Is propylene a gas or a liquid


As Liquefied petroleum gas are gases liquefied through cooling and compression, which either remain cold and liquid at normal pressure due to the enthalpy of vaporization with appropriate thermal insulation (e.g. oxygen and nitrogen tanks) or, in order to remain liquid, are under pressure (e.g. propane / butane in lighters, in camping -Gas bottles, in liquid gas tanks for heating purposes).
In the narrower sense, one understands under liquid gas LPG (Liquefied Petroleum Gas)i.e. propane, butane and their mixtures, which remain liquid at room temperature under comparatively low pressure and are used as fuel for gasoline engines in vehicles. The mixed gas is also LPG or Propellant called.

Liquid gas is not to be confused with liquefied natural gas (LNG from Engl. Liquefied natural gas) or compressed natural gas (CNG from Engl. Compressed natural gas).


Liquid gas consists of easily liquefied hydrocarbon compounds (C.mHn) with 3 or 4 carbon atoms. It can be a single compound or a mixture of several compounds.

The main components of liquefied petroleum gas can be:

  • Propane C3H8
  • Propene (propylene) C3H6 (with C double bond)
  • Butane C4H10
  • Butene (butylene) C4H8 (with C double bond)
  • Isobutane (methyl propane) C4H10
  • Isobutene (methylpropene) C4H8 (with C double bond)

Often it only consists of propane and butane (e.g. with LPG and camping gas). In its gaseous state, liquid gas has a higher density than air. It is transported and stored under pressure. At a pressure of around 8 bar it becomes liquid and reduces its volume to one second. If it becomes gaseous again, it is easily flammable and forms explosive mixtures with air. Depending on the mixing ratio, the explosion limits are between 1.5 and 11% by volume in the air.

The boiling point depends on the pressure and the mixing ratio. At ambient pressure, it is between -42 ° C (pure propane) and -0.5 ° C (pure butane) for a propane / butane mixture.

Transports must have a dangerous goods label according to ADR (UN number1965 and Kemler number23).

Liquid gas has an energy density (calorific value) of 12.9 kWh / kg and at 20 ° C a density of 540 kg / m³ (propane 510 kg / m³ and butane 580 kg / m³)

Heating and cooking purposes

Liquid gas is used for heating purposes. For this purpose, it is stored on site mostly above ground in liquid gas storage containers (volume from a few hundred to several thousand liters), which are filled by tank vehicles. In many areas in Europe it can be found, especially in rural areas, for heating purposes in single-family houses.

In smaller quantities it is in gas bottles or in gas cartridges, e.g. B. used in camping, grilling or soft soldering of copper pipe soldering fittings.

For household purposes, e.g. gas grills, gas bottles with a filling weight of 5 kg, 11 kg or 33 kg are usually used.

Cooking with liquefied gas is very common in France, southern Europe and many other countries around the world; in contrast to Germany, where this way of cooking is little known.

In Germany, too, cooking with a gas bottle (up to a maximum of 14 kg) is permitted in the kitchen, provided that all safety regulations are complied with, as well as installation and acceptance by a specialist.

Lighter gas

The gas is often used in commercially available lighters.


Use in air conditioning systems as a CFC substitute.

Liquid gas fuel (autogas, LPG)

Is a gas mixture of propane / butane in different mixing ratios, depending on the country and provider. See LPG

Safety regulations

Liquefied gas storage tank systems are systems that require monitoring in accordance with the Industrial Safety Ordinance and must therefore be checked by an approved monitoring body prior to commissioning and must be checked regularly at certain intervals. The provisions of the Ordinance on Industrial Safety and Health with regard to explosion protection must also be observed.

Special measures are required when working below ground level (cellar, etc.), as liquid gas is heavier than air and can collect as a "lake". Floor openings (manhole covers, hatches, basement exits) must also be included in the safety assessment.

The transport of liquid gas is regulated by the ADR regulations.

The garage regulations in particular are often different, so you have to pay attention to the signs when driving in. Even within Austria, the ordinances are not uniform, as they fall within the competence of the federal states.


  • Sven Geitmann: Renewable energies and alternative fuels. Hydrogeit Verlag, 2nd edition, Jan. 2005, ISBN 3937863052
  • Technical rules for liquid gas: TRF 1996; Publisher: DVGW / DVFG; 1st edition 1996, ISBN 3-87793-039-5
  • Ralf Ortmayr, Wolfgang Schüler: Guide to LPG information and tips Self-published, 1st edition July 2006, ISBN 3-00-017181-9


Categories: Mixture of substances | gas