United States Patent (19)
`McCue et al.
`
`Patent Number:
`11
`(45) Date of Patent:
`
`4,677,086
`Jun. 30, 1987
`
`(54) SHAPED WOOD-BASED ACTIVE CARBON
`75) Inventors: John C. McCue, Covington, Va.;
`Albert J. Repik, Charleston; Charles
`E. Miller, Jr., Mt. Pleasant, both of
`S.C.
`73) Assignee: Westvaco Corporation, New York,
`N.Y.
`21 Appl. No.: 611,595
`(22) Filed:
`May 18, 1984
`51) Int. Cl. ......................... B01J 20/12; B01J 20/20
`52 U.S. C. ........................................ 502/62; 502/80;
`502/413; 123/519; 55/387
`58) Field of Search ........................... 502/62, 80,413;
`123/519; 55/387
`
`56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`Re. 25,400 6/1963 Doying ................................. 502/62
`617,079 1/1899 Catlett ...
`... SO2/62
`1,524,843 2/1925 Ruprecht .............................. 502/62
`1,589,081 6/1926 Adler ................................ 502/80 X
`1,985,840 12/1934 Sadtler .............................. 502/80 X
`2,108,860 2/1938 Kauffman ............................. 502/62
`2,391,312 12/1945 Ewing et al. ......................... 502/80
`2,455,509 12/1948 Luaces .................................... 18/55
`2,951,087 8/1960 Hauser .................................. 502/62
`3,454,502 7/1969 Hiltgen et al.
`... 252/428
`3,592,779 7/1971 Kiikka .........
`... 252/421
`3,864,277 2/1975 Kovach ............................... 252/423
`
`
`
`3,960,761 6/1976 Burger et al. ....................... 252/421
`3,960,771 6/1976 Tanaka et al. ......
`... 502/413
`4,029,600 6/1977 Schmitt, Jr. et al. ............... 252/.444
`4,051,098 9/1977 Takemura et al. .................... 260/38
`4,124,529 11/1978 Juntgen et al. .....
`252/421
`4,338,106 7/1982 Mizuno et al. ........................ 55/387
`4,518,704 5/1985 Okabayashi et al. ............... 502/413
`FOREIGN PATENT DOCUMENTS
`69146 4/1984 Japan ................................... 502/413
`341233 1/1931 United Kingdom ................ 502/413
`Primary Examiner-Carl F. Dees
`Attorney, Agent, or Firm-Terry B. McDaniel; Richard
`L. Schmalz
`ABSTRACT
`57
`A shaped activated wood-based carbon with essentially
`no pore volume in pores greater than one micron in
`diameter and a higher apparent density is prepared from
`an active granular wood-based carbon with a significant
`pore volume in pores greater than one micron in diame
`ter and a lower apparent density by the invention pro
`cess of grinding the active granular wood-based carbon
`to a fine powder, mixing the ground carbon with a
`liquid selected from water or other polar molecule and
`a bentonite clay binder, shaping the mixture, drying the .
`shaped active carbon to remove the liquid, and heat
`treating the dried product to calcine, or fix, the clay
`binder.
`
`16 Claims, 1 Drawing Figure
`
` MAHLE-1023
`U.S. Patent No. RE38,844
`
`

`

`U.S. Patent
`U.S. Patent
`
`Jun. 30, 1987
`Jun. 30, 1987
`
`4,677,086
`4,677,086
`
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`SHAPED WOOD-BASED ACTIVE CARBON
`SHAPED WOOD-BASED ACTIVE CARBON
`
`4,677,086
`4,677,086
`2
`2
`ates and polyvinyl alcohols which are soluble or emulsi
`ates and polyvinyl alcohols which are soluble or emulsi-
`fiable in water or phosphoric acid solutions.
`fiable in water or phosphoric acid solutions.
