An overview of new approaches to deep desulfurization for ultra-clean gasoline, diesel fuel and jet fuel

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

This paper is a selective review on design approaches and associated catalysis and chemistry for deep desulfurization and deep dearomatization (hydrogenation) of hydrocarbon fuels, particularly diesel fuels. The challenge for deep desulfurization of diesel fuels is the difficulty of removing the refractory sulfur compounds, particularly 4,6-dimethyldibenzothiophene, with conventional hydrodesulfurization processes. The problem is exacerbated by the inhibiting effect of polyaromatics and nitrogen compounds, which exist in some diesel blend stocks on deep HDS. With the new Environmental Protection Agency (EPA) Tier II regulations to cut the diesel sulfur from current 500 ppmw down to 15 ppmw by June 2006, refineries are facing major challenges to meet the fuel sulfur specification along with the required reduction of aromatics contents. The principles and problems for the existing hydrodesulfurization processes, and the concepts, advantages and disadvantages of various new approaches will be discussed. Specifically, the following new design approaches for sulfur removal will be discussed: (1) novel catalysts for ultra-deep hydrodesulfurization under conventional HDS process conditions; (2) new design concept for sulfur-tolerant noble metal catalysts for low-temperature hydrogenation; (3) new desulfurization process by sulfur adsorption and capture under H2; (4) new desulfurization process by selective adsorption at ambient temperature without H2 and a related integrated process concept; (5) oxidative desulfurization in liquid-phase; and (6) biodesulfurization.

New design approaches to ultra-clean diesel fuels by deep desulfurization and deep dearomatization

Traditional chemical, physical and biological processes for treating wastewater containing textile dye have such disadvantages as high cost, high energy requirement and generation of secondary pollution during treatment process. The advanced oxidation processes technology has been attracting growing attention for the decomposition of organic dyes. Such processes are based on the light-enhanced generation of highly reactive hydroxyl radicals, which oxidize the organic matter in solution and convert it completely into water, CO2 and inorganic compounds. In this presentation, the photocatalytic degradation of dyes in aqueous solution using TiO2 as photocatalyst under solar and UV irradiation has been reviewed. It is observed that the degradation of dyes depends on several parameters such as pH, catalyst concentration, substrate concentration and the presence of oxidants. Reaction temperature and the intensity of light also affect the degradation of dyes. Particle size, BET-surface area and different mineral forms of TiO2 also have influence on the degradation rate.

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Parameters affecting the photocatalytic degradation of dyes using TiO2: a review

The need for lighter, thinner, and smaller products makes lithium ion batteries popular power sources for applications such as mobile phones, laptop computers, digital cameras, electric vehicles, and hybrid electric vehicles. For high power applications, the development of high capacity and high voltage electrode materials is in progress. Battery performance and safety issues are also related to the properties of the electrolytes used. To improve the properties of the electrolytes, small amounts of other components, known as electrolyte additives, are incorporated. This paper reviews the recent progress in electrolyte additives used to improve performance and other properties, such as safety. This review classifies the additives based on their functions and their effects on specific electrode materials focusing on electrodes under current development. From anodes: carbonaceous electrodes, silicon, tin and Li4Ti5O12; from layered cathodes: LiCoO2, Li-rich and LiNiyMnyCo1−2yO2 (NMC); from spinel: LiMn2O4, and from olivine: LiFePO4 are selected. We believe that this approach will help readers easily identify and understand the additives suitable for their target materials.

Electrolyte additives for lithium ion battery electrodes: progress and perspectives

The catalytic performances of supported gold nanoparticles depend critically on the nature of support. Here, we report the first evidence of strong metal-support interactions (SMSI) between gold nanoparticles and ZnO nanorods based on results of structural and spectroscopic characterization. The catalyst shows encapsulation of gold nanoparticles by ZnO and the electron transfer between gold and the support. Detailed characterizations of the interaction between Au nanoparticles and ZnO were done with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR), and FTIR study of adsorbed CO. The significance of the SMSI effect is further investigated by probing the efficiency of CO oxidation over the Au/ZnO-nanorod. In contrast to the classical reductive SMSI in the TiO(2) supported group VIII metals which appears after high temperature reduction in H(2) with electron transfer from the support to metals, the oxidative SMSI in Au/ZnO-nanorod system gives oxygen-induced burial and electron transfer from gold to support. In CO oxidation, we found that the oxidative SMSI state is associated with positively charged gold nanoparticles with strong effect on its catalytic activity before and after encapsulation. The oxidative SMSI can be reversed by hydrogen treatment to induce AuZn alloy formation, de-encapsulation, and electron transfer from support to Au. Our discovery of the SMSI effects in Au/ZnO nanorods gives new understandings of the interaction between gold and support and provides new way to control the interaction between gold and the support as well as catalytic activity.

