Utilization Of CH4 Research Articles

Activation and Catalysis of Methane over Metal-Organic Framework Materials.

Methane (CH4), which is the main component of natural gas, is an abundant and widely available carbon resource. However, CH4 has a low energy density of only 36 kJ L-1 under ambient conditions, which is significantly lower than that of gasoline (ca. 34 MJ L-1). The activation and catalytic conversion of CH4 into value-added chemicals [e.g., methanol (CH3OH), which has an energy density of ca. 17 MJ L-1], can effectively lift its energy density. However, this conversion is highly challenging due to the inert nature of CH4, characterized by its strong C-H bonds and high stability. Consequently, the development of efficient materials that can optimize the binding and activation pathway of CH4 with control of product selectivity has attracted considerable recent interest. Metal-organic framework (MOF) materials have emerged as particularly attractive candidates for the development of efficient sorbents and heterogeneous catalysts due to their high porosity, low density, high surface area and structural versatility. These properties enable MOFs to act as effective platforms for the adsorption, binding and catalytic conversion of CH4 into valuable chemicals. Recent reports have highlighted MOFs as promising materials for these applications, leading to new insights into the structure-activity relationships that govern their performance in various systems. In this Account, we present analysis of state-of-the-art MOF-based sorbents and catalysts, particularly focusing on materials that incorporate well-defined active sites within confined space. The precise control of these active sites and their surrounding microenvironment is crucial as it directly influences the efficiency of CH4 activation and the selectivity of the resulting chemical products. Our discussion covers key reactions involving CH4, including its activation, selective oxidation of CH4 to CH3OH, dry reforming of CH4, nonoxidative coupling of CH4, and borylation of CH4. We analyze the role of active sites and their microenvironment in the binding and activation of CH4 using a wide range of experimental and computational studies, including neutron diffraction, inelastic neutron scattering, and electron paramagnetic resonance, solid-state nuclear magnetic resonance, infrared and X-ray absorption spectroscopies coupled to density functional theory calculations. In particular, neutron scattering has notable advantages in elucidating host-guest interactions and the mechanisms of the conversion and catalysis of CH4 and CD4. In addition to exploring current advances, the limitations and future direction of research in this area are also discussed. Key challenges include improvements in the stability, scalability, and performance of MOFs under practical conditions, as well as achieving higher selectivity and yields of targeted products. The ongoing development of MOFs and related materials holds great promise for the efficient and sustainable utilization of CH4, transforming it from a low-density energy source into a versatile precursor for a wide range of value-added chemicals. This Account summarizes the design and development of functional MOF and related materials for the adsorption and conversion of CH4.

Methane capture, utilization, and sequestration technology based on biological ectoine production using Methylotuvimicrobium alcaliphilum 20Z

Methanotroph-based CH4 conversion technology is a promising alternative to conventional CH4 utilization methods that rely on energy-intensive CO2 capture processes. In this study, we introduce a novel CH4 capture, utilization, and sequestration (MCUS) technology as a proof-of-concept for eco-friendly CH4 conversion that is applicable to various methanotroph strains. We validated this hypothesis by evaluating ectoine production in Methylotuvimicrobium alcaliphilum 20Z. Cultivation experiments were conducted using pure O2 pulse injection to facilitate the separation of the CO2 generated during CH4 oxidation by concentrating it. To verify the MCUS concept systematically, we performed a model-based process analysis. The operational strategies for the reactors were developed using experiment-based kinetics and reactor models, followed by the design of a rigorous process flow diagram. Economic and environmental impact analyses were conducted to compare MCUS with air-based cultures and existing oxidative CH4 conversion technologies. The key advantage of MCUS is its significantly lower CO2 emissions (0.71 kg-CO2 eq/kg-CH4) than oxidative CH4 utilization (>2.75 kg-CO2 eq/kg-CH4). Moreover, the net present value per CH4 molecule was estimated at 0.7 $/kg-CH4, substantially higher than existing oxidative conversion methods (0.03 $/kg-CH4). Additionally, compared with air-based cultivation, the MCUS process exhibits superior economic and environmental performances. We used methanotrophs for CH4 “capture” and “utilization,” effectively leveraging “sequestration” to convert emissions into pure CO2. The proposed MCUS technology holds promise for practical applications of methanotrophs in producing various high-value-added products, emphasizing eco-friendly approaches.

