Gas-phase Acetone Research Articles

BODIPY-based fluorescent sensor material for airborne acetone and benzene with aggregation-driven selectivity

Paper highlights advances in design of fluorescent sensors for solvent vapors with boron-dipyrromethene (BODIPY) as a model active component. The present study demonstrates that BODIPY-based fluorescent materials could be successfully utilized for detection of benzene and acetone in gas phase. Concentration of luminophore was found to affect sensory response to benzene (up to 3-fold increase in adjusted conditions). At the same time, sensory response to acetone is concentration-independent, suggesting different underlying response mechanisms and allowing to tune selectivity with choice of concentration. Detection limits achieved for sensory materials are 1.2·104 mg/m3 for acetone and 0.94·104 mg/m3 for benzene. Ultimately, obtained sensor materials could be completely regenerated without need for inert gas purge.

Intensified gas-phase hydrogenation of acetone to isopropanol catalyzed at metal-oxide interfacial sites

The gas-phase acetone hydrogenation to isopropanol is an environmentally benign process relevant to chemical, energy and medical fields, but the catalysts qualified at low temperature and pressure remain challenging. Herein, we show the intensified gas-phase hydrogenation of acetone to isopropanol at metal-oxide interface. The Pt/CeO2 catalyst with highly active and stable Pt-CeO2 interface delivers 92 % acetone conversion with 99 % isopropanol selectivity at 80 °C, weight hourly space velocity of 10 h−1, H2/acetone molar ratio of 2, and 0.1 MPa, and its catalytic performance is preserved during a single-running test of 200 h. A series of electron microscopic, thermal, and spectroscopic analyses testify that acetone could be efficiently adsorbed on oxygen vacancy at Pt-CeO2 interface. The H atoms dissociated by Pt spill over to the interface to hydrogenate the chemically-adsorbed acetone thereon to form isopropanol. Inspired by such observation, the Pt-CeO2 interface was extended to other metal-oxide interfaces (metal: Pt and Ni; oxide: CeO2, TiO2, ZrO2 and Fe3O4), all exhibiting excellent catalytic performance. For example, the Ni/CeO2 could offer 91 % acetone conversion and 99 % isopropanol selectivity, identical to that of Pt/CeO2 under the same conditions. This work particularly investigated the acetone adsorption at the metal-oxide interface, establishing the foundation for rational design of high cost performance catalysts for aldehydes/ketones hydrogenation and other reactions.

Unveiling the effect of metallic and oxidized phases of cobalt on acetone hydrodeoxygenation

The impact of metallic and oxidized phases of cobalt and the nature of different catalytic sites in the gas-phase acetone hydrodeoxygenation were evaluated using Co3O4 nanopowder as catalyst. Mild pretreatments (reduction/oxidation up to 400 °C) were performed to vary the oxidation degree of the catalyst, aiming to favor the selective CO bond cleavage. We found that the Co3O4 nanopowder was not able to deoxygenate acetone at 200 °C, even by halving the acetone weight hourly space velocity (WHSV). At this temperature, only products of hydrogenation (isopropanol) and condensation (mesityl oxide) were obtained. A different selectivity was achieved by the pretreated catalysts. Methane formation was enhanced in the prereduced catalyst whereas isopropanol was the favored product after reoxidizing the catalyst at 400 °C. The best compromise was achieved when the prereduced catalyst was calcined at a lower temperature, 200 °C, achieving about 1:1 CC: CO bond cleavage ratio. The results pointed out the nature of different catalytic sites, and their correlation with the reaction pathways was proposed.

Photodissociation of acetone revisited: Femtosecond transient absorption of S1 state and highly excited Rydberg state in the gas phase

AbstractPhotodissociation dynamics of acetone in gas phase were, for the first time, investigated using the pump‐probe technique of femtosecond transient absorption. To obtain a genuine time profile of nR state, we employed 200‐nm and 400‐nm pulses for two‐photon excitation and three‐photon excitation, respectively. In gas phase of acetone, the extraordinarily stable nR state originated from nR states in the Franck–Condon region, whose decay time constant was 350 ± 10 fs, was observed after excitation by three‐photon absorption of 400‐nm pulses. In the low‐power case of 267 nm, the photodissociation dynamics in the S1 state by one‐photon absorption showed that acetone was completely dissociated into two methyl radicals and C=O via an acetyl radical intermediate with a lifetime of 200 ± 10 fs. In the high‐power case of 267‐nm light, we interpreted the transient, although this is a subject of ongoing debate, as caused by both the photodissociation dynamics of the S1 state for a fast component and the dynamics of nR states for long‐lived species.

