Prediction of diffusion coefficients of chlorophenols in water by computer simulation

Intra-diffusion coefficients of seven chlorophenols (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,4,6-dichlorophenol and pentachlorophenol) in water were determined by computer simulation (molecular dynamics) for dilute solutions at three different temperatures and the corresponding mutual diffusion coefficients estimated. The mutual diffusion coefficients of 2-chlorophenol in water agree with the available experimental results from the literature for all the temperatures studied. From the dependence of the diffusion coefficients on temperature, diffusion activation energies were estimated for all the solutes inwater. Analyzing the radial distribution functions and spatial distribution functions of water around chlorophenols sites enable a discussion about intermolecular interactions (dominated by hydrogen bonding) between solute and solvent and its importance on the relative magnitude of diffusion coefficients. Finally the mutual diffusion coefficients obtained by simulation were correlated by the well-known Wilke–Chang equation

Fluorinated surfactants in solution: Diffusion coefficients of fluorinated alcohols in water

Intra-diffusion coefficients of three fluorinated alcohols, 2,2,3,3,3-pentafluoropropan-1-ol (PFP), 2,2,3,3,4,4,4-heptafluorobutan-1-ol (HFB) and 2,2,3,3,4,4,5,5,5-nonafluoropentan-1-ol (NFP) in water have been measured by the PFG–NMR spin-echo technique as a function of temperature and composition, focusing on the alcohol dilute region. For comparison, intra-diffusion coefficients of 2,2,2- trifluoroethanol (TFE) and HFB have also been measured in heavy water using the same method and conditions. As far as we know, these are the first experimental measurements of this property for these binary systems. Intra-diffusion coefficients for NFP in water and for TFE and HFB in heavy water have also been obtained by molecular dynamics simulation, complementing those for TFE, PFP and HFB reported in a previous work. The agreement between experimental and simulated results for PFP, HFB and NFP in water is reasonable, although presenting higher deviations than for the TFE/water system. From the dependence of the intra-diffusion coefficients on temperature, diffusion activation energies were estimated for all the solutes in water and heavy water

Ambipolar Pentacyclic Diamides with Interesting Electrochemical and Optoelectronic Properties

Developing organic semiconductors (OSCs) for organic thin film transistors (OTFT) and optoelectronic applications is a challenge. We developed highly crystalline pentacyclic diamides (3) and (4) which showed good OTFT and OLED potential and energy gaps of 2.60 eV and 2.54 eV. They exhibited interesting photo and eletroluminescence activity. Both compounds showed good quantum yields (0.56 for (3) and 0.6 for (4))

Effect of dietary inclusion of Spirulina on production performance, nutrient digestibility and meat quality traits in post-weaning piglets

The effect of Spirulina (Arthrospira platensis), individually or in combination with two commercial carbohydrases, in piglet diets was assessed on growth performance, nutrient digestibility and meat quality traits. Forty post-weaned male piglets from Large White × Landrace sows crossed with Pietrain boars with an initial live weight of 12.0 ± 0.89 kg were used. Piglets were assigned to one of four dietary treatments (n = 10): cereal and soya bean meal base diet (control), base diet with 10% Spirulina (SP), SP diet supplemented with 0.005% Rovabio® Excel AP (SP + R) and SP diet supplemented with 0.01% lysozyme (SP + L). Animals were slaughtered after a 4-week experimental period. Growth performance was negatively affected by the incorporation of Spirulina in the diets, with an average decrease of 9.1% on final weight, in comparison with control animals. Total tract apparent digestibility (TTAD) of crude protein was higher (p < .05) in the control group than in other groups. In addition, lysozyme increased TTAD of crude fat and acid detergent fibre, relative to the SP and control groups, respectively. In addition, the incorporation of Spirulina, individually and supplemented with enzymes, did not impair meat quality traits. Surprisingly, no protective effect against lipid oxidation was observed with the inclusion of Spirulina in pork after 7 days of storage. This study indicates that growth performance of post-weaning piglets was impaired by the incorporation of 10% Spirulina in the diets, which is mediated by an increase in digesta viscosity and a lower protein digestibility, as a consequence of the resistance of microalga proteins to the action of endogenous peptidases. In addition, it also indicates that lysozyme, in contrast to Rovabio® Excel AP, is efficient in the degradation of Spirulina cell wall in piglet's intestine. However, the digestion of proteins liberated by Spirulina cell wall disruption is still a challengeinfo:eu-repo/semantics/publishedVersio

