Classification of Kerogen from Aleksinac (Yugoslavia) Oil Shale Based on its Oxidation Products*

Transcription

1 CRATICA CREMICA ACTA CCACAA 58 (4) (1985) CCA-1597 YU ISSN UDC riginal Scientific Paper Classificatin f Kergen frm Aleksinac (Yugslavia) il Shale Based n its xidatin Prducts* Dragmir Vitrvić Institute f Chemistry, Faculty f Science, University f Belqrtule, P Bx 550, Yu-1100I, Belqriuie, Yugslavia Snežana Bajc Institute f Chemistry, Technlgy and MetaHurgy, Belgrade and Andre Ambles Department f Chemistry, Faculty f Science, University f Pitiers, Pitiers, France Received April 11, 1985 A twenty-three step alkaline permanganate degradatin f kergen frm Aleksinac (Yugslavia) shale was carried ut. A very high ttal yield f xidatin prducts was btained (92.840/0 based n riginal kergen). Detailed GC-MS analyses f ether-sluble acids, sluble prducts f further cntrlled permanganate degradatin f precipitated acids and acids frm aqueus slutins, served as basis fr quantitative estimatin f the participatin f varius types f prducts and fr cmparisn with ther kergens based n similar criteria. The prevailing saturated lng-chain aliphatic structure f xidatin prducts suggested a predminantly pen-chain crss-linked aliphatic structure f Aleksinac shale kergen, classified as type Ikergen. Nevertheless, nticeable prprtin f alkane-plycarbxylic and armatic acids in the xidatin prducts indicated a larger share f alicyclic, hetercyclic, and armatic structures in this kergen. xidative degradatin prducts were shwn t enable mre precise structural interpretatin than the classificatin based n elemental analysis. INTRDUCTIN Kergens, cmprismg the slvent insluble rganic matter frm sedimentary rcks, are the mst abundant rganic material in the crust f the Earth. They have mst ften ben classified n the basis f their atmic RIC and IC ratis (kergens f type I, II and III)1,,2.Recently a new methd fr classificatin f kergens was prpsed based n the prducts f their multistep xidative degradatinš". Cntrary t elemental analysis, xidative degradatin was expected t reflect minr structural differences between kergens, which, being hetergeneus, may represent infinite cmbinatins f mixtures f tw * Dedicated t Prfessr Mihail Lj. Mihailvić n the ccasin f his 60th birthday.

2 454 D. VITRVIĆ ET AL. r mre end-types. Hwever, this prpsal was based n examinatin f nly three selected representative ker gen samples, i. e. type I frm Green River shale, type II frm Tarcian shale, Paris Basin, and type III frm Mannvi11e shale, Canada."? Therefre, further degradatin studies f ker gen s f varius prvenance were expected t shw hw general were the cnclusins btained in the initial study f a limited number f kergen samples. The currently mst detailed structural study f the kergen frm Aleksinac (Yugslavia) il shale, presented in this paper, will at the same time represent the first case f verificatin f the nvel ker gen classificatin methd. The kergen frm Aleksinac shale, being mst ften f type I (infrequently f type II), will primarily be cmpared with the ker gen frm the Green River shale, Clrad, USA, as representative f type I kergens''.". A careful, 23-step alkaline permanganate degradatin f the kergen cncentrate was carried ut. The examinatin f the prducts cnsisted f: (a) capillary gas chrmatgraphic (GC) and gas chrmatgraphic-mass spectrmetric (GC-MS) analysis f the methyl esters f ether-sluble acids, and (b) further cntrlled, stepwise alkaline permanganate xidatinf precipitated, ether-insluble acids, fllwed by Gc::-MS analysis f the ether-sluble acids thus btained. Furthermre, having in mind that sme f the xidatin prducts, being very sluble in water, may have avided the rutine islatin prcedure, a further step was intrduced. In this step all aqueus slutins remaining after the usual ethereal extractin f xidatiqn prducts, were separately wrked up in rder t islate the water sluble xidatin prducts. These prducts were als analyzed by GC and GC-MS. EXPERIMENTAL Sample Preparatin and xidative Degradatin A sample f il shale (n. 5 frm cre S-I, t m, Fischer assay: 13.00%), was btained frm the Aleksinac cal mine (Serbia, Yugslavia). The il shale frm Aleksinac is a lacustrine, Tertiary (Micene) immature sediment. It was difficult t estimate the maturity because f the absence f indigenus vitrinite. An equilavent vitrinite reflectance value was estimated as abut The kergen cncentrate was prepared by treatment f the pwdered shale with hydrchlric acid (1: 4) at 70 ac and then with hydrfluric acid (1: 1), fllwed by a 60 h Sxhlet extractin f the washed and dried residue with an azetrpic mixture f benzene and methanl. The kergen cncentrate cntained ash and 65.57% kergen, cnsisting f /0 carbn, 8.730/0 hydrgen and 3.21/ nitrgen, + S (by difference) being /0. The atmic HjC and jc ratis were 1.46 and 0.17, respectively, crrespnding t type Ikergen. The kergen cncentrate ( g, cntaining g kergen) was xidized in 23 steps with 0.5 g KMn04 per step in 100 cm" f 10/0 KH, accrding t the standard degradatin scheme as described by Ambles et al.", Experimental cnditins were chsen t be identical t thse used in the preceding structural studiesš". Permanganate prtins (0.5 g) were added in aqueus slutin (10 cmš) t kergen cncentrate suspensin heated t areactin temperature f 75 ac. At the end f each xidatin stage, established by disappearance f the vilet and green clurs, the remaining slids were separated by centrifugatin and washed thrughly with 0.5-1% KH t remve all xidatin prducts. Fllwing each five steps, the accumulated Mn02 was remved by treatment with an excess f a slutin f xalic acid and thrugh rinsing with distilled water. The final xidatin mixture was treated in a similar way. The slid residue was dried at 80 ac and analyzed fr rganic matter.

