Analysis of changes in gingiva-occlusal parameters as perceived by three Middle-East population.

Purpose. This study aims to compare the effect of various smile parameters (buccal corridor, gummy smile, midline to face discrepancy, with and without upper lip filling) on the perception of smile attractiveness by applying the digital modification of images judged by laypersons from different Middle East populations. Materials and Methods. One hundred and eighty participants are divided into 3 groups (n=60: 30 men and 30 women): Lebanese, Syrian, and Egyptian laypersons. A frontal photo of a woman\u27s smile is manipulated with Photoshop to modify each smile parameter gradually into 3 grades. The total number of smiles assessed is 18. In addition, each evaluator must indicate which feature she or he finds most attractive in a face. Analysis of repeated measures variances followed by univariate analyses and multiple comparisons of Bonferroni are performed. Results: Eyes and smile are the most attractive elements in the face. For midline to face discrepancy, only Lebanese laypeople and Egyptian women prefer the coincidence of the midline to face compared with other positions with significant difference (p value 0.05). Concerning the buccal corridor, its size does not influence smile attractive (p value\u3e 0.05). Upper lip filling affected the perception of smile aesthetics for the midline (for Syrians and Egyptians). Conclusion: Sex and culture affect the perception of the smile attractiveness for certain parameters. Alteration of the buccal corridor does not seem to influence the smile attractiveness. Upper lip filling may be advantageous in some cases and unfavorable in others. Clinical significance: Dentists should take into consideration cultural differences when restoring smile aesthetics

Advances in reforming and partial oxidation of hydrocarbons for hydrogen production and fuel cell applications

One of the most attractive routes for the production of hydrogen or syngas for use in fuel cell applications is the reforming and partial oxidation of hydrocarbons. The use of hydrocarbons in high temperature fuel cells is achieved through either external or internal reforming. Reforming and partial oxidation catalysis to convert hydrocarbons to hydrogen rich syngas plays an important role in fuel processing technology. The current research in the area of reforming and partial oxidation of methane, methanol and ethanol includes catalysts for reforming and oxidation, methods of catalyst synthesis, and the effective utilization of fuel for both external and internal reforming processes. In this paper the recent progress in these areas of research is reviewed along with the reforming of liquid hydrocarbons, from this an overview of the current best performing catalysts for the reforming and partial oxidizing of hydrocarbons for hydrogen production is summarized

Effet de confinement du nickel dans des catalyseurs à base de silice mésoporeuse pour la production de gaz de synthèse par reformage du méthane avec le CO2

Although economically and environmentally advantageous, the methane dry reforming process using supported nickel based catalysts still faces problems of active phase (a transition metal) sintering and of carbon deposition, which result in catalytic activity loss. This thesis is focused on the study of the confinement effect of nickel in mesoporous silica-based catalysts for syngas production by reforming of methane with CO2. In this study, the samples were characterized by N2 sorption, XRD, TEM/SEM, TPR, in addition to Raman, XPS, TPH/MS, TGA/MS for the spent catalysts. The results indicate that a well-structured mesoporous support with high surface area and large pore volume is important for better dispersion and stabilization of the active phase inside the porosity. The mesoporous SBA-15 silica support (prepared in large quantity), composed of elongated grains, appear to be suitable for the purpose. Moreover, it is demonstrated that the formation of small nickel particles well-confined inside the pores favors carbon resistance. This can be achieved by applying hydrothermal treatment to the support, using two solvents method for Ni deposition, using direct reduction of uncalcined samples, adding Rh in small quantities or promoting with Ce, provided that Ni and Ce are in interaction.Malgré ses avantages économiques et environnementaux, le procédé de reformage à sec du méthane sur des catalyseurs au nickel supporté se heurte encore à des problèmes de frittage de la phase active (un métal de transition) et de dépôt de carbone, ce qui entraîne une diminution de l'activité catalytique. Cette thèse porte sur l'étude de l'effet de confinement du nickel dans des catalyseurs à base de silice mésoporeuse pour la production de gaz de synthèse par reformage du méthane par le CO2. Dans cette étude, les échantillons ont été caractérisés par physisorption de N2, DRX, MET/MEB, RTP, et, en plus, par Raman, SPX, HTP/SM, ATG/SM pour les catalyseurs après test catalytique. Les résultats montrent qu'un support mésoporeux bien structuré ayant une grande surface spécifique et un grand volume poreux est important pour une meilleure dispersion et stabilisation de la phase active à l'intérieur de la porosité. La silice mésoporeuse de SBA-15 (préparée en grande quantité), composée de grains allongés, semble être appropriée pour atteindre cet objectif. Il est de plus démontré que la formation de petites particules bien confinées à l'intérieur des pores favorise la résistance au dépôt de carbone. Ceci peut être obtenu en imposant un traitement hydrothermal au support, en utilisant la méthode deux solvants pour le dépôt de Ni, en passant à une réduction directe des échantillons non calcinés, en ajoutant du Rh en faibles quantités ou en utilisant du Ce comme promoteur, à condition que le Ni et Ce soient en interaction

