Petrochemicals: Classification, Applications, Disadvantages

Petrochemicals are substances produced by petroleum or natural gas. They are an important aspect of the chemical industry since the need for synthetic materials is always increasing and plays an important role in today’s economy and society. Petrochemicals are used to make thousands of various items that people use on a daily basis, such as plastics, medications, cosmetics, furniture, appliances, electronics, solar panels, and wind turbines.

Nowadays, there is such a huge demand for petrochemicals and the goods made from them that we must purposefully use the cracking process to reduce larger hydrocarbons to smaller gaseous hydrocarbons.

What are Petrochemicals?

Petroleum is a complex mixture of hydrocarbons formed by the decomposition of fossil remains. In other words, petrochemicals are chemical substances derived from the refining and processing of crude oil and natural gas.

They are significant components in many everyday items such as plastics, soaps, fertilizers, paints, and insulation. Furthermore, petrochemicals offer the raw ingredients required to build cutting-edge energy technologies such as solar panels, wind turbine blades, and electric vehicle components. It can be discovered deep down or beneath the seabed as a liquid (crude oil), gas (natural gas), or solid (oil shales).

Petroleum is refined into a variety of usable fractions that are used as fuel (LPG, petrol, diesel, etc.) or lubricants. Approximately 10% of petroleum is used to generate a variety of chemicals known as petrochemicals. Petrochemicals are defined as a collection of chemicals produced directly or indirectly from petroleum or natural gas hydrocarbons. Some gaseous hydrocarbons are produced as byproducts of petroleum processing. Methane, ethane, propane, butane, iso-butane, pentane, and other hydrocarbons with one to five carbon atoms are examples. Methane (CH4) is another important hydrocarbon component of natural gas that occurs in conjunction with petroleum.
Petrochemicals come in a limitless variety. Methyl alcohol, methyl alcohol, acetaldehyde, acetic acid, acetic anhydride, acetone, benzene, toluene, xylenes, phenol, vinyl chloride, etc. are a few significant petrochemicals. Some of these can be utilized straight away or as inputs to make other beneficial items. These are employed in the production of a wide range of practical products, including plastics, nylon, polyester, synthetic rubbers, synthetic fibers, adhesives, antifreezes, and rocket fuels.

Classification of Petrochemicals

Primary Petrochemicals

Primary petrochemicals are compounds derived from feedstock and utilized to produce petrochemical intermediates. Because the feedstock comprises of natural gas, naphtha, and reformed naphtha, the principal petrochemicals produced varies.

Natural gas Ethene CH2 = CH2
  Propene CH3 – CH = CH2
Naphtha Ethene CH2 = CH2
  Propene CH3 – CH = CH2
  Butadiene CH2 = CH – CH = CH2

Intermediate Petrochemicals and Derivatives

The petrochemicals produced by chemical reaction from primary petrochemicals are known as (secondary) intermediate petrochemicals. Petrochemicals are also classified as first generation and second generation. First generation petrochemicals are transformed to second generation petrochemicals. These intermediate petrochemicals may be used directly or further processed to produce petrochemical derivatives via a chemical reaction or series of reactions to produce products for additional end purposes.

Down Stream Petrochemicals

Downstream petrochemicals are the petrochemicals produced from a particular feedstock through a sequence of reactions. Downstream denotes that a certain petrochemical appears later in the chemical production chain.

CH4 →  CH3Cl →  CH3OH

Methyl alcohol is a downstream petrochemical.

Methane-Derived Petrochemicals

Methane is the most abundant hydrocarbon in natural gas. CNG stands for compressed natural gas, whereas LNG is for liquefied natural gas. Furthermore, methane is produced in vast amounts as a byproduct of petroleum refining.

The primary petrochemicals derived from methane are:

    • Chlorinated products: Chlorination of methane produces methyl chloride (CH3CI), methylene chloride (CH2CI2), chloroform (CHCI3), and carbon tetrachloride (CCI4). The majority of methane chlorinated products are employed as solvents.

    • Unsaturated hydrocarbons: Methane breaks down (by pyrolysis) with appropriate catalysts to produce ethylene, propylene, and acetylene.

    • Carbon black: Pyrolysis (cracking) converts methane into carbon black (a kind of carbon), and hydrogen is produced as a byproduct. Carbon black is a black pigment used in the production of black printing ink in the rubber tire industry.

    • Hydrogen: The hydrogen produced by the pyrolysis of methane is utilized to produce ammonia gas. Ammonia is used as a raw ingredient in the production of urea (a fertilizer), ammonium nitrate, and a variety of other goods.

    • Methyl alcohol: Catalytic oxidation converts methane to methanol (methyl alcohol, CH3OH). Methanol is further oxidized to produce formaldehyde. Formaldehyde is a critical raw ingredient for a variety of useful products, including phenol-formaldehyde resins (Bakelite). Methyl alcohol is a widely used industrial solvent.

