62
T. Rakitskaya et al.
placed into a glass cell with an enclosed volume of 2 × 1 × 0.1 cm
3 for XRD pattern
recording in the 2θ range from 0° to 90° with a step of 0.03° and an accumulation
time at every position of 60 s.
OMS-2 samples were also characterized by scanning electron microscopy using
a JEOL-JSM5410 scanning microscope with an AZtech Energy X-max
n 50 energydispersive spectrometer. A resolving power and an accelerating voltage of the
scanning microscope were 10 nm and 15 kV, respectively.
Infrared analysis of the OSM-2 samples was carried out using a Perkin Elmer FTIR Spectrometer with resolution of 4 cm
−1 ; pellets consisting of 1 mg of the material
under study and 200 mg of KBr were compressed under pressure of 7 tons/cm
2 for
30 s.
Nitrogen ad/desorption measurements were performed by a volumetric method
on a Sorptomatic adsorption instrument (Thermo Electron Corporation) at liquid
nitrogen temperature (~196 °C). Before the measurements, samples were outgassed
at 200 °C for 5 h. A specific surface area was calculated using the BET method in the
P/Ps ranging from 0.04 to 0.34. A pore size distribution was calculated using Barrett–
Joyner–Halenda (BJH) method based on a desorption branch in the P/P S ranging from
0.1 to 0.996. A micropore volume was determined using the t-plot method proposed
by Gregg and Sing [37].
Equilibrium pH values measured for samples (0.2 g) suspended in distilled water
(20 mL) were used to characterize protolytic properties of their surface functional
groups. pH values were measured by a pH-340 instrument with an ESL 43-07
glass electrode and an EVL 1M3 chlorsilver electrode at continuous stirring of the
suspension at 20 °C.
2.3 Catalytic Studies
The samples were tested in the reaction of ozone decomposition as follows. The
ozone air mixture, OAM, with a required ozone concentration was obtained with the
help of an IG-1Sh ozonizer by a silent electric discharge action on air oxygen. An
OAM feed was controlled based on rheometer readings. The corresponding sample
(0.5 g) was placed into a gas flow fixed bed reactor and the OAM with RH of 65%
at 20 °C passed through the sample at a linear velocity (u) of 6.2 cm/s and a specific
volume flow rate of 120 L/g × h. Ozone decomposition was monitored by measuring
the final (outlet) ozone concentration, C
f
O 3
. An initial ozone concentration, C
in
O 3
, equal
to 100 mg/m
3 was controlled by a Tsyclon-Reverse optical analyzer, whereas C
f
O 3
values were measured either by the Tsyclon-Reverse optical analyzer (detection
limit of 1 mg/m
3 ) or by a 652EKh04 electrochemical gas analyzer (detection limit
of 0.01 mg/m
3 ).
An activity of the manganese dioxide samples was evaluated based on the
following parameters:
T. Rakitskaya et al.
placed into a glass cell with an enclosed volume of 2 × 1 × 0.1 cm
3 for XRD pattern
recording in the 2θ range from 0° to 90° with a step of 0.03° and an accumulation
time at every position of 60 s.
OMS-2 samples were also characterized by scanning electron microscopy using
a JEOL-JSM5410 scanning microscope with an AZtech Energy X-max
n 50 energydispersive spectrometer. A resolving power and an accelerating voltage of the
scanning microscope were 10 nm and 15 kV, respectively.
Infrared analysis of the OSM-2 samples was carried out using a Perkin Elmer FTIR Spectrometer with resolution of 4 cm
−1 ; pellets consisting of 1 mg of the material
under study and 200 mg of KBr were compressed under pressure of 7 tons/cm
2 for
30 s.
Nitrogen ad/desorption measurements were performed by a volumetric method
on a Sorptomatic adsorption instrument (Thermo Electron Corporation) at liquid
nitrogen temperature (~196 °C). Before the measurements, samples were outgassed
at 200 °C for 5 h. A specific surface area was calculated using the BET method in the
P/Ps ranging from 0.04 to 0.34. A pore size distribution was calculated using Barrett–
Joyner–Halenda (BJH) method based on a desorption branch in the P/P S ranging from
0.1 to 0.996. A micropore volume was determined using the t-plot method proposed
by Gregg and Sing [37].
Equilibrium pH values measured for samples (0.2 g) suspended in distilled water
(20 mL) were used to characterize protolytic properties of their surface functional
groups. pH values were measured by a pH-340 instrument with an ESL 43-07
glass electrode and an EVL 1M3 chlorsilver electrode at continuous stirring of the
suspension at 20 °C.
2.3 Catalytic Studies
The samples were tested in the reaction of ozone decomposition as follows. The
ozone air mixture, OAM, with a required ozone concentration was obtained with the
help of an IG-1Sh ozonizer by a silent electric discharge action on air oxygen. An
OAM feed was controlled based on rheometer readings. The corresponding sample
(0.5 g) was placed into a gas flow fixed bed reactor and the OAM with RH of 65%
at 20 °C passed through the sample at a linear velocity (u) of 6.2 cm/s and a specific
volume flow rate of 120 L/g × h. Ozone decomposition was monitored by measuring
the final (outlet) ozone concentration, C
f
O 3
. An initial ozone concentration, C
in
O 3
, equal
to 100 mg/m
3 was controlled by a Tsyclon-Reverse optical analyzer, whereas C
f
O 3
values were measured either by the Tsyclon-Reverse optical analyzer (detection
limit of 1 mg/m
3 ) or by a 652EKh04 electrochemical gas analyzer (detection limit
of 0.01 mg/m
3 ).
An activity of the manganese dioxide samples was evaluated based on the
following parameters: