Industrial and Laboratory Pyrolyses

15 Pyrolysis of Propane in Tubular Flow Reactors Constructed of Different Materials JOHN J. D U N K L E M A N * and L Y L E F. ALBRIGHT

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 4, 2017 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/bk-1976-0032.ch015

School of Chemical Engineering, Purdue University, West Lafayette, Ind. 47907

Recent results of Dunkleman and Albright (1) who pyrolyzed ethane have shown that the composition of the product often varies significantly depending on the material of construction of the reactor and on the type of pretreatment of the inner surface of the reactor. Considerably higher yields of ethylene were obtained in a laboratory Vycor reactor as compared to an Incoloy 800 reactor and especially a 304 stainless steel (SS) reactor. Oxidized inner metal surfaces promote the production of coke (or carbon) and carbon oxides, but sulfided surfaces suppress such production. When olefins are the desired products of propane pyrolysis, ethylene, propylene, methane, and hydrogen are the major products. Brown and Albright (2) found that both ethylene and propylene react to a significant extent on the surface of metal reactors. In general, 304 SS steel reactors result in more olefin reactions and in the formation of more coke and hydrogen than occurs on an Incoloy 800 surface. Ethylene is generally more reactive on the surface than propylene. Metal oxides on the surfaces of these reactors react with hydrocarbons forming carbon oxides, water, and hydrogen; such reactions result in the reduction of the surface. Metal sulfides on the surface, however, minimize surface reactions. Preliminary investigations (3,4,5) have shown that surface reactions are important during the pyrolysis of propane at temperatures of commercial importance. Until now, however, experimental data were not available to make direct comparisons between reactors constructed of different materials or between propane and ethane relative to surface reactions. Such information has now been obtained in the present investigation. Experimental Details The same laboratory apparatus and tubular reactors used for pyrolysis of ethane (1) were employed in this investigation. The gas chromatograph and the method of product analysis used by Herriott (6) were modified, however, in order to obtain a more accurate analysis of the gaseous products up to butane. This was * Current address: Exxon Research and Engineering Co., Baytown, Texas. 261

Albright and Crynes; Industrial and Laboratory Pyrolyses ACS Symposium Series; American Chemical Society: Washington, DC, 1976.


262

INDUSTRIAL AND LABORATORY PYROLYSES

achieved by a combination of techniques including lowering the temperature of the chromatographic column, using Porapak-Q as the column packing, and increasing the s e n s i t i v i t y and chart speed of the recorder. These improvements enabled the oeak areas for the individual hydrocarbon products to be more accurately measured. Although helium was retained as the c a r r i e r gas, the analysis of hydrogen was improved by use of an atom balance around the flow system (7). Because of these improvements, the e a r l i e r results (3,4) were found to be less accurate especially at low propane conversions as w i l l be discussed in more detail l a t e r in this paper. Furthermore, the improved analytical techniques used here enabled the analysis of carbon monoxide and carbon dioxide which were present when steam was added to the propane feed for experiments in the metal reactors; such analyses had not been made e a r l i e r . In general, r e l a t i v e l y l i t t l e carbon dioxide was produced during a pyrolysis run. Material balance calculations based on both the i n l e t and the e x i t gaseous streams to the tubular reactor indicated the amount of coke deposited on the reactor w a l l . On several occasions, an oxygen burn-out technique was used in an attempt to check the amount of carbon formed based on the above calculations. In the bum-out technique, pure oxygen was Passed through the hot reactor and the amounts of carbon oxides formed were measured. Less carbon was in each case burned out of the reactor than indicated by the material balance. Some of the carbon was, however, l a t e r found to have been blown from the reactor, and hence not burned, as indicated by carbon eventually found in the r e l a t i v e l y cool exit line. Results Significant differences were noted in the composition of the resulting gaseous product when prooane was pyrolyzed in Vycor, 304 SS, and Incoloy 800 reactors. Comparative runs were made both at 750 and 800 C; in some cases, the propane was fed to the reactor dry, and in other cases, i t was oremixed with steam in a 1:1 mole r a t i o . Table I shows the results of experimental runs in the three reactors at 800 C and using wet propane as feed. Yields of p a r t i c u l a r l y ethylene, hydrogen, and coke often varied s i g n i f i c a n t l y for comparative runs. In such cases whenever higher ethylene yields occurred, yields of both hydrogen and coke were less. Furthermore, the composition of the product gases frequently changed appreciably during the f i r s t few minutes of runs in metal reactors. For the runs in the Incoloy 800 and the 304 SS reactors, shown in Table I, ethylene yields increased subs t a n t i a l l y during the i n i t i a l phases of the runs. In general, the ethylene yields varied in the three reactors as follows: Vycor glass

>

Incoloy 800 and 304 SS


15.

