Partial Oxidation Of Methane Reaction Research Articles

Constructing the Ni-O-Ce interface to enhance the activity and stability for partial oxidation of methane to syngas under high temperatures

Catalyst interface determines the activity and stability of partial oxidation of methane (POM) toward syngas under high temperatures crucially. Herein, Ni catalysts supported on CeO2 were prepared under different pretreatment atmospheres to construct an optimal and robust interface. Ni/CeO2 catalyst pretreated in H2 (Ni/CeO2-H2) exhibits the higher activity and the better stability than Ni/CeO2-Ar and Ni/CeO2-air catalysts. The Ni-O-Ce interfacial site in Ni/CeO2-H2 catalyst shows the lower reduction temperature, indicating the enhanced H-spillover effect and enhanced oxidation resistance of Ni under POM conditions. Moreover, the XPS and in situ Raman results show that Ni/CeO2-H2 contains more surface oxygen vacancies for adsorbing and activating oxygen, further contributing to the reaction activity. The in situ DRIFTS results indicate that the CH4 could react with the lattice oxygen to form formate and carbonate, and further decompose to CO and CO2. These findings deepen the fundamental understanding of Ni/CeO2 catalysts for POM reaction.

Tailored SrFeO3-δ for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a highly efficient process that converts two major greenhouse gases (CH4 and CO2) into syngas ready for the feedstock of liquid fuel production. One of the major obstacles facing this technology now is creating oxygen carriers that are stable and reactive. We fabricated high-performance Sr0.98Fe0.7Co0.3O3-δ perovskite-structured oxygen carrier by combining A-site defects and B-site doping of SrFeO3-δ. During isothermal CL-DRM tests at 850 °C, Sr0.98Fe0.7Co0.3O3-δ achieved 87% CH4 conversion and 94% CO selectivity in the CH4 partial oxidation reaction, followed by a syngas yield of 8.5 mmol/g, and CO yield of 4.2 mmol/g in CO2 decomposition. A-site defect engineering of the perovskite creates abundant oxygen vacancies and enhances oxygen storage capacity (OSC). Co-doping of the B-site of Sr0.98FeO3-δ increases oxygen mobility and CH4/CO2 activation, resulting in high activity in the CL-DRM process. This methodology resulted in high ionic mobility and facilitated the rapid diffusion of oxygen in the bulk phase, thereby increasing the redox properties of SrFeO3-δ. The oxygen carrier exhibits excellent structural stability and regeneration ability in successive redox cycles. This strategy offers a simple but very effective pathway to tailor OSC, oxygen mobility, and oxygen vacancies of perovskite-structured materials for chemical looping or redox-involved processes.

Nano-crystalline NiO-MgO/NiAl2O4 catalyst for coking free low temperature partial oxidation of methane

Here, we report an ultra-small-sized nano-crystalline NiO-MgO/NiAl2O4 catalyst for coking-free partial oxidation of methane reaction at low temperature (450 °C). The catalyst was tested in a packed-bed reactor over a temperature range of 350 to 850 °C. The NiO-MgO/NiAl2O4 catalyst was optimized for calcination temperature and nickel content. The best-optimized sample was then tested for different gas hourly space velocities (GHSVs), resulting in 99 % CH4 conversion and varying H2/CO selectivities from 90 % to 70 % at 450 °C. A stability test was conducted at 500 °C for 100 h for stream on reaction conditions, resulting in 95 % CH4 conversion, 90 % H2 selectivity, and 60 % CO selectivity without any significant deactivation. The excellent catalytic activity and stable performance were attributed to the ultra-small size and nanocrystalline structure of NiO-MgO, as well as the presence of lattice oxygen reservoirs. Additionally, the synergistic interaction between the NiO-MgO solid solution and the support NiAl2O4 contributed to these properties.

