Showing papers on "Partial oxidation published in 2015"
TL;DR: In this paper, the authors comprehensively review the recent advances for chemical-looping reforming of CH4 (CLR) technology, which breaks down the traditional CH4 reforming process (including steam and dry reforming) into two separate half-steps, namely CH4 oxidation and replenishment of oxygen carrier (OC) with appropriate oxidizing agents.
382 citations
TL;DR: In this article, a series of bimetallic Fe-Ni/MgAl2O4 catalysts with Fe/Ni ratios between 0 and 1.5 have been examined for methane dry reforming at 923-1073 K, atmospheric pressure, and a CH4/CO2 ratio of 1.
Abstract: A series of bimetallic Fe-Ni/MgAl2O4 catalysts with Fe/Ni ratios between 0 and 1.5 have been examined for methane dry reforming at 923–1073 K, atmospheric pressure, and a CH4/CO2 ratio of 1. The evolution of the catalyst structure during H2 temperature-programmed reduction (TPR), CO2 temperature-programmed oxidation (TPO), and dry reforming is examined using time-resolved in situ X-ray diffraction (XRD). During H2-TPR up to 973 K, Fe2O3 and NiO are reduced to Fe and Ni. Higher temperatures lead to Fe-Ni alloy formation. The alloy remains stable up to 900 K under CO2-TPO and is decomposed to Ni and Fe3O4 at higher temperatures. The Fe-Ni alloy is the active phase while Fe partially segregates from the alloy forming FeOx during dry reforming. This is beneficial as it reduces the surface carbon accumulation through interaction with FeOx lattice oxygen, producing CO. Alternate CH4 and CO2 pulse experiments over Ni, Fe, and Ni-Fe samples showed that dry reforming over Fe-Ni catalysts can follow a Mars–van Krev...
361 citations
TL;DR: In this paper, the photocatalytic conversion of methane into methanol from an aqueous suspension containing mesoporous WO3 was studied, as well as the effect of the addition of electron scavengers (Fe3+, Cu2+, Ag+) and H2O2 species.
Abstract: Mesoporous WO3 was synthesized by replicating technique using ordered mesoporous silica KIT-6 as the template. The obtained material exhibits high surface area (151 m2 g−1) and porous structure. The photocatalytic conversion of methane into methanol from an aqueous suspension containing mesoporous WO3 was studied, as well as the effect of the addition of electron scavengers (Fe3+, Cu2+, Ag+) and H2O2 species. In the presence of Fe3+ ions the production of methanol was about two and a half times higher than that of pure mesoporous WO3, which was principally attributed to the largely improved electron-hole separation in this system. However, the CO2 generation rates were also increased, mainly in the presence of Ag+ ions. It was also corroborated that extra hydroxyl radicals in the aqueous medium do not improve the generation of methanol but a noticeable increase in the formation of ethane was evidenced. This suggests that only a higher availability of HO•’s adsorbed on the catalyst can enhance the performance of methanol generation in the photocatalytic process.
143 citations
TL;DR: An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented in this paper, where the numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species.
Abstract: An experimental and kinetic modeling study on the Ni-catalyzed conversion of methane under oxidative and reforming conditions is presented. The numerical model is based on a surface reaction mechanism consisting of 52 elementary-step like reactions with 14 surface and six gas-phase species. Reactions for the conversion of methane with oxygen, steam, and CO2 as well as methanation, water-gas shift reaction and carbon formation via Boudouard reaction are included. The mechanism is implemented in a one-dimensional flow field description of a fixed bed reactor. The model is evaluated by comparison of numerical simulations with data derived from isothermal experiments in a flow reactor over a powdered nickel-based catalyst using varying inlet gas compositions and operating temperatures. Furthermore, the influence of hydrogen and water as co-feed on methane dry reforming with CO2 is also investigated.
122 citations
TL;DR: Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis and this reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation of hydroxyl-containing fuels.
Abstract: Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis. In this report, reversible acceptorless dehydrogenation of secondary alcohols and diols on iron pincer complexes and reversible oxidative dehydrogenation of primary alcohols/reduction of aldehydes with separate transfer of protons and electrons on iridium complexes are shown. This reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation (dehydrogenation) of hydroxyl-containing fuels.
