Investigation on catalytic systems containing nickel supported on silica and bonded with organic ligands and complexed by lewis acids

Abstract

The catalytic properties of the ▪ ( n = 0–3) system, resulting from the reaction of (C 3H 5) 2Ni with hydroxide groups of silica gel and complexation with a Lewis acid, MeAlCl 2, have been studied in the oligomerization of propylene. It has been ascertained that when n > 3 the excess of MeAlCl 2 is carried out from the catalyst bed by the products. The yield of the product is influenced by the rate of propylene flow and the composition of the catalyst. The yield of products increases with the rise in the propylene flow rate. The highest yield was obtained for n = 1 and the flow of propylene = 360 ml/min g. The elimination by the olefin of the allyl group from the complex in the initial stages of oligomerization was ascertained. This testifies to the formation of new forms of the surface nickel complex that should contain catalytically active NiH or NiR bonds. The EPR studies determined the valence of nickel in this system ( n = 1) to be +2 and thus made it possible to propose its structure.