Mesoporous configuration effects on the physicochemical features of hierarchical ZSM-5 supported cobalt oxide as catalysts in methane partial oxidation

Hierarchical porous system has become a prevalent method to overcome the diffusion limitation of conventional zeolites. Two types of mesopores characterized as intra-crystalline (mesopores in the zeolite pore wall) and inter-crystalline mesopores (meso-sized voids between nano-zeolite aggregates) could be formed in the synthesis of hierarchical zeolites. In an attempt to investigate the influence of mesopores structure on the physicochemical properties of hierarchical ZSM-5, specifically cobalt oxide impregnated ZSM-5 zeolite samples with intra- and inter-crystalline mesopores were synthesized through two different synthesis strategies. Analysis of the physicochemical properties of the as-modified hierarchical ZSM-5 catalysts were carried out using SEM, TEM, XPS, and H2-TPR which showed distinct features given by the two mesopores configurations. Co-oxide impregnated on ZSM-5 with inter-crystalline mesopores was dominated by Co(II) species, while Co-oxide/ZSM-5 showed a fair amount of Co(III) and Co(II). Furthermore, analysis of the catalytic activity was conducted using methane partial oxidation as a model reaction. With a variation in reaction time, various types of oxygenated products, i.e. methanol, formaldehyde, formic acid, and a small trace of carbon dioxide were observed. Catalytic results suggested that the Co-oxide/ZSM-5 material with inter-crystalline mesopores configuration is more active for the methane partial oxidation reaction compared to the Co-oxide/ZSM-5 with intracrystalline mesopores. This was confirmed by the formation of formaldehyde rather than methanol as the major product in the brief reaction time of 30 min.

Reactivity of Group 5 and 6 Single-Site Photocatalysts for Partial Oxidation of Methane: Comparison of Chromium, Niobium, and Tungsten-Doped Mesoporous Amorphous Silica.

Single-site transition-metal-doped photocatalysts can potentially be used for partial oxidation of methane (POM) at remote sites where natural gas is extracted and methane is often flared or released to the atmosphere. While there have been several investigations into the performance of vanadium, there has been no general survey of the performance of other metals. This work aims and examines Cr, Nb, and W metal oxide materials embedded in amorphous SiO2 to determine the viability of each metal in catalyzing the POM. Photoexcited states are examined to determine the nature of the photoactivated species, and then the subsequent POM reaction mechanisms are elucidated. Using the calculated energies of reaction intermediates and transition states, the rate of methanol formation is evaluated through the use of a microkinetic model. The findings indicate that all three metals are potentially more suitable for catalyzing POM than vanadium but that niobium shows the most favorable energy profile.

Thermocatalytic partial oxidation of methane to syngas (H2, CO) production using Ni/La2O3 modified biomass fly ash supported catalyst

In this work, the biomass fly ash (BFA) supported Ni/La2O3 catalyst was synthesized for the first time to produce syngas, a mixture of CO and H2 via the partial oxidation of methane (POM). The BFA support was modified using laboratory synthesized Ni/La2O3 through the wetness impregnation technique. The Ni/La2O3-BFA catalyst was characterized by several techniques to investigate its suitability for the POM reaction. The characterization results showed that the crystalline structure, better metal support interaction and enhanced thermal stability of Ni/La2O3-BFA make it suitable for the POM. The synthesized Ni/La2O3-BFA catalyst remained stable for 30 h on stream during POM at 850 °C. The addition of La2O3 promoter and active metal Ni to the BFA improved the CH4 conversion from 55% to 85% and enhanced the H2/CO ratio from 1.4 to 2.0 while maintaining a reactants stoichiometric ratio of (CH4:O2 = 2:1). The study of spent catalyst by using various techniques confirmed that the stable catalyst exhibited coke resistance in the POM even after 30 h time on stream. Thus, the performance of BFA supported Ni/La2O3 catalyst shows more potential for catalytic applications due to its suitable physiochemical properties as it is a combination of multiple oxides that synergistically participate in the reaction steps and increases syngas production. It also provides low-cost, abundant, greener, and waste based alternative to expensive metal oxide as supports for catalytic applications.