Ethylene-Derived Petrochemicals

Ethylene is produced via pyrolysis of natural gas or by splitting naphtha. Ethylene is an unsaturated hydrocarbon with a double carbon link. As a result, ethylene is highly reactive and may be transformed into a wide range of petrochemicals and valuable end products.
The primary petrochemicals derived from ethylene are:

    • Ethyl alcohol: Ethyl alcohol (ethanol) is produced by hydration of ethylene. In addition to being a raw material and solvent, ethyl alcohol is utilized in the production of ethyl acetate, acetic acid, and many other beneficial compounds.

    • Ethylene oxide: When ethylene is exposed to air or oxygen and a catalyst, it oxidizes to ethylene oxide. It serves as a raw ingredient for the production of ethylene glycol, a necessary precursor to polyester production.

    • Ethylene glycol: Starting with ethylene, ethylene glycol (1,2-dihydroxyethane) is produced. The process of turning ethylene into ethylene glycol has many steps. In cars, glycol is used as an antifreeze. An essential raw element for the production of polyester is ethylene glycol.

    • Dichloroethane: Chlorine reacts with ethylene to produce dichloroethane (1,2-dichloroethane). It serves as an intermediate for the synthesis of several other raw materials, including vinyl chloride and ethylene glycol.

    • Vinyl chloride: Vinyl chloride is made directly from ethylene or is made from ethylene dichloride

    • Polyethylene: An essential plastic substance, polyethylene (polyethene), is produced when ethylene is polymerized.

    • Ethyl benzene: In the presence of an appropriate catalyst, ethylene and benzene react to produce ethyl benzene. One transforms ethyl benzene into styrene. A crucial plastic substance called polystyrene is made from styrene as a basic ingredient.

Propylene-Derived Petrochemicals

Propylene can be produced by splitting naphtha or by pyrolyzing natural gas. One type of unsaturated hydrocarbon is propylene.
Principal petrochemicals derived from propylene include:

    • Iso-propyl alcohol

    • Polypropylene

    • Cumene (isopropyl benzene)

    • Glycerol

Butadiene-Derived Petroleum Chemicals

By breaking naphtha, 1, 3-butadiene is obtained. It is a diene, which means it has two carbon-carbon double bonds. It is a monomer for polybutadine, which is a synthetic rubber replacement. When butadiene and styrene are polymerized, they form the copolymer BUNA-S.

Benzene-Derived Petrochemicals

Reformed naphtha is used to produce benzene. Catalytic reformation (also known as aromatization) is used to naphtha. Aliphatic hydrocarbons in naphtha are transformed to aromatic hydrocarbons during the process.
The following are important petrochemicals derived from benzene:

    • Ethyl benzene and cumene

    • Chlorobenzene

    • Nitrobenzene

    • Cyclohexane

    • Linear alkyl benzenes (LAB)

    • Branched alkyl benzenes (BAB)

Applications of Petrochemicals


The primary application of petrochemicals is as a fuel. The burning of crude oil paved the way for the discovery of several petroleum-derived energy. Petroleum has been used as a source of energy for lighting, warmth, and movement, as well as the most convenient fuel for internal combustion engines. With the introduction of the automobile and a wide range of other internal combustion engine uses, this usage grew rapidly in importance.

Petroleum has been employed as a crucial source in the synthesis of chemical molecules, in addition to its usage in transportation. By 1965, petroleum had been used to produce more than 80% of the world’s organic compounds. This figure rose to 98% in 1980 and 99% by the end of the decade. As a result, petroleum chemicals (petrochemicals) cover a wide variety of compounds.

Gasoline and kerosene are industrially relevant examples. Petroleum jelly is a fatty gelatinous fluid derived from petroleum that is used as a foundation for ointments, lubricants, and protective coverings

Industrial Sector

Petrochemicals play a key role in a variety of other industrial areas. Wax, fertilizers, preservatives, soaps and detergents, colors, plastic goods, plasters, sports shoes, and explosives are examples of industrial raw materials derived or manufactured from petrochemicals. Despite significant growth and advancement, petrochemicals remain a major problem for the global industrial sector.


Wax is a petroleum byproduct that is used to make candles and molds. The technique of preparing high wax emulsion was revealed, and the influencing elements on preparation were explored. In this work, wax emulsions were created utilizing the emulsifier-oil technique with paraffin wax as the primary ingredient. The effects of emulsifier type and quantity, temperature and time of emulsification, speed of stirring, and amount of emulsifying water on emulsification have also been studied.


Detergent is another petrochemical product that is utilized in everyday life. It has been classified into two types: soap less and soapy. The majority of soap-free detergents are powdered, liquids, or gels. Detergents have been created by combining oils, alcohol (a petrochemical product), and petrochemicals as basic components.


