Ga-Fe based liquid alloy catalyst, its preparation method and application

Abstract

The present application relates to a kind of Ga-Fe base liquid alloy catalyst and its preparation method and application, the Ga-Fe base liquid alloy catalyst includes metal Ga, metal Fe and metal M, the metal M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo, W.The Ga-Fe base liquid alloy catalyst provided in the present application is with metal Ga as matrix, with metal Fe and metal M as active catalytic site, based on metal Ga can be mutually soluble with other metals and form low melting point alloy characteristics, so that in the alloy catalyst formed can become liquid at reaction temperature and carry out reaction, due to the flow characteristics of liquid, it is advantageous to the metal active component of synthesis ammonia constantly refreshes at interface, so that nitrogen and hydrogen and metal Fe, metal M contact more fully, mass transfer efficiency is higher, and the phenomenon of traditional solid catalyst active site poisoning deactivation does not occur, so that N2 and H2 can effectively react to generate ammonia under low temperature and low pressure conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal catalysis, in particular to a Ga-Fe-based liquid alloy catalyst and a preparation method and application thereof. BACKGROUND

[0002] The importance of ammonia is self-evident, and it plays an irreplaceable role in agricultural production, military medical treatment, energy application, etc. The research on thermal catalytic synthesis of ammonia has never stopped for more than a hundred years. However, the CO2 produced in industrial production for years has caused serious greenhouse effect, and the problem of energy consumption cannot be ignored. Under the development concept of green chemistry, ammonia synthesis under the condition of low temperature and low pressure is a field worth studying, which can effectively reduce the double burden of energy and environment.

[0003] Under this premise, liquid alloy has entered the researchers' field of vision, especially Ga-based liquid alloy, which has been the subject of many related studies, such as: Unveiling metal mobility in a liquid Cu-Ga catalyst for ammonia synthesis and Conversion of CO2 into fibrous carbon materials using Ga-based liquid alloys and Gallium-rich Pd-Ga phases as supported liquid metal catalysts, etc. Liquid alloy catalysts do not rely on noble metals, which reduces costs and meets the needs of sustainable development, which is crucial to reduce dependence on rare and expensive resources. Liquid alloy catalysts exhibit higher activity and stability than traditional catalysts in some cases, for example, Cu-Ga liquid alloy catalysts exhibit 100 hours of stability in thermal catalytic synthesis of ammonia. In addition, liquid metal catalysts, due to their unique fluidity and high catalytic surface area, may revolutionize traditional chemical engineering processes, especially in the field of green chemical solutions for manufacturing plastics, fertilizers, fuels, etc. Liquid metal catalysts provide a possible "green chemical" solution, which helps to reduce the energy consumption of the chemical industry and promote green chemical reactions.

[0004] For example, the patent with publication number CN112266002A discloses a method for catalytic synthesis of ammonia at normal pressure. In the method, hydrogen and nitrogen are synthesized into ammonia at normal pressure in a reactor with liquid alloy as catalyst. In the method, the preparation method of the liquid alloy is as follows: in an argon glove box, Li and Sn are mixed and placed in a crucible; LiCl and KCl are mixed and covered on the surface to isolate the metal from the atmosphere; the whole crucible is transferred to a tube furnace, heated under argon protection, cooled to room temperature after holding, and then the LiCl and KCl are removed to obtain a pre-prepared Li-Sn alloy; and the liquid alloy prepared by the method still needs to use molten salt when catalytically synthesizing ammonia. The liquid alloy uses alkali metals with high activity, and the alkali metals are easy to react with nitrogen to form alkali metal nitride. The molten salt provides a new reaction interface for the reaction of metal nitride and hydrogen to synthesize ammonia, so that the metal nitride continuously generates ammonia. The first metal nitride reacts with hydrogen to synthesize ammonia, and the second metal and the third metal catalyze the decomposition of the first metal hydride into the first metal and hydrogen. However, the method needs to use molten salt under inert gas conditions, which has high requirements for equipment and method. SUMMARY

[0005] Therefore, the Ga-Fe-based liquid alloy catalyst, the preparation method and the application thereof are provided.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows.

[0007] The Ga-Fe-based liquid alloy catalyst provided by the present application comprises metal Ga, metal Fe and metal M, and the metal M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo and W.

[0008] The Ga-Fe-based liquid alloy catalyst provided by the present application comprises metal Ga, metal Fe and metal M, and the metal M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo and W. The Ga-Fe-based liquid alloy catalyst provided by the present application comprises metal Ga, metal Fe and metal M, and the metal M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo and W. The Ga-Fe-based liquid alloy catalyst provided by the present application comprises metal Ga, metal Fe and metal M, and the metal M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo and W.

