The new small-angle neutron scattering instrument SANS-1 at MLZ—characterization and first results

AbstractA thorough characterization of the key features of the new small-angle neutron scattering instrument SANS-1 at MLZ, a joint project of Technische Universität München and Helmholtz Zentrum Geesthacht, is presented. Measurements of the neutron beam profile, divergency and flux are given for various positions along the instrument including the sample position, and agree well with Monte Carlo simulations of SANS-1 using the program McStas. Secondly, the polarization option of SANS-1 is characterized for a broad wavelength band. A key feature of SANS-1 is the large accessible Q-range facilitated by the sideways movement of the detector. Particular attention is hence paid to the effects that arise due to large scattering angles on the detector where a standard cos3 solid angle correction is no longer applicable. Finally the performance of the instrument is characterized by a set of standard samples

Solid-state incorporation of Mn²⁺ ions in H-ZSM-5 zeolite

The high-temperature interaction between H-ZSM-5 zeolite and solid MnCl2, MnSO4, Mn(CH3CO2)2 and Mn3O4 has been studied by temperature-programmed desorption of ammonia, IR, EPR and mass spectrometry. It has been shown that the degree of solid-state ion exchange for MnCl2 is strongly affected by the temperature of the heat treatment. Depending on the amount of manganese cations present in the zeolite–salt mixture, at 770 K an exchange degree of 60–85% can be obtained. The solid-state reaction of MnSO4 at the same temperature leads only to 20% exchange of Mn2+ ions, while that of Mn3O4 results in ca. 50% exchange of Mn2+. Owing to its decomposition above 520 K to Mn oxides, Mn(CH3CO2)2 behaves similarly to these oxides; only part of the bridging OH groups are replaced by Mn ions. For all the Mn compounds studied, the solid-state reaction, resulting in replacement of protons of acidic skeletal OH groups by Mn2+ ions, appears to take the same course: most of the Mn2+ ions are exchanged in the initial stage of the reaction and then the reaction rate considerably decreases, levelling off to zero

Characterization of Activated States of Ruthenium-Containing Zeolite NaHY

As has been proven earlier, ruthenium-containing NaHY zeolites are able to catalyze the decomposition of ammonia at temperatures from 300 to 450°C. In such catalysts, ruthenium cations are still present, even after heat treatment in high vacuum at 400°C; they can be detected using ammonia and/or pyridine as probes for Fourier transform IR spectroscopy. They reside both in supercages and in sodalite cages. Various intermediates of the decomposition of the Ru(NH3)6NaY complex on heat treatment in high vacuum were identified viain situIR spectroscopy; in particular, evidence for the formation of complexes with nitrosyl ligands was obtained. It was shown that partially decomposed (deammoniated) Ru(NH3)6NaY complexes can be recovered to some extent by readsorption of ammonia. Ruthenium-containing species were localized either in the supercages or in the small cavities as shown by IR spectroscopy employing ammonia and pyridine as probes. The acidic properties of variously treated Ru(NH3)6NaY zeolites were characterized via temperature-programmed desorption (TPD) of ammonia, which was monitored by mass spectrometry. A strong interaction between ruthenium-containing species and the zeolite framework, leading to a lack of overtone and combination modes in the near infrared, is confirmed. Investigations of Ru(NH3)6NaY samples by X-ray photoelectron spectroscopy under the same conditions as applied for IR and TPD studies revealed that, at variance with the results usually obtained after heat treatment of Ru(NH3)6NaY in high vacuum, no significant formation of ruthenium metal species through autoreduction occurred. Rather, a particular form of a cation-exchanged Ru, Na-Y zeolite was obtained

XPS investigations of lanthanum in faujasite-type zeolites

Faujasite-type zeolites containing lanthanum introduced by various techniques and in different amounts were studied by X-ray photoelectron spectroscopy to elucidate the influence of the zeolite matrix on the binding energy and the shape of the La(3d) line. The results were discussed with regard to the spectral properties of the La(3d) line in La2O3. Significant differences in the La(3d) line shapes and binding energies between La2O3 and La zeolites were ascribed to final-state effects arising from the hybridization of La final states with valence bands of different extension. The La(3d) line shape of the La zeolites investigated at elevated temperatures was found to respond to structural changes in the surface region of the samples (dehydration, ion migration, formation of highly dispersed La-O structures on extraframework sites). These were also reflected in bulkphase properties of the samples (lattice parameters, determined by X-ray diffraction

Preparation and characterisation of ru-exchanged NaY zeolite: An infrared study of CO adsorption at low temperatures

RuNaY zeolitenext term was prepared by ion exchange of NaY with an aqueous solution of [Ru(NH3)6]Cl3. The resulting complex was decomposed and reduced. The IR spectra of CO adsorbed at 110 K on the highly dispersed Ru o clusters inside the supercages (1–1.5 nm) and on the sintered clusters at the external surface (5.5, 10–15 and 30 nm) display a broad band at not, vert, similar 2040 cm−1 and a low frequency shoulder at not, vert, similar 2000 cm−1. The former corresponds to linearly bonded CO species and the latter to CO adsorbed on the Ru atoms with low coordination numbers. The autoreduced sample produced an additional shoulder at 2098 cm−1 which is assigned to the CO species weakly σ-bonded to the residual Ru x+ ions in the zeolite or to CO adsorbed on single ru atoms perturbed by surrounding oxygen atoms. The band width was found to be sensitive to reduction conditions and hence particle sizes

Zeolite MCM-22: Synthesis, Dealumination and Structural Characterization

Zeolite MCM-22 was synthesized and characterized by selected physico-chemical methods. MAS NMR spectroscopic studies reveal that at least five crystallographically non-equivalent T-sites exist in the structure of MCM-22 and that they are affected to different degrees by dealumination with Sicl4vapors. From IR and TPDA experiments it can be concluded that the acidic properties of HMCM-22 are very similar to HZSM-5. A Spaciousness Index of ca. 8 is indicative of an effective pore width in the intermediate region between 10- and 12-membered ring zeolites