Structure of oxidic NiMo/SiO{sub 2} hydrotreating catalyst precursors
- Eidgenoessische Technische Hochschule, Zuerich (Switzerland)
The structures of Ni and Mo in dried, but not calcined, oxidic NiMo/SiO{sub 2} hydrotreating catalyst precursors and in the corresponding impregnation solutions were analyzed by means of UV-VIS, Raman, infrared, and X-ray absorption spectroscopies as a function of the impregnation order of the Ni and Mo salts and of the addition of the chelating agent nitrilotriacetic acid (NTA) to the impregnation solutions. The Ni-ions in the impregnation solutions which contained Ni, Mo, and NTA, and in the corresponding dried catalyst precursors, were preferentially complexed with NTA. As a consequence of the Ni:Mo:NTA = 0.5:1:1 molar ratios, Mo was present in about equal amounts as the [MoO{sub 3}(NTA)]{sup 3{minus}} complex and as well-dispersed molybdates, grafted through Si-O-Mo bonds to the support. In NiMo/SiO{sub 2} samples prepared by sequential impregnation with the Mo salt and Ni in the absence of NTA, all Mo was present as well-dispersed polymolybdate grated on the support after drying only without calcination. When the impregnation order was reversed, Ni(OH){sub 2} crystallites were formed on the surface of SiO{sub 2}, onto which MoO{sub 4}{sup 2{minus}} ions attached during the second impregnation. 41 refs., 13 figs., 2 tabs.
- OSTI ID:
- 508456
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 163; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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