NOTES
July, 1958
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Therefore, we believe that species B1 is not the main catalyst. I n the alkaline region the principal active catalyst is the unchargea chelated metil hydroxide Dip y C ~ ( 0 H ) ~Since . the rate of hydrolysis of this species depends solely on its concentration, it is believed to act via a basic catalysis mechanism (as discussed by the Kilpatricks in the reference cited) by accepting a proton from a hydrated DFP molecule. Acknowledgment.-The authors wish to acknowledge the helpful suggestions and criticisms of this study by members of the staff of the Army Chemical Center, especially Dr. T. WagnerJauregg and Mr. Joseph Epstein.
869
bon monoxide partial pressures, the equilibrium proportion of the catalyst system which exists in an insoluble state is increased, thus increasing the catalytically active cobalt surface area. This effect is observable if the reaction is studied at various hydrogen and carbon monoxide ratios and various total cobalt concentrations. In the hydroformylation of a C7 olefin (cut from the polymerization product of propylene and butene) in a small continuous unit with an oil soluble cobalt salt as the “catalyst,” it was found that the proportion of cobalt insoluble in the reactor effluent increases with increasing hydrogen to carbon monoxide ratio (Fig.
1). 80
.
I
I
HETEROGENEOUS CHARACTER OF HYDROFORMYLATION CATALYSIS BY CLYDEL. ALDRIDQE, Ea1 V. FASCE AND HANSB. JON ASSEN Contribution from ESSOResearch Laboratories, Baton R O U Q La., ~ , and Dept. of Chemistry, TuEane University, New Orleans, La. Received December 67,1867
Although the first observers of the reaction of an olefin with hydrogen and carbon monoxide to form oxygenated compounds believed the reaction to be heterogeneous,l later the reaction was described as homogeneous.2 Recent authors appear to have assumed homogeneity of this catalysis with dicobalt octacarbonyl and cobalt hydrocarbonyl as the active catalyst. 2-9 Various complexes have been proposed as the reaction intermediate.+* We have found that certain phenomena can be best explained by a heterogeneous mechanism, wherein cobalt in an insoluble form is essential. This insoluble cobalt may provide a fresh, highly active metal surface which is constantly being consumed and redeposited by carbonyl formation and breakdown. Data have been reported from which it can be deduced that the rate of hydroformylation of an olefin is not directly dependent upon the amounts of soluble cobalt present under reaction conditions. l o The effects of hydrogen and carbon monoxide partial pressures on the reaction rates of the hydroformylation reaction have been interpreted as resulting from a mass action competition with the olefin in the reactive complex.6 Hypothesis of a heterogeneous mechanism allows an alternative interpretation; Le., at higher hydrogen and lower car(1) D. F. Emith, C. 0. Hawk and P. L. Golden,
sa, 3221 (1930).
1.5 2.0 2.5 H2/C0 ratio. Fig. 1.-Insoluble cobalt, % of total cobalt in reactor effluent, as a function of &/CO ratio in exit gas: C7 olefin (mixed isomers) feed; 2750-2900 p.s.i.g.; 177’; 0.7 hr. reaction time. 1.0
Scatter of the data may arise from two causes: (1) insoluble cobalt was obtained by difference and (2) slight decomposition of soluble cobalt compounds may have occurred. Product was accumulated 8 hours at 0”under an atmosphere of synthesis gas before a composite sample was preserved at Dry Ice temperature. At 0” and these low concentrations a half-life of cobalt hydrocarbonyl in the range of 40 hours should be expected.” Mole % ’ conversion (by distillation and chemical analysis) of olefin to oxygenated products increases with concentration of insoluble cobalt and is, within this limited range of conversions, a linear function thereof (Fig. 2a). At constant total cobalt con-
J . Am. Chem. Soc.,
(2) H.Adkins and G. Kraek, ibid., 70,383 (1948). (3) FIAT, Final Report 1000, “The Oxo Process,” issued by the Office of Military Government for Germany through t h e O 5 c e of Technical Service of the U. 9. Department of Commeroe PB 81383, p. 29. (4) I. Wender, H. Greenfield, 8. Metlin and M. Orchin, J. Am. Chem. SOC.,74,4079 (1952). ( 5 ) I. Wender, H. W. Sternberg and M. Orohin, ibid., 76, 3041 (1953). ( 6 ) G. Natta, R. Ercoli, 9. Castellano and F. H. Barbieri, iW., 76, 4049 (1954). (7) A. R. Martin, Chemistry & Industry, 1536 (1954). (8) I. Wender, 8. Metlin, 8. Ergun, H. W. Sternberg and H. Greenfield, J. Am. Chem. SOC.,7 8 , 5401 (1956). (9) M. Orchin. L. Kirch and I. Goldfarb, ibid., 78, 5450 (1956). (10) C. L. Aldridge and E. V. Fasce, U. S. Patent 2,812,356(1957).
0.2 0.1 0.2 0.3 0.4 0.5 Cobalt in product, wt. %. Fig. 2.-Conversion to ox genated products as a function of cobalt concentration: olefin (mixed isomers) feed; 2750-2900 p.8.i.g.; 177’; 0.7 hr. reaction time; cobalt in feed, 0,0.30-0.32 wt. %; 0, 0.489 wt. %; A, 0.879 wt. %. 0.1
&
centration the conversion is inversely proportional to the concentration of soluble cobalt, while with varying total cobalt concentrations no correlation of soluble cobalt and conversion exists (Fig. 2b). It may be significant that the reported reaction
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of cobalt hydrocarbonyl with cyclohexene5 apparently occurred only when the temperature of the mixture had risen to a point (15") where cobalt hydrocarbonyl in the concentrations used is known to decompose rapidly. l1 We believe these results are sufficient to warrant a re-examination of the fundamental postulate as to the nature of cobalt catalysis of the hydroformylation reaction. It appears likely that any direct role in hydroformylation catalysis that cobalt carbonyl or cobalt hydrocarbonyl may play must be carried out in conjunction with a solid cobalt surface.
