Petrochemical Feedstock

1. Petrochemicals Feedstocks
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2. CONTENTS
• Petrochemicals & Feedstocks
• Petrochemical processes
2

3. Basic Petrochemicals
3
Aromatics

4. Petrochemical Feedstocks
4

5. Typical composition of raw Natural Gas
• CH4 (Methane) : 70-90%
• C2H6 (Ethane) : 0-20%
• C3H8 (Propane) : 0-20%
• C4H10 (Butane) : 0-20%
• CO2 (Carbon-dioxide) : 0-8%
• N2 (Nitrogen) : 0-5%
• H2S (Hydrogen sulphide) : 0-5%
• O2 (Oxygen) : 0-0.2%
• Rare noble gasses: Argon, Helium, Neon, Xeon etc. are
in traces

6. General Flow Diagram of Natural Gas
Processing

8. Crude Oil / Petroleum
General information
• Crude oil / petroleum occurs in nature. It is usually coloured ; dark
brown to black
• It is a homogeneous mixture of various hydrocarbons
• The other major elements of importance in crude oils are sulphur,
oxygen and nitrogen and these impart odour, corrosiveness etc.
• The average ultimate composition of petroleum is
Carbon : 84 - 86 %
Hydrogen : 11 - 14%
S , N & O combined - 5% on an average

9. Crude Oils..contd.
• Complex mixture of hydrocarbons, characteristics change widely with
 geographical location
 mix of individual wells
 change in crude quality with time
• Gravity ranges from 10 - 45o
API (Density 1.0-0.80)
• Boiling range : Methane to 875o
C (typical)
• Impurity (Salt, S, N, O & Trace Metals etc) levels also vary among
crude oils
• Price of crude oil varies with its quality

10. Petrochemical Feedstocks
• Use of petroleum fractions as petrochemical feedstocks
began in early 1920s
• Earlier feedstocks were derived from coal during
preparing of coke for steel manufacturing
• Petroleum is now a superior source of petrochemicals
• Olefins production by cracking became an industrial
reality in about 1930s 10

11. Petrochemical Feedstocks - Preparation
• Preparation of petrochemical feedstocks is a significant
operation in today’s petroleum refineries
• Three major classes of these feedstocks;
 Aromatics ,
 Unsaturates (olefins & diolefins) and
 Saturates ( n-paraffins )
11

12. Petrochemical Feedstocks..contd.
• Olefins (C3 & C4 ) are produced by FCC unit in a refinery and some
olefins (C2 & C3 ) are also produced in cat cracker and coker
• Steam cracking of naphtha is the most important process to
produce wide range of olefins for petrochemical use
• Aromatics (BTX) are produced from naphtha reforming and
extraction of reformate
• N-paraffins are recovered from petroleum fractions by vapour
phase adsorption on molecular sieves having an average pour dia
of 5 Ao
Another source
• Carbon monoxide / hydrogen (synthesis gas or syngas ) from partial oxidation of
coal and reforming natural gas is also a source of petrochemicals
12

13. Processes of Petrochemicals Production
• Stream Cracking of Naphtha
- A thermal cracking process – operates at high
temperature ( 800-850o
C), on low aromatic (4 to 6 %)
naphtha, with a very short residence time ; 0.25
seconds in presence of steam
- Products are light olefins ( mostly ethylene along with
propylene and butylene / butadiene)
- Some liquid fractions (C5 cuts) also are obtained which
can be added to gasoline pool after hydrogenation and
a source for light aromatics ( BTX)
13

14. Typical Operating conditions of Naphtha Cracker
• Naphtha cracker constitutes:
– Hot section : Heaters
– Mid section: Quench Tower
– Cold section : Recovery
• Operating temperature of heaters : 950 Deg. C
• Cold section :
– Minimum temperature for methane recovery: - 180
Deg. C
– Pressure : Around 35 Kg./cm2 14

15. Refinery- Naphtha /Steam Cracker
Hydrogen
LPG
Gasoline
Gas oil
Jet Fuel
Heavy Fuel
Ethylene
Propylene
C4 Cuts
Petrochemical
Products
Petroleum
Products
LPG
Naphtha
ATM GO
VGO
Hydrogen
Gas
Pyrolysis Gasoline
Fuel
Refinery
Steam
Cracker
Crude
Import
Feedstocks

16. Naphtha Cracker
Hydrogen
Methane
Ethylene
Ethane
Acetylene
Propylene
Propane
1,3-Butadiene
Other C4
gasoline
Fuel fraction
10
20
30
40
50
60
70
80
90
100
Naphtha
C5-C7
C2 Cut
C4 Cut
C3 Cut

17. Ethylene to PE / MEG Unit
Propylene to PP Unit
Hydrogen from NCU
Naphtha LPG
Butadiene
Hydrogen from NCU
Raw Py Gas Benzene
Py Gas
CBFS
C-5 +, C-6 Recycle
C-4 Raffinate Recycle
C-4 Recycle
N
C
U
&
A
S
S
O
C
I
A
T
E
D
U
N
I
T
S
C-4 Hyd Unit
BDEU
PGHU BEU
Naphtha Cracker & Associated Units – Block Flow Diagram
17

18. Processes of Petrochemicals (Aromatics)
Production
• Catalytic Reforming
• Catalytic reforming process converts straight run naphtha into
reformate
• The hydrocarbon molecules are not cracked but their structures
are rearranged to form higher octane aromatics
• Reformate contains a large amount of aromatic components, and
is the main feedstock in benzene, toluene, xylene (BTX)
production
• The reforming plant plays an important role in oil refinery;
supplies 30-40% of gasoline demand and produces a large
amount of hydrogen rich gas (Reforming plant plays a role of
hydrogen supplier)

