Propyne Hydrogenation over a Pd/Cu(111) Single-Atom Alloy Studied using Ambient Pressure Infrared Spectroscopy

Abstract

The hydrogenation of propyne (C 3 H 4 ) to propene (C 3 H 6 ) using a Pd/Cu(111) single-atom alloy (SAA) has been studied using polarization-dependent reflection absorption infrared spectroscopy. This method allows for simultaneous monitoring of reactants and products in the gas phase and species adsorbed on the surface during the reaction. The results were compared with the hydrogenation of propyne using Pd-free Cu(111) as well as with previous studies on Pd/Cu SAA catalysts supported on alumina. Propene production occurs at temperatures of 383 K and above as indicated by the appearance of an infrared peak at 912 cm −1 , which is a unique characteristic feature of gas phase propene. Propyne was found to adsorb on the surface at 300 K in the presence of gas phase propyne to form a di-σ/di-π structure, as the spectrum was identical to that reported in the literature for propyne adsorbed on Cu(111) at 150 K in ultrahigh vacuum. The presence of a carbonaceous layer on the surface is indicated by a dramatic increase in the intensity of a peak at 2968 cm −1 at temperatures above 400 K. The progression of gas phase peaks at 912 and 3322 cm −1 was used to calculate the rate of production of propene and the rate of consumption of propyne, respectively. This reaction rate was used to determine a turnover frequency of 25.4 s −1 at 383 K for the reaction on the Pd/Cu(111) SAA surface. The reaction was not impeded by the presence of the carbonaceous layer, even for a layer so thick that only carbon was detectable on the surface with Auger electron spectroscopy.

Selective visible-light photocatalysis of acetylene to ethylene using a cobalt molecular catalyst and water as a proton source

“…This result demonstrates the suitability of this system for the isolation of a pure industrial propylene stream from propyne 41 , a task not accomplished by steam cracking but necessary for the production of polymer-grade propylene, which together with ethylene accounts for ~80% of global plastic demand 2 .…”

Heat of Adsorption of Propyne on Cu(111) from Isotherms Measured by Reflection Absorption Infrared Spectroscopy

“…In accord with the study of Chesters and McCash, 9 we assign the three major peaks at 2825, 2850, and 2883 cm −1 (enlarged spectra in the inset of Figure 1) to the first overtone of the asymmetric CH 3 deformation, the alkynic C−H stretch, and the symmetric CH 3 stretch, respectively. In a previous study, 15 we assigned the peak at 1358 cm −1 to a normal mode with mixed C 1 −C 2 stretch and δ(CH 3 ) character, as confirmed by the DFT calculations of Valcaŕcel et al 14 In the presence of 100 nTorr of propyne, the peak intensities shown in Figure 1 were constant up to 307.5 K but were lower at 310 and 320 K. At these higher temperatures, coupling reactions occur, leading to irreversible adsorption. The development of the peak at 2904 cm −1 was likely associated with a coupling product.…”

NO Reduction on Cu‐Based Model Catalysts Studied by in‐situIRAS

“…Note that the IR intensity for the gas phase CO 2 can be well correlated with the amount of CO 2 under the experimental pressure. [ 21 ] In each reaction, 2 Torr gas mixture (CO: NO = 1 : 1) was filled, then risen to 623 K and held for 10 min, so the amounts of CO 2 can be compared.…”

“…In recent years, single‐atom catalysts (SAC) have attracted great attention in heterogeneous catalysis. It had been shown that single‐atom catalysts exhibited a much better catalytic performance than traditional nanoparticle catalysts in many reactions, such as CO oxidation, [ 16‐19 ] selective hydrogenation/dehydrogenation [ 20‐21 ] and water‐gas shift reaction (WGS). [ 22‐24 ] However, clusters and nanoparticles exhibited a higher catalytic activity than single‐atom for some reactions.…”