WO2018229220A1

WO2018229220A1 - Porous carbon materials

Info

Publication number: WO2018229220A1
Application number: PCT/EP2018/065869
Authority: WO
Inventors: Douglas Wicks; Alexandra JAKOB; Patrick LANZ; Michael Spahr
Original assignee: Imerys Graphite & Carbon Switzerland Ltd.; Imerys Carbonates Usa, Inc; Imerys Pcc France Sas
Priority date: 2017-06-14
Filing date: 2018-06-14
Publication date: 2018-12-20

Abstract

Porous carbon materials are discussed as well was methods of preparing such porous carbon materials. For example, the method may include combining a carbon precursor and a carbonate compound to form a mixture, heating the mixture to form a composite material, and leaching with an acidic solution to produce a porous carbon material and a second acidic solution. The carbonate compound may be regenerated from the second acidic solution. Using the disclosed methods may permit improved control of the characteristics, including pore size, of the produced porous carbon material.

Description

POROUS CARBON MATERIALS

TECHNICAL FIELD

[0001 ] Embodiments of the present disclosure relate generally to porous carbon compositions including the synthesis and methods of use thereof. BACKGROUND

[0002] Porous carbon compositions are useful for filtration of liquids, purification of liquids and gases, catalyst supports and energy storage and conversion systems. The various applications for porous carbon materials require different pore structure, size and volume, thus a need arises for controlling the pore size of the carbon composition. [0003] Porous carbon compositions are typically manufactured by treating carbon materials or the template-supported synthesis of porous carbon. Carbon materials can be treated with acids to etch pores in the carbon material. Or carbon materials can undergo activation by treatment with air, C0₂, or ZnCI₂/H₂0 to create pores in the carbon material. However, it is difficult to control pore size and distribution using etching, activation, and other treatment methods. Template-supported synthesis of porous carbon is a process in which a carbon precursor is mixed with a templating material to form a mixture. The mixture is then carbonized, and the template structure is removed. Traditional templating materials include silica, zeolites, or quartz. Removal of traditional templating materials is costly, difficult and dangerous, usually requiring the use of concentrated hydrofluoric acid. Further, the rigid structure of some traditional templating materials, such as quartz, restricts the ability to tailor the pore size of the resulting carbon composition. Synthesis of porous carbon compositions with a controlled porosity via an easily removable template is therefore desired.

[0004] Synthesis of porous carbon materials generally requires a significant amount of energy and production of C0₂. Optimizing the production of porous carbon materials can therefore reduce the environmental impact of the process. Recycling materials used and created during the production of porous carbon materials can decrease waste production while increasing cost and energy efficiencies. Thus, it is desirable to develop a closed synthesis loop that reuses materials from the carbon synthesis process. SUMMARY

[0005] The present disclosure includes a porous carbon material, preparation of such materials and method of use thereof.

[0006] For example, disclosed herein is a method of preparing a porous carbon material, the method comprising combining a carbon precursor and a carbonate compound to form a mixture; heating the mixture to produce a composite material; placing the composite material in contact with an acidic solution to produce the porous carbon material and a second solution; and regenerating the carbonate compound from the second solution.

[0007] The carbon precursor may comprise sucrose, ammonium lignosulfonate, polyvinyl alcohol, polyvinylpyrrolidone, resins, or combinations thereof. Additionally, or alternatively, the carbon precursor may comprise at least one functional group chosen from hydroxyl, carboxylic acid, phosphonate, and sulfonate.

[0008] According to some aspects, the carbonate compound may comprise calcium carbonate. For example, the carbonate compound may have an elementary particle size (dp) ranging from about 1 nm to about 100 nm, or from about 2 nm to about 50 nm. In some examples, the dp of the carbonate compound may differ by less than 50% from an average pore size of the porous carbon material. For example, the elementary particle size (dp) of the carbonate compound may differ from an average pore size of the porous carbon material by less than 40%, less than 30%, less than 25%, less than 15%, or less than 10%. Additionally or alternatively, the ratio of the dp of the carbonate compound to an average pore size of the porous carbon material may range from 0.9 to 1.1. The porous carbon material may have an average pore size ranging from about 0.1 nm to about 1000 nm, or from about 0.1 nm to about 50 nm. In further examples, the porous carbon material may have a specific surface area (SSA) of between about 100 m²/g and about 1000 m²/g, such as between about 300 m²/g and about 1000 m²/g, or between about 500 m²/g and 800 m²/g, e.g., a SSA of about 100 m²/g, about 250 m²/g, about 500 m²/g, about 750 m²/g, or about 1000 m²/g.

[0009] The mixture may comprise from about 5 g/L to about 350 g/L of the carbonate compound, from about 150 g/L to about 250 g/L of the carbonate compound, from about 50 g/L to about 2100 g/L of the carbon precursor, or from about 200 to about 500 g/L of the carbon precursor. In additional aspects of the disclosure, the weight ratio of the carbonate compound to the carbon precursor may range from about 1 :200 to about 200:1 , from about 1 :100 to about 100:1 , from about 1 :50 to about 50:1 , from about 1 :10 to about 10:1 , from about 1 :5 to about 5:1 , from about 1 :3 to about 3:1 , or from about 3:7 to about 7:3. [0010] In certain aspects of the disclosure, the heating step may be carried out at a temperature ranging from about 500 °C to 3000 °C. In some examples, the mixture may be heated for a period of time ranging from about 30 minutes to about 24 hours, or from about 1 to about 3 hours. Additionally or alternatively, the mixture may be heated in a vacuum or in an inert atmosphere; e.g. nitrogen, helium, or argon. Further, the acidic solution may comprise acetic acid, nitric acid, sulfuric acid, hydrochloric acid, an ammonium salt thereof (e.g., ammonium acetate, ammonium nitrate, ammonium sulfate, or ammonium chloride), or any combination thereof. Additionally or alternatively, the acidic solution may have a concentration ranging from about 0.1 M to about 5.0 M, such as from about 0.5 M to about 3.0 M, from about 1 .0 M to about 2.0 M or from about 2.0 M to 3.0 M. In some examples, the composite material may be in contact with the acidic solution for a period of time ranging from about 5 minutes to about 24 hours, e.g., from about 30 minutes to about 12 hours, from about 1 hour to about 6 hours, or from about 1 hour to about 24 hours.

[001 1 ] The method may further comprise filtering the second solution before regenerating the carbonate compound. In another example, the method may further comprise drying the porous carbon material at a temperature ranging from about 80 °C to about 200 °C. The second solution may comprise calcium chloride, calcium sulfate, calcium nitrate, calcium acetate, or a combination thereof. Additionally or alternatively, the second solution may comprise a calcium salt having a concentration ranging from about 1 g/L to about 350 g/L, e.g., from about 5 g/L to about 100 g/L, or from about 10 g/L to about 50 g/L.

