HydrotreatingOil Refining ProcessesTKP-4150 - Group AApril 8th, 2013AgendaBackground & Basics.Chemistry of Hydrotreating.Thermodynamics of Hydrotreating.Description of Hydrotreating Processes.Safety & Environmental Issues.Hydrotreating09.04.201322Background & Basics Definition of HydrotreatingHydrotreatingUse of hydrogen for:Removal of heteroatoms (S, N, O).Removal of heavy metals (V, Ni).Saturation of olefins and aromatics.
No significant reduction of molecular weight.
Driving forces:Process requirements.Environmental policies.Product specifications.09.04.20133Background & Basics The Role of Hydrotreating in a RefineryHydrotreating09.04.20134
Simplified processing scheme of an oil refinery (I. Chorkendorff and J. W. Niemantsverdriet, 2003) Chemistry of HydrotreatingHydrotreating ReactionsHydrotreatingHydrodesulfurization (HDS).Hydrodenitrogenation (HDN).Hydrodeoxygenation (HDO).Hydrodearomatization (HDA).Olefin & diolefin saturation.Hydrodemetallization (HDM).Halides removal.
Chemistry of HydrotreatingHydrodesulfurization (HDS)HydrotreatingSulfur: most abundant heteroatom.Removed as H2S.Simple removal reactions:
09.04.20136MercaptanesSulfidesDisulfidesRSH + H2 RH + H2SR2S + 2H2 2RH + H2S(RS)2 + 3H2 2RH + 2H2SChemistry of HydrotreatingHydrodesulfurization (HDS)HydrotreatingThiophenes are more difficult to treat:09.04.20137
Global reaction mechanism for hydrodesulfurization of thiophene (I. Chorkendorff and J. W. Niemantsverdriet, 2003)
Chemistry of HydrotreatingHydrodesulfurization (HDS)HydrotreatingSulfur is commonly present as thiophene:09.04.20138Example of sulfur types distribution as a function of distillation temperature (fraction) in Arab medium distillate (Stanislaus et al, 2010) Chemistry of HydrotreatingHydrodenitrogenation (HDN)HydrotreatingMostly found in heavy fractions.Nitrogen removed as NH3.09.04.20139
AminesPyrrolePyridineQuinolineChemistry of HydrotreatingHydrodeoxygenation (HDO)HydrotreatingLow and medium boiling point fractions.Non-conventional sources.Oxygen removed as water.09.04.201310
PhenolsPeroxidesNaphtenicacidsChemistry of HydrotreatingHydrodemetallization and halides removalHydrotreatingMost common: nickel and vanadium.Removed as metal sulfides.
Chloride and bromide present at trace levels.09.04.201311
Chemistry of HydrotreatingHydrodearomatization & olefin saturationHydrotreatingAromatics: naphtha to gasoil boiling range.Olefins and diolefins: formed in thermal and catalytic units.09.04.201312
TolueneNaphthalenePhenanthreneChemistry of HydrotreatingHydrotreating CatalystsHydrotreatingMost common: -alumina base, promoted MoS2Co-Mo: Preferred for HDS.Lowest hydrogenation activity.Low sensitivity to H2 consumption and operating pressure.Ni-Mo:Better HDN and hydrogenation performance.Higher sensitivity to H2 partial pressure.09.04.201313
Topse catalysts for hydroprocessing of petroleum fractions (Brochure, 2009) Chemistry of HydrotreatingDeactivation of Hydrotreating Catalysts HydrotreatingTemporary:Coke formation:Defines when to regenerate catalyst.Deposition of nitrogen and sulfur compounds.
Irreversible:Metal deposition:V, Ni, Pb, Fe, As, among others.Catalyst support sintering.09.04.201314
Example of coke buildup on catalystand the agglomeration from unstable dienesin feed. (Sanghavi, K. & Schmidt, J., 2011.) Thermodynamics of HydrotreatingHeat of ReactionHydrotreatingHydrotreating reactions are exothermic.High temperatures decrease equilibrium conversion.09.04.201315Reaction H [kJ/mol]Desulfurization of sulfides-117.0Desulfurization of disulfides-209.0Desulfurization of thiophenes-284.2Deoxidation of phenol-66.9Hydrogenation of benzene-209.0Hydrogenation of naphthene-125.4Typical heat of reaction for some hydrotreating reactions. (Fahim et al. 2010) Thermodynamics of HydrotreatingEquilibrium & Heat of ReactionHydrotreatingHydrotreating reactions are exothermic.
Increasing temperature: Kinetic rates. Metal removal.But: Equilibrium conversion. Coke formation.Aromatic saturation maximum activity at 385C.Other parameters to favor reaction: H2 partial pressure. LHSV.09.04.201316
Equilibrium data of selected HDS reactions.(Fahim et al, 2010) ABCHydrotreating ProcessesGeneral Process DescriptionHydrotreatingLiquid feedstock is mixed with hydrogen.Furnace preheat the mix. Naphtha (vapor). Heavier residues: gas oil or residue (mixed-phase).
Catalytic reactor.Cooling and separation steps:Liquids to fractionator Gases to treatment.
Main elements of Hydrotreating Processes. (Fahim et al, 2010) Hydrotreating ProcessesNaphtha HydrotreatingHydrotreatingMain objective:Remove impurities upstream catalytic reformer, to avoid poisoning noble metal catalyst.
