CO2 Reforming Research Articles

Integrated syngas and nitrogen production in La0.6Ca0.4Co0.2Fe0.8O3−δ hollow fiber membrane reactor through oxidative CO2 reforming of methane

Utilizing mixed ion-electronic conducting (MIEC) oxygen permeable ceramic membrane to introduce oxygen from air into the oxidative CO2 reforming of methane (OCRM), which integrates exothermic partial oxidation of methane (POM) with endothermic dry reforming of methane (DRM), not only reduces the energy consumption but also effectively mitigates carbon accumulation. In this study, La0.6Ca0.4Co0.2Fe0.8O3−δ (LCCF) hollow fiber (HF) membrane was fabricated via a phase inversion and sintering technique using LCCF oxide powder. A 10 wt% Ni/LCCF catalyst was prepared by mechanical mixing and high temperature reduction of NiO and LCCF powder. The catalyst and LCCF HF membrane were integrated into an OCRM membrane reactor. The findings indicate that moderate temperature increment was beneficial to the combined OCRM reaction in the membrane reactor. However, the increase in air flow rates, CH4/CO2 ratio, and feed flow rates were found to deteriorate the OCRM performance. At 825 °C, the CO selectivity and carbon balance were maintained at about 99 %. The stabilized oxygen permeation rate at about 2.08 mL min−1 signifies that the permeated oxygen significantly inhibits carbon accumulation in the catalyst. Notably, N2 with purity of 99.47 vol% was obtained at the air feed side of the setup, underlining the potential for efficient carbon management and high-purity N2 production within this OCRM membrane reactor.

Challenging thermodynamics: combining immiscible elements in a single-phase nano-ceramic

The Hume-Rothery rules governing solid-state miscibility limit the compositional space for new inorganic material discovery. Here, we report a non-equilibrium, one-step, and scalable flame synthesis method to overcome thermodynamic limits and incorporate immiscible elements into single phase ceramic nanoshells. Starting from prototype examples including (NiMg)O, (NiAl)Ox, and (NiZr)Ox, we then extend this method to a broad range of Ni-containing ceramic solid solutions, and finally to general binary combinations of elements. Furthermore, we report an “encapsulated exsolution” phenomenon observed upon reducing the metastable porous (Ni0.07Al0.93)Ox to create ultra-stable Ni nanoparticles embedded within the walls of porous Al2O3 nanoshells. This nanoconfined structure demonstrated high sintering resistance during 640 h of catalysis of CO2 reforming of methane, maintaining constant 96% CH4 and CO2 conversion at 800 °C and dramatically outperforming conventional catalysts. Our findings could greatly expand opportunities to develop novel inorganic energy, structural, and functional materials.

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.

Improving catalytic activity of MoP for CO2 reforming of methane via ZrO2 modification

Molybdenum phosphide (MoP) has attracted increasing attention as a novel catalytic material for CO2 reforming of methane in virtue of superior coke resistance, but its catalytic reactivity is still relatively low. This work for the first time improved the reforming activity of MoP via ZrO2 modification. The Zr0.01MoP catalyst with Zr/Mo molar ratio of 0.01 possessed much higher activity than bare MoP at 800–900 °C. Structural characterizations revealed that the introduction of ZrO2 would decrease the particle size, modify the electronic structure and change the reducibility property of MoP, which may function together to deliver the higher activity.

Phase Transformation of Zr-Modified LaNiO3 Perovskite Materials: Effect of CO2 Reforming of Methane to Syngas

Zr-modified LaNiO3 catalysts (LaNixZr1−xO3; 0 ≤ x ≤ 1) are synthesized by the sol–gel method. The physio-chemical properties of materials are investigated using different characterization techniques and evaluated for the CO2 reforming of methane to syngas. Interestingly, the characterization studies revealed the phase transformation from La-Zr pyrochlore to La-Ni perovskite depending on the Ni:Zr ratio in the material. The formation of the pyrochlore phase is observed for high-Zr-containing catalysts, thus leading to the production of bulk NiO. The formation of La-Ni perovskite is observed for high-Ni-containing catalysts and the ZrO2 acted as a support. The formation of La-Ni perovskite supported on ZrO2 enhanced the Ni dispersion of the catalysts. The high dispersion of Ni enhanced the catalytic activity, and LaNi0.8Zr0.2O3 showed the best performance among all of the studied catalysts in terms of conversions and the H2/CO ratio.

