Znd. Eng. C h e m . Res. 1988,27, 759-764 Tibbetts, G. G. GMR-4518 Report, Oct 21, 1983a; General Motors Research Laboratories, Warren, MI. Tibbetts, G. G. Appl. Phys. Lett. 1983b, 42(8), 666. Tibbetts, G. G., personal communications, 1984. Trimm, D. L. Catal. Reu.-Sci. Eng. 1977,16, 155. Trimm, D. L. In Pyrolysis: Theory and Industrial Practice; Al-
759
bright, L. F., Crynes, B. L., Corcoran, W. H., Eds.; Academic: New York, 1983; Chapter 9, pp 203-232.
Received for review September 19, 1986 Revised manuscript received September 21, 1987 Accepted December 11, 1987
Thermal Decomposition of Cyclohexane at Approximately 810 "C F. Billaud,*t P. Chaverot,t M. Berthelin,* and E. Freundg Departement de Chimie Physique des Rgactions, U A 328, CNRS, INPL-ENSIC, 1 rue Grandville, 54042 Nancy, France, Direction de Recherches, Recherche et Ddueloppement, Institut Franqais du Pdtrole, Centre d'Etudes et de Ddveloppement Industriels, Solaize, B P 3, 69390 Vernaison, France, and Direction de Recherche Physico-Chimie Applique6 et Analyses, Institut Franqais d u Pdtrole, 1 et 4 Avenue de Bois PrQau, B P 311, 92506 Rueil-Malmaison, France
In order to determine the behavior of cycloparaffins in steam cracking reactions, a study of the thermal decomposition of cyclohexane in the presence of n-decane has been carried out at ca. 810 "C by using the technique of plug flow reactor. Cyclohexane chiefly decomposes into ethylene, hydrogen, 1,3butadiene, and small amounts of cyclohexene. We propose a primary mechanism of the decomposition of cyclohexane initiated by n-decane. This mechanism leads to three main primary stoichiometries which account for the whole range of reaction products. 1. Introduction: Aims and State-of-the-Art Mushrush and Hazlett (1984) have pyrolyzed model compounds representative of shale crude to confirm that molecules containing long unbranched alkyl groups may be the source of n-alkanes in jet fuels derived from this source. We have used a rather similar approach in the present paper to describe and explain olefin production during the steam cracking of petroleum cuts liable to contain large amounts of naphthenic compounds in relation to linear alkanes. We began by investigating the n-decane-cyclohexane mixture. This model can simulate the behavior of cycloparaffins in naphtha. A better understanding of the initial decomposition processes of cyclohexane is thus very important for improving our understanding of the cracking and oxidation of cycloparaffins. Decompositions of naphthenic compounds have not been analyzed with as much precision as those of paraffins. Although a number of studies of cyclohexane or substituted cyclohexane pyrolyses have been reported, these were mainly concerned with product distributions and yields at high conversion and with possible contributions of surface effects (Fabuss et al., 1964a,b;Romavacek et al., 1972; Levish et al., 1969; Zdonik et al., 1967; Frey, 1949; Garnett et al., 1976); Gordon (1962) and Stein and Rabinovitch (1975) detected the isomerization of the cyclohexyl radical into methylcyclopentyl radicals in low-temperature experiments. Above 400 "C, cyclic radicals begin to split up (Gordon, 1962; Stein and Rabinovitch, 1975; Arai et al., 1960). Mechanistic modeling has been useful in studying the kinetics of pyrolytic reactions at low conversion (Tanaka et al., 1975;Powers and Corcoran, 1974; Murata and Saito, 1975). Few attempts have been reported at high conver-
sion levels similar to those of industrial cracking (Sundaram and Froment, 1978; Aribike et al., 1981). This stems from the large number of molecular species and free radicals with their associated reactions. The number of these reactive species drastically increases with conversion and leads to excessive computation time. Most of these studies have a particular emphasis on kinetics within the Rice (1931, 1933), Rice and Herzfeld (1934),and Rice and Kossiakoff (1943) theory parameters. Tsang (1978a,b) investigated the decomposition mechanism and initial velocities of cyclohexane from singlepulse stock tube experiments and demonstrated that the main initial process is the isomerization of cyclohexane into 1-hexene followed by the decomposition of 1-hexene. The initiation of chains during the dissociation of pure cyclohexane is difficult. The breaking of the C-H bonds requires an energy expenditure of 95.2 kcal/mol (Kondratiev, 1974), whereas breaking along the C-C bonds occurs at much lower velocity. This breaking requires only 77 kcal/mol and does not lead to the formation of any monoradicals. The isomerization of the biradical that is formed
through the intermediary of an activated complex with six centers considerably facilitates the initiation of chains following the formation of a weakened C-C bond in 1hexene. The breaking of this bond leads to a resonant allyl form (C3H5.):
+
C3H~
CH2=CH(CH2)&H3
-
I *CH2CH2CH3
1
t CNRS.
