Decomposition Of Acetone Research Articles

Raman Spectroscopic Study of As-Deposited and Exfoliated Defected Graphene Grown on (001) Si Substrates by CVD

We present here results on a Raman spectroscopic study of the deposited defected graphene on Si substrates by chemical vapor deposition (thermal decomposition of acetone). The graphene films are not deposited on the (001) Si substrate directly but on two types of interlayers of mixed phases unintentionally deposited on the substrates: а diamond-like carbon (designated here as DLC) and amorphous carbon (designated here as αC) are dominated ones. The performed thorough Raman spectroscopic study of as-deposited as well as exfoliated specimens by two different techniques using different excitation wavelengths (488, 514, and 613 nm) as well as polarized Raman spectroscopy establishes that the composition of the designated DLC layers varies with depth: the initial layers on the Si substrate consist of DLC, nanodiamond species, and C70 fullerenes while the upper ones are dominated by DLC with an occasional presence of C70 fullerenes. The αC interlayer is dominated by turbostratic graphite and contains a larger quantity of C70 than the DLC-designated interlayers. The results of polarized and unpolarized Raman spectroscopic studies of as-grown and exfoliated graphene films tend to assume that single- to three-layered defected graphene is deposited on the interlayers. It can be concluded that the observed slight upshift of the 2D band as well as the broadening of 2D band should be related to the strain and doping.

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

The properties of Ni/Co/Co-Ni/MgAl2O4 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 HC and CCO bonds cleavage, leading to the formation of CO, H2, and C on the metal surface. At low temperatures (200°C) and in the presence of H2 in the reactor feed, the Ni catalyst catalyzed the hydrogenation of the CO and CHx species formed from acetone activation on the metallic sites, producing CH4. 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 CHx and CO species to CH4 was determined by the nanoparticle oxidation degree, which decreased in the order Ni>Co-Ni>Co. With increased temperature, the CHx species decomposed to C and H2, instead of being hydrogenated to CH4. The oxidation of C by H2O was favored on Co-containing catalysts. The reaction pathways are discussed based on theoretical data obtained from the literature.

Deposition of graphene/graphene-related phases on different substrates by thermal decomposition of acetone

Here we present results on the deposition of graphene and graphene-related phases by chemical vapour deposition (CVD) method. The source of carbon is thermally decomposed acetone (C2H6CO) in Ar main gas flow at different temperatures depending on the substrate used. The deposition of graphene and/or graphene related phases is carried out on commercially available Cu, Ni, (Cu0.70 + Ni0.30), μ-metal (Fe0.16 + Ni0.77 + Cu0.05 + Cr0.2) and SS304 (Fe0.60 + Ni0.09 + Cr0.19 + Mn0.02 + Si0.008) metal foils. The obtained thin films are studied by optical microscopy, Raman and X-ray photoelectron spectroscopies. We determined the optimal temperature and fixed values of the remaining parameters of the CVD process for each substrate.

Synthesis of VC-C Nanocomposite for Electrochemical Applications

Carbon-coated vanadium carbide (VC-C) nanocomposite were synthesized by single-step chemical-reduction route in an autoclave at the temperature of 600oC. In this experiment, vanadium pentode (V2O5) was used as precursor, magnesium as reducing agent (Mg) and acetone as carbon source. The gases produced by the decomposition of acetone generate carbon and H2/CO2 gases at high temperature which further creates high pressure inside the autoclave. The processing parameters were optimized for the formation of single phase vanadium carbide (VC). The structure, morphology, and thermal stability of the obtained product were studied by XRD, TEM and TGA/DTA techniques, respectively. The N2 adsorption-desorption isotherm indicated the mesoporous structure of the VC. The electrochemical properties of the obtained C@VC were studied by the cyclic voltammetric studies.

Effect of Cobalt Particle Size on Acetone Steam Reforming

AbstractCarbon‐supported cobalt nanoparticles with different particle sizes were synthesized and characterized by complementary characterization techniques such as X‐ray diffraction, N2 sorption, acetone temperature‐programmed desorption, transmission electron microscopy, and CO chemisorption. Using acetone steam reforming reaction as a probe reaction, we revealed a volcano‐shape curve of the intrinsic activity (turnover frequency of acetone) and the CO2 selectivity as a function of the cobalt particle size with the highest activity and selectivity observed at a particle size of approximately 12.8 nm. Our results indicate that the overall performance of acetone steam reforming is related to a combination of particle‐size‐dependent acetone decomposition, water dissociation, and the oxidation state of the cobalt nanoparticles.

