HYDROCRACKING
OUTLINE
HYDROCRACKING
I. Principles
II. Hydrocracking reaction
III. Feed preparation
IV.Process requirements
V. Hydrocracking Catalyst
PRINCIPLES
• Hydrogenation – oldest catalytic processes used in
petroleum refining.
• Why hydrocracking?
• Demand shifted to high
ratios of gasoline and jet
demand of
fuel compared with the
petroleum usages of diesel fuel and
products home heating oils.
• By-product hydrogen at
low cost and in large
amounts has become
WHY? available from catalytic
reforming operations
By-product • Environmental concern
Environmental limiting sulfur and
hydrogen compound
concern aromatic
at low cost concentrations in motor
fuels have increased.
ADVANTAGES OF HYDROCRACKING
• Hydrocracking is one of the most versatile process,
which facilitate product balance with the market
demand.
Improved gasoline
pool octane numbers
MODERN REFINERY
• Catalytic cracking (FCC) & hydrocracking work as a
team.
• FCC takes more easily cracked paraffinic gas oils as
charge stocks, while hydrocracker is capable of using
aromatics and cycle oils and coker distillates as feed
(these compounds resist FCC)
• Cycle oils and aromatics formed in FCC make
satisfactory feedstock for hydrocracking.
• Middle distillate and even light crude oil can be used
in hydrocracking.
FEEDSTOCK
• Typical hydrocracker feedstock is shown below
• LCGO = light coker gas oil
• LCO = light cycle oil (produced in FCC, high in aromatics
and sulfur)
• HCGO = heavy coker gas oil
HYDROCRACKING PROCESSES
• There are a number of hydrocracking processes
available for licensing.
• These processes are fixed bed catalytic processes,
in which liquid is moving downward and gas is
moving upward/downward.
• The process employs either single stage or two
stage hydrocracking.
• The temperature and pressure may vary with the
age of catalyst, desired products and the
properties of feedstock.
HYDROCRACKING PROCESSES
PROCESS COMPANY
Unicracking UOP
GOFining EXXON Research & Eng
Ultracracking British Pet.Amoco
Shell Shell Development Center
BASF-IFB Badische Anilin, IFP
Unibon UOP, LLC
Isomax Chevron, UOP, LLC
There are other processes such as LC-Fining,
which are not based on fixed bed reactors.
(expanded bed reactor with continuous on
stream addition and withdrawal of catalyst)
HYDROCRACKING OBJECTIVE
NITROGEN
NAPHTHA
REMOVE FEED
CONTAMINANTS
CONVERT
METALS SULFUR LOW VALUE
GAS OILS TO
ULTRA VALUABLE
CLEAN LUBE MIDDLE
BASE PRODUCTS DISTILLATES
STOCKS
PRIMARY PROCESS TECHNIQUE
Hydrogenation in fixed Followed by one or more reactors
hydrotreating catalyst with fixed hydrocracking catalyst
beds to dealkylate aromatic rings,
bed to improve H/C open naphthene rings &
ratios & remove feed hydrocrack parafin chains
contaminants
HYDROCRACKING BFD
HYDROCRACKING PROCESS FLOW
Fresh feed is mixed with H2 and recycle
gas (high in H2 content) and passed
through a heater to the first reactor
Feed that high in sulfur & nitrogen a
guard reactor is employed to convert
sulfur to H2S and N2 to NH3 ( to protect
precious catalyst in the following
reactor)
HC reactors are operated at high temp
to produce materials with boiling point
below 400 F
HYDROCRACKING PROCESS FLOW
Reactor gaseous effluent goes tru
heat exchangers and a high pressure
separator where the H2 rich gases are
separated and recycled to the first
stage.
Liquid product from the reactor is sent to a
distillation column where C4 and lighter gases
are taken off and the jet fuel, naphta and
diesel fuel streams are removed as liquid side
streams
Distillation bottom product is sent back
to hydrocracker
REACTIONS
• Hundreds of simultaneous chemical reactions
occuring in hydrocracking
Assumption – mechanism of hydrocracking
is that of FCC with hydrogen superimposed
Hydrogenation – Cracking – Hydrogenation –
In FCC, the C-C exothermic
bond is broken H2 is added to endothermic
reaction
C=C reaction
MAIN CHEMICAL REACTIONS
CATALYTI
SATURATION
C
of the newly
CRACKING HYDRO
formed
of heavy hydrocarbons CRACKING
hydrocarbons with
into lighter hydrogen
unsaturated
hydrocarbons
HYDROCRACKING REACTIONS
CRACKING & HYDROGENATION AS BELOW – the
scission of a C-C followed by hydrogenation
HYDROCRACKING REACTIONS
Aromatics
which are
difficult to
process in FCCU
are converted
to useful
products in
Hydrocrackers
HYDROCRACKING REACTIONS
• Cracking provides olefins for hydrogenation and
hydrogenation provides heat for cracking.
• Overall reaction provides excess of heat as
hydrogenation produces much larger heat than
the heat required
Therefore, the for cracking
process is operation.
exothermic and
•
quenching (rapid cooling) is achieved by injection
cold hydrogen into the reactor and apply other
• means of heatistransfer
Isomerization another type of reaction, which
occurs in hydrocracking.
CATALYST
• Hydrocracking Scatalyst are dual functional
(having metallic and acidic sites) promoting
cracking and hydrogenation.
Cracking
Hydrogenolysis of Hydrogenation –
naphthenic unsaturated
structure hydrocarbons
Hydrogenation of
aromatic
compounds
CATALYST FUCNTIONS
SITE
Cracking is promoted by
metallic sites of catalyst To minimize coke
To formation
minimize ca
Acid sites transform the proper balance
alkenes formed into ions achie
must be achieved
Hydrogenation reactions also with the two sites
on the catalyst,
occurs on metallic sites depends
depends on
on the
conditions of the
Both metallic and acidic sites operation
take part in the 4th reactions
HYDROCRACKING CATALYSTS
• Generally a crystalline silica alumina base.
• Catalysts susceptible to sulfur poisoning if
hydrogen sulfide is present in large quantities.
• Catalysts not affected by ammonia.
• Sometimes necessary to remove moisture to
protect the catalyst.
• Catalyst deactivate and coke does form even with
hydrogen present.
• Hydrocarbons require periodic regeneration of
the fixed bed catalyst systems.
