CN117258799A

CN117258799A - Ruthenium nickel-aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis, and preparation method and application thereof

Info

Publication number: CN117258799A
Application number: CN202210676965.7A
Authority: CN
Inventors: 李孟蓉; 郑家伟; 刘树平; 牛双霞; 翟玲玲; 王昭硕
Original assignee: Hong Kong Polytechnic University HKPU
Current assignee: Hong Kong Polytechnic University HKPU
Priority date: 2022-06-15
Filing date: 2022-06-15
Publication date: 2023-12-22
Also published as: WO2023241557A1

Abstract

The invention discloses a ruthenium nickel aluminum-based catalyst for preparing a large amount of nitrogen and hydrogen by ammonia catalysis, wherein the main active component is ruthenium, the carrier is nickel oxide and aluminum oxide, and the auxiliary agent is one or more of alkali metals such as sodium, potassium or alkaline earth metals such as calcium. The invention also provides a preparation method of the catalyst, which comprises the following steps: (a) Adding nickel oxide and aluminum oxide into a mixed solution containing ruthenium ions or a catalytic auxiliary agent for impregnation; (b) And (c) drying and calcining the carrier containing ruthenium and the auxiliary agent obtained in the step (a) to activate the carrier to obtain the ruthenium nickel-aluminum-based catalyst.

Description

Ruthenium nickel-aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis, and preparation method and application thereof

Technical Field

The invention relates to a preparation method and application of a high-efficiency ruthenium nickel-aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis.

Background

With rapid development of technology, demands for energy are rapidly rising, and environmental protection issues are widely discussed by the international society. In recent years, the major economy in the world is developing emission reduction plans. Worldwide enterprises are actively developing new low-carbon energy sources. Hydrogen energy sources are the winner of many new energy sources due to its advantages. First, hydrogen is undoubtedly the cleanest of many existing fuels in terms of pollution emissions. Fossil fuels commonly used at present release greenhouse gases such as carbon dioxide in the combustion process, causing air pollution and water pollution. And hydrogen is used as fuel of the fuel cell and is combined with oxygen in the atmosphere to generate clean water. Second, the fuel cell does not emit carbon oxides during operation. Although hydrogen energy is paid attention to as the cleanest energy source, the inflammable and explosive characteristics of hydrogen lead to technical problems of storage, safe transportation and the like, and the large-scale utilization of the hydrogen energy technology is directly affected.

At present, various countries develop research on new energy sources for replacing hydrogen, and ammonia is attracting attention due to various advantages. Ammonia is a compound of nitrogen and hydrogen, is a gas at ordinary temperature, and is colorless and has an offensive odor. Ammonia gas has the molecular formula NH ₃ The carbon in the molecule is not contained, and carbon dioxide is not discharged in the using process. Ammonia is important for life on earth and is an important source of nitrogen necessary for plants and animals. Ammonia is also an integral part of many pharmaceutical and commercial cleaning products. Because of its wide range of applications, ammonia is one of the most productive inorganic compounds in the world, about eight of which are used to make fertilizers. Ammonia gas can liquefy in a lower pressure environment than hydrogen gas. Therefore, the ammonia gas storage environment is relatively simpler, and the storage cost can be reduced. In recent years, the conversion of ammonia to hydrogen using renewable energy sources is a research hotspot in the new energy field.

The patent CN 110270338B discloses a nickel and/or ruthenium ammonia decomposition catalyst and a preparation method thereof, wherein the main active components of the catalyst are one or two of nickel and ruthenium, the carrier comprises graphitized active carbon and an auxiliary agent, the auxiliary agent is one or more of alkali metal oxide and alkaline earth metal oxide, the weight percentage of nickel is 8-24%, and the weight percentage of ruthenium is 0.5-12%. The catalyst desirably operates at a temperature of 550 ℃ to 750 ℃. The catalytic activity at low temperature is low, the ammonia content of the exhaust gas is high, the ammonia conversion effect is poor, and the method is not beneficial to industrialization or large-scale use.

The patent CN 113289693A discloses an ammonia decomposition catalyst and a preparation method thereof, wherein the main active component of the catalyst is ruthenium, the weight percentage of the catalyst is 3-5%, the carrier is magnesia and potassium oxide, and the weight percentage of the carrier is 90.4-95.6% and 1.4-4.6% respectively. Although the catalyst can be cooled to 500 ℃, and the temperature required by catalytic reaction is low, the reaction condition only uses fifty milligrams of catalyst, and when the catalyst is amplified to an industrial level, the efficiency of the catalyst can be influenced by factors such as heat conduction, particle size and the like. Meanwhile, the ruthenium content of the catalyst is high, the manufacturing cost is greatly improved, and the catalyst is not beneficial to industrialization or large-scale use.

Disclosure of Invention

The present invention provides a novel catalyst for decomposing ammonia into hydrogen and nitrogen, which has high performance and is inexpensive, and a process for producing the same. The invention also provides a method for preparing hydrogen and nitrogen by catalyzing ammonia decomposition by using the catalyst.

