CN115121293A - Nanofiber catalyst, preparation method and application thereof, and method for preparing hexanediamine through hydrogenation - Google Patents

Nanofiber catalyst, preparation method and application thereof, and method for preparing hexanediamine through hydrogenation Download PDF

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CN115121293A
CN115121293A CN202110336223.5A CN202110336223A CN115121293A CN 115121293 A CN115121293 A CN 115121293A CN 202110336223 A CN202110336223 A CN 202110336223A CN 115121293 A CN115121293 A CN 115121293A
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aluminum
nanofiber
catalyst
high molecular
solution
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CN115121293B (en
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甄栋兴
王海京
刘凌涛
丁晖殿
郑博
宗保宁
朱振兴
罗一斌
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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Abstract

The invention relates to the technical field of nanofiber materials, in particular to a nanofiber catalyst, a preparation method and application thereof, and a method for preparing hexanediamine through hydrogenation. The preparation method of the nanofiber catalyst comprises the following steps: (1) preparing a spinning solution containing an aluminum source, a high molecular polymer and a solvent; (2) performing electrostatic spinning and solvent removal treatment on the spinning solution to obtain aluminum-containing nanofibers; 3) and (3) dipping the aluminum-containing nanofiber in an active component solution, and then drying and roasting to obtain the nanofiber catalyst. The method combines an electrostatic spinning technology and an impregnation technology, so that the nanofiber catalyst has controllable diameter and higher specific surface area; meanwhile, the nanofiber catalyst provided by the invention is used for preparing the hexanediamine by hydrogenation, and has higher adiponitrile conversion rate and hexamethylenediamine selectivity.

Description

Nanofiber catalyst, preparation method and application thereof, and method for preparing hexanediamine through hydrogenation
Technical Field
The invention relates to the technical field of nanofiber materials, in particular to a nanofiber catalyst, a preparation method and application thereof, and a method for preparing hexanediamine through hydrogenation.
Background
Hexamethylenediamine is an important chemical raw material, can be used for organic synthesis and polymerization of high molecular compounds, and most of hexamethylenediamine is used as an intermediate to react with adipic acid, sebacic acid and the like to produce polyamide, such as nylon 66, nylon 610 and the like. Furthermore, HDI (1, 6-hexamethylene diisocyanate) produced by photochemical reaction of hexamethylene diamine is a high-grade environment-friendly coating, and the demand of the HDI is sharply increased along with the increasing strictness of the environment-friendly standard.
Hexamethylenediamine can be produced from adiponitrile, hexanediol and caprolactam, but the mass production of hexamethylenediamine in the world almost always uses the adiponitrile process, i.e. the adiponitrile is subjected to hydrogenation reduction under the action of a catalyst to form hexamethylenediamine. Global adiponitrile supply is a high oligopolistic monopoly, with four major producers, the united states inflatada, the american olyde, the french solvay, the japan asahi company, having market share of the first three size up to 97%.
Raney Ni type catalyst is adopted for preparing hexanediamine by hydrogenation of adiponitrile in industry, but the catalyst is easy to self-ignite, a large amount of alkali liquor is needed in the preparation process, the reaction process is also needed to be carried out under alkaline conditions, the corrosion to equipment is large, and the separation difficulty of products is large.
《Ni-MgO/Al 2 O 3 Research on the catalytic hydrogenation of adiponitrile to hexamethylenediamine (oil refining and chemical engineering, 2012,43(9), 44-49) discloses the co-impregnation of Al with solutions of nickel nitrate and magnesium nitrate 2 O 3 Preparation of Ni-MgO/Al 2 O 3 Catalyst for hydrogenation of adiponitrile to synthesize hexanediamine.
CN108084035A discloses Al prepared by coprecipitation method 2 O 3 The supported metal nickel catalyst is modified by alkaline earth or rare earth metal oxide and is used for preparing hexamethylene diamine by hydrogenating adiponitrile ethanol solution under the alkali-free condition.
CN111116376A discloses a Ni-based catalyst prepared by a coprecipitation method, the Ni-based catalyst is prepared by Ni 2+ Preparing hydrotalcite; the method adopts Ni-based hydrotalcite catalyst loaded with alkali metal, and uses hexanedial to prepare hexanediamine through reductive amination.
CN104262168A discloses a supported nickel-based hydrogenation catalyst prepared by loading Ni on a silica carrier by an impregnation method, which is used for preparing hexamethylenediamine by hydroamination of hexanedialdehyde.
At present, most of supported catalysts for preparing hexamethylene diamine adopt a precipitation method, an immersion method, a hydrothermal method and the like, and catalysts prepared by the methods are single in structure, micron-sized, difficult to control in morphology from a nanometer scale, easy to agglomerate active sites, large in mass transfer resistance and not beneficial to efficient reaction.
Disclosure of Invention
The invention aims to solve the problems that the existing catalyst for hexamethylene diamine hydrofining is easy to be natural, has a single structure, low catalytic efficiency, needs to be prepared in an alkaline solution, has a complex process and the like, and provides a nanofiber catalyst, a preparation method and application thereof, and a method for preparing hexanediamine by hydrogenation; the nanofiber catalyst has controllable diameter and high specific surface area; meanwhile, the nanofiber catalyst is used for preparing hexamethylene diamine, and has high catalytic efficiency.
