Bureau of Mines interest in methane adsorption was developed from re- search
on ... and hydrogen are lowest if the methane is adsorbed by ctivated carbon! 7 .
-1 32-
E l e v a t e d P r e s s u r e A d s o r p t i o n o f Methane on A c t i v a t e d Carbon; E f f e c t s o f Contaminant Gases and Repeated C y c l i n g
J . W . M u l v i h i l l , W . P . Haynes, R . J . Haren, and J. H . F i e l d U . S. Bureau o f Mines, 4800 Forbes Avenue P i t t s b u r g h , P e n n s y l v a n i a 15213
IhT RODUC TION I
Bureau of Mines i n t e r e s t i n methane a d s o r p t i o n w a s developed from res e a r c h on h y d r o g a s i f i c a t i o n of c o a l t o produce s y n t h e t i c p i p e l i n e g a s . The p r o d u c t from h y d r o g a s i f i c a t i o n c o n s i s t s p r i n c i p a l l y o f methane and hydrog e u ! t h e methane c o n t e n t v a r y i n g from 5 t o 80 p e r c e n t depending on p r o c e s s v a r i a b l e s . The minor c o n s t i t u e n t s are n i t r o g e n , carbon o x i d e s , s u l f u r compounds, u n s a t u r a t e s , h i g h e r molecular weight hydrocarbons i n c l u d i n g a r o m a t i c s , and w a t e r v a p o r . S y n t h e t i c p i p e l i n e gas w i t h a h e a t i n g v a l u e of a p p r o x i m a t e l y 1,000 B t u ' s c a n b e produced from h y d r o g a s i f i c a t i o n p r o d u c t by r e c o v e r i n g t h e methane. The Bureau o f Mines h a s r e p o r t e d t h a t e s t i m a t e d c a p i t a l and o p e r a t i n g c o s t s f o r s e p a r a t i n g methane from m i x t u r e s of met ane and hydrogen a r e lowest i f t h e methane i s adsorbed by c t i v a t e d carbon! The estimate, however, w a s based on e x t r a p o l a t e d data?$for t h e a d s o r p t i o n o f - p u r e methane a t r e l a t i v e l y low p r e s s u r e s . The o b j e c t i v e o f t h i s i n v e s t i g a t i o n was t o e s t a b l i s h a d s o r p i i o n isorherms f o r nethane on a c t i v a t e d c a r b o n a t 40" C and p r e s s u r e s o f 14.2 t o 806 p s i a and s t u d y t h e tendency of a c t i v a t e d carbon t o l o s e i t s a d s o r p t i v e c a p a c i t y f o r methane when t h e methane is contaminated w i t h o t h e r gases and/or t h e r e i s repeated c y c l i n g .
7.
E f f e c t s of a d d i n g benzene, hydrogen, e t h y l e n e , o r hydrogen s u l f i d e were i n v e s t i g a t e d . These g a s e s w e r e chosen as c o n t a m i n a n t s because t h e y are i n t h e gaseous m i x t u r e produced by h y d r o g a s i f i c a t i o n . Two of t h e contaminant g a s e s , benzene and hydrogen, used i n t h e experiments were given c o n c e n t r a t i o n s s i m i l a r t o t h o s e found i n a h y d r o g a s i f i c a t i o n p r o d u c t . The o t h e r two c o n t a m i n a n t s , e t h y l e n e and hydrogen s u l f i d e , were g i v e n much h i g h e r c o n c e n t r a t i o n s t h a n would b e found i n a h y d r o g a s i f i c a t i o n product i n o r d e r t o s i m u l a t e r a p i d p o i s o n i n g of t h e a d s o r b e n t .
