Showing papers on "Partial oxidation published in 2010"
TL;DR: Nanoporous Au, prepared by the dealloying of AuAg alloys, is a new catalyst with a stable structure that is active without any support that catalyzes the selective oxidative coupling of methanol to methyl formate with selectivities above 97% and high turnover frequencies at temperatures below 80°C.
Abstract: Gold (Au) is an interesting catalytic material because of its ability to catalyze reactions, such as partial oxidations, with high selectivities at low temperatures; but limitations arise from the low O2 dissociation probability on Au. This problem can be overcome by using Au nanoparticles supported on suitable oxides which, however, are prone to sintering. Nanoporous Au, prepared by the dealloying of AuAg alloys, is a new catalyst with a stable structure that is active without any support. It catalyzes the selective oxidative coupling of methanol to methyl formate with selectivities above 97% and high turnover frequencies at temperatures below 80 degrees C. Because the overall catalytic characteristics of nanoporous Au are in agreement with studies on Au single crystals, we deduced that the selective surface chemistry of Au is unaltered but that O2 can be readily activated with this material. Residual silver is shown to regulate the availability of reactive oxygen.
1,022 citations
TL;DR: In this article, the authors investigated the performance of noble metal catalysts (Pt, Pd, Ir, Rh and Au) supported by liquid phase reduction deposition (LPRD) and incipient wetness impregnation (IMP) for CO, ethanol and toluene.
Abstract: The oxidation of CO, ethanol and toluene was investigated on noble metal catalysts (Pt, Pd, Ir, Rh and Au) supported on TiO 2 . The catalysts were prepared by liquid phase reduction deposition (LPRD) and by incipient wetness impregnation (IMP). It was observed that the preparation method can have a significant effect on the dispersion of the metallic phase, and subsequently on the performance of the catalysts towards total oxidation of CO or VOC. For CO oxidation, Au IMP was the worst catalyst, while Au LPRD was the most active. This can be explained in terms of different Au particle sizes, well known to be related with catalytic activity. For all the other metals, LPRD also produces better results, although the differences are not so marked as with gold. Iridium seems to be the only exception since results were very similar. In VOC oxidation, the following performance trend was observed: Pt/TiO 2 > Pd/TiO 2 ≫ Rh/TiO 2 ≈ Ir/TiO 2 ≫ Au/TiO 2 , for both preparation methods. Ethanol and toluene oxidation over Pt and Pd catalysts were found to be structure sensitive reactions. Some experiments with ethanol/toluene mixtures were performed using the best catalyst (Pt/TiO 2 ). It was observed that toluene inhibits the combustion of ethanol, namely by slowing down the partial oxidation of ethanol towards acetaldehyde. Ethanol also has a slight inhibition effect on the total oxidation of toluene.
219 citations
TL;DR: In this paper, the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure were investigated.
Abstract: The objective of the present work has been the study of the physicochemical and catalytic properties of a Ni/La2O3 catalyst obtained by reduction of a lanthanum nickelite, LaNiO3, with perovskite structure. The perovskite, obtained by means of a spray pyrolysis method, provides a Ni/La2O3 system active in different methane reforming reactions. The catalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-Ray photoemission spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO) and catalytic activity tests. Although not evidenced by XRD data, XAS and TPR measurements show the presence of an amorphous NiO phase in the original sample, together with the crystalline LaNiO3 phase. Upon reoxidation treatment of the reduced Ni/La2O3 catalyst, the LaNiO3 structure is partly recovered which provides a convenient way to regenerate a waste catalyst (reoxidation and new reduction in hydrogen). The catalyst is active in several reactions of methane with oxygen, water and CO2, showing a remarkable stability specially under dry reforming of methane (DRM) reaction conditions. This quite great catalytic performance has been explained by the high resistance of the nickel particles to be oxidized, as detected by in situ XAS. In the presence of water, as in steam reforming of methane (SRM) reaction conditions, these metallic particles are gradually oxidized, which explains the linear decreasing of the catalytic performance observed for the SRM reaction.
184 citations
TL;DR: In this article, the catalytic activity of Pt-doped CeO2 for the oxidation and the dry reforming of methane was studied and it was found that the presence of Pt activates the oxygen atoms next to it in the surface layer and this decreases the activation energy for dissociative adsorption of methane.
182 citations
TL;DR: In this paper, the catalytic partial oxidation of methane (CPOM) was studied on Ni-based catalysts, which showed nearly 95% CH4 conversion and nearly 96% H2 selectivity under the flow of 157,500 (L ǫ kg−1ǫ h−1) with the ratio of CH4/O2 2 = 2 by using air as an oxidant.
