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Processes in the oil refinery

Crude oil

Straight run gasoline

LPG and Gas

Naphtha

Hydro-treating

Reformate

Middle distillates

Heavy atm. gas oil

Solventextraction

Lube base stocks

Gasoline

Vacuum gas oil

Solventdewaxing

Lube oils

Waxes

Gasoline, Naphtha, Middle distillates

Gasoline, Naphtha, Middle distillates

Gasoline, Naphtha, Middle distillates

Slurry oil

Refinery fuel gas

LPG

Gasoline

Solvents

Kerosene

Diesel

Heating oil

Lube oil

Greases

Asphalt

Industrial fuels

Coke

Trea

ting

and

Blen

ding

Delayed coker / Flexicoker

Propanedeasphalter

Hydro-treating

Catalyticreforming

Catalyticcracking

Visbreaker

Hydro-cracking

Fuel oil

Asphalt

LPG and Gas

Cycle oil

Alkylation AlkylateLPG

Hydro-treating

Vacu

umD

istil

latio

nAt

mos

pher

icD

istil

latio

n

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Crude Oil RefiningDistillate fraction Boiling point

(oC)C-atoms/molecule

Gases <30 1-4Gasoline 30-210 5-12Naphtha 100-200 8-12Kerosine (jet fuel) 150-250 11-13Diesel, Fuel oil 160-400 13-17AtmosphericGasoil

220-345

Heavy Fuel Oil 315-540 20-45AtmosphericResidue

>540 >30

Vacuum Residue >615 >60

MiddleDistillates

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Chemical processesThermal Catalytic

Visbreaking HydrotreatingDelayed coking Catalytic reformingFlexicoking Catalytic cracking

HydrocrackingCatalytic dewaxingAlkylationPolymerizationIsomerization

Processes in an Oil Refinery

Physical processes

DistillationSolvent extractionPropane deasphaltingSolvent dewaxingBlending

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620 K

C1 - C4

Gases

Gasoline

Kerosene

Gas oil

ResidueCrude oil

steam

steam

steam

reflux water

Fractionator Stripper StripperFurnace

Simple Crude Distillation

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Market DemandsMarket Demands

•• Clean products (no S, N, O, metals, etc.)Clean products (no S, N, O, metals, etc.)•• More gasoline (high octane number)More gasoline (high octane number)•• More diesel (high cetane number)More diesel (high cetane number)•• Specific products (Aromatics, alkenes, etc.)Specific products (Aromatics, alkenes, etc.)•• Less residueLess residue

How to meet these demands?How to meet these demands?

•• More sophisticated distillationMore sophisticated distillation•• Physical separation stepsPhysical separation steps•• Chemical conversion stepsChemical conversion steps

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620 K

C1 - C4

Gases

Gasoline

Kerosene

Gas oil

ResidueCrude oil

steam

steam

steam

reflux water

Fractionator Stripper StripperFurnace

More sophisticated ???Higher T Higher T distillation distillation ????

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Modern Crude Distillation Unit

reflux water

vacuumsteam

Crude Oil

vacuum

Intermediate gas oil

Heavygas oil

Slops

Gases

Gasoline

vacuum residue

Kerosene

Lightgas oil

steam

Mainfractionator

Strippers Mild vacuumcolumn

Driers

circulating reflux

circulating reflux

FurnaceFurnace

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Propane DeasphaltingExtraction

ReasonReasonCokeCoke--forming tendencies of forming tendencies of asphaltenicasphaltenic materialsmaterials

How?How?Reduction by removal of suitable solventReduction by removal of suitable solvent

propane propane butane, pentanebutane, pentane

Why propane?Why propane? Conditions?Conditions? Flow scheme?Flow scheme?Easy separationEasy separationAvailableAvailable......

Modest temperatureHigh pressure

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Propane Deasphalting

Deasphalted oil

Vacuum residue

Liquid propane

Asphalt

Propane recycle

Flash drumDeasphalting tower Strippers

Steam

Steam

Condensers

Steam condenser

Water

Propane storage

Make-up propane

310 - 330 K35 - 40 bar

Steam

Propane evaporatorCond.

