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WO1994001714A1 - Stockage de gaz naturel - Google Patents

Stockage de gaz naturel Download PDF

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Publication number
WO1994001714A1
WO1994001714A1 PCT/US1993/006002 US9306002W WO9401714A1 WO 1994001714 A1 WO1994001714 A1 WO 1994001714A1 US 9306002 W US9306002 W US 9306002W WO 9401714 A1 WO9401714 A1 WO 9401714A1
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WIPO (PCT)
Prior art keywords
carbon
molecular sieve
natural gas
carbon molecular
polymer
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PCT/US1993/006002
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English (en)
Inventor
Chin-Hsiung Chang
Gary Joseph Seminara
Alan Everett Van Til
Li Wang
Mark Kaiser
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Honeywell International Inc
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AlliedSignal Inc
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Priority claimed from US07/906,993 external-priority patent/US5308821A/en
Priority claimed from US07/964,174 external-priority patent/US5292706A/en
Application filed by AlliedSignal Inc filed Critical AlliedSignal Inc
Publication of WO1994001714A1 publication Critical patent/WO1994001714A1/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C11/00—Use of gas-solvents or gas-sorbents in vessels
    • F17C11/007—Use of gas-solvents or gas-sorbents in vessels for hydrocarbon gases, such as methane or natural gas, propane, butane or mixtures thereof [LPG]

Definitions

  • This invention relates to a method of storing natural gas. More particularly, the invention relates to storage of natural gas at near ambient temperatures using a solid adsorbent, in particular, a carbon molecular sieve.
  • Natural gas being substantially methane, has a low molecular weight and it occupies a large volume per unit weight compared to liquid fuels. Thus, reducing the volume of natural gas is necessary for most practical applications of natural gas as a fuel. Methods for doing this could include (1) storage at high pressure, (2) liquefaction and storage at low temperatures, and (3) adsorption on solids. Of these methods the last is of particular interest since compact storage of natural gas at moderate pressures may be achieved, while avoiding the cryogenic temperatures needed for liquid natural gas or the high pressures needed for storage as a gas in reasonable volumes.
  • Natural gas is stored at near ambient temperatures and at pressures of about 100 - 900 psig (791 to 6305 kPa abs.) on a carbon molecular sieve having a capacity for said natural gas greater than 0.095 grams per gram of carbon at 300 psig (2,169 kPa abs.) preferably greater than 0.13 grams per gram of carbon.
  • the pressure is about 200-600 psig (1479 to 4234 kPa abs.) and the temperature is about 10o to 50oC.
  • the carbon molecular sieves are particles characterized by having at least 60% of the total particle pore volume, preferably at least 75%, consisting of micropores having diameters greater than 4 ⁇ (0.4 nm) and less than 20 ⁇ (2 nm). Typically, as initially formed the micropores have diameters substantially between 5 and 7 ⁇ (0.5 and 0.7 nm) and have a slit-like shape. Larger pores may be created by an activation step.
  • the carbon particles preferably are shaped as spheres, as cylinders having an aspect ratio of about 1/1, or as flat disks.
  • the carbon molecular sieve is derived from carbonization in an inert atmosphere of an oxygen-free polymer, preferably vinylidene chloride. In one embodiment the carbonization process is carried out in the presence of carbon dioxide.
  • the invention includes a process for preparing a carbon molecular sieve by polymerizing vinylidene chloride in a two-phase solution including a suspending agent, such as hydroxypropyl methyl cellulose or related compound in the aqueous phase and a polymerization initiator in the organic phase.
  • the two-phase mixture is heated to about 40o to 80oC and maintained at that temperature until all the vinylidene chloride has been polymerized.
  • the polymer is recovered and carbonized in an inert atmosphere to produce a carbon molecular sieve. Heating in the range of about 140o to 180oC is limited to a rate up to about 25oC/hr, preferably about 2 to 10oC/hr in order to increase the particle density.
  • the carbonized polymer preferably is activated by heating in an atmosphere containing steam, carbon dioxide, or oxygen to optimize the pore size and to increase the micropore volume and thereby optimize the deliverable volume of natural gas.
  • the activation is carried out in an inert atmosphere containing an effective amount of CO 2 at a temperature of at least 750oC.
  • the carbon molecular sieves When packed in a vessel the carbon molecular sieves can adsorb natural gas at 300 psig (2,169 kPa abs.) and deliver at 0 psig (101.32 kPa abs.) at least 70 times the volume of the vessel, preferably at least 95 times the vessel volume, most preferably at least 110 times the vessel volume.
