29 research outputs found
Entwicklung und Anwendung optischer Diagnostiktechniken zur Untersuchung des Effektes der preferentialen Verdampfung von multikomponenten Kraftstoffen unter motorisch-relevanten Bedingungen
A non-intrusive quantitative laser-induced
fluorescence (LIF) technique capable of
simultaneously measuring preferential evaporation,
temperature distribution, and fuel-mass
concentration across a multi-component vaporized
spray has been developed and investigated
under engine-relevant conditions. The measurement
technique is based on two-tracer LIF with
single wavelength excitation.
To assess preferential evaporation, a tracer pair
with suitable co-evaporation and spectral properties
was selected based on vapor-liquid equilibrium
calculations representative for gasoline
fuels. Evaporation studies have shown that one
tracer (p-difluorobenzene) co-evaporates with
the high-to-medium-volatility end of the multicomponent
fuel while the other (1-methylnaphthalene)
co-evaporates with the low-volatility
end. For quantitative measurements the photophysical
properties of both tracers (each tracer
separately and the combined tracers) were determined
under a wide range of pressure, temperature,
and bath-gas composition conditions. 1-
Methylnaphthalene LIF shows a strong red-shift
with temperature which enables measurements
of the temperature distribution across the spray.
Spray evaporation and vapor mixing experiments
were performed in a high-pressure hightemperature
vessel capable of simulating in-cylinder
conditions. An ECN Spray-G and a
piezo-electric outward opening injector were
used in this study. Initial measurements were carried
out with each tracer added separately to the
fuel to assess signal cross-talk and to determine
the best tracer concentrations. Once the proportions
were determined, accuracy and precision of
the method were calculated from the LIF-signal
ratio of spray images within identical spectral
bands. Temperature fields, obtained by two-color
1-methylnaphthalene LIF and derived from fuel
concentration maps based on the assumption of
adiabatic evaporation, were examined for inhomogeneities
in the area of interest since fluctuations
potentially influence the two-color method.
It was shown that the temperature is homogeneous
in the measurement volume.
To localize preferential evaporation, two-color
two-tracer LIF images were evaluated. Taking
into account the measurement accuracy and precision,
variations in the spatial distribution of the
fuel volatility classes were observed for 550â600
K. At higher temperatures, the effect is less pronounced,
which is consistent with the fact that
evaporation is faster. The localization of preferential
evaporation varied with each injector used
indicating the impact of injector nozzle geometry
and jet structure on mixture formationEine berĂŒhrungsfreies quantitatives
Verfahren auf Basis von laserinduzierter Fluoreszenz
(LIF) wurde entwickelt, um simultan
prÀferenzielle Verdampfung, Temperaturverteilung
und Kraftstoffkonzentration im verdampften
Bereich eines Mehrkomponenten-Kraftstoffsprays
unter motorrelevanten Bedingungen
zu messen. Verfahren beruht auf Zwei-tracerLIF
mit Anregung mit einem Laser.
Es wurde ein Tracer-Paar mit geeigneten
Verdampfungs- und spektralen Eigenschaften
auf Basis von Dampf-FlĂŒssigkeitsGleichgewichtsrechnungen
fĂŒr Otto-Kraftstoffe
ausgewÀhlt. Verdampfungsmessungen haben
gezeigt, dass ein Tracer (p-Difluorbenzol)
gleichzeitig mit dem mittel- und höherflĂŒchtigen
Siedeklassen verdampft, wÀhrend der andere (1-
Methylnaphthalin) den schwerflĂŒchtigen Komponenten
folgt. FĂŒr quantitative Messungen
wurden die photophysikalischen Eigenschaften
beider Tracer (einzeln und als Kombination) in
einem weiten Bereich von Druck, Temperatur
und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF
zeigt eine starke Rotverschiebung
mit der Temperatur, die Messungen der
Temperaturverteilung ermöglicht.
