Chloe Zhang
Plastic is everywhere, but where does it come from? Plastic can be synthetic or 'biobased'. Synthetic plastics are derived from fossil fuels like crude oil, natural gas, and coal, while biobased plastics come from renewable sources like vegetable fats and oils. Most of the plastic we use today is synthetic, made from hydrocarbons derived from crude oil. This process starts with drilling and pumping crude oil from underground to refineries, where it is heated and separated into different groups of lighter components called fractions. One of these fractions, naphtha, is crucial for plastic production. Through a process called steam cracking, naphtha is further decomposed into ethylene and propylene, which are the raw materials for plastics. These small molecules are then linked together to form long molecular chains called polymers, which are the building blocks of plastic.
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What You'll Learn
Plastic is made from petrochemicals derived from crude oil
Crude oil is a complex mixture of hydrocarbons, compounds made from combinations of carbon and hydrogen atoms that form chains of varying lengths, resulting in different properties. The process of extracting crude oil involves drilling holes through rocks and pumping the oil to the surface, where it is transported to refineries. At the refineries, crude oil is heated and distilled, separating it into different groups based on the number of atoms and molecular weight.
One of the crucial compounds obtained from crude oil distillation is naphtha, a mixture of volatile hydrocarbons. Naphtha is further decomposed at high temperatures of around 800°C in a steam cracker, resulting in the formation of olefins and aromatics. Ethylene and propylene, derived from naphtha, are the primary raw materials for oil-based plastics. These small molecules are linked together through polymerization to form long molecular chains called polymers, which are the building blocks of plastics.
The majority of plastic in use today is synthetic, derived from crude oil, natural gas, or coal. Synthetic plastics are favoured due to the ease of manufacturing methods involved in processing crude oil. However, the growing demand for limited oil reserves is driving the need for newer plastics derived from renewable resources.
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Oil is extracted by drilling holes and pumping it to the surface
Plastic can be synthetic or biobased. Synthetic plastic, which makes up the majority of plastic in use today, is derived from fossil fuels such as crude oil, natural gas, and coal. Crude oil is a mixture of hundreds of hydrocarbons, solids, and gases.
Once the drilling is complete, the drill pipe is removed and a steel pipe, known as the "well casing," is pushed to the bottom and cemented in place. Tests are performed to ensure the pipe is impermeable before natural gas or oil extraction can occur. A perforating gun is then lowered into the ground and fired into the rock layer, creating holes that connect the rock holding the oil and the wellhead.
After the first stage of the well is open, fracking fluid, which is primarily composed of water and sand with a small percentage of chemicals, is pumped at high pressure through the perforating holes. This creates thin cracks in the shale rock, freeing the trapped oil. Other methods to increase oil flow include water injection, gas reinjection, and carbon dioxide flooding, which all work to reduce the viscosity of the oil and make it easier to extract.
Once the oil has been extracted, it is pumped through pipelines to an oil refinery, where it undergoes further processing to create synthetic plastic.
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Oil is heated and separated into hydrocarbons
Oil is a fossil fuel, made from the remains of ancient living organisms, such as algae, bacteria, and plants. These organisms were buried deep underground for millions of years, where they were subjected to heat and pressure, transforming them into fossil fuels. Crude oil, a type of fossil fuel, is a mixture of hydrocarbons, compounds made from combinations of carbon and hydrogen atoms that form chains of varying lengths, giving them different properties. These hydrocarbons are the raw materials of plastic.
To extract crude oil, holes are drilled through rocks, and the oil is pumped from underground to the surface, where tankers transport it to the shore. Oil drilling can also occur under the ocean with support from platforms. Once extracted, the oil is transported to an oil refinery, where it undergoes distillation.
During distillation, the crude oil is heated and separated into different hydrocarbons based on their molecular weight and the number of atoms they contain. This process, called "steam cracking," breaks down the hydrocarbons into shorter molecules called monomers. The specific hydrocarbons of interest for plastic production are ethane and propene, which can be further broken down into ethylene and propylene, respectively. These monomers are then linked together to form long molecular chains called polymers, which are the building blocks of plastic.
Naphtha, a mixture of hydrocarbons obtained through the distillation of crude oil, is particularly important in plastic production. When naphtha undergoes thermal decomposition at high temperatures of around 800 °C in the presence of water vapor, it splits into light hydrocarbons called olefins (such as ethylene and propylene) and aromatics (such as benzene, toluene, and xylene). These small molecules are then linked together through polymerization, a process that utilizes heat, light, and additives, to form polymers.