Efficient recycling and conversion of CO2 to methanol: Process design and environmental assessment

Carbon capture and carbon reuse in the chemical plants is one of the attractive prospective approaches to decrease the concerns about global warming and climate change. In the present study, is focused on the synthesis gas production from carbon dioxide in a methanol synthesis plant. In this regard, two methanol processes are proposed based on CO2 separation, recycling, and reforming. In the first scenario, CO2 is separated and recycled to the conventional reformer, while the process is equipped by a CO2 separation unit and dry methane reformer in the second scenario. The proposed processes are simulated and a sensitivity analysis is performed to investigated the effect of inputs on methanol productivity and carbon conversion. The operational parameters of proposed processes are optimized to enhance methanol productivity and CO2 conversion. Then, the processes are compared from energy efficiency, carbon efficiency, CO2 emission rate and methanol productivity viewpoints. The results showed that, in the second proposed scenario, methanol production rate approach to 5367 tons per day in comparison to 5030 tons per day for industrial unit. In addition, modification of conventional methanol process based on the second scenario could decrease CO2 emission rate about 56 tons per day.

Thermo-photo catalytic anode process for carbonate-superstructured solid fuel cells.

Converting hydrocarbons and greenhouse gases (i.e., carbon dioxide, CO2) directly into electricity through fuel cells at intermediate temperatures (450 to 550 °C) remains a significant challenge, primarily due to the sluggish activation of C-H and C=O bonds. Here, we demonstrated a unique strategy to address this issue, in which light illumination was introduced into the thermal catalytic CO2 reforming of ethane in the anode as a unique thermo-photo anode process for carbonate-superstructured solid fuel cells. The light-enhanced fuel activation led to excellent cell performance with a record-high peak power density of 168 mW cm-2 at an intermediate temperature of 550 °C. Furthermore, no degradation was observed during ~50 h operation. Such a successful integration of photo energy into the fuel cell system provides a new direction for the development of efficient fuel cells.

Carbon Dioxide Reforming of Methane in a Microchannel Reactor

In this work, an experimental study of CO2 reforming of methane in a microchannel reactor was carried out. Two types of microchannel reactors were used in the experiments: a slot ring channel with a catalyst applied to the outer surface of the inner cylinder, a pack of corrugated plates, on the surface of which the catalyst was applied.

Revisiting the mitigation of coke formation: Synergism between support & promoters' role toward robust yield in the CO2 reformation of methane

CO2 reformation of methane (CRM) and CO2 methanation are two interconnected processes with significant implications for greenhouse gas reduction and sustainable energy production for industrial purposes. While Ni-based catalysis suffers from poor stability due to coke formation or sintering, we report a super stable remedy. The active sites of mesoporous MgO were loaded using wet impregnation. The incorporation of Ni and promoters altered the physical features of the catalysts. Sm–Ni/MgO showed the smallest crystallite size, specific surface area, and pore volume. The Sm–Ni/MgO catalyst was selected as the most suitable candidate for CRM, with 82 ​% CH4 and H2/CO ratio of approximately 100 ​% and also for CO2 methanation with the conversion of carbon dioxide (82 ​%) and the selectivity toward methane reaches 100 ​% at temperatures above 300 ᵒC. Furthermore, the Sm–Ni/MgO catalyst was stable for 900 ​min of continuous reaction, without significant carbon deposition. This stability was largely due to the high oxygen mobility on the catalyst surface in the presence of Sm. Overall, we demonstrated the efficacy of using promoted Ni catalysts supported by mesoporous magnesia for the improved reformation of greenhouse gases.