The invention discloses a ruthenium nickel aluminum-based catalyst for catalyzing ammonia to prepare a large amount of nitrogen hydrogen, which comprises the main active component of ruthenium, and the carrier of nickel and aluminum oxides such as nickel oxide (NiO) and aluminum oxide (Al) ₂ O ₃ ) The auxiliary agent is one or more of alkali metal such as sodium, potassium or alkaline earth metal such as calcium.

The invention provides a preparation method of the ruthenium nickel-aluminum-based catalyst, which comprises the following steps: (a) Adding the crushed carrier into a mixed solution containing ruthenium ions and a catalytic auxiliary agent for soaking; (b) And (c) drying and calcining the carrier containing ruthenium and the auxiliary agent obtained in the step (a) to activate the carrier to obtain a catalyst finished product. In an alternative embodiment, a certain amount of a dispersing agent such as one or more of iron oxide, silicon carbide, activated carbon, silicon oxide is added to the catalyst obtained in step (b) above.

The invention provides application of the catalyst in hydrogen production.Experiments prove that the catalyst of the invention is used, and the ammonia gas feeding volume space velocity is 6000h at the reaction temperature of 550-600 DEG C ^-1 The residual ammonia concentration of the exhaust gas can surprisingly be reduced below 0.1vol%, which conversion is close to the highest ammonia conversion of the thermodynamic limit of the ammonia decomposition reaction. Such high conversion rates make the subsequent residual ammonia purification process easier.

The ruthenium nickel-aluminum-based catalyst has excellent stability. The ammonia decomposition temperature can be greatly reduced by about 150-200 c compared to the iron-or nickel-based catalysts currently used industrially. The catalyst has industrialized conditions, and can realize high space velocity ammonia conversion at a lower temperature in large-scale industrial production. In addition, the preparation method of the catalyst is simple, and the synthesis cost is low.

In one aspect, the present application provides a method for preparing a ruthenium-based nickel-aluminum-based catalyst for ammonia-catalyzed nitrogen-hydrogen production, comprising the steps of:

(a) Adding nickel oxide and an alumina carrier into a mixed solution containing active component ruthenium ions and a catalytic auxiliary agent for impregnation; and

(b) And (3) drying and calcining the carrier containing ruthenium and the catalyst promoter obtained in the step (a) to activate the carrier to obtain the ruthenium nickel aluminum-based ammonia decomposition catalyst.

In an alternative embodiment, the method of the present invention further comprises step (c): adding a dispersing agent to the ruthenium-based nickel-aluminum-based catalyst obtained in the step (b).

In one embodiment, the support is prepared by mixing, pulverizing, and oven drying nickel oxide and aluminum oxide; the mixed solution of ruthenium ions and catalyst promoter is prepared by dissolving a metal salt containing ruthenium ions and a metal salt of catalyst promoter in deionized water simultaneously or separately.

In one embodiment, the calcination activation is performed at 350-900 ℃ for 3-5 hours under an atmosphere containing hydrogen/nitrogen/oxygen or a mixture thereof.

In one embodiment, the nickel and aluminum oxides are NiO and Al, respectively ₂ O ₃ The method comprises the steps of carrying out a first treatment on the surface of the The metal salt of ruthenium ions includes ruthenium chloride and/or ruthenium chloride hydrate.

In one embodiment, the catalytic promoter comprises one or more of sodium oxide, potassium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium acetate, potassium acetate, calcium acetate.

In an alternative embodiment, the dispersant comprises one or more of iron oxide, silicon carbide, activated carbon, and silicon oxide.

In one embodiment, the ruthenium comprises 0.5 to 5% of the catalyst, the support comprises 85 to 98%, and the promoter comprises 1 to 10% by mass.

In one embodiment, the molar ratio of nickel oxide and aluminum oxide to the support ranges from 1:4 to 1:5, respectively.

In an alternative embodiment, the mass ratio of dispersant to active ingredient + carrier + adjuvant is from 1:100 to 1:3.

In one embodiment, the nickel oxide and aluminum oxide are mixed and crushed in a molar ratio of 2:3 to 1:18.

In one embodiment, the catalyst is subjected to two activations before being actually applied, the first gas is hydrogen-nitrogen mixed gas, and the mass percentage concentration of hydrogen in the mixed gas is 5%; the gas used for the second time is high-purity ammonia gas with the purity of 99.99 percent.

The second aspect of the application provides a ruthenium-based nickel-aluminum-based ammonia decomposition catalyst, wherein the ruthenium accounts for 0.5-5% of the catalyst, the carrier containing nickel and aluminum oxide accounts for 85-98% of the catalyst, and the catalyst auxiliary accounts for 1-10% of the catalyst auxiliary.

In one embodiment, the nickel oxide and the oxidation are NiO and Al, respectively ₂ O ₃ 。

In one embodiment, the molar ratio of nickel oxide to aluminum oxide is from 2:3 to 1:18.

In an alternative embodiment, the catalyst further comprises a dispersant comprising one or more of iron oxide, silicon carbide, activated carbon, and silicon oxide.

