2298
Ind. Eng. Chem. Res. 1995,34, 2298-2304
Formation of Propylene Oxide by the Gas-Phase Reaction of Propane and Propene Mixture with Oxygen Toshio Hayashi3 Li-Biao Han, Susumu Tsubota, and Masatake Haruta* Osaka National Research Institute, AIST, Midorigaoka 1-8-31,Zkeda, Osaka 563, Japan
The homogeneous gas-phase reaction of propane and propene with molecular oxygen was investigated at 360-520 "C under atmospheric pressure using a quartz reactor in a continuousflow system. At a high concentration (65 ~ 0 1 %and ) low conversions of hydrocarbons, the overall oxidation rate and the selectivity to propylene oxide were markedly enhanced by mixing propane and propene. At a specific propandpropene ratio, for example 10:3, the net conversion of propene was found to become zero a t around 450 "C, indicating that the consumption of propene was compensated by the formation from propane and only propane substantially reacted to form propylene oxide and the others. The major product was propylene oxide, and its selectivity exceeded 30%. Other products were ethylene, CO, acetaldehyde, methane, COZ, acrolein, propanal, methanol, and so forth.
Introduction The functionalization of alkanes by means of molecular oxygen has been attracting growing interest because it promises significant innovation in the supply of chemical feedstocks. Since lower alkanes such as methane, ethane, and propane are chemically less reactive, it seems very difficult to selectively obtain their partially oxidized products which have much higher reactivities. Concerning the oxidative coupling of methane, there are an increasing number of publications in literature proposing mechanisms involving gas-phase radicals (Driscoll et al., 1987). For methanol formation by the direct oxidation of methane, it has often been reported that homogeneous gas-phase reactions permit relatively high efficiency under high pressure (Casey et al., 1994; Omata et al., 1994). The partial oxidation of ethane and propane has also been investigated in the gas phase (Burch et al., 1993; Layokun et al., 1979; Nguyen et al., 1991). Propane oxidation by homogeneous gas-phase reaction has been known to produce mainly propene. Satterfield and Wilson (Satterfield et al., 1954) studied the oxidation of propane with oxygen using a glass flow reactor a t 350-475 "C, and showed that propene was the major product. Falconer and Knox (1959) also reported similar results from experiments carried out at temperatures above 400 "C using a static Pyrex glass reaction vessel. They detected a considerable amount of condensable products in addition to propene; however, they did not identify them except for acetaldehyde. They also found that overall reactivity was enhanced in the presence of propene. Burch and Crabb (1993) have recently investigated the noncatalytic oxidative dehydrogenation of propane t o propene using a quartz reactor and have shown that the homogeneous gasphase oxidative dehydrogenation reaction is more efficient than any purely heterogeneous catalyzed reaction yet discovered for the formation of alkenes from propane. Moro-oka and his co-workers (Kim et al., 1991) have studied the direct catalytic formation of acrolein from propane and have suggested that the reaction might
* To whom correspondence should be addressed. ' On leave from Nippon Shokubai Co., Ltd., Osaka, Japan.
proceed via propene as an intermediate which is formed from propane in a noncatalytic radical process. On the other hand, the direct propylene oxide formation from propane under high pressures was claimed in a few patents (Cook et al., 1950; Lemon et al., 1964). It was also claimed by Lemon et al. that the coexistence of propene brought about an enhancement in propylene oxide formation; however, the role and consumption of propene was not described. Propylene oxide is one of the most important chemical feedstocks in industry and is presently manufactured by two-step processes using peroxides as oxidant with propene (Ainsworth, 1992). Thus, if the direct one-step formation of propylene oxide from propane, which is much cheaper than propene, by molecular oxygen is feasible, it would give us a novel alternative to replace the present processes. The object of our work is to seek for the possibility of the direct formation of propylene oxide and other oxygenated chemical feedstocks from propane and molecular oxygen. In the present paper, we report our preliminary results of the effect of propene addition on the formation of propylene oxide in the gas-phase oxidation of propane under normal pressure.