[0012] In further examples, regenerating the carbonate compound may comprise adjusting the pH of the second solution to produce a basic solution comprising calcium hydroxide; and carbonating the basic solution with carbon dioxide to produce precipitated calcium carbonate In at least one example, the porous carbon material may have a ratio of mesopores to micropores ranging from about 1 :10 to about 10:1 ; e.g. a ratio of about 10:1 , a ratio of about 1 :3, about 1 :2, about 1 :1 , about 2:1 , about 3:1 , or about 10:1.

[0013] In another aspect, the method may comprise combining a carbon precursor and calcium carbonate particles to form a mixture, the calcium carbonate particles having a dp ranging from about 2 nm to about 50 nm; heating the mixture to produce carbon dioxide and a composite material; adding an acidic solution to the composite material to produce the porous carbon material and a second solution comprising calcium ions; increasing the pH of the second solution; and adding the carbon dioxide to produce precipitated calcium carbonate. In at least one further example, the porous carbon material has an average pore size ranging from about 2 nm to about 50 nm. The calcium carbonate particles may have a dp ranging from about 2 nm to about 20 nm, or from about 30 nm to about 50 nm. And the calcium carbonate particles may comprise precipitated calcium carbonate that further comprises sodium carbonate, calcium citrate, magnesium citrate, magnesium carbonate strontium carbonate, or a mixture thereof. [0014] In additional aspects of the disclosure, the carbon precursor may be a first carbon precursor, and the method may further comprise combining the precipitated calcium carbonate with a second carbon precursor to form a second porous carbon material. For example, the first carbon precursor and the second carbon precursor may each be chosen from a sugar, lignosulfonate, polyvinyl alcohol, polyvinylpyrrolidone, cellulose, a cellulose derivative, a resin, or a combination thereof. In at least one aspect of the disclosure, at least 50% by weight of the calcium of the calcium carbonate may be regenerated in the precipitated calcium carbonate.

[0015] A further aspect of the disclosure includes the porous carbon material obtainable by any one of the methods described herein. [0016] The present disclosure further includes methods of using the porous carbon materials described above and elsewhere herein, e.g., in filtration and/or electrochemical devices and applications. For example, the porous carbon materials disclosed herein may be used in or as a filtration device, an electrode or a catalyst support. Accordingly, such filtration devices, electrodes or catalyst supports represent yet another aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary aspects of the disclosure, and together with the description, serve to explain the principles of the present disclosure. [0018] Fig. 1 is a diagrammatic flow diagram showing an exemplary method of forming a porous carbon material.

[0019] Figs. 2A and 2B show images of precipitated calcium carbonate (PCC) described in Examples 1 and 2.

[0020] Figs. 3A and3B show images of porous carbon materials prepared as discussed in Example 1 . [0021 ] Fig. 4 shows a chart of the particle size distributions of porous carbon materials prepared as discussed in Example 1.

[0022] Fig. 5 shows an SEM image of Sample 8 (carbon from the carbonization of pure cellulose powder as described In Example 3) at a magnification of 25,000 x. [0023] Fig. 6 shows an SEM image of Sample 9 (as described In Example 3) at a magnification of 25,000 x.

DETAILED DESCRIPTION

[0024] Particular aspects of the present disclosure are described in greater detail below. The terms and definitions provided herein control, if in conflict with terms and/or definitions incorporated by reference.

[0025] As used herein, the terms "comprises," "comprising," or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, composition, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, composition, article, or apparatus. The term "exemplary" is used in the sense of "example" rather than "ideal."

[0026] As used herein, the singular forms "a," "an," and "the" include plural reference unless the context dictates otherwise. The terms "approximately" and "about" refer to being nearly the same as a referenced number or value. As used herein, the terms

"approximately" and "about" should be understood to encompass ± 5% of a specified amount or value. When a range is used herein as "(a first number)" to (a second number)" or "(a first number)-(a second number)," this refers to a range whose lower limit is the first number, and whose upper limit is the second number. [0027] As used herein, the term "at least" followed by a number denotes the start of a range beginning with that number, which may be a range having an upper limit or no upper limit depending on the variable term being defined.

[0028] Porous carbon generally refers to carbonaceous materials that include pores, e.g., mesopores and/or micropores. According to some aspects of the present disclosure, the porous carbon materials may be prepared from a carbon precursor, e.g., by combining the carbon precursor with at least one carbonate compound. Without being bound by theory, it is believed that the inclusion of the carbonate compound(s) (and the selection of carbonate compounds with certain characteristics) permits controlled porosity of the porous carbon material. [0029] A carbon precursor generally refers to an organic compound capable of undergoing carbonization. Exemplary carbon precursors suitable for the compositions and methods herein include, but are not limited to, sugars (e.g., sucrose, glucose, maltodextrin and other sugars), anthracene, decacyclene, acenaphthalene, acenaphthene, lignosulfonates (e.g., ammonium lignosulfonate, sodium lignosulfonate, and potassium lignosulfonate), polyvinyl alcohol, polyvinylpyrrolidone, cellulose and derivatives thereof (e.g., cellulose ethers, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, methyl cellulose, and other cellulose derivatives), resins (e.g., imide resins, chain vinyl resins, phenol resins, furan resins, furfuryl alcohol resins, formaldehyde phenol resins, formaldehyde

tetrahydrofuran resins, and other resins), polyacrylonitrile, polyethylene-propylene ether blockpolymers, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, petroleum pitch, coal tar pitch and oils, aromatic hydrocarbons (e.g., aromatic polymers and other polyaromatic hydrocarbons), cyclic organic nitrogen, sulfur, and oxygen containing compounds, starch, polyacrylates (e.g., polystyrene-acrylate, polymethylmethacrylate, polymethylacrylate, and polymethacrylonitrile, among other polyacrylates), polyurethanes, furfuryl alcohol, furfural, polyethyl ether ketone, polyphenylene sulfide, pyromellitic acid, citric acid, polyaniline, styrene, tannic acid, latex (e.g., natural latex and synthetic latex based on styrene butyl rubber, nitrile butyl rubber, or the like, including polystyrene latex), ammonia, acetic acid, formic acid, gum arabic, gelatins, polyvinyl pyrrolidone, polylactic acid, malic acid, stearic acid, polystyrene acryl rubber, polyglycol ethers, alkyl-aryl polyethylene, polyethylene glycol ethers, aryl-ethyl-phenyl polyglycol ethers, aryl polyglycol ether, carboxylic acid polyethylene glycol ester nonionic surfactant, alkyl polyoxyethylene ethers, aryl polyoxyethylene ethers, nonyl phenol novolac ethoxylate, polystyrene methacrylate copolymers, polyacrylate co-polymers, alkyl-, phenyl- and polyalkylphenyl sulfonates, acetate, butyrate, polyacrylonitrile, polystyrene butadiene, polyacryl styrene butadiene,

polyoxymethylene, poly(methyl atropate), polyisobutene, polyethyleneoxide,

polypropyleneoxide, polypropylene, polybutadiene, polyisoprene, and combinations thereof. To promote compatibility with the carbonate material, the carbon precursor may comprise at least one functional group. For example, the carbon precursor may include one or more functional groups such as hydroxyl, carboxylic acid, phosphonate, sulfonate, amine, amide, ester, and other suitable functional groups. [0030] The carbon precursor may be combined with the carbonate compound in dry form or as part of a slurry, as discussed below. Suitable carbonate compounds include, but are not limited to, calcium carbonate, sodium carbonate, magnesium carbonate, calcium magnesium carbonate (dolomite), strontium carbonate, and mixtures thereof. In some examples, the carbonate compound may comprise calcium carbonate. In at least one example, the carbonate compound may comprise at least 50% by weight calcium carbonate and up to 50% by weight of other types of carbonate, such as, e.g., sodium carbonate, magnesium carbonate and/or strontium carbonate.

