Raman microspectroscopy was used to study the preparation of industrial MoS 2 /Al 2 O 3 extrudates. Using this technique, the influence of the impregnation solution composition on the nature and macrodistribution of Mo complexes inside these catalyst bodies was evaluated during their preparation process (impregnation, drying, and calcination). It was found that poor dispersion of the MoO x phase in the calcined samples can be brought about by the formation of bulk (NH 4) 3 [Al(OH) 6 Mo 6 O 18 ] during impregnation or redistribution of Mo complexes during drying. The formation of crystalline MoO 3 and Al 2 (MoO 4) 3 in the oxidic precursors leads to a poorly dispersed MoS 2 phase in the final catalyst and significantly lower hydrodesulfurization activity. The spatially resolved information that can be obtained, and its inherent sensitivity for the detection of crystalline phases make Raman microspectroscopy a powerful characterization technique for studying the preparation of industrial supported metal oxide catalysts.

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The column dynamics of simple ion-exchange processes involving acetic acid and

ion-exchange processes involving weak electrolytes are influenced strongly by the pH via the occurrence of association/dissociation equilibria. This influence was investigated quantitatively through binary displacement experiments with different electrolytes to gain better insight in the role of the pH and to test a jived-bed ion-exchange model used for the description of multicomponent processes. The two major factors determining the ion-exchange behavior of weak electrolytes are the actual exchange of counterions and the sorption of neutral species. The sorption of neutral species resulted in concentration fluctuations superimposed on the normal ion-exchange profiles, whereas pH fluctuations inherent to ion-exchange processes in general also influenced concentration through modified ionic ji-actions. The relative importance of these contributions is determined by the magnitude of parameters such as resin capacity, distribution coefficients of neutral species, and selectivities of ions, as well as by operating conditions such as concentrations of all species.