The effect of solvent and pH on the preparation of MnAl2O4 catalyst for the conversion of furfural to bio-jet fuel precursor

Dehydrogenation of 1,4-butanediol and reductive self-condensation of furfural. • The influence of solvent and pH on the properties of catalysts has been established. • Catalytic activity was correlated with Mn/Al molar ratio and particle homogeneity. • The synthesis of the samples is efficient in basic medium. • Reaction conditions were optimized for high yield in hydrofuroin. Furfural reductive self-coupling, using 1,4-butanediol as source of hydrogen, has been studied over a series of manganese aluminate catalysts, synthesized under various pH conditions and solvents for precursors. Liquid organic hydrogen carriers have many technical, environmental, and economic advantages. The influences of reaction time, temperature, 1,4-butanediol to furfural molar ratio, the kinetic and pathway of reaction have been explored. The best results were obtained at 150 °C and a 1,4-butanediol to furfural ratio of 3. For the above-mentioned reaction, it was observed that the high catalytic activity was clearly related to the surface ratio manganese to aluminium, particle homogeneity, crystalline microstrain and the Mn 2+ /Mn 3+ ratio. The excellent catalytic performance was determined for the sample synthesized from precursors dissolved in ethanol and ammonia as the hydrolysis rate controller (pH 8). This sample exhibits all the mentioned characteristics, namely the presence of particles with a good homogeneity (evidenced by SEM microscopy), the Mn/Al ratio close to the formula MnAl 2 O 4 , the highest Mn 2+ /Mn 3+ ratio (from XPS spectroscopy), and last but not least, it presents the highest values of residual strain and crystal defects (microstrain, determined from XRD measurements). This study provides a basis for further development of sustainable jet fuels production from furfural.