Heterogeneous Catalysis Before 1934

Heterogeneous Catalysis Before 1934

Downloaded by TUFTS UNIV on September 27, 2014 | http://pubs.acs.org Publication Date: June 3, 1983 | doi: 10.1021/bk-1983-0222.ch001

ROBERT L . BURWELL, JR. Northwestern University, The Ipatieff Catalytic Laboratory, Department of Chemistry, Evanston, IL 60201

This a r t i c l e was prepared as an introduction to t h i s symposium. Its aim was to provide a b r i e f survey of heterogeneous c a t a l y s i s before American contributions began. It makes no pretence to any contribution to scholarship (1). We s h a l l then go back to some s u i t a b l y remote time i n the past and proceed to the terminal date rather r a p i d l y . Ingoing back i n time, l e t us, however, make a stop at 1909. In h i s Nobel Award address of that year, Wilhelm Ostwald said: "The employment of the concept of c a t a l y s i s has served hitherto as an i n d i c a t i o n of s c i e n t i f i c backwardness." We may hope that t h i s i s no longer true and presumably Ostwald f e l t that he had made c a t a l y s i s respectable. But what l e d Ostwald to make t h i s statement? During the nineteenth century, a l l kinds of interpretations of c a t a l y s i s were advanced and most had a closer r e l a t i o n s h i p with metaphysics than with science. Here i s a example from Stohmann i n 1894 (2). "Catalysis is a process involving the motion of atoms i n molecules of l a b i l e compounds which r e s u l t s from the presence of a force emitted by another compound and which leads to the formation of a more stable compound and the l i b e r a t i o n of energy." (Emphasis added). In the same year Ostwald gave a d e f i n i t i o n of c a t a l y s i s which looks rather better (3): "Cataly s i s i s the acceleration of a slow reaction by the presence of a foreign m a t e r i a l . " 0097-6156/83/0222-0003$06.00/0 © 1983 American Chemical Society In Heterogeneous Catalysis; Davis, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

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Let us now see what l e d to some of the curious theories of c a t a l y s i s , although we should keep i n mind that even theories of uncatalyzed reactions were necessarily very inadequate and sometimes rather metaphysical. The philosophers stone of the alchemist was of course a c a t a l y s t and i t was not u n t i l nearly 1800 that chemical theory - the ideas of chemical elements and the nature of chemical change - made transmutation suspect. The l i n g e r i n g idea of the philosophers' stone may have influenced the development of the idea of c a t a l y s i s . The following c l e a r l y describes a c a t a l y t i c experiment although the text i s unclear as to whether the experiment involves homogeneous or heterogeneous catalysis (4).


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"Paracelsus sent h i s waiting man to d e l i v e r a piece of paper containing a small amount of a blood-red powder with the command that i t be poured into molten lead and s t i r r e d well.... The master of the mint paid several thousand guilders for the r e s u l t i n g gold." The experiment was not reproducible, but we have no record that the work was formally withdrawn. During the eighteenth century various reports of what we would c a l l transmutations appeared i n the l i t e r a t u r e . But, i n the absence of the theory of chemical elements, there was no way to d i s t i n guish between what we would now c a l l a chemical change and a transmutation. Although most educated people came to believe that most alchemists were charlatans, there was no s c i e n t i f i c reason why transmutation was impossible and another master of the mint, S i r Isaac Newton, took i t seriously. But, i n the nineteenth century, alchemy disappeared from the s c i e n t i f i c l i t e r a t u r e . The discovery of radioactive transmutations r e v i v i f i e d "alchemy" f o r a short period i n the e a r l i e r 1900's and the p h i l o s ophers stone made i t s l a s t appearance i n the form of a Pd/asbestos c a t a l y s t . In the Berichte der Deutschen Chemisches Gesellshaft f o r 1926 (59B, 2039), the eminent radiochemist F r i t z Paneth and K. Peters published a paper entitled "On the Transmutation (Verwandlung) o f Hydrogen Into Helium." Paneth had developed a method f o r the measurement of very small quantities of helium. In t h i s paper, he reported that 1 g 1

In Heterogeneous Catalysis; Davis, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


