Petrochemicals for Chemical Industries

Embed Size (px)

Citation preview

  • 7/24/2019 Petrochemicals for Chemical Industries

    1/32

    Petrochemicals

  • 7/24/2019 Petrochemicals for Chemical Industries

    2/32

    Lower alkenes Chemicals industry uses 10% of available

    petroleum and NG as feed, 4-5% as fuel

    Ethylene, Propylene, butadiene Produced from steam cracking of various

    refinery streams.

    Dehydrogenation reactions.

    Lower alkenes or olefins an important feedfor products we will discuss (ex. LDPP orHDPP)

  • 7/24/2019 Petrochemicals for Chemical Industries

    3/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    4/32

    Steam cracking: Free radical reactions form and propagate, decompose

    to an olefin plus hydrogen radical, etc.

    Obeys first order kinetics

    Reaction rate increases with partial pressure, and

    secondary reactions do as well.

    Uncatalysed reaction takes place in furnace tubes.

    Near atmospheric pressure, 30-40% steam,

    temperatures 750 oC -850 oC but as high as 900 oC.

  • 7/24/2019 Petrochemicals for Chemical Industries

    5/32

    Rate constants as a function of T

    Reactivity increases with chain length

  • 7/24/2019 Petrochemicals for Chemical Industries

    6/32

    Industrial Process A mixture of HC and steam is passed through

    tubes inside a furnace

    Heating occurs by convection and radiation Considerable heat input at a high temperature

    level

    Limited HC partial pressure

    Very short residence times (

  • 7/24/2019 Petrochemicals for Chemical Industries

    7/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    8/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    9/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    10/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    11/32

    Dehydrogenation Recently, the demand for propenes and

    butenes has been increasing.

    Direct production for these specificalkenes is important

    Selectively dehydrogenate the specific

    alkane (ie propane to form propylene) Alkane dehydrogenation is highly

    endothermic

  • 7/24/2019 Petrochemicals for Chemical Industries

    12/32

    Variables in these processes include:

    Type of catalyst used

    Reactor design

    Method of heat supply

    Method for catalyst regeneration

  • 7/24/2019 Petrochemicals for Chemical Industries

    13/32

    Major dehydrogenation processes

  • 7/24/2019 Petrochemicals for Chemical Industries

    14/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    15/32

    Major outlets for alkenes

  • 7/24/2019 Petrochemicals for Chemical Industries

    16/32

    Uses of ethylene LDPE 15%

    HDPE 23 %

    LLDPE 13 %

    Ethylene oxide 13 %

    Dichloroethane 10-11 % (to make vinyl chloride)

    Ethylbenzene 7% ( to make styrene)

    Vinyl acetate 3 %

    Acetaldehyde 2 % Ethanol 1 %

  • 7/24/2019 Petrochemicals for Chemical Industries

    17/32

    Synthesis Gas, Syngas A mixture of CO and H in varying ratios

    Uses:

    refinery hydrotreating, hydrocracking

    Ammonia

    Alkenes (via Fischer Tropsch reaction)

    Methanol, higher alcohols Aldehydes

    acids

  • 7/24/2019 Petrochemicals for Chemical Industries

    18/32

    Produced from coal, natural gas, etc.

    Major processes:

    Steam reforming of NG or light HC in thepresence of O2 or CO2

    Partial oxidation of heavy HC with steam

    (H2O) and O2

    Partial oxidation of coal with steam (H2O) and

    O2

    Raw materials depend on cost and availability

  • 7/24/2019 Petrochemicals for Chemical Industries

    19/32

    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 shi ft)

    (3) CH4 + CO2 2CO + 2H2(4) CH4 C + CO

    (5) 2COC + CO2(6) CH4 + O2 CO + H2 (partial oxidation)

