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Berkeley,CA94709

O. A. Beeck and a talented team of collaborators (Smith, Wheeler, Ritchie) were pioneers in the application of evaporated, porous, metal films as "clean" surfaces for the study of chemisorption, heats of adsorption and the catalytic hydrogenation of ethylene. They discovered also the development of preferred orientation in such films. With another team of gifted investigators (Otvos, Stevenson, Wagner), Beeck also made early important contributions to the study of acid catalysis in hydrocarbon reactions by means of both stable and radioactive isotopes together with mass spectromentry. Beeck was not only a creative scientist but also a warm and generous person and an able organizer and administrator. The highlights of these investigations and some reflections about the people involved are presented. Though I never had t h e p r i v i l e g e o f working on c a t a l y s i s w i t h t h e l a t e Dr. Otto Beeck, I knew most of h i s c o l l e a g u e s i n t h a t f i e l d as f r i e n d s and t a l k e d on many o c c a s i o n s w i t h them, and o c c a s i o n a l l y w i t h him, about t h e i r work. F o r what f o l l o w s , I have drawn upon my memory, r e c e n t c o n v e r s a t i o n s w i t h J . W. Otvos, A. W. R i t c h i e , F r e d Rust and A. E. Smith, t h e p u b l i s h e d l i t e r a t u r e and a b r i e f b i o g r a p h y t h a t I wrote i n 1962 (_1) . I f i r s t met Beeck i n 194-3, when he h i r e d me t o work a t S h e l l Development Company, i n E m e r y v i l l e , California, as a p h y s i c a l chemist i n h i s Physics Department. Over t h e e n s u i n g y e a r s , I came t o know him f a i r l y w e l l as both c o l l e a g u e and f r i e n d and dev e l o p e d a s t r o n g a d m i r a t i o n f o r him, n o t o n l y as a man o f v i s i o n and a c r e a t i v e s c i e n t i s t , b u t a l s o as 1

Retired from Shell Development Company

0097-6156/83/0222-0153$06.00/0 © 1983 American Chemical Society

Davis and Hettinger; Heterogeneous Catalysis ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

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Figure 1. Photograph of Otto Beek taken during the 1940s.


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a warm, o u t g o i n g and empathetic person and a s t r o n g and inspiring l e a d e r who used a l o o s e r e i n v e r y effectively. In h i s l a t e r y e a r s he developed a r e markable knack f o r p u t t i n g t o g e t h e r c r e a t i v e and e f f e c t i v e r e s e a r c h teams o f people whose t a l e n t s , knowledge and e x p e r t i s e combined w e l l t o g e t h e r f o r the p r o j e c t a t hand. Many o f t h e r e s e a r c h r e s u l t s f o r which he i s w e l l known were accomplished through such teams, many o f whose members deserve a l a r g e share o f t h e c r e d i t . N e v e r t h e l e s s , t h e importance o f h i s r o l e as i n s t i g a t o r , o r g a n i z e r and l e a d e r i s n o t t o be minimized. He p l a y e d another r o l e t h a t i s a l ways important i n a l a r g e i n d u s t r i a l o r g a n i z a t i o n : t h a t was as a promoter and defender o f t h e work t o h i g h e r management. To c h a r a c t e r i z e him b r i e f l y , he was a v e r y a c t i v e and s e l e c t i v e human c a t a l y s t . D u r i n g t h e y e a r s I knew him, he was a v e r y busy man. H i s a d m i n i s t r a t i v e r e s p o n s i b i l i t i e s were subs t a n t i a l , n o t o n l y as Head o f t h e P h y s i c s Department but a l s o as an A s s o c i a t e D i r e c t o r o f Research w i t h broader concerns. He s e r v e d t h e N a t i o n a l Research C o u n c i l as an a c t i v e member o f i t s Committee on Catalysis and t h e N a t i o n a l A d v i s o r y Committee f o r A e r o n a u t i c s as a prominent member o f i t s subcommittee on L u b r i c a t i o n , F r i c t i o n and Wear. Those were heavy r e s p o n s i b i l i t i e s d u r i n g t h e y e a r s o f World War I I . He was a member o f t h e A d v i s o r y C o u n c i l o f t h e American I n s t i t u t e o f P h y s i c s and was an A s s o c i a t e E d i t o r of the Journal of Applied Physics. He was a c t i v e a l s o on t h e A d v i s o r y Committee o f t h e American P e t r o leum I n s t i t u t e ' s Research P r o j e c t 44-, which was a v e r y a c t i v e one d u r i n g t h e war. Needless t o say, he t r a v e l l e d a l o t . In h i s spare time he l e d an a c t i v e personal l i f e . He l i v e d on a s m a l l ranch i n t h e c o u n t r y s i d e t o t h e east o f San F r a n c i s c o Bay; t h e r e he b r e d and rode h o r s e s ; he was a l s o a s k i e r and had a l i v e l y i n t e r e s t i n photography and o t h e r visual arts. H i s w i f e was an accomplished s c u l p t r e s s and they had many f r i e n d s i n t h e world o f t h e a r t s . H i s c a r e e r came t o an u n t i m e l y end on J u l y 7, 1950, when he d i e d from a massive c o r o n a r y i n f a r c t i o n shortly after a c o m p l e t e l y unexpected h e a r t a t t a c k . He was then n o t q u i t e 46 y e a r s o l d . In h i s b r i e f c a r e e r , however, he accomplished a g r e a t d e a l . Achievements He was author o r co-author o f 46 p u b l i c a t i o n s , i n c l u d i n g twenty-four on heterogeneous c a t a l y s i s and r e l a t e d t o p i c s and f i v e on t h e s u r f a c e c h e m i s t r y and


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physics involved i n lubrication, f r i c t i o n and wear under c o n d i t i o n s o f h i g h l o a d i n g o r o f s t a r t - u p . Many o f h i s p u b l i c a t i o n s p r e s e n t e d n o t o n l y s i g n i f i c a n t e x p e r i m e n t a l f a c t s b u t a l s o some i n s t r u c t i v e i n s i g h t s ; some o f them were s t i l l b e i n g c i t e d i n 1980 and 1981. Two papers, which bear h i s name as c o - a u t h o r , were w r i t t e n by h i s c o l l e a g u e s over a y e a r a f t e r h i s death. He l e c t u r e d from time t o time a t u n i v e r s i t i e s s e r v e d as chairman f o r many s p e c i a l i z e d technical meetings, i n c l u d i n g s e v e r a l o f t h e Gordon Research Conferences. He p l a y e d a s i g n i f i c a n t r o l e i n t h e o r g a n i z a t i o n and e a r l y development o f those j u s t l y renowned Conferences; indeed, t h e y grew o u t o f t h e s e r i e s o f annual c o n f e r e n c e s h e l d a t Gibson I s l a n d on Heterogeneous C a t a l y s i s i n which Beeck was a v i g o r o u s p a r t i c i p a n t and developed f r i e n d s h i p s w i t h many l e a d ers o f c a t a l y s i s r e s e a r c h i n both i n d u s t r y and academia. Among Beeck's important c o n t r i b u t i o n s t o t h e progress o f c h e m i c a l r e s e a r c h was h i s e a r l y and s u s t a i n e d encouragement o f t h e a p p l i c a t i o n o f spect r o m e t r i c t e c h n i q u e s t o problems o f c h e m i c a l a n a l y sis. The existence o f t h e modern analytical i n s t r u m e n t a t i o n i n d u s t r y i s an e x p r e s s i o n o f t h e f a c t t h a t r a p i d and a c c u r a t e c h e m i c a l a n a l y s e s a r e v i t a l to modern t e c h n o l o g y . Beeck was d i r e c t l y r e s p o n s i b l e f o r t h e r e c r u i t m e n t o f R. Robert B r a t t a i n t o l e a d a program i n i n f r a r e d s p e c t r o m e t r y f o r a n a l y t i c a l r e search; these e f f o r t s , together with those o f other collaborators, l e d t o t h e development of rapid methods f o r multicomponent a n a l y s i s o f hydrocarbon m i x t u r e s by i n f r a r e d and u l t r a v i o l e t s p e c t r o m e t r y . These methods p r o v i d e d important s a v i n g s i n manpower and time d u r i n g t h e development o f p r o c e s s e s f o r t h e manufacture o f b u t a d i e n e f o r s y n t h e t i c rubber and o f t o l u e n e and o t h e r h i g h - o c t a n e components o f f u e l s d u r i n g t h e war. S i m i l a r a p p l i c a t i o n s o f mass spect r o m e t r y t o hydrocarbon a n a l y s i s were d e v e l o p e d e a r l y by D a v i d P. Stevenson w i t h Beeck's s u p p o r t . Important c o n t r i b u t i o n s t o t h e development o f such methods came from many i n d i v i d u a l s i n o t h e r i n d u s t r i a l organizations during that period. One o f the i m p o r t a n t p i o n e e r i n g groups i n t h e f i e l d , howe v e r , was t h e one a t E m e r y v i l l e a s s o c i a t e d w i t h Otto Beeck. E a r l y H i s t o r y and the Road t o C a t a l y s i s Born