In one embodiment, the mass ratio of dispersant to active ingredient + carrier + adjuvant is 1:20 to 1:4.5.

In one embodiment, the particles of the catalyst of the present invention are in the range of 18-80 mesh, for example 18-70 mesh, 18-60 mesh, 18-50 mesh, 18-45 mesh, 20-70 mesh, 30-60 mesh, 45-60 mesh, preferably in the range of 45-60 mesh.

A third aspect of the present application provides the use of the catalyst disclosed herein for catalyzing ammonia to produce hydrogen and nitrogen.

Drawings

FIG. 1 is a schematic representation of the weight content of the catalyst components of the present invention.

FIG. 2 is a schematic diagram of a preparation flow of the catalyst of the present invention.

FIG. 3 is a schematic diagram of a test flow of the catalyst of the present invention in ammonia conversion.

Fig. 4 is a sample of the catalyst synthesized in example 3 of the present application.

FIG. 5 is a schematic diagram of a catalyst-containing reaction tube.

FIG. 6 is a scanning electron microscope image of the support (nickel oxide) to a scale of 200. Mu.m.

FIG. 7 is a scanning electron microscope image of the catalyst synthesized in example 3, on a scale of 20. Mu.m.

FIG. 8 is a scanning electron microscope image of a dispersant (ferric oxide) to a scale of 500 μm.

Fig. 9 is an ammonia decomposition comparison of a catalyst prepared according to example 3 of the present application and a commercially available catalyst.

Detailed Description

The invention provides a preparation method of a ruthenium nickel aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis. The preparation method is exemplarily described in fig. 2, and mainly includes the steps of:

(a) Adding a carrier containing nickel oxide and aluminum oxide into a mixed solution containing active component ruthenium ions and a catalytic auxiliary agent for impregnation; and

(b) And (c) drying and calcining the carrier containing ruthenium and the catalyst promoter obtained in the step (a) to activate the carrier to obtain a ruthenium nickel aluminum-based ammonia decomposition catalyst finished product.

In the step (a), the carrier accounts for 85-98% of the catalyst, such as 86-97%, 87-96%,88-95%,89-94%,90-98%,92-98%,95-98% by mass. Ruthenium may be a metal salt of ruthenium ions such as ruthenium chloride or ruthenium chloride hydrate. The ruthenium accounts for 0.5-5% of the catalyst by mass, for example 0.5-4%, 1-3%,1-2%,1.2%,1.5%,1.8% and the like. The catalyst auxiliary agent comprises one or more of alkali metal such as sodium, potassium or alkaline earth metal such as calcium, wherein the catalyst auxiliary agent accounts for 1-10wt%, for example 1-9wt%, 1-8wt%, 1-7wt%, 1-6wt%, 1-5wt%, 2-10wt%, 3-10wt%, 4-8wt%, 5-9wt%, 6-10wt%, 4-7wt% and 7-10wt%. In one embodiment, the catalytic promoter comprises one or more of sodium oxide, potassium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium acetate, potassium acetate, calcium acetate. In a preferred embodiment, the promoter is calcium acetate.

In the above step (a), the carrier may be prepared by pulverizing, mixing, and drying nickel oxide and aluminum oxide. The comminution of nickel and aluminum oxides can be carried out by methods conventional in the art, such as comminution. After pulverization, the particles of 18 to 80 mesh, for example, 18 to 70 mesh, 18 to 60 mesh, 18 to 50 mesh, 18 to 45 mesh, 20 to 70 mesh, 30 to 60 mesh, preferably 45 to 60 mesh are selected.

After the crushed nickel oxide and aluminum oxide are obtained, the crushed nickel oxide and aluminum oxide are mixed in a molar ratio of 1:18 to 2:3, and then the mixture is treated for 2 to 24 hours at 65 to 95 ℃ to obtain the carrier. In one embodiment, the nickel and aluminum oxides are mixed in a vacuum oven at 1:17, 1:16, 1:15, 1:14, 1:10, 1:8, 1:6, 1:5, 1: 4.5,2:15, 2:2 equimolar ratios. In one embodiment, a preferred drying temperature is 90-95 ℃. The person skilled in the art can choose the drying device and the drying time according to the actual need. In one embodiment, the molar ratio of nickel oxide and aluminum oxide to the support ranges from 1:4 to 1:5, respectively.

In the above step (a), ruthenium and the catalyst promoter may be added simultaneously or separately to a certain amount of deionized water and stirred at 550 to 850rpm for more than 30 minutes. The ruthenium metal salt and the catalyst promoter metal salt solution can be dispersed by adopting ultrasonic. The dried nickel oxide and alumina mixture support is then poured into the ruthenium and catalyst promoter solution, the stirring speed is reduced to 500rpm or less per minute, stirring is maintained for a period of time, for example, 5 to 10 minutes, and then allowed to stand for 5 to 10 minutes. The foregoing stirring and standing are repeated at least 3 times, for example, 4,5 or 6 times. The mixture is suction filtered and the sample is then placed in a vacuum oven and allowed to stand at a temperature of 90-99 c, e.g. 95 c, for at least 24 hours.

