WO2024147021A1

WO2024147021A1 - A thermochemical process using heterogeneous catalysts for the production of nanocrystalline carbon materials

Info

Publication number: WO2024147021A1
Application number: PCT/IB2022/061917
Authority: WO
Inventors: Rungkiat NGANGLUMPOON
Original assignee: Crystallyte Co., Ltd.
Priority date: 2023-01-05
Filing date: 2023-01-05
Publication date: 2024-07-11
Also published as: WO2024147021A8

Abstract

A new process for producing a nanocrystalline carbon with a 1D, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof, by thermochemically reducing an oxygenic carbon source at an atmospheric pressure and an onset temperature within the range of 25 – 100 °C in presence of (a) an ionic solution comprising a solvent and an ionic salt, and (b) metallic cations acting as a homogeneous catalyst. The atmospheric pressure and the low onset temperature enabled by embodiments simplify the production, and the nanocrystalline carbon yield can be scaled up to reach a mass production scale. A product obtained from the new process comprises a nanocrystalline carbon with a 1D, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal. Such product can be a mixture that contains various carbon structures, comprising: a nanocrystalline diamond, an amorphous carbon, a graphitic carbon, and a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal. Said product may further comprise a graphite or a graphene.

Description

TITLE OF THE INVENTION

A THERMOCHEMICAL PROCESS USING HETEROGENEOUS CATALYSTS FOR THE PRODUCTION OF NANOCRYSTALLINE CARBON MATERIALS

FIELD OF INVENTION

The present disclosure relates to the production of a carbon nanomaterial, including a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or transition metal, and/or a mixture thereof, particularly when said production of carbon nanomaterials involves homogeneous catalytic thermochemical reduction.

BACKGROUND OF THE INVENTION

Several industries see a high demand for a carbon nanomaterial, including a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or transition metal, and/or a mixture thereof. Said demand arises from both the material’s excellent properties and the lack of a production process that is cost-effective and scalable.

Against such requirements, the current state of the art suggests that catalytic thermochemical reduction of an oxygenic carbon source is a promising production route for carbon nanomaterial. Its simple construction and straightforward operation are key factors for such recognition.

Nevertheless, catalytic thermochemical processes in the arts have major downsides: a high reaction temperature and the limitation of mass transfer. High reaction temperature leads to high energy consumption and costs; limitation of mass transfer hampers the production rate. Both downsides are more substantial in an upscaled process.

International patent publication No. WO 2000/017102 A 1 discloses a process of catalytic thermochemical reduction of carbon monoxide and ethylene (both are oxygenic carbon sources) into single wall carbon nanotubes. This process uses a transition metal as a heterogeneous catalyst at the temperature in the range of 700 - 850 °C, and thus requires high energy.

Similarly, the US patent publication No. US 2005/0079118 Al discloses a catalytic thermochemical process that converts an oxygenic organic carbon source into single wall carbon nanotubes using a solid metal as a heterogeneous catalyst. The process still requires an operating temperature of 500 - 1,500 °C, which is achievable only by consuming high thermal energy.

Alternatively, some prior arts adopt thermochemical processes with homogeneous catalysts to reduce the necessary operating temperature. Examples include Dai et. al. [Dai 2021], which reports the use of homogeneous catalyst to synthesize a wide range of known carbon nanostructures from the reaction between KOH and ethanol. A process according to Dai 2021 achieves said synthesis at a room temperature, albeit at the great expense of the reaction rate: the synthesis takes several days to complete, and the yields are unsatisfactorily low.

Accordingly, it is necessary to provide new method for producing carbon nanomaterials which not only addresses the energy consumption problem, but also mitigates the limitations and trade-offs arising in the prior arts.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a new process for industrially producing a carbon nanomaterial. The inventor has found that embodiments according to the concept of the present invention enable the production of such products at a significantly less energy-intensive condition, as well as satisfactory yield and reaction time.

In the first aspect, the present invention provides a new process for producing a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. Said process comprises thermochemically reducing an oxygenic carbon source at an atmospheric pressure and an onset temperature within the range of 25 - 100 °C in presence of (a) an ionic solution comprising a solvent and an ionic salt, and (b) metallic cations acting as a homogeneous catalyst.

