Methane dry reforming method

Abstract

The invention provides a methane dry reforming method which comprises the following steps: mixing methane and carbon dioxide, introducing the mixture into a fixed bed reactor filled with a catalyst, and reacting at 600-800 DEG C, preferably 650-780 DEG C, so as to form a mixed gas of carbon monoxide and hydrogen, and is characterized in that the catalyst with an Ma-MbOx / Al2O3 structure is used, Ma is selected from noble metals, preferably Pt, Pd, Ru, Ir, Au or Rh, Mb is selected from Ce, Zn, Zr, Mn, La, Mg or Ca, x is selected from 0.1-6, y is selected from 0.1-6, and y is selected from 0.1-6. Preferably, the Ma metal is Ce, Zn, Zr or Mn, and the Ma metal exists in a monatomic site state. The catalyst has excellent methane dry reforming catalytic activity and stability, sintering and carbon deposition are avoided under the long-time high-temperature reaction condition, and the methane dry reforming catalytic activity and stability of the catalyst are far better than those of other types of catalysts.

Description

Technical Field

[0001] The invention relates to a method for preparing a methane dry reforming single-atom catalyst, and belongs to the technical field of methane dry reforming single-atom catalysts. Background Art

[0002] Carbon dioxide and methane are important greenhouse gases, and their large-scale emissions contribute significantly to the global warming effect. In recent years, various carbon capture and conversion technologies have been developed to reduce carbon dioxide emissions. Methane dry reforming (CH4 + CO2 = 2CO + 2H2) simultaneously converts both greenhouse gases into synthesis gas (syngas), which can be further used to synthesize fuels and various chemicals. This process not only reduces greenhouse gas emissions but also provides important raw materials for the chemical industry, offering significant environmental, energy, and social benefits.

[0003] Nickel- and cobalt-based catalysts have been widely studied in methane reforming reactions due to their low cost. Despite their high initial activity, they rapidly deactivate due to carbon deposition over extended periods. Therefore, there is an urgent need to develop a methane dry reforming catalyst that combines low cost with excellent resistance to sintering and carbon deposition, and exhibits excellent carbon deposition resistance and stability under prolonged, high-temperature reaction conditions. Summary of the Invention

[0004] The present invention provides a method for dry reforming of methane, comprising: mixing methane and carbon dioxide, introducing the mixture into a fixed bed reactor containing a catalyst, reacting at 600-800°C, preferably 650-780°C, to form a mixed gas of carbon monoxide and hydrogen, characterized in that a mixture of methane and carbon dioxide is used. a -M b O x / Al2O3 structured catalyst, where M a is selected from noble metals, preferably Pt, Pd, Ru, Ir, Au or Rh, M b is selected from Ce, Zn, Zr, Mn, La, Mg or Ca, x is selected from 0.1-6, preferably Ce, Zn, Zr or Mn, M a Metals exist in a single atomic site state.

[0005] Further, in the catalyst, based on the total weight of the catalyst, M a The metal content is 0.1-10wt%, M b The content is 0.5-20wt%.

[0006] In the method, water vapor and methane are added in a molar ratio of (1-10 / 1), preferably (4.8-5.2) / 1.

[0007] The alumina as a carrier can be either shaped or unshaped. The shaped carrier is selected from spheres, strips, cylinders, honeycombs, and other forms. The present invention implements spherical alumina, preferably Al2O3 microspheres with a diameter of 0.5-10 mm.

[0008] Preferably, the catalyst is Ir-ZnO / Al2O3, Ir-ZrO2 / Al2O3, Ir-CeO2 / Al2O3, Ir-MnO x / Al2O3, Ru-ZnO / Al2O3, Ru-ZrO2 / Al2O3, Ru-CeO2 / Al2O3, Ru-MnO x / Al2O3, Pd-ZnO / Al2O3, Pd-ZrO2 / Al2O3, Pd-CeO2 / Al2O3, Pd-MnO x / Al2O3, Pt-ZnO / Al2O3, Pt-ZrO2 / Al2O3, Pt-CeO2 / Al2O3, or Pt-MnO x / Al2O3, in which the noble metal exists in a single atomic site state.

[0009] The present invention also provides a method for preparing a single-atom catalyst for methane dry reforming, which comprises the following steps:

[0010] S1. Prepare M a Metal salt solution and configuration M b Metal salt solutions;

[0011] S2, using precious metal salt solution and M b The metal salt solution is sequentially or simultaneously impregnated into the alumina support;

[0012] S3. calcining the alumina after standing to obtain a catalyst.