Dry reforming process using microwave plasma generator with high carbon dioxide conversion efficiency for syngas production

The proposed CO2 reforming solution has improved CO2 conversion efficiency by developing a new double helix type plasma generator (DHTPG) to preheat the discharge gas and increase residence time of CO2 at DHTPG. In addition, injecting CH4 independently allows for a stable increase in the temperature of the CO2 plasma in the microwave plasma generator compared with other conventional methods. To verify the performance of the DHTPG, we experimentally investigated the distribution of the plasma gas temperature using an enthalpy probe system as a function of the specific energy input, which is a key parameter for understanding the mechanisms of CO2 reforming of CH4. We performed the CO2 reforming of CH4 using the newly designed plasma generator and a comparative analysis of its characteristics with those of other plasma generators. Without catalyst materials, our method significantly enhanced the CO2 conversion efficiency to 91.4 % with an energy efficiency of 67 % at a specific energy input of 245 kJ/mol. The main advantage of our method is an increase in energy-consumption selectivity, in which the energy injected through the plasma decomposes CO2 rather than CH4. In addition, it reduces the energy required to stably maintain the plasma to improve energy efficiency.

Ternary Fe- or Mo-Au-Ni/GDC as Candidate Fuel Electrodes for the Internal Dry Reforming of CH4: Physicochemical and Kinetic Investigation

The present study deals with the physicochemical and catalytic/kinetic investigation of Fe, Au, Fe-Au, and Mo-Au modified Ni/GDC electrocatalysts towards their performance for the DRM, RWGS, and CH4 decomposition reactions. For this purpose, Au-NiO/GDC (where Au = 1 or 3 wt.%), Fe-NiO/GDC (where Fe = 0.5 or 2 wt.%), 0.5Fe-3Au-NiO/GDC, and 0.4Mo-3Au-NiO/GDC were synthesized via deposition (co-) precipitation. There is discussion on the structural properties of the electrocatalysts on the oxidized and reduced state, as well as their use as electrolyte-supported (half) cells. A key remark after H2-reduction is the formation of binary or ternary solid solutions. Ni/GDC was the most active for the catalytic CO2 reforming of CH4 and the CH4 decomposition reactions and as a result the most prone to carbon deposition. On the other hand, the modified 3Au-Ni/GDC, 0.5Fe-3Au-Ni/GDC, and 0.4Mo-3Au-Ni/GDC exhibited the following properties: (i) the highest Ea,app for the non-desired RWGS reaction, (ii) high tolerance to carbon formation due to lower activity for the CH4 decomposition, and (iii) were also less active for H2 and CO production. Finally, 0.4Mo-3Au-Ni/GDC seems to perform the DRM reaction through a different mechanism when compared to Ni/GDC. Overall, the above three samples are proposed as potential fuel electrodes for further electrocatalytic measurements for the SOFC internal DRM process.

Ce doping boosted photothermal synergistic catalytic reforming of CH4 and CO2 into syngas over Ni/ZrO2 at medium-low temperature

Syngas production from dry reforming (DRM) of CO2 and CH4 is a promising technology to reduce carbon emission, however, harsh reaction condition required in conventional thermal catalytic DRM frequently leads to poor economy and severe carbon deposition in catalysts. Herein, the present work reports a novel photothermal synergistic catalytic (PTSC) DRM over Ce-doping Ni/ZrO2 catalyst at medium-low temperature. The maximum CO2/CH4 conversions (51.6% and 54.6%) were obtained for Ni–Ce/ZrO2 at 600 °C via synergy of illumination, which was about 1.3 times higher than that under thermal catalytic DRM. Ce doped catalyst maintained good activity and thermal stability after the aging test over 23 h. The TOF values of Ni–Ce bimetallic catalyst under PTSC condition have 1.2–3.3 times enhancement compared to thermal condition. Characterization and DFT calculation results reveal that Ce doping facilitates the formation of oxygen vacancies and effectively weakens C adsorption on Ni metal to suppress carbon deposition.

