Effect of gallium as an additive in hydrodesulfurization WS2/gamma-Al2O3 catalysts

Diaz de Leon, J. N. Picquart, M. Villarroel, M. Vrinat, M. Gil Llambias, F. J. Murrieta, F. de los Reyes, J. A.The effect of gallium in W/Ga(x)-gamma-Al2O3 catalysts was investigated in the hydrodesulfurization of dibenzothiophene. The gamma-Al2O3 carrier was modified by the gallium addition prior to W impregnation and further calcination at 723 K. An electrophoretic study was carried out on the calcined Ga samples at 0, 0.29, 0.55, 0.84, 1.09, 1.43, 1.71 and 2.22 wt.% of Ga and it indicated that Ga addition affected significantly the surface of alumina. The presence of at least two gallium species was proposed, at low gallium content GaAl2O4 species decreased the isoelectric point (IEP) and probably the formation of Ga2O3 at higher contents increased again the IEP. Raman spectroscopy showed that the gallium incorporation had a strong effect in the formation of WOx species at the surface of catalysts. The highest amount of irregular WOx particles calculated by the Raman (O=W=O+W=O)/W-O-W band intensities ratio was found on the W/Ga(1.09)-gamma-Al2O3 catalyst. The presence of gallium induced higher activity on the dibenzothiophene hydrodesulfurization reaction in all catalysts tested. The highest Raman ratio and the highest activity were found for the W/Ga(1.09)-gamma-Al2O3 catalyst, suggesting that better dispersed W species could be responsible for the highest HDS activities. (C) 2010 Elsevier B.V. All rights reserved

The design of artificial nestboxes for the study of secondary hole-nesting birds: a review of methodological inconsistencies and potential biases.

26 pagesInternational audienceThe widespread use of artificial nestboxes has led to significant advances in our knowledge of the ecology, behaviour and physiology of cavity nesting birds, especially small passerines. Nestboxes have made it easier to perform routine monitoring and experimental manipulation of eggs or nestlings, and also repeatedly to capture, identify and manipulate the parents. However, when comparing results across study sites the use of nestboxes may also introduce a potentially significant confounding variable in the form of differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. However, the use of nestboxes may also introduce an unconsidered and potentially significant confounding variable due to differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. Here we review to what extent the characteristics of artificial nestboxes (e.g. size, shape, construction material, colour) are documented in the ‘methods' sections of publications involving hole-nesting passerine birds using natural or excavated cavities or artificial nestboxes for reproduction and roosting. Despite explicit previous recommendations that authors describe in detail the characteristics of the nestboxes used, we found that the description of nestbox characteristics in most recent publications remains poor and insufficient. We therefore list the types of descriptive data that should be included in the methods sections of relevant manuscripts and justify this by discussing how variation in nestbox characteristics can affect or confound conclusions from nestbox studies. We also propose several recommendations to improve the reliability and usefulness of research based on long-term studies of any secondary hole-nesting species using artificial nestboxes for breeding or roosting