Gasoline Finishing: Gasoline Finishing:

Catalytic Reforming, Isomerization, & AlkylationCatalytic Reforming, Isomerization, & Alkylation

Chapters 10 & 11

Light Naphtha

CrudeOil

Desalter

Atmospheric

Distillation

Vacuum Distillation

Gas

Separation & Stabilizer

Solvent

Deasphal-ting

Coking

Visbreaking

Fluidized

Catalytic Cracking

Hydro-

cracking

Naphtha

Reforming

Isom-erization

Sat Gas

Plant

Polymer-

ization

Alkylation

Naphtha

Hydro-treating

Treating & Blending

Coke

Fuel Gas

LPG

Aviation Gasoline

Automotive Gasoline

Solvents

Jet Fuels

Kerosene

Solvents

Heating Oils

Diesel

ResidualFuel Oils

Lubricant

Greases

Waxes

Asphalts

HeavyNaphtha

Kerosene

Distillate

AGO

LVGO

HVGO

VacuumResiduum

CatDistillates

Gas Oil

Hydro-treating

DAO

Isomerate

Gas

AlkylFeed

Alkylate

PolymerizationNaphtha

Gases

Butanes

LPG

Reformate

Naphtha

Fuel OilBottoms

Distillates

Distillate

Hydro-

treating

CatNaphtha

Cycle Oils

SDABottoms

CokerNaphtha

HeavyCokerGasOil

Light CokerGas Oil

Sulfur

PlantSulfur

Naphtha

Fuel Oil

SolventDewaxing

Lube Oil

Waxes

PurposePurpose

‣ Previous conversion processes

• Feed stocks higher boiling than gasoline

• Break apart large molecules to form smaller molecules

‣ Gasoline finishing processes

• Feed stocks same boiling range as gasoline or slightly lower

• Start with low-octane gasoline blend stocks

� Catalytic Reforming

» Converts naphthenes to aromatics

» Produces hydrogen

� Isomerization

» Re-arranges straight chains to branched isomers

» Very little change in boiling points

• Increase molecular size

� Alkylation

» Use olefins produced in other processes (primarily FCCU)

Characteristics of Petroleum ProductsCharacteristics of Petroleum Products

Contributions to Gasoline Blending Contributions to Gasoline Blending

PoolPool

15 vol%Isomerization

20 vol%Alkylation

30 vol%Reformer

35 vol%FCCU

U.S. Refinery ImplementationU.S. Refinery Implementation

Top 20 Atmospheric Distillation Capacity

Company State Site

Atmospheric

Crude Distillation

Capacity (barrels

per stream day)

Cat Reforming:

High Pressure

Downstream

Charge Capacity,

Current Year

(barrels per

stream day)

Cat Reforming:

Low Pressure

Downstream

Charge Capacity,

Current Year

(barrels per

stream day)

Isomerization(Is

ooctane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Isomerization

(Isobutane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Isomerization

(Isopentane/Iso

hexane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Alkylates

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

ExxonMobil Refining Texas BAYTOWN 596,400 0 126,000 0 0 0 37,000

Hovensa LLC Virgin Islands KINGSHILL 525,000 25,000 85,000 0 0 20,000 19,000

ExxonMobil Refining Louisiana BATON ROUGE 524,000 0 78,000 0 0 0 39,700

BP Texas TEXAS CITY 475,000 75,000 63,000 0 18,000 24,000 46,000

PDVSA Louisiana LAKE CHARLES 440,000 52,800 58,000 0 0 28,000 18,000

BP Indiana WHITING 420,000 71,500 0 0 0 26,000 36,000

Chevron USA Inc Mississippi PASCAGOULA 360,000 34,000 62,000 1,400 0 0 18,600

ExxonMobil Refining Texas BEAUMONT 359,100 0 146,000 0 11,200 24,500 16,300

Sunoco Pennsylvania PHILADELPHIA 355,000 86,000 0 0 8,000 0 26,000

Deer Park Refining Ltd Partnership Texas DEER PARK 340,000 25,000 44,000 0 0 0 18,500

Koch Industries Minnesota SAINT PAUL 330,000 13,800 37,500 0 0 0 12,500

WRB Refining LLC Illinois WOOD RIVER 322,000 17,700 78,800 0 0 0 21,800

Valero Energy Corp Texas PORT ARTHUR 320,000 0 55,000 0 0 0 19,900

Koch Industries Texas CORPUS CHRISTI 305,000 18,000 49,500 0 4,900 2,500 14,700

Motiva Enterprises Texas PORT ARTHUR 300,000 0 48,000 0 0 0 20,000

Access Industries Texas HOUSTON 299,300 0 0 0 0 0 11,250

Chevron USA Inc California EL SEGUNDO 294,000 0 49,000 0 7,700 22,300 33,500

Marathon Petroleum Louisiana GARYVILLE 275,000 0 48,000 0 23,000 21,000 28,000

BP California LOS ANGELES 265,500 43,000 10,000 2,500 3,500 23,000 17,000

ConocoPhillips Texas SWEENY 260,000 0 37,500 0 0 10,100 21,700

ConocoPhillips StatisticsConocoPhillips Statistics

Company State Site

Atmospheric

Crude

Distillation

Capacity

(barrels per

stream day)

