Preparation of Nanostructured Microporous Metal Foams through Flow Induced Electroless Deposition

Abstract

Monolithic nanostructured metallic porous structures with a hierarchy of pore size ranging from ca. 10 m to 1 nm are processed for use as microreactors. The technique is based on flow induced electroless deposition of metals on a porous template known as PolyHIPE Polymer. The process is conducted in a purpose built flow reactor using a processing protocol to allow uniform and efficient metal deposition under flow. Nickel chloride and sodium hypophosphite were used as the metal and reducing agent, respectively. Electroless deposition occurs in the form of grains with a composition of Ni P in which the grain size range was ca. 20-0.2 m depending on the composition of the metal deposition solution. Structure formation in the monoliths starts with heat treatment above 600 ∘ C resulting in the formation of a 3-dimensional network of capillary-like porous structures which form the walls of large arterial pores. These monoliths have a dense but porous surface providing mechanical strength for the monolith. The porous capillary-like arterial pore walls provide a large surface area for any catalytic activity. The mechanisms of metal deposition and nanostructure formation are evaluated using scanning electron microscopy, energy dispersive X-ray analysis, XRD, BET-surface area, and mercury intrusion porosimetry.

Co-Assembled Supported Catalysts: Synthesis of Nano-Structured Supported Catalysts with Hierarchic Pores through Combined Flow and Radiation Induced Co-Assembled Nano-Reactors

“…In order to enhance the interfacial surface area for heat and mass transfer, porous monoliths have also been used as a catalyst support [10][11][12]. These so called structured catalysts in the form of monoliths with a hierarchic pore structure also provide convective heat and mass transfer through the interconnecting holes whereas conductive processes take place at the walls.…”

“…10 µm and ca. 10 nm have been produced [12] using flow induced electroless metal deposition on microporous templates, followed by calcination when nanostructure was formed. Such monoliths can be used as catalytic reactors [12].…”

Flow-Through PolyHIPE Silver-Based Catalytic Reactor

“…Furthermore, poor attachment causes leakage of the metal nanoparticles, affecting its catalysis activity and efficiency [ 2 ]. An alternative to immobilization is the formation of the catalyst nanoparticles directly on the pore surface, for example, by reducing the dissolved ions from the solution [ 5 , 12 , 13 , 14 ].…”

Catalytic Plasma Fischer–Tropsch Synthesis Using Hierarchically Connected Porous Co/SiO2 Catalysts Prepared by Microwave-Induced Co-assembly

“…A popular technique for FTS is based on so-called “flow chemistry” in which catalyst-coated microcapillary, monolithic, or foamed reactors are used . One of the advantages of this technique is that heat transfer can also be intensified by using cross-flow reactor configuration in which the reaction channels are separated from the heat-transfer channels by a thin section of highly conductive metal plates , The intensification of FT synthesis using the basic capillary, monolith, or foamed reactors can be further improved by reactor optimization , and through the enhancement of surface area density (surface area per unit volume) for heat and mass transfer in capillary/monolithic reactors and metallic foam reactors where the surface area density enhancement over 100 times is achieved compared with the commercially available foams.…”

“…Furthermore, the catalytic plasma reactors and processing conditions also need to be optimized in order to initiate and maintain a plasma across the catalyst bed. This is achieved essentially by using “annual capillary reactors”, as opposed to capillary reactors used in process intensification − as well as in the intensified FT synthesis. , An important advantage of such capillary reactors is the absence of scale-up since “scale-up” in microreactors is equivalent to “numbering-up”. Therefore, a single reactor would also be one of many of working microreactors.…”