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Conversion of Ethylene to Higher Olefins Using Homogeneous Catalysis

By Timothy Barnhill, Joshua Blease, Hassan Abuthaibah, Nick Nadorff

Shell Higher Olefins Process

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Higher Olefins in Industry

• Olefins (ethylene, butylene)– Key building blocks– High availability, reactivity, low cost

• Higher molecular weight olefins (C6-C20)– Synthetic automotive oils– Biodegradable surfactants– Stronger plastics

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Production of Higher Olefins

• Wax Pyrolyis (Chevron, 1966)– Conversion of 20-40% per pass– Higher conversions produced undesired aromatics

• Ethylene Oligomerization (Gulf Oil, 1966)– Production of wide variety of alkenes– Modifying selectivity for desired olefins was

difficult

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Shell Higher Olefin Process (1977)

• Able to adjust product output to meet market needs

• Produced α-olefins which could be sold as is• Converted olefins with low market value to

detergent range fatty alcohols (C6-C11)

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Process Overview

B. Reuben

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Process Overview• Oligomerization:

• Isomerization:

• Metathesis:

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Oligomerization

• Oligomer – Complex consisting of a few monomers

• Catalyst – Nickel complex• Ethylene “oligomerized” into even α-olefins– Desired olefins recovered by distillation– Non-marketable olefins sent to isomerization

(usually small (< C6) and large (> C18) olefins)

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OligomerizationMechanism

Ni Catalyst

Ligands added

CoordinationComplex

Ethylene reacts

Even-numberedα-olefins

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Isomerization

• Smaller and larger α-olefins isomerized to form internal double bonds

• Catalyst – Na/K on Al2O3

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Metathesis

• Metathesis is defined as a catalytic reaction in which alkenes are converted into products by breaking and reforming C-C double bonds.

• Phillips Petroleum developed a unique reaction called olefin metathesis.

• Originally developed to convert cheap propylene into high value ethylene and 2-butene.

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Internal Olefins• The internal olefins pass to the metathesis reactor

where the short- and long-chain internal olefins disproportionate.

• After this the products of the metathesis reaction are fed to the fractionating column to separate desired C10-

14 olefins for hydroformulation.

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Applications of Linear Olefins

• Drilling Fluid: (C16 – C18) alpha olefins– Physical properties

• High purity• Viscosity

• Monomers: (C4 – C10) alpha olefins– Production of polymers

and polyethylene

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• Detergents: (C12 – C20) alpha olefins

• Plasticizers: (C6 – C10) alpha olefins– Production of plasticizer alcohols

and surfactants.

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References

“Shell Higher Olefins Process,” E.F. Lutz, Shell Development Company, Journal of Chemical Education, 63 (3) p. 202, 1986.

“The SHOP process: An example of industrial creativity,” Bryan Reuben and Harold Wittcoff, Journal of Chemical Education, 65 (7) p. 605, 1988.

“Developments in LAO Comonomer Technologies for Polyethylene,” Nexant, Inc., http://www.chemsystems.com/about/cs/news/items/PERP2011S11_LAOr.cfm