I n d . Eng. Chem. Res. 1990,29, 1546-1549
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Loughlin, K. F.; Ruthven, D. M. A Generalized Correlation of Equilibrium Data for the Sorption of Light Paraffins in Linde 5A Zeolite. J. Colloid Interfacial Sci. 1972, 30(2), 331-338. Loughlin, K. F.; Holborow, K. A,; Ruthven, D. M. Multicomponent Sorption Equilibria of Light Hydrocarbons in 5A Zeoltie. AIChE Symp. Ser. 1975, 71(152), 24-29. Mathews, A. P.; Weber, W. J., Jr. Mathematical Modeling of Adsorption in Multicomponent Systems; Flank, W. H., Ed.; Advances in Chemistry Series 135; American Chemical Society: Washington, DC, 1980; pp 27-53. Miller, G. W. Adsorption of Nitrogen, Oxygen, Argon and Ternary Mixtures of these Gases in 13X Molecular Sieves. AIChE Symp. Ser. 1987, 83(259), 28-39. Myers, A. L. Personal Communication, 1989. O’Brien, J. A,; Myers, A. L. A Comprehensive Technique for Equilibrium Calculations in Adsorbed Mixtures: The Generalized FastIAS Method. Ind. Eng. Chem. Res. 1988, 27, 2085-2092. Prausnitz, J. M.; Shair, F. H. A Thermodynamic Correlation of Gas Solubilities. AZChE J. 1961, 7, 682-687. Richards, E. R.; Stroud, H. J. F.; Parsonage, N. G. Thermodynamic Study of the Linde Sieve 5A + Ethane System. J. Chem. Soc., Faraday Trans. 1 1976, 72, 1759-1769. Rolniak, P. Sorption of Methane and Methane-Carbon Dioxide Mixtures on a 5A and 13X Molecular Sieves a t High Pressures and Ambient Temperatures Determined by Elution Chromatography. Ph.D. Dissertation, Rice University, Houston, 1976. Rolniak, P.; Kobayashi, R. Analysis of Methane and Several Mixtures of Methane and Carbon Dioxide a t Elevated Pressures a t near Ambient Temperatures on 5A and 13X Molecular Sieves by Tracer Perturbation Chromatography. AIChE J . 1980, 26(4), 616-624. Ruthven, D. M., Simple Theoretical Adsorption Isotherm for Zeolites. Nature Phys. Sci. 1970, 232,70-72. Ruthven, D. M. Principles of Adsorption and Adsorptive Separative Processes; Wiley-Interscience: New York, 1984. Ruthven, D. M. Sorption of Oxygen, Nitrogen, Carbon Monoxide, Methane and Binary Mixtures of These Gases in 5A Zeolite. AIChE J . 1976,22(4), 753-760. Ruthven, D. M.; Kumar, R. An Experimental Study of Single Component and Binary Adsorption Equilibria by a Chromatographic Method. Ind. Eng. Chem. Fundam. 1980, 19, 27-32. Ruthven, D. M.; Loughlin, K. F. Sorption of Light Paraffins in Type A Zeolites: Analysis and Interpretation of Equilibrium Isotherms. J . Chem. SOC.,Faraday Trans. 1 , 1972,68,696-708. Ruthven, D. M.; Wong, F. Generalized Statistical Model for the Prediction of Binary Adsorption Equilibria in Zeolites. Ind. Eng. Chem. Fundam. 1985,24,27-32. Ruthven, D. M.; Loughlin, K. F.; Derrah, R. I. Sorption and Diffusion of Light Hydrocarbons and other Simple Nonpolar Mole-
cules rn Type A Zeolite; Meier, W. H., Uytterhoeven, J. B., Eds.; Advances in Chemistry Series 121; American Chemical Society: Washington, DC, 1973a, pp 330-344. Ruthven, D. M.; Loughlin, K. F.; Holborow, K. A. Multicomponent Sorption Equilibria in Molecular Sieve Zeolites. Chem. Eng. SCL. 1973b, 28, 701-709. Rybolt, T. R.; English, K. J. Virial Isotherm Analysis of Methane Adsorption in 5A Zeolite. AlChE J . 