Oxygen Carrier For Chemical Looping Combustion Research Articles

Ilmenite with addition of NiO as oxygen carrier for chemical-looping combustion

The naturally occurring mineral ilmenite, FeTiO 3, has been examined as oxygen carrier for chemical-looping combustion. NiO-based particles have been used as an additive, in order to examine if it is possible to utilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactive combustion intermediates such as CO and H 2. Firstly, ilmenite was examined by oxidation and reduction experiments in a batch fluidized-bed reactor. These experiments indicated moderate reactivity between ilmenite and CH 4, which was used as reducing gas. However, adding 5 wt.% of NiO-based particles to the ilmenite improved the conversion of CH 4 greatly, resulting in an increase in combustion efficiency with a factor of 3. Secondly, 83 h of chemical-looping combustion experiments were conducted in a small circulating fluidized-bed reactor, using ilmenite as oxygen carrier and natural gas as fuel. A wide range of process parameters and different levels of NiO addition were examined. Occasionally, there were problems with the circulation of solids between the air reactor and fuel reactor, but most of the time the experiments worked well. The products were mostly CO 2, H 2O and unconverted CH 4. Adding small amounts of NiO-based particles to the reactor increased the conversion of the fuel considerably. For the base case conducted at 900°, the combustion efficiency was 76% for pure ilmenite and 90% for the corresponding experiments with 1 wt.% NiO-based particles added to the reactor. The properties of ilmenite were found to change considerably during operation. Used particles had lower density, were more reactive and more porous than fresh particles. These changes appear to have been physical, and no unexpected chemical phases could be identified.

Kinetics of the Oxidation of a Co-precipitated Mixture of Cu and Al2O3 by O2 for Chemical-Looping Combustion

A co-precipitated mixture of CuO and Al2O3 is a good oxygen carrier for chemical-looping combustion in, e.g., CuO + CO → Cu + CO2. The kinetics of regeneration of this reduced oxygen carrier (parti...

Ilmenite Activation during Consecutive Redox Cycles in Chemical-Looping Combustion

Ilmenite, a natural mineral composed of FeTiO3, is a low-cost and promising oxygen carrier (OC) for solid fuels combustion in a chemical-looping combustion (CLC) system. The aim of this study is to analyze the behavior of ilmenite as an OC in CLC and the changes in its properties through redox cycles. Experiments consisting of reduction−oxidation cycles in a thermogravimetric analyzer were carried out using the main products of coal pyrolysis and gasification, that is, CH4, H2, and CO, as reducing gases. Characterizations of ilmenite through scanning electron microscopy−energy-dispersive X-ray (SEM−EDX), X-ray diffraction (XRD), Hg porosimetry, N2 fisisorption, He pycnometry, and hardness measures have been performed. Both fresh and previously calcined at 1223 K ilmenite have been used as initial OCs. Fresh ilmenite reacts slowly; nevertheless, there is a gain in reactivity in reduction as well as in oxidation with the number of cycles. This activation occurs for all tested fuel gases and is faster if ilm...

Investigation of NiO/NiAl 2O 4 oxygen carriers for chemical-looping combustion produced by spray-drying

Chemical-looping combustion is a novel combustion technology with inherent separation of the greenhouse gas CO 2. The technology uses circulating oxygen carriers to transfer oxygen from the combustion air to the fuel. In this paper, oxygen carriers based on commercially available NiO and α-Al 2O 3 were prepared using the industrial spray-drying method, and compared with particles prepared by freeze-granulation. The materials were investigated under alternating oxidizing and reducing conditions in a laboratory fluidized bed, thus simulating the cyclic conditions of a chemical-looping combustion system. The particles produced by spray-drying displayed a remarkable similarity to the freeze-granulated oxygen carriers, with high reactivity when the bed was fluidized and similar physical properties when sintered at the same temperature. This is an important result as it shows that the scaling-up from a laboratory production method, i.e. freeze-granulation, to a commercial method suitable for large-scale production, i.e. spray-drying, did not involve any unexpected difficulties. A difference noticed between the spray-dried and freeze-granulated particles was the sphericity. Whereas the freeze-granulated particles showed near perfect sphericity, a large portion of the spray-dried particles had hollow interiors. Defluidization was most likely to occur for highly reduced particles, at low gas velocities. The apparent density and crushing strength of the oxygen carriers could be increased either by increasing the sintering temperature or by increasing the sintering time. However, the fuel conversion was fairly unchanged when the sintering temperature was increased but was clearly improved when the sintering time was increased.

