Ind.
Eng. Chem. Process Des. Dev. 1981, 20, 625-629
relatively well for a single solute at low adsorption POtentials (high concentrations). Acknowledgment
This work was supported by the U.S. Department of Energy under Contract No. E(29-20-3780). The authors gratefully acknowledge the efforts of Mr. Jorge Vierma for assisting in taking the experimental data. L i t e r a t u r e Cited Dubinin, M. M. Chem. Rev. 1960, 60, 235. Gustatson, R. L.; A W t . R. L.; Heisk, J.; Lkb, J. A.; ReM, 0. T., Jr. I d . €4. Chem. Rod. Res. Dev. 1968, 7, 107. Hensen, R. S.;Fackler, W. V. J . Phys. Chem. 1953, 57, 634. Manes, M.; Hofec, L. J. E. J . phys. Chem. 1969, 73, 584.
825
Paleos, J. J . coudd Interface Scl. 1969, 37, 7. Polanyi, M. V e h . Deut. FWsk, Ges. 1916, 78, 55. Polanyi, M. Z . phys. 1920, 2, 111. Radke, C. J.; Prausnitz, J. M. I d . Eng. Chem. Fundam. 1972, 7 7 , 445. Wohleber, D. A.; Manes, M. J. phys. Chem. 1971a, 75, 61. M. J . them. 1g71b* 759 3720. Wohleber, D. A.;
Received for review July 14,1980 Revised manuscript received May 26, 1981 Accepted May 26, 1981 Supplementary Material Available: Tables of equilibrium adsorption data of acetic, propionic, n-butyric, and n-hexanoic acids on Amberlite XAD-2 resin (4 pages). Ordering information is given on any current masthead page.
Kinetics of Hydrogenation of Cardanol V. Madhusudhan, M. A. Slvasamban,' and R. Valdyeswaran Regional Research Laboratory, Hyderabad, India
M. Bhagawantha Rao University College of Technology. Osmanla University, Hyderabad, India
The kinetics of liquid-phase hydrogenation of cardanol to 3-pentadecylphenol has been studied with Raney nickel and Rufert nickel catalysts. With Raney nickel the variables studied were temperature (100-160 O C ) , pressure (45-200 psig), and catalyst concentration (0.25-2%). With Rufert nickel, temperature was varied between 100 and 160 O C , at pressure 150 psig and catalyst concentration 0.75%. The reaction rate constants, activatlon energies, and frequency factors based on the consecutive reaction mechanism were evaluated.
values (Tyman and Morris, 1967; Murthy et al., 1968).
Introduction
Hydrogenation of cardanol yields 3-pentadecylphenol (3-PDP), a product which offers great chemical maneuverability in the synthesis of a variety of compounds of potential application (Caplan, 1942; Sethi et al., 1963; Hemalatha et al., 1963; Pansare and Kdkami, 1964; Gulati and Subba Rao, 1966; Jones and Robson, 1950; Hemalatha and Aggarwal, 1969; Harvey, 1952; Ramalingam, 1975). Several studies have been reported on the catalytic hydrogenation of cardanol at normal and elevated temperatures and pressures, employing various catalysts (Caplan, 1942; Hemalatha et al., 1963; Sethi and Subbarao, 1964; Madhusudhan et al., 1973; Smit, 1931; Wasserman and Dawson, 1945). Although hydrogenation of cardanol using b e y nickel and other commercial Catalysts gives 3-PDP of high purity, kinetics and mechanism of the hydrogenation reaction have not been studied, possibly because of the complications involved in interpreting the results as cardanol obtained by distillation of cashew nut shell liquid is not a single compound but a mixture of a number of meta alkyl-substituted phenols, varying in the degree of unsaturation in the side chain. Argentated thin-layer chromatography (TLC) of cardanoi (I) has shown that it consists of four components which have been characterized 89 saturated (II),mono- (III),di- (IV) and tri- (V) olefins, with reference to the side chain, from their hydrogenation 0196-4305/81/1120-0625$01.25/0
OH
OH
I
I
I1
OH
I11 OH
IV OH
1
V
