Liquefied Petroleum Gas (LPG) is a globally used energy source that powers everything from home heating to vehicle engines. This fuel is valued for its portability, high energy density, and clean-burning properties. Understanding where LPG originates requires looking into the processes that extract and refine primary hydrocarbon resources.
Defining Liquefied Petroleum Gas
LPG is a flammable mixture of hydrocarbon gases, specifically propane and butane. The “liquefied” part of its name describes its state when stored and transported. While these substances exist as gases at normal atmospheric pressure, they convert to a liquid under moderate pressure.
This compression allows a substantial amount of fuel to be contained in a small volume, making storage and distribution highly efficient. The liquid volume is roughly 250 times denser than its gaseous form, which is why LPG is delivered in pressurized cylinders and tanks.
Extraction During Natural Gas Processing
The largest portion of the world’s LPG supply, approximately 60% of total production, is recovered during the purification of raw natural gas. When extracted, natural gas is a “wet” mixture containing methane and heavier hydrocarbon compounds. These heavier components are called Natural Gas Liquids (NGLs), which include the propane and butane that make up LPG.
NGLs must be separated from the methane because they would condense into liquids inside high-pressure pipelines, causing operational issues. This separation occurs at a gas processing plant, where the raw gas stream is cooled to cryogenic temperatures. This cooling causes the NGLs, which have higher boiling points, to condense into a liquid state while the lighter methane remains a gas.
The resulting liquid mixture then undergoes fractional distillation, which separates the NGLs into individual components: ethane, propane, and butane. The recovered propane and butane streams are treated and blended to create the final commercial LPG product. This operation purifies the methane for use as natural gas while simultaneously yielding LPG.
Creation as a Crude Oil Refining Byproduct
The secondary source of LPG, contributing about 40% of the global supply, is the refining of crude oil. LPG is generated as a co-product during the conversion of crude oil into higher-value fuels, such as gasoline, jet fuel, and diesel. The yield of LPG from this process is relatively small, usually ranging between 1% and 4% of the volume of crude oil processed.
LPG is created during thermal and catalytic “cracking,” a process where heavy, long-chain hydrocarbon molecules are broken down into smaller, lighter molecules. These lighter components include propane and butane, which are gases at refinery temperatures. These gases are collected and separated from the other refined products.
Although LPG production is not the primary goal, it is a valuable outcome of producing transportation fuels. Refineries must carefully manage the pressure and temperature of their streams to isolate these lighter hydrocarbons. The composition of the resulting LPG can vary depending on the type of crude oil used and the specific refining methods employed.