Metal-rare earth / molybdenum nitride catalyst and preparation method and application thereof

Abstract

The invention provides a metal-rare earth / molybdenum nitride catalyst and a preparation method and application thereof. The optimal rare earth element doping range is obtained by finely regulating and controlling the rare earth type, the use amount, the metal type, the metal use amount in the dipping process and the pretreatment temperature. The catalyst is applied to a methanol-water reforming hydrogen production reaction, an efficient low-temperature catalytic process is realized, and the metal utilization rate is relatively high. In addition, the metal consumption of the catalyst is less, so that the cost is more economical. According to the present invention, by introducing the atomic-scale rare earth auxiliary agent, the catalyst shows the continuous stability of more than 1300 h in the stability test, the TON catalytic effect of more than 10 million is obtained, and the stability of the methanol-water reforming hydrogen production reaction and the hydrogen yield are significantly improved.

Description

Technical Field

[0001] The present application relates to the technical field of hydrogen production by methanol reforming reaction, and in particular to a metal-rare earth / molybdenum nitride catalyst and a preparation method and use thereof. Background Art

[0002] As fossil fuels are gradually depleted and environmental protection requirements become increasingly stringent, the potential of hydrogen as a clean energy source is becoming increasingly prominent. Compared with coal and gasoline of the same quality, hydrogen has many advantages such as high energy density, clean products, and extensive resources. As the demand for hydrogen increases, hydrogen production technology is developing rapidly. Among them, methanol-water reforming hydrogen production technology is widely used in the field of hydrogen production due to its high hydrogen production efficiency, easy methanol conversion, low energy consumption, and mild operation. However, achieving highly active, stable, and selective catalysts remains a key challenge for this technology.

[0003] At present, there are three main types of catalysts commonly used in methanol-water reforming reaction to produce hydrogen. Traditional copper-based catalysts are cheap, but copper has low intrinsic activity at low temperatures and is prone to lose stability under high temperatures and water vapor; noble metal / oxide catalysts are easy to undergo dehydrogenation reactions, but hydrolysis reactions are more difficult, resulting in reduced activity and increased CO selectivity in the product; and Pt / MoC catalysts show extremely high activity at low temperatures, but in some cases, problems such as oxidation, carbon deposition and metal aggregation of the catalyst still exist. Therefore, the development of catalysts that have both low-temperature activity and high stability has become a problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of this application is to provide a metal-rare earth / molybdenum nitride catalyst for hydrogen production from methanol-water reforming and its preparation method and use, so as to achieve higher metal utilization and low temperature reaction conditions, while maintaining ultra-long stability at high temperatures. The specific technical solution is as follows:

[0005] The first aspect of the present application provides a method for preparing a metal-rare earth / molybdenum nitride catalyst, which comprises the following steps:

[0006] (1) preparing a rare earth oxide / molybdenum oxide precursor; wherein the rare earth oxide is selected from at least one of La2O3, CeO2, Y2O3, PrO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Er2O3 and Ho2O3;

[0007] (2) heat-treating the rare earth oxide / molybdenum oxide precursor in ammonia to obtain a rare earth-molybdenum nitride carrier; wherein the flow rate of the ammonia is 10 mL / min-400 mL / min;

[0008] (3) adding the rare earth-molybdenum nitride carrier to a metal precursor solution, stirring under an argon atmosphere, and drying to obtain a catalyst precursor; wherein the metal element in the metal precursor solution is selected from at least one of ruthenium, rhodium, palladium, iridium, platinum, gold, nickel, and cobalt, the mass fraction of the metal precursor solution is 0.01wt%-0.35wt%, and the ratio of the mass of the rare earth-molybdenum nitride carrier to the volume of the metal precursor solution is 400:(10-20)mg / mL;

[0009] (4) reducing the catalyst precursor in a hydrogen / argon mixed atmosphere to obtain the metal-rare earth / molybdenum nitride catalyst; wherein the volume ratio of the hydrogen to the argon is 10:(10-100).

[0010] In some embodiments of the present application, the rare earth oxide / molybdenum oxide precursor is obtained by grinding and mixing rare earth oxide and molybdenum oxide powder, and calcining in air, wherein the calcination temperature is 400°C-700°C, and the calcination time is 2h-12h.

[0011] In some embodiments of the present application, the rare earth oxide / molybdenum oxide precursor is obtained by impregnating a rare earth-containing solution in molybdenum oxide powder and drying it, and calcining it in air, wherein the calcination temperature is 400°C-700°C, the calcination time is 2h-12h, and the rare earth-containing solution is selected from a rare earth nitrate solution or a rare earth chloride solution.