Enhanced Stability of Iridium Nanocatalysts via Exsolution for the CO2 Reforming of Methane.

The reforming reactions of greenhouse gases require catalysts with high reactivity, coking resistance, and structural stability for efficient and durable use. Among the possible strategies, exsolution has been shown to demonstrate the requirements needed to produce appropriate catalysts for the dry reforming of methane, the conversion of which strongly depends on the choice of active species, its interaction with the support, and the catalyst size and dispersion properties. Here, we exploit the exsolution approach, known to produce stable and highly active nanoparticle-supported catalysts, to develop iridium-nanoparticle-decorated perovskites and apply them as catalysts for the dry reforming of methane. By studying the effect of several parameters, we tune the degree of exsolution, and consequently the catalytic activity, thereby identifying the most efficient sample, 0.5 atomic % Ir-BaTiO3, which showed 82% and 86% conversion of CO2 and CH4, respectively. By comparison with standard impregnated catalysts (e.g., Ir/Al2O3), we benchmark the activity and stability of our exsolved systems. We find almost identical conversion and syngas rates of formation but observe no carbon deposition for the exsolved samples after catalytic testing; such deposition was significant for the traditionally prepared impregnated Ir/Al2O3, with almost 30 mgC/gsample measured, compared to 0 mgC/gsample detected for the exsolved system. These findings highlight the possibility of achieving in a single step the mutual interaction of the parameters enhancing the catalytic efficiency, leading to a promising pathway for the design of catalysts for reforming reactions.

Structure Characteristics and Removal Behavior of the Deposited Carbon on Ni-Al2O3 Catalyst for CO2 Reforming of CH4

Four catalysts were prepared in our previous work using the solution combustion method, incipient-wetness impregnation method, colloid mill circulating impregnation method, and hydrothermal-precipitation method, respectively, labeled as SCM, IMP, T310, and HTP. And the performance (stability) of the four catalysts for CO2 reforming of CH4 was investigated at 800 °C. In this paper, the composition and structure characteristics of the deposited carbon on the above four catalysts were tested through TEM, Raman, TPH, and TG-DTG technologies. The results showed that filamentous carbon was the primary type of carbon deposition on the catalysts, and a large amount of accumulated carbon would block the catalyst pores, affecting the catalytic performance. The carbon deposited on the catalyst prepared using the hydrothermal-precipitation method calcined at 800 °C exhibited a high degree of graphitization, and the proportion of graphitized carbon was considerable, which is harmful to the stability of the catalyst. The decarburization temperature of the deposited carbon on the four catalysts was mainly in the range of 500–700 °C. Using the Coats–Redfern model, as the reaction order was set as 1, 2, 3, 4, and 5, the decarburization activation energy ranged between 50 and 80 kJ/mol.

Design of Ru-Co/MgO-Al2O3 catalyst system for CO2 reforming of methane: Performance investigation concerning the Mg/Al ratio

This study explores the design of bimetallic Co-Ru nanoclusters deposited on surface-tuned mesoporous Mg-Al mixed oxide support for the CO2 reforming of methane (DRM) process. The evaporation-induced self-assembly technique was used to create a series of MgO-Al2O3 mixed oxide supports with various Mg/Al molar ratios. Co and Ru nanoclusters over the MgO-Al2O3 supports were decorated using a urea precipitation-deposition approach. Results revealed that the activity and stability of the DRM catalyst were substantially reliant on the Mg/Al molar ratio and Co-Ru metal combination. Among the series of Co-loaded catalysts, the best performance was obtained over an unpromoted CoMg20Al catalyst (20 wt.% Mg), with only a 10 % activity loss after 50 h of study. A modification of CoMg20Al by 0.5 wt.% Ru significantly enhanced the catalytic activity, demonstrating a 93 % methane conversion with raw feed and stable activity over a 100-h extended activity analysis. The catalyst characterization showed that Mg concentration increased basic sites over Mg-Al support. Due to the separation of crystalline phases as MgO-MgAl2O4, CoMg40Al had the most basic sites but poor DRM reaction performance. Balanced acidic/basic properties and well-dispersed Co-Rh nanoclusters-maintained DRM activity and stability. Ru-promoted CoMg20Al catalyzed the lowest activation energies.

