Ind. Eng. Chem. Res. 1997, 36, 1485-1490
1485
Epoxidation of Oleic Acid in the Presence of Benzaldehyde Using Cobalt(II) Tetraphenylporphyrin as Catalyst Tse-Chuan Chou* and Shan-Van Lee Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan, Republic of China 701
Epoxidation of oleic acid with oxygen in the presence of benzaldehyde using cobalt(II) tetraphenylporphyrin (Co2+-TPP) as catalyst was studied. The results show that high yield of epoxidized oleic acid is obtained by the liquid phase epoxidation of oleic acid in the presence of benzaldehyde using Co2+-TPP as catalyst, which does not catalyze the decomposition of perbenzoic acid, which is one of the oxidation reagents for epoxidation and is formed by the oxidation of benzaldehyde. The oleic acid can be easily epoxidized in this system. The reaction mechanism was proposed. The experimental and theoretical results indicate that the epoxidized oleic acid is formed by a series of free-radical reaction steps. The rate-determining steps were experimentally identified, and the rate equation of epoxidation was obtained. The factors affecting the rate of epoxidation of oleic acid were also obtained. Introduction Epoxidized soybean oil and vegetable oil are useful commercial chemicals mainly used for the stabilizer of poly(vinyl chloride) (PVC) and other polymers. The epoxidized oil efficiently reacts with hydrochloric acid which may be liberated from the degradation of poly(vinyl chloride) by adsorbing heat or ultraviolet light. There are many methods to produce epoxides. However, only a few of them have been commercialized. In our previous papers (Kuo and Chou, 1987; Kuo and Chou, 1990), we indicated that good yields and selectivity of epoxidized oleic acid could be obtained from the epoxidation of oleic acid in the presence of both benzaldehyde and oxygen using both a homogeneous and a Co-type ion-exchange membrane as catalysts. In this study, epoxidation of oleic acid in the presence of benzaldehyde using cobalt(II) tetraphenylporphyrin (Co2+-TPP) as catalyst was carried out. The Co2+-TPP serves as a catalyst to produce free radicals and perbenzoic acid for epoxidizing oleic acid. The organic compounds containing double bonds easily react with peracids, in general, which are produced by reacting organic carboxylic acids with hydrogen peroxide either performed in two stages or in situ (Metelitsa, 1972; Chou and Chang, 1986; Kuo and Chou, 1990). The in situ process is better. The organic peracids can be also synthesized from aldehydes and oxygen by using Co3+ ion as homogeneous catalyst in the liquid phase (Chou and Lin, 1983). The decompositions of organic peracids were very rapid in liquid solution in the presence of Co2+ ion (Allen and Aquilo, 1968). On the other hand, some investigators (Koubeck et al., 1963) indicated that the decompositions of organic peracids were rather slow in a solution without the metal ions. In general, the metal ion catalyst is not recovered in the commercial process. The stability of organic peracid product is improved by adding stabilizer. However, methods to decrease the amount of byproduct and to improve the stability of organic peracids simultaneously are seldom discussed. Recently, several investigations reported that high yields of organic peracids could be * Author to whom correspondence should be addressed. Tel 886-6-2757575 ext. 62639; fax 886-6-236-5969; e-mail
[email protected]. S0888-5885(96)00454-X CCC: $14.00
obtained using a heterogenized homogeneous metal ion on resin as catalyst (Chou and Lee, 1985; Hwang and Chou, 1987; Kuo and Chou, 1987; Chou et al., 1990; Chou and Yeh, 1992a,b, Chen and Chou, 1994). The immobilized metal ions by other supports are seldom mentioned. Several investigations (Tezuka et al., 1976; Honda et al., 1976; Walker, 1973; Walker et al., 1976) reported that metal porphyrin was a type of immobilized homogeneous metal ion which was successfully used as a catalyst. Tezuka et al. (1976) indicated that good yield of peracetic acid could be obtained from the oxidation of acetaldehyde catalyzed by Co2+-TPP in the presence of molecular oxygen. The oxidation of aldehyde is