153 citations
TL;DR: In this article, the surface modification methods of oxides into four methods: (1) formation of complex oxide layer containing active sites, (2) substitutional doping of nitrogen, (3) introduction of surface oxygen defect and (4) partial oxidation of carbonitrides.
146 citations
TL;DR: In this article, the reaction characteristics of hydrogen production from a one-stage and a two-stage reaction were studied and compared with each other by means of thermodynamic analyses, and the results indicated that the reaction temperature of ATR plays an important role in determining H2 yield.
120 citations
TL;DR: In this paper, a perovskite material with the general formula La 1− x Sr x FeO 3 (x = ǫ 0, 0.3, 0., 0.7, 1) for application in a dense mixed conducting membrane reactor process for simultaneous production of synthesis gas and pure hydrogen.
114 citations
TL;DR: In this article, two cobalt oxidation states (Co3O4 and CoO) were prepared and investigated as regards their influence on the catalytic activity and selectivity, and adsorbed species were monitored in the transition of the catalyst from the nonactive to active state.
113 citations
TL;DR: In this paper, deep oxidation of 48 hydrocarbons (HCs) from 6 to 20 carbon atoms was studied over a 1%Pt/Al 2 O 3 catalyst (105m 2 ǫg −1 ; mean particle size of Pt: 1.nm).
Abstract: Deep oxidation of 48 hydrocarbons (HCs), from 6 to 20 carbon atoms, was studied over a 1%Pt/Al 2 O 3 catalyst (105 m 2 g −1 ; mean particle size of Pt: 1 nm). The oxidation reaction (1500 ppm C of HC in air) was carried out by increasing the temperature by step of 5 °C from 100 to 400 °C. The reactivity of HCs was characterized by their T 50 (temperature at 50% conversion). The reactivity of n -alkanes increases with the chain length, following the same evolution with n as the ionization potential of the molecule. Isoalkanes are more difficult to oxidize than the corresponding n -alkanes. Hydrocarbon reactivity depends on the nature of carbon in the molecule. The ability to be oxidized is greater with C II and C III carbons while C I and C IV carbons, still more than C I , are refractory to oxidation. The reactivity of n -alkenes depends relatively little on the number of carbons in the molecule. Light alkenes are much more reactive than light alkanes while the reverse can be observed with long-chain hydrocarbons. Contrary to branched alkanes, isoalkenes or cyclenic hydrocarbons are generally more reactive than the corresponding n -alkenes. Short side-chain alkylbenzenes (toluene, ethylbenzene, …) and polymethylbenzenes are more difficult to oxidize than benzene. When the length of the alkyl group is increased, the behaviour of the hydrocarbon in oxidation resembles more and more to long-chain alkanes with a better oxidability. Polyalkylbenzenes with hindered heavy alkyl groups are quite easy to oxidize. The behaviour of bicyclic or tricyclic hydrocarbons is much more complex. Partial or complete hydrogenation increases their reactivity. For instance, oxidability of bicyclic hydrocarbons is in the order: decaline > tetraline > naphthalene. The reactivity of heavier aromatics also depends on their ability to form partial oxidation intermediates (for instance: fluorene to fluorenone) or to possess extremely rigid internal C C bonds (for instance: acenaphthylene and acenaphthene). These results were discussed in the light of several factors which can affect the reactivity in oxidation: (i) an electron transfer between adsorbed hydrocarbon and adsorbed oxygen species via the surface metal atoms; (ii) the mean C–H bond strength in the molecule and hindrance effects in branched hydrocarbons; (iii) the relative adsorption strength of oxygen and hydrocarbons; (iv) the relative reactivity of hydrocarbons and partially oxidized molecules, intermediates in total oxidation.
109 citations
TL;DR: In this article, a perovskite membrane was successfully synthesized from BaCO 3, Co 2 O 3, Fe O 3 and Ta 2 O 5 by a simple solid state reaction.
TL;DR: In this paper, the fuel conversion performance of two gliding arc plasma reformers was investigated with the goal of syn-gas production on-board vehicles, and the results showed that gliding arcs are capable of reforming heavy hydrocarbon fuels with high conversion efficiency.
TL;DR: In this article, the performance of Ni/CeZrO 2 catalysts promoted by Ag, Fe, Pt and Pd were investigated for methane autothermal reforming and partial oxidation of methane.
TL;DR: In this article, a dual-phase composite membrane (SDC-SSF) was used for the partial oxidation of methane (POM) in a 75 wt. cm(-2) min(-1) container.
TL;DR: In this paper, the authors describe the equilibrium composition of carbon deposits represented as graphite, nanotubes, and amorphous carbon in a steam/ethanol ratio equal to 4.0.
