alkylasi, reforming, dan isomerisai
TRANSCRIPT
PRESENTATION MATERIAL FOR ISOMERISATION,
PLATFORMING, AND ALKYLATION
Bandung, 20 April 2011
Crude Distillation Column
Desalter
Vacuum Distillation Column
Desalter
VacuumGas Oils
Vapor Recovery Units
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Sulfur Removal
Sulfur Removal
Hydrotreating Units
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Hydrotreating Unit
Sulfur Removal
Hydrotreating Unit
Catalytic Reformer
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Hydrotreating Unit
Sulfur Removal
Hydrotreating Unit
Isomerization Unit
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Hydrotreating Unit
C5/C6 Isomerization
Sulfur Removal
Hydrotreating Unit
Fluid Catalytic Cracking Unit
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Fluid Catalytic Cracking Unit
Hydrotreating Unit
C5/C6 Isomerization
Sulfur Removal
Hydrotreating Unit
Hydrocracking Unit
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Hydrocracking Unit
Fluid Catalytic Cracking Unit
Hydrotreating Unit
C5/C6 Isomerization
Sulfur Removal
Hydrotreating Unit
Alkylation Unit
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Fluid Catalytic Cracking Unit
Hydrocracking Unit Alkylation
Hydrotreating Unit
C5/C6 Isomerization
CatalyticCondensatio
n
Sulfur Removal
Hydrotreating Unit
Residual Units
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Fluid Catalytic Cracking Unit
Hydrocracking Unit Alkylation
Hydrotreating Unit
C5/C6 Isomerization
CatalyticCondensatio
n
Sulfur Removal
VisbreakingThermal Cracking
AsphaltAsphalt
Oxidation
Hydrotreating Unit
Coking Unit
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Fluid Catalytic Cracking Unit
Hydrocracking Unit Alkylation
Coking
Hydrotreating Unit
C5/C6 Isomerization
Sulfur Removal
CatalyticCondensatio
n
Hydrotreating Unit
Focus of Discussion
Desalter
VacuumGas Oils
Saturate Vapor Recovery
Unsaturate Vapor Recovery
Hydrotreating Unit
Hydrotreating Unit
Hydrotreating Unit
Sulfur Removal
Catalytic Reformer
Fluid Catalytic Cracking Unit
Hydrocracking Unit Alkylation
Coking
Hydrotreating Unit
C5/C6 Isomerization
Sulfur Removal
CatalyticCondensatio
n
Hydrotreating Unit
ParaffinIsomerization
Paraffin Isomerization Background• WWII requirement for iso-butane for alkylation• 1941 – 1st unit based on Friedel-Craft chemistry
– Used corrosive aluminum chloride catalyst– High costly maintenance– 38 units fulfilled needs of the time
• 1950s – Development of high temperature dual function, reforming-like catalyst systems
• 1959 – 1st C4 unit based on low temperature dual function catalyst systems
• 1969 – 1st C5/C6 unit; • 1970s - Industry-wide lead reduction created need to
upgrade C5-C6 octane.• 2000s – Benzene reduction added benefit
Paraffin Isomerization• Conversion of normal paraffins to iso-paraffins is
one type of isomerization• Principal application of isomerization is the
conversion of normal C4, C5 and C6 material
• Butane (C4) Isomerization provides iso-butane feed to an alkylation process or MTBE Complex
• Pentane (C5) – Hexane (C6) Isomerization provides higher octane (82-91 RONC) components to the gasoline pool– Gasoline is less aromatic when C5/C6 isomers are added– Benzene saturation side reaction helps meet aromatic
concentration standards
Component Blended Octane ValuesComponent RONC MONC iC4 100.2 97.6 nC4 95.0 93.5 iC5 93.5 89.5 nC5 61.7 61.3 Cyclopentane 102.3 85.0 22 DMB 94.0 95.5 23 DMB 105.0 104.3 2 MP 74.4 74.9 3 MP 75.5 76.0 nC6 31.0 30.0 MCP 96.0 85.0 Cyclohexane 84.0 77.2 Benzene 120.0 114.8 Feed C7- 55.0 55.0
C5 - C6 Isomerization Terms
• Product Ratios, wt% or mol%– iC5/C5P = iC5/(iC5+nC5) x 100%– 2,2DMB/C6P = 2,2DMB/C6 Paraffins x 100%– 2,3DMB/C6P = 2,3 DMB/C6 Paraffins x 100%– C6 Paraffins = 2,2DMB + 2,3DMB + MP + MCP + CH + nC6
• PIN (Paraffin Isomerization Number), wt%– Σ (iC5/C5P + 2,2DMB/C6P + 2,3DMB/C6P)
• Feed X-factor, wt%– Σ (MCP + CH + BZ + C7+)
Component Iso Ratios
Lt SR Naphtha Product Octane 72 RONC 83 RONC iC5/C5P 40 77 22 DMB/C6P 2 32 23 DMB/C6P 5 10 2 MP/C6P 31 30 3 MP/C6P 19 17 nC6/C6P 43 11
C5 - C6 Isomerization Process Benefits
• High C5+ product yields (99-100 volume%) • 100% benzene saturation• Low severity reactor operations
– Typical: 450 psig (31.5 kg/cm2(g))– 250-400°F (120-204C)
• Excellent catalyst stability – Up to 10-15 year catalyst lives
• Capable of processing wide range of feedstocks
Isomerization Feedstocks
• C4 Isomerization– Vapor Recovery Unit Butane– Alkylation Product Butane
• C5/C6 Isomerization– Light Straight Run Naphtha– Feed Fractionation
• Feed should consist of C5 and C6 material
• C7 material should be kept to a minimum
Chemistry
