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 K 2 CO 3 , Fe, ZrO 2 , Fe-K 2 CO 3 and ZrO 2 -K 2 CO 3 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-K 2 CO 3 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. • Hydrothermal liquefaction of wheat straw with and without catalysts was performed. • Optimized HTL temperature, reaction time and feed concentration were 299.8 °C, 39.9 min and 7.7 wt.%, respectively. • Fe-K 2 CO 3 led to the highest bio-crude oil yield (29 wt.%) and lowest oxygen content (14 wt.%). • Catalysts reduced the formation of phenolic and oxygenated components in bio-crude oil. • A variety of value-added biochemical precursors were obtained in bio-crude oil.