Said range of the onset temperature, which simplifies the production, is an effect that distinguishes a process in accordance with the present invention from the currently available ones. The metal -carbon nanomaterial composite product yield per a single run of an embodiment, which depends on the type of metallic cation catalyst and the carbon source, the concentration of metallic cation catalyst, and the reaction time of a batch, is approximately 10 - 100 g-L^-h"¹. Such yield is conducive to the scale-up to a mass production scale.

Preferably, said metallic cations are transition metal cations or post-transition metal cations. Also preferably, the concentration of said metallic cations is within the range of 0.001 - 0.1 M. Also preferably, said transition metal cations are Ag (I) cations and said post-transition metal cations are Bi (III) cations. In an embodiment, the metallic cations are derived from a precursor, the precursor for Ag (I) cations being AgNO? and the precursor for Bi (III) cations being Bi (NOs -

In an embodiment, said oxygenic carbon source is dissolved in the solvent. In such case, it is preferable that said oxygenic carbon source is dissolved in the solvent at the concentration within the range of 0. 1 - 10 M.

In another embodiment, said solvent is a polar solvent. In such case, it is preferable that said polar solvent is water. Also in such case, it is preferable that said oxygenic carbon source is water-soluble. Also in such case, it is preferable that said oxygenic carbon source is water- soluble. More preferably, said oxygenic carbon source is (i) an oxygenic organic compound or (ii) a carbonate salt, a bicarbonate salt or a mixture thereof.

In an embodiment where the oxygenic carbon source is an oxygenic organic compound, it is even more preferable that such oxygenic organic compound is a carboxylic acid, an alcohol, a ketone, an aldehyde, or a carbamate.

In an embodiment where the oxygenic organic compound is a carboxylic acid, it is most preferably acetic acid. In an embodiment where the oxygenic organic compound is an alcohol, it is most preferably ethanol. In an embodiment where the oxygenic organic compound is a ketone, it is most preferably acetone. In an embodiment where the oxygenic organic compound is an aldehyde, it is most preferably acetaldehyde. In an embodiment where the oxygenic organic compound is a carbamate, said carbamate is preferably prepared by saturating a primary amine aqueous solution with CO2; and in such embodiment, it is most preferred that the primary amine is mono ethanolamine and/or that the concentration of the primary amine aqueous solution is within the range of 0. 1 - 10 M.

In an embodiment where the oxygenic carbon source is or involves a carbonate salt, the carbonate salt is most preferably Na2CC>3. In an embodiment where the oxygenic carbon source is or involves a bicarbonate salt, the bicarbonate salt is most preferably NH4HCO3.

The carbonate salt is preferably prepared by saturating an aqueous solution of a strong base with CO2. In such embodiment, most preferably the strong base is KOH; also most preferably, the strong base’s concentration in the aqueous solution is within the range of 0.1 - 10 M.

The bicarbonate salt is preferably prepared by saturating an aqueous solution of a tertiary amine, or by saturating an ammonia aqueous solution, with CO2.

More preferably, the tertiary amine is dimethylethanolamine (DMAE); also more preferably, the tertiary amine’s concentration in the aqueous solution is within the range of 0. 1 - 10 M.

Also more preferably, the ammonia’s concentration in the aqueous solution is within the range of 0.1 - 10 M.

Preferably, the ionic salt comprises a cation selected from ammonium cation, imidazolium cation, and a mixture thereof. Preferably, said ammonium cation is ammonium cation (NEU⁺) and choline cation. Preferably, said imidazolium cation is l-butyl-3- methylimidazolium ([bmim]).

Preferably, the anion of said ionic salt is selected from the group comprising tetrafluoroborate (BEp), hexafluorophosphate (PFr>“). halides (O’, Br, F", I"), hexafluoroantimonate (SbFr,-)- sulfate (SO4² )- and nitrate (NO<)-

The most preferable ionic salts are: l-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]) or ammonium sulfate ((NFU^SCh) or choline chloride.

Preferably, the concentration of said ionic salt in the ionic solution is within the range of 0.1 - 10 M.

Preferably, H2O2, Fe (II) ion or Sn (II) ion is added to the ionic solution.

