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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Effect of oxygen vacancy on half metallicity in Ni-doped CeO{sub 2} diluted magnetic semiconductor

The electronic and magnetic properties of Ni-doped CeO{sub 2} diluted amgentic semiconductor (DMS) including the effect of oxygen vacancy (V{sub o}) with doping concentration, x = 0.125 have been calculated using FPLAPW method based on Density Functional Theory (DFT) as implemented in WIEN2k. In the present supercell approach, the XC potential was constructed using GGA+U formalism in which Coulomb correction is applied to standard GGA functional within the parameterization of Perdew-Burke-Ernzerhof (PBE). We have found that the ground state properties of bulk CeO{sub 2} compound have been modified significantly due to the substitution of Ni-dopant at the cation (Ce) site with/without V{sub O} and realized that the ferromagnetism in CeO{sub 2} remarkably depends on the V{sub o} concentrations. The presence of V{sub o}, in Ni-doped CeO{sub 2}, can leads to strong ferromagnetic coupling between the nearest neighboring Ni-ions and induces a HMF in this compound. Such ferromagnetic exchange coupling is mainly attributed to spin splitting of Ni-d states, via electrons trapped in V{sub o}. The HMF characteristics of Ni-doped CeO{sub 2} including V{sub o} makes it an ideal material for spintronic devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Electroluminescence from metal-oxide-semiconductor devices with erbium-doped CeO{sub 2} films on silicon

We report on erbium (Er)-related electroluminescence (EL) in the visible and near-infrared (NIR) from metal-oxide-semiconductor (MOS) devices with Er-doped CeO{sub 2} (CeO{sub 2}:Er) films on silicon. The onset voltage of such EL under either forward or reverse bias is smaller than 10 V. Moreover, the EL quenching can be avoidable for the CeO{sub 2}:Er-based MOS devices. Analysis on the current-voltage characteristic of the device indicates that the electron transportation at the EL-enabling voltages under either forward or reverse bias is dominated by trap-assisted tunneling mechanism. Namely, electrons in n{sup +}-Si/ITO can tunnel into the conduction band of CeO{sub 2} host via defect states at sufficiently high forward/reverse bias voltages. Then, a fraction of such electrons are accelerated by electric field to become hot electrons, which impact-excite the Er{sup 3+} ions, thus leading to characteristic emissions. It is believed that this work has laid the foundation for developing viable silicon-based emitters using CeO{sub 2}:Er films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Structural and growth aspects of electron beam physical vapor deposited NiO-CeO{sub 2} nanocomposite films

Deposition of composite materials as thin film by electron beam physical vapor deposition technique (EB-PVD) still remains as a challenge. Here, the authors report the deposition of NiO-CeO{sub 2} (30/70 wt. %) composites on quartz substrate by EB-PVD. Two NiO-CeO{sub 2} nanocomposite targets—one as green compact and the other after sintering at 1250 °C—were used for the deposition. Though the targets varied with respect to physical properties such as crystallite size (11–45 nm) and relative density (44% and 96%), the resultant thin films exhibited a mean crystallite size in the range of 20–25 nm underlining the role of physical nature of deposition. In spite of the crystalline nature of the targets and similar elemental concentration, a transformation from amorphous to crystalline structure was observed in thin films on using sintered target. Postannealing of the as deposited film at 800 °C resulted in a polycrystalline structure consisting of CeO{sub 2} and NiO. Deposition using pure CeO{sub 2} or NiO as target resulted in the preferential orientation toward (111) and (200) planes, respectively, showing the influence of adatoms on the evaporation and growth process of NiO-CeO{sub 2} composite. The results demonstrate the influence of electron beam gun power on the adatom energy for the growth process of composite oxide thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