  • the density of the carbon molecular sieve may be increased by impregnating the polymer precursor of the carbon molecular sieve with monomer, polymerizing the monomer, and repeating the process until the desired density is achieved. This may be up to about 125% of the initial polymer density. After carbonization, the densified polymer yields a more dense carbon molecular sieve, which provides increased packing density and greater deliverable capacity for natural gas.
  • the particles may be spherical in shape or cylindrical pellets having a length to diameter ratio of about 1/1. They are graded into two or three sizes having a ratio of their diameters of at least 7/1.
  • the smaller particles can be dispersed between the larger particles with the assistance of a means of vibration.
  • the packing density can be increased by about 25% or more compared to the packing density of a single size particle.
  • the large particles typically make up about 80% of the total absorbent. Owing to the uniformity and shape of the particles the bed of adsorbent can be uniformly and reproducibly packed.
  • Figure 1 is a plot of pore diameter vs. pore volume for carbon molecular sieve particles of the invention.
  • Figure 2 is a plot showing the effect of activation on methane capacity.
  • adsorbents may be useful for low pressure storage of natural gas and carbons have been found to have higher capacities for natural gas than other solid adsorbents such as zeolites, silica gel, and alumina. Even so, not all carbons have adequate capacity to meet the standards considered necessary for practical applications.
  • the carbon molecular sieves of the present invention are superior to others and provide a higher capacity for natural gas.
  • Another advantage for carbon compared to other adsorbents is its lower tendency to adsorb impurities in the natural gas which could decrease the storage capacity for the natural gas. Since the carbon molecular sieves of the invention are typically hydrophobic, they avoid loss of capacity resulting from adsorption of water as well as adsorption of CO 2 or other impurities.
  • Natural gas will be stored in the pores of the carbon and in spaces around the carbon particles.
  • the optimum pore size for natural gas adsorption is believed to be about 4 to 12 ⁇ (0.4 to 1.2 nm) since the pores do not just hold compressed gas, but cause the gas molecules to behave as if more highly compressed, that is, to have a higher density than the gas normally has at the storage pressure.
  • the volume of such micropores in a carbon particle should be as large as possible to maximize gas storage. Gas in the void spaces around the carbon would be expected to have its normal density and therefore, these spaces should be minimized.
  • the carbon should have the highest possible packing density. Another factor to be considered is the need to provide for access to the carbon so that the natural gas can be efficiently stored and recovered.
  • pores are believed to be needed, say about 20 to 500 ⁇ (2 to 50 nm). These have been termed meso pores. Larger pores, i.e. above 500 ⁇ (50 nm) are considered macro pores.
  • natural gas can be stored in the micropores, the meso and macro pores, and in the void volume. Preferably the largest possible fraction of the volume should be in the micropores.
  • the carbon molecular sieves and activated carbons made by prior art methods using waste materials from the manufacture of Saran or other low cost feedstocks are considered inferior to the adsorbent of the present invention for the storage of natural gas since they have not been optimized for the desired properties.
  • Hydrophobic carbon molecular sieves for the adsorption of natural gas are produced by a unique method.
  • This method comprises three steps: (1) polymerization of an oxygen-free monomer optionally but not preferably in the presence of a minor amount of an oxygen-free cross-linking agent; (2) forming particles of the resultant polymer into a desired shape; and then, (3) carbonizing the shaped material in a substantially oxygen-free environment, which may include carbon dioxide in one embodiment of the invention.
  • the monomers should be readily polymerizable, essentially free of oxygen in their molecular structure and preferably consisting of hydrogen, a halogen, and carbon.
  • materials which may be employed as the monomer are acrylonitrile (AN), vinylidene fluoride (VDF), chlorotrifluoroethylene (HALAR), vinylidene chloride (VDC), mixtures of two or more monomers such as mixtures of vinylidene chloride and vinyl chloride, vinylidene chloride and acrylonitrile, and a mixture of styrene and divinylbenzene.
  • monomers include vinyl fluoride, vinyl bromide, chlorinated ethylene, chlorofluoroethylene, vinyl chlorobenzene, vinylidene bromide and vinylidene-fluoride-chlorotrifluoro-ethylene.
  • the preferred monomer is vinylidene chloride, most preferably alone, i.e. without a cross-linking agent.