In order to achieve the above object, a first aspect of the present invention provides a method for preparing a nanofiber catalyst, comprising the steps of:
(1) preparing a spinning solution containing an aluminum source, a high molecular polymer and a solvent;
(2) performing electrostatic spinning and solvent removal treatment on the spinning solution to obtain aluminum-containing nanofibers;
(3) and (3) soaking the aluminum-containing nanofiber in an active component solution, and then drying and roasting to obtain the nanofiber catalyst.
The inventor of the invention researches and finds that: compared with the prior art that the active component is impregnated on the surface of the catalyst carrier (alumina nanofiber) which is converted into the oxide by an impregnation method, the invention impregnates the aluminum-containing nanofiber which is not subjected to high-temperature sintering treatment with the active component solution, and because the metal elements in the system are all in an ionic state, the catalyst has stronger diffusion mobility, so that the active component elements are more easily and uniformly dispersed, and the catalytic activity of the nanofiber catalyst is improved.
Preferably, the preparation process of the spinning solution comprises: a. dissolving the high molecular polymer in the solvent to obtain a high molecular polymer solution; b. and dissolving the aluminum source in the high molecular polymer solution to obtain the spinning solution.
In a second aspect, the invention provides a nanofiber catalyst prepared by the method provided in the first aspect.
The third aspect of the invention provides an application of the nanofiber catalyst provided by the second aspect in preparing the hexanediamine through hydrogenation.
In a fourth aspect, the present invention provides a process for preparing adipamide by hydrogenation, which comprises: in the presence of a nanofiber catalyst, enabling adiponitrile and hydrogen to contact and react to obtain hexamethylene diamine; wherein the nanofiber catalyst is subjected to in situ reduction prior to the reaction; wherein the nanofiber catalyst is the nanofiber catalyst provided in the second aspect.
Compared with the prior art, the invention has the following advantages:
(1) according to the preparation method of the nanofiber catalyst, the electrostatic spinning technology and the dipping technology are combined, so that the nanofiber catalyst has controllable diameter and higher specific surface area; specifically, the aluminum-containing nanofiber carrier is prepared by an electrostatic spinning technology, so that the diameter of the aluminum-containing nanofiber is uniform and controllable; the metal elements in the active components are uniformly loaded on the surface and inside of the alumina nano-fiber in the form of oxides by means of soaking and then roasting, so that active sites are improved;
(2) compared with the traditional coprecipitation impregnation or alkali liquor impregnation, the preparation method of the nanofiber catalyst provided by the invention has the advantages of simple process, low cost and convenience for industrial production;
(3) the nanofiber catalyst provided by the invention has higher catalytic activity, and particularly has higher adiponitrile conversion rate and hexamethylenediamine selectivity when being used for preparing hexanediamine by hydrogenation.
Drawings
FIG. 1 is an SEM image of aluminum-containing nanofibers A1 prepared in example 1;
FIG. 2 is an SEM image of the nanofiber catalyst S1 prepared in example 1;
FIG. 3 is a TEM image of the nanofiber catalyst S1 prepared in example 1;
FIG. 4 is an EDS diagram of the nanofiber catalyst S1 prepared in example 1; FIG. 4a is an EDS map of nickel in the nanofiber catalyst S1, and FIG. 4b is an EDS map of magnesium in the nanofiber catalyst S1;
FIG. 5 is an SEM photograph of catalyst DS1 prepared in comparative example 1.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
In a first aspect, the present invention provides a method for preparing a nanofiber catalyst, comprising the steps of:
(1) preparing a spinning solution containing an aluminum source, a high molecular polymer and a solvent;
(2) performing electrostatic spinning and solvent removal treatment on the spinning solution to obtain aluminum-containing nanofibers;
(3) and (3) dipping the aluminum-containing nanofiber in an active component solution, and then drying and roasting to obtain the nanofiber catalyst.
The inventor of the present invention found out that: compared with the modes of electrostatic spinning, roasting, dipping and roasting, the mode of electrostatic spinning, solvent removal treatment, dipping and roasting provided by the invention is more favorable for the contact and combination of metal elements in active components and nanofiber carriers, so that the metal elements are uniformly and firmly loaded on the nanofibers in the form of oxides, and are particularly uniformly distributed on the surfaces and the interiors of the nanofibers, thereby improving the catalytic efficiency of the nanofiber catalyst.
In some embodiments of the invention, the viscosity of the spinning dope is preferably 3 to 30Pa · s, preferably 4 to 16Pa · s. In the present invention, the viscosity of the spinning dope is measured by a Brookfield viscometer in the united states.
In some embodiments of the present invention, preferably, the content of the aluminum source in the spinning solution is 1 to 30 wt%, preferably 10 to 18 wt%; the content of the high molecular polymer is 5-30 wt%, preferably 10-15 wt%; the content of the solvent is 40 to 94 wt%, preferably 67 to 80 wt%. This arrangement is intended to obtain a homogeneous spinning dope having a suitable viscosity. Wherein, the contents of the aluminum source, the high molecular polymer and the solvent are calculated by the feeding amount of each component and the total amount of the spinning solution.
The present invention is not particularly limited in the preparation process of the spinning solution, as long as the aluminum source, the high molecular polymer and the solvent are uniformly mixed. Preferably, the preparation process of the spinning solution in the step (1) comprises the following steps: a. dissolving the high molecular polymer in the solvent to obtain a high molecular polymer solution; b. and dissolving the aluminum source in the high molecular polymer solution to obtain the spinning solution.