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of a 50% Pd/asbestos l e d to the formation of 10-7 cm3 of helium per day. The authors were well aware of the energetics of the process. Certainly, this was the most significant heterogeneous c a t a l y t i c reaction ever to be reported. Unfortunately, the authors had to withdraw the paper very s h o r t l y a f t e r i t s appearance. Despite the statements of the authors i n the communications withdrawing the work, my suspicion i s that the helium c o l l e c t e d had d i f f u s e d through the glass walls of the apparatus. In the second h a l f of the eighteenth century there were various reports of what we would recognize today as c a t a l y t i c reactions. However, the idea of a c a t a l y t i c reaction could not have been understood before chemical elements and chemical change had appeared. This e a r l y work i s a h i s t o r i c a l c u r i o s i t y which had no influence on the development of c a t a l y s i s . The idea of c a t a l y s i s can be taken as s t a r t i n g i n 1814 when K i r c h o f f published his work on the hydrolysis of starch to glucose by acids. A number of people had investigated the hydrolysis, but Kirchoff was the f i r s t c l e a r l y to understand what was going on. The second event i n the development of c a t a l y s i s came i n 1817 when S i r Humphry Davy discovered that the introduction of a hot platinum wire into a mixture of a i r and coal gas l e d the platinum to become white hot. Davy considered that there was oxidation but no flame and that the platinum was unchanged. His cousin, Edmund Davy, continued the work and i n 1820 he discovered that the platinum could be introduced at room temperature provided that i t was f i n e l y divided. Dobereiner continued t h i s work and i n 1823, he found that, i n the presence of platinum, vapors of ethanol reacted with oxygen to form a c e t i c acid. Work on s e l e c t i v e oxidation continues to t h i s day but Dobereiner d i d i t f i r s t . He also noticed, i n l i n e with the work of Edmund Davy, that divided platinum became red hot i n the presence of hydrogen and oxygen. Dobereiner d i d more than notice. He developed Dobereiner s Tinder Box (Dôbereiners Feuerzeug) (5). This involved a small Kipp generator containing zinc and d i l u t e s u l f u r i c acid. When a valve was opened a j e t of hydrogen emerged, the acid rose into the zinc and the j e t continued. The j e t f e l l upon spongy p l a t inum and burst into flame. One then l i g h t e d h i s f i r e or h i s pipe. Over a m i l l i o n Tinder Boxes were 1


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sold. Dobereiner s Tinder Box represented the f i r s t technological a p p l i c a t i o n of heterogeneous c a t a l ysis . In 1824, Henry reported the f i r s t example of poisoning. Ethylene i n h i b i t e d the reaction between hydrogen and oxygen on platinum. He also noted s e l e c t i v e oxidation i n the reaction between oxygen and a mixture of hydrogen, carbon monoxide, and methane. Continuing the l i n e of c a t a l y t i c oxidation on platinum, Peregrine P h i l i p s (1831, B r i t i s h Patent No. 6096) patented the oxidation of S O 2 to S O 3 on platinum, but he must have died before the f i r s t contact process plant f o r the production of s u l f u r i c acid went on stream. And f i n a l l y , along t h i s l i n e of work, Schweigger i n the same year discovered that hydrogen s u l f i d e poisoned platinum. Another l i n e of c a t a l y t i c work was started by Thenard (1818). He discovered hydrogen peroxide and he who discovers H 2 O 2 i s apt also to discover i t s c a t a l y t i c decomposition. Thenard did, and he invest i g a t e d the matter c a r e f u l l y using both homogeneous and heterogeneous c a t a l y s t s . Today, someone might possibly write an annual review of the coordination chemistry of chromium. But, Baron Jacob Berzelius, the "Mr. Chemistry" of his day, wrote an annual review of chemistry every year f o r twenty-eight years. In 1835, he surveyed K i r c h o f f s work on acid hydrolysis, the c a t a l y t i c oxidations on platinum and Thenard s work on the decomposition of H 0 . He discerned a phenomenon common to the three areas, and he invented c a t a l y s i s and c a t a l y s t . Unfortunately, he coined another term, c a t a l y t i c force (6). " C a t a l y t i c force a c t u a l l y means that substances are able to awaken a f f i n i t i e s which are asleep at t h i s temperature by t h e i r mere presence and not by t h e i r own a f f i n i t y . " (Emphasis added). During the rest of the century, much f r u i t l e s s e f f o r t was devoted to t r y i n g to develop explanations for c a t a l y t i c force. I t was t h i s that gave c a t a l y s i s something of a bad reputation and l e d to Ostwald s unfriendly remark. However, a l l through the century there were those who advanced chemical theories of c a t a l y s i s . For example, de l a Rive (7) i n 1838 proposed that platinum catalyzed the oxidat i o n of hydrogen by a cycle of alternate oxidations of platinum followed by reduction of the surface oxide. He said: 1