Direct CH4–CO2 solid oxide fuel cells combined with Li-doped perovskite dry reforming catalysts for high efficiency power generation

Direct CH4–CO2 solid oxide fuel cells (SOFC) have attracted considerable attention due to their potential for high-efficiency power generation with low environmental impact. However, carbon deposition on Ni-based cermet anodes remains a critical challenge, leading to performance degradation. In this study, we propose a novel approach to address this issue by using a Li-doped perovskite, (La0.75Sr0.25)0.95Li0.1Cr0.5Fe0.4Ni0.1O3-δ (LSLCFN), as an exsolution system and a dry reforming catalyst for SOFCs. The LSLCFN catalyst exhibits enhanced carbon dioxide adsorption capacity, effectively reducing carbon deposition on the anode surface. In addition, the incorporation of Ni–Fe alloy nanoparticles facilitates dissolution in a reducing atmosphere and exhibits remarkable stability in the presence of carbon dioxide. Anode-supported single cells incorporating a LSLCFN-Ce0.9Gd0.1O2–δ(LSLCFN-GDC) composite as the anode active reforming layer exhibit excellent electrochemical performance when operated with both H2 and CH4–CO2 fuels. The peak power densities reach 904.86 and 825.37 mW cm−2 at 800 °C, respectively. Furthermore, the LSLCFN-GDC reforming layer maintains stable performance during the dry reforming of a 50%CH4–50%CO2 fuel mixture for 100 h at 700 °C, with negligible carbon deposition. These results highlight the effectiveness of employing a dry reforming catalyst to enhance CH4–CO2 reforming and optimize electrochemical performance for efficient energy conversion in SOFCs.

Mathematical Modeling of CO2 Reforming of Methane with Reverse Water-Gas Shift Reaction

Mathematical Modeling of CO2 Reforming of Methane with Reverse Water-Gas Shift Reaction

Effects of MgO on Ni/Al2O3 catalysts for CO2 reforming of methane to syngas

Carbon dioxide reforming of methane (CRM) converts CH4 and CO2 greenhouse gases into syngas over nickel-based catalysts. We performed CRM in a tubular microreactor at 700 °C by using 5.0 wt.% NiO catalyst, supported over mixtures of γ-Al2O3 + x MgO (x = 20, 30, 63, and 70 wt.%). The process of impregnation was used to prepare the catalysts. For characterization, N2-physisorption, XRD, H2-TPR, TGA, and Raman spectroscopy techniques were employed. Among the examined catalysts, 5Ni/Al2O3 + 63%MgO was found the most active, where it showed ≅ 72% CH4 conversion, 73% CO2 conversion, and 0.82 H2/CO mole ratio over 7 h of reaction. The MgO modifier was the primary component, which favorably affected both Ni dispersion and stability, for the good interaction between NiO and γ-alumina. The mono-supported samples displayed the lowest total hydrogen consumption. In TGA, the 5Ni/Al2O3 + 63%MgO exhibited a significant weight decrease (40%), reflecting its activity. Furthermore, the Raman spectroscopy analysis showed that the crystallinity of the carbon over this catalyst was more pronounced than the others.

Mathematical Modeling of CO<sub>2</sub> Reforming of Methane with Reverse Water Gas Shift Reaction

Synthesis gas is the cornerstone of many chemical processes for manufacturing a broad range of petrochemical products. In this work, a mathematical model was developed for investigation of the CO2 reforming of methane in a catalytic packed bed reactor. To simulate the reformer, a pseudo homogenous two-dimensional mathematical model was developed and the resulting nonlinear second order partial differential equations were solved using the finite difference method. It was assumed that equilibrium reverse water gas shift reaction always takes place in the reactor to adjust H2/CO ratio (≤1). The effect of operating conditions, including bulk density, porosity, inlet gas and wall temperature, reactor diameter, total molar flow of gas and inlet CH4/CO2 ratio on the reactor performance were investigated. Finally, the study investigated the effect of H2/CO ratio on the outlet synthesis gas product at the range of 0.7–1. The validity of the model was investigated and the deviation between the model results and the experimental data was acceptable.

