TiO2-modulated surface oxygen dynamics in Fe-based mixed oxides for enhanced hydrocarbon aquathermolysis

Aquathermolysis has emerged as a promising technique for the purification of contaminated low-grade hydrocarbons and the enhancement of light-fuel yield. In this study, we investigated the TiO 2 -modulated surface oxygen dynamics and water adsorption behavior of Ni–Fe–Ti (NFT) mixed oxides to elucidate their role in catalytic aquathermolysis. NFT catalysts with different Fe:Ti ratios were synthesized and characterized to evaluate the influence of TiO 2 /Fe 2 TiO 5 /α-Fe 2 O 3 mixed phases and surface oxygen dynamics on catalytic performance. In situ H 2 O–FTIR analysis revealed that variations in the Fe:Ti ratio influenced the water adsorption behavior, leading to distinct hydrogen transfer capabilities. Crystallographic analysis and X-ray photoelectron spectroscopy confirmed the presence of highly active surface oxygen in Fe-rich NFTs and the enhanced phase stability of Ti-rich NFTs. Morphological and microstructural characterization of fresh and spent catalysts showed that an Fe 2 TiO 5 phase formed at the edges of Fe particles, preserving the core α-Fe 2 O 3 active sites throughout the reaction. Among the synthesized catalysts, NFT-75 exhibited the optimal Fe:Ti ratio, and achieved excellent performance with increases in light oil yield and reductions in coke formation of approximately 4 and 2 wt%, respectively. Moreover, NFT-75 demonstrated good recyclability, maintaining its contaminant removal performance over repeated cycles. Therefore, this study suggests an effective strategy for designing Fe-based catalysts with a balance between active α-Fe 2 O 3 sites for water adsorption and TiO 2 promoters with stable lattice oxygen for coke suppression in low-grade hydrocarbon aquathermolysis, providing insights for the design of aquathermolysis catalysts.