[0009] As a further improvement of the above-mentioned scheme of the present application, the mass percentage of the metal Ga in the Ga-Fe-based liquid alloy catalyst is 90% to 99%.

[0010] As a further improvement of the above-mentioned scheme of the present application, the mass ratio of the metal Fe and the metal M in the Ga-Fe-based liquid alloy catalyst is 1 to 2:1.

[0011] The present application also provides a method for preparing the Ga-Fe-based liquid alloy catalyst as mentioned above, which comprises the following steps: under a protective atmosphere, adding metal Ga powder, metal Fe powder and metal M powder into a ball milling jar and sealing, and carrying out ball milling under the sealed state to obtain the Ga-Fe-based liquid alloy catalyst.

[0012] As a further improvement of the above-mentioned scheme of the present application, the ball-to-material ratio of the ball milling is 20 to 30:1, the rotation speed is 200 to 600 rpm, and the time is 10 to 60 min.

[0013] As a further improvement of the above-mentioned scheme of the present application, the protective atmosphere is in an N2 or Ar glove box.

[0014] As a further improvement of the above-mentioned scheme of the present application, the purity of the metal Ga powder and the metal Fe powder is 99.99%.

[0015] The present application also provides an application of the Ga-Fe-based liquid alloy catalyst as mentioned above in the thermal catalytic synthesis of ammonia.

[0016] As a further improvement of the above-mentioned scheme of the present application, it comprises the following steps: filling the Ga-Fe-based liquid alloy catalyst at one end of a U-shaped reaction tube with a sieve plate of an ammonia synthesis fixed reaction bed, introducing a mixed gas of N2 and H2, and heating reaction.

[0017] As a further improvement of the above-mentioned scheme of the present application, in the mixed gas, the molar ratio of N2 and H2 is 1:1 to 5, and the flow rate of the mixed gas is 20 to 300 mL / min.

[0018] As a further improvement of the above-mentioned scheme of the present application, the temperature of the heating reaction is 200 to 500℃, and the pressure is 1 to 5 MPa.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1.The Ga-Fe-based liquid alloy catalyst provided by the application takes metal Ga as a matrix, takes metal Fe and metal M as active catalytic sites, and is based on the feature that metal Ga can be mutually soluble with other metals to form a low-melting-point alloy, so that the formed alloy catalyst can become liquid at a reaction temperature to perform a reaction, due to the flowability of the liquid state, the metal active components for synthesizing ammonia are constantly refreshed at an interface, nitrogen and hydrogen are more fully contacted with the metal Fe and the metal M, the mass transfer efficiency is higher, and the phenomenon of poisoning and deactivation of the active sites in traditional solid catalysts does not occur, so that N2 and H2 can effectively react to generate ammonia under low-temperature and low-pressure conditions; and the metal Fe and the metal M can strongly and weakly interact with each other, the electronic structure of the catalyst can be adjusted, and then the activity and selectivity of the ammonia synthesis reaction can be adjusted.

[0021] 2.In the preparation of the Ga-Fe-based liquid alloy catalyst, inert gas protection is used to prevent oxidation, the Ga-Fe-based liquid alloy is simply and quickly synthesized through ball milling, the metal Ga powder, the metal Fe powder, and the metal M powder can be fully mixed through ball milling, the grinding medium and the metal material in the ball milling tank are mutually impacted and rubbed through rotation and vibration, so that the size of the material particles is significantly reduced, the surface area of the particles is increased, and the activity and usability of the catalyst are improved; the high-energy impact and local high temperature in the ball milling process can promote a solid-state reaction, so that the alloying process among Ga, Fe, and M is more thorough; through appropriate ball milling conditions, a catalyst with nanometer size, high surface area, and unique physical and chemical properties can be obtained. The preparation method of the application is simple in operation, high in repeatability, and can be prepared in large quantities.