TL;DR: In this paper, partial oxidation of iso-octane over a rhodium/alumina coated honeycomb monolith is experimentally and numerically studied at short contact times for varying fuel-to-oxygen ratios.
TL;DR: In this paper, the authors investigated the influence of the preparation method on the nature of the cobalt species and discussed the catalytic activity and selectivity for methane oxidation as a function of cobalt speciation.
Abstract: For the first time the possibility to partially oxidize methane to methanol and formaldehyde at low temperature over Co-ZSM-5 using air is shown. The influence of the preparation method on the nature of the cobalt species is investigated. In addition, the catalytic activity and selectivity for methane oxidation as a function of the cobalt speciation is discussed. Based on UV–vis–NIR and FT-IR spectroscopy, H2-TPR, TEM and kinetic measurements it is concluded that cobalt in ion-exchange positions results mainly in the formation of formaldehyde, while larger Co-oxide particles prepared by impregnation result in the formation of methanol.
TL;DR: In this paper, a detailed C 1 microkinetic approach was adopted in the numerical analysis by introducing in the model the experimentally estimated catalyst metal surface area and state-of-the-art correlations for heat and mass transfer in foams.
TL;DR: A series of nanosized W,N-co-doped anatase TiO2 catalysts with different dopant contents has been prepared by a microemulsion method and examined in the sunlight selective photo-oxidation of toluene and styrene as mentioned in this paper.
Abstract: A series of nanosized W,N-co-doped anatase TiO2 catalysts with different dopant contents has been prepared by a microemulsion method and examined in the sunlight selective photo-oxidation of toluene and styrene. The activity results have been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD–Rietveld, N2 physisorption and NH3 chemisorption–calorimetry, XPS, Infrared, and UV–visible spectroscopies. Irrespective of the reaction, a consistent reaction rate enhancement with respect to titania (nano-TiO2, P25) references and W-doped TiO2 systems is observed for single-phase anatase W,N-co-doped samples. This is likely linked with the decrease of the band gap energy decrease and results from a combined W–N cooperative effect on structural properties of the anatase network. W,N simultaneous presence also makes a drastic effect on selectivity, maximizing the yield to partial oxidation products. This appears related with surface properties of the materials.
TL;DR: Tantalum oxide-based compounds were examined as new non-noble cathodes for polymer electrolyte fuel cell as discussed by the authors, and the partial oxidation of tantalum carboniride was effective to enhance the catalytic activity for the ORR.
TL;DR: In this paper, the effects of the composition of hydrotalcite precursors and their method of preparation have on the chemical-physical properties and catalytic performances of systems which are active in the partial oxidation and steam reforming of methane to produce H 2.
TL;DR: In this article, the stability of anode-supported solid oxide fuel cells (SOFCs), operated with fuel mixtures of methane-CO2 and methane-air, was evaluated in terms of voltage decrease at constant current density, was affected by coke deposits.
TL;DR: In this article, the conversion of bio-oils to syngas via catalytic partial oxidation over Rh-Ce is evaluated using two reactor configurations, where pyrolysis oils are oxidized in excess steam in a freeboard and passed over the catalyst in a second zone.
TL;DR: In this paper, the authors identify the thermodynamic domain of the process operation, study the variation of product distribution pattern and describe the optimum conditions to maximize yield of the desired product and minimize the undesired product formation.
TL;DR: In this article, a Rh/γAl2O3 monolith catalyst was used for dry reforming of methane and carbon dioxide mixtures at temperatures between 300°C and 800°C at atmospheric pressures.
Abstract: Auto-thermal and dry reforming of methane and carbon dioxide mixtures was investigated experimentally at temperatures between 300 °C and 800 °C at atmospheric pressures using a Rh/γAl2O3 monolith catalyst. CH4:CO2 ratios of 1:1 and 1.4:1 were tested. The Rh catalyst reached equilibrium conversions of CH4 and CO2 to H2 and CO for both CH4:CO2 ratios. Equilibrium analysis shows that carbon formation is likely for dry reforming but not for auto-thermal reforming. Experimentally, carbon formation was seen after long-term exposure to 1.4:1 CH4:CO2 ratios without oxygen, but the catalyst has shown the ability to be regenerated in air. Auto-thermal tests, with and without external heat input, operating at an equivalence ratio of 4.3 (O2:CH4 = 0.46) and maintaining the CH4:CO2 ratio of either 1:1 or 1.4:1, did not show signs of carbon formation or deactivation. ATR experiments resulted in H2:CO ratios between 1.0 and 2.0 that can be tuned depending on the monolith temperature, beneficial in the case of downstream Fischer–Tropsch processes. For the auto-thermal experiments, theoretical reaction extents were calculated based on experimental data and showed two primary regimes in catalyst operation: a CH4 combustion and partial oxidation regime, and reforming and water–gas shift regime.
