Composite catalyst, its preparation method and application

Abstract

The application discloses a composite catalyst and a preparation method and application thereof. The composite catalyst comprises a transition metal nitride and a rare earth metal nitride; and the molar ratio of the transition metal nitride to the rare earth metal nitride is 1:0.1-10. The combination of the two kinds of nitrides as a catalyst can obviously improve the ammonia decomposition activity of a single nitride as a catalyst, can realize efficient decomposition of ammonia at a lower temperature (400-500 DEG C), and prepare CO x free hydrogen. The composite nitride catalyst prepared by the application has a simple preparation process, raw materials are easy to obtain, and has a potential application prospect in the field of ammonia decomposition for hydrogen production.

Description

Technical Field

[0001] This application relates to a composite catalyst, its preparation method, and its application, belonging to the field of ammonia decomposition technology. Background Technology

[0002] The utilization of clean energy is becoming increasingly important. Hydrogen is considered a major energy carrier that can replace traditional fossil fuels. However, hydrogen has a relatively low volumetric energy density, and its storage and transportation are difficult due to its difficulty in liquefaction. Therefore, developing hydrogen storage and transportation carriers has become a research hotspot. Hydrogen-rich substances such as methane, natural gas, and coal are considered potential hydrogen storage carriers, but their high carbon content makes them less than ideal. NH3 is one of the world's most produced chemical products, and it has a high hydrogen loading capacity (17 wt%) and energy density (3000 Wh·kg⁻¹). -1 NH3 is considered an ideal hydrogen storage carrier due to its advantages of easy liquefaction and storage (20℃~0.8MPa or -33.35℃~atmospheric pressure). The decomposition products of NH3 are N2 and H2, which do not contain carbon oxides and can be directly used in fuel cells. Therefore, NH3 has attracted widespread attention from researchers as a hydrogen storage carrier.

[0003] NH3 decomposition is an endothermic reaction with increasing volume, and high temperature and low pressure are conducive to the reaction. Among them, the catalysts for ammonia decomposition reaction can be mainly divided into metal catalysts, nitride or carbide catalysts, and transition metal nitride-metal amino / imino composite catalysts. Among metal-based catalysts, they are mainly divided into noble metal catalysts represented by Ru and non-noble metal catalysts represented by Ni. However, noble metal catalysts are relatively expensive and not suitable for large-scale application; although Ni-based catalysts have been applied to industrial NH3 decomposition, the implementation temperature is high (>600℃), so there is still a lot of room for development. Transition metal nitrides can be applied in the field of catalysis due to their metal-like properties. Among them, TiN, VN, MnN and FeN have also shown certain catalytic performance in the field of ammonia decomposition. In addition to single-component metal nitrides, catalysts composed of metal / metal nitride and (imino)lithium composites have high NH3 decomposition activity (Angewandte Chemie, 2015, 54(10):2950-2954.ACS Catalysis, 2015.). Summary of the Invention

[0004] To address the issues of low ammonia decomposition efficiency and harsh conditions for ammonia decomposition, this application provides a composite catalyst comprising transition metal nitrides and rare earth metal nitrides.

[0005] The molar ratio of the transition metal nitride to the rare earth metal nitride is 1:0.1 to 10.

[0006] Optionally, the molar ratio of the transition metal nitride to the rare earth metal nitride is any value or a range between two values ​​from 1:0.1, 1:1, 1:2, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10.

[0007] Optionally, the transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride.

[0008] Optionally, the rare earth metal nitrides include at least one of lanthanum nitride, cerium nitride, praseodymium nitride, neodymium nitride, promethium nitride, samarium nitride, europium nitride, gadolinium nitride, terbium nitride, dysprosium nitride, holmium nitride, erbium nitride, thulium nitride, ytterbium nitride, and lutetium nitride.

[0009] According to another aspect of this application, a method for preparing the above-mentioned composite catalyst is provided, wherein a mixture containing transition metal nitrides and rare earth metal nitrides is mechanically ball-milled under an inactive atmosphere to obtain the composite catalyst.

