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Al2O3 csatalyst
Studies in Surface Science and Catalysis 133 G.F. Froment and K.C. Waugh (Editors) (c3 2001 Elsevier Science B.V. All rights reserved.
521
H y d r o d e c h l o r i n a t i o n of c h l o r o b e n z e n e - t e t r a c h l o r o e t h y l e n e m i x t u r e s over a Pd/A1203 catalyst E. L6pez, S. Ord6fiez, F. V. Diez, H. Sastre Department of Chemical and Environmental Engineering, University of Oviedo, Julian Claveria s/n, 33006 Oviedo, Spain
The hydrodechlorination of mixtures of tetrachloroethylene (TTCE) and chlorobenzene (CBZ) over a supported palladium catalyst has been studied in this work. Experiments have been carried out in large excess of hydrogen at 250~ and 0.5 MPa. Inhibition effects have been found, being especially strong the effect of TTCE on the CBZ hydrodechlorination. Kinetic data were fitted to Langmuir-Hinselwood rate models, the best results being obtained supposing that adsorption of H2, CBZ and TTCE takes place in the same active sites.
1. INTRODUCTION Organochlorinated compounds constitute a very important environmental problem, their toxicity and carcinogenic character having been widely proven. Moreover, these compounds contribute both to the greenhouse effect and to the formation of photochemical smog [1,2]. Chlorobenzene ( C B Z ) and tetrachloroethylene (TTCE) are environmentally important, considering their hazardous character and the amounts released to the environment. CBZ is used as solvent and in the production of phenol, aniline and diphenol oxide, and TTCE is widely used in the dry-cleaning and preparation of textile fibbers. In addition, CBZ and TTCE are usually present in wastes in the presence of an organic matrix (solvents, fats, etc.). Hence, methods for the safe and environmentally acceptable destruction of recovered wastes or stocks of these compounds are needed. Catalytic hydrodechlorination has proved to be an effective method for the detoxification of hazardous chlorinated wastes [3], presenting several advantages over other methods such as thermal or catalytic oxidation: hydrodechlorination reaction products (hydrogen chloride, which can be easily separated by caustic washing, and hydrocarbons, which can be safely burned) are harmless, as opposed to incineration emissions, which may contain highly toxic compounds such as chlorine, phosgene and dioxines. Furthermore, the low temperatures required in comparison to incineration suppose an important economic advantage [3,4]. Although, in general, the catalysts most studied for the hydrodechlorination of organochlorinated compounds in organic matrix are the hydrotreatment ones [5], in previous works of our group it was found that precious metal catalysts are
522 more active [6]. In addition, these catalysts are active at moderate pressure and temperature (1-5 bar, 250 ~ while the hydrotreatment catalysts operate at more severe conditions (100 bar, T>350 ~ The most active metal for these reactions was found to be palladium [6]; consequently, this was the catalyst selected in our experiments. Most studies on hydrodechlorination reactions in presence of an organic solvent have been devoted to hydrotreatment catalysts, being very scarce the studies using palladium [5, 7]. On the other hand, to the best of our knowledge, there are no works published dealing with mixture effects when different organochlorinated compounds are processed together, even though inhibition effects are important in similar processes such as hydrodesulfurization [8]. The main aim of this work is to study the kinetics of the hydrodechlorination of TTCE and CBZ, both alone and in mixtures, in an organic matrix, over a commercial palladium catalyst. A model based on the postulates of LangmuirHinselwood was used to model the mixture effects 2. E X P E R I M E N T A L S E C T I O N The chemicals used in this work, TTCE, CBZ, benzene, toluene and decahydronaphtalene were supplied by Panreac