,,
The a d s o r p t i v e c a p a c i t y o f a c t i v a t e d c a r b o n c a n b e a f f e c t e d by s i d e r e a c t i o n s . A c t i v a t e d c a r b o n may a c t c a t a l y t i c a l l y t o c o n v e r t hydrogen s u l f i d e t o f r e e s u l f u r i n the p r e s e n c e of t r a c e amounts of oxyge and t h e f r e e s u l f u r may occupy s p a c e t h a t c o u l d be t a k e n up by t h e methane., 17'
J I
I
I
-133LPPARATUS AND PROCEDURE
Some o f t h e main components of t h e fixed-bed a d s o r p t i o n u n i t a r e shown i n f i g u r e 1. The a d s o r b e r was made of t y p e 304 s t a i n l e s s s t e e l a s were t h e v a l v e s , f i t t i n g s , t u b i n g , and gas c o l l e c t i o n r e s e r v o i r s , because o f t h e i r c o n t a c t w i t h hydrogen s u l f i d e . The a d s o r b e r was 24 i n c h e s l o n g w i t h LIP-inch o u t s i d e d i a m e t e r and 3 / 8 - i n c h i n s i d e d i a m e t e r . It had a maximum working P r e s s u r e of 1 , 5 0 0 p s i and a maximum working t e m p e r a t u r e o f 450' C . During d e s o r p t i o n , h e a t w a s s u p p l i e d e l e c t r i c a l l y u s i n g t h e a d s o r b e r w a l l as an electrical r e s i s t o r . Power f o s h e a t i n g was s u p p l i e d by a 7 . 5 KVA, 10: 1 s t e p down t r a n s f o r m e r . During t h e c o o l i n g c y c l e , t h e a d s o r b e r was r a p i d l y c o o l e d a l o n g i t s e n t i r e l e n g t h by a i r blown from a s e r i e s of small n o z z l e s . During t h e r a p i d c 9 c l i n g s t u d i e s , t h e a d s o r p t i o n , d e s o r p t i o n , and c o o l i n g c y c l e s were a u t o m a t i c a l l y c o n t r o l l e d by a t i m e c y c l e c o n t r o l l e r . A complete c y c l e c o n s i s t e d of a 9-minute a d s o r p t i o n p e r i o d a t 40' C , 6 m i n u t e s d e s o r p t i o n a t 450° C , and 3 m i n u t e s c o o l i n g .
\
F i g u r e 2 i s a s c h e m a t i c flow diagram of t h e r a p i d c y c l i n g , fixed-bed a d s o r p t i o n system. The d e s i r e d feed gas o f known c o m p o s i t i o n i s s u p p l i e d t o t h e u n i t from h i g h - p r e s s u r e s t o r a g e c y l i n d e r s . The g a s f l o w r a t e I s meaeured by, p r e s s u r e drop through a c a l i b r a t e d c a p i l l a r y manometer. The g a s s a t u r a t o r was used t o add benzene t o t h e feed g a s when t h e c o n t a m i n a t i n g e f f e c t o f benzene was s t u d i e d .
A weighed sample o f f r e s h a c t i v a t e d c a r b o n was placed i n t h e a d s o r b e r p r i o r t o each s e r i e s o f e x p e r i m e n t s . The a c t i v a t e d c a r b o n was degassed under vacuum f o r 2 t o 3 h o u r s a t 450' C . A t t h e end of t h i s p e r i o d t h e p r e s s u r e i n t h e a d s o r p t i o n chambet, measured by a McLeod gage, was a b o u t 15 m i c r o n s Hg. The "dead s p a c e " i n . t h e r e a c t o r system was t h e volume of t h e a d s o r p t i o n chamber bounded by t h r e e s o l e n o i d v a l v e s , SV-1, SV-2, and SV-3. It r e p r e s e n t e d t h e a d s o r b e n t p o r e volume, t h e i n t e r p a r t i c l e v o i d s p a c e , p l u s t h e volume of t h e a p p a r a t u s c a p i l l a r y l i n e s i n s i d e t h e r e s p e c t i v e b o u n d a r i e s . Dead s p a c e was determined by i n t r o d u c i n g measured amounts of helium a t a t m o s p h e r i c p r e s s u r e i n t o t h e e v a c u a t e d a d s o r p t i o n chamber, n o t i n g t h e e q u i l i b r i u m p r e s s u r e , and a p p l y i n g t h e i d e a l g a s law. Adsorption of helium was assumed t o b e n e g l i g i b l e under t h e s e c o n d i t i o n s . I n d e t e r m i n i n g t h e amount of methane adsorbed f o r t h e pure methane exp e r i m e n t s ( s t a t i c s t u d i e s ) , methane was fed i n t o t h e a d s o r p t i o n chamber u n t i l e q u i l i b r i u m c o n d i t i o n s were a t t a i n e d . E q u i l i b r i u m was a t t a i n e d r a p i d l y , i n some c a s e s w i t h i n 15 m i n u t e s . The gas was t h e n desorbed from t h e a d s o r p t i o n chamber i n t o a 500-cc c a l i b r a t e d c o l l e c t i o n r e s e r v o i r . The d e s o r p t i o n temperat u r e was 450' C f o r a l l t h e e x p e r i m e n t s . A slow h e l i u m purge w a s a l s o used i n c o n j u n c t i o n w i t h t h e h i g h t e m p e r a t u r e t o remove t h e l a s t t r a c e s of methane. The amount o f methane adsorbed on t h e a c t i v a t e d carbon was t h e d i f f e r e n c e between t h e t o t a l methane c o l l e c t e d and t h a t c o n t a i n e d i n t h e dead s p a c e .
