CN109926046B - Catalyst for hydrogen production by hydroiodic acid decomposition and preparation method thereof - Google Patents
Catalyst for hydrogen production by hydroiodic acid decomposition and preparation method thereof Download PDFInfo
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Abstract
A catalyst for hydrogen production by hydroiodic acid decomposition and a preparation method thereof, belonging to the technical field of catalytic reaction. The catalyst consists of a carrier and an active metal component, wherein the carrier adopts micron-sized mesoporous hollow silica spheres or core-shell structure glass fiber spheres, and the active metal component is loaded on the inner surface of a mesoporous hollow silica sphere shell or inside a shell layer of core-shell structure glass fibers. The active metal component is at least one element from the eighth group of the periodic table; the mass percentage of the active metal in the catalyst is 0.1-50%. The catalyst can catalyze the hydroiodic acid decomposition reaction at the temperature of 300-900 ℃ and under the normal pressure of-50 atm, and shows excellent catalytic activity and stability. The catalyst structurally strengthens the interaction between the carrier and the active metal components, reduces the phenomenon of high-temperature agglomeration or loss of the active metal, improves the activity and stability of the catalyst, and ensures that the reaction of decomposing the hydroiodic acid to produce hydrogen can be efficiently and stably operated.
Description
Technical Field
The invention relates to a catalyst for decomposing hydrogen iodide and a method for preparing hydrogen by decomposing the hydrogen iodide, and belongs to the technical field of catalytic reaction.
Background
Hydrogen is used as an energy carrier, has the advantages of high combustion heat value, combustion products only containing water, easiness in storage and transportation, environmental friendliness and the like, so that the hydrogen can be considered as an ideal energy source. The traditional hydrogen production method mainly comprises hydrogen production by fossil fuel and hydrogen production by water electrolysis, wherein the former has the defects of greenhouse gas emission and unfriendliness to the environment, and the latter has the defect of low hydrogen production efficiency. Under the drive of external heat, the thermochemical cycle hydrogen production method for realizing hydrogen production by water decomposition by coupling a plurality of chemical reactions can reduce the water decomposition reaction which can be carried out at the temperature of more than 2500 ℃ originally to be carried out below 1000 ℃. The method for producing hydrogen by thermochemical cycle decomposition of water also has the advantages of no greenhouse gas emission, environmental friendliness, high efficiency and the like. Since this method has been proposed to date, hundreds of cycles have been studied. Among the various thermochemical cycles, the iodine-sulfur thermochemical cycle hydrogen production method proposed by the united states GA in the last 70 th century has the advantages of cleanness, high-efficiency full-fluid cycle, good heat matching with a high-temperature reactor and the like, and is concerned by various national scholars such as the united states, the japan, the korea, the law, and the like, and the iodine-sulfur thermochemical cycle hydrogen production in 2009 is evaluated as one of the most promising large-scale hydrogen production methods by the united states energy department. The iodine sulfur thermochemical cycle consists of 3 reactions as follows:
(1) bunsen reaction: SO (SO)2+I2+2H2O→2HI+H2SO4(120 ℃), exothermic reaction;
(2) sulfuric acid decomposition reaction: h2SO4→H2O+SO2+1/2O2(800 ℃ C.) and 900 ℃ C.), endothermic reaction;
(3) decomposition reaction of hydrogen iodide 2HI → H2+I2(300 ℃ C.) and 500 ℃ C.), and carrying out endothermic reaction.
The catalytic decomposition reaction of hydrogen iodide is a key hydrogen production step in iodine-sulfur circulation, and has the following characteristics: (1) in the aspect of thermodynamics, the thermodynamic equilibrium conversion rate of the hydrogen iodide decomposition reaction is lower, and the equilibrium conversion rate is about 23% under the reaction condition of normal pressure and 500 ℃; (2) in the aspect of dynamics, the conversion rate is extremely low under the condition that no catalyst exists in the reaction, even if the temperature reaches 500 ℃, the decomposition conversion rate of the hydrogen iodide is only about 1 percent; (3) the reaction temperature of the hydrogen iodide decomposition reaction is generally 400-500 ℃, and the reaction system comprises HI-I2-H2O-H2The four components, wherein hydroiodic acid is a strong acid, iodine also has strong corrosivity, and hydrogen can cause metal to be hydrogen brittle at high temperature, so that the complex high-temperature corrosive environment puts very strict requirements on a catalyst for decomposing hydrogen iodide and a decomposition process.