and Merck, with a minimum purity of 99%. The commercial palladium catalyst used was ESCAT -16, 0.5% Pd/A1203, Engelhard (specific surface:103.35 m2/g). Hydrogen was supplied by Air Products with a minimum purity of 99.999% and a-alumina was supplied by Acros. Reactions were carried out in an 11 mm internal diameter fixed-bed reactor containing 0.25 or 0.5 g of catalyst. Solutions of TTCE and CBZ in toluene in the range 0- 1 molfl were used as reactor feed. A hydrogen excess of 10:1 over the stoichiometric required was fed co-currently to the reactor. All the experiments were carried out at 0.5 MPa pressure. Operation temperature (250~ was fixed in order to make sure that all reactants were present in the reactor as gases, and to ensure the stability of the catalyst during the experiments (higher temperatures lead to fast deactivation of the catalyst). Space times of 0-3 min.g/mmol of reactant) were reached changing the flow rate of liquid feed, the concentrations in the feed and the amount of catalyst, keeping constant the H2/organochlorinated compound ratio. In previous experiments it was demonstrated t h a t the solvent (aliphatic or aromatic) did not have relevant influence on the catalyst activity. A more detailed description of the experimental set-up and further studies about the selection of the operation conditions are given in reference [9]. Liquid reaction products were analysed by gas chromatography in a HewlettPackard 5890A apparatus equipped with a HP-1 30-m capillary column and a FID detector. Decahydronaphtalene was used as internal standard. The response factors were determined using standard calibration mixtures.
523 3. R E S U L T S AND D I S C U S S I O N 3.1. R e a c t i o n s t u d i e s The main reaction products were ethane (from TTCE) and benzene (from CBZ) (i.e. total dechlorination), in both cases with selectivities higher than 99 %. This result is very important considering that the final aim of this work is the development of a clean technology for the treatment of wastes. Very little amount of trichloroethylene were found in the hydrodechlorination of TTCE, whereas in the case of CBZ hydrodechlorination neither chlorocyclohexane nor cyclohexane were found. Likewise, the solvent (toluene) did not react in appreciable extension, being observed only small amounts of methyl-cyclohexane. TTCE was found to be more reactive t h a n CBZ. Experiments with TTCE and CBZ mixtures were carried out at 250~ and 0.5 MPa (5 bar), with 10% (w/w) concentration of CBZ and CBZ/TTCE molar ratios of 1:1, 1:0.5, 1:0.25 and 1:0, and with 10% (w/w) concentration of TTCE and TTCE/CBZ molar ratios of 1:1, 1:0.5, 1:0.25 and 1:0. Important mixture effects were observed when the two compounds were reacted together: the reactivity of CBZ is drastically reduced in presence of TTCE (Fig.l), whereas the effect of CBZ in the hydrodechlorination of TTCE is not so marked (Fig.2).
.2
0.9
o
0.8
o
0.7
O
0.6
0.8
"-----.o
ra~
0.6 0
r N
0.4 0.2
0.5 0.4
' 0
'
,
,
,
,
0.2
0.4
0.6
0.8
Inlet CBZ concentration
1
(mol/1)
Fig.1. Influence of CBZ concentration in TTCE conversion (0.8 molfl TTCE). Space time 0.6 (O), 0.8 (~) and 1 (A) min'g/mmol
0
0.2
0.4
0.6
0.8
1
Inlet TTCE concentration(mol/1) Fig.2. Influence of TTCE concentration in CBZ conversion (0.8 molfl CBZ). Space time and symbols: see Fig. 1
This result can be explained assuming that the number of chlorine atoms attached to the organic structure has a stronger influence on the adsorption strength than the type of organic structure (TTCE has four chlorine atoms and CBZ only one, while aromatic structures are considered to hold stronger interaction with the metallic surface). The large importance of the chlorine atoms in the metal-catalysed hydrodechlorination reactions and their substantial role in
524 the adsorption of the molecule was stated by some authors [10, 11]. This hypothesis is also consistent with the observed negligible effect of the solvent in the catalyst performance.
