catalytic conversion process

1. Module 7
CATALYTIC CONVERSION PROCESSES
CATALYTIC CONVERSION PROCESSES
 Fluid catalytic cracking
 Hydrocracking Heavy Oil cracking
 Isomerisation
 Catalytic Polymerization

2.  CATALYTIC CONVERSION PROCESSES
 Catalytic processes make it possible to remove unwanted
impurities such as sulfur compounds and to convert certain
hydrocarbons into the products which cannot be obtained by
simple distillation or through thermal conversion processes.
 Catalytic conversion processes may be broadly classified as
those:
i. Which change the carbon number
ii. Change the carbon / hydrogen ratio or
iii. Do not change the carbon number or C/H ratio
 Fluid catalytic cracking, hydrocracking and polymerization
processes change the carbon number.
C/H ratio is changed by hydrogenation and dehydrogenation.
Isomerization is the process that does not alter the carbon
number or C/H ratio.

3.  Fluid Catalytic Cracking:
FCC is a catalytic conversion process for converting heavy gas
oils such as vacuum distillates into more valuable products
such as LPG, Gasoline, Olefins, cycle oils etc. FCC is a low
pressure, intermediate to high temp. process. This process may
be designed and operated to achieve either of the following
objectives:
• Maximization of middle distillates
• Maximization of LPG and Gasoline.
 FCC process can accept a variety of feedstocks. FCC process
is a relatively low investment; reliable long run operations, and
an operating versatility that enables the refiner to produce a
variety of yield patterns by simple adjustment of operating
parameters.

4.  Process Description:
Hot regenerated catalyst is mixed at the bottom of reactor with
raw feed and steam. After pre-acceleration , it is brought in to
contact with the staged feeds supplied as finely atomized
droplets. Feed instantaneously vaporizes and travels up the
riser with the catalyst where conversion reaction takes place, At
the top of reactor, the vapour is disengaged from catalyst. The
vapour is sent to main fractionating column. In this column,
mainly LPG, Gasoline, middle distillates and decanted oil are
obtained. The spent catalyst is steam stripped to remove
hydrocarbon vapour and then sent to two stage regenerators
for burning coke before it is recycled to rector alongwith
makeup catalyst to reactor.
Air is injected in catalysts regenerator for burning coke. Water
generated in the system leaves with flue gas from Power
Recovery Train. Flue gases are sent to CO boiler and thereafter
to a clean up system to remove particulates, SOx and NOx.
ZSM additives is added to catalysts to increase LPG yield.
Residues are also used as feedstock in RFCC

5. Power
Recovery
Train
Regenerator Reactor
Unsat
Gas conc.
FCC
Process air
BFW
Main
column
Gasoline
LPG
O/H gases
Reactor vapors
Steam
Flue gas
Spent
catalyst
Regen
catalyst
Raw oil
Steam
Fuel Oil
LCO
Heavy
Naphtha
Treated gas
M/ u catalyst
Process air
FCC UNIT BLOCK FLOW DIAGRAM
Naphtha

6. Fluid Catalytic cracking process
GAS
CONCENT-
RATION
UNIT
18 PSIG
Flue
gas
16 PSIG
17 PSIG
Catalyst
Stripper
LCO Side cut
Stripper
Light
Cycle Oil
HCO Side
Cut
Stripper
Heavy
Cycle Oil
Clarified
Oil
Gas to
Gas Conc.
Unit
Refinery
Fuel
Gas
12 PSIG
Stabilized
Gasoline
Unstabilised
Gasoline To
Gas Conc. Unit
F
R
A
C
T
I
O
N
A
T
O
R
18 PSIG
R
E
A
C
T
O
R
R
E
G
E
N
A
T
O
R
25 PSIG
Combined
Feed to Riser

7. Principles of Operation:
 FCC process converts heavy gas oils into light hydrocarbon
gases, high octane gasoline and lower boiling gas oil
components. This is accomplished by cracking the vaporized
feed over the catalysts at a temp. between 4700C-5400C and a
pressure between 0.5 -1.5 Kg /cm2g. The catalysts lead to better
product selectivity as compared with that of thermal cracking
process.
 Catalyst:
•The catalyst used in the catalytic cracking process is a fine
powder made up of alumina and silica.
• The cracking reactions are accompanied by a heavy coke lay
down on the catalyst. The catalyst has to be frequently
regenerated by burning off the coke deposits. The problems
associated with frequent regeneration of catalyst have been
solved in the FCC units by circulating the catalyst in the fluidized
state from the reactor to the regenerator.

