Pore structure of soot deposits from several combustion sources

Soot was harvested from five combustion sources: a dodecane flame, marine a nd bus diesel engines, a wood stove, and an oil furnace. The soots ranged f rom 20% to 90% carbon by weight and molar C/H ratios from 1 to 7, the latte r suggesting a highly condensed aromatic structure. Total surface areas (by nitrogen adsorption using the Brunauer Emmett Teller, BET method) ranged f rom 1 to 85 m(2) g(-1). Comparison of the surface area and meso-pore (pores 2-50 nm) surface area predicted by density functional theory (DFT) suggest ed that the soot was highly porous. Total mesopore volume and surface area ranged from 0.004-0.08 cm(3) g(-1) and from 0.33-6.9 m(2) g(-1), respective ly, accounting for up 33% of the BET surface area. The micro-pore volume (p ores <2 nm) calculated from CO2 adsorption data (by DFT) ranged from 0.0009 to 0.013 cm(3) g(-1) and micro-pore surface area was 3.1-41 m(2) g(-1), ac counting for 10-20% of the total intra-particle (meso-plus micro-pores) por e volume and 70-90% of the total intra-particle surface area. Higher pore v olume and surface area values were computed using the Dubinin Radushkevich plot technique; ranging from 0.004-0.04 cm(3) g(-1) to 11-102 m(2) g(-1) fo r micro-pore volume and surface area, respectively. Comparison of the C/H r atio and the micro-pore structure showed a strong correlation, suggesting a relationship between the condensation of the skeletal structure and micro- porosity of the soot. These data contradict literature reports that soot pa rticles are non-porous and are consistent with recent literature reports th at soil organic matter has large micro-pore surface areas. (C) 2000 Elsevie r Science Ltd. All rights reserved.