Showing papers on "Partial oxidation published in 2012"
TL;DR: In this article, a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO 2, with a special focus on conversion of aliphatic and aromatic organic species, is provided.
Abstract: This review provides the reader with a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO 2 , with a special address to conversion of aliphatic and aromatic organic species. The aim was to clarify the steps of the photo-oxidation of the various classes of compounds and to relate them with the properties of the catalysts and the experimental conditions used. Reactions carried out to perform complete degradation and photocatalytic partial oxidations have been deeply discussed. Recent isotopic studies highlighted new reaction pathways concerning partial oxidation of alcohols to aldehyde and oxidation of benzene while EPR investigations confirmed that not only the photogenerated hole but also the OH radicals are involved in the oxidation of the substrates.
264 citations
TL;DR: In this article, the site requirements for the methane total combustion, partial oxidation, and decomposition on LaFeO3 perovskite catalysts during the chemical looping process were addressed by a kinetic study through varying the O content and the crystal size.
152 citations
TL;DR: In this article, Ni nanoparticles of narrow size distribution encapsulated inside meso- and microporous silica were prepared through in situ reduction of NiO NPs coated with silica.
147 citations
TL;DR: In this paper, the influence of vanadia catalysts on the reaction rate, activation energies, and defect formation enthalpies was investigated for the oxidative dehydrogenation of ethanol and propane.
138 citations
TL;DR: In this paper, the catalytic performance of NiAl 2 O 4 catalyst in the partial oxidation of methane (CH 4 (1)/O 2 (0.5)/N 2 (8.5)) was investigated.
Abstract: In this work the catalytic performance of NiAl 2 O 4 catalyst in the partial oxidation of methane (CH 4 (1)/O 2 (0.5)/N 2 (8.5) and 4800 mL CH 4 g −1 h −1 ) was investigated. This bulk catalyst resulted more active (70% conversion at 625 °C) than alumina supported nickel catalysts prepared by conventional impregnation (11%Ni/Al 2 O 3 -30% conversion at 625 °C and 14%Ni/Al 2 O 3 -65% conversion at 625 °C) and a commercial platinum catalyst (1%Pt/Al 2 O 3 -30% conversion at 625 °C). Further, the behaviour of NiAl 2 O 4 was comparable to that of a commercial rhodium catalyst (1%Rh/Al 2 O 3 -75% conversion at 625 °C). Fresh and spent catalysts were characterised by N 2 -physisorption, H 2 -TPR, UV-vis-DRS, WDXRF, XRD, TGA-MS, TEM and Raman spectroscopy. After catalyst reduction CH 4 conversion over bulk NiAl 2 O 4 was associated with the formation of large amounts of metallic nickel crystallites with a relatively small size. Although significant coking was noticed, conversion and selectivity to H 2 /CO were not significantly affected after prolonged time on stream.
121 citations
TL;DR: In this article, a cobalt-free and noble metal-free dual-phase oxygen-transporting membrane with a composition of 40 wt % Pr0.6Sr0.4FeO3−δ−60 wt% Ce0.9Pr0.1O2−ε (40PSFO-60CPO) has been successfully developed via an in situ one-pot one-step glycine-nitrate combustion process.
Abstract: A novel cobalt-free and noble metal-free dual-phase oxygen-transporting membrane with a composition of 40 wt % Pr0.6Sr0.4FeO3−δ–60 wt % Ce0.9Pr0.1O2−δ (40PSFO–60CPO) has been successfully developed via an in situ one-pot one-step glycine-nitrate combustion process. In situ XRD demonstrated that the 40PSFO–60CPO dual-phase membrane shows a good phase stability not only in air but also in 50 vol % CO2/50 vol % N2 atmosphere. When using pure He or pure CO2 as sweep gases, at 950 °C steady oxygen permeation fluxes of 0.26 cm3 min–1 cm–2 and 0.18 cm3 min–1 cm–2 are obtained through the 40PSFO–60CPO dual-phase membrane. The partial oxidation of methane (POM) to syngas was also successfully investigated in the 40PSFO–60CPO dual-phase membrane reactor. Methane conversion was found to be higher than 99.0% with 97.0% CO selectivity and 4.4 cm3 min–1 cm–2 oxygen permeation flux in steady state at 950 °C. Our dual-phase membrane - without any noble metals such as Ag, Pd or easily reducible metals oxides of Co or Ni -...
