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Petrochemical Processes industry

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  • Chapter 38 P747Petrochemical Processes

    Dr. Hind Barghash CPI-14

  • Petrochemical processes are:1- Lower alkenes 2- Synthesis gases (Syngas)3- Polymerization4- Formalin


  • Lower Alkenes: Building block Chemicals Ethylene Propylene Butadiene (1,3) Benzene Toulene Xylenes

  • Petrochemicals from Ethylene

  • Petrochemicals from Propylene

  • AdiponitrileADNPolybutadieneRubberPBRStyrene-ButadieneRubber SBRAcrylonitrile-Butadiene-Styrene ABSButadienePetrochemicals from ButadienePetrochemicals from BSpecialty Polymers /Chemicals

  • Petrochemicals from Benzene

  • TolueneSpecialty/Functionalized chemicalsXylenesBenzenePetrochemicals from Toluene

  • XylenesO-Xylenep-Xylenem-XylenePhthalic anhydrideTerephthalic acidPTAIso-phthalic acidPlasticizersPolyestersPETPetrochemicals from Xylenes

  • Lower alkenes from oilChemical industry uses - 10% of available petroleum and natural gas as feed - 5% as fuel

    Produced from steam cracking of various refinery streams. dehydrogenation reactions.Example: Lower alkenes or olefins an important feed for products such as LDPP or HDPP.

  • Lower alkenes from oilC5 olefins (CH2=CH-CH=CH2)

  • Steam Cracking: Industrial ProcessA mixture of HC and steam are passed through tubes inside a furnaceHeating occurs by convection and radiationConsiderable heat input at a high temperature levelLimited HC partial pressureVery short residence times (
  • DehydrogenationRecently, the demand for propenes and butenes has been increasing.Direct production for these specific alkenes is importantSelectively dehydrogenate the specific alkane (ie propane to form propylene)Alkane dehyrogenation is highly endothermic

  • DehydrogenationVariables in these processes include:Type of catalyst usedReactor designMethod of heat supplyMethod for catalyst regeneration

  • Synthesis Gas - Syngas1/2A mixture of CO and H in varying ratiosUses:Refinery hydrotreating, hydrocrackingAmmoniaAlkenes Methanol, higher alcoholsAldehydesAcids

  • Synthesis Gas - Syngas2/2Produced from coal, natural gas, etc.Major processes:Steam reforming of NG or light HC in the presence of O2 or CO2Partial oxidation of heavy HC with steam (H2O) and O2Partial oxidation of coal with steam (H2O) and O2Raw materials depend on cost and availability

  • Production of Syngas

  • Reactions to form SyngasGeneral reactions(1)C + H2O CO + H2 (steam reforming, endothermic)(2)C + O2 CO(partial oxidation, exothermic)(3)CO + H2O CO2 + H2(water gas shift)

    NG as a feed:(1)CH4 + H2O CO + 3H2 (steam reforming, endothermic)(2)CO + H2O CO2 + H2 (water gas shift)(3)CH4 + CO2 2CO + 2H2(4) 2CO C + CO2(6)CH4 + O2 CO + H2 (partial oxidation)(7)CH4 + 2O2 CO2 + 2H2O(8)CO + O2 CO2(9)H2 + O2 H2O

  • Steam Reforming1/2High temperaturesNickel catalyst contained in tubes heated by a furnaceA mixture of NG and steam are passed through tubes inside a furnace. May contain 500-600 tubes that are 7-12 m long with ID of 70-130 mmHeating occurs by convection and radiationFeed pretreatment required a sulfur removalCoke deposits can form that deactivate the catalyst and can block the furnace tubes, so excess steam is used to prevent coke depositProduct is cooled in order to separate the condensed

  • Steam Reforming2/2

  • Ammonia synthesis1/2

    A major product of the CPIEarly sources were natural, or byproduct of coke ovensMajor use in fertilizers (agricultural) and explosives In 1909 Fritz Haber established the conditions under which nitrogen, N2(g), and hydrogen, H2(g), would combine using medium temperature (~500oC) very high pressure (~250 atmospheres, ~351kPa) a catalyst such as: 1-a porous iron catalyst prepared by reducing magnetite, Fe3O4). 2-Osmium is a much better catalyst for the reaction but is very expensive. Requires a H2:N2 ratio of 3:1N2 sources is air, H2 from Syngas 3H2+N2 2NH3 DH= -91.44 kJ/ml

