Coke Deposition From Acetylene, Butadiene and Benzene Decomposition at 500 - 900 C on Solid Surfaces(1)

8/17/2019 Coke Deposition From Acetylene, Butadiene and Benzene Decomposition at 500 - 900 C on Solid Surfaces(1)

1/12

Carbon Vol 20, No. 4. pp 319-330. 19R2 00086223:8?/04031~12~3.~/0

Printed in Great Britain.

Pergamon Rest Lid.

COKEDEPOSITIONFROMACETYLENE,BUTADlENEAND

BENZENE DECOMPOSITIONS T 500-900°C

ONSOLIDSURFACES

MICHAEL .

GRAFF? nd

LYLE F, AL~RIGH~

School of Chemical Engineering, Purdue University, West Lafayette, IN 47907,U.S.A.

Receiwd IO Ckiuber

1981)

Abstract-Coke formation from decomposition of acetylene, butadiene, and benzene and decoking were in-

vestigated on Incoloy 800, aluminized Incoloy 800, and

Vycor glass

surfaces at SOO-900°C. n Incoloy 800, the

coke was greater in quantity and contained iron and nickel particles. On aluminized Incoloy 800, he coke contained

a trace of aluminum, but on Vycor glass, no metal was in the coke. Coking-decoking sequences were highly corrosive

on Incoloy800 surfaces, but they had much less effect on the aluminized

Incolny

8OOorVycor glass. Filamenteous coke

which is formed catalytically and contains nickel and iron was formed only on Incoloy 800 surfaces. A general

mechanism for formation and deposition of coke is proposed. Filamenteous coke helps collect tar droplets formed by

gas-phase reactions. Such droplets decompose on the surface to produce coke that contains no metal.

Although coke is produced in only relatively small

amounts when hydrocarbons are pyrolyzed to produce

ethylene and valuable by-products or when 1, 2-di-

chloroethane is dehydrochlorinated to produce vinyl

chloride, coke production results in a significant increase

in operating expenses. Because of coking, the pyrolysis

furnaces have to be shut down periodically to decoke,

the heat transfer coefficients in the furnaces are often

drastically reduced, and coking generally results in cor-

rosion of the stainless steel surfaces on which the coke is

deposited. Significant advantages would occur if coking

could be reduced, and there is a need to better under-

stand the mechanism of coking and of decoking.

Albright, McConnell and Welther[l] demonstrated that

valuable new information can be obtained by comparing

the character of coke formed from acetylene, butadiene,

ethylene and propylene. The former two compounds are

generally considered to be important coke precursors.

They had employed a scanning-electron microscope

equipped with EDAX to analyze the metal content of the

coke. The coke formed on Incoloy 800 surfaces often

contained highly dispersed metal particles making the

coke magnetic in nature. These metal particles contained

nickel, chromium and especially iron that had obviously

been removed in some manner from the surfaces. Baker

and

associates [2-4] and Bernard0 ef al. [5,6]

have postutated a mechanism that explains the simul-

taneous corrosion of the surface and the catalytic

production of a filament-type coke. Of interest, Incoloy

800 surfaces that had first been aluminized were never

found to contain these three transition metals.

The results of Albright, McConnell and Welther[l] are

most interesting but they raise more questions than they

answer. In the present investigation, more information

has been obtained relative to the coke produced from

acetylene, butadiene and benzene. Information has been

obtained on the effect of temperature, partial pressure of

*Present

address: Amoco Oil Co., Chicago, Illinois, U.S.A.

coke precursor and time of operation for cokes deposited

on Incoloy 800, aluminized Incoloy 800 and Vycor glass

surfaces.

