Spectroscopic analysis of metabolic profile in patients with relapsed multiple sclerosis

Introduction. Managing patients with relapsing-remitting multiple sclerosis (RMS) remains a pressing issue. Objective. To detect the reversible metabolic changes of the brain matter in patients with clinically exacerbated RMS and to follow them up after intravenous glucocorticoid (IVGC) treatment. Materials and methods. Neurological examination and neuroimaging in the RMS patients included expanded disability status scale (EDSS) scoring, conventional brain magnetic resonance imaging (MRI), and proton nuclear magnetic resonance spectroscopy (1H-NMR spectroscopy) before and after IVGC treatment. Multivoxel 1H-NMR spectroscopy was used to assess metabolism in the centra semiovale and cingulate gyri. Results. Based on the multivoxel 1H-NMR spectroscopy, relative metabolite concentrations in the grey and white matter statistically differed within the study cohort before and after the IVGC treatment. The N-acetylaspartate/choline ratio significantly recovered and the choline/creatine ratio decreased in the anterior cingulate gyri in 27% of patients. The brainstem function score significantly improved in the metabolic response group as compared to the non-metabolic response group. Conclusion. We should study the potential predictors of RMS activity and the IVGC response to select the RMS relapses when pulse-therapy with IVGCs is definitely indicated. Spectroscopy may reveal RMS pathogenesis variability earlier than conventional MRI

Synthesis and characterization of the titanium doped nanostructural V2O5

Using scanning and analytical transmission electron microscopies (TEM), the morphology and structure of nanostructurally assembled V2O5 doped with Ti has been studied. It was found that the bulk structure of the oxide particles crystallized in rod-like shape is of the V2O5 type whereas Ti atoms are located mainly on the thin surface layer of the rods. Such surface coating is nonuniform and contains up to 3 at.% of titanium. Modification of the oxide sample with titanium atoms seems to stabilize the V2O5 structure against electron beam irradiation

Preparation of a single phase (MoVW)5O14-mixed oxide catalyst

Motivation Mixed oxide catalysts containing molybdenum, vanadium and tungsten are widely used in industry for partial oxidation reactions [1, 2, 3]. Previous work revealed (MoVW)5O14 to be the active phase of the catalyst. The partial oxidation from acrolein to acrylic acid is performed on such a system [4, 5]. This catalytic system is characterised by high long term stability, excellent turn-over rates and high selectivity. Different preparation steps are necessary to form a single phase, crystalline, ternary oxide (MoVW)5O14 as a model catalyst. In a previous paper [6] it was suggested that a precursor of this oxide is already formed in solution. Therefore this poster is dedicated to propose a structure of the dissolved species and a reaction mechanism leading to the formation of this structure in solution. Experimental For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed in solution were studied using UV/Vis Raman and ESR spectroscopy. Results It is suggested from this data that a molecular structure is already formed in solution which seems to be closely related to that of the final crystalline Mo5O14-type oxide. Raman spectroscopy shows bands at 964, 943, 912, 821, 792, 709 and 682 cm-1. The bands at 943 and 792 cm-1 could be assigned to AHM. Bands at 964, 879, 821, 709, und 682 cm-1 do not belong to AHM and point to a polymeric species This result could be corroborated by UV/Vis and ESR spectroscopy. Moreover ESR shows that the state of oxidation of molybdenum and tungsten is +6. The state of oxidation of vanadium is +4. Vanadium exists as vanadyl type. The spray-dried sample shows bands at 943, 872, and 818 cm-1. A higher degree of polymerisation in the dried sample could be responsible for the shift of the band at 872 cm-1 compared to the spectrum in solution 879 cm-1. Literature [1] Hibst, H.,Unverricht, S. (BASF), DE 19815281 A 1. [2] Tanimoto, M., Himeji-shi, H., Mihara, I., Aboshi-ku, H., H., Kawajiri, T., Himeji-shi, H., (Nippon Shokubai), EP 0 711 745 B1. [3] Tenten, A., Hibst, H., Martin, F-G., Marosi, L., Kohl, V., (BASF), DE 4405514 A1. [4] Mestl, G., Linsmeier, C., Gottschall, R., Dieterle, M., Find, J., Herein, D., Jäger, J., Uchida, Y., Schlögl, R., J. Mol. Catal. A 162 (2000) 455-484. [5] Dieterle, M., Mestl, G., Jäger, J., Hibst, H., Schlögl, R., J. Mol. Catal. A 174 (2001) 169-185. [6] Knobl, S., Zenkovets, G. A., Kryukova, G. N., Ovsitser, O., Dieterle, M., Mestl, G. , Schlögl, R., J. Catal, submitted

The Synthesis and Structure of a Single Phase, Nanocrystalline MoVW Mixed Oxide Catalyst of the Mo5O14-Type

