Environmental Chemistry & Fractional Distillation of Crude Oil

Environmental Chemistry

  • Produced when sulfur containing fossil fuel is burned
  • Effects – Irritation in eyes, Stiffening of flower beds which eventually fall from plants, Asthama, Bronchitis in human beings
  • NO3-  Acts as a fertilizer to the soil
  • Automobile exhaust produces NO2 which damages plant leaves & retard rate of photosynthesis
  • Automobile exhaust also causes red haze & lung irritation
  • Formed by incomplete combustion of fuels esp. automobile
  • Carcinogenic – Causes cancer, Causes early aging, Plants leaves shredding
  • Formed by respiration, burning of fuels, decomposition of lime, volcanic eruption
  • A major greenhouse gas
  • Formed by incomplete combustion of C, Automobile exhaust, Cigarette smoke
  • Blocks delivery of oxygen to tissues (Combines with hemoglobin to form carboxy-hemoglobin, which is highly stable & reduces oxygen carrying capacity of blood)
  • Helps in production of steel & in extraction of Fe from Fe ore
Classical Smog 
  • Occurs in cool humid climate
  • Chemically reducing hence called reducing smog
  • Smoke + fog + SO2
Green House Gases
  • CO2, CH4, CFC, N2O, SF6, HFCs, PFCs, CCl4, CH3CCl3
  • It is mainly CH4 which burns in fossil fuels, produced by burning of vegetation or rotting


Photochemical Smog

  • Occurs in warm, dry & sunny climate
  • Results from the action of sunlight on unsaturated HC & oxides of Nitrogen produced by factories & automobile
  • Chemically oxidizing hence called oxidizing smog
  • Ozone + Acrolein + Formaldehyde + Peroxyacetyl Nitrate (PAN) are produced which cause serious health problems, severe plant damage, cracking of rubber & corrosion
  • Catalytic Converter – Prevent release of NO & HC to environment

Photochemical Smog


Ozone Depletion

  • Ozone protects us from UV rays which causes skin cancer (Melanoma)
  • Depletion of ozone layer – By Ozone depleting substances (ODS) which are non-toxic, non-reactive & nonflammable
  • Main ODS- CFCs, HCFCs, Halons, CCl4, NOx, CH3CCl3 (Methyl chloroform)
  • Major Sources – Solvent Cleansing products >Refrigeration & Air conditioners > Foam Products
  • CFCs are the most widely used ODS, accounting for over 80% of total stratospheric ozone depletion
  • ODS + UV Cl (Chlorine radicals which causes breakdown of Ozone)


Acid Rain

  • Acid rain (Ph < 5.6) is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids (H2SO4& HNO3) 
  • Rain with Ph < 5.6
  • Rain with oxides of sulfur & nitrogen (SO2 & NO2)

 Acid Rain


Fractional Distillation of Crude Oil

  • Crude oil is heated until it boils and then the hydrocarbon gases are entered into the bottom of the fractionating column.
  • As the gases go up the column the temperature decreases.

Fractional Distillation of Crude Oil

  • The hydrocarbon gases condense back into liquids and the fractions are removed from the sides of the column.
  • Higher HC degrade into lower HC by high heating (cracking) in following order –
  • Gaseous HCs
  • Petroleum Ether
  • Gasoline
  • Kerosene
  • Diesel / Gas Oil
  • Lubricating oil / Greases
  • Paraffin Wax
  • Asphalt & Coke
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