Showing papers on "Acetone published in 2000"

Reactions of ethanol over metal oxides

Abstract: The reaction of ethanol over a series of oxides (Fe2O3, Fe2O3/CaO, Fe3O4, TiO2, CaO, and SiO2) has been investigated. The main reaction product in all cases is acetaldehyde, with secondary products acetone and ethyl acetate. At 473 K, the rate constant k decreases according to the series Fe2O3>Fe3O4>CaO>TiO2≫SiO2. Titration of basic sites by CO2 adsorption at room temperature shows that the reaction rate can be successfully normalised by basic site density for oxides that adsorb CO2 except for CaO. Acetone production, presumably via acetate ketonization, is highest over TiO2 while ethyl acetate formation, by Tishchenko reaction, is highest over Fe2O3.

Degradation pathways during the treatment of methyl tert-butyl ether by the uv/h2o2 process

Abstract: The application of the UV/H2O2 process to the degradation of methyl tert-butyl ether (MTBE) in dilute aqueous solution resulted in the generation of tert-butyl formate (TBF), 2-methoxy-2-methyl propionaldehyde (MMP), formaldehyde, acetone, tert-butyl alcohol (TBA), and methyl acetate as primary byproducts. Other intermediates, such as carbonyl compounds (hydroxy-iso-butyraldehyde, hydroxyacetone, pyruvaldehyde) and organic acids (hydroxy-iso-butyric, formic, pyruvic, acetic, oxalic) were also detected and quantified during the irradiation. A good organic carbon balance is obtained throughout the treatment, indicating that almost all of the intermediates have been detected. The TOC pattern shows that eventually all the organic compounds are mineralized. Various analytical techniques, such as GC/MS, GC, IC, HPLC, and TOC analysis, were employed in order to identify and quantify the organic products. The detailed reaction mechanism proposed in this study for the degradation of MTBE by •OH-driven oxidation pr...

Emissions of volatile organic compounds from Quercus ilex L. measured by Proton Transfer Reaction Mass Spectrometry under different environmental conditions

Abstract: Volatile organic compound (VOC) emissions of the Mediterranean holm oak (Quercus ilex L.) were investigated using a fast Proton Transfer Reaction Mass Spectrometry (PTR-MS) instrument for analysis. This technique is able to measure compounds with a proton affinity higher than water with a high time resolution of 1 s per compound. Hence nearly all VOCs can be detected on-line. We could clearly identify the emission of methanol, acetaldehyde, ethanol, acetone, acetic acid, isoprene, monoterpenes, toluene, and C10-benzenes. Some other species could be tentatively denominated. Among these are the masses 67 (cyclo pentadiene), mass 71 (tentatively attributed to methyl vinyl ketone (MVK) and metacrolein (MACR)), 73 (attributed to methyl ethyl ketone (MEK)), 85 (C6H12 or hexanol), and 95 (vinylfuran or phenol). The emissions of all these compounds (identified as well as nonidentified) together represent 99% of all masses detected and account for a carbon loss of 0.7–2.9% of the net photosynthesis. Of special interest was a change in the emission behavior under changing environmental conditions such as flooding or fast light/dark changes. Flooding of the root system caused an increase of several VOCs between 60 and 2000%, dominated by the emission of ethanol and acetaldehyde, which can be explained by the well described production of ethanol under anoxic conditions of the root system and the recently described subsequent transport and partial oxidation to acetaldehyde within the green leaves. However, ethanol emissions were dominant. Additionally, bursts of acetaldehyde with lower ethanol emission were also found under fast light/dark changes. These bursts are not understood.

Butanol production using Clostridium beijerinckii BA101 hyper-butanol producing mutant strain and recovery by pervaporation

Abstract: Clostridium beijerinckii BA101 (mutant strain) and C. beijerinckii 8052 (wild type) were compared for substrate and butanol inhibition. The wild-type strain is more strongly inhibited by added butanol than is the mutant strain. Acetone and butanol were removed from a fed-batch reactor inoculated with C. beijerinckii BA101 by pervaporation using a silicone membrane. In the batch reactor, C. beijerinckii BA101 produced 25.3 g/L of total solvents, whereas in the fermentation-recovery experiment it produced 165.1 g/L of total solvents. Solvent productivity increased from 0.35 (batch reactor) to 0.98 g/L.h (fed-batch reactor). The fed-batch reactor was fed with 500 g/L of glucose-based P2 medium. Acetone selectivities ranged from 2 to 10 whereas butanol selectivities ranged from 7 to 19. Total flux varied from 26 to 31 g/m2.h.

