Fe-based Oxygen Carrier Research Articles

Microscopic insights into the reaction mechanism of Fe-based oxygen carrier with CH4 in chemical-looping combustion

Fe-based oxygen carriers are regarded as a promising class of oxygen carriers in the field of chemical looping combustion. However, the elucidation of the detailed microscopic reaction mechanism of oxygen carriers remains a significant challenge. In this work, we combine in situ spectroscopy, density-functional theory (DFT) calculations, and micro-kinetic modelling to reveal the microscopic reaction mechanism of CH4 combustion on α-Fe2O3. The macroscopic reaction characterization of hematite with CH4 was carried out on a fixed bed, and gas chromatography (GC) was utilized to detect the combustion products (CO2, H2O and H2). Subsequently, in situ spectroscopy and DFT were combined to reveal the detailed pathways for the CH₄ oxidation process. The results indicated that the reaction intermediates evolve from methoxy (CH3O*) to the bridged bidentate formate (b-HCOO*) to the monodentate formate (m-HCOO*), which ultimately leads to the formation of CO2 through a combination of H transfer and lattice oxygen oxidation. A micro-kinetic model was developed which incorporates surface reaction with the oxygen transport. This revealed that CH3O* and CH3O* → CH2OO* are the key intermediates and radical reactions, respectively, for CO2 production. The elucidation of the reaction mechanism may prove beneficial for the future development of novel Fe-based oxygen carriers.

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.

Decarbonized core-shell-like structure: Enhancing Fe-based oxygen carriers for superior hydrogen selectivity and stability

Fe-based oxygen carriers undergo deactivation due to repeated oxidation-reduction cycles in chemical looping gasification. The primary cause of deactivation lies in the agglomeration and phase separation behavior exhibited by Fe-based oxygen carriers. In this research, a core-shell-like structure was developed to strengthen the structural stability of the oxygen carrier. This was achieved by constraining the thermal motion dimensions of active sites and establishing two pathways for oxygen ion transport. Briefly, the core-shell-like structure was constructed with NiFe2O4 as the core and CaO as the shell. Through characterization analysis, it was found that the interaction between the core-shell-like structures resulted in lattice distortion, promoting the generation of oxygen vacancies and providing a prerequisite foundation for the rapid reaction of lattice oxygen. Furthermore, the protective mechanism of the core-shell-like structure on the active sites inhibited the agglomeration behavior of the oxygen carrier. Remarkably, a hydrogen yield of 70 % was achieved at a temperature of 600 °C, and the reaction characteristics remained stable over 20 cycles of experimentation. Density functional theory calculations revealed that C atoms present stronger electron transfer at the core-shell-like structure, which induces stronger adsorption energy.

Investigations on oxygen carriers derived from natural ores or industrial solid wastes for chemical looping hydrogen generation using biomass pyrolysis gas

Chemical looping process based on multiple-step redox reactions of oxygen carriers (OCs) holds great promise for producing high purity hydrogen with inherent CO2 separation, however, there is a challenge to prepare environmental-friendly OCs with low-cost. Herein, a series of natural ores and industrial solid wastes were screened and made into Fe-based OCs for chemical looping hydrogen generation (CLHG). The results show that OCs prepared by pyrite cinder (OC-PC) feature 94.8% biomass pyrolysis gas (BPG) conversion and 94.5% CO2 concentration in OCs reduction stage. In hydrogen production stage, OC-PC achieves maximum H2 yield, 3.04 mmol g−1, which is 2∼9 times high than other OCs. The highest H2 purity is approximately 99.99%. Long term testing results indicate that OC-PC has excellent stable activity and anti-sinter ability. OCs prepared by red mud correspond to better BPG conversion (96.0%), however, the H2 yield (0.83 mmol g−1) is much lower than that of OC-PC. For OCs prepared from natural ores, they show unsatisfactory H2 production and BPG conversion compared with OC-PC. OCs prepared by ilmenite are with low specific surface area which restrains the heterogeneous reaction. The content of metal element (Mg, K, Ca) also influences the behavior of OC, which is beneficial for the fuel conversion. Moreover, the distribution of inert, anti-coking ability, oxygen vacancy also influence the sinter, H2 purity and H2 yield. Comprehensively evaluating the OCs performance, pyrite cinder is considered to be the most suitable OC raw material for CLHG.

