About Propylene. Propylene (a.k.a. Propene, Methyl Ethylene) has been established as a major component of the global olefins business, second only to ethylene. Having one double bond, this was the first petrochemical employed on an industrial scale and is the second in natural abundance. Being a byproduct in ethylene production, propene’s development and expansion grew tremendously since 1965, due to ethylene's success as a chemical building block.

On a global scale, the predominant source of Propylene is derived from NGL (Natural Gas Liquids) or naphtha steam crackers, which concurrently generate ethylene in the so called 'olefins plants.' Within a plant, the synthesis of Propylene involves the pyrolysis of the incoming feed, followed by subsequent purification steps. With the exception of ethane-based feedstocks, the production of Propylene typically ranges from 40 to 60 wt% of the ethylene yield. The specific yield of Propylene in the pyrolysis furnace is influenced by the choice of feedstock and the operating conditions. Furthermore, Propylene can also be intentionally generated in dedicated processes such as propane dehydrogenation or metathesis plants.

Other forms that generate Propylene as a by-product are the refinery cracking processes, especially fluid-catalytic cracking (FCC). In this case, coking units can transform, by severe cracking, crude oil residues into gas oil, coke, gasoline, and a smaller portion of cracked gas with 10-15 mol% C3, which is almost Propylene. This cracked gas containing Propylene can also be formed in visbreaker units but by a mild cracking process. Lastly, Propylene can also be intentionally generated in dedicated processes such as propane dehydrogenation or metathesis plants, which have been developed commercially due to an increase in Propylene derivatives demand, such as polypropylene, since the 1980s.

Propylene Handling. Liquid propylene exhibits different storage methods depending on the volume and specific requirements. It can be stored at ambient temperature in spherical pressure tanks, but for exceedingly large quantities, storage at an ultra-low temperature of -47 °C, where the propylene is nearly pressureless, becomes more suitable. When it comes to transportation, propylene is commonly transported via road and rail using cylindrical pressurized tanks maintained at ambient temperature. Railway tankers for propylene transportation typically have a capacity of 42 tons. For road transport, the maximum allowable weight of around 40 tons restricts the propylene load to approximately 20 tons. In ship transportation, a combination of smaller pressurized tanks and larger atmospheric tanks equipped with reliquefaction devices are employed to ensure safe and efficient delivery.

Propylene Production. As previously mentioned, the largest volume of PG Propylene is produced from NGL or naphtha in steam cracking processes, which generates ethylene as well. However, it can also be manufactured through other routes, based on propane dehydrogenation, metathesis or syngas-to-olefins processes. Raw materials and the respective production processes employed in the manufacturing of Propylene are listed below.

Propylene Uses. The uses and applications of Propylene may vary according to its specification. The main forms of Propylene are polymer grade (PG, 99.5% minimum purity); chemical grade (CG, 90-96% minimum purity); and refinery grade (RG, 50-70% minimum purity).

The propylene market is predominantly driven by Polymer Grade Propylene, which serves as the main source in the production of polypropylene and propylene oxide. On the other hand, most chemical derivatives (e.g. oxo-alcohols, acrylonitrile, etc.) are directly derived from the less pure Chemical Grade Propylene. For Refinery Grade Propylene, the main use is the conversion to PG or CG Propylene. It is also used in liquefied petroleum gas (LPG) for thermal applications or as an octane enhancer in motor gasoline. On a smaller scale, it is used in the synthesis of cumene and isopropanol. Finally, Chemical Grade Propylene has its main application in the production of chemical products.