Composite nitride catalysts, methods of making and use
By preparing a composite catalyst of transition metals and rare earth metal nitrides, the problem of insufficient catalytic activity under high temperature and high pressure was solved, and efficient ammonia synthesis catalysis under mild conditions was achieved, reducing energy consumption and cost.
Patent Information
- Application Number
- CN202311567625.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2023-09-21
- Filing Date
- 2023-11-22
- Publication Date
- 2025-11-18
- Estimated Expiration
- 2043-11-22
AI Technical Summary
Existing ammonia synthesis catalysts have insufficient catalytic activity under high temperature and high pressure, resulting in high energy consumption, high cost and large CO2 emissions. Furthermore, rare earth metal nitrides and pre-transition metal nitrides have low ammonia synthesis activity when used alone.
A composite nitride catalyst was prepared by combining transition metal nitrides and rare earth metal nitrides through ball milling and activation treatment, and used for the catalytic synthesis of ammonia under relatively mild conditions.
This improves catalytic activity and stability, reduces energy consumption and cost in ammonia synthesis, and provides new ideas for designing highly efficient catalysts.
Smart Images
Figure CN119657191B_ABST
Abstract
Description
Technical Field
[0001] This application relates to a composite nitride catalyst, its preparation method, and its application, belonging to the field of catalyst preparation technology. Background Technology
[0002] Ammonia is mainly used in the production of fertilizers, nitric acid, ammonium salts, and soda ash, and is one of the world's largest-produced chemical products. Social development and population growth have greatly boosted the production and consumption of ammonia-related industrial chemicals. Currently, the demand for ammonia-related industrial chemicals in fertilizers, plastics, pharmaceuticals, explosives, metallurgy, and environmental protection sectors is increasing daily. my country is the world's largest producer of synthetic ammonia, and the synthetic ammonia industry plays a vital role in the national economy. Compared with advanced international levels, my country's synthetic ammonia industry generally suffers from high energy consumption, high costs, and large CO2 emissions. In recent years, increasingly stringent policies on sustainable development and energy conservation and emission reduction have placed higher demands on my country's synthetic ammonia industry.
[0003] Ammonia synthesis has undergone a century of development, and its production processes have matured. Technological innovation in ammonia synthesis catalysts is key to reducing energy consumption and costs in the ammonia synthesis industry. Currently, molten iron catalysts are widely used in ammonia synthesis processes based on the Harber-Bosch process, requiring high-temperature (400–500℃) and high-pressure (10–30 MPa) reaction conditions. In 1992, BP and Kellogg successfully developed the KAAP process based on graphitized carbon-supported ruthenium catalysts (Ru / C), which offers advantages such as high reactivity, relatively mild reaction conditions, and low energy consumption. However, the methanation reaction of the carbon support under ammonia synthesis conditions leads to catalyst deactivation, limiting the widespread application of Ru / C catalysts. Therefore, although two generations of ammonia synthesis catalysts have been developed, the development of novel, highly efficient ammonia synthesis catalysts still faces significant challenges due to the requirement of high temperatures and pressures for their catalytic synthesis.
[0004] Besides iron-based and ruthenium-based catalysts, transition metal nitrides, due to their metalloid properties, can be applied in catalysis. Among them, post-transition metals (Fe, Co, Ni) have been extensively studied in ammonia synthesis. However, the weak nitrogen adsorption capacity of pre-transition metals limits their application in ammonia synthesis. The manganese nitride-lithium hydride system, with its dual reactive centers of manganese nitride and Li-NH species, effectively separates the nitrogen activation and hydrogenation steps by activating N2 and releasing ammonia, thus exhibiting better ammonia synthesis performance. However, manganese nitride itself has relatively low ammonia synthesis activity. Besides the pre-transition metals, rare earth metal nitrides can form nitrogen vacancies and, after loading transition metals Co and Ni on their surface (ACS Catalysis, 2021, 11(12): 7595-7603. Journal of the American Chemical Society, 2021, 143(32): 12857-12866.), also exhibit good ammonia synthesis performance. However, the ammonia synthesis activity of rare earth metal nitrides themselves is very low. Summary of the Invention
[0005] This invention provides a composite nitride ammonia synthesis catalyst composed of transition metal nitrides and rare earth metal nitrides, in which the two nitrides work synergistically to catalyze ammonia synthesis.
