CN112174134A - Method for preparing graphite oxide by circulating sulfuric acid - Google Patents
Method for preparing graphite oxide by circulating sulfuric acid Download PDFInfo
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- CN112174134A CN112174134A CN202011263737.4A CN202011263737A CN112174134A CN 112174134 A CN112174134 A CN 112174134A CN 202011263737 A CN202011263737 A CN 202011263737A CN 112174134 A CN112174134 A CN 112174134A
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- C01B32/00—Carbon; Compounds thereof
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- C01B32/21—After-treatment
- C01B32/23—Oxidation
Abstract
The invention discloses a method for preparing graphite oxide by circulating sulfuric acid. The invention breaks through the traditional inertial thinking, and separates partial concentrated sulfuric acid from the reaction solution by adding a solid-liquid separation process after the intercalation oxidation process, on one hand, the heat release of sulfuric acid dilution in the water adding process is reduced along with the reduction of the sulfuric acid amount in the reaction solution, so that the water adding process time can be shortened, and more stable process temperature control can be realized; on the other hand, the separated sulfuric acid can be used for preparing a new round of graphite oxide, so that the aim of recycling is fulfilled. The invention saves the consumption of new sulfuric acid in the preparation process of graphite oxide by recycling the sulfuric acid, shortens the water adding time by more than 30 percent, and reduces the refrigeration energy consumption in the water adding process by more than 30 percent.
Description
Technical Field
The invention belongs to the field of material preparation, and relates to a method for preparing graphite oxide by circulating sulfuric acid.
Background
The modified Hummer's method is generally adopted in industry to prepare graphite oxide in a modeling manner, in short, graphite undergoes intercalation oxidation reaction in a strong oxidation environment provided by potassium permanganate and sulfuric acid, water is added into a reaction system at a later stage, sulfuric acid is diluted, and graphite sheets are dissociated at the same time, and the process flow schematic diagram is shown in fig. 1. Concentrated sulfuric acid and water are mixed to release heat in a diluted mode, in the dissociation process, in order to control the temperature stably, the water adding speed is controlled not to be too high (the water adding time is prolonged), otherwise, the heat release speed is higher than the refrigeration speed, the temperature of the solution is increased and even boiling occurs, and safety risks exist; on the other hand, a large amount of energy is consumed in the process to carry out cooling and temperature control.
Disclosure of Invention
The invention aims to provide a method for preparing graphite oxide by circulating sulfuric acid.
Because concentrated sulfuric acid and water are mixed and can release heat in a large amount, two problems exist in the large-scale production process of graphite oxide due to the requirement of stable temperature control in the reaction process: 1) the water adding process is long; 2) the energy consumption is high.
In order to improve the above problems, the present invention intends to add a solid-liquid separation process step of a reaction stock solution in a graphite oxide preparation process (as shown in fig. 2, an improved graphite oxide preparation process), specifically comprising: after the intercalation reaction is finished, the reaction stock solution is separated, and part of sulfuric acid is removed, so that the dilution heat released by mixing sulfuric acid and water in the water adding process is reduced, and the aims of stabilizing the process temperature control and shortening the water adding period are fulfilled.
On the other hand, before the dissociation process, the solid-liquid separation is performed on the reaction system, and the separated sulfuric acid belongs to concentrated sulfuric acid, and can be reused as a raw material for preparing graphite oxide, as shown in fig. 3.
Because the reaction consumes sulfuric acid, and the solid part separated from solid and liquid carries the sulfuric acid, the amount of the separated sulfuric acid is necessarily less than the initial sulfuric acid feeding amount, if concentrated sulfuric acid obtained by solid and liquid separation is fed back to a new reaction system again, the more the amount of the sulfuric acid is, the more the new sulfuric acid is supplemented properly to compensate the loss, and a new round of preparation can be carried out. From the angle, the solid-liquid separation can not only improve the problem of pain points in large-scale production, but also realize the recycling of the sulfuric acid in the process and reduce the consumption of the raw material sulfuric acid.
It is worth to say that the academic community has been continuously researching the preparation method of graphite oxide, and the variants thereof comprise the change of oxidizing agents, such as one or more of potassium permanganate, potassium ferrate, potassium persulfate, sodium persulfate and the like; the solvent system also comprises sulfuric acid, and a system which takes the sulfuric acid as a main component and is compounded with phosphoric acid or nitric acid and the like. The patent mainly highlights that the technical scheme that the solvent can be recycled and reused in the reaction process.
The method for preparing graphite oxide by circulating sulfuric acid, as shown in fig. 3, comprises the following steps:
1) mixing graphite powder and concentrated sulfuric acid;
2) adding an oxidant until the oxidant is completely dissolved, heating to perform intercalation reaction, performing solid-liquid separation after the reaction is finished, and respectively collecting upper-layer liquid and lower-layer solid;
and adding water into the lower-layer solid, stirring for 5-10min after the water is added, adding hydrogen peroxide, and stirring until no bubbles are generated to obtain the graphite oxide.