[0010] Optionally, the media balls used in the mechanical ball mill are selected from at least one of steel balls, zirconia balls, alumina balls, silica balls, and agate balls.

[0011] Optionally, the ratio of the medium balls to the mixture balls is 50 to 500:1.

[0012] Optionally, the ratio of the medium balls to the mixture is any value or a range between two values ​​from 50:1, 100:1, 150:1, 200:1, 300:1, 400:1, and 500:1.

[0013] Optionally, the inactive atmosphere is selected from at least one of nitrogen, argon, and helium.

[0014] Optionally, the rotation speed of the mechanical ball mill is 50-300 r / min, the temperature of the mechanical ball mill is 20-50℃, and the time of the mechanical ball mill is 1-200 h.

[0015] According to another aspect of this application, the application of the above-described composite catalyst or the composite catalyst obtained by the above preparation method in ammonia decomposition is provided, wherein an ammonia-containing feed gas is contacted with the composite catalyst and reacted to obtain hydrogen.

[0016] Optionally, the space velocity of the feed gas is 100–100,000 mL g. -1 h -1 .

[0017] Optionally, the space velocity of the feed gas is 100 mL g. -1 h -11000mL g -1 h -1 5000mL g -1 h -1 10000mLg -1 h -1 50000mL g -1 h -1 100000mL g -1 h -1 Any value in the range or between two values.

[0018] Optionally, the raw material gas may also contain at least one of nitrogen, argon, and hydrogen.

[0019] Optionally, the volume of ammonia in the raw material gas is 5% to 100%.

[0020] Optionally, the volume of ammonia in the raw material gas is any value or a range between two values ​​from 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%.

[0021] Optionally, the reaction temperature is 300–350°C.

[0022] Optionally, the reaction temperature is any value or a range between two of 300°C, 320°C, 330°C, 340°C, and 350°C.

[0023] The beneficial effects that this application can produce include:

[0024] 1) The composite catalyst provided in this application can achieve efficient decomposition of ammonia at low temperatures, producing CO-free products. x Hydrogen gas.

[0025] 2) The preparation method provided in this application is simple in process and the raw materials are readily available, and it has potential application prospects in the field of ammonia decomposition to produce hydrogen. Attached Figure Description

[0026] Figure 1 The XRD pattern of 3.45MnN-LaN before reaction in Example 3 of this application;

[0027] Figure 2 This is a graph showing the NH3 decomposition activity of different MnN-LaN molar ratios in this application;

[0028] Figure 3 This application relates the ball milling speed to the activity.

[0029] Figure 4 This study examines the relationship between the mixing conditions of MnN and LaN and the catalytic activity for ammonia decomposition in this application.

[0030] Figure 5 This application compares the ammonia decomposition catalytic performance of 3.45MnN-LaN with that of MnN and LaN.

[0031] Figure 6 This application compares the ammonia decomposition catalytic performance of 3.45MnN-CeN with that of MnN and CeN.

[0032] Figure 7 This paper compares the ammonia decomposition catalytic performance of 3.45MnN-PrN with that of MnN and PrN in this application. Detailed Implementation

[0033] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0034] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0035] The ammonia conversion rate is calculated as follows in the embodiments of this application:

[0036] x=(F in,NH3 -F out,NH3 ) / F in,NH3 ×100%

[0037] Where x represents the ammonia conversion rate; F in,NH3 F represents the ammonia inlet flow rate; out,NH3 This represents the outlet flow rate of ammonia gas.

[0038] Example 1:

[0039] Weigh 0.006 mol (0.9174 g) of LaN and 0.0015 mol (0.1034 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 20℃, and the ball milling time to 2 h. The resulting catalyst is denoted as MnN-4LaN (the molar ratio of MnN to LaN is 1:4).

