Debrominated high quality oil production by the two-step catalytic pyrolysis of phenolic printed circuit boards (PPCB) using natural clays and HY

•Two-step catalytic pyrolysis of phenolic-printed circuit board was evaluated.•Dolomite was most effective on debromination among in-situ natural clays.•The combination of dolomite and HY(30) minimizes brominated compounds and allows the longer life time of HY(30). The two-step catalytic pyrolysis (CP) of a phenolic-printed circuit board (PPCB) over in-situ natural clays (dolomite, bentonite, and olivine) and ex-situ HY(30, SiO2/Al2O3: 30) was investigated by tandem micro reactor-gas chromatography/mass spectrometry. The non-catalytic pyrolysis (NCP) of PPCB produced oxygenated, phosphorous, and brominated compounds due to the presence of paper, tetrabromo bisphenol A (TBBA), phosphorous flame retardants, and phenol resin in the PPCB. Among the natural clays, dolomite showed the highest debromination and aromatics formation efficiency during the in-situ CP of PPCB followed by bentonite and olivine owing to the different catalyst properties. Two-step CP of PPCB over in-situ natural clays and ex-situ HY(30) achieved higher efficiency on the formation of higher quality oil (mono-phenol and aromatic hydrocarbons) with a lower Br content than the one-step CP of PPCB. Among the two-step catalysts, the combination of in-situ dolomite and ex-situ HY(30) provided the highest quality oil production due to the high acidity and sufficiently large pore size of dolomite. Two-step CP of PPCB over in-situ dolomite and ex-situ HY(30) also revealed a longer lifetime than the one-step CP of PPCB over ex-situ HY(30), not only for the formation of aromatic hydrocarbons and mono-phenols, but also for debromination.