Chemistry Reference
In-Depth Information
Fig. 13 a) Cathodic scans of a catalyst-coated RRDE in 0.5M H
2
SO
4
saturated with O
2
,
1000 rpm, 10mV/s, 426
m
g/cm
2
. (Inset) Transmission Electron Microscope images of
catalyst nanostructures. (b). Selectivity measured during activity testing. Legend: molar
ratio of P/Fe in the growth media. Reproduced from Ref. 129 page 4907 with permission
of Elsevier.
zirconia,
133
Amberlyst-15 or Nafion.
134
Recently, it has been reported a new
class of sulphonated carbon material which exhibits an excellent activity in
esterification and transesterification reactions such as biodiesel syn-
thesis.
135-141
This carbon material is derived from the incomplete car-
bonisation of renewable resources such as sugars (glucose), starch or
cellulose. It is a low-cost catalysts and it is prepared using either one-
step
142,143
or a two-step processes. The two step process involves (i)first,a
natural product such as sugar, starch or glucose is pyrolized in inert
atmosphere at low temperature (573-723 K), resulting in a material con-
sisting of polycyclic aromatic hydrocarbons; (ii) second, this hydrocarbon
is sulphonated to generate a solid with high density of sulphonic acid sites.
Depending on the sulphonation conditions, the acid density of the
sulphonated carbons can be in the range of 0.48-1.74mmol/g, a density
exceeding that described for solid inorganic acids such as sulphated
zirconia (0.1-0.5mmol/g), although lower than the acid density of
