CN109772362B - Preparation method of ultrahigh-temperature ammonia decomposition catalyst, ultrahigh-temperature ammonia decomposition catalyst prepared by method and application of ultrahigh-temperature ammonia decomposition catalyst - Google Patents
Preparation method of ultrahigh-temperature ammonia decomposition catalyst, ultrahigh-temperature ammonia decomposition catalyst prepared by method and application of ultrahigh-temperature ammonia decomposition catalyst Download PDFInfo
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Abstract
The invention provides a preparation method of an ultrahigh-temperature ammonia decomposition catalyst, the ultrahigh-temperature ammonia decomposition catalyst prepared by the method and application of the ultrahigh-temperature ammonia decomposition catalyst. The method comprises the following steps: performing first roasting on 50-90 parts of hydrotalcite-like compound oxide powder; preparing a first mixed solution from the first roasting product and sodium chloride to prepare a reconstructed material; mixing the reconstructed material and 5-10 parts of alkaline metal oxide for second roasting, uniformly mixing a second roasting product and 3-10 parts of oxygen storage component, pressing into cylindrical particles, and performing third roasting; and (3) dipping the third burned product in a solution containing 5-16 parts of nickel nitrate and/or 0-15 parts of cosolvent until the active components are loaded to the designed amount, and then carrying out fourth roasting to obtain the ultrahigh-temperature ammonia decomposition catalyst. The ultrahigh-temperature ammonia decomposition catalyst can solve the problems of migration, aggregation, volatilization loss and high-temperature sintering of active component metal particles of the catalyst, and has the advantages of ultrahigh-temperature sintering resistance, high bed pressure resistance and high falling resistance.
Description
Technical Field
The invention relates to the technical field of chemical catalysts, in particular to a preparation method of an ultrahigh-temperature ammonia decomposition catalyst, the ultrahigh-temperature ammonia decomposition catalyst prepared by the method and application thereof, wherein the ultrahigh-temperature ammonia decomposition catalyst is particularly suitable for an ultra-large coke oven gas purification device.
Background
The single-line processing capacity of the comparatively typical domestic ammonia decomposition process of the Claus furnace is generally 5 multiplied by 104m3H or 10X 104m3The industrial application of ammonia decomposition catalysts for Claus furnaces is relatively mature (corresponding to the coke oven gas throughput).
In order to improve the operation level of the equipment, two sets of AS purification devices can be combined into one set, and the single-system treatment capacity of the combined gas treatment system is up to 18 multiplied by 104m3H, operating temperatures up to 1000
1300 ℃ is adopted. The reformed system becomes the largest domestic gas purification treatment system, the steam quantity of the raw materials in the composite Claus furnace of the system is multiplied, and H in the furnace2Full oxidation, increased water vapor content in the furnace and poor uniformity of the temperature field. And after the volume of the Claus furnace is multiplied, the amount of the used catalyst is also multiplied, the pressure drop of a catalyst bed layer is greatly improved, and the operation condition is more rigorous. It puts new demands on the ammonia decomposition catalyst in the Claus furnace in the aspects of compressive strength, drop resistance, pulverization resistance, service life and the like. The present invention is a new catalyst development aiming at such a current situation.
Research shows that magnesia-alumina spinel has been used as the material of ammonia decomposing catalyst carrier in Claus furnace owing to its excellent performance, including high hardness, high heat strength, high shock resistance, high corrosion resistance, small heat expansion coefficient, etc. The unit cell of the magnesium aluminate spinel is formed by stacking 32 cubesFormation of anion O2-And 16 aluminum ions Al in the octahedral voids3+And 8 magnesium ions in tetrahedral voids Mg2+And (4) forming. There are 4 metal coordination sites for oxygen, 3 of which are in the octahedron and the remaining 1 in the tetrahedron. The unit cell structure of the magnesium aluminate spinel is shown in figure 1. The magnesium aluminate spinel has high thermal stability due to the saturated structure, the crystalline phase structure of the magnesium aluminate spinel can be kept unchanged at high temperature, and the melting point of the magnesium aluminate spinel is up to 2135 ℃.
Patent CN108031474A provides a coke oven gas ammonia decomposition catalyst using magnesium aluminate spinel as a carrier, which has good high-temperature activity and stability. However, it has also been found that under high temperature conditions, the sintering of spinel is a solid phase sintering which is dominated by ion diffusion, and in the spinel lattice, O2-The radius of the ion is larger, the diffusion speed is slower, and only Mg with smaller diameter actually participates in diffusion2+And Al3+Generally, only a close packing frame can be formed, and the cubic crystal structure is difficult to form.
