Partial Oxidation Of CH4 Research Articles

Methane conversion to higher value-added product and energy co-generation using anodes OF PdCu/C in a solid electrolyte reactor: alkaline fuel cell type monitored by differential mass spectroscopy

PdxCuy/C catalysts combinations were employed to CH4 partial oxidation in mild condition using a solid electrolyte reactor—alkaline fuel cell type. The differential mass spectroscopy on line method was used to monitor the oxidation products obtained as methanol, dimethyl ether, methyl formate and potassium formate. It was observed that as the electrical potential of the reactor increases, the generation of products decreases. The best results for conversion of methane into methanol and energy co-generation was obtained from Pd90Cu10/C and Pd50Cu50/C due to better H2O activation effects and adsorption site for CH4 oxidation.

Pt/Al2O3La2O3 catalysts stable at high temperature in air, prepared using a “one-pot” sol–gel process: Synthesis, characterization, and catalytic activity in the partial oxidation of CH4

Pt/Al2O3La2O3 catalysts were prepared by a “one-pot” sol–gel method, with different final synthesis temperatures. The catalysts were characterized by in situ X-ray absorption spectroscopy (XAS). The partial oxidation of methane (POM) reaction was used to evaluate catalyst stability. DRIFTS-CO analysis indicated the interaction of Pt with the support by Pt-O-(Al-O, La-O) bonds, which suppressed bridge CO adsorption. In situ POM-DXAS-MS analysis showed that after use in the POM reaction at about 1000 K and cooling to room temperature, the Pt/Al2O3La2O3 catalysts presented partial oxidation of Pt0, indicating the formation of a core–shell structure. The nanoparticles generated using the “one-pot” method showed higher Pt-O-Al type interaction with the support, relative to free Pt-O at the surface, resulting in high resistance to sintering in the POM reaction. The temperature used in the “one-pot” synthesis significantly influenced the Pt-O-Al interaction, which modified the resistance to sintering at 1073 K in air.

FeO6 Octahedral Distortion Activates Lattice Oxygen in Perovskite Ferrite for Methane Partial Oxidation Coupled with CO2 Splitting.

Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C-H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO6 octahedra in La1-xCexFeO3 (x = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO6 octahedral distortion in La1-xCexFeO3 promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La0.5Ce0.5FeO3 with the highest FeO6 distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO3 and CeFeO3, respectively, in CH4 partial oxidation step with simultaneous high CO2 conversion (92%) in the CO2-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.

An Overview of Reforming Technologies and the Effect of Parameters on the Catalytic Performance of Mesoporous Silica/Alumina Supported Nickel Catalysts for Syngas Production by Methane Dry Reforming

Synthetic gas - a combination of (H2) and (CO) - is an important chemical intermediate for the production of liquid hydrocarbon, olefin, gasoline, and other valuable chemicals. Several reforming methods that use steam, carbon dioxide, and oxygen in the presence of various catalytic systems have been extensively investigated, and this paper reviews the recent research on the state-of-the-art of reforming technologies and the effect of parameters on the catalytic activity of mesoporous silica/alumina supported nickel catalysts for syngas production by methane dry reforming. First, we provide an overview of reforming technologies, including methane dry reforming, steam methane reforming, partial oxidation of CH4, and auto thermal reforming of CH4. Then, we review the literature on dry reforming catalysts. Next, we describe recent findings on the effect of parameters on the catalytic activity of mesoporous silica/alumina supported nickel catalysts for syngas production. Finally, we make proposals for future research. This study can help achieve a better understanding of the reforming technologies and the effects of parameters on catalytic performance for syngas production, thus contributing to the development of green technologies.

(Ag)Pd-Fe3O4 Nanocomposites as Novel Catalysts for Methane Partial Oxidation at Low Temperature.

