Volatile–Char Interactions during Biomass Pyrolysis: A Case Study of a Lignin Model Compound and Functionalized Graphitized Carbon Nanotubes

To further understand the secondary reactions during biomass pyrolysis, this study employs the pyrolysis–gas chromatography/mass spectrometry detection technique to investigate interactions between volatiles and char at 400 °C using benzyl phenyl ether (BPE) and different graphitized carbon nanotubes (GCNT, CNT–COOH, CNT–OH, and CNT–NH2) as model compounds, separately. The results show the BPE conversion increases from 0.1% (blank run), to 49.2% (with GCNT), to 55.1% (with CNT–COOH), to 61.3% (with CNT–OH), and to 70.2% (with CNT–NH2), caused by π–π stacking of aromatic rings between BPE and carbon nanotubes as well as hydrogen-bond formation between BPE and heteroatoms in functional groups. Such kinds of interactions significantly promote the cleavage of Cα–O to mainly form phenol and toluene. In the case of CNT–NH2, the breakage of Caryl–O is also facilitated by the synergistic effect of hydrogen-bond and aromatic–hydrogen interactions.