Looping Dry Reforming Of Methane Research Articles

DFT insights into oxygen vacancy formation and chemical looping dry reforming of methane on metal-substituted CeO2 (111) surface

DFT insights into oxygen vacancy formation and chemical looping dry reforming of methane on metal-substituted CeO2 (111) surface

(Ni or/and Co) Supported over Praseodymia as Oxygen Carriers for Chemical Looping Syngas Production

AbstractThe present research describes one of the processes outlined in the literature, known as Chemical Looping Dry Reforming of Methane, which is currently to gain attraction to produce clean fuels from natural gas using a metal oxide support as a catalyst. This two‐step method offers distinct advantages by physically separating the reaction steps. This spatial separation effectively eliminates undesirable side reactions, leading to highly efficient syngas production with minimal carbon deposition. Crucial to optimizing this process is a deep understanding of the oxygen storage capacity (OSC) of the support (oxygen carrier) that will work in synergy with the supported active phase. Among the candidates, praseodymium stands out due to its favourable redox properties and exceptional OSC characteristics, making it a promising option for cleaner fuel technologies. In particular, this study emphasizes the significant influence of the nature of the active phases (Ni, Co or their bimetallic combinations), with bimetallic phases being the most promising (even without reduction, they can exhibit activity that equals or improves that of the Ru as benchmark), underscoring the fundamental role of catalyst design in achieving optimal performance. The results indicate that these compositions have high activities to generate the products, remaining close to the activity of ruthenium and generating minimal coke deposits in one reaction cycle.

Experimental and kinetic study on the solar-driven iron-based chemical looping dry reforming of methane

The chemical looping dry reforming of methane (CL-DRM) represents a promising pathway for large-scale engineering applications of thermochemical decarbonization techniques. To elucidate the intricate reaction mechanism of CL-DRM, a comprehensive kinetic model encompassing both gas-phase reactions and ferrite surface reactions is developed in this study. This model can serve as a numerical foundation for tracing the reaction progression of comparable iron-based oxygen carriers, allowing visualization of all reaction pathways and further determination of optimal reaction conditions. Besides, foam-structured materials employing NiO-doped CoFe2O4 as oxygen carriers were prepared to conduct application experiments for the CL-DRM on a self-designed solar thermochemical platform. The experimental outcomes, obtained under temperature conditions guided by numerical predictions, validate the promising feasibility of employing Ni-doped ferrite in the CL-DRM reaction system. At a reaction temperature of only 1150 K, remarkable peaks in H2 yield of 23.5 mLmin−1g−1, CO yield of 11.6 mLmin−1g−1, and CH4 conversion around 90% are attained, with a net solar-to-fuel conversion efficiency of 1.93%. A comparative analysis conducted with the conventional two-step thermochemical cycle under the same experimental setup underscores the notable advantages of CL-DRM in terms of syngas production capacity and conversion efficiency. Consequently, CL-DRM can be regarded as a pivotal transition towards the realization of a fully carbon-free thermochemical technology.

Performance of Iron-Based Perovskite-type Oxides for Chemical Looping Dry Reforming of Methane

Performance of Iron-Based Perovskite-type Oxides for Chemical Looping Dry Reforming of Methane

Life-cycle assessment of hydrogen produced through chemical looping dry reforming of biogas

Chemical looping dry reforming of methane (CLDRM) using perovskites as a catalyst is considered a promising option for producing hydrogen from biogas. In this work, the life-cycle performance of a system compiling a CLDRM unit paired with a water gas shift unit, a pressure swing adsorption unit, and a combined cycle scheme to provide steam and electricity was assessed. The main data needed to reflect the behavior of the reforming reaction was obtained experimentally and implemented in an Aspen Plus® simulation. Inventory data was obtained through process simulation and used to assess the environmental performance of the process in terms of carbon footprint, acidification, freshwater eutrophication, ozone depletion, photochemical ozone formation, and depletion of minerals and metals. Overall, the environmental viability of the production of green hydrogen from biogas was found to be heavily dependent on the biogas leakage in anaerobic digestion plants. The CLDRM system was benchmarked against a conventional DRM implementation for the same feedstock. While the conventional DRM plant environmentally outperformed the perovskite-based CLDRM, the latter might present advantages from an implementation point of view.

