Kinetic Study of Noncatalytic Dissolution of Cellulose Biochar in Hydrogen Donor Solvent

Abstract

Biochar was produced from cellulose by hydrothermal carbonization at 220 and 300 °C. The produced biochars were subjected to dissolution in hydrogen donor solvent (tetralin) at 400 °C for 1 h. To understand the kinetics of biochar dissolution, various experiments were carried out at various temperatures of the heating stage and at different times during the isothermal stage (at 400 °C). It was observed that most of the conversion of biochar occurred during the heating stage of the dissolution reaction (200–400 °C), and there was no significant change in conversion during the isothermal stage (400 °C). It was concluded that the dissolution of biochar prepared at 220 °C consisted of two different steps in the heating stage based on its conversion to products where first the unconverted cellulose (present in the biochar) decomposed at a lower temperature (200–325 °C) to form products followed by the decomposition of biochar (325–400 °C). However, for the dissolution of biochar prepared at 300 °C, only one step (biochar decomposition) in the heating stage was observed above 300 °C (300–400 °C) to form products due to the absence of unconverted cellulose and its higher C/O ratio. A temperature-dependent two-step kinetic model was proposed where the pre-exponential factor and activation energies were determined by nonlinear regression of the experimental data.