Propane in Tubular Flow Reactors

DUNKLEMAN AND ALBRIGHT

263

Table I Product Composition and Carbon Yield for Propane Pyrolysis in Different Reactors (800 C, 50% steam in feed) e


60%

Propane Conversion

85%

Propane Conversion

Time Composition of Carbon During Composition of Coke Product Gas, % Product Gas, % Run, Yield, Yield, Reactor min. Ethylene Hydrogen wt.% Ethylene Hydrogen wt.% Model * Vycor Incoloy 800 304SS**

24.0

12.5

0.0

33.0

11.0

0.0

10-60

23.8

14.2

0.2

33.6

10.0

1.4

10

19.9

16.9

0.8

23.9

30.2

8.7

27.4

20.1

4.4

60 10

—

—

—

24.0

27.3

7.0

40

—

—

—

26.0

19.2

3.1

*

The mechanistic model was described e a r l i e r (1).

**

Both metal reactors were treated with H S for 15 minutes and then used for several hours of pyrolysis of wet ethane before being used for propane pyrolysis. ?

I n s u f f i c i e n t data were, however, obtained to compare the y i e l d results in the two metal reactors under essentially identical levels of surface oxidation. I f there were any differences in the results for these two reactors, these differences were probably, at most, small. Figure 1 shows the product composition for a run in a Vycor glass reactor maintained at 800 C and using wet ethane feed; the major products (ethylene, propylene, hydrogen, and methane) and ethane are shown as a function of space time. Propane conversion is also shown. The results of a l l propane runs including the one used to prepare Figure 1 indicated the following: (a) The mole fractions of both hydrogen and ethylene in the gaseous product stream passed through maxima at r e l a t i v e l y low propane conversions, perhaps about 30%. Obviously, both propylene and hydrogen were reactive, entering into secondary reactions, especially at higher conversions.



264


(b) A t propane conversions up t o perhaps 70-80%, the mole f r a c t i o n s o f ethylene i n the gaseous product streams were g r e a t e r than those o f methane. A crossover o c c u r r e d , however, a t higher conversions; apparently considerable ethylene was destroyed by secondary reactions a t higher propane conversions. Methane was however r e l a t i v e l y unreactive a t the c o n d i t i o n s i n v e s t i g a t e d . For runs a t 800 C and a t f a i r l y low propane conversions, the f r a c t i o n s o f propylene and hydrogen i n the gaseous product exceeded those o f ethylene and methane. These f i n d i n g s d i f f e r from the r e s u l t s reported by o t h e r i n v e s t i g a t o r s (3,4) who are thought t o have used less accurate a n a l y t i c a l techniques. S t i l l o t h e r i n v e s t i g a t o r s ( 8, 9) r e p o r t r e s u l t s s i m i l a r t o those found i n t h i s i n v e s t i g a t i o n . I t i s n o t c l e a r though i f propylene and hydrogen compositions are g r e a t e r a t lower temperatures, such as 750 C o r l e s s . For the r e s u l t s at 800 C, apparently propyl r a d i cals decompose more r a p i d l y i n t o propylene and hydrogen r a d i c a l s than i n t o ethylene and methyl r a d i c a l s .



