Liquefaction of Mixed Plastics Containing PVC and Dechlorination by Calcium-Based Sorbent

Abstract

The pyrolysis of PVC-containing mixed plastics (PVC/PP/PE/PS) was carried out at 430 °C under atmospheric pressure by semibatch operation using a carbon composite of calcium carbonate sorbent (Ca−C) and also in the absence of sorbent (thermal). An amount of 4 g of Ca−C sorbent was used for consecutive 6 batches (each batch 10 g plastic) of the mixed plastic (PVC/PP/PE/PS:1/3/3/3) pyrolysis process. Hydrogen chloride and chlorinated hydrocarbons were produced during the pyrolysis of the mixed plastics containing PVC (PVC/PP/PE/PS). The Ca−C sorbent captured the hydrogen chloride evolved from the pyrolysis process. The theoretical sorbent capacity (71%) was utilized by repeatedly using the same sorbent for up to 5 consecutive batch processes without chlorine compounds in liquid products. The chlorinated hydrocarbons observed in the liquid products were obtained during run 5 (theoretical sorbent capacity 89%) and also during run 6 (theoretical sorbent capacity 106%). The hydrocarbons produced during the pyrolysis process reacted with the sorbent (during run 5) and yielded the chlorinated hydrocarbons in liquid products. X-ray diffraction studies revealed that the calcium carbonate sorbent was converted into calcium chloride during the pyrolysis process. The calcium-based sorbent was successfully utilized for the removal of chlorine content (inorganic and organic) from the pyrolysis process (PVC/PP/PE/PS:1/3/3/3) and produced halogen-free liquid products for 4 consecutive batch processes. The liquid products can be used as a fuel oil or feedstock in refinery.