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Ordered mesoporous titanosilicate materials prepared at room temperature

Nabais, Joao; Galacho, Cristina; Carrott, Peter; Ribeiro Carrott, Manuela
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica Formato: 92814 bytes; application/pdf
ENG
Relevância na Pesquisa
69.881816%
Mesoporous titanosilicates were directly synthesised at ambient temperature and pressure, considering a wide range of metal content (0.01Ti/Si0.5) and using cationic surfactants of different alkyl chain length. It is shown that the use of tetradecyl-, hexadecyl- and octadecyltrimethylammonium bromide as structure-directing agents provide higher quality Ti-MCM-41 materials, than those prepared with surfactants of shorter alkyl chain. The pore volume and surface areas are gradually reduced by the increase of Ti content but up to Ti/Si=0.02 the alterations in the pore structural properties are negligible as compared with pure silica grades, becoming more noticeable for Ti/Si0.1. Nevertheless, for Ti/Si=0.1 the directly synthesised materials still have high pore volumes as well as high regularity and uniformity of the hexagonal pore array, with superior pore structural properties to those of materials prepared by post synthesis deposition of titanium on silica MCM-41, which did not provide a valid alternative for minimising the disruptive effect of high metal content on the hexagonal porous structure.

Materiais com estrutura mesoporosa ordenada contendo titânio: Preparação, Caracterização, Estudos de Adsorção e Propriedades Catalíticas

Galacho, Cristina
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
71.08549%
his PhD thesis presents studies on the preparation, characterisation, thermal stability, stability during long term exposure to water vapour at 298K and evaluation of the catalytic properties of Ti-MCM-41 materials. Studies related to the synthesis and structural characterisation of Si-MCM-41 materials, prepared at room temperature, from structure directing agents with different chain lengths and by direct addition of the silica source or by its addition in alcoholic solution, allowed selection of tetra-, hexa- and octadecyltrimethylammonium bromides as the most suitable structure directing agents for the preparation of M41S type materials of high quality and exclusion of BuOH as the alcohol in the process of synthesis of the these materials. After developing and implementing a new method for the synthesis of Ti-MCM-41 materials, carried out at room temperature and based on the procedure for preparing Si-MCM-41 solids, a systematic studied of the effect of the principal synthesis parameters on the structural and chemical properties of the materials, namely, chain length of the structure directing agent, order of addition of the silicon and titanium precursors, direct or alcoholic solution addition of the titanium alcoxide, nature of the metal alcoxide used as titanium source and silicon/titanium molar synthesis ratio...

Ti-MCM-41 materials synthesised at room temperature as catalysts for cyclisation of (±)-citronellal”

Ramos, S.S.; Castilho, P.; Rodrigues, A.I.; Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
99.59672%
In the present work we extend the applicability of those Ti-MCM-41 materials, as heterogeneous catalysts, to produce an important intermediate, isopulegol, from the cyclisation of citronellal. The use of this kind of materials appears to be a good option over homogeneous catalysts, because they offer the advantage of recovery and, consequently, contribute to environmentally friendly processes.

CATALYTIC AND ADSORPTION PROPERTIES OF Al- AND Ti-MCM-41 SYNTHESIZED AT ROOM TEMPERATURE

Silva, Tiago N.; Lopes, José Madeira; Ribeiro, Fernando Ramôa; Carrott, Manuela Ribeiro; Galacho, Cristina; Sousa, Maria José; Carrott, Peter
Fonte: Akadémiai Kiadó and Kluwer Academic Publishers Publicador: Akadémiai Kiadó and Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
79.065396%
Aluminosilicate and titanosilicate MCM-41 were synthesized using a room temperature method. A preliminary catalytic evaluation was performed in the promotion of the 1-butene double bond isomerization, which was successful in probing differences in the acidity of the samples prepared.

