Oxygen-Containing Fuels from High Acid Water Phase Pyrolysis Bio-Oils by ZSM−5 Catalysis: Kinetic and Mechanism Studies

This study developed an upgrading process focusing on acid transformations of water phase pyrolysis bio-oils to esters of oxygen-containing fuels via ZSM−5 catalyst. Temperature was set as a factor with five levels ranging from 60 to 135 °C with reaction time from 1 to 8 h. The results showed that 89% of high acid conversion and over 90% of ester selectivity was obtained from the feedstock via 2 wt % ZSM−5 catalysts in a fixed feedstock to methanol ratio analyzed by HPLC and GC–MS. The upgrading process followed Langmuir–Hinshelwood and reaction constants were calculated to build a practical upgrading model for bio-oil compounds. Thermodynamics of the process showed endothermic properties during the breaking bonds’ reaction on carbonyl of acid while the reaction between the carbon in methanol and electrophile acid intermediate demonstrated exothermic performance. The optimum reaction conditions for the process was at a temperature of 100.1 °C with catalyst loading of 3.98 wt %.