Structural and growth kinetics of in-situ reduced V2O5

Vanadium carbide (VC) nanopowder has been prepared from V2O5 by chemical-reduction route under high pressure of hydrogen and carbon dioxide gases. The reduction of V2O5 to VC has occurred in the presence of magnesium in a closed vessel at 800°C where acetone is used as a carbon source. Generation of gases via decomposition of acetone is responsible for generating high pressure and hence for reduction. Rietveld refinement shows that the product phase VC is cubic with space group Fm-3m. TEM analysis shows the non-agglomerated VC particles with faceted morphology having an average diameter of 2040nm. The mechanism of transformation and formation of nanoparticles is discussed in light of the obtained structure. It confirmed that the conversion of V2O5 to VC is a multi step phenomenon and takes place with variation in the experimental parameters. Wide band-gap in UV-Vis spectroscopy indicates that the obtained product is optically active and has the potential for use in optical applications.

Plasma-catalytic oxidation of acetone in annular porous monolithic ceramic-supported catalysts

Oxidative decomposition of acetone over multichannel monolithic ceramic-supported catalysts combined with non-thermal plasma was investigated. Plasma was generated inside the porous ceramic by applying an alternating current (AC) voltage to the coaxial electrodes. The tandem plasma-catalytic reactor consisted of two ceramic-supported catalysts containing zinc oxide (ZnO) and/or manganese oxide (MnO2), in which the first supported catalyst was exposed to the plasma discharge and the second one was placed in the post-plasma region. Several sets of catalyst arrangements such as MnO2-loaded monolith followed by bare monolith, ZnO-loaded monolith followed by bare monolith, ZnO-loaded monolith followed by MnO2-loaded monolith and two consecutive MnO2-loaded monoliths with different Mn contents were examined in relation to the acetone decomposition and the byproducts formation. More than 90% of acetone was decomposed at a specific input energy (SIE) of about 1.0 kJ L−1 with the catalyst arrangement of MnO2 (0.1% Mn) followed by MnO2 (5.0% Mn), while the decomposition efficiency obtained with two consecutive bare monoliths was about 66% at the same SIE. The use of ZnO in the plasma discharge region did not largely improve the acetone decomposition efficiency. Wherever it is placed either in the plasma discharge region or in the post-plasma region, MnO2 catalyst substantially promoted the acetone decomposition, obviously due to the dissociation of ozone into far more reactive oxygen atoms available for oxidizing acetone molecules.

Role of Keto–Enol Isomerization on Surface Chemistry and Hydrogenation of Acetone on Pt(111): A DFT study

The adsorption, tautomerization, and hydrogenation of acetone on Pt(111) surfaces were investigated by using density function theory calculations. The role of the keto–enol isomerization on selective hydrogenation and unselective decomposition of acetone was also studied. The results revealed that only a small amount of the adsorbed acetone could undergo enolization and subsequently decompose on clean Pt(111) surface at moderate condition. The enol tautomer is the origin of acetone decomposition on Pt(111) surface. The effect of the keto–enol isomerization on hydrogenation of acetone on Pt(111) under sufficient hydrogen pressure is not significant. These results suggested that the keto–enol isomerization could not enhance the selective hydrogenation of acetone on Pt(111) surface.

One Step Synthesis and Growth Mechanism of Carbon Nanotubes

A simple one step, reproducible, synthesis route for carbon nanotubes was proposed. No external catalyst was used for the synthesis. These nanotubes were obtained after decomposition of acetone at 650 °C in a specially designed autoclave. The pressure generated due to decomposition of acetone played a vital role in the synthesis. The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3–14 nm. The thermo gravimetric analysis showed 3% weight loss below 500 °C; the content of amorphous carbon is very less. The growth mechanism of CNTs was also proposed in the present paper.