  • Bulk polymerization is the direct conversion of liquid monomer to polymer in a reaction system in which the polymer remains soluble in its own monomer.
  • Solution polymerization uses a solvent capable of dissolving the monomer, the polymer, and the polymerization initiator.
  • Suspension polymerization and emulsion polymerization have also been used to produce materials having the same level of desired properties, contrary to the previous findings of U.S. Pat. No. 4,820,681.
  • suspension polymerization the monomer is dispersed rather than dissolved in the medium, with water being a typical suspension medium.
  • emulsion polymerization a suspended particle of colloidal size will be the site of the polymerization.
  • the initiator is dissolved in the monomer, the monomer is dispersed in water, and a dispersing agent is incorporated to stabilize the suspension formed.
  • Precipitation polymerization and vapor phase polymerization may also be suitable.
  • the polymers produced in the initial polymerization step optionally may be cross-linked with a substantially oxygen-free cross-linking agent.
  • the cross-linking agent will typically be present during the polymerization at a concentration equal to less than 10 mole percent of the monomer preferably less than 5 mol.%, and most preferably less than 1 mol.%.
  • a preferred cross-linking agent is divinylbenzene.
  • Other possible cross-linking agents include trivinyl benzene, divinyl acetylene, and divinyl sulfide.
  • the polymerization initiator is also preferably an oxygen-free compound. Therefore, a carbon or azo rather than an oxygen initiator is preferably used.
  • a carbon or azo rather than an oxygen initiator is preferably used.
  • One suitable non-oxygen containing initiator is 2,2'-azobis(isobutyronitrile), (AIBN).
  • Another suitable polymerization initiator is the compound 2,2'-azobis (2,4-dimethylvaleronitrile) which is available from DuPont Chemical Company and is sold under the trade VAZO 52.
  • Typical solvents include normal hexane. chloroform, carbon tetrachloride, orthodichlorobenzene, and 1,1,2,2-tetrachloroethane. Of these materials, orthodichlorobenzene and 1,1,2,2-tetrachloroethane are preferred.
  • General characteristics for the selection of a solvent include a high-solubility for the monomer, the absence of oxygen in the molecular structure, and a large difference in boiling point between the solvent and the monomer. A weight ratio between monomer and solvent between 1:1 to 1:2 will normally be suitable.
  • the monomer When suspension or emulsion polymerization is used, the monomer is usually suspended or emulsified in water. The ratio of the monomer to the suspending fluid is about 0.1 - 1 to 1.
  • a suspending agent such as hydroxypropyl methyl cellulose is added in amounts of about 0.1 to 2%.
  • Related compounds may also be used such as poly vinyl alcohol and Polyox (WRPA 3154) from Union Carbide.
  • the polymer For ease in fabricating the polymer into a desired shape, it is preferably reduced in size to small free-flowing particles, which may be shaped into a desired configuration by conventional means.
  • a preferred form is a cylindrical pellet having an aspect ratio (diameter ⁇ height) of about 1/1.
  • the polymer When suspension polymerization is used, the polymer is produced as spherical particles which may not require additional shaping.
  • Improvements to the capacity of carbon molecular sieves may include increased packing density, i.e. g/mL. For a given porosity the more carbon which can be packed into a given volume the greater the amount of natural gas which can be adsorbed. Increased packing density can be achieved by interspersing small particles in the spaces between larger particles.
  • a convenient source of such small particles is the spherical polymer beads produced by suspension polymerization. These beads are carbonized and used to increase packing density. However, since they are not compressed into pellets they are less dense.
  • the density can be increased by impregnation of additional monomer and polymerization initiator into the polymer, then polymerizing the added monomer and repeating the procedure until the desired density is obtained. An increase of up to about 125% of the original polymer density can be obtained. After carbonization, this increased density is retained in the carbon molecular sieve and significantly improves the capacity for natural gas.
  • the polymeric material is carbonized by heating to a high temperature in the presence of an inert gas such as nitrogen or helium.
  • concentration of oxygen in the atmosphere surrounding the particles undergoing carbonization should be less than 0.1 mole percent and is preferably less than 0.05 mole percent.
  • the carbonization will result in the evolution of a hydrogen halide.
  • the inert gas should be flowing at a sufficient rate to remove this material from the particles. It is preferred that prior to high temperature carbonization the polymer be heated slowly in the range of 140o-180oC (preferably about 2 to 10oC/hr) and held at this temperature for several hours.
