Study on pine sawdust pyrolysis behavior by fast pyrolysis under inert and reductive atmospheres

- More acceptable bio-oils acquired from fast pyrolysis of PS under H2 than Ar.
- H2 can promote the generation of phenols and aldehydes.
- H2 can enhance disintegration of macromolecule organic vapors.
- H2 can advance oxygen and carbon transferring from material to volatile.
- The influence of H2 on reaction network is also discussed.

Fast pyrolysis of pine sawdust (PS) was investigated in a drop tube quartz reactor to understand the effects of temperature and atmosphere (Ar and H2) on the product yields, gas composition, bio-oil characteristics (organic composition and molecular mass distributions (MMDs)), and the carbon and oxygen conversion. The pyrolysis behavior and typical products from PS pyrolysis were also conducted using a thermogravimetry-mass spectroscopy (TG-MS) and pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS). The results show that the highest oil yields can be obtained at 500 °C of 55.09 and 54.41 wt.% under Ar and H2 atmosphere, respectively. In comparison to an inert atmosphere, H2 created lower oil yields but higher gas yields, especially for CO and CH4 yields, and narrower MMDs, smaller Mn and Mw, and fewer char especially at high temperatures. The high temperatures and H2 atmosphere contribute to the oxygen and carbon transferring from material to volatile, especially to the gaseous products. H2 can promote the secondary cracking of macromolecules and weaken the re-polymerization of anhydrosugar and lignin oligomers.