Heterogeneous Catalysis - American Chemical Society

15 Early Infrared Studies of Adsorbed Molecules at Beacon

Downloaded by CORNELL UNIV on October 10, 2016 | http://pubs.acs.org Publication Date: June 3, 1983 | doi: 10.1021/bk-1983-0222.ch015

R. P. EISCHENS Broomall, PA 19008

When Professor Davis asked me to describe the early phases of infrared efforts at Beacon, he emphasized that he did not want a review of published work. Rather, he wanted to learn the o r i g i n of ideas and the nature of problems encountered before it was evident that infrared would provide a feasible approach to surface studies. He was also interested i n the p e r s o n a l i t i e s involved i n establishing a r e search environment which made possible a twenty-five year period of fundamental work i n an i n d u s t r i a l laboratory. I s h a l l try to fulfill t h i s request because, i n l a t e r years, as I have learned more about research p o l i c i e s , I more f u l l y appreciate the rare and valuable opportunities enjoyed by my colleagues and I at Texaco's Beacon Laboratory. When the infrared work was started, Dr. W.E. Kuhn was overseeing Texaco research and Dr. W.J. Coppoc was the Director responsible for the research area which included our Physical Research Section. Wayne Kuhn and Joe Coppoc have been active i n the ACS and are well known and respected. They had assigned the l a t e Dr. Louis C. Roess to e s t a b l i s h and supervise a fundamental research group. His personal research i n t e r e s t s were mainly i n the area of e l e c t r o n i c s . He had received his B . S . degree i n E l e c t r i c a l Engineering and his Ph.D. i n Physics. When I joined Texaco i n 1948, one of the company's major research efforts was i n the production of synthetic fuels by an iron catalyzed F i s c h e r Tropsch reaction. At that time there was fear of a worldwide oil shortage. The oil f i e l d s i n Arabia had been discovered but t h e i r potential was not yet realized. Because of t h i s company i n t e r e s t , my first projects were studies of CO chemisorption on i r o n . The most s i g n i f i c a n t of these studies were c a r r i e d out i n c o l l a b o r a t i o n with Dr. A . N . Webb. 0097-6156/83/0222-0183$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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Our i n f r a r e d work stemmed from t h e 1949 Gordon Research C o n f e r e n c e on C a t a l y s i s . At t h i s c o n f e r ence, I had l i s t e n e d t o a s p i r i t e d d i s c u s s i o n o f the q u e s t i o n o f whether c r a c k i n g c a t a l y s t a c i d i t y was due t o Lewis o r B r o n s t e d a c i d s i t e s . Prior to this d i s c u s s i o n , I had been o n l y v a g u e l y aware o f the importance o f c a t a l y s t a c i d i t y even though chemisorpt i o n o f b a s i c n i t r o g e n compounds was b e i n g used as an index o f c r a c k i n g a c t i v i t y . A f t e r the conference, i t o c c u r r e d t o me t h a t ammonia would r e t a i n t h e NH^ s t r u c t u r e on a Lewis s i t e and would be c o n v e r t e d t o NH on a B r o n s t e d s i t e and t h a t i n f r a r e d might be able to i d e n t i f y these s t r u c t u r e s . I went t o J . E . Mapes who was working w i t h one o f t h e i n f r a r e d spect r o p h o t o m e t e r s a v a i l a b l e t o our group. Mapes agreed to c o o p e r a t e i n an attempt t o determine whether i n f r a r e d c o u l d d i f f e r e n t i a t e between the two p o s s i b l e forms o f chemisorbed ammonia. Success i n t h e s e exp e r i m e n t s encouraged us t o a p p l y i n f r a r e d t o o t h e r chemisorption systems. Professor Davis may be d i s a p p o i n t e d t o l e a r n t h a t the i n f r a r e d work e v o l v e d from an e f f o r t t o answer a l i m i t e d , s p e c i f i c q u e s t i o n r a t h e r than from a keen i n s i g h t o f the p o t e n t i a l a p p l i c a t i o n o f i n f r a r e d t o a broad range o f c a t a l y s i s studies. Mapes and I d i d not have an i n s i t u sample c e l l . Our sample was p l a c e d i n a tube t o which s a l t windows were a t t a c h e d w i t h s e a l i n g wax a f t e r t h e sample had been d r i e d and ammonia chemisorbed. Despite t h i s p r i m i t i v e t e c h n i q u e , w i t h i t s danger o f c o n v e r t i n g Lewis s i t e s t o B r o n s t e d s i t e s by i n a d v e r t e n t exposure t o water vapor, the i n f r a r e d spectrum i n d i c a t e d t h a t most o f t h e ammonia was i n t h e Lewis c o n f i g u r a t i o n (1). D u r i n g the e a r l y s t a g e s o f t h e ammonia work we r e c e i v e d i m p o r t a n t a s s i s t a n c e which was made p o s s i b l e by Texaco's s p o n s o r s h i p o f a f e l l o w s h i p a t Columbia University. P a r t o f the Columbia work was devoted t o i n f r a r e d spectra of minerals. To minimize s c a t t e r i n g o f the i n f r a r e d beam, the Columbia workers ground t h e m i n e r a l s i n a mortar and p e s t l e and used t h e s m a l l e r p a r t i c l e s o b t a i n e d by s e d i m e n t a t i o n . Mapes and I o b t a i n e d d e t a i l s o f t h i s p r o c e d u r e and we used i t w i t h our c r a c k i n g c a t a l y s t sample. I t i s l i k e l y that our ammonia experiment would have been u n s a t i s f a c t o r y , due t o e x c e s s i v e s c a t t e r i n g , i f we had n o t had a c c e s s t o t h i s method o f p r e p a r i n g t h e sample. We used a P e r k i n - E l m e r Model 12 i n s t r u m e n t . T h i s i n s t r u m e n t had an i n t e r e s t i n g background which a l s o

