Surface Science Approaches for the Preparation of Alumina‐Supported Hydrotreating Catalysts. Issue 21 (18th September 2015) - Bara, Cédric
Abstract: New developments and breakthroughs in the design of hydrotreating (HDT) catalysts for complying with fuel specifications and reduced sulfur contents ask for a continuous improvement in the molecular scale description of the active phase both at the oxide and sulfide states. HDT catalysts are mainly based on alumina‐supported molybdenum nanophases and the present contribution is dedicated to review the surface science approaches that have helped gain a molecular‐scale insight into the structure of the active‐phase (mainly molybdenum) and the role of metal‐support (mainly alumina) interactions through the use of well‐defined surfaces and surface sensitive analysis techniques. The main focus of this Review is placed on model systems that can bridge the gap with industrial catalysts, that is, oxide‐supported active phases prepared in aqueous conditions, as opposed to more traditional surface‐science studies that consider metal‐supported nanophases prepared in UHV conditions. The synthesis and structure of well‐defined alumina surfaces (thin films and single crystal wafers) is first presented before discussing aqueous‐deposition of Mo precursors on flat surfaces. The detailed role of the oxide support is then addressed with an emphasis on the genesis and structure of the MoS2 phase namely sulfidation rate, stacking, and orientation. Abstract : I can see clearly now : This contribution reviews surface science approaches based on aqueous deposition of the active phase on oxide substrates to bridge the gap with industrial alumina supported hydrotreating catalysts. Advantages of using planar model oxide supports with well‐defined surface structures are discussed for a better molecular‐scale understanding of the support effect on sulfidation, orientation and morphology of the active phase.