'
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1
_ j
I n t h e m i x t u r e e x p e r i m e n t s (dynamic s t u d i e s ) , i t was assumed t h a t methane e q u i l i b r i u m was a t t a i n e d i n approximately t h e same l e n g t h of time r e q u i r e d d u r i n g t h e pure methane e x p e r i m e n t s ( s t a t i c s t u d i e s ) . A f t e r methane e q u i l i b r i u m was a t t a i n e d , t h e g a s r e m a i n i n g i n t h e dead space and on a c t i v a t e d c a r b o n ' s s u r f a c e was d e s o r b e d i n t o t h e 500-cc c a l i b r a t e d c o l l e c t i o n r e s e r v o i r . The amount of methane a d s o r b e d was determined i n a manner s i m i l a r t o t h a t used f o r the s t a t i c s t u d i e s . The i d e a l g a s l a w was used f o r computing t h e amount of adsorbed gas when t h e t o t a l a d s o r t i o n p r e s s u r e d i d n o t exceed 50 p s i . G e n e r a l i z e d compressi b i l i t y f a c t o r s j i were used i n c o n j u n c t i o n w i t h Amagat's law when t o t a l p r e s s u r e exceeded 50 p s i .
All g a s e s were a n a l y z e d by chromatography and mass s p e c t r o m e t r y . The methane used i n t h e e x p e r i m e n t s c o n t a i n e d 0.2 p e r c e n t e t h a n e and 0.1 p e r c e n t n i t r o g e n . The a d s o r b e n t w a s a 12x30 mesh P i t t s b u r g h Coke and Chemical Co. Type BPI, a c t i v a t e d c a r b o n manufactured from v a r i o u s g r a d e s o f bituminous c o a l combined w i t h s u i t a b l e b i n d e r s . RESULTS AND DISCUSSION When a d s o r p t i o n t a k e s p l a c e i n a u n i m o l e c u l a r l a y e r , o r p a r t of a l a y e r , t h e d a t a c a n o f t e n b e f i t t e d s a t i s f a c t o r i l y by means of t h e s i m p l e Langmuir e q u a t i o d l a b P x/m = l + a P
-.
I n t h i s formula x m P a, b
= = =
=
weight of g a s a d s o r b e d . weight o f s o l i d a d s o r b e n t . P a r t i a l p r e s s u r e of t h e gas i n q u e s t i o n a t e q u i l i b r i u m . experimental c o n s t a n t s .
The Langmuir e q u a t i o n is based on t h e assumption t h a t t h e m o l e c u l e s o f t h e adsorbed gas a r e p r e s e n t on t h e s u r f a c e of t h e a d s o r b e n t as a monolayer. The g r e a t e r t h e f r a c t i o n o f t h e s u r f a c e covered by t h e monolayer, t h e l e s s tendency t h e r e is t o a c c u m u l a t e more molecules and t h e g r e a t e r t h e p a r t i a l p r e s s u r e must be t o c o n t i n u e such accumulation. The Langmuir f o r m u l a may be r e w r i t t e n as t h e e q u a t i o n of a s t r a i g h t line, I
P/(x/m)
=
(l/b) P
+
l / ( a b).
The e x p e r i m e n t a l c o n s t a n t s a and b can be c a l c u l a t e d i f t h e p l o t of P/(x/m) v e r s u s P i s a s t r a i g h t l i n e . F i g u r e 3 shows Langmuir p l o t s o f o u r exp e r i m e n t a l d a t a and d a t a of , f o u r o t h e r i n v e s t i g a t o r s , Per K. F r o l i c & / ,
I
\
i L
Y
-135-
.
L. S z e p e 111 sr ,
51 G. C . R a?', and R. J. GrantCurve 5 r e p r e s e n t s & a n t ' s e x t r a p o l a t e d d a t a . These e x t r a p o l a t e d d a t a were used i n o u r o r i g i n a l c o s t
estimates. P l o t s of b o t h S z e p e s y ' s and our d a t a , c u r v e s 2 and 3 , produced s t r a i g h t l i n e s . The upper p o r t i o n o f F r o l i c h ' s d a t a , c u r v e 1, i s a l s o a s t r a i g h t l i n e . The e x p e r i m e n t a l c o n 6 t a n t s f o r c u r v e s 2 and 3 become:
a =
I) Curve 2: 2) Curve 3:
'
9 . 6 4 ~ 1 0 - p~ s i a
a = 1 2 . 8 5 ~ 1 0 - p~s i a
-1 , b = 7.41 g/100 g. -1
,
b = 5.56 g/100 g .