    (7) CH4 + 2O2 CO2 + 2H2O

    (8) CO + O2 CO2(9) H2 + O2 H2O

  • 7/24/2019 Petrochemicals for Chemical Industries

    20/32

    Production of Syngas

  • 7/24/2019 Petrochemicals for Chemical Industries

    21/32

    Steam reforming High temperatures

    Nickel catalyst contained in tubes heated by afurnace

    May contain 500-600 tubes that are 7-12 m longwith ID of 70-130 mm

    Convection section and radiation section

    Feed pretreatment required to remove sulfur

    Coke deposits can form that deactivate thecatalyst and can block the furnace tubes, soexcess steam is used to prevent this

  • 7/24/2019 Petrochemicals for Chemical Industries

    22/32

    Steam reforming

  • 7/24/2019 Petrochemicals for Chemical Industries

    23/32

    Ammonia synthesis

    3H2+N2 2NH3 DH+ -91.44 kJ/ml

    A major product of the CPI

    Early sources were natural (saltpeter), or byproduct of coke ovens

    Major use in fertilizers (agricultural), explosives (increasing due toWWI)

    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 (a porous iron catalyst prepared by reducing magnetite, Fe3O4).Osmium is a much better catalyst for the reaction but is very expensive.

    Requires a H2:N2 ratio of 3:1

    N2 sources is air, H2 from syngas

  • 7/24/2019 Petrochemicals for Chemical Industries

    24/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    25/32

    The key to development of the Haber process was the availability of reliable thermodynamic data At atmospheric P it was noted that NH3 did not form from a mixture of the reactants

    Haber extrapolated to lower T and concluded that a feasible process could be developed

    Low T and high P are favoured

  • 7/24/2019 Petrochemicals for Chemical Industries

    26/32

  • 7/24/2019 Petrochemicals for Chemical Industries

    27/32

    Uses of ammonia

    Fertiliser ammonium sulfate, (NH4)2SO4

    ammonium phosphate, (NH4)3PO4

    ammonium nitrate, NH4NO3

    urea, (NH2)2CO

    Chemicals nitric 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)

    Explosives ammonium nitrate (NH4NO3)

    Fibres & Plastics nylon, -[(CH2)4-CO-NH-(CH2)6-NH-CO]-,and other polyamides

    Refrigeration used for making ice, large scale refrigeration plants, air-conditioning units in buildings and plants

    Pharmaceutical used in the manufacture of drugs such as sulfonamide which inhibit the growth and multiplication of bacteria thatrequire p-aminobenzoic acid (PABA) for the biosynthesis of folic acids, anti-malarials and vitamins such as the B

    vitamins nicotinamide (niacinamide) and thiamine

    Pulp & Paper ammonium hydrogen sulfite, NH4HSO3, enables some hardwoods to be used

    Mining & Metallurgy used in nitriding (bright annealing) steel,used in zinc and nickel extraction

    Cleaning

  • 7/24/2019 Petrochemicals for Chemical Industries

    28/32

    MethanolCO+ 2H2 CH3OH

    CO2+3H2 CH3OH+H2O

    Coupled by: CO+H2O CO2+H2

    Second large scale process involving catalyst and high P

    Equilibrium data:

  • 7/24/2019 Petrochemicals for Chemical Industries

    29/32

    Catalyst selectivity is very important, as other products

    may form. Cu/ZnO/Al2O3 catalysts are newer catalysts that enable

    lower P

  • 7/24/2019 Petrochemicals for Chemical Industries

    30/32

    Methanol synthesis

  • 7/24/2019 Petrochemicals for Chemical Industries

    31/32

    Methanol uses Formaldehyde

    Methyl tert-butyl ether (MTBE) used as

    octane booster

  • 7/24/2019 Petrochemicals for Chemical Industries

    32/32

    Fischer Tropsch Synthesis German scientist who discovered in 1923 that syngas

    could be converted to a wide range of HC and alcohols

    Economically not competitive

    Used in South Africa (Sasol) to produce fuels from coal

    Recently used to convert NG to liquid fuels