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V. N. IPATIEFF, B. B. CORBON AND J. D. KURBATOV
Temperature has been shown to have little effect on 0 over a fairly wide range but the normal large effect on the residual viscosity. The results have been interpreted in terms of the “impulse theory” of thixotropy. The authors desire to record their indebtedness to Mr. A. C. Stevenson, of this College, for his valuable advice, and criticism of the mathematical treatment in section 111. REFERENCES
(1) FREUNDLICH, H.:Thirotropy. Hermann e t Cie, Paris (1935). (2) GOODEVE, C. F.: Trans. Faraday SOC.86, 342 (1939). (3) GOODEVE, C. F.: J. Sci. Instruments 16, 19 (1939). (4) GOODEVE, C.F., AND WHITFIELD,G. W.: Trans. Faraday SOC.34, 511 (1938). (5) KUHN,W.: 2. physik. Chem. A161, 1 (1932). C. M., AND USHER,F. L.: Proc. Roy. SOC.(London) A151, 573 (6) MCDOWELL, (1931). (7) REINER,M., AND RIWLIN,R.: Kolloid 2.43,1 (1927). (8) Rossr, C.:Gam. chim. ital. 67, 691,751 (1937);68,3 (1938). C. W.: Official Digest, Federation of Paint and Production Clubs, (9) SWEITZER, February, 1935;and Messrs. Binney & Smith & Ashby, Ltd., London. (10) SZEQVARI, A,: 2. physik. Chem. 100, 175 (1924). (11) DE WAELE,A., AND DINNIB,G.: Physics 7, 426 (1936).
MIXED COPPER-CHROMIUM OXIDE HYDROGENATION CATALYSTS V. N. IPATIEFF, B. B. CORSON, AND J. D. KURBATOV Research Laboratories, Universal Oil Produels Company, Riverside, Illinois
Received October 3, lQ3Q INTRODUCTION
It has been shown (7) that pure copper does not hydrogenate benzene a t ordinary pressure at 225°C.) but that the presence of certain impurities enables it to do so. It was thirty years ago that the senior author discovered this promoter action in hydrogenation (5, 9). Pure copper is able to hydrogenate benzene only under superatmospheric pressure. This paper describes a series of coprecipitated copper-chromium oxide catalysts whose activities were evaluated by the hydrogenation of benzene and of isopentene at ordinary and superatmospheric pressures. Under the test conditions both of the pure components-copper and chromium oxide-were inactive, but as chromium oxide was added to copper the activity rose abruptly to a maximum at 5 per cent of oxide, and then
COPPER-CHROMIUM
OXIDE HYDROGENATION CATALYSTS
671
fell with continued addition. Incidentally, catalytic activity in these copper-chromium oxide catalysts was accompanied by pyrophoricity, although there is no simple relationship between these two characteristics' (2). We propose to call this composition of maximum activity the eucoactic composition. It will be interesting in the future to study the dependence of the eucoactic composition upon the type of unsaturation and upon the operating conditions. Another problem for future study concerns poisoning and heat deactivation as a function of chemical composition. Adkins (1, 4) and Calingaert (3) have previously described a number of copper-chromium oxide catalysts, with and without calcium, barium, strontium, and magnesium as stabilizers, but they used a much higher concentration of chromium oxide than would be recommended on the basis of this work. This paper describes for the first time the hydrogenation of isopentene (trimethylethylene) with pure copper. Sabatier (15, 16) was unable to hydrogenate this olefin with copper and made the generalization that only those olefins which contained the =CH2 group could be hydrogenated in the presence of copper. Kistiakowsky (11, 12) has hydrogenated isopentene over copper, but his catalyst was prepared from the commercial granular oxide, which doubtless contained impurities.2 Pure copper (containing about 0.001 per cent of nickel) does not hydrogenate isopentene at ordinary pressure in 10 sec. a t 75OC., but it does so to the extent of 6 per cent in 14 see. a t 100°C. and 85 per cent in 20 sec. a t 225°C. Under 125 atmospheres of hydrogen a t lOO"C., hydrogenation is complete. The effect of small amounts of chromium oxide is remarkable. Copper requires a temperature of 225°C. to hydrogenate isopentene to the extent of 55 per cent in 10 sec., whereas copper containing 0.1 per cent of chromium oxide shows the same activity a t 75°C. Thus, the presence of 1 mole of chromium oxide in 2500 atoms of copper lowers the temperature requirement 150°C., although chromium oxide alone has no hydrogenating ability, even a t 350°C. under 150 atmospheres of hydrogen. However, even the best of the copper-chromium oxide catalysts is weak when compared with supported nickel (6), which hydrogenates benzene to the extent of 100 per cent in 1 sec. a t 50°C. and ordinary presIn some unpublished work we found very active copper-nickel and coppercobalt catalysts to be non-pyrophoric, whereas much less active copper-chromium oxide catalysts were very pyrophoric. * Considerable work has been done in the past on the catalytic properties of copper, but the source of the copper was usually the commercial granular oxide, which contains catalytically significant amounts of nickel, iron oxide, alumina, magnesia, silica, and other impurities, and with this complicated system i t is impossible t o learn anything about the catalytic ptoperties of copper itself.
