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UBC Theses and Dissertations

The reductive capacity of an absorbent charcoal surface Wright, Frances Mary 1938

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The Reduc t i v e C a p a c i t y o f an Adso rben t Cha r c o a l S u r f a c e . by F r an ce s M. Wr igh t unde r the d i r e c t i o n o f Dr . M. J . M a r s h a l l A T h e s i s Submi t t ed i n p a r t r equ i r emen t f o r the degree o f Ma s t e r o f A r t s i n the Department o f Chem i s t r y . The U n i v e r s i t y o f B r i t i s h Co lumbia A p r i l , 1938 Tab le o f C on t en t s . - •-, Page I n t r o d u c t i o n 1 A im . • 6 P a r t I • • 7 E x p e r i m e n t a l 7 R e s u l t s 10 P a r t I I . . . . . . . . . 16 E x p e r i m e n t a l 16 R e s u l t s 16 P a r t I I I 18 E x p e r i m e n t a l 18 R e s u l t s 19 Con c l u s i o n s 19 B i b l i o g r a p h y 21 Tab l e s and g r a p h s . Tab le I . . . . . . . . . . . . . . . . . . . . . . " 8 Tab l e I I . . . . 11 Tab l e I I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Tab le IV . 14 Tab l e V * . . 17 Graph 1 15 Graph 2 15 Graph 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Graph 4 15 Graph 5 17 Graph 6 . . . 19 The Reduc t i v e C a p a c i t y o f an Adsorben t Cha r c oa l S u r f a c e . I n t r o d u c t i o n S i n c e t h i s t h e s i s i s conce rned w i t h t he t rea tment o f a c t i v a t e d - c h a r c o a l to i n c r e a s e the s u r f a c e energy a v a i l a b l e f o r the c h e m i s o r p t i o n o f carbon d i o x i d e at l ow p r e s s u r e s , i t appeared a d v i s a b l e to i n c l u d e a resume o f the p r e s en t i n f o r -ma t i on conee rn i ng the s t r u c t u r e and c h a r a c t e r i s t i c s o f a c t i v a t e d c h a r c o a l . A r e v i ew of t h e l i t e r a t u r e d e a l i n g w i t h c h a r c o a l a c t i v a t i o n i s g i v e n by F i n d l a y . ^ ^ There a r e s e v e r a l main p o i n t s o f c o n t r o v e r s y about the c h a r a c t e r i s t i c s o f c h a r c o a l . Most au tho r s t r e a t i s o l a t e d p o i n t s r a t h e r than t he p rob lem o f how the s u r f a c e atoms a c q u i r e g r e a t e r f r e e energy than the b u l k phase . The energy a v a i l a b l e f o r c hem i ca l a d s o r p t i o n , s p e c i f i c i t y , r e t e n t i v i t y and the s t r i c t l y p h y s i c a l p r o p e r t i e s v a r y w i d e l y w i t h t h e sou r ces f r om wh i ch t h e c h a r c o a l s a r e p roduced . Bu r r age, ^ ) d e a l i n g w i t h wood c h a r c o a l s , c l a im s t h a t the a c t i v e c h a r c o a l i s d e r i v e d f rom the c e l l u l o s e and the i n a c t i v e carbon f rom t h e l i g n i n . H i s b a s i s f o r t h i s t h eo r y i s the l owe r carbon con ten t and the r e l a t i v e ease o f o x i d a t i o n o f c e l l u l o s e . S e v e r a l i n v e s t i g a t o r s have no ted a r e l a t i o n s h i p (2) between hydrogen con ten t and a d s o r p t i v e ene rgy . B a r k e r showed tha t the hydrogen con ten t o f cocoanut c h a r c o a l s dec reased du r i n g the u s u a l commerc ia l s team a c t i v a t i o n p r o c e s s . From R a y 1 s ^ 2 3 ) f i g u r e s i t i s seen t h a t on a c t i v a t i o n t he dec rease i n hydrogen con ten t i s p r o p o r t i o n a l to t h e i n c r e a s e d r e t e n t i v i t y f o r ca rbon t e t r a c h l o r i d e o f the c h a r c o a l . F o r B i r c h wood c h a r c o a l , P h i l i p and Ja rman^^)quote a G:H r a t i o i n c r e a s i n g w i t h h i g h e r t empera tu res and l o nge r p e r i o d s o f h e a t i n g . There was a s t eady improvement i n a d s o r p t i v e ( 1 ) a b i l i t y w i t h r i s e i n t empe r a t u r e . Bangham and S t a f f o r d , d u r i n g work on the bombardment o f g r a p h i t e w i t h hyd rogen , came to the c o n c l u s i o n t h a t hydrogen broke up the hexagona l arrangement o f ca rbon atoms, thus i n c r e a s i n g t he a d s o r p t i v e energy . The