  • the polymer is then preferably subjected to a programmed temperature increase to a temperature above 700°C.
  • the temperature is preferably raised at a rate greater than 50oC per hour but less than 200oC per hour. It is preferred to hold the final temperature for a period of at least 45 minutes and preferably for at least one hour. A preferred rate of programmed heating is 75-125°C per hour. The highest temperature is normally required for less than 5 hours. The required holding period can be determined by weight loss measurements.
  • the second carbonization step of some prior art methods is not required.
  • the second carbonization step of the prior art is done after the product of the first carbonization has been pulverized, admixed with a binder or other material such as coal tar pitch or high carbon content material and then shaped again.
  • the sieve precursors are derived from polymeric materials and include no binders, they are substantially free of the inorganic materials such as metals and inorganic oxides which may be present when the precursor material is made from a naturally occurring substance such as coal, coconut shells, peat, or wood. Materials which contain a binder will normally have impurities derived from the binder in addition to impurities present in the precursor materials.
  • the product After carbonization on a hydrogen- and oxygen-free basis, the product should contain at least 99.5 wt.% carbon and preferably at least 99.8 wt.% carbon. This measurement does not include any material applied as a surface treatment or coating.
  • the polymeric material will shrink during the carbonization step in a proportional manner along each dimension.
  • the amount of shrinkage is also proportional to the amount of weight loss caused by the driving off of the hydrogen halide from the shaped polymer.
  • a cylindrical pellet will lose approximately 70 percent of its weight and size during the carbonization procedure due to the evolution of hydrogen chloride, hydrogen bromide, or hydrogen fluoride or a mixture of these gases.
  • the final carbonized material will often equal about 25 to 28 weight percent of the initial or starting polymerized material.
  • the density of the initial material and the final carbonized material are related. That is, the density measured in terms of grams per mL of the finished carbon molecular sieves is dependent on the density of the initial uncarbonized polymer and the carbonization process conditions.
  • the carbon molecular sieves of the invention as produced are hydrophobic rather than hydrophilic and thus do not preferentially adsorb water which may be present in natural gas.
  • activation has been used in connection with processes intended to improve the adsorptive capacity of carbons and will be used in the present discussion to avoid confusion.
  • activation often refers to the chemical treatment of a solid to change its active form, as in the activation of catalyst precursors.
  • activation is considered to be the removal of a portion of the carbon which increases the total pore volume of particles and the size of the pores. Thus, it might be more properly termed an adjustment or optimization of the pores rather than a change of the chemical nature of the carbon.
  • the pores formed may not be the most desirable size and the total pore volume of a particle may be less than the maximum possible. Ideally, one would want to achieve the largest pore volume consistent with the necessary structural integrity.
  • the pores themselves should have a size which provides the maximum adsorptive capacity. This could be a single size or a distribution of pore sizes which accommodates the maximum amount of the gas to be stored.
  • a process for activating carbon molecular sieves by removing carbon must involve a number of factors. As suggested above one would attempt to selectively increase the pore size so that the optimum total pore volume and pore size distribution is achieved.
  • the temperature at which the reactive gas contacts the carbon will be of particular importance. Preferably the temperature will be at least 750oC. In some cases, it may be desirable to use staged temperatures where more than one contacting step is used. As with many chemical reactions the time at which the reactive gas is in contact with the carbon will have to be considered. The concentration of the reactive gas could be an important factor in determining the rate at which the carbon is removed.
  • This example illustrates the production of CMS pellets beginning with the bulk polymerization of a polyvinylidene chloride cross-linked with divinyl benzene
  • the monomers were purified by contact with activated carbon (Calgon PCB, 20 X 50 mesh) at the ratio of 2 grams activated carbon per 100 mL of the monomer and the divinyl benzene to remove any polymerization inhibitors.
  • activated carbon Calgon PCB, 20 X 50 mesh
  • 0.1 gram of AIBN solids were introduced into a 125 mL Teflon-lined Parr bomb. 82.4 mL of vinylidene chloride monomer and 1 mL divinylbenzene were transferred into the reactor and the reactor was sealed and shaken. The reactor was then kept in an oven at 70°C for at least 8 hours. Then, the polymer products were collected and weighed. The yield of polymerization reaction product was determined after the polymer was evacuated until a constant weight was obtained.
  • the polymer was then pulverized with an electric blender. Cylindrical pellets of 3.2 millimeter diameter and 3.2 mm height (aspect ratio 1/1) were made with a handpress.