• Isomerization• Benzene Saturation• Ring Opening• Hydrocracking
Reactions take place over a dual function catalyst- Metal function (platinum)- Acid function (chloride)
Isomerization Reactions
C
Methylcyclopentane (MCP)
96.0 RON
Cyclohexane (CH)84.0 RON
C-C-C-Cn-Butane (nC4) Isobutane (iC4)
C-C-CC
C-C-C-C-Cn-Pentane (nC5)
61.7 RONIsopentane (iC5)
93.5 RON
C-C-C-CC
Isomerization Reactions
C-C-C-C-C-Cn-hexane (nC6)
31.0 RON
2-Methylpentane (2MP)74.4 RON
C-C-C-C-CC
3-Methylpentane (3MP)75.5 RON
C-C-C-C-CC
2,3-Dimethlybutane (2,3DMB)105.0 RON
C-C-C-CC
C2,2-Dimethylbutane (2,2DMB)
93.5 RON
C-C-C-CC
C
Isomerization Reactions
• Requires metal and acid functions• Equilibrium limited• Slightly exothermic• No hydrogen consumed• Increases octane
Benzene Saturation• Benzene saturates to cyclohexane• Cyclohexane (CH) in equilibrium with
methylcyclopentane (MCP)
C
MCPentane96.0 RON
Cyclohexane84.0 RON
Benzene120.0 RON
100% 40-60%3H2 + Pt
Benzene Saturation Reaction
• Immediate with platinum sites and presence of hydrogen• No acid sites required• 100% complete• Highly exothermic (25x isomerization, 5x hydrocracking)• Consumes 3 moles H2 per mole of benzene• Reduces octane (120 Bz 84 CH & 96 MCP)• Limit Bz in feed to ~5 vol%
– ~20ºF (11ºC) rx bed deltaT / 1 vol% Bz– ~100ºF (55ºC) total deltaT / reactor
Lead Rx
DT 1DT 2
DT 4DT 3Lead Rx
DT 1DT 2
DT 4DT 3
Ring Opening Reactions
• CH and MCP open to C6 paraffins• Cyclohexane (CH) in equilibrium with
methylcyclopentane (MCP)
C
MCPentane96.0 RON
Cyclohexane84.0 RON
Benzene120.0 RON
100% 40-60%3H2 + Pt
C-C-C-C-C-C
30% 30%
Ring Opening Reactions
• Competes for the platinum sites• Moderately exothermic• 20-40 wt% opening• Consumes 1 moles H2 per mole of ring opened• Reduces octane• Necessary to prevent cyclic buildup with DIH• Increases with lead reactor temperature increases• Higher temperatures favor MCP
Hydrocracking
• Longer chain molecules break to smaller ones
R-C-C-C + H2 R-H + C-C-CC
H
C
Hydrocracking• Triggered by high reactor temperatures and catalyst
acid sites• Exothermic• Consumes 1 moles H2 per mole of cracked material• C5 and C6 paraffin hydrocracking is minimal• About 50% of C7+ paraffins hydrocrack to C4 and C3
paraffins• C5+ yield loss• Caused by:
– Higher C7+ in feed– Higher rx temperatures pushing equilibrium– Temperature excursion
Isomerization Catalyst• Dual function catalyst (metal/acid)
– Metal is always platinum– Acid is always chloride
• Metal impregnated on a high surface area alumina-oxide• Active sites are bound alumina-chloride• Gray extrudate or gray trilobe extrudate
• Dual function balance is maintained by:– Perchloroethylene injection
• Sensitive to contaminants and non-regenerable
Cl
Pt
Cl
Pt
Cl
Pt
Cl
Pt
Cl
Pt
ClCl
Pt
Catalyst Promotor - Chloride
ClClCl-Cl-
HH++ClCl--
Cl-Cl-Cl-Cl-
Cl-Cl-Cl-Cl-
H2H2C5C5
C6C6
C5, C6, H2, HClC5, C6, H2, HCl
• Continuous chloride injection required to maintain activity.
- Hydrogen and hydrocarbon can strip bound chlorides from the catalyst if the partial pressure of chloride
surrounding the catalyst is too low.• Low or loss of chloride injection will permanently
deactivate the catalyst.
Reactor Feed ContaminantsContaminant Effect Limit
Total sulfur Attenuates metal activity, reduces benzene saturation, reversible
0.1 wtppm max.
Nitrogen Organic/Basic
Neutralizes acid sites, deactivates catalyst, irreversible; NH4Cl fouling
0.1 wtppm max.
Water Removes bound chloride, blocks active sites, plug flow, irreversible1 lb H2O kills 100 lb catalyst
0.1 wtppm max.
Oxygenates OH groups displace Cl, neutralizes acid site, irreversible
0.1 wtppm max.
Fluorides Displaces chloride, less acidic, irreversible (very rare)
0.1 wtppm max.
Metals Block active sites, attach Pt, plug flow, irreversible (Mercury, Co, Ni)
ppb
Makeup Gas ContaminantsContaminant Effect Limit
Sulfur (H2S) Attenuates metal activity, reduces benzene saturation, reversible
1 molppm
Nitrogen Organic
Neutralizes acid sites, deactivates catalyst, irreversible; NH4Cl fouling
0.5 molppm
Water Removes bound chloride, blocks active sites, plug flow, irreversible1 lb H2O kills 100 lb catalyst
0.1 volppm
CO + CO2 CO2 irreversibly adsorbs on drier sieve hence higher spec, less reactive than CO on catalyst
10 molppm max.
CO Attaches to metal, similar to sulfur, eventually methanates with H2, somewhat reversible
1 molppm max.
Chloride (HCl) Adsorbs on drier sieve, irreversible 0.5 molppm
Note: Limits at drier inlet except water spec
Contaminants – Final Words• CO/CO2 & HCl are the most common makeup gas
problems• Cyclics can act as temporary poison
– Adsorbs on the catalyst– Inhibits isomerization equilibrium & hence conversion– Monitor X-factor
WATER, WATER, WATER!
