A modified graphene catalyst, a preparation method and application thereof

Abstract

The application relates to the technical field of catalytic composite materials, and particularly discloses a modified graphene catalyst as well as a preparation method and application thereof. The preparation method provided by the application first modifies graphene with a specific modifier, then respectively processes the first modified graphene with a fluorinating agent, stannous sulfide and a soluble zinc salt to obtain the modified graphene catalyst; wherein the mixture of nonylphenol polyoxyethylene ether and polyacrylate is selected as the specific modifier for modifying the graphene, the dispersibility and adsorbability of the graphene are improved, then the fluorine ion, the stannous sulfide and the zinc ion are sequentially introduced, the interaction among the zinc ion, the fluorine ion and the stannous sulfide promotes the transfer of photoelectrons, the surface chemical reaction activity of the modified graphene catalyst and the selectivity of formic acid are improved, the service life of the modified graphene catalyst is also improved to a certain extent, and the modified graphene catalyst has great market value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic composite materials, and specifically discloses a modified graphene catalyst as well as a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of economy, a large amount of fossil fuels is consumed, resulting in the release of a large amount of carbon dioxide, causing the greenhouse effect, thereby breaking the world ecological balance, and the increase of carbon dioxide concentration seriously affects the human habitat and the earth's ecological system. Therefore, exploring how to reduce the content of carbon dioxide in the atmosphere and reasonably utilize has become one of the most important research topics in the world today.

[0003] Photocatalysis technology provides an excellent solution for the conversion of carbon dioxide into important chemical fuels such as methane, methanol and formic acid, therefore, it is crucial to utilize photocatalysis to reduce carbon dioxide in the atmosphere and collect and store solar energy in chemical fuels. However, carbon dioxide is an inert gas and is difficult to react with other substances, and a catalyst is needed to complete the photocatalytic reaction.

[0004] In recent years, catalysts for photocatalytic reduction of carbon dioxide have been widely studied, and graphene as a new catalyst has a wide range of applications and low cost. However, there are some problems in the use of graphene catalysts, such as: the service life of graphene catalysts is short, and the activity is reduced during the reaction due to the influence of oxygen and water in the air, and the long-term catalytic stability is poor, thereby reducing the service life; the purity and yield of formic acid in the process of graphene catalysts applied in photocatalytic conversion of carbon dioxide to formic acid still have a lot of room for improvement. Therefore, it is of great significance to develop a catalyst with high catalytic activity, simple preparation, and obvious improvement in product yield and purity. SUMMARY

[0005] In view of this, the present application provides a modified graphene catalyst as well as a preparation method and application thereof, a mixture of nonylphenol polyoxyethylene ether and polyacrylate is selected as a specific modifier to modify graphene, the dispersibility and adsorbability of graphene are improved, then fluorine ions, stannous sulfide and zinc ions are introduced in sequence, the transfer of photoelectrons is promoted through the interaction between zinc ions, fluorine ions and stannous sulfide, the activity of surface chemical reaction of the modified graphene catalyst and the selectivity of formic acid are improved, to a certain extent, the service life of the modified graphene catalyst is also improved, and the modified graphene catalyst has great market value.

[0006] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The first aspect of the present application provides a preparation method of a modified graphene catalyst, comprising the following steps:

[0008] S1, mix graphene and modifier uniformly, stir at 80-100 DEG C, filter, wash with water, obtain primary modified graphene;

[0009] S2, mix the primary modified graphene, fluorination agent and water uniformly, react at 210-230 DEG C, filter, wash with water, obtain secondary modified graphene;

[0010] S3, mix the secondary modified graphene and soluble zinc salt into stannous sulfide dispersion liquid, mix uniformly, react at 210-230 DEG C, filter, dry, obtain tertiary modified graphene;

[0011] S4, calcine the tertiary modified graphene at 380-400 DEG C for 2-3h, obtain the modified graphene catalyst;

[0012] In S1, the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate.