3 ALEKSINAC SHALE KER GEN CLASSIFICATIN KERGEN CNCENTRATE FRM ALEKSINAC SHALE FRM GREEN RIVER SHALE 4- e -\Il e )..2 i g I S 10 STEP NUMBER Figure 1. Duratin f single degradatin steps (lg tls = lg time in secnds). The reductin perids gradually increased during the xidatin prcedure as shwn in Figure 1. ccasinal shrter reductin perids (11th and 21st steps) fllwed the remval f Mn02. They were prbably partly a result f increased reactivity f purified kergen cncentrates. In Figure 1, as well as in sme ther figures in this paper, crrespnding parallel data btained in the degradatin f the Green River shale type I kergen" are als shwn, fr the sake f cmparisn. The last, 23rd prtin f permanganate was reduced in 29 h. This was taken as final degradatin step",

4 456 D. VITRVIC ET AL. The prducts frm each five steps were cmbined. The prducts f the last three steps were als cllected int ne fractin, s that altgether five fractins f prducts were btained. These five fractins were separately wrked up accrding t the scheme described by Ambles et al.7 8 Mrever, the aqueus slutins remaining after the islatin f neutrals and bases, ether-sluble and precipitated acids were first made alkaline by adding KH slutin and then evaprated n a steam bath t small vlume. The crystallized salts were separated by filtratin and rinsed with 1% KH slutin. The alkaline slutins were acidified with hydrchlric acid and finally diluted with distilled water t a standard vlume f 100 cmt, The sluble acidic xidatin prducts were finally extracted with ether. Hence, fur types f prducts were btained frm each f the five fractins: neutrals and bases, ether-sluble acids marked A-1 t A-5, precipitated, ether- -insluble acids, and acids frm aqueus slutins marked A-1(2) t A-5(2). Investigatin f Ether-Sluble Acids The sluble acids A-1 t A-5 and A-1(2) t A-5(2) were methylated with ethereal diazmethane. The esters were analyzed by GC and identified by GC-MS. The GC separatins were carried ut in a Packard Mdel 427 gas chrmatgraph, using a 25 m fused silica WCT CP Sil 5 (0.16 um) capillary clumn, cupled t an mtegratr-calculatr Spectra Physics»System 1«. The temperature f the clumn was prgrammed frm 70 c (10 min isthermally) t 300 (5 min isthermally) at 2 min-i. The GC-MS analyses were perfrmed with a system cnsisting f a gas chrmatgraph (Perkin-Elmer Sigrna 3) cupled t a mass spectrmeter (Krats MS 25). The clumn was temperature-prgrammed frm 70 t 300 at 2 min-i, with a He carrier gas flw rate maintained at 1 cm" min-i. The mass spectra were recrded fr all the separated significant peaks. Identificatins f individual cmpnents were accmplished by cmparisn f the mass spectra btained with the mass spectra f available authentic cmpunds, literature data, and the available spectral data bank. Further xidatin f Precipitated Acids The precipitated acids frm the five fractins were cmbined ( g) and xidized in 26 steps with small amunts (0.5 g) f KMn04 per step in 100 cm" f l/ KH. Prir t additin f each new prtin f permanganate (0.5 g in 10 crn" f aqueus slutin), the acids were disslved in the alkali slutin and heated t the reactin temperature f 75 c. After the reductin f each prtin f the reagent, the reactin mixture was wrked up in the same way as kergen degradatin prducts. The precipitated acids thus btained were always further xidized in the next step with a new prtin f perrnanganate. The Mn02 was reduced fllwing each 5 steps. The reductin perids gradually increased twards the later steps (Figure 2). Hwever, this trend invlved several shrter reductin perids (6th, llth, 16th and 21st steps) which regularly fllwed the remval f Mn02. The small quantity f precipitated acids btained in the last step was washed and dried at 80 0 C. The ether-sluble acids frm each five successive steps were cmbined int five fractins: AP-1 t AP-5. The aqueus slutins frm the five stages were wrked up in the same way as in the degradatin f the kergen cncentrate. Hence, five fractins f acids were islated. They were marked AP-1(2) t AP-5(2). All the acids were methylated with ethereal diazmethane and analyzed by GC and GC-MS in the same way as the prducts btained in the degradatin f the ker gen cncentrate.

