ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
CHEMICAL RATE PROCESSES
Heterogeneous Catalysis M. BOUDART T h e James Forrestal Research Center, Princeton University, Princeton,
HE Mth volume of “Advances in Catalysis” (W9B)contains as usual valuable reviews. Especially worthy of attention are two chapters by Rhodin and Gulbransen mho describe the acconiplishments of the vacuum microbalance a t low and high temperatures, respectively. hnother 1953 collection of review papers, covering material presented a t a conference arranged by the Kational Research Council, is “Structure and Properties of Solid Surfaces” (38B). All aspects of the physics and chemistry of surfaces are treated in this book, including adsorption and catalysis. Still another worth-while review is that of Gwathmey ( 3 Q B )who discusses the use of macroscopic single crystals in surface research. The papers assembled for review were all published in 1953 and made available to the writer by March 1, 1954, in extenso. I n spite of an effort to include all contributions that have advanced our basic knowledge in chemisorption and catalysis during 1953, some omissions are unavoidable-for instance, those caused by delay in arrival of certain foreign journals. Chemisorption and Catalysis en Clean Metal Surfaces.
Classical and new techniques are gathering a rich booty of information a t an increasingly fast pace. Evaporated films are used extensively. To chemisorb or not to chemisorb is one of the interesting questions in this field. Thus, Trapnell (105B) demonstrates that chemisorption may or may not take place between -183” and 0’ C. depending both on the nature of the metal and that of the gaseous molecule. The gases tried are: nitrogen, hydrogen, carbon monoxide, ethylene, acetylene, and oxygen; the metals are: tungsten, tantalum, molybdenum, titanium, zirconium, iron, calcium, barium, nickel, palladium, rhodium, platinum, copper, aluminum, potassium, zinc, cadmium, indium, tin, lead, silver, and gold. Sitrogen is chemisorbed only by the first eight metals in this series. Oxygen is taken up by all of them except gold. Trapnell’s data have many far-reaching implications as to the specificity and activated nature of chemisorption. The inability of copper films to chemisorb hydrogen up to room temperature is independently confirmed by Xington and Holmes (62B). These authors also try to find out whether oxygen will act as a promoter in this case. Their results were negative, but since the quantity of oxygen on the copper surface is left unspecified, this problem must not be considered as solved. When chemisorption does actually take place on a film, the next question is: a t what rate? Porter and Tompkins (8SB) present an answer for hydrogen on iron a t liquid air temperature. It is a striking answer, because they find a logarithmic rate law and provide an explanation for it: the rate falls exponentially, because it is controlled by activated surface diffusion of hydrogen atoms to sites characterized by a uniform distribution of absorption heats. With carbon monoxide the result is similar on an iron film, but the diffusing species is the undissociated molecule. Porter and Tompkins also confirm that nitrogen is chemisorbed as a molecule a t log- temperature on a clean iron film but as atoms at room temperature. Heat of chemisorption of hydrogen and ammonia a t 21’ C. on iron, tungsten, and nickel films are measured calorimetrically by Wahba and Kemball (109B). The essential difference be884
N. J.
tween iron or tungsten and nickel is that the heat for ammonia is higher a t all values of coverage on iron and tungsten and is sufficient to dissociate the molecule into N H or even N radicals with evolution of hydrogen. I n all cases, there was a considerable fall in absorption heats with coverage. I n a theoretical analysis mainly concerned with modification of metal work function by absorbed layers, Gomer ( S 6 B ) shows that this fall in adsorption heat cannot be due solely to electrostatic double layer effects. Gomer’s model is that of a classical array of dipoles on a metal surface. Measurements of Volta potentials provide additional information on the existence and polarity of adsorbed layers. Thus, Giner and Lange (34B) find chemisorption of oxygen on gold a t 300’ C. Other contact potential differences are reported by Weissler and Wilson (110B) and Anderson and Blexander ( B ) . Interesting properties of water on mercury are reported by Karpachev et al. (47B). By surface tension, they first determine adsorption isotherms; these are logarithmic isotherms. The work function of mercury is then measured as modified by watei by taking the characteristics of a diode. The cathode is an electrically heated platinum filament; the anode is the liquid mercury surface. Water increases the work function of mercury by 1 volt, which cannot be explained by dipole orientation alone but must involve some kind of chemisorption bond between mercury and water. Suhrmann and Schulz (101B)show that nitrous oxide and carbon monoxide increase the resistance of nickel films while water, benzene, triphenylmethane, and xylene decrease it. This is related to the electron accepting ability of the first two molecules as contrasted to the electron donating capacity of the latter. Metallic films as catalysts are studied by Kemball (51B). He generalizes his earlier results on nickel, the catalyzed reaction being the exchange between methane and deuterium. Films of rhodium, platinum, palladium, and tungsten are used. Iron has no activity u p to 420” C. B complete analysis of the data appears difficult, although it has been attempted by Laidlcr et al. ( 7 l B ) . A simple fact emerges clearly; the energies