Cat Reforming:

High Pressure

Downstream

Charge

Capacity,

Current Year

(barrels per

stream day)

Cat Reforming:

Low Pressure

Downstream

Charge

Capacity,

Current Year

(barrels per

stream day)

Isomerization

(Isooctane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Isomerization

(Isobutane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Isomerization

(Isopentane/Is

ohexane)

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

Alkylates

Production

Capacity,

Current Year

(barrels per

steam day

except sulfur

and hydrogen)

WRB Refining LLC Illinois WOOD RIVER 322,000 17,700 78,800 0 0 0 21,800

ConocoPhillips Louisiana BELLE CHASSE 260,000 44,600 0 0 2,000 0 38,000

ConocoPhillips Texas SWEENY 260,000 0 37,500 0 0 10,100 21,700

ConocoPhillips Louisiana WESTLAKE 252,000 0 44,000 0 0 0 6,000

ConocoPhillips New Jersey LINDEN 250,000 0 32,000 0 4,000 0 18,000

ConocoPhillips Oklahoma PONCA CITY 210,381 52,704 0 0 8,000 0 15,758

ConocoPhillips Pennsylvania TRAINER 190,000 0 50,000 0 0 0 12,000

WRB Refining LLC Texas BORGER 154,000 31,690 0 0 15,000 29,300 14,000

ConocoPhillips California WILMINGTON 147,000 36,000 0 0 3,100 12,800 9,900

ConocoPhillips California RODEO 128,000 32,000 0 0 3,500 9,400 0

ConocoPhillips Washington FERNDALE 107,500 0 17,400 0 2,600 0 9,500

ConocoPhillips Montana BILLINGS 62,000 13,550 0 0 4,000 0 7,250

ConocoPhillips Alaska PRUDHOE BAY 16,000 0 0 0 0 0 0

Dependency of Octane on Chemical StructureDependency of Octane on Chemical StructureBPT [F] RON MON BPT [F] RON MON

Paraffins Naphthenes

n-butane 31 94 89.6 cyclopentane 121 100 84.9

isobutane 11 102 97.6 cyclohexane 177 82.5 77.2

n-pentane 97 62 62.6 m-cyclopentane 161 91.3 80

i-pentane 82 92 90.3 C7 naphthenes 203 82 77

n-hexane 156 24.8 26 C8 naphthenes 253 55 50

C6 monomethyls 143 76 73.9 C9 naphthenes 309 35 30

2,2-dimethylbutane 122 91.8 93.4

2,3-dimethylbutane 136 105.8 94.3 Aromatics

n-heptane 209 0 0 benzene 176 102.7 105

C7 monomethyls 196 52 52 toluene 231 118 103.5

C7 dimethyls 183 93.76 90 C8 aromatics 283 112 105

2,2,3-trimethylbutane 178 112.8 101.32 C9 aromatics 327 110 101

n-octane 258 -15 -20 C10 aromatics 365 109 98

C8 monomethyls 245 25 32.3 C11 aromatics 402 105 94

C8 dimethyls 233 69 74.5 C12 aromatics 439 102 90

C8 trimethyls 229 105 98.8

n-nonane 303 -20 -20 Olefins/Cyclic Olefins

C9 monomethyls 290 15 22.3 n-butenes 30 98.7 82.1

C9 dimethyls 273 50 60 n-pentenes 94 90 77.2

C9 trimethyls 267 100 93 i-pentenes 95 103 82

n-decane 345 -30 -30 cyclopentene 112 93.3 69.7

C10 monomethyls 332 10 10 n-hexenes 152 90 80

C10 dimethyls 40 40 i-hexenes 143 100 83

C10 trimethyls 95 87 Total C6 cyclic olefins 175 95 80

n-undecane 385 -35 -35 total C7d 193 90 78

C11 monomethyl 5 5 total C8d 244 90 77

C11 dimethyls 35 35

C11 trimethyls 90 82 Oxygenates

n-dodecane 421 -40 -40 MTBE 115.2 97.2

C12 monomethyl 5 5 TAME 115 98

C12 dimethyls 30 30 EtOH 108 92.9

C12 trimethyls 85 80

Dependency of Octane on Chemical StructureDependency of Octane on Chemical Structure

-60

-40

-20

0

20

40

60

80

100

120

140

0 50 100 150 200 250 300 350 400 450 500

Boiling Point [°F]

