Ruthenium-based supported catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a ruthenium-based supported catalyst as well as a preparation method and application thereof. The ruthenium-based supported catalyst provided by the invention comprises a composite carrier and ruthenium supported on the composite carrier, the composite carrier is one or more of a perovskite type metal oxide and an alkali metal oxide, an alkali metal hydroxide, an alkaline earth metal oxide and an alkaline earth metal hydroxide which are dispersed on the surface of the perovskite type metal oxide; the preparation method of the composite carrier comprises the following steps: mixing a perovskite type oxide with an alkali metal hydride and / or an alkaline earth metal hydride, and carrying out first calcination; soaking the first calcined product in a solvent to obtain a composite carrier; the perovskite type oxide comprises one or two of MgTiO3 (magnesium titanate), SrTiO5 (strontium titanate), BaTiO3 (barium titanate) and CaTiO3 (calcium titanate); the solvent comprises an alcohol solvent and / or water. The catalyst provided by the invention can catalyze an ammonia synthesis reaction under a relatively low pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a ruthenium-based supported catalyst and a preparation method and application thereof. Background Art

[0002] Synthetic ammonia is one of the most important basic chemicals in the chemical industry. The traditional Haber-Bosch process for synthesizing ammonia requires the extensive use of iron oxide catalysts and potassium hydroxide promoters. However, this method must be carried out under high temperature (300-500°C) and high pressure (20-40MPa). These harsh production conditions (high temperature and high pressure) pose a huge challenge to environmental protection, and they also produce large carbon dioxide emissions and high energy consumption.

[0003] Compared to traditional iron-based ammonia synthesis catalysts, ruthenium-based ammonia synthesis catalysts can effectively activate nitrogen molecules under low-temperature and low-pressure conditions, achieving excellent catalytic performance and significantly reducing energy consumption in the ammonia synthesis process. Ruthenium-based ammonia synthesis catalysts supported on graphitized activated carbon have achieved industrial application (KAAP process). However, carbon materials are prone to methanation reactions under ammonia synthesis conditions, which reduces the catalyst's stability and service life. Therefore, developing an ammonia synthesis catalyst with high activity, low energy consumption, and high stability is of great significance. Summary of the Invention

[0004] In view of this, the present invention provides a ruthenium-based supported catalyst and its preparation method and application. The catalyst provided by the present invention has high stability and good catalytic activity for synthesizing ammonia, can be used for synthesizing ammonia at a lower pressure and has a long service life.

[0005] In order to solve the above technical problems, the present invention provides a ruthenium-based supported catalyst, comprising a composite support and ruthenium supported on the composite support;

[0006] The composite support is a perovskite-type metal oxide and one or more of an alkali metal oxide, an alkali metal hydroxide, an alkaline earth metal oxide, and an alkaline earth metal hydroxide dispersed on the surface of the perovskite-type metal oxide;

[0007] The preparation method of the composite carrier comprises the following steps:

[0008] A perovskite-type oxide and a metal hydride are mixed and then subjected to a first calcination, and the first calcined product is immersed in a first solvent to obtain the composite support; the perovskite-type oxide includes one or two of MgTiO3, SrTiO5, BaTiO3 and CaTiO3; the metal hydride includes an alkali metal hydride and / or an alkaline earth metal hydride; and the first solvent includes an alcohol solvent and / or water.

[0009] Preferably, the mass percentage of ruthenium in the ruthenium-based supported catalyst is 0.5-2.6%.

[0010] Preferably, the molar ratio of hydrogen element in the metal hydride to titanium element in the perovskite-type oxide is (1-7):1.

[0011] Preferably, the temperature of the first calcination is 400-850°C, and the holding time of the first calcination is 5-288h;

[0012] The first calcination is carried out under vacuum conditions, and the vacuum degree of the vacuum conditions is 10 -1 ~10 -5 Pa.

[0013] Preferably, the soaking time is 0.5 to 24 hours, and the mass ratio of the volume of the first solvent to the first calcined product is 100 mL:1 to 25 g.

[0014] Preferably, the mass percentage of the perovskite-type metal oxide in the ruthenium-based supported catalyst is 40 to 95%.

[0015] The present invention also provides a method for preparing the ruthenium-based supported catalyst described in the above technical solution, comprising the following steps:

[0016] The composite support, the ruthenium source and the second solvent are mixed and then calcined for the second time to obtain the ruthenium-based supported catalyst.