h i g h degree o f mu tua l s a t u r a t i o n o f the atoms i n any one p l a ne r ende r s g r a p h i t e a poo r " s o r b e n t " . I n the above manner the g r e a t e r hydrogen con ten t of s o - c a l l e d amorphous ca rbons c o n t r i b u t e s t o t he a d s o r p t i v e a b i l i t y . Lowry and Hn l e t t ( ^ ) a n a l y s e d the gases removed by o u t g a s s i n g a sample o f c h a r c o a l a f t e r oxygen had been adsorbed on i t . Be low 1 0 0 0 ° 0 ca rbon d i o x i d e and ca rbon monoxide were d r i v e n o f f ; above t ha t t empera tu re hydrogen and a s m a l l pe r cen tage o f methane were the e f f l u e n t g a s e s . The a c t u a l s t r u c t u r e o f adso rben t c h a r c o a l s has been s t u d i e d i n s e v e r a l ways . In t he hands o f d i f f e r e n t i n v e s -t i g a t o r s the ev i dence o f Z - r a y ana l y s e s c o n f l i c t s . But o p i n i o n s concur t ha t a g r a p h i t i c c r y s t a l s t r u c t u r e i s p r e s e n t , a l t h ough the d i f f r a c t i o n p a t t e r n s are o v e r l a i d , i n some eases , w i t h s c a t t e r i n g . Debye and S c h e r r e r ^ 5 ^ c l a i m t h a t amorphous ca rbon i s g r a p h i t e i n f i n e l y d i v i d e d p a r t i c l e s . R u f f , Schmidt and O l r i c b J * ^ s t a t e t ha t a o t i v e carbon i s a t r ue m o d i f i c a t i o n and does no t have e x a c t l y t h e l a t t i c e s t r u c t u r e o f g r a p h i t e . J e n k i n s ^ ^concurs w i t h Debye. Barker^ ^shows tha t p r ima r y c h a r c o a l gave no d i f f r a c t i o n r i n g s . On a c t i v a t i o n the r i n g s o f g r a p h i t e appea r . Th i s ev idence would appear to d i m i n i s h the impor tance o f the adsorbed hyd roca rbon t heo r y o f a c t i -v a t i o n . On ly on l o ng h e a t i n g d i d the d i f f r a c t i o n p a t t e r n s (22) become nar row and sha rp . Raman and K r i s t n a t u r i ' ' w h i l e s t u d y i n g the d i f f r a c t i o n p a t t e r n o f g r a p h i t e found s c a t t e r i n g wh i ch wou l d be due t o " f r e e " e l e c t r o n s . I t i s p r o b a b l y these u n p a i r e d e l e c t r o n s wh ich g i v e r i s e to t he s u r f a c e f o r c e s . Theo r i e s o f the po lymer s t r u c t u r e , o f c h a r c o a l have been b u i l t upon s e v e r a l b a s e s . An adsorbent ca rbon can be made f rom g r a p h i t e by o x i d i z i n g i t t o g r a p h i t i c a c i d and then (17 £3) e x p l o d i n g the p roduc t o r r e d u c i n g i t w i t h h yd r o x y l am i ne . ' T h i s sugges t s t h a t the s u r f a c e p o t e n t i a l i s due" to l a c k o f o r i e n t a t i o n o f the ca rbon atoms i n c h a r c o a l . Bu r r age c l a i m s t ha t t he o r i g i n a l mac ro s cop i c f o rm o f the sou rce i s p r e s e r v ed i n t he p a r t i c l e s o f c h a r c o a l . The a c t i v i t y i s due to t he u n s a t u r a t i o n o f carbon atoms, l e f t i n the c e l l u l o s e s t r u c t u r e and f r om w h i c h hydrogen has been o x i d i z e d away. Lowry^ ^ ) c o n s i d e r s t h a t a l l m a t e r i a l s between l i g n i n and g r a p h i t e can be c o n s i d e r e d as po l ymers b u i l t o f u n i t s o f s i x - r i n g "hydrocarbons. The more complex the po lymer t h e l e s s hydrogen i t c o n t a i n s . The hydrogen c on t en t i s a f u n c t i o n o f the tempera ture to wh i c h t he c h a r c o a l has been hea ted and o f the l e n g t h o f t ime tha t i t has been m a i n t a i n e d a t t h a t tem-p e r a t u r e . . Thus "amorphous" carbon i s a complex hyd ro ca rbon o f a r oma t i c s t r u c t u r e . B r i g g s ^ ^ a l s o p o i n t s out t h a t we are not concerned w i t h the u l t i m a t e atom but w i t h e l a b o r a t e po l yme r s . The o n l y s t r u c t u r e s impe r v i ou s to gases a r e c r y s t a l s and g l a s s e s wh ioh a r e made o f a t om i c l i n k a g e s . Hea t i n g s i m p l i f i e s the po l ymers p r e s en t i n the c h a r c o a l and , as