Study of Ni Catalysts with Different Al2O3 Supports in the Partial Oxidation of Methane Reaction

Study of Ni Catalysts with Different Al₂O₃ Supports in the Partial Oxidation of Methane Reaction

Oscillatory behavior of Ni/TiO2 catalyst during partial oxidation of methane: Understanding the role of strong metal-support interaction

The restructuring of a catalyst under working conditions has been recognized as a critical factor that can significantly impact their performance in recent years. In this study, we investigate the behavior of a highly dispersed Ni supported on TiO2 (P25) catalyst during the partial oxidation of methane (POM) to produce syngas. Our results reveal a distinct oscillation phenomenon in the catalyst's performance over time. The simultaneous oscillations of rapid deactivation and activation are observed, while the catalyst remains active for continuous POM reaction. Comprehensive characterizations suggest that this deactivation is not caused by traditional deactivation mechanisms with coke formation or Ni sintering. The formation of inactive NiTiO3 results in catalyst deactivation, which is formed between Ni and TiO2 support in the reductive atmosphere of POM products under high temperature due to strong metal-support interaction (SMSI). The simultaneous presence of oxidative and reductive atmospheres of the reactants and products in the POM reaction leads to the generation or demise of NiTiO3. The dynamic change of the Ni active sites during the in-situ reaction leads to the oscillation of the catalytic activity. This study sheds new light on the importance of SMSI in understanding the behavior of catalysts under working conditions.

Development of Membrane Reactor Coupling Hydrogen and Syngas Production.

Simultaneous syngas and pure hydrogen production through partial oxidation of methane and water splitting, respectively, were demonstrated by using mixed ionic-electronic conductors. Tubular ceramic membranes prepared from La0.5Sr0.5FeO3 perovskite were successfully utilized in a 10 M lab scale reactor by applying a radial arrangement. The supply of methane to the middle area of the reaction zone was shown to provide a uniform distribution of the chemical load along the tubes' length. A steady flow of steam feeding the inner part of the membranes was used as oxidative media. A described configuration was found to be favorable to maintaining oxygen permeability values exceeding 1.1 mL∙cm-2∙min-1 and long-term stability of related functional characteristics. Methane's partial oxidation reaction assisted by 10%Ni@Al2O3 catalyst proceeded with selectivity values above 90% and conversion of almost 100%. The transition from a laboratory model of a reactor operating on one tubular membrane to a ten-tube one resulted in no losses in the specific performance. The optimized supply of gaseous fuel opens up the possibility of scaling up the reaction zone and creating a promising prototype of a multitubular reaction zone with a simplified sealing procedure.

Mechanistic Understanding of the Use of Single-Atom and Nanocluster Catalysts for Syngas Production via Partial Oxidation of Methane

Single-atom and nanocluster catalysts presenting potent catalytic activity and excellent stability are used in high-temperature applications such as in structural composites, electrical devices, and catalytic chemical reactions. Recently, more attention has been drawn to application of these materials in clean fuel processing based on oxidation in terms of recovery and purification. The most popular media for catalytic oxidation reactions include gas phases, pure organic liquid phases, and aqueous solutions. It has been proven from the literature that catalysts are frequently selected as the finest in regulating organic wastewater, solar energy utilization, and environmental treatment applications in most catalytic oxidation of methane vis-à-vis photons and in environmental treatment applications. Single-atom and nanocluster catalysts have been engineered and applied in catalytic oxidations considering metal–support interactions and mechanisms facilitating catalytic deactivation. In this review, the present improvements on engineering single-atom and nano-catalysts are discussed. In detail, we summarize structure modification strategies, catalytic mechanisms, methods of synthesis, and application of single-atom and nano-catalysts for partial oxidation of methane (POM). We also present the catalytic performance of various atoms in the POM reaction. Full knowledge of the use of remarkable POM vis-à-vis the excellent structure is revealed. Based on the review conducted on single-atom and nanoclustered catalysts, we conclude their viability for POM reactions; however, the catalyst design must be carefully considered not only for isolating the individual influences from the active metal and support but also for incorporating the interactions of these components.

