Ind. Eng. Chem. Res. 1992,31,1597-1601 Dewar, M. J. S.; Dieter, K. M. Evaluation of AM1 Calculated Proton Affiitiea and Reprotonation Enthalpies. J. Am. Chem. SOC.1986, 108,8075-8086. Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P. AM1: A New General Purpose Quantum Mechanical Molecular Model. J. Am. Chem. SOC. 1985,107, 3902-3909. Fletcher, R.; Powell, M. J. D. A Rapidly Convergent Descent Algorithm for Minimization. Comput. J. 1963, 6, 163. Frank, I. E.; Kalivas, J. H.; Kowalski, B. R. Partial Least Squares Solutions for Multicomponent Analysis. Anal. Chem. 1983, 55, 1800-1804. Fu, C. M.; Schaffer, A. M. Effect of Nitrogen Compounds on Cracking Catalysts. Ind. Eng. Chem. Prod. Res. Deu. 1985, 24, 68-75, Furnival, G. M.; Wileon, R. W., Jr. Regression by Leaps and Bounds. Technometrics 1974, 16, 499-500. Ho, T.C. Hydrodenitrogenation Catalysis. Catal. Rev.-Sci. Eng. 1988,30 ( l ) , 117-160. Jurs, P. C.; co-workers. Pennsylvania State University, 1987 (available from Molecular Design Ltd., San Leandro, CA 94577). Kier, L. B.; Hall, L. H. Molecular Connectiuity in Structure-Activity Analysis; John Wiley & Sons: New York, 1986. LaVopa, V.; Satterfield, C. N. Poisoning of Thiophene Hydrodesulfurization by Nitrogen Compounds. J. Catal. 1988, 100, 375-387. Lindberg, W.; Person, J. A.; Wold, S. Partial Least-Squares Method for Spectrofluorimetric Analysis of Mixtures of Humic Acid and Lignineulfonate. Anal. Chem. 1983,55,643-648. Nagai, M.; Sato, T.;Aiba, A. Poisoning Effect of Nitrogen Compounds on Dibenzothiophene Hydrodesulfurization on Sulfided
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NiMo/A1203Catalysts and Relation to Gas-Phase Basicity. J. Catd. 1986, 97, 52-58. Pearlman, R. S. QCPE Bull. 1981,16, 1. Perrin, D. D. Dissociation Constants of Organic Bases in Aqueous Solutions; Butterworth London, 1965. Randic, M. On Characterization of Molecular Branching. J. Am. Chem. SOC.1975,97,6609. Sharaf, M. A.; Illman, D. L.; Kowalski, B. R. Chemometrics; John Wiley & Sons: New York, 1986; Chapter 5. Stull, D. R.; Prophet, J. JANAF Thermochemical Tables; National Standard Reference Data Series, NSRDS-NBS37; National Bureau of Standards: Washington, DC, 1971. Taft, R. W. In Progress in Physical Organic Chemistry; Taft,R. W., Ed.; John Wiley & Sons: New York, 1983; Vol. 14, p 247. Voltz, S. E.; Nace, D. M.; Jacobs, S. M.; Weekman, V. W., Jr. Application of a Kinetic Model for Catalytic Cracking. 111. Some Effects of Nitrogen Poisoning and Recycle. Ind. Eng. Chem. Process Des. Deu. 1972, 11, 261. Wipke, W. T.;Verbalis, J.; Dyott, T. Three-Dimensional Interactive Model Building, 162nd National Meeting of the American Chemical Society, Los Angeles, CA; American Chemical Society; Washington, DC, 1972 (available from Molecular Design Ltd.). Wold, S.; Geladi, P.; Esbensen, K.; Ohman, J. Multi-Way Principal Components and PLS-Analysis. J. Chemom. 1987, I, 41. Young, G. W. Fluid Catalytic Cracker Catalyst Design for Nitrogen Tolerance. J. Phys. Chem. 1986,90,4894-4900. Receiued for reuiew November 12, 1991 Reuised manuscript receiued March 9, 1992 Accepted March 30, 1992
Hydroformylation of Propylene Using an Unmodified Cobalt Carbonyl Catalyst: A Kinetic Study Raghuraj V. Gholap, Oemer M. Kut, and John R. Bourne* Technisch Chemisches Laboratorium, ETH-Z,CH-8092Zurich, Switzerland The kinetics of hydroformylation of propylene using an unmodified cobalt carbonyl catalyst has been investigated in a temperature range of 383-423 K and a pressure range of 35-100 bar. Effects of the propylene and catalyst concentrations and the partial pressures of carbon monoxide and hydrogen on the rate of hydroformylation have been measured. Initial rates were found to be in the kinetic regime for the intensively stirred reactor used. An empirical rate model has been propoeed, which wa8 found to represent the rate data with a standard deviation of 7%. Its two kinetic parameters were evaluated, and the activation energy was found to be 77 kJ mol-'.
