Solid gas sorption, storage and separation

Abstract

The present invention relates to a method for promoting the adsorption of one or more gases onto a solid particulate material, the method comprising the step of ball-milling the solid particulate material at an operating speed of at least 200 rpm, (i) in the presence of one or more gases maintained at a pressure of at least 300 kPa, and (ii) using a ratio of milling balls to solid particulate material of at least 60:1.

Description

Technical Field

[0001] The present invention generally relates to solid phase gas sorption, storage and separation. More particularly, the present invention relates to a method for promoting solid phase gas sorption that can facilitate gas storage and separation.

Background Art

[0002] Modern society has a long history of developing techniques for storing gases. For example, the basic storage of fuel gas dates back to the early 1800s. Early techniques for storing gases involved compressing the gas into a container to produce compressed or liquefied gas. Compressed gas storage today requires the use of special high-pressure containers that exhibit drawbacks such as high cost and safety issues.

[0003] More recent techniques employed for gas storage include so-called solid phase techniques, where the gas either chemically reacts with a suitable solid substrate or is physically adsorbed. Although such techniques are not plagued by high-pressure equivalents, they still have drawbacks.

[0004] For example, in so-called chemical reaction techniques, the gas to be stored chemically reacts with an adsorbent material to form new species such as oxides, nitrides, and hydrides. Even if the gas is suitably stored, its recovery requires a significant energy (e.g., high temperature) input to drive the reverse chemical reaction and promote gas reforming / release. Additionally, the possible combinations of gases with realizable chemically reactive adsorbent materials are limited.

[0005] So-called physical adsorption techniques rely on gases that form physical associations (e.g., via van der Waals forces) with an adsorbent material. Gases adsorbed in this way can be recovered using very little energy input (e.g., low temperature), but the technique traditionally tends to provide a relatively low storage capacity.

[0006] Gas storage is often linked to the requirement of separating gas mixtures. For example, in addition to the requirement of storing gas, an important requirement in the petrochemical industry is the separation of gas mixtures. A common method of separating gas mixtures is the use of cryogenic distillation processes. However, cryogenic distillation is very energy-intensive and is reported to account for up to 15% of the world's energy consumption in such industries.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, there remains an opportunity to develop alternative technologies that facilitate the storage and separation of gases, addressing one or more of the drawbacks associated with the state of the art.

Means for Solving the Problems

[0008] The present invention provides a method for promoting the adsorption of one or more gases onto a solid particulate material, comprising the steps of: (i) in the presence of one or more gases maintained at a pressure of at least 300 kPa; (ii) using a weight ratio of milling balls to solid particulate material of at least 60:1 (a weight ratio of milling balls to solid particulate material); and (iii) ball milling the solid particulate material at an operating speed of at least 200 rpm.

[0009] Ball milling has long been used as a technique for grinding solid materials and / or promoting intimate mixing between two or more different materials. Surprisingly, it has been found that ball milling can promote a high gas adsorption capacity in solid particulate materials when performed using a defined combination of parameters. 1500 cm 3A weight adsorption capacity exceeding / g can be achieved. The technique has been found to be very effective, cost-efficient, environmentally friendly, energy-efficient, and particularly well-suited for scale-up. According to the unique method of the present invention, the solid particulate material is advantageously processed into an excellent solid-phase gas storage material. Furthermore, the unique adsorption of gas performed according to the method of the present invention can be advantageously used to facilitate the separation of a mixture of gases.

[0010] Although not wishing to be bound by theory, the ball milling of the solid particulate material using a defined combination of working parameters subjects the particulate material to a unique intensive energy process, and it is thought that gas molecules are thereby efficiently adsorbed onto the solid particulate material. The method according to the present invention advantageously allows the gas to pre-form without undergoing a chemical reaction with the solid particulate material, and as a result, the gas is not converted into a new species, such as an oxide, nitride, or hydride. Rather, the method advantageously promotes one or more forms of non-covalent bonding between the gas and the solid particulate material, achieving a weight adsorption capacity similar to that of conventional chemical reaction techniques, but having a low energy gas release profile of conventional physical adsorption techniques.

[0011] Furthermore, a given gas is thought to bind uniquely to a given solid particulate material, which means that the binding affinities of other gas / solid particulate material combinations are different. Those different binding affinities can be used to facilitate the separation of gas mixtures.

[0012] In particular, the method according to the present invention is thought not to promote a chemical reaction between the solid particulate material and the gas in the sense that no new molecular species is formed between the gas and the solid particulate material. In other words, the gas molecules processed according to the method of the present invention are thought to remain as molecules. Although not wishing to be bound by theory, the ball milling method is thought to promote the physical adsorption of gas molecules onto the solid particulate material (e.g., by van der Waals forces) and / or electrostatic / ionic bonding.

[0013] Surprisingly, it has been found that gases can be stored in large volumes by solid phase storage techniques using controlled ball mill grinding and recovered using a relatively low energy (low temperature) input.

[0014] According to the present invention, the adsorption of one or more gases onto a solid particulate material is not obtained by a chemical reaction or covalent bond formation between the one or more gases and the solid particulate material. Thus, combinations of gases and solid particulate materials contemplated for use according to the present invention are not intended to include those that essentially undergo a chemical reaction (such as a combination of a metal and hydrogen).

[0015] Thus, the present invention also provides a method for promoting the adsorption of one or more gases onto a solid particulate material that does not involve a chemical reaction occurring between the one or more gases and the solid particulate material, the method comprising the steps of: (i) in the presence of one or more gases maintained at a pressure of at least 300 kPa; (ii) using a weight ratio of milling balls to solid particulate material of at least 60:1; and (iii) ball mill grinding the solid particulate material at an operating speed of at least 200 rpm.

[0016] The present invention also provides a method for promoting non-covalent bond adsorption of one or more gases onto a solid particulate material, the method comprising the steps of: (i) in the presence of one or more gases maintained at a pressure of at least 300 kPa; (ii) using a weight ratio of milling balls to solid particulate material of at least 60:1; and (iii) ball mill grinding the solid particulate material at an operating speed of at least 200 rpm.

[0017] "Non-covalent bond" adsorption means that one or more gases are adsorbed onto the solid particulate material by a bonding mechanism other than covalent bond formation. As such, the gas remains as a molecule.

[0018] Suitable solid particulate materials for use according to the present invention include, but are not limited to, for example, layered structures such as boron nitride and graphite, transition metal dichalcogenides such as molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, and molybdenum ditelluride, and crystalline materials having non-layered materials such as boron, iron, and silicon.

[0019] In one embodiment, the solid particulate material is selected from boron nitride, graphite, molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, molybdenum ditelluride, boron, iron, and silicon.

