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 Pd on acidic supports, like SiO2, but demonstrated lower selectivity to B2 as compared to the basic oxides. The highest yield (similar to 99%) of the target B2 and stability over four consecutive runs were attained over the 0.2% Pd-0/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.