Nanostructured composite materials based on noble mono-(Pd) or bi-metallic (Ag/Pd) particles supported on mixed iron oxides (II/III) with bulk magnetite structure (Fe3O4) have been developed in order to assess their potential for heterogeneous catalysis applications in methane partial oxidation. Advancing the direct transformation of methane into value-added chemicals is consensually accepted as the key to ensuring sustainable development in the forthcoming future. On the one hand, nanosized Fe3O4 particles with spherical morphology were synthesized by an aqueous-based reflux method employing different Fe (II)/Fe (III) molar ratios (2 or 4) and reflux temperatures (80, 95 or 110 °C). The solids obtained from a Fe (II)/Fe (III) nominal molar ratio of 4 showed higher specific surface areas which were also found to increase on lowering the reflux temperature. The starting 80 m2 g−1 was enhanced up to 140 m2 g−1 for the resulting optimized Fe3O4-based solid consisting of nanoparticles with a 15 nm average diameter. On the other hand, Pd or Pd-Ag were incorporated post-synthesis, by impregnation on the highest surface Fe3O4 nanostructured substrate, using 1–3 wt.% metal load range and maintaining a constant Pd:Ag ratio of 8:2 in the bimetallic sample. The prepared nanocomposite materials were investigated by different physicochemical techniques, such as X-ray diffraction, thermogravimetry (TG) in air or H2, as well as several compositions and structural aspects using field emission scanning and scanning transmission electron microscopy techniques coupled to energy-dispersive X-ray spectroscopy (EDS). Finally, the catalytic results from a preliminary reactivity study confirmed the potential of magnetite-supported (Ag)Pd catalysts for CH4 partial oxidation into formaldehyde, with low reaction rates, methane conversion starting at 200 °C, far below temperatures reported in the literature up to now; and very high selectivity to formaldehyde, above 95%, for Fe3O4 samples with 3 wt.% metal, either Pd or Pd-Ag.

Regeneration behavior of reforming catalysts based on perovskite oxides LaM0.95Rh0.05O3 (M: Cr, Co, Fe) by redox treatment

Perovskite-based catalysts with a self-regeneration property, named intelligent catalysts, were developed for CH4 partial oxidation, and the effect of redox treatment on regeneration behavior of the catalytic activity was investigated. Rh-substituted catalysts such as LaM0.95Rh0.05O3 (M: Cr, Co, Fe) were prepared by the Pechini method. Among the catalysts, LaCr0.95Rh0.05O3 exhibited the highest and the most stable catalytic activity for partial oxidation of methane before and after redox treatment. The precipitation and dissolution of Rh species were confirmed by X-ray photoelectron microscopy and transmission electron microscopy, indicating that the catalyst regenerated itself via the redox process.

The coupling of CH4 partial oxidation and CO2 splitting for syngas production via double perovskite-type oxides LaFexCo1−xO3

In the paper, the influences of a series of LaFexCo1−xO3 perovskites with different Co:Fe ratios (3:1, 1:1, and 1:3) were synthesized as oxygen carriers (OCs) in the coupling of CH4 partial oxidation and CO2 splitting for syngas. The influence of the Fe:Co ratio on H2:CO ratio was investigated. In fixed-bed experiments, the OCs were reduced by methane before reacting with CO2 to produce CO. The results indicated that an increase in the proportion of Fe caused the improvement of both H2 and CO selectivity and the enhancement of reduction performance of the OCs, which is beneficial to the CO2 reduction. Additionally, the stability of the advanced samples was examined in which the oxygen carrier exhibited good CH4 conversion and stability simultaneously at the Co:Fe ratio of 1:1. Furthermore, the mechanism showed that Fe formed by dissociation of the alloy limited the formation of stable intermediate La2O2CO3, which prevented oxidation of the reduced product by CO2.

Direct-methane solid oxide fuel cells with an in situ formed Ni–Fe alloy composite catalyst layer over Ni–YSZ anodes

Coking on Ni surfaces limits the direct application of methane-based fuels in SOFCs with Ni-cermet anodes. Loading an anodic catalytic layer with a high catalytic activity for CH4 conversion can effectively protect the Ni-based anode from coking and increase the cell durability. In this work, a Ni–Fe alloy composite catalyst was prepared by reducing perovskite La0.7Sr0.3Fe0.8Ni0.2O3-δ (LSFN) and then evaluating its catalytic activity in the partial oxidation of CH4. The catalyst was applied on a conventional Ni–8 mol.% Y-stabilized ZrO2 (YSZ) anode for methane SOFCs using two methane-containing fuels (97% CH4–3% H2O and 30% CH4–70% air). The catalyst-modified cells showed much higher performances and durability than the conventional cell using a Ni–YSZ anode, indicating the potential application for direct-methane SOFCs.

