G Model
CATTOD-9901; No. of Pages10
ARTICLE IN PRESS
J. Młodzik et al. / Catalysis Today xxx (2015) xxx–xxx
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The crystallite size of Fe O4 was calculated using Scherrer’s
equation on the basis of three peaks (35.40 , 57.00 , 62.58 ).
also blank experiment was done and it shows that hydrogen
peroxide and TBHP did not oxidize limonene without the catalyst.
Samples taken at different reaction time were analyzed by
a GC-method on a Focus apparatus equipped with a flame-
ionization detector and fitted with the Restek Rtx-WAX capillary
column filled with polyethylene glycol. The parameter of the GC-
3
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2
.3.2. Specific surface area and pore structure analysis
Nitrogen sorption experiments were carried out using volumet-
ric gas sorption instrument Quadrasorb evo, Quantachrome. Before
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−6
method were as follows: helium pressure of 50 kPa, sensitivity
analysis, samples were outgassed at 250 C and at 1 × 10 bar dur-
ing 16 h. The specific surface area (SBET) was measured by means
of BET (Brunauer–Emmett–Teller) equation applied in the relative
pressure range of 0.03–0.3. The total pore volume (TPV) was cal-
culated on the basis of the amount of nitrogen adsorbed at the
highest relative pressure. Micropore volume (MPV) was estimated
by Density Functional Theory method.
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1
00, the temperature of the sample chamber 200 C, the detec-
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tor temperature 250 C, and the temperature of the thermostat
was increased according to the following program: isothermally
at the temperature 60 C for 2 min, an increase to the tem-
perature 240 C at the rate of 15 C/min, isothermally at the
temperature 240 C for 4 min, and at the last stage cooling to
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the temperature 60 C. The products of limonene epoxidation
were also qualitative identified by GC–MS method. The hydro-
gen peroxide conversion was measured by the iodometric titration
method.
On the basis of mass balances the main functions describ-
ing the process of limonene oxidation were calculated:
the selectivities of the appropriate products in relation
2
.3.3. The Field Emission Scanning Electron Microscopy (FESEM)
and Energy Dispersive Spectrometer (EDS) analysis
The micrographs and X-rays spectra were obtained using Ultra-
High Resolution Field Emission Scanning Electron Microscope (UHR
FE-SEM Hitachi SU8020) equipped with the Secondary Electron
(
SE) detectors, four quadrant Photo-Diode Backscattered Electron
to limonene consumed (L)—Sproduct/L
,
the conversion of
Detector (PD-BSE) and Energy Dispersive Spectroscopy system.
Carbon tape was used for mounting powder catalyst. The micro-
graphs were obtained with an acceleration of 15 kV. The X-ray
spectra were taken with an acceleration of 20 kV.
The four quadrant photo-diode backscattered electron detector
was used to generate compositional and crystallographic contrast
images. The images obtained using PD-BSE detectors provide direct
information on the distribution of heavier elements presented
on the surface. Iron particles distribution observations were per-
formed using the PD-BSE detector via electron channeling contrast
imaging.
limonene—CL and the selectivity of transformation to organic
compounds in relation to hydrogen peroxide consumed
(the efficiency of hydrogen peroxide conversion)—Sorg. comp./H2O2 .
The ways of the calculations these main functions are presented
below:
amount of moles of product
amount of moles of limonene consumed
Sproduct/L =
· 100 (mol%)
amount of moles of limonene consumed
amount of moles of limonene introduced into reactor
CL =
· 100 (mol%)
Sorg. comp./H2
O
= amount
of moles of formed organic compounds
amount of moles of H2O2 consumed
· 100 (mol%)
2
.3.4. Determination of iron content by the Inductively Coupled
2
Plasma-Atomic Emission Spectrometry (ICP-AES) method
Determination of iron concentration was investigated by the
ICP-AES method. Iron was extracted using boiling hydrochloric
acid. The samples (about 0.1 g) were treated by 50 ml of concen-
trated HCl (36 wt%) and heated to boiling point. After cooling, water
was added up to 100 ml in a volumetric flask. The solid powder of
carbon was removed by filtration. The iron content in the filtrate
was measured by ICP-AES method.
The samples of the FeEP catalysts used in the process of
limonene oxidation were next separated from the post-reaction
mixture, washed with 500 ml of the deionized water and dried at
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the temperature of 119 C for 5 h. After drying the FeEP catalysts
were again used in the process of limonene oxidation. The oxida-
tion was perfumed at the same condition as previously, but the
progress of the reaction was checked only for the reaction time: 3 h
and 24 h.
2.4. Epoxidation method
3. Results and discussion
In the oxidation of limonene the following reactants were used:
R(+)-limonene (97%, Sigma), hydrogen peroxide (60 wt% water
solution, Chempur), t-butyl hydroperoxide—TBHP (5.5 M solution
in decane, Fluka) and methanol (analytical grade, Chempur).
The oxidation of limonene was carried out at the tempera-
3.1. X-rays diffraction analysis
Fig. 1 shows X-ray diffraction patterns of the catalysts and
the support. All the samples showed three distinguishable signals
(0 0 2), (1 0 0) and (1 1 0), which indicated a partially graphitic struc-
ture of the support – activated carbon [26]. These signals are very
broad and the peak (0 0 4), (1 0 1) and (0 0 6), typical for high graphi-
tized carbons [27], are not observed. The degree of graphitization
activated carbon EP is not high.
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ture of 70 C and in the range of the reaction time from 0.5 h to
4
8 h. The other parameters were as follows: the molar ratio of
limonene/H O or limonene/TBHP = 1:2 (for hydrogen peroxide
2
2
the concentrations of the reactants in the reaction mixture were as
follows: limonene – about 2.8 wt%, and hydrogen peroxide about
1
.6 wt% and for TBHP: limonene – about 2.9 wt%, and TBHP 1.5 wt%,
No additional peaks were observed in the XRD pattern of the
catalyst contained 0.68 wt% of iron. The XRD pattern of catalyst con-
respectively), methanol concentration 95 wt% and the catalyst
content in the reaction mixture of 2.45 wt%. The process was
carried out in a glass reactor with the capacity of 25 cm , equipped
with a reflux condenser, a thermometer and a magnetic stirrer.
The raw materials were introduced into the glass reactor in the
following order: catalyst, limonene, methanol and 60 wt% water
solution of hydrogen peroxide (or TBHP). The temperature of 70 C
was achieved with help of a silicon oil bath. The progress of the
reaction was examined after the following reaction time: 30 min,
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tained 2.64 wt% of Fe shows additional, quite sharp peaks at 30.06 ,
3
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35.41 , 53.38 , 56.90 , 62.49 , and 89.54 which indicate that cubic
Fe O was formed. The signals of (0 0 2) and (1 0 0) were slightly
3
4
changed because of the reflections at 18.28, 43.03 characteristic for
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cubic Fe O . Very slight peak at 35.41 (the strongest signal of cubic
3
4
◦
Fe O ) can be observed in the XRD pattern of catalyst contained
3 4
2+
3+
port are presented in Table 1. It is worth to say that, the calculated
1
h, 1.5 h, 2 h, 2.5 h, 3 h, 4 h, 5 h, 24 h and 48 h. During the studies
Please cite this article in press as: J. Młodzik, et al., Fe/EuroPh catalysts for limonene oxidation to 1,2-epoxylimonene, its diol, carveol,