(U) Equation of State and Compaction Modeling for CeO 2

Recent efforts have focused on developing a solid-liquid and three-phase equation of state (EOS) for CeO 2 , while parallel experimental efforts have focused on obtaining high-fidelity Hugoniot measurements on CeO 2 in the porous state. The current work examines the robustness of two CeO 2 SESAME equations of state, a solid-liquid EOS, 96170, and a three-phase EOS, 96171, by validating the EOS against a suite of high-pressure shock compression experiments on initially porous CeO 2 . At lower pressures compaction is considered by incorporating a two-term exponential form of the P-compaction model, using three separate definitions for α(P). Simulations are executed spanning the partially compacted and fully compacted EOS regimes over the pressure range 0.5 - 109 GPa. Comparison of calculated Hugoniot results with those obtained experimentally indicate good agreement for all definitions of α(P) with both the solid-liquid and three-phase EOS in the low-pressure compaction regime. At higher pressures the three-phase EOS does a better job at predicting the measured Hugoniot response, though at the highest pressures EOS 96171 predicts a less compliant response than is observed experimentally. Measured material velocity profiles of the shock-wave after it has transmitted through the powder are also compared with those simulated using with solid-liquid and three-phase EOS. Profiles lend insight into limits of the current experimental design, as well as the threshold conditions for the shock-induced phase transition in CeO 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis and Characterization of Silicon Carbide Ceramic Composites with CeO 2 Powder

This study pioneers the fabrication and characterization of silicon carbide (SiC) containing cerium dioxide (CeO 2 ). CeO 2 powder was tested as a surrogate for actinide oxide waste forms such as uranium dioxide (UO 2 ) and plutonium dioxide (PuO 2 ). Several syntheses were evaluated with varying amounts of preceramic polymer (SMP-10 resin) and CeO 2 containing either SiC fiber, carbon fiber, or no fibers. Scanning electron microscopy (SEM) was used to characterize morphology and compositional differences, and energy-dispersive x-ray spectroscopy (EDS) was used to provide semiquantitative elemental analysis. In addition, each sample was characterized by density, powder x-ray diffraction (pXRD), and Raman spectroscopy. Samples containing nearly more than four times CeO 2 powder than SMP-10 resin by mass had the best properties. This research establishes a unique synthesis for SiC containing high concentrations of CeO 2 powder to illustrate how it may be managed as a potential waste form.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1992

New developments in the coordination of Earth observation from space activities: The role of the Committee on Earth Observations Satellites (CEOS)

The Committee on Earth Observations Satellites (CEOS) is outlined and the dynamics of the expanded CEOS with its increased focus on activities related to global climate change are examined. The participation of affiliate organizations at the Dec. 1991 Plenary is highlighted. The roles and current activities of constituted CEOS Working Groups on Data and on Sensor Calibration and Performance Validation are examined. The status of CEOS deliberations in Earth observation data policy is examined. The expanded CEOS is believed to be well suited to carry forward and help further the legacy already well established in the myriad of Earth observation activities associated with the 1992 International Space Year.

Smith, B.↗
NASA NTRS1998

Remote Sensing Education and Development Countries: Multilateral Efforts through the Committee on Earth Observation Satellites (CEOS)

The Committee on Earth Observation Satellites (CEOS) is an international organization which coordinates space-based Earth observations world wide. Created in 1984, CEOS now comprises 38 national space agencies, regional organizations and international space-related and research groups. The aim of CEOS is to achieve international coordination in the planning of satellite missions for Earth observation and to maximize the utilization of data from these missions world-wide. With regard to developing countries, the fundamental aim of CEOS is to encourage the creation and maintenance of indigenous capability that is integrated into the local decision-making process, thereby enabling developing countries to obtain the maximum benefit from Earth observation. Obtaining adequate access to remote sensing information is difficult for developing countries and students and teachers alike. High unit data prices, the specialized nature of the technology , difficulty in locating specific data, complexities of copyright provisions, the emphasis on "leading edge" technology and research, and the lack of training materials relating to readily understood application are frequently noted obstacles. CEOS has developed an education CD-ROM which is aimed at increasing the integration of space-based data into school curricula, meeting the heretofore unsatisfied needs of developing countries for information about Earth observation application, data sources and future plans; and raising awareness around the world of the value of Earth observation data from space. The CD-ROM is designed to be used with an Internet web browser, increasing the information available to the user, but it can also be used on a stand-alone machine. It contains suggested lesson plans and additional resources for educators and users in developing countries.