The hydrogen iodide decomposition catalysts reported in the literature at present mainly consist of three types: activated carbon, supported nickel catalysts, and supported noble metal catalysts (e.g., supported platinum and supported palladium catalysts). Many studies have shown that the supported platinum catalyst exhibits excellent hydrogen iodide decomposition activity. However, the catalyst is high in cost and not ideal in stability. Although the cost of the activated carbon and the supported nickel catalyst is low, the activated carbon and the supported nickel catalyst have problems of low activity and poor stability. The high-temperature strong corrosive environment of the hydriodic acid decomposition reaction enables metal particles of the traditional supported metal catalyst to easily agglomerate and grow, so that the activity of the catalyst is reduced and even the catalyst is inactivated. Therefore, research and development of the supported catalyst with high activity and good stability and the HI catalytic decomposition process thereof are structurally satisfied, and the supported catalyst has important theoretical and practical significance for promoting stable and efficient decomposition of the hydroiodic acid and further improving the iodine-sulfur cycle hydrogen production efficiency.
Disclosure of Invention
The invention provides a high-efficiency and stable catalyst for catalytic decomposition of hydrogen iodide and a method for catalytically decomposing hydrogen iodide by using the catalyst, aiming at solving the problem that the traditional supported metal catalyst for decomposing hydrogen iodide is difficult to meet the requirement of long-term operation of iodine-sulfur cycle in terms of thermal stability and chemical stability.
The technical scheme of the invention is as follows:
the catalyst for hydrogen production by hydroiodic acid decomposition is characterized by comprising a spherical carrier and an active metal component, wherein the carrier is a mesoporous hollow silica sphere or a core-shell structure glass fiber sphere, the active metal component is loaded on the inner surface of a mesoporous hollow silica sphere shell or the inside of a core-shell structure glass fiber shell, the loaded active metal component is at least one element of the eighth group of the periodic table of elements, and the mass percentage of the active metal component in the catalyst is 0.1-50%.
In the technical scheme, the outer diameter of the mesoporous hollow silica sphere is 100nm-100um, and the shell layer thickness is 10nm-10 um. The core of the glass fiber ball with the core-shell structure is a solid glass fiber ball, the shell is an outer layer of the etched glass fiber ball with high specific surface area, and the specific surface area of the etched glass fiber ball is 10-500m2(ii)/g; the outer diameter of the core-shell structure glass fiber ball is 500nm-5000um, and the thickness of the shell layer is 50nm-500 um. The supported active metal particles have an average particle diameter of 1 to 50 nm.
The invention provides a preparation method of a catalyst for hydrogen production by hydroiodic acid decomposition, which is characterized by comprising the following steps:
1) placing the glass fiber ball in a pressure container, etching the outer layer of the glass ball by using subcritical water, wherein the temperature of the subcritical water is 200-;
2) adding the core-shell structure glass fiber balls obtained by etching into an ion exchange liquid containing an active metal compound through an ion exchange method, and fully stirring and mixing, wherein the mass ratio of the active metal to the core-shell structure glass fiber balls is (1: 1) - (1): 1000, mixing, placing in a constant-temperature water bath shaking table at 50-85 ℃, shaking, and performing suction filtration; the mass concentration of active metal ions in the ion exchange liquid is 50-1000 ppm.
3) And drying the solid obtained after filtering at the temperature of between 10 and 200 ℃ to obtain the catalyst with the active metal component loaded in the shell layer of the glass fiber with the core-shell structure.
The invention provides another preparation method of a catalyst for hydrogen production by hydroiodic acid decomposition, which is characterized by comprising the following steps:
1) adopting an equal-volume impregnation method to impregnate at least one solution of active metal compound on the outer surface of the mesoporous solid silica sphere, drying at the temperature of 10-200 ℃, and calcining for 1-8h in the air atmosphere at the temperature of 350-650 ℃;
2) dispersing the calcined sample obtained in the step 1) in a positive polyelectrolyte solution, stirring for self-assembly reaction for 1-8h, centrifuging, washing to neutrality, and drying at 10-200 ℃;
3) adding the dried sample obtained in the step 2) into 1-10M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 85-95 ℃ for 2-8h, cooling to room temperature, filtering, washing to be neutral, and drying at 10-200 ℃ to obtain the catalyst with the active metal component loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal to the mesoporous hollow silica sphere is 1: 1-1: 1000.
in the method of the present invention, preferably, the shaking table is oscillated at a speed of 100-500rpm for 1-6 h. The positive polyelectrolyte solution adopts polydiallyldimethylammonium chloride (PDDA) solution, polyvinyl sulfate (PVS) solution or Polyacrylamide (PAH) solution. The active metal compound is at least one of nitrate, acetate, sulfate, hydrochloride, chloroiridic acid and chloroplatinic acid of the metal element of the eighth group.
