Catalytic role of pre-adsorbed CO in platinum-based catalysts : the reduction of SO 2 by CO on Pt l Au m (CO) n

Using density functional theory, we have investigated the catalytic properties of bimetallic complex catalysts PtlAum(CO)n (l + m = 2, n = 1–3) in the reduction of SO2 by CO. Due to the strong coupling between the C-2p and metal 5d orbitals, pre-adsorption of CO molecules on the PtlAum is found to be very effective in not only reducing the activation energy, but also preventing poisoning by sulfur. As result of the coupling, the metal 5d band is broadened and down-shifted, and charge is transferred from the CO molecules to the PtlAum. As SO2 is adsorbed on the catalyst, partial charge moves to the anti-σ bonding orbitals between S and O in SO2, weakening the S–O bond strength. This effect is enhanced by pre-adsorbing up to three CO molecules, therefore the S–O bonds become vulnerable. Our results revealed the mechanism of the excellent catalytic properties of the bimetallic complex catalysts.

Effect of SO(2) on the Transport Properties of an Imidazolium Ionic Liquid and Its Lithium Solution

Transport coefficients have been measured as a function of the concentration of sulfur dioxide, SO(2), dissolved in 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)-imide, [BMMI][Tf(2)N], as well as in its lithium salt solution, Li[Tf(2)N]. The SO(2) reduces viscosity and density and increases conductivity and diffusion coefficients in both the neat [BMMI] [Tf(2)N] and the [BMMI][Tf(2)N]-Li[Tf(2)N] solution. The conductivity enhancement is not assigned to a simple viscosity effect; the weakening of ionic interactions upon SO(2) addition also plays a role. Microscopic details of the SO(2) effect were unraveled using Raman spectroscopy and molecular dynamics (MD) simulations. The Raman spectra suggest that the Li(+)-[Tf(2)N] interaction is barely affected by SO(2), and the SO(2)-[Tf(2)N] interaction is weaker than previously observed in an investigation of an ionic liquid containing the bromide anion. Transport coefficients calculated by MD simulations show the same trend as the experimental data with respect to SO(2) content. The MD simulations provide structural information on SO(2) molecules around [Tf(2)N], in particular the interaction of the sulfur atom of SO(2) with oxygen and fluorine atoms of the anion. The SO(2)-[BMMI] interaction is also important because the [BMMI] cations with above-average mobility have a larger number of nearest-neighbor SO(2) molecules.

Detailed analysis of the charge transfer complex N,N-dimethylaniline-SO(2) by Raman spectroscopy and density functional theory calculations

Although the amine sulfur dioxide chemistry was well characterized in the past both experimentally and theoretically, no systematic Raman spectroscopic study describes the interaction between N,N-dimethylaniline (DMA) and sulfur dioxide (SO(2)). The formation of a deep red oil by the reaction of SO(2) with DMA is an evidence of the charge transfer (CT) nature of the DMA-SO(2) interaction. The DMA -SO(2) normal Raman spectrum shows the appearance of two intense bands at 1110 and 1151 cm(-1), which are enhanced when resonance is approached. These bands are assigned to nu(s)(SO(2)) and nu(phi-N) vibrational modes, respectively, confirming the interaction between SO(2) and the amine via the nitrogen atom. The dimethyl group steric effect favors the interaction of SO(2) with the ring pi electrons, which gives rise to a pi-pi* low-energy CT electronic transition, as confirmed by time-dependent density functional theory (TDDFT) calculations. In addition, the calculated Raman DMA-SO(2) spectrum at the B3LYP/6-311++g(3df,3pd) level shows good agreement with the experimental results (vibrational wavenumbers and relative intensities), allowing a complete assignment of the vibrational modes. A better understanding of the intermolecular interactions in this model system can be extremely useful in designing new materials to absorb, detect, or even quantify SO(2). Copyright (C) 2009 John Wiley & Sons, Ltd.

GENERAL POTENTIALS DESCRIBED BY SO(2,1) DYNAMIC ALGEBRA IN PARABOLIC-COORDINATE SYSTEMS

We propose general three-dimensional potentials in rotational and cylindrical parabolic coordinates which are generated by direct products of the SO(2, 1) dynamical group. Then we construct their Green functions algebraically and find their spectra. Particular cases of these potentials which appear in the literature are also briefly discussed.