2. XPERIMENTAL

The equipment and operating procedures were essen-

tially identical to those employed by Albright, McConnell

and Welther[l]. Coupons that were about 0.5 x 2 x

0.15 cm were positioned inside a Vycor glass tube that

was 2.2cm I.D. and 107cm long. This tube was posi-

tioned horizontally in an electrical furnace controlled at

any desired temperature in the 500-900°C range. Acetyl-

ene, butadiene, helium and oxygen flows were metered as

desired to the inlet of the Vycor glass tube. For benzene

experiments, helium was bubbled through liquid benzene

at room temperature to produce gas mixtures containing

about 12% benzene. Steam was provided by boiling a

flask filled with water. Residence times of the gas stream

in the constant-temperature portion of the Vycor glass

tube were about 20 sec. In most cases, the coupons were

positioned at the beginning of this portion of the reactor

which is designated as the lead position. The rear posi-

tion, or end of this portion of the reactor, was about

25cm beyond. The aluminized (or aionized) Incoloy

800 coupons were furnished by Alon Processing, Inc. of

Tarentum, Pa. Incoloy 800 coupons had been subjected

at high temperatures to gaseous aluminum; as a result,

some aluminum diffused into the metal resulting in a high

concentration of aluminum of the surface.

Coupons after being removed from the Vycor glass

tube were cooled in an inert atmosphere, and pictures

were then taken using a JSM-U3 scanning-electron

microscope at magnifications varying from 1000 to

20,000. The metal content of the solid surfaces of the

coupon or of the coke produced was measured using an

EDAX, model 707.

3.CO~GANDDECO~NG~~~TS

Significant changes were noted in the surface com-

position and appearance of the Incoloy 800 as a result of

319


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320

MICHAEL . GRAFFand LYLE F, ALBRIGHT

coking and subsequent decoking, especially for runs at

900°C. To clarify the effect of heating, an Incoloy 800

coupon was heated to 900°C in a helium atmosphere. The

chromium content of the surface increased from 22 to

60% after 8 hr heating as indicated by EDAX. Similar

chromium enrichment of the surface also occurred at

900°C when acetylene, butadiene or benzene was

employed. The titanium content of the surface of the

coupon also increased to perhaps 2-370 because of heat-

ing at 900°C.

The appearance of the Incoloy 800 surface changed

significantly during helium treatment at 900°C as in-

dicated in Fig. 1; coupons are shown before and after the

heat treatment. The Incoloy 800 coupons as received has

a rather heterogeneous surface. The white areas shown

in the upper left picture were iron-rich particles covering

Fig. 1. Untreated

and helium treated metal coupons.


3/12

Coke deposition rom chemicalsat 500-900°C n solid surfaces 321

about .5-10% of the surface. EDAX analysis of the

remainder of the surface indicated 45% iron, 33% nickel

and 22% chromium. Heat treatment in the presence of

helium resulted in tiny whiskers, columns or spikes which

are mainly iron or chromium rich particles.

Heat treatment of aluminized Incoloy 800 coupons at

900°C in the presence of helium resulted in little change

of either the composition or the appearance of the sur-

face. The surface exhibited “chicken wire” markings and

contained some almost pure aluminum deposits which

are the white areas of pictures shown in Fig. 1. Part of

the surface aluminum, however, undoubtedly existed as

alumina. The areas between the markings analyzed ap-

proximately 46% aluminum, 27% iron, 1% nickel and 9%

chromium. The few pitted areas shown were somewhat

less aluminum rich. With heat treatment, there were

probably fewer pitted areas.

3.1 Coke formation from acetylene

Filmenteous coke was the predominant type of coke

formed in Incoloy 800 surfaces at 500°C when either pure

acetylene or helium-acetylene mixtures containing 5%

acetylene were used. Both constant-diameter and braided

(or rope-like) filaments were produced as shown in Fig.

2, and most filaments had diameters of about 0.1-0.2 pm.

A few very long and almost straight filaments with

constant diameters of 0.5-1.0 pm were also noted; three

such filaments are shown in the lower left picture of Fig.

2. The length-to-diameter ratios of the filaments were

often at least 200: 1. The upper right picture of Fig. 2

shows a double helix of filaments; such a double helix

was also noted in another case. The coupon treated with

pure acetylene at 500°C was re-examined after several

months, and one filament was then found that appeared

to be hollow or basically a tube. All filaments contained

metal particles as indicated by EDAX analysis. Nickel

and especially iron were predominant in these particles.

