CN116020457A - A kind of ruthenium-based catalyst and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of ammonia synthesis catalysts, and provides a ruthenium-based catalyst and its preparation method and application. The ruthenium-based catalyst uses ruthenium as the active catalytic center and YHO as the carrier. The preparation method comprises the following steps: mixing YHO, Ru ₃ (CO) ₁₂ and tetrahydrofuran, performing rotary evaporation and calcining in sequence to obtain an intermediate; and performing a reduction reaction on the intermediate in a hydrogen atmosphere to obtain a ruthenium-based catalyst. The ruthenium-based catalyst obtained by the preparation method of the present invention exhibits excellent activity in the process of synthesizing ammonia, wherein the catalyst with a mass fraction of ruthenium of 2% can synthesize ammonia at a rate of 85mmol·g ^-1 ·h ^-1 at 500°C and 5MPa, It has a good application prospect.

Description

A kind of ruthenium-based catalyst and its preparation method and application

technical field

The invention relates to the technical field of ammonia synthesis catalysts, in particular to a ruthenium-based catalyst and its preparation method and application.

Background technique

As an important chemical raw material and source of nitrogen fertilizer, ammonia supports the survival and development of all human beings and promotes the progress of society. The synthesis of ammonia mainly comes from the Haber-Bosch process, that is, Fe is used as the main catalyst, and an appropriate amount of calcium oxide is added as a co-catalyst to catalyze the reaction of N ₂ and H ₂ to generate NH ₃ . Fe-based catalysts have a series of advantages such as low cost and good stability, but their disadvantages are also obvious, such as low efficiency and the need for high temperature and high pressure reaction conditions (400-500°C, 10-30MPa). With the development of science and technology, a large number of ammonia synthesis catalysts have been prepared, which greatly reduces the reaction conditions of ammonia synthesis and improves the efficiency. Among them, Ru-based catalysts - ammonia synthesis catalysts with Ru as the main catalytic active center and oxides, hydrides, activated carbon, etc. as supports, can reduce the reaction temperature and pressure to a certain extent, but their activity is low. In summary, it is of great significance to provide an ammonia synthesis catalyst with high activity and low energy consumption.

Contents of the invention

The object of the present invention is to overcome the problems existing in the prior art and provide a ruthenium-based catalyst and its preparation method and application.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a ruthenium-based catalyst, the mass fraction of each component in the catalyst is:

Ruthenium 1-2%, YHO 98-99%.

The present invention also provides a preparation method of the ruthenium-based catalyst, comprising the following steps:

(1) mixing YHO, Ru ₃ (CO) ₁₂ and tetrahydrofuran, performing rotary evaporation and calcining in sequence to obtain an intermediate;

(2) In a hydrogen atmosphere, reducing the intermediate to obtain the ruthenium-based catalyst.

Preferably, the mass volume ratio of YHO to tetrahydrofuran in step (1) is 0.8-1.2 g:75-85 mL.

As a preference, the temperature of the rotary steaming in step (1) is 35-45°C, the pressure of the rotary steaming is -0.05--0.15MPa, the rotating speed of the rotary steaming is 170-190r/min, the rotary steaming The time is 8 ~ 12min.

As a preference, the vacuum degree of the calcination in step (1) is -0.05～-0.15MPa, the heating rate of the calcination is 5～7°C/min, the target temperature of the calcination is 380～400°C, reaching the target temperature The final holding time is 3 to 4 hours.

Preferably, the flow rate of hydrogen in step (2) is 95-105 mL/min.

Preferably, the heating rate of the reduction reaction in step (2) is 5-7°C/min, the target temperature of the reduction reaction is 390-410°C, and the holding time after reaching the target temperature is 1-1.5h.

The invention also provides the application of the ruthenium-based catalyst in ammonia synthesis.

The present invention also provides a method for synthesizing ammonia using the ruthenium-based catalyst, comprising the following steps:

Nitrogen, hydrogen and catalyst are mixed and reacted to obtain ammonia.

Preferably, the molar ratio of nitrogen to hydrogen is 1:2.5-3.5; the mass of the catalyst is 0.15-0.25g; the gas flow rate of the reaction is 100-120mL/min, and the reaction temperature is 300- At 500°C, the reaction pressure is 0.1-5 MPa.