Re

sea

rch

Oct

an

e N

um

be

r

Aromatics

Naphthenes

Olefins & Cyclic Olefins

Iso-paraffins

Normal Paraffins

Light Naphtha

CrudeOil

Desalter

Atmospheric

Distillation

Vacuum Distillation

Gas

Separation & Stabilizer

Solvent

Deasphal-ting

Coking

Visbreaking

Fluidized

Catalytic Cracking

Hydro-

cracking

Naphtha

Reforming

Isom-erization

Sat Gas

Plant

Polymer-

ization

Alkylation

Naphtha

Hydro-treating

Treating & Blending

Coke

Fuel Gas

LPG

Aviation Gasoline

Automotive Gasoline

Solvents

Jet Fuels

Kerosene

Solvents

Heating Oils

Diesel

ResidualFuel Oils

Lubricant

Greases

Waxes

Asphalts

HeavyNaphtha

Kerosene

Distillate

AGO

LVGO

HVGO

VacuumResiduum

CatDistillates

Gas Oil

Hydro-treating

DAO

Isomerate

Gas

AlkylFeed

Alkylate

PolymerizationNaphtha

Gases

Butanes

LPG

Reformate

Naphtha

Fuel OilBottoms

Distillates

Distillate

Hydro-

treating

CatNaphtha

Cycle Oils

SDABottoms

CokerNaphtha

HeavyCokerGasOil

Light CokerGas Oil

Sulfur

PlantSulfur

Naphtha

Fuel Oil

SolventDewaxing

Lube Oil

Waxes

Naphtha ReformingNaphtha Reforming

‣ Almost every refinery in the world has a reformer‣ Purpose to enhance aromatic content of naphtha

• Feed stocks to aromatics complex• Improve the octane rating for gasoline

‣ Many different commercial catalytic reforming processes• Hydroforming• Platforming• Powerforming• Ultraforming• Thermofor catalytic reforming

‣ Primary reactions• Dehydrogenation — naphthenes → aromatics• Isomerization – normal paraffins → branched isoparaffins• Hydrogen as by-product

� Ultimately used in hydrotreating� Catalytic reforming 2nd to FCC in commercial importance to refiners

‣ Reformate desirable component for gasoline• High octane number, low vapor pressure, very low sulfur levels, & low olefins concentration• US regulations on levels of benzene, aromatics, & olefins

� Air quality concerns

FeedstocksFeedstocks & Products& Products

‣ Hydrotreated heavy naphtha feedstock• Light straight run naphtha tends to crack to butanes & lighter

• Gas oil streams tend to hydrocrack & deposit coke on the reforming catalyst

‣ Catalyst is noble metal (e.g. platinum) – very sensitive to sulfur & nitrogen

• Feed stocks hydrotreated for sulfur & nitrogen removal

• Control of chloride & water also important

‣ Severity• High severity used to maximize aromatics

� Sent to BTX separation for aromatic feedstocks

• Low severity used for gasoline blend stocks

‣ Produces the majority of the hydrogen used for hydrotreating

Reforming ChemistryReforming Chemistry

‣ Uses a solid catalyst to convert naphthenes to the corresponding aromatics & isomerize paraffinic structures to isomeric forms

• Both reactions lead to a marked increase in octane number

• Both reactions lead to volume shrinkage

‣ Correlations permit the use of a PONA analysis of the feed for prediction of yield and quality of the product

• Originally feed qualities measured in terms of Watson "K" Factor —a rough indication of amount of paraffins

‣ Aromatics largely untouched by reactions

Reforming ChemistryReforming Chemistry

CH3 CH3

+ 3 H2

Dehydrogenation

+ H2

Dehydrocyclization

CH3

CH3

CH3

CH3

+ H2

Isomerization

CH3CH3

CH2

CH3CH3

HydrocrackingCH2CH3 CH3

+ H2 +

Use of Yield ChartsUse of Yield Charts

100%Total

Ratio∆Fig 10.4C5+ Gasoline

PureRatio58.5%NC4

PureRatio41.5%

Fig 10.5IC4

C4s

PureFig 10.6RatioC3

Fig 10.6C1 + C2

Fig 10.7Hydrogen

DensityWt%Vol%

Notes:

• Y-axis of Fig 10.4 is C5+ gasoline yield

• Typically use the Watson K Factor of feed in Fig 10.4.

