Mesoporous alumina catalytic material prepared by grafting wide-pore MCM-41 with an alumina multilayer

Landau, Miron V.; Dafa, E.; Kaliya, M.L.; Sen, Tapas; Herskowitz, M.

doi:10.1016/s1387-1811(01)00404-8

Cited by 74 publications

(57 citation statements)

References 31 publications

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“…The remaining solid was filtered, washed with water (1000 cm 3 ) and dried at room temperature before calcining at 500 °C for 6 h under flowing air (ramp rate 1 °C min -1 ). The protocol of Landau and co-workers was used to deposit a uniform alumina coating onto SBA-15 (Al-SBA-15(n) where n corresponds to the number of grafting cycles) [36]. Aluminium-tri-sec-butoxide (14.…”

Section: Catalyst Synthesismentioning

confidence: 99%

“…The growth of conformal alumina coatings over a mesostructured silica framework opens the way to new catalyst supports combining the structural stability (and diverse topologies) accessible through silica materials chemistry, with the surface chemistry of alumina. Alumina coated MCM-41 [36] and SBA-15 [37] have been reported via hydrolysis of alkoxyaluminium species. Such dual-oxide supports have shown enhanced immobilisation of heteropoly acids [38] and attendant activity in o-xylene alkylation [39], and strong metal support interactions in bimetallic PtSn catalysts promoting propane dehydrogenation [40].…”

Section: Introductionmentioning

confidence: 99%

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Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation

et al. 2014

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eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Operando, liquid phase XAS highlights the interplay between dissolved oxygen and the oxidation state of palladium nanoparticles dispersed over Al-SBA-15 towards on-stream reduction: ambient pressures of flowing oxygen are sufficient to hinder palladium oxide reduction to metal, enabling a high selox activity to be maintained, whereas rapid PdO reduction and concomitant catalyst deactivation occurs under static oxygen.Selectivity to the desired cinnamaldehyde product mirrors these trends in activity, with flowing oxygen minimising C-O cleavage of the cinnamyl alcohol reactant to trans--methylstyrene, and of cinnamaldehyde decarbonylation to styrene. Highlights: An ultrathin alumina coating has been grafted onto a SBA-15 mesoporous silica architecture. Pd impregnated Al-SBA-15 materials are superior catalysts for the aerobic selox of allylic alcohols to aldehydes compared to pure silica or alumina supports.  Operando XAS confirms cinnamyl alcohol selox occurs over a PdO active species, which is prone to on-stream reduction and associated catalyst deactivation under static oxygen. [20,21] have highlighted PdO reduction to metallic palladium as a potential deactivation pathway, and hence the importance of generating highly dispersed nanoparticles which favour an oxide phase [20,[22][23][24]. KeywordsTemperature-programmed desorption and XPS of crotyl alcohol (but-2-en-1-ol) and crotonaldehyde (but-2-en-1-al) over Pd(111) and palladium-rich Au/Pd surface alloys suggest deactivation arises from crotonaldehyde decarbonylation and subsequent site-blocking by strongly adsorbed propylidyne and CO [20,21]. Computational modelling predicts Pd(111) can also drive propanoic acid decarbonylation [25]. Vapour phase studies of crotyl alcohol oxidation show that such in-situ palladium reduction is reversible under oxidising environments [17,19], enabling selox to be maintained, however the ability of dissolved oxygen to preserve palladium as PdO during liquid phase selox is unknown. Experimental Catalyst synthesisThe parent SBA-15 silica framework was synthesised following the method of Zhao et al [30]. Pluronic P123 (10 g) was dissolved in water (75.5 ...

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Section: Catalyst Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation

et al. 2014

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“…Furthermore, Al-MCM-41 gave a much higher yield of dihydrobenzopyran than conventional catalysts, such as H 2 SO 4 (12%) and amorphous silica-alumina (6%) catalysts. Al-MCM-41 is also used in the alkylation of unsubstituted phenol with methanol [413,440]. Friedel-Crafts alkylation of benzene with benzyl chloride in liquid phase uses Ga impregnated MCM-41 as well as Fe-impregnated MCM-41, Al-MCM-41, and La-MCM-41 [413,441].…”

Section: Fine Chemical Synthesismentioning

confidence: 99%

Template-based syntheses for shape controlled nanostructures

Pérez-Page

et al. 2016

Advances in Colloid and Interface Science

129

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A variety of nanostructured materials are produced through template-based synthesis methods, including zerodimensional, one-dimensional, and two-dimensional structures. These span different forms such as nanoparticles, nanowires, nanotubes, nanoflakes, and nanosheets. Many physical characteristics of these materials such as the shape and size can be finely controlled through template selection and as a result, their properties as well. Reviewed here are several examples of these nanomaterials, with emphasis specifically on the templates and synthesis routes used to produce the final nanostructures. In the first section, the templates have been discussed while in the second section, their corresponding synthesis methods have been briefly reviewed, and lastly in the third section, applications of the materials themselves are highlighted. Some examples of the templates frequently encountered are organic structure directing agents, surfactants, polymers, carbon frameworks, colloidal sol-gels, inorganic frameworks, and nanoporous membranes. Synthesis methods that adopt these templates include emulsion-based routes and template-filling approaches, such as self-assembly, electrodeposition, electroless deposition, vapor deposition, and other methods including layer-by-layer and lithography. Templatebased synthesized nanomaterials are frequently encountered in select fields such as solar energy, thermoelectric materials, catalysis, biomedical applications, and magnetowetting of surfaces.

