Search results for " dehydration"
showing 10 items of 30 documents
Enhanced (photo)catalytic activity of Wells-Dawson (H6P2W18O62) in comparison to Keggin (H3PW12O40) heteropolyacids for 2-propanol dehydration in gas…
2016
Abstract Catalytic and photocatalytic 2-propanol dehydration to propene at atmospheric pressure and a temperature range of 60–120 °C were carried out in gas-solid regime by using bare and supported Keggin H 3 PW 12 O 40 (PW 12 ) and Wells-Dawson H 6 P 2 W 18 O 62 (P 2 W 18 ) heteropolyacids (HPAs). Binary materials were prepared by impregnation of the HPAs on commercial SiO 2 and TiO 2 . The Wells-Dawson was in any case more active than the Keggin heteropolyacid and the differences were enhanced when the supported samples were used. In particular, Wells-Dawson HPA supported on TiO 2 and under irradiation showed the highest activity. The HPA species played the key role both in the catalytic …
Halogenido ligand exchange synthesis, spectroscopic properties and thermal behaviour of the inorganic–organic hydrogen-bonded network solid [4,4′-H2b…
2014
Abstract Dark-red single crystals of 4,4′-bipyridinium triaquahydrogen(1+) hexabromidorhodate(III) [4,4′-H2bipy][H7O3][RhBr6] (1) have been synthesized by a diffusion-controlled ligand exchange process from rhodium(III) chloride trihydrate and 4,4′-bipyridine dissolved in hydrochloric and hydrobromic acid, respectively. 1 could be considered as an inorganic–organic hydrogen-bonded network solid built up from the inorganic isolated hexabromidorhodate [RhBr6]3− octahedra, organic 4,4′-bipyridinium(2+) [4,4′-H2bipy]2+ and triaquahydrogen(1+) [H7O3]+ cations with nearly symmetrical O⋯O distances. The oppositely charged components in the structure of 1 are bound together by an intricate system o…
Heterogeneous photo-assisted catalytic hydration/dehydration reactions based on Keggin and Wells-Dawson type heteropolytungstates
2021
Polyoxometalates (POMs) are a wide class of metal-oxygen clusters that can be applied in acid and oxidation catalysis, medicine, electrochemistry, materials design, or models for self-assembling nanoscale systems as long as green and cheap photocatalysts. Heteropolyacids (HPAs) are a POM subclass extensively used as homogeneous photocatalysts for the oxidation of organic substrates. Dispersing HPAs onto solid supports with a high surface area increases their specific surface area and hence (photo)catalytic activity. This chapter reports the use of selected HPAs, heteropolytungstates, immobilized on different supports as heterogeneous photocatalysts.
Heteropolyacids supported on boron nitride and carbon nitride for catalytic and catalytic photo-assisted alcohol dehydration
2021
Keggin H3PW12O40 (PW12) and Wells-Dawson H6P2W18O60 (P2W18) heteropolyacids (HPAs) are photo(catalysts) for various acid-promoted and redox catalytic reactions. Their activity increases if they are deposited on certain supports as metal oxides or carbon materials. Although the surface area and acid-base interactions of the HPAs with supports are considered as key factors for the performance of the binary material, the role of the local structure changes in the HPAs upon their immobilization on solids must be also of primary importance, directly affecting both acidity and photoredox properties. Here, the (photo)catalytic performance of Keggin and Wells-Dawson heteropolytungstates supported o…
Physiological engineering of Pseudomonas aurantiaca antimicrobial activity: effects of sodium chloride treatment
2012
The influence of sodium chloride (NaCl) treatment on the antifungal activity of the bacterium Pseudomonas aurantiaca, a producer of biopesticide for vegetable plants, was investigated. It was shown that an increase in the NaCl concentration in incubation solutions from 1 M to 3 M led to a significant increase in the antifungal activity of this bacterium. Antifungal activity continued to increase with prolonged treatment of bacteria in fresh nutrient medium from 72 h to 96 h. These findings could be very important for the further development of biotechnological processes directed not only to the production of new active biopesticides but also of other valuable resources.
Industrial production of dried yeast: plasma membrane as a survival indicator of air drying process
2011
International audience; Preservation of microorganisms by desiccationis a major industrial interest.However, study of cell survival mechanismsthat occur during desiccation is complex. In this work, the impact of the magnitude and the kinetics of dehydration on yeastsurvival wereevaluatedin either hyperosmotic liquid medium or a gaseous environment. Asame lethal magnitude of dehydration and a same lethal kinetic effect were found. As previously shown for osmotic stress, this work demonstrate that yeast survival after drying was also related to plasma membrane disorganization, suggesting a similar passive rearrangement of the membrane components.Hyperosmotic treatment in liquid medium represe…
Mild dehydration: a risk factor of urinary tract infection?
2003
Bacterial growth in the urinary tract is usually prevented by host factors including bacterial eradication by urinary and mucus flow, urothelial bactericidal activity, urinary secretory IgA, and blood group antigens in secretions which interfere with bacterial adherence. Bacterial eradication from the urinary tract is partially dependent on urine flow and voiding frequency. Therefore, it seems logical to postulate a connection between fluid intake and the risk of urinary tract infections (UTIs). However, experimental and clinical data on this subject are conflicting. Experimental studies concerning the effect of water intake on susceptibility and course of UTIs were predominantly performed …
Prediction of mass fluxes in the pervaporation process of the ethanol dehydration, based on the free volume theory
2014
Metodę obliczania współczynników dyfuzji Maxwella-Stefana opartą na współczynnikach dyfuzji własnej przewidywanych wg zależności wynikających z teorii wolnych objętości, zastosowano do obliczania strumieni masy w procesie perwaporacyjnego odwadniania etanolu na membranie z alkoholu poliwinylowego PVA. Parametry metody wolnych objętości dla badanego układu wyznaczono oraz obliczono stężenia równowagowe w PVA stosując zmodyfikowaną metodę UNIFAC-FV a następnie obliczono udziały masowe w permeacie oraz współczynniki wzbogacenia. Obliczenia przeprowadzono dla danych eksperymentalnych opublikowanych w pracy [3]. Wyniki obliczeń porównano z wynikami uzyskanymi na instalacji doświadczalnej.
Vesicle formation in the membrane of onion cells (Allium cepa) during rapid osmotic dehydration
2009
BACKGROUND AND AIMS Optimization of osmotic dehydration in different plant cells has been investigated through the variation of parameters such as the nature of the sugar used, the concentration of osmotic solutions and the processing time. In micro-organisms such as the yeast, Saccharomyces cerevisiae, the exposure of a cell to a slow increase in osmotic pressure preserves cell viability after rehydration, while sudden dehydration involves a lower rate of cell viability, which could be due to membrane vesiculation. The aim of this work is to study cytoplasmic vesicle formation in onion epidermal cells (Allium cepa) as a function of the kinetics of osmotic pressure variation in the external…
Nature of sterols affects plasma membrane behavior and yeast survival during dehydration.
2011
International audience; The plasma membrane (PM) is a main site of injury during osmotic perturbation. Sterols, major lipids of the PM structure in eukaryotes, are thought to play a role in ensuring the stability of the lipid bilayer during physicochemical perturbations. Here, we investigated the relationship between the nature of PM sterols and resistance of the yeast Saccharomyces cerevisiae to hyperosmotic treatment. We compared the responses to osmotic dehydration (viability, sterol quantification, ultrastructure, cell volume, and membrane permeability) in the wild-type (WT) strain and the ergosterol mutant erg6Δ strain. Our main results suggest that the nature of membrane sterols gover…