Introduction Propylene reacts with carbon monoxide and hydrogen under preseure, in the presence of cobalt carbonyl catalyst, to give isobutyraldehydeand n-butyraldehyde as the major products, although, under certain conditions, small amounts of side products are possible. There are various reports on the hydroformylation of propylene using different catalytic systems (Falbe, 1973; Pruett, 1979; Cornils, 1980). Progress in this field has led to the development of very active and selective catalysts for the manufacture of aliphatic aldehydes and alcohols (Bach et al., 1988; Weissermel and Arpe, 1988). However, the traditional cobalt system seems to have maintained some industrial importance due to its much lower cost. The present work was undertaken using dicobalt octacarbonyl as a catalyst precursor for the hydroformylation of propylene. This reaction can be described as [cobalt]
CHj-CH=CHz
+
CO
+
H2
--E
CH~CH~CHZCHO (1)
negative order with respect to CO in a certain range (Natta et al., 1955). While extensive studies on the effects of various parameters on the propylene hydroformylation reaction have been reported in the literature (Cornils, 19801, a detailed investigation of the kinetics of this industrially important reaction using cobalt carbonyl catalyst is lacking. Therefore, the aim of this work was to investigate the overall kinetics of the hydroformylation of ) ~ a catalyst and develop a propylene using C O ~ ( C Oas suitable rate equation for a wide range of reaction conditions. Kinetic experiments were carried out under different operating conditions with an unmodified cobalt carbonyl catalyst. The effects of propylene and catalyst concentrations and partial pressures of carbon monoxide and hydrogen on the rate of hydroformylation have been studied in a temperature range of 383-423 K, with total partial pressures up to 100 bar. A two-parameter rate model has been proposed.
CHjCH(CHO)CH3
It is reported that the rate of hydroformylation is first order with respect to hydrogen, olefin, and catalyst and
* Author to whom correspondence should be addressed.
Experimental Section Materials. Dicobalt octacarbonyl and toluene (p.a. grade), obtained from Fluka AG,Switzerland, were used without further pretreatment. Hydrogen, propylene, and
osss-~ss~/92/263~-~5~~0 ~ o1992 3 . ~American o~o Chemical Society
1598 Ind. Eng. Chem. Res., Vol. 31, No. 7, 1992 5
Lo1 2
9
9e-
EP
8 b
l l
8
O'* 0.6
0.2
0.0 0
loo0
m
3030
4003
TIME, 6ec
Figure 1. Schematic diagram of experimental setup: 1, syngas cylinder; 2, gas regulator; 3,gas inlet; 4,sampling valve; 5, stirrer shaft; 6, baffles; 7, temperature probe; 8, pressure indicator; 9, gas vent; 10,propylene cylinder; 11, balance.
Figure 2. Typical concentration profile of propylene hydroformylation. Catalyst concentration, 14.6 mol m-3; PCO,50 bar; PH, 50 bar; agitation speed, 1500 rpm; temperature 403 K; initial propylene concentration, 1.19 X 103 mol m-3; X, CO or H2consumed;0, n-butyraldehyde formed; A, isobutyraldehyde formed.
carbon monoxide with >99.8% purity were used directly from the cylinders. Setup. All the hydroformylation experiments were carried out in a oil-thermostated 2-L-capacity autoclave, having an internal diameter of 0.0735 m, which was desigred for a working pressure of 170 bar and temperatures up to 450 K. A schematic diagram of the experimental setup is shown in Figure 1. The autoclave was provided with arrangements for sampling of gaseous and liquid components, three propeller-type stirrers, baffles, automatic temperature control, and variable stirrer speed through a magnetic coupling. The propellers in the reactor were fixed at positions in which an improved gas distribution was observed leading to intensive gas-liquid contact with gas bubbles reaching all parts of the liquid. This was optimized visually by using a glass vessel of the same dimensions as the autoclave. The gases were sparged into the reactor below the lowest stirrer and were not induced. The syngas was supplied to the autoclave only to the extent of consumption in a "dead-end" mode. The hydrogen and carbon monoxide pressures were kept almost constant during each experiment by feeding the reactor with premixed CO and H2 from a high-pressure cylinder. Procedure. In a typical experiment, known amounts of the catalyst C O ~ ( C Oand ) ~ the solvent toluene were charged into the reactor. The active catalytic species HCO(CO)~ was formed in solution from the dicobalt octacarbonyl precursor. The contents were flushed initially with nitrogen and then with a mixture of CO + H2 and heated to a desired temperature. After the reactor had been brought up to the conditions, the desired amount of propylene, which was controlled by a balance (Figure 11, was introduced and then the reactor was pressurized with the indicated mixture of CO + HP. A sample of the liquid was withdrawn and the reaction was started by switching the stirrer on. The reaction was then continued by supplying the mixture of carbon monoxide and hydrogen having a ratio of 1:1, as required by the stoichiometry (eq 1). The progress of the reaction was followed by observing a prescribed pressure drop in the reactor with time. While recording the pressure drop vs time data, necessary corrections for the vapor pressures under different experimental conditions were made. The partial pressures of CO and H2were calculated by deducting the partial pressures of the solvent (toluene) and of propylene from the total pressure. During the experiments, the deviations from the assigned process conditions were no greater than 2 K for
temperature and no greater than i 3 bar for pressure. In each experiment, the liquid samples were withdrawn after various periods of time and were analyzed by gas chromatography, in order to follow the concentrations of the products during the reaction. For this purpose, a Philips PU4400 gas chromatograph was used with 10% PEGA on a Chromosorb AW packed column of 2.1-m length. Following this procedure, the effects of the catalyst and propylene concentrations, agitation speed, partial pressures of CO and Ha, and temperature on the overall rate of hydroformylation have been studied. Results and Discussion Preliminary Studies. Since the main objective of this work was to investigate the kinetics of propylene hydroformylation, it was thought necessary to first check the material balance and reproducibility of the experiments. Therefore, a few experiments were carried out in which the amounts of products formed and CO + H, consumed were compared. The experiments were reproducible and propane formation was not observed. The material balance of CO + H, consumed was consistent (>99%) with the amount of butyraldehydes formed, at low propylene conversions (