of activation for the exchanges are much lower on tungsten than on the other metals, presumably because of the low activation energy for the adsorption of methane on tungaten. But the frequency factor on tungsten is also low and in this connection, Kemball makes a very interesting suggestion using the observation that entropies and heats of adsorption are often related in a linear manner. If this is granted, Kemball shows that a strongly adsorbed inhibitor will increase both the activation energy and the frequency factor of a catalytic reaction in the manner found by so many workers. The mechanism of the para-hydrogen conversion on clean tungsten surfaces is still the object of controversies. Thus, an attempt by Laidler (65B) to decide the mechanism by quantitative arguments is criticized by Sandler (93B) on the grounds that tungsten films and a clean tungsten filament might well behave differently. The field emission microscope is providing new information on chemisorption (35B, 63B), surface mobility or diffusion (6B, W B ) , and even, a t least qualitatively, surface reactions (54B).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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FUNDAMENTALS REVIEW ~
~~~~
In all observations, the marked differences of various crystallographic regions (geometrical factor) show up clearly. Another new technique for observing kinetics of chemisorption ii, that of the flashed filament described by Becker and Hartman ( 6 B ) , using an improved ionization gage, measuring pressures between 10-10 and 10-8 mm. of mercury. These authors calculate the sticking probability, S , of a nitrogen molecule on a clean tungsten ribbon as a function of coverage. They find S = 0.5 up to 6 = 1 (corresponding to 1 nitrogen atom for 4 tungsten atoms); then S decreases exponentially, reaching a value a t a = 2. of 4 x The kinetics of Chemisorption on Catalyst Surfaces. rapid gas uptake by porous catalysts a t constant volume and low pressures in the object of theoretical and experimental studies by Winfield et al. (102B, 117B). A criterion is given that permits to decide between various rate controlling mechanisms. It is gas flow through the depth of the bed if n = 0, probably surface migration if n < 1, gas flow into the pores of the granules if n = 1 and certainly chemisorption if n > 1. Here n is defined by r = S" where r is the rate and S is the available surface area. The possibility of surface diffusion to and from active centers or regions being the rate determining step of the catalytic reaction is considered by Patterson (81B). Surface diffusion extends the apparent active area, and the apparent activation energy of the reaction may decrease a t sufficiently high temperatures when the adsorption ceases to be rate determining step. Copper powders are investigated by Dell, Stone, and Tiley (2SB). They show that decomposition of nitrous oxide a t 20" C., adsorption of carbon monoxide a t -78' and 20' C., and one clearly defined phase of the uptake of oxygen a t 20' C. correspond numerically t o the same area of the copper powder (20 to 25% of a monolayer). They further compare a copper powder reduced in hydrogen a t 320' C. The higher temperature reduces the surface area by 35% and the activity for carbon monoxide adsorption and nitrous oxide decomposition by 60%. This would indicate a priori heterogeneity of the copper powder if it could be shown that the higher temperature reduction did not change the chemical composition of the surface. Heats of adsorption of hydrogen on reduced nickel catalysts are obtained from adsorption isotherms taken between 195" and 673' K. and 0.1 and 100 mm. of mercury by Schuit and De Boer (96B). Three samples are studied-one obtained by reduction of an imperfectly crystallized nickel-montmorillonite, one coprecipitate, and one impregnation catalyst. All results can be rep14.4 ah, where &d is the resented by the equation &a = 25.1 differential heat a t adsorption at 273'K. in kcal. per mole. Among the implications of this remarkable result, especially when compared t o other data on the literature, one may single out the following: heats of adsorption are generally Iower on reduced materials than on films, and support or average particle size seems unimportant. A linear variation of adsorption heats with coverage was also reported in 1953 for a doubly promoted iron catalyst in ammonia synthesis. Temkin et al. (9OB) have measured adsorption isotherms of nitrogen on this catalyst a t 300°, 350°, and 400' C. and in a very large pressure range (six orders of magnitude). This was made possible by a very elegant method based on the fact that the equilibrium between adsorbed nitrogen and ammonia and hydrogen in the gas phase is readily established. The corresponding equilibrium constant can then be combined with that of the gas phase homogeneous reaction in order to obtain the adsorption isotherms. These are of the logarithmic type. The heat of nitrogen adsorption falls linearly from 60 to 17.5 kcal. per mole. Another adsorption study on iron surfaces is that of Podgurski and Emmett (89B). On a single promoter catalyst, these authors show hydrogen chemisorption a t -195' C. is very much like that taking place on metallic films. Another important aspect of their work is the demonstration that high temperature chemisorption of hydrogen (type B) is very sensitive to pressure and
-
May 1954
increases with alumina content of the catalyst. A study of molybdenum reduced powders by Healey, Chessick, and Zettlemoyer (/OB)shows that surface heterogeneity for physical adsorption can be altered by sintering while heterogeneity for chemisorption of oxygen a t low temperature remains.
Figure 1.
