Process for pure carbon production

Abstract

The disclosure provides for methods of oxidizing carbide anions, or negative ions, from salt like carbides at low temperatures below about 600 C. In another aspect, the disclosure provides for reactions with intermediate transition metal carbides. In yet another aspect, the disclosure provides for a system of reactions where salt-like carbide anions and intermediate carbide anions are oxidized to produce pure carbon of various allotropes.

Claims

1. A method for the production of carbon with a diamond or graphene like structure comprising: chemically oxidatively reacting a ground carbide chemical compound with an anhydrous molten metal salt reactant at a reaction temperature of below 600 C. in an oxygen, moisture free environment to form a reaction product comprising carbon from the oxidation of the ground carbide chemical compound and also to form a reaction product which is elemental metal from the reduction of the cation of the anhydrous metal salt, wherein the chemical oxidative reaction takes place in the anhydrous molten metal salt, and wherein the anhydrous metal salt is used in excess with respect to the ground carbide chemical compound.

2. The method of claim 1, wherein the carbide is aluminum carbide, the metal salt is stannous chloride, and the reaction temperature is below 300 C.

3. The method of claim 2, wherein the excess is an excess of at least twice the stoichiometric ratio, and wherein the reaction temperature is 280 C. or below.

4. The method of claim 2, wherein the carbon comprises carbon with a diamond like structure.

5. The method of claim 1, wherein the carbide is calcium carbide, wherein the metal salt is zinc chloride, and wherein the reaction temperature is below 600 C.

6. The method of claim 5, wherein the excess is an excess of at least twice the stoichiometric ratio, and wherein the reaction temperature is 425 C. or below.

7. The method of claim 5, wherein the carbon comprises carbon with a diamond like structure.

8. The method of claim 1, wherein the carbide is calcium carbide, wherein the metal salt is stannous chloride, and wherein the reaction temperature is below 300 C.

9. The method of claim 8, wherein the excess is an excess of at least twice the stoichiometric ratio, and wherein the reaction temperature is 280 C. or below.

10. The method of claim 8, wherein the carbon comprises carbon with a graphene like structure.

Description

DETAILED DESCRIPTION

(1) In an aspect, the disclosure provides for methods of oxidizing carbide anions, or negative ions, from salt like carbides at low temperatures below about 600 C. Oxidization means that the ion being oxidized gives up electrons. The negative ions of the salt like carbides are reacted to produce elemental carbon in its various allotropes, or crystal structures, with sp1, sp2, and/or sp3 hybridizations. In another aspect, the disclosure provides for reactions with intermediate transition metal carbides. In yet another aspect, the disclosure provides for a system of reactions where salt-like carbide anions and intermediate carbide anions are oxidized to produce pure carbon of various allotropes.

(2) The methodology described herein can be distinguished from previous reactions patented in 1919 for several reasons. For one, the reaction in equation (1) occurs at high temperatures of around 800 C. in previously known reaction mechanisms whereas the methodology described herein includes reactions at lower temperatures below around 600 C. Second, the reaction in equation (1) only produces graphite as a pure carbon product. Graphite is a crystalline allotrope of carbon with an sp2 hybridization. Until now, it was not recognized that such a reaction provides for a diamond with an sp3 hybridization, superconducting material with an sp1 hybridization, fullerenes, carbon nano tubes, or any of other forms of pure carbon. To this end, the disclosure differentiates from what was previously recognized in the art.

(3) In an aspect, the first step of the reaction system is to oxidize the carbide ions at low temperature below 600 C., but typically the reactions occur below 300 C. The reactions use low melting point salts, for example stannous chloride (SnCl.sub.2), that have melting points less than 280 C. as the reactants. The reaction medium is the molten salt, for example, molten stannous chloride. This means that there is an excess of salt during the reaction which takes place in the molten salt liquid. Chemically, the cation (positive ion) of the salt is reduced to the elemental state. Therefore, stannous ion Sn.sup.+2 would become elemental tin (Sn.sup.o). The standard reduction potential of the stannous ion Sn.sup.+2 is only about 0.136V. Reduction potential refers to the ability of a chemical species to acquire electrons and thus have its charge reduced. So not much energy is required to reduce the stannous ion, therefore the reaction reacts to completion. There is an excess of reduction potential in the carbide anions since they are shown to reduce the potassium ion in Equation (1) which requires 2.94V.

(4) The reduction of Sn.sup.+2 by acetylide or any carbide anion is not mentioned anywhere in the literature. Only certain metallic salts are applicable for this reaction. It is preferred that the cation of the salt does not produce a carbide by direct reaction with carbon at low temperatures or the temperature of the reduction reaction. If the cation does produce carbide, then pure carbon would not be produced. Examples of the preferred salts contain tin, lead, mercury, and zinc. Furthermore, the salts must have a low melting point. The temperature of the reaction must be high enough to melt the salts but low enough to control the electronic hybridization of the carbon. As mentioned in the background information, graphite is the most thermodynamically stable form of pure carbon. So if the temperature of the reaction is too high, the pure carbon will form crystalline graphite in the sp2 hybridization instead of the desired sp1 or sp3 hybridizations.

(5) The next item in the reaction system is the low temperature oxidation of methanides to produce diamond, or carbon in that has an sp3 hybridization. Aluminum carbide (Al.sub.4C.sub.3) and beryllium carbide (Be.sub.2C) are the only two known salt like carbides that produce methane when they react with water. The methane molecule contains a carbon atom in the sp3 hybridized state, which is the same as diamond. The idea is to oxidize the methanide anion in a controlled manner at temperatures low enough to maintain the electronic configuration, or sp3 hybridization and produce diamond. Thus, the controlled oxidization of aluminum carbide at low enough temperatures will preferentially produce diamonds. This reduction takes place at about 280 C. and atmospheric pressure.

