Reforming Of CH4 Research Articles

Enhancing coke resistance of Ni-based spinel-type oxides by tuning the configurational entropy

The reforming of CH4 and CO2 into syngas is a highly relevant technology for energy conservation and reducing greenhouse gas emissions, attracting widespread attention in the industry. Inspired by this, this work proposes a general criterion for coke-resistant nickel-based catalysts. By leveraging the high-entropy effect and the lattice distortion of the structure, a high-entropy (NiCaMgZnCo)Al10Ox catalyst was synthesized. The high-entropy oxide exhibited good activity and stability during the DRM reaction over 100 h at 800°C and 650°C, producing only a minimal amount of easily removable carbon deposition. O2-TPO, CO2-TPD, CH4-TPSR, CO2-TPSR, DFT and in situ DRIFT were employed to investigate the mechanism of carbon deposition elimination on the surface of the high-entropy catalyst. Then, a high-entropy strategy for designing coke-resistant catalysts was proposed. This strategy may soon inspire the development of catalysts with enhanced stability and anti-coke deposition properties for various catalytic applications.

Exploring Dry Reforming of CH4 to Syngas Using High Entropy Materials: A Novel Emerging Approach

The high global warming potential of natural gas methane necessitates its conversion to valuable products, typically achieved through syngas production, with dry reforming of methane and integrating carbon capture followed by dry reforming of methane standing out among different technologies for methane valorization. However, persistent challenges such as the reverse water gas shift reaction, coke formation, and sintering associated with methane dry reforming have redirected scientific focus toward multi‐metallic catalysts with supports or promoters. High entropy materials have gained attention as promising catalysts because their flexible composition allows fine‐tuning of lattice oxygen reactivity and catalytic activity. Entropy plays a key role in catalysis, and recent research focuses on the enthalpy‐entropy relationship that influences reaction pathways. Alongside entropy, core effects like lattice distortion, sluggish diffusion, and cocktail effects improve catalytic performance by synergistic effects, prevent carbon buildup, and maintain stability at high temperatures, enabling efficient methane conversion. These advancements in high entropy materials drive interest in using entropy‐stabilized systems to address the challenges of methane dry reforming. This review summarizes the recent progress in dry reforming of methane and integrating carbon capture followed by dry reforming of methane using high entropy materials.

Plasma-catalytic dry reforming of CH4: Effects of plasma-generated species on the surface chemistry

By means of steady-state experiments and a global model, we studied the effects of plasma-generated reactive species on the surface chemistry and coking in plasma-catalytic CH4/CO2 reforming at reduced pressure (8–40 kPa). We used a hybrid ZDPlasKin-CHEMKIN model to predict the species densities over time. The detailed plasma-catalytic mechanism consists of the plasma discharge scheme, a gas-phase chemistry set and a surface mechanism. Our experimental results show that the coupling of Ni/SiO2 catalyst with plasma is more effective in CH4/CO2 activation and conversion than unpacked DBD plasma, with syngas being the main products. The highest total conversion of 16 % was achieved at 8000 V and 473 K, with corresponding CO and H2 yields of 15 % and 12 %, respectively. The reactants conversion and product selectivity are well captured by the kinetic model. Our simulation results suggest that vibrational species and radicals can accelerate the dissociative adsorption and Eley-Rideal (E-R) reactions. Path flux analysis shows that E-R reactions dominate the surface reaction pathways, which differs from thermal catalysis, indicating that the coupling of non-equilibrium plasma and catalysis can effectively shift the formation and consumption pathways of important adsorbates. For instance, our model suggests that HCOO(s) is primarily generated through the E-R reaction CO2(v) + H(s) → HCOO(s), while the hydrogenation reaction HCOO(s) + H → HCOOH(s) is the main source of HCOOH(s). Carbon deposition on the catalyst surface is primarily formed through the stepwise dehydrogenation of CH4, while the E-R reactions enhanced by plasma-generated H and O atoms dominate the consumption of carbon deposition. This work provides new insights into the effects of reactive species on the surface chemistry in plasma-catalytic CH4/CO2 reforming.