In step (b) above, the mixture obtained in step (a) is placed in a tube furnace, and a reducing gas such as hydrogen is introduced and maintained for a period of time, for example, 20 to 40 minutes, preferably 30 minutes. Then heating to a reaction temperature of 550-750 ℃ at a speed of 5 ℃ per minute, continuously reacting for 3-6 hours under a hydrogen atmosphere, and naturally cooling to room temperature to obtain the activated catalyst. In another embodiment, the catalyst may be activated by calcination at 550 ℃ to 750 ℃ for 3 to 5 hours under a nitrogen, oxygen or hydrogen mixed gas atmosphere. In one embodiment, the reducing gas is introduced for a period of 25 to 40, 30 to 40 or 35 minutes; the reaction temperature was 550 ℃,600 ℃,625 ℃, 700 ℃ or 750 ℃. And after the reaction is finished, taking out the reaction materials. In a preferred embodiment, the activated catalyst is obtained by screening with a 45-60 mesh screen.

In an alternative embodiment, after step (b) above, a step (c) may be further included: a dispersant is added to the catalyst. In one embodiment, the dispersing agent comprises one or more of ferric oxide, silicon carbide, activated carbon and silicon oxide, and the particle size of the dispersing agent is 18-80 meshes. In one specific embodiment, a dispersant such as silicon carbide powder (45-60 mesh) is placed in a vacuum oven and allowed to stand at 95℃for 24 hours. And then physically mixing the dispersant powder with the ruthenium calcium-containing alumina and the nickel oxide to obtain the catalyst. In one embodiment, the mass ratio of dispersant to active ingredient + carrier + adjuvant is from 1:100 to 1:3.

The catalyst can undergo secondary activation before application, the gas used for the first time is hydrogen-nitrogen mixed gas, and the mass percentage concentration of hydrogen in the mixed gas is 5%; the gas used for the second time is high-purity ammonia gas with the purity of 99.99 percent.

In one embodiment, the preparation method of the ruthenium-based nickel-aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis comprises the following steps:

step 1: dispersing a metal salt of ruthenium in water, for example by ultrasound, to obtain an active ingredient solution;

step 2: adding the catalyst auxiliary agent into the solution obtained in the step 1 respectively or simultaneously, and stirring for 5-30min at 550-850 rpm;

step 3: adding alumina and nickel oxide carriers into the active component solution;

step 4: stirring the solid-liquid mixture obtained in the step 3 for 5-30min, and then standing for 5-30min;

step 5: repeating the step 4 for three times until the ruthenium content reaches the target load capacity, and obtaining a precipitate;

step 6: filtering, washing and drying the precipitate obtained in the step 5;

step 7: calcining the dried product obtained in the step 6 at 500-750 ℃ and reducing the calcined product by hydrogen to obtain the catalyst.

The invention provides a ruthenium nickel aluminum-based ammonia decomposition catalyst for preparing nitrogen and hydrogen by ammonia catalysis, wherein the mass percentage of ruthenium in the catalyst is 0.5-5%, the carrier containing nickel oxide and aluminum oxide is 85-98%, and the catalytic auxiliary agent is 1-10%.

The molar ratio of nickel oxide to aluminum oxide in the catalyst of the invention is 2:3 to 1:18.

In one catalyst, the catalyst promoter comprises one or more of sodium oxide, potassium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium acetate, potassium acetate and calcium acetate.

In an alternative embodiment, the catalyst of the present invention further comprises a dispersant. The dispersing agent comprises one or more of ferric oxide, silicon carbide, active carbon and silicon oxide. Wherein the mass ratio of dispersant to active ingredient to carrier to adjuvant is 1:100 to 1:3, for example 1:7.

In one embodiment, ruthenium comprises 0.5 to 5%, such as 0.5 to 4%,1 to 3%,1 to 2%,2 to 5%,3 to 4%,1.5%,2%, or 3% of the catalyst by mass.

Methods and apparatus for catalytic ammonia decomposition using catalysts are well known in the art and are not particularly limited. Disclosed herein is an exemplary apparatus and method for catalyzing ammonia decomposition using the catalyst of the present invention. As shown in fig. 5: the stainless steel tube is fixed with quartz cotton as catalyst, ammonia gas is introduced, and the ammonia gas is decomposed at the temperature of 550 ℃ or above to obtain hydrogen, nitrogen and a small amount of residual ammonia. Experiments prove that the ammonia gas feeding volume airspeed is 6000h at the reaction temperature of 550-600 DEG C ^-1 The residual ammonia concentration of the exhaust gas can surprisingly be reduced to below 0.1 vol%.

The invention has the following advantages:

1. the ruthenium-based nickel aluminum-based ammonia decomposition catalyst disclosed by the invention adopts ruthenium as an active component, and nickel oxide and aluminum oxide are used as carriers, so that the adsorption and dissociation of ammonia gas are promoted, the adsorption of hydrogen gas is inhibited, the efficient high-flow ammonia decomposition is achieved, and the hydrogen gas manufacturing efficiency is improved. Experiments prove that the catalyst of the invention is used, and the ammonia gas feeding volume space velocity is 6000h at the reaction temperature of 550-600 DEG C ^-1 The residual ammonia concentration of the effluent gas surprisingly falls below 0.1vol%, which is close to the maximum ammonia conversion of the thermodynamic limit of the ammonia decomposition reaction.