Product studies of the OH- and ozone-initiated oxidation of some monoterpenes

Abstract: The OH- and O3-initiated oxidation of five monoterpenes (myrcene, terpinolene, Δ3-carene, α-pinene, and β-pinene) has been studied in environmental chambers equipped with either a Fourier transform infrared spectrometer or a gas chromatography/flame ionization detector system. The OH-oxidation of myrcene and terpinolene is shown to lead to substantial yields of acetone (36 and 39%, respectively), while the acetone yield from the pinene compounds is quite small (4% and ∼2%, for α- and β-pinene, respectively). Formaldehyde has been identified as a major product (yields of 20–40%) in the OH-initiated oxidation of all five species. Formic acid was also observed in the OH-initiated oxidation of all five monoterpenes, with yields of 2% from β-pinene and 5–9% from the other species studied. The production of acetone from the reaction of monoterpenes with ozone in the presence of an OH scavenger was measured. The yields of acetone for the O3 reactions were α-pinene, 0.03±0.01; β-pinene, 0.009±0.009; Δ3-carene, 0.10±0.015; myrcene, 0.25±0.06; and terpinolene, 0.50±0.06. The mechanism leading to the production of these compounds is discussed, as is the atmospheric relevance of the results. In particular, an estimate of the contribution of monoterpene oxidation to observed atmospheric levels of acetone and formic acid is made.

Effect of various water-miscible solvents on enzymatic activity of fungal laccases

Abstract: The effect of acetonitrile, acetone and dimethyl sulfoxide (DMSO) on the catalytic activity of laccase from P. radiata and the effect of DMSO on the catalytic activity of laccase from P. oryzae in the oxidation of 2,6-dimethoxyphenol were studied. The results obtained in the studied solvent–water mixtures were satisfactorily described using the equations equivalent to the mixed enzyme inhibition. The fitted inhibition parameters were correlated with various physical and chemical parameters characterizing the mixed systems or used solvents, such as: effective pH of the reaction mixture, log P and E T N of the solvent, solubility of the substrate and thermodynamic activity of water in mixed systems. Moreover, a good correlation between the inhibitory effects and the denaturation capacity of the studied solvents was observed.

Surface Chemistry of Acetone on Metal Oxides: IR Observation of Acetone Adsorption and Consequent Surface Reactions on Silica−Alumina versus Silica and Alumina

Abstract: Pathways and generated surface species of adsorption and consequent surface reactions of acetone vapor on characterized silica, alumina, and ∼5 wt % silica−alumina were examined by in-situ infrared (IR) spectroscopy, following degassing at room (RT) and higher temperatures (100−400 °C). For reference and confirmatory purposes, adsorptives of mesityl oxide and acetic acid, and adsorbents of K-modified and pyridine-covered silica−alumina, were employed. In the absence of Lewis and Bronsted acid sites, as well as of basic sites (i.e., on silica), acetone molecules are weakly hydrogen-bonded to surface OHδ+ groups to desorb completely at 100 °C, without involvement in any further surface reactions. The availability of such acid−base sites on alumina and silica−alumina facilitates acetone chemisorption and activation for aldol condensation type surface reactions, leading to formation of surface species of mesityl oxide at RT to 200 °C and their oxidative conversion into acetate species at 300−400 °C. A more ob...

APC values and volatile compounds formed in commercially processed, raw chicken parts during storage at 4 and 13 °C and under simulated temperature abuse conditions†

Abstract: Skinless chicken breast fillets, thighs, wings and boneless breast with skin were selected from the production line of a commercial processor. Samples were evaluated over time in storage at 4 and 13 °C and under temperature abuse conditions for microbial proliferation and production of volatile compounds (VCs). Aerobic plate counts (APCs) were enumerated and VCs quantitated at 24 h storage intervals; however, APC increases were not reflected by significant correlations with headspace VCs. Compounds isolated from sample headspaces by solid phase microextraction (SPME) and direct headspace sampling and then analysed by gas chromatography (GC), gas chromatography/mass spectrometry (GC/MS) and gas chromatography/chemiluminescence detection (GC/SCD) were hydrogen sulphide, methanethiol, ethanol, acetone, C5, C6 and C7 hydrocarbons, dimethyl sulphide, methyl ethyl ketone, carbon disulphide, 1-propanol, ethyl acetate, 1-butanol, S-methyl thioacetate, 3-methyl-1-butanol, dimethyl disulphide and dimethyl trisulphide. Compounds appearing in the samples with any degree of consistency and therefore considered pertinent for these analyses were ethanol, acetone, methyl ethyl ketone, ethyl acetate, hydrogen sulfide, dimethyl sulphide and carbon disulphide. Elevated APCs and VC diversity occurred more prevalently in those samples from higher-temperature storage. Published in 2000 for SCI by John Wiley & Sons, Ltd.