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"Ce n'est pas nécessaire de recourir a une force mystérieuse telle que c e l l e que Berzelius a admise sous l e nom de force catalytique. [ I t i s unnecessary to resort to a mysterious force l i k e that which Berzelius has proposed under the name, catalytic force]." However, believers i n a chemical explanation were i n the minority up into the twentieth century. Berzelius d i d not r e f e r to Faraday's paper of 1834 (8), but we should. I t was an excellent study of the c a t a l y t i c c h a r a c t e r i s t i c s of platinum f o i l s f o r the oxidation of hydrogen: e f f e c t of pretreatment, rates of reaction i n a p r i m i t i v e fashion, deactivation, r e a c t i v a t i o n and poisoning. For example, ethylene i n h i b i t e d the reaction of a H 2 + O 2 mixture, but a f t e r some hours vigorous action commenced. H 2 S and P H 3 were, however, permanent p o i sons . I t would be i n t e r e s t i n g to rewrite Faraday * s a r t i c l e i n modern form and terminology, to add a few imaginary experiments with XPS and EXAFS, and to submit the r e s u l t to J.Catal. I t would not be wise, however, to i n s e r t Faraday's mechanism i n such a paper. He thought that hydrogen and oxygen were condensed (one might say, physisorbed) on the surface of the platinum and that reaction to form water resulted from the mere proximity of H 2 and 0 2 . "The platinum i s not considered as causing the combination of any p a r t i c l e s with i t s e l f , but only by associating them c l o s e l y around i t . " One cannot f a u l t Faraday f o r not inventing d i s s o c i a t i v e chemisorption. Hydrogen and oxygen were not known to be diatomic i n 1834. Anyway, Faraday d i d not believe i n atoms and assigned such ideas to metaphysics. The concept of atoms " d i d not a f f o r d me the l e a s t help i n my endeavour to form an idea of a p a r t i c l e of matter...with experience, I outgrew the idea of atoms.... Such ideas are mere hindrance to the progress of science (9)." Following Faraday, there was a long, rather dry s p e l l i n academic heterogeneous c a t a l y s i s . Most of the e a r l i e r work involved c a t a l y s i s of oxidations or the l i k e . The world was not ready f o r the oxidation of naphthalene to phthalic anhydride - either academi c a l l y or technologically. Organic heterogeneous c a t a l y s i s remained unexplored f o r many years a f t e r 1834. However, the beginning of the technology of heterogeneous c a t a l y s i s came i n t h i s period ( s t i l l oxidations). The Deacon process was developed i n



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the I860's - the oxidation of hydrogen chloride to chlorine on copper chloride - and Messel started the f i r s t plant f o r the oxidation of s u l f u r dioxide to sulfur trioxide i n 1875, 44 years after the Peregrine P h i l i p s patent. Things began to pick up towards the end of the century. In 1888, Ludwig Mond discovered steam reforming of hydrocarbons on nickel/pumice to give carbon monoxide and hydrogen. S i r James Dewar noted that oxygen adsorbed i n large amounts on charcoal at the temperature of l i q u i d a i r and that i t desorbed as such on warming. However, oxygen adsorbed at 250C could be desorbed only at high temperatures and as oxides of carbon. These observations can be taken as the beginning of physisorption and chemisorption. The development of thermodynamics l e d to the recognition that a c a t a l y s t could only promote a rate i n the d i r e c t i o n of the p o s i t i o n of equilibrium and that a c a t a l y s t could not change the p o s i t i o n of equilibrium. Further, s t a r t i n g with Nernst, i t became l i k e l y that one would need to worry about d i f f u s i o n a l problems i n heterogeneous c a t a l y s i s . In 1909, Ostwald was awarded the Nobel Prize i n chemistry f o r h i s work i n c a t a l y s i s . My suspicion i s that the committee decided to award him the p r i z e - he was the "Mr. Physical Chemistry" of h i s day and they chose h i s work i n c a t a l y s i s as providing as good a basis as any other. In f a c t , not much of h i s career had been devoted to c a t a l y s i s . In 1884, he reported a study of the acid-catalyzed hydrolysis of methyl acetate which introduced k i n e t i c s , i n the modern sense, into c a t a l y s i s . He also t i e d the concept of c a t a l y t i c a c t i v i t y to rate. Both of these items were important. Then i n 1901-1904 he and h i s former student, Brauer, developed the Ostwald process f o r the oxidation on platinum of ammonia to n i t r i c oxide. The f i r s t plant went on stream i n Bochum i n 1906 at a l e v e l of 300 kg of n i t r i c acid per day. In 1908, the production was 3000 kg per day. The process a c t u a l l y goes back to Kuhlmann i n 1838, but there had been no i n d u s t r i a l i n t e r e s t i n such a process, because C h i l i saltpeter was cheaper source of n i t r i c acid than ammonia. However, at the beginning of the twentieth century, the ease with which the B r i t i s h f l e e t could sever the sea lane between C h i l i and Germany had become a stimulus to the development of the Ostwald process. German writers tend to make Ostwald the giant of c a t a l y s i s as the following quotation (1) from G.-M. Schwab i l l u s t r a t e s .


