Fluid Catalytic Cracking

A.Meenakshisundaram

Chennai Petroleum Corporation Limited

Worldwide Petroleum Product Distribution

OIL USE – SECTOR WISE (million tons oil equivalent)

4300

54

3600

52

3200

50

2800

42

Total

Share of Transport

250215192140Other

1430126512161340Heating and Industrial

300250192140Petrochemical

2320187016001180Transportation

2010200019951985

WORLD CRUDE OIL QUALITY

PROPERTIES OF 1985 1990 1995 1999 2010CRUDE OIL (PROJECTED)

'S' IN CRUDE 1.14 1.12 1.31 1.41 1.51 WT% (AVG.)

API GRAVITY 32.7 32.6 32.4 32.2 31.8

METALS IN RESIDUE 275 286 297 309 320(PPM WT)

RESIDUE IN CRUDE 19.0 19.4 19.8 20.2 21.3OIL (VOL%)

"S" IN RESIDUE 3.07 3.26 3.61 3.91 4.0

Petroleum Refining

• Crude as obtained can not be used as fuel products as it is a complex mixture of various light and heavy hydrocarbons

• Refining involves separation of light fractions by distillation to produce distillate fuels.

• Heavier fractions are converted into useful fuel products by secondary processing such as FCC,Hydrocracking etc..

• Environmental and Engine requirements require further transformations to make improved quality fuel products (e.g Reforming, Hydrotreating etc.)

Catalytic Processes in Refining• Processes for Secondary Conversion - converting heavier fractions

into lighter products - FCC, Hydrocracking etc..

• Processes for meeting fuel engine requirements - Catalytic Reforming, Alkylation, Catalytic Dewaxing etc..

• Processes for meeting Environmental requirements of fuels - HDS, Oxygenates Production, Benzene /Aromatics reduction etc.

• Processes for Production of Lubes - Catalytic Dewaxing, Catalytic Iso Dewaxing , Hydrocracking, Hydrofinishing etc..

• Apart from the above, catalytic processes are also used in refineries for Hydrogen Production, Petrochemical Feedstocks and Speciality Products etc..

World Catalyst Market Sales in Billion US $

Catalyst use by Industry

1997 1999 2001 2007

Environmental 1.63 2.61 2.88 4.05

Refining 2.07 2.17 2.32 2.84

Polymers 1.70 2.06 2.22 2.97

Petrochemicals,Fine Chemicals

2.00 2.16 3.17 3.64

Total 7.40 9.0 10.59 13.51

Refining Catalyst Market

F C C

H Y D R O P R O C E S S I N G

R E F O R M I N G , I S O M ER I S A T I O N

A L K Y L A T I O N

O T H E R S

FCC 40%

HYDROPROCESSING 25% REF.,ISOMERIATION 15%

ALKYLATION 15%

OTHERS 5%

Petroleum Refining - Effect of Catalysis Innovations

% oil converted to 1990 2000 Gasoline 29% 29% Middle Distillates 34% 37% Other Products 17% 18% Fuel Oil 20% 16% Source ; BP Statistical review of world energy, EIA

FLUID CATALYTIC CRACKING

Fluid Catalytic Cracking

• Refinery process that “cracks”high molecular weight

hydrocarbons to lower molecular weight.

•Refinery process that provides ~50 % of all transportation

fuels indirectly.

•Provides ~35 % of total gasoline pool directly from FCC

produced naphtha.

•~80 % of the sulfur in gasolines comes from the FCC

naphtha.

FLUID CATALYTIC CRACKING

• MAJOR SECONDARY REFINING PROCESS

• CONVERSION OF HEAVY FRACTIONS ( VGO -370 C+)INTO LIGHTER FUEL PRODUCTS(LPG,GASOLINE,DIESEL)

• CIRCULATING FLUID BED REACTOR SYSTEM (REACTOR-REGENERATOR CONFIGURATION )

• MULTI COMPONENT CATALYST SYSTEM

• CATALYST TAILORED FOR EACH UNIT BASED ON UNIT OBJECTIVES AND CONSTRAINTS

• FCC IS THE WORKHORSE FOR REFINERY - MOST PROFITABLE TOO!

