Alumina-supported copper chloride 1. Characterization of freshly prepared catalyst

Alumina-supported CuCl2, the basic catalyst for ethylene oxychlorination, h as been investigated 1 hour after preparation by UV-vis spectroscopy, a sol ubility test, EPR, EXAFS, and XRD in a wide range (0.25-9.0 wt%) of Cu conc entration. We have evidenced that, at low Cu content, the formation of a su rface aluminate species takes place, where isolated Cu(II) ions occupy octa hedral vacancies of the alumina surface, having (within experimental errors ) five oxygen ligands at 1.92 +/- 0.02 A. The chlorine released by copper c hloride during its interaction with alumina gives >Al-Cl species. The forma tion of this surface copper aluminate stops at 0.95 wt% Cu/100 m(2); at hig her Cu concentrations excess copper chloride precipitates directly from sol ution during the drying step, forming an amorphous CuCl2. 2H(2)O phase, ove rlapping progressively the surface aluminate. A slow hydrolysis, giving tra ces of paratacamite, an insoluble Cu hydroxochloride, also occurs. A room t emperature dehydration process up to 10(-3) Torr implies the evolution of C uCl2. 2H(2)O into anhydrous CuCl2 as a consequence of the loss of the cryst allization water. (C) 2000 Academic Press.