Water Ingress Mitigation Techniques• Acidizing of all equipment in the reactor circuit• Dry nitrogen blanketing of reactor circuit equipment
– If exposed to air during maintenance, must be re-acidized
• Tube rolling and strength welding to charge heater exchanger tubesheet
• Catalyst handling & loading under inert atmosphere• All liquid feed MUST be charged directly from NHT
stripper bottoms or naphtha splitter overhead after NHT• Regenerative driers on makeup gas and feed streams• Moisture analyzers between lead & lag driers.• Dry hydrogen as feed surge drum pressure medium
Prevention is much easier than curing the problem
Isomerization Unit Basics• Feed and makeup hydrogen driers• Switchable lead/lag reactors• Reactions under nominal hydrogen atmosphere
– Isomerization reaction hydrogen neutral
• Exothermic equilibrium and saturation reactions require inter-reactor cooling
• To maintain product quality, severity (temperature) must be gradually increased– Performance gradually deteriorates– Catalyst non-regenerable
• Fractionation (stabilizer) to remove acid gas
Butane Isomerization Process(UOP Hydrogen Once Through Butamer)
Receiver
Isomerate
Stabilizer
Reboiler
Treated Butanes
Condenser
Gas to Scrubbingand FuelSteam
C2Cl4
MU GasDriers
Reactors
Make-upHydrogen
LiquidDriers
Pentane-Hexane Isomerization (UOP Hydrogen Once Through Penex)
Receiver
Isomerate
Stabilizer
Reboiler
Fresh/SpentCaustic
Gasto Fuel
Scrubber
MU GasDriers
Reactors
LiquidDriers
Make-upHydrogen
LightNaphtha
SurgeDrum
C2Cl4
SteamHeater
CCFEHCFE
Pentane-Hexane Isomerization (UOP Recycle Gas Penex)
Receiver
Isomerate
Stabilizer
Reboiler
Fresh/SpentCaustic
Gasto Fuel
Scrubber
MU GasDriers
Reactors
LiquidDriers
Make-upHydrogen
LightNaphtha
SurgeDrum
C2Cl4
SteamHeater
HCFE CCFE
Pentane-Hexane Isomerization with DIH
Increased Octane – More C6 isomers producedBetter for RVP limits
Increases LHSV – recycle offsets
ProductSide DrawMPs, n-C6
Deisohexanizer (DIH)
Bottoms C7+, min n-C6
OverheadC5p, DMB
LP Stm
Receiver
Isomerate
Stabilizer
ReboilerFresh/Spent
Caustic
Gasto Fuel
Scrubber
MU GasDriers
Reactors
LiquidDriers
Make-upHydrogen
LightNaphtha
SurgeDrum
C2Cl4
SteamHeater
CCFEHCFE
H.O.T. Penex
Light Naphtha - FractionationComponent Boiling Point F [C]
Relative Volatility
iC5 82 [28] 3.18 nC5 97 [36] 2.71 22 DMB 122 [50] 1.90 23 DMB 136 [58] 1.59 2 MP 140 [60] 1.53 3 MP 146 [63] 1.42 nC6 156 [69] 1.26 MCP 161 [72] 1.21 Bz 176 [80] 1.25 CH 177 [81] 1.00
Process Variables
C4 Unit C5/C6 UnitPressure 500 psig
(34 bars) 250-500 psig (17-34 bars)
Temperature 300-350F (150-175C)
280-330F (138-166C)
H2/HCBN Ratio 0.05 mol/molAt Outlet
0.05 mol/molAt Outlet
LHSV, hr-1 2-4 1-4Chloride Promotor ~150 wt ppm ~150 wt ppm
Paraffin IsomerizationProcess Variables
• Reactor Temperature– Main process variable– Higher iso ratio (octane) possible at lower temperature– Reaction rate faster at higher temperature– Higher temperature increases cracking and reduces
catalyst life– Lead reactor outlet temperature runs higher than lag
reactor outlet temperature
iC5/C5P
iC4/C4P
Equilibrium Curves
0
20
40
60
80
100
200 250 300 350 400Temperature (F)
Prod
uct R
atio
s (m
ol%
)
MCP/(MCP+CH)(2MP+3MP)/C6P
2-3 DMB/C6P
2-2 DMB/C6P
nC6/C6P
121 C 149 C 177 C
Lag
Rx
Lead
Rx
Octanes of Equilibrium Mixtures
Total C5-C6
C5 Paraffins
C6 Paraffins
7072747678808284868890
100 150 200 250 300Temperature, °C
RO
N
302ºF 392ºF
Lag
Rx
Lead
Rx
Lead and Lag Rx IC5 Product Ratio
400330
EOR
EOR
350240
SOR
SOR
77
45
72
Reactor Outlet Temperature, F
IC5 Product Ratio Equilibrium
IC5/
C5 P
ARAF
FIN
S PR
OD
UCT
RAT
IO, W
t%
Feed (Minimum)116 C 167 C 204 C
Reactor Temperature ProfileExample
100
110
120
130
140
150
160
A Inlet
A Outl
et
B Inlet
B Outl
et
Tem
pera
ture
, C
© 2006 UOP LLC. All rights reserved.
Paraffin IsomerizationVariations
Isomerization Octane Portfolio
556065707580859095
LightNaphtha
Feed
Par Isom Penex PenexDIH
PenexMolex
DIP PenexDIH
RO
NC
60-7060-70
8585
Once Through Hydrocarbon Recycle
8888 89899191
8181
Relative Erected CostsIsomerization Flow Schemes
3.03.0R
elat
ive
Ere
cted
Cos
t 2.52.5
1.51.5
1.01.0
00Par-Isom
Penex Penex/
DIH
PenexMolex
DIP/Penex/DIH
2.02.0
0.50.5
© 2006 UOP LLC. All rights reserved.
Catalytic Reforming
History• Development during and after WWII• Commercialized in 1949 to meet increase demand for
motor fuel post-WWII– Mono-metallic catalyst (platinum)
• Bi-metallic catalyst introduced in 1969• Continuous catalyst regeneration (CCR) introduced in
1970• Licensees have different names but all are reforming
processes
Catalytic Reforming
• Catalytic reforming upgrades low octane naphthas to higher octane motor fuel by promoting specific groups of chemical reactions, primarily to produce high octane aromatics
• Reforming is the mainstay of almost all fuels refineries• Originally, reformate was used to upgrade the gasoline
pool• Today the reforming process is also designed to
produce specific aromatic hydrocarbons for use in the petrochemical industry
• High purity hydrogen and LPG are important and valuable byproducts
Process FeedstocksProcesses feed stocks from various sources
Hyd
rotr
eate
r
Ref
orm
er
S.R. Naph.FCC Naph.T.C. Naph.Coker Naph.H.C. Naph.