[0020] In another embodiment, the solid particulate material is selected from boron nitride, graphite, molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, and molybdenum ditelluride.

[0021] In yet a further embodiment, the one or more gases are selected from hydrogen, carbon dioxide, carbon monoxide, C1-C4 hydrocarbons, ammonia, nitric oxide, nitrogen dioxide, sulfur dioxide, and nitrogen.

[0022] In another embodiment, ball milling produces a product of solid particulate material adsorbed with one or more gases, and the product is contained in a container to store the one or more gases.

[0023] The present invention also provides a method for solid-phase storage of one or more gases, the method including the step of ball milling the solid particulate material described herein to produce a product of solid particulate material adsorbed with one or more gases, and the product being contained in a container to store the one or more gases.

[0024] The product contained in the container can be treated to release the one or more gases adsorbed to the solid particulate material, thereby recovering the one or more stored gases. One or more gases may also be described as being non-covalently bound to the solid particulate material.

[0025] The unique and specific adsorption of gases to the solid dispersion particle material according to the present invention advantageously enables the separation of gas mixtures. In one embodiment, ball milling is carried out in the presence of a mixture of two or more gases, which produces a solid particulate material adsorbed with the gas mixture as a product, and the product is treated to selectively release at least one adsorbed gas from the solid particulate material, thereby separating the released gas from the mixture of two or more gases.

[0026] The present invention also provides a method for separating a mixture of two or more gases, comprising the step of ball milling the solid particulate material described herein, wherein the ball milling produces a solid particulate material adsorbed with the mixture of two or more gases as a product, and the product is treated to selectively release at least one adsorbed gas from the solid particulate material, thereby separating the released gas from the mixture of two or more gases.

[0027] In one embodiment, the product of the solid particulate material adsorbed with the mixture of two or more gases is treated by raising its temperature to selectively release at least one adsorbed gas from the solid particulate material.

[0028] In a further embodiment, ball milling is carried out in the presence of a mixture of two or more gases, which produces as a product a solid particulate material having (i) at least one gas from the mixture of gases adsorbed thereto and (ii) at least one gas from the mixture of gases not adsorbed thereto, thereby separating at least one gas not adsorbed from the mixture of two or more gases.

[0029] The present invention further provides a method for separating a mixture of two or more gases, which includes the step of ball milling a solid particulate material as described herein, wherein the ball milling produces a solid particulate material having (i) at least one gas from the mixture of gases adsorbed thereon and (ii) at least one gas from the mixture of gases not adsorbed thereon as a product, thereby separating at least one gas not adsorbed from the mixture of two or more gases.

[0030] Additional aspects and features of the present invention are discussed in more detail below. Embodiments of the present invention are now described with reference to the following non-limiting drawings.

Brief Description of the Drawings

[0031]

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Mode for Carrying Out the Invention

[0032] The present invention will also be described with reference to the following non-limiting examples. The present invention provides a method for promoting the adsorption of one or more gases onto a solid particulate material.

[0033] The one or more gases that cause or become adsorbed onto the solid particulate material refer to the gas molecules that constitute one or more gases that bind or adhere to the solid particulate material. In other words, the gas molecules remain as such as molecules and adhere to the solid particulate material without undergoing a chemical reaction. Without wishing to be bound by theory, the unique intensive energy milling process operating in accordance with the present invention is believed to promote the physical adsorption and / or electrostatic / ionic bonding of gas molecules to the solid particulate material.

[0034] References herein to one or more gases that are bound or adhered to the solid particulate material are thus intended to mean that one or more gases are adsorbed onto the solid particulates.

[0035] The method according to the present invention is not considered to promote a chemical reaction and formation of a covalent bond between the gas molecule and the solid particulate material. The method according to the present invention is thus intended to exclude the use of a solid particulate material that chemically reacts with one or more gases to form a covalent bond between the one or more gas molecules and a particular material of the solid.

[0036] Taking into account the non-chemical reaction requirement, there is no special restriction on the gases that can be used in accordance with the present invention. Suitable gases also include those that cause adsorption onto the solid particulate material and those that do not. As will be discussed in more detail below, the present invention must be practiced using at least one gas that causes adsorption onto the solid particulate material, but non-adsorption of the gas onto the solid particulate material can be used to facilitate the separation of gas mixtures.

[0037] According to the present invention, the affinity of a given gas that causes adsorption to a solid particulate material varies depending not only on the nature of the specific gas but also on the nature of the solid particulate material. Guidelines for the adsorption affinity of various gases to various solid particulate materials are outlined below. Furthermore, such adsorption affinity of gases to solid particulate materials can be readily verified experimentally.

[0038] Examples of suitable gases that may be used according to the present invention include, but are not limited to, hydrogen, carbon monoxide, carbon dioxide, C1-C4 hydrocarbons, nitric oxide, nitrogen dioxide, sulfur dioxide, ammonia, and nitrogen.

[0039] Examples of suitable C1-C4 hydrocarbons, such as C1-C2 and C1-C3 hydrocarbons, include, but are not limited to, CH4, C2H2, C2H4, C2H6, C3H6, C3H8, C4H8, and C4H 10 including.

[0040] There are no special restrictions on the solid particulate materials that can be used according to the present invention as long as (i) they can cause adsorption of at least one gas and (ii) they do not chemically react with one or more gases so as to form a covalent bond between the one or more gas molecules and the solid specific material.

[0041] The solid particulate material may take any shape, for example, in the form of substantially spherical particles, sheet-like particles, fibers, and rod / wire-like particles. Examples of suitable materials from which the solid particulate material can be derived include, but are not limited to, crystalline materials having a layered structure such as boron nitride, graphite, and transition metal dichalcogenides such as molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide, and molybdenum ditelluride, as well as non-layered materials such as boron, iron, and silicon.

[0042] The process of ball mill grinding according to the present invention essentially grinds solid particulate materials and increases their surface area. There are no special restrictions on the size of the particulate materials that can be used as long as they can be properly ball milled.

[0043] Generally, the average particle size of the solid particulate material before ball mill grinding ranges from about 1 μm to about 5 mm. Generally, the average particle size of the solid particulate material after ball mill grinding ranges from about 10 nm to about 100 μm.

[0044] An important feature of the present invention is the use of ball mill grinding. Using a defined combination of operating parameters, the present invention can advantageously be carried out using conventional ball mill grinding equipment.

[0045] Suitable ball milling equipment includes, but is not limited to, planetary ball mills, horizontal ball mills and vertical ball mills. Those skilled in the art will recognize that the ball mill grinding equipment includes a grinding container / bottle and grinding balls. There are no special restrictions on the materials from which the grinding container and balls are manufactured as long as they can withstand the operating parameters and are substantially inert to the reagents being processed.

