Chemical Looping Combustion Of Methane Research Articles

Modification of KNO3 on the reducibility and reactivity of Fe2O3‐based oxygen carriers for chemical‐looping combustion of methane

This work presented a comparative study on the Fe2O3‐based oxygen carriers modified by different potassium salts (i.e. KNO3, K3PO4, KOH, K2CO3) for chemical looping combustion of methane (CLC with methane). The effect of Al2O3 support on the reactivity of Fe2O3 was also investigated. The Fe2O3‐based oxygen carriers were prepared by a co‐precipitation method and the potassium salts were added via an incipient wetness impregnation method. The obtained oxygen carriers were characterized by XRD, XPS, H2‐TPR, and CH4‐TPR technologies. It was found that the presence of KNO3 could improve the reducibility of the Fe2O3‐based oxygen carrier in the surface, resulting in relatively high selectivity towards CO2 during the CLC with methane. The content of KNO3 also affected the reactivity of oxygen carriers, and 10 % KNO3/Fe2O3 sample showed the best activity. Moreover, it was also demonstrated that the addition of Al2O3 support into the 10 % KNO3/Fe2O3 oxygen carrier could improve its redox performance, and the stability of 10 % KNO3/Fe2O3/Al2O3 was proved to be favourable after twenty successive cycles for CLC with methane.

A cost-effective approach to reducing carbon deposition and resulting deactivation of oxygen carriers for improvement of energy efficiency and CO2 capture during methane chemical-looping combustion

The objective of this research is to investigate the effect of steam on reducing carbon deposition during CH4 chemical looping combustion (CLC) on a fixed bed reactor. Steam proved to be significantly effective not only for the fuel utilization efficiency of CLC but also for the stability of the oxygen carrier (OC). The evaluation tests were performed with CuO/γ-Al2O3 OCs prepared with three different methods. The results showed that OC prepared using co-precipitation method performed the best with the highest reactivity for CH4 combustion at low temperature (700°C) compared to that prepared using mechanical mixture and impregnation methods. It was also found that the carbon deposition was the main reason for the low combustion efficiency and the deactivation of OCs in redox cycles. For OCs at 800°C, after 10 cycles without steam, 25–44% CO2 selectivity reductions were observed, accompanied by Barrett-Joyner-Halenda (BJH) pore volume decreases of 31–47%. With the steam introduction, the CO2 selectivity consistently achieved ∼100% in 10-cycle CLC, and the pore volumes of OCs decreased by only 11–22%, which was mostly attributed to the carbon-steam gasification reaction. The OCs for CH4 CLC with and without steam were characterized by using different methods, including surface area and pore analysis, thermal gravimetric analysis (TGA), X-ray diffraction (XRD), H2 temperature programming reduction (TPR), and scanning electron microscope (SEM). The results demonstrated that steam could easily gasify the carbon deposition, greatly intensify the redox degree of OCs at 800°C, and strengthen the redistribution of Cu on the surface of Al2O3, contributing to the fine and uniform distribution of CuO. Therefore, steam can be successfully used for considerable enhancement of the overall performance of CH4 CLC.

Particulate Formation from a Copper Oxide-Based Oxygen Carrier in Chemical Looping Combustion for CO2 Capture.

Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicrometer particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm. Cyclic reduction and oxidation reactions in CLC have been determined to weaken the oxygen carrier particles, resulting in increased particulate emission rates when compared to those of oxygen carriers without redox reactions. The generation rate for particulates <10 μm was found to decrease with progressive cycles over as-prepared oxygen carrier particles and then reach a steady state. The surface of the oxygen carrier is also found to be coarsened due to a Kirkendall effect, which also explains the enrichment of Cu on particle surfaces and in small particles.

Improved reversible redox cycles on MTiOx (M = Fe, Co, Ni, and Cu) particles afforded by rapid and stable oxygen carrier capacity for use in chemical looping combustion of methane