15. D U N K L E M A N A N D A L B R I G H T


265

The results of the present Investigation for propane pyrolysis and those of the e a r l i e r investigation (1) describing ethane pyrolysis were compared at operating conditions of commercial importance. Clearly surface reactions in the case of propane pyrolysis are of lesser importance as compared to those for ethane pyrolysis. Specific comparisons were made using the results of ethane pyrolyses at about 65% ethane conversions and those for propane pyrolyses at about 85-90% propane conversions. The l e s ser importance of surface reactions for propane pyrolyses i s based on lower levels of coke formation and smaller yields of carbon oxides. Table I of the present investigation and Table I of the e a r l i e r paper (1) describing ethane pyrolysis results show three s p e c i f i c comparisons of the carbon (or coke) yields at 800 C using wet paraffins as feedstocks. In the Vycor reactor, carbon yields were lower for propane pyrolysis by a factor of about two. In the metal reactors, the factor was even greater, especially when steam was used as a diluent. Surface reactions are thought to be r e l a t i v e l y unimportant when propane i s pyrolyzed in a Vycor glass reactor. This conclusion i s based on two factors. F i r s t , surface reactions in the Vycor reactor were of f a i r l y minor importance for ethane pyrolysis (1) and are considered to be even less s i g n i f i c a n t for propane pyr o l y s i s . Secondly, as was shown in both table I and Figure 1 and as w i l l be described l a t e r in this paper, there was good agreement between the experimental results for the Vycor reactor and the predictions of the mechanistic model described e a r l i e r (1). The pyrolysis results obtained using the Vycor reactor were used to make various comparisons. Increased temperatures and decreased p a r t i a l pressures of entering propane both result in i n creased ethylene y i e l d s . Such findings are consistent with the general trends reported by many previous investigators for pyrolyses of other hydrocarbons and s p e c i f i c a l l y by those (3,4) who have investigated propane pyrolyses in metal reactors. The oretreatments of metal surfaces also affected product composition. Less surface reactions occur on H S-treated metal surface as compared to untreated surfaces. Oxygen-treated surfaces that have metal oxides on the surface tend to promote undesired surface reactions and to produce considerably more carbon oxides. 2

Modeling of Propane Pyrolysis Data Several mechanistic models involving numerous free-radical gas-phase reactions were tested and compared to prooane pyrolysis results obtained in the Vycor glass reactor. Data obtained in metal reactors were not compared since surface reactions were obviously of much greater importance in these l a t t e r reactors. The model developed as a result of this preliminary testing i s presented in Table II of the previous chapter of this book (1). Good agreement occurred between the predicted values and a l l experimental results obtained in the Vycor reactor (at both 750 and 800 C with and without steam as a diluent). Figures 1 and 2 show



266

INDUSTRIAL A N D L A B O R A T O R Y

PYROLYSES

comparisons f o r the product composition and f o r propane conversions respectively. Good agreement was a l s o noted when the isothermal data o f Kinney and Crowley ( 8 ) f o r both propane and ethane p y r o l y ses were compared w i t h the p r e d i c t i o n s o f the model. The mechanistic model ( o f Table II o f the previous chapter) was developed by successive approximations. F i r s t , o n l y those r e a c t i o n s assumed t o be most important were used i n the model, and l a t e r secondary r e a c t i o n steps were added u n t i l good p r e d i c t i o n s were obtained o f the experimental r e s u l t s . In the previous chapt e r o f the book, the parameters f o r the various r e a c t i o n steps are r e p o r t e d . The major r e a c t i o n s f o r pyrolyses o f both ethane and propane are grouped i n Table I I (1). When ethane i s p y r o l y z e d , the propane r e a c t i o n s are jDf r e l a t i v e l y minor Importance and e l i m i n a t i n g them from the model has l i t t l e e f f e c t on the ethane p y r o l y s i s p r e d i c t i o n s . When propane 1s p y r o l y z e d , however, s i g n i f i c a n t l y b e t t e r p r e d i c t i o n s r e s u l t when the ethane r e a c t i o n s are i n c l u d e d and the e n t i r e s e t o f r e a c t i o n s are employed.



Propane in Tubufor Flow Reactors

267

Table II Corrected Product Composition Results (800 C, 50:50 Mixture of Ethane and Steam) e


Incoloy (oxidized) Reactor 1 Sample 83 Conversion, % 0.95 Space time, sec. Gas Composition H

2

CH

4

CH 2

6

C

2 4

C

3 8

C

3 6

Exp. Data Corrected Exp. Data Corrected 10.9 20.1 30.2 15.4

Model 83 0.98 11.3 32.2

25.6

28.6

29.8

31.7

2.3

2.6

2.3 27.4

2.4

3.0

34.0

32.6

10.0

10.6

9.6 8.7

35.9

23.9

H

Incoloy (reduced) 4 81 0.96

8.0

8.9

7.5

8.4

9.6

10.2

4 10 CO

0.1

0.1

0.0

0.0

1.0

2.1

0.6

co

0.3

-

-

-

H

H

C

H

2

Carbon Y i e l d , % Reactor Sample Conversion, % Space time, sec. Gas Composition 2 CH