The object of the present investigation has been to arrive at a kinetic model and a reaction mechanism for the hy0 1981 American
Chemical Society
626
Ind. Eng. Chem. Process Des. Dev., Vol. 20, No. 4, 1981
Table I. Iodine Values, Their Relationship to the Concentrations of Various Components of Cardanol (Raney Nickel, cat. concn 2%; temperature 140 'C; pressure 150 psig; rpm 550) iodine values (I.V.) calcd from TLC species concns triolefin
CASg-
diolefin
time. min'
mol/L. exptl'
I.V.. calcd
0 20 40 60 80
0.8103
142.5
-
monoolefin
cc, g-
CB, gmol/L. exptl'
I.V.. calcd
mol/L. exptl'
I.V.. calcd
0.7412 1.4756 1.1841
101.1 201.3 161.6
1.4843 1.6136 1.9030 1,4350 1.2779
162.0 176.1 207.7 156.6 139.5
drogenation of cardanol to 3-PDP using Raney nickel and Rufert nickel catalysts in a batch autoclave. Experimental Section Materials. Cardanol. Cardanol used in the present study had the following characteristics: iodine value (determined by Rosenmund Kuhnhenn (RK) methodASTM designation, D1541-58T), 395.4; specific gravity, 30°/30 OC, 0.93. Composition (determined by TLC followed by densitometry technique of Chobanov et al., 1976) % by weight: saturated, nil; monoolefin, 48.20; diolefin, , 0 23.91; triolefin, 27.89. Hydrogen. Electrolytic hydrogen gas from cylinders. Catalysts. Raney nickel, prepared according to the W-2 method (Mozingo, 1955). Commercial Rufert nickel catalyst (16.2% nickel content). Procedure. Cardanol(500 g) and the required quantity of catalyst were charged into a Parr medium-pressure hydrogenator of 1 L capacity provided with a Variac to control the heat input, thermocouple, mechanical stirrer, and pressure gauge. The unit was heated keeping the stirrer on. When the reactor temperature reached a value about 10 "C below the operating temperature, hydrogen gas was introduced into the hydrogenator to displace air inside the reactor. The vent valve was then closed and the reactor was pressurized to the desired value. The pressure was maintained constant throughout the run by means of a pressure-regulating valve. As soon as the hydrogen gas was introduced into the reactor, the liquid temperature rose rapidly. The temperature was maintained at the desired value (fl-2 "C) by the manual operation of the Variac. Six to nine samples were collected at regular intervals during each experiment by operating the outlet valve and closing the gas inlet. Each time the first few milliliters of the sample were discarded and the next 10 mL were collected and filtered through Whatman filter paper, while hot, to separate the catalyst. The extent of hydrogenation was followed by determining the iodine values of the collected samples by RK method (ASTM designation, D1541-58T). The different components in the hydrogenated samples were quantitatively estimated using TLC and densitometry technique (Chobanov et al., 1976). In the case of Raney nickel catalyst, the variables studied were: temperature, 100, 120, 140, and 160 "C; pressure, 45 and 65 psig (at 100 "C) and 100,150, and 200 psig (at all temperatures); catalyst concentration, 0.25,0.5, 1.0, 1.5, and 2.0%; stirrer speed, 550 rpm. In the case of Rufert nickel catalyst, the conditions were: temperature, 100,120, 140,and 160 "C; pressure, 150 psig; catalyst concentration, 0.75%; stirrer speed, 775 rpm. To examine the effect of agitation on the hydrogenation, a set of experiments was carried out with Raney nickel at a stirring speed of 775 rpm and Rufert nickel at a stirring speed of 550 rpm keeping temperature, pressure, and catalyst concentration constant.
0
saturated CD, g-
mol/L. exptl .
