Catalytic Partial Oxidation Of Methane Research Articles

Catalytic Partial Oxidation of Methane to Methanol over Fe2O3/MWCNTs

The catalytic partial oxidation of methane (CPOM) to methanol has been regarded as a promising approach for methane utilization, despite that the conversion remains a formidable challenge in the perspective of catalysts. A novel catalyst system of multi-wall carbon nanotubes (MWCNTs) that supported Fe2O3 with existing I2, consisting of non-noble metal and working in weak acid at an ambient temperature, was investigated for CPOM. MWCNTs supported the Fe2O3 catalyst, which was prepared by the impregnation method and characterized via HRTEM, XRD, XPS, FT-IR, and BET techniques. The characterization results reveal that, as a non-noble metal catalyst, the Fe2O3/MWCNTs catalyst had a good catalytic performance and stability in the CPOM. With the variation of reaction pressure and the dosage of Fe2O3/MWCNTs, the catalyst system obtained the highest methane conversion rate of 7.41% and methanol selectivity of 86.3%, which is analogous to that of the equivalently strong acid catalyst system. The I2-Fe2O3/MWCNTs catalyst system has great potential in the application of CPOM under mild, environmentally benign conditions, such as non-noble metal requirement, ambient temperature, and weak acid. The reaction mechanism was discussed.

Comparison of Various Hydrogen Production Technologies from Natural Gas

The article provides an overview of the present condition and immediate future potential in the realm of hydrogen energy technologies. The paper delves into the most renowned approaches for generating hydrogen from natural gas: a) Steam-Methane Reforming (SMR); b) Partial Oxidation (POX); and c) Autothermal Reforming (ATR). Nevertheless, employing these technologies on an industrial scale requires substantial R&D efforts, often on the scale of experimental ventures. The article also examines the global energy landscape, energy sources, the historical discovery of hydrogen, and the various production methods. It addresses the intricacies associated with hydrogen production technologies, with a focal point on the technology of extracting hydrogen from natural gas. Through a comparison of the benefits and drawbacks of each method and, as explicated in the concluding section of the study, several significant insights have been derived. Among the three technologies, SMR, the steam conversion process, boasts the highest hydrogen production rate. Catalytic partial oxidation of methane exhibits the swiftest reaction rate; however, it necessitates the use of pure oxygen, which poses safety concerns. The process of methane auto-thermal reforming requires no external heat and is characterized by minimal energy consumption. Steam reforming of methane emerges as an ecologically sound and scientifically promising avenue, offering high effectiveness. Nevertheless, its deployment on an industrial scale remains to be fully refined. Developing cost-effective catalysts and continuous reactor systems for methane steam conversion technology is essential to rendering it economically viable. In conclusion, there is substantial potential for advancements at hydrogen energy technologies, particularly through refining and integrating these different production methods.

Solution combustion derived nanoalloys: Robust and efficient catalyst systems for partial oxidation of methane

Noble metals like Pt, Pd, Ir, Os, and Ru showed excellent performance for catalytic conversion of methane to syngas by catalytic partial oxidation of methane (CPOM), nevertheless, monometallic catalysts always suffer either from partial deactivation due to coke oxidation or hotspot formation inside the reactor tube wall. Therefore, a series of bimetallic catalysts of Pd–Pt, Pt–Ru, and Pd–Ru supported on ceria have been prepared by a unique facile solution combustion method (SCS) to stabilize the metallic particles as nanoalloys and understand the intermetallic synergy to improve both catalyst conversion and lifetime. All the catalysts were characterized by XRD, BET, TPR, XPS, HRTEM, and RAMAN to delineate the structure-function relationship. DFT study has been carried out to explain the H2/CO selectivity discrepancy between bimetallic and monometallic catalysts. XPS and Raman studies confirm a strong interaction between active metals and support to facilitate the synergistic effect during the reaction. The strong interaction and higher dispersion of nano-particles of active metals could enhance active sites for the efficient conversion of methane to syngas. HRTEM proves the nanoalloy formation of these bimetallic catalysts, which improved the reaction thermodynamics of the newly prepared catalyst systems.

