The University of Southampton
University of Southampton Institutional Repository

Synthesis, characterisation and chemistry of silica supported Acids

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
Ship, Chee Peng

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.

Text
823628.pdf - Version of Record
Available under License University of Southampton Thesis Licence.
Download (10MB)

More information

Published date: 2002

Identifiers

Local EPrints ID: 464520
URI: http://eprints.soton.ac.uk/id/eprint/464520
PURE UUID: 6cd76c39-298f-481f-908e-1bd19f1e94f6

Catalogue record

Date deposited: 04 Jul 2022 23:43
Last modified: 05 Jul 2022 02:06

Export record

Contributors

Author: Chee Peng Ship

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×