  • a pellet was carbonized by heating in a one-inch diameter quartz tube placed in a tube furnace. A steady stream of nitrogen was introduced into the quartz tube for at least 30 minutes prior to the heating of the furnace. The temperature of the furnace was increased at 110oC per hour to the final temperature of 900oC and then held for one and one-half hours before the product was allowed to cool to room temperature.
  • This example illustrates the preparation of the polymer using solution polymerization.
  • the same general procedure used in the Example 1 for the purification of the monomer and cross-linking agent were followed.
  • a 125 mL Parr bomb as described in the previous example was filled to about 85 mL.
  • the ratio of vinylidene chloride to solvent (orthodichlorobenzene) was maintained at 1:1.5.
  • Divinyl benzene was included at 0.5 wt.% relative to the vinylidene chloride.
  • the reactor was held at 70°C for 21 hours.
  • a polymer yield of 50.9 weight percent was obtained, with the solvent being removed from the polymer products by a vacuum (10 -3 mm mercury 1.33 ⁇ 10 -4 kPa absolute) until a constant weight was obtained.
  • the material was then pulverized, shaped and carbonized as described in Example 1.
  • Polymers were produced using emulsion polymerization techniques. 43.7 grams of vinylidene chloride was mixed with 0.9 g of divinylbenzene cross-linking agent. Both of these materials had been purified as previously described in Example 1. The mixture was added to 137.8 g of a mixture containing 1.35 g of ammonium sulfate, 0.67 g of hydrazine sulfate, 0.81 g of sodium hydroxide and 135 g of distilled water which formed the continuous phase during the polymerization. 0.45 g of sodium lauryl sulfate was added to aid in formation of the emulsion. This admixture was maintained in a rapidly agitated 500 mL reactor maintained at a temperature of 25°C for 24 hours. The polymer was recovered and then pulverized, pressed into pellets and carbonized following the procedure described for Example 1.
  • VDC vinylidene chloride
  • PPG Industries, Inc. commercial grade VDC (PPG Industries, Inc.) were passed through 40 mL of PCB activated carbon to remove the inhibitor content.
  • AIBN azobisisobutytonitrile
  • the VDC was then slowly added to 703.03 g of an aqueous solution containing 0.6% hydropropyl methyl cellulose and agitation of a 1000 mL Parr reactor was begun at 10-100 rpm.
  • the vessel containing the mixture was held in a constant temperature bath at 70oC for about 8 hours, to complete the polymerization of VDC.
  • the polymer was produced as spherical beads of about 2 mm diameter. These were recovered, washed with water, and dried at 100oC.
  • the VDC polymer was carbonized either as produced or else ground to about 100 ⁇ m and then pelletized to about 3.2 mm diameter and 3.2 mm height. Samples of the polymer were carbonized in a flowing stream of nitrogen. The temperature was raised from 25o to 175' in 30 min. to 2 hours and held for 2-4 hours. It was then increased at a rate of 100oC per hour to 700oC and held for 2 hours before the product was allowed to cool to room temperature.
  • the distribution of volume in a packed vessel was determined by the following method.
  • the individual density of the particles (“piece density”) was measured by weighing a particle and then dividing that weight by the volume of the particle. Assuming the density of the carbon itself is 2.2 g/mL, the total pore volume of the particle was calculated.
  • the packing density was measured by placing about 10-30 grams of the particles in a 50 mL graduated cylinder and vibrating the cylinder with an electric vibrator (60 cycles/sec) until a constant volume was obtained. The interparticle void volume was then calculated, knowing the particle density and the packing density.
  • the volume of the micropores was measured with Micromeritics ASAP 2000 micropore equipment using methane adsorption at 87.3oK.
  • the pore size distribution was analyzed with a Horvath-Kawazoe method. It was found that the micropores of the carbonized polymer were generally in the region of 5-7 ⁇ (0.5-0.7 nm). Using this information the volume of the pores in the meso pore range and of larger size were calculated by difference from the total pore volume. Photo micrographs have shown that the micro pores are very uniform and elongated in a slit-like configuration.
  • the carbon molecular sieves of the invention have a larger fraction of micropores (0.4 nm to 2.0 nm, preferably at least 60% of the total pore volume of each particle, which are considered most important in achieving a high capacity for natural gas. It can also be seen that disks formed of carbon would be a preferred shape since the void volume is substantially reduced. However, the advantage of the carbon molecular sieves of the invention is in the larger volume of micropores in each particle, regardless of the shape used.
