Showing papers on "Acetone published in 2008"

Application of microwave-assisted extraction to the fast extraction of plant phenolic compounds

Abstract: The analysis of phenolic compounds in plants attracts considerable attention. Conventional (reflux) extraction as well as microwave-assisted extraction of phenolic substances from aromatic plants using different solvents has been studied. RP-HPLC with UV detection was employed for the analysis of phenolic compounds. Total phenolic compounds were determined by the Folin–Ciocalteu assay. The amount of extractable phenolic substances for this method decreased with decreasing polarity of the solvent in the order water, 60% methanol, 60% acetone, and ethyl acetate/water (60:30, v/v) by using the conventional method. When microwave-assisted extraction was performed, the previous order was changed to 60% acetone, 60% methanol, water and ethyl acetate/water. The HPLC results have shown similar solvent effect for the two extraction methods. It was also proved that microwave-assisted extraction is a more effective technique compared to the conventional method. The extraction time was reduced, less solvent was used and the amount of extracted phenolic compounds was increased.

Carbon–carbon bond formation for biomass-derived furfurals and ketones by aldol condensation in a biphasic system

Abstract: Production of liquid alkanes in the range of C8–C15 from renewable sources, such as xylose and fructose (C5 and C6), requires the formation of CC bonds between the carbon chains. We have investigated aldol condensation as a catalytic route for this conversion in a biphasic system between various furfurals (furaldehyde (FUR), methyl furfural, and 5-hydroxylmethyl furfural (HMF)) and ketones (acetone, acetol, dihydroxyacetone, 2-hexanone, and 3-hexanone) derived from biomass. This system employs a reactive aqueous phase containing a basic NaOH catalyst, an organic extracting phase to remove the aldol-adducts from the homogeneous catalyst, with the addition of salt (NaCl) to the aqueous phase employed to expand the miscibility gap between the aqueous and organic phases. The effect of reagent ratios and reaction conditions on the final product distribution, such as ketone to furfural and base to furfural ratio, was investigated and a simple first order model was used to gain insight into the reaction network. High yields to single and double condensation products can be achieved for acetone condensation with furfural compounds by proper choice of reagent ratios. Degradation of HMF appears to be catalyzed by base, leading to the formation of organic acids that subsequently neutralize the base catalyst. This degradation process limits the recycling of the aqueous phase and also decreases the condensation yield of species such as hexanones that do not readily dissolve in the aqueous phase. FUR, which does not readily degrade, is more completely condensed to form products; however, because FUR is less soluble in the reactive aqueous phase compared to HMF, high concentrations of base must be used to increase the rate of reaction.

Selective Conversion of D-Fructose to 5-Hydroxymethylfurfural by Ion-Exchange Resin in Acetone/Dimethyl sulfoxide Solvent Mixtures

Abstract: Catalytic dehydration of D-fructose to 5-Hydroxymethylfurfural (5-HMF) in acetone/dimethyl sulfoxide solvent mixtures was studied in the presence of a strong acidic cation-exchange resin catalyst (DOWEX 50WX8−100) by microwave heating. The addition of acetone to the dimethyl sulfoxide (DMSO) solvent promoted the formation of 5-HMF from D-fructose. For a D-fructose conversion of 97.9%, the 5-HMF selectivity was 91.7% for a 20-min reaction time in 70:30 (w/w) acetone/DMSO solvent mixtures. Concentrations as high as 10 wt % D-fructose were studied, for which it was found that 5-HMF yields of 82.1% for a reaction time of 10 min could be obtained. The stability of the ion-exchange resin used as the catalyst was confirmed. Compared to pure DMSO solvent, the combination of low-boiling-point acetone with DMSO used as the reaction medium not only gives highly selective 5-HMF formation, but also improves the separation efficiency and reduces environmental risk.

Hydrogen production via steam reforming of bio-oil components over calcium aluminate supported nickel and noble metal catalysts