3.2. Kinetic m o d e l l i n g of m i x t u r e s Internal and external mass transfer limitations were estimated not to be important, according to standard correlations [12]. In the same way, a PFR-like behaviour was also demonstrated. When mixture effects on hydrogenolysis or hydrogenation reactions are considered, the most successful models are often the based on the LangmuirHinselwood (LH) mechanisms [8]. The main assumption of this model is that the reaction occurs between two adsorbed species. Considering the high affinity of hydrogen for the palladium surface, the chemisorption of hydrogen is usually considered as dissociative. Concerning to the adsorption of the organochlorinated compound, two possibilities can be considered: chemisorption on the same active sites than hydrogen, or chemisorption of hydrogen and organochlorinated compound on different adsorption sites. According to the literature [8], the first supposition is more accurate for hydrogenolysis reactions (such as hydrodechlorination) whereas the second is considered more accurate for hydrogenation reactions. In the case of CBZ, the only reaction is the hydrogenolysis of a C-C1 bond, whereas in the case of TTCE two reactions occur: hydrogenation of the double-bond and hydrogenolysis of C-C1 bonds. Even some authors state that the mechanism of TTCE hydrodechlorination is a succession of catalytic hydrogenation of C-C double bond and thermal elimination of HC1 [6,13]. Kinetic expressions were derived for both cases. In the case of chemisorption of chlorinated and hydrogen over the analogous sites (LHA), the reaction rate is given by the following equation:
J,4KuKiPu:P, (-r,.) = (1 + ~KMp M + Kip, + Xjpj) z
(1)
When the hydrogen and the chlorinated are adsorbed on different active sites (LHNA), the equation is: 0.5
/,~KHKipH~pi (-~) = (1 + ~/KH PH + Ki p, + K i P i)(1 + ~KH PH )
(2)
In these equations ji is the intrinsic kinetic constant and Ki are the adsorption constant of component i. Considering that the hydrogen is present in large excess and its partial pressure is almost constant in all the experiments (0.43 MPa), equations [1] and [2] can be rearranged:
525
(-r~) =
J" p' (1 + K'~ p~ + K'j pj )"
(3)
The new constants ji' and Ki' are defined in Table 1 for both models, and n is equal to 1 for LHNA model and n=2 for LHA model. Experimental data were fitted to these rate expressions. Considering the high conversion attained in some experiments, the reactor was considered as integral.
Table 1
Summary of rate models with estimated parameters and correlation coefficient
j'i (MPa:l"mm01/min'g)
K'i (MPa -1)
j;= J'K'K~PH~.2=. (l+K~P~)
K,'= K~ (l+K~P~)
TTCE
2.374" 1012
1.896" 10 ~
CBZ
3.873.109
1.615-104
j,K,K~P~ J;= (1+ K~P~)
K I = K,
TTCE
6.527" 1011
2.075" 107
CBZ
2.214"1010
5.351"106
Model LHA
Parameter definition
LHNA Parameter definition
r
0.995
0.964
The kinetic parameters for the two models were estimated by fitting the rate expressions to the experimental data by means of a non-linear least squares minimisation of the error in the prediction of conversions, with a simplex algorithm followed by a Powell minimisation algorithm. The differential equations have been integrated using the EPISODE package. These mathematical tools are implemented i n t h e commercial programme Scientist. The goodness of the fit is quantified using the correlation coefficient (r). Results of the fit and parameter estimation are shown in Table 1. The correlation coefficients reveal that LHA model gives a better fit. The tendency of the values of the constant of the LHA model are in good agreement with the experimental observations (TTCE is more reactive and has the higher inhibition capacity).
526
~9 0.8 0.6 0.4 "~ o
,Jb~"A
,~~
0.2 0
'pTl /0 /
"i 0.8 ' 0"61]/i*~
S 9~ o ~
.
0
.
.
0.2
.
.
0.4
0.4 r~
.
0.6
0.8
1
Conversion, Experimental Fig. 3. Parity plot comparing the experimentally measured conversion of CBZ ( i ) and TTCE (0) with the prediction of LHA model.
o ~ 0
2
4
6
8
10
Space time (g-rain/retoolCBZ) Fig. 4. Experimental (points) and predicted (line) conversion of CBZ at the following TTCE/CBZ molar ratios: 0 (F1), 1 (*), 2 (O) and 4 (A). LHA model.
