Characterization of Oil Shales - American Chemical Society

27 Characterization of Oil Shales Analytical Techniques R. A. NADKARNI

Downloaded by CORNELL UNIV on May 9, 2017 | http://pubs.acs.org Publication Date: August 1, 1983 | doi: 10.1021/bk-1983-0230.ch027

Exxon Research and Engineering Company, Analytical Research Laboratory, Baytown, TX 77522

Extensive analytical efforts to fully characterize the oil shales are underway at Exxon Research and Engineering Company's Baytown Laboratories. No significant losses of any metals of concern are observed during high temperature ashing. An alternate means of rapid ash determination uses a Parr combustion bomb. The ash can be dissolved by alkaline fusion in a Claisse fluxer or by acid dissolution in a Parr bomb. The solutions thus prepared are analyzed by atomic absorption or by inductively coupled plasma emission spectrometry for major (Al, Ca, Fe, K, Mg, Na, Si, Ti) and trace elements (As, B, Ba, Be, Cd, Co, Cr, Cu, L i ,Mn,Mo, Ni, P, Sr, U, V, Zn). Kerogen enriched shales need to be ashed before the dissolution, otherwise low recoveries are obtained. Overall accuracy and precision of metals determination is within ±5 - 10%. Other major shale constituents such as C, H, N, and S are determined by thermal decomposition and instrumental detection methods. Oxygen is determined by 14 MeV neutron activation analysis. Parr or Leco BTU bomb combustion and subsequent ion chromatographic determination is used for halogens, sulfate and nitrate. Ion chromatography is also suitable for anionic characterization of shale process waters. Two analytical procedures for o i l shales should be used with caution. Kjeldahl nitrogen procedure has been found to give reproducible but considerably low results for certain oil shales. Similarly, ASTM procedure for the determination of sulfur forms in coal, when applied to oil shales, gives reproducible but erroneous results.

0097-6156/ 83/0230-0477S06.00/0 © 1983 A m e r i c a n C h e m i c a l S o c i e t y

Miknis and McKay; Geochemistry and Chemistry of Oil Shales ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

