Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Petroleum or Crude Oil
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Petroleum or Crude Oil
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Subject: Chemistry
Class: Senior Secondary 3
Term: 1st Term
Week: 2
Theme: Chemistry And Industry
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explain the or igin and state the composition of crude oil (petroleum) discuss the explorationof and drilling for crude oilin Nigeria explain the fractionaldistillation of petroleumand list the major fractions(products). list the location of Nigerian refineries explain the termscracking and reforming discuss the use of petrochemicals as startingmaterials of or ganicsynthesis leading to or ganiccompounds like plastics,synthetic rubber, drugs,in secticides, detergents,fibres, etc explain the use of octanenumbers in determining the quality of petrol explain the occurrence, packagingand uses of naturalgases. state the economicimportance of petroleum
cryogenic tankers over long distances (e.g., Nigeria LNG Ltd. exports LNG from Bonny Island).
Compressed Natural Gas (CNG): Natural gas is compressed to high pressures (200-250 bar) and stored in strong cylindrical tanks. It is primarily used as a vehicular fuel in Nigeria (e.g., for buses, taxis) as an alternative to petrol/diesel.
Liquefied Petroleum Gas (LPG): This is not pure natural gas, but rather a mixture of propane and butane (which are also present in natural gas and derived from petroleum refining). It is liquefied under pressure at ambient temperatures and stored in cylinders for domestic and industrial use.
Uses: Fuel: Primary source of energy for electricity generation in power plants, industrial boilers, domestic cooking and heating, and vehicular fuel (CNG).
Petrochemical Feedstock: Used to produce ammonia (for fertilizers), methanol, and other chemicals.
Industrial Processes: Used in manufacturing, steel production, and as a reducing agent.
Flaring (Undesirable): Historically, much of Nigeria's associated natural gas was simply burned off ("flared") at oil wellheads due to lack of infrastructure for capture and utilization, causing significant environmental pollution. Efforts are now being made to reduce gas flaring through projects like NLNG. 2.
9. Economic Importance of Petroleum Major Source of Foreign Exchange: Crude oil exports are Nigeria's primary source of foreign currency earnings, accounting for over 90% of export revenues. This revenue is vital for funding government projects, imports, and maintaining economic stability.
Contribution to National Budget: Oil revenues constitute a significant portion (often over 50%) of the Nigerian government's annual budget.
Employment Generation: The oil and gas industry directly and indirectly employs thousands of Nigerians in exploration, drilling, refining, transportation, marketing, and ancillary services.
Infrastructure Development: Revenues from oil have historically funded the development of roads, schools, hospitals, power plants, and other critical infrastructure.
Source of Energy: Petroleum products (petrol, diesel, kerosene, LPG) are essential for transportation, electricity generation, industrial operations, and domestic use across the country.
Raw Material for Industries: Petrochemicals derived from crude oil and natural gas are raw materials for numerous manufacturing industries, producing plastics, textiles, detergents, pharmaceuticals, and agricultural chemicals, fostering industrial growth and diversification.
Investment and Technology Transfer: The industry attracts foreign direct investment and facilitates the transfer of advanced technology and expertise into the country. 2.
1. Origin and Composition of Crude Oil (Petroleum)
Origin (Fossil Fuel Theory): Crude oil is a fossil fuel formed over millions of years from the decomposition of dead marine organisms (plankton, algae) and other organic matter buried under layers of sedimentary rock.
Process:
1. Ancient marine organisms die and settle on the seabed.
2. They are covered by layers of sand, silt, and rock.
3. Under intense heat (from the Earth's interior) and immense pressure (from overlying layers), and in the absence of oxygen, these organic remains slowly transform into kerogen.
4. With continued heat and pressure over millions of years, kerogen breaks down into liquid hydrocarbons (crude oil) and natural gas.
5. This oil and gas migrate through porous rocks and accumulate in traps formed by non-porous rock layers, forming reservoirs.
Composition: Crude oil is a complex, dark, viscous liquid mixture primarily composed of various hydrocarbons.
Major Components (Hydrocarbons): Alkanes (Paraffins): Straight-chain and branched-chain saturated hydrocarbons (e.g., methane, ethane, propane, butane, pentane, octane). They make up a significant portion.
Cycloalkanes (Naphthenes): Saturated cyclic hydrocarbons (e.g., cyclopentane, cyclohexane).
Aromatic Hydrocarbons: Unsaturated cyclic hydrocarbons containing benzene rings (e.g., benzene, toluene, xylenes).
Minor Components (Impurities): Compounds containing sulphur, nitrogen, oxygen, and trace metals (e.g., nickel, vanadium). These are undesirable as they can cause corrosion and environmental pollution.
