75
Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 75-77
and the data gathered by nitrogen adsorption. On the other hand, this anomaly does not appear to affect catalyst E. A VIP ratio of 2 for 20-30 mesh particles and 1/16-in. extrudates is between the ratio of 3 which indicates that possibly only the external surface is involved in the adsorption and the ratio of 1 which is characteristic of a non-diffusion-limited process on a porous catalyst of large internal surface area.
Drushel, H.V., Am. Chem. SOC.,Div. Pet. Chem. Prepr., 17,No. 4 (1972). Funk, E. W., Gomez, E., Anal. Chem., 49, 972 (1977). Moschopedis, S. E., Fryer, J . F., Speight, J . G., Fuel, 55, 227 (1976). Prasher, B. D., Ma, Y. H., AIChE J . , 23. 303 (1977). SaintJust, J.. Anal. Chem.. 50, 1647 (1978). Satterfield, C. N., Cotton, C. K.. Pitcher, W. H., Jr., AIChE J., 19, 629 (1973). Schwager, I., Lee, W. C., Yen, T. F., Anal. Chem., 49, 2363 (1977).
Literature Cited
Presented before the Division of Petroleum Chemistry, 176th National Meeting of the American Chemical Society, Miami, Fla., Sept 15, 1978.
Alpert, S. B., Wolk, R . H.. Maruhnic, P., Chervenac, M. C. (to Hydrocarbon Research), US. Patent 3630888 (Dec 28, 1971).
Received f o r review February 28, 1979 Accepted October 11, 1979
Liquid-Phase Oxidation of Ethylbenzene over Cobalt Complexes Supported by Polymeric Materials Ayaz
A. Efendiev,' Togrul N. Shakhtakhtinsky, Leila F. Mustafaeva, and Harry L. Shick
Institute of Theoretical Problems of Chemical Technology of the Academy of Sciences of the Azerbaijan SSR, 29, Narimanov Prospect, 370 143, Baku, USSR
The oxidation reaction of ethylbenzene proceeding in the liquid phase in the presence of complexes of cobalt with a specially arranged for cobalt sorption copolymer of diethyl ester of vinylphosphonic acid with acrylic acid cross-linked by methylenediacrybmidewas studied in a gasometric unit. The experiments were performed at atmospheric pressure in a temperature range of 70-135 O C in the absence of solvent. The catalyst amount ranged from 1.5 to 6 g/L, which corresponds to a cobalt content of 6.45 to 25.8 mequiv/L. The catalyst can be used repeatedly without losing its catalytic activity. The influence of the amount of catalyst and the temperature on the reaction has been studied. The activation energy of the oxidation reaction appears to be 10 kcal/mol.
Introduction The last few years have witnessed a growing interest in the preparation and use of catalysts on the base of transition metal complexes with cross-linked polymers having complex forming groups. Such catalytic systems are of particular interest because they can combine the advantages of heterogeneous catalysts, such as simplicity of separation from the reaction mixture and stability. as well as homogeneous catalysts, such as high selectivity and possibility of handling more exact information about active centers structure. At the Institute of Theoretical Problems of Chemical Technology of the Academy of Sciences of Azerbaijan SSR (USSR) we have developed a method of preparation of transition metal complexes with specially arranged polymers. The general principle of our method involves interaction of linear polymer and ions to be sorbed in solution, Le., under conditions when macromolecules' segments are still mobile enough, subsequent fixation of optimal for the ion uptake conformation of macromolecules by cross-linking of metal-polymer complexes, and removal of ions from cross-linked sorbent. As a result of such treatment, we managed to improve essential sorption characteristics of cross-linked sorbent, namely its capacity, selectivity, and sorption kinetics. As an object for such treatment we used a copolymer of' diethyl ester of vinylphosphonic acid and acrylic acid 0196-4321/80/1219-0075$01.00/0
(Efendiev et al., 1977; Kabanov et al., 1974) containing 9.2% by weight of phosphorus having molecular mass of 160000. Cross-linked sorbents on the base of that copolymer could form complexes with ions of copper, cobalt, and nickel. Experimental Section Diethyl ester of vinylphosphonic acid was prepared in accordance with the method of Kolesnikov et al. (1959), and after double distillation the product with bp 62 "C (2 torr), nmD1.4300 (lit.bp 68-70 "C (3 torr), nmD1.4300) was isolated. Conventional acrylic acid was distilled twice in vacuo (bp 39 "C (10 torr) before use. Bulk copolymerization of the monomers was carried out by photochemical initiation of the mixture of monomers with 1 wt % cumene hydroperoxide in a sealed test tube of quartz glass which was evacuated at lo4 torr. UV light was supplied from a high-pressure mercury lamp of 300 W. The resulting copolymer was dissolved in ethanol and then precipitated dropwise in an excess amount of diethyl ether. After three reprecipitations the copolymer was dried in a vacuum desiccator a t only a slightly elevated temperature. A fairly dilute ethanol solution of copolymer (0.8 g/100 cm3) was mixed with a double amount of 0.075 M solution of cobalt chloride salt adjusted to pH 1.1with HC1. The resulting mixture was then slowly titrated by ammonia solution until a pH value of 5.20 was achieved. The rate of titration was so chosen that the p H increase was not 1980 American Chemical Society
76
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 1, 1980
- GH - GH,
- GH, OR
I
\
-
0 1 ;"C
,P=O
OR
-CH
I
10
'\
5
I
/
40
0 " 30
0 a
a
0 I
01
,
20
m
IO
- CH - GH,-GH-
-GH,
TIME ( m i n )
Figure 1. Structural formula of cobalt-polymer complex.
