A YHO synthetic ammonia catalyst and its preparation method

Abstract

The present invention relates to the field of ammonia synthesis catalysts, and particularly to a YHO ammonia synthesis catalyst and a preparation method thereof. The YHO ammonia synthesis catalyst is prepared by first calcining Y2O3, mixing the obtained Y2O3 with CaH2 after annealing, and pelletizing the resulting mixture to obtain flaky particles; the obtained flaky particles are calcined under vacuum conditions and obtained after annealing. The YHO ammonia synthesis catalyst prepared by the preparation method of the present invention mainly presents a gully-like shape similar to a mountain peak macroscopically, and more canyon-like cavities appear; microscopically, it is mainly composed of massive bodies with different particle sizes. Such a unique morphology endows the YHO ammonia synthesis catalyst with better ammonia synthesis activity; when the dosage of the YHO catalyst is only 200 mg, it can have good catalytic activity and stability while reducing the temperature and pressure of the ammonia synthesis reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic ammonia catalysts, and particularly relates to a YHO synthetic ammonia catalyst and a preparation method thereof. Background Art

[0002] As an important chemical raw material and a source of nitrogen fertilizer, ammonia supports the survival and development of all mankind and promotes social progress. Ammonia mainly comes from the Haber-Bosch process, using Fe as the main catalyst and adding appropriate amounts of calcium oxide, etc. as co-catalysts to catalyze the reaction of N 2 and H 2 to generate NH 3 . Although Fe-based catalysts have a series of advantages such as low cost and good stability, their disadvantages are also obvious. For example, the efficiency is relatively low, and high temperature and high pressure (400 - 500 °C, 10 - 30 MPa) are required. With the development of technology, a large number of synthetic ammonia catalysts have been prepared, greatly reducing the reaction conditions of synthetic ammonia and improving the efficiency. Currently, Ru-based catalysts are catalysts with relatively high activity. The synthetic ammonia catalysts with Ru as the main catalytic active center and oxides, hydrides, activated carbon, etc. as carriers can reduce the reaction temperature and pressure to a certain extent, but the activity is not high enough. Therefore, catalysts with higher activity, lower energy consumption, and good stability are needed. Summary of the Invention

[0003] The purpose of the present invention is to provide a YHO synthetic ammonia catalyst and a preparation method thereof to solve the problems existing in the prior art.

[0004] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of a YHO synthetic ammonia catalyst, comprising the following steps:

[0006] (1) Calcine and then anneal Y 2 O 3 to obtain Y 2 O 3 with completely removed moisture;

[0007] (2) Tablet the mixture obtained by mixing Y 2 O 3 obtained in step (1) and CaH 2 to obtain flaky particles;

[0008] (3) Calcine the flaky particles obtained in step (2) under vacuum conditions and then anneal to obtain the YHO synthetic ammonia catalyst.

[0009] Preferably, in the step (1), the calcination temperature is 700 - 900 °C and the time is 6 - 10 h;

[0010] In the step (1), the annealing rate is 5 - 10 °C / min.

[0011] Preferably, in the step (2), the molar ratio of Y 2 O 3 and CaH 2 is 1 - 3:3 - 9.

[0012] Preferably, in the step (2), the pressure for tablet pressing is 1 - 3 MPa.

[0013] Preferably, in the step (3), the calcination temperature is 300 - 400 °C, the time is 3 - 5 h, and the vacuum pressure is -0.5 - -1 MPa.

[0014] Preferably, in the step (3), the annealing rate is 5 - 8 °C / min.

[0015] The present invention also provides a YHO ammonia synthesis catalyst prepared by the preparation method of the above-mentioned YHO ammonia synthesis catalyst.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] In the present invention, Y 2 O 3 and CaH 2 are mixed and ground in a certain proportion, and the combination between solids is made closer by tablet pressing, which is more conducive to solid-phase reaction. Then, the tablet particles are calcined and annealed to obtain a YHO ammonia synthesis catalyst. The YHO ammonia synthesis catalyst prepared by the preparation method of the present invention mainly shows a gully-like shape similar to a mountain peak macroscopically, and more canyon-like cavities appear; microscopically, it is mainly composed of massive bodies with different particle sizes. Such a unique morphology endows the YHO ammonia synthesis catalyst with better ammonia synthesis activity; when the dosage of the YHO catalyst is only 200 mg, it can have good catalytic activity and stability while reducing the temperature and pressure of the ammonia synthesis reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the SEM macroscopic image of the YHO ammonia synthesis catalyst prepared in Example 1;