2. The ruthenium-based nickel-aluminum-based ammonia decomposition catalyst according to the present invention has excellent ammonia conversion activity and stability. The ammonia decomposition temperature can be reduced by about 200 c compared to the iron-based catalysts currently used industrially.

3. The preparation method of the ruthenium-based nickel-aluminum-based ammonia decomposition catalyst is simple and has low synthesis cost.

4. The ruthenium-based nickel aluminum-based ammonia decomposition catalyst according to the present invention, wherein the main active component is ruthenium, and the ruthenium accounts for 1-5% of the catalyst in terms of mass percent, and the content of the noble metal active component in the catalyst can be minimized by limiting the mass percent of the active component, thereby achieving a balance in terms of ammonia decomposition effect and manufacturing cost.

5. According to the ruthenium-based nickel-aluminum-based ammonia decomposition catalyst, the active components can be evenly distributed on the carrier through the content of the specific carrier and the catalytic auxiliary agent, the transfer effect of electrons is enhanced, the adsorption and dissociation of ammonia are promoted, the adsorption of hydrogen is inhibited, excellent high-flow ammonia decomposition is achieved, and the efficiency of producing hydrogen is improved.

4. The ruthenium-based nickel aluminum-based ammonia decomposition catalyst according to the present invention, wherein nickel oxide and aluminum oxide are pulverized respectively with a pulverizer. By controlling the particle size of the particles, the active ingredient can be evenly distributed on the carrier.

5. The ruthenium-based nickel aluminum-based ammonia decomposition catalyst according to the present invention, wherein the active components can be uniformly distributed on the carrier by using different combinations with the catalyst auxiliary, further enhancing the interaction between the carrier and the active components.

6. According to the ruthenium-based nickel aluminum-based ammonia decomposition catalyst, the dispersion degree of the ammonia decomposition catalyst composition and the heat conduction efficiency of a catalytic system can be improved by the dispersing agent, so that the energy utilization efficiency is improved and the ammonia decomposition is promoted.

The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, one of ordinary skill in the art would obtain all other embodiments without undue burden.

Examples

The apparatus and flow of the present invention for detecting ammonia decomposition can be referred to as fig. 3. Those skilled in the art are familiar with the apparatus and methods of ammonia catalytic decomposition, and can be variously selected and combined according to the actual practice.

Before the experiment starts, an ammonia gas bottle is opened, the flow of a mass flow controller is regulated to be 200ml/min, the temperature of a reaction furnace is raised to 700 ℃ at a heating rate of 5 ℃/min, and the temperature is kept for 2 hours, so that the catalyst activation is completed. The reactor was then cooled to 500 ℃ and maintained for 40min, until the temperature of the catalyst was reduced to the reaction temperature. Then the ammonia flow is regulated to ensure that GHSV=6000 h ^-1 Ammonia gas enters a reaction furnace and is separated by a catalystAnd after the solution, the solution enters a buffer bottle, and finally enters a mass spectrometer for conversion rate testing. The reaction furnace starts at 500 ℃, takes a temperature rising gradient at 25 ℃ and takes eight test points from 500 ℃ to 700 ℃, and at each temperature test point, 50ml/min of tail gas is shunted into a mass spectrometer for component analysis, and the mass spectrometer model is HPR-20EGA of Hiden Analytical.

Example 1

The alumina and nickel oxide (18-45 mesh) were physically mixed at an alumina/nickel molar ratio of 4.5:1, and the 40.42g mixture was placed in a vacuum oven and allowed to stand at 60℃for 24 hours. 1.68g of ruthenium chloride and 15.37g of calcium acetate were added to deionized water (about 550 ml) while maintaining stirring for 30min at 750rpm per minute. 40.42g of dry alumina, nickel oxide were poured into a solution of ruthenium chloride and calcium acetate and the mixture was stirred for 15 min. And then further left to stand for 30min. Sodium hydroxide solution was added to the mixture and stirred for another 30min. The mixture was suction-filtered with deionized water. The sample was placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours in a hydrogen atmosphere, and naturally cooling to room temperature after the reaction is finished. The reaction mass was removed and screened with 18 and 45 mesh screens. Thereafter, the ruthenium calcium-containing alumina and nickel oxide were placed in a 1/2 "316 stainless steel tube and activated with ammonia gas for four hours at a Gas Hourly Space Velocity (GHSV) =6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 600℃was 99.3%.+ -. 0.5% and the conversion at 650℃was 99.6.+ -. 0.5%.