i n Stettin,

Germany,

Beeck

received h i s


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h i g h e r e d u c a t i o n i n the Free C i t y o f Danzig, now the P o l i s h c i t y o f Gdansk. There he earned a degree i n e n g i n e e r i n g i n 1928 and a d o c t o r a t e i n p h y s i c s o n l y two y e a r s l a t e r . H i s t h e s i s i n v o l v e d the measurement of c r o s s - s e c t i o n s and i o n i z a t i o n p o t e n t i a l s o f n o b l e gas atoms as determined from a study o f t h e i r c o l l i s i o n s w i t h m o l e c u l a r beams o f a l k a l i i o n s and atoms. He c o n t i n u e d t h a t work as a r e s e a r c h f e l l o w and i n s t r u c t o r i n p h y s i c s a t C a l t e c h from 1930 t o 1933. He p u b l i s h e d a t o t a l o f twelve papers i n t h a t d i f f i c u l t f i e l d , a testament t o h i s e x p e r i m e n t a l s k i l l and productivity. D u r i n g t h a t p e r i o d , h i s name came t o the a t t e n t i o n o f Dr. E. C. W i l l i a m s , who was then D i r e c t o r o f the young and growing l a b o r a t o r y a t E m e r y v i l l e . He t a l k e d w i t h Beeck about the i n t e l l e c t u a l c h a l l e n g e s posed by the phenomena o f heterogeneous c a t a l y s i s and i n v i t e d him t o come t o E m e r y v i l l e t o see whether the d i s c i p l i n e s o f p h y s i c s would be u s e f u l i n a l a b o r a t o r y whose p r i m a r y m i s s i o n was t o e x p l o r e and e x p l o i t t h e c h e m i s t r y o f hydrocarbons and t h e i r d e r i v a t i v e s . Beeck a c c e p t e d the c h a l l e n g e and came t o Emeryv i l l e i n 1933, a d e p r e s s i o n y e a r when good j o b s were scarce. H i s f i r s t s t u d i e s o f c a t a l y s i s made use o f the m o l e c u l a r beam t e c h n i q u e s w i t h which he was f a m i l i a r ; he impinged beams o f hydrocarbon m o l e c u l e s on t h i n s t r i p s o f t r a n s i t i o n m e t a l s h e a t e d i n h i g h vacua. In 1934 and 1935 he p u b l i s h e d a c o u p l e o f i n t e r e s t i n g papers (2,3) on the c a t a l y t i c decomposit i o n o f p a r a f f i n s under t h e s e c o n d i t i o n s . An i n t e r e s t i n g by-product o f t h a t work was a thorough i n v e s t i g a t i o n o f the Knudsen accomodation c o e f f i c i e n t s and t h e i r v a r i a t i o n w i t h temperature f o r a number o f s i m p l e p a r a f f i n s and o l e f i n s . From t h e s e d a t a he c a l c u l a t e d the f i r s t r e l i a b l e v a l u e s f o r the s p e c i f i c h e a t s o f many o f these compounds i n the range C to Cy , and he c o r r e l a t e d these numbers w i t h the c o r r e s ponding i n f r a r e d s p e c t r a (4,5). By now he had r e a l i z e d t h a t , w i t h the vacuum t e c h n i q u e s a v a i l a b l e a t the time, a s m a l l s u r f a c e c o u l d not be kept f r e e o f c o n t a m i n a t i o n l o n g enough for c a t a l y t i c studies. He t h e r e f o r e d e c i d e d t o use e v a p o r a t e d metal f i l m s as model c a t a l y s t s . T h i s was by no means a new i d e a ; papers d e s c r i b i n g r e s u l t s w i t h such systems had been p u b l i s h e d , e s p e c i a l l y i n the European l i t e r a t u r e , s i n c e the l a t e 1920's. The r e s u l t s , however, were not m u t u a l l y c o n s i s t e n t ; t h e r e was c l e a r l y room f o r improvement. Around t h i s time he a c q u i r e d an a s s i s t a n t , a b r i g h t young chemist named F r e d Rust, who l a t e r went on t o a d i s t i n g u i s h e d 2


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career i n f r e e - r a d i c a l chemistry. They began t o study the hydrogénation o f e t h y l e n e over e v a p o r a t e d f i l m s of n i c k e l . They l e a r n e d t h a t such f i l m s were so a c t i v e t h a t the r e a c t i o n was diffusion-limited; the ethane produced i n t e r f e r e d w i t h the t r a n s p o r t o f r e a c t a n t s t o the a c t i v e s u r f a c e i n a s t a t i c system. An important development o c c u r r e d i n 1936; Beeck was a u t h o r i z e d t o o r g a n i z e and l e a d a P h y s i c s Department and he s t a r t e d t o r e c r u i t p e o p l e . One o f h i s f i r s t r e c r u i t s was A l b e r t E. Smith. A l Smith had an i n t e r e s t i n g background. In the e a r l y 1930's, he was a graduate s t u d e n t i n p h y s i c s a t the U n i v e r s i t y o f C a l i f o r n i a i n B e r k e l e y and working i n Ε. 0. Lawrence's new R a d i a t i o n L a b o r a t o r y . He had hopes o f g o i n g on t o a c a r e e r i n n u c l e a r p h y s i c s . He had taken the graduate c o u r s e s i n p h y s i c s , a l l the advanced mathematics he c o u l d l a y h i s hands on, many c o u r s e s i n c h e m i s t r y and had a master's degree t o a t t e s t t o h i s s c h o l a s t i c achievements. He was w e l l v e r s e d i n the l a b o r a t o r y a r t s and metal-working and was an accomplished g l a s s - b l o w e r ; indeed, he had earned h i s way through s c h o o l by p a r t - t i m e work i n that capacity. In l a t e 1935, however, the economic e x i g e n c i e s o f the time r e q u i r e d him t o i n t e r r u p t h i s d o c t o r a l work and earn some money t o a s s i s t h i s f a m i ly. He a p p l i e d f o r a job a t S h e l l Development Company and was a c c e p t e d . A f t e r a couple of shortterm assignments he was asked by Mirko Tamele, o f c r a c k i n g c a t a l y s t fame, t o develop a s p e c t r o s c o p i c method t o measure the c o n c e n t r a t i o n s o f p o r p h y r i n s and o t h e r condensed p o l y a r o m a t i c s i n heavy petroleum fractions. T h i s was r e l e v a n t t o the t h e n - c u r r e n t debates about the o r i g i n s o f petroleum. In those days one c o u l d not buy a s p e c t r o m e t e r o f f the s h e l f , so Smith d e s i g n e d and b u i l t one, w i t h p h o t o g r a p h i c r e c o r d i n g o f a b s o r p t i o n s p e c t r a i n the v i s i b l e and near u l t r a v i o l e t . While he was busy a p p l y i n g t h i s t o o l t o the p o r p h y r i n problem, Beeck beckoned w i t h an o p p o r t u n i t y t o b u i l d an e l e c t r o n d i f f r a c t i o n machine f o r the study o f s u r f a c e s . Though Tamele was r e l u c t a n t t o l e t him go, Smith f i n a l l y j o i n e d the new P h y s i c s Department. Guided by Germer's p u b l i c a t i o n s , he proceeded t o d e s i g n an e l e c t r o n d i f f r a c t i o n appar atus, i n c l u d i n g a p r e c i s e l y s t a b i l i z e d high voltage s u p p l y and the vacuum system. The system was b u i l t i n the l a b o r a t o r y shops, w i t h some s p e c i a l i z e d work by Smith h i m s e l f and i t worked. At Beeck's i n s t i g a t i o n , he s e t out t o use i t t o s t u d y the s t r u c t u r e o f the f i l m s formed on metal s u r f a c e s under "boundary l u b r i c a t i o n " c o n d i t i o n s i n the presence o f l u b r i c a n t s containing certain polar additives.