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


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c o n t r i b u t e d t o t h e s u c c e s s o f t h e ammonia work. I t was one o f t h e f i r s t c o m m e r c i a l l y a v a i l a b l e i n f r a r e d units. When t h i s i n s t r u m e n t was purchased, s p e c t r a were r e c o r d e d on a p h o t o g r a p h i c f i l m . Dr. Roess had used t h e i n s t r u m e n t t o develop t h e , now w i d e l y used, e l e c t r o n i c system i n v o l v i n g a chopped beam and a l t e r nating current amplification. T h i s made i t p o s s i b l e to r e c o r d s p e c t r a on a paper c h a r t . Roess had a l s o designed an attachment which made i t p o s s i b l e t o s u b t r a c t t h e background without a f f e c t i n g absorbance of t h e bands. The o p e r a t o r would f i r s t o b t a i n t h e background spectrum o f t h e c a t a l y s t p r i o r t o chemisorption. A f t e r t h e adsorbate had been added, t h e o p e r a t o r would f o l l o w t h e background w i t h a s t y l u s as the second spectrum was b e i n g scanned. T h i s gave t h e advantage o f c o n v e n i e n t and a c c u r a t e background subtraction. After t h e ammonia results encouraged further e f f o r t , our p r e v i o u s i n t e r e s t s caused us t o s e l e c t the C O - i r o n system f o r t h e next i n f r a r e d work. T h i s was an u n f o r t u n a t e c h o i c e which almost l e d t o e a r l y t e r m i n a t i o n o f our i n f r a r e d s t u d i e s o f metal a d s o r bents. Our CO-iron c h e m i s o r p t i o n s t u d i e s had been l i m i t e d t o i r o n samples produced by r e d u c i n g unsupported iron oxide. We had e x p e r i e n c e d no d i f f i c u l t y i n o b t a i n i n g s a t i s f a c t o r y c h e m i s o r p t i o n o f CO on t h i s unsupported i r o n . S i n c e i t was apparent t h a t s m a l l e r metal p a r t i c l e s would be e s s e n t i a l i n t h e i n f r a r e d work, we attempted t o produce s m a l l i r o n p a r t i c l e s by r e d u c t i o n o f supported i r o n o x i d e . We d i d n o t a n t i c i p a t e the d i f f i c u l t y o f reducing supported iron. S e v e r a l months o f e f f o r t produced s p e c t r a which, w i t h s t r e t c h e s o f i m a g i n a t i o n , might have been a t t r i b u t a b l e t o chemisorbed CO, but which were n o t r e p r o d u cible. We t r i e d t h e CO-platinum system a f t e r we became d i s c o u r a g e d w i t h i r o n . This l e d to infrared s t u d i e s o f CO on a v a r i e t y o f m e t a l s . At a l a t e r time, we were a b l e t o o b t a i n r e p r o d u c i b l e s p e c t r a o f CO on i r o n . However, except f o r one study o f vapor phase c o r r o s i o n i n h i b i t o r s (2) , sample p r e p a r a t i o n problems d i s c o u r a g e d us from expending e f f o r t on iron. About a y e a r p r i o r t o t h e s t a r t o f o u r i n f r a r e d work, I a t t e n d e d a l e c t u r e by P r o f e s s o r W.A. P a t r i c k , of Johns Hopkins U n i v e r s i t y , a t a meeting o f The C a t a l y s i s Club o f P h i l a d e l p h i a . Professor Patrick d e s c r i b e d t h e p r o p e r t i e s o f a s i l i c a which was p r o duced by b u r n i n g s i l i c o n c h l o r i d e . A unique p r o p e r t y of t h i s s i l i c a was t h a t i t s h i g h s u r f a c e area was a t t r i b u t a b l e t o s m a l l , non-porous s p h e r e s . With t h e