[0013] Among them, M a The metal is selected from noble metals, preferably Ru, Rh, Pt, Pd, Au or Ir.

[0014] The M a The metal salt is metal M a Inorganic or organic salts, M a The metal complex solution replaces the metal salt solution. a The metal salt or metal complex is selected from chloride, nitrate, sulfate, phosphate, oxalate or acetylacetone complex, etc. The solvent of the solution is water, alcohol, acetone or a mixture of the two.

[0015] M b The metal is selected from Ce, Zn, Zr, Mn, La, Mg or Ca. bThe metal salt or complex is selected from cerium nitrate, zinc nitrate, zirconium nitrate, manganese nitrate, lanthanum nitrate, magnesium nitrate, calcium nitrate, cerium chloride, zinc chloride, zirconium chloride, manganese chloride, lanthanum chloride, magnesium chloride, calcium chloride, cerium acetylacetonate, zinc acetylacetonate, zirconium acetylacetonate, manganese acetylacetonate, lanthanum acetylacetonate, magnesium acetylacetonate, calcium acetylacetonate, cerium oxalate, zinc oxalate, zirconium oxalate, manganese oxalate, lanthanum oxalate, magnesium oxalate or calcium oxalate. b In the metal salt solution, the solvent is a methanol-water, acetone-water or ethanol-water mixed solvent, wherein the mass ratio of water / alcohol or water / ketone is 1 / 10-10 / 1.

[0016] Furthermore, the calcination temperature in S3 is 700-900° C., preferably 750-850° C., and the calcination time is 0.5-10 hours, preferably 1-4 hours.

[0017] In the catalyst prepared, M a The loading amount is 0.1-10wt%, and the present invention implements 0.5, 0.75, and 1wt%. M b The content is 0.5-20 wt%, and the present invention implements 5, 7.5 and 10 wt%.

[0018] M b When preparing the metal salt solution, chloride ions, cyanide ions, or nitrogen-containing organic compounds are added as ligands to adjust the electronic state of the active metal and enhance the interaction between the active component and the support. The nitrogen-containing organic compound is diethylenetriamine, ethylenediamine, ethylenediaminetetraacetic acid, or acetamide, preferably diethylenetriamine.

[0019] As in the above-mentioned method for preparing the catalyst, in step S2, the order of the sequential impregnation is not limited. a Metal salt solution impregnation and then M b Metal salt solution impregnation, or the reverse order.

[0020] The inorganic salt is selected from common chlorides (hydrochlorides), nitrates, nitrites, phosphates, sulfates, sulfites, carbonates and the like.

[0021] The organic salt is selected from common acetate (acetate), citrate, oxalate,

[0022] The metal complexes include complexes formed between metal ions (atoms) and organic ligands or inorganic ligands, such as phosphate complexes, chlorine complexes, nitrile complexes, ammonia complexes, nitrogen-containing ligand complexes, acetylacetone complexes, metallocenes, and the like.

[0023] Beneficial effects:

[0024] Compared to existing methane dry reforming catalysts, this catalyst offers lower cost, simpler synthesis, and readily available raw materials, enabling large-scale production. The Al2O3 microspheres have a high surface area, and the catalytically active components are distributed monoatomically on their surface, endowing the catalyst with excellent catalytic activity and stability.

[0025] The catalyst is prepared by loading Ir on the surface of Al2O3-microspheres and then modifying them with single-atom additives. Al2O3-microspheres have a high specific surface area, Ir and MO x It has a single-atom distribution on its surface, which reduces the formation of carbon deposits and gives the catalyst excellent catalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron micrograph of Ru-CeO2 / Al2O3 microspheres (Ir loading 0.75 wt%, CeO2 loading 7.5 wt%).

[0027] Figure 2 This is a transmission electron micrograph of Ir-CeO2 / Al2O3 microspheres (Ir loading 0.5 wt%, CeO2 loading 5 wt%).

[0028] Figure 3 This is a transmission electron micrograph of Ir-CeO2 / Al2O3 microspheres (Ir loading 0.75 wt%, CeO2 loading 7.5 wt%).

[0029] Figure 4 This is a transmission electron micrograph of Ir-CeO2 / Al2O3 microspheres (Ir loading 1 wt%, CeO2 loading 10 wt%).

[0030] Figure 5 Ru-CeO2 / Al2O3-microspheres (Ru loading 0.75wt%, CeO2 loading 7.5wt%) were heated at 750℃ and 2000mL -1 g -1 Dry reforming stability test diagram under h conditions.

