Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, 415-418
cos
+ s = cos2
(8)
Since reaction 7 is in competition with the COS hydrolysis reaction 5, the effective number of sites available for reaction 5 decreases when C0,H2 are present in the gas stream. This hypothesis is consistent with the observation (see Figure 8) that while the conversion of COS decreases when Co,H2are present, the slope of COS output vs. 1/T is independent of these gases. On the other hand, the conversion of H2Sby oxidation with SO2 is independent of C0,H2 concentrations since there are more than enough available sites on these catalysts to facilitate the latter reaction. Studies by Haas and Khalafalla (1973) and Baglio (1982) support this conclusion. These authors demonstrated that significant improvements in catalytic activity can be achieved by combining a transition metal with either alumina or lanthanum oxysulfide when these catalysts are used for the reduction of SO2 by CO. This enhanced activity is due to the formation of COS by reactions 7 and 8 and subsequent reduction of SO2 by COS which proceeds at a faster rate than the CO, SO2 counterpart. When SO2 is reduced directly with COS, the more effective catalysts are alumina or lanthanum oxysulfide alone without the presence of a transition metal. The results reported by Fukuda et al. (1977) also support this analysis. These investigators focused on the catalytic activity of transition metal sulfides using as the test reaction H2S + CO = H2 + COS (9) It was found that at temperatures ranging from 170 to 380 "C this reaction is second order and is catalyzed by the transition metal sulfides NiS = Cogss > V3S4> FeS(FeS2) > Cr2S3>> Ti5& A first stage catalyst should consist of a material that does not form sulfates under process stream conditions.
415
Lanthanum oxide-based catalysts do form sulfates. One may limit the sulfation process by either increasing the H2S/S02ratio, thus regenerating the catalyst in situ, or by putting a sacrificial layer (Grancher, 1978) above the catalyst bed. The former has the disadvantage of decreasing conversion of H2S to unacceptable levels. The problem associated with the protective layer is the possibility of generating unacceptable concentrations of COS when CO and H2 are present in the gas stream. Further research is necessary to find a suitable protective layer which does not produce COS when C0,H2 are present and which prevents sulfate formation. Finally, the data presented in this work demonstrate that under final stage conditions transition metals are better catalysts than their lanthanum counterparts. The life of the alumina-supported Fe catalysts was found to be four times greater than the Co counterparts. The regeneration behavior of these catalysts demonstrates that they can be regenerated by subjecting them to a gas stream containing 10% H2S. Thus alumina-supported iron catalysts are effective catalysts under final stage conditions.
Literature Cited Baglio, J. A. Ind. Eng. Chem. Prod. Res. D e v . 1982, 21, 38. Burns, R. A.; Lippert, R. B.; Kerr, R. K. Hydrocarbon Process. 1974, 53,181. Cook, W. 0.; Ross, R. A. Atm. Envlron. 1973, 1 , 145. Fukuda, K.; Dokiya, M.; Kameyama, T.; Kotera, Y. J. Catal. 1977, 49, 379. Gamson, B. W.; Elkins, R. W. Chem. Eng. Prog. 1953, 49, 203. George, 2. M. J. Catal. 1974, 35, 218. Gordon, G.; McBride, B. NASA Report SP-273, NASA: Washington, DC, 1976. Grancher, P. Hydrocarbon Process. 1978, 5 7 , 155. Haas, L. A.; Khalafalla. S. E. J. Catal. 1973, 3 0 , 451. Kerr, R. K. Energyplocess. Can. 1976, 6 8 , 28. Pearson, M. J. Hydrocarbon Process. 1973, 52, 81. Singleton, D. M. US. Patent 4012486, 1977. Steljns, M.; Mars, P. Ind. Eng. Chem. Prod. Res. Dev. 1977, 16, 35.
