WO2017035086A1 - Carbohydrate pyrolyzate adsosrbent and systems and processes utilizing same - Google Patents

Abstract

A carbohydrate carbon pyrolyzate material is described, having utility as an adsorbent as well as for energy storage and other applications. The carbohydrate carbon pyrolyzate material includes microporous carbon derived from carbohydrate precursor material. In adsorbent applications, the carbohydrate carbon pyrolyzate may for example be produced in a particulate form or a monolithic form, having high density and high pore volume to maximize volumetric gas capacity, with the pore size distribution of the carbon pyrolyzate adsorbent being tunable via activation conditions to optimize adsorptive capacity and selectivity for specific gases of interest.

Description

CARBOHYDRATE PYROLYZATE ADSORBENT AND SYSTEMS AND PROCESSES

UTILIZING SAME

CROSS-REFERENCE TO RELATED APPLICATION

The benefit under 35 USC 119 of U.S. Provisional Patent Application No. 62/208,666 filed August 22, 2015 in the names of Edward A. Sturm, et al. for "CARBOHYDRATE PYROLYZATE ADSORBENT AND SYSTEMS AND PROCESSES UTILIZING SAME" is hereby claimed. The disclosure of U.S. Provisional Patent Application No. 62208666 is hereby incorporated herein by reference, in its entirety, for all purposes.

Field of the Disclosure

The present disclosure generally relates to carbon pyrolyzate materials, and more specifically relates to carbohydrate carbon pyrolyzate adsorbent materials, such as high purity microporous carbon materials, derived from renewable natural carbohydrate sources, to methods of making such carbon materials, and to systems and processes utilizing such carbon pyrolyzate materials. Such systems and processes include electrochemical double layer capacitor (EDLC) carbon electrodes for energy storage devices, adsorbent- based heating and refrigeration systems and processes, adsorptive gaseous recovery systems for valued compounds from a process stream or effluent, apparatus and methods for C0₂ capture from coal-fired electric power plants, from refinery preheaters, from industrial boilers, and the like, systems and processes for adsorptive removal of carbon dioxide from gas mixtures containing carbon dioxide in combination with other gases, e.g. natural gas, biogas from anaerobic digestion processes, coal bed methane and output gas mixtures from steam-methane-reforming processes, and other gas capture, separation, and sequestering processes.

Description of Related Art

Non-graphitizable carbons, also known as "hard" carbons, offer several advantages over graphite, graphitic carbon, or graphitizable "soft" carbons in many adsorbent applications. These non-graphitizable (or non-graphitizing) carbons have a high degree of structural disorder as a result of solid phase decomposition during processing. Thus, hard carbons possess isotropic properties. Soft carbons go through a fluid or liquid phase during thermal processing or carbonization, and this fluid state enables these materials to achieve much more crystallographic order and anisotropy resembling the crystalline graphite (see FIG. 1). While graphitizable (or graphitizing) carbons (see FIG. 2) have pore sizes determined by the interplanar spacing in the graphitic crystallographic structure, the pore size distribution in the non-graphitizable carbons (see FIG. 3) can be tailored to the needs of the targeted adsorbent application.

BrightBlack® carbon, developed and offered commercially by Entegris, Inc. (Billerica, MA, USA), is a very useful non-graphitizable carbon prepared by pyrolysis of polymers or co-polymers of polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), and/or polymethyl acrylate (PMA), and is attractive for use in a variety of applications based on its high density, high micropore volume, strength, processability, purity, and pore size tunability. Since this hard carbon decomposes in the solid state, never passing through a liquid or fluid state, and is filled with micropores and can be heated to 3000°C without graphitizing, the pore size distribution can readily be adjusted as desired using well-controlled inert heat treatment. This allows tuning the carbon adsorbent for various applications. With the appropriate selected heat treatment, the carbon material can be processed to provide an effective carbon molecular sieve, which, for example, can achieve separation of gases as close in molecular geometry as carbon dioxide and methane. The BrightBlack® family of adsorbents has demonstrated superior performance and attracted commercial interest in a range of applications including gas storage and delivery, gas separations, gas purification and upgrading, adsorption heating and cooling, gas capture and sequestration, and energy storage. In energy storage applications, this hard carbon offers a higher energy storage capacity and is resistant to the decomposition and exfoliation issues that are often observed for graphitic or soft carbons.

Despite the success of the BrightBlack® family of high-performance carbons, and although these specialty adsorbents are ideally suited to a wide range of customer needs, the art continues to seek new lower cost adsorbent materials, based on renewable source materials, in the interests of competitiveness and sustainability.

It therefore would be a significant advance in the art to provide a family of adsorbent materials that is economically manufactured from readily available renewable materials, that is able to provide a high capacity, and that is usefully employed in a wide variety of systems and processes, such as electrochemical double layer capacitor (EDLC) carbon electrodes for energy storage devices, adsorbent- based heating and refrigeration systems and processes, adsorptive gaseous recovery systems for valued compounds from a process stream or effluent, apparatus and methods for C0₂ capture from coal-fired electric power plants, from refinery preheaters, from industrial boilers, and the like, systems and processes for adsorptive removal of carbon dioxide from gas mixtures containing carbon dioxide in combination with other gases, e.g. natural gas, biogas from anaerobic digestion processes, coal bed methane and output gas mixtures from steam-methane-reforming processes, as well as other gas capture, separation and sequestering processes.

SUMMARY

The present disclosure generally relates to carbon pyrolyzate materials derived from carbohydrate starting materials, e.g., plant starches, maltodextrin, microcrystalline cellulose, etc., having utility in systems and processes involving electrochemical cells, energy storage, adsorbent-based heating and refrigeration systems and processes, gas capture, gas sequestration, gas separations, gas or air purification, and the like.

In one aspect, the disclosure relates to high purity microporous carbon pyrolyzate adsorbents prepared from renewable natural carbohydrate sources, to methods of making such carbon pyrolyzate adsorbents, to use of such materials in forming electrochemical double layer capacitor (EDLC) carbon electrodes and constructing electrochemical energy devices, and to related methods of making and using such EDLC carbon electrodes and electrochemical energy devices.

In one aspect, the disclosure relates to a microporous carbon pyrolyzate derived from the pyrolysis of carbohydrate material such as plant starches, maltodextrin, and microcrystalline cellulose.

In another aspect, the disclosure relates to a carbon pyrolyzate adsorbent, comprising a pyrolyzate of at least one of starch, maltodextrin, and microcrystalline cellulose, that is useful for carbon dioxide capture, to C0₂ capture apparatus utilizing such carbon material, and to methods of making and using the carbon pyrolyzate adsorbent.

In one aspect, the disclosure relates to a carbon adsorbent, having the following characteristics:

(a) C0₂ capacity greater than 100 cc/gram at one bar pressure and temperature of 273° Kelvin;

(b) C0₂ Working Capacity greater than 7.0 weight percent;

(c) C0₂ heats of adsorption and desorption each of which is in a range of from 10 to 50 kJ/mole; and

(d) C0₂/N₂ Henry's Law Separation Factor greater than 3.

A still further aspect of the disclosure relates to a method of making a monolithic or particulate carbon adsorbent, comprising: compressing a precursor carbohydrate material into a near net shape preform; heating in a controlled manner in an inert gas environment to thermally decompose the carbohydrate material to carbon in the solid state; and, optionally, activating the carbon to increase surface area by one or more of (i) chemical activation, and (ii) physical activation. In another aspect, the disclosure relates to adsorbent articles and assemblies for use in adsorption heating and/or cooling systems.

Yet another aspect of the disclosure relates to an adsorbent assembly for use in an adsorption heating and/or cooling system, such adsorbent assembly comprising a stacked array of carbohydrate carbon pyrolyzate adsorbent articles arranged to maximize thermal contact while maintaining a communicating gas flow passage throughout.

The disclosure relates in a still further aspect to a method of recovering high-value gas from a process stream, material or environment containing same, such method comprising contacting the process stream, material or sample from the environment with a carbon adsorbent selective for such high-value gas. The carbon adsorbent can have a bulk density in a range of from 500 to 1200 kg per cubic meter (kg/m³), and a porosity in which a majority of pores are in a size (diameter) range of from 5 to 8 Angstroms.

In another aspect, the disclosure relates to a system for recovering high-value gas from a process stream, material or environment containing same, such system comprising a carbon adsorbent arranged for contacting such process stream, material or sample from the environment to sorptively capture the high- value gas. The carbon adsorbent can have a bulk density in a range of from 500 to 1200 kg per cubic meter (kg/m³), and a porosity in which the majority of pores are in a size (diameter) range of from 5 to 8 Angstroms.

One aspect of the disclosure relates to systems and methods for removing C0₂ from gases containing same, and to robust and easily regenerated physical adsorbents useful for such systems and methods.

In another aspect, the disclosure relates to a carbohydrate -based carbon adsorbent derived from at least one of a group of natural sources comprising starch, maltodextrin and microcrystalline cellulose, such carbon adsorbent characterized by:

(a) surface area greater than 800m²/gm adsorbent;

(b) greater than 80% of total surface area in micropores (pores <2 nanometers diameter);

(c) C0₂ capacity greater than lOOcc/g at one bar pressure and temperature of 273° Kelvin;

(d) C0₂ heats of adsorption and desorption each of which is in a range of from 10 to 50 KJ/mole;

(e) C0₂/N₂ Henry's Law Separation Factor of >3; and

(f) C0₂/0₂ Henry's Law Separation Factor of >3. In a further aspect, the disclosure relates to a system for removing carbon dioxide from gas containing same, such system comprising a natural carbohydrate-based carbon adsorbent of the present disclosure, wherein such adsorbent is arranged for contacting C0₂-containing gas to adsorb C0₂ therefrom and yield C0₂-reduced gas.

An additional aspect of the disclosure relates to a method for removing C0₂ from gas containing same, said method comprising contacting C0₂-containing gas with a natural carbohydrate-based carbon adsorbent of the present disclosure, for sufficient time to reduce C0₂ content of said C0₂-containing gas by at least 50%.

In one aspect, the disclosure relates to an adsorbent material with utility for adsorptive removal of carbon dioxide from gas mixtures containing same, such as gas mixtures containing carbon dioxide in combination with methane, e.g., natural gas containing carbon dioxide, biogas from anaerobic digestion processes, coal bed methane, and output gas mixtures from steam-methane-reforming processes.

The disclosure relates in another aspect to an adsorbent material that is selective for carbon dioxide in contact with gas mixtures including carbon dioxide and methane, such adsorbent having a carbon dioxide adsorption capacity at 1 bar pressure of greater than 50 cm³ carbon dioxide per gram of adsorbent at 273 °K, a methane adsorption capacity at 1 bar pressure of less than 35 cm³ methane per gram of adsorbent at 21°C, and a bulk density of greater than 0.50 gram per cubic centimeter of volume.

In another aspect, the disclosure relates to an adsorbent, e.g., a carbon pyrolyzate adsorbent, which is selective for carbon dioxide in contact with gas mixtures including carbon dioxide and methane. Such adsorbent exhibits the following properties: i) total ash content of less than 1.5%, preferably <1.3%, and most preferably <1.0%, as measured by the procedure of ASTM D2866; ii) bulk density, as measured by the procedure of ASTM D2854, of greater than 0.45 g/cc and less than 1.20 g/cc, preferably >0.50 g/cc and <1.15 g/cc, and most preferably >0.55 g/cc and <1.00 g/cc; iii) carbon dioxide adsorption capacity measured at 1 bar pressure and a temperature of 273° Kelvin of greater than 50 cm³ carbon dioxide per gram of adsorbent, preferably >65 cc/g, and most preferably >75 cc/g; iv) methane adsorption capacity measured at 1 bar pressure and a temperature of 21 °C of less than 35 cm³ methane per gram of adsorbent, preferably <30 cc/g, and most preferably <20 cm /g; v) C0₂ heats of adsorption and desorption, each of which is in a range of 10 to 50 kJ/mole, preferably in a range of 10 to 40 kJ/mole, and most preferably in a range of 10 to 35 kJ/mole; and vi) single pellet radial crush strength for a nominal 3mm pellet of greater than 2 kilopond (kP), preferably >4 kP, and most preferably >5 kP as measured by ASTM D4179.

