Mg–Al ratio‐tuned hydrotalcite‐derived mixed oxides for catalytic upgrading of wood tar

Abstract Biomass‐derived pyrolysis tar is difficult to valorize efficiently because of its high content of oxygenated compounds and the resulting low product quality. In this work, a series of porous mixed oxide catalysts were prepared by calcination of Mg–Al layered double hydroxide precursors with different molar ratios [ x = Al 3+ /(Mg 2+ + Al 3+ ), x = 0.15–0.35]. The effects of the Mg–Al ratio on the phase structure, morphology, textural properties, and NH 3 ‐responsive surface acidic features of the derived catalysts were investigated systematically, together with their catalytic performance in wood tar upgrading under supercritical methanol conditions. Among the tested samples, MgAl‐0.30 exhibited a favorable combination of mesoporous accessibility and strong ammonia temperature‐programmed desorption (NH 3 ‐TPD) response, with an average pore diameter of 24.93 nm and a specific surface area of 184.96 m 2 g −1 . At 240 °C and 8 MPa, this catalyst afforded a product yield of 62.00% and a deoxygenation extent (DE) of 69.88%. Heteronuclear single quantum coherence nuclear magnetic resonance (HSQC‐NMR) analysis showed that the catalyst with the optimized Mg–Al ratio more effectively promoted the removal of methoxy groups and aliphatic side chains while retaining detectable aromatic structural features. Pearson correlation analysis further revealed that the NH 3 ‐TPD response was positively correlated with DE ( r = 0.98), while average pore diameter showed a positive correlation with product yield ( r = 0.67). These results suggest that tuning the Mg–Al ratio can effectively regulate the structure–property relationship of calcined MgAl mixed oxides, thereby influencing wood tar upgrading performance. This study provides a structure–performance perspective for the design of MgAl‐derived catalysts for biomass‐derived tar upgrading.