Magnetite
Sin le Crystal Before (Left) and After (Ris!t) Reduction Reprinted from (JJSB)
In connection with an adsorption study of nitrogen on an iron catalyst, Kwan (61B) points out that the exponential rate law and the corresponding logarithmic isotherm are not universally applicable. He quotes a number of data, including his own, where a power law and the corresponding Freundlich isotherni give a better fit. Other adsorption rate data that are interpreted by means of an exponential distribution of activation energies are those of Keier (49B) for acetylene on nickel and of Man'ko et al. (7OB) for hydrogen and oxygen on a variety of carbon eurfaces. From a purely formal point of view, these laws correspond to a change of adsorption potential with coverage (25B),but the reasons underlying this change are still the object of many speculations (19B). The A r t of Catalyst Preparation. I n an effort to find the requirements of a good alumina adsorbent or catalyst, Prettre et al. (84B) combine thermogravimetry, x-ray scattering (DebyeScherrer and low angle), electron diffraction, B.E.T. measurements, and pore volume determinations on samples prepared by heat treatment of hydrargillite, bohmitc, and alumina gels. This kind of justification post facto is typical of many cases of catalyst preparation. Thus, a Badische Anilin- & Soda-Fabrik 1914 patent described a way t o obtain active hydrogenation catalysts. Forty years later, Langenbeck and Giller (6'7B) find out why-magnesium and nickel formates form solid solutions as shown by x-rays. The nickel on magnesia catalysts resulting from the reduction of the mixed salts are in some instances superior to Raney nickel. Pseudomorphism (memory effect) is another important factor in catalyst preparation. Thus, Westrik and Zwietering (115B) show that a single crystal of magnetite (octahedral faces [111] planes) does not change its shape or its dimensions after reduction (Figure 1). This observation was confirmed by x-ray studies and carbon monoxide adsorption data on reduced iron powders. The carbon monoxide adsorption data indicate that iron powders reduced from magnetite predominantly expose [111] planes. The importance of the starting
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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT material is also illustrated by a kinetic study of the dehydrogenation of isopropyl alcohol on zinc oxide prepared in various ways (118B). All samples mere overwhelmingly dehydrogenating but the activation energies and frequency factors change from sample to sample. This effect is also shown by a study of benzene hydrogenation on nickel and cobalt powders (68B). The temperature of pretreatment also affects catalyst activity. Shekhter et al. (97B) investigate the activity for decomposition of methanol of a zinc oxide catalyst obtained from a carbonate heated a t increasingly high temperatures. They find activation energies (from 28 t o 11 kcal. per mole) and frequency fact,ors per unit surface (varying over five orders of magnitude) obeying the familiar compensation law already mentioned in connection with Kemball's work. A similar story for the decomposition of formic acid on silver and copper powders is presented by Rienacker and Bremer (85B). Here also the activation energy and frequency factor change in a complicated manner with sintering temperature but the compensation law is formally applicable. Heinle and Krogmann ( 4 l B ) report essentially the same thing for the same reaction on nickel powders preheated in argon between 200' and 1000" C. The effect of pressures of pretreatment up to 20,000 atmospheres on pore structure, specific activity, and selectivity of a number of catalysts for a variety of rcactions is st'udied by Russian workers ( S I B , SdB, 10023). High pressures seem to have a beneficial effect on catalyst stability both mechanical and chemical. The effect of catalyst support is studied by Johnson and Ries (44B). Promoter action is still another aspect of catalyst preparation. Atwood and Arnold ( S B ) tried, without success, 33 elements as possible promoters of an iron oxide-chromium oxide catalyst. Freidlin et al. (SOB)emphasize the role of hydrogen as a required constituent of skeleton met,al catalysts. Sccording to Roginskii et al. (LVB,5 8 s ) oxygen is a promoter for the hydrogen-oxygen reaction on plat,inum and palladium foils. Thus, plat,inum evacuated at 800" C. is inactive. Activation consists in a pretreatment in oxygen during 15 minutes at increasing temperatures between 300' and 800' C. While oxygen sorption increase monotonically with temperature to reach more than ten monolayers at 800" C., the activity passes through a maximum corresponding to a pretreatment at 550' C. Meanwhile, the activation energy for the hydrogen-oxygen reaction stays practically constant; the activation is due to a 1000-fold increase of the frequency factor. It is emphasized that catalytic corrosion-i.e., the change in surface structure by the reaction itself-produces the same result but it is not due t o the increase in surface roughness but to the specific act,ion of oxygen. Cat,alytic corrosion is the object of further studies (89B,98B); its particularities are examined by electron microscopy. The oxygen effect is also observed by Joncich and Hackerman (45B) who observe a peculiar periodic change of reaction rat,e between hydrogen and oxygen on platinum and rhodium anodes (but not rhodium and iridium): they ascribed this phenomenon t o a periodic build-up and decomposition of an oxide film. Electronic Effect in M e t a l and Alloys. The effect of electronic configuration of a metal or an alloy on its surface properties continues t o attract attention. Burgers and Brabers (11B, 1SB ) use silver-cadmium, palladium-gold, bismuth-tin, bismuthlead, and bismuth-selenium alloys in order to elucidate the influence of electronic structure of an electrode on the rate of an electrochemical reaction taking place a t its surface. Boreskov et al. ( 9 B ) study the hydrogen-oxygen reaction on nickel, palladium, and platinum by a new technique worthy of attention. The activation energies are, respectively, 16, 11.2, and 11 kcal. per mole. Boreskov et al. (10B) also investigate the activity of chromium, rhodium, lead, silver, tungsten, platinum, gold, and platinumgold alloys for the oxidation of sulfur dioxide. Only platinum, gold, and their alloys are stable catalysts. It is found that 5% gold in platinum increases the activation energy from 23 t o 31 kcal. per mole and deweases the activity of platinum 100-fold.
1888
Further addition of gold up to 100% does not bring about any new change in activity. Benzene hydrogenation on nickel, cobalt, nickel-cobalt, nickel-iron, and nickel-copper powders is investigated by Rienacker and Unger (86B). The result,s are not clear. Cremer and Kerber ($le)measure para-hydrogen conversion and hydrogen overvoltage on nickel, cobalt, copper, copper-zinc, and nickel-iron-molybdenum and observe the parallelism between both phenomena. Chemisorption and Catalysis on Semiconducting Oxides.