In situ surface chemical properties and catalytic performances of Pt/CeO2 catalyst in methane partial oxidation under different conditions

The changes of oxygen vacancies and Pt valence on ceria supported precious metals materials often occur in methane partial oxidation reaction, leading to catalyst and reactivity variability. In this work, in situ X-ray photoelectron spectroscopy were used to investigate the surface chemical properties under no or different gas-phase oxygen concentrations and reaction temperatures, then the correlation between the chemistries with reaction performance were proposed. When only methane is present, reactive oxygen on catalyst surface are the oxygen source for methane oxidation. The oxygen vacancies on catalyst are abundant and part of Pt is reduced to zero valence. However, when the mixture of methane and oxygen is present at low temperature, gas-phase oxygen cannot be utilized directly, but could absorb on the oxygen vacancies and Pt, making oxygen vacancies reduction and Pt oxidation. Only when the temperature is higher than 400 °C, it can be converted into reactive oxygen species to participate in reaction, simultaneously, oxygen vacancy generation and Pt reduction, promoting the reaction continuous. Before the reaction begins, it is necessary to keep the catalyst rich in oxygen vacancies and metallic state of Pt for methane conversion at low temperature. The research is helpful to design catalysts and improve reactivity.

Monomeric Fe Species in Square Planar Geometry Active for Low Temperature NH3-SCR of NO

Monomeric Fe species in zeolites are considered to be the active sites for the low temperature activity toward ammonia-assisted selective catalytic reduction of nitrogen oxides (NH3-SCR) in exhaust gases. Herein, we report on a preparation method to synthesize single-site Fe/ZSM-5 by combination of dealumination with the use of a bulky iron complex to introduce Fe. Transient in situ XAS experiments at the Fe K-edge under dynamic NH3-SCR reaction conditions demonstrated the involvement of all iron atoms in the redox cycle and, with that, suggest that Fe species in the studied Fe/ZSM-5 catalyst are monomers. Simulation of experimental X-ray absorption data revealed that the Fe species in the sample obtained by this approach adopt a square planar geometry, which changes into fivefold coordination at low temperature by strongly binding either NO or NH3 as the ligand. The presence of monomeric Fe species in this Fe/ZSM-5 conveys molecular level insights into the temperature-dependent NH3-SCR activity and might prove useful in the study of other reactions over monomeric Fe species, such as methane partial oxidation or dehydroaromatization reactions.

Identifying the Metallic State of Rh Catalyst on Boron Nitride during Partial Oxidation of Methane by Using the Product Molecule as the Infrared Probe

The partial oxidation of methane (POM) is a promising method for converting methane to syngas. The transition metal supported on boron nitride (BN) has recently been studied as part of a catalog of emerging catalysts. However, the chemical state of the metal supported on BN during methane reforming is still in debate. In this work, we report a rhodium catalyst on boron nitride (Rh/BN) for the POM, with exceptional activity and long-term stability at 600 °C for 230 h. The Rh/BN catalyst was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS). As revealed by in situ DRIFTS, the infrared band (2020 cm−1) of the product molecule, CO, adsorbed on the Rh, as the probe confirms the metallic state of Rh during the POM reaction. In addition, the results of in situ DRIFTS indicate that the reactive gaseous environment would react with the catalyst to form B-OH and B-H, which synergistically boost the POM activity.

Coupling water splitting and partial oxidation of methane (POM) in Ag modified La0.8Ca0.2Fe0.94O3-δ hollow fiber membrane reactors for co-production of H2 and syngas