Unraveling the catalytic performance of RuO2(1 1 0) for highly-selective ethylene production from methane at low temperature: Insights from first-principles and microkinetic simulations

Despite significant progress in low-temperature methane (CH4) activation, commercial viability, specifically obtaining high yields of C1/C2 products, remains a challenge. High desorption energy (>2 eV) and overoxidation of the target products are key limitations in CH4 utilization. Herein, we employ first-principles density functional theory (DFT) and microkinetics simulations to investigate the CH4 activation and the feasibility of its conversion to ethylene (C2H4) on the RuO2 (1 1 0) surface. The CH activation and CH4 dehydrogenation processes are thoroughly investigated, with a particular focus on the diffusion of surface intermediates. The results show that the RuO2 (1 1 0) surface exhibits high reactivity in CH4 activation (Ea = 0.60 eV), with CH3 and CH2 are the predominant species, and CH2 being the most mobile intermediate on the surface. Consequently, self-coupling of CH2* species via CC coupling occurs more readily, yielding C2H4, a potential raw material for the chemical industry. More importantly, we demonstrate that the produced C2H4 can easily desorb under mild conditions due to its low desorption energy of 0.97 eV. Microkinetic simulations based on the DFT energetics indicate that CH4 activation can occur at temperatures below 200 K, and C2H4 can be desorbed at room temperature. Further, the selectivity analysis predicts that C2H4 is the major product at low temperatures (300–450 K) with 100 % selectivity, then competes with formaldehyde at intermediate temperatures in the CH4 conversion over RuO2 (1 1 0) surface. The present findings suggest that the RuO2 (1 1 0) surface is a potential catalyst for facilitating ethylene production under mild conditions.

Methylosinus trichosporium OB3b drives composition-independent application of biogas in poly(3-hydroxybutyrate) synthesis

Biological conversion of biogas into poly(3-hydroxybutyrate) (PHB) via Type II methanotrophs holds great promise. However, a prerequisite for widespread biogas utilization is a comprehensive understanding of the effects of biogas composition on methanotrophic PHB synthesis. Herein, we explore the effects of biogas composition on the microbial growth and PHB accumulation of Methylosinus trichosporium OB3b under five different artificial biogas conditions with varying the ratio of methane (CH4) to carbon dioxide (CO2), the two main components of raw biogas. Stoichiometric and kinetic analyses revealed that increased CO2 concentrations correlated with higher maximum specific growth rates (0.021–0.029 h−1) and maximum CH4 utilization rates (0.029–0.042 mg CH4/mg TSS-h). Besides, no significant correlation was found between the CH4-to-CO2 ratio and other growth parameters. Consistent PHB contents (20.2–25.3 wt%) were achieved, irrespective of the CH4-to-CO2 ratio. Furthermore, the ability of M. trichosporium OB3b to grow and synthesize PHB (13.2 wt%) was confirmed using pilot-scale biogas. Our findings highlight the potential of biogas as a feedstock for producing valuable biodegradable polymers, thus contributing to waste-derived fuel (WDF) innovation and environmental sustainability.

Unveiling Direct Electrochemical Oxidation of Methane at the Ceria/Gas Interface.

Solid oxide fuel cells (SOFCs) stand out in sustainable energy systems for their unique ability to efficiently utilize hydrocarbon fuels, particularly those from carbon-neutral sources. CeO2-δ (ceria) based oxides embedded in SOFCs are recognized for their critical role in managing hydrocarbon activation and carbon coking. However, even for the simplest hydrocarbon molecule, CH4, the mechanism of electrochemical oxidation at the ceria/gas interface is not well understood and the capability of ceria to electrochemically oxidize methane remains a topic of debate. This lack of clarity stems from the intricate design of standard metal/oxide composite electrodes and the complex nature of electrode reactions involving multiple chemical and electrochemical steps. This study presents a Sm-doped ceria thin-film model cell that selectively monitors CH4 direct-electro-oxidation on the ceria surface. Using impedance spectroscopy, operando X-ray photoelectron spectroscopy, and density functional theory, it is unveiled that ceria surfaces facilitate C─H bond cleavage and that H2O formation is key in determining the overall reaction rate at the electrode. These insights effectively address the longstanding debate regarding the direct utilization of CH4 in SOFCs. Moreover, these findings pave the way for an optimized electrode design strategy, essential for developing high-performance, environmentally sustainable fuel cells.