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In 1937, w h i l e this work was i n p r o g r e s s , A h l b o r n Wheeler j o i n e d t h e department. "Bud" Wheeler was a new Ph.D. from P r i n c e t o n , where he had worked w i t h Henry E y r i n g . Though he had a keen a p p r e c i a t i o n f o r good e x p e r i m e n t a l d e s i g n and t e c h n i q u e , h i s p r i mary l e a n i n g s and a p t i t u d e s were t h e o r e t i c a l . During h i s y e a r s a t E m e r y v i l l e , he devoted a l o t o f e f f o r t t o an a n a l y s i s o f t h e e f f e c t s o f c a t a l y s t p o r o s i t y on the apparent k i n e t i c s and a c t i v a t i o n energy o f c a t a lytic r e a c t i o n s , with a t t e n t i o n to the e f f e c t s o f b o t h pore shapes and p o r e - s i z e d i s t r i b u t i o n s . Many o f h i s f i n d i n g s were communicated i n f o r m a l l y from time t o time a t Gordon Research C o n f e r e n c e s ; they were l a t e r summarized i n an important monograph ( 6 ) . His f i r s t assignment, however, was t o take over Rust's r e s p o n s i b i l i t i e s i n t h e metal f i l m work. Rust was g l a d o f t h e chance t o r e t u r n t o h i s p r i m a r y interest: e x p l o r a t o r y r e s e a r c h on homogeneous r e a c tions . In t h e metal f i l m work, t h e immediate need was t o overcome t h e problem o f d i f f u s i o n limitation. T h i s was accomplished by t h e i n v e n t i o n o f an i n g e n i ous g l a s s t u r b i n e which c o u l d be mounted i n s i d e t h e vacuum system and used t o c i r c u l a t e t h e r e a c t a n t gas m i x t u r e s a t a h i g h r a t e over t h e c a t a l y t i c f i l m s u r face. Normal t o i t s a x i s , i t c a r r i e d an e n c a p s u l a t e d rod o f s o f t i r o n , so t h a t i t c o u l d be d r i v e n from o u t s i d e t h e vacuum system as a k i n d o f synchronous i n d u c t i o n motor by a p u l s e d 6 0 - c y c l e magnetic f i e l d . T h i s d e v i c e must have been v e r y d i f f i c u l t t o b u i l d and b a l a n c e , but i t was made t o work. While i t was b e i n g developed, they c a r r i e d o u t a study o f t h e chemisorption o f n i t r o g e n on i r o n f i l m s a t 23 and 100 C and found i t t o be an a c t i v a t e d p r o c e s s . By t r e a t i n g t h e s a t u r a t e d f i l m s w i t h a c i d and f i n d i n g ammonium i o n i n t h e r e s u l t i n g s o l u t i o n , they d e t e r mined a l s o t h a t i t was a d i s s o c i a t i v e a d s o r p t i o n ( 7 ) . Then they r e t u r n e d t o t h e study o f e t h y l e n e hydrogéna t i o n on n i c k e l . Comprehensive S t u d i e s

of Ethylene

Hydrogénation

For t h i s work, Beeck and Wheeler used a more e l a b o r a t e vacuum system than had been used i n t h e e a r l i e r e x p l o r a t o r y work. They used l a r g e McLeod gauges f o r p r e s s u r e measurements, w i t h which noncondensible gas p r e s s u r e s o f 1 0 ~ T o r r . c o u l d be d e t e c t e d and a " s t i c k i n g vacuum" i m p l i e d 10" T o r r . o r less. Higher p r e s s u r e s were measured w i t h a mercury 7


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manometer and an a c c u r a t e cathetometer. The r e a c t o r system was i s o l a t e d from the pumps and gauges by means o f c o l d t r a p s . To o b t a i n r e p r o d u c i b l e r e s u l t s , they found i t n e c e s s a r y t o outgas the metal f i l a m e n t s b e f o r e e v a p o r a t i n g the f i l m s ; t h i s was done by h e a t i n g them e l e c t r i c a l l y under vacuum t o a temperature j u s t below t h a t a t which e v a p o r a t i o n r a t e s became appreciable. I t was n e c e s s a r y a l s o t o bake out the c y l i n d r i c a l g l a s s r e a c t i o n tube a t 500° C f o r some time b e f o r e d e p o s i t i n g the f i l m on i t s i n n e r s u r f a c e and t o c o n t r o l the temperature o f the s u b s t r a t e w h i l e d e p o s i t i n g the f i l m . With t h e s e p r e c a u t i o n s and use o f the c i r c u l a t i o n t u r b i n e they c o u l d o b t a i n r e p r o ducible r e a c t i o n r a t e s t h a t were not diffusionlimited. They found t h a t the r e a c t i o n r a t e was a c c u r a t e l y f i r s t o r d e r i n the p a r t i a l p r e s s u r e o f hydrogen but independent o f t h a t o f e t h y l e n e ; t h i s i m p l i e d t h a t e t h y l e n e was an i n h i b i t o r as w e l l as a r e a c t a n t and they c o u l d now d e f i n e a r a t e c o n s t a n t . C h e m i s o r p t i o n o f hydrogen or o f carbon monoxide was too f a s t t o f o l l o w w i t h a McLeod gauge, even a t low temperatures. These p r o c e s s e s t h e r e f o r e had v e r y low a c t i v a t i o n energies, contrary to e a r l i e r l i t e r a t u r e r e s u l t s f o r conventional supported n i c k e l c a t a l y s t s . Now they made a s u r p r i s i n g d i s c o v e r y . Guided by a r e c e n t European p u b l i c a t i o n , they evaporated a n i c k e l f i l m i n a low p r e s s u r e o f p u r i f i e d i n e r t gas i n s t e a d o f i n vacuum. The r e s u l t i n g f i l m was about t e n times as a c t i v e as the same mass o f vacuumd e p o s i t e d f i l m , even though i t s c h e m i s o r p t i v e s u r f a c e a r e a was o n l y about t w i c e as g r e a t . These e f f e c t s c o u l d be repeated; t h e r e must be a s t r u c t u r a l d i f f e r ence. Beeck immediately i n v i t e d A l Smith t o j o i n the investigation. Smith undertook an exhaustive study of the nature of these f i l m s . To do so, he had t o b u i l d h i s own s p e c i a l i z e d vacuum system because he had t o dep o s i t h i s f i l m s on f l a t p l a t e s i n o r d e r t o examine them by e l e c t r o n d i f f r a c t i o n . He a l s o had t o be a b l e t o t r a n s f e r them i n t o the e l e c t r o n d i f f r a c t i o n camera w i t h o u t exposure t o atmospheric c o n t a m i n a t i o n . For p r e s s u r e measurements he, too, used a McLeod gauge because the i o n i z a t i o n gauges one c o u l d b u i l d a t t h a t time were prone t o o u t g a s s i n g , which would contaminate the f i l m s . He made f i l m s o f a g r e a t many t r a n s i t i o n metals, i n a d d i t i o n t o n i c k e l . He s t u d i e d f i l m s grown i n vacuo and i n i n e r t gas r a n g i n g i n p r e s s u r e from 1 0 t o about 20 T o r r . A l l were found t o have the u s u a l metal c r y s t a l s t r u c t u r e . As f i l m t h i c k n e s s i n c r e a s e d , the f i l m s , even those _ 5


