Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41

Alcohol is a useful compound, but the excessive exposure of alcohol is hazardous to human and must be treated. Therefore, photocatalysis has been proposed to be an alternative method to oxidize the alcohol and titanium dioxide (TiO2) has been recognized as the most potential photocatalyst. In this s...

Full description

Saved in:

Bibliographic Details
Main Author:	Mohd. Nor, Nur Umisyuhada
Format:	Thesis
Language:	English
Published:	2015
Subjects:	QD Chemistry
Online Access:	http://eprints.utm.my/id/eprint/53775/25/NurUmisyuhadaMohdNorMFS2015.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!

id	my-utm-ep.53775
record_format	uketd_dc
spelling	my-utm-ep.537752020-09-02T05:58:28Z Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41 2015-02 Mohd. Nor, Nur Umisyuhada QD Chemistry Alcohol is a useful compound, but the excessive exposure of alcohol is hazardous to human and must be treated. Therefore, photocatalysis has been proposed to be an alternative method to oxidize the alcohol and titanium dioxide (TiO2) has been recognized as the most potential photocatalyst. In this study, in order to increase the efficiency of TiO2, TiO2-MCM-41 series were prepared by an impregnation method. The X-ray diffraction patterns and nitrogen adsorptiondesorption analysis revealed the successful formation of MCM-41. The X-ray diffraction patterns also showed that the pure phase of TiO2 is anatase. The structure of MCM-41 was maintained when the loading amount of TiO2 was low (up to 5 wt%). The successful formation of TiO2-MCM-41 was also confirmed by fluorescence spectroscopy. On the other hand, diffuse reflectance ultraviolet visible spectrum showed that the sample with 5 wt% of TiO2 (TiO2(5)-MCM-41) loading has the most dispersed TiO2 among the TiO2-MCM-41 samples. The good dispersion of TiO2 on the MCM-41 was also observed by field emission scanning electron microscopy and the energy dispersive X-ray mapping analyses. The TiO2-MCM-41 with 5 wt% of TiO2 loading showed the highest turnover number (TON) which is 0.27 for phenol oxidation. The dispersion of TiO2 and well maintained MCM-41 structure were proposed to be the important parameters for the high activity of the photocatalyst. The kinetic study revealed that phenol oxidation followed first order with the rate constant of 0.33 h-1, while the study on the mechanism of reaction proposed that the positive holes acted as the active sites in phenol oxidation. The activity of the best photocatalyst, TiO2(5)-MCM-41 was also tested for oxidations of cyclohexanol and hexanol. The photocatalytic activity increased in the order of hexanol < cyclohexanol < phenol. It is suggested that the strongest interaction and adsorption between phenol and the photocatalyst led to the highest activity. In contrast, cyclohexanol oxidation followed second order with the rate constant of 0.026 M-1 h-1 while, the hexanol oxidation followed pseudo-first order with the rate constant of 0.014 h-1. Scavenger tests results proposed that the superoxide radicals acted as the active species for both cyclohexanol and hexanol oxidations. 2015-02 Thesis http://eprints.utm.my/id/eprint/53775/ http://eprints.utm.my/id/eprint/53775/25/NurUmisyuhadaMohdNorMFS2015.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:85470 masters Universiti Teknologi Malaysia, Faculty of Science Faculty of Science
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	QD Chemistry
spellingShingle	QD Chemistry Mohd. Nor, Nur Umisyuhada Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
description	Alcohol is a useful compound, but the excessive exposure of alcohol is hazardous to human and must be treated. Therefore, photocatalysis has been proposed to be an alternative method to oxidize the alcohol and titanium dioxide (TiO2) has been recognized as the most potential photocatalyst. In this study, in order to increase the efficiency of TiO2, TiO2-MCM-41 series were prepared by an impregnation method. The X-ray diffraction patterns and nitrogen adsorptiondesorption analysis revealed the successful formation of MCM-41. The X-ray diffraction patterns also showed that the pure phase of TiO2 is anatase. The structure of MCM-41 was maintained when the loading amount of TiO2 was low (up to 5 wt%). The successful formation of TiO2-MCM-41 was also confirmed by fluorescence spectroscopy. On the other hand, diffuse reflectance ultraviolet visible spectrum showed that the sample with 5 wt% of TiO2 (TiO2(5)-MCM-41) loading has the most dispersed TiO2 among the TiO2-MCM-41 samples. The good dispersion of TiO2 on the MCM-41 was also observed by field emission scanning electron microscopy and the energy dispersive X-ray mapping analyses. The TiO2-MCM-41 with 5 wt% of TiO2 loading showed the highest turnover number (TON) which is 0.27 for phenol oxidation. The dispersion of TiO2 and well maintained MCM-41 structure were proposed to be the important parameters for the high activity of the photocatalyst. The kinetic study revealed that phenol oxidation followed first order with the rate constant of 0.33 h-1, while the study on the mechanism of reaction proposed that the positive holes acted as the active sites in phenol oxidation. The activity of the best photocatalyst, TiO2(5)-MCM-41 was also tested for oxidations of cyclohexanol and hexanol. The photocatalytic activity increased in the order of hexanol < cyclohexanol < phenol. It is suggested that the strongest interaction and adsorption between phenol and the photocatalyst led to the highest activity. In contrast, cyclohexanol oxidation followed second order with the rate constant of 0.026 M-1 h-1 while, the hexanol oxidation followed pseudo-first order with the rate constant of 0.014 h-1. Scavenger tests results proposed that the superoxide radicals acted as the active species for both cyclohexanol and hexanol oxidations.
format	Thesis
qualification_level	Master's degree
author	Mohd. Nor, Nur Umisyuhada
author_facet	Mohd. Nor, Nur Umisyuhada
author_sort	Mohd. Nor, Nur Umisyuhada
title	Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
title_short	Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
title_full	Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
title_fullStr	Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
title_full_unstemmed	Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41
title_sort	photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica mcm-41
granting_institution	Universiti Teknologi Malaysia, Faculty of Science
granting_department	Faculty of Science
publishDate	2015
url	http://eprints.utm.my/id/eprint/53775/25/NurUmisyuhadaMohdNorMFS2015.pdf
_version_	1747817624343937024

Photocatalytic oxidation of phenol, cyclohexanol and hexanol by titania dispersed on mesoporous silica MCM-41

Similar Items