CN110947381A - Carbon black limited nano gold catalyst and preparation method thereof - Google Patents

Carbon black limited nano gold catalyst and preparation method thereof Download PDF

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CN110947381A
CN110947381A CN201811132319.4A CN201811132319A CN110947381A CN 110947381 A CN110947381 A CN 110947381A CN 201811132319 A CN201811132319 A CN 201811132319A CN 110947381 A CN110947381 A CN 110947381A
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carbon black
catalyst
nanogold
limited
nano gold
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CN110947381B (en
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秦蕾
曾光明
赖萃
何江凡
黄丹莲
许飘
易欢
李必胜
刘洋
段阿冰
杜雪雨
曹伟成
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Hunan University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/52—Gold
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures

Abstract

The invention discloses a carbon black limited nano gold catalyst and a preparation method thereof. The preparation method comprises the following steps: mixing carbon black with ethylene glycol, stirring, performing ultrasonic treatment, heating the obtained carbon black-ethylene glycol suspension to 65-100 ℃, and adding Au-containing solution3+The solution is subjected to reduction reaction, filtered and washed to obtain the carbon black limited nano gold catalyst. The carbon black-limited nano gold catalyst has the advantages of economy, good stability, high catalytic activity, good recycling performance, easy recycling and the like, and can efficiently degrade and remove organic pollutants in the environmentThe preparation method has the advantages of wide raw material source, low cost, simple process, mild reaction conditions, no need of special equipment and the like, is suitable for large-scale preparation, and is favorable for industrial production.

Description

Carbon black limited nano gold catalyst and preparation method thereof
Technical Field
The invention belongs to the technical field of catalyst preparation, relates to a nanogold catalyst and a preparation method thereof, and particularly relates to a carbon black-limited nanogold catalyst and a preparation method thereof.
Background
The nano gold is used as an important nano material, has the advantages of wide application, easy synthesis, large specific surface area, biocompatibility, no toxicity and the like, has good catalytic activity in the aspect of reducing nitroaromatic substances, and particularly has good catalytic activity in the aspect of reducing the nitroaromatic substances in the fields of medicine, chemistry, environment and the like; on the other hand, the amines can be used as chemical raw materials to carry out industrial production, and have certain economic value. Therefore, the method for reducing the nitroaromatic substances by using the nanogold catalyst has good application prospect and has important significance for reducing environmental pollution and maintaining human health.
The nano-sized colloidal gold has better catalytic action, can quickly reduce specific nitroaromatic hydrocarbon, and has further enhanced catalytic activity along with the reduction of the particle size, but the smaller the particle size is, the larger the surface energy of the colloidal gold is caused by the size effect, and the colloidal gold is easy to be affected by the outside to generate plasma resonance so as to be easy to precipitate. The precipitated colloidal gold has larger particle size, fewer active sites and reduced catalytic activity, and meanwhile, the colloidal gold nanoparticles exist in the solution and cannot be well recycled, so that resource waste is caused, and the development of green economy is not met. Based on the above problems of nanogold, such as easy precipitation, poor catalytic activity, difficulty in recycling, and resource waste, researchers have tried to load nanogold colloids on a suitable carrier to improve stability of nanogold and promote recycling of gold catalysts. However, the existing supported nano-gold catalyst still has the problems of poor stability, poor catalytic activity, poor recycling performance and the like, and the main reason is that nano-gold in the existing supported nano-gold catalyst is usually supported on the surface of a carrier, and the carrier material cannot effectively fix nano-gold particles, so that the supported nano-gold catalyst is easily influenced by external factors, and thus the stability is insufficient, and better catalytic activity and recycling performance cannot be obtained. Therefore, the novel nano-gold catalyst with good stability, high catalytic activity and good recycling performance is obtained, and has very important significance for expanding the application field of the nano-gold catalyst.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art and provide the carbon black-limited nano gold catalyst with good stability, high catalytic activity and good recycling performance and the preparation method thereof.
In order to solve the technical problems, the invention adopts the technical scheme that:
a carbon black-limited nanogold catalyst comprises carbon black and nanogold particles, wherein the nanogold particles are fixed in the carbon black and on the surface of the carbon black.
