Two-Step Catalytic Oxidative Dehydrogenation of Propane:  An Alternative Route to Propene

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

doi:10.1021/op050020r

Cited by 24 publications

(16 citation statements)

References 25 publications

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“…Sb 2 O 4 , In 2 O 3 and Bi 2 O 3 ). [102][103][104][105] These are, however, unstable under high temperature redox cycling. Conversely, ceria is stable under redox cycling and has a good oxygen storage capacity.…”

Section: Combined Dehydrogenation and Selective Hydrogen Combustionmentioning

confidence: 99%

Sustainable selective oxidations using ceria-based materials

2010

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This Perspective covers sustainable oxidation processes using doped cerias, ceria-supported catalysts and ceria-based mixed oxides. Firstly, we consider the general properties of ceria-based catalysts. We outline the advantages of the ceria redox cycle, and explain the dynamic behaviour of these catalysts in the presence of metal additives and dopants. We then review three types of catalytic oxidation processes: preferential CO oxidation (PROX), oxidative dehydrogenation and the selective oxidations of hydrocarbons and inorganics. The preferential oxidation of CO from hydrogen-rich mixtures is interesting for fuel cell applications. Copper-ceria catalysts, where the copper species are well dispersed and interact strongly with the ceria surface, show good selectivity and activity. The oxidative dehydrogenation of small alkanes is another important potential application. To avoid mixing oxygen and hydrocarbons at high temperatures, one can run the dehydrogenation over a conventional Pt/Sn catalyst while burning the hydrogen formed using the ceria lattice oxygen. This safer redox process allows separate tuning of the dehydrogenation and hydrogen combustion stages. A combinatorial screening showed good results for ceria doped with Pb, Cr or Bi, amongst others. Finally, we also discuss the catalytic selective oxidation of various hydrocarbons, oxygenates and inorganic molecules (H 2 S, H 2 and NH 3). The goal here is either product valorisation or waste stream purification. Ceria-based materials show promise in a variety of such selective oxidations.

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Section: Combined Dehydrogenation and Selective Hydrogen Combustionmentioning

confidence: 99%

Sustainable selective oxidations using ceria-based materials

2010

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“…[3][4][5] Instead of using gaseous O 2 , the hydrogen is combusted with the oxygen of the ceria lattice. The dehydrogenation step is performed over a conventional dehydrogenation catalyst, such as Pt/Sn/ Al 2 O 3 (see Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Selective Hydrogen Oxidation in the Presence of C₃ Hydrocarbons Using Perovskite Oxygen Reservoirs

et al. 2008

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Perovskite-type oxides, ABO(3), can be successfully applied as solid "oxygen reservoirs" in redox reactions such as selective hydrogen combustion. This reaction is part of a novel process for propane oxidative dehydrogenation, wherein the lattice oxygen of the perovskite is used to combust hydrogen selectively from the dehydrogenation mixture at 550 degrees C. This gives three key advantages: it shifts the dehydrogenation equilibrium to the side of the desired products, heat is generated, thus aiding the endothermic dehydrogenation, and it simplifies product separation (H(2)O vs H(2)). Furthermore, the process is safer since it uses the catalysts' lattice oxygen instead of gaseous O(2). We screened fourteen perovskites for activity, selectivity and stability in selective hydrogen combustion. The catalytic properties depend strongly on the composition. Changing the B atom in a series of LaBO(3) perovskites shows that Mn and Co give a higher selectivity than Fe and Cr. Replacing some of the La atoms with Sr or Ca also affects the catalytic properties. Doping with Sr increases the selectivity of the LaFeO(3) perovskite, but yields a catalyst with low selectivity in the case of LaCrO(3). Conversely, doping LaCrO(3) with Ca increases the selectivity. The best results are achieved with Sr-doped LaMnO(3), with selectivities of up to 93 % and activities of around 150 mumol O m(-2). This catalyst, La(0.9)Sr(0.1)MnO(3), shows excellent stability, even after 125 redox cycles at 550 degrees C (70 h on stream). Notably, the activity per unit surface area of the perovskite catalysts is higher than that of doped cerias, the current benchmark of solid oxygen reservoirs.

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“…Figure 2 shows a scheme of the proposed redox process, where the reactor contains both the SOR (black) and dehydrogenation catalyst (grey). [41] The alkane is fed over the reactor bed and is dehydrogenated by the dehydrogenation catalyst. The formed H 2 is selectively burned from the gas mixture by the SOR (Figure 2, A).…”

Section: Selectivity Towards Hydrogen Oxidationmentioning

confidence: 99%

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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Two-Step Catalytic Oxidative Dehydrogenation of Propane: An Alternative Route to Propene

Cited by 24 publications

References 25 publications

Sustainable selective oxidations using ceria-based materials

Sustainable selective oxidations using ceria-based materials

Selective Hydrogen Oxidation in the Presence of C₃ Hydrocarbons Using Perovskite Oxygen Reservoirs

Selective Hydrogen Oxidation Catalysts via Genetic Algorithms

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Two-Step Catalytic Oxidative Dehydrogenation of Propane: An Alternative Route to Propene

Cited by 24 publications

References 25 publications

Sustainable selective oxidations using ceria-based materials

Sustainable selective oxidations using ceria-based materials

Selective Hydrogen Oxidation in the Presence of C3 Hydrocarbons Using Perovskite Oxygen Reservoirs

Selective Hydrogen Oxidation Catalysts via Genetic Algorithms

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Selective Hydrogen Oxidation in the Presence of C₃ Hydrocarbons Using Perovskite Oxygen Reservoirs