Institut Frangais d u PBtrole, Vernaison.
* Institute Frangais du PBtrole, Rueil-Malmaison. f
0888-5885/88/2627-0759$01.50/0
Ho
CH ,,
+
0 1988 American Chemical Society
C H j
+
CH2=CHCH2*
760 Ind. Eng. Chem. Res., Vol. 27, No. 5, 1988 Table I. Gas Chromatographic Analysis analysis for
column detector temp programming thermal conductivity 293 K isothermal H2 C,: silica gel, 2 m x in. ext., 2 m m int. flame ionization 8 min a t 293 K, C,-C4 hydrocarbons C2: 10% squalane on alumina, 140/220 mesh, 6.5 m X in., 2 mm int.; 10% squalane on Spherosil, 293-353 K at 4 K/min 100/140 mesh, 2.5 m X in., 2 mm int.; 10% squalane on Chromosorb PAW, SO/lOO mesh, 2.5 m X in., 2 mm int. CSf hydrocarbons C,: squalane, 100 m X in. ext., 0.2 mm int. flame ionization 8 min at 293 K, 293-372 K a t 4 K/min in. ext., 0.2 mm int. hydrocarbon liquids CB: squalane, 100 m X flame ionization 8 min a t 293 K, 293-372 K a t 4 K/min; back flush, 1000 s for the liquids
Pease and Norton (1933) and Tsang (1978a,b) has also proposed isomerization: cyclohexane s methylcyclopentane
+
products
Goubeau (1938), however, did not observe any methylcyclopentane by Raman spectrometry, so the above isomerization process must be minor. Kuchler (1939) also proposed the overall stoichiometry which cannot be very great because the amount of propene remaining is of the same order of magnitude as for the decomposition of pure n-decane. In fact, it seems that the mechanism of naphthenes decomposition is known with insufficient precision to permit good simulations of the distribution of the main primary products. Therefore, it seems interesting to resume the study of the pyrolysis of cyclohexane, especially because there is a demand from industry for a better understanding of this type of reaction (in particular for cycloparaffin cracking). This model compound was pyrolyzed in a 20 w t % mixture in relation to n-decane in a steam-cracking micropilot plant. Before comparing the different characteristic yields of steam cracking, we made a gas chromatography analysis of all the principal products. In light of the excess n-decane in the mixtures, we naturally observed all the principal products of the pyrolysis of n-decane alone. Emphasis will be placed on the nature of the products appearing in the pyrolysis of the mixture but not appearing in the pyrolysis of the reference compound (n-decane) or the changes in the kinetics configuration (primary or secondary products). To write the mechanism covering the products of decomposition, we considered cyclohexane in an environment of free radicals formed mainly by the decomposition of n-decane. To give a quantitative explanation of the principal primary stoichiometries of the decomposition of cyclohexane in the presence of n-decane, we defined the RA(B)ratios for the formation of a product B from A: RA(B)= no. of moles of B produced/ no. of moles of A transformed We will also make the assumption of noninteraction, thus implying that the difference in the ratios between n-decane alone and the mixture is due exclusively to the decomposition of cyclohexane. 2. Experimental Procedure With a hydrocarbon mixture containing 20 wt % cyclohexane as compared to n-decane (Prolabo R.P. Norma pure), the amount of vapor fed in was changed so that the partial pressure of n-decane at 810 “C remained constant with or without additive. The total pressure is near at-
