Novel, High Activity Hydroprocessing Catalysts: Iron Group Phosphides
| dc.contributor.author | Wang, Xianqin | en |
| dc.contributor.committeechair | Oyama, Shigeo Ted | en |
| dc.contributor.committeemember | Deck, Paul A. | en |
| dc.contributor.committeemember | Cox, David F. | en |
| dc.contributor.committeemember | Saraf, Ravi F. | en |
| dc.contributor.committeemember | Hanson, Brian E. | en |
| dc.contributor.department | Chemical Engineering | en |
| dc.date.accessioned | 2014-03-14T20:08:32Z | en |
| dc.date.adate | 2002-03-27 | en |
| dc.date.available | 2014-03-14T20:08:32Z | en |
| dc.date.issued | 2002-03-21 | en |
| dc.date.rdate | 2003-03-27 | en |
| dc.date.sdate | 2002-03-27 | en |
| dc.description.abstract | A series of iron, cobalt and nickel transition metal phosphides was synthesized by means of temperature-programmed reduction (TPR) of the corresponding phosphates. The same materials, Fe₂P, CoP and Ni₂P, were also prepared on a silica (SiO₂) support. The phase purity of these catalysts was established by x-ray diffraction (XRD), and the surface properties were determined by N₂ BET specific surface area (Sg) measurements and CO chemisorption. The activities of the silica-supported catalysts were tested in a three-phase trickle bed reactor for the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene using a model liquid feed at realistic conditions (30 atm, 370 °C). The reactivity studies showed that the nickel phosphide (Ni₂P/SiO₂) was the most active of the catalysts. Compared with a commercial Ni-Mo-S/g-Al₂O₃ catalyst at the same conditions, Ni₂P/silica had a substantially higher HDS activity (100 % vs. 76 %) and HDN activity (82 % vs. 38 %). Because of their good hydrotreating activity, an extensive study of the preparation of silica supported nickel phosphides, Ni₂P/SiO₂, was carried out. The parameters investigated were the phosphorus content and the weight loading of the active phase. The most active composition was found to have a starting synthesis Ni/P ratio close to 1/2, and the best loading of this sample on silica was observed to be 18 wt.%. Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES) measurements were employed to determine the structures of the supported samples. The main phase before and after reaction was found to be Ni₂P, but some sulfur was found to be retained after reaction. A comprehensive scrutiny of the HDN reaction mechanism was also made over the Ni₂P/SiO₂ sample (Ni/P = 1/2) by comparing the HDN activity of a series of piperidine derivatives of different structure. It was found that piperidine adsorption involved an a-H activation and nitrogen removal proceeded mainly by means of a b-H activation though an elimination (E2) mechanism. The relative elimination rates depended on the type and number of b-hydrogen atoms. Elimination of b-H atoms attached to tertiary carbon atoms occurred faster than those attached to secondary carbon atoms. Also, the greater the number of the b-H atoms, the higher the elimination rates. The nature of the adsorbed intermediates was probed by Fourier transform infrared spectroscopy (FTIR) and temperature-programmed desorption (TPD) of the probe molecule, ethylamine. This measurement allowed the determination of the likely steps in the hydrodenitrogenation reaction. | en |
| dc.description.degree | Ph. D. | en |
| dc.identifier.other | etd-03272002-001809 | en |
| dc.identifier.sourceurl | http://scholar.lib.vt.edu/theses/available/etd-03272002-001809/ | en |
| dc.identifier.uri | http://hdl.handle.net/10919/26516 | en |
| dc.publisher | Virginia Tech | en |
| dc.relation.haspart | Xianqin-ETD.pdf | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Hydrodenitrogenation mechanism | en |
| dc.subject | Hydrodenitrogenation | en |
| dc.subject | Hydrodesulfurization | en |
| dc.subject | Phosphorus effect | en |
| dc.subject | Iron group phosphide | en |
| dc.subject | EXAFS | en |
| dc.subject | Structure-sensitivity | en |
| dc.title | Novel, High Activity Hydroprocessing Catalysts: Iron Group Phosphides | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Chemical Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Ph. D. | en |
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