Method for sequestering a carbon-containing compound on particles having a graphitic surface of sp{1}2{2} carbon

Abstract

The invention proposes methods for recovering value from various organic compounds such as carbon dioxide or industrial plastic waste, implementing storage on particles having a graphitic carbon surface of predominantly sp2 type present in a weakly concentrated liquid medium. The invention proposes an application for energy generation by combustion of the solid compound.

Description

Description Title of the invention: Method for sequestration of a carbon compound on sp-carbon graphite-surfaced particles 2 Technical Field

[0001] This presentation concerns the sequestration of a carbon compound on particles having a predominantly sp-type graphitic carbon surface 2 , in particular on carbon nanotubes. The invention relates specifically to the sequestration of carbon contained in carbon dioxide, but is not limited to this aspect, as will be detailed later. According to one particular aspect, the invention proposes using the sequestered carbon as a fuel to provide energy. Previous technique

[0002] Carbon dioxide (COz) emissions are a major concern due to their impact on climate change. It would be desirable to develop new methods for capturing carbon dioxide that have a favorable carbon footprint and allow for its storage, particularly for later use as fuel for energy generation. A similar desire exists for utilizing industrial plastic waste, or pollutants present in the air or water.

[0003] The invention offers a solution to these problems. Description of the invention

[0004] This presentation relates, according to a first embodiment, to a process for sequestration of carbon contained in carbon dioxide, comprising: - a carboxylation or carbonation, for example carried out in a solution of a strong base, of an organic compound A by reaction with carbon dioxide to obtain an organic compound B, in which compound A is an alcohol having a carbon chain from C1 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, a polyalcohol having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkene having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a carbon chain from C2 to Cw, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an aromatic compound having a benzene ring, such as benzene or phenol, - an oligomerization or polymerization using compound B to obtain an oligomer O or a polymer P, - optionally a reduction of the carboxyl or carbonate group(s) present in the oligomer O or polymer P, and - Sequestration by contacting the oligomer O or the polymer P, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester the oligomer O or polymer P onto this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated by excluding the oligomer O or polymer P possibly reduced, of between 10 -5 % and 1%, preferably between 10 -4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

[0005] The present presentation relates, according to a second embodiment, to a process for sequestration of carbon contained in carbon dioxide, comprising: - a carboxylation or carbonation, for example carried out in a solution of a strong base, of an organic compound A by reaction with carbon dioxide to obtain an organic compound B, in which compound A is an alcohol having a carbon chain from C1 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, a polyalcohol having a carbon chain from C2 to Cw, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkene having a carbon chain from C2 to C, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a carbon chain from C2 to Cw, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an aromatic compound having a benzene ring, such as benzene or phenol, - optionally a reduction of the carboxyl or carbonate group(s) present in organic compound B, and - Sequestration by contacting the organic compound B, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester compound B on this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated excluding compound B, of between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

[0006] The present presentation relates, according to a third embodiment, to a process for sequestration of carbon contained in carbon dioxide, comprising: - an electrochemical reduction, preferably carried out in a solution of a strong base, of carbon dioxide so as to obtain a mixture of carbon compounds in the liquid phase, - a treatment of the mixture thus obtained including at least one of the following treatments: (1) dehydration of one or more alcohols present in the mixture to form one or more alkenes, (2) carbonylation of one or more alkenes present in the mixture by reaction with carbon monoxide, possibly produced during the electrochemical reduction of carbon dioxide, this carbonylation possibly being carried out in the presence of dihydrogen possibly produced during the electrochemical reduction of carbon dioxide, or (3) carboxylation or carbonation of one or more alkenes and / or one or more alcohols present in the mixture by reaction with carbon dioxide, - an oligomerization or polymerization of one or more carbon compounds present in the mixture thus treated in order to obtain at least one oligomer 01 or polymer PI, - optionally a reduction of the carboxyl or carbonate group(s) present in the oligomer 01 or polymer PI, and - sequestration by contacting the oligomer O1 or the PI polymer, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester by non-covalent adsorption the oligomer 01 or the polymer PI onto this surface, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated by excluding the oligomer 01 or the possibly reduced polymer PI, between 1(T 5 % and 1%, preferably between 10 -4% and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

[0007] The present presentation relates, according to a fourth embodiment, to a process for sequestration of carbon contained in carbon dioxide, comprising: - a dissolution, in a liquid solvent, of a plastic material comprising poly(vinyl chloride), low-density polyethylene, polypropylene or polystyrene, preferably poly(vinyl chloride) or polystyrene, - carbon dioxide capture by chemical reaction with the plastic material in dissolved form to obtain compound C, with at least one of the following alternatives being verified: (i) Dechlorination of poly(vinyl chloride) in dissolved form is carried out in the presence of carbon dioxide, resulting in the substitution of the chlorine in poly(vinyl chloride) by a carboxylic acid function, (ii) the achene(s) present in the liquid solvent, comprising low-density polyethylene or polypropylene in dissolved form, are subjected to carboxylation or carbonation in the presence of carbon dioxide or to carbonylation in the presence of carbon monoxide obtained after reduction of carbon dioxide, (iii) the benzene ring of polystyrene in the dissolved state is transformed into phenol which then reacts with carbon dioxide via a Kolbe-Schmitt carboxylation reaction, or (iv) a direct carboxylation of polystyrene in the dissolved state is carried out, - optionally a reduction of the carboxyl or carbonate group(s) present in compound C, and - Sequestration by contacting compound C with particles having a predominantly sp-type graphitic carbon surface 2to sequester compound C on this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated excluding compound C, of ​​between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

[0008] In general, the carboxylation or carbonation mentioned in the first, second, third and fourth embodiments above can be carried out by imposing the following conditions: - a pressure between 0.4 mbar and 50 bar, and - a temperature between 40°C and 250°C, for example between 80°C and 180°C, possibly with: - presence of a catalyst, the catalyst being metallic, including for example palladium, platinum, ruthenium, copper or nickel, or being a photocatalyst capable of catalyzing the reaction under predetermined light irradiation, the photocatalyst including for example TiO2, WO3, ZnO, SiC and / or - presence of an additional reducing agent, including for example at least one of an alkoxysilane, for example tetraethyl orthosilicate (TEOS), a Grignard reagent or a nickelalactone.

