Albemarle’s AFX Lifts Propylene to new Levels

MEDW 2011

Stephen Amalraj, Carel Pouwels
2

Content

Understanding the mechanisms to maximize propylene in FCC

Optimizing Unit Conditions

Catalyst Design Considerations

Maximum Propylene Applications in Practice
3

1.0

Understanding the mechanisms to 

maximize Propylene in FCC
4

Understanding the mechanisms of cracking

Thermal Cracking proceeds by a free radical process:

 Occurs at high Temperature: initial step forming radicals

 Radicals further react to Ethylene and new radicals

 Major product is C2, followed by CH4 and C3 

 Very little isomerization / branched products

Catalytic Cracking mostly proceeds by acid catalyzed reactions:

 Involving Carbo-cation intermediates

 Aliphatic products which are mostly 

branched

Comparison of Products by Cracking n-Hexadecane at 500 °C

0

20

40

60

80

100

120

140

C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14

C-number moles Product/100 moles Cracked

Thermal Cracking

Quartz Chips

Catalytic Cracking

Amorphous SiO2/Al2O3

Ref: Greensfelder, 1949
5

Catalytic cracking mechanism considerations:

Y-zeolite less favored for light olefins

History: Amorphous Cracking Catalyst -> Zeolite Based Cracking

 Drastic increase in gasoline yields, lower coke and gas

 But dramatic loss in gasoline RON, attributed to lower olefins content

 Changes in selectivity attributed to Hydrogen Transfer:

– Initially formed Olefins converted to more stable Paraffins

 Loss in light olefins yield by zeolite cracking catalysts:

Conversion Gasoline (vol%) Propylene (vol%)

Silica-Alumina gel 75.5 47.5 8.5

REHY 85.5 61.0 5.9
6

ZSM5 mainly converts C6 and C7

ZSM-5: 

 Smaller pores (5.5 Å) than Y-zeolite (7-8 Å) and two i.s.o. three dimensional

 Restricts access of branched and cyclic hydrocarbons into its interior

 Allows straight chain and mono methyl paraffins and olefins to enter

Yield by C-Number

0

2

4

6

8

10

12

14

16

18

C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12

C-Number Yield, wt%

FCC Catalyst

FCC Catalyst + ZSM-5
7

Mainly C6 and C7 olefins and iso paraffins contribute to 

propylene by ZSM-5 cracking

 Particularly C6 and C7 are cracked by ZSM-5, forming propylene and butylenes

 O6 and O7 are best precursors for propylene and butylenes

 Leaving the gasoline more concentrated in aromatics

iP: iso Paraffin

O: Olefin

A: Aromatic

Number indicates # of C atoms Gasoline components most and least affected by ZSM-5

-2.8 -2.1 -2.0 -1.7 -1.5 0.3 0.5 0

1

2

3

4

5

iP6 O6 iP5 iP7 O7 A7 A6

C-numbers and Component Type Yield, wt% on feed

FCC Catalyst

FCC Catalyst + ZSM-5
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Functionality of catalyst key components

Catalyst components in perspective

 Y-Zeolites can be optimized for 

specific functionalities and 

applications:

– UCS, RE2O3, SAR

 Matrices exists for large range of 

functionalities and applications:

– Bottoms conversion, metal 

trapping 9

11

13

15

17

40 50 60 70 80 90

Conversion (wt%) C3= yield (wt%)

0.00

0.10

0.20

0.30

0.40 Hydrogen Transfer Index

C3=: Matrix 2

C3=: Matrix 1

HTI: Matrix 2

HTI: Matrix 1

Acidity Cracking Hydrogen Transfer Isomerization

ZSM5 - Zeolite Very High High* - High

Y - Zeolite High High High Moderate

Matrices Low-Moderate Low-High Low to Moderate Low

* Size and shape of molecules determines cracking rate
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Preserving gasoline olefins is the key to maximizing propylene 

yield

Gasoline olefin

Cracking by ZSM-5

Favored by:

• Low pressure,

• High temperature

• Fast diffusion of primary cracking 

products from the catalyst

Secondary Catalyst Reactions

• H-Transfer, Isomerization, Cyclization

Favored by:

• High zeolite acid strength, high UCS,

• Slow diffusion of primary cracking 

products from the catalyst

H

H

H H H

H H H

H

H

H

R

’

H

H

H

H

H

H

Light Olefins

Naphthenes

Paraffins

Aromatics

Suppressing competition 

from secondary reactions 

is the major key for 

maximizing propylene

Feed

Primary Cracking

Highly olefinic 

products
10

2.0

Optimizing Unit Conditions

How to make best use of mechanisms for maximum propylene
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Increasing propylene demand

Moderate Propylene increase can be achieved by:

 Raised Cracking Temperature

 Increased Catalyst Circulation

 Reduced oil partial pressure

 Increased steam partial pressure

 Apply of Naphtha recycle

 Better Feed

Large Propylene increase can be achieved by:

 Special FCC catalyst solution
12

Effect of reactor temperature

Increased Reactor Temperature:

 Increases Cracking/Hydrogen Transfer Ratio

 Thermal Cracking increases

– Thus lowers the C4/(C3+C4) ratio thus enhances C3/(C3+C4)

 Effect: + 0.8 to 0.9 wt% C3= per 10 °C increase RXT

 Basis for high severity operations like DCC, HSFCC, IndMax

 Disadvantage: increased dry gas

C4/(C3+C4)

Catalytic Cracking 0.68

Thermal Cracking 0.50

* for FCC catalyst without ZSM-5 zeolite
13

Effect of hydrocarbon partial pressure / steam

Lower hydrocarbon partial pressure / Higher steam rates favor propylene yield

 Reduces secondary reactions:

– Maintaining primary products

 Reduces any bi-molecular reactions:

– Hydrogen transfer of precursors in gasoline range

– Oligomerization of propylene

 Effect: - 1 bar RxP: +0.7 wt% up to 2.5 wt% propylene gain

 Disadvantage: increasing CAPEX and OPEX

ROT °C 553 551

RxP barg 2.1 2.8

Steam mol% on feed 71% 60%

C3= wt% on feed 11.6 9.9
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Designing a max C3= FCC cat

Understanding the chemistry

 Influence cat properties on C3=

Understanding the constraints

 How much propylene can be produced in FCC?

