Showing papers on "Acetone published in 2016"

Partial Oxidation of Alcohols on Visible-Light-Responsive WO3 Photocatalysts Loaded with Palladium Oxide Cocatalyst

Abstract: Particles of tungsten oxide loaded with a palladium oxide cocatalyst (PdOx/WO3) exhibit higher selectivity in comparison to other photocatalysts, such as Pt/WO3, Pd/TiO2, and Pt/TiO2, in the partial oxidation of alcohols such as 2-propanol to the corresponding aldehydes or ketones (e.g., 80% selectivity for acetone production with ca. 96% conversion of 2-propanol) in water containing molecular O2. A detailed investigation of 2-propanol oxidation as a model reaction revealed significant differences between the reactivities of the WO3 and TiO2 systems. On TiO2 photocatalysts, complete decomposition to CO2 proceeded readily, due to the occurrence of direct oxidation of 2-propanol and acetone adsorbed by holes, resulting in significantly low selectivity for partial oxidation. On the other hand, the rates of acetone peroxidation on WO3 photocatalysts were much lower than those on TiO2 due to the low affinity of the WO3 surface to the substrates, particularly acetone. The low affinity of the WO3 surface also en...

One-step selective hydroxylation of benzene to phenol with hydrogen peroxide catalysed by copper complexes incorporated into mesoporous silica–alumina

Abstract: Benzene was hydroxylated with hydrogen peroxide (H2O2) in the presence of catalytic amounts of copper complexes in acetone to yield phenol at 298 K. At higher temperatures, phenol was further hydroxylated with H2O2 by catalysis of copper complexes to yield p-benzoquinone. The kinetic study revealed that the rate was proportional to concentrations of benzene and H2O2, but to the square root of the concentration of a copper(II) complex ([Cu(tmpa)]2+: tmpa = tris(2-pyridylmethyl)amine). The addition of a spin trapping reagent resulted in formation of a spin adduct of hydroperoxyl radical (HO2˙), as observed by EPR spectroscopy, inhibiting phenol formation. HO2˙ produced by the reaction of [Cu(tmpa)]2+ with H2O2 acts as a chain carrier for the radical chain reactions for formation of phenol. When [Cu(tmpa)]2+ was incorporated into mesoporous silica–alumina (Al-MCM-41) by a cation exchange reaction, the selectivity for production of phenol was much enhanced by prevention of hydroxylation of phenol, which was not adsorbed to Al-MCM-41. The high durability with a turnover number of 4320 for the hydroxylation of benzene to phenol with H2O2 was achieved using [Cu(tmpa)]2+ incorporated into Al-MCM-41 as an efficient and selective catalyst.

Acetone Hydrodeoxygenation over Bifunctional Metallic–Acidic Molybdenum Carbide Catalysts

Abstract: Metallic–acidic bifunctionality of molybdenum carbidic catalytic formulations can be tuned by oxygen cofeed and reductive pretreatments to control carbonyl hydrodeoxygenation (HDO). Acetone is deoxygenated over activated Mo2C via sequential hydrogenation of acetone to equilibrium and subsequent dehydration of isopropyl alcohol (IPA). Dehydration to propylene occurs over Bronsted acid sites with an intrinsic activation energy of 103 ± 1 kJ mol–1 and a rate-determining step of β-hydrogen scission, as inferred from a kinetic isotope effect (KIE) of 1.85. HDO rate-determining dehydration rates were kinetically independent of H2 and oxygenate pressure from 10 to 82 kPa and from 0.05 to 4 kPa, respectively. Both the kinetics and the deoxygenation reaction pathway were shown to be similar for the aldehyde group of propanal. Oxygen treatment of activated carbides via 13.5 kPa O2 cofeed was shown to decrease the catalyst surface area from 68 to 9 m2 g–1 and to suppress metallic hydrogenation of acetone to IPA. IPA...

Solubility Measurement and Thermodynamic Modeling of 4-Nitrophthalimide in Twelve Pure Solvents at Elevated Temperatures Ranging from (273.15 to 323.15) K

Abstract: The solubility of 4-nitrophthalimide in different solvents are of great importance for the design of its purification process via crystallization. The work reported new solubility data for 4-nitrophthalimide in 12 pure solvents of methanol, ethanol, isopropanol, cyclohexanone, acetone, acetonitrile, ethyl acetate, 2-butanone, chloroform, 1,4-dioxane benzyl alcohol and N,N-dimethylformamide. They were determined by a high-performance liquid chromatography at T = (273.15 to 323.15) K under pressure of 0.1 MPa. The 4-nitrophthalimide solubility in the selected solvents increased with the temperature increase. At a given temperature, the solubility of 4-nitrophthalimide is largest in N,N-dimethylformamide and lowest in chloroform. The solubility data in the these solvents ranked as N,N-dimethylformamide > cyclohexanone > (1,4-dioxane, acetone, 2-butanone, benzyl alcohol) > ethyl acetate > acetonitrile > methanol > ethanol > isopropanol > chloroform. The experimental solubility data were correlated by modified...

