1. Department of Chemistry, Federal University of Viçosa, Minas Gerais 36570-000 Viçosa, Brazil
2. Brazilian Agricultural Research Corporation, Embrapa Agroenergia, DF 70770-901 Brasília, Brazil
3. Department of Forest Biomaterials, College of Natural Resources, North Carolina State University, North Carolina 27695-8005 Raleigh, United States
4. Department of Forestry Engineering, Federal University of Viçosa, Minas Gerais 36570-000 Viçosa, Brazil