[0031 ] In additional or alternative embodiments, the carbonate compound(s) and carbon precursor may be combined with one or more other minerals to form a mixture, e.g., a dry mixture or a slurry. For example, such a mixture may comprise at least 80% by weight carbonate compound(s) and carbon precursor (e.g., the carbonate compound(s) comprising calcium carbonate or calcium carbonate in combination with one or more other carbonate compounds), and up to 20% by weight of other minerals, such as, e.g. calcium citrate, magnesium citrate, or a mixture thereof.

[0032] The carbonate compound particles may be characterized in terms of the diameter of a sphere of equivalent diameter ("equivalent spherical diameter" (ESD)) that sediments through a fully dispersed suspension of the particles in an aqueous medium. For example, particle size may be measured by Sedigraph and the corresponding particle size distribution may be obtained by plotting the cumulative percentage by weight of particles having a given ESD. For example, d₅₀ is the particle ESD at which 50% by weight of the particles have a smaller ESD. According to some aspects of the present disclosure, the carbonate compound may have a d₅₀ ranging from about 300 nm to about 1000 nm, , from about 500 nm to about 1000 nm, from about 300 nm to about 500 nm, or from about 750 nm to about 900 nm. [0033] Calcium carbonate obtained by precipitation is known as precipitated calcium carbonate (PCC), and typically comprises aggregates of primary or elementary particles. PCC used in accordance with the present disclosure may be prepared by any suitable method, such as, e.g., from a lime-based solution (e.g., comprising CaO), a CaS0₄-based solution, or a CaCI₂-based solution. In at least one aspect of the disclosure, the PCC may be prepared with the use of one or more crystallization controlling agents. Exemplary

crystallization controlling agents include, but are not limited to, citric acid,

ethylenediaminetetraacetic acid (EDTA), and polyaspartic acid. According to some aspects of the present disclosure, synthesis of PCC may allow for control of physical and/or chemical characteristics of the PCC, such as morphology, particle size, and chemical composition. Control of the PCC characteristics in turn can affect the characteristics of the porous carbon material. For example, PCC morphology may be selected such that PCC aggregates combine in a manner to create a template for porous carbon material, described in more detail below, to produce an interconnected pore structure within the porous carbon material. According to some aspects of the present disclosure, the PCC may result in various polymorphs including calcite, aragonite, or vaterite. Suitable elementary particle

morphologies for PCC include rhomboidal, scalenohedron, needle-like, and flower like.

[0034] As mentioned above, PCC particles may form aggregates, which may exhibit various structures. Such structures include, for example, spheres or anisotropic shapes such as nano-fibres, nano-platelets and nano-sheaves. In some aspects of the disclosure, the aforementioned nano-fibres may vary in length from about 20 to about 1000 nm, or from about 40 to about 500 nm. Aggregation of PCC particles can be random or controlled.

Without intending to be bound by theory, controlled aggregation may be advantageous in that the control may be used to create an interconnected porous network having a defined distribution of pore shapes and/or sizes in the porous carbon material.

[0035] PCC aggregates (comprising two or more elementary particles) may be

characterized by their mean elementary particle size (dp). As used herein, "primary particle size" and "elementary particle size" are used interchangeably to refer to the approximated average diameter of particles that make up aggregates. The dp may be determined by permeability measured according to a method derived from BS 4359-2. The basis of this derived method is the measurement of the air permeability of a pellet of the same material, analogous to the "Blaine" or the "Lea & Nurse method." The calculation of the dp derives from the Carman & Malherbe equation:

. 1.05ε² , ₇ , 2.88ε² , ._ .. .

q x L = - ds H ds Equation 1

^¾ (1-ε)² 1-ε where q is volumetric rate of air flow passed through the PCC pellet (cm³/g), ds is the mean particle diameter (μηη), L is the thickness of the pellet, and ε is the porosity of the pellet. The porosity of the pellet ε calculated as:

where W is the weight of the pellet, D is the density of the pellet (g/cm³), and A is the area of the cross section of the pellet (cm²). It can then be shown that the mean particle diameter ds, which is determined according to Equation 1 is not absolutely independent from the porosity of the pellet. Consequently, the dp can be calculated by a correction to the mean particle diameter considering a reference porosity ε = 0.45 according to the formula: dp = ds x _e-³-²(^£-°-⁴⁵) Equation 3 where ε is the porosity of the pellet as determined in Equation 2, ds is the mean particle diameter according to Equation 1 , and dp is the mean particle diameter (μηη).

[0036] The carbonate compound may have a dp ranging from about 1 nm to about 700 nm. For example, the carbonate compound may have a dp ranging from about 2 nm to about 100 nm, from about 2 nm to about 50 nm, from about 2 nm to about 20 nm, from about 30 nm to about 50 nm. [0037] In certain aspects of the present disclosure, the carbonate compound may be surface treated with one or more compounds, which may comprise organic and/or inorganic compounds. For example the carbonate compound(s) may be surface treated with fatty acids (e.g. stearic acid), phosphonate-based compounds, sulfonate-based compounds, amines, citric dicarboxylic acids, or combinations thereof. The term "surface treatment" as used herein is meant to be interpreted broadly, and not limited to uniform, monolayer coatings which cover the entire surface area of a particle. The surface treatment compound may be present in an amount sufficient to alter the polarity of the carbonate compound such that the carbonate compound will be more compatible with the carbon precursor and/or any solvent(s). The surface treatment compound may be hydrophobic or hydrophilic depending on the hydrophilicity or hydrophobicity of the carbon precursor and the carbonate compound. In at least some aspects, the surface treatment compound may be present in an amount ranging from about 0.01 % to about 0.60% by weight, e.g. from about 0.10% to about 50% by weight, or from about 1 .0 % to about 0.30% by weight based on the dry weight of the carbonate compound. [0038] As mentioned above, the carbon precursor and carbonate compound (and any additional materials, such as, e.g., calcium citrate and/or magnesium citrate) may be combined to form a mixture. In some examples, the mixture may be in the form of a slurry, e.g., when the carbon precursor and carbonate compound are combined in a suitable liquid, e.g., water. The mixture may comprise from about 5 g/L to about 350 g/L of the carbonate compound, such as from about 100 g/L to about 300 g/L, or from about 150 g/L to about 250 g/L. Further, for example, the mixture may comprise from about 5 g/L to about 2100 g/L of the carbon precursor, such as from about 100 g/L to about 750 g/L, from about 200 g/L to about 500 g/L, or from about 250 g/L to about 400 g/L of the carbon precursor. Mixing may be performed by stirring and/or utrasonication of the mixture. In some embodiments, the mixture may also comprise one or more dispersants. Exemplary dispersants include, but are not limited to, polyacrylic acid, polyacrylate (e.g. sodium polyacrylate) and

