Naphtha Sulfur Guards
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Naphtha Sulfur Guards

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Catalytic Reactions in Catalytic Reforming ...

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

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Naphtha Sulfur Guards Naphtha Sulfur Guards Presentation Transcript

  • Gerard B. Hawkins Managing Director Naphtha Sulfur Guards
  • 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
  • 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
  • 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
  • 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
  •  Catalytic Reformers & Isomerization Units ◦ Operational Efficiency ◦ Catalyst Poisoning ◦ Product Specifications
  • 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.
  • 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
  • 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.
  • 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
  • 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
  • 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
  • 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:
  • 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.
  • 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
  •  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
  • 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
  • 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
  •  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
  • REFORMATE LPG Key : VULCAN guard RECYCLE GAS MAKE GAS OFF GAS NAPHTHA FEED
  • Light Naphtha Hydrogen VGP-S201 ReactorStripper Isomerization Unit NHT Hydro- Treater
  • 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.
  • 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
  • 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.
  • Liquid phase treating Liquid Phase Sulfur Guards: Dis-advantages - Single pass feature limits sulfur removal to H2S or RSH. - Slower recovery from sulfur upsets.
  • 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
  •  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
  • • 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
  • 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.
  • Ni Ni S Thiophene adsorption on nickel Orientation flip Parallel vertical approach alignment
  • ◦ 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
  • 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
  •  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
  • 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
  • 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
  • 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
  • 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