Performance descriptors of nanostructured metal catalysts for acetylene hydrochlorination

Abstract

Controlling the precise atomic architectures of supported metals is central to unlock their potential as heterogeneous catalysts, as recently exemplified for nanostructured platinum and ruthenium systems in acetylene hydrochlorination, a key industrial technology for vinyl chloride production. This opens the possibility to build on historically established activity correlations. Here, we derive quantitative activity, selectivity, and stability descriptors, accounting for the metal-dependent speciation and host effects. To achieve this, we generate a platform of Au, Pt, Ru, Ir, Rh, and Pd single atoms and nanoparticles supported on functionalized carbons and assess their evolution during synthesis and under reaction conditions. Combining kinetic, transient and chemisorption analyses with modelling, we identify the acetylene adsorption energy as a speciation-sensitive activity descriptor, further determining the catalyst's selectivity with respect to coke formation.The stability of the different metal nanostructures is governed by the interplay between single atomsupport interaction and the chlorine affinity, promoting redispersion or agglomeration, respectively.

Catalytic Synergies in Bimetallic RuPt Single–Atom Catalysts via Speciation Control

“…To gain further insights into the structural and electronic features of the RuPt SACs, the possible presence of intermetallic interactions in the first coordination shell is assessed. Similarly to analogous NC–supported Au–Ru SACs, [ 14 ] and in line with the affinity of both metal atoms for N–functionalities, [ 14,16 ] no RuPt bonds are detected in either [RuPt] SA /NC–w–473 or [RuPt] SA /NC–w–1073. Therefore, the presence of RuPt dimers, and thus of direct intermetallic electron density transfer, is excluded.…”

“…Carbon–supported Pt single atoms (“SA” in the sample code) are derived by simple incipient wetness impregnation of a polyaniline–derived N–doped carbon (NC) with a solution of H 2 PtCl 6 dissolved in water (w), followed by thermal activation in the range of 473–1073 K ( T , Pt SACs denoted as Pt SA /NC–w– T , Figure ; Figures S1 and S2, Supporting Information). [ 16 ] Conversely, the generation of Ru single atoms requires a strongly oxidizing agent, i.e., aqua regia (a), and mild activation temperatures (Ru SAC denoted as Ru SA /NC–a–473, Figure 1; Figures S1 and S2, Supporting Information). [ 16 ] In aqueous solutions, the RuCl 3 precursor undergoes hydrolysis, exchanging Cl − ligands for H 2 O molecules.…”

“…[ 16 ] Conversely, the generation of Ru single atoms requires a strongly oxidizing agent, i.e., aqua regia (a), and mild activation temperatures (Ru SAC denoted as Ru SA /NC–a–473, Figure 1; Figures S1 and S2, Supporting Information). [ 16 ] In aqueous solutions, the RuCl 3 precursor undergoes hydrolysis, exchanging Cl − ligands for H 2 O molecules. [ 17 ] The resulting Ru species are then reduced by surface functional groups of the carbon support, yielding Ru nanoparticles.…”

Highlights from the 55th Bürgenstock Conference on Stereochemistry 2022

“…They generated a platform of carbon-supported metal catalysts with different nanostructures, from single atoms to nanoparticles, to explore the metal-dependent speciation and host effects in acetylene hydrochlorination. 4 The importance of a catalyst atomic architecture was also demonstrated with the development of single-atom and bi-metallic heterogeneous catalysts for cross-coupling.…”

Construction of Ru–N Single Sites for Effective Acetylene Hydrochlorination: Effect of Polyethyleneimine Modifiers

“…Researchers have extensively explored nonmercury catalysts, including transition precious metals, − nonprecious metals, − and nonmetallic materials. − Hutchings identified a catalyst containing cationic Au, among others, as the most active catalyst. − However, the Au/AC catalyst is slowly deactivated due to the accumulation of coking on its surface and the reduction and loss of Au components. Researchers have also tried stabilizing the active valence states of the Au components by introducing a second or third metal component, − ionic liquid (IL), or ligands .…”