{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/29306"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/29306","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"Hydrocracking of n-C16 over MFI Zeolite Nano-sheets - Effect of the Si/Al Ratio","abstract":"The combination of MFI zeolite nano-sheets with competitive adsorption of water (H2O) in hydrocracking of long-chain paraffins presents a promising opportunity to produce diesel with high yield and with high cetane number. Thus, in wet hydrocracking of a long-chain paraffin (n-hexadecane (n-C16)) over MFI nano-sheets, it was investigated whether catalytic activity increased with increasing number of Brønsted acid (H + ) sites (decreasing silicon-to-aluminium (Si/Al) ratio), while secondary cracking remained completely suppressed. Also, it was investigated whether more Al atoms could be incorporated into the framework of MFI nano-sheets by modifying the new synthesis method. It was demonstrated that the new synthesis method, which utilizes C22H45–N + (CH3)2–C6H12–N + (CH3)2–C6H13 (C22-6-6) as structure-directing agent (SDA), could be extended to various Si/Al ratios in the range 25 – 100. The nano-sheets exhibited extra-framework Al (EFAl) species. Nano-sheets with Si/Al = 75 exhibited an oddly large amount of EFAl species compared to the other nano-sheets. For nano-sheets with Si/Al = 75, a high fraction of the EFAl species may have formed during calcination of the ammonium form and may encompass flexible Al species with predominantly Al in octahedral coordination (AlVI). Nano-sheets were loaded with 0.9 wt% platinum (Pt) via incipient wetness impregnation (IWI). Pt/nano-sheets with Si/Al = 25, 50 and 100 exhibited similar and high Pt dispersion (γPt). In contrast, Pt/nano-sheets with Si/Al = 75 exhibited a very low γPt, which was probably a result of the abundance, nature and/or location of EFAl species present in the support. In dry hydrocracking of n-C16, the catalytic activity increased with decreasing Si/Al ratio, strongly suggesting that the number of H+ sites increased with decreasing Si/Al ratio. Nano-sheets with Si/Al = 75 most likely contained AlVI species associated with Brønsted acidity, supporting the presence of flexible AlVI species. In wet hydrocracking of n-C16, at a constant and sufficiently high γPt, the activity increased with increasing number of H+ sites (decreasing Si/Al ratio), while secondary cracking remained completely suppressed. Pt/nano-sheets with Si/Al = 75 displayed a lower activity than 2 Pt/nano-sheets with Si/Al = 100, which may be a result of the very low γPt of Pt/nano-sheets with Si/Al = 75, underlining the importance of high γPt. For Pt/nano-sheets with Si/Al = 25, 50 and 100, H2O favoured linear cracking products at low cracking yields. In contrast, for Pt/nano-sheets with Si/Al = 75, H2O favoured branched cracking products, which may be a result of Pt sites on the external surface of the support being too far from the H+ sites inside the micropores. The new synthesis method could be extended to a modified SDA, namely C22H45–N + (CH3)2–C6H12–N + (CH3)2–C3H7 (C22-6-3), at various Si/Al ratios in the range 25 – 100. Replacing the terminal –C6H13 group in C22-6-6 with –C3H7 resulted in an increase in the framework Al (FAl) content of MFI nano-sheets with Si/Al ≥ 50, with the increase being the most pronounced for nano-sheets with Si/Al = 50. This was due to the increased occupancy of the zeolite framework by the hydrophilic region of C22-6-3 in comparison to the hydrophilic region of C22-6-6 under the given set of synthesis conditions, since –C3H7 was less bulky than –C6H13. Calcined nano-sheets were loaded with 1 wt% Pt via competitive ion exchange (CIE). In dry and wet hydrocracking of n-C16, the activity increased with decreasing Si/Al ratio and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to the presence of additional H+ sites generated after SDA removal. H2O favoured linear cracking products at low cracking yields. Sodium (Na+ ) ion-exchanged nano-sheets were loaded with 1 wt% Pt via CIE. The average Pt size (dPt) of the Pt/Na+ nano-sheets were larger than the dPt of the Pt/calcined nano-sheets, which may be a result of the nature and/or location of EFAl species present in the Na+ supports. In dry and wet hydrocracking of n-C16, differences in activity were observed and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to insufficient intimacy between H+ sites and Pt sites such that the rate was controlled by diffusion of olefinic intermediates from H+ sites to Pt sites and vice versa. H2O favoured linear cracking products at low cracking yields.","abstract_html":"The combination of MFI zeolite nano-sheets with competitive adsorption of water (H2O) in hydrocracking of long-chain paraffins presents a promising opportunity to produce diesel with high yield and with high cetane number. Thus, in wet hydrocracking of a long-chain paraffin (n-hexadecane (n-C16)) over MFI