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191
(55) Martin, F. OelKohle, 1937, ! 3 , 691. (56) Mills, G. A.: Steffgen, F. W. Catal. Methanation Catal. Rev. 1973, 8(2), 159-2 10. (57) Mittsach, A.: Schneider, C. (assigned to Badische Anilin und Soda-Fabrik). German Patent 293787, Aug 23, 1916. (58) O'Hare, J. 9.; Bela, A.: Jentz, N. E.; Khaderi. S. K. Chem. Enq. - Proq. Aug 1976, 65--67. (59) O'Hare, J. 6.; Bela, A.: Jentz, N. E.; Khaderi, S. K.; Klumpe, H. W.: Loran, 6. I.; Reynolds, D. G.; Teeple, R. V.ERDA R8D Report No. 114---Inlerim Report No. 3, Contract No. E(49-18)-1755, 197i. Pennline, H. W.; Schehl, R. R.: Haynes, W. P. Ind. Eng. Chem. Process Des. Dev. 1979, 18, 156-162. Pichler, H. Adv. Catal. 1952, 4, 272-341. Pichler, H.; Hector, A. "Kirk-Othmer Encyclopedia of Chemical Technology", Vol. 4. 2nd ed.; Wiley: New York, 1964; pp 446--483. Pichler, H.; Merkel, H. U . S . Bur. Mines Tech. Pap. 1949, No. 718. Ponec, V. Cafal. Rev. Sci. Eng. 1978, 18(1), 155-171. Porter, J. C.; Wiebe. R. Ind. Eng. Chem., 1952. 44, 1098-1104. Reichl, E. H. U S . Dept. Comm.. OTS Report, PB 22841, 1945. Schlesinger, M. D.; Benson, H. E. I n d . Eng. Chem., 1955, 47, 2104. Schiesinger, M.D.: Benson, H. E : Murphy, E. M.: Storch, H H. Ind. Eng. Chem., 1954, 46, 1322. (69) Schlesinger, M. D.; Crowell, J. H.; Leva, M.; Storch, H. H. Ind. E r g . Chem. 1953, 43, 1474. (70) Schroeder, W. W.: Benson, H. E.; Field, J. H. 'Hydrocarbon Synthesis and Hydroformylation", P. H. Groggins, Ed., 5th ed.; McGraw-Hill: New York. 1958: Chanter 11 (71) Schukz, J F Seigman, B Shaw, L , Anderson, R B Ind Eng Chem 1952. 44(2). 397-401 (72) Shah, Y. T.f Perrotta, A. J. Ind. Eng. Chem., Prod. Res. Dev. 1976. 75, 123-131. (73) Smith, D. F.: Davis, J. D.; Reynolds, D.A . Ind. f n g . Chem. 1928, 2G. 462. (74) Storch, H. H.; Gclumbic, N.; Anderson, R. B. "The Fischer-Tropsch and Related Syntheses", Wiley: New York, 1951; p 610. (75) Vannice, M. A. Catal. Rev. 1976, 14(2), 153-191.
