T H E O D O R E S . P O L A N S K Y A N D C O R L IS S R . K IN N E Y T h e P e n n sylva n ia Sta te
in i n v e s t i g a t i o n o f t h e s o l v e n t e x t r a c t i o n o f t h e h u m i c
; i d - l i k e p r o d u c t s f r o m n i t r i c a c i d - t r e a t e d b i t u m i n o u s j a l le d t o t h e d is c o v e r y o f a l a r g e v a r i e t y o f a c t i v e o r g a n i c j lv e n t s a n d s o l v e n t m i x t u r e s . M a n y o f t h e s e e x t r a c t 80
> 8 5 % o f t r e a t e d c o a l , a n d le a v e b e h i n d t h e m i n e r a l m a t -
;r a n d f u s a i n i n c o a l . T w o p r o m i s i n g c o m m e r c i a l m e t h - ds w e r e d e v e l o p e d , b a s e d o n t h e u s e o f a q u e o u s m i x t u r e s f o r g a n i c s o l v e n t s a n d o n m i x t u r e s o f lo w b o i l i n g s o l v e n t s f s i m i l a r b o i l i n g p o i n t .
D
U M IC acidlike products, w hich are sim ilar to th e n a tu ra lly occurring hum ic acids, are readily obtained from oxidized itum inous coal by extraction w ith alkali ( 1 ) . Since th is effects separation of m ost of th e organic m a tte r from th e m ineral la tte r and fusain in a coal, th e process has com m ercial possi- ilities as a s ta rtin g p o in t for th e production of carbon chemicals, 'he use of alkali, how ever, is expensive, since alkali m u s t be eutralized to lib erate th e ex tracted hum ic acids. T h e extraction I th e hum ic acids by organic solvents w hich m ay be recovered asily an d re-used w ould lower th e cost. W ith th is in m ind, Fuchs iatented th e use of furfural and heterocyclic oxygen com pounds 2). F urfural, however, can n o t be recovered q u a n tita tiv e ly for e-use. D istillation of th e e x tra c t leaves considerable polym er- zed an d condensed furfural adsorbed on th e residual hum ic acids, iven in a high vacuum . T h e add itio n of several volum es of iso->ropyl e th e r to th e furfural solution will p recip itate th e hum ic tcids, b u t several per cen t of furfural rem ain firmly adsorbed on
>r possibly com bined w ith th e hum ic acids. T h is can n o t be vashed off w ith additional isopropyl eth er b u t can be rem oved iy prolonged steam distillation. Because of th ese difficulties in
;he use of furfural, an d because it seem ed probable th a t o th er sol
vents could be found w hich w ould h ave b e tte r properties, a sys-
;ematic search of th e whole field of organic solvents w as m ade.
This w as fu rth er encouraged by th e observations of M arcusson U), Francis an d W heeler ( 1 ) , an d Sm ith an d H ow ard (5) on th e solubility of hum ic acids in acetone, pyridine, a n d catechol, re
spectively.
C ollege, S ta te College, Pa.
T R E A T M E N T O F COALS
Tw o sam ples of n itric a c id -tre a te d coals were used. Coal A w as a sam ple of high volatile A b itu m in o u s coal ta k e n from th e U pper F re e p o rt seam in In d ia n a C ounty, P a. Coal B w as a sim ilar coal o btained from bo th th e U pper an d Lower F reep o rt seam s m ined to g eth er in Clearfield C ounty, P a. Analyses of the coals ap p ear in T ables I an d II.
Coal A was preoxidized an d th en tre a te d w ith n itric acid ac
cording to procedures 2, 3, an d 4 described by Fuchs, Polansky, an d Sandhoff (S). T h e coal w as passed th ro u g h th e ro ta ry furnace eleven tim es in procedure 2. P ro b ab ly th e coal did n o t reach th e tem p e ra tu re of th e furnace, 350° C., since it tlid n o t ta k e fire. In th e n itric acid tre a tm e n t, lots of 500 gram s were tre a te d w ith 750 ml. of co n cen trated n itric acid. A fter being washed free from n itric acid, th e tre a te d coal w as air-dried.
F in ally th e individual batches were thoroughly mixed a n d stored in a screw -capped b o ttle. Coal B w as preoxidized according to procedure 1 ( 3 ) a t 150° C. for th ree weeks. I t w as th e n treated in lots of 500 gram s w ith 1250 ml. of concentrated n itric acid, according to procedure 4 (3). A fter washing, air-drying, an d thorough mixing, th e p ro d u ct w as also stored in a screw-capped b o ttle. Analyses of th e different pro d u cts of th e coals ap p ear in T ables I an d II.