In the present invention, the method for dissolving the high molecular weight polymer in the solvent is not particularly limited as long as the high molecular weight polymer can be dissolved in the solvent. Preferably, the high molecular polymer is added into the solvent and stirred by an oil bath to obtain a high molecular polymer solution, wherein the stirring conditions of the oil bath include: the temperature is 20-90 ℃ and the time is 6-10 h.
In the present invention, the manner of dissolving the aluminum source in the polymer solution is not particularly limited as long as the aluminum source is dissolved in the polymer solution. Preferably, the high molecular polymer solution is cooled to room temperature, and then the aluminum source is added for stirring and dissolving.
In some embodiments of the present invention, preferably, in step (1), the weight ratio of the aluminum source, the high molecular polymer and the solvent is 1 to 30: 5-30: 40-94, preferably 10-18: 10-15: 67-80. Wherein the weight ratio is the feeding ratio or the dosage ratio of each component.
In the present invention, there is a wide selection range for the aluminum source. Preferably, the aluminium source is a soluble aluminium salt, preferably selected from soluble aluminium-containing inorganic salts and/or aluminium-containing organic salts; the inorganic salt containing aluminum is preferably at least one selected from the group consisting of aluminum chloride, aluminum sulfate and aluminum nitrate, and the organic salt containing aluminum is preferably at least one selected from the group consisting of aluminum isopropoxide, aluminum tri-sec-butoxide, aluminum n-butoxide, aluminum acetylacetonate and aluminum acetate.
In the present invention, the solubility means that the solvent is easily dissolved or dissolved in a solvent by the aid of an auxiliary agent without specific description.
In the present invention, the high molecular weight polymer has a specific number average molecular weight and a comparable solubility, i.e., has a certain solubility in a solvent, as a spinning aid.
In some embodiments of the present invention, it is preferable that the number average molecular weight of the high molecular polymer is 1 × 10 5 -4×10 5 g/mol。
In some embodiments of the present invention, preferably, the high molecular polymer is at least one selected from polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate, polyvinyl chloride, and polystyrene.
In the present invention, the solvent has a wide range of choice as long as the solvent can dissolve the high molecular polymer and the aluminum source. Preferably, the solvent is selected from at least one of N, N-dimethylformamide, dimethyl sulfoxide, dimethylacetamide, dichloromethane, and chloroform.
The electrostatic spinning conditions in step (2) are not particularly limited in the present invention, and those skilled in the art can select the electrostatic spinning conditions according to the needs of the product.
In some embodiments of the present invention, preferably, the conditions of the electrospinning include: the feeding speed is 0.1-5mL/h, the spinning voltage is 10-30kV, the receiving distance is 10-30cm, the ambient temperature is 15-30 ℃, and the ambient humidity is 20-50%.
Further preferably, the electrospinning conditions include: the feeding speed is 0.5-2mL/h, the spinning voltage is 18-25kV, the receiving distance is 12-20cm, the ambient temperature is 20-25 ℃, and the ambient humidity is 35-45%.
In some embodiments of the present invention, preferably, the conditions of the desolvation treatment include: the temperature is 80-150 ℃, preferably 80-120 ℃; the time is 1-36h, preferably 8-24 h.
According to a preferred embodiment of the invention, the desolvation treatment is carried out in a vacuum drying oven to rapidly desolvate the solvent at a relatively low temperature to avoid cohesive deformation between the fibers.
In some embodiments of the present invention, preferably, the diameter of the aluminum-containing nanofiber is 400-2000nm, preferably 531-875 nm. In the invention, the diameter of the aluminum-containing nanofiber is measured by a scanning electron micrograph statistical method.
In the present invention, the aluminum-containing nanofibers in step (2) are nanofibers comprising an aluminum source and a high molecular polymer. Preferably, the aluminum source is present in an amount of 40 to 70 wt%, preferably 50 to 60 wt%, based on the total weight of the aluminum-containing nanofibers; the content of the high molecular polymer is 30 to 60 wt%, preferably 40 to 50 wt%.
In the present invention, the active ingredient solution means a solution containing an active ingredient. Preferably, the active ingredient content of the active ingredient solution is 5 to 40 wt%, preferably 8 to 15 wt%, based on the total weight of the active ingredient solution.
In the present invention, there is no particular limitation on the solvent of the active ingredient solution as long as the active ingredient is soluble in the solvent and the content of the active ingredient in the active ingredient solution satisfies the above-mentioned limitation.
According to the invention, preferably, the active component is a compound I containing at least one element from group IIA and a compound II containing at least one element from group VIII.
In some embodiments of the present invention, preferably, the group IIA element in the compound I is selected from at least one of beryllium, magnesium, calcium, strontium, and barium, preferably magnesium and/or calcium, more preferably magnesium.
In some embodiments of the present invention, preferably, the group VIII element in the compound II is at least one selected from iron, nickel, cobalt, ruthenium, rhodium and palladium, preferably at least one selected from iron, nickel and cobalt, and more preferably nickel.
In some embodiments of the present invention, preferably, the compound I is calculated by group IIA element, the compound II is calculated by group VIII element, and the molar ratio of the compound I to the compound II is 1: 0.5 to 5, preferably 1: 0.5-2. Wherein the mol of the compound I is calculated by the mol of the group IIA element in the compound I, and the mol of the compound II is calculated by the mol of the group VIII element in the compound II.