Es wurde ein Tracer-Paar mit geeigneten
Verdampfungs- und spektralen Eigenschaften
auf Basis von Dampf-FlĂŒssigkeitsGleichgewichtsrechnungen
fĂŒr Otto-Kraftstoffe
ausgewÀhlt. Verdampfungsmessungen haben
gezeigt, dass ein Tracer (p-Difluorbenzol)
gleichzeitig mit dem mittel- und höherflĂŒchtigen
Siedeklassen verdampft, wÀhrend der andere (1-
Methylnaphthalin) den schwerflĂŒchtigen Komponenten
folgt. FĂŒr quantitative Messungen
wurden die photophysikalischen Eigenschaften
beider Tracer (einzeln und als Kombination) in
einem weiten Bereich von Druck, Temperatur
und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF
zeigt eine starke Rotverschiebung
mit der Temperatur, die Messungen der
Temperaturverteilung ermöglicht
Internal and near nozzle measurements of Engine Combustion Network "Spray G" gasoline direct injectors
[EN] Gasoline direct injection (GDI) sprays are complex multiphase flows. When compared to multi-hole diesel sprays, the plumes are closely spaced, and the sprays are more likely to interact. The effects of multi-jet interaction on entrainment and spray targeting can be influenced by small variations in the mass fluxes from the holes, which in turn depend on transients in the needle movement and small-scale details of the internal geometry. In this paper, we present a comprehensive overview of a multi-institutional effort to experimentally characterize the internal geometry and near-nozzle flow of the Engine Combustion Network (ECN) Spray G gasoline injector. In order to develop a complete pictitre of the near-nozzle flow, a standardized setup was shared between facilities. A wide range of techniques were employed, including both X-ray and visible-light diagnostics. The novel aspects of this work include both new experimental measurements, and a comparison of the results across different techniques and facilities. The breadth and depth of the data reveal phenomena which were not apparent from analysis of the individual data sets. We show that plume-to-plume variations in the mass fluxes from the holes can cause large-scale asymmetries in the entrainment field and spray structure. Both internal flow transients and small-scale geometric features can have an effect on the external flow. The sharp turning angle of the flow into the holes also causes an inward vectoring of the plumes relative to the hole drill angle, which increases with time due to entrainment of gas into a low-pressure region between the plumes. These factors increase the likelihood of spray collapse with longer injection durations.The X-ray experiments were performed at the 7-BM and 32-ID beam lines of the APS at Argonne National Laboratory. Use of the APS is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-06CH11357. Research was also performed at the Combustion Research Facility, Sandia National Laboratories, Livermore, California. Sandia National Laboratories is managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy National Nuclear Security Administration under contract DE-NA-0003525.Duke, DJ.; Kastengren, AL.; Matusik, KE.; Swantek, AB.; Powell, CF.; Payri, R.; Vaquerizo, D.... (2017). Internal and near nozzle measurements of Engine Combustion Network "Spray G" gasoline direct injectors. Experimental Thermal and Fluid Science. 88:608-621. https://doi.org/10.1016/j.expthermflusci.2017.07.015S6086218
Effectiveness of Mechanisms and Models of Coordination between Organizations, Agencies and Bodies Providing or Financing Health Services in Humanitarian Crises: A Systematic Review.
