Biomass valorization by using a sequence of acid hydrolysis and pyrolysis processes. Application to Leucaena leucocephala

Abstract

Among main ways to provide an environmentally friendly energy and platform chemicals are the lignocellulosic conversion processes. The proper execution of this way will depend on the correct selection of lignocellulosic materials. A compelling plant is Leucaena leucocephala because its great variety of uses, its high biomass production and its leguminous nature. In this study, acid hydrolysis (130-170°C and 0.5-2% H2SO4, to extract valuable hemicelluloses) as pretreatment and pyrolysis of the solid residue (to get a gaseous fuel) as treatment have been used in its valorization. A laboratory-scale reactor was used for the pyrolysis experiments (550ºC, N2) for both Leucaena leucocephala, as raw material, and the solid residues after hydrolysis process and raw material. The amounts of CO, CO2 and H2 found in the raw material are similar to those found in the solids obtained after the different studied hydrolysis conditions. Moreover, the thermal behavior of studied solids has been studied by thermogravimetric analysis under nitrogen atmosphere at different heating rates (5, 10, 15 and 20 ºC min-1). Activation energy for all samples has been obtained by the Flynn-Wall-Ozawa method. The optimum value, in which a high relationship between recoverable hemicelluloses fraction and H2 concentration is found, under medium hydrolysis temperature (150ºC) has been obtained and was independent of the amount of acid added to the hydrolysis process.