The physicochemical processes that occur during the preparation of CoMo–Al2O3 hydrodesulfurization catalyst bodies have been investigated. To this end, the distribution of Mo and Co complexes, after impregnation of γ‐Al2O3 pellets with different CoMoP solutions (i.e., solutions containing Co, Mo, and phosphate), was monitored by Raman and UV‐visible‐NIR microspectroscopy. From the speciation of the different complexes over the catalyst bodies, insight was obtained into the interaction of the different components in the impregnation solution with the Al2O3 surface. It is shown that, after impregnation with a solution containing H2PMo11CoO405−, the reaction of phosphate with the Al2O3 leads to the disintegration of this complex. The consecutive independent transport of Co2+ complexes (fast) and Mo6+ complexes (slow) through the pores of the Al2O3 is envisaged. By the addition of extra phosphate and citrate to the impregnation solution, the formation of the desired heteropolyanion can be achieved inside the pellets. Ultimately, the H2PMo11CoO405− distribution could be controlled by varying the aging time applied after impregnation. The power of a combination of spatially resolved spectroscopic techniques to monitor the preparation of supported catalyst bodies is illustrated.

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A UV-vis microspectroscopy methodology for monitoring the speciation and macrodistribution of catalyst-precursor species inside catalyst-support bodies at the initial stages of catalyst preparation has been developed. The setup is based upon optical-fiber technology and allows spatially resolved analysis of bisected catalyst bodies. The potential of this tool is demonstrated by two pore-volume impregnation studies involving Ni2+ d-d transition bands and Cr6+ charge-transfer bands.

Understanding precursor transformation to active catalysts is crucial to heterogeneous Fischer-Tropsch (FT) catalysis directed towards production of hydrocarbons for transportation fuels. Despite considerable literature on FT catalysis, the effect of pre-treatment of supported cobalt catalysts on cobalt dispersion, dynamic atomic structure and the activity of the catalysts is not well understood. Here we present systematic studies into the formation of active catalyst phases in supported Co catalyst precursors in FT catalysis using in-situ environmental (scanning) transmission electron microscopy (E(S)TEM) with single atom resolution under controlled reaction environments for in-situ visualization, imaging and analysis of reacting atomic species in real time, EXAFS, XAS, DRIFTS analyses and catalytic activity measurements. We have synthesized and analyzed dried-reduced (D) and dried-calcined reduced (DC) Co real catalysts on reducible and non-reducible supports, such as SiO2, Al2O3, TiO2 and ZrO2. Comparisons of dynamic in-situ atomic structural observations of reacting single atoms, atomic clusters and nanoparticles of Co, DRIFTS, XAS, EXAFS and catalytic activity data of the D and DC samples reveal in most cases better dispersion in the D samples, leading to a larger number of low-coordination Co 0 sites and a higher number of active sites for CO adsorption. The experimental findings on the degree of reduction of D and DC catalysts on reducible and non-reducible supports and correlations between hexagonal (hcp) Co sites and the activity of the catalysts generate structural insights into the catalyst dynamics, important to the development of efficient FT catalysts.

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