Propane is not manufactured from scratch in a factory. It’s separated from mixtures of hydrocarbons that already contain it, primarily natural gas and crude oil. The two main commercial sources are natural gas processing plants and oil refineries, with a small but growing share coming from renewable feedstocks like animal fats and vegetable oils.
Separation From Natural Gas
Most propane starts underground, mixed into raw natural gas alongside methane, ethane, butane, and heavier hydrocarbons. When natural gas comes out of a well, it’s a wet, messy mixture. Before that gas can travel through pipelines to heat homes or power stoves, the heavier components need to be stripped out. Those heavier components are called natural gas liquids, and propane is one of them.
At a gas processing plant, the raw gas is chilled or pressurized until the heavier hydrocarbons condense into liquid form and separate from the methane. The resulting liquid mixture then goes through a series of tall distillation columns called fractionators. Each column is tuned to boil off and capture one specific hydrocarbon based on its boiling point. Ethane comes off first (lowest boiling point), then propane, then butane. The process works like a cascade: each tower peels away one layer, leaving the rest to move on to the next. The end result is individual streams of high-purity ethane, propane, butane, and heavier liquids, each routed to storage or transport.
Production in Oil Refineries
Oil refineries are the second major source. Propane shows up at two different stages of the refining process. First, when crude oil enters the atmospheric distillation column (the initial step in any refinery), the lightest gases rise to the top. Propane is among them.
The bigger share comes later, in a unit called a fluid catalytic cracker. This is where refineries take heavy, long-chain hydrocarbon molecules and break them apart under intense heat and pressure to produce lighter products suitable for gasoline. That cracking process generates a mix of lighter molecules as byproducts, including propane, butane, and their chemical cousins propylene and isobutane. The propane is then separated from these other gases using the same type of fractionation columns found at gas processing plants.
Renewable Propane From Fats and Oils
A newer production pathway creates propane from biological feedstocks: animal fats, vegetable oils, and used cooking grease. The process is called hydrotreating, and it’s the same technology used to make renewable diesel and sustainable aviation fuel. Hydrogen is added to the fat or oil molecules at high temperature and pressure, stripping away oxygen and breaking the molecules into shorter hydrocarbon chains. Propane is a byproduct of this reaction, not the primary target. The main products are renewable diesel or jet fuel, with propane coming off as a lighter fraction.
Commercial-scale renewable propane production is still small compared to fossil sources, but it’s expected to grow as demand for renewable diesel and sustainable aviation fuel increases, since every batch of those fuels generates some propane on the side.
Turning CO₂ Into Propane
Researchers have also demonstrated a way to synthesize propane directly from carbon dioxide and hydrogen. A team published results in JACS Au showing a specially designed catalyst system that converts CO₂ into propane with greater than 50% selectivity. The process works in stages: CO₂ and hydrogen first react on one part of the catalyst to form methanol, which then converts into propylene on a second catalyst component, and finally gets hydrogenated into propane. The reaction runs at about 350°C and 50 times atmospheric pressure.
This is still a laboratory-scale achievement, not a commercial process. But it represents a potential future route for making propane from captured carbon emissions rather than fossil sources.
How Propane Becomes a Liquid for Transport
Propane is a gas at normal room temperature and pressure. Its boiling point sits at roughly minus 44°F (minus 42°C), meaning it evaporates instantly if you release it into open air. To store and ship it practically, producers either chill it below that boiling point or compress it into pressurized tanks. Under moderate pressure (around 120 to 200 psi at typical outdoor temperatures), propane stays liquid inside the familiar cylindrical tanks you see at barbecue grills and on delivery trucks. This is why it’s classified as liquefied petroleum gas, or LPG.
Purity Standards and the Smell
Not all propane is the same grade. The most common consumer specification in the United States is called HD-5, which requires at least 90% propane by volume, no more than 5% propylene, and up to 5% other gases (mostly butane). This standard ensures consistent burning characteristics in furnaces, grills, and vehicle engines.
Pure propane is colorless and odorless, which would make leaks impossible to detect by smell. So before propane reaches any consumer, an odorant is added. The standard calls for 1.0 pound of ethyl mercaptan per 10,000 gallons of propane. Ethyl mercaptan has a sharp, sulfur-like smell (often described as rotten eggs or rotten cabbage), and the concentration is set so you can smell propane in air at just one-fifth of the level needed for it to ignite. This odorization must happen before delivery to any bulk storage facility, ensuring the safety measure is in place long before the gas reaches your home.
What Happens to the Other Gases
Propane production always generates sibling products. Ethane, the lightest of the natural gas liquids, is primarily used as a raw material for making plastics. Butane goes into gasoline blending, lighter fuel, and aerosol propellants. Isobutane serves as a refrigerant and a feedstock for high-octane gasoline components. The methane left behind after fractionation becomes the pipeline-quality natural gas delivered to residential and commercial customers for heating and cooking. Nothing from the original gas stream goes to waste.