Future Refinery FCCs Role in Refinery Petrochemical Integration

Publication / Presented:2001 NPRA Meeting

Date:March 18, 2001

FUTURE REFINERY -- FCC'S ROLE IN REFINERY / PETROCHEMICAL INTEGRATION

Authors:Phillip K. Niccum - KBR

Maureen F. Gilbert - KBR

Michael J. Tallman - KBR

Chris R. Santner - KBR

AM-01-61Page 1

Future Refinery -- FCC's Role InRefinery / Petrochemical Integration

Phillip K. Niccum, Maureen F. GilbertMichael J. Tallman and Chris R. Santner

Kellogg Brown & Root, Inc.Houston, Texas USA

Presented at 2001 NPRA Meeting (18 March 2001)

Introduction

Light olefins, ethylene, propylene and butylenes, have long been basic building blocks forthe manufacture of a variety of petrochemical products and fuels. Today, light olefins areused for the production of gasoline, polymers, antifreezes, petrochemicals, explosives, sol-vents, medicinals, fumigants, resins, synthetic rubber, and many other products.

Ethylene is the largest volume petrochemical industry feedstock, and almost all of the ethy-ene supply comes from thermal (steam) cracking of hydrocarbon feedstocks such as ethane,propane, naphthas and gas oils.

Propylene is second in im-portance to ethylene as araw material for petro-chemical manufacture.The largest source ofpetrochemical propyleneis that produced as theprimary byproduct of eth-ylene manufacture. Eth-ylene plants charging liq-uid feedstocks typicallyproduce about 15 wt%propylene and provide al-most 70 percent of thepropylene consumed bythe petrochemical indus-try, as shown in Figure 1.Petroleum refining, nearlyall from fluid catalyticcracking (FCC), is by farthe next largest supplierof propylene, supplying about 30 percent of the petrochemical requirement (1). In theU.S., FCC supplies about one-half of the petrochemical propylene demand.

Propylene demand has been increasing at a faster rate than that of ethylene. Since steamcrackers are limited in the amount of propylene they are able to produce, alternate sourcesof propylene are becoming of increased interest, including increasing production from FCCunits.

Orthoflow™ FCC

From Refineries31.7 Mi l l ion Tons per Year

D i m e r s o l

& P o l y

2 %

A l k y l a t i o n

20%

LPG/Fuel

2 6 %T o

C h e m i c a l

52%

Figure 1: 2000 World Propylene Supply

To Petrochemicals51.2 Million Tons per Year

O t h e r

2%

F r o m

R e f i n e r i e s

32%

S t e a m

C r a c k e r

66%

CMAI

Future Refinery - FCC's Role In Refinery / Petrochemical Integration

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This paper discusses the evolution of the propylene market and catalytic fluid bed processesdesigned to meet the rising petrochemical industry demand.

Propylene Market

The demand for propylene has increased rapidly during the past twenty years, primarilydriven by the demand for polypropylene manufacture as shown in Figure 2. The demand forpropylene by the petrochemical industry has increased more rapidly than the demand forethylene, and this trend is expected to continue. In the next 20 years, the demand for pro-pylene is expected to more than double. During the next five years, the demand for ethyl-ene, propylene and gasoline/distillates are expected to increase annually by 5.3, 5.6 and3.0 percent, respectively (2).

Since ethylene plants produce more ethylene than propylene, and since the construction ofethylene plants is tied to the demand for ethylene not propylene, significant increases inFCC produced propylene will be required to meet the increased propylene demand. At thesame time, since installation of new FCC units is driven by the demand for gasoline ratherthan propylene, most of the increased propylene supply will have to come from investmentsin existing FCC installations.

Chemical Market Associ-ates, Inc (CMAI) esti-mates that during thenext five years 4.1 MMtons per year of propylenemust be “pulled” from ex-isting refinery sources tomeet the projected petro-chemical propylene de-mand. This increasedpropylene production fromexisting FCC units forpetrochemicals will beobtained by (1) increasingpropylene yield from theFCC units, as well as by(2) increasing the per-centage of FCC propylenerecovered for petrochemi-cal manufacture as op-posed to other uses.