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grown i n vacuo, developed an i n c r e a s i n g tendency t o grow c r y s t a l l i t e s w i t h a p r e f e r r e d o r i e n t a t i o n . For f a c e - c e n t e r e d c u b i c metals, such as n i c k e l , the o r i e n t a t i o n was such t h a t the 110 p l a n e s were r o u g h l y p a r a l l e l t o the s u b s t r a t e s u r f a c e . For b o d y - c e n t e r e d m e t a l s , such as i r o n , the 111 p l a n e s became so o r i ented. T h i s f i n d i n g , o f c o u r s e , gave e s s e n t i a l l y no i n f o r m a t i o n about which c r y s t a l p l a n e s were exposed to the gas phase. The major o b s e r v a b l e d i s t i n c t i o n o f the gasgrown f i l m s was t h a t p r e f e r r e d o r i e n t a t i o n developed much more r a p i d l y as t h i c k n e s s i n c r e a s e d . The o p t i mum p r e s s u r e f o r t h i s e f f e c t was one t o two T o r r ; a t higher pressures, the preferred orientation was i n c r e a s i n g l y suppressed. Smith s t u d i e d a l s o the s i n t e r i n g o f the f i l m s , e i t h e r by a n n e a l i n g a t temperatures above t h a t o f d e p o s i t i o n or by growing them on s u b s t r a t e s h e l d a t h i g h e r temperatures. One b y - p r o d u c t o f t h a t work was one o f the f i r s t and perhaps the f i r s t example o f what we now c a l l e p i t a x i a l growth o f s i n g l e - c r y s t a l films. By e v a p o r a t i n g p a l l a d i u m on t o the c l e a v a g e plane o f a sodium c h l o r i d e c r y s t a l h e l d a t 350°C, he made a s i n g l e c r y s t a l f i l m o f the metal w i t h i t s 100 p l a n e p a r a l l e l t o the b a c k i n g . These o b s e r v a t i o n s , o f c o u r s e , g u i d e d the ong o i n g work by Beeck and Wheeler on c h e m i s o r p t i o n and catalysis. In 194-0, Beeck, Smith and Wheeler publ i s h e d a landmark paper d e s c r i b i n g t h e i r f i n d i n g s i n the P r o c e e d i n g s o f the Royal S o c i e t y (8) . I t s t i m u l a t e d s i m i l a r work elsewhere, because i t showed t h a t e v a p o r a t e d metal f i l m s , p r o p e r l y made, were r e p r o d u c ble, porous and pretty uniform throughout their thickness. On u n s i n t e r e d f i l m s , g i v e n t h a t a molec u l e o f hydrogen d i s s o c i a t i v e l y o c c u p i e s two s u r f a c e c h e m i s o r p t i o n s i t e s , a m o l e c u l e o f carbon monoxide o c c u p i e d o n l y one, whereas a m o l e c u l e o f e t h y l e n e occupied at l e a s t four. S i n t e r i n g o f the films b e f o r e use i n t r o d u c e d c o m p l i c a t i o n s i n t o both chemis o r p t i o n and c a t a l y s i s . The work c o n t i n u e d t h e r e a f t e r but w i t h little f u r t h e r p a r t i c i p a t i o n by Smith, who went on t o o t h e r problems. By s e l f - t r a i n i n g , he l a t e r became a d i s t i n g u i s h e d X-ray c r y s t a l l o g r a p h e r . The main burden of the l a t e r l a b o r a t o r y work was c a r r i e d by Wheeler, w i t h a s s i s t a n c e a t v a r i o u s times from v a r i o u s p e o p l e , i n c l u d i n g W. A. C o l e , W. H. T h u r s t o n , J . W. Givens and A. W. R i t c h i e . Walt R i t c h i e ' s s t o r y i s an i n t e r e s t i n g one. For economic r e a s o n s , he had t o i n t e r r u p t h i s c o l l e g e c a r e e r when he had taken o n l y a


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couple of courses i n chemistry. He j o i n e d the p r o j e c t as a l a b o r a t o r y a s s i s t a n t . He was a b r i g h t young man, however, and e x p r e s s e d an i n t e r e s t i n what was g o i n g on. Wheeler l e n t him t e x t books, encouraged him t o work the problems and even o f f e r e d t o c o r r e c t them. When Beeck h e a r d about t h i s , he had s e v e r a l t a l k s w i t h R i t c h i e and encouraged him i n h i s self-education. In time, w i t h c o n t i n u e d l e a r n i n g and b r o a d e r l a b o r a t o r y e x p e r i e n c e , R i t c h i e was promoted to p r o f e s s i o n a l s t a t u s . He was a c o - a u t h o r o f some of Beeck's l a t e r p u b l i c a t i o n s . The f i r s t important development a f t e r the 1940 paper was a s i m p l e but e l e g a n t c a l o r i m e t e r f o r measu r i n g the heat o f a d s o r p t i o n o f f r a c t i o n s o f a monolayer on e v a p o r a t e d metal films (9). For both hydrogen and carbon monoxide on n i c k e l , the magnitude of the i n i t i a l h e a t s showed t h a t s t r o n g c h e m i c a l bonds t o the s u r f a c e were b e i n g formed. The h e a t s d e c r e a s e d m o n o t o n i c a l l y as coverage i n c r e a s e d , and more r a p i d l y as monolayer coverage was approached. T h i s r e s u l t i m p l i e d some k i n d o f i n t e r a c t i o n among chemisorbed s p e c i e s ; i t a l s o i m p l i e d t h a t chemisorbed hydrogen atoms were mobile over the metal s u r f a c e . C u r i o u s l y , the c u r v e s f o r heat o f a d s o r p t i o n v e r s u s coverage f o r hydrogen on o r i e n t e d and u n o r i e n t e d n i c k e l f i l m s were e s s e n t i a l l y s u p e r p o s a b l e , d e s p i t e the l a r g e d i f f e r e n c e i n c a t a l y t i c a c t i v i t y p e r u n i t surface. A s i g n i f i c a n t o b s e r v a t i o n was made d u r i n g measurements o f the h e a t s o f a d s o r p t i o n o f e t h y l e n e : a f t e r p a r t i a l coverage o f the s u r f a c e , a r e s i d u a l p r e s s u r e o f ethane was d e t e c t e d i n the gas phase. E t h y l e n e was h y d r o g e n a t i n g i t s e l f ! This fact, tog e t h e r w i t h the number o f s i t e s c o v e r e d by a chemis o r b e d e t h y l e n e molecule, l e d t o the concept o f the s o - c a l l e d " a c e t y l e n i c complexes". The c h e m i s o r p t i o n of e t h y l e n e was dissociative t o form chemisorbed hydrogen and a s t r o n g l y adsorbed, l e s s h y d r o g e n - r i c h residue. D u r i n g the c a t a l y t i c hydrogénation o f e t h y l e n e under s t e a d y - s t a t e c o n d i t i o n s , the s u r f a c e was presumed t o be c o v e r e d l a r g e l y by such hydrogen-poor r e s i d u e s , whose removal by hydrogénation then became the rate-determining step. T h i s would account f o r the o b s e r v e d k i n e t i c s . A second important development was the e x t e n s i o n of the c a t a l y t i c and thermochemical measurements t o most o f the t r a n s i t i o n m e t a l s . Most o f t h i s had been done by 1945, when Beeck p u b l i s h e d a review a r t i c l e e n t i t l e d " C a t a l y s i s - a C h a l l e n g e t o the P h y s i c i s t " (10) . A second review was i s s u e d i n 1947 . In


