Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano
Autor(a) principal: | |
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Data de Publicação: | 2013 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Repositório Institucional da UFSCAR |
Texto Completo: | https://repositorio.ufscar.br/handle/ufscar/3944 |
Resumo: | The research addressed the generation of mesoporosity in the zeolite ZSM-12 (MTW). In the first part we studied the synthesis of ZSM-12 via conventional methodology and in the presence of a mesopore directing agent, organosilane [3-(Trimethoxy-silyl)propyl] octadecyldimethylammonium chloride (TPOAC). It was verified to influence the TPOAC/SiO2 and H2O/SiO2 ratios and, also the aging of the reaction mixture, temperature and time of the hydrothermal treatment. In the second part we studied the formation of mesoporosity by post-synthesis treatment with alkaline solution (NaOH). For optimization of such treatment the concentration of the NaOH solution and the temperature were varied. The zeolites were characterized by X-ray diffraction, chemical analysis by energy-dispersive X-ray spectroscopy, N2 adsorption/desorption, scanning electron microscopy, nuclear magnetic resonance of 27Al, and temperature-programmed desorption of ammonia. By the analyses of X-ray diffraction and Rietveld refinement, we verified a decrease in crystallization kinetics with increasing TPOAC/SiO2 ratio and a tendency for simultaneous crystallization of MFI and MTW phases with increasing H2O/SiO2 ratio, temperature and aging time. It was possible to obtain mesoporous ZSM-12 with high purity and crystallinity with only small quantities of TPOAC and relatively long crystallization times. For ZSM-12 zeolites treated in basic medium, there was the formation of mesopores in the range from 2.9 to 23 nm due to the silicon extraction from the crystalline framework, which caused a decrease in the volume of micropores and an increase in the total acidity, assigned to the decrease in Si/Al ratio. In the cracking of cyclohexane at 400 °C, although the presence of mesoporosity had caused a decrease in the total acidity, the zeolites synthesized with TPOAC showed similar conversions to conventional zeolite with minimal catalytic deactivation, which was attributed to the better mass transfer and less coke formation. The ZSM-12 zeolites treated with NaOH exhibited activity and stability similar to those obtained in the presence of TPOAC. By its higher proportion of strong acid sites, the conventional ZSM-12 zeolite showed higher hydrocarbon yields in the range from C2 to C4 in comparison with the mesoporous zeolites, with the latter showing a higher yield for C6 hydrocarbons. |
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Carvalho, Kele Tatiane GomesUrquieta-González, Ernesto Antoniohttp://lattes.cnpq.br/72633457055418752016-06-02T19:55:38Z2014-02-172016-06-02T19:55:38Z2013-09-12CARVALHO, Kele Tatiane Gomes. Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano. 2013. 142 f. Tese (Doutorado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2013.https://repositorio.ufscar.br/handle/ufscar/3944The research addressed the generation of mesoporosity in the zeolite ZSM-12 (MTW). In the first part we studied the synthesis of ZSM-12 via conventional methodology and in the presence of a mesopore directing agent, organosilane [3-(Trimethoxy-silyl)propyl] octadecyldimethylammonium chloride (TPOAC). It was verified to influence the TPOAC/SiO2 and H2O/SiO2 ratios and, also the aging of the reaction mixture, temperature and time of the hydrothermal treatment. In the second part we studied the formation of mesoporosity by post-synthesis treatment with alkaline solution (NaOH). For optimization of such treatment the concentration of the NaOH solution and the temperature were varied. The zeolites were characterized by X-ray diffraction, chemical analysis by energy-dispersive X-ray spectroscopy, N2 adsorption/desorption, scanning electron microscopy, nuclear magnetic resonance of 27Al, and temperature-programmed desorption of ammonia. By the analyses of X-ray diffraction and Rietveld refinement, we verified a decrease in crystallization kinetics with increasing TPOAC/SiO2 ratio and a tendency for simultaneous crystallization of MFI and MTW phases with increasing H2O/SiO2 ratio, temperature and aging time. It was possible to obtain mesoporous ZSM-12 with high purity and crystallinity with only small quantities of TPOAC and relatively long crystallization times. For ZSM-12 zeolites treated in basic medium, there was the formation of mesopores in the range from 2.9 to 23 nm due to the silicon extraction from the crystalline framework, which caused a decrease in the volume of micropores and an increase in the total acidity, assigned to the decrease in Si/Al ratio. In the cracking