BACKGROUND: Effective coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises is required to ensure efficiency of services, avoid duplication, and improve equity. The objective of this review was to assess how, during and after humanitarian crises, different mechanisms and models of coordination between organizations, agencies and bodies providing or financing health services compare in terms of access to health services and health outcomes. METHODS: We registered a protocol for this review in PROSPERO International prospective register of systematic reviews under number PROSPERO2014:CRD42014009267. Eligible studies included randomized and nonrandomized designs, process evaluations and qualitative methods. We electronically searched Medline, PubMed, EMBASE, Cochrane Central Register of Controlled Trials, CINAHL, PsycINFO, and the WHO Global Health Library and websites of relevant organizations. We followed standard systematic review methodology for the selection, data abstraction, and risk of bias assessment. We assessed the quality of evidence using the GRADE approach. RESULTS: Of 14,309 identified citations from databases and organizations' websites, we identified four eligible studies. Two studies used mixed-methods, one used quantitative methods, and one used qualitative methods. The available evidence suggests that information coordination between bodies providing health services in humanitarian crises settings may be effective in improving health systems inputs. There is additional evidence suggesting that management/directive coordination such as the cluster model may improve health system inputs in addition to access to health services. None of the included studies assessed coordination through common representation and framework coordination. The evidence was judged to be of very low quality. CONCLUSION: This systematic review provides evidence of possible effectiveness of information coordination and management/directive coordination between organizations, agencies and bodies providing or financing health services in humanitarian crises. Our findings can inform the research agenda and highlight the need for improving conduct and reporting of research in this field
Développement et exploitation de techniques de diagnostics optiques pour la compréhension de l'évaporation de carburants mufti-composants dans les moteurs essence
Eine berĂŒhrungsfreies quantitatives Verfahren auf Basis von laserinduzierter Fluoreszenz (LIF) wurde entwickelt, um simultan prĂ€ferenzielle Verdampfung, Temperaturverteilung und Kraftstoffkonzentration im verdampften Bereich eines Mehrkomponenten-Kraftstoffsprays unter motorrelevanten Bedingungen zu messen. Verfahren beruht auf Zwei-tracer-LIF mit Anregungmit einem Laser.Es wurde ein Tracer-Paar mit geeigneten Verdampfungs- und spektralen Eigenschaften auf Basis von Dampf-FlĂŒssigkeits-Gleichgewichtsrechnungen fĂŒr Otto-Kraftstoffe ausgewĂ€hlt. Verdampfungsmessungen haben gezeigt, dass ein Tracer (p-Difluorbenzol) gleichzeitig mit dem mittel- und höherflĂŒchtigen Siedeklassen verdampft, wĂ€hrend der andere (1-Methylnaphthalin) den schwerflĂŒchtigen Komponentenfolgt. FĂŒr quantitative Messungen wurden die photophysikalischen Eigenschaften beider Tracer (einzeln und als Kombination) in einem weiten Bereich von Druck, Temperatur und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF zeigt eine starke Rotverschiebung mit der Temperatur, die Messungen der Temperaturverteilung ermöglicht. Es wurde ein Tracer-Paar mit geeigneten Verdampfungs- und spektralen Eigenschaften auf Basis von Dampf-FlĂŒssigkeits-Gleichgewichtsrechnungen fĂŒr Otto-Kraftstoffe ausgewĂ€hlt. Verdampfungsmessungen haben gezeigt, dass ein Tracer (p-Difluorbenzol) gleichzeitig mit dem mittel- und höherflĂŒchtigen Siedeklassen verdampft, wĂ€hrend der andere (1-Methylnaphthalin) den schwerflĂŒchtigen Komponentenfolgt. FĂŒr quantitative Messungen wurden die photophysikalischen Eigenschaften beider Tracer (einzeln und als Kombination) in einem weiten Bereich von Druck, Temperatur und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF zeigt eine starke Rotverschiebungmit der Temperatur, die Messungen der Temperaturverteilung ermöglicht.A