GEOCHEMISTRY A N D CHEMISTRY O F OIL S H A L E S

478


Oil s h a l e , a f i n e grained sedimentary rock c o n t a i n i n g insoluble organic material that y i e l d s o i l by d e s t r u c t i v e d i s t i l l a t i o n , o r r e t o r t i n g , o c c u r s i n l a r g e q u a n t i t i e s i n many p a r t s o f t h e w o r l d and i n t h e U n i t e d S t a t e s . The i d e n t i f i e d r e s o u r c e s o f s h a l e s o u t s i d e t h e U n i t e d S t a t e s t o t a l o v e r 1.1 t r i l l i o n b a r r e l s o f o i l (I). The r i c h e s t d e p o s i t s i n t h e U n i t e d S t a t e s a r e l o c a t e d i n t h e Eocene G r e e n R i v e r f o r m a t i o n o f C o l o r a d o , U t a h , and Wyoming. I n p a r t o f t h i s f o r m a t i o n , t h e Piceance B a s i n , the o i l s h a l e s a r e thought t o c o n t a i n energy e q u i v a l e n t o f about 1.2 t r i l l i o n b a r r e l s o f o i l , o r a b o u t f o r t y times the nation's present proven reserves of petroleum. Environmental issues associated with shale r e t o r t i n g require s u b s t a n t i a l m o n i t o r i n g and c o n t r o l o f w a s t e p r o d u c t s , w h i c h c a n be q u i t e l a r g e . At Exxon Research and E n g i n e e r i n g Company's Baytown R e s e a r c h and Development D i v i s i o n , a n a l y t i c a l methods f o r c o a l and c o a l products have been d e v e l o p e d and a r e b e i n g used (2-4). These methods a r e now being extended to the characterization of o i l shales. This extension i s not s t r a i g h t f o r w a r d i n a l l cases because i n s e v e r a l r e s p e c t s s h a l e i s almost the exact o p p o s i t e o f c o a l . F o r example, s h a l e i s h i g h i n i n o r g a n i c s and l o w i n o r g a n i c s , t h e o p p o s i t e o f most c o a l s , and s h a l e o r g a n i c s have a h i g h H/C r a t i o , a l s o t h e opposite of coal. The major analytical techniques used f o r the shale analyses are neutron activation analysis ( 5 ) , X-ray f l u o r e s c e n c e ( 5 ) , and a t o m i c s p e c t r o s c o p y ( 6 - 8 ) . In addition, we d e s c r i b e o u r a p p r o a c h t o t h e m u l t i e l e m e n t a n a l y s i s o f o i l s h a l e s and t h e i r p r o d u c t s u t i l i z i n g m a i n l y i n d u c t i v e l y c o u p l e d plasma e m i s s i o n spectrometry (ICPES) f o r metals, and i o n c h r o m a t o g r a p h y ( I C ) f o r some n o n m e t a l s . Other major elements s u c h as c a r b o n , h y d r o g e n , n i t r o g e n , s u l f u r , and oxygen a r e d e t e r m i n e d by a v a r i e t y o f c o m b u s t i o n t e c h n i q u e s . Experimental Shale P r e p a r a t i o n . The o i l s h a l e samples were p u l v e r i z e d t o -100 mesh b e f o r e s a m p l i n g . Representative p o r t i o n s of the s a m p l e s were ashed a t 750°C f o r f i v e h o u r s s t a r t i n g w i t h a c o l d m u f f l e f u r n a c e f o l l o w i n g t h e ASTM p r o c e d u r e . K e r o g e n was i s o l a t e d from t h e s h a l e samples by s e q u e n t i a l d e m i n e r a l i z a t i o n w i t h HC1 and HF, a p r o c e d u r e d e v e l o p e d a t t h e U.S. B u r e a u o f M i n e s (9). P a r r Bombs. Two t y p e s o f P a r r bombs were u s e d . The a c i d d i g e s t i o n bombs were u s e d f o r t h e a s h d i s s o l u t i o n s . About 0.2 g o f s h a l e o r a s h was d i s s o l v e d i n 3 mL aqua r e g i a and 2 mL HF i n t h e a c i d d i g e s t i o n bomb and h e a t e d a t 110°C i n an a i r - o v e n f o r two h o u r s . A f t e r t h e d i s s o l u t i o n , 1 g o f b o r i c a c i d was added t o e a c h sample s o l u t i o n , w h i c h was h e a t e d on a w a t e r - b a t h



27.