5 ALEKSINAC SHALE KER GEN CLASSIFICATIN PRECIPITATED ACIDS' FR. ALEKSINAC SHALE FR. GREEN RIVER SHALE - I/).... 0' I I 5 10 IS STEP NUMBER Figure 2. Duratin f single degradatin steps (lg t/s = lg time in secnds). I 30 RESULTS Degradatin f the Kergen Cncentrate The rate f permanganate xidatin, based n ne gram f ker gen is presented in Figure 3a. Data btained in the degradatin f the Green River shale type I kergen" are given fr cmparisn purpses. Twenty three steps were necessary fr the degradatin f the kergen and a ttal amunt f 11.5 g f KMn04 was cnsumed (4.91 g per gram f kergen). Apprximately 41 h were needed fr the twenty three steps, the last, 23rd step being 29 h. The yields f prducts in the five xidatin stages are shwn in Figure 4a. The yields f neutrals and bases, ether-sluble acids, and precipitated acids were 1.00%, 27.97%, and 45.57%, respectively, relative t the riginal kergen, the ttal yield being 74.54%. The rati f insluble vs ether-sluble acids was The ttal yield f acids islated frm aqueus slutins was % relative t the riginal kergen, raising the ttal yield f xidatin prducts t 92.84/. The slid residue which remained after the final xidatin step ( g) cntained g rganic matter (9.72% relative t the riginal kergen).

6 D. VITRVIC ET AL. KERGEN 40." PRECIPITATED ACIDS FRM ALEKSINAC SHALE FRM GREEN RIVER SHALE FRM ALEKSINAC SHALE KERGEN FRM GREEN RIVER SHALE KERGEN a ,---,---, gkmn,jlgkergen gkmn,/lgacids Figure 3. Rates f permanganate xidatin, based n 1 g f kergen (a) r precipitated acids (b). 15 The GC-MS analyses f the varius fractins f ether-sluble acids revealed the presenee f saturated nrmal mn-and dicarbxylic acids, alkane tri- and tetracarbxylic, isprenid and different armatic mn-, di- and tricarbxylic acids. The identified ether-sluble acids are list ed in Table 1. There was n marked difference in the cmpsitins f the ether-sluble acids frm the five xidatin stages. The gas chrmatgram f cmbined ether-sluble acids A-l t A-5 is shwn in Figure 5.

7 ALEKSINAC SHALE KER GEN CLASSIFICATIN 459 TABLE I Ether-sLubLe Acids btained by xidatin f Kergen frm ALeksinac Shaie ACIDS Frm kergen Frm Frm Frm crrespnding precipitated crrespnding aqueus slutin acids aqueus slutins ALIPHATIC n-mncarbxylic Cl0-C30 C14, C16-C18 C12C32 C12-C14, C16-C1S c.i-dicarbxylic C7-C31 CS-Cl1 C7-C33 C6-C11, (Cs br) isprenid C14"--C175, C1S C19'" C20P, C21Y ALKANEtricarbxylic CS-C1S C6-C9 CCl1 C6, C7, C6br-s-C, br(?) tetracarbxylic C9-C18 (C7), CS-Cl0 C9-C13 c; C9, C9br, Cl br ARMATIC mncarbxylic C11H9 Cl1H9, (ClsH23) C11H9 dicarbxylic C6H4, C9Hl0 C6H4(2)*, C7H6 C6H4, C7H6 C6H4(2), C11HS,C7H60 C13H12 C7H6, Cl1Hs tricarbxylic C6H3 C6H3(3), C7Hs C6H3 C6H3(2), C7HS * Numbers in parentheses indicate the number f ismers fund. Identificatins f the acids A-l(2) t A-5(2), islated frm the crrespnding aqueus slutins, are als reviewed in Table 1. ne gas chrmatgram f these acids in the frm f methyl esters is given as an example in Figure 6. The GC-MS analyses revealed the presence f saturated nrmal mnand dicarbxylic acids, alkane tri- and tetracarbxylic acids and varius armatic mri-, di- and tri-carbxylic acids. The cmpsitins f the five fractins f acids frm aqueus slutins were almst identical. Deqrtuiaticni f Precipitated Acids The rate f permanganate xidatin f precipitated acids, based n ne gram f the acids, is shwn in Figure 3b, invlving parallel data fr the degradatin f the Green River shale type Ikergen. Twenty-six steps were nt sufficient fr cmplete degradatin f g f precipitated acids. In 26 steps, a ttal amunt f 13 g f KMn04 was cnsumed (12.19 g per gram f acids). The ttal duratin f the twenty-six steps was almst 9 h. The yields f the prducts btained in the degradatin f the precipitated acids are shwn in Figure 4b. The ttal yields f neutrals and bases and ether-sluble acids were 3.25% and /0, respectively, relative t riginal precipitated acids. The yield f precipitated acids in the 26th step was g (13.35%). Finally, the ttal yield f acids islated frm aqueus slutins was 14.01% relative t riginal acids, making the ttal yield f prducts %.