In the carbon black-limited nano gold catalyst, the nano gold particles are fixed in the pore channels in the carbon black in an embedded manner; the nano gold particles are fixed on the surface of the carbon black in a wrapping mode.
In the carbon black-limited nano gold catalyst, the content of nano gold particles in the carbon black-limited nano gold catalyst is further improved to be 0.4-1.39 wt%.
In the carbon black-limited nano gold catalyst, the carbon black is further improved, and is nano spherical particles, and the particle size is 20-40 nm; the average grain diameter of the nano gold particles is 2 nm-10 nm.
As a general inventive concept, the present invention also provides a preparation method of the above carbon black-limited nanogold catalyst, comprising the steps of:
s1, mixing carbon black and ethylene glycol, stirring, and performing ultrasonic treatment to obtain a carbon black-ethylene glycol suspension;
s2, heating the carbon black-ethylene glycol suspension obtained in the step S1 to 65-100 ℃, and adding Au3+The solution is subjected to reduction reaction, filtered and washed to obtain the carbon black limited nano gold catalyst.
In the above preparation method, further improvement is provided, in the step S1, the ratio of the carbon black to the ethylene glycol is 200 mg: 50 mL-80 mL.
In the above preparation method, further improvement is provided, in the step S1, the rotation speed of the stirring is 400r/min to 1500 r/min; the stirring time is 10min to 30 min; the ultrasound is carried out at the temperature of 5-40 ℃; the ultrasonic time is 30-60 min.
In a further improvement of the above preparation method, in step S2, the carbon black-ethylene glycol suspension and the solution contain Au3+The volume ratio of the solution (A) is 70: 1-5.
In the above preparation method, further improvement is that in the step S2, the composition contains Au3+The solution of (a) is a chloroauric acid solution; the chlorineThe concentration of the gold acid solution is 8 g/L-12 g/L.
In the above preparation method, further improvement is provided, in the step S2, the heating is performed under stirring, and the rotation speed of the stirring is 400r/min to 1500 r/min; the reduction reaction is carried out under the condition of stirring, and the rotating speed of the stirring is 400 r/min-1500 r/min; the time of the reduction reaction is 2-6 h; the washing is 3 to 5 times by respectively adopting water and absolute ethyl alcohol.
Compared with the prior art, the invention has the advantages that:
(1) the invention provides a carbon black-limited nano gold catalyst, which comprises carbon black and nano gold particles, wherein the nano gold particles are fixed in the carbon black and on the surface of the carbon black. According to the invention, the carbon black contains rich pore channel structures, which is beneficial to anchoring and limiting nano gold particles, so that the nano gold particles can be stably fixed in the carbon black, and oxygen-containing groups such as carboxyl (-COOH), hydroxyl (-OH) and the like are contained on the surface of the carbon black, and the oxygen-containing groups can further anchor the nano gold particles and fix the nano gold particles on the surface of the carbon black, so that the surface of the carbon black is coated with the nano gold particles, and finally, the nano gold particles are limited in the interior and the surface of the carbon black under the action of double fixing of the nano gold, so that the carbon black-limited nano gold catalyst which takes the carbon black as a carrier and is coated with the nano gold particles inside. According to the invention, the nano gold particles are fixed in the carbon black and on the surface of the carbon black, so that on one hand, the content of the nano gold particles is favorably improved, and the catalytic performance of the material is enhanced, on the other hand, the nano gold particles are limited in the carbon black, so that the nano gold particles are not easy to fall off and sink, the stability is obviously improved, the material can be repeatedly utilized for many times, and the material shows better catalytic activity. Meanwhile, as the carbon black is of a mixed layer and a porous structure, the carbon black has better electron transfer capacity and adsorption capacity, and when the nano-gold is triggered and active hydrogen is obtained, the carbon black can further promote electron transfer, so that more active hydrogen and target substances are adsorbed, and the reaction of the hydrogen and the target substances is promoted, thereby accelerating the reaction; due to the abundant pore structure and the graphene-like property, a strong pi-pi stacking effect is generated between the carbon black and the target substance, the adsorption of the target substance is further promoted, the active hydrogen transfer distance of the nano-gold is shortened, the target substance is favorably close to a catalyst, the mass transfer can be promoted, the reaction is further promoted, and the catalytic efficiency is improved. In addition, the carbon black has the advantages of large specific surface area, wide contact with a target substance and the like, and is beneficial to realizing catalytic reduction of the target substance in practical application. Compared with a nano gold colloid catalyst, the carbon black limiting nano gold catalyst has the advantages of economy, good stability, high catalytic activity, good recycling performance, easy recycling and the like, is a novel nano gold catalyst which can be widely used, can efficiently degrade and remove organic pollutants in the environment, particularly can reduce high-toxicity nitro aromatic hydrocarbon substances into corresponding low-toxicity amines, and has good application value and application range.