672
V. N. IPATIEFF, B. B. CORSON AND J. D. KURBATOV
sure, whereas the eucoactic copper-chromium oxide catalyst is completely inactive under these conditions and hydrogenates benzene to the extent of only 16 per cent a t 225°C. in 90 sec. Mixed copper-chromium oxide catalysts are even more susceptible to activation by traces of nickel than is copper alone. For instance, copper containing not more than 0.001 per cent of nickel does not hydrogenate benzene a t ordinary pressure and 225OC. in 90 sec. and the presence of 0.005 per cent of nickel raises the hydrogenation to 4 per cent. On the other hand, the hydrogenating activity of the 95 per cent copper5 per cent chromium oxide is raised from 16 per cent to 24 per cent by the addition of 0.005 per cent of nickel. Another example of this amplifier effect is the following: The addition of 0.2 per cent of nickel raises the hydrogenating activity of copper from 0 to 19 (per cent hydrogenation of benzene a t ordinary pressure and 225°C. in a contact time of 12 sec.), whereas the same addition of nickel raises the activity of the 95 per cent copper-5 per cent chromium oxide catalyst from 2 to 62. The promotion of copper by nickel and cobalt, and the poisoning of copper by bismuth, cadmium, lead, mercury, and tin, will be described in a subsequent paper. In view of the importance of small amounts of impurities and the difficulty of detecting these traces by the usual qualitative tests, a serious doubt arises as to the reliability of much of the data in the field of catalysis. EXPERIMENTAL
Apparatus and procedure for hydrogenation at atmospheric pressure; calculation The apparatus was essentially the same as previously described (7), except that the hydrogen-purification train was as follows: copper gauze in a silica tube a t 5OO0C.,lead acetate solution, potassium hydroxide solution, anhydrous calcium chloride, ascarite, and activated alumina. After several months' operation the inlet tube of the lead acetate wash bottle had blackened, indicating a trace of hydrogen sulfide in the electrolytic hydrogen. In the benzene tests the hydrocarbon saturator was thermostated a t 25.0"C. f 0.lo, and the hydrogen-benzene ratio of the gas issuing from the saturator averaged 7. The free space of the reduced catalyst ww determined by adding water to the charged tube. In the hydrogenation of isopentene, the saturator was packed in ice, and the hydrogen-isopentene ratio of the exit gas averaged 3, the vapor pressure of the sample of isopentene being 184 111111. of mercury a t 0°C.