non-intrusive quantitative laser-induced fluorescence (LIF) technique capable of simultaneously measuring preferential evaporation, temperature distribution, and fuel-mass concentration across a multi-component vaporized spray has been developed and investigated under engine-relevant conditions. The measurement technique is based on two-tracer LIF with single wavelength excitation.To assess preferential evaporation, a tracer pair with suitable co-evaporation and spectral properties was selected based on vapor-liquid equilibrium calculations repre-sentative for gasoline fuels. Evaporation studies have shown that one tracer (p-difluoro-benzene) co-evaporates with the high-to-medium-volatility end of the multi-component fuel while the other (1-methylnaphthalene) co-evaporates with the low-volatility end. For quantitative measurements the photophysical properties of both tracers (each tracer separately and the combined tracers) were determined under a wide range of pressure, temperature, and bath-gas composition conditions. 1-methylnaphthalene LIF shows a strong red-shift with temperature which enables measurements of the temperature distribution across the spray.Spray evaporation and vapor mixing experiments were performed in a high-pressure high-temperature vessel capable of simulating in-cylinder conditions. An ECN Spray-G and a piezo-electric outward opening injector were used in this study. Initial measure-ments were carried out with each tracer added separately to the fuel to assess signal cross-talk and to determine the best tracer concentrations. Once the proportions were determined, accuracy and precision of the method were determined from the LIF-signal ratio of spray images within identical spectral bands. Temperature fields, obtained by two-color 1-methylnaphthalene LIF and derived from fuel concentration maps based on the assumption of adiabatic evaporation, were examined for inhomogeneities in the area of interest since fluctuations potentially influence the two-color method. It was shown that the temperature is homogeneous in the measurement volume.To localize preferential evaporation, two-color two-tracer LIF images were evaluated. Taking into account the measurement accuracy and precision, variations in the spatial distribution of the fuel volatility classes were observed for 550â600 K. At higher tem-peratures, the effect is less pronounced, which is consistent with the fact that evapora-tion is faster. The localization of preferential evaporation varied with each injector used indicating the impact of injector nozzle geometry and jet structure on mixture formation.Dans le cadre de cette thĂšse, une technique de diagnostic optique a Ă©tĂ© dĂ©veloppĂ©e pour mesurer simultanĂ©ment lâĂ©vaporation diffĂ©rentielle, la distribution de tempĂ©rature, et la concentration massique de fuel dans un jet multi-composant. Cette technique a Ă©tĂ© examinĂ©e dans les conditions dâun moteurs essence. La technique de mesure est basĂ©e sur lâutilisation des deux traceurs excitĂ©s par une seule longueur dâonde.Pour pouvoir examiner lâĂ©vaporation diffĂ©rentielle dâun carburant multi-composant, deux traceurs ont Ă©tĂ© sĂ©lectionnĂ©s : le p-difluorobenzĂšne et le 1-methylnaphtalĂšne. Ces traceurs reproduisent deux types de volatilitĂ© : faible et moyenne Ă Ă©levĂ©e. Les traceurs choisis fluorescent dans deux rĂ©gions spectrales distinctes ce qui rend lâapplication de cette technique possible. Une Ă©tude photophysique a Ă©tĂ© menĂ©e pour caractĂ©riser les deux traceurs, indĂ©pendamment puis en mĂ©lange, pour diffĂ©rentes conditions de pression, tempĂ©rature, et composition du bain gazeux. LâĂ©tude photophysique est essentielle pour pouvoir mesurer quantitativement lâĂ©vaporation diffĂ©rentielle. Les rĂ©sultats photophysiques montrent que le spectre du 1-methylnaphthalĂšne est sensible Ă la tempĂ©rature. Cette caractĂ©ristique permet de mesurer la distribution en tempĂ©rature dans le jet.Les essais ont Ă©tĂ© rĂ©alisĂ©s dans une cellule haute pression / haute tempĂ©rature, ca-pable de simuler les conditions dâun moteur thermique. Des sprays gĂ©nĂ©rĂ©s par un injecteur ECN Spray G et un piĂ©zo-Ă©lectrique dâune ouverture annulaire ont Ă©tĂ© Ă©tudiĂ©s. Des mesures