[0017] Preferably, the ruthenium source comprises an organic ruthenium complex or an inorganic ruthenium salt;

[0018] The second solvent includes a polar organic solvent or water;

[0019] The mixing is stirred under vacuum conditions; after the mixing, the method further comprises: removing the second solvent from the mixed system;

[0020] The temperature of the second calcination is 25 to 500° C., and the holding time of the second calcination is 0.5 to 24 hours;

[0021] The second calcination is carried out under vacuum, protective atmosphere or air conditions; the heating rate of the second calcination is 1-10°C / min.

[0022] The present invention also provides the use of the ruthenium-based supported catalyst described in the above technical solution or the ruthenium-based supported catalyst prepared by the preparation method described in the above technical solution in synthesizing ammonia.

[0023] Preferably, the temperature for synthesizing ammonia using the ruthenium-based supported catalyst is 350-470° C. and the pressure is 1-10 MPa.

[0024] The present invention provides a ruthenium-based supported catalyst, comprising a composite support and ruthenium supported on the composite support; the composite support is a perovskite-type metal oxide and one or more of an alkali metal oxide, an alkali metal hydroxide, an alkaline earth metal oxide and an alkaline earth metal hydroxide dispersed on the surface of the perovskite-type metal oxide; a method for preparing the composite support comprises the following steps: mixing the perovskite-type oxide and a metal hydride, performing a first calcination, and immersing the product after the first calcination in a first solvent to obtain the composite support; the perovskite-type oxide comprises one or two of MgTiO3, SrTiO5, BaTiO3 and CaTiO3; the metal hydride comprises an alkali metal hydride and / or an alkaline earth metal hydride; and the first solvent comprises an alcohol solvent and / or water. In the present invention, the Mg, Ca, Sr, or Ba (derived from perovskite-type oxides) in the composite support has a strong electron-donating ability, which promotes the bond-breaking effect of ruthenium (Ru) atoms on N≡N. The activated composite support material can capture N2 molecules and weaken N≡N. It can also quickly transfer hydrogen atoms generated by H2 dissociation on Ru to the support, reducing hydrogen poisoning of Ru and improving the stability of the catalyst. At the same time, the presence of alkali metals and / or alkaline earth metals in the composite support can synergistically enhance the electron-donating ability of the composite support through atomic interactions, further improving the activity of the catalyst. When using the ruthenium-based supported catalyst provided by the present invention for ammonia synthesis, very high catalytic activity can be obtained at relatively low pressures (1 to 10 MPa), significantly reducing the energy consumption of the ammonia synthesis reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD spectra of the carriers prepared in Example 3 and Comparative Example 1 are shown;

[0026] Figure 2 Column comparison chart of the catalysts obtained in Examples 1 to 8 and Comparative Examples 1 to 2 and the ammonia synthesis rate;

[0027] Figure 3 The dotted line graph shows the ammonia synthesis rate of the ruthenium-based supported catalyst prepared in Example 3 within 120 hours. DETAILED DESCRIPTION

[0028] The present invention provides a ruthenium-based supported catalyst, comprising a composite support and ruthenium supported on the composite support;

[0029] The composite support is a perovskite-type metal oxide and one or more of an alkali metal oxide, an alkali metal hydroxide, an alkaline earth metal oxide, and an alkaline earth metal hydroxide dispersed on the surface of the perovskite-type metal oxide;

[0030] The preparation method of the composite carrier comprises the following steps:

[0031] A perovskite-type oxide and a metal hydride are mixed and then subjected to a first calcination, and the first calcined product is immersed in a first solvent to obtain the composite support; the perovskite-type oxide includes one or two of MgTiO3, SrTiO5, BaTiO3 and CaTiO3; the metal hydride includes an alkali metal hydride and / or an alkaline earth metal hydride; and the first solvent includes an alcohol solvent and / or water.

[0032] As a specific embodiment of the present invention, the ruthenium-based supported catalyst includes an active component ruthenium, and the mass percentage of ruthenium in the ruthenium-based supported catalyst can be 0.5-2.6%, specifically 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.2% or 2.6%.