[0019] Figure 2 is the SEM microscopic image of the YHO ammonia synthesis catalyst prepared in Example 1;

[0020] Figure 3Schematic diagram of the activity of the 100 / 200 mg YHO ammonia synthesis catalyst prepared in Example 1 within different reaction pressure and temperature ranges for NH 3 synthesis;

[0021] Figure 4 XRD spectrum of the YHO ammonia synthesis catalyst prepared in Example 1. Detailed implementation manners

[0022] The present invention provides a preparation method of a YHO ammonia synthesis catalyst, comprising the following steps:

[0023] (1) Calcine Y 2 O 3 and then anneal it to obtain Y 2 O 3 with completely removed moisture;

[0024] (2) Tablet the mixture obtained by mixing Y 2 O 3 and CaH 2 to obtain flaky particles;

[0025] (3) Calcine the flaky particles obtained in step (2) under vacuum conditions and then anneal to obtain the YHO ammonia synthesis catalyst.

[0026] In the present invention, the temperature of the calcination treatment in step (1) is 700 - 900 °C, preferably 720 - 780 °C, and the time is 6 - 10 h, preferably 7 - 9 h;

[0027] The annealing rate in step (1) is 5 - 10 °C / min, preferably 8 - 9 °C / min.

[0028] In the present invention, the purpose of calcining Y 2 O 3 is to completely remove the water molecules on the surface and avoid reacting with the water molecules on the surfaces of CaH 2 and Y 2 O 3 .

[0029] In the present invention, the molar ratio of Y 2 O 3 to CaH 2 in step (2) is 1 - 3:3 - 9, preferably 1.5 - 2.5:4.5 - 7.5.

[0030] In the present invention, the pressure of the tableting treatment in step (2) is 1 - 3 MPa, and more preferably 1.5 - 2.5 MPa;

[0031] The form of the tablet can make the combination between solids closer, which is more conducive to solid-phase reaction.

[0032] In the present invention, in the step (2), Y 2 O 3 and CaH 2 are ground and mixed in an agate mortar for 20 - 60 min, preferably 30 - 55 min, and further preferably 45 - 50 min.

[0033] In the present invention, in the step (3), the temperature of the calcination treatment is 300 - 400 °C, preferably 320 - 380 °C, the time is 3 - 5 h, preferably 3.5 - 4.3 h, and the vacuum pressure is -0.5 - -1 MPa, preferably -0.6 - -0.8 MPa.

[0034] In the present invention, in the step (3), the annealing rate is 5 - 8 °C / min, preferably 6 - 7 °C / min.

[0035] In the present invention, in the step (3), the annealed flaky particles are mixed with ammonium chloride and an organic solvent and magnetically stirred for 2 - 5 h, preferably 3 - 4 h, and then filtered and purified to obtain the YHO ammonia synthesis catalyst solid;

[0036] In the step (3), the dosage ratio of the flaky particles, ammonium chloride and the organic solvent is 1 - 2 g: 2 - 5 g: 200 - 500 mL, preferably 1.3 - 1.8 g: 3 - 4 g: 250 - 400 mL;

[0037] In the step (3), the organic solvent includes one or more of ethanol, methanol and tetrahydrofuran, preferably one or more of ethanol and methanol.

[0038] The present invention also provides a YHO ammonia synthesis catalyst prepared by the preparation method of the above YHO ammonia synthesis catalyst.

[0039] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] (1) The raw material Y 2 O 3 is calcined at 850 °C for 8 h, and after annealing at a rate of 10 °C / min, Y 2 O 3 completely free of surface moisture is obtained;

[0042] (2) 0.01 mol of Y 2 O 3 in the step (1) and 0.03 mol of CaH2 The mixture was obtained by grinding and mixing in an agate mortar for 30 min, and the mixture was tableted under a pressure of 1 MPa to obtain tableted particles.

[0043] (3) The tableted particles prepared in step (2) were calcined for 3 h under the conditions of a vacuum degree of -0.5 MPa and a temperature of 300 °C. After annealing the obtained tableted particles at a rate of 5 °C / min, 2 g of the annealed tableted particles were mixed with 5 g of ammonium chloride and 200 ml of methanol, and after magnetic stirring for 3 h, filtration was carried out to obtain a solid, thus obtaining the YHO ammonia synthesis catalyst.

[0044] It can be seen from Figure 1 that the YHO ammonia synthesis catalyst mainly presents a gully shape similar to a mountain peak macroscopically, and there are more cavities similar to canyons. According to Figure 2 the further magnification, it can be observed that the YHO ammonia synthesis catalyst is mainly composed of massive bodies with different particle sizes microscopically.

