Thermal Decomposition Of Ethanol Research Articles

Clarification on the Gassing Behavior of Carbon‐Coated Li4Ti5O12 at Elevated Temperature: Importance of Coating Coverage

AbstractLithium‐ion batteries (LIBs) have become vital energy‐storage devices in electric vehicles (EVs). Li4Ti5O12 (LTO) is a promising material of LIB because of its high rate capability, cyclability, and safety compared to the graphite‐based anode materials in commercial LIBs. However, one of the major concerns in LTO‐based LIBs is gassing, which results from the interfacial reaction between LTO and organic electrolyte solutions, unlike the reduction decomposition of an electrolyte in graphite electrodes. Carbon coating on LTO has been proposed to mitigate the gassing by preventing such side reactions, even though reports have been conflicting. In this work, there are different kinds of carbon‐coated LTO deposited using the thermal decomposition of ethanol that has been investigated at elevated temperature using In Operando pressure analysis to answer the paradox of the effect of carbon coating on the gassing behavior on LTO. Our Spatial Raman Spectroscopy Analysis (SRS) shows that the carbon coating coverage is likely responsible for the discrepancy in the gassing behavior reported by other studies. Our proposed deposition process achieves complete coverage with an ultrathin 3 nm carbon coating layer which mitigates the interfacial reactions while improving electrochemical performance.

Synthesis, characterization and cyclic voltammetry studies of helical carbon nanostructures produced by thermal decomposition of ethanol on Cu-foils

Cu-foils have been used intensively to fabricate graphene and other carbon nanostructures. Several routes have been implemented to improve the synthesis of such carbonaceous nanomaterials. We investigated the growth of carbon materials on Cu-foils by mapping the reactor in a chemical vapor deposition method. Several Cu-foils were pretreated by sonication to modify their surface and were placed alongside the reactor and exposed to a flow of ethanol vapor. After carbon materials deposition, the Cu-foils were analyzed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and cyclic voltammetry (CV). It was demonstrated that the type of synthesized carbon nanostructure depends strongly on the position where the Cu-foils were placed. XRD characterizations revealed the presence of graphite materials, Cu, and CuO crystal structures. SEM characterizations revealed the presence of helical, herringbone and straight multiwalled carbon nanotubes with internal bamboo-shape morphology and formation of Cu nanoparticles. Important electrochemical properties of Cu-foils rich in helical carbon nanostructures were observed, suggesting this material can be used for redox reactions (RR) promotion. In addition, the hydrophobic properties were evaluated by contact angle measurements.

Theoretical Study of the Formation Methane in the Reaction of Methyl Radical with Propanol-2

Theoretical Study of the Formation Methane in the Reaction of Methyl Radical with Propanol-2

Ethanol pyrolysis kinetics using H2O time history measurements behind reflected shock waves

Abstract The thermal decomposition of ethanol has been studied under pyrolytic conditions behind reflected shock waves in the 1250 to 1677 K temperature range, at an average pressure of 1.31 atm for a mixture highly diluted in Ar. A laser absorption technique was utilized to measure H2O time-histories, and the detailed kinetics mechanism (AramcoMech2.0) was selected among various models from the literature based on its a priori agreement with the experimental data in the present study. Sensitivity and rate-of-production analyses were performed and showed that the C2H5OH→C2H4+ H2O (R1) decomposition pathway is almost the sole reaction contributing to H2O formation at the early times under the present conditions, allowing an a priori direct measurement of its rate coefficient k1. The rate coefficient was determined to be defined as the Arrhenius equation k1 (s−1) = 3.37 × 1011 exp (–27174 K/T), which is in very good agreement with Kiecherer et al. (2015), where k1 was also directly determined under similar conditions. Secondary chemical reactions taking place in the thermal decomposition have very low influence in the H2O formation during the time-frame selected, leading to an uncertainty for k1 of approximately 20%. The full H2O time histories are useful for validating the full ethanol kinetics mechanism for future validation.

