TG–FTIR analysis of pyrolusite reduction by major biomass components

Pyrolusite reduction processes by three major biomass components cellulose, hemicelluloses and lignin, represented by CP, HP and LP, respectively, were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG–FTIR). The Šesták–Berggren (SB) equation was used to evaluate the kinetics of reduction processes. TG analysis reveals that the main reduction processes occur at 250–410 °C, 220–390 °C, and 190–410 °C for CP, HP, and LP, respectively. FT-IR and XRD results indicate that various reducing volatiles (e.g. aldehydes, furans, ketones and alcohols) are produced from the pyrolysis with the three major components, which directly reduce MnO2 in ore to MnO. The processes are described by the SB equation with three parameters (m, n, p). Their non-zero values suggest that pyrolusite reduction is controlled by the diffusion of reducing gaseous products through an ash/inert layer associated with minerals. The apparent activation energies for pyrolusite reduction by CP, HP and LP are 40.48, 25.70 and 40.10 kJ·mol− 1, respectively.