2446
Ind. Eng. Chem. Res. 1992,31, 2446-2450
Gullett, B. K. Reduction of Chlorinated Organics in the Incineration of Wastes. U.S. Patent 5,021,229, June 4, 1991. Gullett, B. K.; Bruce, K. R.; Beach, L. 0. Formation Mechanisms of Chlorinated Organics and Impacts of Sorbent Injection. In Proceedings: 1989International Conference on Municipal Waste Combustion, Volume 3; EPA-600/R-92-052~;pp 8C-1 to 8C-25. Gullett, B. K.; Bruce, K. R.; Machilek, R. M. Apparatus for Short Time Measurements in a Fixed-Bed Gas/Solid Reactor. Rev. Sci. Instrum. 1990,61,904. Jost, W. Diffusion in Solids, Liquids, and Gases; Academic Press: New York, 1960; pp 285-323, 366-367. Karlsson, H. G.; Klingspor, J.; Bjerle, I. Adsorption of Hydrochloric Acid on Solid Slaked Lime for Flue Gas Clean Up. J. Air Pollut. Control Assoc. 1981, 31, 1177. Levenspiel, 0. Chemical Reaction Engineering, 2nd ed.; Wiley: New York, 1972; pp 357-408. Mayer-Schwinning,G.; Laibold, E. Basic Processes for Cleaning Flue Gases from Waste Incineration Plants. In Proceedings: 1989 International Conference on Municipal Waste Combustion, Volume 3; EPA-600/R-92-052~;pp 7C-1 to 7C-18. Newton, G. H.; Moyeda, D. K.; Kindt, G.; McCarthy, J. M.; Chen, S. L.; Cole, J. A.; Kramlich, J. C. ‘Fundamental Studies of Dry Injection of Calcium-Based Sorbents for SO2 Control in Utility Boilers”: EPA-600/2-88-069 (NTIS PB89-134142); December 1988; pp 1-6. Ranz, W. E.; Marshall, W. R. Evaporation from Drops. Chem. Eng. Pro#. 1952, 48 (31, 141-146. Schmd, D.; Verbeek, A,; van der Harst, C. Dry Techniques for Abatement of Acid Emissions in Flue Gases. Proceedings of the 8th World Clean Air Congress 1989, The Hague, The Netherlands,
Sept 11-15,1989. Published in Man and His Ecosystem; Brasser, L. J., Mulder, W. C., Eds.; Elsevier: Amsterdam, 1989; Vol. 4, pp 213-218. Szekely,J.; Evans, J. W.; Sohn,H. Y. Gas-Solid Reactions; Academic Press: New York, 1976; pp 65-107. Torres-Ordoiiez, R. J.; Longwell, J. P.; Sarofim, A. F. The Intrinsic Kinetics of CaS(s) Oxidation. Energy Fuels 1989, 3 (4), 506. Verbeek, A.; Schmal, D.; van der Harst, C. Abatement of HC1 and HF Emissions From Waste Incinerators by Injection of Hydrated Lime. Proceedings of the Second European Conference on Environmental Technology, Amsterdam, June 22-26,1987; Nijhoff: Amsterdam, 1987; pp 157-164. Walters, J. K.; Daoudi, M. The Removal of Hydrogen Chloride From Hot Gases Using Calcined Limestone. In Management of Hazardous and Toxic Wastes in the Process Industries; Kolaczkowski, S . T., Crittenden, B. D., Eds.; Elsevier: London, 1987; pp 574-583. Weinell, C. E.; Jensen, P. I.; Dam-Johansen, K.; Livbjerg, H. Hydrogen Chloride Reaction with Lime and Limestone: Kinetics and Sorption Capacity. Ind. Eng. Chem. Res. 1992,31, 164. Wen, C. Y. Noncatalytic Heterogeneous Solid Fluid Reaction Models. Ind. Eng. Chem. 1968, 60 (9), 34. White, D. M.; Vancil, M. A. Review of Dry Injection Technology for Reducing Emissions from Municipal Waste Combustors. In Proceedings: 1989International Conference on Municipal Waste Combustion, Volume 4 ; EPA-600/R-92-052& pp 1OC-31 to 1OC45.