Solar-Driven membrane reactors with wide temperature range for chemical looping dry reforming of Methane: Concept validation and one-dimensional analysis

Solar thermochemical fuel conversion technology offers a significant potential to mitigate the challenges of intermittency and variability inherent in solar energy utilization. Traditional two-step methane chemical looping processes for fuel production are often hampered by complex apparatus requirements, operational intermittency, and persistent temperature variations, contributing to energy loss. In contrast, the chemical looping dry reforming of methane (CL-DRM) membrane reactor technology, as developed in this study, facilitates continuous fuel synthesis under isothermal conditions. Through the construction and analysis of a one-dimensional + one-dimensional model for a single channel of this innovative reactor, the impact of structural and operational parameters on the reactor performance is elucidated. This model enables a swift prediction of the membrane reactor’s operational efficacy. The results indicate that the reactor sustains a high energy conversion efficiency across a broad temperature spectrum, thereby enhancing its adaptability to the dynamic conditions of solar energy input. Notably, temperature and feed ratio (RCH4/CO2) are pivotal determinants of the conversion rate and the concentration of products. At a temperature of 1000 °C, with an optimal RCH4/CO2 ratio of 1, the efficiency is projected to attain 78 %, considering heat dissipation and thermal recovery mechanisms. These results underscore the promise of the solar-driven CL-DRM membrane reactor as a viable and efficient method for solar fuel production. This study provides a new perspective on the design of continuous solar fuel conversion reactors.

Microwave heating-assisted chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CLDRM) offers a sustainable pathway to convert methane (CH4) and carbon dioxide (CO2) to syngas, i.e., a mixture of hydrogen (H2) and carbon monoxide (CO). However, carbon deposition caused by high gas temperature remains a crucial challenge for the CLDRM. We proposed microwave (MW) heating-assisted CLDRM to leverage the selective heating feature of MWs to create a thermal gradient between solid and gas phases. This thermal gradient, i.e., a higher solid temperature than the gas temperature, can promote desired reduction and oxidation (redox) reactions, while suppressing undesired gas phase reactions, in particular, CH4 decomposition. At bulk temperature of 800 °C, the MW heating-assisted CLDRM achieved a maximum CH4 conversion of 97% and H2/CO ratio of around 2. Compared to the conventionally heated CLDRM, the MW heating increased the redox extents of magnetite (the oxygen carrier) by 2.5 and 1.5 times, respectively, and suppressed carbon deposition.

Optimizing the sulfur-resistance and activity of perovskite oxygen carrier for chemical looping dry reforming of methane

Perovskite oxides has been attracted much attention as high-performance oxygen carriers for chemical looping reforming of methane, but they are easily inactivated by the presence of trace H2S. Here, we propose to modulate both the activity and resistance to sulfur poisoning by dual substitution of Mo and Ni ions with the Fe-sites of LaFeO3 perovskite. It is found that partial substitution of Ni for Fe substantially improves the activity of LaFeO3 perovskite, while Ni particles prefer to grow and react with H2S during the long-term successive redox process, resulting in the deactivation of oxygen carriers. With the presence of Mo in LaNi0.05Fe0.95O3−σ perovskite, H2S preferentially reacts with Mo to generate MoS2, and then the CO2 oxidation can regenerate Mo via removing sulfur. In addition, Mo can inhibit the accumulation and growth of Ni, which helps to improve the redox stability of oxygen carriers. The LaNi0.05Mo0.07Fe0.88O3−σ oxygen carrier exhibits stable and excellent performance, with the CH4 conversion higher than 90% during the 50 redox cycles in the presence of 50 ppm H2S at 800 °C. This work highlights a synergistic effect in the perovskite oxides induced by dual substitution of different cations for the development of high-performance oxygen carriers with excellent sulfur tolerance.