Compared with the traditional supported catalyst for decomposing hydrogen iodide, the invention adopts a mode of loading the active metal of the catalyst in an internal manner, namely, the active metal is loaded on the inner surface of the mesoporous hollow silica sphere shell or the shell of the glass fiber with the core-shell structure through a specific preparation process method, thereby structurally strengthening the interaction between the carrier and the active metal components, improving the reaction activity, simultaneously improving the thermal stability and the chemical stability of the catalyst, reducing the high-temperature agglomeration phenomenon or the loss phenomenon of the active metal, and ensuring that the catalytic decomposition hydrogen production reaction can still run efficiently and stably in the high-temperature strong corrosive environment of the catalyst. Moreover, when the catalyst is applied to the hydrogen production reaction by catalytic decomposition of hydroiodic acid, compared with the traditional catalyst for decomposing hydroiodic acid, the catalyst has wider reaction temperature range and pressure range, and the reaction temperature is 300-900 ℃, and the reaction pressure is as follows: under the condition of normal pressure to 50atm, the invention is used for catalyzing the decomposition of the hydrogen iodide, the conversion rate of the hydrogen iodide is close to the thermodynamic equilibrium conversion rate under the corresponding condition, and the catalyst has the advantages of good catalytic activity and high stability.
Detailed Description
The technical scheme of the invention comprises a catalyst for hydrogen production by hydroiodic acid decomposition and a preparation method thereof, wherein the catalyst comprises a spherical carrier and an active metal component, the carrier adopts a mesoporous hollow silica sphere or a core-shell structure glass fiber sphere, the active metal component is loaded on the inner surface of the mesoporous hollow silica sphere shell or inside the shell layer of the core-shell structure glass fiber, the loaded active metal component is at least one element of the eighth group of elements in the periodic table, and the mass percentage of the active metal component in the catalyst is 0.1-50%. The outer diameter of the mesoporous hollow silica sphere is 100nm-100um,the thickness of the shell layer is 10nm-10 um. The core of the glass fiber ball with the core-shell structure is a solid glass fiber ball, the shell is an outer layer of the etched glass fiber ball with high specific surface area, and the specific surface area of the etched glass fiber ball is 10-500m2(ii)/g; the outer diameter of the core-shell structure glass fiber ball is 500nm-5000um, and the thickness of the shell layer is 50nm-500 um. The supported active metal particles have an average particle diameter of 1 to 50 nm.
The invention provides a preparation method of a catalyst for hydrogen production by hydroiodic acid decomposition, wherein a carrier of the catalyst adopts a glass fiber ball with a core-shell structure, and the method comprises the following steps:
1) placing the glass fiber ball in a pressure container, etching the outer layer of the glass ball by using subcritical water, wherein the temperature of the subcritical water is 200-;
2) adding the core-shell structure glass fiber balls obtained by etching into ion exchange liquid containing active metal compounds through an ion exchange method, and fully stirring and mixing, wherein the mass ratio of the active metal to the core-shell structure glass fiber balls is 1: 1-1: 1000, mixing, placing in a constant-temperature water bath shaking table at 50-85 ℃, shaking at the speed of 100-500rpm for 1-6h, and performing suction filtration; the mass concentration of active metal ions in the ion exchange liquid is 50-1000 ppm.
3) And drying the solid obtained after filtering at the temperature of between 10 and 200 ℃ to obtain the catalyst with the active metal component loaded in the shell layer of the glass fiber with the core-shell structure.
The invention provides a preparation method of a catalyst for hydrogen production by hydroiodic acid decomposition, wherein a carrier of the catalyst adopts mesoporous hollow silica spheres, and the method comprises the following steps:
1) adopting an equal-volume impregnation method to impregnate at least one solution of active metal compound on the outer surface of the mesoporous solid silica sphere, drying at the temperature of 10-200 ℃, and calcining for 1-8h in the air atmosphere at the temperature of 350-650 ℃;
2) dispersing the calcined sample obtained in the step 1) in a positive polyelectrolyte solution, stirring for self-assembly reaction for 1-8h, centrifuging, washing to neutrality, and drying at 10-200 ℃; the positive polyelectrolyte solution comprises: polydiallyldimethylammonium chloride (PDDA) solutions, polyvinyl sulfate (PVS) solutions, and polypropylene ammonium chloride (PAH) solutions.