[0046] Suitable grinding containers include, but are not limited to, those made of stainless steel, zirconia, nylon, polytetrafluoroethylene and quartz. Suitable grinding balls include, but are not limited to, those made of silicon carbide, stainless steel, hardened steel, zirconia and quartz.

[0047] Those skilled in the art can easily adjust the sizes of the grinding container and balls used to suit the scale of the operation. The present invention can advantageously be carried out on a laboratory, pilot and industrial scale.

[0048] In one embodiment, the grinding container has a volume in the range of about 25 ml to about 1000 L. One of ordinary skill in the art can readily select the size of the grinding balls to be suitable for in-hand work, including taking into account the volume of the grinding container and the required ratio to the solid particulate material of the grinding balls (discussed below).

[0049] In one embodiment, the grinding balls have a diameter in the range of about 1 mm to about 200 mm. There are at least three ball mill grinding operation parameters required in total to promote the desired adsorption of one or more gases to the solid particulate material.

[0050] According to the present invention, the solid particulate material is ball milled (i.e., undergoes ball mill grinding) in the presence of one or more gases maintained at a pressure of at least 300 kPa. In other words, to promote the desired adsorption of one or more gases, the ball mill grinding is carried out at a pressure of at least 300 kPa in the atmosphere of one or more gases. If necessary, the gas can be introduced into the ball mill during operation to maintain the required pressure.

[0051] In one embodiment, the one or more gases are maintained at a pressure of at least about 400, 500, 600, 700 or 800 kPa. In a further embodiment, the one or more gases are maintained at a pressure in the range of at least about 300 kPa to about 30,000 kPa, 400 kPa to about 30,000 kPa, 500 kPa to about 30,000 kPa, 600 kPa to about 30,000 kPa, 700 kPa to about 30,000 kPa, or 800 kPa to about 30,000 kPa.

[0052] One or more gases can be introduced into the ball mill grinding equipment using techniques known in the art to provide the required pressure. As the ball mill grinding operation progresses, the gas pressure in the ball mill grinding equipment generally gradually decreases because one or more gases adsorb onto the solid particulate material. The gas pressure can be easily monitored and, if necessary, repressurized back to at least 300, 400, 500, 600, 700, or 800 kPa.

[0053] According to the present invention, the solid particulate material is ball mill ground using a weight ratio of grinding balls to the solid particulate material of at least 60:1. The required weight ratio can be easily determined using conventional devices for measuring weight.

[0054] In one embodiment, the weight ratio of the grinding balls to the solid particulate material is at least about 70:1, or about 80:1, or about 90:1, or about 100:1, or about 120:1, or about 150:1.

[0055] In one embodiment, the weight ratio of the grinding balls to the solid particulate material is in the range of at least 60:1 to about 300:1, such as about 70:1 to about 300:1, or about 80:1 to about 300:1, or about 90:1 to about 300:1, or about 100:1 to about 300:1, or about 120:1 to about 300:1, or about 150:1 to about 300:1.

[0056] Considering the weight ratio of the grinding balls to the solid particulate material, the volume of the grinding container and the number of grinding balls may also need to be taken into account to ensure that sufficient space remains in the grinding container to facilitate an intensive energy impact from the grinding balls on the solid particulate material. Generally, the size of the grinding balls is selected to provide the required weight ratio of the grinding balls to the solid particulate material, and as a result, about 4 to about 20 grinding balls are used.

[0057] In one embodiment, about 4 to about 20 grinding balls are used. According to the present invention, the solid particulate material is ball mill ground at an operating speed of at least 200 rpm in the presence of one or more gases.

[0058] In one embodiment, the operating speed is at least about 250 rpm, or at least about 300 rpm, or at least about 400 rpm, or at least about 600 rpm. In one embodiment, the operating speed ranges from at least 200 rpm to about 600 rpm, such as from about 250 rpm to about 600 rpm, or from about 300 rpm to about 600 rpm, or from about 400 rpm to about 600 rpm.

[0059] Ball mill grinding has long been used as a technique for grinding solid materials and / or facilitating intimate mixing between two or more different materials. Surprisingly, when carried out using the overall defined grinding parameters, ball mill grinding has been found to impart grinding energy that promotes a high gas adsorption capacity in solid particulate materials. The technique has been found to be very effective, cost-efficient, and energy-efficient, and is particularly well-suited for scale-up. Due to the promotion of excellent weight adsorption capacity, the gas-adsorbed solid particulate material product produced according to the present invention functions as an excellent solid-phase gas storage material. The product has been found to be stable at room temperature and pressure in the sense that one or more bound gases can remain bound to the solid particulate material at room temperature (i.e., about 25°C) and room pressure (i.e., about 1 atmosphere).

[0060] Without wishing to be bound by theory, the overall defined ball mill grinding operating parameters are thought to subject the particulate material to a unique intensive energy process, whereby gas molecules become physically adsorbed and / or electrostatically bound to the solid particulate material. The adsorption process is advantageously thought to uniquely bind a given species of gas molecule to a given solid particulate material, meaning that the binding affinities of other gas / solid particulate material combinations are different. As discussed in more detail below, those different binding affinities can be used to facilitate the separation of gas mixtures.

[0061] The method according to the present invention can advantageously be produced as a solid particulate material product having a gas adsorption gravimetric capacity of at least 300, or at least 400, or at least 500, or at least 600, or at least 700, or at least 800, or at least 900, or at least 1000, or at least 1100, or at least 1200, or at least 1300, or at least 1400, or at least 1500 cm 3 / g.

[0062] The adsorption gravimetric capacity of the product according to the method of the present invention can vary depending on the properties of the gas and the solid particulate material. Despite such variations, the method has been found to advantageously provide a substantially higher adsorption gravimetric capacity for a given combination of gas and solid particulate material compared to the values obtained by conventional techniques.

[0063] For example, the present invention provides a boron nitride solid particulate material having an adsorption gravimetric capacity of at least 580 cm 3 / g for CH4, at least 300, or 400, 500, or 600, or 700 cm 3 / g for C2H2, at least 200, or 400, or 600, or 800, or 1000 cm 3 / g for C2H4, at least 200, or 300, or 400, or 500, or 600 cm 3 / g for C2H6, at least 800, or 900, or 1000, or 1100, or 1200 cm 3 / g for CO2, at least 400, or at least 500, or at least 600 cm 3 / g for NH3, and at least 1300, or 1400, or 1500 cm 3 / g for H2.

[0064] The sorption weight capacity or simply the weight capacity referred to herein is a measurement parameter determined according to Equation 1 for a solid particulate material milled in a ball mill according to the present invention.