Waste products from the steel industry with NiO as additive as oxygen carrier for chemical-looping combustion

Fe 2O 3-containing waste materials from the steel industry are proposed as oxygen carrier for chemical-looping combustion. Three such materials, red iron oxide, brown iron oxide and iron oxide scales, have been examined by oxidation and reduction experiments in a batch fluidized-bed reactor at temperatures between 800 and 950 °C. NiO-based particles have been used as additive, in order to examine if it is possible to utilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactive combustion intermediates such as CO and H 2. The experiments indicated modest reactivity between the waste materials and CH 4, which was used as reducing gas. Adding small amounts of NiO-based particles to the sample increased the yield of CO 2 in a standard experiment, typically by a factor of 1.5–3.5. The fraction of unconverted fuel typically was reduced by 70–90%. The conversion of CH 4 to CO 2 was 94% at best, corresponding to a combustion efficiency of 96%. This was achieved using a bed mass corresponding to 57 kg oxygen carrier per MW fuel, of which only 5 wt% was NiO-based synthetic particles. The different materials fared differently well during the experiments. Red iron oxide was fairly stable, while brown iron oxide was soft and subject to considerable erosion. Iron oxide scales experienced increased reactivity and porosity as function of the numbers of reduction cycles.

Use of Ores and Industrial Products As Oxygen Carriers in Chemical-Looping Combustion

A screening of Fe- and Mn-based ores and industrial products was made in order to identify suitable low-cost materials that could be used as oxygen carriers in chemical-looping combustion (CLC). A laboratory fluidized bed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions, was used. Fifteen grams of each material with a particle size of 125−180 μm was exposed to a flow of 450 mLn/min of either methane or syngas (50% CO, 50% H2) during reduction. During the oxidizing phase to a flow of 1000 mLn/min, 5% O2 in nitrogen was used. All materials had a high reactivity with syngas. Some materials such as the Mn-based Colormax and the Fe-based Glödskal had also a high reactivity with methane making them possible candidates for CLC with gaseous fuel. Some of the materials, especially the Mn-based ones, showed poor mechanical stability and poor fluidizing properties. Roughly half of the Fe-based materials, but only one of the Mn-based materials, had properties that could make them suitable as oxygen carriers in a CLC system for solid fuels.

Reactivity of a CaSO4-oxygen carrier in chemical-looping combustion of methane in a fixed bed reactor

Chemical-looping combustion (CLC) is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO2. A reactivity study of CaSO4 oxygen carrier in CLC of methane was conducted in a laboratory scale fixed bed reactor. The oxygen carrier particles were exposed in six cycles of alternating reduction methane and oxidation air. A majority of CH4 reacted with CaSO4 to form CO2 and H2O. The oxidation was incomplete, possibly due to the CaSO4 product layer. The reactivity of CaSO4 oxygen carrier increased for the initial cycles but slightly decreased after four cycles. The product gas yields of CO2, CH4, and CO with cycles were analyzed. Carbon deposition during the reduction period was confirmed with the combustible gas (CO+H2) in the product gas and slight CO2 formed during the early stage of oxidation. The mechanism of carbon deposition and effect was also discussed. SO2 release behavior during reduction and oxidation was investigated, and the possible formation mechanism and mitigation method was discussed. The oxygen carrier conversion after the reduction decreased gradually in the cyclic test while it could not restore its oxygen capacity after the oxidation. The mass-based reaction rates during the reduction and oxidation also demonstrated the variation of reactivity of CaSO4 oxygen carrier. XRD analysis illustrated the phase change of CaSO4 oxygen carrier. CaS was the main reduction product, while a slight amount of CaO also formed in the cyclic test. ESEM analysis demonstrated the surface change of particles during the cyclic test. The reacted particles tested in the fixed bed reactor were not uniform in porosity. EDS analysis demonstrated the transfer of oxygen from CaSO4 to fuel gas while leaving CaS as the dominant reduced product. The results show that CaSO4 oxygen carrier may be an interesting candidate for oxygen carrier in CLC.

