Influence of activation conditions on textural properties and performance of activated biochars for pyrolysis vapors upgrading

The main aim of the present study is to provide a comprehensive assessment of the effects of process activation conditions on the textural properties of the resulting activated carbons, which were produced from wheat straw-derived biochar through chemical activation (with K2CO3 at different pressures and mass impregnation ratios) and physical activation (with CO2 at different temperatures and pressures). For chemically activated biochars, it was found that specific surface area and pore size distribution were both only positively affected by increasing the carbonate loading. However, physically activated biochars produced at the highest pressure and lowest temperature (1.0 MPa and 700 °C) had the highest surface areas and widest pore size distributions. The materials with the most appropriate textural properties were then tested as catalysts for steam and dry reforming of the aqueous phase of pyrolysis oil. The best catalytic performance (a total gas yield of 74% and a selectivity toward H2 of almost 40%) was observed for a physically activated biochar. This good performance was ascribed to the high availability of K0 on the catalyst surface, which could effectively promote the reactions involved in the upgrading process.