1988,34, 1207-1210. Schirmer, W. Results and Perspectives of the Investigation of Hydrocarbon Adsorption in the Central Institute of Physical Chemistry of the Academy of Sciences of the GDR. Workshop Preprints, Adsorption of Hydrocarbons in Zeolites; Academy of Sciences: GDR, 1979; pp 1-14. Schirmer, W.; Fiedrich, G.; Grossman, A.; Stach, H. Adsorption Behavior of Pure and Mixed n-Alkanes of Medium Chain Length on Zeolites. Molecular Sieves; SOC.Chem. Ind.: London, 1968. Schirmer, W.; Meinert, G.; Grossman, A. Structurally Specific Influences on the Adsorption of Hydrocarbons and Alkylamines on Zeolite 5A. Monatsber. Dtsch. Akad. Wiss. Berlin 1969, 11. 886-900. Singhal, A. K. Multicomponent Sorption Equilibria of Hydrocarbon Mixtures in Zeolitic Molecular Sieves. AIChE Symp. Ser. 1978, 74(179), 36-41. Stach, H.; Thamm, H.; Fiedler, K.; Schirmer, W. Contribution to the Thermodynamics of Adsorption of n-Paraffins on NaX Type Zeolite. Workshop Preprints, Adsorption of Hydrocarbons in Zeolites; Academy of Sciences: GDR, 1979; pp 85-93. Stroud, H. F. J.; Richards, E; Parsonage, N. G. Thermodynamic Study of the Linde Sieve 5A + Methane System. Advances in Chemistry Series 102; American Chemical Society: Washington, DC, 1971. Suwanayuen, S.; Danner, R. P., A Gas Adsorption Isotherm Equation Based on the Vacancy Solution Theory. AIChE J . 1980. 26. 68-83. Valenzuela, D. P.; Myers, A. L. Adsorption Equilibrium Data Handbook; Prentice Hall: Englewood Cliffs, NJ, 1989. Valderamma, J. 0. Personal communication, 1988. Veyssiere, M.-C.; Cointot, A. Adsorption en phase gazeuse d’hydrocarbures et de leurs Melanges Binaries. Bull. SOC. Chim. Fr. 1975, 5/6, 1071-1075. Yon, C. M.; Turnock, P. H. Multicomponent Adsorption on Molecular Sieves. AIChE Symp. Ser. 1971, 67(117), 75-83. Zuech, J. L.; Hines, A. L.; Sloan, E. D. Methane Adsorption on 5A Molecular Sieve in the Pressure Range 4 to 690 kPa. Ind. Eng. Chem. Process Des. Deu. 1983, 22, 172-174. Receioed for review October 11, 1988 Revised manuscript received July 14, 1989 Accepted August 1, 1989
COMMUNICATIONS Effectiveness Factor in a Three-phase Spinning Basket Reactor: Hydrogenation of Butynediol Two types of spinning basket catalytic reactors were compared by measuring the hydrogenation rates of butynediole with a nickel catalyst. The experiments were performed semibacthwise during variations of rotary speed and catalyst mass. The mass-transfer gas-liquid inhibition was calculated using the measured hydrogen absorption rate, and the liquid-catalyst inhibition transfer was tested by hydrodynamic examinations. The effectiveness factor of the catalyst pellets was determined with the reference reaction rate in a slurry reactor. The results show the annular catalyst basket is more favorable for estimating the effective reaction rate without external mass-transfer inhibitions. Catalytic gas-liquid reaction processes in fixed bed reactors are characterized by the coupling of reaction kinetics, transport processes between the phases and in the 0888-5885/90/2629-1546$02.50/0
catalyst particles, and hydrodynamic effects in the catalyst bed. Reaction rate data for catalyst pellets that are unaltered by external mass-transfer effects or partial 0 1990 American Chemical Society
Ind. Eng. Chem. Res., Vol. 29, No. 7, 1990 1547
W Figure 1. Sketch of the design of the basket system with four single cylindrical baskets: 1, shaft; 2, cylindrical basket; 3, catalyst; 4, agitator.