`U.S. Pat. No. 3,960,761 discloses a method of produc
`U.S. Pat. No. 3,960,761 discloses a method of produc-
`tion of strong active carbon moldings by extruding or
`tion of strong active carbon moldings by extruding or
`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`briquetting low ash mineral coals with phenols and
`briquetting low ash mineral coals with phenols and
`(1) Field of the Invention
`(1) Field of the Invention
`aldehydes used as binders. In teaching carbon particu
`aldehydes used as binders. In teaching carbon particu-
`This invention relates to an active carbon formed into
`This inventionrelates to an active carbon formed into
`lates comprising carbon black spheres and a carbon
`lates comprising carbon black spheres and a carbon
`a granular or other suitable shape by using bentonite
`a granular or other suitable shape by using bentonite
`binder with desirable pore size distribution, U.S. Pat.
`binder with desirable pore size distribution, U.S. Pat.
`clay as a binder. More particularly, the invention deals
`clay as a binder. Moreparticularly, the invention deals
`No. 4,029,600 discloses certain polymers and coal tar
`No. 4,029,600 discloses certain polymers and coal tar
`with a method for producing a shaped wood-based
`with a method for producing a shaped wood-based
`pitch as the carbon binder. Also, U.S. Pat. No. 4,051,098
`pitch as the carbon binder. Also, U.S. Pat. No. 4,051,098
`activated carbon with essentially no pore volume in
`activated carbon with essentially no pore volume in
`discloses a one step phenol-formaldehyde resin, a modi
`discloses a one step phenol-formaldehyde resin, a modi-
`pores greater than one micron in diameter. Thus, the
`pores greater than one micron in diameter. Thus, the
`fied phenol-formaldehyde resin or a mixture thereof as
`fied phenol-formaldehyde resin or a mixture thereof as
`invention product is particularly well adapted for use as
`invention productis particularly well adapted for use as
`a binder in a process for manufacturing a shaped active
`contact mass in adsorption and catalytic processes.
`a binderin a process for manufacturing a shaped active
`contact mass in adsorption and catalytic processes.
`carbon. The patentees note that the resins do not dam
`(2) Description of the Prior Art
`carbon. The patentees note that the resins do not dam-
`(2) Description of the Prior Art
`age the adsorption property of the active carbon due to
`Granular carbons and carbon pellets are typically
`Granular carbons and carbon pellets are typically
`age the adsorption propertyofthe active carbon due to
`used in columns or beds for gas and vapor systems and
`their markedly high carbonization rates in the high
`used in columns or beds for gas and vapor systems and
`their markedly high carbonization rates in the high
`also for processing a number of liquids. To qualify for
`temperature treatment employed in the manufacturing
`also for processing a numberofliquids. To qualify for
`temperature treatment employed in the manufacturing
`this application, a carbon must posses sufficient me
`this application, a carbon must posses sufficient me-
`process.
`process.
`chanical strength to withstand the abrasion incident to
`chanical strength to withstand the abrasion incident to
`Finally, U.S. Pat. No. 4,124,529 teaches carbona
`Finally, U.S. Pat. No. 4,124,529 teaches carbona-
`20
`20
`continued use. Gas-adsorbing carbons should be as
`continued use. Gas-adsorbing carbons should be as
`ceous adsorbents produced by shaping the carbon with
`ceous adsorbents produced by shaping the carbon with
`dense as is consistent with high adsorptive power so as
`dense as is consistent with high adsorptive powerso as
`elastomeric plastics and thermoplastic materials such as
`elastomeric plastics and thermoplastic materials such as
`not to require a large space for the adsorber. The devel
`notto require a large space for the adsorber. The devel-
`polyvinyl alcohol, polypropylene, and polyethylene.
`polyvinyl alcohol, polypropylene, and polyethylene.