Investigation of an Intermediate Temperature SOFC Operation in Series with a CPOx Reformer

Solid oxide fuel cells are known for their fuel flexibility which makes them a great candidate for decentralized power generation and off-grid applications. Depending on the target application, there have been different system configurations such as steam reforming vs. CPOx reforming, external reforming vs. internal reforming, anode recirculation vs. single pass. The CPOx reforming in series with SOFC with single pass configuration opens up the intermittent power source market, due to its unique benefit of low cost, short startup time and easy maintenance. In this scheme fuel cell electrochemical performance is directly related to the syngas composition, i.e. H2 and CO fractions in the fuel stream, as well as any unreformed methane.In this study a computational fluid dynamics (CFD) model has been developed to study the dynamic and steady state behavior of a commercial intermediate temperature SOFC stack operating in series with a CPOx reformer. The CFD model of the SOFC accounts for the charge, species, momentum and energy balances, whereas a reduced order model for the CPOx incorporates equilibrium thermodynamics. CPOx is an exothermic catalytic reaction with an overall balance of:CH4+1/2O2 → 2H2+CO (1)which is defined in stoichiometric ratios. In practice the air flow is regulated to control the reactor temperature and syngas yield. Hence, along with temperature and pressure the ratio of oxygen to carbon (O-C ratio) in the left hand side of Eq. 1 is a critical parameter for determining the overall performance and efficiency of the system. Moreover, the CPOx operation typically has different routes to achieve desired products which constitutes a system with various reaction equilibria [i]. However, apart from Eq.(1) the dominant reaction paths can be summarized as [ii]:Reformation CH4+CO2 ↔ 2H2+2CO (2)Water gas shift CO+H2O ↔ H2+CO2 (3)Boudouard CO2 + C ↔ 2CO (4)CH4 Combustion CH4+2O2 → 2H2O+CO2 (5)CO Combustion 2CO+O2 → 2CO2 (6)H2 Combustion 2H2+O2 → 2H2O (7)Of these, combustion reactions can be practically considered as irreversible. Overall system equilibrium is a result of these reactions and is a function of temperature, pressure and O/C ratio. Any changes in these parameters shift the reaction equilibrium, hence the conversion efficiency and syngas yield. As a result, SOFC performance will be directly dependent on these parameters.In this study different operating regimes of CPOX and SOFC have been investigated. The model is validated experimentally with polarization data and gas chromatography analysis. The model predictions show good agreement with the GC data for both the CPOX and SOFC outlet gas compositions.Performance of the SOFC running on syngas obtained as a result of different CPOx equilibria is compared and a fuel cell efficiency map as a function of temperature and O-C ratio has been constructed. Also, dynamic response of SOFC to the changes in CPOx operating parameters is estimated with the transient simulations. Moreover, selectivity of SOFC toward H2 and CO has been investigated by outlining the different energy conversion paths inside the fuel cell electrode. It is found that SOFC at intermediate temperatures has an overall tendency for CO conversion due to enhanced WGSR reaction inside the electrodes although the standalone CO oxidation overvoltage is higher than that of H2 oxidation. Finally, SOFC performance is analyzed for injecting various amounts of unreformed CH4 into the syngas stream.[i] Bjørn Christian Enger, Rune Lødeng, Anders Holmen, A review of catalytic partial oxidation of methane to synthesis gas with emphasis on reaction mechanisms over transition metal catalysts, Applied Catalysis A: General 346 (2008) 1–27.[ii] Ruoshui Ma, Bang Xu, Xiao Zhang, Catalytic partial oxidation (CPOX) of natural gas and renewable hydrocarbons/oxygenated hydrocarbons—A review, Catalysis Today 338 (2019) 18–30. Figure 1