[0065] [Number]

[0066] Where n is the number of moles, P is the pressure, V is the volume of the ball mill grinding container, R is the gas constant, 8.314, and T is the temperature. Then the number of moles converted to liters is divided by the grams of the solid particulate material used in the ball mill.

[0067] The measured sorption weight capacity for a given combination of solid particulate material and gas was found to increase with ball mill grinding time. However, the solid particulate material eventually reaches a saturation point, beyond which further ball mill grinding time results in a negligible increase in its weight capacity. In addition to providing an overall higher weight capacity achievable by conventional means for a given period of ball mill grinding time as described above, the method according to the present invention also advantageously produces a solid particulate material having a higher weight capacity than achievable by conventional means.

[0068] The amount of time required to perform ball mill grinding can vary depending on the nature of the solid particulate material and one or more gases, and also if the goal is to reach the saturation sorption weight capacity of the solid particulate material.

[0069] Generally, ball mill grinding is carried out over a period ranging from about 2 hours to about 30 hours. In one embodiment, one or more gases are maintained at a pressure of at least 300 kPa for at least 2 hours, or at least 3 hours, or at least 4 hours, 5 hours, 6 hours, or at least 10 hours, or at least 15 hours, or at least 20 hours, at least 25 hours, or at least 30 hours.

[0070] A particular advantage of the present invention is that a higher adsorption weight capacity can be achieved not only relative to the use of conventional techniques, but also in a shorter time frame than can be achieved using conventional techniques.

[0071] The gas adsorption product produced in accordance with the present invention is stable at room temperature and pressure in the sense that one or more bound gases can remain bound to the solid particulate material at room temperature (i.e., about 25 °C) and room pressure (i.e., about 1 atmosphere). Thus, the product so formed is particularly well suited as a medium for gas storage. The product so formed of the solid particulate material with one or more gases bound thereto can be readily contained in a vessel to store one or more gases.

[0072] Accordingly, the present invention also provides a method for solid-phase storage of one or more gases, comprising the steps of ball-milling a solid particulate material (i) in the presence of one or more gases maintained at a pressure of at least 300 kPa, (ii) using a ratio of milling balls to solid particulate material of at least 60:1, and (iii) at an operating speed of at least 200 rpm to produce a solid particulate material having one or more gases adsorbed thereon as a product, and containing the product in a vessel to store one or more gases.

[0073] There are no particular restrictions on the type of vessel that can be used as, contain, and thereby store one or more gases as a product produced in accordance with the present invention, such as the stability described above. However, if the storage vessel is also to be used as a vessel from which one or more bound gases are released (e.g., to recover the gas), the vessel may require certain properties that make it suitable for performing the release process.

[0074] Notwithstanding the products produced in accordance with the present invention having the aforementioned stability, one or more adsorbed gases can nevertheless be readily released from the solid particulate material. For example, one or more gases adsorbed to the solid particulate material can be released therefrom by simply applying heat to the gas-adsorbed solid particulate material. Since the one or more gases are not covalently bonded to the solid particulate material, the gas adsorbed to the solid particulate material can be released using a relatively low energy input.

[0075] In one embodiment, the product contained in the container is heated to release one or more gases adsorbed to the solid particulate material. The product contained in the container can be heated to a temperature in the range of about 50 °C to about 500 °C to facilitate the release of one or more gases adsorbed to the solid particulate material.

[0076] The unique and specific adsorption of gases to the solid phase particulate material advantageously enables the separation of gas mixtures. When the method according to the present invention involves the adsorption of two or more gases, those gases have different binding affinities for the solid particulate material. In particular, each gas will become adsorbed to the solid particulate material, but at least one gas has a stronger binding affinity for the solid particulate material than the other. For example, boron nitride has the following adsorption affinities: CH4 < C2H6 < C2H4 < C2H2, and it has been found that boron nitride has a stronger adsorption affinity for olefin gases (C2H2 and C2H4) than for paraffin gases (CH4 and C2H6). That difference in binding affinity enables the selective release of gases from the solid particulate material, and its practical effect advantageously enables the separation of the selectively released gas from the mixed gas composition adsorbed to the solid particulate material.

[0077] Selective release of a given gas species from a solid particulate material can be readily achieved simply by subjecting it to one or more processing steps. Such process steps may include heating the solid particulate material described herein. For the purpose of selective release of a particular gas species, any given heat conditioning performed to promote gas release, as compared to bulk release of all adsorbed gas species, may need to be carried out in a controlled manner. Such controlled heat conditioning to promote selective gas release from a solid particulate material can be readily accomplished by one of ordinary skill in the art.

[0078] In the context of the present invention, “separated” one or more gases from a gas mixture means that one or more gases are adsorbed by the solid particulate material and the other one or more gases are not adsorbed by the solid particulate material. In other words, one or more gases adsorbed by the solid particulate material effectively form part of the solid phase material, and one or more gases not adsorbed by the solid particulate material remain in the gaseous state. The binding and non-binding of those gas species results in a separated state of the gases.

[0079] In one embodiment, ball milling is carried out in the presence of a mixture of two or more gases, which produces a solid particulate material adsorbed with the gas mixture as a product, and the product is processed to selectively release at least one adsorbed gas from the solid particulate material, thereby separating the released gas from the mixture of two or more gases.

[0080] Accordingly, the present invention also provides a method for separating a mixture of two or more gases, comprising the steps of: (i) in the presence of a mixture of two or more gases maintained at a pressure of at least 300 kPa, (ii) using a ratio of solid particulate material to milling balls of at least 60:1, and (iii) ball-milling the solid particulate material at an operating speed of at least 200 rpm, wherein the ball-milling produces a solid particulate material having adsorbed thereon the mixture of two or more gases as a product, and the product is treated to selectively release at least one adsorbed gas from the solid particulate material, thereby separating the released gas from the mixture of two or more gases.

[0081] Advantageously, the energy input requirements for promoting the separation of one or more gases from the gas-adsorbed solid particulate material are substantially less than conventional means such as cryogenic distillation used for gas separation.

[0082] The practice of the present invention presupposes one or more gases that cause adsorption to the solid particulate material, but the present invention also utilizes the situation where one or more gases do not cause adsorption and have a low adsorption reaction rate with respect to the solid particulate material, and thus are not adsorbed by the solid particulate material.

[0083] For example, when the mixture of two or more gases used in accordance with the present invention contains a gas having little or no adsorption affinity for the solid particulate material, the practice of the method of the present invention essentially promotes the separation of the gas mixture by that one gas that is not adsorbed by the solid particulate material, while the remaining one or more gases become adsorbed by the solid particulate material. In that case, gas separation is simply achieved by the practice of the method of the present invention, and it is not necessarily required to perform a dedicated gas release step.

