Enhancement of catalytic activity of Ir/TiO2 by partially reduced titanium oxide in aerobic oxidation of alcohols

Yoshida, Akihiro; Mori, Yoshinori; Ikeda, Tsuyoshi; Azemoto, Kazuki; Naito, Shuichi

doi:10.1016/j.cattod.2012.04.020

Cited by 24 publications

(17 citation statements)

References 22 publications

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“…Peaks observed at binding energies of ~62 eV and ~64.7 eV are attributed to the IrO 2 phase. The binding energies also coincide with Ir 4f 7/2 , which suggests that Ir is present in the IrO 2 phase [24,25]. Table 2 gives the binding energies observed for the Zr 3d 5/2 , Ti 2p 3/2 , Ir 4f 7/2 , and O 1s, of the supported Ir catalysts.…”

Section: X-ray Photon Spectroscopymentioning

confidence: 67%

“…Reduction peaks observed for both of the catalysts above 300 • C could be attributed to the surface oxygen of the supports, or reduction by H 2 spillover [22,23,[28][29][30][31][32]. Yoshida et al [24] reported the formation of partially reduced TiO 2 by H 2 in Ir-TiO 2 catalysts, and a well-known phenomenon referred to as the strong metal-support interaction. Similarly to the observed profiles in the literature [29,30,[33][34][35], under reducing environments, reducible supported PGM metals with strong metal-support interactions tend to become partially decorated by support interstitials that migrate towards and/or over the active metal at the metal-support interface.…”

Section: X-ray Photon Spectroscopymentioning

confidence: 95%

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The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts

Mohamed¹,

Dasireddy²,

Singh³

et al. 2021

Catalysts

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CO hydrogenation and oxidation were conducted over Ir supported on TiO2 and ZrO2 catalysts using a feed mimicking the water–gas shift reformate stream. The influence of the support interaction with Ir and the catalysts’ redox and CO chemisorption properties on activity and selectivity were evaluated. Both catalysts oxidised CO to CO2 in the absence of H2, and a conversion of 70% was obtained at 200 °C. For the CO oxidation in the presence of H2 over these catalysts, the oxidation of H2 was favoured over CO due to H2 spillover occurring at the active metal and support interface, resulting in the formation of interstitials catalysed by Ir. However, both catalysts showed promising activity for CO hydrogenation. Ir-ZrO2 was more active, giving 99.9% CO conversions from 350 to 370 °C, with high selectivity towards CH4 using minimal H2 from the feed. Furthermore, results for the Ir-ZrO2 catalyst showed that the superior activity compared to the Ir-TiO2 catalyst was mainly due to the reducibility of the support and its interaction with the active metal. Controlling the isoelectric point during the synthesis allowed for a stronger interaction between Ir and the ZrO2 support, which resulted in higher catalytic activity due to better metal dispersions, and higher CO chemisorption capacities than obtained for the Ir-TiO2 catalyst.

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Section: X-ray Photon Spectroscopymentioning

confidence: 67%

Section: X-ray Photon Spectroscopymentioning

confidence: 95%

The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts

Mohamed¹,

Dasireddy²,

Singh³

et al. 2021

Catalysts

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show abstract

“…(1)], suggesting the reaction rate hinges on the formation of benzylamine from benzyl alcohol and ammonia. As one possible reason for the different time course profiles in air or argon, the oxidation of benzyl alcohol to benzaldehyde by air and subsequent conversion to imines might accelerate the reaction at the early stage [55–57] . The further detailed study on the different behaviours in the reactions in air and argon is ongoing.…”

Section: Entry Catalysts[b] Yield [%][C]mentioning

confidence: 99%

“…To understand the reaction mechanisms, a serial of separate experiments was performed. Since Ir/TiO 2 is well known for its high performance in the aerobic oxidation of 1 a , [55–57] we first investigated the conversion of 1 a in the presence of the catalyst for one hour in argon or air [Eq. (S1)].…”

Section: Entry Catalysts[b] Yield [%][C]mentioning

confidence: 99%

Rapid Multialkylation of Aqueous Ammonia with Alcohols by Heterogeneous Iridium Catalyst under Simple Conditions

Han

Wada

et al. 2021

ChemCatChem

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This paper reports the synthesis of tertiary and secondary amines from aqueous ammonia and benzylic alcohols by titania‐supported iridium catalyst. It is a successful example of heterogeneous systems at moderate temperature without either additional solvent or high pressure. The catalytic system showed good tolerance to the atmosphere condition and performed rapidly to give tribenzylamine a yield of over 99 % within 6 hours in argon. The crystal structure of titania supports for iridium catalysts strongly affected their activity. The catalysis smoothly proceeded on larger scales. The catalyst could be easily reused and run at least for 5 cycles without significant loss of activity. The highly‐dispersed iridium species of less than 2 nm in diameter would be responsible for the excellent catalytic activity. This catalyst is well applicable in multialkylation of aqueous ammonia with various primary and secondary benzylic alcohols.

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“…The present authors previously developed heterogeneous supported ruthenium 17g),17h) and rhodium 19) catalysts which enable various highly atom-efficient organic transformations. In particular, titania-supported iridium catalysts are effective for the synthesis of benzimidazoles via acceptor-less dehydrogenative or hydrogen transfer routes 20) 23) , which are dependent on the high activity of iridium in hydrogen activation 24) and coordinatively unsaturated titanium sites on the TiO2 surface as adsorption and/or activation sites of alcohols 25) . Pt/Al2O3 catalysts have also been developed for the acceptor-less dehydrogenative synthesis of benzothiazoles and benzimidazoles 26) .…”

Section: Introductionmentioning

confidence: 99%

Development of Titania-supported Iridium Catalysts for the Acceptor-less Dehydrogenative Synthesis of Benzoxazoles

Han

Wada

et al. 2021

J. Jpn. Petrol. Inst.

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Iridium catalysts supported on anatase with high surface area showed excellent activities for the acceptor-less dehydrogenation synthesis of benzoxazoles from 2-aminophenol and primary alcohols. The catalytic activity greatly depended on the titania supports, iridium precursors, and loading of iridium species. Catalysts supported on anatase JRC (Japan Reference Catalyst)-TIO-10 showed the highest activity for the dehydrogenative reaction. Preparation of catalysts using [Ir(cod)Cl]2 (cod 1,5-cyclooctadiene) as an iridium precursor resulted in higher activity than using Ir(acac)3 (acac acetylacetonate). Various primary alcohols were reacted to give corresponding benzoxazoles in high to moderate yields. The catalyst could be recycled without significant loss of activity, and no leaching of iridium species occurred into the solution. The hot filtration test strongly suggested that the catalysis occurs on the catalyst surface. Highly dispersed iridium species of less than 2 nm in diameter, which could be reduced at low temperature, were responsible for the excellent activity.

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Enhancement of catalytic activity of Ir/TiO2 by partially reduced titanium oxide in aerobic oxidation of alcohols

Cited by 24 publications

References 22 publications

The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts

The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts

Rapid Multialkylation of Aqueous Ammonia with Alcohols by Heterogeneous Iridium Catalyst under Simple Conditions

Development of Titania-supported Iridium Catalysts for the Acceptor-less Dehydrogenative Synthesis of Benzoxazoles

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