[0009] In general, the carbonylation mentioned in the third embodiment above can be carried out under the following conditions: - a pressure between 0.4 mbar and 50 bar, and - a temperature between 80°C and 600°C, for example between 150°C and 400°C, possibly with: - presence of a catalyst, the catalyst being metallic, including for example palladium, platinum, ruthenium, copper, cobalt or nickel, or being a photocatalyst capable of catalyzing the reaction under predetermined light irradiation, the photocatalyst including for example TiOz, WO3, ZnO, SiC and / or - presence of an additional reducing agent, including for example at least one of dihydrogen, an alkoxysilane, for example tetraethyl orthosilicate (TEOS), a Grignard reagent or a nickelalactone.

[0010] The present description relates, according to a fifth embodiment, to a process for sequestration of one or more volatile organic compounds, in particular one or more hydrocarbons, contained in the air, comprising: - Sequestration by bubbling of air containing the volatile organic compound(s) in an organic liquid medium in which particles with a predominantly sp-type graphitic carbon surface are dispersed 2 to sequester by non-covalent adsorption the volatile organic compound(s) on this surface, the following conditions being met: (a) the particles are present in the liquid medium, before initiation of bubbling, in a mass concentration between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

[0011] The present presentation relates, according to a sixth embodiment, to a process for sequestration of one or more plastics contained in a polluted water stream, comprising: - Sequestration by mixing the polluted water stream with an aqueous liquid medium in which particles with a predominantly sp-type graphitic carbon surface are dispersed 2 to sequester the plastic material(s) on this surface by non-covalent adsorption, the following conditions being met: (a) the particles are present in the liquid medium, before mixing, in a mass content between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the surface of the particles is functionalized by -OH and / or -COOH groups.

[0012] The plastic material(s) may be chosen from: polypropylene, polystyrene, poly(vinyl chloride), poly(ethylene terephthalate), polyethylene, polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyetheretherketone (PEEK), polypyrrole, polyalkylthiophene, polyfluorene, polycarbazole, polyimide, polyphenylene-vinylene, or from polyvinyl derivatives; the plastic material(s) may be copolymers or mixtures of these polymers, or chemical derivatives, for example carboxylated, acidified or hydroxylated derivatives, of these polymers.

[0013] Unless otherwise stated, the expression "particles having a predominantly sp-type graphitic carbon surface" 2 » will be referred to hereafter as “graphite particles”.

[0014] The embodiments described above each rely on the use of a specific dispersion of graphitic particles that allows for the sequestration of significant quantities of carbon by non-covalent adsorption. Generally, non-covalent adsorption can be achieved through Van der Waals interactions, including, for example, an nn interaction when the compound to be sequestered has one or more unsaturated carbon rings. The chosen liquid medium, along with the low concentration of graphitic particles and any surface functionalization, ensures good dispersion of the particles, which are isolated rather than agglomerated, thus contributing to effective sequestration. The choice of a liquid dispersion implemented in the invention differs markedly from prior art solutions using a porous material, for example, in the form of a filter membrane made of carbon nanotubes or activated carbon.Indeed, the quantity of graphitic particles used in the invention is much smaller, and the adsorption is very strong compared to this type of known solution. Furthermore, the sequestration achieved in the invention is more robust (less reversible) than in the case of porous matrices, thus allowing, in particular, the use of the resulting material in other applications without risk of releasing the stored carbon.

[0015] The invention provides a solution for valorizing sequestered carbon that is favorable in terms of carbon balance, by allowing its storage, in particular for subsequent use such as energy generation as will be described below.

[0016] More specifically, the first, second, third, and fourth embodiments propose a solution for valorizing carbon derived from carbon dioxide, in which the carbon dioxide reacts to obtain an intermediate that is sequestered on the surface of graphitic particles. The solution according to the invention has the advantage of not requiring purification of the adsorbable intermediate, and the invention remains within the scope of the invention even if several different intermediates are sequestered on the particles. As will be discussed below, the invention also remains within the scope of the invention even if compound A is mixed with other organic products during its reaction with carbon dioxide, i.e., if it is in an unpurified form. This makes it possible to limit the amount of energy required for the production of adsorbable molecules (since compound purification and syntheses selectivity require a greater energy expenditure).

[0017] The first and second embodiments employ a specific organic compound A, which reacts with carbon dioxide via a known carboxylation or carbonation reaction. This compound is selected to ensure, firstly, a reaction sequence with a favorable carbon balance and, secondly, the production of an intermediate that is adsorbed in significant proportions on the surface of the graphitic particles. Reference can be made, in particular, to the publication by Liu et al. ("Using carbon dioxide as a building block in organic synthesis", DOI: 10.1038 / ncomms6933) concerning these carboxylation or carbonation reactions. The compound B resulting from carboxylation is a carboxylic acid, and the compound B resulting from carbonation is a carbonate, for example, a dialkyl carbonate or a cyclic carbonate. Various examples of compounds B that can be obtained will be provided later.