[0031] Figure 6 Ir-CeO2 / Al2O3-microspheres (Ir loading 0.75wt%, CeO2 loading 7.5wt%) were heated at 750℃ and 2000mL -1 g -1 Dry reforming stability test diagram under h conditions.

[0032] Figure 7 Ni-CeO2 / Al2O3-microspheres (Ni loading 8wt%, CeO2 loading 7.5wt%) were heated at 750℃ and 2000mL -1 g -1Methane dry reforming stability test diagram under h conditions.

[0033] Figure 8 These are the TGA test graphs of 8Ni-7.5CeO2 / Al2O3-microspheres (nanoparticles), 0.75Ru-7.5CeO2 / Al2O3-microspheres, and 0.75Ir-7.5CeO2 / Al2O3-microspheres after dry reforming reaction. DETAILED DESCRIPTION

[0034] Test Method and Apparatus: Catalyst evaluation was conducted in a quartz fixed bed reactor (inner diameter = 9 mm, length = 700 mm) at atmospheric pressure. 1 gram of catalyst was loaded into a quartz tube and fixed in the constant temperature zone of a tube furnace with quartz wool. Prior to testing, the catalyst was heated with hydrogen (30 mL min -1 ) for 1 hour. After the reduction treatment, N2 (30 mL / min) was introduced into the reactor to purge. After the reactor was cooled to 600°C, an equimolar mixture of CH4 / CO2 (33.3 mL / min) was introduced into the reactor for reaction. The reaction products were analyzed by an online gas chromatograph (GC9890B) equipped with a thermal conductivity detector (TCD) and a TDX-1 packed column. The reaction gas conversion (X) was defined using the following equations: i ) (Equations 2-1, 2-2) and the H2 / CO molar ratio (Equation 2-3):

[0035] CH4 conversion rate:

[0036] CO2 conversion rate: H2 / CO: Pd / Al2O3-microsphere modified additive is MO x (M=Ce, Zn, Zr, Mn)

[0037] Example 1

[0038] (1) 1 ml of chloropalladic acid solution (containing 0.13 g PdCl2 / ml) and 0.25 g NaCl were added to 1 ml of deionized water and dissolved at 80°C;

[0039] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0040] (3) drying in air at 120°C for 12 hours and calcining in air at 400°C for 1 hour to obtain Pd / Al2O3 microspheres;

[0041] (4) adding 0.259 g of Zn(NO3)2·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a zinc nitrate additive source solution;

[0042] (5) 2 g of Pd / Al2O3-microspheres were placed in a centrifuge tube, and the zinc nitrate source solution was added dropwise to the centrifuge tube to make the microspheres initially wet;

[0043] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0044] (7) Dry in an oven at 100°C for 12 hours;

[0045] (8) The dried microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain single-atom catalyst Pd-ZnO / Al2O3-microspheres (Pd loading 0.75 wt%, ZnO loading 7.5 wt%);

[0046] (9) CH4 and CO2 were mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g) under normal pressure. - 1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0047] Example 2

[0048] A catalyst was prepared using a method similar to that of Example 1, except that 0.518 g of Zr(NO)₃₄₄5H₂O was used instead of 0.259 g of Zn(NO)₂·6H₂O. The resulting single-atom catalyst, Pd-ZrO₂ / Al₂O₃ microspheres, had a Pd loading of 0.75 wt% and a ZrO₂ loading of 7.5 wt%.

[0049] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0050] Example 3

[0051] The catalyst was prepared using a method similar to that of Example 1, except that 0.250 g of Mn(NO3)2·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O. x / Al2O3-microspheres (Pd loading 0.75wt%, MnO x Loading amount 7.5wt%).

[0052] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0053] Example 4

[0054] The catalyst was prepared using a method similar to that in Example 1, except that 0.252 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pd-CeO2 / Al2O3-microspheres (Pd loading 0.5 wt%, CeO2 loading 5 wt%).

[0055] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0056] Example 5

[0057] The catalyst was prepared using a method similar to that in Example 1, except that 0.378 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pd-CeO2 / Al2O3-microspheres (Pd loading 0.75 wt%, CeO2 loading 7.5 wt%).

[0058] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0059] Example 6

[0060] The catalyst was prepared using a method similar to that in Example 1, except that 0.504 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pd-CeO2 / Al2O3-microspheres (Pd loading 1 wt%, CeO2 loading 10 wt%).