Synthesis of carbon nanotubes from acetone

The process of synthesizing carbon nanotubes (CNTs) using the method of catalytic gas-phase pyrolysis has been studied using acetone as a source of carbon. CNTs with outer diameters of 8–10 nm were prepared. The highest yield of the CNTs with the best quality is achieved when (Co, Mo)/MgO-Al2O3 catalyst is used. When (Fe, Co, Mo)/Al2O3 is used, the yield and quality of CNTs are lower. For comparison, CNTs obtained on the same catalysts but with propylene as the source of carbon have been investigated. It has been shown that, in this case, the best yield is achieved if (Fe, Co, Mo)/Al2O3 catalyst is used. According to the thermogravimetric data, CNT prepared at optimal conditions from acetone have fewer structural defects than those prepared from polypropylene. The optimal temperature and concentration conditions of the CNT synthesis from acetone have been determined. Based on the kinetic data, it has been assumed that the growth of CNTs takes place due to the ketene formed under the thermal decomposition of acetone. The ecological aspects of the CNT preparation from hydrocarbons and acetone are considered.

Feasible Synthesis of TiO2 Deposited on Kaolin for Photocatalytic Applications

AbstractThe aim of the present study was to synthesize a photocatalyst on the basis of TiO2 with kaolin as the support material. Properties such as layered structure and a suitable particle size of kaolin could be beneficial in the production of a high-quality and relatively cheap photocatalyst on an industrial scale. Homogeneous hydrolysis with urea as a precipitation agent and kaolin as support material was used to obtain a kaolin surface covered with TiO2. Samples were characterized by means of X-ray powder diffraction, infrared and Raman spectroscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller surface area, and Barrett-Joyner-Halenda porosity determination. Photocatalytic activity was assessed by a Reactive Black 5 azo dye discoloration in a water suspension and by acetone decomposition on a thin layer of sample in a gas phase. The characterization confirmed that the well crystallized TiO2 was distributed effectively over the whole surface of a kaolin substrate, and photocatalytic tests revealed that the active surface layer of titania particles on kaolin performed well, suggesting that kaolin acts as a suitable support.

Photocatalytic decomposition of 2-propanol and acetone in air by nanocomposites of pre-formed TiO2 particles and mesoporous silica

The photocatalytic efficiency in the degradations of gaseous 2-propanol and acetone has been studied on nanocomposite materials prepared by embedding well-crystallized titanium dioxide (TiO2) particles (Degussa P25) into surfactant-templated mesoporous silica. The composite materials adsorbed the organic substances considerably in dark conditions and decomposed them completely to CO2 under photoirradiation. The efficiency was influenced remarkably by the surface modification of TiO2 particles. According to the transmission electron microscope observations, using carbon-coated TiO2 particles gave a composite MCT-C with well-ordered channels of the mesoporous silica, but not all the TiO2 particles were embedded in silica. MCT-C showed a high CO2 production rate comparable to that of pristine TiO2 (P25) when the concentrations of gaseous 2-propanol and acetone were as low as several ppm. On the other hand, using n-octadecyl-grafted TiO2 particles resulted in a composite MCT-S in which most of the TiO2 particles were well embedded in mesoporous silica, but the degree of channel-ordering was comparatively lower than that in MCT-C. The CO2 production rate for MCT-S was lower than that for P25. This is probably due to the deactivation of TiO2 surface by the silane-coupling reagent and/or the disorder of the mesopore channels. These composite photocatalysts could suppress the emission of unhealthy degradation products by adsorptive capacity of mesoporous silica.

Cyclic organic peroxides thermal decomposition in the presence of CuFe2O4 magnetic nanoparticles

The effect of magnetically recoverable CuFe2O4 nanoparticles on thermal decomposition of acetone and pinacolone cyclic organic diperoxides, and acetone triperoxide was studied. Ethanol, toluene or ethylbenzene were used as reaction solvents, the initial peroxide concentration was ca. 0.02molL−1 and the amount of heterogeneous catalyst added was ca. 0.5mgmL−1. CuFe2O4 nanoparticles, obtained according to the citric acid-aided process, greatly accelerates the thermal decomposition of methyl substituted cyclic peroxide, but in the case of pinacolone diperoxide only slightly catalytic effects can be detected, probably due to the presence of the bulky tert-butyl substituent in the proximity of the OO bond. This heterogeneously catalyzed reaction can be explained by a free radical mechanism which involves the initiation reaction on the catalyst surface. The products detected (ethane, 2,2-dimethylpropane, ethylbenzene, bibenzyl and 2,3-diphenylbutane) can be interpreted in terms of the initial OO bond homolysis catalyzed by copper ferrites to form an iron peroxo radical species which later undergoes CO and CC bond cleavage. The reduction of the reaction temperature in the styrene and methylmethacrylate polymerization processes could be the main application of the results obtained in the present work, where the thermal decomposition of multifunctional cyclic peroxides in the presence of copper ferrites can be reached decreasing the working temperatures.