COPPER-CRROMIUM OXIDE HYDROGENATION CATALYSTS
673
Blank experiments made under the conditions of the tests, by passing hydrogen-benzene and hydrogen-isopentene mixtures through a tube filled with glass balls, showed that the apparatus was non-catalytic. The method of calculating the results was the same as previously described. Preparation of materials Benzene. C.P. benzene was purified by repeated washing with concentrated sulfuric acid, followed by washing with caustic soda and water; it was then distilled through a Podbielniak column (reflux ratio, 20), collecting the middle third of the distillate. Isopentene. Isopenterie was prepared by dehydrating dimethylethylcarbinol over activated alumina a t 427OC. After separating the water layer, the dehydration product was distilled through a Podbielniak column (reflux ratio, 20) and the middle third of the distillate was collected (b.p., 35-37°C. at 747 mm.; bromine number, 225; n:’, 1.3848). According to its refractive index the olefin mixture contained about 75 per cent of trimethylethylene and 25 per cent of as-methylethylethylene. Catalysts. The catalysts were prepared by coprecipitating basic copper carbonate and chromium hydroxide from the corresponding nitrates by ammonium carbonate, followed by drying, granulation, decomposition, and reduction. The compositions of the reduced catalysts were checked by analysis. The catalysts containing a known amount of nickel were made by adding the calculated amount of dilute nickel nitrate solution to freshly precipitated copper or copper-chromium catalysts and stirring the mixture to a homogeneous slurry, the mixture being then processed as usual. The reagents were of the highest “reagent” purity; they were examined spectroscopically, as were also the final catalysts. Reduction of catalysts Granular 6- to 10-mesh oxide catalyst was charged to a 14-mm. I.D. glass tube and hydrogen was passed for 20 hr. a t 225°C. The length of the catalyst bed averaged 35 cm. in the benzene tests and 18 cm. in the isopentene tests; the hydrogen rate was 2000 cc. per hour in the former case and 1000 cc. per hour in the latter. After reduction, the tube was tapped to compact the catalyst bed, the shrinkage averaging 20 per cent. Practically all of the copper oxide was reduced, even in the presence of chromium oxide, as evidenced by the water produced. For example, the catalysts containing 99.9, 68.2, and 11.3 per cent of copper (the remainder being chromium oxide) produced 97, 98, and 96 per cent, respectively, of the theoretical amount of water.
674
V. N . IPATIEFF. B. B. CORSON AND J. D. KURBATOV
Analysis of liquid catalysate The composition of the liquid catalysate was estimated from its refractive index. The composition-index curve for isopentane-isopentene was plotted from the following data: weight per cent of isopentane, 0.0, 31.8, 65.2, 100.0; n:', 1.3848, 1.3747, 1.3645, 1.3545. The isopentane was prepared by the hydrogenation of the original isopentene with supported nickel (6) a t room temperature under 100 atmospheres of hydrogen. The hydrogenated product was stable to a nitrating mixture and showed a bromine number of 0.1. TABLE 1 Hydrogenation o/ ben%eneover copper-chromium oxide catalysts Conditions of hydrogenation: 225°C.; 90 sec. contact time; ratio of Hz t o CsHa = 7 ; atmospheric pressure MOLES OF
CrrOa TO ATOMS
0 0.1 0.5 1 .o 5
10 25 50 75 90 99
100
OF
Cu
HYDROQENATION OF BBNZENE
w&ht pw cmt
weight per em1
0
O.ooo4 0.002 0.004
0.02 0.05 0.1 0.4 1.3 3.7 41 a
0 3 13 13 16 14 8 4 2 1 0 0
Hydrogenation of benzene at atmospheric pressure The data in table 1 show that the most active hydrogenating catalyst of the copper-chromium oxide series, for the experimental conditions used, contains 95 per cent of copper and 5 per cent of chromium oxide. The pyrophoric characteristics of the used catalysts ran roughly parallel to their activities, the first one (table 1) being non-pyrophoric, the next one pyrophoric, the next three very pyrophoric, the next three less pyrophoric, and the last four non-pyrophoric. The colors of the used catalysts, given in the order in which they occur in table 1, were S, S-B, B, B, B1-B, B1-B, B1-B, B1-B, B1, G, G, and G (S, B, B1, and G denoting salmon, brown, black, and green, respectively). In one experiment with pure copper (0.001 per cent of nickel), hydrogen and benzene were passed simultaneously over the granulated oxide a t 225°C. It was thought that the.reduced copper might be sufficiently
675
COPPER-CHROMIUM OXIDE HYDROGENATION CATALYBTS
active in statu nascendi to hydrogenate benzene, but this waa not so. The hydrocarbon catalysate was unchanged benzene (n:, 1.5014).