F r e u n d l i c h ' s e q u a t i o n , x/m = a PIin 'I, i s used f r e q u e n t l y t o c o r r e l a t e ads o r p t i o n d a t a . The l e t t e r s x , m, and P have t h e same meaning as i n t h e Langmuir e q u a t i o n , and t h e l e t t e r s a and l / n r e p r e s e n t e m p i r i c a l c o n s t a n t s . The v a l i d i t y o f t h e formula f o r t h e e x p e r i m e n t a l d a t a can b e t e s t e d by p l o t t i n g t h e l o g a r i t h m o f x / m a g a i n s t t h e l o g a r i t h m of P, s i n c e r e w r i t i n g t h e formula i n i t s l o g a r i t h m form, l o g (x/m) = l o g a + ( l h ) l o g P, g i v e s the equation of a s t r a i g h t l i n e . F i g u r e 4 shows F r e u n d l i c h p l o t s of our e x p e r i m e n t a l d a t a and d a t a of t h e L f o u r o t h e r i n v e s t i g a t o r s p r e v i o u s l y mentioned. None o f t h e c u r v e s obeys the Freundlich equation.
,.
T a b l e 1 shows t h e e f f e c t o f 76.5 p e r c e n t hydrogen i n t h e methane f e e d gas upon a c t i v a t e d c a r b o n ' s a d s o r p t i v e c a p a c i t y f o r methane. I n t h e s e s e r i e s of e x p e r i m e n t s , two methane p a r t i a l p r e s s u r e l e v e l s were i n v e s t i g a t e d , 50 and 300 p s i a . A c t i v a t e d c a r b o n ' s e q u i l i b r i u m c a p a c i t y f o r methane was r e duced 10.0 and 22.8 p e r c e n t , r e s p e c t i v e l y , owing t o t h e p r e s e n c e of hydrogen. Experiments w i t h a methane-hydrogen m i x t u r e showed t h a t t h e s e l e c t i v i t y of t h e c a r b o n f o r methane o v e r hydrogen was 11:l a t 50 p s i a p a r t i a l p r e s s u r e , and 28:l a t 300 p s i a . F i g u r e 5 shows t h e e f f e c t of methane c o n t a m i n a t i o n and r e p e a t e d c y c l i n g upon a c t i v a t e d c a r b o n ' s a d s o r p t i v e c a p a c i t y o f methane. Benzene, hydrogen, e t h y l e n e , and hydrogen s u l f i d e were t h e c o n t a m i n a n t s t e s t e d . A f t e r t h e f i r s t a d s o r p t i o n s t e p , a l l t h e c o n t a m i n a n t s reduced t h e c a p a c i t y of a c t i v a t e d c a r b o n f o r methane. The i n i t i a l r e d u c t i o n s i n c a p a c i t y f o r methane owing t o t h e p r e s e n c e of t h e c o n t a m i n a n t s a r e g i v e n i n p e r c e n t i n t a b l e 2 . The p r e s e n c e o f 8.3 p e r c e n t hydrogen s u l f i d e produced t h e g r e a t e s t i n i t i a l loss o f c a p a c i t y , r e d u c i n g t h e c a r b o n ' s c a p a c i t y f o r methane by 53 p e r c e n t . Benzene, hydrogen, and e t h y l e n e reduced t h e methane c a p a c i t y of t h e c a r b o n by 1 3 , 2 5 , and 37 p e r c e n t , r e s p e c t i v e l y . A d d i t i o n a l a d s o r p t i o n - d e s o r p t i o n c y c l e s u s i n g t h e contaminated methane f e e d g a s e s i n c u r r e d no f u r t h e r d e c r e a s e i n c a r b o n c a p a c i t y f o r methane exc e p t i n t h e t e s t s u s i n g 1 0 . 3 p e r c e n t e t h y l e n e i n t h e methane f e e d g a s . A f t e r 150 c y c l e s , a c t i v a t e d c a r b o n ' s c a p a c i t y f o r methane was reduced an a d d i t i o n a l 1 3 p e r c e n t from 37 t o 50 p e r c e n t .
