Molybdenum metal catalyzed reaction of ethylene

The reaction of ethylene catalyzed by clean molybdenum foil is examined between 800 and 880 K. Products up to C-7 are detected in measurable quantities and hydrocarbons up to C-8 are observed. The product distribution is well described by a Schulz-Flory function where a plot of In(W-n/n) versus n, where W-n is the yield of each C-n hydrocarbon, is a good straight line. Analysis of the slope and intercept of the distribution shows that the slope has a zero-order ethylene pressure dependence and varies with temperature with an activation energy of 4.6 +/- 0.6 kcal/mol, while the intercept has a pressure dependence of 1.3 +/- 0.3 and an activation energy of 46 +/- 4 kcal/mol. A kinetic model is proposed that successfully accounts for these pressure dependences. These data suggest that the activation energy for degenerate ethylene metathesis should be 55 +/- 5 kcal/mol and that the reaction should be first order in ethylene. These kinetic parameters are in good agreement with those found experimentally for the non-degenerate metathesis of propylene.