[0022] 3.The Ga-Fe-based liquid alloy synthesized by the application can be used as a hot catalytic ammonia synthesis catalyst, and good catalytic effects can be achieved under low-temperature and low-pressure conditions; the liquid alloy is constantly turned over under the action of the gas flow during the reaction process, which is beneficial to the refreshing of the active components at the interface, so that the deactivation of the reaction sites can be avoided, good reaction activity and cyclic stability are ensured, and large-scale synthesis of ammonia is easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The XRD pattern of the Ga-Fe3Ni2 liquid alloy prepared in Example 1 of the application; 95 The XRD pattern of the Ga-Fe3Ni2 liquid alloy prepared in Example 1 of the application;

[0024] Figure 2 The SEM and Mapping images of the Ga-Fe3Ni2 liquid alloy prepared in Example 1 of the application; 95 The SEM and Mapping images of the Ga-Fe3Ni2 liquid alloy prepared in Example 1 of the application;

[0025] Figure 3 The XRD pattern of the Ga-Fe3Ni2 liquid alloy prepared in Example 2 of the application; 90SEM and Mapping images of Fe6Co4 liquid alloy. DETAILED DESCRIPTION

[0026] For the purpose of promoting an understanding of the application, the application will be described in greater detail below with reference to specific embodiments. However, the application can be realized in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0028] Example 1

[0029] This example proposes a Ga-Fe-based liquid alloy catalyst, and the preparation method thereof comprises the following steps: in a glove box filled with N2, 1.9 g of Ga powder, 0.06 g of Fe powder and 0.04 g of Ni powder are weighed and placed in a polytetrafluoroethylene grinding jar, the mass ratio of grinding balls to materials is 30:1, the grinding jar is sealed, and ball milling is performed under N2 protection for 30 min to obtain a Ga-Fe-based liquid alloy catalyst Ga 95 Fe3Ni2.

[0030] Figure 1 Ga 95 Fe3Ni2 liquid alloy is characterized by XRD (XRD, Cu-Ka, λ = 1.5406 Å) to obtain an X-ray diffraction spectrum, from which it can be seen that the Ga Figure 1 Fe3Ni2 prepared in this example has good crystallinity and corresponds to standard cards (Ga PDF # 05-0601), (Fe PDF # 85-1410) and (Ni PDF # 87-0712) respectively. 95

[0031] Figure 2 Ga 95 Fe3Ni2 liquid alloy is characterized by scanning electron microscopy to obtain scanning electron microscope images and element distribution maps, from which it can be seen that the Ga Figure 2 Fe3Ni2 prepared in this example has good crystallinity and corresponds to standard cards (Ga PDF # 05-0601), (Fe PDF # 85-1410) and (Ni PDF # 87-0712) respectively. 95 Fe3Ni2 prepared in this example is a solid particle at room temperature, and the Ga, Fe and Ni elements are very uniformly distributed.

[0032] Comparative Example 1

[0033] ​The present comparative example proposes a liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.94 g of Ga powder and 0.06 g of Fe powder in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, sealing the grinding tank, and ball milling for 30 min under the protection of N2 to obtain a Ga-Fe-based liquid alloy catalyst Ga 97 Fe3.

[0034] Comparative Example 2

[0035] The present comparative example proposes a liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.94 g of Ga powder and 0.06 g of Fe powder in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, sealing the grinding tank, and ball milling for 30 min under the protection of N2 to obtain a Ga-Fe-based liquid alloy catalyst Ga 98 Ni2.

[0036] Test Example 1

[0037] The present test example tests the catalytic activity of the liquid alloy catalysts of Example 1 and Comparative Examples 1-2 as a catalyst for thermocatalytic synthesis of ammonia, wherein the method for thermocatalytic synthesis of ammonia is as follows: 500 mg of the catalyst is loaded in a U-shaped reaction tube with a sieve plate at one end of an ammonia synthesis fixed bed reactor, the fixed reaction temperature is 400 ℃, the reaction pressure is 3 MPa, the molar ratio of N2:H2 is 1:3, the flow rate of the mixed gas is 120 mL / min, the generated ammonia is collected and the ammonia yield is calculated, and the results are shown in Table 1.

[0038] The ammonia yield calculation method is as follows: the collected ammonia gas is introduced into an H2SO4 solution (0.1 mol / L), NH3 in the acid solution is converted into NH4 + , the concentration of NH4 + in the H2SO4 solution is calculated by using an ultraviolet spectrophotometer, the specific method is salicylic acid-hypochlorite spectrophotometry, and the specific principle is that in the presence of an alkaline medium (pH=11.7) and sodium nitroprusside, ammonia and ammonium ions in water react with salicylate and hypochlorite ions to generate a blue compound, the compound has a maximum absorption peak at 697 nm, the absorbance is measured by a spectrophotometer, and the concentration of ammonia can be quantitatively analyzed; NH4Cl is used as a standard substance of NH4 + , different concentrations of NH4Cl solution are prepared, a standard curve of NH4 + concentration-absorbance can be drawn according to the above salicylic acid-hypochlorite spectrophotometry; the H2SO4 solution after absorbing ammonia is detected by the same test method of the standard curve, and the concentration of NH4 + in the H2SO4 solution can be obtained by substituting into the standard curve. The ammonia yield is calculated according to the following formula:

[0039]

[0040] In the formula: NH4 during the reaction time + Concentration difference, Represents catalyst quality. t This represents the reaction time.