initiales ont Ă©tĂ© menĂ©es avec chaque traceur pour pouvoir fixer la proportion de mĂ©lange des traceurs. La prĂ©cision de la mĂ©thode de mesure a Ă©tĂ© calculĂ©e suivant une configuration de filtres identiques. Ensuite, les champs de tempĂ©-rature calculĂ©s par la LIF et ceux dĂ©terminĂ©s depuis les champs de concentration massique, ont Ă©tĂ© comparĂ©s. Les rĂ©sultats dĂ©montrent que la tempĂ©rature est homo-gĂšne ce qui signifie que les mesures dâĂ©vaporation diffĂ©rentielle nâont pas influencĂ© par la distribution de tempĂ©rature dans le jet.Les images obtenues en dĂ©tectant les signaux depuis le mĂ©lange de traceurs ont permis de localiser lâĂ©vaporation diffĂ©rentielle. Une variation en distribution spatiale des composants est observĂ©e 550â600 K. Cet effet disparaĂźt en augmentant la tempĂ©rature, ce qui explique que lâĂ©vaporation est plus rapide Ă haute tempĂ©rature. La localisation de lâĂ©vaporation diffĂ©rentielle varie avec le type dâinjecteur. La gĂ©omĂ©trie du nez ainsi que la structure du jet a donc un impact sur la formation du mĂ©lange
Mécanismes de formation et mise en forme de cristaux zéolithiques
The present study includes two parts: i) fundamental study of zeolite nucleation-crystal growth mechanism; and ii) preparation of zeolite bodies with controlled interparticle porosity.Thus the first part of the present work deals with the study of the effect of physico-chemical characteristics of initial hydrogel on the nucleation and crystal growth kinetics of zeolite crystals. The obtained data revealed that the concentration of alkali metal hydroxide in the initial system controls the rate of polymerization of the aluminosilicate species, the size of initial gel particles, and the textural properties of the gel. Consequently, the following reaction was to great extent predetermined by the events taking place during mixing the initial reactants.The second part of this work was targeted at the preparation of centimeter-sized zeolite bodies of *BEA- and MFI-type with reduced to minimum inter-particle porosity. A preparation method consisting in assembling of zeolite nanocrystals (with or without a binder) was developed and further optimized. The preformed bodies were subjected to a hydrothermal treatrnent in a fresh zeolite synthesis solution in order to till up the inter-particle porosity. Depending onthe zeolite type, different methods of secondary growth treatrnents were employed. A particular attention has been paid on the study of the binder evolution during the calcination and secondary growth processes.Ce travail de thĂšse inclut deux parties : i) l'Ă©tude fondamentale de la formation de cristaux zĂ©olithiques ; et ii) la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©triques Ă porositĂ© interparticulaire contrĂŽlĂ©e. La premiĂšre partie de ce travail est donc consacrĂ©e Ă l'Ă©tude de l'effet de la microstructure (propriĂ©tĂ©s physiques et texturales) et de la composition chimique du gel sur la vitesse de nuclĂ©ation et la taille des cristaux formĂ©s. Les rĂ©sultats de cette Ă©tude se rĂ©sument par le rĂŽle important que joue la composition du gel (plus particuliĂšrement sa concentration en hydroxyde de cation alcalin) sur le degrĂ© de polymĂ©risation des particules du gel, la dĂ©termination de sa microstructure et par consĂ©quent sur la vitesse de nuclĂ©ation des zĂ©olithes et la taille des cristaux. Les connaissances acquises dans la premiĂšre partie ont Ă©tĂ© utilisĂ©es dans le dĂ©veloppement du deuxiĂšme objective. Notamment, la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©trique de types structuraux *BEA et MFI. Le contrĂŽle post-synthĂšse de la porositĂ© interparticulaire de ces massifs Ă©tait essentiel pour leur utilisation dans des applications bien prĂ©cises. A cette fin, une mĂ©thode en deux Ă©tapes, comportant un assemblage de nanocristaux de zĂ©olithes prĂ©formĂ©s (en prĂ©sence ou en absence d'un liant) puis un traitement de croissance secondaire pour l'Ă©limination de la porositĂ© interparticulaire, a Ă©tĂ© mise en Ćuvre. Plusieurs traitements de croissance secondaire furent Ă©valuĂ©s selon le type de zĂ©olithe Ă©tudiĂ©. Une attention particuliĂšre fut accordĂ©e Ă l'Ă©tude de l'Ă©volution du liant au cours des processus de prĂ©paration et de calcination des massifs zĂ©olithiques