112 citations
TL;DR: In this paper, a Pd(3.3 wt %)/γ-Al2O3 catalyst in a low temperature range of 473-673 K was used for lean-burn methane combustion.
Abstract: Operando and kinetic studies of lean-burn methane combustion were preformed on a Pd(3.3 wt %)/γ-Al2O3 catalyst in a low temperature range of 473–673 K. The reaction order with respect to oxygen decreased with temperature, and the order with respect to methane remained constant. The working catalyst is characterized using operando Raman spectroscopy and in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption (DRIFTS), and the Pd chemical states were measured with X-ray photoelectron spectroscopy (XPS). Partial oxidation of Pd atoms during reaction was identified by Raman and XPS spectroscopies. In particular, the DRIFT spectra revealed that ∼45% of Pd atoms at the top layers were transferred into PdOx species above 523 K. The reaction was assumed to occur primarily on the metallic Pd sites below 673 K, proceeding through the Langmuir–Hinshelwood mechanism, and Pd oxide may affect the adsorption and activation of reactants.
109 citations
TL;DR: In this paper, the perovskite metal-oxides LaNi0.4Fe0.6O3 were synthesized by a sol-gel method and investigated for the DR, POM, and CRM into synthesis gas.
98 citations
TL;DR: A systematic study of the kinetic parameters and mechanistic features of the methane activation route, and a reaction network consisting of the activation of methane, the formation of an activated hydroperoxy species, and the by-production of hydroxyl radicals are presented.
Abstract: The partial oxidation of methane to methanol presents one of the most challenging targets in catalysis. Although this is the focus of much research, until recently, approaches had proceeded at low catalytic rates (<10 h−1), not resulted in a closed catalytic cycle, or were unable to produce methanol with a reasonable selectivity. Recent research has demonstrated, however, that a system composed of an iron- and copper-containing zeolite is able to catalytically convert methane to methanol with turnover frequencies (TOFs) of over 14 000 h−1 by using H2O2 as terminal oxidant. However, the precise roles of the catalyst and the full mechanistic cycle remain unclear. We hereby report a systematic study of the kinetic parameters and mechanistic features of the process, and present a reaction network consisting of the activation of methane, the formation of an activated hydroperoxy species, and the by-production of hydroxyl radicals. The catalytic system in question results in a low-energy methane activation route, and allows selective C1-oxidation to proceed under intrinsically mild reaction conditions.
96 citations
TL;DR: In this paper, two kinds of supported silver catalysts, namely Ag/HZSM-5 and Ag-MnO x-CeO 2, were investigated as catalysts for this cycling process.
96 citations
TL;DR: In this paper, a novel technique is proposed for potential use in oil reservoirs, which consists in incorporating 6 amphiphilic nanoparticles into the water injection, which can simultaneously act as emulsion stabilizers as well as carriers for catalytic species, e.g., metals.
Abstract: 5 ABSTRACT: A novel technique is proposed for potential use in oil reservoirs. The technique consists in incorporating 6 amphiphilic nanoparticles into the water injection. These hybrid nanoparticles can simultaneously act as emulsion stabilizers as 7 well as carriers for catalytic species, e.g., metals. They can be active for in situ reactions, such as partial oxidation and 8 hydrogenation, which may result in changes in rheological and interfacial properties of the oil, as well as modifying the wettability 9 of the walls. These changes might be efficiently used to improve the oil recovery process. Specifically, partial oxidation of organic 10 compounds lowers the water! oil interfacial tension and consequently increases the capillary number (Nc) of the system. 11 Alternatively, partial hydrogenation of polynuclear aromatics can enhance the viscosity of the oil phase in the emulsion, thus 12 improving the mobility ratio (MR). In addition, partial hydrogenation can be an effective pretreatment of the oil to favor the 13 subsequent partial oxidation.
