Production of Materials

Production of Materials

1. Crude Oil

   • Demand for natural resources putting a strain on supply. Need to meet the requirements of society using renewable things
   • Catalytic/Steam (Thermal) Cracking
     • Converts the excess long chain, high molecular weight substances (15 to 25 carbon alkanes) into shorter, lower molecular weight chains which would then be economically viable and usable for a wide range of appliances (eg. Aircraft fuel must be pure.....)  Carried about at higher pressures and temperatures (500 degrees) and without air (otherwise combustion occurs). Zeolite (porous Aluminosilicate)
     • Thermal/Steam Cracking - Non catalytic, (700 to 1000 degrees) - Just above atmospheric pressure to decompose alkanes into ethylene and butene eg.  C11H24 --> 4C2H4 + C3H6 + H2 - Steam facilitates easy flow of gases through the hot tube, while keeping the concentration of the reacting gases low enough to ensure desired reactions.
     • Ethylene
       • Alkenes and Alkanes  - Have a reactive double bond which opens up to form an addition reaction. - Alkanes require the presence of U.V. light to undergo substitution reaction.
       • Hydro/Halo/Hydrohalogenation
         • Vinyl Chloride
         • Styrene
       • Free Radical Polymerization, Gas Phase, Ziegler Natta Process
         • Polyethylene
           • High Density Polyethylene (HDPE)
             • Kitchen Utensils
           • Low Density Polyethylene
             • Cling wrap
         • Gas Phase Process
           • Product depends on conditions and inclusions of catalyst
           • Initiation
             • Benzyl peroxide (initiator) is introduced into an ethene chamber where it is decomposed by light or heat. This forms a free radical, which is highly reactive and beaks down ethene's double bond to form an activated monomer radical. eg: RO- + C2H4 --> RO-CH2CH2- This provides further sites of bonding.
             • Propagation
               • Activated Monomer reacts with many more ethylene monomers to increase chain length and form a polymer radical Catalysts are introduced in this step to speed up rate of reactino and control the properties of the product formed. RO-CH2CH2- + n[C2H4]
               • Termination
                 • In the ethene chamber, polymer radicals collide and react randomly, each with different chain lengths. Thus, as the free radical on the polymer free radicals met with another free radical like itself, their spare electrons join, forming a stable bond This stabilizers both parts as a single long polymer molecule.

2. Bio-polymers

   • Potato/Starch
     • Acid Hydrolosis
       • Decomposition of enzymes
         • Glucose
           • C6H12OH (aq) --> 2C2H5OH (aq) + 2CO2 (g)
           • Fermentation
             • Fractional distillation
               • Ethanol
                 • Dehydration
                   • Ethylene
                     • C2H5OH (aq) --> C2H4(g) + H2O (l)

3. Polymerisation

   • Addition reaction
     • Compared to a condensation reaction, it is a reaction where there is no loss in molecules. eg Polyethane eg. In condensation reactions, H2O is lost.
     • Hydrogenation
       • Alkene + Hydrogen gas (Ni, Pd, Pt catalyst)
     • Halogenation
       • Alkene + halogen
     • Hydrohalogenation
       • Alkene + hydrogen hallide
   • Alkenes/Alkanes
     • Reactive double bond
       • Opens up to form an addition reaction
     • Require the presence of UV light to undergo a substitution reaction
   • Important monomers
     • Vinyl Chloride: choroethane
     • Styrene: phenyl ethene/ethenyl benzyl