(Digital Presentation) Au-Mo-Fe-Ni/CeO2(Gd2O3) As Potential Fuel Electrodes for Internal CO2 Reforming of CH4 in Single SOFCs

Recycling biogas to produce syngas (H2 + CO) through Dry Reforming of Methane (DRM) has currently attract resurgent interest. Biogas consists mainly of CH4 (55-65%) and CO2 (35-45%) and is widely produced by anaerobic fermentation of biomass [1]. DRM provides a feasible solution to eliminate greenhouse gases via production of useful chemicals and hydrocarbons.Considering the DRM energy applications the produced syngas can be used as a fuel in high temperature solid oxide fuel cells (SOFCs) for electricity production or biogas can be directly fueled in the cell without the need of an external reformer (Internal Dry Reforming of Methane, IDRM), which simplifies the SOFC system and reduces the cost [2,3]. Specifically, during IDRM at temperatures higher than 800 oC, the catalytic Reverse Water Gas Shift (RWGS) reaction may run in parallel with electrocatalytic reactions, resulting in the consumption of valuable H2. In addition, carbon deposition on the electrocatalyst surface due to CH4 decomposition, which is favored at elevated temperatures (≥ 700 oC), may also occur resulting in progressive electrocatalyst deactivation [4].Ni-based ceramic-metal composites with Yttria Stabilized Zirconia (YSZ) and Gadolinia Doped Ceria (GDC) are widely used as electrocatalysts in SOFCs because of their activity and inexpensiveness. However, nickel catalyses the formation of carbon deposits from hydrocarbons and exhibits a tendency to agglomerate after prolonged operation [3,4]. The carbon tolerance and anti-sintering tendency of nickel and specifically of Ni/GDC can be enhanced, by dispersing trace amounts of transition noble (Rh, Pt, Pd, Ru, Au) or non-noble (Co, Cu, Mo, Fe) metal elements [3,5].In this study the catalytic and electro-catalytic performance, as well as the coking resistance of Au (1 and 3 wt.%), Mo (0.4 wt.%) and Fe (0.5 and 2 wt.%) modified Ni/CeO2(Gd2O3) electro-catalysts were studied as half and full electrolyte supported cells under internal CO2 reforming of CH4 in single SOFCs, at 750-900 oC. The aim was to elucidate their activity towards the consumption of CH4, CO2, the production of H2, H2O, CO and the production of carbon, as a function of temperature and the applied current density under a biogas fuel mixture of CH4/CO2=1. Additionally, the cells comprising a modified Ni/GDC fuel electrode, an 8 mol% Y2O3 stabilized ZrO2 (8YSZ) electrolyte were characterized using I-V measurements and Electrochemical Impedance Spectra (EIS) analysis in order to investigate the evolution of the ohmic and polarization resistance values as a reflection of current. Complementary physicochemical characterization includes thermo-gravimetric measurements for the catalytic dissociation of CH4 and CO2 at 800 oC. In brief, the cell with Ni/GDC was more active catalytically compared to the modified cells, but exhibited worst electrocatalytic performance. The cells with 3 wt.% Au-0.4 wt.% Mo-Ni/GDC and 3 wt.% Au-0.5 wt.% Fe-Ni/GDC fuel electrodes were moderately active catalytically, but performed better. The main degradation factor for the unmodified cell was the higher carbon formation, which increased gradually with the increased current and was reflected on higher ohmic and polarization resistance values compared to the modified cells. Acknowledgments This research has been co-financed by the European Union and Greek national funds through the operational program ‘Regional Excellence’ and the operational program ‘Competitiveness, Entrepreneurship and Innovation’, under the call “RESEARCH-CREATE-INNOVATE” (Project code: T2EΔK-00955).