Studies on the Adsorption and Dissociation of Methane and Carbon Dioxide on Nickel Catalysts

The adsorption and dissociation of methane and carbon dioxide for reforming on nickel catalysts were extensively investigated by TPSR, TPD, XPS and pulse reaction methods. These studies showed that the decomposition of methane results in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic Cα, carbonaceous Cβ and carbidic clusters C-γ surface carbon species formed by the decomposition of methane demonstrated different surface mobility, thermal stability and reactivity. Carbidic Cα is a very active and important intermediate in carbon dioxide reforming with methane, and the carbidic clusters Cγ species might be the precursor of surface carbon deposition. The partially dehydrogenated Cβ species can react with H2 or CO2 to form CH4 or CO. On the other hand, it was proven that CO2 can be weakly adsorbed on supported nickel catalysts, and only one kind of CO2 adsorption state is formed. The interaction mechanism between the species dissociated from CH4     

Theoretical Studies on Adsorption Sites and States of O and N on Ni（311）

The adsorption of O and N atoms on the Ni(311) surface was investigated by the 5-parameter Morse potential(5-MP) method in detail. For the O-Ni(311) system, there are three surface adsorption states and thefcc-3-fold site is metastable; the frequency of 75 meV[67 meV in high resolution electron energy loss spectroscopy(HREELS) experiment] is attributed to the vibration at the hcp-3-fold site. For the N-Ni(311) system, however, there are only two surface adsorption states(no surface adsorption state was calculated at fcc-3-fold site). In addition, subsurface states were predicted and all critical characteris-tics were obtained for the two systems.     

Study on polymerization and structure of polydiphenylamine

The electrochemical oxidation of diphenylamine in acetonitrile produces an adherent uniform polymer film which exhibits mutiple colour variation(yellow-green-blue) in a wide range of potential scan. The polymerization mechanism and the structure of the polymer were studied by cyclic voltammetry, FT-IR and in situ ESR. The results indicate that the electrochemical polymerization of diphenylamine belongs to a cationic radical polymerization process. During electrolysis, only oligomers were initialy produced, then polymer film was formed on the electrode surface. The electropolymerization performs via the 4,4' C-C phenyl-phenyl coupling mechanism.     

Experimental and Theoretical Studies on the Enantioseparation and Chiral Recognition of Mandelate and Cyclohexylmandelate on Permethylated ��-Cyclodextrin Chiral Stationary Phase

Enantioseparations of methyl mandelate (MMA) and methyl ??-cyclohexylmandelate (MCHMA) on permethylated ??-cyclodextrin (PM-??-CD) chiral stationary phase were explored in detail using high-performance liquid chromatography. The influence of the concentration of organic modifiers, along with the column temperature, was studied. In addition, the thermodynamics parameters of the enantioseparations were determined to discuss driven power in the process of enantioseparations. In addition, host?guest complexation of PM-??-CD with MMA enantiomers was simulated by quantum mechanics PM3 method for understanding the chiral recognition mechanism. The experimental results showed that the retention factor (k), separation factor (??), and resolution factor (Rs) for MMA and MCHMA resolved on the PM-??-CD column all generally decreased with the increase of methanol content, which indicated that the main chiral recognition mechanism is that the hydrophobic portions of MMA and MCHMA are included in the hydrophobic cavity of PM-??-CD to form inclusion complexes. In addition, there is an excellent linear relationship between the logarithms of retention factors (k) of MMA and MCHMA enantiomers and 1/T. It was demonstrated that the enantioseparations of MMA and MCHMA on PM-??-CD chiral column were enthalpy-driven processes. The modeling results can correctly predict the retention order and provide an atomistic account of how chiral discrimination takes place. It is found that the most stable structure of (R)-MMA/PM-??-CD complex is different with that of (S)-MMA/PM-??-CD complex. The main driving forces responsible for chiral recognition are hydrophobic forces and weak hydrogen bondings.     