[0012] In some embodiments of the present application, the temperature of the heat treatment is 750°C-800°C, and the time of the heat treatment is 2h-12h.

[0013] In some embodiments of the present application, the reduction temperature is 250° C.-450° C., and the reduction time is 1 h-3 h.

[0014] The second aspect of the present application provides a metal-rare earth / molybdenum nitride catalyst prepared by the preparation method in any of the aforementioned embodiments, wherein the loading amount of the metal element is 0.2wt%-5wt%, and the doping amount of the rare earth element is 0.5wt%-10wt%.

[0015] The third aspect of the present application provides a use of a metal-rare earth / molybdenum nitride catalyst prepared by the preparation method in any of the aforementioned embodiments for hydrogen production by methanol-water reforming.

[0016] The present application provides a metal-rare earth / molybdenum nitride catalyst and its preparation method and use. By regulating the rare earth type, rare earth dosage, metal type, metal content and pretreatment temperature, a metal-rare earth / molybdenum nitride catalyst with low temperature, high efficiency and high stability is obtained, and the efficient catalytic process under less precious metal dosage is achieved. The introduction of cheap rare earth elements significantly improves the stability of the catalyst. The metal-rare earth / molybdenum nitride catalyst of the present application is used for methanol-water reforming hydrogen production, wherein the platinum-rare earth / molybdenum nitride catalyst finally obtains a stability evaluation of more than 1,300 hours, and at the same time reaches a catalytic index of more than 10 million turnover numbers (TON, turnover number).

[0017] Of course, it is not necessary to achieve all the advantages described above at the same time to implement any embodiment of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0019] Figure 1 X-ray diffraction (XRD) patterns of molybdenum nitride, lanthanum oxide, and the catalyst 1Pt / 2La-Mo2N obtained in Example 1, the catalyst 1Pt / 0.5La-Mo2N obtained in Example 11, and the catalyst 1Pt / 10La-Mo2N obtained in Example 12;

[0020] Figure 2 This is a scanning transmission electron microscope (STEM) photograph of the catalyst 1Pt / 2La-Mo2N obtained in Example 1;

[0021] Figure 3 ATOF (apparent turnover frequency)-time point line graph for evaluating the long-term stability of the catalyst 1Pt / 2La-Mo2N obtained in Example 1 and the catalyst 1Pt / γ-Mo2N obtained in Comparative Example 1;

[0022] Figure 4 This is a line graph of hydrogen production rate-time points of catalyst 2La-Mo2N obtained in Comparative Example 2.

[0023] Figure 5 This is a line graph of hydrogen production rate-time of catalyst 1Pt / SiO2 obtained in Comparative Example 8. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of this application.

[0025] The first aspect of the present application provides a method for preparing a metal-rare earth / molybdenum nitride catalyst, which comprises the following steps:

[0026] (1) Preparing a rare earth oxide / molybdenum oxide precursor; wherein the rare earth oxide is selected from at least one of La2O3 (lanthanum oxide), CeO2 (cerium oxide), Y2O3 (yttrium oxide), PrO2 (praseodymium oxide), Nd2O3 (neodymium oxide), Sm2O3 (samarium oxide), Eu2O3 (europium oxide), Gd2O3 (gadolinium oxide), Tb2O3 (terbium oxide), Dy2O3 (dysprosium oxide), Er2O3 (erbium oxide) and Ho2O3 (holmium oxide).

[0027] (2) heat-treating the rare earth oxide / molybdenum oxide precursor in ammonia to obtain a rare earth-molybdenum nitride carrier; wherein the flow rate of ammonia is 10 mL / min-400 mL / min, preferably 60 mL / min-400 mL / min;

[0028] (3) adding a rare earth-molybdenum nitride carrier to a metal precursor solution, stirring under an argon atmosphere, and drying to obtain a catalyst precursor; wherein the metal element in the metal precursor solution is selected from at least one of ruthenium, rhodium, palladium, iridium, platinum, gold, nickel, and cobalt, the mass fraction of the metal solution is 0.01wt%-0.35wt%, and the ratio of the mass of the rare earth-molybdenum nitride carrier to the volume of the metal precursor solution is 400:(10-20)mg / mL;

[0029] (4) reducing the catalyst precursor in a hydrogen / argon mixed atmosphere to obtain a metal-rare earth / molybdenum nitride catalyst; wherein the volume ratio of hydrogen to the argon is 10:(10-100).