Revisit the PAH and soot formation in high-temperature pyrolysis of methane

As the major component of natural gas, most basic and stable hydrocarbon molecule, methane (CH4) is an important source in industrial processing. The polycyclic aromatic hydrocarbons (PAHs) and the soot produced in the utilization of CH4 also attract particular attention. In this work, CH4 pyrolysis was studied with gas chromatographs (GCs) and a gas chromatography-mass (GC-MS) spectrometry within the temperature range of 1073–1623 K at atmospheric pressure. Mole fraction profiles of 11 species, including CH4, C2H2, C2H4, C2H6, aC3H4, pC3H4, C3H6, C4H6, C6H6, C10H8 (naphthalene) and C12H8 (acenaphthylene) were quantified. C10H8 and C12H8 were detected during the pyrolysis of CH4. A detailed kinetic model involving 300 species and 1840 reactions was proposed with reasonable prediction against the measured data. During pyrolysis, CH4 is mainly consumed by the H-abstraction reactions. 2CH3=C2H5+H and C9H7+C3H3=A2R5+H2 are the two major reactions controlling CH4 consumption according to sensitivity analysis. In addition, the soot generated in the reactor was analyzed by Raman spectroscopy and Scanning Electron Microscope (SEM), showing the morphology and structural characteristics of the soot. The detailed formation and consumption pathways of PAHs such as naphthalene and acenaphthylene were analyzed. This work will enrich the understanding of CH4 pyrolysis and promote experimental and theoretical studies on the formation of PAHs and soot.

Low Content Ga2O3 Enables the Direct Methane Conversion.

The direct conversion of methane (CH4), a main greenhouse gas, to value-added chemicals has attracted increasing attention in order to alleviate the current energy crisis and environmental concern. Nevertheless, the oriented conversion of CH4 to target product is formidably challenging due to the inertness of CH4. In this work, we demonstrate that zeolite modified by a low amount of Ga2O3 (GS-1) can serve as a highly active and stable catalyst for direct conversion to hydrogen (H2) and solid carbon. The optimal GS-1 with 0.62 wt % of Ga displays a CH4 conversion rate of 70.6 mol/gGa/h with a H2 productivity of 134 mol/gGa/h at 800 °C. Analysis on NH3 temperature-programmed desorption (TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) suggests that the introduction of Ga2O3 can poison the acidic site of zeolite and promote the dehydrogenation of CH4. This work reports a highly active and stable catalyst for direct methane conversion, which may provide a feasible strategy for the sustainable utilization of CH4.

Synergistic effect of Ni and CeOx in NiCeOx/SSZ-13 catalyst for boosting activity and stability during dry reforming of methane

The stability of industrial catalysts for dry reforming of methane (DRM) reaction is still an urgent challenge. The multifunctional nanocatalyst of SSZ-13 supported Ni/CeOx bimetallic catalysts was successfully fabricated by the impregnation method. The Ni/CeOx species was dispersed highly in the microporous structure of SSZ-13, and the Ni active sites can activate the C-H bond dissociation of CH4, while the oxygen vacancy could promote the adsorption and activation of CO2. The NiCeOx/SSZ-13 catalyst showed excellent catalytic performance for dry reforming of methane, i.e., its conversion of CH4 and CO2 were 91 and 94%, and the ratio of H2/CO was about 0.88 at 750 °C after 50 h. Based on the results of CH4&CO2-TPSR and NH3-TPD, the synergy effect of NiCeOx species can promote the adsorption and activation of CH4 and CO2, and the coke on the surface during DRM is readily converted to CO by reacting with the surface oxygen from CeOx species, which effectively boost the elimination of carbon deposits. It highlights a new strategy for the fabrication of high-efficient zeolite catalysts for DRM to enhance the utilization of CH4 and CO2.