[0041] Table 1. Results of ammonia synthesis catalytic activity tests in Example 1 and Comparative Examples 1-2

[0042]

[0043] As can be seen from the results in Table 1, compared with single-metal modified Ga liquid alloys Ga 98 Ni2 and Ga 97 Fe3, the bimetallic modified Ga liquid alloy prepared in Example 1 95 Fe3Ni2 exhibits a good ammonia synthesis reaction rate and a significant activity enhancement.

[0044] Example 2

[0045] This embodiment proposes a Ga-Fe based liquid alloy catalyst, the preparation method of which includes the following steps: In a glove box filled with N2, 1.8g of Ga powder, 0.12g of Fe powder, and 0.08g of Co powder are weighed and placed in a polytetrafluoroethylene grinding jar. The mass ratio of grinding balls to materials is 30:1. The grinding jar is sealed, and the mixture is ball-milled for 40 minutes under N2 protection to obtain the Ga-Fe based liquid alloy catalyst. 90 Fe6Co4.

[0046] Figure 3 The Ga prepared in this embodiment 90 The Fe6Co4 liquid alloy was characterized by scanning electron microscopy, resulting in scanning electron microscope images and elemental distribution maps. Figure 3 It can be seen that the Ga prepared in this embodiment 90 Fe6Co4 is a solid particle at room temperature, and the Ga, Fe, and Co elements are distributed very evenly.

[0047] Comparative Example 3

[0048] This comparative example presents a liquid alloy catalyst, the preparation method of which includes the following steps: In a glove box filled with N2, 1.88 g of Ga powder and 0.12 g of Fe powder are weighed and placed in a polytetrafluoroethylene grinding jar, with a grinding ball to material mass ratio of 30:1. The grinding jar is sealed, and the mixture is ball-milled for 40 min under N2 protection to obtain Ga. 94 Fe6.

[0049] Comparative Example 4

[0050] The comparative example proposes a liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.92 g of Ga powder and 0.08 g of Co powder in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, the grinding tank is sealed, and ball milling is performed under the protection of N2 for 40 min to obtain Ga 90 Co4.

[0051] Test Example 2

[0052] The test example tests the catalytic activity of the liquid alloy catalysts of Example 2 and Comparative Examples 3-4 as a catalyst for the thermal catalytic synthesis of ammonia, wherein the method for the thermal catalytic synthesis of ammonia is as follows: 500 mg of the catalyst is loaded in a U-shaped reaction tube with a sieve plate at one end of an ammonia synthesis fixed bed reactor, the fixed reaction temperature is 300 DEG C, the reaction pressure is 3 MPa, the molar ratio of N2 to H2 is 1:3, the flow rate of the mixed gas is 120 mL / min, the generated ammonia is collected and the ammonia yield is calculated (the ammonia yield calculation method is the same as that in Test Example 1), and the results are shown in Table 2.

[0053] Table 2: Test results of the ammonia synthesis catalytic reaction activity of Example 2 and Comparative Examples 3-4

[0054]

[0055] As can be seen from the results in Table 2, compared with the single metal modified Ga liquid alloy Ga 94 Fe6 and Ga 90 Co4, the bimetallic modified Ga liquid alloy Ga 90 Fe6Co4 prepared in Example 2 has a good ammonia synthesis reaction rate and a relatively obvious activity improvement.

[0056] Example 3

[0057] The example proposes a Ga-Fe-based liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.84 g of Ga powder, 0.08 g of Fe powder and 0.08 g of Mo in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, the grinding tank is sealed, and ball milling is performed under the protection of N2 for 20 min to obtain a Ga-Fe-based liquid alloy catalyst Ga 92 Fe4Mo4.

[0058] Comparative Example 5

[0059] The comparative example proposes a liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.92 g of Ga powder and 0.08 g of Fe powder in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, the grinding tank is sealed, and ball milling is carried out under the protection of N2 for 20 min, thereby obtaining Ga 96 Fe4.

[0060] Comparative example 6

[0061] The comparative example proposes a liquid alloy catalyst, and the preparation method thereof comprises the following steps: weighing 1.92 g of Ga powder and 0.08 g of Mo powder in a polytetrafluoroethylene grinding tank in a glove box filled with N2, the mass ratio of grinding balls to materials is 30:1, the grinding tank is sealed, and ball milling is carried out under the protection of N2 for 20 min, thereby obtaining Ga 96 Mo4.