In some embodiments of the present invention, preferably, the compound I and the compound II are each independently at least one of nitrate, chlorate, sulfate and acetate, preferably nitrate and/or acetate, more preferably nitrate. For example, magnesium nitrate, nickel nitrate, magnesium chloride, nickel chloride, magnesium sulfate, nickel sulfate, magnesium acetate, nickel acetate, but the present invention is not limited thereto.
In the present invention, the manner of the impregnation in the step (3) is not particularly limited as long as the aluminum-containing nanofibers are impregnated in the active component solution.
In some embodiments of the present invention, preferably, the impregnation conditions include: the temperature is 15-30 ℃, preferably 20-27 ℃; the time is 2-12h, preferably 4-8 h.
In the present invention, the drying is intended to remove the solvent from the impregnation product. Preferably, the drying conditions include: the temperature is 80-150 ℃, preferably 80-120 ℃; the time is 1-30h, preferably 12-24 h. Wherein the drying refers to drying for 1-30h at a constant temperature of 80-150 ℃.
In the present invention, the calcination is to calcine the aluminum source and the active component in the impregnated product to obtain the alumina nanofibers and the metal oxide supported on the alumina nanofibers. Preferably, the conditions of the calcination include: the temperature is 300-1000 ℃, preferably 400-900 ℃, and more preferably 400-600 ℃; the time is 1-10h, preferably 2-6 h. Wherein, the roasting is carried out at the constant temperature of 300-1000 ℃ for 1-10 h.
In some embodiments of the present invention, preferably, the roasting conditions further include: the heating rate is 1-15 deg.C/min, preferably 1-10 deg.C/min. This arrangement is intended to obtain a neat and uniform nanofiber structure.
In a second aspect, the invention provides a nanofiber catalyst prepared by the method provided in the first aspect.
The nano-fiber catalyst prepared by the method provided by the invention has a nano-scale diameter, a higher specific surface area and higher catalytic activity.
In some embodiments of the present invention, preferably, the diameter of the nanofiber catalyst is 100-900nm, preferably 280-450 nm; the specific surface area is 70-200m 2 /g, preferably 100- 2 (ii) in terms of/g. In the invention, the diameter of the nanofiber catalyst is measured by adopting a scanning electron microscope photo statistical method, and the specific surface area is measured by adopting an American Mac ASAP 2020 specific surface area analyzer.
In some embodiments of the present invention, preferably, the nanofiber catalyst comprises: the metal oxide is an oxide I containing at least one element in group IIA and an oxide II containing at least one element in group VIII. In the present invention, the supporting means that the metal oxide is supported on the surface and inside of the alumina nanofiber.
In the present invention, without special indication, the group IIA element in the oxide I is at least one selected from beryllium, magnesium, calcium, strontium, and barium, preferably magnesium and/or calcium, and more preferably magnesium; the group VIII element in the oxide II is at least one selected from iron, nickel, cobalt, ruthenium, rhodium and palladium, preferably at least one selected from iron, nickel and cobalt, and more preferably nickel.
In some embodiments of the present invention, the oxide I is selected from at least one of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, preferably magnesium oxide and/or calcium oxide, more preferably magnesium oxide; the oxide II is at least one selected from the group consisting of iron oxide, nickel oxide, cobalt oxide, ruthenium oxide, rhodium oxide, and palladium oxide, preferably at least one selected from the group consisting of iron oxide, nickel oxide, and cobalt oxide, and more preferably nickel oxide.
According to a preferred embodiment of the present invention, the metal oxide is magnesium oxide and nickel oxide.
In some embodiments of the present invention, preferably, the alumina nanofibers are present in an amount of 60 to 90 wt%, preferably 80 to 85 wt%, based on the total weight of the catalyst; the content of the metal oxide is 10 to 40 wt%, preferably 15 to 20 wt%.
The third aspect of the invention provides an application of the nanofiber catalyst provided by the second aspect in the preparation of hexanediamine through hydrogenation.
In a fourth aspect, the present invention provides a process for preparing adipamide by hydrogenation, which comprises: in the presence of the nanofiber catalyst provided by the second aspect, adiponitrile and hydrogen are contacted and reacted to obtain hexamethylenediamine; wherein the nanofiber catalyst is subjected to in situ reduction prior to the reaction.
In the present invention, said subjecting said nanofiber catalyst to in situ reduction aims at reducing the metal oxide in the nanofiber catalyst to metal.
In the present invention, there is a wide range of options for the reaction conditions, as long as the adiponitrile is reduced to hexamethylenediamine in the presence of hydrogen and a nanofiber catalyst. Preferably, the conditions of the reaction include: the temperature is 300-700 ℃, preferably 400-600 ℃; the pressure is 0.1-5MPa, preferably 0.5-2 MPa; the time is 0.1-5h, preferably 0.5-3 h.
In some embodiments of the present invention, preferably, the weight ratio of the nanofiber catalyst to adiponitrile is from 0.1 to 5, preferably from 0.5 to 1.5.
The present invention will be described in detail below by way of examples.
In the examples and comparative examples, the room temperature was 25 ℃.