Estabilidade estrutural de materiais Ti-MCM-41 preparados à temperatura ambiente: Adsorção de vapor de água a 298K

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: 2nd International Congress Energy and Environment and Management Publicador: 2nd International Congress Energy and Environment and Management
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
99.70911%
neste trabalho apresentam-se os resultados de um estudo mais abrangente onde são considerados os efeitos da dimensão da cadeia alifática dos sais de brometo de alquiltrimetilamónio, usados como agentes estruturantes de síntese, e da razão molar Si/Ti na estabilidade dos materiais Ti-MCM-41 em relação à exposição prolongada ao vapor de água a 298K. Para além da questão da estabilidade o estudo apresentado permite avaliar, em simultâneo, a química superficial e as propriedades estruturais dos referidos materiais.

Materiais do tipo MCM-41 preparados à temperatura ambiente: Síntese, caracterização e estabilidade mecânica

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: 2nd International Congress Energy and Environment and Management Publicador: 2nd International Congress Energy and Environment and Management
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
79.065396%
Materiais do tipo MCM-41 preparados à temperatura ambiente: Síntese, caracterização e estabilidade mecânica

Evaluation of pore structural stability of mesoporous titanium silicates

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: 8th International Symposium on the Caracterisation of Porous Solids - COPS VIII Publicador: 8th International Symposium on the Caracterisation of Porous Solids - COPS VIII
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
69.78525%
Therefore one of the purposes of the work presented here is to complement the stability features by studying the hydrothermal resistance of the Ti-MCM-41 materials prepared by the same procedure. A similar study of Ti-SBA-15 materials, synthesised by conventional procedures, will also be presented and the results compared with those of Ti-MCM-41 materials. The metal content was the main parameter considered. The pore structural alterations were evaluated by characterising by X-ray diffraction and nitrogen adsorption at 77K before and after the materials were submitted to increasing temperature, increasing unidirectional pressure or after 12h in boiling water under static conditions.

Effect of calcination parameters on structural properties of Ti-MCM-41 materials synthesized at room temperature

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: XX Encontro Nacional da Sociedade Portuguesa de Química Publicador: XX Encontro Nacional da Sociedade Portuguesa de Química
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
99.78525%
In this work is presented a study of the effect of calcination parameters namely, heating rate, calcination temperature, total calcination time and time at final temperature, on pore structural properties of Ti-MCM-41 materials. The materials were prepared by direct synthesis at ambient temperature and pressure, using tetraethoxysilane, titanium alcoxides, cationic surfactants and ammonia, as previously described and were characterised by X-ray diffraction, nitrogen adsorption at 77K and DR UV-Vis absorption spectroscopy. The Si/Ti values of the final calcined materials were determined by AA (Si) and ICP (Ti).

“Estudo sistemático do efeito dos principais parâmetros de síntese nas propriedades estruturais de materiais Si e Ti-MCM-41 preparados à temperatura ambiente

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: Actas da XXXI Reunião Ibérica de Adsorção Publicador: Actas da XXXI Reunião Ibérica de Adsorção
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
99.88182%
No presente trabalho apresentam-se os resultados de um estudo sistemático do efeito dos parâmetros de síntese nas propriedades estruturais e químicas dos materiais Ti-MCM-41, obtidos por substituição isomórfica do titânio na matriz de sílica e de acordo com um novo método desenvolvido, nomeadamente dimensão da cadeia alifática do agente estruturante (CnTMABr, n = 8, 10, 12, 14, 16, 18), ordem de adição dos precursores de Si e Ti (conjunta ou sequencial), natureza do alcóxido metálico usado como fonte de titânio (Ti(OR)4, R=Et, Pri eBun), tipo de álcool usado na preparação da solução do Ti(OR)4, (EtOH, 2-PrOH e BuOH) e razão molar de síntese Si/Ti (100, 50, 30, 10, 5, 3.3 e 2).

Avaliação da estabilidade estrutural de materiais Ti-MCM-41 preparados à temperatura ambiente: Adsorção de N2 a 77K, e, de n-pentano e de vapor de água a 298K

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: Actas da XXXI Reunião Ibérica de Adsorção, Publicador: Actas da XXXI Reunião Ibérica de Adsorção,
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
99.78525%
No presente trabalho apresentam-se os resultados de estabilidade térmica, estabilidade em relação à exposição prolongada ao vapor de água à temperatura ambiente e estabilidade mecânica de amostras de Ti-MCM-41 preparadas, com diferentes razões molares Si/Ti, segundo um novo processo realizado à temperatura ambiente a partir do Si(OEt)4 como fonte de silício e do Ti(OEt)4 como fonte de titânio, por adição directa ou em solução de 2-PrOH, usando C16TMABr ou C18TMABr como agentes estruturantes e amónia como catalisador.

