Supercritical Fluids in Catalysis: Opportunities of In Situ Spectroscopic Studies and Monitoring Phase Behavior

Grunwaldt, Jan‐Dierk; Wandeler, Roland; Baiker, Alfons

doi:10.1081/cr-120015738

Cited by 141 publications

(118 citation statements)

References 416 publications

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“…Furthermore, scCO 2 can show interesting effects on reaction rates and product selectivity [19][20][21][22][23][24][25]. Recently the present authors studied the hydrogenation of NB in scCO 2 over noble metal catalysts including Pd, Pt, Ru, and Rh supported on carbon, silica, and alumina.…”

Section: Introductionmentioning

confidence: 99%

Selective hydrogenation of nitrobenzene to aniline in dense phase carbon dioxide over Ni/γ-Al2O3: Significance of molecular interactions

Meng

Cheng

Akiyama

et al. 2009

Journal of Catalysis

143

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The selective hydrogenation of nitrobenzene (NB) over Ni/γ-Al 2 O 3 catalysts was investigated using different media of dense phase CO 2 , ethanol, and n-hexane. In dense phase CO 2 , the total rate of NB hydrogenation was larger than that in organic solvents under similar reaction conditions; the selectivity to the desired product, aniline, was almost 100% over the whole conversion range of 0-100%. The phase behavior of the reactant mixture in/under dense phase CO 2 was examined at reaction conditions. In situ high-pressure Fourier transform infrared measurements were made to study the molecular interactions of CO 2 with the following reactant and reaction intermediates: NB, nitrosobenzene (NSB), and N-phenylhydroxylamine (PHA). Dense phase CO 2 strongly interacts with NB, NSB, and PHA, modifying the reactivity of each species and contributing to positive effects on the reaction rate and the selectivity to aniline. A possible reaction pathway for the hydrogenation of NB in/under dense phase CO 2 over Ni/γ-Al 2 O 3 is also proposed.

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Section: Introductionmentioning

confidence: 99%

Selective hydrogenation of nitrobenzene to aniline in dense phase carbon dioxide over Ni/γ-Al2O3: Significance of molecular interactions

Meng

Cheng

Akiyama

et al. 2009

Journal of Catalysis

143

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“…The almost gas-like diffusion coefficients of solutes in dense carbon dioxide and the avoidance of phase boundaries under single-phase conditions in combination with its ability to solvate nonpolar gases as well as many organic compounds render it a promising reaction medium [52][53][54][55].…”

Section: Introductionmentioning

confidence: 99%

Gold-Catalyzed Aerobic Oxidation of Benzyl Alcohol: Effect of Gold Particle Size on Activity and Selectivity in Different Solvents

et al. 2008

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The effect of the size of gold particles deposited on CeO 2 and TiO 2 supports on their catalytic behavior in the aerobic oxidation of benzyl alcohol in different solvents (mesitylene, toluene, and supercritical carbon dioxide) has been investigated. The size of supported gold particles deposited via a colloidal route was in the range 1.3-11.3 nm, as determined by means of EXAFS and HAADF-STEM measurements. The catalytic performance of the supported gold catalysts in the different solvents revealed a significant effect of the gold particle size. Optimal activity was observed for catalysts with medium particle size (ca. 6.9 nm) whereas smaller and bigger particles showed inferior activity. Identical trends for the activity-particle size relationship were found using Au/CeO 2 and Au/TiO 2 for the reaction at atmospheric pressure in conventional solvents (mesitylene, toluene) as well as under supercritical conditions (scCO 2 ). Selectivity to benzaldehyde was only weakly affected by the gold particle size and mainly depended on reaction conditions. In supercritical CO 2 (scCO 2 ) selectivity was higher than in the conventional solvents under atmospheric pressure. All catalysts tested with particle sizes ranging from 1.3 to 11.3 nm showed excellent selectivity of 99% or higher under supercritical conditions.

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“…It is also possible to study reactions in the liquid phase [ 15 ] or under supercritical conditions. [ 16 ] Knowing the structure under in situ conditions is only part of the story. Ortega y Gasset followed up his comment on circumstance: "It is wrong to tell that we are determined by our circumstances.…”

Section: From In Situ To Operandomentioning

confidence: 99%

Operando Spectroscopy: the Knowledge Bridge to Assessing Structure–Performance Relationships in Catalyst Nanoparticles

Bañares

2011

Advanced Materials

118

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Progress in nanomaterials and catalysis stands on three pillars: 1) synthesis of nanomaterials, including the preparation of hierarchically dispersed nanoparticles; 2) theoretical studies of materials that enable experimental results to be understood; and 3) advanced, in situ characterization during operation (operando methodology). This Research News brings a perspective on how these three pillars are blending for research in materials science, with particular emphasis on catalysis.

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Supercritical Fluids in Catalysis: Opportunities of In Situ Spectroscopic Studies and Monitoring Phase Behavior

Cited by 141 publications

References 416 publications

Selective hydrogenation of nitrobenzene to aniline in dense phase carbon dioxide over Ni/γ-Al2O3: Significance of molecular interactions

Selective hydrogenation of nitrobenzene to aniline in dense phase carbon dioxide over Ni/γ-Al2O3: Significance of molecular interactions

Gold-Catalyzed Aerobic Oxidation of Benzyl Alcohol: Effect of Gold Particle Size on Activity and Selectivity in Different Solvents

Operando Spectroscopy: the Knowledge Bridge to Assessing Structure–Performance Relationships in Catalyst Nanoparticles

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