The viscosity parameter of the spinning solution was measured by a Brookfield viscometer in the united states;
the diameter parameter of the aluminum-containing nanofiber is measured by a scanning electron microscope photograph statistical method;
the diameter parameter of the nanofiber catalyst is measured by a scanning electron micrograph statistical method, and the specific surface area parameter is measured by an American Mac ASAP 2020 specific surface area analyzer.
The properties of the aluminum-containing nanofiber and nanofiber catalysts of examples 1-9 and comparative examples 1-4 are shown in Table 1.
Example 1
(1) Adding 12.5g of polyvinylpyrrolidone (with the number average molecular weight of 360000g/mol) into 70g of N, N-dimethylformamide, stirring by an oil bath (at the temperature of 25 ℃ for 8 hours) to dissolve, cooling the obtained polyvinylpyrrolidone solution to room temperature, adding 15g of aluminum acetylacetonate, and stirring to fully dissolve the polyvinylpyrrolidone solution to obtain a spinning solution with the viscosity of 16Pa & s;
(2) and (2) performing electrostatic spinning on the spinning solution in an electrostatic spinning device, and putting the obtained electrostatic spinning product in a vacuum oven at 90 ℃ for 24h to perform solvent removal treatment to obtain the aluminum-containing nanofiber A1, wherein the electrostatic spinning conditions comprise: the feeding rate is 1mL/h, the spinning voltage is 23kV, the receiving distance is 15cm, the ambient temperature is room temperature, and the ambient humidity is controlled at 35%;
(3) soaking the aluminum-containing nanofiber A1 in a mixed solution containing nickel nitrate hexahydrate and magnesium nitrate, wherein the content of nickel nitrate and magnesium nitrate is 15 wt%, the molar ratio of Ni to Mg is 1.5:1, the soaking temperature is 25 ℃, and the soaking time is 4 hours; drying the impregnated product at 120 ℃ for 12h, transferring the dried product into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, and roasting for 5h to obtain the nanofiber catalyst S1, wherein the nanofiber catalyst S1 comprises: alumina nanofibers and nickel oxide and magnesium oxide supported on the alumina nanofibers.
The SEM image of the aluminum-containing nanofiber a1 is shown in fig. 1, and it can be seen from fig. 1 that the aluminum-containing nanofiber a1 has a uniform and continuous nanofiber structure and a diameter of 431 nm.
Among them, the SEM image of the nanofiber catalyst S1 is shown in FIG. 2, and it can be seen from FIG. 2 that nickel oxide and magnesium oxide are uniformly supported on the surface and inside of alumina nanofibers, and the diameter of the nanofiber catalyst S1 is 288nm, ratioSurface area of 122m 2 /g。
Among them, a TEM image of the nanofiber catalyst S1 is shown in fig. 3, and it can be seen from fig. 3 that the catalyst has a clear porous structure and a continuous nanofiber structure
As shown in fig. 4(a and b), the EDS of the nanofiber catalyst S1 shows that the active components (nickel and magnesium) in the nanofiber catalyst S1 are uniformly dispersed on the surface and inside the alumina nanofibers, as shown in fig. 4(a and b).
Example 2
(1) Adding 5g of polyacrylonitrile (the number average molecular weight is 150000g/mol) into 45g of N, N-dimethylformamide, stirring by an oil bath (the temperature is 80 ℃ and the time is 8 hours) to dissolve, cooling the obtained polyacrylonitrile solution to room temperature, adding 5g of aluminum acetylacetonate, and stirring to fully dissolve the polyacrylonitrile solution to obtain a spinning solution with the viscosity of 4 Pa.s;
(2) and (2) performing electrostatic spinning on the spinning solution in an electrostatic spinning device, and putting the obtained electrostatic spinning product in a vacuum oven at 90 ℃ for 24h to perform solvent removal treatment to obtain the aluminum-containing nanofiber A2, wherein the electrostatic spinning conditions comprise: the feeding rate is 0.4mL/h, the spinning voltage is 20kV, the receiving distance is 15cm, the ambient temperature is room temperature, and the ambient humidity is controlled at 20%;
(3) soaking the aluminum-containing nanofiber A2 in a mixed solution containing nickel nitrate hexahydrate and magnesium nitrate, wherein the content of nickel nitrate and magnesium nitrate is 8 wt%, the molar ratio of Ni to Mg is 0.5:1, the soaking temperature is 25 ℃, and the soaking time is 8 hours; drying the impregnated product at 120 ℃ for 12h, transferring the dried product into a muffle furnace, heating to 450 ℃ at the speed of 2 ℃/min, and roasting for 3h to obtain the nanofiber catalyst S2, wherein the nanofiber catalyst S2 comprises: alumina nano-fiber and nickel oxide and magnesium oxide loaded on the alumina nano-fiber.
Wherein, the SEM image of the aluminum-containing nanofiber A2 is similar to that of figure 1, the SEM image of the nanofiber catalyst S2 is similar to that of figure 2, the TEM image of the nanofiber catalyst S2 is similar to that of figure 3, and the EDS image of the nanofiber catalyst S3 is similar to that of figure 4.
