Quasi in situ sequential sulfidation of CoMo/Al2O3 studied using high-resolution electron microscopy

P.J. Kooyman, J.G. Buglass, H.R. Reinhoudt, Dick van Langeveld, E.J.M. Hensen, H.W. Zandbergen, J.A.R. Veen, van

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Using a specially developed, quasi in situ vacuum-sample-transfer system, the stepwise sequential sulfidation of CoMo/g-Al2O3 was studied with transmission electron microscopy without exposing the catalyst to air. In a first step, the sulfidation was performed at 400 DegC at either 1 or 10 bar pressure. In a second step, the sulfidation was performed at 600 DegC and 1 bar. As the second sulfidation step was performed on the sample on the transmission electron microscopy grid, the same areas of the samples that had been studied for the first sulfidation step could be studied once more, providing detailed data on the changes in the sulfided phase. The slab length and degree of stacking have been studied in detail from the TEM/HREM images. Sulfidation at higher pressure or higher temp. results in a higher av. slab size. Detailed study of the same areas of the catalysts before and after the second, more severe, sulfidation step shows that although the dispersion of the sulfided phase decreases, the total amt. visible in the TEM images remains unchanged. This indicates that practically all the sulfide present is actually imaged on the micrographs. Addnl., detailed HRTEM study shows increased crystallinity of the slabs after the second sulfidation step. XPS anal. shows that after sulfidation at 400 DegC and 1 bar, the degree of sulfidation is 95%, whereas after sulfidation at 600 DegC and 1 bar, sulfidation is complete. The catalytic performance for thiophene hydrodesulfurization is much higher after sulfidation at 10 bar and 400 DegC as compared to 1 bar and 400 DegC, and decreases after the second sulfidation step (1 bar 600 DegC). The latter effect is more pronounced for the sample sulfided at 10 bar in the first step, indicating that a distorted yet fully sulfided structure is the most active phase for thiophene HDS. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)11795-11799
Number of pages5
JournalJournal of Physical Chemistry B
Issue number45
Publication statusPublished - 2002


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