[0013] Compared with the prior art, the application provides a preparation method of modified graphene, first, the graphene is modified by a specific modifier, which improves the catalytic property, wear resistance and service life of the catalyst to a certain extent, the inventor finds through a large number of researches that the nonylphenol polyoxyethylene ether and polyacrylate are selected as the modifier for modifying the graphene, which can avoid the agglomeration of the graphene and improve the dispersion performance of the graphene, thereby improving the specific surface area of the graphene, and the specific modifier also improves the adsorption performance of the graphene, which is beneficial to the polymerization of fluorine ions, stannous sulfide and zinc ions in the later stage; further, the first modified graphene is further modified by a fluorination agent, due to the special structure of the first modified graphene, the polymerization of fluorine ions is improved, the introduction of fluorine ions further improves the specific surface area of the modified graphene catalyst and the thermal stability of the modified graphene catalyst, thereby improving the service life of the catalyst; the activity of the second modified graphene is improved by doping fluorine ions, thereby facilitating the maximum introduction of stannous sulfide and zinc ions, the adsorption performance of the modified graphene catalyst for carbon dioxide is stronger after the modification of fluorine ions, which improves the catalytic performance of the modified graphene catalyst to a certain extent; the introduction of stannous sulfide can improve the selectivity to formic acid, so that the prepared formic acid has the characteristics of high purity, but stannous sulfide is not stable and is easy to be oxidized in use, the inventor solves the instability of stannous sulfide by introducing zinc ions, a large number of screening and tests show that the zinc ions can improve the covalence of divalent tin and sulfur, thereby effectively inhibiting the oxidation of stannous sulfide, thereby greatly improving the purity and yield of formic acid and improving the catalytic effect of the modified graphene catalyst.

[0014] The inventors also found in the research process that the catalyst doped with fluorine ions and stannous sulfide has higher formic acid purity than the catalyst doped with only stannous sulfide, which proves that the doping of fluorine ions can further improve the selectivity of stannous sulfide to formic acid; the polymeric zinc ions and stannous sulfide in the graphene modified by the specific modifier are highly dispersed on the surface of the modified graphene catalyst; and through the interaction among the zinc ions, fluorine ions and stannous sulfide, the transfer of photoelectrons is promoted, the activity of the chemical reaction on the surface of the modified graphene catalyst is improved, the selectivity of formic acid is improved, and the purpose of efficiently catalyzing the conversion of carbon dioxide into formic acid is achieved.

[0015] The application first selects a mixture of nonylphenol polyoxyethylene ether and polyacrylate as a specific modifier to modify graphene, improves the dispersibility and adsorbability of graphene, and then introduces fluorine ions, stannous sulfide and zinc ions in sequence, promotes the transfer of photoelectrons through the interaction among the zinc ions, fluorine ions and stannous sulfide, improves the activity of the chemical reaction on the surface of the modified graphene catalyst and the selectivity of formic acid, and to some extent, also improves the service life of the modified graphene catalyst, which has great market value.

[0016] Preferably, in S1, the mass ratio of nonylphenol polyoxyethylene ether to polyacrylate in the modifier is 1:(1.3-1.5).

[0017] Further preferably, the polyacrylate is P43041 from Shanghai Jizhisheng Biotechnology Co., Ltd.

[0018] Preferably, in S1, the mass ratio of graphene to the modifier is 1:(3-5).

[0019] The preferred ratio is conducive to further improving the catalytic performance of the modified graphene catalyst.

[0020] Preferably, in S1, the stirring rate is 700rpm-1000rpm.

[0021] Preferably, in S1, the stirring time is 4h-5h.

[0022] Preferably, in S2, the fluorination agent is at least one of potassium fluoride or lithium fluoride.

[0023] Preferably, in S2, the mass ratio of the first modified graphene to water is 1:(10-12).

[0024] Preferably, in S2, the mass ratio of the first modified graphene to the fluorination agent is 1:(6-7.5).

[0025] Preferably, in S2, the reaction time is 18h-22h.

[0026] Preferably, in S3, the concentration of the stannous fluoride dispersion solution is 0.1 mol / L-0.2 mol / L.

[0027] Preferably, in S3, the soluble zinc salt is zinc chloride.

