Vacuum co-pyrolysis of Chinese fir sawdust and waste printed circuit boards. Part I: Influence of mass ratio of reactants

• Co-pyrolysis process presents antagonistic effect in the yields of the volatiles.
• Co-pyrolysis process is good for the formation of brominated aromatic compounds.
• The volatiles were mainly formed between 300 and 450 °C in the pyrolysis process.
• Noncondensable gases (CO2, CO, CH4, etc.) were the main components after 450 °C.
• Co-pyrolysis oils show better synthetic properties than the separate ones.

Vacuum co-pyrolysis of Chinese fir sawdust (CFS) and waste printed circuit boards (WPCBs) at different mass ratios were examined in this paper. The structures and contents of the pyrolysis oils were analyzed by Fourier transform infrared (FTIR) spectroscopy and gas chromatography–mass spectrometry (GC–MS). The results showed that co-pyrolysis processes presented antagonistic effect in the yield of the total volatiles (liquid plus gas) at the experimental conditions, but it is beneficial to the formation of brominated aromatic compounds (whose total content in WPCBs pyrolysis oil was only 6.51 wt%, while in co-pyrolysis processes (CFS/WPCBs = 4:1, 1:1, 1:4), they were 10.96 wt%, 7.98 wt% and 14.84 wt%, respectively). The co-pyrolysis processes were also analyzed by thermogravimetric (TG) analysis with evolved product analysis by FTIR. The results showed that the volatiles were mainly formed between 300 and 450 °C, and after 450 °C, there were mainly some noncondensable gases (CO2, CO and CH4) formed.