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Hydrocarbons are the raw materials for plastic
Plastic is derived from crude oil, natural gas, and coal, which are fossil fuels. Crude oil, in particular, is a complex mixture of thousands of compounds, including hydrocarbons. Hydrocarbons are molecules of hydrogen and carbon, with the latter having an atomic number of 6 and the former, 1. The distillation of crude oil separates it into lighter groups of components called fractions, which are hydrocarbon chains. One of these fractions, naphtha, is crucial for plastic production.
Naphtha is a volatile mixture of liquid hydrocarbons, specifically C5 to C10 hydrocarbons. It is decomposed at high temperatures of around 800°C in a steam cracker, splitting into light hydrocarbons called olefins and aromatics. Olefins include ethylene (C2), propylene (C3), and butylene (C4). Aromatics consist of benzene, toluene, and xylene. These small molecules are then linked together into long molecular chains called polymers, which are the raw materials for plastics.
The process of linking the molecules together is called polymerization. Heat, light, and additives such as enzymes are used to facilitate this reaction. The resulting polymers are thick, viscous substances known as resins, which are used to make plastic products. For example, ethylene, a gaseous hydrocarbon, can be subjected to heat, pressure, and a catalyst to form long, repeating carbon chains. These molecules form a plastic resin called polyethylene (PE). The PE is processed into plastic pellets, which are melted into a thick liquid and cast into a mould to create a plastic product.
While most plastic today is synthetic, derived from fossil fuels, there are also biobased plastics made from renewable sources such as carbohydrates, starch, vegetable fats and oils, bacteria, and other biological substances. The majority of plastic production still relies on synthetic methods due to the ease of manufacturing and the flexibility of the feedstock consumed. However, with growing demands on limited oil reserves, there is a driving need to develop newer plastics from renewable resources, such as waste biomass or animal waste products.
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Plastics are polymers made from hydrocarbon monomers
Plastics are derived from natural, organic materials such as cellulose, coal, natural gas, salt, and, most commonly, crude oil. Crude oil is a complex mixture of thousands of compounds and needs to be processed before it can be used to create synthetic plastic.
The production of plastics begins with the distillation of crude oil in an oil refinery. This separates the heavy crude oil into groups of lighter components, called fractions. Each fraction is a mixture of hydrocarbon chains (chemical compounds made up of carbon and hydrogen), which differ in terms of the size and structure of their molecules. One of these fractions, naphtha, is the crucial compound for the production of plastics. Naphtha is a group of volatile mixtures of liquid hydrocarbons, obtained by the distillation of crude oil. It is a mixture of C5 to C10 hydrocarbons.
Naphtha is decomposed at high temperatures in the presence of water vapour, splitting into light hydrocarbons known as olefins and aromatics. The olefins include ethylene (C2), propylene (C3), and butylene (C4). These small molecules are then linked together by a process called polymerisation to create long molecular chains called polymers.
Polymerisation is a process in the petroleum industry where light olefin gases (gasoline) such as ethylene, propylene, and butylene (monomers) are converted into higher molecular weight hydrocarbons (polymers). This happens when monomers are chemically bonded into chains. There are two different mechanisms for polymerisation: addition polymerisation and condensation polymerisation.
Addition polymerisation is when one monomer connects to the next one (dimer) and the dimer to the next one (trimer) and so on. This is achieved by introducing a catalyst, typically a peroxide. Common examples of addition polymers are polyethylene, polystyrene, and polyvinyl chloride. Condensation polymerisation includes joining two or more different monomers, by the removal of small molecules such as water.
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Frequently asked questions
Plastic is made from polymers, which are molecules made up of many repeating units. There are two types of plastic: synthetic and bio-based. Synthetic plastic is made from petrochemicals derived from crude oil and natural gas. Bio-based plastic is made from renewable products such as carbohydrates, starch, vegetable fats and oils, bacteria and other biological substances.
Crude oil is heated and separated into different groups based on the number of atoms they contain and their molecular weight. This process is called distillation. One of the products of distillation is naphtha, which is further decomposed into ethylene and propylene, the raw materials for plastic. These small molecules are then linked together into long molecular chains called polymers.
Oil is extracted by drilling holes through rocks and pumping the oil to the surface. It is then transported via pipelines to oil refineries.
