Tunable Pt nanocatalysts for the aerobic selox of cinnamyl alcohol

Durndell, Lee J.; Parlett, Christopher M. A.; Hondow, Nicole; Wilson, Karen; Lee, Adam F.

doi:10.1039/c3nr00184a

Cited by 28 publications

(38 citation statements)

References 50 publications

(88 reference statements)

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“…mesopores for KIT-6 [48], and the incorporation of 300 nm macropores between hexagonal close-packed mesopore channels in MM-SBA-15 [50]. Physicochemical characteristics of the Pt/silica analogues are summarised in Table S2, and are in excellent agreement with literature reports [32,51,52]. XRD, HRTEM and N2 porosimetry confirmed retention of the parent silica pore structures following platinum impregnation (Table S2, Figure S3-4), but a loss of BET surface area and pore volume proportional to Pt loading, attributed to partial pore blockage, as previously observed.…”

Section: Characterisationsupporting

confidence: 84%

“…Nevertheless, the nature of the active site and role(s) of promoters and base remain poorly understood, reflecting the complex solid-liquid-gas interface and necessity for (but attendant difficulties in performing and interpreting) in-situ/operando studies on supported metal catalysts for aerobic selox [30,31]. Recent spectroscopic and kinetic studies of cinnamyl alcohol aerobic oxidation over silica supported Pt nanoparticles identified surface PtO2 as the active site for the selective production of cinnamaldehyde [32].…”

Section: Introductionmentioning

confidence: 99%

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Platinum catalysed aerobic selective oxidation of cinnamaldehyde to cinnamic acid

et al. 2019

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Platinum catalysed aerobic selective oxidation of cinnamaldehyde to cinnamic acid, Catalysis Today https://doi.Graphical abstract Highlights  Silica supported Pt nanoparticles are active and selective for base-free cinnamaldehyde aerobic oxidation  High area, mesoporous silica supports increase Pt dispersion and hence activity and cinnamic acid yield  Surface PtO2 is the active site for selective oxidation of cinnamaldehydecinnamic acid  Continuous flow operation stabilises surface PtO2 thereby significantly enhancing catalyst stability and acid yield Abstract Aerobic selective oxidation of allylic aldehydes offers an atom and energy efficient route to unsaturated carboxylic acids, however suitable heterogeneous catalysts offering high selectivity and productivity have to date proved elusive. Herein, we demonstrate the direct aerobic oxidation of cinnamaldehyde to cinnamic acid employing silica supported Pt nanoparticles under base-free, batch and continuous flow operation. Surface and bulk characterisation of four families of related Pt/silica catalysts by XRD, XPS, HRTEM, CO chemisorption and N2 porosimetry evidence surface PtO2 as the common active site for cinnamaldehyde oxidation, with a common turnover frequency of 49,000±600 h -1 ; competing cinnamaldehyde hydrogenolysis is favoured over metallic Pt. High area mesoporous (SBA-15 or KIT-6) and macroporous-mesoporous SBA-15 silicas confer significant rate and cinnamic acid yield enhancements versus low area 2 fumed silica, due to superior platinum dispersion. High oxygen partial pressures and continuous flow operation stabilise PtO2 active sites against in-situ reduction and concomitant deactivation, further enhancing cinnamic acid productivity.

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Section: Characterisationsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Platinum catalysed aerobic selective oxidation of cinnamaldehyde to cinnamic acid

et al. 2019

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“…Kumar et al [15], Scott et al [16] and Hara et al [17] have likewise reported a heterogeneous Pd(II) active species responsible for aerobic alcohol selox, while homogeneous Pd(II) complexes are well known to catalyse such alcohol oxidations [18], [19] and [20]. Interestingly, surface PtO2 has also been recently reported as the active phase in the analogous Pt catalysed aerobic selox of allylic alcohols [21].…”

Section: Introductionmentioning

confidence: 99%

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Parlett

Durndell

Wilson

et al. 2014

Catalysis Communications

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Highly ordered mesoporous alumina was prepared via evaporation induced self-assembly and was impregnated to afford a family of Pd/meso-Al 2 O 3 catalysts for the aerobic selective oxidation (selox) of allylic alcohols under mild reaction conditions. CO chemisorption and XPS identify the presence of highly dispersed (0.9 2 nm) nanoparticles comprising heavily oxidised PdO surfaces, evidencing a strong palladium-alumina interaction. Surface PdO is confirmed as the catalytically active phase responsible for allylic alcohol selox, with initial rates for Pd/meso-Al 2 O 3 far exceeding those achievable for palladium over either amorphous alumina or mesoporous silica supports. Pd/meso-Al 2 O 3 is exceptionally active for the atom efficient selox of diverse allylic alcohols, with activity inversely proportional to alcohol mass.

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“…The catalytic advantage of spatially segregating Pt NPs within mesopores, accessible overwhelmingly only through interconnected macropores containing Pd NPs, was explored for the cascade oxidative dehydrogenation of cinnamyl alcohol  cinnamaldehyde  cinnamic acid, the latter an important flavorant and essential oil 21,22 . Pd is highly selective for catalyzing cinnamyl alcohol oxidation to cinnamaldehyde 23,24 , but promotes decarbonylation of the resultant aldehyde product; in contrast, Pt favours undesired hydrogenation of cinnamyl alcohol (via reactively-formed surface hydrogen) to 3-phenylpropionaldehyde 25 , but is highly selective towards cinnamaldehyde oxidation to the desirable cinnamic acid product 26 . An optimal catalyst design would therefore ensure that cinnamyl alcohol was oxidized over Pd prior to encountering Pt sites, while permitting the reactively-formed cinnamaldehyde to subsequently access Pt sites for the selective production of cinnamic acid in the second oxidation step.…”

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Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions

et al. 2015

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. (2016) 'Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions.', Nature materials., 15 (2). pp. 178-182.Further information on publisher's website:Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

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Tunable Pt nanocatalysts for the aerobic selox of cinnamyl alcohol

Cited by 28 publications

References 50 publications

Platinum catalysed aerobic selective oxidation of cinnamaldehyde to cinnamic acid

Platinum catalysed aerobic selective oxidation of cinnamaldehyde to cinnamic acid

Selective oxidation of allylic alcohols over highly ordered Pd/meso-Al2O3 catalysts

Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions

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