Short answers, pulled from the story.
A team led by NASA scientist Conor Nixon confirmed the presence of propylene in Titan's atmosphere on the 30th of September 2013 using data from the Cassini orbiter spacecraft. This discovery solved a 32-year-old mystery in planetary science and added the C3H6 species to the family of hydrocarbons known to exist on the moon.
John Williams Reynolds isolated propylene in 1850 as the only gaseous product of the thermal decomposition of amyl alcohol. Reynolds was a student of the renowned chemist A. W. von Hoffmann and his experiment revealed the unique reactivity of the double bond that defines the modern plastics industry.
The dominant technology for producing propylene today is steam cracking, which uses propane as the primary feedstock to yield a mixture of ethylene, propylene, methane, and hydrogen gas. In this high-temperature reaction, the yield of propylene is typically about 15 percent, and the process relies on naphtha or shale gas as feedstocks depending on the region.
In 2013, about 85 million tonnes of propylene were processed worldwide, highlighting the scale of its industrial importance. Total world production of propene is currently about half that of ethylene, yet it remains the second most important starting product in the petrochemical industry.
Propene is not listed by the U.S. Environmental Protection Agency as a hazardous air pollutant under the Clean Air Act, although it is considered a hazardous air pollutant in some contexts. Observed concentrations range from 0.1 to 4.8 parts per billion in rural air and up to 260 parts per billion in industrial air samples.