Promoting effect of nickel o n copper and copper-chromium oxide catalysts The data in table 2 illustrate the promoting effect of nickel on copper and copper-chromium oxide catalysts, as measured by their ability to hydrogenate benzene. TABLE 2 Promoting effect of nickel o n copper and COpper-chTOmiUm oxide catalysts Conditions o f hydrogenation: 225°C.; ratio of HZto CJL = 7: atmospheric pressure i
CrDa weight p a cent
Ni
HYDBOQENATION OF BlNZBNE
CONTACT TIYE
weight p a cent
weight per cent
asconds
0.001 0.005
0 4
90 90
5 5
0.001 0.005
16 24
90 90
0
0.2 0.001 0.2
19 2 62
12 12 12
0 0
~
5 5
TABLE 3 Hydrogenation of isopentene over copper-chromium ozide catalysts Conditions o f hydrogenation: 75°C.; 10 sec. contact time; ratio of HZto CaHlo = 3 ; atmospheric pressure CrlO: weight p~ cent
0 0.1 1.0 2.5
1
HYDROQBNATION O F IBOPENTENE
CIrOI
BYDBOQBNATION OF ISOPlNTlNE
weight per cent
weight per cent
weight per cent
0 46 51
25 50 75 100
85 66 40
0
96
Hydrogenation of isopentene at atmospheric pressure The data in table 3 were obtained with copper-chromium oxide catalysts which contained about 0.003 per cent of nickel, and experiments were not made with catalysts containing 0.001 per cent of nickel, as was done in the case of benzene. A preliminary survey showed t.hat it was impossible to differentiate between these catalysts a t 100°C. and contact times which were practical for
676
V. N. IPATIEFF, B. B. CORSON AND J. D. KURBAMV
the apparatus. At this temperature all the catalysts in the series, except pure copper and pure chromium oxide, were about equally active, as shown by the following data: per cent chromium oxide in catalyst, 0, 0.05, 0.1, 1, 2.5, 25, 50, 75, 100; per cent hydrogenation of isopentene, 6, 98, 90, 98, 100, 100, 98, 100, 0; contact time in seconds a t lOO"C., 14, 12, 9, 17, 7, 15, 8, 20, 13.
Effect of temperature An exploratory run was made a t ordinary pressure on the effect of temperature. At the conclusion of the run the temperature was brought back to the original value and the activity of the catalyst was found to be unchanged. In a contact time of 90 sec. the 95 per cent copper5 per cent chromium oxide mixture hydrogenated benzene to the extent of 16, 9, 2, and 0 per cent at 225", 200°, 175", and 15OoC., respectively. Hydrogenation of ethylene at atmospheric pressure An attempt was made to evaluate the copper-chromium oxide series of catalysts by the hydrogenation of ethylene a t 25°C. and ordinary pressure, but the results were erratic. The catalysts were probably deactivated by oxygen (14). Inactivity of pressure-reduced copper Copper which had been precipitated by hydrogen under pressure (8, 10) was unable to hydrogenate ethylene in 70 sec. a t 225°C. and ordinary pressure with a hydrogen-ethylene ratio of 5.5, whereas copper prepared from the basic carbonate hydrogenated ethylene completely under these conditions, and also in 26 sec. at 100°C.