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Characterization

of Oil Shales

479

f o r 15 m i n u t e s . I f any unburned c a r b o n was v i s i b l e , t h e s o l u t i o n s were f i l t e r e d ; o t h e r w i s e , t h e y were d i l u t e d t o 100 mL. A b l a n k c o n t a i n i n g t h e same amounts o f t h e a c i d s was a l s o prepared. The P a r r oxygen c o m b u s t i o n bombs were u s e d f o r a r a p i d a s h d e t e r m i n a t i o n and f o r sample p r e p a r a t i o n f o r I C . About 0.5 g o f s h a l e o r s h a l e o i l was m i x e d w i t h 0.5 g o f w h i t e o i l i n a s t a i n l e s s s t e e l c u p . F i v e mL o f w a t e r was p l a c e d i n t h e b o t t o m o f t h e bomb w h i c h was t h e n a s s e m b l e d and p r e s s u r i z e d t o 30 atmospheres o f oxygen. A f t e r c o m b u s t i o n , t h e bomb was a l l o w e d t o c o o l f o r t e n m i n u t e s and t h e n opened s l o w l y . The i n s i d e w a l l s o f t h e bomb were washed w i t h w a t e r , and a l l t h e w a s h i n g s were combined, f i l t e r e d i f n e c e s s a r y , and d i l u t e d t o 50 mL. The r e s i d u e i n t h e c u p was d r i e d a t 110°C f o r 15 m i n u t e s a n d reweighed f o r ash d e t e r m i n a t i o n . C l a i s s e Fusion Device. The d e t a i l e d p r o c e d u r e i s d e s c r i b e d b y Botto (10). T h i s i s a n automated d e v i c e w h i c h s i m u l t a n e o u s l y fuses s i x samples. I n t h i s p r o c e d u r e , t h e f i n e l y powdered sample was m i x e d with t e n times i t s weight of lithium m e t a b o r a t e i n a p l a t i n u m c r u c i b l e and h e a t e d a t ~950°C f o r 15 minutes. The m e l t was d i s s o l v e d i n e i t h e r d i l u t e HC1 o r HNO^ and t h e e l e m e n t s o f i n t e r e s t were t h e n d e t e r m i n e d b y AAS o r ICPES. P h o s p h o r u s was d e t e r m i n e d f r o m t h e same s o l u t i o n b y a s e p a r a t e molybdenum b l u e c o l o r i m e t r i c p r o c e d u r e . I n d u c t i v e l y Coupled Plasma E m i s s i o n S p e c t r o m e t e r . Details of our i n s t r u m e n t a t i o n a r e g i v e n by B o t t o ( 1 1 ) . I t i s a J a r r e l l Ash AtomComp Model 750 w i t h 34 e l e m e n t a l c h a n n e l s . A l i s t o f these elemental channels, the wavelengths used for the d e t e r m i n a t i o n s , t h e d e t e c t i o n l i m i t s , and t h e u p p e r dynamic r a n g e f o r each e l e m e n t was g i v e n i n t h e p r e c e d i n g p a p e r . S i x o f t h e e l e m e n t a l c h a n n e l s a r e a l s o f o c u s s e d o n weaker l i n e s o f lesser sensitivity f o r determining the higher elemental concentrations. This e l i m i n a t e s the n e c e s s i t y o f d i l u t i n g t h e samples further t o prevent major elements i n shale from e x c e e d i n g t h e u p p e r dynamic l i m i t . The d a t a f r o m ICPES a r e processed by an o n - l i n e PDP-8M computer interfaced t o an HP-1000 o f f - l i n e computer. Ion Chromatograph. A Dionex Model 14 was u s e d f o r the determination o f anions. The w o r k i n g p a r a m e t e r s a r e g i v e n e l s e w h e r e ( 1 2 ) . Q u a n t i f i c a t i o n was done by c o m p a r i n g t h e peak h e i g h t s on the s t r i p - c h a r t r e c o r d e r o f the s t a n d a r d s w i t h t h e sample s o l u t i o n s . O t h e r I n s t r u m e n t a t i o n . - An O r i o n M o d e l 901 m i c r o p r o c e s s o r i o n a n a l y z e r was u s e d f o r pH and f o r i o n s e l e c t i v e electrode measurements. A Norelco PW-1212 was u s e d f o r X-ray f l u o r e s c e n c e measurements. C e r t a i n o f t h e ICPES r e s u l t s were


480

G E O C H E M I S T R Y A N D C H E M I S T R Y OF OIL

SHALES

checked with an Instrumentation Laboratory 951 atomic absorption spectrophotometer. C a r b o n , h y d r o g e n , and n i t r o g e n were d e t e r m i n e d u s i n g a H a l l i k a i n e n CH a n a l y z e r o r L e c o CHN-600 analyzer. S u l f u r was d e t e r m i n e d u s i n g a L e c o SC-32 a n a l y z e r . Oxygen was d e t e r m i n e d u s i n g 14 MeV n e u t r o n a c t i v a t i o n a n a l y s i s .


Reagents. A l l o f the a c i d s used i n t h i s work were o f " U l t r e x " q u a l i t y from J . T. B a k e r C h e m i c a l Company. D e i o n i z e d w a t e r was o b t a i n e d from a M i l l i p o r e C o r p o r a t i o n M i l l i Q system. An ICPES s c a n o f t h i s w a t e r showed a t o t a l o f 33 e l e m e n t s t o be ~1 ppm or less. Oil shale standards were provided by Dr. F. J . F l a n a g a n o f the U.S. G e o l o g i c a l Survey. These were d r i e d f o r two h o u r s a t 110°C b e f o r e a n a l y s i s . R e s u l t s and

