Depolymerization Behavior Of PE In Supercritical Water

Supercritical Fluid (SCF) technique is a useful method for disposing plastic waste because it can convert waste plastics to fuel oil or monomers for resource-recycling. But the reaction temperature and pressure of SCF are so hard to reach that theythinder the wide application. So it is urgent to find new ways for lowering the reaction conditions.In this research, a SCF reaction system was re-designed and constructed. The depolymerization behavior of high density polyethylene (HDPE) in supercritical water and effect of an additive, benzoyl peroxide (BPO) were studied. BPO, PE and H₂O with mass ratio of 1:10:100 were used as starting materials in a series of experiments, which were called BPO experiments. Comparison experiments (CP experiments) were carried out by using initial materials of PE and H₂O with mass ratio of 1:10. Two kinds of experiments were run at temperatures of 380℃, 400℃ or 420℃ for 30, 60 or 120 minutes under pressure about 25 MPa. The color and phase character of products were observed and compared, the mean molecular weights of samples wwre estimated by the Ostwald viscometer, and components and configurations of products were analyzed with GC-MS and IR. The characteristic surface configurations of glass tube in the reactor were examined by SEM.The results show: 1. Supercritical water reaction is a promising method in waste plastics disposal, for PE can be entirely decomposed to monomers. 2. The efficiency of depolymerization is the utmost in the first 30 minutes. 3. In supercritical water condition the decomposition of PE can be promoted with temperature increase. 4. It is noticeable that at lower temperature and shorter reaction time , the effect of the additive BPO on depolymerization of HDPE can be worthy of comparison of those which carried out at higher reaction temperature and longer reaction time in CP experiments. 5. In the...