Halite-structured (MgCoNiMnFe)Ox high entropy oxide (HEO) for chemical looping dry reforming of methane

The configurational disorder of high entropy oxides (HEOs) promotes the reversible exsolution–redissolution of constituent metal species. This unique feature could be exploited to facilitate cyclic lattice oxygen storage and exchange. Herein, we report an in situ generated, halite-structured (MgCoNiMnFe)Ox HEO, which simultaneously functions as a redox catalyst and an oxygen carrier for dry reforming of methane in a chemical looping process (CL–DRM). Accordingly, the (MgCoNiMnFe)Ox/ZrO2 HEO catalyst exhibits outstanding DRM activity, syngas selectivity and cyclic stability compared to medium-entropy oxides and bimetallic oxides over 100 CL–DRM cycles at 800 °C. XRD analysis verified the entropy-mediated preservation of the alloy/HEO/ZrO2 catalytic structure over CL–DRM cycles. XAFS studies revealed the reversible and cyclic evolution–dissolution of Ni, Fe, Co over redox cycles. The exsolved NiFeCo nanoalloy exhibited high efficiency in activating CH4. This study has demonstrated the potential applications of HEO-based catalysts in efficient chemical looping processes.

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.

A nickel-modified perovskite-supported iron oxide oxygen carrier for chemical looping dry reforming of methane for syngas production

The chemical looping dry reforming of methane (CLDRM) process, which converts methane and carbon dioxide into syngas, is an environmentally friendly greenhouse gas utilization strategy. In this work, it is demonstrated that a nickel-modified perovskite-supported iron-based oxygen carrier (Ni-Fe2O3/La0.8Sr0.2FeO3) significantly enhances the reactivity of CLDRM in the temperature range of 770–800 °C while maintaining high CO selectivity and oxygen capacity, as well as good carbon deposition resistance. With the addition of nickel, the methane conversion is 52 % higher than that without nickel at 800 °C. Rational coupling of the oxygen carrier components achieves over 99 % CO selectivity. 160 consecutive isothermal cycles confirm the outstanding stability of Ni-Fe2O3/La0.8Sr0.2FeO3. Based on the experimental results and characterizations, the evolution scheme and synergistic effects between the components of the Ni-Fe2O3/La0.8Sr0.2FeO3 oxygen carrier for CLDRM reaction are proposed. The results provide a pathway for oxygen carrier design to decrease the reforming temperature while maintaining excellent reaction performance in iron-based chemical looping systems.

High-reactive and coke-resistant polyhedral NiO/Fe2O3 oxygen carrier for enhancing chemical looping CH4–CO2 dry reforming

Chemical looping dry reforming of methane (CL-DRM) is a promising technology for syngas production and efficient CH4 and CO2 utilization to provide appropriate H2/CO ratio in the reducer for Fischer-Tropsch synthesis. The crucial issue in CL-DRM is to find a highly reactive oxygen carrier (OC) with good stability. Polyhedral NiO/Fe2O3 composite oxygen carriers were successfully fabricated via a hydrothermal and calcination method based on different solubility product constants of nickel carbonate (NiCO3) and ferrous carbonate (FeCO3) in aqueous solution. The physicochemical properties of the OCs were characterized by XRD, XRF, SEM, TEM, TG/DTA, XPS, H2-TPR and Raman spectroscopy. The performance of NiO/Fe2O3 OCs was measured in a fixed-bed reactor. The experimental results indicated that the Fe2O3-0.6Ni OC has the highest syngas yield up to 90.25% with ideal H2/CO mole ratio (approximately 2) in the reducer at 750 °C. In addition, in reducing atmospheres, the Ni3Fe alloy was formed instead of metallic Ni and Fe, thus significantly improves coke resistance. Density functional theory (DFT) calculations demonstrated that the energy barrier of rate determining step of dehydrogenation process (CH3 releases H to form CH2) is 2.64 eV with OC of pure Fe2O3, which is higher than that of the condition with OC of NiO/Fe2O3 composite (2.21 eV). Therefore, the addition of NiO to Fe2O3 favors the CH4 dehydrogenation process on the surface of OCs. This study provides guidance for the design of oxygen carriers for chemical looping dry reforming of methane with the better coke-resistant property.

Syngas Production by Chemical Looping Dry Reforming of Methane over Ni-modified MoO3/ZrO2.

