Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves

Simple item page
dc.contributor.advisorO'Connor, Cyril Ten_ZA
dc.contributor.advisorFletcher, Jack C Qen_ZA
dc.contributor.authorVaughan, James Stuarten_ZA
dc.date.accessioned2016-09-28T19:06:22Z
dc.date.available2016-09-28T19:06:22Z
dc.date.issued1993en_ZA
dc.descriptionBibliography: pages 219-232.en_ZA
dc.description.abstractHeteropoly acids, HPAs, and SAPO-11 and MeAPSO-11 molecular sieves have been proposed to be active for the oligomerization of propene to high quality distillate fuels. In this study these catalysts have been synthesized, characterized, modified and screened for the oligomerization of propene to distillate fuels. Heteropoly acids consist of high molecular weight poly-oxoanions, counter cations and water of hydration and are strongly acidic. The following salts of 12-tungstophosphoric acid, a 12-type HPA with the Keggin anion structure, were synthesized: AI, Fe, Ce, Ni, Co, Cu, K and NH₄, as well as the AI and NH₄ salts of 12-tungstosilicic acid. Physicochemical characterization of the HPA salts revealed that, depending on the counter cation, these salts exhibited different thermal characteristics and surface areas. The salts were classified into two types, viz.: Type A:- low surface area salts, typically less than 15m²/g, with multiple endothermic mass losses (e.g. AI, Fe, Ce, Ni, Co, Cu) and; Type 8:- high surface area salts, typically 35-150 m²/g, with a single endothermic mass loss (e.g. K and NH₄). The Type A salts were multi-crystalline, consisting of more than one phase, and exhibited a non-uniform morphology. The Type B salts, on the other hand, were uniformly crystalline and consisted of small rounded cubic crystallites. Ammonia desorption, monitored by both TCD and FT-IR, revealed that both the Type A and B salts were strongly acidic with the majority of the ammonia being released only upon decomposition of the salt. However, as ammonia and other polar molecules are known to readily absorb into the bulk of HPAs, the ammonia TPD results did not correlate with catalytic activity for surface type reactions such as alkene isomerization and oligomerization. The Type B salts were active for cracking and skeletal isomerization reactions which suggested strong acid sites were present on their surface. The Type A salts only exhibited double bond shift isomerization activity, suggesting sites of only weak to medium acid strength.en_ZA
dc.identifier.apacitationVaughan, J. S. (1993). <i>Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/21991en_ZA
dc.identifier.chicagocitationVaughan, James Stuart. <i>"Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1993. http://hdl.handle.net/11427/21991en_ZA
dc.identifier.citationVaughan, J. 1993. Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Vaughan, James Stuart AB - Heteropoly acids, HPAs, and SAPO-11 and MeAPSO-11 molecular sieves have been proposed to be active for the oligomerization of propene to high quality distillate fuels. In this study these catalysts have been synthesized, characterized, modified and screened for the oligomerization of propene to distillate fuels. Heteropoly acids consist of high molecular weight poly-oxoanions, counter cations and water of hydration and are strongly acidic. The following salts of 12-tungstophosphoric acid, a 12-type HPA with the Keggin anion structure, were synthesized: AI, Fe, Ce, Ni, Co, Cu, K and NH₄, as well as the AI and NH₄ salts of 12-tungstosilicic acid. Physicochemical characterization of the HPA salts revealed that, depending on the counter cation, these salts exhibited different thermal characteristics and surface areas. The salts were classified into two types, viz.: Type A:- low surface area salts, typically less than 15m²/g, with multiple endothermic mass losses (e.g. AI, Fe, Ce, Ni, Co, Cu) and; Type 8:- high surface area salts, typically 35-150 m²/g, with a single endothermic mass loss (e.g. K and NH₄). The Type A salts were multi-crystalline, consisting of more than one phase, and exhibited a non-uniform morphology. The Type B salts, on the other hand, were uniformly crystalline and consisted of small rounded cubic crystallites. Ammonia desorption, monitored by both TCD and FT-IR, revealed that both the Type A and B salts were strongly acidic with the majority of the ammonia being released only upon decomposition of the salt. However, as ammonia and other polar molecules are known to readily absorb into the bulk of HPAs, the ammonia TPD results did not correlate with catalytic activity for surface type reactions such as alkene isomerization and oligomerization. The Type B salts were active for cracking and skeletal isomerization reactions which suggested strong acid sites were present on their surface. The Type A salts only exhibited double bond shift isomerization activity, suggesting sites of only weak to medium acid strength. DA - 1993 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1993 T1 - Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves TI - Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves UR - http://hdl.handle.net/11427/21991 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21991
dc.identifier.vancouvercitationVaughan JS. Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1993 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21991en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Chemical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherChemical Engineeringen_ZA
dc.titleSynthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sievesen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
thesis_ebe_1993_vaughan_james_stuart.pdf
Size:
4.73 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
PhD / Doctoral