Pyrolysis behaviors of four O-acetyl-preserved hemicelluloses isolated from hardwoods and softwoods

• O-acetyl-preserved hemicelluloses were isolated successfully from woody biomass.
• Pyrolysis of hardwood hemicellulose with high content of O-acetyl yield more acids.
• Hydroxymethyl in softwood hemicellulose leads to HMF and anhydro sugars formation.
• DG-DAEM showed softwood hemicellulose pyrolysis having higher activation energy.

The pyrolysis mechanisms of O-acetyl-preserved hemicelluloses isolated from both hardwoods and softwoods have been investigated. Their chemical structures, pyrolysis kinetics, pyrolytic product distributions, and pyrolytic gaseous evolutions have been systematically studied. Hardwood hemicellulose was mainly composed of 4-O-methyl-d-glucurono-d-xylan and had high contents of O-acetyl and uronic acid units, whereas softwood hemicelluloses were composed of d-galacto-d-gluco-d-mannan and l-arabino-4-O-methyl-d-glucurono-d-xylan. A double-Gaussian distributed activation energy model has been introduced to simulate the pyrolysis kinetics. Hardwood hemicellulose pyrolysis showed lower activation energies than softwood hemicellulose pyrolysis. Hardwood hemicellulose pyrolysis mainly yielded furfural and acids, whereas for softwood hemicellulose pyrolysis, 5-hydroxymethylfurfural and anhydro sugars were typical products. The evolution behaviors of H2O, CO2, CO, and acids from the pyrolyzes of the four hemicelluloses are discussed.

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