Received for reuiew August 6 , 1981 Reuised manuscript received February 11, 1982 Accepted April 21, 1982
Selective Conversion of 1,3,7-Octatriene to Aromatics Thomas Anstock, Arno Behr, and Wllhelm Kelm' Institut fijr Technische Chemie und Petrolchemie der Technischen Hochschule Aachen, Worringer Weg 1, 5 100 Aachen, Federal Republic of Oermany
Butadiene can be converted to aromatics in a two-step process. In the first step butadiene is dimerized by homogeneous palladium catalysts to 1,3,7-octatriene which in the second step is dehydrocyclized almost quantitatively to the aromatics o-xylene and ethylbenzene. With CO,(CO)~/AI,O, the yield of 97% of CBaromatics consisting of o-xylene (68%), ethylbenzene (27%),p-xylene (1%) and m-xylene (1%) could be obtained. Optimum reaction conditions were found at a temperature of 450 O C and a hydrogen pressure of 10 bar. After 20 h the catalyst lost activity and selectivity. Regeneration with air proved successful.
Introduction At all times the chemical industry has been challenged by a changing supply of raw materials and feedstocks. Therefore, predicting the future of the availability of any hydrocarbon is a risky operation. This is certainly true for forecasting the development of the butadiene supply and demand market. But there seems to be a certain consensus of opinion that the availability of butadiene will 0196-4321 18211221-0415$01.2510
exceed the consumption (Chemical Market Associates, 1981; Brownstein, 1976; Russell, 1980). In the past many research efforts have been expended in an attempt to find new markets for butadiene outside the synthetic rubber industry. Chemicals such as cyclododecatriene, 1,7-octadiene,sulfolane, and adiponitrile are synthesized from butadiene. An additional alternative under consideration is the conversion of butadiene to C8 0
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aromatics because of the rapidity of growth in demand for these chemicals (Field, 1970; Spernol, 1974; Hatch and Matar, 1979). Two approaches have been considered to convert butadiene into aromatics: (1) Direct conversion, a route which lacks selectivity and is in an early exploratory stage (Yates and Wheatley, 1969; Hession, 1976; Janowski, 1980); (2) catalytic conversion of butadiene to 4-vinyl-l-cyclohexene followed by dehydrogenation to ethylbenzene, which in existing plants can be converted to styrene (Vogel et al., 1974; Ruckelshaup and Kosswig, 1977; Valitov et al., 1978).
I
I
4 Because of its high cost butadiene has never been seriously considered for the manufacture of styrene. However, in recent years benzene and ethylene values have risen in comparison to butadiene and if this trend continues butadiene may be an alternative to current ethylbenzene and aromatics technology. In this paper we would like to propose a third route to aromatics, namely the conversion to xylenes.
The dimerization of butadiene to 1,3,7-octatriene is well established and has been the subject of numerous papers (Smutny, 1967;Takahashi et al., 1967; Kohnle and Slaugh, 1969). In a conversion of greater than 80% 1,3,7-octatriene can be obtained. The only byproduct, 4-vinyl-l-cyclohexene, can be separated by distillation. The second step, the dehydrocyclization of 1,3,7-&triene to xylenes, to our knowledge, has not been investigated. Generally the dehydrocyclization of hydrocarbons is a well-studied reaction. In reforming processes mixtures of alkanes and naphthenes are converted to aromatics on bifunctional catalysts. Also the dehydrocyclization of individual hydrocarbons has been investigated. Whitesides and Budnik (1973) report that cis-1,3,5-hexatriene can be converted to benzene in the presence of R u ~ ( C O ) Ko~~. matsu (1968) synthesized xylenes by the dehydrocyclization of 3-methyl-1,4,6-heptatriene using a chromia-alumina catalyst. Rozengart el al. (1969) studied the dehydrocyclization of n-octane over chromium oxide and molybdenum oxide catalysts. They assume a stepwise cyclization mechanism with two octatriene intermediates: 1,3,5-octatriene would lead to ethylbenzene and 2,4,6-octatriene to o-xylene. A mixture of 1,3,6- and 1,3,7-octatrieneshas been converted into methylcycloheptadienes with sodium alkyl amides as catalysts (Zuech et al., 1968).