[0030] In step (1), the preparation process of the rare earth oxide / molybdenum oxide precursor includes: grinding and mixing the rare earth oxide and molybdenum oxide powder, and then roasting in air at 400°C-700°C for 2h-12h; the roasting temperature is preferably 500°C-550°C. By controlling the roasting temperature within the scope of this application, it is conducive to the full roasting of the rare earth oxide and molybdenum oxide powder, and the full crystallization of the rare earth oxide / molybdenum oxide precursor. The roasting time is preferably 4h-6h. By controlling the roasting time within the scope of this application, it is conducive to the crystal formation of the rare earth oxide / molybdenum oxide precursor and the particle size does not grow too large. The present application does not particularly limit the roasting method, as long as the purpose of the present application can be achieved. For example, a tubular furnace, a muffle furnace, and an oven can be used. In the present application, molybdenum oxide refers to molybdenum oxide, specifically MoO3, MoO2, etc.; molybdenum nitride refers to molybdenum nitride, specifically Mo2N, etc.

[0031] In step (1), the preparation process of the rare earth oxide / MoO3 precursor can also be: firstly impregnate 0.5wt%-10wt% rare earth nitrate solution or 0.5wt%-10wt% rare earth chloride solution into MoO3 powder and dry it, and then roast it in air at 400℃-700℃ for 2h-12h; the roasting temperature is preferably 500℃-600℃, and by controlling the roasting temperature within the scope of the present application, it is beneficial to fully roast the rare earth oxide and MoO3 powder, and fully combine the rare earth and MoO3. The roasting time is preferably 6h-10h, and by controlling the roasting time within the scope of the present application, it is beneficial to fully combine the rare earth and MoO3 and the particle size does not grow too large. The present application does not particularly limit the drying method, as long as the purpose of the present application can be achieved, for example, an oven, a freeze dryer, and an infrared lamp can be used. The present application does not particularly limit the roasting method, as long as the purpose of the present application can be achieved, for example, a tubular furnace, a muffle furnace, and an oven can be used.

[0032] In step (2), the heat treatment temperature is 750°C-800°C, preferably 780°C-790°C. By controlling the heat treatment temperature within the scope of this application, it is conducive to the formation of nitride phase and the formation of a higher specific surface area. The heat treatment time is 2h-12h, preferably 2h-6h, and more preferably 4h-4.5h. By controlling the heat treatment time within the scope of this application, it is conducive to the formation of nitride phase and the formation of a higher specific surface area. The ammonia flow rate is 160mL / min-400mL / min, preferably 200mL / min-350mL / min. By controlling the ammonia flow rate within the scope of this application, it is conducive to the formation of nitride phase and the formation of a higher specific surface area. The present application does not particularly limit the method of heat treatment, as long as the purpose of the present application can be achieved. For example, a tubular furnace or a muffle furnace can be used. The present application does not particularly limit the method of introducing ammonia, as long as the purpose of the present application can be achieved.

[0033] In step (3), the stirring time is 0.5h-2.5h, preferably 1h-1.5h, until the rare earth-molybdenum nitride carrier is uniformly dispersed in the metal precursor solution. The present application has no particular limitation on the drying method in step (3), as long as the purpose of the present application can be achieved. For example, the drying can be performed using a rotary evaporator at a temperature of 0°C-40°C.

[0034] In step (3), the metal precursor solution can be a solution of a compound containing the above-mentioned metal elements. For example, the compound containing the metal element can include but is not limited to at least one of ruthenium chloride, ruthenium nitrate, ruthenium acetate, rhodium chloride, rhodium nitrate, rhodium acetate, palladium chloride, palladium nitrate, palladium acetate, acetylacetonate palladium, chloroiridic acid, iridium nitrate, acetylacetonate iridium, tetraammineplatinum chloride, chloroplatinic acid, platinum nitrate, tetraamminegold chloride, chloroauric acid, gold nitrate, nickel chloride, nickel nitrate, nickel acetate, cobalt chloride, cobalt nitrate, and cobalt acetate.