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i t , Beeck mentioned t h a t Wheeler had been a b l e , by means o f an approximate quantum-chemical c a l c u l a t i o n , to account f o r the shapes o f the c u r v e s r e l a t i n g heat c f a d s o r p t i o n t o f r a c t i o n a l coverage. Unfortunately, no d e t a i l s o f t h a t c a l c u l a t i o n were ever p u b l i s h e d . Almost every year from 1940 t o 1949, Beeck a t t e n d e d the Gordon Research Conference on C a t a l y s i s , sometimes accompanied by Wheeler. There he u s u a l l y p r e s e n t e d a r e p o r t o f t h e i r r e c e n t p r o g r e s s , so the c a t a l y s i s community was a p p r i s e d o f new developments. A paper on the a d s o r p t i o n o f hydrogen on s i n t e r e d n i c k e l f i l m s was p u b l i s h e d i n 1948 {~L2) . I t r e v e a l e d t h a t the u s u a l v e r y r a p i d a d s o r p t i o n was accompanied by a slower, a c t i v a t e d p r o c e s s . T h i s slower s t e p was a t t r i b u t e d t o the p e n e t r a t i o n o f hydrogen i n t o r e g i o n s t h a t had been c l o s e d o f f by t h i n b a r r i e r s formed by s i n t e r i n g . The f i n d i n g r e s o l v e d , a t l e a s t i n p a r t , the d i f f e r e n c e between the r e s u l t s o b t a i n e d i n i t i a l l y w i t h evaporated f i l m s and those r e p o r t e d f o r s u p p o r t e d n i c k e l c a t a l y s t s formed by c o n v e n t i o n a l c h e m i c a l means. In 1948, Beeck p u b l i s h e d h i s t h i r d review a r t i c l e on s u r f a c e c a t a l y s i s ; i t summarized the f i n d i n g s and practical applications of a l l the preceding s t u d i e s by him and h i s c o l l e a g u e s s i n c e 1934 (1) . For example, i n the e a r l y work w i t h p l a t i n u m f o i l s (3), i t was found t h a t c a r e f u l l y d r i e d hydrocarbons did not decompose r a p i d l y on such s u r f a c e s u n t i l a temperature o f 1600°C was reached, a t which p o i n t the r e s u l t i n g f r a g m e n t a t i o n o f the r e a c t a n t was severe. A d d i t i o n o f t r a c e s o f water vapor l e d t o decomposit i o n t o s i m p l e r p r o d u c t s at much lower temperatures. He a t t r i b u t e d the p r o m o t i o n a l e f f e c t t o d i s s o c i a t i o n of the water on the s u r f a c e t o produce chemisorbed H. and OH. r a d i c a l s which r e a c t e d w i t h the i m p i n g i n g hydrocarbon. T h i s f i n d i n g l e d t o a p a t e n t (140 . He mentions a l s o t h a t i n the e a r l y work w i t h e v a p o r a t e d n i c k e l f i l m s , i t was found t h a t a c e t y l e n e i n a m i x t u r e w i t h e t h y l e n e was hydrogenated select i v e l y and almost c o m p l e t e l y b e f o r e the e t h y l e n e was attacked. This f i n d i n g l e d to a u s e f u l method f o r removing t r a c e s o f v i n y l a c e t y l e n e from b u t a d i e n e f o r s y n t h e t i c rubber manufacture d u r i n g World War II. A l s o , d u r i n g t h a t war, he a s s i g n e d A. E. Smith t o use X-ray d i f f r a c t i o n t o study the reason f o r the r a p i d d e a c t i v a t i o n o f hydroforming c a t a l y s t s . The problem was t r a c e d t o a r a p i d t r a n s f o r m a t i o n , under r e a c t i o n c o n d i t i o n s , o f the h i g h - a r e a alumina support t o a l p h a alumina w i t h a much lower a r e a . A method was found to stabilize high-area alumina supports by the


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i n c o r p o r a t i o n o f s m a l l amounts o f a l k a l i i o n s , espec i a l l y l i t h i u m (1_5,16) . Before the war, u s i n g one of the earliest samples o f t r i t i u m from the R a d i a t i o n L a b o r a t o r y c.t B e r k e l e y , he found the r a t e o f i s o m e r i z a t i o n o f nbutane t o i s o b u t a n e , over aluminum c h l o r i d e promoted w i t h water, was p r o p o r t i o n a l t o the r a t e o f exchange o f hydrogens between the hydrocarbon and a c a t a l y s t promoted w i t h t r i t i a t e d water. T h i s o b s e r v a t i o n may have been p a r t o f the s t i m u l u s f o r the more d e t a i l e d studies with i s o t o p i c t r a c e r s of a c i d c a t a l y s i s a f t e r the war. F i n a l P u b l i c a t i o n s on M e t a l

Films

1950, the y e a r o f Beeck ' s death, was a l s o an important p u b l i c a t i o n year. A monograph d e s c r i b i n g the c h e m i s o r p t i o n r e s u l t s appeared i n Advances i n Catalysis (17). Beeck a l s o a t t e n d e d the Faraday S o c i e t y D i s c u s s i o n on Heterogeneous C a t a l y s i s , an international meeting, where he presented three papers: a summary review by h i m s e l f (ljS) , a paper w i t h R i t c h i e on the r e a c t i o n r a t e s w i t h a v a r i e t y o f metal c a t a l y s t s (1J3) and one w i t h C o l e and Wheeler (9) d e s c r i b i n g the a d s o r p t i o n c a l o r i m e t e r and the r e s u l t s obtained therewith. A number o f s t i m u l a t i n g e x p e r i m e n t a l f a c t s , i d e a s and c o r r e l a t i o n s were p r e sented, i n c l u d i n g the famous "volcano-shaped curve" i n which the l o g a r i t h m o f the i s o t h e r m a l r a t e constant f o r hydrogénation, c o v e r i n g f o u r o r d e r s o f magnitude, was p l o t t e d a g a i n s t the l a t t i c e s p a c i n g f o r eleven t r a n s i t i o n metals. The curve peaked a t rhodium, the most a c t i v e c a t a l y s t , and fell off s h a r p l y on e i t h e r s i d e . That c o r r e l a t i o n was marred, however, by the presence of several s i g n i f i c a n t l y o u t - l y i n g data p o i n t s . A b e t t e r c o r r e l a t i o n was a p l o t o f l o g k v e r s u s the i n i t i a l heat o f a d s o r p t i o n o f e i t h e r hydrogen or e t h y l e n e . Rhodium e x h i b i t s the lowest heat w h i l e t u n g s t e n , the l e a s t a c t i v e c a t a l y s t , has the h i g h e s t . S t r a n g e l y , the a c t i v a t i o n energy f o r the o v e r a l l hydrogénation r a t e c o n s t a n t was s t a t e d t o be 1 0 . 7 k c a l / m o l f o r a l l the metals t e s t e d , i n c l u d i n g both o r i e n t e d and u n o r i e n t e d f i l m s of n i c k e l . U n f o r t u n a t e l y , few e x p e r i m e n t a l d a t a were p r e s e n t e d t o support t h a t statement, nor was t h e r e a d i s c u s s i o n o f how the e f f e c t s o f s i n t e r i n g were c i r cumvented i n the measurement o f a c t i v a t i o n e n e r g i e s . Some p r e v i o u s l y u n p u b l i s h e d r e s u l t s were p r e s e n t e d about the r a t e o f removal by hydrogénation o f p r e - a d s o r b e d e t h y l e n e from a c o v e r e d f i l m s u r f a c e .


