Hydrogenation of tetralin on silica–alumina-supported Pt catalysts II. Influence of the support on catalytic activity

Williams, M.F.; Fonfé, Benjamin; Woltz, Christian; Jentys, Andreas; Veen, J.A.R. van; Lercher, Johannes A.

doi:10.1016/j.jcat.2007.06.010

Cited by 43 publications

(48 citation statements)

References 49 publications

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“…Previous studies have not always provided a consistent answer to the effect of particle size on XANES as some authors have found an increase in the L 3 edge intensity as particle size decreases [5,6]. However, a number of studies have demonstrated similar behavior as our observations here even if the experiments were not performed for a large number of samples with varying size [16,49,50].…”

Section: Resultssupporting

confidence: 68%

Effect of Particle Size and Adsorbates on the L3, L2 and L1 X-ray Absorption Near Edge Structure of Supported Pt Nanoparticles

et al. 2011

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Pt nano-particles from about 1 to 10 nm have been prepared on silica, alkali-silica, alumina, silica-alumina, carbon and SBA-15 supports. EXAFS spectra of the reduced catalysts in He show a contraction of the Pt-Pt bond distance as particle size is decreased below 3 nm. The bond length decreased as much as 0.13 Å for 1 nm Pt particles. Adsorption of CO and H 2 lead to a increase in PtPt bond distance to that near Pt foil, e.g., 2.77 Å . In addition to changes in the Pt bond distance with size, as the particle size decreases below about 5 nm there is a shift in the XANES to higher energy at the L 3 edge, a decrease in intensity near the edge and an increase in intensity beyond the edge. We suggest these features correspond to effects of coordination (the decrease at the edge) and lattice contraction (the increase beyond the edge). At the L 2 edge, there are only small shifts to higher energy at the edge. However, beyond the edge, there are large increases in intensity with decreasing particle size. At the L 1 edge there are no changes in position or shape of the XANES spectra. Adsorption of CO and H 2 also lead to changes in the L 3 and L 2 edges, however, no changes are observed at the L 1 edge. Density Functional Theory and XANES calculations show that the trends in the experimental XANES can be explained in terms of the states available near the edge. Both CO and H 2 adsorption result in a depletion of states at the Fermi level but the creation of anti-bonding states above the Fermi level which give rise to intensity increases beyond the edge.Keywords Pt nanoparticles Á Bond length contraction Á Particle size effect in XANES spectra Á Particle size effect in Pt bond length Á Pt XANES Á EXAFS

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Section: Resultssupporting

confidence: 68%

Effect of Particle Size and Adsorbates on the L3, L2 and L1 X-ray Absorption Near Edge Structure of Supported Pt Nanoparticles

et al. 2011

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“…3b). Overall the spectra of SiAl (6) is very close to amorphous silicaaluminas with similar Al content [27,29]. Figure 3a shows that the spectra of the blank and catalyst samples dried at 150°C are very similar and differ significantly from that of SiAl(6), with a lower proportion of octahedral Al and a higher proportion of tetrahedral Al.…”

Section: Structural Characterizationmentioning

confidence: 80%

“…It is often reported for silica-aluminas and its assignment has long been debated (either pentacoordinated Al or distorted tetracoordinated Al) [28]. It is now generally accepted that this peak can be assigned to pentacoordinated Al [10,29], possibly located at the interface between aluminic and silicic domains, between silica-alumina domains [29] or in an amorphous alumina phase [30]. The presence of this peak together with the peak corresponding to octahedral Al confirms the existence of Al-rich zones.…”

Section: Structural Characterizationmentioning

confidence: 81%

Comparing Al-SBA-15 Support and Pt/Al-SBA-15 Catalyst: Changes in Al Speciation and Acidic Properties Induced by the Introduction of Pt via Aqueous Medium

et al. 2009

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Differences between the acidic properties of silicoaluminic Pt-containing catalysts and those assessed on their parent supports have been reported in the literature and attributed to the presence of the metal nanoparticles and to their influence on the acid sites. It is shown here that for mesoporous materials containing various types of Al species, an alternative explanation can be proposed. 27 Al NMR spectroscopy, FTIR of adsorbed CO and probe catalytic tests suggest the redistribution of aluminium atoms upon contact of the parent support with the aqueous solution containing the Pt precursor. Upon contact with water and thermal treatment, strong and mild Brønsted sites (Si-O(H)-Al) transform into strong Lewis sites (isolated tetracoordinated Al atoms). As a consequence, it may not be straightforward to deduce the acidic properties of metalcontaining catalysts supported on Al-containing mesoporous materials from those of the bare support, because the surface species may differ significantly.

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“…Interfacial effects are of great interest for various catalytic applications [69][70][71]. Specifically, we investigated the compatibility of the NHSG TiO 2 deposition with the presence of Pt nanoparticles (NPs) supported on SiO 2 spheres.…”

Section: Metal-acid Bifunctional Catalysismentioning

confidence: 99%

Controlled deposition of titanium oxide overcoats by non-hydrolytic sol gel for improved catalyst selectivity and stability

Héroguel

Silvioli

et al. 2018

Journal of Catalysis

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a b s t r a c tAdvances in the synthetic control of surface nanostructures could improve the activity, selectivity and stability of heterogeneous catalysts. Here, we present a technique for the controlled deposition of TiO 2 overcoats based on non-hydrolytic sol-gel chemistry. Continuous injection of Ti( i PrO) 4 and TiCl 4 mixtures led to the formation of conformal TiO 2 overcoats with a growth rate of 0.4 nm/injected monolayer on several materials including high surface area SBA-15. Deposition of TiO 2 on SBA-15 generated mediumstrength Lewis acid sites, which catalyzed 1-phenylethanol dehydration at high selectivities and decreased deactivation rates compared to typically used HZSM-5. When supported metal nanoparticles were similarly overcoated, the intimate contact between the metal and acid sites at the supportovercoat interface significantly increased propylcyclohexane selectivity during the deoxygenation of lignin-derived propyl guaiacol (89% at 90% conversion compared to 30% for the uncoated catalyst). For both materials, the surface reactivity could be tuned with the overcoat thickness.

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Hydrogenation of tetralin on silica–alumina-supported Pt catalysts II. Influence of the support on catalytic activity

Cited by 43 publications

References 49 publications

Effect of Particle Size and Adsorbates on the L3, L2 and L1 X-ray Absorption Near Edge Structure of Supported Pt Nanoparticles

Effect of Particle Size and Adsorbates on the L3, L2 and L1 X-ray Absorption Near Edge Structure of Supported Pt Nanoparticles

Comparing Al-SBA-15 Support and Pt/Al-SBA-15 Catalyst: Changes in Al Speciation and Acidic Properties Induced by the Introduction of Pt via Aqueous Medium

Controlled deposition of titanium oxide overcoats by non-hydrolytic sol gel for improved catalyst selectivity and stability

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