some o f the carbon i s removed as ca rbon d i o x i d e , recom-b i n a t i o n does no t t a k e p l a c e . In two o t h e r papers Lowry^ 16»lc3) a e a ] _ s w i t h t h i s t h e o r y . I f , a t a s u r f a c e , t h e r e a re 0 - H bonds whose ca rbon atoms a re so s i t u a t e d w i t h r e s p e c t to t he r e s t o f t he s o l i d t ha t when the bonds a re b roken t h e carbons cannot o r i e n t i n t o a g r a p h i t e l a t t i c e , then the s u r f a c e carbon atoms have f r e e energy f o r adsorpt ion*, In t he f o r m a t i o n o f amorphous c a r bon -po l yme r i z e d r e s i d u e s f rom the t he rma l d e compos i t i o n o f h yd r o -carbons o f g r e a t e r hydrogen cont ent - any t r ea tmen t wh i ch i n c r e a s e s the u n s a t u r a t i o n must i n c r e a s e the a d s o r p t i v e c a p a c i t y . He sugges t s t ha t v / i th r i s i n g tempera tu re ( d r i v i n g o f f hydrogen) the a d s o r p t i v e a b i l i t y i n c r e a s e s to a maximum and then dec reases as g r a p h i t i z a t i o n s e t s i n . K ing^-^sugges t s t h a t the hydrogen i s i n the b i n d i n g between u n s a t u r a t e d v a l e n c e s . The remova l of t h i s hydrogen l e a v e s these v a l e n c e s w i t h a p o t e n t i a l depending on the p o s i t i o n o f the ca rbon atoms i n the l a t t i c e o r c h a i n . Z i n g^ 1 1 ^and Ko l t ho f f^ - 1 - 2 )des c r i be an a c i d s u r f a c e r e s u l t i n g f rom o x i d a t i o n a t t empe ra tu re s be l ow 450° 0 and a b a s i c one f rom t r ea tmen t s at h i g h e r t empe r a t u r e s . Th i s c o n d i t i o n may be a f u n c t i o n o f the s o l u t i o n s w i t h wh i ch they were wo r k i ng o r i t may be a f e a t u r e o f the fundamenta l s u r f a c e bond ing r e s u l t a n t f r om the heat t r e a tmen t . The main r e s u l t o f the Quantum mechan i c a l t r ea tmen t o f s u r f a c e f o r c e s i s a r e a l i s a t i o n o f t h e impor tance o f the n u c l e a r d i s t a n c e s o f the ca rbon atoms. Sherman and Eyr ing^ ^5) show t ha t f o r any g i v e n s t r e n g t h o f the 0 - C bond ( i . e . , s i n g l e , doub le , t r i p l e ) t h e r e i s a n u c l e a r d i s t a n c e most f a v o u r a b l e f o r a d s o r p t i o n . I t wou ld seem more p r o f i t a b l e to work, f r om d i s t a n c e apa r t o f t h e carbon atoms and known e n e r g i e s o f a d s o r p t i o n to t he energy o f the s u r f a c e atoms s i n c e t h e i r e n e r g i e s need no t co r r e spond t o those o f carbon atoms i n hyd roca rbon m o l e c u l e s . L e n n a r d - J o n e s ( 1 4 ) sugges t s t ha t i f the e l e c t r o n i c c o n f i g u r a t i o n s o f ca rbon atom and app roach i ng mo l e c u l e a re such t h a t the r e s u l t i n g - e l e c t r o n i c s t a t e i s p o s s i b l e , and i f the energy o f the p a t t e r n , wh ich depends on i n t e r n u c l e a r d i s t a n c e s , i s a minimum, then a s t a b l e adso rba te r e s u l t s . 6. The po lymer and " s t r u c t u r e r e s i d u a l f rom sou r c e " t h e o r i e s to account f o r the s u r f a c e energy o f c h a r c o a l s a re suppo r ted by the two l a t t e r ma thema t i c a l t r e a t m e n t s . A im . - T h i s was a c o n t i n u a t i o n o f an i n v e s t i g a t i o n s t a r t e d ( *>) i n c o n j u n c t i o n w i t h IP. Goolr ' i n o r d e r t o unde r s t and the anomalous b e h a v i o u r , at l ow p r e s s u r e s , o f two samples o f a c t i v a t e d cocoanut f rom the same source ( N a t i o n a l Garbon Go. 1929 ) . One was used by R. A . F i n d l a y ^ 8 ^ and found by H. 0 . McMahon^ 2(-*^to reduce CO2 to GO a t room tempera tu re d u r i n g s t u d i e s on the mechanism o f gas a d s o r p t i o n . The second sample , i n u se i n the heat measurement appa r a t u s , d i d not reduce G0£, even at t he l owes t c o n c e n t r a t i o n s (2 m i c r o -mo l s pe r g r am ) . The t rea tment o f the two samples had d i f f e r e d v e r y l