(2) The carbon black limited nano gold catalyst can be used for treating nitro aromatic hydrocarbon substances, 4-nitrophenol is taken as an example, the catalytic action of nano gold in the carbon black limited nano gold catalyst is activated under the condition that a small amount of sodium borohydride exists, and the sodium borohydride generates active hydrogen (H) under the condition that water molecules exist2) Active hydrogen is absorbed on the surface of the nano-gold to form an Au-H intermediate with the nano-gold, and the nano-gold becomes a hydride transfer medium. When the target substance (4-NP) exists, the target substance can be diffused and adsorbed to the surface of the nanogold, active hydrogen on the surface of the nanogold is transferred to the target substance under the pushing action of the nanogold to form hydrogenation reaction with the target substance, the target substance is reduced by the hydrogen to gradually form nitrosophenol and hydroxylamine, and finally, p-nitroamine is formed, so that the purpose of degradation is achieved. In the process, the carbon black and the target substance (4-NP) have stronger pi-pi stacking effect, so that the adsorption of the catalyst on the 4-NP is promoted, the mass transfer process is accelerated, the contact of the 4-NP and the active sites of the nano gold particles is facilitated, and the catalytic efficiency of the nano gold particles is further promoted. The carbon black-limited nano gold catalyst has good stability when being used for treating nitro-aromatic hydrocarbon substances, can be repeatedly utilized for multiple times, has a removal rate of 89 percent after being repeatedly used for 10 times, is favorable for reducing the treatment cost, has good catalytic activity, and can treat nitro-aromatic hydrocarbon substancesThe complete removal of the pollutants is realized in a short time, for example, 4-nitrophenol can be removed from the water body within 5 min. When the black-limited nano gold catalyst is used for treating the nitroaromatic substances, the method has the advantages of simple operation, quick reaction, stable catalyst, easy recycling, economy and the like, and can be widely applied to treating the nitroaromatic substances.
(3) The invention also provides a preparation method of the carbon black-limited nano gold catalyst, which comprises the steps of taking carbon black as a carrier and ethylene glycol as a reducing agent, uniformly dispersing the carbon black in the ethylene glycol by stirring and ultrasonic treatment, and then, adding Au into the mixture3+The solution is added into hot carbon black-ethylene glycol suspension, and because the carbon black has rich pore channel structures, Au is favorably added3+Adsorbed on the surface and in the pores of carbon black, these Au3+Reducing the gold into simple substance gold under the reducing action of hot ethylene glycol, and fixing the formed nano gold particles in the carbon black and on the surface of the carbon black along with the continuous increase of the simple substance gold so as to limit the nano gold particles in the carbon black and on the surface of the carbon black; meanwhile, the oxygen-containing group contained on the surface of the carbon black is beneficial to further anchoring the nano-gold particles, so that the nano-gold particles are coated on the surface of the carbon black, and finally, the carbon black-limited nano-gold catalyst with the inside and the outside of the carbon black being coated by the nano-gold particles is formed under the action of double fixing of the nano-gold. In the preparation method, because the glycol is polyhydric alcohol and contains a plurality of hydroxyl groups (-OH), the hydroxyl groups (-OH) can rapidly react Au under the heating condition3+The capability of reducing into nano gold, for example, the reduction reaction only needs a few minutes at the temperature of 100 ℃; meanwhile, through full stirring, the formed nano gold particles are uniform and have small particle size, which is beneficial to improving the catalytic activity of the catalyst. In addition, the carbon black has wide source and low price, can further control the cost of the nano gold catalyst, and accords with economic development. Therefore, the preparation method has the advantages of wide raw material source, low cost, simple process, mild reaction conditions, no need of special equipment and the like, is suitable for large-scale preparation, and is favorable for industrial production.