In this study, rutile TiO2 particles (MTiOx) incorporating 3d-metals, with their electrons more than half-filled, are synthesized for use in the chemical looping combustion of methane. The specific structures are obtained by doping the M-sites with Fe, Co, Ni, and Cu (FeTiOx, CoTiOx, NiTiOx, and CuTiOx), and they have the same M/Ti molar ratio of 1.0. XRD, SEM, CH4-TPD, TGA, and BET techniques were used to characterize the prepared materials. The XRD results confirmed that all of the prepared materials possessed pure hexagonal phases in the case of Co1Ti1Ox and Ni1Ti1Ox and mixed formations composed of metal oxides and rutile TiO2 in the case of Fe1Ti1Ox and Cu1Ti1Ox. The CH4-TPD and H2-TPR analyses showed that the highest adsorption is obtained on CuTiOx, in particular on Cu1.5Ti1Ox. The oxygen carrier capacities of the samples were measured in H2 (FR)/air (AR) and CH4-CO2 (FR)/air (AR) redox systems at 850°C using TGA analysis. Their variability was shown to be associated with the different doping elements and doping concentrations. In particular, the Cu1.5Ti1Ox material in the CH4-CO2 (FR)/air (AR) redox system exhibits oxygen uncoupling behaviour, leading to improved capture and release of oxygen compared to the other materials.

Modeling of the Reduction of Hematite in the Chemical Looping Combustion of Methane using Barracuda

AbstractChemical looping combustion is a promising technology for the capture of CO2, which involves the reduction and oxidation of materials known as oxygen carriers. One particular carrier is hematite as it is readily available, relatively inexpensive, and nontoxic. We present a new particle model and reaction kinetics that can be applied to Barracuda simulations of the fuel reactor. This was performed as Barracuda does not allow for the Johnson–Mehl–Avrami (JMA) (nucleation and growth)‐type kinetics that were developed from the results of an analytical study, thermogravimetric analysis, and fixed‐bed experiments. We summarize the analytical analysis of the fixed‐bed reduction experiments conducted in a cycling fixed‐bed reactor and subsequently modeled with Barracuda computational fluid dynamics software to develop the new model. The experiments were conducted using 1000 g of hematite material. The cyclic processing began with the reduction step then proceeded to the oxidation step, and this analysis was repeated for several cycles (5–10). The effect of fuel partial pressure (8.4, 7.2, and 5 mol %) on the conversion was investigated. The JMA analysis assumed that the reactions occurred in the shell that surrounds the particle grains with the diffusion of oxygen to the grain surface from the core. In contrast, working with the particle kinetics allowed in Barracuda, the reactions occur with different hematite species (surface and core) mixed homogeneously. Therefore, it is necessary to develop a new particle model in which the rates are related to the amount of reactant (surface or core) in the particle. We present the development of such a particle model and compare the results with experimental values.

Study and analyses of a CLC oxygen carrier degradation mechanism in a fixed bed reactor

This paper deals with the study, analysis and determination of the oxygen carrier degradation in the Chemical Looping Combustion of methane with NiO/NiAl2O4 as oxygen carrier. A fixed bed reactor fed alternatively with oxygen (5% in Argon) and a mixture of methane (5%) and steam (from 0.3% to 2% in Argon) has been used with. operating temperature ranging from 700 to 850°C. Without fluidization, and with only 10 cycles of reduction/oxidation, a high degradation of the material has been observed using X-ray diffraction analysis, SEM observations and BET or PSD characterizations. It is shown that this degradation is caused by the carbon, produced by the methane cracking reaction catalyzed by reduced nickel, and deposited at the surface of the material. The contraction and expansion of the elementary particles composing the grains during the CLC reactions is also a cause of the observed degradations. These phenomena of contraction/expansion cannot be avoided, unless the reduction degree of the material is reduced during the cycles. Therefore, an increase of the operating temperature or of the feeding steam concentrations can lead to a decrease of the material degradation.

Thermodynamic analysis of a solar-hybrid trigeneration system integrated with methane chemical-looping combustion

Chemical-looping combustion (CLC) that occurs without reacting air and fuel is a promising technology for achieving CO2 capture with a low energy penalty and without additional energy consumption. This paper proposed a solar-hybrid trigeneration system based on methane CLC to produce electricity, chilled water for cooling, and hot water. CaS and CaSO4 are the cycle materials of the CLC, and the reduction reaction in the CLC is driven by solar thermal energy. The thermodynamic performances of the new CLC trigeneration system, including energy and exergy efficiencies, are analyzed and compared on the basis of design conditions and variable parameters, respectively. The results indicate that the optimal solar heat collection temperature is approximately 900°C, the pressure ratio of the air compressor is 20, and the energy and exergy efficiencies reach 67% and 55%, respectively. The output ratios of the three products vary with the solar collection temperature and pressure ratio. Meanwhile, the net SCLC-to-exergy efficiency and the saving rate of the solar collection area are expected to be 24% and 63%, respectively.

