Catalytic hydrothermal liquefaction of wheat straw and chemical profiling of bio-crude oil

In this study, a central composite design model was generated under response surface methodologies for the hydrothermal liquefaction of the wheat straw by considering the different process variables such as temperature (270–330 °C), reaction time (20–60 min) and feed concentration (5–15 wt%) to optimize the bio-crude oil yield and generate an experimental model. Moreover, at the optimized conditions, different catalysts such as K₂CO₃, Fe, ZrO₂, Fe-K₂CO₃ and ZrO₂-K₂CO₃ were employed for the hydrothermal liquefaction of wheat straw to maximize the bio-crude oil yield and decrease the oxygen content. Among all catalysts, Fe-K₂CO₃ delivered the highest bio-crude oil yield of 29 wt% with the lowest oxygen content of 14 wt%. The chromatographic analysis established molecular profiling of bio-crude oil samples, which revealed the presence of different phenolic compounds like phenol, 2-methoxy phenol and catechol including other components such as aldehydes, cyclic ketones, octene, hexadecane and octadecane. Spectroscopic and compositional profiling of bio-crude oil revealed different organic functional groups and aromatic compounds essential for the generation of molecular-level reaction mechanisms and subsequent upgrading of bio-crude oil for transportation fuel and various chemicals.