Efeito da aplicação de pressão externa unidireccional nas propriedades estruturais de materiais Si-MCM-41 e Ti-MCM-41 preparados à temperatura ambiente

Galacho, Cristina; Carrott, Manuela; Carrott, Peter
Fonte: Sociedade Portuguesa de Química Publicador: Sociedade Portuguesa de Química
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
100.00131%
Na presente comunicação apresenta-se um estudo referente à estabilidade mecânica de materiais Ti-MCM-41 preparados, por substituição isomórfica durante a síntese, segundo um processo realizado à temperatura e pressão ambiente, tendo sido avaliado o efeito do aumento progressivo de uma pressão externa unidireccional nas propriedades estruturais dos referidos materiais. A título comparativo são também estudadas amostras constituídas unicamente por sílica.

Adsorção de n-Pentano e de Vapor de Água em Materiais Mesoporosos Ti-MCM-41 Preparados à Temperatura Ambiente

Galacho, C.; Carrott, M.R.; Carrott, P.
Fonte: Sociedade Portuguesa de Química Publicador: Sociedade Portuguesa de Química
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
69.02213%
Nesta comunicação apresentam-se os resultados de adsorção de n-pentano e vapor de água em amostras de Ti-MCM-41 preparadas por substituição isomórfica durante a síntese e segundo um novo processo realizado à temperatura ambiente.

Kinetic study of the catalytic pyrolysis of elephant grass using Ti-MCM-41

Fontes,Maria do Socorro Braga; Melo,Dulce Maria de Araújo; Barros,Joana Maria de Farias; Braga,Renata Martins; Rodrigues,Gicélia
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
Relevância na Pesquisa
99.95031%
This work aimed to study the kinetics of thermal and catalytic pyrolysis using Ti-MCM-41 as catalyst in order to assess the catalytic pyrolysis efficiency compared to thermal pyrolysis of elephant grass. Ti-MCM-41 molecular sieve was synthesized by hydrothermal method from hydrogel with the following molar composition:1.00 CTMABr: 4.00 SiO2:X TiO2: 1 + X Na2O: 200.00 H2O, whichstructure template used was cetyltrimethylammonium bromide (CTMABr). The materials synthesized were characterized by X-ray diffraction, IR spectroscopy, thermogravimetric analysis and specific area by the BET method, for subsequent application in the biomass pyrolysis process. The kinetic models proposed by Vyazovkin and Flynn-Wall were used to determine the apparent activation energy involved in the thermal and catalytic pyrolysis of elephant grass and the results showed that the catalyst used was effective in reducing the apparent activation energy involved in the thermal decomposition of elephant grass.

Artificial sunlight and ultraviolet light induced photo-epoxidation of propylene over V-Ti/MCM-41 photocatalyst

Nguyen, Van-Huy; Lin, Shawn D; Wu, Jeffrey Chi-Sheng; Bai, Hsunling
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 05/05/2014 EN
Relevância na Pesquisa
69.59672%
The light irradiation parameters, including the wavelength spectrum and intensity of light source, can significantly influence a photocatalytic reaction. This study examines the propylene photo-epoxidation over V-Ti/MCM-41 photocatalyst by using artificial sunlight (Xe lamp with/without an Air Mass 1.5 Global Filter at 1.6/18.5 mW·cm−2) and ultraviolet light (Mercury Arc lamp with different filters in the range of 0.1–0.8 mW·cm−2). This is the first report of using artificial sunlight to drive the photo-epoxidation of propylene. Over V-Ti/MCM-41 photocatalyst, the propylene oxide (PO) formation rate is 193.0 and 112.1 µmol·gcat −1·h−1 with a PO selectivity of 35.0 and 53.7% under UV light and artificial sunlight, respectively. A normalized light utilization (NLU) index is defined and found to correlate well with the rate of both PO formation and C3H6 consumption in log–log scale. The light utilization with a mercury arc lamp is better than with a xenon lamp. The selectivity to PO remains practically unchanged with respect to NLU, suggesting that the photo-epoxidation occurs through the same mechanism under the conditions tested in this study.