(33) Forney, A. J.: Bienstock, D.: Demski, R. J. U.S.Bur. Mines Rep. Invest. 1962, No. 6126, 30. (34) Forney, A. J.: Demski, 17. J.: Bienstock, D.; Fiela, J. H. U . S . Bur. Mines Rep. Invest. 1965, No. 6609,32. (35) Forney. A. J.; Haynes, \N. P. Am. Chem. SOC.Div. FuelChem. Prepr. 1971, 15(3), 32-39. (36) Forney, A. J.: Haynes, W. P.; Elliott, J. J.; Zarochak, M. F. Preprint, 2nd Seminar on Desulfurization of Fuels and Comb. Gases, Chicago, 1975. (37) Frohning. C. D.: Cornils B. Hydrocarbon Process. Nov 1974, 143-146. (38) Govaarts, J. H.: Schutte, C. W. S. Afr. Chem. Process. OctINov 1973, 23. (39) Hall, C. C.: Gall, D.: Smith, S. L. J . Inst. Pet. 1952, 38, 845-876. (40) Haynes, W. P.; Baird, M. J.; Schehl, R. R.: Zarochak. M. F. Am. Chem. SOC. Div. Pet. Chem. Prepr. Mar 1978. (41) Haynes, W. P.; Elliott, J. J.; Forney, A. J. Am. Chem. SOC.Div. Fuel Chem. Prepr. 1972. 16(2), 47-57. (42) Haynes, W. P.; Elliott, J. J.; Youngblocd, A. J.; Forney, A. J. Am. Chem. SOC.Div. Fuel Chem Prepr. 1970, 15(4), A121-A130. (43) Haynes, W. P.: Schehl, I?. R.; Baird, M. J.: Zarochak, M. F.: Cinquegrane, G. J.; Strakey, J. P. "Synthesis of Liquids and Pipeline Gas by FischerTropsch", Dept. of EnergyIPETC, Quaterly Report, July-Sept 1978. (44) Hawk, C. 0.: Golden, .1' L.;Storch, H. H.; Fieldner, A. C. Ind. Eng. Chem. 1932, 24, 23. (45) Henrici-Olive, G.; Olive, !3. Angew. Chem. Int. Ed. Engl., 1976, 75, 136. (46) Hoogendoorn, J. C. Ninth Synthetic Pipeline Gas Symposium, Chicago, IL, Nov 1977. (47) Hoogendoorn, J. C.; Solomon, J. M. Brit. Chem. Eng. June 1957, 308-3 12. (48) Ingham, H. S.:Shepard A. P. "Flame-Spray . . Handbook", Vol. 111; Metco Inc.: New York, 1965, p 188. (49) Kastens, M. L.; Hirst, L. I-.;Dressler, R. G. Ind. Eng. Chem., 1952, 44(3), 450-466. (50) Karn, F. S . ; Shultz, J. F : Kelly, R. E.; Anderson. R. B. Ind. Eng. Chem. Prod. Res. Dev. 1964, 3 , 33-38. (51) Kodama, S. J . SOC.Chem. Ind. (Jpn) 1929, 32, 285. (52) Kolbel, H.; Ackermann, P. "Proceedings of the 3rd World Petroleum Congress", The Hague 1951: pp 2-14. (53) Kolbel, H.: Ackermann. P. Chem.-Ing.-Tech. June 1956, 6 .381-388. (54) Kolbel, H.; Ackermann, P.: Englehardt, F. "Proceedings, 4th World Petroleum Congress", Rome, 1955, pp 227-247.
.
CATALYST SECTION
Strong Acid Chemistry. 8. Alkane Alkylation Reactions in HF-TaF, Michael Siskin* and Ivan Mayer Corporai'e Research Science Laboratories, Exxon Research and Engineering Company, Linden, New Jersey 07036
The direct alkylation of n-butane by larger alkanes in HF-TaF5 has been demonstrated. Evidence for the analogous direct alkylation of propane has been presented but the data are not conclusive. A general mechanism has been elucidated for this alkane alkylation reaction.
