Hydrothermal Dechlorination of a Reclaimed Oil in a Continuous Packed-Bed Reactor

Abstract

The liquid-phase hydrothermal dechlorination of a reclaimed oil (Cl content = 2280 ppm) derived from waste lubricating oils was investigated at 275–325°C by using a continuous packed-bed reactor. The reaction proceeded readily in aqueous NaOH solutions, especially at higher NaOH concentrations and at higher reaction temperatures. Thus, the chlorine content in the oil decreased to 57 ppm at 325°C when 0.4 mol/L NaOH was used at the weight feed ratio of 1.3 and at the residence time of 8.0 min. However, the reaction did not proceed further even when the concentrated NaOH solutions of more than 0.4 mol/L were used. The rate of the dechlorination could be well described in terms of a homogeneous SN2-type reaction kinetics involving the participation of water molecules and OH– ions. In contrast to the contribution of water molecules to the reaction, that of OH– ions increased at higher NaOH concentrations and at higher reaction temperatures.