Disclosure of Invention
The first invention aims to provide a preparation method of an ultra-high temperature ammonia decomposition catalyst with ultra-high temperature sintering resistance, high bed pressure resistance and high falling resistance aiming at more severe operating conditions of an ultra-large coke oven gas purification device.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The preparation method of the ultrahigh-temperature ammonia decomposition catalyst provided by the invention comprises the following steps of:
(1) preparing a reconstruction material:
carrying out first roasting on the powder of the hydrotalcite-like compound oxide;
preparing a first mixed solution from the first roasted product and sodium chloride, introducing inert gas at a certain temperature, stirring, standing, cooling, washing, filtering, and drying in vacuum to obtain a reconstructed material;
(2) preparation of catalyst carrier particles:
uniformly mixing the reconstructed material and the alkaline metal oxide for second roasting;
cooling the second roasted product, uniformly mixing the second roasted product with an oxygen storage component, pressing the second roasted product into cylindrical particles with the height of 15-20 mm and the diameter of 10-20 mm, and carrying out third roasting to obtain cylindrical catalyst carrier particles;
(3) catalyst active component attachment:
and (3) soaking the cylindrical catalyst carrier particles in a second mixed solution containing nickel nitrate and/or a cosolvent for multiple times until the active components of the catalyst are loaded to the designed amount, and then carrying out fourth roasting to obtain the ultrahigh-temperature ammonia decomposition catalyst.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the ultra-high temperature ammonia decomposition catalyst is prepared from the following raw materials in parts by mass:
preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the hydrotalcite-like composite oxide is at least one selected from a magnesium-aluminum binary hydrotalcite-like composite oxide, a zinc-magnesium-aluminum ternary hydrotalcite-like composite oxide, or a copper-magnesium-aluminum ternary hydrotalcite-like composite oxide.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the alkali metal oxide is selected from crystalline micro powder or electrofused micro powder thereof.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the steps of selecting the oxygen storage component from transition metal oxides and/or rare earth metal oxides; the transition metal oxide is at least one of molybdenum oxide, iron oxide, copper oxide, cobalt oxide or zirconium oxide; the rare earth metal oxide is at least one selected from cerium oxide, lanthanum oxide and praseodymium oxide.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the step of using a co-solvent selected from at least one of scandium oxide, yttrium oxide and oxides of lanthanoid.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the roasting temperature of the first roasting is 800-1300 ℃; or the roasting temperature of the second roasting is 1400-1500 ℃; or the roasting temperature of the third roasting is 900-1700 ℃; or, the roasting temperature of the fourth roasting is 600 ℃.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the first mixed solution contains metal ions and Cl-The molar ratio of (a) to (b) is 1:2 to 3: 5.
The second invention aims to provide the ultrahigh-temperature ammonia decomposition catalyst with ultrahigh-temperature sintering resistance, high bed pressure resistance and high falling resistance.
The third invention aims to provide the application of the ultrahigh-temperature ammonia decomposition catalyst with ultrahigh-temperature sintering resistance, high bed pressure resistance and high falling resistance in the ultra-large coke oven gas purification device.