Fluoride and lead adsorption on carbon nanotubes

The properties and applications of CNT have been studied extensively since Iijima discovered them in 1991[1,2]. They have exceptional mechanical properties and unique electrical property, highly chemical stability and large specific surface area. Thus far, they have widely potential applications in many fields. They can be used as reinforcing materials in composites[3], field emissions[4], hydrogen storage[5], nanoelectronic components[6], catalyst supports[7], adsorption material and so on.…     

Photochromic fulgides and spirooxazines: mechanism and substituent effect on photoreactions

Molecular design, synthesis and photochromic properties of spirooxazines and fulgides are described. In the case of fulgides, the change of the substituents may lead to different photochromic properties and different photoreactions of the kind of compounds. In photochromic process of pyrryl-substituted fulgides, the excited singlet state is the mam species, but the excited triplet state is also involved. However, no excited triplet state has been observed in cyclization of aryl-substituted fulgides. In the case of spirooxazines, the substituents at 2'-position have great effect on the formation of photoproduct and on the mechanism of photoreaction. The increase of steric hindrance of the 2'-position substituent gives rise to the decrease of the quantum yield for the formation of photochromic merocyanine (PMC) and the increase of the relative quantum yield for the charge separated twist intermediate (CT).     

Qualitatively graph-theoretical study on stability and formation of fullerenes and nanotubes

Kekule structures of different carbon species have been determined. On the basis of Kekule structure and C-C bond counts as well as the surface curvature, stability of diverse carbon species, driving force for curling of graphite fragments and formation of fullerenes and nanotubes, have been discussed. Curling of graphite flat fragments, end-capping of nanotubes, and closure of curved structures are driven by a tremendous increase in Kekule structures as terminal carbon atoms couple their dangling bonds into C-C o bonds. The increasing tendency becomes particularly striking for large cages and nanotubes. Resonance among numerous Kekule structures will stabilize the curved structure and dominate formation of closed carbon species. For similar carbon cages with comparable Kekule structure counts in magnitude, the surface curvature of carbon cages, as a measure for the strain energy, also plays an important role in determining their most stable forms.     

Structure and characteristics of copolyamides based on ε-caprolactam and diisocyanates

The main supramolecular characteristics and the processing and service characteristics of copolyamides based on -caprolactam and hexamethylene diisocyanate were studied. The relation between the comonomer composition and supramolecular structure of copolymers was established.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1891–1894.Original Russian Text Copyright © 2004 by Galibeev, Barnyagina, Kochnev, Arkhireev, Galimov.     

QSPR Studies on lgK_(ow) and lgK_(oc) of Fluorobenzenes and Property Parameters Based on HF and DFT Calculations

1 INTRODUCTION Quantitative structure-activity relationship (QSAR) equation could be employed to predict the biological activities of unknown compounds, which is signifi- cant for initial screening and evaluation of toxic compounds[1]. Soil sorption coeff…     

Studies on the Syntheses and Properties of UV-sensitive Organosilicon Monomers and Polymers

Photosensitive organosilicon monomers and polymers containing furylacrylate, cinnamate or methacrylate groups were synthesized. The chemical structure of these organosilicon monomers were confirmed by 1H NMR and elemental analysis.The curing rates of these photosensitive polysiloxanes were also determined, all of them show a good UV-sensitivity. The UV-sensitivity of polysiloxanes containing pendent furylacrylates are comparable to that of polysiloxanes with either pendent cinnamate or pendent methacrylate groups.     

Amination reaction on copper and germanium β-nitrocorrolates

Copper and germanium complexes of β-substituted nitrocorroles were reacted with 4-amino-4H-1,2,4-triazole to give the corresponding β-amino-β-nitro derivatives, in moderate to good yields. This is the first successful example of a vicarious nucleophilic substitution performed on corrole derivatives, because the same reaction carried out on silver complexes afforded the corresponding 6-azahemiporphycenes by way of corrole ring expansion. The first step of this work is related to the modification of a synthetic protocol for preparation of the β-substituted nitro corroles. The nitration reaction was carried out on a copper corrole using NaNO(2) as the primary source of NO(2)(-) coupled with AgNO(2) used as oxidant. By variation of the molar ratio of the reagents it was possible to direct the product distribution toward mono- and dinitro derivatives. The reaction between mono- and dinitro derivatives of (TtBuCorrCu) with 4-amino-4H-1,2,4-triazole gave good results, leading to the isolation of 2-(NH(2))-3-(NO(2))-TtBuCorrCu and 2,18-(NH(2))(2)-3,17-(NO(2))(2)-TtBuCorrCu in moderate yields. To elucidate factors that influence the reaction, and to highlight the different behavior observed for different metal complex substrates, the electrochemistry of three copper complexes, TtBuPCorrCu, (NO(2))TtBuPCorrCu, and (NO(2))(2)TtBuPCorrCu, was studied by cyclic voltammetry and thin-layer UV-visible spectroelectrochemistry. The nitro groups on (NO(2))(x)TtBuPCorrCu are highly electron-withdrawing, which leads not only to a substantial positive shift of all redox potentials but also to a unique redox behavior and UV-vis spectrum of the singly reduced product as compared to the parent compound, TtBuPCorrCu. Finally, the amination reaction was carried out on a Ge(IV) nitrocorrolate, giving in good yield the 2-amino-3-nitroderivative, which was structurally characterized by single crystal X-ray crystallography.     