Q U A LITA TIV E SO L U B IL IT Y T E S T S
T h e search for active solvents for th e hum ic acids w as m ade using tre a te d coal A. T he procedure used to estim ate th e ac
tiv ity of th e solvent w as as follows: A bout 0.1 gram of th e tre a te d coal w as placcd on a w atch glass an d covered w ith 10 nil. of the solvent. If red-brow n stream e rs im m ediately appeared flowing o u t from th e tre a te d coal particles, th e solvent w as considered to be highly activ e. U pon stirring, a deep red-brow n solution was o btained im m ediately. W ith som ew hat less activ e solvents, the particles of coal seem to swell or soften, b u t no color stream ed out from th e coal. U pon stirring, how ever, th e sam e deep red- brow n color w as obtained, b u t a longer tim e w as required to
at-Ta b l e I. An a l y s i so f Co a l A a n d Pr o d u c t s
P roxim ate U ltim ate Calorific
Condi- Mois Volatile Fixed H ydro N itro
Sulfur Oxygen Value,
Sam ple tion° ture m a tte r carbon Ash Carbon gen gen B .t.u ./L b .
Raw coal 1 0 . 8 2 9.9 6 2.5 6 . 8 80.1 5 .1 1.4 1 . 0 5 .6 14,175
2 30.1 63 .0 6 .9 80.7 5 .0 1.4 1 . 1 4 .9
3 3 1.3 68.7 86.9 5 .3 1.5 6 .3
Air-oxidized coal a t 350° C. (passed 11 1 Ö. 3 2 8 .8 6 3.5 7 .4 7 3 .8 3 .2 1 .9 i ‘.ö 12.7 11,500
tim es through furnace) 2 2 8.9 63.7 7 .4 74.1 3 .2 1.9 1 . 0 12.4
3 30 .5 6 9.5 8 1.0 3 .4 2 . 1 * 13.5 ■
N H *N O j-treated coal (air-oxidized 1 2 . 4 2 6.4 63.9 7 .3 7 2.0 3 .5 2 .7 Ö. 9 13.6 11,735
coal treated with N H4NO* a t 150° 2 2 7.0 6 5.5 7 .5 73.7 3 .3 2 . 8 0 .9 1 1 . 8
C -) 3 2 8.5 7 1.5 SO. 6 3 .5 3 .0 12.9
H N O i-trea ted coal (NH<NOj coal 1 7 .7 46 .8 3 9.7 5 .8 5 3.6 2 . 8 4 .0 6 . 4 3 3.4 8,075
treated with HNOa a t 90-100° C.) 2 50.7 43.1 6 . 2 5 8.0 2 . 1 4 .4 0 .5 2 8 .8
3 5 3.8 4 6.2 62.4 2 . 2 4 .7 30.7
Humic acids (extracted by furfural and 1 9*5 54.7 34.4 1.4 5 9.8 2 . 6 3 .6 Ö . 4 3 2.2 9,830
precipitated with isopropyl ether) 2 6 0.5 3 8 .0 1.5 6 6 . 1 1.7 3 .9 0 .5 2 6.3
3 61.3 3 8.7 6 7.4 1.7 4 .0 27.9
Air-oxidized coal (raw coal oxidized in 1 0 * 2 34.3 5 8 .8 6 .7 69.6 2 . 6 1.5 0 .9 18.7 10,255
oven a t 150° C. for 21 days) 2 34.4 58.9 6 .7 69.7 2 .5 1.5 0 .9 18.7
3 3 6.3 63.7 75 .5 2 .7 1 . 6 2 0 . 2
0 1 — as received, 2 *» m oisture-free , 3 » moisture- and mineral- m atter-free.
925
926 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 39, No. 7 single solvents, b u t, since th e single solvents are indicative of the kind of substances th a t are active, th e y are listed in T ab le II I.
Among th em are representatives of th e acids, aldehydes, alcohols, am ines, amides, esters, phenols, an d n itro com pounds. Over solvents, benzene, various esters, and carboxylic acids. All of th e m ixtures contain either w ater o r an alcohol as one co n stitu en t.
2. Benzyl alcohol (satd. with 7. T etrahydrofurfuryl alcohol 3.
water)
E thylene diam ine 8. T riethanolam ine ethyl phos
4. E thylene glycol monobenzyl phate
ether 9. T rieth y l phosphate
5. Form am ide 10. T rim ethyl phosphate
El e v a t e d Te m p e r a t u r e aliphatic an d arom atic aldehydes, am ides, am ines, esters, halides, ketones, nitriles, an d n itro com pounds.
A liphatic or arom atic hydroxy compounds A liphatic or arom atic ketones
A liphatic or arom atic nitriles A liphatic or arom atic n itro compounds Alicyclic or heterocyclic aldehydes or ketones W ater
g-ly 1947 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 927
C onsiderable h e a t w as evolved when m oist solvents were added to th e dried, tre a te d coal. H e a t w as also evolved when th e h u mic acids ex tracted from b o th tre a te d coals w ere dried a t 110° C.
for 2 hours a n d th e n tre a te d w ith m oist solvents. Solvents such as acetone-w ater, acetonitrile-w ater, form am ide-w ater, m ethyl a c e ta te -m e th y l alcohol-w ater, an d e th y l alcohol (95% ), were
tone— th e residue w as dried before w ashing w ith acetone.