[0033] In the present invention, the preparation method of the composite carrier comprises the following steps:

[0034] The perovskite-type oxide and the metal hydride are mixed and then subjected to a first calcination, and the product after the first calcination is immersed in a first solvent to obtain the composite support.

[0035] As a specific embodiment of the present invention, the perovskite oxide includes one or two of MgTiO3, SrTiO5, BaTiO3 and CaTiO3, and can be specifically MgTiO3, SrTiO5, BaTiO3 or CaTiO3; the metal hydride includes alkali metal hydride and / or alkaline earth metal hydride; the alkali metal hydride can include one or more of lithium hydride, sodium hydride and potassium hydride; the alkaline earth metal hydride can include one or more of calcium hydride, magnesium hydride and barium hydride; the molar ratio of hydrogen element to perovskite oxide in the metal hydride can be 1 to 7:1, and can be specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1 or 7:1. As a specific embodiment of the present invention, the mixing can be stirred or ground under vacuum conditions or in a protective atmosphere; the vacuum degree of the vacuum condition can be 10 -1 ~10 -5 Pa, the protective atmosphere may include nitrogen or argon.

[0036] As a specific embodiment of the present invention, the first solvent may include an alcohol solvent and / or water, and may specifically be a mixed solvent of an alcohol solvent and water, an alcohol solvent, or water; the alcohol solvent may include methanol, ethanol, or ethylene glycol, and the water may be deionized water; when the first solvent is a mixture of an alcohol solvent and water, the present invention has no special requirements for the mass ratio of the alcohol solvent to water, and any ratio may be used. As a specific embodiment of the present invention, the volume ratio of the first solvent to the mass ratio of the first calcined product may be 100 mL:1-25 g, or 100 mL:5-20 g, or further 100 mL:10-15 g.

[0037] As a specific embodiment of the present invention, the temperature of the first calcination can be 400-850°C, specifically 400°C, 450°C, 500°C, 550°C, 580°C, 600°C, 650°C, 700°C, 750°C, 800°C or 850°C; the holding time of the first calcination can be 5-288h, 24-200h, and further 50-150h; the first calcination can be carried out under vacuum conditions, and the vacuum degree of the vacuum conditions can be 10 -1 ~10 -5 Pa, can also be 10 -2 ~10 -4 In the present invention, an excessively high first calcination temperature and an excessively long first calcination time will cause the carrier particles to agglomerate; an excessively low first calcination temperature and an excessively short first calcination time will result in incomplete activation of the carrier, resulting in a poor final catalytic effect; when the vacuum degree is too low, the material reacts with oxygen and carbon dioxide in the air, the proportion of carbonate (e.g., BaCO3) in the product increases, and the carrier activity is poor; when the vacuum degree is too high, the experimental conditions are harsh, the requirements for equipment and instruments are high, and the synthesis cost is high.

[0038] As a specific embodiment of the present invention, the soaking can be accompanied by stirring; the soaking temperature can be room temperature, and the room temperature can be 20-35°C, or 25-30°C; the soaking time can be 0.5-24h, or 5-20h.

[0039] The present invention decomposes the metal hydride through a first calcination, and the generated hydrogen replaces part of the oxygen in the perovskite-type oxide to form an alkali metal and / or alkaline earth metal element. The alkali metal and / or alkaline earth metal element further reacts to generate oxides and / or hydroxides during immersion in a first solvent; the generated oxides and / or hydroxides are uniformly dispersed on the surface of the perovskite-type oxide particles to activate them; the ruthenium-based supported catalyst provided by the present invention needs to be activated before use.

[0040] As a specific embodiment of the present invention, the soaking may further include: performing solid-liquid separation on the soaked system, and drying the solid obtained by the solid-liquid separation to obtain the composite carrier. As a specific embodiment of the present invention, the solid-liquid separation may include filtration, rotary evaporation or centrifugal separation; the drying time may be 0.5 to 24 hours, 5 to 20 hours, and further 8 to 15 hours. The present invention has no special requirements for the drying temperature, as long as the first solvent on the solid surface can be removed.

[0041] In the present invention, one or more of alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides and alkaline earth metal hydroxides are dispersed in the composite support; the alkali metal oxides may include one or more of lithium oxide, sodium oxide and potassium oxide; the alkali metal hydroxides may include one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide; the alkaline earth metal oxides may include one or more of calcium oxide, magnesium oxide and barium oxide; the alkaline earth metal hydroxides may include one or more of calcium hydroxide, magnesium hydroxide and barium hydroxide; the total mass percentage of the alkali metal and / or alkaline earth metal oxides and the alkali metal and / or alkaline earth metal hydroxides in the composite support may be 5 to 60%, or may be 10 to 50%.

