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Removal of Pb2+ from aqueous solutions using two Brazilian rocks containing zeolites

Shinzato, M. C.; Montanheiro, T. J.; Janasi, Valdecir de Assis; Andrade, S.; Yamamoto, Jorge Kazuo
Fonte: SPRINGER; NEW YORK Publicador: SPRINGER; NEW YORK
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.44%
The removal of Pb2+ from aqueous solution by two Brazilian rocks that contain zeolites-amygdaloidal dacite (ZD) and sandstone (ZS)-was examined by batch experiments. ZD contains mordenite and ZS, stilbite. The effects of contact time, concentration of metal in solution and capacity of Na+ to recover the adsorbed metals were evaluated at room temperature (20A degrees C). The sorption equilibrium was reached in the 30 min of agitation time. Both materials removed 100% of Pb2+ from solutions at concentrations up to 50 mg/L, and at concentrations larger than 100 mg/L of Pb2+, the adsorption capacity of sandstone was more efficient than that of amygdaloidal dacite due to the larger quantities and the type of zeolites (stilbite) in the cement of this rock. All adsorbed Pb2+ was easily replaced by Na+ in both samples. The analysis of the adsorption models using nonlinear regression revealed that the Sips and the Freundlich isotherms provided the best fit for the ZS and ZD experimental data, respectively, indicating the heterogeneous adsorption surfaces of these zeolites.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [03/06259-4]

Espectroscopia de alta resolução por ressonância magnética multinuclear aplicada ao estudo de zeólitas; High resolution multinuclear magnetic resonance spectroscopy applied to the study of zeolites

Freitas, Jair Carlos Checon de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/09/1994 PT
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37.44%
Este trabalho consiste de um estudo detalhado a respeito da Espectroscopia de Alta Resolução em Sólidos por RMN e da sua aplicação à análise de zeólitas Y e *, sendo utilizadas as técnicas de Rotação em torno do Ângulo Mágico, Desacoplamento e Polarização Cruzada para a obtenção dos espectros de alta resolução. Dedicamos uma atenção especial à interação quadrupolar, existente quando o núcleo apresenta spin > 1/2, devido aos seus efeitos importantíssimos em zeólitas, e procuramos apresentar um material teórico abrangente e acessível sobre o assunto. As análises de zeólitas foram feitas por RMN dos núcleos 29Si, 27Al, 13C e 23Na, o que permitiu a obtenção de uma variada quantidade de informações sobre suas propriedades e modificações ocorridas ao longo dos tratamentos com elas realizados. Todas as medidas foram efetuadas com um espectrômetro desenvolvido em nosso laboratório; o campo magnético utilizado foi de 2T, um valor baixo mas que permite a extração de valiosas informações a respeito dos materiais analisados; This work consists in a detailed study of High Resolution NMR Spectroscopy in Solids and its application to the analysis of zeolites Y and *. In these studies, we have used the techniques of Magic Angle Spinning...

Caracterização de zeolitas utilizando espectroscopia de alta resolução em sólidos por ressonância magnética nuclear; Characterization of zeolites using high-resolution solid-state nuclear magnetic resonance spectroscopy

Mello, Nilson Camargo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/04/1993 PT
Relevância na Pesquisa
37.32%
O objetivo deste trabalho consistiu na caracterização das zeólitas Y e ZSM-5, usando a técnica de Espectroscopia de Alta resolução em sólidos por Ressonância Magnética Nuclear (RMN). Os espectros de alta resolução do 13C e 27Al foram obtidos usando, simultaneamente, as técnicas de desacoplamento em alta potência (DEC) e rotação da amostra em torno de ângulo mágico (MAS). Utilizamos os espectros de alta resolução dos núcleos de 27Al para analisarmos a coordenação e a quantificação dos alumínios estruturais e extra-estruturais em zeólitas Y e de 13C para analisarmos o posicionamento de moléculas direcionadas localizadas nos canais da ZSM-5; The objective of this work consisted of the characterization of zeolites Y and ZSM-5, using Solid State High Resolution Nuclear Magnetic Resonance Spectrsocopy. The 13C and 27Al high resolution spectra were obtained using simultaneously, High Power Decoupling (DEC) and Magic Angle Spinning (MAS). The high resolution 27Al spectra were used to distinguish and quantify framework and non-framework aluminium in zeolites Y. The high resolution 13C spectra were used to probe the position and configuration of the guest organic molecules within the framework of the ZSM-5 zeolite