In a further aspect, the disclosure relates to a method of making a carbon pyrolyzate adsorbent with the above characteristics (i)-(vi), such method comprising pyrolyzing a natural carbohydrate such as starch, maltodextrin or microcrystalline cellulose, or mixtures of two or more of such natural carbohydrates, to form a pyrolyzate, and activating the pyrolyzate under sufficient conditions of environment, pressure, temperature, and time to yield the carbon pyrolyzate adsorbent having the characteristics (i)-(vi).

Another aspect of the disclosure relates to an apparatus for removing carbon dioxide from a gas mixture including carbon dioxide and methane. Such apparatus comprises at least one adsorbent bed of carbon pyrolyzate adsorbent that is selective for carbon dioxide in contact with the gas mixture. The carbon pyrolyzate adsorbent has a carbon dioxide adsorbent capacity at 1 bar pressure of greater than 50 cm³ carbon dioxide per gram of adsorbent, a methane adsorption capacity at 1 bar pressure of less than 35 cm³ methane per gram of adsorbent, and a bulk density of greater than 0.50 gram per cubic centimeter of volume. The at least one adsorbent bed is arranged (i) for contacting with the gas mixture during a first period of time to adsorb carbon dioxide on the carbon pyrolyzate adsorbent in the bed, and to discharge from the bed a carbon dioxide-reduced methane gas, and (ii) for desorbing previously adsorbed carbon dioxide from the carbon pyrolyzate adsorbent in the bed during a second period of time. The adsorbent in such apparatus may comprise a carbon adsorbent having the aforementioned characteristics (i)-(vi).

In a further aspect, the disclosure relates to a method of removing carbon dioxide from a gas mixture including carbon dioxide and methane, such method comprising contacting the gas mixture with a carbon pyrolyzate adsorbent having a carbon dioxide adsorbent capacity at 1 bar pressure of greater than 50 cm³ carbon dioxide per gram of adsorbent at 273°K, a methane adsorption capacity at 1 bar pressure of less than 35 cm³ methane per gram of adsorbent at 21°C, and a bulk density of greater than 0.50 gram per cubic centimeter of volume, and for example up to 1.4 grams per cubic centimeter of volume of the adsorbent. Such method may be carried out using a carbon adsorbent having the above-mentioned characteristics (i)-(vi).

Yet another aspect of the disclosure relates to a gas purifier, comprising a housing defining an interior volume and adapted for flow of gas therethrough, and a natural carbohydrate carbon pyrolyzate adsorbent in the interior volume of the housing, arranged for contact with the gas flowed through the housing to sorptively purify the gas.

The disclosure relates in another aspect to gas or air filtration and/or purification devices and processes containing natural carbohydrate carbon pyrolyzate adsorbents as variously described herein.

In one aspect, the disclosure relates to a carbohydrate carbon pyrolyzate adsorbent characterized by: a) amorphous or semi-crystalline structure which is non-graphitizable below 1500°C; b) derivation from naturally sourced carbohydrate precursor material; c) total ash content of less than 1.5% as determined by the procedure of ASTM D2866-11; d) N₂ BET surface area greater than 750 m²/gram; e) bulk density in the range of 0.45 grams/cubic centimeter to 1.25 grams/cubic centimeter; and f) microporous structure with a pore volume of greater than 0.35 cubic centimeters per gram in pores that are smaller than 2 nanometers in size.

The disclosure relates in another aspect to a method of producing the carbohydrate carbon pyrolyzate adsorbent of the disclosure, comprising: a) drying, dewatering and stabilizing the natural carbohydrate source to carbon char under non-oxidizing environment between 110°C and 235°C; b) thermally decomposing or pyrolyzing the char to amorphous microporous carbon in inert or reducing atmosphere at temperatures of 500°C to 950°C; and c) thermally activating or physically enhancing the amorphous carbon under oxidizing environment between 600°C and 1200°C to high surface area.

Other aspects, features and embodiments of the disclosure will be more fully apparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the crystallographic order and structure of natural graphite.

FIG. 2 is a schematic representation of the semi -crystalline structure achieved with graphitizable "soft" carbons.

FIG. 3 is a schematic representation of the primarily amorphous structure obtained from non-graphitizable "hard" carbons.

FIG. 4 is a schematic representation of an in-line gas purifier disposed in a process line for purification of gas flowed therethrough, utilizing a carbohydrate carbon pyrolyzate material of the present disclosure. FIG. 5 is a schematic representation of an electrochemical energy device comprising an arrangement of carbohydrate carbon pyrolyzate electrodes forming an EDLC conformation with electrolyte therebetween, according to one embodiment of the present disclosure.

FIG. 6 is a photograph of self-adherent tablets of natural carbohydrate formed by direct compression, without an added binder, and having a raw material density in excess of 1.32g/cc.

FIG. 7 is a photograph showing a range of sizes of disks compressed from various natural carbohydrate sources.

FIG. 8 is a photograph of press-formed microcrystalline cellulose tablets having an average piece density of >1.30g/cc.

FIG. 9 is a photograph of press-formed microcrystalline cellulose tablets as pressed, following pyrolysis to carbon, and after oxidative activation.

FIG. 10 is a photograph of several cellulosic carbon pyrolyzate articles prepared from microcrystalline cellulose, according to one embodiment of the present disclosure, as they have been removed from a pyrolysis furnace, and having an average density of >0.95g/cc.

FIG. 11 is a photograph showing a variety of shapes and sizes of formed carbon pyrolyzate adsorbent pieces prepared via preforming and controlled pyrolysis.

FIG. 12 is a photograph of one embodiment of carbon pyrolyzate adsorbent articles having a space-filling shape, which can be arranged so that adjacent carbon pyrolyzate adsorbent articles are in contact with one another, so that the corresponding array of carbon pyrolyzate adsorbent articles can be employed for maximizing adsorbent density within a fixed enclosed volume of an adsorbent vessel, e.g., for adsorption, capture, purification, or treatment of gas for which the carbon pyrolyzate adsorbent has designed sorptive affinity.

FIG. 13 is a graph of burn-off level (%wt.) as a function of processing time at 900°C in C0₂ for cellulosic carbon pyrolyzate articles prepared from microcrystalline cellulose.

FIG. 14 is a graph of surface area (both gravimetric and volumetric) of cellulosic carbon pyrolyzate articles prepared from microcrystalline cellulose, as a function of the level of burn-off

FIG. 15 is a plot of nitrogen adsorption isotherms for cellulosic carbon pyrolyzate articles prepared from microcrystalline cellulose, at 77° Kelvin (volume of nitrogen adsorbed (cc nitrogen/gram adsorbent), as a function of pressure). FIG. 16 is a plot of C0₂ adsorption isotherms for cellulosic carbon pyrolyzate articles prepared from microcrystalline cellulose, at 0°C (volume of C0₂ adsorbed (cc nitrogen/gram adsorbent), as a function of pressure (torr)).

FIG. 17 is a plot showing the relationship between the level of oxidative burn-off on a carbohydrate derived carbon pyrolyzate adsorbent and its measured gravimetric nitrogen BET surface area.

FIG. 18 is a plot showing the relationship between the level of oxidative burn-off on a carbohydrate derived carbon pyrolyzate adsorbent and its measured tablet density.

FIG. 19 is a plot showing the effect on measured volumetric nitrogen BET surface area as a function of degree of oxidative burn-off

FIG. 20 is a plot showing the ability to closely replicate the methane adsorption performance of a hard carbon pyrolyzate from a synthetic polymer source with renewable, naturally sourced starch and maltodextrin starting materials.

FIG. 21 is a plot of the nitrogen isotherms for C0₂-activated carbohydrate carbon pyrolyzate materials, including pyrolyzates of potato starch, cassava starch, wheat starch, corn starch, and maltodextrin.

FIG. 22 is a plot of differential pore size distribution (Dubinin-Radushkevich) as a function of pore width (pore equivalent width in Angstroms) for C0₂-activated carbohydrate carbon pyrolyzate materials, including pyrolyzates of potato starch, cassava starch, wheat starch, corn starch, and maltodextrin.

DETAILED DESCRIPTION

The present disclosure is based on the discovery by the applicant that high purity, high value non- graphitizing "hard" carbon adsorbents, essentially comparable in physical properties and performance to various of the commercial BrightBlack® carbon products, can be prepared at a fraction of the cost, using renewable, naturally occurring precursors along with well controlled pyrolysis and activation methodologies.

The present disclosure generally relates to non-graphitizing carbon pyrolyzate materials. In particular aspects, the disclosure relates more specifically to carbon adsorbents, such as a carbon adsorbent that is derived from naturally sourced carbohydrate starting materials, e.g., starch(es), maltodextrin(s), microcrystalline cellulose, and which are usefully employed for adsorptive applications including, but not limited to, electrochemical double layer capacitor (EDLC) carbon electrodes for energy storage devices, adsorbent-based heating and refrigeration systems and processes, gaseous recovery systems for valued compounds from a process stream or effluent, C0₂ capture from coal-fired electric power plants, from refinery preheaters, from industrial boilers, and the like, removal of carbon dioxide from gas mixtures containing carbon dioxide in combination with other gases, e.g., natural gas, biogas from anaerobic digestion processes, coal bed methane, and output gas mixtures from steam-methane-reforming processes, and other gas capture, separation, and sequestering processes.

In specific embodiments, the present disclosure relates to carbon materials, and electrodes and energy storage device structures formed therefrom, as well as to methods of making and using same.

As set out herein, EDLC performance values dependent on voltage and electrolyte compositions are determined under an applied voltage of 2.7 volts in organic electrolyte comprising 1M tetraethyl ammonium tetrafluoroborate (TEABF₄) in acetonitrile (AN).

The method used to determine capacitance herein is the IEC 62391 -1 standard (page 15) method, in which the specific capacitance is the measured cell capacitance (C cell = (I* At)/ AV) divided by the total amount of carbon in the cell, with the cell being operated at 2.7 V in organic electrolyte comprising 1M tetraethyl ammonium tetrafluoroborate (TEABF₄) in acetonitrile (AN).

ELDC device performance values described herein, which are dependent on ELDC device size, are based on a 3000 Farad capacitor device.

EDLC electrode densities described herein are based solely on the carbon in the electrode, and do not include current collectors or metallizations of such carbon material.

In other specific embodiments, the present disclosure relates to adsorbent assemblies for use in adsorption heating and/or cooling systems.

The adsorption heating and/or cooling systems with which the adsorbent assemblies of the present disclosure are employed, can be of any suitable type. The adsorption heating and/or cooling system may for example be embodied as a refrigeration system that includes a refrigerated container having an evaporator associated therewith, with the adsorbent assembly of the present disclosure arranged for adsorbing and desorbing a reversibly adsorbable gas such as ammonia (NH₃), water/steam (H₂0) or nitrogen (N₂) or other suitable reversibly adsorbable fluid. The adsorption heating and/or cooling system in other applications may comprise solar collectors or other heat sources, such as supplies of waste heat, electrical heat sources, gas combustion heat sources such as natural gas or propane heating units, geothermal heat sources, or any other source or sources of heat useful in the adsorption-based heating and/or cooling system, and may additionally include sorption generators, condensers, and any other suitable apparatus and components, etc., as arranged with one or more adsorbent assemblies of the present disclosure, in an operational system to facilitate the heating and/or cooling cycle. The heating and/or cooling system may utilize a heat transfer fluid of any suitable type, and appropriate ancillary equipment, to facilitate heat exchange within the system.

Other specific embodiments of the present disclosure refer to pyrolyzate carbon adsorbents having finely tuned pore size distribution and adsorptive affinity for specialty gases as well as low heats of adsorption and desorption allowing efficient reversible gas adsorption thereby providing utility for selective adsorptive recovery of high-value gases, e.g. xenon, from mixed process effluent or waste streams.