Experimental and predicted values are compared in Fig. 3 for all the experimental points considered in this work. With more than 70 points for each species, it can be observed that the fitting for the proposed model is fairly good. As an example, Fig. 4 shows that the LHA model predicts CBZ conversion (the compound that is affected in higher extension by the mixture effects).with reasonable accuracy.
REFERENCES 1. E. Goldberg, Sci. Total Environ. 100 (1991) 17. 2. M. Tancrede, R. Wilson, L. Zeise, E. A. C. Crouch, Atmos. Environ. 21 (1987) 2187. 3. T. N. Kalnes, R. B. James, Environ. Prog. 7 (1988) 185. 4. R. C. Dampsey, T. Oppelt, T. Air and Waste 43 (1993) 25. 5. D.I. Kim, D. T. Allen, Ind. Eng. Chem. Res. 36 (1997) 3019. 6. S. Ord6fiez, H. Sastre, F. V. Diez, Appl. Catal. B 20 (1999) 309. 7. R. J. Meyer, D. I. Kim, D. T. Allen, J. H. Jo, Chem. Eng. Sci., 54 (1999) 3627. 8. M.J. Girgis, B.C. Gates, Ind. Eng. Chem. Res., 30 (1991) 2021. 9. S. Ord6fiez, Ph.D. Thesis, University of Oviedo, Oviedo (1999) 10.A.H. Weiss, B. S. Gambhir, R. B. Leon, J. Catal., 22 (1971) 245. l l . A . H . Weiss, K. A. Krieger, J. Catal., 6 (1966) 167. 12.J.A. Moulijn, P.W.N.M. van Leeeuwen, R.A. van Santen (eds.), Catalysis: an integrated approach to homogeneous, heterogeneous and industrial catalysis, Elsevier, Amsterdam 1993. 13.A.R. Pinder, Synthesis, 79 (1980) 425.
521
H y d r o d e c h l o r i n a t i o n of c h l o r o b e n z e n e - t e t r a c h l o r o e t h y l e n e m i x t u r e s over a Pd/A1203 catalyst E. L6pez, S. Ord6fiez, F. V. Diez, H. Sastre Department of Chemical and Environmental Engineering, University of Oviedo, Julian Claveria s/n, 33006 Oviedo, Spain
The hydrodechlorination of mixtures of tetrachloroethylene (TTCE) and chlorobenzene (CBZ) over a supported palladium catalyst has been studied in this work. Experiments have been carried out in large excess of hydrogen at 250~ and 0.5 MPa. Inhibition effects have been found, being especially strong the effect of TTCE on the CBZ hydrodechlorination. Kinetic data were fitted to Langmuir-Hinselwood rate models, the best results being obtained supposing that adsorption of H2, CBZ and TTCE takes place in the same active sites.