By means of the technical scheme, the preparation method of the ultra-high temperature ammonia decomposition catalyst, the ultra-high temperature ammonia decomposition catalyst prepared by the method and the application of the ultra-high temperature ammonia decomposition catalyst at least have the following advantages:
1. according to the ultrahigh-temperature ammonia decomposition catalyst, the cubic structure of the catalyst carrier is modified in a manner of adding fine alkaline metal oxide particles, so that a large number of three-dimensional through pore channels are formed, and a high-strength material with a stable cubic phase structure is formed;
2. the ultrahigh-temperature ammonia decomposition catalyst provided by the application has the advantages that the transition metal oxide and/or the rare earth metal oxide are/is added as the oxygen storage component, so that the effect of improving the dispersibility of the active component is achieved, and the high-temperature activity of the catalyst is further improved;
3. the ultrahigh-temperature ammonia decomposition catalyst provided by the application is modified by adding a cosolvent with a special function, so that the aim of inhibiting the formation of difficultly reduced species is fulfilled, and the aims of improving the dispersion degree of active components on the surface of the catalyst, reducing the concentration of the surface active components and forming smaller surface particles are fulfilled;
4. the ultra-high temperature ammonia decomposition catalyst provided by the application can meet the requirement of high gas velocity (more than or equal to 6000 h)-1) High ammonia gas treatment capacity (not less than 18X 10)4m3H), high bed pressure (at space velocity of 6000 h)-1The use of a Claus furnace with a bed thickness of 1.2m, a bed pressure drop of 300Pa) and an operating temperature of 1000-1400 ℃ has the greatest advantages of high compressive strength (not less than 2.5KN) and high ammonia conversion rate (not less than 99.9%) under the conditions of ultrahigh temperature and high gas velocity compared with similar catalysts, and solves the problems of high gas velocity, high ammonia treatment capacity, cracking and pulverization of the catalyst under the condition of high bed pressure, high-temperature sintering and loss of active components;
5. the ultrahigh-temperature ammonia decomposition catalyst provided by the application can be used for a long time at the high temperature of 1100-1400 ℃, and the sintering phenomenon does not occur.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a unit cell structure of magnesium aluminate spinel;
FIG. 2 is an SEM image of the ultra-high temperature ammonia decomposition catalyst of the present invention at 1400 ℃;
FIG. 3 is an SEM photograph of an ammonia decomposition catalyst of a comparative example at 1400 ℃;
FIG. 4 is a TEM image of a super high temperature ammonia decomposition catalyst without added co-solvent as proposed in the present invention;
FIG. 5 is a TEM image of a super high temperature ammonia decomposition catalyst with added co-solvent according to the present invention.
Description of reference numerals:
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given to the preparation method of the ultra-high temperature ammonia decomposition catalyst, the ultra-high temperature ammonia decomposition catalyst prepared by the method and the application thereof, the specific implementation manner, the structure, the characteristics and the effects thereof according to the present invention, in combination with the accompanying drawings and the preferred embodiments.
The invention provides a preparation method of an ultrahigh-temperature ammonia decomposition catalyst, which comprises the following steps:
(1) preparing a reconstruction material:
carrying out first roasting on the powder of the hydrotalcite-like compound oxide;
preparing a first mixed solution from the first roasted product and sodium chloride, introducing inert gas at a certain temperature, stirring, standing, cooling, washing, filtering, and drying in vacuum to obtain a reconstructed material;
(2) preparation of catalyst carrier particles:
uniformly mixing the reconstructed material and the alkaline metal oxide for second roasting;
cooling the second roasted product, uniformly mixing the second roasted product with an oxygen storage component, pressing the second roasted product into cylindrical particles with the height of 15-20 mm and the diameter of 10-20 mm, and carrying out third roasting to obtain cylindrical catalyst carrier particles;
(3) catalyst active component attachment:
and (3) soaking the cylindrical catalyst carrier particles in a second mixed solution containing nickel nitrate and/or a cosolvent for multiple times until the active components of the catalyst are loaded to the designed amount, and then carrying out fourth roasting to obtain the ultrahigh-temperature ammonia decomposition catalyst.
The method is characterized in that fine particles of a basic metal compound are added into aggregate, and the fine particles are sintered on a large particle connecting part through evaporation and migration at a certain temperature, so that large particles are connected. Because each aggregate is connected with other particles at only a few points, a large number of three-dimensional through channels are formed in the sintered body, so that the sufficient number of vacancies are provided for the lattice structure, the vacancy energy is improved, a stable cubic phase structure is formed, and the compressive strength and the high-temperature sintering performance of the catalyst are improved.
The formation of the cubic system requires that the vacancy energy of vacancies and the kinetic energy for driving ions to move are firstly formed at the initial stage of particle diffusion, so that the materials with large lattice constant and more crystal defects are researched to provide enough vacancy quantity for crystal lattices, thereby improving the vacancy energy, forming a stable cubic spinel structure, and greatly improving the compressive strength and the high-temperature sintering performance of the catalyst.
The hydrotalcite-like compound oxide is used as aggregate of a catalyst carrier; the basic metal oxide connects the particles of the hydrotalcite-like compound oxide together to form a catalyst carrier; the oxygen storage component is mixed with the catalyst carrier and sintered to form catalyst carrier particles; the nickel nitrate and the cosolvent are sintered on the surfaces of the catalyst carrier particles.