History of Fluid Catalytic Light Olefins Production

During the latter 1930's, propylene and butylene were largely supplied as a byproduct ofthermal cracking of petroleum, and the major use of these light olefins was for the manu-facture of gasoline using catalytic polymerization (3). During WW II, fluid catalytic crackingwas developed for the production of high octane aviation gasoline and C4's (isobutylene andbutadiene precursors for a new and rapidly expanding U.S. synthetic rubber industry as thesupply of natural rubber was being cut-off).

Orthoflow™ FCC

Figure 2: PROPYLENE DEMAND FORECASTOverall Growth of 4% - 5% per year

0

20

40

60

80

100

120

140

160

1995 2000 2005 2010 2015 2020

Mill

ion

To

ns

per

Yea

r

OthersCumenePropylene OxideAcrylonitrilePolypropylene

CMAI


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The first commercial FCC unit was built by The M.W. Kellogg Company in Standard Oil ofNew Jersey’s Baton Rouge, Louisiana refinery and commissioned in May 1942. Between1942 and 1944 Kellogg built 22 of 34 FCC units constructed throughout the U.S and the FCCprocess quickly became a major contributor to worldwide propylene and butylene produc-tion.

Rare Earth exchanged Y zeolite catalyst was first synthesized by Mobil in 1959. By the late1960's, over 90% of U.S. FCC units were operating with the Mobil invented zeolite catalyst.The high activity of the zeolite catalysts, compared to the earlier amorphous catalysts,greatly improved gasoline yield and reduced coke and dry gas yields from the FCC units, butthe catalyst's high hydrogen transfer characteristic greatly reduced light olefin yield andgasoline octane (4). These changes in product selectivity are demonstrated in the followingdata.

Table 1Fixed Bed Pilot Plant Data

Waxy Gas Oil Feedstock over Commercial Equilibrium FCC Catalysts950 F cracking temperature at constant conversion

Amorphous ZeoliteYields Catalyst Catalyst

Hydrogen, wt% 0.08 0.04C1 + C2’s, wt% 3.8 2.1Propylene, vol% 16.1 11.8Propane, vol% 1.5 1.3i-Butane, vol% 7.9 7.2n-Butane, vol% 0.7 0.4Butylenes, vol% 12.2 7.8C5+ Gasoline, vol% 55.5 62.0LCO, vol% 4.2 6.1Bottoms, vol% 15.8 13.9Coke, wt% 5.6 4.1

Gasoline OctaneRON Clear 94.0 89.8

In the 1970's after introduction of zeolite catalyst, FCC unit design and operation evolved toregain some of the lost octane and light olefin yield, primarily with higher reactor operatingtemperature and riser cracking (5). Increasing reactor temperatures increased light olefinyield, but this came at the expense of increased yield of dry gas, a lower value FCC product.During the 1980's Mobil introduced two new technologies with application to increasing theproduction of light olefins and octane while limiting incremental dry gas production: (1) Mo-bil developed ZSM-5 catalyst additive to crack low octane (linear) gasoline boiling rangeolefins and paraffins into light olefins, and (2) Mobil invented Closed Cyclones which mini-mize product vapor residence time between the riser outlet and the main fractionator.

Refinery Options for Production of Petrochemical Feedstocks

In March 1998, Kellogg (now Kellogg Brown & Root (KBR)) and Mobil (now ExxonMobil) in-troduced the MAXOFIN™ FCC Process for maximization of propylene yield from FCC feed-


AM-01-61Page 4

stocks (6). While FCC operations typically produce less than 6 wt% propylene, the MAXO-FIN™ FCC Process can produce as much as 20 wt% or more propylene from traditional FCCFeedstocks.

Another fluidized catalytic process offered by KBR, the SUPERFLEXSM Process, is based onArco Chemical Company (now Lyondell Chemical Company) developments and patents to-gether with KBR’s more than 50 years of catalytic cracking experience. SUPERFLEX is de-signed to produce ultimate propylene yields as high as 40 wt% or more from selectednaphthas and C4 feedstocks.