[0084] In one embodiment, ball milling is carried out in the presence of a mixture of two or more gases, which produces a solid particulate material having (i) at least one gas from the mixture of adsorbed gases and (ii) at least one gas from the mixture of non-adsorbed gases as a product, thereby separating at least one gas not adsorbed from the mixture of two or more gases.

[0085] The present invention further provides a method for separating a mixture of two or more gases, comprising the step of ball milling a solid particulate material at an operating speed of at least 200 rpm, using a ratio of milling balls to the solid particulate material of at least 60:1, in the presence of a mixture of two or more gases maintained at a pressure of at least 300 kPa, wherein the ball milling produces a solid particulate material having (i) at least one gas from the mixture of adsorbed gases and (ii) at least one gas from the mixture of non-adsorbed gases as a product, thereby separating at least one gas not adsorbed from the mixture of two or more gases.

[0086] In one embodiment, the method according to the present invention is used to separate C2H2 from CH4, or C2H6 from C2H4, or CH4 from CO2, or N2 from CO2, or N2 from H2, or CH4 from H2, or C2H6 from C2H2, or CH4 from C2H4, or NH3 from H2.

Examples

[0087] Example 1 Ball Milling, Materials and Gases Hexagonal boron nitride (BN) powder (PT110 grade, purity 99%, particle size about 20 μm) purchased from Momentive Performance Materials Inc., graphite (particle size about 15 μm), iron (particle size about 85 μm), boron (particle size about 5 mm), MoS2 (particle size about 6 μm), silicon (particle size about 2 mm) purchased from Sigma Aldrich.

[0088] Acetylene (C2H2), ethylene (C2H4), ethane (C2H6), methane (CH4), ammonia (NH3), hydrogen (H2), carbon dioxide (CO2), and nitrogen (N2) with a purity of 99.99% were purchased from Coregas Pty Ltd, Australia.

[0089] In the examples, a vertical planetary ball mill (Figure 1) was used. The grinding bottle / container has a pressure valve that enables atmosphere control. The gas pressure was measured with a gas meter attached to the bottle. In each experiment, 2 - 4 g of the material was loaded into the bottle. Then the bottle was depressurized and purged three times with Ar, and finally filled with the target gas at an initial pressure of 400 kPa. The rotational speed of the ball mill was 160 - 600 rpm.

[0090] Example 2 Characteristic evaluation After ball milling, the solid particulate material samples adsorbed with gas were collected and stored in a glove box filled with argon. For FTIR and TGA experiments, a small amount of the sample was taken from the glove box and tested immediately to avoid contamination.

[0091] Scanning electron microscopy (SEM) was used with a Hitachi S4500 Zeiss Supra 55VP machine, operating at 3 - 10 kV, to examine the morphology of the samples.

[0092] Thermogravimetric analysis (TGA) was performed using a TA Q50 machine under an argon flow of 40 ml / min. The heating rate was 25 °C / min. X-ray diffraction (XRD) was used to investigate the crystal structure of the samples with a PANalytical X’pert powder system (Cu Kα irradiation λ = 0.15418 nm), operating at 40 kV and a current of 30 mA.

[0093] For the BET nitrogen adsorption isotherm, the sample was degassed at 110 °C for 4 hours to clean the surface and then BET analysis was performed. The pore size distribution was calculated by Barrett-Joyner-Halenda (BJH) desorption. The ball-milled BN samples were heated to 700 °C at a heating rate of 25 °C / min in a tube furnace under an argon atmosphere to remove the adsorbed gas molecules. These samples were further used for the BET test.

[0094] The chemical composition of various samples was investigated with a Thermo Scientific K-Alpha instrument (monochromatic Al Kα irradiation). The binding energy (B.E) for each case, i.e., the inner shell level and the valence band maximum, was corrected using the internal reference peak of the C 1s peak centered at 284.5 eV. Thermo Advantage software was used to deconvolute the inner shell level spectra.

[0095] Fourier transform infrared spectroscopy (FTIR) was used to examine the gas molecules. The powder samples were tested using a Bruker Vertex 70 infrared spectrometer in the total reflection absorption spectroscopy mode. Two different FTIR systems were used to analyze the gas samples: (1) A Perkin Elmer (Spectrum 100 model) FTIR system connected to a gas cell was used to analyze the gas samples. FTIR data was collected in the range of 4000~600 cm -1 at a resolution of 1 cm -1 . (2) The gas released from the BN samples milled by heat treatment was examined using a coupled simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR), Perkin Elmer STA 8000 and Perkin Elmer Frontier FTIR system, via the connection of a transfer line using a TL9000 interface. Approximately 5 mg of the milled material was used and heated from 30 to 600 °C at a heating rate of 25 °C / min to perform the measurement. The released gas was immediately transferred to the STA-FTIR through the transfer line (balance flow generation gas analyzer, TL9000). FTIR data was collected in the range of 4000~600 cm -1 at a resolution of 4 cm -1FTIR data was collected in the range of.

[0096] Example 3 Gas storage / gas uptake The gas did not adsorb onto the BN powder without milling, and no pressure change was observed. Once milling was initiated, a significant pressure drop was observed due to gas adsorption as shown in Figure 2a. In a sealed milling reactor, the pressure of the alkyne gas, acetylene (C2H2), dropped from 400 to 20 kPa within 20 h, suggesting that almost all of the C2H2 gas had adsorbed onto the BN. For the olefin gas ethylene (C2H4), the pressure dropped to 95 kPa after 20 h of milling under the same conditions. For the two paraffin gases (CH4 and C2H6), a relatively slow pressure drop was recorded.

[0097] The corresponding gravimetric capacities as a function of milling time for the gas adsorption of four hydrocarbon gases are shown in Figure 2b. After 20 h of continuous milling, 282 cm 3 / g of C2H2 and 228 cm 3 / g of C2H4 were adsorbed onto the BN powder. The uptake capacities were lower for the paraffin gases (ethane and methane): 188 cm 3 / g for ethane (C2H6) and 152 cm 3 / g for methane (CH4). Figure 2b shows that the capacity curve did not flatten out by 20 h, suggesting that gas adsorption did not saturate after 20 h.

[0098] Upon further milling, gas adsorption continued at a reduced adsorption rate due to the reduced gas pressure in the sealed milling reactor (Figure 2a). To maintain a high adsorption rate, the milling reactor was replenished (to at least 400 kPa) with fresh gas every 5 h during the milling process.