Incorporação de dióxido de titânio em zeólitas para emprego em fotocatálise heterogênea; Titanium oxide incorporation on zeolites for heterogeneous photocatalisis

Merg, Jean C.; Rossett, Franciele; Penha, Fábio G.; Pergher, Sibele Berenice Castellã; Petkowicz, Diego Ivan; Santos, Joao Henrique Zimnoch dos
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
POR
Relevância na Pesquisa
37.32%
This work proposes the study of heterogeneous photocatalysis using TiO2 impregnated in zeolites beta, ZSM-5, mordenite, NaXb, NaXp and NaY for the decomposition of methylene blue. The catalysts were characterized by XRD, IR, textural analyses by N2 adsorption, SEM, DRS and the reaction of decomposition was monitored by UV visible. The results indicated that didnft have structural changes in the catalysts after Ti impregnations, only in the case of NaY and NaX zeolites. The better photocatalyst to metylene blue decomposition was beta/Ti zeolite due had one structure more accessible (with bigger porous) helping in TiO2 dispersion and catalytic active.

A comparative study of glycerol dehydration catalyzed by micro/mesoporous MFI zeolites

Possato, Luiz Gustavo; Diniz, Rosiane N.; Garetto, Teresita; Pulcinelli, Sandra H.; Santilli, Celso V.; Martins, Leandro
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 102-112
ENG
Relevância na Pesquisa
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The catalytic properties of monomodal microporous and bimodal micro-mesoporous zeolites were investigated in the gas-phase dehydration of glycerol. The desilication methodology used to produce the mesoporous zeolites minimized diffusion limitations and increased glycerol conversion in the catalytic reaction due to the hierarchical system of secondary pores created in the zeolite crystals. The chemical and structural properties of the catalyst were studied by X-ray diffraction, nitrogen adsorption-desorption isotherms, NH3-TPD and pyridine chemisorption followed by IR-spectroscopy. Although the aim was to desilicate to create mesoporosity in the zeolite crystals, the desilication promoted the formation of extra-framework aluminum species that affected the conversion of glycerol and the products distribution. The results clearly show that the mesoporous zeolites with designed mesopore structure allowed a rapid diffusion and consequently improved the reaction kinetics. However, especial attention must be given to the desilication procedure because the severity of the treatment negatively interfered on the Brønsted and Lewis acid sites relative concentration and, consequently, in the efficiency of the catalysis performed by these materials. On the other hand...

Estudo de recuperação xilitol produzido por fermentação do hidrolisado de bagaço de cana-de-açucar utilizando zeolitas.; Study of the recovery of xilitol produced by fermentation of the hidrolisate one of bagasse of sugar cane-of-sugar using zeolites.

Tihany Morita Antero dos Santos
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/12/2004 PT
Relevância na Pesquisa
37.44%
O xilitol é um açúcar-álcool com ampla utilização na indústria alimentícia, porém mesmo sendo numerosos os estudos sobre a sua produção a partir da fermentação de hidrolisados hemicelulósicos, poucos são os trabalhos que tratam da sua separação e purificação. O objetivo principal deste trabalho é, portanto, desenvolver uma metodologia de separação do xilitol dos compostos remanescentes no meio fermentado obtido por fermentação do hidrolisado de bagaço de cana-de-açúcar por Candida guilliermondii. Inicialmente, ensaios conduzidos com as zeólitas Na86X, Baylith 415 e Baylith WE 894 em diferentes formas catiônicas permitiram constatar a maior eficácia das zeólitas NaWE e BaWE na adsorção do xilitol e posteriormente, o uso de colunas de leito fixo empacotadas com estas duas zeólitas em diferentes granulometrias, a 30 e 50 ºC, revelou que a separação do xilitol foi superior com o uso da zeólita BaWE com partículas de 53-125 µm a 50 ºC. Estas condições foram empregadas na determinação da constante de equilíbrio deste composto usando a resposta a pulsos cromatográficos, sendo o valor obtido igual a 1,03. Os efeitos da temperatura, da velocidade superficial e da razão volume de pulso/volume de leito (Vp/Vl) sobre a separação do xilitol foram investigados através de análise estatística de experimentos delineados por um planejamento fatorial 23...