nano-sheets, it was investigated whether catalytic activity increased with increasing number of Brønsted acid (H + ) sites (decreasing silicon-to-aluminium (Si/Al) ratio), while secondary cracking remained completely suppressed. Also, it was investigated whether more Al atoms could be incorporated into the framework of MFI nano-sheets by modifying the new synthesis method. It was demonstrated that the new synthesis method, which utilizes C22H45–N + (CH3)2–C6H12–N + (CH3)2–C6H13 (C22-6-6) as structure-directing agent (SDA), could be extended to various Si/Al ratios in the range 25 – 100. The nano-sheets exhibited extra-framework Al (EFAl) species. Nano-sheets with Si/Al = 75 exhibited an oddly large amount of EFAl species compared to the other nano-sheets. For nano-sheets with Si/Al = 75, a high fraction of the EFAl species may have formed during calcination of the ammonium form and may encompass flexible Al species with predominantly Al in octahedral coordination (AlVI). Nano-sheets were loaded with 0.9 wt% platinum (Pt) via incipient wetness impregnation (IWI). Pt/nano-sheets with Si/Al = 25, 50 and 100 exhibited similar and high Pt dispersion (γPt). In contrast, Pt/nano-sheets with Si/Al = 75 exhibited a very low γPt, which was probably a result of the abundance, nature and/or location of EFAl species present in the support. In dry hydrocracking of n-C16, the catalytic activity increased with decreasing Si/Al ratio, strongly suggesting that the number of H+ sites increased with decreasing Si/Al ratio. Nano-sheets with Si/Al = 75 most likely contained AlVI species associated with Brønsted acidity, supporting the presence of flexible AlVI species. In wet hydrocracking of n-C16, at a constant and sufficiently high γPt, the activity increased with increasing number of H+ sites (decreasing Si/Al ratio), while secondary cracking remained completely suppressed. Pt/nano-sheets with Si/Al = 75 displayed a lower activity than 2 Pt/nano-sheets with Si/Al = 100, which may be a result of the very low γPt of Pt/nano-sheets with Si/Al = 75, underlining the importance of high γPt. For Pt/nano-sheets with Si/Al = 25, 50 and 100, H2O favoured linear cracking products at low cracking yields. In contrast, for Pt/nano-sheets with Si/Al = 75, H2O favoured branched cracking products, which may be a result of Pt sites on the external surface of the support being too far from the H+ sites inside the micropores. The new synthesis method could be extended to a modified SDA, namely C22H45–N + (CH3)2–C6H12–N + (CH3)2–C3H7 (C22-6-3), at various Si/Al ratios in the range 25 – 100. Replacing the terminal –C6H13 group in C22-6-6 with –C3H7 resulted in an increase in the framework Al (FAl) content of MFI nano-sheets with Si/Al ≥ 50, with the increase being the most pronounced for nano-sheets with Si/Al = 50. This was due to the increased occupancy of the zeolite framework by the hydrophilic region of C22-6-3 in comparison to the hydrophilic region of C22-6-6 under the given set of synthesis conditions, since –C3H7 was less bulky than –C6H13. Calcined nano-sheets were loaded with 1 wt% Pt via competitive ion exchange (CIE). In dry and wet hydrocracking of n-C16, the activity increased with decreasing Si/Al ratio and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to the presence of additional H+ sites generated after SDA removal. H2O favoured linear cracking products at low cracking yields. Sodium (Na+ ) ion-exchanged nano-sheets were loaded with 1 wt% Pt via CIE. The average Pt size (dPt) of the Pt/Na+ nano-sheets were larger than the dPt of the Pt/calcined nano-sheets, which may be a result of the nature and/or location of EFAl species present in the Na+ supports. In dry and wet hydrocracking of n-C16, differences in activity were observed and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to insufficient intimacy between H+ sites and Pt sites such that the rate was controlled by diffusion of olefinic intermediates from H+ sites to Pt sites and vice versa. H2O favoured linear cracking products at low cracking yields.","abstract_has_math":false,"creators":["Parker, Mohamed Habeeb"],"institution":"Department of Chemical Engineering","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Kooyman, Patricia J","Brosius, Roald"],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018","date_published":"2018","updated_at":"2026-07-22T22:22:55Z","subjects":[],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/29306","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Kooyman, Patricia J","Brosius, Roald"]},{"key":"dc:creator","label":"Author","values":["Parker, Mohamed Habeeb"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-02-05T07:15:04Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2019-02-05T07:15:04Z"]},{"key":"dc:date.issued","label":"Date","values":["2018"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Chemical Engineering"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cape