[0035] In step (3), the reduction temperature is 250°C-450°C, preferably 350°C-400°C. By controlling the reduction temperature within the scope of the present application, it is beneficial for the active metal and the active molybdenum nitride carrier to be fully reduced, and the generation of too many defects on the catalyst surface is not allowed. The reduction time is 1h-3h, preferably 1.5h-2.5h. By controlling the reduction time within the scope of the present application, it is beneficial for the active metal and the active molybdenum nitride carrier to be reduced, and the generation of too many defects on the catalyst surface is not allowed. The volume ratio of hydrogen to argon is preferably 10:90, and the precursor is reduced by hydrogen to obtain a gray-black powdery solid, i.e., a metal-rare earth / molybdenum nitride catalyst. In the present application, active metal refers to the above-mentioned metal element.

[0036] The second aspect of the present application provides a metal-rare earth / molybdenum nitride catalyst prepared by the method provided in the first aspect of the present application, wherein, based on the mass of the metal-rare earth / molybdenum nitride catalyst, the loading amount of the metal element is 0.2wt%-5wt%, and the doping amount of the rare earth element as an auxiliary agent is 0.5wt%-10wt%. The present application uses less precious metals and has lower costs. The highly dispersed metal / molybdenum nitride interface realizes a low-temperature and efficient methanol-water reforming reaction. The introduction of atomic-level rare earth auxiliary agents significantly improves the stability of the catalyst, obtains a stability evaluation of more than 1,300 hours, and achieves a catalytic index of more than 10 million turnover numbers (TON).

[0037] The third aspect of the present application provides a use of a metal-rare earth / molybdenum nitride catalyst prepared by the preparation method in any of the aforementioned embodiments for hydrogen production by methanol-water reforming.

[0038] Example

[0039] Test methods and equipment:

[0040] XRD test:

[0041] The X-ray powder diffraction (XRD) spectrum was collected by a PANalytical Powder X-ray diffractometer. The X-ray powder diffractometer has a Cu-Kα target, and the voltage of the X-ray tube is 40kV and the current is 40mA. The samples were all exposed to air for offline testing after being passivated for 12 hours at room temperature by passing through a 0.5% O2 / 99.5% Ar atmosphere. Among them, the 0.5% O2 / 99.5% Ar atmosphere means that based on the total volume of the atmosphere, the volume percentage of O2 is 0.5%, and the volume percentage of Ar is 99.5%.

[0042] Morphological characterization:

[0043] The imaging and EDS spectroscopic characterization of the samples were performed using a spherical aberration-corrected electron microscope (Titan, FEI Company, USA). The operating voltage was 300 kV, the incident electron convergence angle of the electron microscope was 25 mrad, and the half-collection angle of the STEM imaging mode was 53-260 mrad. The samples were dispersed in an ethanol solution and directly dripped on the microgrid for testing.

[0044] Element content determination:

[0045] The catalysts prepared in the examples and comparative examples were digested with aqua regia by microwave at room temperature, and then the loading amount of metal elements and the doping amount of rare earth elements were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES) on a Prodigy 7 instrument.

[0046] Long-term stability evaluation:

[0047] ATOF of long-term stability evaluation of 1Pt / 2La-Mo2N (Example 1) and 1Pt / γ-Mo2N (Comparative Example 1).

[0048] Reaction conditions: catalyst, 150 mg, 40-60 mesh; temperature, 200°C; pressure: 5 bar; methanol: water = 1:3 (molar ratio); WHSV methanol (weight hourly space velocity) = 12.87h -1 .

[0049] The methanol-water steam reforming experiment was carried out in a dual-channel gas-solid phase reactor. The reaction raw liquid was pumped into the reaction device at a constant flow rate by a high-pressure injection pump. The raw liquid with a specific ratio was first mixed with an inert carrier at the front end of the gasifier, and then passed through the coil in the gasifier at 150°C to fully vaporize the liquid and flow into the reactor and flow through the catalyst bed. The catalyst was loaded into a straight quartz tube with an outer diameter of 6mm and an inner diameter of 4mm. The upper end was isolated with quartz wool and filled with quartz sand about 10cm high to make the raw liquid more fully vaporized before flowing through the catalyst. After the reaction raw gas and inert gas mixed and flowed through the reaction chamber, they passed through three-stage series condensers in sequence to cool the unreacted methanol and water as much as possible, so that the dry gas products (H2, CO2, CO, CH4) and the inert gas with internal standard entered the chromatogram. The gas products of the reaction were analyzed online by Agilent 6890GC gas chromatograph, and the unreacted residual liquid was recovered by the condenser. After accumulating a certain amount, it was analyzed by liquid chromatography. The gas phase products were analyzed using an Agilent HP-5 capillary column, and the gas phase products (H2, CO2, CO, CH4) and inert carrier gas (Ar, N2) generated by the reaction were detected by a thermal conductivity detector (TCD).