Purificação de oligossacarideos utilizando coluna de leito fixo de zeolitas.; Oligossacarides purification using fixed bed column of zeolites.

Raquel Cristine Kuhn
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/09/2006 PT
Relevância na Pesquisa
37.32%
Os frutooligossacarídeos (FOS) são considerados ingredientes naturais de alimentos devido aos efeitos benéficos na proliferação de bifidobactérias no cólon humano, sendo classificados como prebióticos. Estudos recentes demonstram que a separação cromatográfica de monossacarídeos e misturas de dissacarídeos pode melhorar através da utilização de zeólitas Y, sendo também promissoras na separação de oligossacarídeos. Neste estudo, colunas com zeólitas foram utilizadas na separação de oligossacarídeos. A enzima produtora dos frutooligossacarídeos foi isolada de Rhodotorula sp., produzindo seletivamente GF2 (kestose), GF3 (nistose) e GF4 (frutofuranosilnistose). O rendimento de frutooligossacarídeos produzidos foi de 52% quando foi utilizada sacarose 50% como substrato. A separação dos frutooligossacarídeos foi realizada através de coluna empacotada com zeólitas Y trocadas com íons Ba2+. A eficiência de separação foi utilizada como critério para caracterizar a separação. Efeitos de temperatura (400C a 500C), quantidade de amostra injetada (1 a 3 mL), vazão (0,08 a 0,12 mL.min-1) e composição do desorvente (etanol 40 a 60%) foram analisados, através de um planejamento experimental fracionário, onde a vazão se mostrou significativa. O estudo de separação dos açúcares demonstrou que a condição mais favorável para a separação foi com duas colunas em série com etanol 60% como desorvente...

Purificação de acido clavulanico utilizando zeolitas.; Purification of clavulanic acid using zeolites.

Marcus Bruno Soares Forte
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/04/2008 PT
Relevância na Pesquisa
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O presente trabalho teve como objetivo principal a separação e purificação de acido clavulanico a partir de caldo fermentado utilizando zeolitas. Foram utilizadas zeolita natural (ZN) e sintetica faujasita (13X), ambas modificadas por troca ionica com diferentes cations de compensação (Na+1, K+1, Ca+2, Ba+2, Mg+2, Sr+2). Atraves de estudos cineticos de adsorcao de AC, usando as diferentes zeolitas nas respectivas formas cationicas, selecionou-se a zeolita 13X-Na como a mais promissora na adsorcao do referido composto. No equilibrio, houve retencao de 17,4% do AC inicial (CAC*/CAC0 = 0,826) e a quantidade de AC adsorvida, em relacao a quantidade de zeolita (q*) foi 0,4927 mg/g. O diametro médio da molecula de AC (DAC) foi estimado em 9,6 A. A zeolita 13X-Na foi caracterizada em termos de composicao (Si/Al = 1,5), densidade (dz = 2,248 g/cm3), área superficial (SBET = 444,860 m2/g), volume total de poros (Vporos = 0,308 cm3/g), volume de microporos (Vmicro = 0,203 cm3/g) e diâmetro médio de poros (Dporos = 28 A). Através desses resultados, a porosidade da particula calculada foi ?p = 0,69. O leito de particulas de 13X-Na apresentou porosidade ?b = 0,85. Soluções de AC puro foram obtidas através de HPLC em escala semi-preparativa. Isotermas de adsorção nas temperaturas 10...