Catalytic partial oxidation of methane over bimetallic Ru–Ni supported on CeO2 for syngas production

Methane (CH4) is the second most abundant greenhouse gas (GHG) after carbon dioxide (CO2) and is widely recognized as one of the most destructive GHGs, exerting negative impacts on the Earth's atmosphere. In order to effectively reduce CH4 emissions, the conversion of methane into synthesis gas, which is a mixture of hydrogen (H2) and carbon monoxide (CO), has emerged as an appealing approach. Recent advancements have demonstrated that catalytic partial oxidation of methane (POM) holds great promise as a reaction pathway for syngas production. Here we study a series of catalysts consisting of monometallic Ru and Ni, and bimetallic Ru–Ni supported on CeO2. These catalysts were synthesized using both mechanochemical and conventional incipient wetness impregnation methods. Various preparation parameters were investigated, including the Ru:Ni metal ratio, the order of metal addition, and the milling energy and time for the mechanochemically prepared samples. The catalysts were subjected to low-temperature POM (350–600 °C) experiments to evaluate their performance. The experimental results reveal that the bimetallic Ru–Ni/CeO2 catalysts exhibit superior catalytic activity and stability compared to the monometallic Ru–CeO2 and Ni–CeO2 catalysts. Notably, the bimetallic Ru–Ni/CeO2 catalysts prepared through ball milling demonstrate a significantly lower temperature requirement for syngas production compared to the conventional catalysts prepared via incipient wetness impregnation.

Theoretical Investigation on Syngas Production by Catalytic Partial Oxidation of Methane in a Reverse-Flow Microchannel Monolithic Reactor

Theoretical Investigation on Syngas Production by Catalytic Partial Oxidation of Methane in a Reverse-Flow Microchannel Monolithic Reactor

Structural Evolution of Iron-Loaded Metal-Organic Framework Catalysts for Continuous Gas-Phase Oxidation of Methane to Methanol.

Catalytic partial oxidation of methane presents a promising route to convert the abundant but environmentally undesired methane gas to liquid methanol with applications as an energy carrier and a platform chemical. However, an outstanding challenge for this process remains in developing a catalyst that can oxidize methane selectively to methanol with good activity under continuous flow conditions in the gas phase using O2 as an oxidant. Here, we report a Fe catalyst supported by a metal-organic framework (MOF), Fe/UiO-66, for the selective and on-stream partial oxidation of methane to methanol. Kinetic studies indicate the continuous production of methanol at a superior reaction rate of 5.9 × 10-2 μmolMeOH gFe-1 s-1 at 180 °C and high selectivity toward methanol, with the catalytic turnover verified by transient methane isotopic measurements. Through an array of spectroscopic characterizations, electron-deficient Fe species rendered by the MOF support is identified as the probable active site for the reaction.

Improving the Coke Resistance of Ni-Ceria Catalysts for Partial Oxidation of Methane to Syngas: Experimental and Computational Study.

The synthesis of syngas (H2 : CO=2) via catalytic partial oxidation of methane (CPOM) is studied over noble metal doped Ni-CeO2 bimetallic catalysts for CPOM reaction. The catalysts were synthesized via a controlled deposition approach and were characterized using XRD, BET-surface area analysis, H2 -TPR, TEM, Raman and TGA analysis. The catalysts were experimentally and computationally studied for their activity, selectivity, and long-term stability. Although the pure 5Ni/CeO2 catalyst showed high initial activity (∼90%) of CH4 conversion, it rapidly deactivates around 20% of its initial activity within 140 hours of TOS. Doping of Ni/CeO2 catalyst with noble metal was found to be coke resistant with the best-performing Ni-Pt/CeO2 catalyst showed ∼95% methane conversion with >90% selectivity at a temperature of 800 °C, having exceptional stability for about 300 hours of time-on-stream (TOS). DFT studies were performed to calculate the activation barrier for the C-H activation of methane over the Ni, Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces showed nearly equal activation energy over all the studied surfaces. DFT studies showed high coke formation tendency of the pure Ni (111) having a very small C-C coupling activation barrier (14.2 kJ/mol). In contrast, the Ni3 Pt, Ni3 Pd, and Ni3 Ru (111) surfaces show appreciably higher C-C coupling activation barrier (∼70 kJ/mol) and hence are more resistant against coke formation as observed in the experiments. The combined experimental and DFT study showed Ni-Pt/CeO2 as a promising CPOM catalyst for producing syngas with high conversion, selectivity and long-term stability suited for future industrial applications.