117 citations
TL;DR: One-pot complete catalytic ethanolysis of Kraft lignin into C6-C10 chemicals, that is, aliphatic alcohols, esters, phenols, benzyl alcohols and arenes, is achieved with a batch reactor over a number of supported molybdenum-based catalysts at 553 K in pure ethanol under autogenous pressure of 10.6 MPa as mentioned in this paper.
Abstract: One-pot complete catalytic ethanolysis of Kraft lignin into C6–C10 chemicals, that is, aliphatic alcohols, esters, phenols, benzyl alcohols, and arenes, is achieved with a batch reactor over a number of supported molybdenum-based catalysts at 553 K in pure ethanol under autogenous pressure of 10.6 MPa. Metallic molybdenum, its carbide, and nitride all show remarkable activity, with the carbide and metallic catalysts giving the higher overall yields: 1640 and 1390 mg/g lignin, respectively. The major phases composing the catalysts are well-preserved after the reaction; however, the detection of Mo(V) species verifies the partial oxidation of molybdenum, which leads to the formation of the dissociative Mo species, such as molybdenum V ethoxide, in the fluid phase. Through the product analysis and catalyst characterization, the common route of lignin conversion to value added chemicals over the Mo-based catalyst is presented in detail. Kraft lignin is first fragmented into segments with m/z ∼ 700–1400 via a ...
115 citations
TL;DR: In this article, a series of mixed-linker zirconium-based metal-organic frameworks (Zr-MOFs) have been synthesized in one-pot reactions.
102 citations
TL;DR: In this article, a one-dimensional fluid model for a dielectric barrier discharge in CH4/O2 and CH 4/CO2 gas mixtures is developed, and the main underlying reaction pathways for the formation of syngas, methanol, formaldehyde and other higher oxygenates are determined.
Abstract: A one-dimensional fluid model for a dielectric barrier discharge in CH4/O2 and CH4/CO2 gas mixtures is developed. The model describes the gas-phase chemistry for partial oxidation and for dry reforming of methane. The spatially averaged densities of the various plasma species are presented as a function of time and initial gas mixing ratio. Besides, the conversion of the inlet gases and the selectivities of the reaction products are calculated. Syngas, higher hydrocarbons, and higher oxygenates are typically found to be important reaction products. Furthermore, the main underlying reaction pathways for the formation of syngas, methanol, formaldehyde, and other higher oxygenates are determined.
96 citations
TL;DR: In this paper, the authors explore oxygen carriers that utilize the advantages of both perovskites and first-row transition metal oxides by integrating a transition metal oxide core with a mixed ionic-electronic conductive (MIEC) support/shell.
94 citations
TL;DR: The composition, structure, and electrical properties of mechanically exfoliated WSe2 nanosheets on SiO2/Si substrates were studied as a function of the extent of thermal oxidation.
Abstract: Because of the drastically different intralayer versus interlayer bonding strengths, the mechanical, thermal, and electrical properties of two-dimensional (2D) materials are highly anisotropic between the in-plane and out-of-plane directions. The structural anisotropy may also play a role in chemical reactions, such as oxidation, reduction, and etching. Here, the composition, structure, and electrical properties of mechanically exfoliated WSe2 nanosheets on SiO2/Si substrates were studied as a function of the extent of thermal oxidation. A major component of the oxidation, as indicated from optical and Raman data, starts from the nanosheet edges and propagates laterally toward the center. Partial oxidation also occurs in certain areas at the surface of the flakes, which are shown to be highly conductive by microwave impedance microscopy. Using secondary ion mass spectroscopy, we also observed extensive oxidation at the WSe2–SiO2 interface. The combination of multiple microcopy methods can thus provide vit...
93 citations
TL;DR: In this paper, the performance of dry reforming of methane was studied by Gibbs free energy minimization at elevated pressures and it was found that carbon formation can be reduced by introducing oxygen.