8 b 'l "'" ::>;l <: H t<j.., z w 20 W «NEUTRAL AND BASIC PRUCTS 25 FRM ALEKSINAC SHALE a FRM GREEN RIVER SHALE ETHER SLUBLE ACIDS FRM ALEKSINAC SHALE b. FRM GREEN RIVER SHALE PRECIPITATED ACIDS FRM ALEKSINAC SHALE n FRM GREEN RIVER SHALE ACIDS FRM AQUEUS SLUTlNS Đ (ALEKSINAC SHALE) NEUTRAL AND BASIC PRDUCTS FRM ALEKSINAC SHALE FRM GREEN RIVER SHALE ETHER SLUBLE ACIDS FRM ALEKSINAC SHALE b. FRM GREEN RIVER SHALE ACIDS FRM AQUEUS SLUTlNS e (ALEKSINAC SHALE) 1 ck: W >10 ; XIDATIN STAGE (FRACTlN) 2 3, 4 5 XIDATIN STAGE (FRACTIN) Figure 4. Yields f prducts in varius xidatin stages: (a) xidatin f kergen cncentrates, (b) xidatin f precipitated acids, 6

9 Figure 5. Gas chrmatgram f ether-sluble acids A-l t A-5, in the frm f methyl esters. Cx d1 dentes saturated nrmal Cl,r-dicarbxylicacids, C.: - li isprenid acids, c;rl alkane-tricarbxylic, and Cx'ctm alkane-tetracarbxylic acids. :;j H n :tj Z en :l A-(1-S) cltj pht cg i l'il n k C di Ce pht I?J Z n t< :tl'il l'il

10 Figure 6. Gas chrmatgram f acids A-4(2) islated frm aqueus slutin, btained by xidatin f kergen cncentrate (stage 4),in the frm f methyl esters. Dentatins are the same as in Figure 5. pht.... :> I>:l H 0-3 ::d H I?J 0-3 > r A-4(2) C 2 MC)2 2 2 MC)2 2 MC)3 2 MC)3 c cctr c9 i i di c9 c tri 2 Mc? \. i cltr cg i

11 ALEKSINAC SHALE KERGEN CLASSIFICATIN 463 A gas chrmatgram f ne f the fractins f xidatin prducts f precipitated acids is shwn as an example in Figure 7. The GC-MS analyses f the five fractins AP-1 t AP-5 revealed the presence f all types f acids that were fund in the xidatin prducts f the kergen cncentrate. The identified acids are listed in Table 1. Slight differences were bserved in the distributins f acids btained in the five xidatin stages. Identificatins f acids AP-1(2) t AP-5(2), islated frm the crrespnding aqueus slutins, are als reviewed in Table 1. ne f the gas chrmatgrams is given as an example (Figure 8). Identificatins included aliphatic nrmal mn- and dicarbxylic, alkane-tri- and tetracarbxylic, armatic mn-, diand tricarbxylic, and several branched dicarbxylic and alkane-tri- and tetracarbxylic acids. N marked difference was bserved between the cmpsitins f the five fractins. DISCUSSIN AND CNCLUSINS There were tw main aims f this paper. n ne hand, it was f interest t perfrm a mst detailed structural study f the kergen frm the best knwn Yugslav il shale. n the ther hand, a recently prpsed cla:ssificatin f kergens based n their xidatin prducts=" was expected t be validated by examinatin f kergens f different gegraphic rigin. Therefre, the type I kergen frm Aleksinac shale was chsen fr detailed stepwise alkaline permanganate degradatin, t be carried ut under the same cnditins as used in all preceding kergen structural studies=" which led t the prpsal f the new basis fr ker gen classificatin. The chice f experimental cnditins was aimed at btaining as high as pssible yields f xidatin prducts with retained kergen structural characteristics. A twenty-three-step alkaline permanganate degradatin f Aleksinac shale ker gen, described in this paper, resulted in very high yield f xidatin prducts, such as neutrals and bases, ether-sluble, and precipitated, ether-insluble acids (74.54'010relative t initial kergen). Hwever, in this wrk, fr the first time in Aleksinac shale kergen structural studies, the xidatin prducts frm aqueus slutins were als examined, resulting in additinal f acidic xidatin prducts. Hence, the ttal yield f degradatin prducts reached a very high figure f relative t riginal kergen. The majr cnstituents in the fractin f ether-sluble acids (27.97! yield) were fund t be the saturated unbranched CC31 n.m-dicarbxylic acids ( ).Amng them, the mst abundant were the acids in the range CC19, althugh a bimdal distributin f a,m-dicarbxylic acids was bserved (Figure 9). The mst abundant cmpnent was the CIdicarbxylic acid. The range f identified saturated nrmal mncarbxylic acids (CI-C30; f ether-sluble acids) is als ihustrated in Figure 9. The maximum was fund t be at C16. An even/dd predminance was bserved in the C16-C30 range f nrmal mncarbxylic acids. The yield f alkane-tricarbxylic (CS-C1S) and alkane-tetracarbxylic (C9-C1S)acids was nticeable ( f ether-sluble acids). Isprenid ( ) and armatic ( )acids were less imprtant but still significant cmpnents. The evidence btained frm ether-sluble acids nly, i. e., the dminance f saturated unbranched a,m-dicarbxylic acids f relatively high mlecular mass (> C 7 ), mncarbxylic acids (> CI)and isprenid acids, making alt-