Received for review April 27, 1992 Accepted August 10, 1992
Hydroformylation of Propylene Using Unmodified Cobalt Carbonyl Catalyst: Selectivity Studies Raghuraj V. Gholap, Oemer M. Kut, and John R. Bourne* Technisch Chemisches Laboratorium, ETH-Z, CH-8092 Zurich, Switzerland
Isomer distribution and kinetics of the formation of n-butyraldehyde and isobutyraldehyde have been determined for the hydroformylation of propylene using unmodified cobalt carbonyl catalyst. Effects of the propylene and catalyst concentrations and the partial pressures of carbon monoxide and hydrogen on the n/iso ratio as well as on the individual reaction rates have been measured in a temperature range of 383-423 K and a pressure range of 35-100 bar. An empirical rate model describing the intrinsic kinetics for each butyraldehyde has been proposed and ita kinetic parameters evaluated. Such information is useful for the preferential production of n-butyraldehyde.
Introduction It is known that hydroformylation of propylene, in the presence of cobalt carbonyl catalyst, gives a mixture of two isomeric aldehydes namely, isobutyraldehyde and nbutyraldehyde, although, under certain conditions, small amounts of side products are formed. The problem of directing this reaction to give preferential formation of n-butyraldehyde, o w i y to ita greater practical importance, has mainly been mentioned in the patent literature. Little has been reported on how to influence the product distribution of isomeric butyraldehydes (Falbe, 1973; Pino et al., 1977; Pruett, 1979; Cornils, 1980; Weissermel and Arpe, 1988; Piacenti et al., 1991). From the literature data, variations in the ratio of nbutyraldehyde to isobutyraldehydes from 1.6 to 4.4 were observed under widely different conditions of temperature, catalyst concentration, and partial pressures of carbon monoxide and hydrogen. The most influential parameter was found to be the partial pressure of carbon monoxide. The partial pressure of hydrogen has a small but repro-
* Author to whom correspondence should be addressed.
ducible effect on the product distribution. Temperature has a strong influence on the n/iso ratio, and conflicting results have been reported for the effect of catalyst concentration. Despite these invest,igations of the product distributiori in the hydroformylation of propylene, the factors influencing the n-butyraldehydelisobutyraldehyde ratio are still rather obscure (Piacenti et al., 1991). Also, detailed kinetics of these individual reactions is lacking. Therefore, as a first step toward understanding the more complex problem of isomer distribution, the overall kinetics of the hydroformylation of propylene using unmodified cobalt carbonyl catalyst was investigated and modeled (Gholap et al., 1992). In the present work, the objectives were to investigate the effect of proceas variables on the isomer distribution during the hydroformylation of propylene using Co2(CO)8as a catalyst precursor and to determine the individual kinetics of the formation of n-butyraldehyde and isobutyraldehyde. For this purpose, experiments were carried out under different operating variables with unmodified cobalt carbonyl catalyst. The variables included temperature, propylene and catalyst concentrations, and partial pressures of carbon monoxide and hydrogen. On the basis of these
0888-5885/92/ 2631-2446$03.O0/0 0 1992 American Chemical Society
Ind. Eng. Chem. Res., Vol. 31, No. 11, 1992 2447 Table I. Range of Variables Studied in the Present Work 1.46-14.6 catalyst concentration, mol m-3 (0.595-3.57) X lo3 propylene Concentration, mol rnv3 25-75 PH,bar 10-75 Pco,bar 383-423 temperature, K agitation speed, rpm 1500 solvent toluene 1.0 x 10-3 reaction volume, m3
4-
results, two-parameter rate models have been developed for the formation of the individual butyraldehydes.
3-
Experimental Section All the hydroformylation experiments were carried out in an oil-thermostated 2-L-capacity autoclave, with three propeller-type stirrers. 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. The syngas having a H2:C0 ratio of 1:l was supplied to the autoclave in a “dead-end” mode, Le., corresponding to the rate of consumption. Details regarding the experimental setup, the procedure followed, the analysis,and the material used have been reported (Gholap et al., 1992). During the experiments, the deviations from the assigned process conditions were no greater than 2 K for temperature and f 3 bar for pressure. Several experiments were carried out in order to study the effects of propylene and catalyst concentrations, partial pressures of carbon monoxide and hydrogen, and temperature on the product distribution of isomeric butyraldehydes as well as on their rates of formation. The ranges of variables covered in this work are given in Table I. The quantities of n-butyraldehyde and isobutyraldehyde formed were obtained as a function of time and, at the end of each experiment (X,> 95901, the integral n/iso ratio was also determined. Details regarding the reproducibility, material balance, conversion, and induction period observed were given earlier (Gholap et al., 1992). The solubilities of CO and H2in the reaction medium were also obtained from our previous work.