of cyclohexane at 400 °C, although the presence of mesoporosity had caused a decrease in the total acidity, the zeolites synthesized with TPOAC showed similar conversions to conventional zeolite with minimal catalytic deactivation, which was attributed to the better mass transfer and less coke formation. The ZSM-12 zeolites treated with NaOH exhibited activity and stability similar to those obtained in the presence of TPOAC. By its higher proportion of strong acid sites, the conventional ZSM-12 zeolite showed higher hydrocarbon yields in the range from C2 to C4 in comparison with the mesoporous zeolites, with the latter showing a higher yield for C6 hydrocarbons.A pesquisa abordou a geração de mesoporosidade na zeólita ZSM-12 (MTW). Numa primeira parte estudou-se a síntese da ZSM-12 via metodologia convencional (hidrotérmica) e na presença de um agente direcionador de mesoporos, o organossilano cloreto de 3-(trimetoxi-silil)propil-octadecildimetil amônio (TPOAC). Verificou-se a influência das razões TPOAC/SiO2 e H2O/SiO2 e, também, da temperatura, tempo de envelhecimento da mistura reacional e tempo de tratamento hidrotérmico. Na segunda parte estudou-se a formação de mesoporosidade por tratamento pós-síntese com solução alcalina (NaOH). Para a otimização desse tratamento, variou-se a concentração da solução de NaOH e a temperatura. As zeólitas obtidas foram caracterizadas por difratometria de raios X, análise química por espectroscopia de energia dispersiva de raios X, fisissorção de N2, microscopia eletrônica de varredura, ressonância magnética nuclear do 27Al e dessorção de amônia à temperatura programada. Pelas análises de difratometria de raios X e refinamento de Rietveld, verificou-se um decréscimo da cinética de cristalização com o aumento da razão TPOAC/SiO2 e uma tendência à cristalização simultânea das fases MTW e MFI com o aumento da razão H2O/SiO2, da temperatura e do tempo de envelhecimento. Foi possível obter ZSM-12 mesoporosa com alta pureza e cristalinidade somente com pequenas quantidades de TPOAC e tempos de cristalização relativamente longos. Para as zeólitas ZSM-12 tratadas em meio básico, houve a formação de mesoporos na faixa de 2,9 a 23 nm devido à extração de silício da rede cristalina, o que provocou uma diminuição do volume de microporos e um aumento da acidez total pela diminuição da razão Si/Al. No craqueamento de cicloexano em fase gasosa a 400 °C, as zeólitas sintetizadas com TPAOC, embora a presença de mesoporosidade tenha provocado uma diminuição na acidez total, apresentaram conversões semelhantes às da zeólita convencional com mínima desativação catalítica, o que foi atribuído à boa transferência de massa e menor formação de coque. As zeólitas ZSM-12 tratadas com NaOH exibiram atividade e estabilidade similares às obtidas na presença de TPOAC. Pela sua maior proporção de sítios ácidos fortes, a zeólita ZSM-12 convencional apresentou rendimentos maiores a hidrocarbonetos C2 a C4 do que as zeólitas contendo mesoporos, com estas últimas apresentando maior rendimento a hidrocarbonetos C6.Universidade Federal de Sao Carlosapplication/pdfporUniversidade Federal de São CarlosPrograma de Pós-Graduação em Engenharia Química - PPGEQUFSCarBRCatáliseCraqueamento catalíticoZeólita ZSM-12Síntese hidrotérmicaGeração de mesoporosZSM-12 zeoliteMesopores generationCatalytic crackingENGENHARIAS::ENGENHARIA QUIMICAZéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexanoinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFSCARinstname:Universidade Federal de São Carlos (UFSCAR)instacron:UFSCARORIGINAL5665.pdfapplication/pdf8947970https://{{ getenv "DSPACE_HOST" "repositorio.ufscar.br" }}/bitstream/ufscar/3944/1/5665.pdf3a1ee8be44b336d4926a11f4c9cc20ebMD51TEXT5665.pdf.txt5665.pdf.txtExtracted texttext/plain0https://{{ getenv "DSPACE_HOST" "repositorio.ufscar.br" }}/bitstream/ufscar/3944/2/5665.pdf.txtd41d8cd98f00b204e9800998ecf8427eMD52THUMBNAIL5665.pdf.jpg5665.pdf.jpgIM Thumbnailimage/jpeg5873https://{{ getenv "DSPACE_HOST" "repositorio.ufscar.br" }}/bitstream/ufscar/3944/3/5665.pdf.jpg91b10668c9d7cb18d4b0c9a9cfb786fcMD53ufscar/39442019-09-11 04:12:50.777oai:repositorio.ufscar.br:ufscar/3944Repositório InstitucionalPUBhttps://repositorio.ufscar.br/oai/requestopendoar:43222019-09-11T04:12:50Repositório Institucional da UFSCAR - Universidade Federal de São Carlos (UFSCAR)false |
dc.title.por.fl_str_mv |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
title |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
spellingShingle |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano Carvalho, Kele Tatiane Gomes Catálise Craqueamento catalítico Zeólita ZSM-12 Síntese hidrotérmica Geração de mesoporos ZSM-12 zeolite Mesopores generation Catalytic cracking ENGENHARIAS::ENGENHARIA QUIMICA |
title_short |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