mospheric pressure. This n-paraffin was chosen as a “cracking solvent” because at high temperature it is capable of creating a radical environment close to the one existing in industrial pyrolysis tubes. The cracking bench used has been described by Billaud et al. (1983) and Billaud and Freund (1984). The reaction section consisted of an Incoloy 800 tube in. in rated diameter and with an inside diameter of 2 mm, coiled around a nucleus of the same steel, and heated by highfrequency electromagnetic induction. The gaseous effluents were analyzed on line by gas chromatography. The liquid phase obtained in the cold decanter at the outlet of the quenching cooler was then analyzed by the same method. The overall column characteristics and operating conditions are summarized in Table I. Concerning the mass balances, n-Cloand c-C6flows were injected by a “Milton Roy” injection pump and the inlet mass of hydrocarbons is well defined (Heentv). After a run of an how, we weighed, after the decantation of the hydrocarbons-water mixture, the liquid hydrocarbon fraction (HC liquid). A gas meter measures the gas flow, the weight of which is determined (HC gas) by the gas chromatographic analysis and the assumption of perfect gases. The error in the mass balance is then HC,,,,, HCliquid- HC,,. We eliminate all the runs for which the error is larger than 0.5% f reactant. 3. Experimental Results
3.1. Surface Effects. There was no evidence of catalysis by the tube w& except after approximately 10 runs for n-decanecyclohexane. A literature search gives several examples where stainless steel does not show catalytic properties for this type of reaction (Mushrush and Hazlett, 1984; Crynes and Albright, 1969;Marschner, 1938; Kunzru et al., 1972). However, for low molecular weight hydrocarbons, surface effects have been found to be significant (Albright and Tsai, 1983; Albright and Yu, 1979). To inhibit any catalytic effects of the surface, a small amount of thiophene (300 ppm, C4H4S)was added to the feed. CO formation is then very small and is comparable to what is observed in industrial steam cracking plants. With a sulfur-free feed, the reaction of steam cracking, decomposition, and chemical reaction of water and hydrocarbons is (l/n)(CH2), + H20 -+ CO + 2Hz
It is catalyzed by nickel, a major component of the Incoloy 800 alloy, and CO formation (as well as H,) is multiplied by a factor of 200: HC flow, g h “ CO, % w t (without C4H4S) CO, % wt (with 300 ppm of C,H4S)
41 4.60 0.02
52 2.80 0.02
3.2. Products. The following figures (yields versus residence time) review some of the overall results at 810 “C for the pyrolysis of n-decane (Billaud and Freund,
Ind. Eng. Chem. Res., Vol. 27, No. 5, 1988 761 %
%
wt/Re;tants
wt/Reactants
% wt/Reactants
40
100
50
10 10
20
30
Figure 1. Yields of characteristic products: (-) C~H12-n-CloHzz, (- - -1 n-CloHn (reference).
%
wt/Reoctants
%
mixture c-
2 o eR.103
3O
Figure 3. Yields of characteristic products: (-) CsH12-n-CloHzz,(- - -) n-CloHz2(reference).
%
wt/ Reoctants
mixture c-
wt/Reactants
20
C3H6 c
15
I
I
,' I
y /
10
I
~enzene
I
1 5
0'
Figure 2. Yields of characteristic products: (-) C&12-n-C1,&2, (- - -) n-CloHzz(reference).
10
mixture c-
1986), and we will use them as references of n-decanecyclohexane mixtures. As for n-decane, we plot the yields of the characteristic products as a function of the residence time. According to Figure 1,in the presence of cyclohexane we can see that the amount of gas diminishes and that more cracking gasoline is formed. The 200+ quantities (the fraction which distills over 200 "C) seem to be unchanged. Figures 2-6 respectively represent H2, CHI, C3H6,1,3C4H6, 1-C4H8, and 1-C5HI0; cyclohexene and mono-
Figure 4. Yields of characteristic products: (-) C6H12-n-C10H22, (- -) n-CloHz2(reference).