Optimization of greenhouse gas valorization over ceria‐promoted Co–Ni/graphene oxide catalytic materials using response surface methodology

AbstractBackgroundThe mitigation of global warming effect requires intensified research efforts to reduce greenhouse gas emissions. This study was aimed at investigating the valorization of two principal greenhouse gases, namely carbon dioxide (CO2) and methane (CH4), over CeO2‐doped Co–Ni/GO catalytic materials. The CeO2‐doped Co–Ni/GO catalysts were synthesized using a sequential wet impregnation method and employed for CO2 reforming of CH4. The catalytic materials were characterized using various instrumental techniques. Response surface methodology (RSM) was employed to investigate the impact of process factors, namely reaction temperature (ranging from 700 to 800 °C), CeO2 loading (ranging from 5% to 15%) and feed flowrate (ranging from 10n to 50 mL min−1), on the CH4 conversions.ResultsThe three factors were observed to have significant influence on the CH4 conversion based on analysis of variance. The analysis of the RSM quadratic model revealed that the optimum conditions of 800 °C, 14.22% and 10.00 mL min−1 were obtained for the reaction temperature, CeO2 loading and feed flowrate resulting in maximum CH4 conversion of 98.24%. The desirability function for these results was calculated to be 0.934. The predicted process parameters aligned with the results of the actual experimental analysis.ConclusionThis study has demonstrated that the conversion of CH4 to value‐added products such as syngas can be optimized using RSM. The optimum conditions obtained could be used to improve the process performance. © 2024 Society of Chemical Industry (SCI).

Ni modified ZSM-5 promoted syngas production in chemical looping via the structural regulation of Ni particles under redox conditions

Chemical looping reforming of CH4 coupled with CO2 reduction stands out as a promising method for the syngas production. In this process, it is significant to design the oxygen carrier with high reactivity and stability. In this work, a highly efficient oxygen carrier is obtained by physically mixing Metal-modified ZSM-5 with LaFe0.85Ni0.15O3 (LFN). The physical and chemical properties of the oxygen carriers are characterized by XRD, Raman, XPS, BET, TEM, NH3-TPD, CO2-TPD and CH4-TPD techniques. It is noted that mesoporous structures are formed over the Ni modified ZSM-5, due to that part of Ni elements replace Al in the silicaluminate framework. The structure change of the ZSM-5 promotes the gas adsorption capacity. CH4 and CO2 cannot be adsorbed on the surface of ZSM-5, while Ni-modified ZSM-5 enhances the adsorption capacity for CO2 to a large degree. Moreover, Ni species are acted as active sites to facilitate the activation of CH4 and CO2 during the redox process. The aggregation-redispersion of Ni particles during the reduction-oxidation process inhibits the deactivation of Ni particles, which improves the stability of the oxygen carrier. Among all the obtained samples, LFN/10 wt% Ni-ZSM-5 exhibits the highest yields of syngas (8.38 mmol g−1) and CO (2.42 mmol g−1).

Enhancement of non-thermal plasma-catalytic CO2 reforming of CH4 using Ni/Mg–Al2O3 catalysts in a parallel plate dielectric barrier discharge reactor

CO2 and CH4 are converted to syngas by dry reforming of methane (DRM) reaction. This research investigated the effects of the Mg promoter on Al2O3-supported Ni catalysts and Mg calcination temperature on the DRM performance in a parallel plate dielectric barrier discharge reactor. The Mg promoter played a crucial role in the DRM performance, as increasing the Mg calcination temperature from 700 °C to 800 °C significantly improved the DRM performance and catalyst properties, including increased specific surface area, decreased total acidity, reduced crystallite and particle sizes, and more uniform dispersion of the Ni nanoparticles. Under these conditions, the H2 and CO selectivity were 77.0 % and 70.7 %, the CH4 and CO2 conversion were 25.1 % and 20.6 %, and the energy efficiency was 8.4 %. In addition, the catalyst was associated with a lower coking rate (0.5 mg C/gcat h), a relatively low carbon deposit of 1.5 %, and a carbon loss of 2.8 %, possibly because the weak acidity hindered the Boudouard reaction and CH4 decomposition. However, increasing the Mg calcination temperature to 900 °C increased the total acidity and Ni particle size, decreasing H2 and CO selectivities and increasing carbon deposits on the catalyst surface.

