Thermochemistry and Kinetics of the Thermal Degradation of 2-Methoxyethanol as Possible Biofuel Additives

Oxygenated organic compounds derived from biomass (biofuel) are a promising alternative renewable energy resource. Alcohols are widely used as biofuels, but studies on bifunctional alcohols are still limited. This work investigates the unimolecular thermal degradation of 2-methoxyethanol (2ME) using DFT/BMK and ab initio (CBS-QB3 and G3) methods. Enthalpies of the formation of 2ME and its decomposition species have been calculated. Conventional transition state theory has been used to estimate the rate constant of the pyrolysis of 2ME over a temperature range of 298–2000 K. Production of methoxyethene via 1,3-H atom transfer represents the most kinetically favored path in the course of 2ME pyrolysis at room temperature and requires less energy than the weakest C α − C β simple bond fission. Thermodynamically, the most preferred channel is methane and glycoladhyde formation. A ninefold frequency factor gives a superiority of the C α − C β bond breaking over the C γ − O β bond fission despite comparable activation energies of these two processes. © 2019, The Author(s).Scopu

Computational Studies on the Thermodynamic and Kinetic Parameters of Oxidation of 2-Methoxyethanol Biofuel via H-Atom Abstraction by Methyl Radical

In this work, a theoretical investigation of thermochemistry and kinetics of the oxidation of bifunctional 2-Methoxyethanol (2ME) biofuel using methyl radical was introduced. Potential-energy surface for various channels for the oxidation of 2ME was studied at density function theory (M06-2X) and ab initio CBS-QB3 levels of theory. H-atom abstraction reactions, which are essential processes occurring in the initial stages of the combustion or oxidation of organic compounds, from different sites of 2ME were examined. A similar study was conducted for the isoelectronic n-butanol to highlight the consequences of replacing the ϒ CH2 group by an oxygen atom on the thermodynamic and kinetic parameters of the oxidation processes. Rate coefficients were calculated from the transition state theory. Our calculations show that energy barriers for n-butanol oxidation increase in the order of α ‹ O ‹ ϒ ‹ β ‹ ξ, which are consistent with previous data. However, for 2ME the energy barriers increase in the order α ‹ β ‹ ξ ‹ O. At elevated temperatures, a slightly high total abstraction rate is observed for the bifunctional 2ME (4 abstraction positions) over n-butanol (5 abstraction positions). © 2019, The Author(s).Scopu

AEO7 Surfactant as an Eco-Friendly Corrosion Inhibitor for Carbon Steel in HCl solution

The impact of AEO7 surfactant on the corrosion inhibition of carbon steel (C-steel) in 0.5 M HCl solution at temperatures between 20 °C and 50 °C was elucidated using weight loss and different electrochemical techniques. The kinetics and thermodynamic parameters of the corrosion and inhibition processes were reported. The corrosion inhibition efficiency (IE%) improved as the concentration of AEO7 increased. In addition, a synergistic effect was observed when a concentration of 1 × 10 −3 mol L −1 or higher of potassium iodide (KI) was added to 40 µmol L −1 of the AEO7 inhibitor where the corrosion IE% increased from 87.4% to 99.2%. Also, it was found that the adsorption of AEO7 surfactant on C-steel surface followed the Freundlich isotherm. Furthermore, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements indicated that AEO7 was physically adsorbed on the steel surface. The surface topography was examined using an optical profilometer, an atomic force microscope (AFM), and a scanning electron-microscope (SEM) coupled with an energy dispersion X-ray (EDX) unit. Quantum chemical calculations based on the density functional theory were performed to understand the relationship between the corrosion IE% and the molecular structure of the AEO7 molecule. © 2019, The Author(s).This publication was supported by Qatar University Internal Grant N° GCC-2017-012. The findings achieved herein are solely the responsibility of the authors. The authors gratefully thank the Center for Advanced Materials at Qatar University and the Chemistry Department at Cairo University for their support. The permanent address of Dr. Mohamed F. Shibl is Chemistry Department, Faculty of Science, Cairo University, Giza 12613, Egypt.Scopu

Distribution of serotypes and antibiotic resistance of invasive pneumococcal disease isolates among children aged 5 years and under in Saudi Arabia (2000–2004)

ABSTRACTTo determine vaccine coverage of invasive pneumococcal disease (IPD) in Saudi Arabian children aged 5 years and under, 350 IPD isolates were tested for antibiotic susceptibility. Of these 46%, 42% and 12% were penicillin-sensitive, pencillin-intermediate, and penicillin-resistant, respectively. Rates of resistance to erythromycin and cefotaxime were 26% and 6%, respectively. The potential serotype coverage of the PCV7 vaccine in Saudi Arabia among children <5 years of age is 62%, and vaccine coverage significantly improved in children <2 years of age, to reach 83% against IPD isolates. PCV7 is expected to have a substantial impact on the burden of invasive and antibiotic-resistant pneumococcal disease in Saudi Arabia

First-principle studies on the gas phase OH-initiated oxidation of O-toluidine

In the present work, the gas phase reaction of OH radical initiated O-toluidine (OTOD) oxidation is investigated at ROCBS-QB3. Different pathways for OH radical additions to the benzene ring sites and H-atom abstractions are explored in details. At 200 K, the oxidation mechanism of OTOD is thoroughly dominated by the OH-addition to the aromatic ring, whereas the main favorable route is the OH addition to C2 atom with a branching ratio of 52.76%. Raising temperature to 1000 K, the total abstraction of amine's hydrogens becomes the main oxidation pathway for OTOD with contributions of 29.29%. The atmospheric lifetimes of aniline and OTOD are calculated to be 20.74 and 11.23 min., respectively. The fate of OTOD-OH2 (P2) adduct with atmospheric O2 molecule is inspected using the unimolecular Rice-Ramsperger-Kassel-Marcus (RRKM-ME) to verify our results at transition state theory (TST) and shows pressure and temperature dependence of the secondary oxidation mechanism. - 2019 Elsevier B.V.Scopu