Structured catalyst of Pd/ZnO on sintered metal fibers for 2-methyl-3-butyn-2-ol selective hydrogenation

Abstract

An innovative structured catalyst based on sintered metal fibers (SMFs) coated by a grain-structured ZnO layer was developed for the selective 3-phase hydrogenation of functionalized alkynes. The catalyst was synthesized by the deposition of Pd 0-sol with 7-nm nanoparticles stabilized by molybdate anions on ZnO/SMF after reduction in hydrogen at 773 K. The crystallites of PdZn alloy (24 nm) were formed by high-temperature treatment in hydrogen and contained partly Pd(0) nanoparticles. Pd/ZnO/SMF (0.2 wt% Pd, 6 wt% ZnO) allowed > 95 % yield of 2-methyl-3-buten-2-ol (MBE) during 2-methyl-3-butyn-2-ol hydrogenation at 308 K and 5 bar pressure using water as the solvent and adding a small amount of quinoline. The consecutive reaction of MBE hydrogenation was suppressed due to the presence of PdZn in the active phase. The catalyst activity of the catalyst was an order of magnitude higher compared with that of commercial Lindlar catalyst (Pd, Pb/CaCO 3), which quickly deactivated in aqueous media due to irreversible chemical transformations of the CaCO 3 support. The structured catalyst developed in this study could be reused after ultrasonic regeneration, retaining the original selectivity and most of its initial activity. The catalyst showed high mechanical stability, precluding leaching of its components during the reaction. Due to easy shaping, high permeability, and low pressure drop during the fluid passage, the structured Pd/ZnO/SMF catalyst is suitable for a continuously operated staged bubble column reactor.