Superatmospheric hydrogenation of benzene The apparatus was an 850-cc. rotating Ipatieff bomb which was equipped with a glass liner. The charge was 50 cc. of benzene, 20 g. of reduced catalyst, and 100 atmospheres of hydrogen. The time of rotation was 12 hr. Blank runs made in the absence of catalyst showed that the bomb was non-catalytic under the conditions of the experiments. Although it was impossible to differentiate between these catalysts a t 350°C., it was possible to do so at lower temperatures, and the peak of the activity curve was in the vicinity of 5 to 25 per cent of chromium oxide (table 4). Perhaps the eucoactic composition was displaced at superatmospheric pressure toward higher chromium oxide concentrations, but the data are incomplete on this point. Superatmospheric hydrogenation of isopentene and ethylene Isopentene was completely hydrogenated by pure copper in 12 hr. a t 100°C. under 125 atmospheres of hydrogen, and by all the mixed copper-
677
COPPER-CHROMIUM OXIDE HYDROGENATION CATALYSTS
chromium oxide catalysts, including the 1 per cent copper-99 per cent chromium oxide mixture, but it was not hydrogenated by chromium oxide itself a t lOO"C., or even a t 350°C., in 12 hr. TABLE 4 Superatmospheric hydrogenation of benzene at different temperatures HYDBOOENATION AT DIFFERENT TEYPEBATUREB
CrzOr 200'C.
wcight p a cent
0 0.1
5 25 50
75
90 99 100
I
250°C.
350'C.
weight p a cent
weight per cent
m i g h t per cent
w 4 h t per cent
1 2 7 6 6 1 0 0 0
0 26 39 30 17 17 5 0 0
19 81 100
90 100 100 99 99 100 100 2 0
90 83 86 38 0 0
TABLE 5 Deactivation of reduced copper by heat Conditions o f hydrogenation test: 225°C.; ratio of H I t o CsHs = 7; atmospheric pressure DEACTIIATION TEMPEBATURE
CONTACT TIME
ACTIVITY'
1
ACTIVITY EXTRAPOLATED TO 150 BEC. CONTACT TIME
'C.
8WOnd8
225
52 104 125
400
53 103 126
12 23 32
36
500
58 110 135
0 2 2
2
* Per cent hydrogenation of benzene under the conditions of the test. Pure copper prepared from the basic carbonate hydrogenated ethylene to the extent of 100 per cent in less than half an hour a t 2OO0C., starting with an initial ethylene partial pressure a t room temperature of 35 atmospheres and 65 atmospheres of hydrogen, but pure copper, prepared by reduction of copper ions under pressure, hydrogenated ethylene to the extent of only 20 per cent in 12 hr. at 200°C.
678
V. N. IPATIEFF, B. B . CORSON AND J. D. KURBATOV
Heat-deactivation of copper catalyst A 200.4-g. sample of granular (6-to 10-mesh) copper oxide (KahlbaumSchering, fur Analyse), which contained 0.1 per cent of nickel and smaller amounts of other impurities, was reduced at 225°C. for 60 hr. with a hydrogen rate of 2000 cc. per hour, 44.5 g. of water being produced. The reduced catalyst was cooled in hydrogen and divided into three samples which were treated as follows: The first sample w&s heated 15 hr. in hydrogen a t 225°C. and then tested with benzene at 225°C. in the usual manner. The second sample was heated 10 hr. in hydrogen a t 4OO0C., cooled in hydrogen during 5 hr. to 225OC., and tested with benzene a t 225°C. The third sample was heated 10 hr. in hydrogen a t 5OO0C., cooled in hydrogen during 5 hr. to 225"C., and tested with benzene a t 225OC. The only variable was the temperature a t which the reduced catalyst was heated just before being tested for hydrogenating activity. The activities (per cent hydrogenations of benzene) are given in table 5. The relative activities for the catalysts treated a t 225"C., 4OO0C., and 500°C. are 27, 18, and 1, respectively. SUMMARY
1. The hydrogenating activities of copper-chromium oxide catalysts have been evaluated by the hydrogenation of benzene and isopentene a t atmospheric and superatmospheric pressures. 2. As chromium oxide is added to copper, the hydrogenating activity of the mixture rises abruptly to a maximum a t about 5 per cent of chromium oxide, and then falls with continued addition of chromium oxide. 3. This optimum concentration has been named the eucoactic concentration. 4. Copper is very susceptible to activation by traces of nickel, and the 95 per cent copper-5 per cent chromium oxide is even more susceptible.