1. INTRODUCTION Organochlorinated compounds constitute a very important environmental problem, their toxicity and carcinogenic character having been widely proven. Moreover, these compounds contribute both to the greenhouse effect and to the formation of photochemical smog [1,2]. Chlorobenzene ( C B Z ) and tetrachloroethylene (TTCE) are environmentally important, considering their hazardous character and the amounts released to the environment. CBZ is used as solvent and in the production of phenol, aniline and diphenol oxide, and TTCE is widely used in the dry-cleaning and preparation of textile fibbers. In addition, CBZ and TTCE are usually present in wastes in the presence of an organic matrix (solvents, fats, etc.). Hence, methods for the safe and environmentally acceptable destruction of recovered wastes or stocks of these compounds are needed. Catalytic hydrodechlorination has proved to be an effective method for the detoxification of hazardous chlorinated wastes [3], presenting several advantages over other methods such as thermal or catalytic oxidation: hydrodechlorination reaction products (hydrogen chloride, which can be easily separated by caustic washing, and hydrocarbons, which can be safely burned) are harmless, as opposed to incineration emissions, which may contain highly toxic compounds such as chlorine, phosgene and dioxines. Furthermore, the low temperatures required in comparison to incineration suppose an important economic advantage [3,4]. Although, in general, the catalysts most studied for the hydrodechlorination of organochlorinated compounds in organic matrix are the hydrotreatment ones [5], in previous works of our group it was found that precious metal catalysts are
522 more active [6]. In addition, these catalysts are active at moderate pressure and temperature (1-5 bar, 250 ~ while the hydrotreatment catalysts operate at more severe conditions (100 bar, T>350 ~ The most active metal for these reactions was found to be palladium [6]; consequently, this was the catalyst selected in our experiments. Most studies on hydrodechlorination reactions in presence of an organic solvent have been devoted to hydrotreatment catalysts, being very scarce the studies using palladium [5, 7]. On the other hand, to the best of our knowledge, there are no works published dealing with mixture effects when different organochlorinated compounds are processed together, even though inhibition effects are important in similar processes such as hydrodesulfurization [8]. The main aim of this work is to study the kinetics of the hydrodechlorination of TTCE and CBZ, both alone and in mixtures, in an organic matrix, over a commercial palladium catalyst. A model based on the postulates of LangmuirHinselwood was used to model the mixture effects 2. E X P E R I M E N T A L S E C T I O N The chemicals used in this work, TTCE, CBZ, benzene, toluene and decahydronaphtalene were supplied by Panreac and Merck, with a minimum purity of 99%. The commercial palladium catalyst used was ESCAT -16, 0.5% Pd/A1203, Engelhard (specific surface:103.35 m2/g). Hydrogen was supplied by Air Products with a minimum purity of 99.999% and a-alumina was supplied by Acros. Reactions were carried out in an 11 mm internal diameter fixed-bed reactor containing 0.25 or 0.5 g of catalyst. Solutions of TTCE and CBZ in toluene in the range 0- 1 molfl were used as reactor feed. A hydrogen excess of 10:1 over the stoichiometric required was fed co-currently to the reactor. All the experiments were carried out at 0.5 MPa pressure. Operation temperature (250~ was fixed in order to make sure that all reactants were present in the reactor as gases, and to ensure the stability of the catalyst during the experiments (higher temperatures lead to fast deactivation of the catalyst). Space times of 0-3 min.g/mmol of reactant) were reached changing the flow rate of liquid feed, the concentrations in the feed and the amount of catalyst, keeping constant the H2/organochlorinated compound ratio. In previous experiments it was demonstrated t h a t the solvent (aliphatic or aromatic) did not have relevant influence on the catalyst activity. A more detailed description of the experimental set-up and further studies about the selection of the operation conditions are given in reference [9]. Liquid reaction products were analysed by gas chromatography in a HewlettPackard 5890A apparatus equipped with a HP-1 30-m capillary column and a FID detector. Decahydronaphtalene was used as internal standard. The response factors were determined using standard calibration mixtures.
523 3. R E S U L T S AND D I S C U S S I O N 3.1. R e a c t i o n s t u d i e s The main reaction products were ethane (from TTCE) and benzene (from CBZ) (i.e. total dechlorination), in both cases with selectivities higher than 99 %. This result is very important considering that the final aim of this work is the development of a clean technology for the treatment of wastes. Very little amount of trichloroethylene were found in the hydrodechlorination of TTCE, whereas in the case of CBZ hydrodechlorination neither chlorocyclohexane nor cyclohexane were found. Likewise, the solvent (toluene) did not react in appreciable extension, being observed only small amounts of methyl-cyclohexane. TTCE was found to be more reactive t h a n CBZ. Experiments with TTCE and CBZ mixtures were carried out at 250~ and 0.5 MPa (5 bar), with 10% (w/w) concentration of CBZ and CBZ/TTCE molar ratios of 1:1, 1:0.5, 1:0.25 and 1:0, and with 10% (w/w) concentration of TTCE and TTCE/CBZ molar ratios of 1:1, 1:0.5, 1:0.25 and 1:0. Important mixture effects were observed when the two compounds were reacted together: the reactivity of CBZ is drastically reduced in presence of TTCE (Fig.l), whereas the effect of CBZ in the hydrodechlorination of TTCE is not so marked (Fig.2).