[0042] The present invention also provides a method for preparing the ruthenium-based supported catalyst described in the above technical solution, comprising the following steps:

[0043] The composite support, the ruthenium source and the second solvent are mixed and then calcined for the second time to obtain the ruthenium-based supported catalyst.

[0044] In one embodiment of the present invention, the ruthenium source may include an organic ruthenium complex or an inorganic ruthenium salt; the organic ruthenium complex may be triruthenium dodecacarbonyl or ruthenium acetylacetonate; and the inorganic ruthenium salt may be ruthenium chloride, ruthenium acetate, or ruthenium nitrate. The present invention has no particular requirements for the amount of the ruthenium source, as long as the desired ruthenium loading is achieved.

[0045] As a specific embodiment of the present invention, the solvent may include a polar organic solvent or water; the polar organic solvent may include tetrahydrofuran, acetone or cyclohexane; the present invention has no special limitation on the amount of the solvent, as long as the materials can be mixed evenly. As a specific embodiment of the present invention, the mixing of the composite carrier, the ruthenium source and the solvent may be stirred under vacuum conditions; the vacuum degree of the vacuum conditions may be -0.09 to -0.1 MPa; the stirring may be magnetic stirring, and the time of the magnetic stirring may be 8 to 1440 minutes, specifically 10 minutes. The present invention mixes the composite carrier, the ruthenium source and the solvent under vacuum conditions, which can reduce the hydroxide contained in the composite carrier (generated during the washing process) from absorbing moisture or reacting with CO2 under air conditions.

[0046] As a specific embodiment of the present invention, after the mixing, the further step may be: removing the solvent from the mixed system; the solvent removal method may include rotary evaporation. The present invention has no special requirements for the rotary evaporation, as long as it can remove the solvent.

[0047] As a specific embodiment of the present invention, the temperature of the second calcination can be 25 to 500°C, specifically 25°C, 50°C, 60°C, 120°C, 150°C, 300°C, 350°C or 450°C; the holding time of the second calcination can be 0.5 to 24h, specifically 0.5h, 3h, 4h, 10h, 12h, 15h, 18h, 20h or 24h; the second calcination can be carried out under vacuum, protective atmosphere or air conditions, and the vacuum degree of the vacuum can be 10 -1 ~10 -5 Pa, the protective gas can be nitrogen or argon; the heating rate of the second calcination can be 1-10°C / min, specifically 1°C / min, 2°C / min, 5°C / min, 6°C / min, 8°C / min or 10°C / min.

[0048] The present invention also provides the use of the ruthenium-based supported catalyst described in the above technical solution or the ruthenium-based supported catalyst prepared by the preparation method described in the above technical solution in synthesizing ammonia.

[0049] As a specific embodiment of the present invention, the ruthenium-based supported catalyst provided by the present invention needs to be activated before catalytic ammonia synthesis; the activation atmosphere can be a mixture of hydrogen and nitrogen or pure hydrogen; the volume percentage of hydrogen in the mixture of hydrogen and nitrogen can be 20-100%, specifically 25%, 50%, 75% or 100%; the activation temperature can be 180-500°C, specifically 300°C, 350°C, 400°C, 450°C or 500°C; the activation pressure can be 0-8MPa, specifically atmospheric pressure, 1MPa, 2MPa, 3Mpa, 4MPa, 5Mpa, 6Mpa, 7MPa or 8MPa; the activation time can be 1-30h, specifically 1h, 5h, 10h, 15h, 20h, 25h or 30h.

[0050] As a specific embodiment of the present invention, the temperature for synthesizing ammonia using the ruthenium-based supported catalyst can be 350-470°C, specifically 375°C, 400°C, 425°C or 450°C; the pressure of the synthesized ammonia can be 1-10MPa, specifically 3MPa, 4MPa, 5MPa, 6MPa, 7MPa or 8MPa.