Refiners can choose to increase production of light olefins through revamp and debottle-necking of the entire FCC Unit (reactor, regenerator, main fractionator and VRU). In gen-eral, revamping an FCC unit to incorporate MAXOFIN FCC Technology will require addition ofthe second riser system, including a standpipe, catalyst control valve, feed injection system,and riser. The mechanical layout of the FCC converter and its structure is studied to deter-mine the optimum placement and configuration of the new riser system. And lastly, be-cause of the substantial increase in light ends production, modifications to the FCC vaporrecovery unit will be required (unless FCC feedrate is reduced while operating in the maxi-mum propylene mode of operation).

As the FCC unit operates at higher and higher reactor temperature to increase propyleneyield, the yield of ethylene from the FCC unit reactor also increases. In the past, ethyleneproduced by the FCC unit has been viewed almost exclusively as a component for use in re-finery fuel gas, and its yield has been minimized with such technologies as Closed Cyclonesand ATOMAX™ feed injection nozzles.

Today, however, a MAXOFIN FCC unit or a SUPERFLEX unit can produce an economic vol-ume of ethylene for petrochemical consumption if there is ready access to a petrochemicalplant or ethylene pipeline. For instance, while traditional FCC operations have produced lessthan about 2 wt% ethylene, the MAXOFIN FCC Process can produce as much as 8 wt% eth-ylene, and SUPERFLEX can produce ethylene yields as high as 20 wt% from C4 to C8 olefin-containing feedstocks.

Refiners can choose to make investments to increase the purity of propylene producedrelative to a traditional refinery grade propylene product. Higher purity options includechemical grade propylene and polymer grade propylene, with typical specifications shown inTable 2 below.

Table 2Typical Propy lene Quality Specifications

Component RefineryGrade

ChemicalGrade

PolymerGrade

Propylene (% min)H2, CO, CO2, N2 (ppm max)C2 & Lighter (ppm max)Ethylene (ppm max)C4 & Heavier (ppm max)Butadiene (ppm max)MAPD (ppm max)Sulfur (ppm max)Water (ppm max)

65.0100

10,00010,00010,000

20015020100

92.0100

400010080020100130

99.55

1501001501010110


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Some of these options for increasing petrochemicals feedstock production from existing FCCunits are further discussed below:

• Recovery of refinery grade propylene typically requires investments in a depropanizer(C3/C4 splitter), metering systems, storage tanks, railcar/tank truck loading facilities, orpipeline connections.

• Recovery of chemical grade propylene would typically include investments in a propylenesplitter in addition to the other facilities described above.

• Production of polymer grade propylene is an even more expensive option, but one withpotentially higher return. In addition to the investments listed above, this option wouldtypically include addition of a deethanizer tower as well as COS/Arsine removal reactorsand dryers. Hydrogenation reactors may also be required to meet the tight specific a-tions on dienes/acetylenes.

• Production of 99.9 vol% purity petrochemical grade ethylene requires the addition of stillmore fractionation towers as well as equipment designed to remove associated contami-nants such as acetylene, water, oxygen, carbon monoxide, sulfur and nitrogen com-pounds. Design of a low temperature FCC vapor recovery system to meet all these re-quirements will more than double the cost of a VRU installation relative to that of a tra-ditional absorption oil based VRU system. Alternatively, a dilute ethylene stream maybe sent directly to a nearby petrochemical plant for use as feed to an ethylbenzene unitor steam cracker gas recovery system.

Balancing Supply and Demand

The relative productionrates of propylene andethylene from units in therefinery and petrochemicalplant are key considera-tions in refinery / petro-chemical plant integration.Within each type of proc-ess unit, selection of feed-stock and operating con-ditions, as well as catalystsystems where applicable,can dramatically alter lightolefin production ratesand propylene to ethyleneratio (P/E). Figure 3shows typical propyleneand ethylene yield char-acteristics of various proc-essing options, includingdata on steam cracking for reference.

