Determination of the surface coverage of Mo/Al₂O₃ catalysts

Methodical aspects in the surface analysis of supported molybdena catalysts

“…16 -19 In combination with chemisorption techniques, ISS even has been employed to determine surface coverages quantitatively. 10,16,20 The method is based on quantitative use of the Al/O ISS intensity ratios, which decrease with increasing transition-metal oxide content. On the basis of such measurements it has been argued that the support is only covered to ¾85% (55%) in WO 3 /TiO 2 WO 3 /ZrO 2 catalysts with tungsten contents above the theoretical monolayer surface coverage.…”

Comparison of surface coverage values of tungsten-alumina catalysts determined by different methods

“…The observed correspondence can be considered as remarkable, due to the major differences in the nature of methods involved. carried out after different heat pretreatments and at low gas pressure [2,3]. Moreover, taking into account the limitations of the EM method, e.g., assumption of the same IEP for the W supported species and for bulk WO3, possible losses of W supported species to the solution, and the reported limitations of the ISS and CO methods [2,3], the agreement among the different sets of data can be considered as very good.…”

“…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.…”

Surface coverage of WO3/ZrO2 catalysts measured by ion scattering spectroscopy and low temperature CO adsorption

“…Clearly, the coverage values obtained from ISS are in reasonable agreement with those estimated from the CO adsorption method. This suggests that the proposed methodology for coverage measurements, which has proven e †ective for alumina-supported Mo, Re and W catalysts, 11,17,18 …”

“…This approach has proven e †ective for alumina-supported molybdenum (Mo), rhenium (Re) and tungsten (W) catalysts. 11,17,18 The present work is a part of a systematic study aimed at evaluating the potential use of the proposed methodology when other supports are used. The study will be restricted to the system.…”