[0040] Weigh 0.05g of MnN-4LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0041] Example 2:

[0042] Weigh 0.004 mol (0.6116 g) of LaN and 0.002 mol (0.137 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them at a speed of 150 r / min, a temperature of 20°C, and a milling time of 2 h. The resulting catalyst is denoted as MnN-2LaN (the molar ratio of MnN to LaN is 1:2).

[0043] Weigh 0.05g of MnN-2LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0044] Example 3:

[0045] Weigh 0.006 mol (0.9174 g) of LaN and 0.0207 mol (1.426 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them at a speed of 150 r / min, a temperature of 20 °C, and a milling time of 2 h. The resulting catalyst is denoted as 3.45MnN-LaN (the molar ratio of MnN to LaN is 3.45:1).

[0046] Weigh 0.05 g of 3.45 MnN-LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0047] Example 4:

[0048] Weigh 0.001 mol (0.1529 g) of LaN and 0.008 mol (0.55144 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and mill them in a ball mill. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 20℃, and the milling time to 2 h. The resulting catalyst is denoted as 8MnN-LaN (the molar ratio of MnN to LaN is 8:1).

[0049] Weigh 0.05g of 8MnN-LaN and place it into a quartz U-shaped reaction tube. Pass pure ammonia (99.99%) into the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0050] Example 5:

[0051] Weigh 0.006 mol (0.9246 g) of CeN and 0.01035 mol (1.427 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them at a speed of 150 r / min, a temperature of 20 °C, and a milling time of 2 h. The resulting catalyst is denoted as 3.45MnN-CeN (the molar ratio of MnN to CeN is 3.45:1).

[0052] Weigh 0.05g of 3.45MnN-CeN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0053] Example 6:

[0054] Weigh 0.003 mol (0.4647 g) of PrN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 20℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-PrN (the molar ratio of MnN to PrN is 3.45:1).

[0055] Weigh 0.05 g of 3.45MnN-PrN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0056] Example 7:

[0057] Weigh 0.003 mol (0.474 g) of NdN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and mill them in a ball mill. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 20℃, and the milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-NdN (the molar ratio of MnN to NdN is 3.45:1).

[0058] Weigh 0.05g of 3.45MnN-NdN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0059] Example 8:

[0060] Weigh 0.003 mol (0.477 g) of PmN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-PmN (the molar ratio of MnN to PmN is 3.45:1).

[0061] Weigh 0.05 g of 3.45MnN-PmN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0062] Example 9:

[0063] Weigh 0.003 mol (0.492 g) of SmN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-SmN (the molar ratio of MnN to NdN is 3.45:1).

[0064] Weigh 0.05g of 3.45MnN-SmN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0065] Example 10:

[0066] Weigh 0.003 mol (0.497 g) of EuN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-EuN (the molar ratio of MnN to EuN is 3.45:1).

[0067] Weigh 0.05 g of 3.45MnN-EuN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0068] Example 11:

[0069] Weigh 0.003 mol (0.513 g) of GdN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-GdN (the molar ratio of MnN to GdN is 3.45:1).

[0070] Weigh 0.05g of 3.45MnN-GdN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0071] Example 12:

[0072] Weigh 0.003 mol (0.516 g) of TbN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and mill them in a ball mill. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-TbN (the molar ratio of MnN to TbN is 3.45:1).

[0073] Weigh 0.05g of 3.45MnN-TbN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0074] Example 13:

[0075] Weigh 0.003 mol (0.529 g) of DyN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-DyN (the molar ratio of MnN to DyN is 3.45:1).

[0076] Weigh 0.05g of 3.45MnN-DyN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0077] Example 14:

[0078] Weigh 0.003 mol (0.536 g) of HoN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 30℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-HoN (the molar ratio of MnN to HoN is 3.45:1).

[0079] Weigh 0.05g of 3.45MnN-HoN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0080] Example 15:

[0081] Weigh 0.003 mol (0.543 g) of ErN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 40℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-ErN (the molar ratio of MnN to ErN is 3.45:1).