Higher normal alkanes (>C,) undergo rapid ionization via hydride abstraction in strong acids. The reactive secondary ions so formed rearrange to the more stable tertiary ions. These tertiary ions can then undergo cleavage by a @-scissionmechanism to form the most stable tertiary cation and the complementary lower alkene (Condon, 1958). If the same reaction is carried out in an excess of a solvent, such as isobutane or isopentane, the ionized higher normal alkane preferentially loses a proton and the corresponding branched alkene formed is immediately alkylated by the ionized solvent. The larger cation thus formed is still more reactive and cracks to a smaller carbocation and a lower alkene (Condon, 1958). In the case 0 196-432 1/80/ 1219-0191$01 .OO/O
of n-heptane in isobutane solvent the following sequence of reactions takes place (eq 1-4). hydride abstraction n-C;H,, + H' i-C;HlS+ + H, (1) deprotonation (alkene formation) T
h
-H+
i-CjHl>+ i-CiH,, alkylation of Ci alkene i-C7H14+ t-C,HS+ CllH2,3+ @-scission
-
C,lH,,+ C
H+
C,Hl,+ + CsH,2
1980 American Chemical Society
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(3)
(4)
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 2, 1980
Table I. Alkylation of Isobutane in HF-TaF, reactants in i-C4Hl, n-C,H,,n-C,H16 n-CRHI,n-CIIH24a
T, “ C t , min wt % i-C4Hlo in reaction
40 30 73.3
40 30 65.9
40 30 61.1
mixture
63
Total Product Distribution (Wt 7%) C3HR 3.23 2.67 C4H10’S 63.3 53.7 R i-C,H,, in C4HIo’s 74.3 76.7 C,H,,’s 21.2 20.7 % i-C,H,, in C5H12’s 82.7 83.5 9.69 15.1 Cf,”’S % 2,2-DMChbin C6HI4’s 52.4 52.8 C, H ,:-C , H,, ’S 7.37 2.54
3-06 46.9 74.6 22.0 81.1 23.2 44.8 4.78
Table 11. Alkylation of n-Butane with n-Heptane after 20 inin at 40 “ C .total product distribution, wt % I IIa
a
7.03 66.8 56.7 15.4 84.4 7.51 49.7 3.26
Duplicate of run I.
Because the steady-state carbocation concentration is very low, especially for the CllH23+ cation, the overall reaction scheme can be summarized by the following equilibria (eq 5 and 6) and it is not sensitive to the size of the alkane reactant.
+ i-C4Hlo ===i-CSHj2 + i-CGH14 i-CGH1, + i-CdH1o + 2i-C5H12
n-C,Hi,
(5) (6)
Reactions of this type employing liquid phase FriedelCrafts catalysts and an isoalkane solvent have been referred to in the literature by Kramer (19601, McCaulay (1974), and Schreisheim (1960), and represent an interesting method to convert high molecular weight alkanes into high octane equilibrium mixtures of essentially C5 and c6 branched alkanes. The high activity of the HF--TaF,
C3HR C4HI”’S % i-C4H10in C4H10’s c c H 12’s % i-C;H,, in CSH12’s c6
%
2,2-DMC4 in CbHI4’s
“lH16”
system a t low temperatures for both alkylation (Siskin, 1976) and isomerization (Siskin et al., 1980) and the fact that alkanes such as n-butane (Brouwer, 1968) and propane (Beeck et al., 1948 and Olah and White, 1969) undergo carbon scrambling reactions thru cyclopropane transition states without undergoing observable isomerization in strong acid systems led us to test the efficiency of similar alkane alkylation reactions in HF-TaF, and to see if the reaction could be carried out directly on n-butane and propane.
Results and Discussion The first four reactions summarized in Table I show that, as expected, the reaction proceeds smoothly in isobutane a t 40 “C with (a) n-C7H16,(b) n-C8H18,and (c) a mixture of C7-CI1 normal alkanes. Under the same reaction conditions, n-butane (80.0 g, 1.4 mol) was stirred with the catalyst. After 1 h there was essentially no isomerization to isobutane (k, = 1.28 X lo4 5-l). n-Heptane (26.0 g, 0.26 mol, 24.5 wt % ) was then added to the reaction mixture. After 20 min of reaction (duplicate runs) the hydrocarbon layer of the reaction mixture was sampled (Table I1 and Figure 1);a portion of the butanes was found to be consumed and the remainder of the n-butane was converted to -75% of isomerization equilibrium. Similarly, nmC7H16(25.0 g, 0.25 mol) in C3Hs (105 g, 2.39 mol) reacted a t 30 “ C gave the following product distribution after 20 min of reaction (Table 111, Column 1 and Figure 2). A control reaction with only n-C7HlG (150 cm3) gave results as indicated in column I1 which is not comparable to the reaction with propane after factoring out the propane (column IA) and did not change significantly after 30 min of reaction. A good material balance as in
I1 b
IIIC
20 min
20 min
20 min
30 rnin
20 min
30 rnin
71.1 18.7 79.1 5.65 86.0 3.65 58.4 0.96
____ 64.7 ____ 19.5 ____ 12.6 -___
4.38 32.7 86.0 20.1 85 .O 21.6 47.1 19.2
2.84 33.9 79.8 23.9 84.4 24.9 52.4 14.5
25.4 59.8 66.6 21.1 77.4 18.5 46.0 5.12
23.7 32.2 64.3 21.2 78.8 19.4 44.1 3.63
3.3
Propane material has been factored out and the product distribution normalized. Reaction of n-heptane diluted in Freon 113. a
‘in
Figure 1. Course of the reaction of n-heptane with n-butane at 40 “C in HF-TaF,.