Reformate
Contaminates
Lt. HCBN
Hydrogen
Feedstock Properties
• Feed is normally a C6 to C11 fraction for motor fuel applications– 170-400F (77-204C) D-86 Distillation Range– Sulfur 0.25-0.5 wt-ppm min– Nitrogen less than 0.5 wt-ppm– No olefins, metals, halides or oxygenates
• Narrow range, e.g. C6-C8, for petrochemical applications• Difficulty of reforming basically set by distillation and
PONA (paraffins, olefins, naphthenes, aromatics)– Lean naphtha
• High paraffin, low naphthene content– Rich naphtha
• Low paraffin, high naphthene content
Feed Type Impact on Product Yield
• Conversion of lean and rich naphthas to moderate octane reformates at constant operating conditions
P
N
AA
P
A
P
N
A
P
A
}
}
}}}
}
}}
}}
}
LeanNaphtha
RichNaphthaReformate Reformate
Loss Loss
NFrom P
From NFrom A
From P
From N
From ALegendP = ParaffinsN = NaphthenesA = Aromatics
Loss: Due to both cracking and shrinkage
NP
N
AA
P
A
P
N
A
P
A
}
}
}}}
}
}}
}}
}
LeanNaphtha
RichNaphthaReformate Reformate
Loss Loss
NFrom P
From NFrom A
From P
From N
From ALegendP = ParaffinsN = NaphthenesA = Aromatics
Loss: Due to both cracking and shrinkage
N
Reforming Chemistry• Aromatics
– Pass essentially unchanged through the reactors• Naphthenes
– Almost complete conversion to aromatics, above 90 RONC– Cyclohexanes easier to convert than cyclopentanes
• Paraffins– Some conversion to aromatics– Some isomerization to more highly branched isomers– Some cracking– Many remain in product as paraffins
• Difficulty generally increases with decreasing number of carbon atoms
RONC = Research Octane Number, Clear
Reforming Catalyst• Dual function catalyst (metal/acid)
– Metal is always platinum– Acid is almost always chloride
• Other metals usually added for stability and/or yield improvement
• Metals impregnated on a high surface area alumina-oxide base. Bases are usually 1/16-1/8 inch (1.6-3.2 mm) diameter spheres or extrudates of various configurations and lengths.
• Regenerable• Dual function balance maintained by:
– Water-chloride control– Regeneration technique
Reforming Reactions
• Naphthene dehydrogenation• Naphthene isomerization• Paraffin isomerization• Paraffin dehydrocyclization• Hydrocracking• Demethylation• Aromatic dealkylation
Naphthene Dehydrogenation
• Formation of an aromatic from cyclohexanes• Reaction is easy and very rapid• Reaction is very endothermic (consumes heat)• Hydrogen is produced• Reaction is promoted by the catalyst metal function• Reaction favored by high temperature and low pressure
SR R
+ 3H2
Naphthene Isomerization
• Enables N5 napthenes to convert to aromatics• Naphthene isomerization converts branched
alkylcyclopentanes to alkylcyclohexanes, then to aromatics• Ring opening occurs, so paraffins may be produced• Reaction is promoted by both acid and metal functions• Reaction favored by low temperatures; little pressure influence.
S R SR'
Paraffin Isomerization
• Paraffin isomerization occurs readily• Branched isomers are higher in octane than straight chained
molecules• Reaction is slightly exothermic and equilibrium limited• Hydrogen neutral• Reaction is promoted by both acid and metal functions• Reaction favored by low temperatures; little pressure influence.
– Low temperatures favor higher iso-/normal ratios– Higher temperatures increase the reaction rate
R-C-C-C-C-C-C R-C-C-C-C-CC
Paraffin Dehydrocyclization
• Ring closure - conversion of paraffins to naphthenes– Required for conversion of paraffins to aromatics
• Slowest and most difficult reforming reaction to promote• Reaction is endothermic• Hydrogen in produced• Reaction promoted by both acid and metal functions• Reaction favored by high temperature and low pressure
R-C-C-C-C-C-C
R'
SR"
+ H2
+ H2
S
Hydrocracking
• Splitting of longer, chained molecules into shorter, lighter compounds– Reduces reformate yield– Increases light ends yield– Serves to concentrate aromatics; therefore, increases octane
• Reaction is exothermic and hydrogen is consumed• Reaction is promoted by the catalyst acid function• Reaction favored by high temperatures and pressures
R – C – C – C + H2
CRH + C – C – C
C
H
Demethylation
• Removal of methyl groups from branched compounds• Only occurs in severe operations or on initial startup• Reaction is exothermic and consumes hydrogen• Promoted by the catalyst metal function• Reaction favored by high temperature and pressure
R–C–C–C–C + H2 R–C–C–CH + CH4
andR-C + H2
RH+ CH4
Aromatic Dealkylation
R+ H2
R'+ R"
• Removal or splitting of alkyl groups from aromatic compounds
• Reaction is exothermic and consumes hydrogen• Promoted by the catalyst acid and metal functions
• Reaction favored by high temperature and pressure
Reaction Scheme
Acid M = Metal =
CrackedProducts
N-Paraffins
M or A M / A
M / AM or A
CyclopentanesA
A
NaphtheneIsomerization
Cyclohexanes
Dehydrogenation
Aromatics
Dealkylationand
Demethylation
LighterAromatics
M M or A
Isoparaf fins
I II III Predominant Active Sites: A
Legend:
I II III= Hydrocracking and Demethylation (M) = Paraf fin Isomerization = Dehydrocyclization