[0018] The third embodiment concerns the treatment of a mixture resulting from the electrochemical reduction of carbon dioxide. The resulting mixture depends on the electrolyte, catalyst, potential, and current, and the treatment performed depends on the chemical species present in the mixture. It has been demonstrated that the use of a copper catalyst allows the formation of carbon-cobalt bonds (CCBs), a technique used for the production of ethylene or ethanol by CO2 electrolysis. For example, see the publication by Chen et al. ("Electrochemical CO2-to-ethylene conversion on polyamine-incorporated Cu electrodes," DOI: 10.1038 / s41929-020-00547-0), which provides an example of the use of this type of catalyst to obtain ethylene with one of the highest faradaic yields. In this protocol, ethylene is obtained by CO2 electrolysis using a copper electrode onto which a polyamine catalyst has been electrodeposited.A platinum electrode is used as a counter electrode and an Ag / AgCl electrode as a reference electrode. A potential of -0.97 V (vs RHE) and a current density of 312 mA are applied. 2Electrolysis of CO2 in a KOH electrolyte solution at room temperature and pressure yields ethylene with a faradaic yield of 72%. Ethanol can also be obtained by CO2 electrolysis as described in the publication by Liu et al. ("Selective Electrochemical Reduction of Carbon Dioxide to Ethanol on a Boron-and Nitrogen-Co-doped Nanodiamond", DOI: 10.1002 / anie.201706311) using a nanodiamond electrode co-doped with boron and nitrogen to catalyze the reaction. The counter electrode is platinum, and the reference electrode is Ag / AgCl₂. Applying a potential around -1.0 V (vs. RHE) in a NaHCO₃ electrolyte solution at room temperature and pressure yields ethanol with a faradaic yield of 93%.In general, alkenes or alcohols can be formed by electrochemical reduction of CO2 using a working electrode, for example, made of copper, functionalized with an organic material, such as a polyamine, or a nanomaterial. Advantageously, the electrode functionalization can include nitrogen. The electrode surface can be textured to enhance its interaction with the solution. A potential (vs. RHE) of between -0.8 V (vs. RHE) and -1.2 V can be applied, with a current density of up to 50 mA. 2 and 1000 mA.cnr 2 and use an electrolyte made up of a strong base, such as KOH. The reference electrode and the counter electrode can be conventional, for example being respectively an Ag / AgCl electrode and a platinum electrode.

[0019] Carbon compounds in the liquid phase may include, but are not limited to: one or more alcohols, including one or more alcohols having a carbon chain ranging from C1 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, for example, ethanol; one or more alkenes, including one or more alkenes having a carbon chain ranging from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, for example, ethylene; or a mixture of these compounds. As a non-limiting example, the treatment includes dehydration of the alcohols present into alkenes, which may then be polymerized by a known technique, such as Ziegler-Natta catalysis.Other treatment possibilities exist based on known reactions such as carbonylation, using carbon monoxide, or carboxylation or carbonation which may be similar to that implemented in the first and second embodiments.

[0020] In the case of the first and third embodiments, oligomerization or polymerization is carried out using techniques known in themselves. The resulting oligomer or polymer exhibits enhanced non-covalent interaction with graphitic particles due to its increased size and flexibility. It should be noted that the oligomer or polymer can be formed solely by the repetition of a single monomer, or it can incorporate several distinct repeating units, each of which contributes to the interaction with the graphitic particles, for example, via its carbon chain. Generally, an oligomer comprises at most ten monomers, while a polymer comprises more than ten. The processing of oligomers may be preferred over that of polymers to avoid the risk of entanglement due to excessively long chains and to limit the energy required for synthesis. The conditions imposed during oligomerization or polymerization depend on the specific compound.For example, the oligomerization or polymerization of a dialkyl carbonate, obtained by carbonation of one or more alcohols, or of 2-hydroxybenzoic acid, obtained by carboxylation of phenol, can be carried out at a temperature between 150°C and 200°C, possibly in the presence of a long-chain diol, which may be added or already present in the reaction mixture. Similarly, the oligomerization or polymerization of an acrylate can be carried out by group transfer polymerization (GTP) at a temperature between 20°C and 80°C, with or without a catalyst.

[0021] The second embodiment involves sequestration of compound B in monomeric form (without oligomerization or polymerization).

[0022] A chemical reduction of the carboxyl or carbonate group(s) present in the oligomer, polymer, compound B, or compound C may or may not be carried out according to the embodiments described above. This reduction employs techniques known per se, which can result in the reduction of the carboxyl group(s) to hydroxyl group(s), or of the carbonate group(s) to carbonyl, carboxyl, or even hydroxyl group(s). Such a reduction facilitates interaction with the graphitic particles by reducing the proportion of highly electronegative oxygen. However, this reduction is not essential, as the carbon chain of the compound in question may be sufficient to achieve the desired sequestration on the graphitic particles without the need to control the degree of oxidation.It should also be noted that carboxylation is advantageous over carbonation in order to limit the proportion of oxygen in the compound to be sequestered.

[0023] The fourth embodiment concerns the recovery of plastic waste, the reuse of which has a positive impact on environmental pollution and reduces the overall carbon cost of the material in question.

[0024] The dissolution of plastic material can be carried out at moderate temperatures, for example, below or equal to 120°C, or even between 100°C and 120°C, and with stirring, possibly coupled with centrifugation. The solvent is chosen according to the polymer in question; for example, N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), or tetrahydrofuran (THF) can be used for polyvinyl chloride; xylene or toluene, at high temperatures, for low-density polyethylene; p-xylene, at high temperatures, for polypropylene; and toluene, xylene, chloroform, THF, or dichloromethane for polystyrene.