Effects of Process VariablesEffects of Process Variables

‣ Primary control for changing conditions or qualities is reactor temperature

• Normally about 950°F at reactor inlet

• May be raised for declining catalyst activity or to compensate for lower quality feedstock

• Higher reactor temperature increases octane rating but reduces yield and run length

Effects of Process VariablesEffects of Process Variables

‣ Design considerations for improvement in quality will include pressure, recycle ratio, reactor residence time, & catalyst activity

• Low reactor pressure increases yield & octane but increases coke make

• Increased hydrogen partial pressure due to hydrogen recycle (hydrogen to hydrocarbon ratio) suppresses coke formation, hydrogen yield & octane gain, but promotes hydrocracking

• Low space velocity favors aromatics formation but also promotes cracking by operating closer to equilibrium conditions

• Higher activity catalysts cost more but increases run lengths and or yields

Effects of Process VariablesEffects of Process Variables

High temperatureHigh pressureHydrocracking

Slight dependenceSlight dependenceIsomerization of normal paraffins

to isoparaffins

High temperatureLow pressureDehydrogenation of naphthenes

to aromatics

High temperatureLow pressureDehydrocyclization of paraffins to

naphthenes

IndeterminateIndeterminateIsomerization of naphthenes

TemperaturePressureReaction

Specific Catalytic Reforming ProcessesSpecific Catalytic Reforming Processes

‣ Hydroforming

• Early cyclic process used to produce toluene for TNT during World War II

• Molybdenum oxide on alumina catalyst

• Rapid coking of the catalyst, requiring a cyclic regeneration of reactors about every four hours

� Timing mechanism used for lawn sprinkler systems used to switch from reforming to regeneration service

� Reactor system included one extra "swing" reactor

» Facilitate periodic removal & regeneration of a reactor

Specific Catalytic Reforming ProcessesSpecific Catalytic Reforming Processes

‣ UOP Semi-Regenerative Platforming• Low platinum

• Regeneration once a year

• Made naphtha octane improvement accessible to all refiners

‣ UOP Continuous Regeneration of Reforming Catalyst • Moving bed process

� Continuously regenerating a portion of a moving bed of catalyst to remove coke & sustain activity

� Operating pressures lowered to 50 psig

• Three reactors stacked one on top of the other

� Gravity flow of the catalyst from top to bottom

� Reactants pass radially through the catalyst to the inner conduit and then to the next bed

� Mode of regeneration is proprietary – probably employs air or oxygen burning of the coke followed by reduction & acidification

UOP UOP PlatformingPlatforming

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

Light Naphtha

CrudeOil

Desalter

Atmospheric

Distillation

Vacuum Distillation

Gas

Separation & Stabilizer

Solvent

Deasphal-ting

Coking

Visbreaking

Fluidized

Catalytic Cracking

Hydro-

cracking

Naphtha

Reforming

Isom-erization

Sat Gas

Plant

Polymer-

ization

Alkylation

Naphtha

Hydro-treating

Treating & Blending

Coke

Fuel Gas

LPG

Aviation Gasoline

Automotive Gasoline

Solvents

Jet Fuels

Kerosene

Solvents

Heating Oils

Diesel

ResidualFuel Oils

Lubricant

Greases

Waxes

Asphalts

HeavyNaphtha

Kerosene

Distillate

AGO

LVGO

HVGO

VacuumResiduum

CatDistillates

Gas Oil

Hydro-treating

DAO

Isomerate

Gas

AlkylFeed

Alkylate

PolymerizationNaphtha

Gases

Butanes

LPG

Reformate

Naphtha

Fuel OilBottoms

Distillates

Distillate

Hydro-

treating

CatNaphtha

Cycle Oils

SDABottoms

CokerNaphtha

HeavyCokerGasOil

Light CokerGas Oil

Sulfur

PlantSulfur

Naphtha

Fuel Oil

SolventDewaxing

Lube Oil

Waxes

Gasoline IsomerizationGasoline Isomerization

‣ Major process for octane improvement

‣ Improve the octane rating of straight run gasoline• N-paraffins isomerized to branched isoparaffins

• Also converts normal butane to isobutane – used in alkylation

‣ High RVP (about 17 psi) — limits its use in gasoline pool

Dependency of Octane on Chemical StructureDependency of Octane on Chemical StructureBPT [F] RON MON BPT [F] RON MON