So(2,1) Lie algebra and the Green's functions for the conditionally exactly solvable potentials

The Green's functions of the recently discovered conditionally exactly solvable potentials are computed. This is done through the use of a second-order differential realization of the so(2,1) Lie algebra. So we present the dynamical symmetry underlying the solvability of such potentials and show that they belong to a general class of solvable and partially solvable potentials. © 1994 The American Physical Society.

Response surface methodology applied to the evaluation of the SO 2 sorption process in two Brazilian limestones

This paper proposes a response surface methodology to evaluate the influence of the particle size and temperature as variables and their interaction on the sulfation process using two Brazilian limestones, a calcite (ICB) and a dolomite (DP). Experiments were performed according to an experimental design [central composite rotatable design (CCRD)] carried out on a thermogravimetric balance and a nitrogen adsorption porosimeter. In the SO 2 sorption process, DP was shown to be more efficient than ICB. The best results for both limestones in relation to conversion and Brunauer-Emmett-Teller (BET) surface area were obtained under central point conditions (545 μm and 850 C for DP and 274 μm and 815 C for ICB). The optimal values for conversion were 52% for DP and 37% for ICB. For BET surface area, the optimal values were 35 m2 g-1 for DP and 45 m2 g-1 for ICB. A relationship between conversion and pore size distribution has been established. The experiments that showed higher conversions also exhibited more pores in the region between 20 and 150 Å and larger BET surface area, indicating that the amount of smaller pores may be an important factor in the reactivity of limestones. © 2013 American Chemical Society.

Using sulfur isotope fractionation to understand the atmospheric oxidation of SO 2

Sulfate aerosol plays an important but uncertain role in cloud formation and radiative forcing of the climate, and is also important for acid deposition and human health. The oxidation of SO2 to sulfate is a key reaction in determining the impact of sulfate in the environment through its effect on aerosol size distribution and composition. This thesis presents a laboratory investigation of sulfur isotope fractionation during SO2 oxidation by the most important gas-phase and heterogeneous pathways occurring in the atmosphere. The fractionation factors are then used to examine the role of sulfate formation in cloud processing of aerosol particles during the HCCT campaign in Thuringia, central Germany. The fractionation factor for the oxidation of SO2 by ·OH radicals was measured by reacting SO2 gas, with a known initial isotopic composition, with ·OH radicals generated from the photolysis of water at -25, 0, 19 and 40°C (Chapter 2). The product sulfate and the residual SO2 were collected as BaSO4 and the sulfur isotopic compositions measured with the Cameca NanoSIMS 50. The measured fractionation factor for 34S/32S during gas phase oxidation is αOH = (1.0089 ± 0.0007) − ((4 ± 5) × 10−5 )T (°C). Fractionation during oxidation by major aqueous pathways was measured by bubbling the SO2 gas through a solution of H2 O2

SO(2,1)-Invariant Double Integral Transforms and Formulas for the Whittaker Functions

MSC 2010: 33C15, 33C05, 33C45, 65R10, 20C40

A monoidal algebraic model for rational SO(2)-spectra

The category of rational SO(2)--equivariant spectra admits an algebraic model. That is, there is an abelian category A(SO(2)) whose derived category is equivalent to the homotopy category of rational$SO(2)--equivariant spectra. An important question is: does this algebraic model capture the smash product of spectra? The category A(SO(2)) is known as Greenlees' standard model, it is an abelian category that has no projective objects and is constructed from modules over a non--Noetherian ring. As a consequence, the standard techniques for constructing a monoidal model structure cannot be applied. In this paper a monoidal model structure on A(SO(2)) is constructed and the derived tensor product on the homotopy category is shown to be compatible with the smash product of spectra. The method used is related to techniques developed by the author in earlier joint work with Roitzheim. That work constructed a monoidal model structure on Franke's exotic model for the K_(p)--local stable homotopy category. A monoidal Quillen equivalence to a simpler monoidal model category that has explicit generating sets is also given. Having monoidal model structures on the two categories removes a serious obstruction to constructing a series of monoidal Quillen equivalences between the algebraic model and rational SO(2)--equivariant spectra.