The authors express their thanks to Mr. W. J. Cerveny for much of the experimental work, and to Dr. W. C. Pierce of the University of Chicago for spectroscopic analyses. REFERENCES ADKINSAND CONNOR: J. Am. Chem. SOC.53, 1091 (1931). ARMSTRONG AND HILDITCH: Proc. Roy. SOC. (London) 99, 490 (1921). CALINOAERT AND EDGAR: Ind. Eng. Chem. 26, 878 (1934). CONNOR, FALKERS, AND ADKINS:J. Am. Chem. SOC.64, 1138 (1932). (5) IPATIEFF: Ber. Pa, 2090 (1909). (6) IPATIEFF AND CORSON: Ind. Eng. Chem. 30, 1039 (1938). (7) IPATIEFF,CORSON, AND KURBATOV: J. Phys. Chem. 43, 589 (1939). (8) IPATIEFFAND IPATIEFF: Ber. 62, 386 (1929).
(1) (2) (3) (4)
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(9) IPATIEFFAND MATOV:J. Russ. Phys. Chem. Soc. 44, 1695 (1912);Ber. 45, 3205 (1912). (10) IPATIEFF AND WERCHOWSKY: Ber. 42, 2078 (1909). (11) KISTIAKOWSKY, ROMEYN,RUHOFF,SMITH,AND VAUGHAN: J. Am. Chem. SOC. 57, 65 (1935). (12) KISTIAKOWSKY, RUEOFF,SMITH,AND VAUGHAN:J. Am. Chem. Soc. 68, 137 (1936). AND PURDUM: J. Am. Chem. SOC.47, 1435 (1925). (13)PEASE (14) RUSSELLAND GHERINO:J. Am. Chem. SOC. 67, 2544 (1935). (15) SABATIER:50th Congr. 800. sav., J. offic., p. 3628,April 11, 1912. AND SENDERENS: Compt. rend. 134, 1127 (1902).. (16) SABATIER
NEW BOOKS Theoretical Electrochemistry. By N. C. MCKENNA.469 pp. New York: D. Van NostrandGompany, Inc., 1939. Price: $5.50. This is a modern, quite up-to-date text on theoretical electrochemistry which is well balanced with regard t o theory, experimental technique, and results. The author distinguishes between irreversible and reversible (or free energy) properties of solutions of electrolytes and he discusses these on the basis of the theory of Debye and Huckel and its more recent extensions. Due credit is given to the work of Onsager, MacInnes, and many other workers. The second part of the book is devoted to the thermodynamics of reversible cells and the theories of the galvanic cell. A chapter on “irreversible electrode processes” and one on “ions in solution” are included, in which recent views on these important subjects have been given in a satisfactory way. The author states in the preface that the book is not comprehensive. However, a more detailed discussion of electrolytes in non-aqueous solution would have been desirable. Also a discussion of membrane potentials in general and of the glass electrode in particular might have been anticipated in a book of this nature. The first eleven chapters are so good that the monograph could be recommended unreservedly, were i t not for the fact that the last three chapters, dealing with ionic equilibria, the hydrolysis of salts, and neutralization and the theory of indicators, are decidedly bad. These chapters are classical in nature, and they give so many details of older work based on the theory of Arrhenius that one wonders why the author has not modernized these topics and condensed them. For example, to write the acid-base equilibrium of an acid salt (equation 561 on page 379) in terms of concentrations of undissociated salts is objectionable. The abscissa of figure 96 (page 399) is incorrect. So is the statement on page 400 that an amino acid shows complete acid and base dissociFtion a t the isoelectric point. Several mistakes are found on page 421. It is a serious omission that the glass electrode is not mentioned on page 426 for the measurement of the pH of ferric salts. The calculation of the percentage dissociation of rosolic acid a t various pH values is incorrect. On page 437 i t is stated that the pH a t which the indicator is half dissociated is called the titration exponent; this is never done. The discussion on page 439 of the change of pH close to the end point is confusing and very bad. Also incorrect is the statement on page 431 of the behavior of an acidified solution of the sodium salt of p nitrophenol. Probably the author had in mind phenylnitromethane.