A detailed surface reaction mechanism to investigate oxidation of methane over nickel catalyst

AbstractWe have developed a kinetically consistent detailed surface reaction mechanism for modeling the oxidation of methane over a nickel‐based catalyst. A one‐dimensional model, LOGEcat based on the single‐channel 1D catalyst model, is used to perform the simulations. The original multi‐step reaction mechanism is thermodynamically consistent and consists of 52 reactions. By thermodynamic consistency, we mean that the equilibrium is achieved with the support of the Arrhenius parameters and does not depend on the thermochemistry of the species involved in the considered reactions. The detailed mechanism developed in this investigation contains 26 reversible reactions. These reactions are obtained with the use of the thermochemistry of the species. The study focuses on ensuring kinetic consistency and this is done with the help of thermodynamic analysis by bringing the thermochemistry of the species in play in order to develop a surface reaction mechanism. The new mechanism can be used to understand the other processes, for example, steam‐ and dry‐reforming of methane over nickel, however, the main focus of the paper is to check the performance of the detailed mechanism for catalytic partial oxidation of methane. The applicability of the mechanism is checked for various reactor conditions in terms of parameters such as temperature and pressure by comparing the results with the available reference data. The detailed mechanism developed in this study is able to accurately express oxidation of methane over the nickel catalyst for the considered reactor conditions.

Bimetallic Ru–Pd supported on CeO2 for the catalytic partial oxidation of methane into syngas

A series of monometallic Ru, Pd, and bimetallic Ru–Pd catalysts loaded on CeO2 support have been prepared via mechanochemical and conventional incipient wetness impregnation methods and used in the partial oxidation of methane (POM) to obtain synthesis gas (H2 and CO). The influence of the preparation method, the order of addition of the metals, the Ru:Pd metal ratio, and the milling energy and time for samples prepared by the mechanochemical method, have been evaluated between 300 and 600 °C. The results revealed that bimetallic Ru–Pd/CeO2 catalysts outperform monometallic Ru–CeO2 and Pd–CeO2 for POM, both in terms of catalytic activity and stability. Additionally, the bimetallic Ru–Pd/CeO2 catalysts prepared by ball milling produced syngas at a much lower temperature compared to the conventional catalysts prepared by incipient wetness impregnation. Raman spectroscopy, temperature programmed reduction (H2–TPR), X–ray photoelectron spectroscopy (XPS) and high–resolution transmission electron microscopy (HRTEM) have been used to characterize the catalysts before and after reaction.

Partial Oxidation of Methane over CaO Decorated TiO2 Nanocatalyst for Syngas Production in a Fixed Bed Reactor

Syngas is a valuable entity for downstream liquid fuel production and chemical industries. The efficient production of syngas via catalytic partial oxidation of methane (CPOM) is an important process. In this study, partial oxidation of methane (POM) was carried out using CaO decorated TiO2 catalysts. The catalysts were synthesized employing the sol-gel method, while the decoration of TiO2 with CaO was achieved in an aqueous solution by wetness impregnation method. The prepared catalysts were characterized by employing XRD, Raman, TG-DTG, and SEM-EDX for structural and morphological analysis. On testing for POM, at 750 °C the catalysts demonstrate excellent CH4 conversion of 83.6 and 79.5% for 2% and 3% CaO loaded TiO2, respectively. While the average H2/CO ratio for both 2% and 3% CaO loaded TiO2, 2.25 and 2.28, respectively, remained slightly above the theoretical value (H2/CO = 2.0) of POM. The improved POM performance is attributed to the optimally loaded CaO on the TiO2 surface that promotes the reaction where TiO2 support ensure less agglomerated particles, resulting into a fine distribution of the active catalytic sites.