TL;DR: In this paper, a perovskite promoted iron oxide was used as a highly effective redox catalyst in a hybrid solar-redox scheme for partial oxidation and water-splitting of methane.
Abstract: We report a perovskite promoted iron oxide as a highly effective redox catalyst in a hybrid solar-redox scheme for partial oxidation and water-splitting of methane. In contrast to previously reported ferrite materials, which typically exhibit 20% or lower steam to hydrogen conversion, La0.8Sr0.2FeO3−δ (LSF) promoted Fe3O4 is capable of converting more than 67% steam with high redox stability. Both experiments and a defect model indicate that the synergistic effect of reduced LSF and metallic iron phases is attributable to the exceptional steam conversion. To further enhance such a synergistic effect, a layered reverse-flow reactor concept is proposed. Using this concept, over 77% steam to hydrogen conversion is achieved at 930 °C, which is 15% higher than the maximum conversion predicted by the second law for unpromoted iron (oxides). When applied to the hybrid solar-redox scheme for liquid fuels and hydrogen co-generation, significant improvements in the energy conversion efficiency can be achieved with reduced CO2 emissions.
TL;DR: In this article, a new method for facile and reproducible activation of nanoporous gold (npAu) materials of different forms for the catalytic selective partial oxidation of alcohols under ambient pressure, steady flow conditions is presented.
Abstract: We report a new method for facile and reproducible activation of nanoporous gold (npAu) materials of different forms for the catalytic selective partial oxidation of alcohols under ambient pressure, steady flow conditions. This method, based on the surface cleaning of npAu ingots with ozone to remove carbon documented in ultrahigh vacuum conditions, produces active npAu catalysts from ingots, foils, and shells by flowing an ozone/dioxygen mixture over the catalyst at 150 °C, followed by a temperature ramp from 50 to 150 °C in a flowing stream of 10% methanol and 20% oxygen. With this treatment, all three materials (ingots, foils, and shells) can be reproducibly activated, despite potential carbonaceous poisons resulting from their synthesis, and are highly active for the selective oxidation of primary alcohols over prolonged periods of time. The npAu materials activated in this manner exhibit catalytic behavior substantially different from those activated under different conditions previously reported. On...
TL;DR: In this paper, the preparation methods for Ni catalysts were studied by dielectric barrier discharge (DBD) plasma and thermal decomposition, and different Ni structures were produced by different preparation methods.
TL;DR: The experimental results have shown that there indeed was a close relationship between the defects and the oxidation degree, which appeared in the form of S-type curve, and it was found that a low KMnO4 addition would lead to a partial oxidation of graphite, leaving defects mainly on the edges of RGO.
TL;DR: A transient pulse injection approach is used to investigate the mechanisms of methane partial oxidation over the Fe2O3@LSF redox catalyst, and the reaction between methane and the catalyst is found to be highly dynamic, resulting from changes in lattice oxygen availability and surface properties.
Abstract: The chemical looping reforming (CLR) process, which utilizes a transition metal oxide based redox catalyst to partially oxidize methane to syngas, represents a potentially efficient approach for methane valorization. The CLR process inherently avoids costly cryogenic air separation by replacing gaseous oxygen with regenerable ionic oxygen (O2−) from the catalyst lattice. Our recent studies show that an Fe2O3@La0.8Sr0.2FeO3−δ core–shell redox catalyst is effective for CLR, as it combines the selectivity of an LSF shell with the oxygen capacity of an iron oxide core. The reaction between methane and the catalyst is also found to be highly dynamic, resulting from changes in lattice oxygen availability and surface properties. In this study, a transient pulse injection approach is used to investigate the mechanisms of methane partial oxidation over the Fe2O3@LSF redox catalyst. As confirmed by isotope exchange, the catalyst undergoes transitions between reaction “regions” with markedly different mechanisms. While oxygen evolution maintains a modified Mars–van Krevelen mechanism throughout the reaction with O2− conduction being the rate limiting step, the mechanism of methane conversion changes from an Eley–Rideal type in the first reaction region to a Langmuir–Hinshelwood-like mechanism in the third region. Availability of surface oxygen controls the reduction scheme of the catalyst and the underlying reaction mechanism.
