Selective H2 production from plastic waste through pyrolysis and in-line oxidative steam reforming

This study deals with the proposal of pyrolysis and in-line oxidative steam reforming (P-OSR) for plastic waste valorization and assesses the potential of this strategy for the selective production of H-2. Overall, the study aims at progressing towards the fine-tuning of the pyrolysis-reforming technology by co-feeding O-2. Thus, a multipoint O-2 injection system has been developed to ensure a suitable O-2 distribution in the reforming reactor and avoid the formation of hot spots, as they may cause catalyst deactivation by metal sintering. Moreover, as O-2 is directly supplied into the catalytic bed, pre-combustion of the volatile stream before contacting the catalyst is avoided and in-situ coke combustion is promoted. The P-OSR of HDPE was carried out in a two-step reaction system, which combines CSBR (conical spouted bed reactor) and FBR (fluidized bed reactor) technologies. The experiments were conducted in continuous mode and the influence of the main process conditions at zero time on stream was analyzed. Thus, the effect of reforming temperature was studied in the 550-750 degrees C range, that of the space time from 3.12 to 15.62 gcat min g(HDPE)(-1) , steam to plastic (S/P) ratio between 2 and 5 and equivalence ratio (ER) from 0 to 0.3. Under the optimum conditions (700 degrees C, S/P of 3, 12.5 gcat min gHDPE production of 25.0 wt% was obtained, which is only 28.6 % lower than that obtained in the conventional pyrolysis-steam reforming (P-SR) process. The results obtained confirm the potential of continuous P-OSR process for the selective production of H-2.