Studies on the formation of zeolite crystals and zeolite macrostructures with controlled interparticle porosity
Ce travail de thĂšse inclut deux parties : i) l'Ă©tude fondamentale de la formation de cristaux zĂ©olithiques ; et ii) la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©triques Ă porositĂ© interparticulaire contrĂŽlĂ©e. La premiĂšre partie de ce travail est donc consacrĂ©e Ă l'Ă©tude de l'effet de la microstructure (propriĂ©tĂ©s physiques et texturales) et de la composition chimique du gel sur la vitesse de nuclĂ©ation et la taille des cristaux formĂ©s. Les rĂ©sultats de cette Ă©tude se rĂ©sument par le rĂŽle important que joue la composition du gel (plus particuliĂšrement sa concentration en hydroxyde de cation alcalin) sur le degrĂ© de polymĂ©risation des particules du gel, la dĂ©termination de sa microstructure et par consĂ©quent sur la vitesse de nuclĂ©ation des zĂ©olithes et la taille des cristaux. Les connaissances acquises dans la premiĂšre partie ont Ă©tĂ© utilisĂ©es dans le dĂ©veloppement du deuxiĂšme objective. Notamment, la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©trique de types structuraux *BEA et MFI. Le contrĂŽle post-synthĂšse de la porositĂ© interparticulaire de ces massifs Ă©tait essentiel pour leur utilisation dans des applications bien prĂ©cises. A cette fin, une mĂ©thode en deux Ă©tapes, comportant un assemblage de nanocristaux de zĂ©olithes prĂ©formĂ©s (en prĂ©sence ou en absence d'un liant) puis un traitement de croissance secondaire pour l'Ă©limination de la porositĂ© interparticulaire, a Ă©tĂ© mise en Ćuvre. Plusieurs traitements de croissance secondaire furent Ă©valuĂ©s selon le type de zĂ©olithe Ă©tudiĂ©. Une attention particuliĂšre fut accordĂ©e Ă l'Ă©tude de l'Ă©volution du liant au cours des processus de prĂ©paration et de calcination des massifs zĂ©olithiques.The present study includes two parts: i) fundamental study of zeolite nucleation-crystal growth mechanism; and ii) preparation of zeolite bodies with controlled interparticle porosity.Thus the first part of the present work deals with the study of the effect of physico-chemical characteristics of initial hydrogel on the nucleation and crystal growth kinetics of zeolite crystals. The obtained data revealed that the concentration of alkali metal hydroxide in the initial system controls the rate of polymerization of the aluminosilicate species, the size of initial gel particles, and the textural properties of the gel. Consequently, the following reaction was to great extent predetermined by the events taking place during mixing the initial reactants.The second part of this work was targeted at the preparation of centimeter-sized zeolite bodies of *BEA- and MFI-type with reduced to minimum inter-particle porosity. A preparation method consisting in assembling of zeolite nanocrystals (with or without a binder) was developed and further optimized. The preformed bodies were subjected to a hydrothermal treatrnent in a fresh zeolite synthesis solution in order to till up the inter-particle porosity. Depending onthe zeolite type, different methods of secondary growth treatrnents were employed. A particular attention has been paid on the study of the binder evolution during the calcination and secondary growth processes
Mécanismes de formation et mise en forme de cristaux zéolithiques
Ce travail de thĂšse inclut deux parties : i) l'Ă©tude fondamentale de la formation de cristaux zĂ©olithiques ; et ii) la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©triques Ă porositĂ© interparticulaire contrĂŽlĂ©e. La premiĂšre partie de ce travail est donc consacrĂ©e Ă l'Ă©tude de l'effet de la microstructure (propriĂ©tĂ©s physiques et texturales) et de la composition chimique du gel sur la vitesse de nuclĂ©ation et la taille des cristaux formĂ©s. Les rĂ©sultats de cette Ă©tude se rĂ©sument par le rĂŽle important que joue la composition du gel (plus particuliĂšrement sa concentration en hydroxyde de cation alcalin) sur le degrĂ© de polymĂ©risation des particules du gel, la dĂ©termination de sa microstructure et par consĂ©quent sur la vitesse de nuclĂ©ation des