[0051] By utilizing a composite support, the present invention significantly reduces the amount of precious metal Ru used while maintaining high ammonia synthesis activity under low-temperature, low-pressure conditions. The presence of alkali metal and / or alkaline earth metal oxides and hydroxides in the composite support, the relative Ru loading, and the catalyst synthesis method play a crucial role in the catalyst's performance in low-temperature, low-pressure ammonia synthesis. The present invention utilizes a supported Ru-based catalyst for low-pressure ammonia synthesis at a catalytic temperature of 350-470°C and a pressure range of 1-10 MPa, significantly reducing energy consumption during the feed gas pressurization process.

[0052] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] 0.466g (0.002mol) BaTiO3 and 0.042g (0.001mol) CaH2 were stirred and mixed uniformly. -3 Pa under vacuum conditions and calcined at 580 ° C for 144 hours; after cooling, 1 g of the calcined product was evenly dispersed in 100 mL of methanol aqueous solution (a mixture of methanol and deionized water), stirred with a magnetic stirrer for 240 minutes, and then filtered and separated using slow-setting filter paper. The obtained solid was placed in a vacuum drying oven and dried for 12 hours to obtain the desired composite carrier.

[0055] 20 mL of tetrahydrofuran and 21.31 mg of triruthenium dodecacarbonyl were added to the eggplant-shaped flask, and stirred with a magnetic stirrer for 10 min under a vacuum condition of -0.1 MPa. Then 0.5 g of the composite carrier powder was added and the solution was evaporated to dryness at 60 ° C and 0.1 MPa. The collected powder was heated to 10 -3 The catalyst was calcined at 400 nm Pa and 120° C. (heating at a heating rate of 8° C. / min) for 3 h to obtain a ruthenium-based supported catalyst.

[0056] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.5 wt.%.

[0057] Example 2

[0058] The composite support was prepared according to the method of Example 1, except that the amount of CaH2 added was 0.126 g (0.003 mol).

[0059] A ruthenium-based supported catalyst was prepared according to the method of Example 1, except that the composite support prepared in Example 2 was used.

[0060] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.5 wt.%.

[0061] Example 3

[0062] The composite support was prepared according to the method of Example 1, except that the amount of CaH2 added was 0.252 g (0.006 mol).

[0063] A ruthenium-based supported catalyst was prepared according to the method of Example 1, except that the composite support prepared in Example 3 was used.

[0064] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.5 wt.%.

[0065] Example 4

[0066] The active composite carrier was prepared according to the method of Example 1, except that the amount of CaH2 added was 0.294 g (0.007 mol).

[0067] A ruthenium-based supported catalyst was prepared according to the method of Example 1, except that the composite support prepared in Example 4 was used.

[0068] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.5 wt.%.

[0069] Example 5

[0070] The composite carrier was prepared according to the method of Example 3.

[0071] A ruthenium-based supported catalyst was prepared according to the method of Example 3, except that the amount of triruthenium dodecacarbonyl added was changed from 21.31 mg to 10.66 mg.

[0072] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 0.8 wt.%.

[0073] Example 6

[0074] The composite carrier was prepared according to the method of Example 3.

[0075] A ruthenium-based supported catalyst was prepared according to the method of Example 3, except that the amount of triruthenium dodecacarbonyl added was changed from 21.31 mg to 15.98 mg.

[0076] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.2 wt.%.

[0077] Example 7

[0078] The composite carrier was prepared according to the method of Example 3.

[0079] A ruthenium-based supported catalyst was prepared according to the method of Example 3, except that the amount of triruthenium dodecacarbonyl added was changed from 21.31 mg to 26.64 mg.

[0080] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 2.2 wt.%.

[0081] Example 8

[0082] The composite carrier was prepared according to the method of Example 3, except that 0.02 g KH was added. Specifically, 0.466 g (0.002 mol) of BaTiO3, 0.252 g (0.006 mol) of CaH2 and 0.02 g (0.0005 mol) of KH2 were mixed under vacuum at 10 - 3 Pa and stirred under vacuum conditions.

[0083] A ruthenium-based supported catalyst was prepared according to the method of Example 1, except that the composite support prepared in Example 8 was used.

[0084] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 1.5 wt.%.