Process elements:Feed heater.Bed reactor.High and low pressure separators (scrubber).Recycle compressor for un-reacted hydrogen. Gas purge to decrease the light hydrocarbon. Treated naphtha is sent to fractionators to obtain light and heavy naphtha.
09.04.201318Hydrotreating ProcessesNaphtha HydrotreatingHydrotreating09.04.201319
Naphta Hydrotreating Process. (Fahim et al, 2010) Hydrotreating ProcessesMiddle Distillates HydrotreatingHydrotreatingFeedstock: kerosene, jet fuel oil, and diesel.09.04.201320
Diesel Fuel Hydrotreating Unit. (Fahim et al, 2010) Hydrotreating ProcessesAtmospheric Residue HydrotreatingHydrotreatingReduce metal content:Ni and V, from 75-90 ppmw.Reduce sulfur content:From 5 to 0.5 wt%.
Process temperature is 370C.To avoid coke formation, steam is fed to the heater.Guard reactor contains 8 % of the total catalyst. (retains 30% of V).Produces: Naphtha, Diesel, and Low Sulfur Oil.
09.04.201321Hydrotreating ProcessesAtmospheric Residue HydrotreatingHydrotreating09.04.201322
Atmospheric Hydrotreating Process. (Fahim et al, 2010) Hydrotreating ProcessesOperating ConditionsHydrotreatingVary due to the broad variety of applications.The most important operating conditions are:
09.04.201323FeedstockNaphthaKeroseneGas oilVGO*ResidueTemperatureC260-300300-340320-350360-380360-380Hydrogenpressurebar5-1015-3015-4040-70120-160partial pressurebar10-2020-3126-4150-9090-200consumptionwt%0.05-0.100.1-0.20.3-0.50.4-0.71.5-2.0LHSVhr-14-102-41-31-20.15-0.3H2/HC ratiostd m3/m336-4836-4836-4836-4812-24Catalyst life years3-10---0.5-1Typical Process Parameters for Hydrotreating of Different Feedstocks. (Fahim et al, 2010; Speight et al, 2011) * VGO = Vacuum gas oilHydrotreating ProcessesFixed-Bed ReactorHydrotreatingAdiabatic reactor:To control temperature, the outflow is quenched between reactors.
Works as a plug-ow reactor:Pressure drop and reaction rate must be balanced.
Mechanical work over the catalyst.Attrition decreases catalyst particle size:Reactivity is favored.Pressure drop is increased.09.04.201324
Fixed Bed Reactor(Ullmanns Encyclopedia of Industrial Chemistry, 1992) Hydrotreating ProcessesTrickle-Bed Reactor (TBRs)HydrotreatingPreferred for two-phase fluids.Multiple randomly fixed-beds in the same body. Quenching points to control temperature. Distributor design is a very important issue.09.04.201325
Trickle Bed Reactor and Examples of Distributors(Lee , 2006; Renade et al. 2011)
Safety & Environmental IssuesByproducts, Emissions, Catalyst HandlingHydrotreatingClosed process.Hydrotreating reduces SOx and NOx emissions.
Possible risk during inspections, maintenance, regeneraton/loading/ unloading of catalyst.
Catalyst may be regenerated several times to remove coke and sulfur.
CO2 and CO are produced. Sulfur reacts to form SO2.
09.04.201326HydrotreatingHighlightsHydrotreatingH2 to remove heteroatoms (S, N, O, metals) and saturate aromatics and olefins.No significant reduction of molecular weight.Several locations in a refinery.Catalysts: Co-Mo and Ni-Mo.Exothermic reactions.Kinetics mostly favored by high temperature.Vapor or mixed phase reaction.Common reactors: fixed-bed and trickle bed.Common products: naphtha, diesel, low sulfur fuel oil.
09.04.201327HydrotreatingSelected ReferencesHydrotreatingM. A. Fahim, T. A. Al- Sahhaf and A. S. Elkilani, Fundamentals of Petroleum Refining, Elsevier, 2010.I. Chorkendorff and J. W. Niemantsverdriet, Concepts of Modern Catalysis and Kinetics, Weinheim: WILEY-VCH Verlag GmbH & Co., 2003.Topse catalysts for hydroprocessing of petroleum fractions, http://www.topsoe.com/business_areas/refining/~/media/PDF%20files/Refining/topsoe_hydroprocessing_catalysts_aug09.ashx; Brochure, 2009. Visited: March 26th, 2013.A. Stanislaus, A. Mara and M. S. Rana, "Recent advances in the science and technology of ultra low sulfur diesel (ULSD) production," Catalysis Today, no. 153, p. 168, 2010.Sanghavi, K. & Schmidt, J., 2011. http://www.hydrocarbonprocessing.com/Article/2892145/Achieve-success-in-gasoline-hydrotreating.html Visited : March 26th, 2013J. G. Speight, "Chapter 8 Hydrotreating and Desulfurization," in The Refinery of the Future, Elsevier, 2011, p. 237273.S. Lee, Ed., Encyclopedia of Chemical Processing, New York: Taylor & Francis Group, LLC, 2006.V. Ranade, R. Chaudhari and P. R. Gunjal, Reactor Engineering and Applications, Elsevier, 2011.Ullmann's Encyclopedia of Industrial Chemistry, vol. B4, VCH Publishers, 1992.09.04.201328HydrotreatingOil Refining ProcessesTKP-4150 - Group AApril 8th, 2013Thank you for your attention!Questions?
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