Co2+-TPP + O2 f [Co2+-TPP]‚‚‚O2
(1)
[Co2+-TPP]‚‚‚O2 + RCHO f [Co3+-TPP]‚‚‚O2H + RC•O (2) On the basis of eqs 1 and 2, the free radical RC•O can be generated. According to the reports (Chou and Lee, 1985; Chen and Chou, 1994), the RC•O free radicals react with O2 to form the peroxy free radical RCO•3 or organic peracids RCO3H, which are very powerful oxidation reagents to epoxidize the olefins (Kuo and Chou, 1987; Kuo and Chou, 1990). The advantages of cobalt porphyrin catalyst for producing organic peracids or peroxy free radicals are as follows: (1) there is no leakage of cobalt ion; (2) the catalyst can be recovered and regenerated; (3) the product is not contaminated with used catalyst which can be easily separated from the solution. In this work, epoxidation of oleic acid in the presence of both benzaldehyde and oxygen using cobalt(II) tetraphenylporphyrin as catalyst is carried out systematically. The reaction mechanism is proposed. The kinetic data and the rate equation are presented. Experimental Section The cobalt(II) tetraphenylporphyrin catalyst was prepared by mixing 50 mL of chloroform, 50 mL of cobalt acetate, and 0.5 g of tetraphenylporphyrin in a flask and refluxing about 2 h. The reacted solution was cooled to © 1997 American Chemical Society
1486 Ind. Eng. Chem. Res., Vol. 36, No. 5, 1997
room temperature, and then 100 mL of methanol was added into the solution. The cobalt(II) tetraphenylporphyrin crystal formed, and the crystals were separated from the solution by filtration under vacuum. The Co2+TPP crystals were washed with methanol and dried. If the exchange of cobalt ion on TPP crystals is incomplete, the procedures of refluxing, crystallization, filtration, washing, and drying can be repeated. The prepared Co2+-TPP was used as a catalyst for epoxidation, or partial oxidation was carried out in a setup as reported in our previous paper (Hwang and Chou, 1987). All chemicals used were reagent grade. A desired amount of benzaldehyde, oleic acid, acetone, and catalyst was added to the reactor. When the liquid solution had reached the desired reaction temperature, the oxygen stream was introduced at a constant rate, and the time was recorded. The reacting fluid was stirred by the oxygen stream. Samples were taken periodically from the reactor using a hypodermic syringe and analyzed by the methods described in our previous paper (Kuo and Chou, 1990). Theoretical Analysis The epoxidation of oleic acid in the presence of both benzaldehyde and oxygen to produce epoxidized oleic acid with Co2+-TPP as catalyst is the combination of the oxidation of benzaldehyde and epoxidation of oleic acid. In this work, Co2+-TPP catalyst was used to form a oxygen carrier complex as shown in eq 1. The oxygen carrier Co2+-TPP complex abstracts hydrogen atom from benzaldehyde and forms the free radical C6H5CO as shown in eq 2, which then reacts with oxygen in bulk solution to form free radical C6H5CO•3. The reaction mechanism of oxidation of benzaldehyde to form perbenzoic acid using Co2+-TPP as catalyst is proposed as follows (Chou and Lee, 1985; Tezuka et al., 1976). Dissolving oxygen:
O2(g) T O2(l)
k2
PhC•O + [Co3+-TPP]‚‚‚O2H- (4) where the notation g and l indicate the gas phase and liquid phase, respectively. Propagation:
k4
PhCO•3 + PhCHO 98 PhCO3H + PhC•O
2PhCO•3 98 inactive
Epoxidation: The epoxidation reaction steps include the reaction steps 3-10 and the following steps (Kuo and Chou, 1987). R1HC CHR2 + PhCO2H
k6
CHR2 + PhCO2H
R1HC
(11)
O R1HC CHR2 + PhCO3• αR1HC
k7
CHR2 + αPhCO2• + (1 – α)other products
(12)
O k8
PhCO•2 + PhCHO 98 PhCO2H + PhC•O
(13)
where R1, R2, and R1HCdCHR2 indicate CH3(CH2)7and -(CH2)7COOH, oleic acid, respectively. The factor R in eq 12 is the fraction of free radical PhCO•3 to form epoxide and (1 - R) fraction to form the other compounds. The changes of the concentrations of free radicals are
