Chemical looping glycerol reforming for hydrogen production by Ni@ZrO2 nanocomposite oxygen carriers

The research describes the synthesis of nanocomposite Ni@ZrO₂ oxygen carriers (OCs) and lanthanide doping effect on maintaining the platelet-structure of the nanocomposite OCs. The prepared OCs were tested in chemical looping reforming of glycerol (CLR) process and sorption enhanced chemical looping reforming of glycerol (SE-CLR) process. A series of characterization techniques including N₂ adsorption-desorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), high resolution transmission electron microscopy (HRTEM), H₂ temperature-programmed reduction (H₂-TPR), H₂ pulse chemisorption and O₂ temperature-programmed desorption (O₂-TPD) were used to investigate the physical properties of the fresh and used OCs. The results show that the platelet-stack structure of nanocomposite OCs could significantly improve the metal support interaction (MSI), thus enhancing the sintering resistance. The effect of lanthanide promotion on maintaining this platelet-stack structure increased with the lanthanide radius, namely, La³⁺ > Ce³⁺ > Pr³⁺ > Yb³⁺. Additionally, the oxygen mobility was also enhanced because of the coordination of oxygen transfer channel size by doping small radius lanthanide ions. The CeNi@ZrO₂ showed a moderate ‘dead time’ of 220 s, a high H₂ selectivity of 94% and a nearly complete glycerol conversion throughout a 50-cycle CLR test. In a 50-cycle SE-CLR stability test, the CeNi@ZrO₂CaO showed high H₂ purity of 96.3%, and an average CaCO₃ decomposition percentage of 53% without external heating was achieved.     

Synergistic effects of binary oxygen carriers during chemical looping hydrogen production

The use of binary oxygen carrier allows for the materials of enhanced activity or stability during chemical looping process. However, the lack of mechanical understanding of the origin of the improvements hindered the rational design and control of the doping process in the oxygen carrier production. Here, we synthesized a series of M_0.6Fe_2.4O_y (M = Ni, Cu, Co, Mn) binary spinel materials and carried out various characterization techniques to study how the dopants influenced the material phase change, the oxygen transfer as well as the chemical looping performance. The results showed the chemical looping reactivity can be related to the oxygen transformation between lattice oxygen and oxygen vacancy, which was determined by the redox properties of both dopants and iron. The metal in tetrahedral site for Cu, Mn, Ni-doped sample were relatively stable, limiting oxygen transformation ability. In comparison, Co dopant promoted the reducibility of iron in tetrahedral site as well as metals in other sites, making almost all lattice oxygen rapidly transformed to oxygen vacancy during reduction. This was the main cause for the subsequent high hydrogen production rate (average ∼0.02 mmol. g⁻¹.s⁻¹) and yield (∼15.9 mmol.g⁻¹). Upon cycling, the phase separation of single oxides from Co_0.6Fe_2.4O_y and Mn_0.6Fe_2.4O_y spinels led to the decreased ability of oxygen transformation. However, the performance was extremely stable for Cu_0.6Fe_2.4O_y with reversible phase change between spinel and (Fe, Cu) wusitite by the Cu-Fe interaction. Based on the current results, this work points to a promising Cu-Co co-doping material with both good reactivity and stability.     

Double perovskite (La2-xCa-Bax)NiO4 oxygen carriers for chemical looping reforming applications

Double perovskites La_2-xNiO_4-δ doped with Ca and Ba were synthesized via microwave-assisted combustion method and studied as an alternative oxygen carrier (OC) for chemical looping reforming processes (CLR). The OCs, La₂NiO₄, La_1.8Ca_0.2NiO₄, La_1.8Ba_0.2NiO₄ and La_1.8Ca_0.1Ba_0.1NiO₄ were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed reduction and oxidation (TPR/TPO) and cyclic thermogravimetric analysis (TGA). Rietveld's refinement, performed after each redox cycle, confirmed that doping allows smaller amounts of nickel to migrate from the perovskite structure. The double perovskites synthesized for the chemical looping reforming process behave as simple nickel oxide and are considered as alternative oxygen carriers to solve the problems of deactivation due to the interaction of NiO with the support. The Ca-doped OC (La_1.8Ca_0.2NiO₄) showed lower NiO concentration outside the structure and smaller crystallite size after the redox cycles, which was associated with a change in the crystal structure, presenting superior performance and stability. The results show that all perovskites have high reactivity in both reduction and oxidation reactions, however the perovskites were not able to uncouple oxygen, which is an unsual behavior for perovskites.     