[0050] Quality Activity Test:

[0051] Mass activity of 2La-Mo2N (Comparative Example 2) and 1Pt / SiO2 (Comparative Example 8).

[0052] Reaction conditions: catalyst, 150 mg, 40-60 mesh; temperature, 200°C; pressure: 5 bar; methanol: water = 1:3 (molar ratio); WHSV methanol =12.87h -1 .

[0053] Example 1

[0054] <Preparation of Platinum-Rare Earth / Molybdenum Nitride Catalyst 1Pt / 2La-Mo2N>

[0055] 0.4 g of La2O3 powder and 2 g of MoO3 powder were fully ground and mixed, and calcined at 500° C. for 6 h in air to obtain a La2O3 / MoO3 oxide precursor, wherein the mass percentage of La was 2 wt % based on the mass of the La2O3 / MoO3 oxide precursor.

[0056] Next, the La2O3 / MoO3 oxide precursor was heat treated at 785°C for 4 hours under 300 mL / min of ammonia to obtain a 2La-Mo2N carrier. 400 mg of the obtained 2La-Mo2N carrier was added to 15 mL of an aqueous solution of H2PtCl6 with a solute mass fraction of 0.061 wt%, and stirred for 1 hour under an argon atmosphere until a uniform turbid liquid was obtained. The obtained turbid liquid was dried by rotary evaporation to obtain a catalyst precursor.

[0057] The obtained catalyst precursor was reduced at 350° C. for 2 h in a mixed atmosphere of hydrogen and argon with a volume ratio of 10:90 for activation to obtain a platinum-rare earth / molybdenum nitride catalyst 1Pt / 2La-Mo2N.

[0058] Example 2

[0059] Except that the rare earth oxide La2O3 is replaced by CeO2, the rest is the same as Example 1.

[0060] Example 3

[0061] Except for replacing the rare earth oxide La2O3 with Y2O3, the rest is the same as Example 1.

[0062] Example 4

[0063] Except for replacing the rare earth oxide La2O3 with PrO2, the rest is the same as Example 1.

[0064] Example 5

[0065] Except for replacing the rare earth oxide La2O3 with Sm2O3, the rest is the same as Example 1.

[0066] Example 6

[0067] Except for replacing the rare earth oxide La2O3 with Ho2O3, the rest is the same as Example 1.

[0068] Example 7

[0069] The process is the same as in Example 1 except that the La2O3 powder and the MoO3 powder are fully ground and mixed, and the La(NO3)2 solution is impregnated into the MoO3 powder and then dried.

[0070] Example 8

[0071] The process is the same as in Example 1 except that the La2O3 powder and the MoO3 powder are fully ground and mixed, and the LaCl2 solution is impregnated into the MoO3 powder and then dried.

[0072] Example 9

[0073] Except that the H2PtCl6 solution with a solute mass fraction of 0.061wt% is replaced by the H2PtCl6 solution with a solute mass fraction of 0.0122wt%, the rest is the same as Example 1.

[0074] Example 10

[0075] Except that the H2PtCl6 solution with a solute mass fraction of 0.061wt% is replaced by the H2PtCl6 solution with a solute mass fraction of 0.305wt%, the rest is the same as Example 1.

[0076] Embodiment 11

[0077] Except that the mass ratio of La2O3 powder to MoO3 powder is adjusted so that the mass fraction of La is 0.5wt%, the rest is the same as Example 1.

[0078] Example 12

[0079] Except that the mass ratio of La2O3 powder to MoO3 powder is adjusted so that the mass fraction of La is 10wt%, the rest is the same as Example 1.

[0080] Example 13

[0081] Except that the activation was performed at 250°C for 2h instead of 350°C for reduction, the rest was the same as in Example 1.

[0082] Embodiment 14

[0083] The activation was performed at 450°C for 2 h instead of 350°C for 2 h, and the rest was the same as in Example 1.

[0084] Embodiment 15

[0085] Except for replacing the H2PtCl6 aqueous solution with the RuCl3 aqueous solution, the rest is the same as Example 1.

[0086] Example 16

[0087] Except that the H2PtCl6 aqueous solution is replaced by the RhCl3 aqueous solution, the rest is the same as Example 1.

[0088] Embodiment 17

[0089] Except that the H2PtCl6 aqueous solution is replaced by the PdCl2 aqueous solution, the rest is the same as Example 1.

