US2681318A - Conversion of tar pitches into activated carbons - Google Patents

Description

P. E. MAYER June 15, 1954 CONVERSION OF TAR PITCHES INTO ACTIVATED CARBONS F'led Aug. 9, 1951 Patented June 15, 1954 CONVERSION OF TAR PITCHES INTO ACTIVATED CAR-BONS Perry E. Mayer, Audubon, Chemical & Dye Corpor N. J., assignor to Allied ation, New York, N. Y.,

a corporation of New York Application August 9, 1951, Serial No. 241,113

12 Claims.

This invention relates to the conversion of pitches into activated carbons and more particularly refers to a new and improved method of converting pitches derived from coal tars, watergas tars and oil-gas tars into highly activated carbons especially adapted for decolorizing, deodorizing and for gas and vapor adsorption purposes.

An object of the present invention is to provide a method for converting pitches into uniformly-sized grain suitable for processing into activated carbons without the necessity for passing through the pulverulent state.

Another object is to provide a method for controlling the porosity of granular' activated carbon produced from coal tar, Water-gas tar and oil-gas tar pitches.

A further object of this invention is to provide a method for obtaining an increased yield of activated carbons from coal tar, water-gas tar and oil-gas tar pitches by converting the bitumen components normally unsuitable for production of activated carbon into additional activated carbons.

A still further object is to provide an eiiicient economical process for converting coal tar, water-gas tar and oil-gas tar pitches into high yields of strong granular highly active carbons.

Other objects and advantages of the present invention will be apparent from the following description and the accompanying drawing.

A preferred method for the conversion of coal tar, water-gas tar and oil-gas tar pitches in accordance with the present invention comprises passing air or other oxygen-containing gases such as flue gases containing oxygen, flue gas-air mixtures, and steam-air mixtures, in intimate contact with molten pitch, continuing the passage oi air in contact with the molten pitch until the pitch has a benzol-insoluble content in excess of 45%, preferably within the range of Ll5--55%, cooling the resultant molten pitch to solid form, grinding the solid pitch to granular size, preferably within the range of 4 to 50 mesh, extracting benzol-soluble components from the pitch granules by contacting the pitch granules with a solvent, preferably a predominantly aromatic liquid or a constituent thereof such as benzol, toluol and xylol, heating the extracted granules in a stream of oxygen-containing gas, preferably air, to a temperature within the range of about 200 to 400 C'. until an infusible activatable char is obtained, regulating the temperature during such heating so that the granules remain in an unfused condition, and activating the char by the action of steam or flue gases.

The solvent containing dissolved benzol-soluble components (bitumen) resulting from leaching the pitch granules may be subjected to distillation for separation into puried solvent and bitumen. The bitumen may be withdrawn from the still for use as such, or if desired, may be recharged to the blow still for additional oxida; tion and ultimate conversion into activated carbon.

If desired, the benzol-insoluble content of the air-blown pitch may be reduced by blending with compatible hydrocarbon materials of lower insoluble content, a procedure which is particularly useful if the pitch shall have been blown to a benzol-insoluble content in excess of Suitable iluxes for this purpose would be, for example, normal pitches obtained by direct distillation of the tars, soluble bitumens recovered from the extraction of the air-blown pitch, heavy distillate oils or the salt components which crystallize out of creosote oil and other heavy coal-tar distillates. The blend of molten pitch and ilux is cooled, ground, solvent extracted, calcined and activated in the manner described above.

The accompanying drawing diagrammatically illustrates a preferred operation of the present invention when air blowing is used to increase the benzol-insoluble content of the pitch. Referring to the drawing, coal tar pitch or watergas tar pitch or oil-gas tar pitch or mixtures thereof are introduced through lines I and 2 into nre heated still designated by numeral 3. For convenience in operation the pitch is desirably heated to a liquid state prior to introduction in re heated still 3 and maintained therein in a molten condition at a temperature of about 3DO-400 C. by burning fuel introduced through line 4 at the bottom of the still. Air is blown through conduit 5 connecting to crosspipe B which latter has a series of small orifices through which the air rises upwardly, as indicated by the arrows, in intimate contact with the body of molten pitch in still 3i. As a result of the passage of air or other oxygen-containing gas the benzol-insoluble content of the molten pitch increases. Air is blown through the molten pitch until it has a benzol-insoluble content in excess of 45%; best results are obtained with the pitch having a benzol-insoluble content within the range of Ll5-6'5%. As will be explained later, the resultant air-blown pitch is solidified, ground to granular size and the granules subjected to extraction with solvent for removing the major portion of the benzol-soluble constituents from the granules. If the granules contain an amount of benzol-insoluble constituents appreciably lower Vcooled gas and condensate i ing the blow oil in liquid l pitch contained than 45% the granules after leaching with the solvent will be structurally weak and subject to attrition and deterioration into fines, whereas if the granules contain an amount of benzolinsoluble components appreciably greater than 65% the leached granules will be less porous and less suceptible to activation treatment to activated carbons.