I
I.V.. calcd
-
-
-
1.6335 1.7896
0
1
133.7 146.5
I.V. obtained aggregate by exptl I.V.. determicalcd nation
405.6 317.4 369.3 290.3 286.0
0
550RPM
0
775RPM
eo
120
dev, %
395.4
+2.5
311.0
tO.l
351.0 343.5 294.4
+3.4 -15.5 -2.8
I60
TIME,MIMJTES
Figure 1. Effect of agitation on hydrogenation rate: temperature, 140 "C; pressure, 150 psig; and 2% h e y nickel. I
0O 60 I
/
160°/
/
TIME,
/
MINUTES
Figure 2. Test for the first-order reaction: pressure, 150 psig; 550 rpm and 2% b e y nickel.
Results and Discussion Effect of Agitation. A comparison of the results obtained when the hydrogenation was carried out using Raney nickel catalyst at stirring speeds of 550 and 775 rpm, respectively, keeping temperature, pressure, and catalyst concentration constant, is made in Figure 1. Taking into consideration the theoretical iodine value of 3-PDP (250.5), it is evident from Figure 1 that at both stirring speeds completion of hydrogenation in the side chain as indicated by an iodine value of 254.2 is obtained at 120 min with no perceptible difference in the rate of hydrogenation. In the case of Rufert nickel catalyst also the rate of hydrogenation at the two stirring speeds was identical. Relationship Between Iodine Value and Species Concentration with Respect to Cardanol. Iodine values of the samples were computed based on the theoretical iodine values of the components and their concentrations in each sample. These iodine values are compared with experimentally determined values in Table I. The good agreement between the values indicates that the iodine value can be employed as a measure of the species concentration, within reasonable range of errors. Order of Reaction and Overall Reaction Rate Constant. For obtaining the order of reaction and overall reaction rate constant of hydrogenation of cardanol, the
Ind. Eng. Chem. Process Des. Dev., Vol. 20, No. 4, 1981 627
Table 11. Pseudo First-Order Rate Constants, Activation Energies and Frequency Factors temperature, "C
rate constant, min-'
k' k' k'
0.0029 0.0050 0.0084 0.1716 0.0082 0.0071
kl k2 k3
k' kl
0.0115
k2 k3
a
app act. energy, 140 120 100 kcal/gmol Raney Nickel (cat. concn 2%; pressure 150 psig; rpm 550) 0.0022 0.00200 0.00110 5.43 0.00210 5.05 0.0033 0.00260 0.0061 0.00420 0.00280 6.57 0.1260 0.09200 0.04400 7.93 0.0064 0.00600 0.00530 2.44 0.0055 0.00496 0.00366 3.75
160
Pressure 100 psig.
app frequency factor, min-'
1.88 1.84 19.64 2.03 x 103 0.14 0.60
Rufert Nickel (cat. concn 0.75%;pressure 150 psig; rpm 775) 0.0071 0.00340 0.00240 9.68 0.2571 0.13510 0.06800 14.52 0.0160 0.00560 0.00595 10.48 0.0140 0.00485 0.09416 12.99
9.90 x lo2 1 . 6 6 ~107 5 . 8 5 ~103 1.17 X 10'
Pressure 200 psig.