Drawings
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
FIG. 1 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) SEM image of (d).
FIG. 2 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) Energy spectrum of (2).
FIG. 3 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) And Carbon Black (CB) in which a to c are CB, d to f are CB/Au(3)。
FIG. 4 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) BET diagram of Carbon Black (CB).
FIG. 5 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) Pore size distribution of Carbon Black (CB).
FIG. 6 is a graph showing the degradation effect of different carbon black-limited nanogold catalysts on 4-nitrophenol (4-NP) in example 6 of the present invention.
FIG. 7 is a graph comparing the kinetic constants for the degradation of 4-nitrophenol (4-NP) by different carbon black-limited nanogold catalysts in example 6 of the invention.
FIG. 8 shows a carbon black-confined nanogold catalyst (CB/Au) in example 6 of the invention(3)) Corresponding UV spectrograms when 4-nitrophenol (4-NP) is degraded at different reaction times.
FIG. 9 is a graph showing the effect of the carbon black-confined nanogold catalyst on the cyclic degradation of 4-nitrophenol (4-NP) in example 7 of the present invention.
FIG. 10 is an XPS chart of carbon black-confined nanogold catalyst before and after the reaction in example 7 of the present invention, wherein (a) is a full spectrum, (b) is C element, and (C) is Au element.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
In the examples of the present invention, the raw materials and instruments used were all commercially available. If not stated otherwise, the process adopted is a conventional process, the equipment adopted is conventional equipment, and the obtained data are average values of more than three repeated experiments.
Example 1
A carbon black-limited nano-gold catalyst comprises carbon black and nano-gold particles, wherein the nano-gold particles are fixed in the carbon black and on the surface of the carbon black.
In this embodiment, the gold nanoparticles are fixed in the pores inside the carbon black in an inlaid manner, and the gold nanoparticles are fixed on the surface of the carbon black in a wrapped manner.
In this example, the content of the gold nanoparticles in the carbon black-confined gold nanoparticle catalyst was 0.40 wt%.
In this example, the carbon black is nanosphere particles, and the particle size is 30 nm; the average particle diameter of the gold nanoparticles was 2.5 nm.
The preparation method of the carbon black-limited nanogold catalyst comprises the following steps:
(1) weighing 200mg of carbon black solid particles, adding the carbon black solid particles into 70mL of ethylene glycol, fully stirring for 15min at the rotating speed of 500r/min, uniformly mixing, and carrying out ultrasonic treatment for 30min at the temperature of 30 ℃ to obtain carbon black-ethylene glycol suspension.
(2) And (2) placing the carbon black-ethylene glycol suspension obtained in the step (1) in an oil bath kettle at 85 ℃, and fully stirring under the mechanical stirring of 600r/min to ensure that the temperature of the carbon black-ethylene glycol suspension is raised to 85 ℃.
(3) Adding 1mL of chloroauric acid solution (10g/L) with the mass concentration of 1% into the carbon black-ethylene glycol suspension with the temperature of 85 ℃ in the step (2), keeping the temperature, stirring for 4h under mechanical stirring at 600r/min (namely, carrying out reduction reaction for 4h), and reducing Au adsorbed in and on the surface of the carbon black by the reduction action of hot ethylene glycol3+Reducing the solid substance into nano gold particles to enable the nano gold particles to be fixed in the carbon black and on the surface of the carbon black to form a carbon black limiting nano gold catalyst, filtering a product solution after stirring is finished, repeatedly washing the obtained solid substance with deionized water and absolute ethyl alcohol for 3 times respectively, and then drying the solid substance in a vacuum drying oven for 24 hours to obtain the carbon blackLimited nanogold catalyst, noted CB/Au(1)。
Example 2
A carbon black-limited nanogold catalyst, which is substantially the same as the carbon black-limited nanogold catalyst in example 1, except that: the content of the nano gold particles in the carbon black-confined nano gold catalyst of example 2 was 0.88 wt%.
The preparation method of the carbon black-limited nanogold catalyst in the above embodiment is basically the same as the preparation method of the carbon black-limited nanogold catalyst in embodiment 1, and the difference is only that: the amount of the chloroauric acid solution used in the preparation method of example 2 was 2 mL.
