Atomistic Simulation Of The Nano-structural
Evolution Of Raney-type Catalysts From
Spray-atomized NiAl Precursor Alloys
During Leaching With NaOH Solution
Author(s)
N. C. Barnard, S. G. R. Brown, F. Devred, B. E. Nieuwenhuys
& J. W. Bakker
Abstract
A model for the nano-structural evolution of Raney-type nickel catalysts (widely
used in hydrogenation reactions) from the constituent intermetallic phases
present in nickel-aluminium precursor alloys is presented here. Nano-porous
nickel catalysts are prepared via a caustic leaching process where the NiAl alloy
powder (typically 50-50 at.%) is immersed in concentrated NaOH solution in
order to leach away the aluminium present to leave a highly-porous nickel
catalyst (often referred to as spongy nickel).
The temporal evolution of the nickel catalyst is described by a kinetic Monte
Carlo (kMC) method, which captures two dominant processes taking place on
leaching with NaOH solution: rapid aluminium dissolution from the crystalline
intermetallic phases and surface adatom diffusion of nickel and aluminium.
Structural changes from NiAl3 and Ni2Al3 phases present in the starting alloy are
considered on an event-by-event basis. Individual crystallite size, pore diameter
and effective surface area are predicted. Finally, a Metropolis Monte Carlo
method is used to investigate the surface nature of the as-leached catalyst and
compared to concurrent experimental investigations.
Keywords: de-alloying, leaching, Raney-Ni catalysts, Monte Carlo simulation.
Keywords
de-alloying, leaching, Raney-Ni catalysts, Monte Carlo simulation
Related Book
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