[0025] In dissolved form, the resulting solution consists of oligomers, polymers, and plastic nanoparticles. These particles have a well-defined chemical composition depending on the source polymer. Processes similar to those described previously are applied to these molecules: - for poly(vinyl chloride) [CH2-HCCl] n : it reacts with CO2 in the presence of a catalyst (or not) at moderate temperature to obtain molecules of typical formula CH2-HC-COOH and oligomers of typical formula [CH2-CH(COOH)] nSeveral methods exist to activate the electrophilicity of CO2 carbon or the nucleophilicity of PVC. The methods employed may utilize electrochemistry to allow for moderate pressures and temperatures. A first protocol, described by Sarkar et al. ("Ambient Electroreductive Carboxylation of Unactivated Alkyl Chlorides and Polyvinyl Chloride (PVC) Upgrading", DOI: 10.1002 / cssc.202400517), involves using a nickel catalyst to activate the electrophilicity of CO2 and enable the formation of the C-C bond through the binding of the two reactants to the catalyst. For this, a current of 10 mA and a potential of about -2 V are applied between a carbon felt cathode and a zinc anode, in the presence of anhydrous MgBr2 and a nickel-based catalyst in NMP at 80°C and at ambient pressure for several hours leading to carboxylation of the PVC with a rate of up to 95%.Another reaction under similar pressure and temperature conditions, in the presence of an aluminum cathode and a lead anode, led to the carboxylation of 14% recycled PVC by applying a 50 mA current in a DMF solution containing bis(2-ethylhexyl) phthalate and tetra-n-butylammonium iodide, without the use of a catalyst, according to the publication by Li et al. ("Electro-reductive carboxylation of C-Cl bonds in unactivated alkyl chlorides and polyvinyl chloride with CO2", DOI: 10.1016 / j.cclet.2024.110104). Another possibility is the formation of a Grignard reagent with the chlorine present on the PVC. It has been shown that Grignard formation is not favorable on PVC, which is why the team of Sevovet et al. (“Electroreductive Borylation of Chloroalkanes and Polyvinyl Chloride Plastics”, DOI: 10.1021 / jacs.5c07692) developed an electrochemical method for the reactivity of magnesium by applying a 3 mA current between a magnesium and nickel electrode in the presence of lithium bis(trifluoromethanesulfonyl)imide as the electrolyte in THF. The Grignard reagent formed in situ is then highly reactive towards CO2 present in the solution. CO2 capture by PVC is a particularly advantageous solution because it offers a highly favorable carbon balance. - For polystyrene (PS): [CH(benzene)-CH2-]n: two reaction pathways are possible after dissolution of the polystyrene. The first is to perform a direct carboxylation on the polystyrene after the formation of a Grignard reagent in situ, as described in the publication by Rezaei et al. ("Novel Strategies for the Synthesis of Hydroxylated and Carboxylated Polystyrenes", DOI: 10.1007 / sl0965-018-1490-x). To do this, the polystyrene is first brominated in the presence of dibromine and iron chloride in chloroform. The Grignard reagent is then formed in situ by reacting powdered magnesium in the presence of diiodine in THF with the brominated polystyrene at room temperature. CO2 is introduced simultaneously into the reaction medium to react immediately after the formation of the organomagnesium compound. Hydrolysis in acidic medium then releases the carboxylic acid. Another method is based on an analogy with the Kolbe-Schmitt reaction on phenol.The first step involves hydroxylating polystyrene to obtain poly(4-hydroxystyrene). A first synthetic route, described in the article by Deokar et al. ("Easy synthesis of poly(4-hydroxystyrene) from polystyrene," DOI: 10.1002 / app.13488), begins with a Friedel-Craft acylation reaction on polystyrene (PS) in the presence of aluminum chloride and acyl chloride or acetic anhydride in dichloromethane. The acetylated PS is then oxidized, typically with hydrogen peroxide in the presence of peracetic acid or with sodium perborate and trichloroacetic acid, at room temperature for several hours. Finally, the resulting acetate is hydrolyzed in methanol in the presence of sodium hydroxide to release the alcohol.The Kolbe-Schmitt reaction can then be carried out on the hydroxylated PS at ambient pressure and at a fairly high temperature (180°C) in the presence of NaH, CO2 and 2,4,6-trimethylphenol as a catalyst according to the conditions described by Luo et al. (“Carboxylation of Phenols with CO2 at Atmospheric Pressure”, DOI: 10.1002 / chem.201601114). CO2 capture by PS is a particularly advantageous solution because it has a very favorable carbon balance. - For low-density polyethylene or polypropylene: dissolution results in a solution of linear alkene oligomers. For example, a reaction with CO2 + H2 (hydroformylation) or a reaction with CO after the reduction of CO2 to CO is applied.

[0026] For all reactions requiring anhydrous conditions, particularly those involving Grignard reactions, the incoming air stream must be pre-dried to remove all water molecules. Water vapor removal can be achieved through adsorption, chemical adsorption, or cooling. For example, the air stream can be passed through a 3Å molecular sieve, silica gel, or calcium chloride. For these same reactions, the solvent can be chosen to preferentially dissolve CO2 over water at the expected reaction temperatures and pressures. For example, toluene, cyclopentyl methyl ether, 2-methyltetrahydrofuran, or diethoxymethane can be used (https: / / pubs.rsc.org / en / content / articlehtml / 2013 / gc / c3gc40702k and https: / / doi.org / 10.1039 / C3GC40702K).

[0027] Regardless of the reaction chosen in the liquid phase, the solvent can also be selected to preferentially dissolve CO2 over O2. For example, possible solvents include THF, toluene, or methylcyclohexane. (https: / / doi.org / 10.1016 / 0021-9614(74)90175-X).

[0028] The fifth embodiment relates to an application for air pollution control using the dispersion of graphitic particles in an organic liquid medium described above.

[0029] The sixth embodiment relates to an application for water pollution control using the dispersion of graphitic particles in aqueous liquid medium as described above.

[0030] Various reactions are indicated above as being able to be carried out in a strong base, they can for example be carried out in a solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH).

[0031] In an example of an embodiment relating to the first and second embodiments, the carboxylation or carbonation of compound A to obtain organic compound B is carried out in a solution of a strong base during a carbon dioxide capture step by introducing carbon dioxide into the solution of the strong base.

[0032] Such a strong base carbon dioxide capture step is known from the state of the art for forming a carbonate, which traditionally then undergoes a series of reactions leading to a purified carbon dioxide stream. This embodiment falls within the framework of a traditional strong base carbon dioxide capture process but has the advantage of minimizing the number of steps (and therefore the energy consumption) required to capture the carbon, compared to this traditional process which aims not only to capture CO2, but also to create a purified CO2 stream (for use or storage) or to mineralize the CO2 in the form of carbonates.

[0033] In an example of an embodiment relating to the first and second embodiments, compound A is an alcohol having a carbon chain saturated in C1 to C2, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or a polyalcohol having a carbon chain saturated in C2 to C2, substituted or unsubstituted, interrupted or not by one or more heteroatoms.

[0034] The use of a saturated compound A advantageously enhances the interaction with the graphitic particles. Furthermore, the saturated chain exhibits a higher heat capacity than an unsaturated chain, making it more suitable for the energy generation process described below.

[0035] In an example of an embodiment relating to the first and second embodiments, compound A is an alcohol having a carbon chain from C1 to C2, preferably from C1 to C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or a polyalcohol having a carbon chain from C2 to C6, preferably from C2 or C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms.

[0036] Limiting the number of carbon atoms in compound A advantageously favors the ratio of captured carbon to the total number of carbon atoms.

[0037] In particular, compound A can be chosen from: methanol, ethanol, propanediol, glycerol or phenol.

