In-Depth Notes on Petrochemicals and Polymers

Millions of years ago, marine life accumulated on the sea floor after dying.
Over time, layers of sand and mud (sediments) built up on top.
Shells and skeletons formed limestone.
Heat and pressure transformed soft tissues into crude oil over millions of years.

Crude oil is a mixture of hydrocarbons, which are compounds made up of carbon and hydrogen only.
It is classified as a finite, non-renewable resource. Once depleted, it cannot be replaced for millions of years.
Viscous: This term refers to crude oil's thick and sticky nature, meaning it does not flow easily.

Increasing Carbon Counts: As the number of carbon atoms in hydrocarbons increases:
- Physical properties such as boiling and melting points change.
- Intermolecular forces grow stronger, requiring more energy (higher boiling points).
- Hydrocarbons become darker, more viscous (flow less easily), and less volatile.

Crude oil must be refined to be useful. This is done in an oil refinery using fractional distillation, which separates the oil into fractions based on boiling points.
Fractional Distillation Process:
1. Crude oil is heated until it vaporizes.
2. The vapor rises in a fractionating column, which is cooler at the top and hotter at the bottom.
3. Different hydrocarbons condense back into liquids at specific temperatures.
4. Fractions are collected:
- Examples of Fractions:
  - Refinery Gas (bp < 25°C): Small hydrocarbons (1-3 carbon atoms).
  - Gasoline (bp 60-180°C): 5-10 carbon atoms.
  - Kerosene (bp 180-220°C).
  - Diesel (bp 220-300°C).
  - Fuel Oil (bp 300-350°C).
  - Bitumen (bp > 350°C).

Fossil fuel combustion releases greenhouse gases like CO$_2$, contributing to global warming.
Acid Rain: Formed when sulfur dioxide and nitrogen oxides react with atmospheric water, leading to sulfuric and nitric acids which lower rain pH below 5.6.
Emissions from burning fuels include carbon monoxide, which poses health hazards by binding with hemoglobin in the blood, reducing oxygen transport (hypoxia).

Cracking breaks down long-chain hydrocarbons into shorter, more useful alkanes and alkenes (like ethene and propene).
Types of Cracking:
- Catalytic Cracking: uses heat (600-700 °C) and a catalyst (Silicon and Aluminum oxides).
- Thermal Cracking: involves very high temperatures without a catalyst.

Polymers: Large molecules made of repeating units (monomers).
Addition Polymerization: Characterized by the addition of monomers with C=C bonds, resulting in polymers like polythene and PVC.
Condensation Polymerization: Forms polymers by joining monomers with the loss of small molecules (like water).

Low-Density Polyethene (LDPE): Flexible, used in bags and containers.
High-Density Polyethene (HDPE): Rigid, used in containers and pipes.
Polyvinyl Chloride (PVC): Strong and flexible, used in pipes and insulation.
Polytetrafluoroethene (Teflon): Non-stick coatings, resistant to chemicals.

Advantages:
- Easily molded, inexpensive, durable, resist corrosion, and are lightweight.
Disadvantages:
- Inert towards environmental degradation, non-biodegradable, and can emit toxic fumes when burned.

Landfill: Long-lasting impact as plastics take hundreds of years to decompose.
Incineration: Generates energy but releases CO$_2$ and toxic gases.
Recycling: Reduces waste but can lower plastic strength over time due to contamination.