[0006] This application utilizes a former transition metal nitride and a rare earth metal nitride to prepare a highly active composite nitride ammonia synthesis catalyst, which provides a new approach for the design and preparation of novel and efficient ammonia synthesis catalysts; moreover, there are currently no reports on the composite catalysis of ammonia synthesis using rare earth metal nitrides and former transition metal nitrides.
[0007] According to one aspect of this application, a composite nitride catalyst is provided, the composite nitride catalyst comprising transition metal nitrides and rare earth metal nitrides;
[0008] In the composite nitride catalyst, the molar ratio of the transition metal nitride to the rare earth metal nitride is 0.5:1 to 50:1.
[0009] Optionally, in the composite nitride catalyst, the molar ratio of the transition metal nitride to the rare earth metal nitride is selected from any value of 0.5:1, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1 or a range between any two of the above.
[0010] Optionally, the transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride.
[0011] Optionally, the rare earth metal nitride is selected from at least one of lanthanum nitride, cerium nitride, praseodymium nitride, neodymium nitride, samarium nitride, europium nitride, gadolinium nitride, erbium nitride, yttrium nitride, terbium nitride, dysprosium nitride, holmium nitride, thulium nitride, and ytterbium nitride.
[0012] According to another aspect of this application, a method for preparing the above-described composite nitride catalyst is provided, comprising the following steps:
[0013] (1) Under an inactive atmosphere, the raw material containing transition metal nitride and rare earth metal nitride precursors is ball-milled to obtain catalyst precursor;
[0014] (2) The catalyst precursor is activated under an active atmosphere to obtain the composite nitride catalyst.
[0015] Optionally, the rare earth metal nitride precursor is a rare earth metal hydride corresponding to the rare earth metal nitride.
[0016] Optionally, the rare earth metal hydride is selected from at least one of lanthanum hydride, cerium hydride, praseodymium hydride, neodymium hydride, samarium hydride, europium hydride, gadolinium hydride, terbium hydride, dysprosium hydride, holmium hydride, erbium hydride, thulium hydride, ytterbium hydride, and yttrium hydride.
[0017] Optionally, the transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride.
[0018] Optionally, the molar ratio of the transition metal nitride to the rare earth metal nitride precursor is 0.5:1 to 50:1.
[0019] Optionally, the molar ratio of the transition metal nitride to the rare earth metal nitride precursor is selected from any value of 0.5:1, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1 or a range between any two of the above.
[0020] Optionally, the media balls used in the ball mill are selected from at least one of steel balls, zirconia balls, alumina balls, silicon nitride balls, and agate balls.
[0021] Optionally, the ratio of the medium balls to the raw material balls is 50 to 500:1.
[0022] Optionally, the ball-to-material ratio of the medium ball to the raw material is selected from any value of 50:1, 100:1, 200:1, 300:1, 400:1, 500:1 or a range between any two of the above.
[0023] Optionally, the ball mill rotation speed is 50-300 r / min, and the ball milling time is 0.1-200 h.
[0024] Optionally, the rotational speed of the ball mill is selected from any value of 50 r / min, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min or a range between any two of the above.
[0025] Optionally, the temperature of the ball mill is 20–50°C.
[0026] Optionally, the ball milling temperature is any value among 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C, or a range between any two of the above.
[0027] Optionally, in step (2), the activation temperature is 300-500℃ and the activation time is 0.1-12h.
[0028] Optionally, the activation temperature is selected from any value of 300°C, 350°C, 400°C, 450°C, 500°C, or a range between any two of the above.