[0061] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0062] Table 1. Test results of Examples 1-6

[0063]

[0064]

[0065] The modified additive of Pt / Al2O3-microspheres is MO x (M=Ce, Zn, Zr, Mn)

[0066] Example 7

[0067] (1) 1 ml of chloroplatinic acid solution (containing 0.24 g of PtCl4 / ml) and 0.25 g of NaCl were added to 1 ml of deionized water and dissolved at 80°C;

[0068] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0069] (3) drying in air at 120°C for 12 hours and calcining in air at 400°C for 1 hour to obtain Pt / Al2O3 microspheres;

[0070] (4) adding 0.259 g of Zn(NO3)2·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a zinc nitrate additive source solution;

[0071] (5) 2 g of Pt / Al2O3-microspheres were placed in a centrifuge tube, and the zinc nitrate source solution was added dropwise to the centrifuge tube to allow the microspheres to be initially wetted;

[0072] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0073] (7) Dry in an oven at 100°C for 12 hours;

[0074] (8) The dried microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain single-atom catalyst Pt-ZnO / Al2O3-microspheres (Pt loading 0.75 wt%, ZnO loading 7.5 wt%).

[0075] (9) CH4 and CO2 were mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g) under normal pressure. - 1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0076] Example 8

[0077] The catalyst was prepared using a method similar to that in Example 7, except that 0.518 g of Zr(NO3)4·5H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pt-ZrO2 / Al2O3-microspheres (Pt loading 0.75 wt%, ZrO2 loading 7.5 wt%).

[0078] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0079] Example 9

[0080] The catalyst was prepared using a method similar to that of Example 7, except that 0.250 g of Mn(NO3)2·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to obtain a single-atom catalyst Pt-MnO x / Al2O3-microspheres (Pt loading 0.75wt%, MnO x Loading amount 7.5wt%).

[0081] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0082] Example 10

[0083] The catalyst was prepared using a method similar to that in Example 7, except that 0.252 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pt-CeO2 / Al2O3-microspheres (Pt loading 0.5 wt%, CeO2 loading 5 wt%).

[0084] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0085] Example 11

[0086] The catalyst was prepared using a method similar to that in Example 7, except that 0.378 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pt-CeO2 / Al2O3-microspheres (Pd loading 0.75 wt%, CeO2 loading 7.5 wt%).

[0087] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0088] Example 12

[0089] The catalyst was prepared using a method similar to that in Example 7, except that 0.504 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Pt-CeO2 / Al2O3-microspheres (Pt loading 1 wt%, CeO2 loading 10 wt%).

[0090] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 2.

[0091] Table 2

[0092]

[0093] Ru / Al2O3-microsphere modified additive is MO x (M=Ce, Zn, Zr, Mn)

[0094] Example 13

[0095] (1) Add 0.23 g of RuCl3·3H2O and 0.25 g of NaCl to 2 ml of deionized water and heat at 80°C.

[0096] Dissolve under

[0097] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0098] (3) drying in air at 120°C for 12 hours and calcining in air at 400°C for 1 hour to obtain Ru / Al2O3-microspheres;

[0099] (4) adding 0.259 g of Zn(NO3)2·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a zinc nitrate additive source solution;

[0100] (5) 2 g of Ru / Al2O3-microspheres were placed in a centrifuge tube, and zinc nitrate source solution was added dropwise to the centrifuge tube to make the microspheres initially wet;

[0101] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0102] (7) Dry in an oven at 100°C for 12 hours;

[0103] (8) The dried microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain single-atom catalyst Ru-ZnO / Al2O3-microspheres (Ru loading 0.75 wt%, ZnO loading 7.5 wt%);

[0104] (9) CH4 and CO2 were mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g) under normal pressure. - 1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 1.

[0105] Example 14

[0106] The catalyst was prepared using a method similar to that of Example 13, except that 0.518 g of Zr(NO3)45H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ru-ZrO2 / Al2O3-microspheres (Ru loading 0.75 wt%, ZrO2 loading 7.5 wt%).

[0107] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g-1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 3.

[0108] Example 15

[0109] The catalyst was prepared using a method similar to that of Example 13, except that 0.250 g of Mn(NO3)2·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to obtain a single-atom catalyst Ru-MnO x / Al2O3-microspheres (Ru loading 0.75wt%, MnO x Loading amount 7.5wt%).

[0110] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 3.

[0111] Example 16

[0112] The catalyst was prepared using a method similar to that in Example 13, except that 0.252 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ru-CeO2 / Al2O3-microspheres (Ru loading 0.5 wt%, CeO2 loading 5 wt%).

