Recent Developments in Gold Nanomaterial Catalysts for Oxidation Reaction through Green and Sustainable Routes - Advanced Materials for Agriculture, Food and Environmental Safety - page 201

[51, 52]. It was demonstrated that the catalytic activity of gold nanopar-
ticles strongly depends on the type of the support material [32, 53, 54].
Ot en an electron transfer from the support to the gold cluster promotes
its catalytic activity because it opens a route for an extra charge transfer
to the adsorbed O 2 .

8.1.3 Formation of Reactive Gold-Metal Oxide Perimeter

Interfaces

According to Prof. Haruta, the perimeter interface sites between gold
nanoparticles and oxide supports act as a reactive site for high surface
area gold catalysts [32, 53, 55]. In the case of oxidation reaction by using
molecular O 2, the perimeter interface of gold nanoparticles is important.
It was assumed that the perimeter interface of gold nanoparticles activate/
dissociate the molecular oxygen to give reactive oxygen species for oxida-
tion reaction [56, 57]. In the case of CO oxidation reaction, it is considered
that the CO is adsorbed on the gold surfaces, most likely at the edges and
corners, and oxygen molecule is activated at the perimeter interfaces [58,
53, 59-60]. h e fractions of edges and corners and of perimeter interface
changes with a decrease in diameter of gold nanoparticles [55]. However,
in the cases of glucose oxidation and alcohol oxidation, small gold nano-
clusters play a crucial role.

8.2 Propylene Epoxidation Reaction

h e selective addition of oxygen across a carbon-carbon double bond to
form an epoxide or oxirane function embodies a class of chemical trans-
formation of great importance, not only in the production of industrial
organic chemicals, but also in organic synthesis. Although heterogeneous
epoxidation of ethylene over supported silver catalyst has been practiced
since 1937, the process is a singularity in several respects. An important
characteristic is its use of the simplest oxidant, O 2 , either as air or in purii ed
form. However, lack of success for using silver catalyst for higher homo-
logue of ethylene such as propylene could trigger the development of other
catalyst systems. At present there are many processes that operate to pro-
duce propylene epoxide commercially by dif erent processes. h e synthesis
of ethane oxide and propene oxide using the chlorohydrin route was i rst
described in 1859 by Wurtz. In this reaction, the alkene reacts with hypo-
chlorous acid (HOCl) to produce the chlorohydrin. h e hypochlorous acid
is produced in situ by an equilibrium reaction of the acid with water and