Paraffins Naphthenes

n-butane 31 94 89.6 cyclopentane 121 100 84.9

isobutane 11 102 97.6 cyclohexane 177 82.5 77.2

n-pentane 97 62 62.6 m-cyclopentane 161 91.3 80

i-pentane 82 92 90.3 C7 naphthenes 203 82 77

n-hexane 156 24.8 26 C8 naphthenes 253 55 50

C6 monomethyls 143 76 73.9 C9 naphthenes 309 35 30

2,2-dimethylbutane 122 91.8 93.4

2,3-dimethylbutane 136 105.8 94.3 Aromatics

n-heptane 209 0 0 benzene 176 102.7 105

C7 monomethyls 196 52 52 toluene 231 118 103.5

C7 dimethyls 183 93.76 90 C8 aromatics 283 112 105

2,2,3-trimethylbutane 178 112.8 101.32 C9 aromatics 327 110 101

n-octane 258 -15 -20 C10 aromatics 365 109 98

C8 monomethyls 245 25 32.3 C11 aromatics 402 105 94

C8 dimethyls 233 69 74.5 C12 aromatics 439 102 90

C8 trimethyls 229 105 98.8

n-nonane 303 -20 -20 Olefins/Cyclic Olefins

C9 monomethyls 290 15 22.3 n-butenes 30 98.7 82.1

C9 dimethyls 273 50 60 n-pentenes 94 90 77.2

C9 trimethyls 267 100 93 i-pentenes 95 103 82

n-decane 345 -30 -30 cyclopentene 112 93.3 69.7

C10 monomethyls 332 10 10 n-hexenes 152 90 80

C10 dimethyls 40 40 i-hexenes 143 100 83

C10 trimethyls 95 87 Total C6 cyclic olefins 175 95 80

n-undecane 385 -35 -35 total C7d 193 90 78

C11 monomethyl 5 5 total C8d 244 90 77

C11 dimethyls 35 35

C11 trimethyls 90 82 Oxygenates

n-dodecane 421 -40 -40 MTBE 115.2 97.2

C12 monomethyl 5 5 TAME 115 98

C12 dimethyls 30 30 EtOH 108 92.9

C12 trimethyls 85 80

History of IsomerizationHistory of Isomerization

‣ Aviation gasoline for World War II

• Butane isomerization was developed to create the needed isobutane feedstock

• Aluminum chloride catalyst

• Many of these units were shut down after the war

‣ Tetra Ethyl Lead Phase-Out in 1970s

• Straight Run Gasoline (SRG) relied on TEL for octane improvement

• Research Octane Number (RON) of only 70

� SRG mostly paraffinic pentanes & hexanes with some heptanes and octanes

‣ Isomerization could provide needed octane boost

• Equivalent Isoparaffins have higher RON

Isomerization ProcessesIsomerization Processes

‣ Vapor phase process• Hydrogen used to suppress dehydrogenation & coking

• High yields & high selectivity to high-octane isomeric forms

• Provides moderate (but important) contribution to the gasoline pool

‣ Catalyst types• Chloride alumina catalyst

� Organic chloride deposited on active metal sites

» High temperature treatment with carbon tetrachloride

� Chlorides sensitive to moisture – drying of feed & hydrogen make-up essential

• Acidic zeolite with noble metal catalyst

� Platinum catalyst

� Does not require activation by hydrogen chloride

Isomerization ProcessesIsomerization Processes

‣ Pros

• Reforming conditions not appropriate for the paraffinic components in SRG

• Essentially zero benzene, aromatics, & olefins

• Very low sulfur levels

‣ Cons

• High vapor pressure

• Moderate octane levels — (R+M)/2 only 85

Isomerization TechnologiesIsomerization Technologies

Provider Features

Axens

Either once-through or Ipsorb Isom with normal

paraffin recycle to exinction.

CDTECH ISOMPLUS zeolite-based catalyst.

UOP (1)

Par-Isom process uses high-performance

nonchlorided-alumina catalysts

UOP (2)

HOT (hydrogen-once-through) Penex process

eliminates need of recycle-gas compressor. Fixed

bed using high-activity chloride-promoted catalyst.

UOP (3)

HOT (hydrogen-once-through) Butamer process

eliminates need of recycle-gas compressor. Two

series reactors provide high onstream efficiency.

FeedstocksFeedstocks

‣ Lightest naphtha feed stock (SRG) with pentanes, hexanes, & small amounts of heptanes

• Feed often debutanized — ‘Debutanized Straight Run’

‣ Sulfur & nitrogen must be removed since catalysts employ an ‘acid site’ for activity

• Merox

• Clay treating

• Hydrotreating

‣ Common for Straight Run Gasoline & Naphtha to be hydrotreated as one stream & then separated

ProductsProducts

‣ Products

• Isoparaffins & cycloparaffins

• Small amounts of light gasses from hydrocracking

• Unconverted feedstock

‣ Increased severity increases octane but also increases yield of light ends

‣ Yields depend on feedstock characteristics & product octane

• Poor quality feeds might yield 85% or less liquid product

• Good feeds might yield 97% liquid product

Isomerization ChemistryIsomerization Chemistry

‣ Primary reaction is to convert normal paraffins to isomeric paraffins

‣ Olefins may isomerize and shift the position of the double bond

• 1-butene coluld shift to a mixture of cis-2-butene & trans-2-butene

‣ Cycloparaffins (naphthenes) may isomerize & break the ring forming an olefin

• Cyclobutane to butene

Effects of Process VariablesEffects of Process Variables

‣ Low temperature, moderate hydrogen partial pressure, low space

velocity promote long run lengths

‣ Isomerization yields controlled by chemical equilibrium• Removing isoparaffins from feedstock can shift the reactor equilibrium &

increase the final product octane

‣ Temperature primary process control variable• Higher temperatures increase processing severity (including hydrocracking)