i t t l e but an i n v e s t i g a t i o n was i n i t i a t e d to de c i de wh i ch o f the d i f f e r e n c e s had caused the s u r f a c e v a r i a t i o n . The r e d u c t i v e a c t i v e s u r f a c e had been more e x t e n -s i v e l y o x i d i z e d and had been s u b j e c t e d to h e a t i n g , gas r e a d s o r p t i o n and subsequent c o o l i n g ; i t had a l s o been w i d e l y o x i d i z e d by s a t u r a t i n g the s u r f a c e w i t h oxygen added a t 90°A and a l l o w e d to chemisorb at room t empe r a t u r e . B o t h samples had on o c c a s i o n been ou tgassed a t h i g h e r t empera tu res than the u s u a l 1000°C. Each o f these d i f f e r e n c e s was i n v e s t i g a t e d i n t u r n . , 7. P a r t I . E x p e r i m e n t a l . The c h a r c o a l s t u d i e d was t h a t removed f rom the heat measurement appa ra tus by Gook and Wr igh t i n March , 1937. I t was v e r y i n a c t i v e i n r e d u c i n g carbon d i o x i d e . On add ing 1.83 m io ro -mo l s pe r gram o f carbon d i o x i d e the e q u i l i b r i u m p r e s s u r e was 224 x 10"^ mm. and o n l y 5% o f i t was due to carbon monox ide . The appa ra tus u sed was t ha t d e s c r i b e d by McMahon i n h i s t h e s i s . The s a t u r a t e d we igh t o f the c h a r c o a l was 24.4635 grams. Carbon d i o x i d e was p repa red f rom commerc i a l " d r y i c e " . I t was p u r e f i e d by f r e e z i n g i n a l i q u i d a i r t r a p , pumping o f f any r e s i d u a l ga s and r e s u b l i m i n g the CO . Th i s p rocedure was r epea ted s e v e r a l t i m e s . A f t e r an o u t g a s s i n g at 1100° C f o r 20 hou r s McMahon found an i n c r e a s e i n a c t i v i t y . On add ing 2 .05 M-M/gm. o f gas the p r e s s u r e f e l l s l o w l y t o 36 x 10~ 4 mm; the r e s i d u a l gas was 47$ CO. A f t e r 20 hou r s the p r e s s u r e was 25 x 10"*^ mm. and the gas was 8@fo CO. A s t anda r d r u n was made by wh i ch to gauge the r e s u l t s o f methods o f a c t i v a t i o n . The c h a r c o a l was ou tgas sed f o r 12 . 5 hou r s , the tempera tu re neve r r i s i n g above 1074° C. I n each o u t g a s s i n g the tempera tu re was r a i s e d s l o w l y to d r i v e o f f gases at as l ow a t empera tu re as p o s s i b l e . A t the end o f the o u t g a s s i n g the c h a r c o a l was c oo l ed q u i c k l y w i t h the pumps r u n n i n g . 8. A s u r f a c e c o n c e n t r a t i o n o f 2.56 m i c r o -mo l s pe r gram o f CC-2 was added. The change o f p r e s s u r e and GOg con ten t o f the r e s i d u a l gas w i t h t ime w e r e ' n o t e d . The r e s u l t s a re g i v e n i n t a b l e I. The f i r s t column g i v e s the t empe ra tu re , the second t he t ime a f t e r a d d i t i o n , t h i r d , g i v e s the t o t a l p r e s s u r e , f o u r t h the p r e s s u r e o f gas uncondensab le i n l i q u i d a i r and the f i f t h the GOg con ten t o f t he gas as a p e r c e n t a g e . TABLE I. Temp Time i n P r e s s u r e i n MM.x!0 V fo 0 0 2 i n (°Q) Hours T o t a l L i q . A i r . On. R e s i d u a l Gas 20°G .12 4000 - - ' • " , . 1.87 1300 185 - mfo 2.33 850 115.' mfo 4.87 600 •'• 77 mfo 6 .33 430 -56 ' • • 87$ » 19 ' ' 57; •' 11 .8 .79$ ; B4° • o 297 ' ~ . 72 1.12 ' 550 :,: 65 • 88 126 3 . 5 : 1270 - -'it • 4 . 0 780 ' - -• '4.5 . 560 ,40 ; > x 93 128° 6 .0 370 32 91 171 7 .5 1920 42. . 96 180 21 .0 500 260 48$ 238 1.5 8000 Appro: - • it 2 . 5 8000 " 4500 Approx . 