The ultra-high temperature is more than or equal to 1100 ℃.
The hydrotalcite-like compound oxide is a binary, ternary or quaternary hydrotalcite-like compound oxide.
The nickel nitrate is used as an active component of the catalyst and is impregnated on the catalyst carrier in the form of an aqueous solution with the mass concentration of 50-90%.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the ultra-high temperature ammonia decomposition catalyst is prepared from the following raw materials in parts by mass:
the reconstruction material is prepared by reconstructing hydrotalcite-like compound oxide.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the hydrotalcite-like composite oxide is at least one selected from a magnesium-aluminum binary hydrotalcite-like composite oxide, a zinc-magnesium-aluminum ternary hydrotalcite-like composite oxide, or a copper-magnesium-aluminum ternary hydrotalcite-like composite oxide.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the alkali metal oxide is selected from crystalline micro powder or electrofused micro powder thereof.
Preferably, the preparation method of the ultra-high temperature ammonia decomposition catalyst comprises the step of preparing the alkali metal oxide containing SiO2The content is less than 3 wt%.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the alkali metal oxide includes MgO, and the content of MgO is greater than or equal to 60%.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the alkali metal oxide includes MgO, and the content of MgO is greater than or equal to 90%.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the step of preparing the alkali metal oxide having a specific surface area of more than 0.2m2/g。
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the step of preparing the alkali metal oxide having a specific surface area of 0.6 to 1.2m2/g。
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the crystalline metal oxide is obtained by electric melting magnesite with MgO content being more than or equal to 35%.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the step of selecting the oxygen storage component from transition metal oxides and/or rare earth metal oxides.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the transition metal oxide is at least one selected from molybdenum oxide, iron oxide, copper oxide, cobalt oxide and zirconium oxide.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the rare earth metal oxide is at least one selected from cerium oxide, lanthanum oxide and praseodymium oxide.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst comprises the step of using a co-solvent selected from at least one of scandium oxide, yttrium oxide and oxides of lanthanoid.
The lanthanide is a general term for 15 chemical elements with atomic numbers of 57-71 in IIIB group in the periodic table, and includes lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.
The particles of the catalyst are cylinders with the diameter of 10-20 mm and the height of 10-30 mm.
The particles of the catalyst are cylinders with the average diameter of 10-15 mm and the average height of 15-25 mm.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the inert gas is nitrogen.
Preferably, the method for preparing the ultra-high temperature ammonia decomposition catalyst is characterized in that the washing in the step (1) is to remove CL in the system-。
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the roasting temperature of the first roasting is 800-1300 ℃.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the roasting temperature of the second roasting is 1400-1500 ℃.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the calcination temperature of the third calcination is 900-1700 ℃.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the calcination temperature of the fourth calcination is 600 ℃.
Preferably, in the preparation method of the ultra-high temperature ammonia decomposition catalyst, the first mixed solution contains metal ions and Cl-The molar ratio of (a) to (b) is 1:2 to 3: 5.
The invention also provides an ultrahigh-temperature ammonia decomposition catalyst with ultrahigh-temperature sintering resistance, high bed pressure resistance and high falling resistance.
Preferably, the catalyst has a single-particle compressive strength of not less than 1900N.
Preferably, the catalyst for the ultra-high temperature ammonia decomposition has a single-particle compressive strength of 2500-3000N.
The compressive strength of the single particles is measured by a strength meter.
Preferably, the superhigh temperature ammonia decomposition catalyst has a loss resistant temperature of 1000-1500 ℃.
Preferably, the superhigh temperature ammonia decomposition catalyst has a loss resistant temperature of 1000-1400 ℃.
The loss resistant temperature is obtained by observing the ammonia decomposition rate and an electron microscope photo; the higher the ammonia decomposition rate of the catalyst under the temperature conditions described, the better the bleed resistance of the catalyst under the conditions described. The loss tolerant temperature range of the present invention means a temperature range in which the ammonia decomposition rate of the catalyst is more than 80%.
The invention also provides an application of the ultra-high temperature ammonia decomposition catalyst in an ultra-large coal gas purification device.
The ultra-high temperature ammonia decomposition catalyst and the preparation method and application thereof proposed by the present invention will be further described by the following specific examples.
