Non-isothermal kinetics of CrO3 decomposition pathways in air

The course of the non-isothermal decomposition of CrO₃ in air was explored kinetically, by using a number of widely accepted methods. The credibility of the values obtained from a given kinetic parameter (the reaction order, the activation energy and the frequency factor) was justified on the grounds of (i) a multiple correlation coefficient, and (ii) the merits and demerits of the method adopted. The results obtained may help towards a characterization of the non-isothermal conditions under which the encountered decomposition events and products could be resolved. The study was motivated by the results of previous physicochemical characterization studies [1, 2], in which catalytically important intermediates CrO_x(3<x<6) were structurally identified.     

MWCNTs/Ionic Liquid/Graphene Quantum Dots Nanocomposite Coated with Nickel‐Cobalt Bimetallic Catalyst as a Highly Selective Non‐enzymatic Sensor for Determination of Glucose

In this work, a glassy carbon electrode (GCE) was modified with multiwall carbon nanotubes/ionic liquid/graphene quantum dots (MWCNTs/IL/GQDs) nanocomposite. Then, the nanocomposite was decorated with nickel‐cobalt nanoparticles (Ni?Co NPs), and it was used as a non‐enzymatic glucose sensor. Field emission scanning electron microscopy, X‐ray diffraction spectroscopy, and energy dispersive spectroscopy were employed to prove the electrodeposition of the Ni?Co NPs on the surface of MWCNTs/IL/GQDs/GCE. Also, cyclic voltammetric and amperometric methods were utilized for the investigation of the electrochemical behaviour of the Ni?Co NPs/MWCNTs/IL/GQDs/GCE for glucose oxidation. The novel amperometric sensor displayed two linear ranges from 1.0 to 190.0 μmol L^?1 and 190.0 to 4910 μmol L^?1 with a low detection limit of 0.3 μmol L^?1 as well as fast response time (2 s) and high stability. Also, the sensor showed good selectivity for glucose determination in the presence of ascorbic acid, citric acid, dopamine, uric acid, fructose, and sucrose, as potential interference species. Finally, the performance of the proposed sensor was investigated for the glucose determination in real samples. Ni?Co NPs/MWCNTs/IL/GQDs/GCE showed good sensitivity and excellent selectivity.     

Single and binary catalyst systems based on nickel and palladium in polymerization of ethylene

The catalyst (N,N‐bis(2,6‐dibenzhydryl‐4‐ethoxyphenyl)butane‐2,3‐diimine)nickel dibromide, a late transition metal catalyst, was prepared and used in ethylene polymerization. The effects of reaction parameters such as polymerization temperature, co‐catalyst to catalyst molar ratio and monomer pressure on the polymerization were investigated. The α‐diimine nickel‐based catalyst was demonstrated to be thermally robust at a temperature as high as 90 °C. The highest activity of the catalyst (494 kg polyethylene (mol cat)^?1 h^?1) was obtained at [Al]/[Ni] = 600:1, temperature of 90 °C and pressure of 5 bar. In addition, the performance of a binary catalyst using nickel‐ and palladium‐based complexes was compared with that of the corresponding individual catalytic systems in ethylene polymerization. In a study of the catalyst systems, the average molecular weight and molecular weight distribution for the binary polymerization were between those for the individual catalytic polymerizations; however, the binary catalyst activity was lower than that of the two individual ones. The obtained polyethylenes had high molecular weights in the region of 10⁵ g mol^?1. Gel permeation chromatography analysis showed a narrow molecular weight distribution of 1.44 for the nickel‐based catalyst and 1.61 for the binary catalyst system. The branching density of the polyethylenes generated using the binary catalytic system (30 branches/1000 C) was lower than that generated using the nickel‐based catalyst (51/1000 C). X‐ray diffraction study of the polymer chains showed higher crystallinity with lower branching of the polymer obtained. Also Fourier transform infrared spectra confirmed that all obtained polymers were low‐density polyethylene.     

An investigation of the use of line widths in quantitative spectrographic analysis

A satisfactory and accurate spectrographic analysis is obtained through the use of line width measurements. The precautions necessary to permit reasonably accurate application of the method are described.     