8. FCC complex has following sections :
(i) Reactor and Regenerator: In the reactor, the feedstock is
cracked to an effluent containing hydrocarbons ranging
from methane through the highest boiling material in the
feedstock plus hydrogen and H2S. In the regenerator; the
circulating spent catalysts is rejuvenated by burning the
deposited coke with air at high temperatures.
(ii) Main Fractionation column: In this column, the reactor
effluents are separated into various products, heavier
naphtha and cycle oils are separated as side cuts and
slurry oil is separated as a bottom product.
(iii) Gas concentration unit: In this section, usually referred
to as the ‘unsaturated Gas Plant’; the unstable gasoline
and the lighter products from the main-fractionators
overhead are separated into fuel gas, C1-C4’s for alkylation
or polymerization and debutanized gasoline.

9. A
B
S
O
R
B
E
R
S
T
R
I
P
P
E
R
D
E
B
U
T
A
N
I
Z
E
R
Gas
Wet Gas
Compressor
Gas
Unstabilized
Gasoline
Wash
Water
Sour
Water
Gasoline
Gas Concentration system

10. Energy Recovery in FCC unit:
In a FCC plant, the flue gases from the regenerator
contains significant amount of available energy that can be
recovered. The flue gas exits the regenerator at about
7000C- 7800C and at about 2 Kg/Cm2 g press. The thermal
and kinetic energy of the flue gas can be converted to steam
or used to drive a turboexpander-generator system for
power generation. Unconverted CO in the flue gas can be
combusted to CO2 in a CO boiler with production of high
pressure steam.

11.  HYDROCRACKING
Hydrocracking is cracking in presence of hydrogen.
Hydrocracking is vary versatile petroleum refining process.
Any fraction from naphtha to asphalt can be processed.
Depending upon the feedstock used, two types of
Hydrocracking is practised Industrially.
If the feedstock is a heavy distillate obtained from straight run
refining or cracking operation; it is called distillate
hydrocracking.
Residual Hydrocracking is the name given to the process if
the feedstcok happens to be residue of the straight run
refining. Residues are usually lower in API, higher in carbon
residues and C:H:Ratio as compared to the distillates. In
Residuum Hydrocracking a different type of catalyst is used at
relatively higher temps. Because the feedstocks in RH have
more metals and asphaltenes.

12.  The selective hydrocracking of vacuum gas oils and
propane deasphalted oil to produce high quality
Lubricating Oil Base Stocks (LOBS) is an important
application of Hydrocracking. Hydrocracking processes
Hydrocrack compounds of low viscosity Index into high
quality naphtha and distillates. By hydrocracking of
vacuum gas oils, the yield of Lubricating Oil can be
considerably increased compared to conventional
extraction processes.

13. Applications of Hydrocracking
Feedstock Products
Naphthas Propane and butane (LPG)
Kerosine Naphtha
Atmospheric gas oils Naphtha, jet fuel and /or distillates
Natural gas condensates Naphtha
Vaccum gas oils Naphtha, jet fuel, distillates, lube
oils
Deasphalted oils Naphtha, jet fuel, lube oils
Reduced crude oils Distillates and low-sulphur fuel oil
Vaccum residue Naphtha, distillates, vacuum gas
oil and low sulphur fuel oil
Light cycle oils (from FCC) Naphtha
Heavy cycle oils (from FCC) Naphtha and/or distillates
Coker distillates Naphtha
Coker heavy gas oils Naphtha and/or distillates

14.  A hydrocracking unit is costlier compared to catalytic
cracking unit (about 1.6 times). Products from
Hydrocracking are very stable but the operating cost of the
Hydrocracking unit is higher than a catalytic cracker unit.
The metallurgy of the hydrocracking unit needs special care,
is costly and more maintenance-intensive.

15.  Process Description:
The reactions in hydrocracking are:
 Cracking
 Saturation of Aromatics by Hydrogenation
 Saturation of Olefinic material present in feedstock
 Reaction of desulfurization, denitrogenation and deoxygenation.
There are 2 steps of reactions in Hydrocracking
-- Cracking step
-- Treating step
The cracking function is provided by Silica Alumina catalyst or
Zeolite Catalyst. Zeolite catalyst permits operation at lower
temperatures. Tungsten oxide or Nickel oxide catalysts promote
hydrogenation reaction.
 The simplest Hydrocracker configuration - the single stage
process - in which the cracking and treating step are
combined in one reactor finds application in cases where only
moderate degree of conversion (<60%) is required.

16. In a multistage process, the cracking reaction mainly takes
place in an added reactor. There could be 2 stages or 3 stages
Hydrocracker.
In the first reactor, desulfurization and denitrogenation occurs
besides a limited amount of hydrocracking. The catalyst is
arranged in a number of fixed beds. Reaction temps. are
controlled by introducing part of the recycle gas as a quench
medium between beds. The liquid from the first reactor is
fractionated to remove the product made in the first reactor.
The bottoms for the fractionators, after heat exchange with
reactor effluent and mixing with heated recycle gas; is sent to
the 2nd reactor. Most of the hydrocracking occurs here.