Table 111. Alkylation of Propane with n-Heptane at 30 “ C I IA a product distribution, wt %
i
-,?e
To isobutane ( 5 5 g, 1 5 0 c m 3 )was added a reaction mixture (35 g, 52 c m 3 )composed of cpd (wt %): n-C,HI, (6.5), n-C,H,, (25.8), n-C9H2, (41.9), n-CloH2,(12.9), and n-C,,HZ4(12.9). At equilibrium the mixture of hexanes contains -54% of the 2,2-dimethylbutane isomer in the liquid phase at 40 “C.
5.27 70.6 58.7 15.1 84.3 7.52 52.1 1.46
i
! I-
a
C,H, CIH;,’s 5% i-C,Hlo in C4HLO’s C, H ,, ’s % i - 1 5 ~in~ c,H,,’s ~~ % C6HI4’s % 2,2-DMC4 in C6H14’s % C,H,,’s
-
Control reaction of neat n-heptane.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 2, 1980
A
so-
-2
e
0
Hevaies Hepia-es
-
I4
a
Timeii.in.1
Figure 2. Course of the reaction of n-heptane with propane at 30 "C in HF-TaF5.
.2;J Bbtanes
?entaw
0
hexanes Heptanes
A , -
Figure 3. Course of the reaction of n-heptane in Freon 113 at 30 "C in HF-TaF,.
Figure 1 could not be obtained in the propane solvent. In this case, with propane, absolute proof of the participation of propane would require I4C labeling which we were not able to carry out. In order to help resolve the question, a reaction was carried out with n-heptane in Freon 113 at 30 "C (Figure 3) to see if the product mixtures more closely resembled the propane-heptane alkylation or the neat heptane reaction products. The results (Table 111, column 111) show a fairly close comparison to the neat heptane reaction and the material balance shows evidence for propane participation in that the propane peaks in concentration after 5 min of reaction and is consumed thereafter. (Note: The initial increase in propane concentration is due to a higher solubility of propane in the acid which is reversed as an equilibrium concentration of ions in the acid are built up.)
