# Albemarle’s AFX Lifts Propylene to new Levels

MEDW 2011 

### Stephen Amalraj, Carel Pouwels2 

# Content
Understanding the mechanisms to maximize propylene in FCC Optimizing Unit Conditions Catalyst Design Considerations Maximum Propylene Applications in Practice3 

# 1.0 Understanding the mechanisms to maximize Propylene in FCC4 

# 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 C 2 , followed by CH 4 and C 3  Very little isomerization / branched products Catalytic Cracking mostly proceeds by acid catalyzed reactions:

 Involving Carbo - cation intermediates

 Aliphatic products which are mostly branched

Ref: Greensfelder, 19495 

# 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: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 enter7 

# 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 atoms8 

# 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 trapping9 

# 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 products10 

# 2.0 Optimizing Unit Conditions How to make best use of mechanisms for maximum propylene11 

# 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 solution12 

# 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 gas13 

# 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 OPEX14 

# 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, N15 

# Hydrogen Transfer Index (HTI) of base catalyst defines 

# maximum propylene16 

## 0.10 0.12 

# HTI can be reduced by decreasing Rare Earth of zeolite or by increasing AAI17 

# Albemarle’s high AAI technology results in lowest HTI18



### Catalyst ACCESSIBILITY is another independent manufacturing variable that Albemarle can apply and which is key to lower Hydrogen Transfer19 

# 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...20 

# 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 oils21 

# 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 tolerance22 

# 4.0 Maximum Propylene Applications in Practice Experience with Albemarle’s AFX23 

# 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 technologies24 

# 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 yields25 

# 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
5926 

# 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