The length of time required to raise the benzolinsoluble content of the molten pitch to within the range of l-65% will vary dependentfupon the rateof air flow, temperature and nature of the individual pitch undergoing treatment. En general about 3 to 8 hours are required to raise the bonzol-insoluble content of the pitch to the desired value, when blowing pitch with air at a rate of cubic feet per minute per ton of pitch at a temperature of e. g. `W-400 C.

During the air blowing of the molten pitch, evolved gases and vapors top of still 3 through line l, pass through water cooled condenser 8 to liquefy the vapors, and the ilow through line il to be collected in steam jacketed receiver Il.

.Non-condensable gases are released from receiver Il through gas vent line l2. Condensate comprising hydrocarbon oils, designated generally in Vthe industry as blow oil, collected in the bottom l of receiver Il is discharged through line i3 for use Vas fuel or other disposition. To avoid plugging of line i3 due to the crystallization of high boiling hydrocarbon constituents in the blow oil a steam jacket, as clearly shown in the drawing, surrounds receiver Il for heating and maintaincondition.

In a modified method ofoperation air may be blown through line 5 into the molten body of in still.3 until the benzol-insoluble content of the pitch is irl-excess of for example r15% sultant granules may not have the desiredv porosity and may be difficult to activate toa high quality activated carbon. Therefore, a compatible hydrocarbon iiux of substantially lower benzel-insoluble content such as normal residual pitch, extracted bitumen, `heavy distillate oil', or Vanthracene salts is added through line i4 to the molten air-blown pitch, blending therewith and:

reducing the benzlol-insoluble content of the resulant fluxed pitch to within the range of L15-65 Thus, by the addition of regulated amounts of,

e. g. anthracene salts to the air-blown ptch,1the

porosity of the carbon granules may be controlled,

and further this addition permits extended air s blowing ot the molten pitch to 'ahigh benzolinsoluble content. Anthracene salts,5a common product ofthe coal tar industry, 'comprise the kcrystalline phase whichseparates out on cooling coal tar dstillates boiling .within the vrange of about250-400f C.V VAnthrancene salts, which are VSheatedstill `3 through line l5 onto conventional v flaking roll .IB Ywhere itis cooled and solidied.

Cooling and solidii'ication Vof the-V molten-pitch are released from the 'l Upon'cooling, grinding and leacht Ying of such high Vbenzol--insoluble pitch the re- 1 enhancing the yield of 4 may also be accomplished by discharging pitch into a pitch bay or into a tank containing water or the solvent to be used for the ultimate extraction. Fine streams of molten pitch may be cooled by quenching in water or solvent to produce solid pitch in the formof granules suitable for preparation of activated carbon grain without the necessity of crushing and sizing the airblown pitch. In the embodiment shown in the Y drawing the solid pitch from flaking roll i6 passes via line l? toxconventional grinder it wherein it is crushed to form granules of about 4 to 50 mesh size with, `as usual, the formation of a minor amount of fines and a small amount of oversized particles. The crushed pitch Vpasses through line I9 to a conventional two-deck screen 2l for the purpose of separating out the nes and oversized particles, which latter may be returned'to grinder I8 for further crushing. The separated fines may be discharged from thesystem through line 22, or preferably are Vreturned through line 23 to fire heated still 3 in admixture with the molten pitch and thus are ultimatelyV recovered in the form of the desired carbon granules thereby eliminating a waste product and activated carbon.