Table 111. Experimental and Calculated Values of Composition and Their Deviation (Raney Nickel, cat. wncn 2%;temperature 140 "C;pressure 150 psig; rpm 550) CA,g-mol/L CB,g-mol/L CC, g-mol/L time min exptl calcd dev,% exptl calcd dev,% exptl calcd dev,% 0.7412 0 0.8703 1.4843 5 0.4836 0.4638 -4.0 1.0911 1.1175 +2.4 1.5182 1.4743 -2.8 -5.1 10 0.2557 0.2471 -3.3 1.2834 12.949 +0.8 1.5522 1.4727 -7.1 15 0.1309 0.1314 +0.4 1.3701 1.3678 -0.2 1.5890 1.4754 -8.2 1.4756 1.3848 -6.1 1.6136 1.4799 20 1.1841 1.2772 +7.8 1.9030 1.4856 -21.9 40 1.4350 1.4801 -3.1 60 1.2779 1.4550 +13.8 80
CD ,g-mol/L exptl 0
calcd
dev,%
1.6335 1.7896
1.6157 1.6408
-1.1 -8.3
Table IV. Experimental and Calculated Values of Composition and Their Deviation (Raney Nickel, cat. concn 2%;temperature 160 "C;pressure 150 psig; rpm 550) ~
time, min
0 4 8 12 15 30 45
CA,g-mol/L
Cg, g-mol/L
exptl
calcd
dev,%
exptl
calcd
dev,%
exptl
calcd
dev,%
exptl
0.8703 0.4523 0.2308 0.1184
-
1.1421 1.3189 1.3832 1.3933 1.2890
+0.9 +4.7 +5.4 +0.7 +2.9
1.4843 1.5089 1.5982 1.6597 1.7061 1.8292 1.4350
1.4737 1.4712 1.4732 1.4182 1.4830 1.4766
-2.2 -7.9 -11.2 -16.8 -18.9 +2.8
0
-3.0 -4.6 -5.2
0.7412 1.1315 1.2585 1.3113 1.3826 1.2524
-
0.4386 0.2201 0.1122
-
-
~~
CD,g-mol/L
CC, g-mol/L
1.6335
calcd
dev,%
1.6192
-0.9
Table V. Experimental and Calculated Values of Composition and Their Deviation (Rufert Nickel, cat. concn 0.75%;temperature 120 "C; pressure 150 psig;rpm 775) time, min 0 5 10 15 20 40 60 80
CR,g-mol/L
Cn, g-mol/L
exptl 0.8703 0.4556 0.2278 0.1061
calcd
dev, %
0.4421 0.2249 0.1148
-2.9 -1.3 +8.2
exptl 0.7412 1.1439 1.3516 1.4353 1.4942 1.1594
CD,g-mol/L
calcd
dev, %
1.1420 1.3240 1.3967 1.4247 1.3138
-0.2 -2.0 -2.6 -4.6 + 13.3
data obtained in all the experiments were tested for the first-order reaction by plotting -In (I.V.)/(I.V.),, vs. time (typical example, Figure 2), where (I.V.) is iodine value at time t and (I.V.), is the initial iodine value of cardanol. These plots give straight lines. The linear relationship is found to be statistically significant with correlation coefficient varying from 0.98 to 0.99. The slopes of the straight lines are equal to the pseudo-first-order overall reaction rate constant, k', m the equation (Ibrahim and Lyle, 1957; Lyle and Jaime, 1962) (-r) = k'(1.V.) (1) The experimental values of k' are shown in Table 11.
exptl 1.4843 1.4936 1.5121 1.5490 1.5952 1.7092 1.3858 1.2318
calcd
1.4734 1.4743 1.4771 1.4800 1.4902 1.4856 1.4685
dev, %
exptl 0
calcd
dev, %
-1.3 -2.4 -4.6 -7.2 -12.8 0.2172 0.2918 +34.3 +7.2 1.6826 1.6102 -4.3 + 19.2 1.8356 1.6273 -11.3
Effect of Temperature. Results of the experiments on hydrogenation of cardanol at different temperatures are given in Table 11. The values indicate that the rate constants for the hydrogenation of cardanol increase with temperature in the range 100 to 160 O C . Effect of Pressure. The results of experiments on hydrogenation of cardanol at different pressures, the pressure being maintained constant during each experiment, are illustrated in Figure 3. It is evident from the figure that the rate of hydrogenation increases with increasing pressure. Effect of Catalyst Concentration. The results illustrated in Figure 4 indicate that the reaction rate increases
828
,
Ind. Eng. Chem. Process Des. Dev., Vol. 20, No. 4, 1981
80
oi
"
"
"
80
120
40
0
'
"
160
"
200
'
240
PRESSURE, PSlA
Figure 3. Effect of pressure on hydrogenation: 550 rpm and 2% Raney nickel.
7
6'o
5.0
TIME , MINUTES
Figure 5. Determination of relative rate constant, k~ pressure, 150 psig; 550 rpm; and 2% Raney nickel.
t
c
CAT CONC , * I .
