Dégradation photocatalytique des ions ammonium en présence de TiO2 dopé

A new process is proposed for the treatment of the nitrogenous compounds (NH₄⁺, NO₂^–et NO₃^–) in water, based upon the coupling of two catalytic reactions: the hydrogenation of NO₃^– and NO₂^– and the photooxidation of NH₄⁺. The present work is aimed at the study of the photooxidation part of the process. The effect of metals upon the activity and selectivity of TiO₂-based photocatalysts is investigated. The effect of pH, amount of TiO₂, temperature and concentration of ammonium and hydroxide ions on the photocatalytic activity and selectivity have been measured.     

Kinetics and Mechanism of the Pudovik Reaction

Abstract

The kinetics and the mechanism of the Pudovik reaction for the series of α, β-unsaturated carbonyl compounds have been studied. The factors which determine the addition locoselectivity and the reactivity of the hydrophosphoryl and unsaturated compounds in this process are established. The qualitative and quantitative relationships obtained allow to predict the reaction rate and its direction depending on the reagents structure and also on the nature of catalyst and solvent used.     

A witness for coherent electronic vs vibronic-only oscillations in ultrafast spectroscopy

We report a conceptually straightforward witness that distinguishes coherent electronic oscillations from their vibronic-only counterparts in nonlinear optical spectra of molecular aggregates. Coherent oscillations as a function of waiting time in broadband pump/broadband probe spectra correspond to coherent electronic oscillations in the singly excited manifold. Oscillations in individual peaks of 2D electronic spectra do not necessarily yield this conclusion. Our witness is simpler to implement than quantum process tomography and potentially resolves a long-standing controversy on the character of oscillations in ultrafast spectra of photosynthetic light harvesting systems.     

Synthesis,Characterization, and Structures of Palladium(II) and Platinum(II) Complexes Containing N,N‐Bis(diphenylphos­phanyl)Naphthylamine

The reaction of 1‐naphthylamine with two equivalents of chlorodiphenylphosphine in the presence of triethylamine gave the ligand C₁₀H₇‐1‐N(PPh₂)₂ ( 1 ). Reaction of 1 with PdCl₂(CH₃CN)₂ or PtCl₂(cod) (1:1 molar ratio) afforded the complexes cis‐[PdCl₂{C₁₀H₇‐1‐N(PPh₂)₂}] ( 2 ) and cis‐[PtCl₂{C₁₀H₇‐1‐N(PPh₂)₂}] ( 3 ), respectively. Compounds 1 – 3 were identified and characterized by multinuclear NMR (¹H, ¹³C, ³¹P NMR) and IR spectroscopy. Crystal structure determinations of complexes 2 and 3 were carried out.     

Influence of selected biowaste materials pre-treatment on their anaerobic digestion

The topic of this study is the pre-treatment of substrates for anaerobic digestion. Two different substrates of algae Scenedesmus subspicatus (SAG 86.81), Chlorella kessleri (LARG/1) and foliage of Prunus serrulata were subjected to anaerobic digestion. A mixture of commercially available cellulolytic enzymes (Analytical science s.r.o., Modra, Slovakia) was used for anaerobic treatment of algae while the foliage of Prunus serrulata was pre-treated by lignolytic fungi. The highest production of methane per mass of volatile solids was reached with untreated Chlorella kessleri at (0.59 ± 0.04) L g⁻¹. The addition of cellulolytic enzymes did not increase the production of methane from the algal substrate; however, a faster substrate degradation and thus also higher speed of methane production at the beginning of cultivation was achieved. After foliage pre-treatment by fungal isolate Pleurotus pulmonarius, isolated from natural habitats, the methane production increased five times. In this way we were able to speed up the processes of biological degradation of ligno-cellulose materials and thereby to increase the production of methane. Our results show the possibility of using algae as a suitable substrate for biogas production. On the other hand, also aerobic pre-treatment of foliage (Pleurotus pulmonarius) presents a successful way for speeding up the degradation of ligno-cellulose waste leading to increased methane yields.     

Reverse shape selectivity in the liquid-phase adsorption of xylene isomers in zirconium terephthalate MOF UiO-66

Powder, agglomerates, and tablets of the microporous zirconium(IV) terephthalate metal-organic framework UiO-66 were evaluated for the selective adsorption and separation of xylene isomers in the liquid phase using n-heptane as the eluent. Pulse experiments, performed at 313 K in the presence of n-heptane, revealed the o-xylene preference of this material, which was further confirmed by binary and multicomponent breakthrough experiments in the presence of m- and p-xylene, resulting in selectivities at 313 K of 1.8 and 2.4 with regards to m-xylene and p-xylene, respectively. Additionally, because p-xylene is the less retained isomer, UiO-66 presents a selectivity pattern that is reverse of that of the xylenes' molecular dimension with respect to shape selectivity. The shaping of the material as tablets did not significantly change its selectivity toward the o-xylene isomer or toward p-xylene, which was the less retained isomer, despite a loss in capacity. Finally, the selectivity behavior of UiO-66 in the liquid n-heptane phase makes it a suitable material for o-xylene separation in the extract (heavy product) or p-xylene separation in the raffinate (light product) by simulated moving bed technology.     