[0113] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 3.

[0114] Example 17

[0115] The catalyst was prepared using a method similar to that of Example 13, except that 0.378 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ru-CeO2 / Al2O3-microspheres (Ru loading 0.75 wt%, CeO2 loading 7.5 wt%), the morphology of which is shown in FIG. Figure 1 shown.

[0116] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 3.

[0117] Stability test: Under normal pressure, CH4 and CO2 were mixed in a 1:1 ratio with a space velocity of 2000 mL g -1 h -1 , passed into a fixed bed reactor containing 1 gram of catalyst, and stability test was carried out at 750℃. Figure 5 shown.

[0118] Example 18

[0119] A catalyst was prepared using a method similar to that of Example 13, except that 0.504 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ir-CeO2 / Al2O3-microspheres (Ru loading 1 wt%, CeO2 loading 10 wt%).

[0120] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 3.

[0121] Table 3. Comparison of methane dry reforming performance of different Ru-based catalysts at different space velocities at 750℃

[0122]

[0123] Ir / Al2O3-microsphere modified additive is MO x (M=Ce, Zn, Zr, Mn)

[0124] Example 19

[0125] (1) Add 0.25 g of IrCl3·3H2O and 0.25 g of NaCl to 2 ml of deionized water and dissolve at 80°C;

[0126] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0127] (3) drying in air at 120°C for 12 hours and calcining in air at 400°C for 1 hour to obtain Ir / Al2O3-microspheres;

[0128] (4) adding 0.259 g of Zn(NO3)2·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a zinc nitrate additive source solution;

[0129] (5) 2 g of Ir / Al2O3-microspheres were placed in a centrifuge tube, and the zinc nitrate source solution was added dropwise to the centrifuge tube to make the microspheres initially wet;

[0130] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0131] (7) Dry in an oven at 100°C for 12 hours;

[0132] (8) The dried microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain single-atom catalyst Ir-ZnO / Al2O3-microspheres (Ir loading 0.75 wt%, ZnO loading 7.5 wt%).

[0133] (9) CH4 and CO2 were mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g) under normal pressure. - 1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0134] Example 20

[0135] The catalyst was prepared using a method similar to that of Example 19, except that 0.518 g of Zr(NO3)45H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ir-ZrO2 / Al2O3-microspheres (Ir loading 0.75 wt%, ZrO2 loading 7.5 wt%).

[0136] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), was introduced into a fixed bed reactor containing 1 gram of catalyst and reacted at 750°C. The catalytic performance is shown in Table 4.

[0137] Example 21

[0138] The catalyst was prepared using a method similar to that of Example 19, except that 0.250 g of Mn(NO3)2·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to obtain the single-atom catalyst Ir-MnOx / Al2O3-microspheres (Ir loading 0.75wt%, MnO x Loading amount 7.5wt%).

[0139] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0140] Example 22

[0141] The catalyst was prepared using a method similar to that of Example 19, except that 0.252 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ir-CeO2 / Al2O3-microspheres (Ir loading 0.5 wt%, CeO2 loading 5 wt%), the morphology of which is shown in FIG. Figure 2 shown.

[0142] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0143] Example 23

[0144] The catalyst was prepared using a method similar to that of Example 19, except that 0.378 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ir-CeO2 / Al2O3-microspheres (Ir loading 0.75 wt%, CeO2 loading 7.5 wt%), the morphology of which is shown in FIG. Figure 3 shown.

[0145] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0146] Stability test: Under normal pressure, CH4 and CO2 were mixed in a 1:1 ratio with a space velocity of 2000 mL g -1 h -1, passed into a fixed bed reactor containing 1 gram of catalyst, and stability test was carried out at 750℃. Figure 7 shown.

[0147] Example 24

[0148] The catalyst was prepared using a method similar to that of Example 19, except that 0.504 g of Ce(NO3)3·6H2O was used instead of 0.259 g of Zn(NO3)2·6H2O to prepare single-atom catalyst Ir-CeO2 / Al2O3-microspheres (Ir loading 1 wt%, CeO2 loading 10 wt%), the morphology of which is shown in FIG. Figure 4 shown.

