AU6227280A - Hard granular activated carbon manufactured from sub- bituminous coal treated with solid boric acid - Google Patents

Description

HARD GRANULAR ACTIVATED CARBON MANUFACTURED FROM SUB-BITUMINOUS COAL TREATED WITH SOLID BORIC ACID

^■ BACKGROUND OF THE TNVENTION

1. Field of the Invention

This invention relates to granular activated carbon manu¬ facture, and more particularly to a new and improved process for making hard granular activated carbon from sub-bituminous coal treated with solid boric acid, and to a new and improved hard granular activated carbon made by such process and having properties which make it suitable for use in liquid or gas phase applications, depending upon the amount of acid employed.

2. ^' Glossary of Terms

In order to facilitate a clear understanding of this in- vention, various terms of art employed herein are defined as follows.

^" Abrasion number - is a measure of the resistance of the activated carbon granules to degrading on being mechanically abraded. It is measured by contacting a sample with steel balls in a pan on a machine and shaking the contents for a given time and determining the resultant particle size distri¬ bution and hence the mean particle diameter. The abrasion number is the ratio of the final average (mean) particle dia¬ meter to the original average (mean) particle diameter (deter- mined by screen analysis) times 100.

OMPI Activated carbon - is carbon which is "activated" by heating to high termperature preferably with steam of carb dioxide as the gaseous activating agent in producing an in nal porous particle structure.

Activation or activating - means heating coal at high temperatures on the order of about 600°C. to about 1100°C. the presence of a gaseous activating agent, as is ell kno in the art. The heating rate during activation from the m mum activation temperature to the maximum activation tempe ture may vary widely, e.g., from about 100° to about 1000° per hour, but usually is nearer 100°C. per hour.

Adsorption isotherm - is a measurement of the adsorpt capacity of an adsorbent (viz. granular activated carbon) a function of the concentration, or pressure, of the adsor (viz. N-) at a given temperature. It is defined as the co stant temperature-relationship between the amount absorbed per unit weight of adsorbent and the equilibrium concentra or partial pressure.

Apparent density - is the weight per unit volume of h geneous granular activated carbon. To assure uniform pack of the granules during measurement, a vibrating trough is used to fill the measuring device.

⁷-^s-¹ ~ is ^a principal mineral constituent of coal, car and pitch. It is normally defined as a weight percent bas after a given amount of sample is reduced to ash.

" Average (mean) particle diameter - is a weighted aver diameter of a granular activated carbon sample. A screen sis is run and the average particle diameter is calculated by multiplying the weight of each fraction by its average meter, adding the products, and dividing by the total weig of the sample. The average diameter of each fraction is t as the size midway between the sieve opening through which fraction has passed and the sieve opening on which the fraction was retained. It usually is expressed in mm.

Carbon tetrachloride activity number - is the steady state percentage increase in the weight of a bed of activated carbon after air which has been saturated with carbon tetrachloride at 0°C. is passed through the carbon at 25°C. It is expressed as a percentage number.

Charring - means heating coal at low temperatures on the order of about 175°C. to about 275°C. in the presence of oxygen.

^' Coking alue,- is usually expressed as percent residual carbon .obtained when a dry sample of coal, tar or pitch is vaporized or pyrolized for a specific time at a specific tem¬ perature that limits the available oxygen supply (ASTM Method D-2416) . The coking value, expressed as percent residual carbon, indicates the coke forming properties of the material.

Devolatilizing - means heating coal at intermediate temp- eraturreess oonn tthhee oorrddeerr oo:f about 400°C. to about 600°C. in an oxygen-free atmosphere.

Direct activation or directly activating - means heating a coal, preferably in a.granular form, directly (without prior charring and devolatilization) and rapidly (at a heating rate of about 500 C per hour or more) to an activating temperature higher than the devolatilization temperature (of the order of - 600 to 1100 C.) in an atmosphere containing a gaseous activa- ting agent and maintaining the desired activating temperature for the desired period of time.

^* Granular activated carbon - is "activated carbon" which has a particle size, i.e., "mesh", which is not less than about 60 and preferably not less than about 40.

