Ni adsorbate dynamics on a NiO(0 0 1) surface

We present results concerning the dynamical behavior of a Ni³⁺ adsorbate on a NiO(0 0 1) surface obtained by molecular dynamics simulations. In a first place, we examined at low temperature the position of the Ni³⁺ ion as an adatom on the surface and the corresponding modification of its local environment as reflected on the pair-wise radial distribution function. The calculation of the vibrational properties of the adatom by means of the phonon local density of states (LDOS) shows that there is an anisotropic behavior both in the two principal in-plane directions as well as in the direction normal to the surface in accordance with the structural results. We compare the phonon LDOS of the Ni³⁺ adatom with the corresponding results for the Ni²⁺ adatom and the Ni²⁺ surface cations.Static energetic calculations are indicative that the exchange of the Ni³⁺ ion with a surface Ni²⁺ ion could be favorable. Such a behavior is confirmed by results observed at temperatures higher than 700 K where the Ni³⁺ adsorbate is located on a substitutional position on the surface and not on adatom position. The exchange takes place through simple or double exchange mechanisms. The structural and dynamical behavior of the Ni³⁺ ion at the substitution position was investigated in the temperature range 700-2000 K through the calculation of the pair distribution function, the relaxed interlayer relative position (RIRP), mean-square displacements (MSDs) and phonon LDOS. Results show that in comparison with the Ni²⁺ surface ions the Ni³⁺ ion at substitution position is more tightly bound especially in the direction normal to the surface as is indicated by the local structure and the contraction it presents as well as its phonon LDOS. As temperature increases the binding of the Ni³⁺ ion becomes less important as reflected on the physical properties mentioned above.     

Oxidation and thermal stability of nickel deposited on a thin alumina support

The activity of supported Ni catalysts can easily be affected by high temperatures and oxidative atmosphere. In order to study the origin of this behaviour, we performed systematic LEED and XPS investigations on a model system prepared by physical vapour deposition of Ni on a thin epitaxial alumina film on NiAl(1 1 0). Annealing experiments showed that deposited Ni is thermally stable up to ∼370 K. Further annealing seems to lead first to changes in the island structure and then, at temperatures above ∼480 K, to diffusion of Ni through the alumina film. Analysis of the complex oxidation behaviour revealed that there is a competition between oxidation of the Ni deposit and of the NiAl support. The latter process is probably enabled by a solid state reaction at the interface which means that Ni catalyses the further oxidation of the support. While the surface of the deposited Ni clusters is easily oxidised, the further oxidation processes of the Ni particles and the support were found to be diffusion-controlled.     

流动注射在线分离富集火焰原子吸收法快速顺序测定环境样品中六种元素

本文采用双柱富集的在线分离富集系统与 2 2 0FS顺序多元素原子吸收分光光度计联用 ,以PT C18色谱预处理柱为预富集柱 ,二乙基二硫代氨基甲酸钠 (DDTC)和吡咯啶二硫代氨基甲酸铵 (APDC)混合物为螯合剂 ,甲醇为洗脱剂 ,首次实现了Cu ,Pb,Cd ,Co ,Ni,Mn六种元素的快速同时测定。富集倍数为 10 2～ 2 1 7之间。34s富集 (4 4 0mL)的检出限分别为Cu 2 91,Pb 5 81,Cd 0 35 ,Co 3 6 1,Ni4 0 5和Mn 1 94 μg·L-1,相对标准偏差分别为Cu 2 6 4 % ,Pb 2 93% ,Cd 2 5 9% ,Co 2 5 7% ,Ni 2 78%和Mn 3 6 8%。该方法操作简便、快速 ,用于环境样品中痕量元素的测定 ,得到了满意的结果。     