.2
0.9
o
0.8
o
0.7
O
0.6
0.8
"-----.o
ra~
0.6 0
r N
0.4 0.2
0.5 0.4
' 0
'
,
,
,
,
0.2
0.4
0.6
0.8
Inlet CBZ concentration
1
(mol/1)
Fig.1. Influence of CBZ concentration in TTCE conversion (0.8 molfl TTCE). Space time 0.6 (O), 0.8 (~) and 1 (A) min'g/mmol
0
0.2
0.4
0.6
0.8
1
Inlet TTCE concentration(mol/1) Fig.2. Influence of TTCE concentration in CBZ conversion (0.8 molfl CBZ). Space time and symbols: see Fig. 1
This result can be explained assuming that the number of chlorine atoms attached to the organic structure has a stronger influence on the adsorption strength than the type of organic structure (TTCE has four chlorine atoms and CBZ only one, while aromatic structures are considered to hold stronger interaction with the metallic surface). The large importance of the chlorine atoms in the metal-catalysed hydrodechlorination reactions and their substantial role in
524 the adsorption of the molecule was stated by some authors [10, 11]. This hypothesis is also consistent with the observed negligible effect of the solvent in the catalyst performance.
3.2. Kinetic m o d e l l i n g of m i x t u r e s Internal and external mass transfer limitations were estimated not to be important, according to standard correlations [12]. In the same way, a PFR-like behaviour was also demonstrated. When mixture effects on hydrogenolysis or hydrogenation reactions are considered, the most successful models are often the based on the LangmuirHinselwood (LH) mechanisms [8]. The main assumption of this model is that the reaction occurs between two adsorbed species. Considering the high affinity of hydrogen for the palladium surface, the chemisorption of hydrogen is usually considered as dissociative. Concerning to the adsorption of the organochlorinated compound, two possibilities can be considered: chemisorption on the same active sites than hydrogen, or chemisorption of hydrogen and organochlorinated compound on different adsorption sites. According to the literature [8], the first supposition is more accurate for hydrogenolysis reactions (such as hydrodechlorination) whereas the second is considered more accurate for hydrogenation reactions. In the case of CBZ, the only reaction is the hydrogenolysis of a C-C1 bond, whereas in the case of TTCE two reactions occur: hydrogenation of the double-bond and hydrogenolysis of C-C1 bonds. Even some authors state that the mechanism of TTCE hydrodechlorination is a succession of catalytic hydrogenation of C-C double bond and thermal elimination of HC1 [6,13]. Kinetic expressions were derived for both cases. In the case of chemisorption of chlorinated and hydrogen over the analogous sites (LHA), the reaction rate is given by the following equation:
J,4KuKiPu:P, (-r,.) = (1 + ~KMp M + Kip, + Xjpj) z
(1)
When the hydrogen and the chlorinated are adsorbed on different active sites (LHNA), the equation is: 0.5
/,~KHKipH~pi (-~) = (1 + ~/KH PH + Ki p, + K i P i)(1 + ~KH PH )
(2)
In these equations ji is the intrinsic kinetic constant and Ki are the adsorption constant of component i. Considering that the hydrogen is present in large excess and its partial pressure is almost constant in all the experiments (0.43 MPa), equations [1] and [2] can be rearranged:
525
(-r~) =
J" p' (1 + K'~ p~ + K'j pj )"
(3)
The new constants ji' and Ki' are defined in Table 1 for both models, and n is equal to 1 for LHNA model and n=2 for LHA model. Experimental data were fitted to these rate expressions. Considering the high conversion attained in some experiments, the reactor was considered as integral.
