c
Solvent Extraction of Humic Acids from Nitric Acid-Treated Bituminous Coal THEODORE S. POL,INSKY AND CORLISS R. KINSE'I' T h e Pennsylcania S t a t e College, State College, Pa.
An iiire3tigation
acid-like products from nitric acid-treated bituminous coal led to the disco*er? of a large \ariet> of actibe organic sol\ents and solkent mixtures. \Ian) of these extract 80 t o 85yc of treated coal, and lea\e behind the mineral matter and fusairi in coal. THOpromising commercial methods were deieloped, based on the use of aqueous mixtures of organic solTents and on mixtures of low boiling sol\ents of similar boiling-point.
H
TREATMENT O F COALS
of the sol\ent extraction of the humic
I-MIC acidlike products, \\-liicli are similar t o the naturally
occurring huniic acid3, are readily obtained from oxidized bituminous coal hy extraction n.ith alkali ( 1 ) . Since this effects ;I. sep:iration of moat of tlie organic matter from the mineral matter and fusain in a coal. the process has commercial pos-ia starting point for the production of carbon chemicals. T h e use of alkali, however, is expensive, since alkali must be neutralized to liberate t h e extracted humic acids. The extraction of the humic acids by organic solvents n-hich may be recovered easily and re-used Lvould lower the cost. With this in mind, Fuchs patented the use of furfural and heteroc>-clicoxygen compounds ( 2 ) . Furfural, however, cannot he recorered quantitatirely for rc-ure. Distillation oi the extract leave3 conqiderable polymerized and condensed furfural ad-orbed 011 the re,qidual humic acids, even i n 8 high vacuum. The addition of several volumes of isopropyl ether t o the furfural solution \vi11 preciliitate the liuniic avids, but several per cent of furfural reinaiii firmly adsorlied on or pihihly combined x i t h the humic acids. Thi. cannot be nxslied off \\-it11 additionid isopropyl ether but c ~ i ibe removed tiy prcilringed s t e m i di~tilltitioir. Uecau-e oi these tlificultie:. i n tlic 11-P ( i f fui,furd. a n d I ) ~ ( . a u rite *eenied pi;ohhle that other m1vrnt. could I)? found \\-liic.h \vould have lietter propertie., ii tc~iiiiiti(j ~ m r c hof t h e \\.hole field of organic solvent 1l i i , - \\-:I- f u i they enc,oui,azctl by tlie ol)-er\-ations o 1 i ) . F ~ n r i and Klieeler (I!, :ind Smith aiid Hon-urd i.? on tlir ~rilul)ilityc i i humic :icitl. in acrtone, pyridine, and catechol, I C .Iwi,ti\-i~iy.
-.
Two samples of nitric acid-treated coals were used. Coal A was a sample of high volatile -ibituminous coal taken from the l-pper Freeport seam in Indiana County, Pa. Coal I3 was a similar coal obtained from both the Upper aiid Lower Freeport seams mined together i n Clearfield County, Pa. AnalyseP of the coals appear in Tshles I and 11. Coal d was preoxidized and then treated with nitric arid according t o procedures 2, 3, and 1 described by Fuchs, Polansky, and Sandhoff (5'). The coal was p a s e d through the rotary furnace eleven tinies in procedure 2. Prohably the coal did not reach the temperature of the furnace, 350" C., since it did not take firr. In the nitric acid treatment, lot9 of ROO grams \\-ere treated n-ith 750 ml. of concentrated nitric acid. .ifter being washed free from nitric arid, t h e treated coal \\-as air-dried. Finally tlie individual hatehe? n-ere thoroughly mixed and stored in a screw-capped hottle. Coal B n-as preoxidized according t o procedure 1 13) a t 150" C . for three weeks. It was then treated in lots of 300 grams \\-ith 1230 ml. of concentrated nitric acid, according to procedure 4 (3). After \\-ash:ng, air-drying, aiid thorough mixing, the product \vas also stored in a scre\\--c:ipped bottle. .inalyses of the different products of the coals appear in Tables I and 11. QUALIT.ATIVE SOLUBILITY TESTS
The search for active solvents for the humic acids i v i i ~made using treated coal -4. The procedure used to estimate the activity of the rolvent waq a~follo\i-s:.$bout 0.1 gram of tlie ti.eatec1 coal n-as placed on a watch gla- and covered ivitli 10 nil, ot t h r solvent. If rrcl-l)ro\\-n stremier.: immediately :Lppe:ired flii\\-iiiq out from the treated c d particles, the rolvent \v:~.s coiisidei.pd t o be highly active. 17poii stiri,ing, a deep reil-l)rin\-li -elution \v:iG olitained iniiiietliatel~-. VYth wniewlint le- ai>tive-ol\-wt-, t l ~ c partirlrs ~f co:il seem to -\veil or d t e n , h u t iio color stiwnicyl out from the coal. I-poii stirt.iiiq, however., the WIIP tlcc!~ 1.c~1IJroum volor I\-:L- oiitaiiied, h i t :I loiigcr tiiiie I Y ~ Yr q u i i i d t i l :it-
O b
2
..
