- Title
- Coordination polymers for denitrogenation of fuel oils
- Creator
- Dembaremba, Tendai O
- Subject
- Port Elizabeth (South Africa)
- Subject
- Eastern Cape (South Africa)
- Subject
- South Africa
- Date Issued
- 2021-12
- Date
- 2021-12
- Type
- Doctoral theses
- Type
- text
- Identifier
- http://hdl.handle.net/10948/53630
- Identifier
- vital:45682
- Description
- In this thesis, we present adsorptive removal of nitrogen-containing compounds from fuel oil as an alternative to complement conventional hydrotreatment to obtain ultra-low sulfur and nitrogen levels. This is in cognizance of the challenges nitrogen-containing compounds pose to the hydrotreatment process, particularly their inhibition and/or poisoning of the catalysts used in the process, of which basic nitrogen-containing compounds are the major culprits. Selectivity is the biggest challenge for adsorptive removal of nitrogen-containing compounds. We explore reticular synthesis of metal organic frameworks and the use of coordinatively unsaturated metal sites in 1-dimensional coordination polymers to achieve good selectivity for nitrogen-containing compounds. In the first part of the thesis, reticular synthesis of metal organic frameworks to control the size of the cavity, and strategically use the linkers and metal centres was envisaged. In this work we explored variation of the metal centres in the secondary building units (SBUs of the MOFs as the first step to the testing and implementation of the design strategies. Carbazole, representing carbazoles which the major compounds that remain in hydrotreated fuel, was the target compound. Four MOFs of zinc (Zn-CDC-bpe), copper (Cu-CDC-bpe), nickel (Ni-CDC-bpe) and cobalt (Co-CDC-bpe) based on the formation of a dinuclear metal paddlewheel SBUs with the ligand 9H-Carbazole-3,6-dicarboxylic acid (H2CDC) and occupation of the axial positions of the paddlewheel by 1,2-Bis(4-pyridyl)ethane (bpe) to form porous networks were synthesized. A fifth MOF containing only CDC which forms a [Zn4O(O2C-R)5(O2HC-R)] SBU was also synthesized (Zn-CDC). The ligand H2CDC was inspired by the possibility of improving selectivity for carbazole via π–π interactions through the more preferred parallel-offset stacking as well as the possibility for further substitution of the carbazole N-H to add groups that improve selectivity. The sizes of the MOF cavities can then be controlled by choosing different lengths of ligands analogous to 1,2-Bis(4-pyridyl)ethane (bpe), e.g. 4,4’-bipyridine and pyrazine. All the MOFs showed good selectivity of carbazole. The Zn-CDC MOF also had good selectivity for the basic nitrogen-containing compounds tested: quinoline, isoquinoline, quinaldine and 1-naphthylamine. Its uptake of carbazole was also slightly higher. This was attributed to the presence of an unsaturated Zn site in the SBU. Adsorption in all the MOFs was primarily due to physisorption. It was concluded that the role of the metal centre does not play a significant role in the adsorption of carbazole besides providing a template for reticular synthesis.
- Description
- Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (xxvi, 226 leaves)
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
- Rights
- All Rights Reserved
- Rights
- Open Access
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