Although propylene demand is high, refiners are still cautious about committing large capitalinvestments for propylene production alone because of the historically large swings in pro-pylene-fuels margins. A recent study by CMAI estimated the margin and Return on In-vestment (ROI) for installation of facilities for recovering polymer grade propylene from ex-

Orthoflow™ FCC

Figure 3: Process CharacteristicsRelative production of ethylene vs. propylene

0.1

1.0

10.0

100.0

1 10 100Propylene Yield, wt%

Eth

ylen

e Y

ield

, wt%

MAXOFIN

C3, C4 & Liquid Feed Steam Cracker

SUPERFLEX

Ethane Feed Steam Cracker

FCC


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isting FCC unit operations. The analysis was based on estimates of the margin betweenpolymer grade propylene value to a petrochemical plant and the refinery propylene cost(assumed equal to the alternative value of propylene in a fuels refinery). ROI is estimatedfrom the margin assuming a typical investment cost of $75 MM for a 250,000 ton per yearpolymer grade propylene recovery facility (1).

Figure 4 summarizes themargins and resultant ROIestimated for U.S. refinersover the period of 1994through 2004, and showsthe variability in the re-covered propylene marginduring the period. Thedata in the figure show astrong recovery from low-er margin levels experi-enced during the 1998and 1999 time frame. Thedata also suggest thatnow is a very good time toinvest in propylene recov-ery facilities that cancome on steam to takeadvantage of the peak ex-pected in 2003 and 2004.

MAXOFIN™ FCC

The proprietary MAXOFIN™ FCCProcess, licensed by KBR and de-picted in Figure 5, is designed tomaximize the production of pro-pylene from traditional FCC feed-stocks and selected naphthas.The process increases propyleneyield relative to that produced byconventional FCC units by com-bining the effects of MAXOFIN-3™ catalyst additive and pro-prietary hardware, including asecond high severity riser de-signed to crack surplus naphthainto incremental light olefins.

In addition to processing recycledlight naphtha and C4 LPG, theriser also can accept naphtha from elsewhere in the refinery complex, such as coker naph-tha streams, and upgrades these streams into additional light olefins. Olefinic streams,such as coker naphtha, convert most readily into light olefins with the MAXOFIN FCC proc-ess. Paraffinic naphthas, such as light straight run naphtha, also can be upgraded in theMAXOFIN FCC unit, but to a lesser extent than olefinic feedstocks.

Orthoflow™ FCC

ZSM-5

Figure 5: MAXOFIN™ Highlights

u FCC’s will supply much of increasedPropylene demand

u MAXOFIN™ combines advancedcatalyst & hardwareä High ZSM-5 MAXOFIN-3™ Additiveä KBR Orthoflow™ Hardware

u MAXOFIN™ providesflexibility for lightolefins or fuelsproduction

Orthoflow™ FCC

Figure 4: U.S. Refinery Propylene ProfitabilityThe variability of VRU Revamp project margins

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1994 1996 1998 2000 2002 2004

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per

To

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Perc

en

t R

OI

US Cost US Margin ROI


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The following table shows the result of MAXOFIN pilot tests which demonstrates the flexibil-ity of the MAXOFIN Process with respect to propylene to ethylene ratio. The tests wereperformed on a single feedstock while operating conditions and catalyst formulation differbetween the runs. This flexibility allows the MAXOFIN unit performance to be tailored to theneeds of the refinery/petrochemical complex.

Table 3MAXOFIN FCC Circulating Pilot Plant Data

Hydrocracked Gas Oil Feedstock

Yields, wt% Run A Run B Run C Run D

Ethylene 3.2 3.9 6.4 8.2Propylene 16.0 18.7 19.1 21.5C5+ Gasoline 37.9 28.8 26.2 25.0

P/E (wt/wt) 5.0 4.8 3.0 2.6

The number of product streams, the degree of product fractionation and several other as-pects of the vapor recovery process will differ from unit to unit, depending on the marketrequirements of the application.

Design of a vapor recovery unit to produce polymer grade ethylene and propylene productsincludes consideration of several factors not typically addressed in FCC VRU design.

• The cold fractionation train begins with a Depropanizer system, followed by a Demetha-nizer, Deethanizer and ethylene-ethane Splitter. Polymerization fouling is minimized inboth columns as a consequence of the low operating temperatures.

• Facilities are required to remove impurities from the process gas and to prevent freezingand hydrate formation in low temperature operations.

• In the recycle tower, the heavy gasoline components (200 °F +) are removed from theoverhead C4’s and lighter gasoline components. The C4’s and lighter gasoline compo-nents from the recycle tower overhead are recycled to the MAXOFIN FCC reactor.