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" I t i s a very wide ranging undertaking to t a l k on Ostwald's work on c a t a l y s i s . I t i s s i m i l a r to that which would be involved i n t a l k i n g on Newton's contributions to mechanics or Planck's to quantum theory." I doubt that many French, English, Russian or American workers would write so strongly. Persona l l y , I would put the influence of Sabatier who d i d not get the Nobel Prize u n t i l three years a f t e r Ostwald; I p a t i e f f who never got i t , and perhaps Haber and Mittasch as great or greater. However, i n the years a f t e r Ostwald, h i s former students and collaborators dominated c a t a l y s i s i n Germany. We can mention Bodenstein who put the study of the k i n e t i c s of heterogeneous c a t a l y s i s e s s e n t i a l l y i n i t s modern state. The Ostwald school made l i t t l e contribution to mechanism, but i t adhered to a view s u r p r i s i n g l y close to that of Faraday. The famous paper of Bodenstein and Fink of 1907 interpreted the k i n e t i c s o f the oxidation of s u l f u r dioxide on platinum i n terms of the d i f f u s i o n of s u l f u r dioxide or oxygen through a polymolecular layer o f adsorbed material. In extreme cases, accord with the observed i n h i b i t i o n by s u l f u r t r i oxide would have required adsorbed layers so t h i c k that they could have been pared with a razor. Langmuir's work put a f i n a l quietus to such ideas, but independently support f o r chemical theories of c a t a l y s i s came from such workers as I p a t i e f f and Sabatier. The l a t t e r said i n an a r t i c l e written at the end of h i s career (10): "Like my i l l u s t r i o u s master, M a r c e l l i n Berthelot, I always assumed that the fundamental cause of a l l types of c a t a l y s i s i s the formation of a temporary and very rapi d combination (he meant a chemical combination) of one of the reactants with a body c a l l e d the c a t a l y s t . . . . This theory has been much discussed. Other theories more or less complex and based on modern concepts of the atom, have been proposed. I have tenaciously held to my theory of a temporary combination. I t has guided my work both i n hydrogénations and i n dehydrations . "



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He had won the b a t t l e completely, but he was s t i l l rather defensive. By 1934, the only remaining trace of c a t a l y t i c force lay i n the low temperature c a t a l y s i s of the interconversion of the newly discovered ortho- and parahydrogen by paramagnetic surface s i t e s . Starting about 1900, Sabatier (10) and I p a t i e f f opened up the area of organic heterogeneous c a t a l ysis. The impact of Sabatier*s work was more immediate. Anyone, i n a day or two could set up the apparatus needed to duplicate Sabatier's discovery of the hydrogénation of olefins and benzene. Further, before Sabatier, the conversion of an alkene to an alkane was an operation of such d i f f i c u l t y and of such low y i e l d that i t was r a r e l y c a r r i e d out. Sabatier's discovery created something of a sensation. Furthermore, i t was r a p i d l y put to hydrogenating vegetable o i l s to make margarine. As an a r t i l l e r y o f f i c e r , I p a t i e f f started with autoclaves and high pressures. His work was not so r e a d i l y applied i n the usual laboratory. In the long run, however, I p a t i e f f s work was as influe n t i a l as Sabatier ' s and i t was more important i n technological applications of c a t a l y s i s to the modern industries of petroleum r e f i n i n g and the production of petroleum-based chemicals. Further, as w i l l have been noticed, c a t a l y s t s before I p a t i e f f were l a r g e l y Group VIII metals. He introduced oxides l i k e alumina into the c a t a l y t i c repertory. Overall, the work of Sabatier and I p a t i e f f l e d to the development of organic heterogeneous c a t a l y s i s , an area which had hardly existed i n the nineteenth century and which was to provide a powerful stimulus to heterogeneous c a t a l y s i s both academically, and industrially. The work of Haber and Mittasch during the f i r s t decade of the twentieth century i n developing the synthesis of ammonia by the hydrogénation of n i t r o gen was of major importance although more l i m i t e d i n scope. The i n d u s t r i a l a p p l i c a t i o n of heterogeneous c a t a l y s i s was further extended by the development of the commercial hydrogénation of carbon monoxide to methanol by the Badische A n i l i n - und Soda-fabrik. Commercial production started at Merseburg i n 1923 and the plant was producing 10-20 tons of methanol per day at the end of that year (11). The c a t a l y s t was not a Group VIII metal (we now know that they could have used palladium) but ZnO«Cr203. F i n a l l y , I should note that the e a r l y t h i r t i e s saw the beginnings of d e t a i l e d mechanistic proposals



