Cu/SiO2 and Cu/SiO2-TiO2 catalysts II. Identification of the active sites during polymerisation of 2,6-dimethylphenol in the presence of molecular O-2

8% Cu/SiO2 and Cu/SiO2-TiO2 catalysts, prepared by the chemisorption hydrol ysis method and characterised in the preceding paper (Boccuzzi et al., 1999 , J. Catal., 184, 316-326) have been tested in the oxidative coupling of 2, 6-dimethylphenol, a well-known copper catalysed reaction in the homogeneous phase. All of them proved to be active after reduction of the copper oxide initially present giving similar to 75% of PPE and <4% DPQ. Although they lost similar to 30% of the metal during the first run, they appeared to be reusable and more active during the second run. From HRTEM and FTIR charact erisation before and after the polymerisation reaction, it can be deduced t hat three-dimensional copper particles are preferentially leached under the reaction conditions, while electron deficient two-dimensional metallic par ticles can be responsible for the catalytic activity. (C) 1999 Academic Pre ss.