[0149] The test operation is as follows: CH4 and CO2 are mixed at a molar ratio of 1:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0150] Adjust M a / M b Order of metal addition

[0151] Example 25

[0152] (1) Add 1.9 g of Ce(NO3)3·6H2O to 1.5 ml of a methanol-water mixed solvent and add diethylenetriamine to prepare a cerium nitrate source solution;

[0153] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0154] (3) Drying at 120 °C for 12 h and calcining in air at 400 °C for 1 h to obtain CeO2 / Al2O3-microspheres;

[0155] (4) adding 0.05 g of IrCl3·3H2O and 0.25 g of NaCl to 2 ml of deionized water and dissolving them at 80°C to prepare an iridium source solution;

[0156] (5) 2 g of CeO2 / Al2O3-microspheres were placed in a centrifuge tube, and the iridium source solution was added dropwise to the centrifuge tube to allow the microspheres to be initially wetted;

[0157] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0158] (7) Dry in an oven at 100°C for 12 hours;

[0159] (8) The dried catalyst microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain single-atom catalyst Ir-CeO2 / Al2O3-microspheres-2 (Ir loading 0.75 wt%, CeO2 loading 7.5 wt%);

[0160] (9) Under normal pressure, CH4 and CO2 were mixed in a 1:1 ratio (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0161] Example 26

[0162] (1) 0.25 g of IrCl3·3H2O and 0.25 g of NaCl were added to 2 ml of deionized water and dissolved at 80°C to prepare an iridium source solution;

[0163] (2) adding 0.19 g of Ce(NO3)3·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a cerium source solution;

[0164] (3) Place 10 g of Al2O3-microspheres into a centrifuge tube.

[0165] (4) The iridium source solution and the cerium source solution were simultaneously initially wetted and impregnated into 10 g of Al2O 3- microspheres;

[0166] (5) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0167] (6) Dry in an oven at 100°C for 12 hours;

[0168] (7) The dried catalyst microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 hours at a heating rate of 2°C / min to obtain single-atom catalyst Ir-CeO2 / Al2O3-microspheres-3 (Ir loading 0.75 wt%, CeO2 loading 7.5 wt%);

[0169] (8) CH4 and CO2 were mixed in a 1:1 ratio (space velocities of 1000, 2000, and 3000 mL g) at atmospheric pressure. -1 h -1 ), was introduced into a fixed bed reactor containing 1 gram of catalyst and reacted at 750°C. The catalytic performance is shown in Table 4.

[0170] Comparative Example 1Ni / Al2O3-microspheres

[0171] (1) Add 0.17 g of NiCl2·6H2O and 0.25 g of NaCl to 2 ml of deionized water and heat at 80°C.

[0172] Dissolve under

[0173] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0174] (3) drying at 120 °C for 12 h and calcining in air at 400 °C for 1 h to obtain Ni / Al2O3-microspheres;

[0175] (4) adding 0.378 g of Ce(NO3)3·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a cerium nitrate additive source solution;

[0176] (5) 2 g of Ni / Al2O3-microspheres were placed in a centrifuge tube, and the cerium nitrate source solution was added dropwise to the centrifuge tube to make the microspheres initially wet;

[0177] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0178] (7) Dry in an oven at 100°C for 12 hours;

[0179] (8) The dried catalyst microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain catalyst Ni-CeO2 / Al2O3-microspheres (Ni loading 0.75 wt%, CeO2 loading 7.5 wt%);

[0180] (9) Under normal pressure, CH4 and CO2 were mixed in a 1:1 ratio (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), was introduced into a fixed bed reactor containing 1 gram of catalyst and reacted at 750°C. The catalytic performance is shown in Table 4.

[0181] Comparative Example 2Ni / Al2O3-microspheres

[0182] (1) Dissolve 1.8 g of NiCl2·6H2O in 2 ml of deionized water;

[0183] (2) impregnating 10 g of Al2O3 microspheres with the solution;

[0184] (3) drying at 120 °C for 12 h and calcining in air at 400 °C for 1 h to obtain Ni / Al2O3-microspheres (nanoparticles);

[0185] (4) adding 0.378 g of Ce(NO3)3·6H2O to 1.5 ml of a methanol-water mixed solvent and adding diethylenetriamine to prepare a cerium nitrate additive source solution;

[0186] (5) 2 g of Ni / Al2O3-microspheres were placed in a centrifuge tube, and the cerium nitrate source solution was added dropwise to the centrifuge tube to make the microspheres initially wet;

[0187] (6) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0188] (7) Dry in an oven at 100°C for 12 hours;

[0189] (8) The dried catalyst microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain catalyst Ni-CeO2 / Al2O3-microspheres (Ni loading 8 wt%, CeO2 loading 7.5 wt%);

