We describe a new method for estimating the positions of double bonds in mixtures of linear olefins longer than octene. The method requires about a gram of olefin and a 5-10 min reaction catalyzed by a homogeneous metathesis catalyst. The carbon number distribution of the product mixture, as determined by gas chromatography, depends upon the distribution of double-bond isomers in the starting mixture. We describe a computer algorithm for using the final carbon number distribution to determine the locations of double bonds in the starting mixture. Examples are based on tetradecenes, hexadecenes, and octadecenes.

We present kinetic data for the double bond and skeletal isomerization of 1-tetradecene on SAPO-11 at 142 and 180 degrees C. The kinetic model permitted calculation of five different rate constants for double bond movements, methyl branch formation, and dimerization, as well as the corresponding Arrhenius parameters. We also discuss observations on the mechanism of the skeletal isomerization, concluding that methyl groups can form at significant distances from the carbon-carbon double bonds, apparently via rapidly interconverting carbenium ions on the catalyst's surface. (C) 2009 Elsevier B.V. All rights reserved.