The carbon black-limited nanogold catalyst prepared in example 2, noted as CB/Au(2)。
Example 3
A carbon black-limited nanogold catalyst, which is substantially the same as the carbon black-limited nanogold catalyst in example 1, except that: the content of the nano gold particles in the carbon black-restricted nano gold catalyst of example 3 was 1.20 wt%.
The preparation method of the carbon black-limited nanogold catalyst in the above embodiment is basically the same as the preparation method of the carbon black-limited nanogold catalyst in embodiment 1, and the difference is only that: the amount of chloroauric acid solution used in the preparation of example 3 was 3 mL.
The carbon black-limited nanogold catalyst prepared in example 3, noted as CB/Au(3)。
FIG. 1 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) SEM image of (d). In fig. 1, the magnification of (a) is 10000 times and the magnification of (b) is 50000 times. As can be seen from fig. 1, the carbon black had a certain aggregation, and there were relatively many aggregation pores between the carbon black and the carbon black.
FIG. 2 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) Energy spectrum of (2). In fig. 2, (a) corresponds to a block in fig. 1(a), and (b) corresponds to a block in fig. 1 (b). As can be seen from FIG. 2, the carbon black-confined nanogold catalyst mainly contains C, O and Au unitThe contents of element, C and O are higher, the content of Au is lower, and the surface of some places does not contain Au element.
FIG. 3 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) And Carbon Black (CB) in which a to c are CB, d to f are CB/Au(3). As can be seen from a to c in fig. 3, the carbon black is a nanoparticle with a quasi-spherical structure, the particle size of the nanoparticle is 30nm, and the nanoparticle contains rich pore channels, the interplanar spacing of the pore channels is 0.34nm, and the nanoparticle is of a graphene-like structure. As can be seen from d to f in fig. 3, in the carbon black-limited nanogold catalyst, nanogold particles are fixed inside and on the surface of carbon black, specifically, nanogold particles are uniformly dispersed in carbon black and fixed in pore channels of carbon black in an inlaid manner, and nanogold particles are fixed on the surface of carbon black in a wrapping manner, that is, nanogold particles are limited inside and on the surface of carbon black. Meanwhile, as can be seen from d to f in fig. 3, the average particle size of the nano gold particles is 2.5nm, the distance between the major crystal planes of the nano gold is 0.236nm, and the corresponding crystal plane is a (111) plane. Therefore, in the carbon black-limited nano gold catalyst, nano gold particles are limited in the carbon black and on the surface of the carbon black, so that the nano gold particles are arranged on the surface of the carbon black, and the nano gold is also limited in the pore channels of the carbon black-limited nano gold catalyst.
FIG. 4 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) BET diagram of Carbon Black (CB). As can be seen from FIG. 4, Carbon Black (CB) and carbon black-limited nanogold catalyst (CB/Au)(3)) All conform to IUPAC type IV adsorption and carry H3The hysteresis loop shows that both the carbon black and the gold nanoparticle contain rich mesopores and macropores, which is consistent with a TEM image, and can prove that the carbon black-limited type nanogold catalyst (CB/Au) disclosed by the invention(3)) The porous membrane contains rich pore channel structures, and is beneficial to adsorbing target substances.
FIG. 5 shows a carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 of the invention(3)) Pore size distribution of Carbon Black (CB). As can be seen from FIG. 5, the carbon black-limited nanogold catalyst (CB/Au)(3)) The pore size contributions of (a) are mainly distributed at 114.38nm (macropores) and 0.75nm (micropores), while the pore size contributions of carbon black are mainly distributed at 108.61nm (macropores) and 0.73nm (micropores). Simultaneously internally andthe specific surface area, the pore diameter and the total pore volume of the carbon black are reduced by fixing the nanogold on the surface, but the higher specific surface area is still reserved, which shows that the nanogold is successfully limited in the carbon black, and the formed carbon black limited nanogold catalyst still retains better adsorption capacity.
Example 4
A carbon black-limited nanogold catalyst, which is substantially the same as the carbon black-limited nanogold catalyst in example 1, except that: the content of the nano gold particles in the carbon black-restricted nano gold catalyst of example 4 was 1.34 wt%.