3) Adding the dried sample obtained in the step 2) into 1-10M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 85-95 ℃ for 2-8h, cooling to room temperature, filtering, washing to be neutral, and drying at 10-200 ℃ to obtain the catalyst with the active metal component loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal to the mesoporous hollow silica sphere is 1: 1-1: 1000.
in the above method for preparing a catalyst for hydrogen production by hydroiodic acid decomposition, the active metal compound is at least one of nitrate, acetate, sulfate, hydrochloride, chloroiridic acid and chloroplatinic acid of a group VIII metal element.
Compared with the traditional catalyst for decomposing hydroiodic acid, the catalyst provided by the invention is applied to the hydrogen production reaction by catalytic decomposition of hydroiodic acid, the reaction temperature range and the pressure range are wider, and the reaction temperature is 300-900 ℃, the reaction pressure is as follows: the catalyst shows excellent catalytic activity and stability under the condition of normal pressure to 50 atm. The catalyst structurally strengthens the interaction between the carrier and the active metal components, reduces the phenomenon of high-temperature agglomeration or loss of the active metal, improves the activity and stability of the catalyst, and ensures that the reaction of decomposing the hydroiodic acid to produce hydrogen can be efficiently and stably operated.
The present invention is illustrated in detail below by means of several examples.
Example 1: preparation of mesoporous hollow silica sphere (HMS, sphere outer diameter 100nm, shell thickness 10nm) with active metal Pt catalyst 0.1% Pt @ HMS loaded on inner surface
Adopting an equal-volume impregnation method, impregnating the outer surface of mesoporous solid silica (with the outer diameter of 90nm) with an aqueous solution containing chloroplatinic acid, drying at 200 ℃, and calcining at 350 ℃ in an air atmosphere for 8 h. Dispersing the obtained sample in a mixed solution of 2.5 wt% of PDDA in a positive polyelectrolyte solution and 0.5M NaCl, stirring for self-assembly reaction for 8 hours, centrifuging, washing to be neutral, and drying at the temperature of 200 ℃. Adding the dried sample into 1M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 85 ℃ for 8h, cooling to room temperature, filtering, washing to be neutral, and drying at 10 ℃ to obtain the catalyst with the active metal component Pt loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal to the mesoporous hollow silica sphere is 1: 1000. reported as 0.1% Pt @ HMS.
Comparative example 1: preparation of 0.1% Pt/HMS active metal loaded Pt catalyst on outer surface of mesoporous hollow silica sphere (HMS, sphere outer diameter is 100nm, shell thickness is 10nm)
Mesoporous solid silica (with the outer diameter of 100nm) is dispersed in a mixed solution of 2.5 wt% of PDDA and 0.5M NaCl in a positive polyelectrolyte solution, self-assembly reaction is carried out for 8 hours by stirring, then centrifugation and washing are carried out until the solution is neutral, and drying is carried out at the temperature of 200 ℃. And adding the dried sample into 1M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 85 ℃ for 8h, cooling to room temperature, filtering, washing to be neutral, and drying at 10 ℃ to obtain the hollow mesoporous silica sphere carrier. Dipping the outer surface of the hollow mesoporous silicon sphere in dipping liquid containing chloroplatinic acid by adopting a dipping method. After the completion of the impregnation, the catalyst was dried at 10 ℃ to obtain a platinum externally supported mesoporous hollow silica spherical shell catalyst, which was referred to as 0.1% Pt/HMS.
Example 2: preparation of mesoporous hollow silica spherical shell (outer diameter of sphere is 100um, thickness of shell layer is 10um)) with active metal Ni catalyst loaded on inner surface of 50% Ni @ HMS
Adopting an equal-volume impregnation method, impregnating the outer surface of mesoporous solid silica (with the outer diameter of 90um) with an aqueous solution containing nickel acetate, drying at 10 ℃, and calcining at 650 ℃ for 1h in an air atmosphere. Dispersing the obtained sample in positive polyelectrolyte PVS solution, stirring for self-assembly reaction for 1h, then centrifuging, washing to be neutral, and drying at 10 ℃. Adding the dried sample into 10M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 95 ℃ for 2h, cooling to room temperature, filtering, washing to be neutral, and drying at 200 ℃ to obtain the catalyst with the active metal component Ni loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal Ni to the mesoporous hollow silica sphere is 1: 1. denoted as 50% Ni @ HMS.