High-Pressure Electro-Fenton Driving CH4 Conversion by O2 at Room Temperature.

Electrochemical conversion of CH4 to easily transportable and value-added liquid fuels is highly attractive for energy-efficient CH4 utilization, but it is challenging due to the low reactivity and solubility of CH4 in the electrolyte. Herein, we report a high-pressure electro-Fenton (HPEF) strategy to establish a hetero-homogeneous process for the electrocatalytic conversion of CH4 by O2 at room temperature. In combination with elevation of reactant pressure to accelerate reaction kinetics, it delivers an unprecedented HCOOH productivity of 11.5 mmol h-1 gFe-1 with 220 times enhancement compared to that under ambient pressure. Remarkably, an HCOOH Faradic efficiency of 81.4% can be achieved with an ultralow cathodic overpotential of 0.38 V. The elevated pressure not only promotes the electrocatalytic reduction of O2 to H2O2 but also increases the reaction collision probability between CH4 and •OH, which is in situ generated from the Fe2+-facilitated decomposition of H2O2.

Metagenomics coupled with thermodynamic analysis revealed a potential way to improve the nitrogen removal efficiency of the aerobic methane oxidation coupled to denitrification process under the hypoxic condition

Aerobic methane (CH4) oxidation coupled to denitrification (AME-D) is a promising wastewater treatment process for CH4 utilization and nitrogen removal. However, it is unclear which CH4-derived carbons are suitable for the AME-D process and how these organics are metabolized. In this study, metagenomics coupled with a thermodynamic model were used to explore the microorganisms and their metabolic mechanisms in an AME-D membrane biofilm reactor (MBfR) with high nitrogen removal efficiency. Results revealed that the aerobic methanotrophs of Methylomonas with the CH4-based fermentation potential were highly enriched and played an important role in CH4 conversion in the MBfR. Bacteria of Xanthomonadaceae, Methylophilaceae, Bacteroidetes, Rhodocyclaceae, Hyphomicrobium were the main denitrifiers. C1 compounds (methanol, formaldehyde and formate) and CH4-based fermentation products are promising cross-feeding intermediates of the AME-D. Specially, by means of integrating the CH4-based fermentation with denitrification, the minimum amount of CH4 required to remove per mole of nitrate can be further reduced to 1.25 mol-CH4 mol−1-NO3−, even lower than that of methanol. Compared to the choice to secrete methanol, type I aerobic methanotrophs require a 15 % reduction in the amount of oxygen required to secrete fermentation metabolites, but a 72 % increase in the amount of CH4-C released. Based on this trade-off, optimizing oxygen supply strategies will help to construct engineered microbiomes focused on aerobic methanotrophs with CH4-based fermentation potential. This study gives an insight into C and N conversions in the AME-D process and highlights the role of CH4-based fermentation in improving the nitrogen removal efficiency of the AME-D process.

Methane dehydroaromatization process in a carbon-neutral strategy

Methane dehydroaromatization (MDA) process is a “non-oxidative” technology for CH4 utilization, esteemed as a propitious substitution for fossil fuel-based counterparts in the synthesis of benzene, toluene, and xylene (BTX). However, the MDA process is less cost-effective than both commercial BTX production and “oxidative” CH4 conversion technologies, primarily due to its inherently low BTX yield and CH4 conversion rate. As the focus on attaining net-zero emissions escalates and concerns regarding the usage of abundant CH4 arise, the MDA process has emerged as an environmentally efficient alternative that can generate high-value products while decreasing direct CO2 emissions. In this study, we evaluate various MDA reaction systems, including MDA utilizing only pure CH4, additive co-feeding MDA, and hydrocarbons co-feeding MDA, employing a Mo/HZSM-5 catalyst. The proposed process design comprehensively analyzes the impact of MDA reaction systems on product distribution and energy consumption. Furthermore, we confirm the feasibility of the proposed MDA processes through an exhaustive environmental and economic assessment of “oxidative” CH4 conversion methods and commercial BTX production processes. By decentralizing some of the immense direct CO2 emissions from existing CH4 utilization to controllable indirect CO2 emissions, the MDA processes prove to be more advantageous under the net-zero strategy. The results of this analysis reinforce the potential of MDA reaction processes as a carbon-neutral technology that can effectively replace oxidative CH4 conversion while producing high-value products.

