Showing papers on "Acetone published in 2003"

Catalytic activity of LaMnO3 and LaCoO3 perovskites towards VOCs combustion

Abstract: The catalytic combustion of some volatile organic compounds (VOCs) has been investigated over LaMnO3 and LaCoO3 perovskite-type oxides. Redox titration has shown that cobalt is present in LaCoO3 exclusively in the 3+ oxidation state whereas LaMnO3 contains considerable amount of Mn4+ (35%) in addition to Mn3+. VOCs reactivity towards total oxidation follows the trend: acetone > isopropanol > benzene. The oxidation of isopropanol occurs through the formation of acetone in the homogeneous reaction. The increase of the oxygen partial pressure is beneficial for total oxidation of acetone. The adsorptive properties of the catalysts towards the VOCs and H2 have been examined by means of temperature programmed desorption. The LaMnO3 surface is the most reactive to the adsorption of VOCs and H2. The role of the adsorbed oxygen has been studied by examining the variations of the electrical conductivity of the catalysts during the processes of oxygen adsorption–desorption.

General study of catalytic oxidation of various VOCs over La0.8Sr0.2MnO3+x perovskite catalyst—influence of mixture

Abstract: The catalytic oxidation of volatile organic compounds (VOCs) with different functional groups: propane, propene, hexane, cyclohexane, methylcyclohexane, benzene, toluene, ethanol, propan-2-ol, propanal, acetone, ethyl acetate, isopropyl acetate, MEK are studied, individually or in two-component mixtures over La 0.8 Sr 0.2 MnO 3+ x perovskite in air. Total conversion to CO 2 and H 2 O occurs at temperature below 623 K. However, some by-products are detected in the flue gas, especially during the oxy-derivative compounds oxidation. For the mixtures, the comportment of the VOCs is modified. A “mixture effect” is observed depending on the composition of the mixture.

Oxide-catalyzed conversion of acetic acid into acetone: an FTIR spectroscopic investigation

Abstract: Adsorptive and catalytic interactions of gas phase acetic acid with surfaces of alumina, titania and ceria were observed by in situ Fourier-transform infrared (FTIR) spectroscopy on heating from room temperature up to 400 °C. The results revealed that, on alumina the acid was irreversibly, non-dissociatively adsorbed in the form of hydrogen-bonded molecules, and dissociatively in the form of bidentate bound acetate species over the full range of temperature scanned. In the gas phase, no chemical change was observed. On titania, the gas phase remained unchanged on heating up to 300 °C, but at 400 °C the acetic acid was largely converted into acetone (as well as CO 2 and H 2 O) and minor products of isobutene and methane. Similar changes to the gas phase were observed on ceria, however, at 300 °C. The acetic acid conversion on ceria was almost complete. The appearance of acetone molecules in the gas phase was pertained by the emergence of IR absorptions implying the formation on the surface of unsaturated carbonyl species. Thus, the formation of these surface species, together with isobutene and CH 4 molecules in the gas phase, was considered consequent to the occurrence of further surface reactions of acetone molecules. Observance of structural and chemical stability of the surface and bulk of TiO 2 and CeO 2 throughout the reaction was taken to emphasize the catalytic nature of the acetic acid conversion into acetone in the gas phase, a process that is evidently more simple and economic than the conventional pyrolytic synthesis of acetone from metal acetate compounds in the solid state. The catalytic sites were suggested to be Lewis acid–base pair sites, with the Lewis acid sites (Ti 4+ or Ce 4+ ) being reducible. Mechanistic pathways were proposed for the observed adsorptive and catalytic interactions of acetic acid molecules on the test oxides.

Photocatalytic oxidation of ketones in the gas phase over TiO2 thin films: a kinetic study on the influence of water vapor

Abstract: Photocatalytic oxidation of two ketones having different hydrophilicity, acetone and methyl isobutyl ketone (MIBK), over TiO2 thin films supported on glass rings was studied under different relative humidity (RH) conditions. Adsorption isotherms of both ketones in the dark under different concentrations of water vapor were also measured and modeled considering a two-site Langmuir model. As expected, an increase in RH resulted in a decrease in the surface concentration of the organic molecules, but the photocatalytic oxidation rates did not show a parallel variation. In the case of acetone, almost total mineralization was achieved, and the kinetic constants obtained from fitting the data to the Langmuir–Hinselwood–Hougen–Watson (LHHW) model, were significantly larger in the presence of water vapor. Photocatalytic elimination of methyl isobutyl ketone (MIBK) is proposed to take place simultaneously by a direct oxidation route and by a sequential mechanism. Acetone is a stable intermediate in this last reaction pathway. Photodegradation of MIBK at different levels of RH was also modeled using LHHW kinetic expressions, and the rates obtained were slightly lower than those obtained for the photooxidation of acetone. However, a carbon balance was not achieved for MIBK, very likely due to the accumulation of partially oxidized products on the surface of the photocatalyst. The influence of water vapor on the photocatalytic oxidation rate of this larger ketone is more complex, and both inhibition and promotion effects can be envisaged. In addition, experimental results show that humidity exerts a significant influence in the mineralization efficiency of MIBK.