Experimental Section Apparatus. The oxidation reaction of propane (hereafter denoted as C3) and propene (hereafter denoted as C'3) was carried out under atmospheric pressure in a quartz reactor by using the continuous-flow system shown in Figure 1. The reactor tube with an inside diameter of 12 mm was placed horizontally in an electric furnace. The outside diameter of a thermocouple-holder tube located in the center of the reactor tube was 4 mm, and the reaction space length was 100 mm. The temperature profiles in the reaction zone showed a deviation between maximum and minimum ranging from 20 to 40 "C. The maximum temperature inside the reactor, not wall, was taken as the reaction temperature for convenience. Materials. The reactant gases used were propane and propene (Sumitomo Seika Co., Ltd.) of 99.0% and 99.5% minimum purity, respectively, oxygen (Suzuki Shokan Co., Ltd.) of 99.8% minimum purity, and helium (Suzuki Shokan Co., Ltd.) of 99.9% minimum purity. The standard composition of mixture was (propane
Chemical Society o a a a - ~ a ~ ~ i 9 ~ i 2 6 3 4 - 2 2 ~ ~ ~0 0 ~1995 . 0 0 American 10
+
Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995 2299 Table 1. Analytical Conditions for Gas Chromatograph compounds C3H6, C3H8, co2, C2H6, C2H4, CH4 02, co PO, CH3CH0, (CH3)2CO, CH2=CHCHO, C2H5CH0, CH30H, HCHO, C3H70H
column Porapak Q (3 m) molecular sieve 13X (3 m) HR-2OM (50 m)
detector TCD TCD FID
carrier gas He He He
column temp ("C) 100 100 50-200
(a) Gas flow system flow
auto sampler
reactor
\ propene
\ \
W
I
helium
17 /feed
2
I
I
I
!
quartz cell
n
wool
I
I !
Figure 1. Schematic representation of reaction apparatus. (a)Gas flow system; (b) reactor.
propene)/oxygen/helium = 65/10/25 unless otherwise noted, and the reaction gas was fed a t a flow rate of 1300-2500 mL/h. Analysis. The products were analyzed by two online gas chromatographs using three types of columns: Porapak Q (3 m) and molecular sieve 13X (3 m) as packed columns with a thermal conductivity detector (TCD) and a HR-20M 0.53 mm x 50 m (Shinwa Chemical Industries, Ltd.) capillary column with a flame ionization detector (FID). Detailed analytical conditions are summarized in Table 1. Product yield (Yi, %) is defined as
Figure 2. Conversion of 0 2 and yield of propylene oxide as a function of molar ratio C'3/(C3 C'3). Reaction gases, (C3 C'3/ O n e = 65/10/25 (vol %); flow rate, 1700 mL/h. (- 0 -) 380 "C; (- 0 -) 415 "C; (-); 455 "C; (- 0 -) 495 "C.
+
+
The product selectivity (Si,%) is defined as
si=
l0OYi ~
C
Yi
products
where F i n (mmoVh)= flow rate of inlet gas, Fout(mmol/ h) = flow rate of outlet gas, C C ~ + (%) C $= ~ concentration of propane propene in inlet gas, Ci (%) = concentration of product i in outlet gas, and Ni = carbon number of product i. The conversions of propane and propene can be estimated in a similar manner. The products corresponding to more than 95%of propane converted were detected by GC. The conversion of oxygen is also defined and estimated in a similar manner. To avoid confusion between the conversion of propane to propene and the "net" formation of propene (production minus consumption),the net formation of propene (Xc3, %) is defined as
+
The formation of propylene oxide was confirmed by condensing the liquid products and by analyzing them using lH-NMR spectroscopy.
Results The effect of propene addition for 0 2 conversion and the yield of propylene oxide (hereafter denoted as PO) is shown in Figure 2 as a function of the molar ratio of C'3 to (C3 C'3) under different reaction temperatures. With C3 alone or C'3 alone the oxidation does not take place a t temperatures below 495 "C. At 495 "C only a small amount of PO is produced from C3. Mixing C3 and C'3 a t a variety of composition not only accelerates the overall reactions but also produces PO. A notable mixing effect is observed especially a t C'3/(C3 C'3) = 0.23 (C3/C'3/02/He = 50/15/10/25) and C'3/(C3 C'3) = 0.50 (C3/C'3/02/He = 32.5/32.5/10/25). With C'3 alone the formation of PO was hardly observed under the reaction conditions tested; however, a higher 0 2 con-
+
+
where C ~ ' 3 i n(%) = concentration of propene in inlet gas and C ~ p 3 (%) ~ ~= t concentration of propene in outlet gas.
