Acknowledgment
We appreciate the valued assistance of N. G. McDuffie, H. Steinfink, and G. W. Watt in interpreting and critically examining certain aspects of the experimental data. The Robert L. Stone Division, Tracor, Inc., performed the DTA. J. R. Holmes did the illustrations. literature Cited
Applequist, J., Doty, P., “Polyamino Acids, Polypeptides, Proteins,” Proceedings of International Symposium, Madison, Wis., 1961, pp. 161-76, 1962. Bond, G. C., “Catalysis by Metals,” pp. 2, 409, Academic Press, New York, 1962. Boynton, G. W., Ph.D. dissertation, University of Texas a t Austin, August 1967. Chen, N. Y., Weisz, P. B., Chem. E w . P w r . Sump. Ser. 63, No. 73, 86 (1967). Cotton, F. A., Wilkinson, G., “Advanced Inorganic Chemistry,” pp. 753, 522, Interscience, New York, 1962.
Florkin, M., Stotz, E. H., “Comprehensive Biochemistry,” Vol. 12, p. 1, 158, 170, 187, 236, Elsevier, New York, 1964. Hall, J. Rase, H. F., I N D . ENG.CHEw FUNDAMENTALS 3,
2,
158 (1964).
LawsoIl, K. E., Spectrochim. Acta 17, 249 (1961). Low, B., “Chemical Basis of Heredity,” Johns Hopkins University, McCollum-Pratt Institute, Contrib. 163, 574 (1957). Mair, B. J., Shamaiengar, M., Anal. Chenz. 30, 276 (1958). Moriguchi, Y., Miura, M., Bull. Chenz. SOC. Japan 38, 4, 678 ,,ncc\
(1YUJ).
Morrison, R. T. Boyd, R. N., “Organic Chemistry,” p. 873, Allyn and Bacon, Boston, 1959. Powell, D. B., Sheppard, N., J. Chenz. SOC.1961, 1114. Rich, A,, “Biophysical Science-A Study Program,” J. L. Oncley, F. 0. Schmitt, R . C. Williams, M. D. Rosenberg, and R . H. Bolt, eds., p. 60, Wiley, New York, 1959. Weisz, P. B., Frillette, V. J., Maatman, R . W., Mower, E. B., J . Catalysis 1, 307 (1962). Wingard, L. B., Finn, R. K., “Development of Industrial Catalysts Based on Enzyme Models,” -4.I.Ch.E. Symposium, Minneapolis, September 1965. cryst. 6, 724 (1953). Yakel, H, L., RECEITED for review May 9, 1968 ACCEPTEDDecember 13, 1968
OLIGOMERIZATION OF 1-BUTENE I N SULFURIC ACID Mechanisms and Rates J . S.
NAWORSKI’ AND PETER HARRIOTT
Cornell University, Zthaca, N . Y The oligomerizstion of liquid 1 -butene catalyzed by concentrated sulfuric acid was studied in an adiabatic, capillary-flow reactor at 17.5” and 2 5 ” C. The reaction products were analyzed by gas-liquid chromatography. The maior products were 5-methyl-2-heptene, 5-methyl- 1 -heptene, 2,2-dimethyl-3-hexene, and 5-methyl-3-heptene. Butene cgnsumption rates were calculated from axial temperature profiles measured by thermistors. The reaction rates per unit area of the butene drops were 0.98 X lod3 g. mole/ g. mole/(min.)(sq. cm.) at 25” C. Based on the theory for (min.)(sq. cm.) at 17.5” C. and 1.07 X simultaneous diffusion and reaction, a first-order rate constant for butene consumption was estimated to be 3.4 X l o 4sec.-l at 2 5 ” C.
LTHOUGH the sulfuric acid-catalyzed alkylation of iso-
A butane with butenes has been a n important commercial
process since the late 1930’s, the fundamental chemistry of the process is still not completely understood. This is not surprising when one considers the high number of possible reaction steps, the complexity of the product mixture, and the fact that the reaction takes place in a two-phase system. The reaction mechanism proposed by Schmerling (1953) explains the formation of the major products satisfactorily. Recent research has been directed at explaining secondary productsparticularly the dimethylhexanes and the high and low boiling fractions. Hofmann and Schreisheim (1962) radioactively labeled the butene and then measured the radioactivity of each reaction product. They concluded that fragments smaller than CS were derived from a C12 intermediate formed primarily from two molecules of isobutane and one molecule of olefin. Zimmerman et al. (1962) studied the effect of the three butene isomers on product composition. They were particularly interested in dimethylhexane formation and postulated that Present address, Virginia Polytechnic Institute, Blacksburg, Va. 24061.