Iodine number - is the milligrams of iodine adsorbed by one gram of granular activated carbon at an equilibrium fi trate concentration of 0.02 N iodine. It is measured by contacting a single sample of carbon with an iodine soluti and extrapolating to 0.02 N by an assumed isotherm slope. This number can be correlated with the ability of granular activated carbon to adsorb low molecular weight substances

Mesh - (or mesh size) is the particle size of granule determined by the U.S. Sieve Series or the Tyler Series. ally, this term refers to the sizes of the two screens, in either of the above Series, between which the bulk of a sa falls. For example, . "8/30 mesh" (or "8 by 30 mesh" or "8 mesh") .means that 90% by weight of the sample will pass th a No. 8 screen but will be retained on a No. 30 screen. A natively, this term refers to a maximum particle size, suc in defining. the fineness of powder material. For example, by weight-325 mesh powder" means that 65% by weight of a g sample passes through a No. 325 mesh screen.

Molasses number - is calculated from the ratio of the tical densities of the filtrate of a molasses solution tre with a standard activated carbon and the activated carbon question.

Pitch - is a black or dark viscous substance obtained a residue in the distillation of organic materials and esp ially tars.

Powder.- means powdered activated carbon which has a particle size, i.e., "mesh", which is smaller than about 40 and preferably smaller than about 60. The larger the mesh number, the smaller the size.

Sub-bituminous coal - is an intermediate stage coal wh ranks above lignite and brown coals, but below bituminous coal. In the as received condition it has, by weight, (1) proximate analysis of: from about 10% to about 25% moistu

OM from about 35% to about 45% volatile material, from about 2% to about 5% ash, and from about 25% to about 45% fixed carbon, and (2) an ultimate analysis of: from about 65% to about 75% carbon, from about 4% to about 8% hydrogen, from about 0.6% to about 2.0% nitrogen, and from about 0.5% to about 1.0% sul¬ fur. See ASTM Standard D-388-66.

Surface area - is the amount of surface area per unit weight of granular activated carbon; it is determined from the nitrogen adsorption isotherm by the Brunauer, Emmett and Teller (BET) method, and it is expressed in m /gram.

^* Volumetric Todihe and Molasses .-lumbers - are determined by multiplying by the apparent density, in order to express these properties independently of such density.

3. Discussion of Art

Granular activated carbon is useful in both liquid and gas phase applications. In the former, granular activated carbon has been found to be particularly useful in water and waste water treatment, not only because it is highly effective in purifying the intake, as well as the effluent from municipal and industrial systems, but also because it can be regenerated for repeated use. However, in order to accomplish these ob¬ jectives, it must possess certain properties, namely a minimum

2 surface area of about 900 m /gram for adequate adsorption cap¬ acity, a minimum volumetric Iodine number of about 410, pre- ferably about 480, for adequate adsorption, especially of low molecular weight substances, a minimum volumetric Molasses number of about 90, preferably about 100, for adequate decolor¬ izing, a maximum ash content (by weight) of not more than about 12%, and preferably not more than about 8% for purity, a min- imum abrasion number of about 70 and preferably not less than about 80, for adequate hardness in maintaining granular integ¬ rity in use and in regeneration, and a minimum apparent density of not less than about 0.46 gram/cc, preferably not less than about 0.48 gram/cc, for obtaining the dense, closely packed beds and columns needed in water and waste water treatment^gτj j_ In gas phase applications, granular activated carbon is particularly useful for gas and air purification. In a tion to the above properties of density, hardness and puri the volumetric Iodine number should not be below a minimum about 460 and the volumetric Molasses number should be les than 90, preferably a volumetric Iodine number of at least 480 and a volumetric Molasses number of not more than abou Likewise, the carbon should have a minimum carbon tetrachl number of about 50, preferably at least about 60.

Hard granular activated carbon can be obtained from b minous, sub-bituminous and. brown.coals,^' such as disclosed U.S..Patents 4,144,193, 4,032,476, 4,131,566, 4,149,994, 4,149,995, and 4,157,314.

However, in each of these patents, liquid mineral aci were employed, and until the present invention, it was not known that anyone else had accomplished this objective by solid boric acid treatment of sub-bituminous coal.

In the '193, '566, and ^•994 patents, a dilute aqueous tion of inorganic mineral acid was employed, requiring an removal step prior to further processing, in order to avoi corrosion of the heat treating equipment. In the '476 and patents, a small amount of concentrated mineral acid was m with the coal granules, thereby eliminating the acid remov step, but requiring special lining of the heat treating eq ent in order to avoid the corrosive action of the acid.

