[Chemistry Class Notes] LPG Gas Composition Pdf for Exam

Liquefied Petroleum Gas, also known as LPG, is used in almost every household in the country mainly for cooking purposes. It can also easily be transformed into a liquid, hence it is called by that name. LPG can expand up to 250-270 times its size when it is in a liquid state if it is converted into a gaseous state. This is why LPG comes in high-pressure tanks and it gets burned to provide fuel for various purposes.

 

In India, they are popularly called ‘gas cylinders’.

What is the Pressure inside an LPG Cylinder?

In most cases, the propane pressure inside LPG cylinders should be between 100-200 psi, since the propane will stay at a liquid state only within this pressure range. The pressure inside tanks can change slightly on account of changes in the temperature outside the tank, but in most cases, this does not affect the pressure inside.

 

LPG Composition

The primary liquefied petroleum gas composition includes propane, butane, isobutane, propylene and butylene. LPG is known to be an extremely flammable mixture of all these hydrocarbons mentioned and is greatly used in the form of fuel for different purposes including household cooking and automobiles. However, out of all the constituents, the most active and main composition of LPG includes propane and butane. Given below are the LPG gas constituents.

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Propane

Propane is a type of a hydrocarbon which has the chemical formula C₃H₈ and is amongst the primary and essential lp gas composition. It tends to exist in the gaseous state under the standard temperature and pressure conditions. However, it is compressed into liquid if the required pressure is applied to it. Propane is generally derived in the form of a by-product when petroleum is refined and the natural gas is processed.

Propane tends to undergo evaporation faster when it gets released from the pressurised container. This is due to the lower boiling point of propane which is around -42.2 °C. Also, the melting point of propane is -187.7 °C. The molecular weight of propane is known to be 44.097 gm/mole. Propane is a colourless and odourless gas under the standard conditions.

 

Butane

Butane is kind of organic compound having the chemical formula C₄H₁₀. It is amongst the most flammable compounds that are used in the LPG chemical composition. Under the standard conditions of temperature and pressure, butane exists in the form of a colourless gas which has a smell similar to the one of gasoline or natural gas. Butane can also be compressed to the liquid form to transport it easily. Butane has two isomers structurally which are known as isobutane and n-butane.

Isobutane

Isobutane is also referred to as 2-methylpropane and it is an organic compound having the structural formula CH(CH₃)₃. Isobutane is known to be a structural isomer of the compound butane is amongst the chemical components of the liquefied petroleum gas. Isobutane has a melting point of -159.42 °C and the boiling point of -11.7 °C. Isobutane is generally used in the form of propellant in aerosol cans.

Propylene

Propylene is also called propene and it is an organic compound having a chemical formula denoted by C₃H₆. It is an unsaturated hydrocarbon and consists of a carbon-carbon double bond. It is also a part of the chemical composition of LPG gas. The molecular weight of propylene is found to be 42.081 gm/mol. Its boiling point is -47.6 °C and its melting point is -185.2 °C. Under the standard temperature and pressure conditions, it exists in the form of a colourless gas. However, it can also be compressed into the liquid form.

 

Butylene

Butylene is also referred to as butene and is a chemical compound having the formula C₄H₈. It has several isomers because of the double bond present in it can be present at several different points in its parent carbon chain. However, amongst the most prominent isomers are isobutylene, 1-butylene and 2-butylene. All these isomers tend to exist in the gaseous form under the standard conditions of pressure and temperature.

LPG is usually extracted from ‘wet’ natural gases through a process known as absorption, and the substance formed as a result has a very low boiling point. This is then distilled, treated with water and a number of chemicals such as carbon dioxide and hydrogen sulphide. The gas that is obtained from this is then transported using special pipelines meant only for transporting LPG. Nowadays, however, they are also being transported through roads and railways.

When the LPG gas is distributed to households for non-industrial purposes, it is stored in a tank so that the gas does not leak out. Industrial LPG is not the same as household LPG, and it is supplied differently. Other than cooking, LPG can also be used in a wide range of household activities that require heat or fuel. This can include central heating, water heaters and fireplaces. In industries, LPG is used to provide engine fuel and run backup generators.