The screened granules designatedas blow pitch grain are transferred `via line Zitto` blowrptch grain storage 25, a hopper, fronivvhiclflV the blow pitch grain is tractor 2l. Y Extractor 27 as shown in the drawing may be a cylindrical vessel with a conical bottom having the screen 2t on which the blow pitch grain rests inside the base of extractorV 21. An opening at the bottom of screen 28 provided with valve 29 permits the discharge of blow pitch grain after solvent extraction. f

The blow pitch grain is subjected to solvent extraction to remove benzol-soluble constituents from the grain thereby producing a structurally strong highly porous grain having an increased benzol-insoluble content without loss of particulate identity of the grain. Extraction of benzolsoluble constituents from the lgrain may be conveniently carried out by lling extractor 21 Y about one-half full with blow pitch grain, then line 32, thence in indirect contact with steam in heat exchanger t3,Y and Vthen by pump 34 through line 35 into the bottom of extractor 2l. Additional temperature control and more efficient contact with the blow pitch grain may be obtained by circulating a portion ofY the solvent from the bottom of extractor 21 through line "3S and forcing it by pump 3l through line es to the top of extractor 2l. By thus maintaining rapid circulation of the solvent through the bed of grain on screen 2B, lit was found unnecessary to employ mechanical stirring or agitating devices. After digesting the grain with'solvent for about one hour the liquor is withdrawn from the bottom of extractor 2l through line 353 and forced by pump 3l through line 39 to storage tanks. Fresh solvent may then be charged intoextractor 2i for asecond and thirdleaching similar to the iirst'extraction. Ordinarily, three batchwise solvent leachings as just described will be adequateV to removev most of the benzol-soluble kccmponents from the blow pitch grain. At the lend of the solvent extractions liquid remaining 1in vextractor' Z1 Vis drained through line A35 and the solvent'remainin'g on the grain .isremoved :by j

fed through conduit Y26 into expassing steam introduced through line 4| upwardly through the grain. Steam and solvent vapors are released from the top of extractor 21 through line 42, cooled in Water condenser 43 and the cooled products passing through line 44 co1- lected in receiver 45. Water may be drained from the bottom of receiver 45 through line 46. Incondensable gases are released from the top of receiver 45 through vent line 41. Solvent condensate Withdrawn from receiver 45 is returend through line 48 to solvent tank 49 for further use.

As will be noted three solvent tanks numbered 49, 5| and 52 are provided with suitable manifolding to permit them to be used interchangeably. Ordinarily, the liquor from the rst washing of the grain in extractor 21 will be directed by pump 31 through lines 36, 39, 53 and valve 54 into solvent extractor tank 52. Liquor containing less dissolved benzol-soluble components from the second and third leachings will be directed to solvent wash tank 5| via lines 39, 55 and valve 56. In some cases the liquor in tank 5| from the second or third washings of the grain may be satisfactory for reuse without preliminary purification of the liquor as the solvent for the rst leaching of a subsequent batch of grain in which event solvent is withdrawn from tank 5| through lines 51, 58 and valve 59 and directed by pump 6| through line 92, valve 83y and line 3| into extractor 21. As is apparent from the drawing fresh solvent from tank 49 passes through line 64, valve 65, line 58 and is forced by pump 8| through lines 52, 3| and valve 93 into extractor 21. Impure solvent, i. e. solvent containing dissolved bitumen from previous leachings of blow pitch grain in extractor 21 may be periodically withdrawn from solvent wash tank 5| through line 51 and valve 59 and solvent extract tank 52 through line 69 and valve 61 and thence through line 58 to be forced by pump 6| through line 62, valve 88, line 69 into solvent still 1| which may be any conventional still commonly employed in the industry for steam distilling solvent. Heat is applied to solvent still 1| by means of enclosed steam coil 12, and in addition to facilitate vaporization of the solvent, steam is introduced through line 13 in direct contact with the liquid in the still. Vapors comprising substantially pure solvent and water evolved from solvent still 1| are released through line 14, cooled in condenser 43, thence discharged through line 44 into receiver 45 from which the solvent condensate is withdrawn through line 48 and collected in solvent tank 49 for further use. Bitumen extracted from the pitch, benzol-soluble constituents, remaining as residue in solvent still 1|, is withdrawn from the bottom of the still through line 15 and directed by pump 15 through line 11 and valve 18 to storage for use as fuel or other disposition, or preferably the bitumen is returned through line 19 and valve 8|, thence through line 2 into nre heated still 3 wherein the bitumen inadmixture with molten pitch entering through line is air blown into additional yields of pitch suitable for activation.

