Regeneration: MS + 1.5O
2
→ MO + SO
2
51 SO
2
must be captured and ultimately be converted to elemental sulphur or sulphuric acid.
Copper oxide is able to achieve low levels of H2S in the clean fuel gas provided the sorbent is not
reduced to elemental copper. This is because copper oxide readily reduces in high temperature
reducing atmospheres, and elemental copper is an order of magnitude less active for sulfidation than
Cu
2
O and CuO [299]. Binary Cu Cr O oxides were studied as
regenerable sorbents for high temperature fuel gas desulphurization by Li and Stephanopoulos [21].
CuO Cr
2
O
3
sorbents can remove H
2
S from simulated coal derived fuel gas to less than 5 10
ppmv in the temperature range of 650 850 C. The
presence of stable CuCr
2
O
4
in CuO Cr
2
O
3
solids retains some copper in the Cu
+2
or Cu
+1
oxidation state, which can account for the high H
2
S removal efficiency. A regenerable copper chromite sorbent
with superior hot fuel gas desulfurization performance has been developed for IGCC
applications by Abbasian and Slimane [300] in the temperature range of 550 650
C. This sorbent is capable of achieving less than 5 ppmv H
2
S concentration in the cleaned fuel gas.
2.6 Mercury capture from hot coal gas
Coal fired utilities are the largest source of anthropogenic mercury emissions. Because of its
high volatility, almost all the mercury present in coal is transformed into gas phase during
combustion or gasification of coal. Control of mercury emissions from coal fired power plants is
a difficult task, in part due to its high volatility and its much lower concentration 5 20 jgm3 in a
large volume of flue gas. In addition, depending on the type of coal and combustion conditions, a
majority of mercury in the flue gas can exist in the elemental form Hg
, which is more difficult to capture than its oxidized Hg
2+
or particulate Hg
p
forms. Jadhav [301] evaluated Nano Active sorbents CuO Cr
2
O
3
for Hg capture. He explained the role of Cr, which would suppress the
reduction of Cu in the presence of H
2
and would maintain Cu in Cu
2+
state [4], which would have enhanced reactivity towards Hg. This experimental
study has demonstrated that supported forms of binary oxides of Cu and Cr have showed their
potential as effective Hg sorbents. 2.7 Removal of aqueous organic waste
The main polluting branches of industry are refineries,
coke ovens,
organic compounds
production plants, pharmaceuticals factories, pulp and paper mills, textile, leather industries, etc.
Waste water from these industrial and agricultural activities contains refractory organic pollutants
such as plaguicides, organochloride compounds, phenols,
detergents, polycyclic
aromatic hydrocarbons, etc. that must be treated before
discharge to comply with the environmental regulations. Water treatment technologies require
revision, modernization and enriching by utilizing more effective methods and catalyst to achieve
required standards for drinking water along with keeping in mind the conomic aspects [302].
Therefore, it is important to have efficient catalyst at our disposal for removal and oxidation of
pollutants present in wastewater in reduced forms
NO
2
, NH
4+
, phenols etc.
2.7.1 Wet oxidation of phenol