Example 3
(1) Adding 8g of polyacrylonitrile (the number average molecular weight is 150000g/mol) into 60g of dimethyl sulfoxide, dissolving the polyacrylonitrile (the number average molecular weight is 150000g/mol) by stirring in an oil bath (the temperature is 80 ℃ and the time is 8 hours), cooling the obtained polyacrylonitrile solution to room temperature, adding 10g of aluminum acetylacetonate, and stirring the mixture to fully dissolve the polyacrylonitrile solution to obtain a spinning solution with the viscosity of 9Pa & s;
(2) and (2) performing electrostatic spinning on the spinning solution in an electrostatic spinning device, and placing the obtained electrostatic spinning product in a vacuum oven at 90 ℃ for 24 hours to perform solvent removal treatment to obtain the aluminum-containing nanofiber A3, wherein the electrostatic spinning conditions comprise: the feeding rate is 0.5mL/h, the spinning voltage is 20kV, the receiving distance is 15cm, the ambient temperature is room temperature, and the ambient humidity is controlled at 40%;
(3) soaking the aluminum-containing nanofiber A3 in a mixed solution containing nickel nitrate hexahydrate and magnesium nitrate, wherein the content of nickel nitrate and magnesium nitrate is 10 wt%, the molar ratio of Ni to Mg is 1:1, the soaking temperature is 25 ℃, and the soaking time is 8 hours; drying the impregnated product at 120 ℃ for 12h, transferring the dried product into a muffle furnace, heating to 500 ℃ at the speed of 2 ℃/min, and roasting for 4h to obtain the nanofiber catalyst S3, wherein the nanofiber catalyst S3 comprises: alumina nanofibers and nickel oxide and magnesium oxide supported on the alumina nanofibers.
Wherein, the SEM image of the aluminum-containing nanofiber A3 is similar to that of figure 1, the SEM image of the nanofiber catalyst S3 is similar to that of figure 2, the TEM image of the nanofiber catalyst S3 is similar to that of figure 3, and the EDS image of the nanofiber catalyst S3 is similar to that of figure 4.
Example 4
(1) Adding 18g of polyvinylpyrrolidone (with the number average molecular weight of 360000g/mol) into 80g of dimethyl sulfoxide, stirring in an oil bath (at the temperature of 25 ℃ for 8 hours) to dissolve, cooling the obtained polyvinylpyrrolidone solution to room temperature, adding 20g of aluminum acetylacetonate, and stirring to fully dissolve the polyvinylpyrrolidone solution to obtain a spinning solution with the viscosity of 18 pas;
(2) and (2) performing electrostatic spinning on the spinning solution in an electrostatic spinning device, and putting the obtained electrostatic spinning product in a vacuum oven at 90 ℃ for 24h to perform solvent removal treatment to obtain the aluminum-containing nanofiber A4, wherein the electrostatic spinning conditions comprise: the feeding speed is 1.5mL/h, the spinning voltage is 25kV, the receiving distance is 15cm, the ambient temperature is room temperature, and the ambient humidity is controlled at 40%;
(3) soaking the aluminum-containing nanofiber A4 in a mixed solution containing nickel nitrate hexahydrate and magnesium nitrate, wherein the content of nickel nitrate and magnesium nitrate is 20 wt%, the molar ratio of Ni to Mg is 2:1, the soaking temperature is 25 ℃, and the soaking time is 4 hours; drying the impregnated product at 120 ℃ for 12h, transferring the dried product into a muffle furnace, heating to 550 ℃ at the speed of 5 ℃/min, and roasting for 4h to obtain the nanofiber catalyst S4, wherein the nanofiber catalyst S4 comprises: alumina nanofibers and nickel oxide and magnesium oxide supported on the alumina nanofibers.
Wherein, the SEM picture of the aluminum-containing nanofiber A4 is similar to that of figure 1, the SEM picture of the nanofiber catalyst S4 is similar to that of figure 2, the TEM picture of the nanofiber catalyst S4 is similar to that of figure 3, and the EDS picture of the nanofiber catalyst S4 is similar to that of figure 4.
Example 5
(1) Adding 20g of polyacrylonitrile (the number average molecular weight is 150000g/mol) into 100g of dimethyl sulfoxide, stirring by an oil bath (the temperature is 80 ℃, and the time is 8 hours) to dissolve, cooling the obtained polyacrylonitrile solution to room temperature, adding 25g of aluminum acetylacetonate, and stirring to fully dissolve the polyacrylonitrile solution to obtain a spinning solution with the viscosity of 22Pa & s;
(2) and (2) performing electrostatic spinning on the spinning solution in an electrostatic spinning device, and placing the obtained electrostatic spinning product in a vacuum oven at 90 ℃ for 24 hours to perform solvent removal treatment to obtain the aluminum-containing nanofiber A5, wherein the electrostatic spinning conditions comprise: the feeding speed is 1.5mL/h, the spinning voltage is 28kV, the receiving distance is 15cm, the ambient temperature is room temperature, and the ambient humidity is controlled at 40%;
(3) soaking the aluminum-containing nanofiber A5 in a mixed solution containing nickel nitrate hexahydrate and magnesium nitrate, wherein the content of nickel nitrate and magnesium nitrate is 25 wt%, the molar ratio of Ni to Mg is 2.5:1, the soaking temperature is 25 ℃, and the soaking time is 8 hours; drying the impregnated product at 120 ℃ for 12h, transferring the dried product into a muffle furnace, heating to 600 ℃ at the speed of 8 ℃/min, and roasting for 5h to obtain the nanofiber catalyst S5, wherein the nanofiber catalyst S5 comprises: alumina nanofibers and nickel oxide and magnesium oxide supported on the alumina nanofibers.