Acetone sensing properties and mechanism of nano-LaFeO3 thick-films

Abstract: LaFeO3 nanocrystalline powders prepared by sol–gel method with annealing at 800 °C for 4 h can sensitively detect low concentration of acetone. When exposed to 0.5 ppm acetone, the response of LaFeO3 thick film at 260 °C is 2.068 with response time of 62 s and recovery time of 107 s, respectively. The possible acetone sensing mechanisms for LaFeO3 sensor are investigated with first principles calculations. Calculated results demonstrate that acetone could release electrons to the surface of LaFeO3 (010) pre-adsorbed with oxygen species O − and O 2 − . The acetone molecule reacts with oxygen species in the following ways: (1) adsorbs on oxygen species O − or (2) replaces of the weakly pre-adsorbed oxygen species O 2 − on Fe site, accompanying the formation of oxygen molecule. These above two processes may play important roles in acetone sensing for LaFeO3. We also find that the acetone molecule can be directly adsorbed on Fe site, transferring some electrons to the LaFeO3 (010) surface. The latter processes may also provide additional contribution to acetone sensing.

The Role of the Hydrogen Source on the Selective Production of γ-Valerolactone and 2-Methyltetrahydrofuran from Levulinic Acid.

Abstract: A mechanistic study of the hydrogenation reaction of levulinic acid (LA) to 2-methyltetrahydrofuyran (MTHF) was performed using three different solvents under reactive H2 and inert N2 atmospheres. Under the applied reaction conditions, catalytic transfer hydrogenation and hydrogenation with molecular H2 were effective at producing high yields of γ-valerolactone. However, the conversion of this stable intermediate to MTHF required the combination of both hydrogen sources (the solvent and the H2 atmosphere) to achieve good yields. The reaction system with 2-propanol as solvent and Ni-Cu/Al2 O3 as catalyst allowed full conversion of LA and a MTHF yield of 80 % after 20 h reaction time at 250 °C and 40 bar of H2 (at room temperature). The system showed the same catalytic activity at LA feed concentrations of 5 and up to 30 wt%, and also when high acetone concentration at the beginning of the reaction were added, which confirmed the potential industrial applications of this solvent/catalyst system.

Aldol condensation of furfural with acetone over ion-exchanged and impregnated potassium BEA zeolites

Abstract: Potassium-containing BEA zeolites were prepared by ion-exchange from NH4-BEA with potassium nitrate aqueous solution or ion-exchange combined with impregnation. The samples were used as basic catalysts for aldol condensation of furfural and acetone studied in a batch reactor at 100 °C, autogenous pressure and a reaction time of 2 h. To establish a relationship between physico-chemical properties and catalytic behavior of BEA zeolites, the samples were characterized by XRD, N2 adsorption, FTIR, calorimetry, and TGA. The ion-exchanged K-BEA catalysts exhibited low activity in the aldol condensation because of a weak strength of intrinsic basic sites. In contrast, the samples prepared by ion exchange combined with impregnation possessed strong basic sites, plausibly K2O clusters, and demonstrated appreciable activity in the aldol condensation. TGA results proved that, in contrast to acidic zeolites, basic sites of impregnated BEA samples hardly contribute to the formation of heavy carbonaceous deposits during the reaction what could be advantageous for the stable behavior of catalysts.

Steam reforming of acetone over Ni- and Co-based catalysts: Effect of the composition of reactants and catalysts on reaction pathways