[0028] Preferably, in S3, the mass ratio of the secondary modified graphene and the soluble zinc salt is 1:(0.4-0.6).

[0029] Preferably, in S3, the mass-volume ratio of the secondary modified graphene and the stannous fluoride dispersion solution is 1g:(0.8-1)L.

[0030] Preferably, in S3, the reaction time is 12h-15h.

[0031] Preferably, in S4, the temperature is raised to 380℃-400℃ by programmed temperature raising, and the programmed temperature raising rate is 12℃ / min-15℃ / min.

[0032] The second aspect of the present application provides a modified graphene catalyst prepared by the above method for preparing a modified graphene catalyst.

[0033] The third aspect of the present application provides the use of the above modified graphene catalyst in photocatalytic conversion of carbon dioxide into formic acid.

[0034] The nonylphenol polyoxyethylene ether and the polyacrylate in the modified graphene catalyst provided by the present application improve the dispersibility and adsorbability of the graphene, the interaction between the zinc ions, the fluorine ions and the stannous fluoride in the modified graphene catalyst promotes the transfer of photoelectrons, improves the activity of the surface chemical reaction of the modified graphene catalyst and the selectivity of formic acid, and to some extent, also improves the service life of the modified graphene catalyst, which has great market value. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] Embodiment 1

[0037] The present embodiment provides a modified graphene catalyst, which specifically comprises the following steps:

[0038] S1, mix graphene (1 g) and modifier (3 g) uniformly, stir at 700 rpm for 4 h at 100°C, filter, water wash, primary modified graphene; wherein the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate with a mass ratio of 1:1.3;

[0039] S2, mix the primary modified graphene (1 g), potassium fluoride (6 g) and water (10 g) uniformly, react at 210°C for 18 h, filter, water wash, obtain secondary modified graphene;

[0040] S3, disperse stannous sulfide in water to obtain a stannous sulfide dispersion liquid with a concentration of 0.1 mol / L;

[0041] S4, add secondary modified graphene (1 g) and zinc chloride (0.4 g) to the stannous sulfide dispersion liquid (0.8 L), react at 230°C for 15 h, filter, dry, obtain tertiary modified graphene;

[0042] S5, under an inert atmosphere, heat the tertiary modified graphene to 380°C at a heating rate of 12°C / min, calcine for 2 h, obtain the modified graphene catalyst.

[0043] Example 2

[0044] The embodiment provides a modified graphene catalyst, specifically comprising the following steps:

[0045] S1, mix graphene (1 g) and modifier (5 g) uniformly, stir at 1000 rpm for 5 h at 80°C, filter, water wash, primary modified graphene; wherein the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate with a mass ratio of 1:1.5;

[0046] S2, mix the primary modified graphene (1 g), potassium fluoride (7.5 g) and water (12 g) uniformly, react at 230°C for 22 h, filter, water wash, obtain secondary modified graphene;

[0047] S3, disperse stannous sulfide in water to obtain a stannous sulfide dispersion liquid with a concentration of 0.2 mol / L;

[0048] S4, add secondary modified graphene (1 g) and zinc chloride (0.6 g) to the stannous sulfide dispersion liquid (1 L), react at 210°C for 12 h, filter, dry, obtain tertiary modified graphene;

[0049] S5, under an inert atmosphere, heat the tertiary modified graphene to 400°C at a heating rate of 15°C / min, calcine for 3 h, obtain the modified graphene catalyst.

[0050] Example 3

[0051] The embodiment provides a modified graphene catalyst, and specifically comprises the following steps:

[0052] S1, uniformly mixing graphene (1 g) and a modifier (4.2 g), stirring at 90 DEG C and a speed of 800 rpm for 4.5 h, filtering, and washing with water to obtain first modified graphene; wherein the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate at a mass ratio of 1:1.4;

[0053] S2, uniformly mixing the first modified graphene (1 g), potassium fluoride (7 g) and water (11 g), reacting at 220 DEG C for 20 h, filtering, and washing with water to obtain second modified graphene;

[0054] S3, dispersing stannous sulfide in water to obtain a stannous sulfide dispersion liquid with a concentration of 0.15 mol / L;

[0055] S4, adding the second modified graphene (1 g) and zinc chloride (0.5 g) into the stannous sulfide dispersion liquid (0.9 L), reacting at 220 DEG C for 14 h, filtering, and drying to obtain third modified graphene;

[0056] S5, under an inert atmosphere, heating the third modified graphene to 390 DEG C at a heating rate of 13 DEG C / min, and calcining for 3 h to obtain the modified graphene catalyst.

