FCC Gasoline Treating UsingCatalytic Distillation

Texas Technology ShowcaseMarch 2003, Houston, Texas

Dr. Mitchell E. Loescher

Gasoline of the FutureGasoline of the Future

Lead is outOlefins reducedAromatics reducedBenzene reducedSulfur reduced

Gasoline Desulfurization RequirementsGasoline Desulfurization Requirements

– Pool sulfur specification• Europe

– European Union– 50 ppm max - 2005– 10 ppm max – - available 2005– - standard 2008

• US, Canada– 30 ppm avg - 2002 to 2008

• Future– 15 -10 -5 ppm? - 2005+

Sulfur SourcesSulfur Sources

FCC Naphtha– 200 to 3000 ppm– 25 to 40% of refinery pool volume– 85 to 99% of refinery pool sulfur

FCC Gasoline Feed CompositionFCC Gasoline Feed Composition

02000400060008000

1000012000

50 100 150 200 250

Temperature, C

Sulfu

r, pp

m

0

10

20

30

40

Ole

fins,

%

Sulfur Olefins

Optimized HDS ProcessOptimized HDS Process

FCC C5+GASOLINE

LCNMild HDSMild HDS

MediumMediumHDSHDS

SevereSevereHDSHDS

MCN

HCN

MCN/HCN

Conventional LCN TreatingConventional LCN Treating

Fractionate LCN from FCC Gasoline

SelectiveHydrogenation

TREATED LCN

HYDROGEN

HydrogenCompression

FCC C5+GASOLINE

MCN/HCN

FRESH CAUSTIC

MercaptanRemoval

SPENT CAUSTIC

Caustic wash for mercaptan removal– ~90% effective

Selective hydrogenation of dienes for alky/ethersCompression of makeup hydrogen

LCN

Hydrogenation / DistillationHydrogenation / Distillation

Vent Gas

CW

Steam

Hydrogen

Bottoms

Treated Distillate

HydrocarbonFeed

CDHydro® Process

Add Hydrogen Feed

Replace trays with structureddistillation packing containing catalyst

Vent excess Hydrogen

CDCDHydroHydro ReactionsReactions

Thioetherification

C CCC

C+

SHCC

C

C

C

CC S CC

Selective Hydrogenation

C CCC

C+ H H

C CCC

C

CDCDHydroHydro ReactionsReactions

Isomerization

CCC

C C

RON

118

CDCDHydroHydro ReactionsReactions

Isomerization

CCC

C C

RON

118 150

Hydroisomerization boosts full range FCC naphtha by 0.5 RON

+0.5

Catalytic DistillationCatalytic Distillation

Catalyst SectionDrawing

WireMesh

Catalyst

Vapor

RefluxH2

Optimized FCC Naphtha HDSOptimized FCC Naphtha HDS

FCC C5+GASOLINE

LCN

MCN/HCN

HydrogenCDHydro®

HDSHDS

CW

LPSteam

Low SulfurFCCGasoline

LightEnds LightEnds

StripperReactors

FCCGasoline

Make-upHydrogen Recycle

Hydrogen

Conventional MCN/HCN HDSConventional MCN/HCN HDS

Conventional Reactor DesignConventional Reactor Design

Severity of reactor conditions set by most refractory species– Temperature– H2 partial pressure

Lighter sulfur species react to very high conversionsAll olefins exposed to the most severe conditions

Reactors

Conventional Fixed Bed HDSConventional Fixed Bed HDS

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1

Reactor Length

Conv

ersi

on (%

)

Total SLight SHeavy SOlefin 1Olefin 2

Olefin 1 Olefin 1 -- with recombinant mercaptan in productwith recombinant mercaptan in productOlefin 2 Olefin 2 -- w/o recombinant mercaptanw/o recombinant mercaptan

Recombinant Mercaptan ExperienceRecombinant Mercaptan Experience

Mercaptan Levels

0 2 4 6 8 10

Octane Loss (R+M)/2

RSH

Lev

el, p

pm

fixed bed RSH

FCC C5+GASOLINE

Optimized FCC Gasoline HDSOptimized FCC Gasoline HDS

LCNMild HDSMild HDS

MediumMediumHDSHDS

SevereSevereHDSHDS

MCN

HCN

MCN/HCN

80

82

84

86

88

90

92

50 100 150 200 250

Boiling Point, C

Oct

ane

No.,

(R+M

)/2FCC Gasoline Octane DistributionFCC Gasoline Octane Distribution

MCN/HCN with CDMCN/HCN with CDHDSHDS

Conditions milder than conventional fixed bed (17 barg vs 28+)

> 99% HDSHeavy sulfur to bottom

Off GasCW

Hydrogen

CDHDS®

FCC C7+ Gasoline

Light olefins to top Min octane loss(<1@ 90% HDS) Low H2 consumptionLow sulfur bottoms product good for

gasolineNo yield loss due to crackingNo makeup compressorNo mid-cycle shutdown for catalyst regenNo feed storage required

Selectivity CurveSelectivity Curve

0

0.2

0.4

0.6

0.8

1

200 250 300 350 400 450 500

Temperature, F

Conv

ersi

on, F

ract

ion

Sulfur reduction Olefin reduction

Olefin saturation is higher for heavy olefins

Octane vs. Carbon NumberOctane vs. Carbon NumberRON Linear Olefin - Linear Saturate

0

20

40

60

80

100

120

5 6 7 8 9 10 11

Carbon Number

RON

Why isWhy is CDTECH’sCDTECH’s octane loss lower?octane loss lower?

Conventional fixed bed hydrotreaters– Saturate primarily light olefins– Light olefin saturation causes high octane loss

CDHDS– Higher saturation of heavy olefins– Less octane to lose in heavy olefins– Lower octane loss at a given olefin reduction

Fixed Bed HDS Catalyst Life?Fixed Bed HDS Catalyst Life?

FCC turnaround cycle– Modern refineries target 5 year cycle

Conventional fixed bed hydrotreaters– Olefins form oligomers– Oligomers form coke that fouls catalyst– Catalyst activity reduced– Regenerate or replace catalyst– Must shutdown before end of FCC cycle– Fixed bed catalyst life insufficient

Commercial Catalyst Activity for FCC Gasoline HDS

0.000 365.000 730.000

Days on Oil

Rel

ativ

e A

ctiv

ity

Fixed Bed HDS

Catalyst Activity History for Commercial CDHDS Units

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 100 200 300 400 500 600 700 800 900 1000

Days Since Start-up

Obs

erve

d R

ate

Con

st.

Irving Oil Motiva ChevronTexaco

Conventional Fixed Bed Unit Conventional Fixed Bed Unit ShutdownShutdown

FCC unit Sulfur ReductionUnit

Untreated FCC Gasoline storage

x

Conventional Unit RestartConventional Unit Restart

FCC unit Sulfur ReductionUnit

Untreated FCC Gasoline storage

x

Extra Capacity Required

ConclusionsCDHydro

Lowest sulfur and diolefins in LCNEliminates separate mercaptan and diolefin removal units

CDHDSLowest FCC cycle olefin loss via HDSNo cracking yield lossNo diene pretreatment requiredNo regeneration/feed storage required

CDHydro/CDHDSLowest overall octane lossCommercially provenMost cost effective HDS in FR FCC CNLong catalyst life via catalytic distillationLow capital cost

Recommendations

•Plan for 10 ppm sulfur

•Evaluate full FCC cycle performance

•Include shutdown related capital cost

•Thank you to DOE for 1980 funding for CR&L