Size-Controlled Pd Nanoparticles in 2-Butyne-1,4-diol Hydrogenation: Support Effect and Kinetics Study
Structured catalyst has been developed for C–C triple bond three-phase hydrogenation. The sintered metal fiber (SMF) coated by different oxides served as support for monodispersed Pd nanoparticles (6.4 ± 0.5 nm). The effect of acid–base properties and reducibility of metal oxide coating on catalytic performance in the liquid phase (T = 303–348 K; P = 1–20 bar) hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol (B2) has been studied. The oxides MgO, ZnO, Ga2O3, Al2O3, ZrO2, SnO2, and SiO2 and the mixtures of MgO + ZnO + Al2O3, MgO + Al2O3, and ZnO + Al2O3 were tested. The catalyst activity was higher up to 10-fold for Pd0 on acidic supports, like SiO2, but demonstrated lower selectivity to B2 as compared to the basic oxides. The highest yield (99%) of the target B2 and stability over four consecutive runs were attained over the 0.2% Pd0/ZnO/SMF catalyst. The high selectivity to B2 was attributed to the formation of an active phase containing intermetallic PdZn alloy as confirmed by XPS. The reaction kinetics was modeled using a Langmuir–Hinshelwood mechanism and found consistent with the experimental data. The developed structured catalyst is suitable for a design of flow multiphase reactors to perform alkyne semihydrogenations in continuous mode.