As for the heat treatment itself, each of the aforesa patents except the '566 patent discloses the elimination o the charring or low temperature heat oxidation step found necessary in dealing with bituminous coal. In the '566 pa both the acid treatment and charring steps were found to b necessary for attaining the desired results when treating rank agglomerating but not good coking bituminous coal. I '314 patent, it has been found that both the charring and volatilization steps could be eliminated prior to the tion step. Likewise the disclosures of U.S. Patents 3,483,134, 3,876,505, and 4,014,817 are of interest, but each requires the charring or low temperature heat oxidation step, and none discloses a hard granular activated carbon product.

While the use of aqueous boric acid has been disclosed in U.S. Patent 1,438,113 for making decolorizing carbon, the source material was of either vegetable or animal origin, with the boric acid merely being considered as a possible substitute for the preferred phosphoric acid in the aqueous solution, and with the liquid acid constituting at least one third and preferably two thirds of the mixture prior to carbonization. Hence, this patent does not teach the manufacture of hard granu¬ lar activated carbon from sub-bituminous coal treated with a considerably smaller amount of solid boric acid.

Moreover, U.S. Patent 2,437,174 discloses the use of an aqueous solution of boric acid in treating vegetable matter in order to produce active carbon by burning in air, with suf¬ ficient liquid boric acid being used until 1-15% by weight of boron compound is impregnated into the material. Once again, the patent does not suggest employing solid boric acid to treat mineral matter such a sub-bituminous coal nor producing a hard granular activated carbon, but rather a fibrous product. In each of these two patents, the resulting product is leached with water to extract the boric acid following the heat treatment.

In contrast, in the present inventive process, recognition- of the property of boric acid as being solid at room temperature permits the use of a considerably smaller amount of this acid in solid form, in order to simplify the production of hard gran¬ ular activated carbon, with the amount of the solid acid employed determining the suitability of the resulting hard granular pro¬ duct for use in liquid or gas phase applications. Although the coal, as received, may be crushed and sized to for granules prior to blending with the solid boric acid followed by powder- izing, this is not absolutely necessary, because the coal and solid boric acid readily may be simultaneously blended and duced to form a uniform mixture in fine powder form, with without the admixture of a carbonaceous binder such as pit This is particularly helpful when treating the coal on a l scale, because the initial granulating step can be elimina and the blending and powderizing steps can be combined. M over, there is no necessity for washing out the boric acid either prior to or following the appropriate heat treatmen which not only eliminates the charring or low temperature oxidation step, but also can eliminate the separate devola izing step, such as by direct activation.

Alternatively, the blending step can precede the powd izing step, and separate devolatilization and activation s can be employed, with the charring step being eliminated i any event.

SUMMARY OF THE INVENTION

Accordingly, a primary objective of the present inven is (1) to provide a new and improved process for making ha granular activated carbon from sub-bituminous coal wherein acid treatment is greatly simplified by completely elimina not only the need for separate initial granulating and ble steps, as well as the use of an elevated temperature durin blending, as when an acid in liquid form is employed, but any necessity for removing the acid, either prior to or fol iieat treatment, which is further simplified by elimination the charring or low temperature oxidation step or both this and the separate devolatilization step prior to activation; (2) to provide a new and improved hard granular activated c made by such process and having the aforementioned desired erties of adsorption (as measured by volumetric Iodine num and carbon tetrachloride number) , decolorization (as measur by volumetric Molasses number) , purity (as measured by ash tent) , hardness (as measured by abrasion number) , and densi (as measured by apparent density) , which make it suitable f use in liquid and/or gas phase applications. To this end, the invention includes (1) a process for making hard granular activated carbon from sub-bituminous coal com¬ prising: compressing fine powder containing the coal to form shapes, reducing the shapes to form granules, and heat treating the granules until activated, wherein the improvement comprises: blending and reducing a uniform mixture including the coal, from about 1% to about 10% of solid boric acid, and 0% to about 10% of carbonaceous binder to form such fine powder having a moisture content of not less than about 10% and not more than about 25% prior to compressing, and (2) hard granular activated carbon made by such process and having the physical characteristic of high granular integrity permitting repeated handling, use, regen¬ eration and reuse. All percentages used herein are by weight, unless otherwise specified, and the shapes formed by compressing may be of various configurations larger than the granules such as pellets, briquettes, thin sheets of corrugated cross section, etc.

