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CATALYTIC REFORMING
CATALYTIC REFORMING
INTRODUCTION
• Demand of high-octane gasoline.
• 30-40 % of US gasoline production is by C.R.
• The production might decrease by the implementation on the aromatic content of gasoline.
• Only change in molecular structure so B.P of the feedstock after the process is small.
• C.R increases the octane of motor gasoline rather than increasing its yield. (in fact due to cracking there is a decrease in yield).
FEED STOCK
• Feed consists of
Heavy run gasoline (HSR)
Naphtha
Heavy hydro cracker naphtha
• Naphtha containing (C6-C11) chain paraffins, olefins, naphthenes & aromatics.
• Aromatics in feed remains unchanged
PONA ANALYSIS (VOL%)
REACTIONS
4 major reactions are categorized as
• Dehydrogenation of naphthenes to aromatics
• Dehydocyclization of paraffins to aromatics
• Isomerization
• Hydrocracking
Dehydrogenation & Dehydrocyclization
Isomerization
• Branched isomers increase octane rating
• Small heat effect
• Fairly rapid reactions
Favourable conditions
• High temperature
• Low pressure
• Low space velocity
• H2/HC ratio no significant effect
Hydrocracking
• Exothermic reactions
• Slow reactions
• Consume hydrogen
• Produce light gases
• Lead to coking
• Causes are high paraffin conc feed
Favourable conditions
• High temperature
• High pressure
• Low space velocity
PROCESS VARIABLES
• Chosen to meet refiners yield, activity and stability need
• Primary control of changing conditions or qualities in reactor.
• High temp increase octane rating but decrease run length.
• High temp reduce catalyst stability but may be increased for declining catalyst activity.
• Pressure effects the reformer yield & catalyst stability.
• Low pressure increases yield & octane but also increases coke make.
• Low pressure decreases the temperature requirement for the given product quality
PROCESS VARIABLES
• Amount of Naphtha processed over a given amount of catalyst.
• Low space velocity favors aromatic formation but also promote cracking.
• Higher space velocity allows less reaction time.
• Moles of recycle hydrogen / mole of naphtha charge
• Recycle H2 plays a sweeping effect on the catalyst surface supplying catalyst with readily available hydrogen
• Increase H2 partial pressure or increasing the ratio suppresses coke formation but promotes hydrocracking.
REFORMING CATALYST
• Catalyst used now a days is platinum on alumina base.
• For lower pressure stability is increased by combining rhenium with platinum.
• Pt serve as a catalytic site for hydrogenation and dehydrogenation reactions
• Chlorinated alumina provides acid site for isomerization, cyclization & hydrocracking reactions.
• Catalyst activity reduced by coke deposition and chlorine loss.
• As catalyst age’s activity of the catalyst decreases so temperature is increased as to maintain the desired severity.
CATALYST CHEMISTRY
Properly balanced catalyst
VARIOUS C.R PROCESSES
• Platforming (UOP)
• Powerforming (Exxon)
• Ultraforming (Amoco)
• Magnaforming (ARCO)
• Rheniforming (Cheveron)
Classification of processes
UOP PLATFORMING PROCESS
Octane & Temp reactors profile
CATAYST REGENERATION
• Performance of the catalyst decreases wrt time due to deactivation.
• Reasons for deactivation
Coke formation
Contamination on active sites
Agglomeration
Catalyst poisoning
• Activity could be restored if deactivation occurred because of coke formation or temporary poisons.
CATAYST REGENERATION
• Objective of regeneration
Surface area should be high
Metal Pt should be highly dispersed
Acidity must be at a proper level
• Regeneration changes by the severity of the operating conditions
• Coke formation can be offset for a time by increasing reaction temperatures.
CATAYST REGENERATION STEPS
REACTOR DESIGN
CONCLUSION
• Purpose of reforming process is to improve RONC.
• The basic and fastest reaction is naphthene conversion to aromatic so the feed rich in naphthene that is rich naphtha is preferred as a feed.
• Useful operating condition is at low pressure, low space velocity & high temperatures.
• The platinum is thought to serve as a catalytic site for hydrogenation & dehydrogenation reactions
• While chlorinated alumina as an acid site for isomerization & hydrocracking reactions.
• The activity of the catalyst decreases during the on stream period hence leading to regeneration.
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