Strong metal-support interactions between gold nanoparticles and ZnO nanorods in CO oxidation.

The operating conditions of SRE (steam reforming of ethanol) reaction were evaluated by thermodynamics, in considering of the application requirements in hydrogen concentration and energy consumption. Under the select operating conditions, 5% CuNi/SiO 2 catalysts with different Cu/Ni ratios prepared through incipient-wetness co-impregnation were tested for SRE. The catalysts were reduced with NaBH 4 at room temperature, and again reduced by H 2 at 623 K prior to temperature-programmed SRE testing to remove surface oxygen. The SRE reaction products indicate a reaction scheme involving ethanol dehydrogenation to acetaldehyde, wherein acetaldehyde steam reforming and acetaldehyde decomposition compete, and with subsequent CO conversion to CO 2 via water gas shift reaction. The catalysts with Cu/Ni ≥ 1 showed higher ethanol conversion, higher acetaldehyde conversion, higher selectivity of acetaldehyde steam reforming, and lower coking at temperatures below 673 K than the Ni-rich catalysts. Analyses by XRD, XPS, and EXAFS indicate that the Cu-rich catalysts had formed an alloy structure with Ni-enriched surface. The catalyst with Cu/Ni = 1 showed the highest performance in ethanol conversion, acetaldehyde conversion, the selectivity of acetaldehyde steam reforming, and the stability against particle sintering.

The ethanol steam reforming over Cu-Ni/SiO2 catalysts: Effect of Cu/Ni ratio

Noble metal catalysts for low-temperature naphthalene hydrogenation in the presence of benzothiophene

The hydrogenation of aromatic and polyaromatic compounds are typically exothermic; therefore, a lower reaction temperature is thermodynamically favorable. However, in considering the hydrotreating process of heavy liquids where polycyclic aromatic compounds are abundant, a reaction temperature above 623K is typical which consequently requires a high concentration of hydrogen to offset the limitation of thermodynamic equilibrium conversion. Noble metal catalysts are active for the hydrogenation of aromatics even at a temperature below 473K, but they were not used for hydrotreating purpose owing to the cost and their susceptibility to the poisoning by sulfur-containing compounds. However, recent studies showed that noble metal catalysts may not be as sensitive to sulfur as what has been recognized. This study is therefore attempted to probe the possibility of using noble metal catalysts for low-temperature hydrotreating reaction in the presence of sulfur-containing compounds, and the model reaction of naphthalene hydrogenation in the presence of benzothiophene was used.

A space-confined synthesis method, using a mesoporous template that produces nano-sized copper (∼3.6 nm crystal size) by the thermal hydrogen reduction (THR) of spinel CuFe 2 O 4 nano-crystals, that have a high surface area ∼126 m 2 /g, (c.f. commonly cited literature values 2 /g) and a rod-like morphology, is described. In situ XRD and temperature program reduction (TPR) results showed that the generation of the copper nanoparticles occurred at 210 °C, which is lower than other reported literature values—due to the fine crystal size of the spinel CuFe 2 O 4 . The generated copper nanoparticles were also characterized by XANES, and FT-EXAFS. We have used the steam reforming of methanol (SRM) as a model reaction to demonstrate the capability of the materials formed in which a 100% conversion of methanol by steam reforming was achieved at approximately 240 °C. The proposed synthesis method combines metallurgy and THR while at the same time effectively resolving issues related to the large crystal sizes, higher calcinations temperature (above 750 °C) and low surface areas (below 10 m 2 /g), that commonly occur in conventional solid state methods. The mixed metal oxide synthesis method, using a mesoporous template, can also be applied to other heterogeneous metal oxide systems.

Shawn D. Lin

Papers

Strong metal-support interactions between gold nanoparticles and ZnO nanorods in CO oxidation.

The ethanol steam reforming over Cu-Ni/SiO2 catalysts: Effect of Cu/Ni ratio

Noble metal catalysts for low-temperature naphthalene hydrogenation in the presence of benzothiophene

Noble metal catalysts for low-temperature naphthalene hydrogenation in the presence of benzothiophene

Preparation of nano-sized Cu from a rod-like CuFe2O4: Suitable for high performance catalytic applications