Palladium Nanohexagons and Nanospheres in Selective Alkyne Hydrogenation

Palladium nanohexagons were prepared using a seed-mediated method. Their catalytic performance in 2-methyl-3-butyn-2-ol hydrogenation was compared to the one of monodispersed Pd nanospheres. Quantitative correlations between initial turnover frequencies (TOFs) and nanoparticle surface compositions showed independence of TOFs calculated per atoms on Pd(111) facets on particle size and shap

Shape and Size-Tailored Pd Nanocrystals to Study the Structure Sensitivity of 2-Methyl-3-butyn-2-ol Hydrogenation: Effect of the Stabilizing Agent

Uniform Pd nanocrystals of cubic, octahedral and cube-octahedral shapes were synthesized via a solution-phase method using two stabilizers: poly (vinyl pyrrolidone) (PVP) and di-2-ethylhexylsulfoccinate (AOT) and tested in the hydrogenation of 2-methyl-3-butyn-2-ol. The AOT-stabilized Pd nanocrystals were found to be an order of magnitude more active, but less selective than those stabilized by PVP. This could be attributed to a stronger interaction of PVP with surface Pd by adsorbed N-containing groups. The results obtained were rationalized applying a two-site Langmuir-Hinshelwood kinetic model that allowed predicting 3-4nm cubic or octahedral nanocrystals stabilized by AOT as the optimum active phase ensuring the highest production rate of target MB

Palladium Nanohexagons and Nanospheres in Selective Alkyne Hydrogenation

Palladium nanohexagons were prepared using a seed-mediated method. Their catalytic performance in 2-methyl-3-butyn-2-ol hydrogenation was compared to the one of monodispersed Pd nanospheres. Quantitative correlations between initial turnover frequencies (TOFs) and nanoparticle surface compositions showed independence of TOFs calculated per atoms on Pd(111) facets on particle size and shape

Recent Advances in the Liquid-Phase Synthesis of Metal Nanostructures with Controlled Shape and Size for Catalysis

Recent advances in the liquid-phase synthesis of metal nanostructures of different sizes and shapes are reviewed regarding their catalytic properties. The controlled synthesis of nanostructures is based on the colloid chemistry techniques in the solution, which use organic nanoreactors and a variety of stabilizers. Their catalytic activity and selectivity depend on the particle’s shape and size, as shown for Suzuki and Heck coupling, hydrogenations, hydrogenolysis, oxidations, and electron-transfer reactions. The knowledge of a reaction’s structure-sensitivity relationship is important for the rational catalyst design in view of process intensification. Nanostructures can be used per se and in supported form to meet the requirements of an eventual process

Microstructured reactors for catalytic reactions

A review. This review addresses the catalytic reactions performed in microstructured reactors, which are more and more recognized in recent years as a novel approach for chem. and chem. process industry. They are particularly suited for highly exothermic and fast reactions allowing temp. control and isothermal operation. A brief evaluation of the advantages for gas-phase, liq.-phase, and gas-liq.-solid reactions carried out in miniaturized devices is discussed. Alternative designs to achieve microstructured fluid patterns, besides microfabrication, are also described. [on SciFinder (R)

Intensification of slow reversible chemical transformation: carboxylation of resorcinol as a case study

Conjugated kinetic and thermodynamic modeling is suggested as a suitable approach to identify a novel process window (NPW) for the intensification of slow reversible reactions. The aqueous Kolbe-Schmitt synthesis of β-resorcylic acid is taken as a model. The potential of operating at high pressure (P) and temperature (T) is evaluated in order to reduce the characteristic reaction time (tr) and increase the specific productivity. For the first time, a reliable kinetic model for this reaction is derived from batch experiments. Based on this model, an NPW of P=10 bars, T=453 K is determined for a continuous reactor operated at a residence time of 28 s. It is predicted that the specific productivity can be increased by a factor of 100 with a 4.2 times less concentrated KHCO3 solution, as compared to a conventional batch process, if the reaction is kinetically controlled. The model prediction is experimentally validated with a continuously operated milli-reactor equipped by SMXS mixer elements (Sulzer Chemtech, Switzerland) ensuring a fast mixing (characteristic mixing time ~4.10-2 s). The milli-reactor renders exclusively β-resorcylic acid (selectivity 100%) and confirms process intensification (PI) of two orders of magnitude as compared to conventional batch operatio

Shape and Size-Tailored Pd Nanocrystals to Study the Structure Sensitivity of 2-Methyl-3-butyn-2-ol Hydrogenation: Effect of the Stabilizing Agent

Uniform Pd nanocrystals of cubic, octahedral and cube-octahedral shapes were synthesized via a solution-phase method using two stabilizers: poly (vinyl pyrrolidone) (PVP) and di-2-ethylhexylsulfoccinate (AOT) and tested in the hydrogenation of 2-methyl-3-butyn-2-ol. The AOT-stabilized Pd nanocrystals were found to be an order of magnitude more active, but less selective than those stabilized by PVP. This could be attributed to a stronger interaction of PVP with surface Pd by adsorbed N-containing groups. The results obtained were rationalized applying a two-site Langmuir-Hinshelwood kinetic model that allowed predicting 3-4 nm cubic or octahedral nanocrystals stabilized by AOT as the optimum active phase ensuring the highest production rate of target MBE

One-step vapor-phase synthesis of 2-methyl-1-naphthol from 1-tetralone

A one-step reaction scheme is proposed for prepn. of 2-methyl-1-naphthol from 1-tetralone. The process includes two fixed-bed reactors in line or a single reactor with a double-layered or mixed catalytic bed. The main advantage of the proposed scheme is to avoid the intermediate sepn. and purifn. steps. [on SciFinder (R)