Catalytic degradation of O‐cresol using H2O2 onto Algerian Clay‐Na

Clay material is used as a catalyst to degrade an organic pollutant,. This study focused on the O‐cresol oxidative degradation in aqueous solution by adding H2O2 and Mont‐Na. The catalytic tests showed a high catalytic activity of Mont‐Na, which made it possible to achieve more than 84.6% conversion after 90 minutes of reaction time at 55 °C in 23.2 mM H2O2. The pH value was found to be negatively correlated with the degradation rate of O‐cresol. UV‐Vis spectrophotometry revealed that the increase of degradation rate at low pH is related to the formation of 2‐Methylbenzoquinone as intermediate product. In addition, the content of iron in Mont‐Na decreased after the catalytic test, bringing further evidence about the O‐cresol catalytic oxidation. The mineralization of O‐cresol is also confirmed by the different methods of characterization of Mont‐Na after the catalytic oxidation test. The effect of the O‐cresol oxidation catalyzed by natural clay is significant.Financial support for this work by the Algerian Directorate General of Scientific Research and Technological Development (DGRSDT) and the Ministry for Higher Education and Scientific Research is gratefully appreciated

The Influence of the Nature of the Support on the Copper–Palladium Catalysed Suzuki–Miyaura-Coupling

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Copper(II)- and palladium(II)-modified molecular sieve, a reusable catalyst for the Suzuki-Miyaura-coupling

International audienceCopper-palladium bimetallic catalysts supported on 4 angstrom molecular sieve were prepared with two step impregnation (TSI) and co-impregnation (CI). These materials were studied to determine the importance of the preparation method, the interaction between the Cu-Pd particles, the activity, selectivity and stability in Suzuki-Miyaura reaction. The key-role of the preparation method in the composition of the metal species on the surface of the support was pointed out with catalyst characterisation methods (ICP, BET, XRD, TEM, EDS and TPR). The relationship between the properties of surface material and the catalytic performance and stability were examined too. The two metals (Cu, Pd) were brought to close interaction on the surface of the support. A correlation between these interactions and improvement of stability were found and proven with surface analysis methods. We found that a Cu-Pd alloy with atom ratio 1:1 is responsible for the catalytic activity. Our catalyst TSI was active and selective during six catalytic cycles in Suzuki coupling, whilst the activity of the catalyst prepared with CI dropped after the sixth use. This loss was due to the absence of Cu-Pd 1:1 alloy and the growth of the particle size

Catalytic activity of metal-doped porous materials in the salicylaldehyde Petasis-Borono Mannich reaction

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Synthèse et caractérisation des oxydes mixtes type MxOy-TiO2 (M = V, Zr et Si) par voie sol-gel (Application à l'époxydation du cyclohexène)