In the second aspect, the present invention provides a process for producing a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof. Said process comprises steps of: (i) thermochemically reducing an oxygenic carbon source in presence of (a) an ionic solution, and (b) metallic cations homogeneously dissolved in said ionic solution and acting as a homogeneous catalyst; and (ii) stirring said ionic solution. Said ionic solution comprises a mixture of (a) l-butyl-3 -methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate ((NFU SCF) or choline chloride, and (b) water. Said thermochemically reducing the oxygenic carbon source occurs at an atmospheric pressure and an onset temperature within the range of 25 - 100 °C. The above step of (ii), stirring the ionic solution, may be carried out before or during the thermochemical reduction and may be carried out continuously or intermittently. Preferably, the ionic solution is stirred continuously during the thermochemical reduction.

Accordingly, the present disclosure provides examples to illustrate the conditions of such processes and the characteristic properties of such products. The preferred embodiments will be described in detail later on.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows a schematic diagram of a thermochemical reactor for thermochemically reducing an oxygenic carbon source in accordance with a preferred embodiment (not to scale).

Fig. 2A shows a Raman spectrum exhibiting merged peaks of a product of Example 1.

Fig. 2B shows a matching of d-spacing, as obtained from Selected Area Electron Diffraction (SAED), of the product of Example 1.

Fig. 2C shows a first Transmission Electron Microscopy (TEM) image of the product of Example 1.

Fig. 2D shows a second Transmission Electron Microscopy (TEM) image of the product of Example 1.

Fig. 2E shows Energy Dispersive X-ray (EDX) peaks of the product of Example 1.

Fig. 3A shows a Raman spectrum exhibiting merged peaks of a product of Example 2.

Fig. 3B shows a matching of d-spacing, as obtained from Selected Area Electron Diffraction (SAED), of the product of Example 2.

Fig. 3C shows a first Transmission Electron Microscopy (TEM) image of the product of Example 2.

Fig. 3D shows a second Transmission Electron Microscopy (TEM) image of the product of Example 2.

Fig. 3E shows Energy Dispersive X-ray (EDX) peaks of the product of Example 2.

Fig. 4 shows a Raman spectrum exhibiting merged peaks of a product of Example 3.

Fig. 5 shows a Raman spectrum exhibiting merged peaks of a product of Example 4.

Fig. 6 shows a Raman spectrum exhibiting merged peaks of a product of Example 5.

Fig. 7 shows a Raman spectrum exhibiting merged peaks of a product of Example 6.

Fig. 8 shows a Raman spectrum exhibiting merged peaks of a product of Example 7.

Fig. 9 shows a Raman spectrum exhibiting merged peaks of a product of Example 8.

Fig. 10 shows a Raman spectrum exhibiting merged peaks of a product of Example 9. Fig. 11 shows a Raman spectrum exhibiting merged peaks of a product of Example 10.

Fig. 12 shows a Raman spectrum exhibiting merged peaks of a product of Example 11.

Fig. 13 shows a Raman spectrum exhibiting merged peaks of a product of Example 12.

Fig. 14 shows a Raman spectrum exhibiting merged peaks of a product of Example 13.

Fig. 15 shows a Raman spectrum exhibiting merged peaks of a product of Example 14.

Fig. 16A shows a Raman spectrum exhibiting merged peaks of a product of Example 15.

Fig. 16B shows a matching of d-spacing, as obtained from Selected Area Electron Diffraction (SAED), of the product of Example 15.

Fig. 16C shows a first Transmission Electron Microscopy (TEM) image of the product of Example 15.

Fig. 16D shows a second Transmission Electron Microscopy (TEM) image of the product of Example 15.

Fig. 16E shows Energy Dispersive X-ray (EDX) peaks of the product of Example 15.

Fig. 17 shows a Raman spectrum exhibiting merged peaks of a product of Example 16.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

It is to be understood that the following detailed description will be directed to embodiments, provided as examples for illustrating the concept of the present invention only. The present invention is in fact not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of this invention will be limited only by the appended claims.

The detailed description of the invention is divided into various sections only for the reader’s convenience and disclosure found in any section may be combined with that in another section.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

The term “about” when used before a numerical designation, e.g., dimensions, time, amount, and such other, including a range, indicates approximations which may vary by ( + ) or ( - ) 10 %, 5 % or 1 %, or any sub-range or sub-value there between. “Comprising” or “comprises” is intended to mean that the compositions and processes include the recited elements, but not excluding others. “Consisting essentially of’ when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination for the stated purpose. Thus, a process or product consisting essentially of the elements as defined herein would not exclude other materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consisting of’ shall mean excluding more than trace elements of other ingredients and substantial steps. Embodiments defined by each of these transition terms are within the scope of this invention.

