Hydrogenation of Epoxides to Anti-Markovnikov Alcohols over a Nickel Heterogenous Catalyst Prepared from Biomass (Rice) Waste

The synthesis of primary alcohols (from olefins) is an important and challenging transformation, as most of the current methods suffer from regioselectivity issues. This work describes the utilization of rice husk (RH) from agricultural waste as support for the preparation of a catalyst for the conversion of olefin oxides to primary alcohols. The catalyst was synthesized by pyrolysis of RH impregnated with nickel, and characterized by IR, AAS, XRD, BET, XPS, TEM, and TPD technics. The catalyst shows excellent activity and selectivity towards anti-Markovnikov alcohols, acting simultaneously as Brønsted acid, solid Lewis acid, and as hydrogenation catalyst. A substrate screening was done, the catalyst's recycling stability was assessed, and a plausibly reaction mechanism was proposed.     

Derivation of a double integral via convolution of Student t-densities

The Ramanujan Journal - In this paper, we establish a quicker approximation with continued fraction and some inequalities for the gamma function based on Windschitl’s formula. We also give...     

Plastic membrane electrodes for amprolium

The construction and general performance characteristics of two PVC membrane sensors responsive to the amprolium (AmpH²⁺) cation are described. These sensors are based on the ion-associates amprolium-tetraphenylborate (AmpH-TPB) and amprolium-reineckate (AmpH-Rk). The electrodes exhibit near-Nernstian response for the doubly charged amprolium cation over the concentration ranges 0.1–100 and 0.01–100 mM for AmpH-TPB and AmpH-Rk, respectively. The pH does not affect electrode performance within the range 7.0–11.0. No interferences are caused by many inorganic cations, sugars and amino acids. The isothermal coefficients are found to be 0.0001306 and 0.0010438 V/ °C for AmpH-TPB and AmpH-Rk, respectively. Potentiometric titration and standard addition methods were used to determine amprolium in pure solutions and in veterinary soluble powder, with high accuracy and precision.     

Adsorption of Mercury(II) on Amidoxime Chelating Resins with Magnetic Properties

Two amidoxime chelating resins were prepared. The preparation process was carried out through copolymerization of acrylonitrile with N,N′-methylene-bis-acrylamide (MBA) as a crosslinker in the presence and absence of magnetite (Fe₃O₄) particles. The resins obtained were subsequently treated with hydroxylamine to give the corresponding amidoxime chelating resins. The uptake behavior of the resins toward Hg(II) in aqueous solutions using batch and column techniques was studied. The oxide containing resin gave higher uptake capacities relative to oxide free resin confirming the advantage of embedded particles on the uptake capacity. Thermodynamic and kinetic parameters of the uptake process were calculated. Regeneration of the resins was carried out using 0.5 M KI and the desorption ratio was found to be more than 97%.     

Extraction-spectrophotometric determination of amprolium hydrochloride using bromocresol green, bromophenol blue and bromothymol blue

A new procedure for the determination of amprolium hydrochloride by reaction with bromocresol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB) has been developed. The method consists of extracting the yellow ion-pair formed into chloroform from aqueous medium. The ion-pairs have absorption maxima at 420, 410 and 415 nm with molar absorptivities of 3.64 × 10⁴, 3.12 × 10⁴ and 2.31 × 10⁴1 mol^–1 cm^–1 for BCG, BPB and BTB, respectively. The method obeys Beer's law over the concentration ranges 0.6–12.0, 0.12–8.8 and 1.2–11.3 ag/ml amprolium hydrochloride for BCG, BPB and BTB, respectively. The method is simple, precise (relative standard deviation 0.665–2.210%), accurate (recovery 97.8–100.8%) and easily applied for pharmaceutical quality assurance for amprolium hydrochloride in raw materials and in formulated veterinary soluble powder.     

An online identification algorithm of unknown time-varying delay and internal multimodel control for discrete non-linear systems

In this paper, an online algorithm is proposed for the identification of unknown time-varying input delay in the case of discrete non-linear systems described by decoupled multimodel. This method relies on the minimization of a performance index based on the error between the real system and the partial internal models outputs. In addition, a decoupled internal multimodel control is proposed for the compensation of discrete non-linear systems with time-varying delay. This control scheme incorporates partial internal model controls. Each partial controller is associated to a specified operating zone of the non-linear system. The switching between these controllers is ensured by a supervisor that contains a set of local predictors. A simulation example is carried out to illustrate the significance of the proposed time-varying delay identification algorithm and the proposed internal multimodel control scheme.     

Albedo for an inhomogeneous half space

The Albedo is calculated for an inhomogeneous half-space by assuming that the single scattering albedo behaves like c(z) = c_oe^-(z/s). The modified Eddington method is used to obtain the outgoing flux and hence the albedo. Numerical calculations and comparisons with Pomraning et al. and with an improved version of the F_N- method indicate that the approach is reasonably accurate.     

A State-of-the-Art Heterogeneous Catalyst for Efficient and General Nitrile Hydrogenation

Cobalt-doped hybrid materials consisting of metal oxides and carbon derived from chitin were prepared, characterized and tested for industrially relevant nitrile hydrogenations. The optimal catalyst supported onto MgO showed, after pyrolysis at 700 °C, magnesium oxide nanocubes decorated with carbon-enveloped Co nanoparticles. This special structure allows for the selective hydrogenation of diverse and demanding nitriles to the corresponding primary amines under mild conditions (e.g. 70 °C, 20 bar H₂). The advantage of this novel catalytic material is showcased for industrially important substrates, including adipodinitrile, picolinonitrile, and fatty acid nitriles. Notably, the developed system outperformed all other tested commercial catalysts, for example, Raney Nickel and even noble-metal-based systems in these transformations.     

Selective separation of Th(IV) from its solutions using amine modified silica gel produced from leached zircon

A solution of sodium silicate produced as a waste from the alkali fusion of Egyptian Rosetta zircon mineral was used for preparation of a silica gel in the pH range 6–7. A silica gel modified with tetraethylenepentamine (TEP) and diethylenetriamine (DET) functionalities were prepared. The success of immobilization process was confirmed by means of FT-IR, energy dispersive X-ray spectrometric analysis (EDX) and elemental analysis. The surface properties of the modified silica obtained were investigated by means of nitrogen surface area. The uptake behaviour of the modified silica towards Th(IV) ions at different experimental conditions of pH, time, concentration and temperature using batch method was studied. Kinetics and thermodynamics studies showed an endothermic pseudo-second order adsorption process. Regeneration of the loaded silica was performed using 1 M HNO₃. The investigated silicas have successfully been applied for separating of Th(IV) from U(VI) in nitric acid solution obtained from alkaline leaching of Egyptian monazite sand.