Chemical looping reforming of CH4 in the presence of CO2 using ilmenite ore and NiO-modified ilmenite ore oxygen carriers

In this paper, a naturally occurring ilmenite ore and the same ore modified with NiO were employed as oxygen carriers for chemical looping reforming of CH4 for syngas production. The reactivity of the oxygen carriers and the syngas selectivity with CH4-based feedstocks were quantitatively examined in a fixed-bed reactor in the presence of CO2. The results showed that calcined ilmenite ore partially oxidizes CH4 to syngas and the reactivity of the calcined ilmenite can be greatly improved by a redox activation treatment. With the reaction of CH4 and calcined ilmenite, there is an initial period in which CH4 is fully oxidized via the reduction of Fe3+ to Fe2+ containing species; while subsequently, CH4 is partially oxidized leading to the reduction of Fe2+ to Fe0 containing species. However, the presence of CO2 in the feedstock stops any iron-containing species reduction beyond Fe2+, which is a critical reaction for syngas production. In order to permit syngas production in the presence of CO2, a NiO-modified ilmenite ore oxygen carrier was developed and evaluated, largely eliminating the negative effect of CO2. Consequently, syngas was successfully produced through partial CH4 oxidation in the presence of CO2. We have attributed this phenomenon to the catalytic effect of the metallic Ni or FeNi alloys generated during oxygen carrier reduction by CH4, which converted CO2 and CH4 into CO and H2via dry-reforming. Additionally, the incorporation of NiO within ilmenite ore significantly improved the reactivity of the ilmenite-based oxygen carrier. We believe that this dual-function catalyst-modified oxygen carrier will enable CH4-based syngas generation through both chemical looping reforming and dry-reforming processes simultaneously, ultimately allowing for syngas production in combination with CO2 utilization.

H2 production from a plasma-assisted chemical looping system from the partial oxidation of CH4 at mild temperatures

A plasma-assisted chemical looping system for the production of H2 (PCLH) was investigated in this study. This system allows the partial oxidation of CH4 at mild temperatures (573–773 K). Four active oxygen carriers: Fe2O3, NiO-impregnated Fe2O3 (NiO/Fe2O3), SrFeO3−δ and NiO-impregnated SrFeO3−δ (NiO/SrFeO3−δ) were compared, each working both as a packed material for the plasma reactor and an oxygen source for the partial oxidation of CH4. Similar conversions of CH4, and low yields of H2 were obtained in Fe2O3 and SrFeO3−δ. It was concluded that in these cases, H2 was mainly produced from direct cracking of CH4 by plasma. In contrast, when using NiO/Fe2O3 and NiO/SrFeO3−δ, substantial production of H2 was achieved. It is proposed that there is a synergistic effect between the catalyst and the oxygen carrier; the presence of the metallic Ni phase was responsible for catalysing the production of H2, and the oxygen from the support helped prevent the build-up of coke. As a result, the activity of Ni was continuously maintained for H2 production. The chemical loop is closed with the oxygen carriers being regenerated in air with plasma and then used in the next looping cycle. The high H2 production capability in NiO/Fe2O3 was repeatable; whilst, NiO/SrFeO3−δ deactivated in the second and third cycles. Amongst the temperatures studied, NiO/Fe2O3 at 673 K resulted in the best performance for H2-rich gas production. A further increase in the operating temperature led to a total combustion of CH4.