Metal/Acid Sites – for dehydrocyclization, hydrocracking, dealkylation
Properly Balanced Catalyst
DesiredDesiredMetal-AcidMetal-Acid
BalanceBalance(Pt)(Pt)
Increasing MetalIncreasing MetalFunctionFunction
DemethylationDemethylation
(Cl)(Cl)Increasing AcidIncreasing Acid
FunctionFunction
CrackingCracking
DehydrogenationDehydrogenationDehydrocyclizationDehydrocyclization
IsomerizationIsomerization
Reactor Feed ContaminantsContaminant Effect Limit
Total sulfur Attenuates metal activity, suppresses dehydrogenation, reversible
0.25-0.5 wtppm min
Total Nitrogen
Neutralizes acid sites, deactivates catalyst, irreversible; NH4Cl fouling
0.5 wtppm max
Water Affects water/chloride balance ~1 wtppm
Oxygen (Dissolved and Combined)
Forms water, affects water/chloride balance
2 ppm as oxygen
Fluorides Displaces chloride, less acidic, irreversible
<0.5 wtppm
Metals Block active sites, attach Pt, plug flow, irreversible (Arsenic, Pb, Cu)
ppb
Catalytic Reforming Basics• Multiple reactors in series• Reactions under hydrogen atmosphere
– Hydrogen producer
• Endothermic reactions require inter-reactor heaters• To maintain product quality, severity (temperature)
must be gradually increased– Performance gradually deteriorates– Catalyst regeneration periodically required to return catalyst
quality back to acceptable levels
• Fractionation (stabilizer or debutanizer) to ‘stabilize’ products– Gasoline RVP adjustment
Types of Reforming Process Units
• Fixed Bed (semi-regen unit)– Unit must be shut down and complete catalyst
inventory is regenerated
• Cyclic Reformer– Catalyst is regenerated one reactor at a time– Unit is on stream continuously
• CCR Platforming Unit– Continuous Catalyst Regeneration– Unit is on stream continuously
Fixed-Bed Semi-Regeneration Reforming
• Catalyst is stationary in separate reactors• Reactors are normally separate and in series• A high H2/HC ratio is used
– Typically between 6-9 mol/mol
• Moderate to high pressure – 300 to 600 psig (21 to 42 bars)
• Water/chloride injections used to balance catalyst performance
Fixed-Bed Semi-Regeneration Reforming
H2O/Cl-
Injection
Net GasFuel Gas
LPG
Reformate
Feed
Reactors
Separator
Debutanizer
CombinedFeed
Exchanger
HH H
H
Cyclic Catalytic Reforming
Flue Gas
Air
Inert Gas Furnace
Furnace Furnace Furnace
Separator
Reformate
Overhead
PretreatedNaphtha
SwingReactor
Reactor Reactor Reactor
H2-Rich Gas
Flue Gas
Air
Inert Gas Furnace
Furnace Furnace Furnace
Separator
Reformate
Overhead
PretreatedNaphtha
SwingReactor
Reactor Reactor Reactor
H2-Rich Gas
UOP CCR Platforming Unit• Catalyst is circulated through the reactor and
regenerator sections– Reactors are stacked with free flowing piping between them– Special equipment used to transport catalyst
• Constant regeneration means a constant catalyst performance throughout most of its life
• Operations at more severe conditions– Lower pressure, less catalyst, higher temperatures, less hydrogen circulation, higher octane
• Reformate product is high quality and consistent
– More hydrogen produced and at higher purity
UOP CCR Platforming Unit with Two-Stage Counter-Current Recontact
LegendRC = Recontact DrumREC = ReceiverCON = Convection Section
RCR
C
Fresh Catalyst
Net Gas
LPGSpentCatalyst
FeedH H
SEP
REC
CON
StackedReactors
H
Debutanizer
Reformate
H
CombinedFeed
Exchanger
LegendRC = Recontact DrumREC = ReceiverCON = Convection Section
RCR
C
Fresh Catalyst
Net Gas
LPGSpentCatalyst
FeedH H
SEP
REC
CON
StackedReactors
HH
Debutanizer
Reformate
H
CombinedFeed
Exchanger
UOP CCR Platforming Unit Atmospheric Catalyst Regeneration Section
LiftEngager
No. 1
CatalystCollector
DisengagingHopper
RegenerationTower
CatalystLift Lines
DustCollector
Lift GasBlower
Hydrogen Lift Gas
SurgeHopper
NitrogenLift Gas
ReductionZone
PlatformingReactors
LockHopper
No. 1
FinesRemovalBlower
LiftEngager
No. 2
Flow ControlHopper
CatalystAdditionHopper
LockHopper
No. 2
RegenerationTower
LockHopper
ReductionZone
SpecialElbows
N2 Seal Drum
DustCollector
IsolationValves
CatalystCollector
Booster Gas
Lift GasL-Valve Assemblies
CatalystAdditionHopper
DisengagingHopper
Nitrogen
Reactors
N2 Lift Gas
IsolationValves
RegenerationTower
LockHopper
ReductionZone
SpecialElbows
N2 Seal Drum
DustCollector
IsolationValves
CatalystCollector
Booster Gas
Lift GasL-Valve Assemblies
CatalystAdditionHopper
DisengagingHopper
Nitrogen
Reactors
N2 Lift Gas
IsolationValves
UOP CCR Platforming Unit CycleMax Regeneration Section
Process Variables• Feed Stock Quality
– Boiling range – 170-400F (77-204C) D-86 – Paraffin/naphthene/aromatic content (PNA)
• Catalyst Type• Reactor Temperature
– 890-1020F (477-550C)– Mostly endothermic reactions
• Space Velocity– 0.8-3.0 hr-1
• Reactor Pressure– 50-600 psig (3.4-42 bars)
• H2/HC Ratio– 2-9 mol/mol
Feed Type Impact on Product Yield
• Conversion of lean and rich naphthas to moderate octane reformates at constant operating conditions
P
N
AA
P
A
P
N
A
P
A
}
}
}}}
}
}}
}}
}
LeanNaphtha
RichNaphthaReformate Reformate
Loss Loss
NFrom P
From NFrom A
From P
From N