[0085] Comparative Example 1

[0086] 0.466g (0.002mol) BaTiO3 and 0.252g (0.006mol) CaH2 were stirred and mixed uniformly. -3 calcined at 580 °C for 144 h under vacuum conditions of Pa;

[0087] Take 1 g of the calcined product and evenly disperse it in 100 mL of ammonium chloride methanol solution (the molar concentration of NH4Cl is 0.1 mol / L) and stir it with a magnetic stirrer for 240 minutes. Then, filter it using slow-setting filter paper to separate it. The resulting solid is placed in a vacuum drying oven and dried for 12 hours to obtain a carrier that does not contain calcium oxides and hydroxides.

[0088] Then, 20 mL of tetrahydrofuran and 21.31 mg of triruthenium dodecacarbonyl were added to the eggplant-shaped flask, and magnetic stirring was performed for 10 min under a vacuum condition of -0.1 MPa. Then, 0.5 g of a carrier without calcium oxide and hydroxide was added, and the solution was evaporated to dryness at 60 ° C and 0.1 MPa. The collected powder was heated for 10 min. -3 The ruthenium-based catalyst was obtained by calcining at 120°C for 3 h.

[0089] It was determined that the mass fraction of Ru in the ruthenium-based negative catalyst of this embodiment was approximately 1.5 wt.%.

[0090] Comparative Example 2

[0091] The composite carrier was prepared according to the method of Example 3.

[0092] A ruthenium-based supported catalyst was prepared according to the method of Example 3, except that the amount of triruthenium dodecacarbonyl added was changed from 21.31 mg to 5.33 mg.

[0093] It was determined that the mass fraction of Ru in the ruthenium-based supported catalyst of this embodiment was approximately 0.4 wt.%.

[0094] The carriers prepared in Example 3 and Comparative Example 1 were subjected to X-ray diffraction detection to obtain XRD spectra, as shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the composite carrier prepared in Example 3 contains calcium hydroxide, which indicates that calcium hydroxide is generated during the soaking process of preparing the composite carrier.

[0095] Catalyst performance evaluation:

[0096] 80 mg of each ruthenium-based supported catalyst prepared in Examples 1 to 8 was weighed, and the reaction gas flow rate was 60 mL / min. The ammonia synthesis conversion rate was measured in a continuous flow micro fixed bed reactor. The reaction gas composition was 25% N 2～A 75% H₂ mixture was used. After the catalyst was pre-reduced at 400°C and atmospheric pressure for 5 h, the catalyst conversion rate for ammonia synthesis (average conversion rate per 100 s) was measured at 400°C and 5 MPa. The NH₃ concentration in the tail gas was quantitatively analyzed by gas chromatography (Micro GC 990, Agilent). Inlet temperature: 80°C, column temperature: 80°C, column: Volamine, detector: Thermal conductivity detector (TCD), carrier gas: Helium. An external standard method was used to establish a calibration curve with ammonia standard gas concentrations of 0.1%, 0.3%, 0.5%, 0.69%, 0.98%, 3.04%, 5.05%, 10.09%, and 15.02%. Example calibration curve data are shown in Table 1, and the test results are shown in Table 2.

[0097] The calculation formula for the conversion rate of synthetic ammonia reaction (mmol / g / h) is as follows:

[0098]

[0099] Where: NH3% is the net ammonia value obtained by GC test; f is the reaction flow rate (standard conditions), mL / min; m is the mass of the catalyst, g; 22.4 L / mol is the molar volume of the gas under standard conditions.

[0100] Table 1 Detection results obtained by external standard calibration curve

[0101]

[0102]

[0103] The standard curve obtained according to Table 1 is y=19.4233x-1.5587; R 2 =0.99969.

[0104] Table 2 Catalytic performance of the catalysts obtained in Examples 1 to 8 and Comparative Examples 1 to 2 for catalytic ammonia synthesis

[0105] Example <![CDATA[Ammonia synthesis rate (mmolNH3gcat -1 h -1 ) <!-- 7 -->]]> Example 1 12.95 Example 2 26.85 Example 3 51.15 Example 4 28.69 Example 5 32.70 Example 6 37.34 Example 7 40.61 Example 8 52.87 Comparative Example 1 22.41 Comparative Example 2 3.64

