Synthesis of mixed metal oxides for use as selective oxidation catalysts
Date
2007-03
Authors
Motshweni, Jim Sipho
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
The synthesis of mixed metal oxides, specifically the need and ability to successfully and
accurately control the particle size, their stability and the reactivity of these nanoparticles is
required, so as to allow the attachment of catalyst nanoparticle to the surface of a substrate
or to other particles without leading to coalescence of the catalyst particle and hence to loss
of their size induced properties. However, the synthesis of mixed metal oxides is a
complex problem. Though various methods of preparing these types of oxides have been
reported and applied, such methods they rarely produced pure forms and have often been
recorded as having been contaminated with other phases. Often the particle sizes are too
large in the micrometer range, and the size distribution is overly wide. Moreover, even if
particles of nanometer size are formed, they tend to aggregate or agglomerate.
In the current research, microemulsions were used to synthesize the nanoparticles. Such
microemulsion consists of water droplets encapsulated by surfactant molecules in a pool of
oil, comprising: water in oil (w/o) or reverse micelles. Reverse micelles in the nanometer
size range are thermodynamically stable and optically transparent in the solution. They are
believed to be highly dynamic structures whose components rearrange themselves over
time and space through interaction or collision, coalescing and redispersing. However, the
advantage of this method over using the standard method is that the particle size can
largely be controlled, and a narrow size distribution obtained.
The aim of the research was to investigate the feasibility of using the reverse micelle
technique for the synthesis of mixed metal oxides - specifically α-bismuth molybdate (α-
Bi2Mo3O12) with a controlled and desirable particle size and a narrow size distribution...
Description
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2007.
Keywords
Dissertations -- Process engineering, Theses -- Process engineering, Catalysis, Oxidation, Metal catalysts, Metallic oxides