A method for the nitrogen fixation of rare earth metal hydrides

Abstract

The application discloses a method for nitrogen fixation of rare earth metal hydride, and belongs to the technical field of nitrogen fixation of metal hydride. The rare earth metal hydride is contacted with nitrogen gas, and then reacts to obtain a rare earth metal nitrogen-hydrogen compound and a rare earth metal nitride after adding nitrogen. The application provides new insights and ideas for the design of a rare earth-based catalyst and a nitrogen carrier for catalytic ammonia synthesis and chemical chain ammonia synthesis, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth metal hydride nitrogen fixation, and particularly to a nitrogen fixation method applicable to normal temperature and pressure conditions. BACKGROUND

[0002] Ammonia is an essential raw material for large-scale production of fertilizers and synthesis of organic nitrogen-containing chemicals. In recent years, ammonia has been widely recognized as a promising energy carrier, providing a possible solution to renewable energy storage and transportation. Currently, artificial ammonia synthesis is mainly based on the Haber-Bosch process, which requires harsh conditions and consumes nearly 2% of the world's annual power generation, accompanied by high carbon emissions. Therefore, the development of efficient catalysts that can operate at lower temperatures and pressures, and the search for alternative methods such as electrochemical, photochemical, and chemical chain ammonia synthesis, have attracted increasing attention.

[0003] In recent years, hydrides and H - Materials such as alkali or alkaline earth metal hydrides, transition metal alkali metal hydride composite catalysts, transition metal hydrides and hydroxides, composite metal hydrides, and molecular metal complexes have received increasing attention. H - They can act as electron or hydrogen donors and play a key role in N2 reduction and N-H bond formation. It has been reported that lithium hydride (LiH) and barium hydride (BaH2) can fix N2 to form corresponding Li2NH and BaNH, and subsequent hydrogenation reaction generates ammonia and regenerates alkali or alkaline earth metal hydride.

[0004] Similar to alkali or alkaline earth metals, rare earth metals can also form metal hydrides. Previous studies have shown that rare earth metal hydrides can be used as hydrogen storage materials, catalyst supports, and high-temperature superconductors. Rare earth metal oxides have many applications in ammonia synthesis catalysis. Early studies have shown that rare earth oxides (CeO2, Sm2O3, and La2O3) in Ru-based catalysts are effective promoters or good supports in ammonia synthesis reactions. Recent studies on rare earth oxide and oxyhydride supported Ru-based or Co-based catalysts have shown that strong interactions between active metals and carriers with oxygen vacancies are crucial for high activity of the reaction. However, there have been very few studies on N2 activation and ammonia synthesis reactions on rare earth metal hydrides. SUMMARY

[0005] The application aims to provide a method for fixing nitrogen by using rare earth metal hydride under normal pressure and normal temperature conditions, and a new phase of rare earth metal nitrogen hydride is formed in the process of fixing nitrogen, and rare earth metal nitride is finally generated at a higher temperature or for a longer time of fixing nitrogen.

[0006] According to one aspect of the application, a method for fixing nitrogen by using rare earth metal hydride is provided, which comprises contacting rare earth metal hydride with nitrogen gas to obtain nitrogen-added rare earth metal nitrogen hydride and / or rare earth metal nitride.

[0007] Optionally, the nitrogen gas pressure is 0.01-10 MPa, and the nitrogen gas flow rate is 10-100 mL·min -1 .

[0008] Optionally, the nitrogen gas pressure is selected from 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.5 MPa, 9 MPa, 9.5 MPa, or any value between any two of the above values.

[0009] Optionally, the reaction temperature of the reaction is 20-500 DEG C, the heating rate is 2-5 DEG C / min, and the reaction time is 0-100 h.

[0010] Optionally, the reaction temperature is selected from 50 DEG C, 60 DEG C, 80 DEG C, 100 DEG C, 120 DEG C, 150 DEG C, 180 DEG C, 200 DEG C, 250 DEG C, 260 DEG C, 280 DEG C, 300 DEG C, 350 DEG C, 380 DEG C, 400 DEG C, 420 DEG C, 450 DEG C, 470 DEG C, 490 DEG C, or any value between any two of the above values.

