Improvement of stability of out-layer MgAl2O4 spinel for a Ni/MgAl2O4/Al2O3 catalyst in dry reforming of methane

Summary The stability of Ni/-Al₂O₃ catalyst in dry reforming of methane was found to be improved by the addition of MgO into the catalyst, probably due to the formation of out-layer MgAl₂O₄ spinels, which can effectively suppress the phase transformation to form NiAl₂O₄ spinel phases, stabilize the tiny Ni crystallites and suppress carbon deposition in dry reforming of methane.     

Carbon-based leaving group in substitution reactions: functionalization of sp3-hybridized quaternary and tertiary benzylic carbon centers

Lewis acid promoted substitution reactions employing Meldrum's acid and 5-methyl Meldrum's acid as carbon-based leaving groups are described which transform unstrained quaternary and tertiary benzylic C(sp(3))-C(sp(3)) bonds into C(sp(3))-X bonds (X = C, H, N). Importantly, this reaction has a broad scope in terms of both suitable substrates and nucleophiles with good to excellent yields obtained (typically >90%).     

Disproportionation of Bromous Acid HOBrO by Direct O-Transfer and via Anhydrides O(BrO)(2) and BrO-BrO(2). An Ab Initio Study of the Mechanism of a Key Step of the Belousov-Zhabotinsky Oscillating Reaction

The results are reported of an ab initio study of the thermochemistry and of the kinetics of the HOBrO disproportionation reaction 2HOBrO (2) ? HOBr (1) + HBrO(3) (3), reaction ( R4' ), in gas phase (MP2(full)/6-311G*) and aqueous solution (SMD(MP2(full)/6-311G*)). The reaction energy of bromous acid disproportionation is discussed in the context of the coupled reaction system R2-R4 of the FKN mechanism of the Belousov-Zhabotinsky reaction and considering the acidities of HBr and HOBrO(2). The structures were determined of ten dimeric aggregates 4 of bromous acid, (HOBrO)(2), of eight mixed aggregates 5 formed between the products of disproportionation, (HOBr)(HOBrO(2)), and of four transition states structures 6 for disproportionation by direct O-transfer. It was found that the condensation of two HOBrO molecules provides facile access to bromous acid anhydride 7, O(BrO)(2). A discussion of the potential energy surface of Br(2)O(3) shows that O(BrO)(2) is prone to isomerization to the mixed anhydride 8, BrO-BrO(2), and to dissociation to 9, BrO, and 10, BrO(2), and their radical pair 11. Hence, three possible paths from O(BrO)(2) to the products of disproportionation, HOBr and HOBrO(2), are discussed: (1) hydrolysis of O(BrO)(2) along a path that differs from its formation, (2) isomerization of O(BrO)(2) to BrO-BrO(2) followed by hydrolysis, and (3) O(BrO)(2) dissociation to BrO and BrO(2) and their reactions with water. The results of the potential energy surface analysis show that the rate-limiting step in the disproportionation of HOBrO consists of the formation of the hydrate 12a of bromous acid anhydride 7 via transition state structure 14a. The computed activation free enthalpy ΔG(act)(SMD) = 13.6 kcal/mol for the process 2·2a → [14a](?) → 12a corresponds to the reaction rate constant k(4) = 667.5 M(-1) s(-1) and is in very good agreement with experimental measurements. The potential energy surface analysis further shows that anhydride 7 is kinetically and thermodynamically unstable with regard to hydrolysis to HOBr and HOBrO(2) via transition state structure 14b. The transition state structure 14b is much more stable than 14a, and, hence, the formation of the "symmetrical anhydride" from bromous acid becomes an irreversible reaction for all practical purposes because 7 will instead be hydrolyzed as a "mixed anhydride" to afford HOBr and HOBrO(2). The mixed anhydride 8, BrO-BrO(2), does not play a significant role in bromous acid disproportionation.     

Guiding of 150 keV O6＋ ions through nanocapillaries in an uncoated Al2O3 membrane： special time dependence of the transmission profile width

<正>This paper reports that the transmission of O⁶⁺ ions with energy of 150keV through capillaries in an uncoated Al₂O₃ membrane was measured,and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed.Due to using an uncoated capillary membrane,ourψ_c is larger than that using a gold-coated one with a smaller value of（?）,which suggests a larger equilibrium charge Q_∞in our experiment.The observed special width variation with time and a larger width than that using a smaller（?） were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation.     

Analysis of the secondary stability of compressible boundary layer flows over a two-dimensional plate

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Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection: analysis of amino acid and organic acid trimethylsilyl derivatives, with application to the analysis of metabolites in rye grass samples

First, standard mixtures of trimethylsilyl (TMS) derivatives of amino acid and organic acid are analyzed by comprehensive two-dimensional (2D) gas chromatography (GC) coupled to time-of-flight mass spectrometry (GC × GC/TOFMS) in order to illustrate important issues regarding application of the technique. Specifically of interest is the extent to which the peak capacity of the 2D separation space has been utilized and the procedure by which the derivative standards are identified in the 2D separations using the mass spectral information. The resulting 2D separation is found to make extensive use of the GC × GC separation space provided by the complementary stationary phases employed.Second, in order to demonstrate GC × GC/TOFMS on two real sample types, trimethylsilyl metabolite derivatives were analyzed from extracts of common lawn grass samples (i.e., perennial rye grass), as a means to provide insight into both the pre and post harvest physiology. Various chemical components in the two rye grass extract samples were found to either emerge or disappear in relation to the trauma response. For example, a significant difference in the peak for the TMS derivative of malic acid was found. The successful analysis of various components was readily facilitated by the 2D separation, while a 1D separation would have produced too much peak overlap, thus impeding the analysis. The importance of using a GC × GC separation approach for the analysis of complex samples, such as metabolite extracts, is therefore demonstrated. The real-time analysis capability of GC × GC/TOFMS for multidimensional metabolite analysis makes this technique well suited to the high-throughput analysis of metabolomic samples, especially compared to slower, stopped-flow type separation approaches.     

Self-trapping and oscillation of quadruple beams in high band gap of 2D photonic lattices

through single-site excitation. By changing the initial to the lattices, periodic oscillations of the localized quadruple state becomes a rotating doubly charged undergo charge-flipping when the rotating direction is orientation of the incident quadruple beam related quadruple mode may be obtained. The localized optical vortex （DCV） during rotation and should reversed.     

Formation of Hierarchical FeCoS2–CoS2 Double‐Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2

Hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO₂ reduction under visible light. The synthetic strategy, engaging the two‐step cation‐exchange reactions, precisely integrates two metal sulfides into a double‐shelled tubular heterostructure with both of the shells assembled from ultrathin two‐dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS₂–CoS₂ hybrid can reduce bulk‐to‐surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO₂ adsorption and surface‐dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS₂–CoS₂ double‐shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO₂ reduction, affording a high CO‐generating rate of 28.1 μmol h^?1 (per 0.5 mg of catalyst).     

On Cayley digraphs on nonisomorphic 2‐groups

A necessary and sufficient condition is given for two Cayley digraphs X₁ = Cay(G₁, S₁) and X₂ = Cay(G₂, S₂) to be isomorphic, where the groups G_i are nonisomorphic abelian 2‐groups, and the digraphs X_i have a regular cyclic group of automorphisms. Our result extends that of Morris [J Graph Theory 3 (1999), 345–362] concerning p‐groups G_i, where p is an odd prime. Copyright © 2011 Wiley Periodicals, Inc. J Graph Theory