dimethylhexanes resulted mainly from isomerization of trimethylpentyl cations. Mosby and Albright (1966) alkylated isobutane with l-butene at residence times between 15and 60 seconds. They concluded that three reactions were important when alkylatiug with 1-butene: Polymerization, primarily t o the dimer-tetramer range Alkylation of isobutane to form dimethylhexanes Isomerization t o 2-butene Mosby and Albright (1966) concluded that polymerization in alkylation reactions is more important than was previously believed and that trimethylpentanes are produced mainly in the later stages of the reaction. An understanding of butene oligomerization is thus a logical first step toward complete understanding of the alkylation reaction. I n the present study, the sulfuric acid-catalyzed oligomerization of 1-butene is investigated in an adiabatic capillary flow reactor. Reaction times are very short-less than 5 seconds. Product distributions are obtained from chromatographic analyses of quenched samples. Detailed reaction mechanisms, using carbonium ion theory, are proposed t o explain the product distribution. Reaction rates are calculated from the increase in temperature along the length of VOL.
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the reactor. The results of this study are related to results of investigations of the alkylation reaction. This is the first time that a rate study on any segment of the alkylation reaction has been reported. Residence times in all previous studies except Kramer's (1966) exploratory work were greater than 15 seconds, and the butenes were completely converted. Experimental
Figure 1 is a flow diagram of the reaction system. Cylindrical stainless steel reservoirs for the butene and sulfuric acid were submerged in a constant temperature bath controlled to within f0.02' C. The liquid reactants were forced by nitrogen pressure through the regulating valves and rotameters to a mixing block at the bottom of the reactor. Each liquid then passed through two tapered holes, about 0.3 mm. in diameter, in the glass wall of the capillary itself. The butene formed droplets which were carried upward in the larger stream of acid. The main reaction tube was soft-glass capillary tubing (5.5-mm. o d. X 0.82-mm. i.d.). Four glasscoated thermistors were positioned in the center of the capillary a t 6-cm. intervals to measure the axial temperature rise of the reacting stream and permanently sealed in the capillary with Corning solder glass 7570 (Figure 2). A 25-mm. borosilicate glass cylinder surrounded the capillary flow reactor, providing a stagnant air layer for insulation, and protecting the thermistor lead wires from the water of the constant temperature bath. The stream leaving the reactor was directed to either a quench cylinder or a waste collector. The quench cylinder contained a chilled (about 5' C.) saturated sodium sulfate solution to deactivate the acid catalyst. Quench was used only when samples for product distribution studies were desired. A back pressure of 20 to 30 p.s.i.g. was maintained on the system to prevent hydrocarbon vaporization. After the experimental run was completed, the organic material was extracted from the sodium sulfate with high purity pentane and stored over calcium chloride for analysis by gasliquid chromatography. The range of the variables for the kinetic runs were:
butene flow rate, 0.0015 to 0.0079 g. mole/min.; acid flow rate, 0.028 to 0.166 g. mole/min.; temperature 17.5' and 25' C. The ratio of moles of butene to moles of butene plus acid a t the reactor inlet varied from 0.0128 to 0.0612. Residence times a t the thermistors ranged from 0.86 to 3.10 seconds. Total residence times were estimated to be between 4 and 10 seconds before quenching stopped the reactions. The 1-butene had a minimum purity of 99.0% and the fresh sulfuric acid strength ranged from 95.8 to 97.4y0 titratable acid. Analytical. The reaction products were analyzed with a Perkin-Elmer Model 154 chromatograph. The 5-mm. X %foot column was packed with 60/80-mesh GC (a special Perkin-Elmer solid support material) , coated with DowCorning silicone oil No. 200 (dimethylsiloxane polymer). Helium was the carrier gas, and detection was by means of a thermal conductivity cell. Other chromatographic parameters were: temperature, 88' C.; column inlet pressure, 30 p.s.i.g.; detector voltage, 8 volts; sample injection size, 5 111. Product peaks were identified by comparing their elution distances with elution distances of high purity olefinic and paraffinic samples. The boiling point of an unknown peak was predictable from its elution distance to within f 0 . 5 ' C. Normalized per cent of peak area was used to calculate the weight fraction of each component as recommended by Rosie and Grob (1957).