Example 2

42.01g of alumina (60-80 mesh) was placed in a vacuum oven and allowed to stand at 95℃for 2 hours. 51.26 g nickel acetate and 15.97g calcium acetate were added to deionized water (about 600 ml) and kept stirring for 30min at 750rpm. 42.01g of dry alumina was poured into a nickel acetate, calcium acetate solution while maintaining stirring for 5min, after which it was allowed to stand for a further 30min. The sample was suction filtered and placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is finished, the sample is placed in a horseCalcining in a furfurer with air, heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials. 27.35g of the mixture was placed in a vacuum oven and allowed to stand at 95℃for 2 hours. 0.57g ruthenium chloride was added to deionized water (about 600 ml) and stirring was maintained for 30min at 750rpm per minute. 27.35g of alumina containing nickel calcium was poured into the ruthenium chloride solution and the rpm was reduced to 500rpm. And then further left to stand for 30min. The sample was suction filtered and placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter, alumina containing nickel, calcium and ruthenium was placed in a 1/2 "316 stainless steel tube and activated with ammonia for four hours and with ghsv=6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 600℃was 99.2.+ -. 0.5%, and the conversion at 650℃was 99.4.+ -. 0.5%.

Example 3

The alumina and nickel oxide (45-60 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. 15.24g of the mixture was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 0.32g of ruthenium chloride and 5.79g of calcium acetate were added to deionized water (about 250 ml) and stirring was maintained for 30min at 750rpm per minute. All dry alumina, nickel oxide mixtures were poured into ruthenium chloride and calcium acetate solutions and the rpm was reduced to 500rpm, kept stirring for 5 minutes, and then allowed to stand for 5 minutes. Stirring and standing are repeated for a minimum of three times. The mixture was suction filtered and the sample was then placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter placing ruthenium-containing alumina and nickel oxideThe inside of the 1/2 "316 stainless steel tube was activated with ammonia gas for four hours and with ghsv=6000 h ^-1 The ammonia decomposition conversion changes at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 550℃was 99.9.+ -. 0.5%, and the conversion at 600℃and 650℃was 99.9.+ -. 0.5%.

Example 4

The alumina and nickel oxide (45-60 mesh) were physically mixed in a molar ratio of 4.5:1. Wherein 13.32. 13.32 g was taken out and placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 0.28g ruthenium chloride, 0.30g potassium hydroxide and 5.06g calcium acetate were added to deionized water (about 200 ml) and stirring was maintained for 30min at 750rpm per minute. All dry alumina, nickel oxide mixtures were poured into ruthenium chloride, potassium hydroxide and calcium acetate solutions and the rpm was reduced to 500rpm, kept stirring for 5 minutes, and then allowed to stand for 5 minutes. Stirring and standing are repeated for a minimum of three times. The mixture was suction filtered and washed with deionized water, and then the sample was placed in a vacuum oven and allowed to stand at 95 ℃ for 24 hours. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter, the ruthenium potassium calcium containing alumina, nickel oxide was placed in a 1/2 "316 stainless steel tube and activated with ammonia gas for four hours and with ghsv=6000 h ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 650℃was 99.8.+ -. 0.5%.

Example 5

The alumina and nickel oxide (45-60 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. Wherein 12g was taken and placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 0.25g of ruthenium chloride and 4.56g of calcium acetate were added to deionized water (about 250 ml) and stirring was maintained for 30min at 750rpm per minute. All dry alumina, nickel oxide mixtures were poured into ruthenium chloride and calcium acetate solutions and the rpm was reduced to 500rpm, kept stirring for 5 minutes, and then allowed to stand for 5 minutes. Repeated stirringStanding for a minimum of three times. The mixture was suction filtered and the sample was then placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter, the iron oxide powder (45-60 mesh) was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 2.29g of iron oxide powder, 10.5g of aluminum oxide containing ruthenium calcium and nickel oxide were physically mixed and placed in a 1/2' 316 stainless steel tube and activated with ammonia for four hours at GHSV=6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 625℃was 99.7.+ -. 0.5%, and the conversion at 675℃was 99.89.+ -. 0.5%.

Example 6

The alumina and nickel oxide (45-60 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. 13.7g of the mixture was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 0.28g of ruthenium chloride and 5.21g of calcium acetate were added to deionized water (about 200 ml) and stirring was maintained for 30min at 750rpm per minute. All dry alumina, nickel oxide mixtures were poured into ruthenium chloride and calcium acetate solutions and the rpm was reduced to 500rpm, kept stirring for 5 minutes, and then allowed to stand for 5 minutes. Stirring and standing are repeated for a minimum of three times. The mixture was suction filtered and the sample was then placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter, the silicon carbide powder (45-60 mesh) was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 1.85g of silicon carbide powder, 8.40g of aluminum oxide containing ruthenium and calcium and nickel oxide are physically mixed, and are placed in a 1/2' 316 stainless steel tube to be activated by ammonia gas for four hours, and GHSV=6000 hours ^-1 Is measured by mass spectrometer for the change of ammonia decomposition conversion rate at different temperatures. As a result, it was found that the conversion at 625℃was 99.8.+ -. 0.5%, and the conversion at 675℃was 99.9.+ -. 0.5%.