‣ Other process variables• Higher pressures increase catalyst life but increases undesirable

hydrocracking reactions

• Increased hydrogen partial pressure promotes hydrocracking but prolongs catalyst life

• Space velocity balanced against capital cost, temperature, run length & yields

Process ImprovementsProcess Improvements

‣ Number of combinations of fractionation and isomerization

• Removing isopentane from feed increases the product’s RON to 84

• Addition of a depentanizer on product stream recycle of n-pentane recycle increases product’s RON to 86

• Separation using molecular sieves increases the product’s RON to 89

� UOP combines Penex with Molex

� Separation carried out entirely in vapor phase — no reflux utilities but cyclic operation

• Total recycle with a deisohexanizer increases the product’s RON to 89

• Suitable for blending into premium at no octane penalty

Isomerization With & Without Isomerization With & Without IsopentaneIsopentane

RemovalRemoval

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

Catalytic Reforming TechnologiesCatalytic Reforming Technologies

Provider Features

Axens (1)

Catalyst regenerated in-place at end of cycle. Operates in

pressure range of 170 - 350 psig.

Axens (2)

Advanced Octanizing process, uses continuous catalyst

regeneration allowing pressures as low as 50 psig.

UOP

CCR Platforming process. Radial-flow reactors arranged in

vertical stack.

Light Naphtha

CrudeOil

Desalter

Atmospheric

Distillation

Vacuum Distillation

Gas

Separation & Stabilizer

Solvent

Deasphal-ting

Coking

Visbreaking

Fluidized

Catalytic Cracking

Hydro-

cracking

Naphtha

Reforming

Isom-erization

Sat Gas

Plant

Polymer-

ization

Alkylation

Naphtha

Hydro-treating

Treating & Blending

Coke

Fuel Gas

LPG

Aviation Gasoline

Automotive Gasoline

Solvents

Jet Fuels

Kerosene

Solvents

Heating Oils

Diesel

ResidualFuel Oils

Lubricant

Greases

Waxes

Asphalts

HeavyNaphtha

Kerosene

Distillate

AGO

LVGO

HVGO

VacuumResiduum

CatDistillates

Gas Oil

Hydro-treating

DAO

Isomerate

Gas

AlkylFeed

Alkylate

PolymerizationNaphtha

Gases

Butanes

LPG

Reformate

Naphtha

Fuel OilBottoms

Distillates

Distillate

Hydro-

treating

CatNaphtha

Cycle Oils

SDABottoms

CokerNaphtha

HeavyCokerGasOil

Light CokerGas Oil

Sulfur

PlantSulfur

Naphtha

Fuel Oil

SolventDewaxing

Lube Oil

Waxes

Alkylation & PolymerizationAlkylation & Polymerization

‣ Processes to make gasoline components from materials that are too light to otherwise be in gasoline

‣ Alkylation

• Form a longer chain highly branched isoparaffin by reacting an alkyl group (almost exclusively isobutane) with a light olefin (predominately butylene)

• Produces high-octane gasoline

‣ Polymerization

• Formation of very short chains

• Product is nearly all olefinic — high research octane but moderate motor octane number

Alkylation TechnologiesAlkylation Technologies

Provider Features

CDTECH (1) CDAlkyl low-temperature sulfuric acid alkylation.

CDTECH (2)

CDAlkylPlus low-temperature sulfuric acid alkylation

coupled with olefin pretreatment step.

DuPont

Uses STRATCO Effluent Refrigeration Alkylation

process using sulfuric acid

Lummus Technology

AlkylClean process using solid acid catalyst.

Demonstation unit only.

Refining Hydrocarbon

Technologies LLC

RHT-Alkylation process uses sulfuric acid. Eductor

mixing device.

ExxonMobil Research &

Engineering

Sulfuric acid alkylation using autorefrigerated

reactor.

UOP (1) Modified HF Alkylation to reduce aerosol formation.

UOP (2)

Indirect Alkylation (InAlk) uses solid catalyst. Olefins

polymerize & higher molecular weight material

hydrogenated.