  • Ammonia Synthesis2/2See chapter 2 for process description

  • Uses of Ammonia

    Fertiliserammonium sulfate, (NH4)2SO4 ammonium phosphate, (NH4)3PO4 ammonium nitrate, NH4NO3 urea, (NH2)2CO Chemicalsnitric acid, HNO3, which is used in making explosives such as TNT (2,4,6-trinitrotoluene), nitroglycerine which is also used as a vasodilator (a substance that dilates blood vessels) and PETN (pentaerythritol nitrate). sodium hydrogen carbonate (sodium bicarbonate), NaHCO3 sodium carbonate, Na2CO3 hydrogen cyanide (hydrocyanic acid), HCN hydrazine, N2H4 (used in rocket propulsion systems) Explosivesammonium nitrate (NH4NO3)Fibres & Plasticsnylon, -[(CH2)4-CO-NH-(CH2)6-NH-CO]-,and other polyamidesRefrigerationused for making ice, large scale refrigeration plants, air-conditioning units in buildings and plantsPharmaceuticalused in the manufacture of drugs such as sulfonamide which inhibit the growth and multiplication of bacteria that require p-aminobenzoic acid (PABA) for the biosynthesis of folic acids, anti-malarials and vitamins such as the B vitamins nicotinamide (niacinamide) and thiaminePulp & Paperammonium hydrogen sulfite, NH4HSO3, enables some hardwoods to be usedMining & Metallurgyused in nitriding (bright annealing) steel, used in zinc and nickel extractionCleaning

  • CO+ 2H2 CH3OHCO2+3H2 CH3OH+H2OCoupled by:CO+H2O CO2+H2

    Second large scale process involving catalyst and high pressureCatalyst selectivity is very important, as other products may form.Cu/ZnO/Al2O3 catalysts are newer catalysts that enable lower pressure

    Methanol Synthesis1/3

  • Methanol Synthesis2/3Equilibrium data:

  • Methanol Synthesis3/3CO, CO2 & H2 from steam reforming, To distillation

  • Methanol usesFormaldehydeOctane booster as Methyl tert-butyl ether (MTBE)

  • Sources of PolymersNatural polymers since prehistoric times are: WoodRubberCellulose, rayonFirst synthetic polymers: Phenol formaldehyde resinsUsed of polymersMain component of food:Starch, proteinClothes:Silk, cotton, polyester, nylonBuilding materialsWood, paints, PVC etc.

    Polymers & Polymerization

  • *What is a polymer?The terms polymer and monomer are part of our everyday speech.Poly = manyMono = oneMer is derived from the Greek meros, meaning part. So, a monomer is a one part and a polymer is a many part.Polymers

  • PolymersConstructed of monomer units connected by a covalent bond:-R-R-R-R- Or [R]n-

    R: a bi-functional entity not capable of separate existencen: degree of polymerization DPMW: molecular weight, obtained from the MW of the monomer multiplied by n

  • *Example: PolyethylenePolyethylene is an example of a synthetic polymer.Ethylene, derived from petroleum: is made to react with itself to form polyethylene.

  • Thermoplastic Become flexible solids above a certain Tthen become rigid again upon cooling below this Tflexible/rigid cycle can be repeatedWhen flexible it can be molded into shapesFibers can be drawn into strands, non fibers cannotThermoset resinsNetwork co-polymers that do not become flexible until the T is so high thermal decomposition takes placeSynthetic rubberDeformed by small stresses but regain original shapeCategories of Polymers1/2

  • Categories of Polymers2/2

  • Engineered polymersHigh % growthSpecial properties, replacements for metals, chemical inertness, etc. used in carpet and tirereinforcement.Examples:Acetal (poly-oxy-methylene POM)Nylons (polyamides)Polyethylene or poly-butylene terephthalate (PET or PBT)Polycarbonate PCPolyphenylene oxide PPO

  • Polymerization reactions2 mechanisms: chain growth and step growthChain growth (or additional polymer)Reaction occurs by successive addition of a monomer to the reactive endExample, polymerization of a monomers such as ethylene, propylene, styrene, vinyl chloride nCH2=CHX-(-CH2-CHX)n-Where X can be H, CH3, C5H6 or Cl

    Initiator or catalyst is required to start the chain growth reactionHigh MW product is produced right away (during polymerization)Polymerization is generally fast, irreversible and moderately to highly exothermic.

  • Step growth (or condensation polymerization) Formed when monomers combine and split out water or some other simple substance.Essentially a substitution reaction Nylon is a condensation polymer. High MW product is produced from the end of polymerization

    Commodity PolymersPolyethylene (PE)Polypropylene (PP)Polyvinylchloride (PVC)Polystyrene (PS)

  • Polyethylenes1/2Classification and properties

    linear, unbranched polymers are more densely packed therefore more orderedSide branches interfere with alignment of polymer chainsDensity can be controlled by operating T, P, catalysts and co-monomers used Example: LDPE is produced at high T and high P higher T results in more side reactions and branching, thus lower densityPolymer density is degree of crystallinity

  • Polyethylenes2/2

  • Applications

  • *

  • Production of LDPE1/3Ethylene fed to reactor at high T, PNo catalystInitiator can be used (oxygen, peroxide)Ethylene behaves like a liquid and a solventCSTR or tubular reactor

  • Production of LDPE2/3Using a tubular r

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