d[PhC•O]/dt ) k2[PhCHO][Co2+-TPP][O2(l)] k3[PhC•O][O2(l)] + k4[PhCO•3][PhCHO] + k8[PhCO•2][PhCHO] (14) d[PhCO•3]/dt ) k3[PhC•O][O2(l)] k4[PhCO•3][PhCHO] - 2k5[PhCO•3]2 k7[R1HCdCHR2][PhCO•3] (15) d[PhCO•2]/dt ) Rk7[R1HCdCHR2][PhCO•3] k8[PhCO•2][PhCHO] (16)
d[PhCO•3]/dt ) d[PhC•O]/dt ) d[PhCO•2]/dt )0 (17) Substituting eq 21 into eqs 14-16 and then summing them yields
2k5[PhCO•3]2 + (1 - R)k7[R1HCdCHR2][PhCO•3] k2[PhCHO][Co2+-TPP][O2(l)] ) 0 (18)
(5)
By use of eq 18, the concentration of free radical PhCO•3 can be solved to be
(6)
[PhCO•3] ) (1/4k5){-(1 - R)k7[R1HCdCHR2] +
In general, the free radical PhC•O combines quickly with oxygen to form the free radical PhCO•3. Termination: The main termination step is k5
(10)
Assuming pseudo steady state, eqs 14-16 become
PhCHO + Co2+-TPP + O2(l) 98
k3
[Co3+-TPP]‚‚‚O2H- f Co2+-TPP + HO•2
(3)
Initiation: The initiation reaction step is the combination of eqs 1 and 2
PhC•O + O2(l) 98 PhCO•3
Catalyst regeneration:
(7)
{(1 - R)2k72[RHCdCHR2]2 + 8k2k5[PhCHO][Co+2-TPP][O2(l)]}0.5} (19) By use of eq 11 and 12, the rate equation of epoxidized oleic acid, Re, can be expressed as CHR2]/dt = Re = k6[PhCO3H][R1HC
d[R1HC
The other termination steps are
CHR2] +
O
PhCO•3 + PhC•O f inactive
(8)
2PhC•O f inactive
(9)
αk7[R1HC
CHR2][PhCO3•] (20)
At the initial condition, the concentration of perbenzoic acid is very small and eq 20 can be simplified to
Ind. Eng. Chem. Res., Vol. 36, No. 5, 1997 1487
Re ) Rk7[R1HCdCHR2][PhCO•3]
(21)
By substitution of eq 19 into eq 21, the general rate equation Re is a more complex equation compared with the equation, in general, expressed by a power law. Equation 19 can be simplified to a simple form: Case i.
(1 - R)2k72[R1HCdCHR2]2 . 8k2k5[PhCHO][Co2+-TPP][O2(l)] (22) Substitution of eq 22 into eq 19 and reducing gives
[PhCO•3] ) 0
(23)
Equation 23 is not reasonable for a chain reaction where the free-radical concentration is zero. It indicates that the reactions are completely retarded or inhibited. Case ii.
(1 - R)2k72[R1HCdCHR2]2 , 8k2k5[PhCHO][Co2+-TPP][O2(l)] (24) Equation 24 indicates that the selectivity of epoxidized oleic acid is high, i.e. (1 - R) is very small, (1 - R)2 , 1. It shows that the main product is epoxidized oleic acid. Substitution of eq 24 into eq 19 gives
[PhCO•3] ) -(1 - R)k7[R1HCdCHR2](1/4k5) + (k2/2k5)0.5[PhCHO]0.5[Co2+-TPP]0.5[O2(l)]0.5 (25) Substitution of eq 25 into eq 21 gives
Re ) -R(1 - R)k72[R1HCdCHR2]2(1/4k5) + Rk7(k2/2k5)0.5[PhCHO]0.5[Co2+-TPP]0.5[O2(l)]0.5 × [RHCdCHR2] (26) Results and Discussion Product Compositions. The product compositions of a typical run are shown in Figure 1. The concentration of perbenzoic acid is less than the epoxidized oleic acid as shown in Figure 1. The increase of the concentration of the epoxidized oleic acid is almost sinuous with the concentration of benzoic acid. It indicates that the epoxidized oleic acid is mainly produced by reaction steps of eqs 11 and 12. The results indicate that the reaction rate of forming epoxidized oleic acid is slower than the reaction rate of benzaldehyde. The formation of perbenzoic acid is about zero during the period from the beginning to 20 min into the run. After about 20 min from the beginning of the run, the concentration of perbenzoic acid increases slightly and the concentration of epoxidized oleic acid increases sharply. It indicates that the decomposition of perbenzoic acid is significant at higher concentration of perbenzoic acid. However, there is still some perbenzoic acid that does not decompose. Effect of the Concentration of Benzaldehyde. The results indicate that increasing the concentration of benzaldehyde from 1.0 to 3.0 M resulted in an increase of the initial rate of epoxidized oleic acid from 0.42 × 10-3 to 1.92 × 10-3 M/min as shown in Table 1. The plot of the epoxidized reaction rate, Re, against (PhCHO)0.5 yields a straight line with a -0.022 intercept as shown in Figure 2.