(6) Oxidation of the methanide (aluminum carbide) anion in molten tin halide salt blends to produce diamond. There is no literature that mentions the reduction of aluminum carbide much less anything that mentions this reaction to produce diamond, or sp3 hybridized carbon. Experiments for this reaction have been carried out using stannous fluoride (SnF.sub.2) and stannous chloride (SnCl.sub.2), which have melting points of 214 C. and 235 C., respectively. These reactions can be seen in Equation (2) and Equation (3) below:
Equation 2
Al.sub.4C.sub.3+6SnF.sub.26Sn.sup.o+4AlF.sub.3+3C.sup.o.sub.(diamond) reaction at T=235 C.(2)
Equation 3
Al.sub.4C.sub.3+6SnCl.sub.26Sn.sup.o+4AlCl.sub.3+3C.sup.o.sub.(diamond) reaction at T=280 C.(3)
The proof of the diamond, or carbon with sp3 hybridization, material produced was established using X-Ray Diffraction patterns (XRD) both at WVU and independently at Wright Patterson Air Force Base. Early diamond production studied certain metallic catalysts needed to make diamonds. These catalysts gave similar XRD patterns to diamonds which caused some confusion. However, no metallic catalysts or catalysts of any kind were used in this system of reactions. The fact that diamonds were produced was unexpected and provides support for the experiments described herein.

(7) Since the chemical hypothesis to maintain the sp3 hybridization of pure carbon is confirmed with the production of diamonds, it can extended to include the potential superconducting material to maintain the sp1 hybridization of pure carbon. From the literature, there have been many different attempts to make this material but none have been successful. The process begins with a carbide that contains carbon in an sp1 hybridized state. As mentioned in the background information, acetylides have the ability to satisfy this requirement. The most common example is calcium carbide (CaC.sub.2). However, sp1 carbon in the acetylide anion can be reconfigured even at very low energy or low temperatures. A more desired reactant is one that has a tendency to maintain the sp1 configuration throughout the rigors of the reaction. The disclosure provides for two compounds that have the ability to act as a sufficient reactant: magnesium sesquicarbide (Mg.sub.2C.sub.3) and lithium sesquicarbide (Li.sub.4C.sub.3), also mentioned in the background information. From the literature, a structural analysis using X-Ray diffraction was completed and shows that two of the carbon atoms are equivalent with an sp1 configuration. With a hydrolysis reaction, methyl acetylene (CH.sub.3C.sub.2H) is produced. One terminal carbon, the methyl carbon (CH.sub.3) end is sp3 in nature while the other two carbons maintain their sp1 character. The goal is to polymerize the carbon atoms while maintaining the sp1 configuration. This would produce a completely new allotrope of carbon that has an sp1 configuration. Due to the electronic properties of such a material, it may be a high temperature superconductor. Based on the literature, this approach has never been attempted.

EXAMPLES

Example 1

(8) In an oxygen moisture free environment, aluminum carbide, Al.sub.4C.sub.3 was ground to less than 20 mesh. A quantity of anhydrous stannous chloride, SnCl.sub.2 was blended with the ground aluminum carbide at twice the stoichiometric ratio for the reaction below
Al.sub.4C.sub.3+6SnCl.sub.2.fwdarw.AlCl.sub.3+6Sn+3C
The blend was poured into a glass ampoule that was subsequently placed into a stainless steel tube. The stainless steel tube was sealed and removed from the controlled environment. The tube and its contents were heated to 280 C. for 2 hours. The contents of the ampoule were washed with 6M HCl to remove all the aluminum chloride, excess stannous chloride and Sn metal. The remaining carbon was in two forms (1) a graphene like compressed set of platelets and (2) a cubic/orthorhombic diamond like structure. The preponderance of the carbon product was the latter structure.

Example 2

(9) In an oxygen moisture free environment, calcium carbide, CaC.sub.2 was ground to less than 20 mesh. A quantity of anhydrous zinc chloride, ZnCl.sub.2 was blended with the ground aluminum carbide at twice the stoichiometric ratio for the reaction below
3CaC.sub.2+3ZnCl.sub.2.fwdarw.3CaCl.sub.2+3Zn+6C
The blend was poured into a glass ampoule that was subsequently placed in a stainless steel tube. The stainless steel tube was sealed and removed from the controlled environment. The tube and its contents were heated to 425 C. for 2 hours. The contents of the ampoule were washed with 6M HCl to remove all the Zinc chloride, calcium chloride, and Zn metal. The remaining carbon was in two forms (1) a graphene like compressed set of platelets and (2) a cubic/orthorhombic diamond like structure. The preponderance of the carbon product was the latter structure.

Example 3

(10) In an oxygen moisture free environment, calcium carbide, CaC.sub.2 was ground to less than 20 mesh. A quantity of anhydrous stannous chloride, SnCl.sub.2 was blended with the ground aluminum carbide at twice the stoichiometric ratio for the reaction below
3CaC.sub.2+3SnCl.sub.2.fwdarw.3CaCl.sub.2+3Sn+6C
The blend was poured into a glass ampoule that was subsequently placed in a stainless steel tube. The stainless steel tube was sealed and removed from the controlled environment. The tube and its contents were heated to 280 C. for 2 hours. The contents of the ampoule were washed with 6M HCl to remove all the stannous chloride, calcium chloride, and Sn metal. The remaining carbon was in only one form a graphene like compressed set of platelets