Solvent‐Free Synthesis of Rechargeable Solid Oxygen Reservoirs for Clean Hydrogen Oxidation

Rothenberg, Gadi; Graaf, E.A. de; Bliek, A.

doi:10.1002/ange.200351545

Cited by 18 publications

(34 citation statements)

References 23 publications

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“…In addition to catalysts 1-18, we also tried preparing Ce 0.9 In 0.1 O 2 (19) (25). However, all of these samples showed secondary phases that were identified as the dopant oxides or dopant metals (see, for example, Figure 1, bottom Scheme 2.…”

Section: Resultsmentioning

confidence: 98%

“…[25] This method enabled the preparation of multiple samples on a 5-10 g scale (Figure 1, left). In a typical synthesis, the metal nitrates (or chlorides or ammonium metallates when nitrates were not available) were co-melted under vacuum, left to boil for four hours, and then calcined at 700 8C, ground, and sieved (70-120 mesh).…”

Section: Resultsmentioning

confidence: 99%

“…In a preliminary communication, working with hydrogen/ethane/ ethene mixtures, we demonstrated the "oxygen reservoir" by using a series of doped cerium oxides. [25] Ceria is known for its ability to store, release, and transport oxygen, and doping can be used to tune the 2 CeO 2 QCe 2 O 3 + O redox cycle. [26,27] Choosing the right dopant can increase the selectivity towards hydrogen oxidation.…”

Section: Introductionmentioning

confidence: 99%

“…Surface enrichment has been observed for these types of catalysts. [34][35][36] With this in mind, one wonders whether the doped fluorite lattice is accountable for the selectivity, or just offers a stable support for the dopant oxides. However, in the latter case, one would expect the same trends in selectivity as seen for the supported oxides, [9,24] which is not the case.…”

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confidence: 98%

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A “Green Route” to Propene through Selective Hydrogen Oxidation

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Beckers

Collignon

et al. 2007

Chemistry A European J

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The pros and cons of oxidative dehydrogenation of propane are outlined and a new catalytic system based on metal-doped cerianite catalysts is introduced. These novel materials catalyze the selective combustion of hydrogen from a mixture of hydrogen, propane, and propene at 550 degrees C. This gives three key advantages: energy is supplied directly where needed, product separation is made easier, and the dehydrogenation equilibrium is shifted to the desired products. A set of eighteen doped cerianites was synthesized in parallel, characterized, and screened for activity, selectivity, and stability in a cyclic redox system. The best results were obtained with Ce(0.89)Cr(0.02)Fe(0.09)O(2), Ce(0.98)Sn(0.02)O(2), and Ce(0.96)Cu(0.02)Zn(0.02)O(2), which gave 98 %, 91 %, and 98 % selectivity, respectively. Ce(0.89)Cr(0.02)Fe(0.09)O(2) also shows excellent stability in over 120 cycles (66 h on stream at 550 degrees C). Importantly, these doped cerias are monophasic crystalline materials. The dopants are incorporated as solid solutions throughout the fluorite lattice. This means that these catalysts are very stable (they do not sinter during reduction) as opposed to traditional supported metal oxides. The results show that both activity and selectivity towards hydrogen combustion can be tuned (increased or decreased) by selecting the appropriate dopant. Furthermore, the trends in selectivity differ from those measured on supported oxides of the same elements, which indicates that these novel materials indeed contain unique active sites. The factors governing selectivity towards hydrogen oxidation and the nature of the active site are discussed.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 98%

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A “Green Route” to Propene through Selective Hydrogen Oxidation

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Beckers

Collignon

et al. 2007

Chemistry A European J

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“…However, dopant-enriched surface phases can occur for these type of catalysts, and cannot be detected by XRD. [38][39][40] Indeed, in the case of a copper-ceria mixed oxide, Bera et al observed both surface enrichment and bulk incorporation of the copper. [40] .…”