“Oxygenic carbon source” is intended to mean a mono-molecular compound or an ionic compound containing both carbon and oxygen atoms.

“Oxygenic organic compound” is intended to mean a mono-molecular organic compound having an oxygen atom.

Thermochemical reactor

Fig. 1 shows a schematic diagram of a thermochemical reactor in which a process for producing a carbon nanomaterial is conducted in accordance with a preferred embodiment. The thermochemical reactor (10) comprises a receptacle (100), a heating element (200), a stirrer (300), and a vent (400). The receptacle (100) contains an ionic solution (110) in which metallic cations are present and act as a homogeneous catalyst. The ionic solution (110) is a mixture of an ionic salt and a solvent in which an oxygenic carbon source is dissolved. The heating element (200), the source of thermal energy, is preferably connected to the lower part or the bottom of the receptacle (100) and configured to heat the ionic solution (110). The stirrer (300) is preferably disposed so as to immerse in the ionic solution (110) and configured to disperse the metallic cations in the ionic solution (110). In this preferred embodiment, the stirrer (300) takes the form of a propeller having a shaft (310), an end of which is connected to multiple blades (320), and another end of which, to a motor (330). The shaft (310) is disposed substantially vertically so that the blades (320) are effectively immersed in the ionic solution (110) and the motor (330) is located away from the ionic solution (110). The vent (400), through which the gaseous byproducts leave the receptacle (100), is preferably located at the top of the receptacle (100).

Oxygenic carbon source

In the present invention, the carbon source is an oxygenic carbon source. Preferably, a water-soluble oxygenic carbon source is used. Preferably, the oxygenic carbon source is a carbonate salt or a bicarbonate salt. Preferred carbonate and bicarbonate salts include: Na2CO and NH4HCO3. The carbonate salt is prepared by saturating an aqueous solution of a strong base with CO2. The bicarbonate salt is prepared by saturating (i) an ammonia aqueous solution or (ii) an aqueous solution of a tertiary amine, with CO2. More preferably, the concentration of the strong base, ammonia, or the tertiary amine, in their respective aqueous solution, is within the range of 0.1 - 10 M. Also preferably, the oxygenic carbon source is an oxygenic organic compound. Preferred oxygenic organic compounds include: an alcohol, carboxylic acid, ketone, aldehyde, and carbamate. Preferably, the carbamate is prepared by saturating primary amine aqueous solution with CO2. More preferably, the primary amine is mono ethanolamine and/or the concentration of the primary amine aqueous solution is within the range of 0.1 - 10 M. In addition, the oxygenic carbon source may be supplied to the ionic solution in any desired form, for example, in the solid, liquid, gaseous, or solvated form, depending on the phase stability at the operating temperature and pressure. Preferably, the oxygenic carbon source is dissolved in the ionic solution (i.e., supplied in the solvated form).

Pressure

A process according to the concept of the present invention may be carried out in various conditions which may be adjusted according to the circumstantial requirements. The applicable pressure is within the range of about 1 to about 20 atm.

The pressure in accordance with the preferred embodiment is an ambient pressure. The ambient pressure refers to a common or usual condition surrounding any person in a room. An ambient pressure for operating the process is preferably 1 atm. Because a process in accordance with the preferred embodiment allows the catalytic thermochemical reduction to occur effectively at such ambient pressure, it obviates the need to pressurize, depressurize, vacuumize or control the pressure at any part of the thermochemical reactor (10) and thus substantially simplifies the production.

Onset temperature

Generally, the onset temperature of the thermochemical reactor (10) is at least of the thermal energy sufficient to initiate the catalytic thermochemical reduction of the oxygenic carbon source. Preferably, the onset temperature in the ionic solution (110) is substantially constant during the catalytic thermochemical reduction.

The onset temperature of the thermochemical reactor (10) depends on the carbon source and the metallic cations being selected. In an embodiment, the thermochemical reactor (10) comprises a heating element (200) to provide the onset temperature, which is preferably within the range of about 25 to about 100 °C. Preferably, the heating element (200) is adapted to monitor and control the onset temperature. In the following Examples, the catalytic thermochemical reduction occurred in an autoclave which is capable of both monitoring and regulating the onset temperature. The autoclave is commonly used as an industry-scale thermochemical reactor, which is applicable to the concept of the present invention.