Encapsulation de nanoparticules en cristaux creux de zéolithe Beta

Hollow zeolite single crystals have received particular interest in catalysis. The presence of a large cavity in these model zeolites enables the study of diffusional limitation in Catalysis. The cavity also enables the encapsulation of metal nanoparticles. However, their synthesis requires specific structural characteristics and it has been limited for long to zeolites with the MFI structure. The objective of this PhD work was to investigate the synthesis of hollow Beta zeolites (*BEA framework type) and study the impact of the hollow morphology on molecular diffusion and catalysis. Two different strategies have been envisaged: a dissolution/recrystallization approach using CIT-6, a zincosilicate with the same *BEA topology and a selective desilication route. Pt nanoparticles encapsulated in hollow crystals obtained from CIT-6 showed remarkable size-selectivity in the hydrogenation of aromatics. The effect of the hollow morphology in molecular diffusion was studied using the ZLC technique; the characteristic diffusion time of the hollow morphology was reduced by 30-83% compared to the corresponding bulk zeolite. Despite that, the hollow structure had no influence on the catalytic activities for the hydroisomerization of n-C16 and for the cracking of cyclohexane. The presence/absence of diffusional limitation is discussedDe par leur morphologie, les cristaux creux de zéolithe permettent d’étudier les phénomènes de limitations diffusionnelles en catalyse et également d’encapsuler des particules métalliques ; les nano-réacteurs ainsi obtenus ont montré des activités catalytiques originales. Leur synthèse, qui nécessite des caractéristiques structurales particulières, a longtemps été limitée aux zéolithes de structure MFI. Le but de cette thèse était d’étudier différentes voies de synthèse pour préparer des cristaux creux de zéolithe Beta, une des zéolithes les plus utilisées dans l’industrie. Deux voies ont été suivies : l’utilisation d’un zincosilicate de même structure que la zéolithe Beta comme gabarit sacrificiel et une méthode plus classique de désilication sélective. L’encapsulation de nanoparticules de platine dans les cristaux obtenus selon la première voie a été confirmée par l’hydrogénation d’aromatiques substitués. L’’influence de la morphologie sur la diffusion de différentes molécules a été étudiée par ZLC : le temps caractéristique de diffusion a été réduit de 30 à 83 % par rapport à des cristaux conventionnels. Malgré cela, la présence d’une cavité dans les cristaux de zéolithe Beta n’a pas d’effets sur l’activité catalytique dans les réactions d’hydro-isomérisation du nC16 et du craquage du cyclohexane. La thèse discute de la présence/absence de limitations diffusionnelle

Encapsulation de nanoparticules en cristaux creux de zéolithe Beta

Hollow zeolite single crystals have received particular interest in catalysis. The presence of a large cavity in these model zeolites enables the study of diffusional limitation in Catalysis. The cavity also enables the encapsulation of metal nanoparticles. However, their synthesis requires specific structural characteristics and it has been limited for long to zeolites with the MFI structure. The objective of this PhD work was to investigate the synthesis of hollow Beta zeolites (*BEA framework type) and study the impact of the hollow morphology on molecular diffusion and catalysis. Two different strategies have been envisaged: a dissolution/recrystallization approach using CIT-6, a zincosilicate with the same *BEA topology and a selective desilication route. Pt nanoparticles encapsulated in hollow crystals obtained from CIT-6 showed remarkable size-selectivity in the hydrogenation of aromatics. The effect of the hollow morphology in molecular diffusion was studied using the ZLC technique; the characteristic diffusion time of the hollow morphology was reduced by 30-83% compared to the corresponding bulk zeolite. Despite that, the hollow structure had no influence on the catalytic activities for the hydroisomerization of n-C16 and for the cracking of cyclohexane. The presence/absence of diffusional limitation is discussedDe par leur morphologie, les cristaux creux de zéolithe permettent d’étudier les phénomènes de limitations diffusionnelles en catalyse et également d’encapsuler des particules métalliques ; les nano-réacteurs ainsi obtenus ont montré des activités catalytiques originales. Leur synthèse, qui nécessite des caractéristiques structurales particulières, a longtemps été limitée aux zéolithes de structure MFI. Le but de cette thèse était d’étudier différentes voies de synthèse pour préparer des cristaux creux de zéolithe Beta, une des zéolithes les plus utilisées dans l’industrie. Deux voies ont été suivies : l’utilisation d’un zincosilicate de même structure que la zéolithe Beta comme gabarit sacrificiel et une méthode plus classique de désilication sélective. L’encapsulation de nanoparticules de platine dans les cristaux obtenus selon la première voie a été confirmée par l’hydrogénation d’aromatiques substitués. L’’influence de la morphologie sur la diffusion de différentes molécules a été étudiée par ZLC : le temps caractéristique de diffusion a été réduit de 30 à 83 % par rapport à des cristaux conventionnels. Malgré cela, la présence d’une cavité dans les cristaux de zéolithe Beta n’a pas d’effets sur l’activité catalytique dans les réactions d’hydro-isomérisation du nC16 et du craquage du cyclohexane. La thèse discute de la présence/absence de limitations diffusionnelle

Faster transport in hollow zeolites

Nano-zeolites and hierarchical zeolites have shown enhanced transport properties that are generally attributed to a shorter diffusion path length (L). However, the concomitant increase in the external surface of these types of zeolites may also affect overall transport as the interfaces may act as diffusion barriers. Recently, hollow zeolite crystals have been presented as an alternative zeolite morphology. They possess a large inner cavity and an overall size and shape similar to those of plain microporous zeolite. In contrast to classic hierarchical zeolite materials, the inner cavity of the hollow zeolite induces a shortened diffusion path length with no effect on external surface area. In this work, we have studied the impact of diffusion path length on transport properties by comparing the characteristic time of transport of hydrocarbons in plain zeolite crystals and their hollow counterparts, using zero-length column (ZLC) measurements. Our results show that hollow morphology doubles or quadruples the transport speed for Silicalite-1 and Beta zeolites, respectively. Compared to other reports focusing on nanosized or hierarchical zeolites, this study is free of any bias due to major modifications in external surface area, because hollow and plain zeolites have very similar crystal dimensions