[0090] Embodiment 18

[0091] Except for replacing the H2PtCl6 aqueous solution with the H2IrCl6 aqueous solution, the rest is the same as Example 1.

[0092] Embodiment 19

[0093] Except that the H2PtCl6 aqueous solution was replaced by the HAuCl4 aqueous solution, the rest was the same as Example 1.

[0094] Embodiment 20

[0095] Except that the H2PtCl6 aqueous solution is replaced by Ni(NO3)2 aqueous solution and the reduction temperature is 450°C, the rest is the same as Example 1.

[0096] Embodiment 21

[0097] Except that the H2PtCl6 aqueous solution is replaced by Co(NO3)2 aqueous solution and the reduction temperature is 450°C, the rest is the same as Example 1.

[0098] Comparative Example 1

[0099] <Preparation of Catalyst 1Pt / γ-Mo2N>

[0100] 2g of MoO3 powder was heat treated at 785℃ for 4h under 300mL / min of ammonia to obtain a γ-Mo2N carrier. Then, 400mg of the obtained γ-Mo2N carrier was added to 15mL of H2PtCl6 solution with a solute mass fraction of 0.061wt%, and stirred for 1h under argon atmosphere until a uniform turbid liquid was obtained. The obtained turbid liquid was dried by rotary evaporation to obtain a catalyst precursor. The obtained catalyst precursor was reduced at 350℃ for 2h in a mixed atmosphere of hydrogen and argon with a volume ratio of 10:90 to obtain a catalyst 1Pt / γ-Mo2N.

[0101] Comparative Example 2

[0102] <Preparation of Catalyst 2La-Mo2N>

[0103] 0.4g of La2O3 powder and 2g of MoO3 powder were fully ground and mixed, and calcined at 500℃ in air for 12h to obtain La2O3 / MoO3 oxide precursor. Then, the oxide precursor was heat treated at 785℃ for 4h under 300mL / min ammonia to obtain 2La-Mo2N carrier. The obtained 2La-Mo2N carrier was directly reduced at 350℃ for 2h in a mixed atmosphere of hydrogen and argon with a volume ratio of 10:90 to obtain catalyst 2La-Mo2N.

[0104] Comparative Example 3

[0105] The La2O3 powder and the MoO3 powder are fully ground and mixed, and the Nb2O5 powder and the MoO3 powder are fully ground and mixed instead. The rest is the same as in Example 1.

[0106] Comparative Example 4

[0107] The La2O3 powder and the MoO3 powder are fully ground and mixed, and Ga(NO3)3 powder and the MoO3 powder are replaced by fully ground and mixed. The rest is the same as Example 1.

[0108] Comparative Example 5

[0109] The La2O3 powder and the MoO3 powder are fully ground and mixed, and the V2O5 powder and the MoO3 powder are fully ground and mixed instead. The rest is the same as in Example 1.

[0110] Comparative Example 6

[0111] The La2O3 powder and the MoO3 powder are fully ground and mixed, and the Zr(NO3)4 powder and the MoO3 powder are replaced by fully ground and mixed. The rest is the same as Example 1.

[0112] Comparative Example 7

[0113] The La2O3 powder and the MoO3 powder are fully ground and mixed, and the Mn(NO3)2 powder and the MoO3 powder are replaced by fully ground and mixed. The rest is the same as Example 1.

[0114] Comparative Example 8

[0115] <Preparation of Catalyst 1Pt / SiO2>

[0116] 1Pt / SiO2 was prepared by an isovolumetric precipitation method. First, 800 μL of H2PtCl6 aqueous solution (0.061 wt%) was added dropwise to 1 g of hydrophilic SiO2 powder (CAS No.: 60676-86-0), stirred until completely dry, and dried in a vacuum oven at 60°C overnight. After that, the catalyst 1Pt / SiO2 was activated in an atmosphere of 10% H2 / 90% Ar at 350°C for 2 hours before being used for reaction or characterization. Among them, the 10% H2 / 90% Ar atmosphere means that based on the total volume of the atmosphere, the volume percentage of H2 is 10% and the volume percentage of Ar is 90%.

[0117] The preparation parameters of each embodiment and comparative example are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] Note: “ / ” in Table 1 indicates that there is no corresponding preparation parameter or performance.