I
I
-136TABLE 1.- E f f e c t o f hydrogen upon a c t i v a t e d c a r b o n ' s a d s o r p t i v e c a p a c i t y f o r methane I
I
,I t
Feed gas
cH4
a)
Adsorption temperaequilibrium tures, pressure, O C psia
-11
Activated carbon's capacity f u r methane, CHn
100 g carbon
Activated carbon 's capacity f o r hydrogen,
Selectivity,
g H7 Carbon c a p a c i t y ( C q 100 F: carbon Carbon capacity(H7)
40
50
2.49
--
--
40
50
2.24
0.02
11: 1
40
300
5.49
--
--
40
300
4.23
0.15
28: 1
23.7 p c t C&
+
b)
76.3 p c t H2
11 a) C H 4 -
23.7 p c t C& b)
L+
76.3 p c t H2
-1 /
C o n t a i n i n g 0.2 p c t C2H6 and 0 . 1 p c t N2.
TABLE 2 . -
Reduction i n a c t i v a t e d c a r b o n ' s c a p a c i t y f o r methane by c o n t a m i n a t i n g gases and r e p e a t e d c y c l i n g 11 Percent
Contaminating ~
gas 3 vol-pct
I n iti a l reduction in capacity f o r methane (without r e c y c l i n g )
Reduction i n capacity f o r methane a f t e r 150 c y c l e s
13.0 25.0 37 .O 53.0
14.0 25 .O 50.0 53.0
.
S a t u r a t i o n of a c t i v a t e d carbon w i t h impurity
I ,
ti
0.35 76.3 10.3 8.3
-11
CgHg H2 C2H4 H2S Conditions:
10.0 100.0
75.0 100.0
Adsorption t e m p e r a t u r e 40" C ; Methane e q u i l i b r i u m p r e s u r e 300 p s i a .
i
-137-
I n t h e s e c o n t a m i n a t i n g and c y c l i n g t e s t s , hydrogen and hydrogen s u l f i d e were t h e o n l y two c o n t a m i n a n t s t h a t c o m p l e t e l y s a t u r a t e d t h e a c t i v a t e d c a r b o n . Benzene and e t h y l e n e o n l y reached 10 and 7 5 p e r c e n t c a r b o n s a t u r a t i o n , respectively. I n a l l o f t h e t e s t s c o n d u c t e d , methane a t t a i n e d e q u i l i b r i u m c o n d i t i o n s OK 100 p e r c e n t s a t u r a t i o n b e f o r e d e s o r p t i o n was i n i t i a t e d . Degree o f s a t u r a t i o n was determined t h r o u g h a d s o r b e r t a i l gas a n a l y s e s . Experiments were conducted about f i v e t i m e s f o r e a c h p u r e methane e q u i l i b r i u m p o i n t . S t a n d a r d d e v i a t i o n from t h e mean v a l u e was 1-2 p e r c e n t f o r t h e s e e x p e r i m e n t s . Stan'dard d e v i a t i o n f o r t h e methane-hydrogen m i x t u r e e x p e r i m e n t s conducted a t t h e two p a r t i a l p r e s s u r e l e v e l s was 2 15 p e r c e n t . G r e a t e r s c a t t e r i n g of d a t a o c c u r r e d when t h e s m a l l q u a n t i t i e s of hydrogen adsorbed were b e i n g d e t e r m i n e d .
-+
CONCLUSIONS 1. I n c r e a s e d t o t a l p r e s s u r e f a v o r s t h e p r e f e r e n t i a l a d s o r p t i o n of methane from methane-hydrogen m i x t u r e s . However, methane is l e s s s t r o n g l y adsorbed from t h e m i x t u r e t h a n when i t i s p r e s e n t a t t h e same p z r t i a l p r e s s u r e i n t h e pure s t a t e . Lower v a l u e s f o r methane a d s o r p t i o n a t h i g h p a r t i a l p r e s s u r e s were found e x p e r i m e n t a l l y t h a n t h o s e e x t r a p o l a t e d from e x i s t i n g d a t a a t lower pressures. 2: Each i m p u r i t y of h y d r o g a s i f i c a t i o n p r o d u c t g a s t e s t e d d e c r e a s e d a c t i v a t e d c a r b o n ' s c a p a c i t y f o r methane. Although t h e c a r b o n was n o t comp l e t e l y s a t u r a t e d w i t h benzene and e t h y l e n e , t h e s e i m p u r i t i e s s t i l l c o n t r i b u t e d s i g n i f i c a n t l y t o t h e i n i t i a l l o w e r i n g of t h e a d s o r b e n t ' s c a p a c i t y f o r methane.