Preservatives are another type of petrochemical that is widely utilized in cosmetics and food additives. Preservatives extend the shelf life of cosmetics and canned foods in order to keep them fresh. Petrochemical is also used in the production of vitamins, such as ASA (Acetyl salicylic acid).


Dyes are well-known petrochemical chemicals that come in a variety of hues, most notably the color of the ink used in pens. A printing reactive dye stock thickener based on polypropylene acid sodium Alginate was introduced. This innovative printing gum is made up of both natural and artificial gum, as well as an optimal proportion and reasonable emulsifying procedure. The new gum retains the sodium alginate properties.

It also has higher structural viscosity, alkali stability, permeability, and other properties. According to the procedures, the novel gum produced a high apparent color yield and a great printing result. Because of the printed textiles’ clear contour and clean lines, it was thought to be an ideal paste for reactive printing.


Ethylene is a result of heating or distilling the oil and is one of the most important constituents of petrochemical oil, which is used to manufacture rubbish bags, camera films, milk cartons, bags, and other products. The industrial manufacturing using thermal cracking received extensive attention. Ethylene is the most abundant building element in many petrochemicals. Ethylene is a colorless gas with a slight odor that is not harmful to the eyes or respiratory system and is thus classified as a minor asphyxiant.


Petrochemicals are also used to make plastic bottles. The majority of plastic goods are made from polyester. Furthermore, compact discs and cassettes are constructed of polyester or petrochemical oil.

Demerits of Petrochemicals

Emission of Hazardous Gases: Combustion emits hazardous gases into the atmosphere. When petroleum is burned, it emits a large amount of carbon dioxide. Methane and other greenhouse gases can also be created depending on how the petroleum is processed. Even when petroleum is categorized as sweet, traces of sulfur permeate the environment. This might be a role in the environmental changes that have been noticed since the 1970s.

Oil is a limited resource: Petroleum is a fossil fuel, hence it is a limited resource. We are always discovering new petroleum resources to extract, which gives us with new reserves to store, but those stocks may eventually run out. According to some estimates, two-thirds of the world’s petroleum supplies may have already been depleted.

The petroleum refining process can be harmful: Petroleum may be fatal to all kinds of life in some way on its own. It is fatal to fish at concentrations as low as 0.4%. The carcinogen benzene is contained in crude oil and the fuels derived from it. Petroleum exposure reduces white blood cell numbers in individuals, making them more prone to sickness.

Petroleum can act as a catalyst for acid rain: When petroleum burns, it produces a high-temperature collision with the surrounding air. As a result, the nitrogen in the atmosphere oxidizes. When nitrous oxide is mixed with the sulfur component of petroleum, it can interact with atmospheric moisture to form acid rain. Acid rain, when it rains, can cause acidic water in lakes, ponds, and rivers.

Effects of Petrochemicals in Environment

Petrochemical manufacturing contributes to air, water, and soil pollution. This can have an influence on local systems, such as specific ecosystems, but it also has global implications. Greenhouse gases released during the manufacture of petrochemicals, for example, can contribute to global climate change.

Impact on Air Pollution

Petrochemical plants emit dangerous chemicals into the atmosphere during manufacturing, whether through routine emissions or unintentional releases. Researchers have found probable cancer-causing chemicals in petrochemical plant emissions and have seen an upsurge in respiratory diseases in the surrounding communities. Particulate particles, carbon monoxide, nitrogen oxide, hydrogen sulfide, and other air pollutants are released by petrochemical facilities.

Impact on Water Pollution

Petrochemical manufacturing also contributes to water contamination, both at the surface in lakes, ponds, and streams and in groundwater. The petrochemical manufacturing process generates wastewater tainted with sulfides, ammonia, and other chemicals. Some plants use wells to inject wastewater underground, which has traditionally contaminated aquifers and groundwater from which people derive their drinking water.

Impact on Soil Pollution

Soil contamination usually mainly affects the area around the petrochemical facility, although it can contribute to water pollution through runoff. Spills and leaks cause chemical accumulation in the soil, which can harm the environment and lead to other types of pollution.

Plants, on the other hand, may successfully employ bacteria to break down and remove spills and soil contamination, therefore mitigating this type of pollution. Petrochemical manufacturing residue can also accumulate in landfills and other disposal sites.




    •  Jean-Pierre Favennec, ed. (2001). Petroleum Refining: Refinery Operation and Management. Editions Technip. ISBN 2-7108-0801-3.




About Author

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Kabita Sharma

Kabita Sharma is a graduate student from the central department of chemistry, Tribhuvan University. She has been actively involved in research related to natural products, computational chemistry, and nanochemistry. She is currently working on enzyme assay, molecular docking, and molecular dynamic simulation.

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