T"

I S D C S T R I B L AAYD EJVGIA~EERISGCHEIIIISTRY

December, 1929

fermentation rids the pomace of sugar, so that pectin extracts of high pectin content and low sugar content can be prepared. Hydrolysis of pectin by P. glaucum was more rapid in media of p H 6 and 5 than in one of p H 3. This is in keeping with the finding of ivilson (11) and others that pectin iS more stable in solutions of moderately low p H value than in t'hose of high p H value. stock solution, is not Dextrose, when present in a altogether objectionable, as i t has a protective effect against the hydrolysis of pectin by P. glauc?on. This effect would probably apply to other organisms.

1295

Literature Cited Physiol., 12 379 (1926). Davison and Willaman, Botan. Gaz., 83, 329 (1927). Hardy, Biochem, J , , 18, 283 (1921), Jones, x, Y.Agr. Expt. Sta., Tech. B U L L 11 (1909). Myers and Baker, Delaware Agr. Expt. Sta., Bull. 149 ( 1 9 2 i ) . Ohn, IXD. END.CHEJI.,18, 1295 (1926). Sin&, Master's Thesis, University of California, 1922. ( 8 ) Sucharipa, J . Assocn. O f i c i o l Agv. Chem., 7, 57 (1923). (9) Wichmann, Ibid,, 8 , 123 (192j), (10) Willaman, ~ o t u n Gaz., . 70, 221 (1920). (11) Wilson, IND. E x . CHEM.,17,1065 (1923).

(l)

(2) (3) (4) (5) (6) (7)

Benzene-Pressure Extraction of Coal' J. I). Davis and D. A. Reynolds PITTEBL-RCH EXPBRIJIBNT STATION, U. S. R U R B A U O F MINBS, PITTSBURGH, PA.

T"

'REE years ago the writers investigated the coking

properties of two coals, following in general the method of benzene-pressure extraction developed by Fischer (6) and his associates. Our conclusions (S),drawn from this investigation, were not in agreement with those of Fischer, and, because our study had included only tmo coals, further study of additional coals was necessary to support those conclusions. The later investigation, herein described, includes the study of six coals, each representati1.e of a distinct type as regards industrial carbonization. Nature of Coals Tested

Table I gives proximate and ultimate analyses of the coals tested. a n d U l t i m a t e Analyses of Coals Extracted on As-Received Basis

Table I-Proximate

1 c0.4L

I

PROXIMATE

'

la- Fixed iMois-'t?k car- Ash ture matter bon

1%

70

%

1

ULTIMATE

H

701%

C

N

0

S

70

%

%

70

Ash I3.t.u.

R

Mesa Verda 3 . 4 4 2 . 9 4 6 . 2 7 . 5 5 . 6 69.9 1 . 4 1 4 . 8 0 . 8 7 . 6 12,790 IllinoisNo. 6 7 . 4 3 5 . 5 52.fi 4 . 5 5 . 8 7 1 . 5 1 . 6 l 5 , 2 1 . 4 4 . 5 12,760 Lower Kit1 . 6 2 5 . 3 63.R 9 . 6 4 . 9 7 7 . 5 1 . 4 4 . 6 2 . 0 9 . 6 13,730 tanning Pratt Pittsburgh

1 . 0 2 9 . 2 5 9 . 6 1 0 . 2 5 . 1 7 6 . 3 1 . 6 6 . 0 0 . 8 1 0 . 2 13,640 1 . 4 3 4 . 2 5 8 . 3 6.1 5 . 4 7 5 . 8 1 . 7 6 . 8 1 . 2 6 . 1 14,160

The Mesa Verda coal is weakly coking and not adaptable to by-product coking. Illinois No. 6 coal is a moderately coking coal which may be coked under suitable conditions. Lower Kittanning coal represents about the lower limit in volatile content in coking coals, as charged to by-product ovens, in the United States. Ruhr is a coking coal and was used by Fischer in his study of this problem. Pratt coal is representative of the medium volatile coals yielding good metallurgical coke. Pittsburgh coal represents the high-volatile coking coals; this sample comes from a portion of the Pittsburgh bed characterized by a lower oxygen content than that sampled for our previous investigation. Experimental Method

