Avaliação da degradação térmica do caroço de abacate residual para a produção de biocarvões

Abstract

The thermal degradation kinetics of avocado seed biomass (Persea americana) was investigated at the heating rates of 5, 15, 20 and 25 ºC min-1 using thermogravimetric (TGA) and differential thermogravimetric (DTG) analysis techniques in the temperature range from ambient to 780 ºC. Chemical analysis of the avocado seed resulted in: 51.4% cellulose, 42.4% hemicellulose, 20.1% lignin, 2.1% ash, 5.6% extractives. The pyrolysis products were characterized via FTIR, SEM/EDS. The isoconversional methods of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) have yielded activation energy, Eα, varying from 36-323 kJ mol-1, respectively. The calorific value of biochars produced in the present study in the range of 265 to 475 ºC was 16,17 to 20,24 MJ kg-1, respectively, which are comparable to those reported values in the literature. Analyzing the DTG simultaneously with the addition of thermal energy, it can be seen that low molecular weight compounds represent the first degradation curves, followed by hemicellulose, cellulose and, lignin. The results obtained in the present work indicate that its feasible to prepare biochars with tunable properties from residual avocado seeds using a slow pyrolysis process, adding commercial value and reducing the environmental impact caused by the inadequate disposal of lignocellulosic materials.