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The r a t e o f removal from a rhodium s u r f a c e was much h i g h e r than from the s u r f a c e s o f l e s s a c t i v e m e t a l s , i n c o n f o r m i t y w i t h the k i n e t i c model. Morever, the p r o d u c t o b t a i n e d from the rhodium s u r f a c e was l a r g e l y ethane, whereas from the l e s s a c t i v e s u r f a c e s o f o t h e r m e t a l s , s a t u r a t e d o l i g o m e r s o f e t h y l e n e were obtained also. T h i s showed t h a t the "acetylenic complexes" c o u l d p o l y m e r i z e on the s u r f a c e , thus p r o v i d i n g a r o u t e toward the known phenomenon o f c a r b o n i z a t i o n of c a t a l y s t surfaces during hydrogénation. The format o f t h a t meeting was such t h a t each a u t h o r was r e q u i r e d t o submit a complete m a n u s c r i p t o f h i s paper w e l l i n advance o f the meeting. Prep r i n t s o f the papers were sent t o a l l e x p e c t e d p a r t i c i p a n t s b e f o r e the meeting so t h a t they c o u l d p r e p a r e their discussions. At the meeting itself, each a u t h o r was g i v e n o n l y a s h o r t time t o i n t r o d u c e and summarize h i s paper, so t h a t most o f the time c o u l d be devoted t o d i s c u s s i o n . A l e x Oblad t o l d me an i n t e r e s t i n g s t o r y about t h a t . As the meeting s t a r t ed, the d i s c u s s i o n f o l l o w i n g the f i r s t few papers was rather desultory. D u r i n g a break, Beeck, who was s c h e d u l e d t o come on next, s u g g e s t e d t o Oblad, who was t o f o l l o w him, t h a t they l i v e n t h i n g s up. Beeck would devote most o f h i s a l l o t t e d time t o a s p i r i t e d a t t a c k on Oblad's work and A l e x , i n t u r n , would r e ciprocate. A l e x agreed; the r e s u l t i n g exchange l e d t o a l i v e l y d i s c u s s i o n which c o n t i n u e d t h r o u g h the meeting, as the p u b l i s h e d p r o c e e d i n g s a t t e s t . A l s o i n 1950 a paper was p u b l i s h e d d e s c r i b i n g a d s o r p t i o n i s o b a r s f o r hydrogen on n i c k e l f i l m s from 20° Κ t o room temperature (20). These r e s u l t s were a c h i e v e d w i t h the a i d o f the newly d e v e l o p e d C o l l i n s helium c r y o s t a t . I t i s extremely fortunate, I b e l i e v e , that t h i s f i n a l b u r s t o f papers appeared b e f o r e Beeck's un t i m e l y death. At the same time, i t i s r e g r e t t a b l e t h a t a g r e a t d e a l o f the e x p e r i m e n t a l d e t a i l u n d e r l y i n g t h i s l a r g e and s t i m u l a t i n g body o f work was never p u b l i s h e d and, presumably, never w i l l be. Acid

Catalysis

The h i s t o r y o f Beeck's involvement i n the study o f a c i d c a t a l y s i s was v e r y d i f f e r e n t from the f o r e going. Here h i s r o l e was p r i m a r i l y t o assemble a t a l e n t e d r e s e a r c h team t o a t t a c k a broad o b j e c t i v e . That o b j e c t i v e was t o use s t a b l e i s o t o p e s , which became a v a i l a b l e a f t e r the war, t o study mechanisms o f c a t a l y s i s ; the i d e a may have been s t i m u l a t e d by


166

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c o n v e r s a t i o n s w i t h D. P. Stevenson. The team com p r i s e d Stevenson, an a c c o m p l i s h e d mass s p e c t r o m e t r i s t and a b r o a d l y e x p e r i e n c e d p h y s i c a l and structural chemist; John W. Otvos, a p h y s i c a l chemist and spect r o s c o p i s t w i t h background i n r e a c t i o n k i n e t i c s and r a d i o t r a c e r s , and C h a r l e s D. ("Chuck") Wagner, an o r g a n i c chemist w i t h s t r o n g p h y s i c a l l e a n i n g s ; h i s p r i m a r y r o l e was t o s y n t h e s i z e hydrocarbons with carbon-13 or deuterium i n known m o l e c u l a r p o s i t i o n s . A c i d c a t a l y s i s was a n a t u r a l f i e l d f o r such a group t o study s i n c e i t i n v o l v e d both s k e l e t a l r e a r rangements and p r o b a b l e hydrogen t r a n s f e r s . So f a r as I know, t h e r e was l i t t l e f o r m a l r e s e a r c h d i r e c t i o n of t h i s work by Beeck; experiments were p l a n n e d i n f o r m a l l y among the t h r e e i n v e s t i g a t o r s and p r o d u c t s were usually analyzed mass spectrometrically by Stevenson. Beeck dropped i n a t the l a b o r a t o r y from time t o time t o l e a r n what was g o i n g on and t o o f f e r encouragement and i n f o r m a l s u g g e s t i o n s . T h i s work r e s u l t e d , over the p e r i o d 1948-1952, i n e i g h t p u b l i c a t i o n s d e a l i n g w i t h the i s o m e r i z a t i o n o f p a r a f f i n s and t h e i r hydrogen-exchange r e a c t i o n s i n a c i d i c systems. The i n t e r f a c e s i n v o l v e d were e i t h e r s o l i d , w i t h c a t a l y s t s based on aluminum c h l o r i d e , or l i q u i d , with concentrated s u l f u r i c acid. The r e s u l t s provided s t r o n g support f o r the u t i l i t y of the carbonium-ion model and new i n f o r m a t i o n about the p r o p e r t i e s o f the p o s t u l a t e d t r a n s i e n t i n t e r m e d i a t e s . F i r s t came a thorough i n v e s t i g a t i o n by Stevenson o f the n a t u r e o f aluminum h a l i d e c a t a l y s t s and t h e i r a c t i v i t y f o r the i s o m e r i z a t i o n between m e t h y l c y c l o pentane and cyclohexane (2^,22). In agreement w i t h i n d u s t r i a l l o r e and w i t h s l i g h t l y e a r l i e r p u b l i c a t i o n s by o t h e r s on r e l a t e d r e a c t i o n s , i t was found t h a t s m a l l amounts o f water were e s s e n t i a l t o c a t a l y t i c a c t i v i t y ; pure hydrogen h a l i d e s , on the o t h e r hand, were not e f f e c t i v e promoters. The a c t i v e spe c i e s were proposed t o be Α ΐ Χ 5 _ ( 0 Η ) ; t h i s p r o p o s a l was s u p o r t e d by X-ray powder d i f f r a c t i o n data ob tained i n c o l l a b o r a t i o n w i t h A. E. Smith. The e q u i l i b r i u m c o n s t a n t and i t s temperature c o e f f i c i e n t were r e - d e t e r m i n e d and the thermodynamic parameters f o r the r e a c t i o n were computed. Many o f the byprod u c t s were a l s o determined by mass s p e c t r o m e t r y . C o n c u r r e n t l y , a s e r i e s o f papers began t o appear on the i s o m e r i z a t i o n and hydrogen-exchange r e a c t i o n s o f hydrocarbons w i t h a c i d c a t a l y s t s . Over s l i g h t l y h y d r a t e d aluminum bromide a t room temperature^ p r o pane c o n t a i n i n g carbon-13 a t one end ( C H Q - 1 - C )was found t o i s o m e r i z e toward a s t a t i s t i c a l mixture w i t h 2

χ

χ

3


12.