12 Figure 7. Gas chrmatgram f ether-sluble acids AP-1, btained by xidatin f precipitated acids (stage 1), in the frm f methyl esters. Dentatins are the same as in Figure 5. e ("!Ii ';'Jl "'" cl) "'" tj ;:l t-l :: ;:l t'1 t-l (ec)2 c;.,1\ e \, di - -clyl phl edi 9 c1{ eg i e12 edi 12 edi,13 e16 phl ć,li 14 d' e15 Ie 22 edi 8,2S e di 26 edi 127 ell1 1eW ly I e26 \e e23bi\] Ift3,1 II eleilc31le32

13 Figure 8. Gas chrmatgram f acids AP-4(2) islated frm aqueus slutin, btained by xidatin f precipitated acids (stage 4), in the frm f methyl esters. Dentatins are the same as in Figure 5. pht > ul ul t<j ::u t<j Z I:'" >ul ul H "IH >>'l H Z *'" :> en C16 IC16 2 Mc.)2 i ctri W.7-b c tri,7 C tri 6-b c1 C 2 )(C02MC)2 C \ 1c'!"I(C02""] ctra

14 466 D. VITRVIC ET AL. gether almst 82 0 /0 f ether-sluble acids, suggested a predminantly pen- -chain and partially branched, crss-linked aliphatic structure f Aleksinac shale kergen. n the ther hand, the presence f nticeable amunt (15.62'%) f alkane-tri- and tetracarbxylic acids in the xidatin prducts indicated that alicyclic and/r hetercyclic rings were als significantly invlved in the lng-chain aliphatic structure. Relatively small yield f armatic acids (2.58%) suggested a smaller participatin f armatic structures in this ker gen. 30 NRMAL MNACIDS A-1-5 NRMAL DIACIDS ;--- UJ 20 U Z <{ 10 A-1(2)-5(2) Z => m <{ 30 UJ 2: 20 <---J 10 UJ a::: A P-1-5 S 40 AP-1(2)-5(2) S 10 IS 20 2S 30 3S CARBN 5 10 IS NUMBER Figure 9. Distributin f saturated nrmal mncarbxylic and a,w-dicarbxylic acids btained in xidatins f ker gen cncentrate and precipitated acids.

