Thermal Conversion of Lignin-Cellulose Composite Particles into Aggregates of Fine Carbon Grains Holding Micro- and Mesoporous Spaces

Composite particles of lignin hydroxyethylcellulose were fabricated by means of reverse-micelle formation using H2O-CHCl3 in the presence of a surfactant, and an aggregate of the particles was obtained by successive precipitation from acetone, filtration, and drying. The aggregate was carbonized by pyrolysis with heating up to 900 degrees C under flowing of argon. The carbonized product was a hierarchical porous carbon that had a Brunauer-Emmett-Teller (BET) surface area of 405 m(2)/g with micropore volume (0.11 cm(3)/g) and no small mesopore volume (0.58 cm(3)/g). Higher porous spherical carbon aggregates were obtained by fitting an in situ surface activation in the carbon conversion process, i.e., composite particles similarly prepared from lignin and hydroxyethylcellulose in the presence of NaOH were carbonized. One of them showed a BET surface area of 1790 m(2)/g with a micropore volume (0.54 cm(3)/g) and large mesopore volume (2.08 cm(3)/g). This in situ activation process added rnicropores and mesoporous cavities to the microporous carbon grains and enhanced development of mesoporous voids between the grains. The aggregate of the activated carbon grains in 1 M H2SO4 showed a good electrical double layer capacitance of 394 F/g at a current density of 0.05 A/g, which declined logarithmic functionally to 269 F/g at a higher current density of 0.4 A/g.