Dennstedt, A.

Deshpande, A.

Frank, B.

Mastalir, A.

Niederberger, M.

Ressler, T.

Schlögl, R.

Schomäcker, R.

Soerijanto, H.

Szizybalski, A.

English

MPG.PuRe

Structure–activity relationships of ternary Cu/ZrO2/CeO2 catalysts for methanol steam reformingA.Dennstedt a, A. Mastalir a,b, B. Frank b, A. Szizybalski a, H. Soerijanto a,b, A. Deshpande c, M. Niederberger c, R. Schomäcker b, R. Schlögl a, T. Ressler a,ba Fritz-Haber-Institut der MPG, Abteilung Anorganische Chemie, Faradayweg 4-6, 14195 Berlin, Germanyb Institut für Chemie, TU Berlin, Straße des 17. Juni 124, 10623 Berlin, Germanyc Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Abteilung Kolloidchemie, MPI-KG, 14424 Potsdam, GermanyIntroductionTwo different types of experiments were performed: I) Ex situ (25 °C): XAS (Zr K edge + Ce L3 edge), XRDII) In situ (25 °C – 250 °C, reduction in 2% H2/He):XAS (Cu K edge ), TG/DSC, XRDSteam Reforming:     CH3OH + H2O          3 H2 + CO2                   T = 250 °C  ;  p = 1 barApplication:                H2 production for fuel cell application (e.g. in cars) [1]Catalyst:                     Cu/ZrO2/CeO2In order to eliminate the need for gas purification, more selective catalysts need to be developed.Sample preparation(NH4)2Ce(NO3)6ZrO(NO3)2•H2OCu(NO3)2•2.5H2Odistilled water+ à coprecipitationStep 1:Step 2: Templating: XAD-16 nonfunctional polystyrene beads4 samples: CZC35CZC25CZC15CZC5X-ray fluorescence analysis (%) [2]BET area (m2 g-1) [2] CeZrCu 36.332.731.08338.537.623.99443.644.312.110251.044.64.496arrows indicate CuOCatalysis040801201600 2 4 6 8 10 12 14 16 18time-on-stream [day]p CO[Pa]CZC5CZC15CZC25CZC35- no systematic variation with Cu content- samples > 5 % Cu show good long-term stability- samples > 5 % Cu: after 5 days CO levels were stabilized05101520253035400 2 4 6 8 10 12 14 16 18time on stream [day]Conversion (%) ZCC-5ZCC 15ZCC 25ZCC-35In situCZC35CZC25CZC15CZC5Cu - CuCu - OCu2OCuOCu CZC3550 °C250 °C50 °C- Cu2O detectable at high temperature during in situ XRD- TG/DSC and position of edge duringXAS showed for samples with Cu >5%:Reduction needs more time and ends athigher temperatures with higher Cu content- different amount of Cu-O in the reduced samplesà similar to Cu/ZrO2 where an amount of oxygen in the copper particles was found [4]- highest oxygen content in CZC5 ßà highest PCOà Possible to fit RDF of CZC5 with a combination of Cu and Cu2OReferences:[1] P. J. de Wild, M. J. F. M. Verhaak, Catal. Today 60 (2000) 3[2] A. Mastalir, B. Frank, A. Szizybalski, H. Soerijanto, A.Desphande, M. Niederberger, R. Schomäcker, R. Schlögl, T. Ressler, J. Catal. 230 (2005) 464[3] L. Douillard, M. Gautier, N. Thromat, J. P. Duraud, Nucl. Instrum. Methods Phys. Res. B 97 (1995) 133[4] A. Szizybalski, F. Girgsdies, A. Rabis, Y. Wang, M. Niederberger, T. Ressler, J. Catal. 233 (2005) 297[5] P. Li, I. W. Chen, J. E. Penner-Hahn, Phys. Rev. B 48 (1993) 10063Conclusions• CZC5 shows different behaviour compared to the other CZC samplesü more oxygen in the reduced sampleü smaller Cu particlesü stronger metal-support interaction• XANES of Zr K edge and XRD indicate tetragonal structure• low intensity of RDF at higher distances is indicative of a (Zr,Ce)O2 solid solution• for samples with >5% Cu, the Cu content influences the duration of reduction• increase in Cu content from 5 % to 15 % has a beneficial effect on the catalytic performance of the CZC catalysts8981898489870 100 200temperature (°C)edge position (eV)CZC5 CZC15 CZC25 CZC354060801000 10 20 30Cu content (%)duration of reduction (K) TG/DSCSample characterization (ex situ)12 34- difference between 3rd and 4th Lorentziancorrelates with Ce-O distance [3]à with lower Zr/Ce ratio a larger Ce-O distance is observed à good agreement with Vegard´s lawZr - O Zr - Zr- shape of the RDF in the region of 3 – 4 Å does not correspond to that of CeO2 or ZrO2à indicates tetragonal solid solutionCZC25Cu K0,8500,9000,9501,0001,0500,00715 0,00725 0,00735 0,00745distance between 3rd and 4th Lorentzian (keV)Zr/CeCZC15CZC5CZC35CZC25Zr/Ce0,0090,010,0110,0120 30 60 90 120Cu content (%)distance between 1st and 3rd Gaussian (keV)CZC samplesCuO referencePre-edgefeatureXANES Ce L3- only minor differences between the CZC samplesEXAFSZr K-pre-edge feature is typical for tetragonal structure in ZrO2 [5]Zr KXANES- fit of the 1st shell identified CuO- XANES fit with 3 Gaussian functions à log dependence of distance from Cu content, may indicatecontinuous size variationCe L3- different amplitudes in 1st shellFurthermore, catalytic performance was investigated in a fixed bed reactor at atmospheric pressure.

Structure–activity relationships of ternary Cu/ZrO<sub>2</sub>/CeO<sub>2</sub> catalysts for methanol steam reforming

Structure–activity relationships of ternary Cu/ZrO<sub>2</sub>/CeO<sub>2</sub> catalysts for methanol steam reforming

Abstract

Similar works

Full text

Available Versions

MPG.PuRe