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The CuCl2/Al2O3 Catalyst Investigated in Interaction with Reagents
Department of Inorganic, Physical and Material Chemistry, University of Turin, Via P. Giuria 7 10125 Torino Italy
INFM UdR di Torino Università, Italy
INSTM Research unit of Turin University, Italy
ESRF, BP 220, F-38043 Grenoble Cedex, France
EVC Italia, Technological Centre, Via della Chimica 5, 30175 Porto Marghera (Venezia), Italy
* Author to whom correspondence should be addressed.
Received: 2 October 2001 / Accepted: 7 November 2001 / Published: 13 November 2001
Abstract: Alumina supported CuCl2, the basic catalyst for ethylene oxychlorination, has been investigated by UV-Vis spectroscopy, EPR, EXAFS and XANES in a wide range (0.25-9.0 wt%) of Cu concentration. We have evidenced that, at low Cu content, the formation of a surface aluminate species takes place. The formation of this surface copper aluminate stops at 0.95 wt% Cu / 100 m2; at higher Cu concentrations excess copper chloride precipitates directly from solution during the drying step forming an highly dispersed CuCl2.H2O, phase, overlapping progressively the surface aluminate. Depletion tests and IR spectroscopy of adsorbed NO have demonstrated that the latter is the only active phase. A complete catalytic cycle has then been performed on CuCl2/Al2O3 catalyst. EPR, XANES and EXAFS, have been used to demonstrate that the ethylene oxychlorination reaction: C2H4 + 2HCl + ½ O2 --> C2H4Cl2 + H2O follows a three steps mechanism: (i) reduction of CuCl2 to CuCl (2CuCl2 + C2H4 --> C2H4Cl2 + 2CuCl), (ii) oxidation of CuCl to give an oxychloride (2CuCl + ½ O2 --> Cu2OCl2) and (iii) closure of the catalytic circle by rechlorination with HCl, restoring the original CuCl2 (Cu2OCl2 + 2HCl --> 2CuCl2 + H2O). Finally, we have shown that time resolved, in situ, spectroscopy is a very promising technique to investigate the interplay between catalyst activity and oxidation state of copper.
Keywords: Al2O3 supported CuCl2; ethylene oxychlorination; EPR; XANES; EXAFS
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Lamberti, C.; Prestipino, C.; Capello, L.; Bordiga, S.; Zecchina, A.; Spoto, G.; Moreno, S.D.; Marsella, A.; Cremaschi, B.; Garilli, M.; Vidotto, S.; Leofanti, G. The CuCl2/Al2O3 Catalyst Investigated in Interaction with Reagents. Int. J. Mol. Sci. 2001, 2, 230-245.
Lamberti C, Prestipino C, Capello L, Bordiga S, Zecchina A, Spoto G, Moreno SD, Marsella A, Cremaschi B, Garilli M, Vidotto S, Leofanti G. The CuCl2/Al2O3 Catalyst Investigated in Interaction with Reagents. International Journal of Molecular Sciences. 2001; 2(5):230-245.
Lamberti, Carlo; Prestipino, Carmelo; Capello, Luciana; Bordiga, Silvia; Zecchina, Adriano; Spoto, Giuseppe; Moreno, Sofia D.; Marsella, Andrea; Cremaschi, Barbara; Garilli, Marco; Vidotto, Sandro; Leofanti, Giuseppe. 2001. "The CuCl2/Al2O3 Catalyst Investigated in Interaction with Reagents." Int. J. Mol. Sci. 2, no. 5: 230-245.