Thermodynamically consistent modeling of redox-stable perovskite oxides for thermochemical energy conversion and storage

This paper describes an approach for thermodynamically consistent modeling of perovskite redox cycles for thermochemical energy storage and chemical-looping combustion applications. Prior modeling approaches to perovskite redox processes do not provide exact closure of the energy balance or thermodynamic consistency for calculating enthalpies and exergies of multiphase solid–gas flows needed in system-level process analysis. The approach documented here implements solid species thermodynamic functions derived from the enthalpies and entropies of reactions including oxidation/reduction and additional point defect reactions. The approach is fundamentally different than the typical approach of using partial molar properties to perform process flow modeling. Coupling process flow modeling to point defect reactions captures complex trends observed for oxygen non-stoichiometry and varying specific heat capacities during reduction and oxidation, maintains thermodynamic consistency between the solid and gas phase species, and thereby enables modeling of flow conservation equations for both the solid and gas phases. The thermodynamic model is fit to reported measurements for a highly reducible perovskite, strontium-doped calcium manganite (Ca0.6Sr0.4MnO3−δ), and then demonstrated through equilibrium thermodynamic calculations in process energy and exergy balances. Energetic and exergetic analyses for Ca0.6Sr0.4MnO3−δ redox cycles are presented for thermochemical energy storage and chemical-looping combustion systems where component exergy destructions are calculated. The model predicts roundtrip thermochemical energy storage efficiencies with Ca0.6Sr0.4MnO3−δ as high as 89% and 63% by first and second law analyses, respectively. The chemical-looping combustion of methane using Ca0.6Sr0.4MnO3−δ indicates first and second law efficiencies up to 90% and 66%, respectively. The modeling approach is used to explore trends in performance with operating conditions for both redox cycles thereby enabling new insight regarding design trade-offs for these emerging energy storage and conversion cycles.

Fe‐substituted Ba‐hexaaluminates oxygen carrier for carbon dioxide capture by chemical looping combustion of methane

Fe‐substituted Ba‐hexaaluninates (BFA‐x (x = 1–3), x indicates Fe content) oxygen carrier (OC) were found to exhibit excellent sintering‐resistance under cyclic redox atmosphere at 800°C thanks to the reservations of the structure during the CH4 reduction step, thus preventing the agglomeration of particles during the subsequent reoxidation step. Lattice oxygen highly active for the total combustion of CH4 was observed in the hexaaluminate structure and its chemical state was influenced by Fe content. The highest amount of active O coordinated with Fe3+ in the mirror plane (O‐Fe3+(M)) for the total combustion was reacted (0.77 mmol/g) for BaFe3Al9O19 hexaaluminate OC. As a result, it exhibited the best reactivity with the CH4 conversion of 83% and CO2 selectivity of 100%. Moreover, superior regeneration and recyclability was also obtained, which originated from the fully recovery of O‐Fe3+(M) in the hexaaluminate structure. © 2015 American Institute of Chemical Engineers AIChE J, 62: 792–801, 2016

The Effect of Thermal Treatment of Hematite Ore for Chemical Looping Combustion of Methane

For chemical looping processes to become an economically viable technology, an inexpensive carrier that can endure repeated reduction and oxidation cycles needs to be identified or developed. Unfortunately, the reduction of hematite ore with methane in both batch and fluidized beds has revealed that the performance (methane conversion) decreases with time. Previous analysis had shown that the grains within the particle grew with the net effect of reducing the surface area of the particles and thereby reducing the rate and net conversion for a fixed reduction time. To improve the lifespan of hematite ore, it is hypothesized that if the grain size could be stabilized, then the conversion could be stabilized. In this work, series of tests were conducted in an electrically heated fluidized bed. The hematite ore was first pretreated at a temperature higher than the subsequent reduction temperatures. After pretreatment, the hematite ore was subjected to a series of cyclic reduction/oxidation experiments. The results show that the ore can be stabilized for cycles at different conditions up to the pretreatment temperature without any degradation. Details of the pretreatment process and the test results will be presented.