  • Measurement of the methane capacity of the carbon pellets of Example 1 was carried out in quartz or stainless steel containers having volumes of 40, 46, and 80 mL.
  • the pellets were packed into the container using an electric vibrator to obtain the maximum packing density.
  • the container was evacuated to lm torr (0.001 mm Hg) and heated to 175°C for 4 hours. After cooling to room temperature, the weight of the container and contents was measured and then methane gas was introduced at various pressures. The temperature was measured by a thermocouple placed in the center of the bed of pellets. After equilibrium was reached, the container was weighed again and the total methane uptake determined. This includes methane in the micropores, the meso and macro pores, and the void space between pellets.
  • (g/g)' represent the total methane uptake per gram of carbon, while the values of (g/g) give the capacity of the micropores of the carbon.
  • the carbon molecular sieve of the invention has a higher capacity for methane storage than activated carbons or the commercial carbon molecular sieves which were tested.
  • Example 6 The measurements of Example 6 were made on carbon molecular sieves prepared as in Examples 1 and 4. They are compared below, along with another carbon molecular sieve made as in Example 4 but in a larger scale preparation. The results are presented in the table below.
  • Polymer pellets produced by the process of Example 4 were carbonized by heating in N 2 or CO 2 .
  • the programmed heating, the inert gas used, and the results are shown in the following table.
  • samples 1-4 suggest that rapid heating of the polymer pellets in the range of 140o-180oC, where PVDC is known to begin decomposing, provides a lower density product and thus heating in that temperature range should be slower in order to increase the particle (piece) density, which will increase the amount of carbon which can be stored in a given container.
  • the change in heating rate does not appear to significantly affect the surface area or the micropore volume.
  • Sample 5 shows that the use of CO 2 as the purging gas has no effect on the surface area or micropore volume when the carbonization is done with a maximum temperature of about 700o -710oC.
  • increasing the maximum carbonization temperature provides an increase in surface area and micropore volume, with some decrease in piece density. It appears that an activation effect is obtained.
  • the effect of activating carbon molecular sieves is to increase the stored and deliverable amount of natural gas, resulting from the increase in micropore volume.
  • the carbon molecular sieves were produced by carbonizing in nitrogen at a maximum temperature of 700oC the polymer precursors made by the suspension polymerization process described in Example 4. The activation conditions are given along with the capacity for methane in the following table.
  • the disks (samples 21,22) were compressed powdered carbon molecular sieves with a diameter of 21 mm and a thickness of 6.5 mm. By minimizing void space between the particles, these disks provide a higher storage capacity based on volume than do the pellets of samples 17-20. It will be seen that the activation process, although it removes carbon, provides improved storage capacity. However, there is an optimum activation, as will be seen.
  • the carbon molecular sieves have a pore diameter of about 5-6 ⁇ (0.5-0.6 nm) with only a minor portion of the pores being larger (the curve changes rapidly from a vertical line to a horizontal one).
  • the activated carbon molecular sieve has a major portion of the micropore volume in the region above 6 ⁇ (0.6 nm).
  • samples of PVDC precursor polymer produced using the suspension polymerization method described in Example 4 were carbonized by heating in nitrogen at 700oC for 2 hrs. Then, samples were given activation treatments with CO 2 at varying temperatures and times to increase the total pore volume. The samples were tested for methane capacity as described previously. The results are shown in Figure 2.
  • Unactivated carbon molecular sieves are shown as 100% carbon yield. As the severity of the activation is increased, the carbon yield goes down (carbon is oxidized and removed). At the same time the methane loading at the discharge pressure decreases rather than increasing as might be expected since there is less carbon present and the space available to hold methane at discharge pressure has increased. However, it is found that the ⁇ (v/v), that is, the amount of methane discharged increases until 60-70% of the initial carbon remains, after which the ability of the carbon to deliver methane begins to drop off. The capacity of the carbon at pressure (v/v) 300 [the sum of (v/v) 0 and ⁇ (v/v)] also increases to a maximum and then decreases. Consequently, it is believed that the increase of the pore size resulting from the activation procedure has provided a larger capacity for methane, but only insofar as the pores do not become so large that the density of the methane is reduced.
  • the carbon molecular sieves can absorb natural gas at 300 psig (2,169 kPa abs.) and deliver at 0 psig (101.32 kPa abs.) at least 70 times the volume of the vessel, preferably at least 95, most preferably at least 110 times the vessel volume, as the data suggests.
