PENEX PROCESS TECHNOLOGY OVERVIEW
PENEX Process Objectives • Why PENEX??? • Conversion of normal paraffins to iso-paraffins • Principal application of isomerization is the conversion of normal C5 and C6 material • Pentane (C5) – Hexane (C6) Isomerization provides higher octane (82-91 RONC) components to the gasoline pool. • Benzene saturation reaction helps meet aromatic concentration standards
Component Blended Octane Values
Process Benefits • 100% benzene saturation • High Yields • Low severity reactor operations – Operating pressure (31.5 kg/cm2(g)) – Low Temperatures (< 204C)
• Excellent catalyst stability – Up to 10-12 year catalyst lives
• Capable of processing wide range of feedstocks
Chemistry
• Isomerization • Benzene Saturation • Ring Opening • Hydrocracking • Heavies Formation Reactions take place over a dual function catalyst - Metal function (platinum) - Acid function (chloride)
Isomerization Reactions
C-C-C-C-C
C C-C-C-C
n-Pentane (nC5)
Isopentane (iC5)
61.8 RON 6RON
93 RON 93.5 RON
C Cyclohexane (CH)
Methylcyclopentane (MCP)
84 RON 84.0 RON
89.3 RON 96.0 RON
Isomerization Reactions C C-C-C-C-C
C C-C-C-C-C
2-Methylpentane (2MP) 73.4 RONN
3-Methylpentane (3MP) 74.5 RON
C-C-C-C-C-C C C-C-C-C C
n-hexane (nC6) 24.8 RON 31.0 RON
2,2-Dimethylbutane (2,2DMB) 91.8 RON
C C-C-C-C C
2,3-Dimethlybutane (2,3DMB) 104.3 RON
Isomerization Reactions • • • • •
Requires metal and acid functions Equilibrium limited Slightly exothermic No hydrogen consumed Increases octane
Benzene Saturation • Benzene saturates to cyclohexane • Cyclohexane (CH) in equilibrium with methylcyclopentane (MCP) • Requires only metal function 100%
3H2 + Benzene 120.0 RON
40-60%
C
Pt
Cyclohexane 84.0 RON
MCPentane 96.0 RON
Benzene Saturation • • • • • • •
Immediate with platinum sites and presence of hydrogen No acid sites required 100% complete Highly exothermic (25x isomerization, 5x hydrocracking) Consumes 3 moles H2 per mole of benzene Reduces octane (120 Bz 84 CH & 96 MCP) Limit Bz in feed to ~5 vol% – ~11ºC Rx bed deltaT / 1 vol% Bz – ~55ºC total deltaT / reactor
Ring Opening Reactions • CH and MCP open to C6 paraffins • Cyclohexane (CH) in equilibrium with methylcyclopentane (MCP) C-C-C-C-CC
30% 100%
3H2 + Benzene 120.0 RON
30%
40-60%
C
Pt
Cyclohexane 84.0 RON
MCPentane 96.0 RON
Ring Opening Reactions • • • • • • •
Competes for the platinum sites Moderately exothermic 20-40 wt% opening Consumes 1 moles H2 per mole of ring opened Reduces octane Increases with lead reactor temperature increase Higher temperatures favor MCP
Hydrocracking • Longer chain molecules break to smaller ones
Hydrocracking • Triggered by high reactor temperatures and catalyst acid sites • Exothermic • Consumes 1 moles H2 per mole of cracked material • C5 and C6 paraffin hydrocracking is minimal • About 50% of C7+ paraffins hydrocrack to C4 and C3 paraffins • C5+ yield loss • Caused by: – Higher C7+ in feed – Higher rx temperatures pushing equilibrium – Temperature excursion
Heavies Formation • C7+ Formed in PENEX reactors due to Alkylation • Formation of C7+ &Hydrocracking are simultaneous.
Isomerization Catalyst • Dual function catalyst (metal/acid) – Metal is platinum – Acid is chloride
• Metal impregnated on a high surface area alumina-oxide • Active sites are bound alumina-chloride • Gray extrudate or gray trilobe extrudate
• Dual function balance is maintained by: – Perchloroethylene injection
• Sensitive to contaminants and non-regenerable
Catalyst Promotor - Chloride • Continuous chloride injection required to maintain activity. C2Cl4 + 5H2 --------> 4HCl + C2H6 , T>105OC • Hydrogen and hydrocarbon can strip bound chlorides from the catalyst if the partial pressure of chloride surrounding the catalyst is too low. • Low or loss of chloride injection will permanently deactivate the catalyst.