Key Characteristic: The hydrocarbons in crude oil range widely in molecular mass and boiling points, from simple gases (like methane) to complex, heavy solids (like asphalt). 2.
2. Exploration and Drilling for Crude Oil in Nigeria Exploration: The process of locating potential oil and gas reservoirs.
Geophysical Surveys: Primarily seismic surveys. Sound waves are generated at the Earth's surface, travel through rock layers, and reflect back. Geophones detect these reflected waves. Analysis of the wave patterns helps geologists create 3D maps of subsurface rock structures to identify potential traps.
Geological Studies: Examination of rock outcrops, analysis of rock samples, and understanding sedimentary basins.
Drilling: Once a potential reservoir is identified, a well is drilled to confirm the presence of oil or gas and to extract it.
Process:
1. Site Preparation: Clearing land (onshore) or positioning drilling rigs (offshore).
2. Rig Setup: Erection of a derrick (tower-like structure) that supports drilling equipment.
3. Drilling: A rotating drill bit cuts through rock layers. Drilling mud is continuously pumped down the drill pipe to cool the bit, lubricate it, carry rock cuttings to the surface, and maintain pressure to prevent blowouts.
4. Casing and Cementing: Steel pipes (casing) are inserted into the drilled hole and cemented in place to prevent the hole from collapsing and to isolate different rock layers and fluids.
5. Completion: Perforations are made in the casing at the reservoir depth to allow oil and gas to flow into the wellbore. Production tubing is installed, and a "Christmas tree" (a complex set of valves) is installed at the wellhead to control flow.
Nigerian Context: Major exploration and drilling activities occur in the Niger Delta basin (onshore and shallow offshore) and increasingly in deep offshore fields. Onshore drilling involves land-based rigs. Offshore drilling uses platforms (fixed or floating) for shallow waters and drillships/semi-submersibles for deep waters. Companies like Shell, ExxonMobil, Chevron, TotalEnergies, Eni (Agip), and the Nigerian National Petroleum Company Limited (NNPCL) are major players. 2.
3. Fractional Distillation of Petroleum Principle: Fractional distillation separates the components of crude oil based on their different boiling points. Since crude oil is a mixture of hydrocarbons with varying molecular sizes, they have distinct boiling ranges. Lighter hydrocarbons have lower boiling points, while heavier ones have higher boiling points.
Process:
1. Heating: Crude oil is heated in a furnace to about 350-400°C, causing most of it to vaporize.
2. Fractionating Column: The hot mixture of liquid and vapour is pumped into the bottom of a tall, cylindrical fractionating column (or fractionating tower). The column has trays or plates at different levels.
3. Vaporisation and Condensation: As the hot vapour rises up the column, it gradually cools. Vapours with higher boiling points condense at lower, hotter levels of the column. Vapours with lower boiling while heavier ones have higher boiling points.
Process:
1. Heating: Crude oil is heated in a furnace to about 350-400°C, causing most of it to vaporize.
2. Fractionating Column: The hot mixture of liquid and vapour is pumped into the bottom of a tall, cylindrical fractionating column (or fractionating tower). The column has trays or plates at different levels.
3. Vaporisation and Condensation: As the hot vapour rises up the column, it gradually cools. Vapours with higher boiling points condense at lower, hotter levels of the column. Vapours with lower boiling points continue to rise higher up the column before condensing at cooler, upper levels.
4. Collection: Different fractions are collected at various levels of the column. The lightest fractions (lowest boiling points) are collected at the top, and the heaviest fractions (highest boiling points) remain at the bottom.
Major Fractions (Products) and Uses: Refinery Gases (Petroleum Gas): C1-C4 hydrocarbons (methane, ethane, propane, butane).
Boiling Point: Below 40°C Uses: Used as fuel for refineries, LPG (Liquefied Petroleum Gas) for domestic cooking and heating (e.g., "cooking gas" cylinders), and as petrochemical feedstock.
Gasoline (Petrol): C5-C12 hydrocarbons.
Boiling Point: 40-200°C Uses: Fuel for internal combustion engines (cars, motorcycles).
Naphtha: C5-C10 hydrocarbons.
Boiling Point: 60-180°C Uses: Primarily as a feedstock for the petrochemical industry (e.g., producing ethene, propene) and as a solvent.
Kerosene (Paraffin): C12-C16 hydrocarbons.
Boiling Point: 180-250°C Uses: Aviation fuel (jet fuel), domestic lighting and cooking fuel (e.g., kerosene stoves, lamps), and as a solvent.
Diesel Oil (Gas Oil): C15-C18 hydrocarbons.
Boiling Point: 250-350°C Uses: Fuel for diesel engines (buses, trucks, generators), heating oil.
Lubricating Oils: C18-C25 hydrocarbons.
