Amorphous mesoporous silica-alumina with controlled pore size as acid catalysts

Bellussi, Giuseppe; Perego, Carlo; Carati, Angela; Peratello, S.; Massara, Elisabetta Previde; Perego, G.

doi:10.1016/s0167-2991(08)64100-2

Cited by 95 publications

(46 citation statements)

References 12 publications

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“…14,15 The Ti-O bond distance R Ti -O of 1.80-1.81Å R Si -O D 1.61Å and a coordination number N of 4 were obtained. Both R and N were found to increase when TS-1 is in the presence of H 2 O, NH 3 or CH 3 OH, or immersed in water, as a consequence of coordination of the polar molecules to Ti(IV) species.…”

Section: X-ray Absorption Fine Structurementioning

confidence: 97%

“…The TS-1 and MST were prepared according to the well-established procedure described by the researchers of EniTecnologie. 2,14,15 Commercial TiO 2 from Tioxide Ltd (a very poor crystalline anatase phase with a surface area of ¾200 m 2 g 1 ) was used as a reference compound for the XPS characterization. The Ti content was determined by inductively coupled plasma atomic emission spectroscopy.…”

Section: And References Cited Therein)mentioning

confidence: 99%

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An XPS study of microporous and mesoporous titanosilicates

Moretti¹,

Salvi

Guascito

et al. 2004

Surface & Interface Analysis

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In this contribution we report on an XPS study of microporous and mesoporous titanosilicates, in particular microporous titanium silicalite TS-1, ordered mesoporous Ti-MCM-41 and [Ti]-MCM-41 and amorphous mesoporous silica-titania (MST) catalysts. Our aim was to obtain both photoemission and x-ray-excited Auger data for Ti species on these catalysts and use them in a Ti Wagner plot to rationalize the dependence of the local electronic structure on the atomic environment. Isolated Ti(IV) species coordinated to four and six oxygen anions and segregated TiO2 clusters were detected on all catalysts by a curve-fitting procedure of Ti 2p, O 1s and related peaks. The presence of the Si 2p peak excited by an O Kalpha ghost makes the detection of Ti LMM Auger transitions in mesoporous samples impossible due to the low Ti loadings and its homogeneous distribution in the silica matrix. Small TiO2 clusters are eventually segregated within the mesopores of the catalysts and not at their external surface. On TS-1 microporous catalysts with similar Ti loadings to the mesoporous catalysts we were able to detect Ti LMM Auger transitions, and by the Ti Wagner plot we clearly identify the presence of octahedrally coordinated Ti(IV) species. Thus, it is suggested that on TS-1 the in-framework (-O)(4)Ti species are easily changed to (-O)(4)(H2O)(2)Ti species by insertion of water molecules from the atmosphere. Small TiO2 clusters (diameter <5 nm), eventually present on samples with Ti loading >2 wt.%, are segregated at their external surface and present spectroscopic features similar to (-O)(4)(H2O)(2)Ti species. Copyright (C) 2004 John Wiley Sons, Ltd

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Section: X-ray Absorption Fine Structurementioning

confidence: 97%

Section: And References Cited Therein)mentioning

confidence: 99%

An XPS study of microporous and mesoporous titanosilicates

Moretti¹,

Salvi

Guascito

et al. 2004

Surface & Interface Analysis

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“…This can be explained both qualitatively considering the influence on Ti 2p binding energy of the oxygen being shared with the Si ions [8 -11] and quantitatively by comparing the Ti (3)/Si atomic ratio reported in Table 2 with the Ti/Si ratio obtained by XRD. [6] It is known, in fact, that a linear correlation exists between the volume of the uc in Å 3 , V, of T-S1 samples and the molar fraction of Ti in the framework, x : V = 2210.4x + 5339.4 (r = 0.9993), [12] the maximum solubility corresponding to ca 2.4 Ti atoms per uc (Ti 1.98 wt%). For both TS-1 samples the volume cell was reported to be the same (≈5376.7 Å 3 ) giving a framework Ti/Si ratio of ca 0.016.…”

Section: As Received Samplesmentioning

confidence: 99%

XPS characterization of a synthetic Ti‐containing MFI zeolite framework: the titanosilicalites, TS‐1

Langerame

Salvi

Silletti

et al. 2008

Surface & Interface Analysis

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Following a previous investigation on micro-and mesoporous titanosilicates, we have here deepened the XPS and Xray-excited Auger electron spectroscopy (XAES) studies on the surface properties of microporous titanosilicalites-1 (TS-1) and reference silicalites-1 (S-1), both characterized by the MFI framework type. The aim was that of complementing the information already obtained on these compounds with other techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dielectric relaxation spectroscopy (DRS), electron spin resonance (ESR), and quantomechanical calculations. Notwithstanding the expected low photoelectron intensity due to the very low solubility of Ti (IV) ions in the MFI framework, an accurate XPS curve-fitting procedure and the simultaneous use of the XPS and Auger signals (Wagner plot) have made possible, both qualitatively and quantitatively, the distinction of two Ti (IV) sites: the framework tetrahedral species -Ti (IV) substituting Si (IV) -and the Ti(IV) tetrahedral species grafted to surface hydroxyl groups. Both species are prone to convert into octahedrally coordinated Ti (IV) species as a consequence of interaction with water and other ligands.

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“…Amorphous silica alumina (SAM) with a Si/Al ratio of 50, with a very narrow pore distribution at $ 1.5 nm, and with a surface area of 719 m 2 g À1 was prepared according to the procedure reported by Bellusi et al [14] Elemental analyses of the pure as-synthesized ALPON's were carried out by using a CHNS analyzer (Fisons EA 1108).…”

Section: Experimental Section Materialsmentioning

confidence: 99%

Aldol Condensations on Solid Catalysts: A Cooperative Effect between Weak Acid and Base Sites

Climent

Corma

Fornés

et al. 2002

Advanced Synthesis & Catalysis

127

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An amorphous aluminophosphate (ALPO) catalyst containing weak acid and base centers can carry out the aldol condensation of heptanal with benzaldehyde at much higher rates and selectivities than conventional solid acid (amorphous or crystalline aluminosilicates) or base catalysts (MgO, hydrotalcites, KF/Al2O3, nitrurated ALPO). With the weak acid‐base catalyst, the reaction occurs through a bifunctional acid‐base mechanism that involves the activation of benzaldehyde, by protonation‐polarization of the carbonyl group on the acid sites, and the attack of the enolate heptanal intermediate generated on the basic sites. With this type of bifunctional acid‐base catalyst, compounds with weak basicities are already able to undergo the reaction with a much higher selectivity than those obtained on stronger acid or base catalysts.

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Amorphous mesoporous silica-alumina with controlled pore size as acid catalysts

Cited by 95 publications

References 12 publications

An XPS study of microporous and mesoporous titanosilicates

An XPS study of microporous and mesoporous titanosilicates

XPS characterization of a synthetic Ti‐containing MFI zeolite framework: the titanosilicalites, TS‐1

Aldol Condensations on Solid Catalysts: A Cooperative Effect between Weak Acid and Base Sites

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