6 8 6 9
1
0 3
7 4 7 4
7 :i 7 5
1
:1 1
' 4
3 1
-( -,
:i
...
..
5 s
, . .
6 "
9 5
2 3
..
1.4 1 3
1
0 2
6 7 6 7
1
3
1 4
.iti 4 'I
INDUSTRIAL AND ENGINEERING CHEMISTRY
926
TABLE 11. AXALYSISOF COALB Saniple Raw coal
Condition"
1 2 3 1 2 3 21
*
Moisture 0.9
..
Proximate Volatile Fixed m a t t e r rarbon 30.8 601 31.1 60.6 82 9 67.1 29 4 58.1 30.6 604 32 8 67.2 69.6 9.5 77.4 10.6
AND
Ash 8.2 8.3
.. 86.6 Air-oxidizedcoal(rawcual i:8 8 7 66.9 oxidieed i n oven a t 150' .. 9.0 69.6 C.f o r 21 days) 77.7 HN O a t r e a t ecoal d coal (air1O:l 10:8 47.9 oxidized treated .. 12.0 53.3 yiLh H S O a a t 90-100° 3 .. 879 12.1 .. 61.4 C.) Humicacids (extracted,by 1 6.8 54.1 37.9 1.2 56.5 furfural a n d preclpl2 58.0 40.7 1.3 60.1 t a t e d with isopropyl 3 .. .. 58.6 41.4 .. 61.1 ether) a 1 = a s received, 2 = moisture-free, 3 = moisture- a n d mineral-matter-free.
tain the same depth of color. Still less active solvents gave less deeply colored solutions. Using these qualitative color tests, over 250 aolvents were discovered which appeared t o extract the humic acids from the nitric acid-treated coal in high yield. Relatively f a r - of these were single solvents, but, since t h e single solvents are indicative of the kind of substances t h a t are active, they are listed in Table 111. Among them are representatives of t h e acids, aldehydes, alcohols, amines, amides, esters, phenols, and nitro compounds. Over half of them are aromatic derivatives, but a considerable variety of aliphatic compounds are also active. I n general, t h e higher members of t h e aliphatic series lose their activity as the chain is lengthened. I n a like manner, alkyl groups tend to decrease the effectiveness of aromatic compounds. Many other substances were found which were able t o disperse a part of the humic acids but unable t o extract all of them, no matter how much solvent was used. -4large number of these were improved by adding other substances, and it was soon discovered t h a t many more solvent mixtures had high solvent poxer for the humic ahids than did individual compounds. These are classified in Table I V according to the number and types of solvents present in t h e mixture. The binary mixtures are subdivided into three maih groups which contain either acetone, alcohol, or water as the characteristic or basic solvent. The ternary mixtures contain, in addition t o these, three other basic solvents, benzene, various esters, and carijoxylic acids. All of the mixtures contain either water or an alcohol as one constituent. With the acet,one-alcohol mixtures in section 4,1-a, of Table IV, more complex alcohols such as benzyl alcohol, cyclohexanol,
TABLE
111.
I N D I V I D U A L SoLVEXTs
water) 3. Ethylene diamine 4. Ethylene glycol monobenzyl ether 5. Formamide
6.
