阅读说明：本技术 用于由膨胀的结晶石墨制造经还原的氧化石墨烯的方法 (Method for producing reduced graphene oxide from expanded crystalline graphite ) 是由 蒂·坦·吴 大卫·诺列加佩雷斯 罗伯托·苏亚雷斯桑切斯 于 2020-05-12 设计创作，主要内容包括：本发明涉及用于由结晶石墨制造经还原的氧化石墨烯的方法,所述方法包括：A.提供结晶石墨,B.任选地,结晶石墨的预处理,C.在室温下用过硫酸盐和酸进行结晶石墨的插层以获得插层的结晶石墨,D.进行插层的结晶石墨的膨胀以获得膨胀的结晶石墨,以及E.进行膨胀的结晶石墨的氧化步骤以获得氧化石墨烯,以及F.将氧化石墨烯还原成经还原的氧化石墨烯。(The present invention relates to a method for producing reduced graphene oxide from crystalline graphite, the method comprising: A. providing crystalline graphite, b. optionally, pre-treatment of the crystalline graphite, c. intercalation of the crystalline graphite with persulfate and acid at room temperature to obtain intercalated crystalline graphite, d. expansion of the intercalated crystalline graphite to obtain expanded crystalline graphite, and e. oxidation step of the expanded crystalline graphite to obtain graphene oxide, and f. reduction of the graphene oxide to reduced graphene oxide.)

1. A method for producing reduced graphene oxide from crystalline graphite, comprising:

A. there is provided a crystalline graphite which is,

B. optionally, a pre-treatment of the crystalline graphite,

C. intercalating the crystalline graphite with a persulfate and an acid at room temperature to obtain an intercalated crystalline graphite,

D. expansion of the intercalated crystalline graphite is carried out at room temperature to obtain expanded crystalline graphite,

E. performing an oxidation step of the expanded crystalline graphite to obtain graphene oxide, an

F. Reducing the graphene oxide to reduced graphene oxide.

2. The process according to claim 1, wherein in step B), the pre-treatment of the crystalline graphite comprises the following sequence of sub-steps:

i. a sieving step, wherein the crystalline graphite is classified by size as follows:

a) crystalline graphite having a size of less than 50 μm,

b) crystalline graphite having a size of 50 μm or more,

fraction a) of crystalline graphite having a size of less than 50 μm is removed,

a flotation step on a fraction b) of crystalline graphite having a size greater than or equal to 50 μm,

an acid leaching step, wherein an acid is added so that the weight ratio (amount of acid)/(amount of crystalline graphite) is from 0.25 to 1.0,

optionally, washing and drying the crystalline graphite.

3. The process according to any one of claims 1 or 2, wherein in step C) the weight ratio of persulfate to crystalline graphite is from 1 to 8.

4. The process according to any one of claims 1 to 3, wherein in step C), the weight ratio of the acid to the crystalline graphite is from 2 to 8.

5. The process according to any one of claims 1 to 4, wherein in step C), the persulfate is selected from: sodium persulfate (Na)₂S₂O₈) Ammonium persulfate ((NH)₄)₂S₂O₈) And potassium persulfate (K)₂S₂O₈) Or mixtures thereof.

6. The process according to any one of claims 1 to 5, wherein in step C) the acid is selected from: h₂SO₄、HCl、HNO₃、H₃PO₄、C₂H₂Cl₂O₂(Dichloroacetic acid), HSO₂OH (alkyl sulfonic acid) or mixtures thereof.

7. The method according to any one of claims 1 to 6, wherein in step D), the expansion is naturally performed by placing the crystalline graphite, the persulfate salt and the acid in an open container at room temperature.

8. The method according to any one of claims 1 to 7, wherein step E) comprises the following sequence of sub-steps:

i. mixing the expanded crystalline graphite with an acid, an oxidizing agent and optionally a salt,

adding a chemical component to stop the oxidation reaction,

separating the graphite oxide from the mixture obtained in step E.ii),

exfoliating the graphite oxide into graphene oxide.

9. The method of claim 8, wherein in step E.i), the salt is a nitrate salt selected from the group consisting of: NaNO₃、NH₄NO₃、KNO₃、Ni(NO₃)₂、Cu(NO₃)₂、Zn(NO₃)₂、Al(NO₃)₃Or mixtures thereof.

10. The process of any one of claims 8 or 9, wherein in step E.i), the acid is selected from: h₂SO₄、HCl、HNO₃、H₃PO₄、C₂H₂Cl₂O₂(Dichloroacetic acid), HSO₂OH (alkyl sulfonic acid) or mixtures thereof.

11. The method of any one of claims 8 to 10, wherein in step E.i), the oxidizing agent is selected from the group consisting of: potassium permanganate, H₂O₂、O₃、H₂S₂O₈、H₂SO₅、KNO₃NaClO or mixtures thereof.

12. The method according to any one of claims 8 to 11, wherein in step e.ii), the chemical component for stopping the oxidation reaction is selected from: acid, non-deionized water, H₂O₂Or mixtures thereof.

13. The method of claim 12, wherein at least two chemical components are used sequentially or simultaneously when they are selected to stop the reaction.

14. The method according to any one of claims 8 to 13, wherein in step e.ii) the mixture obtained in step E.i) is gradually pumped into the chemical composition for stopping the oxidation reaction.