Dinâmica molecular de zeólitos com matriz flexível; Molecular dynamics of zeolites with flexible framework

Tatiana Mello da Costa Faro
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/02/2011 PT
Relevância na Pesquisa
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Zeólitos são aluminossilicatos cuja estrutura consiste em tetraedros TO4 (com T=Si,Al) que compartilham todos os seus vértices com os tetraedros vizinhos, formando uma rede tridimensional altamente porosa e de baixa densidade. A substituição de Si por Al na matriz zeolítica leva à formação de uma carga total negativa, contrabalanceada pela presença de cátions trocáveis no material. Os zeólitos são objetos de estudo importantes por serem muito usados na indústria como peneiras moleculares, trocadores iônicos e catalisadores. A localização dos cátions trocáveis nos sítios cristalográficos de um zeólito e a identidade desses cátions são fatores que governam a adsorção de gases e outras moléculas pequenas no zeólito e o comportamento catalítico dos zeólitos. Embora várias técnicas experimentais sejam usadas para caracterizar tais cátions, é comum ocorrerem situações nas quais alguns dos cátions trocáveis não conseguem ser localizados com exatidão pelos métodos experimentais; nesses casos, estudos computacionais por simulações de Dinâmica Molecular (DM) são bastante úteis para ajudar a elucidar o posicionamento dos cátions trocáveis na estrutura zeolítica e as suas respectivas mobilidades. Neste trabalho...

Spent-grains and zeolites as potential carriers for trypsin immobilisation

Rocha, Cristina M. R.; Ducso, L.; Gonçalves, M. P.; Teixeira, J. A.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2005 ENG
Relevância na Pesquisa
37.32%
Trypsin is a widely used enzyme for protein hydrolysis and can be used to improve functional and nutritional properties of foods. The immobilization of enzymes on solid supports can offer several advantages over free enzymes including easy handling, recovery from the reaction medium, reuse and operation in continuous reactors. Traditional carriers include porous silica, porous glass and cellulose derivatives. Zeolites are porous alumino-silicates available in a wide range of particle size and porosity and can also be used as carriers. Spent grains are a brewing by-product with a high content in cellulose and can also be interesting as carriers for enzyme immobilization because, besides having the necessary conditions (as stability, rigidity, low mass transfer limitations, for instance), they are cheap and food grade. This work proposes the use of spent grains and zeolites as alternative carriers for trypsin immobilization and compares them with a traditional support (silica). Physical adsorption, ionic attachment and covalent attachment to the supports were tested. The efficiency of immobilization and activity, as well as the operation and storage stability of free and immobilized enzyme on the three supports were studied. Trypsin was most successfully immobilized on the supports by covalent attachment using glutaraldehyde. Though the best efficiencies were still obtained with silica...

Comparative study between natural and artificial zeolites as supports for biosorption systems

Tavares, M. T.; Quintelas, C.; Figueiredo, Hugo; Neves, Isabel C.
Fonte: Trans Tech Publications Inc. Publicador: Trans Tech Publications Inc.
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
37.44%
This study aims the definition of a new material that may act as a robust and yet cost effective biosorbent for treatment of wastewater with low concentration of heavy metals. A comparative study was made between two biosorption systems composed of an Arthrobacter viscosus biofilm supported on Cuban natural zeolites and on prepared NaY and NaX, in terms of their ability to retain ionic chromium. The bacterium is able to reduce Cr(VI) to Cr(III) and, only then, this smaller and positive ion may be entrapped in the zeolite cages by ion exchange. The first support was tested in a continuous flow semipacked bed column. The highest removal ratio, 42%, was achieved for initial chromium concentration of 10 mg/L, but the best up-take, 5.5 mg/gzeolite, was obtained for initial concentration of 70 mg/L. Biosorbents prepared with the same biofilm supported in NaY and NaX zeolites were also considered in batch studies, with a typical kinetics of biosorption processes, reaching 20% of initial chromium removal within an initial range of Cr(VI) concentration between 50 and 250 mg/L. These last structures were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). All these techniques indicated that the biosorption process does not modify the morphology and structure of the FAU-zeolites.; Departamento de Ciências da Terra da Universidade do Minho; La Habana University; Fundação para a Ciência e Tecnologia...