-
mixture c-
aromatics; and C2H, and a-olefins from (26 to clo. According to these yields and in relation to the reference, there is less overall formation of ethylene, propene, and 1-butene, while the amounts of CS-C,~a-olefins remain unchanged. The amounts of hydrogen formed increase. Monoaromatics (benzene, toluene, ethylbenzene, styrene, and xylenes) are secondary products, as is the case in the steam cracking of n-decane. Nevertheless, benzene appears for much shorter residence times (about 3 ms instead of 10 ms for pure n-decane) (Figure 4).
762 Ind. Eng. Chem. Res., Vol. 27, No. 5, 1988 50
%
w!/Reactants
%
wt/Reac!an!s
I
40
30
20
10
10
Figure 5. Yields of characteristic products: CsH,2-n-CIoH22,(- - -) n-CIoHz2(reference).
(-)
mixture c-
In the Interpretation section, it will be shown that benzene is a product issuing from the dehydrogenation of cyclohexene, the principal primary product of the decomposition of cyclohexane. The formation of 1,3-butadiene (secondary product of n-decane pyrolysis) is primary for the reaction. 4. Interpretation 4.1. Radical-Chain Mechanism. It has already been said that the dissociation of pure cyclohexane is difficult. A reasonable explanation is the formation of cyclohexene, known as a free-radicalscavenger. Tsang (1978a,b), Brown et al. (1986), and Kalra et al. (1979) have carried out a single-pulse rate shock-tube study of the pyrolysis of cyclohexane. The dominant primary process was found to be isomerization to the open-chain hex-1-ene, followed by subsequent decomposition of this primary product. However, cyclohexene is less efficient than toluene as free-radical scavenger. For an n-decane-cyclohexane mixture, the primary decomposition of n-decane will be not influenced by the presence of cyclohexane, while cyclohexane does not increase the initiation velocity of the radical-chain decomposition of n-decane. On the other hand, the most reactive radicals present in the reaction medium and formed from the decomposition of n-decane (Billaud and Freund, 1986) can form a C6Hll*radical, by transfer processes. Even though there are about 5 times fewer free hydrogen atoms than CH,' radicals during the decomposition of noncyclic alkanes (Shevelikova et al., 1981),in a first approximation we will take into consideration only the free hydrogen atoms which are about 300 times more reactive than the methyl radicals (Kalinenko et al., 1978). This assumption was widely used in the laboratory for interpreting the pyrolysis of lighter alkanes such as propane (Jezequel et al., 1983) or neo-
30
20 e R . 1 0 3 ,
Figure 6. Yields of characteristic products: C6H12-n-CloH22, (- - -1 n-CloH22(reference).
(-)
mixture c-
pentane at high temperature ( h a y , 1981) or investigations of coreactions (Billaud et al., 1980, 1982a-c). On the basis of Rice-Kossiakoff free-radical theory, we propose the following primary mechanism for the radical decomposition of cyclohexane in the presence of a linear alkane, taking into consideration specific products of Cyclohexane decomposition (1,3-butadiene and cyclohexene) and the relative amounts of products already having come from the decomposition of pure n-decane. Let us consider a free hydrogen atom H' formed during the relatively easy decomposition of n-decane. H' can then react only bimolecularly on cyclohexane to form hydrogen and a C6Hll' radical (process 1 in Figure 7, H' R and H2 = RH)
He+@
-H2+o
This radical can either become dehydrogenated or can react by the breaking of a carbon-carbon bond at the (Y position of the carbon bearing the free electron. If we consider the dehydrogenation process (process 2 in Figure 7)
which leads to cyclohexene and a free hydrogen atom, the linear combination of processes 1 and 2 leads to stoichiometry I of the decomposition of cyclohexane in the presence of n-decane:
O;O+H2
(I
Ind. Eng. Chem. Res., Vol. 27, No. 5 , 1988 763 11.