hexametaphosphate (e.g. sodium hexametaphosphate). [0039] The mixture may be heated, e.g., to carbonize the carbon precursor to obtain a composite material. The heating temperature may range from about 500 °C to 3000 °C, such as 650 °C to 2000 °C, or 750 °C to 1250 °C, or greater than 650 °C. The mixture may be heated for a duration of time ranging from about 30 minutes to about 24 hours, such as from about 30 minutes to about 12 hours, from about 30 minutes to about 10 hours, from about 1 hour to about 3 hours, e.g., about 30 minutes, about 1 hour, about 1 .5 hours, about 2 hours, about 2.5 hours, about 3 hours. The mixture may be heated in a vacuum or an inert atmosphere, for example, under helium, argon, or nitrogen. The heat treatment may release C0₂, e.g., during carbonization of the organic carbon precursor. Depending on the temperature, the heat treatment may produce a carbon/carbonate composite, such as carbon/CaC0₃ composite (e.g., for temperatures less than about 650°C or about 670°C), or a carbon/oxide composite, such as a carbon/CaO composite (e.g., for temperatures greater than about 650°C or about 670°C). For example, a higher temperature may cause thermal decomposition of calcium carbonate to produce calcium oxide and C0₂.

[0040] Without intending to be bound by theory, it is believed that the carbonate compound serves as a porogen or template for the porous carbon. For example, as the carbon precursor and carbonate compound are mixed in water or other suitable solvent, the carbon precursor may cluster or assemble around the carbonate particles. In some cases, and depending on the chemical characteristics of the carbon precursor, the carbon precursor may become at least partially cross-linked, e.g., forming an interconnected network or

agglomerate generally surrounding the carbonate particles (e.g., PCC aggregates). Then, as the mixture is heated, the organic carbon precursor may carbonize (e.g., releasing one or more gases) to leave behind a composite material comprising a carbonaceous residue having the same or similar structure generally surrounding the carbonate particles. For example, heating the mixture may release C0₂, CO, CH₄, and/or other gases resulting from the decomposition of the carbon precursor. If the temperature is sufficient to cause at least partial or complete decomposition of the carbonate, the composite material may comprise a carbonaceous residue (from the carbon precursor) and an oxide compound (e.g., releasing additional C0₂). Accordingly, the heat treatment may form a composite structure of interconnected pores of carbonaceous material defined by the carbonate compound or oxide derived from the carbonate compound. [0041 ] Again, without intending to be bound by theory, increasing or decreasing the heating temperature may affect the porosity and/or yield of the porous carbon material. For example, increasing the heating temperature may improve the oxidization of carbon dioxide produced from decomposition of carbonate composition. Alternatively, lowering the heating

temperature below the temperature at which the carbonate compound decomposes may reduce or prevent oxidation of the carbon precursor.

[0042] All or at least a portion of the carbonate or oxide compound then may be removed from the composite material with an acid or acidic solution, e.g., leaving behind the carbonaceous residue having pores in the absence of the carbonate or oxide compound. For example, the composite material produced from the heat treatment may be placed in contact with an acidic solution, e.g., by placing the composite material in an acid bath, with or without agitation, or by spraying the composite material with the acidic solution. Using a carbonate template in synthesis of the porous carbon material as described herein allows the carbonate material to be removed, e.g., leached, from the composite material without hydrofluoric acid, a highly corrosive acid, used in prior methods. For example, acids other than hydrofluoric acid, including a variety of relatively weak acids, may be used to remove carbonate from the composite material. According to certain aspects of the present disclosure, the acidic solution may comprise acetic acid, nitric acid, sulfuric acid, hydrochloric acid, ammonium salts thereof (such as ammonium chloride, etc.), or a combination thereof. [0043] The concentration of the acidic solution may range from about 0.1 M to about 5.0 M, such as from about 0.5 M to about 4 M, or from about 1 .0 to about 3.0 M. In some examples, the composite material may be in contact with the acidic solution for a period of time ranging from about 5 minutes to about 24 hours, such as from about 30 minutes to about 18 hours, from about 30 minutes to about 4 hours, from about 1 hour to about 24 hours, or from about 1 hour to about 3 hours. The acidic solution may remove at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, or all or substantially all of the carbonate compound from the composite material. Without intending to be bound by theory, it is generally believed that a more acidic solution may remove the templating material from the carbonaceous material more quickly. For example, as the pH of the acidic solution is lowered, the amount of time necessary for the acidic solution to be in contact with the composite material to remove all or substantially all of the carbonate or oxide templating material may be reduced. [0044] Thus, the physical and/or chemical properties of the carbonate compound may define or otherwise affect the pore size, shape, and structure of the porous carbon material that is ultimately produced. For example, the use of a carbonate compound with a specific elementary particle size (or relatively narrow particle size distribution) may create a template of similarly sized features. Removal of the template with acid as discussed above may provide a porous carbon material with an average pore size that is the same as, or similar to, the elementary particle size of the carbonate compound.

[0045] As the acidic solution breaks down the carbonate or oxide portion of the composite material, cations from the carbonate compound may be released from the composite material and enter the acidic solution, e.g., forming a second solution or second acidic solution. The acidic solution and carbonate/oxide compound leached from the composite material thus may produce a porous carbon material and a second acidic solution, e.g., comprising the acid and dissolved alkali and/or alkaline earth ions. Depending on the chemical composition of the carbonate compound, the second solution may, for example, comprise Ca²⁺, Mg²⁺, Sr²*, Na⁺, and/or K⁺ ions. Thus, when the carbonate compound comprises calcium carbonate, the second solution may comprise calcium chloride, calcium sulfate, calcium nitrate, calcium acetate, or a combination thereof, depending on the anion of the acid(s). In certain embodiments, the second solution comprises a calcium salt having a concentration ranging from about 1 g/L to about 350 g/L, for example about 10 g/L to 250 g/L, or about 15 g/L to about 100 g/L, or about 25 g/L to about 50 g/L.

[0046] Following the acid treatment, in some aspects of the disclosure, the resulting porous carbon material may be dried. For example, the porous carbon material may be dried at a temperature ranging from about 80 °C to about 200 °C, about 100 °C to about 160 °C, or about 1 10 °C to about 130 °C, e.g., a temperature of about 120 °C. The drying step may be carried out in an oven or other suitable heating apparatus. Further, for example, the porous carbon material may be dried in a vacuum, inert atmosphere, or air.