Effect of reaction conditions on the agglomeration of the oxygen carrier in biomass chemical looping gasification

The oxygen carrier (OC) agglomeration is an important factor limiting the development of biomass chemical looping gasification (CLG) technology. However, the agglomeration behavior of OC is not clear under multiple perspectives of reaction conditions. In this study, we investigated the Fe-based OC agglomeration behavior during CLG from three perspectives of biomass species, reaction temperature and steam/biomass (S/B). The results showed that biomass with high ash and K content was easy to form more low melting point substances, causing a lower deformation temperature (DT) and more severe agglomeration of OC after CLG. Moreover, with the increase of reaction temperature from 700 °C to 900 °C, the DT of OC decreased by 6.8 %, while the average particle size and agglomeration degree of OC increased by 26.2 % and 209.5 %, respectively. Although high temperature was beneficial for improving reaction performance and shortening reaction time, the excessive temperature would cause severe agglomeration and inhibit CLG process. In addition, the higher the S/B was, the more severe the agglomeration became. With the increase of S/B from 0 to 1.8, the DT of OC decreased by 3.2 %, while the average particle size and agglomeration degree of OC increased by 28.2 % and 75.5 %, respectively. The excessive S/B would form more KOH and NaOH with lower melting point, exacerbating the OC agglomeration and inhibiting the gasification.

Interactions of Mg-Fe-Al-O oxygen carriers with rare earth dopants (Ce, Y, Sm, La, and Pr) in chemical looping steam reforming

Chemical looping steam reforming (CLSR) is a novel process for syngas and hydrogen co-production. In this work, rare earth metals (Ce, Y, Sm, La, and Pr) were doped to improve the reactivity and cyclic stability of the Fe-based oxygen carrier for CLSR. The cyclic tests indicate that the oxygen carrier doped with rare earth possesses a higher CH4 conversion rate, oxygen transport capacity, and hydrogen selectivity and yield. The crystal structure, surface morphology, and reactivity of the oxygen carrier were characterized by different analytical methods (e.g., XRD, H2-TPR, XPS, and SEM). The rare earth-doped oxygen carrier shows higher active site dispersion and smaller crystallite size owing to stronger metal-support interactions between the metallic Fe and the rare earth. XRD and SEM results revealed that the introduction of rare earth increases the oxygen transport capacity and oxygen vacancy concentration, promoting the reactivity of oxygen carriers. However, the rare earth doping reduces the CO purity, possibly because the high reactivity favors full CH4 oxidation. Among the prepared oxygen carriers, Fe10La exhibited the best performance and stability over cycles, with a high CH4 conversion rate (89.2%) and hydrogen purity (95 vol%).

Investigation on the attrition behavior and reactivity characteristic of Fe-based oxygen carriers in long-term chemical looping catalytic oxidation process

Human activities and industrial processes result in substantial methane emissions, predominantly at low concentration. This is particularly evident in coal mining where the gas concentration is notably low, posing challenges for effective utilization. Chemical looping catalytic oxidation (CLCO) is believed to be a potential approach for the disposal of ultra-low concentration methane (UCM) and the capture of CO2. Unlike pure air, which is generally used to oxidize OC in air reactor, UCM typically contains 0.1 ∼ 1 %CH4 and less than 60 ppm H2S, therefore, the introduction of UCM into the air reactor would potentially threaten oxygen carrier (OC). In this study, the evolution of OC in CLCO process was investigated in terms of reaction performance and physicochemical parameters compared to traditional chemical looping process. XRD showed that the phase compositions of OC remained stable over 300 cycles and no sulfur-containing compounds were detected. The comparison showed that CLCO process negatively affected the performance of OC, especially for attrition. The attrition behavior of OC can be summarized in three stages: fines blowing out, steady-state attrition and intense-attrition stage. The main reason for increased attrition was attributed to methane oxidation, which released a large amount of heat and would impose a heat shock on OC. Contrary to the commonly reported “L”-shape, our data showed a “U”-shaped attrition rate trend in long-term cycles. The difference was that the attrition rate would suddenly increase after a certain number of cycles, indicating that the actual service life of OC may be significantly lower than predicted.