Efficient adsorptive recovery of high-value gases such as xenon can be achieved utilizing carbon adsorbent having a bulk density in a range of from 750 to 1300 kg per cubic meter (kg/m³), and a porosity in which the majority of pores are in a size range of from 5 to 8 Angstroms. Such carbon adsorbent has a desirable volumetric sorptive capacity for xenon.

It has been found that carbon adsorbents of the foregoing characteristics enable effective adsorbent recovery of high-value gases such as xenon to be accomplished in a very compact sorbent arrangement having a small footprint in the facility in which same is used, e.g., a semiconductor manufacturing facility.

In specific embodiments, the carbon adsorbent may have a bulk density in a range of from 800 to 1200 kg/m³, and in still other embodiments, the carbon adsorbent may have a bulk density in a range of from 900 to 1050 kg/m³.

The carbon adsorbent of the present disclosure is advantageously used to adsorptively recover high-value compounds from a process stream, material, or environment containing same, e.g., in arrangements for recovery of high-value gases for reuse, recirculation or other disposition that realize value otherwise lost in the absence of such recovery.

As used herein, the term "high value," in reference to recovered gases, compounds, and fluids, refers to such materials as having significant value upon recovery thereof, as compared to (i) the loss, dissipation or degradation of such materials if not recovered and/or (ii) the cost of remediation, abatement or other necessary action incurred in the absence of recovery of such materials as a result of their loss, dissipation or degradation in the environment. In other specific embodiments, the present disclosure relates to carbon pyrolyzate adsorbents useful for carbon dioxide capture, and to C0₂ capture apparatus and processes utilizing same, as well as to methods of making and using such carbon pyrolyzate adsorbents.

The carbon pyrolyzate adsorbents of the present disclosure are useful for selective adsorption of carbon dioxide, e.g., from environments or gas streams such as flue gases containing carbon dioxide.

The carbon pyrolyzate adsorbents comprise porous amorphous carbon that is highly effective for sorptive uptake and retention of carbon dioxide, and that readily releases carbon dioxide under desorption conditions, such as reduced pressure and/or elevated temperature conditions (relative to adsorption conditions) that may be carried out in pressure swing and/or thermal swing adsorption/de sorption apparatus, or by contact of the carbon pyrolyzate adsorbent with a stripping gas, such as steam, nitrogen, argon, etc.

The carbon adsorbent can be of any appropriate form, but preferably is in a bead or particulate form for C0₂ capture applications in which the adsorbent is provided in a bed, e.g., a fixed or fluidized bed with which the C0₂-containing gas is contacted to effect C0₂ capture. Alternatively, the carbon adsorbent can be of monolithic form, e.g., as a unitary solid mass of substantial size that may be of a geometrically regular form, such as a block, brick, disk, or the like, or that may be of a suitable geometrically irregular form.

In other specific embodiments the present disclosure relates to carbon pyrolyzate adsorbents having a unique combination of high capacity for reversible physical adsorption of C0₂ along with low heat of adsorption and desorption, thereby keeping energy required for cyclic adsorption/desorption minimal. Such adsorbent can be provided in a powder, tablet, or monolith form, and is readily integrated in a wide variety of gas generation and gas processing systems. For example, the adsorbent of the present disclosure can be used in building air handling equipment, e.g., heating and/or air conditioning units, to efficiently remove C0₂ from re-circulated air. Additional applications for such adsorbent include purification of biogas methane produced from anaerobic decomposition of organic material, purification of hydrogen generated by steam-methane -reforming operations, and purification of gases produced in various refining operations.

Still other specific embodiments relate to systems and methods for adsorptive removal of carbon dioxide from gases containing same, and to adsorbents useful in such systems and methods.

Although the disclosure of gas separations hereinafter is set forth with particular emphasis on removal of C0₂ from gases containing same, it will be appreciated that the adsorbent materials, systems, and methods of the present disclosure may alternatively or additionally achieve purification of gases to remove additional, or other, contaminant species therefrom, such as odors, ammonia, carbon monoxide, methanol, ethanol, natural gas, VOCs (volatile organic components), or other potentially toxic, hazardous or detrimental contaminants of gases that are processed in accordance with the present disclosure.

The disclosure, as variously set out herein in respect of features, aspects and embodiments thereof, may in particular implementations be constituted as comprising, consisting, or consisting essentially of, some or all of such features, aspects and embodiments, as well as elements and components thereof being aggregated to constitute various further implementations of the disclosure. The disclosure correspondingly contemplates such features, aspects and embodiments, or a selected one or ones thereof, in various permutations and combinations, as being within the scope of the present disclosure.

As used herein and in the appended claims, the following terms have the following meanings:

The singular forms "a", "and", and "the" include plural referents unless the context clearly dictates otherwise.

The term "high purity" in reference to carbon pyrolyzates of the present disclosure means that the carbon pyrolyzate is characterized by < 1% total ash content, as determined by the procedure of ASTM D2866- 11.

The term "carbohydrates" refers to large biological molecules or macromolecules that are constituted by carbon (C), hydrogen (H), and oxygen (O) atoms. Such molecules may have a hydrogen: oxygen atom ratio of 2: 1, and an empirical formula of C_x(H₂0)_Y , wherein X can be different from Y. Technically, these molecules are hydrates of carbon. Generally the term "carbohydrates" is considered synonymous with "saccharides." Carbohydrates reside in four chemical classes: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

The term "sugars" is a generalized name for sweet, short-chain, soluble carbohydrates, constituted by carbon, hydrogen, and oxygen atoms. Examples include arabinose, fructose, galactose, glucose (dextrose), lactose, maltose, mannose, sucrose, xylose, and their derivatives.

The term "monosaccharides" refers to simple sugars, the most basic unit, or building block, of carbohydrates. Examples include arabinose, deoxyribose, fructose (or levulose), galactose, glucose (or dextrose), glyceraldehyde (or glyceral), mannose, ribose, and xylose. The term "disaccharides" refers to carbohydrates that are formed when two monosaccharides undergo a condensation reaction with the elimination of a water molecule. Examples include lactose, maltose, sucrose, cellobiose, and melibiose.

The term "oligosaccharides" refers to saccharide polymers that contain a small number (typically 3 to 9) of simple sugars (monosaccharides). Examples include cellodextrins, fructo-oligosaccharides, galacto- oligosaccharides, isomalto-oligosaccharides, maltodextrins, mannan oligosaccharides, and raffinose, among others.

The term "polysaccharides" refers to polymeric carbohydrate molecules that are constituted by long chains of monosaccharide units bound together by glycosidic linkages. Examples include agar, amylopectin, amylose, arabinoxylan, cellulose, chitin, chitosan, dextran, dextrin, fructan, galactomannan, glucan, glycogen, guar gum, hemicellulose, lentinan, lichenin, mannan, natural gum, pectin, polysaccharide peptide, sepharose, starches (e.g., of amaranth, arrowroot, banana, cassava, coconut, corn, pea, plantain, potato, quinoa, rice, sorghum, tapioca, wheat, etc.), welan gum, xanthan gum, and xylan, among others.

The term "cellulose" refers to naturally occurring organic polymers of (C₆Hi₀O₅)_n formula, comprising the structural fibrous cell wall of green plants, woods, nut shells, fruit pits, algae, etc. which are high molecular weight linear chain polymeric carbohydrates. Cellulosic materials comprise wood pulp, sawdust, newsprint, coconut shells, olives stones, peach stones, apricot pits, viscose, viscose-rayon, cotton, cotton linters, argan nutshell, macadamia nutshell, cellulose acetate, bacterial cellulose, lignin, blackthorn stones, walnut shells, date stones, rice husks, coffee parchment, coffee dregs, bagasse, sorghum millets straws, bamboo woods, mango pits, almond shells, corncobs, cherry stones, and grape seeds.

The term "microcrystalline cellulose" refers to highly refined wood pulp cellulose prepared by separation of the insoluble three -dimensionally bonded "crystalline" portion of the wood cellulose microfibers from the weaker bonded amorphous regions and purification thereof. Microcrystalline cellulose has found broad use as a texturizer, extender, or bulking agent in production of processed foods and as an excipient and tableting aid for vitamins and dietary supplements.

The term "macropores" refers to pores that are greater than 50 nm in size (diameter). The term "mesopores" refers to pores that are from 2 nm to 50 nm in size (diameter). The term "micropores" refers to pores that are smaller than 2 nm in size (diameter). The term "ultra-micropores" refers to pores that are smaller than 0.7 nm in size (diameter).

The term "monolith" refers to carbon pyrolyzate material that is in a bulk form, having a block, brick, cylinder, puck, rod, or other geometrically regular or irregular bulk form, as distinguished from non- monolith carbon pyrolyzate forms such as beads, pellets, extrudates, powders, granules, or particulates. Monolithic carbon pyrolyzates of the present disclosure are advantageously formed as dense solid articles by pyrolysis of "near net shape" pyrolyzable precursor preforms that have a size and conformation that substantially correspond to the monolithic carbon pyrolyzate product. The resulting bulk form microporous carbon articles can be used as single piece adsorbent, or as a stack of multiple pieces (e.g., when the monolithic carbon pyrolyzate is of disk-shaped form and a stack of such disk-shaped bodies is vertically stacked in face-to-face abutment of successive disk-shaped bodies in the stack), or other arrangements in which the bulk form carbon pyrolyzate articles contact each other over substantial portion(s) of their respective surfaces, thereby eliminating the high void volumes that are observed in adsorbent vessels that are filled by beads, pellets, extrudates, powders, granules, or particulates of adsorbent, in which there is substantial interstitial volume and gross voids that results in diminution of sorptive capacity of the spatial volume containing such beads, pellets, extrudates, powders, granules, or particulates. In various specific embodiments, the monolith carbon pyrolyzate may have a dimensional character in which each of its (x,y,z) dimensions is at least 1 cm, e.g., wherein each of its (x,y,z) dimensions is in a range of from 1 cm to 25 cm, or higher.

The term "piece density" refers to mass per unit volume of a single piece of solid adsorbent, expressed in units of grams per cubic centimeter.

The term "binderless" used in reference to carbon pyrolyzates that are formed from pyrolyzable precursor material means that the pyrolyzable precursor composition contains no more than 1% by weight, based on total weight of the composition, of binder material, and preferably being devoid of any binder material. Binderless carbon pyrolyzates thus can be formed from precursor material that is sufficiently cohesive so that it can be formed in a near net shape form by press-molding and/or other shaping operations, and retain that near net shape form during and subsequent to the pyrolysis of the precursor material. In this respect, residual adsorbed species, e.g., water or moisture, resulting from standard processing operations such as milling and packaging are considered to be part of the raw source material and not to be additive or binder components of the raw source material.

The term "pyrolysis" refers to thermal decomposition of precursor material under inert gas cover at conditions in which the precursor material is converted substantially to carbon. The term "near net shape" in reference to the pyrolyzable precursor article that is pyrolyzed to form the carbon pyrolyzate, means that the precursor article has a conformation that is consistent shape-wise with the product carbon pyrolyzate resulting from the pyrolysis. Such character of the pyrolyzable precursor article in relation to the pyrolyzed product article is highly advantageous, since it eliminates the need for extensive cutting, grinding, etc. to effect material removal in the processing of the carbon pyrolyzate, inasmuch as a reasonably consistent form factor is maintained in progressing from the precursor article to the carbon pyrolyzate adsorbent product.

The term "carbohydrate carbon pyrolyzate" refers to a carbon pyrolyzate formed by pyrolysis of precursor material comprising carbohydrate.

The terms "non-graphitizing carbon", "non-graphitizable carbon", and "hard carbon" are used synonymously and refer to carbon materials which do not yield crystalline graphitic structure even when heated above 1300°C.

The terms "graphitizing carbon", "graphitizable carbon" and "soft carbon" are used synonymously and refer to carbon materials which can be converted to an ordered crystalline or semi-crystalline structure approximating that of natural graphite when heated above 1300°C.

The precursor material for the carbohydrate carbon pyrolyzate may be constituted by only carbohydrate precursor material, or the precursor material for the carbohydrate carbon pyrolyzate may comprise the carbohydrate precursor material together with (i) additives to facilitate or enhance the pyrolysis process or the carbon pyrolyzate product of the process (e.g., pore formers, viscosity control agents, surfactants, etc.), and/or (ii) other pyrolyzable precursor material(s). Such other pyrolyzable precursor material(s) may include cellulosic precursor materials (e.g., microcrystalline cellulose) or synthetic polymeric materials (e.g., polyvinylidene chloride polymers and copolymers, polyvinylidene fluoride polymers and copolymers, etc.), petroleum-based materials, petroleum-derived materials, and combinations, blends, and mixtures of the foregoing. The carbohydrate precursor material may comprise different carbohydrate constituents, such as for example a mixture of potato starch and maltodextrin, or a mixture of wheat starch and cassava starch.

In various embodiments, the carbohydrate precursor material may be employed as a component of a pyrolyzable precursor material mixture comprising the carbohydrate precursor material and non- carbohydrate precursor material, and in such precursor material mixture, the carbohydrate precursor material may be present at a concentration of from 5% to 98% by weight, based on total weight of the carbohydrate and non-carbohydrate precursor materials in the mixture. In other embodiments, the carbohydrate precursor material may be present at a concentration of at least 50% by weight, on the same total weight basis, e.g., at concentration of at least one of 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95% by weight, on the same total weight basis, or in a range in which end point maximum and minimum values are selected from the foregoing individual values, wherein the maximum value exceeds the minimum value.

The term "cellulosic carbon pyrolyzate" refers to a carbon pyrolyzate formed by pyrolysis of precursor material comprising cellulose.

The precursor material for the cellulosic carbon pyrolyzate may be constituted by only cellulose precursor material, or the precursor material for the cellulosic carbon pyrolyzate may comprise the cellulose precursor material together with (i) additives to facilitate or enhance the pyrolysis process or the carbon pyrolyzate product of the process (e.g., pore formers, viscosity control agents, surfactants, etc.), and/or (ii) other pyrolyzable precursor material(s). Such other pyrolyzable precursor material(s) may include synthetic polymeric materials (e.g., polyvinylidene chloride polymers and copolymers, polyvinylidene fluoride polymers and copolymers, etc.), petroleum-based materials, petroleum-derived materials, carbohydrates other than cellulose (e.g., sugars, saccharides, starches, maltodextrin, etc.), and combinations, blends, and mixtures of the foregoing. The cellulose precursor material may comprise different cellulose constituents, such as for example a mixture of wood pulp and apricot pits, or a mixture of rice husks and cotton linters.

A preferred form of the cellulose starting material for the cellulosic carbon pyrolyzate is microcrystalline cellulose.

In various embodiments, the cellulose precursor material may be employed as a component of a pyrolyzable precursor material mixture comprising the cellulose precursor material and non-cellulose precursor material, and in such precursor material mixture, the cellulose precursor material may be present at a concentration of from 5% to 98% by weight, based on total weight of the cellulose and non- cellulose precursor materials in the mixture. In other embodiments, the cellulose precursor material may be present at a concentration of at least 50% by weight, on the same total weight basis, e.g., at concentration of at least one of 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95% by weight, on the same total weight basis, or in a range in which end point maximum and minimum values are selected from the foregoing individual values, wherein the maximum value exceeds the minimum value.

In various aspects, the disclosure relates to a carbohydrate carbon pyrolyzate. The carbohydrate carbon pyrolyzate in various embodiments may be characterized by: < 1.5% total ash content, as determined by the procedure of ASTM D2866-1 1; piece density in a range of from 0.60 g/cc to 1.25 g/cc; N₂ BET surface area greater than 750 m²/gm; and methane adsorption capacity, at 21°C and 35 bar pressure, of greater than 100V/V.

The carbohydrate carbon pyrolyzate adsorbent for such use may be in an activated form, e.g., wherein the activated form has been activated by chemical and/or physical activation. In one specific embodiment, the activated form has been chemically activated by reaction with an acid, e.g., an acid selected from the group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, and carbonic acid. In other embodiments, the activated form has been chemically activated by reaction with a hydroxide of sodium, lithium, potassium, calcium, or ammonium. In still other embodiments, the activated form has been physically activated by burn-off in exposure to C0₂, air, or steam in mixture with an inert gas, e.g., nitrogen or argon, or as a pure gas stream at temperature in a range of from 600°C to 1200°C. In a specific embodiment, the activated form has been physically activated by burn-off in exposure to C0₂, air, or steam in mixture with an inert gas or as a pure gas stream at temperature in a range of from 750°C to 1 100°C.

The disclosure in another aspect relates to a method of making a carbohydrate carbon pyrolyzate, comprising: compressing a carbohydrate precursor material into a near net shape preform; heating in a controlled manner in an inert gas environment to thermally decompose the carbohydrate to carbon; and, optionally, activating the carbon to increase surface area by one or more of (i) chemical activation, and (ii) physical activation.

The carbohydrate precursor material can be easily formed or pressed into a desired shape or shapes, e.g., particulate or monolithic shapes, before undergoing subsequent carbonization and activation. Byproducts of the non-oxidative pyrolysis of carbohydrates are primarily water vapor with low levels of carbon dioxide and/or carbon monoxide. These are easily managed process effluents.

The precursor material for the carbohydrate carbon pyrolyzate can be pyrolyzed at any suitable temperature, e.g., temperature of at least 400°C and up to 1200°C, or higher, in an inert atmosphere. Activation can be carried out in any suitable manner, and may be carried out by chemical and/or physical activation techniques, e.g., (1) chemical activation by reaction of the pyrolyzed carbon with KOH, LiOH, NaOH, NH₄OH, NaHC0₃, (NH₄)₂S0₄, H₂S0₄, HC1, or H₃P0₄ at room temperature, followed by heating, and then removal of any residual activation chemistry by appropriate acid or base neutralization wash/water rinse filtering and drying; or (2) physical activation by high-temperature exposure of the carbon to steam, C0₂, air, or other oxidizing gas, or by any combination of these various techniques. In various adsorbent embodiments, the carbohydrate carbon pyrolyzate adsorbent comprises a binderless, high density carbon monolith that is in a shape-filling form with respect to the vessel or other containment structure in which the adsorbent is to be deployed as a gas storage and dispensing medium. As used in such context, the term "high density" means that the carbon pyrolyzate has a piece density of at least 0.50 g/cc, preferably at least 0.70 g/cc, and most preferably greater than 0.75 g/cc, e.g., in a range of from 0.50 g/cc to 1.70 g/cc, or from 0.70 g/cc to 1.70 g/cc, or from 0.75 g/cc to 1.70 g/cc. Alternatively, the carbohydrate carbon pyrolyzate adsorbent may be in a particulate form, e.g., as powders, granules, pellets, or other particulate form.

The carbohydrate carbon pyrolyzate adsorbent may be prepared to provide a N₂ BET surface area of at least 750 m²/g, preferably at least 800m²/g; and most preferably greater than 900 m²/g, e.g., in a range of from 750 m²/g to 2500 m²/g, in a range of from 800 to 2500 m²/g, etc.

The disclosure in another aspect relates to carbohydrate precursor material compressed into near net shape preforms under compressive force of 4,000 psi or greater, preferably between 5,000 psi and 50,000 psi, prior to thermal decomposition.

The disclosure in yet another aspect relates to thermal conversion of the consolidated near net shape carbohydrate preform to carbon by treatment to a temperature ranging from 500°C to 950°C to yield a carbohydrate carbon pyrolyzate.

The disclosure in a further aspect relates to activation of the formed carbohydrate carbon pyrolyzate by chemical and/or physical means to enhance surface area and micropore volume thereof.

The carbohydrate carbon pyrolyzate materials of the present disclosure can be made at relatively high yields, low cost, high purity, and minimized environmental hazards. Preparing compressed preforms of the carbohydrate precursor material enables the production of high density monolithic forms of the carbon pyrolyzate. Pyrolysis of such materials results in easily managed byproducts. Physical activation at elevated temperature with steam, C0₂, or air in combination with inert purge gas such as nitrogen or argon can be utilized to achieve very precise control over properties such as surface area, bulk density, and pore-size distribution, without introducing new impurities or contaminants. Self-adherent (cohesive) carbohydrate precursor material enables processing without the use of binders that may alter the desired properties of the carbon pyrolyzate, while still achieving carbon pyrolyzate articles of high density, superior strength and durability, high heat capacity, and good thermal conductivity. As a result, it is possible to produce a solid adsorbent carbon pyrolyzate with high gas adsorption capacity, low heating during adsorption to enable rapid gas filling, minimized chemical reactivity with the adsorbed gas for shelf storage and transport stability and maximized gas delivery, with low cooling upon gas delivery to enable sustainable high use rates and a sustainable supply chain.

It will be recognized that the carbohydrate carbon pyrolyzate adsorbent of the present disclosure may incorporate any of the various characteristics and features described hereinabove, and any combinations of two or more of such characteristics and features.

Carbohydrate carbon pyrolyzate in accordance with the present disclosure may be provided in any suitable size, shape and form. For example, the carbohydrate carbon pyrolyzate in various embodiments can be particulate in character, and in specific embodiments particles may be in a size (diameter or major dimension) range of from 0.3 to 4 mm, with a piece density that is greater than 0.8 g/cc, or with size and density of any other suitable values. In other embodiments, the carbohydrate carbon pyrolyzate may be in a monolithic form. Carbon pyrolyzate monoliths useful in the broad practice of the present disclosure may in specific embodiments include gross brick, block, tablet, and ingot forms, as bulk forms. In various embodiments, carbon pyrolyzate monoliths may have three-dimensional (x, y, z) character wherein each of such dimensions is greater than 1.5, and preferably greater than 2 centimeters.

In a specific aspect, the carbohydrate carbon pyrolyzate comprises a pyrolyzate of microcrystalline cellulose.

The carbohydrate carbon pyrolyzate of the disclosure in various embodiments may comprise a pyrolyzate of carbohydrate precursor material and one or more non-carbohydrate precursor material. For example, the one or more non-carbohydrate precursor material may be selected from the group consisting of synthetic polymeric materials, petroleum-based materials, petroleum-derived materials, and combinations, blends, and mixtures of the foregoing. As a further specific example, the one or more non-carbohydrate precursor material may be selected from the group consisting of polyvinylidene chloride polymers and copolymers, and polyvinylidene fluoride polymers and copolymers. As yet another example, the carbohydrate carbon pyrolyzate may comprise a pyrolyzate of cellulose precursor material comprising two or more different cellulose materials. When the carbohydrate carbon pyrolyzate comprises a pyrolyzate of carbohydrate precursor material and non-carbohydrate precursor material, the concentration of carbohydrate precursor material in specific embodiments may be at least 50% by weight, based on total weight of the carbohydrate precursor material and non-carbohydrate precursor material. In other embodiments, the carbohydrate precursor material may be present at a concentration of at least one of 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95% by weight, up to 98% by weight on the same total weight basis. For example, the carbohydrate precursor material may be present at concentration of from 55% to 98% by weight, based on total weight of the carbohydrate and non-carbohydrate precursor materials in the mixture, or from 60% to 80% by weight, or from 65% to 95% by weight, or from 70% to 90% by weight percent, or in other ranges having endpoints selected from the individual percentages above, wherein all such weight percentages are on the same total weight basis.

The carbohydrate carbon pyrolyzate of the disclosure may be activated, and may comprise a pyrolyzate activated by chemical and/or physical activation, e.g., wherein the pyrolyzate has been activated by burn- off in exposure to C0₂, air, or steam in mixture with an inert gas or as a pure gas stream at temperature in a range of from 600°C to 1200°C.

