Controllable preparation of ruthenium-based catalysts modified with lithium and study of catalytic performance in the hydrogenation of 2,4-diaminotoluene

Abstract

Hydrogenated toluene diisocyanate (HTDI) is crucial in military and new energy industries, with its synthesis challenged by the deamination side reaction during the hydrogenation of 2,4-toluenediamine (2,4-TDA) to 1-methyl-2,4-cyclohexanediamine (2,4-MCDA). This study addresses this by designing Ru-based catalysts with controlled acidity through LiOH-induced surface defect engineering on γ-Al₂O₃ supports. Ru/γ-Al₂O₃ catalysts were synthesized via impregnation–precipitation and characterized using TEM, NH₃-TPD, and XPS. Optimal LiOH concentration (5 wt%) enhanced the Ru loading and dispersion, improving catalytic activity and 2,4-MCDA selectivity. At 180 °C and 5.0 MPa, the 2,4-TDA conversion reached 67.5% with 78.58% 2,4-MCDA selectivity. The catalyst maintained high performance over 10 cycles, offering a theoretical basis for advancing 2,4-TDA hydrogenation and catalyst design.