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Article

Tuning the Activity of NbOPO4 with NiO for the Selective Conversion of Cyclohexanone as a Model Intermediate of Lignin Pyrolysis Bio-Oils

Energy and Bioproducts Research Institute, College of Engineering and Physical Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
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Energies 2025, 18(15), 4106; https://doi.org/10.3390/en18154106 (registering DOI)
Submission received: 4 July 2025 / Revised: 29 July 2025 / Accepted: 30 July 2025 / Published: 2 August 2025

Abstract

Catalytic upgrading of pyrolysis oils is an important step for producing replacement hydrocarbon-rich liquid biofuels from biomass and can help to advance pyrolysis technology. Catalysts play a pivotal role in influencing the selectivity of chemical reactions leading to the formation of main compounds in the final upgraded liquid products. The present work involved a systematic study of solvent-free catalytic reactions of cyclohexanone in the presence of hydrogen gas at 160 °C for 3 h in a batch reactor. Cyclohexanone can be produced from biomass through the selective hydrogenation of lignin-derived phenolics. Three types of catalysts comprising undoped NbOPO4, 10 wt% NiO/NbOPO4, and 30 wt% NiO/NbOPO4 were studied. Undoped NbOPO4 promoted both aldol condensation and the dehydration of cyclohexanol, producing fused ring aromatic hydrocarbons and hard char. With 30 wt% NiO/NbOPO4, extensive competitive hydrogenation of cyclohexanone to cyclohexanol was observed, along with the formation of C6 cyclic hydrocarbons. When compared to NbOPO4 and 30 wt% NiO/NbOPO4, the use of 10 wt% NiO/NbOPO4 produced superior selectivity towards bi-cycloalkanones (i.e., C12) at cyclohexanone conversion of 66.8 ± 1.82%. Overall, the 10 wt% NiO/NbOPO4 catalyst exhibited the best performance towards the production of precursor compounds that can be further hydrodeoxygenated into energy-dense aviation fuel hydrocarbons. Hence, the presence and loading of NiO was able to tune the activity and selectivity of NbOPO4, thereby influencing the final products obtained from the same cyclohexanone feedstock. This study underscores the potential of lignin-derived pyrolysis oils as important renewable feedstocks for producing replacement hydrocarbon solvents or feedstocks and high-density sustainable liquid hydrocarbon fuels via sequential and selective catalytic upgrading.
Keywords: niobium phosphate; nickel oxide; catalysis; pyrolysis; bio-oils; cyclohexanone; sustainable aviation fuel; sustainable solvents niobium phosphate; nickel oxide; catalysis; pyrolysis; bio-oils; cyclohexanone; sustainable aviation fuel; sustainable solvents

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MDPI and ACS Style

Hart, A.; Onwudili, J.A. Tuning the Activity of NbOPO4 with NiO for the Selective Conversion of Cyclohexanone as a Model Intermediate of Lignin Pyrolysis Bio-Oils. Energies 2025, 18, 4106. https://doi.org/10.3390/en18154106

AMA Style

Hart A, Onwudili JA. Tuning the Activity of NbOPO4 with NiO for the Selective Conversion of Cyclohexanone as a Model Intermediate of Lignin Pyrolysis Bio-Oils. Energies. 2025; 18(15):4106. https://doi.org/10.3390/en18154106

Chicago/Turabian Style

Hart, Abarasi, and Jude A. Onwudili. 2025. "Tuning the Activity of NbOPO4 with NiO for the Selective Conversion of Cyclohexanone as a Model Intermediate of Lignin Pyrolysis Bio-Oils" Energies 18, no. 15: 4106. https://doi.org/10.3390/en18154106

APA Style

Hart, A., & Onwudili, J. A. (2025). Tuning the Activity of NbOPO4 with NiO for the Selective Conversion of Cyclohexanone as a Model Intermediate of Lignin Pyrolysis Bio-Oils. Energies, 18(15), 4106. https://doi.org/10.3390/en18154106

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