Figure 1. Typical run of the epoxidation using Co2+-TPP as catalyst: temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; oxygen flow rate, 150 mL/ min; stirring rate, 800 rpm. Table 1. Effect of Concentration of Benzaldehyde on the Epoxidation Rate in the Presence of Benzaldehydea concentration of PhCHO, M
[PhCHO]0.5, M0.5
Re × 103, M/min
1.20 1.80 2.40 3.00
1.10 1.34 1.55 1.73
2.61 3.18 3.70 4.13
a Concentration of oleic acid, 0.3 M; concentration of Co2+-TPP, 7.3 × 10-5 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
On the basis of the intercept, the initial epoxidized rate is negative, which is impossible. However, the minimum or zero epoxidation rate occurred at a benzaldehyde concentration of 6.4 × 10-5 M. The results reveal that the epoxidation of oleic acid does not take place when the benzaldehyde concentration is less than 6.4 × 10-5 M because the free radical reaction is retarded in the presence of oleic acid as shown in Figure 2. The result can be expressed as
Re ) -0.022 + [PhCHO]0.5, [PhCHO] > 6.4 × 10-5 M (27) Effect of the Concentration of Oleic Acid. The results indicate that increasing the concentration of oleic acid from 0.20 to 0.44 M decreases the epoxidation rate from 2.13 × 10-3 to 1.29 × 10-3 M/min. It indicates that oleic acid makes the reactions of this system slow down as shown in Table 2. A plot of Re/[R1HCdCHR2] against the concentration of R1HCdCHR2 yields a straight line with a slope equal to 1.0 as shown in Figure 3. The results can be expressed as
Re/[R1HCdCHR2] ∝ [R1HCdCHR2]
(28)
Effect of the Concentration of the Catalyst. The results indicate that increasing the concentration of the
1488 Ind. Eng. Chem. Res., Vol. 36, No. 5, 1997 Table 3. Effect of Concentration of Co2+-TPP on the Epoxidation Rate in the Presence of Benzaldehydea concentration of Co2+-TPP × 104, M
[Co2+-TPP]0.5 × 102, M0.5
Re × 103, M/min
0.75 1.45 2.90 4.88
0.87 1.20 1.70 2.21
1.10 1.84 2.40 3.55
a Temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; oxygen flow rate, 150 mL/ min; stirring rate, 800 rpm.
Figure 2. Effect of the concentration of benzaldehyde on the epoxidation rate in the presence of benzaldehyde: temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of Co2+-TPP, 7.3 × 10-5 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm. Table 2. Effect of Concentration of Oleic Acid on the Epoxidation Rate in the Presence of Benzaldehydea concentration of oleic acid, M
Re × 103, M/min
Re/[oleic acid] × 103, L/min
0.20 0.25 0.30 0.44
2.13 2.00 1.84 1.29
10.65 8.00 6.15 2.92
a Temperature, 303 K; concentration of benzaldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
Figure 4. Effect of the concentration of Co2+-TPP on the epoxidation rate in the presence of benzaldehyde: temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
against the concentration of [Co2+-TPP]0.5 yields a straight line with a -0.388 intercept as shown in Figure 4. The intercept corresponds to a minus epoxidation rate which is unreasonable. However, the zero epoxidation rate occurred at 4.8 × 10-6 M catalyst Co2+-TPP. Again, a minimum catalyst concentration is required because the epoxidation is retarded by oleic acid. The results can be expressed as
Re ) -0.388 + [Co2+-TPP]0.5, [Co2+-TPP] > 4.8 × 10-6 M (29)
Figure 3. Effect of the concentration of oleic acid on the epoxidation rate in the presence of benzaldehyde: temperature, 303 K; concentration of benzaldehyde, 1.8 M; concentration of Co2+TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
catalyst results in an increase of the initial reaction rate. Increasing the concentration of catalyst from 0.75 × 10-4 to 4.88 × 10-4 M increases the rate of epoxidation from 1.1 × 10-3 to 3.55 × 10-3 M/min as shown in Table 3. The plot of the initial rate of epoxidized oleic acid
Effect of Partial Pressure of Oxygen. The partial pressure of oxygen is adjusted by mixing the oxygen stream with a desired nitrogen stream at a constant total flow rate. When the partial pressure of oxygen is increased from 0.37 to 1.0 atm, the rate of epoxidation increases from 1.03 × 10-3 to 1.84 × 10-3 M/min as shown in Table 4. The plot of the initial rate of epoxidation of oleic acid against the partial pressure of oxygen, [Po2]0.5, yields a straight line with a -0.262 intercept as shown in Figure 5. The results reveal that at least 0.017 atm of oxygen partial pressure is required to make the epoxidation occur. The results can be expressed by
Re ) -0.262 + [Po2]0.5, [Po2] > 0.017 atm
(30)
Effect of Temperature. A straight line is obtained for the logarithmic plot of the initial reaction rate of epoxidized oleic acid against the reciprocal of temper-
Ind. Eng. Chem. Res., Vol. 36, No. 5, 1997 1489 Table 4. Effect of Partial Pressure of Oxygen on the Epoxidation Rate in the Presence of Benzaldehyde partial pressure of O2, atm
[Po2]0.5, atm0.5
Re × 103, M/min
0.37 0.55 0.75 1.00
0.61 0.74 0.87 1.00
1.03 1.22 1.45 1.84
a
Temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; stirring rate, 800 rpm.