Direct Ethanol Anode-Supported Solid Oxide Fuel Cell

Long term durability was demonstrated on high-performance direct ethanol solid oxide fuel cell operating in gradual internal reforming. Anode supported single cells, fabricated at Forschungszentrum Jülich, composed of (La,Sr)MnO3 cathode, 8 mol% yttria-stabilized zirconia (YSZ) electrolyte, and YSZ-Ni anode were used for long term testing on anhydrous (direct) ethanol. Gadolinia-doped ceria (CGO), with 0.1 wt.% of Ir, catalyst was produced by the impregnation of Ir salt in commercial CGO (Praxair) and mixed with organic additives. The CGO-Ir suspension was deposited onto the surface of the YSZ-Ni anode support with an air brush. Such a catalytic layer acts both as a physical barrier to avoid direct contact of the fuel with Ni-based anode and to promote the gradual internal reforming of ethanol. The CGO-Ir catalyst was designed for the reforming of the main compounds resulting from the thermal decomposition of ethanol at high temperature and to inhibit the formation of ethylene, which is a known source of carbon deposits. After deposition the sample was heated at 850ºC in inert atmosphere to ensure good adhesion between the catalytic layer and the anode. Gold grid and paint were used as current collectors in both cathode and anode sides. The single fuel cells were mounted in the test apparatus, sealed with gold rings and alumina cement and heated to the measuring temperature (850°C) under inert atmosphere. After gas tightness was checked by flowing air on the cathode side and argon on the anode side, the anode was reduced under hydrogen. The fuel cell was kept at 0.6 V while monitoring the current drained from the cell at 850 °C. Samples were initially operated in hydrogen for a few hours and fuel was switched to dry ethanol, carried by nitrogen. It is important to mention that no oxidizing agent was added to the fuel and that water produced by the electrochemical reaction of hydrogen at the anode promoted the reforming of the ethanol in the CGO-based layer, in the so-called gradual internal reforming. In such conditions the current output was recorded and observed to not be significantly different form that under hydrogen. Moreover, the direct ethanol fuel cell was continuously operated for 650 hours without major losses due to carbon formation. The experimental results demonstrate that the water released by the electrochemical oxidation of reformate hydrogen at the electrolyte/anode active interfaces is sufficient for the reforming of the primary fuel in the catalytic layer, provided that a minimum fuel utilization is respected. After the durability tests, energy dispersive X-ray spectroscopy and scanning electron microscopy analyses of the samples revealed no carbon deposit formation in the anode. The experimental results provided compelling evidence for the viability of gradual internal reforming of ethanol in high performance solid oxide fuel cells.

Diameter-controlled growth of aligned single-walled carbon nanotubes on quartz using molecular nanoclusters as catalyst precursors

Molecular nanoclusters containing Fe and Mo atoms have been used as catalyst precursors for the growth of single-walled carbon nanotubes (SWNTs) on stable temperature (ST)-cut quartz substrates by chemical vapor deposition. Attribute to the uniform catalyst nanoparticles and the confinement effect of the crystalline substrates, well-aligned SWNTs with narrow diameter distribution have been synthesized. Atomic force microscopy measurements show that the mean diameter of the nanotubes obtained by thermal decomposition of ethanol at 900°C is 0.76 ± 0.16 nm, which is the smallest among all reported results for aligned SWNTs. The mean diameter of the nanotubes increases with growth temperature. In addition to using identical nanoclusters as the catalyst precursors, the avoidance of annealing treatment of catalyst precursors is also a key point for obtaining SWNTs with controlled diameters. Using these identical nanoclusters as catalyst precursors and carefully tuning the growth parameters make us closer to the ultimate goal of controlling the chirality of SWNTs.

Ni supported high surface area CeO2–ZrO2 catalysts for hydrogen production from ethanol steam reforming

The catalytic activity of nano-sized x%Ni/Ce0.74Zr0.26O2 (x = 0, 2, 10 and 20wt%) catalysts have been investigated to develop highly active catalysts for ethanol steam reforming (ESR) into hydrogen. The structure and surface properties of the catalysts were tested by XRD, TPR, HRTEM and BET surface areas. The effect of reaction temperature from 200 °C to 600 °C was studied in a flow system at atmospheric pressure with an ethanol/water molar ratio of 1 : 8. Selectivity was calculated for the catalytic products H2, CO, CO2 and CH4, as well as the intermediates C2H6, C2H4, C3H8, CH3CHO and CH3COCH3, at different reaction temperatures. It was found that complete conversion of ethanol with considerable amounts of H2 was obtained at 400 °C over all catalysts. H2 was produced at a very low temperature (200 °C) over 10% and 20% Ni loadings, while a maximum H2 selectivity (75%) is reached at 600 °C over the 2%Ni/Ce0.74Zr0.26O2 catalyst; this is most likely due to the small nickel particle size (2–4 nm) in 2%Ni, which results in enhancement of the metal–support interactions. Thermal decomposition of ethanol in an ethanol/water mixture under the same reaction conditions, but in the absence of catalyst, was also studied. HRTEM of the spent catalyst (8 h ESR) shows the deposition of carbon in the form of carbon nanotubes (CNTs).

