* Corresponding authors

^a Laboratory of Separation and Reaction Engineering, Associate Laboratory LSRE-LCM, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, Porto, Portugal

^b LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

^c School of Engineering (ISEP), Polytechnic of Porto (P.Porto), R. Dr. António Bernardino de Almeida 431, 4249-015 Porto, Portugal
E-mail: afccu@isep.ipp.pt
Fax: +351 22 83 21 159
Tel: +351 22 83 41 904

^d Carbon Materials Research Group, Department of Inorganic Chemistry, Faculty of Sciences, University of Granada, Avenida de Fuentenueva, s/n, Granada, Spain
E-mail: semoto@ugr.es
Fax: +34 958248526
Tel: +34 958240443