+
2300 Ind. Eng. Chem. Res., Vol. 34, No. 7, 1995 100
’
co
S 0
. I
U
m
m
L .cI
C2H4
:H3CH0
CH30H*
(CH,),C=O
2c A
CH ,=CHCHO’
PO’
c
0
0.08
0.23
0.5
0.69
1
C13/(C3+C’3) +
Figure 3. Product distribution as a function of molar ratio C’3/(C3 C’3). Reaction gases (C3 + C’3)/0z/He= 65/10/25(~01%);reaction temperature, 495 “C; flow rate, 1700 mUh.
centration yielded a small amount of PO. Higher pressures seemed to be also effective for PO formation in C’3 oxidation (Lemon et al., 1964). Since C’3 is known as an inhibitor of simple chain reactions due to the stability of allyl radical (Bell et al., 1957; Boyd et al., 1990), the successive chain reactions with C’3 could occur only under extreme conditions, such as high temperature, high 0 2 concentration, and high pressure. The oxidation of C3 alone a t 495 “Cproduced mainly C’3 (around 70% selectivity). This result is in agreement with data published in the literature (for example, Burch et al., 1993). Other products were ethylene, carbon monoxide, carbon dioxide, methane, methanol, PO (selectivity 4%),propanal, acrolein, acetone, and so forth. The product distribution after subtracting C’3 gives a PO fraction of about 13%. The oxidation of C’3 alone yielded appreciably different product distribution with no PO formation as mentioned above. Figure 3 shows the effect of propene addition on product distribution after subtracting C’3 as a function of C’3/(C3 C’3) ratio a t 495 “C. When the C3 C’3 mixture was used, the proportion of PO noticeably increased and exceeded that for C3 alone after subtracting C’3 produced. At C’3/(C3 C’3) = 0.23 and 0.50 PO formation reached a value higher than 30%. As byproducts,
+
+
+
considerable amounts of ethylene, carbon monoxide, acetaldehyde, methane, etc. were formed. The effect of temperature for product distribution is shown in Figure 4 a t a ratio of C’3/(C3 C’3) = 0.23. The formation of PO was always observed in the temperature range of 380-510 “C. The highest selectivity to PO was obtained a t 476 “C, and it seemed to result from opposite contributionsfrom an enhancement in ethylene formation on the one hand and a deceleration in acetaldehyde and carbon monoxide formation on the other hand, with an increase in temperature. At low temperatures between 380 and 435 “C, products resulting from C-C bond scission tend to increase in proportion. To investigate the behavior of added propene, the conversions of C‘3 were measured and found to be minus in some cases. The “net”formation of C’3 defined under Experimental Section was plotted accordingly as a function of reaction temperature in Figure 5. With a small amount of C’3 added to C3, C’3/(C3 C’3) = 0.08 (C3/C’3 = 60/5), the net formations of C’3 are positive, which means that the amount of the production of C’3 exceeded that of the consumption of C’3. With a large amount of C’3 added, C’3/(C3 C’3) = 0.50 (C3/C’3 = 32.5/32.5) and 0.69 (20/45), the net formations are
+
+
+
Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995 2301 100
-
80
-
60
*
40
(CH,),C=O
20
0 380 391 402 415 435 455 476 496 516
Temperature ("C) Figure 4. Product distribution as a function of reaction temperature. Reaction gases, (C3 1700 mL/h.
negative, showing that the amount of the production of C'3 does not exceed that of the consumption of C'3. In a specific ratio, for example C'3/(C3 C'3) = 0.23 (C3/ C'3 = 50/15), at around 450 "C, the net formation of C'3 is almost zero. This means that there are specific points where the amount of the production of C'3 is equal to that of the consumption of C'3, namely, only propane is actually consumed. Thus, under suitable reaction conditions, PO can be produced with a relatively high selectivity through the consumption of C3 alone. It should also be noted that the temperature range for reaction of 450-500 "C, where maximum selectivity is obtained, corresponds to the temperature range where the net formation of C'3 remains around zero. Figure 6 shows 0 2 conversion and PO selectivity as a function of temperature for different concentrations of 02. Oxygen conversion reaches a maximum around 400 "C, and a minimum around 460 "Cfor 0 2 concentrations of 10.0% and above. A higher concentration of 0 2 results in a wider temperature range for the maximum around 400 "C. This phenomenon can be explained by the property of alkylperoxy radicals, which would be formed in radical propagation reactions as discussed later. The selectivity of PO formation reaches a maximum at 450-500 "C.