NiO particles with Ca and Mg based additives produced by spray- drying as oxygen carriers for chemical-looping combustion

Chemical-looping combustion is a two-step combustion process where CO2 is obtained in a separate stream, ready for compression and sequestration. The technique involves two interconnected fluidized bed reactors, with a solid oxygen carrier circulating between them. Results of reactivity experiments with 24 different oxygen carriers, based on NiO with NiAl2O4 and/or MgAl2O4 and produced with spray-drying, are presented. The investigation revealed that oxygen carriers supported by MgAl2O4, or where a small amount of MgO was added, displayed an increased fuel conversion when compared to oxygen carriers of NiO supported by NiAl2O4.

NiO/Al 2O 3 oxygen carriers for chemical-looping combustion prepared by impregnation and deposition–precipitation methods

Ni-based oxygen carriers (OC) with different NiO content were prepared by incipient wet impregnation, at ambient (AI), and hot conditions (HI) and by deposition–precipitation (DP) methods using γ-Al 2O 3 and α-Al 2O 3 as supports. The OC were characterized by BET, Hg porosimetry, mechanical strength, TPR, XRD and SEM/EDX techniques. Reactivity of the OC was measured in a thermogravimetric analyzer and methane combustion selectivity towards CO 2 and H 2O, attrition rate, and agglomeration behavior were analyzed in a batch fluidized bed reactor during multicycle reduction–oxidation tests. XRD and TPR analysis showed the presence of both free NiO and NiAl 2O 4 phases in most of the OC. The interaction of the NiO with the alumina during OC preparation formed NiAl 2O 4 that affected negatively to the OC reactivity and methane combustion selectivity towards CO 2 and H 2O during the reduction reaction. The NiO–alumina interaction was more affected by the support type than by the preparation method used. The NiO–alumina interaction was stronger in the OC prepared on γ-Al 2O 3. The OC were evaluated in the fluidized bed reactor with respect to the agglomeration process. OC prepared by the AI and HI methods with NiO contents up to 25 wt%, OC prepared by the DP method on γ-Al 2O 3 with NiO content lower than 30 wt%, and OC prepared by the DP method on α-Al 2O 3 with a NiO content lower than 26 wt% did not agglomerated. OC that agglomerated showed an external layer of NiO over the particles. It seems that the most important factor affecting to the formation of the external NiO layer on the OC, and so to the agglomeration process, was the metal content of the OC. The attrition rates of the OC prepared using γ-Al 2O 3 as support were higher than the ones prepared using α-Al 2O 3 as support, and in general the attrition rates of all the OC were low. The OC prepared by AI, HI or DP methods on α-Al 2O 3 as support had appropriated characteristics to be used in the chemical-looping combustion process.

NiO supported on Mg–ZrO2 as oxygen carrier for chemical-looping combustion and chemical-looping reforming

Oxygen-carrier particles consisting of 40 wt% NiO supported on 60 wt% Mg-stabilized ZrO2 were produced by freeze granulation and examined as oxygen carrier for chemical-looping applications. Firstly, the particles were examined by oxidation and reduction experiments in a batch fluidized-bed reactor. These experiments indicated very high reactivity with CH4 and low affinity for carbon formation. For highly oxidized particles the products were CO2 and H2O, while for reduced particles they were CO and H2. Secondly, the particles were examined by 40 hours of operation in a small circulating fluidized-bed reactor, using natural gas as fuel. For chemical-looping combustion, there was complete conversion of fuel into products with high selectivity towards CO2 and H2O. At 950 °C, a combustion efficiency of 99.3% was achieved, which is only 0.1% point below the theoretical maximum, i.e. thermodynamic equilibrium. For chemical-looping reforming, the conversion of fuel was 99.9% or higher, with high selectivity towards CO and H2. Operating at the desired process parameters, which was a fuel reactor temperature of 950 °C and an air ratio of 0.30, worked flawlessly. When only natural gas was used as fuel there was slight formation of solid carbon in the fuel reactor. Adding 30 vol% steam to the fuel removed the carbon formation. The particles retained their physical and chemical structure reasonably well during operation. Approximately 5% of the particles added to the reactor were lost as fines during the first hours of operation. Further, the porosity of the particles increased somewhat during operation. The density was 10% lower for used particles, compared to fresh.