[0122] Catalyst performance

[0123] The performance of the catalyst for methanol-water reforming reaction was evaluated in a fixed bed catalyst. 150 mg of catalyst with a 40-60 mesh size was filled into the catalyst bed. -1 The mixture was heated to 200°C (catalytic experiment temperature) under nitrogen flow and the system pressure was 5 bar. Then, a solution with a molar ratio of methanol to water = 1:3 was introduced through a high-pressure injection pump at a flow rate of 5.7 mL / h to carry out the reduction reaction. The H2 content at the outlet of the cooler was analyzed by chromatography to obtain the ATOF value and the average hydrogen production rate, and it was calculated that the ATOF value could be maintained at 7000 mol H2 ·mol metal -1 ·h -1 The calculation formula of ATOF value and average hydrogen production rate is as follows:

[0124]

[0125]

[0126] Wherein, n(H2) refers to the amount of hydrogen (H2), n(metal) refers to the amount of active metal element in the catalyst, m(catalyst) refers to the mass of the catalyst, and t refers to time. The above-mentioned "active metal element" refers to one of the elements of ruthenium, rhodium, palladium, iridium, platinum, gold, nickel, and cobalt loaded.

[0127] Using the above method, the catalysts obtained in Examples 1 to 14 and Comparative Examples 1 to 8 were used for methanol-water catalytic reforming reaction. The catalytic results are shown in Table 2.

[0128] Table 2

[0129]

[0130]

[0131] Note: “ / ” in Table 2 indicates that there is no corresponding performance.

[0132] As can be seen from Table 2, the use of the metal-rare earth / molybdenum nitride catalyst provided in this application to catalyze the methanol-water reforming hydrogen production reaction has ultra-long stability and a high hydrogen production rate. Under the condition of a catalytic temperature of 200°C, the average hydrogen production rate of the methanol-water reforming reaction catalyzed by the catalyst 1Pt / 2La-Mo2N in Example 1 is 86μmol·g cat -1 ·s -1 The average hydrogen production rate of the catalyst 1Pt / γ-Mo2N in Comparative Example 1 was only 44 μmol·g cat -1 ·s -1 , proving the high efficiency of the catalyst after doping with rare earth elements. In addition, the ATOF value of the catalyst 1Pt / 2La-Mo2N in Example 1 for methanol-water reforming reaction is 7000 mol H2 ·mol metal -1 ·h -1 The above can be maintained for at least 1000h, while the ATOF value of the catalyst 1Pt / γ-Mo2N in Comparative Example 1 is 7000mol H2 ·mol metal -1 ·h -1 The above condition can only be maintained for 140 h, which proves the ultra-long stability of the catalyst after doping with rare earth elements.

[0133] Specifically, Figure 1The XRD spectra of the catalyst 1Pt / 2La-Mo2N in Example 1, the catalyst 1Pt / 0.5La-Mo2N in Example 11, the catalyst 1Pt / 10La-Mo2N in Example 12, La2O3 powder and Mo2N powder, show that in 1Pt / 2La-Mo2N, 1Pt / 0.5La-Mo2N and 1Pt / 10La-Mo2N, strong diffraction peaks of 2θ of 37°, 43°, 63° and 75° are observed, which correspond to the diffraction peaks of Mo2N, proving that the Mo2N skeleton is retained in each of the prepared catalysts and has a face-centered cubic crystal structure. At the same time, no characteristic diffraction peaks of lanthanum oxide are observed, proving that the rare earth element La is successfully incorporated as an auxiliary agent and presents a highly dispersed structure, which is conducive to the efficient utilization of rare earth elements and the full modification of the surface.

[0134] Figure 2 This is a scanning transmission electron microscope photograph of the catalyst 1Pt / 2La-Mo2N in Example 1. From the high-angle annular dark field imaging results, it can be seen that, microscopically, the catalyst is composed of dense aggregates of porous nanoparticles with a size of hundreds of nanometers.

[0135] Figure 3 The ATOF-time point line diagram of the catalyst 1Pt / 2La-Mo2N in Example 1 and the catalyst 1Pt / γ-Mo2N in Comparative Example 1 of the same mass used for catalyzing the methanol-water reforming reaction shows that both catalysts show increasingly higher ATOF values ​​in the 0h-50h and 0h-200h stages, indicating that the rate of hydrogen production by the catalytic reforming reaction per unit mass of metal per unit time is increasing. However, after 30h, the catalytic efficiency of the undoped rare earth catalyst 1Pt / γ-Mo2N drops rapidly, and its ATOF value drops to 5600mol / mol after 200h of reaction. H2 ·mol metal -1 ·h -1 The ATOF value of the rare earth-doped 1Pt / 2La-Mo2N catalyst was still 7800 mol after 1300 hours of reaction. H2 ·mol metal -1 ·h -1 , which proves the long-term stability of the 1Pt / 2La-Mo2N catalyst. This is because the addition of rare earth elements significantly improves the antioxidant ability of the catalyst, thereby improving the reaction stability.