+
+ C'3)/02/He = 65/10/25 (vol %); flow rate,
Figure 7 shows relations between the total conversion of C3 and PO selectivity a t C'3/(C3 C'3) = 0.23 (C3/ C'3 = 50/15). Different conversions were obtained by varying the residence time. The selectivityto PO tends to decrease with increasing conversion, and this trend becomes more appreciable at lower reaction temperatures. The maximum PO selectivity which can be potentially reached is extrapolated to about 40%. In order to clarify the experimental conditions required for reproducible results, we investigated the effect of filling the reactor with glass beads and glass wool and the effect of other reactor materials such as Pyrex and stainless steel 304. When glass beads or glass wool was packed in the reactor, the reaction was significantly retarded and produced no PO. A Pyrex reactor yielded PO formation showing no appreciable difference from the quartz reactor; however, a stainless steel 304 reactor also retarded the reaction and brought about mainly carbon dioxide formation and no PO formation.
+
Discussion Initiation and Inhibition. The above results indicate that free space is important for the formation of PO in the oxidation of propane and propene and
Ind. Eng. Chem. Res., Vol. 34, No. 7, 1995 20
100
r
15
80
10 60
5 40
0
20 -5
-10 -
320
I
I
I
I
I
360
400
440
480
520
0 560
320
360
Temperature ( "C)
+
heterogeneous surface may quench and oxidize the intermediates further into C02. The importance of free space was also underlined in the oxidation of propane (Burch et al., 1993), ethane (Burch et al., 19931, and methane (Baldwin et al., 1991). Radical reactions which take place in the gas phase are most likely to form propylene oxide. It is not clear whether quartz and Pyrex can initiate the reaction; however, at least they are less active than stainless steel 304 so that they inhibit radical chain reactions to a lesser extent. The role of oxygen is probably to initiate reaction 1,and to propagate the radical chain by reactions 2 and 3.
+ 0, R' + 'OOH R' + 0, tROO' ROO' + RH ROOH + R' ,
,
480
520
560
Temperature(OC)
Figure 5. Net formation of propene (C'3) as a function of reaction temperature. Reaction gases, (C3 C'3)/02/He = 65/10/25 (vol %); flow rate, 1700 m u . (- 0 -1 C3/C'3 = 60/5; (- v -1 C3/C'3 = 50/15; (-) C3/C'3 = 32.5/32.5.
RH
440
400
Figure 6. 0 2 conversion and propylene oxide selectivity as a function of reaction temperature. Reaction gases, C3/C'3/02Me = 50/15/7.5-15/20-27.5 (~01%); flow rate, 1700 m u .02 conver-) 12.0%; sion (02 vol %): (- 0 -1 7.5%; (- A -) 10.0%; ((-1 15.0%. PO selectivity ( 0 2 vol %): (- 0 -) 7.5%; (- A -1 10.0%; (- 0 -) 12.0%; (- 0 -) 15.0%. 40
(1)
(2)
5t
(3)
O
Temperature Dependence. The equilibrium constants for reaction 2 are reported for isopropyl and allyl radicals (Benson, 1965): log Keq (Keq = [ROO'Y[Rl[O21) a t 27, 223, and 423 "C for isopropyl radical (C3H7.1 are 14.1, 5.5, and 1.85, respectively, and for allyl radical (C3H5.1 are 5.0,0.75, and -0.97, respectively. Then, the dissociation energy of allylperoxy, n-propylperoxy, and isopropylperoxy radicals to each alkyl radical and oxygen has been calculated to be 89, 136 and 146 kJf mol, respectively (Boyd et al., 1990). Accordingly, the two equilibrium constants for n-propyl and isopropyl radicals can be assumed to be closer to each other than to that for allyl radical. Reaction 2 shifts toward the right side with a decrease in temperature, and the shifts for two radicals are larger than that for allyl radical.
6
;
2
3
;
5
6
+
I
C3 conversion (%) Figure 7. Propylene oxide selectivity as a function of conversion of propane. Reaction gases, (C3 + C'3)/02/He = 65/10/25 (vol %). (- 0 -) 380 "c; (- A -1 415 "c; (- 0 -) 455 "c; (- 0 -) 495 "c.