For runs at longer times, such as 8 hr, more coke was

noted on the surface and a higher fraction of the coke

appeared to be chunky or amorphous coke such as

shown on the center left section of the lower left picture.

Some globular coke, such as will be described later, was

also noted.

No filamentous coke was ever observed on aluminized

(or alonized) Incoloy 800 or on Vycor surfaces regardless

of the conditions used or the hydrocarbon feed stream

employed. Only amorphous coke was formed from

acetylene in such cases at SOoOC[l].Lesser amounts of

coke were apparently formed on both aluminized and

Vycor glass surfaces based on visual observations. The

coke formed on both aluminized steel and Vycor glass

surfaces never contained detectable amounts of iron or

nickel. Cokes deposited on aluminized steel surfaces

contained however traces of aluminum or alumina.

Figure 3 shows the coke formed at 500°C with a feed

stream having an acetylene partial pressure of 0.05 atm.

Only a very few filaments were noted on the coupon

located in the lead position of the Vycor glass tube; these

filaments were, however, very long. One constant-

diameter filament and one braided filament appear to be

joined. The other end of the constant-diameter filament

seems to be connected to surface. The coupon located in

the rear position of the constant-temperature zone was

apparently almost coke free.

Coke formed from acetylene at 900°C appeared to be a

mass of rather spherical droplets that had partially fused

together as shown in Fig. 3. This type of coke is called

globular in this investigation whereas it was called

knobby by Albright, McConnell and Welther[l]. The

globular coke varied in shape from rather perfect

spheres, partly fused together, to droplets that were

fused to a much greater extent. The general charac-

teristics of cokes deposited at 900°C on Incoloy 800,

aluminized Incoloy 800 and Vycor glass surfaces were

similar in all cases but with perhaps some differences in

the diameter of the “droplets”. In some portions of an

aluminized coupon, it was possible to see the metal

surface below or through the coke; apparently less coke

was deposited on these surfaces as compared to Incoloy

800 coupons. When the globular cokes deposited in In-

coloy 800 coupons were scrapped with a knife blade,

there were essentially two layers of coke. The layer

closest to the metal surface was highly adherent to the

metal, but the top layer was rather easily removed. The

top layer of coke formed on all coupons contained no

detectable iron, nickel or other metals. The amount of

coke increased with time of operation and with higher

partial pressures of acetylene. At 900°C and with acety-

lene at atmospheric pressures, the Vycor glass tube

plugged after about 1 hr. With a partial pressure of

0.05 atm, only a relatively small thickness of coke was

noted after 16 hr of operation. It is estimated, based on

this finding, that the rate of globular coke deposition at

900°C is second order or higher based on the acetylene

partial pressure. Such a finding seems consistent with the

fact that condensation reactions of acetylene to produce

heavier hydrocarbons are probably mainly second-order

reactions.

3.2 Coke formation from butadiene

Coke was produced from butadiene at temperatures of

500, 700 and 900°C and at partial pressures of 0.05 and

1.0 atm.

Temperature had a major effect on the morphology of

the deposited coke. Figure 4 shows the results for In-

coloy 800 coupons subjected for 8 and 16 hr to a helium-

butadiene mixture containing 5% butadiene. At 5OO”C,

thin brown but smooth film of coke was formed. At

700°C more coke was present on the coupon and ap-

peared to be a cloudy film. At 9OO”C, rofuse needle coke

was present; in some cases the coke gave the appear-

ance of finely cut ribbons

which seemed to

originate at iron- or chromium-enriched particles on the

surfaces of the coupons. The lower right picture of Fig. 4

shows a column-like filament growing out of a

chromium-enriched particle on the surface. This column

was formed on the coupon positioned at the rear position

of the constant-temperature zone, and it was similar in

appearance to formations noted on the Incoloy 800 cou-

pon heated to 900°C in the presence of helium. Both

coupons also had concentrations of about 3% titanium on

their surfaces.