Example 1
Weighing 100g of magnalium binary hydrotalcite-like compound oxide powder, wherein the mass percentage of magnesium oxide is more than 75%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2+)：n(Cl-) Preparing a first mixed solution at a ratio of 1:2, introducing nitrogen at 80 ℃, stirring, reacting, purifying for 30 hours, standing, cooling and washing to remove Cl-，AgNO3Checking to Cl free-And drying in vacuum to obtain the reconstructed material.
And (2) taking 5g of high-purity fused magnesium oxide powder and 90g of the prepared reconstructed material, uniformly mixing, presintering for 16h at the temperature of 1400 ℃ and 1500 ℃, cooling, uniformly mixing with 10g of oxygen storage components, pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles for 24h at the temperature of 1450 ℃, and cooling to obtain the catalyst carrier. The oxygen storage component in this example was selected from molybdenum oxide 4g and zirconium oxide 6 g.
The prepared catalyst carrier is repeatedly dipped and roasted in a nickel nitrate solution with the concentration of 80 wt% until the loading amount of active components in the catalyst reaches 10 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample.
FIG. 4 is a TEM image of the ultra-high temperature ammonia decomposition catalyst proposed in this example, wherein no co-solvent is added.
Example 2
Weighing 100g of (Mg + Zn) -Al ternary hydrotalcite-like composite oxide powder, wherein the mass percentage of magnesium oxide is more than 60%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2++Zn2+)：n(Cl-) Preparing a first mixed solution at a ratio of 1:2, introducing nitrogen at 80 ℃, stirring, reacting, purifying for 30 hours, standing, cooling and washing to remove Cl-，AgNO3Checking to Cl free-And drying in vacuum to obtain the reconstructed material.
And (2) taking 5g of high-purity fused magnesium oxide powder and 90g of the prepared reconstructed material, uniformly mixing, presintering for 16h at the temperature of 1400 ℃ and 1500 ℃, cooling, uniformly mixing with 3g of oxygen storage components, pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles for 24h at the temperature of 1450 ℃, and cooling to obtain the catalyst carrier. In this example, 1g of iron oxide and 2g of cerium oxide were used as oxygen storage components
The prepared catalyst carrier is repeatedly dipped and roasted in a second mixed solution of nickel nitrate with the concentration of 80 wt% and a cosolvent until the loading capacity of active components in the catalyst reaches 10g and the loading capacity of the cosolvent reaches 7 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample. Cerium oxide was used as the co-solvent in this example.
Example 3
Weighing 100g of (Mg + Cu) -Al ternary hydrotalcite-like composite oxide powder, wherein the mass percentage of magnesium oxide is more than 60%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2++Cu2+)：n(Cl-) First mix was prepared at 80 ℃ with 1:2Introducing nitrogen, stirring, reacting, purifying for 30h, standing, cooling, and washing to remove Cl-，AgNO3Checking to Cl free-And drying in vacuum to obtain the reconstructed material.
And (2) taking 5g of high-purity fused magnesium oxide powder and 90g of the prepared reconstructed material, uniformly mixing, presintering for 16h at the temperature of 1400 ℃ and 1500 ℃, cooling, uniformly mixing with 6g of oxygen storage components, pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles for 24h at the temperature of 1450 ℃, and cooling to obtain the catalyst carrier. The oxygen storage component of this example was selected to be zirconia.
The prepared catalyst carrier is repeatedly dipped and roasted in a second mixed solution of nickel nitrate with the concentration of 80 wt% and a cosolvent until the loading capacity of active components in the catalyst reaches 5g and the loading capacity of the cosolvent reaches 9 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample. Lanthanum oxide is selected as the cosolvent in this example.
Example 4
Weighing 100g of magnalium binary hydrotalcite-like compound oxide powder, wherein the mass percentage of magnesium oxide is more than 90%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2+)：n(Cl-) Preparing a first mixed solution with the ratio of 3:5, introducing nitrogen at 80 ℃, stirring, reacting, purifying for 30 hours, standing, cooling and washing to remove Cl-，AgNO3Checking to Cl free-And drying in vacuum to obtain the reconstructed material.
And (2) taking 5g of high-purity fused magnesium oxide powder and 90g of the prepared reconstructed material, uniformly mixing, presintering for 16h at the temperature of 1400 ℃ and 1500 ℃, cooling, uniformly mixing with 5g of oxygen storage components, pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles for 24h at the temperature of 1450 ℃, and cooling to obtain the catalyst carrier. The oxygen storage component of this example was selected to be zirconia.