The idea that free charge carriers in N- or P-type semiconductors have something to do with the properties of oxides in chemisorption and catalysis receives much attention theoretically and experimentally. On the theoretical side, Vol'kenshtein (106B, 107B) and Bontch-Bruevich ( 8 B ) explore the quantum mechanics of chemisorption on defective ionic crystals. If conduction electrons are important in the adsorption process, a number of well-known consequences (act,ivationenergy for adsorption, variation of adsorption heat with coverage, the compensation law) readily follow. Theoretically, a larger heat of adsorption is obtained if an adsorbed atom traps a conduction electron. These authors do not consider adsorption of molecules. Engell and Hauffe (26B) and Weisz ( I l 1 B ) push the analysis one step further. Recognizing the possibility of formation of a space charge layer a t the free surface of say, an N-type semiconductor following this trapping of conduction electrons by an electronegative adsorbate, they assume that the rate of arrival of electrons a t the surface will be the rate determining step in the adsorption process. Space charge layers as a result of surface states have been well established in the case of germanium semiconductors (12B). Morrison (Y6B) further shows that' as a result of this layer, an K-type germanium sample may get a P-type surface. The opposite effect-a P sample acquiring an K-type surface-seems t o have been first observed by Weisz et al. (112B) with a chromiaalumina catalyst as a result of cyclohexane adsorption and dehydrogenation. However, Zuckler (11QB) apparently failed t o observe the effect of surface states on selenium and cuprous oxide samples. Semiconducting characterhics of oxides are related to their ability to decompose nitrous oxide by Dell, Stone, and Tiley (R4B) and Engell and Hauffe ( 2 7 B ) . The first authors show, on the basis of t'heir own work and of lit'erature data, that P-type oxides tend to be good cat,alysts for that reaction whereas N-type oxides are poor catalysts. The latter show that small amounts of lithium in nickel oxide, that are known to increase the P-type conductivity of the latter, also accelerate the decomposition of nitrous oxide. I n a more detailed investigation, Parravano (79B) studies the catalytic oxidation of carbon monoxide on nickel oxide with and without foreign ions. This work shows that a t least a t high temperatures, the introduction of monovalent cations increases the activation energy whereas cations with a valency higher than two decrease the activation energy. Since carbon monoxide behaves as an electron donor on P-type oxides, the effect of impurities confirms the conclusion reached on kinetic grounds that the interaction of carbon monoxide with the oxide surface is the rate determining step in the high temperatures interval of the reaction. Similar generalizations do not appear to hold true for hydrogenation reactions as measured by the hydrogen-deuterium exchange (17B). Thus, Molinari and Parravano (?'@), using zinc oxide with or without impurities do not find a clear-cut effect of impurities but conclude that the activation of the catalyst for the exchange probably involves removal of adsorbed oxygen. The same picture emerges from exchange data on chromia and ohromipalumina catalysts. Voltz and Weller (108B) show that catalytic activity is greater if the catalyst surface is reduced although the conductivity of this P-type material is higher in an oxidizing atmosphere. Water poisoning experiments confirm the Impression that here special surface sites are required which
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vo1. 46, No. 5
FUNDAMENTALS REVIEW are not present in an oxidizing atmosphere or prior to catalyst reduction. A characteristic of semiconducting oxides is the mobility of their lattice oxygen. Ryerson and Honig (9ZB) propose a new method for investigating lattice defects related to departure from stoichiometry; it is the adsorption of nitrogen dioxidenitrogen tetroxide. They have applied this method to titanium dioxide and checked it by magnetic data. Another method is the exchange of labeled oxygen. Cameron, Farkas, and Lita (16B) have measured the rate of isotopic exchange of 0 1 8 between oxygen, water, and oxygen-water in the gas phase and vanadium pentoxide catalysts on the other hand. The exchange between oxygen and vanadium-pentoxide is controlled by the surface process between 400' and 550' C. Diffusion is fast, presumably because of lattice defects. The exchange with water is considerably more rapid. In order to elucidate the mechanism of carbon monoxide oxidation on manganese dioxide, Karpacheva and Rozen (48B)measure the rate of 0 1 8 exchange between this catalyst and oxygen, carbon dioxide, and carbon monoxide oxygen reacting mixtures. They observe a much faster rate of exchange during the reaction than with oxygen and carbon monoxide separately and conclude that an oxidation-reduction mechanism can explain these data. The same conclusion is reached by these authors (91B) after showing that 0 1 8 exchange of magnetite or chromic oxide with