17. LPG
F
R
A
C
T
I
O
N
A
T
O
R
H
P
S
E
P
A
R
A
T
O
R
L
P
S
E
P
A
R
A
T
O
R
S
T
A
B
I
L
I
Z
E
R
S
P
L
I
T
T
E
R
Recycle Gas
Compressor
Furnace
From Hydrogen Plant
Make-Up Gas
Compressor
Air Cooler
Flash Gas
Water
Fired
Heater
Sour
Water
Water
Light Gasoline
Heavy Gasoline
Naphtha
Kerosine
Gas Oil
Bottoms
Feed
Reactor
Hydrocracking Process

18. • Hydrocracking is an extremely versatile process that
can be utilized in many different ways. One of the
advantages of hydrocracking is its ability to
breakdown high-boiling aromatic stocks produced by
catalytic cracking or coking.

19.  Hydrocracking Process Operations:
Conditions:
Solid acid catalyst (silica Alumina with rare earths)
2600C-4500C(Solid –Liquid Contact)
68-140 Kg/ Cm2 (g) H2 press.
Feeds:
Refractory (aromatics) stream
Most S,N, metals and H2O removed
Coker oils, Cycle oils.
Products:
Lower Mol.wt. isoparaffins
Some C4 gases
Residual Tar (recycle)
Variations
Fixed Bed
Ebullating Bed

20. Heavy Oil Cracking
The H oil process is basically a catalytic hydrogenation
technique in which, during the reaction, considerable
hydrocracking takes place. The process is used to upgrade
heavy sulfur containing crudes and residual stocks to high
quality sweet distillates, thus reducing fuel oil yield.
H. Oil ebullated bed reactor consists of a back-mixed
isothermal vessel with hydrogen and liquid feed flowing
upward expanding the catalyst evenly across the reactor
cross section while maintaining the suspended catalyst
particles in a well mixed state. Catalyst is added and with
drawn from the reaction chamber without shutdown, to
maintain uniform catalyst activity. After high pressure
recovery of liquid from recycled gas, products are separated
in a conventional distillation column.

21. The operating pressure for an H-oil unit is a function of feed
boiling point with operating pressure upto 200 bars used
when charging vacuum tower residuum.
H-oil process adopts an ebullated-bed reactor system
which has the advantage that small solid particles are
flushed out of the reactor and do not contribute to plugging
or increase in pressure drop through the reactor.

22. HYDROCRACKER
H2S
Removal
Heavy Fuel
Fractionators
Diesel
Ist Pool
Heavy Naphtha
Light Naphtha
Light Ends
L.P.seperator
Make Up
H2
Gas Oil
Heater
Recycle H2
Recycle H2
Stabilizer
Heater
Ist STG
Reactor
2nd STG
Reactor

23. COKE PRECURSOR
REMOVAL
L.P.
SEPERATOR
Make-up Hydrogen
Recycle Hydrogen
Products
stripper
steam
Heaters
Feed
Reactor
Separator
PSA
Unit
H.P .Separator
Ebullated Bed Resid Hydrocracking Unit

24.  CATALYTIC ISOMERIZATION:
Cataltic Isomerization process is used to convert n-butane to
isobutane which can be alkylated to give Liquid hydrocarbon in
the boiling range of motor gasoline. This process is also used to
convert low octane-number paraffins (C5/C6) contained in light
straight-run naphtha and raffinates from solvent extrn. units into
the higher octane-number products such as Isoparaffins.
Reactions: CH3
H3C—CH2– CH2– CH3 CH3 CH
CH3
Examples:
UOP’s Butamer Isomerizaion Process
UOP Penex Process

25.  The Isomerization process has become of utmost
importance in preparing the isobutane needed for making
alkylate as a basis for aviation gasoline

26.  CATALYTIC ALKYLATION:
Catalytic Alkylation process is used in Petroleum Refineries to
upgrade light olefins-mainly from FCC units, cokers and
visbreaker—and isobutane into highly branched paraffins. This
product is called alkylate which is used as a blending
component for making gasolines.
Reaction:
Alkylation reaction involves the reaction of isobutanes with a
light olefins such as propene or butenes, in the presence of an
acid catalyst-either concentrated sulfuric acid or anhydrous
Hydrofluoric Acid-to produce alkylate which is a mixture of
saturated, stable isoparaffins distilling in the gasoline range.
Processes:
HF Alkylation –UOP. Phillips Petroleum : H2SO4 based
Alkaylation-Exxon.

27.  CATALYTIC POLYMERIZATION
Catalytic polymerization in a petroleum refinery is used to
convert light olefins, such as propene and butenes; into a high
octane number motor gasoline components (polymer
gasoline). Catalytic polymerization is also used for producing
straight chain C7-C9 olefins which go into manufactures of
specialty alcohols.
The process can also be used for the alkylation of aromatics
with olefins to produce cumene or Ethyl Benzene.
Feedstock to the catalytic polymerization unit consist of C3-C4
products from fluid catalytic cracking as well as visbreaking
and coking operations.
UOP
IFP