Physical characterization of pyrolyzed tobacco and tobacco components

摘要

Morphological changes in pyrolyzed tobacco and components of tobacco, i.e. cellulose, pectin, and lignin, at temperatures ranging from 250 to 750℃ in helium were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and surface area with N_2 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 micro-crystalline 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℃ 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.