Oxidation of methane and ethylene over Al incorporated N-doped graphene: A comparative mechanistic DFT study

It is generally recognized that developing effective methods for selective oxidation of hydrocarbons to generate more useful chemicals is a major challenge for the chemical industry. In the present study, density functional theory calculations are conducted to examine the catalytic partial oxidation of methane (CH4) and ethylene (C2H4) by nitrous oxide (N2O) over Al-incorporated porphyrin-like N-doped graphene (AlN4-Gr). Adsorption energies for the most stable configurations of CH4, C2H4, and N2O molecules over the AlN4-Gr catalyst are determined to be −0.25, −0.64, and −0.40 eV, respectively. According to our findings, N2O can be efficiently split into N2 and Oads species with a negligible activation energy on the AlN4-Gr surface. Meanwhile, CH4 and C2H4 molecules compete for reaction with the activated oxygen atom (Oads) that stays on the surface. The energy barriers for partial methane oxidation through the CH4 + Oads → CH3° + HOads and CH3° + HOads → CH3OH reaction steps are 0.16 eV and 0.27 eV, respectively. Furthermore, the produced CH3OH may be overoxidized by Oads to give formaldehyde and water molecules by overcoming a relatively low activation barrier. The activation barriers for C2H4 epoxidation are small and comparable to those for CH4 oxidation, implying that AlN4-Gr is highly active for both reactions. The high energy barrier for the 1,2-hydrogen shift in the OCH2CH2 intermediate, on the other hand, makes the production of acetaldehyde impossible under normal conditions. According to the population analysis, the AlN4-Gr serves as a strong electron donor to aid in the charge transfer between the Al atom and the Oads moiety, which is necessary for the activation of CH4 and C2H4. The findings of the present study may pave the way for a better understanding of the catalytic oxidation the CH4 and C2H4, as well as for the development of highly efficient noble-metal free catalysts for these reactions.

Fuel-rich hetero-/homogeneous combustion of C3H8/O2/N2 mixtures over rhodium

The catalytic (heterogeneous) and gas-phase (homogeneous) combustion of C3H8/O2/N2 mixtures over rhodium was investigated experimentally and numerically at 5 bar and at fuel-rich equivalence ratios φ = 2.0-3.5 relevant to propane Catalytic Partial Oxidation (CPO). In situ spatially-resolved Raman measurements of major gas-phase species concentrations and Planar Laser Induced Fluorescence (PLIF) of formaldehyde were applied in an optically accessible channel-flow reactor to monitor the catalytic and gas-phase processes, respectively, while accompanying 2D simulations were carried out with detailed hetero-/homogeneous chemical reaction mechanisms. Due to the high gas-phase reactivity of propane, homogeneous chemistry could not be ignored over most of the reactor's oxidation zone length (upstream zone where the deficient reactant oxygen is not fully consumed). The presence of gas-phase chemistry deteriorated the otherwise high catalytic syngas (H2 and CO) selectivities over the oxidation zone. Raman measurements of major gas-phase species concentrations over the restricted oxidation zone length without appreciable gas-phase chemistry showed that the catalytic reaction mechanism slightly underpredicted (overpredicted) the H2 (CO) formation. The same behavior was also attested over the remaining length of the oxidation zone where combined catalytic and gas-phase chemistry was present. The production of considerable amounts of H2 at the highest investigated equivalence ratio of 3.5 accelerated the onset of homogeneous ignition and the formation of strong flames. The discrepancies between measured and predicted homogeneous ignition distances were less than 6.8% in all cases, illustrating the validity of the employed hetero-/homogeneous kinetic schemes. Contrary to past methane CPO studies, the contribution of gas-phase chemistry and the formation of strong flames in propane CPO was detrimental to syngas production.

