Catalytic Reactions in Catalytic Reforming Catalytic Reforming Reactions Sulfur Related Problems Effects of Sulfur in Catalytic Reforming Reactions in Catalytic Reforming Catalytic Reforming Catalysts Effect of Sulfur on Catalytic Reforming Catalysts Catalytic Reformer Efficiency VULCAN Sulfur Guards VULCAN Sulfur Guards for Catalytic Reformers VULCAN Guard Installation Protects Isomerization Catalysts Liquid Phase vs Gas Phase: Relative Advantages Liquid Phase Treating Which active metal is best? Thiophenes and Nickel Sulfur Guards Sulfiding mechanisms with reduced metals Thiophene adsorption on nickel Advantages of Cu/Zn Over Nickel Sulfur Guards Copper oxide vs Nickel Nickel Sulfur Guards Manganese Sulfur Guards

1. Gerard B. Hawkins
Managing Director
Naphtha Sulfur Guards

2. Contents
Catalytic Reactions in Catalytic Reforming
Catalytic Reforming Reactions
Sulfur Related Problems
Effects of Sulfur in Catalytic Reforming
Reactions in Catalytic Reforming
Catalytic Reforming Catalysts
Effect of Sulfur on Catalytic Reforming Catalysts
Catalytic Reformer Efficiency
VULCAN Sulfur Guards
VULCAN Sulfur Guards for Catalytic Reformers
VULCAN Guard Installation Protects Isomerization
Catalysts

3. Contents
Liquid Phase vs Gas Phase: Relative Advantages
Liquid Phase Treating
Which active metal is best?
Thiophenes and Nickel Sulfur Guards
Sulfiding mechanisms with reduced metals
Thiophene adsorption on nickel
Advantages of Cu/Zn Over Nickel Sulfur Guards
Copper oxide vs Nickel
Nickel Sulfur Guards
Manganese Sulfur Guards

4. There are 4 major reactions that occur during reforming.
1. Dehydrogenation of naphthenes to aromatics
2. Dehydrocyclization of paraffins to aromatics
3. Isomerization
4. hydrocracking

5. Desirable reactions in catalytic reforming
1. Paraffins are isomerised and converted to naphthenes
2. Olefins are saturated to form paraffins which react as in (1)
3. Naphthenes are converted to aromatics
Undesirable reactions in catalytic reforming
1. Dealkylation of side chains to form butane and lighter HC’s
2. Cracking of paraffins and naphthenes to form butane and
lighter paraffins

6.  Catalytic Reformers & Isomerization Units
◦ Operational Efficiency
◦ Catalyst Poisoning
◦ Product Specifications

7. Catalytic reforming catalysts are precious metal based .
The active species is platinum and in most cases rhenium
is combined to retard sintering of the platinum and form a
more stable catalyst which permits operation at lower
pressures.
Platinum acts as a catalytic site for hydrogenation and
dehydrogenation reactions
Chlorinated alumina provides acid sites for isomerization,
cyclization and hydrocracking reactions.

8. Sulfur is a temporary poison but has a detrimental effect
on the catalytic reforming process.
Sulfur poisons the platinum dehydrogenation function of
the reaction. For operation at a constant octane, or
severity, the effects are:
•Decrease in C5+ reformate yield and hydrogen
make
•Increased rate of coking and hydrocracking

9. The effect of Sulfur is more severe on bimetallic
catalysts and is worse for high Rhenium / Low
Platinum skewed catalysts.
Also, the effect is worse in ‘semi-regen’ than modern
CCR’s.