[0045] Performance test of the YHO ammonia synthesis catalyst: The prepared YHO ammonia synthesis catalyst was placed on the catalyst bed (quartz wool) and fixed in a stainless steel reaction tube; within the pressure range of 5 MPa and within the range of 400 - 475 °C, N 2 :H 2 = 1:3, and the catalyst was continuously heated under the condition of a flow rate of 110 mL / min; the generated NH 3 was captured by hydrazine hydrate composed of NH 4 Cl and NaOH solution; NH 3 was quantitatively analyzed by an NH 3 gas-sensing electrode; after ammonia gas entered the capture solution, it would cause the conductivity of the solution to decrease, and the total value of the conductivity decrease within 1 h was recorded, and the amount of ammonia produced was calculated; through Figure 3 analysis, it was obtained that under the same conditions, the ammonia synthesis rate of 200 mg of YHO was higher than that of 100 mg of YHO. That is, the optimal dosage of the YHO ammonia synthesis catalyst of the present invention is 200 mg.

[0046] Stability test of the YHO ammonia synthesis catalyst: It can be seen from Figure 4 that the YHO ammonia synthesis catalyst prepared by the present invention has good stability. The present invention carried out a stability test on the YHO ammonia synthesis catalyst before and after the reaction, and after exposing the YHO ammonia synthesis catalyst to the air for one week, according to Figure 4 it can be seen that the XRD peaks of the YHO ammonia synthesis catalyst did not change at all, which fully reflects the stability of the YHO ammonia synthesis catalyst.

[0047] Example 2

[0048] (1) The raw material Y 2O 3 Calcined at 850 °C for 8 h and annealed at a rate of 10 °C / min to obtain Y with completely removed surface moisture 2 O 3 ;

[0049] (2) Grind and mix 0.03 mol of Y 2 O 3 and 0.09 mol of CaH 2 in an agate mortar for 30 min to obtain a mixture, and tablet the mixture under a pressure of 1 MPa to obtain tablet particles

[0050] (3) Calcinate the tablet particles prepared in step (2) under a vacuum of -0.1 MPa and a temperature of 350 °C for 5 h, anneal the obtained tablet particles, control the annealing rate to 8 °C / min, mix 2 g of the annealed tablet particles with 5 g of ammonium chloride and 200 ml of methanol, magnetically stir for 3 h and then filter to obtain a solid, namely the YHO ammonia synthesis catalyst

[0051] The YHO ammonia synthesis catalyst mainly presents a gully-like shape similar to a mountain peak macroscopically, and there are more canyon-like cavities. The YHO ammonia synthesis catalyst is mainly composed of massive bodies with different particle sizes microscopically

[0052] Performance test of YHO ammonia synthesis catalyst: Place the prepared YHO ammonia synthesis catalyst on the catalyst bed (quartz wool) and fix it in a stainless steel reaction tube; within a pressure range of 5 MPa and a temperature range of 400 - 475 °C, N 2 :H 2 = 1:3, continuously heat the catalyst under the condition of a flow rate of 110 mL / min; the generated NH 3 is captured by hydrazine hydrate composed of NH 4 Cl and NaOH solution; NH 3 is quantitatively analyzed through an NH 3 gas-sensitive electrode; when ammonia enters the capture solution, it will cause the conductivity of the solution to decrease, record the total value of the conductivity decrease within 1 h, and convert the amount of ammonia produced; the ammonia synthesis rates of 200 mg of YHO are 180 μmolg -1 h -1 , 420 μmolg -1 h -1 , 830 μmolg -1 h -1 ; 1600 μmolg -1 h -1 .

[0053] YHO ammonia synthesis catalyst stability test: After exposing the prepared YHO ammonia synthesis catalyst to air for one week, the performance of the YHO ammonia synthesis catalyst did not change at all, which fully demonstrated the stability of the YHO ammonia synthesis catalyst.

[0054] Example 3

[0055] (1) Calcinate the raw material Y 2 O 3 at 850 °C for 8 h, and anneal it at a rate of 10 °C / min to obtain Y 2 O 3 with completely removed surface moisture;

[0056] (2) Grind and mix 0.02 mol of Y 2 O 3 from step (1) and 0.06 mol of CaH 2 in an agate mortar for 30 min to obtain a mixture. Press the mixture under a pressure of 1 MPa to obtain pressed particles.