water is slow a t 400" C. but strongly accelerated if hydrogen is added to water. Finally chemisorption data of carbon dioxide on several oxide catalysts with a spinel structure ( CuFeeOa, CuCrp04, ZnCrz04, and Fe304)are reported by Kwan et al. (6ZB, 6SB). Silica Alumina Catalysts. Isotopic exchange between H2018 and a silica-alumina catalyst a t cracking conditions is measured by Oblad, Hindin, and Mills (77B). The rapidity of exchange supports their ideas on the dynamic mobile structure of a silica-alumina surface and the comparison of this surface to a fluid acid. I n particular, according to their views, the surface activity depends on the ability of the aluminum ion to undergo a reversible change from a coordination number of 6 to 4. A different opinion is held by Miesserov (72B, 73B) who pictures the active center for the cracking process as follows:
+
[
(A1 Si) -E7Al. -O\
OH
1-
H+
and supports his thesis by poisoning experiments with pyridine. The rapid fouling of a cracking catalyst by carbon deposition was observed by Blanding ( 6 B ) who shows that after one minute of operation, the activity is only 0.01 of its initial value. On the other hand, Robinovich et al. (87B)study the rate of cracking of kerosine and gasoline on various soot samples and a silica-alumina catalyst. They report that the specific activity does not depend on the origin of the soot and, in particular, is the same on soot and on carbon deposited as a result of the cracking reaction. Furthermore, activities on soot and on silica-alumina are of the same order of magnitude. Schmerling (95B) summarizes the accomplishments of the carbonium ion mechanism in acid-base hydrocarbon catalysis. Studies of Reaction Mechanisms. The kinetic method is still a popular one. I n this connection, Thon and Taylor (IOSB) warn against the indiscriminate use of initial rates in the determination of rate laws in static systems. The meaning of such rate laws may be in doubt because the catalyst has had no time t o adapt itself t o the reacting mixture. The influence of interactions between adsorbed molecules on the absolute rate of surface reactions is analyzed by Laidler (64B). Interaction terms may cancel out in special cases. The use of the kinetic method in determining the slow step of a surface process is reviewed by Hougen (43s)and applied by Natta et al. (76B) to the high pressure synthesis of methanol on a zinc oxide-chromium oxide catalyst between 150 and 300 atmospheres from 200" to 400' C. May 1954
The rate determining step is the surface reaction between one adsorbed molecule of carbon monoxide and two adsorbed molecules of hydrogen. A similar kinetic analysis is performed by Corrigan et al. ($OB)for the cracking of cumene on silica-alumina catalysts. I n this case, a single-site surface reaction controlling step suggests itself. The ammonia synthesis on a doubly promoted iron catalyst is studied between 100 and 300 atmospheres from 350' to 500' C. by Adams and Comings ( I B ) . The kinetic data do not fit the Temkin-Pyahev equation. Passing cyclohexene on a vanadium oxide catalyst in the presence of hydrogen between 250' and 450" C., Komarewsky and Erikson (66B) observe no hydrogen disproportionation. This is contrasted with the behavior of metal catalysts in this respect and suggests that edgewise adsorption of cyclohexene takes place on the oxide but flat adsorption on the metal. Further considerations on the multiplet theory have been presented by Balandin (4B). According t o d'Or and Orzechowski (78B) phenol hydrogenation on a nickel-ceria catalyst involves phenol molecules striking hydrogen atoms adsorbed on the fraction of the nickel surface unpoisoned by phenol. The catalytic hydrogenation of aniline was studied by Debus and Jungers (ZZB). Hydrogenating or dehydrogenating the various reaction intermediates and determining their relative adsorption coefficients, they were able to explain the mechanism of the over-all process. A new method has been proposed by Horiuti (48B) to determine the slow step of a complex process. It depends on the measurement of the stoichiometric number of this slow step. Thus, for a chain reaction the stoichiometric number of the chain initiating step is the,reciprocal of the chain length. For the hydrogen-iodine reaction, it is equal to 1.3 =!= 0.2 in agreement with the bimolecular mechanism of Bodenstein. The method is applied (28B)to the ammonia synthesis on an iron catalyst below atmospheric pressure. Kinetic data of both the synthesis and decomposition in the neighborhood of equilibrium and the rate of nitrogen isotope exchange between N16H3 and NZa t equilibrium permit the calculate ion of the stoichiometric number. It is found to be equal to 2. This seems t o rule out nitrogen chemisorption as a rate determining step The mechanism of olefin hydrogenation was clarified by Bond and Turkevich ( 7 B ) by means of a study of the products of t h e deuteration of propylene on a platinum catalyst. The following steps are proposed: D2+2D
I
C3H6 D
CH3-CH-CH,
I
CHI-CH-CH~
I
I
CHs-CH-CHzD
1
1 +
I
CHs-CH-CHzD
I
+
CH2--CH-CH2D
I
I
I