  • Example 14
  • Example 14 The beads produced in Example 14 were carbonized in a flow of helium as previously described. The temperature was raised from 25o to
  • the carbonized beads from Example 15 were activated by treatment with CO 2 at 800oC for 3-9 hours.
  • the storage capacity was measured as described in Example 6 and compared with non-impregnated beads in the following table.
  • Example 16 The beads activated in Example 16 were combined with pellets similar to Sample 19 in Table H to form a high packing density system (0.666 g/mL). The capacity of this system for methane storage was measured and compared to a system containing only the pellets and to a competing activated carbon (AX-21 Anderson Carbon). The deliverable methane capacity (A v/v) at various storage pressures is compared in the following table.
  • the large particles of about 2 mm size were prepared as in Example 4 by pelletizing powdered polymer.
  • the smaller particles were made by carbonizing small particles of polymer as made in Example 4 which are approximately spherical shaped beads.
  • the larger particles were packed into a 40 mL container using an electrical vibrator (60 cycles/sec) until the maximum packing density was obtained.
  • the smaller particles were added to the larger particles using the electrical vibration until no more could be added. It was found that the density of the mixed particle bed was greater than that obtained for either size alone. Data from several experiments are shown in the following table.
  • Measurement of the methane capacity of the carbon particles was carried out in stainless steel containers having volumes of 40 mL. A comparison was made between single size pellets and mixed-size particles of the invention. The pellets and particles were packed into the container using an electric vibrator to obtain the maximum packing density. The container was evacuated to lm torr (0.001 mm Hg) and heated to 175°C for 4 hours. The weight of the container and contents was measured and then methane gas was introduced at various pressures. The temperature was measured by a thermocouple placed in the center of the bed of pellets. After equilibrium was reached, the container was weighed again and the total methane uptake determined. This includes methane in the micropores, the meso and macro pores, and the void space between pellets.
  • the effective volumetric capacity of the absorbent ( ⁇ v/v) was determined as the difference between the v/v at absorption pressure and the v/v at delivery pressure.
  • v/v g.CH 4 adsorbed ⁇ 0.000643 g/mL ⁇ cell volume
  • 0.000643 g/mL is the density of CH 4 at delivery conditions [29.40 in (746.7 mm) Hg, 26.3°C]
  • a generally accepted target value for ⁇ v/v is 150, which is considered necessary for commercial success in storage of natural gas for vehicular use.
  • the results in Table N show that this value can be achieved with a storage pressure of about 500-600 psig (3,548-4,237 kPa gauge) using the packing method of the invention and the preferred carbon molecular sieve adsorbent.

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  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

Du gaz naturel est conservé dans une cuve fermée, à une pression comprise entre 1400 et 4500 kPa, à l'aide d'un adsorbant formant un tamis moléculaire dont au moins 60 % du volume poreux des particules est composé de micropores présentant des diamètres compris entre 0,4 nm et 2 nm, en particulier entre 0,4 et 1,5 nm. La capacité de tels micropores par rapport au méthane est d'au moins 0,095 g de méthane par g de carbone (à 300 psig ou 2169 kPa absolu). Le volume distribuable de gaz naturel, à partir d'une cuve remplie de particules de carbone formant un tamis moléculaire, représente au moins 70 fois le volume de la cuve. Ce volume distribuable peut être optimalisé par activation d'un polymère carbonisé afin d'augmenter le volume des pores. On augmente davantage ce volume en imprégnant un précurseur polymère du tamis moléculaire carboné avec des monomères supplémentaires, et en polymérisant les monomères avant la carbonisation du précurseur. La capacité du lit d'adsorbant est de préférence accrue par l'utilisation de particules adsorbantes d'au moins deux dimensions, dont les diamètres nominaux différent de l'ordre d'au moins 7/1.
