Search results for " dehydration"

Photocatalytic Gas-Solid Propene Hydration and Liquid-Solid Glycerol Dehydration by using Keggin Heteropolyacids Supported on TiO2

2015

Photo)catalytic propylene hydration to 2-propanol and glycerol dehydration to acrolein reactions were carried out by using Keggin heteropolyacids (HPAs) supported on TiO2. Binary materials have been prepared by impregnation of H3PW12O40, H3PMo12O40 and H4SiW12O40, on TiO2 Evonik P25. Moreover, a binary material consisting of H4SiW12O40 and TiO2 was prepared via a hydrothermal treatment and tested for the same reactions. All the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with energy dispersive X-rayand (EDX) measurements, diffuse reflectance spectroscopy (DRS), Raman spectroscopy and Fourier transform infrared spectroscopy…

Propan-2-ol dehydration on H-ZSM-5 and H-Y zeolite: a DFT study

2012

The catalytic dehydration of propan-2-ol over H-Y and H-ZMS-5 aluminated zeolite models, mimicking both internal cavities and external surfaces, was studied by DFT calculations to investigate the reaction mechanism. After the adsorption of propan-2-ol on the zeolite, the dehydration mechanism starts with alcohol protonation, occurring by one acidic –OH group of the zeolite fragment, followed by a concerted β-elimination to give propene. The catalytic activity is affected by the size of the zeolite cavity, which is larger in the H-Y than in the H-ZMS-5 zeolite. The adsorption energy of the reagent, as an example, decreases in the order: H-Y cavity ≃ H-ZMS-5 surface > H-ZMS-5 cavity, pointing…

Keggin and Wells-Dawson supported heteropolyacids as heterogeneous (photo)catalysts for gas-solid 2-propanol dehydration

2016

Catalytic and photocatalytic tests for 2-propanol dehydration to propene were successfully carried out by using binary materials obtained by supporting a Keggin or Wells-Dawson heteropolyacids via impregnation method to commercial SiO2 or TiO2. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regime by using a continuous (photo)reactor working at atmospheric pressure and 80 °C. Propene and diisopropyl ether were the main reaction products. For the continuous photo-assisted runs the reactor was also illuminated with UV light. The heteropolyacid species played a key role both for the catalytic and the photo-assisted catalytic reactions; indicating that the acidity of the clust…

Heteropolyacids supported on C3N4 and BN: Comparison between catalytic and photocatalytic alcohol dehydration

Qualitative and quantitative characterization of the in vitro dehydration process of hydrogel contact lenses

2007

Purpose: To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel contact lens materials. Methods: Eight conventional hydrogel and five silicone-hydrogel contact lenses were dehydrated under controlled environmental conditions on an analytical balance. Data were taken at 1-min intervals and dehydration curves of cumulative dehydration (CD), valid dehydration (VD), and dehydration rate (DR) were obtained. Several quantitative descriptors of the dehydration process were obtained by further processing of the information. Results: Duration of phase I (r 2 5 0.921), CD at end of phase I (r 2 5 0.971), time to achieve a DR of � 1%/min (r 2 5 0.946) were stron…

Dehydration of Fructose to 5-HMF over Acidic TiO2 Catalysts

2020

Different solid sulfonic titania-based catalysts were investigated for the hydrothermal dehydration of fructose to 5-hydroxymethylfurfural (5-HMF). The catalytic behavior of the materials was evaluated in terms of fructose conversion and selectivity to 5-HMF. The surface and structural properties of the catalysts were investigated by means of X-ray diffraction (XRD), N2 adsorption isotherms, thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and acid capacity measurements. Special attention was focused on the reaction conditions, both in terms of 5-HMF selectivity and the sustainability of the process, choosing water as the solvent. Among the various process condition…

Supported Poly(Ionic Liquid)-Heteropolyacid Based Materials for Heterogeneous Catalytic Fructose Dehydration in Aqueous Medium

2022

Two sets of four different supported catalyst materials were prepared. One set was obtained by polymerization of a bis-vinylimidazolium salt, which formed a poly(ionic liquid) coating on SiO2, TiO2, boron nitride BN, and carbon nitride C3N4. The other set was, instead, obtained by immobilizing Keggin heteropolyacid H3PW12O40 onto poly-imidazolium functionalized materials. All the catalysts, including the bare supports, were subjected to physical and chemical characterization by XRD, SEM, Specific Surface Area and pore size measurements, TGA, FTIR, and acidity-basicity measurements. The catalytic activity of the materials was tested versus the fructose dehydration in water solution at two di…

Influence of different dehydration levels on volatile profiles, phenolic contents and skin hardness of alkaline pre-treated grapes cv Muscat of Alexa…

2020

A dehydration experiment was carried out on Vitis vinifera L. cv Muscat of Alexandria (synonym Zibibbo) following the process for the production of renowned special dessert wines produced on Pantelleria island (Sicily, Italy). Harvested berries were pre-treated in a sodium hydroxide dipping solution (45 g/L, dipped for 185 s, 25 &deg

Propan-2-ol dehydration on acidic zeolite fragments: a DFT study

2008

Cryopreservation of Hazelnut (Corylus avellana L.) Axillary Buds from In Vitro Shoots Using the Droplet Vitrification Method

2021

Cryopreservation by droplet vitrification was applied to hazelnut (Corylus avellana L.). axillary buds of the Italian cultivated variety Tonda Gentile Romana, which were collected from in vitro growing shoots, immersed in ice cooled PVS2 or PVS3 for 60 or 90 min, then transferred to a droplet of vitrification solution, placed on a strip of aluminium foil, and plunged into liquid nitrogen (LN). Additionally, the effect on the recovery of the mother plant after cryopreservation was evaluated, following a cold pre-treatment at 4 °C for 3 months. The highest regrowth percentage (56.7%) was obtained after applying PVS3 for 60 min, while the application of PVS2 for the same amount of time reduced…