Figure 3. Kinetic curves of the oxygen absorption for different runs. 80
-
60
-ap Y
z
2
I
I
32
I
I
I
20
28
c)
0
40
c -E ' -0
20
o
E
80
24 20
18 I2
08
I
L
N
0-
60
z a
a
3
40
9
15
CONCENTRATION
20 n 1900
1500
1100
700
(cdl Figure 2. Infrared spectra of the initial copolymer (a) and its complex with cobalt containing 4.3 mequiv/g of cobalt (b).
21
27
33
OF COBALT ( m e q /
1)
Figure 4. Dependence of the reaction rate and the maximum amount of the absorbed oxygen on the amount of the catalyst. ( t = 100 " C ) .
WAVELENGTH
4
i
t
20
15
greater than 0.2 h. The precipitated metal-polymer complex was filtered, repeatedly washed with distilled water until the washings gave a negative test for cobalt, and dried in vacuo a t 35-40 O C . The dry metal-polymer complex was mixed with methylenediacrylamide as the cross-linking agent and the mixture was ground in a vibrating ball mill having a ball diameter of 0.8 cm for 1min. The resulting mixture had a particle size within the range of 150-200 mesh. A small amount (up to 5%) of smaller particles was set aside. Tablets with a thickness of 0.025 cm and a diameter of 0.8 cm were prepared from the mixture by pressing. The tablets were evacuated a t torr and heated in sealed test tubes a t 150 "C for 5 h. The cobalt held by the cross-linked copolymer was fully desorbed into 1 M HCl. Cross-linked tablets of specially prepared cobalt ion polymers were treated by CoC1, solution to obtain the complexes. The complex containing 4.3 mequiv of Co/g of dry sorbent was used to study the catalytic activity. Tablets were repeatedly washed with distilled water to remove any excess of cobalt, dried at 105 "C, and ground. Results and Discussion The scheme shown in Figure 1 illustrates the possible coordination of cobalt with the functional groups of the polymer. The scheme is based on data of cobalt uptake and IR spectroscopy. The uptake of cobalt ions by the polymer from CoClz solution is not accompanied by a change in C12- anion concentration. At the same time, the concentration of H+ increases equivalent to that of sorbed cobalt. This points out the fact that the sorption occurs by means of the replacement of hydrogen of the carboxylic group by cobalt ions. Meanwhile, the ions of alkali-earth metals are not sorbed by the sorbent. This shows that a sorption process involving nonionized carboxylic groups might take place only due to the formation of additional
-
N
0
10
80
90
100
TEMPERATURE
110
120
130
140
("C)
Figure 5. Dependence of the reaction rate and the maximum amount of the absorbed oxygen on the temperature.
coordination bonds between the ions and corresponding functional groups of the sorbent. Comparison of the infrared spectra recorded for both the initial copolymer (Figure 2a) and its complex (Figure 2b) shows that characteristic frequencies at 1740 cm-' and the broadened band with two maxima at 1180 and 1240 cm-' associated respectively with C=O and P=O groups undergo changes due to complex formation. The peak a t 1740 cm-' diminishes and extra peaks a t 1640 and 1580 cm-' appear. The ratio of the maximum a t 1180 cm-' to the maximum a t 1210 cm-' also changes because of complexing with cobalt ions. This shows that both C=O and P=O groups form coordination bonds with copper. The reaction of liquid-phase oxidation of ethylbenzene has been chosen for that investigation. The experiments were carried out in the gasometric unit under conditions when oxidation of ethylbenzene did not take place in the absence of a catalyst. Gaseous oxygen was used as the oxidizer at atmospheric pressure. The reaction was carried out in the absence of solvent. The catalytic activity of the taken sample was evaluated according to the oxygen absorption rate and the maximum amount of 0, consumed in the reaction. We found that the catalyst can be used many times without losing its catalytic activity. Moreover, when using
77
Ind. Eng. Chem. Prod. Res. Dev. 1980, 79,77-82
the catalyst repeatedly the reaction proceeded without an induction period (Figure 3). T o refine the influence of the amount of catalyst used and the temperature of the proceeding reaction, catalyst concentrations have been ranged from 1.5 to 6 g/L, which corresponds to a cobalt content of from 6.45 to 25.8 mequiv/L, and the temperature has been ranged from 70 to 135 "C. T h e results are shown in Figures 4 and 5 . As can be seen from the Figure 4, the highest rate is reached a t polymer concentrations corresponding to 20 mequiv/L of Co. The influence of temperature on the reaction over the range 70-135 "C (Figure 5) has been studied. The maximum rate is reached a t 125 "C. The amount of oxygen consumed in oxidation decreases when the temperature increases above 90 "C; i.e., inhibition takes place. The dependence of the reaction rate vs. temperature in Arrhenius coordinates is a straight line and this makes it possible to estimate the activation energy of the oxidation
reaction of ethylbenzene over cobalt supported by polymer. It proved to be 10 kcal/mol. Thus, the results obtained show that the complexes of cobalt with specially arranged polymers can be used repeatedly as catalysts for liquid-phase oxidation reactions without losing their catalytic activity. Literature Cited Efendiev. A. A., Orujev, D.D.,Kabanov, V.