4/12

322

MICHAEL GRAFF nd LYLEF ALBRIGHT

Fig 2 Pure CzHz over Incoloy 800 at 500°C

At 900°C and for 1 hr runs, globular and/or spaghetti- as will be discussed later. On aluminized Incoloy 800, the

like cokes were formed on al1 three surfaces. The diameter of the coke “spheres” increased with time, as

spaghetti-like characteristics were particularly noted on shown for exampie in the lower right hand picture of Fig.

the Incoloy 800 coupons as compared to aluminized

5.

Incoloy coupons as indicated by Fig. 5. The globular and

For 900°C runs using fncoloy 800 coupons, the outer

spaghetti cokes were fused together in many cases. The

layers of coke after 8 and 16hr were primarily needle or

precursor for these cokes is thought to be tar droplets

cut ribbon-type cokes. Some chunks of amo~hous coke

that flowed rather readily before being converted to coke were also observed after 16 hr. Less coke formed on the


5/12

Coke deposition from chemicals at 500-900°Con solid surfaces

323

1

mcron = f - - w

1

mcron = e- - - 4

Fig. 3. 5% C2H2 ver Incoloy 800

or 8 hr.

aluminized Incoloy 800 or Vycor glass surfaces as com- were mainly butadiene, but some liquid product was

pared to the Incoloy 800 surface; portions of the alu-

collected in an ice trap. Based on gas chromatography,

minized metal could sometimes be seen for coupons

this liquid was mainly Cs hydrocarbons with lesser

investigated at 900°C. More coke was formed in all cases

amounts of C6 and C4 hydrocarbons. The G’s and G’s

when pure butadiene was employed as compared to a

are probably mainly aromatics based on the more

mixture containing 5% butadiene.

detailed analyses by Albright and Yu[7] for comparable

For runs at SOO”C,he exit gases from the Vycor tube

experiments. At 9OO“C,most of the butadiene reacted in


6/12

MICHAEL . GRAFF and LYLE F. ALBRIGHT

Fig. 4. 5% C& over Incoloy 800 (1 pm = ---I.

the Vycor glass reactor, and considerable hydrogen and

For a 7OOT run, brown liquid droplets formed in the exit

methane were noted in the exit gas stream. Essentially

end of the tube where temperatures varied from about

no liquid product was obtained, however, for 16 hr of

600 to 3OOT. For a 900°C run, brown tar collected in the

operation when a feed mixture containing 5% butadiene

exit end where the temperatures dropped from 800 to

was employed.

170°C.

For all runs considerable tars were deposited in espe-

cially in the cool exit end of the Vycor glass tube. For a

run at SOT using pure butadiene, liquid deposits formed

in the tube where the temperatures are 170°C or lower.

3.3 Coke ~o~~~~oR from benzene

For a benzene run at 5OO”C, n Incoloy 800 coupon

was tarnished with a spotted, light-brown residue after


7/12

Coke deposition from chemicals at NC-900°C on solid surfaces

325

16hr. With the scanning-electron microscope, the base

metal was still cleariy visible through the coke which

appeared amorphous in character. At 7OO”C,more coke

formed in the lncoloy 800 coupon which appeared to

have a filmy clouded surface. Figure 6 shows pictures

taken of both the Incoloy 800 and aluminized Incoloy

800 surfaces. An amorphous coke with the beginnings of

globular coke were noted on both surfaces. In one area

of the aluminized surface, there were large columns or

chunks of coke (see lower right picture of Fig. 6); such

deposits were not observed on any other coupons.

At 900°C, globular coke was observed on both Incoloy

800 and aluminized Incoloy 800 surfaces as shown in Fig.

7; the top two pictures are for runs of 1 hr whereas the

bottom two pictures are for runs of 8 hr. Three features

are of interest. First, considerable more coke occurred in


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326

MICHAEL. GRAFF nd LYLE

F.