Ultimate Hydro- Kitrogen gen Sulfur 5.0 1.3 0.8 4.9 1.3 0.8 5.3 1.4 3.2 1.3 113 2.9 1.4 1.4 3.2 1.6 2.6 2 .8 0:i 1.7 3.1 0.3 1.8 3.6 ..
.4.
Binary mixtures
1. Acetone mixtures a. b.
2.
Furfural
Ethylene glycol (100' C . ) Glycerol (140' C.) Hydroquinone (172' C . ) Sitrobenzene (150" C . ) Phenol (110' C.) Pyrogallol (135' C.) Resorcinol (112' C . ) Salicylic acid (133' C.) Tricresyl phosphate (140' C.) Triphenyl phosphate ( 5 0 " C.) Urea (140' C . )
.Ilcohol mixtures Aliphatic or aromatic aldehydes Aliphatic or aromatic amides Aliphatic or aromatic amines Aliphatic or aromatic esters Aliphatic o r aromatic halides f . Aromatic hydrocarbons g . Aliphatic or aromatic hydroxy compounds h . Aliphatic or aromatic ketones i. Aliphatic or aromatic nitriles j . Aliphatic or aromatic n i t r o compounds k. Alicyclic or heterocyclic aldehydes or ketones 1. Water
3. Water mixtures a. Aliphatic alcohols b. Aliphatic aldehydes c. Aliphatic amides d. Aliphatic a n d aromatic amines e. Aliphatic ketones f . Aliphatic nitriles g. Heterocyclic nitrogen a n d oxygen compounds
2.
Ternary mixtures . 4 ~ e t o n e water mixtures a. Alcohols b. Aliphatic esters c. Aliphatic or aromatic nitriles
+
+
Alcohol benzene (or derivatives) mixtures Aliphatic or aromatic aldehydes b. Aliphatic or aromatic esters c. .4lipbatic or aromatic halides d . .iliphatic or aromatic ketones e. Aliphatic or aromatic nitriles f . Aliphatic or aromatic nitro compounds a.
E L E V A T ETDE N P E R A T U R E Acetamide (82' C.) 12. Benzamide (130' C.) 13. Benzene sulfonamide (160' C.) 14. Benzoic acid (122' C . ) 15. Catechol (105' C . ) 16. Cinnamic acid (133' C . i 17. o-Cresol (115' C . ) 18. m-Cresol (110' C . ) 19. p-Cresol (110' C.) 20. 21. 10. n-Dinitrobenzene (90' C . ) 11. 2,4-Dinitrochlorobenzene (75' C.) 22.
1. 2. 3. 4. 5. 6. 7. 8. 9.
Alcohols Water
a. b. c. d. e.
1.
phos-
Or
TABLE Iv. CLASSES O F ORG.4XIC COMPOVNDS I N D U C I S G Xaxnruu DISPERSIOS WITH BASICSOLVENTS
7. Tetrahydrofurfuryl alcohol 8. Triethanolamine e t h y l phate 9. Triethyl phosphate 10. Trimethyl phosphate
Oxygen 6.1 5.2 . 6, 18.6
the
higher alkanols rapidly becoming ineffective as the length of the hydrocarhon chain is in15.7 creased. 17.5 35.6 S o n e of the basic conimoii 29.6 33.2 solvents have a marked solvent 2.6 3.0 0.3 36.4 action on the humic acids alone, 1.9 3.2 0 . 3. 33.2 and, with the exception of the 1.9 3.3 33.7 compounds which have high solvent poiver by themselveP (Table III), none of the added components have marked solvent action. However, when these compounds are mixed, highly active solvents.are obtained. Usually, mixtures of equal parts by volume were tested, although in certain cases improvements were obtained by varj-ing the ratio. This was particularly true of water mixtures. T h e important types of substances which activate the common solvents include aliphatic and aromatic aldehydes, amides, amines, esters, halides, ketones, nitriles, and nitro compounds.
B.
ROOMT E M P E R A T U R E 1. Benzaldehyde (satd. with water) 2. Benzyl alcohol (satd.
glycol, or terpineol are required for maximum activity. I n all other cases "alcohol" refers t,o
PRODUCTS
Carbon 78.6 79.3
Vol. 39, No. 7
+
3. Alcohol ester mixtures a . Aliphatic or aromatic halides b. Aliphatic or aromatic nitro compounds c. Benzene (or derivatives) d. T a t e r 4.