The disclosure in another aspect contemplates a gas purifier, comprising a housing defining an interior volume and adapted for flow of gas therethrough, and a carbohydrate carbon pyrolyzate adsorbent in the interior volume of the housing, arranged for contact with the gas flowed through the housing to sorptively purify the gas.

Referring now to the drawings, FIG. 4 is a schematic representation of an in-line gas purifier 10 disposed in a process line for purification of gas flowed therethrough, utilizing a carbohydrate carbon pyrolyzate material according to one embodiment of the present disclosure.

As illustrated, the purifier 10 comprises a purifier vessel 12 of cylindrical elongate shape, coupled in gas flow relationship with a gas inlet line 18 at a first end of the vessel, and coupled in gas flow relationship with a gas outlet line 20 at a second end of the vessel opposite the first end thereof. The purifier vessel 12 includes a circumscribing cylindrical wall 14 defining an enclosed interior volume therewithin, bounded by end walls at the first and second ends of the vessel. In the interior volume is disposed a particulate carbohydrate carbon pyrolyzate adsorbent in accordance with the present disclosure. Such adsorbent has selective adsorptive affinity for one or more components of a gas mixture flowed from gas inlet line 18 through the interior volume of the vessel 12 to the gas outlet line 20, so that such components are selectively removed from the gas mixture flowed through the purifier to produce a purified gas depleted in such components.

The gas inlet line 18 and gas outlet line 20 may be part of flow circuitry in a semiconductor manufacturing facility, in which the gas mixture flowed to the purifier from gas inlet line 18 is desired to be purified of the selectively removable components. The purifier thus may purify gas to be utilized in a specific gas-utilizing operation in the semiconductor manufacturing facility, or the purifier may be used to remove residual toxic or otherwise hazardous components from the gas prior to its release as effluent from the facility. The purifier may be deployed in clean room and lithography track applications. The carbohydrate carbon pyrolyzate adsorbent material may thus be utilized in the purifier in a particulate form, as a powder, beads, pellets, or the like. Alternatively, if the pressure drop in the purifier is sufficiently low, the carbohydrate carbon pyrolyzate adsorbent material may be provided in a monolithic form. As a still further arrangement in various embodiments, the carbohydrate carbon pyrolyzate adsorbent material may be provided on a support material or batting, to effect contact of the gas with the adsorbent material so that undesired components are adsorptively removed therefrom by such contacting.

FIG. 5 is a schematic representation of an illustrative electrochemical energy device comprising an arrangement of carbohydrate carbon pyrolyzate electrodes of the present disclosure, forming an electric double layer capacitor (EDLC) conformation with electrolyte therebetween, according to one embodiment of the disclosure.

The electrochemical energy device 30 of FIG. 5 comprises an arrangement of carbon electrodes 32 and 34 forming an EDLC conformation with electrolyte 36 therebetween, according to another embodiment of the present disclosure. Electrode 32 is metallized on an outer face thereof to constitute current collector 38 thereon, and electrode 34 is correspondingly metallized on an outer face thereof to constitute current collector 40 thereon.

The carbohydrate carbon pyrolyzate material of the present disclosure may alternatively be employed for construction of electrochemical energy devices of other configurations.

Regardless of the specific configuration employed for the electrochemical energy device, the carbohydrate carbon pyrolyzates with their associated metallization elements form electrodes that are electrically coupled to respective terminals, and upon addition of suitable electrolyte form EDLC cells. The electrolyte may comprise a liquid-phase electrolyte, of an organic or aqueous character, or may comprise a solid state electrolyte material.

The carbohydrate carbon pyrolyzate material of the present disclosure thus can be used to fabricate electrodes that have the capacity to handle high current densities, that exhibit high current efficiency, that possess low capacity fade during repetitive cycling, and that otherwise exhibit high capacitance, high power, and high energy density, and accommodate high voltages in electrochemical double layer capacitor devices.

As previously discussed herein, it will be appreciated that the carbohydrate carbon pyrolyzate materials of the present disclosure may be utilized together with non-carbohydrate carbon pyrolyzate materials.

FIG. 6 is a photograph of self-adherent tablets of natural carbohydrate formed by direct compression, without an added binder, and having a raw material density in excess of 1.32g/cc. FIG. 7 is a photograph showing a range of sizes of disks compressed from various natural carbohydrate sources.

The features and characteristics of carbohydrate carbon pyrolyzate materials are more fully illustrated by the following non-limiting examples.

EXAMPLE 1

A supply of natural corn starch was obtained and a sample of the starch taken from this supply was weighed and heated to 195°C in a laboratory air oven to dry and stabilize such precursor material. The dried starch was then pyrolyzed under flowing nitrogen in a tube furnace at 600°C. After cooling, the N₂ BET surface area of the corn starch-derived carbon pyrolyzate was determined as 578 m² per gram, using a Micromeritics ASAP 2420 Porosimeter.

Another sample of the corn starch from the same supply was weighed and compressed into tablet form under pressure of approximately 0.17 mPa (25,000 psi) to obtain preform tablets. The tablets were weighed and measured to enable determination of a piece density for each. The compressed corn starch tablets had an average piece density of 1.20 grams/cc.

These corn starch tablets were then pyrolyzed under flowing nitrogen in a tube furnace at temperature of 600°C. After cooling, the resulting carbon tablets were weighed and measured, and their piece density was calculated. The average piece density of the corn starch-derived carbon tablets was 0.90grams/cc. The corn starch-derived carbon tablets were analyzed for N₂ BET surface area and found to have surface area of 431 m² per gram. Then the corn starch-derived carbon tablets were reloaded into the tube furnace and heated to 600°C in flowing nitrogen. Next, the carbon tablets were further heated to 735°C at which temperature they were exposed to flowing C0₂ for a period determined to be adequate for a 20 - 25% burn-off (oxidative weight loss), and then the carbon tablets were cooled in nitrogen to room temperature. After this physical oxidative activation, the density of the carbon tablets was measured as 0.78grams/cc. The activated carbon tablets then were measured for N₂ BET surface area and found to have surface area of 890 m² per gram.

EXAMPLE 2

A supply of industrial corn starch-derived maltodextrin was obtained. A sample of the maltodextrin was weighed and heated in a laboratory air oven to dry and stabilize the sample at temperature of 235°C. The dried maltodextrin was then pyrolyzed under flowing nitrogen in a tube furnace at temperature of 600°C. After cooling, the corn starch-derived maltodextrin carbon was analyzed for N₂ BET surface area using a Micromeritics ASAP 2420 Porosimeter. A surface area of 465 m² per gram was determined.

Another sample of the same corn starch-derived maltodextrin was weighed out and compressed into cylindrical tablet form under approximately 185.2 MPa (-26,857 psi) to obtain preform tablets. The tablets were weighed and measured so that a piece density could be calculated. The compressed maltodextrin tablets had an average piece density of 1.36 grams/cc. A number of the cassava starch tablets were pyrolyzed under flowing nitrogen in a tube furnace at temperature of 600°C. After cooling, the resulting carbon tablets were weighed and measured, and the piece density was calculated. The average piece density of the corn starch-derived maltodextrin carbon tablets was 1.06 grams/cc. The corn starch- derived maltodextrin carbon tablets were analyzed for N₂ BET surface area and found to have surface area of 588 m² per gram.

The corn starch-derived maltodextrin carbon tablets were reloaded into the tube furnace and heated to 600°C in flowing nitrogen, and then further heated to 950°C while exposed to flowing C0₂ for a period of time to yield 49.9%wt burn-off, following which the tablets were cooled in nitrogen to room temperature. After this physical oxidative activation, the density of the carbon tablets was reduced to 0.76 grams/cc. The activated carbon tablets were again measured for N₂ BET surface area and surface area was determined to have risen to 1581 m² per gram. Subsequent measurement of methane adsorption on this adsorbent showed a capacity of 152.5cc CH₄/g at 21°C and 35 bar pressure which yielded an absolute CH₄ working capacity between 35 bar and 1 bar pressure of 121V V.

Cylindrical tablets combining varied ratios of native corn starch, such as discussed in Example 1, mixed with corn starch-derived maltodextrin, such as discussed in Example 2, were formed under a range of compressive conditions between 28 and 338 MPa (-4050 psi to 49,000 psi) to obtain preform tablets. The tablets were weighed and measured and evaluated in several ways for strength and other important physical properties. The blended materials followed a very linear rule of mixtures relationship to the properties obtained with either the pure corn starch or the pure maltodextrin.

Upon pyrolysis to 600°C this adherence to the rule of mixtures was maintained. Thus, it was determined that blending of maltodextrin and corn starch, or likely any of the natural starches, at the optimal ratios could take advantage of the beneficial qualities of each of these materials.

EXAMPLE 3

Some of the more common natural carbohydrates that were found to give excellent properties and performance included starches of corn, potato, wheat, and cassava. These materials along with starches of rice, sweet potato and arrowroot, as well as scientific grade amylopectin were pressed into self- adhering binderless tablets under a range of compressive conditions between 28 and 338 MPa (-4050 psi to 49,000 psi) to obtain preform tablets. The tablets were pyrolyzed to 600°C and activated to higher surface area under an atmosphere of C0₂ at temperatures between 750°C and 950°C.

Table 1 below summarizes the properties of several of the embodiments described herein. The table gives density, surface area, and methane adsorption capacity data.

Table 1. Measured Properties of Activated Carbon Monolith Tablets Prepared from Carbohydrates

Table 2 below includes isosteric methane heat of adsorption/de sorption data obtained for a few of the carbohydrate carbon adsorbent embodiments.

Table 2. Measured Methane Heat of Adsorption/Desorption of Activated Carbon Tablets Prepared from Carbohydrates

EXAMPLE 4

Cellulosic as well as non-cellulosic carbohydrate precursor materials were evaluated for forming of carbohydrate carbon pyrolyzate materials useful as adsorbents. Microcrystalline cellulose was evaluated, along with sugars, starches, chitin, chitosan, pectin, and maltodextrin, as precursor materials. Microcrystalline cellulose materials considered in this effort included anhydrous cellulose microcrystalline powder having crystal size of approximately 50 μιη, commercially available from Acros Organics (Thermo Fisher Scientific, http://www.acros.com), and from Microcrystalline Cellulose - Ultra Pure Powder (Avicel® PH-101, Sigma-Aldrich Co., LLC).

The microcrystalline cellulose was utilized to make microporous carbon pyrolyzate material in both powder and tablet form. Under the right conditions, the material was found to form strong, solid tablets via direct compression (without use of a binder) and the tablet structure was sufficiently open so that byproduct gases during thermal decomposition could escape the structure readily without significantly swelling or damaging the formed pieces. Resulting carbon pyrolyzate tablets were strong and appeared to have good gas permeability and were found to be readily activated with C0₂. Representative carbon pyrolyzate tablets exhibited the following properties: ~400-600m²/g N₂ BET surface area as pyrolyzed; ~1100-1500m²/g N₂ BET surface area at ~25%-40% burn-off (~19%-15% yield); a pyrolyzed density of -0.90-1.15g/cc; an activated density of ~0.67-0.90g/cc; and a permeability constant K of -1-2X10^"14 m².

The microcrystalline cellulose was processed as follows. Round tablets were prepared using a Carver Laboratory Press and a 0.5" diameter stainless steel die mold. Each tablet was made to be approximately 1.5g and pressed under approximately 14,000-28,000psi load pressure for hold times ranging from 60 seconds to 30 minutes. All tablets were judged to be satisfactory in appearance. Such tablets are shown in FIG. 8. Densities were measured and ranged from approximately 1.00 - 1.35g/cc. The pressed tablets had a height of -8.5-9.5mm. No obvious advantage was observed for the 30 minute press hold versus the 60 second press hold, and no obvious advantage was observed for the 28,000psi press loading versus the 14,000psi press loading.