The prepared catalyst carrier is repeatedly dipped and roasted in a second mixed solution of nickel nitrate with the concentration of 80 wt% and a cosolvent until the loading capacity of active components in the catalyst reaches 12g and the loading capacity of the cosolvent reaches 3 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample. Lanthanum oxide is selected as the cosolvent in this example.
FIG. 2 is an SEM photograph of the ultra-high temperature ammonia decomposition catalyst of this example at 1400 ℃; as shown in fig. 2, in which the active component of the catalyst and the support are not significantly sintered.
FIG. 5 is a TEM image of the UHT ammonia decomposition catalyst of this example with the addition of a co-solvent.
Example 5
Weighing 100g of magnalium binary hydrotalcite-like compound oxide powder, wherein the mass percentage of magnesium oxide is more than 90%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2+)：n(Cl-) Preparing a first mixed solution with the ratio of 3:5, introducing nitrogen at 80 ℃, stirring, reacting, purifying for 30 hours, standing, cooling and washing to remove Cl-，AgNO3Checking to Cl free-And drying in vacuum to obtain the reconstructed material.
And (2) taking 10g of high-purity fused magnesium oxide powder and 60g of the prepared reconstructed material, uniformly mixing, presintering for 16h at the temperature of 1400 ℃ and 1500 ℃, cooling, uniformly mixing with 10g of oxygen storage components, pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles for 24h at the temperature of 1450 ℃, and cooling to obtain the catalyst carrier. The oxygen storage component of this example was selected to be zirconia.
The prepared catalyst carrier is repeatedly dipped and roasted in a second mixed solution of nickel nitrate with the concentration of 80 wt% and a cosolvent until the loading capacity of active components in the catalyst reaches 16g and the loading capacity of the cosolvent reaches 14 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample. Scandium oxide is selected as the cosolvent in this example.
Comparative example
Weighing 100g of magnalium binary hydrotalcite-like compound oxide powder, wherein the mass percentage of magnesium oxide is more than 90%, and roasting the powder for 2h at 850 ℃. Taking the roasted product and sodium chloride according to the molar ratio n (Mg)2+)：n(Cl-) Preparing a first mixed solution with the ratio of 3:5, introducing nitrogen at 80 ℃, stirring, reacting, purifying for 30 hours, standing, cooling and washing to remove Cl-，AgNO3Checking to Cl free-Vacuum drying to obtain the reconstituted woodAnd (5) feeding.
Pre-burning the reconstructed material at 1400-1500 ℃ for 16h, cooling and pressing into cylindrical particles with the diameter of 15mm, roasting the cylindrical particles at 1450 ℃ for 24h, and cooling to obtain the catalyst carrier.
The prepared catalyst carrier is repeatedly dipped and roasted in a nickel nitrate solution with the concentration of 80 wt% until the loading amount of active components in the catalyst reaches 12 g. And roasting the impregnated sample at 600 ℃ for 8h to obtain the catalyst sample.
FIG. 3 is an SEM photograph of an ammonia decomposition catalyst of a comparative example at 1400 ℃; as shown in fig. 3, in which the active component of the catalyst and the support are significantly sintered.
In the above examples 1 to 5, the optimum conditions for the preparation of the catalyst were experimentally optimized, and no consideration was made in the examples. The compositions and properties of the catalysts prepared in the respective examples and comparative examples are shown in Table 1.
TABLE 1 composition and Properties of the catalysts
As can be seen from the test data shown in table 1, in examples 1 to 5 of the present invention, by adopting the above technical scheme, the ultra-high temperature catalyst has very good high temperature loss resistance, has very high ammonia decomposition performance at an ultra-high temperature of 1400 ℃, and has an ammonia decomposition rate of more than 99%; the single-particle compressive strength of the ultra-high temperature catalyst is more than 1900N, and the ultra-high temperature catalyst has good strength and hardness and can resist high bed pressure; the ultrahigh-temperature catalyst is not easy to crack and pulverize during filling, and has good anti-falling performance; meanwhile, the dispersion type of the active component of the ultra-high temperature ammonia decomposition catalyst is good, the migration and aggregation of metal particles hardly occur, the volatilization and loss resistance is good, and the high temperature sintering is resistant. The main components of the catalyst carrier and the active component in the comparative example are basically the same as those in examples 1 to 5, but basic metal oxide modification is not introduced by adopting the technical scheme of the invention, an oxygen storage component is not introduced into the catalyst carrier, and a cosolvent is not introduced during the adhesion of the catalyst, so that the performance of the catalyst is poor due to the combined action of a plurality of factors, the ammonia decomposition rate under ultrahigh temperature is low, the compressive strength of catalyst particles is poor, and a severe sintering phenomenon occurs under the ultrahigh temperature condition.