Measurements of Binary Diffusion Coefficients and Partition Ratios for Acetone, Phenol, α-Tocopherol, and β-Carotene in Supercritical Carbon Dioxide with a Poly(ethylene glycol)-Coated Capillary Column

Abstract: Binary diffusion coefficients, D 12 , and partition ratios, k, for the poly(ethylene glycol) (PEG) layer to supercritical carbon dioxide for acetone and some solid solutes such as phenol, α-tocopherol, and β-carotene were measured with a PEG-coated capillary column by a tracer response technique. The D 12 values for acetone with the PEG-coated column were consistent with those measured by the Taylor dispersion method in which an uncoated capillary column was employed. The D 12 and k values for all of the solutes decrease simply with increasing pressure, and the D 12 values were represented by the Schmidt number correlation.

Solubility of Paracetamol in Binary and Ternary Mixtures of Water + Acetone + Toluene

Abstract: The solubility of paracetamol (4-hydroxyacetanilide) in binary mixtures of acetone + water and acetone + toluene and in ternary mixtures of water + acetone + toluene is reported. The temperature range is −5 to +30 °C. In acetone + water the solubility increases to a maximum at approximately 25 mass % water before decreasing to a much lower value in pure water as compared to pure acetone. In acetone + toluene the solubility decreases monotonically with increasing toluene concentration. The water content has a strong influence also in ternary mixtures. Activity coefficients in the saturated solutions are estimated.

Synthesis of bisphenol-A over heteropoly compounds encapsulated into mesoporous molecular sieves

Abstract: The 12-tungstophosphoric acid (HPW) and its insoluble salts containing either caesium or ammonium cations were encapsulated into channels of a MCM-41 molecular sieve and they were used as catalyst for the liquid phase synthesis of Bisphenol-A from phenol and acetone. For comparison, zeolites ZSM-5, H-Y and dealuminated H-DY have also been tested in this reaction. The CsHPW/MCM system appeared to be the most selective towards p,p′ isomer formation.

Complexes of Hydroxyl and Hydroperoxyl Radical with Formaldehyde, Acetaldehyde, and Acetone

Abstract: Likewise, for the organic molecules studied, the strength of binding energies is consistently acetone > acetaldehyde > formaldehyde. Vibrational frequencies are also calculated and some relationships between these and binding energies and geometries are discussed. These data may be useful when laboratory data is present for these complexes. Equilibrium constants for the formation of these complexes are also calculated. As a result of this, it is predicted that the strongest of these complexes, the hydroperoxyl radical -acetone complex, will exist in the atmosphere under certain conditions.

Pervaporative stripping of acetone, butanol and ethanol to improve ABE fermentation.

Abstract: Acetone-butanol-ethanol fermentation by anaerobic bacterium C. acetobutylicum is a potential source for feedstock chemicals. The problem of product induced inhibition makes this fermentation economically infeasible. Pervaporation is studied as an effective separation technique to remove the toxic inhibitory products. Various membranes like Styrene Butadiene Rubber (SBR), Ethylene Propylene Diene Rubber (EPDM), plain Poly Dimethyl Siloxane (PDMS) and silicalite filled PDMS were studied for the removal of acetone, butanol and ethanol, from binary aqueous mixtures and from a quaternary mixture. It was found that the overall performance of PDMS filled with 15% w/w of silicalite was the best for removal of butanol in binary mixture study. SBR performance was best for the quaternary mixture studied.

Theoretical Study of the Formation of Acetone in the OH-Initiated Atmospheric Oxidation of α-Pinene

Abstract: A mechanism is proposed for the formation of acetone in the OH-initiated atmospheric oxidation of α-pinene. In a first step, addition of the OH radical onto the α-pinene double bond forms a chemica...

New water soluble cellulose esters synthesized by an effective acylation procedure

Abstract: Non-ionic cellulose esters were synthesized in homogeneous phase (N,N-dimethyl acetamide/LiCl) with mixedd oxacarbonic acid/p-toluenesulfonic acid anhydrides. This effective synthetic method yields the pure caboxylic acid esters within the wide range of the degree of substitution (DS) from 0.4 to 3.0. The polymers were characterized by means of FTIR and 13 C NMR spectroscopy as well as by means of 1 H NMR spectroscopy of the additionally peracetylated samples. The polymers are water soluble starting with a DS of 0.4 and they are even soluble in acetone and ethanol at higher DS values. They are thermally stable up to 325°C.

