Modeling of Breakthrough Curves for Adsorption of Propane, <Emphasis Type="Italic">n</Emphasis>-Butane,and Iso-Butane Mixture on 5A Molecular Sieve Zeolite

Breakthrough curves for the adsorption of propane, n-butane, and iso-butane mixture on 5A molecular sieve zeolite were obtained experimentally and theoretically at a constant temperature of 301 K. The equilibrium model and linear driving force model were used to predict the experimental breakthrough curves for this multicomponent mixture. The equilibrium model gave a satisfactory fit for experimental data. The model equations were solved by a numerical method based on backward finite difference with a fixed griding technique. The effects of feed flow rate (0.552–3.496 l/min), feed concentration (60.72–141.68 mmol/l), and adsorbates composition (58.75–75.32%) on these breakthrough curves were examined.     

Stability Number and f-Factors in Graphs

Let ${f:V \longrightarrow N}$ be an integer function. An f-factor is a spanning subgraph of a graph G = (V,E) whose vertices have degrees defined by f. In this paper, we prove sufficient condition for the existence of a f-factor which involves the stability number, the minimum degree of G or the connectivity of the graph.     

Validated Stability-Indicating Chromatographic Methods for the Determination of Veralipride in Presence of Its Degradation Products

Two sensitive and selective chromatographic methods were developed and validated for determination of veralipride in presence of its degradation products. Forced degradation studies were performed, using HCl, NaOH and 3% H₂O₂. The first method is based on thin-layer chromatographic separation of the intact drug spot from its degradation, followed by densitometric measurements. The second method is based on isocratic liquid chromatographic separation of the studied drug from its degradation on a reversed phase C₁₈ column. The proposed LC method was utilized to investigate the kinetics of alkaline degradation process of the selected drug at different temperatures.     

Transition metal atoms on oxide supports density functional calculations

The adsorption properties of Cu, Ag, Ni, and Pd atoms on O^2?, F, and F⁺ sites of MgO, CaO, SrO, and BaO (001) surfaces have been studied by means of density functional calculations. The examined clusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The adsorption properties have been analyzed with reference to the basicity and energy gap of the oxide support in addition to orbital interactions. While the free Ni d⁹s¹ triplet ground state is preserved on adsorption on the O^2? sites of MgO, CaO, and SrO surfaces, it is no longer preserved on the O^2? site of BaO. For all adsorbates considered, adsorption is found to be stronger on F⁺ sites compared with regular O^2? sites. While on the O^2? site, Pd and Ni form the most stable complexes, on the F site, Pd and Cu form the most stable counterparts. On the F⁺ site, the single valence electron of Cu and Ag atoms couples with the unpaired electron of the vacancy forming a covalent bond. As a result, the adsorption energies of these atoms on the F⁺ site are stronger than those on the F and O^2? sites. The adsorption properties correlate linearly with the basicity and energy gap of the oxide support in addition to orbital interactions. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Synthesis and characterization of UV-irradiated silver/montmorillonite nanocomposites

We have successfully developed a simple method for preparing silver nanoparticles (Ag NPs) using UV irradiation of AgNO₃ in the interlamellar space of a montmorillonite (MMT) without any reducing agent or heat treatment. The properties of Ag/MMT nanocomposites were studied as a function of the UV irradiation period. UV irradiation disintegrated the Ag NPs into smaller size until a relatively stable size and size distribution were achieved. The results from UV–vis spectroscopy show that particles size of Ag NPs decrease with the increase of irradiation period. The crystalline structure of Ag NPs was determined by powder X-ray diffraction (PXRD).     

