Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports. Part III – grafting titanium alkoxides and sulphate derivatives on silica

Iengo, P.; Aprile, Giulia; Serio, Martino Di; Gazzoli, Delia; Santacesaria, E.

doi:10.1016/s0926-860x(98)00279-8

Cited by 38 publications

(18 citation statements)

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“…This observation points to an improved interaction between fully isolated TiO x and NH 3 . The presence of acidic sites in similar systems was already reported by Iengo et al 17 Using pyridine as basic probe molecule for TPD experiments, they reported a nearly linear relationship between the TiO x content and the surface acidic sites. 48 In a more recent study Srivastava et al 46 pointed out that Ti-SBA-15 possesses only weak Lewis centers, whereas SBA-15 did not contain any acidic sites.…”

Section: ■ Introductionsupporting

confidence: 81%

“…The adsorption of CO 2 usually requires the presence of basic sites, and CO 2 is a frequently used probe molecule for the detection of basic sites . The acidic properties of grafted TiO 2 /SiO 2 materials have been characterized by Iengo et al by means of TPD of pyridine. In a study of amine-functionalized TiO x /SBA-15, Srivastava et al detected a small amount of CO 2 adsorbed on amine-free TiO x /SBA-15.…”

Section: Introductionmentioning

confidence: 99%

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Tuning the Acid/Base and Structural Properties of Titanate-Loaded Mesoporous Silica by Grafting of Zinc Oxide

et al. 2012

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Mesoporous silica (SBA-15) loaded with TiO x species was synthesized by anhydrous grafting of titanium isopropoxide, and a novel procedure for the preparation of ZnO x /SBA-15 materials by grafting of Zn(acac) 2 was explored.The TiO x /SBA-15 and ZnO x /SBA-15 materials as well as subsequently prepared bifunctional ZnO x -and TiO x -containing SBA-15 materials were characterized in depth by combining N 2 physisorption measurements, UV−vis, X-ray photoelectron and Xray absorption spectroscopy, and CO 2 and NH 3 temperatureprogrammed desorption experiments. The characterization results confirmed a close proximity of ZnO x and TiO x in the subsequently grafted materials. Because of strong interactions between the Zn precursor and the SiO 2 surface, the order of the ZnO x and TiO x grafting steps affected the amount of Ti−O−Zn bonds formed in the materials. When ZnO x is present in SBA-15, subsequently grafted TiO x is higher coordinated and more Ti−O−Zn bonds are formed compared to SBA-15 in which TiO x was introduced first, indicating strong interactions between the Ti precursor and ZnO x . While all TiO x and ZnO x -containing samples exhibit a large amount of acidic sites, ZnO x present as isolated species or small clusters in SBA-15 significantly improves the CO 2 adsorption capacity by introducing basic sites. In the subsequently grafted samples the amount of acidic and basic sites is found to be unaffected by the order in which the two transition metals are introduced.

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Section: ■ Introductionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Tuning the Acid/Base and Structural Properties of Titanate-Loaded Mesoporous Silica by Grafting of Zinc Oxide

et al. 2012

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“…Ti-Si binary oxides are interesting materials applied in many fields such as titanium silicalites, [1][2][3] Ti-substituted MCM-41, 4 mixed oxides, [5][6][7][8][9][10][11][12][13][14][15][16][17][18] and TiO 2 -coated silica. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] Most applications take advantage of the properties of binary oxides which are better than or absent in properties of titania itself. These are used as advanced glasses, 11,12,16 improved catalysts for epoxidations [7][8][9]17,26 and transesterification, 19 and catalyst supports.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Ti−O−Si and Ti−O−Ti Bonds in Ti−Si Binary Oxides by the Linear Combination of XANES

2000

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X-ray absorption near edge structure (XANES) of Ti K-edge of Ti-Si mixed oxides and titania supported on silica with various Ti contents was studied to investigate the fractions of Ti-O-Si and Ti-O-Ti bonds quantitatively by fitting the preedge of Ti K-edge with the linear combination of two reference XANES spectra. In mixed oxides, the fraction of Ti-O-Ti was increased up to 0.55 when Ti/Si was varied from 0.04 to 0.5. The greatest change of each fraction occurred around 0.15-0.2 of Ti/Si, which was coincident with the formation of anatase titania as observed by XRD. For titania supported on silica with a surface area of 300 m 2 g -1 , the preedge fitting results combined with XRD and XPS indicated that monolayer coverage was reached around 7-10 wt % Ti loading where the amount of Ti in Ti-O-Si was saturated to 0.56 mmol-Ti/g-material. This work demonstrated the possibility of the quantification of Ti-O-Si and Ti-O-Ti bonds in Ti-Si binary oxides by using the linear combination of reference XANES spectra.

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“…As previously reported, grafting reactions of isopropoxy titanium and aluminium complexes may occur with different possible stoichiometries through tripodal, bipodal and monopodal connections, the proportion of them depending on the metal content. 35 The spectra obtained for Zn and Mg-SBA-15 suggest the presence of different types of species grafted onto the silica surface, naked magnesium and zinc species, as well as butyl magnesium and methyl zinc grafted complexes. Diffuse reflectance UV-vis spectroscopy (DRUV-vis) is a useful corroborative tool in indicating the coordination environment of titanium sites.…”

Section: Dalton Transactions Papermentioning

confidence: 94%

The catalytic performance of metal complexes immobilized on SBA-15 in the ring opening polymerization of ε-caprolactone with different metals (Ti, Al, Zn and Mg) and immobilization procedures

et al. 2015

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A family of heterogeneous catalysts has been prepared by employing different strategies: firstly by direct reaction or grafting of titanium, zinc, aluminium and magnesium precursors with dehydrated SBA-15 and secondly by reaction of the metallic derivatives with a hybrid SBA-15 mesoporous material, which possesses a new covalently bonded linker based on an amino alcohol chelate ligand. These materials have been characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption-desorption, FT-IR and multi-nuclear NMR spectroscopy. The catalytic performance of the prepared materials has been studied in the ring opening polymerization of ε-caprolactone and compared with that of their homogeneous counterparts. Conversion values obtained by using homogeneous and heterogeneous catalysts depend on the metal precursor and the synthetic procedure. The most active heterogeneous Ti-SBA-15, Zn-SBA-15 and Zn-PADO-HMDS-SBA-15 catalysts produced poly(ε-caprolactone) with a narrow molecular weight distribution, close to one. In all cases polymerization was confirmed to proceed via a coordination insertion mechanism after end group analysis by (1)H NMR.

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Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports. Part III – grafting titanium alkoxides and sulphate derivatives on silica

Cited by 38 publications

References 50 publications

Tuning the Acid/Base and Structural Properties of Titanate-Loaded Mesoporous Silica by Grafting of Zinc Oxide

Tuning the Acid/Base and Structural Properties of Titanate-Loaded Mesoporous Silica by Grafting of Zinc Oxide

Quantitative Analysis of Ti−O−Si and Ti−O−Ti Bonds in Ti−Si Binary Oxides by the Linear Combination of XANES

The catalytic performance of metal complexes immobilized on SBA-15 in the ring opening polymerization of ε-caprolactone with different metals (Ti, Al, Zn and Mg) and immobilization procedures

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