Development and Verification of Conformer-Specific Vibrational Spectroscopy.

Conformers have similar vibrational structures both in neutral (S0) and cationic (D0) states owing to the comparable force fields between their nuclei. Nevertheless, there is a continuous development of vibrational spectroscopic techniques to rigorously identify individual conformers in the designated molecule but only in the S0 state. We developed an inventive conformer-specific vibrational spectroscopic technique to measure identifiable vibrational spectra of individual conformers in both S0 and D0 states. We measured isomer-specific vibrational spectra in both states for gas-phase acetone and oxetane isomers from a solution with azeotropic composition to verify the proposed techniques that are based on infrared (IR) resonant vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. The measured IR dip VUV-MATI and IR hole-burn VUV-MATI spectra for each isomer, which correspond to isomer-specific vibrational spectra in both states, can be represented by IR-resonant VUV photoionization and one-photon VUV-MATI spectra of the binary mixture, respectively, under supersonic expansion conditions. The partial pressures of the individual isomers in the binary mixture with different mole fractions estimated according to the relative peak intensities in the measured spectra provide insights on solute-solvent interactions. We suggest that the verified IR-resonant VUV-MATI spectroscopy can form the basis of effective schemes toward conformational chemistry.

New light on acetone: a master equation model for gas phase photophysics and photochemistry

This paper presents a unified model of gas phase acetone photophysics and photochemistry that is based on experimental data, which are reviewed and discussed in detail, and a detailed microcanonical master equation formulation. The model accounts for experimental measurements in molecular beams as well as in thermal systems, leads to a new interpretation of some experiments, and reveals a fundamental property of quantum yield measurements that are relevant to atmospheric chemistry. It also furnishes a platform for future theoretical and experimental developments.

Bodipy Based Fluorescent Materials in Cellulose Matrices: Synthesis, Spectral Properties and Vapochromic Fluorescent Recognition of Alcohols and Acetone.

This paper highlights advances made using the 4-bora-3a,4a-diaza-s-indacene (BODIPY) as a fluorophore in design and application of fluorescent sensors for microenvironment polarity. Sections of the paper cover broad analysis of a range of fluorescent indicators immobilized in ethyl- and methyl cellulose matrices. The present study demonstrates that BODIPY-based fluorescent materials could be successfully utilized for ratiometric detection of ethanol and acetone in gas phase. The achieved limit of detection value equals 0.02mg/ml for acetone and 0.08mg/ml for ethanol, whereas obtained sensoric materials are reusable without regeneration required.

Ni-Foam-Structured Ni-Al2O3 Ensemble as an Efficient Catalyst for Gas-Phase Acetone Hydrogenation to Isopropanol.

The free-standing Ni-Al2O3 ensemble derived from NiAl-layered double hydroxides (NiAl-LDHs) grown onto a Ni-foam has been developed for the exothermic gas-phase acetone hydrogenation to isopropanol. This approach works effectively and efficiently to achieve a unique combination of high activity/selectivity and enhanced heat/mass transfer stemmed from the Ni-foam. The outstanding catalyst is obtained by direct reduction of the un-calcined NiAl-LDH/Ni-foam, with a high turnover frequency of 0.90 s-1, being capable of converting 90.8% acetone into isopropanol with almost 100% selectivity under stoichiometric H2/acetone molar ratio, atmospheric pressure at 80 °C, and a WHSVacetone of 10 h-1. The catalyst derivation using the un-calcined NiAl-LDH/Ni-foam enables the Ni nanoparticles to be intertwined with Al2O3 to form a large Ni-Al2O3 interface, without interruption of impurities such as irreducible NiO (in the case of calcined NiAl-LDH/Ni-foam samples), which markedly improves the strong acetone adsorption next to the Ni0 hydrogenation sites, thereby leading to a dramatic improvement of catalyst activity.