Discussion

Ashing of O i l Shales. B e c a u s e o f p o t e n t i a l d i f f i c u l t i e s due t o carbonate content of the shales, the n o r m a l ASTM ashing p r o c e d u r e f o r c o a l s was e v a l u a t e d t o f i n d t h e optimum a s h i n g t e m p e r a t u r e w i t h minimum e l e m e n t a l losses for shales. A C o l o r a d o o i l s h a l e was ashed a t 750*C f o r 15 h o u r s , and t h e n s u c c e s s i v e l y ashed f o r 3 h o u r s each a t 850, 950, and 1050°C. From e a c h s t a g e , the p e r c e n t a g e ash was d e t e r m i n e d . A l l of t h e s e a s h e s and the o r i g i n a l s h a l e sample were a n a l y z e d for their carbonate content by evolution-gravimetry, and for e l e m e n t a l c o m p o s i t i o n by ICPES. The r e s u l t s a r e summarized i n Table I. E s s e n t i a l l y a l l o f the c a r b o n a t e i s decomposed a t 750°C; h e a t i n g f u r t h e r up t o 1050*C showed no l o s s o f any element determined. T h u s , i t seems f e a s i b l e t h a t a s h a l e sample can be heated overnight to ~800°C and the ash subsequently analyzed f o r the e l e m e n t s o f i n t e r e s t w i t h good precision. The P a r r o x y g e n bomb can be used i f o n l y a r a p i d ash determination i s desired. The r e s i d u e l e f t i n the i g n i t i o n cup i s e q u i v a l e n t t o the ash c o n t e n t o f a g i v e n s h a l e . Having w a t e r as an a b s o r b a n t i n t h e bomb i s n o t n e c e s s a r y ; h o w e v e r , i f water absorbant i s used, i t i s n e c e s s a r y to dry the r e s i d u a l ash b e f o r e f i n a l w e i g h i n g t o remove the m o i s t u r e . P r e s s i n g the shale sample into a pellet helps in achieving uniform c o m b u s t i o n and i n r e d u c i n g the r i s k o f some sample b e i n g b l o w n o u t o f the cup d u r i n g c o m b u s t i o n . T y p i c a l r e s u l t s on two raw s h a l e s and two s h a l e o i l s a m p l e s a r e g i v e n i n T a b l e I I . The agreement between the v a l u e s by the ASTM method f o r c o a l s and t h e p r o p o s e d method i s v e r y good ( a c c u r a c y b e t w e e n 0.2 and 5% w i t h an a v e r a g e o f 4 % ) . The p r e c i s i o n o f the method v a r i e s f r o m 0.6 t o 13% w i t h an a v e r a g e r e l a t i v e s t a n d a r d d e v i a t i o n o f 5%. T h u s , the P a r r oxygen bomb method can be used f o r a q u i c k ash d e t e r m i n a t i o n o f c o a l o r s h a l e i n a p i l o t p l a n t l a b o r a t o r y s i t u a t i o n as an a l t e r n a t i v e t o the t i m e - c o n s u m i n g ASTM D-3174 procedure.


27.

NADKARNI

Characterization


Table I . Ashing i p e r a t u r e , °C A s h , wt % C0 , % Al, % Ca, % Fe, % 3

K, %

Mg, % Na, % P, % Si, % Ti, % Ba, ppm C r , ppm Cu, ppm L i , ppm Mn, ppm S r , ppm V, ppm Zn, ppm

* Remaining

of Oil Shales

Analysis o fInorganic Constituents i n Colorado O i l Shale Unashed 26.4 3.30 12.0 1.69 0.98 2.85 1.37 0.12 10.7 0.12 502 31 134 48 302 762 55 79

750 63.1 *0.81 3.15 12.5 1.64 1.00 2.71 1.35 0.11 10.5 0.10 515 33 133 50 282 726 68 85

850 62.8 *0.42 3.15 12.8 1.63 0.97 2.85 1.35 0.11 10.5 0.11 516 29 130 49 283 738 56 79

950 62.6 *0.27 3.18 12.3 1.62 0.95 2.78 1.34 0.10 10.6 0.12 512 24 136 51 282 726 50 85

1050 61.9 *0.19 3.14 12.7 1.61 0.95 2.79 1.36 0.10 10.8 0.12 513 35 126 49 277 722 78 78

i n ash


GEOCHEMISTRY A N D CHEMISTRY OF OIL SHALES

482

T a b l e I I . A s h D e t e r m i n a t i o n by P a r r Oxygen C o m b u s t i o n Bomb High Sample/Wt % A s h By: T e m p e r a t u r e A s h i n g Colorado Shale 62.8 Colorado Shale 72.7 A u s t r a l i a n Shale O i l 1.80 A u s t r a l i a n Shale O i l 1.87

P a r r Oxygen C o m b u s t i o n Bomb 62.7 ± 0.4 ( 5 ) 72.2 ± 0.4 ( 2 ) 1.72 ± 0.11 ( 3 ) 1.64 ± 0.21 ( 3 )

(a)


Number o f r e p l i c a t e

analysis.

