Comparative study on the pyrolysis of cellulose and its model compounds

In order to determine the cellulose pyrolysis mechanism, the difference of pyrolysis behavior among cellulose, cellobiose and glucose was investigated. The residue evolution of these three materials during pyrolysis process was originally explored. The morphology evolution shows that the color of all them changes from white to brown, and being black finally, and it is noteworthy that both the cellobiose and glucose evolve from initial powders to molten state and become puffy and porous char ultimately, while cellulose whether undergo the molten stage highly depends on the heating rate according to its residue evolution under different temperatures. Both the TG analysis of original samples and FTIR analysis of pyrolyzed residues reveal the different pyrolysis behavior of them, and the thermal stability follows the order: cellulose > cellobiose > glucose. Kinetic analysis shows that the glucose has the lowest global activation energy in pyrolysis. The products distribution results show that cellulose pyrolysis produces more non-condensable gases and less bio-oil than cellobiose and glucose. The GC–MS analysis of the bio-oil indicates that glucose bio-oil contains more 1,6-anhydro-β-d-glucofuranose than cellulose and cellobiose, while cellobiose bio-oil holds the highest content of furans compounds (furfural and 5-hydroxymethyl furfural), and cellulose bio-oil riches in levoglucosenone, cyclic ketones and low molecular weight compounds (acetic acid, hydroxyacetaldehyde, hydroxyacetone etc.). Finally, the cellulose model compounds based on the present and other work are discussed and the potential use of anhydro-oligosaccharides as a model compound in exploring the cellulose pyrolysis is suggested.