Determination of Butene Drop Size. Butene drops were photographed as they passed an observation point about 50 cm. downstream from the mixer outlet. The average drop diameter measured at six sets of experimental conditions was 0.233 f 0.030 mm. (1-sigma limits). Typical butene conversions a t this observation point were about 50%. Assuming that the reaction takes place in the acid phase (Albright, 1966; Jernigan et al., 1965), that the reaction products remain in the acid phase and that there is negligible drop coalescence, the drop size would decrease as the drop travels through the reaction tube. The average drop diameter for the entire reactor length was back-calculated to be 0.266 mm. Drop diameter varied little with acid flow rate, butene flow rate, or reaction temperature. The drop size estimation was considered good enough, especially in view of other uncertainties. Results
Product Identification and Interpretation. Polymerization samples were obtained from a variety of reactor conditions, but the product distribution was insensitive to both relative flow rate and reaction temperature. The major product in all cases was 5-methyl-2-heptene. The results of the product identification work are summarized in Table I. The carbonium ion theory of Whitmore (1934) has been applied to acid-catalyzed olefin oligomerization by Schmerling and Ipatieff (1950), Langlois (1953), Oblad et al. (1958), and McMahon et al. (1963). The rules for carbonium ion
Figure 1.
Flow diagram of reactor system THERMISTOR AND
LEAD WIRE
CAPILLARY GLASS TU8lNG
8UTENE
I
I
Figure 2. 398
l&EC
Reactant inlet of capillary reactor
FUNDAMENTALS
Summary of Product Analyses % of Product Component Peak Area Low boilers 11 Unidentified C, 9 2,2-Dimethyl-3-hexene 11 &Methyl-3-heptene 6 &Methyl-1-heptene 11 5-Methyl-2-heptene 22 Unidentified CB'S(4peaks)" 10 20 High boilers (in CB-C12 range) Table 1.
a Demonstrated to be neither dimethylhexenes nor trimethylgentenes.
behavior-by now well formulated-are used to explain the formation of the reaction products of this study. The development of the proposed reaction mechanism and an exhaustive elimination of competing mechanisms are discussed by Naworski (1966). The following reaction sequence is proposed for the formation of the methylheptenes: 1. Proton addition to 1-butene to form the initial carbonium ion. The sec-butyl cation is formed.
+
c-c-e-c
(1) 2. The addition reaction of the sec-butyl cation to 1-butene to form a CS cation. C
+
C-c-c-c+c=C-c-c-+C-c-c-c-c-c-C
I
+
(2 1 3. Isomerization of the CScation by hydride rearrangement. The most important isomer is C
+
1
(3)
CC-c-C-C-c-c Another likely isomer is
c I
+
c-e-c-e-C-e-C
(4)
The major reaction product, 5-methyl-2-heptene, can be formed via proton elimination from either Cs cation 2 or 3; 5-methyl-1-heptene is formed via proton elimination from cation 3 ; and 5-methyl-3-heptene can be formed from either ion 2 or 4. Carbonium ion 4 is probably of minor importance since 4 would be expected to rearrange to the 3-methyl-3heptyl cation and then yield 3-methyl-2-heptene and -3heptene. Both these methylheptenes were absent from the products. Carbonium ions 3 and 4 are isomers of 2, and 2 is the product of the direct addition of 1-butene and the sec-butyl cation (1). Thus, all the methylheptenes are direct derivatives of a true polymerization reaction step between 1-butene and the sec-butyl cation. 2,2-Dimethy1-3-hexene is formed from the products of the reaction of a tert-butyl cation with 1-butene:
c + c-c-e-e-e-c
+
c-e-c I C
+ c=c-c-c
P \
;:+
C-C-C-'2-C-C
I
(5)
(6)
c Both ions 5 and 6 are capable of producing 2,2dimethyl-3hexene by proton expulsion. Cation 5 is probably the major contributor to 2,2-dimethyl-3-hexene formation, since some 2,3-dimethylhexenes would be expected from cation 6 (Schmerling and Ipatieff, 1950). The tert-butyl cation necessary for the preceding reaction could possibly be formed by isomerization of the sec-butyl cation or protonation of isobutylene. Evidence that little