Reactivity of 4-hydroxy-2-methyl-7,8,9,10-tetrahydrobenzo[h] quinoline towards base-catalyzed cyclization,mannich and turpin reactions

Mannich reaction upon 4-hydroxy-2-methyl-7,8,9,10-tetrahydrobenzo[h]quinoline ( 1 ) as well as its nitration were studied. Condensation of the chloroquinoline 6b with sodium azide, benzylamine and ethanolamine gave the quinoline derivatives 6c, 6f and 6g , respectively. Phenylhydrazine and sodium borohydride effected reduction of the azidoquinoline 6c to the corresponding amino- and hydroxyamino derivatives 6d and 6e , respectively. Also, Turpin's reaction gave the benzoquinobenzoxazines 7a-d when applied to 6b . Treatment of 6f, 6g with alkali and the condensation of 6b with glycine in alcoholic sodium carbonate solution afforded the imidazo[4,5-c]quinoline derivatives 9a-c , respectively.     

Synthesis,crystal structure,vibrational, optical properties,and a theoretical study of a new Pb(II) complex with bis(1-methylpiperazine-1,4-diium): [C5H14N2]2PbCl6·3H2O

An investigation of the solid-state X-ray structure of the new organic–inorganic compound [C₅H₁₄N₂]₂PbCl₆·3H₂O shows a layered organization of the (PbCl₆)^4– anions, with (R₂NH₂)⁺ groups and water molecules developed in the [001 A. Hu, H.L. Ngo, W. Lin. J. Am. Chem. Soc., 125, 11490 (2003).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]] plane at x = (2n?+?1)/4. The crystal structure is stabilized by N???H···Cl, N???H···O, O???H···Cl, O???H···O, and C???H···Cl hydrogen bonds. The powder X-ray diffraction and X-ray photoelectron spectroscopic (XPS) analyses confirm the phase purity of the crystal sample. The intermolecular contacts are quantified using the Hirshfeld surfaces computational method. The major inter-contacts contributing to the Hirshfeld surfaces are H…Cl, H…H, and O…H. The vibrational modes were identified and assigned by IR and Raman spectroscopies. The optical properties were investigated by UV–visible and photoluminescence spectroscopic studies. The compound was characterized by thermal analysis to determine its thermal behavior with respect to the temperature. Finally, X-ray photoelectron spectroscopy analysis is reported for analyzing the surface chemistry of [C₅H₁₄N₂]₂PbCl₆·3H₂O.     

Effect of the Preparation Methodof Al–Mg–O Catalysts on the Selective Decomposition of Ethanol

Summary.  Selective decomposition of ethanol was used as a test reaction at 350°C to evaluate the catalytic activity of two Al–Mg–O mixed oxides prepared by two different methods (wet impregnation and coprecipitation). The catalyst precursors were examined by TG and DTA and were calcined between 500–900°C for 5 h in air. The surface area of all catalysts was measured by N₂ sorption using the BET method. The total acidity and basicity were determined by TPD using pyridine and formic acid. The catalysts were characterized by XRD analysis. It was found that the preparation method of Al–Mg–O catalyst has a great effect on the selective decomposition of ethanol. Al–Mg–O (I) catalysts, prepared by wet impregnation, were more selective towards ethene formation during dehydration of ethanol. This is ascribed to their high total surface acidity. On the other hand, Al–Mg–O (II) catalysts, prepared by coprecipitation, were highly selective in the oxidative dehydrogenation of ethanol to yield acetaldehyde. This could be attributed to their high concentration of basic sites. In addition, the production of traces of diethyl ether was also observed (three times more for Al–Mg–O (II) than for Al–Mg–O (I)). Corresponding author. E-mail: shalawy99@yahoo.com Received October 12, 2001. Accepted (revised) January 7, 2002     

New ring of a class of Bessel integral operators

In this paper, we introduce a new ring of ponderation functions which allowed us to describe and classify a large class of ring of Bessel integral operators. The main result is to give an explicit form of some ideals of such a ring of operators.     

A characterization of fourier transforms in L2(R)

Conditions characterizing Fourier transforms in L₂(R) are given.     

Neutron scattering experiments on fully deuterated liquid N-methylformamide DCONDCD3 at various temperatures and under pressure. Comparison to X-ray results

Neutron scattering experiments are performed on fully deuterated liquid N-methylformamide (C2D5NO) at various temperatures and under pressure. The recorded data at atmospheric pressure and room temperature are analyzed to yield the molecular form factor and the distinct pair correlation function. Our measurements clearly show that the hydrogen-bond network, of which the parameters are deduced, persists locally in the liquid. The experimental structure factor could be explained in terms of short-range crystal structure. The r(N...O) distance decreases with increasing temperature from 293 to 398 K, whereas no significant variation of the intermolecular structure is detected when varying pressure from 1 bar to 4 kbar. Along the study, some comparison is made with complementary X-ray results.