10.1002/cctc.201800981
ChemCatChem
FULL PAPER
detector used was a 3.5 mm Si(Li) drifted crystal with a Peltier cooling (ca.
185 K). For quantitative analysis, calibration with a series of metallic
standards and a UniQuant software were used.
The conversion (X) of sulfoxidation reaction was calculated as the ratio of
consumed and initial molar amount of the substrate (eqn 1). Yield of
sulphoxide resp. sulphone was calculated as the ratio between produced
sulphoxide resp. sulphone and consumed sulphide (eqn 2).
Nitrogen adsorption isotherms were determined by the standard method
at -196 °C (liquid nitrogen temperature) using an ASAP 2025
(Micromeritics) static volumetric apparatus. Before the adsorption
experiments samples were outgassed at 350 °C using turbomolecular
pump to remove pre-adsorbed water.
(
)
(
)
n sulphide initial − n sulphide
sample
( )
1
X =
(
)
initial
n sulphide
The DR-UV-Vis spectroscopy was carried out using an Evolution 600
(Thermo) spectrophotometer. The measurements of non-calcined
samples were performed at room temperature in the range 200–900 nm
with resolution of 2 nm.
(
)
sample
n product
(
)
( )
2
y
product
=
(
)
( )
−n sulphide
sample
n sulphide
initial
The epoxidations of cis-cyclooctene (Aldrich, 95%) were carried out
according to the procedure presented by Prech et al.,[5a] in a 25 ml
magnetically stirred glass three-necked round bottom flask equipped with
a Dimroth condenser at 60 °C. The alkene/catalyst mass ratio was 10 and
alkene/H2O2 molar ratio was 2. Acetonitrile (Fisher chemical, HPLC grade)
was used as a solvent and mesitylene (99%, Acros-Organics) served as
an internal standard. In a standard experiment, 500 mg of cyclooctene
were mixed with 250 mg of the internal standard, 50 mg of the catalyst and
6.65 ml of acetonitrile. The reaction was started by addition of H2O2
aqueous solution (35 wt.%, Aldrich) into the mixture. Samples were taken
in regular intervals, centrifuged, cooled and analyzed using an Agilent
6850 GC system with 50 m long DB-5 column, an autosampler and a FID
or a MS detector. Helium was used as a carrier gas.
Calcination in situ in was carried out by DR-UV-Vis using an Ocean Optics
HR2000+ instrument (integration time 20 ms, 20 scans) equipped with an
Ocean Optics DH-2000 BAL halogen-deuterium light source and a high-
temperature reflection probe (FCR-7UV400-2-ME-HTX, 7 × 400 μm
fibres). The spectra were collected within the wavelength range 225–
1100 nm using BaSO4 as a reflection standard. The spectra are shown in
the Kubelka-Munk format (F(R) = (1 − R)2/2R, where
R stands for
reflectance). A high-temperature probe was attached at the top of the
quartz microreactor. The distance between the sample bed and the high-
temperature probe tip was 2-3 mm. The sample bed thickness was 4–5
mm.
IR spectra were recorded on Perkin Elmer Frontier spectrometer equipped
with DTGS detector and a single reflection diamond ATR module, working
with spectral resolution of 4 cm-1. ATR spectra were normalized to the
intensity of the 800 cm-1 band, characteristic of T-O internal vibrations.
Acidity was investigated by FITR spectroscopy based on adsorption of CO
and pyridine used as probe molecules. The samples were activated in the
form of self-supporting wafers for 1 hour at 450 °C prior to the adsorption
of probe molecules at the following temperatures: 170 °C for pyridine
(POCh Gliwice, analytical grade) and -100 °C for CO (Linde Gas Polska,
99.95% used without further purification). All spectra in absorbance mode,
presented in this work have been normalized to the standard 10 mg pellet
(density 3.2 mg cm-2). The concentrations of Lewis and Brønsted acid sites
The conversion (X) of epoxidation reaction was calculated as the ratio of
consumed and initial molar amount of the substrate (eqn 3), while the yield
was calculated by analogy to eqn (2).
n(cyclooctene)
initial
−n(cyclooctene)
sample
X =
(3)
n(cyclooctene)
initial
Acknowledgements
were evaluated using previously reported absorption coefficients[25]
:
ε(LAS) = 0.165 cm2μmol-1, and ε(BAS) = 0.044 cm2μmol-1 and calculated
from intensities of the corresponding pyridine maxima after pyridine
desorption at 170 °C to ensure complete removal of weakly adsorbed
species.
Financial support from National Science Centre Poland, grant no
2016/21/B/ST5/00858 is gratefully acknowledged. J.P. and J.Č.
acknowledge the Czech Science Foundation for the project
P106/12/G015.
The oxidations of methylphenyl sulphide (Aldrich, 99%) were carried out
at 30 °C in a 25 ml magnetically stirred round bottom three-neck glass flask
equipped with a Dimroth condenser (procedure taken from ref.[28]).
Samples before reaction were activated at in air, at 450 °C for 90 min,
cooled down in a desiccator and then transferred to the reaction flask.
Typically, 8 mmol (1 g) of the sulphide was dissolved in 10 ml of acetonitrile
(Fisher chemical, HPLC grade) together with 250 μl of 1,3-
diisopropylbenzene as internal standard (Fluka, 95%) and 50 mg of a
catalyst were introduced into the mixture. The substrate/catalyst mass
ratio was S/C = 20. The mixture was heated to the reaction temperature
and the reaction was started by addition of H2O2 aqueous solution (Aldrich,
35 wt%). The typically sulphide/H2O2 molar ratio was equal 2.
Keywords: • zeolites • layered compounds • Ti-MWW •
pyramidal Ti-sites • oxidation reaction
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Scheme 2. General schemes of sulfoxidation and epoxidation reactions.
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