Physical characterization of pyrolyzed tobacco and tobacco components

Morphological changes in pyrolyzed tobacco and components of tobacco, i.e. cellulose, pectin, and lignin, at temperatures ranging from 250 to 750 degreesC in helium were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and surface area with NZ BET. Tobacco and pectin char were also characterized by high-resolution transmission electron microscopy. Changes in tobacco included the separation and degradation of the cuticle layer, the formation of inorganic precipitates, formation of a melt phase, volatile gas and vesicle formation, and surface etching. The carbon matrix of tobacco ranged from a homogeneous amorphous character at lower temperatures to a heterogeneous, mixed microcrystalline structure at high temperatures with domains of graphene sheets, fullerenes, and graphite. Xylem elements that were dissected from burley tobacco stems formed a melt/liquid phase and precipitates of inorganic salts. Individual, single components such as Avicel cellulose, alkali lignin, and citrus pectin were used to simulate components found in tobacco. Avicel cellulose formed a melt phase and vesicles. Pectin formed a melt/liquid phase at 250 degreesC followed by vesicle formation, surface etching, inorganic precipitate formation, and condensate formation of carbonaceous materials. The micro-crystalline structure of pectin ranged from amorphous at low temperatures to graphene sheets at high temperatures. In pyrolyzed lignin, changes included the formation of a melt/liquid phase, vesicles, and precipitates of inorganic salts and the occurrence of surface etching. (C) 2002 Elsevier Science B.V. All rights reserved.