Charles, Leslie Bermann↗
DOE OSTI2016

High thermal stability of La 2 O 3 and CeO 2 -stabilized tetragonal ZrO 2

Catalyst support materials of tetragonal ZrO 2 , stabilized by either La 2 O 3 (La 2 O 3 -ZrO 2 ) or CeO 2 (CeO 2 -ZrO 2 ), were synthesized under hydrothermal conditions at 200 °C with NH 4 OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La 2 O 3 -ZrO 2 and CeO 2 -ZrO 2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m 2 /g. The catalysts Pt/La 2 O 3 -ZrO 2 and Pt/CeO 2 -ZrO 2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %. Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La 2 O 3 and CeO 2 into the t-ZrO 2 structure did not affect the nature of the active sites for the Pt/ZrO 2 catalysts for the water-gas-shift (WGS) reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Surface-structure sensitivity of CeO 2 nanocrystals in photocatalysis and enhancing the reactivity with nanogold

Structure–function correlations are a central theme in heterogeneous (photo)catalysis. In this research, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO 2 nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO 2 NCs predominantly expose the {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of the {100} facet is nearly O-terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. The surface of CeO 2 NRs is highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO2 nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} >> {100}. The underlying surface-structure sensitivity can be attributed to the variation in low-coordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) are deposited on CeO 2 NRs to form Au/CeO 2 plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size- and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity are discussed, highlighting the crucial role of photoexcited charge carrier transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Methane Catalytic Combustion over Hierarchical Pd@CeO 2 /Si‐Al 2 O 3 : Effect of the Presence of Water

Abstract The influence of water vapor on methane catalytic combustion was studied over a Pd@CeO 2 /Si‐Al 2 O 3 catalyst, carefully designed to maximize Pd‐CeO 2 interaction and prevent metal sintering and compared to a conventional impregnated catalyst with identical chemical composition. Although the nanostructured Pd@CeO 2 /Si‐Al 2 O 3 catalyst is thermally stable, the addition of water to the reaction feed leads to a transient deactivation at low temperatures, consistent with the well documented competitive adsorption. In addition to this, the hierarchically structured catalyst exhibits an additional severe deactivation after methane oxidation in the presence of water vapor at 600 °C that can be reversed only by heating the catalyst above 700 °C. The presence of water in the reaction feed deactivates the conventional impregnated catalyst less severely and the activity largely returns upon water removal. Catalytic FTIR and CO‐chemisorption data indicate that this severe deactivation process in the hierarchical catalyst is due to the formation of stable OH groups on the surface of the ceria nanoparticles. These hydroxyl groups are suggested to significantly inhibit the oxygen spillover from the CeO 2 nanoparticles to Pd, preventing its efficient re‐oxidation, as observed by operando X‐ray absorption near edge spectroscopy (XANES) experiments. At the same time, their presence can contribute to limit the gas phase accessibility of Pd, as indicated by the decrease of CO chemisorption capability. The presence of hydroxyls plays a minor role on the deactivation of the conventional catalyst at 600 °C.

Monai, Matteo↗
DOE OSTI2018

Morphology-Tuneable Synthesis and Magnetic Performances of CeO{sub 2} Hollow Nanospheres Fabricated by a Simple Template-Free Hydrothermal Method

The large-scale uniform CeO{sub 2} hollow nanospheres with a diameter of about 200–300 nm were fabricated by a facile template-free hydrothermal method using Ce(NO{sub 3}){sub 3} ⋅6H{sub 2}O as cerium source, NH{sub 4}HCO{sub 3} as precipitator, and ethanediamine as surfactant. X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and Raman spectrum showed that the CeO{sub 2} hollow nanospheres with no crystalline impurity phase have a cubic fluorite structure, and many Ce{sup 3+} ions and oxygen vacancies exist in its surface. The magnetic measurements show that the CeO{sub 2} hollow nanospheres have excellent room temperature ferromagnetism while its precursors exhibit paramagnetism The dominating influences on RTFM may be assigned to the morphology and size of obtained CeO{sub 2} samples.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Theoretical investigation of dephosphorylation of phosphate monoesters on CeO 2 (111)

The dephosphorylation of neutral model phosphate monoesters on CeO 2 (111), including para -nitrophenyl phosphate and methyl phosphate, has been studied theoretically using self-consistent, periodic density functional theory calculations at the GGA+U-PW91 level. These phosphate monoesters interact strongly with CeO 2 (111) by forming a bond between the P atom and a surface lattice O atom. A surface-assisted hydrolysis mechanism is proposed for the catalytic dephosphorylation of the phosphate monoesters on CeO 2 (111), which involves P-O ester bond scission followed by phosphate hydration and product desorption. The energies of the transition states for the P-O ester bond scission are found to follow a linear scaling relation with respect to the energies of the dissociated fragments reasonably well. A nearly spontaneous transfer of one of the H atoms on the phosphate group to the alkoxide group produces the corresponding alcohol. The hydration of the remaining HPO 3 group has a maximum activation energy of ca. 1.1 eV in vacuo. So, although the nature of the alkoxide group affects the activation of the P-O ester bond, it should not affect the overall catalytic activity of CeO 2 (111) for dephosphorylation because the hydration of the phosphate group is rate-limiting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Highly efficient Pt catalyst on newly designed CeO 2 -ZrO 2 -Al 2 O 3 support for catalytic removal of pollutants from vehicle exhaust