[0047] The efficiency in production of the porous carbon material may be characterized by the carbon yield, e.g., as a comparison of the amount of porous carbon material produced and the amount of carbon precursor. Carbon yield may be expressed as a percentage calculated by dividing the mass of porous carbon material produced by the mass of the carbon precursor. In at least some examples of the present disclosure, the carbon yield is at least 5%. For example, the methods disclosed herein may have a carbon yield greater than 10%, e.g. 12%, 15%, 20%, 25%, 30%, 35%, or 40%. [0048] The porous carbon material may be characterized based on the size of its pores, e.g., the pore size distribution. As used herein "pore size" and "pore diameter" both mean the approximate diameter of pores, or the width for slit-shaped pores. According to the

International Union of Pure and Applied Chemistry (lUPAC), pore size may be classified as follows: (i) "micropore" for pores having a diameter (or width for slit-shaped pores) of less than 2 nm; (ii) "mesopore" for pores having a diameter (or width) between 2 nm and 50 nm; and (iii) "macropore" for pores having a diameter (or width) greater than 50 nm. These terms also may be applied to materials comprising a majority of pores that primarily fall within one of the pore classifications. The composition of the number and type of pores in a material can be determined from the material's pore size distribution.

[0049] The pore size distribution of a material may be obtained by the BJH (Barrett-Joyner- Halenda) model wherein the adsorption and desorption of a gas, for example nitrogen or argon, is measured at 77K on the porous material. The modified Kelvin equation may be used to relate the amount of adsorbed gas removed from the pores, as the relative pressure is decreased, to the size of the pores. The porous material thus may be characterized according to the lUPAC classifications by analyzing the maximum (or peak) of the pore size distribution to determine which classification applies. If pore size distribution is multimodal, the largest maximum may be used to determine the lUPAC classification. The pore diameter corresponding with the maximum of the pore size distribution may also be referred to herein as the average pore size of the material. For example, a porous material with a pore size distribution having a maximum between 2 nm and 50 nm may be described as being mesoporous.

[0050] According to some aspects of the present disclosure, the porous carbon material may have an average pore size ranging from about 0.1 nm to about 1000 nm. For example, the porous carbon material may have an average pore size ranging from about 1 nm to about 700 nm, from about 100 nm to about 200 nm, from about 50 nm to about 150 nm, from about 5 nm to about 50 nm, from about 1 nm to about 100 nm, from about 2 nm to about 50 nm, from about 5 nm to about 20 nm, from about 30 nm to about 50 nm, or from about 10 nm to about 50 nm. In some examples, the porous carbon material may have a ratio of mesopores to micropores ranging from about 1 :10 to about 10:1 ; from about 1 :5 to about 5:1 , from about 1 :3 to about 3:1 ; from about 2:3 to about 3:2; or about 1 :1. The ratio of mesopores to micropores may be characterized as the ratio of the surface area of the porous carbon material comprising mesopores as measured by the BJH model to the surface area of the porous carbon material comprising micropores as measured using the t-plot method (ISO 15901 -3). [0051 ] The methods disclosed herein may provide for the pore size of the porous carbon material to be essentially equal to the elementary particle size or aggregate size of the carbonate compound. For example, according to some aspects of the present disclosure, the elementary particle size of the carbonate compound may differ by less than 20% from the average pore size of the porous carbon material, such as, e.g., less than 15%, less than 10%, or less than 5%. In some examples, the ratio of the elementary particle size of the carbonate compound to the average pore size of the porous carbon material may range from about 0.8 to about 1.2, or from about 0.9 to about 1 .1.

[0052] Pore size distribution of a porous material may affect the performance of the material in a particular application. For example, certain applications may prefer or require specific pore sizes or pore size distributions. The methods herein may be used to control the pore size distribution of the porous material for a given application, e.g., resulting in a more uniform pore size or a desired distribution of pore sizes as compared to traditional methods.

[0053] The porous carbon material may also be characterized based on its specific surface area (SSA) as measured by the BET method (ISO 9277). Porous carbon materials according to the present disclosure may have a BET SSA ranging from about 100 m²/g to about 2000 m²/g, such as from about 300 m²/g to about 1000 m²/g, or from about 500 m²/g to about 800 m²/g, e.g., a BET SSA of about 100 m²/g, about 250 m²/g, about 500 m²/g, about 750 m²/g, or about 1000 m²/g or greater. [0054] Referring again to preparation of the porous carbon material discussed above, according to some aspects of the present disclosure, the C0₂ and/or alkali/alkaline earth ion byproducts may be used to prepare a carbonate compound or regenerate the carbonate compound used as a starting material. For example, the second solution (e.g., acidic solution comprising alkali and/or alkaline earth ions from the carbonate/oxide compound(s)) may be used to prepare a carbonate compound. To create a closed synthesis loop, the second solution may be used to regenerate the carbonate compound, e.g., as PCC. For example, the alkali and/or alkaline earth ions may be filtered from the second solution with a suitable filtering material or apparatus, such as, e.g., frits, filter paper, filter press, or vacuum filter. Filtering may be carried out at reduced or added pressure. The pH of the second solution may be adjusted, for example, by increasing the pH to produce a basic solution (comprising calcium hydroxide in the case of Ca2+ ions). PCC then may be produced, for example, by adding carbon dioxide or CaCI₂ to the pH-adjusted second solution. [0055] The efficiency in regenerating carbonate may be determined by comparing the mass of carbonate produced to the mass of the initial carbonate compound combined with the carbon precursor, e.g., expressed as a percentage. According to some aspects of the present disclosure, the amount of carbonate compound regenerated may range from 0% to about 80% by weight of the original carbonate compound; for example, from about 1 % to about 75%; from about 5% to about 50%; e.g. up to 10%; up to 15%; up to 25%; or up to 30%.

[0056] Optionally, the regenerated carbonate compound may be reused to prepare additional porous carbon material using the same or a different carbon precursor. For example, in the initial process, a first carbon precursor may combined with a first carbonate compound to form a first porous carbon material, wherein byproducts of C0₂ and

alkali/alkaline earth ions of the heat treatment and acid treatment steps are used to regenerate the carbonate compound as a second carbonate compound. The second carbonate compound then may be combined with a second carbon precursor to form a second porous carbon material. According to some aspects of the present disclosure, the first carbon precursor and the second carbon precursor may each be chosen from a sugar, lignosulfonate, polyvinyl alcohol, polyvinylpyrrolidone, cellulose, a cellulose derivative, a resin, or combinations thereof. The regenerated carbonate compound (second carbonate compound) may be PCC. [0057] The porous carbon material prepared according to the methods herein may be useful in a variety of applications, including, but not limited to, electrical/electrochemical applications, catalytic application, and filtration. Of particular note, mesoporous carbon materials may exhibit improved properties compared to activated carbon and graphite, such as, e.g., improved conductivity, specific or volumetric electrochemical capacity, specific or volumetric capacitance, and/or cycle life, e.g., due to a more efficient use of the material bulk and surface by the tailored morphology. Using such mesoporous carbon materials may also increase specific energy, energy density, specific power, power density, durability, and/or longevity of energy storage and conversion systems. It may be desirable to use mesoporous carbon materials produced according to the methods herein for various electrical applications in which such properties affect performance. Without being bound by theory, it is believed that carbon materials containing a relatively high volume of mesopores (or relatively high surface area comprising mesopores) may exhibit improved performance, e.g., due to their specific pore size or pore size distribution. For example, the specific pore size and/or pore size distribution of the material may enable or otherwise facilitate the acceptance of ions, e.g., providing greater access to the pores, therefore improving efficient use of the large surface area created by the pores and the geometrical surface area of the material.

