B. Elleuch - Institute of Researches on Catalysis and Environment in Lyon
Y. Ben Taarit - Catalyse
J. M. Basset - Institute of Researches on Catalysis and Environment in Lyon
J. Kervennal - Societe Chimique Pechiney Ugine Kuhlman Centre de recherches de Pierre Benite 69310 Pierre Benite (France)