Section: Catalyst Preparation and Characterisationmentioning

confidence: 96%

Selective Hydrogen Oxidation Catalysts via Genetic Algorithms

et al. 2008

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Solid "oxygen reservoirs," such as doped ceria, can be successfully applied in a novel process for the oxidative dehydrogenation of propane. The ceria lattice oxygen selectively burns hydrogen from the dehydrogenation mixture at 550 8C. This gives three key advantages: it shifts the dehydrogenation equilibrium to the desired product side, generates heat in situ, which aids the endothermic dehydrogenation, and simplifies product separation. We have applied a genetic algorithm to screen doped cerias for their performance in the selective hydrogen oxidation. Three generations of doped ceria catalysts (61 catalysts in total), were synthesised. Dopants were chosen from a set of 26 elements, and with a maximum of two dopants per catalyst, at five different concentrations. The catalyst performance (activity and selectivity), is expressed by a fitness value. Each generation shows a higher average fitness value. The dopant type has a large effect on the catalyst fitness. We identified six dopant atoms which lead to selective hydrogen combustion catalysts, namely bismuth (Bi), chromium (Cr), copper (Cu), potassium (K), manganese (Mn), lead (Pb) and tin (Sn) ("good" dopants). Analysis of the effect of electronegativity, ionic radius and dopant concentration shows that most elements yielding a high fitness have electronegativities ranging from 1.5-1.9. Generally, the properties of catalysts containing two dopants can be predicted from the behaviour of singly doped ones. Synergy does occur for certain copper-, iron-and platinum-containing catalysts. The addition of calcium (Ca) or magnesium (Mg) to copper-doped catalysts doubles the activity, and the selectivity of iron doped catalysts can be improved by adding chromium (Cr), manganese (Mn) or zirconium (Zr). Importantly, the doped cerias show a high stability in the redox cycling, much higher than that of supported oxides. A Cr-and Zr-doped catalyst (Ce 0.90 Cr 0.05 Zr 0.05 O 2 ) was highly selective and active over 250 redox cycles (a total of 148 h on stream), with no phase segregation or change in particle size.

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Bismuth‐Doped Ceria, Ce_0.90Bi_0.10O₂: A Selective and Stable Catalyst for Clean Hydrogen Combustion

Beckers¹,

Lee²,

Rothenberg³

2009

Adv Synth Catal

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Bismuth-doped cerias are successfully applied as solid "oxygen reservoirs" in the oxidative dehydrogenation of propane. The lattice oxygen of the ceria is used to selectively combust hydrogen from the dehydrogenation mixture at 550 8C. This process has three key advantages: it shifts the dehydrogenation equilibrium to the desired products side, generates heat, aiding the endothermic dehydrogenation, and simplifies product separation (water vs. hydrogen). Furthermore, the process is safer, since it uses the catalysts lattice oxygen instead of gaseous oxygen. We show here that bismuth-doped cerias are highly active and stable towards hydrogen combustion, and explore four different approaches for optimising their application in the oxidative dehydrogenation of propane: first, the addition of extra hydrogen which lowers hydrocarbon conversion by suppressing both combustion and coking; second, the addition of tin which completely inhibits coking; third, the addition of platinum which increases selectivity, but at the expense of lower activity. The best results are obtained through tuning the reaction temperature. At 400 8C, high activity and selectivity were obtained for the bismuth-doped ceria Ce 0.90 Bi 0.10 O 2 . Here, 90% of the hydrogen feed is converted at 98% selectivity. This optimal reaction temperature can be rationalised from the hydrogen and propene temperature-programmed reduction (TPR) profiles: 400 8C lies above the reduction maximum of hydrogen, yet below that of propene. That is, this temperature is sufficiently high to facilitate rapid hydrogen combustion, but low enough to prevent hydrocarbon conversion.

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Solvent‐Free Synthesis of Rechargeable Solid Oxygen Reservoirs for Clean Hydrogen Oxidation

Cited by 18 publications

References 23 publications

A “Green Route” to Propene through Selective Hydrogen Oxidation

A “Green Route” to Propene through Selective Hydrogen Oxidation

Selective Hydrogen Oxidation Catalysts via Genetic Algorithms

Bismuth‐Doped Ceria, Ce_0.90Bi_0.10O₂: A Selective and Stable Catalyst for Clean Hydrogen Combustion

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Solvent‐Free Synthesis of Rechargeable Solid Oxygen Reservoirs for Clean Hydrogen Oxidation

Cited by 18 publications

References 23 publications

A “Green Route” to Propene through Selective Hydrogen Oxidation

A “Green Route” to Propene through Selective Hydrogen Oxidation

Selective Hydrogen Oxidation Catalysts via Genetic Algorithms

Bismuth‐Doped Ceria, Ce0.90Bi0.10O2: A Selective and Stable Catalyst for Clean Hydrogen Combustion

Contact Info

Product

Resources

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Bismuth‐Doped Ceria, Ce_0.90Bi_0.10O₂: A Selective and Stable Catalyst for Clean Hydrogen Combustion