Manganese Catalyzed Partial Oxidation of Light Alkanes

The catalytic partial oxidation of methane is achieved at low temperatures (<200 °C) using manganese oxides and manganese salts in mixtures of trifluoroacetic acid and trifluoroacetic anhydride. Dioxygen is used as the in situ terminal oxidant. For Mn oxides (e.g., MnO2, Mn2O3, and Mn3O4), we studied stoichiometric methane partial oxidation in HTFA (TFA = trifluoroacetate). Using a Mn trifluoroacetate salt, at 180 °C and under 25 psig of methane, product selectivity for the mono-oxidized product methyl trifluoroacetate (MeTFA) is observed to be >90% at ∼35% methane conversion at approximately 6 turnovers. Under our catalytic methane oxidation reaction conditions, MeTFA is stable against overoxidation, which explains the likely high selectivity at conversions >15%. Using combined experimental studies and DFT calculations, a mechanism involving soluble and molecular Mn species in the catalytic cycle is proposed. The proposed reaction pathway involves initial activation of MnII by dioxygen, cleavage of a methane C–H bond by a MnIII hydroxo intermediate, rebound of the methyl radical to generate MeTFA, and finally regeneration of the starting MnII complex. Also, this process is shown to be applicable to the oxidation of ethane, favoring the mono-oxidized product ethyl trifluoroacetate (EtTFA) and reaching ∼46% conversion.

Insight into deactivation of the carbon-/sintering-resistant Ni@Silicalite-1 for catalytic partial oxidation of methane to syngas

Ni-based catalysts show good activity and selectivity for the catalytic partial oxidation of methane (CPOM) to syngas, but still suffer from carbon deposition and Ni-sintering. Herein, Ni nanoparticles of 3–7 nm are successfully embedded inside the crystal of silicalite-1 (S-1) zeolite via one-pot hydrothermal synthesis. The Ni@S-1 catalysts, with high activity/selectivity, show high carbon-/sintering-resistance but still deactivates fast. The surface of Ni nanoparticles involved in the reaction is oxidized to form intermediate NiO species, which may react with the circumambient SiO2 (from S-1) in the presence of water vapor (by-product and/or intermediate-product of CPOM reaction) to form a dense Ni3(Si2O5)2(OH)2 layer around Ni nanoparticles. The formed Ni3(Si2O5)2(OH)2 compounds are hard to be reduced (even in H2 at 800 °C; thus losing capacity to involve catalytic reaction cycle) while completely blocking the Ni0 sites from contacting with reactants, which is the main cause for the Ni@S-1 deactivation. Not surprisingly, such deactivation problem can be solved easily by replacing Ni with highly anti-oxidative metals such as Rh.

Bimetallic Ru–Pd Supported on Ceo2 for the Catalytic Partial Oxidation of Methane into Syngas

Bimetallic Ru–Pd Supported on Ceo2 for the Catalytic Partial Oxidation of Methane into Syngas

Accelerating particle-resolved CFD simulations of catalytic fixed-bed reactors with DUO