 What determines the maximum C3= yield, and how can this be predicted?

Understanding the bigger picture

 High (Hydro-)thermal stability of catalyst

 Resistance towards, V, Ni, Fe, N
15

Hydrogen Transfer Index (HTI) of base catalyst defines 

maximum propylene

Delta Propylene Yield vs ZSM-5 Crystal

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16 18 20

ZSM-5 Crystal, wt% Delta Propylene Yield, wt%

Decreasing Base Catalyst 

Hydrogen Transfer Index
16

0.10

0.12

HTI can be reduced by decreasing Rare Earth of zeolite or by 

increasing AAI

H-Transfer Index @ Constant Conv

Cyclic Deactivation V=5000ppm, Ni=5000ppm

0.10

0.15

0.20

0.25

0.30

0

Rare Earth on Zeolite HTI

Low Accessibility

High Accessibility

Max
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Albemarle’s high AAI technology results in lowest HTI

HTI vs Ecat Activity

(FST Selectivities from Ecat Database - excluding samples with ZSM-5)

0.15

0.20

0.25

0.30

0.35

0.40

0.45

60 64 68 72 76 80

Ecat FST Conversion, wt% Ecat H-Transfer Index

Albemarle - high AAI

Competitor A

Competitor B

Albemarle's high AAI 

technology results in lower HTI
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Catalyst ACCESSIBILITY is another independent 

manufacturing variable that Albemarle can apply 

and which is key to lower Hydrogen Transfer
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Balance between HTI and activity

 Low Hydrogen Transfer maximizes propylene

 If achieved by reducing Rare Earth, activity is lower.

 Dilution effects from large amounts of ZSM-5 must also be overcome.

 Increasing AAI also reduces HTI, with no activity penalty

 The challenge, particularly for Resid, is achieving high propylene yield AND 

good conversion with acceptable catalyst addition rate...
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Unique solutions for maximum propylene in FCC: AFX

 Proprietary specialty zeolites 

 Unique combination of micro, meso and macro activity

 High AAI catalyst to be used alone or together with olefins/octane additives

 All feed types from heavy resids to hydrotreated gas oils
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Other unique performance benefits of technology used in AFX

Maximum resid with superior bottoms conversion 

Fingerprint of technology:

 Lowest bottoms yield

 Highest LCO/bottoms ratio

 Highest LPG olefinicity

 Highest GLN/LPG ratio

 Excellent metals tolerance
22

4.0

Maximum Propylene Applications in Practice

Experience with Albemarle’s AFX
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AFX’s successes in laboratory evaluations

AFX has shown to be the state-of-art 

catalyst in numerous laboratory 

evaluations

 Confirming the understanding of 

complex and competing reaction steps

 Demonstrating record propylene 

yields

Studies conducted:

 In several customers labs

 On both clean feed and heavy 

residue applications

 At pilot scale as well as bench scale

 Benchmarking against other 

commercially used cat technologies
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AFX used in wide range of applications

Applied in challenging applications:

 At or close to plateau level of C3=

 High pressure operations

 Heavy residue applications

 Record propylene yields

RxT Rx-Pres SG API S CCR Ni V C3=

RFCC-1 543 1.4 0.931 20.6 0.38 4.7 4.7 9 10.5

RFCC-2 528 1.7 0.921 22.1 0.32 3.9 4.4 6.7 9.0

RFCC-3 545 1.8 0.912 23.5 0.30 4.4 8.4 2.2 10.5

RFCC-4* 549 1.4 0.930 20.5 0.50 6.0 10 10 11.0

FCC-1 545 2.5 0.899 25.8 0.10 0.1 11.8

FCC-2 555 2.6 0.908 24.3 0.16 0.1 10.7
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Track Record of superior metals resistance of technology 

used in AFX

1

st choice of refiners to remedy collapse in accessibility: e.g. caused 

by Fe poisoning

Superior Vanadium resistance with typical Ecat values of 7000 ppm 

and above

Extreme Nickel applications at 8.000 – 11.000 ppm

Highly Resistant to Calcium poisoning up to 1.7 wt% CaO

Ca

20

40

V

23

51

Fe

26

56

Ni

28

59
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Summary 

Complex reaction mechanisms are involved in propylene generation

A good understanding of the reaction steps and catalyst design is required for record 

propylene yields

Crucial is the generation and preservation of gasoline precursors (particularly C6 and C7 

olefins and isoparaffins):

 Minimum hydrogen transfer of the individual catalyst components

Catalyst ACCESSIBILITY is another independent manufacturing variable that Albemarle 

can apply and which is key to lower Hydrogen Transfer

Albemarle has a wealth of experience in a variety of challenging maximum propylene 

applications

AFX is recognized as the preferred catalyst for those applications