Effect of metal modification of titania and hydrogen co-feeding on the reaction pathways and catalytic stability in the acetone aldol condensation

A stable performance of TiO2 catalysts for gas-phase acetone aldol condensation was observed when reduced metals were added (Pt or Ni, 1.5 wt%) and the reactions were conducted in presence of hydrogen. In both cases, the resulting metal-loaded catalysts are stable for 10 h, whereas continuous deactivation is observed for the parent TiO2 catalyst (573 K). Both the activation of the H2 molecule by metal nanoparticles and the change of the catalytic surface by metal insertion (in the case of Ni-loaded catalyst) enable suppressing oligomerization (by hindering enolates formation) and the strong adsorption of intermediates (by decreasing the concentration of high-strength acid-basic active sites), respectively.More interestingly, these metals allow to tune the selectivity of the reaction. Indeed, the Ni-loaded titania catalyst is highly selective for the synthesis of α,β-unsaturated ketones (selectivity to unsaturated C6 and C9 species >98%, at ∼12% acetone conversion), whereas the Pt-loaded one is highly selective to the formation of saturated C6 and C9 ketones (MIBK and DIBK, with selectivities >95% at ∼42% acetone conversion).The catalytic activity and stability of the two materials (Ni/TiO2 and Pt/TiO2) in both absence and presence of H2 are compared between them and with those of the parent TiO2. The results obtained by the reaction gas-phase analysis are supplemented through different solid characterization techniques (i.e., CO2-TPD and NH3-TPD, HRTEM, XPS, TPO, and DRIFTS).

Acetone Reaction with Hydrogen over Mesoporous Magnesium Oxide-Supported Rhodium Nanoparticles

Acetone is a cheap commodity chemical which can be used as an intermediate for the synthesis of numerous chemicals. Coupled with reductive hydrogenation, a multifunctional heterogeneous catalyst is required for the green chemistry of aldol condensation of acetone to produce β-hydroxyketone, enone (α,β-unsaturated ketone), ketone, and saturated and unsaturated alcohol. To that end, we prepared a rhodium nanoparticle-supported (RhNPs) on mesoporous magnesia to conduct a one-step, gas-phase acetone self-condensation. We observed both acetone conversion and selectivity towards either isopropyl alcohol or methyl isobutyl ketone depended on the hydrogen to acetone mole ratio, total flow rate, and reaction temperature. The optimum reaction conditions for a maximum yield of isopropyl alcohol (IPA) or methyl isobutyl ketone (MIBK) were established. Furthermore, 100 h on stream evidenced the long stability of our synthesized catalyst system for the production of isopropyl alcohol.

In-Situ Measurement of Exhaled Formaldehyde and Acetone Kinetics As Early-Stage Non-Invasive Markers of Lung Disease Using Nanostructured Polymeric Membranes

Early stage discovery of lung cancer can significantly improve patient prognosis. Unfortunately, the impact of a well-known technique such as computed tomography screening on mortality rates is uncertain. It has been postulated that tumor growth may lead to peroxidation of cell membranes and is responsible for the observed emission of volatile organic compounds (VOC’s) such as acetone and formaldehyde. This observation has stimulated significant recent effort in the measurement of these compounds in exhaled breath. While promising approaches have been developed for analyzing average VOC concentrations in exhaled breath, an unrecognized drawback to current efforts is the presumption that gas partitioning between the blood and gas phases occurs so rapidly that the time averaged concentration of collected VOCs is representative of their saturation concentration in the lungs. In fact, when one considers the mass transport resistances encountered, VOC lung concentration is likely to be time-dependent and any sensing approach must have sufficient time resolution to capture the dynamic evolution of this concentration during a typical breath exhalation period of not more than 40 seconds in a high humidity environment. In this presentation, we describe development of an optical exhaled gas sensing approach utilizing a nanostructured polymeric membrane that meets these requirements and demonstrates the dynamic evolution of exhaled breath biomarker concentration. We show that the activity of a solid acid catalyst toward the heterogeneous condensation reactions of immobilized resorcinol reagent with gas-phase acetone and formaldehyde can be preserved even at 100% ambient relative humidity through the incorporation of organic acids such as vanillic or tiglic. The reaction produces a colored flavan and poly-condensation products that permits highly selective and sensitive correlation to acetone and formaldehyde concentrations in exhaled breath. Such behavior relies on the complex heterophase morphology of the membrane as will be described. Figure 1

Water-Resistant Polymeric Acid Membrane Catalyst for Acetone Detection in the Exhaled Breath of Diabetics.

