Cr2O3-Al2O3 mixed oxide material: synthesis, structure and catalytic behavior for C-H activation

This work reports the synthesis of Cr2O3-Al2O3 mixed oxide material via the sol-gel process. The characterization techniques used are X-ray diffraction, Nitrogen adsorption, scanning Electron Microscopy, UV-visible and FT-IR spectroscopy. The results show the presence of the boehmite phase and it cannot be possible to identify crystalline phase of Cr2O3. The surface BET of Cr2O3-Al2O3 is about 130.5 m2/g. The catalytic behavior of the mesoporous material is evaluated for the liquid- phase oxidation of cyclohexane with hydrogen peroxide as oxidant.  Cr2O3-Al2O3 was shown to be mild and efficient catalyst. The use of acetone as solvent presented an approximate 12.4% conversion with 89.66 % selectivity into cyclohexanol

Catalytic Properties of Alumina-Supported Ruthenium, Platinum, and Cobalt Nanoparticles towards the Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone

A series of metal-loaded (Ru, Pt, Co) alumina catalysts were evaluated for the catalytic oxidation of cyclohexane using tertbutylhydroperoxide (TBHP) as oxidant and acetonitrile or acetic acid as solvent. These materials were prepared by the impregnation method and then characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), H2 chemisorption, Fourier Transformed Infrared Spectroscopy (FTIR), High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray Diffraction (XRD). All the prepared materials acted as efficient catalysts. Among them, Ru/Al2O3 was found to have the best catalytic activity with enhanced cyclohexane conversion of 36 %, selectivity to cyclohexanol and cyclohexanone of 96 % (57.6 mmol), and cyclohexane turnover frequency (TOF) of 288 h-1. Copyright © 2018 BCREC Group. All rights reservedReceived: 26th May 2017; Revised: 17th July 2017; Accepted: 18th July 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018How to Cite: Rekkab-Hammoumraoui, I., Choukchou-Braham, A. (2018). Catalytic Properties of Alumina-Supported Ruthenium, Platinum, and Cobalt Nanoparticles towards the Oxidation of Cyclohexane to Cyclohexanol and Cyclohexanone. Bulletin of Chemical Reaction Engineering & Catalysis, 13(1): 24-36 (doi:10.9767/bcrec.13.1.1226.24-35)

Corrosion Inhibition, Adsorption and Thermodynamic Properties of Poly (Sodium 4-Styrenesulfonate) on Carbon Steel in Phosphoric Acid Medium

The use of polymers as corrosion inhibitors has attracted much attention due to their low prices, inherent stability, availability and cost-effectiveness. The corrosion inhibiting effect of poly(sodium-4-styrenesulfonate) on carbon steel in phosphoric acid solution has been investigated using weight loss and scanning electron microscopy techniques (SEM) and theoretical calculations based on density functional theory (DFT). In the presence of 1.0×10-3 mol/L of inhibitor, a maximum inhibition effect of 98.06 % was observed. The influence of the concentration of the inhibitor, the temperature of the solution and the immersion time on the corrosion of carbon steel was investigated. Activation parameters such as activation energy (Eact), activation enthalpy (ΔHact), activation entropy (ΔSact), heat of adsorption (Qads) and adsorption free energy (ΔGads) were evaluated based on the effect of temperature on the corrosion and inhibition processes. It was found that the adsorption behaviour of poly(sodium-4-styrenesulfonate) (PSS) follows the Langmuir isotherm and the free energy change values indicate mixed chemical and physical adsorption on the carbon steel surface. The results obtained with the different methods agree well

Enhancing Corrosion Resistance of Carbon Steel in Sulfuric Acid Using β-cyclodextrin as an Inhibitor

The corrosion process leads to substantial economic losses, particularly in the industrial sector, emphasizing the importance of preventive measures. This study aimed to investigate the impact of inhibitor concentration, immersion duration, and temperature on the corrosion of carbon steel in a sulfuric acid environment, assessed through mass loss measurements. Inhibition efficiency displayed a positive correlation with increasing inhibitor concentration, while it declined as temperatures rose. In a 0.5 M sulfuric acid solution, β-cyclodextrin (β-CD) exhibited an inhibition efficiency of 62.26% at a concentration of 1 mM. The addition of potassium iodide (KI) significantly enhanced the inhibition efficiency to 97.98%, indicating a synergistic effect. The study encompassed various calculations, including the determination of activation energy (Ea), activation enthalpy (ΔHa), activation entropy (ΔSa), adsorption-free energy (ΔGads), adsorption enthalpy (ΔHads), and adsorption entropy (ΔSads). The adsorption of the inhibitor onto the carbon steel surface conformed to the Langmuir adsorption isotherm. Additionally, Scanning Electron Microscopy (SEM) investigations provided further verification of β-cyclodextrin's adsorption on the carbon steel surface