`opment of high adsorptive power during thermal acti
`opmentof high adsorptive power during thermal acti-
`It has now been discovered that bentonite clay, a
`It has now been discovered that bentonite clay, a
`vation, however, is accompanied by a loss of mechani
`vation, however, is accompanied by a loss of mechani-
`non-carbon containing material, when mixed with a
`‘non-carbon containing material, when mixed with a
`25
`cal strength and density; therefore, some compromise is
`cal strength and density; therefore, some compromiseis
`pulverized, activated wood-based carbon in a liquid and
`pulverized, activated wood-basedcarbonina liquid and
`required in selecting the degree to which the activation
`required in selecting the degree to which theactivation
`agglomerated or shaped, dried, and heat-treated, per
`agglomerated or shaped, dried, and heat-treated, per-
`is conducted.
`is conducted.
`forms as an effective carbon binder to produce a shaped
`forms as an effective carbon binder to produce a shaped
`Activated carbon currently produced from wood
`Activated carbon currently produced from wood
`active carbon material with higher apparent density and
`active carbon material with higher apparent density and
`waste has an exceptionally high internal surface area
`waste has an exceptionally high internal surface area
`hardness, reduced pressure drop in gas phase applica
`hardness, reduced pressure drop in gas phase applica-
`30
`and activity level. However, the granular portion is
`and activity level. However, the granular portion is
`tions, and increased volumetric adsorption capacity.
`tions, and increased volumetric adsorption capacity.
`relatively soft and its shape is irregular. Therefore, ap
`relatively soft and its shapeis irregular. Therefore, ap-
`Particularly surprising is the increased volumetric ad
`Particularly surprising is the increased volumetric ad-
`plication of granular wood-based carbon in general gas
`plication of granular wood-based carbon in general gas
`sorption capacity of the shaped product in view of the
`sorption capacity of the shaped productin view of the
`phase and liquid phase adsorption is limited by a number
`phase and liquid phase adsorptionis limited by a number
`fact that the weight bases adsorption capacity has been
`fact that the weight bases adsorption capacity has been
`of constraints, to wit: (1) its low apparent density results
`of constraints, to wit: (1) its low apparent density results
`35
`decreased by the presence of the inert clay binder. Ad
`decreased by the presenceofthe inert clay binder. Ad- .
`in low volumetric adsorption capacity; (2) its low hard
`35
`in low volumetric adsorption capacity; (2) its low hard-
`vantageously, the extruded carbon product of this in
`vantageously, the extruded carbon productofthis in-
`ness results in a high fines generation rate (dusting); and
`ness results in a high fines generation rate (dusting); and
`vention produces particles of uniform activity through
`vention producesparticles of uniform activity through-
`(3) its limited maximum particle size and its irregular
`(3) its limited maximum particle size and its irregular
`out. Prior art thermally activated granular carbon parti
`granular shape both result in a high pressure drop in gas
`out. Prior art thermally activated granular carbonparti-
`granular shape bothresult in a high pressure drop in gas
`phase applications. It has been found that changes in
`cles exhibit high activity on the outer surface with de
`cles exhibit high activity on the outer surface with de-
`phase applications. It has been found that changes in
`40
`creasing activity toward the center.
`hardness and shape can be effected by agglomerating or
`hardness and shape can be effected by agglomerating or
`creasing activity toward the center.
`shaping an active wood-based carbon with bentonite
`shaping an active wood-based carbon with bentonite
`SUMMARY OF THE INVENTION
`SUMMARYOF THE INVENTION
`clay in the particular manner of the invention which
`clay in the particular manner of the invention which
`achieves properties which provide shipping advantages
`A shaped activated wood-based carbon with essen
`A shaped activated wood-based carbon with essen-
`achieves properties which provide shipping advantages
`by reducing dusting tendancies, as well as properties
`tially no pore volume in pores greater than one micron
`by reducing dusting tendancies, as well as properties
`tially no pore volume in pores greater than one micron
`45
`suited to gas and liquid phase applications. Particularly,
`in diameter and a higher apparent density is prepared
`suited to gas andliquid phase applications. Particularly,
`45
`in diameter and a higher apparent density is prepared
`invention process provides shaped active carbon the
`invention process provides shaped active carbon the
`from an active granular wood-based carbon with a
`from an active granular wood-based carbon with a
`maximum particle size of which is limited only by the
`maximum particle size of which is limited only by the
`significant pore volume in pores greater than one mi
`significant pore volume in pores greater than one mi-
`equipment used in the shaping process.