Bulk monolithic Ce–Zr–Fe–O/Al2O3 oxygen carriers for a fixed bed scheme of the chemical looping combustion: Reactivity of oxygen carrier

The size and geometry of oxygen carriers are one of the key factors to determine the efficiency of a large-scale chemical looping combustion (CLC) system in fixed bed reactors, because they strongly affect the dynamic conditions of the gas–solid reactions, such as the intra particle mass transfer limitation for reactants, the pressure drop and the flow distribution. In the present work, we describe for the first time the utilization of bulk monolithic oxygen carriers for chemical looping combustion of methane in a fixed bed reactor. The comparison on the structure and reactivity of the monolithic Ce–Zr–Fe–O/Al2O3 oxygen carrier with the powder one is investigated in detail. The successive CH4-reduction/air-oxidation redox testing of the monolithic oxygen carrier is also performed. It is found that the Ce–Zr–Fe–O/Al2O3 oxygen carriers own high activity for methane complete oxidation due to the strong active component (i.e., Ce–Zr–Fe–O) to support (i.e., Al2O3) interaction. The powder and monolithic oxygen carriers show similar reduction behaviors either in hydrogen or in methane atmosphere. This indicates that the utilization of organic binders and additives in the fabrication procedures of the monolith has no significant effect on the reducibility of the oxygen carrier. The monolithic oxygen carriers used in the chemical looping combustion of methane in its natural form (4.5cm long, 6.0cm in diameter, square cell size of 2.0mm, and wall thickness of 0.9mm) represent high activity in a high gas hourly space velocity (GHSV, 6000h−1). This can be attributed to the special geometric structure and layered microstructure. The activity of the monolithic oxygen carrier is also very stable in the successive redox process. On the other hand, the requirement on the mechanical strength of the monolithic oxygen carrier is much lower than that toward the pellets, which allows the oxygen carrier to have relatively high specific surface area in a large-scale CLC system. The monolith reveals very high structure stability in both macro and micro aspect during the chemical looping process.

Trimetallic Oxygen Carriers CuFeMnO4, CuFeMn2O4, and CuFe0.5Mn1.5O4 for Chemical Looping Combustion

Several trimetallic ferrites with different ratios of Cu, Fe, and Mn were synthesized by direct decomposition method and tested for chemical looping combustion of methane, synthesis gas, and carbon. For comparison, several bimetallic ferrites were also tested, and NiFe2O4 and CuFe2O4 showed the best performance. During a 55-cycle test, trimetallic CuFeMnO4 showed better overall performance than both NiFe2O4 and CuFe2O4, which had shown the best performance among the bimetallic ferrites for CLC of methane. From all the trimetallic oxygen carriers with different atomic ratios of Cu, Fe, and Mn, CuFeMnO4, CuFeMn2O4, and CuFe0.5Mn1.5O4 showed the best performance for CLC of methane. The oxygen carriers CuFeMnO4, CuFeMn2O4, and CuFe0.5Mn1.5O4, even without a support, showed very stable performance during a 100-cycle TGA test. The CuFeMnO4 oxygen carrier also showed excellent performance during a multicycle CLC test with synthesis gas. CuFeMnO4 is also suitable for CLC of a solid fuel, such as carbon, which sho...

Isotopic steam investigations of hematite (Fe2O3) for chemical looping combustion of methane

The effect of steam on the chemical looping combustion of methane over hematite (Fe2O3) is studied by the isotopic exchange method coupled with mass spectroscopy. Traditional steam was replaced with deuterium-oxide providing interesting mechanistic information not previously reported. The rapid kinetics of steam reforming were established before complete combustion reaction, and adsorption of deuterium into the iron structure was observed. Additionally, the presence of deuterium-oxide drastically reduced the combustion conversion of methane to carbon dioxide.

Fluidized-bed and fixed-bed reactor testing of methane chemical looping combustion with MgO-promoted hematite

Abstract In this study MgO-promoted Fe2O3 hematite oxygen carriers were synthesized from various Mg sources and evaluated for methane chemical looping combustion. Particles suitable for fluidized bed flow reactor studies were prepared in the lab. Cyclic CLC tests conducted in the fluidized bed with MgO promoted hematite showed better performance than that with hematite. Attrition resistance of laboratory prepared MgO promoted hematite was excellent. Reactivity and stability of the oxygen carrier materials were also tested in the thermogravimetric analyzer and bench-scale reactors. Scanning electron microscopy and energy-dispersive X-ray spectroscopy, and X-ray diffraction were used to study the morphology and elemental compositions present in the hematite and promoted hematite oxygen carriers prior to and following the multi-cycle chemical looping reaction. The incorporation of 5 wt% MgO led to an increased reaction rate and an increase in oxygen utilized as compared to the pure hematite oxygen carrier. Possible reasons for the promotion effect by MgO were evaluated. These studies reveal that the best performing oxygen carrier was the 5 wt% MgO/Fe2O3 which exhibited no observed degradation in the kinetics and conversion performance in the methane step over 15 reduction and oxidation cycles. The Mg promoted oxygen carrier also showed reduced coke formation as compared to the pure hematite carrier.