44 n 7.25 it -Dar i ng the f i r s t s i x runs the t ime (1 /2 h r . ) t ha t the gas i n the McLeod gauge was out o f f f r om the c h a r c o a l d u r i n g a n a l y s e s , was deduc t ed . But i t was obse rved t ha t when the c u t - o f f was l owered the p r e s s u r e v e r y q u i c k l y reaohed a new v a l u e wh i c h f i t t e d the t ime p r e s s u r e curve i n wh i ch the l / 2 hou r was not deduc ted . I n the r e s u l t s the l / 2 h r . p e r i o d s have been added to the t imes o f the f i r s t s i x runs as g i v e n i n the l a b o r a t o r y n o t e s . The r e s i d u a l gas q u i c k l y adso rbs on the spaces l e f t v a can t by the rear rangement o f the adsorbed m o l e c u l e s i n the i n t e r v e n i n g t ime . S i n c e p r e v i o u s work had shown no a c t i v a t i o n r e s u l -t a n t f r om d e s o r p t i o n and r e a d s o r p t i o n o f added o x i d e s o f ca rbon th rough tempera tu re v a r i a t i o n , i t was dec i ded to obse rve the e f f e c t o f o u t g a s s i n g o f l o n g e r d u r a t i o n and a t h i g h e r t empera tu res than was c u s t o m a r i l y employed. In t he s u c ceed i ng s i x runs the same p ro cedu re as i n Run I was f o l l o w e d . A p p r o x i m a t e l y 15 cms o f C 0 2 on the p i p e t t e s c a l e were added a f t e r o u t g a s s i n g f o r a g i v e n t ime a t a c a r e f u l l y no ted t empe ra tu r e . Run I I o u t g a s s i n g was f o r 15 h r s at 1015° G and f o r 6 h r s at 1100°C. COg added - 2.22 m i c r o -mo l s p e r g ram. Run I I I o u t g a s s i n g at 1020° f o r 6 l / 2 h r s . a t 1100° f o r 12 h r s . - 5 the p r e s s u r e b u i l d - u p i n 5 m i n s . was 100 x 10 mm. C0 2 added - 2 . 5 . M-M/gm. 10 . Run IY o u t g a s s i n g at-; 1100°C f o r 22 h r s . P r e s s u r e b u i l d - u p 17 h r s . - 115x10 mm. 20 h r s . - 62x10 mm. 21 l / 2 h r s . - 56x10" 5mm. C0 g .added - 2.39 M-M/gm. Run V o u t g a s s i n g at 1100°0 f o r 20 h r s . P r e s s u r e b u i l d - u p above 63xl0"^mm. d u r i n g r u n . 0G 2 added - 2.275 M-M/gm. Run ¥1 o u t g a s s i n g f o r ano the r 20 h r s . a t 1100°G. P r e s s u r e b u i l t - u p f e l l to 37x10" 5 mm. C 0 2 added - 2.37 M-M/gm. Run V I I Cha r c oa l was ou tgassed f o r 15 1/2 h r s . a t 1100°C, then the t empera tu re was r a i s e d to 1150°C. f o r 4 l / 2 h r s . 00g added - 2.56 M-M/gm. R e s u l t s : F o r ease i n r e ad i ng the g raphs , Tab l e I I i s a d e s c r i p t i o n o f eve ry run made d u r i n g the i n v e s t i g a t i o n . Column (1) i s the r u n number, Columns (2) and (3) a re the l e n g t h o f t ime and tempera tu re o f o u t g a s s i n g and Column (4) i s the c o n c e n t r a t i o n o f C 0 o added. TABLE I I . Run Wo. i ft i tgass Time i n Hours i n g Temperature (°C) Gone, o f Added G0 2(M-M/gm I 12 , 5 1074 2.56 I I 015 C. 6 (1015 (1100 2.22 I I I v 6 . 5 ((12 1.(1020 (1100 IY 22 1100 2 .31 V 20 1100 2 .275 •VI £0 1100 2.37 V I I ('•15.5 (i 4 . 5 CllOO (1150 2.56 V I I I Cf23 (!' 5 V1100 (1150 4 .09 IX • If 3.1 H 5 CllOO (1150 4*05 X • | -8 • k 5 x . .; 11100 ^1150 4 .57 . X I • • i . 4 t i l (1100 (1200 8.39 X I I u • l i o (1100 (1200 •11*315 X I I I 10 1100 11.44 X IV 15 1100 11.67 XV 16 1100 11.68 XV I 14 1100 11.70 X V I I 19 1150 14.56 X V I I I 16 1150 16.38 X IX 17 1150 18.29 12 . A f t e r the f i r s t o u t g a s s i n g a t 1100°C. the p r e s s u r e ove r the oha r c o a l was c o n s i d e r a b l y l owe r ; i n Bun I , 290 m inu tes a f t e r a d d i t i o n o f GOg the p r e s s u r e was 85x10°°" mm., i n Run I I the p r e s s u r e a f t e r 220 m inu t e s was 140x10"^ mm. The G 0 2 and GO p r e s s u r e s f e l l c o r r e s p o n d i n g l y , f o r t he GOg con t en t , 80 m inu tes a f t e r ze ro t ime , was 80%. In 6 3/4 h r s . the GOg con ten t o f the r e s i d u a l gas f e l l to 64%. In Run I I I a f t e r a t o t a l o u t g a s s i n g at 1100°G. o f 18 h r s , the p r e s s u r e s ove r the c h a r c o a l were o f the same o r de r as i n Run I I . The gas phase was s t i l l o ve r 60% C0g. In Run IV a f t e r a t o t a l o f 40 h r s . o u t g a s s i n g a t 1100°G. t h e r e was a marked r e d u c t i o n i n bo th p r e s s u r e and GOg con ten t o f the r e s i d u a l gas . The r e s u l t s o f the run a r e shown i n Tab le I I I . 13 TABLE I I I . Temp. (°c.) Time ( h r s . ) P ressur* T o t a l p i n mm.xlO^ L i q . A i r On % OOg i n R e s i d u a l Gas E l ' .4£ 830 £1 £.4£ 79 35 55 £1 4 . 7 5 £7 £4 11 £1 7 .25 16 14 1£ £1 20.00 6 5 1£ 6£ 1.5 47 £5 47 6£ 3 ,0 £ £ .14 37 6£ 5.0 15 8 ? 