ALBRIGHT

all ca es on the Incoloy 800 coupons as compared to the

3.4

Decoking of metal coupons

alumiisized Incoloy coupons; the aluminized surface can

Two decoking experiments were made using Inr

be set

n even after 8 hr operation. Second, the diameter

800 coupons on which coke had been deposited

of the

coke spheres increased in the 1-8 hr time period.

deposit the coke, the coupons were exposed to a mi:

Third , the spheres of coke on the aluminized surfaces

of 5% acetylene in helium for 8 hr at 900X Decc

were sometimes transparent to the SEM beam as shown

was accomplished for one coupon by contacting it

in the lower right picture of Fig. 7.

pure steam at 700°C for 24 hr; the other coupon

Fig. 6. 12% C6H6 t 700°Cfor 16hr (IO Fm = -).

:oloy

.

To

vture

&king

with

was


9/12

Coke deposition

rom chemicals at 5WWC on solid surfaces

327

contacted with pure oxygen at 800°C for

24

hr. Pho-

tographs of the resulting surfaces are shown in Fig. 8.

After steam, the surface indicated numerous iron-rich

particles, but several protruding chromium-rich spikes

were also noted. These spikes appeared white in the

pictures, and were estimated to be as great as 1.5-2.0 pm

in length. One prominent spike is shown in the two

pictures for steam butnoff shown in Fig. 8; in each case

CAR Vol. 20, No. 4-E

this spike is slightly to the left of the center of the

picture. EDAX analyses of one spike indicate the fol-

lowing approximate compositions: 62% chromium, 22%

iron and 16% nickel. The composition of the remaining

surface except for iron-rich regions was about 42%

chromium, 36% iron and 22% nickel. There was

obviously both a significant change in surface com-

position and also in roughness of the decoked Incoloy


10/12

328

MICHAEL GRAFF

nd

LYLEF. ALBRIGHT

Fig. 8. Carbon burn-off for 24 hr at 7W’C of an Incoloy 800 surface, originally treated with 5% C2H2 t 900°Cfor

8 hr.

800 surface as compared to the surface before coking

and decoking.

With oxygen decoking, the surface was also roughened

significantly. The background metal indicated ap-

proximately 50% chromium, 30% iron and 20% nickel;

the spikes indicated about 62% chromium, 26% iron and

12% nickel.

One steam burnoff was made at 800°C of coke on an

aluminized Incoloy 800 coupon. The coke had been

deposited at 900°C in 16 hr using a gas mixture containing

5% butadiene in helium. After 24 hr of steam decoking,

the surface still showed some “chicken wire” markings,

but dark but smooth blemishes were now visible. EDAX

analysis indicated a much higher nickel content on the

surface than in the original aluminized coupons. White

deposits of aluminum (or alumina) were still present over


11/12

Coke

deposition

rom chemicals at 500-900°Con solid surfaces

329

a portion of the surface. The pitted areas had however

almost disappeared. Of interest, a burnoff at 700°C by

Albright, McConnell and Welther

[ ]

indicated essentially

no changes of the aluminized Incoloy 800 surface. Prob-

ably the advantages of an aluminized surface will be

retained much longer if temperatures for decoking are

700°C or lower.

4.DISCUS SIONOFRESULTS

Coking mechanisms have been clarified to a significant

extent for pyrolysis processes and for dehydroch-

lorination of 1 Zdichloroethane since acetylene, buta-

diene and benzene are always formed to some extent

in both processes. Figure 9 is a summary of major

mechanisms by which coke are formed. Some of the

coke is formed by catalytic reactions in which stainless

steels such as Incoloy 800 participate and are as a result

corroded. Adsorption of the precursor on the surface is

undoubtedly a first step in the coking mechanism. Details

on the production of filamentous cokes have been repor-

ted earlier by Baker

et al.[2 4]

and by Bernard0 et

al.[5,6]. Excellent examples of filamentous cokes are

shown in Figs. 2 and 3. Coke formed from butadiene to

yield cut-ribbon coke is another example of coke formed

by surface catalytic reactions; the lower left hand picture

of Fig. 4 shows an example of this coke. Cokes formed

by catalytic reactions are apparently the predominant

types of coke formed at lower temperatures and perhaps

especially during the early stage of a pyrolysis run when

the metal surfaces are fairly clean. Yet evidence has

been obtained that during pyrolysis of ethane some

filamentous coke containing metal particles was

produced at 800°C[8] and that coke containing metal

particles promotes additional coke formation[9].