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hope t h a t t h i s type o f s i l i c a would e l i m i n a t e the need f o r o b t a i n i n g s m a l l p a r t i c l e s by the sedimenta t i o n procedure, a s e a r c h was made throughout the Beacon l a b o r a t o r y . T h i s l e d t o C a b o s i l which was b e i n g t e s t e d as a grease t h i c k e n e r . P r i o r t o the pressed disc t e c h n i q u e , the i n f r a r e d transmitting properties o f C a b o s i l proved t o be an important advantage. More s i g n i f i c a n t l y , Cabosil had the u n a n t i c i p a t e d advantage o f b e i n g the s u p p o r t which i s l e a s t l i k e l y t o a f f e c t the p r o p e r t i e s o f supported metals. When Mapes t r a n s f e r r e d t o another p o s i t i o n , he was r e p l a c e d by W.A. P l i s k i n whose Ph.D. t r a i n i n g had been devoted t o t h e o r e t i c a l i n f r a r e d work. This began a p r o d u c t i v e c o l l a b o r a t i o n which extended over a p e r i o d of ten years. As the i n f r a r e d work p r o g r e s s e d , we encountered numerous u n e x p l a i n e d e f f e c t s such as minor d i f f e r e n c e s i n band p o s i t i o n s and band shapes. We d i d not attempt t o e x p l a i n such e f f e c t s u n l e s s we had a w e l l d e f i n e d e x p e r i m e n t a l approach which gave promise o f c l a r i f y i n g them. There were a l s o some major " l o o s e ends" which s h o u l d have been pursued f u r t h e r . Anamolous bands were observed when impure z i n c o x i d e was exposed t o oxygen. Our work w i t h z i n c o x i d e had i n v o l v e d a study o f the h e t e r o l y t i c c l e a v age o f adsorbed hydrogen, ZnO + — • Z n H + ZnOH (_3) . T h i s had been observed w i t h a c o m m e r i c a l l y a v a i l a b l e z i n c o x i d e , Kadox-25, which was produced by b u r n i n g metallic zinc. We wanted t o work w i t h a sample h a v i n g a h i g h e r s u r f a c e a r e a so we p r e p a r e d z i n c o x i d e by decomposing z i n c o x a l a t e . The o x a l a t e had been made from z i n c n i t r a t e and ammonium o x a l a t e . U n l i k e Kadox-25, our l a b o r a t o r y p r e p a r e d z i n c o x i d e produced bands i n the 1700-2200 cm" r e g i o n when ex posed t o oxygen (4) . These bands are shown i n Spectrum Β o f F i g u r e 1. Spectrum A i s the back ground. The bands i n Spectrum Β were r e v e r s i b l e . T h e i r i n t e n s i t y was a f u n c t i o n o f the oxygen p r e s sure. A n a l y s i s o f our z i n c o x i d e showed t h a t i t was contaminated with 0.2 wt% n i t r o g e n and 0.4-1.0% carbon. It first appeared as though the bands were produced by the r e a c t i o n o f adsorbed oxygen w i t h the n i t r o g e n and carbon i m p u r i t i e s . This i n t e r p r e t a t i o n wa^ weakened when i t was found t h a t treatment w i t h 0 f a i l e d t o produce s h i f t s i n the f r e q u e n c i e s o f tne bands. I t was abandoned when the bands appeared after exposing the impure z i n c o x i d e t o c h l o r i n e because i t was not r e a s o n a b l e t o a t t r i b u t e the bands 8

?



