Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

Espinal, Raúl; Taboada, Elena; Molins, Elı́es; Chimentão, R.J.; Medina, Françesc; Llorca, Jordi

doi:10.1016/j.apcatb.2012.08.006

Cited by 78 publications

(46 citation statements)

References 22 publications

(31 reference statements)

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“…An efficient catalyst for hydrogen production from ethanol has to dissociate the C C bond, maintain low CO concentration and also be stable under catalytic operation conditions (avoid coke accumulation). Catalysts based on nickel and cobalt tend to sinter under reaction conditions and have a strong propensity for the methanation process [4,5]. In contrast, noble metals, and in particular Rh and Ru, are known to successfully break the C C bond leading to less coke deposition and thus results in more stable catalysts.…”

Section: Introductionmentioning

confidence: 99%

The influence of nano-architectured CeO supports in RhPd/CeO2 for the catalytic ethanol steam reforming reaction

Divins

Casanovas

et al. 2015

Catalysis Today

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a b s t r a c tThe ethanol steam reforming (ESR) reaction has been tested over RhPd supported on polycrystalline ceria in comparison to structured supports composed of nanoshaped CeO2 cubes and CeO2 rods tailored toward the production of hydrogen. At 650-700 K the hydrogen yield follows the trend RhPd/CeO2 -cubes > RhPd/CeO2 -rods > RhPd/CeO2 -polycrystalline, whereas at temperatures higher than 800 K the catalytic performance of all samples is similar and close to the thermodynamic equilibrium. The improved performance of RhPd/CeO2 -cubes and RhPd/CeO2 -rods for ESR at low temperature is mainly ascribed to higher water-gas shift activity and a strong interaction between the bimetallic-oxide support interaction. STEM analysis shows the existence of RhPd alloyed nanoparticles in all samples, with no apparent relationship between ESR performance and RhPd particle size. X-ray diffraction under operating conditions shows metal reorganization on {1 0 0} and {1 1 0} ceria crystallographic planes during catalyst activation and ESR, but not on {1 1 1} ceria crystallographic planes. The RhPd reconstructing and tuned activation over ceria nanocubes and nanorods is considered the main reason for better catalytic activity with respect to conventional catalysts based on polycrystalline ceria.

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Section: Introductionmentioning

confidence: 99%

The influence of nano-architectured CeO supports in RhPd/CeO2 for the catalytic ethanol steam reforming reaction

Divins

Casanovas

et al. 2015

Catalysis Today

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“…15,48,65 In contrast, Ni-based catalysts are not stable for more than 10 h of reaction time as they incur coke deposition. [61][62][63] Furthermore, the addition of new metals or alkaline elements is found to improve the properties of the catalyst and make it more stable.…”

Section: Stability and Durability Tests In Sre Catalystsmentioning

confidence: 99%

“…Oxidative activation cycles are performed by subjecting the catalyst to oxygen currents in air for 0.5 h. Co/ZnO doped with Na maintains a 100% conversion of ethanol and a H 2 selectivity of 74.3% for 240 h. 64 Co-based catalysts were also doped with Na hydrocalcites based on Co, and the tests were conducted at 550 °C. 65 The catalyst remain stable for 300 h while catalyzing the complete conversion of crude bioethanol.…”

Section: Stability and Durability Tests In Sre Catalystsmentioning

confidence: 99%

Advances in Ethanol Reforming for the Production of Hydrogen

2014

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Catalytic steam reforming of ethanol (SRE) is a promising route for the production of renewable hydrogen (H 2 ). This article reviews the influence of doping supported-catalysts used in SRE on the conversion of ethanol, selectivity for H 2 , and stability during long reaction periods. In addition, promising new technologies such as membrane reactors and electrochemical reforming for performing SRE are presented.