WILSON

167


a t a r a t e comparable t o t h a t o f t h e i s o m e r i z a t i o n o f η-butane t o ]ί-butane under t h e same c o n d i t i o n s ( 2 3 ) . Under s i m i l a r c o n d i t i o n s , n-butane1-C was found t o i s o m e r i z e t o a s t a t i s t i c a l l y weighted m i x t u r e o f t h e isomers w i t h t h e carbon-13 i n a l l p o s s i b l e p o s i t i o n s ( 2 4 ) . The d a t a showed t h a t the a c t i v a t i o n p r o c e s s was p u r e l y i n t r a m o l e c u l a r and suggested t h a t t h e a c t i v a t e d complex was c a p a b l e o f r e a r r a n g i n g among a l l p o s s i b l e isomers b e f o r e r e v e r t i n g t o the u n a c t i v a t e d hydrocarbon. A study was then made o f t h e hydrogen-exchange r e a c t i o n s o f a l l seven o f t h e monodeuterated C ,C3 and C^ hydrocarbon isomers a t room temperature over a water-promoted aluminum c h l o r i d e - a l u m i n a c a t a l y s t . C o n t r a r y t o e x p e c t a t i o n , no exchange o f deuterium between t h e c a t a l y s t and any o f t h e d e u t e r a t e d hydro carbon isomers was d e t e c t e d , even though most o f t h e hydrogen i n t h e r e a c t i o n systems was i n c o r p o r a t e d i n the c a t a l y s t . On t h e o t h e r hand, a v a r i e t y o f i n t e r m o l e c u l a r exchanges between hydrocarbon m o l e c u l e s was observed, though no e v i d e n c e was found f o r d i s p r o p o r t i o n a t i o n r e a c t i o n s ( 2 5 ) . Some o f t h e s e r e a c t i o n s were i d e n t i f i e d by t h e use o f d o u b l y - l a b e l e d hydro carbons, w i t h carbon-13 i n one p o s i t i o n and deuterium i n another. Under t h e c o n d i t i o n s s t u d i e d , some o f the exchange r e a c t i o n s were v e r y f a s t , w i t h a c t i v a t i o n e n e r g i e s o f a p p r o x i m a t e l y z e r o and h a l f - t i m e s o f the o r d e r o f two minutes o r l e s s . O t h e r s , such as the i n t e r m o l e c u l a r exchange between t h e p r i m a r y and secondary hydrogens o f propane, were much slower. A s u b s t a n t i a l number o f g e n e r a l o b s e r v a t i o n s were made, but d e t a i l e d m e c h a n i s t i c c o n c l u s i o n s were d e f e r r e d . An important d i f f e r e n c e between i s o m e r i z a t i o n and hydrogen exchange was s i g n a l l e d by the f a c t t h a t t h e a c t i v i t y o f the c a t a l y s t f o r i s o m e r i z a t i o n d e c l i n e d by a f a c t o r o f 10 d u r i n g t h e c o u r s e o f t h e s e r i e s o f experiments, whereas t h e a c t i v i t y f o r t h e exchange reactions d i d not diminish n o t i c e a b l y . T h i s important s h o r t communication was accompan i e d by another on hydrogen exchange r e a c t i o n s o f t h e butanes i n c o n c e n t r a t e d s u l f u r i c a c i d (26). In t h i s case, ^-butane was found t o exchange i t s p r i m a r y hydrogens w i t h t h e hydrogens o f s u l f u r i c a c i d a t a s i g n i f i c a n t r a t e , t h e h a l f - t i m e a t 25° C d e c r e a s i n g from 1700 minutes i n 91.5 p e r c e n t s u l f u r i c a c i d t o 48 minutes i n 98.3 p e r c e n t a c i d . The r e a c t i o n d i s p l a y e d a s h o r t i n d u c t i o n p e r i o d which c o u l d be e l i m i n a t e d by a d d i n g 0.1% o f i s o b u t e n e t o t h e s t a r t i n g hydrocarbon. The i n d u c t i o n p e r i o d was thus a t t r i b u t e d t o t h e 3

2


168

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CATALYSIS

n e c e s s i t y f o r t r a c e o x i d a t i o n o f the s t a r t i n g p a r a f fin to form o l e f i n , l e a d i n g t o a carbonium i o n , before r e a c t i o n could proceed. The o v e r a l l k i n e t i c s were found t o be pseudof i r s t o r d e r , as i s r e q u i r e d f o r most exchange r e a c t i o n s , r e g a r d l e s s o f mechanism (27,_28) . The logarithm of the apparent r a t e c o n s t a n t was found t o vary l i n e a r l y w i t h the Hammett a c i d i t y f u n c t i o n . A r e a c t i o n w i t h the same r a t e c o n s t a n t s was found t o be the exchange o f t e r t i a r y hydrogens between i s o b u t a n e m o l e c u l e s , one o f which was l a b e l l e d w i t h d e u t e r i u m i n the t e r t i a r y p o s i t i o n and the o t h e r w i t h carbon-13 i n a p r i m a r y p o s i t i o n . Nevertheless, exchange o f the t e r t i a r y hydrogen o f i s o b u t a n e w i t h the hydrogens o f the s u l f u r i c a c i d was not o b s e r v e d at a l l , e x c e p t w i t h 98.3 p e r c e n t a c i d , i n which case s i g n i f i c a n t o x i d a t i o n o f the h y d r o c a r b o n was shown by d i s c o l o r a t i o n o f the a c i d and l i b e r a t i o n o f s u l f u r dioxide. With the n-butanes, n e i t h e r the p r i m a r y nor secondary hydrogens showed any s i g n i f i c a n t r e a c t i o n i n 96 p e r c e n t a c i d . These f i n d i n g s had important i m p l i c a t i o n s f o r the p r o p e r t i e s o f the h y p o t h e t i c a l carbonium i o n s . Though several qualitative generalizations were drawn, d e t a i l e d d i s c u s s i o n was deferred f o r longer communications t h a t f o l l o w e d . P r e p a r a t i o n and c h a r a c t e r i z a t i o n o f the i s o t o p i c a l l y l a b e l l e d hydrocarbons were d e s c r i b e d i n two p a p e r s (29,30); a t h i r d d e s c r i b e d a method f o r d e t e r m i n i n g the i s o t o p i c p u r i t y (3^2) o f p e r d e u t e r o s u l f u r i c acid. With t h i s foundation~7~ the b e h a v i o r o f i s o b u tane was d i s c u s s e d (31.) i n terms o f a c a r b o n i u m - i o n c h a i n r e a c t i o n i n which the c h a i n - c a r r y i n g s t e p i s the t r a n s f e r o f the t e r t i a r y hydrogen atom, c a r r y i n g i t s e l e c t r o n p a i r , from an i s o b u t a n e m o l e c u l e t o the t e r t i a r y carbon o f a t e r t i a r y carbonium i o n t o t e r m i n a t e the l i f e o f one i o n and g e n e r a t e a n o t h e r . The l i f e t i m e o f a g i v e n carbonium i o n i s l o n g enough so t h a t a l l , or n e a r l y a l l o f i t s p r i m a r y hydrogen atoms are exchanged w i t h hydrogens o f the acid. Then f o l l o w e d a s u b s t a n t i a l paper (32) i n which a d e t a i l e d d e s c r i p t i o n and d i s c u s s i o n was g i v e n o f the hydrogen exchange and i s o m e r i z a t i o n r e a c t i o n s o f a number o f C^ t o C j a l k a n e s and s e v e r a l c y c l o a l k a n e s i n the presence of s u l f u r i c a c i d . A g a i n the k i n e t i c s were found t o be p s e u d o - f i r s t o r d e r and the p r o d u c t s were a c c o u n t e d f o r i n terms o f the c a r b o n i u m - i o n mechanism. A number o f generalizations were adduced c o n c e r n i n g the many d e t a i l s o f the hydrogen-exchange r e a c t i o n s ; t h e s e c o u l d a l l be a c c o u n t e d f o r by the mechanism.