Preparação e caracterização de catalisadores à base de titânio suportado em MCM-41 para produção de compostos oxigenados através da pirólise catalítica do capim elefante

Fontes, Maria do Socorro Braga
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
90.74609%
In recent years, the area of advanced materials has been considerably, especially when it comes to materials for industrial use, such as is the case with structured porosity of catalysts suitable for catalytic processes. The use of catalysts combined with the fast pyrolysis process is an alternative to the oxygenate production of high added value, because, in addition to increasing the yield and quality of products, allows you to manipulate the selectivity to a product of interest, and therefore allows greater control over the characteristics of the final product. Based on these arguments, in this work were prepared titanium catalysts supported on MCM-41 for use in catalytic pyrolysis of biomass, called elephant grass. The reactions of pyrolysis of biomass were performed in a micro pyrolyzer, Py-5200, coupled to GC / MS, the company CDS Corporation, headquartered in the United States. The catalysts Ti-MCM-41 in different molar ratios were characterized by XRD, TG / DTG, FT-IR, SEM, XRF, UV-visible adsorption of nitrogen and the distribution of particle diameter and specific surface area measurement by the BET method. From the catalytic tests it was observed that the catalysts synthesized showed good results for the pyrolysis reaction.The main products were obtained a higher yield of aldehydes...

Avaliação da remoção de hidrocarbonetos aromáticos (BTEX) em águas utilizando materiais nanoestruturados do tipo Ti-MCM-41

Morais, Lidiane Alves de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
100.76297%
Volatile Organic Compounds are pollutants coming mainly from activities that use fossil fuels. Within this class are the BTEX (benzene, toluene, ethylbenzene and xylenes) compounds that are considered hazardous. Among the various existing techniques for degradation of pollutants, there is advanced oxidation using H2O2 generating hidoxil radical ( OH). In this work, the mesoporous material of MCM-41 was synthesized by hydrothermal method and then was used as support, the impregnation of titanium by the method of synthesis with excess solvent to obtain the catalyst Ti-MCM-41. The catalyst was used in the reaction catalyzed removal of BTEX in water using H2O2 as oxidant. The materials were characterized by: XRD, TG/DTG, FTIR, nitrogen adsorption-desorption and FRX-EDX, in order to verify the method of impregnation of the mesoporous titanium support was effective. Catalytic tests were carried out in reactors of 20 mL containing BTEX (100.0 μg/L), H2O2 (2.0 M) and Ti-MCM-41 (2.0 g/L) in acid medium. The reaction occurred for 5 h at 60 °C and analysis were performed by gas chromatography with photoionization detector and static headspace sampler. The characterizations have proven the effectiveness of the synthesis method used and the incorporation of titanium lt in the support. The catalytic tests showed satisfactory results with conversion of more than 95 % for the studied compounds...

Comparison of Kinetic Study of CTMA+ Removal of Molecular Sieve Ti-MCM-41 Synthesized with Natural and Commercial Silica

Fontes,Maria do Socorro Braga; Melo,Dulce Maria de Araújo; Costa,Cintia de Castro; Braga,Renata Martins; Melo,Marcus Antonio de Freitas; Alves,José Antônio Barros Leal Reis
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2015 EN
Relevância na Pesquisa
90.05379%
This work aimed to determine and compare the apparent activation energy, involved in thermal decomposition of CTMA+ from the pores of Ti-MCM-41 synthesized by two different source of silica in order to evaluate their influence in the template removal. The molecular sieves Ti-MCM-41 were synthesized using rice husk ash (RHA), as alternative low cost source of silica, and commercial silica gel, obtaining two mesoporous material by hydrothermal synthesis of gel molar composition of: 1.0 CTMABr: 4.0 SiO2: X TiO2: 1.0 Na2O: 200.0 H2O. The samples were characterized to compare its properties by X-ray diffraction, IR spectroscopy, BET method and thermogravimetric analysis (TGA). The kinetic study using the model proposed by Flynn and Wall to determine the apparent activation energy for CTMA+ removal was performed using TGA data. The thermogravimetric analysis results of the material obtained from RHA confirmed intrinsic properties of mesoporous MCM-41 as the synthesized with commercial silica gel, such as high specific area, mesoporous range of pore diameter and hexagonal structure. According to the kinetics results the RHA showed similar chemical interaction to commercial silica gel, which makes it an interesting material, since it is a low cost source of natural silica from agricultural waste.