Abstract: The properties of Ni/Co/Co-Ni/MgAl 2 O 4 catalysts in the steam reforming of acetone (SRA) were investigated regarding the metallic composition and nature of catalytic site. The catalysts were characterized by nitrogen physisorption, X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, and temperature programmed reduction and desorption of acetone. Experimental data revealed that the acetone conversion pathway on the Co, Co-Ni, or Ni catalysts was strongly dependent on the nature of the metal, reaction temperature, and the oxidation state of the metal atoms in nanoparticles surface atoms. Reaction data indicated that the acetone decomposition on reduced metal catalysts at high temperatures (>350 °C) occurred mainly via the H C and C CO bonds cleavage, leading to the formation of CO, H 2 , and C on the metal surface. At low temperatures (200 °C) and in the presence of H 2 in the reactor feed, the Ni catalyst catalyzed the hydrogenation of the CO and CH x species formed from acetone activation on the metallic sites, producing CH 4 . For Co-containing catalysts, at low temperatures (200–350 °C) the metal nanoparticles surface was in a higher oxidation degree and promoted the oxidation of acetone. At high temperatures (>350 °C), the hydrogenation of CH x and CO species to CH 4 was determined by the nanoparticle oxidation degree, which decreased in the order Ni > Co-Ni > Co. With increased temperature, the CH x species decomposed to C and H 2 , instead of being hydrogenated to CH 4 . The oxidation of C by H 2 O was favored on Co-containing catalysts. The reaction pathways are discussed based on theoretical data obtained from the literature.

Production of phenolics via photocatalysis of ball milled lignin–TiO2 mixtures in aqueous suspension

Abstract: In this study, photocatalytic conversion of lignin to valuable phenolics and aromatic hydrocarbons is demonstrated by subjecting ball milled mixtures of lignin and TiO2 to ultraviolet (UV) radiation. Unlike a majority of the existing studies that reported photocatalytic degradation of lignin that is solubilized in alkaline medium, this study evaluates the decomposition of lignin under natural conditions in aqueous medium. In order to facilitate better contact between lignin and nano-TiO2, the two materials were ball milled in the presence of different media, viz. without solvent, hexane, acetone and water. The ball milled mixtures were characterized using powder XRD, FT-IR and photoluminescence spectroscopy, and scanning electron microscopy. Intimate contact between lignin and TiO2 was achieved using water and acetone as the solvents in wet milling. Photocatalysis experiments were conducted in a batch photoreactor. The aqueous phase products were analyzed using UV-visible spectroscopy, MALDI-TOF and GC mass spectrometry, while the molecular weight of solid lignin was analyzed using GPC. Ball milling resulted in the formation of phenolic compounds even during dark mixing of the mixtures prior to photocatalysis. Ball milled mixtures obtained using acetone and water resulted in a high yield of phenolic compounds after 3–4 hours of UV exposure. At long UV exposure periods, the phenolics production got saturated, possibly due to the deactivation of TiO2 active sites by the intermediates. The main organic compounds produced during photocatalysis include ethyl benzene, acetovanillone, syringaldehyde, acetosyringone, vanillin, 2,6-dimethoxy benzoquinone and diisobutyl phthalate. Free radical depolymerization reactions of lignin mediated by active hydroxyl and superoxide radicals are responsible for the observed products.

Clogging-Free Electrospinning of Polycaprolactone Using Acetic Acid/Acetone Mixture

Abstract: Clogging of polymer at the tip of the needle is a major problem in electrospinning that hinders the continuous electrospinning. A new combination of two environmentally benign solvents, acetone/acetic acid mixture, was investigated to eliminate clogging. Our results show that the use of acetone/acetic acid mixture in the ratio 3:7 as the solvent system completely avoided the clogging.

Mechanistic Origins of Unselective Oxidation Products in the Conversion of Propylene to Acrolein on Bi2Mo3O12

Abstract: A reaction network detailing the formation and consumption of all C1–C3 products of propylene oxidation on Bi2Mo3O12 at 623 K is developed to show that acrolein, acetaldehyde, acetone, and acetic acid are direct oxidation products of propylene while acrylic acid and ethylene are secondary products. Coprocessing acetaldehyde, acetone, acrylic acid, and acetic acid, separately, with propylene, oxygen, and water revealed (i) the existence of overoxidation reactions of acrolein to acrylic acid and ethylene and oxidation pathways from acetone to acetaldehyde and acetic acid, (ii) the promotional effects of water on the synthesis rates of acetaldehyde from acrolein, acetone from propylene, and acetic acid from acetaldehyde and acrylic acid, and (iii) the inhibitory effects of water on the decomposition of acetic acid to COx and acrylic acid to acetaldehyde and ethylene. A kinetic model is developed to quantitatively capture the kinetic behavior of all species using pseudo-first-order rate expressions in the org...

