Sodium, zinc and magnesium chlorides as additives for soybean hulls pyrolysis

Thermogravimetric analysis and analytical pyrolysis were used to investigate the decomposition of pure soybean hulls and hulls impregnated with metal chlorides (NaCl, ZnCl2 and MgCl2). Each additive was studied at contents of 10, 20 and 30 % in mass concentration. Thermogravimetric analyses were performed at different heating rates (5, 10, 15, 20 and 25 °C min−1) under inert nitrogen atmosphere. Analytical pyrolysis experiments were carried out at 550 and 650 °C, and the pyrolysis products were analyzed by gas chromatography and mass spectrometry. The mass loss and derivative mass loss curves of soybean hulls impregnated with salts showed a decrease in the decomposition temperature and reduction in maximum degradation rate for the samples containing ZnCl2 and MgCl2. The samples impregnated with NaCl showed an increase in the decomposition temperature and reductions in the maximum degradation rate. Considering analytical pyrolysis results, samples with MgCl2 and ZnCl2 presented increases in aldehydes and reductions in acid and ester contents. The addition of NaCl did not present an important effect on pyrolysis products from soybean hulls. The study concerning the thermal decomposition of soybean hulls to which metal chlorides were added is not registered in previous works. Results indicated that the addition of ZnCl2 and MgCl2 reduced the thermal degradation temperatures and that the studied mixtures can be used as sustainable raw materials for the production platform of fuels and value-added chemicals.