A repetition of these steps accounts not only for the distribution of observed products but also for the changes in this distribution under varying conditions. An analogous mechanism is presented by Wilson et al. (116B) following a similar study of the deuteration of ethylene, cis-2-butene and isobutylene on a nickel catalyst. Depending on the system, hydrogenation may take place in a relatively straightforward manner. Thus, w:&h isobutylene a t - 78" C. the product is mostly isobutane-1,2-c12, suggesting addition of two absorbed deuterium atoms to the double bond of a physically adsorbed olefin molecule. Kinetic analyses of olefin deuteration were also made by Keii (50B) and Laidler et al. (66B). The oxidation of ethylene on silver is unique in the sense t h a t on this catalyst, ethylene oxide is oxidized into carbon dioxide and water at a slower rate than that a t which it is produced.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT This situation, according to Todes and Andrianova (104B) does not obtain on other catalysts. These authors think that carbon dioxide is produced solely from ethylene oxide. Roginskii and Margolis (88B) do not subscribe to this view. Using radioactive carbon, they present evidence t o show that carbon dioxide comes not only from ethylene oxide but also from some other intermediate product, possibly of the peroxide type. I n order t o prove that the slow step in the CO H20 = Hz COZ reaction on Fe30ais the reaction between carbon monoxide and adsorbed oxygen-a conclusion arrived a t by kinetic reasoning-Kul’kova et d.(59B) measure the rates of the following COO = CO Cool* and of its reverse. reaction: CO1* From the rate constants of the isotopic exchange reactions, at 300°, 350’, and 400’ C. they calculate the rate constant of the waicr gas shift. Calculated and experimental values are in satisfactory agreement. Mechanism of t h e Hydrocarbon Synthesis. Evidence against the carbide theory is being accumulated from adsorption data by Sistri et al. (94B) on a cobalt catalyst and from x-ray and electron diffraction studies by RIcCartney et a2. (69B)on iron catalysts. .4 detailed study of the products of the hydrocarbon synthesis on iron catalysts ( I @ , IbB,ggB, I l 4 B ) provides further arguments in favor of Beeck’s hydropolymcrization theory. According t o Weitkamp and Frye ( I l S B ) chains initiated by a CH2 or CH3 radical are enlarged by the one b y one addition and reduction of carbon monoxide molecules and terminated with production mainly of alcohols, aldehydes, and/or olefins. Competition between growth and termination accounts for the exponential decrease in yields of successive carbon number fractions. Distribution of straight and branched chain isomers is dztermined by the probability that a carbon atom be added to the end of the chain rather than t o the carbon adjacent to the end. Further evidence in favor of such a mechanism is presented by Kummer and Emmett (GOB). Using radioactive alcohols they show that primary alcohols can act as starting nuclei in building up higher hydrocarbons. Secondary alcohols are much less capable of doing so. Tertiary alcohols do not have such an ability. Furthermore, for instance when radioactive n-propyl alcohol is used, radioactive n-butane is produced (not isobutane). Thus, complexes resembling adsorbed alcohols are formed from carbon monoxide and hydrogen and act as intermediates in the synthesis. The results of Gibson (3SB) are also consistent with the conception that alcohols are the true primary products of the synthesis. Studying the thermal reactions of the higher iron carbides, Cohn and Hofer (28B)submit that the stabilizing effect of copper on hexagonal close-packed iron carbide is only apparent; copper would facilitate reduction and carburization of the iron catalyst, the stability of the carbide increasing with the extent of carburization. Special Effects. Justi and Vieth (466’) have discovered a n external magnetocatalytic effecc. They show that even weak magnetic fields accelerate the rate of p-hydrogen conversion in nickel capillaries. The internal magnetocatalytic or Hedvall effect was observed by Parravano (80B) around the Curie temperature of strontium lanthanum manganites during the oxidation of cai ban monoxide. Finally, Krasil’shchikov and Antonova (56B) report a n effect of an electric field on the rate of the hydrogen-oxygen reaction on silver, palladium, and platinum.
+
+
Becker, J. A., and Hartman, C. D., J . Phys. Chem., 57, 165 (1953). Blanding, F. H., IND.ENG.CHEM.,45, 1186 (1953). Bond, G. C., and Turkevich, J., Trans. Faraday SOC.,49, 281 (1953). Bontch-Bruevich, V. L., Zhur. Fiz. K h i m . , 27,602,960 (1953). Boreskov, G. K., Slin’ko, M. G., and Filippova, A. G., Doklady Alcad. N a u k S.S.S.R., 92, 353 (1953). Boreskov, G. K., Slin’ko, M. G., and Volkova, E. I., Ibid.. 92, 109 (1953). Brabers, 11. J., and Burgers, W. G., Proc. Koninkl. Ned. Akad. Wetenschap., B56, 439 (1953). Brattain, W. H., and Bardeen, J., Bell System Tech. J . , 32, 1 (1953). Burgers. W.G.: and Brabers, >I. J., Proc. Koninkl. Ned. A k a d . Wetenschap., B56, 1 , 12 (1953). Cady, W. E., Launer, P. J., and Weitkamp, A. W., IND.