Ionic solution

According to the concept of the present invention, the ionic solution (110) comprises a solvent and an ionic salt. Preferably, the solvent is a polar solvent, and more preferably is water.

According to the concept of the present invention, all known ionic salts may be part of the mixture that forms the ionic solution (110). Preferably, the ionic salts in an embodiment are compounds represented by Formula (I):

[A]n⁺ [Y]_n- - (I) wherein: n is 1 or 2;

[Y]_n‘ is selected from the group comprising tetrafluoroborate ([BF4]"), hexafluorophosphate ([ PFr, ]’), halides (C1‘, Br, F", I"), hexafluoroantimonate ([ SbFr, ]’), sulfate ([SO ’]), and nitrate ([NCh]’);

[A]⁺ is selected from —

(a) the group comprising ammonium cations represented by Formula (II):

R¹, R², R³, and R⁴ being selected from hydrogen atom, Cl-C6-alkyl, Cl-C6-alkoxy, Cl- C6-aminoalkyl, Cl-C6-hydroxylalkyl, C5-C12-aryl, and C5-C12-aryl-Cl-C6-alkyl groups; and

(b) the group comprising imidazolium cations represented by Formula (III):

R, R¹, and R² being selected from Cl-C6-alkyl, Cl-C6-alkoxy, Cl-C6-aminoalkyl, C5- C12-aryl, and C5-C12-aryl-Cl-C6-alkyl groups.

The preferred combination of the ionic salt, the oxygenic carbon source, and water is as follows: (a) the ionic salt being a mixture of l-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate((NH4)2SC>4), or choline chloride, (b) an oxygenic carbon source, and (c) water.

In some embodiments, the ionic salt also functions as a stabilizer of nanoparticles/carbon nanomaterial formed during the catalytic thermochemical reduction of the oxygenic carbon source in the thermochemical reactor (10). Preferably, the ionic salt is selected from ([bmim][BF4]), (NFU^SCh, and choline chloride.

Metallic cations

According to an embodiment, metallic cations act as a homogeneous catalyst for the catalytic thermochemical reduction.

Preferably, the metallic cations are transition metal cations or post-transition metal cations. More preferably, the transition metal cations are Ag (I) cations, and the post-transition metal cations are Bi (III) cations. Preferably, the metallic cations are derived from a precursor. More preferably, the precursor for Ag (I) cations is AgNO v and the precursor for Bi (III) cations is Bi(NO3)3.

Preferably, the concentration of the metallic cations in the ionic solution is within the range of 0.001 - 0.1 M.

Reaction time

According to an embodiment, the catalytic thermochemical reduction occurs in the thermochemical reactor (10) as a batch operation. The crystal structure and size of the resulting product depends on the nature of metallic cations and carbon source used, the energy supplied, and the reaction time, among others. A longer reaction time results in a larger crystallite size.

According to the embodiments, the reaction time for each batch of production can be ranged from about 5 minutes to 150 minutes. Preferably, the reaction time for each batch of production is about 15 minutes to 75 minutes. Nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof

In a preferred embodiment, the process for producing a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or mixture thereof in the thermochemical reactor (10) is a batch operation.

The nanocrystalline carbon with the ID, 2D, or 3D structure and/or the nanocrystalline diamond and/or the amorphous carbon and/or the metal-carbon nanomaterial composite, said composite containing a post-transition metal or transition metal, and/or the mixture thereof, is formed and precipitated, along with the metallic particles formed of the metallic cations, in the ionic solution (110).

The carbon product obtained from a process in accordance with a preferred embodiment comprises a graphite and/or a graphene and/or a graphitic carbon and/or the nanocrystalline diamond and/or the amorphous carbon, and/or the metal-carbon nanomaterial composite, said composite containing the post-transition metal or the transition metal, and/or the mixture thereof.

In some embodiments, the carbon product being produced is further separated from said metallic particles by a known separation process. Preferably, said separation process is a mechanical removal process, such as mechanical abrasion, or ultrasonication.

After being separated from metallic particles, the carbon product may contain metallic material residues, which can be further removed from the carbon product by means of a conventional chemical removal process, preferably acid leaching. Preferably, said acid leaching involves the use of nitric acid (HNO3), hydrochloric acid (HC1), or their mixture.