Town"]},{"key":"dc:type","label":"Dc Type","values":["Master Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Masters"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["MSc"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/29306"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The combination of MFI zeolite nano-sheets with competitive adsorption of water (H2O) in hydrocracking of long-chain paraffins presents a promising opportunity to produce diesel with high yield and with high cetane number. Thus, in wet hydrocracking of a long-chain paraffin (n-hexadecane (n-C16)) over MFI nano-sheets, it was investigated whether catalytic activity increased with increasing number of Brønsted acid (H + ) sites (decreasing silicon-to-aluminium (Si/Al) ratio), while secondary cracking remained completely suppressed. Also, it was investigated whether more Al atoms could be incorporated into the framework of MFI nano-sheets by modifying the new synthesis method. It was demonstrated that the new synthesis method, which utilizes C22H45–N + (CH3)2–C6H12–N + (CH3)2–C6H13 (C22-6-6) as structure-directing agent (SDA), could be extended to various Si/Al ratios in the range 25 – 100. The nano-sheets exhibited extra-framework Al (EFAl) species. Nano-sheets with Si/Al = 75 exhibited an oddly large amount of EFAl species compared to the other nano-sheets. For nano-sheets with Si/Al = 75, a high fraction of the EFAl species may have formed during calcination of the ammonium form and may encompass flexible Al species with predominantly Al in octahedral coordination (AlVI). Nano-sheets were loaded with 0.9 wt% platinum (Pt) via incipient wetness impregnation (IWI). Pt/nano-sheets with Si/Al = 25, 50 and 100 exhibited similar and high Pt dispersion (γPt). In contrast, Pt/nano-sheets with Si/Al = 75 exhibited a very low γPt, which was probably a result of the abundance, nature and/or location of EFAl species present in the support. In dry hydrocracking of n-C16, the catalytic activity increased with decreasing Si/Al ratio, strongly suggesting that the number of H+ sites increased with decreasing Si/Al ratio. Nano-sheets with Si/Al = 75 most likely contained AlVI species associated with Brønsted acidity, supporting the presence of flexible AlVI species. In wet hydrocracking of n-C16, at a constant and sufficiently high γPt, the activity increased with increasing number of H+ sites (decreasing Si/Al ratio), while secondary cracking remained completely suppressed. Pt/nano-sheets with Si/Al = 75 displayed a lower activity than 2 Pt/nano-sheets with Si/Al = 100, which may be a result of the very low γPt of Pt/nano-sheets with Si/Al = 75, underlining the importance of high γPt. For Pt/nano-sheets with Si/Al = 25, 50 and 100, H2O favoured linear cracking products at low cracking yields. In contrast, for Pt/nano-sheets with Si/Al = 75, H2O favoured branched cracking products, which may be a result of Pt sites on the external surface of the support being too far from the H+ sites inside the micropores. The new synthesis method could be extended to a modified SDA, namely C22H45–N + (CH3)2–C6H12–N + (CH3)2–C3H7 (C22-6-3), at various Si/Al ratios in the range 25 – 100. Replacing the terminal –C6H13 group in C22-6-6 with –C3H7 resulted in an increase in the framework Al (FAl) content of MFI nano-sheets with Si/Al ≥ 50, with the increase being the most pronounced for nano-sheets with Si/Al = 50. This was due to the increased occupancy of the zeolite framework by the hydrophilic region of C22-6-3 in comparison to the hydrophilic region of C22-6-6 under the given set of synthesis conditions, since –C3H7 was less bulky than –C6H13. Calcined nano-sheets were loaded with 1 wt% Pt via competitive ion exchange (CIE). In dry and wet hydrocracking of n-C16, the activity increased with decreasing Si/Al ratio and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to the presence of additional H+ sites generated after SDA removal. H2O favoured linear cracking products at low cracking yields. Sodium (Na+ ) ion-exchanged nano-sheets were loaded with 1 wt% Pt via CIE. The average Pt size (dPt) of the Pt/Na+ nano-sheets were larger than the dPt of the Pt/calcined nano-sheets, which may be a result of the nature and/or location of EFAl species present in the Na+ supports. In dry and wet hydrocracking of n-C16, differences in activity were observed and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to insufficient intimacy between H+ sites and Pt sites such that the rate was controlled by diffusion of olefinic intermediates from H+ sites to Pt sites and vice versa. H2O favoured linear cracking products at low cracking yields."]