15 ALEKSINAC SHALE KERGEN CLASSIFICATIN 467 Hwever, since ether-sluble acids rep resen ted less than 30'010 f all xidatin prducts, cnfirmatin f such structural interpretatin required further examinatin f ther xidatin prducts, primarily the main prduct, the precipitated, ether-insluble acids ( yield), as well as the acids frm aqueus slutins (18.30'010 yield). Degradatin prducts f cntrlled xidatin f precipitated acids were btained in high yield in the frm f ether-sluble acids ( , relative t riginal precipitated acids). Again, saturated unbranched a,w-dicarbxylic (C 7 -C 33 ) acids with a bimdal distributin and a maximum at CI(Figure 9), were fund t be the majr xidatin prduct (69.11'010). Nrmal mncarbxylic acids (C I2 -C 32 ) with a maximum at C I6 and an even/dd predminance (Figure 9) were als btained in high yield ( ). Alkane-plycarbxylic and armatic acids were minr xidatin prducts (5.45'010 and , respectively). Hence, the structure f precipitated acids, as suggested by xidative degradatin studies, crrbrated the structural interpretatin based n ether- -sluble acids. Finally, acids frm aqueus slutins frm bth the degradatin f kergen cncentrate and the precipitated acids remained t be tested befre a final structural interpretatin can be attempted. The cmpsitins f acidic mixtures islated frm aqueus slutin were different cmpared t ether- -sluble acids frm bth the degradatins f ker gen cncentrate and precipitated acids. With the exceptin f armatic acids, the distributins f acids were mre simple and were displaced twards lwer mlecular weights. The majr cnstituents f the acidic mixtures islated frm aqueus slutins in the degradatin f the kergen cncentrate were alkane-plycarbxylic acids, 41.0'3010 (tricarbxylic C 6 -C 9 acids.9.65'010, and tetracarbxylic C 7 -CI acids 31.38{)/), and armatic acids ( ). Amng aliphatic acids, the nrmal {l,w-dicarbxylic acids dminated (C-C II ; 23.43()/ relative t ttal acids). As shwn in Figure 9, their maximum was at Cg The prprtin f nrmal mncarbxylic acids (C I6 -Clg) was fund t be the smallest ( ), but the maximum was again at C 16 The participatin f varius types f acids islated frm aqueus slutins in the degradatin f precipitated acids was mre unifrm: alkane-tri-(c 6 -C 9 ) and tetra-(cg-ci) carbxylic acids 27.70'010 ( and , respectively), armatic acids 26.75'010, nrmal mncarbxylic C 12 -C lg acids and n.m-dicarbcxylic C 6 -C II acids 18.90'010. With mncarbxylic acids the maximum was fund t be at C I6 and with a,w-dicarbxylic acids at C 9. A higher prprtin f alkane-plycarbxylic and armatic acids as well as lwer mlecular weight nrmal u.m-dicarbxylic acids in the prducts islated frm aqueus slutins, may have been expected because f higher water slubility f these prducts. The ttal balance f all xidatin prducts is presented in Table II. It shws that islatin f acids frm aqueus slutins has changed nticeably the cmpsitin f ttal xidatin prducts. The prprtin f alkane-plycarbxylic and armatic acids increased. A similar trend has already been bserved in the examinatin f type I (Green River shale) and type II (Tarcian shale Paris Basin) kergensv'".

16 468 D. VITRVrC ET AL. TABLE Cmpsitin f xidatin Prducts btained frm Aleksinac Shale Kergen II ACIDS / relative t ttal xidatin prduct Nt cunting acids frm aqueus slutins Including acids frm aqueus slutins ALIPHATIC mncarbxylic a,w-dicarbxylic isprenid ALKANEtricarbxylic tetracarbxylic ARMATIC Taking int accunt the high yields f xidatin prducts and their prevailing saturated lng-chain aliphatic structure, a predminantly pen-chain and partly branched, crss-linked aliphatic structure is suggested fr the ker gen frm Aleksinac shale. Hwever, in spite f the fact that accrding t atmic R/C-/C ratis this kergen may be classified as type l kergen, nticeable participatin f alkane-tri- and tetracarbxylic and armatic acids in the xidatin prducts (Table II) indicates a larger share f alicyclic and/r hetercyclic and armatic structural elements in the Aleksinac shale kergen. The prprtins f individual types f xidatin prducts may serve as basis fr semiquantitative estimatin f the share f varius types f structures in the kergen matrix. bviusly, several facts such as applicatin f better degradatin methd which led t very high yields f xidatin prducts and pwerful separatin and identificatin techniques, as well as examinatin f previusly neglected degradatin prducts frm aqueus slutins, enabled imprvement f frmer structural interpretatins f Aleksinac shale kergen ll.,12. Nw, hw can the type l kergen frm Aleksinac shale be cmpared with the three mentined selected representative kergen samples (type I, II and III)S-, particularly with the kergen frm the Green River shale, the representative f type l kergensš-"? A review f parallel experimental data n the degradatins f the tw examined type l kergens is given in Table III. Further basis fr cmparisn f the tw kergens has already been prvided by parallel presentatin f experimental data in Figures 1, 2 and 3. Althugh the tw type l kergens behaved quite similarly, certain differences shuld be emphasized. The Aleksinac shale ker gen seems t have been mre easily degraded: it had shrter reductin perids, larger amunt f KMn04 cnsumed per gram f ker gen, shrter ttal time necessary fr degradatin, smaller yields f ttal xidatin prducts and higher yield f primary ether-sluble acids. These facts may suggest a higher degree f crss- -linking in the structure f kergen frm Aleksinac shale, but may als be due t a larger cntent f xygen functinal grups (atmic te rati being