Experimental Section Apparatus. The reaction unit used is shown schematically in Figure 1. The flow reactor (R), made of stainless steel (no. 1.4988, 50 cm length), was filled with 40 mL of catalyst. The reactor had three sections which could be heated separately and controlled by thermocouples which were placed at the start, in the middle, and at the end of the catalyst bed. The octatriene diluted in toluene (B) was added via a piston pump (P, 18-185 mL/h). The gas flow could be regulated by a needle valve. The reaction products were passed through a water cooler (Cl) followed by cooling to -30 "C (CP). Liquid (S) and gaseous ( G ) samples could be taken continuously. Procedure. After the reactor was charged with the catalyst, the system was purged with nitrogen. When the
Is
Figure 1. Flow sheet: (B) octatriene buret; (M) manometer; (Cl) condenser; (C2) cooler; (P) pump; (R)reactor; (S) separator; (G) gas sampler.
requested temperature was reached the nitrogen gas flow was switched to hydrogen and the 1,3,7-octatriene was pumped into the reactor. If the octatriene was charged undiluted, polymerization occurred. Therefore toluene solutions with a concentration of 20% octatriene were used. Besides, a polymer inhibitor (tert-butylcatechol)was added to 1,3,7-octatriene. After 20 h the catalyst lost activity and selectivity. Regeneration with air was possible. For this purpose air diluted with nitrogen was blown over the catalyst and the temperature was raised to 600 "C. Analysis. The gaseous and liquid samples were analyzed by GLC. The separation of the liquid phase was carried out on a WG 11 glass capillary column of 50 m length with the carrier gas nitrogen (90 "C, isothermal). n-Octane was used as an internal standard. Materials Used. 1,3,7-0ctatriene was synthesized according to the method of Takahashi et al. (1967): 400 mL of butadiene was dimerized in a l-L steel autoclave at 100 "C by catalysis of 1.61 g (5.26 mmol) of palladium acetylacetonate, 0.52 g (5.26 mmol) of maleic anhydride, and 4.14 g (15.8 mmol) of triphenylphosphine; 250 mL of acetone was used as solvent. The 1,3,7-octatriene formed consisted of 60% trans and 40% cis isomers. The catalysts used for octatriene dehydrocyclization were inorganic supports impregnated with transition metal carbonyls or salts. Different aluminum oxides (Girdler) and molecular sieves (Union Carbide) were employed as supports. One of the best carriers was the aly-aluminum oxide Girdler T 1746 with a surface area of 302 m2/g and a pore volume of 0.04 mL/g. Therefore, all results reported in this paper refer to this support. The metal content of the catalysts was 3 wt% in each experiment. The impregnation with the metals chromium, ruthenium, cobalt, and rhodium was carried out with their carbonyls dissolved in methylene chloride. The impregnation with nickel and palladium was done with their acetylacetonates dissolved in acetone. The preparation of the catalysts was carried out in an argon atmosphere; the solvent was removed under vacuum at 40 "C. By treating the catalysts in the reactor with H2 at a temperature of 500 "C,the metal compounds decomposed and the metal was distributed at the support.
Results and Discussions Activity and Selectivity of the Catalysts Used. 1,3,7-Octatrienewas converted to aromatics with catalysts containing metals shown in Figure 2. In each case the conversion of octatriene approached 100%. o-Xylene and
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 3, 1982 417
1.
d
conversion 01 o c t a t r i e n e
o
o-xylene
. 1 C8-oromattcs
c -*-
* ethylbenzene
'
-_1_+,-.-X-L1 10
;b
-,-, 50
i0
30
60
7G-Y"
Figure 4. Activity and selectivity behavior with time (cat., Coz(CO)8/A1203;p = 10 bar H,;T = 450 OC; LHSV = 0.2 h-l).
-
Scheme I
::: 70.
./---.-.