From ALegendP = ParaffinsN = NaphthenesA = Aromatics
Loss: Due to both cracking and shrinkage
NP
N
AA
P
A
P
N
A
P
A
}
}
}}}
}
}}
}}
}
LeanNaphtha
RichNaphthaReformate Reformate
Loss Loss
NFrom P
From NFrom A
From P
From N
From ALegendP = ParaffinsN = NaphthenesA = Aromatics
Loss: Due to both cracking and shrinkage
N
Octane-Barrel Yield Response toProduct Octane and Feed Composition
RONCRONC
Oct
ane
- Bar
rel Y
ield
Oct
ane
- Bar
rel Y
ield
per
100
BB
L F
eed
per
100
BB
L F
eed
90906,5006,500
7,0007,000
7,5007,500
8,0008,000
8,5008,500
(Pressure = Constant)(Pressure = Constant)
9292 9494 9696 9898 100100 102102 104104
N + 2A = 40N + 2A = 40
N + 2A = 80N + 2A = 80
N + 2A = 60N + 2A = 60
Reactor Temperature Profile
1.01.00.50.50.250.250.10.100Fraction of Total Catalyst
Tem
pera
ture
, °
C(°
F)
-80-80(-144)(-144)
-60-60(-108)(-108)
-40-40(-72)(-72)
-20-20(-38)(-38)
InletInlet
Hydrocarbon Types ConversionReactor Profile
Fraction of Total Catalyst
Mol
es p
er 1
00 M
oles
of F
eed
CHCHCPCP
PP
AA6060
4040
3030
2020
1010
00
5050
0.00.0 0.100.10 0.250.25 0.500.50 1.01.0
Effect of Pressure on Yield StructurePr
oduc
t Yie
ld, w
t-%
Prod
uct Y
ield
, wt-
%
C5+ ReformateC5+ Reformate
HydrogenHydrogen
Pressure psig (kg/cmPressure psig (kg/cm22))
00
CC1 1 + C+ C2 2 + C+ C3 3 + C+ C4 4
143143(10)(10)
285285(20)(20)
428428(30)(30)
570570(40)(40)
7070
8080
9090
100100
450450(31.6)(31.6)
Average Reactor Pressure, psig (kg/cm2)
Rea
ctor
C5 +
ΔLV
-% Y
ield
00
FB Reforming
400400(28.1)(28.1)
350350(24.8)(24.8)
300300(21.1)(21.1)
250250(17.6)(17.6)
200200(14.1)(14.1)
150150(10.5)(10.5)
100100
Continuous Reforming
112233445566778899
1010
Liquid Yield Variations with PressureContinuous vs. Fixed-Bed Reforming
Lean Middle East Naphtha 100 RONC
“Perfect” Reformer• Low pressure to max yields• High catalyst activity to max octane and aromatics• High on-stream factor• CCR > cyclic > semi-regen
Catalyst Issues
• Contaminants• Feedstock boiling range• Water-chloride balance• High temperatures• Low space velocity• Low H2/HC ratios
Summary – Reforming• Complex high temperature process• 3 types of reformers• Mechanical issues include compressors,
heaters, fractionators, catalyst handling / regeneration
• Critical to refinery profitability octane pool, hydrogen system, aromatics sales
Alkylation Processes
Background
• Alkylation was developed during WWII to make aviation gasoline
• Today its main purpose is to convert light ends into gasoline
• The gasoline is ideal for ultra low sulfur and RFG premium – high MON – low emissions – very low in sulfur, olefins, and aromatics
What is Alkylation?• Alkylation combines C3-C5 olefins with iso-butane to
produce highly-branched, high-octane C7-C9 isoparaffins
• Reaction is catalyzed by strong acids
– HF– H2SO4
– Solid catalysts (UOP Inalk, Alkylene)– Superacids (BF3, HSO3F, HSO3CF3)
Alkylation Feeds
FCC
Alkylate Product
FCC Feed
AlkylationUnit
n-Butane
MixedButanes from
Hydrocracking, ReformingAnd Crude Units
Butamer
Propane
C3/C4 OlefinRich Stream
FCC Products(Gasoline, etc.)
C3/C4 OlefinCoker
Alkylate Product• Ideal RFG Blending Component
– High Octane (RON & MON)• C3=/C4= Feed
– 91-94 RON / 90-93 MON
• C4= Feed– 94-96 RON / 92-94 MON
– No Aromatics– No Olefins– Low RVP
• 3 - 6 psig• Highly Dependant on Fractionation (nC4,iC5)
– Low Sulfur
• 10-15% of Gasoline Pool
Primary Products and OctanesOlefin Primary Products Research Motor
Propylene 2,3-Dimethylpentane 91 892,4-Dimethylpentane 83 84
Isobutylene 2,2,4-Trimethylpentane 100 100
Butene-2 2,2,3-Trimethylpentane 109 1002,2,4-Trimethylpentane 100 1002,3,3-Trimethylpentane 106 992,3,4-Trimethylpentane 103 96
Butene-1 2,2-Dimethylhexane 72 772,4-Dimethylhexane 65 70 2,3-Dimethylhexane 71 79
Pentenes 2,2,3,4-Tetramethylpentane2,2,4-Trimethylhexane
2,2,5-Trimethylhexane 92 902,2,3-Trimethylhexane2,3,4-Trimethylhexane2,3-Dimethylheptane2,4-Dimethylheptane
Chemistry
Alkylation Reaction:
C-C=C-C + C-C-C iC7-9 Alkylate Olefin isobutane Acid
Hydrogen Transfer Reaction:
Olefin + 2 isobutane iC8 Alkylate + C3-C5 paraffins
• Olefins highly soluble in acid, isobutane sparingly so• Reaction requires 6-15 fold excess isobutane for selectivity• Two liquid phases (emulsion) in reactor, reaction occurs in acid phase• Hydrogen transfer reaction makes iC8, which has higher octane• However, it consumes more isobutane and makes light paraffins• In HF alkylation, hydrogen transfer occurs for all olefins• In H2SO4 alkylation, only for C5 and heavier olefins
C
Catalyst Selection
• The current commercial catalysts HF and H2SO4 each have advantages and disadvantages
• Main difference in processes is reactor cooling– HF uses cooling water– H2SO4 uses integral refrigeration
• Feedstock, economics and safety control selection
Acid Selection Criteria
• FeedstockHF better on C3
= and iC4 =
H2SO4 better on C5 = and dirty feeds
• Size and LocationHF cheaper for small units HF requires 1/40 as much acid shippingH2SO4 more favorable with on-site acid plant
• Community SafetyH2SO4 does not form aerosols at alkylation conditions