EiscHENS


F i g u r e 1. E f f e c t o f oxygen on ZnO (N,C): 30 °C under vacuum; (B) i n 20 cm 0 ( 4 ) .

(A) a t

9



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to chlorine-carbon and chlorine-nitrogen species. The bands a t t r i b u t a b l e t o carbpn-oxygen s p e c i e s werg s h i f t e d , as expected for a C c a r b o n y l , when C l a b e l e d o x a l a t e was used t o p r e p a r e z i n c o x i d e . The p u b l i s h e d e x p l a n a t i o n o f the above e x p e r i mental r e s u l t s was t h a t a d s o r p t i o n o f e l e c t r o n e g a t i v e adsorbates on impure z i n c o x i d e produces new functional groups by r e a c t i o n of the impurity with l a t t i c e oxygen w i t h i n the b u l k o f the z i n c o x i d e . In l a t e r u n p u b l i s h e d work a t the U n i v e r s i t y o f Denver, P r o f e s s o r Smith p r e p a r e d z i n c o x i d e which c o n t a i n e d o n l y n i t r o g e n as an i m p u r i t y . Exposure o f t h i s z i n c o x i d e t o oxygen produced the bands a t t r i b u t a b l e t o nitrogen-oxygen v i b r a t i o n s i n Spectrum B. However, our q u a l i t a t i v e e x p l a n a t i o n which i m p l i e s t h a t ads o r p t i o n causes r e a c t i o n w i t h i n the b u l k z i n c o x i d e has been n e i t h e r supported nor c h a l l e n g e d by more sophisticated interpretations. Another l o o s e end i n v o l v e s e f f o r t s t o use d i p o l e d i p o l e i n t e r a c t i o n s between adsorbed CO ' s t o d e t e r mine which c r y s t a l f a c e s are exposed on p a r t i c l e s o£ s u p p o r t e d p l a t i n u m (5) . The band i n the 2060 cm r e g i o n , a t t r i b u t a b l e t o CO chemisorbed on p l a t i n u m , s h i f t s toward h i g h e r frequency as s u r f a c e coverage i s increased. A s h i f t i n t h i s d i r e c t i o n would be exp e c t e d t o be produced by d i p o l e - d i p o l e i n t e r a c t i o n s . However, by i t s e l f , the s h i f t i s not adequate f o r study o f d i p o l e - d i p o l e e f f e c t s . I t c o u l d a l s o be due by surface heterogeneity, which causes CO to be adsorbed p r e f e r e n t i a l l y on s i t e s where bonding i s s t r o n g e s t , o r by induced h e t e r o g e n e i t y whereby the i n i t i a l l y adsorbed CO m o d i f i e s the p l a t i n u m so subseq u e n t l y adsorbed CO i s more weakly h e l d . Because o f these d i f f i c u l t i e s , the CO i n t e r a c t i o n s were s t u d i e d by u s i n g i n t e n s i t y d a t a d e r i v e d from c o - a d s o r p t i o n o f normal C 0 and C 0. In the most simple case where o n l y a p a i r o f adsorbed CO ' s are c o n s i d e r e d , d i p o l e - d i p o l e i n t e r a c t i o n s would l e a d t o c o u p l i n g and produce an i n phase mode 0 0 , and an o u t - o f - p h a s e mode, 0 0 . The t t t I ±

C

C

C

C

i n t e n s i t y o f the in-phase band would be e q u i v a l e n t t o t h a t o f two i s o l a t e d CO s. However, the i n t e n s i t y o f the o u t - o f - p h a s e band would be c l o s e t o z e r o because the two d i p o l e changes would c a n c e l . For reasons t h a t are not o b v i o u s , • ^ Ççequency o f the in-phase mode f o r a c o u p l e d C p-C Ο p a i r f a l l s near the f r e q u e n c y o f i s o l a t e d C O's and the frequency f o r the o u t - o f - p h a s e mode f a l l s i n the r e g j o n expected 1

i e


15.