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Thermal Processes

Feedgasoilcoke

Furnace

T, tres

Visbreakingmild conditions

Delayed Cokinglong residence time (24 h)

Flexicokingcombination thermal cracking and coke gasification/combustion

Steam Crackingproduction lower olefins

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~ 10 wt%

~ 80 wt%

Heavy gas oil

Fractionator Vacuum fractionator

Gasoline

FlashReactor

Cracked residue

Light gas oil

730 K20 bar1-8 min

Furnace

Visbreaking

Vacuum residue

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UnstabilizedNaphtha

Gas

Furnace Fractionator

CokeFeed

Coke drums Gas oil stripper

Gas oil

2 bar

24 h

770 K

710 K

Delayed Coking

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Modern oil refinery

Crude oil

Straight run gasoline

LPG and Gas

Naphtha

Hydro-treating

Reformate

Middle distillates

Heavy atm. gas oil

Solventextraction

Lube base stocks

Gasoline

Vacuum gas oil

Solventdewaxing

Lube oils

Waxes

Gasoline, Naphtha, Middle distillates

Gasoline, Naphtha, Middle distillates

Gasoline, Naphtha, Middle distillates

Slurry oil

Refinery fuel gas

LPG

Gasoline

Solvents

Kerosene

Diesel

Heating oil

Lube oil

Greases

Asphalt

Industrial fuels

Coke

Trea

ting

and

Blen

ding

Delayed coker / Flexicoker

Propanedeasphalter

Hydro-treating

Catalyticreforming

Catalyticcracking

Visbreaker

Hydro-cracking

Fuel oil

Asphalt

LPG and Gas

Cycle oil

Alkylation AlkylateLPG

Hydro-treating

Vacu

umD

istil

latio

nAt

mos

pher

icD

istil

latio

n

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Octane Numbers, Boiling Points•• nn--pentanepentane 6262 309 K309 K•• 22--methyl butanemethyl butane 9090 301301•• cyclopentanecyclopentane 8585 322322•• nn--hexanehexane 2626 342342•• 2,22,2--dimethylbutanedimethylbutane 9393 323323•• benzenebenzene >100>100 353353•• cyclohexanecyclohexane 7777 354354•• nn--octaneoctane 00 399399•• 2,2,32,2,3--trimethylpentanetrimethylpentane 100100 372372•• methylmethyl--tertiarytertiary--butylbutyl--etherether 118118 328328

•• straight run gasolinestraight run gasoline 6868 67 (MON)67 (MON)•• FCC light gasolineFCC light gasoline 9393 8282•• alkylatealkylate 9595 9292•• reformate reformate (CCR)(CCR) 9999 8888

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Cetane Numbers•• nn--alkanesalkanes 100100--110110•• nn--hexadecane (cetane)hexadecane (cetane) 100100•• isoiso--alkanesalkanes 3030--7070•• alkenesalkenes 4040--6060•• cycloalkanescycloalkanes 4040--7070•• alkylbenzenesalkylbenzenes 2020--6060•• naphtalenesnaphtalenes 00--2020•• αα--methyl naphthalenemethyl naphthalene 00

•• straight run gas oilstraight run gas oil 4040--5050•• FCC cycle oilFCC cycle oil 00--2525•• thermal gas oilthermal gas oil 3030--5050•• hydrocracking gas oilhydrocracking gas oil 5555--6060

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Product DistributionThermal versus Catalytic Cracking

0

20

40

60

80

100

120

140

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Carbon Number

mol

per

100

mol

cra

cked

n-C

16 Thermal

Catalytic

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CH2 C CH3C+H3CCH3 CH3

CH3

H3C CCH3

CH2 + C CH3

CH3

CH3+

Catalytic Cracking•• World capacity: > 500 million metric ton/yearWorld capacity: > 500 million metric ton/year

•• Reactions:Reactions:–– CC--C bond cleavage:C bond cleavage:–– IsomerizationIsomerization–– ProtonationProtonation//deprotonationdeprotonation–– AlkylationAlkylation–– PolymerizationPolymerization–– CyclizationCyclization, condensation , condensation coke formationcoke formation

“β scission”

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+ H + o rC H C H 2R C H 2 C +RH

HR C + C H 3

H

Alkenes:

via carbenium ions

Stability: tertiary > secondary > primary > ethyl > methyl

+ H+ C +RH

HHC H3 + H2C H2 C H3R R C + C H3

H

Alkanes:

via carbonium ions

Or, if carbenium ions are present:

C H 2 C H 2 C H 3C +H 3CC H 3

H 3C C C H 2 C H 2 C H 2 C H 3

H

H

+

+

H 3C C C H 2 C H 2 C H 2 C H 3

H

C H 2 C H 2 C H 3C HC H 3

H 3C+

Cracking Mechanism

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+

H3C CH2 CH2 CH2 CH2 CH2 CH3

H3C CH CH3

CH3

H3C CH CH2 CH2 CH2 CH2 CH3

H3C CHCH2

CH CH3CH2CH2

H+

CH CH3H2C

H3C CH CH3

CH3

H3C CH CH CH2 CH2 CH3

CH3

+

hydride shifts +C-C bond breaking

hydride transfer

Isomerization

etc.