After the blow pitch grain has been adequately leached to remove the benzol-soluble constituents therefrom, steamed free of solvent and, if desired, dried by passing warm air through the bed, valve 29 adjacent the bottom of screen 28 of extractor 21 is opened and the porous grain discharged through line 82 and valve 83 and directed via line 84 into calciner 85 which may be an externally heated rotary retort provided with an inlet 86 at one end for the introduction of air or oxygen- `solidified on a aking containing gas and a discharge line 81 at the other end for the release of waste gas. The grain in calciner is heated to a temperature below 200 C. and an air stream at the rate of about 1.5 to 7.5 cubic feet per minute per 100 pounds of grain continuously introduced through line 8E in direct contact with the `heated grain. The temperature of the grain is gradually increased while continuously passing air in contact therewith until the grain reaches a temperature not to exceed about 400 C. The rate of calcination is controlled to avoid fusion of the grain. Ordinarily, heating for about 6 hours will produce an infusible grain with the elimination of fusible residues.

The infusible grains are transferred via line 88 into activator 89 which may also be an externally heated retort provided with an inlet 9| for the introduction of an activating gas such as steam or flue gases and a vent gas line 92 at the other end for the discharge of gases from activator 89. Temperature of the order of 900l200 C. are employed to effect activation of the grain in activator 89 as is conventional in the art. The hot activated carbon grains are discharged from activator 89 through line 93. cooled by indirect heat exchange with water in cooler 94 and the cooled grain discharged via line 95 to conventional two-deck screen 98 for removal of any small amounts of fines or oversized particles, and the granular activated carbon product discharged from two-deck screen 96 through line 91 to loading platform 98 for shipment.

If it be desired to produce activated carbon for use in decolorizing liquid media it is simply required that the granular end product be pulverized to, for example, 80% passing a No. 325 sieve, prior to packaging.

If desired, other processes such as sulfurization, chlorination, reaction with oxidizing agents such as ammonium sulfate, solvent extraction, etc., may be used to increase the benzol-insoluble content of the pitch to within the preferred range prior to granulation, but air-blowing is economical and effective and, therefore, preferred. If the pitch charged to the process be above I15% in benzol-insoluble content (e. g.. a residuum from horizontal retort tar) the solid pitch may be fed directly to the granulator for processing.

The following examples illustrate the present invention for the conversion of pitch into granular activated carbons:

Example 1 A coal tar pitch having a melting point of 90 C. and containing 28% benzol-insoluble constituents was heated to 375 C. and maintained at that temperature during which time air at the rate of 1.0 cubic foot per minute per pounds of pitch was blown through the body of molten pitch. At the end of 41A hours the benzol-insoluble content of the pitch increased to 57%. The air-blown pitch while still in a iiuid state was roll and then crushed to 10-50 mesh size grain. This grain was digested batchwise at 100 C. for one hour with sufficient xylol to completely cover the bed of grain. Two additional similar solvent extractions of the grain with fresh xylol were made leaving a porous grain analyzing 80.6% benzol-insoluble. The grain was steamed to eliminate solvent therefrom and then air dried. The solvent extracted grain was then heated from a temperature below 200 C. to a temperature of 375 C. in an air stream of 2 cubic feet per minute per 100 pounds Ysubstantially all passing ograin.- for Vaperiod ofl hours.v The calcined grain was then activated* at 975 C. Vwith' steam toproducea highly active carbon. The activated carbonV product was oi such activity that 0.25 gram removed 88 of theiodine from the standard solution. Y

Example Z Example 3 Pitch from the same source as Example 1 was air blown'for a period'oi about 7 hours to increase the benzol-insoluble content of the pitch to 72%. anthracene salts were added to the molten air-blown pitch to give a benzol-insoluble content oi 57%. The resultant mixture was solidified in a pitch bay and crushed to grain of 6-14 mesh size. The grain was extracted in three batchwise operations with xylol, steamed to eliminate Example 4 ,Y Water-gas tar pitch of 200y F. melting point solvent therefrom and Yvalue of 80%.

f tent of the pitch increased to 72%.

