Jung et al.
Additive Effect of Nano-Size Platinum to Pretreated Iron Based Catalyst on Complete Oxidation of Toluene
ꢀ
each solution of precursor, and the resultant material was
were heated sufficiently at 120 C to prevent the adsorp-
tion and condensation of reactant and product in the tubes.
Experimental data were collected after ensuring the steady
state condition in each step.
ꢀ
dried at 90 C under stirring. The impregnated samples
ꢀ
were dried at 120 C in an oven forꢀovernight. Then the
dried samples were calcined at 400 C for 6 h in a fur-
nace to obtain the final form of catalysts. Each catalyst
was denoted x Pt–Fe, where x is the weight percent of Pt
loading on iron oxide.
The concentration of inlet and outlet gas stream was
determined using a gas chromatograph, GC-14A model
(Shimadzu) equipped with thermal conductivity detector
(TCD). The chromatographic column used was composed
of a 5% bentone-34 and 5% DNP/simalite (60–80 mesh,
3 mm × 3 m) for toluene analysis, and a parapak Q
(50–80 mesh, 3 mm×3 m) was used for CO2 separation.
The GC/MS (Shimadzu, QP5050) was also employed for
the quantitative and qualitative analysis of the products and
by-products. In the present work, most experimental con-
ditions produced only CO2 and H2O and other by-products
were not detected. The conversion was calculated on the
basis of toluene consumption.
2.2. Characterization of Catalysts
The Brunauer Emmett Teller (BET) surface areas of the
spent catalyst (parent) and the pretreated samples were
ꢀ
determined by nitrogen adsorption at −196 C using a
Micromeritics ASAP 2020 analyzer. Prior to sorption anal-
ysis, all the samples were degassed under vacuum (5 ×
ꢀ
10−3 mm Hg) for 6 h at 150 C. The crystal structures of
samples used in this work were examined by X-ray diffrac-
tion (XRD) data using a Phillips PW3123 diffractometer
equipped with a graphite monochrometer and Cu Kꢂ radi-
ation of wavelength 0.154 nm. The samples used were
investigated in the 2ꢃ range of 20–90ꢀ at a scanning speed
of 70 ꢀ/h. To determine the elemental compositions of
the spent and its pretreated catalysts, inductively coupled
plasma atomic emission spectroscopy (ICP) was employed
using a Perkin Elmer OPTIMA 4300DV. Before the anal-
ysis, the samples were prepared using microwave assisted
acid (a mixture of HCl and HNO3ꢁ digestion method. Tem-
3. RESULTS AND DISCUSSION
Toluene conversion was measured as a function of reac-
tion temperature over the Pt–Fe catalyst to investigate the
additive effect of platinum on the catalytic performance
of Fe catalyst. Figure 1 exhibits the conversion curves of
toluene oxidation on Fe, 0.1 Pt–Fe and 0.3 Pt–Fe. The
experimental results indicate that adding platinum into Fe
significantly improves its catalytic activity. For example,
perature programmed reduction (TPR) used a ChemBET
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the reaction temperatures for T50 and T90 conversions (the
values of the temperature when conversions approach 50%
3000 setup. The gas mixture (10% H and 90% He) was
IP: 174.26.245.141 On: Wed, 02 Mar 2016 10:12:32
2
Copyright: American Scientific Publishers
passed through the catalyst sample (0.4 g) at a rate of
ꢀ
and 90%, respectively) of toluene are 239 and 277 C for
60 ml min−1, while the temperature was increased up to
0.1 Pt–Fe, and 237 and 270 ꢀC for 0.3 Pt–Fe, respectively,
ꢀ
ꢀ
600 C at a rate of 10 C min−1
.
ꢀ
compared to 350 and 373 C for the Fe catalyst. In addi-
tion, it was observed that the increase in additive amount
of platinum brought about an increasing catalytic activity.
The XRD and the BET surface area measurement were
carried out to examine the properties of the catalysts.
2.3. Catalytic Oxidation
The catalytic oxidations were carried out using a conven-
tional fixed bed flow reactor as described in our previous
work.8 The reactor has three major sections:
(1) apparatus for preparation of vapors,
(2) fixed bed flow reactor in a heating system, and
(3) apparatus for the analysis of reactants and products.
100
80
60
40
20
0
The catalytic reactor consisted of a vertical tube of diam-
eter 1.0 cm and 35 cm length, fitted within an electrical
heating system controlled by a proportional integral deriva-
tive (PID) controller. In order to get an accurate measure-
ment of the catalyst temperature, a K-type thermocouple
was positioned in the catalyst bed. A catalyst sample of
0.3 g was loaded in the middle of the reactor supported
by quartz wool. Toluene was purchased from Fisher and
used without further treatment. An air stream bubbling
through a saturator filled with toluene carried its vapor.
For accurate and stable controlling the gas flow rates,
mass flow controllers (UNIT Instrument, UFC-8100) were
employed. The concentration of toluene was 1,000 ppm,
controlled by the temperature of the saturator and mixed
with another air stream. The reactant flows were tuned to a
gas hourly space velocity (GHSV) of 25,000 h−1. All lines
150
200
250
300
350
400
Temperature (ºC)
Figure 1. Toluene conversion according to reaction temperature. (Reac-
tion condition: catalyst weight = 0ꢄ3 g. Toluene concentration =
1ꢀ000 ppm, GHSV = 25,000 hr−1ꢄꢁ • Fe, ꢀ 0.1 Pt–Fe, ꢁ 0.3 Pt–Fe.
J. Nanosci. Nanotechnol. 14, 6390–6393, 2014
6391
Jung, Sang Chul