Chemical looping combustion process in fixed-bed reactors using ilmenite as oxygen carrier: Conceptual design and operation strategy

A process scheme based on fixed-bed reactors is presented as a possible alternative for carrying out the chemical looping combustion of methane at high pressure with ilmenite as oxygen carrier. The operation at high pressure permits the use of highly efficient power cycles. However, complex heat management strategies and switching valves able to function at very high temperatures are required. The continuous cyclic operation of a packed-bed chemical looping combustion process is described using a basic reactor model. A sequence of four stages: reduction, steam reforming, oxidation and heat removal ensures the production of a continuous high temperature and high pressure gas able to efficiently drive a gas turbine for power generation in combination with a steam cycle. At the same time, a concentrated stream of CO2 suitable for transport and storage is also produced. The use of suitable recycles of product gases makes it possible to control the progression of the reaction and the heat exchange fronts, which improves the heat management of the CLC process. The inclusion of steam methane reforming in the process allows the conversion of the ingoing methane to syngas, which enhances the reduction kinetics of the ilmenite and the overall combustion efficiency of the process. A preliminary conceptual design for an inlet flow of 10kg/s of methane (500MWt) has shown that a minimum of five reactors, 10m long, with an inner diameter of 6.7m, would be required to fulfil the overall process assuming cycles of 10min with maximum pressure drops per stage of less than 6%. These results demonstrate the potential of this novel technology for power generation in combination with CO2 capture.

Copper-manganese mixed oxides: CO2-selectivity, stable, and cyclic performance for chemical looping combustion of methane.

Chemical looping combustion (CLC) is a key technology for oxy-fuel combustion with inherent separation of CO2 from a flue gas, in which oxygen is derived from a solid oxygen carrier. Multi-cycle CLC performance and the product selectivity towards CO2 formation were achieved using mixed oxide of Cu and Mn (CuMn2O4) (Fd3[combining macron]m, a = b = c = 0.83 nm) as an oxygen carrier. CuMn2O4 was prepared by the co-precipitation method followed by annealing at 900 °C using copper(II) nitrate trihydrate and manganese(II) nitrate tetrahydrate as metal precursors. CuMn2O4 showed oxygen-desorption as well as reducibility at elevated temperatures under CLC conditions. The lattice of CuMn2O4 was altered significantly at higher temperature, however, it was reinstated virtually upon cooling in the presence of air. CuMn2O4 was reduced to CuMnO2, Mn3O4, and Cu2O phases at the intermediate stages, which were further reduced to metallic Cu and MnO upon the removal of reactive oxygen from their lattice. CuMn2O4 showed a remarkable activity towards methane combustion reaction at 750 °C. The reduced phase of CuMn2O4 containing Cu and MnO was readily reinstated when treated with air or oxygen at 750 °C, confirming efficient regeneration of the oxygen carrier. Neither methane combustion efficiency nor oxygen carrying capacity was altered with the increase of CLC cycles at any tested time. The average oxygen carrying capacity of CuMn2O4 was estimated to be 114 mg g(-1), which was not altered significantly with the repeated CLC cycles. Pure CO2 but no CO, which is one of the possible toxic by-products, was formed solely upon methane combustion reaction of CuMn2O4. CuMn2O4 shows potential as a practical CLC material both in terms of multi-cycle performance and product selectivity towards CO2 formation.

The Preparation Methods of Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Oxygen Carriers and their Chemical Looping Combustion Performance

60wt%Fe2O3/Al2O3 oxygen carriers were prepared by different methods and characterized by means of XRD, H2-TPR, infrared gas analyzer. The effects of preparation methods on the structure and activity of Fe2O3/Al2O3 oxygen carriers for chemical looping combustion of methane were also investigated. The factors on the selectivity of CO2 in the chemical looping combustion process at different reaction temperatures were discussed. Methane can be quickly converted to CO2 and H2O with high selectivity at 850°C for 15 min. After redox cycling in alternant methane/air atmosphere for 30 times, the formation of CO2 was enhanced, indicating higher activity of oxygen carrier after the redox experiment.