Oxidation catalysts prepared from biosorbents supported on zeolites

Figueiredo, Hugo; Neves, Isabel C.; Quintelas, C.; Tavares, M. T.; Taralunga, M.; Mijoin, J.; Magnoux, P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /04/2006 ENG
Relevância na Pesquisa
37.32%
The catalytic oxidation of 1,2-dichlorobenzene was investigated over NaYand NaX zeolites, loaded with chromiumthrough the action of a robust biosorption system consisting of a bacterial biofilm supported on the zeolites. The results of biosorption showed that the maximum metal removal efficiencywas 20%, in both systems based on NaYorNaX, starting fromsolutions with chromium(VI) concentrations ranging from 50 to 250 mgCr/L. The bacterial biofilm, Arthrobacter viscosus, supported on the zeolite reduces Cr(VI) to Cr(III). The Cr(III) is retained in the zeolite by ion exchange. The new catalysts were characterized by spectroscopic methods (FTIR ), chemical analyses (ICP-AES), surface analysis (XRD) and thermal analysis (TGA). The various techniques of characterization show that this biosorption process does not modify the morphology and structure of the FAUzeolites. These catalysts,Cr/FAU, prepared through this newprocedure present good activity and selectivity for dichlorobenzene oxidation in wet air at 350 ºC. The Cr50-Y was selected as the most active, selective and stable catalyst for oxidation of 1,2-dichlorobenzene in wet air.; Departamento de Ciências da Terra of Universidade do Minho; Fundação para a Ciência e a Tecnologia (FCT) ; Agence de l’Environnement et de la Maîtrise de l’Energie (ADEME); Région Poitou-Charentes.

Comparative study between natural and artificial zeolites as supports for biosorption systems

Tavares, M. T.; Quintelas, C.; Figueiredo, Hugo; Neves, Isabel C.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
Publicado em //2005 ENG
Relevância na Pesquisa
37.44%
This study aims the definition of a new material that may act as a robust and yet cost effective biosorbent for treatment of wastewater with low concentration of heavy metals. A comparative study was made between two biosorption systems composed of an Arthrobacter viscosus biofilm supported on Cuban natural zeolites and on prepared NaY and NaX, in terms of their ability to retain ionic chromium. The bacterium is able to reduce Cr(VI) to Cr(III) and, only then, this smaller and positive ion may be entrapped in the zeolite cages by ion exchange. The first support was tested in a continuous flow semi-packed bed column. The highest removal ratio, 42%, was achieved for initial chromium concentration of 10 mg/L, but the best up-take, 5.5 mg/gzeolite, was obtained for initial concentration of 70 mg/L. Biosorbents prepared with the same biofilm supported in NaY and NaX zeolites were also considered in batch studies, with a typical kinetics of biosorption processes, reaching 20% of initial chromium removal within an initial range of Cr(VI) concentration between 50 and 250 mg/L. These last structures were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). All these techniques indicated that the biosorption process does not modify the morphology and structure of the FAU-zeolites.; Fundação para a Ciência e a Tecnologia (FCT) - POCTI/EQU/12017/2001...

Encapsulated pyridazine Cr(III) complexes prepared from biosorbents supported in zeolites

Figueiredo, Hugo; Raposo, M. Manuela M.; Fonseca, A. Maurício C.; Neves, Isabel C.; Quintelas, C.; Tavares, M. T.
Fonte: Elsevier Publicador: Elsevier
Tipo: Parte de Livro
Publicado em //2005 ENG
Relevância na Pesquisa
37.32%
The encapsulation of a pyridazine Cr(III) complex was prepared from a robust biosorption system consisting of a bacterial biofilm supported on NaY or NaX zeolites. The maximum removal efficiency was 20% for Cr in both systems based in NaY or NaX. The bacterial biofilm, Arthrobacter viscosus, supported on the zeolite reduce Cr(VI) to Cr(III). The Cr(III) is retained in the zeolite by ion exchange. These occluded complexes were characterized by chemical analysis, spectroscopic methods (FTIR and UV/Vis) and surface analysis (DRX). The various techniques of characterization used show that the Cr(III) complex was effectively encapsulated in the zeolite and this process does not modified the morphology and structure of the NaY/NaX zeolites. These materials have potential applications in heterogeneous catalysis in mild conditions.; Departamento de Ciências da Terra of Universidade do Minho; Fundação para a Ciência e a Tecnologia (FCT)