`equipment used in the shaping process.
`cron and a lower apparent density by the invention
`cron and a lower apparent density by the invention
`Shaping of carbons, generally, is taught in the prior
`Shaping of carbons, generally, is taught in the prior
`process of grinding the active granular wood-based
`process of grinding the active granular wood-based
`art. U.S. Pat. No. 2,455,509, for example, teaches a
`art. U.S. Pat. No. 2,455,509, for example,
`teaches a
`carbon to a fine powder, mixing the ground carbon with
`carbonto a fine powder, mixing the ground carbon with
`method of extruding irregularly shaped carbon rods but
`method of extrudingirregularly shaped carbon rodsbut
`a liquid selected from water or other polar molecules
`a liquid selected from water or other polar molecules
`does not teach any particular binder material. The or
`does not teach any particular binder material. The or-
`and a bentonite clay binder, shaping the mixture, drying
`and a bentonite clay binder, shaping the mixture, drying
`ganic binders most commonly used are substances
`ganic binders most commonly used are substances
`the shaped active carbon to remove the liquid, and
`the shaped active carbon to remove the liquid, and
`which when heat-treated in an inert or non-oxidizing
`which when heat-treated in an inert or non-oxidizing
`heat-treating the dried product to calcine, or fix, the
`heat-treating the dried product to calcine, or fix, the
`atmosphere yield a high proportion of fixed or residual
`atmosphere yield a high proportion of fixed or residual
`clay binder.
`clay binder.
`carbon.
`carbon.
`Thus, U.S. Pat. No. 3,454,502 teaches activated car
`Thus, U.S. Pat. No. 3,454,502 teaches activated car-
`DESCRIPTION OF THE PREFERRED
`DESCRIPTION OF THE PREFERRED
`bon tablets formed from powdered activated carbon
`EMBODIMENT(S)
`bon tablets formed from powdered activated carbon
`EMBODIMENT(S)
`with water soluble aliphatic petroleum hydrocarbon
`with water soluble aliphatic petroleum hydrocarbon
`The invention process involves the steps of (1) grind
`The invention process involvesthe steps of (1) grind-
`sulfonate detergent as binder, and U.S. Pat. No.
`sulfonate detergent as binder, and U.S. Pat. No.
`ing activated wood-base carbon to a fine powder, (2)
`ing activated wood-base carbon to a fine powder, (2)
`3,592,779 teaches the use of acid sludge formed by the
`3,592,779 teaches the use of acid sludge formed by the
`mixing the ground carbon with a liquid and a binding
`mixing the ground carbon with a liquid and a binding
`reaction of a mineral acid with a relatively high molecu
`reaction of a mineral acid with a relatively high molecu-
`amount of bentonite clay, (3) agglomerating or shaping
`amountof bentonite clay, (3) agglomerating or shaping
`lar weight hydrocarbon as a binder for particulate car
`lar weight hydrocarbon as a binder for particulate car-
`the mixture, (4) drying to remove the liquid to produce
`the mixture, (4) drying to removethe liquid to produce
`bon and the subsequent activation thereof. U.S. Pat. No.
`bon and the subsequentactivation thereof. U.S. Pat. No.