TL;DR: In this article, the performance of platinum-based catalysts for the room temperature removal of formaldehyde is evaluated by means of temperature-programmed desorption (TPD), temperatureprogrammed oxidation (TPO) and catalytic tests.
TL;DR: In this article, the catalytic oxidative and non-oxidative steam reforming of crude bio-ethanol for hydrogen production was studied in a tubular fixed bed reaction system over 30.5%Ni/CeO2-ZrO2 and 1.1%Rh-30.5%.
Abstract: The catalytic oxidative and non-oxidative steam reforming of crude bio-ethanol for hydrogen production was studied in a tubular fixed bed reaction system over 30 wt.%Ni/CeO2-ZrO2 and 1 wt.%Rh-30 wt.%Ni/CeO2-ZrO2 catalysts. The catalysts were prepared by impregnation-co-precipitation method and characterized by BET, XRD, TPR, TGA, XPS, XANES and EXAFS techniques. Characterization results revealed that the addition of Rh promotes reducibility of NiO at lower temperature for the bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis depicted that NiO with 6-fold local co-ordination is present in all the samples. Ethanol conversion, hydrogen yield and product selectivity were investigated at 600 °C and space time of 9.17 kgcat h/kg mol[EtOH]) at atmospheric pressure. In steam reforming of crude bio-ethanol, 81% ethanol conversion was achieved with 59% hydrogen selectivity on Ni/CeO2-ZrO2 catalyst, whereas, higher ethanol conversion (86%) with 73% hydrogen selectivity was achieved using Rh-Ni/CeO2-ZrO2 catalysts. In oxidative steam reforming of crude bio-ethanol, hydrogen yield and selectivity reduced due to the partial oxidation of oxygenate compounds present in the feed. The used catalysts were also analysed by BET, TGA/DTA, TPR, TPO, Raman spectroscopy, SEM, and TEM techniques to identify the cause of catalyst deactivation. The results indicate that the catalyst deactivation occurred mainly due to amorphous and filamentous carbon deposition on the catalysts surface, due to the presence of the impurities in the feed.
TL;DR: In this article, the authors investigated the performance of bimetallic catalysts for the oxidation of volatile organic compounds (VOC) and preferential oxidation of CO in the excess of H2 (CO-PROX).
Abstract: Oxidation of volatile organic compounds (VOC) and preferential oxidation of CO in the excess of H2 (CO-PROX) were investigated over mono and bimetallic Au–Ag/CeO2 and Au–Cu/CeO2 catalysts. For the oxidation of VOC (2-propanol, ethanol and toluene) Au/CeO2 was the most active catalyst for the combustion of alcohols to CO2, Ag/CeO2 gave the best performance in the toluene total oxidation, Au–Ag/CeO2 and Au–Cu/CeO2 showed the highest selectivity to partial oxidation products. For CO-PROX Au–Ag/CeO2 and Au–Cu/CeO2 samples exhibited higher CO2 yield at low temperature than monometallic ones. The improved performance of bimetallic catalysts were accounted for an enhancement of surface ceria oxygens mobility caused by the addition of Ag or Cu to Au/CeO2 and involved in both investigated reactions. This effect was more evident on Au–Ag/CeO2 where a strong Au–Ag interaction occurred with formation of Au–Ag alloy or linked monometallic nanoparticles.
TL;DR: In this paper, the formation of Ni-phyllosilicates on the outer layer of Stober silica by simply using an impregnation method was investigated. But the results showed that the strong metal-support interaction and the porous SiO2 produced by the reduction of Ni particles led to a catalyst with high anti-sintering and coke-resistance performance for the partial oxidation of methane to syngas.
TL;DR: In this article, formaldehyde production via hydrogenation of carbon monoxide in the aqueous phase was presented, which eliminates the need for methanol synthesis, which may potentially save capital costs and reduce energy consumption.
TL;DR: In this article, the authors used Ni/La 0.8Sr 0.2AlO3 and Ni/α-Al2O3 catalysts for steam reforming of toluene.
