726
2.2 Characterization of Catalysts
The BET surface areas of the catalysts were estimated by using N 2 adsorptiondesorption method at −196 °C in an Autosorb 3000 equipment. Powder XRD patterns were recorded using a Rigaku MiniFlex X-ray diffractometer instrument using
Ni-filtered Cu K α radiation (λ = 0.15406 nm) with a scan rate of 2° min
−1
between
2θ = 20° and 80°. Raman spectroscopic analysis of the catalysts was carried out
using a Horiba Jobin Yvon lab ram HR Raman spectrometer with beam excitation
of λ = 632.81 nm. The UV-Vis spectra in diffuse reflectance mode were obtained in
UV-Vis spectrophotometer (UV-2000 from Shimadzu) consisting of BaSO 4 reference and an integrating sphere in the range of 800–185 nm with a slit width of 2 nm
and sampling interval of 0.5 nm at ambient temperature. The Fourier transform
infrared (FTIR) spectra of the catalyst samples were analyzed by diluting the samples with KBr as pressed wafers using IR spectrometer (Thermo Nicolet Nexus 670)
from 4000 to 400 cm
−1
region. The surface elemental analyses of the catalysts were
obtained from X-ray photoelectron (XPS; Kratos Axis Ultra Imaging) spectrometer,
equipped with multichannel detector and Mg anode. Background correction
(Shirley-type) was done by referencing the obtained spectra with C 1 s at a binding
energy of 284.8 eV.
2.3 Activity Tests
The dehydrocyclization activities were conducted using −18/+23 sieved (BSS) catalyst particles. The carbon mass balance was calculated based on the inlet and outlet
concentration of the organic moiety. In a typical measurement, prior to the reaction,
about 0.2 g of calcined catalyst (sieved particles −18/+25 BSS) was treated in 5%
H 2 /Ar at 400 °C for 5 h. A 20 wt% aqueous glycerol solution was used, and the
glycerol to EDA mole ratio of 1:1 with a flow rate of the reaction mixture of 2 mL h
−1
along with N 2 as carrier gas at a flow rate of 1800 cc h
−1
was maintained. The reaction mixture contained a glycerol flow rate = 88.2 cc h
−1
, EDA flow rate = 87.4 cc h
−1
,
H 2 O flow rate = 1806.2 cc h
−1
, and N 2 flow rate = 1800 cc h
−1
. The collected samples
(after 6 h) were analyzed by gas chromatography (Shimadzu, GC-17A) equipped
with a flame ionization detector (FID) using ZB-5 capillary column.
3 Results and Discussion
3.1 Powder XRD Analysis
The XRD patterns of various loadings of ZnO on Cr 2 O 3 are presented in Fig. 1. It
shows that 2ZnO/Cr 2 O 3 , 5ZnO/Cr 2 O 3 , and 7ZnO/Cr 2 O 3 samples displayed Cr 2 O 3
phase prominently, and no ZnO and ZnCr 2 O 4 phases were detected. The catalysts
R. Sarkari et al.
2.2 Characterization of Catalysts
The BET surface areas of the catalysts were estimated by using N 2 adsorptiondesorption method at −196 °C in an Autosorb 3000 equipment. Powder XRD patterns were recorded using a Rigaku MiniFlex X-ray diffractometer instrument using
Ni-filtered Cu K α radiation (λ = 0.15406 nm) with a scan rate of 2° min
−1
between
2θ = 20° and 80°. Raman spectroscopic analysis of the catalysts was carried out
using a Horiba Jobin Yvon lab ram HR Raman spectrometer with beam excitation
of λ = 632.81 nm. The UV-Vis spectra in diffuse reflectance mode were obtained in
UV-Vis spectrophotometer (UV-2000 from Shimadzu) consisting of BaSO 4 reference and an integrating sphere in the range of 800–185 nm with a slit width of 2 nm
and sampling interval of 0.5 nm at ambient temperature. The Fourier transform
infrared (FTIR) spectra of the catalyst samples were analyzed by diluting the samples with KBr as pressed wafers using IR spectrometer (Thermo Nicolet Nexus 670)
from 4000 to 400 cm
−1
region. The surface elemental analyses of the catalysts were
obtained from X-ray photoelectron (XPS; Kratos Axis Ultra Imaging) spectrometer,
equipped with multichannel detector and Mg anode. Background correction
(Shirley-type) was done by referencing the obtained spectra with C 1 s at a binding
energy of 284.8 eV.
2.3 Activity Tests
The dehydrocyclization activities were conducted using −18/+23 sieved (BSS) catalyst particles. The carbon mass balance was calculated based on the inlet and outlet
concentration of the organic moiety. In a typical measurement, prior to the reaction,
about 0.2 g of calcined catalyst (sieved particles −18/+25 BSS) was treated in 5%
H 2 /Ar at 400 °C for 5 h. A 20 wt% aqueous glycerol solution was used, and the
glycerol to EDA mole ratio of 1:1 with a flow rate of the reaction mixture of 2 mL h
−1
along with N 2 as carrier gas at a flow rate of 1800 cc h
−1
was maintained. The reaction mixture contained a glycerol flow rate = 88.2 cc h
−1
, EDA flow rate = 87.4 cc h
−1
,
H 2 O flow rate = 1806.2 cc h
−1
, and N 2 flow rate = 1800 cc h
−1
. The collected samples
(after 6 h) were analyzed by gas chromatography (Shimadzu, GC-17A) equipped
with a flame ionization detector (FID) using ZB-5 capillary column.
3 Results and Discussion
3.1 Powder XRD Analysis
The XRD patterns of various loadings of ZnO on Cr 2 O 3 are presented in Fig. 1. It
shows that 2ZnO/Cr 2 O 3 , 5ZnO/Cr 2 O 3 , and 7ZnO/Cr 2 O 3 samples displayed Cr 2 O 3
phase prominently, and no ZnO and ZnCr 2 O 4 phases were detected. The catalysts
R. Sarkari et al.