A ternary Fe-based oxygen carrier with ZrO2-LaFeO3 as support for chemical looping hydrogen generation

Fe2O3 is usually supported by inert materials to improve the sintering resistance and redox stability in chemical looping hydrogen generation (CLHG). It is reasonable to apply inert together with perovskite as a composite support for Fe-based oxygen carrier in CLHG. In this work, the Fe2O3/ZrO2/LaFeO3 ternary oxygen carriers were synthesized, and the synergistic effects of ZrO2 and LaFeO3 on the reactivity and redox stability and the intrinsic mechanisms were investigated. The results showed that the 3LF (the mass ratio of LaFeO3 and ZrO2 was 30:10 with Fe2O3 loading at 60 wt %) demonstrated the best hydrogen generation performance with an average H2 yield of 8.3 mmol g-1 and H2 purity of over 99.5%. The LaFeO3 reacted with ZrO2 to form pyrochlore La2Zr2O7 with high melting point, which could be beneficial to the sintering resistance, though it led to the decline of the LaFeO3 quantity. All the cycled samples exhibited a core-shell structure in view of Fe element distribution, owing to the outward migration of Fe cations. The ternary Fe-based oxygen carrier 3LF displayed the most desirable performance in hindering the Fe migration, resulting in enhanced sintering resistance. Furthermore, the high oxygen vacancy concentration in the 3LF facilitated the lattice oxygen transport and hence promoted the reactivity and redox stability in CLHG.

Upcycling plastic waste into syngas by staged chemical looping gasification with modified Fe-based oxygen carriers

A novel staged approach, termed staged chemical looping gasification (SCLG) was proposed in this work, for the efficient upcycling of plastic waste into H2-rich syngas with exceptional carbon conversion reaching up to 99%. In such staged system, plastic was firstly pyrolyzed to generate hydrocarbon volatiles, followed by chemical looping reforming in the presence of oxygen carriers, and steam and air was also feed in sequence for carbon removal, syngas regulation and lattice oxygen recovery. A series of Fe-M-Al oxygen carriers (OCs, where M represents Mg, Ca, Mn, Mo, La, Ce) were synthesized and employed for SCLG of waste disposable masks. The performance and stability of these OCs were thoroughly investigated and compared in terms of H2 content and syngas production, while the physicochemical properties characterized by various techniques such as N2 isothermal adsorption-desorption, FESEM, XRD, TPO, and H2-TPR. Results showed that compared with the controlled FeAl sample, all the six modified OCs exhibited higher activity towards syngas production, due to the simultaneously enhanced both partial oxidation reactions and thermal decomposition reactions during the proposed SCLG process. However, the modifiers displayed different role for promoting gasification. Specifically, the addition of Ca significantly promoted the thermal cracking of plastic pyrolysis volatiles and lead to the deep extraction of carbon and H2, whereas the deposited carbon was further gasified into syngas in steam stage. As a result, Fe-Ca-Al showed the highest syngas yield and carbon conversion of 177.89 mmol/gOC and 99.03%, respectively. Fe-Mg-Al possessed relatively high CO selectivity, with the CO/(CO + CO2) ratio of 90.40%. The presence of MoO3 made the Fe-Mo-Al equipped with strong oxygen supply ability, leading to high content of oxygen-containing gases. Furthermore, the cycle stability of OCs was also conducted. The slight decrease in activity of Fe-Ca-Al was due to the metal sintering, whereas Fe-Mo-Al presented relatively stable syngas yield. The proposed staged chemical looping gasification with modified FeAl was demonstrated as a promising upcycling utilization of disposal plastic waste.

Hydrogen by glycerol chemical looping reforming over Fe-based oxygen carriers derived from LaNi1−xFexO3-λ perovskite

Hydrogen energy is now widely concerned as one of the new energy sources. Hydrogen production by using chemical looping steam reforming is an effective way. Fe-based oxygen carriers are widely used in chemical looping reforming for hydrogen production. However, pure Fe2O3 as the oxygen carrier has low activity and poor stability. In order to improve the activity and stability of the Fe-based oxygen carriers, the perovskite structure and the transition metal were introduced into the oxygen carriers for modification. The LaFeO3-λ oxygen carriers were subjected to B-site doping with metal Ni, Cu and Co, respectively. The effect of Ni doping content and metal species on the performance of hydrogen production were explored. The results show that, for the research of Ni doping content, the H2 selectivity of using LaNi0.1Fe0.9O3-λ is up to 91%. For 10 cycle tests of performance stability about oxygen carriers, H2 selectivity stabilizes at 90% and CO selectivity fluctuates in the range of 62%−84% using LaNi0.1Fe0.9O3-λ. On the whole LaNi0.1Fe0.9O3-λ shows higher reactivity than other types of oxygen carriers built in this research. This study provides a basis for the development of efficient oxygen carriers in the chemical looping steam reforming system.