Pt-CeO 2 catalysts have been widely studied for the vehicle emission control. Designing novel CeO 2 based supports with improved physical-chemical properties has become a research hotspot to further promote the catalytic performance and stability of Pt-CeO 2 catalysts. In this work, through utilizing a unique, two-step incipient wetness impregnation (T-IWI) method for ceria-zirconia-alumina (CZA-T) support preparation, a Pt single site catalyst (Pt/CZA-T) with excellent thermal stability was synthesized. Higher oxidation activity and Oxygen storage capacity (OSC) were achieved on activated Pt/CZA-T, comparing to Pt catalysts on regular CeO 2 /Al 2 O 3 (Pt/CA) and one-step prepared CeZrO x /Al 2 O 3 (Pt/CZA). Via the modification of hydrophilic/hydrophobic properties of γ-Al 2 O 3 by this unique T-IWI method, finer Ce 0.9 Zr 0.1 O 2 particles with higher density of surface defects were formed on CZA-T, on which a higher Pt dispersion and stronger Pt-O-Ce interaction were achieved. Upon activation, smaller, well-dispersed Pt clusters on CZA-T were generated. It was concluded that the CO oxidation performance and OSC were highly related to the size of Pt clusters on different supports that we have developed. Finally, more Pt sites located at Pt cluster-CeZrO x interfaces, which were the real active sites, were responsible for the highest OSC function and CO oxidation activity of activated Pt/CZA-T catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Reverse micelles directed synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides and investigation of their crystal structure and morphology

The synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides based on the sol-gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption. The brannerite-type CeTi{sub 2}O{sub 6} crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO{sub 2} and anatase TiO{sub 2} for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO{sub 2} anatase, rutile and cubic CeO{sub 2} appear. In these mixtures TiO{sub 2} rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data. The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character. - Graphical abstract: The phase composition of Ti90--Ce10 and Ti50--Ce50 oxide mixtures as a function of annealing temperature. The amount of the amorphous phase was estimated and attributed to TiO{sub 2}. Highlights: Black-Right-Pointing-Pointer Ti/Ce oxides were prepared using reverse micelles of Triton X-114. Black-Right-Pointing-Pointer Crystallization of TiO{sub 2}, CeO{sub 2} or CeTi{sub 2}O{sub 6} depends on Ti:Ce molar ratio. Black-Right-Pointing-Pointer Amorphous phase attributed to TiO{sub 2} was identified. Black-Right-Pointing-Pointer Metal oxides surface area is influenced by the character of present carbon impurities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Influence of oxidizing and reducing pretreatment on the catalytic performance of CeO 2 for CO oxidation

Cerium oxide (CeO 2 ) and ceria-based materials have been extensively investigated as catalyst and support materials for various catalytic reactions, due to higher oxygen storage capacity and excellent redox properties. In the current work, we investigated the impact of pretreatment conditions (e.g., oxidation and reduction) on the physical properties of bulk CeO 2 and catalytic activity for CO oxidation as a model reaction. To understand the physical properties of pretreated CeO 2 catalysts, a suite of complementary characterization techniques, including X-ray diffraction (XRD), surface area analysis (BET), X-ray photoemission spectroscopy (XPS), and Raman spectroscopy, were applied. The results showed that a higher pretreatment temperature led to a decreased specific surface area (SSA), a decrease in oxygen vacancy/defect sites, and increased crystallite size, while surface Ce 3+ /Ce 4+ ratio did not show a specific relationship to the treatment conditions. The 700 °C treated CeO 2 samples under oxidizing and reducing conditions showed higher specific oxidation rate (μmolCO/s/m 2 ) compared to other samples at 280 and 300 °C (or < 15% CO conversion). The CO conversion per total mass of catalysts, however, decreased with increasing temperatures, especially at 700 °C under reducing condition, indicating that the catalytic performance was affected by the physical properties (SSA, oxygen vacancy/defect sites, and crystallite size).