8 benzol-insolubles, the proportions Vbeing 80 parts of the blown pitch to 20 of the straight run. The resultantJ blend analyzed 58% insolubles. After crushing to a 10-20 mesh grain, the pitch was extracted with xylol as in previous examples, calcined and activated. The activated grain was strong and hard and had an. iodine ing 32% Example 7 Y Coal-tar pitch from the same source as used in Example l was heated to 400 C. and maintained at that, temperature while air blowing for Y hours. The benzolinsoluble con- Moltenbituinen, obtained by solvent distillation from prior air-blown pitch extract, was added to the airblown pitch in sufficient quantity to reduce the beutel-insoluble content to The air-blown pitch blend was discharged to apitch bay, cooled, crushed, solvent extracted, calcined, and activated as described in Example 1 to produce a a period ci 71/2 strong granular activated carbon.

was air blown for 4 hours at 400 C. using l cc. i

air per gram per minute. The product hada benZol-insoluble content of '57 ing to 10-20 mesh, the pitchvwas extracted with xylol, steam-stripped of solvent and dried. Calcination with air for 41/2 hours within the range of 200 to 400 C. was followed by steam activation at 975"v C. Theproduct had an iodine value of 88%.

Example 5Y A water-gas tar pitclfi having a melting point of. 167 C. and containing 20% benZol-insoluble constituents was heated to 875 C. and air blown for 6 hours to increase the beutel-insoluble content to 52%. The molten pitch was .discharged from the blowing still into a pitch bay and al? lowed to cool. The solid-pitch was crushedszed by screening to 832 mesh; solventextracted in 5.leaches using counter-current procedures, the iirst contact conducted at 50 vent extract containing 7% of bitumen and the. final contact made at 110V C. with distilled solvent; calcined andactivatedwith steam in the same manner as described in Example l. The iinal activated carbon wasa strongcarbongrain, l0 mesh and retained on 48 meshand having a bull; density of 28 pounds,l per cubicfoot with anviodine value of' 88.5%.

Emample 6' Air blown coke-oven pitch oi` .65% benzolinV-' soluble content Y,was blended with a conventional colte-eventax1 pitch oi 217 F. meltingpoint'hav- After granulat.l l..

, retained on a No. 2e sieve. tracted with solvent, vsteamed and dried, after a sugar decoiorizing carbon. carbon removed 93.6%

C. with used sol- Erample 8 A residuurn obtained by distillation of oil-gas tarrhad a melting point of 125 C. Vand analyzed 42% insoluble in benaol.V After Yair blowing for 10 hours at 375-400 C. with 1. cubic foot per ton perhcur of air, the benzin-insoluble content had increasedY to 54.8%. This blow-n pitch was granulated to 10-20 mesh and extracted with xylol to give an extracted grain which, after solvent elimination and drying, analyzed %-bentoi-insoluble. After calcination in air by the procedure used in Exampie i, the grain was steam activated at 975 C. to a product having a bulk density of 0.340 gram per cubic centimeter and an iodine value of 88%.

Example 9 A blend comprising 35 parts of coke-oven tar pitch (melting point 296 E), 15 parts of Vbitumen recovered from extractsY from air-blown pitch and 12.5 parts of fines resulting from the crushing of airblown pitch was blown withair at 375 C. for 5 hours, rihe air-blown product, whichV analyzed 50% hemel-insoluble, was crushed andgradcd to pass a No. 8 sieve and be The. grain was exwhich it was calcined in airv at 250 to400 C. and nally steam activated at l050 C. The resultant product was pulverized and evaluated as 0.5 gram of this ard brown sugar solution. A highly active com--l meicial decolorizing carbon removed 92% of the color from this same solution.

Coal tar and coal-tar pitch. derived therefrom areV heavy hydrocarbons which may be termed a pyrogenous hydrocarbon condensate resulting romthe destructive distillation of coals. Water-V gas tar and watergas tar pitch derived therefrom and oilegas tar and oil-gas tar pitch derived therefrom are heavy hydrocarbons Vwhich may beterrned a pyrogenous hydrocarbon condensate resulting from the pyroiysis of petroleum at high temperature to produce predominantly gas.

rIhe term biturneras used in the appended claims shall mean the benZol-soluble components leached fromv the air-blown pitch in thev solvent extraction operation and subsequently recovered frornthe solvent extract asa distillation residue.v

The term hydrocarbon fiux as used in the ap` pendedclaims shall mean a compatiblel'iydrocar-l of the color from a stand- Y `is obtained.

