Potential of thermal analysis in preparation and characterization of solid catalysis

Supported catalysts contain often only small amounts of active component(s) which renders their characterization difficult, particularly because they usually contain a substantial amount of water. Thermal analysis (TA) coupled with mass spectrometry (MS) offers an interesting potential for characterizing such material, various steps of catalyst preparation as well as crucial properties of fresh and used catalysts can be investigated. Some examples illustrating the versatility of TA-MS in catalysis research, such as solid-state reactions occurring upon exposure of the precursors or catalysts to reducing, oxidizing or inert atmosphere, are presented in this study. The combined use of TA and MS allows in many cases a much more detailed interpretation of the observed phenomena than could be achieved by one of these methods alon

Role and distribution of different Ba-containing phases in supported Pt-Ba NSR catalysts

Pt-Ba/MeO (where MeO=Al2O3, CeO2, SiO2 and ZrO2) NO x storage-reduction catalysts with Ba-loading varying from 0wt.% to 28wt.% were investigated concerning stability of Ba phases and NO x storage-reduction efficiency. For Pt-Ba/Al2O3 three different Ba-containing phases with different thermal stability are distinguished based on their interaction with the support. The relative concentration of these phases varies with the Ba-loading and NO x storage tests indicated that the BaCO3 phase decomposing between 400°C and 800°C (LT-BaCO3) is the most efficient Ba containing phase for NO x storage. Similar investigations of Pt-Ba catalysts supported on CeO2, SiO2 and ZrO2 showed that the relative amount of LT-BaCO3 phase depends also on the support material. NO x storage measurements confirmed a correlation between the concentration of LT-BaCO3 and NO x storage efficiency. Basicity and textural properties of the support are identified as crucial parameters for efficient NO x storage catalyst

Influenceof measuring conditions on the quantification of spectroscopic signals inTA-FTIR-MS systems

Simultaneous thermal analysis (TA) and evolved gas analysis by mass spectrometry (MS) and/or Fourier transform infrared spectroscopy (FTIR) is a powerful hyphenated technique combining direct measurement of mass loss and sensitive spectroscopic analysis. In the present study the influence of several experimental parameters which may affect the quantification of FTIR signals have been studied using a combined TA-FTIR-MS system. Parameters studied include: sample mass (1-400 mg), carrier gas flow rate (25-200 mL min-1), resolution of the FTIR spectrometer (1-32 cm-1), and location of injection of the calibrating gas. MS analysis, which was not significantly affected by the experimental conditions, was used as a reference for assessing the accuracy of quantification by FTIR. The quantification of the spectroscopic signals was verified by the decomposition (NaHCO3) or dehydration (CuSO4·5H2O) of compounds with well-known stoichiometry. The systematic study of the parametric sensitivity revealed that spectral resolution and carrier gas flow rate, which affect the acquisition time in the IR-cell, are key parameters that must be adjusted carefully for reliable quantification. The dependence of the reliability of quantification on these parameters is illustrated and conditions leading to proper quantification are discussed. As an example, for a standard spectral resolution of 4 cm-1 and a FTIR gas cell volume of 8.7 mL, the carrier gas flow must be lower than 100 mL min-1 for warranting accurate results (relative deviation <2%). The concentration range of analyzed species is limited but can be extended by proper selection of the wavenumber regions for molecules giving strong IR signal

Role of support in lean DeNO x catalysis

FTIR and pulse thermal analysis were applied to investigate catalysts containing Pt (1 wt%)/Ba (17 wt%) supported on γ−Al2O3, SiO2 and ZrO2. The aim was to learn how the support material affects the thermal stability of barium carbonate and its activity in the reaction to bulk Ba(NO3)2. The lower thermal stability of BaCO3 in alumina supported samples was found to influence the formation of barium nitrate during the NO x storage process. Quantification of Ba(NO3)2 formed during NO x storage indicated that for alumina supported catalysts only ca. 30% of barium present in the sample is involved in the storage process. The low thermal stability found for alumina supported barium nitrite excludes its role in the formation of barium nitrate during interaction of NO x with the catalyst at 300°C. The studies indicate that γ-Al2O3 plays a major role in influencing the thermal stability of BaCO3 and Ba(NO3)2. This finding seems to be relevant for the higher activity of γ-Al2O3-supported catalysts in NO x storage reduction reaction