Ruthenium-doped Titania-pillared Clay for The Selective Catalytic Oxidation of Cyclohexene: Influence of Ru Loading

A series of ruthenium-based catalysts supported on acid-activated montmorillonite (PILC) and interspersed with titanium (Ru/Ti-PILCs) were prepared with various amounts of ruthenium. Their catalytic performances in the selective oxidation of cyclohexene, using tert-butylhydroperoxide (TBHP) as oxidant were checked. The clay structure modification by acid activation and impregnation of transition metals resulted in an enhanced Lewis and Bronsted acidities. The Ru/Ti-PILCs materials were characterized using X-ray diffraction (XRD), surface area and pore volume measurements, surface acidity followed by Fourier transform infrared (FTIR) spectroscopy, chemical analysis, and Scanning Electron Microscopy (SEM). It was found that all catalysts can selectively oxidize cyclohexene through allylic oxidation leading mainly to 2-cyclohexene-1-one (Enone) as the major product, and 2-cyclohexene-1-ol (Enol) as secondary product. With the 5 %Ru/Ti-PILC, it was possible to reach 59 % cyclohexene total conversion, and 87 % selectivity into 2-cyclohexene-1-one and 13 % selectivity into 2-cyclohexene-1-ol.

Polyvinylpyrrolidone as a Corrosion Inhibitor for Carbon Steel in a Perchloric Acid Solution: Effect of Structural Size

Polymers are materials composed of macromolecules characterized by duplicates of smaller molecules that are covalently bonded together to provide a set of properties. Corrosion inhibition by such compounds is usually attributed to their adsorption on the metal-solution interface. The inhibition effect of different sizes of polyvinylpyrrolidone (PVP) on the corrosion of carbon steel (C-steel) in solutions of perchloric acid was investigated. The inhibition efficiency increases as the size of the inhibitor and its concentration increases, but decreases as the temperature increases and can reach a value of 81.53% and 5.0x10^-3 mol L^-1(PVP: 58,000 g mol^-1) at 30°C. The most remarkable inhibition efficiency was confirmed by the presence of the film formed on the metal surface by scanning electron microscopy. The kinetic and thermodynamic parameters for the corrosion of C-steel and adsorption of the inhibitor were determined and discussed. The combination of PVP with potassium iodide produced a strong synergistic effect on the inhibition of C-steel corrosion leading to a significant improvement in the inhibition efficiency. Quantum chemical parameters were studied using density functional theory to determine the possible relationship between the inhibitor and its electronic properties

Mesoporous Co3O4 as a New Catalyst for Allylic Oxidation of Cyclohexene

Mesoporous cobalt oxide was investigated for the liquid phase oxidation of cyclohexene using tertiobutylhydroperoxide (TBHP) as an oxidant. The results were compared with several series of supported cobalt catalysts to study the influence of the cobalt loading and solvents on the overall conversion and selectivity. Mesoporous cobalt was synthesized through the nanocasting route using siliceous SBA-15 mesoporous material as a hard template and cobalt nitrate as the cobalt oxide precursor. Supported cobalt oxide catalysts (Co/MxOy) were synthesized by the impregnation method using two loadings (1 and 5 wt.%) and Al2O3, TiO2, and ZrO2 as supports. Samples were characterised by means: elemental analysis, X-ray powder Diffraction (XRD), BET (surface area), UV-Vis DR Spectroscopy, and MET. The results obtained showed that the cobalt oxide retains the mesoporous structure of SBA-15, and in all Co/MxOy, crystalline Co3O4 and CoO phases are observed. The mesoporous cobalt oxide is more active than the supported cobalt catalysts in the allylic oxidation of cyclohexene, with a conversion of 78 % of cyclohexene and 43.3 % selectivity toward 2-cyclohexene-1-ol. The highest activity of mesoporous cobalt oxide could be ascribed to its largest surface area. Furthermore, Co3O4 has both Lewis and Brönsted acidic sites whereas Co/MxOy has only Lewis acidic sites, which could also explain its superior catalytic activity. Moreover, mesoporous cobalt oxide was more stable than supported cobalt catalysts. Therefore, this catalyst is promising for allylic oxidation of alkenes.  Copyright © 2019 BCREC Group. All rights reserve

Synthesis and Biological Evaluation of New Chromenes and Chromeno[2,3-d] pyrimidines

A simple and efficient approach has been developed to synthesise novel and functionalised 5H-chromeno[2,3-d] pyrimidines derivatives (4a–h). This  approach entails treating 2-amino-3-cyano-4H-chromenes (3a–h) with formamidine acetate under microwave irradiations and solvent-free conditions. All  structures of new compounds obtained in this study were characterised by IR, MS, 1H and 13C NMR analysis. Additionally, the synthesised compounds  were investigated for their antibacterial and antioxidant potential. Compounds 3b, 3c, 3e, 4c and 4e showed significant activities