Short answers, pulled from the story.
Propylene is the second most important starting material in the petrochemical industry after ethylene. Polypropylene manufacturers consume nearly two thirds of global production, and the compound also feeds the production of propylene oxide, acrylonitrile, cumene, butyraldehyde, acrylic acid, acetone, phenol, and isopropyl alcohol. In 2013, about 85 million tonnes of propylene were processed worldwide.
The dominant production method is steam cracking, which yields about 15% propylene when propane is the feedstock. Other routes include the Phillips olefin conversion technology, which achieves yields of about 90% by weight using rhenium and molybdenum catalysts, and high severity fluid catalytic cracking, which yields roughly 20-25% propylene from gas oils and residues. Propane dehydrogenation processes such as CATOFIN and OLEFLEX have also been commercialized.
Propylene was discovered in 1850 by John Williams Reynolds, a student working under A. W. von Hoffmann. Reynolds identified it as the only gaseous product of the thermal decomposition of amyl alcohol to react with both chlorine and bromine.
Yes. On the 30th of September 2013, NASA announced the detection of small amounts of propylene in the atmosphere of Titan using infrared spectroscopy. The detection was led by Conor Nixon of NASA's Goddard Space Flight Center, using data from the CIRS instrument on the Cassini orbiter. It resolved a 32-year-old gap in the inventory of three-carbon hydrocarbons in Titan's atmosphere.
Propylene has low acute toxicity from inhalation and is not considered carcinogenic. Humans briefly exposed to 4,000 parts per million reported no noticeable effects. Its primary hazards are its high flammability and explosion risk, and its ability to act as an asphyxiant by displacing oxygen.
Propylene is classified as a volatile organic compound and its emissions are regulated by many governments. The U.S. Environmental Protection Agency does not list it as a hazardous air pollutant under the Clean Air Act. Occupational exposure limits in the United States and several European countries are set at 500 parts per million as an eight-hour time-weighted average.