[0099] When C2H4 was replenished at 5, 10, and 15 h, a much higher adsorption capacity of C2H4 (412 cm 3 / g was achieved after 20 hours of milling (Figure 2c(i)). By increasing the milling intensity by varying the weight ratio of the milling balls to BN, the adsorption rate further increased. The higher the milling intensity, the greater the energy imparted to the BN, accelerating the reaction rate during milling. When the weight ratio was increased from 65:1 to 81:1 and 130:1, the adsorption capacity after 20 hours increased to 585 and 730 cm 3 / g, respectively (Figure 2c(ii) and (iii)).

[0100] Prolonging the milling treatment can also increase adsorption. For example, extending the milling in C2H4 gas to 30 hours resulted in an adsorption capacity reaching 1048 cm 3 / g (Figure 2c(iii)). Even under mild milling conditions, i.e., 20 hours of milling and a weight ratio of 130:1, the milling treatment with three gas replenishments produced an uptake capacity of 708 cm 3 / g for C2H2 (Figure 2d). The overall adsorption of CH4 was 564 cm 3 / g after 20 hours of milling. For C2H6, the uptake capacity was 600 cm 3 / g. The curve in Figure 2c shows that C2H4 gas adsorption maintained a high adsorption rate and did not saturate until 30 hours.

[0101] Reducing the starting BN to 1 g resulted in a saturated gas adsorption of 534.9 cm 3 / g after 28 hours of milling (Figure 3). Therefore, it is considered that the adsorption capacity depends on the adsorption test conditions (i.e., gas pressure, BN, milling intensity, and time). Even under average ball mill milling conditions (e.g., 20 hours of milling in sufficient gas, 4 g of BN), the BN nanosheet achieved a higher uptake capacity for olefins and alkynes, ammonia, hydrogen, and carbon dioxide than all other materials. Gas storage was further enhanced by replenishing the gas up to 400 kPa every 5 hours up to a total milling time of 20 hours. BN had 838.5 cm 3 / g of CO2, 730.1 cm 3 / g of C2H4, 708.4 cm 3C2H2 of / g, 600 cm 3 C2H6 of / g, 592.7 cm 3 NH3 of / g, and 563.8 cm 3 CH4 of / g, 620 cm 3 (Figure 2d) was stored with H2 of / g. It is worth noting that the weight capacities of these gases are not yet saturated and more gas can be stored by extending the milling or fine-tuning the ball milling parameters. Various additional materials were used to store carbon dioxide (Figure 2e).

[0102] Under the same milling conditions, the adsorption rates were varied among the different gases investigated (Figure 2b). The highest adsorption rate observed was 21.6 cm 3 g -1 h -1 for C2H2, which is nearly three times faster than that of CH4 (7.2 cm 3 g -1 h -1 ). The trend in adsorption capacity is CH4 < C2H6 < C2H4 < C2H2, indicating that BN shows a stronger affinity for olefin gases (C2H2 and C2H4) than for paraffin gases (CH4 and C2H6). The large differences in adsorption capacity and adsorption rate for these hydrocarbon gases suggest that they can be separated by selective adsorption by BN under controlled milling conditions. Furthermore, the ball milling process should be applicable for the separation of other gas groups with different adsorption rates.

[0103] Example 4 Separation of various gas mixtures This example shows the separation of gas mixtures including C2H2 / CH4; C2H4 / C2H6; CO2 / N2; CO2 / CH4.

[0104] High-purity CH4 gas is considered a relatively clean fuel and is used as an important feedstock in the production of various chemicals; small amounts of C2H2 often coexist with CH4 and thus need to be removed. To test the ability of a method to separate such gases, a mixture of C2H2 (20 vol%) and CH4 (80 vol%) was added at 410 kPa to a grinding reactor containing 4 grams of BN and 4 grinding balls. After grinding for 2 hours at a weight ratio of 65:1, the pressure of the gas mixture decreased to 350 kPa, indicating that gas adsorption occurred. The remaining gas in the grinding reactor was collected in a gas cell and analyzed by gas-phase FTIR (g-FTIR).

[0105] The g-FTIR spectrum of the initial gas mixture (Figure 4a(i)) showed the presence of both gases, however, after 2 hours of grinding, only CH4 was detected in the remaining gas (Figure 4a(ii)). From the spectral results after 4 hours of grinding, it was confirmed that C2H2 was completely removed from the gas mixture. C2H2 adsorption onto the ground BN was confirmed by FTIR analysis (Figure 5a). A longer grinding duration was required to remove higher concentrations of C2H2.

[0106] For a mixture containing 30 vol% C2H2 and 70 vol% CH4, at least 4 hours of grinding was required to sufficiently remove C2H2 from the gas mixture whose pressure had decreased to 90 kPa. The g-FTIR spectrum in Figure 4a(iii) of the remaining gas after 2 hours of grinding treatment shows the presence of both gases, however, the FTIR spectrum of the remaining gas after 4 hours of grinding shows that only CH4 was detected (Figure 4a(iv)). This process can be applied to separate C2H4 and C2H6, which is another industrial product that requires purification.

[0107] BN powder was milled in the presence of C2H4 (20 vol%) and C2H6 (80 vol%). After 2 hours of milling, a pressure drop of 60 kPa was observed. Comparing the g-FTIR spectra of the gas mixture after 2 hours of milling (Figure 4b(iv)) with the g-FTIR spectra of the individual gases and the initial gas mixture (Figure 4b(i - iii)), it was shown that only C2H6 was present in the remaining gas, indicating that C2H4 was successfully removed. After 4 hours of milling, the separation of C2H4 and C2H6 was confirmed (Figure 4b(v)). The FTIR spectrum of the BN sample milled for 2 hours in the gas mixture (Figure 5b(i)) revealed that C2H4 was adsorbed onto the BN sample. By heating the milled BN to 550 °C, the adsorbed C2H4 gas was extracted, and the g-FTIR spectrum of the released gas confirmed that it was C2H4 (Figure 5b(ii)).

[0108] Furthermore, this technique can also separate CO2 from a gas mixture of CH4 and N2. Figure 4c shows the g-FTIR of the initial CO2 / CH4 gas mixture and the remaining gas after regular time intervals. In Figure 4d, it is confirmed from the gas chromatogram that the separation of CO2 from N2 occurs after 5 hours of milling.

[0109] Example 5 Presentation of Gas Storage Mechanism The adsorption of C2H4 molecules as an exemplary gas onto the BN sample was further investigated by Fourier transform infrared spectroscopy (FTIR). The FTIR spectra shown in Figure 6a are partial spectra targeting the fingerprint region (2700 - 3150 cm -1 ) of hydrocarbon molecules. From the featureless FTIR spectrum (Figure 6a(i)), it was confirmed that the initial BN powder did not contain adsorbed C2H4. The FTIR spectrum of the BN sample after 20 hours of continuous milling in the presence of C2H4 (Figure 6a(ii)) shows two peaks at 2850 cm -1 and 2920 cm -1 , representing the sp 3 C-H stretching of the adsorbed C2H4 molecules.