The beneficial effects of the present invention are:

The invention provides a preparation method of a ruthenium-based catalyst, comprising the following steps: mixing YHO, Ru ₃ (CO) ₁₂ and tetrahydrofuran, performing rotary evaporation and calcining in sequence to obtain an intermediate; in a hydrogen atmosphere, the intermediate A reduction reaction is carried out to obtain a ruthenium-based catalyst. The ruthenium-based catalyst prepared by the present invention exhibits excellent activity in the process of synthesizing ammonia, wherein the catalyst with 2% ruthenium can synthesize ammonia at a rate of 85mmol·g ^-1 ·h ^-1 at 500°C and 5MPa.

Description of drawings

Fig. 1 is the XRD characterization figure of YHO in embodiment 1;

Fig. 2 is the rate diagram (Pressure-pressure, NH ₃ synthesis rate-ammonia synthesis rate) of the ruthenium-based catalyst that ruthenium mass fraction is 1% and 2% under different temperatures and pressures synthetic ammonia among the embodiment 1;

Fig. 3 is the rate diagram of ammonia synthesis by the ruthenium-based catalyst in Example 2 at different temperatures and pressures.

Detailed ways

The invention provides a ruthenium-based catalyst, the mass fraction of each component in the catalyst is:

Ruthenium 1-2%, YHO 98-99%.

In the present invention, ruthenium is used as the active catalytic center of the ruthenium-based catalyst, and YHO is used as the carrier of the ruthenium-based catalyst.

In the present invention, the mass fraction of the ruthenium is preferably 1.2-1.8%, more preferably 1.3-1.7%, and more preferably 1.4-1.6%.

In the present invention, the mass fraction of YHO is preferably 98.2-98.8%, more preferably 98.3-98.7%, more preferably 98.4-98.6%.

The present invention also provides a preparation method of the ruthenium-based catalyst, comprising the following steps:

(1) mixing YHO, Ru ₃ (CO) ₁₂ and tetrahydrofuran, performing rotary evaporation and calcining in sequence to obtain an intermediate;

(2) In a hydrogen atmosphere, reducing the intermediate to obtain the ruthenium-based catalyst.

In the present invention, the YHO is synthesized according to the literature [Zapp, N.; Auer, H.; Kohlmann, H., YHO, an Air-StableIonic Hydride. InorgChem2019, 58(21), 14635-14641.].

In the present invention, the mass volume ratio of YHO to THF in step (1) is preferably 0.8-1.2g: 75-85mL, more preferably 0.9-1.1g: 77-83mL, more preferably 0.95-1.05g: 79 ~81mL.

In the present invention, the mixing in step (1) is preferably mixing Ru ₃ (CO) ₁₂ and YHO and immersing them together in a tetrahydrofuran solution.

In the present invention, the temperature of the rotary steaming in step (1) is preferably 35 to 45°C, more preferably 37 to 43°C, more preferably 39 to 41°C; the pressure of the rotary steaming is preferably -0.05 to - 0.15MPa, more preferably -0.07～-0.13MPa, more preferably -0.09～-0.11MPa; the rotating speed of the rotary steamer is preferably 170～190r/min, more preferably 175～185r/min, more preferably 177 ~183r/min; the time of the rotary steaming is preferably 8-12min, more preferably 9-11min, more preferably 9.5-10.5min; the function of the rotary steaming is to remove tetrahydrofuran.

In the present invention, the vacuum degree of the calcination in step (1) is preferably -0.05～-0.15MPa, more preferably -0.07～-0.13MPa, more preferably -0.09～-0.11MPa; the heating rate of the calcination Preferably it is 5-7°C/min, more preferably 5.5-6.5°C/min, more preferably 5.7-6.3°C/min; the target temperature of the calcination is preferably 380-400°C, more preferably 385-395°C, It is more preferably 387-393° C.; the holding time after reaching the target temperature is preferably 3-4 hours, more preferably 3.2-3.8 hours, and more preferably 3.4-3.6 hours.

In the present invention, after the calcination in step (1), the intermediate is naturally cooled to room temperature to obtain the intermediate.

In the present invention, the flow rate of hydrogen in step (2) is preferably 95-105 mL/min, more preferably 97-103 mL/min, more preferably 99-101 mL/min.