Potentiation of 5-fluorouracil encapsulated in zeolites as drug delivery systems for in vitro models of colorectal carcinoma

Vilaça, Natália; Amorim, Ricardo; Machado, Ana F.; Parpot, Pier; Pereira, M. F. R.; Sardo, Mariana; Rocha, João; Fonseca, António Manuel; Neves, Isabel C.; Baltazar, Fátima
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
37.44%
The studies of potentiation of 5-fluorouracil (5-FU), a traditional drug used in the treatment of several cancers, including colorectal (CRC), were carried out with zeolites Faujasite in the sodium form, with different particle sizes (NaY, 700nm and nanoNaY, 150nm) and Linde type L in the potassium form (LTL) with a particle size of 80nm. 5-FU was loaded into zeolites by liquid-phase adsorption. Characterization by spectroscopic techniques (FTIR, 1H NMR and 13C and 27Al solid-state MAS NMR), chemical analysis, thermal analysis (TGA), nitrogen adsorption isotherms and scanning electron microscopy (SEM), demonstrated the successful loading of 5-FU into the zeolite hosts. In vitro drug release studies (PBS buffer pH 7.4, 37°C) revealed the release of 80-90% of 5-FU in the first 10min. To ascertain the drug release kinetics, the release profiles were fitted to zero-order, first-order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas and Weibull kinetic models. The in vitro dissolution from the drug delivery systems (DDS) was explained by the Weibull model. The DDS efficacy was evaluated using two human colorectal carcinoma cell lines, HCT-15 and RKO. Unloaded zeolites presented no toxicity to both cancer cells, while all DDS allowed an important potentiation of the 5-FU effect on the cell viability. Immunofluorescence studies provided evidence for zeolite-cell internalization.

Carbocations on zeolites: quo vadis?

Mota,Claudio J. A; Rosenbach Jr,Nilton
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2011 EN
Relevância na Pesquisa
37.32%
The nature of carbocations on the zeolite surface is discussed in this account, highlighting experimental and theoretical studies. The adsorption of alkylhalides over metal-exchanged zeolites has been used to study the equilibrium between covalent alkoxides and ionic carbocations. Theoretical calculations indicated that the carbocations are minima (intermediates) on the potential energy surface and stabilized by hydrogen bonds with the framework oxygen atoms. The results indicate that zeolites behave like solid solvents, stabilizing the formation of ionic species.

Glycerol dehydration catalyzed by MWW zeolites and the changes in the catalyst deactivation caused by porosity modification

Rodrigues, Mariana Veiga; Vignatti, Charito; Garetto, Teresita; Pulcinelli, Sandra Helena; Santilli, Celso Valentim; Martins, Leandro
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 84-91
ENG
Relevância na Pesquisa
37.44%
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 2010/01449-3; Processo FAPESP: 2012/08305-2; Processo FAPESP: 2013/01328-0; Processo FAPESP: 2013/08541-0; Members of the layered MWW family, including microporous MCM-22, pillared MCM-36 and delaminated ITQ-2 zeolites, were used as catalysts for the gas phase dehydration of glycerol. The chemical, structural and surface properties of the catalysts were characterized by X-ray diffraction, N-2 adsorption-desorption isotherms, SEM, TEM, NH3-TPD and pyridine chemisorption followed by IR spectroscopy. The results clearly showed that the modified zeolites with designed mesopore structure enabled rapid diffusion and consequently improved the glycerol conversion. Characterization of the acid sites revealed that the relative abundance of Bronsted and Lewis acid sites influenced the efficiency of the catalysis performed by these materials. C-13 NMR spectra of the spent catalysts confirmed that differences in the nature and amount of carbonaceous deposits are related to the pore structures of the catalysts, with greater formation of polyaromatic compounds inside zeolite pores, while polyglycols are preferentially formed at the external surfaces of the MCM-36 and ITQ-2 zeolites...