Endogenous volatile organic compounds (VOCs) such as acetone in exhaled human breath are associated with metabolic conditions in the bloodstream. Development of compact, rapid detectors of exhaled breath chemical composition in clinical settings is challenging due to the small sample size that can be collected during a single exhalation as well as spectroscopic interference by the abundance of water. In this paper, we show that the activity of a catalytic polymer membrane (Nafion 117) toward the heterogeneous condensation reaction of immobilized resorcinol reagent with gas-phase acetone can be preserved even at 100% ambient relative humidity through the incorporation of organic acids such as vanillic or tiglic. The reaction produces a colored flavan product that permits highly selective and sensitive correlation to acetone concentration in exhaled breath. Such behavior suggests solvent displacement, analogous to homogeneous liquid-phase systems. However, unlike classic acid-base equilibria, the extent of optode water resistance is shown to increase with the pKa of the imbibed organic acid while peak signal intensity of the imbibed acid undergoes a bathochromic shift to longer wavelengths. These observations are consistent with competition between organic acid deprotonation by water in a mixed solvent system on the one hand and immobilization on the other. Finally, we demonstrate how when applied to the direct chemical analysis of acetone in exhaled human breath, the approach yields excellent correlation to blood glucose in diabetics.

Direct observation of a photochemical activation energy: a case study of acetone photodissociation

The ability to observe and quantify the conversion of electronic potential energy to vibrational kinetic energy in a molecule after photoexcitation is essential to understand and control the outcome of photoinduced molecular fragmentation. We exploit the high selectivity of photoelectron–photoion coincidence detection to distinguish different relaxation channels and observe the fragmentation behavior of each channel. We demonstrate the concept by investigating the fragmentation of gas-phase acetone molecules initiated by three-photon excitation to high lying Rydberg states between 9.0 and 9.5 eV above the ground state. By applying variations of the photon energy, pulse duration (100–200 fs) and pulse energy, we are able to fully characterize the fragmentation process. Rydberg states between 5s and 8s are populated, which undergo ultrafast internal conversion to lower states. The corresponding non-adiabatic dynamics in the neutral molecule cause the conversion of electronic to vibrational energy, leading to fragmentation. Our scheme allows us to directly measure the activation energy for fragmentation of acetone to an acetyl ion and a methyl radical, which we determine to be (0.79 ± 0.04) eV. Longer laser pulses result in an increased fragment-to-parent ratio, representing a higher probability for relaxation because the relaxation time constants are comparable to the pulse duration. Upon excitation to Rydberg states at 9.5 eV we surprisingly observe reduced fragmentation, although ∼2 eV are coupled into vibrational energy, indicating that different relaxation pathways become active, which results in a change of the redistribution of vibrational energy within the molecule. Fragmentation due to subsequent excitation of the cation is found to play a minor role.

Mesoporous MgO synthesized by a homogeneous-hydrothermal method and its catalytic performance on gas-phase acetone condensation at low temperatures

Mesoporous MgO micro-particles (20–80μm) with crystalline phase framework wall were synthesized through a simple hydrothermal homogeneous precipitation route using urea as precipitating reagent. It possesses high specific area (278m2/g), pseudo parallel pore and wall arrangement and large amount of basic sites and exhibits excellent catalytic activity for acetone condensation to mesityl oxide and isophorone even at low temperatures (<200°C).

Synthesis of transition metal doped lamellar double hydroxides as base catalysts for acetone aldol condensation

Transition metals TM (TM=Fe+2, Zn+2, Ni+2 and Cu+2) doped lamellar double hydroxides (LDHs) were prepared by coprecipitation method and characterized with N2 adsorption–desorption isotherms, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and temperature-programmed desorption of CO2 (TPD–CO2). XRD patterns of the dried samples showed that these solids contained the crystallized lamellar double hydroxides (LDHs) after calcination. TPD–CO2 experiments revealed that these LDHs contain both moderate and strong basic sites varying with transition metal dopants. It was found that the gas-phase acetone aldol condensation was a surface basicity and texture-sensitive reaction. The basicity of the catalysts followed the sequence MgZnAlO>MgFeAlO>MgCuAlO>MgNiAlO, which agreed well with the variation of the catalytic activity in the acetone aldol condensation. The selectivity to isophorone and phorone could be correlated to the textural properties of the catalysts. Catalyst with large surface area and bigger pore diameter favored the formation of isophorone.