For example, under 0.1 atm of 02 the temperatures where [El = [ROO'] is reached are about 500 "C for isopropyl radical (C3H7') and about 200 "C for allyl radical (CsH5') (Benson, 1965). At 400-500 "C, the value of [C3H,OO'I is calculated to be about 1 order of magnitude larger than that of [C3H500], which suggests that propylperoxy radical formed from propane may act a greater role than allylperoxy radical formed from propene in gas-phase reactions. The maximum conversion of 0 2 observed
Ind. Eng. Chem. Res., Vol. 34, No. 7,1995 2303 Koelewijn, 1972). The radical produced in reaction 5 will decompose, as shown in reaction 7, into propylene oxide and alkoxy radical, which is one of the most reactive radical propagators. C,H,OO' 4-C,H,
-
C,H,OOC,H,'
(5)
C3H7OO
,O, +*OH CHzCHCH3
0 + C3H70 / \ CH2CHCH3 C3H7 00 H ".., (12) k-. Cab %
+ L
,0,
+ C3H7OH CH2CHCH3
As for the formation of hydroperoxy radical, 'OOH, reaction 8 may also contribute in addition t o reactions 1 and 4. Satterfield and Wilson (1954) have reported that the contribution of reaction 8 becomes larger with increasing temperature.
main route less probable
Figure 8. Probable reaction scheme for the partial oxidation of propane and propene to produce propylene oxide.
around 400 "Cin Figure 6 can be explained in terms of these equilibria, which potentially lead to an increase in [ROO'] fraction with a decrease in temperature. In addition, the contribution of reaction 4 should also be
considered, since it can take place at higher temperatures, competing with reaction 2. Satterfield and Wilson (1954) have attributed the high conversion at low temperatures t o the reactivity of the products formed in the two alternative reactions of the propyl radical with oxygen, reactions 2 and 4, indicating that the products of reaction 4 are less reactive than those of reaction 2. As for the lower PO selectivity at lower temperatures, it may be due to the increasing proportions of acetaldehyde, other partially oxidized products, and CO, which are formed through C-C bond scission induced in the vigorous radical chain reactions resulting from the increase in [ROO']. Effect of Propene Addition. The partial oxidation of propane and propene involves many elementary reactions. Figure 8 shows major reaction paths for propane. Concerning the enhancing effect of propene addition on PO formation, it is likely that PO is formed through the reaction between propene and oxygen-containing species and therefore an increase in propene concentration results in an enhancement of reaction rate. In addition, the enhancing effect on the overall reactions seems t o be due to the formation of radical propagators accompanied by PO formation. Falconer and Knox (1958) have attributed the latter effect to the formation of higher aldehydes which occurs due to the accumulation of propene and induces the formation of the propagators. Since higher aldehydes were scarcely detected in the products under the present experimental conditions, another explanation might be more plausible. Alkylperoxy radicals can add to olefins that have allylic hydrogen as shown in reaction 5, competing with the abstraction of hydrogen from olefin in reaction 6 with a comparable rate (Mayo, 1968; Ingold, 1969;
Reactions 9 and 10 including hydroperoxy radical can also take place as one of the routes for PO formation accompanied by the formation of radical, which act as a radical propagator.
White et al. (1965)have suggested a similar mechanism involving the direct interaction of propene with hydroperoxy radical for PO or propanal formation from a carbon-14 tracer study of propene oxidation. On the other hand, it is also probable that the propylperoxy radical itself decomposes into PO and hydroxy radical. Both n-propyl and isopropyl radicals can form PO in reactions l l a and l l b . The contribution
of these routes, however, seems to be not so large, because the enhancing effect of propene addition cannot be obtained directly. For the alternative PO formation, the reactions 12 and 13 of propene with alkyl hydroperoxide and hydro-
gen peroxide can also take place; however, their contribution appears to be small because alcohol (n-propyl alcohol or isopropyl alcohol) was not detected and the products to enhance overall reactions are not formed. On the basis of the above considerations, it is most likely that PO formation takes place by the reaction between propene and peroxy radical species and at the same time these reactions yield other more active radical species such as alkoxy or hydroxy radicals, which
2304 Ind. Eng. Chem. Res., Vol. 34, No. 7, 1995
in turn act as radical propagators to accelerate the overall reactions.