Effet de l'ordre d'ajout du Ni et du Ce dans SBA-15 sur l'activité en reformage à sec du methane

International audienceDry reforming of methane has been carried out on SBA-15 catalysts containing 5 wt% Ni and 6 wt% Ce. The effect of the order of Ni and Ce impregnation on the catalytic activity has been studied. Both metals were added using the “two-solvent” method that favors metal dispersion inside the pores. Characterizations by XRD (low and high angles), N2 sorption, SEM and TEM of the materials after metal addition and calcination indicate good preservation of the porosities and high NiO and CeO2 dispersion inside the porous channels. Reduction was carried out before the catalytic tests and followed by TPR measurements. The most active reduced catalyst was the Ni–Ce/SBA-15 sample prepared by impregnating cerium first, then nickel. All catalysts were highly active and selective towards H2 and CO at atmospheric pressure. Full CH4 conversion was obtained below 650 °C. The higher performances compared to those reported in the literature for mesoporous silica with supported Ni and Ce catalysts are discussed.Le reformage à sec du méthane a été étudié sur des catalyseurs SBA-15 contenant 5 % en poids de Ni et 6 % en poids de Ce. L’effet de l’ordre d’imprégnation de Ni et Ce sur l’activité catalytique a été étudié. Ces deux métaux ont été ajoutés en utilisant la méthode « à deux solvants », qui favorise la dispersion du métal à l’intérieur des pores. Les caractérisations par DRX (petits et grands angles), adsorption de N2, MEB et MET des matériaux après ajout du métal et calcination montrent une bonne préservation de la porosité et une grande dispersion des nanoparticules de NiO et CeO2 à l’intérieur des pores. La réduction des catalyseurs suivie par RTP a été effectuée avant tests catalytiques. Le catalyseur le plus actif est le Ni–Ce/SBA-15 réduit, préparé par imprégnation, tout d’abord du cérium, puis du nickel. Les catalyseurs étaient très actifs et sélectifs en H2 et CO sous pression atmosphérique, avec une conversion complète de CH4 atteinte avant 650 °C. Les performances supérieures à celles décrites dans la littérature pour des catalyseurs à base de silice mésoporeuse contenant du Ni et du Ce sont discutées

Effect of pore geometry of mesoporous supports on catalytic performances in methane reforming

Catalysts prepared using three dimensional SBA-16 silica support (composed of micropores and cage-like mesopores) were tested in the reaction of methane dry reforming, in comparison with 2D hexagonal mesoporous SBA-15 support. The samples were evaluated by N2 sorption and X-Ray diffraction (XRD) for the assessment of their textural and structural properties. The reducibility was characterized by temperature programmed reduction (TPR). The catalytic performances were evaluated in methane dry reforming and spent catalysts (after reaction) were characterized for the evaluation of sintering and coke formation by TPH/MS, XRD and HR-TEM

Effect of pore geometry of mesoporous supports on catalytic performances in methane reforming

Catalysts prepared using three dimensional SBA-16 silica support (composed of micropores and cage-like mesopores) were tested in the reaction of methane dry reforming, in comparison with 2D hexagonal mesoporous SBA-15 support. The samples were evaluated by N2 sorption and X-Ray diffraction (XRD) for the assessment of their textural and structural properties. The reducibility was characterized by temperature programmed reduction (TPR). The catalytic performances were evaluated in methane dry reforming and spent catalysts (after reaction) were characterized for the evaluation of sintering and coke formation by TPH/MS, XRD and HR-TEM

Low temperature dry reforming of methane on rhodium and cobalt based catalysts: active phase stabilization by confinement in the mesoporous SBA-15

International audienceTwo silica supports either non porous (SiO2) or mesoporous (SBA-15) were impregnated with cobalt (12 wt%) in order to study the confinement effect on catalytic performances in dry reforming of methane. Further increase of activity was obtained by adding small amounts of rhodium (0.2 and 0.5 wt%) to the Co/SBA-15 catalyst. The structural and morphological properties of the calcined samples were characterized by N2 sorption, X-ray diffraction and high-resolution transmission electron microscopy (ultra-thin sections). Their reducibility was studied by temperature-programmed reduction. After in situ reduction of the materials, their catalytic activity was tested in dry reforming of methane up to 800 °C followed by stability testing at 550 °C for 550 minutes. Cobalt confinement in the mesopores of SBA-15 is shown to be highly beneficial towards not only activity but also stability, the reduced nanoparticles being then more resistant against sintering under stream. Rh plays a role as an additional active phase. It also strongly favors cobalt stabilization in the mesopores by permitting its reduction at a much lower temperature, which allows avoiding metal migration to the surface of the silica grains. The nature of coke is also shown to depend on rhodium addition, with less amount of carbon gamma (graphitic and destructive form) formed on the Rh-containing sample compared to the Rh-free Co/SBA-15 catalyst

Mesocellular silica foam-based Ni catalysts for dry reforming of CH4 (by CO2)

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