Hydrogen-rich syngas production by chemical looping steam reforming of acetic acid as bio-oil model compound over Fe-doped LaNiO3 oxygen carriers

Ni-based perovskites are promising oxygen carriers for chemical looping steam reforming to produce H₂-rich gas from organics. In this study, a series of Fe-doped LaNiO₃ perovskites with various Ni/Fe ratios (LaNi_xFe_1-xO₃ (0 ≤ x ≤ 1)) were investigated for chemical looping steam reforming of acetic acid as a model compounds of bio-oil. Results illustrated that although LaNiO₃ showed higher activity for gas production, the Ni–Fe bimetallic perovskites were more stable during the steam reforming reactions. It was found that Fe doping can promote the content of lattice oxygen in the perovskite which could be released during the steam reforming reaction, thus coking resistant of the perovskite was effectively improved. Among the LaNi_xFe_1-xO₃ (0 ≤ x ≤ 1) perovskites, LaNi_0.8Fe_0.2O₃ exhibited the best synergistic effect between Ni and Fe to achieve the highest H₂/CO for H₂-rich gas production. Operational variables of the steam reforming reactions catalyzed by LaNi_0.8Fe_0.2O₃ for H₂ production were further optimized.     

Thermodynamic screening of suitable oxygen carriers for a three reactor chemical looping reforming system

Hydrogen (H₂) production by using a three reactor chemical looping reforming (TRCLR) technology is an innovative process which utilizes fossil fuels as feed stocks. This process occurs in three steps by employing an oxygen carrier (OC), which is generally a transition metal. As the OC plays an important role, its selection should be done after carefully considering the chemical and physical properties of the material. In this study, various candidate materials for use in a TRCLR process, with methane (CH₄) as a fuel stock, were investigated. The results show that the iron (Fe)- and molybdenum (Mo)-based OCs oxidize CH₄ completely in the FR at low temperatures. In terms of H₂ yield, tungsten (W)-based OCs produce the highest yield, ～3.9 mol-H₂/mol-CH₄. The equilibrium oxygen partial pressures and the solid circulation rates are the highest for Fe-based OCs. The oxygen carrying capacity of Fe-based OCs is relatively high while its price is low. Therefore, among the OCs investigated, Fe-based OCs were identified as the preferred OC option for a TRCLR process.     

Nickel-iron modified natural ore oxygen carriers for chemical looping steam methane reforming to produce hydrogen

Chemical looping steam methane reforming (CL-SMR) is a promising and efficient method to produce hydrogen and syngas. However, oxygen carrier (OC) prepared by synthesis are complex, expensive and poor mechanical performance, while natural ore OCs are low activity and poor selectivity. In order to avoid these problems, Ni/Fe modification of natural ores were proposed to improve the reactivity and stability of OC to CL-SMR. The results indicated that the modified calcite recombined and improved the structural phase during the reaction, enhancing performance and inhibiting agglomeration. Moreover, high ratio of iron to nickel was easy to sinter and decline the OC performance. In addition, with the increase of steam flow, both CH₄ conversion and carbon deposition decreased. Thereinto, the highest H₂ concentration, CH₄ conversion efficiency and H₂ yield were obtained when the ratio of steam to OC was 0.05. Furthermore, CH₄ flow rate had a great impact on CL-SMR performance. When the ratio of CH₄ to OC was 0.04, it achieved the highest CH₄ conversion efficiency of 98.96%, the highest H₂ concentration of 98.83% and the lowest carbon deposition of 3.23%. However, the carbon deposition increased with the increase of CH₄ flow rate. After a long-time chemical looping process, the Ni/Fe modified calcite showed a consistently stable performance with average H₂ concentration of 93.08%, CH₄ conversion efficiency of 88.03%, and carbon deposition of 2.15%.     