In step 1) of the above method, the graphite powder is selected from at least one of expandable graphite, expanded graphite and flake graphite;
the dosage ratio of the graphite powder to the concentrated sulfuric acid is 1g (30-80); specifically 1: 45;
the concentration of the concentrated sulfuric acid is 98 wt%;
in the step 2), the oxidant is at least one selected from potassium permanganate, potassium ferrate and potassium perchlorate;
in the step of adding the oxidant to completely dissolve, the temperature of the system is lower than 15 ℃;
in the intercalation reaction step, the temperature is 10-40 ℃; the time is 2-24 h;
the solid-liquid separation mode is centrifugation;
in the centrifugal separation, the rotating speed is 3000-10000 rpm; the time is 15-2 min;
in the step of adding water and hydrogen peroxide into the lower-layer solid, the ratio of the water consumption to the initial graphite feeding amount is (40-85) g:10g, specifically 50: 1;
the ratio of the amount of the hydrogen peroxide to the initial graphite feeding amount is (5-15) ml to 10g, specifically 10ml to 10 g;
the system temperature is not higher than 95 ℃; in particular 50-75 ℃ or 85 ℃.
The invention provides a method for preparing graphite oxide by using circulating sulfuric acid, which comprises the following steps:
a. mixing new concentrated sulfuric acid with the upper layer liquid obtained in the step 2) of the method to obtain mixed sulfuric acid, and then uniformly mixing the mixed sulfuric acid with graphite powder;
b. repeating step 2) of the aforementioned method;
c. repeating the steps a and b of the method for a plurality of times.
In the step a of the method, the ratio of the graphite powder to the mixed sulfuric acid is 1g (30-80); specifically 1: 45;
the mass ratio of the new sulfuric acid to the upper layer liquid in the step 2) of the method is 1: 1.0-1.5; specifically 191.5: 258.5, 192.5: 257.5 or 197: 253;
in the step b, the plurality of times is 1 to 5 times.
The invention breaks through the traditional inertial thinking, and separates partial concentrated sulfuric acid from the reaction solution by adding a solid-liquid separation process after the intercalation oxidation process, on one hand, the heat release of sulfuric acid dilution in the water adding process is reduced along with the reduction of the sulfuric acid amount in the reaction solution, so that the water adding process time can be shortened, and more stable process temperature control can be realized; on the other hand, the separated sulfuric acid can be used for preparing a new round of graphite oxide, so that the aim of recycling is fulfilled.
The invention has the following beneficial effects:
the invention saves the consumption of new sulfuric acid in the preparation process of graphite oxide by recycling the sulfuric acid, shortens the water adding time by more than 30 percent, and reduces the refrigeration energy consumption in the water adding process by more than 30 percent.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a flow chart of a graphite oxide preparation process commonly used in the prior art;
FIG. 2 is a modified process for preparing graphite oxide;
FIG. 3 shows a process for preparing graphite oxide by circulating sulfuric acid.
Detailed Description
The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.
The graphite is purchased from a national pharmaceutical reagent factory, and the chemical purity is 99.85%; potassium permanganate is purchased from a pharmaceutical reagent factory, and the chemical purity is 99.9%; hydrogen peroxide is purchased from a national pharmaceutical reagent factory; concentrated sulfuric acid is analytically pure and purchased from the pharmaceutical reagent factory.
Comparative example 1 preparation of graphite oxide from New sulfuric acid (conventional Process)
(1) Putting 10g of graphite and 450g of concentrated sulfuric acid into a dry reactor for stirring and mixing, and starting refrigeration in the mixing process;
(2) when the temperature of the solution is reduced to 5 ℃ and the mixing time of the graphite and the sulfuric acid reaches 30min, slowly adding 30g of potassium permanganate while stirring, and controlling the temperature of the solution to be less than or equal to 15 ℃;
(3) heating the solution obtained in the step (2), keeping stirring and starting, slowly heating the solution to 35 +/-1 ℃, and reacting for 2.5 hours at the temperature;
(4) and (3) weighing 500g of water in advance in another reactor, keeping stirring and starting, keeping refrigeration and starting (the temperature of circulating cooling water is 15-25 ℃, and the opening degree is-30%), slowly adding the solution obtained in the step (3) into 500g of water (the adding time is-30 min), raising the temperature of the solution to-75 ℃, continuing stirring for 10min, adding 10ml of hydrogen peroxide, and stirring until no bubbles are generated, thus finishing the reaction.