Impacts of granular sludge properties on the bioreactor performing nitrate/nitrite-dependent anaerobic methane oxidation/anammox processes

In this work, a bioprocess model was applied to first determine the impacts of influent substrates conditions on the granular bioreactor performing nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) and anammox integrated processes and then investigate the roles of granular sludge properties in regulating the bioreactor performance and start-up process. The ideal influent substrates conditions were identified at NO2−-N/NH4+-N of 1:1 and dissolved CH4 concentration of 85 g COD m−3, which achieved 98.6% total nitrogen removal and 87.7% dissolved CH4 utilization. Under such ideal influent conditions, the initial properties of granular sludge didn’t significantly affect the granular bioreactor performance. However, inoculation of granular sludge with a relatively small granular sludge size and a high abundance of n-DAMO archaea or/and anammox bacteria could effectively shorten the bioreactor start-up. Meanwhile, reducing the diffusivity of solutes within granular sludge was also beneficial for expediting the start-up process and promoting dissolved CH4 utilization.

Oxygen vacancies enriched Ni-Co/SiO2@CeO2 redox catalyst for cycling methane partial oxidation and CO2 splitting

Redox catalysts play a vital role in the interconversion of two significant greenhouse gases, CO2 and CH4, via chemical looping methane dry reforming technology. Herein, a series of transition metals-alloyed and core–shell structured Ni-M/SiO2@CeO2 (M = Fe, Co, Cu, Mn, Zr) redox catalyst were fabricated and evaluated in a gas–solid fixed-bed reactor for cycling CH4 partial oxidation (POx) and CO2 splitting. The catalysts are composed of spherical SiO2 core and CeO2 shell, and the highly dispersed Ni alloy nanoparticles are the interlayer between core and shell. The oxygen vacancy concentration of Ni-M/SiO2@CeO2 followed the order of Co > Cu > Fe > Mn > Zr, and Ni alloying with transition metals significantly enhanced oxygen storage capacity (OSC). Ni-Co/SiO2@CeO2 catalyst with abundant oxygen vacancies and a high OSC showed the lowest temperatures of CH4 activation (610 °C) and CO2 decomposition (590 °C), thus demonstrating excellent redox reactivity. The catalyst exhibited superior activity and structural stability in the continuous CH4/CO2 redox cycles at 615 °C, achieving 87% CH4 conversion and 83% CO selectivity. The proposed catalyst shows great potential for the utilization of CH4 and CO2 in a redox mode, providing a new sight for design redox catalyst in chemical looping or related fields.

A finger-like anode with infiltrated Ni0.1Ce0.9O2-δ catalyst using new phase inversion combined tape-casting technology for optimized dry reforming of methane

The direct use of synthesis gas produced by the dry reforming of methane is strongly limited by the catalyst deactivation and performance degradation owing to the carbon deposition in solid oxide fuel cells (SOFCs). In this work, we fabricated a finger-like porous NiO-8%mol doped ZrO2 (YSZ) by a new phase-inversion combined tape casting technique as anode substrate, impregnated with Ni0.1Ce0.9O2-δ as catalyst. After the anode infiltrated Ni0.1Ce0.9O2-δ catalyst for the dry reforming of methane under the open circuit voltage, the conversion rates of CH4 and CO2 are increased from 49.65% and 55.2% to 69.3% and 67.2% at 750 °C, respectively. Strikingly, the button cells by the direct utilization of CH4–CO2 (1:1) fuels deliver high electrochemical performance as well as high stability of fuel conversion rates, where the peak power density is increased from 457 mW/cm2 to 850 mW/cm2 at 800 °C and the corresponding polarization resistance is reduced from 0.436 Ωcm2 to 0.286 Ωcm2, respectively. The great improvement of electrochemical performance is due to the dissolved nanoparticles and reactive oxygen species of the anode infiltrated Ni0.1Ce0.9O2-δ catalyst. And the open finger-like pore microstructure of the anode accelerates the methane transport. This strategy provides a promising solution for direct utilization of dry reforming of methane.

