A Kinetic Insight into the Activation of n-Octane with Alkaline-Earth Metal Hydroxyapatites

Alkaline-earth metal hydroxyapatites are prepared by the co-precipitation method and characterized using XRD, ICP,NH3-TPD, SEM-EDX, TEM and N2 physisorption analysis. The metal present in the hydroxyapatite influences the acidity of the catalyst. Oxidative dehydrogenation reactions carried out in a continuous flow fixed bed reactor showed that the selectivity towards desired products was dependent on the alkaline-earth metal in the hydroxyapatite. All hydroxyapatite catalysts showed high selectivity towards carbon oxides, followed by cracked products, octenes and aromatics. The highest selectivity and turnover numbers towards C8 products and a high specific rate was shown by Sr-HAp. The activation of n-octane over these catalysts followed the Eley-Rideal mechanism.KEYWORDS Hydroxyapatite, acidity, chemisorption, n-octane, octenes, aromatics, oxidative dehydrogenation

Kinetics and Mechanism of the Oxidation of Coomassie Brilliant Blue-R Dye by Hypochlorite and Role of Acid Therein

The kinetics of the oxidation of a triphenylmethane dye, Brilliant Blue-R (BB–Na+), in aqueous solution by hypochlorite as a function of pH was investigated. While the degradation of dye obeyed pseudo-first-order kinetics, the oxidation of the dye occurred through two competitive reactions facilitated by [OCl–] and [HOCl]. Both reactions exhibited first-order dependence on [OCl–] and [HOCl], respectively, but the hypochlorous acid initiated reaction was about ten times faster. The relative importance of the two paths rested on the pH-dependent concentrations of hypochlorite and hypochlorous acid. The overall second-order rate constants for the OCl– and HOCl initiated reactions are 1.2±0.2M–1 s–1 and 22.2±1.2M–1 s–1, respectively. The reaction energy parameters were determined as Ea=35.5 kJ mol–1,ΔHt=33.1 kJ mol–1 and ΔSt=–191.9 JK–1 mol–1 for the OCl– driven oxidation; and Ea= 26.8 kJ mol–1, ΔHt=29.3 kJ mol–1 and ΔSt=–204.6 JK–1 mol–1 for the HOCl facilitated reaction. The governing rate law and probable reaction mechanism were elucidated and validated by simulation. The three main oxidation products were 4-(4-ethoxyphenylamino)benzoic acid, 3-[(ethyl-hydroxyamino)methyl]benzene sulfonic acid and 6’-chloro-5’-hydroxybicyclohexylidene-2,5,2’-triene-4,4’-dione.KEYWORDS Brilliant Blue-R, oxidative degradation, hypochlorite, hypochlorous acid, kinetics, simulations.PDF and Supp files attache

Advances on Emerging Materials for Flexible Supercapacitors: Current Trends and Beyond

The progressive size reduction of electronic components is experiencing bottlenecks in shrinking charge storage devices like batteries and supercapacitors, limiting their development into wearable and flexible zero-pollution technologies. The inherent long cycle life, rapid charge–discharge patterns, and power density of supercapacitors rank them superior over other energy storage devices. In the modern market of zero-pollution energy devices, currently the lightweight formula and shape adaptability are trending to meet the current requirement of wearables. Carbon nanomaterials have the potential to meet this demand, as they are the core of active electrode materials for supercapacitors and texturally tailored to demonstrate flexible and stretchable properties. With this perspective, the latest progress in novel materials from conventional carbons to recently developed and emerging nanomaterials toward lightweight stretchable active compounds for flexi-wearable supercapacitors is presented. In addition, the limitations and challenges in realizing wearable energy storage systems and integrating the future of nanomaterials for efficient wearable technology are provided. Moreover, future perspectives on economically viable materials for wearables are also discussed, which could motivate researchers to pursue fabrication of cheap and efficient flexible nanomaterials for energy storage and pave the way for enabling a wide-range of material-based applications