Example 7

The alumina and nickel oxide (45-60 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. 10.78g of the mixture was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 0.11g of ruthenium chloride and 4.10g of calcium acetate were added to deionized water (about 150 ml) and stirring was maintained for 30min at 750rpm per minute. All dry alumina, nickel oxide mixtures were poured into ruthenium chloride and calcium acetate solutions and the rpm was reduced to 500rpm, kept stirring for 5 minutes, and then allowed to stand for 5 minutes. Stirring and standing are repeated for a minimum of three times. The mixture was suction filtered and the sample was then placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a tube furnace, hydrogen is introduced and maintained for 30min. Heating to a reaction temperature of 550 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a hydrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh and 60-mesh filter screen. Thereafter, the ruthenium-containing alumina, nickel oxide was placed in a 1"316 stainless steel tube and activated with ammonia for four hours and with ghsv=6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer.

The conversion of ammonia decomposition was measured by mass spectrometry in this example and was 99.6.+ -. 0.5% at 700 ℃.

Comparative example 1

The alumina and nickel oxide (45-60 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. 14.24g of the mixture was placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 5.41g of calcium acetate was added to deionized water (about 300 ml) and stirring was maintained for 30min at 750rpm per minute. 14.24g of dry alumina, nickel oxide was poured into the calcium acetate solution while maintaining stirring for 5min, after which it was further left to stand for 30min. The sample was suction filtered and placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a muffle furnace to be calcined by air, the sample is heated to the reaction temperature of 550 ℃ at the speed of 5 ℃ per minute, the reaction is continued for 4 hours, and then the temperature is naturally reduced to the room temperature. To be reactedAfter the completion, the reaction mass was taken out. Screening with 45 and 60 mesh filter screen. Thereafter the calcium-containing alumina, nickel oxide mixture was placed in a 1/2 "316 stainless steel tube and activated with ammonia for four hours at ghsv=6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 600℃was 22.7%.+ -. 0.5%, the conversion at 650℃was 49.9.+ -. 0.5%, and the conversion at 750℃was 99.7.+ -. 0.5%.

Comparative example 2

The alumina and nickel oxide (both 18-45 mesh) were physically mixed at an aluminum/nickel molar ratio of 4.5:1. Wherein 205g was taken and placed in a vacuum oven and allowed to stand at 95℃for 24 hours. 77.95g of calcium acetate was added to deionized water (about 4500 ml) and kept stirring for 30min at 750rpm per minute. 205g of dry alumina, nickel oxide was poured into the calcium acetate solution while maintaining stirring for 5min, after which it was further left to stand for 30min. The sample was suction filtered and placed in a vacuum oven and allowed to stand at 95℃for 24h. After the drying is completed, the sample is placed in a muffle furnace to be calcined by air, the sample is heated to the reaction temperature of 550 ℃ at the speed of 5 ℃ per minute, the reaction is continued for 4 hours, and then the temperature is naturally reduced to the room temperature. And after the reaction is finished, taking out the reaction materials, and screening by using 18-mesh and 45-mesh filter screens. Thereafter, the calcium-containing alumina, nickel oxide mixture was placed in a 1"316 stainless steel tube and activated with ammonia gas for four hours and with ghsv=6000 hours ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 600℃was 21.9%.+ -. 0.5%, the conversion at 650℃was 35.2.+ -. 0.5%, the conversion at 700℃was 52.3.+ -. 0.5%, the conversion at 750℃was 80.9.+ -. 1.0%, and the conversion at 800℃was 99.6%.+ -. 0.5%.

Comparative example 3

22.15g of activated carbon, 78.68g of magnesium oxide and 21.71g of alumina (18-45 mesh) were placed in a vacuum oven and allowed to stand at 65℃for 4 hours. 5.0847g of ruthenium chloride and 5.21g of calcium acetate are added to 470ml of ethanol while stirring is maintained for 30min at 750rpm per minute. After the drying process, the active carbon, the magnesia and the alumina are directly added into the solution of ruthenium chloride and calcium acetate, and the rotating speed per minute is ensuredAt 250rpm, during which stirring was maintained for 15min, after which it was allowed to stand for a further 30min. The activated carbon, the magnesia, the alumina particles and the rest ruthenium chloride and calcium acetate solution are put into a vacuum oven and are kept at a low temperature of 60 ℃ for 2 hours. To ruthenium chloride, calcium acetate powder obtained from the dried sample was added a small amount of ethanol. And adding the dried active carbon containing ruthenium and calcium back into the ethanol solution. The ruthenium-containing activated carbon was again placed in a vacuum oven, allowed to stand at a low temperature of 60℃for 2 hours and dried again. After the drying is completed, the sample is placed in a tube furnace, nitrogen is introduced and maintained for 30min. Heating to a reaction temperature of 600 ℃ at a speed of 5 ℃ per minute, continuously reacting for 4 hours under a nitrogen atmosphere, and naturally cooling to room temperature. And after the reaction is finished, taking out the reaction materials, and screening by a 45-mesh filter screen. Thereafter activated carbon containing ruthenium calcium, magnesia, alumina were activated with ammonia gas in a 1/2 "316 stainless steel tube for four hours and at ghsv=6000 h ^-1 The conversion changes of ammonia decomposition at different temperatures were measured with a mass spectrometer. As a result, it was found that the conversion at 600℃was 29.3%.+ -. 0.5%, the conversion at 650℃was 40.7.+ -. 0.5%, the conversion at 700℃was 53.6.+ -. 0.5%, and the conversion at 750℃was 60.8.+ -. 1.0%.