Catalyst-enhanced autothermal chemical looping reforming: Intrinsic SMR kinetics and numerical simulation

In this work, we propose a catalyst-enhanced autothermal chemical looping reforming (CE-aCLR) to address the environmental concerns associated with toxic Ni-based oxygen carrier (OC) and the low fuel conversion related to the low reactivity of Fe-based OC. In this process, a non-toxic noble-metal-based steam methane reforming (SMR) catalyst is employed for methane conversion, while a Fe-based OC is employed for oxygen transfer between two reactors. Firstly, a commercial Rh-based SMR catalyst is studied in a micro-fixed bed reactor and its intrinsic reaction kinetics are determined. Then, a 1-D CE-aCLR model is developed based on a verified multi-scale aCLR model to facilitate analyzing commercial-scale feasibility. This model accounts for the essentials of the reactor hydrodynamics, mass and heat transfer, detailed reaction kinetics, and the influence of the solids residence time distribution in the fuel reactor. The main dimensions of a commercial CE-aCLR unit are determined and this unit is simulated using the developed model. The results demonstrate the feasibility of the novel, environmentally friendly process that enables high methane conversion using Fe-based OC within realistically sized reactors and an acceptable solid circulation rate. Moreover, sensitivity study shows that the CE-aCLR allows using OCs with low activity (potentially low cost) while maintaining high CH4 conversion.

Lattice oxygen migration of iron-based oxygen carrier during chemical looping reaction process

Chemical looping combustion relies on high performance oxygen carriers (OCs). Iron-based OCs have excellent overall properties, but the disadvantage of low reduction reactivity limits their application prospects. Clarification of oxygen transfer pathways and bulk phase properties is essential to improve oxygen transfer rates and increase the reactivity of OCs. High-resolution transmission electron microscopy, electron energy loss spectroscopy and X-ray photoelectron spectroscopy had been used to study the lattice oxygen transport properties, the Fe and O elemental contents and Fe elemental valence changes at different positions on the radial surface of Fe2O3 OC, as well as the related elemental compositions, atomic valence and surface energy distribution on the surface of the OC during the reduction process of OC. The results show that during the reduction process, the active components at different locations of the OC are simultaneously reduced and lattice oxygen is released. Both internal and external lattice oxygen are involved in the reaction. Besides, reaction interface is believed to be fixed at a OC surface. This study reveals the migration direction of the reduction interface and the mechanism of oxygen release in the bulk phase, and would provide a theoretical basis for the structural design of Fe-based OCs.

Effect of alkali metals and alkaline earth metals on promotion and agglomeration of Fe-based oxygen carrier during chemical looping gasification

Alkali metals and alkaline earth metals (AAEMs) are the most abundant trace elements in biomass, which will provide different effects of catalytic or inhibitory at different time during chemical looping gasification (CLG). However, the role of AAEMs in the catalysis or agglomeration at different time remains unclear in biomass CLG. In this study, the promotion and agglomeration effects of AAEMs on CLG performance is studied under different time and different AAEMs. The results show that K plays a major role in promoting CLG before 20 min and inhibiting CLG at 30 min. Moreover, K promotes the conversion from Fe3+ to Fe2+ and the earlier existence of more FeAl2O4 and Fe2Al4Si5O18, causing obvious agglomeration. Na and Mg provide obvious catalytic and promotional effects after the excitation. Further, more FeO is converted from Fe3+ at 3–8 min in Na-AH, leading to the earlier formation of Fe2Al4Si5O18 and agglomeration between particles. Ca obviously promotes the whole CLG process. Furthermore, Ca helps to promote the conversion of Fe2O3 to Fe3O4, but delay the conversion to FeO and a slower generation of FeAl2O4, resulting in less adhesion and obvious inhibition of agglomeration. Mg slightly slows down the conversion of Fe2O3 to Fe3O4, but earlier generates FeO with a lower strength than other samples, leading to low FeAl2O4 and slight agglomeration. In addition, the effect of Mg on reducing agglomeration is weaker than that of Ca, but better than that of K and Na.

