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The use of Liquid Organic Hydrogen Carriers (LOHC) is one of the potential options to store hydrogen. Today, the vast majority of compounds used as LOHC come from the oil industry. Using biosourced LOHC would be a step forward in the development of this CO2-free solution. This article looks at LOHC candidates that can be obtained from biomass. The special case of formic acid and methanol, which do not fall within the definition of LOHC, is also considered. The synthesis of alcohols, polyols, amines, aminoalcohols and N-heterocyclic compounds from biosourced compounds is reviewed. [ABSTRACT FROM AUTHOR]

The so-called dibenzyltoluene (H0-DBT) heat transfer oil contains numerous isomers of dibenzyltoluene as well as (benzyl)benzyltoluene (methyl group on the central vs. the side aromatic ring). As it is used as a liquid organic hydrogen carrier (LOHC), a detailed analysis of its composition is crucial in assessing the kinetic rate of hydrogenation for each constituent and studying the mechanism of H0-DBT hydrogenation. To identify all of the compounds in the oil, an in-depth analysis of the GC–MS spectra was performed. To confirm peak attribution, we synthesized some DBTs and characterized the pure compounds using NMR and Raman spectroscopies. Moreover, a fast-GC analysis was developed to rapidly determine the degree of hydrogenation of the mixture. [ABSTRACT FROM AUTHOR]

The application of open cell foams as catalytic supports has been developed in recent years due to their interesting features: large specific surface area (>300 m2 m−3), high void fractions (>0.9) and enhanced internal mass transport. Catalytic foams are highly appealing for the development of structured reactors, especially for multiphase systems. In this paper, catalytic packing material with potential application in structured reactors was developed. Aluminum foams with different macropore sizes were chosen as support for a TiO2−WOx catalyst. The main features, geometric and structural, of the foams were established. At optimized conditions a maximum catalyst loading of 234 kgcatalyst m−3support was obtained, while maintaining significant void fraction (>0.8). The structured catalyst was successfully implemented in batch reactor for a model reaction, esterification of glycolic acid with ethanol. It was shown that the catalyst does not lose performance during the coating steps and remains active for at least 3 catalytic runs, i. e. 18 h. [ABSTRACT FROM AUTHOR]

We describe here a simple protocol yielding small (<2 nm) crystalline Pd2Sn nanoparticles (NPs) along with Pd homologues for sake of comparison. These NPs were obtained via an organometallic approach using Pd2(dba)3·dba (dba = dibenzylideneacetone) in THF with 2 equivalents of tributyltin hydride under 4 bars of H2 at room temperature. The Pd NP homologues were prepared similarly, using Pd2(dba)3·dba with 2 equivalents of n-octylsilane. These NPs were found to be crystalline and very small with a similar mean size (ca. 1.5 nm). These NPs were finally used as nanocatalysts in solution for a benchmark Suzuki–Miyaura cross-coupling reaction. The Pd2Sn NPs were found to be more active than Pd NPs analogues, exhibiting remarkable performances with Pd loading as low as 13 ppb. This result demonstrates a beneficial effect of tin on palladium in catalysis. [ABSTRACT FROM AUTHOR]

Four catalysts—1%Pd-2%Mn/ γ -Al2O3, 1%Pd/ γ -Al2O3, 2%Mn/ γ -Al2O3 and γ -Al2O3—were synthesized via a sol–gel method and characterized using various techniques to evaluate their physicochemical, textural, surface and acidic properties. They were used in the catalytic transformation of ozone and nitrogen oxides using in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis. Different consecutive gas sequences were followed to unravel the poisoning role of nitrogen oxides and the possible reactivation by ozone. It has been proven that on palladium and manganese-based catalysts, the inhibition effect of nitrogen oxides was due to the formation of monodentate nitrites, monodentate, bidentate and bridged nitrates, which are difficult to desorb and decompose into gaseous NOx, either by oxidation or by thermal treatment. Interestingly, monodentate nitrites could be eliminated if the catalyst went through a co-adsorption of NOx and ozone prior to exposure in clean ozone flow. This transformation could be the reason why the catalytic conversion of ozone could return to its original value before the poison effect of nitrogen oxides. [ABSTRACT FROM AUTHOR]

This work describes the synthesis of very small non‐crystalline and non‐metallic iron‐based nanoparticles in solution from easily accessible commercial products in mild conditions. These colloidal suspensions were further used to generate well‐defined solids containing metallic iron or iron oxide NPs. While classical magnetic and crystalline Fe nanoparticles are inactive in alkene hydrosilylation, such original NPs were active in 1‐octene hydrosilylation with 1,1,1,2,3,3,3‐heptamethyltrisiloxane (MD'M) showing that the non‐crystallinity and the organometallic character of the starting Fe NPs are an asset to generate a specific catalytic activity. [ABSTRACT FROM AUTHOR]