CATALYST CONCENTRATION mol m.3 Figure 2. Effect of catalyst concentration on the n/iso ratio (initial propylene concentration, 1-19x 109 mol m-3;PH,50 bar,Pco,50 bar, agitation speed, 1500 rpm; -A-, 383 K; -0-,403 K;-0-, 423 K).
Results and Discussion Isomer Distribution: n -Butyraldehyde to Isobutyraldehyde Ratio (n/iso). In the experimental range of conditions studied, the major products formed in the hydroformylation of propylene using C O ~ ( C Ocatalyst )~ in toluene were found to be n-butyraldehyde and isobutyraldehyde up to conversion levels over 95% (Gholap et al., 1992). In order to study the selectivity behavior, the formation of these isomeric butyraldehydes was investigated under different operating conditions in the temperature range of 383-423 K. In each case, the final nbutyraldehyde/isobutyraldehyderatio was obtained, and its observed trends with these parameters will now be presented. Effect of Propylene Concentration. The effect of initial propylene concentration on the n/iso ratio was studied by keeping the other reaction conditions constant. The results are shown in Figure 1 for different temperatures. The n/iso ratio was found to decrease with increase in propylene concentration suggesting that, with increasing propylene concentration, the isobutyraldehyde formation increaees faster than that of n-butyraldehyde. It was also observed in an individual run that the n / b ratio gradually increased. This indicates that the propylene dependences of these individual reactions are different, isobutyraldehyde formation having a higher order of propylene
dependence than that for n-butyraldehyde formation. Effect of Catalyst Concentration. Figure 2 shows the effect of catalyst concentration on the n/iso ratio, at a partial pressure of syngas of 100 bar, in the temperature range of 383-423 K. Some conflicting results have been reported in the literature for the effect of cobalt carbonyl catalyst concentration on the n/iso ratio of butyraldehydes. In early work, Hughes and Kirshenbaum (1957) stated that high catalyst concentrations resulted in products containing decreased amount of the n-butyraldehyde. However, later Pino et al. (1977) suggested that the n/iso ratio is virtually unaffected by a change in catalyst concentration. In both these investigations, gently rocked autoclaves were employed, whereas in the present work (Gholap et al., 1992) a high stirrer speed and efficient gas distribution were used. The differing observations are probably due to insufficient stirring of the liquid in the earlier investigations which caused a diffusion-controlled concentration of carbon monoxide in the liquid phase, In the present work, the a/iso ratio was found to increase with increase in catalyst concentration as shown in Figure 2. This important aspect has been observed for the first time for this system. A poseible explanation is that the experiments were performed so as to make certain that the CO concentration in the liquid phase was not influ-
I
24 0
1
2
3
4
PROPYLENECONCENTRATION x mol m-3 Figure 1. Effect of propylene concentration on the n/iso ratio (catalyst concentration, 2.92 mol m-3;PH,50 bar; PCO,50 bar; agitation speed, 1500 rpm; -A-, 383 K;-0-,403 K; -0-, 423 K).
;i
3-1
2
I 0
5
10
E
20
2448 Ind. Eng. Chem. Res., Vol. 31,No. 11,1992
I
a,
0
40
1 ex,
Bo
CO PARTIAL PRESSURE,bar
Figure 3. Effect of partial pressure of CO on the n/iso ratio (catalyst concentration, 7.30 mol m-3; PH,25 bar; agitation speed, 1500 rpm; initial propylene concentration, 1.19 x 109 mol m-3; -A-, 383 K.; -0-, 403 K; 0-,423 K). = I
0
.8 1
1
15)
2
I
05)
I
:9
3-
!
.
Figure 5. Effect of catalyst concentration on the rates RN and Rw, (initial propylene concentration, 1.19 x Iol mol m-3; PH,5O bar,Pm, 50 bar; agitation speed, 1500 rpm; -A-, 383 K; -0-,403 K; 0-,423 K; -, fitted).