[0190] (9) Under normal pressure, CH4 and CO2 were mixed in a 1:1 ratio (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), passed into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. Its catalytic performance is shown in Table 4;

[0191] (10) Under normal pressure, CH4 and CO2 are mixed in a 1:1 ratio with a space velocity of 2000 mL g -1 h -1 , passed into a fixed bed reactor containing 1 gram of catalyst, and stability test was carried out at 750℃. Figure 8 As shown;

[0192] (11) Under normal pressure, water vapor and methane were mixed in a molar ratio of 5:1 (space velocities of 1000, 2000, and 3000 mL g -1 h -1 ), introduced into a fixed bed reactor containing 1 gram of catalyst, and reacted at 750°C. The catalytic performance is shown in Table 4.

[0193] Comparative Example 3 Ir / Al2O3-microspheres

[0194] (1) Add 0.25 g of IrCl3·H2O to 1.5 ml of deionized water to prepare an iridium chloride source solution;

[0195] (2) 10 g of ordinary Al2O3 microspheres were placed in a centrifuge tube, and the iridium chloride source solution was added dropwise to the centrifuge tube to make the microspheres initially wet and impregnated;

[0196] (3) Seal the centrifuge tube, invert it 10 times, and place it upright at room temperature for 5 hours;

[0197] (4) Dry in an oven at 100°C for 12 hours;

[0198] (5) The dried catalyst microspheres were evenly spread in a porcelain boat and calcined in a muffle furnace at 800°C for 2 h at a heating rate of 2°C / min to obtain Ir / Al2O3-microspheres (Ir loading of 0.75 wt%, nanoparticles).

[0199] (6) CH4 and CO2 were mixed in a 1:1 ratio (space velocities of 1000, 2000, and 3000 mL g) at atmospheric pressure. -1 h -1 ), was introduced into a fixed bed reactor containing 1 gram of catalyst and reacted at 750°C. The catalytic performance is shown in Table 4.

[0200] Table 4. Comparison of methane dry reforming performance of different Ir-based and Ni-based catalysts at different space velocities at 750℃

[0201]

[0202]

[0203] in conclusion:

[0204] Depend on Figure 1-4 It shows that the M a Metal single atom sites exist and are evenly distributed on the surface of the support. Figure 5-6 It shows that the stability of 0.75Ru-7.5CeO2 / Al2O3-microspheres and 0.75Ir-7.5CeO2 / Al2O3-microspheres is very good, and their performance has not decreased after 1400 hours of stability testing. Figure 7 It shows that the stability of 8Ni-7.5CeO2 / Al2O3-microspheres (nanoparticles) is poor, and the catalytic activity decreases rapidly after 180 hours of reaction. Figure 8 It shows that 0.75Ru-7.5CeO2 / Al2O3-microspheres and 0.75Ir-7.5CeO2 / Al2O3-microspheres after dry reforming reaction do not produce carbon deposition, while 8Ni-7.5CeO2 / Al2O3-microspheres (nanoparticles) after dry reforming reaction have obvious carbon deposition.

[0205] The comparison between the test data in Table 1-4 and Comparative Examples 1-3 shows that: 1. After being modified with additives, different single-atom noble metal / Al2O3-microsphere catalysts all have good performance, among which -1 g -1 h -1At the same space velocity, the CH4 conversion rate is greater than 70%. Especially the 0.75Ru-7.5CeO2 / Al2O3-microspheres and 7.5Ir-7.5CeO2 / Al2O3-microspheres modified by CeO2, at 2000mL - 1 g -1 h -1 At the same space velocity, the CH4 conversion rate is as high as 85% or more; 2. Adding additive-modified single-atom Ir-MO x The catalytic performance of the single-atom 0.75Ni-7.5CeO2 / Al2O3-microspheres is significantly better than that of comparative examples 1-3, such as comparative example 1 (single-atom 0.75Ni-7.5CeO2 / Al2O3-microspheres), comparative example 2 (8Ni-7.5CeO2 / Al2O3-microspheres (nanoparticles)), and comparative example 3 (0.75Ir / Al2O3-microspheres, impregnation method). Although comparative example 2 (8Ni-7.5CeO2 / Al2O3-microspheres (nanoparticles)) has good initial performance, its stability is only 180 hours, which is much lower than the 1400 hours of 0.75Ir-7.5CeO2 / Al2O3-microspheres, indicating that the single-atom catalyst has better stability. Table 4 further shows that changing M a / M b The order of addition, such as the order of addition of nickel source and cerium source, does not make much difference in the performance of the catalyst.

