Green coconut fiber thermal behaviour under the presence of a cobalt spinel catalyst

Abstract

With increasing environmental concerns, much effort has been spent in research regarding development of sustainable processes for production of fuels and chemical products. In this context, hydrothermal liquefaction (HTL) has gained increasing attention, as a possible route for the chemical transformation of organic raw-materials, some sort of biomass, for example, into liquid oils at temperatures usually below 400°C, under moderate to high pressures (5 - 25 MPa), usually in the presence of a suitable catalyst. In the present work the thermogravimetric (TG) behavior under inert atmosphere of pure green coconut fiber and mixtures thereof with a spinel phase (Fe2CoO4), acting as catalyst has been studied. Spinel samples have been produced at 1000°C and different calcination times (3h, 6h and 9h). Both raw and synthesized materials were characterized through different techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and Infrared Absorption Spectroscopy (FTIR). According to the TG data, the catalyst produced during a calcination time of 9h showed a superior behavior regarding the lignin full thermal decomposition, which developed without fixed carbon formation. The results further suggest that the mixing process has a significant effect over the measured degradation kinetics, as it has a direct influence over the contact between catalyst and fibers. The kinetic modelling applied to the dynamic TG signal allowed a quantitative representation of the experimental data. The global process activation energy and order have proven to be respectively, 85.291 kJ / mol and 0.1227.