Evaluation on the characteristics of homogeneous catalytic hydrothermal gasification of waste rubber based on ReaxFF-MD simulation

Massive waste tires unrecycled will pose a significant threat to the urban environment. Hydrothermal gasification (HTG) is a promising technology converting polymer wastes into H2-rich syngas. The homogeneous catalytic hydrothermal gasification behavior of natural rubber (NR) and styrene-butadiene rubber (SBR) was estimated based on reactive force field molecular dynamics (ReaxFF-MD). KOH had the highest catalytic performance in enhancing the degradation efficiency (22.5 %) and H2 yield (27.4 %) in HTG of NR, and K2CO3 demonstrated the most optimal alkaline catalyst for SBR to enhance the degradation efficiency (27.2 %) and H2 yield (37.9 %). K2CO3 loading with 6 wt% manifested the optimum amount for lifting DE and H2 yield in HTG of SBR, while 10 wt% K2CO3 loading represented the best effect for lifting DE (26.5 %) and H2 yield (42.6 %) in HTG of NR. The activation energy of SBR in HTG was about 259 kJ/mol, which was about 72 kJ/mol higher than that of NR. With 6 wt% K2CO3, the activation energy of SBR and NR in HTG decreased to about 143 kJ/mol and 122 kJ/mol, respectively. The present work could provide essential theoretical support and fundamental data for the application of the homogeneous catalysts in HTG recycling of waste rubber materials.