Table 5. Effect of Types of Benzaldehyde Derivatives on the Epoxidation Rate in the Presence of Benzaldehydea types of benzaldehyde derivatives
Re × 103, M/min
4-methoxybenzaldehyde benzaldehyde 4-chlorobenzaldehyde
14.1 1.84 0.47
a Temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of aldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
Table 6. Effect of Pyridine on the Epoxidation Rate in the Presence of Benzaldehydea concentration of pyridine × 104, M
Re × 103, M/min
induction period, min
0 0.38 0.75 1.45 2.90
1.84 1.20 1.07 0.89 b
27.00 34.00 40.00 47.00
a Temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of aldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm. b No reaction after 2 h.
Figure 5. Effect of the partial pressure of oxygen on the epoxidation rate in the presence of benzaldehyde: temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; stirring rate, 800 rpm.
Figure 7. Effect of pyridine on the epoxidation rate in the presence of benzaldehyde: temperature, 303 K; concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
Figure 6. Effect of temperature on the epoxidation rate in the presence of benzaldehyde: concentration of oleic acid, 0.3 M; concentration of benzaldehyde, 1.8 M; concentration of Co2+-TPP, 1.45 × 10-4 M; oxygen flow rate, 150 mL/min; stirring rate, 800 rpm.
ature as shown in Figure 6. The slope of this straight line is -10 032, which corresponds to an activation energy of 19.87 kcal/mol. Effect of Types of Benzaldehyde Derivatives. The strength of how the types of benzaldehyde deriva-
tives affect the rate of epoxidation of oleic acid is in the order 4-methoxybenzaldehyde > benzaldehyde > 4-chlorobenzaldehyde as shown in Table 5. The results indicate that the benzaldehyde with a electron donor functional group can promote the rate of epoxidation. Effect of Pyridine. The experimental results indicate that increasing the concentration of pyridine decreases the rate of epoxidation of oleic acid. When the concentration of pyridine is increased from 0 to 1.45 × 10-4 M, the rate of epoxidation of oleic acid decreases from 1.84 × 10-3 to 0.89 × 10-3 M/min as shown in Table 6, while the induction period of epoxidation increases from 27 to 47 min as shown in Figure 7. It indicates that the pyridine retards the free-radical reaction. On the basis of the experimental results of eqs 2730, the rate equation of epoxidation of oleic acid can be combined and expressed by
1490 Ind. Eng. Chem. Res., Vol. 36, No. 5, 1997 Table 7. Comparison of Experimental Results and Theoretical Analysis of Reaction Kinetics for the Epoxidation of Oleic Acid reaction order
a
parameter
experimental
theoretical
PhCHO R1HCdCHR2 Co2+-TPP Po2
0.5 a 0.5 0.5
0.5 a 0.5 0.5
Re/[R1HCdCHR2] ) const1 + const2[R1HCdCHR2].