[0110] To further confirm the adsorption of C2H4, a simultaneous thermal analysis (STA)-FTIR coupled system was used to heat the milled BN sample from room temperature to 550 °C at a rate of 25 °C / min. The spectrum obtained as a result of the gas collected during heating to 550 °C (Figure 6a(iii)) shows the same two characteristic peaks attributable to C2H4 molecules that confirm the adsorption of C2H4 gas. The gas collected from the milling device after the heat treatment gives a recovery rate of 82% for C2H4. The FTIR of the heated BN (Figure 6a(iv)) shows that the BN sample was cleaned after the heat treatment and all the adsorbed C2H4 was removed from the BN surface. When the BN cleaned in C2H4 was remilled, a similar gas pressure drop was observed during the subsequent milling (Figure 7), and the same sample was cleaned and milled as 4 cycles with a pressure / volume drop of less than 100 kPa for the first milling treatment. The re-adsorption of C2H4 molecules was confirmed by FTIR (Figure 6a(v))). The small N-H peak at 3427 cm -1 indicates that there was a weak non-covalent interaction between the hydrogen of the C2H4 molecule and the nitrogen in the BN powder. The N-H peak was not observed in the spectrum of the evolved gas (Figure 6a(iii)). The FTIR analysis also confirmed the adsorption of other hydrocarbon gases by BN during ball milling (Figure 6b). The overall FTIR spectrum of Figure 6b shows two characteristic peaks of h-BN at 787 cm -1 and 1336 cm -1 corresponding to the out-of-plane B-N bending and in-plane B-N stretching, respectively. For the spectrum (i) recorded from BN milled in C2H2 gas, the unique C-H peak at 673 cm -1 is associated with the C2H2 molecule and does not exist in other spectra. Since the other characteristic C-H peaks are of relatively low intensity, the spectra in the hydrocarbon fingerprint region are enlarged and shown in Figure 6b. The peaks at 2925, 3033 cm -1 , 3070 cm -1 , 3089 cm -1 correspond to the sp 2 C-H stretching of the C2H2 molecule. The spectrum of BN milled in CH4 for 20 h is at 2855, 2925 - 2955 cm -1It has characteristic C-H stretching of CH4. The peaks at 2875-2958 are C-H stretching of C2H6 molecules. In all spectra of BN milled in various gases, an N-H peak can be seen at 3427 cm -1 confirming the bonding parts of non-covalent bonds of various gases on the BN surface.

[0111] Gas adsorption onto BN at room temperature was achieved by mechanical energy via ball milling. The adsorbed gas can be released from the milled sample by heating. The purified BN sample can be reused for further adsorption.

[0112] The mechanism underlying gas adsorption onto BN during ball milling was investigated. Mechanical grinding of powders can substantially reduce their particle size and increase their surface area, thereby enabling more gas molecules to be physically adsorbed for the generation of new surfaces.

[0113] The Brunauer-Emmett-Teller (BET) surface area of BN powder as a function of milling time is shown in Fig. 8. After milling for 20 h in CH4, the surface area of BN increased by 623.6 m 2 / g, while for the BN sample milled in C2H4 under the same milling conditions, a smaller change in surface area (99.8 m 2 / g) was observed.

[0114] Fig. 2a shows that much more C2H4 (228 cm 3 / g) was adsorbed onto BN with a smaller surface area. In contrast, BN with a larger surface area adsorbed less CH4 (152 cm 3 / g).

[0115] Although not intended to be restricted by theory, those results indicate that the adsorption capacity does not depend on the surface area of the BN sample, suggesting that the adsorption mechanism for olefin gases cannot be attributed solely to physical adsorption.

[0116] The different crystal structures in the milled BN are seen in the X-ray diffraction (XRD) pattern shown in Fig. 9a, which indicates that the h-BN sample milled in C2H4 for 20 h maintains the hexagonal crystal structure of the initial BN powder. However, the h-BN sample milled in CH4 for the same duration has a disordered structure, as indicated by the decreased intensity and broadening of the (002) diffraction peak of the sample. Different morphologies of these two samples were confirmed from scanning electron microscope (SEM) analysis. The SEM image of the BN sample in Fig. 9a (insert) shows that the BN powder milled in the presence of C2H4 has a nanosheet-like morphology with a size of several micrometers and a thickness of <30 nm, while the BN powder milled in the presence of CH4 is spherical with a diameter of less than 80 nm.

[0117] The corresponding TEM images (Figs. 10a, b) and selected area electron diffraction (SAED) patterns show consistent results. BN nanosheets were formed due to gas adsorption during milling in olefin gas, which is thought to be because these olefin gases have a lubricating role, prevent cross-linking between different layers, the nanosheets exfoliate and are protected by the olefin molecules adsorbed on the surface.

[0118] For comparison, hBNs of different sizes were tested (Fig. 11), confirming that size is not the main factor for gas adsorption in the ball milling process. The different morphologies and crystal structures of the milled BN samples are thought to indicate that different mechanisms are responsible for the adsorption of olefin and paraffin gases.

[0119] To determine the mechanisms involved in the adsorption of these two different types of gases, a BN sample milled continuously for 20 hours in the presence of either CH4 or C2H4 was heated to 700 °C at 25 °C / min under a constant argon gas flow using a thermogravimetric analyzer (TGA) (Figure 9b). The desorption of the previously adsorbed CH4 occurred gradually, and a total mass loss of 2.8 wt% was measured, indicating that CH4 was physically adsorbed on the BN nanoparticles. Similar gas desorption behavior was observed for C2H6 (Figure 12a).

[0120] For BN milled in C2H4, the TGA curve showed a gradual weight loss (2.5 wt%) up to 400 °C due to the release of physically adsorbed gas, followed by a sharp curve change with a large and rapid weight loss (14.5 wt%) from 400 - 550 °C (Figure 9b). This high desorption temperature and narrow temperature range indicate that C2H4 was more strongly adsorbed on the BN nanosheet. The observed desorption temperature range was broader than the desorption temperatures of C2H4 in zeolite (350 - 380 °C) and defect-containing BN (287 °C). The desorption energy of 88.7 J / g was determined by in-situ differential scanning calorimetry (DSC). A sharp weight loss was also observed in the TGA curve of the BN sample milled in C2H2 (Figure 12b).