[0011] Optionally, the mass of the rare earth metal hydride is 10-100 mg, and the reactor of the reaction is a fixed bed reactor.

[0012] Optionally, the rare earth metal hydride is synthesized by using rare earth metal as raw material and adopting hydrogenation pressure mixing mode.

[0013] Optionally, the rare earth metal is selected from one of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), and gadolinium (Gd) in group III B.

[0014] Optionally, in the hydrogenation pressure mixing mode, the hydrogenation pressure is 10-50 MPa, the mixing time is 1-24 hours, and the mixing temperature is 0-100℃.

[0015] Optionally, the hydrogenation pressure mixing mode is mechanical mixing or mechanical ball milling under a hydrogen atmosphere.

[0016] The mechanical mixing or mechanical ball milling is carried out under a hydrogen atmosphere.

[0017] The mechanical mixing is carried out by using an automatic mechanical powder mixing machine.

[0018] The mechanical ball milling is carried out by using a planetary ball mill, a swing ball mill or a vibration ball mill.

[0019] The grinding ball used in the mechanical ball milling is at least one of a stainless steel ball, a tungsten carbide ball, an alumina ball, an agate ball or a zirconia ball.

[0020] Optionally, the weight ratio of the grinding ball to the raw material is 1-100; the rotation speed of the planetary ball mill is 10-500 rpm; the swing frequency of the swing ball mill is 50-600 cycles per minute; and the rotation speed of the automatic powder mixing machine is 10-100 rpm.

[0021] As an embodiment of the present application, a method for fixing nitrogen by a rare earth metal hydride comprises the following steps:

[0022] 1) Under the condition of air isolation, a rare earth metal is loaded into a ball mill tank;

[0023] 2) The ball mill tank of step 1) is vacuumized, and hydrogen is added into the tank;

[0024] 3) The rare earth metal is chemically reacted by using a temperature-controlled mechanical mixing or mechanical ball milling mode;

[0025] 4) The rare earth metal hydride obtained in 3) is transferred to a fixed bed reactor, nitrogen is introduced into the reactor to contact with the rare earth metal hydride, and reaction is carried out to obtain a rare earth metal nitrogen hydride and a rare earth metal nitride after adding nitrogen.

[0026] The present application has the following beneficial effects:

[0027] The present application provides a new method for fixing nitrogen by a rare earth metal hydride, which provides new insights and ideas for the design of a rare earth-based catalyst and a nitrogen carrier for catalytic ammonia synthesis and chemical chain ammonia synthesis, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The lanthanum hydride (LaH 2.46X-ray powder diffraction pattern of ).

[0029] Figure 2 Example 2: Lanthanum hydride (LaH) 2.46 X-ray powder diffraction patterns of samples after nitrogen reaction under nitrogen pressure of 1 bar and different temperatures.

[0030] Figure 3 Example 3: Lanthanum hydride (LaH) 2.46 X-ray powder diffraction patterns of the samples after reaction under nitrogen pressure of 1 bar, temperature of 300℃, and different nitrogen addition times.

[0031] Figure 4 Example 4: Lanthanum hydride (LaH) 2.46 X-ray powder diffraction pattern of the ball-milled sample under nitrogen pressure of 1 bar and room temperature. Detailed Implementation

[0032] To further illustrate the present invention, the following specific embodiments are provided, but they do not limit the scope of the invention as defined by the appended claims.

[0033] Example 1

[0034] The synthesis of rare earth metal hydrides is described below. Accurately weigh 500 mg of lanthanum powder (La) and place it in a self-made stainless steel ball mill jar. After sealing the jar, evacuate it using a vacuum pump, introduce hydrogen gas into the jar, and pressurize it to 30 bar. Place the jar into a planetary ball mill and mill at 200 rpm for 3 hours. In an argon glove box, collect the resulting solid, add silicon powder as a reference, and perform X-ray diffraction analysis on the sample. The results are as follows. Figure 1 As shown, the prepared solid substance is LaH 2.46 .