L'objectif de ce travail est : (i) pour préparer des oxydes mixtes X% MxOy-TiO2 (M = V, Zr et Si), (X = 5, 10, 15 et 20 wt-.% MxOy.) par la méthode sol-gel et suivie par une calcination à 500 C, (ii) de caractériser les échantillons préparés par différentes méthodes d'analyse physico-chimique (AAF, ICP, DRX, BET, TG-DTA et FT-IR) et (iii) d'étudier leur réactivité dans l'époxydation de cyclohexène.D'après les résultats des caractérisations, nous constatons que :- L'analyse DRX montre que pour les trois systèmes nous avons l'apparition de la phase anatase de TiO2. La meilleure cristallinité a été observée pour le système en présence de V2O5. La phase de SiO2 est amorphe et la phase de ZrO2 n'a pas été détectée.- L'analyse par adsorption d'azote, donne le classement de ces systèmes selon leurs surfaces spécifiques comme suit :SiO2-TiO2>ZrO2-TiO2>V2O5-TiO2- L'analyse FT-IR de l'adsorption de la pyridine in situ montre que les trois systèmes présentent des sites acides de Lewis, alors que le 15%V2O5-TiO2 présente en plus les sites de Brönsted.Nous avons étudié aussi l'influence de divers paramètres expérimentaux sur la réaction d'époxydation du cyclohexène. Les résultats des tests catalytiques montrent que :- Les meilleurs résultats sont obtenus pour le système V2O5-TiO2.- Les meilleurs solvants sont l'heptane et l'acétonitrile qui donnent une bonne activité catalytique et une bonne sélectivité en époxyde.- La réaction d'époxydation du cyclohexène est une réaction du second ordre.- Le catalyseur 20% V2O5-TiO2 est stable au cours de la réaction catalytique et recyclable.The aim of this work is: (i) to prepare mixed oxides X%MxOy-TiO2 (M = V, Zr and Si), (X = 5, 10, 15 and 20 wt.-% MxOy) by sol-gel method followed by calcination at 500C, (ii) to characterize the prepared samples by different methods of physicochemical analysis (AAF, ICP, XRD, BET, TG-DTA and FT-IR) and (iii) to study their reactivity in the epoxidation of cyclohexene. According to the characterization results, we found that:- The XRD analysis shows that, for the three systems, TiO2 anatase has been evidenced. The best crystallinity was observed for the V2O5-TiO2 system. The TiO2 rutile phase has been obeserved for sample 5% ZrO2-TiO2, while the SiO2 phase is amorphous and ZrO2 phase was not detected.- Analysis by nitrogen adsorption, gave the sorting of these systems according to their specific surface areas as follows: SiO2-TiO2 > ZrO2-TiO2 > TiO2-V2O5- The FTIR analysis of in situ pyridine adsorption showed that all three systems display Lewis acid sites, whereassample 15% V2O5-TiO2 present Bronsted sites too.We studied the effect of different reaction parameters in the oxidation of cyclohexene. The results of the catalytic tests show that:- The best results are obtained for V2O5-TiO2 system.- The best solvents are heptane and acetonitrile which give good catalytic activity and high epoxide selectivity.- The epoxidation reaction of cyclohexene is a second-order reaction.- The catalyst 20%V2O5-TiO2 is stable during the catalytic reaction and suitable for recycling.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

Investigation of platinum species in different three-way catalysts

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Ethylcyclopentane ring opening reaction over PtGe/Al2O3 catalysts prepared by controlled surface reaction

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PROPULSION AND CATALYSIS − HISTORICAL SURVEY, UP-TO-DATE OVERVIEW, AND CURRENT CHALLENGES

International audienceThis review presents a survey on the application of catalysis to propulsion. The first application was developed for the decomposition of concentrated aqueous solutions of hydrogen peroxide before WWII in Germany (He-176 plane, V1 and V2 rocket programs, torpedoes, and submarines). After WWII, the UK Black Knight rocket program associated kerosene with H2O2 and a silver screen catalyst bed. The beginning of the space programs led to the replacement of H2O2 by more stable hydrazine, using Ir/Al2O3 catalysts, for satellites and launchers. In recent years, hydrazine substitutes (called "green propellants") have been proposed to satisfy new environmental concerns, improve performance, and reduce cost. The most studied substitutes are energetic aqueous ionic mixtures containing an ionic oxidizer and a fuel. Commonly studied oxidizers are hydroxylammonium nitrate or ammonium dinitramide. The current challenge is to develop a catalyst that is active at low temperatures and able to sustain the high temperatures of the product gases. Other candidates that have also been proposed include highly concentrated hydrogen peroxide (90−98 wt-%) and nitrous oxide N2O(g). Other applications of catalysis to propulsion are: (1) hybrid engines, which could use a liquid oxidizer that would be able to burn a solid fuel, after catalytic decomposition; (2) hypergolic bipropellants with a soluble catalyst in the fuel; (3) catalytic cracking of endothermic fuel for hypersonic jets or for air breathing pulse detonating engines; (4) catalytic ignition of cryogenic H2−O2 mixtures; or (5) as a catalyst to modify burn rates for solid propulsio