Abstract: Steam reforming of two representative bio-oil components, acetic acid and acetone, was investigated thermally and catalytically over nickel (5 wt%) and noble metal (0.5 wt% Rh or Ir) catalysts supported on calcium aluminates (CaO·2Al2O3 and 12CaO·7Al2O3). The thermal reactions (with or without water) were studied in the presence of inert quartz particles and showed that at 750 °C, acetone and to a lesser extent acetic acid undergo a series of homogeneous reactions forming CO, CO2, CH4 and H2 in concentrations which depend on the organic, and the presence or absence of water. Characteristic of acetone thermal steam reforming is that high amounts of acetic acid are produced. The catalysts prepared were tested at three reaction temperatures 550–650–750 °C using steam/carbon = 3 and space velocities around 30 000 h−1. The results showed that acetic acid is easily reformed over the catalysts to hydrogen rich gas with yield approaching that of equilibrium. Hydrogen yields depend on the metal type and loading and the ratio of CaO to Al2O3 of the support. The best performance in terms of highest hydrogen yield is achieved with the 5 wt% Ni/CaO·2Al2O3 catalyst, while the 0.5 wt% Rh/CaO·2Al2O3 catalyst presents the highest resistant to coking. These catalysts were tested in acetone reforming showing also very high activity, low coking deposition rate and slight superiority of the Rh catalyst in terms of hydrogen yield.

Control of the Heterogeneous Azeotropic n-Butanol/Water Distillation System

Abstract: The interest in n-butanol as a biofuel has increased in recent years because of its superior fuel qualities compared to ethanol: higher octane number, lower heat of vaporization, higher energy density (energy/volume), and lower vapor pressure. However, the concentration of n-butanol coming from the fermenter is lower than that achieved in ethanol fermentation. In addition, acetone and ethanol are also produced. Recent studies to improve yield and increase n-butanol concentration have explored fed-batch systems with stripping, adsorption, liquid−liquid extraction, distillation, and/or pervaporation to recover products. The production of n-butanol involves removing the acetone and ethanol and separating the n-butanol from the water. This separation is made difficult by the presence of an azeotrope. Fortunately, unlike the homogeneous azeotrope found in the ethanol/water system, the n-butanol/water azeotrope is heterogeneous; thus, two liquid phases occur in the decanter. Therefore, a simple two-column disti...

Freeze-substitution: the addition of water to polar solvents enhances the retention of structure and acts at temperatures around -60 degrees C.

Abstract: Summary High-pressure freezing followed by freeze substitution and plastic embedding is becoming a more widely used method for TEM sample preparation. Here, we have investigated the influence of solvents, fixative concentrations and water content in the substitution medium on the sample quality of high-pressure frozen, freeze-substituted and plastic embedded mammalian cell culture monolayers. We found that the visibility of structural details was optimal with acetone and that extraction increased with both increasing and decreasing solvent polarity. Interestingly, the addition of water to polar solvents increased the sample quality, while being destructive when added to apolar solvents. The positive effect of water addition is saturable in acetone and ethanol at 5%(v/v), but even addition of up to 20% water has no negative effect on the sample structure. Therefore, a medium based on acetone containing fixatives and 5% water is most optimal for the substitution of mammalian cell cultures. In addition, our results suggest that the presence of water is critical for the retention of structure at temperatures around –60°C.

Sensitive and selective acetone sensor based on its cataluminescence from nano-La2O3 surface

Abstract: In the present paper, a highly sensitive and selective sensor for acetone was demonstrated, which was based on intensive cataluminescence (CTL) emission on the surface of nano-sized La 2 O 3 . The CTL characteristics and the optimum conditions for the sensor, including La 2 O 3 morphology, wavelength, working temperature, and airflow rate, were investigated in detail. Under the optimized conditions, the CTL intensity versus concentration of acetone was linear in the range of 0.19–140 μg mL −1 , with a correlation coefficient ( r ) of 0.9981 and a detection limit (signal-to-noise ratio is 3; and noise is the width of baseline) of 0.08 μg mL −1 . The relative standard deviation (R.S.D.) for 9.3 μg mL −1 acetone ( n = 5) was 1.4%. There was no or weak response to common foreign substances, such as ammonia, toluene, benzene, formaldehyde, ethanol, methanol, ethyl acetate, and acetaldehyde. The gas sensor also exhibited good stability and durability for continuously introducing 19 μg mL −1 acetone for 80 h over 8 days, with a long-term R.S.D. less than 5%.

Engineered microorganisms for producing isopropanol

Abstract: In an embodiment, there is disclosed a recombinant microbial host cell having each of the DNA molecules encoding a polypeptide or group of polypeptides that catalyze the conversion: (i) Acetyl-CoA to Acetate and CoA (conversion 1) (ii) Acetyl-CoA to Acetoacetyl-CoA and CoA (conversion 2) (iii) Acetoacetyl-CoA and Acetate to Acetoacetate and Acetyl-CoA (conversion 3.1) (iv) Acetoacetate to Acetone and CO2 (conversion 4) (v) Acetone and NAD(P)H and H+ to Isopropanol and NAD(P)+ (conversion 5) wherein the at least one DNA molecule is heterologous to the microbial host cell and wherein the microbial host cell produces isopropanol. In another embodiment, a method is disclosed for the production of isopropanol including providing a recombinant microbial host cell, the host cell of (i) with a fermentable carbon substrate in a fermentation medium under conditions whereby isopropanol is produced, and recovering the isopropanol.

