Synthesis, characterisation and chemistry of silica supported Acids
Synthesis, characterisation and chemistry of silica supported Acids
A series of silica based supports modified with 12-phosphotungstic acid (HPW), methane and trifluoromethanesulphonic acids have been synthesised. As a support, an amorphous silica and a liquid crystal templated mesoporous silica H1SiO2 were utilised. The effects of the acids on the structure and surface properties of the silica supports and further on the immobilisation of transition metals (metal carbonyl, zirconocene) on the support surface were investigated.
The supported acids were prepared by adsorption technique with an anhydrous organic solvent and followed by vacuum evaporation or filtration to obtain the dry modified silica with acids. EDX-SEM analysis for the tungsten content of the silica modified with HPW was found to be 15-18% for low loaded samples and 35-40% for high loaded samples. No crystal phase due to HPW was observed from the powder X-ray diffraction (PXRD) patterns even for high loaded samples. The supported HPW on both types of silica exhibited narrow pore size distributions with no large reduction in the pore diameter measurements. Pyridine adsorption study on the supported HPW showed that HPW supported on Aerosil 200 displayed intense absorption peaks due to Bronsted acidity as compared to HPW on mesoporous silica, H1SiO2. Under comparable conditions, the loading was 0.24 molecules/nm2 for HPW (18wt%)/Aerosil 200 but only 0.06 molecules/nm2 for HPW (15wt%)H1SiO2. 31P solid state NMR results showed unambiguously that the Keggin structure was retained upon loading HPW on silica. TEM images of high loaded HPW on mesoporous silica showed strong contrast dark lines indicative of the regular crystal lattice of H1SiO2. After amorphisation with the electron beam, similar structures were observed which could be due to the presence of the HPW species in the pores.
University of Southampton
Ship, Chee Peng
c4cc8d7b-c1f4-455e-9e9d-41aac80355a0
2002
Ship, Chee Peng
c4cc8d7b-c1f4-455e-9e9d-41aac80355a0
Ship, Chee Peng
(2002)
Synthesis, characterisation and chemistry of silica supported Acids.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
A series of silica based supports modified with 12-phosphotungstic acid (HPW), methane and trifluoromethanesulphonic acids have been synthesised. As a support, an amorphous silica and a liquid crystal templated mesoporous silica H1SiO2 were utilised. The effects of the acids on the structure and surface properties of the silica supports and further on the immobilisation of transition metals (metal carbonyl, zirconocene) on the support surface were investigated.
The supported acids were prepared by adsorption technique with an anhydrous organic solvent and followed by vacuum evaporation or filtration to obtain the dry modified silica with acids. EDX-SEM analysis for the tungsten content of the silica modified with HPW was found to be 15-18% for low loaded samples and 35-40% for high loaded samples. No crystal phase due to HPW was observed from the powder X-ray diffraction (PXRD) patterns even for high loaded samples. The supported HPW on both types of silica exhibited narrow pore size distributions with no large reduction in the pore diameter measurements. Pyridine adsorption study on the supported HPW showed that HPW supported on Aerosil 200 displayed intense absorption peaks due to Bronsted acidity as compared to HPW on mesoporous silica, H1SiO2. Under comparable conditions, the loading was 0.24 molecules/nm2 for HPW (18wt%)/Aerosil 200 but only 0.06 molecules/nm2 for HPW (15wt%)H1SiO2. 31P solid state NMR results showed unambiguously that the Keggin structure was retained upon loading HPW on silica. TEM images of high loaded HPW on mesoporous silica showed strong contrast dark lines indicative of the regular crystal lattice of H1SiO2. After amorphisation with the electron beam, similar structures were observed which could be due to the presence of the HPW species in the pores.
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Published date: 2002
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Local EPrints ID: 464520
URI: http://eprints.soton.ac.uk/id/eprint/464520
PURE UUID: 6cd76c39-298f-481f-908e-1bd19f1e94f6
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Date deposited: 04 Jul 2022 23:43
Last modified: 16 Mar 2024 19:34
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Author:
Chee Peng Ship
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