Understanding the Deactivation of Ni–WO _x /SiO ₂ Catalysts During Aqueous‐Phase 5‐Hydroxymethylfu

Converting 5‐hydroxymethylfurfural (HMF) to 2,5‐tetrahydrofurandimethanol (THFDM) is a critical route for biomass valorization. In this study, we designed a silica‐supported Ni–WO _x /SiO ₂ catalyst for this reaction, which showed high initial activity with near‐complete HMF conversion and a 95.64% THFDM yield under mild aqueous conditions (90 °C, 5 MPa H ₂ , 4 h). This performance originates from a synergistic Ni–WO _x interaction that promotes furan ring hydrogenation, and no significant sintering was observed. However, selectivity progressively declines upon recycling despite stable conversion. Comprehensive characterizations (TGA, liquid‐phase ICP, BET, and HRTEM) rule out graphitic carbon deposition, actual tungsten leaching (<0.34%), and metal sintering as primary causes. Instead, the selectivity loss is a dual‐pathway deactivation: physical masking of critical Ni ⁰ –WO _x active sites by strongly adsorbed humin‐like oligomers, and irreversible thermal collapse of the mesoporous SiO ₂ support during high‐temperature regeneration. This mechanistic elucidation provides valuable guidance for rationally designing more durable Ni‐based catalysts for aqueous‐phase biomass conversion.