The effect of acetone addition on the properties of epoxy

Abstract: In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone. Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease in viscosity (around 50%) which may promote a better dispersion of nanofillers.

Removing Organic Compounds from Aqueous Medium via Wet Peroxidation by Gold Catalysts

Abstract: A new heterogeneous Fenton-like system, consisting of supported Au catalysts and hydrogen peroxide, was proved to be effective in removing low level organic compounds (ca. 100 ppm) such as phenol, ethanol, formaldehyde, and acetone in aqueous solution. Among all gold catalysts the Au/hydroxyapatite (Au/HAp) exhibits the highest activity, and even better than the conventional iron ions exchanged zeolite (Fe/ZSM-5) catalyst. In particular, unlike the limited operational pH range (pH: 2∼5) for the other heterogeneous Fenton catalysts such as Fe/ZSM-5, Au/HAp shows higher stability even in strong acid solution (pH ∼ 2), due to almost no leaching of active metal from supports into solution. It can be potentially applied in treating the industrial wastewaters with strong acidity and purifying drinking water. In addition, in the case of complete oxidation of phenol, a plausible route was suggested for deep understanding of this process.

Solubility of l-(+)-Ascorbic Acid in Water, Ethanol, Methanol, Propan-2-ol, Acetone, Acetonitrile, Ethyl Acetate, and Tetrahydrofuran from (293 to 323) K

Abstract: The solubility of l-(+)-ascorbic acid in water, ethanol, methanol, propan-2-ol, acetone, acetonitrile, ethyl acetate, and tetrahydrofuran was measured by a gravimetrical method from (293 to 323) K, and the solubility data were correlated against temperature. The solubility of l-(+)-ascorbic acid in water and methanol was high compared with other solvents.

Acetone gas sensing properties of Smfe1-xMgxO3 perovskite oxides

Abstract: Novel sensing materials, SmFe1−xMgxO3, were applied for an acetone vapor sensor. Fine powders of the oxides were prepared by a sol–gel method using citric acid. The compounds had a perovskite phase. The Mg-doping restrained the growth of the grain size. The Mg-doping strongly influenced the resistance, activation energy for conduction and gas response of the SmFeO3. The highest response to 300 ppm acetone gas reached 353 for SmFe0.9Mg0.1O3-based sensor at 260 °C. The sensor also exhibited good selectivity to acetone gas and its response increased with an increase in acetone gas concentration. Furthermore, the sensing mechanism was discussed in detail.

Solubility of Acetylsalicylic Acid in Ethanol, Acetone, Propylene Glycol, and 2-Propanol

Abstract: As one of the most regularly traded-in medicines in the world, acetylsalicylic acid has been scarcely researched when in solution. This study is aimed at determining the solubility of acetylsalicylic acid in ethanol, acetone, propylene glycol, and 2-propanol, in addition to comparing their solubility values with the expected from an ideal solution. The solubility of acetylsalicylic acid is highest in acetone in all studied temperature ranges until T/K = 326.3. Propylene glycol presents lower solubility data in all studied temperature ranges. The solvent that presented the lowest average percent logarithmic deviation, concerning the ideality of the system, was ethanol, and the highest value of average percent logarithmic deviation was found in propylene glycol solutions. The experimental solubility data were correlated with the Nývlt model. We conclude that the Nývlt model is capable of representing properly the experimental data.

Relationship of O2 Photodesorption in Photooxidation of Acetone on TiO2

Abstract: Organic photooxidation on TiO 2 invariably involves the coexistence of organic species with oxygen on the surface at the same time. In the case of acetone and oxygen, both species exhibit their own interesting photochemistry on TiO 2, but interdependences between the two are not understood. In this study, a rutile TiO 2(110) surface possessing 7% surface oxygen vacancy sites is used as a model surface to probe the relationship between O 2 photodesorption and acetone photodecomposition. Temperature programmed desorption and photon stimulated desorption (PSD) measurements indicate that coadsorbed oxygen is essential to acetone photodecomposition on this surface; however, the form of oxygen (molecular or dissociative) involved is not known. The first steps in acetone photodecomposition on TiO 2(110) involve thermal activation with oxygen to form an acetone diolate ((CH 3) 2COO) species followed by photochemical decomposition to adsorbed acetate (CH 3COO) and an ejected CH 3 radical that is detected in PSD. D...