[0058] For example, the porous carbon material may be used as an electrode material in energy devices such as fuel cells, batteries, or supercapacitors. In at least one example, the porous carbon material may be used in supercapacitor electrodes. Without intending to be bound by theory, controlling the average pore size of the porous carbon material may improve access of the electrolyte electroactive ion species inside the pores, thereby increasing the electroactive electrode surface area of the porous carbon material. In a lithium ion battery electrode the controlled pore distribution of the porous carbon material may have advantageous properties. For example, the pores may improve the ability for the electrolyte to penetrate the porous carbon material for suitable ionic conductivity within the electrode. And controlling the pore size of porous carbon material acting as electroactive insertion electrode material in the negative electrode of a lithium-ion battery may improve specific and volumetric electrochemical capacity, and charge acceptance rate of the battery. [0059] Further, the porous carbon material may be useful as a catalyst support, e.g., in fuel cells or in metal-air batteries. In metal-air batteries, such as lithium-air and zinc-air batteries, for example, porous carbon may act as a catalyst support of the positive electrode. It may be beneficial to control the porosity of a catalyst support, such that the pore size is large enough to allow fuel or oxidant to enter the pores where catalyst particles may be anchored and allow product gases to escape. Further, for example, increased surface area of a catalyst support may facilitate electron transfer. Therefore it may be advantageous to use a porous carbon material created by the methods described herein that allow control of pore size while maintaining a high surface area.

[0060] In yet other applications, the porous carbon material produced herein may be useful as a filtration material, e.g., in waste treatment applications. The porous carbon material produced by the methods disclosed herein may have adsorptive properties useful for adsorbing organic compounds or heavy metals in filtration applications .The porous carbon material may be prepared with a selected pore size or pore size distribution, for example, based on chemical and/or physical characteristics of the compound or other chemical species to be adsorbed and/or filtered by the porous carbon material.

[0061 ] Fig. 1 shows an exemplary process flow for some methods disclosed herein. The methods disclosed herein may include all or only a portion of the steps illustrated, e.g., some of the steps may be optional. In Fig. 1 , a carbon precursor (e.g., sucrose) is delivered from a source 1 (e.g., carbon feed bin), together with water from a source 2, to a suspension tank 3 to form a carbon precursor solution, suspension or mixture. The carbon precursor suspension is then added to a mixing tank 5, together with additional water from a source 4 (or source 2) and a carbonate compound (added to the mixing tank 5 from a carbonate feed tank 23). The carbonate compound may be PCC, e.g., with an elementary particle size ranging from about 2 nm to about 50 nm or any other size or range of sizes as discussed above. The carbon precursor suspension, additional water, and carbonate compound are mixed thoroughly to form a mixture or slurry. The concentration of carbonate compound in the mixture may range from about 10 g/L to about 350 g/L, for example. In some

embodiments the concentration of carbon precursor in the mixture may be greater than 350 g/L, such as ranging from about 500 g/L to about 2100 g/L.

[0062] After mixing, the carbon precursor/carbonate mixture is delivered to a dryer 6. The dryer 6 dries the mixture at a temperature ranging from about 20 °C to about 90 °C.

Following this drying, the carbon precursor/carbonate mixture is delivered as a feed to a furnace 7 which heats the mixture. For example, the mixture may be heated at a temperature of at least 650°C (or generally a temperature ranging from about 500°C to 3000°C as discussed above). Heating the mixture in the furnace produces a carbon/CaO composite material and exhaust gas comprising C0₂. The composite material is delivered with air from a source 8 and water from a source 9 to a cooling tank 10, e.g., to form a composite material slurry. The exhaust gas of the furnace, which includes carbon dioxide, is collected in a receiver 1 1 . Optionally, the exhaust gas is purified and/or compressed before collection in the receiver 1 1.

[0063] The composite material slurry is then delivered to one or more acid wash tanks 13. An acidic solution (e.g. comprising acetic acid) is added from a source 12 (e.g., a tank) to the composite material slurry in the acid wash tank 13. The acid-treated slurry is then filtered through a filter press 15. The filter press 15 separates the solid porous carbon material from the acidic solution. Water is added from a source 14 to the filter press 15 to wash the porous carbon material. After washing, the porous carbon material is delivered to a dryer 16 and dried, for example, at a temperature ranging from about 80 °C to about 200 °C. The porous carbon material may be dried in air or under a vacuum. Further processing of the porous carbon material may include pulverizing, classifying, and/or coating.

[0064] The acidic solution filtrate from the filter press 15 is delivered to a rinsate tank 17. The acidic solution may contain calcium chloride (e.g., if hydrochloric acid is used) and/or calcium acetate (e.g., if acetic acid is used). The acidic solution may then be delivered to a slaking mixer 20, e.g., depending on the chemical composition, pH, and/or other

characteristics of the acidic solution. The pH of the acidic solution can be adjusted in the slaking mixer 20 by adding an alkaline material (e.g., calcium oxide) from a source 18. Additionally or alternatively, the acidic solution may be diluted in the slaking mixer 20 by adding water from a source 19. Thereafter, the pH-adjusted solution is delivered to a carbonator 22.

[0065] The pH-adjusted solution is carbonated in the carbonator 22 by the addition of carbon dioxide from the receiver 1 1 and optionally or alternatively from another supply of carbon dioxide 21 . Carbonating the pH-adjusted solution causes precipitation of calcium carbonate, effectively regenerating at least a portion of the original carbonate compound. The regenerated carbonate compound can optionally be delivered to the carbonate feed bin 1 to be reused in the process to produce additional porous carbon material. It is understood that some methods herein may omit certain steps illustrated in Fig. 1.

[0066] Other aspects and embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein.

EXAMPLES

[0067] The following examples are intended to illustrate the present disclosure without, however, being limiting in nature. It is understood that the present disclosure encompasses additional aspects and embodiments consistent with the foregoing description and following examples.

Example 1

[0068] Studies were performed to prepare and characterize carbon materials produced using a carbon precursor and carbonate compound template according to the present disclosure. The carbonate compound was PCC (Imerys) with a primary particle size of 22 nm, and a BET SSA of 78 m²/g. The PCC was a calcite polymorph with a rhomboidal morphology. Fig. 2A shows an SEM image of the PCC particles used in Example 1 .