Protonated cyclopropane

Classical carbenium ion

Initation

n-Alkene

n-Alkane

iso-Alkane

+

+

Cracking Mechanism

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Mechanism: HMechanism: H++ donor or Hdonor or H-- acceptor acceptor acid sitesacid sites

Catalysts for FCC

OriginallyOriginally•• AlClAlCl33 solution:solution:

–– corrosioncorrosion–– waste streamswaste streams

SubsequentlySubsequently•• Clays (acidClays (acid--treated)treated)•• Amorphous silicaAmorphous silica--aluminaalumina

–– more stable and more selectivemore stable and more selective–– better pore structurebetter pore structure–– better attrition stabilitybetter attrition stability

•• ZeolitesZeolites–– even more active and stable (less coke, higher thermal stabilityeven more active and stable (less coke, higher thermal stability))

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4.5

5

5.5

6

6.5

7

1960 1965 1970 1975 1980 1985 1990 1995

Year

Feed

thro

ughp

ut (m

illion

bar

rels

/day

)Capacity required with amorphous catalysts(extrapolated)

Capacity with zeolitic catalysts(actual situation)

Catalytic Cracking Capacity in the US

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-

-

silica-alumina:

silica:

SiO

OO

Si

Si

Si SiO

OOO

Si

Si

SiOH H++

OO

O

Si

Si

SiO

OOO

Si

Si

Si H++Al HO Si Al Si

Weak acid

Strong acid

Cracking Catalysts

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• Large number found and/or synthesized

• Total porosity up to 0.5 ml/g

• Examples:

Supercage0.8 nm

Sodalite cage

FAU

SOD

LTA

Y (Faujasite)Zeolite A

Sodalite

Zeolites

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RECl3, NH4Cl

Wash liquor

Sodium silicate

Sodium aluminate

Water

NaOH

Al2O3 source

SiO2 source

Water

NaOH

Na zeolitecrystallization

Silica-aluminasynthesis

Filter Dryer

Mixer

Ion exchange

FCC catalyst particles

Spray dryer

Matrix material

Zeolite

matrixzeolite (dp = 2-10 µm)

50-70 µm

Micro pores < 3 nmMeso pores 3 - 50 nmMacro pores > 50 nm

Production of FCC catalyst

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Coke: carbon deposited

“Mixed Blessing”

• Catalyst poisoned

• Regeneration provides heat

0

20

40

60

80

100

1950s 1960s 1970s 1980s

% w

t on

feed

Gas

LPG

Gasoline

LCO

HCO/slurry

Coke

Amorphous ZeoliteLow Al High Al REY USY

Product Distribution of Gas Oil Cracking

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Cracking

C + O2→ CO / CO2

Air

Flue gas

Spent catalyst

Regenerated catalyst

Feed

To fractionation

970 K

775 K

SteamGrid

2-stage Cyclones

Regenerator Reactor

Riser

Fluidized bed

Fluidized bed

2-stage Cyclones

FCC: Fluidized-bed Reactor and Regenerator

Latermuch moreactive catalyst

Consequencesfor process?

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Modern FCC Unit: Riser Reactor

waste heat boiler

compression

expansion

catalyst fines

propane

propene

butane

butene

L/L sep.water

G/L sep.gas (C2 and lighter)

slurry oil

light cycle oil

heavy cycle oil

flue gas

spent cat.

regenerated cat.

steam

riser

steam

cyclones

FeedAir

Gasoline

Regenerator Reactor Fractionator Absorber Debu-tanizer

Depro-panizer

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0 20Time (s)

Cat

alys

t fra

ctio

n (a

.u)

Total area = 1

Riser Reactor: Plug flow Reactor??Residence Time Distribution ?

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Reactor Regenerator

Temperature (K) 775 973

Pressure (bar) 1 2

Residence time 1-5 s minutes/half hour

Typical Conditions in Riser FCC

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Sulfur Distribution in FCC Products

“product” % of sulfur in feed ton/day* S (SO2)H2Sliquid productscoke → SOx

50 ± 1043 ± 5 7 ± 3

83.671.911.7 (23.3)

•• Capacity: Capacity: 50000 barrels /day50000 barrels /day•• catalyst / oil ratio: catalyst / oil ratio: •• Catalyst inventory: Catalyst inventory: •• Catalyst Catalyst recirculationrecirculation rate: rate: •• feedstockfeedstock sulfursulfur content:content: 2 wt%2 wt%

6 kg/kg6 kg/kg500 ton500 ton50000 ton/day50000 ton/day

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Removal of SO2 in FCC unit

Is it possible to reduce emission of SOIs it possible to reduce emission of SO22 at low at low investment???investment???

•Change selectivity catalyst?•Add novel catalyst?•………………..

ClueSome sulphates stable under oxidation and unstable under reducing conditions

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Removal of SO2 in FCC unit

Oxidation of SO2 in regenerator and adsorption of SO3 on MO:

Reduction of metal sulfate in riser and release of H2S:

Regeneration of metal oxide in stripper with release of H2S:

2 SO2 + O2 → 2 SO3

SO3 + MO → MSO4Stable in oxidizing conditions

MSO4 + H2 → MSO3 + H2O

MO + H2Sor

MS + H2O

MS + H2O → MO + H2S

M: Ce, Mg,..