The features of the invention claimed and/or described in the specification may be combined, and are not limited to the combinations set forth in the claims by the recitations therein. The technical solutions obtained by combining the technical features in the claims and/or the specification also belong to the scope of the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.
Claims (7)
1. The preparation method of the ultrahigh-temperature ammonia decomposition catalyst is characterized by comprising the following steps of:
(1) preparing a reconstruction material:
carrying out first roasting on the powder of the hydrotalcite-like compound oxide;
preparing a first mixed solution from the first roasted product and sodium chloride, introducing inert gas at a certain temperature, stirring, standing, cooling, washing, filtering, and drying in vacuum to obtain a reconstructed material;
(2) preparation of catalyst carrier particles:
uniformly mixing the reconstructed material and the alkaline metal oxide for second roasting; the alkaline metal oxide is selected from crystalline micro powder or electrofused micro powder;
cooling the second roasted product, uniformly mixing the second roasted product with an oxygen storage component, pressing the second roasted product into cylindrical particles with the height of 15-20 mm and the diameter of 10-20 mm, and carrying out third roasting to obtain cylindrical catalyst carrier particles; the oxygen storage component is selected from transition metal oxide and/or rare earth metal oxide; the transition metal oxide is at least one of molybdenum oxide, iron oxide, copper oxide, cobalt oxide or zirconium oxide; the rare earth metal oxide is at least one of cerium oxide, lanthanum oxide or praseodymium oxide;
(3) catalyst active component attachment:
dipping the cylindrical catalyst carrier particles in a second mixed solution containing nickel nitrate and a cosolvent for multiple times until the active components of the catalyst are loaded to the designed amount, and then carrying out fourth roasting to obtain the ultrahigh-temperature ammonia decomposition catalyst; the cosolvent is at least one of scandium oxide, yttrium oxide or lanthanide oxide.
2. The preparation method of the ultra-high temperature ammonia decomposition catalyst according to claim 1, wherein the ultra-high temperature ammonia decomposition catalyst is prepared from the following raw materials in parts by mass:
50-90 parts of a reconstruction material;
5-10 parts of alkaline metal oxide;
3-10 parts of an oxygen storage component;
5-16 parts of nickel nitrate;
0-15 parts of cosolvent.
3. The method for preparing the ultra-high temperature ammonia decomposition catalyst according to claim 1, wherein the hydrotalcite-like composite oxide is at least one selected from a magnesium-aluminum binary hydrotalcite-like composite oxide, a zinc-magnesium-aluminum ternary hydrotalcite-like composite oxide, or a copper-magnesium-aluminum ternary hydrotalcite-like composite oxide.
4. The method for preparing an ultra-high temperature ammonia decomposition catalyst according to claim 1,
the roasting temperature of the first roasting is 800-1300 ℃; or the like, or, alternatively,
the roasting temperature of the second roasting is 1400-1500 ℃; or the like, or, alternatively,
the roasting temperature of the third roasting is 900-1700 ℃; or the like, or, alternatively,
the roasting temperature of the fourth roasting is 600 ℃.
5. The method for preparing an ultra-high temperature ammonia decomposition catalyst according to claim 1,
the first mixed solution contains metal ions and Cl-The molar ratio of (a) to (b) is 1:2 to 3: 5.
6. An ultra-high temperature ammonia decomposition catalyst prepared according to the method of any one of claims 1-5.
7. Use of the ultra-high temperature ammonia decomposition catalyst according to claim 6 in ultra-large gas purification units.
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| CN101628238A (en) * | 2009-08-11 | 2010-01-20 | 无锡市强亚耐火材料有限公司 | Ultrahigh-temperature ammonia decomposition catalyzer for coke oven gas and preparation method thereof |
| CN102139902A (en) * | 2011-01-20 | 2011-08-03 | 桂林理工大学 | Method for synthesizing magnesia-alumina spinel by roasting chloride ion type Mg-Al hydrotalcite at low temperature |
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