Catalytic potential of low-cost natural zeolite and influence of various pretreatments of biomass on pyro-oil up-gradation during co-pyrolysis with scrap rubber tires

Abstract

This study investigates the influence of low-cost natural zeolite (NZ) catalyst, metallic content and various pretreatments of rice straw (RS) on quality and quantity of oil derived from co-pyrolysis and catalytic co-pyrolysis of RS and scrap rubber tire (SRT). Oil obtained from co-pyrolysis of combined acid-washed and torrefied RS (WT-RS) and SRT (WT-RS/SRT) had 41% less oxygenates, 17% more hydrocarbons (HCs) and a significant amount of levoglucosan compared to the combination of raw RS and SRT (R-RS/SRT). Besides, char from WT-RS/SRT combination had more HHV (30.15 MJ/kg) than that of R-RS/SRT combination (26.85 MJ/kg). NZ incorporation into co-pyrolysis enhanced deoxygenation by 34% for catalytic combination of R-RS/SRT/NZ than non-catalytic co-pyrolysis of R-RS/SRT combination whilst the combination of WT-RS/SRT/NZ encountered 77.27%, 61.53% and 65.51% more deoxygenation than R-RS/SRT, WT-RS/SRT and R-RS/SRT/NZ combinations, respectively. An increase in HCs was found to be 40% and 31.25% for WT-RS/SRT/NZ contrary to WT-RS/SRT and R-RS/SRT/NZ, respectively. Additionally, 69.23% more mono aromatics along with more valuable gaseous composition were obtained in WT-RS/SRT/NZ than R-RS/SRT/NZ. HHV and physical characteristics of oil were superior for WT-RS/SRT/NZ. Results showed co-pyrolysis of pretreated RS-SRT as an effective route to improve product quality, which was further improved by the catalyst incorporation.