[0038] The choice of these compounds is particularly interesting because it allows for the reuse of organic synthesis waste or compounds derived from surplus agricultural production. In particular, compound A could be propanediol, which represents a particularly favorable solution in terms of carbon footprint. Propanediol can potentially be obtained from glycerol.

[0039] When compound A is methanol, compound B, obtained after carbonation, is dimethyl carbonate (DMC) with the chemical formula below. The production of DMC by reacting CO2 with methanol has been the subject of numerous studies aimed at improving the catalyst used, lowering the pressure and temperature conditions, and optimizing the choice of drying agent to remove the water formed during the process and shift the equilibrium. For example, this reaction can be carried out using the protocol described by Zhao et al. ("Direct Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol at Room Temperature Using Imidazolium Hydrogen Carbonate Ionic Liquid as a Recyclable Catalyst and Dehydrant", DOI: 10.1002 / cssc.201700128), which synthesizes dimethyl carbonate at room temperature and under a pressure of 10 bar with a conversion of 72% in the presence of an ionic liquid of imidazolium hydrogen carbonate, serving as a catalyst and drying agent.

[0040] [Chem. 1]

[0041] When compound A is ethanol, compound B, obtained after carbonation, is diethyl carbonate with the chemical formula below. This compound can be obtained by a sustainable approach recently developed by Fukaya's team. ("Sustainable Catalytic Synthesis of Diethyl Carbonate", DOI: 10.1002 / cssc.20200247), which reacts ethanol and CO2 with alkoxysilanes on a zirconium catalyst at a pressure of 50 bar and at 180°C.

[0042] [Chem. 2] O

[0043] When compound A is glycerol, compound B, obtained after carbonation, is glycerol carbonate with the chemical formula below. Numerous operating conditions exist for carrying out this reaction using metallic catalysts in homogeneous or heterogeneous phases, or even metal-free catalysts as described in the review by Lukato et al. ("Glycerol carbonylation with CO2 to form glycerol carbonate: A review of recent developments and challenges", D01:10.1016 / j.crgsc.2021.100199). For example, the operating conditions developed by Zhang et al. can be reproduced. ("Calcium carbide as a dehydrating agent for the synthesis of carbamates, glycerol carbonate, and cyclic carbonates from carbon dioxide", DOI: 10.1039 / D0GC01402H) using a homogeneous catalyst based on zinc(II) solubilized in N-methyl-2-pyrrolidone under a pressure of 50 bar at 180°C which allows the formation of glycerol carbonate with a yield of 92%.

[0044] [Chem. 3]

[0045] More generally, when compound A is an alcohol or a polyalcohol, the compound B obtained following carbonation is a carbonate, for example a dialkyl carbonate or a cyclic carbonate.

[0046] In an example of an embodiment relating to the first and second embodiments, compound A is phenol and compound B is obtained from compound A by a Kolbe-Schmitt carboxylation reaction. The protocol described by the Larossa group ("Carboxylation of Phenols with CO2 at Atmospheric Pressure", DOI: ) can be followed. 10.1002 / chem.201601114) in which, under an inert atmosphere, sodium hydride and 2,4,6-trimethylphenol are mixed with phenol and then heated to 100°C for 5 minutes to allow the formation of phenolate. Gaseous CO2 is then injected into the flask and heated to 185°C for 2 hours at atmospheric pressure to yield the carboxylated product.

[0047] In this case, compound B is 2-hydroxybenzoic acid having the chemical formula below.

[0048] [Chem. 4] O II G-OH OH

[0049] The Kolbe-Schmitt carboxylation reaction may include: - the formation of a phenolate ion salt by treating phenol with a base such as sodium hydride, - a carboxylation reaction of the phenolate ion with carbon dioxide under a pressure between 1 bar and 50 bar, and under a temperature between 40°C and 250°C, for example between 150°C and 200°C, and - a treatment of the product obtained following this carboxylation reaction with acid, such as sulfuric acid, to obtain 2-hydroxybenzoic acid which forms compound B.

[0050] In an example of an embodiment relating to the first and second embodiments, compound A is an alkene having a C2 to Ce carbon chain, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a C2 to Ce carbon chain, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or benzene.

[0051] Specifically, compound A is an alkene with a C2 or C3 carbon chain, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an alkyne with a C2 or C3 carbon chain, substituted or unsubstituted, interrupted or not by one or more heteroatoms. More specifically, compound A can be chosen from: ethylene, propene, or acetylene. Even more specifically, compound A can be ethylene. Such a choice is particularly advantageous for obtaining a solution for utilizing sequestered carbon that is especially favorable in terms of carbon balance.

[0052] When compound A is ethylene, compound B, obtained after carboxylation, is acrylic acid with the chemical formula below. This compound can be obtained by reacting CO2 with ethylene using a nickel- or palladium-based catalyst. For example, one can follow the experimental conditions described in the article by Manzini et al. ("Synthesis of acrylates from olefins and CO2 using sodium alkoxides as bases," DOI: 10.1016 / j.cattod.2016.03.025), which involves reacting ethylene and CO2 under an anhydrous atmosphere for about twenty hours, at a temperature of 145°C and a pressure of 30 bar, with a palladium-based catalyst formed from the precursor Pd(PPh3)4 and 1,2-bis(dicyclohexylphosphino)ethane in the presence of sodium tert-butoxide as a base in anisole.

[0053] [Chem. 5]

[0054] When compound A is propene, compound B, obtained after carboxylation, is methacrylic acid with the chemical formula below. The same operating conditions described previously for obtaining acrylic acid can be used to synthesize methacrylic acid from propene and CO2.

[0055] [Chem. 6] H2C OH

[0056] When compound A is benzene, compound B, obtained after carboxylation, is benzoic acid with the chemical formula shown below. Benzene carboxylation can be carried out using various methods, for example, an electrochemical method developed by Behrouz et al. ("Electrode Development for Electro-Organic Kolbe-Schmitt CH Carboxylation of Benzene Using Cu Nanoparticles on Graphene Oxide Modified With MIL-101 MOF for CO2Capture in a DES Electrolyte System", DOI: 10.1002 / aoc.7905), which allows for milder experimental conditions than those used in classical organic chemistry. The protocol uses an electrode decorated with graphene oxide modified with a metallic organic structure (MIL-101 MOF) and coated with copper nanoparticles.Choline chloride urea is used as the electrolyte and a current of 20mA is applied for 2h at ambient temperature and pressure, to produce benzoic acid with a yield of up to 97%.