The method of extraction with benzene under prcssure and separation of the extract into oily and solid bitumens was the same as that described by Fischer and used by us in the previous work. Briefly, the procedure is as follows: Presented before the Dixicion of Gas and Fuel Chemistry at the 78th Meeting of the .4merican Chemical Society, Minneapolis, 3Iinn September 9 to 13, 1929 J

Dry 400 grams of 6- t o 10-mesh coal "as received" by distilling from it 600 cc. of benzene. Charge this sample with 1000 cc. of benzene in a cylindrical autoclave placed in a swinging, electrically heated furnace. Raise the temperature to 285" in one hour and continue heating 4 hours a t that temperature. After cooling, filter off the benzene solution, add fresh benzene, and repeat the extraction. Free insoluble residue and extract of solvent by warming in vacuo. fieparate the extract into oily and solid bitumens by pouring a concentrated benzene solution of the extract into a large e x c ~ s sof petroleum ether (b. p . 30-60" C.), whereupon the solid is precipitated and the oily bitumen remains in solution. An important point not mentioned by other investigators and noted early in this work was the increase in hardness of the extract with successive extractions. For this reason the total extract from each sample TTas combined and the separation into oily and solid bitumens was made on R sample representative of the whole Separation of the individual extracts obtained from repeated extraction of the same sample showed that the proportion of solid bitumen increased with the duration of extraction. I n other words, oily bitumen is more readily removed from the coal by benzene-pressure extraction. Ruhr coal extracted the first time yielded a n extract containing 51.7 per cent of solid bitumen, whereas the third estract contained 82 3 per cent. Lower Kittanning coal yielded nearly pure solid bitumen from the seventh extraction. This increase in the ratio of solid to oily bitumen with continued extraction readily accounts for the increase in the hardness of the extract noted. I n addition to the three fractions (insoluble residue, oily bitumen, and solid bitumen) obtained by the method outlined, a fourth fraction not mentioned by other investigators was noted in this work. Upon cooling the autoclave, the substance precipitated upon the granules of coal and the autoclave walls. This substance, a brown powder similar t o solid bitumen, will be referred t o as "insoluble" bitumen. The writers modified the previously outlined procedure by filtering the solution of extract from the coal before cooling, thereby permitting the insoluble bitumen to precipitate out of contact with the coal. I n this manner it was readily recovered. Results of Extractions

Extractions were continued until the yield of soluble substance obtained during a 4-hour extraction did not exceed 0.5 per cent of the coal (moisture- and ash-free basis). Table I1 gives the yields of the extracts obtained, together Tvith other extraction data.

Vol. 21, s o . 12

XNEEIZIIVC CHL#E.1lIS?'RY

Cram* 267 335 Lower K i i f i " ~ niog 3.55 Riihr 870 Prati 3.52 I~iltubuiiih 370

hfeslvcidl lilinokn'o.

6

N O . Hours

3 4

4 4 4 4

8 IX 0

1X.5

17.0 1x:i IS5

G"or( A ) , IIoffrnanii (!i andTwanda ), (9)olita.incd apprriuiinilt,cly equal amourrt,s of oily and solid hit,umeiis from liig1ii.r rank coals. 1)arnni ( 8 ) has obtsinrd a larger proportion of the solid Miinien t,lint approximates tlie yielrle reoor~ledIicrciii

The effect of the extraction upon Lower Kittanning and Pittsburgh coals was most surprising in that their swelling was very definitely increased. Tlii?writers had neither noted a similar result in their ow11 experiments nor liad they read of it in tlie work of other invest,igators. In the miters' previous investigation the standard volatile matter test of the A. S.T. >I. was used in nraking these crueihle tests. Subsequently Fischcr has suggested that our failure to obtain swelling might he due to this method of heating. Our study of the Xuck and A. 6. T. $1. niet.tiods has shown that tile former metllrid, wiiercin tiie crucible is heated in the flame of the liitnsen buriier, is iliiurc conducive to smlling. Ttiwefore, the hluck method \\'as adopted for this investigai,ion. We believe t,liat this method is not ge~ierallyas good as the A. S.T. hl. method bccau owing t o tiie variat,ion ilr hurriers, gas pressures, atid quality of gases among ilifTercnt laboratories, it is exceedingly difhult, if not impossible, to duplicate heating conditions hy any method io\wlviiig the use of direct heating in a Ixtrncr flame. Additional Extraction of Lower Kittanning and Pittsburgh Cod8