[0057] (3) Calcinate the pressed particles prepared in step (2) under a vacuum of -0.1 MPa and a temperature of 400 °C for 4 h. Anneal the obtained pressed particles, control the annealing rate at 5 °C / min. Mix 2 g of the annealed pressed particles with 5 g of ammonium chloride and 200 ml of methanol, stir magnetically for 3 h, and then filter to obtain a solid, that is, the YHO ammonia synthesis catalyst.

[0058] Macroscopically, the YHO ammonia synthesis catalyst mainly presents a gully shape similar to a mountain peak, with more canyon-like cavities. Microscopically, the YHO ammonia synthesis catalyst is mainly composed of massive bodies with different particle sizes.

[0059] YHO ammonia synthesis catalyst ammonia synthesis performance test: Place the prepared YHO ammonia synthesis catalyst on the catalyst bed (quartz wool) and fix it in a stainless steel reaction tube; within a pressure range of 5 MPa and a temperature range of 400 - 475 °C, under the condition of N 2 :H 2 = 1:3 and a flow rate of 110 mL / min, continuously heat the catalyst; the generated NH 3 is captured by hydrazine hydrate composed of NH 4 Cl and NaOH solution; NH 3 is quantitatively analyzed through an NH 3 gas-sensing electrode; when ammonia gas enters the capture solution, it will cause the conductivity of the solution to decrease. Record the total value of the conductivity decrease within 1 h and convert it to the amount of ammonia produced; the ammonia synthesis rates of 200 mg of YHO at 5 MPa, 400 °C, 420 °C, 450 °C, and 475 °C are 160 μmolg -1 h-1 ,400 μmol / g -1 h -1 ,850 μmol / g -1 h -1 ;1650 μmol / g -1 h -1 。

[0060] YHO ammonia synthesis catalyst stability test: After exposing the prepared YHO ammonia synthesis catalyst to air for one week, the performance of the YHO ammonia synthesis catalyst did not change at all, which fully demonstrated the stability of the YHO ammonia synthesis catalyst.

[0061] As can be seen from the above examples, the present invention combines Y 2 O 3 and CaH 2 in a certain proportion, grinds them, and makes the solids bond more tightly in the form of tabletting, which is more conducive to solid-phase reaction. Then, the tablet particles are calcined, annealed, and treated in ammonium chloride and methanol solutions. Finally, the YHO ammonia synthesis catalyst is obtained. The YHO ammonia synthesis catalyst prepared by the preparation method of the present invention mainly presents a gully-like shape similar to a mountain peak macroscopically, with more canyon-like cavities; microscopically, it is mainly composed of massive bodies of different particle sizes. Such a unique morphology endows the YHO ammonia synthesis catalyst with better ammonia synthesis activity. When the dosage of the YHO catalyst is only 200 mg, it can have good catalytic activity and stability while reducing the temperature and pressure of the ammonia synthesis reaction.

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Application of a YHO catalyst in the reaction of synthesizing ammonia from N 2 and H 2 ​ It is characterized in that The prepared YHO catalyst was directly used for the 2 synthesis of ammonia from N 2 and H. the preparation method of the YHO catalyst comprises the following steps: (1) Calcinate Y 2 O 3 and then anneal it to obtain Y 2 O 3 with completely removed moisture; (2) Press the mixture obtained by mixing Y 2 O 3 and CaH 2 to obtain sheet-like particles; (3) Calcining the flaky particles obtained in step (2) under vacuum conditions, and annealing to obtain the YHO ammonia synthesis catalyst; In the step (3), the temperature of the calcination treatment is 300-400 °C, the time is 3-5 h, and the vacuum pressure is -0.1 MPa.

2. Use of a YHO catalyst according to claim 1 in the 2 synthesis of ammonia from N 2 and H It is characterized in that in the step (1), the temperature of the calcination treatment is 700-900 °C, and the time is 6-10 h; in the step (1), the annealing rate is 5-10 °C / min.

3. Use of a YHO catalyst according to claim 2 in the 2 synthesis of ammonia from N 2 and H It is characterized in that Y in the step (2) 2 O 3 and CaH 2 have a molar ratio of 1 to 3: 3 to 9.

4. Use of a YHO catalyst according to any one of claims 1 to 3 in the 2 synthesis of ammonia from 2 nitrogen and hydrogen It is characterized in that in the step (2), the pressure of the tablet pressing treatment is 1-3 MPa.

5. Use of a YHO catalyst according to claim 1 in the 2 synthesis of ammonia from N 2 and H It is characterized in that in the step (3), the annealing rate is 5-8 °C / min.

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