Comparison of Two Methods for Phytoplankton Chlorophyll-a Concentration Measurement

Abstract: This study compared two simplified methods for phytoplankton chlorophyll a concentration measurement-the hot ethanol method which use 90% hot ethanol as the chlorophyll a extraction agent and the cool acetone method which use 90% cool acetone as the chlorophyll a extraction agent The hot ethanol method is used widely in the world now but the cool acetone method is normally used in China The results show that the hot ethanol method has more advantages than the cool acetone method, which are faster and easier to handle, more complete extraction and lower toxic There is significant statistical difference between these two methods By using the formula Chla ethanol =1261 Chla acetone -35, the cool acetone method data can be transfered to the hot ethanol method data

Effects of reaction conditions on laccase-catalyzed α-naphthol polymerization

Abstract: Enzymatic oxidative polymerization of α-naphthol was carried out batch-wise with the laccase enzyme, produced by Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone (solvent) and sodium acetate buffer for pH control. The effects of the organic solvent (acetone) composition, monomer (α-naphthol) and enzyme concentrations, buffer pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen. The optimum acetone composition, pH, monomer, dissolved oxygen and enzyme concentrations were determined as 50% (v/v), 5, 3409 gm−3, 20.3 gm−3 and 0.173 U cm−3, respectively; these values provided the most desirable conditions for initial reaction rate. Temperature rise supported the rate increase up to 37 °C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration. The product polymer, poly(α-naphthol), with an average molecular weight of 4920 Da was soluble in common organic solvents. © 2000 Society of Chemical Industry

An Improved Method for The Determination of Hydrogen Peroxide in Leaves.

Abstract: Levels of hydrogen peroxide in plant extracts were overestimated by the method of only using titanium(Ⅳ) because of the interference of pigments and other materials while underestimated by the method of adding activated charcoal(A.C.) in 5% trichloroacetic acid extracts to remove pigments. These problems were avoided by a developed method of extraction, which could not only remove the pigments in acetone extracts conveniently but also get a high recovery more than 95%. Hydrogen peroxide was determined by its reaction with the complex of titanium(Ⅳ)and 4 (2 pyridylazo) resorcinol against references catalase treated. The minimum concentration of hydrogen peroxide determinated in this essay was 0 25 μmol·L -1 . Levels of hydrogen peroxide in leaves of some plant species ranged from 0 1～0 8 μmol·g -1 .

Lipase-catalyzed synthesis of 6-O-eicosapentaenoyl L-ascorbate in acetone and its autoxidation

Abstract: 6-O-Eicosapentaenoyl l-ascorbate (EPA-AsA) was synthesized through condensation of eicosapentaenoic acid (EPA) and l-ascorbic acid in acetone using immobilized lipase from Candida antarctica, Chirazyme l-2. The maximum yield of 47% was attained with 620 mmol EPA and 0.125 mmol l-ascorbic acid in 2.5 ml acetone dehydrated by molecular sieves at 55 °C. More than 80% of the EPA-AsA remained in the unoxidized state at 65 °C and at 0% relative humidity although the unmodified EPA was completely oxidized within 3 h under these conditions.

Steroid 5α-Reductase Inhibitory Activity and Hair Regrowth Effects of an Extract from Boehmeria nipononivea

Abstract: The acetone extract of Boehmeria nipononivea showed both potent 5alpha-reductase inhibitory activity and hair regrowth promotion effects on mice. 5alpha-Reductase inhibitory activity-guided fractionation led to six active fatty acids: alpha-linolenic, linoleic, palmitic, elaidic, oleic and stearic acids. The extract of B. nipononivea, and alphalinolenic, elaidic and stearic acids exhibited a hair regrowth effect.

Synthesis of lauroyl saccharides through lipase-catalyzed condensation in microaqueous water-miscible solvents

Abstract: Lauroyl saccharides were synthesized at 50°C through condensation in acetonitrile, acetone and tert-butanol with various water contents using the immobilized lipase Novozym®435. Saccharides used were glucose, galactose, mannose and fructose. The equilibrium yields of the monoesters in acetonitrile were significantly different among the saccharides tested. The apparent equilibrium constants based on the concentrations of substrates and products in acetonitrile could be correlated to the dynamic hydration numbers of the saccharides, indicating that the water activity played an important role during the condensation in the microaqueous water-miscible solvent. However, a significant correlation between the equilibrium constant for lauroyl fructose formation and parameters characterizing the solvent property could not be found.