[0082] Weigh 0.05g of 3.45MnN-ErN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0083] Example 16:

[0084] Weigh 0.003 mol (0.548 g) of TmN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 40℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-TmN (the molar ratio of MnN to TmN is 3.45:1).

[0085] Weigh 0.05g of 3.45MnN-TmN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0086] Example 17:

[0087] Weigh 0.003 mol (0.561 g) of YbN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both in a ball mill jar and mill them in a ball mill. Set the rotation speed to 200 r / min, the temperature inside the ball mill jar to 50℃, and the milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-YbN (the molar ratio of MnN to YbN is 3.45:1).

[0088] Weigh 0.05g of 3.45MnN-YbN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0089] Example 18:

[0090] Weigh 0.003 mol (0.567 g) of LuN and 0.01035 mol (0.7134 g) of MnN in an argon-filled glove box. Place both into a ball mill jar and ball mill them. Set the rotation speed to 200 r / min, the temperature inside the ball mill jar to 50℃, and the ball milling time to 2 h. This mixture is denoted as catalyst 3.45MnN-LuN (the molar ratio of MnN to LuN is 3.45:1).

[0091] Weigh 0.05g of 3.45MnN-LuN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0092] Example 19:

[0093] Weigh 0.006 mol (0.9174 g) of LaN and 0.0207 mol (1.34 g) of VN in an argon-filled glove box. Place both in a ball mill jar and ball mill them at a speed of 150 r / min, a temperature of 20 °C, and a milling time of 2 h. The resulting catalyst is denoted as 3.45VN-LaN (the molar ratio of VN to LaN is 3.45:1).

[0094] Weigh 0.05 g of 3.45VN-LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0095] Example 20:

[0096] Weigh 0.006 mol (0.9174 g) of LaN and 0.0207 mol (1.36 g) of CrN in an argon-filled glove box. Place both in a ball mill jar and ball mill them. Set the rotation speed to 150 r / min, the temperature inside the ball mill jar to 20℃, and the ball milling time to 2 h. The resulting catalyst is denoted as 3.45CrN-LaN (the molar ratio of CrN to LaN is 3.45:1).

[0097] Weigh 0.05g of 3.45CrN-LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0098] Example 21:

[0099] Weigh 0.006 mol (0.9174 g) of LaN and 0.0207 mol (1.44 g) of FeN in an argon-filled glove box. Place both in a ball mill jar and ball mill them at a speed of 150 r / min, a temperature of 20 °C, and a milling time of 2 h. The resulting catalyst is denoted as 3.45FeN-LaN (the molar ratio of FeN to LaN is 3.45:1).

[0100] Weigh 0.05g of 3.45FeN-LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0101] Comparative Example 1:

[0102] Weigh 0.0006 mol (0.09174 g) of LaN and 0.00207 mol (0.1426 g) of MnN in an argon-filled glove box, and mix them thoroughly with a spatula. This mixture is denoted as catalyst 3.45MnN-LaN-mixture (the molar ratio of MnN to LaN is 3.45:1).

[0103] Weigh 0.05g of 3.45MnN-LaN- mixture and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0104] Comparative Example 2:

[0105] Weigh 0.0195 g of LaN and 0.03085 g of MnN in an argon-filled glove box. Place them separately in quartz tubes, with LaN on top and MnN on the bottom, without mixing. This mixture is designated as catalyst 3.45MnN-LaN(top) (the molar ratio of MnN to LaN is 3.45:1). Introduce pure ammonia (99.99%) as the reaction gas, and raise the sample to the reaction temperature at a rate of 5 °C / min. Analyze the resulting atmosphere using chromatography.

