Study of the reducibility of copper in CuOZnO catalysts by temperature-programmed reduction

Fierro, G.; Jacono, M. Lo; Inversi, M.; Porta, P.; Cioci, Federico; Lavecchia, Roberto

doi:10.1016/0926-860x(95)00311-8

Cited by 215 publications

(123 citation statements)

References 47 publications

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“…The reduction peak of CuO for the CZ catalyst was displaced by almost 90 K towards lower temperatures in comparison with that of the CuO reference compound. This result indicates that the ZnO had enhanced the reducibility of the copper oxide phase and agrees with previous observations [23]. In addition, the ratio between the amount of hydrogen consumed and the amount of reducible species present (H 2 /M ratio in table 2) was determined quantitatively.…”

Section: Resultssupporting

confidence: 79%

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2002

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Effect of Pd on Cu-Zn catalysts for the hydrogenation of CO2 to methanol López Granados, M.; Melián-Cabrera, I.; Fierro, J.L.G. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. A palladium±copper±zinc catalyst (PdO : CuO : ZnO 2 : 28 : 70), prepared by sequential precipitation of the respective cations, was tested in the hydrogenation of CO 2 at high pressure (conditions: 60 bar, CO 2 : H 2 1 : 3 (molar), WaF 0X0675 kg h/m 3 , 453±513 K). The methanol yield was improved on using this Pd-containing catalyst at all temperatures with respect to the reference copper±zinc catalyst (CuO : ZnO 30 : 70). This improvement was not due to an additional e ect in which palladium was acting as an independent catalytic site but was caused by a synergetic e ect of Pd on the active Cu sites. This e ect was explained in terms of hydrogen spillover and an increased stability against CO 2 oxidation of the surface copper. Therefore, the present contribution not only supports previous literature ®ndings concerning the hydrogen spillover mechanism but also resulted in a complementary view regarding the role of palladium in Pd-modi®ed CuO-ZnO-based catalysts.

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Section: Resultssupporting

confidence: 79%

“…It has been shown that H 2 /CO 2 /H 2 cycles constitute a very useful tool in determining the resistance of reduced Cu against oxidation [23]. These cycles were measured to determine the in¯uence of Pd on the redox properties of the copper phase in the reduced catalysts.…”

Section: Resultsmentioning

confidence: 99%

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2002

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“…23,29 On CuO-ZnO mixed oxides catalysts prepared by coprecipitation it was reported that ZnO promotes the copper reduction. 30 The Zn addition to Cu(30wt%)/SiO 2 catalysts also caused an increase in the copper reducibility. 31 The discrepancies can be ascribed to the presence of Cu _ Ce interactions which are significantly modified by Zn addition.…”

Section: -26mentioning

confidence: 99%

Methanol steam reforming over Cu/CeO2 catalysts: influence of zinc addition

Tonelli¹,

Gorriz²,

Arrúa³

et al. 2011

Quím. Nova

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Recebido em 20/10/10; aceito em 17/3/11; publicado na web em 5/5/11Methanol steam reforming reaction was studied over Cu(5 wt.%)/CeO 2 with and without the presence of Zn. The Zn addition decreased the Cu +2 reducibility and increased the oxygen mobility of ceria. The main products were CO 2 and H 2 with small amount of CO. Selectivity to CO decreased with the Zn addition and it was lower at lower reaction temperatures and lower space velocities. At 230 ºC and W/F MeOH = 648 g min mol -1 selectivities to H 2 and to CO 2 were 100% on Zn/Cu/Ce. The catalytic results indicated that CO was mainly a secondary product formed from reverse water gas shift reaction.

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“…al. studied the reduction of CuO/ZnO with different Cu/Zn ratios and found a promoting effect of ZnO on the reducibility of CuO (14). The reduction kinetics of copper oxide were determined by thermogravimetric methods ( 15,16) which afforded sigmoidal curves indicating a nucleation growth mechanism.…”

Section: Introductionmentioning

confidence: 99%

Redox Behavior of Copper Oxide/Zinc Oxide Catalysts in the Steam Reforming of Methanol Studied by in Situ X-Ray Diffraction and Absorption Spectroscopy

Günter

Ressler

Jentoft

et al. 2001

Journal of Catalysis

248

162

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The bulk structure of copper in various binary Cu/ZnO catalysts for steam reforming of methanol under activation and working conditions is studied by in situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The evolution of bulk phases from CuO/ZnO precursors during activation with hydrogen was studied using temperature programmed reduction (TPR) (448 -523 K, 2 vol-% H 2 with and without water vapor). With decreasing copper content the onset of reduction is shifted from 473 K (pure CuO) to 443 K (40 mol-% Cu) accompanied by a decrease in Cu crystallite sizes (from 210 Å to 40 Å). Using time -resolved in situ XANES measurements at the Cu K edge during TPR experiments the degree of reduction was monitored. It is shown that Cu(I) oxide forms prior to Cu. Adding oxygen to the feed gas leads to the formation of a mixture of Cu(II) and Cu(I) oxide accompanied by a complete loss of activity. After switching back to steam reforming conditions a higher activity is attained while the catalyst shows an increased Cu crystallite size (up to 40%). EXAFS measurements at the Cu K and the Zn K edge indicate a structural disorder of the Cu particles in the medium range order based on increasing Debye-Waller factors for higher Cu-Cu shells . Furthermore, the dissolution of Zn atoms (up to ~ 4 mol-%) in the copper lattice is detected. Upon oxidation/reduction cycles activity is increased, the disorder in the copper particles increases, and Zn segregates out of the copper bulk. A structural model is proposed which ascribes the enhanced activity to structurally disordered (strained) copper particles due to an improved interface interaction with ZnO.

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Study of the reducibility of copper in CuOZnO catalysts by temperature-programmed reduction

Cited by 215 publications

References 47 publications

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Methanol steam reforming over Cu/CeO2 catalysts: influence of zinc addition

Redox Behavior of Copper Oxide/Zinc Oxide Catalysts in the Steam Reforming of Methanol Studied by in Situ X-Ray Diffraction and Absorption Spectroscopy

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