In some embodiments, the separation process of the carbon product from the metallic particles comprises the following steps:

(1) mechanically removing the solid product from the metallic particles

(2) placing the solid product that was removed by step (1) in a microcentrifuge tube

(3) slowly dropping a mixture of nitric acid and hydrochloric acid into the microcentrifuge tube to perform acid leaching. Preferably, the mixture of nitric acid and hydrochloric acid is in a molar ratio of 1:3 in 0.3 ml of the solution

(4) shaking the solution before ultrasonicating the solution for approximately 5 minutes

(5) centrifuging the solution to separate the solid product from the solution (6) collecting the solid product and neutralizing the solid product with deionized water (DI water). Preferably, the neutralization is conducted three times.

The abovementioned process results in a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon product and/or a metal- carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof, which is a mixture having various carbon structures. Said structures are inclusive of, and selectable from: an amorphous carbon, a graphite, a graphene, a nanocrystalline diamond, and a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal.

Examples of embodiments

In the sixteen Examples carried out for the preferred embodiment, the following applies: Catalytic thermochemical reductions took place in a batch thermochemical reactor. The thermochemical reactor (10) further contained the ionic solution (110), the onset temperature of which was generated and measured by the heating element (200). The ionic solution (110) was dispersed with the metallic cations and stirred by the stirrer (300) at the agitation rate of 10 - 1,000 rpm. The reaction was carried out under a pressure of about 1 atm. After the reaction time, the carbon nanomaterial product was formed and precipitated along with the metallic particles (the latter being formed by the reduction of said metallic cations). Said precipitation was then removed from the ionic solution (110) and dried.

Some oxygenic carbon sources were directly mixed with and dissolved in the ionic solution (110). Other oxygenic carbon sources were prepared by saturating the ionic solution (110) with carbon dioxide gas (CO2) at ambient conditions. More particularly, where the oxygenic carbon source was a carbonate salt, the ionic solution (110) contained KOH (a strong base); where the oxygenic carbon source was a bicarbonate salt, the ionic solution (110) contained ammonia or dimethylethanolamine (a tertiary amine); where the oxygenic carbon source was a carbamate, the ionic solution (110) contained mono ethanolamine (a primary amine). The flow rate of CO2 per volume of the ionic solution (110) was within the range of 0.04 - 40 cm³ CCh/cm³ ionic solution per minute. The CO2 purging time was within 1-1,000 minutes.

Table 1 in the next sheet shows the particulars of Examples 1-16. Description of the product obtained from each Example shall follow Table 1.

Example 1 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. Fig. 2A shows the Raman spectrum of the product of Example 1. Moreover, the Selected Area Electron Diffraction (SAED) analysis revealed the lattice spacing of said product as 0.238, 0.204, 0.144, 0.122, 0.094, 0.092, and 0.083 nanometer (nm) which, as shown in Fig. 2B, matched the lattice spacing references of cubic silver and graphite. Next, images from the Transmission Electron Microscopy (TEM) are shown in Figs. 2C and 2D. Finally, the peaks from Energy Dispersive X-ray (EDX) analysis, shown in Fig. 2E, revealed the following atomic percentages of said product: 13.4 % carbon; 9.41 % copper; and 77.19 % silver. All the foregoing results confirmed that the product of Example 1 comprised graphitic carbon and amorphous carbon structures

Example 2 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. Fig. 3A shows the Raman spectrum of the product of Example 2. Moreover, the Selected Area Electron Diffraction (SAED) analysis revealed the lattice spacing of said product as 0.234, 0.205, 0.197, 0.145, 0.125, and 0.119 nanometer (nm) which, as shown in Fig. 3B, matched the lattice spacing references of cubic silver, hexagonal diamond, and graphite. Next, images from the Transmission Electron Microscopy (TEM) are shown in Figs. 3C and 3D. Finally, the peaks from Energy Dispersive X-ray (EDX) analysis, shown in Fig. 3E, revealed the following atomic percentages of said product: 18.34 % carbon; 1.09 % oxygen; 17.37 % copper; and 63.19 % silver. All the foregoing results confirmed that the product of Example 2 comprised nanocrystalline diamond, comprising hexagonal diamond, graphitic carbon, and amorphous carbon structures.