Investigation of NO2 Formation Kinetics in Dual-Fuel Engines With Lean Premixed Methane–Air Charge

A dual fuel engine concept with lean premixed methane–air charge ignited by a diesel pilot flame is highly promising for reducing NOx and soot emissions. One drawback of this combustion method, however, is the high nitric dioxide (NO2) emissions observed at certain operating points. The conditions leading to increased NO2 formation have been investigated using a batch reactor model in cantera. It has been found that the high emission levels of NO2 can be traced back to the mixing of small amounts of quenched CH4 with NO from the hot combustion zones followed by postoxidation in the presence of O2, requiring that the temperatures are within a certain range. NO2 formation in the exhaust duct of a test engine has been modeled and compared to the experimental results. The well-stirred reactor model has been used that calculates the steady-state of a uniform composition for a certain residence time. An appropriate reaction mechanism that considers the effect of NO/NO2 on methane oxidation at low temperature levels has been used. The numerical results of NO–NO2 conversion in the duct at low temperature levels show good agreement with the experimental results. The partial oxidation of CH4 can be predicted well. It can be shown that methane oxidation in the presence of NO/NO2 at low temperature levels is enhanced via the reaction steps CH3+NO2⇌CH3O+NO and CH3O2+NO⇌CH3O+NO2. In addition, the elementary reaction HO2+NO⇌NO2+OH is the important NO oxidizing step.

Utilization of CO2 for syngas production by CH4 partial oxidation using a catalytic membrane reactor

In this research, a synthetic flue gas mixture with added methane was used as the feed gas in the process of dry reforming with partial oxidation of methane using a laboratory scale catalytic membrane reactor to produce hydrogen and carbon monoxide that can present the starting point for methanol or ammonia synthesis and Fischer-Tropsch reactions. 0.5% wt% Rh catalyst was deposited on a γ-alumina support using rhodium (III) chloride precursor and incorporated into a shell and tube membrane reactor to measure the yield of synthesis gas (CO and H2) and conversion of CH4, O2 and CO2 respectively. These measurements were used to determine the reaction order and rate of CO2. The conversion of CO2 and CH4 were determined at different gas hourly space velocities. The reaction order was determined to be a first-order with respect to CO2. The rate of reaction for CO2 was found to follow an Arrhenius equation having an activation energy of 49.88 × 10−1 kJ mol−1. Experiments were conducted at 2.5, 5 and 8 ml h−1 g−1 gas hourly space velocities and it was observed that increasing the hourly gas velocities resulted in a higher CO2 and CH4 conversions while O2 conversion remained fairly constant. CO2 had a high conversion rate of 96% at 8 ml h−1 g−1. The synthesized catalytic membrane was characterized by Scanning Electron Microscopy (SEM) and the Energy Dispersive X-ray Analysis (EDXA) respectively. The micrographs showed the Rh particles deposited on the alumina support. Single gas permeation of CH4, CO2 and H2 through the alumina support showed that the permeance of H2 increased as the pressure was increased to 1 × 105 Pa. The order of gas permeance was H2 (2.00 g/mol) > CH4 (16.04 g/mol) > N2 (28.01 g/mol) > O2 (32 g/mol) > CO2 (44.00 g/mol) which is indicative of Knudsen flow mechanism. The novelty of the work lies in the combination of exothermic partial oxidation and endothermic CO2 and steam reforming in a single step in the membrane reactor to achieve near thermoneutrality while simultaneously consuming almost all the greenhouse gases in the feed gas stream.

Chemical looping dry reforming of methane with hydrogen generation on Fe2O3/Al2O3 oxygen carrier

