Pyrolysis of Cascabela thevetia seeds over ZSM-5 catalysts: fuel properties and compositional analysis

In the present study, Cascabela thevetia seed (SK), waste biomass supported by its physicochemical characterization exhibited significant potential for the production of renewable fuel and valuable chemicals. Thermal and catalytic pyrolysis of SK was performed in a cylindrical shaped semi-batch reactor using varying biomass to catalyst ratios (B/C) (3:1, 6:1, 8:1 and 10:1). ZSM-5 was calcined at 900 °C for 6 h and characterized by BET, FTIR, XRD and FESEM. Catalyst characterization results showed an increase in surface area (518 m² g⁻¹) along with a slight change in the crystallinity (peak intensity of calcined ZSM-5 at 2θ = 23.35°, 23.97° and 24.67°). Further, it was noted that catalytic pyrolysis reduced the pyrolytic liquid yield (55.55 wt.% at 8:1) in comparison to the thermal pyrolytic liquid yield (64.23 wt.%). However, the introduction of ZSM-5 at 8:1 ratio improved the overall properties and characteristics of pyrolytic oil by reducing density, viscosity, oxygen content, and increasing gross heating value, carbon content and acidity. FTIR analysis showed that pyrolytic oil contained phenols, hydrocarbons, aromatics, ethers, esters, ketones, alcohols and water, while NMR analysis supported the FTIR results. GC-MS investigation revealed that introduction of catalysts significantly reduced the oxygenated compounds such as esters, ether and ketones and substantially enhanced the hydrocarbons in the pyrolytic oil. Further, ash content analysis of pyrolytic oil confirmed that the ash content in catalytic pyrolytic oil was less than that of thermal pyrolytic oil.