TPR STUDY OF AL2O3-SUPPORTED AND SIO2-SUPPORTED CUCL2 CATALYSTS

The reduction and oxidation of Al2O3- and SiO2-supported CuCl2 has been re-investigated using TPR. The two peaks observed in the TPR profiles of dried samples are attributed to a two-step reduction of CuCl2 as opposed to previous assignments in which they were attributed to two types of immobilized cupric species with different reducibilities. EPR measurements of an Al2O3-supported sample after programmed reduction up to a point between the two TPR peaks, confirm the absence of cupric species. TPR measurements carried out after sequential treatments in C2H4, air and HCl show that the cycle CuCl2-CuCl-Cu2OCl2-CuCl2 does not occur with either support because HCl reduces the oxychloride to CuCl. It is also shown that the formation of Cu2OCl2 from CuCl requires temperatures higher than 498 K on SiO2, whereas it can be formed at room temperature on Al2O3. The addition of KCl or LaCl3 allows the reoxidation at 498 K of the reduced species on SiO2.