Synthesis of MWCNTs and hydrogen from ethanol catalytic decomposition over a Ni/La 2O 3 catalyst produced by the reduction of LaNiO 3

In the present paper we present a clean process that allows the simultaneous production of hydrogen and carbon nanotubes based on catalytic decomposition of ethanol, which is a renewable energy source. The catalyst consists of Ni nanoparticles highly dispersed on La 2O 3, obtained by the reduction of LaNiO 3. The effect of reaction conditions, such as reaction temperature and ethanol heating temperature, on the gaseous composition of the produced gas and the characteristics of the carbonaceous deposits was studied. An increase of the reaction temperature leads to an increase in H 2 production. The carbonaceous deposits were characterized by TGA, Raman spectroscopy TEM and HRTEM analysis. TEM micrographs show that the nanotubes were multi-walled with inner diameters ranging from 4 nm to 12 nm and outer diameters up to 75 nm. At low reaction temperatures the production of fibers is favored. The best graphitized carbon material was obtained when ethanol reacts at the surface of the catalyst instead of products issued from the thermal decomposition of ethanol (CH 4, CO, CO 2, C 2H 6 and C 2H 4). The yield of carbon nanotube (CNT) and H 2 were 3.5 g CNT (g cat h) −1 and 39 L H 2 ( g h ) − 1 respectively at 700 °C. The inner diameter of the CNTs does not depend on the experimental conditions used, whereas the outer diameter strongly depends on the reaction temperature (from 500 °C to 700 °C). From HRTEM images two types of carbon materials were shown: one with parallel graphene layers and one with fishbone structure. The intershell spacings d ˆ 0 0 2 were measured, the average value was equal to 0.344 nm for parallel tubes, while in curvature the d spacing is higher: 0.360 nm.

Structural Changes in Fibrous Carbon Nanomaterials Produced by Adding Sulfur During Chemical Vapor Deposition

Vapor-grown carbon fibers (VGCFs), platelet graphite nanofibers (PGNFs), turbostratic carbon nanofibers (CNFs), and carbon spheres were continuously produced by the thermal decomposition of ethanol in the presence of an Fe catalyst and a sulfur promoter at 1100 degrees C under a nitrogen/hydrogen atmosphere in a vertical chemical vapor deposition reactor. The sulfur concentration dramatically affected the morphology and microstructure of the carbon materials produced. A large amount of sulfur in the catalytic precursor led to the direct pyrolysis of hydrocarbons and the formation of carbon spheres (Fe:S = 1:10) while a lower amount of sulfur led to the formation of fibrous carbon materials, including VGCFs (Fe:S = 1:0.2), PGNFs (Fe:S = 1:2), and turbostratic CNFs (Fe:S = 1:5). The degree of poisoning of the catalysts determined the precipitation of the graphene layers, allowing the different types of carbon material to form.

Synthesis of large-scale SiC–SiO 2 nanowires decorated with amorphous carbon nanoparticles and Raman and PL properties

Large-scale SiC–SiO 2 core–shell nanowires decorated with carbon nanoparticles have been synthesized on Si substrate using thermal decomposition of ethanol. The amorphous carbon nanoparticles on SiO 2 shell are of hemispherical configuration hiving a mean diameter of about 20 nm. The average size of carbon nanoparticles estimated from Raman measurement is 23.4 nm close to that evaluated from transmission electron microscopic observation. Strong enhancement of blue emission band and appearance of a new yellow emission band were observed in SiC–SiO 2 core–shell nanowires decorated with carbon nanoparticles and their origins were discussed. A possible synthesis mechanism of SiC–SiO 2 core–shell nanowires decorated with carbon nanoparticles was proposed.

Acetylene-Accelerated Alcohol Catalytic Chemical Vapor Deposition Growth of Vertically Aligned Single-Walled Carbon Nanotubes

Addition of only 1% acetylene into ethanol was found to enhance the growth rate of single-walled carbon nanotubes (SWNTs) by up to 10-fold. This accelerated growth, however, only occurred in the presence of ethanol, whereas pure acetylene at the same partial pressure resulted in negligible growth and quickly deactivated the catalyst. The dormant catalyst could be revived by reintroduction of ethanol, indicating that catalyst deactivation is divided into reversible and irreversible stages. Since the thermal decomposition of ethanol also yields some amount of acetylene, the possible contribution to the formation of SWNTs from these decomposed gases is also discussed.