A,, Vysokomol. Soedin., Ser. 8 , 19, 91 (1977). Kabanov, V. A,, Efendiev, A. A,, Orujev, D. D., Auth. Cert. USSR,502, 907 (1974);Bull. Inv., 8 (1976). Kolesnikov, G.S.,Rodionova, E. F., Fedorova, L. S.,Vysokomol. Soedin., 3,
367 (1959).
Received for review July 16, 1979 Accepted August 16, 1979 Presented a t the 6th Joint US-USSR Symposium on Catalysis, Cherry Hill, N.J., J u n e 1979.
Tri- and Perchloroethylene. 1. Fluid Catalytic Oxyhydrochlorination of Ethylene Adolfo Arcoya, Antonio Corti%,' and Xose L. Seoane Instituto de Catrilisis y PefroleoqGmica, C.S.I.C., Serrano, 119, Madrid (6), Spain
The fluid catalytic oxyhydrochlorination of ethylene to tri- and perchloroethylene has been studied at atmospheric pressure and temperatures between 370 and 430 O C over a catalyst containing a mixture of copper, potassium, and praseodymium chlorides supported on microspheroidal silica gel. Product distributions appear to depend mostly on reaction temperature and feed stoichiometry. We found that trichloroethylene yields increase with temperature and also with the ratio of chlorinating mixture (HCI 0,) to ethylene. Though it is less significant, the product yields do depend on reactor diameter and residence time. This makes scale-up of fluidized reactor difficult. On the basis of the data reported in this work a reaction scheme is postulated to account for all the reaction products: Le., chlorinated derivatives of ethylene, ethane, and methane.
+
Introduction
One of the possible routes for the production of tri- and perchloroethylene is the direct oxyhydrochlorination of ethylene. Oxyhydrochlorination takes place with HCl + O2 (air) + CzH4over a Deacon type catalyst between 350 and 400 "C as described by Knoop and Neikirk (1972). Together with the overall reactions
-
C2H, + 3HC1 + 3/202 C2HC13+ 3 H 2 0 CzH4
+ 4HC1 + 2 0 2
-
C2C14 + 4H20
(1)
(2)
which account for the formation of tri- and perchloroethylene, a number of oxyhydrochloro addition, oxyhydrochloro substitution, and oxyhydrochlorinolysis steps must also take place during the course of the reaction. This explains the appearance of other chlorinated compounds in the reaction products, namely the various chloro derivatives of ethylene, ethane, and methane. Because of the high amount of heat evolved in the process this is usually carried out in a fluid-bed catalytic reactor. Practically all the information concerning this oxyhydrochlorination process is found in patents. These normally describe the preparation of the catalysts employed and selected examples of the reaction. To our knowledge, the effect of the operating variables on the 0196-4321/80/1219-0077$01 .OO/O
product yields and selectivities has not been published. This has been the aim of the present investigation. Our purpose was to study the oxyhydrochlorination reaction with complete conversion of ethylene and maximum combustion to CO + C 0 2 of only about 10%. Under these conditions we attempted to maximize the production of trichloroethylene without decreasing perchloroethylene yield. In the second part of this series we shall describe the oxyhydrochlorination of 1,2-dichloroethane,also to triand perchloroethylene, in a fluidized reactor. Methods
The experiments were carried out in a conventional electrically heated catalytic unit, made of Pyrex glass. The fluidized reactor has a porous frit to support the catalyst and an internal coaxial thermowell to allow temperature reading inside the fluid bed. The reactor has two inlets, one for ethylene and the other for the mixture of air plus hydrogen chloride. Ethylene, purified air, and dry HC1 (299% pure) was fed from cylinders through rotameters and control valves. The rotatometers were calibrated many times throughout this work with flow metering "bubble burets". In the case of HCl, an acid aqueous solution of acetylpyridinium bromide was used in order to obtain a durable bubble in the corresponding buret. 0 1980
American Chemical Society