title_full |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
title_fullStr |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
title_full_unstemmed |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
title_sort |
Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano |
author |
Carvalho, Kele Tatiane Gomes |
author_facet |
Carvalho, Kele Tatiane Gomes |
author_role |
author |
dc.contributor.authorlattes.por.fl_str_mv |
http://lattes.cnpq.br/7263345705541875 |
dc.contributor.author.fl_str_mv |
Carvalho, Kele Tatiane Gomes |
dc.contributor.advisor1.fl_str_mv |
Urquieta-González, Ernesto Antonio |
contributor_str_mv |
Urquieta-González, Ernesto Antonio |
dc.subject.por.fl_str_mv |
Catálise Craqueamento catalítico Zeólita ZSM-12 Síntese hidrotérmica Geração de mesoporos |
topic |
Catálise Craqueamento catalítico Zeólita ZSM-12 Síntese hidrotérmica Geração de mesoporos ZSM-12 zeolite Mesopores generation Catalytic cracking ENGENHARIAS::ENGENHARIA QUIMICA |
dc.subject.eng.fl_str_mv |
ZSM-12 zeolite Mesopores generation Catalytic cracking |
dc.subject.cnpq.fl_str_mv |
ENGENHARIAS::ENGENHARIA QUIMICA |
description |
The research addressed the generation of mesoporosity in the zeolite ZSM-12 (MTW). In the first part we studied the synthesis of ZSM-12 via conventional methodology and in the presence of a mesopore directing agent, organosilane [3-(Trimethoxy-silyl)propyl] octadecyldimethylammonium chloride (TPOAC). It was verified to influence the TPOAC/SiO2 and H2O/SiO2 ratios and, also the aging of the reaction mixture, temperature and time of the hydrothermal treatment. In the second part we studied the formation of mesoporosity by post-synthesis treatment with alkaline solution (NaOH). For optimization of such treatment the concentration of the NaOH solution and the temperature were varied. The zeolites were characterized by X-ray diffraction, chemical analysis by energy-dispersive X-ray spectroscopy, N2 adsorption/desorption, scanning electron microscopy, nuclear magnetic resonance of 27Al, and temperature-programmed desorption of ammonia. By the analyses of X-ray diffraction and Rietveld refinement, we verified a decrease in crystallization kinetics with increasing TPOAC/SiO2 ratio and a tendency for simultaneous crystallization of MFI and MTW phases with increasing H2O/SiO2 ratio, temperature and aging time. It was possible to obtain mesoporous ZSM-12 with high purity and crystallinity with only small quantities of TPOAC and relatively long crystallization times. For ZSM-12 zeolites treated in basic medium, there was the formation of mesopores in the range from 2.9 to 23 nm due to the silicon extraction from the crystalline framework, which caused a decrease in the volume of micropores and an increase in the total acidity, assigned to the decrease in Si/Al ratio. In the cracking of cyclohexane at 400 °C, although the presence of mesoporosity had caused a decrease in the total acidity, the zeolites synthesized with TPOAC showed similar conversions to conventional zeolite with minimal catalytic deactivation, which was attributed to the better mass transfer and less coke formation. The ZSM-12 zeolites treated with NaOH exhibited activity and stability similar to those obtained in the presence of TPOAC. By its higher proportion of strong acid sites, the conventional ZSM-12 zeolite showed higher hydrocarbon yields in the range from C2 to C4 in comparison with the mesoporous zeolites, with the latter showing a higher yield for C6 hydrocarbons. |
publishDate |
2013 |
dc.date.issued.fl_str_mv |
2013-09-12 |
dc.date.available.fl_str_mv |
2014-02-17 2016-06-02T19:55:38Z |
dc.date.accessioned.fl_str_mv |
2016-06-02T19:55:38Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.citation.fl_str_mv |
CARVALHO, Kele Tatiane Gomes. Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano. 2013. 142 f. Tese (Doutorado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2013. |
dc.identifier.uri.fl_str_mv |
https://repositorio.ufscar.br/handle/ufscar/3944 |
identifier_str_mv |
CARVALHO, Kele Tatiane Gomes. Zéolitas ZSM-12 mesoporosas textura, cristalinidade e atividade ácida para o craqueamento de cicloexano. 2013. 142 f. Tese (Doutorado em Ciências Exatas e da Terra) - Universidade Federal de São Carlos, São Carlos, 2013. |
url |
https://repositorio.ufscar.br/handle/ufscar/3944 |
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Universidade Federal de São Carlos |
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Programa de Pós-Graduação em Engenharia Química - PPGEQ |
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UFSCar |
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BR |
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Universidade Federal de São Carlos |
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