We investigated supported-MoO3 materials effective for the chemical looping dry reforming of methane (CL-DRM) to decrease the reaction temperature. Ni-modified molybdenum zirconia (Ni/MoO3/ZrO2) showed CL-DRM activity under isothermal reaction conditions of 650 °C, which was 100-200 °C lower than the previously reported oxide-based materials. Ni/MoO3/ZrO2 activity strongly depends on the MoO3 loading amount. The optimal loading amount was 9.0 wt.% (Ni/MoO3(9.0)/ZrO2), wherein two-dimensional polymolybdate species were dominantly formed. Increasing the loading amount to more than 12.0 wt.% resulted in a loss of activity owing to the formation of bulk Zr(MoO4)2 and/or MoO3. In situ Mo K-edge XANES studies revealed that the surface polymolybdate species serve as oxygen storage sites. The Mo6+ species were reduced to Mo4+ species by CH4 to produce CO and H2. The reduced Mo species reoxidized by CO2 with the concomitant formation of CO. The developed Ni/MoO3(9.0)/ZrO2 was applied to the long-term CL-DRM under high concentration conditions (20 % CH4 and 20 % CO2) at 650 °C, with two pathways possible for converting CH4 and CO2 to CO and H2 via the redox reaction of the Mo species and coke formation.

Polymetallic doping of Mn-based perovskite oxides for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is an efficient pathway for the conversion of methane and CO2 into synthesis gas ready for Fischer-Tropsch process, which largely depends on the...

A mechanistic analysis of particle flow in a pulsatile circulating dual fluidized bed for chemical looping technology based on CDF-DEM simulation

This paper presents a three-dimensional computational fluid dynamic–discrete element method (CFD-DEM) model using Geldart class D particles for studying the fluid flow pattern in a circulating dual fluidized bed (CDFB) for chemical looping dry reforming of methane (CLDRM). The system design comprised a high-velocity air reactor (AR) also known as riser fluidized bed, a riser tube, a cyclone chamber, a fluidizing bed fuel reactor (FR), and a connecting loop, which closes the loop between AR and FR. The particles distribution, volume fraction, flow pattern, velocity and their circulation between the AR (riser) and FR (second fluidized bed) in CDFB were deeply investigated. The results showed that the CLDRM system experiences a pressure imbalance between the reduction and oxidation zones, causing solid particles to undergo a highly intricate and turbulent pulse flow. As a result, the operation of the system is alternately governed by two flow regimes: bubbling fluidization and pulsatile circulating fluidization. The burst of a high pressure pulses provide the pressure head required for circulation of the particles. The pulses also led to the intermittent transportation of particles ― in the form of particles clusters ― from high-pressure area to the region with a lower pressure.

Effect of Nickel and Cobalt Doping on the Redox Performance of SrFeO3−δ toward Chemical Looping Dry Reforming of Methane

Effect of Nickel and Cobalt Doping on the Redox Performance of SrFeO_3−δ toward Chemical Looping Dry Reforming of Methane

Effect of low-loading of Ni on the activity of La0.9Sr0.1FeO3 perovskites for chemical looping dry reforming of methane

Methane dry reforming (MDR) is a very appealing process to bring back waste CO2 into the chemical production chain. Operating in chemical looping (CL) conditions allows to reduce deactivation by coke deposition and facilitates the use of concentrating solar energy to power this reaction. Perovskites have successfully applied as oxygen carriers for chemical looping, and those of the family La1−xSrxFeO3 having lower Sr content have showed high activity and cycling stability for MDR. To further enhance the performance of these oxygen carriers, in this work we evaluate the impact of dispersing Ni in low concentration (<1 mol %) on the performance of La0.9Sr0.1FeO3 for CL-MDR. Simple impregnation allows to distribute evenly the metal, which according to XPS is present as Ni2+ in the fresh material. CH4-TPR reveal that NiOx species are firstly reduced at around 650 ºC and they shift the onset of methane partial oxidation to lower temperatures with regards to the unmodified perovskite. However, during isothermal CL tests at 850 ºC, the presence of Ni does not modify much the syngas production during the methane reforming stage, although the H2/CO ratio increases with the presence of this metal. This indicates an increment in the contribution of methane cracking. In contrast, when feeding CO2, the generation of CO is greatly enhanced by the incorporation of Ni, particularly at a loading of 0.4 mol %, while higher metal concentration are slightly less effective. Higher CO generation is attributed to the promotion of reverse Boudouard reaction, which can remove the coke previously deposited in the methane reforming stage. Accordingly, the Ni/ La0.9Sr0.1FeO3 presents stable activity during several consecutive cycles.

