A unique application of acid-Nafion as a co-catalyst and support

Abstract

The perfluorinated ion-exchange polymer, Nafion-H⁺, has been used as a Brönsted acid to activate [Ni{P(OEt)₃}₄] and as a support for the resulting cationic species. Spectroscopic evidence has confirmed that the species present within the Nafion-H⁺ film are the same as those found in a homogeneous solution using H₂SO₄ as the Brönsted acid. Activity for oct-1-ene isomerization in the first 30 min was approximately one third of the activity obtained in homogeneous solution using H₂SO₄ as co-catalyst with a similar [Ni{P(OEt)₃}₄]: H⁺ ratio, and the activity varied linearly with the amount of Nafion-H⁺ present. Comparative tests with but-1-ene employing homogeneous and supported catalyst systems have demonstrated a significant increase in isomerization rate on changing from oct-1-ene to but-1-ene when using the supported catalyst. This indicates that diffusion of oct-1-ene into, and/or products out of, Nafion-H⁺ are controlling factors. Diffusion coefficients of oct-1-ene and but-1-ene in Nafion have been determined and support this conclusion. It has also been demonstrated that very little, if any, of the catalyst species is leached from the Nafion support during catalysis.