[0035] Example 2

[0036] Lanthanum hydride (LaH) 2.46 The reaction was carried out under nitrogen pressure of 1 bar and different temperatures, and the specific process is described below. Accurately weigh the lanthanum hydride (LaH) obtained in Example 1. 2.46 30 mg was placed in a fixed-bed stainless steel reactor, and a nitrogen flow was introduced at a pressure of 1 bar and a gas flow rate of 30 mL / min. The temperature was increased to 200℃, 250℃, 300℃, 350℃, and 400℃ respectively. Heating was stopped directly at the temperature point, and the samples were allowed to cool naturally to room temperature in nitrogen. Samples were collected under different temperature conditions, and X-ray diffraction tests were performed on the samples. The results are summarized as follows. Figure 2 As shown, between 200 and 350 °C, the diffraction peaks of the reaction product LaNH gradually increase with increasing heating temperature, indicating that LaNH...2.46 The reaction degree of nitrogenation to form LaNH gradually increased. When the final temperature was higher than 300 DEG C, LaN diffraction peaks appeared in the reaction product, and the intensity of the LaN diffraction peaks increased with the increase of temperature. When the final temperature was 400 DEG C, the LaNH diffraction peaks disappeared, and only LaN diffraction peaks existed, indicating that at 400 DEG C, LaH 2.46 The nitrogenation product was LaN.

[0037] Example 3

[0038] Lanthanum hydride (LaH 2.46 ) was nitrogenated under the conditions of 1 bar nitrogen pressure and 300 DEG C temperature for different nitrogenation times, and the specific process was as follows. 30 mg of the lanthanum hydride (LaH 2.46 ) prepared in Example 1 was placed in a fixed bed stainless steel reactor, nitrogen gas was introduced, the pressure was 1 bar, the gas flow rate was 30 mL / min, the heating rate was 2 DEG C / min to heat to 300 DEG C, and the temperature was kept constant for 0 h, 0.5 h, 1 h and 3 h respectively. After natural cooling to room temperature in nitrogen, the samples under different constant temperature conditions were collected, and the samples were tested by X-ray diffraction, and the results were as shown in Figure 3 , the LaH 2.46 could fix nitrogen to form LaNH; with the increase of constant temperature time, the diffraction peaks of the reaction product LaNH gradually weakened, and the LaN diffraction peaks gradually increased. When the constant temperature time was 3 h, no LaNH diffraction peak was observed in the reaction product, and only LaN diffraction peak existed, indicating that with the increase of constant temperature time, LaH 2.46 The nitrogenation product was finally LaN.

[0039] Example 4

[0040] Lanthanum hydride (LaH 2.46 ) was nitrogenated under the conditions of 1 bar nitrogen pressure and room temperature by ball milling, and the specific process was as follows. 100 mg of the lanthanum hydride (LaH 2.46 ) prepared in Example 1 was placed in a stainless steel ball mill pot. After the ball mill pot was closed, vacuum pumping was performed, nitrogen was introduced into the ball mill pot, and the nitrogenation pressure was 1 bar. The ball mill pot was loaded into a planetary ball mill, and ball milling was performed at room temperature. The ball milling conditions were 150 rpm for 10 hours. In an argon glove box, the obtained solid was collected, silicon powder was added as a reference, and the sample was tested by X-ray diffraction, and the results were as shown in Figure 1 , the solid material obtained after ball milling was LaNH, indicating that under this condition, LaH 2.46 could fix nitrogen.

[0041] The above merely describes several embodiments of the present application, and does not limit the present application in any form. Although the present application is disclosed with the preferred embodiments, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the disclosed technical contents without departing from the scope of the technical solutions of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solutions.

Claims

1. A method for nitrogen fixation using rare earth metal hydrides, characterized in that, Accurately weigh lanthanum hydride LaH 2.46 100 mg was placed in a stainless steel ball mill jar; after sealing the ball mill jar, a vacuum pump was used to evacuate the jar, and nitrogen gas was introduced into the ball mill jar to pressurize it to 1 bar; the ball mill jar was then placed in a planetary ball mill and ball milled at room temperature at 150 rpm for 10 hours; the solid substance obtained after ball milling was LaNH.

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