Chemical recycling of polycarbonate to raw materials by thermal decomposition with calcium hydroxide/steam

We investigated the influence of the decomposition conditions (temperature: 500, 700, 900°C, steam concentration: 0, 35, 86 vol %, Ca(OH) ₂/PC molar ratio: 0 or 5) on polycarbonate (PC). Without steam and Ca(OH)₂ the liquefaction yield was 57 wt % (low and high boiling products 14, 43 wt %, respectively), the gasification yield 12 wt %, and the carbonization yield 31 wt % at 500°C. At a steam concentration of 86 vol %, 84 wt % liquids (low and high boiling products 17, 67 wt %, respectively), 1 wt % gases and 15 wt % residues were observed. The amount of low boiling products increased from 17 to 31 wt %, and the amount of high boiling products decreased from 67 to 49 wt % when Ca(OH)₂ was added at a steam concentration 86 vol %. At this time, the yield of phenol in the low boiling fraction increased from 15 to 74 mol % (20 wt % of all products).