H

2 6 CH H

2

4

C

3 8

C

3 6

H

H

4 10 CO C

304

SS (oxidized) 1 77 0.68

H

co

2

Carbon Y i e l d , %

5.8 304

SS (reduced) 3 73 0.69

Exp. Data Corrected Exp. Data Corrected 13.0 19.2 15.1 27.3 24.5

4

C

11.4

0.1

1.9

26.4 2.0

26.2 1.9

Model 74 0.61 13.6

27.3

26.9

2.0

2.6

24.0

33.1

25.9

30.3

29.1

12.0

12.9

15.2

15.8

15.3

9.7

10.4

11.2

11.6

0.0

0.0

0.0

0.0

10.6 0.9

0.6

-

0.3

-

-

0.1 9.2

0.0 4.3

-


-


268


The agreement between the values predicted by the model and the experimental data are somewhat poorer, however, for propane pyrolysis as compared to ethane pyrolysis. Such a finding i s not surprising since pyrolysis of propane i s more complicated, i n volving more gas phase reactions. More uncertain!ties also e x i s t in the k i n e t i c parameters given in the l i t e r a t u r e for some of the propane pyrolysis reactions. I t was necessary to make judicious choices for parameters for especially reactions 6,7, and 10 in order to obtain good f i t s with the experimental data. The values for the parameters used were always within the l i m i t s reported in the l i t e r a t u r e , except for reaction 20. In this l a t t e r case, a value that differed by about 10 was f i n a l l y selected in order to obtain better agreement of the predicted values with the data. Even though the model contains 39 reaction steps, i t i s s t i l l r e l a t i v e l y incomplete for propane pyrolysis. Reaction steps to produce acetylene, d i o l e f l n s , aromatics, and other heavier (C* and higher) hydrocarbons are of at least minor importance. Further more, reactions to differentiate between η - p r o p y l and isoρropy! radicals l i k e l y are needed. Reactions involving a l l y ! radicals also occur to some extent. Although additional reactions have been proposed (7), r e l i a b l e parameters (activation energies, E, and frequency factors, A) for such equations are not yet available. Although the model used here for propane pyrolysis can cer t a i n l y be improved in the future, i t i s much superior to other models that have been used to predict propane pyrolysis data ob tained at conditions approximating those of commercial plants (4, 10). Correction of Composition Results to Surfaceless Basis Attempts were made to correct the product composition results obtained for propane pyrolysis in different reactors to a surface less basis. Assuming a perfect correction procedure could be de veloped, the corrected composition of the product stream would be identical for a l l runs at the same operating conditions regardless of the reactor used or the past history of the reactor. The cor rection technique used e a r l i e r (1) for ethane pyrolysis and which assumes that ethylene i s the only hydrocarbon reacting at the sur face was found to be less successful in the case of oropane py r o l y s i s . Table II shows several comparisons of experimental data, corrected values, and values predicted using the mechanistic model (1) for runs made at 800 C with wet ethane feed in the two metal reactors. When essentially steady-state operation was obtained after 1-2 hours of operation (at which time the Inner reactor sur face was in a r e l a t i v e l y reduced condition), f a i r l y good agreement, within about 10% on a relative basis, was obtained between the corrected values and those predicted by the mechanistic model. Based on the mechanistic model, the ethylene values were overcorrected but the hydrogen values were not corrected enough. Some what poorer agreement resulted between the corrected and predicted



15.



