A study of the formation of CuAl2O4 from CuO and Al2O3 by solid state reaction at 1000°C and 950°C

Paulsson, Heléne; Rosén, Erik

doi:10.1002/zaac.19734010207

Cited by 17 publications

(4 citation statements)

References 4 publications

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“…See Table 1 for the summary of the structural information. Our estimate of the lattice parameter of 8.07683 (5) Å is close to those values reported in the previous works: 8.078(1) and 8.079 Å [22,23]: we note that Ref 18 reported a smaller value of the lattice parameter, 8.045 Å. Our full structure analysis was carried out by the joint refinement of both neutron HRPD data and HR-XRD data taken at 40 and 300 K. The final refinement data show a significant siteinversion for Cu 2+ ions, which occupy the otherwise forbidden octahedral B-sites (see Table 1).…”

Section: Resultssupporting

confidence: 91%

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Nirmala

Jang

Sim

et al. 2017

J. Phys.: Condens. Matter

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CuAl2O4 is a normal spinel oxide having quantum spin, S=1/2 for Cu is a Jahn-Teller active ion. Thus, we claim that an orbital liquid state is the most likely ground state in CuAl2O4. Of further interest, it also exhibits a large frustration parameter, f = CW/Tm ~67, one of the largest values reported for spinel oxides. Our observations suggest that CuAl2O4 should be a rare example of a frustrated quantum spin glass with a good candidate for an orbital liquid state.

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Section: Resultssupporting

confidence: 91%

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Nirmala

Jang

Sim

et al. 2017

J. Phys.: Condens. Matter

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“…The TGA results suggest that there was no detectable interaction of the CuO with the support. However, in batches 1 to 4, CuAl 2 O 4 was detected by XRD, and is known to diminish the effective oxygen release capacity R OC,Cu 2 O . , CuAl 2 O 4 is fully reducible by CO, and although it is the stable phase when CuO and Al 2 O 3 coexist, its rate of formation is rather slow . The XRD pattern of batch 2 that had been fully reduced and reoxidized once at 900 °C (not shown here) did not contain any significant peaks corresponding to the CuAl 2 O 4 phase, as opposed to the fresh batch 2 (labeled as B in Figure ).…”

Section: Resultsmentioning

confidence: 80%

Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

Donat

Dennis

2015

Ind. Eng. Chem. Res.

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Eight different oxygen carriers (OC) containing CuO (60 wt %) and different mass ratios of CaO to Al 2 O 3 as the support were synthesized by wet-mixing followed by calcination at 1000 °C. The method of synthesis used involved the formation of calcium aluminum hydrate phases and ensured homogeneous mixing of the Ca 2+ and Al 3+ ions in the support at the molecular level. The performance of the OCs for up to 100 cycles of reduction and oxidation was evaluated in both a thermogravimetric analyzer (TGA) and a fluidized bed reactor, covering a temperature range of 800 to 950 °C. In these cycling experiments, complete conversion of the OC, from CuO to Cu and vice versa, was always achieved for all OCs. The reactivity of the materials was so high that no deactivation could be observed in the TGA, owing to mass transfer limitations. It was found that OCs prepared with a mass ratio of CaO to Al 2 O 3 in the support >0.55 agglomerated in the fluidized bed, resulting in an apparent deactivation over 25 cycles for all temperatures investigated. High ratios of mass of CaO to Al 2 O 3 in the support resulted in CuO interacting with CaO, forming mixed oxides that have low melting temperatures, and this explains the tendency of these materials to agglomerate. This behavior was not observed when the mass ratio of CaO to Al 2 O 3 in the support was ≤0.55 and such materials showed excellent cyclic stability operating under redox conditions at temperatures as high as 950 °C.

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“…Hot nitric acid extraction, coupled with atomic absorption spectroscopy (AAS), was used to determine quantitatively the amounts of CuA1204, CuO, and A1203 present in a given sample. Paulsson and Rosen (1973) have reported that copper in the form of CuAl204 cannot be extracted by hot nitric acid; however, copper present as a pure oxide is easily extracted. This wet chemistry has been confirmed in our laboratories.…”

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confidence: 99%

High-temperature sulfidation-regeneration of copper(II) oxide-alumina sorbents

Patrick¹,

Gavalas²,

Flytzani‐Stephanopoulos³

et al. 1989

Ind. Eng. Chem. Res.

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Thermogravimetric analysis (TGA) and flow-reactor experiments were used to study sulfidationregeneration of highly porous Cu0-A1203 sorbents. In TGA studies, sulfidation of reduced sorbents produced a high-temperature form of digenite (Cu9+xS5) as the major crystalline product. When a platinum pan was used in the TGA, significant sulfur chemisorption on alumina occurred. Sulfur chemisorption on alumina was eliminated by use of a quartz sample pan. Reaction of the mixed-oxide sorbents with a mixture of H2S, H2, H20, and N2 in a packed-bed microreactor, at temperatures between 550 and 800 °C, yielded prebreakthrough outlet-H2S levels considerably lower than those predicted by the sulfidation equilibrium of metallic copper. Independent reduction experiments confirmed that alumina stabilizes CuO against complete reduction to Cu. With this mechanism at work, low prebreakthrough H2S levels are attributed to sulfidation reactions of copper at oxidation states of +1 or +2. The sulfided sorbents were completely regenerable in air/N2 mixtures with no deterioration of subsequent sulfidation performance.Among the most promising new technologies of power generation from coal are gasification integrated with combined-cycle power generation (gas turbine in series with

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A study of the formation of CuAl₂O₄ from CuO and Al₂O₃ by solid state reaction at 1000°C and 950°C

Cited by 17 publications

References 4 publications

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

High-temperature sulfidation-regeneration of copper(II) oxide-alumina sorbents

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A study of the formation of CuAl2O4 from CuO and Al2O3 by solid state reaction at 1000°C and 950°C

Cited by 17 publications

References 4 publications

Spin glass behavior in frustrated quantum spin system CuAl2O4with a possible orbital liquid state

Spin glass behavior in frustrated quantum spin system CuAl2O4with a possible orbital liquid state

Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

High-temperature sulfidation-regeneration of copper(II) oxide-alumina sorbents

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A study of the formation of CuAl₂O₄ from CuO and Al₂O₃ by solid state reaction at 1000°C and 950°C

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state

Spin glass behavior in frustrated quantum spin system CuAl₂O₄with a possible orbital liquid state