Authors:B. Hunger, S. Matysik, M. Heuchel, E. Geidel, and H. Toufar
We have investigated the interaction of water with Na+-ion exchanged zeolites of different structures (LTA, FAU, ERI, MOR and MFI) by means of temperature-programmed desorption
(TPD). The non-isothermal desorption of water shows, depending on the zeolite type, differently structured desorption profiles.
In every case the profiles have, however, two main ranges. Using a regularization method, desorption energy distribution functions
have been calculated. The desorption energy distributions between 42–60 kJ mol−1, which can be attributed to a non-specific interaction of water, show two clearly distinguished energy ranges. The water
desorption behaviour of this range correlates with the electronegativity of the zeolites and the average charge of the lattice
oxygen atoms calculated by means of the electronegativity equalization method (EEM). The part of the desorption energy distributions
in the range of 60–90 kJ mol−1, reflecting interactions of water with Na+ cations, shows two more or less pronounced maxima. In agreement with vibrational spectroscopic studies in the far infrared
region, it may be concluded that all samples under study possess at least two different cation sites.
Authors:J. A. Navio, M. Macias, A. Justo, and C. Real
The thermal decomposition of sodium nitrite or nitrate pre-adsorbed upon TiO2 surfaces has been investigated by employing several techniques as infrared spectroscopy (IR) and temperature programmed desorption in conjunction with mass spectrometry analysis (TPD-MS) to study the features observed during these thermal decompositions. Differential thermal analysis (DTA) in combination with X-ray diffraction analysis (XRD) were used to investigate the possibility of a solid state chemical reaction between the solid products originated from the thermal decomposition of the pre-adsorbed species and the TiO2. On the basis of our results, various characteristic features of these thermal decomposition reactions will be discussed.
Authors:S. Aukkaravittayapun, C. Thanachayanont, T. Theapsiri, W. Veerasai, Y. Sawada, T. Kondo, S. Tokiwa, and T. Nishide
Fluorine-doped tin dioxide
(FTO) films were deposited on silicon wafers by inverted pyrosol technique
using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75
and 2.50). The physical and electrical properties of the deposited films were
analyzed by SEM, XRF, resistivity measurement by four-point-probe method and
Hall coefficient measurement by van der Pauw method. The electrical properties
showed that the FTO film deposited using the solution with F/Sn=0.75 gave
a lowest resistivity of 3.210–4 ohm
cm. The FTO films were analyzed by temperature programmed desorption (TPD).
Evolved gases from the heated specimens were detected using a quadruple mass
analyzer for mass fragments m/z, 1(H+),
16(O+), 17(OH+ or NH3+),
18(H2O+ or NH4+),
19(F+), 20(HF+), 28(CO+
or N2+), 32(O2+),
and 152(SnO2+). The majority
of evolved gases from all FTO films were water vapor, carbon monoxide and
carbon dioxide. Fluorine (m/z 19) was detected
only in doped films and its intensity was very strong for highly-doped films
at temperature above 400C.
Authors:I. Ferino, R. Monaci, E. Rombi, and V. Solinas
Interaction between 1-methylnaphthalene and alkali-metal X and Y zeolites has been investigated using TPD. All spectra show
only a single peak, the temperature of which changes with the nature and amount of the alkali-metal cation and the Si/Al ratio
of the faujasite. A correlation between peak temperature and average charge of structural oxygen atoms of the zeolite is shown.
On the basis of the atomic charge distribution in the 1-methylnaphthalene molecule, it is, suggested that adsorption is initiated
by interaction between the alkali-metal cation and the carbon atom of the methyl group. Simultaneously, an interaction involving
hydrogens atoms of the aromatic rings and structural oxygen atoms of the zeolite occurs, except for X samples containing high
amounts of large alkali-metal cations.
