Solvothermal liquefaction of orange peels and catalytic upgrading of biocrude into transportation fuel over a hybrid catalyst

Abstract

The efficient valorization of biomass for energy-derived biocrudes is essential for effective waste management. However, the production of biocrudes with high energy and reduced oxygen contents during the liquefaction process requires further improvement. This study investigates the impact of reaction temperature, residence time, and ratio of ethanol to acetone on the energy compositions and bio-product’s yield enhancement were investigated under non catalytic and catalytic process with further upgrading. The biocrudes obtained via the non catalytic liquefaction were characterized for elemental composition, bio-oil compositions, functional group, molecular weight and thermal stability to understand the effects of process parameters on the biocrudes’ compositions. An improved bio-oil with High Heating Value (HHV) (38.18 MJ/kg) and lower oxygen: carbon (O/C) ratio (0.11) were obtained at 430 ◦C, 35 min and 50% ethanol with a significant boost in the enhancement factor, deoxygenation, and percentage hydrogenation of 2.63, 36.88%, and 77.87%, respectively. The presence of ketones with composition of 32.58 area% suggests the needs for the removal of oxygen from the bio-oil. Using a central composite design (CCD), catalyst dosage (3-6 wt.%) and reaction temperature (330-430°C) were optimized, maintaining constant orange feedstock weight (10g), reaction time (15 minutes), and a solvent ratio of 3:1 (acetone to ethanol). Optimal biofuel yield (71.09 wt.%), solid residue (28.18 wt.%), biomass conversion (71.82 wt.%), and gas yield (40.14 mL/g) were achieved at 430°C and 3 wt.% catalyst loading. The Fe/CNSs catalysts possess high selectivity to acid formation. High correlation coefficients indicated the model’s strong fit with experimental data. The hydrodeoxygenation (HDO) of cyclohexanone under both catalytic and non-catalytic conditions involved mechanisms such as hydrogenation, decarboxylation, decarbonylation, and dehydration. The NiCeMo catalysts shows an even particle dispersion where 11.3 area % of hydrocarbon and highest conversion of ketones and phenols were obtained. However, the performance of NiCeMo catalysts for HDO was hampered by the Guerbet reaction, which led to the formation of side products which are primarily alcohols. Modifying the acidity and using water as a solvent could potentially increase the HHV of the biofuel hence, promote the usage for transportation purposes. Biofuel produced through the non-catalytic process demonstrated a higher energy value of 38.18 MJ/kg, highlighting orange peels as a viable renewable energy resource