A chemical looping dry reforming process for co-production of hydrogen and syngas was proposed. This process contains four different stages, i.e. reduction, dry reforming, steam oxidation and air oxidation. The partial oxidation of CH4 with lattice oxygen occurred along with dry reforming reaction on the reduced iron oxide in the dry reforming stage, which helps to obtain the flexibility syngas ratio and increase hydrogen yield in the next steam oxidation stages. In this study, Fe2O3/Al2O3 oxygen carrier was used to verify the feasibility of this process in a fluidized-bed reactor at 900 °C and 1.01 bar. Carbon deposition and physical properties of the carrier were studied by using O2-TPO, XRD and BET methods. It was found that the efficient conversion of CO2 and CH4 to syngas can be achieved on the reduced iron oxygen carrier. When the feed ratio of CH4/CO2 was 1 and the reduction extent of iron was 33%, the CH4 conversion and syngas yield (the output of syngas/the input of CH4) reached 98.32% and 3.84 during the dry reforming stage, respectively. Moreover, increasing the feed ratio of CH4/CO2 raised the H2/CO ratio of syngas, but the deposited carbon would form with the available lattice oxygen depleted. Finally, superior redox activity and stability were obtained during the 15 cycles, although slight sintering was observed on the reacted oxygen carrier.

Reaction-based kinetic model for the reduction of supported NiO oxygen transfer materials by CH4

Abstract The focus of this study is to assess the reaction rate-based kinetics of three NiO-based oxygen transfer materials (OTMs) supported on ZrO2, Al2O3 and SiO2 under CH4 reduction. Both NiO weight change data and gaseous phase composition from TGA-MS tests are utilized for the elucidation of the reaction scheme. We show that mainly CH4, as well as CO and H2 (primary NiO reduction products by CH4), are involved in the reduction process under a varying extent that depends on the support used. The developed kinetic model is first order dependent on the concentration of the main reductant at each reaction and a function of the NiO/Ni concentration. On ZrO2, NiO is exclusively reduced by CH4 via both total and partial oxidation. On the other hand, in addition to CH4, CO and H2 also contribute to NiO reduction on Al2O3 and SiO2. Still, total and partial CH4 oxidation are the dominant routes. In the case of SiO2 in particular, the reduction rate of NiO by CO and H2 is the highest among all OTMs. The CH4 decomposition reaction, catalyzed by the metallic nickel sites, also takes place via the Langmuir-Hinshelwood mechanism after the completion of the NiO reduction. The rate of this reaction correlates with the surface area of the materials due to the higher population of active metallic nickel sites on the surface, leading to carbon deposition in the order NiO/Al2O3 > NiO/SiO2 > NiO/ZrO2.

Catalytic methane reforming into synthesis gas over developed composite materials prepared by combustion synthesis

In this work, the results of carbon dioxide reforming and partial oxidation of CH4 on the catalysts prepared by solution combustion synthesis (SCS) and impregnation of moisture capacity methods are presented. Investigation of the activity of catalysts produced from initial mixture of Co(NO3)2-Μg(NO3)2-H3BO3 and glycine/urea of different composition was carried out for the production of synthesis gas and comparison of carbon dioxide reforming and partial oxidation of methane. Co(ΝΟ3)2 + Mg(NO3)2 + H3BO3 catalyst containing glycine has a higher activity than the catalyst containing urea. The CH4 conversion reaches 54.6%, and the conversion of CO2 increases to 51.7%, while the yield of H2 and CO is 54.1% and 51.3%, respectively, at 900 °C. It was found that CoMg3O4 spinel formation is due to magnesium cations substitution of cobalt cations. Mg2+ ions are replaced by ions of Co2+, as a consequence CoMg3O4 lattice parameters increase, since the ionic radius of Mg2+ (0.66 A) less than Cο2+ (0.72 A). Some advantage of SCS catalysts in comparison with catalysts prepared by the traditional impregnation method in the processes of dry reforming and partial oxidation of methane was shown.

In situ catalyst exsolution on perovskite oxides for the production of CO and synthesis gas in ceramic membrane reactors

In situ exsolution of nickel nano-particles on both sides of ceramic membrane reactors to accelerate the co-production of CO and synthesis gas through CO2 splitting and CH4 partial oxidation, respectively.