17 ALEKSINAC SHALE KERGEN CLASSIFICATIN 469 TABLE xidative Degradatin f Tw Type I Kergens III Clrad shale3 6 Aleksinac shale Amunt f initiai kergen cncentrate, g Amunt f initial kergen, g Kergen atmic H/C rati atmic /C rati type Number f steps necessary fr degradatin Ttal amunt f KMn04 cnsumed, g Amunt f KMn04 cnsumed per gram f kergen, Ttal time necessary fr degradatin, h nt cunting the last 30 h step Ttal yields, % relative t kergen neutrals and bases ether-sluble acids precipitated, ether-insluble acids ttal xidatin prducts rganic residue Rati f precipitated ver ether-siuble acids Acids frm aqueus slutins, Ja Amunt f initial precipitated acids fr further degradatin, g Number f steps Amunt f KMn04 cnsumed per gram f precipitated acids, g Ttal time necessary, h Ttal yields, Ja relative t precipitated acids neutrals and bases ether-sluble acids residual precipitated acids Acids frm aqueus slutins, Ja I I g (22 steps) 29 (23rd step) ' vs 0.09 fr the Green River shale kergen). Paradxically, in the case f Aleksinac shale ker gen, the rganie residues after bth the kergen encentrate and the precipitated acids degradatins were larger, indicating higher chemical resistanee twards the xidatin reagent f ne small prtin f the kergen. n the ther hand, the cmpared ranges f identified ether-sluble acids and acids frm aqueus slutins 3,,6,9.10, wuld suggest a great similarity between the tw kergens. The distributins f identified nrmal mn- and a,c-dicarbxylie aeids, generally speaking, were quite similar. Fr example, a maximum at C 16 with unbranched mncarbxylic acids and at CI with a,c-dicarbxylie aeids was typical fr the xidatin prducts f bth kergens. The majr differenee was a bimdal distributin f nrmal mn- and diearbxylie acids with the degradatin prduets frm Aleksinac shale (Figure 9), which has nt been bserved with the Green River shale kergen xidatin prducts.

18 470 D. VITRVIC ET AL. In spite f the bserved similarity in the ranges f identified acids, there was a nticeable difference in the prprtins f individual types f acids btained as xidatin prducts, indicating definite structural differences between these tw kergens. AlIPHATIC ACIS 100 NT CUNTING ACIDS FRM AQUEUS SLUTlNS t:. INCLUDING ACIDS FRM AQUEUS SLUTINS.t:. KERGEN FRM ALEKSINAC SHALE...--''-----'''----'''----'''_--''_--''-_--''-_--''-_-K..._..J ALKANE-PLY- ARMATIC CARBXYlIC ACI S ACIS Figure 10. Cmpsitins f xidatin prducts btained frm Aleksinac shale kergen and ther kergens f varius structural types. Cnsidering unbranched and isprenid acids as xidatin prducts f aliphatic type structures, alkane-tri- and tetra-carbxylic acids as ne f the pssible xidatin prducts f alicyclic r hetercyclic type structures, and armatic acids f armatic type material, these three types f acids have already been prpsed as basis fr classificatin f kergens", Therefre, in the same way as with the three representative ker gen types", the prprtins f varius kinds f ether-sluble acids btained frm Aleksinac shale kergen cncentrate and precipitated acids were als estimated (Table II) n the basis f GC chrmatgrams f individual fractins. The estimated quantitative data frm Table II were intrduced in a triangular diagram, shwn in Figure 10, parallel with data btained fr the representative type I, II and III kergens. In rder t demnstrate the imprtance f islatin and examinatin f acids frm aqueus slutins, the prprtins f varius types f acids in xidatin prducts in all cases were calculated in tw ways, i. e. nt cunting the acids frm aqueus slutins, and als including these acids. bviusly,