In the present invention, the heating rate of the reduction reaction in step (2) is preferably 5-7°C/min, more preferably 5.5-6.5°C/min, more preferably 5.7-6.3°C/min; The target temperature is preferably 390-410°C, more preferably 395-405°C, more preferably 398-402°C; the holding time after reaching the target temperature is preferably 1-1.5h, more preferably 1.1-1.4h, and more preferably 1.2～1.3h.

In the present invention, after the reduction reaction in step (2) is finished, the catalyst is naturally cooled to room temperature, subjected to tableting treatment in an argon atmosphere, and then vacuum-sealed in a quartz tube for use; the quality of a single piece of the tableting treatment is preferably It is 1.5-2.5g, More preferably, it is 1.7-2.3g, More preferably, it is 1.9-2.1g.

The invention also provides the application of the ruthenium-based catalyst in ammonia synthesis.

The present invention also provides a method for synthesizing ammonia using the ruthenium-based catalyst, comprising the following steps:

Nitrogen, hydrogen and catalyst are mixed and reacted to obtain ammonia.

In the present invention, argon is introduced into the reaction before the reaction, and the air is evacuated.

In the present invention, the molar ratio of nitrogen to hydrogen is preferably 1:2.5-3.5, more preferably 1:2.7-3.3, more preferably 1:2.9-3.1; the mass of the catalyst is preferably 0.15-0.25g , more preferably 0.17～0.23g, more preferably 0.19～0.21g; the gas flow rate of the reaction is preferably 100～120mL/min, more preferably 105～115mL/min, more preferably 107～113mL/min; The temperature of the reaction is preferably 300-500°C, more preferably 350-450°C, more preferably 370-430°C; the pressure of the reaction is preferably 0.1-5MPa, more preferably 1-4MPa, more preferably 2-4MPa 3MPa.

In the present invention, the obtained ammonia is captured with hydrazine, and the hydrazine contains ammonium chloride solution and sodium hydroxide solution; the concentration of the ammonium chloride solution is preferably 0.8-1.2mg/L, more preferably 0.85- 1.15mg/L, more preferably 0.9～1.1mg/L; The volume of described ammonium chloride solution is preferably 280～320mL, is more preferably 290～310mL, is more preferably 295～305mL; The volume of described sodium hydroxide solution The concentration is preferably 0.8-1.2 mol/L, more preferably 0.85-1.15 mol/L, more preferably 0.9-1.1 mol/L; the volume of the sodium hydroxide solution is preferably 30-36 mL, more preferably 31-35 mL , more preferably 32 to 34 mL.

The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

Example 1

Mix 1 mol _{Y 2} O ₃ and 4 mol CaH ₂ , grind for 30 min, then press into tablets, then raise the temperature to 890 °C at a heating rate of 0.83 °C/min, and anneal for 48 h to obtain a YHO sample; take 2 g of YHO sample and 1.5 g of ammonium chloride, 100 mL of methanol Mix and stir for 4 hours at a speed of 240r/min, and then perform suction filtration to obtain a gray powder, which is YHO;

Mix Ru ₃ (CO) ₁₂ and 1g YHO, soak in 80mL tetrahydrofuran solution, rotate steam for 10min at a temperature of 40°C, a pressure of -0.1MPa, and a rotation speed of 180r/min. The heating rate of 6°C/min was raised to 390°C and then kept for 3h, then naturally cooled to room temperature to obtain the intermediate (RuO _x /YHO); The heating rate of min was raised to 400° C., the reduction reaction was carried out for 1.3 h, and finally cooled naturally to room temperature to obtain the ruthenium-based catalyst (the mass fraction of ruthenium in the ruthenium-based catalyst was 2%).

The YHO obtained in this example was analyzed by XRD test, and the XRD characterization diagram of YHO was obtained, as shown in FIG. 1 . It can be analyzed from the figure that YHO was successfully synthesized.

Place 0.2g of catalyst on quartz wool, suspend it in a stainless steel tube, pass in argon to evacuate the air, and then pass in a mixture of nitrogen and hydrogen, control the molar ratio of nitrogen and hydrogen to 1:3, and the gas flow rate to 110mL /min, the temperature of the reaction is 500°C, and the pressure is 1MPa, the generated ammonia is captured with hydrazine (the concentration of ammonium chloride solution in hydrazine is 1mg/L, and the volume is 300mL; the concentration of sodium hydroxide solution is 1mol/L , volume is 33mL).

