Thiophene as Internal Promoter of Selectivity for the Liquid Phase Hydrogenation of Citral Over Ru/KL Catalysts

Álvarez-Rodríguez, J.; Guerrero-Ruı́z, A.; Arcoya, A.; Rodrı́guez-Ramos, I.

doi:10.1007/s10562-009-9841-1

Cited by 9 publications

(9 citation statements)

References 32 publications

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“…The use of thiophene to promote chemoselective hydrogenation of unsaturated aldehydes has been reported on Ru [109] and Au [110] catalysts. Similarly, the modification of Pd-nanoparticles with thiols can promote the selective hydrogenation of unsaturated oxygenates [111] and amines [112].…”

Section: Sulfurmentioning

confidence: 99%

Surface-level mechanistic studies of adsorbate–adsorbate interactions in heterogeneous catalysis by metals

Marshall

Medlin

2011

Surface Science Reports

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Section: Sulfurmentioning

confidence: 99%

Surface-level mechanistic studies of adsorbate–adsorbate interactions in heterogeneous catalysis by metals

Marshall

Medlin

2011

Surface Science Reports

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“…The addition of thiophene to Ru/KL catalysts gave a maximum selectivity to geraniol and nerol of 46% (at 15% citral conversion with 3 ppm thiophene); in the absence of the thiophene, the Ru catalysts typically favor CC hydrogenation. 5 Therein, it was also reported that the adsorption mode of the thiophene (relating to thiophene concentration/surface coverage) altered whether the citral adsorbed through the CC or the CO bond. Addition of ethylenediamine during the hydrogenation of citral over a Ru/AlO(OH) catalyst (in water) resulting in 87% selectivity to geraniol/nerol (93% conversion), whereas selectivity of 74.3% (at 60.5% conversion) was obtained without the additive.…”

Section: ■ Introductionmentioning

confidence: 99%

Use of Short Time-on-Stream Attenuated Total Internal Reflection Infrared Spectroscopy To Probe Changes in Adsorption Geometry for Determination of Selectivity in the Hydrogenation of Citral

et al. 2014

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A new experimental procedure based on attenuated total reflection infrared spectroscopy has been developed to investigate surface species under liquid phase reaction conditions. The technique has been tested by investigating the enhanced selectivity in the hydrogenation of α,β-unsaturated aldehyde citral over a 5% Pt/SiO 2 catalyst toward unsaturated alcohols geraniol/nerol, which occurs when citronellal is added to the reaction. The change in selectivity is proposed to be the result of a change in the citral adsorption mode in the presence of citronellal. Short time on stream attenuated total internal reflection infrared spectroscopy has allowed identification of the adsorption modes of citral. With no citronellal, citral adsorbs through both the CC and CO groups; however, in the presence of citronellal, citral adsorption occurs through the CO group only, which is proposed to be the cause of the altered reaction selectivity.In chemoselective hydrogenations, such as the hydrogenation of α,β-unsaturated aldehydes, there is the desire to understand and control the reaction pathway so as to obtain a specific product with high selectivity. The hydrogenation of citral is of particular interest because of the complex reaction network resulting from the preferential adsorption geometry and strength of interaction of different functional groups within the molecule, namely the CO, conjugated CC, and isolated CC bonds the hydrogenation and further reaction of which can form a wide range of products illustrated in Scheme 1. The hydrogenation of citral has been studied extensively with the choice of metal, support, reaction conditions, and solvent all reported to affect the selectivity. 1 With unsaturated alcohols being important fine chemical and pharmaceutical intermediates, there is significant interest in improving the selectivity to these desired products. Modification of the catalyst through addition of a second metal, such as Sn, Fe or Ge, has been reported to alter reaction selectivity toward CO hydrogenation. 2 For other chemoselective hydrogenations, modification of the catalyst surface via the adsorption of organic compounds has also been reported, with n-alkanethiol self-assembled-monolayer-coated Pd catalysts and thiol-modified Pt/TiO 2 catalysts giving excellent selectivity enhancements in hydrogenation of unsaturated epoxides to saturated epoxides 3 and a complete switch in the products formed for 4-nitrostyrene hydrogenation following modification, respectively. 4The attainment of higher selectivity upon addition of an organic compound into the liquid phase reaction has also been reported for the hydrogenation of citral. The addition of thiophene to Ru/KL catalysts gave a maximum selectivity to geraniol and nerol of 46% (at 15% citral conversion with 3 ppm thiophene); in the absence of the thiophene, the Ru catalysts typically favor CC hydrogenation. 5 Therein, it was also reported that the adsorption mode of the thiophene (relating to thiophene concentration/surface coverage) altered whether the citr...

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“…69 Such experimental and theoretical studies help to explain the enhanced selective hydrogenation of a,b unsaturated aldehydes to allylic alcohols over Cu/Al 2 O 3 and Ru/KL zeolite catalysts in the presence of trace thiophene. 70,71 High selectivity in the crotonaldehyde/S-Cu( 111) system may also reflect the formation of crotyl alcohol molecules themselves possessing a significant CQC bond tilt, which, as for acrolein, may protect the unsaturated alcohol against further hydrogenation to n-butanol.…”

Section: Hydrogenationmentioning

confidence: 99%

Surface X-ray studies of catalytic clean technologies

2010

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The rational design of new heterogeneous catalysts for clean chemical technologies can be accelerated by molecular level insight into surface chemical processes. In situ methodologies, able to provide time-resolved and/or pressure dependent information on the evolution of reacting adsorbed layers over catalytically relevant surfaces, are therefore of especial interest. Here we discuss recent applications of surface X-ray techniques to surface-catalysed oxidations, (de)hydrogenations, C-C coupling, dehalogenation and associated catalyst restructuring, and explore how these may help to shape future sustainable chemistry.

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Thiophene as Internal Promoter of Selectivity for the Liquid Phase Hydrogenation of Citral Over Ru/KL Catalysts

Cited by 9 publications

References 32 publications

Surface-level mechanistic studies of adsorbate–adsorbate interactions in heterogeneous catalysis by metals

Surface-level mechanistic studies of adsorbate–adsorbate interactions in heterogeneous catalysis by metals

Use of Short Time-on-Stream Attenuated Total Internal Reflection Infrared Spectroscopy To Probe Changes in Adsorption Geometry for Determination of Selectivity in the Hydrogenation of Citral

Surface X-ray studies of catalytic clean technologies

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