`shaped carbon which may be easily dispersed to its fine
`65
`shaped carbon which maybeeasily dispersed to its fine
`3,864,277 teaches a hard granular activated carbon and
`3,864,277 teaches a hard granular activated carbon and
`65
`powder form upon contact with water, and subse
`powder form upon contact with water, and subse-
`preparation by extrusion of a mixture of a carbonaceous
`preparation by extrusion of a mixture of a carbonaceous
`quently, (5) heat-treating the shaped carbon at tempera
`quently,(5) heat-treating the shaped carbon at tempera-
`material, a binder, and an inorganic activating agent
`material, a binder, and an inorganic activating agent
`tures from above 700° F. to about 1800° F., to fix the
`tures from above 700 F. to about 1800' F., to fix the
`(phosphoric acid). The binders taught are lignosulfon
`(phosphoric acid). The binders taught are lignosulfon-
`
`50
`50
`
`55
`55
`
`60
`
`

`

`4,677,086
`4,677,086
`4.
`3.
`4
`3
`are acceptable, such as a ram extruder, pellet mill, disc
`clay binder (i.e., destroying the water swelling charac
`are acceptable, such as a ram extruder, pellet mill, disc
`clay binder(i.e., destroying the water swelling charac-
`agglomerator, or briquette press.
`ter thereof).
`ter thereof).
`agglomerator, or briquette press.
`Wood-based active carbon typically has a significant
`The extruded shaped carbon is heated at drying tem
`Wood-based active carbon typically has a significant
`The extruded shaped carbonis heated at drying tem-
`pore volume in pores greater than one micron (10,000
`peratures up to 700 F. to remove the liquid therefrom.
`pore volumein pores greater than one micron (10,000
`peratures up to 700° F. to removethe liquid therefrom.
`angstroms) in diameter (0.6 cc/gm). Pores this size do 5
`Attemperatures above about 500 F., heating should be
`angstroms) in diameter (0.6 cc/gm). Pores this size do
`At temperatures above about 500° F., heating should be
`not contribute to the carbon's adsorption capacity. In
`conducted in an inert atmosphere to prevent ignition of
`not contribute to the carbon’s adsorption capacity. In-
`conductedin an inert atmosphereto preventignition of
`deed, the major result of this pore volume is lower
`the carbon.
`deed, the major result of this pore volume is lower
`the carbon.
`product apparent density. Processing the wood-based
`product apparent density. Processing the wood-based
`Following the drying step, the dried shaped carbon
`Following the drying step, the dried shaped carbon
`active carbon, however, results in a shaped active car
`active carbon, however, results in a shaped active car-
`may be heat treated at temperatures from about 700 F.
`maybe heat treated at temperatures from about 700° F.
`bon product with essentially no pore volume in pores
`bon product with essentially no pore volume in pores
`10
`to 1800" F. to calcine, or fix, the clay binder. Typically,
`to 1800° F.to calcine, or fix, the clay binder. Typically,
`greater than one micron in diameter and yields a prod
`greater than one micron in diameter and yields a prod-
`the heat treatment may be conducted in a nitrogen envi
`the heat treatment may be conductedin a nitrogen envi-
`uct with increased apparent density. Therefore, al
`uct with increased apparent density. Therefore, al-
`ronment; however, for that portion of the temperature
`ronment; however, for that portion of the temperature
`though the weight basis adsorption capacity is de
`though the weight basis adsorption capacity is de-
`range up to 1,300 F., steam may be economically em
`range up to 1,300° F., steam may be economically em-
`creased by the presence of the inert clay binder, the
`creased by the presence of the inert clay binder, the
`ployed to displace oxygen. While a rotary kiln is pre
`ployed to displace oxygen. While a rotary kiln is pre-
`volumetric capacity of the carbon is increased, as 15
`volumetric capacity of the carbon is increased, as
`ferred for the heat treatment step, other types of equip
`ferred for the heat treatment step, other types of equip-
`shown in the following table.
`shown in the following table.
`ment are acceptable. The heat treatment temperature is
`mentare acceptable. The heat treatment temperature is
`TABLEI
`dependent upon the pellet dispersal properties desired.
`TABLE I
`dependent uponthepellet dispersal properties desired.
