Stabilization of Copper Catalysts for Liquid‐Phase Reactions by Atomic Layer Deposition

Abstract

Atomic layer deposition (ALD) of an alumina overcoat can stabilize a base metal catalyst (e.g., copper) for liquid‐phase catalytic reactions (e.g., hydrogenation of biomass‐derived furfural in alcoholic solvents or water), thereby eliminating the deactivation of conventional catalysts by sintering and leaching. This method of catalyst stabilization alleviates the need to employ precious metals (e.g., platinum) in liquid‐phase catalytic processing. The alumina overcoat initially covers the catalyst surface completely. By using solid state NMR spectroscopy, X‐ray diffraction, and electron microscopy, it was shown that high temperature treatment opens porosity in the overcoat by forming crystallites of γ‐Al2O3. Infrared spectroscopic measurements and scanning tunneling microscopy studies of trimethylaluminum ALD on copper show that the remarkable stability imparted to the nanoparticles arises from selective armoring of under‐coordinated copper atoms on the nanoparticle surface.

Improving Heterogeneous Catalyst Stability for Liquid-phase Biomass Conversion and Reforming

“…[39] More recently, O'Neill et al used the same strategy for the stabilization of alumina-supported copper nanoparticles by the deposition of an Al 2 O 3 overcoat. [33] Stabilization of copper was especially noteworthy because, while precious metal catalysts are generally preferred due to their great stability, base metals such as copper suffer from irreversible competitive processes, catalyst lifetime is of prime importance under the harsh, often hydrothermal, conditions used for biomass conversion processes. Liquid-phase conditions can often increase the reactivity of catalyst surfaces.…”

“…In addition, both a significant surface area decrease (from 190 to 16 m 2 /g) and the absence of accessible Cu 0 sites detected by N 2 O chemisorption after reduction were observed. [33] Subsequent calcination at 700°C under air flow allowed for pore formation within the overcoat (Fig. 3a) as attested by the surface Pd/niobia Formation of mixed oxide Doping by addition of 5% SiO 2 GVL to pentanoic acid [44] Pd/SBA silica Deposition of hydrothermally stable overcoat Niobia ALD [45] Coke deposition and dealumination Microporous HZSM-5 Change reaction media Methanol co-feed Bio-oil to hydrocarbons [46] a preferential interaction of the overcoat with undercoordinated Cu atoms which are more exposed to sintering and leaching.…”

Highly Dispersed Copper Nanoparticles Supported on Activated Carbon as an Efficient Catalyst for Selective Reduction of Vanillin

“…More seriously, noble metal‐based catalysts are usually limited to practical application by coke formation, easy deactivation, as well as their low reserves and high cost. On these basis, there is a pressing need for developing highly active, selective and steady non‐noble metal‐based catalysts with the prospects in practical application …”

Highly Stable Copper Nanoparticles Linked to Organic Frameworks as Recyclable Catalyst for Three‐Component Click Cycloaddition in Water

“…have been used extensively for the preparation of supported Cu and copper oxide nanoparticles. In most of the reported cases synthesis of the stabilizing ligands involved multi‐step procedures and the catalysts generally have low metal contents . Herein, we report novel Cu nanoparticle catalysts designated as copper nanoparticle‐linked organic frameworks (CNOFs), where the metal nanoparticles are covalently linked to an aromatic frame work support.…”