At over a million tons of capacity, the Shell Higher Olefins Process (SHOP) is one of the standards of industrial olefin metathesis chemistry. SHOP is remarkable in both its chemistry and process engineering. The process was developed for the conversion of ethylene to C10-C14 internal olefins (for conversion to linear primary detergent alcohols by hydroformylation), but can be modified to obtain linear olefins of just about any desired range.
1) Ethylene oligomerization
In this step, a nickel catalyst is used to oligomerize ethylene, giving a broad distribution of C4-C40 linear alpha (terminal) olefins. The mixture is fractionated and the target olefins (C10-14) are collected. The light (C4-C8) and heavy (>C14) fractions (most of the mass balance) are transferred to an isomerization unit.
2) Olefin isomerization
The mixture of linear alpha olefins is passed over an olefin isomerization catalyst to give a statistical mixture of linear internal olefins, which are then carried forward to a metathesis unit.
3) Metathesis
The mixed olefins are subjected to metathesis with a supported molybdenum catalyst. This gives a broad mixture of linear internal olefins, of which 10-15% are in the desired range. These are collected from the stream and the undesired fractions are recycled back to be isomerized.
4) Recycle
Because the byproducts of this process are all linear olefins, they can be recycled by isomerization and metathesis to extinction.
References
1) Wittcoff, H.; Reuben, B. G.; Plotkin, J. S. Industrial organic chemicals, 2nd ed.; Wiley-Interscience, 2004.
2) Mol, J. C. Industrial Applications of Olefin Metathesis. J. Mol. Catal. A: Chem. 2004, 213, 39-45.
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