Valentina Trevisan

Highly Dispersed Gold on Zirconia: Characterization and Activity in Low‐Temperature Water Gas Shift Tests

Gold-loaded zirconia and sulfated zirconia catalysts were tested in the low-temperature water gas shift reaction. The samples were characterized by N2 adsorption analysis, temperature-programmed reduction, X-ray diffraction, pulse-flow CO chemisorption, FTIR spectroscopy, and high-resolution transmission electron microscopy. A reference catalyst, Au/TiO2, provided by the World Gold Council was investigated for comparison. CO chemisorption and FTIR data indicate the presence of only highly dispersed gold clusters on the sulfated sample and both small clusters and small particles on the non-sulfated sample. Both gold-zirconia catalysts are much more active than the Au/TiO2 reference sample over all the temperature range investigated. The sample prepared on sulfated zirconia exhibits higher stability than the catalyst on unmodified zirconia. The prominent role in the water gas shift reaction of gold clusters in close contact with the support was deduced.

How the manufacturing technology of industrial catalysts can influence their mechanical strength

Abstract The various physical properties characterizing the mechanical strength of catalysts are discussed: abrasion resistance, crush strength, attrition resistance. The related measurements have been performed mainly using ASTM standard methods with some improvements. It is shown how modifications of the manufacturing technology can improve the abrasion resistance of the traditional ammonia synthesis catalyst (oxidepromoted magnetite) and of the PTA catalyst (Pd on active carbon). As to crush strength, it is discussed how some preparation variables can be changed to improve the performance of catalysts for the production of styrene (Fe-K-Ca-Ce-Mo oxides), formaldehyde (Fe-Mo oxides), methanol (Cu-Zn-Al oxides). As to powders, it is shown that the attrition resistance of aluminas to be used for fluid bed catalysts can be improved by suitable fluorination. Finally, it is stressed that mechanical strength is a property not less important than activity and selectivity for industrial catalysts and that no catalyst must be loaded in an industrial reactor without previous check of its mechanical properties.