Example 3 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 4, as observed from the shown Raman spectrum, the carbon product obtained from Example 3 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 4 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 5, as observed from the shown Raman spectrum, the carbon product obtained from Example 4 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 5 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 6, as observed from the shown Raman spectrum, the carbon product obtained from Example 5 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures. Example 6 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 7, as observed from the shown Raman spectrum, the carbon product obtained from Example 6 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 7 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 8, as observed from the shown Raman spectrum, the carbon product obtained from Example 7 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 8 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 9, as observed from the shown Raman spectrum, the carbon product obtained from Example 8 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 9 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 10, as observed from the shown Raman spectrum, the carbon product obtained from Example 9 comprised graphitic carbon and amorphous carbon structures.

Example 10 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 11, as observed from the shown Raman spectrum, the carbon product obtained from Example 10 comprised graphitic carbon and amorphous carbon structures.

Example 11 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 12, as observed from the shown Raman spectrum, the carbon product obtained from Example 11 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 12 produced a metal -carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 13, as observed from the shown Raman spectrum, the carbon product obtained from Example 12 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures.

Example 13 produced a metal -carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 14, as observed from the shown Raman spectrum, the carbon product obtained from Example 13 comprised nanocrystalline diamond, graphitic carbon, and amorphous carbon structures. Example 14 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 15, as observed from the shown Raman spectrum, the carbon product obtained from Example 14 comprised graphitic carbon and amorphous carbon structures.

Example 15 produced a metal-carbon composite product in the form of metallic Bi/Bi oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. Fig. 16A shows the Raman spectrum of the product of Example 15. Moreover, the Selected Area Electron Diffraction (SAED) analysis revealed the lattice spacing of said product as 0.344, 0.222, 0.194, 0. 169, 0. 154, and 0.124 nanometer (nm) which, as shown in Fig. 16B, matched the lattice spacing references of graphite. Next, images from the Transmission Electron Microscopy (TEM) are shown in Figs. 16C and 16D. Finally, the peaks from Energy Dispersive X-ray (EDX) analysis, shown in Fig. 16E, revealed the following atomic percentages of said product: 81.21 % carbon; 10.3 % oxygen; 0.92 % tin; and 7.57 % bismuth. All the foregoing results confirmed that the product of Example 15 comprised graphitic carbon and amorphous carbon structures.

Example 16 produced a metal-carbon composite product in the form of metallic Ag/Ag oxides and nanocrystalline carbon with a ID, 2D, and 3D structure. According to Fig. 17, as observed from the shown Raman spectrum, the carbon product obtained from Example 16 comprised graphitic carbon and amorphous carbon structures.

Reference

[Dai 2021] Room-temperature synthesis of various allotropes of carbon nanostructures (graphene, graphene polyhedra, carbon nanotubes and nano-onions, n-diamond nanocrystals) with aid of ultrasonic shock using ethanol and potassium hydroxide, Dai et al., Carbon, 2021, 179, pp 133 - 141.

List of Drawing References

10 thermochemical reactor

100 receptacle

110 ionic solution

200 heating element

300 stirrer

310 shaft

320 blade motor vent power supply

Claims

1. A process for producing a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof, by thermochemically reducing an oxygenic carbon source at an atmospheric pressure and an onset temperature within the range of 25 - 100 °C in presence of (a) an ionic solution comprising a solvent and an ionic salt, and (b) metallic cations acting as a homogeneous catalyst.

2. The process according to claim 1, wherein said metallic cations are transition metal cations or post-transition metal cations.

3. The process according to claim 1, wherein the concentration of said metallic cations is within the range of 0.001 - 0. 1 M.

4. The process according to claim 2, wherein said transition metal cations are Ag (I) cations and said post-transition metal cations are Bi (III) cations.

5. The process according to claim 4, wherein the metallic cations are derived from a precursor, the precursor for Ag (I) cations being AgNCh and the precursor for Bi (III) cations being Bi (NCh .

6. The process according to claim 1, wherein said oxygenic carbon source is dissolved in the solvent.

7. The process according to claim 6, wherein said oxygenic carbon source is dissolved in the solvent at the concentration within the range of 0. 1 - 10 M.