[0069] Samples 1 -3 were prepared using sucrose as the carbon precursor. Sample 4 (discussed below) was prepared using lignosulfonate as the carbon precursor. [0070] To prepare Samples 1 -3, 15 g of sucrose was added to 50 g of water in a container and magnetically stirred for 15 minutes to dissolve the sucrose, producing a solution. Once the sucrose dissolved, 10 g of the PCC was slowly added to the solution while stirring continued for 15 minutes and the carbonate compound dispersed throughout the solution. Once the PCC was adequately dispersed, the resulting mixture was ultrasonicated for 5 minutes. The container was then heated at 80°C in a silicon oil bath overnight while the mixture was stirred. During heating, the water in the mixture evaporated in part, leading to a paste. After heating overnight, the mixture was removed from the silicon oil bath and allowed to cool at room temperature for 1 hour.

[0071 ] The mixture was then heated in a tube furnace (Tube Furnace 21 100, Thermolyne) that had been preheated to 800°C for 1 hour. At the end of the preheating time period, the air within the furnace was flushed with nitrogen for 10 minutes. The mixture was heated for 2 hours at 800°C in a nitrogen atmosphere. Heating of the mixture carbonized the sucrose and caused thermal decomposition of the carbonate to form a composite material comprising carbonaceous material (residue of the sucrose) and CaO. The composite material was allowed to cool for 30 minutes. The composite material was allocated into three separate samples of 2.50 g each: Samples 1 , 2 and 3.

[0072] Sample 1 (composite material) received no further treatment, whereas Samples 2 and 3 were treated with acid to at least partially remove CaO from the carbonaceous material.

[0073] 200 ml of an acidic solution comprising 10 wt% of HCI (2.742 M) in water was prepared. Then 100 ml of the acidic solution was placed in two 300 ml beakers. Samples 2 and 3 were each added to one of the two beakers containing the acidic solution while stirring magnetically for 2 hours and 15 minutes. Sample 3 was ground with a mortar and pestle for 3 minutes before the acid treatment. After stirring, the contents of the beakers for Samples 2 and 3 were filtered with a frit under reduced pressure to produce respective porous carbon materials and acidic filtrate. The materials were each washed with 100 ml H₂0 three times and then dried under vacuum at 120°C overnight. Once dried, each material was weighed on a lab scale. Sample 2 weighed 0.60 g, and Sample 3 weighed 0.61 g. The total porous carbon material produced (1 .21 g) equates to a 12.1 % overall carbon yield (based on the amount of sucrose). [0074] Figs. 3A and 3B show images of the materials taken by scanning electron microscopy (SEM) at 10,000x magnification and 1.0 kV, wherein Fig. 3A shows the porous carbon material produced from Sample 2, and Fig. 3B shows the porous carbon material produced from Sample 3. The specific surface area of the composite material of Sample 1 , and the porous carbon materials of Samples 2 and 3 were calculated using the BET method. The BET SSA of Sample 1 was 126 m²/g. The BET SSA of Sample 2 was 695 m²/g. The BET SSA of Sample 3 was 707 m²/g.

[0075] The pore size distribution for Samples 2 and 3 were calculated using the BJH method, and are shown in Figure 4. The pore size distributions show a pore volume maximum of about 4 cm³/g at a pore size of about 22 nm, with pores ranging from 0.1 nm to 50 nm. This pronounced peak at 22 nm suggests good correlation between the PCC elementary particle size and the pore size of the resulting carbonaceous material. The pore size distributions also show a ratio of micro pores to mesopores of about 50:50 (or 1 :1 ). [0076] Sample 4 was prepared according to the procedure for Sample 3 (e.g., grinding the material with a mortar and pestle for 3 minutes before acid treatment) but using

Iignosulfonate in place of sucrose as the carbon precursor. The BET SSA of Sample 4 was 374 m²/g, and the pore size distribution showed a maximum volume at 17 nm. The final carbon yield starting with a weight ratio of PCC:ammonium Iignosulfonate of 2:3 was about 25 %.

[0077] However, the BET SSA of the resulting porous carbon could be increased when increasing the PCC amounts. Sample 5 was prepared like Sample 4 but at a weight ratio of PCC versus ammonium Iignosulfonate of 2:1. The resulting carbon material was prepared at about 20 % carbon yield and showed a BET SSA of 621 m²/g at a maximum pore size of 18 nm.

Example 2

[0078] Additional studies were performed using a different PCC (Imerys) having a primary particle size of 32 nm, and a BET SSA of 26 m²/g. Fig. 2B shows an SEM image of the PCC particles used in Example 2, showing a generally more fibrous, anisotropic shape as compared to the PCC particles of Example 1.

[0079] Samples 6 and 7 were prepared according to the process described in Example 1 , wherein sucrose was used as the carbon precursor for Sample 6, and ammonium

Iignosulfonate was used as the carbon precursor for Sample 7. The porous carbon materials were ground with a mortar and pestle for 3 minutes following acid treatment (similar to Sample 3). The BET SSA for Sample 6 was 718 m²/g, and the pore size distribution showed a maximum pore volume at 71 nm. The BET SSA for Sample 7 was 333 m²/g, and the pore size distribution showed a maximum pore volume at 44 nm. These results suggest that the more fibrous, anisotropic PCC resulted in carbonaceous material having a wider pore size distribution as compared to the materials of Example 1 .

Example 3

[0080] Additional studies were performed with the PCC of Example 1 having a primary particle size of 20 nm, and a BET SSA of 78 m²/g with a calcite polymorph of rhomboid morphology and a cellulose microcrystalline powder with 20 μηη average particle size (Sigma Aldrich) at a weight ratio of PCC to cellulose of 2:3.

[0081 ] 15 g of the dried cellulose powder (weight loss on drying at 80°C ca. 5 wt%) and 10 g of the PCC were dispersed in 50 g of water by mixing and ultrasonication for 5 minutes. The drying, heat treatment and leaching process was carried out as in Example 1 . The resulting carbon material (Sample 8) showed a BET SSA of 704 m²/g and mesopores at a maximum of around 20 nm. The carbon yield was 9 %.

[0082] An SEM image of the carbon based on cellulose demonstrates the mesoporous morphology of the modified material (see Fig. 5). [0083] Carbonization of the pure cellulose powder at 800°C in a nitrogen atmosphere resulted in a carbon material with a BET SSA of 290 m²/g (Sample 9). The carbon showed no mesoporosity but some larger pores in the submicron range, as illustrated by the SEM image shown in Fig. 6.

Example 4 [0084] Further studies were performed with the PCC of Example 1 having a primary particle size of 22 nm, and a BET SSA of 78 m²/g with a calcite polymorph of rhomboid morphology and polyvinylalcohol as a carbon precursor at a weight ratio PCC to carbon precursor of 2:3.