bon material of the lower benzol-insoluble con'- tent than the air-blown pitch with which it is blended. Examples of suitable fluxes are normal pitches obtained by direct distillation of the tars, soluble bitumen recovered from the extraction of the blown pitch, heavy distillate oils, and salt components which crystallize out of creosote oil and other heavy coal-tar distillates;

Although certain preferred embodiments of the invention have been disclosed for purpose of illustration it will be evident that various changes and modifications may be made therein without departing from the scope and spirit of the invention. Y

I claim:

1. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate `contact with a molten pitch selected from the group consisting of coal-tar pitch, water-gas tar pitch and oil-gas tar pitch until said pitch has a benzol-insoluble content in excess of 45% and less than 65% by weight, thereafter and in sequence and without passing through the pul- -verulent state, cooling and reducing resultant molten pitch to solid form of granular size of between about 4-50 mesh, contacting the pitch granules with a solvent to extract the benzolsoluble components from the pitch granules thereby producing highly porous granules Without loss of particulate identity of the granules, and heating the resultantrgranules at regulated temperatures below the fusion point of the granules in the presence of oxygen-containing gas until an infusible activatable granular char 2. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate contact with a molten mixture of a pitch selected from the group consisting of coal-tar pitch, water-gas tar pitch and oil-gas tar pitch, and benzol-soluble components leached from airblown pitch until said mixture has a benzol-insoluble content in excess of 45% and less than 65% by weight, thereafter and in sequence and without passing through the pulverulent state, cooling and reducing the resultant molten mixture to solid form of granular size of between about 4-50 mesh, contacting the granules with 'a solvent to extract the benzol-soluble components thereby producing highly porous granules without loss of particulate identity of the granules, and heating the resultant granules at regulated temperatures below the fusion point of the granules in the presence of oxygen-containing gas until an infusible activatable granular char is obtained.

3. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate contact with a molten pitch selected from the `verulent state, cooling and reducing the molten mixture to solid form of granular size of between about 4-50 mesh, contacting the granules with a `solvent to extract the benzol-soluble components thereby producinghlghly porous granules without loss of particulate identity of the granules, and

lated temperatures below the fusion point of the granules in the presence of oxygen-containing gas until an infusible activatable granular char is obtained.

4. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate contact with a molten pitch selected from the group consisting of coal-tar pitch, water-gas tar pitch and oil-gas tar pitch until said pitch has a benzol-insoluble content in excess of by weight, admixing anthracene salts with the gastreated molten pitch thereby producing a mixture having a reduced benzol-insoluble content of between ll5-65%, thereafter and in sequence and without passing through the pulverulent state, cooling the mixture to solid form, grinding the solid to granular size of between 4-50 mesh, contacting the granules with a solvent to extract the benzol-soluble components thereby producing highly porous granules without loss of of the granules, and heating the resultant granules at regulated temperatures below the fusion point of the granules in the presence of oxygen-containing gas until an infusible activatable granular char is obtained.

5. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate contact with molten coal-tar pitch unt-il said pitch has a benzol-insoluble content within the range of l5-65% by weight, thereafter and in `sequence and without passing through the pulverulent state, cooling the resultant molten pitch to solid form, grinding the solid pitch to granular size to within the range of about 4-50 mesh," contacting the pitch granules with a solvent to extract the benzol-soluble components from the pitch granules thereby producing highly porous granules without loss of particulate identity of the granules, and heating the resultant granules in a stream of oxygen-containing gas to a temperature within the range of about 20C-400 C. until an infusible activatable char is obtained, regulating the temperature during such heating so that the granules remain in an unfused condition.

6. A process for the conversion of pitch into granules of activatable char which comprises passing an oxygen-containing gas in intimate contact with molten water-gas tar pitch until said pitch has a benzol-insoluble content within the range of ti565% by weight, thereafter and in sequence and without passing through the pulverulent state, cooling the resultant molten pitch to solid form, grinding the solid pitch to granular size to within the range of about 4-50 mesh, contacting the pitch granules with a solvent to extract the benzol-soluble components from the pitch granules thereby producing highly porous granules without loss of particulate identity of the granules, and heating the resultant granules in a streamof oxygencontaining gas to a temperature within the range of about 20G-400 C. until an infusible activatable char is obtained, regulating the temperature during such heating so that the gran- 'ules remain in an unfused condition.