The catalytic membrane reactor, a kind of process intensification technology, can enhance chemical engineering efficiencies by combining multi-steps of reaction and separation into one unit. However, the prerequisite to realize such a promising technology is the good match between reaction efficiency, transport rate and membrane stability to withstand the real reacting conditions particularly for these high temperature reactions. In this work, we showcased the development of catalytic La0.8Ca0.2Fe0.94O3-δ-0.05Ag (LCF-Ag) hollow fiber membrane reactor to couple water splitting and partial oxidation of methane (POM) for simultaneous H2 and syngas production. Without addition of extra catalyst, LCF-Ag membrane provides the best H2 production rates (fluxes) from thermal water splitting of 3.6 and 0.69 mL min-1 cm-2 by coupling hydrogen or methane oxidation at 950 °C to consume the permeated oxygen, respectively. Noteworthy that H2 flux, methane conversion and CO selectivity is closely correlated with the presence of catalyst and operating conditions. By integrating the Ni/LaNiO3/γ-Al2O3 catalytic layer in the lumen surface to improve the POM reaction kinetics, the optimized LCF-Ag hollow fibre membrane reactor could give the best H2 flux of 7.9 mL min-1 cm-2, CH4 conversion of 58% and CO selectivity of 89%, respectively. The membrane reactor was stably operated at 950 °C for more than 20 h without failure. These results are compared favorably with literature, encouraging more future exploration to further improve membrane reactor performance for practical applications.

Synthesis-Gas Production from Methane over Ni/CeO2 Catalysts Synthesized by Co-Precipitation Method in Different Solvents

Ni/CeO2 catalysts were synthesized by the coprecipitation method in a basic medium, using different solvents: water, methanol, ethanol, and isopropanol (Ni content, 10% wt.). These catalysts were tested in the production of syngas through the oxidative reforming of methane (ORM), and partial oxidation of methane (POM). The results of this research demonstrated that the use of alcohols (methanol, ethanol, and isopropanol) during the preparation of the Ni/CeO2 catalysts by the coprecipitation method, improved their characteristics such as crystallite size (nm), surface area (m2·g−1), and reducibility (measured by H2-TPR) that influenced on their catalytic performance in ORM and POM reactions. The best solvent of this study was isopropanol. The use of alcohols (methanol, ethanol, isopropanol) in the co-precipitation method led to the formation of filamentous carbon on the catalyst after the reactions. The catalyst synthesized in the water proved to be inefficient in the POM and ORM reactions and led to the formation of amorphous carbon after the reactions.

Tri-reforming of methane for syngas production using Ni catalysts: Current status and future outlook

Tri-reforming of methane (TRM) emerged as an attractive approach for syngas production that combines the methane steam reforming (SMR), dry reforming (DRM) and partial oxidation (POX) reactions in a single process. The key merits of the TRM process are the ability to use flue gas directly in the process feedstock, the great flexibility to control the H2/CO ratio for downstream processes, and the relatively lower energy demand and carbon footprint. Considerable progress was achieved over the past decade in catalyst development, process modeling and optimization for syngas production using the TRM process. In this work a critical review of the literature pertaining to Ni-based catalyst development, TRM reaction kinetics, process development, and economics is presented. The use of Ni-based catalysts has received significant attention in recent years; hence this work aims to provide a summary and a critical analysis of the advancement achieved in the design of Ni-based catalysts. Developing active Ni-based catalysts with enhanced resistance to coke formation for the TRM process is anticipated to pave the way for further commercialization ventures. Ni catalysts supported on a wide range of support materials such as Al2O3, CeO2, ZrO2, TiO2, MgO and their mixed oxides are the most widely used catalysts for TRM processes. This review provides a critical analysis of the different attempts made to tune the catalyst properties such as the use of different supports, promotors, and synthesis protocols. Catalyst properties such as Ni dispersion, basicity, Ni particle size, thermal stability is evaluated for various catalytic systems to develop structure-property relationship in TRM processes. Moreover, studies on TRM reaction kinetics, process modeling, and economics are also reviewed. Future outlook in catalysts and process development is also presented in this review to shed lights on the potential pathways to develop TRM processes in an environmentally friendly, and cost-effective manner.