Coke can also be produced by a sequence of reactions

of which the initial reactions are in the gas phase.

Hydrocarbons such as acetylene, butadiene and benzene

react to form first various condensation products leading

to production of fairly heavy materials such as tars.

Albright and Yu[7] have published some information on

the initial condensation products. Some tars condense

forming droplets that are suspended in tthe gas phase.

Three routes are available for the production of coke

from these heavy hydrocarbons or tars. In two methods,

the liquid droplets grow in size because of coalescnce

and further condensation of tars. Eventually these dro-

plets impinge and collect on solid surfaces such as

pyrolysis coils or transfer line exchangers. On the hot

surfaces, dehydrogenation occurs with the production of

coke that is essentially pure carbon. When the tar dro-

plets collect on the surface, the droplets can wet the

surface and coalesce with other droplets or the droplets

can fail to coalesce. The degrees to which these two

phenomena occur depends on several factors including

the following:

(a) The viscosity of the droplets which depends on the

temperature and the chemical composition of the liquid.

Higher molecular weight compounds tend to be more

viscous. As dehydrogenation occurs and the tar ap-

proaches coke, the viscosity also increases.

(b) The wetting ability between liquid droplets and the

solid surface; this ability depends on the composition

and roughness of the solid surface. Droplets also collect

more readily on lower temperature surfaces.

(c) The velocity of the gas stream near the droplet. In

the present investigation, slow velocities occurred

whereas in commercial units extremely high velocities

are prevalent. In the latter case, there is a greater ten-

dency for spreading of the droplets and for shearing of

filament coke.

(d) The rate of cracking or of dehydrogenation in the

liquid or tar on the surface. At high temperatures, the

liquid tar droplets on the surface would be dehy-

drogenated more rapidly; hence the original shape of the

C2HZ and other acetylenes

He and other dloleflns

Chemvx condensatton

Wetting of Non-w;tt,nq

I

Formatton

of coke I”

qos phase.

then collection

on surface

Fig. 9. Mechanism for production of coke.


12/12

330

MICHAEL . GRAFF and LYLE

F.

ALBRIGHT

droplets would be retained to a greater extent. Figures 3

and 9 show examples in which globular coke retains, to a

considerable extent, the spherical shape of the droplets.

At lower temperatures, there would generally be more

time (or a greater tendency) for the droplets to wet and

spread out on the surface. This postulate explains the

results obtained with butadiene at 500-9OO’C.Black mir-

ror finishes such as noted at fairly low temperatures for

coke formed from butadiene by Yu and Albright [7] can

also be explained.

Some coke is also formed by a sequence of reactions

that occur entirely in the gas phase. Dehydrogenation

and coking reactions occur in the gas phase before liquid

droplets of any appreciable size are formed. Such coke

in sub-microscopic sizes, however, collects on solid sur-

faces to form initially so-called gas-phase or cotton-like

coke[l]. Filamentous coke on the surface aids in collec-

ting both gas-phase cokes and tar droplets because of a

filtering action. Roughened surfaces also serve as collec-

tion points. Both filamentous coke and roughened SW-

faces explain why more coke was noted on Incoioy 800

surfaces as ~ompated to aluminized Incoloy 800 sur-

faces. It also explains why the top layer of globular or

amorphous coke is rather easily removed by scraping

whereas the bottom layer is more adherent.

Gas-phase coke or tar droplets would of course contain

no metal particles. Further confirmation that the top

layer was gas-phase coke is the evidence based on

EDAX analysis that it contained no metal. The bottom

layer on Incoloy 800 coupons was, however, a mixture of

filamentous and globular cokes; this mixture of course

contains some metal particles because of the filamentous

coke. The increased diameter of globular coke formed

during longer length runs and for coupons positioned at

greater distances in the Vycor tube can be accounted for

by increased agglomeration of the tar droplets either on

the surface or in the gas phase.