Another object is to provide such process wherein the mix¬ ture is blended either before or simultaneously with reduction of the mixture to form the powder.

A further objective is to provide such a process wherein the amount of acid employed is selected to make the resulting hard granular activated carbon suitable for use in liquid and/ or gas phase applications. For liquid phase applications, the acid range should be from about 1% to about 5%, preferably from about 2% to about 3%. For gas phase applications, the acid range should be from 5% to about 10%, preferably from about 7% to about 9%.

Additional objectives and advantages of the invention will become apparent upon consideration of the following de¬ tailed description and accompanying drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE is a block diagram or flow sheet illustrating schematically the various steps of the proces as well as the resulting product, both embodying the inven tion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this detailed description, reference will be made eight Examples which are illustrative of the invention.

The following Examples 1-8 represent preferred embodi ments of the present invention, which is represented schem ically in the drawing. Referring to the drawing, it is to noted that the sub-bituminous coal, as defined above, usua contains in the as-received condition, a moisture content from about 10% to about 25%. Under such circumstances, it neither necessary nor desirable to further adjust or contr the moisture content of the coal prior to further processi However, should the coal be unusually dry or unusually wet, the moisture can be adjusted to facilitate further processi as indicated in the upper right hand corner of the drawing. Likewise, the moisture adjustment can take place prior to c pressing the fine powder, as indicated in the upper left ha side of the drawing. The important point to keep in mind a to moisture control is that the powder prior to compressin has a moisture content of not less than about 10% and not m than about 25% so that the shapes produced during compressi will become densely packed and yield compact granules suita for obtaining hard granular activated carbon following heat treatment. Continuing with the drawing, it is noted that t blending and powderizing steps are schematically illustrate together, although the blending step could be performed as separate step following an initial granulation step and pri to the powderizing step, and if desired, moisture adjustmen could be made prior to or between such separate steps.

Likewise, the heat treatment of the granules is genera indicated in the drawing, but this general indication is in to include either the direct activation or separate devolatil¬ ization and activation steps, but without a charring or low temperature heat oxidation step in any event.

The various batches of sub-bituminous coal employed in the ensuing Examples, had the following typical weight percent anal¬ ysis, in the as received condition and on a dry basis:

^• PROXIMATE ANALYSIS

' As Received 5____.

Moisture 18.1 —

Volatile Material 35.86 43.78.

Ash .2.95 3.605

Fixed Carbon 43.09 52.61

^'.EXAMPLE 1

2000 grams of coal of 8/20 mesh, 174 grams of coal tar pitch (7.86%) and 40 grams of solid boric acid (1-81%) were blended by stirring together in a Hobart mixer for approximately 10 minutes. The mixture was pulverized in a hammer mill to give a powder, 91% of which passed through a standard 325 mesh screen. The powder was compacted into cylindrical pellets approximately 0.5 inch in diameter and 0.5 inch high, and having a density of 1.06 grams/cc. These pellets were crushed in a jaw mill and granules in the size range of -6 + 20 (6/20) were selected for further processing.

600 grams of the 6/20 mesh granules were placed in a stainless steel screen basket which was caused to be rotated within a tube furnace at about 2 rpm. The furnace was con¬ structed so that the gaseous environment of the basket and granules could be controlled. The granules were heated to about 470°C while in an inner atmosphere of nitrogen or argon, and this temperature and atmosphere were maintained for 1 hour, after which time the material was allowed to cool to room

_OMPI temperature. 362 grams of carbonized (i.e., devolatilized) material (+20 mesh) with an apparent density of 0.651 gram were obtained, giving a yield on devolatilization of 60.3%

300 grams of this material were activated as follows: the granules were placed in a controlled atmosphere rotary kiln and were heated to a temperature of 870°C under a nit flow, at which time steam carried by flowing nitrogen was passed through the system at a rate corresponding to about 700 grams of water per hour. This was continued for a per of 2 hours, after which time the material was allowed to c to room temperature under flowing nitrogen. 139 grams of granular activated carbon (+30 mesh) were obtained, produc an activation yield of 46.3% and an overall yield of 28%, The activated granules have the following properties: apparent density 0.480 gram/cc; Iodine number 1045 (volume 502); Molasses number 217 (volumetric 104), abrasion numbe and mean particle diameter 1.70 mm.

