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The decomposition of NO and of N2O over a CuZSM-5 zeolite and a Fe-mordenite, respectively, has been studied using tracer techniques. The results demonstrate the high mobility of the lattice oxygen ions in self-diffusion. They afford a possible explanation for the problem of how two extralattice oxygens located at positions remote from each other may combine to form the O2 molecules which are spontaneously desorbed in these redox reactions. They show that a portion of the lattice oxygen mixes into the O2 released on decomposition. The data also show that N18O and N2
18O undergo exchange with the catalyst oxygen under reaction conditions.On leave from Central Research Institute for Chemistry, Hungarian Academy of Sciences, H-1525 Budapest, Hungary. 相似文献
2.
Equilibrium exchange isotherms were determined for the exchange of Cu2+ with NaZSM-5 at varying Cu(Ac)2 concentrations in solutions of constant volume and zeolite weight. At low Cu2+ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary. 相似文献
3.
Gy. P?lczmann J. Valyon ��. Szegedi R. M. Mih��lyi J. Hancs��k 《Topics in Catalysis》2011,54(16-18):1079-1083
A Pt/AlSBA-15 catalyst was investigated in the selective isomerisation of Fischer?CTropsch wax, which type of catalyst have not been studied in detail in this reaction system yet. Its hydroconversion activity was compared with that of the Pt/SAPO-11 catalyst. Based on the results it was concluded that the selective isomerization of the Fischer?CTropsch wax can be a new application of the Pt/AlSBA-15 catalyst. 相似文献
4.
In the preceding Letter Shelef [1] has proposed a mechanism for NO decomposition involving coordinatively unsaturated Cu2+ sites on which NO molecules are chemisorbed in the gem-dinitrosyl form. At reaction temperature this complex is supposed to decompose into N2 and O2 without involving a redox process. That such a process is feasible has been pointed out by Moser [2]. Shelef cited several reasons in support of this view and others that have led him to think that a cyclic redox mechanism is not operative. These arguments are countered herein and some new data are presented showing the infrared spectra of surface species recorded under in situ reaction conditions.On leave from Central Research Institute for Chemistry, Hungarian Academy of Sciences, H-1525 Budapest, Hungary. 相似文献
5.
Protonated pyridine (PyH+) was not found on ZrO2 (Z) or ZrO2–TiO2 (ZT), but was detected on sulfated oxides (ZS, ZTS) by IR spectroscopy. In contrast, ZrO2–SiO2 samples containing about 30–80 mol% ZrO2 showed Brønsted acidity both in nonsulfated (ZS) and sulfated (ZSS) forms. The total acidity was determined by NH3TPD. Introduction of sulfate ions increased the sitespecific catalytic activity (TOF) in the conversion of cyclopropane or nhexane. The effect of sulfate ions was more significant on samples rich in zirconia. Results suggest that Zr is homogeneously distributed in ZS samples rich in silica. Zirconiabound dimeric sulfate, generating strong acidity, could not be formed in these preparations due to the absence of fairly large ZrO2 domains. 相似文献
6.
Mesoporous Ti-MCM-41 materials as photodegradation catalysts of 2,4,6-trichlorophenol in water 总被引:1,自引:0,他引:1
Ahmed?K.?Aboul-Gheit Sohair?M.?Abdel-Hamid Sawsan?A.?Mahmoud Radwa?A.?El-Salamony József?Valyon Magdolna?R.?Mihályi ágnes?SzegediEmail author 《Journal of Materials Science》2011,46(10):3319-3329
Titanium-modified MCM-41 type mesoporous silica materials were prepared by hydrothermal [Ti-MCM-41(HT)], sol–gel [Ti-MCM-41(SG)]
and post-synthesis impregnation [TiO2/MCM-41] methods. The materials were characterized and tested as photocatalysts in the oxidative degradation reaction of 2,4,6-trichlorophenol
(2,4,6-TCP) in water. The catalysts showed high initial activity. The produced acetate and chloride ions were found to inhibit
the degradation reaction. The Ti-MCM-41(HT) sample showed higher overall activity than the Ti-MCM-41(SG) catalyst. One of
the probable reasons for this is the difference in the distribution of the active sites that determines the rates of electron
(e−)–hole (h+) recombination within the photoactive species. The HT preparation was found to contain silica-bound titania in higher dispersion,
while the SG preparation contained also polymerized species with Ti–O–Ti bonds. 相似文献
7.
The H/D exchange was studied between CD4 and H-zeolites using pulsed a microcatalytic reactor and MS analysis. Methane-d3 was the only exchange product, while a large fraction of the reactant was retained by the zeolite. The apparent activation energies (Ea) were determined for CHD3 production assuming first-order reaction kinetics. The Ea was close to 80 kJ mol-1 over the H-ZSM-5 and H-mordenite, and about 50 kJ mol-1 over H-beta. Results suggested that, at the low methane loading applied, the H/D exchange was initiated predominantly by heterolytic dissociation of CD4 to CD3
- and D+ over Lewis acid-Lewis base pair sites. 相似文献
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