Shell higher olefin process

The Shell higher olefin process is a chemical process for the production of linear alpha olefins via ethylene oligomerization and olefin metathesis invented and exploited by Royal Dutch Shell.^[1] The olefin products are converted to fatty aldehydes and then to fatty alcohols, which are precursors plasticizers and detergents.

Process

Ethylene reacts by the catalyst to give longer chains. Unlike the Ziegler-Natta process, which aims to produce very long polymers, the oligomer stops growing after addition of 1-10 repeating units of ethylene. The fraction containing C₆ to C₁₈ olefins has commercial value and is removed. The remaining higher and lower olefins next undergo isomerization reactions leading to internal double bonds and then, in the presence of ethylene, to olefin metathesis, which causes the internal double bond to break up into new internal double bonds in olefins of the desired intermediate molecular weight.^[2]

The C₆ to C₁₈ olefins subsequently are subjected to hydroformylation (oxo process) to give aldehydes. Use of a cobalt catalyst (dicobalt octacarbonyl) allows internal alkenes used, as they are isomerized to primary alkenes which thereafter undergo hydroformylation. The aldehyde is hydrogenated to give fatty alcohols, which are suitable for manufacturing detergents.^[2]

The process was commercialized in 1977 by Royal Dutch Shell and in 1993 global annual production capacity was ten million tons.

Catalytic cycle

The first step in this process is the ethylene oligomerization to a mixture of even-numbered α-olefins at 80 to 120 °C and 70 to 140 bar (7 to 14 MPa) catalyzed by a nickel-phosphine complex. Such catalysts are typically prepared from diarylphosphinoacetic acids, such as (C₆H₅)₂PCH₂CO₂H.^[3] The process and its mechanism was intensively studied by the group of Professor Wilhelm Keim at the RWTH Aachen, who is also regarded as one of the key figures in the development of the process.^[4]

Alternative routes

In another olefin application of Shell cyclododecatriene is partially hydrogenated to cyclododecene and then subjected to ethenolysis to the terminal linear open-chain diene. The process is still in use at Shell Stanlow refinery.

References

1. ^ Industrial Organic Chemistry, Klaus Weissermel, Hans-Jurgen Arpe John Wiley & Sons; 3rd 1997 ISBN 3-527-28838-4
2. ^ ^{a b} Reuben, Bryan; Wittcoff, Harold (1988). "The SHOP process: An example of industrial creativity". J. Chem. Ed. 65 (7): 605. doi:10.1021/ed065p605. 
3. ^ Kuhn, P.; Semeril, D.; Matt, D.; Chetcuti, M. J.; Lutz, P. (2007). "Structure–reactivity relationships in SHOP-type complexes: tunable catalysts for the oligomerisation and polymerisation of ethylene". Dalton Trans.: 515–528. doi:10.1039/B615259G. 
4. ^ Gadi Rothenberg (Google Books excerpt). Catalysis: Concepts and Green Applications. pp. 97. http://books.google.de/books?id=1LkPd_nfdQkC&pg=PA97.