In-situ steam reforming of biomass tar over sawdust biochar in mild catalytic temperature

In order to fully understand the catalytic activities of sawdust biochar on in-situ tar steam reforming in mild catalysis temperatures (650-800 °C), the experiment was carried out in a two-stage fluidized bed/fixed bed reactor. The structural characteristics of biochar were analyzed by the Raman and XPS spectroscopies. The results of in-situ tar steam reforming over biochar were performed by gas chromatograph/mass spectrometer (GC/MS). Kinetic aspects of tar steam reforming in mild temperatures were calculated to evaluate the catalytic effect of sawdust biochar on in-situ tar reforming. The results indicate that sawdust biochar has a positive effect on in-situ tar steam reforming, while the effect is not proportional to biochar amount. During the in-situ tar steam reforming over biochar, the changes of oxygen-containing functional groups on biochar surface are mainly caused by the C-O bonds. The first order kinetic rate constant of sawdust biochar for the heterogeneous reforming of biomass tar at 650-800 °C is found to have an apparent activation energy (Eapp) of 35.03 kJ/mol with the apparent pre-exponential factor (kapp) of 1.8 × 104 m3 kg−1h−1. The biochar structures were considerably transformed during the tar steam reforming. According to GC/MS analysis of biomass tar, the biochar seems to promote the cracking of large ring polyaromatic tar compounds to form 1-ring aromatic ones.