Deactivation of platinum catalysts by oxygen 1. Kinetics of the catalyst deactivation

Abstract

Dijkgraaf, P.J.M.; Rijk, M.J.M.; Meuldijk, J.; van der Wiele, K.

Unraveling the Surface Reactions during Liquid-Phase Oxidation of Benzyl Alcohol on Pd/Al2O3: an in Situ ATR−IR Study

“…Oxidative removal of CO by molecular oxygen can minimize this difficulty. However, high surface oxygen concentration should be avoided to prevent the successive oxidation and thus deactivation of Pd, the so-called over-oxidation phenomenon. − …”

“…An important feature of the reaction is that too high an oxygen concentration can lead to excessive oxygen coverage of the active sites that diminishes the catalytic activity. This type of catalyst deactivation (termed as over-oxidation) , can simply be avoided by operating the reactor in the mass-transport-limited regime, where the surface reaction is not rate determining. , …”

Immobilization of a Ligand-Preserved Giant Palladium Cluster on a Metal Oxide Surface and Its Nobel Heterogeneous Catalysis for Oxidation of Allylic Alcohols in the Presence of Molecular Oxygen

“…In the liquid-phase oxidations of alcohols using supported metal catalysts such as Pt/carbon and Pd/carbon, molecular oxygen irreversibly deactivates the catalyst surfaces to form inactive surface metal oxides. 12b,− Low catalytic activities of Pd/carbon or Pd/Al 2 O 3 in our oxidation of cinnamyl alcohol might be ascribed to such an irreversible poisoning of molecular oxygen onto the metallic surface of the small Pd particles. On the contrary, in the case of the giant Pd cluster, such an oxidation of Pd particles by molecular oxygen would be presumably prevented because of the slightly cationic Pd atoms on the cluster surface.…”

Mechanistic Insights into Solution-Phase Oxidative Esterification of Primary Alcohols on Pd(111) from First-Principles Microkinetic Modeling

“…The exact process by which the aldehyde forms is not known. Under basic conditions, it has been proposed that the alcohol becomes deprotonated in solution and undergoes hydride elimination on the catalyst surface to form the aldehyde. , This hypothesis has been disputed on the basis of the observation that oxidation also occurs under acidic conditions, and it has been proposed instead that the alkoxide is formed on the catalyst surface. , Other authors have suggested that it is the C–H bond that is broken first because of its lower bond strength. , …”