Boiling Point: 350-400°C Uses: Lubricants for machinery, motor oils, waxes.
Fuel Oil (Heavy Fuel Oil): >C20 hydrocarbons.
Boiling Point: Above 400°C Uses: Fuel for power stations, industrial furnaces, ships.
Bitumen/Asphalt: Residue with very high molecular weight.
Boiling Point: Residue (boiling point too high to vaporize easily)
Uses: Road surfacing (asphalt roads), roofing, waterproofing. 2.
4. Location of Nigerian Refineries Nigeria has four major refineries, though their operational status and capacity utilization vary significantly.
1. Port Harcourt Refining Company (PHRC): Located in Eleme, Rivers State.
It has two plants: Old Port Harcourt Refinery (60,000 bpd) and New Port Harcourt Refinery (150,000 bpd).
Total capacity: 210,000 barrels per day (bpd).
2. Warri Refining and Petrochemical Company (WRPC): Located in Warri, Delta State.
Capacity: 125,000 bpd.
3. Kaduna Refining and Petrochemical Company (KRPC): Located in Kaduna, Kaduna State.
Capacity: 110,000 bpd.
4. Dangote Refinery: Located in Lekki, Lagos State. This is a private refinery with a massive capacity of 650,000 bpd, the largest single-train refinery in the world. It began operations in 2024. 2.
5. Cracking and Reforming Cracking: Definition: The process of breaking down large, long-chain hydrocarbon molecules (found in less valuable heavy crude oil fractions like gas oil or fuel oil) into smaller, more useful, lighter hydrocarbon molecules (like gasoline, kerosene, or alkenes). This is crucial because fractional distillation often produces more heavy fractions than desired, while demand for lighter fractions (especially petrol) is higher.
Types: Thermal Cracking: High temperatures (450-750°C) and high pressures are used. It produces mainly alkenes (e.g., ethene, propene) and shorter alkanes.
Catalytic Cracking: Lower temperatures (400-500°C) and lower pressures are used with a catalyst (e.g., zeolites, aluminium silicates). It produces branched alkanes and aromatic hydrocarbons, which are valuable components of high-octane petrol.
Importance: Increases the yield of valuable products like gasoline and petrochemical feedstock (e.g., ethene for plastics).
Reforming (Platforming): Definition: A process that converts straight-chain alkanes (which cause knocking in engines) and cycloalkanes into branched-chain alkanes and aromatic hydrocarbons.
Process: Carried out at high temperatures and pressures in the presence of a catalyst, typically platinum (hence "platforming").
Importance: Improves the octane number (anti-knocking property) of petrol, making it a more efficient fuel. It also produces aromatic compounds that are valuable petrochemical feedstocks. 2.
6. Use of Petrochemicals as Starting Materials of Organic Synthesis * Petrochemicals: Chemicals derived from petroleum and natural gas. They are the fundamental building Reforming (Platforming): Definition: A process that converts straight-chain alkanes (which cause knocking in engines) and cycloalkanes into branched-chain alkanes and aromatic hydrocarbons.
Process: Carried out at high temperatures and pressures in the presence of a catalyst, typically platinum (hence "platforming").
Importance: Improves the octane number (anti-knocking property) of petrol, making it a more efficient fuel. It also produces aromatic compounds that are valuable petrochemical feedstocks. 2.
6. Use of Petrochemicals as Starting Materials of Organic Synthesis Petrochemicals: Chemicals derived from petroleum and natural gas. They are the fundamental building blocks for a vast array of synthetic organic compounds. Key Petrochemicals (often produced via cracking naphtha): Ethene (Ethylene): Used to produce polyethylene (plastics), ethanol, PVC (another plastic), antifreeze.
Propene (Propylene): Used to produce polypropylene (plastics), propanol, acetone.
Butenes: Used to produce synthetic rubber. Benzene, Toluene, Xylenes (BTX aromatics): Used to produce various plastics (e.g., polystyrene, nylon), synthetic fibres, dyes, and pharmaceutical intermediates. Products of Organic Synthesis from Petrochemicals: Plastics: Polyethylene, polypropylene, PVC, polystyrene, nylon (for clothing, containers, pipes, insulation, car parts).
Synthetic Rubber: For tyres, seals, hoses.
Drugs/Pharmaceuticals: Many active pharmaceutical ingredients are synthesized from petrochemical precursors.
Insecticides: Pesticides for agriculture.
Detergents: Surfactants used in cleaning products.
Synthetic Fibres: Nylon, polyester, acrylics (for clothing, carpets, ropes).
Fertilizers: Ammonia (from natural gas, a related fossil fuel). Solvents, Paints, Adhesives, Cosmetics. 2.