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“…Em geral, os óxi-dos de alumínio, titânio e zircônio, enxertados na superfície da sílica, aumentam a acidez da superfície e propiciam melhores resultados em alguns processos catalíticos 8,10,18,19 . Adicionalmente, melhoram as estabilidades química e térmica dos catalisadores 3,9.17 .…”

Section: Introductionunclassified

“…A presença de óxido de titânio, além de aumentar a acidez da superfície, pode produzir um aumento na densidade eletrônica de catalisadores metálicos dispersos 20 . Outros métodos de síntese de sílica modificada com óxidos metálicos têm sido propostos como, por exemplo, a deposição físi-ca de precursores metálicos, seguida de calcinação 18 . Entretanto, no caso de óxido de alumínio disperso sobre sílica, observou-se a formação de aglomerados de alumina, que resultam em bloqueio parcial dos poros originais da matriz sílica.…”

Section: Introductionunclassified

Evidências da formação de monocamada de óxido de alumínio sobre sílica, através de reações de enxerto

Cónsul¹,

Baibich²,

Benvenutti³

et al. 2005

Quím. Nova

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REACTIONS. Aluminum oxide was dispersed on a commercial silica gel surface, using successive grafting reactions. The reaction products were characterized by N 2 adsorption-desorption isotherms, scanning electron microscopy and infrared spectroscopy. The progressive incorporation of aluminum, up to 5.5% (w/w), does not produce agglomeration of alumina, since changes in the original pore size distribution of the silica matrix were not observed. The aluminum oxide covers homogeneously the silica surface.Keywords: grafting; atomic dispersion, surface synthesis. INTRODUÇÃOO suporte inorgânico é um aspecto importante a ser considerado no processo de preparação de um catalisador heterogêneo. Além das características físicas como porosidade e rigidez estrutural, o suporte também pode contribuir para a estabilização e prevenção de sinterização das espécies cataliticamente ativas, que se encontram dispersas em sua superfície. Dentre os suportes inorgânicos mais utilizados em catálise heterogênea tem-se a alumina e a sílica [1][2][3][4] . As sílicas também têm sido usadas na sua forma modificada. Nesse caso, a modificação química da superfície pode ser feita com outros óxidos inorgânicos 3-5 , ou então, com grupos orgânicos quelantes que podem imobilizar um catalisador metálico na forma de um complexo 6,7 . Uma das formas de se modificar a superfície de sílicas com outros óxidos inorgânicos é através do uso de reações de enxerto. Com esse método de síntese é possível combinar as características desejáveis das sílicas comercialmente disponíveis, como área superficial, porosidade e granulometria, com a funcionalidade quí-mica da superfície dos outros óxidos [8][9][10] . Portanto, as propriedades físicas originais da matriz sílica não devem ser profundamente alteradas, visto que se admite que as reações de enxerto devem produzir monocamadas de óxido disperso, isto é, filmes bidimensionais dos óxidos enxertados na superfície da sílica.A modificação química da superfície de sílica pelo método enxerto pode ser descrita, de maneira simplificada, através de duas reações: i) reação dos grupos silanóis da superfície da sílica com o reagente precursor do óxido metálico a ser enxertado, que pode ser um alcóxido ou haleto. Em geral, os alcóxidos são preferidos pois embora menos reativos, não deixam resíduos de haletos no catalisador que possam resultar em efeitos inibidores dos processos catalíticos 11 e b) reação de hidrólise do alcóxido imobilizado. Para o caso de óxido de alumínio disperso sobre sílica, as reações de enxerto estão representadas pelas Equações 1 e 2. n ≡SiOH + Al (OR) 3 → (≡SiO) n Al (OR) 3-n + nROH(1)onde R representa um grupo orgânico, geralmente etil, metil ou isopropil.A modificação da sílica, através de reações de enxerto com vários óxidos inorgânicos, tem sido extensivamente utilizada na obtenção de novos materiais com propriedades adsorventes 12,13 , sensores eletroquímicos 14,15 e catalisadores 4,16,17 . Em geral, os óxi-dos de alumínio, titânio e zircônio, enxertados na superfície da sílica, aumentam a acide...

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Mesoporous alumina catalytic material prepared by grafting wide-pore MCM-41 with an alumina multilayer

Cited by 74 publications

References 31 publications

Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation

Alumina-grafted SBA-15 as a high performance support for Pd-catalysed cinnamyl alcohol selective oxidation

Template-based syntheses for shape controlled nanostructures

Evidências da formação de monocamada de óxido de alumínio sobre sílica, através de reações de enxerto

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