wetting are of importance for catalyst development and for scaling up, but eliminating these effects in three-phase reactions is difficult because of the high mass-transfer resistance of the liquid phase. A number of laboratory reactors with stirred contained catalyst designs have been developed for studying the reaction rate for catalyst pellets and the effectiveness factor. The use of rotating catalyst baskets in experimental reactors for catalytic gas-phase reactions was proposed by Carberry (1964). For catalytic gas-liquid-solid reactions, some more or less complicated spinning basket reactors have been designed. Kenney and Sedriks (1972) used a spinning basket reactor with four equally spaced low-mesh wire baskets supported on a central shaft to estimate the apparent rate and the catalyst effectiveness of the liquid-phase hydrogenation of cortonaldehyde. Mahoney et al. (1978) describe a spinning annular catalyst basket with internal baffles. This reactor was used to study the effective kinetics of desulfurization of a model compound. The semibatch hydrogenation of styrene was carried out in a basket reactor with four basket impellers by Kawakami et al. (1976). Ohta et al. (1980) used the same basket assembly for studing the oxidation of phenol. To investigate the global rate of glucose hydrogenation, experiments in a reactor with two spinning paddle baskets were performed by Turek et al. (1983). In all cases, the decisive technological problem is to achieve a sufficiently high flow rate through the catalyst baskets. Further, the necessary gas-liquid mass-transfer rate has to be secured. The present work deals with the characterization and comparison of two types of spinning basket reactors which were used for studying the hydrogenation of butynediol.
Experimental Section The aim was to design special catalyst basket systems to be mounted in a laboratory stirred tank reactor for determining the effective reaction rate and the effectiveness factor. The catalyst baskets tested are shown in Figures 1 and 2. The range of operating conditions is given in Table 1. The test reaction studied was the liquid-phase hydrogenation of butynediol to butenediol in aqueous solution by a nickel catalyst. For estimating the hydrogenation rate,
Figure 2. Sketch of the design of the annular basket: 1,shaft; 2, annular basket; 3, catalyst; 4, basket baffles; 5, agitator.
0
200
600
600min' 800
n-
Figure 3. Gas-liquid mass-transfer coefficients in experimental stirred reactors: 1, with blade stirrer; 2, with cylindrical baskets; 3, with annular basket. Table I. Operating Conditions of t h e Spinning Basket Reactors basket cylindrical annular 2 or 4 1 no. of baskets 40, 50, or 90 cm3 23 cm3 basket volume 4 or 5 and 5 or 6 cm diameter 2 cm 740 min-' 800 min-' max rotary speed 0.5-1.5 L 0.7-1.5 L liquid volume 0.1-4 MPa 0.1-4 MPa hydrogen pressure 323-393 K 323-393 K temp 0.1-0.5 cm 0.1-0.5 cm particle size
concentration-time curves were observed by gas chromatography.
Gas-Liquid and Liquid-Solid Mass Transfer The necessary gas-liquid mass-transfer rate was achieved with the help of an agitator above the catalyst baskets and, during the operation of the cylindrical baskets, by additional wall baffles. The gas-liquid masstransfer Coefficients determined on the basis of hydrogen absorption data are shown in Figure 3. Using the masstransfer coefficients, we can calculate that the gas-liquid mass-transfer inhibition is negligible in the hydrogenation runs. The conditions of liquid flow at and through the catalyst baskets are the principal difference between the two types of spinning baskets tested. In the case of the annular
1548 Ind. Eng. Chem. Res., Vol. 29, No. 7, 1990
I 004 01
I
I
0
400
200
‘ i -* I
1
600 min-‘ 800
n-
Figure 4. Effect of rotary speed on the hydrogenation rate: 1, cylindrical baskets; 2,annular basket.
1
1
Table 11. Hydrogenation Rate of Butynediol, Effectiveness Factor, a n d Tortuosity for Catalyst Pellets ( T =353 K) rH2,mol g-1 8-1 4,cm 7 D H ~ , .cma ~ , 5-1 0.18 3.75 x 10” 0.045 4.0 x 10-5 2.8 0.26 2.50 X 10” 0.030 3.8 X 2.9 0.48 1.33 X lo* 0.016 3.6 X lod 3.1
\
Using the values of the effectivenessfactor for the pellets and the kinetic equation rH2/
= kCHzJ
(1)
I
0
0
04
02
03
4
-
O 4 c m 05
Figure 5. Comparison of the effect of the catalyst size on the hydrogenation rates for different types of catalyst baskets: 1, cylindrical baskets; 2,annular basket.