8. The process according to claim 1, wherein said solvent is a polar solvent.

9. The process according to claim 8, wherein said polar solvent is water.

10. The process according to claim 1, said oxygenic carbon source is water-soluble.

11. The process according to claim 10, wherein the oxygenic carbon source is an oxygenic organic compound.

12. The process according to claim 11, wherein the oxygenic organic compound is a carboxylic acid.

13. The process according to claim 12, wherein the oxygenic organic compound is acetic acid.

14. The process according to claim 11, wherein the oxygenic organic compound is an alcohol.

15. The process according to claim 14, wherein the oxygenic organic compound is ethanol.

16. The process according to claim 11, wherein the oxygenic organic compound is a ketone.

17. The process according to claim 16, wherein the oxygenic organic compound is acetone.

18. The process according to claim 11, wherein the oxygenic organic compound is an aldehyde.

19. The process according to claim 18, wherein the oxygenic organic compound is acetaldehyde.

20. The process according to claim 11, wherein the oxygenic organic compound is a carbamate.

21. The process according to claim 20, wherein the carbamate is prepared by saturating a primary amine aqueous solution with CO2.

22. The process according to claim 21, wherein the primary amine is mono ethanolamine.

23. The process according to claim 21, wherein the concentration of the primary amine aqueous solution is within the range of 0.1 - 10 M.

24. The process according to claim 10, wherein the oxygenic carbon source is a carbonate salt, a bicarbonate salt, or a mixture thereof.

25. The process according to claim 24, wherein the carbonate salt is Na2CC>3.

26. The process according to claim 24, wherein the bicarbonate salt is NH4HCO3.

27. The process according to claim 24, wherein the carbonate salt is prepared by saturating an aqueous solution of a strong base with CO2.

28. The process according to claim 27, wherein the strong base is KOH.

29. The process according to claim 27, wherein the concentration of the strong base in the aqueous solution is within the range of 0. 1 - 10 M.

30. The process according to claim 24, wherein the bicarbonate salt is prepared by saturating an aqueous solution of a tertiary amine with CO2.

31. The process according to claim 30, wherein the tertiary amine is dimethylethanolamine (DMAE).

32. The process according to claim 30, wherein the concentration of the tertiary amine in the aqueous solution is within the range of 0. 1 - 10 M.

33. The process according to claim 24, wherein the bicarbonate salt is prepared by saturating an ammonia aqueous solution with CO2.

34. The process according to claim 33, wherein the concentration of the ammonia aqueous solution is within the range of 0. 1 - 10 M.

35. The process according to claim 1, wherein the ionic salt is a compound represented by Formula (I)

[A]n⁺ [Y]_n- - (I) wherein, n is 1 or 2;

[A]⁺ is selected from —

(a) the group comprising ammonium cations represented by Formula (II):

R¹, R², R³, and R⁴ being selected from hydrogen atom, Cl- C6-alkyl, Cl-C6-alkoxy, Cl-C6-aminoalkyl, C1-C6- hydroxylalkyl, C5-C12-aryl, and C5-C12-aryl-Cl-C6-alkyl groups; and

(b) the group comprising imidazolium cations represented by Formula (III):

R, R¹, and R² being selected from Cl-C6-alkyl, C1-C6- alkoxy, C1-C6 -aminoalkyl, C5-C12-aryl, and C5-C12-aryl-Cl- C6-alkyl groups.

36. The process according to claim 35, wherein the ionic solution contains the ionic salt at the concentration within the range of 0. 1 - 10 M.

37. The process according to claim 35, wherein said ionic salt is l-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]) or ammonium sulfate ((NH^SCh) or choline chloride.

38. The process according to claim 1, wherein H2O2, Fe (II) ion or Sn (II) ion is added to the ionic solution.

39. A process for producing a nanocrystalline carbon with a ID, 2D, or 3D structure and/or a nanocrystalline diamond and/or an amorphous carbon and/or a metal-carbon nanomaterial composite, said composite containing a post-transition metal or a transition metal, and/or a mixture thereof, said process comprising steps of: thermochemically reducing an oxygenic carbon source in presence of (a) an ionic solution (110), and (b) metallic cations homogeneously dissolved in said ionic solution (110) and acting as a homogeneous catalyst; and stirring said ionic solution (110), wherein said ionic solution (110) comprises a mixture of (a) l-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]), ammonium sulfate ((NFL^SCh) or choline chloride, and (b) water, and wherein said thermochemically reducing the oxygenic carbon source occurs at an atmospheric pressure and an onset temperature within the range 25 - 100 °C.