zĂ©olithes et la taille des cristaux. Les connaissances acquises dans la premiĂšre partie ont Ă©tĂ© utilisĂ©es dans le dĂ©veloppement du deuxiĂšme objective. Notamment, la prĂ©paration de massifs zĂ©olithiques de taille centimĂ©trique de types structuraux *BEA et MFI. Le contrĂŽle post-synthĂšse de la porositĂ© interparticulaire de ces massifs Ă©tait essentiel pour leur utilisation dans des applications bien prĂ©cises. A cette fin, une mĂ©thode en deux Ă©tapes, comportant un assemblage de nanocristaux de zĂ©olithes prĂ©formĂ©s (en prĂ©sence ou en absence d'un liant) puis un traitement de croissance secondaire pour l'Ă©limination de la porositĂ© interparticulaire, a Ă©tĂ© mise en Ćuvre. Plusieurs traitements de croissance secondaire furent Ă©valuĂ©s selon le type de zĂ©olithe Ă©tudiĂ©. Une attention particuliĂšre fut accordĂ©e Ă l'Ă©tude de l'Ă©volution du liant au cours des processus de prĂ©paration et de calcination des massifs zĂ©olithiques.The present study includes two parts: i) fundamental study of zeolite nucleation-crystal growth mechanism; and ii) preparation of zeolite bodies with controlled interparticle porosity.Thus the first part of the present work deals with the study of the effect of physico-chemical characteristics of initial hydrogel on the nucleation and crystal growth kinetics of zeolite crystals. The obtained data revealed that the concentration of alkali metal hydroxide in the initial system controls the rate of polymerization of the aluminosilicate species, the size of initial gel particles, and the textural properties of the gel. Consequently, the following reaction was to great extent predetermined by the events taking place during mixing the initial reactants.The second part of this work was targeted at the preparation of centimeter-sized zeolite bodies of *BEA- and MFI-type with reduced to minimum inter-particle porosity. A preparation method consisting in assembling of zeolite nanocrystals (with or without a binder) was developed and further optimized. The preformed bodies were subjected to a hydrothermal treatrnent in a fresh zeolite synthesis solution in order to till up the inter-particle porosity. Depending onthe zeolite type, different methods of secondary growth treatrnents were employed. A particular attention has been paid on the study of the binder evolution during the calcination and secondary growth processes.MULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF
Influence of alkalinity of the starting system on size and morphology of the zeolite A crystals
International audienc
Micro- to Macroscopic Observations of MnAlPO-5 Nanocrystal Growth in Ionic-Liquid Media
International audienceMicroâ and macroscopic studies of nucleation and growth processes of MnAlPOâ5 nanosized crystals under ionothermal synthesis conditions are reported herein. The samples treated at 150â°C were extracted from the reaction mixture at various stages of crystallization, and characterized by XRD; SEM; thermogravimetric analysis (TGA); 31P and 27Al solidâstate magic angle spinning (MAS) NMR, Raman, UV/Vis, and Xâray fluorescence spectroscopy (XRF). The starting raw materials (alumina, manganese, and phosphorous) were dissolved completely in the ionic liquid and transformed into an amorphous solid after 5â
h of ionothermal treatment. This amorphous solid then undergoes structural changes over the following 5â25â
h, which result in an intermediate phase that consists of octahedral Al species linked to the manganese and phosphate species. The first MnAlPOâ5 nuclei on the surface of the intermediate can be observed after 50â
h ionoheating. These nuclei further grow, as the surface of the intermediate is in full contact with the ionic liquid, to give crystalline MnAlPOâ5 nanoparticles with a mean diameter of 80â
nm. The crystals become fully detached from the intermediate and are then liberated as discrete particles after 90â
h heating. The transformation process from amorphous to intermediate and then to the crystalline MnAlPOâ5 nanoparticles shows that nucleation starts at the solidâliquid interface and continues through surfaceâtoâcore reversedâgrowth until the entire amorphous solid is transformed into discrete nanocrystals