+
Alcohol mater mixtures a . Aliphatic or aromatic aldehydes b . Aliphatic or aromatic esters c. Aliphatic or aromatic ketones d . Aliphatic or aromatic nitriles
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1947
TABLE v.
E x m a c n o h - s O F SITRIC ACID-TREATED COALB A T 24' C. _ _ _ ~ _55_Extracted, ~__ Moisture-Free Basis
SCCCESSIVE
.Icetone-R-ater Solvent, Ratio b y Vol, 70:30 60 : 40
First
Second
Third a n d fourth
Total
78.8 i8.2
5.0
0.6 0.7
84.4 84.4
5.5
TABLES VI. EFFECTO F
.IDDING TREATED C0.4L B COVPONESTS OF MIXTUREBEFORE ~ I I X I N G
TO
E t h y l Alcohol (95%)-Benzene, 50:50 a t 24' C . % E x t r a c t e d , Moisture.Inal. of Free Basis Humic Acids as Third Received, % and Loss a t Ash a t Treatment First Second fourth T o t a l 105' C. 750' C. Coal \ r e t b y alcohol first Coal w e t b y benzene first Coal n-et b y niixture
54.9 5%.1
..
15.5 16.6
4.5 6.2
..
74.9
zj 9 ,,,2
4.23 4.63 3.53
0.84
0.78 1.01
PRELIMINARY QU.ANTIT.iTIVE EXPERIMENTS
Based on the qualitative results, several of the more interesting solvents were selected for quantitative study. I n the preliminary experiments the effect of successive extractions on the yield was determined first. TKOmixtures of acetone and water n'ere used for this purpose (Table 17). Twenty grams of treated coal B were added slon-ly to 100 ml. of the solvent stirred mechanically in a centrifuge bottle. After all of the treated coal had been added, the mixture x a s stirred 4 hours at room temperature. For many solrents this i.5 much longer than is necessary, but this time was set in order t o make comparisons with the less active solvents. The mixture was then centrifuged for 30 minutes a t 2100 revolutions per minute. The extract m-as decanted into another centrifuge bottle and centrifuged a second time. The extract was then decanted through filter paper and evaporated t o dryness a t 80" C., and the humic acids were weighed. The residues in the t n o centrifuge bottles: were combined v i t h 25 ml. of freah s o l ~ e n t and , the stirring, centrifuging, and isolation of the extracted humic acids carried out ab beiore. This wao repeated n third and a fourth time, n-ith the exception t h a t these tn-o extracts ivere comhined after filtering, evaporated t o dryness, and neighed together. The residual solvent left in the humic acids vas determined a t 105" C., and the yields of humic acids were calculited on a moisture-free basis for the treated coal and a solvent-free basis for the humic acids. Table I' shows t h a t most of the humic acids xere extracted with the first portion of solvent and t h a t tn-o extractions removed practically all of the humic acids. In the case of mixed solvents i t is possible t h a t improved yields might be obtained by wetting the treated coal x i t h one of the components of a mixture before adding the other. This was tested using the same procedure, but with alcohol and benzene as the solvent. The results are given in Table 1'1. The total extract was identical regardless of IT-hichsolvent was added first. When the treated coal was extracted with a mixture of the two, the total extract was slightly greater; this further indicated t h a t there was no advantage in first n-etting the coal with either component of the mixture. Table V I also-shoxs that the extraction was not complete even after four extractions. However, it is doubtful n-hetlier additional extractions would bring the total t o the level obtained n-ith acetone and water. I n certain cases the proportion of the components of the solvent mixture is very critical. One such example is alcohol, benzene, and ethylene chloride. When the volume of alcohol was lowered from 50 t o 4O7,, the yield of extract from treated coal B dropped from over 80 t o less than 507,. These results are compared in Table VII. As before, variations in the order in which the reagents ivere added made little difference in the yield.