C l a i s s e F l u x e r A n a l y s i s - L i t h i u m t e t r a b o r a t e o r metaborate f u s i o n f o r t h e d i s s o l u t i o n o f r o c k s h a s been i n u s e f o r many years. The C l a i s s e F l u x e r f u s i o n d e v i c e s i m p l y makes t h i s f u s i o n a u t o m a t e d . We have u s e d t h e method i n t h e p a s t f o r t h e f u s i o n o f c o a l and f l y a s h e s ( 1 0 , 1 3 ) . O i l s h a l e s c a n be d i s s o l v e d by t h i s method w i t h o u t p r e - a s h i n g . Once t h e s o l u t i o n i s p r e p a r e d , i t may be a n a l y z e d f o r t h e most p a r t by ICPES o r by AAS. A n a l y s i s o f U.S.G.S. D e v o n i a n O h i o s h a l e SDO-1 by f u s i o n f o l l o w e d by AAS o r ICPES measurements i s i l l u s t r a t e d i n Table I I I . I n t h e p r e d o m i n a n t l y AAS scheme, p h o s p h o r u s and t i t a n i u m are c o l o r i m e t r i c a l l y determined. The r e s u l t s o b t a i n e d on f i v e replicates o f the s o l u t i o n by e a c h method are given i n T a b l e I I I and a r e compared w i t h t h e v a l u e s o b t a i n e d f o r t h i s s t a n d a r d a t t h e I n d i a n a G e o l o g i c a l S u r v e y . (_7) The ICPES and AAS r e s u l t s a r e i n v e r y good agreement w i t h each o t h e r and w i t h the l i t e r a t u r e v a l u e s . The p r e c i s i o n and t h e a c c u r a c y o f t h e measurements a r e ±5% f o r most e l e m e n t s a n a l y z e d . T a b l e I I I . A n a l y s i s o f S h a l e SDO-1 By F u s i o n and ICPES-AAS Oxide/Wt % By:

ICPES

AAS

XT^Ol

15.6 ± 0.15

15.4 ± 0.12

Calf Fe 0 K 0 MgO Na 0 Si0 Ti0 P 0 BaO MnO Total

1.37 + 0.02 11.8 ± 0.1 4.13 ± 0.12 1.91 ± 0.02 0.46 ± 0.01 62.4 ± 0.6 0.87 ± 0.01 0.37 ± 0.07 0.05 ± 0.01 0.06 ± 0.00 99.0

1.33 ± 0.01 11.7 ± 0.1 4.00 ± 0.06 1.86 ± 0.00 0.44 ± 0.00 63.7 ± 1.1 0.97 0.18 — — 99.4

2

3

2

2

2

2

2

5

L i t e r a t u r e (7)