I
cC6H12
1 , 3 C4H6
+
C2H4
+
+
5
H2
2.5-
/
/ - / -/---
, , ,
/O
2.0-
/O
, , , ,
00
C2H4
, /
-
/ /
, /
1.5-
,
/
I 0.03
I
i
-
CH2=CH-CH2-CHi + cC6H12 = H
2
C2H4
+
+
c
1
CH -CH-CH=CH 2 21
C6H12 = 3 C2H4
) 1'
+m
'ZH3'
RH
+
R.
Figure 7. Reaction path for cyclohexane pyrolysis.
Let us consider the second possibility of a reaction of the CGHll' radical which can also be decomposed by the breaking of the carbon-carbon bond (process 3 of Figure 7 ) and lead t o the CGHll* radical: CH,= CHCH2CH2CH2CH2'. This large radical can either be isomerized from a transition state with five centers including hydrogen (1,4 transfer, process 4 of Figure 7 ) or be decomposed by the breaking of a carbon-carbon bond (process 5 of Figure 7 ) . If we consider process 4, the secondary C6H11*radical formed can then lead after C-C scission to 1,3-butadiene and C2H5'. The combination of processes 1, 3, 4, and subsequent processes leads to a second stoichiometry for the decomposition of cyclohexane (Figure 7 ) : C-CgH12 = 1,3-C4H6 + C2H4 + H2 (11) If we consider the carbon-carbon breaking at the CY position of the carbon atom bearing the free electron of the CH&HCH2CH2CH2' radical, this radical then leads via process 5 to an ethylene molecule and the C4H; radical (process 5 of Figure 7 ) : CH2=CHCH,CH2CH&H2* CzH4 CHZ=CHCHCHz'
-
0.02
0.01
m+
1
I
' 6 H6
1,3 C4H6
H. +
I
I
+
C4H; can then be decomposed by the breaking of a C-C bond into ethylene and the C2H3*radical via process 8, which quickly captures an H' to lead to another ethylene molecule (process 9). Combining proceases 1,3,5,8, and 9 can be used to write a third stoichiometry for the decomposition of cyclohexane: c-C~H12= 3CzH4 (111) At a temperature of 810 OC, the CH2=CHCHCH2'radical can also be monomolecularly decomposed by the breaking of a C-H bond to lead to the free hydrogen atom and a 1,3-butadiene molecule (process 10). If processes 1,3,5, and 10 are combined, we again find stoichiometry 11. There are thus two closed sequences that lead to stoichiometry I1 (see Figure 7 ) . The following mechanism represents all the elementary processes written and the four propagation chains that lead
60
70
80
90
1 n decane conversion
0
Figure 8. Ratio in Hz, CzHd, 1,3-C4H6,C6&, and C-C~HIO (c-C6-) a function of n-decane conversion: (-) mixture c-C6Hlz-n-Cl0Hzz, (- -) n-CloHzz(reference).
-
to the three main primary stoichiometries for the decomposition of cyclohexane in the presence of n-decane: C-CgH12 = 3CzH4 (1) C-CgH12 = H2 + CzH4 -I- 1,3-C4H6 (11) C-CeH12 = H2 -I- C - C ~ H I ~ (111) According to the configurations of the curves for the formation of cyclohexene and benzene (Figure 2), cyclohexene is fairly easily dehydrogenated into benzene, and even at very low extents of reaction, stoichiometry 111can be replaced by the secondary stoichiometry 111': (111') c-C~H12= C&& + 3H2 4.2. Distribution of Stoichiometries. To try to take the three stoichiomemtries into consideration quantitatively, let us remember that we have earlier defined the R,(B) ratios in different decomposition products: Figure 8 represents the ethylene, hydrogen, 1,3-butadiene, cyclobenzene, and benzene ratios as a function of n-decane conversion. According to this figure, the hydrogen, ethylene, and 18-butadiene ratios are considerably increased compared to the ones observed in the reference body. The case of cyclohexene and benzene is slightly more difficult to interpret. Indeed, the cyclohexene ratio curve diminishes sharply with n-decane conversion, apparently showing that this primary product becomes dehydrogenated fairly easily into benzene, while the benzene ratio increases much more quickly than with pure n-decane. This is in full agreement with the proposed mechanism having three principal primary stoichiometries, including one cyclohexene and hydrogen stoichiometry. Assuming that the difference in yield of one product between n-decane alone and in the presence of cyclohexane is due exclusively to the decomposition of cyclohexane (assumption of noninteraction), the relative importance of the stoichiometries deduced from the mechanism can be determined.