927
The effect of moisture on the yield of humic acids extracted was also investigated. Treated coal B was used in these experiments and was dried for 2 hours a t 110" C. It still retained 1.1% moisture as compared with 10.1% in the air-dried sample. ilcetone and furfural were used as solvents. T h e results are compared in Table VIII. With both a'cetone and furfural, decreased yields were obtained with dry solvents and dried, treated coal. K h e n moisture v a s added to the acetone and t o the furfural, the dried, treated coal gave almost the same yield as the treated coal containing over 10% moisture. This indicates that the dispersibility of these humic acids is not permanently destroyed by drying at 110' C.
TABLE VII. - h I O U X T .4ND ,IS.4LYSIS O F HGMIC ~ x D EXTRACTED S FROM TREATED COAL B BY VARYINGMIXTURES OF ETHYL ALCOHOL-BENZESE-ETHYLESE CHLORIDE AT 23-24 C. E t h y l Alcohol (95'7,): .Imt. Extracted - h a 1 . Of Acids by Difference, as Received, % 'Benzene: Ethylene Chloride, Solvent Moisture-Ffee L o ~ sa t Ash a t Ratio by Vol, Basis, X 105' C. 750' C. 3:2:15 82.2 4.51 1.08 2:l:l 5.50 0 98 81.8 ?:2:1 5.42 0 19 45.5 2:2:lb 5.26 0.21 47.7 Coal wet first b y t h e alcohol-benzene mixture, then ethylene chloride added. b Coal wet first by alcohol. Q
Considerable heat Tvas evolved when moist solvents were added to the dried, treated coal. H r a t was also evolved when the humic acids ext,ractedfrom both treated coals were dried at 110" C. for 2 hours and then treated n-ith moist solvents. Solvents such as acetone-water, acetonitrile-water, formsmide-water, methyl acetate-methyl alcohol-water, and ethyl alcohol (%%), were raised 0.5" to 1.5" C. by the addition of 10 ml. of the solvent t o 1 gram of humic acids. Other solvents such as furfural are strongly adsorbed and cannot be removed by washing with another solvent leas strongly adsorbed. These results indicate the importance of solvation of the humic acids in obtaining dispersion.
TABLE VIII. EFFECT OF
?\IOISTCRh O S Y I E L D O F
AT
Solvent Furfural, dry F u r f u r a l , sard. water Acetone, d r y Acetone 107' water
+
23" C.
H v m c LkCIDS
C/o Humic Acid Extracted b y Difference, hIoisture-Free Basis Oven-dried coal, .Gr-dried coal, l.lwcmoisture 10.lCX moisture 75.5 84.4 83.9 84.4 13.8 21.0 84.0 84.2
QUANTITATIVE DATA
Since the preliminary experiments indicated that four extractions removed most of the humic acids which that solvent was capable oi extracting, that no advantage n'as obtained by Tvetting the treated coal with one or another component of mixed solvents, and that better yields of extract were obtained with air-dried, treated coal containing about 10% moisture, quantitative yields for a variety of solvents vere determined using this information. The yields were determined by taking the difference between the dry aeight of residue after the fourth extraction and the calculated dry weight of treated coal. The residue after extraction was prepared for weighing in each case by washing it with four successive portions of 100 ml. of acetone and then drying a t 110" C. for 15 hours. Where water or alcohol solutions nere usedwhich, if left on the residue, might induce dispersion with acetone-the residue XTas dried before washing with acetone.
928
Vol. 39, No. 7
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
I n choosing a solvent for extracting the treated coal, the
TABLEI X . EXTRACTION YIELDS AND ANALYSESOF H ~ M I C properties which seem t o have the greatest effect on solvent power A C I D S FROM AIR-DRIED, S I T R I C .kCID-TREATED COAL h for the humic acids are structure and surface tension. I n general, Anal. of Humic % ~~~~~~~~dAcids as_Received, b y Difference, 7 G Moisture- LOPSa t Ash a t Solvents a n d Ratios b y Vol. 105' C . 750' C . Free Benzyl alcohol 7 38 1.16 86 5 Ethylene glycol 37 6 Ethylene glycol monobenzyl ether 5 93 1.49 85 6 Furfural S o . 1 7 83 0 30 81 1 Furlural No. 2 0 57 3 65 61 1 Trimethvl nhosuhate 65 6 4 09 3.54 Triethy1"ph'osph'ate S o 1 85 6 4 48 2.84 Triethyl phosphate No 2 65 6 5 69 1 12 Tributyl phosphate 6 02 1.31 81 1 ethylene chloAnhydrous methyl alcohol ride S o . 1, 1 : 1 51 2 8 27 0 03 Anhydrous methyl alcohol ethylene chloride S o 2 , 1 : l 51 2 8 26 0 27 nitromethane, Anhydrous methyl alcohol 1:I 79 3 8 07 0 40 \Iethy!alcohol methyl acetate water, 82 7 0.69 4 93 4 71 66 2 0.15 64 3 64 3 6 45 O'BS 5 41 0 40 84 9 5 39 0.43 81 6
+ + +
+
80 1
5 11
0 3%
84 3
3 78
0.30
83 i A t 80' C . o n coal dried a t 110' C . f o r 2 hours.