HF safety requirements reduce its capital advantage
Alkylate RON for Feed Olefins
C3=
1-C4=
2-C4=
iso-C4=
C5=
H2SO4
89
96
96
92
91
HF91
91
97
95
89
Alkylation Yields
Sulfuric Acid AlkylationC3Alkylate C4Alkylate C5Alkylate
iC4con/olefin (v/v) 1.27-1.32 1.1-1.16 0.96-1.14Alkylate yield (v/volefin) 1.75-1.78 1.7-1.78 1.55-1.60
R+M/2 88-91 93-95 91-92Acid con (#/bbl alky) 34-42 13-25 25-34
HF Acid AlkylationC3Alkylate C4Alkylate C5Alkylate
iC4con/olefin (v/v) 1.33-1.41 1.14-1.16 1.17Alkylate yield (C5+) 1.78 1.76 1.85
R+M/2 90-91 92-94 90-91Acid con (#/bbl alky) 0.2 0.1 0.2
HF Acid Unit Features
• Good feedstock flexibility• Low operating cost• Lowest capital cost• Low catalyst usage (0.1-0.2 lb/bbl product)• 95F (35C) reactor temperature• HF acid requires special attention
HF Processes
• Accounts for most of the recent new units• Higher iC4 solubility in acid (2.7%)• Does not require refrigeration, can use cooling water (To=100oF)• Mixing easy due to low interfacial tension• Favored by small remote refiners because of poor availability of cheap
sulfuric acid• Acid recovery by distillation at unit (rerun)• Lower acid costs. Higher yield• Consumes more iC4; makes propane, n-butane• Requires dry feed (HF + H2O corrosive)• Stripper column needed to separate HF from hydrocarbon products (HF is
1% soluble in hydrocarbon)• Economically favored • More toxic, corrosive• Area dominated by safety issues
Sulfuric Acid Features• C4 feeds make best alkylate• Acid is handled more easily• 50F (10°C) reactor temperature requires refrigeration
cooling• Catalyst usage is higher and generally requires offsite
regeneration (13-42 lb/bbl product)• Catalyst costs are usually higher• Large quantities of acid are handled
Acid Properties
Sulfuric Acid• Boiling point 640oF at 1 atm• Specific gravity 1.83• Higher surface tension and
viscosity• Isobutane only slightly soluble in
acid (0.1%)• Less corrosive• Sulfuric acid insoluble in
hydrocarbon phase• $15-120/ton, depending on
location
HF Acid• Boiling point 67oF at 1 atm• Specific gravity 0.93• Low surface tension and viscosity• Isobutane solubility about 30 times
higher (2.7%)• HF+water extremely corrosive • HF acid about 1% soluble in
hydrocarbon phase • $1,700/ton + processing costs
Advantages and Disadvantages of the Acids
Sulfuric Acid+ Higher Octane, less iC5 from
Pentenes+ Non aerosoling+ Less corrosive
+ Less product treating+ Tolerates dirty feedstocks- More Expensive to Build
- Requires refrigeration- High Mixer HP Requirement
- Higher Catalyst Use and Cost- Large Acid Requirement
- Higher Energy Use- Higher CO2 Make
HF Acid+ Higher Octane and Yield from
Propylene, Isobutylene + Recoverable
Lower net catalyst cost+ Cheaper to build No refrigeration
Easier to mixFavored for smaller units - Forms Toxic Aerosols (dominated by safety issues)
- More corrosive- Must remove HF, Fluorides from LPG
Alkylation Processes
Alkylation Process Concept
iC4
Olefin
Acid
iC4
Reactor SettlerEffluent
Distillation
Propane
n-butane
Alkylate
H2SO4 Processes
• Exxon/Kellogg Cascade reactor, Kellogg Jet reactor, and Stratco Contactor reactor.
• Accounts for 65% of the worldwide capacity • Accounts for 60% of U.S. capacity• Requires refrigeration (compressors)• More mixing required• Acid is less toxic• Simpler feed treating• Acid is insoluble in hydrocarbon product• Acid recovery in acid plant (off-site or on-site)
H2SO4 Processes
• Stratco Contactor reactor- Refrigerated by flashing effluent through tubes in the
reactor• Exxon/Kellogg and Amoco Cascade reactor
- Auto-refrigerated by allowing the reactor contents to flash into compressor suction in multiple stages
• Older Kellogg Jet and Time Tank reactors- Auto-refrigerated by one-stage flashing of reactor
contents
Stratco Process with Effluent Refrigeration
Propane
Compressor
Flash Drum
SuctionTrap
Dep
ropa
nize
r
Contactor
Recycle Isobutane
Product Treatingand Distillation
60 MBSD
Refrigerant
Fresh Feed
3 MBSD
31 MBSDE
fflue
nt
110 MBSD
28 MBSD
52 MBSD
DIB
24 MBSD
Settler
Emulsion170 MBSD
Acid Recycle
PressureControl Valve
H2SO4 Alkylation Process Variables
• Isobutane concentration– Rx HC effluent > 50% or iC4/Olefin mol ratio > 7– Higher values are highly desirable– Might be limited by effluent pump design and condition – Optimum depends on incremental energy and acid costs versus
octane value
• Temperature– 35-55°F (2-13°C)– T <35°F : acid carryover, high acid consumption– T >55°F : high acid consumption, increased corrosion
• Mixing– Maximize mixing as limited by acid carryover
H2SO4 Alkylation Process Variables• Acidity
– Maximum octane occurs at 93-94 wt% for butylene feeds– Optimum acidity depends on acid costs and octane value– Keep >89% acidity in tail reactor. Units with excellent feed quality
and low water content can be at 88%– Risk of acid runaway at <87%
• Olefin Space Velocity– Olefin feed rate/reactor acid holdup. 0.2 - 0.6 hr-1
– Typically outside the control of the Alky unit– Low is better. However, the economics of alkylate production
generally overrides.
