1. Postgraduate Program in Materials Science and Engineering, Federal University of Rio Grande do Norte, 59078-970 Natal, RN, Brazil
2. Environmental Technology Laboratory (LabTam), Federal University of Rio Grande do Norte, 59078-970 Natal, RN, Brazil
3. Postgraduate Program in Chemistry, Federal University of Rio Grande do Norte, 59078-970 Natal, RN, Brazil
4. Department of Petroleum Engineering, Federal University of Rio Grande do Norte, 59078-970 Natal, RN, Brazil
5. Instituto de Carboquimica (CSIC). Miguel Luesma Castan 4, 50018 Zaragoza, Spain