+
+
Literature Cited Adams, R. 31.,and Comings, E. W., Chem. Eng. Progr., 49, 359 (1953). Anderson, 3. R., and Alexander, A. E., Australian J . Chem., 6, 109 (1953). Atwood, II., Stone, F. S., and Tiley. P. F., Trans. Faraday Soc., 49, 195 (1953). Ibid., p. 201. Eley, D. D., Trans. Faraday Soc., 49, 643 (1953). Engell, H. J., and Hauffe, IC, 2. Elektrochem., 57, 782, 773 I
(1 9 5 3 . \----,
Ibid., p. 776. Enomoto, S,, and Horiuti, J., J . Research Inst. Catalysis,
(33B) (34B) (S5B)
(36B) (37B)
Hokkaido Univ., 2, 87 (1953). Frankenburg, W.G., Komarewski, V. I., and Rideal, E. K., “Advances in Catalysis and Related Subjects,” Vol. 5, New York. Academic Press. 1953. Freidlin, L. Kh.. and Rudneva, K. G., Doklady A k a d . N a u k S.S.S.R., 91, 539, 1171, 1349 (1953). Freidlin, L. Kh., Vereshchagin, L. F., Neimark, I. E., and Numanov, I. U.. Izvest. Akad. N a u k S.S.S.R., Otaez. Khim. X a u k , 1953, 945. Freidlin. L. Kh.. Vereshchagin. L. F.. and Numanov.’ I. U.. Doklady A k a d . N a u k S.S.S.R., 88, 1011 (1953). Gibson, E. J., J . AppZ. Chem., 3, 375 (1953). Giner, J., and Lange, E., Naturwiss., 40, 506 (1953). Gomer, R., J . Chem. Phys., 21, 293 (1953). Ibid., p. 1869. Gomer.. R... and Hulm. J. K.. J . Am. Chem. SOC.. . 75.. 4114 (1953). Gomer, R., and Smith, C. S. (editors), “Structure and Properties of Solid Surfaces,” Chicago Univ. Press (1953). Gwathmey, A. T., Record Chem. Progr. (Kresge-Hooker Sci. Lab.), 14, 117 (1953). Healey, F. H., Chessick, J. J., and Zettlemoyer, A. C., J . Phys. Chem., 57, 178 (1953). HeinIe, K., and Krogmann, K., ‘~-aturwissenschaften,40, 528 (1953). Horiuti, J., Proc. J a p a n Acad., 29, No. 4 (1953); J . Research I n s t . Catalysis, Hokkaido Univ,, 3, No. 1 (1953). Hougen, 0. A., 2. Elektrochem., 57, 479 (1953). Johnson, AI. F. L., and Ries, H. E., Jr., J. Phys. Chem., 57, 865 (1953). Joncich, M. J., and Hackerman, N., Ibid., p. 674. Justi, E., and Vieth, G., 2. Naturforsch., 8a, 538 (1953). Karpachev, S. V., et al., Zhur. Fiz. Khim., 27, 1228, 1370 (1953). and Rosen, A. M., Ibid., 27, 146 (1953). Karpacheva, S. .M., Keier, N. P., Izvest. Akad. Nauk S.S.S.R., Otdel. K h i m N a u k , 1953, 48. Keii, T., J. Research Inst. Catalysis, Hokkaido Univ., 3, 36 (1953). Kemball, C., Proc. Roy. Soc. (London), A217, 376 (1953). Kington, G. L., and Holmes, J. M., T r a m Faraday Soc., 49, 417, 425 (1953). Kirchner, F., Z. Angew. Phys., 5 , 281 (1953). Klein, R., J . Chem. Phys., 21, 1177 (1953). Komarewsky, V. I., and Erikson, T. A., J . Am. Chem. Soc., 75, 4082 (1953). Krasil’shchikov, A. I., and Antonova, L. G., Dolclady A k a d . A‘auk S.S.S.R., 91, 291 (1953).
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FUNDAMENTALS REVIEW (57B) Krylov, 0. V., and Roginskii, S.Z., Ibid., 88, 293 (1953). (58B) Krylov, 0. V., Roginskii, S. Z., and Tret’yakov, I. I., Ibid., 92, 75 (1953). (59B) Kul’kova, N. V., Kuznets, 2. D., and Temkin, M. I., Ibid., 90, 1067 (1953). (60B) Kummer, J. T.. and Emmett, P. H., J . Am. Chem. SOC.,75. 5177 (1953). Kwan, T., J . Research I n s t . Catalysis, Hokkaido Univ., 3, 16 fl953). \ - - - -- , Kwan, T., and Fujita, Y., Ibid., 2, 110 (1953). Kwan, T., Kinuyama, T., and Fujita, Y . ,Ibid., 3, 28 (1953). Laidler, K. J., J . P h y s . Chem., 57, 318 (1953). Ibid., p. 320. Laidler, K. J., Wall, M. C., and Markham, M. C., J . Chem. Phys., 21, 949 (1953). Langenbeck, W., and Giller, A., 2. anorg u. allgem. Chem., 272, 64 (1953). Lihl, F., and Zemsch, P., 2. EEektrochem., 57, 58 (1953). RilcCartney, J. T., Hofer, L. J. E., Seligman, B., Lecky, J. A., Peebles, W.C., and Anderson, R. B., J. P h y s . Chem., 57, 730 (1953). hlan’ko, N. AI., and Levin, V. I., Izuest. A k a d . N a u k S.S.S.R., Otdel. Khim. N a u k , 1953, 409. Markham, iLI. C., Wall, M. C., and Laidler, K. J., J . P h y s . Chem., 57, 321 (1953). Miesserov, K. G., Doklady A k a d . N a u k S.S.S.R., 88, 503 (1953). Ibid., 91, 553 (1953). Molinari, E., and Parravano, G., J . Am. Chem. SOC.,75, 5233 (1953). Morrison, S. R., J . Phys. Chem., 57, 860 (1953). Natta, G., Pino, P., Marzanti, G., and Pasquon, I , Chimica e industria ( M i l a n ) , 35, 705 (1953). Oblad, A. G., Hindin, S. G., and Mills, G. A., J . Am. Chem. SOC.,75, 4096 (1953). Or, L. d’, and Orzechowski, A., Bull. SOC. chim. Belges, 62, 138 (1953). Parravano, G., J . Am. Chem., SOC.,75, 1448, 1452 (1953). Ibid., p. 1597. Patterson, D., T r a n s . Faraday SOC.,49, 802 (1953). Podgurski. H. H., and Emmett, P. H., J. P h y s . Chem., 57, 159 (1953). Porter, A. S., and Tompkins, F. C., Proc. Roy. SOC.(London), A217, 529, 544 (1953). Prettre, M., Imelick, B., Blanchin, L., and Petitjean, M., Angew. Chem., 65, 549 (1953). Rienacker, G., and Bremer, H., 2. anorg. u. allgem. chem., 272, 126 (1953). Rienacker, G., and Unger, S., Ibid., 274,47 (1953). Robinovich, E. Ya., Snegireva, T. D., and Tesner, P. A., Doklady Akad. N a u k S.S.S.R., 88, 95 (1953). Roginskii, S. Z., and Margolis, L. Ya., Ibid., 89, 515 (1953). Roginskii, S. Z., Tret’yakov, I. I., and Shekhter, A. B., Ibid., 91, 881, 1167 (1953).