./
/
. 1 Ca -aromatics o
o-xylene
*
ethylbenzene
137
c-ada J216
cycl
dehydr
I
+fy-r-QJ135
showed that the concentration of carbon after a reaction time of 60 h was 25 w t % . Also investigations by electron microscopy showed pictures typical for catalyst covered by carbon. Without hydrogen the deactivation of the catalyst occurred much faster. An increase in hydrogen pressure to 20 bar showed no significant improvement. Therefore, catalyst regeneration by air was attempted. After 30 h the reaction was interrupted and the catalyst was reactivated for 3 h with air at 600 "C. This regeneration could be repeated 5 times without significant loss of selectivity. After 112 h and 5 regenerations the yields of c8 aromatics still amounted to 91% consisting of 52% o-xylene and 37% ethylbenzene. Reaction Mechanism. Our results are in agreement with a mechanism shown in Scheme I. First the isomerization of 1,3,7-octatriene to 2,4,6-octatriene and 1,3,5octatriene takes place. These rearrange into substituted cyclohexadienes, a reaction which can occur thermally. The cyclohexadienes dehydrogenize forming the thermodynamic favored aromatics o-xylene and ethylbenzene, the main products observed. The byproducts m- and p-xylene are thought to stem from skeletal isomerization of 1,3,7octatriene (indeed, methyl-branched heptanes could be identified after hydrogenation of the nonaromatics). In addition, omitting 1,3,7-octatriene and reacting only toluene, which is used as diluent, no benzene or xylenes are observed. Using o-xylene, no isomerization to m- or p-xylenes takes place. Furthermore, with 4-vinyl-lcyclohexene practically only ethylbenzene is obtained.
Acknowledgment The authors would like to thank the Ministerium fur Wissenschaft und Forschung des Landes NRW and the Hermann-Schlosser-Stiftung for supporting this work, and the Girdler Chemical Inc. for donating the aluminum oxides. Literature Cited Brownstein, A. M. Hydrocarbon Process. 1976, 55(2), 95. Chemical Market Associates, Houston, 198 1 World Butadiene Analysis: Chem. Eng. News Apr. 20, 1981, 14. Field, S. wdrocarbon Process. 1970, 49(5), 113. Hatch, L. F.; Matar, S . wdrocarbon Process. 1979, 58(1), 189. Hession, M.; Senior, R. J. Catal. 1976, 44, 163. Janowski, F. Z . Chem. 1980, 2 0 , 41. Kohnle, J. F.; Slaugh, L. H. U.S. Patent 3444258, M a y 13, 1989.
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Komatsu, Y. Bull. Chem. SOC.Jpn. 1988, 4 1 , 167. Rozengart, M. J.; Pollnin, V. L.: Btyukhanov, V. G.; Kazanskli, B. A. Dokl. Akad. Nauk SSSR 1889, 187, 585. Ruckelshau& G.; Kosswlg, K. Chem. Ztg. 1877, 101, 103. Russell, R. W. Hydrocarbon Rocess. 1980, 69(5), 223. Smutny, E. J. J. Am. Chem. SOC.1987, 89, 6793. Spernol, H. Er&l Kohk Erdgas Petrochem. 1974, 2 7 , 82. Takahashi, S.; Shlbano, T.; Haglhara, N. Tetrahedron Lett. 1887, 2451. Valltov. R. B.; Prusenko, E. B.; Blkbulatov, I . Kh. Zh. Pr/k/.Khlm. 1978, 51, 2146.
Vogel, H.-H.; Weitz, H A . ; Lorenz, E.; Platz, R. Ger. Offen. 2 256 449, May 22, 1974. Whitesides, T. H.; Budnlk, R. A. Chem. Commun. 1973, 87. Yates, J. G.; Wheatley, K. W. J. Catal. 1989, 15, 302. Zuech, E. A.; Craln, D. L.; Klelnschmldt. R. F. J. Org. Chem. l988, 33, 771.
Received for review August 28, 1981 Revised manuscript received March 29, 1982 Accepted April 21, 1982
CO-H, Reactions in Liquid Phase in Presence of Metals of Group 8 Alaln Klennemann, GOrard Jenner, Ebrahlm Baghersadah, and Antonin Deluzarche Laboratoire de Chimie Organique Appliqu&, E.R.A. au CNRS No. 826, Universit6 Louis Pasteur, 1. Rue Blaise Pascal, 67008 Strasbourg, France
The influence of metal catalysts group 8 has been considered in the synthesis of hydrocarbons and alcohols through hydrocondensation of CO. Rhodium, ruthenium, and cobalt complexes are the most active. The effect of ruthenium catalysts has been particularly investigated. The use of very high pressures (>3000bar) leads to the successful
synthesis of saturated long-chain alcohols (C,to C,) with ruthenium catatysts according to a SchuJz-Flory distribution. The influence of several other parameters (temperature, COIH,, ratio, solvent, pH, additives) has also been studii.
