Chemical Industries

The growth of chemical industries greatly influenced the advancement of chemistry. In 1749, the Chamber process was introduced for the commercial production of hydrogen tetraoxosulphate(VI) (H2SO4).

What Is the Chemical Industry?

The chemical industry involves the transformation of raw chemical substances into other useful chemicals through chemical processes.

Major Raw Materials in the Chemical Industry

Some of the key raw materials used in chemical production include:

These naturally occurring substances serve as starting materials for the large-scale manufacture of various chemical products. With the exception of air, all these raw materials are typically extracted from the earth's crust. Salt, for example, is primarily sourced from seawater.

Sources of Raw Materials in the Chemical Industry

Air

Air is a key source of oxygen and nitrogen. Nitrogen is used in the Haber process to produce ammonia (NH3), which is important in making nitric acid (HNO3), fertilizers (e.g., NH4NO3, (NH4)2SO4), explosives, and plastics.

Seawater and Rock Salt

Rock salt (NaCl) is found in underground deposits and seawater. It is a major raw material for many chemical industries. Electrolysis of NaCl produces chlorine and sodium hydroxide (NaOH), used in soap, textiles, and petroleum refining. Other chemicals like sodium trioxocarbonate(IV) (Na2CO3) are derived from it and used in glassmaking and detergents. Seawater is also a source of sodium bromide (NaBr) for producing bromine.

Coal

Coal is used to produce coal gas, coke, coal tar, benzene, ethyne, and plastics. Coal tar contains useful chemicals such as benzene, toluene, phenol, cresol, and naphthalene.

Sulphur

Sulphur is obtained from underground sources using the Frasch process or from minerals like iron pyrites (FeS2) and gypsum (CaSO4.2H2O). It is used to manufacture sulphur dioxide (SO2), sulphurous acid (H2SO3), and sulphuric acid (H2SO4), which are essential in producing fertilizers, dyes, synthetic fibres, paints, and explosives.

Natural Gas and Petroleum

Petroleum is a vital raw material for petrochemicals like methane, ethane, ethyne, butadiene, and benzene. These are used to make fertilizers, plastics, and synthetic fibres. Petroleum also yields fuels such as petrol, diesel, and kerosene.

Metallic Mineral Ores

Metals like aluminium, iron, and copper are extracted from ores. Aluminium ores include bauxite (Al2O3.2H2O), kaolin, and cryolite (Na3AlF6).

Calcium Carbonate (CaCO3)

Found in limestone, chalk, and marble, calcium carbonate is used to make lime (CaO) for cement and concrete. It is also used to produce baking powder and carbon dioxide, which is essential in the Solvay process for making sodium trioxocarbonate(IV).

Heavy and Fine Chemicals

Heavy Chemicals

Heavy chemicals are produced and used in large quantities across various chemical industries. A key example is tetraoxosulphate(VI) acid (H2SO4), essential in many chemical processes.

Other common heavy chemicals include:

Metals like iron, aluminium, copper, zinc, and tin, as well as organic materials such as coke, coal tar, benzene, and methylbenzene, are also classified as heavy chemicals. Ammonia (NH3) is another important heavy chemical used primarily in the production of fertilizers and explosives.

Fine Chemicals

Fine chemicals are produced in smaller quantities and are typically high in purity, making them more expensive than heavy chemicals. They are used in specialized industries such as:

Crude Oil

Crude oil, also known as petroleum (Latin: "rock oil"), is a dark, sticky liquid found in underground reservoirs. It is a complex mixture of hydrocarbons including alkanes, alkenes, cycloalkanes, and aromatic compounds. Natural gas, primarily methane, is often found alongside crude oil.

Occurrence

Crude oil is abundant in Nigeria, especially in Bayelsa, Edo, Imo, Rivers, Delta, Abia, Ondo, and Cross River states. Its composition and quality vary by location. There are two types: light crude (low in metals and sulfur, more expensive) and heavy crude (higher in metals and sulfur, thicker, less expensive).

Origin of Crude Oil and Natural Gas

Crude oil and natural gas were formed from the remains of marine organisms that settled on seabeds. Over time, layers of sediment compressed these remains, and under heat and pressure, they transformed into oil and gas.

Refining of Crude Oil

Refining is the process of separating crude oil into useful components called fractions using fractional distillation. Each fraction contains hydrocarbons with similar boiling points and molecular sizes.

Fractional Distillation

Fractional distillation involves heating crude oil until it vaporizes. The vapors rise through a tall fractionating column, which is hotter at the bottom and cooler at the top. Fractions condense at different levels based on their boiling points.

Substances with higher boiling points condense lower in the column, while those with lower boiling points rise higher before condensing. The process runs continuously in industrial settings.

Common Fractions from Crude Oil

Cracking

After distillation, long hydrocarbon chains can be broken into smaller ones through cracking. This process involves breaking single bonds to produce shorter chains and alkenes, with hydrogen gas often released as a by-product.

Reforming

Reforming increases the octane number of petrol by converting straight-chain alkanes (like heptane) into branched-chain hydrocarbons using heat and a platinum catalyst.

Octane Number

The octane number is a measure of the percentage of branched hydrocarbons in petrol. A higher octane number means better fuel performance and less engine knocking.

Knocking

Knocking is a metallic sound from engines caused by premature fuel ignition. It is common with fuels having low octane numbers, often due to straight-chain hydrocarbons that burn too quickly.

Synthetic Petrol

From Coal

Coal is heated with hydrogen at 500°C and 200 atm using iron or tin as catalyst:

The resulting mixture is distilled to obtain petrol and other residues.

From Coke

When steam passes over hot coke at 1000°C, water gas is formed:

C(s) + H2O(g) → CO(g) + H2(g)

This gas is hydrogenated over nickel catalyst at 200°C to form hydrocarbons, including petrol.

Fractions of Crude Oil