Example 1 first preparation of graphite oxide from fresh sulfuric acid
(1) Putting 10g of graphite and 450g of concentrated sulfuric acid into a dry reactor for stirring and mixing, and starting refrigeration in the mixing process;
(2) when the temperature of the solution is reduced to 5 ℃ and the mixing time of the graphite and the sulfuric acid reaches 30min, slowly adding 30g of potassium permanganate while stirring, and controlling the temperature of the solution to be less than or equal to 15 ℃;
(3) heating the solution obtained in the step (2), keeping stirring and starting, slowly heating the solution to 35 +/-1 ℃, and reacting for 2.5 hours at the temperature;
(4) and (4) putting the solution obtained in the step (3) into a centrifugal tube, and carrying out centrifugal treatment at the centrifugal speed of 10000rpm for 2 min. Pouring the centrifuged upper-layer liquid into a new drying container for storage for later use, and weighing 258.5g of the separated upper-layer liquid;
(5) weighing 500g of water in advance into a reactor, keeping stirring on, adding the lower-layer solid obtained by centrifuging in the step (4), dispersing and mixing by stirring (the adding time is less than or equal to 10min), gradually increasing the solution temperature to 65-75 ℃ along with the dispersion, continuing stirring for 5min after the material is added, adding 10ml of hydrogen peroxide, and continuing stirring until no bubbles are generated, thus finishing the reaction.
Example 2 Process for the preparation of graphite oxide with recycled sulfuric acid
EXAMPLE 1 preparation of graphite oxide by recovery of sulfuric acid in round 1
(1) Adding 10g of graphite, 258.5g of liquid (the main component is concentrated sulfuric acid) obtained by solid-liquid separation in the last reaction and 191.5g of new concentrated sulfuric acid into a dry reactor for stirring and mixing, and starting refrigeration in the mixing process;
(2) when the temperature of the solution is reduced to 5 ℃ and the mixing time of the graphite and the sulfuric acid reaches 30min, slowly adding 30g of potassium permanganate while stirring, and controlling the temperature of the solution to be less than or equal to 15 ℃;
(3) heating the solution obtained in the step (2), keeping stirring and starting, slowly heating the solution to 35 +/-1 ℃, and reacting for 2.5 hours at the temperature;
(4) and (4) putting the solution obtained in the step (3) into a centrifuge tube, and carrying out centrifugation at the centrifuge speed of 3000rpm for 15 min. Pouring the centrifuged upper-layer liquid into a new drying container for storage for later use, and weighing and separating to obtain 253g of upper-layer liquid;
(5) weighing 500g of normal temperature water in advance, placing the normal temperature water in a reactor, keeping stirring and opening, adding the centrifuged lower layer solid, performing dispersion mixing by strong stirring, gradually increasing the temperature of the solution to 85 ℃ along with the dispersion, continuing stirring for 5min, adding 10ml of hydrogen peroxide, and stirring until no bubbles are generated, thus finishing the reaction.
EXAMPLE 1 preparation of graphite oxide by recovery of sulfuric acid in run 2
(1) Adding 10g of graphite, 253g of liquid (the main component is concentrated sulfuric acid) obtained by solid-liquid separation in the last reaction, and 197g of new concentrated sulfuric acid into a dry reactor for stirring and mixing, and starting refrigeration in the mixing process;
(2) when the temperature of the solution is reduced to 5 ℃ and the mixing time of the graphite and the sulfuric acid reaches 30min, slowly adding 30g of potassium permanganate while stirring, and controlling the temperature of the solution to be less than or equal to 15 ℃;
(3) heating the solution obtained in the step (2), keeping stirring and starting, slowly heating the solution to 35 +/-1 ℃, and reacting for 2.5 hours at the temperature;
(4) and (4) putting the solution obtained in the step (3) into a centrifuge tube, and carrying out centrifugation at the rotation speed of 7000rpm for 5 min. Pouring the centrifuged upper-layer liquid into a new drying container for storage for later use, and weighing 257.5g of the separated upper-layer liquid;
(5) weighing 500g of normal temperature water in advance, placing the normal temperature water in a reactor, keeping stirring and opening, adding the centrifuged lower-layer solid, performing dispersion mixing by strong stirring, and gradually increasing the temperature of the solution to 85 ℃ along with the dispersion. After the materials are added, the stirring is continued for 5min, 10ml of hydrogen peroxide is added and stirred until no bubbles are generated, and the reaction can be finished.