[0136] Figure 4 and Figure 5The hydrogen production rate-time point line graphs of catalyst 2La-Mo2N in comparative example 2 and catalyst 1Pt / SiO2 in comparative example 8 show that both of them show low catalytic activity within the test time range. Specifically, the average hydrogen production rate of catalyst 2La-Mo2N is 0.6 μmol·g in 0h-100h. cat -1 ·s -1 The average hydrogen production rate of the catalyst 1Pt / SiO2 is 0.75 μmol·g cat -1 ·s -1 , while the average hydrogen production rate of the catalyst 1Pt / 2La-Mo2N in Example 1 is 86 μmol·g cat -1 ·s -1 , which is much greater than the mass activity of the catalysts in the above two comparative examples. This result proves that in order to achieve a high catalytic efficiency of the catalyst, both the doping of rare earth elements and the loading of Pt are indispensable. This is because the highly dispersed platinum / molybdenum nitride interface is conducive to the efficient dissociation and catalytic conversion of methanol and water, while the rare earth elements are conducive to improving the antioxidant performance of the catalyst.

[0137] In summary, the metal-rare earth / molybdenum nitride catalyst provided by the present application can catalyze the methanol-water reforming hydrogen production reaction at low temperature and high efficiency, has high metal utilization, uses less precious metals in the preparation process, and has low cost. The introduction of atomic-level rare earth additives significantly improves the stability of the catalyst, and ultimately obtains a stability evaluation of more than 1,300 hours, while achieving a catalytic index of more than 10 million turnover numbers (TON).

[0138] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A method for preparing a metal-rare earth / molybdenum nitride catalyst, comprising the following steps: (1) preparing a rare earth oxide / molybdenum oxide precursor; wherein the rare earth oxide is selected from at least one of La2O3, CeO2, Y2O3, PrO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Er2O3 and Ho2O3; (2) heat-treating the rare earth oxide / molybdenum oxide precursor in ammonia to obtain a rare earth-molybdenum nitride carrier; wherein the flow rate of the ammonia is 10 mL / min-400 mL / min; (3) adding the rare earth-molybdenum nitride carrier to a metal precursor solution, stirring under an argon atmosphere, and drying to obtain a catalyst precursor; wherein the metal element in the metal precursor solution is selected from at least one of ruthenium, rhodium, palladium, iridium, platinum, gold, nickel, and cobalt, the mass fraction of the metal precursor solution is 0.01wt%-0.35wt%, and the ratio of the mass of the rare earth-molybdenum nitride carrier to the volume of the metal precursor solution is 400:(10-20)mg / mL; (4) reducing the catalyst precursor in a hydrogen / argon mixed atmosphere to obtain the metal-rare earth / molybdenum nitride catalyst; wherein the volume ratio of the hydrogen to the argon is 10:(10-100).

2. The preparation method according to claim 1, wherein The rare earth oxide / molybdenum oxide precursor is obtained by grinding and mixing rare earth oxide powder and molybdenum oxide powder, and calcining in air, wherein the calcination temperature is 400° C.-700° C., and the calcination time is 2 h-12 h.

3. The preparation method according to claim 1, wherein The rare earth oxide / molybdenum oxide precursor is obtained by impregnating molybdenum oxide powder with a rare earth-containing solution, drying it, and calcining it in air, wherein the calcination temperature is 400°C-700°C, the calcination time is 2h-12h, and the rare earth-containing solution is selected from a rare earth nitrate solution or a rare earth chloride solution.

4. The preparation method according to claim 1, wherein The temperature of the heat treatment is 750° C.-800° C., and the time of the heat treatment is 2 h-12 h.

5. The preparation method according to claim 1, wherein The reduction temperature is 250° C.-450° C., and the reduction time is 1 h-3 h.

6. A metal-rare earth / molybdenum nitride catalyst prepared by the preparation method according to any one of claims 1 to 5, wherein: The loading amount of the metal element is 0.2wt%-5wt%, and the doping amount of the rare earth element is 0.5wt%-10wt%.

7. Use of the metal-rare earth / molybdenum nitride catalyst prepared by the preparation method according to any one of claims 1 to 5 for producing hydrogen by methanol-water reforming.

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