isobutylene was present is the absence of any 2,4-dimethylhexene, the product expected from reaction of isobutylene with the dominant cation, the sec-butyl cation. Hence it is postulated that the tert-butyl cation, necessary for dimethylhexene formation, is derived from isomerization of the secbutyl cation. Absence of 3,4dimethylhexenes indicates that very little 2-butene is present in the reaction mixture. Since neither molecular 2-butene nor isobutylene participated in the reaction mechanisms for methylheptene or dimethylhexene formation, isomerization of the molecular forms of butylene is not rapid compared to the time for carbonium ion isomerization and reaction. Fragments smaller than CS could be formed from the cracking of a Clz cation, as Hofmann and Schreisheim (1962) postulated for the alkylation reaction. The high boilers result from subsequent reactions of the cracked products and oligomerization to the (212 trimer. Reaction Rates from Thermistor Data. In an adiabatic tubular flow reactor, reactant conversion can be calculated by equating the change in the sensible heat of the reactant stream to the heat produced by the chemical reaction. The rate of reaction can be calcu'ated from the temperature rise a t given observation points, the reactant flow rates, the heat capacities of reactants and products, and the heats of reaction. The necessary estimations and approximations are discussed in detail by Naworski (1966). The raw data-temperature rise us. distance from the mixer, for various liquid flow rates-were transformed to fraction of butene converted us. time. Fractional butene conversions varied from 0.127 to 0.696. Using the conversion-time data, average butene consumption rates between the mixer and each of the thermistors were calculated. It was not possible to determine rates between thermistor pairs because of scatter in the thermistor data. In effect, the capillary flow reactor has been treated as four integral reactors. Average rate of butene consumption us. relative molal flow rate of butene (molal flow rate of butene/molal flow rate of butene and acid) is plotted in Figure 3 for 25' C. This plot gives an indication of the experimental error. A least squares regression line of the general form y =
bx
was calculated from the data. An equation of this form was selected to force the regression line through the origin (0, 0 ) , which assumes that: The rate of reaction during drop formation is not significantly different from the rate for completely formed drops. There is no induction period for the reaction. Butene consumption rates a t 25' C. are about 9% greater than a t 17.5' C. The slopes of the average butene consumption rate us. relative butene flow rate plots are 0.314 k 0.031 a t 25' C. and 0.288 =t0.024 a t 17.5' C. (1-sigma limits). The,3e plots are the basis of the kinetic calculations which folk rv. A more meaningful way to express the reaction rate is in terms of the surface area of the butene drops, rather than the reactor volume. This rate would have units of gram moles of butene consumed/min., sq. cm. of butene drop area. A4t 17.5 and 25' C. the rates are: r17.6 r25
= 0.98 X 10-~ g. mole/min., sq. cm. = 1.07
X
g. mole/min., sq. cm.
The speed of the reaction can be appreciated by considering the half life of a butene drop in sulfuric acid. If the drop were VOL.
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o_ X
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but their model can be applied to only a narrow range of systems. The diffusivity of butene in sulfuric acid was estimated by an empirical extension of the data of Gainer and Metzner (1965) to be 4.8 X sq. cm. per second a t 25" C. and 3.5 X lob sq. cm. per second at 17.5' C. These diffusivities could be in error by a factor of 2. The transfer coefficient for mass transfer accompanied by chemical reaction, k,, was calculated using the equation:
Nr= krAAC or k,= Nr/AAC where
N, A
=
rate of butene consumption, g. moles/min., cc.
= area for mass transfer per unit of reactor volume,
sq. cm./cc. A C = butene concentration gradient in the sulfuric acid, g. moles/cc.
a
The A C term requires further clarification.