Olefin Alkylation & Polymerization Olefin Alkylation & Polymerization

‣ 1920s & 1930s other methods used to improve gasoline octane• Tetra Ethyl Lead in Straight Run Gasoline

• Thermal reforming of naphtha

• Thermal polymerization of olefinic light ends to hexenes, heptenes, & octenes

‣ In late 1930s & early 1940s, alkylation of olefins was developedto improve the octane of aviation gasoline

• Vladimir Ipatieff had discovered aluminum chloride catalysis in 1932

‣ FCC significantly increased the production of light ends • High concentration of the C3, C4, & C5 isomers, both olefinic & paraffinic

• Led to development of both catalytic polymerization & alkylation

Sulfuric Acid AlkylationSulfuric Acid Alkylation

‣ A consortium of major refiners & contractors developed process with sulfuric acid as the catalyst

• Anglo-Iranian Oil, Humble Oil & Refining, Shell Development, Standard Oil Development, & the Texas Company

‣ First alkylation unit at the Humble Baytown Refinery in 1938

‣ Many alkylation plants were built at the same time as the catalytic cracking units

• Operated during World War II for aviation gasoline production

‣ Sulfuric acid alkylation required access to acid regeneration on a large scale

• Most sulfuric acid alkylation plants were located on deep water for barge transport of spent acid to regeneration at acid plants & return of fresh acid

• Economic handicap for inland midwestern refineries

HF Acid AlkylationHF Acid Alkylation

‣ Phillips Petroleum & UOP developed process using hydrofluoric acid as a catalyst

• HF could be readily regenerated in alkylation plant facilities

• No need to transport catalyst in large quantities for regeneration

‣ HF alkylate in general was not quite as high quality as sulfuric acid alkylate

Alkylation vs. PolymerizationAlkylation vs. Polymerization

‣ Following end of the Korean conflict (1953) refiners investigated use of their catalytic polymerization and alkylation capacity for production of higher-octane motor fuels

‣ Both polymerization & alkylation were adapted — alkylation

became the dominant process

‣ By the 1960s, polymerization units were being phased out and new plants utilized alkylation technology

‣ Chicken & egg — increasing octane production capacity & higher performance engines in automobiles led to the octane race in mid 1950s

FeedstocksFeedstocks

‣ Olefinic stream from the catalytic cracker

• Butylene is the preferred olefin since it produces the highest octane number & yields

• isobutane & isopentane can be reacted with the olefin

� Isopentane not usually used since it is a good gasoline blend stock

‣ High octane number & low vapor pressure

‣ Catalytic cracker feed contains significant sulfur

• Treating unit often precedes alkylation unit

ProductsProducts

‣ Alkylate desirable component for high performance automotive fuels

• Very high octane index (R+M)/2 of 95

• Low vapor pressure

� Vapor pressure is adjusted for final boiling point

� IBP adjusted for addition of normal butane

• Low sulfur levels

• Essentially no olefins, benzene or aromatics

‣ Contributes large volume to the gasoline pool (19% vol)

• Catalytic cracker (34% vol)

• Reformer (28% vol)

• Isomerization unit (15% vol)

Process ChemistryProcess Chemistry

‣ Acid catalyzed alkylation combines isoparaffins & olefins to form alkylate, highly branched alkanes

• Usually only isobutane is used

� Isopentane is a good gasoline blend stock

‣ Friedel-Crafts reaction — Lewis acid (HF or H2S04) promotes carbonium ion on a tertiary isoparaffin that rapidly reacts with any double bond it encounters (propylene, butylenes, or pentylenes)

‣ The reaction carried out in the liquid phase with an acid/reactant emulsion maintained at moderate temperatures

Process ChemistryProcess Chemistry

‣ Propylene, butylene, & pentenes are olefins used — butylenepreferred

• High octane isooctane alkylate produced

• Lower reactant consumption

‣ Alkylation reactions have complex mechanisms & may produce many different varieties

Process Chemistry ExamplesProcess Chemistry Examples

‣ Isobutylene & isobutane form 2,2,4-trimethylpentane (isooctane)

‣ Propylene & isobutane form 2,2-dimethylpentane as primary product with 2,3-dimethylpentane & 2,4-dimethylpentane as secondary products

C CH2

CH3

CH3

+ H+ C

+CH3

CH3

CH3

C+

CH3

CH3

CH3 CH

CH3

CH3

CH3 + H+

C

CH3

CH3

CH3 CH CH3

CH3

CH2+

Operating Variables & Their Effects Operating Variables & Their Effects

‣ Capacity expressed in terms of alkylate product, not feed capacity

‣ Most important variables• Type of olefin

� Propylene, butylene, or pentene

• Isobutane concentration

• Olefin injection & mixing

• Reaction temperature

• Catalyst type & strength

‣ Critical measures for success• Alkylate octane number

• Volume olefin & isobutane consumed per volume alkylate produced

� Degree of undesirable side reactions

• Acid consumption

Type of OlefinType of Olefin

‣ Butylene preferred

• Produces the highest isooctane levels

� Resulting Research Octane Numbers of 93-95 (with isobutane)

� RON and MON are about equal for alkylation

• Amounts of butylene consumed per alkylate produced is the lowest

• Side reactions are limited

‣ Propylene worse

• Octane numbers are low (89-92 RON)