Coking and decoking results of this investigation have

further demonstrated that rather severe corrosion occurs

on stainless steels such as Incoloy 800 during pyrolysis.

Relatively little quantitative or mechanistic information

can be found in the literature on decoking; clearly a

need

for such information exists. Additional information is

also needed on how surface reactions depend on the

specific stainless steel used. This investigation has, for

example, further confirmed that aluminized Incoloy 800

surfaces (and also Vycor glass surfaces) result in com-

plete or essentially complete elimination of all catalytic-

ally formed coke and in a significant reduction in surface

corrosion because of coking and decoking. It was

encouraging to learn recently that aluminum was retained

on alonized surfaces for a coil operated for over a year

in a pyrolysis furnace. No specific

evidence is

yet

available, however, whether the beneficial improve-

ments obtained with aluminized surfaces are maintained

over extended periods of operation. Hopefully such tests

can be obtained in the near future since the benefits to be

obtained with improved materials of construction for

both pyrolysis coils and transfer line exchangers may be

substanti~. Of interest, metal surfaces coated with

microscopic thick layers of silica have also been found

effective in significantly reducing coke formation or

collection[lO].

Quantitative information on weight changes of cou-

pons because of coking, decoking, and various gas

treatments will shortly be reported by the Purdue group.

These measurements will provide further information

relative to coke formation and deposition and to decok-

ing on various metal surfaces.

Ac~ow~edgemen~~-A~~owledgement is made to the donors of

the Petrole~ Research Fund, administered by the Americas

Chemical Society, for partial

support

of the research. Alon

Processing, Inc. of Tarentum, PA also provided support. Dr. Carl

King of E. I. duPont DeNemours and Co., Inc. suggested the

arrangement for Fig. 9.

1.

2.

3.

4.

5.

6.

7.

8.

9.

REFERENCES

L. F. Albrigbt, C. F. McConnell and K. Welther, Thermal

Hydrocarbon

Chemistry (Edited by A. G. Oblad, H. G. Davis

and T. R. Eddinger), Advances in Chemistry Series, No. 183,

DO

175-191.American Chemical Societv. Washington. D.C.

ii979).

_

R. T. K. Baker, P. S. Harris, R. B. Thomas and R. J. Waite, J.

Cata~ysjsSO 36

(1973).

R. T. K. Baker and R. J. Waite, I. Cu~~~y~~s7, 101 1975).

R. T. K. Baker and P. S. Harris, Chem. Pfiys. Carbon 14,83

(1978).

C. A. Bernard0 and L. S. Lobo, i. Cufa~ysi~ 7,267 (1975).

L. S. Lobo and D. L. Trimm, .J.

Catalysis 29

15 (1973).

L. F, Albright and C. Yu,

Thermal Hydrocarbon Chemistry

(Edited by A. G. Oblad, H. G. Davis and T. R. Eddinger),

Advances in Chemistry Series, No. 183,pp. 193-203.Ameri-

can Chemical Society, Washington, D.C. (1979).

L. F. Albright and 6. F. McCbnnell,

Thermal Hydrocarbon

Chemisfrv

(Edited bv A. G. Oblad. H. G. Davis and T. R.

Eddingerj, kdvanceiin Chemistry Series, No. 183,pp. 20%

224. American Chemical Society, Washington, D.C. (1979).

J. J. Dunkleman and L. F. Albright, Industrial

and Labora-

tory Pyrolyses

(Edited by L. F. Albright and B. L. Crynes),

ACS Symposium Series, No. 32, pp. 241-260, American

Chemical Society, Washi~ton, D.C. (1976).

10. D. E. Brown, 1. T. K. Clark, A. I. Foster, J. J. McCarroll and

M. L. Sims, The

~nhibifio~of Coke Fo~atioa in Ethylene

Steam Cracking.

National Meeting of American Chemical

Society, New York (1981).

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Coke Deposition From Acetylene, Butadiene and Benzene Decomposition at 500 - 900 C on Solid Surfaces(1)