Preparation of visible light sensitive nano-sized N-TiO$_{2}$ photocatalysts and their photocatalytic activity under visible light

This study aimed to develop a photocatalyst that responds to visible light. For the preparation of visible light sensitive photocatalysts, N was doped into TiO2 (N-TiO2). To inhibit the recombination of excited electrons and holes, transition metals (M = Pt, Cu, Fe, Cr) were loaded on the N-TiO2. N-TiO2 nanotubes were also synthesized by a hydrothermal treatment of the prepared N-TiO2 in a strong basic environment. The prepared photocatalysts were characterized by XRD, FESEM, HRTEM, XPS, and UV/VIS spectrophotometer, and their photocatalytic activity was tested by the photodecomposition of liquid-phase methylene blue and gas-phase acetone.

TiO2 Macroscopic Fibers Bearing Outstanding Photocatalytic Properties Obtained through an Integrative Chemistry-Based Scale-Up Semi-Industrial Process

ABSTRACTIn here we depict the morphogenesis and associated properties of TiO2-based macroscopic fibers designed for the photodecomposition of volatile organic compounds (VOC). We employed a continuous industrially scalable extrusion-based process making the use of hybrid sols of amorphous titania nanoparticles, polyvinyl alcohol (PVA) and occasionally latex nanoparticles. This process allowed for the continuous generation of hybrid TiO2/latex/PVA or TiO2/PVA macroscopic fibers. Upon thermal treatment, biphasic porous fibers are obtained containing the anatase phase of TiO2 with 10-15% of brookite. These fibers, which can be manufactured under several hundred meter of length, are offering significantly improved phototocatalytic efficiency now comparable to the commercial Quartzel®PCO photocatalyst for gas-phase acetone mineralization.

A UV-Vis photoacoustic spectrophotometer.

A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles.

Ru–C–ZnO Composite Catalysts for the Synthesis of Methyl Isobutyl Ketone via Single Step Gas Phase Acetone Self-Condensation

Ruthenium/activated charcoal (Ru-C) was modified by a solid-solid interaction method with synthe- sized nano-zinc oxide (n-ZnO). Three different ratios of Ru-C:n-ZnO (1:2, 1:1 and 3:2) were used to prepare Ru- C-ZnO composite catalysts. These were used in the gas- phase, one-step self-condensation of acetone to methyl isobutyl ketone (MIBK). The composite catalyst (1:1 ratio) contained 2.5 wt% Ru showed superior conversion of acetone and selectivity for MIBK. Furthermore, this cata- lyst showed good consistency for MIBK formation for 100 h without any deactivation. Characterization of the catalysts revealed that balanced hydrogenation and acid- base functional character is crucial to obtain high catalytic performance.

A new peroxo-route for the synthesis of Mg–Zr mixed oxides catalysts: Application in the gas phase acetone self-condensation

We propose in this manuscript a new peroxo-mediated procedure for preparing magnesia–zirconia mixed oxides, with Mg/Zr molar ratio between 1 and 3, with enhanced distribution of basic sites. The mixed magnesia–zirconia oxides have been prepared from the gelled complex by Pechini-type method. The MgO–ZrO2 materials have been characterized and used as catalysts for acetone aldol condensation. The proposed preparation method provides a high degree of molecular homogeneity and favours the formation of magnesia-stabilized zirconia phase. Acetone gas-phase self-condensation was carried out over these catalysts as model reaction requiring the presence of basic sites. The condensation yields diacetone alcohol and mesityl oxide as mean C6 products, and phorones, isophorones and mesitylene as C9 products. In comparison to Mg–Zr oxide prepared by co-precipitation, these new materials present better conversions and higher selectivity to linear dimers and trimers (as mesitylene), whereas the selectivity for isophorones is significantly lower.