Mechanistic insights into the kinetic compensation effects during the gasification of biochar: Effects of the partial pressure of H2O

Abstract

This study has focused on the kinetic compensation effects (KCE) during the gasification of biochar in 15% H2O-Ar and 2% H2O-Ar. The biochar samples were characterised by FT-Raman and X-ray photoelectron spectroscopies. We found that the extent of the KCE of char gasification and formation of CO, CO2, and H2 was higher during the gasification in 15% H2O-Ar than that in 2% H2O-Ar. The relative ratio of ID/(I(Gr+Vl+Vr) was higher in 15% H2O-Ar than that in 2% H2O-Ar, which reflects that the relative concentration of large aromatic rings is higher during the gasification in 15% H2O-Ar than that in 2% H2O-Ar. The partial pressure of H2O affected the relative concentration of O-containing surface species [C(O)] on the biochar external surface and inside the pores of the char matrix. The concentration of these O-containing species [C(O)] on the char surface led to different relative rates of CO and CO2 release, resulting in lower CO/CO2 ratios (at lower char conversions) during the gasification in 15% H2O-Ar than those in 2% H2O-Ar. The lower relative ratio of ID/(I(Gr+Vl+Vr) and lower extent of the kinetic compensation effects revealed that the relative concentration of active sites (with similar properties), which were created on the activation of aromatic rings, was lower for the gasification in 2% H2O-Ar than that in 15% H2O-Ar.