Preparation of Stable Low‐Oxidation‐State Group 14 Element Amidohydrides and Hydride‐Mediated Ring‐Expansion Chemistry of N‐Heterocyclic Carbenes

Various low oxidation state (+2) group 14 element amidohydride adducts, IPr ? EH(BH₃)NHDipp (E=Si or Ge; IPr=[(HCNDipp)₂C:], Dipp=2,6‐iPr₂C₆H₃), were synthesized. Thermolysis of the reported adducts was investigated as a potential route to Si‐ and Ge‐based clusters; however, unexpected transmetallation chemistry occurred to yield the carbene–borane adduct, IPr ? BH₂NHDipp. When a solution of IPr ? BH₂NHDipp in toluene was heated to 100 °C, a rare C? N bond‐activation/ring‐expansion reaction involving the bound N‐heterocyclic carbene donor (IPr) transpired.     

Chemical Adaptability: The Integration of Different Kinds of Matter into Giant Molecular Metal Oxides

Unique properties of the two giant wheel‐shaped molybdenum‐oxides of the type {Mo₁₅₄}≡[{Mo₂}{Mo₈}{Mo₁}]₁₄ ( 1 ) and {Mo₁₇₆}≡[{Mo₂}{Mo₈}{Mo₁}]₁₆ ( 2 ) that have the same building blocks either 14 or 16 times, respectively, are considered and show a “chemical adaptability” as a new phenomenon regarding the integration of a large number of appropriate cations and anions, for example, in form of the large “salt‐like” {M(SO₄)}₁₆ rings (M=K⁺, NH₄⁺), while the two resulting {Mo₁₄₆ (K(SO₄))₁₆} ( 3 ) and {Mo₁₄₆ (NH₄(SO₄))₁₆} ( 4 ) type hybrid compounds have the same shape as the parent ring structures. The chemical adaptability, which also allows the integration of anions and cations even at the same positions in the {Mo₄O₆}‐type units of 1 and 2 , is caused by easy changes in constitution by reorganisation and simultaneous release of (some) building blocks (one example: two opposite orientations of the same functional groups, that is, of H₂O{Mo?O} ( I ) and O?{Mo(H₂O)} ( II ) are possible). Whereas Cu²⁺ in [(H₄Cu^II₅)Mo^V₂₈Mo^VI₁₁₄O₄₃₂(H₂O)₅₈]^26? ( 5 a ) is simply coordinated to two parent O^2? ions of {Mo₄O₆} and to two fragments of type II , the SO₄^2? integration in 3 and 4 occurs through the substitution of two oxo ligands of {Mo₄O₆} as well as two H₂O ligands of fragment I . Complexes 3 and now 4 were characterised by different physical methods, for example, solutions of 4 in DMSO with sophisticated NMR spectroscopy (EXSY, DOSY and HSQC). The NH₄⁺ ions integrated in the cluster anion of 4 “communicate” with those in solution in the sense that the related H⁺ ion exchange is in equilibrium. The important message: the reported “chemical adaptability” has its formal counterpart in solutions of “molybdates”, which can form unique dynamic libraries containing constituents/building blocks that may form and break reversibly and can lead to the isolation of a variety of giant clusters with unusual properties.     

High Temperature Thermal Gradient Interaction Chromatography (HT-TGIC) for Microstructure Analysis of Polyolefins

Summary: High temperature thermal gradient interaction chromatography (HT-TGIC) is a newly developed technique to analyze comonomer distributions in polyolefins. This paper documents the key differences between crystallization elution fractionation (CEF) and HT-TGIC, and the advantages of using multiple detectors in HT-TGIC to provide comprehensive microstructure characterization. A demonstration of the technique using a specifically designed blend, provides comprehensive data in less than 1.5 hours of analysis time by HT-TGIC. This paper also reports that HT-TGIC has excellent short term repeatability.     

Influence of turbulent flow on the deflagration-to-detonation transition in hydrogen-oxygen-air mixtures in a pulse combustor

The effect of turbulization of a hydrogen-oxygen-air mixture flow on the deflagration-to-detonation transition in a pulse combustor (PC) is studied. The parameters of operation of the PC with flame front propagation in a quiescent and strongly turbulized mixtures (Re ? 10⁴) are compared. It is shown that, in case of a quiescent mixture no detonation occurs because of a small length of the PC. The presence of intense pulsations (Re > 2 · 10⁴) created by elements of special configuration in the mixing chamber promotes the formation of a detonation wave, the velocity of which depends on the fuel-to-oxidizer equivalence ratio.