1575 1.42 12.2 4.23 1.87 0.52 64.4 0.90 0.14 0.055 0.056 101.3


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Characterization

483

of Oil Shales


Combining t h e f u s i o n technique w i t h ICPES measurements gives a r a p i d and a c c u r a t e method f o r the ash elemental analysis. The t o t a l a n a l y s i s t i m e needed i s 20-25 m i n u t e s p e r sample. However, a l t h o u g h t h e f u s i o n p r o c e d u r e i s e x c e l l e n t for the d e t e r m i n a t i o n o f a l l major elements, i t i s not s u i t a b l e for t h e d e t e r m i n a t i o n o f t r a c e elements, because t h e f i n a l s o l u t i o n (1 L ) i s t o o d i l u t e f o r d e t e c t i o n o f t r a c e e l e m e n t s . If the solution volume i s kept small, extremely high c o n c e n t r a t i o n s o f l i t h i u m and b o r o n i n t h e s o l u t i o n g i v e a n undesirable high background spectrum f o r trace element measurements. Hence, i t i s n e c e s s a r y t o r e s o r t t o a s e p a r a t e procedure where both trace and m a j o r elements c a n be simultaneously determined. P a r r Bomb D i s s o l u t i o n o f S h a l e s . O r i g i n a l l y the acid d i g e s t i o n bomb was d e v e l o p e d by Bernas (14) f o r t h e d i s s o l u t i o n o f s i l i c a t e matrices. An a d a p t a t i o n o f t h i s bomb i s now m a r k e t e d by Parr Instrument Company o f Moline, Illinois. The dissolution p r o c e d u r e h a s been a d a p t e d t o s h a l e s and was described i n the Experimental S e c t i o n . O t h e r w o r k e r s have used d i f f e r e n t a c i d c o m b i n a t i o n s f o r the d i s s o l u t i o n o f a s h e s i n t h e a c i d d i g e s t i o n bomb. T h u s , HC1 + HF, H N 0 , H C 1 0 + HF, aqua r e g i a + HF, and HN0 + H C 1 0 h a v e a l l b e e n used i n t h e a c i d d i g e s t i o n bombs. We h a v e found t h e aqua r e g i a + HF m i x t u r e t o be q u i t e e f f e c t i v e i n a c c o m p l i s h i n g the d i s s o l u t i o n . I t i s i m p o r t a n t t o have a b o r i c a c i d b l a n k s u b t r a c t e d f r o m t h e sample s p e c t r u m i n t h e ICPES a n a l y s i s t o correct f o r t h e boron interferences with other elemental lines. I t i s a l s o n e c e s s a r y t o add b o r i c a c i d t o t h e sample s o l u t i o n i m m e d i a t e l y a f t e r o p e n i n g t h e bomb, a n d t h e n t o h e a t t h e s o l u t i o n o n a w a t e r b a t h f o r 15 m i n u t e s s o t h a t a l l o f t h e boric acid goes i n solution and r e a c t s with insoluble fluorides. When b o r i c a c i d was added o n l y d u r i n g t h e f i n a l d i l u t i o n s t e p , l o w r e c o v e r i e s were o b t a i n e d , s i n c e A l , B a , C a , and Mg, w h i c h form i n s o l u b l e f l u o r i d e s , were f i l t e r e d o f f a l o n g w i t h the unburned carbon. The r e s u l t s o f u s i n g t h e a c i d d i g e s t i o n bomb f o r s h a l e s a r e i n c l u d e d i n T a b l e I V . These t h r e e s h a l e s a r e d i s t r i b u t e d by t h e U.S. G e o l o g i c a l S u r v e y as " s t a n d a r d " s h a l e s : Green R i v e r s h a l e SGR-1, Cody s h a l e SCO-1, a n d D e v o n i a n O h i o s h a l e SDO-1. N o t enough i n f o r m a t i o n i s a v a i l a b l e i n t h e l i t e r a t u r e on t h e c o m p o s i t i o n o f t h e s e s h a l e s . The U.S.G.S. v a l u e s g i v e n i n T a b l e I V f o r s h a l e s SGR-1 and SCO-1 a r e a v e r a g e s o f v a l u e s f r o m f i v e p a p e r s g i v e n i n a n U.S.G.S. r e p o r t ( 1 5 ) , w h i l e t h e l i t e r a t u r e v a l u e s f o r t h e s h a l e SDO-1 a r e f r o m t h e I n d i a n a Geological Survey (7). We a n a l y z e d e a c h sample i n f o u r r e p l i c a t e s b y t h e P a r r a c i d d i g e s t i o n bomb p r o c e d u r e . Overall, t h e agreement between t h i s p r o c e d u r e and t h e l i t e r a t u r e r e s u l t s i s good. F o r SGR and SCO s h a l e s , chromium and n i c k e l r e s u l t s c o u l d n o t be o b t a i n e d b y t h i s p r o c e d u r e due t o c o n t a m i n a t i o n 3

4

3


4


j j 6.52±0.12

Ca, %

j

j]

Be

Fe, %

Cu

7

6

±

8

"

j j 1.59±0.05

11

II

[ j 13.5±4.5

Co

Cr

j j 10.3±2.7

Cd

0.5-1.0

259*6

J

1

1

j

j

J

j

J

J

1

j j

25-40

j|

As

1

j j 3.31*0.27 J

Found

SGR-1

Al, %

1|

Jj

J J

1 Element, I wppm

1 15

2.25

65.2

-

11.6

-

5.64

0.91

337

75

3.71

USGS

0.4-2.3

558*10

Characterization of Oil Shales - American Chemical Society

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