Hydrodeoxygenation of bis(2-hydroxyethyl) terephthalate as a model compound of polyethylene terephthalate waste using spray pyrolysis synthesis of γ-Al₂O₃ supported Ni-Fe catalyst

Polyethylene terephthalate (PET) waste poses a significant environmental challenge due to its persistence and limited chemical recycling options. Conventional hydrodeoxygenation (HDO) strategies for PET depolymerization products often require high pressure or noble metals, limiting their scalability and economic viability. In this study, bis(2-hydroxyethyl) terephthalate (BHET), a primary glycolysis product of PET, was employed as a model compound to evaluate an efficient HDO route using non-noble, bimetallic Ni–Fe catalysts supported on γ-Al₂O₃ under atmospheric pressure. The reaction was conducted in a fixed-bed reactor at 400 - 500 °C using 2-ethylphenol as both solvent and hydrogen donor. Among the catalysts tested, Ni5-Fe15 exhibited superior performance, achieving 99.41 % BHET conversion and 76.57 % deoxygenation degree at 475 ℃. The incorporation of Fe improved acid site density and facilitated the formation of a NiFe alloy, enhancing C-O bond cleavage and selectivity toward aromatic hydrocarbons such as benzene (37.37 %) and naphthalene (18.80 %). Gas analysis revealed the evolution of C₁-C₃ hydrocarbons and dominant CO₂ formation, indicating decarboxylation as a primary pathway. The gas product analysis detected hydrocarbon gases C₁-C₃, suggesting various reaction pathways, including decarboxylation, decarbonylation, and demethylation. Using bimetallic catalysts resulted in a decrease in CO selectivity but an increase in CO₂ selectivity, which may be attributed to the formation of NiFe alloy within the catalyst.