10. R R
+ 3H2
Naphthene dehydrogenation, eg methyl cyclohexane to toluene
N-C7H16
R + 4H2
Dehydrocyclization of paraffins to aromatics
CH3-CH2-CH2-CH2-CH2-CH3 CH3-CH-CH2-CH2-CH3
CH3Isomerization
Hydrocracking
C10H22 + H2 isohexane + n-Butane
X Sulfur
X Sulfur

11. Catalytic Reforming Catalysts
Platinum Catalysts
• Recommended when feedstock contains S< 2ppm S
• Usually lead reactors of fixed bed semi-regenerative or fixed-
bed cyclic reformer units
• High platinum loading recommended when S > 2ppm
Platinum / Rhenium
• Equal metal loading recommended when S< 1 ppm with a
target of 0.5 ppm
• Skewed metals loadings recommended for maximum cycle
lengths and S < 0.5 ppm with a target of 0.2ppm

12. Catalytic Reforming Catalysts
Modified Platinum / Rhenium
• Recommended for increased hydrogen, C5+ and aromatics
• Equal metals loadings are general purpose when S < 1ppm
• Skewed metals when S < 0.5 ppm and recommend a Sulfur
guard upstream
Platinum / Tin
• In low pressure operations, offer higher H2 and C5+ than
above catalysts.
• Recommended for CCR units and also fixed bed cyclic
designs
• Preserves the ring compounds to increase aromatics and H2
yields

13. Effect of Sulfur on catalytic
reforming catalysts
• Sulfur contamination of the bi-metallic
reforming catalyst system, through the
formation of a platinum sulfide species
and ultimately leads to the presence of
sulfate, SO4, on the catalyst during
regeneration which results in the
following:

14. Effect of Sulfur on catalytic
reforming catalysts
1) Sulfate promotes platinum (Pt) mobility
which can lead to Pt agglomeration and loss
of active surface area. This ultimately results
in a loss catalyst stability.
2) Pt crystals can not be properly re-dispersed
whilst sulfate is present on the catalyst
surface.
3) Sulfate hinders the chloride pick-up ability of
the catalyst leading to a loss in catalyst
activity. A loss in yield follows.

15. HIGH SEVERITY OPERATION
0 0.2 0.4 0.6 0.8 1 1.2 1.4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Feed sulphur ppm
C5+ yield vol% change
Pt only
Balanced
Skewed
LOW SEVERITY OPERATION
0 0.2 0.4 0.6 0.8 1 1.2 1.4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Feed sulphur ppm
C5+ yield vol % change
Pt only
Balanced
Skewed

16.  Liquid or gas duty
 High Capacity
 Sharp absorption profile
 Effective in dry streams
 Easy discharge and disposal
 Products for H2S, mercaptans, thiophenes
 Applications
– catalytic reformers
– isomerisation units
– lube oil units
– benzene saturation units

17. SULFUR SPECIES H2S Mercaptan
Organic Sulphide
Thiophene
Increasing
difficulty
of removal
SULFUR GUARD DESIGN
Temperature H2S = no constraint
Organic S = 100 to 200oC
140 to 180oC preferred
Sulphur Loading Depends on S species &
temperature
LHSV <15 h-1
Typical S inlet 0.2 - 0.4 ppmw
Typical S outlet Not Detectable

18. GBH Enterprises offer a comprehensive range of
proven absorbents for naphtha Sulfur guard
duties.
The active metal composition is based upon :
1. Zinc Oxide
2. Copper oxide/ zinc oxide
3. Manganese
4. Nickel
GBHE will recommend the most appropriate
absorbent for a particular catalytic reformer duty.
VULCAN Sulfur Guards

19.  Selectivity varies depending on S
species -
◦ H2S - full removal
◦ RSH - full removal
◦ RSR - partial removal
◦ RSSR - partial removal
◦ thiophenes - no removal
 Thiophenes do not “poison” the guard

20. REFORMATE
LPG
Key : VULCAN guard
RECYCLE
GAS
MAKE GAS OFF
GAS
NAPHTHA
FEED

21. Light
Naphtha
Hydrogen
VGP-S201
ReactorStripper
Isomerization
Unit
NHT
Hydro-
Treater

22. Liquid phase vs Gas Phase: Relative
Advantages
Vapor Phase Sulfur Guards:
Advantages
- Unit treats both feed and the recycle gas, thus:
- More effective in responding to major sulfur upset.
- Faster recovery from major sulfur upsets.
- If the upset exceeds the ability of the guard on the first pass,
the recycle gas feature results in complete removal on the second
pass.

