Production of hydrogen from methanol over binary Cu/ZnO catalysts - Part I. Catalyst preparation and characterisation
2003 (English)In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 253, no 1, 201-211 p.Article in journal (Refereed) Published
Mixed copper-zinc oxide catalysts (Cu/ZnO) were prepared by two different techniques, i.e. from hydroxycarbonate precursors formed in aqueous solution and from oxalate precursors formed in water-in-oil microemulsion. Their physicochemical properties were characterised by nitrogen adsorption-desorption, N2O chemisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and oxidation (TPO). The BET surface areas ranged from 34 to 87 m(2)/g, depending on the method of preparation. Cu surface areas between 6.6 and 22 m(2)/g were measured. It was a general observation that catalysts prepared by microemulsion technique had lower Cu dispersions than expected (3.4-5.7%), due to a proposed partial embedding of Cu in ZnO. The catalyst prepared by carbonate co-precipitation exhibited a significantly higher Cu dispersion (10.3%). In addition, this catalyst displayed better resistance to successive TPR/TPO than the microemulsion catalysts, which exhibited significant Cu crystallite growth. However, the microemulsion route provided well-mixed materials with a narrow particle size distribution and the possibility to obtain high BET surface areas (up to 87 m(2)/g) by controlling the water/surfactant ratio in the microemulsion. XPS measurements revealed the existence of Cu+ species on the surface of both types of catalysts after exposure to a O-2/CH3OH mixture. The surface composition of the hydroxycarbonate-derived sample was unaffected by reduction in hydrogen and exposure to O-2/CH3OH, while Zn-enrichment on the surface was observed in the microemulsion catalysts after reduction, indicating sintering of the Cu particles. These observations were consistent with the TPR/TPO measurements.
Place, publisher, year, edition, pages
2003. Vol. 253, no 1, 201-211 p.
Cu/ZnO catalyst, hydroxycarbonate precursor, oxalate precursor, microemulsion, characterisation, N2O chemisorption, XPS, TPR/TPO, ray photoelectron-spectroscopy, gel-oxalate coprecipitation, gas shift, reaction, partial oxidation, surface characterization, structural-changes, oxide catalysts, chemical-state, copper surface, zinc-oxide
IdentifiersURN: urn:nbn:se:kth:diva-22935DOI: 10.1016/s0926-860x(03)00520-9ISI: 000186388000017OAI: oai:DiVA.org:kth-22935DiVA: diva2:341633
QC 201005252010-08-102010-08-10Bibliographically approved