6 10
0.33
1:1
Ethy1,alcohol ( 9 5 % ) nitrile, 2 : 2 : 1 E t h y l alcohol (95';,) methane, 2 : 2 : 1 a
+
+ benzene + aceto+ benzene + nitro-
The humic acids were recovered from the extract in each case and analyzed for the amount of solvent retained by heatins to 105' and for ash a t 730' C. The humic acids from those solvents boiling below 100" C. were recovered by evaporation or tiistillation of the solvent. The humic acids were then dried at about 80" C. for 24 hours. With solvents boiling above 100" C., ivitli the exception of ethylene glycol arid forniamide-water disper.ions, the humic acids were precipitated by adding an excess of isopropyl ether. t-sually about 700 ml. were required t o induce complete precipitation, but without doubt some of the humic acids remained because the volume of solvent The humic acids n.ere filtered, washed four times with 200 nil. of isopropyl ether, and air-dried a t about 80' C. for 24 hours. The ethylene glycol and formamide-n-ater extracts xere diluted Fvith 1000 ml. of water. However this did not precipitate the humic acids; it \\-as necessary to add 10 ml. of dilute hyclrochloric acid, which caused an immediate flocculation. The humic acids were then filtered, washed ivith acidulated \\-atel. nnd air-dried at 80" C. for 24 hours as before. Quantitative yields and analyjes of humic acids extracted by representative solvents are givrn in Table I S tor treated coal X and in Tahle S for treated c.oa1 13.
doubly or triply bonded oxygen or nitrogen compounds are highly effective. Aliphatic chains should be as short as possible and usually first members of homologous series are most active. Longer chains are active if additional groups are attached. Many aliphatic comp0und.s are active in aqueous solution where similar aromatic derivatives cannot he used because they are insoluble in water. However, many of these are soluble in alcohol and make active solutions. Prohahly aromatic compounds are more active than the aliphat,ic analog of the same number of carbon atoms. For example, benzene is far more active than hexane, and phenol is more active than hexyl alcohol. On the other hand, benzyl alcohol is more active than either phenol or hexyl alcohol. SOLVEXT POWER AND SURFACE TESSION
All of the compounds n-hich are able t o disperse the humic acids without aid from other solvents have surface tensions, either ohserved or predicted, higher than 30 dynes per centimeter a t 20" C. Furthermore, all of the compounds which were found to he active in mixed solvents have surface tensions higher than 20 dyne$. On the other hand, not all compounds having surface tensions higher than 20 dynes make good solvents. That structure plays an important part is demonstrated h!- the discovery that tetrachloroethane is an excellent solvent mixed with %yo ethyl alcohol \\-hereas tetrachloroethylene in 0517~ethyl alcohol i. very poor although the surface tension of each i s over 30 dyne.. I l i o , pentachloroethane is very poor, as are chloroform and cartion tetrachloride. On t h e other hand, methylrw arid ethylene chlorides are ver\- good. I t appears likely, t i n the basis of evidence such a3 this, that hoth rhemicsl and pli?.sicnl propertie- are important for the dispersion of the humic. acid?. Po+silily increased di9persion with mixed solvents is the result ot an ndjuolv:itiori followed by di-perlion of the solvated molecules. COMMERCIAL EXTRACTION OF HUJIIC ACIDS