TL;DR: Schwach et al. as discussed by the authors studied the role of surface structure and defects in the oxidative coupling of methane (OCM) over magnesium oxide as a model catalyst and found that the initial performance of freshly calcined MgO is governed by a surface-mediated coupling mechanism involving direct electron transfer between methane and oxygen.
TL;DR: In this article, a ceria-supported cobalt catalyst was synthesized using wet-impregnation method and tested for the production of syngas from methane dry reforming.
TL;DR: In this paper, the photocatalytic partial oxidation of methane to methanol has been investigated on WO3 and the surface fluorination of the catalyst has given an insight on the reaction mechanism which proceeds mainly through the interaction with surface hydroxyl groups.
TL;DR: In this paper, the authors reported the development of a highly crystalline Ni/CeO2 catalyst with varying amounts of Ni content using ammonium carbonate complex solution of cerium(IV) at low temperature.
Abstract: We report the development of a highly crystalline Ni/CeO2 catalyst with varying amounts of Ni content using ammonium carbonate complex solution of cerium(IV) at a low temperature. The catalyst was characterized by XRD, XPS, BET-surface area, TEM, and H2-TPR analysis. We have observed that the maximum incorporation of Ni in CeO2 crystal system as the substitution point defect took place up to impregnation of 2.5% Ni, and an almost maximum reduction of unit cell parameter was observed. Further increase in the amount of Ni, the additional Ni may create interstitial point defects with surface defects. The synthesized catalysts showed defect-dependent catalytic activity for low temperature (∼450 °C) methane activation to form synthesis gas. The 7.5 wt % Ni/CeO2 catalyst showed 98% conversion of methane with 73 and 71% selectivity of CO and H2, respectively, at 800 °C without any deactivation until 50 h on time on stream. We also believe that with enhancement of Ni loading, the interstitial point defects and th...
TL;DR: In this paper, the effect of co-precipitation and wet impregnation on the catalytic behavior of Ni-supported catalysts was investigated in the methane partial oxidation reaction performed at 1-atm in a temperature range of 400-800°C using dilute feed gas mixture with CH 4 /O 2 ǫ = 2 and gas hourly space velocity of 60,000mlg −1 Âh −1.
Abstract: Two series of Ni (6 wt%) catalysts supported over CeO 2 , La 2 O 3 and mixed CeO 2 –La 2 O 3 were prepared by co-precipitation and by wet-impregnation. The effect of the two Ni loading procedures on the catalyst structural properties was investigated by XRD, TPR and XPS. The catalytic behavior of the catalysts was tested in the methane partial oxidation reaction performed at 1 atm in a temperature range of 400–800 °C using dilute feed gas mixture with CH 4 /O 2 = 2 and gas hourly space velocity of 60,000 ml g −1 h −1 . Total methane combustion was observed within the 450 °C ≤ T ≤ 650 °C temperature range. Above 650 °C partial oxidation of methane started to occur, reaching at 800 °C a CO selectivity close to 90%. The lanthanum containing catalysts prepared by wet impregnation exhibited higher CPO activity at lower temperature as compared to the co-precipitated ones. Opposite behavior was observed with the Ni–CeO 2 catalysts. During the stability test at high temperature, carbon formed only over the single oxide supported catalysts, Ni–CeO 2 and Ni–La 2 O 3 . According to the characterization results carbon was not responsible for catalyst deactivation but it prevented the sintering of the nickel particle. The interplay of the crystallite sizes and the formation of various nickel–lanthanum oxide species with different Ni oxidation states were responsible for the differences in the CPO performance.
TL;DR: In this paper, the catalytic performance of four types of Co/ZSM-5 zeolites in partial oxidation of methane were compared to observe the effect of pore size and cobalt species to the reaction.
TL;DR: In this article, partial oxidation of methanol over a Pt/Al2O3 catalyst with low Pt content is studied where the influences of the (GHSV) gas hourly space velocity and oxygen-to-methanol molar ratio (O2/C) on the gas formation, reaction temperature, and methenol conversion are evaluated.