[0106] According to Table 2, a columnar comparison chart of the catalysts obtained in Examples 1 to 8 and Comparative Examples 1 to 2 and the ammonia synthesis rate is drawn, as shown in FIG. Figure 2 Combined with Table 2 and Figure 2 It can be seen that the ammonia synthesis rate of the catalyst indicates that the ammonia synthesis reaction rate is closely related to the activation of the carrier and the ratio of the precious metal loading. Example 8 shows the best ammonia synthesis reaction rate, reaching 52.87mmolNH3 gcat -1 h -1Ammonia synthesis was carried out using the catalyst of Example 3 at 400°C and 5 MPa for 120 h according to the above method. The conversion rate of ammonia synthesis was measured at 24-h intervals (the catalyst was pre-reduced at 400°C and atmospheric pressure for 5 h, then the temperature and pressure were raised to 400°C and 5 MPa, and the temperature and pressure were stabilized for 3 h before testing began). The results are listed in Table 3.

[0107] Table 3 Ammonia synthesis rate of the catalyst of Example 3 at different times during the ammonia synthesis process

[0108]

[0109] According to Table 3, a dotted line graph of the ammonia synthesis rate of the ruthenium-based supported catalyst prepared in Example 3 within 120 hours is drawn, as shown in FIG. Figure 3 shown.

[0110] Combined with Table 3 and Figure 3 It can be seen that the ammonia synthesis rate of the catalyst has no downward trend within 120 hours and remains basically stable, indicating that the catalyst has good catalytic stability.

[0111] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A ruthenium-based supported catalyst, characterized in that It includes a composite carrier and ruthenium loaded on the composite carrier; The composite support is a perovskite-type metal oxide and one or more of an alkali metal oxide, an alkali metal hydroxide, an alkaline earth metal oxide, and an alkaline earth metal hydroxide dispersed on the surface of the perovskite-type metal oxide; The preparation method of the composite carrier comprises the following steps: A perovskite-type oxide and a metal hydride are mixed and then subjected to a first calcination, and the first calcined product is immersed in a first solvent to obtain the composite support; the perovskite-type oxide includes one or two of MgTiO3, SrTiO5, BaTiO3 and CaTiO3; the metal hydride includes an alkali metal hydride and / or an alkaline earth metal hydride; and the first solvent includes an alcohol solvent and / or water.

2. The ruthenium-based supported catalyst according to claim 1, wherein The mass percentage of ruthenium in the ruthenium-based supported catalyst is 0.5-2.6%.

3. The ruthenium-based supported catalyst according to claim 1, wherein The molar ratio of hydrogen element in the metal hydride to titanium element in the perovskite-type oxide is (1-7):

1.

4. The ruthenium-based supported catalyst according to claim 1 or 3, characterized in that The temperature of the first calcination is 400 to 850° C., and the holding time of the first calcination is 5 to 288 hours; The first calcination is carried out under vacuum conditions, and the vacuum degree of the vacuum conditions is 10 -1 ~10 -5 Pa.

5. The ruthenium-based supported catalyst according to claim 1, characterized in that The soaking time is 0.5 to 24 hours, and the mass ratio of the volume of the first solvent to the first calcined product is 100 mL:1 to 25 g.

6. The ruthenium-based supported catalyst according to claim 1, characterized in that The total mass percentage of the alkali metal and / or alkaline earth metal oxides and the alkali metal and / or alkaline earth metal hydroxides in the composite carrier is 5-60%.

7. The method for preparing the ruthenium-based supported catalyst according to any one of claims 1 to 6, characterized in that: The following steps are involved: The composite support, the ruthenium source and the second solvent are mixed and then calcined for the second time to obtain the ruthenium-based supported catalyst.

8. The preparation method according to claim 7, characterized in that: The ruthenium source includes an organic ruthenium complex or an inorganic ruthenium salt; The second solvent includes a polar organic solvent or water; The mixing is stirred under vacuum conditions; after the mixing, the method further comprises: removing the second solvent from the mixed system; The temperature of the second calcination is 25 to 500° C., and the holding time of the second calcination is 0.5 to 24 hours; The second calcination is carried out under vacuum, protective atmosphere or air conditions; the heating rate of the second calcination is 1-10°C / min.

9. Use of the ruthenium-based supported catalyst according to any one of claims 1 to 6 or the ruthenium-based supported catalyst prepared by the preparation method according to claim 7 or 8 in synthesizing ammonia.

10. The use according to claim 9, characterized in that: The temperature for synthesizing ammonia using the ruthenium-based supported catalyst is 350-470° C. and the pressure is 1-10 MPa.

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