Variation of pore development scenarios by changing gasification atmosphere and temperature

Finding a good replacement for the commercially produced activated carbons among the residual biochars should begin with a thorough evaluation of their pore size distribution and its development under different gasification conditions. Materials of various pore structures may be found useful depending on the applications. For some applications, ultramicroporous or supermicro-mesoporous materials may be optimal, but in general, a specific pore size distribution should be evaluated to find the best for a given application. We investigated different pore formation scenarios in several biochars gasified with steam, CO2, and diluted O2 using gas adsorption measurement and the dual gas analysis using the 2D-NLDFT model calculation. The detailed characteristics of the ultramicro-, supermicro-, and mesopore volumes showed a consistent trend of pore widening in the presence of steam at 800 °C, regardless of the steam concentration. On the other hand, steam gasification at elevated temperature (1000 °C) created highly ultramicroporous materials, and so did the reaction with diluted oxygen. We conclude that different pore formation patterns can be achieved with the modification of the gasification process and the dual gas analysis can assist in formulating guidance for tailoring chars for specific applications.