Experimental investigation of improved calcium-based CO2 sorbent and Co3O4/SiO2 oxygen carrier for clean production of hydrogen in sorption-enhanced chemical looping reforming

In this study, highly pure hydrogen is produced in sorption enhanced chemical looping steam methane reforming (SE-CLSMR) using cobalt-based oxygen carrier (OC) and cerium promoted CaO-based sorbent. In addition, the CO₂ removal from a gas stream at high temperatures is investigated via calcium looping process prior to SE-CLSMR process. The prepared samples are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and energy dispersive X-ray spectroscopy (EDX) techniques. The effect of Ca/Ce molar ratio (100/0.00–0.91/0.09), sorption temperature (550–650 °C) and sorbent lifetime are studied to find the optimal sorbent. The characterization results show the uniform and orderly CeO₂ dispersed sorbent nanoparticles that notably improved the sorbent morphology compared with blank CaO. The sorption results revealed the negative effect of temperature on CO₂ uptake of all the samples. In addition, the CO₂ sorption evaluations indicate that the molar ratio of cerium to calcium plays a significant role in the stability of sorbent and improved the CO₂ sorption capacity significantly. The high CO₂ removal efficiency in the cerium modified sorbents could be due to decrease in diffusion resistance of CO₂ through the sorbent structure during the carbonation reaction. Furthermore, results show that the addition of cerium to the sorbent structure, effectively improves the thermal resistance of synthesis sorbents. The SE-CLSMR results showed that the H₂ purity could be increased up to about 95% considering Co₃O₄/SiO₂ oxygen carrier and cerium promoted calcium-based sorbent at relatively low temperature of 550 °C, which is comparable with 84% in CLR process.     

Chemical looping reforming of ethanol-containing organic wastewater for high ratio H2/CO syngas with iron-based oxygen carrier

This work focused on chemical looping reforming (CLR) of ethanol-containing wastewater using iron-based oxygen carrier for high ratio H₂/CO syngas. Effects of various operating parameters on CLR experiments have been investigated. High temperature promotes the reactivity of oxygen carrier and release more lattice oxygen for CLR of ethanol-containing wastewater to realize maximum carbon conversion. 5% ethanol-containing wastewater, closed to the actual concentration of alcohol distillery wastewater, favors syngas yield. Ethanol-containing wastewater CLR processes could be divided into three stages, including the catalytic cracking, combination of catalytic cracking and reforming, and mainly catalytic reforming of ethanol, corresponding to three reduction periods Fe₂O₃ → Fe₃O₄, Fe₃O₄ → Fe₂O_2.45, and Fe₂O_2.45 → FeO, respectively. The whole process of ethanol-containing organic wastewater CLR is exothermic. Reaction heat released from the oxidation process of the reduced oxygen carrier can meet heat demand for CLR process. Ethanol-containing organic wastewater CLR opens up a new direction for hydrogen generation and waste treatment.     

Evaluation of redox activity of brownmillerite-structured Ca2Fe2O5 oxygen carrier for chemical looping applications

The brownmillerite-structured Ca₂Fe₂O₅ oxygen carrier has shown its great potential in chemical looping processes, due to it can be completed regeneration in a H₂O or CO₂ atmosphere without the air reactor. However, the low reaction reactivity of Ca₂Fe₂O₅ restricts its application. In this study, Ca₂Fe₂O₅ oxygen carrier was prepared by sol-gel method. The reduction and oxidation kinetics of Ca₂Fe₂O₅ were evaluated in H₂ and CO₂ atmospheres, respectively. The reduction of Ca₂Fe₂O₅ in H₂ atmosphere in good agreement with the random nucleation and growth model with E_a and A of 53.82 kJ/mol and 2.65 s⁻¹, respectively. The dimension of the model increases with conversion (A1.5 → A2 → A3 → A4). The oxidation of reduced Ca₂Fe₂O₅ in CO₂ atmosphere can be described by the zero-order contraction model with E_a and A of 11.66 kJ/mol and 0.05 s⁻¹, respectively. The kinetics analysis showed that both the reduction of H₂ and the oxidation of CO₂ are one-step reactions, as evidenced by the fact that only Fe⁰ and Fe³⁺ phases were detected in semi-in situ XRD analysis. It was inferred that the release and recovery of lattice oxygen is from inside to outside for Ca₂Fe₂O₅ oxygen carrier in the redox process. By reducing the migration energy barrier of lattice oxygen between bulk and surface would be an effective means to improve the reactivity of Ca₂Fe₂O₅ oxygen carriers.     

