Abstract: To meet the requirements of 1-butene isomerization in the resource utilization of mixed C₄ fractions, a series of phosphorus(P)-modified Pd-P/Al₂O₃ catalysts were prepared by the incipient wetness impregnation method. The catalytic performance was investigated in the selective hydrogenation of 1,3-butadiene coupled with 1-butene isomerization. The effects of P loading on the surface acidity, metal dispersion, and electronic structure of the catalysts were studied using a series of characterization techniques. The results indicated that the introduction of P significantly regulated the surface acidity distribution by forming Al—O—P structures, thereby increasing the density of weak Lewis acid sites. Although P loading led to a slight increase in Pd particle size, the electronic interaction between P and Pd enhanced the electron density of the active species. Under the reaction conditions of 60℃, 1.8MPa, and a space velocity of 3.5h^-1, the catalyst with a P loading of 0.5% exhibited the optimal performance: 1,3-butadiene was fully converted, the 1-butene isomerization rate reached 81.50%, and the 2-butene/1-butene molar ratio was 14.25, which approached the thermodynamic equilibrium limit. This study reveals the structure-activity relationship between surface weak Lewis acid sites and 1-butene isomerization performance, providing a theoretical basis for the development of highly efficient industrial catalysts.

Key words: 1,3-butadiene, selective hydrogenation, 1-butene, isomerization, phosphorus modification, structure-activity relationship