gas tar pitch .leaching with vsolvent .in a

:agcsigeis contact with Vmolten l oil-gas tar lpitclfruntil said `pitch'has a benzolfinsoluble content 4Within the Yto solid form, grindingthe solid pitch to "granular size to Within the range of about 'x4-.'50 lmesh, -contacting the pitchl granuleswith a Lsolvent to extract the benzol-soluble components fromthe thereby producing highlyporous pitch granules granules without loss rof 'particulate identityvof Vthe-granules, andheating the'resultant granules in astream-of oxygen-containing gas `toa temperature within the `range Vof about 20`0-400-5C. .until an infusible activatable Achar is obtained, regulating the-temperature during 'such heating lsothat the granulesremain in lan unfused conn dition.

8. vAprocessior the conversion ofpitch into granular activated carbon-Which comprises pass- :ing astream of airin intimatecontactwvitha `molten pitch selected Yromthe group consisting -o coal-tar pitchywater-gas vtar pitch and oilmaintained at a temperature o'f about'300-400 C. until saidrpitch yhas a benzolinsoluble content withinthe range of Ll5-65% by weight, thereafter and in sequence and Without passing' through the pulverulent state, cooling the resultant` molten pitch tosolidform, grinding'the .t

solidpitch to granular size to Within'the range of about 4-50mesh, screening andseparating the `oversizeV and undersize particles from vthe 'groun'dxpitch leaching `theV pitch granules With- @inthe range of :about 4-50 mesh size with a predominantly Varomaticliquid solvent to extract' the benzol-solublev components frornthe pitch granules thereby fproducing lhighly porous vgranules Without loss 'of particulate identity of' the grannies, heating'the resultant granules in the stream of air toa temperatureY Withinv the'rangeof about 200=400'C, until an infusible activatable char is obtained regulating the temperature during suchheating-so that thegranules remain in an unfused-condition, and activating .the granular infusible char to produce activated carbon.

V9. A process for the conversion of pitch into granular activated carbon which comprisespassing 4a fstream Aof 'air .in intimate `contact' with a molten mixture of a pitchselectedffrom the group consisting of coal-tar pitch, Water'gastarrpitch 'and oil-gastar pitch, and benzin-'soluble com- .ponents leached from 'air-blown pitch, maintained' at a'temperature cfa-bout` 30G-400 C;' until `said mixture: hasV a bengel-insoluble content With- Vin ithe range of 45e-65% by weight, thereafter 'andiin'sequen'ce and Without passing through't'he pulverulent state, cooling the resultant molten mixture to solid form, grinding the solidtofgranular sizetovvithin the rangeof about 4450; mesh, screening andseparating the oversize and undersizeparticles from the ground solid, leaching the granules -Within the range or vabout 4 5() :mesh `size Vwith a predominantly aromatic liquid solvent `to `extract the Vbenzol-scluble components from the granules thereby, producing highly por- -ous granules Without loss of particulate identity ofthe granules, separating the dissolved benzolsoluble constituents -from the solvent, returning -therseparated benzol-.soluble constituents forzad- .mixture with additional pitch for conversion into the granules after stream vof -air to a temperature within the range .of about 200- 400 C. untilian infusible activatablechar .ischtained, regulating the temperature during such activated carbon, .heating heatng'rsothat the granules .remain ini-an .unllfused condition, arid activating the granular infusible charto produce activated carbon.

`l0. A` process for the conversion of pitch into 'granular activated carbon whichcomprises passing a stream of air in intimate contact with moltenpitch selected from the group consisting of coal-tar pitch, Water-gas tar pitch and oilgas tar pitch maintained at a temperature of about 30G-400 C. until said pitch has a henzelinsoluble contentwithin the range of i5-65% by Weight, thereafter `and in sequence and A Without passing through the pulverulent state,rc0ol ing the resultant molten pitch to solid "Vform, grinding the solid pitch to granular size to within'the range of about 4-50 mesh, screeningand separating the oversize and undersize particles Vvfromthe'ground pitch, returning the undersize Aparticles in admixture with additional coal-tar pitch to be subjected'to the action ofY a streamof `ain-.leaching Vthe pitch granules lWithin the range of about '4-.50 meshfsize Witha'solventrto extract the benzol-soluble components from the pitch granules thereby producing highly porous granules Without loss 'of particulate identity of the granules, 'heating Vthe 'resultant granules in a stream' oi? air to a 'temperature within the range of about 200e/NWC. until infusibl'eactivatable chariis obtained, regulating the-temperature 'duringsuch heating so'that the granulesrem'ainfin an unfused condition, and kactivating thefgranular infusiblechar to produce'activated carbon.