Conclusions The direct alkylation of n-butane by larger alkanes in HF-TaF5 has been demonstrated. While evidence for the
193
analogous direct alkylation of propane has been presented, the data do not unequivocally demonstrate the involvement of propane. A general mechanism has been elucidated for this alkane alkylation reaction. General Batch Reaction Procedure Into a 500-cm3Hastelloy C Stirred Reactor body under a nitrogen atmosphere was placed TaF5 (83.0 g, 0.30 mol) (white powder, resublimed mp -97" from Ozark Mahoning Co.). The reactor head was then installed onto the body. The reactor was flushed slowly with nitrogen and then pressure tested under 40 psig of nitrogen. The nitrogen was vented and the reactor was carefully evacuated to -5 in. of water. Hydrogen fluoride from Matheson Gas Co. was redistilled in a copper still and the fraction boiling between 19.6 and 20.5 "C was collected into a tared 150cm3 316SS high pressure cylinder (70.0 g, 3.50 mol) and pressured into the reactor. The cylinder was weighed to assure complete H F addition. Another tared cylinder containing isobutane (110 g, 1.90 mol) was then pressured into the reactor, behind 250 psig of hydrogen. The cylinder was weighed to assure complete addition of hydrocarbon reactant. The reactor was then vented. The stirrer was turned on a t 1000 rpm. Steam was then passed through the internal coils and the reaction mixture was thereby heated to 40 "C in 2 min. n-Octane (57.0 g, 0.5 mol) and hydrogen (0.03 mol) at about 30 psi were added to the stirred reaction mixture from a third tared cylinder. At 40 "C the stirrer was stopped; hydrogen was pressured through the hydrocarbon sampling dip leg until the reactor pressure gauge just flickered. This was done to assure no holdup in the dip leg which would lead to a nonrepresentative sample. The valve to the reactor hydrocarbon dip leg was then closed and the sampling system lock-hopper (-2 cm3) and 10-cm3316SS high pressure sampling cylinder attached directly below it were evacuated. The cylinder valve and the valve off a tee to the lock-hopper were closed. A dry ice-acetone bath was in place around the cylinder. After the reaction mixture had settled for about 20 s the valve from the reactor to the lock-hopper was opened, the reactor valve closed, the lock-hopper reevacuated, and then the valve to the reactor reopened and closed. The stirrer was turned on. The 10-cm3 cylinder valve was then opened to allow the sample to flash into it and hydrogen pressure was applied through the lock-hopper tee to assure the transfer. The cylinder was removed, vented in the hood, placed in a vice to loosen the valve (1/8-in. N P T male), and the contents were poured into a 5-cm3vial precooled in dry ice. A 0.1 FL sample of the hydrocarbon product was then taken into a syringe, also precooled in dry ice, and the sample was injected into a Perkin-Elmer Model 900 gas chromatograph containing a SS, 15 f t X 1/8 in. Squalane (15%) on SO/lOO mesh Chromosorb P at 90 "C or a 50 ft X 1/8 in. 40% Squalane Scot column on Chromosorb from P&E at 50 "C. This sampling procedure was repeated periodically after reaction temperature was reached. Acknowledgment The authors thank Drs. R. L. Hartgerink and R. H. Schlosberg for helpful discussion and Mr. W. P. Kocsi for technical assistance. Literature Cited Beeck, O.,Otvos, J. W., Stevenson, D. P., Wagner, C. D., J . Chem. Phys., 18, 225 (1948). Brouwer, D. M., R e d . Trav. Chim., 87, 1435 (1968). Brouwer, D. M., Oelderik, J. M., Am. Chem. SOC. Div. Fuel Chem. Prepr. (1968). Condon, F . E., in "Catalysis",VoI. VI, Chapter 2 and references cited therein, P. H. Emmett, Ed., Reinhold, New York, N.Y., 1958. Kramer, G. M., Gilbert, G. K., US. Patent 2963526 (Dec 6, 1960).
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Ind. Eng. Chem. Prod. Res. Dev. 1980, 79, 194-197
McCaulay, D. A., US. Patent 3 819 743 (June 25, 1974). Olah. G. A.. WhRe, A. M., J . Am. Chem. SOC.,91,5801 (1969). Schriesheim, A., U S . Patent 2943 126 (June 28, 1960). Schriesheim, A., Gilbert, G. R.,U S . Patent 2 966 535 (Dec 27, 1960). Schneider, A., J. Am. Chern. SOC.,74,2553 (1952),and references cited therein. Siskin, M., J. Am. Chem. SOC.,98, 5413 (1976).
Siskin, M., Chludzinski, G. R., Hulme, R., Porcelli, J. J.. Tyler, W. E. 111, pari 9 of this series, submitted for publication in Ind. Eng. Cbem. Prod. Res. Dev.,
1980.