45 1£0 1.E5 115 24 79 1£0 3 .0 . 55 . .... : 160 1.0 £55 9£ 64 166 £ . 5 360 130 64 166 4 . 0 £45 118 50 166 15 .0 10£ 64 '•• . 36 £10 16 .0 £100 1380 34 £10 18 .5 1070 790 £6 , The 5th run a f t e r 60 h r s . o u t g a s s i n g at 1100°0 . showed s l i g h t l y g r e a t e r a c t i v i t y i n t h a t the p r e s s u r e dec reased more q u i c k l y and no GOg c o u l d be de t e c t ed i n the r e s i d u a l gas a f t e r 20 h o u r s . > Run Y I was s i m i l a r t o Run V . The p r e s s u r e dec rease was more r a p i d than p r e v i o u s l y . Run Y I I was the f i r s t i n w h i c h the tempera tu re was r a i s e d to 1150°0 . The p r e s s u r e f e l l a t a pp r o x ima t e l y the same r a t e as i n Run Y I . The GOg con ten t f e l l v e r y much more r a p i d l y . I t was the f i r s t r un i n wh i ch t he GOg con ten t o f the gas d i d not r i s e above 50$ i n the tempera tu re range f r om 110°0 . to 180°C. The f i g u r e s f o r t h i s run a r e g i v e n i n Tab l e IV . TABLE IV . Temp. Time P r e s s u r e i n IvlMxlO^ i 002 i n ( °G . ) ( h r s . ) T o t a l L i q u i d A i r On R e s i d u a l Gas 25 -L a 215 52 46 12 25 21 20 5 23 5*0 15 14 6 23 22 .0 7 .7 74 4 72 1.0 43 "• 35 19 72 3 .0 10 10 158 1.0 167 92 45 158 3 .0 86 57 ."..'54'. 165 18 .0 78 64 : 18 200 1.0 800 J ' .si© .: 24 200 3 .0 670 560 16 200 6 .0 670 600 10 223 22 .0 920 860 6 .5 H EH EH CO •3 ^ o H o <1 GJ .0 p W EH EH EH H O PH EH 0 "PET -EH CO 0 CQ 0 SH PH M • to.. o CO o hH to PS ..t.4: • 15 . I n Graph 1. p r e s s u r e - t i m e cu rves are p l o t t e d f o r Runs I to Y I I . The l o g a r i t h m s o f t h e p r e s s u r e s a re p l o t t e d f o r f a c i l i t y i n h a n d l i n g a w ide range o f v a l u e s . From these cu rves c o r r e s pond i ng p r e s s u r e s f o r each run can be o b t a i n e d . . ' I n Graph 2 the p r e s su r e 1.5 h r s . 1 a f t e r a d d i t i o n o f GOg i s p l o t t e d a g a i n s t the t o t a l t ime o f o u t g a s s i n g p r e v i o u s to the a d d i t i o n . F o r the f i r s t 60 h r s . the p r e s s u r e dec reased r a p i d l y w i t h t ime o f o u t g a s s i n g . On f u r t h e r ou t ga s s i n g the p r e s s u r e dec rease was not so r a p i d . I t was n o t i c e d i n these runs t h a t as the tempera tu r was r a i s e d the ca rbon d i o x i d e con ten t o f the gas phase f i r s t dec reased then r o se aga i n i n t he i n t e r v a l 100° to 160° . Above 180° the GOg con ten t dec reased r a p i d l y . T h i s e f f e c t i shown g r a p h i c a l l y i n Graph 3 . Th i s phenomenon sugges t s t h a t be low 160 Q G02 desorbs more r a p i d l y than 00 as the tempera-t u r e i s r a i s e d and at the new tempera tu re r e - a d s o r b s more s l o w l y . Above 180° r e d u c t i o n t akes p l a c e independent o f the r e d u c i n g energy o f the s u r f a c e a t 20°G. I n every r un the p r e s s u r e i n c r e a s e d s h a r p l y above 175° . T h i s i s shown i n Graph 4 p l o t t e d f rom the f i g u r e s o f Run Y I I . The p r e s s u r e one hour a f t e r the tempera tu re i s reached i s p l o t t e d aga i n s t t empe ra tu re . I t i s n o t i c e a b l e t ha t t h i s change i n the o r de r o f the p r e s s u r e and the change i n the GO con ten t o f the gas o c c u r a t the same t empe ra tu r e . Th i s i s a l s o the tempera ture range i n wh i c h McMahon found a 16 . hump In the d i s t r i b u t i o n cu rve f o r t h e d e s o r p t i o n o f GO f rom a r e d u c t i v e c h a r c o a l s u r f a c e . P a r t I I . E x p e r i m e n t a l . I n Run Y I I I the GOg con ten t o f the r e s i d u a l gas f e l l to ze ro i n l e s s than 3 l / £ hou r s a f t e r the a d d i t i o n o f £.