Particle-resolved simulation of Fe-based oxygen carrier in chemical looping hydrogen generation

Oxygen carrier capability plays an important role in the performance of chemical looping hydrogen generation (CLHG). In this work, particle-scale simulation of oxygen carriers during the CLHG process is carried out, where the coke deposition effect on pore structures is taken into consideration. Meanwhile, the impacts of porosity and active component distribution of oxygen carriers on the CLHG performance are also analyzed. The results demonstrate that the CLHG performance is sensitive to particle porosity and active component distribution, especially for fuel reactor (FR). The increase of particle porosity can promote the carbon formation rate and hydrogen production rate. The flow direction and the diffusion will lead to the discrepancy of temperature between Egg-shell and Egg-yolk particles.

Fe-based oxygen carrier for the chemical looping combustion of CO, H2, and CH4 syngas in fluidized bed reactor under interruption of H2S

Chemical looping combustion (CLC) reduces the CO2 capturing cost, elevates combustion efficiency, and prevents NOx formation. This study applied Fe2O3/SiO2 and Fe2O3/Al2O3 oxygen carriers to react with H2, CO and CH4 under different operating setup and examined the interference of H2S. Examination was also conducted on the reaction kinetics, cycle test, and characterization of oxygen carriers. Reduction of oxygen carrier from Fe2O3 to between FeO and Fe occurred during the reaction. The higher syngas concentration led to higher diffusion capacity and promoted utilization of oxygen carriers. Carbon deposition was enhanced by excess concentration of CO and CH4. Involvement of H2S led to declining of performance due to the presence of carbonyl sulfide (COS) and FeS. With Fe2O3/SiO2, application of multiple redox cycles reduced the utilization value to 43 % due to formation of Fe2SiO4. Analysis of exhausted gas after reaction was applied in study of proposed reaction mechanism. Study of reaction kinetics using Type I deactivation test indicated a well fitted result with experimental data with R2 in the range of 0.9605–0.9976. Thus, compared to other studies with discussion only on CO, H2, or CH4 in CLC, this study offered a comprehensive research on interruption of H2S, characterization, and reaction kinetics.

Surface reaction mechanisms of CO with Fe-based oxygen carrier supported by CaO and K2CO3 in chemical looping combustion: Case study

The density functional theory was used to explore the CO adsorption mechanisms of pure and CaO (100)- and K2CO3 (001) -supported Fe2O3 clusters. The supporting carriers, CaO (100) and K2CO3 (001), had a strong bond with the Fe2O3 cluster and the binding energies were −3.50 eV and −5.54 eV, respectively. The interaction between the Fe2O3 cluster and supporting carriers lengthened the chemical bonds of the cluster. Compared with the pure and K2CO3-supported Fe2O3 clusters, the adsorption performance of the CaO-supported Fe2O3 cluster was improved, and the adsorption energies at the three adsorption sites were greater than 1 eV. The Fe2O3 cluster was activated by CaO and K2CO3, which extended and weakened the bonds, causing the bonds to easily break. Furthermore, CO was adsorbed on the Fe2O3 cluster surface as carbonates. Therefore, the atoms on the Fe2O3 cluster surface required less energy to overcome the potential migration resistance and traveled shorter distances to form new chemical bonds with CO.

Interaction behavior of sand-diluted and mixed Fe-based oxygen carriers with potassium salts