Experimental study on enhanced coal seam gas extraction by uniform pressure/pulse pressure N2 injection

Gas extraction is the fundamental way to prevent and control gas as well as to obtain clean energy. Based on the analysis of the mechanism of conventional negative-pressure gas extraction technology and N2 injection enhanced gas extraction technology, the technology of pulse pressure N2 injection enhanced gas extraction is proposed. The experiments of CH4 displacement by uniform pressure/pulse pressure N2 injection are carried out. The migration pattern of gas components during the whole process of CH4 displacement by N2 injection is quantitatively characterized. The influence pattern and sensitivity of N2 injection pressure on the effect of CH4 displacement are analyzed. The economic benefits of N2 injection by uniform pressure/pulse pressure to displace CH4 are investigated. The results indicate that conventional negative-pressure gas extraction technology has disadvantages such as insufficient seepage power and gas extraction will soon enter the exhaustion stage. While N2 injection enhanced gas extraction technology not only has the flow increasing effect of gas itself factors but also has the flow increasing effect of injected energy for changing coal properties. During the process of displacing CH4 by uniform pressure/pulse pressure N2 injection, the CH4 volume fraction decreases and the N2 volume fraction increases as the N2 injection pressure increases. Increasing the injection pressure of two N2 injection methods can effectively shorten the T50% (the time when the CH4 volume fraction is equal to the N2 volume fraction is equal to 50%), but with a reduced degree of impact. Increasing injection pressure not only increases the amount of CH4 precipitation but also increases the amount of N2 precipitation, which is not conducive to the later utilization of the precipitated CH4. With the increase of N2 injection pressure, the sensitivity of CH4 displacement efficiency by uniform pressure N2 injection decreases, the sensitivity of CH4 displacement efficiency by pulse pressure N2 injection remains the same, and the sensitivity of CH4 displacement ratio by uniform pressure/pulse pressure N2 injection decreases. The CH4 prevent and control effect, N2 injection cost, and CH4 resource utilization of pulse pressure N2 injection are better than that of uniform pressure N2 injection. The technology of enhanced gas extraction by pulse pressure N2 injection not only improves the CH4 prevent and control effect but also reduces N2 injection cost. At the same time, it promotes the efficient utilization of CH4 resources. The research results have great significance and value for improving the level of gas disaster prevention and resource development.

Research Progress of Carbon Deposition on Ni-Based Catalyst for CO2-CH4 Reforming

As we all know, the massive emission of carbon dioxide has become a huge ecological and environmental problem. The extensive exploration, exploitation, transportation, storage, and use of natural gas resources will result in the emittance of a large amount of the greenhouse gas CH4. Therefore, the treatment and utilization of the main greenhouse gases, CO2 and CH4, are extremely urgent. The CH4 + CO2 reaction is usually called the dry methane reforming reaction (CRM/DRM), which can realize the direct conversion and utilization of CH4 and CO2, and it is of great significance for carbon emission reduction and the resource utilization of CO2-rich natural gas. In order to improve the activity, selectivity, and stability of the CO2-CH4 reforming catalyst, the highly active and relatively cheap metal Ni is usually used as the active component of the catalyst. In the CO2-CH4 reforming process, the widely studied Ni-based catalysts are prone to inactivation due to carbon deposition, which limits their large-scale industrial application. Due to the limitation of thermodynamic equilibrium, the CRM reaction needs to obtain high conversion and selectivity at a high temperature. Therefore, how to improve the anti-carbon deposition ability of the Ni-based catalyst, how to improve its stability, and how to eliminate carbon deposition are the main difficulties faced at present.

Biological conversion of methane to methanol at high H2S concentrations with an H2S-tolerant methanotrophic consortium

To develop biological biogas to methanol conversion technology without costly hydrogen sulfide (H2S) removal, a high H2S tolerant methanotrophic consortium (HTMC), was enriched from an anaerobic digester effluent in presence of 5.64 g/m3 H2S in the gas phase. The HTMC can grow stably and produce methanol under conditions with CH4/air mixtures containing 5.64 g/m3 of H2S. There is no significant (p > 0.05) difference in cell yield or CH4 to methanol conversion efficiency between trials with different H2S concentrations from 0 g/m3 to 5.64 g/m3. Under optimal conditions, a cell yield of 0.333 g cells/g CH4, a methanol concentration of 0.28 mg/mL, and a CH4 to methanol conversion efficiency of 0.22 mol/mol were obtained, respectively. Besides methanotrophs (14.85%) and other bacteria, Cyanobacteria were also identified in the HTMC with a high abundancy (32.16%), which could broaden the application of HTMC for simultaneous utilization of CH4 and CO2 from raw biogas.