Mild oxidation of alcohols with o-iodoxybenzoic acid (IBX) in water/acetone mixture in the presence of beta-cyclodextrin.

Abstract: A mild and efficient oxidation of alcohols with o-iodoxybenzoic acid (IBX) catalyzed by β-cyclodextrin in a water/acetone mixture (86:14) has been developed. A series of alcohols were oxidized at room temperature in excellent yields.

Selective decomposition of cumene hydroperoxide into phenol and acetone by a novel cesium substituted heteropolyacid on clay

Abstract: Phenol is industrially produced by the Hock process starting from benzene and propylene to yield cumene, which is subsequently oxidized with oxygen to generate cumene hydroperoxide (CHP) which is then decomposed with sulfuric acid to obtain equimolar phenol and acetone. Both phenol and acetone are important bulk chemicals having separate as well as interrelated markets. The last step of the Hock process is polluting and results in loss of selectivity leading to formation of by-products beside the desired products phenol and acetone. The current work reports the decomposition of CHP by using K-10 clay supported catalysts such as 20% (w/w) dodecatungstophosphoric acid (DTP)/K-10, 20% (w/w) Cs2.5H0.5PW12O40/K-10, 20% (w/w) ZnCl2/K-10 and K-10, and also sulfated zirconia at 40 °C. For the first time, the synthesis of Cs2.5H0.5PW12O40 supported on K-10 clay has been reported with complete intact Keggin anion structure. This catalyst has been found to exhibit excellent activity for decomposition of cumene hydroperoxide exclusively into phenol and acetone. Various kinetic parameters were studied over 20% Cs2.5H0.5PW12O40/K-10. The reaction follows the first order kinetics. The catalyst is stable and reusable giving 100% conversion with exclusive selectivity to 100% phenol and acetone during all the runs.

Effect of the number of flavanol units on the antioxidant activity of procyanidin fractions isolated from chocolate.

Abstract: Of three different solvents (acetone, ethanol, and methanol) mixed with water and acetic acid, the acetone/water/acetic acid mixture (70:28:2, v/v) proved to be best for extracting dark-chocolate procyanidins. High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-MS-ESI) was further used to identify oligomers found in the extract. After HPLC fraction collection, the reduction power of flavanoid fractions was measured in the AAPH [2,2'-azobis(2-amidinopropane)dihydrochloride] assay, where oxidation of linoleic acid is induced in an aqueous dispersion. Even expressed in relative monomeric efficiency units, the oxidation-inhibiting power of polymerized oligomers is much stronger than that of monomers. A comparison with 10 usual antioxidants indicated that oligomers with three or more (epi)catechin units are by far the most efficient.

Effect of Irradiation Sources and Oxygen Concentration on the Photocatalytic Oxidation of 2-Propanol and Acetone Studied by in Situ FTIR

Abstract: The photocatalytic oxidation (PCO) of 2-propanol and acetone was studied on TiO2 powder at high coverage (>2 monolayers) at various oxygen concentrations using in situ FTIR. Two UV irradiation sour...

Iridium-catalyzed Oppenauer oxidations of primary alcohols using acetone or 2-butanone as oxidant.

Abstract: The first Oppenauer oxidation of primary alcohols with acetone or 2-butanone by an amino alcohol-based Ir bifunctional catalyst was accomplished. The reaction proceeds with 1 mol % catalyst in acetone or 2-butanone at 30−80 °C to give the corresponding aldehydes in 33−96% yield.

Investigation of Plasma-Induced Photochemical Reaction on a Polypropylene Surface

Abstract: The surface of a polypropylene (PP) film was modified using acetone and acetone/oxygen. Significant improvement in surface energy was observed due to plasma treatment. The chemical nature and stability of the surface modification was studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The relative change in intensity was calculated for C−H stretch vibrations of a modified PP film to understand the reactive site for surface modification. Studies were carried out to mask the reactive site of PP by pretreatment in nitrogen plasma followed by treatment in acetone/oxygen. The peel strength and effect of aging were studied on acetone and acetone/oxygen plasma modified films.

Infrared spectroscopy of acetone–water liquid mixtures. I. Factor analysis

Abstract: Acetone and water mixtures covering the whole solubility range were measured by Fourier transform infrared attenuated total reflectance spectroscopy. In this system, only water can supply the hydrogen atoms necessary for hydrogen bonding. Using spectral windowing with factor analysis (FA), 10 principal factors were retrieved, five water and five acetone. Hydrogen bonding is observed on the carbonyl stretch band as water is introduced in the solution, redshifting the band further from its gas position than that observed in pure liquid acetone. This indicates that the hydrogen bonding is stronger than the acetone dipole–dipole interactions because it overrides them. A water molecule isolated in acetone is twice H bonded through its two H atoms; although both OH groups are H-bond donors, the OH stretch band is less redshifted (∼138 cm−1) than that of pure liquid water (∼401 cm−1). This is attributable to the two lone electron pairs remaining on the oxygen atom that sustain a large part of the OH valence bond...