Received f o r review April 23, 1979 Accepted January 28, 1980
Unusual Ammoxidation Route to Trimethylpyridine Serge R. Dolhyj" and Louis J. Velenyi Technology and Planning, The Standard Oil Go. (Ohio), Warrensville Heights, Ohio 44 128
The ammoxidation and oxydehydrogenationtype catalysts such as bismuth phosphomolybdates, uranium antimonates, and iron antimonates normally attack the terminal carbon in !he a position to the G==Cdouble bond. Thus in propylene ammoxidation acrylonitrile is produced; similarly, atroponitrile is formed by the ammoxidation of a-methylstyrene. However, when we studied the ammoxidation of d-limonene we found a surprising product indicating an unusual reaction mechanism. In a conventional mechanism we would expect ammoxidation attack on two terminal carbons and potentially two nitrile groups could be formed. Another expected competitive reaction may proceed via aromatization since these catalysts also have strong oxydehydrogenation activity. However, to our surprise trimethylpyridine was predominantly formed in the gas-phase reaction. This unusual reaction may proceed by intramolecular cyclization of a transient mononitrile precursor. Several possible reaction paths will be discussed and the favored mechanism will be postulated.
Introduction Limonene is an interesting model molecule for studying various reaction mechanisms. In this work we selected this species for the study of the ammoxidation reaction. Since the discovery of the propylene ammoxidation process at Sohio in the 1950's this reaction was the subject of extensive mechanistic study. In the original Sohio ammoxidation process, which is now used commercially worldwide, propylene is oxidized in the presence of ammonia to acrylonitrile. If no ammonia is present in the feed then propylene is oxidized to acrolein. The mechanism of the oxidation reaction over bismuth molybdates and CuO was studied by Adams and Jennings (1964) and Adams et al. (1964) using deuterated propylene. They proposed initial formation of surface adsorbed allylic species after first hydrogen abstraction. This allylic intermediate underwent second hydrogen abstraction forming a proposed vinyl carbene species. Oxygen is then incorporated into the molecule to form acrolein. Callahan et al. (1970) concluded from the kinetic study that in the presence of ammonia (i.e., in the ammoxidation mode) over Bi/P/Mo catalyst, acrylonitrile is formed largely (over 90%) by a mechanism not involving acrolein intermediate but proceeds via a parallel path. Grasselli and Suresh (1972) studied the ammoxidation mechanism over U/Sb catalysts and also postulated the parallel paths of oxidation and ammoxidation. Hucknall (1974) summarized the mechanism of selective oxidations and ammoxidations in a book. At this time the predominant evidence suggests a direct path to acrylonitrile not involving acrolein intermediate. Other olefins were also reported to form substituted acrylonitrile species: e.g., isobutylene forms methacrylonitrile and a-methylstyrene is converted to atroponitrile (Mekhtiev et al., 1972; Callahan et al., 1967; Grasselli and Callahan, 1969). These reactions apparently proceed via a mechanism similar to that for propylene, involving initial attack on the terminal carbon in the a position to the C=C double bond. 0196-4321/80/12 19-0 194$0 1.OO/O
Atroponitrile is relatively unstable and dimerizes easily to form a cyclic species. The dimerization does not involve cyclization through N; apparently the nitrile species after it is formed is resistant to cyclization (Newey and Erickson, 1950). Method Recently we extended our ammoxidation studies to cyclic substituted olefins. We used d-limonene as a model reactant. The ammoxidation of d-limonene was conducted in vapor phase and liquid phase environments. A fixed bed microreactor shown schematically in Figure 1 was used for vapor-phase study and a glass reflux reactor was applied for liquid-phase experiments. The liquid products were analyzed by GC techniques and confirmed by a combined GC/MS method. The tailgas was analyzed using a separate GC for CO, C02,NP, and O2 components. The material balances were calculated on a carbon basis. The catalyst systems used in our study constituted bismuth phosphomolybdates, uranium antimonates, and iron antimonates. These systems were described in earlier ammoxidation work in relation to propylene/acrylonitrile reactions. All were act,ive and selective in producing acrylonitrile in high yields (Callahan et al., 1970; Grasselli and Suresh, 1972). Results and Discussion The d-limonene molecule has two terminal carbons ad-
d-LIMONENE
jacent to the C=C double bond. One constitutes a sub0 1980 American Chemical
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