Monodispersed Pd-nanoparticles on carbon fiber fabrics as structured catalyst for selective hydrogenation

Abstract

Monodispersed Pd-nanoparticles (∼ 8 nm) prepared via a modified microemulsion method were deposited on active carbon fibers (ACF) fabrics and studied in a semi-batch 1-hexyne liquid-phase hydrogenation. The catalyst Pd(0.45 wt%)/ACF demonstrated > 96% selectivity to 1-hexene up to 90% of conversion. Initial activity at 303 K, 1.3 MPa pressure, in n-heptane as a solvent was 0.14 kmol H 2 kg −1Pd s −1 . Assuming a Langmuir-Hinshelwood kinetics with a weak hydrogen adsorption a kinetic model was developed. It was shown to be consistent with the experimental data and allowed determining the main kinetic parameters. ᭧

Recent Advances in the Liquid‐Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis

“…Upon deposition, nanoparticles maintain their size, shape and monodispersity (37). This technique allowed synthesizing a structured catalyst based on ME-derived Pd nanoparticles deposited on activated carbon fibre (ACF) fabrics, which showed high activity, selectivity and stability in the repeated use in semi-batch three-phase hydrogenation of 1-hexyne, representing an alternative to a traditional Lindlar catalyst (37). The catalyst arranged structure (Fig.…”

“…99.5% of the surfactant was successfully removed by centrifugation, while residuals stabilized the nanoparticles against agglomeration. The nanoparticles could be dried under mild conditions still preserving their monodispersity (56), or ultrasonically redispersed in water (37) or in reaction mixture (57). The method also allows recovery of the surfactant and hydrocarbon.…”

“…Another widespread technique for preparation of monodispersed spherical nanoparticles with a controlled size for catalytic applications is a microemulsion (ME) technique (37,(55)(56)(57). Water-in-oil (reverse) ME have been generally used for the synthesis of a variety of ultrafine metal particles (55) but there are also some examples of metal nanoparticle formation in normal microemulsions (oil-in-water) (58).…”

“…Finally, there are also some case studies on nanostructures used in gas-and liquid-phase reactions in unsupported and supported form, including Nanocatalysis with Controlled Shape and Size conventional and structured (arranged) (34) supports. Immobilization may alter the nanoparticle size and shape distribution in the supported catalyst compared to the unsupported one (35,36), but typically the stabilized nanostructures do not follow any changes upon immobilization (37,38).…”

The Reduction of Alkynes Over Pd-Based Catalyst Materials - A Pathway to Chemical Synthesis

“…There is however no agreement on the particular reaction mechanism used in the modelling. Some authors assume that hydrogen is adsorbed non-dissociatively [71], while other authors assume dissociative adsorption with the second hydrogen atom addition as the limiting step [72] or simultaneous addition of both atoms [72]. DFT calculations suggest that the addition of the second proton to acetylene and ethylene is the slowest step of hydrogenation [65], while Stacchiola et al assumes that the first protonation is rate-determining [73].…”