Vol. 62
tems with diborane and the following ethers: diethyl ether, methyl ethyl ether, dimethyl ether, ethylene oxide, tetrahydropyran, tetrahydrofuran, perfluoroether [ (CzF&O] and Cyclo-CIFsO.
Experimental Materials.-Diethyl ether, tetrahydropyran and tetrahydrofuran were dried over lithium aluminum hydride and fractionally distilled before use. Methyl ethyl ether was prepared by the reaction of ethyl iodide and sodium methylate in absolute methanol and purified by fractional distillation from lithium aluminum hydride at 5". The above ethers, as well as dimethyl ether, perfluoroether, cycloCdFsO,e ethylene oxide and diborane (su plied by .the Olin Mathieson Chemical Corporation) was Lrther purified if necessary by fractional distillation a t low temperature (11) H.W.Sternberg, I. Wender, R.A.Friede1 and M. Orchin, J . Am. until a purity of better than 98 mole % ' was attained, as Chem. Soc., 7 6 , 2717 (1953). determined by freezing point measurements. Apparatus.-A freezin point cell of the type described by Davidson, Sisler and [toenner? was attached to a vacuum COMPLEXES OF ETHERS gas-handling line which included manometers, calibrated flasks and traps for low temperature distillation. The WITH DIBORANEl composition of the liquid mixtures used was calculated BY HENRY E. WIRTH, FRANKLIN E. MASSOTHAND DAVID from the pressure, volume and temperature of each of the X. GILBERT gaseous components. From the volume of the freezing point cell and the observed pressure, the total moles of diDepartment of ChemiStTtt, Syracuse University, Syracuse, N . Y . borane added were corrected for the moles present in the Received January l i s 1968 gas phase at the freezing point of the mixture, assuming all to be diborane. I n 1938, Schlesinger and Burg2 showed that di- gasApresent copper-constantan thermocouple was used to deterborane and dimethyl ether formed the complex mine temperature. Cooling curves were recorded by a (CH3)20:BH3at -80". Elliot, Roth, Roedel and Brown Electronik recorder (full scale = 1 mv., variable Boldebuck3 found that the solubility of diborane range). Temperatures were reliable to =k0.5", and mole in tetrahydrofuran depended ,on the square root of fraction to f2%.
the diborane pressure, suggesting the formation of a Results and Discussion tetrahydrofuran-borine complex in solution. No Diethyl ether (Fig. 1) forms two complexes with indication of a diethyl ether-borine complex was diborane, the expected borine complex (CzH&O: found. The existence of the complex C4HsO :BH3 BH3 and a second complex having the composition was established definitely by Rice, Livasy and (C2H5)20.3BHa.Methyl ethyl ether (Fig. 2) does Schaeffer4 from the solid-liquid equilibrium in the not form a 1:1borine complex, but does form a congruent melting compound CH30C2H6.2BH3.
1
IbO I -
90
100 0
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10
Po
II 30
I
I
I
1
I
I
J
40
60
60
TO
00
94
100
Mole 'lo Diborane.
Fig, 1.-The
diethyl ether-diborane system.
diborane-tetrahydrofuran system. They suggest that the relative stability of the ether-borines is in the order C4HsO:BHz > (CHa)zO:BH3 >> (CzHs)zO:BH,
This order of stability was confirmed by Raman ~pectra.~ In this work phase diagrams are reported for sys(1) This research was supported in part by the Department of the Navy, Bureau of Aeronautics, through subcontract with the Olin Mathieson Chemical Corporation. (2) H. I. Schlesinger and A. B. Burg, J . Am. Chem. Soc., 60, 290 (1938). (3) J. R. Elliot, W. L. Roth, G . F. Roedel and E. M. Boldebuck, ibid., 74, 5211 (1952). (4) B. Rice, J. Livasy and G . W. Schaeffer, ibid., 77, 2750 (1955). 15) B. Rice and H. 8. Uchida, THISJOURNAL, 59, 650 (1955).
o
I
I
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1
I
I
I
I
l
IO
20
so
40
so
eo
70
80
90
100
Mole "1. D i b o r o n e .
Fig. 2.-The
methyl ethyl ether-diborane system.
Ethylene oxide (Fig. 3) forms no congruent melting compounds, but the freezing point diagram indicates the possibility of one and perhaps two incongruent melting compounds. The initial freezing points and the "flats" at 131 and 121°K. were definite and reproducible, but the secondary breaks between 70 and 95 mole yo diborane were erratic. The formation of solid solutions in this range could explain these observations. While ethylene oxide is known t o react vigorously with diborane at 190°K.,8there was no evidence of reaction at tem(6) The fluorinated ethers were supplied to us through the courtesy of the Minnesota Mining and Manufacturing Co. (7) A. W. Davidson, H. H. Sisler and R. Stoenner, J . A m . Chem. Soc., 6 6 , 779 (1944). (8) F. G . A. Stone and H. J. Emeleus, J . Chem. SOC.,2755 (1950).