basket, it was possible to measure the flow rate through the catalyst layer using a special piece of equipment. A volumetric flow rate of about 1m3 h-’ was measured. By use of this flow rate, the mass-transfer coefficients were predicted by a correlation of Goto and Smith (1975). The calculated liquid-solid mass-transfer inhibition was less than 3%. To analyze the liquid-solid mass-transfer effects in the case of the cylindrical baskets, the comparison of the measured hydroenation rates for both basket types were used. Figure 4 shows the effect of rotary speed and Figure 5 the effect of particle size on the rate. There is a significant difference. This is due to insufficient liquid flow through the cylindrical baskets. From the experimental studies with the catalyst baskets used here, we can conclude that, for the annular basket, the permissible rate with negligible external mass-transfer inhibition may be about 10 times higher than for the cylindrical baskets. Thus, it is evident that this version of spinning basket reactor is better suited for estimating the effective reaction rate and the effectiveness factor.
Determination of the Catalyst Effectiveness Factor and the Tortuosity Factor The effectiveness factor of the catalyst pellets in the spinning basket reactors was determined using the intrinsic reaction rate, free from mass-transfer effects, as the reference rate. The intrinsic rate was determined by experiments in a reactor in which the finely crushed pellets were suspended. Prior to determination of the intrisnic kinetics, examinations were required concerning mass transfer from the gas to the catalyst and the internal diffusion within the catalyst particle. The external and internal mass-transfer resistances were not significant. A comparison of the estimated effectiveness factors for the two types of catalyst baskets is given in Figure 6. Again, the cylindrical catalyst baskets gave smaller values under comparable conditions.
we can obtain the values of the effective diffusion coefficient and the tortuosity factor (T) calculated by combining the molecular diffusion coefficient and the equation =
tDHz/DHz,eff
(2)
These are shown in Table 11. The molecular diffusion coefficient was estimated from a correlation by Akgerman and Gainer (1972). An average value of the tortuosity factor T = 2.9 was obtained with the catalyst porosity t = 0.56.
Nomenclature c = concentration, mol L-’ d = diameter, cm D = diffusion coefficient, cm2s-l k = reaction rate constant, s-l (ka)H2,81 = gas-liquid mass-transfer coefficient, s-l m = mass, g n = rotary speed, m i d p = pressure, MPa r = reaction rate, mol g-’ s-l r‘ = reaction rate, s-’ T = temperature, K V = volume, L Greek Symbols = porosity q = effectiveness factor 7 = tortuosity t
Indices B = butynediol C = catalyst eff = effective value R e g i s t r y No. Ni, 7440-02-0;butynediol, 11070-67-0.
Literature Cited Akgerman, A.; Gainer, J. L. Diffusion of Gaaes in Liquids. Znd. Eng. Chem. Fundam. 1972,11,373. Carberry, J. J. Designing Laboratory Catalytic Reactors. Znd. Eng. Chem. 1964,56,39. Goto, S.; Smith, J. M. Trickle-Bed Reactor Performance-Part I. Holdup and Mass Transfer Effects. AZChE J. 1975, 21, 706. Kawakami, K.; Ura, S.; Kusunoki, K. The Effectiveness Factor of a Catalyst Pellet in the Liquid-Phase Hydrogenation of Styrene. Chem. Eng. Jpn. 1976,9,392.
Znd. Eng. Chem. Res. 1990,29, 1549-1554 Kenney, C. N.; Sedriks, W. Effectiveness Factors in a Three-phase Slurry Reactor: The Reduction of Crotonaldehyde over a Palladium Catalyst. Chem. Eng. Sci. 1972,27, 2029. Mahoney, J. A.; Robinson, K. K.; Myers, E. C. Catalyst Evaluation with Gradientless Reactor. Chem. Technol. 1978,8, 758. Ohta, H.; Goto, S.; Teshima, H. Liquid-Phase Oxidation of Phenol in a Rotating Catalytic Basket Reactor. Ind. Eng. Chem. Fundam. 1980,19,180. Turek, F.; Chakrabarti, R. K.; Lange, R.; Geike, R.; Flock, W. On the Experimental Study and Scale-up of Three-phase Catalytic Reactors. Chem. Eng. Sci. 1983, 38, 275.