Comparative example 2: preparation of mesoporous hollow silica spherical shell (outer diameter of sphere is 100um, shell thickness is 10um) with active metal Ni catalyst loaded on outer surface of 50% Ni/HMS
Dispersing mesoporous solid silica in positive polyelectrolyte PVS solution, stirring for self-assembly reaction for 1h, centrifuging, washing to neutrality, and drying at 10 ℃. And adding the dried sample into 10M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 95 ℃ for 2h, cooling to room temperature, filtering, washing to be neutral, and drying at 200 ℃ to obtain the hollow mesoporous silica sphere carrier. And (3) dipping the outer surface of the hollow mesoporous silicon sphere in a dipping solution containing nickel acetate by adopting a dipping method. After the impregnation is completed, drying is carried out at 200 ℃ to obtain the mesoporous hollow silica spherical shell catalyst which forms the nickel external load and is recorded as 50% Ni/HMS.
Example 3: the method comprises the steps of immersing 19% of Ni-1% of Ir @ HMS (the outer diameter of an HMS sphere is 10 microns, the shell layer thickness is 1 micron) on the outer surface of mesoporous solid silica (the outer diameter is 9 microns) by adopting an equal-volume immersion method, drying at 120 ℃, and calcining for 4 hours at 450 ℃ in an air atmosphere. Dispersing the obtained sample in positive polyelectrolyte PAH solution, stirring for self-assembly reaction for 4h, then centrifuging, washing to neutrality, and drying at 120 ℃. Adding the dried sample into 2M ammonia water, carrying out hydrothermal reaction in a reaction kettle for 4 hours at the temperature of 90 ℃, cooling to room temperature, filtering, washing to be neutral, and drying at the temperature of 120 ℃ to obtain the catalyst with active metal components Ni and Ir loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal components Ni and Ir to the mesoporous hollow silica sphere is 19: 1: 80, written as 19% Ni-1% Ir @ HMS.
Comparative example 3: 19% Ni-1% Ir/HMS (HMS sphere outer diameter of 10um, shell thickness of 1um)
Dispersing mesoporous solid silica in a positive polyelectrolyte PAH solution, stirring for self-assembly reaction for 4h, then centrifuging, washing to be neutral, and drying at 120 ℃. And adding the dried sample into 2M ammonia water, carrying out hydrothermal reaction in a reaction kettle for 4 hours at the temperature of 90 ℃, cooling to room temperature, filtering, washing to be neutral, and drying at the temperature of 120 ℃ to obtain the hollow mesoporous silica sphere carrier. The method is characterized in that impregnation liquid containing nickel chloride and chloroiridic acid is impregnated on the outer surface of the hollow mesoporous silicon spheres by adopting an impregnation method, wherein the contents of nickel and iridium respectively account for 19 percent and 1 percent of the mass of the carrier. After the impregnation is finished, the catalyst is dried for 4 hours at 120 ℃ to obtain the mesoporous hollow silica spherical shell catalyst which forms the nickel iridium external load and is recorded as 19% Ni-1% Ir/HMS.
Example 4: 9% Ni-0.5% Ir-0.5% Pt @ HMS (HMS sphere outer diameter of 1um, shell thickness of 100nm)
Adopting an equal-volume impregnation method, impregnating the outer surface of mesoporous solid silica (with the outer diameter of 0.9um) with an aqueous solution containing nickel chloride, chloroiridic acid and chloroplatinic acid, drying at 100 ℃, and calcining at 500 ℃ in an air atmosphere for 3 h. Dispersing the obtained sample in a positive polyelectrolyte PDDA solution, stirring for self-assembly reaction for 6h, then centrifuging, washing to be neutral, and drying at 100 ℃. Adding the dried sample into 5M ammonia water, carrying out hydrothermal reaction for 5h in a reaction kettle at 88 ℃, cooling to room temperature, filtering, washing to be neutral, and drying at 100 ℃ to obtain the catalyst with active metal components Ni, Ir and Pt loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal components Ni, Ir and Pt to the mesoporous hollow silica sphere is 18: 1: 1: 180, written as 9% Ni-0.5% Ir-0.5% Pt @ HMS.
Example 5: 5% Pt @ HMS (HMS sphere outer diameter 500nm, shell thickness 50nm)
Adopting an equal-volume impregnation method, impregnating the outer surface of mesoporous solid silica (with the outer diameter of 450nm) with an aqueous solution containing chloroplatinic acid, drying at 120 ℃, and calcining at 650 ℃ for 1h in an air atmosphere. The obtained sample is dispersed in 2.5% PDDA solution (containing 0.5M NaCl) by ultrasonic, self-assembly reaction is carried out for 2h by stirring, then centrifugation and washing are carried out until the solution is neutral, and drying is carried out at 120 ℃. Adding the dried sample into 2M ammonia water, carrying out hydrothermal reaction in a reaction kettle for 5 hours at the temperature of 90 ℃, cooling to room temperature, filtering, washing to be neutral, and drying at the temperature of 120 ℃ to obtain an active metal component and a catalyst with Pt loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal Pt to the mesoporous hollow silica sphere is 1: 19, recorded as 5% Pt @ HMS.