EXAMPLE 1 preparation of graphite oxide by recovering sulfuric acid in run 3
(1) 10g of graphite is added into a dry reactor to be stirred and mixed with 257.5g of liquid (the main component is concentrated sulfuric acid) obtained by solid-liquid separation in the last reaction, 192.5g of new concentrated sulfuric acid is supplemented, and refrigeration is started in the mixing process;
(2) when the temperature of the solution is reduced to 3 ℃ and the mixing time of the graphite and the sulfuric acid reaches 30min, slowly adding 30g of potassium permanganate while stirring, and controlling the temperature of the solution to be less than or equal to 15 ℃;
(3) heating the solution obtained in the step (2), keeping stirring and starting, slowly heating the solution to 35 +/-1 ℃, and reacting for 2.5 hours at the temperature;
(4) and (4) putting the solution obtained in the step (3) into a centrifuge tube, and carrying out centrifugation at the rotating speed of 4500rpm for 10 min. Pouring the centrifuged upper layer liquid into a new drying container for storage, and weighing 247.5g of the separated upper layer liquid;
(5) weighing 500g of normal temperature water in advance, placing the normal temperature water in a reactor, keeping stirring and opening, adding the centrifuged lower-layer solid, performing dispersion mixing by strong stirring, and gradually increasing the temperature of the solution to 85 ℃ along with the dispersion. After the materials are added, the stirring is continued for 5min, 10ml of hydrogen peroxide is added and stirred until no bubbles are generated, and the reaction can be finished.
Summary of the amounts of the respective raw materials in Table 1, example 1 and example 2
| Description of the Process/Material ratio | Graphite/g | Potassium permanganate/g | Sulfuric acid/g | Previous recovery of sulfuric acid/g | Water/g |
| Improved process | 10 | 30 | 500 | 0 | 500 |
| Recycle sulfuric acid 1 time | 10 | 30 | 191.5 | 258.5 | 500 |
| Recycle sulfuric acid for 2 times | 10 | 30 | 197 | 253 | 500 |
| Recycle sulfuric acid 3 times | 10 | 30 | 192.5 | 257.5 | 500 |
| Recycle sulfuric acid 4 times | 10 | 30 | 195 | 255 | 500 |
| Circulating sulfuric acid for 5 times | 10 | 30 | 193 | 257 | 500 |
| … | … | … | … | … | … |
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of preparing graphite oxide, comprising:
1) mixing graphite powder and concentrated sulfuric acid;
2) adding an oxidant until the oxidant is completely dissolved, heating to perform intercalation reaction, performing solid-liquid separation after the reaction is finished, and respectively collecting upper-layer liquid and lower-layer solid;
and adding water into the lower-layer solid, stirring for 5-10min after the water is added, adding hydrogen peroxide, and stirring until no bubbles are generated to obtain the graphite oxide.
2. The method of claim 1, wherein: in the step 1), the graphite powder is at least one selected from expandable graphite, expanded graphite and flake graphite.
3. The method according to claim 1 or 2, characterized in that: in the step 1), the dosage ratio of the graphite powder to the concentrated sulfuric acid is 1g (30-80); specifically 1: 45;
the concentration of the concentrated sulfuric acid is 98 wt%.
4. A method according to any one of claims 1 to 3, wherein: in the step 2), the oxidant is at least one selected from potassium permanganate, potassium ferrate and potassium perchlorate.
5. The method according to any one of claims 1 to 4, wherein: in the step 2), the temperature of the system is lower than 15 ℃ in the step of adding the oxidant to completely dissolve.
6. The method according to any one of claims 1 to 5, wherein: in the step 2), the temperature is 10-40 ℃ in the intercalation reaction step; the time is 2-24 h.
7. The method according to any one of claims 1 to 6, wherein: in the step 2), the solid-liquid separation mode is centrifugation;
specifically, in the centrifugal separation, the rotating speed is 3000-10000 rpm; the time is 15-2 min.
8. The method according to any one of claims 1 to 7, wherein: in the step 2), in the step of adding water and hydrogen peroxide into the lower-layer solid, the ratio of the water consumption to the initial graphite feeding amount is (40-85) g:10g, specifically 50: 1;
the ratio of the amount of the hydrogen peroxide to the initial graphite feeding amount is (5-15) ml to 10g, specifically 10ml to 10 g;
the system temperature is not higher than 95 ℃; in particular 50-75 ℃.
9. A method for preparing graphite oxide using recycled sulfuric acid, comprising:
a. mixing new concentrated sulfuric acid with the upper layer liquid in the step 2) of any one of claims 1 to 8 to obtain mixed sulfuric acid, and then mixing the mixed sulfuric acid with graphite powder;
b. repeating step 2) of any one of claims 1 to 8;
c. repeating the steps a, b of claim 9 several times.
10. The method of claim 9, wherein: in the step a, the ratio of the graphite powder to the mixed sulfuric acid is 1g (30-80 g); specifically 1: 45;
the mass ratio of the new sulfuric acid to the upper layer liquid in step 2) of any one of claims 1 to 8 is 1: 1.0-1.5; specifically 191.5: 258.5, 192.5: 257.5 or 197: 253;
in the step b, the plurality of times is 1 to 5 times.
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