Re ) -Kel[R1HCdCHR2]2 + Ke2[R1HCdCHR2][Po2]0.5[PhCHO]0.5[Co2+-TPP]0.5 (31) The experimental results correlate the theoretical analysis well as shown in Table 7. Conclusions On the basis of the epoxidation of oleic acid in the presence of both benzaldehyde and oxygen using Co+2TPP as catalyst, a very good yield of epoxidized oleic acid can be obtained. The reaction mechanism for the epoxidation of oleic acid in the presence of both benzaldehyde and oxygen using Co2+-TPP as catalyst was found to be a series of free-radical reactions. The effects of pyridine and types of benzaldehyde derivatives were obtained. The experimental results correlated well with the theoretical analysis. The rate equation of forming epoxidized oleic acid was also obtained and expressed as eq 31. Acknowledgment The support of the National Science Council (NSC 830416-E-006-016) of Republic of China and National Cheng Kung University is knowledged. Literature Cited Allen, G. C.; Aquilo. Metal-in Catalyzed Oxidation of Aldehydes. In Oxidation of Organic Compounds; Gould, R. F., Ed.; American Chemical Society; Washington, DC, 1986; Vol. 2, pp 36381. Chen, L. C.; Chou, T. C. Heterogenized Homogeneous Catalyst 7. Comparisons of Thermal Oxidation and Heterogenized Homogeneous Co- and Mn-Type Resin Catalyzed Oxidation of Propionaldehyde. Ind. Eng. Chem. Res. 1994, 33, 2533-2529.
Chou, T. C.; Lin, F. S. Effect of Interface Mass Transfer on the Liquid-phase Oxidation of Acetaldehyde. Can. J. Chem. 1983, 61, 1295-1300. Chou, T. C.; Lee, C. C. Heterogenizing Homogeneous Catalyst. 1. Oxidation of Acetaldehyde. Ind. Eng. Chem. Fundam. 1985, 24, 32-39. Chou, T. C.; Yeh, H. J. Heterogenized Homogeneous Catalyst. 5. The Theory of Solvent Effect and the Effect of Solvent on Adsorption and Diffusivity. Ind. Eng. Chem. Res. 1992a, 31, 130-137. Chou, T. C.; Yeh, H. J. Heterogenized Homogeneous Catalyst. 6. Effect of Solvent on Initiation, Propagation-Termination, Decomposition, and an Overall Heterogeneous-Free-Radical Reaction System. Ind. Eng. Chem. Res. 1992b, 31, 804-818. Chou, T. C.; Lin, J. Y.; Do, J. S. Heterogenized Homogeneous Catalyst. 4. Catalyst with a Bias Active Site Distribution, Ind. Eng. Chem. Res. 1990, 29, 180-186. Hwang, B. J.; Chou, T. C. Heterogenizing Homogeneous Catalyst. 2. Effect of Particle Size and Two-phase Mixed Kinetic Model. Ind. Eng. Chem. Res. 1987, 26, 1132-1140. Honda, K.; Hata, S.; Tsuchida, E. Adsorption and Description of Molecular Oxygen in Solid State of Polymeric Hemochrome. Bull. Chem. Soc. Jpn. 1976, 49, 868-71. Kuo, M. C.; Chou, T. C. Kinetics and Mechanism of the Catalyzed Epoxidation of Oleic Acid with Oxygen in the Presence of Benzaldehyde. Ind. Eng. Chem. Res. 1987, 26, 274-284. Kuo, M. C.; Chou, T. C. Epoxidation of Oleic Acid with Oxygen in the Presence of Benzaldehyde Using Heterogenized Homogeneous Co-type Ion-exchange Membrane as Catalyst Can. J. Chem. Eng. 1990, 68, 831-838. Metelitsa, D. I. Reaction Mechanism of the Direct Epoxidation of Alkenes in the Liquid Phase. Russ. Chem. Rev. 1972, 40 (10), 807-821. Tezuka, M.; Sekiguchi, O.; Ohkatus, Y.; Osa, T. Oxidation of Acetaldehyde Catalyzed by Cobalt(II) Tetraphenylporphyrin. Bull. Chem. Soc. Jpn. 1976, 49, 2765-69. Walker, F. A. Steric and Electronic Effect in the Coordination of Amines to a Cobalt(II) Porphyrin. J. Am. Chem. Soc. 1973, 95 (4), 1150-54. Walker, F. A.; Beroiz, D.; Kadish, K. W. Electronic Effect in Transition Metal Porphyrins 2. The Sensitivity of Redox and Camplex of Cobalt(II). J. Am. Chem. Soc. 1976, 98 (12), 348489.
Received for review July 26, 1996 Revised manuscript received January 8, 1997 Accepted January 13, 1997X IE960454Y
X Abstract published in Advance ACS Abstracts, February 15, 1997.
