# Shell higher olefin process

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{{Short description|Chemical production of α-olefins}}
{{Use dmy dates|date=March 2022}}
The '''Shell higher olefin process''' ('''SHOP''') is a [chemical process](/source/chemical_process) for the production of [linear alpha olefin](/source/linear_alpha_olefin)s via ethylene oligomerization and [olefin metathesis](/source/olefin_metathesis) invented and exploited by [Shell plc](/source/Shell_plc).<ref name=Weissermel>''Industrial Organic Chemistry'', Klaus Weissermel, Hans-Jurgen Arpe John Wiley & Sons; 3rd '''1997''' {{ISBN|3-527-28838-4}}</ref> The olefin products are converted to [fatty aldehyde](/source/fatty_aldehyde)s and then to [fatty alcohol](/source/fatty_alcohol)s, which are precursors to [plasticizer](/source/plasticizer)s and [detergent](/source/detergent)s. The annual global production of olefins through this method is over one million [tonnes](/source/tonnes).<ref name="Keim">Keim, W. (2013), ''Oligomerization of Ethylene to α-Olefins: Discovery and Development of the Shell Higher Olefin Process (SHOP)''. Angew. Chem. Int. Ed., 52: 12492–12496. {{doi|10.1002/anie.201305308}}</ref> 

==History==
The process was discovered by chemists at [Shell Development Emeryville](/source/Shell_Development_Emeryville) in 1968. At the time ecological considerations demanded the replacement of branched fatty alcohols used widely in detergents by linear fatty alcohols because the [biodegradation](/source/biodegradation) of the branched compounds was slow, causing foaming of surface water.<ref name="Keim" /> At the same time new [gas oil crackers](/source/Cracking_(chemistry)) were being commissioned and ethylene supply was outpacing demand.<ref name="Keim" />

The process was commercialized in 1977 by [Shell plc](/source/Shell_plc) and following an expansion of the [Geismar, Louisiana](/source/Geismar%2C_Louisiana) (USA) plant in 2002 global annual production capacity was 1.2&nbsp;million tons.<ref>{{cite journal | author = Mol, J. C. | title = Industrial applications of olefin metathesis | journal = Journal of Molecular Catalysis A: Chemical | year = 2004 | volume = 213 | pages = 39–45 | doi = 10.1016/j.molcata.2003.10.049}}</ref>

==Process==
Ethylene reacts by the catalyst to give longer chains. Unlike the [Ziegler–Natta process](/source/Ziegler%E2%80%93Natta_process), which aims to produce very long polymers, the oligomer stops growing after addition of 1–10 repeating units of ethylene. The fraction containing C<sub>12</sub> to C<sub>18</sub> olefins (40–50%) has direct commercial value in detergent production and is removed.<ref name="Keim" /> For the remaining fraction to be of commercial interest two additional steps are required. The first step is liquid-phase [isomerization](/source/isomerization) using alkaline alumina catalyst leading to internal double bonds. For example, [1-octene](/source/1-octene) is converted to 4-[octene](/source/octene) and 1-eicocene (a C20 hydrocarbon) is converted to 10-eicocene. In the second step '''olefin metathesis''' converts mixtures like these to 2-tetradecene which is a C14 component and again within commercial range.<ref name="Keim" />

The internal olefins can also be reacted with an excess of ethylene with [rhenium(VII) oxide](/source/rhenium(VII)_oxide) supported on alumina as catalyst in an [ethenolysis](/source/ethenolysis) reaction, which causes the internal double bond to break up to form a mixture of [α-olefins](/source/Terminal_alkene) with odd and even carbon chain-length of the desired molecular weight.<ref name = reuben>{{cite journal | doi = 10.1021/ed065p605 | journal = [J. Chem. Educ.](/source/J._Chem._Educ.) | title = The SHOP process: An example of industrial creativity | year = 1988 | last1 = Reuben | first1 = Bryan | last2 = Wittcoff | first2 = Harold | volume = 65 | issue = 7 | pages = 605|bibcode = 1988JChEd..65..605R }}</ref>

The C<sub>12</sub> to C<sub>18</sub> olefins subsequently are subjected to [hydroformylation](/source/hydroformylation) (oxo process) to give [aldehydes](/source/aldehydes). The aldehyde is hydrogenated to give fatty alcohols, which are suitable for manufacturing detergents.<ref name = reuben/>

== Catalytic cycle ==
The first step in this process is the [ethylene](/source/ethylene) [oligomerization](/source/oligomerization) to a mixture of even-numbered α-olefins at 80 to 120&nbsp;°C and 70 to 140 bar (7 to 14 MPa) catalyzed by a [nickel](/source/nickel)-[phosphine](/source/phosphine) complex.  Such catalysts are typically prepared from diarylphosphino carboxylic acids, such as (C<sub>6</sub>H<sub>5</sub>)<sub>2</sub>PCH<sub>2</sub>CO<sub>2</sub>H.<ref>{{cite journal |author1=Kuhn, P. |author2=Semeril, D. |author3=Matt, D. |author4=Chetcuti, M. J. |author5=Lutz, P. | title = Structure–Reactivity Relationships in SHOP-Type Complexes: Tunable Catalysts for the Oligomerisation and Polymerisation of Ethylene | journal = [Dalton Trans.](/source/Dalton_Trans.) | year = 2007 |issue=5 | pages = 515–528 | doi = 10.1039/B615259G|pmid=17225902 }}</ref> The process and its mechanism was elucidated by the group of [Wilhelm Keim](/source/Wilhelm_Keim), first at Shell and later at the [RWTH Aachen](/source/RWTH_Aachen).

700px

== Alternative routes ==
In another olefin application of Shell [cyclododecatriene](/source/cyclododecatriene) is partially [hydrogenated](/source/hydrogenation) to [cyclododecene](/source/cyclododecene) and then subjected to ethenolysis to the terminal [linear](/source/linear) [open-chain](/source/open-chain) [diene](/source/diene). The process was still in use at Essar Stanlow refinery until a serious explosion and following fire lead to the closure of the plant and the alcohols units it fed in 2018.

:500px|SHOP application

==References==
{{Reflist|2}}

{{Organometallics}}

Category:Chemical processes
Category:Catalysis
Category:American inventions

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Adapted from the Wikipedia article [Shell higher olefin process](https://en.wikipedia.org/wiki/Shell_higher_olefin_process) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Shell_higher_olefin_process?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.