Pressure-Induced Enhancement in Chemical Looping Reforming of CH4: A Thermodynamic Analysis with Fe-Based Oxygen Carriers.

Chemical looping reforming of methane (CLRM) with Fe-based oxygen carriers is widely acknowledged as an environmentally friendly and cost-effective approach for syngas production, however, sintering-caused deactivate of oxygen carriers at elevated temperatures of above 900 °C is a longstanding issue restricting the development of CLRM. Here, in order to reduce the reaction temperature without compromising the chemical-looping CH4 conversion efficiency, we proposed a novel operation scheme of CLRM by manipulating the reaction pressure to shift the equilibrium of CH4 partial oxidation towards the forward direction based on the Le Chatelier's principle. The results from thermodynamic simulations showed that, at a fixed reaction temperature, the reduction in pressure led to the increase in CH4 conversion, H2 and CO selectivity, as well as carbon deposition rate of all investigated oxygen carriers. The pressure-negative CLRM with Fe3O4, Fe2O3 and MgFe2O4 could reduce the reaction temperature to below 700 °C on the premise of a satisfactory CLRM performance. In a comprehensive consideration of the CLRM performance, energy consumption, and CH4 requirement, NiFe2O4 was the Fe-based OCs best available for pressure-negative CLRM, especially for an excellent syngas yield of 23.08 mmol/gOC. This study offered a new strategy to address sintering-caused deactivation of materials in chemical looping from the reaction thermodynamics point of view.

LaMnO3-Type Perovskite Nanofibers as Effective Catalysts for On-Cell CH4 Reforming via Solid Oxide Fuel Cells.

CH4 has become the most attractive fuel for solid oxide fuel cells due to its wide availability, narrow explosion limit range, low price, and easy storage. Thus, we present the concept of on-cell reforming via SOFC power generation, in which CH4 and CO2 can be converted into H2 and the formed H2 is electrochemically oxidized on a Ni-BZCYYb anode. We modified the porosity and specific surface area of a perovskite reforming catalyst via an optimized electrostatic spinning method, and the prepared LCMN nanofibers, which displayed an ideal LaMnO3-type perovskite structure with a high specific surface area, were imposed on a conventional Ni-BZCYYb anode for on-cell CH4 reforming. Compared to LCMN nanoparticles used as on-cell reforming catalysts, the NF-SOFC showed lower ohmic and polarization resistances, indicating that the porous nanofibers could reduce the resistances of fuel gas transport and charge transport in the anode. Accordingly, the NF-SOFC displayed a maximum power density (MPD) of 781 mW cm-2 and a stable discharge voltage of around 0.62 V for 72 h without coking in the Ni-BZCYYb anode. The present LCMN NF materials and on-cell reforming system demonstrated stability and potential for highly efficient power generation with hydrocarbon fuels.

Encapsulated Pd clusters in S-1 promote the reactivity of chemical looping via synergistic effect of catalysis and oxygen storage

Chemical looping reforming of CH4 coupled with CO2 reduction technology offers a compelling way for effective CO2 emission with the production of syngas and CO. However, the reaction temperature in chemical looping is relatively higher (>800 °C). To solve this problem, it is critical to explore efficient oxygen carriers. In this work, 3DOM LF0.85N0.15/Pd@S-1 oxygen carrier with hierarchical pore structure obtained high reactivity. 3DOM LF0.85N0.15/Pd@S-1 contained three major components, playing different roles. The 3DOM LF0.85N0.15 with ordered macroporous structure possessed excellent oxygen storage capacity and diffusion property. Pd clusters as active sites promoted CH4 activation and strengthen Lewis acid sites. Silicalite-1 zeolite, with larger surface area and well-defined microporous structure, exhibited superior adsorption properties and used as an ideal support to encapsulate Pd clusters. The well-dispersed Pd clusters further strengthened the reducibility at low temperature. Among all samples, 3DOM LF0.85N0.15/Pd@S-1 exhibited highest reactivity and stability during the successive chemical looping.

Integrated CO2 Capture and Dry Reforming of CH4 to Syngas: A Review.