3 . Repeated c y c l i n g , up t o 150 c y c l e s , i n t h e p r e s e n c e of t h e contami n a n t s d i d n o t f u r t h e r d e c r e a s e a c t i v a t e d c a r b o n ' s c a p a c i t y f o r methane e x c e p t when e t h y l e n e was added.
a/
4 . These r e s u l t s i n d i c a t e t h a t t h e c o s t e s t i m a t e s r e p o r t e d e a r l i e r were t o o low because t h e e x t r a p o l a t e d v a l u e s f o r methane a d s o r p t i o n were t o o h i g h . The e f f i c i e n c y of a c t i v a t e d carbon in a d s o i b i n g methane i s lowered by o t h e r g a s e s mixed w i t h t h e methane and, when e t h y l e n e i s p r e s e n t , by r e p e a t e d c y c l i n g . However, f o r most of t h e c a s e s of s e p a r a t i o n i n v e s t i g a t e d ( C h conc e n t r a t i o n s of 5 , 20 and 50 p c t ) , t h e economics of a d s o r p t i o n by a c t i v a t e d c a r b o n a r e now c o n s i d e r e d t o be a p p r o x i m a t e l y t h e same a s s e p a r a t i o n by l i q u e f a c t i o n of methane.
,I1 I.
38 -
1.
't'
B a r r y , H. M . Fixed-bed A d s o r p t i o n 1960, p . 115.
i*
2.
Channabasappa, K. C . , and H. R . Linden. Fluid-Bed P r e t r e a t m e n t of Bituminous C o a l s and L i g n i t e . D i r e c t Hydrogenation of Chars t o Pipeline Gas. I n d . Eng. Chem., v . 50, No. 4 , A p r i l 1958, pp. 637-644.
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F r e u n d l i c h , H e r b e r t . C o l l o i d and C a p i l l a r y Chemistry ( T r a n s l a t e d from t h e t h i r d German e d i t i o n by H . S c a f f o r d H a t f i e l d ) , E . P . Dutton and Co., N e w York, N . Y., 1 9 3 1 , p. 111.
4.
F r o l i c h , Per K . A d s o r p t i o n of Methane and Hydrogen on C h a r c o a l a t High P r e s s u r e . I n d . and E n g . Chem., v . 2 2 , No. 10, Oct. 1930, pp. 1058-1060.
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G r a n t , R . J . , M. Manes, and S . B . Smith. A d s o r p t i o n o f Normal P a r a f f i n s and S u l f u r Compounds on A c t i v a t e d Carbon. A . I . Ch. E . J . , v . 8 , N o . 3 , J u l y 1962, pp. 403-406.
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Chem. Eng., v . 67, No. 3, Feb. 8,
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H i t e s h u e , R. W . , R . B . Andersor., and S . Friedman. Hydrogenation o f Coal and C h a r s . I n d . and Eng. Chem., v . 52, No. 7 , J u l y 1960, pp. 577-579.
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Langmuir, I. The A d s o r p t i o n o f Gases on P l a n e S u r f a c e s o f Glass, Mica, and P l a t i n u m . J . Am. Chem. S O C . , v. 4 0 , No. 9 , S e p t . 1918, p . 1361.
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Mulvihill, J. W . , W . P. Haynes, S. K a t e l l , and G . B . T a y l o r .
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Nelson, L . C . , and E . F . O b e r t . How t o Use t h e New G e n e r a l i z e d Comp r e s s i b i l i t y C h a r t s . Chem. Eng., v. 61, N o . 7, J u l y 1954, pp. 203-208.
I,
Cost Estimates of P r o c e s s e s f o r S e p a r a t i n g M i x t u r e s of Methane and Hydrogen. BuMines Rept. o f I n v . 6530, 1964, 4 3 pp.
i
and E . 0 . Box, Jr. Adsorption of Gases on A c t i v a t e d C h a r c o a l . I n d . and Eng. Chem., v . 4 2 , No. 7 , J u l y 1950, pp. 1315-1318.
10. Ray, G . C . , 11.
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S z e p e s y , L . , and V. I l l e s . Adsorption of Gases and Gas M i x t u r e s . C h i m . Hung. Tomus., v . 35, 1963, p p . 37-50; 53-59.
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