269

values when more oxidized reactors were used; the surface of the reactor was r e l a t i v e l y oxidized in some runs during start-up. Although ethylene was certainly a major precursor for coke and carbon oxides during propane pyrolyses, there were probably also other precursors. Propylene that i s formed in substantial amounts during propane pyrolysis certainly reacts to some extent to form coke (2). Acetylenes, d i o l e f i n s , and aromatics l i k e l y are of minor but nevertheless of greater importance as coke precursors for the following two cases: propane pyrolysis as compared to ethane oyrolysis or pyrolysis in small laboratory reactors with high S/V ratios as compared to pyrolysis in commercial units. Before a completely successful correction technique can be developed for propane pyrolysis, quantitative data w i l l be needed concerning the relative r e a c t i v i t i e s of various carbon precursors. Since the analytical equipment used was not able to analyze with good accuracy C- and heavier hydrocarbons, the yields of carbon reported in tins investigation and in the e a r l i e r one (1) dealing with ethane pyrolyses are really measures of the carbon that formed both s o l i d coke and also the heavier hydrocarbons. Some hydrogen was of course, present in these heavier hydrocarbons, but such hydrogen was not taken into account in the calculations made to determine elemental hydrogen in the product streams. Failure to include any heavier hydrocarbons in procedures (7) employed to calculate the yields of gaseous components causes yields of hydrogen to be s l i g h t l y too low and those of ethylene and propylene to be s l i g h t l y too high. The rates of propane disappearance were s l i g h t l y higher in oxidized reactors as compared to reduced reactors (see for example the propane conversion results shown in Table I I ) . A s i m i l a r finding was reported e a r l i e r by Crynes and Albright (3). Such a finding can be explained by increased concentrations of free radi c a l s in the gas phase as a result of increased carbon formation in the oxidized reactors. As hydrocarbons, probably adsorbed, decompose on the surface to form carbon and hydrogen, obviously carbon-hydrogen bonds are broken. Possibly some hydrogen radicals formed escape into the gas phase. The hydrocarbons that decompose may even include propane in the case of the oxidized reactors. Propane and Ethane Pyrolysis A key finding of this investigation was that the condition of the inner surface of the reactor changed when the feedstock was switched to propane after ethane or vice versa. This conclusion i s based on runs made using a bath temperature of 800 C, with a feed mixture containing 50 mole % steam, and with both 304 SS and Incoloy reactors. The following phenomena occurred in both metal reactors that were i n i t i a l l y used for pyrolysis of ethane: (a) After switching from an ethane to a propane feed, the yields of ethylene increased and the yields of those products (carbon, carbon oxides, and hydrogen) obtained as a result of the surface reactions decreased during



270


the f i r s t hour of the propane portion of the run; ess e n t i a l l y steady-state product compositions were then obtained. (b) When the feed was next switched back to ethane, the i n i t i a l yields of ethylene were s i g n i f i c a n t l y higher and those of the products obtained because of surface reactions were lower as compared to yields before the propane portion of the run. Carbon yields during ethane pyrolysis were 13% and 3.8% respectively in the Incoloy reactor before and Immediately after the propane phase of the run. In the 304 SS reactor, they were 16% and 7.1% respectively. Clearly the a c t i v i t y of the surface relative to promotion of surface reactions differed depending on whether ethane or propane was used as a feedstock. This finding 1s not surprising since Tsai and Albright (5) report that dynamic e q u i l i b r i a occur during pyrolysis relative to the following: oxidation of surface with steam vs reduction of surface with gaseous components; and carbon (or coke) deposition vs removal of coke with steam. The present results are, however, the f i r s t to show conclusively that surface a c t i v i t y depends on the feedstock; surface a c t i v i t y must be related 1n some way to the levels of both surface oxides and surface carbon. As further comparison of propane and ethane pyrolyses, four different mixtures of propane and ethane were pyrolyzed in the Incoloy reactor employing a 800 C bath temperature and one atmosphere total pressure. These mixtures had propane-to-ethane ratios of 0.04:1, 0.29:1 , 1 :1 , and 2.97:1; the l a s t three mixtures were premixed with steam on a 1:1 basis. In estimating the conversions of both propane and ethane during pyrolysis of the mixture, 1t was assumed that no propane was formed as a result of the pyrolysis of ethane and that no ethane was formed from pyrolysis of propane; these two assumptions are certainly not quite accurate since small amounts of both ethane and propane were formed during the pyrolysis of the pure paraffins. Conversions of both ethane and propane at a given residence time varied s i g n i f i c a n t l y as a function of the propane-to-ethane ratio in the feedstream. Ethane conversions decreased as the ratio increased (or as the amount of propane in the mixture Increased). Propane conversions on the other hand Increased s l i g h t ly as more ethane was added to the mixture. Figure 3 shows results for a space time of 0.9 seconds. The kinetic model that was successful for prediction of the pyrolysis results for both pure propane and pure ethane was unable to predict results for propane-ethane mixtures. I t was, of course, appreciated for these runs in the Incoloy reactor that surface reactions may be quite important, and hence the model would predict more olefins than are present in the e x i t product. The model, however, predicts that ethane conversions would Increase, and not decrease as was found, as the amount of propane


15.



271

100

PROPANE

90 O 80 Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 4, 2017 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/bk-1976-0032.ch015

CO

£

BATH TEMP. = 800 C 50 MOLE % STEAM I ATM PRESSURE SPACE TIME = 0.9 SEC

70

30

0

10

20

JL

30

PERCENT Figure 3.