[0029] Optionally, the activation time is selected from any value of 0.1h, 0.5h, 1h, 5h, 8h, 10h, 12h or a range between any two of the above.
[0030] Optionally, in step (2), the active atmosphere is a mixture of hydrogen and nitrogen.
[0031] Optionally, the nitrogen content in the mixed gas is 1% to 90% by volume.
[0032] Optionally, the volume content of nitrogen in the mixed gas is selected from any value of 1%, 5%, 10%, 20%, 30%, 50%, 80%, 90%, or a range between any two of the above.
[0033] Optionally, the flow rate of the active atmosphere is 10–200 mL / min. -1 .
[0034] Optionally, the flow rate of the active atmosphere is selected from 10 mL / min. -1 20mL min -1 50mL min -1 100mLmin -1 150mL min -1 180mL min -1 200mL min -1 Any value in or a range between any two of the above.
[0035] Optionally, the inactive atmosphere is selected from at least one of nitrogen atmosphere, argon atmosphere, and helium atmosphere.
[0036] According to another aspect of this application, a method for preparing synthetic ammonia is provided, the method comprising:
[0037] Ammonia is produced by reacting a feed gas containing hydrogen and nitrogen with a composite nitride catalyst.
[0038] The composite nitride catalyst is selected from the composite nitride catalysts described above.
[0039] Optionally, the volume ratio of nitrogen to hydrogen is 1:3 to 1:1.
[0040] Optionally, the reaction temperature is 250–400°C.
[0041] Optionally, the temperature of the reaction is selected from any value of 250°C, 280°C, 300°C, 350°C, 380°C, 400°C, or a range between any two of the above.
[0042] Optionally, the reaction pressure is 0.1 to 5 MPa.
[0043] Optionally, the pressure of the reaction is selected from any value of 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, or a range between any two of the above.
[0044] Optionally, the space velocity of the feed gas is 1000–30000 mL gcat. -1 h -1 .
[0045] Optionally, the space velocity of the feed gas is selected from 1000 gcat. -1 h -1 1500gcat -1 h -1 2000gcat -1 h -1 2500gcat -1 h -1 10000gcat -1 h -1 20000gcat -1 h -1 30000gcat -1 h -1 Any value in or a range between any two of the above.
[0046] Optionally, the ammonia synthesis conditions are 1 MPa, 400 °C, and the reaction gas composition is 25 vol% N2 and 75 vol% H2.
[0047] The beneficial effects that this application can produce include:
[0048] 1) The composite nitride provided in this application is composed of transition metal nitrides and rare earth metal nitrides, and has good catalytic activity in the ammonia synthesis reaction.
[0049] 2) Compared with single nitride catalysts, the composite nitride catalysts provided in this application can significantly improve the ammonia synthesis activity and have better catalytic activity and stability under milder conditions.
[0050] 3) The composite nitride catalyst provided in this application has a simple preparation process and low cost, and has potential application prospects in the field of ammonia synthesis. Attached Figure Description
[0051] Figure 1 The images show the XRD patterns of the catalysts before reaction in Examples 1, 2, 5, Comparative Example 1, and Comparative Example 2 of this application.
[0052] Figure 2 The XRD patterns of the catalysts after reaction in Examples 1, 2, 5, Comparative Example 1, and Comparative Example 2 of this application are shown. Detailed Implementation
[0053] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0054] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0055] In the embodiments of this application, the ammonia synthesis reaction is carried out on a fixed-bed microreactor using a stainless steel reactor. The composition of the reaction gas is analyzed by a conductivity meter, and the reaction tail gas is passed into a dilute sulfuric acid solution. At the same time, the conductivity meter is used to track the change in conductivity. Finally, the ammonia generation rate is calculated based on the conductivity parameters.
[0056] Example 1
[0057] 0.002 mol EuH2 and 0.001 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 100:1, the rotation speed was 100 r / min, and the ball milling time was 1 hour. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (40 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as 0.5MnN-EuN (the molar ratio of MnN to EuN was 0.5:1).