TL;DR: Haynes et al. as mentioned in this paper compared a ruthenium substituted pyrochlore catalyst (LSRuZ) with a traditional supported Ru/γ-Al2O3 catalyst in the partial oxidation of a diesel surrogate fuel.
TL;DR: In this paper, the degradation of aqueous H-acid and its organic carbon (COD, TOC) with the Photo-Fenton-like advanced oxidation process was optimized in terms of selected major process variables (ferric iron concentration, hydrogen peroxide concentration, initial COD value and reaction time) by employing response surface methodology and central composite design.
Abstract: H-acid is a biologically inert, photochemically stable napthalene sulphonate derivative (1-amino-8-hydroxynaphthalene-3,6-disulphonic acid) being frequently produced as an essential raw material of many commercially available textile azo dyes. Treatability reports dealing with the advanced chemical oxidation of H-acid are limited to a few case studies that do not provide a deep insight into single as well as combinative effects of the main process variables influencing the treatment performance. In the present study, the degradation of aqueous H-acid and its organic carbon (COD, TOC) content with the Photo-Fenton-like advanced oxidation process was optimized in terms of selected major process variables (ferric iron concentration, hydrogen peroxide concentration, initial COD value and reaction time) by employing response surface methodology and central composite design. For this purpose, two main targets were set in the optimization approach, namely (i) the achievement of complete/highest possible oxidation (mineralization) and a (ii) partial oxidation option under relatively mild reaction conditions. The photocatalytic treatment performance was examined by the analysis of the process outputs H-acid, COD and TOC removals. Statistical evaluation of the established polynomial regression models as well as validation experiments run under locally (initial COD-based) optimized reaction conditions to test the reliability of the obtained models revealed that Photo-Fenton-like oxidation of aqueous H-acid is highly efficient and the proposed reaction model successfully predicts organic carbon abatement rates for both treatment targets. From the empirical regression models derived for organic carbon removal it was also evident that the photocatalytic treatment system was mainly affected by the initial COD content (negative effect) closely followed by the parameter initial hydrogen peroxide concentration (positive effect). Activated sludge inhibition experiments conducted with heterotrophic biomass indicated that during the application of Photo-Fenton treatment under optimized reaction conditions, no toxic oxidation products were formed.
TL;DR: In the early 1970s, DuPont designed and operated a circulating fluidized bed reactor (CFB) to produce maleic anhydride from n-butane using a vanadium pyrophosphate catalyst (VPP) encapsulated in a silica shell.
Abstract: DuPont designed and operated a circulating fluidized bed reactor (CFB) to produce maleic anhydride from n-butane using a vanadium pyrophosphate catalyst (VPP) encapsulated in a silica shell. A fraction of the pyrophosphate was oxidized to the V5+ state from the V4+ state in an air fed fluidized bed regenerator. The oxidized VPP was shuttled to a transport bed reactor with a high concentration of butane and oxygen. The gas carried the catalyst up through the bed at velocities of 0.8 m/s and, in the commercial plant, solids circulation rates exceeding 7 kt/h. Early development work was conducted on an experimental scale facility containing 1 kg of catalyst. The pilot plant catalyst inventory exceeded 2000 kg and there was 175 t in the commercial reactor. Throughout the program, significant advances in catalyst manufacture and process design were achieved. The CFB reactor configuration is being considered for several unrelated processes including chemical looping combustion, methanol-to-olefins and hot gas desulphurization. Improvements in spray drying technology reduced attrition losses by an order of magnitude versus expectation based on the pilot plant. Together with the low attrition losses and good stability, catalyst consumption was reduced by successfully re-spray drying used/attrited catalyst. By modifying the solids entrance and exit configurations, we were able to double initial plant capacity. Operability of the plant was excellent with a turn-down ratio of 5 demonstrated. At a production rate of 65,000 t/year of maleic acid – one of the largest single train reactors for a partial oxidation of an alkane – the maximum temperature difference within the bed was less than 20 °C. Heat transfer had been a major design consideration but even at this rate, only 1/3 of the total coil surface for cooling was activated.
TL;DR: The partial oxidation (POX) characteristics of municipal sludge in supercritical water (SCW) were investigated by using batch reactor and the possible reaction mechanisms were proposed.
TL;DR: In this article, a "Y" type reactor is developed and applied in bio-oil steam reforming, partial oxidation, or oxidative steam reforming coupled with CO 2 reforming of bio-OIL to eliminate the emission of CO 2.