Jointlypublishedby Elseviex ScienceB.V., Amsterdam mad Akad&niai Kiad6, Budapest Reaet.Kinet.Catal.Lett. Vol. 66, No. 2, 225-229 (1999) RKCL3396 COMPARISON OF SURFACE COVERAGE VALUES OF TUNGSTEN-ALUMINA CATALYSTS DETERMINED BY DIFFERENT METHODS F. J. Gil Llambias', N. Escalona', C. Pfaft ~, C. Scottb'and J. Goldwasser b ~Departamento de Qulmica, Facultad de Ciencia, Universidad de Santiago de Chile, Casilla 5659, Santiago de Chile, Chile, bCentro de Catdlisis, Petr61eo y Petroqulmica, Escuela de Qulmica, Facultad de Ciencias, Universidad Central de Venezuela, Apartado Postal 47102, Los Chaguaramos, Caracas 1020-A, Venezuela Received September 21, 1998 Accepted December 2, 1998 Abs~a~ Apparent surface coverage (ASC) of a series of ttmgsten-alumina catalysts was determined by the eloctrophoretic migration method (EM). A linear increase in W coverage with increasing W loading (up to 13.1 wt.% W) was observed. The results were in close agreement with those obtained previously by ion scattering spectroscopy (ISS) and low temperature CO adsorption. Keywords: Tongsten-ahtmina catalysts, electrophoretic migration, absolute surface coverage INTRODUCTION Supported tungsten-alumina catalysts have been the subject of numerous studies due to their role in hydrotreating and hydrodesulfurization [ 1 ] processes. As for any metal supported catalyst, the knowledge of the surface coverage (0) of the supported phase is of great importance, since it can be used as a control parameter for monitoring catalyst preparation. Recently ion scattering spectroscopy (ISS) and low temperature CO adsorption have been ,used successfully to determine absolute surface coverages (0iss and 0co ) in molybdenum-alumina [2] and tungsten-alumina [3] catalysts. For the W-alumina catalysts, the 0co values were very similar to those obtained with the ISS method, for a particular loading. A linear increase in 0 with 0133-I 736/99FLIS$12.00. 9Akacl~miaiKiad6, Budapest. All rights reserve&