[0062] Test example 3

[0063] The test example tests the catalytic activity of the liquid alloy catalysts of example 3 and comparative examples 5-6 as a catalyst for the thermal catalytic synthesis of ammonia, wherein the method for the thermal catalytic synthesis of ammonia is as follows: 500 mg of the catalyst is loaded in a U-shaped reaction tube with a sieve plate at one end of an ammonia synthesis fixed bed reactor, the fixed reaction temperature is 300 DEG C, the reaction pressure is 3 MPa, the molar ratio of N2 to H2 is 1:3, the flow rate of the mixed gas is 120 mL / min, the generated ammonia is collected and the ammonia yield is calculated (the ammonia yield calculation method is the same as that of test example 1), and the results are shown in table 3.

[0064] Table 3: Test results of the ammonia synthesis catalytic reaction activity of example 3 and comparative examples 5-6

[0065]

[0066] From the results in table 3, it can be seen that, compared with the single metal modified Ga liquid alloy Ga 96 Fe4 and Ga 96 Mo4, the bimetallic modified Ga liquid alloy Ga 92 Fe4Mo4 prepared in example 3 has a good ammonia synthesis reaction rate and a relatively obvious activity improvement.

[0067] In summary, the Ga-Fe based liquid alloy catalyst of the present application has very good reaction activity at low temperature and low pressure, can reduce the energy consumption of the ammonia synthesis process, improve the ammonia synthesis reaction efficiency, and has a good application prospect.

[0068] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as the combination of the technical features does not exist in contradiction, it shall be considered within the scope of the present disclosure.

[0069] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it shall not be understood as a limitation on the patent scope of the present application. It shall be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these shall be within the protection scope of the present application. Therefore, the protection scope of the present application patent shall be subject to the appended claims.

Claims

1. A Ga-Fe-based liquid alloy catalyst for thermocatalytic ammonia synthesis, characterized in that, The Ga-Fe based liquid alloy catalyst comprises metallic Ga, metallic Fe, and metallic M, wherein metallic M is one of Ti, Mn, Co, Ni, Cu, Zr, Nb, Mo, and W; the mass percentage of metallic Ga in the Ga-Fe based liquid alloy catalyst is 90%~99%; the mass ratio of metallic Fe to metallic M in the Ga-Fe based liquid alloy catalyst is 1~2:1; the preparation method of the Ga-Fe based liquid alloy catalyst includes the following steps: under a protective atmosphere, metallic Ga powder, metallic Fe powder, and metallic M powder are added to a ball mill jar and sealed, and ball milling is performed under sealed conditions to obtain the Ga-Fe based liquid alloy catalyst.

2. A method for preparing a Ga-Fe-based liquid alloy catalyst for thermocatalytic ammonia synthesis as described in claim 1, characterized in that, It includes the following steps: Under a protective atmosphere, Ga powder, Fe powder, and M powder are added to a ball mill jar and sealed. Ball milling is then performed under sealed conditions to obtain a Ga-Fe based liquid alloy catalyst.

3. The method for preparing the Ga-Fe-based liquid alloy catalyst for thermocatalytic ammonia synthesis according to claim 2, characterized in that, The ball mill has a ball-to-material ratio of 20-30:1, a rotation speed of 200-600 rpm, and a time of 10-60 min.

4. The method for preparing the Ga-Fe-based liquid alloy catalyst for thermocatalytic ammonia synthesis according to claim 2, characterized in that, The protective atmosphere is in an N2 or Ar glove box.

5. The method for preparing the Ga-Fe-based liquid alloy catalyst for thermocatalytic ammonia synthesis according to claim 2, characterized in that, The purity of the Ga powder and the Fe powder is 99.99%.

6. The application of the Ga-Fe based liquid alloy catalyst for thermocatalytic ammonia synthesis as described in claim 1 in thermocatalytic ammonia synthesis.

7. The application according to claim 6, characterized in that, It includes the following steps: The Ga-Fe-based liquid alloy catalyst is loaded at one end of the U-shaped reaction tube with a sieve plate in the fixed reaction bed for ammonia synthesis, and a mixture of N2 and H2 gas is introduced to heat the reaction.

8. The application according to claim 7, characterized in that, In the mixed gas, the molar ratio of N2 to H2 is 1:1~5, and the flow rate of the mixed gas is 20~300 mL / min.

9. The application according to claim 7, characterized in that, The heating reaction is carried out at a temperature of 200~500℃ and a pressure of 1~5MPa.

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