764
Ind. Eng. Chem. Res., Vol. 27, No. 5, 1988
In Figure 8, the deviations ARA(B) of RA(B) defined before, in the presence or in the absence of cyclohexene, are almost equal for hydrogene, ethylene, and l,&butadiene. The values corresponding to the lowest decane conversion allow us to describe quantitatively the three primary stoichiometric equations. With these n-decane conversions, let us take R1, R2,and R3 (with R1 + R2 + R3 = 100%), the contributions of stoichiometries I, 11, and I11 to the cyclohexane decomposition. The difference of 22 % between Rn.clo(H,) in the presence or in the absence of cyclohexane is representative of H2formed during the cyclohexane decomposition (with the noninteraction assumption). Since H2 is representative of stoichiometries I1 and 111, we can write the following relationship (K is a constant): 0.22/K = Rz + R3 In the same way, AR(C,H,) and AR(1,3-C4H6)have the respective values 62% and 16%. As ethylene is present respectively with the coefficients 3 and 1 in the stoichiometries I and 11, we can write 0.62/K = 3R1 + Rz Butadiene is only representative of stoichiometry I1 and 0.16/K = R2 Solving of the above equation system leads to the contributions of the three reactions for the decomposition of cyclohexane: R1 = 41 %, R2 = 43%, and R3 = 16%.
Conclusion The decomposition of cyclohexane in the presence of n-decane can be outlined as follows:
lead to the assumption that these hydrocarbons, by thermal decomposition, lead to benzene derivatives and light fragments. Registry No. c-CSHI2,110-82-7; C2H4, 74-85-1; H2, 1333-74-0; 1,3-C4Hs, 106-99-0; C-C&o, 110-83-8; decane, 124-18-5.
Literature Cited Albright, L. F.; Tsai, T. C. Pyrolysis: Theory and Industrial Practice; Academic: New York, 1983; Chapter 10. Albright, L. F.; Yu, C. Thermal Hydrocarbon Chemistry; ACS Symposium Series No 183; American Chemical Society: Washington, D.C., 1979; Chapter 1. Arai, S.; Sato, S.; Shida, S. J. Chem. Phys. 1960, 33, 1277. Aribike, D. S.; Susu, A. A.; Ogunye, A. F. Thermochim. Acta 1981, 47, 1. Azay, P. Ph.D. Thesis, University of Nancy, Nancy, France, 1981. Billaud, F.; Freued, E. J. Anal. Appl. Pyrol. 1984, 6, 341. Billaud, F.; Freund, E. Znd. Eng. Chem. Fundam. 1986, 25, 433. Billaud, F.; Ajot, H.; Freund, E. Rev. Znst. Fr. P6t. 1983,38(6), 763. Billaud, F.; Baronnet, F.; Niclause, M. J. Chim. Phys. 1980, 77, 175. Billaud, F.: Baronnet, F.; Niclause, M. React. Kinet. Catal. Lett. 1982a, 19, 125. Billaud, F.; Baronnet, F.; Niclause, M. React. Kinet. Catal. Lett. 1982b. 20,363. Billaud, F.; Baronnet, F.; Niclause, M. React. Kinet. Catal. Lett. 1982b, 21, 423. Brown, T. C.; King, K. D.; Nguyen, T. T. J. Phys. Chem. 1986,90, 419. Crynes, B. L.; Albright, L. F. Ind. Eng. Chem. Process. Des. Dev. 1969,8, 25. Fabuss, B. M.; Smith, J. 0.; Satterfield, C. N. In Advances in Petroleum Chemical Refining; McKetta, J. J., Ed.; Interscience: New York, 1964a; p 157. Fabuss, B. M.;Kafeajian, R.; Smith, J. 0.;Satterfield, C. N. Ind. Eng. Chem., Process Des. Dev. 196413, 3, 248. Frey, F. E. Znd. Eng. Chem. 1949, 41, 827. Garnett, J. L.; Johnson, W. D.; Sherwood, J. E. Aust. J . Chem. 1976, 29, 599. Gordon, A. S. Pure Appl. Chem. 1962,54, 441. Goubeau, J. 2.Angew. Chem. 1938,51, 11. Jezequel, J. Y.; Baronnet, F.; Niclause, M. J. Chim. Phys. 1983,80, 455. Kalinenko. R. A.; Avdeeva. E. N.: Nametkin, N. S. Neftekhimiya 1978, 48,217. Kalra, B. L.; Feinstein, S. A.; Lewis,K. Can. J.Chem. 1979,57,1324. Kondratiev, V. N. Breaking Energy Chem. Bonds "auka" M . 