Oxygen carriers, in the form of metal oxide particles, are bed materials that transport oxygen in solid form in fluidized bed applications, such as in chemical-looping applications. In biofuel applications, it is well known that alkali from the fuel ash can react with the bed material and cause, among other operation issues, agglomeration. When using oxygen carriers in a fluidized bed, it is likely that the bed material is either a mixture of different metal oxide materials or partly diluted with sand. This is to improve or combine the chemical properties of the materials used or simply for economic reasons.This work investigates how three potassium salts K2CO3, K2SO4 and KH2PO4 interact with the oxygen carriers: Steel converter slag (LD slag), ilmenite, mixtures of the two and each carrier diluted with silica sand. The salts were used as model compounds that can occur in biofuel ash. The set-up used was a fixed bed where a small sample of bed material is mixed with a potassium salt equivalent to 4 wt-% of potassium. The mixture was then exposed to reducing (H2 in steam) conditions at 900 °C during several hours in a tubular furnace. This provides a worst-case scenario for solid–solid interaction in a fluidized bed. If a solid–solid reaction does not take place in this setup, it will most likely never occur in a fluidized bed.When LD slag and ilmenite were combined, the potassium from the salts would prefer to accumulate in the ilmenite rather than the LD slag. Ca from LD slag interacted with KH2PO4 resulting in a less severe agglomeration than when ilmenite was used separately with the same salt. When the oxygen carriers were diluted with silica sand, potassium salt interaction resulted in agglomeration for both the oxygen carriers with all potassium salts. K2CO3 and K2SO4 formed potassium silicates, while KH2PO4 formed a phosphorus-containing melt. When LD slag was present, phosphorus was located in a K-Ca-P phase that was not present if ilmenite was present.

Research Progress and Perspectives of Solid Fuels Chemical Looping Reaction with Fe-Based Oxygen Carriers

Research Progress and Perspectives of Solid Fuels Chemical Looping Reaction with Fe-Based Oxygen Carriers

Thermochemical syngas generation via solid looping process: An experimental demonstration using Fe-based material

Chemical looping is investigated for the production of syngas via reforming or reverse water gas shift in a packed bed reactor using 500 g of Fe on Al2O3 was demonstrated. Oxidation, reduction of the OC and subsequent catalytic reactions of reforming or reverse water gas shift were examined in a temperature range of 600–900 °C and a pressure range of 1–3 bara at high flowrate. Different inlet gas compositions were explored for the considered gas–solid and catalytic reaction stages. Oxidation with air successfully heated the reactor. CH4 resulted ineffective at reducing the Fe-based oxygen carrier while H2 and CO-rich stream were able to achieve full reduction to FeO of the material. In terms of catalytic activity, the maximum conversion of CH4 achieved during the reforming was limited to 62.8 % at 900 °C and 1 bara.Thermally integrated chemical looping reverse water gas shift was studied as option for CCU in combination with green H2 to produce renewable fuels. A H2/CO value of 2 could be achieved by feeding H2/CO2 of 2. The pressure did not substantially affect the conversion and the bed did not present carbon deposition.The ability of a Fe-based packed bed chemical looping reactor to recover after the carbon deposition was also explored. It was found that using a mixture of CH4 and CO2 achieved 92% recovery of the original capacity.

Mechanism of solid state diffusion on the performance evolution of iron-based oxygen carrier at different operating conditions for chemical looping process

In the oxidation half cycle of chemical looping, the outward diffusion of Fe cations occurred for Fe-based oxygen carriers. The focus of this study is to investigate into the influence of operating conditions on Fe segregation, and then reveal the role of operating conditions in performance evolution of Fe2O3/Al2O3 in the presence of solid state diffusion. The chemical looping cycles were performed at different operating conditions (temperature, oxygen concentration, reduction degree of oxygen carrier). This work evaluated the performance evolution of Fe2O3/Al2O3 in redox cycles and indicated that the generally accepted theory of particle sintering deactivation in gas–solid reactions was incomplete, which ignored the solid state diffusion in oxygen carrier particles. Contrary to the traditional view, the effect of reaction temperature on the performance evolution of oxygen carrier is conditional, depending on the dominating mechanism of solid state diffusion in redox cycles. The results of the experiment confirmed that the surface enrichment of active components enabled more active components to participate in gas–solid reactions on the surface of material particles, which leaded to a higher deactivation rate at low temperature: 700 °C (68.33 %) > 800 °C (54.41 %) > 900 °C (29.73 %). Reducing the oxygen concentration in oxidation half cycle and reduction degree can effectively inhibit the solid state diffusion of Fe2O3/Al2O3. When the oxygen concentration is reduced to 1 %, the Fe2O3/Al2O3 has the lowest deactivation rate, which is only 9.92 %. This study provided more experimental and theoretical results for better understanding the performance evolution of iron-based oxygen carriers.