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Novel Developments in FCC0.51 - 0.55 nm

Production of light alkenes (CProduction of light alkenes (C33==, C, C44

==))–– addition of ZSMaddition of ZSM--55–– ApplicationApplication

»» petrochemical feedstockpetrochemical feedstock»» isobutene for MTBE, ETBEisobutene for MTBE, ETBE

Processing of heavier feedstocksProcessing of heavier feedstocks–– improved reactors, strippers, feed injection, gas/solid separaimproved reactors, strippers, feed injection, gas/solid separationtion–– application of catalyst cooling and high application of catalyst cooling and high TT

»» much higher coke production, metal deposits, more much higher coke production, metal deposits, more sulfursulfur

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Hydrotreating and HydrocrackingHYDROTREATINGHYDROTREATING•• Conversion with hydrogenConversion with hydrogen•• Reactions: hydrogenation &Reactions: hydrogenation & hydrogenolysishydrogenolysis•• Removal of heteroRemoval of hetero--atoms (S, N, O)atoms (S, N, O)•• Some hydrogenation of double bonds & Some hydrogenation of double bonds &

aromatic ringsaromatic rings•• Molecular size not drastically alteredMolecular size not drastically altered•• Also termedAlso termed hydropurificationhydropurification

HYDROCRACKINGHYDROCRACKING•• Similar to hydrotreatingSimilar to hydrotreating•• But, drastic reduction in molecular sizeBut, drastic reduction in molecular size

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Objectives Hydrotreating

•• Protection of the environmentProtection of the environment–– reduction acid rainreduction acid rain

•• Protection of downstream catalystsProtection of downstream catalysts–– in further processingin further processing–– SS--compounds in Diesel fuel give difficulties in catalytic compounds in Diesel fuel give difficulties in catalytic

cleaning of exhaust gasescleaning of exhaust gases

•• Improvement of gasoline properties Improvement of gasoline properties –– odour, colour, stability, corrosionodour, colour, stability, corrosion

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Hydrotreating Reactions

5) Phenols

4) Pyridines

3) Benzothiophenes

2) Thiophenes

1) Mercaptans

5

5

3

RSH +

+

+

+

+

+

+

+

+

H2

H2

H2

H2

H2

RH

S

S

H2S

H2S

H2S

+ NH3

H2O

N

OH

HDSHDS

HDSHDS

HDSHDS

HDNHDN

HDOHDO

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0 1 2 3 4 5

1000/Temperature (1/K)

0

10

20

30

40

50

60

70

80

90

100

S

S

CH3SH

lnK e

q

Industrial conditions600-650 K

Equilibrium data

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Naphtha Gas Oil� Temperature (K): 590 - 650 600 - 670� Pressure (bar): 15 - 40 40 - 100� H2/oil (Nm3/kg): 0.1 - 0.3 0.15 - 0.3 � WHSV (kg feed/(m3 catalyst)/h) 2000 - 5000 500 - 3000 � Catalyst: mixed metal sulfides (CoS and MoS2 or NiS and WS2

on Al2O3)

γ-Al2O3

‘CoMoS’S

CoMo

Typical process conditions

Process design ???

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Inert beads

Catalyst bed

Distributor

Support grid

Product

Gas + liquid

Catalyst particle with liquid film

Gas

DeflectorGas

Liquid

Complete wetting

Incomplete wetting

Trickle-bed Reactor

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steam

Hydrogen

hydrogen recycle to H2S removal

Sour water

Product

SeparatorStripperHot HP separator

ReactorFurnace

Gas (C3

-)

Recycle gas scrubbing

NaphthaCold HP separator

H2S

water

Hot LP separator

Hydrotreating Process (trickle bed)

Feed

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Development of maximum Sulfur Content in automotive Diesel in Europe

Year

1 2 3 4

3000

500 35050

0

500

1000

1500

2000

2500

3000

3500

1996 2000 2005< 1996

Max S in Dieselppm

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Activity of Various Catalysts for HDS ofPretreated Gas Oil

CoMo/γ-Al2O3260 ppm

NiW/γ-Al2O3

PtPd/ASA (I)

Pt/ASA

Feed 760 ppm

NiMo/γ-Al2O3230 ppm

200 ppm

140 ppm

60 ppm

S

CH3

S

CH3

SCH3

C2H5

SCH3

Retention time

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1

10

100

1000

10000

0 0.5 1 1.5 2

FCC feedstock sulfur, wt.%

FCC

gas

olin

e su

lfur,

ppm

w

untreated feed

FCC feedstock sulfur, wt.%

FCC gasoline S

ppmw untreated feed

Effect of HDS of FCC feedstock on gasoline sulfur content