The different preparation steps are characterized for the single-phase, crystalline, ternary oxide (MoVW)5O14, which is important for catalytic, mild selective oxidation reactions. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed at each preparation step, starting from the precursor to the final product, were studied using scanning and transmission electron microscopy, X-ray powder diffraction, thermal analysis, and Raman spectroscopy. Raman spectroscopy was also applied to shed some light into the aqueous chemistry of the mixed precursor solutions. Raman data indicate that a molecular structure which seems to be closely related to that of the final crystalline Mo5O14-type oxide is already formed in solution. X-ray diffraction revealed that the thermal treatment steps strongly affect the degree of crystallinity of the ternary Mo5O14 oxide. Transmission electron microscopy with energy-dispersive microanalysis confirmed the presence of V and W in the molybdenum oxide particles and gave evidence for the (010) plane as the most developed face of the crystals of this phase. Details of the structural transformation of this system at the different preparation and calcination steps are discussed in relation to their performance in the selective partial oxidation of acrolein to acryli

Methods for preparation and characterisation of heterogeneous catalysts

Whilst much research effort was spent on optimisation of catalyst performance, less attention has been drawn to problems concerning catalyst preparation. It is commonly known that catalyst research is facing two problems: the Materials gap and the Pressure gap. The “Materials gap” describes the discrepancy between commercial catalyst material that is often too complex to be successfully characterised and (single crystal) model catalysts that are often not able to achieve good product rates. The “Pressure gap” addresses the problem that surface investigations are commonly performed under UHV conditions whereas commercial processes are carried out at ambient or high pressure. As a consequence information of reaction mechanisms or the “real structure” under reaction conditions is very limited. Although catalysis experiments on single crystals led to new information about catalyst behaviour, it is now commonly believed that the main catalytic processes happen on centres with a high- but often unidentified- number of defects. A major task for catalyst preparation is therefore to produce highly defective metastable material. New syntheses have to be developed that fulfil many more requirements such as to ensure high reproducibility and products easy to characterise. Whilst the former can be achieved by monitoring each reaction step in-situ, the latter is taken care of by preparing thin films on a substrate. These new preparation methods will be demonstrated on the example of MoVW supported catalysts, which are used in industry for the synthesis of acrylic acid [1-5]. Despite this industrial importance, there is still a lack of information concerning structure formation during synthesis and the atomic arrangements with respect to different preparation routes and element ratios. Earlier work [6-9] showed a significant increase in selectivity for partial oxidation products in the presence of a Mo5O14 type structure. This structure, which was first identified by Kihlborg et.al. [10], is built up by pentagonal bipyramids and octahedrally coordinated metal centres [Figure 1]. It is metastable until crystallisation and oxidative decomposition into binary oxide phases occurs under high oxygen partial pressure (air and above). The element ratio is (Mo0.68V0.23W0.09)5O14. At the same time binary molybdenum based oxides doped with different elements such as Nb, W and Ta have been synthesised and their structure was identified as that of the Mo5O14-type [11, 12]. These phases were found to be stable at a wide temperature range. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and vanadyl oxalate were spray-dried and subsequently calcined in air and helium. The Mo5O14 structure is an idealised endpoint that is formed under reduced oxygen partial pressure during the organisation process of a mixture of oligo anions, which are generated in solution. It is therefore necessary to characterise not only the structure itself but also the full preparation process with all intermediates. It seems plausible that different thermal treatments of the precursor solutions affect a) the composition of the usually mixed phase catalysts and b) the crystallite sizes of the different constituting phases. Thus, the understanding of the aqueous precursor chemistry is required to control the preparation of such mixed oxide catalysts. Furthermore, subsequent drying and activation procedures from the liquid precursor to the active and selective catalyst are of paramount importance for the development of the optimal catalytic performance. A preparation that is based on understanding of the system would allow precise control of the phase composition of the mixed oxide catalyst, the crystallite size, the crystallinity, and the morphology of the active phase. A developed synthesis routine thus could lead to defined crystallite sizes or even nano-crystalline (MoVW)5O14 mixed oxide catalysts. Moreover, it offers a versatile path to control its elementary composition. Effects of crystallite size / morphology and elemental composition could be studied separately on the catalytic performance. To this end, some steps of the developed aqueous preparation procedure are characterised by in situ micro Raman spectroscopy. The important, subsequent drying process as well as further activation and formation procedures are investigated by in situ Raman spectroscopy, HREM and XRD. Comparison with Raman spectra of well defined, single-crystalline reference oxides [13] can be used to assign the obtained spectra during these catalyst preparation routes to certain oxides, such as MoO2, Mo4O11, Mo8O23, MoO3, or Mo5O14. A different approach is currently carried out to synthesize the MoVW oxide by a Sol gel method. The Sol-gel chemistry is widely used to synthesize metal oxides by inorganic polymerisation of molecular precursors in organic media (alcohols, hydrocarbons). The low synthesis temperatures often lead to the formation of oxides with amorphous or metastable phases, which are not observed using other synthesis routes. The sol-gel synthesis of molybdenum oxides has received little attention, especially in comparison with transition metal oxides such as TiO2, V2O5 and WO3. The overall aim of this work is the rational preparation of molybdenum-based oxides via sol-gel synthesis of alkoxide precursors. The work concentrates on the mechanisms of solid formation from solution by in-situ measurements (Raman and UV-vis) in order to find new synthesis methods for high surface molybdenum oxides