Study of the citral/acetone reaction on MgyAlOx oxides: Effect of the chemical composition on catalyst activity, selectivity and stability

Abstract: The liquid-phase citral/acetone reaction was studied on MgO, Al 2 O 3 and Mg y AlO x mixed oxides with Mg/Al molar ratios of 0.11–3. The density, strength and nature of surface acid sites were determined by NH 3 thermodesorption and FTIR of pyridine. The surface basic properties were probed by temperature-programmed desorption of CO 2 . The rate of the citral/acetone cross-aldolization to pseudoionones increased linearly with the density of strong O 2− base sites. Thus, the pseudoionone synthesis was efficiently promoted on MgO and Mg-rich Mg y AlO x samples. In contrast, the initial rate of the parallel acetone self-condensation reaction increased with the density of Lewis acid sites, and diacetone alcohol was more rapidly formed on Al 2 O 3 and Al-rich Mg y AlO x samples. Differences in the reactant adsorption strength on surface Al 3+ sites may explain the observed differences between the acid-catalyzed mechanisms of cross- and self-aldolization reactions. In situ catalyst deactivation was determined by performing two consecutive catalytic runs. The activity decay of Mg y AlO x samples during the citral/acetone reaction was between 15 and 20%, irrespective of the catalyst composition.

The CH3CO quantum yield in the 248 nm photolysis of acetone, methyl ethyl ketone, and biacetyl

Abstract: We report measurements of the CH3CO quantum yield, Φ C H 3 CO , following the 248 nm pulsed laser photolysis of acetone (CH3C(O)CH3), methyl ethyl ketone (CH3C(O)CH2CH3), and biacetyl (CH3C(O)C(O)CH3). CH3CO quantum yields at 248 nm were measured at 296 K, relative to CH3CO reference systems. CH3CO was detected using cavity ring-down spectroscopy at wavelengths between 490 and 660 nm. Measurements were performed between 60 and 670 Torr (He, N2 bath gases) and the obtained CH3CO quantum yields in the low-pressure limit, Φ C H 3 CO 0 , were 0.535 ± 0.09, 0.41 ± 0.08, and 0.76 ± 0.11, for acetone, methyl ethyl ketone, and biacetyl, respectively. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. An increase in Φ C H 3 CO with increasing bath gas pressure, which depended on the identity of the collision partner (He, N2), was observed. The present results are compared with previous quantum yield determinations.

Ketone photolysis in the presence of oxygen: A useful source of OH for flash photolysis kinetics experiments

Abstract: Previous studies have shown a significant OH yield from the reaction of RCO radicals (generated from the photolysis of corresponding ketone) with oxygen below total pressures of 200 Torr. The potential of these reactions as a source of OH radicals for flash photolytic kinetic studies is investigated. The viability of the method was tested by measuring rate coefficients for the reaction of OH with ethanol using both acetone/O2 mixtures and t-butyl hydroperoxide photolysis. The results (with statistical errors at the 2σ level) are in excellent agreement with each other (kEtOH(acetone) = (5.87 ± 0.34) × 10−18T2 exp((515 ± 21)K/T) cm3 molecule−1 s−1 and kEtOH (t-butyl hydroperoxide) = (5.27 ± 0.34) × 10−18T2 exp((557 ± 20)K/T) cm3 molecule−1 s−1) and with the IUPAC recommendation. The reaction of OH with methyl ethyl ketone (2-butanone) has also been investigated using a similar technique. The results show a strong non-Arrhenius temperature dependence, k = (3.84 ± 0.12) × 10−24× T4 × exp((1038 ± 11)/t). The merits of the ketone/oxygen OH source are contrasted with other established precursors. A major advantage of the technique is the ability to cleanly generate OD without the potential for isotopic scrambling prior to photolysis. © 2008 Wiley Periodicals, Inc. 40: 504–514, 2008

Fermentative production of acetone from renewable resources by means of novel metabolic pathway

Abstract: The invention describes a process for the preparation of acetone starting from acetyl-coenzyme A comprising the process steps A. enzymatic conversion of acetyl-CoA to give acetoacetyl-CoA; B. enzymatic conversion of acetoacetyl-CoA into acetoacetate and CoA; and C. decarboxylation of acetoacetate to give acetone and CO2, which process is characterized in that, in process step B, the coenzyme A is not transferred to an acceptor molecule. Moreover, surprisingly, process step B is catalyzed by enzymes from the classes acyl-CoA thioesterase, acyl-CoA synthetase or acyl-CoA thiokinase.