Enhanced lattice oxygen reactivity over Fe2O3/Al2O3 redox catalyst for chemical-looping dry (CO2) reforming of CH4: Synergistic La-Ce effect

Chemical-looping dry (CO2) reforming (CLDR) of CH4 over the LaxCe1-x-Fe2O3/Al2O3 (x = 0, 0.33, 0.67, and 1) redox catalysts paves a novel path for efficient syngas production and intensive CO2 reduction. The isolation of CO2 splitting (CS) from partial oxidation of CH4 (POM) via the proposed CLDR process makes it possible to economically address the carbon deposition of significant concern in conventional dry reforming and other related applications, and meanwhile enable a straightforward determination of active phases involved in the cyclic CLDR operation. Owing to the rare earth (i.e., La and Ce) incorporations and intimate contacts among the active Fe species, a large amount of perovskite (LaFeO3 and CeFeO3)-derived oxygen defects along with CeO2-assisted surface dispersion improvement hammer out tunnels beneficial for lattice oxygen migration, hence constituting the synergistic La-Ce effect. Moreover, our findings reveal that such La-Ce effect is advantageous for enhancing the resistance of Fe2O3/Al2O3 redox catalyst toward particle sintering and formation of inactive carbon, which guarantees catalyst tolerance against accumulated carbon deposition and more importantly the effective CO2 activation for both lattice oxygen replenishment and carbon removal. Herein, our findings demonstrate the potential of utilizing LaxCe1-x-Fe2O3/Al2O3 (x = 0.33) as a most promising redox catalyst for the proposed CLDR process.

Hydrotalcite-Type Materials Electrodeposited on Open-Cell Metallic Foams as Structured Catalysts

Structured catalysts based on hydrotalcite-derived coatings on open-cell metallic foams combine tailored basic/acidic sites, relatively high specific surface area and/or metal dispersion of the coating as well as low pressure drop and enhanced heat and mass transfer of the 3D metallic support. The properties of the resulting structured catalysts depend on the coating procedure. We have proposed the electro-base generation method for in situ and fast precipitation of Ni/Al and Rh/Mg/Al hydrotalcite-type materials on FeCrAlloy foams, which after calcination at high temperature give rise to structured catalysts for syngas (CO + H2) production through Steam Reforming and Catalytic Partial Oxidation of CH4. The fundamental understanding of the electrochemical-chemical reactions relevant for the electrodeposition and the influence of electrosynthesis parameters on the properties of the as-deposited coatings as well the resulting structured catalysts and, hence, on their catalytic performance, were summarized.

H2 production from partial oxidation of CH4 by Fe2O3-supported Ni-based catalysts in a plasma-assisted packed bed reactor

H2-rich gas production from CH4 at mild temperature (673 K), was achieved in a single step without introducing a separate oxygen stream. This was conducted in a plasma-assisted packed bed reactor in the presence of Ni-based catalysts doped on an active support, i.e. Fe2O3. Among the tested materials, NiO/Fe2O3 was found to be very promising and its excellent catalytic properties seemed to be induced by the presence of Fe2O3, which suppressed the formation of deposited carbon, and thus maintained the catalytic effect of metallic Ni (formed during NiO reduction by the CH4/Ar plasma). This work demonstrates the potential of plasma-assisted chemical looping partial oxidation for H2 production.

Direct Power Generation from Low Concentration Coal‐Bed Gas by a Catalyst‐Modified Solid Oxide Fuel Cell

AbstractClear utilization of low‐concentration coal‐bed gas (LC‐CBG) would save energy, mitigate greenhouse gas emissions, and reduce explosion accidents during a coal‐mining process. In this paper, a novel catalyst Ni/BaO/CeO2 (NBC) is developed for CH4 partial oxidation and is used as an independent catalyst layer of a Ni cermet anode. LC‐CBG with composition of 30 % methane and 70 % air is directly fed to the catalyst‐modified SOFC to generate electricity. Operated on 30 % LC‐CBG, the NBC‐modified cell shows better performance and discharge stability than the conventional cell without the catalyst layer. Gas chromatography (GC) analysis on effluent gases extracted from the operating catalyst‐modified cells also indicates a higher CH4 conversion when the cell is fed with 30 % LC‐CBG than when fed with 3 % H2O‐humidified methane. Post‐mortem microstructures of cell surface were analyzed. The NBC‐modified cell has a potential application for fuels containing low concentration methane and air.