Keeping other conditions unchanged, the reaction pressures were respectively modified to 2MPa, 3MPa, 4MPa, and 5MPa. Use the ammonium chloride solution of 1mg/L, the ammonium chloride solution of 10mg/L, the ammonium chloride solution of 100mg/L and the sodium hydroxide solution of 1mol/L to calibrate the _NH3 gas sensitive electrode successively, make each calibration The linear fitting degree of ≥0.99 (that is, R ² ≥0.99), and then use the calibrated NH ₃ gas sensing electrode to test the process of ammonia synthesis under different pressures, and obtain a catalyst with a mass fraction of ruthenium of 2% at 500 ° C under different pressures The synthesis rate diagram of ammonia is shown in Figure 2 (marked as 500°C 2wt% Ru-loaded).

Control other conditions to be constant, change the consumption of Ru ₃ (CO) ₁₂ in the catalyst synthesis process, make the mass fraction of ruthenium in the obtained catalyst be 1%, adopt the above-mentioned same test method, obtain the catalyst that the mass fraction of ruthenium is 1% at 500 ℃ , the synthesis rate diagram of ammonia under different pressures, as shown in Figure 2 (marked as 500°C 1wt%Ru-loaded).

Controlling other conditions unchanged, changing the reaction temperature in the ammonia synthesis process to 400°C, using the same test method as above, a catalyst with a mass fraction of ruthenium of 2% was obtained at 400°C and the synthesis rate diagram of ammonia under different pressures, as shown in Figure 2 (marked as 400°C 2wt% Ru-loaded).

Control other conditions to be constant, change the amount of Ru ₃ (CO) ₁₂ in the catalyst synthesis process, make the ruthenium mass fraction in the obtained catalyst be 1%, the reaction temperature in the ammonia synthesis process is 400 ℃, adopt the above-mentioned same test method, obtain ruthenium The synthesis rate diagram of ammonia under different pressures at 400°C with a mass fraction of 1% catalyst is shown in Figure 2 (marked as 400°C 1wt%Ru-loaded).

It can be seen from Figure 2 that the ammonia synthesis rate of the ruthenium-based catalyst prepared in this example is remarkable. When the catalyst with a mass fraction of ruthenium of 2% synthesizes ammonia at 500°C and 5 MPa, the rate reaches 85mmol·g ^-1 ·h ^-1 .

Example 2

YHO was prepared by the same method as in Example 1;

Mix Ru ₃ (CO) ₁₂ and 1.1g YHO, immerse in 85mL tetrahydrofuran solution, rotate steam for 11min under the conditions of temperature 37°C, pressure -0.08MPa, rotation speed 175r/min, and then under -0.08MPa Raise the temperature to 395°C at a heating rate of 6.5°C/min, keep it warm for 3.2h, and cool naturally to room temperature to obtain the intermediate; The temperature was raised to 408° C., the reduction reaction was carried out for 1.2 h, and finally cooled naturally to room temperature to obtain the ruthenium-based catalyst (the mass fraction of ruthenium in the ruthenium-based catalyst was 2%).

Place 0.2g of catalyst on quartz wool, suspend it in a stainless steel tube, pass in argon to evacuate the air, and then pass in a mixture of nitrogen and hydrogen, control the molar ratio of nitrogen and hydrogen to 1:3, and the gas flow rate to 110mL /min, the temperature of the reaction is 500°C, and the pressure is 1MPa, the generated ammonia is captured with hydrazine (the concentration of ammonium chloride solution in hydrazine is 1mg/L, and the volume is 300mL; the concentration of sodium hydroxide solution is 1mol/L , volume is 33mL).

Keeping other conditions unchanged, the reaction pressures were respectively modified to 0.1MPa, 2MPa, 3MPa, 4MPa, and 5MPa. Using the same test method as in Example 1, the synthesis rate graph of ammonia at 500° C. under different pressures was obtained for a catalyst with a mass fraction of ruthenium of 2%, as shown in FIG. 3 .

Keeping other conditions unchanged, modify the reaction temperature to 400°C, and set the reaction pressure to 0.1MPa, 1MPa, 2MPa, 3MPa, 4MPa, and 5MPa, respectively. Using the same test method as in Example 1, the synthesis rate graph of ammonia under different pressures at 400° C. was obtained for a catalyst with a mass fraction of ruthenium of 2%, as shown in FIG. 3 .