FLUID CATALYTIC CRACKING

Main Reactions in FCC

• Cracking of Paraffins,Naphthenes and side chain of aromatics

• Isomerisation of olefins• Dehydrogenation of Naphthenes and

Olefins• Hydrogen Transfer• Cyclization and condensation of olefins• Alkylation and dealkylation

FLUID CATALYTIC CRACKING CATALYSTS

INDIAN GASOLINE SPECIFICATIONS

S.No. Characterstics Unit Bharat Stage II Euro III Euro IV

1 Density @15 C kg/m3 710-770 720 - 775 720 - 775

2 Distillation

Recovery upto 180 C Min.Vol% 90 75 75

3 RON min 88 91 91

4 Sulfur Total Max. %Mass 0.05 0.015 0.005

5 Benzene Content Max %Vol 3.0(Metro) 1.0 1.0

6 Olefins max. %vol 21 18

7 Aromatics Max. %vol 42 35

8 RVP Max kPa 35-60 60 60

ADDITIVES IN FCC UNIT

FCC ADDITIVES

• ZSM-5 Additive for boosting octane number and light olefins yields (C3/C4)

• Alumina micro Spheres with dispersed Pt for enhancing CO oxidation in Regenerator dense bed (CO Promoter)

• Bottoms Cracking Additive – Alumina Matrix with tailored pores and acidity for cracking heavier fractions of the feed.

• Gasoline sulfur reduction additive• SOx Reduction Additive for reducing SOx emissions• Metal Passivators – Sb/Bi liquid compounds for Ni

Passivation, Vanadium Trap for V passivation

ZSM-5 Additive• ZSM-5 Additive - Reactant shape selectivity is in play whereby

molecules are sterically discriminated based on their ability to enter the pores of the zeolite for cracking

• Intermediate pore size of ZSM-5 restrict the access of highly branched and cyclic hydrocarbons to the interior of the zeolite for cracking. Thus Higher Octane molecules are retained in the gasoline range

• Only lower octane normal and monomethyl aliphatics enter the pores and preferentially cracked to lighter products

• Increases the iso/normal paraffin and olefin ratio

• Results in higher RON , higher Propylene/Butylene yields, lower Gasoline yield

• About 2 to 5% dosage of additive is used with ZSM-5 crystal content of 25 – 40wt%

Bottom Cracking Additive

• Bottom Cracking Additive (BCA) in general facilitates cracking of heavy ends of the feed into intermediate range molecules suitable for further cracking by the host catalyst.

• Use of BCA in some units is preferred to high activity matrix especially units with coke burning limitation

Options for Gasoline Sulfur Removal

• Pretreatment of FCC Feed

• Treatment of FCC Naphtha

• Undercutting FCC Gasoline

• FCC Gasoline Sulfur Additive

Catalyst for Sulfur Reduction in GasolineCatalyst for Sulfur Reduction in Gasoline

CO Promoter

• Promotes combustion of CO to CO2(200 ppm of CO in flue gas for a 50 000 bpd FCC unit or 1.5 – 2.0 tpd)

• Eliminates the need for CO boiler and improves the environment by reducing CO in flue gas.

• Lower Carbon on Regenerated Catalyst will increase activity and better coke-conversion selectivity.

• Pt at 1 PPM level in the unit will promote CO oxidation.

• Normally a separate additive containing 500 –1000 ppmw Pt on Gamma Alumina is used.