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* Corresponding author. Fritz Turek,* Henry Winter Technical University "Carl Schorlemmer" Leuna-Merse burg Merseburg, 4200, German Democratic Republic Received for review January 13, 1989 Revised manuscript received August 2, 1989 Accepted January 8, 1990
Comparison of Cubic- and Hard-Sphere-Based Equations of State for Associating Fluid Mixtures Recently obtained enthalpy and phase behavior data a t elevated pressures and temperatures for both pure fluids and binary and ternary mixtures of m-cresol, quinoline, and tetralin, combined with phase behavior data for mixtures of methanol, n-pentane, and acetone, were used to compare variations of perturbed hard sphere (PHS) equations of state for mixtures with a typical cubic equation of state, a modified Soave-Redlich-Kwong (SRK) equation, for estimating properties of these highly nonideal systems. By fitting pure fluid vapor pressures, attractive terms, a ( T ) ,were determined for the PHS equations of state, which are much more consistent with the original temperature-independent attractive parameters as suggested by van der Waals. Experimentally determined binary interaction parameters resulted in comparable phase behavior fits and predictions for both equations. However, the PHS equations of state yielded much more accurate predictions of ternary enthalpy differences than the SRK equation of state. 1. Introduction A major limitation of thermodynamic property correlations for fluids is their inability to predict properties of nonpolar/nonideal systems at elevated temperatures and pressures. Equations of state are generally restricted to nonpolar or slightly polar systems, while activity coefficient models are generally restricted to low pressures. A major impediment in extending equations of state to highly nonideal or associating fluids is the almost complete lack of experimental data at elevated pressures. Over the past several years, enthalpy and phase behavior data have been obtained in our laboratory at elevated pressures and temperatures for both pure fluids and binary and ternary mixtures of m-cresol, quinoline, and tetralin (Flanigan, 1986; Flanigan et al., 1986; Flanigan and Yesavage, 1987,1988; Joyce, 1987; DiGiacinto, 1987;Flanigan et al., 1988a,b; Niesen and Yesavage, 1988a,b). In addition, a fairly complete set of binary and ternary vapor-liquid equilibrium data at elevated temperatures and pressures has recently been reported for the n-pentanelacetonel methanol system (Campbell et al., 1986; Wilsak et al., 1986, 1987a,b). These comprehensive data sets offer a unique opportunity for testing equation of state correlations for predicting thermodynamic properties. We have previously made preliminary studies using typical cubic equations of state with conventional mixing rules that included temperature and density dependencies. Our preliminary results indicated that, although density-dependent mixing rules yielded the best results in accurately describing the binary systems, they yielded poorer predictions when exteded to ternary systems (DiGiacinto, 1987). We were also not able to predict both enthalpy and phase behavior simultaneously (Flanigan, 1986). A potential source of error for any cubic equation of state is the incorrect repulsion term in such equations (Henderson, 1979). In an effort to obtain equation of state correlations that are more predictive, we have investigated variations of hard sphere perturbation equations of state for mixtures using, for the repulsion term, the approximate 0888-5885/90/2629-1549$02.50/0
analytical expression for the hard sphere equation of state developed by Carnahan and Starling (1969). Although cubic equations of state are quite popular in process simulation, due to their surprising accuracy and reliability for nonpolar or slightly polar mixtures, they have never been tested as to whether they could be used to determine reliable enthalpies for multicomponent polarlassociating systems. However, this capability is important for prediction methods since they are frequently used in energy balance calculations. 2. Equations Used The general form of the equation of state is that suggested by Wong and Prauznitz (1985):
z=1 + y + y2 - y3 (1- Y ) 3
a,a(T) RT(u + nb)
(1)
where Z, R, T , and u are, respectively, the compressibility factor, the ideal gas constant, the temperature, and the molar volume, y is equal to b / 4 v , where b is the volume parameter, and aCis the energy parameter evaluated at the critical point. 47') is the temperature-dependent part of the attraction term, which in the present study is determined by fitting vapor pressure data. Finally, n is a constant, which enables one to vary the form of the equation of state. Three values of n were considered, n = 0, the van der Waals form; n = 0.2, as suggested by Wong and Prauznitz (1985); and n = 1,as used by Soave (1972) in the development of the SRK equation of state. The analytical form used for a(T), similar to that used by Soave, is the following: a ( T ) = (c - dT,0.5)2
(2)
In applying these equations to mixtures, a molar average value of b was used while the following three mixing rules were considered in the present study for a = a,a(T): mixing rule I 0 1990 American Chemical Society