Titanium Dioxide Coatings Sprayed by a Water-Stabilized Plasma Gun (WSP) with Argon and Nitrogen as the Powder Feeding Gas: Differences in Structural, Mechanical and Photocatalytic Behavior

Titanium dioxide coatings were sprayed by a water-stabilized plasma gun to form robust self-supporting bodies with a photocatalytically active surface. Agglomerated nanometric powder was used as a feedstock. In one case argon was used as a powder-feeding as well as coating-cooling gas whereas in the other case nitrogen was used. Stainless steel was used as a substrate and the coatings were released after the cooling. Over one millimeter thick self-supporting bodies were studied by XRD, HR-TEM, XPS, Raman spectroscopy, UV-VIS spectrophotometry and photocatalytic tests. Selected tests were done at the surface as well as at the bottom side representing the contact surface with the substrate during the spray process. Porosity was studied by image analysis on polished cross sections where also microhardness was measured. The dominant phase present in the sprayed samples was rutile, whereas anatase was only a minor component. The hydrogen content in the nitrogen-assisted coating was higher, but the character of the optical absorption edge remained the same for both samples. Photoelectron spectroscopy revealed differences in the character of the O1s peak between both samples. The photocatalytic activity was tested by decomposition of acetone at UV illumination, whereas also the end products—CO and CO2—were monitored. The nitrogen-assisted coating was revealed as a more efficient photocatalyst. Certain aspects of a thermal post-treatment on the coatings are discussed as well. Color and electrical conductivity are markedly changed at annealing at 760 °C, whereas only very small changes of the as-sprayed coating character correspond to annealing at 500 °C.

Plasma sprayed TiO2: The influence of power of an electric supply on relations among stoichiometry, surface state and photocatalytic decomposition of acetone

The influence of input power on plasma sprayed coating was studied for a water-stabilized plasma spray torch (WSP®) and ceramic coatings formed from titanium dioxide (TiO2). All other spray setup parameters were secured during the experiment with electric supply power as the only variable factor. Physical characteristics of the coatings were tested by means of Raman spectroscopy and X-ray photoelectron spectroscopy which are able to determine the stoichiometry and surface chemical composition of the coatings. Further, stoichiometry and surface states are crucial for the photocatalytic efficiency of the coatings. The photocatalytic procedure involved was UV-induced decomposition of acetone. Links between the tested features are drawn. The lower supply power used during the spraying of TiO2 coating resulted in higher activity with respect to the photocatalytic point of view. Both the stoichiometry and surface composition are in the same time deviated from pure TiO2.

Role of CH, CH3, and OH Radicals in Organic Compound Decomposition by Water Plasmas

Decomposition of acetone, methanol, ethanol, and glycerine by water plasmas at atmospheric pressure has been investigated using a direct current discharge. At torch powers of 910–1,050 W and organic compound concentrations of 1–10 mol%, the decomposition rate of methanol and glycerine was over 99%, while those of acetone and ethanol was 95.4–99%. The concentrations of H2 obtained were 60–80% in the effluent gas for any compounds by pyrolysis. Based on the experimental results, the decomposition mechanism of organic compounds in water plasmas was proposed and the roles of intermediate species such as CH, CH3, and OH have been investigated; CH radical generated from organic compounds decomposition was easily oxidized to form CO; incomplete oxidation of CH3 leads to C2H2 generation as well as soot formation; and negligible amount of soot observed from glycerine decomposition even at high concentration indicated that oxidation of CH×(×:1–3) was enhanced by OH radical.