Introduction A number of recent articles paid attention to the reactions involving CO and H2 catalyzed by transition metal complexes (Eisenberg and Hendricksen, 1979; Masters, 1979; Muetterties and Stein, 1979; Wender and Pino, 1977). Though only a few studies have been considered for industrial applications, it is nevertheless of interest to look into a research area where heterogenous catalysis gave few enthusiastic results. With respect to these studies, a special (and highly interesting) case would be the synthesis of saturated long-chain primary alcohols which could be a possible starting point for the synthesis of a-olefins. The synthesis of such alcohols was claimed in former patents (Gresham, 1949; Hawk, 1949) presumably without any further development. We investigated this reaction in a first stage in the presence of several ruthenium catalysts in 1-propanol as solvent (Jenner et al., 1980). However, the reaction did not afford the desired alcohols; only esters were produced (propyl formate and acetate). We then increased the severity of our operating conditions (P = 1500 bar, T = 230 "C) and confirmed Bradley's results (Bradley, 1979a,b). When using higher pressures (3500 bar), we have been successful in synthesizing longchain linear alcohols (C, to C9). In the present article, we have undertaken the investigation of the effect of various catalysts involving metals of group 8 and, with the ruthenium as a constant catalyst, the study of the influence of several important parameters: pressure, temperature, CO/H2 ratio, solvent, additives, and pH at pressures high enough (3500 bar) to allow the synthesis of saturated long-chain primary alcohols. The following abbreviations will be used in this paper: acac, acetyl acetonate; EG, ethylene glycol; FMe, methyl formate; FEt, ethyl formate. Experimental Section Note. Runs were carried out in conditions allowing reasonable comparisons. However, equilibrium is not reached (the hydrogen diffusion through the wall of the pressure vessel limits the reaction time to 6 or 7 h). The results given here correspond to the reaction kinetics in 0196-4321/82/1221-0418$01.25/0
our experimental conditions. Some compounds could not be identified. For each run we have indicated the percent of the products which could formally be characterized. In a few runs (those with low conversion), the mass balance of the products is less satisfactory; however, as a rule we considered that the correspondence between transformed gases and formed products must be higher than 90%. 1. Description of a Run. The high-pressure design has been described elsewhere (Jenner and Deluzarche, 1977). The vessel is blown off under an argon stream and filled with catalyst (4 X loa mol), solvent (0.04 mol) and additive (3.5 X lo4 mol) if any, and then connected to the pressure line and brought up to the desired pressure. After being disconnected from the line, the vessel is heated and shaken for a constant reaction time. The pressure drop (AP)can be followed continuously with a pressure transducer. After cooling overnight, the vessel is discharged by evacuating the gas phase very slowly. After total decompression the liquid phase is isolated and analyzed by gas chtomatography (GC) as well as the gas phase. 2. GC Conditions. (a) Analysis of CO, C 0 2 ,and HD Chromatograph (F and M 720); detection (catharometer); carrier gas (CHI, 15 mL/min); column (Silica gel: 80-100 mesh, length 5 m, diameter 3.2 mm); temperature (20 "C, 5 min; then 140 "C, 10 min); injection and detection (150 "C). (b) Analysis of C02, Dimethyl Ether and Gaseous Hydrocarbons. Chromatograph (Hewlett-Packard 5700); detection (catharometer); carrier gas (He 30 mL/min); Chromosorb 102, 80-100 mesh, length 2 m, diameter 3.2 mm); program (from 60 to 240 "C, 8 "C/min); injection and detection (200 "C). (c) Analyses of the Liquid Phase (Alcohols, C1and C2 Esters). Conditions as in (b) but column (FFAP, 5% chromosorb 101, 80-100 mesh, length 4 m). (d) Analyses of Alcohols from C1to Cg.Separation from t h e Hydrocarbons (C, t o CZ0). The quantitative analysis of alcohols and hydrocarbons was done by GC after complete separation of alcohols-hydrocarbons. To that purpose, the latter are allowed to react with phthalic 0 1982 American Chemical Society