Thermochemical sulfate reduction a review

The high concentrations of hydrogen sulfide found in many oil and gas fields is thought to arise from the oxidation of petroleum hydrocarbons by sulfate—a reaction that reduces the value of the resource. This review, undertaken in order to better understand the geochemistry of TSR reaction in oil field sediments, covers the relevant information on thermochemical sulfate reduction (TSR) to 1991. The theoretical and experimental aspects of TSR reactions (including sulfur and carbon isotope studies) are reviewed and their significance to the geochemical system discussed. The present review agrees with previous suggestions that biochemical reduction of sulfate dominates in sedimentary environments below 120°C, and supports the possibility that reactive sulfur species will oxidize certain organic molecules at meaningful rates in geochemically reasonable reaction periods at temperatures above 175°C. We conclude that under typical petroleum reservoir reaction conditions, both elemental sulfur and polysulfides are capable of oxidizing some organic molecules under basic conditions. But that sulfate alone will not react unless lower oxidation state sulfur is present. The possible interaction of low-valence-state sulfur with sulfate to form TSR active oxidants is examined. both H₂S and SO ₄ ²⁻ are required for the formation of active polysufide reductants (e.g. thiosulfate or polythionates) in TSR systems. Such intermediates can serve to lower the overall activation energy of the oxidation of hydrocarbons by sulfate via thermal generation of sulfur radicals that can function as TSR active oxidants in many oil field sediments. We suggest that some proposed chemical mechanisms for TSR need to be experimentally verified and the results re-interpreted with respect to TSR relations in geologic systems. Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65^th birthday     

An Efficient and Green Procedure for the Preparation of gem-Dicar- boxylates from Aldehydes Catalyzed by Fe_2(SO_4)_3·xH_2O

~~An Efficient and Green Procedure for the Preparation of gem-Dicar- boxylates from Aldehydes Catalyzed by Fe_2(SO_4)_3·xH_2O~~     

Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate

A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.     

Microwave-assisted synthesis of 4-quinolylhydrazines followed by nickel boride reduction: a convenient approach to 4-aminoquinolines and derivatives

Nickel(II) chloride/sodium borohydride combination was employed for the reduction of 4-hydrazinoquinoline derivatives to the corresponding anilines. This reductive protocol was efficiently applied for the reductive cleavage of monosubstituted hydrazines. We described herein the microwave-assisted synthesis of 4-hydrazinoquinolines, which furnished a high yielding and rapid two-step procedure for the synthesis, under mild conditions, of 4-aminoquinolines as antimalarial precursors.     

（NH_4）_2SO_4─NH_4Cl─NH_4HCO_3—H_2O体系在10

（ＮＨ＿４）＿２ＳＯ＿４─ＮＨ＿４Ｃｌ─ＮＨ＿４ＨＣＯ＿３—Ｈ＿２Ｏ体系在１０℃时的溶解度相图汪庆华，付鹤鉴，宋德镇，刘维铭，于海生（四川联合大学（东区）化学系成都６１００６４）关键词：溶解度相图，硫酸铵，氯化铵，碳酸氢铵在化工生产中，为了降低成本，...     

Photoelectron diffraction study of ultrathin film growth of Ni on Pt(111)

X-ray photoelectron diffraction (PD) based on a forward scattering approach (FS-PD) has been used to study the growth mode of the first few Ni monolayers deposited on the Pt(111) surface, with a particular attention to the initial stages of epitaxy, i.e. the formation of the first atomic layer. Strong evidences for a layer-by-layer (or Frank-Van der Merwe) growth mode are reported, substantiated also by theoretical simulations carried out with the single scattering cluster-spherical wave (SSC-SW) framework. The first Ni monolayer grows strained in-plane to match the substrate pseudomorphically even if there is a 10% mismatch between the lattice parameters of Ni and Pt. The multilayer (up at least to six monolayers) maintains the horizontal strain and consequently shows a vertical spacing contraction (tetragonal distorsion). It retains the overall threefold symmetry and azimuthal orientation of the substrate, indicative of a single-domain epitaxial fcc stacking. There is also some evidence (even if it is not conclusive) for the fact that the Ni atoms of the first monolayer occupy hcp sites of the substrate surface.