A C = Ci - Ce w
where
e t 3
Ci = butene concentration in the acid a t the acid-butene interface CB = butene concentration in the bulk of the acid .01
.02
-03
.04
Since CB is essentially zero, we have:
RELATIVE MOLAL FLOW RATE OF BUTENE
Figure 3. Average butene consumption rate as a function of relative butene flow rate Pure butene feed Temperature 25' F. Relative molal flow rate of butene Molal flow rate of butene Molal flow rate of butene and acid
initially 0.30 mm. in diameter, half of the butene would be consumed in 3.7 seconds a t 25' C. Kinetic Rate Constants. The oligomerization of 1butene is a process of simultaneous mass transfer and reaction in the acid phase. The rapid reaction makes the mass transfer much faster than physical mass transfer for the same concentration driving force. Rate constants in systems such as this can be determined by methods which take into account the enhancement of the mass transfer coefficient (Gilliland et al., 1958; Huang and Kuo, 1963). These methods require estimates of the mass transfer rate in the absence of chemical reaction (the physical mass transfer rate), the molecular diffusivity of butene in sulfuric acid, the solubility of butene in sulfuric ac'd, and the butene drop size. Rate constants for the disappearance of butene were calculated using these methods and assuming that the reaction takes place in the acid phase and is pseudo-first-order. Although the chemical rate constant cannot be calculated exactly because of many uncertainties, the determination of an approximate rate constant should be helpful in the analysis of mechanisms for the alkylation reaction. Predictions of molecular diffusivities of dilute solutes in viscous solvents are subject to large errors. Equations such as the Wilke-Chang (1955) equation are fairly accurate a t solvent viscosities of about 1 centipoise but do not give even good approximations if the viscosity is greater than about 5 centipoises. Gainer and Metzner (1965) formulated a reasonably successful model for solvents with high viscosities, 400
l&EC
FUNDAMENTALS
A C = Ci
ci equals the solubility of butene in sulfuric acid. The solubility of butene in sulfuric acid cannot be measured, since the acid catalyzes butene reactions which cause more butene to transferred to the acid phase than if no reactions were present. The butene solubility was assumed to be 0.10% by weight, which is actually the solubility of isobutane in 99.5y0 sulfuric acid a t 50" F. (Cupit et al., 1962). With this assumption, k, can be calculated. The coefficient for physical mass transfer, k,, was calculated using the Tsubouchi-Masuda (1964) modification of the Ranz-Marshall (1952) equation for rigid spheres: NSh =
2
+ 0.56N~.'/'Nsd'~
where Nsh = Sherwood number, k,dd/DBA k, = physical mass transfer coefficient, cm./sec. dd = drop diameter, cm. DBA = molecular diffusivity of butene in sulfuric acid, sq. cm./sec. NR= ~ Reynolds number Nsc = Schmidt number, C(A/PADAB C(A = acid viscosity, g./cm. sec. PA = acid density, g./cc.
It is assumed that drop circulation i s negligible. The effect of drop circulation would be to increase k , over the value calculated. No error is introduced here, since the value of k,/k, is large enough (50 to 100) to make the rate constant independent of k,. Both Gilliland et al. (1958) and Huang and Kuo (1963) show that for k,/kp greater than 4
or
k,2
kl = DBA
where kl = first-order rate constant for disappearance of
butene, sec-l. The calculated rate constants are presented in Table 11. The best estimate of the first-order rate constant for the oligomerization of 1-butene a t 25' C. is 3.4 X lo4sec.-l. The slightly higher rate constant a t 17.5' C. is probably a result of errors in DBA or C;. The rate constant a t 25' C. could be off by as much as a factor of 8. As more accurate diffusivity and solubility data become available, the uncertainty in the rate constants will correspondingly diminish. The rate constants probably depend on the acid strength, although there was no significant effect of batch to batch variation between 95.8 and 97.4'% acid. In alkylation plants, the acid accumulfites soluble hydrocarbons as well as water, and the effects of both diluents should be investigated for 90 to 98% acid. Experimental Runs with a Diluted Feed. A few reactions were conducted using a feed of 50 volume yo 1-butene and 50 volume yo n-butane. The unreactive n-butane diluted the concentration of 1-butene in the organic phase. Butene consumption rates for this series of runs are plotted in Figure 4, where each point is an average of data from three
Table II. Estimation of Homogeneous Rate Constant for Oligomerization of 1-Butene in Sulfuric Acid 17.5'C.
Surface reaction rate, g. mole/min., 0.98 X l O P
250
c
1.07 X 10W
sq. cm.