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13 12 13 f o r i s o l a t e d C O's. When a m i x t u r e o f C Ο and C 0 is adsorbed, bands a r e observed which are only s l i g h t l y s h i f t e d from the expected f r e q u e n c i e s . How ever, d i p o l e c o u p l i n g causes t h e h i g h e r f r e q u e n c y band i n t h e C Ο r e g i o n t o have a h i g h r e l a t i v e i n t e n s i t y because the coupled p a i r s c o n t r i b u t e t o t h i s i n t e n s i t y and do n o t s i g n i f i c a n t l y c o n t r i b u t e i n t e n s i t y t o t h e low f r e q u e n c y C region. S i n c e t h e d i p o l e - d i p o l e i n t e r a c t i o n has a r e p u l s i v e e f f e c t which w i l l cause t h e CO s t o s t a y as f a r a p a r t as p o s s i b l e , i t i s p o s s i b l e t o c a l c u l a t e a measure o f t h e i n t e n s i t y r a t i o as a f u n c t i o n o f s u r f a c e coverage. T h i s i s accomplished by c o n s i d e r i n g a l l n e i g h b o r s , r a t h e r than p a i r s , and assuming t h a t the d i s t a n c e between adsorbed CO's i s e s t a b l i s h e d by the d i s t a n c e between p l a t i n u m atoms on t h e simple c r y s t a l faces. C a l c u l a t e d curves of the i n t e n s i t y r a ^ i o o f t h e tj^gn and low f r e q u e n c y bands f o r a 67% C 0 and 37% C Ο m i x t u r e a r e shown i n F i g u r e 2. The e x p e r i m e n t a l p o i n t s , i n d i c a t e d by c i r c l e s , s t a r t a t the n o n - c o u p l i n g v a l u e o f 1.7 and f o l l o w t h e [110] c a l c u l a t e d c u r v e t o a coverage o f 0.5. Unfortun a t e l y , a t h i g h e r coverages the e x p e r i m e n t a l v a l u e s do not c o i n c i d e w i t h any o f the c a l c u l a t e d c u r v e s . A d e t e r m i n a t i o n o f f a c e s exposed on s u p p o r t e d p a l l a d i u m has been made by comparing f r e q u e n c i e s o f adsorbed CO s w i t h those observed on s i n g l e c r y s t a l s (6) . There i s m e r i t t o t h i s approach t o study o f f a c e exposure f o r supported m e t a l s . However, t h e K u g l e r - B o u d a r t method i s n o t s u i t a b l e f o r s u p p o r t e d p l a t i n u m where o n l y s m a l l f r e q u e n c y d i f f e r e n c e s a r e expected. D i p o l e - d i p o l e i n t e r a c t i o n s deserve f u r t h e r study and r e f i n e m e n t . Carbon i s d e p o s i t e d when alumina i s exposed t o hydrocarbons a t e l e v a t e d temperature. An i n s i t u study o f carbon d e p o s i t i o n showed t h a t bands a r e produced i n t h e 1580 cm and 1430 cm" r e g i o n s (7) . These bands appear t o be due t o the asymmetric, C


1

1

and

symmetric,

C

0

°' v i b r a t i o n s o f c a r b o x y l a t e groups.

0 0 F i g u r e 3 shows these bands as observed a f t e r exposure o f alumina t o a c e t y l e n e a t 250°C. C a r b o x y l a t e bands are observed even though t h e system i s under r e d u c i n g conditions. The p r o d u c t i o n o f c a r b o x y l a t e s i s t h e r e f o r e a t t r i b u t e d t o h y d r o l y s i s r a t h e r than o x i d a t i o n . H y d r o l y s i s would produce an o x i d i z e d moity, c a r b o x y l a t e , and a reduced moity, hydrogen. Hydrogen i s n o t d e t e c t e d by i n f r a r e d because i t i s n o t r e t a i n e d on




F i g u r e 2. Comparison o f e x p e r i m e n t a l i n t e n s i t y r a t i o s ( c i r c l e s ) and c a l c u l a t e d i n t e n s i t y r a t i o s as a f u n c t i o n o f s u r f a c e coverage f o r 63% 12 CO samples ( 5 ) .

