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.
, B , Szombathely , MV , Hoffmann , J , Brauer , P . 1995 Characterization of the acidic properties of zeolites by means of temperature-programmed desorption (TPD) of ammonia. Calculation of distribution function of the desorption energy . J
Authors:D. Meloni, M. F. Sini, M. G. Cutrufello, R. Monaci, E. Rombi, and I. Ferino
-hydrotalcite oxides, usually assessed by temperature-programmed desorption (TPD) of carbon dioxide, is often invoked for explaining their catalytic activity in many reactions [ 6 – 8 ]. The drawback of such an approach is twofold: (i) it neglects any possible role of
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.