Acidity of unsupported and silica-supported vanadia, molybdena, and titania as studied by pyridine adsorption

Kataoka, Takuo; Dumesic, James A.

doi:10.1016/0021-9517(88)90121-2

Cited by 163 publications

(52 citation statements)

References 41 publications

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“…5C). A third band at 1490 cm À1 can be attributed to both Lewis and Brønsted acid sites but the absence of bands at 1545 or 1640 cm À1 reveals the absence of significant Brønsted acidity on all materials [63,64]. Since Brønsted acidity in silicasupported TiO 2 materials has been recently attributed to the presence of chlorides and alkoxides impurities [60,65], those data further confirmed the efficient elimination of any precursor residue from the metal oxide framework during post-synthetic treatment.…”

Section: Formation Of Acid Sites: Tio 2 @Sba-15supporting

confidence: 64%

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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Section: Formation Of Acid Sites: Tio 2 @Sba-15supporting

confidence: 64%

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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“…The low desorption temperature indicates weak pyridine adsorption on the SiO2 support. The low adsorption observed agrees with the literature data which showed that amorphous silica does not contain acid sites and weak pyridine adsorption is associated with the hydrogen-bonded pyridine molecules over the silanol groups [42][43][44]. However, the Pt/SiO2 catalyst showed much broader peaks centered at about 200 °C and 460 °C.…”

Section: Catalyst Characterizationsupporting

confidence: 81%

Highly Selective Continuous Flow Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol in a Pt/SiO2 Coated Tube Reactor

et al. 2018

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A novel continuous flow process for selective hydrogenation of α, β-unsaturated aldehyde (cinnamaldehyde, CAL) to the unsaturated alcohol (cinnamyl alcohol, COL) has been reported in a tube reactor coated with a Pt/SiO 2 catalyst. A 90% selectivity towards the unsaturated alcohol was obtained at the aldehyde conversion of 98.8%. This is a six-fold improvement in the selectivity compared to a batch process where acetals were the main reaction products. The increased selectivity in the tube reactor was caused by the suppression of acid sites responsible for the acetal formation after a short period on stream in the continuous process. In a fixed bed reactor, it had a similar acetal suppression phenomenon but showed lower product selectivity of about 47-72% due to mass transfer limitations. A minor change in selectivity and conversion caused by product inhibition was observed during the 110 h on stream with a turnover number (TON) reaching 3000 and an alcohol production throughput of 0.36 kg g Pt −1 day −1 in the single tube reactor. The catalysts performance after eight reaction cycles was fully restored by calcination in air at 400 • C. The tube reactors provide an opportunity for process intensification by increasing the reaction rates by a factor of 2.5 at the reaction temperature of 150 • C compared to 90 • C with no detrimental effects on catalyst stability or product selectivity.

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“…Nevertheless, titania samples under the study also exhibited reasonable acidity. Indeed, the presence of different acid sites in TiO 2 was reported repeatedly [55][56][57][58]. It was suggested that the Lewis and Brønsted acid sites responsible for the catalytic activity of these materials could be generated from adsorbed water molecules [57].…”

Section: Tablementioning

confidence: 99%

Nanosized TiO2—A promising catalyst for the aldol condensation of furfural with acetone in biomass upgrading

et al. 2016

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a b s t r a c t Nanosized TiO 2 catalyst was successfully prepared by a simple green procedure and used in liquid phase aldol condensation of furfural with acetone, a key step in bio-fuel processing. In order to determine the effect of calcination temperature on catalytic properties of TiO 2 , the as-prepared TiO 2 and calcined TiO 2 (150-900• C) were studied by XRD, BET, TPD-CO 2 /NH 3 , TGA/DTG and FTIR evaluation. The catalytic performance of TiO 2 samples in aldol condensation of furfural with acetone was evaluated and compared with that of Mg-Al hydrotalcites and a BEA zeolite. These experiments showed that uncalcined TiO 2 possessed reasonable activity in aldol condensation of furfural to acetone and resulted in commonly produced condensation products. The observed catalytic behavior of TiO 2 could be competitive with that reported for other inorganic solids. The calcination of TiO 2 resulted, however, in a decrease in its catalytic activity due to extensive dehydration and surface dehydroxylation as well as due to changes of textural properties resulting in a decrease in the amount of accessible active sites. Thanks to its advanced properties, nanosized TiO 2 is a promising catalyst for aldol condensation of furfural with acetone and could broaden possibilities for optimizing conditions for bio-fuel production.

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Acidity of unsupported and silica-supported vanadia, molybdena, and titania as studied by pyridine adsorption

Cited by 163 publications

References 41 publications

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

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

Highly Selective Continuous Flow Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol in a Pt/SiO2 Coated Tube Reactor

Nanosized TiO2—A promising catalyst for the aldol condensation of furfural with acetone in biomass upgrading

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