[0057] [Chem. 7]

[0058] When compound A is acetylene, compound B, obtained after carboxylation, is succinic acid with the chemical formula below. This compound can be obtained according to the experimental protocol described by Wang et al. ("1,5,7 Triazabicyclo[4.4.0]dec-l-ene-Mediated Acetylene Dicarboxylation and Alkyne Carboxylation Using Carbon Dioxide", DOI: 10.1002 / ejoc.201201608) in which acetylene at a pressure of 3 bar is mixed with CO2, at a pressure of 12 bar, in a solution of 1,5,7 triazabicyclo[4.4.0]dec-l-ene (TBD) and dimethylacetamide at 100°C for 42h leading to the formation of a CO2 adduct with the guanidine base. After condensation of the medium, the compound is brought into contact with Pd / C (10%) in methanol under an H2 atmosphere for 18h to lead to the diacid with a yield of 95%.

[0059] [Chem. 8] O HO. OH O

[0060] In an example of an embodiment relating to the first and second embodiments, carboxylation or carbonation is carried out while compound A is mixed with one or more organic products.

[0061] As mentioned above, this situation allows for the processing of mixtures in an unpurified form, which is very advantageous from an energy standpoint. It should be noted that, in a particular case, the organic product(s) may correspond to a compound A; that is, several distinct compounds A can be processed during carboxylation or carbonation, for example, a mixture of alcohols or at least one alcohol mixed with phenol.

[0062] In general, the carbon chain of compound A can be interrupted by one or more heteroatoms, for example, nitrogen, oxygen, or chlorine. In general, the carbon chain of compound A can be substituted, for example, by at least one saturated, unsaturated, or aromatic heterocyclic group, such as one or more triazole groups.

[0063] In one embodiment example, the particles are carbon nanotubes, preferably single-walled carbon nanotubes.

[0064] The invention is not limited to the use of carbon nanotubes, however, as the particles may alternatively have a surface of graphene, reduced graphene oxide, or graphite. In particular, particles with a graphite surface, such as exfoliated graphite, can be used, this exfoliation having been chemically obtained with peroxyacetic acid. For example, the particles are graphite particles, such as exfoliated graphite. The use of graphite is of particular interest because its carbon footprint is lower than that of nanotubes. Naturally, the invention remains within the scope of the invention if a mixture of different graphitic particles is used for sequestration.

[0065] In one example, the graphitic carbon is predominantly sp-type 2on the surface of the particles has a low defect density characterized by an ID / IG ratio between the intensity of the D band and the intensity of the G band obtained by Raman spectroscopy less than or equal to 2, preferably 1.1.

[0066] Such a feature makes it advantageous to further facilitate sequestration.

[0067] The ID / IG ratio corresponds to a classic characterization in the literature of the defect density of a sp graphitic carbon 2 which is preferred to the calculation of defect density expressed as the number of defects per unit area, which depends on the choice of model, which is much less widely accepted in the literature than the ID / IG ratio.

[0068] Band D is between 1300 cm -1 and 1400 cm -1 and the G band is located at approximately 1580 cm -1. The quantities ID and IG can each correspond to the intensity of the maximum of the peak of the corresponding band, without mathematical adjustment and after removal of the baseline of the spectrum ("baseline" corresponding to the global linear drift of the spectrum).

[0069] In particular, electronic grade carbon nanotubes can be used as graphitic particles with a low defect density.

[0070] In one embodiment, the organic liquid medium comprises N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, 1,2-dichlorobenzene, tetrahydrofuran, acetone, toluene, chloroform, 1,3-dioxolane, a deep eutectic solvent such as choline-glycerol chloride or choline-glycerol-urea chloride, or a mixture of these compounds. The liquid medium may be selected from the aforementioned compounds.

[0071] In one embodiment, the contact of the particles with the compound to be sequestered is carried out for a duration greater than or equal to 10 seconds, preferably greater than or equal to 100 seconds. This duration may be between 10 seconds and 3000 seconds, preferably between 100 seconds and 1000 seconds.

[0072] In general, the compound to be sequestered corresponds to the oligomer O or O1, the polymer P or PI, the compound B, the compound C, the volatile organic compound(s), or the plastic material(s) contained in the polluted water stream, according to the embodiment considered.

[0073] In one example embodiment, the contact of the particles with the compound to be sequestered is carried out at a temperature between 0°C and 150°C, preferably between 15°C and 80°C.

[0074] In one embodiment, the process further comprises, after sequestration, the recovery of particles having the sequestered compound on their surface, followed by additional sequestration by contacting a residual fraction of the compound to be sequestered with additional particles having a predominantly sp-type graphitic carbon surface 2 to sequester this residual fraction.

[0075] Such a characteristic advantageously allows the adsorption of target molecules to continue in case of saturation of the particles during the first sequestration.

[0076] Various techniques can be used to recover the particles after the initial sequestration. One can trigger the precipitation of the graphitic particles sequestering the compound by adding a suitable liquid such as acetone, or recover these particles by centrifugation. Alternatively, recovery can be achieved under the influence of an electric field, for example, using a dielectrophoresis technique. Other variations are possible, employing the functionalization of the graphitic particles with magnetic or highly polarizable elements to facilitate recovery under the influence of an electric or electromagnetic field.

[0077] In general, sequestration can be monitored by UV-Vis spectroscopy and fluorescence, possibly in real time, to recover the graphitic particles sequestering the compound at the appropriate time depending on the desired application.

[0078] In one example, graphitic particles are functionalized, prior to sequestration, to render them biodegradable through the implementation of techniques known per se, such as esterification. Alternatively, or in combination, the particles are rendered biodegradable after sequestration of the compound.

[0079] As an example, the surface chemistry of graphitic particles is modulated depending on the compound to be sequestered. For instance, graphitic particles can be slightly doped with N₂ to promote the adsorption of an oxygen-rich compound, using a technique that is well-established.