Studies on the Peptides and Polysaccharides in Pollen

The peptides RP3I and PSPP1-4 were purified from the rape and the Papaver Somniferunpollens, respectively. Their sequences and physiological activities were determined and synthesized ex-cept PSPP1. The polysaccharides TAA-C and CPA-E were obtained from Typha Angustifilia andCodonopsis Pilosula pollens, respectively. Their partial characterization and structures were studied.     

Theoretical Study on Adsorption and Diffusion of N Atoms on Cu Low-index Surface

The adsorption and diffusion of N atoms on the three low-index Cu planes were studied using 5-parameter Morse potential (5-MP) method, and the best theory-experiment agreement was obtained. N atoms of Cu(100) surface sit on the fourfold hollow site with the vertical height of 0.018 nm closely coplanar with the topmost copper layer, and the four Cu-N bond lengths are 0.182 nm and the fifth Cu-N distance is 0.199 nm. For Cu(111) system, the existence of aberrant Cu(100) reconstructed structure is approved at higher coverage, and at low coverage the structure is almost an ideal Cu(111) surface structure. With respect to Cu(110) system, the N atoms are adsorbed at LB and H3 sites, not at SB site. The diffusion passage and diffusion barrier of adsorbed N atoms were also studied.     

Hydrogen Effect on Coke Removal and Catalytic Performance in Pre-Carburization and Methane Dehydro-Aromatization Reaction on Mo/HZSM-5

1. Introduction As an effective utilization of methane, the methane dehydro-aromatization was focused in the last decade [1-28]. Over the Mo/HZSM-5 bi- functional catalyst at high reaction temperature, methane can be converted into light aromatics (ben- zene and naphthalene) and hydrogen. Mo active species can activate the C—H bond of methane; and HZSM-5 supplies the acid sites for the oligomeriza- tion and cyclization of hydrocarbons to form aromat- ics, and suppresses the deeper condens…     

Structural and mechanistic studies on γ-butyrobetaine hydroxylase

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Highlights? Crystal structure of γ-butyrobetaine hydroxylase in complex with substrate and inhibitor ? N-terminal Zn-binding domain involved in dimerization ? The clinically used inhibitor, THP, is also a substrate for BBOX ? BBOX catalyzed rearrangement reaction     

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natu- ral waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory[1,2]. Derived from a variety of organic precursors (plant biopolymers such as lignin etc.), plant residues and animal debris via both transformation and synthesis processes[3] under the profound ge…     

Study on an electrochemical biosensor for thrombin recognition based on aptamers and nano particles

This paper presents a high specific, sensitive electrochemical biosensor for recognition of protein such as thrombin based on aptamers and nano particles. Two different aptamers were chosen to construct a sandwich manner for detecting thrombin. Aptamer I was immobilized on nano magnetic particle for capturing thrombin, and aptamer II labled with nano gold was used for detection. The electrical current generated from gold after the formation of the complex of magnetic particle, thrombin and nano gold, and then an electrochemical cell designed by ourselves was used for separating, gathering, and electrochemical detecting. Through magnetic separation, high specific and sensitive detection of the target protein, thrombin, was achieved. Linear response was observed over the range 5.6×10-12―1.12×10-9 mol/L, with a detection limit of 1.42×10-12 mol/L. The presence of other protein as BSA did not affect the detection, which indicates that high selective recognition of thrombin can be achieved in complex biological samples such as human plasma.     

Control on Crystal Forms of Ultrafine Barium Carbonate Particles and Study on its Mechanism

1 INTRODUCTION Barium carbonate is one of the important che- mical materials as well as one of the most important barium salts. Its application covers multitudinous in- dustries and fields such as building material, meta- llurgy, electron, chemical industry and so on[1]. With the fast development of science and technology, it is becoming more and more demanding with barium carbonate’s quality, and more and more scientific workers do researches on the control of Barium car- bonate’s crys…     

Investigation on Vibrational Spectra and Structures of 4-Mercaptopyridine Monomer and Its Dihydrate

Introduction4-Mercaptopyridine(4MPY)has been always em-ployed as a model molecule and a probe molecule forRaman spectra in many studies because of its specialstructure with two active groups and its excellent signalin a Raman spectrum.Therefore,4MPY has b…