These microcrystalline cellulose tablets were pyrolyzed to 800°C in flowing N₂, thus yielding fully carbonized tablets, following which oxidative activation was performed in flowing C0₂ at 900°C for varied lengths of time to control degree of burn -off. Such tablets are depicted in FIGS. 9 and 10, and are of cylindrical form. Forms other than cylindrical are contemplated in the broad practice of the present disclosure. For reference, FIG. 11 is a photograph showing a variety of shapes and sizes of formed carbon pyrolyzate adsorbent pieces prepared via preforming and controlled pyrolysis, and FIG. 12 is a photograph of one embodiment of carbon pyrolyzate adsorbent articles having a space-filling shape, which can be arranged so that adjacent carbon pyrolyzate adsorbent articles are in contact with one another, so that the corresponding array of carbon pyrolyzate adsorbent articles can be employed for maximizing adsorbent density within the enclosed volume of an adsorbent vessel adapted for holding gas for which the carbon pyrolyzate adsorbent has sorptive affinity.

The densities of the pyrolyzed tablets were -0.90 - 1.15g/cc. The pyrolyzed tablets were roughly 0.86cm in diameter and 0.54cm in height. Yields on the pyrolyzed tablets were ~19%-24%wt., and yields on the C0₂ activated tablets were ~8-19%wt. The calculated burn-off ranged from ~5%-60%wt.

Carbonized and activated tablets were thereafter subjected to full N₂ and C0₂ isothermal porosimetry analysis. Porosimetry results are set out in Table 3 below.

Table 3. Porosimetry Results on Pyrolyzed and Activated Microcrystalline Cellulose Derived Carbon Tablets

A graph of burn-off level (%wt.) as a function of processing time at 900°C in C0₂ is shown in FIG. 13 for the microcrystalline cellulose carbon tablets.

The rate of burn-off at 900°C thus appeared as a linear function, with the linearity of the FIG. 13 graph evidencing the consistency and reproducibility of the empirical efforts. The data suggest that 60-minute activation under these conditions in C0₂ would yield only about 5%wt burn-off

Surface area (both gravimetric and volumetric) of the microcrystalline cellulose carbon tablets is plotted as a function of the level of burn-off in FIG. 14. From this graph, it is seen that burn-off of approximately 50%wt. yielded a surface area of -1990 m²/g and that burn-off of approximately 57.5%wt. yielded a surface area of approximately 2147m²/g, with the volumetric surface area falling off at these high burn- off levels and the benefit of higher activation level being minimal or perhaps negative when yield is considered.

FIG. 15 shows the nitrogen adsorption isotherms for the microcrystalline cellulose samples at 77° Kelvin (volume of nitrogen adsorbed (cc nitrogen/gram), as a function of pressure). FIG. 16 shows the C0₂ adsorption isotherms for the microcrystalline cellulose samples at 0°C (volume of C0₂ adsorbed (cc nitrogen/gram), as a function of pressure (torr)). From this series of porosimetry plots it can be seen that although surface area continues to increase with burn-off levels above 35%wt the shape of the isotherms indicates pore widening at these higher activation levels. For most of the gas molecules discussed herein for targeted adsorptive storage and desorptive delivery, the wider pores would have no benefit and would sacrifice volumetric capacity.

EXAMPLE 5

A supply of a variety of natural starches and maltodextrins was obtained. Several samples of each starch and maltodextrin material were weighed out and compressed into cylindrical tablet form under approximately 223 MPa (-32,346 psi) to obtain preform tablets. The tablets were weighed and measured so that a piece density could be calculated, and were then heated slowly in a laboratory air oven to dry and stabilize the samples at temperature of 195°C. The dried starch and maltodextrin tablets were then pyrolyzed under flowing nitrogen in a tube furnace at temperature of 600°C. After cooling, the starch- derived carbon tablets were analyzed for N₂ BET surface area using a Micromeritics ASAP 2420 Porosimeter.

After obtaining data on surface area of the carbon pyrolyzate tablets, the starch-derived and maltodextrin- derived carbon tablets were split between several batch loadings into the tube furnace and heated quickly to 600°C in flowing nitrogen, and then further heated to activate in flowing C0₂ for a period of time ranging from 30 to 720 minutes at temperatures between 750°C and 950°C, following which the tablets were cooled in nitrogen to room temperature. After this physical oxidative activation, the density of the carbon tablets was re-measured. The activated carbon tablets were again measured for N₂ BET surface area and rise in surface area on a gravimetric basis was measured. From the density information and the measured gravimetric surface area, volumetric surface areas were calculated. FIG. 17 is a plot showing the relationship between the level of oxidative burn-off, from C0₂ activation, on a variety of carbohydrate derived carbon pyrolyzate adsorbents and their measured gravimetric Nitrogen BET surface areas. It is shown that adsorbent surface area is adjustable and controllable over a wide range with well controlled activation parameters. Surface areas ranging from 400 - 600 m²/gram up to 2000 - 2500 m²/gram were demonstrated

However, long sustained oxidative activation to high surface areas also has a significant impact on the density of the carbon pyrolyzate tablets. FIG. 18 is a plot showing the relationship between the level of oxidative burn-off on a variety of carbohydrate derived carbon pyrolyzate adsorbents and their measured tablet density. Nearly two thirds of the density of the carbon adsorbent tablets, or more, can be lost via long oxidative activation treatment.

This loss of density can be critical for adsorbent applications where volumetric adsorption capacity is important. Such applications typical include those in which adsorbent volume is constrained by system design. FIG. 19 is a plot showing the effect on measured volumetric Nitrogen BET surface area as a function of degree of oxidative burn-off

Subsequent measurement of methane adsorption on a selection of these activated carbon pyrolyzate adsorbents yielded the data shown in FIG. 20, which shows the ability to closely replicate the methane adsorption performance of a hard carbon pyrolyzate from synthetic polymer source with several of these renewable, naturally sourced starch and maltodextrin starting materials.

EXAMPLE 6

Porosity evaluations of carbon dioxide -activated starch carbon pyrolyzate materials were conducted for each of the following carbon pyrolyzate materials:

Sample NO 190-23 -PT2, a pyrolyzed and activated potato starch having an N₂ BET surface area of 1571 m²/g;

Sample N0190-57-CC58, a pyrolyzed and activated cassava starch having an N₂ BET surface area of 1327 m²/g;

Sample N0190-71-PB 17, a pyrolyzed and activated corn starch having an N₂ BET surface area of 1270 m²/g;

Sample N0190-72-WT15, a pyrolyzed and activated wheat starch having an N₂ BET surface area of 1437 m²/g; and Sample N0190-77-AB25, a pyrolyzed and activated maltodextrin having an N₂ BET surface area of 1169 m²/g.

The nitrogen isotherms of these carbon pyrolyzate materials are shown in FIG. 21, in which desorption branches of the isotherms have been omitted for simplicity.

A plot of differential pore size distribution (Dubinin-Radushkevich) as a function of pore width (pore equipment width in Angstroms) is shown in FIG. 22 for each of these materials.

EXAMPLE 7

A supply of natural corn starches and maltodextrins was obtained from Cargill and Grain Processing Corp. (GPC) as well as from several other suppliers. Samples of Cargill Gel®03420 Corn Starch and GPC Maltrin®040 were heated slowly to dry, dewater and stabilize up to 240°C under inert nitrogen gas purge to yield a carbon char and were then pyrolyzed to 600°C - 800°C in nitrogen to complete the carbonization to an amorphous carbon adsorbent with significant microporosity. The carbons were then oxidatively activated in flowing C0₂ at temperatures from 800°C - 875°C for time periods of 1 to 6 hours. The target was to burn off greater than 35 wt% (preferably near 40 wt%) to obtain surface areas in the range of 1200 m²/g to 1300 m²/g or higher. The target was to prepare adsorbent carbon for EDLC electrode applications. In order to open up the pore structure for easy electrolyte movement through the porous network, it is critical to open access porosity to greater than 0.62nm. Neopentane is a molecule of appropriate geometric size to probe such porosity.

Table 4 shows characterization data for a few of these samples, including preparation conditions, N₂ BET surface area measurements, neopentane probe molecule results and estimates of mesoporosity.

Table 4. Properties of C0₂-Activated Carbohydrate Carbons for Electrodes

Samples were milled and electrodes were prepared and analyzed. Test data is shown in Table 5 and is compared to electrode data for a PVDC carbon derived electrode.

Table 5. Electrode Properties of Corn Starch and Maltodextrin Carbons

It is interesting to note that electrodes with comparable Equivalent Series Resistance (ESR) to that of the PVDC-derived carbon electrodes can be achieved from corn starch. Also important is that both maltodextrin and corn starch yield higher density electrodes than the synthetic polymer precursor does and thereby meet the volumetric capacitance in farads/cc despite having lower gravimetric capacitance (farads/gram). The comparable volumetric capacitance and ESR suggest that long term storage performance of the corn starch electrode would be similar to that of the PVDC carbon. Preliminary long term testing suggests the performance of the corn starch derived pyrolyzate carbon is comparable to, and perhaps slightly improved versus the synthetic polymer derived pyrolyzate carbon electrode.

Ash testing and Plasma Induced X-Ray Emission (PIXE) analysis were performed on a few of the carbohydrate samples to determine level of purity. As shown in Table 6, samples have approximately 1% ash.

Table 6. Purity of Activated Carbohydrate Carbon Pyrolyzate Adsorbent Electrodes

The corn starch carbons performed very well in electrode applications with respect to volumetric capacitance and ESR.

EXAMPLE 8

A supply of natural corn starches and maltodextrins was obtained from Cargill and Grain Processing Corp. (GPC) as well as from several other suppliers. Samples of Cargill Gel®03420 Corn Starch and GPC Maltrin®040 were heated slowly to dry, dewater and stabilize up to 240°C under inert nitrogen gas purge to yield a carbon char and were then pyrolyzed to 600°C - 800°C in nitrogen to complete the carbonization to an amorphous carbon adsorbent with significant microporosity.

The carbons were then tested for N₂ BET surface area, C0₂ adsorption capacity at 117 Torr, and Xenon adsorption capacity at 760 Torr and 294K without any oxidative activation step. Results are shown in Table 7.

Table 7. Adsorption Properties of Carbohydrate Carbon Pyrolyzates without Activation

EXAMPLE 9

A supply of natural com starches and maltodextrins was obtained from Cargill, Ingredion and Grain Processing Corp. (GPC) as well as from several other suppliers. Samples of Cargill Gel®03420 Com Starch, Ingredion 030050 Corn Starch and GPC Maltrin®040 were heated slowly to dry, dewater and stabilize up to 240°C under inert nitrogen gas purge to yield a carbon char and were then pyrolyzed to 600°C - 700°C in nitrogen to complete the carbonization to an amorphous carbon adsorbent with significant microporosity.

The carbons were then oxidatively activated in flowing C0₂ at temperatures from 775°C - 850°C for time periods of 0.5 to 24 hours. Bum-off levels of from -15% to -40% were achieved. Table 8 lists the series of samples and the measured properties.