Claims

1. A method for dry reforming of methane, comprising: Methane and carbon dioxide are mixed and introduced into a fixed bed reactor equipped with a catalyst, and reacted at 600-800°C, preferably 650-780°C, to form a mixed gas of carbon monoxide and hydrogen, characterized in that a catalyst having M is used. a -M b O x / Al2O3 structured catalyst, where M a is selected from noble metals, preferably Pt, Pd, Ru, Ir, Au or Rh, M b is selected from Ce, Zn, Zr, Mn, La, Mg or Ca, preferably Ce, Zn, Zr or Mn, x is selected from 0.1-6, M a Metals exist in a single atomic site state.

2. The method according to claim 1, wherein The catalyst is calculated based on the total weight of the catalyst, M a The metal content is 0.1-10wt%, M b The content is 0.5-20wt%.

3. The method according to claim 1 or 2, wherein Water vapor and methane are added in a molar ratio of (1-10 / 1), preferably in a ratio of (4.8-5.2) / 1.

4. The method according to claim 1 or 2, wherein The alumina is selected from a shaped or non-shaped alumina carrier, wherein the shaped carrier is selected from a spherical, strip-shaped, cylindrical, and honeycomb-shaped carrier.

5. The method according to any one of claims 1 to 4, wherein: Ir-ZnO / Al2O3, Ir-ZrO2 / Al2O3, Ir-CeO2 / Al2O3, Ir-MnO x / Al2O3, Ru-ZnO / Al2O3, Ru-ZrO2 / Al2O3, Ru-CeO2 / Al2O3, Ru-MnO x / Al2O3, Pd-ZnO / Al2O3, Pd-ZrO2 / Al2O3, Pd-CeO2 / Al2O3, Pd-MnO x / Al2O3, Pt-ZnO / Al2O3, Pt-ZrO2 / Al2O3, Pt-CeO2 / Al2O3, or Pt-MnO x / Al2O3.

6. A method for preparing a single-atom catalyst for methane dry reforming, the method comprising: S1. Prepare M a Metal salt solution and configuration M b Metal salt solutions; S2, using precious metal salt solution and M b The metal salt solution is sequentially or simultaneously impregnated into the alumina support; S3, calcining the alumina after standing to obtain a catalyst; Among them, M a The metal is selected from noble metals, preferably Ru, Rh, Pt, Pd, Au or Ir; the M a The metal salt is metal M a Inorganic salts, organic salts or M a Metal complexes; M b The metal is selected from Ce, Zn, Zr, Mn, La, Mg or Ca; the M b The metal salt is metal M b Inorganic salts, organic salts or M b Metal complexes; M a The loading amount is 0.1-10wt%, M b The content is 0.5-20wt%.

7. The preparation method according to claim 6, wherein The M a The metal salt or metal complex is selected from chloride, nitrate, sulfate, phosphate, oxalate or acetylacetone complex, and the solvent of the solution is water, alcohol, acetone or a mixture of the two; M b The metal salt or complex is selected from cerium nitrate, zinc nitrate, zirconium nitrate, manganese nitrate, lanthanum nitrate, magnesium nitrate, calcium nitrate, cerium chloride, zinc chloride, zirconium chloride, manganese chloride, lanthanum chloride, magnesium chloride, calcium chloride, cerium acetylacetonate, zinc acetylacetonate, zirconium acetylacetonate, manganese acetylacetonate, lanthanum acetylacetonate, magnesium acetylacetonate, calcium acetylacetonate, cerium oxalate, zinc oxalate, zirconium oxalate, manganese oxalate, lanthanum oxalate, magnesium oxalate or calcium oxalate; the M b In the metal salt solution, the solvent is a methanol-water, acetone-water or ethanol-water mixed solvent, wherein the mass ratio of water / alcohol or water / ketone is 1 / 10-10 / 1.

8. The preparation method according to claim 6 or 7, wherein The calcination temperature in S3 is 700-900° C., preferably 750-850° C., and the calcination time is 0.5-10 hours, preferably 1-4 hours.

9. The preparation method according to claim 6 or 7, wherein M b When the metal salt solution is prepared, chloride ions, cyanide ions or nitrogen-containing organic matter are added as ligands. The nitrogen-containing organic matter is diethylenetriamine, ethylenediamine, ethylenediaminetetraacetic acid or acetamide, preferably diethylenetriamine.

10. The preparation method according to claim 6 or 7, wherein In step S2, the order of the sequential immersion is not limited.

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