Lanthanum-Promoted Nickel-Based Catalysts for the Dry Reforming of Methane at Low Temperatures

In recent decades, considerable attention has been paid to the catalytic dry reforming of methane to obtain syngas. This reaction has very important environmental implications due to the utilization of CH4 and CO2, gases that contribute to the greenhouse effect. The dry reforming of methane is normally carried out over strong basic catalysts with noble metals. Nickel has emerged as an interesting alternative, although it tends to deactivate and form carbon whiskers, which could block the reactor. It is therefore necessary to improve their catalytic performance (conversion, selectivity and stability). In this work, Ni0.69La0.31 and Ni0.14Mg0.55La0.31 were studied in the dry methane reforming reaction. The precursors were prepared by co-precipitation and the oxide phases were obtained by calcining these precursors at 450°C/6 h. The XRD diagrams of the calcined samples show the formation of mixed oxide phases with a periclase-like structure. Analysis of the temperature-programmed reduction shows that the presence of Mg shifts the reduction to higher temperatures. The catalysts, reduced at 650°C, were tested in this reaction as a function of operating time at 650°C. No deactivation occurred after 20 h of operation. Furthermore, the combination of Mg and La drastically improves the conversion and selectivity of the catalyst (> 95%).

Dry reforming of methane over silica zeolite-encapsulated Ni-based catalysts: Effect of preparation method, support structure and Ni content on catalytic performance

Dry reforming of methane (DRM) is a prospective technology for efficient utilization of CH4 and CO2, with the essential challenge being the design and synthesis of efficient catalysts. In this research, serial encapsulated Ni-based catalysts (xNi@S-1, x = 5, 7, 10) by silica zeolite (S-1) were prepared successfully. The effects of support structure, preparation method and Ni content upon the catalytic performance for DRM were investigated and diverse characterizations were utilized for revealing structural features of as-prepared catalysts. Encapsulated 7Ni@S-1 catalyst prepared using the one-pot hydrothermal method could acquire more homogeneously dispersed metallic Ni particles and more Ni species including Ni0, NiO, 1:1/2:1 Ni phyllosilicates that could facilitate forming stable Ni0 sites and Ni2+-O2- ion pairs for adsorption and activation of CH4 and CO2, respectively. Hence, 7Ni@S-1 still maintained the highest CH4 and CO2 conversions of 57.9% and 88.6% and H2/CO molar ratio of 0.90 after 52 h stability tests.

Boron-promoted Ni/MgO catalysts for enhanced activity and coke suppression during dry reforming of methane

The dry reforming of methane (DRM) provides an attractive solution for the utilization of CH4 and CO2 and its performance highly depends on the catalyst. In this study, DRM to syngas was studied using a series of Ni/MgO catalysts modified by B2O3 (0.1–2.0 wt%). The results demonstrated that introducing only 0.25 wt% B2O3 to 4Ni/MgO catalyst significantly improved its activity, stability, and carbon resistance. After 40 h time on stream (TOS), the activity of 4Ni0.25B/MgO catalyst almost unchanged and was approximately 20% higher than that of the unmodified 4Ni/MgO catalyst. The 4Ni0.25B/MgO catalyst also showed the least carbon deposits (0.3 wt%) among all samples. The characterization tests suggest that B2O3 substantially enhanced the Ni reducibility during DRM without weakening the Ni–MgO interaction, thereby improving the activity without sacrificing the dispersion and stability of the Ni nanoparticles (NPs). Intermetallic nickel boride was formed when B2O3 interacted with metallic Ni, which suppressed the formation of filamentous and graphitic carbon. In addition, excess B2O3 has a slight influence on the formation of amorphous carbon.