TL;DR: In this article, a series of Ir/CeO2 catalysts of different oxide and metallic phase dispersions were investigated by XRD, TPR, HRTEM, CO2 TPD/calorimetry, in situ DRIFT spectroscopy, and oxygen isotopic exchange techniques in order to elucidate the specific influence of catalyst morphology and structure on the oxidative steam reforming (OSR) of ethanol.
TL;DR: A review of the literature state-of-the-art has been performed to shed light on some of the possible trade-offs that will have to be done in designing these systems as discussed by the authors.
TL;DR: In this article, a high yield of levulinic acid was produced by directly converting cellulose over a ZrO2 catalyst by a one-pot catalytic aqueous phase partial oxidation (APPO) process.
Abstract: A high yield of levulinic acid was produced by directly converting cellulose over a ZrO2 catalyst by a one-pot catalytic aqueous phase partial oxidation (APPO) process. Compared to conventional acid hydrolysis, APPO is a highly selective and environmentally benign process with merits of easy recovery and re-use of heterogeneous catalysts.
TL;DR: In this paper, a single phase perovskite-type oxides were obtained as single phase and investigated in the partial oxidation of methane through temperature-programmed surface reactions (TPSR).
Abstract: LaCoO 3 and LaCo 0.8 Cu 0.2 O 3 perovskite-type oxides prepared by the polymerizable complex route were obtained as single phase and investigated in the partial oxidation of methane through temperature-programmed surface reactions (TPSR). Characterizations were carried out before and after the reactions under different feed streams CH 4 /O 2 /He = 2/1/37 and 5/1/64, and revealed a dynamic structural transformation in which the perovskite is collapsed towards lanthanum-based matrix and metal cobalt and copper. The copper-substituted perovskite showed better performance in the partial oxidation of methane leading to higher CH 4 conversion and higher syngas production than LaCoO 3 during the transient reaction. Furthermore, copper had significant effect against carbon deposition on the catalyst and it is suggested to be a very important dopant for perovskites applied in reactions with hydrocarbons.
TL;DR: In this paper, the photoformed electrons on the conduction band of WO3 are consumed by a multi-electron reduction of O2 on the Pt particles (formation of H2O and H 2O2), where a single electron reduction is unfavored.
TL;DR: In this article, 5%Ni/Ce(1−x)ZrxO2 (x = 0, 0.25Zr0.75 and 1) catalysts were prepared by precipitation method and tested for methane partial oxidation.
TL;DR: In this paper, simulated equilibrium compositions of ethanol steam reforming (SR), partial oxidation (POX) and auto-thermal reforming (ATR) at a large temperature range, steam-toethanol and oxygen-to-ethanol molar ratios.
TL;DR: Partial oxidation of bitumen was examined in supercritical water from 653 to 723 K at a water/oil ratio from 0 to 3 and up to 5.1 MPa of initial air pressure as discussed by the authors.
TL;DR: In this paper, the effect of some experimental conditions during photodeposition, such as deposition time and Pt loading, was investigated, and a short deposition time at 0.5 and 1.5% Pt nominal loading led to small average particle size of platinum (2-3nm) homogeneously distributed all over the TiO2 surface.
TL;DR: In this paper, bimetallic Co-Ni nanoparticles were synthesized for partial oxidation of methane to syngas, and the CoNi 2 @SiO 2 catalyst outperformed the other counterparts at a reaction temperature of 700°C.
TL;DR: In this paper, the role of carbon and nitrogen contained in the starting materials in partially oxidized tantalum carbonitride (TaCxNy) oxygen-reduction electrocatalysts was investigated.