928 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 39, No. 1 additional solvents w ere n o t studied. T h e residue is largely com
posed of m ineral m a tte r, fusain, an d probably som e unoxidized doubly or trip ly bonded oxygen or nitrogen com pounds are highly effective. A liphatic chains should be as sh o rt as possible and
cohol and m ake active solutions. P robably aro m atic compounds are more active th a n th e alip h atic analog of th e sam e num ber of eith er observed or predicted, higher th a n 30 dynes per centim eter a t 20° C. F urtherm ore, all of th e com pounds w hich were found to be active in m ixed solvents have surface tensions higher th a n 20 dynes. On th e o th er hand, n o t all com pounds having favors solvation followed by dispersion of th e solvated molecules.
C O M M ER C IA L EX TR A CTIO N O F H U M IC ACIDS m ixtures m axim um extraction is-Obtained a t som ew hat lower con
centrations, b u t it is doubtful w hether th is w ould offset the
Anhydrous m ethyl alcohol + ethylene chlo
ride No. 2 ,1 :1
July 1947 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 929
F i g u r e 1. E x t r a c t i o n o f I l u r a i c A c id s f r o m C o a l w i t h W a t e r M i x t u r e s C o n t a i n i n g A c c t o n c , A c c l o n i t r i l e , o r . E t h y l A lc o h o l
greater initial cost of acetonitrile an d its loss th ro u g h hydrolysis.
Ethyl alcohol-w ater solutions could be used also in extraction processes, b u t th e yields w ould be less.
T he acetone-w ater solvents used in T ab le V can be calculated to contain over 15% hum ic acids. T h is is a b o u t th e m axim um con
centration t h a t can be centrifuged an d filtered satisfactorily.
More concentrated solutions m ay be m ade readily b u t are m uch more difficult to handle because of th e finely divided fusain and mineral m a tte r. Based on these observations, th e a m o u n t of acetone required per ton of raw coal w ould be a b o u t 800 gallons.
This is based on a yield of n itric a c id -tre a te d coal of 1.1 tons, th e use of 60% acetone solution, an d ex tractin g in a co u n tercu rren t or sem icountercurrent batch procedure. T h e yield should be about 85% of th e tre a te d coal, or 0.93 to n per to n of raw coal.
The yields arc also dep en d en t upon th e e x te n t of th e reaction with nitric acid (S).
A nother procedure for th e com m ercial ex tractio n of th e hum ic acids 1s based on th e use qf low boiling organic solvents of sim ilar
boiling points, w hich w ould m ake re
covery of th e solvent .very easy.
Several m ixed solvents of th is kind were found w hich h av e high so lv en t power for th e hum ic acids. F o r exam ple, a m ixture of 9 5% eth y l alcohol, ben
zene, an d acetonitrile in a ratio of 2 :2 :1 gives a high ex tractio n yield.
T hese com pounds boil a t 78.5°, 80.1°, an d 82° C ., respectively, an d probably would n o t undergo m arked separation on distillation. Tw o o th er m ixtures are 9 5% ethyl alcohol, benzene, and ethylene dichloride an d alcohol, ben
zene, a n d ethyl acetate, b o th m ixtures in a 2 :1 :1 ratio . T hese m ixtures should be used to e x tra c t tre a te d coal dehy
d ra te d to a b o u t 10% m oisture. Since th ey to le ra te little w ater, m ore solvent m u st be used th an w ith th e aqueous solvents described previously. How
ever, th e hum ic acids produced by these solvents w ould be d ry ; th is w ould offset th e prelim inary dry in g of th e tre a te d coal. Also th e q u a n tity of m ineral m a tte r dispersed along w ith th e hum ic acids by the nonaqueous organic solvents is u su ally less th a n w ith aqueous solvents.
In com parison w ith furfural, b o th th e acetone-w ater an d the volatile solvents are more easily and q u a n tita tiv e ly recovered.
F o r th ese reasons th eir use w ould be preferred to th a t of furfural.
L IT E R A T U R E C IT E I)
(1) F ran cis, W „ and W heeler, R . V .. J . Chem. Soc., 127, 223G (1925).
(2) F uchs, W „ U . S. P a te n t, 2 ,242,822 (M a y 20, 1941).
(3) F uchs, W ., P o la n sk y , T . S ., and Sandhoff, A . G., I n d . E n g . C h e m ., 35, 343>(1943).
(4 ) M arcusson, J., Chem.-Ztg., 42, 437 (1 918).
(5) S m ith , It. C ., and H ow ard, H . C ., J . A m . Chem. Soc., 57, 512 (1 935).
P r e s e n t e d before the Division of Gas and Fuel. Chem istry a t the 109th M eeting of tho A m e r i c a n C h e m i c a l S o c i e t y , A tlantic C ity, N . J.