The homogeneous vs heterogeneous contributions when using solid catalysts for the Suzuki-Miyaura coupling is still disputed. Leaching is often observed and quantified albeit with unclear conclusions about contributions of the leached species and of the solid catalyst to the global catalytic activity. In this work, a new flow reactor design to discriminate both contributions is proposed. With the help of a simple reactor model, it has been possible to conclude that the coupling of 4-iodoacetophenone with phenylboronic acid proceeded with the leached homogeneous species only, whatever the solid Pd/silica used, whereas chloro-derivatives behaves differently. This reactor is simple to build and could be of general use to reveal actual heterogeneous vs homogeneous catalysis for many reactions. [ABSTRACT FROM AUTHOR]

The deposition of TiO2-P25 on Pyrex glass is studied in order to propose a procedure for obtaining uniform and adherent thin films with a controlled thickness in the range between fractions of micrometer to a few tens of micrometers. Different deposition methods such as spray-coating, dip-coating, and drop-coating of liquid suspensions of TiO2-P25 powder are considered. The effects of pretreatment of the glass support, as well as postdeposition steps such as drying condition and thermal treatment, are also reported. A basic glass pretreatment and an acidic TiO2suspension are chosen for an optimized adherence of the film. Drop-coating, associated with a slow drying under 55% relative humidity and a high-temperature thermal treatment is the method of choice to prepare coated glass slides in a large range of film thicknesses. [ABSTRACT FROM PUBLISHER]

Bromination of (R)-2,2'-(diphenylphospnino)-1,1'-binaphthyl (BINAP) in [Hmim]PF6 ionic liquid was performed with N-halosuccinimides at 110°C during 12 h, affording the 4,4'-dibromoBINAP in high yield. The ionic liquid was recycled four times without modification of selectivity or efficiency. [ABSTRACT FROM AUTHOR]

Graphical Abstract Section [ABSTRACT FROM AUTHOR]

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This article presents an experimental kinetic study of the Suzuki–Miyaura reaction of 4-iodoacetophenone with phenylboronic acid catalyzed by the Herrmann–Beller palladacycle. This catalyst, together with the solvent (ethanol) and the base (sodium methylate), were chosen to ensure catalyst stability and reactants solubility all along the reaction. Based on the study of initial reaction rates, a quasi-first-order was found for 4-iodoacetophenone with a first-order dependence on the initial concentration of palladium. A zero-order was found for the base and the phenylboronic acid. The oxidative addition step of the mechanism was thus considered as the rate determining step. A global rate law was derived and validated quantitatively. A global activation energy, with an average value of ca. 63 kJ/mol was determined. [ABSTRACT FROM AUTHOR]

A kinetic study concerning the self-metathesis of methyl oleate and methyl elaidate was performed, using a variety of NHC-ruthenium pre-catalysts, bearing either mesityl groups or di-isopropyl-phenyl groups on the NHC ligand and various trans ligands with respect to the NHC unit. We showed that the system can be satisfactorily described using one initiation constant per pre-catalyst and four propagation constants that, conversely, do not depend on the pre-catalyst. The difference of reactivity with oleate (Z) and elaidate (E) can be fully explained by the propagation parameters; the studied pre-catalysts initiate with the same rate starting from the Z or the E olefin. The ranking of the propagation parameters is driven by the thermodynamic equilibrium. The transformation rates of Z and E isomers is only driven by these propagation constants and nothing differentiates the initiation step. [ABSTRACT FROM AUTHOR]

A critical review of conclusions about the putative heterogeneous mechanism in the Suzuki-Miyaura coupling by supported Pd solids is reported. In the first section, the turnover frequencies (TOF) of 20 well-established homogeneous catalysts are shown to be in the range 200 to 1,000,000,000 h − 1 . The evidences used to prove a heterogeneous mechanism are discussed and another interpretation is proposed, hypothesizing that only the leached species are responsible for the catalytic reaction, even at ppb levels. Considering more than 40 published catalytic systems for which liquid phase Pd content have been reported, activities have been computed based on leached Pd concentrations and are shown to be in the range TOF 150 to 70,000,000 h − 1 . Such values are compatible with those found for the well-established homogeneous catalysts which questions the validity of the conclusions raised by many papers about the heterogeneous (solid) nature of Suzuki-Miyaura catalysis. Last, a tentative methodology is proposed which involves the rational use of well-known tests (hot-filtration test, mercury test...) to help to discriminate between homogeneous and heterogeneous mechanisms. [ABSTRACT FROM AUTHOR]

Developing new stirred gas–liquid–solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas–liquid (GL) and liquid–solid (LS) mass transfer rates in this reactor were compared to a stirred reactor with basket filled with beads. Batch absorption of hydrogen and measurement of α -methylstyrene hydrogenation rate on P d / A l 2 O 3 catalyst were used to evaluate k G L a G L coefficients and k L S coefficients, respectively. With similar LS transfer rates to the basket-reactor and much higher GL transfer rates, the new reactor reveals a very promising tool for intrinsic kinetics investigations. [ABSTRACT FROM AUTHOR]