The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite

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dc.contributor.advisorO'Connor, Cyril Ten_ZA
dc.contributor.authorO'Donovan,Anthony Williamen_ZA
dc.date.accessioned2016-08-24T12:55:20Z
dc.date.available2016-08-24T12:55:20Z
dc.date.issued1995en_ZA
dc.description.abstractAlthough there have been a number of studies of the effect of hydrothermal and acid dealumination on the properties of Mordenite, there is a lack of clarity on many issues related to the changes which these treatments cause to the structure, acidity and catalytic activity of Mordenite. Both methods remove aluminium from the framework thus creating extra framework aluminium species. Although there are some reports that these species, particularly when created by mild steaming, increase the acidity and catalytic activity of the dealuminated sample, it has also been reported that these species have either a negative or no effect on thecatalyst's acidity and activity [Mirodatos and Barthomeuf, 1981; Chen eta/., 1992; Meyerseta/., 1988; Bamwenda eta/., 1994; Brunner eta/., 1994]. These conflicting reports are understandable when one considers that the dealumination conditions in the various studies are usually not equivalent to each other and consequently the resultant catalysts may differ. The use of Mordenite from different sources to compare acidity in one case and structure in another may also lead to different and conflicting results. This has affected the interpretation of observed trends in the structure, acidity and catalytic behaviour of dealuminated Mordenite. A systematic study of the effect of acid washing of sodium Mordenite and hydrogen exchanged Mordenite, both before and after steaming, has been carried out. The bulk removal of aluminium was monitored by elemental analysis of samples. The study investigated the effect of different conditions of acid washing, steaming and steaming followed by acid washing on the solid state properties of Mordenite by use of solid state ²⁷AI and ²⁹Si nuclear magnetic resonance, x-ray diffraction and infrared techniques. The effect of these changes on the number, type and strength of acid sites in Mordenite was then investigated by ammonia temperature programmed desorption, Fourier-Transform infrared analysis of pyridine adsorption and proton nuclear magnetic resonance studies. The changes caused by dealumination to the catalytic activity and shape selective properties of Mordenite as determined by studies of isobutane cracking, cyclohexanol dehydration and isopropylation of naphthalene, were then explained in terms of the acidic and structural properties of the dealuminated Mordenite samples.en_ZA
dc.identifier.apacitation (1995). <i>The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. Retrieved from http://hdl.handle.net/11427/21502en_ZA
dc.identifier.chicagocitation. <i>"The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1995. http://hdl.handle.net/11427/21502en_ZA
dc.identifier.citation 1995. The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite. Thesis. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering. http://hdl.handle.net/11427/21502en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - O'Donovan,Anthony William AB - Although there have been a number of studies of the effect of hydrothermal and acid dealumination on the properties of Mordenite, there is a lack of clarity on many issues related to the changes which these treatments cause to the structure, acidity and catalytic activity of Mordenite. Both methods remove aluminium from the framework thus creating extra framework aluminium species. Although there are some reports that these species, particularly when created by mild steaming, increase the acidity and catalytic activity of the dealuminated sample, it has also been reported that these species have either a negative or no effect on thecatalyst's acidity and activity [Mirodatos and Barthomeuf, 1981; Chen eta/., 1992; Meyerseta/., 1988; Bamwenda eta/., 1994; Brunner eta/., 1994]. These conflicting reports are understandable when one considers that the dealumination conditions in the various studies are usually not equivalent to each other and consequently the resultant catalysts may differ. The use of Mordenite from different sources to compare acidity in one case and structure in another may also lead to different and conflicting results. This has affected the interpretation of observed trends in the structure, acidity and catalytic behaviour of dealuminated Mordenite. A systematic study of the effect of acid washing of sodium Mordenite and hydrogen exchanged Mordenite, both before and after steaming, has been carried out. The bulk removal of aluminium was monitored by elemental analysis of samples. The study investigated the effect of different conditions of acid washing, steaming and steaming followed by acid washing on the solid state properties of Mordenite by use of solid state ²⁷AI and ²⁹Si nuclear magnetic resonance, x-ray diffraction and infrared techniques. The effect of these changes on the number, type and strength of acid sites in Mordenite was then investigated by ammonia temperature programmed desorption, Fourier-Transform infrared analysis of pyridine adsorption and proton nuclear magnetic resonance studies. The changes caused by dealumination to the catalytic activity and shape selective properties of Mordenite as determined by studies of isobutane cracking, cyclohexanol dehydration and isopropylation of naphthalene, were then explained in terms of the acidic and structural properties of the dealuminated Mordenite samples. DA - 1995 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1995 T1 - The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite TI - The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite UR - http://hdl.handle.net/11427/21502 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21502
dc.identifier.vancouvercitation. The effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordenite. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Chemical Engineering, 1995 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21502en_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.titleThe effect of hydrothermal and acid dealumination on the structural, acid and catalytic properties of Mordeniteen_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
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