Synthesis and characterization of Al- and Ti-MCM-41 materials: application to oxidation of anthracene

Araújo,R. S.; Costa,F. S.; Maia,D. A. S.; Sant'Ana,H. B.; Cavalcante Jr.,C. L.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2007 EN
Relevância na Pesquisa
69.27036%
The synthesis and characterization of new molecular sieves of the MCM-41 type are presented in this study. Samples were obtained from the alkoxides of Si, Ti and Al and different long-chain amine and alkylammonium salts surfactants, by the sol-gel method, through moderate agitation at room temperature. The reactions were conducted in two steps, acid hydrolysis (pH=2) and alkaline condensation (pH=10), both taking about 90min. The synthesized crystals were characterized using infrared spectroscopy, thermogravimetry and X-Ray diffraction. Pore diameters and surface areas were measured by N2 adsorption at 77K. Catalytic tests were conducted for anthracene oxidation using different oxidants (H2O2, alkylhydroperoxide) and organic solvents (benzene, tetrahydrofuran).

CARACTERIZACIÓN TEXTURAL Y QUÍMICA DE CATALIZADORES TI-SIO2 CRISTALINOS USADOS EN LA EPOXIDACIÓN DE ÉSTERES GRASOS

RIOS,LUIS; RESTREPO,GLORIA; SUÁREZ,RICARDO; CAICEDO,ROSARIO; MAZO,PAULA; FRANCO,ALEXANDER; ECHEVERRI,DAVID
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2006 ES
Relevância na Pesquisa
79.84024%
Centros discretos de TiIV dispersos en una matriz de SiO2 actúan como fuertes aceptores de electrones por lo cual son útiles para la activación de moléculas o funciones químicas densas en electrones. La cantidad de estos centros, su dispersión, accesibilidad y coordinación, determinan su eficiencia química; para determinar estas propiedades, varios materiales Ti-MCM-41 se caracterizaron mediante DRX, FTIR, UV-Vis e isotermas de adsorción de N2; también se determinaron la cristalinidad, porosidad y superficie específica de la matriz SiO2 permitiendo correlacionar el ambiente fisicoquímico del titanio y las propiedades texturales del catalizador, con su efectividad en la activación de enlaces O-O presentes en moléculas tipo peróxidos, usados en la epoxidación de aceites vegetales. Los resultados sugieren que la presencia de poros cristalinos, en la epoxidación del metiléster del ácido oleico con TBHP y catalizada con Ti-MCM-41, no es necesaria, puesto que la reacción ocurre principalmente en el área externa a los poros. Lo realmente importante es tener centros de Ti finamente dispersos sobre una área superficial alta y accesible. Por otro lado, la temperatura de reacción deber estar por debajo de 70°C para minimizar la formación de subproductos (cetona).

Titanium-modified MCM-41 Prepared by Ultrasound and by Hydrothermal Treatment, Catalysts for Acetylation Reactions

Angeles-Beltrán,Deyanira; Negrón-Silva,Guillermo; Lomas-Romero,Leticia; Iglesias-Arteaga,Martín A.; Cadete Santos-Aires,Francisco J.
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2008 EN
Relevância na Pesquisa
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Mesoporous materials type Ti-MCM-41 prepared by hydrothermal and ultrasound-assisted techniques were characterized by XRD, SEM, TEM, nitrogen physisorption, ammonia TPD, UV-vis and FT-IR. Both showed the MCM-41 characteristic structure. Hydrothermal treatment allowed obtaining a well ordered material and ultrasound procedure gave a better titanium distribution. Electronic microscopy images revealed Ti dispersion zones as well as the quantity of metal in the structure. The catalytic activity of these materials were tested by acetylation of aromatic and steroidal alcohols to afford the corresponding esters in good yields.