The preparation method of the carbon black-limited nanogold catalyst in the above embodiment is basically the same as the preparation method of the carbon black-limited nanogold catalyst in embodiment 1, and the difference is only that: the amount of the chloroauric acid solution used in the preparation method of example 4 was 4 mL.
The carbon black-limited nanogold catalyst prepared in example 4, noted as CB/Au(4)。
Example 5
A carbon black-limited nanogold catalyst, which is substantially the same as the carbon black-limited nanogold catalyst in example 1, except that: the content of the nano gold particles in the carbon black-restricted nano gold catalyst of example 5 was 1.39 wt%.
The preparation method of the carbon black-limited nanogold catalyst in the above embodiment is basically the same as the preparation method of the carbon black-limited nanogold catalyst in embodiment 1, and the difference is only that: the amount of the chloroauric acid solution used in the preparation method of example 5 was 5 mL.
The carbon black-limited nanogold catalyst prepared in example 5, noted as CB/Au(5)。
For the carbon black-limited nanogold catalysts (CB/Au) prepared in examples 1-5(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) And carbon black were subjected to BET test, ICP-OES test and TOF (switching frequency) calculation, and the results are shown in Table 1. Table 1 shows the carbon black-limited nanogold catalysts (CB/Au) prepared in examples 1 to 5 of the present invention(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) And carbon black performance data. As can be seen from table 1, the specific surface area of the carbon black-limited nanogold catalyst gradually decreased with the increase in the content of nanogold particles, and the pore diameter and the total pore volume decreased to some extent. Meanwhile, ICP-OES tests show that the carbon black-limited nano gold catalysts (CB/Au) prepared in the examples 1-5(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) The mass fractions of the nano-gold are respectively as follows: 0.40 wt%, 0.88 wt%, 1.20 wt%, 1.34 wt% and 1.39 wt%, and TOF of the nanogold catalyst prepared according to the invention was calculated, and the result showed that the catalyst (CB/Au) content was 1.20 wt%(3)) Has a TOF of 492.50h at maximum-1This shows that the catalyst (CB/Au) has a gold nanoparticle content of 1.20 wt%(3)) The highest catalytic rate.
Table 1 shows the carbon black-limited nanogold catalysts (CB/Au) prepared in examples 1 to 5 of the present invention(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) And performance data of carbon black
Figure BDA0001813882910000071
Figure BDA0001813882910000081
Example 6
Investigating the influence of carbon black limited nano gold catalysts with different nano gold particle contents on the degradation effect of nitroaromatic substances, in particular to a method for treating 4-nitrophenol (4-NP) in a water body by adopting carbon black limited nano gold catalysts with different nano gold particle contents, which comprises the following steps:
the carbon black-limited nanogold catalyst (CB/Au) prepared in examples 1 to 5 was used(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) 10mg each, respectively, was added to 50mL of a 0.5mM 4-nitrophenol (4-NP) solution, and stirred for 30min to achieve aspirationWith equilibration, 0.1g of NaBH was added each4And (3) fully mixing the solid, and then carrying out catalytic reduction reaction for 30min to complete the treatment of the 4-nitrophenol.