The rommercial extraction ot the liuniic acids from nitric wid treated coal \\-auld probably he mo?t e a d y and economically :ICconiplislied Ivith ac'etone-water mixtures. High yields are 01)tained using 50 to !IO% acetone concentrations (Figure 1 ) . Thi. is of particular importance herause v-et, treated coal, which coilt:tins :iljciut 40% moi-ture, could be Pxtracted immediately s t t w \r-ashing nut the exress nitric acid. -4ss1ioi1-n in Figure 1, MYtonitrile-nxter nixtures could he used also. With the latter mixtures niaxiniuiii extraction is ohtaiiied at somewhat lower concentratioris, hut it i* doubtful ivhether thi- ~vouldoffset the
1)ISCUSSIOI\;
.-1 number of d v e i i t s m r e found ivliich extract aliout 8570 of the treated coal (Tables I S and S). This i a as much as alkali or furfural will extract. Vithout doubt, many more organic solvents of similar activity, based on the qualitative tests, could be found, but the yields given in the tables are indicative of the results t o be expected from other solvents, and for that reason additional solvents were not studied. The residue is largely coniposed of mineral matter, fusain, and probably some unoxidized coal substance. All of the solvents \vhich n-ere utilized disperse some mineral matter. In general, those which extract large amounts of humic acids and which have higher densities, such as the aqueous mixtures, tend to disperse more mineral matter. On the other hand, the more anhydrous, Ioxv boiling, and less dense solvents tend to disperse the least mineral matter. For example, a 3 : 2 mixture of water and acetonitrile extracted humic acids giving 1.37' ash, whereas a 2 : 2 : 1 mixture of 957' ethyl alcohol, benzene, and acetonitrile extracted a product giving 0.37, ash.
EXTR.ACTIOX YIELD;ASU .$SALYSES OF HuArIc ACIDS -\IR-DRIED, SITRIC .\CID-TREATED COALB
T.IBI,BX
FROM
Anal. uf Humic y ~~~~~~~~d.icids a s Received, CI b y Difference, 10 I n s s a t .Ash a t lloistureFree 105OC 7 5 0 O C . S u l r e n l i a n d Ratios b y Vol. 0 19 21 0 4 07 Aretone 84 4 6 26 0 99 Furfural 4 80 0 68 74 9 benzene, 1: 1 E t h y l alcohol ( 9 5 Y ) 4 06 1 17 84 2 E t h y l alcohol (95%) chlorobenzene. 1 : 1 84 2 3 88 1 19 Forrnaniide water, 7 : 3 E t h y l d c o h o l (95",) -C benzene acetone. ,L. .. ni .. l 0 92 84 ' 2 5 40 E t h y l alcohol (95C;) berzene ethyl 81 8 4 92 0 98 acetate, 2 : 2 : 1 ii-.iter, E t h y l alcohol (95';) + acetone 2 03 78 8 1 36 1:2:2 E t h y l alcohol (95:;) benzene A a a t e r , 1 06 3 29 78 8 6:4:1 methyl acetate 3Iethyl alcohol (95Li;) 2 30 82 2 0 90 water, S o . 1, 1 : 4 : 2 Methyl alcohol (95°C) 4- methyl acetate 63 8 1 60 1 20 water, N o . 2 , 1 : 4 : 2
.