[0057] Comparative Example 1

[0058] The comparative example provides a modified graphene catalyst, and the difference from the embodiment 1 is that the polyacrylate is replaced by an equal amount of polyurethane;

[0059] The other components and steps remain unchanged.

[0060] Comparative Example 2

[0061] The comparative example provides a modified graphene catalyst, and the difference from the embodiment 1 is that the nonylphenol polyoxyethylene ether is replaced by an equal amount of fatty acid polyoxyethylene ester;

[0062] The other components and steps remain unchanged.

[0063] Comparative Example 3

[0064] The comparative example provides a modified graphene catalyst, and the difference from the embodiment 1 is that:

[0065] S2 is omitted, and the potassium fluoride is not added;

[0066] The specific steps are as follows:

[0067] S1, mix graphene (1 g) and modifier (3 g) uniformly, stir at 700 rpm for 4 h at 100°C, filter, water wash, primary modified graphene; wherein the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate at a mass ratio of 1:1.3;

[0068] S2, disperse stannous sulfide in water to obtain a stannous sulfide precursor solution of 0.1 mol / L;

[0069] S3, add primary modified graphene (1 g) and zinc chloride (0.4 g) to the stannous sulfide precursor solution (0.8 L), react at 230°C for 15 h, filter, dry, and obtain secondary modified graphene;

[0070] S4, under an inert atmosphere, heat the secondary modified graphene to 380°C at a heating rate of 12°C / min, and calcine for 2 h to obtain the modified graphene catalyst.

[0071] Comparative Example 4

[0072] This comparative example provides a modified graphene catalyst, which is different from Example 1 in that:

[0073] No zinc chloride is added;

[0074] The specific steps are as follows:

[0075] S1, mix graphene (1 g) and modifier (3 g) uniformly, stir at 700 rpm for 4 h at 100°C, filter, water wash, primary modified graphene; wherein the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate at a mass ratio of 1:1.3;

[0076] S2, mix the primary modified graphene (1 g), potassium fluoride (6 g), and water (10 g) uniformly, react at 210°C for 18 h, filter, and water wash to obtain secondary modified graphene;

[0077] S3, disperse stannous sulfide in water to obtain a stannous sulfide precursor solution of 0.1 mol / L;

[0078] S4, add secondary modified graphene (1 g) to the stannous sulfide precursor solution (0.8 L), react at 230°C for 15 h, filter, dry, and obtain tertiary modified graphene;

[0079] S5, under an inert atmosphere, heat the tertiary modified graphene to 380°C at a heating rate of 12°C / min, and calcine for 2 h to obtain the modified graphene catalyst.

[0080] Comparative Example 5

[0081] The comparative example 1 provides a modified graphene catalyst, which is different from the example 1 in that:

[0082] The stannous sulfide is replaced by an equal amount of copper sulfide;

[0083] The other components and steps remain unchanged.

[0084] In order to further embody the technical effect of the modified graphene catalyst provided by the present application, the catalytic effect of the modified graphene catalysts obtained in examples 1-3 and comparative examples 1-5 is tested, and the specific testing method is as follows:

[0085] 10 mg of the modified graphene catalyst is placed in a high-pressure reaction kettle, 100 mL of water is used as the solvent, 20 mL of 1,8-diazabicycloundec-7-ene is used as the base, the reactor is purged with argon before the reaction starts, the carbon dioxide in the reactor is exhausted, the hydrogen gas is introduced for 40 min, the gas flow is 100 mL / min, after the hydrogen gas is introduced, the carbon dioxide gas is introduced, the gas flow of the carbon dioxide is 100 mL / min, the time is 40 min, the reaction temperature is 25℃, the reaction pressure is 0.3 MPa, the xenon lamp light irradiation time is 12 h, the concentration of formic acid in the product is detected by high performance liquid chromatography, the yield of formic acid and the catalytic TOF value (the calculation formula is: TOF = formic acid concentration / (catalyst concentration x reaction time) ) are calculated, and the evaluation performance of the catalysts prepared in examples 1-3 and comparative examples 1-5 for preparing formic acid is shown in Table 1:

[0086] Table 1

[0087] Item Formic acid selectivity (%) Carbon dioxide conversion (%) TOF(h -1 )]]> Example 1 99.2 92.3 14.2 Example 2 98.4 91.8 13.8 Example 3 99.1 91.9 13.1 Comparative Example 1 90.6 83.6 7.2 Comparative Example 2 86.1 80.5 6.9 Comparative Example 3 79.3 75.4 5.2 Comparative Example 4 74.6 81.5 4.9 Comparative Example 5 76.4 79.4 4.8

[0088] As can be seen from Table 1, the catalysts provided in examples 1-3 can catalyze the conversion of carbon dioxide into formic acid, and have high catalytic activity, the TOF value can reach 14.2 h -1 , the conversion rate of carbon dioxide is high, the selectivity of formic acid is strong, which also proves that the catalyst provided by the present application has excellent catalytic performance.

[0089] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. The application of a modified graphene catalyst in the photocatalytic production of formic acid from carbon dioxide, characterized in that: The modified graphene catalyst includes the following steps: S1. Mix graphene and modifier evenly, stir at 80℃-100℃, filter, and wash with water to obtain primary modified graphene. S2. Mix the primary modified graphene, fluorinating agent and water evenly, react at 210℃-230℃, filter, wash with water to obtain secondary modified graphene. S3. Add the secondary modified graphene and soluble zinc salt to the stannous sulfide dispersion, mix evenly, react at 210℃-230℃, filter, and dry to obtain tertiary modified graphene. S4. The tertiary modified graphene is calcined at 380℃-400℃ for 2h-3h to obtain the modified graphene catalyst. In S1, the modifier is a mixture of nonylphenol polyoxyethylene ether and polyacrylate. In S1, the mass ratio of nonylphenol polyoxyethylene ether to polyacrylate in the modifier is 1:(1.3-1.5). In S2, the fluorinating agent is at least one of potassium fluoride or lithium fluoride.

2. The application of the modified graphene catalyst as described in claim 1 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S1, the mass ratio of graphene to modifier is 1:(3-5); and / or In S1, the stirring rate is 700 rpm-1000 rpm; and / or In S1, the stirring time is 4-5 hours.

3. The application of the modified graphene catalyst as described in claim 1 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S2, the mass ratio of the primary modified graphene to water is 1:(10-12); and / or In S2, the mass ratio of the primary modified graphene to the fluorinating agent is 1:(6-7.5); and / or In S2, the reaction time is 18h-22h.

4. The application of the modified graphene catalyst as described in claim 1 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S3, the concentration of the tin sulfide dispersion is 0.1 mol / L-0.2 mol / L.

5. The application of the modified graphene catalyst as described in claim 1 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S3, the soluble zinc salt is zinc chloride.

6. The application of the modified graphene catalyst as described in claim 5 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S3, the mass ratio of the secondary modified graphene to the soluble zinc salt is 1:(0.4-0.6); and / or In S3, the mass-to-volume ratio of the secondary modified graphene and the stannous sulfide dispersion is 1 g:(0.8-1) L; and / or In S3, the reaction time is 12h-15h.

7. The application of the modified graphene catalyst as described in claim 1 in the photocatalytic production of formic acid from carbon dioxide, characterized in that: In S4, the temperature is raised to 380℃-400℃ using a programmed temperature rise method, and the temperature rise rate of the programmed temperature rise is 12℃ / min-15℃ / min.