Authors:Jacek Przepiórski, Justyna Karolczyk, Tomoki Tsumura, Masahiro Toyoda, Michio Inagaki, and Antoni W. Morawski
) applying the same temperature program. Thus, carbon yield could be calculated as a balance between residual masses determined after TG analyses in argon and in air. The temperature programmed desorption (TPD) measurements were carried out with use of
Authors:Yinghua Li, Dae-Won Lee, Yoon-Ki Hong, Seong-Min Kim, Hyun-Sik Han, and Kwan-Young Lee
The performances of selective catalytic reduction (SCR) by CO/H2 over two Pd/TiO2/Al2O3 catalysts prepared from PdCl2 and Pd(NO3)2 precursors were compared. The catalytic activities (NOx conversion and N2 yield) were measured on these two catalysts. The catalytic properties of the prepared catalysts were studied by various characterization
techniques such as BET, CO-chemisorption, TEM, XPS, and TPD. The Pd precursors influenced the Pd particle distribution, resulting
in different catalytic activities.
Authors:Jinbo Ni, Min Wu, Zhaohui Yang, Changfei Bu, and Qin He
SO42−/TiO2–MxOy (M = Zr, Ce, La) were prepared by the precipitation-impregnation method and characterized by X-ray powder diffraction (XRD),
Fourier transform infrared (FT-IR), and temperature-programmed desorption (NH3-TPD). Catalytic activities were evaluated in the acetalization of 1,3-propanediol (1,3-PD) with acetaldehyde and hydrolysis
of 2-methyl-1,3-dioxane (2MD). SO42−/TiO2–ZrO2 (STZ) exhibited the best catalytic activity both in the acetalization and hydrolysis. With the molar ratio of Zr4+/Ti4+ = 1:4, the highest yields were 96.45% in 3 h and 93.68% of 2MD hydrolyzed in 18 h, in contrast to the yields lower than 60%
by using other superacids. These results are consistent with the strongest acidity of the superacid containing Zr4+ among prepared superacids containing other cations.
Authors:Ping Liu, Xingguang Zhang, Yue Yao, and Jun Wang
Alkaline earth metal (Mg, Ca, Sr and Ba) ions were exchanged into Hβ zeolite, which were used as the supports to load the
noble metal Pt to prepare bifunctional catalysts for hydroisomerization of n-heptane. The catalysts were characterized by ICP, XRD, BET, NH3-TPD, H2-TPR and H2-chemisorption techniques, and evaluated in an atmospheric fixed bed reactor. The catalysts promoted by the alkaline earth
metals are revealed to present much higher selectivity to isomerization than the counterpart Pt/Hβ. Moreover, the Ba-bearing
catalyst loaded with 0.4 wt% Pt and 5:1 molar ratio of Ba to Pt gives a very high selectivity to iso-heptanes 95.4% with a
considerable high conversion of n-heptane 61.7%. The promotion effect of alkaline earth metals is briefly discussed in relation to characterization data.
Authors:Lixia Wang, Wanchun Zhu, Dafang Zheng, Xue Yu, Jing Cui, Mingjun Jia, Wenxiang Zhang, and Zhenlu Wang
The reaction of direct transformation of ethanol to ethyl acetate was investigated on reduced Cu/ZrO2 catalysts prepared by a co-precipitation procedure. The catalytic performances of these Cu–Zr mixed oxides were considerably
influenced by changing the molar ratio of Cu to Zr. The highest selectivity to ethyl acetate was found over Cu/ZrO2(1) catalyst (molar ratio of Cu to Zr was 1). A variety of characterization techniques, such as N2 adsorption, XRD, XPS, TPR and NH3-TPD were carried out on the catalysts. The results revealed that the presence of a certain amount of Cu+ species may play very important role in improving the selectivity to ethyl acetate of the Cu/ZrO2 catalysts.
Authors:Mendelssolm de Pietre, Luiz Almeida, Richard Landers, Rita Vinhas, and Fernando Luna
The activity of solid niobic acid treated with sulfuric acid and with phosphoric acid was tested in the catalytic esterification
of oleic acid and in transesterification of soybean oil with methanol. X-ray diffraction studies revealed niobic acid treated
with sulfuric acid to be an amorphous solid, while niobic acid treated with phosphoric acid presented a crystalline phase,
probably due to the formation of hydrogen niobium phosphate. Among the characterization methods employed here, XPS was particularly
instrumental in showing that niobium dihydrogen phosphate and niobium hydrogen sulfate moieties are the acidic active sites
responsible for the catalytic effect. The latter is more active according to ammonia TPD studies. Yields as high as 78% in
the esterification of oleic acid with methanol and 40% in the transesterification of soybean oil catalyzed by NbSO4 were recorded.