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“…13 Llorca et al reported that the supported Co species on Co/hydrotalcite existed as Co 2+ species. 14,15 These reports suggested that cationic Co 2+ species (i.e. CoO) is a highly active species in ethanol steam reforming with scarce coke formation.…”

Section: ¹1mentioning

confidence: 99%

“…coke formation). 14,25 Therefore, the reducibility and electronic state of Co on Co/ Sr-P were evaluated using H 2 -TPR and XAFS measurements. Moreover, the activity and stability of Co/Sr-P could not be improved by reduction at a high temperature of 923 K (data not shown).…”

Section: ¹1mentioning

confidence: 99%

Coke Resistance of Sr-Hydroxyapatite Supported Co Catalyst for Ethanol Steam Reforming

2017

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Co/Sr-hydroxyapatite catalyst (Co/Sr 10 (PO 4 ) 6 (OH) 2 : Co/ Sr-P) shows high activity and low carbon formation on ethanol steam reforming. H 2 -TPR measurements revealed that the Co species supported on Co/Sr-P was reduced only slightly more than that on typical Co/α-Al 2 O 3 . XAFS measurements revealed that Co 2+ species was observed mainly on the Co/Sr-P catalyst after H 2 -reduction at reaction temperature of 823 K. Co 2+ , i.e. CoO particle, on Co/Sr-P catalyst plays an important role as an active site for ethanol steam reforming with high coke resistance.Keywords: Hydrogen production | Hydroxyapatite support | Coke resistanceBiomass-derived ethanol (bioethanol) is anticipated as an important renewable resource.1 Especially, direct production of hydrogen by ethanol steam reforming is being developed intensively as a highly efficient energy production process. 2,3Moreover, since ethanol steam reforming is an endothermic reaction, as shown in eq 1, the reformate has a higher heating value of about 1450.9 kJ mol ¹1 (1277.4 for ethanol ¦H c + 173.5) after ethanol steam reforming. Therefore, ethanol steam reforming might increase the exergy rate considerably. 4 The exergy rate is defined as the ratio of Gibbs free energy (potential useful work) over the combustion enthalpy (energy supplied). Development of highly active and selective catalysts for ethanol steam reforming has been pursued actively. Among transition-metal catalysts, Co-based catalysts have been used extensively because of their higher activity and lower cost than those of noble metal catalysts.511 However, catalyst deactivation by coke formation presents an important difficulty. Therefore, the suppression of coke formation is strongly desired. Two solutions have been proposed for suppressing coke formation in ethanol steam reforming over Co-based catalysts: addition of another element 8,1014 and controlling the catalytic support. 6,7,1416 Reportedly, the use of basic supports (CeO 2 , ZnO, Mg-Al hydrotalcite, perovskite oxides, etc.) can suppress formations of coke and by-products effectively. The substituted hydroxyapatite supports were prepared using a hydrothermal method according to a published procedure with some modifications. 2022 The crystalline structure was confirmed using powder X-ray diffractometry (XRD). These XRD patterns were attributed to each hydroxyapatite with a single phase (not shown). Samples of the prepared M-phosphate and M-vanadate hydroxyapatite (M = Ca and Sr) supports are designated as Ca-P, Sr-P, Ca-V, and Sr-V.The Co catalysts supported on the hydroxyapatite supports were prepared using an impregnation method. Co(NO 3 ) 2 ¢6H 2 O was used as a metal precursor. The Co loading amount was 5 wt %. The hydroxyapatite support was mixed with distilled water in vacuo at room temperature for 2 h using a rotary evaporator. Then aqueous solution of Co precursor was added and stirred for 2 h. The obtained solution was then evaporated under heating and stirring. Subsequently, the obtained powder was dried at 393 K overnigh...

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Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

Cited by 78 publications

References 22 publications

The influence of nano-architectured CeO supports in RhPd/CeO2 for the catalytic ethanol steam reforming reaction

The influence of nano-architectured CeO supports in RhPd/CeO2 for the catalytic ethanol steam reforming reaction

Advances in Ethanol Reforming for the Production of Hydrogen

Coke Resistance of Sr-Hydroxyapatite Supported Co Catalyst for Ethanol Steam Reforming

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