36 MATERIALS SCIENCE↗
DOE OSTI2023

Hydroxyls on CeO 2 Support Promoting CuO/CeO 2 Catalyst for Efficient CO Oxidation and NO Reduction by CO

Transition metal catalysts, such as copper oxide, are more attractive alternatives to noble metal catalysts for emission control due to their higher abundance, lower cost, and excellent catalytic activity. Here, in this study, we report the preparation and application of a novel CuO/CeO 2 catalyst using a hydroxyl-rich Ce(OH) x support for CO oxidation and NO reduction by CO. Compared to the catalyst prepared from a regular CeO 2 support, the new CuO/CeO 2 catalyst prepared from the OH-rich Ce(OH) x (CuO/CeO 2 –OH) showed significantly higher catalytic activity under different testing conditions. The effect of OH species in the CeO 2 support on the catalytic performance and physicochemical properties of the CuO/CeO 2 catalyst was characterized in detail. It is demonstrated that the abundant OH species enhanced the CuO x dispersion on CeO 2 , increased the CuO x –CeO 2 interfaces and surface defects, promoted the oxygen activation and mobility, and boosted the NO adsorption and dissociation on CuO/CeO 2 –OH, thus contributing to its superior catalytic activity for both CO oxidation and NO reduction by CO. These results suggest that the OH-rich Ce(OH) x is a superior support for the preparation of highly efficient metal catalysts for different applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Ni Nanoparticles on CeO 2 (111): Energetics, Electron Transfer, and Structure by Ni Adsorption Calorimetry, Spectroscopies, and Density Functional Theory

The morphology, interfacial bonding energetics and charge transfer of Ni clusters and nanoparticles on slightly-reduced CeO 2-x (111) surfaces at 100 to 300 K have been studied using single crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), Xray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and density functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-reduction (x) of the CeO 2-x (111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO 1.95 (111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidation state, and they bind by ~45 kJ/mol more strongly to step sites than terraces. The measured heat of adsorption versus average particle size on terraces is favorably compared to DFT calculations. The Ce 3d XPS lineshape showed an increase in Ce 3+ /Ce 4+ ratio with Ni coverage, providing the number of electrons donated to the ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both experiments and DFT, and shows large differences between clusters at steps versus terraces. This charge is localized on the interfacial Ni and Ce atoms in their atomic layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni-CeO 2 catalysts for which metal-oxide interactions play a very important role in the activation of O-H and C-H bonds. In conclusion, the changes in these interactions with Ni particle size (metal loading) and the extent of reduction of the ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Ultra-Deep Adsorptive Desulfurization of Light-Irradiated Diesel Fuel over Supported TiO 2 -CeO 2 Adsorbents

This study investigates ultra-deep adsorptive desulfurization (ADS) from light-irradiated diesel fuel over supported TiO 2 –CeO 2 adsorbents. A 30-fold higher desulfurization capacity of 95 mL of fuel per gram of adsorbent (mL-F/g-sorb) or 1.143 mg of sulfur per gram of adsorbent (mg-S/g-sorb) was achieved from light-irradiated fuel over the original low-sulfur fuel containing about 15 ppm by weight (ppmw) of sulfur. The sulfur species on spent TiO 2 –CeO 2 /MCM-48 adsorbent was identified by sulfur K-edge XANES as sulfones and the adsorption selectivity to different compounds tested in a model fuel decreases in the order of indole > dibenzothiophenesulfone → dibenzothiophene > 4-methyldibenzothiophene > benzothiophene > 4,6-dimethyldibenzothiophene > phenanthrene > 2-methylnaphthalene ~ fluorene > naphthalene. The results suggest that during ADS of light-irradiated fuel, the original sulfur species were chemically transformed to sulfones, resulting in the significant increase in desulfurization capacity. For different supports for TiO2–CeO2 oxides, the ADS capacity increases with a decrease in the point of zero charge (PZC) value; for silica-supported TiO 2 –CeO 2 oxides (the lowest PZC value of 2–4) with different surface areas, the ADS capacity increases monotonically with increasing surface area. The supported TiO 2 –CeO 2 /MCM-48 adsorbent can be regenerated using oxidative air treatment. The present study provides an attractive new path to achieve ultraclean fuel more effectively.

Xiao, Jing↗