Purification, isomerisation, and metathesis

The lower alkenes and the heavy alkenes must be disproportionated to give the full range of alkenes. In the second part of the process the higher and 

The typical size of a Shell process plant described here is 250-350,000 tons per year. The total production of higher olefins via this and similar routes is estimated to be 2 million tons annually. A large part of the alkenes are produced for captive use, i.e. for use by the producing company itself. 

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