Reactivity of Co-doped Ca2Fe2O5 brownmillerite oxides as oxygen carriers for microalgae chemical looping gasification

Chemical looping gasification (CLG) is a promising technology to covert solid fuel into synthesis gas efficiently, and oxygen carrier is crucial for CLG. In this work, Co-doped Ca₂Fe₂O₅ brownmillerite oxides were synthesized, and its reactivity as oxygen carriers for microalgae CLG was investigated. The results showed that the Cobalt substitution for Fe improved the activity of oxygen carriers, but excess Cobalt tended to complete oxidation. XPS analysis, thermogravimetric and fixed bed tests indicated that Cobalt doping enhanced the activity of Fe cations in brownmillerite structure, and Ca₂Fe_1.8Co_0.2O₅ was proved to be most suitable for microalgae CLG with the highest H₂ yield. In the initial 10 redox cycles, gasification performance with Ca₂Fe_1.8Co_0.2O₅ oxygen carrier almost kept stable, and the gasification efficiency and carbon conversion respectively dropped by 3.96% and 2.34%, although impurity phase of spinel oxide and agglomeration was detected. In summary, Ca₂Fe_1.8Co_0.2O₅ kept great activity and acceptable stability for synthesis gas production through microalgae CLG.     

Interaction of coal ashes with potassium-decorated Fe2O3/Al2O3 oxygen carrier in coal-direct chemical looping hydrogen generation (CLHG)

Coal-direct CLHG is a novel hydrogen production technology with inherent CO₂ capture. Potassium-decorated Fe₂O₃/Al₂O₃ oxygen carrier (OC) has been proved to be a potential OC for the technology. However, the ash in the coal could influence the OC performance. In this work, the effect of ash addition on the reactivity, the morphology structure and phase composition of OC, and the potassium migration in the reduction stage were investigated. Furthermore, the effect of OC on the ash fusion temperature was discussed. Results indicated that the OC reactivity had no significant change when SM (Shenmu) ash addition was less than 1% in the reduction stage and decreased when the addition was more than 2%. In the steam oxidation stage, the H₂ yield varied between 5.80–5.57 mmol/g when the SM ash addition was less than 10% and decreased to 4.31 mmol/g when the addition was 40%. FeO could react with SiO₂ deriving from coal ash to form Fe₂SiO₄, which could cause the loss of Fe and the OC sintering; K₂CO₃ could react with silicon-aluminum minerals which could cause the potassium loss. The ash with high CaO content had a less negative effect on the OC reactivity. With the increase of SM ash addition, the potassium in OC decreased, the potassium in char increased and the volatile potassium decreased after the reduction stage. After the OC addition, the deformation temperature decreased from 1242 °C to 1114 °C in the weak reduction atmosphere while increased from 1162 °C to 1300 °C in the air atmosphere.     

Hydrogen production by chemical-looping reforming in a circulating fluidized bed reactor using Ni-based oxygen carriers

This work presents the experimental results obtained during auto-thermal chemical-looping reforming (CLR) in a 900 W_th circulating fluidized bed reactor under continuous operation using methane as fuel. Two oxygen carriers based on NiO and supported on γ-Al₂O₃ and α-Al₂O₃ were used during more than 50 h of operation with each oxygen carrier. During operation the effect of different operating variables, like fuel reactor temperature, H₂O/CH₄ molar ratio and solid circulation rate, on CH₄ conversion and gas product distribution was analyzed. It was found that in all operating conditions CH₄ conversion was very high (>98%) and the most important variable affecting to the gas product distribution was the solid circulation rate, that is, NiO/CH₄ molar ratio. Similar gas product distribution was obtained working with both oxygen carriers although at different NiO/CH₄ molar ratios. The oxygen carrier of NiO on α-Al₂O₃ needed lower NiO/CH₄ molar ratio to reach the same gas product composition than the oxygen carrier of NiO on γ-Al₂O₃. Working at optimal operating conditions, 2.5 moles of H₂ per mol of CH₄ could be obtained in this process.During operation the oxygen carrier particles maintained their physical and chemical properties. These results suggest that these oxygen carriers could have a high durability, being suitable oxygen carriers for a CLR system.     

