Liquid crystals as pore template for sulfated zirconia
Autor(a) principal: | |
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Data de Publicação: | 2020 |
Outros Autores: | , , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UNESP |
Texto Completo: | http://dx.doi.org/10.1016/j.colsurfa.2020.124907 http://hdl.handle.net/11449/201744 |
Resumo: | Porous sulfated zirconia was prepared using a sol-gel process associated with liquid crystal templates (LCTs). Evaluation was made of the effects of the Zr4+:SO4 2− molar ratio and aging time on the formation and stability of the lyotropic arrangement of the LCT gel and the features of the resulting mesoporous powders. Polarized light microscopy and small-angle X-ray diffraction (SAXD) analysis of the LCT gel revealed the prevalence of hexagonal mesophase (P6mm) in the sulfated samples. Thermal treatment of the samples resulted in sulfated ZrO2 ceramic powders whose infrared spectra exhibited bands characteristic of mono- and bi-dentate SO4 2− groups bonded to ZrO2. X-Ray diffractograms of the materials showed a mixture of monoclinic and tetragonal phases of zirconia, with the tetragonal phase increasing from 86–90% to 100% as the Zr4+:SO4 2− molar ratio decreases from 15 to 5. Crystallite sizes of about 9.5 and 4.5 nm were observed for the pristine and sulfated zirconia (Zr4+:SO4 2− = 5), respectively. The lattice fringe distances observed for selected areas in the electron diffraction patterns and in high-resolution transmission electron micrographs confirmed the mixture of tetragonal and monoclinic crystalline phases. Small-angle X-Ray scattering analysis showed that the gyration radius was around 2 nm and that the particles were organized as a branched network with a fractal surface when sulfate was inserted in the zirconia structure, improving its porous characteristics. The LCT generated pores with greater diameters (up to 4.4 nm) in the sulfated samples, while the surface area increased to 146 m2 g−1. The gel aging process led to the reinforcement of the pore wall structure, prevented shrinkage effects during calcination, and enabled higher surface areas to be achieved. Scanning and transmission electron microscopy analyses showed that the walls of the pores were composed of platelets of irregular shapes, giving rise to mesopores. The porous structure, combined with the presence of acid sites, improved by sulfate groups at the surface of tetragonal zirconia crystallite, makes these materials promising candidates for application as catalysts in dehydration reactions. |
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Liquid crystals as pore template for sulfated zirconiaCatalystLiquid crystal templatePorous materialsSol-gel processSulfated zirconiaPorous sulfated zirconia was prepared using a sol-gel process associated with liquid crystal templates (LCTs). Evaluation was made of the effects of the Zr4+:SO4 2− molar ratio and aging time on the formation and stability of the lyotropic arrangement of the LCT gel and the features of the resulting mesoporous powders. Polarized light microscopy and small-angle X-ray diffraction (SAXD) analysis of the LCT gel revealed the prevalence of hexagonal mesophase (P6mm) in the sulfated samples. Thermal treatment of the samples resulted in sulfated ZrO2 ceramic powders whose infrared spectra exhibited bands characteristic of mono- and bi-dentate SO4 2− groups bonded to ZrO2. X-Ray diffractograms of the materials showed a mixture of monoclinic and tetragonal phases of zirconia, with the tetragonal phase increasing from 86–90% to 100% as the Zr4+:SO4 2− molar ratio decreases from 15 to 5. Crystallite sizes of about 9.5 and 4.5 nm were observed for the pristine and sulfated zirconia (Zr4+:SO4 2− = 5), respectively. The lattice fringe distances observed for selected areas in the electron diffraction patterns and in high-resolution transmission electron micrographs confirmed the mixture of tetragonal and monoclinic crystalline phases. Small-angle X-Ray scattering analysis showed that the gyration radius was around 2 nm and that the particles were organized as a branched network with a fractal surface when sulfate was inserted in the zirconia structure, improving its porous characteristics. The LCT generated pores with greater diameters (up to 4.4 nm) in the sulfated samples, while the surface area increased to 146 m2 g−1. The gel aging process led to the reinforcement of the pore wall structure, prevented shrinkage effects during calcination, and enabled higher surface areas to be achieved. Scanning and transmission electron microscopy analyses showed that the walls of the pores were composed of platelets of irregular shapes, giving rise to mesopores. The porous structure, combined with the presence of acid sites, improved by sulfate groups at the surface of tetragonal zirconia crystallite, makes these materials promising candidates for application as catalysts in dehydration reactions.São Paulo State University (UNESP) Institute of ChemistrySão Paulo State University (UNESP) Institute of ChemistryUniversidade Estadual Paulista (Unesp)Moris, Carlos Henrique A.A. [UNESP]Alves-Rosa, Marinalva A. [UNESP]Freitas, Fernanda G. [UNESP]Martins, Leandro [UNESP]Santilli, Celso V. [UNESP]Pulcinelli, Sandra H. [UNESP]2020-12-12T02:40:43Z2020-12-12T02:40:43Z2020-09-05info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://dx.doi.org/10.1016/j.colsurfa.2020.124907Colloids and Surfaces A: Physicochemical and Engineering Aspects, v. 600.1873-43590927-7757http://hdl.handle.net/11449/20174410.1016/j.colsurfa.2020.1249072-s2.0-8508454056955842986818708650000-0002-8356-8093Scopusreponame:Repositório Institucional da UNESPinstname:Universidade Estadual Paulista (UNESP)instacron:UNESPengColloids and Surfaces A: Physicochemical and Engineering Aspectsinfo:eu-repo/semantics/openAccess2021-10-22T21:15:47Zoai:repositorio.unesp.br:11449/201744Repositório InstitucionalPUBhttp://repositorio.unesp.br/oai/requestopendoar:29462024-08-05T15:08:12.738770Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP)false |