Integrating carbon capture with dry reforming of methane offers a promising approach to addressing greenhouse gas emissions while producing valuable syngas. This review examines the complexities and progress made in this integrated process, wherein catalysts play a critical role in adsorbing carbon dioxide and facilitating the conversion of methane to syngas. The chemical process entails the concurrent capture of CO2 emissions and their usage in dry reforming, a reaction in which CH4 interacts with CO2 to generate syngas, an essential precursor for various industrial applications. The dual-functional materials can adsorb carbon dioxide and actively reform to an end-use application. The much-studied Ca-based sorbents exhibit a theoretical carbon capture capacity of 17.8 mmol g-1. However, during practical exploration of these materials as a dual-functional catalyst for integrated carbon capture and the dry reforming of methane, the uptake reduces to ∼13 mmol g-1 carbon capacity with 96.5 and 96% conversions of CO2 and CH4, respectively. Therefore, a thorough analysis of the complex relationship between CO2 capture and CH4 reforming catalysis is attempted herein based on various reported materials. Design concepts, structural optimization, and performance evaluation analysis of the dual-functional materials reveal their importance in carbon capture and reformation technology. Additionally, this review covers the field difficulties, future perspectives, and attractive commercial implementation predictions. This scrutiny illustrates the significance of dual-functional materials for sustainable energy production and environmental protection.

Applying high efficiency internal reforming catalyst for direct low concentration coal mine methane solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are green and efficient power generation devices, which can efficiently utilize the abundant low concentration coal mine methane (LC-CMM), and play an important role in energy saving and emission reduction. However, there are still challenges need to be addressed, such as low conversion efficiency and deposit carbon. In this work, a Sr2Fe1.4Ni0.1Mo0.5O6-δ-Gd0.1Ce0.9O2-δ (SFNM-GDC) internal reforming catalyst is prepared, generating abundant oxygen vacancies with in situ precipitates Fe–Ni alloys in the reducing atmosphere, leading to improved methane reforming efficiency and carbon deposition resistance. The results show that the cell exhibits excellent electrochemical performance with the internal reforming catalyst, with the maximum power density (Pmax) of 1212 mW cm−2 and 980 mW cm−2 at 800 °C with H2 and LC-CMM, respectively, corresponding to polarization impedances of 0.16 Ω cm2 and 0.47 Ω cm2. More importantly, the single cell combining SFNM-GDC reformed layer can maintain stable performance for 100 h at 700 °C under the atmosphere of LC-CMM. These results highlight that the reformed layer enhances CH4 reforming, optimizes electrochemistry and increases resistance to carbon deposition.

Dry Reforming of CH4 Using a Microreactor

In the present study, a comparison of the dry reforming of a gas mixture containing methane, carbon dioxide and nitrogen without contaminants to a ruthenium-based Ru/Al2O3 catalyst was carried out in a microreactor for the first time. The influence of the contact time, temperature and composition of the feed on the conversion was exhaustively investigated. The optimal operating conditions were found to be a contact time of 80 milliseconds, a temperature of 700 °C and a CH4:CO2 ratio of 1. The assessment of diffusional limitations reveals that there is no resistance to mass transfer, which reveals the potential benefit of the determination of intrinsic reaction kinetics within a microreactor.

Enhanced CO2 conversion with CH4 for greenfuel generation using coke-neutral nickel-loaded fibrous silica titania catalysts

This study reveals a groundbreaking advancement in utilizing carbon dioxide (CO2) for syngas production through methane (CH4) dry reforming using Fibrous Silica Titania (FST) as a support, loaded with different (1%, 3%, and 5%) nickel dosages. FST is distinguished by its fibrous structure, maintains a stable temperature, facilitates the confinement and dispersion of active metal, and is exceptionally effective at preventing carbon deposition. For a thorough examination of the new catalysts, characterization methods including XRD, FESEM, EDX mapping, N2 physisorption, FTIR-KBr, H2-TPR, and CO2-TPD were employed. Importantly, TEM lattice fringes verified the existence of XRD peaks and planes of Ni (111), Ni (200), and TiO2 (101). Aspects such as O-H stretching, Si-O-Si asymmetry, vibrations caused by external Si-OH groups, and Si-O-Si bending were identified using FTIR-KBr analysis. The study ingeniously identified the superior (3Ni/FST) catalyst, which exhibited moderate basicity sites on the CO2-TPD at approximately 350 °C. The catalyst converted nearly 100% CH4 at 750 °C with minimal coke production and 80% CO2 at 850 °C. Surprisingly, the 3Ni/FST catalyst demonstrated remarkable stability during a 72 h TOS stability test at 650 °C, effectively preventing coke-forming side reactions such as CO disproportionation, CO hydrogenation, CO2 and CH4 cracking with syngas ratio around unity and little coke production. The FST support exhibited exceptional attributes for low temperature carbon neutral CH4 reforming.