15. The process according to any one of claims 8 to 14, wherein in step e.iii) the graphite oxide is separated by centrifugation, decantation, distillation or filtration.

16. The method according to any one of claims 8 to 15, wherein in step e.iv) the stripping is performed by using ultrasound, mechanical stirrer, shaker or thermal stripping.

17. The method according to any one of claims 1 to 16, wherein step F) comprises the sub-steps of:

i. reducing GO to reduced graphene oxide (rGO) comprising one or several layers of graphene having oxygen functionality from 10 to 25 wt% using a reducing agent, and

optionally, reducing the rGO to microwave reduced graphene oxide (MW-rGO) comprising one or several layers of graphene having less than 10 wt% oxygen functionality by microwave treatment of rGO under an air atmosphere in the presence of a catalyst.

18. The method of claim 17, wherein in step F.i), the reducing agent is selected from the group consisting of: ascorbic acid; urea; hydrazine hydrate; alkaline solutions such as NaOH or KOH; phenols such as gallic acid, tannic acid, dopamine or tea polyphenols; alcohols such as methanol, ethanol or isopropanol; glycine; sodium citrate or sodium borohydride.

19. The process according to any one of claims 17 or 18, wherein in step f.ii), the catalyst is selected from: pristine graphene, graphene nanoplatelets, graphite, or graphite nanoplatelets.

Examples

Samples (dials) 1 to 4 were prepared by providing crystalline graphite from a steel mill. The crystalline graphite is then sieved to size fractions as follows:

a) crystalline graphite having a size of less than <63 μm, and

b) crystalline graphite having a size of 63 μm or more.

Fraction a) of crystalline graphite having a size of less than 63 μm is removed.

A flotation step of fraction b) of crystalline graphite having a size greater than or equal to 63 μm is carried out. The flotation step was performed using a Humboldt Wedag flotation machine with MIBC as a frother. The following conditions were applied: cell volume (l): 2; rotor speed (rpm): 2000; solid concentration (%): 5 to 10; blowing agent, type: MIBC; foaming agent, adding (g/T): 40; adjustment time (sec): 10; and water conditions: natural pH, room temperature.

All samples were then leached with aqueous hydrochloric acid at an acid/crystalline graphite weight ratio of 0.5. The samples were then washed with deionized water and dried in air at 90 ℃. The purity of the crystalline graphite was 95%.

Thereafter, the crystalline graphite was then intercalated with ammonium persulfate and sulfuric acid in various ratios at 25 ℃ or 35 ℃ for 5 minutes. The mixture was then placed in an open vessel for 5 minutes to expand the crystalline graphite. The resulting material is known as expanded crystalline graphite.

Samples 1 to 4 were mixed with sulfuric acid and KMnO at room temperature₄And optionally ammonium nitrate. The mixture contained 1 part by weight of expanded crystalline graphite, 3.5 parts by weight of KMnO₄100 parts by weight of sulfuric acid and optionally 0.5 parts by weight of ammonium nitrate. After oxidation, the mixture was gradually pumped into deionized water. Addition of H₂O₂The aqueous solution was taken up until no more gas was generated and the mixture was stirred to remove the remaining H₂O₂。

Then, for all samples, graphite oxide was separated from the mixture by decantation. The graphite oxide is then exfoliated using ultrasound to obtain one or two layers of graphene oxide. Finally, the graphene oxide was separated from the mixture by centrifugation, washed with water and dried with air to obtain a graphene oxide powder.

L-ascorbic acid was mixed with graphene oxide of samples 1 to 4 in water. The reaction mixture was stirred at 90 ℃ to reduce the graphene oxide sheets. The sample was then washed and dried to obtain reduced graphene oxide powder.

Then, for samples 2 and 3, rGO was placed in a microwave oven (800W) under an air atmosphere for a period of 2 seconds. A catalyst was added as pristine graphene. rGO is reduced to MW-rGO by microwave treatment.

The graphene oxide and reduced graphene oxide were analyzed by Scanning Electron Microscopy (SEM), X-ray diffraction spectroscopy (XRD), Transmission Electron Microscopy (TEM), LECO analysis, and raman spectroscopy.

Samples 5 and 6 correspond to sample 1 of WO2018178845 and sample 1 of PCT/IB2019/052805, respectively. Table 1 shows the results obtained.

The methods of samples 1 to 4 are more environmentally friendly than the comparative sample. Furthermore, the oxidation time is significantly reduced with the methods of samples 1 to 4 compared to the prior art methods illustrated with samples 5 and 6.

Determination of ambient temperature or 25 ℃ (samples 1 and 2) with samples 3 and 4 of the intercalation and expansion steps carried out at 35 ℃ is sufficient to obtain graphene oxide containing a high percentage of oxygen groups and correspondingly high quality reduced graphene oxide.

Samples 2 and 4, which took an oxidation time of 1 hour, determined that oxidation times longer than 10 minutes (sample 1) and 30 minutes (sample 3), respectively, did not improve any further quality of the graphene oxide. In other words, a very short oxidation time is sufficient to fully oxidize the expanded crystalline graphite. This significantly reduces the energy consumption.

Sample 1 also confirms that the expanded crystalline graphite can oxidize even faster in the absence of salt than in the presence of salt (sample 3). The ability to remove salts from the oxidation step significantly limits contamination.

Samples 2 and 3 also confirm that the microwave treatment successfully reduced the reduced graphene oxide further, allowing for oxygen group percentages of less than 10%.