12.

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169

A f t e r t h i s work was completed, t h e team d i s b a n d ed and i t s members pursued o t h e r avenues o f r e s e a r c h . Stevenson r e t u r n e d t o mass s p e c t r o m e t r i c r e s e a r c h and o t h e r forms o f s p e c t r o m e t r y . He l a t e r assumed admin i s t r a t i v e r e s p o n s i b i l i t i e s , f i r s t as Manager o f t h e new Chemical P h y s i c s Department and l a t e r as D i r e c t o r o f t h e General S c i e n c e D i v i s i o n . Otvos t u r n e d t o research a p p l i c a t i o n s o f r a d i o t r a c e r s and l a t e r worked w i t h Wagner on r a d i a t i o n c h e m i s t r y . He subse q u e n t l y succeeded Stevenson as Manager o f the Chemi c a l P h y s i c s Department and l a t e r became Manager o f A n a l y t i c a l Research. Wagner went on t o p i o n e e r i n g work i n r a d i a t i o n c h e m i s t r y and a l s o assumed s u p e r v i sory r e s p o n s i b i l i t i e s . He l a t e r a c h i e v e d widespread r e c o g n i t i o n f o r t h i s work i n X-ray p h o t o e l e c t r o n spectroscopy. Concluding

Remarks 1

Though Otto Beeck s r e s e a r c h c a r e e r was a r e l a t i v e l y s h o r t one, h i s achievements were d i v e r s e and substantial. In h i s i n t e r p r e t a t i o n o f t h e h i g h c a t a l y t i c a c t i v i t y o f o r i e n t e d metal f i l m s , however, he espoused and a c t i v e l y promoted one t h e s i s t h a t was not shared by Smith o r Wheeler and has n o t s t o o d t h e t e s t o f time: t h a t was t o suggest t h a t the p l a n e s o f p r e f e r r e d o r i e n t a t i o n were a l s o those exposed t o t h e gas phase. A more p h y s i c a l l y a c c e p t a b l e i n t e r p r e t a t i o n o f t h e observed e f f e c t s c a n now be made, a t least in principle. Nevertheless, the o v e r a l l s i g n i f i c a n c e o f t h e work t h a t he i n s p i r e d and l e d i n h i s chosen f i e l d s o f i n v e s t i g a t i o n was such t h a t h i s s u c c e s s o r s i n those f i e l d s a r e i n h i s debt, whether they r e a l i z e i t o r not. Literature Cited 1.

2. 3. 4. 5. 6.

Wilson, J . Ν. "Dr. Otto A. Beeck", 1962. A bio graphical sketch, a v a i l a b l e i n the f i l e s of the Center for History of Physics, American I n s t i tute of Physics, 335 E . 45th S t . , New York, N.Y. 10017. Contains a complete list of p u b l i c a t i o n s . Beeck, O. A. Phys. Rev. 1934, 45, 331. Beeck, O. A. Nature 1935, 136, 1028-9. Beeck, O. A. J . Chem. Phys. 1936, 4, 680-89. Beeck, O. A. J . Chem. Phys. 1937, 5, 268-73. Wheeler, Ahlborn. "Advances in Catalysis"; Frankenburg, W. G.; Komarewsky, V. I . ; R i d e a l , E . K . E d s . Academic: New York, 1951; 3, p.250-327.


170 7. 8. 9.

10. 11. 12. 13. 14.

15. 16. 17.

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28.

HETEROGENEOUS CATALYSIS Beeck, O. A . ; Wheeler, A. J . Chem. Phys. 1939, 7, 631-2. Beeck, Ο. Α . ; Smith, A. E.; Wheeler, A. Proc. Roy. Soc. (London) 1940, A177, 62-89. Beeck, O. A . ; Cole, W. A . ; Wheeler, A. "Hetero geneous Catalysis"; Discussions of the Faraday Society; Aberdeen University Press: Aberdeen, 1950, 8, 314-21. Beeck, O. A. Revs. Mod. Phys. 1945, 17, 61-71. Beeck, O. A. Record Chem. Progress 1947,8,105-. Beeck, O. Α . ; R i t c h i e , A. W.; Wheeler, A. J . C o l l . S c i . 1948, 3, 505-10. Beeck, O. A. Revs. Modern Phys. 1948, 20,127-30. Beeck, O. Α . ; Burgin, J.; G r o l l , H. P. A. " A c t i vating and Maintaining the A c t i v i t y of Dehydrogenation Catalysts", U.S. Patent 2,131,089 (to Shell Development Company). Smith, A. E.; Beeck, O. A. "Thermally Stable Aluminas for Catalyst Supports", U.S. Patent 2,454,227, 1948, (to Shell Development Company). Smith, A. E . ; Beeck, O. A. "Lithium-Alumina Catalysts", U.S. Patent 2,474,440, 1949 (to Shell Development Company). Beeck. O. A. "Catalysis and Adsorption of Hydro gen on Metal Catalysts", Advances i n C a t a l y s i s , Frankenburg, W. G . ; Komarewsky, V. I . ; Rideal, Ε. Κ., E d s . , Academic: New York, 1950, 2, p. 151-195. Beeck, O. Α.; "Heterogeneous Catalysis", Discus sions Faraday Soc., Aberdeen University Press: Aberdeen, 1950, 8, p. 118-28. Beeck, O. Α . ; R i t c h i e , A. W.; ibid., p. 159-66. Beeck, O. Α . ; Given, J . W.; R i t c h i e , A. W. J . Coll. S c i . 1950, 5, 141-7. Stevenson, D. P . ; Beeck, O. Α . ; J . Am. Chem. Soc. 1948, 70, 2890-94. Stevenson, D. P . ; Morgan, Jane H. J . Am. Chem. Soc. 1948, 70, 2773-7. Beeck, O. Α . ; Otvos, J . W.; Stevenson, D. P . ; Wagner, C. D. J . Chem. Phys. 1948, 16, 255-6. Otvos, J . W.; Stevenson, D. P . ; Wagner, C. D . ; Beeck, O. A. J . Chem. Phys. 1948, 16, 745. Wagner, C. D . ; Beeck, Ο. Α . ; Otvos, J . W.; Stevenson, D. P. J . Chem. Phys. 1949, 17,419-20. Beeck, O. Α . ; Otvos, J . W.; Stevenson, D. P . ; Wagner, C. D. J . Chem. Phys. 1949, 17, 418-19. Wilson, J . N . ; Dickinson, R. G. J . Am. Chem. Soc. 1937, 59, 1358-61. McKay, H. A. C. Nature 1938, 142, 997-8.


12. WILSON Otto Beeck and His Colleagues 29. 30. 31. 32.

171

Wagner, C. D.; Stevenson, D. P. J . Am. Chem. Soc. 1950, 72, 5785. Wagner, C. D.; Stevenson, D. P . ; Otvos, J. W. J. Am. Chem. Soc. 1950, 72, 5786. Otvos, J. W.; Stevenson, D. P . ; Wagner, C. D.; Beeck, O. A. J . Am. Chem. Soc. 1951, 73, 5741-6. Stevenson, D. P . ; Wagner, C. D.; Beeck, O. Α.; Otvos, J. W. J. Am. Chem. Soc. 1952, 74,3269-84.

Received October 29, 1982


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