Simulation of fixed-bed catalytic reactors is important for engineering industrial technologies. The large number of catalytically active surface faces makes the application of microkinetic models too time consuming for large 3D simulations that include fully resolved particle structures (e.g., ≫ 10′s of particles). Such simulations, though, are often required for small tube-to-particle diameter ratio configurations, where local flow effects are difficult to capture with 1D or 2D simulations. A common solution for speeding up reactive computational fluid dynamics (CFD) involves the use of chemistry acceleration methods, including In-Situ Adaptive Tabulation (ISAT) and Cell Agglomeration (CA). In the present contribution, DUO (DETCHEMTM + OpenFOAM coupling) CFD software has been extended to include ISAT and CA methods for surface reactions, in particular, using a CA method that is simpler than other implementations of this acceleration technique. Speedup factors and errors were tabulated for an 86 spherical particle 3D resolved fixed-bed reactor, considering the exothermic methane catalytic partial oxidation (CPOX) and the endothermic dry reforming of methane (DRM) chemistries. For CPOX, a speedup factor of ∼ 7x was achieved, while for DRM, a speedup of ∼ 35x was obtained, with both cases achieving an acceptable error in the solution. Although a tighter error tolerance with ISAT and CA is shown to reduce the overall calculation error, for some engineering situations this tradeoff in speedup and accuracy will be acceptable. Achieving usable results in around 0.5 – 2 h instead of around 20-hours (for these chemistries on this particular grid, run on a 400-core cluster) can vastly improve the feasibility of computational fluid dynamics for the analysis of fixed-bed catalytic reactors including microkinetics mechanisms.

Activated alumina market size & share 2021: North America, Europe, & APAC industry forecasts 2027

Catalytic partial oxidation (CPO) reactors have complex concentration and temperature gradients which make it difficult to understand the mechanism of autothermal operation. Previous research in the Schmidt group on methane CPO using the capillary sampling technique has shown the existence of two zones – oxidation and reforming [1], [2], [3], [4]. Nearly (>90%) all of the oxygen in the feed is converted within the first 2 mm of the catalyst bed. In this paper, temperature and concentration profiles during the CPO of methane and dimethyl ether CH3OCH3, an oxygenated hydrocarbon, are presented. Results with the two feeds are compared and the nature of the profiles was similar, with sharp gradients existing in the oxidation zone with slower chemistries in the reforming section. The rhodium catalyst in the oxidation zone during methane CPO was also analyzed using XPS and XRD and shown to be rhodium metal.

Tracking dynamic structural changes in catalysis by rapid 2D-XANES microscopy.

Many processes and materials in heterogeneous catalysis undergo dynamic structural changes depending on their chemical environment. Monitoring such dynamic changes can be challenging using conventional spectroscopic characterization tools, due to the high time resolution required. Here, a high-resolution 2D X-ray camera operating at 50 Hz full-frame rate was synchronized with a QEXAFS monochromator, enabling rapid spectro-microscopic imaging with chemical contrast over individual pixels. This was used to monitor chemical gradients within a model Pt/Al2O3 catalyst during catalytic partial oxidation of methane to synthesis gas. The transition from methane combustion (partly oxidized Pt) to combustion-reforming and partial oxidation (fully reduced Pt) was observed by a characteristic reduction front, which progressed from the end of the catalyst bed towards its beginning on the second time scale. The full-field QEXAFS imaging method applied here allows acquisition of entire XANES spectra `on the fly' in a rapid and spatially resolved manner. The combination of high spatial and temporal resolution with spectroscopic data offers new opportunities for observing dynamic processes in catalysts and other functional materials at work. The methodology is flexible and can be applied at beamlines equipped with a QEXAFS or other fast-scanning monochromators and a suitable sample environment for gas phase analytics to allow for catalytic studies at the same time.

Studies of Nickel/Samarium-Doped Ceria for Catalytic Partial Oxidation of Methane and Effect of Oxygen Vacancy

We investigated the performance of nickel/samarium-doped ceria (Ni/SDC) nanocatalysts on the catalytic partial oxidation of methane (CPOM). Studies of temperature-programmed surface reaction and reduction reveal that catalytic activity is determined by a synergistic effect produced by Ni metals and metal-support interaction. Catalytic activity was more dependent on the Ni content below 600 °C, while there is not much difference for all catalysts at high temperatures. The catalyst exhibiting high activities toward syngas production (i.e., a CH4 conversion &gt;90% at 700 °C) requires a medium Ni-SDC interaction with an Sm/Ce ratio of about 1/9 to 2/8. This is accounted for by optimum oxygen vacancies and adequate ion diffusivity in the SDCs which, as reported, also display the highest ion conductivity for fuel cell applications.