Comparative example 4

This comparative example used a nickel catalyst from su zhou Hengda purification plant limited [ specification type: (Z-204) the catalyst prepared in example 3 was compared with an industrial nickel-based catalyst to catalyst nickel. The comparative example was screened with 45 mesh and 60 mesh screens and placed in a vacuum oven and allowed to stand at 95℃for 24 hours. After drying, the catalyst was placed in a 1/2 "316 stainless steel tube and activated with ammonia for three hours at ghsv=6000 hours ^-1 Is tested for ammonia conversion changes at 500 ℃ to 750 ℃.

The experimental results are shown in FIG. 9. From the results of fig. 9, it can be seen that the catalyst of the present invention has significantly higher conversion at low temperatures, e.g., 550 ℃, relative to 20.7% ± 1.0% of the commercial control product at the same reaction temperature, and the conversion approaches 100% as the temperature increases.

The above examples show that the preparation method of the ruthenium nickel-aluminum-based catalyst helps to reduce the temperature required for ammonia decomposition. Therefore, the catalyst has the industrialized condition, can realize high-space-velocity ammonia conversion at a lower temperature after large-scale, and has the advantages of simple preparation method, low synthesis cost and the like.

The above examples are given for clarity of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims

1. The preparation method of the ruthenium nickel aluminum-based catalyst for preparing nitrogen and hydrogen by ammonia catalysis comprises the following steps:

2. The method of claim 1, further comprising step (c): adding a dispersing agent to the ruthenium-based nickel-aluminum-based catalyst obtained in the step (b).

3. The method according to claim 1 or 2, wherein:

the carrier is prepared by mixing, crushing and drying nickel oxide and aluminum oxide;

the mixed solution of ruthenium ions and the catalyst promoter is prepared by dissolving a metal salt of ruthenium ions and a metal salt of the catalyst promoter in deionized water simultaneously or separately.

4. The process according to claim 1 or 2, wherein the calcination activation is performed at 350-900 ℃ under an atmosphere containing hydrogen/nitrogen/oxygen or a mixed gas thereof for 3-5 hours.

5. The method of claim 1 or 2, wherein the metal salt of ruthenium ions comprises ruthenium chloride and/or ruthenium chloride hydrate.

6. The method of claim 1 or 2, wherein the catalyst promoter comprises one or more of sodium oxide, potassium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium acetate, potassium acetate, calcium acetate.

7. The method of claim 2, wherein the dispersant comprises one or more of iron oxide, silicon carbide, activated carbon, and silicon oxide.

8. The process according to claim 1 or 2, wherein ruthenium represents 0.5 to 5% of the catalyst, the carrier represents 85 to 98% and the catalyst promoter represents 1 to 10% by mass.

9. A process according to claim 1 or 2, wherein the molar ratio of nickel oxide and aluminium oxide to the support is in the range 1:4 to 1:5, respectively.

10. The method of claim 2, wherein the dispersant: the mass ratio of the active component, the carrier and the auxiliary agent is 1:100 to 1:3.

11. The method according to claim 1 or 2, wherein the nickel oxide and the aluminum oxide are mixed and pulverized in a molar ratio of 2:3 to 1:18.

12. The method according to claim 1 or 2, wherein the catalyst is subjected to two activations before being actually used, the first gas is a hydrogen-nitrogen mixture, and the mass percentage concentration of hydrogen in the mixture is 5%; the gas used for the second time is high-purity ammonia gas with the purity of 99.99 percent.

13. A ruthenium-based nickel-aluminum-based ammonia decomposition catalyst comprises, by mass, 0.5-5% of ruthenium, 85-98% of a carrier containing nickel oxide and aluminum oxide, and 1-10% of a catalytic auxiliary agent.

14. The catalyst of claim 13, wherein the nickel oxide is NiO and the aluminum oxide is Al ₂ O ₃ 。

15. The catalyst of claim 14 wherein the molar content ratio of nickel oxide to aluminum oxide is from 2:3 to 1:18.

16. The catalyst of claim 13, wherein the catalytic promoter comprises one or more of sodium oxide, potassium oxide, calcium oxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium acetate, potassium acetate, calcium acetate.

17. The catalyst of claim 13, further comprising a dispersant.

18. The catalyst of claim 17, wherein the dispersant comprises one or more of iron oxide, silicon carbide, activated carbon, and silicon oxide.

19. The catalyst of claim 17 or 18, wherein the dispersant: the mass ratio of the active component, the carrier and the auxiliary agent is 1:20 to 1:4.5.

20. Use of a catalyst according to any one of claims 1 to 18 for catalyzing ammonia to produce hydrogen and nitrogen.