Reaction of Hydroxyl Radical with Acetone. 2. Products and Reaction Mechanism

Abstract: The products of the reaction of OH with acetone (OH + CH3C(O)CH3 → products) were investigated using a discharge flow tube coupled to a chemical ionization mass spectrometer. It was shown that the yield of acetic acid from the reaction was less than 1% between 237 and 353 K. The yield of acetonyl radical was measured to be (96 ± 11)%, independent of temperature, between 242 and 350 K. The rate coefficients for the reaction were measured with this system to be the same as those reported in part 1 (J. Phys. Chem. A 2003, 107, 5014). The rate coefficients for the removal of OH (v = 1) by acetone and acetone-d6 were shown to be (2.67 ± 0.15) × 10-11 and (3.45 ± 0.24) × 10-11 cm3 molecule-1 s-1, respectively, at 295 K. It was shown that the enthalpy of reaction for the formation of an OH−acetone adduct is more than −8 kcal mol-1 (i.e., the adduct is bound by at most 8 kcal mol-1) at 203 K. On the basis of these observations and those from part 1, we deduce that the reaction of OH with acetone occurs through a ...

Compressed solvents for the extraction of fermentation products within a hollow fiber membrane contactor

Abstract: The feasibility of extracting aqueous ethanol and acetone within a hollow fiber membrane contactor (HFC) has been examined using compressed CO 2 (69 bar), ethane (69 bar), and propane (34.5 bar) at ambient temperature. Ethanol and acetone were chosen as ‘model’ fermentation products to further examine the potential for extractive fermentation with compressed fluids. Aqueous and compressed solvent streams were contacted within a single hydrophobic isotactic polypropylene membrane fiber (0.6 mm ID; 106.7 cm in length; 75% porosity), providing a porous barrier between the two immiscible phases. The amount of solute extracted was determined as a function of the aqueous flowrate (tubeside) and molar solvent to feed ratio. The amount of aqueous ethanol (10 wt.%) and acetone (10 wt.%) extracted from binary feed solutions with compressed propane ranged from 6.4 to 14.3% and 21.8 to 90.6%, respectively, as a function of the aqueous flowrate (0.1 to 2 ml/min) and molar solvent to feed ratio ( S/F =1 to 10). Comparatively, ethanol extraction with compressed CO 2 ranged from 4.7 to 31.9% with similar variations in the aqueous flowrate (0.1 to 1 ml/min) and molar solvent to feed ratio (3 and 10). Acetone extracted with CO 2 ranged from 67.9 to 96.1% when varying the aqueous flowrate (0.1 to 1 ml/min) at a molar solvent to feed ratio of 3. Ternary ethanol/acetone/water mixtures were also examined to determine the effect of multi-solute aqueous solutions. The effect of aqueous and compressed fluid flows on extraction are interpreted based on the equilibrium distributions of the solutes between water and the compressed fluid (estimated using a group contribution association equation of state (GCA–EOS)) and the mass transfer characteristics of the compressed fluid.

The “one-pot” synthesis of 4-methyl-2-pentanone (methyl isobutyl ketone) from acetone over PdCu catalysts prepared from layered double hydroxides

Abstract: Supported PdCu catalysts prepared from layered double hydroxides (LDHs) as precursors were evaluated in the gas phase reaction of acetone with hydrogen to methyl isobutyl ketone (MIBK). Two series of catalysts containing ca. 0.2 wt.% Pd and various amounts of Cu (Cu/Pd molar ratio of ca. 0.25, 0.5 and 1) were elaborated according to different methods. One series of precursors was obtained by impregnation of calcined Mg(Al)O mixed oxide with heterobinuclear PdxCu1−x acetylacetonates. A second series of precursors was synthesized by coprecipitation of Mg/Pd/Cu/Al LDHs. After calcination, both series were reduced at 473 K. The extends of basic, acid and metal functions were evaluated through microcalorimetric adsorption of CO2, TPD of NH3 and TPR of H2. It was found that the multifunctional transformation of acetone to MIBK was rate determined by the basic function. However, the way by which the catalysts were prepared, impregnation or coprecipitation, controls the extend of hydrogenated by-products, isopropyl alcohol and 4-methyl-2-pentanol. The extensive dilution by migrating MgAlOx species onto the metallic particles makes the coprecipitated catalysts highly selective by decreasing selectively the rate of CO bond hydrogenation.

Reaction of Hydroxyl Radical with Acetone. 1. Kinetics of the Reactions of OH, OD, and 18OH with Acetone and Acetone-d6

Abstract: The rate coefficient for the reaction of OH with acetone, k1, was measured by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence to be k1(T) = 1.38 × 10-13 + 3...