01
00
Figure 6. Effect of propylene concentration on the rates RN and (catalyst concentration, 2.92 mol m-3; PH,50 bar; Pco,50 bar; agitation speed, 1500 rpm; -A-, 383 K, -0-,403 K; -0-, 423 K; -, fitted).
1
0
a3
40
Bo
ex,
100
HYDROGEN PARTLAL PRESSURE,bar
Figure 4. Effect of hydrogen partial pressure on the n/iso ratio (catalyst concentration, 7.30 mol m"; Pco, 25 bar; agitation speed, 1500 rpm; initial propylene concentration, 1.19 x 109 mol m-3; -A-, 383 K;-0-,403 K;-0-, 423 K).
enced by the rate of CO absorption. The reactor used in this work was a specially agitated autoclave with intensive mixing, and the liquid phase was almost saturated with carbon monoxide and hydrogen, under all reaction conditions studied (Gholap et al., 1992). Effect of the Partial Pressure of CO (Pco). The effect of Pco on the n/iso ratio was studied at a constant partial pressure of hydrogen of 25 bar. The data are shown in Figure 3 for all the temperatures studied. It is observed that the n/iso ratio increases with increase in Pco. This has already been explained on the basis of a mechanism given in the literature (Cornils, 1980),according to which a 5-fold coordinated species, HCO(CO)~, should be more stable at higher CO partial pressures as well as being responsible for the formation of n-butyraldehyde. Effect of the Partial Pressure of Hydrogen (pH).The effect of hydrogen partial pressure on the n/iso ratio was investigated at a constant CO pressure of 25 atm, and the resulb are shown in Figure 4, at various temperatures. The partial pressure of hydrogen has a reproducible effect on isomer distribution. The higher PHgave higher percentages of n-butyraldehyde. This observation is consistent with the literature studies (Cornils, 1980). Effect of the Temperature. All results showed that the n-butyraldehydelisobutyraldehyde ratio depends upon
co PARIW plx.wm,bnr
co PARIW FTlL?mw,bnr
Figure 7. Effect of partial pressure of CO on the rates RN and RBO (catalyst concentration, 7.30 mol m-3; PH,25 bar; agitation speed, ~ 5 0 0rpm; initial propylene concentration, 1.19 x 109 mol m-3; -A-, 383 K;-0-,403 K;-0-, 423 K;--, fitted).
operating conditions. Low temperatures favor higher percentages of the n-butyraldehyde, indicating a higher activation energy for isobutyraldehyde formation. The results demonstrating this point are shown in Figures 1-4. The decrease of n/iso ratio with increase in temperature observed in the present work is consistent with literature studies (Pino et al., 1977). Formation of the Individual Butyraldehydes. Kinetic studies on the formation of n-butyraldehyde and isobutyraldehyde were also performed under the operating conditions given in Table I. In all experiments, the amounts of n-butyraldehydeand isobutyraldehyde formed, measured by gas chromatographic (GC)analysis,at various times were obtained, from which the initial rates were calculated. The following trends representing the individual kinetics were observed.
Ind. Eng. Chem. Res., Vol. 31, No. 11,1992 2449 Table 111. Rate Parameters temp, 10'kN, (m3 109Km, K mo1-1)2.17 g-l m3 mol-'
383 403 423
2.01 6.20 9.13
8.014 7.260 6.712
I@K~~,
107km, (m3 mol-1)1.w 8-1 2.12 9.50 29.0
m3 mol-' 1.36 1.60 1.76
15-
. a io3 120 o a 1 o m a i o o 1 2 0 Iirmocm,k PARRALPmam OF", be2 Figure 8. Effect of hydrogen partial pressure on the rates RN and Rm (catalyst concentration, 7.30 mol m-3; Pco, 26 bar; agitation speed,1500 rpm; initial propylene concentration, 1.19 x 109 mol m-3; -A-, 383 K, -0-, 403 K;-0-, 423 K -, fitted). n
a0
4
m
PABluLRB(wIIB OF
Table 11. Different Rate Models Propored for I -Butyraldehyde and Isobutyraldehyde FormationD k;A*B*CD
1
Ri
2
R; =
3
Ob
1.0
0.5
ElmluxmALRAl€B,md ma,
.'