H+Cl- C5 H2 C6 Cl- ClClCl ClClC5, C6, H2, HCl
METHANATOR • Sensitivity of isomerisation catalyst to oxygenates (CO/CO2) CO + 3H2 --------> CH4 + CO2 + 4H2 --------> CH4 + • • •
H2O + Heat , T= 204OC 2H2O + Heat , T= 316OC
Side reactions: Olefin hydrogenation, C2+ cracking Operating temperature : 204OC – 250 OC CO2 & moisture removed by Makeup Gas Driers.
18
C5 - C6 Isomerization Terms • Product Ratios, wt% or mol% – – – –
iC5/C5P = iC5/(iC5+nC5) x 100% 2,2DMB/C6P = 2,2DMB/C6 Paraffins x 100% 2,3DMB/C6P = 2,3 DMB/C6 Paraffins x 100% C6 Paraffins = 2,2DMB + 2,3DMB + MP + MCP + CH + nC6
• PIN (Paraffin Isomerization Number), wt% – Σ (iC5/C5P + 2,2DMB/C6P + 2,3DMB/C6P)
• Feed X-factor, wt% – Σ (MCP + CH + BZ + C7+)
Lead Rx
Lag Rx
iC5/C5P iC4/C4P
(2MP+3MP)/C6P 2-2 DMB/C 6P
2-3 DMB/C6P
121 C
149 C
177 C
204 C
RON
Lead Rx
90 88 86 84 82 80 78 76 74 72 70 100
Lag Rx
Octanes of Equilibrium Mixtures
C5 Para ffins Total C 5 -C6
C6 Pa r a f f in s
302ºF 150
392ºF 200 250 Temperature, °C
300
IC5/C5 PARAFFINS PRODUCT RATIO, Wt%
Lead and Lag Rx IC5 Product Ratio IC5 Pro duc 77 t Ra tio SOR Equ ilibr ium 72 EOR SOR
EOR
45
Feed (Minimum) 116 C 240 Reactor Outlet Temperature, F
167 C 204 C 330350 400
PENEX PROCESS FLOW & EQUIPMENTS
PENEX Process Objectives • • • • • •
Basic flow diagram Feed Section Reactor & Exchanger section. Stabilizer Net Gas Scrubber DIH
Basic Flow Diagram MU Gas Driers Steam Heater
Make-up Hydrogen Reactors
H.O.T. Penex
Deisohexanizer (DIH) Overhead
Receiver
C5p, DMB
Scrubber Gas to Fuel
C2Cl4 HCFE
CCFE
Product Side Draw
Stabilizer
MPs, n-C6
Reboiler Surge Drum
Liquid Driers
Fresh/Spent Caustic
Isomerate Light Naphtha
Bottoms C7+, min n-C6
FEED SECTION: FEED & MAKEUP GAS DRIERS
26
FEED DRIERS
27
MAKEUP GAS DRIERS
28
REACTOR & EXCHANGER SECTION Steam Heater
Reactors LEAD
LAG
C2Cl4 To Stabilizer HCFE
CCFE
NAPHTHA FROM FEED SURGE DRUM
HYDROGEN FROM MAKEUP GAS DRIERS 29
Stabilizer & Net Gas Scrubber Chiller
To Fuel Gas Coalescer
To Fuel Gas Header
Receiver
Stabilizer
LPG Stripper
Scrubber
Caustic
To DIH 30
De-Isohexanizer DIH Receiver Overhead
From Stabiliser
C5p, DMB
DIH
Side-draw to Feed Driers
Side Draw MPs, n-C6
Bottoms C7+, min n-C6
MP Steam
Total Isomerate
31
Isomerization Reactions Step 1: Formation of Olefin Intermediate Step 2: Formation of Carbonium Ion Step 3: Carbonium Ion Rearrangement
Step 4: Formation of Iso-olefin intermediary
Step 5:
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INDIAN GASOLINE SPECIFICATIONS Characteristics
Unit
BS-II
BS-III
Sulphur, Total, Max
PPM
500
150
Lead Content(as Pb), Max
g/l
0.013
0.005
Benzene, Content
% Volume
5
1
88
91
Research Octane Number
34