`Two types of bentonite clay are distinguished-a
`Two types of bentonite clay are distinguished—a
`sodium bentonite (also called Wyoming or western) and
`sodium bentonite (also called Wyoming or western) and
`a calcium bentonite (also called southern). Western
`a calcium bentonite (also called southern). Western
`bentonite clay has the property of swelling many times
`bentonite clay has the property of swelling many times
`it original volume when added to water. High tempera
`it original volume when added to water. High tempera-
`ture treatment of the bentonite prevents swelling in
`ture treatment of the bentonite prevents swelling in
`water. For the shaped product, it is possible to control
`water. For the shaped product,it is possible to control
`the pellets' physical changes on water contact by con
`the pellets’ physical changes on water contact by con-
`trolling the heat treatment temperature. Specific con
`trolling the heat treatment temperature. Specific con-
`trolled responses for extruded pellets made by the in
`trolled responses for extruded pellets made by the in-
`vention process with 14% western bentonite binder are
`vention process with 14% western bentonite binder are
`reported in Table II as follows:
`reported in Table II as follows:
`TABLEII
`TABLE II
`
`Granular
`Granular
`Nuchar
`Nuchar
`WV-B(
`Property
`wv—Bl
`Property
`7.9
`Apparent Density, lb/ft
`17.9
`Apparent Density, Ib/ft3
`105.1
`CCl, capacity, gm/100 gm
`05.
`CC4 capacity, gm/100gm.
`30.2
`CC14 capacity, gm/100 cm
`30.2
`CCly capacity, gm/100 cm3
`40.7
`Butane capacity, gm/100 gm
`40.7
`Butane capacity, gm/100gm
`11.
`Butane capacity, gm/100 cm
`11.7
`Butane capacity, gm/100 cm?
`(Westvaco commercial wood-basedactive carbon.
`(Westvaco commercial wood-based active carbon.
`
`Heat Treatment
`Heat Treatment
`Temperature (°F.) Product Properties
`Temperature (F) Product Properties
`700° F.
`At 12% solids content or greater in water, the
`700 F.
`At 12% solids content or greater in water, the
`pellet immediately disintegrates, but the solids
`pellet immediately disintegrates, but the solids
`do notsettle out.
`do not settle out.
`At any solids content, the pellets disintegrate
`At any solids content, the pellets disintegrate
`and the solids settle from the water into a
`and the solids settle from the water into a
`cake.
`cake.
`The pellets become very soft in water, but
`The pellets become very soft in water, but
`remain intact. (See FIG. 1.)
`remain intact. (See FIG. 1.)
`Thepellet hardness on water contact. Shows
`The pellet hardness on water contact. Shows
`negligible change. (See FIG. 1.)
`negligible change. (See FIG. 1.)
`
`850° F.
`850 F.
`
`1,000° F.
`1,000 F.
`1,200° F.
`1,200 F.
`or greater
`or greater
`
`55
`55
`
`Thus, for pellets heated at 700 F. or less, the wetting
`Thus, for pellets heated at 700° F.orless, the wetting
`and dispersal rate, with little or no agitation, is much
`and dispersal rate, with little or no agitation, is much
`faster than for pulverized wood-based carbon. By tak
`faster than for pulverized wood-based carbon. By tak-
`ing advantage of these properties, products with tai
`ing advantage of these properties, products with tai-
`lored dispersal rates can be manufactured. Such prod
`lored dispersal rates can be manufactured. Such prod-
`ucts would provide handling with less dust than pow
`ucts would provide handling with less dust than pow-
`dered carbon products, yet would readily disperse to
`dered carbon products, yet would readily disperse to
`the powder form on contact with water.
`the powder form on contact with water.
