M. Hronec et al. / Applied Catalysis A: General 468 (2013) 426–431
427
Table 1
The physical properties of catalysts.
Catalysts
Metal (wt%)
SBET (m2 g−1
)
Pore diameter (BJH) (nm)
Particle size by XRD (nm)
Mean diameter of catalyst (m)
G-134A
5% Pt/C
5% Pd/C
44
5
5
266
865
3.1
3.2
3.5
–
3.4
4.6
56
25
36
and in this form was used for experiments. The physical properties
of catalysts are in Table 1.
or CO were injected in the flow until the catalyst was saturated
with hydrogen or CO. Adsorption of gases was corrected for the
adsorption by support under such conditions.
The XPS signals were recorded using a Thermo Scientific K-Alpha
XPS system (Thermo Fisher Scientific, UK) equipped with a micro-
focused, monochromatic Al K␣ X-ray source (1486.6 eV). An X-ray
beam of 400 m size was used at 6 mA × 12 kV. The spectra were
acquired in the constant analyzer energy mode with pass energy
of 200 eV for the survey. Narrow regions were collected with pass
energy of 50 eV. Charge compensation was achieved with the sys-
tem flood gun that provides low energy electrons (∼0 eV) and low
energy argon ions (20 eV) from a single source. The argon partial
pressure was 3 × 10−7 mbar in the analysis chamber. The Thermo
Scientific Avantage software, version 4.87 (Thermo Fisher Scien-
tific), was used for digital acquisition and data processing. Spectral
calibration was determined by using the automated calibration
routine and the internal Au, Ag and Cu standards supplied with
the K-Alpha system. The charge shift of the spectra was then cor-
rected by setting the C 1s peak at 285 eV. The overlayer thickness
was measured using the single overlayer calculator in the Thermo
Scientific Avantage software, which uses the following equation to
generate a fit to, derived from the Beer–Lambert Law:
2.2. Catalytic experiments
Catalytic experiments were performed using procedure and
analytical methods described in our previous paper [14]. For a typi-
cal reaction, 20 ml of water, 0.5–1.0 g of reactant and given amount
of metal catalyst was added to the reactor vessel. After sealing
the reactor was several times flushed with low pressure hydrogen
and then pressurized with hydrogen usually to 30–80 bar (ambient
temperature). The reactor was then heated to the desired tem-
perature and the stirring speed adjusted to 1500 rpm to eliminate
external mass-transfer effects. After an appropriate reaction time
the reactor was quickly cooled down, the reactor contents pour out
to vial and the catalyst separated from the aqueous phase by cen-
trifugation. The quantitative determination of the liquid products
concentration was done using gas chromatography by the external
standard method and using response factors of the corresponding
standard compounds. A gas chromatograph–mass spectrometer
combination was used to identify the organic compounds.
The yields of reaction products were calculated on the amount
of the reactant charged into the reactor. In catalytic experiments
where cyclopentanone simultaneously react with other reactant,
e.g. furfural, which can be also converted to cyclopentanone and
cyclopentanol, the amounts of cyclopentanone and cyclopentanol
are in the tables expressed as grams of those compounds deter-
mined in the reaction mixture. The yields of other reaction products
are expressed in the corresponding mol%, which are defined as
1
cosꢀ
t
=
× ln [1 + K × R]
(1)
ꢁ
where t is the thickness of overlayer, ꢀis the emission angle
(measured from surface normal), ꢁ is the attenuation length (the
different attenuation lengths of the overlayer and substrate are con-
sidered), K is the ratio of atomic densities (element/overlayer) (and
sensitivity factor if applicable), R is the measured intensity ratio
(overlayer/element).
(mol of product)
× 100%
(mol of initial reactant)
Temperature programmed reductions (TPR) were carried out
using Micromeritics AutoChem 2910 instrument. Catalyst sam-
ples (30–50 mg) were heated up to 500 ◦C at a rate of 5 ◦C min−1
in a H2–N2 (10:90) gas flow (50 ml min−1). Prior to measure-
ments, the catalysts were dried in nitrogen atmosphere at 90 ◦C
for 1 h. Thermal gravimetric analysis was conducted with a NET-
ZSCH instrument. The samples (5–8 mg) were heated in flowing
oxygen (50 ml min−1) from room temperature to 600 ◦C at a rate of
For the impregnation of fresh heterogeneous catalysts with
furfuryl alcohol polymers two methods were used. By Method A
the catalyst (100 mg) was impregnated with a defined amount of
furfuryl alcohol polymers (FALP) dissolved in toluene or dimethyl-
sulfoxide (DMSO). The FALP were prepared by polymerization of
furfuryl alcohol (1.0 g) in freshly distilled water (20 ml) under nitro-
gen at the temperature of 175 ◦C for 70 min. The NMR analysis
(Varian VNMRS-600) was used for determination of the molecu-
lar weight of FALP. In Method B the catalyst (100 mg) was added
into a water solution of furfuryl alcohol (1 g in 20 ml of water) and
heated at 175 ◦C for 70 min. The reactions were carried out in nitro-
gen atmosphere in a 100 ml Teflon lined stainless steel autoclave
and the reaction mixture was mixed with a Teflon bar. After reac-
tion the catalyst was separated, washed with water and then used
for the catalytic reactions.
5 ◦C min−1
.
3. Results and discussion
The catalytic hydrogenation of furfural in aqueous solution at
the temperatures 130–175 ◦C and hydrogen pressures 40–80 bar
predominantly leads to the rearrangement of the furane ring. Under
these conditions, cyclopentanone and partly cyclopentanol are
formed as the main reaction products [14]. Peculiar is also the fact
that by the prolongation of the reaction time the more reactive
ketone is only slowly hydrogenated to cyclopentanol. However,
with the fresh one and this reaction mixture was again hydro-
genated at the same conditions, almost all cyclopentanone and
other intermediates were converted to the corresponding reaction
products (Table 2 runs 2 and 3). The products of partial hydrogenol-
ysis of alcohols were also detected by GC/MS. The retardation of
subsequent cyclopentanone hydrogenation cannot be associated
2.3. Characterization of catalysts
The surface areas and pore diameters were determined from
BET nitrogen adsorption measurements (Micrometrics ASAP 2020).
The samples were first degassed at 300 ◦C for 2 h before measure-
ments. Metal particles sizes were determined from XRD data. The
metal dispersion of catalyst was measured by hydrogen and CO
chemisorption. A catalyst sample (50 mg) pre-exposed to air was
placed in a glass tube connected to the instrument and stabilized
at 100 ◦C under nitrogen flow. A volume of 50 l pulses of pure H2