Example 6: preparation of core-shell structure Glass fiber ball (Glass bead, abbreviated as GB, with an outer diameter of 500nm and a shell thickness of 50nm) with 10% Pd @ GB as a palladium catalyst loaded in shell
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is 400 deg.C, pressure 5Mpa, and time 5 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into palladium chloride ion exchange liquid with the palladium content of 1000ppm by an ion exchange method, and fully stirring and mixing, wherein the mass ratio of active metal palladium to the core-shell glass fiber balls is 1: 9, fully mixing, placing in a constant-temperature water bath shaking table at 50 ℃, shaking at the speed of 100rpm for 6 hours, and performing suction filtration; the obtained solid after filtration is dried at 10 ℃ to obtain the catalyst with the active metal component Pd loaded in the shell of the glass fiber with the core-shell structure, which is recorded as 10% Pd @ GB.
Example 7: preparation of core-shell structure glass fiber ball (outer diameter 5000um, shell thickness 500um) with platinum catalyst 0.1% Pt @ GB loaded in shell
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is temperature 200 deg.C, pressure 10Mpa, and time 0.5 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into chloroplatinic acid ion exchange liquid with the platinum content of 50ppm by an ion exchange method, and fully stirring and mixing, wherein the mass ratio of active metal platinum to the core-shell glass fiber balls is 1: 1000, fully mixing, placing in a constant-temperature water bath shaking table at 85 ℃, shaking at the speed of 500rpm for 1 hour, and performing suction filtration; drying the obtained filtered solid at 200 ℃ to obtain the catalyst with the active metal component Pt loaded in the shell layer of the core-shell structure glass fiber,
example 8: preparation of 5% Pt @ GB (GB outer diameter 500um, shell thickness 50um)
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is temperature 300 deg.C, pressure 8Mpa, and time 1 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into chloroplatinic acid ion exchange liquid with the platinum content of 1000ppm by an ion exchange method, and fully stirring and mixing, wherein the mass ratio of active metal platinum to the core-shell glass fiber balls is 1: 19, fully mixing, placing in a constant-temperature water bath shaking table at 60 ℃, shaking for 2 hours at the speed of 160rpm, and performing suction filtration; the obtained filtered solid was dried at 100 ℃ to obtain a catalyst in which an active metal component Pt was supported inside the shell layer of the core-shell structured glass fiber, which was denoted as 5% Pt @ GB.
Example 9: 4% Ni-3% Fe-3% Co @ GB (GB external diameter 1000um, shell thickness 100um)
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is temperature 300 deg.C, pressure 8Mpa, and time 3 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into nickel sulfate, ferrous sulfate and cobalt sulfate mixed ion exchange liquid with the nickel, iron and cobalt contents of 400ppm, 300ppm and 300ppm respectively by an ion exchange method, and fully stirring and mixing, wherein the mass ratio of the three active metals of nickel, iron and cobalt to the core-shell structure glass fiber balls is 4: 3: 3: 90, fully mixing, placing in a constant-temperature water bath shaking table at 65 ℃, shaking for 3 hours at the speed of 300rpm, and performing suction filtration; the obtained filtered solid is dried at 120 ℃ to obtain the catalyst with three active metal components loaded in the shell of the core-shell structure glass fiber, and the catalyst is recorded as 4% Ni-3% Fe-3% Co @ GB.
Example 10: 19% Ni-1% Ir @ GB (GB external diameter 800um, shell thickness 80um)
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is temperature 300 deg.C, pressure 8Mpa, and time 1 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into nickel chloride ion and chloroiridic acid exchange liquid with the nickel content and the iridium content of 1000ppm and 50ppm respectively by an ion exchange method, and fully mixing, wherein the mass ratio of active metal nickel to active metal iridium to core-shell structure glass fiber balls is 19: 1: 80, fully mixing, placing in a constant-temperature water bath shaking table at 70 ℃, shaking for 2 hours at the speed of 200rpm, and filtering; and drying the obtained filtered solid at 160 ℃ to obtain the catalyst with the active metal nickel iridium component loaded in the shell layer of the core-shell structure glass fiber, and recording the catalyst as 19% Ni-1% Ir @ GB.