1.5
ExPEmmTALR AW d . 4
1.'
Figure 9. Plot of fitted versua experimental rate values.
(1 + K,BB*)2 k;(A*)'"B*(C)"D
(1 + K,BB*12
kj(A+)"B*(C)"(D)P
Ri =
4
Ri =
6
R; =
(1
+ K@*)2 kiA*B*CD
(1 + K;,A*
+ K;& +
0
E
1 P
k
+ z
s
k;A*B*CD ( 1 + &A*
+ KjcC)(1 + K,&*)2
'A* = P&, mol m-3; B* = Pc&,, mol m-3; C = concentration of the catalyst precursor, mol m-3; D = concentration of propylene, mol m-*; i = either N or ISO.
Figurea 5-8 present the effects of catalyst concentration, propylene concentration, and partial pressures of carbon monoxide and hydrogen on the rates of formation of nbutyraldehyde (RN) and isobutyraldehyde (RBO) over a temperature range of 383-423 K. The experimental rates, RN and RBO,were found to increase with increase in catalyst concentration, propylene concentration, and partial pressure of hydrogen, but they showed a maximum with partial pressure of CO and decreased with further increase in PCO. Thew observations are similar to those for the overall rate of hydroformylation of propylene and can be explained in a similar way (Gholap et al., 1992). In order to develop suitable rate equations for RN and RIM representing the intrinsic kinetics, several empirical rate equations, which are consistent with the observed trends, were considered. Some of these various forms are presented in Table 11. The rate parameters were evaluated for each model as well as for each case, using a well-known optimization technique (Marquardt method). From the predictability of the rate models and the values of the 4- (the minLnizedsum of squarea of the differences between the observed and fitted rates), the following two rate models for RN and RIso were found to fit the results satisfactorily. &N(A*)O.SSB* (C)O.7600.87 RN = (1) (1 + KNBB*)2
0
2
I
0WRATE.R
mdm'38'1
0
1
OVWALLRAIF,R
Figure 10. Plot of R VB (RN + Rm)for the experimental and fitted values.
The rate parameters for the above equations were evaluated at different temperatures and are presented in Table 111. The experimental rates, RN and REO, were compared with those given by the above equations in Figure 9. This comparison shows a reasonably good fit of the data with a standard deviation of 8%. Concerning parametric sensitivity of the above equations kN and kBo were linearly related with RN and R W , respectively, while KNBand KmB were approximately inversely proportional to the square root of their respective rates. It is intereating to note that, under identical experimental conditions, the overall rate of hydroformylation of propylene (R)is within experimental error equal to the s u m of the rates of formation of n-butyraldehyde and isobutyraldehyde (& + Rm). The values of the overall rates of hydroformylation of propylene were obtained from our previous work, and the plots of (RN+ R m ) versus R for experimental as well as fitted rates are shown in Figure 10. This comparison indicates that the formation of individual butyraldehydes is a parallel but still a complex reaction, as suggested by a mechanism given in the literature (Cornils, 1980). The overall rates were observed from the syngas absorption (Gholap et al., 1992) whereas the individual rates of formation of butyraldehydes were calculated by product analysis (GCanalysis), 80 that the above comparison provea the experimental accuracy by both the methods used in our work. Also, the individual trends observed for different operating conditions were found to be in good agreement with the predictions of the above equations, as shown by the calculated solid curves in Figures 5-8. An Arrhenius plot showing the temperature dependence of the reaction
2
2480 Ind. Eng. Chem. Res., Vol. 31, No. 11, 1992
tion of n-butyraldehyde production by hydroformylation of propylene.
10
1
Nomenclature A* = concentration of H2in toluene at the gas-liquid interface, mol m-3 B* = concentration of CO in toluene at the gas-liquid interface, mol m-3 C = concentration of the catalyst precursor, mol m-3 D = concentration of propylene, mol m-3 HA= Henry's law constant for HP-toluene system, mol m-3 bar-' HB = Henry's law constant for CO-toluene system, mol m-3 bar-' kN = intrinsic rate constant for n-butyraldehyde formation,
1 P
Y
10-6
I 10 - I 0.0023
0.0024
0.0025
0.0026
0.0027
1 / T , K"
Figure 1 1 . Arrhenius plot for k~ and kIso (-+,
(m3 m01-1)2.17 s-l
k s o = intrinsic rate constant for isobutyraldehydeformation, (m3 m01-1)1.94
k N ; -0-, kIso).
rate constants, kN and kBO, is given in Figure 11,and the activation energies for the formation of n-butyraldehyde and bobutyraldehyde were found to be 54 and 82 kJ mol-l, respectively. The other rate parameters (K- and are only weakly temperature dependent (Table 111).