40

50

60

PROPANE IN

70

80

90

100

MIXTURE

Conversions for propane-ethane mixtures at 800°C bath temperature and using incoloy reactor

in the feedstream increased. The model also predicts propane conversions would be s l i g h t l y retarded by the presence of large amounts of ethane. The reason for f a i l u r e of the model to predict pyrolysis data for mixtures i s not known. One p o s s i b i l i t y i s that the termination steps may be incomplete; termination steps at the Incoloy Surface or gas-phase termination reactions between ethyl and propyl radicals may be important when mixtures are used, but would be of l i t t l e importance for runs with either pure propane or pure ethane. Discussion of Results The present results s i g n i f i c a n t l y c l a r i f y the role of surface reactions relative to propane pyrolysis. Although the differences in the composition of the product stream obtained in different reactors were not as large as they often were with ethane pyrolyses, nevertheless, the differences were s t i l l s i g n i f i c a n t in many cases. Two factors must be considered in extrapolating the results to commercial reactors. F i r s t , as also discussed e a r l i e r ( 1 ) , the small diameter tubular reactors used in this investigation accentu-




272

ate the relative Importance of surface reactions as compared to larger diameter reactors used commercially. A s p e c i f i c technique for extrapolating to larger diameter reactors has also been proposed e a r l i e r . Second, as a reactor i s used, coke forms on the surface and such coke p a r t i a l l y masks the metal so that i t has less effect on surface reactions. Brown and Albright (2) have recently reported, however, that coke formation was faster on coke surfaces as compared to Vycor glass surfaces. Apparently the coke acts to some extent to adsorb olefins and other hydrocarbons; these adsorbed hydrocarbons seem to decompose rather rapidly to coke. Furthermore, iron and nickel particles are frequently present in the coke formed (11, 12). In f a c t , coke formed i n this investigation was attracted to a magnet, seemingly indicate the presence of such p a r t i c l e s . These particles are in at least some cases both magnetic and c a t a l y t i c 1n character. I t seems safe to conclude that the coke formed on the surface of commercial pyrolyses tubes only p a r t i a l l y masks the inner metal surfaces relative to t h e i r effect on surface reactions. The results obtained in the Vycor reactor are of special interest since surface reactions are of r e l a t i v e l y minor importance in this reactor. The results of this reactor then are most useful in c l a r i f y i n g the mechanism of the gas-phase reactions. The results of the present investigation that indicate that the surface a c t i v i t y of a reactor changes as the feed stream was switched from propane to ethane strongly suggest that changes of surface a c t i v i t y would, in addition, occur i f higher molecular weight feeds were used. It seems safe to conclude that the importance of surface reactions varies with the feed used. The mathematical model used to correlate the propane pyrolysis data obtained in the Vycor reactor can l i k e l y be used for at least moderate extrapolations to temperatures and pressures beyond those investigated. Acknowledgment Professor Pa'l Siklo's of Technical University, Budapest, Hungary made valuable contributions to the modeling of the pyrolysis data. Literature Cited 1)

Dunkleman, J. J. and Albright, L. F., Chapter 14, This Book (1976). 2) Brown, S. M. and Albright, L. F., Chapter 17, This Book (1976). 3) Crynes, B. L. and Albright, L. F., Ind. and Eng. Chem. Proc. Design Develop., 8, 1, 25 (1969). 4) Herriott, G. E . , Eckert, R. E . , and Albriqht, L. F., AIChE J., 18, 1, 84 (1972). 5) Tsai, C. H. and Albright, L. F., Chapter 16, This Book (1976). 6) Herriott, G. E . , "Kinetics of the Pyrolysis of Propane at 700 to 850°C," Ph.D. dissertation, Purdue University, 1970.





7)

273

Dunkleman, J. J., "Kinetics and Surface Effects of the Pyroly= sis of Ethane and Propane in Vycor, Incoloy, and Stainless Steel Tubular Flow Reactors from 750° to 900°C", Ph.D. dis sertation, Purdue University, 1976. 8) Kinney, R. E. and Crowley, D. Μ., Ind. and Eng. Chem. 46, 1, 258 (1954). 9) Buekens, A. G. and Froment, G. F., Ind. and Eng. Chem. Ρroc. Design Develop. 7, 3, 435 (1968). 10) Zdonik, S. B., Green, E. J. and Hallee, L. Ρ., Oil and Gas J. 65, 26, 96 (1967). 11) Lobo, L. S. and Trimm, D. L . , J. Catalysis 29, 15 (1973). 12) Freeh, K. J . , Hoppstock. F. Η., and Hutchings, D. Α., Chapter 12, This Book (1976).


Industrial and Laboratory Pyrolyses

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