£9 M-M/gm. A c c o r d i n g l y a new p rocedu re was adop ted . In suc ceed i ng r un s ca rbon d i o x i d e was added i n c o n c e n t r a t i o n s o f 4 m i c r o -mo l s pe r gram o r l e s s , the p r e s s u r e dec rease f o l l o w e d u n t i l i t became s low, then ano the r a d d i t i o n made, and so on u n t i l an a d d i t i o n was not t o t a l l y reduced i n 30 m i nu t e s . The t o t a l c o n c e n t r a t i o n o f gas added i n d i c a t e d the r e d u c t i v e c a p a c i t y o f the c h a r c o a l . Runs V I I I to X I I a n d ' X V I I t o XIX i n c l u s i v e a re d i s c u s s e d i n t h i s s e c t i o n s i n c e t he t rea tment o f each was o s i m i l a r . In each r un t h e o u t g a s s i n g was a t 1150 C. f o r t imes v a r y i n g f rom 5 t o £0 h o u r s . Runs X I and X I I were ou tgassed a t a h i g h e r tempera tu re (as the bu l b c o l l a p s e d s l i g h t l y i t was p r o b ab l y 1£00°G o r more) due to a f a u l t i n the thermo-coup l e w i r e u sed f o r t empe ra tu re measurement. R e s u l t s . The r e d u c t i v e c a p a c i t y i n c r e a s e d s t e a d i l y w i t h the t o t a l t ime o f o u t g a s s i n g a t 1150°0. 17 . The p r e s s u r e ove r the c h a r c o a l f o r c o r r e spond i ng c o n c e n t r a t i o n s o f GOg dec reased w i t h i n c r e a s e d o u t g a s s i n g at 1150°G. except f o r Bun X I the f i r s t o u t g a s s i n g a t 1200°0. I n Run IX , 1.5 h r s . a f t e r add ing 2.44 M-M/gm the p r e s su r e was 61xl0~ 5mm. In Run X I , £ h r s . a f t e r add ing 2 .31 M-M/gm the p r e s s u r e was 77xl0~^mm. But i n Run X I I , a l t h o u g h the ou t g a s s i n g tempera tu re was as h i g h as i n Run X I , the p r e s s u r e £ h r s . a f t e r add ing £.34 M-M/gm was 61x10 mm. On c on t i n ued o u t g a s s i n g the v e l o c i t y o f a d s o r p t i o n i n c r e a s e d . Th i s i s shown f o r Runs X Y I I , X V I I I , X IX i n Tab le V be l ow . TABLE ¥ . Run T o t a l Time o f Ou tga s s i ng a t 1 1 5 0 o 0 . ( h r s . ) S u r f a c e Cone, o f 00o (M-M) (gm ) P r e s s u r e a f t e r 1/2 h r . i n mm.xlO X V I I 4 . 0 4 5 125 X V I I I . • - so..:,- 3*96 62 XIX 97 4 . 6 8 50 The i n c r e a s e i n r e d u c t i v e c a p a c i t y w i t h t ime o f o u t g a s s i n g i s shown g r a p h i c a l l y i n Sraph 5. i n wh i c h the s u r f a c e c o n c e n t r a t i o n a t wh i&h C 0 g was f i r s t d e t e c t e d i n t he r e s i d u a l gas i s p l o t t e d a g a i n s t t o t a l t ime o f o u t g a s s i n g a t 1150°C. That the r a t e o f change o f r e d u c t i v e c a p a c i t y c ou l d be i n c r e a s e d by h i g h e r t empera tu re s i s i n d i c a t e d by the hump 18 . i n t he curve f o r Runs X I and X I I . The p r e s su r e b u i l d - u p _ p. d u r i n g t he se two o u t g a s s i n g s was g r e a t e r than 100x10 mm. i n 5 m i n u t e s . P a r t I I I . Expe r imen t a i . Deep o x i d a t i o n was t e s t e d as a method o f a c t i v a t i o n . Run X I I I was made as a compar i son . The ou t ga s s i n g was a t 1100°C. f o r 10 h o u r s . GOg was added a t room tempera tu re u n t i l the r e s i d u a l gas was 2&fo GOg. . The added gas was pumped o f f d u r i n g 6 h r s . o u t g a s s i n g o a t 1100 C. The c h a r c o a l bu lb was immersed i n a Dewar f l a s k c o n t a i n i n g l i q u i d a i r . Oxygen, wh i c h was gene r a t ed f r om po t a s s i um c h l o r a t e , was added f r om the s t o r age f l a s k i n q u a n t i t y to s a t u r a t e the c h a r c o a l s u r f a c e c h e m i c a l l y a t room t empe ra t u r e . A f t e r 5 hou r s , when the p r e s su r e was s c a r c e l y measu reab l e , the Dewar f l a s k was removed. The p r e s s u r e r o se to more than one c e n t i m e t r e t hen dropped s l o w l y as the oxygen r e ad s o r b ed . 17 hou r s l a t e r t he p r e s s u r e was - 5 o 17x10 mm. The c h a r c o a l was then ou tgassed at 1100 G. f o r 8 h o u r s . GOg was then added a c c o r d i n g to the p rocedure used i n P a r t I I . The a d d i t i o n o f oxygen and subsequent h e a t i n g were r e p ea t e d t h r e e t i m e s . 