Estimate of D, sq. cm./sec. Estimate of C;, g. mole/cc. Calculated k l , sec.-l
3.5 X 0.0333 4 . 0 x 104
4 . 8 X 10P 0.0333 3 . 4 x 104
n
P X
I
!I
I
I
I
I
I
thermistor pairs for one experimental run. The least squares line of Figure 3 is plotted for comparison. Butene consumption rates for the diluted feed were about 37% of those for the pure feed when the butene feed rates were the same. These data indicate an effective reaction order greater than 1.0, but further tests are needed for confirmation. Application to Alkylation. Combination of the rate data with the product identification work provides detailed information applicable to the initial stages of the alkylation reaction. No previous quantitative measure of the speed of the alkylation reaction has been reported, although the reaction has been assumed to occur rapidly (Albright, 1966; Hofmann and Schreisheini, 1962; Jernigan et al., 1965; Mosby, 1964). The rate measurements support the findings of some earlier investigators. Although Mosby (1964) did not specifically measure rates, he observed in the alkylation of isobutane with 1-butene that essentially all of the butene reacted when the residence times were 15 to 60 seconds. He concluded that butene polymerizatjon mas significant a t these reaction times. When Kramer (1966) mixed butene and isobutane with fresh acid in a rapid mixing tee, he observed complete conversion of the olefin but little production of saturated hydrocarbons. His reaction time was between 1 and 10 seconds. During the alkylation of isobutane with butenes more dimethylhexane is formed with 1-butene than with 2-butene (Zimmerman et al., 1962). The dimethylhexanes are formed by the reaction of 1-butene and the tert-butyl cation which is the major C b carbonium ion present. This conclusion can be inferred from the present study where most of the 1-butene reacted with the sec-butyl cation much faster than it isomerized to 2-butene. Thus the relatively slow isomerization of 1-butene to 2-butene can explain some differences in the chemical behavior of the two isomers. literature Cited
Albright, L. F., Chem. En$.73 (14), 119-26 (1966). Cupit, C. R., Gwyn, J. E., Jernigan, E. E., Petro-C'hem. Eng.
;I
33 (13) (1961); 34 (1) (1962).
I0
Gainer, J. L., Metzner, A. B., A. I. Ch. E..-Chem. E. Symp. Ser. No. 6-Transport Phenomena, 74 (1965). Gilliland, E. R., Baddour, R. F., Brian, P. L. T., A.Z.Ch.E. J. 4,
v V
223 (1958).
Hofmann, J. E., Schreisheim, A., J . Am. Chem. SOC. 84, 957 (1962).
Huang, C. J., Kuo, C. H., A.I.Ch.E. J . 9, 161 (1963). Jernigan, E. C., Gwyn, J. E., Claridge, E. L., Preprint l l d , 56th Sational A.1.Ch.E. Meeting, San Francisco, ?\.lay 1965. Kramer, G. M., personal correspondence, 1966. Langlois, G. E., Ind. Eng. Chem. 46, 1470 (1953). McMahon, J. F., Bednars, C., Solomon, E., Advan. Petrol. Chem. Refining 7, 284-320 (1963). Mosby, J. F., Ph.D. thesis, Purdue University, Layfayette, lnd., 1964. Mosby, J. F., Albright, L. F., Ind. E7q. Chenz. Prod. Res. Develop. 6 , 183-90 (1966). Naworski, J. S., Ph.D. thesis, Cornel1 University, Ithaca, N. Y., DILUTED FEED
1966
Oblad, A. G., Mills, G. A,, Heinemann, H., Catalysis 6, 341-406 (1958).
m
Rana, W. E., Marshall, W. R., Cheni. Eng. Progr. 48, 173-80
W
(1952).
.01 .02 -03 .04 RELATIVE MOLAL FLOW RATE OF BUTENE
Figure 4. Summary curve for average butene consumption rate as a function of relative butene flow rate
Rosie, D. M., Grob, R. L., Anal. Chem. 29, 1263 (1957). Schmerling, L., Ind. Eng. Chem. 46, 1447 (1953). Schmerling, L., Ipatieff, V. N., Advan. Catalysis 2, 21-81 (1950). Tsubouchi, T., Masuda, H., Repts. Inst. High Speed Mechanics 16, 119-35 (1964).
Whitmore, F. C., Znd. Eng. Chem. 26, 94 (1934). Wilke, C. R., Chang, P., A.I.Ch.E. J. 1, 264-70 (1955). Zimmerman, C. A,, Kelley, J. T., Dean, J. C., Znd. Eng. Chem. Process Design Develop. 1, 124 (1962).
Diluted butene f e e d Temperature 25' C.
RECEIVED for review January 29, 1968 ACCEPTED January 10, 1969
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