^' EXAMPLE 2

The procedure of Example 1 was repeated, with the fol- lowing differences. 50 grams of boric acid (2.25%) were us which made the pitch content 7.82%, with 90% of the fine powder being -325 mesh. The pellets had a density of 1.19 grams/cc, and following crushing, the granules were heated to about 600°C for devolatilization. 346 grams of the devolatilized granules were obtained with an apparent densi of 0.643 gram/cc, producing a devolatilization yield of 57.

The activation was continued for a period of 2.5 hours producing 154 grams of granular activated carbon, with an activation yield of 51% and an overall yield of 27% (57.6 x 51/100 = 29.4%). The activated granules had an apparent density of 0.488 gram/cc, an Iodine number of 1027 (volumet ric 501), a Molasses.number of 228 (volumetric 111), an abrasion number of 82 and a mean particle diameter of 1.53 ^' EXAMPLE 3

The procedure of Example 2 was repeated, except that 1000 grams of coal were blended with 87 grams of pitch (7.79%) and 30 grams of boric acid (2.68%). The density of the pellets was 1.2 grams/cc, and following crushing and devolatilization, 331 grams of granules were obtained, with an apparent density of 0.652 gram/cc, producing a devolatili¬ zation yield of 55%. Following activation, 154 grams of granular activated carbon were obtained, producing an activa- tion yield of 52% and an overall yield of 29%. The activated granules had the following properties: apparent density 0.492 gram/cc; Iodine number 1009 (volumetric 496); Molasses number 247 (volumetric 121), abrasion number 82, and mean particle diameter 1.55 mm.

EXAMPLE 4

The procedure of Example 3 was.repeated, but with the pitch being reduced to 57 grams (5.24%), changing the boric acid content to 2.76%. The pellets had a density of 1.17 grams/cc, and following devolatilization, 309 grams.of gran- ules were obtained with an apparent density of 0.644 gram/cc, giving a devolatilization yield of 51.5%. Following activa¬ tion, 148 grams of granules were obtained, producing an activation yield of 49% and an overall yield of 25%. The activated granules had the following properties: apparent density 0.477 gram/cc; Iodine number 1075 (volumetric 513); Molasses number 236 (volumetric 113); abrasion number 83, ash content 10.31%, and mean particle diameter 1.32 mm.

EXAMPLE 5

The procedure of Example 4 was repeated, except that 2000 grams of coal were blended with 60 grams of pitch (2.84%) and 50_.grams of boric acid (2.37%). The pellets had a density of 1.14 grams/cc, and following devolatilization, 330 grams were produced, having an apparent density of 0.643 gram/cc

OMFI ° with a yield on devolatilization of 55%. Activation was continued for 2 hours, resulting in 156 grams of granular activated carbon, with an activation yield of 52% and an overall yield of 29%. The activated granules had an apparent density of 0.491 gram/cc, an Iodine number of 106 (volumetric 520), a Molasses number of 228 (volumetric 112) an abrasion number of 84, an.ash content of 11.7%, and a mean particle diameter of 1.40 mm.

EXAMPLE 6

The procedure of Example 5 was repeated, except that the boric acid content was increased to 60 grams, thereby changing the boric acid and pitch contents to 2.83% each. The compacted pellets had a density of 1.10 grams/cc, and upon devolatilization, 335 grams having an apparent densit of 0.640 gram/cc were obtained, producing a devolatilizati yield of 52%.

Activation was continued for a period of 2.25 hours, resulting in 150 grams of activated granules, producing an activation yield of 50% and an overall yield of 26%. The granular activated carbon had the following properties: apparent density 0.483 gram/cc; Iodine number 1004 (volume 485) ; Molasses number 230 (volumetric 111) ; abrasion numbe 77, ash content 10.9%, and mean particle diameter 1.32 mm.

EXAMPLE 7

< The procedure of Example 6 was repeated, except that no pitch was employed, which increased the boric acid to 2.91%, and 65% of the powder was -325 mesh. The pellets had a density of 1.27 grams/cc, and following crushing 931 grams of 6/20 mesh granules were devolatilized, obtaining 460 grams with an apparent density of 0.644 gram/cc and a yield on devolatilization of 49.4%. 300 grams were activated for 3.25 hours, producing 151 grams of granular activated carbon, at an activation yield of 50.2% and an overall yield 25%. The activated granules had an apparent density of 0.498 gram/cc, an Iodine number of 1050 (volumetric 523) , a Molasses number of 204 (volumetric 102), an abrasion number of 80, an ash content of 11.02%, and a mean particle diameter of 1.56 mm.

