METHOD FOR CARBON MATERIALS SURFACE MODIFICATION BY THE FLUOROCARBONS AND DERIVATIVES

Abstract

A chemical vapor deposition method for fluorine-containing carbon materials preparation provided. The claimed method comprises treating of carbons with fluorocarbons or derivatives that passes at a moderate high temperature. The fluorine-containing carbon materials show hydrophobicity, high thermal stability and can be used as catalysts support, lithium battery anodes, and hydrophobic materials or as surface precursor. Surface fluorine characterized by intensive signal in the XPS spectrum, found in a range of 685-687 eV. Obtained fluoro-containing functionalities is stable at a temperature about 1000° C.

Claims

1. A method for chemical modification of carbon materials by their gas phase treatment in inert medium with fluoro-containing compounds at a temperature above 200° C., at which the surface of porous and/or highly dispersed carbon materials processed with fluorocarbons derivatives that contain at least one of the following substituent: —H, —Hal, —OH, —COH, —COOH, ═O;

2. A method as claimed in claim 1, wherein starting carbon material is subjected to the preliminary heating in an inert gas medium or a vacuum at a temperature above 200° C.;

3. A process as claimed in claim 1, wherein an oxygen and/or a water is present in the reaction gas mixture at the total partial pressure up to 10 kPa.

Description

EXAMPLES

Example 1

[0019] 5 g of carbon material as activated carbon, of trade mark SCN, obtained from carbonized sulphonated polyvinyl-pyridine resin, was heated in purged Ar gas at the flow rate of 50 ml/min to 450° C. and stored at the temperature of 550° C. for 2 h. This stage is necessary for water, CO, CO.sub.2 and physisorbed molecules desorption. Fluorinating reagent such as a Freon gas R-12, CF.sub.2Cl.sub.2, was mixed to an argon flow to treat the activated carbon surface. The treatment was performed at the flow rate of Freon gas of 35 ml/min at the treatment temperature of 550° C. during 2 h. After the treatment, the resulting modified activated carbon was cooled in the Ar flow to r.t. Chemical analysis proves that obtained activated carbon contains 2.07 mmol/g of chlorine and 1.96 mmol/g of fluorine. XPS spectrum shows F and Cl peaks for the fluorinated activated carbon. Peak of F 1s is symmetric with the maximum at 686.8 eV. The Cl 2p doublet components are observed at 199.5 eV (Cl 2p.sub.3/2) and 201 eV (Cl 2p.sub.1/2). Energies of fluorine and chlorine binding refer to that of CF.sub.2-groups in organic fluorides and Cl-groups in organic chlorides.

Example 2

[0020] The process of Example 1 is carried out, but, with activated carbon, KAU, obtained from carbonized fruit stones and as fluorinating reagent was used Ar gas saturated with vapors of R-114B2, BrF.sub.2C—CF.sub.2Br, the saturation was done at the temperature of 0° C. Obtained fluorinated carbon contains 0.85 mmol/g of bromine and 3.98 mmol/g of fluorine.

Example 3

[0021] 5 g of multiwalled carbon nanotubes, which is obtained by CVD method from methane over Ni catalyst, BET surface of 115 m.sup.2/g and pore volume of 0.12 cm.sup.3/g, was treated as in Example 1, but with Freon R-114 (ClCF.sub.2CF.sub.2Cl) as fluorinating agent. Obtained fluorinated carbon contains 0.42 mmol/g of chlorine and 0.90 mmol/g of fluorine.

Example 4

[0022] 5 g of carbon black of K-354 of native trademark was treated as in Example 1, but with Freon R-13 (CClF.sub.3) and the treatment was carried out at the temperature of 570° C. Obtained fluorinated carbon contains 0.72 mmol/g of chlorine and 2.30 mmol/g of fluorine.

Example 5

[0023] 5 g of activated carbon of native SCN trademark was as in Example 2, but with trifluoroacetic acid (CF.sub.3COOH) as fluorinating reagent and the treatment was carried out at the temperature of 480° C. Obtained fluorinated carbon contains 2.55 mmol/g of fluorine.

Example 6

[0024] The process of Example 1 is carried out, but, with 1 g of graphene (BET surface of 480 m.sup.2/g) synthesized by pyrolysis of sodium ethylate as carbon material. Obtained fluorinated carbon contains 0.52 mmol/g of fluorine and 0.49 mmol/g of chlorine.

Example 7

[0025] The process of Example 1 is carried out, but, with Halone 134a, Forane®, CH.sub.2FCF.sub.3, as fluorinating reagent at the temperature of 575° C., and 50 ppm of oxygen was added to a flow of the fluorinating reagent. Obtained fluorinated carbon contains 2.94 mmol/g of fluorine. Intensive XPS F1s signal with two component maximums at 685.5 eV and 686.4 eV is registered for this fluorinated carbon. These components refer to two different surface fluorine forms, one of which corresponds to CF.sub.3-groups. 0.5 g of the obtained fluorinated carbon was heated in purged argon gas flow at 1000° C. for 2 h. The resulted fluorine-containing carbon contains 2.05 mmol/g of residual fluorine. That confirms high thermal stability of fluorine-containing surface layer obtained.

Example 8

[0026] The process of Example 7 is carried out, but, with no oxygen addition to a fluorinating agent. Resulting fluorinated carbon contains 1.75 mmol/g of fluorine.

Example 9

[0027] The process of Example 7 is carried out, but, without oxygen gas in a fluorinating agent flow. Instead oxygen, an admixture of water was added to Forane™, CH.sub.2FCF.sub.3, flow by the gas bubbling through the water at 0° C. Resulting fluorinated carbon contains 3.92 mmol/g of fluorine.

Example 10

[0028] The process of Example 1 is carried out, but, with 5 g of activated carbon, KAU, as carbon material and with hexafluoroacetone, CF.sub.3COCF.sub.3, as fluorinating reagent. Obtained fluorinated carbon contains 0.32 mmol/g of fluorine.

Example 11

[0029] The process of Example 1 is carried out, but, with hexafluoroacetone instead of Freon R-12. Obtained fluorinated carbon contains 0.60 mmol/g of fluorine. XPS spectrum shows F1s symmetric peak centered at 685.3 eV that confirms the fluorination.

Example 12

[0030] 3 g of activated carbon Norit® GAC 830EN, which preliminary de-ashed with diluted HCl solution, was treated as in the Example 2, but, with 2,3,5,6-tetrafluorobenzaldehyde (97%, Sigma-Aldrich) vapor as the fluorinating reagent at the temperature of 620° C. Obtained fluorinated carbon contains 0.81 mmol/g of fluorine.

Example 13

[0031] 3 g of activated carbon Norit® GAC 830EN de-ashed with diluted HCl solution was treated as in the Example 2, but the treatment was carried out at the temperature of 200° C. during 9 h. Obtained fluorinated carbon contains 0.13 mmol/g of fluorine.

Example 14

[0032] 1 g of activated carbon SCN was treated with an isoflurane, C.sub.3H.sub.2ClF.sub.5O, 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether, Aldrich.sup.cPR, as in Example 2, but the treatment was carried out at 570° C. and it accompanies with intense HF and HCl evaluation. Obtained fluorinated carbon contains 3.65 mmol/g of fluorine and 0.52 mmol/g of chlorine.

[0033] Given examples clarify the invention but do not limit the scope of the rights arising from it.