Keeping other conditions unchanged, modify the reaction temperature to 300°C, and set the reaction pressure to 0.1MPa, 1MPa, 2MPa, 3MPa, 4MPa, and 5MPa, respectively. Using the same test method as in Example 1, the synthesis rate graph of ammonia under different pressures at 300° C. was obtained for a catalyst with a mass fraction of ruthenium of 2%, as shown in FIG. 3 .

Example 3

YHO was prepared by the same method as in Example 1;

Mix Ru ₃ (CO) ₁₂ and 0.95g YHO, immerse in 77mL tetrahydrofuran solution, and rotate at 42°C, pressure -0.12MPa, and rotation speed 185r/min for 9 minutes, and then put it under -0.12MPa Raise the temperature to 385°C at a heating rate of 5.5°C/min, then keep it warm for 3.7h, and cool naturally to room temperature to obtain the intermediate (RuO _x /YHO); in a hydrogen atmosphere (the flow rate of hydrogen is 105mL/min), the intermediate is The temperature was raised to 395° C. at a heating rate of °C/min, the reduction reaction was carried out for 1.4 h, and finally cooled to room temperature naturally to obtain the ruthenium-based catalyst (the mass fraction of ruthenium in the ruthenium-based catalyst was 1.5%).

The same test method as in Example 1 was used to test, and the ammonia synthesis rate of the ruthenium-based catalyst obtained in this implementation at 500° C. and 5 MPa was 50 mmol·g ⁻¹ ·h ⁻¹ .

As can be seen from the above examples, the present invention provides a ruthenium-based catalyst, which exhibits excellent activity in the process of ammonia synthesis, wherein the rate of synthesis of ammonia at 500° C. under 5 MPa reaches 85 mmol g ^-1 for a catalyst with a mass fraction of ruthenium of 2%. • h ⁻¹ .

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a ruthenium-based catalyst, characterized in that, the massfraction of each component in the catalyst is: Ruthenium 1-2%, YHO 98-99%. 2. the preparation method of ruthenium-based catalyst described in claim 1 is characterized in that, comprises the following steps: (1) mixing YHO, Ru ₃ (CO) ₁₂ and tetrahydrofuran, performing rotary evaporation and calcining in sequence to obtain an intermediate; (2) In a hydrogen atmosphere, reducing the intermediate to obtain the ruthenium-based catalyst. 3. The preparation method according to claim 2, characterized in that the mass volume ratio of YHO to tetrahydrofuran in step (1) is 0.8-1.2g:75-85mL. 4. The preparation method according to claim 2 or 3, characterized in that, the temperature of the rotary steaming in step (1) is 35～45°C, the pressure of the rotary steaming is -0.05～-0.15MPa, and the The rotational speed of the rotary steaming is 170-190 r/min, and the time of the rotary steaming is 8-12 minutes. 5. The preparation method according to claim 4, characterized in that, the vacuum degree of the calcination in step (1) is -0.05～-0.15MPa, the heating rate of the calcination is 5～7°C/min, the The target temperature for calcination is 380-400°C, and the holding time after reaching the target temperature is 3-4 hours. 6. The preparation method according to claim 2 or 5, characterized in that the flow rate of hydrogen in step (2) is 95-105 mL/min. 7. The preparation method according to claim 6, wherein the heating rate of the reduction reaction in step (2) is 5 to 7°C/min, and the target temperature of the reduction reaction is 390 to 410°C, reaching the target temperature The holding time after temperature is 1~1.5h. 8. the application of ruthenium-based catalyst described in claim 1 in ammonia synthesis. 9. adopt the method for the described ruthenium-based catalyst synthetic ammonia of claim 1, it is characterized in that, comprise the following steps: Nitrogen, hydrogen and catalyst are mixed and reacted to obtain ammonia. 10. The method according to claim 9, characterized in that, the molar ratio of nitrogen to hydrogen is 1:2.5 to 3.5; the mass of the catalyst is 0.15 to 0.25 g; the reaction gas flow rate is 100 to 120mL/min, the temperature of the reaction is 300-500°C, and the pressure of the reaction is 0.1-5MPa.

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