Table 8. Properties of C0₂-Activated Carbohydrate Carbon Pyrolyzate Adsorbents C02 Activation C02 Activation N2 BET Surface CO, Ads. Mesopore

Burn-Off

Sample Precursor Type Temperature Time Area Capacitv Volume

(wt%)

(degC) (hr) (m2/g) (cc/g @ 117Torr) Jcc/g)

N0080-90-3 Cargill Gel 03420 Corn Starch 850 1 17 732 44 0.018

N0080-90-4 Cargill Gel 03420 Corn Starch 850 2 26 884 45 0.026

N0080-90-11 Cargill Gel 03420 Corn Starch 850 3 31 947 46 0.028

N0080-90-7 Cargill Gel 03420 Corn Starch 850 3 29 971 45 0.04

N0080-90-15 Cargill Gel 03420 Corn Starch 850 4.5 36 1075 44 0.061

ATMI-2274-420 Cargill Gel 03420 Corn Starch 850 2 25 870 44 0.044

N0190-75-HTF Ingredion 030050 Corn Starch 775 24 28 1032 47 0.024

N0080-90-30 Maltrin 040 Maltodextrin 825 0.5 19 755 46 0.023

N0080-90-28 Maltrin 040 Maltodextrin 825 1 31 973 48 0.033

N0080-90-21 Maltrin 040 Maltodextrin 825 1 35 1017 48 0.034

ATMI-2276-462 Maltrin 040 Maltodextrin 825 1 22 749 44 0.029

ATMI-2276-473 Maltrin 040 Maltodextrin 850 1 37 1028 44 0.063

Carbon burn-off rate was found to be proportional to activation time and temperature. The maltodextrin carbon was more readily oxidized by the carbon dioxide thermal treatment, and therefore required less time for activation to similar burn-off levels and surface area. Burn-off levels between 25% and 30% from corn starch carbon and between 30% and 35% for maltodextrin carbon give surface areas of approximately 900 to 1000 m²/g and appear to be optimal for maximizing C0₂ adsorption capacity at 1 17 Torr. The maltodextrin carbons show a slightly higher C0₂ adsorption capacity than do the corn starch carbons. Thus, the maltodextrin carbon might have an advantage in performance and processing cost in relation to corn starch carbon.

Thus, the present disclosure relates in one aspect to a carbohydrate carbon pyrolyzate adsorbent characterized by: a) amorphous or semi-crystalline structure which is non-graphitizable below 1500°C; b) derivation from naturally sourced carbohydrate precursor material; c) total ash content of less than 1.5% as determined by the procedure of ASTM D2866-1 1 ; d) N₂ BET surface area greater than 750 m²/gram; e) bulk density in the range of 0.45 grams/cubic centimeter to 1.25 grams/cubic centimeter; and f) microporous structure with a pore volume of greater than 0.35 cubic centimeters per gram in pores that are smaller than 2 nanometers in size.

Such carbohydrate carbon pyrolyzate may be derived from a naturally occurring, renewable material. In various embodiments, the carbohydrate carbon pyrolyzate adsorbent may comprise a pyrolyzate of one or more material of one or more material classes of starches, dextrins, maltodextrins, natural gums, lactose, chitin, chitosan, amylose, amylopectin, cellulose, and mixtures of two or more of the foregoing materials. In other embodiments, the carbohydrate carbon pyrolyzate adsorbent may comprise a pyrolyzate of microcrystalline cellulose, e.g., wherein the microcrystalline cellulose is derived from one or more of wood pulp, sawdust, newsprint, coconut shells, olives stones, peach stones, apricot pits, viscose, viscose- rayon, cotton, cotton linters, argan nutshell, macadamia nutshell, cellulose acetate, bacterial cellulose, lignin, blackthorn stones, walnut shells, date stones, rice husks, coffee parchment, coffee dregs, bagasse, sorghum millets straws, bamboo woods, mango pits, almond shells, corncobs, cherry stones, and grape seeds.

In other embodiments, the carbohydrate carbon pyrolyzate adsorbent may comprise a pyrolyzate of starch, e.g., a starch derived from one or more of corn, wheat, potato, cassava, sweet potato, tapioca, rice, coconut, or arrowroot.

In still other embodiments, the carbohydrate carbon pyrolyzate adsorbent may comprise a pyrolyzate of maltodextrin, e.g., a maltodextrin derived from one or more of corn, wheat, potato, cassava, sweet potato, tapioca, rice, coconut, or arrowroot.

The carbohydrate carbon pyrolyzate adsorbent may be in a particulate form, e.g., characterized by a bulk density, as measured by ASTM D2854, of greater than 0.50 grams/cc and less than 1.20 grams/cc. Alternatively, the carbohydrate carbon pyrolyzate adsorbent may be in a monolithic form, e.g., characterized by a piece density of greater than 0.60 grams/cc and less than 1.25 grams/cc.

In various embodiments, the carbohydrate carbon pyrolyzate adsorbent may comprise a pyrolyzate of two or more of starch, maltodextrin, and microcrystalline cellulose. In other embodiments, the carbohydrate carbon pyrolyzate adsorbent comprises a pyrolyzate of carbohydrate precursor material and one or more non-carbohydrate precursor material, as for example wherein the one or more non-carbohydrate precursor material is selected from the group consisting of synthetic polymeric materials, petroleum-based materials, petroleum-derived materials, and combinations, blends, and mixtures of the foregoing, e.g., wherein the one or more non-carbohydrate precursor material is selected from the group consisting of polyvinylidene chloride polymers and copolymers, and polyvinylidene fluoride polymers and copolymers. In still other embodiments, the carbohydrate carbon pyrolyzate adsorbent comprises a pyrolyzate of carbohydrate precursor material comprising two or more different carbohydrate materials.

In various embodiments, the carbohydrate carbon pyrolyzate adsorbent may have a concentration of carbohydrate precursor material of at least 50% by weight, based on total weight of the carbohydrate precursor material and non-carbohydrate precursor material.

The disclosure relates in another aspect to a method of producing the carbohydrate carbon pyrolyzate adsorbent of the disclosure, comprising: a) drying, dewatering and stabilizing the natural carbohydrate source to carbon char under non-oxidizing environment between 1 10°C and 235°C; b) thermally decomposing or pyrolyzing the char to amorphous microporous carbon in inert or reducing atmosphere at temperatures of 500°C to 950°C; and c) thermally activating or physically enhancing the amorphous carbon under oxidizing environment between 600°C and 1200°C to high surface area.

In various embodiments of such method, the pyrolysis process is conducted for at least 4 hours.

A further aspect of the disclosure relates to a method of producing the carbohydrate carbon pyrolyzate adsorbent of the disclosure, wherein the pyrolyzate has undergone pyrolysis in an inert gas at temperatures of 600°C to 900°C for sufficient time to complete the carbonization process.

Another aspect of the disclosure relates to a method of producing the carbohydrate carbon pyrolyzate adsorbent of the disclosure, comprising activating the pyrolyzate by chemical and/or physical activation, e.g., wherein the pyrolyzate has been activated by any of: burn-off in exposure to C0₂, air, or steam in mixture with an inert gas or as a pure gas stream at temperature in a range of from 600°C to 1200°C; burn- off in exposure to gaseous C0₂ in mixture with an inert gas or as a pure gas stream at temperature in a range of from 750°C to 1100°C; or burn-off in exposure to gaseous C0₂ for at least 2 hours.

The carbohydrate carbon pyrolyzate adsorbent of the disclosure may be variously characterized by any one or more of: a N₂ BET surface area of at least 800 m²/g; a N₂ BET surface area between 900 m²/g and 2500 m²/g; a porosity including at least 50% of pore volume constituted by pores of size between 0.3 nm and 2.0 nm; and porosity including less than 50% of pore volume in mesopores and/or in macropores.

The disclosure relates in a further aspect to an electrochemical double layer capacitor (EDLC) electrode carbon material, comprising the carbohydrate carbon pyrolyzate adsorbent of the disclosure, as variously described herein. Such EDLC electrode carbon material may for example comprise a pyrolyzate of at least one of plant starches, maltodextrin, and microcrystalline cellulose, having the following characteristics:

(i) a nitrogen Brunauer-Emmett-Teller (N₂ BET) surface area measured at 77° Kelvin, which is in a range of from 1200 m² per gram of carbon material to 2250 m² per gram of carbon material;

(ii) a nitrogen Dubinin-Radushkevich micropore volume measured at 77° Kelvin, which is in a range of from 0.45 cc per gram of carbon material to 1 cc per gram of carbon material, and at least 94% of which is constituted by pores larger than 0.6 nm, as determined by Gurvich-based neopentane capacity at neopentane pressure of 450 mmHg, neopentane liquid density of 0.613 g/mL, neopentane kinetic diameter of 0.62 nm, and temperature of 273° Kelvin;

(iii) particulate form in which at least 97% by weight of particles have particle size in a range of from 1 to 20 μπι; (iv) ash content as determined by ASTM 2866-94 of less than 1.2% by weight, based on weight of the carbon material; and

(v) iron content as determined by particle -induced x-ray emission (PIXE) spectrometry, of less than 25 ppm by weight, based on weight of the carbon material.

The disclosure in another aspect contemplates an adsorbent material having utility as an adsorption media in an adsorption heating and/or cooling system, comprising the carbohydrate carbon pyrolyzate adsorbent of the present disclosure, as variously described herein. Such adsorbent material may for example have at least one of the following properties:

(i) piece density in a range of from 0.60 to 1.25 g/cc;

(ii) thermal conductivity in a range of from 0.6 to 6.0 Wm^K^"1;

(iii) radial permeability in a range of from 5 x 10^"16 to 1.5 x 10^"13 m²;

(iv) average pore diameter in a range of from 0.5 to 50 nm.

A further aspect of the disclosure relates to a carbohydrate carbon pyrolyzate adsorbent of the present disclosure, as variously described herein, having utility for capture and recovery for reuse of high value gaseous species, such as xenon or krypton, from process streams containing such in non-pure concentrations. Such adsorbent may for example have a bulk density in a range of from 0.75 to 1.30 grams per cubic centimeter (g/cc), and a porosity in which the majority of pores are in a range of from 5 to 8 Angstroms.

Another aspect of the disclosure relates to a carbohydrate carbon pyrolyzate adsorbent of the present disclosure, as variously described herein, having utility for capture of C0₂, from coal-fired electric power plants, from refinery preheaters, from industrial boilers, and the like. Such carbohydrate carbon pyrolyzate adsorbent may for example have the following characteristics:

(a) C0₂ capacity greater than 100 cc/gram at one bar pressure and temperature of 273° Kelvin;

(b) C0₂ Working Capacity greater than 7.0 weight percent;

(c) C0₂ heats of adsorption and desorption each of which is in a range of from 10 to 50 kJ/mole; and

(d) C0₂/N₂ Henry's Law Separation Factor greater than 3. Yet another aspect of the disclosure relates to a carbohydrate carbon pyrolyzate adsorbent of the present disclosure, as variously described herein, having utility for selective adsorptive removal of C0₂ from gas mixtures containing same in combination with other gases such as natural gas, biogas from anaerobic digestion processes, coal bed methane, and output gas mixtures from steam-methane reforming processes. In various embodiments, such carbohydrate carbon pyrolyzate adsorbent may have a carbon dioxide adsorbent capacity at 1 bar pressure of greater than 50 cm³ carbon dioxide per gram of adsorbent at 273K, a methane adsorption capacity at 1 bar pressure of less than 35 cm³ methane per gram of adsorbent at 21°C, and a bulk density of greater than 0.45 gram per cubic centimeter of volume. In other embodiments, such carbohydrate carbon pyrolyzate adsorbent may have the following characteristics: i) total ash content of less than 1.5%, preferably <1.3%, most preferably <1.1% as measured by

ASTM D2866 ii) bulk density, as measured by ASTM D2854, of greater than 0.45 g/cc and less than 1.20 g/cc, preferably >0.50 g/cc and <1.15 g/cc, most preferably >0.55 g/cc and <1.00 g/cc iii) carbon dioxide adsorption capacity measured at 1 bar pressure and a temperature of 273 Kelvin of greater than 50 cm3 carbon dioxide per gram of adsorbent, preferably >65 cc/g, and most preferably >75 cc/g iv) methane adsorption capacity measured at 1 bar pressure and a temperature of 21 °C of less than 35 cm³ methane per gram of adsorbent, preferably <30 cc/g, and most preferably <20 cm3/g v) C0₂ heats of adsorption and desorption each of which is in the range of 10 to 50 kJ/mole, preferably in the range of 10 to 40 kJ/mole, most preferably 10 to 35 kJ/mole vi) single pellet radial crush strength for a nominal 3mm pellet of greater than 2 kilopond (kP), preferably >4 kP, most preferably >5 kP as measured by ASTM D4179.

Another aspect of the disclosure relates to a gas purifier, comprising a housing defining an interior volume and adapted for flow of gas therethrough, and a carbohydrate carbon pyrolyzate adsorbent of the present disclosure, as variously described herein, in the interior volume of the housing, arranged for contact with the gas flowed through the housing to sorptively purify the gas.