Use of Coal as Fuel for Chemical-Looping Combustion with Ni-Based Oxygen Carrier

Chemical-looping combustion is an indirect combustion technology with inherent separation of the greenhouse gas CO2. The feasibility of using NiO as an oxygen carrier during chemical-looping combustion of coal has been investigated experimentally at 800−960 °C in the present work. The experiments were carried out in a fluidized bed, where the steam acted as the gasification−fluidization medium. Coal gasification and the reaction of oxygen carrier with the water gas take place simultaneously in the reactor. The oxygen carrier particles exhibit high reactivity above 900 °C, and the dry basis concentration of CO2 in the exit gas of the reactor is nearly 95%. The flue gas composition as a function of the reactor temperature and cyclic reduction number is discussed. At 800−960 °C, the dry basis concentration of CO2 in the flue gas presents a monotonously increasing trend, whereas the dry basis concentration of CO, H2, and CH4 decreases monotonously. The concentrations of CO2, CO, H2, and CH4 in the flue gas as a function of cyclic reduction number present a para-curve characteristic at 900 °C. With the increase of cyclic reduction number, the dry basis concentration of CO2 decreases remarkably, while the dry basis concentrations of CO, H2, and CH4 increase rapidly. Moreover, the peak value of H2 concentration is less than that of CO. The performance of the NiO-based oxygen carriers was also evaluated using an X-ray diffractometer and a scanning electron microscope to characterize the solid residues of oxygen carrier. The results indicate that NiO is one of the suitable oxygen carriers for chemical-looping combustion of coal.

Nickel on lanthanum-modified γ-Al 2O 3 oxygen carrier for CLC: Reactivity and stability

This study deals with the development of a lanthanum-modified Ni/La-γ-Al 2O 3 oxygen carrier suitable for a fluidized bed chemical-looping combustion (CLC) process. BET specific surface area analysis shows that the addition of La favors the thermal stability of γ-Al 2O 3 by preventing phase transformation. Temperature programmed characterization shows that the presence of La enhances the reducibility of the oxygen carrier by influencing the metal–support interactions helping the formation of reducible nickel species. Reactive characterization of the prepared oxygen carriers in a Chemical Reactor Engineering Center (CREC) fluidized Riser Simulator, using multiple reduction/oxidation cycles, demonstrates that the Ni/La-γ-Al 2O 3 particles display excellent reactivity and stability. The addition of La in the Ni/La-γ-Al 2O 3 influences the state of the surface minimizing the formation of nickel aluminate. It is argued that the addition of La also inhibits metal particle agglomeration by maintaining consistent metal dispersion during the cyclic oxidation/reduction processes.

Chemical-looping Combustion of Coal-derived Synthesis Gas Over Copper Oxide Oxygen Carriers

CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, bothmore » types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900 °C.« less

Chemical-looping with oxygen uncoupling using CuO/ZrO 2 with petroleum coke

Oxygen carrier particles of CuO/ZrO 2 were reacted with petroleum coke using chemical-looping with oxygen uncoupling (CLOU). The fuel was burnt in gas-phase oxygen released from the oxygen carrier particles during the fuel oxidation. The particles were then regenerated in 5–21% oxygen. In this process, the carbon dioxide from the combustion is inherently separated from the rest of the flue gases without the need for an energy intensive air separation unit. Copper oxide has thermodynamic characteristics that make it suitable as an oxygen carrier in CLOU. Particles were prepared by freeze granulation and were exposed cyclically with petroleum coke and oxygen in a laboratory fluidized bed reactor of quartz. The reaction temperature and oxygen concentration during the oxidation were varied. The average conversion rate of petroleum coke was a function of temperature and varied between 0.5%/s and 5%/s in the set-point temperature interval 885–985 °C. The conversion rate is considerably higher than rates obtained with the same fuel using iron-based oxygen-carrier in chemical-looping combustion. As for the regeneration with oxygen, the reduced particles reacted at low oxygen concentrations, with a considerable part of the reaction occurring near the thermodynamic equilibrium.