Solar driven integrated CO2 capture and CH4 dry reforming via FexMny/Ni/CaAl multi-function materials

Integrated CO2 capture and dry reforming of CH4 (ICCU-DRM) holds great promise in mitigating greenhouse gas emissions and producing value-added syngas simultaneously. However, the in-situ conversion is a highly endothermic process, which requires a large amount of energy to drive, making it very difficult for large-scale applications. The combination of solar energy in ICCU-DRM provide a potential solution to tackle the problem, but it needs to construct and evaluate multi-function materials (MFMs) with good features of CO2 adsorption, catalytic conversion and light absorption. Herein, we report a synthesis approach to prepare Fe5Mn5/Ni/CaAl for use in the solar driven ICCU-DRM, which directly utilize the solar energy for syngas production with excellent comprehensive performance. The material prepared demonstrates an average spectral absorbance of 85.81 %, and a CO2 capacity of 8.46 mmol·g−1 with up to 89 % conversion to syngas. We expect the synthesis strategy has good implications on the development of innovative materials for carbon reduction and energy storage applications.

Equilibrium Study of Carbon Dioxide Reforming of Methane to Syngas

Fugacity coefficients for the components in the gas mixture are determined using the Soave–Redlich–Kwong (SRK) equation of state. The Gibbs free energy minimization method is employed to determine the equilibrium composition of the components for CO2 reforming of CH4 to syngas. To utilize CO2 efficiently and avoid carbon deposition, CO2 composition in the initial feed should not be greater than 1 (nCH4,0 = 1), and the reaction is preferably operated at atmospheric pressure. Setting nCH4,0:nCO2,0 to 1:1, and increasing nO2,0 in the feed from 0 to 1.0 to adjust the initial composition, results in a decrease in the syngas equilibrium yield, and a increase in both nCO2,e and nH2O,e. The temperature required for complete carbon deposition removal decreased. Considering the effective utilization of CO2 at nCH4,0:nCO2,0 1:1, it is recommended to set nO2,0 in the feed to less than 0.5.

Insight into pyrolysis behaviors of cedar under different atmospheres via a fixed-bed reactor

Pyrolysis, as an efficient route for biomass, usually suffers the influence of pyrolysis atmosphere by the interaction with free radicals from biomass pyrolysis. To investigate the effects of pyrolysis atmosphere on cedar pyrolysis, several atmospheres including CH4, H2, CO2, CO, CH4/CO2 and H2/CO were used for CS pyrolysis on a fixed-bed reactor and the pyrolysis process was revealed based on products distribution, tar quality and compositions. The results show that the components in pyrolysis atmosphere apparently affect the distribution of pyrolysis products and play different roles in cedar pyrolysis. Tar yields under different atmospheres follow the order of H2/CO > H2 > CH4/CO2 > CO2 > CO > N2 > CH4. The highest tar yield of 45.5 wt.% was obtained under H2/CO atmosphere at 600 °C. Char yield was decreased under H2 by suppressing secondary reaction and followed the order of H2 < H2/CO < CH4/CO2 < N2 < CO2 < CO < CH4. The content of ketones was improved under CO2 atmosphere. The introduction of H2 mainly increases naphthalenes, benzenes, ketones and phenols; while the formation of acids, esters, aldehydes and furans was inhibited under CO atmosphere. Integrated process of biomass pyrolysis with CO2 reforming of CH4 can greatly increase tar yield and change tar compositions, which is ascribed to the participation of H-rich free radicals from CO2 reforming of CH4. This work provides a route to improve the yield of pyrolysis tar and adjust tar components.