+
++
-
+
+
+
+ +
+ +
July 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
929
boiling points, which svould make recovery of t h e solvent very easy. Several mixed solvents of this kind were 60. found which have high solvent power for t h e humic acids. For example, a mixture of 95% ethyl alcohol, henzene, and acetonitrile in a ratio of 2 : 2 : 1 gives a high extraction sield. These compounds boil at 78.5", 80.1", and 82" C., respectively, and probably would not undergo marked fieparation on distillation. Two other mixtures are 9570 ethyl alcohol, benzene, and ethylene dichloride and alcohol, henzene, and ethyl acetate, both mixtures in a 2 : l : l ratio. These mixtures phould be used to extract treated coal dehyPERCENT WAT€R IN TH€ SOL Vf N T drated to about 10% moisture. Since they tolerate litt,le water, more solvent Figure 1. Extraction of Humic -4cids from Coal with Water 3lixture.s Containing Acetone, icetonitrile, or Ethjl klcohol must he used than kvith the aaueous solvents described previously. However, t h e humic acids produced by these solvents would be dry; this n-ould offset the preliminary drying of greater initial cost of acetonitrile and its loss through hydro the treated coal. Also the quantity of mineral matter dihpersed Ethyl alcohol-water solution7 could be used also in extra along with t h e humic acids by the nonaqueous organic. solvents processes, but the yields would be less. is usually less than n i t h aqueous solvents. The acetone-n-ater solvents used in Table I' can be calculated t o . I n comparison with furfural, both the acetone-water and the contain over 15% humic acids. This is about the maximum convolatile solvents u e more easily and quantitatively recovered. centration t h a t can he centrifuged and filt,ered satisfactorily. For these reasons their use would be preferred t o that of furfural. More concentrated solutions may be made readily hut are much more difficult t o handle because of t h e finely divided fusain and miners1 matter. Based on there observations, t h e amount of LITERATURE CITED acetone required per ton of raw coal would be about 800 gallons. (1) Francis, IT., and Wheeler, 11. V., J . Chem. SOC.,127,223G (19'25). This is based on a yield of nitric acid-treated coal of 1.1tons, the ( 2 ) Fuchs, TY..U. S.Patent, 2,242,822 (Slay 20, 1941). use of 6070 acetone solution, and estracting in a countercurrent or (3) Fuchs. Tf-., Polansky, T. S.,and Sandhoff, A. G., ISD. I?XG. CHEM..35, 313 ( 1 9 4 3 ) . semicountercurrent batch procedure. T h e yield should he ( 4 ) Xarcusson. J., Chem-Ztg.. 42, 437 ( 1 9 1 8 ) . ahout 8570 of the treated coal, or 0.93 ton per ton of raw coal. ( 5 ) Smith, R. C . . and Howard, H . C., J . A m . C'hem. Soc.. 57, 512 The yields are also dependent upon the extent of the reaction (1935). with nitric acid ( 3 ) . ..inother procedure for the commercial extraction of the humic PRESESTED before t h e Dirizion of G a a and Fuel Cheniisrry a t the 109th acids i- based on the use of low hoiling organic solvents of similar N e e t i n g of thr, . ~ M E R I C . A S CHE>IIC.AL SOCIETT,Atlantic City, S . J .
Action of Acrylonitrile on Viscose d
CARBOXYLATED RAYONS J. P. HOLLIH.4S .AND S-AYFORD A. 310SS. JR. American
P iscose Corporation, Marcus H o o k , Pa.
Acrylonitrile reacts readily with cellulose xanthate when added to commercial viscose solutions. Cellulosic cyanoethyl derivatives are formed which hj-drolyze in the alkali riorrnally present to gis e carbosy- ether derivatives. These inodified celluloses are obtained as yarn suitable for the manufacture of specialized fabrics. The derivati\es differ from those previously obtained in that the modifying groups are evenly- distributed throughout and w-ithin the cellulose crystallites. The carbory ether ?;armare alkaline and water-soluble.
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H E S acrylonitrile is added t o viscose, it reacts rapidly with the principal b>--product sulfur constituents, relensing carbon disulfide and raising the salt test C;i). Simultaneously t'he viscose becomes opaque as a result of the formation of a n insoluble thionitrile. On standing, the thionifrile hydrdyzes t o a eoluble thiocarboxy compound, and the opacity disappears.
The salt test also decreases more or less normally during this reaging process. All of these changes can be esplained satisfactorily by reactions involving the by-product sulfur. I n addition it i- evident t h a t reactions occur which involve the cellulose .itself. Thus ~ r h e n viscose which has been treated with acrylonitrile is spun into rayon, a product differing considerably from the normal is ohtained. I n general, i t may be said that the n:itiue :ind extent of this alteration in cellulose properties depend both upon the amount of acrylonitrile added and also upon the extent t o which the viscose has been allowed t o re-age before being spun. In the present discussion the authors are concerned almost entirely with the latter case-that is, the viscoses were allowed t o re-age complet ely. IVhen small amounts of acrylonitrile (up t o 3 5 of the weight of the viscose) are added t o viscose spun under masimum stretch, the effect of the addition of the acrylonitrile on the cellulose itself