23. Vapor Phase Sulfur Guards:
Dis-advantages
- Vapor phase systems are more expensive:
- Located directly in reformer loop and operate at higher
temperatures.
- Additional piping and valving to permit isolation during
regeneration of the cat reformer.
- Sulfur in the liquid feeds hits the catalyst before the recycle
guard bed can take it out.
Liquid phase vs Gas Phase: Relative
Advantages

24. Liquid phase treating
Liquid Phase Sulfur Guards:
Advantages
- Favorable capital cost due to size and metallurgy.
- It does not impact reformer recycle compressor horse power or
flow rate.
- Prevents catalyst exposure to feed sulfur on the first pass.
- Lead-Lag vessels can be readily changed on the run.

25. Liquid phase treating
Liquid Phase Sulfur Guards:
Dis-advantages
- Single pass feature limits sulfur removal to H2S or RSH.
- Slower recovery from sulfur upsets.

26. Which active metal is best?
Nickel is strongly recommended when thiophenic
sulfur species need to be removed .
Copper oxide is recommended for the ‘lighter’ less
refractory Sulfur species due to higher absorption
capacity.
Manganese or zinc oxide is generally used for
desulfurization of recycle gas in presence of
chlorides.
Copper oxide is generally the most
cost effective solution
GBH Enterprises offers all types
of proven absorbents

27.  Experience shows that most naphtha streams contain
predominantly H2S and mercaptan sulphur
 Presence of thiophenes depends on naphtha source
and operation of hydrotreater
 Cracked sources are more likely to contain thiophenes
 For most applications a Cu/Zn product is the best
technical and commercial choice

28. • Thiophenes are removed by reduced nickel
• Typical thiophene pick-up is only 1-2 %w/w
• Thiophenes impair the pick-up of other sulfur species
due to competitive absorption interference
 Nickel products should be used only if:
 Thiophenes are present
 and
 Total sulfur removal is required

29. Sulfiding mechanisms with
reduced metals
Sulfidation mainly occurs through monolayer
chemisorption of thiophene species on surface
layers .
The thiophene is initially adsorbed in a parallel
orientation and this then flips to a perpendicular
arrangement on the reduced nickel surface.
Since the thiophene is unchanged during the
adsorption, the coverage is limited to a surface
monolayer only.

30. Ni Ni
S
Thiophene adsorption on nickel
Orientation
flip
Parallel vertical
approach alignment

31. ◦ Higher sulfur capacity kg/m3
◦ Absorbent not in reduced state
 simpler transportation and handling
 simpler loading procedures
 no costly reduction required
◦ Most streams do not contain thiophenes

32. Nickel is strongly recommended when thiophenic
Sulfur species need to be removed .
Copper oxide is recommended for the ‘lighter’ less
refractory Sulfur species due to higher absorption
capacity.
Copper oxide is generally a more
cost effective solution
Only GBHE offers both types
of proven absorbents

33.  Are complex S species (eg disulfides,
thiophenes) present ?
 If so, are these at a level that will cause a
problem to the downstream process ?
 If so - use
◦ either: 100 % Ni-based absorbent
◦ or: a combination of Cu-based
absorbent over Ni-based as the
optimum solution

34. Pre-reduced
Nickel
Low acidity high
surface area support
Low carbon inducing dehydrogenation
characteristics
Surface Area
> 100m2/g
A.B.D.
1.0 -1.1 kg/l

35. Impurity Optimum Capacity
Species Temperature (C) %
H2S 100 16-18
RSH 150 12-14
RSSR 180 8-10
Thiophenes 200+ 0.5 - 2
Thiophene capacity significantly enhanced if H2 present

36. Manganese Sulfur Guards
0
5
10
15
20
25
30
Inlet 20% 40% 60% 80% Outlet
Percent of bed
Wt % S
100 vppm H2S in feed gas

37. Manganese Sulfur guard
Pre-reduced
manganese
Low acidity high
surface area support
Low carbon inducing dehydrogenation
characteristics
Surface Area
> 80m2/g
A.B.D.
1.1 -1.4 kg/l