The Synthetic Zeolites As Geoinspired Materials

Camblor, Miguel Ángel
Fonte: Sociedad Española de Mineralogía Publicador: Sociedad Española de Mineralogía
Tipo: Artículo Formato: 273443 bytes; application/pdf
ENG
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Paper based on a Plenary Conference, XXVI Anual Meeting, Sociedad Española de Mineralogía, Oviedo (Asturias), September 2006.; The term geoinspiration was coined by Ruiz-Hitzky to simply denote the wealth of motivation that materials scientists can borrow from the mineral world. Any plausible synthetic strategy affording the preparation of new synthetic materials which, by its own characteristics or by the chemical pathway involved in its synthesis, resemble but do not match materials found in nature, would fit into that concept. The idea parallels that of bioinspiration, and intends to highlight the richness of materials and preparation routes that the synthetic scientist can get by studying, copying and modifying natural materials and processes. My purpose here is to show that over the last half a century zeolite scientists have successfully used a geoinspired approach, avant la lettre, to produce a vast range of new materials with a high impact in the industry and in every day life. While the importance of zeolites as industrial catalysts, adsorbents, active phases for industrial gas separation and purification and detergent builders is easily recognized, other applications closer to the man in the street may pass unnoticed. Two examples are the use of zeolites in double-glazing panels to keep windows clear and transparent and...

Monomolecular alkane activation on Al-- and Fe--containing zeolites

Yun, Jang Ho
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Lobo, Raul F.; Zeolites are crystalline aluminosilicate materials with an open micro-porous three-dimensional framework structure and are used as a solid acid catalyst in oil refining and petrochemical industries, in processes such as fluidized catalytic cracking (FCC). FCC catalysts constitute more than 95% of zeolite catalyst consumption. Other zeolite-catalyzed processes include hydroxylation, alkylation, and epoxidation. Even though synthetic zeolites have been used in the industry for decades, prospects are still bright for recent new challenges and applications. Synthetic and post-synthetic modifications of zeolites can be used in the improvement of catalysts; the modification of zeolites can lead to new catalytic chemistry. In this thesis, we first investigated the effect of thermal treatments of SSZ-13 (CHA) with Si/Al ratios of 6 and 12 for the monomolecular propane conversion. SSZ-13 with Si/Al of 12 exhibited a gradual change in selectivity and activation energy with treatment temperature, indicating generation of different active sites. Second, Fe3+ was isomorphously incorporated in the zeolite structure instead of Al3+ initially to compare the difference in acidity on alkane activation. A novel redox catalytic cycle was proposed and a mechanistic study with H-[Fe]ZSM-5 was explored to test the proposed mechanism. In the next section...

AN INTEGRATED REMEDIATION SYSTEM USING SYNTHETIC AND NATURAL ZEOLITES FOR TREATMENT OF WASTEWATER AND CONTAMINATED SEDIMENTS

RIOS REYES,CARLOS; APPASAMY,DANEN; ROBERTS,CLIVE
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 EN
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The major sources of water pollution can be classified as municipal, industrial, and agricultural. Different types of polluted aqueous effluents and sediments may be produced, which contain relatively high levels of heavy metals. During the 1990s, the large-scale development of constructed wetlands around the world drew much attention from public and environmental groups. The present study looks at the use of an integrated remediation system using zeolites for the treatment of wastewater and sediments. Zeolites have been widely studied in the past 10 years due to their attractive properties such as molecular-sieving, high cation exchange capacities, and their affinity for heavy metals. Coal industry by-products-based zeolites (faujasite type) have been tested as an effective and low-cost novel alternative for wastewater treatment, particularly their removing of heavy metals. On the other hand, a preliminary laboratory-scale experiment was conducted on the use of natural zeolites (clinoptilolite type) for the retention of heavy metals from canal sediments. Experimental work revealed promising results, which could be replicated on a bigger scale. Although this has been developed for canal sediments, the remediation strategy can be adapted to different waterways such as rivers. The development of the proposed remediation system in a specific experimental site as the major part of an innovation park can provide great benefits to a population living near contaminated effluents. It provides not only opportunities for the mitigation of environmental impact...