`A specific embodiment of the invention relates to the
`A specific embodimentofthe invention relates to the
`application of the shaped wood-based carbon prepared
`application of the shaped wood-based carbon prepared
`by the invention process in an evaporative emission
`by the invention process in an evaporative emission
`control device for adsorbing the gasoline vapors which
`control device for adsorbing the gasoline vapors which
`emit from the carburetor of an automobile and also to
`emit from the carburetor of an automobile and also to
`adsorb the gasoline vapors which emit from the fuel
`adsorb the gasoline vapors which emit from the fuel
`tank. Accordingly, the shaped carbon is disposed in a
`tank. Accordingly, the shaped carbon is disposed in a
`suitable canister and arranged to receive the vapors
`suitable canister and arranged to receive the vapors
`from the carburetor and/or fuel tank. Preferably, the
`from the carburetor and/or fuel tank. Preferably, the
`shaped carbon is disposed in such a manner that the
`shaped carbon is disposed in such a manner that the
`evaporated fuel from the carburetor and/or fuel tank
`evaporated fuel from the carburetor and/or fuel tank
`must pass through the shaped carbon where it can be
`must pass through the shaped carbon where it can be
`adsorbed to prevent it from exhausting into the atmo
`adsorbed to prevent it from exhausting into the atmo-
`sphere.
`sphere.
`The following examples are provided to illustrate
`The following examples are provided to illustrate
`further the novelty and utility of the present invention.
`further the novelty and utility of the present invention.
`
`Granular WV—B,
`Granular WV-B,
`Pulverized and
`Pulverized and
`Extruded with
`Extruded with
`14% Clay Binder
`14% Clay Binder
`21.2
`21.2
`96.1
`96.1
`32.7
`32.7
`37.8
`37.8
`12.9
`12.9
`
`20
`2O
`
`25
`
`w0
`30
`
`The removal of pores greater than one micron in
`The removal of pores greater than one micron in
`diameter and the resultant increase in apparent density
`-diameter and the resultant increase in apparent density
`was observed to occur even when using a relatively
`was observed to occur even when using a relatively
`coarse grind in the pulverizing step, such as 60% of the
`coarse grind in the pulverizing step, such as 60% ofthe
`sample passing a 325 mesh (44 micron) screen.
`sample passing a 325 mesh (44 micron) screen.
`The mutual weight proportions of the carbon and
`The mutual weight proportions of the carbon and
`clay binder are suitably between 25:75 and 95:5, espe
`clay binder are suitably between 25:75 and 95:5, espe-
`cially between 80:20 and 90:10, respectively. The mix
`35
`cially between 80:20 and 90:10, respectively. The mix-
`ture of carbon and clay is formed in the presence of a
`ture of carbon and clay is formed in the presence of a
`liquid selected from water or other polar molecule,
`liquid selected from water or other polar molecule,
`which can be removed after the forming, or shaping
`which can be removed after the forming, or shaping
`step. The mixture is shaped wet; the proportion of liquid
`step. The mixture is shaped wet; the proportion ofliquid
`in the mixture is chosen to give the consistency required
`in the mixture is chosen to give the consistency required
`for the shaping method to be used, taking into account
`for the shaping method to be used, taking into account
`that liquid tends to be withdrawn from the mixture by
`that liquid tends to be withdrawn from the mixture by
`adsorption by the carbon and clay, thus stiffening the
`adsorption by the carbon and clay, thusstiffening the
`mixiure.
`mixture.
`45
`The proper operation of the mixing step has been
`45
`The proper operation of the mixing step has been
`found to be critical in determining the operability of the
`foundto be critical in determining the operability of the
`extrusion step and setting product properties. Because
`extrusion step and setting product properties. Because
`the bentonite swells in water and the swelled platelets
`the bentonite swells in water and the swelled platelets
`provide the required lubrication to develop plasticity,
`provide the required lubrication to develop plasticity,
`the amount of available water controls the level of plas
`the amountofavailable water controls the level of plas-
`50
`ticity. As noted, the amount of available water is prede
`ticity. As noted, the amountof available water is prede-
`termined by the total water content of the mix and the
`termined by the total water content of the mix and the
`amount adsorbed into the carbon internal pore struc
`amount adsorbed into the carbon internal pore struc-
`ture. The higher the moisture level, the less viscous the
`ture. The higher the moisture level, the less viscous the
`plastic mass and, therefore, the lower the extrusion
`plastic mass and,
`therefore,
`the lower the extrusion
`pressure. Simply blending together the components in
`pressure. Simply blending together the components in
`the proper proportions is not all that is required. For
`the proper proportions is not all that is required. For
`proper operation of the extruder, the batch must be
`proper operation of the extruder, the batch must be
`mixed in a high shear mixer until the viscosity proper
`mixed in a high shear mixer until the viscosity proper-
`60
`ties of the mix do not change with time. If the viscosity
`ties of the mix do not change with time. If the viscosity
`is still changing, unacceptable extruder operation re
`is still changing, unacceptable extruder operation re-
`sults. The preferred mixer is a low speed, high shear
`sulis. The preferred mixer is a low speed, high shear
`type muller mixer, although any high shear type is prob
`type muller mixer, although any high shear typeis prob-
`ably acceptable.