[0121] These results are considered to suggest that the two types of gases (olefin and paraffin) have different adsorption energies with the BN nanosheet after ball-mill milling. The ball-milled BN was investigated using X-ray photoelectron spectroscopy (XPS). For the BN sample milled in C2H4, the B 1s spectrum in Fig. 9c shows two characteristic B-N peaks at binding energies of 190.3 eV and 191.1 eV. The N 1s spectrum in Fig. 9d shows a dominant N-B bond at 397.9 eV and an N-C bond at 398.6 eV. The small peak at 400.1 eV can be attributed to the N-H bond. However, the B1s and N1s spectra of the starting BN powder show BN that contains no gas adsorption at all. The C 1s spectrum in Fig. 9e shows a major peak at 284.5 eV associated with two C-C and C-H bonds from the adsorbed C2H4 molecules, and a C-N bond peak at 285.3 eV. The presence of both N-C bond peaks in both the N 1s and C 1s spectra, and the absence of B-C bonds in the B1s spectrum, suggest a non-covalent N-C bond between the C2H4 molecule and the BN nanosheet. A small portion of C2H4 is physically adsorbed onto the BN nanosheet via the N-H bond, which is indicated by the N-H peak in the N 1s spectrum and the corresponding FTIR spectrum, and is also consistent with the small weight loss in the low temperature range below 400 °C.

[0122] For the BN sample milled in CH4, the B 1s spectrum (Fig. 9f) has two B-N bond peaks at 193.1 eV and one large B-O bond peak.

[38] The milled BN sample has a large surface area and is active in ambient gas and is contaminated by oxygen in air during XPS analysis. The N 1s spectrum in Fig. 9g has the same N-B bond peak and a broad and weak shoulder band centered at 399.5 eV that may be due to N-H. The C 1s spectrum in Fig. 9h shows a major peak at 284.5 eV associated with C-C and C-H bonds and a C-O peak at 286.3 eV. The distinct N-H bond peak at 399.5 eV in Fig. 9g is thought to indicate the physical adsorption of CH4 molecules onto the BN surface via the N-H bond, which is consistent with the FTIR results.

[0123] XPS results reveal that paraffin molecules are adsorbed onto the surface of BN nanoparticles via weak N-H bonds. Nitrogen atoms in BN have high electronegativity, while olefin molecules have unsaturated carbon atoms. As a result, C2H4 has a relatively strong adsorption energy towards BN compared to CH4. From XPS investigations, it is considered that nitrogen atoms in BN can form non-covalent bonds with unsaturated carbon atoms in olefin gases of C2H4. However, these non-covalent C-N bonds cannot be formed on the BN nanosheet under ambient conditions without the assistance of ball milling action that provides the energy required for the unique interaction between BN and the gas.

[0124] Example 6 Method for separating gas mixtures The gas separation process is illustrated in Fig. 13a. When a mixture containing an alkyne or olefin gas (C2H2 or C2H4), and a paraffin gas (CH4 or C2H6) is introduced into the milling reactor, mechanical milling activates the selective adsorption of the alkyne and olefin gases onto the BN powder. The paraffin gas remains in the reactor vessel and can be removed by a vacuum system. The adsorbed alkyne and olefin gases can be recovered through heating of the milling reactor / BN. When fresh gas is continuously supplied, the process can be repeated or carried out continuously. From the FTIR results in Figs. 4a - c, it is shown that the mechanically enhanced selective adsorption process can effectively separate mixed hydrocarbon gases by removing all olefin gases after fine-tuned milling treatments (i.e., milling intensity, time, and gas pressure). For cases of mixed gases containing two or more gases, a separation process involving several milling reactors is proposed (Fig. 13b), provided that these gases have different adsorption rates and capacities. The separation efficiency depends on the selective adsorption ability.

[0125] Any reference in this specification to any prior publication (or information derived therefrom) or to any matter which is known is not an admission or acknowledgment that the prior publication (or information derived therefrom) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates, nor should it be taken as a suggestion of any kind.

[0126] Throughout this specification and the claims, unless the context requires otherwise, words such as "comprise" and its conjugations will be understood to imply the inclusion of the stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

1. A method for promoting the adsorption of one or more gases onto a solid particulate material, comprising the steps of (i) ball milling the solid particulate material in the presence of the one or more gases maintained at a pressure of at least 300 kPa, (ii) using a weight ratio of ground balls to the solid particulate material of at least 60:1, and (iii) at an operating speed of at least 200 rpm, wherein the solid particulate material used does not chemically react with the one or more gases and does not form covalent bonds with the solid particulate material.

2. The method according to claim 1, wherein the ball mill grinding is performed at room temperature.

3. The method according to claim 1 or claim 2, wherein the solid fine particle material is selected from boron nitride, graphite, molybdenum disulfide, tungsten disulfide, molybdenum diselenium, tungsten diselenium, molybdenum ditelluride, boron, iron, and silicon.

4. The method according to claim 1, wherein one or more of the gases are maintained at a pressure of at least about 500 kPa.

5. The method according to claim 1, wherein the weight ratio of the ground balls to the solid fine particle material is at least about 80:

1.

6. The method according to claim 1, wherein the operating speed is at least about 300 rpm.

7. The method according to claim 1, wherein, before ball mill grinding, the solid fine particle material has an average particle size in the range of about 1 μm to about 5 mm.

8. The one or more of the aforementioned gases are hydrogen, carbon dioxide, carbon monoxide, C １ -C ４ The method according to claim 1, selected from hydrocarbons, ammonia, nitric oxide, nitrogen dioxide, sulfur dioxide, and nitrogen.

9. The method according to claim 1, wherein the ball mill grinding produces the solid fine particle material on which one or more gases are adsorbed as a product, and the product is contained in a container for storing the one or more gases.

10. The method according to claim 9, wherein the product on which one or more of the aforementioned gases are adsorbed has a gas adsorption weight capacity of at least 500.

11. The method according to claim 9, wherein the product contained in the container is heated to a temperature in the range of about 50°C to about 500°C to release the one or more gases adsorbed on the solid particulate material.

12. The method according to claim 1, wherein (i) the ball mill grinding is carried out in the presence of a mixture of two or more gases, thereby producing a solid particulate material on which the gas mixture is adsorbed as a product, and (ii) the product is processed to selectively release at least one adsorbed gas from the solid particulate material, thereby separating the released gas from the mixture of two or more gases.

13. The method according to claim 1, wherein the ball mill grinding is carried out in the presence of a mixture of two or more gases, and the ball mill grinding produces a solid particulate material as a product having (i) at least one gas from the mixture of adsorbed gases and (ii) at least one gas from the mixture of non-adsorbed gases, thereby separating the at least one non-adsorbed gas from the mixture of two or more gases.

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