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based on the intermediate compound theory but i n advance of the rather vague ideas of I p a t i e f f and Sabatier. The f i r s t two mechanistic proposals i n the modern sense were the Bonhoeffer-Farkas (12) and the Horiuti-Polanyi (13) mechanisms. In the Bonhoeffer-Farkas mechanism (1931), the ortho- parahydrogen conversion at high temperatures was assumed to proceed v i a d i s s o c i a t i v e adsorption o f hydrogen followed by associative desorption and the mechanism could be immediately extended to H 2 + E>2 —^ 2HD. The Horiuti-Polanyi mechanism (1934) f o r the hydrogénation o f ethylene could also be r e a d i l y extended t o other hydrogénation reactions. Both mechanisms are s t i l l i n use. We have now reached into the period i n which American work i n c a t a l y s i s had started and we have mentioned the European work o f two s c i e n t i s t s whose work continued i n the United States, V.N. I p a t i e f f and A. Farkas. I n d u s t r i a l applications of heterogeneous c a t a l y s i s were well underway i n the chemical industry: The contact process f o r s u l f u r i c acid, the Haber process f o r the synthesis of ammonia, the BASF process f o r the synthesis of methanol, the c a t a l y t i c hydrogénation of vegetable o i l s , and the c a t a l y t i c water-gas s h i f t process f o r producing the hydrogen needed i n the preceding processes. The applications of heterogeneous c a t a l y s i s to the petroleum industry had hardly begun. That was a development which was l a r g e l y to occur i n the United States. Acknowl edgment This a r t i c l e was written while the author was enjoying the h o s p i t a l i t y of Prof. J . Fraissard and the Laboratoire de Chimie des Surfaces of the Université Pierre et Marie Curie, Paris. L i t e r a t u r e Cited 1.

The a r t i c l e s on W. Ostwald by G.-M. Schwab, Z. f ü r Elektrochem. (1953) 25, 878, and by W. Schirmer, Sitzungsber. Akad. Wiss. DDR, Math., Naturwiss. Tech. (1979) 33, (13N) were particularly helpful to the author and he wishes to thank Professors Schwab and Schirmer for providing him with copies of t h e i r papers. Among other secondary sources, the work on Berzelius by J.E. Jorpes ("Jac. Berzelius, His L i f e and Work," Uppsala, 1966) and the excel–


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2. 3. 4.


5. 6. 7. 8. 9. 10. 11. 12. 13.

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lent a r t i c l e s by W.D. Mogerman i n the Inco Reporter for 1965 should receive particular mention. Stohmann, Z. B i o l . (1894), 31, 364. Ostwald, W., Z . physik. Chem. (1894) 15, 705. Schwab, G.-M., "Catalysis", translated by Taylor, H . S . , and Spence, R., van Nostrand, New York, NY, (1937). C o l l i n s , P . , Educ. Chem., (1977) 14, 14. Jorpes, J . E . "Jac. B e r z e l i u s , His L i f e and Work", Uppsala, 1966, p. 112. "Power i n Jorpes has been changed to "force". de l a Rive, Compt. rend. (1838) 7, 1061. Faraday, Μ., P h i l . Trans. Roy. Soc. (1834) 124, 55. Mogerman, W.D., Inco Reporter, (1965) No. 5, July. Sabatier, P . , B u l l . Soc. Chim. France (1939) V6, 1261. This paper provides a fascinating account of how Sabatier came to discover hydrogenation. Lormand, C., Ind. Eng. Chem. (1925) 17, 430. Farkas, Α . , Ζ. physik. Chem. (1931), B14, 371. Horiuti, J., and Polanyi, Μ., Trans. Faraday Soc. (1934) 30, 1164.

Received November 17, 1982


Heterogeneous Catalysis Before 1934

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