• Propylene & acid consumption are high

‣ Pentene results are mixed

• Side reactions frequent

IsobutaneIsobutane concentrationconcentration

‣ Excess isobutane required — normal volume ratio of isobutaneto olefin in the feed is 6-10

• Limited isobutane solubility in acid phase

• Olefins need to be surrounded by isobutane exposed to acid — if not, olefins will polymerize instead of alkylate

‣ Newer plants have multi-injection & vigorous mixing systems

• Effect of isobutane is expressed in terms of concentration in the reaction zone

• Isobutane to olefin ratios maintained at 10,000 to 1

IsobutaneIsobutane/Olefin Injection & Mixing /Olefin Injection & Mixing

‣ More important in sulfuric acid systems

• Acid viscosity at operating temperatures

‣ Provide optimal reaction conditions for the very fast reaction

• Inject olefin feedstock in incremental fashion to increase isobutane/olefin ratios

• Newer plants designed for multi-injection locations into an agitated emulsion to disperse olefin as rapidly as possible

‣ Systems with single point injection can easily have an overload of olefin in the emulsion

• Leads to lower quality & higher acid consumption from esterification reactions

Reaction TemperatureReaction Temperature

‣ Most noticeable variable in both reaction systems

‣ Increasing temperature reduces octane number

• HF systems run at 95°F

• Sulfuric acid systems run at 45°F

� Often employ auto refrigeration of the reactant mass to provide coolant for the reactors

Acid Type & Strength Acid Type & Strength

‣ HF acid strength is not an important variable in the range of 80% to 95%

‣ Sulfuric acid strength is somewhat a function of the diluent

• Water lowers acid activity 3 to 5 times as fast as hydrocarbon diluents

• Acid is considered "spent" at around 88% sulfuric acid

Sulfuric vs. HF Acid Alkylation Sulfuric vs. HF Acid Alkylation

‣ Principal difference is operating temperature

• Sulfuric acid alkylation — refrigeration required

• HF alkylation – can operate at cooling water temperatures

‣ Sulfuric acid alkylation is dominant process

• Sulfuric acid plants require extensive recuperation of the spent acid — generally done off-site

• Larger coastal refiners tend to have sulfuric acid alkylation plants with barge or short haul transportation to acid regeneration facilities

‣ HF plants generally smaller & catalyst regeneration is done in-plant with a small acid makeup

• Urban community concerns to hazards of HF escape

Sulfuric Acid AlkylationSulfuric Acid Alkylation

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

Time Tank ReactorsTime Tank Reactors

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

AutorefrigeratedAutorefrigerated Reactor Sulfuric Acid Reactor Sulfuric Acid

Alkylation (EMRE)Alkylation (EMRE)

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

STRATCO Reactor Sulfuric Acid STRATCO Reactor Sulfuric Acid

Alkylation (DuPont)Alkylation (DuPont)

Refining Overview – Petroleum Processes & Products, by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

HF Alkylation SystemHF Alkylation System

‣ Differences to sulfuric acid systems

• Feed driers essential to minimize catalyst consumption

� Water forms an azeotrope with HF leading to acid loss

• HF stripper required on depropanizer overhead to clean up propane for LPG

• HF regenerator operating on a slip stream from acid settler

� Many acid soluble organic compounds decompose but some must be rejected as acid soluble oil

• Spent acid requires special neutralization

� Convert HF to calcium fluoride & burnable waste

� Overall acid loss should be less than one pound per barrel of acid produced

‣ Elaborate HF venting, neutralization & recovery system

• Considered by the public to be a threat in terms of large releases of HF

• New designs minimize the inventory of HF in the unit far below earlier designs

� Risk is minimized, not eliminated

Phillips Alkylation ProcessPhillips Alkylation Process

Handbook of Petroleum Refining Processes

Robert MeyersMcGraw-Hill, Inc, 1986

Phillips Alkylation ProcessPhillips Alkylation Process

Component Olefin FeedSaturated

ButanesPropane Yield

Motor-Fuel

Butane Yield

Motor-Fuel

Alylate YieldAcid Oils

Ethane 0.49 0.49

Propylene 21.04

Propane 17.42 0.30 18.77

Isobutane 191.81 13.48 0.34 3.13 0.19

Butenes 169.10

n-Butane 63.17 10.11 63.35 9.93

Pentanes 4.90 0.42 3.67 1.65

Alkylate 390.17

Acid Oils 0.55

Total 467.93 24.31 19.60 70.15 401.94 0.55

Stream Totals 492.24 492.24

RVP [psi] 6.0

Specific Gravity 0.70

RON, clear 95.0

MON, clear 93.5

FBP [°C] 195

FBP [°F] 383