7. Octane Numbers in Determining the Quality of Petrol Knocking (Engine Knock/Pinging): In an internal combustion engine, petrol is designed to ignite smoothly by a spark plug. If the fuel ignites prematurely or spontaneously (before the spark plug fires) due to compression, it causes a sharp, rattling sound called knocking. Knocking reduces engine efficiency, causes wear and tear, and can damage the engine.
Octane Number: A measure of a fuel's resistance to knocking or pre-ignition. A higher octane number indicates greater resistance to knocking and therefore a higher quality fuel.
Reference Fuels: n-Heptane: A straight-chain alkane that knocks severely. It is assigned an octane number of
0. Isooctane (2,2,4-trimethylpentane): A highly branched-chain alkane that resists knocking very well. It is assigned an octane number of
1
0
0. Determination: The octane number of a fuel is determined by comparing its knocking characteristics in a test engine to those of a mixture of n-heptane and isooctane. For example, a petrol with an octane number of 95 performs like a mixture of 95% isooctane and 5% n-heptane.
Improvement: Octane numbers can be improved by: Reforming: Converting straight-chain alkanes to branched alkanes and aromatics.
Cracking: Producing more branched and aromatic compounds.
Adding Antiknock Agents: Tetraethyl lead (TEL): Historically used but phased out due to lead pollution (toxic to humans and deactivates catalytic converters). Nigeria has also largely phased out leaded petrol. Methyl tertiary-butyl ether (MTBE), Ethanol, Toluene: Current common additives that are oxygenates and help improve octane rating. 2.
8. Occurrence, Packaging, and Uses of Natural Gases Occurrence: Natural gas is often found associated with crude oil deposits (associated gas) or in separate underground reservoirs (non-associated gas). It is formed through similar geological processes as crude oil.
Composition: Primarily methane (CH4) (typically 70-90%), with smaller amounts of other light alkanes like ethane (C2H6), propane (C3H8), and butane (C4H10). It may also contain impurities like nitrogen, carbon dioxide, hydrogen sulphide, and helium.
Packaging: Liquefied Natural Gas (LNG): Natural gas is cooled to approximately -162°C at atmospheric pressure, converting it into a liquid. This significantly reduces its volume (about 1/600th), making it economical to transport in specialized cryogenic tankers over long distances (e.g., Nigeria LNG Ltd. exports LNG from Bonny Island).
Compressed Natural Gas (CNG): Natural gas is compressed to high pressures (200-250 bar) and stored in strong cylindrical tanks. It is primarily used as a vehicular fuel in Nigeria (e.g., for buses, taxis) as an alternative to petrol/diesel.
Liquefied Petroleum Gas (LPG): This is not pure natural gas, but rather a mixture of propane and butane (which are also present in natural gas and derived from petroleum refining). It is liquefied under pressure at ambient temperatures
Energy Security and Domestic Use: Crude oil products are indispensable for Nigeria's energy needs.
Application: Students see petrol and diesel used daily in vehicles (cars, motorcycles, okadas, keke Napeps, buses), generators powering homes and businesses (due to unreliable grid electricity), and kerosene for lamps and stoves in rural areas. LPG ("cooking gas") is a common domestic fuel, an affordable alternative to firewood. This directly connects the fractions of crude oil to essential aspects of daily Nigerian life.
Integration: Discuss how fluctuations in global crude oil prices directly impact fuel prices at Nigerian filling stations, affecting transportation costs and the cost of living for everyone. Industrial Development and Economic Diversification: The petrochemical industry is a key driver of modern manufacturing.
Application: Students use plastics (polyethylene bags, water bottles, PVC pipes), wear synthetic fabrics (polyester, nylon clothing), and rely on pharmaceuticals. Many of these everyday items are made from petrochemicals derived from crude oil. The establishment of companies like Indorama Eleme Petrochemicals Ltd in Rivers State exemplifies local production of these raw materials.
Integration: Discuss how developing a robust petrochemical industry reduces Nigeria's reliance on imported finished goods, creates local jobs, and adds value to the nation's crude oil resources, contributing to economic diversification away from primary crude oil exports. Environmental and Societal Impact (Niger Delta Focus): The extraction and processing of crude oil have significant environmental and social consequences, particularly in the Niger Delta region.
Application: Gas flaring, oil spills, and pipeline vandalism are real issues that lead to air and water pollution, destruction of farmlands and fishing grounds, and health problems for local communities. The efforts by NLNG to reduce gas flaring illustrate attempts to mitigate environmental damage.
Integration: This topic allows for discussions on environmental ethics, corporate social responsibility, sustainable development, and the balance between economic benefits and environmental protection. Students can analyze the challenges faced by host communities and the government's role in regulation and remediation.