Figure 4. Effect of catalyst (Raney nickel) concentration on hydrogenation: temperature, 140 "C;pressure, 150psig; and 550 rpm.
Figure 6. Arrhenius plots for the hydrogenation of cardanol: 550 rpm and 2% h e y nickel.
with increase in catalyst concentration. Correlation of Concentration Data. The change in concentrations of the four components of cardanol during the hydrogenation using Raney nickel catalyst at 140 "C and 160 "C are shown in Tables I11 and IV, respectively, and using Rufert nickel catalyst a t 120 "C in Table V. While the concentration of component A decreases, the concentrations of components B and C increase to a maximum and then decrease, and the concentration of component D increases continuously. The experimental data,therefore, indicate that the hydrogenation of cardanol is a consecutive reaction. The following reaction sequence is proposed for the hydrogenation of cardanol.
The following equations, derived from the above differential equations, represent concentrations of different components as a function of time.
hi
ki
A-B-C-D
cc =
ha
Since the overall rate of hydrogenation of cardanol is found to be directly proportional to the iodine value (concentration of component), the reaction is first order and it is assumed that each of the reactions is also firstorder and irreversible (Schmidt, 1968). The differential rate equations for the four components a t a particular pressure and at a particular catalyst concentration will then be
(4)
(5)
and
CD = 1 - CA - CB - CC
(9)
The values of kl for hydrogenation of triolefin to diolefin were obtained from the slopes of linear plots (Figure 5 , h e y nickel catalyst) and are given in Table 11. The kz and k3 values were obtained from eq 3 and 4, respectively, and are given in Table 11. Making use of these values and k' values, Arrhenius plots were drawn (Figures 6 and 7) and the apparent activation energies and frequency factors of the different reactions were calculated (Table 11). Calculated Values of Concentrations. The values of CA, CB, and Cc were computed making use of eq 6,7, and 8, respectively, and CDby difference according to eq 9. The deviations between the calculated and experimental values under different conditions were determined. Typical results are given in Table 111. It is found from the results
Ind. Eng. Chem. Process Des. Dev., Vol. 20, No. 4, 1981 829
'
Table VI. Comparison of Relative Reaction Rate Constants temperature, "C
---I
160 140 120 100 Raney Nickel (cat. conc. 2%; pressure 150 psig; rpm 550) kllk, 20.93 19.69 15.33 8.22 kilk3 24.17 22.91 18.55 12.02 kzlk, 1.15 1.16 1.21 1.46
i
0.100
=m
7 : T.
Rufert Nickel (cat. conc. 0.75%; pressure 150 psig; rpm 775) 16.07 24.13 11.43 k,lkz 18.36 27.86 16.35 ki lk3 1.14 1.15 1.43 kzlk3
0.010
I
0001
2.1
2.2
2.3
2.4
I
1
25
2.6
2.7
J
2 4
t/rX103'k
Figure 7. Arrhenius plots for the hydrogenation of cardanol: pressure, 150 psig; 550 rpm; and 2% Raney nickel.
O4
i TIME, MINUTES
Figure 8. Determination of overall reaction rate constant, k1 with calculatad iodine values: temperature, 140 "C;pressure, 150 psig; 550 rpm; and 2% h e y nickel.