Automated analysis and visualization of preclinical whole-body microCT data

In this thesis, several strategies are presented that aim to facilitate the analysis and visualization of whole-body in vivo data of small animals. Based on the particular challenges for image processing, when dealing with whole-body follow-up data, we addressed several aspects in this thesis. The developed methods are tailored to handle data of subjects with significantly varying posture and address the large tissue heterogeneity of entire animals. In addition, we aim to compensate for lacking tissue contrast by relying on approximation of organs based on an animal atlas. Beyond that, we provide a solution to automate the combination of multimodality, multidimensional data.* Advanced School for Computing and Imaging (ASCI), Delft, NL * Bontius Stichting inz Doelfonds Beeldverwerking, Leiden, NL * Caliper Life Sciences, Hopkinton, USA * Foundation Imago, Oegstgeest, NLUBL - phd migration 201

Restructuring during pretreatment of platinum/alumina for enantioselective hydrogenation

The influence of reductive and oxidative heat treatment on the enantioselectivity of chirally modified Pt/alumina has been reinvestigated, using the hydrogenation of ketopantolactone as a test reaction. Enhancement in ee by 39-49% has been observed after treatment in hydrogen at 250-600°C, as compared to untreated or preoxidized catalysts. The changes in ee after reductive and oxidative treatments are reversible, and always the final treatment is decisive. A HRTEM study indicates that adsorbate‐induced restructuring of Pt crystallites during hydrogen treatment at elevated temperature can play a role in the selectivity improvement, but the changes are superimposed by the strong structure‐directing effect of the alumina support. The possible contribution of other effects (complete reduction of Pt n+ surface species, removal of impurities, or change of Pt particle size) could be exclude

Thermal ageing phenomena and strategies towards reactivation of NO x - storage catalysts

The thermal ageing and reactivation of Ba/CeO2 and Ba/Al2O3 based NO x -storage/ reduction (NSR) catalysts was studied on model catalysts and catalyst systems at the engine. The mixed oxides BaAl2O4 and BaCeO3, which lower the storage activity, are formed during ageing above 850°C and 900°C, respectively. Interestingly, the decomposition of BaCeO3 in an atmosphere containing H2O/NO2 leads again to NO x -storage active species, as evidenced by comparison of fresh, aged and reactivated Pt-Ba/CeO2 based model catalysts. This can be technically exploited, particularly for the Ba/CeO2 catalysts, as reactivation studies on thermally aged Ba/CeO2 and Ba/Al2O3 based NSR catalysts on an engine bench showed. An on-board reactivation procedure is presented, that improved the performance of a thermally aged catalyst significantl

ОБЩИННАЯ ТЕОРИЯ Н.Г.ЧЕРНЫШЕВСКОГО В ИСТОРИОГРАФИИ

Розглядається общинна теорія М.Г.Чернишевского та шляхи її вивчення у дореволюційній та радянській історіоргафії. Вказано на досягнення та вади, які були властиві достідникам цього питання.There is investigated a community theory of N.Cheryshevsky and ways of its studying in prerevolutional and revolutional historiography. There are pointed out faults and achievements of this problem researchers

Neuroaxonal dystrophy in a flock of pied imperial pigeons (Ducula bicolor)

Five juvenile pied imperial pigeons (Ducula bicolor) presented with neurological signs including torticollis, ataxia and poor flying ability. All were humanely destroyed and submitted for post-mortem examination. Microscopically, the most significant findings were in the brain and spinal cord. Spheroid formation was evident within the medulla, pons, diencephalon, cortical grey and subcortical white matter, spinal cord white and grey matter and the granular and molecular cell layers of the cerebellum. There was no evidence of associated inflammation. Immunohistochemistry revealed positive labelling within the spheroids for S100 axons and phosphorylated neurofilaments including SMI31, neurofilament cocktail and microtubule-associated protein 2. Transmission electron microscopy confirmed the light microscopical findings of frequent axonal spheroids. These results are consistent with neuroaxonal dystrophy, which has not been described previously in pigeons. This highlights the importance of considering neuroaxonal dystrophy in juvenile birds with neurological signs. A genetic basis is suspected in this group