},{"key":"dc:title","label":"Title","values":["Hydrocracking of n-C16 over MFI Zeolite Nano-sheets - Effect of the Si/Al Ratio"]}]}],"canonical_facts":{"dc:contributor.advisor":["Kooyman, Patricia J","Brosius, Roald"],"dc:creator":["Parker, Mohamed Habeeb"],"dc:date.accessioned":["2019-02-05T07:15:04Z"],"dc:date.available":["2019-02-05T07:15:04Z"],"dc:date.issued":["2018"],"dc:description.abstract":["The combination of MFI zeolite nano-sheets with competitive adsorption of water (H2O) in hydrocracking of long-chain paraffins presents a promising opportunity to produce diesel with high yield and with high cetane number. Thus, in wet hydrocracking of a long-chain paraffin (n-hexadecane (n-C16)) over MFI nano-sheets, it was investigated whether catalytic activity increased with increasing number of Brønsted acid (H + ) sites (decreasing silicon-to-aluminium (Si/Al) ratio), while secondary cracking remained completely suppressed. Also, it was investigated whether more Al atoms could be incorporated into the framework of MFI nano-sheets by modifying the new synthesis method. It was demonstrated that the new synthesis method, which utilizes C22H45–N + (CH3)2–C6H12–N + (CH3)2–C6H13 (C22-6-6) as structure-directing agent (SDA), could be extended to various Si/Al ratios in the range 25 – 100. The nano-sheets exhibited extra-framework Al (EFAl) species. Nano-sheets with Si/Al = 75 exhibited an oddly large amount of EFAl species compared to the other nano-sheets. For nano-sheets with Si/Al = 75, a high fraction of the EFAl species may have formed during calcination of the ammonium form and may encompass flexible Al species with predominantly Al in octahedral coordination (AlVI). Nano-sheets were loaded with 0.9 wt% platinum (Pt) via incipient wetness impregnation (IWI). Pt/nano-sheets with Si/Al = 25, 50 and 100 exhibited similar and high Pt dispersion (γPt). In contrast, Pt/nano-sheets with Si/Al = 75 exhibited a very low γPt, which was probably a result of the abundance, nature and/or location of EFAl species present in the support. In dry hydrocracking of n-C16, the catalytic activity increased with decreasing Si/Al ratio, strongly suggesting that the number of H+ sites increased with decreasing Si/Al ratio. Nano-sheets with Si/Al = 75 most likely contained AlVI species associated with Brønsted acidity, supporting the presence of flexible AlVI species. In wet hydrocracking of n-C16, at a constant and sufficiently high γPt, the activity increased with increasing number of H+ sites (decreasing Si/Al ratio), while secondary cracking remained completely suppressed. Pt/nano-sheets with Si/Al = 75 displayed a lower activity than 2 Pt/nano-sheets with Si/Al = 100, which may be a result of the very low γPt of Pt/nano-sheets with Si/Al = 75, underlining the importance of high γPt. For Pt/nano-sheets with Si/Al = 25, 50 and 100, H2O favoured linear cracking products at low cracking yields. In contrast, for Pt/nano-sheets with Si/Al = 75, H2O favoured branched cracking products, which may be a result of Pt sites on the external surface of the support being too far from the H+ sites inside the micropores. The new synthesis method could be extended to a modified SDA, namely C22H45–N + (CH3)2–C6H12–N + (CH3)2–C3H7 (C22-6-3), at various Si/Al ratios in the range 25 – 100. Replacing the terminal –C6H13 group in C22-6-6 with –C3H7 resulted in an increase in the framework Al (FAl) content of MFI nano-sheets with Si/Al ≥ 50, with the increase being the most pronounced for nano-sheets with Si/Al = 50. This was due to the increased occupancy of the zeolite framework by the hydrophilic region of C22-6-3 in comparison to the hydrophilic region of C22-6-6 under the given set of synthesis conditions, since –C3H7 was less bulky than –C6H13. Calcined nano-sheets were loaded with 1 wt% Pt via competitive ion exchange (CIE). In dry and wet hydrocracking of n-C16, the activity increased with decreasing Si/Al ratio and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to the presence of additional H+ sites generated after SDA removal. H2O favoured linear cracking products at low cracking yields. Sodium (Na+ ) ion-exchanged nano-sheets were loaded with 1 wt% Pt via CIE. The average Pt size (dPt) of the Pt/Na+ nano-sheets were larger than the dPt of the Pt/calcined nano-sheets, which may be a result of the nature and/or location of EFAl species present in the Na+ supports. In dry and wet hydrocracking of n-C16, differences in activity were observed and in wet hydrocracking, secondary cracking was not completely suppressed up to high conversions. This was probably due to insufficient intimacy between H+ sites and Pt sites such that the rate was controlled by diffusion of olefinic intermediates from H+ sites to Pt sites and vice versa. H2O favoured linear cracking products at low cracking yields."],"dc:identifier.uri":["http://hdl.handle.net/11427/29306"],"dc:language.iso":["eng"],"dc:publisher.department":["Department of Chemical Engineering"],"dc:publisher.institution":["University of Cape Town"],"dc:title":["Hydrocracking of n-C16 over MFI Zeolite Nano-sheets - Effect of the Si/Al Ratio"],"dc:type":["Master Thesis"],"dc:type.qualificationlevel":["Masters"],"dc:type.qualificationname":["MSc"]},"updated_at":"2026-07-22T22:22:55Z"}