[0058] Weigh 0.03 g of 0.5 MnN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0059] Example 2:
[0060] 0.002 mol EuH2 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 100:1, the rotation speed was 100 r / min, and the ball milling time was 1 hour. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (40 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-EuN (the molar ratio of MnN to EuN was 1:1).
[0061] Weigh 0.03 g of MnN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0062] Example 3:
[0063] 0.002 mol EuH2 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 100:1, the rotation speed was 100 r / min, and the ball milling time was 1 hour. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (10 mL / min). -1The catalyst was activated at 500℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-EuN (the molar ratio of MnN to EuN was 1:1).
[0064] Weigh 0.03 g of MnN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 375℃ and utilizing the change in conductivity in the dilute sulfuric acid solution. The flow rate was maintained at 20 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0065] Example 4:
[0066] 0.002 mol EuH2 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 100:1, the rotation speed was 100 r / min, and the ball milling time was 1 hour. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (200 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-EuN (the molar ratio of MnN to EuN was 1:1).
[0067] Weigh 0.03 g of MnN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 375℃ and utilizing the change in conductivity in the dilute sulfuric acid solution. The flow rate was maintained at 50 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0068] Example 5:
[0069] 0.00075 mol EuH2 and 0.006 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 100:1, the rotation speed was 200 r / min, and the ball milling time was 3 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (40 mL / min). -1The catalyst was activated at 500℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as 8MnN-EuN (the molar ratio of MnN to EuN was 8:1).
[0070] Weigh 0.03 g of 8MnN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0071] Example 6:
[0072] 0.002 mol LaH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 100:1, the rotation speed was 200 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-LaN (the molar ratio of MnN to LaN was 1:1).
[0073] Weigh 0.03 g of MnN-LaN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0074] Example 7:
[0075] 0.002 mol CeH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 100:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 500℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-CeN (the molar ratio of MnN to CeN was 1:1).
[0076] Weigh 0.03 g of MnN-CeN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0077] Example 8:
[0078] 0.002 mol PrH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 100:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-PrN (the molar ratio of MnN to PrN was 1:1).
[0079] Weigh 0.03 g of MnN-PrN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0080] Example 9:
[0081] 0.002 mol NdH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 500:1, the rotation speed was 200 r / min, and the ball milling time was 3 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-PrN (the molar ratio of MnN to PrN was 1:1).
[0082] Weigh 0.03 g of MnN-PrN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0083] Example 10:
[0084] 0.002 mol SmH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 50:1, the rotation speed was 100 r / min, and the ball milling time was 1 hour. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-SmN (the molar ratio of MnN to SmN was 1:1).
[0085] Weigh 0.03 g of MnN-SmN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0086] Example 11:
[0087] 0.002 mol GdH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 300:1, the rotation speed was 50 r / min, and the ball milling time was 10 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-GdN (the molar ratio of MnN to GdN was 1:1).
[0088] Weigh 0.03 g of MnN-GdN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0089] Example 12:
[0090] 0.002 mol TbH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 500:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-TbN (the molar ratio of MnN to TbN was 1:1).
[0091] Weigh 0.03 g of MnN-TbN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0092] Example 13:
[0093] 0.002 mol DyH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 400:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-DyN (the molar ratio of MnN to DyN was 1:1).
[0094] Weigh 0.03 g of MnN-DyN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0095] Example 14:
[0096] 0.002 mol HoH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 200:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-HoN (the molar ratio of MnN to HoN was 1:1).
[0097] Weigh 0.03 g of MnN-HoN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0098] Example 15:
[0099] 0.002 mol ErH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls. The ball-to-material mass ratio during the ball milling process was 50:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-ErN (the molar ratio of MnN to ErN was 1:1).