19 . R e s u l t s . The t r ea tmen t gave o n l y .a s l i g h t i n c r e a s e i n a c t i v i t y as can be seen i n Graph 6 i n wh i c n t h e pe r cen tage o f carbon d i o x i d e i n the r e s i d u a l gas i s p l o t t e d a g a i n s t the s u r f a c e c o n c e n t r a t i o n o f carbon d i o x i d e . The d i sp l a cemen t towards g r e a t e r r e d u c t i v e c a p a c i t y I s no l a r g e r than t ha t caused by the o u t g a s s i n g t r ea tmen t a l one i n Run X I I I . Tlie f a c t t h a t i t i s l e s s sugges t s a p o s s i b l e d e a c t i v a t i o n due t o the o x i d a t i o n . . Conc l u s i ons . . 1 . The r e d u c t i v e c a p a c i t y o f the c h a r c o a l f o r ca rbon d i o x i d e i s i n c r e a s e d by v a p o u r i z i n g c o n s t i t u e n t s o f the c h a r c o a l a t 1100°C. and h i g h e r . Th i s sugges t s t h a t the r e d u c t i v e a b i l i t y i s a f u n c t i o n o f the bond energy o f the sur face- ca rbon atoms. 2 . O x i d a t i o n o f the s u r f a c e has no a c t i v a t i n g e f f e c t on the r e d u c t i v e c a p a o i t y o f t l i e s u r f a c e , 3 . On f i r s t o u t g a s s i n g at a h i g h e r t empera tu re , the p r e s s u r e ove r the c h a r c o a l was h i g h e r f o r a g i v e n concen-t r a t i o n o f e-arbon d i o x i d e than a f t e r p r e v i o u s l owe r tempera -t u r e o u t g a s s i n g . On f u r t h e r o u t g a s s i n g a t the same tempera-t u r e the p r e s s u r e dec reased to a new l owe r v a l u e . T h i s sugges t s an e x p l a n a t i o n o f the " d e a c t i v a t i o n " found by Lemon ^  )and Lowry^-^on h i g h tempera ture o u t g a s s i n g . They 20 . d i d no t ou tgas l o ng enough t o remove the f r e e d gases f rom the c h a r c o a l . 4 . The p r e s s u r e r o s e s h a r p l y o ve r the i n a c t i v e c h a r c o a l i n the same tempera tu re range i n wh i ch McMahon found a hump i n the d i s t r i b u t i o n curve on de so rb i ng gas f r om a s a t u r a t e d r e d u c t i v e s u r f a c e . The e n e r g i e s o f the two s u r f a c e s a re t h e r e f o r e not g r e a t l y d i f f e r e n t . 5 . There i s a tempera ture range i n wh i ch t he r e s i d u a l gas ove r the i n a c t i v e s u r f a c e has a h i g h ca rbon d i o x i d e c o n t e n t . 2 1 . B i b l i o g r a p h y . 1. Bangham and S t a f f o r d , J o u r . Chem. S o c . , 117, 362, 1920. 2 . B a r k e r , M. E . , Ind . Eng . Chem., 22, 926, 1930. 3 . B r i g g s , H . , P r o c . Roy. S o c . , 10OA, 88, 1922. ' 4 . B a r r a ge , L. J . , T r an s . P a r . S o c . , 29, 445 , 1933. 5. Cook F . , T h e s i s , U n i v e r s i t y o f B. C. 1937. 6 a Debye and S o h e r r e r , P h y s i c k . Z e i t . , 18, 291, 1917. Y . E l n d l a y , R. A . , T h e s i s , U n i v e r s i t y o f B. C. 1934. 8 . F i n d l a y , R. A . , T h e s i s , U n i v e r s i t y o f B. C. 1935. 9 . J e n k i n s , P h i l . Mag . , 17, 457, 1934. 10 . K i n g and Laws on, K o l l . Z e i t . , 69 , 21 , 1934. 1 1 . K i n g , A . , J o u r . Chem.Soc. , 22, 1934. 12 . Ko1thoff, I . M . , J . A . C . S . , 54, 4473, 1932. 1 3 . Lemon, H. B . , Phy s . Re v . , 14, 281 , 1919. 14 . Lenna rd - Jones , J . E , , P r o c . Phys . S o c . , 4 3 , 461 , 1931 . X. 15 # Lowry and H u l e t t , J . A . C . S . , 52, 1393, 1920. 16 . Lowry, H. H . , J . A . C . S . , 46 , 824, 1924. 17 . Lowry and Morgan, J o u r . Phy s . Chem., 29, 1105, 1925. 1 8 . Lowry, H. H . , J o u r . Phys , Chem., 33, 1332, 1929. X9 9 Lowry, H» H . , Ind . Eng . Chem., 26, 326, 1934. 20 . MeMahon, H. 0., T h e s i s , U n i v e r s i t y o f B. C. 1937. 2 1 . P h i l i p and Jarman, J o u r . Phy s . Chem., 28, 346, 1924. 22 . Raman and K r i s t n a t u r i , Na t u r e , 124, 53 , 1929. 23 . Ray, A . , Ghem. Me t . E n g . , 28, 977, 1923. 24. Ray, Chaney and S t . J o h n , I n d . Eng . Ghem., 15, 1244, 1923 . 25 . R u f f , Schmidt and O l r i c h , Z e i t , Ano rg , A l l g e m . Chem., 148, 313, 1925. 26 . Sherman and E y r i n g , J . A . C . S . , 54, 2661, 1932. 

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