FIG. 6 is a graph showing the degradation effect of different carbon black-limited nanogold catalysts on 4-nitrophenol (4-NP) in example 6 of the present invention. FIG. 7 is a graph comparing the kinetic constants for the degradation of 4-nitrophenol (4-NP) by different carbon black-limited nanogold catalysts in example 6 of the invention. As can be seen from FIG. 6, the carbon black-limited nanogold catalyst of the invention can realize effective degradation of 4-nitrophenol (4-NP) in a shorter time, wherein the carbon black-limited nanogold catalyst (CB/Au)(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) The catalytic reduction reaction time for effectively degrading 4-nitrophenol (4-NP) is respectively 12min, 6min, 5min, 7.5min and 9min, and the shorter the catalytic reduction reaction time for completely degrading 4-nitrophenol (4-NP) along with the increase of the content of the gold nanoparticles, when the addition amount of the chloroauric acid solution is 4mL (the content of the gold nanoparticles is 1.34 wt%), the longer the catalytic reduction reaction time is required to reach 10min, but the complete degradation of 4-nitrophenol (4-NP) can still be realized in a shorter time, and the possible reason is that along with the increase of the content of the gold nanoparticles, the more active sites are provided by the gold nanoparticles, so that the catalytic efficiency is accelerated; when the addition amount of the chloroauric acid solution is 4mL (the content of the gold nanoparticles is 1.34 wt% at this time), the amount of the chloroauric acid is too large, so that the gold nanoparticles are partially precipitated, the dispersibility is insufficient, the active sites are provided less, and the catalytic efficiency is affected. In addition, as can be seen from fig. 7, the catalytic reduction reactions corresponding to the carbon black-limited nanogold catalyst of the invention all followed the first order kinetics, and the carbon black-limited nanogold catalyst (CB/Au)(1)、CB/Au(2)、CB/Au(3)、CB/Au(4)、CB/Au(5)) The corresponding kinetic constants are: k1＝0.0884min-1、K2＝0.3239min-1、K3＝0.8302min-1、K4＝0.4269min-1、K5＝0.4519min-1。
Adopts carbon black limited nano gold catalyst (CB/A)u(3)) When 4-nitrophenol (4-NP) is processed, sampling is carried out at regular intervals in the catalytic reduction reaction process, and the ultraviolet spectrum of the sample is measured to obtain the carbon black limited nano gold catalyst (CB/Au)(3)) The absorbance of 4-nitrophenol (4-NP) at different reaction times is shown in FIG. 8. FIG. 8 shows a carbon black-confined nanogold catalyst (CB/Au) in example 6 of the invention(3)) Corresponding UV spectrograms when 4-nitrophenol (4-NP) is degraded at different reaction times. As can be seen from FIG. 8, the characteristic absorption peak of 4-NP was at 400nm when NaBH was added4After the solid, the characteristic peak at 400nm decreased rapidly with the increase of the catalytic reduction reaction time, while a new characteristic peak was formed at 295nm, and the characteristic peak at 295nm became stronger with time, indicating that 4-NP was gradually reduced to p-aminophenol (4-AP) with the increase of the catalytic reduction time, and the concentration of 4-AP was higher. Further, as is clear from FIG. 8, the use of a carbon black-limited nanogold catalyst (CB/Au)(3)) When 4-nitrophenol (4-NP) is treated, the catalytic reduction reaction is basically complete within 5min, and the carbon black-limited nano gold catalyst has better catalytic activity and can efficiently and quickly reduce the 4-NP in a shorter time.
Example 7
The method is used for investigating the stability of the carbon black limited nano-gold catalyst in processing the nitroaromatic substances, and particularly for processing 4-nitrophenol (4-NP) in a water body by adopting the carbon black limited nano-gold catalyst, and comprises the following steps:
(1) 10mg of the carbon black-limited nanogold catalyst (CB/Au) prepared in example 3 was taken(3)) Adding into 50mL of 0.5mM 4-nitrophenol (4-NP) solution, stirring for 30min to reach adsorption equilibrium, adding 0.1g NaBH4And (5) fully mixing the solid, and then carrying out catalytic reduction reaction for 5 min.
(2) And (2) after the reaction in the step (1) is finished, filtering the solution after the reaction, washing the obtained solid matter (the carbon black limiting type nano gold catalyst) with ultrapure water and sewage ethanol, drying, and repeatedly treating the dried solid matter (the carbon black limiting type nano gold catalyst) with the 4-nitrophenol (4-NP) solution according to the method in the step (1) for 10 times.
FIG. 9 is a graph showing the effect of the carbon black-confined nanogold catalyst on the cyclic degradation of 4-nitrophenol (4-NP) in example 7 of the present invention. As can be seen from FIG. 9, the use of a carbon black-limited nanogold catalyst (CB/Au)(3)) After the 4-nitrophenol (4-NP) solution is circularly treated for 10 times, the removal rate of the 4-nitrophenol (4-NP) is still up to 89%, which shows that the carbon black limited nano gold catalyst has stronger stability and catalytic activity.