[0085] 15 g of polyvinylalcohol (PVA) (Mowiol^® 8-88, molecular weight 67Ό00 Da) was dissolved in 50 g of water in a container and magnetically stirred for 15 minutes to dissolve the PVA. 10 g of the PCC was slowly added to the solution while stirring continued for 15 minutes and the carbonate compound dispersed throughout the solution. Once the PCC was adequately dispersed, the resulting mixture was ultrasonicated for 5 minutes. The container was then heated at 80°C in a silicon oil bath overnight while the mixture was stirred. During heating, the water in the mixture evaporated in part. After heating overnight, the mixture was removed from the silicon oil bath and allowed to cool at room temperature for 1 hour. [0086] The carbonization was accomplished in a tube furnace at 800°C in a nitrogen atmosphere for 2 h analogous to Example 1. The sample was cooled and the CaO was leached from the resulting carbon/CaO composite using a solution of 40 g ammonium chloride in 100 ml of water. The composite was stirred for 2 h in this solution, then filtered and washed with 3x100 ml of deionized water and finally dried.

[0087] The BET SSA of the resulting Sample 10 was 526 m²/g with a maximum pore size at 23 nm and a carbon yield of 14 %.

Example 5

[0088] Additional experiments were performed with the PCC of Example 1 having a primary particle size of 22 nm, and a BET SSA of 78 m²/g with a calcite polymorph of rhomboid morphology and a carbonaceous resin powder as a carbon precursor at a weight ratio PCC to carbon precursor of 2:3.

[0089] Sample 1 1 was prepared by mixing 15 g of Carbores^® P resin (Rijttgers, Germany) powder and 10 g of the PCC at 300°C being above the softening point of the resin for 1 h. The mixture then was calcined in a tube furnace at 900°C for 2 hours in a nitrogen atmosphere to carbonize the resin and forming the CaO/carbon composite. After cooling the mixture to room temperature the CaO was leached from the carbon according to Example 1 using the hydrochloric acid solution of Example 1. The BET SSA of Sample 1 1 was

486 m²/g, the carbon yield was 25 % and the pore size distribution showed a maximum volume at 15 nm.

Claims

A method for forming a porous carbon material, the method comprising: combining a carbon precursor and a carbonate compound to form a mixture; heating the mixture to produce a composite material; placing the composite material in contact with an acidic solution to produce the porous carbon material and a second solution; and regenerating the carbonate compound from the second solution; optionally wherein the method further comprises

i) filtering the second solution before regenerating the carbonate compound; and/or

ii) drying the porous carbon material, such as at a temperature ranging from about 80 °C to about 200 °C.

The method of claim 1 , wherein

i) the carbon precursor is chosen from a sugar, lignosulfonate, polyvinyl alcohol, polyvinylpyrrolidone, cellulose, a cellulose derivative, a resin, or a combination thereof; and/or

ii) the carbon precursor comprises at least one functional group chosen from hydroxyl, carboxylic acid, phosphonate, and sulfonate.

3. The method of claim 1 or claim 2, wherein

i) the carbonate compound comprises calcium carbonate; and/or

ii) the carbonate compound comprises precipitated calcium carbonate having an elementary particle size (dp) ranging from about 1 nm to about 100 nm, from about 2 nm to about 50 nm, or from about 10 nm to about 30 nm; and/or

iii) the carbonate compound comprises precipitated calcium carbonate in the form of aggregates having a spherical shape or in the form of aggregates having an anisotropic shape; and/or

iv) the mixture comprises from about 5 g/L to about 350 g/L, or from about 150 g/L to about 250 g/L, or from about 50 g/L to about 1000 g/L, or from about 200 g/L to about 500 g/L of the carbonate compound.

4. The method of any of the preceding claims, wherein

i) the heating is carried out at a temperature ranging from about 500 °C to 3000 °C; and/or

ii) the heating is carried out for a period of time ranging from about 30 minutes to about 24 hours, or from about 1 hour to about 3 hours; and/or

iii) the mixture is heated in a vacuum or in an inert atmosphere.

5. The method of any of the preceding claims, wherein

i) the acidic solution comprises acetic acid, nitric acid, sulfuric acid, hydrochloric acid, an ammonium salt thereof, or any combination thereof; and/or

ii) the acidic solution has a concentration ranging from about 0.1 M to about 5.0 M; and/or

iii) the composite material is in contact with the acidic solution for a period of time ranging from about 1 hour to about 24 hours; and/or

iv) the second solution comprises a calcium salt such as calcium chloride, calcium sulfate, calcium nitrate, calcium acetate, or a combination thereof, optionally having a concentration ranging from about 1 g/L to about 350 g/L.

6. The method of any of the preceding claims, wherein

i) the porous carbon material has an average pore size ranging from about 0.1 nm to about 1000 nm, or from about 0.1 nm to about 50 nm; and/or

ii) the porous carbon material has a ratio of mesopores to micropores ranging from about 1 :3 to about 3:1

iii) the elementary particle size (dp) of the carbonate compound differs by less than 5% from an average pore size of the porous carbon material; and/or iv) the ratio of the elementary particle size (dp) of the carbonate compound to the average pore size of the porous carbon material ranges from about 0.8 to about 1 .2 or from about 0.9 to about 1 .1 .

7. The method of any of the preceding claims, wherein the carbonate compound

comprises calcium carbonate, and wherein regenerating the carbonate compound comprises: adjusting a pH of the second solution to produce a basic solution comprising calcium hydroxide; and carbonating the basic solution with carbon dioxide to produce precipitated calcium carbonate.

8. The method of any of the preceding claims, wherein the acidic solution removes at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, or all of the carbonate compound from the composite material.

9. A method for forming a porous carbon material, the method comprising: combining a carbon precursor and precipitated calcium carbonate (PCC) particles to form a mixture, the PCC particles having an elementary particle size (dp) ranging from about 2 nm to about 50 nm, from about 10 nm to about 30 nm, or from about 20 nm to about 50 nm; heating the mixture to produce a composite material; adding an acidic solution to the composite material to produce the porous carbon material and a second solution comprising calcium ions; adjusting a pH of the second solution; and adding carbon dioxide to the second solution to produce precipitated calcium carbonate; optionally wherein

i) the PCC particles further comprise sodium carbonate, calcium citrate, magnesium citrate, magnesium carbonate strontium carbonate, or a combination thereof; and/or

ii) the carbon precursor comprises sucrose, lignosulfonate, cellulose, or a cellulose derivative.

10. The method of claim 9, wherein the dp of the PCC particles ranges from about 10 nm to about 30 nm, and wherein the porous carbon material has an average pore size ranging from about 10 nm to about 30 nm.

1 1 . The method of claim 9 or claim 10, wherein the carbon precursor is a first carbon precursor, the method further comprising combining the PCC particles with a second carbon precursor to form a second porous carbon material.

12. The method of any of claims 9-1 1 , wherein at least 50% by weight of the calcium of the PCC particles is regenerated in the precipitated calcium carbonate.

13. The method of any of claims 9-12, wherein heating the mixture produces carbon dioxide;

optionally wherein the carbon dioxide added to the second solution comprises the carbon dioxide produced from heating the mixture.

14. A porous carbon material obtainable by a method of any one of claims 1 -13.

15. A filtration device, an electrode or a catalyst support comprising the porous carbon material according to claim 14.