19. Processes of Petrochemicals (Aromatics) Production
• Catalytic reforming of Naphtha
- Catalytic reforming of naphtha yields a C6 to C8
reformate rich in aromatic hydrocarbons ( BTX &
ethyl benzene)
- Raffinate after recovery of aromatics may be used
as feedstock for steam crackers
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20. Catalytic Reforming
Reactions during catalytic reforming:
CH3 CH3
+ 3 H2
CH3
+ 3 H2
CH3
CH3
+ 4 H2
+ H2 +
Dehydrogenation
Dehydrocyclisation
Hydrocracking
Dehydroisomerisation
Isomerisation

21. Catalytic Reforming

22. Reforming Reactions
4 major reactions are categorized as
• Dehydrogenation of naphthenes to aromatics
• Dehydocyclization of paraffins to aromatics
• Isomerization
• Hydrocracking
Undesirable
Desirable

23. Reforming Catalyst
• Catalyst used : Platinum (Pt) on alumina base
• Pt serves as a catalytic site for hydrogenation and
dehydrogenation reactions
• Catalyst activity reduced by coke deposition
• As catalyst activity decreases temperature is
increased as to maintain the desired severity

24. Aromatic Complex
Aromatics production
Cat.
Refor-
ming
unit
Dehepanizer
Pretreater
Bz ,Tol,
Extraction
Benzene
Toluene
Ortho
Meta
splitter
Parex
unit
Re run
Column
C8
Aromatics
Isomerizer
Transalkylation
Disproportion unit
P-Xylene
O-Xylene
Naphtha
Raffinate
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25. Aromatics Production
• Production of aromatics with higher yields - catalytic reformer is operated at
high severity compared to production of motor gasoline
• C6 to C8 aromatics ( benzene, toluene, xylene and ethyl benzene) are large
volume aromatics used by petrochemical industry, benzene having the
greatest demand
• Product from catalytic reformer contains all these aromatics which are
separated into pure components by combination of solvent extraction,
distillation, and crystallization
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26. Aromatic Production - process flow diagram
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27. Solvent extraction of Aromatics
• Recovery of aromatics from hydrocarbon streams by
liquid –liquid extraction and extractive stripping
• Most processes use either sulfolane or polyglycol as
extraction solvents
• These solvents have high selectivity and high capacity /
solubility for aromatics and are thermally stable etc
• Water content in solvents : 2 to 10 % in polyglycols &
about 1.5 % in sulfolane - mixed for better solvent
selectivity
• Aromatic recoveries are typically equal to or better than
99.9, 99.0 and 97.0 % for benzene, toluene & xylenes
respectively 27

28. Aromatic extraction process
(Sulfolane solvent)
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29. Aromatic extraction unit
( Tetra ethylene glycol solvent)
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30. C8 Aromatics production
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31. p-xylene separation
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32. Processes of Petrochemicals Production
N-paraffins recovery
• Are recovered by adsorption on molecular sieves
• Adsorption takes place in vapour phase at a pressure
of 5 to 10 psig (35 to 69 kPa) and temperature from 300
to 350o
C
• A semibatch operation using two beds of 5Ao
mol.
sieves permits continuous operation
• Ammonia is used to desorb the n-paraffins
• Sieves are periodically ( gap of 12 months) regenerated
by controlled burning off the high mol wt hydrocarbons
• The greatest demand for n-paraffins are for use in
manufacture of detergents 32

33. N-paraffins recovery by adsorption
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34. Processes producing Syngas- Source for
Petrochemicals
• Syngas a mixture of hydrogen and carbon monoxide is obtained
from natural gas by following two processes :
Partial oxidation
2CH4 + O2 2CO + 4H2
( Reaction exothermic, 950-1250 o
C , no catalyst)
Steam Reforming
CH4 + H2O CO + H2
( Highly exothermic reaction, 840 to 850
o
C , under
pressure of 30 bar , uses Ni catalyst)
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35. Partial Oxidation/Gasification
Refinery Application
REFINERY
Crude oil
Steam
Air emissions
Power
Hydrogen
Gasoline / Diesel
Distillates
HSFO/Residue
O2/N2
H2
Power Steam
Gasification

36. Gasifier Feedstocks
Coal, 49%
Petroleum, 37%
Natural gas, 10%
Petcoke, 3%
Biomass/waste,
5%

37. Gaseous fuel,
6%
Power, 19%
Chemicals,
45%
Liquid fuels,
30%
Utilization of gasification capacity in the world

38. Use of Refinery Streams as Petrochemical Feedstocks
Refinery Stream Petrochemical Stream Alternative Refinery Use
FCC offgas Ethylene Fuel gas
Refinery propylene (FCC) Propylene Alkylation/polygasoline
Reformate Benzene, toluene, xylenes Gasoline blending
Naphtha and LPG Ethylene Fuel gas/Gasoline Blending
Dilute ethylene (FCC & delayed
coker offgas)
Ethylbenzene Fuel gas
Refinery propylene (FCC product)
Polypropylene, Cumene,
Isopropanol
Alkylation
Butylenes (FCC and delayed coker) MEK (methyl ethyl ketone) Alkylation, MTBE
Butylenes (FCC and delayed coker) MTBE Alkylation, MTBE
Refinery benzene and hydrogen Cyclohexane Gasoline blending
Reformate Orthoxylene Gasoline blending
Reformate Paraxylene Gasoline blending
Kerosine n-Paraffins Refinery product
FCC light cycle oil Naphthalene Diesel blending
Source – Oil & Gas Journal , 1998

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