19 ALEKSINAC SHALE KER GEN CLASSIFICATIN 471 by ignring acids frm aqueus slutins ne neglects, partially r ttally, sme parts f the ker gen structure, particularly thse whse xidatin prducts are very sluble in water. Figure 10 shws that type I kergen frm Aleksinac shale, while generally speaking lcated in the type I kergen zne, changed psitin in the diagram in the directin f higher prprtins f alkane-plycarbxylic and armatic acids, indicating a larger share f alicyclic and/r hetercyclic, and armatic structures in this ker gen. The structural interpretatin f type I kergen frm Aleksinac shale crrbrates the cnclusin which resulted frm the study f the representative type I kergen frm the Green River shale, i. e. that saturated high mlecular mass pen-chain acids are the main xidatin prduct f type I kergens. Nevertheless, it als shws that higher prprtins f alkane-plycarbxylic and armatic acids in the xidatin prducts may be expected, indicating larger shares f alicyc1ic, hetercyc1ic r armatic structures in type I kergens. In cnclusin, c1assificatin f kergens n the basis f their xidative degradatin prducts, presuming that experimental cnditins were chsen as t prvide as high as pssible yields, enables amre precise structural interpretatin as cmpared t the c1assificatin based n atmic R/C-/C ratis nly. Acknwledgements. - The authrs are grateful t Prfessr J.C. Jacquesy, Department f Chemistry, University f Pitiers, France, fr his interest in this wrk. The technical assistance f Mrs. J. Jffre, University f Pitiers, is greatly appreciated. This wrk was supprted in part by the Research Fund f the S. R. Serbia (Yugslavia). REFERENCE 1. Petrleum Frmatin and ccurrence, B. P. T i s s t and D. H. W e 1 t e, Berlin, Springer-Verlag, 1978, p Elemental Analysis f Kergens, in: B. Du r and (Ed.) Kergen, Insluble rganic Matter Frm Sedimentary Rcks, B. Du r and and J. C. M n i n, Paris, Technip, 1980, pp M. D j r d j e v i ć, A. A m b 1 e s, and D. V i tr v i ć, BurI. sc. chim. Begrad 48 (1983) D. Vi tr v i ć, M. Dj r d j e v i ć, A. Am b 1 e s, and J. C. J a c q u e s y, rg. Gechem. 5 (1984) A. Am b 1e s, M. Dj r d j e v i ć, and D. Vi tr v i Ć, Chem. Gel, 48 (1985) D. Vi tr v i Ć, A. Am b 1e s, and M. Dj r dj e v i Ć, rg. Gechem. 6 (1985) A. Am b le s, M. V. Dj u r i č i Ć, and D. Vi tr v i Ć, BulI. sc chim. Begrad 46 (1981) A. Am b e s, M. V. Dj u r i č i Ć, Lj. Dj r d je v i Ć, and D. Vi tr v i Ć, in: M. B j r e y (Ed.) Advances in rganic Gechemistry 1981, Chichester, Wiley, 1983, pp Study f the relatinship between kergens f varius structural types and the prducts f their multistep xidative degradatin (in Serb-Cratian), M. V. Dj r d j e v i Ć, Ph. D. Thesis, Faculty f Sciences, University f Belgrade, 1984, p D. Vi tr v i Ć, A. Am b le s, and M. Dj r d je v i Ć, in: D. Le y tha e u- ser and J. R u 11 k t ter (eds.) Advan. rg. Gechem. 12, xfrd, Pergamn, in press. 11. M. V. Dj u r i č i Ć, D. Vi tr v i Ć, B. D. Andresen. H. S. He r t z, R. C. Murphy, G. Preti, and K. Biemann, in H. R. V. Gaertner and H. W e h ner (Eds.) Advances in rganic Gechemistry 1971, xfrd, Pergamn, 1972, pp S

20 472 D. VITRVIC ET AL. 12. D. Vi tr V i č, M. V. Dj u r i čl č, and B. Il i Č, in: B. T i s s t and F. B i e n ner (Eds.) Advances in rganic Gechemistry 1973, Paris, Technip, 1974, pp SAZETAK Klasifikacija kergena aleksinačkg bituminezng škriljca zasnvana na njegvim ksidacinim prizvdima D. Vitrvić, S. Bajc i A. Ambles Pri pažljivj višestepenj degradaciji kergena aleksinačkg bituminzng škriljca alkalnim rastvrm permanganata dbi ven je vrl visk prins ksidacinih prizvda (92,84% u dnsu na prvbitni kergen), Detaljna gasnhrmatgrafsk-masenspektrmetrijska analiza kiselina rastvrnih u etru, rastvrnih prizvda dalje kntrlisane ksidacije nerastvrnih kiselina i kiselina iz vdenih rastvra pslužila je ka snva za kvantitativnu pre enu zastupljensti pjedinih vrsta prizvda i za pređenje sa drugim kergenima, klasifikvanim na bazi njihvih ksidacinih prizvda. ksidacini prizvdi ker gena aleksinačkg škriljea sastjali su se pretežn d alifatičnih kiselina dugih niz va. T je ukazival na umreženu, pretežn alifatičnu strukturu vg kergena, kji je klasifikvan ka kergen tipa I. Ipak, zapažena kličina alkan-plikarbnskih i armatičnih kiselina u ksidacinim prizvdima ukazivala je na veće učešće alicikličnih, hetercikličnih i armatičnih struktura u vm ker genu. Pkazal se da prizvdi ksidativne degradacije mgućavaju precizniju strukturnu interpretaciju ker gena neg klasifikacija zasnvana na elementarnj analizi.