dc.title.none.fl_str_mv |
Liquid crystals as pore template for sulfated zirconia |
title |
Liquid crystals as pore template for sulfated zirconia |
spellingShingle |
Liquid crystals as pore template for sulfated zirconia Moris, Carlos Henrique A.A. [UNESP] Catalyst Liquid crystal template Porous materials Sol-gel process Sulfated zirconia |
title_short |
Liquid crystals as pore template for sulfated zirconia |
title_full |
Liquid crystals as pore template for sulfated zirconia |
title_fullStr |
Liquid crystals as pore template for sulfated zirconia |
title_full_unstemmed |
Liquid crystals as pore template for sulfated zirconia |
title_sort |
Liquid crystals as pore template for sulfated zirconia |
author |
Moris, Carlos Henrique A.A. [UNESP] |
author_facet |
Moris, Carlos Henrique A.A. [UNESP] Alves-Rosa, Marinalva A. [UNESP] Freitas, Fernanda G. [UNESP] Martins, Leandro [UNESP] Santilli, Celso V. [UNESP] Pulcinelli, Sandra H. [UNESP] |
author_role |
author |
author2 |
Alves-Rosa, Marinalva A. [UNESP] Freitas, Fernanda G. [UNESP] Martins, Leandro [UNESP] Santilli, Celso V. [UNESP] Pulcinelli, Sandra H. [UNESP] |
author2_role |
author author author author author |
dc.contributor.none.fl_str_mv |
Universidade Estadual Paulista (Unesp) |
dc.contributor.author.fl_str_mv |
Moris, Carlos Henrique A.A. [UNESP] Alves-Rosa, Marinalva A. [UNESP] Freitas, Fernanda G. [UNESP] Martins, Leandro [UNESP] Santilli, Celso V. [UNESP] Pulcinelli, Sandra H. [UNESP] |
dc.subject.por.fl_str_mv |
Catalyst Liquid crystal template Porous materials Sol-gel process Sulfated zirconia |
topic |
Catalyst Liquid crystal template Porous materials Sol-gel process Sulfated zirconia |
description |
Porous sulfated zirconia was prepared using a sol-gel process associated with liquid crystal templates (LCTs). Evaluation was made of the effects of the Zr4+:SO4 2− molar ratio and aging time on the formation and stability of the lyotropic arrangement of the LCT gel and the features of the resulting mesoporous powders. Polarized light microscopy and small-angle X-ray diffraction (SAXD) analysis of the LCT gel revealed the prevalence of hexagonal mesophase (P6mm) in the sulfated samples. Thermal treatment of the samples resulted in sulfated ZrO2 ceramic powders whose infrared spectra exhibited bands characteristic of mono- and bi-dentate SO4 2− groups bonded to ZrO2. X-Ray diffractograms of the materials showed a mixture of monoclinic and tetragonal phases of zirconia, with the tetragonal phase increasing from 86–90% to 100% as the Zr4+:SO4 2− molar ratio decreases from 15 to 5. Crystallite sizes of about 9.5 and 4.5 nm were observed for the pristine and sulfated zirconia (Zr4+:SO4 2− = 5), respectively. The lattice fringe distances observed for selected areas in the electron diffraction patterns and in high-resolution transmission electron micrographs confirmed the mixture of tetragonal and monoclinic crystalline phases. Small-angle X-Ray scattering analysis showed that the gyration radius was around 2 nm and that the particles were organized as a branched network with a fractal surface when sulfate was inserted in the zirconia structure, improving its porous characteristics. The LCT generated pores with greater diameters (up to 4.4 nm) in the sulfated samples, while the surface area increased to 146 m2 g−1. The gel aging process led to the reinforcement of the pore wall structure, prevented shrinkage effects during calcination, and enabled higher surface areas to be achieved. Scanning and transmission electron microscopy analyses showed that the walls of the pores were composed of platelets of irregular shapes, giving rise to mesopores. The porous structure, combined with the presence of acid sites, improved by sulfate groups at the surface of tetragonal zirconia crystallite, makes these materials promising candidates for application as catalysts in dehydration reactions. |
publishDate |
2020 |
dc.date.none.fl_str_mv |
2020-12-12T02:40:43Z 2020-12-12T02:40:43Z 2020-09-05 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://dx.doi.org/10.1016/j.colsurfa.2020.124907 Colloids and Surfaces A: Physicochemical and Engineering Aspects, v. 600. 1873-4359 0927-7757 http://hdl.handle.net/11449/201744 10.1016/j.colsurfa.2020.124907 2-s2.0-85084540569 5584298681870865 0000-0002-8356-8093 |
url |
http://dx.doi.org/10.1016/j.colsurfa.2020.124907 http://hdl.handle.net/11449/201744 |
identifier_str_mv |
Colloids and Surfaces A: Physicochemical and Engineering Aspects, v. 600. 1873-4359 0927-7757 10.1016/j.colsurfa.2020.124907 2-s2.0-85084540569 5584298681870865 0000-0002-8356-8093 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Colloids and Surfaces A: Physicochemical and Engineering Aspects |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.source.none.fl_str_mv |
Scopus reponame:Repositório Institucional da UNESP instname:Universidade Estadual Paulista (UNESP) instacron:UNESP |
instname_str |
Universidade Estadual Paulista (UNESP) |
instacron_str |
UNESP |
institution |
UNESP |
reponame_str |
Repositório Institucional da UNESP |
collection |
Repositório Institucional da UNESP |
repository.name.fl_str_mv |
Repositório Institucional da UNESP - Universidade Estadual Paulista (UNESP) |
repository.mail.fl_str_mv |
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1808128466140266496 |