Effect of Temperature on Reduction of CaSO4 Oxygen Carrier in Chemical-Looping Combustion of Simulated Coal Gas in a Fluidized Bed Reactor

Chemical-looping combustion (CLC) is a promising combustion technology for gaseous and solid fuel with efficient use of energy and inherent separation of CO2. The concept of a coal-fueled CLC system using calcium sulfate (CaSO4) as oxygen carrier is proposed in this study. Reduction tests of CaSO4 oxygen carrier with simulated coal gas were performed in a laboratory-scale fluidized bed reactor in the temperature range of 890−950 °C. A high concentration of CO2 was obtained at the initial reduction period. CaSO4 oxygen carrier exhibited high reactivity initially and decreased gradually at the late period of reduction. The sulfur release during the reduction of CaSO4 as oxygen carrier was also observed and analyzed. H2 and CO conversions were greatly influenced by reduction temperature. The carbon deposition ratio was found to be quite low. The oxygen carrier conversion and mass-based reaction rates during the reduction at typical temperatures were compared. Higher temperatures would enhance reaction rates and result in high conversion of oxygen carrier. An XRD patterns study indicated that CaS was the dominant product of reduction and the variation of relative intensity with temperature is in agreement with the solid conversion. The slight content of CaO in reduced oxygen carrier at high temperatures was due to the formation of SO2 and H2S during the reduction period. ESEM analysis indicated that the surface structure of oxygen carrier particles changed significantly from impervious to porous after reduction. Slight agglomeration of small grains occurred for reduced particles at 950 °C. EDS analysis also demonstrated the transfer of oxygen from the oxygen carrier to the fuel gas and a certain amount of sulfur loss and CaO formation on the surface at higher temperatures. The reduction kinetics of CaSO4 oxygen carrier was explored with the shrinking unreacted-core model. The apparent kinetic parameters were obtained, and the kinetic equation well predicted the experimental data. Finally, some basic considerations on the use of CaSO4 oxygen carrier in a CLC system for solid fuels were discussed.

WITHDRAWN: The use of ilmenite as an oxygen carrier in chemical-looping combustion

The Publisher regrets that this article is an accidental duplication of an article that has already been published in 86 (9) (2008) 1017–1026.

Chemical-Looping Combustion and Chemical-Looping Reforming in a Circulating Fluidized-Bed Reactor Using Ni-Based Oxygen Carriers

Three oxygen carriers for chemical-looping combustion and chemical-looping reforming have been investigated in a small circulating fluidized-bed reactor. N2AM1400 was produced by freeze granulation with MgAl 2O 4 as a support material and had a NiO content of 20%. Ni18-αAl was produced by impregnation onto α-Al 2O 3 and had a NiO content of 18%. Ni21-γAl was produced by impregnation onto γ-Al 2O 3 and had a NiO content of 21%. Over 160 h of operation has been recorded. The conversion of natural gas into products was 96−100% depending on oxygen carrier and experimental conditions. For chemical-looping combustion, N2AM1400 and Ni21-γAl provided poor selectivity toward CO 2 and H 2O while Ni18-αAl initially showed very high selectivity, which declined as a function of time. For chemical-looping reforming, operating the reactor at the desired process parameters, which was a fuel reactor temperature of 950 °C and an air factor of 0.30, was possible with all of the tested oxygen-carrier materials. When only natural gas was used as fuel, there was significant formation of solid carbon in the fuel reactor for Ni18-αAl and Ni21-γAl. Adding 30% steam or CO 2 to the fuel removed or decreased the carbon formation. During the course of the experiments, N2AM1400 and Ni18-αAl retained their physical and chemical structure, while Ni21-γAl displayed a significant reduction in porosity but remained highly reactive.