1600 WAVENUMBER C M '

F i g u r e 3. C a r b o x y l a t e bands formed by alumina w i t h a c e t y l e n e a t 250 °C (7_) .

treating



15.

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191

the s u r f a c e . An o v e r l y s i m p l i f i e d i n t e r p r e t a t i o n o f the i n f r a r e d r e s u l t s might l e a d t o t h e c o n c l u s i o n t h a t t h e alumina s u r f a c e has o x i d i z i n g p r o p e r t i e s . Carbon d e p o s i t i o n i s a l i m i t i n g f a c t o r i n many o f t h e most important c a t a l y t i c p r o c e s s e s . P r i o r t o the i n s i t u i n f r a r e d experiments, t h e r e was a consensus t h a t c a r b o n on c a t a l y s t s i s a m i x t u r e o f p o o r l y d e f i n e d hydrocarbon species i n which t h e hydrogen/carbon r a t i o n i s a f u n c t i o n o f the s e v e r i t y o f experimental conditions. The c o n c l u s i o n , based on F i g u r e 3, sugg e s t s t h a t c a r b o x y l a t e f o r m a t i o n may be an a d d i t i o n a l important factor i n catalyst deactivation which m e r i t s f u r t h e r study. Other l o o s e ends which I might have d i s c u s s e d a r e the m i s s i n g asymmetric s t r e t c h i n g band f o r c a r b o x y l a t e s on reduced metals {&) , t h e r e a c t i v e s u r f a c e carbon which i s produced by s e l f hydrogénation o f a c e t y l e n e on n i c k e l (9) , and s i m u l t a n e o u s i n f r a r e d and magnetic s t u d i e s o f c h e m i s o r p t i o n ( 1 0 ) . In some c a s e s t e r m i n a t i o n o f p r o j e c t s was due t o r e a c h i n g t h e l i m i t o f what we c o u l d e f f e c t i v e l y a c c o m p l i s h . In o t h e r c a s e s i t was due t o a shortage o f time because o f t h e numerous worthwhile p r o j e c t s which were open to us i n 1952. The l a t t e r p o i n t i s worth f u r t h e r e x a m i n a t i o n . There had been moderate a c t i v i t y i n a p p l y i n g i n f r a r e d t o study o f m i n e r a l s a t t h e time o u r i n f r a r e d work was s t a r t e d . A paper, which had major i m p l i c a t i o n s to s u r f a c e s t u d i e s was p u b l i s h e d i n 1937 by B u s w e l l , Krebs, and Rodebush ( 1_1 ) . These workers r e p o r t e d an i n f r a r e d study o f t h e d r y i n g o f m o n t m o r i l l i n i t e . They demonstrated t h a t i n f r a r e d c o u l d d e t e c t and d i s t i n g u i s h adsorbed water and s u r f a c e h y d r o x y l s . Despite the f a c t t h a t t h i s work was p u b l i s h e d i n a r e a d i l y a v a i l a b l e j o u r n a l , i t d i d not receive the a t t e n t i o n i t m e r i t e d from c a t a l y s i s r e s e a r c h e r s . At Texaco, we did n o t l e a r n o f t h e Buswell paper u n t i l we were p r e p a r i n g t o w r i t e a review paper i n 1957 ( 9 ) . I f we r e t u r n t o t h e q u e s t i o n s expressed by P r o f e s s o r Davis, i t can be c o n c l u d e d t h a t our e a r l y i n f r a r e d work was n o t i n f l u e n c e d by p u b l i s h e d l i t e r ature. Ideas which stemmed from t h e Gordon Research C o n f e r e n c e and t h e l e c t u r e by P r o f e s s o r P a t r i c k a t the C a t a l y s i s Club o f P h i l a d e l p h i a were o f c r i t i c a l importance. The i n f o r m a t i o n gained through i n f o r m a l c h a n n e l s made p o s s i b l e by Texaco s p o n s o r s h i p o f t h e Columbia f e l l o w s h i p was v i t a l a t a c r i t i c a l stage o f our work. However, t h e most s i g n i f i c a n t f a c t o r was the r e s e a r c h environment which Roess e s t a b l i s h e d f o r h i s group.