Wherein, the SEM image of the aluminum-containing nanofiber A5 is similar to that of figure 1, the SEM image of the nanofiber catalyst S5 is similar to that of figure 2, the TEM image of the nanofiber catalyst S5 is similar to that of figure 3, and the EDS image of the nanofiber catalyst S5 is similar to that of figure 4.
Example 6
According to the method of example 1, except that 12.5g of polyvinylpyrrolidone (number average molecular weight: 360000g/mol), 15g of aluminum acetylacetonate and 70g of N, N-dimethylformamide were mixed and stirred at room temperature in the step (1) to obtain a spinning solution having a viscosity of 19 pas, the same procedure was followed, and aluminum-containing nanofibers A6 and a nanofiber catalyst S6 were obtained.
Example 7
According to the method of example 1, except that the mass of aluminum acetylacetonate was changed to 3g in the step (1), a spinning dope having a viscosity of 15Pa · S was obtained, and the same procedure was followed, the aluminum-containing nanofibers a7 and the nanofiber catalyst S7 were obtained.
Example 8
Following the procedure of example 1, except that in the step (3), the contents of nickel nitrate and magnesium nitrate were replaced by 50 wt%, and the molar ratio of Ni/Mg was replaced by 6:1, the remaining steps were the same, to obtain aluminum-containing nanofibers A8 and a nanofiber catalyst S8.
Example 9
Following the procedure of example 1, except that in step (2), the feed rate was replaced with 2.5mL/h under the electrospinning conditions, the remaining steps were the same, to obtain aluminum-containing nanofibers A9 and nanofiber catalyst S9.
Comparative example 1
15g of aluminum nitrate nonahydrate are dissolved in 100mL of water and 1mol/L of sodium hydroxide solution is added dropwise with continuous stirring until the pH is 10. The resulting colloidal suspension was aged at 65 ℃ for 24 h. And after washing and drying, placing the mixture in a muffle furnace at 500 ℃ for roasting for 5 hours to obtain the alumina carrier.
Immersing alumina carrier in the solution of hexa-alumina with concentration of 15%Hydrated nickel nitrate and magnesium nitrate, wherein the Ni/Mg ratio is 1.5. The solution was then evaporated to dryness and dried at 120 ℃ for 12 h. Transferring the product into a muffle furnace, heating to 500 ℃ at the speed of 5 ℃/min, keeping for 5h, and grinding to obtain NiMg/Al 2 O 3 Catalyst DS 1.
Wherein, NiMg/Al 2 O 3 The SEM image of catalyst DS1 is shown in fig. 5. As can be seen from FIG. 5, NiMg/Al 2 O 3 The catalyst DS1 showed severe agglomeration phenomenon, and meanwhile, the catalyst particles had poor uniformity and the specific surface area was 31m 2 /g。
Comparative example 2
According to the method of CN101185817A, alumina nano-fiber DA2 is prepared, and according to the step (3) of the example 1, a nano-fiber catalyst DS2 is prepared.
Comparative example 3
According to the method of CN102776603A, alumina nano-fiber DA3 is prepared, and according to the step (3) of the example 1, a nano-fiber catalyst DS3 is prepared.
Comparative example 4
Following the procedure of example 1, except that the desolvation treatment in step (2) was replaced by calcination at 500 ℃ for 3h in a muffle furnace to obtain alumina nanofibers DA4, the same procedure was followed to obtain nanofiber catalyst DS4, and nanofiber catalyst DS4 included: alumina nano-fiber and nickel oxide and magnesium oxide loaded on the surface of the alumina nano-fiber.
TABLE 1
Figure BDA0002997779540000161
Figure BDA0002997779540000171
Note: the metal oxide content is the sum of the contents of oxide I and oxide II.
As can be seen from the results in Table 1, the nanofiber catalyst prepared by the method provided by the invention has nanometer-scale diameter and higher specific surface area. Specifically, the method combines the electrostatic spinning technology and the dipping technology, namely, the aluminum-containing nanofiber carrier is prepared by the electrostatic spinning technology, so that the diameter of the aluminum-containing nanofiber is uniform and controllable; the metal elements in the active components are uniformly loaded on the surface and inside of the alumina nano-fiber in the form of oxide by means of soaking and then roasting, so that the active sites are improved, and the diameter and the specific surface area of the nano-fiber catalyst are regulated and controlled.
Test example
The catalysts (S1-S9 and DS1-DS4) prepared in examples 1-9 and comparative examples 1-4 were subjected to a test for the hydrogenation of hexanediamine.
Adding 1g of the prepared catalyst into a high-pressure reaction kettle, introducing hydrogen/nitrogen mixed gas, reducing the catalyst for 4 hours at 500 ℃, adding 1.5g of adiponitrile/absolute ethyl alcohol mixed solution with the mass ratio of 1:2, introducing hydrogen, heating to 60 ℃, boosting to 1MPa, and continuously stirring for reaction for 30 minutes to obtain hexamethylenediamine, wherein the adiponitrile conversion rate and the hexamethylenediamine selectivity are listed in Table 2.