Table 1
Summary of rate models with estimated parameters and correlation coefficient
j'i (MPa:l"mm01/min'g)
K'i (MPa -1)
j;= J'K'K~PH~.2=. (l+K~P~)
K,'= K~ (l+K~P~)
TTCE
2.374" 1012
1.896" 10 ~
CBZ
3.873.109
1.615-104
j,K,K~P~ J;= (1+ K~P~)
K I = K,
TTCE
6.527" 1011
2.075" 107
CBZ
2.214"1010
5.351"106
Model LHA
Parameter definition
LHNA Parameter definition
r
0.995
0.964
The kinetic parameters for the two models were estimated by fitting the rate expressions to the experimental data by means of a non-linear least squares minimisation of the error in the prediction of conversions, with a simplex algorithm followed by a Powell minimisation algorithm. The differential equations have been integrated using the EPISODE package. These mathematical tools are implemented i n t h e commercial programme Scientist. The goodness of the fit is quantified using the correlation coefficient (r). Results of the fit and parameter estimation are shown in Table 1. The correlation coefficients reveal that LHA model gives a better fit. The tendency of the values of the constant of the LHA model are in good agreement with the experimental observations (TTCE is more reactive and has the higher inhibition capacity).
526
~9 0.8 0.6 0.4 "~ o
,Jb~"A
,~~
0.2 0
'pTl /0 /
"i 0.8 ' 0"61]/i*~
S 9~ o ~
.
0
.
.
0.2
.
.
0.4
0.4 r~
.
0.6
0.8
1
Conversion, Experimental Fig. 3. Parity plot comparing the experimentally measured conversion of CBZ ( i ) and TTCE (0) with the prediction of LHA model.
o ~ 0
2
4
6
8
10
Space time (g-rain/retoolCBZ) Fig. 4. Experimental (points) and predicted (line) conversion of CBZ at the following TTCE/CBZ molar ratios: 0 (F1), 1 (*), 2 (O) and 4 (A). LHA model.
Experimental and predicted values are compared in Fig. 3 for all the experimental points considered in this work. With more than 70 points for each species, it can be observed that the fitting for the proposed model is fairly good. As an example, Fig. 4 shows that the LHA model predicts CBZ conversion (the compound that is affected in higher extension by the mixture effects).with reasonable accuracy.
REFERENCES 1. E. Goldberg, Sci. Total Environ. 100 (1991) 17. 2. M. Tancrede, R. Wilson, L. Zeise, E. A. C. Crouch, Atmos. Environ. 21 (1987) 2187. 3. T. N. Kalnes, R. B. James, Environ. Prog. 7 (1988) 185. 4. R. C. Dampsey, T. Oppelt, T. Air and Waste 43 (1993) 25. 5. D.I. Kim, D. T. Allen, Ind. Eng. Chem. Res. 36 (1997) 3019. 6. S. Ord6fiez, H. Sastre, F. V. Diez, Appl. Catal. B 20 (1999) 309. 7. R. J. Meyer, D. I. Kim, D. T. Allen, J. H. Jo, Chem. Eng. Sci., 54 (1999) 3627. 8. M.J. Girgis, B.C. Gates, Ind. Eng. Chem. Res., 30 (1991) 2021. 9. S. Ord6fiez, Ph.D. Thesis, University of Oviedo, Oviedo (1999) 10.A.H. Weiss, B. S. Gambhir, R. B. Leon, J. Catal., 22 (1971) 245. l l . A . H . Weiss, K. A. Krieger, J. Catal., 6 (1966) 167. 12.J.A. Moulijn, P.W.N.M. van Leeeuwen, R.A. van Santen (eds.), Catalysis: an integrated approach to homogeneous, heterogeneous and industrial catalysis, Elsevier, Amsterdam 1993. 13.A.R. Pinder, Synthesis, 79 (1980) 425.