[0080] This presentation also concerns a process for generating energy, comprising: - the implementation of a process as described above in order to obtain coated particles having a predominantly sp-type graphitic carbon surface 2 sequestering a compound, and - energy generation by combustion of the sequestered compound.

[0081] In general, the sequestered compound corresponds to the oligomer O or O1, the polymer P or PI, the compound B, the compound C, the volatile organic compound(s), or the plastic material(s) contained in the polluted water stream, depending on the embodiment considered.

[0082] The compound sequestered on the graphitic particles is highly energetic and its combustion occurs at a much lower temperature than that of the graphitic particles themselves. Therefore, it can be burned to release energy, for example, for heat generation. Because the compound is very densely packed onto the graphitic particles, the amount of energy released per mole is very high compared to more traditional molecules (for example, the conversion of CO2 to methane, which is frequently reported in this field). Furthermore, since the combustion temperature of the graphitic particles is much higher than that of the sequestered compound, the graphitic particles can be recovered after combustion and reused to sequester another compound.

[0083] In one embodiment example, the mass of the sequestered compound represents at least 50%, for example at least 80%, of the mass of the coated particles.

[0084] In one example of implementation, carbon contained in carbon dioxide generated during the combustion of the sequestered compound is then sequestration by implementing a process as described above.

[0085] This characteristic allows for the advantageous recovery of the combustion product to generate usable fuel. Thus, carbon-sequestering graphitic particles can be used as energy storage in an extremely concentrated form. For example, during a peak in electricity production, electricity is used to power the sequestration process. During periods of low electricity production, the combustion of the carbon-sequestering graphitic particles can be used to generate energy (in a thermal power plant modified for this purpose). This combustion occurs with low CO2 emissions, or even zero CO2 emissions, because the CO2 is directly captured during combustion by the process described above.

[0086] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A process for sequestration of carbon contained in carbon dioxide, comprising: - a carboxylation or carbonation of an organic compound A by reaction with carbon dioxide to obtain an organic compound B, wherein compound A is an alcohol having a carbon chain from C1 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, a polyalcohol having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkene having a carbon chain from C2 to Cw, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an aromatic compound having a benzene ring, such as benzene or phenol, - an oligomerization or polymerization using compound B to obtain an oligomer O or a polymer P, - optionally a reduction of the carboxyl or carbonate group(s) present in the oligomer O or polymer P, and - Sequestration by contacting the oligomer O or the polymer P, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester the oligomer O or polymer P onto this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated by excluding the oligomer O or polymer P possibly reduced, of between 10 -5 % and 1%, preferably between 10 -4% and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

2. A process for sequestration of carbon contained in carbon dioxide, comprising: - a carboxylation or carbonation of an organic compound A by reaction with carbon dioxide to obtain an organic compound B, wherein compound A is an alcohol having a carbon chain from C1 to C2, substituted or unsubstituted, interrupted or not by one or more heteroatoms, a polyalcohol having a carbon chain from C2 to C2, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkene having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a carbon chain from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an aromatic compound having a benzene ring, such as benzene or phenol, - optionally a reduction of the carboxyl or carbonate group(s) present in organic compound B, and - Sequestration by contacting the organic compound B, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester compound B on this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated excluding compound B, of between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

3. A process for sequestration of carbon contained in carbon dioxide, comprising: - an electrochemical reduction of carbon dioxide to obtain a mixture of carbon compounds in the liquid phase, - a treatment of the mixture thus obtained including at least one of the following treatments: (1) dehydration of one or more alcohols present in the mixture to form one or more alkenes, (2) carbonylation of one or more alkenes present in the mixture by reaction with carbon monoxide, possibly produced during the electrochemical reduction of carbon dioxide, this carbonylation possibly being carried out in the presence of dihydrogen possibly produced during the electrochemical reduction of carbon dioxide, or (3) carboxylation or carbonation of one or more alkenes and / or one or more alcohols present in the mixture by reaction with carbon dioxide, - an oligomerization or polymerization of one or more carbon compounds present in the mixture thus treated in order to obtain at least one oligomer 01 or polymer PI, - optionally a reduction of the carboxyl or carbonate group(s) present in the oligomer 01 or polymer PI, and - sequestration by contacting the oligomer O1 or the PI polymer, possibly reduced, with particles having a predominantly sp-type graphitic carbon surface 2 to sequester by non-covalent adsorption the oligomer 01 or the polymer PI onto this surface, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass content, calculated by excluding the oligomer 01 or the possibly reduced polymer PI, of between 10' 5 % and 1%, preferably between 10' 4% and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

4. A process for sequestration of carbon contained in carbon dioxide, comprising: - a dissolution, in a liquid solvent, of a plastic material comprising poly(vinyl chloride), low-density polyethylene, polypropylene or polystyrene, preferably poly(vinyl chloride) or polystyrene, - carbon dioxide capture by chemical reaction with the plastic material in dissolved form to obtain compound C, with at least one of the following alternatives being verified: (i) Dechlorination of poly(vinyl chloride) in dissolved form is carried out in the presence of carbon dioxide, resulting in the substitution of the chlorine in poly(vinyl chloride) by a carboxylic acid function, (ii) the linear alkene oligomers, present in the liquid solvent obtained by dissolving low-density polyethylene or polypropylene, are subjected to carboxylation or carbonation in the presence of carbon dioxide, or to carbonylation in the presence of carbon monoxide obtained after reduction of carbon dioxide, (iii) the benzene ring of polystyrene in the dissolved state is transformed into phenol which then reacts with carbon dioxide via a Kolbe-Schmitt carboxylation reaction, or (iv) a direct carboxylation of polystyrene in the dissolved state is carried out, - optionally a reduction of the carboxyl or carbonate group(s) present in compound C, and - Sequestration by contacting compound C with particles having a predominantly sp-type graphitic carbon surface 2to sequester compound C on this surface by non-covalent adsorption, the particles being dispersed in an organic liquid medium and the following conditions being met: (a) the particles are present in the liquid medium in a mass concentration, calculated excluding compound C, of ​​between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

5. A method for sequestration of one or more volatile organic compounds, in particular one or more hydrocarbons, contained in air, comprising: - sequestration by bubbling of the air containing the volatile organic compound(s) in an organic liquid medium in which particles having a predominantly sp-type graphitic carbon surface are dispersed 2to sequester by non-covalent adsorption the volatile organic compound(s) on this surface, the particles being carbon nanotubes or particles having a surface of graphene, reduced graphene oxide or graphite, the following conditions being met: (a) the particles are present in the liquid medium, before initiation of bubbling, in a mass concentration of between 10' 5 % and 1%, preferably between 10' 4 % and 0.05%, and (b) the liquid medium is aprotic and has at least one electron pair donor site.