TABLE 2
Figure BDA0002997779540000172
Figure BDA0002997779540000181
From the results in table 2, compared with the catalyst prepared by the conventional precipitation impregnation method, the nanofiber catalyst prepared by the method provided by the invention has higher specific surface area, i.e. higher catalytic activity, so that the conversion rate of adiponitrile and the selectivity of hexamethylene diamine in the reaction of preparing hexanediamine by hydrogenating adiponitrile are higher.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including various technical features being combined in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A method for preparing a nanofiber catalyst, comprising the steps of:
(1) preparing a spinning solution containing an aluminum source, a high molecular polymer and a solvent;
(2) performing electrostatic spinning and solvent removal treatment on the spinning solution to obtain aluminum-containing nanofibers;
(3) and (3) dipping the aluminum-containing nanofiber in an active component solution, and then drying and roasting to obtain the nanofiber catalyst.
2. The process according to claim 1, wherein the viscosity of the spinning dope is 3-30 Pa-s, preferably 4-16 Pa-s;
preferably, the content of the aluminum source in the spinning solution is 1 to 30 wt%, preferably 10 to 18 wt%; the content of the high molecular polymer is 5-30 wt%, preferably 10-15 wt%; the content of the solvent is 40-94 wt%, preferably 67-80 wt%;
preferably, the preparation process of the spinning solution comprises: a. dissolving the high molecular polymer in the solvent to obtain a high molecular polymer solution; b. dissolving the aluminum source in the high molecular polymer solution to obtain the spinning solution;
preferably, the weight ratio of the aluminum source to the high molecular polymer to the solvent is 1-30: 5-30: 40-94, preferably 10-18: 10-15: 67-80.
3. Process according to claim 1 or 2, wherein the aluminium source is a soluble aluminium salt, preferably selected from soluble aluminium-containing inorganic salts and/or aluminium-containing organic salts; the aluminum-containing inorganic salt is preferably at least one selected from the group consisting of aluminum chloride, aluminum sulfate and aluminum nitrate, and the aluminum-containing organic salt is preferably at least one selected from the group consisting of aluminum isopropoxide, aluminum tri-sec-butoxide, aluminum n-butoxide, aluminum acetylacetonate and aluminum acetate;
preferably, theThe number average molecular weight of the high molecular polymer is 1 x 10 5 -4×10 5 g/mol；
Preferably, the high molecular polymer is at least one selected from polyacrylonitrile, polyvinylpyrrolidone, polyvinyl alcohol, polymethyl methacrylate, polyvinyl chloride and polystyrene;
preferably, the solvent is selected from at least one of N, N-dimethylformamide, dimethyl sulfoxide, dimethylacetamide, dichloromethane, and chloroform.
4. The method of any of claims 1-3, wherein the electrospinning conditions comprise: the feeding speed is 0.1-5mL/h, the spinning voltage is 10-30kV, the receiving distance is 10-30cm, the environmental temperature is 15-30 ℃, and the environmental humidity is 20-50%;
preferably, the conditions of the desolvation treatment include: the temperature is 80-150 ℃, preferably 80-120 ℃; the time is 1-36h, preferably 8-24 h.
5. The method as claimed in any one of claims 1 to 4, wherein the diameter of the aluminium-containing nanofibers is 400-2000nm, preferably 531-875 nm;
preferably, the aluminum source is present in an amount of 40 to 70 wt%, preferably 50 to 60 wt%, based on the total weight of the aluminum-containing nanofibers; the content of the high molecular polymer is 30 to 60 wt%, preferably 40 to 50 wt%.
6. The method according to any one of claims 1 to 5, wherein the active ingredient content of the active ingredient solution is 5 to 40 wt. -%, preferably 8 to 15 wt. -%, based on the total weight of the active ingredient solution;
preferably, the active components are a compound I containing at least one element of group IIA and a compound II containing at least one element of group VIII;
preferably, the compound I is calculated by group IIA element, the compound II is calculated by group VIII element, and the molar ratio of the compound I to the compound II is 1: 0.5 to 5;
preferably, the compound I and the compound II are each independently at least one of nitrate, chlorate, sulfate and acetate, preferably nitrate and/or acetate, more preferably nitrate;
preferably, the impregnation conditions include: the temperature is 15-30 ℃, preferably 20-27 ℃; the time is 2-12h, preferably 4-8 h.
7. A nanofiber catalyst made by the process of any one of claims 1-6;
preferably, the diameter of the nanofiber catalyst is 100-900nm, preferably 280-450 nm; the specific surface area is 70-200m 2 /g, preferably 100- 2 /g。
8. The nanofiber catalyst of claim 7, wherein the nanofiber catalyst comprises: the composite material comprises alumina nano-fibers and metal oxides loaded on the alumina nano-fibers, wherein the metal oxides are an oxide I containing at least one element in group IIA elements and an oxide II containing at least one element in group VIII elements;
preferably, the content of the alumina nanofibers is 60 to 90 wt%, preferably 80 to 85 wt%, based on the total weight of the catalyst; the content of the metal oxide is 10 to 40 wt%, preferably 15 to 20 wt%.
9. Use of the nanofiber catalyst as claimed in claim 7 or 8 in the preparation of hexanediamine by hydrogenation.
10. A process for the hydrogenation of hexanediamine, comprising: contacting adiponitrile and hydrogen and reacting in the presence of the nanofiber catalyst of claim 7 or 8 to obtain hexamethylenediamine;
wherein the nanofiber catalyst is subjected to in situ reduction prior to the reaction.
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