[0106] Comparative Example 3:

[0107] Weigh 0.0195 g of LaN and 0.03085 g of MnN in an argon-filled glove box. Place them separately in quartz tubes, with MnN on top and LaN on the bottom, without mixing. This is denoted as catalyst 3.45MnN-LaN(bottom) (the molar ratio of MnN to LaN is 3.45:1). Introduce pure ammonia (99.99%) as the reaction gas, and raise the sample to the reaction temperature at a rate of 5 °C / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0108] Comparative Example 4:

[0109] Weigh 0.05g of LaN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0110] Comparative Example 5:

[0111] Weigh 0.05g of MnN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0112] Comparative Example 6:

[0113] Weigh 0.05g of CeN and place it into a quartz U-shaped reaction tube. Pass pure ammonia (99.99%) into the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0114] Comparative Example 7:

[0115] Weigh 0.05g of PrN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0116] Comparative Example 8:

[0117] Weigh 0.05g of SmN and place it into a quartz U-shaped reaction tube. Introduce pure ammonia (99.99%) as the reaction gas and raise the sample to the reaction temperature at a rate of 5℃ / min in the reaction atmosphere. Analyze the atmosphere after the reaction using chromatography.

[0118] Table 1. NH3 decomposition activity of different catalysts in the examples at 500℃

[0119]

[0120] DD220907I-DL

[0121]

[0122] Table 1 shows the NH3 conversion rates of the catalysts in the examples and comparative examples at 500°C and 1 atmosphere. Figure 1 The XRD pattern of the catalyst before the reaction indicates that the catalyst composition before the reaction is MnN and LaN. Figure 2 The results show the ammonia decomposition activity of MnN-LaN with different molar ratios, indicating that the catalyst has the highest activity when the molar ratio of MnN to LaN is 3.45. Figure 3 It is the relationship between ball mill speed and activity; Figure 4 The effect of the contact area between MnN and LaN on catalyst performance indicates that the larger the contact area between MnN and LaN, the higher the catalyst activity. Figure 5 , 6 Figures 7 and 8 compare the ammonia decomposition catalytic performance of 3.45MnN-LnN with that of MnN and LnN. It is clear from these three figures that the ammonia decomposition catalytic performance of the catalyst after combining MnN and LnN is significantly improved.

[0123] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A composite catalyst, characterized in that, Including transition metal nitrides and rare earth metal nitrides; The molar ratio of the transition metal nitride to the rare earth metal nitride is 1:0.1~10; The transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride.

2. The composite catalyst according to claim 1, characterized in that, The rare earth metal nitride is selected from at least one of lanthanum nitride, cerium nitride, praseodymium nitride, neodymium nitride, promethium nitride, samarium nitride, europium nitride, gadolinium nitride, terbium nitride, dysprosium nitride, holmium nitride, erbium nitride, thulium nitride, ytterbium nitride, and lutetium nitride.

3. A method for preparing the composite catalyst according to any one of claims 1 to 2, characterized in that, The composite catalyst is obtained by mechanically ball milling a mixture containing transition metal nitrides and rare earth metal nitrides under an inactive atmosphere.

4. The preparation method according to claim 3, characterized in that, The media balls used in the mechanical ball mill are selected from at least one of steel balls, zirconium oxide balls, alumina balls, silica balls, and agate balls; The ratio of the medium spheres to the mixture spheres is 50~500:

1.

5. The preparation method according to claim 3, characterized in that, The inactive atmosphere is selected from at least one of nitrogen, argon, and helium.

6. The preparation method according to claim 3, characterized in that, The mechanical ball mill operates at a speed of 50-300 r / min, at a temperature of 20-50℃, and for a time of 1-200 h.

7. The application of the composite catalyst according to claim 1 or 2, or the composite catalyst prepared according to any one of claims 3 to 6, in ammonia decomposition, characterized in that, The ammonia-containing feed gas is contacted with the composite catalyst to react and produce hydrogen.

8. The application according to claim 7, characterized in that, The space velocity of the feed gas is 100~100000 mL g. -1 h -1 ; The raw material gas also contains at least one of nitrogen, argon, and hydrogen. The volume of ammonia in the raw material gas is 5% to 100%.

9. The application according to claim 7, characterized in that, The reaction temperature is 300~350℃.

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