192


He i n s t i l l e d t h e concept t h a t t h e o b j e c t i v e o f our fundamental work was t o advance knowledge i n f i e l d s o f s p e c i a l i n t e r e s t and was n o t t o be j u s t i f i e d by t h e promise o f immediate c o m p e t i t i v e advantage. Young r e s e a r c h e r s were a l l o w e d maximum freedom but were s u b j e c t e d t o c o n t i n u o u s knowledgeable and skeptical questioning by Roess and by t h e i r coll e a g u e s i n t h e group. Roess had a s o p h i s t i c a t e d a p p r e c i a t i o n o f t h e f a c t t h a t the pace o f r e s e a r c h i s o f t e n slow and he d i s p l a y e d extreme p a t i e n c e d u r i n g d i f f i c u l t n o n - p r o d u c t i v e p e r i o d s such as o u r e a r l y work w i t h i r o n . The P h y s i c a l Research S e c t i o n i n cluded about t e n Ph.D. s whose r e s e a r c h interests c o v e r e d a broad range o f p e t r o l e u m r e l a t e d p r o j e c t s . During t h e p e r i o d when P l i s k i n and I were a p p l y i n g i n f r a r e d t o systems o f c a t a l y t i c i n t e r e s t , F r a n c i s and E l l i s o n were e s t a b l i s h i n g t h e f a c t o r s important to r e f l e c t i o n i n f r a r e d i n s t u d i e s r e l a t e d t o l u b r i c a t i o n (1_2) and Lewis was o r i g i n a t i n g the a p p l i c a t i o n o f x - r a y a b s o r b t i o n edge s t u d i e s t o d e t e r m i n a t i o n o f the o x i d a t i o n s t a t e o f s u p p o r t e d metals ( 1_3) . A l though Roess d i d n o t p e r s o n a l l y p a r t i c i p a t e i n t h e r e s e a r c h b e i n g c a r r i e d o u t i n t h e P h y s i c a l Research Section, h i s evaluation and u n d e r s t a n d i n g o f t h e s i g n i f i c a n c e o f t h e p r o j e c t s was c r i t i c a l t o t h e i r success. Support o f the P h y s i c a l Research S e c t i o n a t the h i g h e r l e v e l s o f a d m i n i s t r a t i o n by Dr. Kuhn and Dr. Coppoc was a n e c e s s a r y f a c t o r i n making i t p o s s i b l e t o have an extended fundamental e f f o r t . Their confidence i n Roess was undoubtedly important i n t h e i r d e c i s i o n t o provide t h i s support.


1

Literature Cited 1. 2. 3. 4. 5. 6. 7.

Mapes, J . E . and Eischens, R . P . J . Phys. Chem 1954, 68, 1959. P o l i n g , G.W. and Eischens, R.P. J. Electrochem. Soc. 1966, 113, 218. Eischens, R . P . ; P l i s k i n , W.A. and Low, M . J . D . J. C a t a l y s i s 1962, 1, 180. Smith, D.M. and Eischens, R . P . J . Phys. Chem. S o l i d s 1967, 28, 2135. Hammaker, R . M . ; F r a n c i s , S.A. and Eischens, R . P . Spectrochimica Acta 1965, 21, 1295. Kugler, E . L . and Boudart, M. J. C a t a l y s i s 1979, 59, 201. Ludlum, K . H . and Eischens, R.P. D i v i s i o n of Petroleum Chemistry, ACS meeting, New York, New York, 1976.


15. EISCHENS 8. 9. 10. 11. 12.


13.


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Eischens, R.P. and P l i s k i n , W.A. Proceedings Second International Congress on C a t a l y s i s , P a r i s , 1960. Eischens, R.P. and P l i s k i n , W.A. Advances i n Catalysis and Related Subjects 1958, 10, 1. Mertens, F . P . and Eischens, R.P. "The Structure and Chemisorption of S o l i d Surfaces", G.A. Somorjai, Ed.,Wiley, New York, N.Y., 1969. Buswell, A . M . ; Krebs, K. and Rodebush, W.H. J. Am. Chem. Soc. 1937, 59, 2603. F r a n c i s , S.A. and E l l i s o n , A.H. J. Opt. Soc. Am. 1959, 49, 131. Lewis, P.H. J. Phys. Chem. 1963, 67, 2151.

Received February 9, 1983


Heterogeneous Catalysis - American Chemical Society

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