• Emulsion Quality (Acid Fraction in Rx)– Keep reactor emulsion at a minimum of 35 vol% acid– Alkylate quality improves with increasing acid concentration and is at
a maximum at 65%– Maximize acid recycle rate as limited by acid carryover
HF Processes
• Phillips - Gravity Acid Flow
• UOP- Pumped Acid Flow- Low Inventory
UOP HF Alkylation Process(Propylene & Butylenes)
Saturate C4’s
iC4’sMakeup
Recycle iC4
ButaneAlkylate Propane
KOH Treaters
KOHTreater
AluminaTreater
HFStripper
Acid
DepropanizerIsostripperSettlerReactor
OlefinFeed Acid
Regenerator
Polymer and CBMTo Neutralization
Water
Steam
Saturate C4’s
iC4’sMakeup
Recycle iC4
ButaneAlkylate Propane
KOH Treaters
KOHTreater
AluminaTreater
HFStripper
Acid
DepropanizerIsostripperSettlerReactor
OlefinFeed Acid
Regenerator
Polymer and CBMTo Neutralization
Water
Steam
HF Alkylation Process Variables• Reactor Temperature
– Significant influence on the octane number of the product– All reactors are operated below 100F (38C)– Higher temperatures lead to lower octane number, higher end points,
and excessive isobutane consumption– Above 120F (50C) excessive side reactions occur– Extremely low temperatures (below 60F or 16C) result in incomplete
alkylation
• Acid to Hydrocarbon Ratio– Normally between 1:1 and 2:1– Below 0.8:1, excess polymer forms and alkylation stops– No advantage to operate above 2:1 for HF
HF Alkylation Process Variables• Isobutane to Olefin Mol Ratio
– iC4/Olefin > 8-14– High iso-butane/olefin ratio promotes:
• Higher octane products• Lower end points• Suppression of tar products
– High iso-butane/olefin ratio cost energy
• Acid Strength– Depends on unit design
• Type and quantity of contaminants• Acid inventory• Process operations
– Generally 85-90% (wt) HF– Low acid strengths lead to incomplete alkylation– Maintain H2O content < 1wt%
Process Contaminants
• Water or water forming compounds• Sulfur compounds• Nitrogen compounds• Ethane, ethylene or non-condensables• Diolefins• Amylenes• Affect acid consumption and regeneration, corrosion and
product quality
Reactor Feed ContaminantsContaminant Effect Limit
Total sulfur Affects acid strength, polymer production, acid consumption
20 wtppm max
Total Nitrogen
Affects acid strength, polymer production, acid consumption
10 wt ppm
Water/water forming compounds
Affects acid strength, polymer production, corrosion
3-5 molppm5 wt% in acid max
Ethane, ethylene & non-condensables
Affects isostripper pressure 0.5 mol%
Diolefins Affects acid strength, polymer production, acid consumption
0.5 mol%
Amylenes Affect alkylate octane
InAlk Simplified Process Flow
Alkylation – Hazardous Materials • HF
– Liquefied gas that forms heavy, toxic aerosols that can travel downwind for miles
– Causes deep, sometimes delayed burns that require immediate flushing and medical treatment to stop tissue destruction
– Most burns occur during equipment maintenance
– Anything that has contacted HF causes burn (scale, rags, PPE, equipment, tools …) Use correct PPE and carefully follow procedures
Economics• What is the cost if the unit is not generating?
– Losses are $10/bbl of olefin (fuel vs. gasoline feedstock) when alky is down
– Losses can reach $20/bbl of olefin (or more) when feedstock must be flared
• How does it enhance the value of the product?– Lowers Gasoline Pool emissions as sulfur, aromatics,
olefins increase without Alky– Improves Gasoline Pool MON, avoids RON Giveaway– Alkylate can trade for $4/bbl above gasoline
Alkylation Summary• Alky Keeps the Refinery Out of the Flare• Alkylate is Great Gasoline• Don’t Liquidate the Asset
– Keep the genie in the bottle – Clamps mean something is wrong inside– Follow PSS and Best Practice Documents
CatalyticCondensation
Catalytic Condensation• Also referred to a Polymerization• Developed in early 1930s because of:
– Excess of thermally cracked olefins– Need for higher performance gasoline
• Discovered in lab testing cracked gasoline– Testing for olefin content with H2SO4 acid– Found increase in gasoline yield.
• 1933 1st commercially viable unit started
Main Applications
• Condensation of light olefins to poly gasoline- With mixed olefin feed, RONC of poly gasoline and
alkylate are equivalent- Higher sensitivity than alkylate (∆RONC & MON)- Particularly relevant where isobutane is not available
• Alkylation of aromatics to cumeme, ethylbenzene and cymene
Feedstocks
• Unsaturated Vapor Recovery Unit• FCC, coking and thermal cracking are sources of
light olefins• C3, C4 or mixed C3/C4 olefin streams• Feeds are generally treated to remove nitrogen
and sulfur compounds
Chemistry
• Acid polymerization of olefins
C–C=C + C-C=C C=C-C-C-C-C
• ExothermicC C
Catalyst
• Phosphoric acid on Kieselguhr clay• Catalyst is attacked by water and basic nitrogen
compounds• Higher pressure favors longer catalyst life
Catalytic Condensation Process/Motor Fuel Production(UOP)
QuenchStreams
FeedDrum
OlefinicFeed
ReactorRecycleDrum Stabilizer Receiver
C3C4
Poly GasolineRecycle
C3C4
FlashDrum
Reactor Types
• Tubular– Catalyst contained in tubes surrounded by water to
remove excess heat
• Chamber– Catalyst exists in layers between which there are
quench lines
Operating Conditions• Pressure
– 450-550 psig (32-39 bars)
• Temperature– 320-420F (160-216C)
• Space Velocity– 0.8-1.5 LHSV
• Combined Feed Olefin Content– 25-30 vol-%