Thermodynamic investigation on hydrogen production via self-sufficient chemical looping reforming of glycerol (CLRG) using metal oxide oxygen carriers

The self-sufficient chemical looping reforming of glycerol (CLRG) utilizes the same basic principles as chemical looping combustion (CLC), the main difference being that the desired product in CLRG is not heat but H₂. Therefore, in the CLR process the O/C ratio is kept low to prevent the complete oxidation of glycerol to H₂O. A systematic thermodynamic study of CLRG using metal oxide oxygen carriers (NiO, CuO, CoO, Co₃O₄, Mn₃O₄, Mn₂O₃ and Fe₂O₃) is performed to analyze the product yield, carbon deposition and energy requirements at different temperatures and pressures. The calculation results show higher temperatures promote, but higher pressures inhibit H₂ production. Favorable conditions (800 °C and 1 atm) are obtained for H₂ manufacture from CLRG process. CuO is the best performing oxygen carrier followed by Mn-based oxygen carriers, while Fe₂O₃ is the least preferred oxygen carrier for CLRG. These results obtained in this theoretical study can offer helpful information for CLRG experimental tests.     

Chemical looping combustion of Victorian brown coal using NiO oxygen carrier

This study is part of a program assessing the suitability of chemical looping for direct combustion of Victorian brown coal. The performance of NiO as an oxygen carrier in presence of a dried Victorian brown coal was assessed during five alternating cycles of reduction and oxidation in a CO₂ environment using a TGA. The experiments indicate a 4.4-7.5% weight loss of the oxygen carrier per cycle. Preliminary SEM-EDX and FACTSAGE predictions also indicate weight loss, but not to the same extent. The percentage of combustion of coal achieved at the 5th cycle was approximately 67%. Cycle 2 showed maximum reactivity (during reduction) with a decreasing trend during the subsequent cycles. These initial experiments did not reveal much agglomeration between ash and NiO although longer duration experiments are required to explore this issue further.     

Techno-economic assessment of a chemical looping reforming combined cycle plant with iron and tungsten based oxygen carriers

Chemical looping reforming (CLR) is an efficient technology that transforms hydrocarbons into hydrogen (H₂) and carbon dioxide (CO₂) with the use of an oxygen carrier. The three-reactor CLR (TRCLR) uses natural gas as fuel similar to a conventional steam-methane reforming (SMR) process. In the current study, two of the most suitable oxygen carriers with base metals iron (Fe) and tungsten (W) are investigated. The model of the CLR unit integrated with a combined cycle power plant is developed using Aspen Plus. The results show that the W-based TRCLR plants are 4 %-points more efficient in terms of H₂ production efficiency. In terms of electrical efficiency, the Fe-based TRCLR plant produces excess power at an efficiency of 1.6% whereas the W-based plant requires 3% of extra power from the grid. As a result, the Fe-based plant is 2.6 %-points more efficient than the W-based plant in terms of global efficiency. The costs of H₂ production for the Fe and W-based plants are estimated to be $1.66/kg and $16.92/kg, respectively. Compared to the SMR process, the cost of H₂ production from the Fe-based TRCLR plant is about 31% lower.     

The use of ferrites as highly active oxygen storage materials for chemical looping hydrogen production under intermediate temperature

Shifting chemical looping from high temperatures to intermediate temperatures could mitigate the materials from sintering and benefit for longer durability as well as process economy. However, oxygen carriers cannot perform sufficiently due to the degrading effect at lower temperatures, resulting in the decrease of hydrogen production ability. Although doping precious metals can improve the poor performance at intermediate temperatures, the high cost impeded their large-scale application. In this paper, a range of oxygen carrier materials consisted of earth abundant elements were prepared for chemical looping hydrogen production. The results indicated that CoFe₂O₄ exhibited the highest hydrogen yield of 11.9 mmol·g⁻¹ and hydrogen production rate of 0.051 mmol g⁻¹·s⁻¹ at 650 °C, which was 1.7 times higher than that of Fe₂O₃. A combined experimental and DFT calculation method was used to understand the mechanism behind the performance. The results indicated that the synergistic effect between Co and Fe increased the reactivity of the ferrite materials. The enhanced hydrogen production performance was attributed to the high reduction degree and reversible phase change. This study can be also extended to develop more active oxygen carrier for chemical looping processes at intermediate temperatures.     