`ably acceptable.
`65
`The preferred method of agglomerating or shaping
`The preferred method of agglomerating or shaping
`65
`the wet carbon-clay mixture is by extrusion for pellet
`the wet carbon-clay mixture is by extrusion for pellet
`formation with a standard auger extruder with a non
`formation with a standard auger extruder with a non-
`compressive screw. However, other shaping methods
`compressive screw. However, other shaping methods
`
`

`

`5
`
`4,677,086
`4,677,086
`6
`6
`The treated pellets were separately soaked in water
`The treated pellets were separately soaked in water
`and gasoline for 10 days and tested for hardness by a
`and gasoline for 10 days and tested for hardness by a
`standard crushing strength test procedure. The effect of
`standard crushing strength test procedure. The effect of
`calcination temperature on pellet hardness was deter
`calcination temperature on pellet hardness was deter-
`mined by graphing the hardness rating of each sample,
`mined by graphing the hardness rating of each sample,
`as well as ratings of dry, unsoaked pellets similarly
`as well as ratings of dry, unsoaked pellets similarly
`treated, representing the original sample hardness. The
`treated, representing the original sample hardness. The
`graph appears as FIG. 1.
`graph appears as FIG.1.
`The heat treatment temperature at which the gasoline
`The heat treatment temperature at which the gasoline
`soaked pellets approach their original hardness is 1,000
`soaked pellets approachtheir original hardnessis 1,000°
`F. For water soaked pellets, a heat treatment of at least
`F. For water soaked pellets, a heat treatment ofat least
`1,100 F. is necessary to compare favorably with the
`1,100° F. is necessary to compare favorably with the
`original sample in hardness after 10 days. No real ad
`original sample in hardness after 10 days. No real ad-
`vantage is observed for treatment above 1,300 F.
`vantage is observed for treatment above 1,300° F.
`Therefore, the preferred heat temperature range for
`Therefore,
`the preferred heat temperature range for
`wood-based active carbons shaped according to the
`wood-based active carbons shaped according to the
`invention process for use in emission control of gasoline
`invention process for use in emission contro! of gasoline
`vapors is from 1,000 F. to 1,300 F.
`vapors is from 1,000° F. to 1,300° F.
`While the invention has been described and illus
`While the invention has been described and illus-
`trated herein by references to various specific materials,
`trated herein by references to various specific materials,
`procedures and examples, it is understood that the in
`procedures and examples, it is understood that the in-
`vention is not restricted to the particular materials,
`vention is not restricted to the particular materials,
`combinations of materials, and procedures selected for
`combinations of materials, and procedures selected for
`that purpose. Numerous variations of such details can
`that purpose. Numerousvariations of such details can
`be employed, as will be appreciated by those skilled in
`be employed, as will be appreciated by those skilled in
`the art.
`the art.
`Whatis claimedis:
`What is claimed is:
`
`5
`5
`EXAMPLE1
`EXAMPLE 1
`To show both the operability of the invention process
`To show both the operability of the invention process
`and the application of the invention product in evapora
`and the application of the invention produ