A further aspect of the disclosure relates to a method of filtering and/or purifying gas, comprising contacting the gas with an adsorbent of the present disclosure, as variously described herein, having sorptive affinity for one or more components of said gas. The disclosure, as variously set out herein in respect of features, aspects and embodiments thereof, may in particular implementations be constituted as comprising, consisting, or consisting essentially of, some or all of such features, aspects and embodiments, as well as elements and components thereof being aggregated to constitute various further implementations of the disclosure. The disclosure correspondingly contemplates such features, aspects and embodiments, or a selected one or ones thereof, in various permutations and combinations, as being within the scope of the present disclosure.

Accordingly, while the disclosure has been set forth herein in reference to specific aspects, features and illustrative embodiments, it will be appreciated that the utility of the disclosure is not thus limited, but rather extends to and encompasses numerous other variations, modifications and alternative embodiments, as will suggest themselves to those of ordinary skill in the field of the present disclosure, based on the description herein. Correspondingly, the disclosure as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its spirit and scope.

Claims

THE CLAIMS What is claimed is:

1. A carbohydrate carbon pyrolyzate adsorbent characterized by: a) amorphous or semi -crystalline structure which is non-graphitizable below 1500°C; b) derivation from naturally sourced carbohydrate precursor material; c) total ash content of less than 1.5% as determined by the procedure of ASTM D2866-1 1 ; d) N₂ BET surface area greater than 750 m²/gram; e) bulk density in the range of 0.45 grams/cubic centimeter to 1.25 grams/cubic centimeter; and f) microporous structure with a pore volume of greater than 0.35 cubic centimeters per gram in pores that are smaller than 2 nanometers in size.

2. The carbohydrate carbon pyrolyzate adsorbent of claim 1, which is derived from a naturally occurring, renewable material.

3. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of one or more material of one or more material classes of starches, dextrins, maltodextrins, natural gums, lactose, chitin, chitosan, amylose, amylopectin, cellulose, and mixtures of two or more of the foregoing materials.

4. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of microcrystalline cellulose.

5. The carbohydrate carbon pyrolyzate adsorbent of claim 4, wherein the microcrystalline cellulose is derived from one or more of wood pulp, sawdust, newsprint, coconut shells, olives stones, peach stones, apricot pits, viscose, viscose-rayon, cotton, cotton linters, argan nutshell, macadamia nutshell, cellulose acetate, bacterial cellulose, lignin, blackthorn stones, walnut shells, date stones, rice husks, coffee parchment, coffee dregs, bagasse, sorghum millets straws, bamboo woods, mango pits, almond shells, corncobs, cherry stones, and grape seeds.

6. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of starch.

7. The carbohydrate carbon pyrolyzate adsorbent of claim 6, wherein the starch is derived from one or more of corn, wheat, potato, cassava, sweet potato, tapioca, rice, coconut, or arrowroot.

8. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of maltodextrin.

9. The carbohydrate carbon pyrolyzate of claim 8, wherein the maltodextrin is derived from one or more of corn, wheat, potato, cassava, sweet potato, tapioca, rice, coconut, or arrowroot.

10. The carbohydrate carbon pyrolyzate adsorbent of claim 1, in a particulate form.

11. The carbohydrate carbon pyrolyzate adsorbent of claim 10, characterized by a bulk density, as measured by ASTM D2854, of greater than 0.50 grams/cc and less than 1.20 grams/cc.

12. The carbohydrate carbon pyrolyzate adsorbent of claim 1, in a monolithic form.

13. The carbohydrate carbon pyrolyzate adsorbent of claim 12, characterized by a piece density of greater than 0.60 grams/cc and less than 1.25 grams/cc.

14. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of two or more of starch, maltodextrin, and microcrystalline cellulose.

15. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of carbohydrate precursor material and one or more non-carbohydrate precursor material.

16. The carbohydrate carbon pyrolyzate adsorbent of claim 15, wherein the one or more non-carbohydrate precursor material is selected from the group consisting of synthetic polymeric materials, petroleum- based materials, petroleum-derived materials, and combinations, blends, and mixtures of the foregoing.

17. The carbohydrate carbon pyrolyzate adsorbent of claim 16, wherein the one or more non-carbohydrate precursor material is selected from the group consisting of polyvinylidene chloride polymers and copolymers, and polyvinylidene fluoride polymers and copolymers.

18. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate of carbohydrate precursor material comprising two or more different carbohydrate materials.

19. The carbohydrate carbon pyrolyzate adsorbent of claim 15, wherein the concentration of carbohydrate precursor material is at least 50% by weight, based on total weight of the carbohydrate precursor material and non-carbohydrate precursor material.

20. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising: a) drying, dewatering and stabilizing the natural carbohydrate source to carbon char under non-oxidizing environment between 110°C and 235°C; b) thermally decomposing or pyrolyzing the char to amorphous microporous carbon in inert or reducing atmosphere at temperatures of 500°C to 950°C; and c) thermally activating or physically enhancing the amorphous carbon under oxidizing environment between 600°C and 1200°C to high surface area.

21. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 1, wherein the pyrolyzate has undergone pyrolysis in an inert gas at temperatures of 600°C to 900°C for sufficient time to complete the carbonization process.

22. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 20, wherein the pyrolysis process is conducted for at least 4 hours.

23. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising a pyrolyzate activated by chemical and/or physical activation.

24. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 23, wherein the pyrolyzate has been activated by burn-off in exposure to C0₂, air, or steam in mixture with an inert gas or as a pure gas stream at temperature in a range of from 600°C to 1200°C.

25. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 23, wherein the pyrolyzate has been activated by burn-off in exposure to gaseous C0₂ in mixture with an inert gas or as a pure gas stream at temperature in a range of from 750°C to 1100°C.

26. A method of producing the carbohydrate carbon pyrolyzate adsorbent of claim 23, wherein the pyrolyzate has been activated by burn-off in exposure to gaseous C0₂ for at least 1 hour.

27. The carbohydrate carbon pyrolyzate adsorbent of claim 1, characterized by a N₂ BET surface area of at least 800 m²/g.

28. The carbohydrate carbon pyrolyzate adsorbent of claim 1, characterized by a N₂ BET surface area between 900 m²/g and 2500 m²/g.

29. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising porosity including at least 50% of pore volume constituted by pores of size between 0.3 nm and 2.0 nm.

30. The carbohydrate carbon pyrolyzate adsorbent of claim 1, comprising porosity including less than 50% of pore volume in mesopores and/or in macropores

31. An electrochemical double layer capacitor (EDLC) electrode carbon material, comprising the carbohydrate carbon pyrolyzate adsorbent according to any one of claims 1 to 30.

32. The EDLC electrode carbon material of claim 31, comprising a pyrolyzate of at least one of plant starches, maltodextrin, and microcrystalline cellulose, having the following characteristics: (i) a nitrogen Brunauer-Emmett-Teller (N₂ BET) surface area measured at 77° Kelvin, which is in a range of from 1200 m² per gram of carbon material to 2250 m² per gram of carbon material;

(ii) a nitrogen Dubinin-Radushkevich micropore volume measured at 77° Kelvin, which is in a range of from 0.45 cc per gram of carbon material to 1 cc per gram of carbon material, and at least 94% of which is constituted by pores larger than 0.6 nm, as determined by Gurvich-based neopentane capacity at neopentane pressure of 450 mmHg, neopentane liquid density of 0.613 g/mL, neopentane kinetic diameter of 0.62 nm, and temperature of 273° Kelvin;

(iii) particulate form in which at least 97% by weight of particles have particle size in a range of from 1 to 20 μιη;

(iv) ash content as determined by ASTM 2866-94 of less than 1.2% by weight, based on weight of the carbon material; and

(v) iron content as determined by particle -induced x-ray emission (PIXE) spectrometry, of less than 25 ppm by weight, based on weight of the carbon material.

33. An adsorbent material having utility as an adsorption media in an adsorption heating and/or cooling system, comprising the carbohydrate carbon pyrolyzate adsorbent according to any one of claims 1 to 30.

34. The adsorbent material of claim 33, wherein the carbon adsorbent has at least one of the following properties:

(i) piece density in a range of from 0.60 to 1.25 g/cc;

(ii) thermal conductivity in a range of from 0.6 to 6.0 Wm^K^"1;

(iii) radial permeability in a range of from 5 x 10^"16 to 1.5 x 10^"13 m²; and

(iv) average pore diameter in a range of from 0.5 to 50 nm.

35. The carbohydrate carbon pyrolyzate adsorbent of any of claims 1 to 30, having utility for capture and recovery for reuse of high value gaseous species, such as xenon or krypton, from process streams containing such in non-pure concentrations.

36. The adsorbent material of claim 35, having a bulk density in a range of from 0.75 to 1.30 grams per cubic centimeter (g/cc), and a porosity in which the majority of pores are in a range of from 5 to 8 Angstroms.

37. The carbohydrate carbon pyrolyzate adsorbent of any of claims 1 to 30, having utility for capture of C0₂, from coal-fired electric power plants, from refinery preheaters, from industrial boilers, and the like.

38. The carbohydrate carbon pyrolyzate adsorbent of claim 37, having the following characteristics:

(a) C0₂ capacity greater than 100 cc/gram at one bar pressure and temperature of 273° Kelvin;

(b) C0₂ Working Capacity greater than 7.0 weight percent;

(c) C0₂ heats of adsorption and desorption each of which is in a range of from 10 to 50 kJ/mole; and

(d) C0₂/N₂ Henry's Law Separation Factor greater than 3.

39. The carbohydrate carbon pyrolyzate adsorbent of any of claims 1 to 30, having utility for selective adsorptive removal of C0₂ from gas mixtures containing same in combination with other gases such as natural gas, biogas from anaerobic digestion processes, coal bed methane, and output gas mixtures from steam-methane reforming processes.

40. The carbohydrate carbon pyrolyzate adsorbent of claim 39, having a carbon dioxide adsorbent capacity at 1 bar pressure of greater than 50 cm³ carbon dioxide per gram of adsorbent at 273K, a methane adsorption capacity at 1 bar pressure of less than 35 cm³ methane per gram of adsorbent at 21°C, and a bulk density of greater than 0.45 gram per cubic centimeter of volume.

41. The carbohydrate carbon pyrolyzate adsorbent of claim 39, having the following characteristics: i) total ash content of less than 1.5%, preferably <1.3%, most preferably <1.1% as measured by

ASTM D2866 ii) bulk density, as measured by ASTM D2854, of greater than 0.45 g/cc and less than 1.20 g/cc, preferably >0.50 g/cc and <1.15 g/cc, most preferably >0.55 g/cc and <1.00 g/cc iii) carbon dioxide adsorption capacity measured at 1 bar pressure and a temperature of 273 Kelvin of greater than 50 cm3 carbon dioxide per gram of adsorbent, preferably >65 cc/g, and most preferably >75 cc/g iv) methane adsorption capacity measured at 1 bar pressure and a temperature of 21 °C of less than 35 cm³ methane per gram of adsorbent, preferably <30 cc/g, and most preferably <20 cm3/g v) C0₂ heats of adsorption and desorption each of which is in the range of 10 to 50 kJ/mole, preferably in the range of 10 to 40 kJ/mole, most preferably 10 to 35 kJ/mole vi) single pellet radial crush strength for a nominal 3mm pellet of greater than 2 kilopond (kP), preferably >4 kP, most preferably >5 kP as measured by ASTM D4179.

42. A gas purifier, comprising a housing defining an interior volume and adapted for flow of gas therethrough, and a carbohydrate carbon pyrolyzate adsorbent, according to any of the claims 1 to 30, in the interior volume of the housing, arranged for contact with the gas flowed through the housing to sorptively purify the gas.

43. A method of filtering and/or purifying gas, comprising contacting the gas with an adsorbent according to any one of claims 1 to 30, having sorptive affinity for one or more components of said gas.