Editing Propylene (section)

==Production==
===Steam cracking===
{{main|Steam cracking}}
The dominant technology for producing propylene is [[steam cracking]], using [[propane]] as the [[feedstock]]. Cracking propane yields a mixture of [[ethylene]], propylene, [[methane]], [[hydrogen gas]], and other related compounds.  The yield of propylene is about 15%.  The other principal feedstock is [[naphtha]], especially in the [[Middle East]] and Asia.<ref>Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, {{ISBN|978-0-9522674-3-0}}, pages 7766-9</ref> 
Propylene can be separated by [[fractional distillation]] from the hydrocarbon mixtures obtained from cracking and other refining processes; refinery-grade propene is about 50 to 70%.<ref name=Dow>{{cite web |url=http://www.dow.com/productsafety/finder/pro.htm |title=Product Safety Assessment(PSA): Propylene |publisher=Dow Chemical Co. |access-date=2011-07-11 |archive-url=https://web.archive.org/web/20130828163039/http://www.dow.com/productsafety/finder/pro.htm |archive-date=2013-08-28  }}</ref> In the United States, [[shale gas]] is a major source of propane.

===Olefin conversion technology===
In the Phillips triolefin or [[olefin conversion technology]], propylene is interconverted with [[ethylene]] and [[2-butene]]s. [[Rhenium]] and [[molybdenum]] catalysts are used:<ref name="MG">{{cite journal|last1=Ghashghaee|first1=Mohammad|title=Heterogeneous catalysts for gas-phase conversion of ethylene to higher olefins|journal=Rev. Chem. Eng.|volume=34|issue=5|pages=595–655|doi=10.1515/revce-2017-0003|year=2018|s2cid=103664623}}</ref> 
:<chem>CH2=CH2{}  +  CH3CH=CHCH3   ->[][\text{Re, Mo} \atop \text{catalyst}]   2 CH2=CHCH3</chem>

The technology is founded on an [[olefin metathesis]] reaction discovered at [[Phillips Petroleum Company]].<ref>{{cite journal | last1 = Banks | first1 = R. L. | last2 = Bailey | first2 = G. C. | title = Olefin Disproportionation. A New Catalytic Process | journal = Industrial & Engineering Chemistry Product Research and Development | volume = 3 |issue=3| pages = 170–173 | year = 1964 | doi = 10.1021/i360011a002}}</ref><ref name=KO>{{cite encyclopedia|chapter=Metathesis|encyclopedia=Kirk-Othmer Encyclopedia of Chemical Technology|author=Lionel Delaude |author2=Alfred F. Noels |year=2005| doi=10.1002/0471238961.metanoel.a01|place=Weinheim|publisher=Wiley-VCH|isbn=978-0-471-23896-6}}</ref> Propylene yields of about 90 wt% are achieved.

{{main|Syngas to gasoline plus}}
Related is the [[Gas to liquids#Methanol to gasoline (MTG) and methanol to olefins|Methanol-to-Olefins/Methanol-to-Propene]] process. It converts [[Gas to liquids#Syngas to gasoline plus process (STG+)|synthesis gas (syngas)]] to [[methanol]], and then [[Syngas to gasoline plus|converts the methanol to ethylene and/or propene]]. The process produces water as a by-product. [[Synthesis gas]] is produced from the reformation of natural gas or by the steam-induced reformation of petroleum products such as naphtha, or by [[coal gasification|gasification of coal]] or natural gas.

===Fluid catalytic cracking===
High severity [[fluid catalytic cracking]] (FCC) uses traditional FCC technology under severe conditions (higher catalyst-to-oil ratios, higher steam injection rates, higher temperatures, etc.) in order to maximize the amount of propene and other light products. A high severity FCC unit is usually fed with gas oils (paraffins) and residues, and produces about 20–25% (by mass) of propene on feedstock together with greater volumes of motor gasoline and distillate byproducts. These high temperature processes are expensive and have a high carbon footprint.  For these reasons, alternative routes to propylene continue to attract attention.<ref>{{cite journal |doi=10.1016/j.joule.2017.07.008|title=Electrification and Decarbonization of the Chemical Industry|year=2017|last1=Schiffer|first1=Zachary J.|last2=Manthiram|first2=Karthish|journal=Joule|volume=1|issue=1 |pages=10–14|bibcode=2017Joule...1...10S |hdl=1721.1/124019|s2cid=117360588 |hdl-access=free}}</ref>

=== Other commercialized methods ===
On-purpose propylene production technologies were developed throughout the twentieth century. Of these, propane dehydrogenation technologies such as the CATOFIN and OLEFLEX processes have become common, although they still make up a minority of the market, with most of the olefin being sourced from the above mentioned cracking technologies. Platinum, chromia, and vanadium catalysts are common in propane dehydrogenation processes.

===Market===
Propene production has remained static at around 35 million [[tonnes]] (Europe and North America only) from 2000 to 2008, but it has been increasing in East Asia, most notably Singapore and China.<ref name=realityck>{{cite journal|doi=10.1016/J.ENG.2017.02.006|title=New Trends in Olefin Production|year=2017|last1=Amghizar|first1=Ismaël|last2=Vandewalle|first2=Laurien A.|last3=Van Geem|first3=Kevin M.|last4=Marin|first4=Guy B.|journal=Engineering|volume=3|issue=2|pages=171–178|doi-access=free|bibcode=2017Engin...3..171A }}</ref> Total world production of propene is currently about half that of ethylene.

===Research===
The use of engineered [[enzyme]]s has been explored but has not been commercialized.<ref>{{cite web |url= https://greenchemicalsblog.com/2012/10/12/global-bioenergies-in-bio-propylene |website= Green Chemicals Blog |title= Global Bioenergies in bio-propylene |first= Doris |last= de Guzman |date= October 12, 2012 }}</ref>

There is ongoing research into the use of oxygen carrier catalysts for the oxidative dehydrogenation of propane. This poses several advantages, as this reaction mechanism can occur at lower temperatures than conventional dehydrogenation, and may not be equilibrium-limited because oxygen is used to combust the hydrogen by-product.<ref name="Wu 2020">{{cite journal | last1=Wu | first1=Tianwei | last2=Yu | first2=Qingbo | last3=Roghair | display-authors=etal | title=Chemical looping oxidative dehydrogenation of propane: A comparative study of Ga-based, Mo-based, V-based oxygen carriers | journal=Chemical Engineering and Processing - Process Intensification | volume=157 | year=2020 | issn=0255-2701 | doi=10.1016/j.cep.2020.108137 | page=108137| doi-access=free | bibcode=2020CEPPI.15708137W }}</ref>