Bifunctional metal-free KAUST Catalysis Center 1 (KCC-1) as highly active catalyst for syngas production via methane partial oxidation

The metal-free KAUST Catalysis Center 1 (KCC-1) was synthesized through microemulsion method with microwave assistance and was assessed for methane partial oxidation (MPO) under various operating conditions. The electronic spin resonance spectroscopy, pyridine-probed infrared spectroscopy, and temperature-programmed desorption of oxygen measurement indicated that the concentration of BrØnsted acid sites and oxygen vacancies in KCC-1 were at least 2-fold higher than its counterparts, which benefited MPO activity via the promotion of adsorption and dissociation of gaseous reactants. The principal species detected by post-reaction X-ray photoelectron spectroscopy (XPS) was surface-adsorbed oxygen species; its relative percentages among all oxygen species reduced in the order spent KCC-1 (77.1%) > spent MCM-41 (Mobil Composition of Matter number 41; 41.4%) > spent SiO2 (−). The catalytic performance followed the same trend, suggesting that the surface-adsorbed oxygen species was the key factor for MPO process. Additionally, the carbon deposition rate increased in the order SiO2 (16.8 mol/gcat/s) > MCM-41 (11.7 mol/gcat/s) > KCC-1 (7.7 mol/gcat/s), consistent with the results of post-reaction Raman measurements. By coupling the in situ Fourier-transform infrared and XPS results, it is suggested that the high concentration of oxygen vacancies in KCC-1 contributed to activate the CH4 molecules on acid sites via different O∗-assisted kinetically relevant C–H bond activation mechanism for combustion-reforming pathway; meanwhile it provided an excellent adsorption-desorption cycle of O2− species to inhibit the carbon deposition, thus creating a bifunctional reaction mechanism in MPO reaction.

Conversion of Methane with Oxygen to Produce Hydrogen Catalyzed by Triatomic Rh3 - Cluster Anion.

Metal catalysts, especially noble metals, have frequently been prepared upon downsizing from nanoparticles to subnanoclusters to catalyze the important reaction of partial oxidation of methane (POM) in order to optimize the catalytic performance and conserve metal resources. Here, benefiting from mass spectrometric experiments in conjunction with photoelectron spectroscopy and quantum chemical calculations, we successfully determine that metal cluster anions composed of only three Rh atoms (Rh3–) can catalyze the POM reaction with O2 to produce 2H2 + CO2 under thermal collision conditions (∼300 K). The interdependence between CH4 and O2 to protect Rh3– from collapse and to promote conversion of CH4 → 2H2 has been clarified. This study not only provides a promising metal cluster displaying good catalytic behavior in POM reaction under mild conditions but also reveals a strictly molecular-level mechanism of direct partial oxidation for the production of hydrogen, a promising renewable energy source in the 21st century.

Mini-Review: Syngas Production Via Partial Oxidation of Methane Reaction and Its Potential Catalyst

Methane as a light gas was generally found in natural gas which was burned freely to gain a high quality of petroleum. This action truly impacted a worst condition in nature, namely greenhouse effect. This brief review described fundamental theory of the important process in methane conversion from natural gas into value-added chemical such as syngas (CO+H 2 ). The methane conversion reaction was commonly divided into direct and indirect reaction. The indirect reaction such as partial oxidation of methane was mostly chosen due to the intermediate product (syngas) can easily generate many raw materials of petrochemicals. This paper also described a potential catalyst to be applied which in heterogeneous type such as perovskite oxide, metal oxide and zeolite.

Reaction analysis and global kinetics of partial oxidation of methane using Ni–hydroxyapatite composite catalysts

Reaction analysis and global kinetics of the partial oxidation of methane (POM) were investigated for Ni–hydroxyapatite composite catalysts (Ni–HAp) containing 5- and 20-wt% Ni. The composite particles were prepared using slurry precursor materials. The amount of each gas component at the exit of the reactor was determined on the basis of the change in the gas volume obtained from the total mass balance. As the Ni–HAp catalyst is believed to undergo a direct mechanism of the POM reaction, in the proposed multiple reaction analysis, we assumed the following three independent reactions; direct POM, complete combustion of methane, and a water–gas shift reaction. The extent of these reactions clearly revealed the dominating reaction profile at each temperature. The results indicate that both direct and indirect mechanisms of the POM reaction were followed in parallel even at high temperatures. The activation energy of POM using Ni–HAp catalyst containing 5-wt% Ni was found to be 71.3 kJ/mol. The catalyst were characterized using XRD, BET method, CO pulse method, and TGA. The results of these tests showed the positive effect of changing the Ni loading on the catalyst structure.