Oxygen release and reduction kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 as oxygen carriers for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a viable technology by converting CH4 and CO2 to various value-added products to achieve carbon neutrality. However, it is vital for the technology to find suitable oxygen carriers with high oxygen capacity and activity. La0.35Sr0.35Ba0.3Fe1-xCoxO3 perovskite-type oxides were proposed as oxygen carriers for CL-DRM. The oxygen (O2) release property and the kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 reduction by CH4 were investigated via thermogravimetric analysis, O2-temperature programmed desorption and then in a fixed-bed reactor. The O2 release process of La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be divided into two phases. The O2 release process and corresponding rate of OCs were facilitated due to the substitution of Fe with Co in B-site. The total amounts of O2 release for these OCs were enhanced about 1.5 times from 0.445 mmol/gOC to 0.706 mmol/gOC as Co atomic fraction in B-site changes from 0 to 1. The linear correlation for high temperature phase and a volcano-curve for low temperature phase was found for the correlations among total O2 release and Co content during the O2 release process. The reduction kinetics of CH4 over OCs was described using the Avrami–Erofe'ev model (A1.5 or A2). The values of apparent activation energy (Ea) for all OCs were obtained. The results indicated the best substitution proportion of Co in La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be set in the range of 0.2–0.4 to emerge the excellent redox performance. The kinetics models and parameters offer valuable information for CL-DRM reactor design and further development of OCs with different A or/and B-site modifications.

Highly active La0.35Sr0.35Ba0.3Fe1-xCoxO3 oxygen carriers with the anchored nanoparticles for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) has the potential as a viable technology to achieve carbon neutrality in terms of converting CH4 and CO2 to various value-added products with the minimal separation requirements. However, the design and development of an appropriate oxygen carrier (OC) with the remarkable reactivity and stability make the CL-DRM process challenging. Herein, the Co-substituted La0.35Sr0.35Ba0.3Fe1-xCoxO3 (LSBFC) perovskite oxides with the anchored nanoparticles as the novel OCs were synthesized and investigated for the redox performance in the CL-DRM process. It is found that the best substitution proportion of Co in the anchored perovskite oxides can be set in range of 0.2–0.6. The optimized OCs can greatly improve the reactivity of the chemical looping process based on various characterizations. Among all samples, La0.35Sr0.35Ba0.3Fe0.6Co0.4O3 OC increases the oxygen mobility and shows a higher oxygen diffusion rate to achieve the CH4 conversion of 84.3% and syngas yield of 15.23 mmol⋅g−1 in the CH4 reduction step, respectively. A detailed analysis of the anchored perovskite oxides reveals the substitution of Co can greatly weaken the perovskite lattice to result in the migration of Fe and the formation of Fe nanoparticles, which tremendously promote the activation of CH4 for the further conversion. Furthermore, the excellent OCs also exhibit the high stability in the enhanced reaction performance, the preservation of material structure and the stable regenerability by CO2 during the successive redox cycles. These features demonstrate that the new perovskite materials with anchored nanoparticles can be the promising oxygen carriers for the CL-DRM process.

Chemical Looping Dry Reforming of Methane over Ni-Modified WO3/ZrO2: Cooperative Work of Dispersed Tungstate Species and Ni over the ZrO2 Surface

In this study, we successfully developed nickel (Ni)-modified tungstate zirconia (Ni/WO3/ZrO2) as an effective material for chemical looping dry reforming of methane (CL-DRM) under isothermal conditions (750 °C). The performance of Ni/WO3/ZrO2 strongly depended on the WO3 loading amount. The optimal amount of 10.0 wt% WO3, corresponding to low surface W density (<4 W atoms/nm2), in Ni/WO3(10)/ZrO2 resulted in the exclusive formation of dispersed tungstate species, such as isolated monotungstate and/or oligomeric polytungstate species. Increasing the loading amount to 30.0 wt% (higher surface W density (>4 W atoms/nm2)) resulted in the formation of crystalline WO3 species, diminishing the CL-DRM performance over Ni/WO3/ZrO2. Comprehensive characterization, including in situ/operando W L3-/L1-, Ni K-, and Zr K-edge X-ray absorption spectroscopy studies, revealed that surface dispersed tungstate species were reduced by CH4 to yield CO and H2, and low-valent W species assignable to W0 to W3+. The low-valent W species were reoxidized by CO2 to produce CO and regenerate the original W6+ species. These active tungstate species cooperatively work with Ni over ZrO2 surface to promote partial CH4 oxidation, leading to efficient CL-DRM.