that the equations proposed for consecutive first-order irreversible reaction for the hydrogenation of cardanol correlate well with the composition data within the range of experimental error. Comparison of kl,kz,and k3with k'. The calculated values of concentrations of various species of cardanol shown in Table I11 were obtained using the relative reaction rate constants kl,k2,and k3 (Table 11, temperature 140 "C)and eq 6 , 7 , and 8, respectively. For example, the iodine values corresponding to these calculated concentrations were computed and used to determine the overall reaction rate constant k' as 0.0038 at 140 "C (Figure 8). The value of k' obtained from the titrated iodine values (Figure 2) at the same temperature of 140 "C is 0.0033 (Table 11). The good agreement between the k' values obtained by these two different methods indicates that the values of relative reaction rate constants can be used to calculate the overall reaction rate constant. Selectivity. The consecutive reaction mechanism shown under correlation of concentration data represents the elimination of triolefin and the formation of diolefin, monoolefin, and saturated components of cardanol during hydrogenation. Selective hydrogenation, i.e., preferential saturation of these components, is expressed by the ratios of the relative reaction rate constants, kl,kp,and k3 (Table VI). I t is evident from the concentration data in Tables 111, IV, and V that the formation of saturated component is negligible until triolefin and diolefin components have almost been eliminated. From the values of relative re-
action rate constants and the concentration data it is obvious that the preference is high for triolefin hydrogenation as compared to diolefin and monoolefin hydrogenation. High temperatures promote selectivity in hydrogenation (Bailey, 1949). In the case of Raney nickel catalyst it is seen that the selectivity increases with temperature over the range studied; in the case of Rufert nickel catalyst, however, it is seen that while the selectivity at 120 "C is higher than at 100 "C,it decreases at a higher temperature (140"C). Further studies are needed to explain the behavior of this catalyst. Nomenclature A = triolefin component of cardanol B = diolefin component of cardanol C = monoolefin component of cardanol CA = concentration of triolefin at time t , g-mol/L CAO = initial concentration of triolefin, g-mol/L CB = concentration of diolefin at time t , g-mol/L Cm = initial concentration of diolefin at time t , g-mol/L Cc = concentration of monoolefin at time t , g-mol/L Cco = initial concentration of monoolefin, g-mol/L CD= concentration of saturated component at time t, g-mol/L CW = initial concentration of saturated component, g-mol/L D = saturated component of cardanol K' = overall reaction rate constant, min-' K1, kz, k3 = relative reaction rate constants, min-I (-r) = reaction rate Literature Cited Albrlght, L. F.; Wisniak, J. J . Am. 011 Chem. Soc. 1962, 39, 14. Bailey, A. E. J. Am. OUChem. Soc. 1949, 28, 644. Caplan, S. US. Patent 2 284 369, 1942. Chobanov, D.; Tarandjiska, R.; Chobanova, R. J . Am. O// Chem. Soc. 1978, 53(2), 48. Eldlb, I. A.; Albrlght, L. F. Ind. Eng. Chem. 1957, 49(5), 825. Gulati, A. S.; Subba Rao, B. C. Indian J. Chem. 1966, 4 , 265. Harvey. M. T. U.S. Patent 2586 19 I , 1952. Hemalatha Isaiah, N.; Slvasamban, M. A.; Aggarwal, J. S. Peinf/ndh 1963. 13(1), 125. Hemalatha Isaiah, N.; Aggarwal, J. S. Paht Menuf. 1969, 39(1I), 41. Jones, E. R. H.; Robson, I.K. M. Br. Patent 634980, 1950. Madhusudhan, V.; Ramaiah, M. S.; NaMu. N. B.; Slvasamban, M. A. Indlan J . Techno/. 1973, 77(8), 347. Mozingo, R. "Organic Syntheses"; Coll. Vol. 111; Wlley: New York, 1955; p 181. Murthy, 8. G. K.; Slvasamban, M. A.; Aggarwal, J. S. J. Chromefogr. 1968. 32,519. Pansare, V. S.; Kulkarni, A. 8. J. Indian Chem. Soc. 1964, 41, 251. Ramallngam, T. Ph.D. Thesis, Osmanla University, 1975. Schmidt, H. J. J. Am. OilChem. Soc. 1968, 45, 520. Sethi, S. C.; Subba Rao, B. C.; Kulkarnl, S. B.; Kattl, S. S. Indian J . Techno/. 1963, I , 348. Sethi, S. C.; Subba Rao, B. C. Indian J . Chem. 1964, 2(7), 277. SmR, A. J. H. Proc. Acad. Sci. Amsf. 1931, 34, 165. Tyman, J. H. P., Morris, L. J. J . Chromatogr. 1967, 27, 287. Wasserman, D.; Dawson, C. R. Ind. Eng. Chem. 1945, 37. 396.
Received for review December 8,1978 Revised manuscript received April 16,1981 Accepted May 30,1981