[0100] Weigh 0.03 g of MnN-ErN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0101] Example 16:
[0102] 0.002 mol TmH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were stainless steel balls, the ball-to-material mass ratio was 300:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-TmN (the molar ratio of MnN to TmN was 1:1).
[0103] Weigh 0.03 g of MnN-TmN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0104] Example 17:
[0105] 0.002 mol YbH3 and 0.002 mol MnN were weighed and placed in a ball mill jar, and ball milled at 20 °C on a planetary ball mill. The media balls were zirconia balls, the ball-to-material mass ratio was 200:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as MnN-YbN (the molar ratio of MnN to YbN was 1:1).
[0106] Weigh 0.03 g of MnN-YbN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0107] Example 18:
[0108] 0.002 mol EuH2 and 0.002 mol VN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were alumina balls, the ball-to-material mass ratio was 500:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as VN-EuN (the molar ratio of VN to EuN was 1:1).
[0109] Weigh 0.03 g of VN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity in the dilute sulfuric acid solution. The flow rate was maintained at 200 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0110] Example 19:
[0111] 0.002 mol EuH2 and 0.002 mol CrN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were silicon nitride balls, the ball-to-material mass ratio was 500:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as CrN-EuN (the molar ratio of CrN to EuN was 1:1).
[0112] Weigh 0.03 g of CrN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 0.1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0113] Example 20:
[0114] 0.002 mol EuH2 and 0.002 mol FeN were weighed and placed in a ball mill jar, and ball milled at 20°C on a planetary ball mill. The media balls were agate balls, the ball-to-material mass ratio was 300:1, the rotation speed was 100 r / min, and the ball milling time was 5 hours. The obtained catalyst precursor solid powder was then subjected to a 75% H2 / N2 gas flow (30 mL / min). -1 The catalyst was activated at 400℃ for 2 hours to obtain a composite nitride catalyst, which was denoted as FeN-EuN (the molar ratio of FeN to EuN was 1:1).
[0115] Weigh 0.03 g of FeN-EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 5 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0116] Comparative Example 1:
[0117] Weigh 0.03 g of MnN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0118] Comparative Example 2:
[0119] Weigh out EuH2 and load it into a stainless steel reaction tube. Purge with 75% H2 / N2 (volume ratio H2:N2 = 3:1), raise the pressure to 1 MPa, and then proceed at 5°C for 1 minute. -1 The temperature was raised to 400℃ and held for 3 hours to obtain the EuN sample.
[0120] Weigh 0.03g of EuN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1MPa and immerse the sample in the reaction atmosphere at 5℃ for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0121] Comparative Example 3:
[0122] Weigh out LaH3 and load it into a stainless steel reaction tube. Purge with 75% H2 / N2 (volume ratio H2:N2 = 3:1), raise the pressure to 1 MPa, and then proceed at 5°C for 1 minute. -1 The temperature was raised to 400℃ and held for 3 hours to obtain the LaN sample.
[0123] Weigh 0.03 g of LaN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0124] Comparative Example 4:
[0125] Weigh out CeH3 and load it into a stainless steel reaction tube. Purge with 75% H2 / N2 (volume ratio H2:N2 = 3:1), raise the pressure to 1 MPa, and then proceed at 5°C for 1 minute. -1 The temperature was raised to 400℃ and held for 3 hours to obtain the CeN sample.
[0126] Weigh 0.03 g of CeN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0127] Comparative Example 5:
[0128] Weigh out PrH3 and place it into a stainless steel reaction tube. Introduce 75% H2 / N2 (volume ratio H2:N2 = 3:1), raise the pressure to 1 MPa, and then proceed at 5°C for 1 minute. -1 The temperature was raised to 400℃ and held for 3 hours to obtain the sample PrN.
