1. SINTEF Energy Research, Thermal Energy, N-7465 Trondheim, Norway, Research Laboratory of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, Budapest 1525, Hungary, and Dipartimento di Ingegneria Chimica, Università degli Studi di Napoli “Federico II”, P.le V. Tecchio, 80125 Napoli, Italy