Mechanism of Methane Chemical Looping Combustion with Hematite Promoted with CeO2

Chemical looping combustion (CLC) is a promising technology for fossil fuel combustion that produces sequestration-ready CO2 stream, reducing the energy penalty of CO2 separation from flue gases. An effective oxygen carrier for CLC will readily react with the fuel gas and will be reoxidized upon contact with oxygen. This study investigated the development of a CeO2-promoted Fe2O3–hematite oxygen carrier suitable for the methane CLC process. Composition of CeO2 is between 5 and 25 wt % and is lower than what is generally used for supports in Fe2O3 carrier preparations. The incorporation of CeO2 to the natural ore hematite strongly modifies the reduction behavior in comparison to that of CeO2 and hematite alone. Temperature-programmed reaction studies revealed that the addition of even 5 wt % CeO2 enhances the reaction capacity of the Fe2O3 oxygen carrier by promoting the decomposition and partial oxidation of methane. Fixed-bed reactor data showed that the 5 wt % cerium oxides with 95 wt % iron oxide produ...

Natural Ores as Oxygen Carriers in Chemical Looping Combustion

Chemical looping combustion (CLC) is a combustion technology that utilizes oxygen from oxygen carriers (OC), such as metal oxides, instead of air to combust fuels. The use of natural minerals as oxygen carriers has advantages, such as lower cost and availability. Eight materials, based on copper or iron oxides, were selected for screening tests of CLC processes using coal and methane as fuels. Thermogravimetric experiments and bench-scale fixed-bed reactor tests were conducted to investigate the oxygen transfer capacity, reaction kinetics, and stability during cyclic reduction/oxidation reaction. Most natural minerals showed lower combustion capacity than pure CuO/Fe2O3 due to low-concentrations of active oxide species in minerals. In coal CLC, chryscolla (Cu-based), magnetite, and limonite (Fe-based) demonstrated better reaction performances than other materials. The addition of steam improved the coal CLC performance when using natural ores because of the steam gasification of coal and the subsequent reaction of gaseous fuels with active oxide species in the natural ores. In methane CLC, chryscolla, hematite, and limonite demonstrated excellent reactivity and stability in 50-cycle thermogravimetric analysis tests. Fe2O3-based ores possess greater oxygen utilization but require an activation period before achieving full performance in methane CLC. Particle agglomeration issues associated with the application of natural ores in CLC processes were also studied by scanning electron microscopy (SEM).

Synergetic effects of mixed copper–iron oxides oxygen carriers in chemical looping combustion

Chemical looping combustion (CLC) is an emerging technology for clean energy production from fuels. CLC produces sequestration-ready CO2-streams without a significant energy penalty. Development of efficient oxygen carriers is essential to successfully operate a CLC system. Copper and iron oxides are promising candidates for CLC. Copper oxide possesses high reactivity but it has issues with particle agglomeration due to its low melting point. Even though iron oxide is an inexpensive oxygen carrier it has a slower reactivity. In this study, mixed metal oxide carriers containing iron and copper oxides were evaluated for coal and methane CLC. The components of CuO and Fe2O3 were optimized to obtain good reactivity while maintaining physical and chemical stability during cyclic reactions for methane-CLC and solid-fuel CLC. Compared with single metal oxygen carriers, the optimized Cu–Fe mixed oxide oxygen carriers demonstrated high reaction rate, better combustion conversion, greater oxygen usage and improved physical stability.Thermodynamic calculations, XRD, TGA, flow reactor studies and TPR experiments suggested that there is a strong interaction between CuO and Fe2O3 contributing to a synergistic effect during CLC reactions. The amount of oxygen release of the mixed oxide carrier in the absence of a fuel was similar to that of the single metal oxides. However, in the presence of fuels, the oxygen consumption and the reaction profiles of the mixed oxide carriers were significantly better than that of the single metal oxides. The nature of the fuel not only influenced the reactivity, but also the final reduction status of the oxygen carriers during chemical looping combustion. Cu oxide of the mixed oxide was fully reduced metallic copper with both coal and methane. Fe oxide of the mixed oxide was fully reduced Fe metal with methane but it was reduced to only FeO with coal. Possible mechanisms of how the presence of CuO enhances the reduction of Fe2O3 are discussed.