FIG. 10 is an XPS chart of carbon black-confined nanogold catalyst before and after the reaction in example 7 of the present invention, wherein (a) is a full spectrum, (b) is C element, and (C) is Au element. In FIG. 10, the carbon black-limited nanogold catalyst (CB/Au) after the reaction(3)) Is carbon black limited nano gold catalyst (CB/Au) collected after being repeatedly used for 10 times(3)). As shown in FIG. 10(a), pure carbon black mainly contains C, O elements, the C element is much higher than the O element, and the carbon black-limited nanogold catalyst (CB/Au) of the invention(3)) Contains C, O elements mainly and has less content of Au elements, which is consistent with SEM results. As can be seen from FIG. 10(b), the spectrum has peaks at 284.78eV, 285.5eV, and 290.0eV, mainly due to sp of C2、sp3The hybridization peaks, as well as the pi-pi transition loss, have peaks at 287.7eV for carbon black and 287.2eV for CB/Au, representing the C ═ O bonds. As shown in FIG. 10(c), Au 4f7/2And 4f5/2There are peaks at 84.7eV, 88.4eV, 84.5eV, and 88.2eV, indicating the formation of nanogold. In addition, as can be seen from FIG. 10, before and after catalytic reduction of 4-nitrophenol (4-NP), the carbon black-confined nanogold catalyst (CB/Au) of the present invention(3)) The content of C is basically unchanged, and sp of C is still maintained2、sp3Hybridization peaks and pi-pi transition loss peaks; after the reaction, the carbon black limited nano gold catalyst (CB/Au) of the invention(3)) The Au content in the carbon black is reduced to a certain extent, which shows that Au on the surface of the carbon black is lost, but Au limited in the carbon black is kept stable, and the carbon black limited nano gold catalyst prepared by the invention has good stability and recycling property, and is consistent with the result of FIG. 9.
The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.

Claims (10)

1. The carbon black-limited nano gold catalyst is characterized by comprising carbon black and nano gold particles, wherein the nano gold particles are fixed in the carbon black and on the surface of the carbon black.
2. The carbon black-confined nanogold catalyst according to claim 1, wherein the nanogold particles are fixed in channels inside the carbon black in a mosaic manner; the nano gold particles are fixed on the surface of the carbon black in a wrapping mode.
3. The carbon black-restricted nanogold catalyst according to claim 2, wherein the content of nanogold particles in the carbon black-restricted nanogold catalyst is 0.4 to 1.39 wt%.
4. The carbon black-restricted nanogold catalyst according to any one of claims 1 to 3, wherein the carbon black is a nanoparticle having a particle diameter of 20nm to 40 nm; the average grain diameter of the nano gold particles is 2 nm-10 nm.
5. A method for preparing the carbon black-limited nanogold catalyst as defined in any one of claims 1 to 4, comprising the steps of:
s1, mixing carbon black and ethylene glycol, stirring, and performing ultrasonic treatment to obtain a carbon black-ethylene glycol suspension;
s2, heating the carbon black-ethylene glycol suspension obtained in the step S1 to 65-100 ℃, and adding Au3+The solution is subjected to reduction reaction, filtered and washed to obtain the carbon black limited nano gold catalyst.
6. The method according to claim 5, wherein in step S1, the ratio of carbon black to ethylene glycol is 200 mg: 50 mL-80 mL.
7. The method according to claim 5, wherein in step S1, the stirring speed is 400 to 1500 r/min; the stirring time is 10min to 30 min; the ultrasound is carried out at the temperature of 5-40 ℃; the ultrasonic time is 30-60 min.
8. The method according to any one of claims 5 to 7, wherein in step S2, the carbon black-ethylene glycol suspension contains Au3+The volume ratio of the solution (A) is 70: 1-5.
9. The method according to claim 8, wherein in step S2, the Au-containing material contains Au3+The solution of (a) is a chloroauric acid solution; the concentration of the chloroauric acid solution is 8 g/L-12 g/L.
10. The production method according to any one of claims 5 to 7, wherein in step S2, the heating is performed under stirring at a rotation speed of 400 to 1500 r/min; the reduction reaction is carried out under the condition of stirring, and the rotating speed of the stirring is 400 r/min-1500 r/min; the time of the reduction reaction is 2-6 h; the washing is 3 to 5 times by respectively adopting water and absolute ethyl alcohol.
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