- Title
- Vanadium-based catalysts for oxidation of organosulfur compounds: synthesis, catalysis and mechanistic studies
- Creator
- Dembaremba, Tendai
- Creator
- Ogunlaja, Adeniyi
- Subject
- Organosulfur compounds
- Date Issued
- 2018
- Date
- 2018
- Type
- Thesis
- Type
- Masters
- Type
- MSc
- Identifier
- http://hdl.handle.net/10948/30248
- Identifier
- vital:30909
- Description
- A series of oxidovanadium(IV) complexes based on the ligand, 2-(2’-hydroxyphenyl)imidazole, with substituent groups of different electronegativities on the phenolic para position, were successfully synthesized, characterized and investigated for their catalytic activities in the oxidation of dibenzothiophene (DBT), a typical refractory sulfur compound found in fuel. It was observed from catalytic oxidation studies that the presence of an electron withdrawing group on the phenolic para position of the ligand results in higher catalytic activity. SC-XRD data and DFT studies were used to explain the trends in activity observed. The highest activity was observed with 6.5 nmol of the nitro derivative catalyst [VO(PIMNO2)2] when 100% of 100 mg (0.543 mmol) of DBT was converted to its sulfone derivative dibenzothiophene sulfoxide (DBTO2) using 2.0 mL (1.05 mmol) of t-BuOOH. Potential to immobilize the complex catalysts was demonstrated through the synthesis of oxidovanadium(IV) copolymer nanofibers. The oxidovanadium nanofibers were successfully employed in the oxidation of sulfur compounds in a real fuel sample (diesel 500) which were then removed through solvent extraction using acetonitrile to give clean fuel. SC-XRD, EPR and UV-Vis spectroscopy were instrumental in providing insight into the mechanism of the catalyzed reaction. Vanadium oxides were also investigated as a cheaper alternative for the catalytic oxidation reaction. Phases of different vanadium oxides were synthesized by calcining NH4VO3 in air at different temperatures with an intention to investigate them for their catalytic activities. The catalyst obtained from calcination at 600⁰C was predominantly the orthorhombic phase of V2O5. Potential to immobilize the vanadium oxides was demonstrated using a silica support where NH4VO3 was impregnated onto silica and calcined in air at 600⁰C. The catalyst showed good potential in the oxidation of DBT to DBTO2, with 10 mg (43.9 μmol) of catalyst successfully converting 100% of 100 mg (0.543 mmol) DBT to DBTO2 using 2.0 mL (1.05 mmol) of t-BuOOH. The catalyst was also employed for a real fuel sample (diesel 500) with good results. The mechanistic aspects of vanadium oxides were also investigated in this study.
- Format
- xiv, 132 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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NMU School of BioMolecular and Chemical Sciences
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Tendai Dembaremba.pdf | 4 MB | Adobe Acrobat PDF | View Details Download |