Solid-state electrochemical synthesis of ammonia: a review

Ammonia is one of the most produced chemicals worldwide, and it is not only a major end product but also an important energy storage intermediate. The solid-state electrochemical synthesis of ammonia has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion, severe environmental pollution and high energy consumption. Solid-state electrolytes either protonic or oxide ion conductors have been reviewed and particular emphasis is placed on their application to synthesise ammonia. The highest rate of ammonia formation according to the type of electrolyte utilised were in the following order; solid polymers > Ce_0.8Gd_0.2O_2−δ-(Ca₃(PO₄)₂-K₃PO₄) composites > fluorites > perovskites > pyrochlores although the catalysts in electrodes also play an important role. The highest rate reported so far is found to be 1.13 × 10⁻⁸ mol s⁻¹ cm⁻² at 80 °C with a potential of 2 V using Nafion membrane, SmFe_0.7Cu_0.1Ni_0.2O₃ (SFCN), and Ni-Ce_0.8Sm_0.2O_2−δ as solid electrolyte, cathode and anode, respectively. Synthesising ammonia from steam and N₂, by-passing H₂ stage offers many advantages such as reduction of device numbers and then the overall costs. The factors affecting the rate of ammonia formation have been discussed as well.     

Synthesis of new iron–NHC complexes as catalysts for hydrosilylation reactions

A series of new piano‐stool iron(II) complexes comprising N‐heterocyclic carbene ligands [Fe(Cp)(CO)₂(NHC)]I (NHC = 1,3‐disubstituted imidazolidin‐2‐ylidene) have been synthesized and analyzed by ¹H NMR, ¹³C NMR, IR, elemental analysis and mass spectrometric techniques. These compounds were easily prepared from the reaction of disubstituted imidazolidin‐2‐ylidene with [FeI(Cp)(CO)₂] in toluene at room temperature. These complexes were tested in the catalytic hydrosilylation reaction of aldehydes and ketones with phenylsilane in solvent‐free conditions. After a basic hydrolysis step, the corresponding alcohols were obtained in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Electronic Structure and Magnetic Anisotropy of an Unsaturated Cyclopentadienyl Iron(I) Complex with 15 Valence Electrons

The 15 valence-electron iron(I) complex [Cp^ArFe(IiPr₂Me₂)] ( 1 , Cp^Ar=C₅(C₆H₄-4-Et)₅; IiPr₂Me₂=1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene) was synthesized in high yield from the Fe^II precursor [Cp^ArFe(μ-Br)]₂. ⁵⁷Fe Mössbauer and EPR spectroscopic data, magnetic measurements, and ab initio ligand-field calculations indicate an S= 3/2 ground state with a large negative zero-field splitting. As a consequence, 1 features magnetic anisotropy with an effective spin-reversal barrier of U_eff=64 cm⁻¹. Moreover, 1 catalyzes the dehydrogenation of N,N-dimethylamine–borane, affording tetramethyl-1,3-diaza-2,4-diboretane under mild conditions.     

Combination of nitroxide‐mediated polymerization and SET‐LRP for the synthesis of high molar mass branched and star‐branched poly(n‐butyl acrylate) characterized by size exclusion chromatography and rheology

Branched and star‐branched polymers were successfully synthesized by the combination of two successive controlled radical polymerization methods. A series of linear and star poly(n‐butyl acrylate)‐co‐poly(2‐(2‐bromoisobutyryloxy) ethyl acrylate) statistical copolymers, P(nBA‐co‐BIEA)_x, were first synthesized by nitroxide‐mediated polymerization (NMP at T > 100 °C). The subsequent polymerization of n‐butyl acrylate by single electron transfer‐living radical polymerization (SET‐LRP at T = 25 °C), initiated from the brominated sites of the P(nBA‐co‐BIEA)_x copolymer, produced branched or star‐branched poly(n‐butyl acrylate) (PnBA). Both types of polymerizations (NMP and SET‐LRP) exhibited features of a controlled polymerization with linear evolutions of logarithmic conversion versus time and number‐average molar masses versus conversion for final M_n superior to 80,000 g mol^?1. The branched and star‐branched architectures with high molar mass and low number of branches were fully characterized by size exclusion chromatography. The Mark–Houwink Sakurada relationship and the analysis of the contraction factor (g′ = ([η]_branched/[η]_linear)_M) confirmed the elaboration of complex PnBA. The zero‐shear viscosities of the linear, star‐shaped, branched, and star‐branched polymers were compared. The modeling of the rheological properties confirmed the synthesis of the branched architectures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Origin of the Enantioselectivity in Organocatalytic Michael Additions of β‐Ketoamides to α,β‐Unsaturated Carbonyls: A Combined Experimental,Spectroscopic and Theoretical Study

The organocatalytic enantioselective conjugate addition of secondary β‐ketoamides to α,β‐unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto’s thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 % ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.     

Unsteady rheometry: can we characterize weak gels with a controlled stress rheometer?

This paper is concerned with the influence of apparatus inertia effects in controlled stress rheometry. As evidenced on creep experiments, the coexistence of apparatus inertia and viscoelasticity leads to a coupling frequency. For weak gels, this coupling frequency is typically between 1 and 100 Hz. Therefore, frequency sweeps around and above this coupling frequency also corresponds to an effective shear stress sweep evolution due to a non-trivial resonant effect. In other words, frequency sweep experiments are not made at constant shear stress. The detailed modelling and analysis of this inertia effect on a typical weak gel shows a clear and fundamental limitation for its characterization using a controlled stress rheometer. Also, alternative approaches to standard rheometer software analysis are proposed to take this coupling effect into account. This paper was presented at the 3rd Annual Rheology Conference, AERC 2006, April 27-29, 2006, Crete, Greece.     

Two-dimensional motion of a set of particles in a free surface flow with image processing

A method to analyze bed load with image processing was developed. The motion of coarse spherical particles on a mobile bed entrained by a shallow turbulent flow down a steep channel was filmed with a high-speed camera. The water free surface and the particle positions were detected combining classical image processing algorithms. We developed a particle-tracking algorithm to calculate all particle trajectories and motion regimes, rolling or saltation. At constant slope, the contribution of the rolling particles to the solid discharge only slightly differed when the particle supply was increased. At a slope of 10%, it represented about 40%. In contrast, rolling became the major regime when the slope increased, at a slope of 15% it represented up to 80% of the total solid discharge.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.