Example 11: 49% Ni-1% Ir @ GB (GB external diameter 2000um, shell thickness 200um)
Placing the glass fiber ball in a pressure container, and etching the outer layer of the glass ball by using subcritical water. The subcritical parameter is temperature 350 deg.C, pressure 6Mpa, and time 4 h. Obtaining glass fiber balls with core-shell structures; adding the etched core-shell glass fiber balls into nickel chloride ion and chloroiridic acid exchange liquid with the nickel content and the iridium content of 1000ppm and 50ppm respectively by an ion exchange method, and fully mixing, wherein the mass ratio of active metal nickel to active metal iridium to core-shell structure glass fiber balls is 49: 1: 50, fully mixing, placing in a constant-temperature water bath shaking table at 70 ℃, shaking for 2 hours at the speed of 200rpm, and filtering; the obtained filtered solid is dried at 180 ℃ to obtain the catalyst with the active metal nickel iridium component loaded inside the shell layer of the core-shell structure glass fiber, and the catalyst is recorded as 49% Ni-1% Ir @ GB.
The catalysts prepared in the examples and the comparative examples are subjected to hydrogen iodide catalytic decomposition performance tests, and the test conditions and results are as follows:
the hydrogen iodide decomposition catalytic performance evaluation is carried out on a self-assembly fixed bed tubular (quartz material for normal pressure and hastelloy C-276 material for high pressure) reaction device, the outer diameter of the reactor is 14mm, and the inner diameter of the reactor is 12 mm; the catalyst dosage is 0.100g-1.0g, the catalyst needs to be activated before reaction, the activation temperature is 300-700 ℃, the time is 0.5-6h, and the activation atmosphere is determined according to the type of the catalyst: for the catalyst containing only the noble metal active component, the activation atmosphere is an inert atmosphere such as nitrogen, helium, argon or the like; for the catalyst containing non-noble metal such as nickel, cobalt and other components, the activation atmosphere is pure hydrogen or hydrogen-containing mixed gas. The flow rate of the reaction raw material (analytically pure hydroiodic acid, Beijing sunshine Deshi chemical Co., Ltd.) is 0.5ml/min-5.0 ml/min. The reaction temperature is 300-900 ℃, the reaction pressure is normal pressure-50 atm, and the reaction time is not less than 1 hour. Conversion of hydrogen iodide H in hydrogen iodide before and after titration with standard sodium hydroxide+Concentration calculation before and after reactionThe average size of the metal particles is obtained by taking a picture of each sample through a Transmission Electron Microscope (TEM) and then counting, and the relative content change of Ni in the catalyst before and after reaction is the content ratio measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).
The experimental research result shows that, compared with the catalyst (comparative examples 1-3) which is loaded with the metal component on the outer surface of the mesoporous hollow silica sphere carrier in structure, the catalyst (examples 1 to 5) in which the active metal component is supported on the inner surface of the mesoporous hollow silica sphere carrier obtained by the preparation method of the present invention, or the catalyst with active metal components is loaded in the outer shell layer of the glass fiber ball with the core-shell structure (examples 6-10), the initial activity of the reaction and the average size of the metal particles before the reaction are not obviously different, but the sintering growth of the metal particles after the reaction is obviously different, the particles of comparative examples (1-3) grow at least 2 times larger, and the corresponding particles of the catalysts of examples (1-11) grow less than 1 time larger, and when the supported metal component is a bimetal or a polymetal, the size increases less than 0.5 time. And compared with published literature reports, the catalyst obtained by the invention has excellent stability. Specifically, the active carbon supported platinum catalyst 5% Pt/AC (which is a hydrogen iodate decomposition catalyst having excellent properties recognized in the world for multiple iodine sulfur hydrogen production) reported in the literature (Laijun Wang, Qi Han, Daocai Li, et al. composites of Pt catalysts supported on active carbon, carbon molecular size, carbon nanotubes and graphite for HI decomposition at differential temperature. int. J. hydrogen Energy,2013,38(1): 109. 116.) was used as the catalyst obtained by the present invention (example 5: 5% Pt HMS and example 8: 5% Pt GB) under the same conditions where the average particle size of the platinum particles was changed from 5.1nm to 22.0nm after 1 hour of reaction at 550 ℃ and the initial activity was changed to about 24 nm under the same conditions where the initial activity was gradually changed from 5% Pt @ 5 to 5% Pt @ GB, the particle size of the platinum particles in the catalyst after the reaction is 5-10nm, which is far lower than the growth of the platinum particles in the 5% Pt/AC of the catalyst in the comparison literature. In addition, from the analysis of the change results of nickel content before and after the catalyst reaction, the hydroiodic acid decomposition is catalyzed at 500 ℃ under normal pressure by using the catalyst of example 3 (19% Ni-1% Ir @ HMS), example 10 (19% Ni-1% Ir @ GB) and comparative example 3 (19% Ni-1% Ir/HMS), respectively, the nickel loss of the catalyst of the former two is about 10% after the reaction, and the nickel loss of the catalyst of the comparative example 3 is more than 20%. Therefore, the nickel is fixed on the inner surface of the carrier or in the shell layer, and the loss of the nickel is effectively reduced. This shows that the invention can obviously improve the thermal stability and chemical stability of the catalyst on the premise of ensuring the high activity of the catalyst.
