Applied Catalysis, 59 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1990) 185-195 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 185 zyxwvut Hydrodesulfurization Activity of WC&,/y-Alumina Prepared by the Equilibrium Adsorption Method F.J. GIL LLAMBIAS*, J. SALVATIERRA, L. BOUYSSIERES and M. ESCUDEY Departamento de Quimica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 5659, Santiago (Chile) and R. CID Departamento de Quimica, Universidad de Concepcidn, Concepcidn (Chile) (Received 19 January 1989, revised manuscript received 31 October 1989) ABSTRACT The electrophoretic properties of WO,/y-A&O3 catalysts prepared by the adsorption equilib- rium method at pH values between 1 and 10 were studied. This study indicates the formation of a tungsten monolayer structure if pH values lower than six are used, and a multilayer structure if pH values higher than six are employed. Activity for the hydrodesulfurization of gas-oil shows that multilayer structure leads to higher activity than monolayer structure. INTRODUCTION Molybdenum and tungsten, supported on y-A&OS, are known catalysts for reactions employed in petroleum chemistry: hydrodesulfurization, hydrode- nitrogenation, hydrodeoxygenation, etc. [ zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ 11. Although there have been many studies of the MoOJy-Al,O, system, the WOJy-A1203 system has received relatively little attention. The formation of a multilayer or a monolayer in MoO,/y-A1203 samples obtained by different preparation methods has been widely studied [2,3]. There is quite a lot of information about the MoOJy- A1203 system in the sulfided state [ 4-71, however with WOJy-A1203 there has been only a few studies. Nag et al. [8] have shown that in the sulfided state tungsten is present as a monolayer or as bulk WS, at low or high tungsten loading, respectively. At low Mo( W) contents, the formation of MO(W) sul- fide sheets partially covering the support has also been proposed by other au- thors [ g-111. 0166-9834/90/$03.50 0 1990 Elsevier Science Publishers B.V.