1974, 351. _--
I
1 A This research has thus resulted in at least a semiquantitative explanation of the products from a complex reaction (decomposition of cyclohexane in the presence of n-decane) from the yield curves and the "noninteraction" assumption. Let us bear in mind that these assumptions consist in considering the differences in yields observed with pure n-decane to be directly proportional to the contribution of each reaction to the composition of cyclohexane. The presence of cyclohexane in a pyrolysis feedstock is thus not detrimental. On the contrary, it is advantageous because it indeed produces ethylene, 1,3-butadiene7and hydrogen in large amounts. At the same time, it also leads to cyclohexene which is transformed by secondary dehydrogenation reactions into benzene, a fundamental intermediate in industrial chemistry. At this level in the investigation, it seems interesting to extrapolate our findings, first to naphthenes substituted by long aliphatic chains, and to assume that these hydrocarbons behave like a mixture of naphthenes and paraffins during steam cracking. Extrapolation to higher naphthenes (decalin and perhydrophenanthrene) would
Korzun, N. V.; Magaril, R. Z.; Maljarenko, I. S.; Trushkova, L. V. Neftekhimiya 1979, 4, 541. Kuchler, L. Trans. Faraday SOC.1939,35, 874. Kunzru, D.; Shah, Y. T.; Stuart, E. B. Ind. Eng. Chem. Process Des. Dev. 1972, 11, 605. Levish, S. S.; Abadzhev, S. S.; Shevchuk, V. U. Neftekimiya 1969, 9, 716. Marschner, R. F. Znd. Eng. Chem. 1938,50, 554. Murata, M.; Saito, S. J. Chem. Eng. Jpn. 1975, 8, 39. Mushrush, G. W.; Hazlett, R. N. Ind. Eng. Chem. Fundam. 1984,23, 288. Pease, R. N.; Norton, J. M. J. Am. Chem. SOC.1933,55, 3190. Powers, D. R.; Corcoran, W. H. Ind. Eng. Chem. Fundam. 1974,13, 351. Rice, F. 0. J. Am. Chem. SOC.1931,53, 1959. Rice, F. 0. J. Am. Chem. SOC.1933,55, 3035. Rice, F. 0.; Herzfeld, K. F. J. Am. Chem. SOC.1934, 56, 289. Rice, F. 0.; Kossiakoff, A. J. Am. Chem. SOC.1943, 65, 590. Romavacek, J.; Buchtele, J.; Weiser, 0. Fuel 1972, 51, 229. Shevelikova, L. V.; Veveneeva, L. M.; Kalinenko, R. A.; Nametkin, I. S. Neftekhimiya 1981, 3, 391. Stein, S.; Rabinovitch, B. S. J. Phys. Chem. 1975, 79, 191. Sundaram, K. M.; Froment, G. F. Ind. Eng. Chem. Fundam. 1978, 17, 174. Tanaka, S.; Arai, Y.; Saito, S. J. Chem. Eng. Jpn. 1975, 8, 305. Tsang, W. Int. J. Chem. Kinet. 1978a, 10, 599. Tsang, W. Int. J. Chem. Kinet. 1978b, 10, 1119. Zdonik, S. B.; Green, E. J.; Hallee, L. P. Oil Gas J . 1967, 65, 98.
Received f o r reuiew October 16, 1986 Reuised manuscript received October 28, 1987 Accepted November 17, 1987