TL;DR: Carbide-derived carbons (CDC) with incorporated transition metal nanoparticles (∼2.5nm) were prepared using a microemulsion approach in this article, which is a technique for the preparation of highly porous carbon materials with a catalytically active component.
TL;DR: In this article, a multitechnique approach was used for the characterization of single-and co-doped S/Fe-TiO 2 nanomaterials in the context of photo-oxidation of toluene.
Abstract: Iron and sulfur single- and co-doped TiO 2 nanocrystals were prepared and characterized by a multitechnique approach. The presence of sulfur affected drastically the crystal size of anatase as well as other morphological characteristics such as BET surface area, pore volume and pore size. Significant differences were also detected on the isolated OH species concentration as a function of sulfur content. On the contrary, X-ray absorption spectroscopy (XAFS) showed that sulfur did not alter substantially the structural and electronic properties of Fe on TiO 2 . The photocatalytic activity of the synthesized TiO 2 powders was studied in the gas-phase oxidation of toluene. The trials showed that the co-doped S/Fe-TiO 2 nanomaterials have enhanced photo-activity compared to the reference single-doped Fe-TiO 2 under both sunlight and UV-light irradiation. This is not however the case if compared with the single S-doped materials. Sulfur additionally modifies the selectivity of toluene photo-oxidation toward partial oxidation products. The partial vs. total oxidation yield ratio increased with increasing S content in both co-doped S/Fe-TiO 2 or single-doped S-TiO 2 series and was attributed to differences in surface properties related to both S-containing and OH entities.
TL;DR: In this paper, a polymerization method was used to synthesize mixtures of NiO, MgO and ZrO 2 for the partial oxidation of methane (POM) in the presence of air (2CH 4 : 1O 2 ) at 750°C for 6h.
TL;DR: In this paper, the primary reactions of coal volatiles for soot formation mechanism were numerically investigated under pyrolysis (thermal decomposition), partial oxidation (O2 gasification) and O2/CO 2 gasification conditions.
TL;DR: The results show that partial oxidation of adsorbed acetate to adsorbing ketenylidyne can be cleanly carried out over Au/TiO(2) catalysts by control of temperature.
Abstract: Chemisorbed acetate species derived from the adsorption of acetic acid have been oxidized on a nano-Au/TiO2 (∼3 nm diameter Au) catalyst at 400 K in the presence of O2(g). It was found that partial oxidation occurs to produce gold ketenylidene species, Au2═C═C═O. The reactive acetate intermediates are bound at the TiO2 perimeter sites of the supported Au/TiO2 catalyst. The ketenylidene species is identified by its measured characteristic stretching frequency ν(CO) = 2040 cm–1 and by 13C and 18O isotopic substitution comparing to calculated frequencies found from density functional theory. The involvement of dual catalytic Ti4+ and Au perimeter sites is postulated on the basis of the absence of reaction on a similar nano-Au/SiO2 catalyst. This observation excludes low coordination number Au sites as being active alone in the reaction. Upon raising the temperature to 473 K, the production of CO2 and H2O is observed as both acetate and ketenylidene species are further oxidized by O2(g). The results show that...
TL;DR: In this paper, a gas-tight La0.7Sr0.3FeO3−α (LSF) perovskite hollow fiber membrane was fabricated by the phase inversion/sintering technique using self-made ceramic powder.
TL;DR: In this article, a detailed experimental study of stationary TPOX within inert porous media has been conducted, where operating characteristics of the process have been examined for two different porous matrices, with different thermal and transport properties, namely SiSiC open foam structure and a packed bed of pure Al2O3 packing material.
TL;DR: In this article, the Gibbs energy minimization was applied to study combined partial oxidation and carbon dioxide reforming of methane in view of carbon formation, and the results showed that the addition of O2 to the feed mixture could lead to a reduction of carbon deposition.