1l. A. process .for the conversion'ofpitch into Vgranular activated carbon Whicheomprises passing a .stream ci airlin intimate contact -with molten coal-tar pitch maintained at aitemperature ofabout 30G-400 C. 'until said pitch .has abenzol-insoluble contentin excessof 65% by Weight,blending anthracene salts with said-airvblown `molten pitch in an amount suiicient to reduce `the'benzol-insoluble content of the mixture to Within therange of45-65% byvveight, cooling the resultant mixture `to solid form; grinding the solid to granular'size to Within-therange of *about 4-50 mesh, screening, andrseparating oversize. and-undersize particles from 1 theground mixture, leaching the granules Within the range of :about ..4-50 mesh size with a predominantly .aromatic liquid solvent to extract vthe .benzol- -solublecomponents from the granules xthereby producing highly porous 'K granules `vc/'itl'icut vloss of particulate identity ofthe granules, heating the resultant granules in a stream .of air toa temperature Withinftheirange of about 20c-400 C. until an infusible activatable char is obtained, .regulating the temperature during suchheating so that theagranulesremain in'an unfusedzcondition, and activating the granular infusible char to produce activated carbon.

V12. A'process for the conversion of pitchinto fgranular 'activatedv carbon which comprises'pass- :ing a stream `of air in intimate contact with molten Water-gas tar pitch'maintained at atem- H perature of about 3D0-490 C. until said pitch "has a benzol-insoluble content'in excess of `55% Aby Weight, blending anthracene `salts with said 'air-blown molten pitch in an amount sufficient 'to reduce the 'benzolinsoluble content of Ythe mixtureto within therange of li5-:5'% by Weight, cooling the resultant mixture to. solid form, grinding the solid to granular size to within the range .of vabout `li-50 mesh, screening andrseparating oversize and undersize particlesfrom theground mixture, leaching the granules within the range of about 10-50 mesh size with a predominantly fused condition, and activating the granular aromatic liquid solvent to extract the benzolinfusible char to produce activated carbon. soluble components from the granules thereby producing porous granules loss References Cited 1n the fue of thls patent of particulate identity of the granules, heating 5 UNITED STATES PATENTS the resultant granules in a stream of air to a temperature Within the range of about 20D-400 buw M Name Date C. until an infusible activatable char is obonen July 16 1935 2,549,298 Donegan Apr. 1.7 1951 tained, regulatmg the temperature during such 2,624,112 Donegan Jan 6 1953 heating so that the granules remain in an unw

Claims (1)

1. A PROCESS FOR THE CONVERSION OF PITCH INTO GRANULES OF ACTIVATABLE CHAR WHICH COMPRISES PASSING AN OXYGEN-CONTAINING GAS IN INTIMATE CONTACT WITH A MOLTEN PITCH SELECTED FROM THE GROUP CONSISTING OF COAL-TAR PITCH, WATER-GAS TAR PITCH AND OIL-GAS TAR PITCH UNTIL SAID PITCH HAS A BENZOL-INSOLUBLE CONTENT IN EXCESS OF 45% AND LESS THAN 65% BY WEIGHT, THEREAFTER AND IN SEQUENCE AND WITHOUT PASSING THROUGH THE PULVERULENT STATE, COOLING AND REDUCING RESULTANT MOLTEN PITCH TO SOLID FORM OF GRANULAR SIZE OF BETWEEN ABOUT 4-50 MESH, CONTACTING THE PITCH GRANULES WITH A SOLVENT TO EXTRACT THE BENZOLSOLUBLE COMPONENTS FROM THE PITCH GRANULES THEREBY PRODUCING HIGHLY POROUS GRANULES WITHOUT LOSS OF PARTICULATE IDENTITY OF THE GRANULES, AND HEATING THE RESULTANT GRANULES AT REGULATED TEMPERATURES BELOW THE FUSION POINT OF THE GRANULES IN THE PRESENCE OF OXYGEN-CONTAINING GAS UNTIL AN INFUSIBLE ACTIVATABLE GRANULAR CHAR IS OBTAINED.

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