Conclusion The homogeneous gas-phase oxidation of a mixture of propane and propene with molecular oxygen can produce propylene oxide with much higher efficiency (conversion 5%, selectivity 30%)than that with propane or propene alone. It was also found that the net consumption of propene was controllable even t o a zero value by choosing adequate reaction conditions, so that only propane was substantially consumed in the reaction. The most plausible reaction scheme includes propene formation by the oxidative dehydrogenation of propane and propylene oxide formation by the reaction between propene and peroxy radical species, which may be key intermediates originating from propane. The enhancing effect of propene addition can be attributed to the formation of radical propagators accompanied by PO formation. Literature Cited Ainsworth, S. J. Propylene Oxide Producers Look for Ways to Counter Sluggish Market. Chem. Eng. News 1992,March 2,9. Baldwin, T. R.; Burch, R Squire, G. D,; Tsang, S. C. Influence of Homogeneous Gas Phase Reactions in the Partial Oxidation of Methane to Methanol and Formaldehyde in the Presence of Oxide Catalysts. Appl. Catal. 1991,74,137. Bell, E. R.; Vaughan, W. E.; Rust, F. F. Hydrogen Peroxide-Olefin Reactions in the Vapor Phase. J. Am. Chem. Soc. 1957,79,3997. Benson, S. W.Effects of Resonance and Structure on the Thermochemistry of Organic Peroxy Radicals and the Kinetics of Combustion Reactions. J.Am. Chem. Soc. 1965,87,972. Boyd, S. L.; Boyd, R. J.; Barclay, L. R. C. A Theoretical Investigation of the Structures and Properties of Peroxyl Radicals. J . Am. Chem. SOC.1990,112,5124. Burch, R.; Crabb, E. M. Homogeneous and Heterogeneous Contributions to the Catalytic Oxidative Dehydrogenation of Ethane. Appl. Catal. 1993a,97,49. Burch, R.; Crabb, E. M. Homogeneous and Heterogeneous Contributions to the Oxidative Dehydrogenation of Propane on Oxide Catalysts. Appl. Catal. 1993b,100,111.
Casey, P. S.; McAllister, T.; Foger, K. Selective Oxidation of Methane to Methanol at High Pressures. Znd. Eng. Chem. Res. 1994,33,1120. Cook, G. A,; et al. Production of Propylene Oxide. US patent 2,530,509, 1950. Driscoll, D. J.;Campbell, K. D.; Lunsford, J. H. Surface-Generated Gas-Phase Radicals: Formation, Detection, and Role in Catalysis. Adv. Catal. 1987,35,139. Falconer, J. W.; Knox, J. H. The High-Temperature Oxidation of Propane. Proc. R. SOC.1959,A250,493. Ingold, K. U. Peroxy Radicals. Acc. Chem. Res. 1969,2,1. Kim, Y.-C.; Ueda, W.; Moro-oka, Y. Selective Oxidation of Propane Involving Homogeneous and Heterogeneous Steps over Multicomponent Metal Oxide Catalysts. Appl. Catal. 1991,70,175. Koelewijn, M. P. Epoxidation of Olefins by Alkylperoxy Radicals. Recl. Trav. Chim. Pays-Bas 1972,91,759. Lemon, R. C.; et al. Selective non-Catalytic, Vapor Phase Oxidation of Saturated Aliphatic Hydrocarbons to Olefin Oxides. US patent 3,132,156, 1964. Layokun, S. K. Oxidative Pyrolysis of Propane. Ind. Eng. Chem. Process Des. Dev. 1979,18,241. Mayo, F. R. Free-Radical Autoxidations of Hydrocarbons. Acc. Chem. Res. 1968,1,193. Nguyen, K. T.; Kung, H. H. Analysis of the Surface-Enhanced Homogeneous Reaction during Oxidative Dehydrogenation of Propane over a V-Mg-0 Catalyst. Znd. Eng. Chem. Res. 1991, 30, 352. Omata, K.; Fukuoka, N.; Fujimoto, K. Methane Partial Oxidation to Methanol. 1. Effects of Reaction Conditions and Additives. Znd. Eng. Chem. Res. 1994,33,784. Satterfield, C.N.; Wilson, R. E. Partial Oxidation of Propane. Znd. Eng. Chem. 1954,46,1001. White, E. R.; Davis, H. G.; Hammack, E. S. Carbon-14 Tracer Study of the High Temperature Oxidation of Propylene. J . Am. Chem. SOC.1965,87,1175.
Received for review September 7, 1994 Revised manuscript received March 1, 1995 Accepted March 27, 1995@ I39405293
@Abstract published in Advance ACS Abstracts, May 1, 1995.