• Pt catalysed CO combustion occurs readily in the dense phase at temp. 650 – 700 C

Refinery CO Control

C + O2 = CO2 H = -94 Kcal/mole C +1/2 O2 = CO H = -26.4 Kcal/mole CO +1/2 O2 = CO2 H = -67.6 Kcal/mole Reduction of After Burn Temperature with Promoted CO

Combustion Component Temperature C Without Promoter With Promoter Typical Flue Gas 700 650 Dense Phase 660 675 After-burn T +40 -15

De SOx Additive

• About 10% Sulfur in FCC feed gets deposited in the coke

• This sulfur in coke is oxidised to SO2(90%) and SO3(10%) in the FCC regenerator.

• Sulfur in Flue Gas Emissions are stringently restricted by emission norms

• DeSOx Additives help in reducing emissions of SOx • An effective Sox reduction catalyst must oxidize SO2 to

SO3 and form a sulfate. This sulfate has to be stable under regenerator conditions and be able to release the sulfur as sulfide in the reactor

Chemistry of SOx Reduction

Reactions in Regenerator

S(in coke) + O2 = SO2

2SO2 + O2 = 2SO3 SO3 + MO = MSO4

Reactions in the Reactor

MSO4 + 4H2 = MO + H2S + 3H2O MSO4 + 4H2 = MS + 4H2O Stripper:

MS + H2O = MO + H2S

S(in coke) + O2 = SO2 2SO2 + O2 = 2SO3 SO3 + MO = MSO4

MSO4 + 4H2 = MO + H2S + 3H2O MSO4 + 4H2 = MS + 4H2O

MS + H2O = MO + H2S

SOx Reduction Catalysts

• MgO,Al2O3,MgAl2O4, La2O3 and CeO2 based catalysts are suitable for FCC unit DeSOx

• Ceria oxidises SO2 to SO3• SO3 is picked up as sulfate on MgO and Mg

spinels• Sulfur picked up in regenerator is stripped in

the reducing atmosphere of the reactor.

Feed Metal Deactivation

• Ni and V present in heavy ends of the feed end in the catalyst

• Both Ni and V function as dehydrogenation catalysts in FCC reactor

• Relative dehydrogenation activity is expressed in terms of 4Ni+V

• Vanadium reacts destructively with zeolitic component of FCC catalyst

• Ni alters the selectivity to coke and gas yields

FCC Passivation Additives

• Ni Passivation is effective with only Antimony,Bismuth and Cerium based compounds.

• Compounds with active ingredients in Organic or Aqueous solvent is generally used

• XRD results suggest that Sb forms Ni-Sb solid solutions with high level of Sb on the Ni surface thus causing the passivation effect.

• Sn reduces the deletirious effect of V by forming inert compounds on the FCC catalyst surface.Sn/V complex is formed

FCC – Recent Trends

Changes in FCCU yields over the years

Time Period 1960 1970 1980 1990

Design Features

Cracking Mode Bed Riser Riser Riser with Rapid disengaging

Combustion Mode

Partial Partial Complete Complete

Feed – Catalyst Mixing

Poor Poor Poor Good

Catalyst Type Amorphous RE Y Zeolite USY Zeolite USY Zeolite with active Matrix

Yields Wt%

C2-

LPG

Gasoline

Cycle oils

Coke

RON

5.0

18.7

45.4

21.5

9.4

92.0

3.8

17.3

49.8

21.7

7.4

91.0

4.0

17.9

50.9

21.8

5.4

92.5

3.3

17.9

52.5

21.5

4.8

93.0

IMPROVEMENTS IN FCCYear Avg.Feed

processed (in tons)per kg of catalyst

Max. Concarbon

of feed

Avg. conversion for VGO

1950 0.5 1% 62%

1975 1.1 2.5% 73%

2000 2.0 7.5% 79%

Source : Akzo Nobel (Albemarle) catalyst data

Fluid Catalytic Cracking Catalysts– Future Trends

• More Resid Cracking and Deep Catalytic Cracking application will require new zeolite materials with larger pores – metal tolerance required

• More FCC units will be designed for Petrochemical feedstocks – Additive usage will increase - More selective Additive for Propylene/Butylene will be required.

• Development of Newer Additives for meeting product quality will be required – Sulfur/Olefins