The effect of zinc addition on the oxidation state of cobalt in Co/ZrO2 catalysts.

The effect of zinc promotion on the oxidation state of cobalt in Co/ZrO(2) catalysts was investigated and correlated with the activity and selectivity for ethanol steam reforming (ESR). Catalysts were synthesized by applying incipient wetness impregnation and characterized by using Brunauer-Emmett-Teller (BET), temperature-programmed reduction (TPR) measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Higher ethanol conversion and lower CH(4) selectivity are observed for the Co/ZrO(2) catalyst promoted with Zn as compared to the Co/ZrO(2) catalyst alone. Addition of Zn inhibits the oxidation of metallic cobalt (Co(0) ) particles and results in a higher ratio of Co(0) /Co(2+) in the Zn-promoted Co/ZrO(2) catalyst. These results suggest that metallic cobalt (Co(0) ) is more active than Co(2+) in the ethanol conversion through dehydrogenation and that Co(2+) may play a role in the CH(4) formation. TPR measurements, on the other hand, reveal that Zn addition inhibits the reduction of Co(2+) and Co(3+) , which would lead to the false conclusion that oxidized Co is required to reduce the CH(4) formation. Therefore, TPR measurements may not be appropriate to correlate the degree of metal reducibility (in this case Co(0)) with the catalyst activity for reactions, such as ESR, where oxidizing conditions exist.

[1]  M. Engelhard,et al.  Catalytic roles of Co0 and Co2+ during steam reforming of ethanol on Co/MgO catalysts , 2011 .

[2]  J. Vohs,et al.  Reaction of ethanol on oxidized and metallic cobalt surfaces , 2011 .

[3]  Wenjie Shen,et al.  Ethanol steam reforming over Ni and Ni–Cu catalysts , 2009 .

[4]  M. Schmal,et al.  Ethanol reforming and partial oxidation with Cu/Nb2O5 catalyst , 2009 .

[5]  U. Ozkan,et al.  Ethanol steam reforming over Co-based catalysts: Role of oxygen mobility , 2009 .

[6]  W. Gac,et al.  Steam reforming of ethanol over Ni/support catalysts for generation of hydrogen for fuel cell applications , 2008 .

[7]  S. Tuti,et al.  On the Catalytic Activity of Cobalt Oxide for the Steam Reforming of Ethanol , 2008 .

[8]  Jianguo Wang,et al.  Adsorption and Dissociation of CO as Well as CHx Coupling and Hydrogenation on the Clean and Oxygen Pre-covered Co(0001) Surfaces , 2008 .

[9]  C. Yeh,et al.  Novel zirconia-supported catalysts for low-temperature oxidative steam reforming of ethanol , 2007 .

[10]  G. Jacobs,et al.  Fischer-Tropsch synthesis : Temperature programmed EXAFS/XANES investigation of the influence of support type, cobalt loading, and noble metal promoter addition to the reduction behavior of cobalt oxide particles , 2007 .

[11]  Umit S. Ozkan,et al.  Investigation of bio-ethanol steam reforming over cobalt-based catalysts , 2007 .

[12]  V. A. L. P. O'Shea,et al.  X-ray diffraction study of Co3O4 activation under ethanol steam-reforming , 2007 .

[13]  A. Valentini,et al.  Hydrogen Production from Ethanol Steam Reforming Over Ni/CeO2 Nanocomposite Catalysts , 2007 .

[14]  J. Torres,et al.  Steam reforming of ethanol at moderate temperature: Multifactorial design analysis of Ni/La2O3-Al2O3, and Fe- and Mn-promoted Co/ZnO catalysts , 2007 .

[15]  U. Ozkan,et al.  Effect of synthesis parameters on the catalytic activity of Co–ZrO2 for bio-ethanol steam reforming , 2007 .

[16]  P. Fornasiero,et al.  Rh(1%)@CexZr1−xO2–Al2O3 nanocomposites: Active and stable catalysts for ethanol steam reforming , 2007 .

[17]  J. Llorca,et al.  Low-temperature steam-reforming of ethanol over ZnO-supported Ni and Cu catalysts: The effect of nickel and copper addition to ZnO-supported cobalt-based catalysts , 2006 .

[18]  Alírio E. Rodrigues,et al.  Insight into steam reforming of ethanol to produce hydrogen for fuel cells , 2006 .

[19]  Agus Haryanto,et al.  Current status of hydrogen production techniques by steam reforming of ethanol : A review , 2005 .

[20]  G. Bonura,et al.  Steam reforming of bio-ethanol on alkali-doped Ni/MgO catalysts: hydrogen production for MC fuel cell , 2004 .

[21]  J. Dalmon,et al.  Transformation of Co3O4 during Ethanol Steam-Re-forming. Activation Process for Hydrogen Production , 2004 .

[22]  Xenophon E. Verykios,et al.  Reaction network of steam reforming of ethanol over Ni-based catalysts , 2004 .

[23]  E. Assaf,et al.  High efficiency steam reforming of ethanol by cobalt-based catalysts , 2004 .

[24]  G. Bonura,et al.  Potassium improved stability of Ni/MgO in the steam reforming of ethanol for the production of hydrogen for MCFC , 2004 .

[25]  P. Tsiakaras,et al.  Hydrogen production by ethanol steam reforming over a commercial Pd/γ-Al2O3 catalyst , 2004 .

[26]  Edson A. Ticianelli,et al.  Characterization of the activity and stability of supported cobalt catalysts for the steam reforming of ethanol , 2003 .

[27]  Xenophon E. Verykios,et al.  Production of hydrogen for fuel cells by steam reforming of ethanol over supported noble metal catalysts , 2003 .

[28]  J. Dalmon,et al.  CO-free hydrogen from steam-reforming of bioethanol over ZnO-supported cobalt catalysts , 2003 .

[29]  J. Dalmon,et al.  In situ magnetic characterisation of supported cobalt catalysts under steam-reforming of ethanol , 2003 .

[30]  Heather M. Coleman,et al.  Metal-catalysed steam reforming of ethanol in the production of hydrogen for fuel cell applications , 2002 .

[31]  Pilar Ramírez de la Piscina,et al.  Efficient Production of Hydrogen over Supported Cobalt Catalysts from Ethanol Steam Reforming , 2002 .

[32]  M. Toney,et al.  Molecular beam epitaxial growth and properties of CoFe2O4 on MgO(001) , 2002 .

[33]  J. Goodwin,et al.  Co-Support Compound Formation in Alumina-Supported Cobalt Catalysts , 2001 .

[34]  V. Parmon,et al.  Metal-support interactions in cobalt-aluminum co-precipitated catalysts: XPS and CO adsorption studies , 2001 .

[35]  C. Bianchi.  TPR and XPS Investigations of Co/Al2O3 Catalysts Promoted with Ru, Ir and Pt , 2001 .

[36]  L. Kępiński,et al.  Reduction study of Co3O4 model catalyst by electron microscopy , 2001 .

[37]  J. Llorca,et al.  Direct production of hydrogen from ethanolic aqueous solutions over oxide catalysts , 2001 .

[38]  G. D. Piero,et al.  Metal–support interaction in Co/SiO2 and Co/TiO2 , 2000 .

[39]  B. Irigaray,et al.  Catalytic transformation of ethanol into acetone using copper–pyrochlore catalysts , 1998 .