(90B) Romanushkina, A. E., Kiperman, S. L., and Temkin, h l . I., Zhur. Fiz. Khim., 27, 1181 (1953). (91B) Rozen, A . , and Karpacheva, S., Doklady A k a d . NaukS.S.S.R,. 88, 507 (1953). (92B) Ryerson, L. H., and Honig, J. II.,J . Am. Chem. SOC.,75, 3917, 3920 (1953). (93B) Sandler, Y. L., J . Chem. P h y s , 21, 2243 (1953) (94B) Sastri, ill. V. C., and Srinivasan, S R., J . Am. Chem. SOC, 75, 2898 (1953). (95B) Schmerling, L., IND. ENG.CHEM.,45, 1447 (1953). (96B) Schuit, G. C. A., and De Boer, N. H., Rec. Trav. Chim., 72, 909 (1953). (97B) Shekhter, A. B., and Moshkovskii, Yu, Sh., Doklady A k a d . hTauk S.S.S.R.. 89. 1075 (1953). (98B) Shekhter, A. B.,’ and Tret’yako;, I. I., Izvest. A k a d . N a u k . S.S.S.R., Otdel. K h i m . N a u k , 1953,442. (99B) Steitz, A , , Jr., and Barnes, D. K., IND.ENG. CHEM..45, 353 (1953). (100B) Sterligov, 0. D., Goniksberg. M. G., Rubinshtein, A. M., and Kazanskii, B. A,, Izvest. A k a d . N a u k S.S.S.R., Otdel. Khim. N a u k , 1953, 28. (101B) Suhrmann, R., and Schulz, K., Naturwissenscha~ten,40, 139 (19533. (102B) Suth&land, K. L., and Winfield, M. E., Australian J . Chem., 6, 234, 244 (1953). (103B) Thon, N., and Taylor, H. A., J . Am. Chem. SOC.,75, 2747 (1953). (104B) Todes, 0. M., and Andrianova, T. I., Doklady A k a d . iVauk S.S.S.R., 88,515 (1953). (105B) Trapnell, B. M. W., Proc. R o y . SOC.(London), A218, 566 (1953). (106B) Vol’kenshtein, F. F., Izvest. Akad. N a u k S.S.S.R., Otdel. IChim. N a u k , 1953, 788. (107B) Vol’kenshtein, F. F., Zhur. Fiz. Khim., 27, 159 (1953). (108B) Voltz, S. E., and Weller, S., J . Am. Chem. SOC.,75, 5227, 5231 (1953). (109B) Wahba, M., and Kemball, C., Trans. Faraday Soc., 49, 1351 (1953). (llOB) Weissler, G. L., and Wilson, T. N., J . A p p l . Phys., 24, 472 (1953). (111B) Weisz, P. B., J . Chem. Phys., 21, 1531 (1953). (112B) Weisz, P. B., Prater, C. D., and Rittenhouse, K. D., Ibid., 21, 2236 (1953). (113B) Weitkamp, A. W., and Frye, C. G., IND.ENG.CHEM.,45, 363 (1953). (114B) Weitkamp, A. W., et al., Ibid., 45, 343 (1953). (115B) Westrik, R., and Zwietering, P., Proc. Koninkl. N e d . A k a d . Wetenschap., B56, 492 (1953). (116B) Wilson, J. N., Otvos, J. W.,Stevenson, D. P., and Wagner, C. D., IND.ENG.CHEM.,45, 1480 (1953). (117B) Winfield, M. E., Australian J . Chem., 6, 221 (1953). (118B) Zhabrova, G. M., Kutseva, L. N., and Roginskii, S. Z., Doklady A k a d . N a u k S.S.S.R., 92, 569 (1953). (119B) Zuckler, K., 2. P h y s i k , 136, 40 (1953).
CHEMICAL RATE PROCESSES
Molecular Transport Properties of Fluids E. F. JOHNSON Princeton University, Princeton,
F
OR the chemical engineer the most important of the molecular transport properties are viscosity, thermal conductivity, and diffusivity. A knowledge of these properties is essential t o the accurate design of processes and equipment, yet, despite the great volume of experimental and theoretical work that has been done over the years, the amount of reliable data on these properties is surprisingly limited. Ideally the engineer would prefer t o have at hand reliable tabulations of data for all systems under all ranges of conditions of temperature and pressure. Lacking such tabulations he would like t o be able t o estimate properties from such data as are available. At the present time relatively few tabulations of transport May 1954
N. J.
properties are available and for the most part these are limited to simple systems. Reliable methods for predicting transport properties in the absence of experimental data or from fragmentary data similarly are limited t o simple systems. The scarcity of data for more complex systems and for extended ranges of conditions has precluded adequate testing of methods for predicting properties. I n general, the main emphasis of effort in this field runs along two paths; first, the experimental determination of the properties with or without attempts t o correlate; and second, the development and application of methods for calculating the properties, primarily b y means of statistical mechanics using simple models of the matter involved.
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