Performance evaluation of carbon-negative syngas production via chemical looping reforming of methane from biomass pyrolysis volatiles

To realize the clean and efficient directional conversion of biomass, chemical looping reforming of biomass volatile CH4 based on a decoupling strategy is expected to carry out carbon-negative production of hydrogen-rich syngas. In this paper, a multi-functional oxygen carrier (NiFe2O4@SBA-16) for encapsulating the active metal oxide component NiFe2O4 with a three-dimensional interconnecting pore molecular sieve SBA-16 was designed. The experimental results showed that the modification strategy of composite metal oxide encapsulation improved syngas selectivity and CH4 conversion based on the fixed-bed reactor. 20 %NiFe2O4@SBA-16 showed 22.1 % CH4 conversion and 92.6 % CO selectivity under 750 °C, and it maintained good cycle stability after 15 cycles. The H2/CO ratio was effectively improved by adding part of CO2 into the feed gas, and the CH4 conversion reached over 35 %. This study provides essential data for the clean preparation of hydrogen-rich syngas from biomass and the development and design of multifunctional oxygen carriers.

Experimental investigation of integrated CO2 capture and conversion to syngas via calcium looping coupled with dry reforming of CH4

Calcium looping integrated with dry reforming of CH4 is a promising strategy for CO2 capture and in situ conversion to syngas. This intensified process is usually conducted with bifunctional materials that combine CO2 capture (CaO) and catalytic (Ni) active sites. Herein, the integrated calcium looping/dry reforming process was examined by investigating various bifunctional materials and operating conditions. The Ni loading of materials affected the interaction between active and inert phases, while adding a CaZrO3 promoter enhanced the CO2 capture and catalytic activities and the resistance toward sintering. Conducting experiments with a fluidized bed reactor (700 °C, 3% CH4 in feed) led to nearly complete CH4 conversion and ∼52% utilization of captured CO2 toward syngas production with steady H2/CO ratio close to unity. Temperature comprised a decisive parameter, with low values enabling high degrees of CO2 conversion up to ∼80%. The increase of CH4 concentration in the gas feedstock enhanced the rate of calcination and the conversion of CO2 over its desorption in the gas phase. Co-feeding O2 with CH4 was proposed to mitigate the energy demand, which reduced the reforming selectivity for the partial oxidation reaction and increased the H2/CO ratio of syngas.

Insights into the role of S-Ti-O bond in Titanium-Based catalyst for photocatalytic CH4 reforming: Experimental and DFT exploration

Given the increasingly severe climate and energy crises, this paper proposes the concept of “room-temperature solar-powered CH4 reforming”, intended to achieve carbon emission reduction and efficiently use carbon-containing resources. However, traditional semiconductors as catalysts have some problems, such as few catalytic active sites and fast recombination of photogenerated electrons and holes, resulting in low efficiency of photocatalytic CH4 reforming. For this reason, a series of doped catalysts X-TiO2 (X = Br, N, and S) are prepared by introducing nonmetallic elements into the TiO2 lattice to construct oxygen defects. Notably, the CO yield of the S-TiO2 catalyst was 1048μ mol g−1, 65 times higher than the catalytic performance of bulk TiO2. Based on the functional density theory (DFT) calculation, the interaction between the S active site and the performance of photocatalytic CH4 reforming with oxygen defects is discussed in detail. The synergistic effect of the S site and the oxygen defect has been shown to rapidly activate C = O and C-H bonds at room temperature. Finally, based on the tracer experiment and DFT calculation, a possible mechanism of photocatalytic CH4 reforming at room temperature is proposed. This work provides a new research direction for achieving carbon neutrality at room temperature and a feasible technical scheme for the large-scale application of photocatalysts.

Research Progress on Stability Control on Ni-Based Catalysts for Methane Dry Reforming

CO2 reforming of CH4 (DRM) utilizes the greenhouse gases of CH4 and CO2 to obtain the synthesis gas, benefiting the achievement of carbon neutrality. However, the deactivation of Ni-based catalysts caused by sintering and carbon deposition limits the industrial application. Focusing on stability improvement, this review first summarizes the reaction mechanism and deactivation mechanism in DRM and then discusses the impact of catalyst active components, supports, and interfacial structure. Finally, we propose the design direction of stable Ni-based catalysts towards DRM, providing guidance for the future development of catalysts suitable for industrial production.