Novel and Simple Synthesis Method for Submillimeter Long Vertically Aligned Single-Walled Carbon Nanotubes by No-Flow Alcohol Catalytic Chemical Vapor Deposition

Using a conventional thermal chemical vapor deposition (CVD) system, ethanol vapor was enclosed in a reactor, i.e., no flow, with Co/Mo dip-coated quartz substrates to synthesize submillimeter long vertically aligned single-walled carbon nanotube (SWNT) films successfully. The no-flow CVD method yielded an increase in film thickness of up to 0.11 mm compared with the normal flowing gas method for 30 min of synthesis. The thermal decomposition of ethanol was investigated using Fourier transform infrared spectroscopy and quadrupole mass spectrometry. At CVD temperatures, ethanol decomposed mainly into ethylene, acetylene, acetaldehyde, and water. Some of these molecules could enhance SWNT growth.

Thermal decomposition of ethanol. III. A computational study of the kinetics and mechanism for the CH3+C2H5OH reaction.

The mechanism for the CH3+C2H5OH reaction has been investigated by the modified Gaussian-2 method based on the geometric parameters of the stationary points optimized at the B3LYP/6-311+G(d,p) level of theory. Five transition states have been identified for the production of CH4+CH3CHOH (TS1), CH4+CH3CH2O (TS2), CH4+CH2CH2OH (TS3), CH3OH+CH3CH2 (TS4), and CH3CH2OCH3+H (TS5) with the corresponding barriers 12.0, 13.2, 16.0, 44.7, and 49.9 kcal/mol, respectively. The predicted rate constants and branching ratios for the three lower-energy H-abstraction reactions were calculated using the conventional and variational transition state theory with quantum-mechanical tunneling corrections for the temperature range 300-3000 K. The predicted total rate constant, kt=8.36 x 10(-76) T(20.00) exp(5258/T) cm3 mol(-1) s(-1) (300-600 K) and 6.10 x 10(-25) T(4.10)exp(-4058/T) cm3 mol(-1) s(-1) (600-3000 K), agrees closely with existing experimental data in the temperature range 403-523 K. Similarly, the predicted rate constants for CH3+CH3CD2OH and CD3+C2H5OD are also in reasonable agreement with available low temperature kinetic data.

Thermal decomposition of ethanol. II. A computational study of the kinetics and mechanism for the H+C2H5OH reaction

The kinetics and mechanism for the H+C2H5OH reaction, a key chain-propagation step in the high temperature decomposition and combustion of ethanol, have been investigated with the modified GAUSSIAN -2 (G2M) method using the structures of the reactants, transition states and products optimized at the B3LYP/6-311+G(d,p) level of theory. Four transition states have been identified for the production of H2+CH3CHOH (TS1), H2+CH2CH2OH (TS2), H2+C2H5O (TS3), and H2O+C2H5 (TS4) with the corresponding barriers, 7.18, 13.30, 14.95, and 27.10 kcal/mol. The predicted rate constants and branching ratios for the three H-abstraction reactions have been calculated over the temperature range 300–3000 K using the conventional and variational transition state theory with quantum-mechanical tunneling corrections. The predicted total rate constant, kt=3.15×103T3.12 exp(−1508/T) cm3 mol−1 s−1, agrees reasonably with existing experimental data; in particular, the result at 423 K was found to agree quantitatively with an available experimental value. The small deviation between the predicted kt and another set of experimental data measured at 295–700 K has been examined by kinetic modeling; the deviation is attributable to insufficient corrections for contributions from secondary reactions.

Chemisorbed methyl as an intermediate surface species in the methanation reaction on nickel

The thermal decomposition of ethanol on Ni(111) provides an efficient source of CH 3(ads) which rapidly hydrogenates to produce CH 4(g). A comparison of the rate of production of ethanol-derived CH 4(g) per Ni site with the turnover number in CH 4(g) synthesis from CO(g)+ H 2(g) on Ni(111) has been made. At 315 K, CH 4(g) is evolved about 10 6 times more rapidly from a monolayer of decomposing ethanol than from CO(g)+H 2(g) reactants. These results suggest that the rate limiting step(s) in CH 4(g) synthesis from CO(g)+H 2(g) exist at an earlier stage than the CH 3(ads)+H(ads) → CH 4(g) elementary process.

Chemisorbed methyl as an intermediate surface species in the methanation reaction on nickel

The thermal decomposition of ethanol on Ni(111) provides an efficient source of CH 3(ads) which rapidly hydrogenates to produce CH 4(g). A comparison of the rate of production of ethanol-derived CH 4(g) per Ni site with the turnover number in CH 4(g) synthesis from CO(g)+ H 2(g) on Ni(111) has been made. At 315 K, CH 4(g) is evolved about 10 6 times more rapidly from a monolayer of decomposing ethanol than from CO(g)+H 2(g) reactants. These results suggest that the rate limiting step(s) in CH 4(g) synthesis from CO(g)+H 2(g) exist at an earlier stage than the CH 3(ads)+H(ads) → CH 4(g) elementary process.