1 ) became higher. In addition, LaMn 0.9 Cu 0.1 In O3, carbon monoxide (1228 μmol·g) -1 ·h -1 ) and hydrogen (910 μmol·g -1 ·h -1 The photocatalytic activity of syngas generation, including ), was improved compared to pure LaMnO3. Partially copper-substituted perovskite LaMn 0.9 Cu 0.1 In O3, the activity of photocatalytic natural gas dehydrogenation was enhanced.

[0060] LaMnO3 and LaMn 0.9 Cu 0.1 By using a hydrothermal method to prepare O3 samples, it is possible to control copper substitution in LaMnO3. In this way, by controlling Cu(II) substitution, LaMn0.9 Cu 0.1 In O3, the Lewis acid-base properties are enhanced compared to LaMnO3, and the photocatalytic performance in ethane and natural gas is improved.

[0061] While embodiments of this disclosure are described in detail, it should be understood that, unless otherwise specified, this disclosure is not limited to specific materials, reactants, manufacturing processes, or manufacturing methods, and can be modified. It should also be understood that the technologies used in this document are intended to describe specific embodiments only, and are not intended to limit them. Furthermore, in this disclosure, steps can be performed in different sequences where logically possible.

Claims

1. A method for dehydrogenating one or more light hydrocarbons, a. Introducing the hydrocarbon into the reactor; and b. The light hydrocarbon in the reactor is subjected to at least about 2 w / cm³ －１ Exposure to a light source having an intensity of Including; A method for dehydrogenating light hydrocarbons, characterized in that the dehydrogenation is carried out in the presence of a metal oxide catalyst.

2. The method according to claim 1, characterized in that the dehydrogenation of the light hydrocarbon involves dissociating at least one such light hydrocarbon into separable gaseous hydrogen and one or more alkene co-products.

3. The use of a metal oxide as a catalyst in a method for the dehydrogenation of one or more light hydrocarbons, a. Introducing the light hydrocarbon into a reaction apparatus containing the metal oxide; b. To bring one or more of the above light hydrocarbons into close contact with the metal oxide; and c. The metal oxide in the reaction apparatus is subjected to at least about 2 W cm －１ Exposure to a light source having an intensity of The use of metal oxides as catalysts, characterized by containing them.

4. The aforementioned metal oxide is a stoichiometric perovskite ABO ３ or ABO, a perovskite with non-stoichiometric ratios ３－ｘ , and other metal oxides of stoichiometric or non-stoichiometric ratios MO ｎ The method according to any one of 1, 2, or 3, characterized in that it is the same.

5. The method according to any one of 1, 2, or 3, characterized in that the metal oxide is a copper-substituted lanthanum manganese oxide-based perovskite.

6. The aforementioned metal oxide ABO ３ or ABO ３－ｘ The method according to 4, characterized in that the perovskite is a redox-active perovskite; or a form thereof doped with isomorphic substitution at the A and / or B sites of the perovskite, or a form modified with a single metal atom supported by the perovskite or a single atom at a dual site.

7. The copper-substituted lanthanum manganese oxide perovskite may have x ranging from 0.01 to about 0.5, and has the formula LaMn １－ｘ Cu ｘ O ３ The method according to any one of claims 1, 2, 3 or 4, characterized in that it is a Cu(II)-substituted lanthanum manganese oxide represented by.

8. The copper-substituted lanthanum manganese oxide perovskite is LaMn ０．９ Cu ０．１ O ３ The method according to any one of 1, 2, 3, or 4, characterized in that it is the same.

9. The intensity of the aforementioned light source is approximately 2 W cm². －１ The method according to any one of 1 to 7, characterized in that it is larger than [a certain value].

10. The intensity of the aforementioned light source is approximately 2 W cm². －１ From 10 W cm －２ The method according to any one of 1 to 7, characterized in that it is up to [a certain point].

11. The method according to any one of 1 to 7, characterized in that the light hydrocarbon is selected from the group consisting of methane, ethane, propane, butane, and methylcyclohexane.

12. The method according to any one of 1 to 7, characterized in that the light hydrocarbon is ethane.

13. The method according to any one of 1 to 7, characterized in that the light hydrocarbon is natural gas.

14. The aforementioned redox-activated perovskite ABO ３ or ABO ３－ｘ The method according to 6, characterized in that the dopant in the present invention may be composed of an element of the periodic table, exemplified by isomorphic substituents of transition metals such as Cu, Fe, Ni, Co, In, Al, and Sn at the B site.

15. A method for preparing a copper-substituted lanthanum manganese oxide perovskite used as a catalyst in the dehydrogenation of one or more light hydrocarbons, The method according to any one of 1 to 11, characterized by: mixing lanthanum nitrate, manganese t, and copper nitrate in stoichiometric ratios to form a mixed salt solution; suspending the salt thus obtained in a solution by adding a base; heating the suspension thus obtained at about 180°C for about 12 hours and then cooling the solution to room temperature; isolating the resulting copper-substituted lanthanum-manganese oxide perovskite precursor by centrifugation and washing; and calcining the dried precursor.

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