PCT/US1993/006002 1992-07-01 1993-06-22 Stockage de gaz naturel Ceased WO1994001714A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US90699592A 1992-07-01 1992-07-01
US07/906,993 US5308821A (en) 1992-07-01 1992-07-01 Packing adsorbent particles for storage of natural gas
US906,995 1992-07-01
US906,993 1992-07-01
US964,174 1992-10-21
US07/964,174 US5292706A (en) 1992-07-01 1992-10-21 Preparing carbon molecular sieves of increased density

Publications (1)

Publication Number Publication Date
WO1994001714A1 true WO1994001714A1 (fr) 1994-01-20

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PCT/US1993/006002 Ceased WO1994001714A1 (fr) 1992-07-01 1993-06-22 Stockage de gaz naturel

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998044289A1 (fr) * 1997-03-31 1998-10-08 Lockheed Martin Energy Research Corporation Systeme de stockage et d'alimentation de gaz avec absorbant electriquement conducteur
EP0847304A4 (fr) * 1995-08-23 1999-10-27 Univ Syracuse Carbones microporeux composites pour stockage de gaz combustible
WO2017222420A3 (fr) * 2016-06-22 2018-02-08 Публичное акционерное общество "Газпром" Matériau carboné nanoporeux en bloc pour l'accumulation de gaz naturel et de méthane, et procédé de production
RU2787636C1 (ru) * 2022-07-18 2023-01-11 Публичное акционерное общество "Газпром" Способ хранения природного газа в слое адсорбента

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FR2322876A1 (fr) * 1975-09-04 1977-04-01 Sumitomo Chemical Co Procede de production de produits carbones poreux et nouveaux produits ainsi obtenus
FR2513543A1 (fr) * 1981-09-29 1983-04-01 Slovenska Akademia Vied Procede pour produire des sorbants poreux a base de carbone
US4420415A (en) * 1980-08-27 1983-12-13 Director-General Of Agency Of Industrial Science & Technology Process for the production of carbon molecular sieves
EP0218403A2 (fr) * 1985-10-03 1987-04-15 Calgon Carbon Corporation Procédé et moyen d'adsorption d'un gaz
US4820681A (en) * 1987-12-24 1989-04-11 Allied-Signal Inc. Preparation of hydrophobic carbon molecular sieves
US5071820A (en) * 1990-05-25 1991-12-10 Atlanta Gas Light Company Carbonaceous material with high micropore and low macropore volume and process for producing same

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FR2322876A1 (fr) * 1975-09-04 1977-04-01 Sumitomo Chemical Co Procede de production de produits carbones poreux et nouveaux produits ainsi obtenus
US4420415A (en) * 1980-08-27 1983-12-13 Director-General Of Agency Of Industrial Science & Technology Process for the production of carbon molecular sieves
FR2513543A1 (fr) * 1981-09-29 1983-04-01 Slovenska Akademia Vied Procede pour produire des sorbants poreux a base de carbone
EP0218403A2 (fr) * 1985-10-03 1987-04-15 Calgon Carbon Corporation Procédé et moyen d'adsorption d'un gaz
US4820681A (en) * 1987-12-24 1989-04-11 Allied-Signal Inc. Preparation of hydrophobic carbon molecular sieves
US5071820A (en) * 1990-05-25 1991-12-10 Atlanta Gas Light Company Carbonaceous material with high micropore and low macropore volume and process for producing same

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0847304A4 (fr) * 1995-08-23 1999-10-27 Univ Syracuse Carbones microporeux composites pour stockage de gaz combustible
WO1998044289A1 (fr) * 1997-03-31 1998-10-08 Lockheed Martin Energy Research Corporation Systeme de stockage et d'alimentation de gaz avec absorbant electriquement conducteur
US5912424A (en) * 1997-03-31 1999-06-15 Lockheed Martin Energy Research Corporation Electrical swing adsorption gas storage and delivery system
WO2017222420A3 (fr) * 2016-06-22 2018-02-08 Публичное акционерное общество "Газпром" Matériau carboné nanoporeux en bloc pour l'accumulation de gaz naturel et de méthane, et procédé de production
CN109689202A (zh) * 2016-06-22 2019-04-26 俄罗斯天然气工业公开股份公司 用于蓄积天然气或甲烷的块状多孔碳材料及其生产方法
JP2019521837A (ja) * 2016-06-22 2019-08-08 パブリチノエ アクツィオネルノエ オブスチェストヴォ “ガズプロム” 天然ガスまたはメタンを蓄積するためのブロック状のナノ多孔質炭素材料、およびその材料を得るための方法
CN109689202B (zh) * 2016-06-22 2022-04-01 俄罗斯天然气工业公开股份公司 用于蓄积天然气或甲烷的块状多孔碳材料及其生产方法
RU2787636C1 (ru) * 2022-07-18 2023-01-11 Публичное акционерное общество "Газпром" Способ хранения природного газа в слое адсорбента

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