Acetone decomposition by water plasmas at atmospheric pressure

Decomposition of aqueous acetone was performed using a direct current (DC) plasma torch at atmospheric pressure. The torch can generate the plasma with water as the plasma-supporting gas in the absence of any additional gas supply system and cooling devices. The results indicated that 5 mol% acetone was drastically decomposed by water plasmas with energy efficiencies of 1.7×10 −7 mol J −1. The major products in the effluent gas were H 2 (60–70%), CO 2 (5–16%), CO (6–16%), and CH 4 (0.2–0.9%). However, trace levels of formic acid (HCOOH) and formaldehyde (HCHO) were observed in the liquid effluent. Based on the experimental results and information from the literature, the following decomposition mechanism was proposed for acetone in water plasmas: first, electron dissociation in arc region generates acetyl (CH 3CO) and methyl (CH 3) radicals; then, chemical oxidation or reduction in plasma flow region forms CO and CH x( x:1–3) radicals there. Finally, the generated intermediate species undergo complex reactions to form stable compounds such as CO in downstream region. However, if little oxygen is present, those intermediate species easily recombine with each other or are oxidized by OH to form unwanted by-products, such as HCOOH and HCHO.

Mechanisms of Decomposition of Organic Compounds by Water Plasmas at Atmospheric Pressure

The decomposition of acetone, methanol, and ethanol by water plasmas at atmospheric pressure has been investigated using a direct current (DC) discharge. At torch powers of 910–1050 W and organic compound concentrations of 1–10 mol %, the decomposition rate of methanol was over 99.99%, while those of acetone and/or ethanol was 96–99%. The concentrations of H2 obtained were 65–71% in the effluent gas and the removal efficiencies of 90–95% for total organic carbon (TOC) were achieved in liquid effluent for any compounds by pyrolysis. Over 50 wt % carbon in acetone or ethanol fed as the plasma supporting gas was transformed into soot, while the soot formation was negligible during methanol decomposition. On the basis of the experimental results, the mechanisms of decomposition of organic compounds in water plasmas were proposed and the mechanism of soot formation was clarified for the first time.

Photocatalytic Degradation of Gaseous Acetone by a Self-Prepared Nano-Sized Composite TiO<sub>2</sub>/In<sub>2</sub>O<sub>3</sub>/SnO<sub>2</sub> Film Photocatalyst

The objective of this study is to decompose gaseous acetone ((CH3)2CO) by a self-prepared nano-sized composite TiO2/In2O3/SnO2 film photocatalyst that was prepared by a multi-target vacuum sputter operating at a vacuum pressure of 3 mtorr. The operating parameters investigated for the sputtering process included oxygen to argon ratio (O2/Ar), sputtering temperature, substrate materials, substrate layers, and sputtering duration. The nano-sized composite TiO2/In2O3/SnO2 film photocatalyst was mainly composed of anatase with a few rutile. The surface roughness of the TiO2/In2O3/SnO2 film photocatalyst in terms of RMS ranged from 2.292 to 7.533 nm, while the thickness of the single- and double-layer film photocatalysts were 473.5 and 506.0 nm, respectively. Gaseous acetone was initially injected into and further degraded in a self-designed batch photocatalytic reactor containing the nano-sized composite TiO2/In2O3/SnO2 film photocatalyst. Experimental results indicated that the highest acetone degradation efficiency of 99.9% was obtained at 50°C and 1 atm with the incident of near-UV illuminated by a fluorescent black light lamp. Under the incidence of blue light (430-500 nm), the reaction rates of acetone decomposition were 2.353x10-5 and 3.478x10-5 μmole/cm2-sec for using single- and double-layer TiO2/In2O3/SnO2 film photocatalysts, respectively.

Decomposition of Acetone by Hydrogen Peroxide/Ozone Process in a Rotating Packed Contactor

The direct use of ozone (O3) in water and wastewater treatment processes is found to be inefficient, incomplete, and limited by the ozone transfer between the gas-liquid interface because of its low solubility and instability in aqueous solutions. Therefore, rotating packed contactors were introduced to improve the transfer of ozone from the gaseous phase to the solution phase, and the effect of several reaction parameters were investigated on the temporal variations of acetone concentration in aqueous solution. The decomposition rate constant of acetone was enhanced by increasing the rotor speed from 450 to 1800 rpm. Increasing the hydrogen peroxide (H2O2)/O3 molar ratios accelerated the decomposition rate until a certain optimum H2O2/O3 molar ratio was reached; further addition of H2O2 inhibited the decomposition of acetone, possibly because excessive amounts of H2O2 added might serve as a scavenger to deplete hydroxyl free radicals.