Claims (5)
1. A catalyst for hydrogen production by hydroiodic acid decomposition is characterized by comprising a spherical carrier and an active metal component; the spherical carrier adopts mesoporous hollow silica spheres, the active metal component is loaded on the inner surface of a mesoporous hollow silica sphere shell, the loaded active metal component is at least one element from the eighth group of elements in the periodic table of elements, and the mass percentage content of the active metal component in the catalyst is 0.1-50%;
the catalyst is prepared by the following method:
1) adopting an equal-volume impregnation method to impregnate at least one solution of active metal compound on the outer surface of the mesoporous solid silica sphere, drying at the temperature of 10-200 ℃, and calcining for 1-8h in the air atmosphere at the temperature of 350-650 ℃;
2) dispersing the calcined sample obtained in the step 1) in a positive polyelectrolyte solution, stirring for self-assembly reaction for 1-8h, centrifuging, washing to be neutral, and drying at the temperature of 10-200 ℃;
3) adding the dried sample obtained in the step 2) into 1-10M ammonia water, carrying out hydrothermal reaction in a reaction kettle at 85-95 ℃ for 2-8h, cooling to room temperature, filtering, washing to neutrality, and drying at 10-200 ℃ to obtain the catalyst with the active metal component loaded on the inner surface of the mesoporous hollow silica sphere shell, wherein the mass ratio of the active metal to the mesoporous hollow silica sphere is 1: 1-1: 1000.
2. the catalyst for the production of hydrogen by the decomposition of hydroiodic acid according to claim 1, wherein: the outer diameter of the mesoporous hollow silica sphere is 100nm-100 μm, and the shell layer thickness is 10nm-10 μm.
3. The catalyst for hydrogen production by hydroiodic acid decomposition according to claim 1 or 2, which comprises: the supported active metal has a particle average particle diameter of 1 to 50 nm.
4. The catalyst for hydrogen production by hydroiodic acid decomposition of claim 1, wherein the positive polyelectrolyte solution in the step 2) is polydiallyldimethylammonium chloride solution, polyvinyl sulfate solution or polyacrylamide chloride solution.
5. The catalyst for hydrogen production by hydroiodic acid decomposition of claim 1 wherein the active metal compound is at least one of the nitrates, acetates, sulfates, hydrochlorides, chloroiridic acid and chloroplatinic acid of the group VIII metal element.
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| US4410505A (en) * | 1982-05-07 | 1983-10-18 | Ga Technologies Inc. | Hydrogen iodide decomposition |
| CN1736604A (en) * | 2005-07-27 | 2006-02-22 | 北京化工大学 | Egg shell type metal catalyst, its preparing process and application method |
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| CN102909036A (en) * | 2012-10-16 | 2013-02-06 | 清华大学 | Catalyst for hydrogen production by virtue of catalytic decomposition of hydrogen iodide and preparation method for catalyst |
| CN106935871A (en) * | 2015-12-31 | 2017-07-07 | 中国科学院化学研究所 | A kind of mesoporous PtAu nano materials of hollow ball-shape and preparation method and application |
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| US4410505A (en) * | 1982-05-07 | 1983-10-18 | Ga Technologies Inc. | Hydrogen iodide decomposition |
| CN1736604A (en) * | 2005-07-27 | 2006-02-22 | 北京化工大学 | Egg shell type metal catalyst, its preparing process and application method |
| CN102580725A (en) * | 2012-01-11 | 2012-07-18 | 清华大学 | Preparation method and application of nano monocrystal Pd core-shell catalyst |
| CN102909036A (en) * | 2012-10-16 | 2013-02-06 | 清华大学 | Catalyst for hydrogen production by virtue of catalytic decomposition of hydrogen iodide and preparation method for catalyst |
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