Comparison of Ethanol and Acetone Mixtures for Extraction of Condensed Tannin from Grape Skin

Abstract: Discrepancies in condensed tannin concentrations in grape skin determined by different analytical methods prompted the closer examination of aspects of the methodologies. One of these was the choice of extraction solvent. Condensed tannins were extracted from Shiraz grape skins using a range of aqueous solvent mixtures ranging from zero to 100% acetone and ethanol to examine the relative effectiveness of each solvent mixture and to determine whether different solvent mixtures extracted similar condensed tannin components. Acetone extracted more condensed tannin than ethanol. Mixtures of 50 to 70% acetone were equally effective. The most effective ethanol concentration was 50%. Epicatechin-gallate terminal subunits were not detected by HPLC following acid-catalysed cleavage in any of the extraction solvents. Extension subunit composition was similar between solvents across most mixtures. Polymers were generally shorter in the ethanol extracts than in the acetone extracts. Despite differences in tannin concentration and polymer length, the subunit composition was similar in 50% ethanol and 70% acetone. More tannin and tannins with longer polymer lengths were extracted with 70% acetone than with 50% ethanol. This suggests that all grape skin tannins are similar in composition, varying only in length. Thus, 50% ethanol and 70% acetone would give a fair indication of the grape skin tannin composition extracted into wine. However, both 50% ethanol and 70% acetone may overestimate the amount of tannin that is extracted into wine, as wine typically has a much lower solvent concentration, ranging between 10 and 15% ethanol.

Adsorption of acetone and isopropanol on organic acid modified activated carbons

Abstract: Commercial activated carbon (AC) was modified using formic acid, oxalic acid, and sulfamic acid separately. The effects of the modification on the physicochemical properties of ACs were evaluated using specific surface area and pore distribution, scanning electron microscope, and Fourier transform infrared spectroscopy. After the modification, (i) the BET specific surface area and total pore volume of ACs decreased, (ii) uneven etching trace and white crystal particles were observed on the surface of AC, and (iii) more oxygen-containing functional groups such as O H, C O, C O, and S O were formed on the surface. The effects of the modifications on the adsorption behavior of acetone and isopropanol on ACs at different inlet concentrations were studied from adsorption equilibrium, kinetics, and energy point of view. The results show that the equilibrium adsorption capacity has been greatly improved by the modification of organic acids. The adsorption isotherms of acetone and isopropanol on ACs are well fitted by both Langmuir and Freundlich equations. Characteristic adsorption energy values of acetone and isopropanol slightly increase with increasing of oxygen functional groups on the ACs surface. The adsorption kinetics of acetone and isopropanol on ACs are best described by Bangham kinetics model.

Sequential Extraction and Thermal Dissolution of Baiyinhua Lignite in Isometric CS2/Acetone and Toluene/Methanol Binary Solvents

Abstract: Baiyinhua lignite (BL) was sequentially extracted and thermally dissolved in isometric CS2/acetone and toluene/methanol binary solvents to obtain an extract in isometric CS2/acetone (EICA) and a soluble portion (SP) in isometric toluene/methanol (SPITM). The yields of EICA and SPITM are notably higher than the total extract yield from sequential extraction with CS2 and acetone (or acetone and CS2) and the total SP yield from sequential thermal dissolution in toluene and methanol (or methanol and toluene), indicating that there exists an obvious synergic effect between CS2 and acetone during the extraction and between toluene and methanol during the thermal dissolution. EICA and SPITM mainly consist of hydrocarbons and oxygen-containing organic species, respectively. Little difference in Fourier transform infrared spectroscopy spectra of BL and its extraction residue was observed, while the intensities of absorbances assigned to the phenolic OH, C═O, and C–O/C–O–C groups of the thermal dissolution residue ...

Protein precipitation of diluted samples in SDS-containing buffer with acetone leads to higher protein recovery and reproducibility in comparison with TCA/acetone approach

Abstract: Proteomic approaches are extremely valuable in many fields of research, where mass spectrometry methods have gained an increasing interest, especially because of the ability to perform quantitative analysis. Nonetheless, sample preparation prior to mass spectrometry analysis is of the utmost importance. In this work, two protein precipitation approaches, widely used for cleaning and concentrating protein samples, were tested and compared in very diluted samples solubilized in a strong buffer (containing SDS). The amount of protein recovered after acetone and TCA/acetone precipitation was assessed, as well as the protein identification and relative quantification by SWATH-MS yields were compared with the results from the same sample without precipitation. From this study, it was possible to conclude that in the case of diluted samples in denaturing buffers, the use of cold acetone as precipitation protocol is more favourable than the use of TCA/acetone in terms of reproducibility in protein recovery and number of identified and quantified proteins. Furthermore, the reproducibility in relative quantification of the proteins is even higher in samples precipitated with acetone compared with the original sample.