• The Deethanizer separates the feed to the column into an overhead C2 stream and abottom C3 stream. The overhead C2’s are routed to the C2 splitter, where polymergrade ethylene product is produced.

• The feed to C3 Splitter comes from the bottoms of the Deethanizer. This column pro-duces a polymer-grade propylene product from the mixed C3 feed.


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SUPERFLEXSM

The SUPERFLEX process provides an economic option for petrochemical producers (or refin-ers) to increase propylene production and the overall cracking complex propylene-to-ethylene ratio us-ing low value, ole-fin rich, light hy-drocarbon feed-stocks generally inthe carbon rangeof C4 to C8 (7).The process copro-duces ethylene at atypical ratio of 1weight ethyleneper 2 weights ofpropylene (P/E ~2). The gasolinebyproduct is highlyaromatic and thuscan contribute oc-tane for gasolineblending or may bevalued as a chem-cals feedstock.

Feedstocks withthe highest conver-sion and best selectivity to propylene are those rich in olefins. The ideal feedstocks for theSUPERFLEX process found in the olefins plant are pyrolysis generated C4 and C5 streamswhich have been selectively hydrogenated, converting acetylenes and diolefins to olefins. Ifbutadiene has a high value relative to propylene and the producer has an extraction plant,then Raffinate-1 can be used. Other possible feedstocks are MTBE Raffinate-2, aromaticsplant raffinate, and refinery streams that are rich in olefins, such as naphthas from theFCCU, coker, or visbreaker. Refinery steams do not require pretreatment nor hydrogena-tion of dienes. There is no limit on feed aromatic or diene content. Paraffins are partiallyconverted with each pass through the reactor, contributing to ultimate light olefins yield andallowing recycle to extinction operation.

The SUPERFLEX reaction system is based on years of design and operating experience withFCCU’s in the refinery and is easily integrated into ethylene plants, sharing a common prod-uct recovery section. Catalyst is continuously regenerated and it is quite robust in terms offeed impurities. No feed pretreatment is required for typical trace components. The systemis comprised of the riser reactor/regenerator vessel, air compressor and catalyst handling,flue gas system, and feed/product heat recovery equipment. SUPERFLEX reactor effluententers the ethylene plant recovery section at the main fractionator or process gas compres-sor suction. SUPERFLEX effluent may also be processed in a refinery vapor recovery unit. Arefiner in close proximity to a petrochemicals facility may consider a partial fractionationscheme, where the light ends (C3-) are sent to the neighbor for purification, the middle cutis recycled to extinction, and the gasoline cut is sent to fuels or chemicals use.

Orthoflow™ FCC

Figure 6: The SUPERFLEX Process

Feed

Fuel Oil

To Fractionator

Flue Gas SystemReactor Effluent

Waste Heat Boiler

Catalyst Storage

Air Compressor/Air Heater


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As shown in the Table 4 below, a typical C4 Raffinate, after butadiene extraction, yields ap-proximately 65 wt% propylene plus ethylene. On a similar basis, almost 60% of a partiallyhydrogenated C5 stream is converted to light olefins (P+E). Where refinery cracked naph-thas may have low value to the blending pool, an alternate use would be to upgrade thestream(s) to valuable petrochemicals. A typical light FCC naphtha could ultimately yieldmore than 30 wt% propylene and 15 wt% ethylene.

Table 4SUPERFLEX Ultimate Yields

Yields, wt% C4 RaffinatePartially

Hydrog. C5'sFCC Lt.Naphtha

Fuel Gas 7.2 12.0 13.6Ethylene 22.5 22.1 20.0Propylene 48.2 43.8 40.1Propane 5.3 6.5 6.6Gasoline 16.8 15.6 19.7

SUPERFLEX can be used in concert with a steam cracker to increase the product P/E of thepetrochemical cracking complex. Ultimate olefin plant propylene to ethylene (P/E) ratios fora low severity naphtha steam cracker are typically limited to 0.60 to 0.65. However, withSUPERFLEX, new plants can be designed for P/E ratios of about 0.80. Using the SUPERFLEXprocess within the olefins complex provides a higher ultimate value as shown in the tablebelow:

Table 5SUPERFLEX/Steam Cracker Integration

Steam Cracker ComplexMaterial Balance (KTPA)

Without SUPERFLEX With SUPERFLEX

Feed: Naphtha 1891 1995Products: Ethylene 700 700 Propylene 419 535 Fuel Gas 327 299 Gasoline 390 421P/E Ratio 0.60 0.76

Economic analyses show that the alternate including the SUPERFLEX reactor in the olefinscomplex has about a 1½ year simple payout on gross margin for a plant designed to pro-duce 700 KTPA ethylene.

SUPERFLEX technology is also available as a standalone unit with its own separation section.Both Arco and KBR have extensively piloted process performance for SUPERFLEX. KBR’s in-house pilot facilities are available for evaluating client feedstocks.


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Conclusion

For more than 50 years, FCC has been a major contributor to worldwide production of pro-pylene and butylene for the expanding petrochemical industry. Due largely to the risingdemand for polypropylene, propylene demand continues to outpace the petrochemical in-dustry demand for other light olefins, and much of this increased demand will have to besupplied from fluid catalytic processes that are particularly adept at propylene manufacture.In addition to traditional FCC and Resid FCC units, much of the increased demand will likelybe satisfied with new generation fluid catalytic processes such as MAXOFIN and SUPERFLEX.As these processes proliferate, they are also expected to make significant contributions tothe supply of the most common, yet smallest, petrochemical feedstock – ethylene.

Epilog

Old Mesopotamian writs mention“strange wells near the caravanroad which do not contain waterbut liquid earth. A man thereboils the earth until it becomeswater, which makes torches burnbrighter”. Evidently this manknew how to distill crude oil andburn it over 2000 years ago.

Almost 2000 years later in 1938,at the worlds oldest known oilrefinery located in Baba Gurgur,Iraq, a man is photographedstanding in a pool of oil and col-lecting crude oil in buckets as itgushes from the earth. He willcarry the oil to the ovens, whereit will be heated and run to a re-tort from which nondescriptproducts flow off. This man maybe wondering - what will we dowhen the oil runs out? How canwe improve the process to getthe most value from this dwin-dling resource? What will thefuture refinery look like? We arestill asking ourselves these samequestions. Even today, petro-leum is still mostly consumed asa fuel, refined to the specific a-tions of the day. However, aspetroleum supplies becomes scarce relative to the demand for higher value petrochemicalproducts, the thought of distilling and burning good quality crude oil will seem as foreign tous as the appearance of the old Baba Gurgur oil refinery pictured below.


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References

1. Steven J. Zinger; The Critical Role of the Refinery in the Propylene Market; 2000World Petrochemical Conference; Houston, Texas; March 29 –30, 2000.

2. Steven J. Zinger, Chemical Market Associates, Inc.; e-mail, September 2000

3. C.E. Jahnig, D.L Campbell, and H.Z. Martin; History of Fluidized Solids Developmentat Exxon; Fluidization, Ed John R. Grace and John M. Matsen, Perseus Books, Janu-ary 1980

4. J.J. Blazek; Oil & Gas Journal; 1971

5. E.L. Whittington, J.R. Murphy, and I.H. Lutz; Catalytic Cracking – Modern Designs;American Chemical Society, New York Meeting, August 27 to September 1, 1972.

6. Phillip K. Niccum, Rik B. Miller, Alan M. Claude, Michael A. Silverman, Nazeer A.Bhore, Ke Liu, Girish K. Chitnis and Steven J. McCarthey; MAXOFIN™: A Novel FCCProcess for Maximizing Light Olefins using a New Generation of ZSM-5 Additive;NPRA Paper AM-98-18; San Francisco, California; March 15-17, 1998

7. Maureen F. Gilbert, Michael J. Tallman, William C. Petterson, and Phillip K. Niccum;Light Olefin Production from SUPERFLEXSM and MAXOFIN™ FCC Technologies; ARTCPetrochemical Conference, Kuala Lumpur, Malaysia, February 2001.

Documents

Future Refinery FCCs Role in Refinery Petrochemical Integration