To reduce Imver Kittaiiiiiiig and Pittsburgh coals to anonswelling state they were subjected t o further extraction. The former was extracted three times for a total uf 0 lioiirs alii1 was rendered non-swelling. Pittsburgh coal was subjected t o two 5-hour extract.iuns, with the result that tlie residue swelled fully as rnucli as the origiilral coal. Figure 3 shows these results and Table 4 gives the yields from tliese estractions. Table IV-Additionnl

Renzenc-Presaure Extractions of Lower

Kittannine. and Pirfsbvrgh Coals

'TOTAL

TRAF. l,DNS

Biaure 1 Crucible Cokes of the Oriainal Coals 2-IiIiriois No. 6: 3-Lower Kittaeniep: 4 - K u h i : 5-~Prrit: G---Pittsburiili

Lower Kittanning Piftrhiirgh

No. 3 2

Yih.i.n

Lerolu. sol"ble

Y,"D

I - - M e s i \'eida;

Cockram and Wlieclcr ( I ) RISO foutrd a largcr prqmrt,ioIl ,jf their extract to be insoluble in light. petrole~~nr, althougli the British coals used by these w r i t m give lower yields hy this method of extraction than do Ainericau coals. The physical properties uf the e m i s were altered greatly by the extractioti. Tlie granules lost their luster arid I w c a n ~ eso friable that they were readily crushed with the fiugcrs. A comparison of the analyses nf the cstracted imals (Talile 111) with tliosc of the original coals (l'able I) slim-s that tlie benzene-pressure extraction brings nhout tlic following: (1) a reduction iii wlat,ile ix,iitcnt; ( 2 ) a redui:i.ii,n in oxygen cotitelit; and ( 3 ) iio appreciable ~:liaiigeiii 1iitrogi:ii coiitmit.

TiON ]'it.

ble

fofd

Elours Grams Grams Gromr 0.6 .i.o 3 . 6 I: 3.6 2.8 6 . 4 ~

vtrro

01 ALI.

I

9;

%>

1.68 1 73

12.05 16.13

Judging from the low solubility of the residual bitumens in these coals, i t appeared to be impossible t.o destroy their caking properties entirely by this method of extraction. To

Table I I I ~ - P r ~ x i m a f eand lilflmute Analysra of Coals after Extraction (As-Received Rarirl

Figure Z~-Crvcible Cukes from Extracted C o d e ?--hiua

N ~ e: . n . - - ~ o r e r~ i i i n n n i ~ ~iog :- R ~ I , ~ ; ll~-Pratt: 12-Pittsb"rgb

vcrda: 8-iiiinoiS

reduce Pittsburgh coal to a nun-swelling state, extraotians with pyridine were made, using a contitroous extraction a p paratus described l,y h I i t x i d ( 7 ) . Irsing the original I'ittsburgh coal, the yield from t,lic first pyridine extraction was 15.9 per miit, wliidr is approsiinately tlie sanie as the yield from six Ijenzciie-pressure extractions. In this case, also, tlie residiinl coal had stronger swelling properties tliaii the iintreatrid coal. A second pyridine extraction of this saiirple hrought the t,otal yield of extract up to 25.4 per (:cut. The rcsidue was iio longer s~vellingbut gave a coliercnt Gut,tori. Figure 3 shows t,lie effect of additional estractiuns of these coals 011 their swelling properties. 1,uwer IGttariiiing coal became tion-swelling after seven cxtractirrns with lienaene which reiiiovcd 1%per cent soluble substance. Pittsburgh