Effect of pyrolysis temperature on composition, surface properties and thermal degradation rates of Brazil Nut shells

Changes in chemical and surface characteristics of Brazil Nut shells (Bertholletia excelsa) due to pyrolysis at different temperatures (350°C, 600°C, 850°C) were examined. For this purpose, proximate and ultimate analyses, physical adsorption measurements of N2 (−196°C) and CO2 (25°C) as well as samples visualisation by scanning electronic microscopy (SEM) were performed. Appreciable differences in the residue characteristics, depending markedly on the pyrolysis temperature, were observed. Release of volatile matter led to the development of pores of different sizes. Progressive increases in micropore development with increasing pyrolysis temperature took place, whereas a maximum development of larger pores occurred at 600°C. Furthermore, kinetics measurements of Brazil Nut shells pyrolysis from ambient temperature up to 900°C were performed by non-isothermal thermogravimetric analysis. A model taking into account the significant changes in the residue during pyrolysis, through an increase in the activation energy with temperature and solid conversion, were found to properly fit the kinetics data over the wide range of degradation investigated.