Conclusions The selectivity behavior and kinetic modeling for the formation of isomeric butyraldehydes have been studied in the hydroformylation of propylene using the homogeneous C O ~ ( C Ocatalyst )~ precursor. The effects of various operating parameters on the n/iso ratio and the formation rates of n-butyraldehyde and isobutyraldehyde have been investigated in a temperature range of 383-423 K. The n/bo ratio was found to increase with increases in catalyst concentration and in the partial pressures of carbon monoxide and hydrogen, but decreased with increase in propylene concentration. The maximum integral n/iso ratio measured over the range of experimental conditions used (Table I) was 4.2. The rates RN and RIS0 showed a fractional order of dependence with respect to catalyst concentration and partial pressure of hydrogen, but a complex dependence on the partial pressure of carbon monoxide showing substrate-inhibited kinetics at higher CO pressures. The rate RIsO was found to be linearly dependent on propylene concentration, whereas RNshowed a slightly weaker dependence. Several empirical rate equations were evaluated, and two rate models, one for each aldehyde, were developed. The comparison between the fittad and experimental rates showed a reasonably good fit, and kinetic parameters were evaluated a t the three temperatures studied. The overall rate of hydroformylation of propylene was found to be almost equal to the sum of the rates of formation of n-butyraldehyde and bobutyraldehyde under identical experimental conditione. The activation energies for the n-butyraldehyde and isobutyraldehyde formation were 54 and 82 kJ mol-', respectively. This study should be useful for the optimiza-
s-l
KA = constant in Table 111, m3 mol-' KNB = constant in eq 1, m3 mol-' KIsoB= constant in eq 2, m3 mol-' Kc = constant in Table 11, m3 mol-' m = constant in Table I1 n = constant in Table I1 p = constant in Table I1 PH= partial pressure of hydrogen, bar Pc0 = partial pressure of CO, bar R = initial rate of hydroformylation, mol m-3 s-l R N = initial rate of n-butyraldehyde formation, mol m-3 RWo = initial rate of isobutyraldehyde formation, mol rnS s-l 5" = reaction temperature, K XA= conversion of propylene
Literature Cited Corn&, B. Hydroformylation oxo synthesis, Roelen reaction. In New synthesis with carbon monoxide; Falbe, J., Ed.; Springer-Verlag: New York, 1980;Vol. 11, Chapter 1. Falbe J. Hydroformylation (OXO-process). In Propylene and its industrial derivatives; Hancock, E. G., Ed.; Ernest Benn: London, 1973;Chapter 9. Gholap, R. V.; Kut, 0. M.; Bourne, J. R. Hydroformylation of propylene using an unmodified cobalt carbonyl catalyst: A kinetic study. Znd. Eng. Chem. Res. 1992,31, 1597-1601. Hughes, V. L.; Kirshenbaum, 1. Isomer distribution in the Oxo reaction. Ind. Eng. Chem. 1957,49, 1999-2003. Piacenti, F.; Bianchi, M.; Frediani, P.; Menchi, G.; Matteoli, U. Hydroformylation of olefins in the presence of dicobalt octacarbonyl: some considerations. J. Organomet. Chem. 1991,417, 17-88. Pino, P.; Piacenti, F.; Bianchi, M. Reactions of carbon monoxide and hydrogen with olefinic substrates: The hydroformylation (OXO) reaction. In Organic synthesis via metal carbonyls; Wender, I., Pino, P., Eds.; Wiley: New York, 1977;Vol. 11, Chapter 2. Pruett, R. L. Hydroformylation. Adv. Organomet. Chem. 1979,17, 1-60. Weissermel, K.; Arpe, J. Zndustrielle Organische Chemie, 3rd ed.; Verlag-Chemie: Weinheim, 1988.
Received for review March 30, 1992 Revised manuscript received June 29, 1992 Accepted August 4,1992
