Dimerization of linear olefins on Amberlyst® 15: Effects of chain length and double-bond position

• Linear C8 to C24 olefins dimerized via an Eley–Rideal mechanism on Amberlyst® 15.
• Neither chain length nor double bond position affected dimerization rate.
• Adsorbed carbenium ions reacted indiscriminately with bulk-phase linear olefins.
• Adsorption coefficients followed C8 > C10 > C12 > C14 ∼ C16 ⋯ ∼ C24.

We investigated acid-catalyzed dimerization for C8 to C24 linear olefins on Amberlyst® 15 at 90 °C. Double bond position and monomer chain length had no effect on dimerization rate of linear monomers. Dimerization was first order in both monomer and catalyst and occurred via an Eley–Rideal mechanism, in which adsorbed monomer reacted with olefin in the bulk phase. Relative dimerization rates between competing monomers of different chain lengths depended solely upon relative adsorptions of the competing monomers, as all linear olefins reacted equally well with any adsorbed monomer. Relative adsorption onto dimerization sites decreased markedly as chain length increased from C8 to C14, but there was no observed change in adsorption coefficients as chain length increased from C14 to C24. Trimerization occurred when bulk dimer reacted with adsorbed monomer. Dimer molecules competed well for dimerization sites and inhibited the rate of monomer dimerization. The rate-limiting step in dimer formation was the reaction of bulk olefin with adsorbed monomer.

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