From the foregoing Examples 1-7, it will be seen that an excellent water phase granular activated carbon can be produced by the inventive process, with or without the use of a carbonaceous binder such as pitch.

The next Example is designed to demonstrate the appli¬ cability of the inventive process to successfully producing a gas phase granular activated carbon.

^' EXAMPLE 8

The procedure of Example 6 was repeated, except that 180 grams of pitch (7.56%) and 200 grams of boric acid (8.40%) were used. Thus the pellets had a density of 1.30 grams/cc, with 1169 grams of the granules produced on crushing resulting in 624 grams of devolatilized granules having an apparent density of 0.617 gram/cc, giving a yield on devolatilization of 53.4%.

Activation was continued for a period of 3 hours and 5 minutes. 153 grams of granular activated carbon was pro- duced upon activation, giving an activation yield of 51% and an overall yield of 27%. The activated granules have the following properties: apparent density 0.461 gram/cc; Iodine number.1090 (volumetric 502); Molasses number 183 (volumetric 84); carbon tetrachloride number 73.9; abrasion number 72, ash content 10.85%, and mean particle diameter 1.55 mm. 1.6

From this Example, it will be seen that an excellent gas phase carbon can be produced by the inventive process where the boric acid content is increased above 5%.

From the foregoing specific Examples, it is evident that hard granular activated carbon suitable for use in li or gas phase applications can be obtained by treatment wit relatively small amount (about 1 to about 10%) of solid bo acid, with the specific amount of boric acid needed being justed within the overall range to produce a liquid phase carbon (about 1% to about 5% acid) or a ga<* phase carbon ( to about 10% acid) . The term "boric acid" as used herein commercially has the formula H₃B0₃ and is also known as ortho-boric acid or boracic acid, and this was the particu form of the acid actually used in the aforesaid Examples. However, this term is intended to encompass metaboric acid, having the formula HBO- and tetra- (or pyro-) boric acid, having the formula H-B.O-, because these forms of boric acid also are solid at room temperature, and are composed of the same elements in slightly different proportions.

O

Claims (1)

1. WHAT IS CLAIMED IS:

   1. A process for making hard granular activated carbon from sub-bituminous coal comprising: compressing fine powder containing said coal to form shapes, without charring, reducing said shapes to form granules, and heat treating said granules until activated, wherein the improve¬ ment comprises: blending and reducing a uniform mixture including said coal, from about 1% to about 10% of solid boric acid, and 0% to about 10% of carbonaceous binder to form said fine.powder having a moisture content of not less than about 10% and not more than about 25% prior to said compressing.

   2. Hard granular activated carbon made by the process of claim 1.

   3. The process of claim 1 wherein said mixture is blended before being reduced to form said powder.

   4. The process of claim 1 wherein said mixture is blended and reduced simultaneously.

   5. The process of claim 1 wherein said mixture includes from about 1 to about 5% of said acid, the amount being selected to provide a minimum volumetric Iodine number of about 410 and a minimum volumetric Molasses number of about 90.

   6. Hard granular activated carbon made by the process of claim 5. being suitable for use in liquid phase applica¬ tions and having a minimum abrasion number of about 70.

   7. The process of claim 1 wherein said mixture includes from about 2% to about 3% of said acid, the amount being selected to provide a minimum volumetric Iodine number of about 480 and a minimum volumetric Molasses number of about 100. 8. Hard granular activated carbon made by the proce of claim 7, being suitable for use in liquid phase applica tions and having a minimum abrasion number of about 75.

   9. The process of claim i wherein said mixture incl from 5% to about 10% of said acid, the amount being select to provide a minimum volumetric Iodine number of about 460 and a volumetric Molasses number below about 90.

   10. Hard granular activated carbon made by the proce of claim 9, being suitable for use in gas phase applicatio and having a minimum carbon tetrachloride number of about 5

   11. The process of claim 1 wherein said mixture inclu from about 7% to about 9% of said acid, the amount being se ected to provide a minimum volumetric Iodine number of abou 480 and a volumetric Molasses number below about 85.

   12. Hard granular activated carbon made by the proces of claim 11, being suitable for use in gas phase applicatio and having a minimum carbon tetrachloride number of about

   60.