Using chemical looping gasification with Fe2O3/Al2O3 oxygen carrier to produce syngas (H2+CO) from rice straw

The chemical looping gasification of rice straw using Fe₂O₃/Al₂O₃ as oxygen carrier was studied at reaction time of 5–25 min, steam-to-biomass (S/B) ratio of 2.0–4.8, reaction temperature of 750–950 °C, and oxygen carrier-to-biomass of 1.0. The gasification can be regarded completed in 20-min reaction. There exist an optimal S/B ratio of 2.8 and reaction temperature of 900 °C leading to maximum performances yielded are 1.22 Nm³/kg gas yield at 54.6% H₂+24.2% CO. The studied Fe₂O₃ oxygen carrier/rice straw is a feasible platform for syngas production from an agricultural waste.     

Advances in the application of active metal-based sorbents and oxygen carriers in chemical looping biomass steam gasification for H2 production

Active metal-based materials (AMMs) as CO₂ sorbents or oxygen carriers (OCs) have been investigated to enhance hydrogen production during various biomass-based chemical looping processes. CaO-based sorbents and Fe-based OCs are widely used in this field; therefore, these two types of materials will be the focus of this review. CaO-based sorbents can promote the water-gas shift reaction towards H₂ generation with in-situ CO₂ removal. OCs partly oxidise biomass, releasing CO – a reactant in the water-gas shift reaction. The use of Fe-based OCs boosts H₂ yield via iron-steam reactions. AMMs possess catalytic activity for tar cracking, generating more H₂. However, these AMMs suffer from sintering over cycles, which hinders their utilisation at industrial scales. The addition of support materials aims to overcome this issue. This review first assesses the impacts of CaO sorbents and OCs on H₂ production, and then examines the material behaviour, cyclic performance and applications in biomass-based chemical looping processes. The mechanism of support materials as a reactivity enhancer and sintering inhibitor is proposed in the review. The effects of operating conditions on H₂ yield are summarised and provided in the Supplementary materials.     

Hydrogen production via chemical looping steam reforming of ethanol by Ni-based oxygen carriers supported on CeO2 and La2O3 promoted Al2O3

This work studies the effects of Ce⁴⁺ and/or La³⁺ on NiO/Al₂O₃ oxygen carrier (OC) on chemical looping steam reforming of ethanol for hydrogen production - alternating between fuel feed step (FFS) and air feed step (AFS). Suitable amount of Ce- and La-doping increases OC carbon tolerance. The solubility limit is found at 50 mol% La in solid solution. At higher La-doping, La₂O₃ disperses on the surface and adsorbs CO₂ forming La₂O₂CO₃ during FFS. From the 1st cycle, 12.5 wt%Ni/7 wt%La₂O₃-3wt%CeO₂–Al₂O₃ (N/7LCA) displays the highest averaged H₂ yield (3.2 mol/mol ethanol) with 87% ethanol conversion. However, after the 5th cycle, 12.5 wt%Ni/3 wt%La₂O₃-7wt%CeO₂–Al₂O₃ (N/3LCA) exhibits more stability and presents the highest ethanol conversion (88%) and H₂ yield (2.7 mol/mol ethanol). Amorphous coke on the OCs decreases with increasing La³⁺ content and can be removed at 500 °C during AFS; nevertheless, fibrous coke and La₂O₂CO₃ cannot be eliminated. Therefore, after multiple redox cycles, highly La-doped OCs exhibits rather low stability.     

铁钴修饰镍基复合载氧体化学链重整制氢研究

采用浸渍法制备Fe₂O₃-NiO-CeO₂/γ-Al₂O₃和CoO-NiO-CeO₂/γ-Al₂O₃复合载氧体,研究了不同复合载氧体对化学链重整制氢反应性能的影响。固定床活性测试实验表明,在镍铈载氧体中加入质量分数为5%的Fe₂O₃复合载氧体(5%Fe-Ni-Ce)的H₂选择性和H₂体积分数最大;在镍铈载氧体中加入CoO后,其复合载氧体的反应性能下降。循环实验表明,5%Fe-Ni-Ce复合载氧体在经过20次循环后仍保持高活性。X射线衍射(XRD)结果表明,5%Fe-Ni-Ce复合载氧体中有固溶体形成,进一步的XRD分析发现5%Fe-Ni-Ce晶粒粒径较小。扫描电子显微镜分析发现,反应前5%Fe-Ni-Ce复合载氧体的颗粒分散度最优,在经过20次循环后复合载氧体仍能保持较好的形貌。进一步的固定床实验研究表明,5%Fe-Ni-Ce...