The use of ilmenite as an oxygen carrier in chemical-looping combustion

The feasibility of using ilmenite as oxygen carrier in chemical-looping combustion has been investigated. It was found that ilmenite is an attractive and inexpensive oxygen carrier for chemical-looping combustion. A laboratory fluidized-bed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions, was used to investigate the reactivity. During the reducing phase, 15 g of ilmenite with a particle size of 125–180 μm was exposed to a flow of 450 mL n/min of either methane or syngas (50% CO, 50% H 2) and during the oxidizing phase to a flow of 1000 mL n/min of 5% O 2 in nitrogen. The ilmenite particles showed no decrease in reactivity in the laboratory experiments after 37 cycles of oxidation and reduction. Equilibrium calculations indicate that the reduced ilmenite is in the form FeTiO 3 and the oxidized carrier is in the form Fe 2TiO 5 + TiO 2. The theoretical oxygen transfer capacity between these oxidation states is 5%. The same oxygen transfer capacity was obtained in the laboratory experiments with syngas. Equilibrium calculations indicate that ilmenite should be able to give high conversion of the gases with the equilibrium ratios CO/(CO 2 + CO) and H 2/(H 2O + H 2) of 0.0006 and 0.0004, respectively. Laboratory experiments suggest a similar ratio for CO. The equilibrium calculations give a reaction enthalpy of the overall oxidation that is 11% higher than for the oxidation of methane per kmol of oxygen. Thus, the reduction from Fe 2TiO 5 + TiO 2 to FeTiO 3 with methane is endothermic, but less endothermic compared to NiO/Ni and Fe 2O 3/Fe 3O 4, and almost similar to Mn 3O 4/MnO.

Effect of support on reactivity and selectivity of Ni-based oxygen carriers for chemical-looping combustion

Different Ni-based oxygen carriers were prepared by dry impregnation using γ-Al 2O 3 as support. The reactivity, selectivity during methane combustion, attrition rate and agglomeration behavior of the oxygen carriers were measured and analyzed in a thermogravimetric analyzer and in a batch fluidized bed during multi-cycle reduction–oxidation tests. Ni-based oxygen carriers prepared on γ-Al 2O 3 showed low reactivity and low methane combustion selectivity to CO 2 and H 2O, because most of the impregnated NiO reacted to NiAl 2O 4. To avoid or to minimize the interaction of NiO with alumina some modifications of the support via thermal treatment or chemical deactivation with Mg or Ca oxides were analyzed. Thermal treatment of γ-Al 2O 3 at 1150 °C produced the phase transformation to α-Al 2O 3. Ni-based oxygen carriers prepared on α-Al 2O 3, MgAl 2O 4, or CaAl 2O 4 as support showed very high reactivity and high methane combustion selectivity to CO 2 and H 2O because the interaction between the NiO and the support was decreased. In addition, these oxygen carriers had very low attrition rates and did not show any agglomeration problems during operation in fluidized beds, and so, they seem to be suitable for the chemical-looping combustion process.

Development and performance of Cu-based oxygen carriers for chemical-looping combustion

Chemical-looping combustion (CLC) has the inherent property of separating the product CO 2 from flue gases. Instead of air, it uses an oxygen carrier, usually in the form of a metal oxide, to provide oxygen for combustion. This paper focuses on the development and performance of a suitable Cu-based oxygen carrier for burning solid fuels using CLC. Carriers were made from CuO and Al 2O 3 (as a support) in three different ways: mechanical mixing, wet impregnation, and co-precipitation. The reactivity of these solids was assessed by measuring their ability to oxidize CO, when in a hot bed of sand fluidized by a mixture of CO and N 2. After that, the Cu in the carrier was oxidized back to CuO by fluidizing the hot bed with air. These oxygen carriers were tested over many such cycles of reduction and oxidation. This work confirms that supporting CuO on Al 2O 3 enhances the ability of the resulting particles to withstand mechanical and thermal stresses in a fluidized bed. Also, only co-precipitation produces particles that have a high loading of copper and do not agglomerate at 800–900 °C. The performance of co-precipitated particles of CuO/Al 2O 3 at oxidizing CO to CO 2 was significantly affected by the pH of the solution in which precipitation occurred: a high pH (9.7) gave particles that reacted completely and rapidly. After 18 cycles, such a co-precipitated carrier with 82.5 wt% CuO yielded all its oxygen when oxidizing CO. X-ray analysis showed that when heated, CuO reacted with Al 2O 3 to form CuAl 2O 4, which was fully reducible, so CuO experienced no loss in extent of reaction after forming this mixed oxide. An increase in operating temperature from 800 to 900 °C led to the CuO providing slightly less oxygen; this was because a little of the CuO decomposed to Cu 2O between its reduction and oxidation, when the bed was fluidized by pure N 2.