Ideal hydrocracking catalysts for the conversion of FT wax to diesel

Simple item page
dc.contributor.advisorGaunt, C Trevoren_ZA
dc.contributor.advisorHerman, Ronalden_ZA
dc.contributor.advisorBöhringer, Walteren_ZA
dc.contributor.authorNdimande, Conraden_ZA
dc.date.accessioned2014-11-05T03:49:29Z
dc.date.available2014-11-05T03:49:29Z
dc.date.issued2014en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThe Fischer-Tropsch wax synthesis process and the subsequent upgrade of the wax to useful distillate fuels by mild hydrocracking is a well-known, economically viable method of producing liquid fuels, in particular diesel fuel. This project seeks to develop an ideal hydrocracking catalyst (i.e. a hydrocracking unit in which only primary cracking occurs) for the conversion of Fischer-Tropsch (FT) wax to diesel and to determine the effect of carbon monoxide on the activity and selectivity of the hydrocracking catalyst for possible integration of low temperature FT wax synthesis with wax hydrocracking into a single stage. Theoretically, a combination of the Fischer-Tropsch unit with an ideal hydrocracking unit can produce diesel yields of up to 80 wt. A non-ideal hydrocracking catalyst would lower the middle distillate yields due to the occurrence of secondary cracking. Primary cracking of the paraffins produced by the low temperature FT process occurs only when the activity of the metal is high and the rate limiting step occurs on the acid site. Integrating the wax synthesis process with the subsequent work up of the wax to produce distillate fuels is not without challenges, mainly the low reaction temperature and pressure (225°C and 20 bar), in which the hydrocracking catalyst is to operate. Noble metals, combined with zeolites are known to be active for hydrocracking at such conditions. Carbon monoxide, a feedstock of the FT process poisons noble metal catalysts; therefore knowledge of its effect on the hydrocracking catalysts performance is essential. The hydrocracking catalysts were tested when the metal and the acid sites were segregated (i.e. the metal supported on an inert carrier, physically mixed with the zeolite), and when the two sites are in close proximity (i.e. the metal impregnated into the zeolite). The tests were carried out both in the presence and absence of CO consistent with the FT feed ratio. The noble metals, Rh, Ru and Pd were used as co-catalysts to H-MFI-90. It was found that the physical distance between the metal and the acid sites has disturbs the balance of the two sites by introduction of a transport steps, this seen through both the activity and selectivity of the catalyst. Pd exhibited higher activity than Rh and Ru. Primary cracking was found to be unattainable when the metal and the acid sites are segregated. When the metal and the acid sites were in close proximity (impregnated catalyst), near primary hydrocracking performance was observed at metal loading of 0.9 wt Pd. Secondary cracking was aggravated upon the introduction of CO on both the segregated and impregnated catalyst.en_ZA
dc.identifier.apacitationNdimande, C. (2014). <i>Ideal hydrocracking catalysts for the conversion of FT wax to diesel</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/9123en_ZA
dc.identifier.chicagocitationNdimande, Conrad. <i>"Ideal hydrocracking catalysts for the conversion of FT wax to diesel."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2014. http://hdl.handle.net/11427/9123en_ZA
dc.identifier.citationNdimande, C. 2014. Ideal hydrocracking catalysts for the conversion of FT wax to diesel. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ndimande, Conrad AB - The Fischer-Tropsch wax synthesis process and the subsequent upgrade of the wax to useful distillate fuels by mild hydrocracking is a well-known, economically viable method of producing liquid fuels, in particular diesel fuel. This project seeks to develop an ideal hydrocracking catalyst (i.e. a hydrocracking unit in which only primary cracking occurs) for the conversion of Fischer-Tropsch (FT) wax to diesel and to determine the effect of carbon monoxide on the activity and selectivity of the hydrocracking catalyst for possible integration of low temperature FT wax synthesis with wax hydrocracking into a single stage. Theoretically, a combination of the Fischer-Tropsch unit with an ideal hydrocracking unit can produce diesel yields of up to 80 wt. A non-ideal hydrocracking catalyst would lower the middle distillate yields due to the occurrence of secondary cracking. Primary cracking of the paraffins produced by the low temperature FT process occurs only when the activity of the metal is high and the rate limiting step occurs on the acid site. Integrating the wax synthesis process with the subsequent work up of the wax to produce distillate fuels is not without challenges, mainly the low reaction temperature and pressure (225°C and 20 bar), in which the hydrocracking catalyst is to operate. Noble metals, combined with zeolites are known to be active for hydrocracking at such conditions. Carbon monoxide, a feedstock of the FT process poisons noble metal catalysts; therefore knowledge of its effect on the hydrocracking catalysts performance is essential. The hydrocracking catalysts were tested when the metal and the acid sites were segregated (i.e. the metal supported on an inert carrier, physically mixed with the zeolite), and when the two sites are in close proximity (i.e. the metal impregnated into the zeolite). The tests were carried out both in the presence and absence of CO consistent with the FT feed ratio. The noble metals, Rh, Ru and Pd were used as co-catalysts to H-MFI-90. It was found that the physical distance between the metal and the acid sites has disturbs the balance of the two sites by introduction of a transport steps, this seen through both the activity and selectivity of the catalyst. Pd exhibited higher activity than Rh and Ru. Primary cracking was found to be unattainable when the metal and the acid sites are segregated. When the metal and the acid sites were in close proximity (impregnated catalyst), near primary hydrocracking performance was observed at metal loading of 0.9 wt Pd. Secondary cracking was aggravated upon the introduction of CO on both the segregated and impregnated catalyst. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - Ideal hydrocracking catalysts for the conversion of FT wax to diesel TI - Ideal hydrocracking catalysts for the conversion of FT wax to diesel UR - http://hdl.handle.net/11427/9123 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9123
dc.identifier.vancouvercitationNdimande C. Ideal hydrocracking catalysts for the conversion of FT wax to diesel. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9123en_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.titleIdeal hydrocracking catalysts for the conversion of FT wax to dieselen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_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_2014_ndimande_cb.pdf
Size:
2.33 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Masters