6. A method for sequestering one or more plastics contained in a polluted water stream, comprising: - Sequestration by mixing the polluted water stream with an aqueous liquid medium in which particles with a predominantly sp-type graphitic carbon surface are dispersed 2to sequester the plastic material(s) on this surface by non-covalent adsorption, the following conditions being met: (a) the particles are present in the liquid medium, before mixing, in a mass concentration between 10 -5 % and 1%, preferably between 10 -4 % and 0.05%, and (b) the surface of the particles is functionalized by -OH and / or -COOH groups.

7. A process according to claim 1 or 2, wherein the carboxylation or carbonation of compound A to obtain organic compound B is carried out in a solution of a strong base during a carbon dioxide capture step by introducing carbon dioxide into the solution of the strong base.

8. A process according to claim 1, 2 or 7, wherein compound A is an alcohol having a carbon chain saturated from C1 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or a polyalcohol having a carbon chain saturated from C2 to C10, substituted or unsubstituted, interrupted or not by one or more heteroatoms.

9. A process according to claim 1, 2, 7 or 8, wherein compound A is an alcohol having a carbon chain from C1 to C2, preferably from C1 to C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or a polyalcohol having a carbon chain from C2 to C2, preferably from C2 or C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms.

10. A process according to claim 1, 2, 7, 8 or 9, wherein compound A is selected from: methanol, ethanol, propanediol, glycerol or phenol.

11. A process according to claim 10, wherein compound A is propanediol.

12. A process according to claim 1, 2, 7 or 10, wherein compound A is phenol and compound B is obtained from compound A by a Kolbe-Schmitt carboxylation reaction.

13. A process according to claim 1, 2 or 7, wherein compound A is an alkene having a carbon chain in C2 to C6, substituted or unsubstituted, interrupted or not by one or more heteroatoms, an alkyne having a carbon chain in C2 to C6, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or benzene.

14. A process according to claim 13, wherein compound A is an alkene having a carbon chain at C2 or C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms, or an alkyne having a carbon chain at C2 or C3, substituted or unsubstituted, interrupted or not by one or more heteroatoms.

15. A method according to claim 14, wherein compound A is selected from: ethylene, propene or acetylene.

16. A process according to claim 15, wherein compound A is ethylene.

17. A process according to any one of claims 1, 2 or 7 to 16, wherein the carboxylation or carbonation is carried out while compound A is in a mixture with one or more organic products.

18. A process according to claim 4, wherein the plastic material comprises poly(vinyl chloride), and wherein the capture of carbon dioxide by chemical reaction with the plastic material in dissolved form to obtain compound C is carried out by dechlorination of the poly(vinyl chloride) in dissolved form in the presence of carbon dioxide resulting in the substitution of the chlorine of the poly(vinyl chloride) by a carboxylic acid function.

19. A process according to claim 4, wherein the plastic material comprises polystyrene, and wherein the capture of carbon dioxide by chemical reaction with the plastic material in dissolved form to obtain compound C is carried out by transformation of the benzene ring of polystyrene in dissolved form into phenol which then reacts with carbon dioxide according to a Kolbe-Schmitt carboxylation reaction.

20. A process according to claim 4, wherein the plastic material comprises polystyrene, and wherein the capture of carbon dioxide by chemical reaction with the plastic material in dissolved form to obtain compound C is carried out by direct carboxylation of the polystyrene in dissolved form.

21. A method according to any one of claims 1 to 20, wherein the particles are carbon nanotubes, preferably single-walled carbon nanotubes.

22. A method according to any one of claims 1 to 21, wherein the particles are graphite particles, for example exfoliated graphite.

23. A method according to any one of claims 1 to 22, wherein the graphitic carbon is predominantly sp-type 2on the surface of the particles has a low defect density characterized by an ID / IG ratio between the intensity of the D band and the intensity of the G band obtained by Raman spectroscopy less than or equal to 2, preferably 1.

1.

24. A method according to any one of claims 1 to 5, 7 to 20, or 21, 22 and 23 related to claims 1 to 5, wherein the organic liquid medium comprises N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, 1,2-dichlorobenzene, tetrahydrofuran, acetone, toluene, chloroform, 1,3-dioxolane, a deep eutectic solvent, such as choline-glycerol chloride or choline-glycerol-urea chloride, or a mixture of these compounds.

25. A method according to any one of claims 1 to 24, wherein the contact of the particles with the compound to be sequestered is carried out for a period greater than or equal to 10 seconds, preferably between 100 seconds and 1000 seconds.

26. A method according to any one of claims 1 to 25, wherein the contact of the particles with the compound to be sequestered is carried out at a temperature between 0°C and 150°C, preferably between 15°C and 80°C.

27. ​​A method according to any one of claims 1 to 26, wherein the method further comprises, after sequestration, recovery of the particles having the sequestered compound on their surface, followed by additional sequestration by contacting a residual fraction of the compound to be sequestered with additional particles having a predominantly sp-type graphitic carbon surface 2to sequester this residual fraction.

28. A method for generating energy, comprising: - an implementation of a process according to any one of claims 1 to 27 in order to obtain coated particles having a predominantly sp-type graphitic carbon surface 2 sequestering a compound, and - energy generation by combustion of the sequestered compound.

29. A method according to claim 28, wherein the mass of the sequestered compound represents at least 50% of the mass of the coated particles.

30. A method according to claim 28 or 29, wherein the carbon contained in carbon dioxide generated during the combustion of the sequestered compound is then sequestration carried out by implementing a method according to any one of claims 1 to 22.

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