Semi-empirical study of ortho-cresol photo degradation in manganese-doped zinc oxide nanoparticles suspensions

ABSTRACT: The optimization processes of photo degradation are complicated and expensive when it is performed with traditional methods such as one variable at a time. In this research, the condition of ortho-cresol (o-cresol) photo degradation was optimized by using a semi empirical method. First of all, the experiments were designed with four effective factors including irradiation time, pH, photo catalyst's amount, o-cresol concentration and photo degradation % as response by response surface methodology (RSM). The RSM used central composite design (CCD) method consists of 30 runs to obtain the actual responses. The actual responses were fitted with the second order algebraic polynomial equation to select a model (suggested model). The suggested model was validated by a few numbers of excellent statistical evidences in analysis of variance (ANOVA). The used evidences include high Fvalue (143.12), very low P-value (<0.0001), non-significant lack of fit, the determination coefficient (R2 = 0.99) and the adequate precision (47.067). To visualize the optimum, the validated model simulated the condition of variables and response (photo degradation %) by a few number of three dimensional plots (3D). To confirm the model, the optimums were performed in laboratory. The results of performed experiments were quite close to the predicted values. In conclusion, the study indicated that the model is successful to simulate the optimum condition of o-cresol photo degradation under visible-light irradiation by manganese doped ZnO nanoparticles.     

Coefficient estimates for a class of meromorphic bi-univalent functions

Applying the Faber polynomial coefficient expansions to a class of meromorphic bi-univalent functions, we obtain the general coefficient estimates for such functions and also examine their early coefficient bounds. A function univalent in the open unit disk is said to be bi-univalent if its inverse map is also univalent there. Both the technique and the coefficient bounds presented here are new on their own kind. We hope that this article will generate future interest in applying our approach to other related problems.     

Synthesis of the ABC tricyclic fragment of the pectenotoxins via stereocontrolled cyclization of a gamma-hydroxyepoxide appended to the AB spiroacetal unit

The stereocontrolled synthesis of the C1-C16 ABC spiroacetal-containing tricyclic fragment of pectenotoxin-7 6 has been accomplished. The key AB spiroacetal aldehyde 9 was successfully synthesized via acid catalyzed cyclization of protected ketone precursor 28 that was readily prepared from aldehyde 12 and sulfone 13. The syn stereochemistry in aldehyde 12 was installed using an asymmetric aldol reaction proceeding via a titanium enolate. The stereogenic centre in sulfone 13 was derived from (R)-(+)-glycidol. The absolute stereochemistry of the final spiroacetal aldehyde 9 was confirmed by NOE studies establishing the (S)-stereochemistry of the spiroacetal centre. Construction of the tetrahydrofuran C ring system began with Wittig olefination of the AB spiroacetal aldehyde 9 with (carbethoxyethylidene)triphenylphosphorane 10 affording the desired (E)-olefin 32. Appendage of a three carbon chain to the AB spiroacetal fragment was achieved via addition of acetylene 11 to the unstable allylic iodide 39. Epoxidation of (E)-enyne 8 via in situ formation of L-fructose derived dioxirane generated the desired syn-epoxide 36. Semi-hydrogenation of the resulting epoxide 36 followed by dihydroxylation of the alkene effected concomitant cyclization, thus completing the synthesis of the ABC spiroacetal ring fragment 6.     

Room‐Temperature Carbide‐Derived Carbon Synthesis by Electrochemical Etching of MAX Phases

Porous carbons are widely used in energy storage and gas separation applications, but their synthesis always involves high temperatures. Herein we electrochemically selectively extract, at ambient temperature, the metal atoms from the ternary layered carbides, Ti₃AlC₂, Ti₂AlC and Ti₃SiC₂ (MAX phases). The result is a predominantly amorphous carbide‐derived carbon, with a narrow distribution of micropores. The latter is produced by placing the carbides in HF, HCl or NaCl solutions and applying anodic potentials. The pores that form when Ti₃AlC₂ is etched in dilute HF are around 0.5 nm in diameter. This approach forgoes energy‐intensive thermal treatments and presents a novel method for developing carbons with finely tuned pores for a variety of applications, such as supercapacitor, battery electrodes or CO₂ capture.