[0129] Weigh 0.03 g of PrN and place it into a stainless steel reaction tube. Introduce a reaction gas of 75% H2 / N2 (volume ratio H2:N2 = 3:1). Increase the reaction pressure to 1 MPa and immerse the sample in the reaction atmosphere at 5 °C for 1 minute. -1 The rate of ammonia synthesis was calculated by increasing the reaction temperature to 400℃ and utilizing the change in conductivity of the dilute sulfuric acid solution. The flow rate was maintained at 30 mL / min. -1 Under the specified conditions, the ammonia synthesis rate was tested, and the specific results are shown in Table 1.
[0130] Table 1
[0131]
[0132]
[0133]
[0134] Table 1 shows the activity values of the catalysts in Examples 1-20 and Comparative Examples 1-5. As can be seen from Table 1, the ammonia synthesis rate of the catalyst after TMN and LnN are combined is significantly improved. Figure 1 The XRD pattern of the catalyst before the reaction shows that the catalyst precursor consists of MnN and EuH2. Figure 2 This is the XRD pattern of the catalyst after the reaction, indicating the reaction results of LnH. x It was transformed into LnN.
[0135] 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 nitride catalyst, characterized in that, The composite nitride catalyst is composed of transition metal nitrides and rare earth metal nitrides; In the composite nitride catalyst, the molar ratio of the transition metal nitride to the rare earth metal nitride is 0.5:1 to 50:1; The transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride.
2. The composite nitride 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, samarium nitride, europium nitride, gadolinium nitride, erbium nitride, yttrium nitride, terbium nitride, dysprosium nitride, holmium nitride, thulium nitride, and ytterbium nitride.
3. The method for preparing the composite nitride catalyst according to any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Under an inactive atmosphere, the raw material containing transition metal nitride and rare earth metal nitride precursors is ball-milled to obtain catalyst precursor; (2) The catalyst precursor is activated under an active atmosphere to obtain the composite nitride catalyst.
4. The preparation method according to claim 3, characterized in that, The rare earth metal nitride precursor is a rare earth metal hydride corresponding to the rare earth metal nitride. The rare earth metal hydride is selected from at least one of lanthanum hydride, cerium hydride, praseodymium hydride, neodymium hydride, samarium hydride, europium hydride, gadolinium hydride, terbium hydride, dysprosium hydride, holmium hydride, erbium hydride, thulium hydride, ytterbium hydride, and yttrium hydride. The transition metal nitride is selected from at least one of vanadium nitride, chromium nitride, manganese nitride, and iron nitride; The molar ratio of the transition metal nitride to the rare earth metal nitride precursor is 0.5:1 to 50:
1.
5. The preparation method according to claim 3, characterized in that, The ball milling media are selected from at least one of steel balls, zirconium oxide balls, alumina balls, silicon nitride balls, and agate balls; The ratio of the medium spheres to the raw material spheres is 50~500:1; The ball milling speed is 50~300 r / min, and the ball milling time is 0.1~200 h; The ball milling temperature is 20~50℃.
6. The preparation method according to claim 3, characterized in that, In step (2), the activation temperature is 300~500℃ and the activation time is 0.1~12h.
7. The preparation method according to claim 3, characterized in that, In step (2), the active atmosphere is a mixture of hydrogen and nitrogen. The nitrogen content in the mixed gas is 1% to 90% by volume; The flow rate of the active atmosphere is 10~200 mL / min. -1 .
8. The preparation method according to claim 3, characterized in that, The inactive atmosphere is selected from at least one of nitrogen atmosphere, argon atmosphere, and helium atmosphere.
9. A method for preparing synthetic ammonia, characterized in that, The preparation method includes: Ammonia is produced by reacting a feed gas containing hydrogen and nitrogen with a composite nitride catalyst. The composite nitride catalyst is selected from the composite nitride catalysts described in any one of claims 1 to 2.
10. The preparation method according to claim 9, characterized in that, The volume ratio of nitrogen to hydrogen is 1:3 to 1:1; The reaction temperature is 250~400℃; The reaction pressure is 0.1~5 MPa; The space velocity of the feed gas is 1000~30000 mL gcat. -1 h -1 .