Narrow Results

The evolution of microstructure of cerium oxide nanoparticles prepared in a sol-gel process was investigated by small-angle X-ray scattering (SAXS) measurements, in which the range of annealing temperature was from 298 K to 973 K in air. It was found that their scattering intensities increased dramatically and was proportional to h^-a as the temperature went up to 873 K. Meanwhile, the average radius of gyration R_g, increased. This suggested that these cerium oxide nanoparticles have self-similar structure behavior or mass fractal structure. When the temperature was higher than 873 K, the feature of the SAXS spectra became identical to that of the sactterers with surface fractal structure rather than the mass fractal structure.

Cerium oxides (CeO₂) were synthesized by two steps solvothermal routes. First, a precursor was precipitated using solutions of cerium (III) nitrate and ammonia, and then this precursor was treated via solvothermal techniques in an autoclave. Narrow distribution of CeO₂ particle size, between 10 to 15 nm, was achieved in different solvents. Hard agglomerates of nano-CeO₂ were mitigated in an ethanol solvent. Most of crystal particles were in the shape of a quadrangle for the precursor. Morphology of CeO₂ particles gradually changed after the precursor was treated by solvothermal techniques. There were both quadrangular and symmetrically hexagonal particles at an alkaline pH value. Alternatively, the quadrangular particles disappeared, instead of geometrically unsymmetrical hexagon with decreasing pH to a more acid value. The evolution mechanism of the morphology was discussed. These results have important implications for recognizing and controlling the crystalline shape by solvothermal techniques.

The kinetic behavior of gas phase mercury sorption on ZSM-5 supported cerium- and lanthanum-based composite oxides in the temperature range of 120–240^∘C is investigated. The Hg⁰ sorption abilities all first increase and then decrease with the elevation of the temperatures, the cerium-based composite oxides show better Hg⁰ sorption abilities than that of the lanthanum-based composite oxides. CeO₂–Mn₂O₃/ZSM-5 performs the best Hg⁰ sorption ability with Hg⁰ removal efficiency of nearly 100% at 180^∘C. Doping Cu or Mn into La₂O₃ lattice causes the decrease in the Hg⁰ removal efficiency of the lanthanum-based composite oxides due to the formation of perovskite or perovskite-like compounds. The sorption of elemental mercury over metal oxides is governed both by diffusion processes as well as chemical reactions, and the sorption of elemental mercury on the cerium- and lanthanum-based composite oxides are chemisorption processes.

The increase in demand for petroleum fuels attracted the attention of the research community to identify a control measure for petroleum source depletion. On the other hand, the heavy usage and burning of petroleum products cause environmental pollutants like oxides of nitrogen, carbon monoxide, hydrocarbons, etc. Therefore, it is important to control all the problems caused by the increasing use of petroleum products, such as diesel, petrol, Kerosene, fuel oil, etc. This investigation aims to reduce the usage of fossil-based petroleum diesel by producing an effective substitute bio-diesel from Juliflora seeds, which exhibit similar properties to diesel. Furthermore, the operational and emission behaviors of the biodiesel in the Reactive Controlled Compression Ignition (RCCI) engine are analyzed by including nanoadditives such as ZnO, ${\mathrm{\text{Al}}}_2{\mathrm{\text{O}}}_3$ and ${\mathrm{\text{CeO}}}_2$. Furthermore, the obtained performance and emission results are optimized using a hybrid deep neural network (DNN) using the Aquila optimization algorithm (AOA). The algorithm chooses the diesel-biodiesel blend with 75 ppm of alumina nanoparticle as the optimum blend. This considered blend provided better performance and emission results at 72.86% loading condition. The obtained results are 28.19% for brake thermal efficiency (BTE), 446.14 g/kWh for brake-specific fuel consumption, 0.105% for carbon monoxide emission, 19.82 ppm of unburnt hydrocarbon, 457 ppm of NO${}_x$ emission and 21.98% of smoke emission.

In this study, the synthesis of a cerium oxide nanoparticle was carried out from Acalypha indica leaf extract. The synthesized nanoparticle was characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) and Transmission Electron Microscope (TEM) for structural confirmation. The studies clearly indicate that the synthesized CeO₂ nanoparticle is a crystalline material with particle size between 25–30 nm. Further analysis was carried out by Fourier Transform infrared spectroscopy (FT-IR), to provide evidence for the presence of Ce-O-Ce asymmetry stretching of the CeO₂ nanoparticle. Thermo Gravimetric and Differential Scanning Calorimetry analyses gave the thermal properties of cerium oxide nanoparticles. Antibacterial studies were conducted using the synthesized CeO₂. This result showed increasing rate of antibacterial behavior with gram positive and gram negative bacteria.

The present work was addressed to study the visible light induced performance as photocatalysts of mesoporous N_yTi_1–xCe_xO_2–y structures obtained under microwave irradiation. The titanium dioxide (TiO₂) was doped with cerium and nitrogen in order to improve the quantum efficiency of the TiO₂ and to shift its adsorption spectra to the visible region. The prepared meso-powders were analyzed by means of X-ray diffraction (XRD), scanning Electron microscopy (SEM), infrared (IR) spectroscopy, transmission electronic microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The surface area was evaluated by means of the Brunauer-Emmett-Teller (BET) method and ultraviolet (UV)-visible diffuse reflectance measurements were performed in order to determine the band gap energy. In addition, the photocatalytic activity of the samples was evaluated by monitoring the photodegradation of methylene blue (MB) under UV and visible light energy irradiation. The results show that our methodology is an effective way for incorporating cerium and nitrogen into TiO₂ compound, which in turn, increases its photocatalytic activity. The diffuse reflectance analysis confirms that the absorption edge was shifted towards the visible region of the optical spectrum. The XRD diffraction patterns indicate homogeneous solid solutions in which prevails the anatase phase. It was observed a reduction in crystal size from 13.1 nm to 7.7 nm for N_yTi_0.98Ce_0.02O_2–y in comparison to TiO₂. The textural properties of the synthesized compounds were determined, by means of adsorption isotherms indicating the formation of mesoporous structures. IR spectra show characteristic vibration signals attributed to Ti–O–Ti bonds, as well as vibrations assigned to cerium and nitrogen bonds. The XPS analyses evidence the presence of Ce³⁺/Ce⁴⁺ redox couple and Ti–N bonds. The photocatalityc efficiency was evaluated in the degradation of MB monitoring the absorbance change at 664 nm. The degradation of this compound was 91.4% using N_yTi_0.98Ce_0.02O_2–y as photocatalyst under UV energy in 90 min. Also 38.7% of MB degradation was achieved in 150 min under visible light radiation.

Europium (3%) doped ceria nanoparticles were successfully prepared by 72 h hydrolysis assisted co-precipitation method. The average grain size of the as-prepared sample was 11 nm. The grain sizes were 12 and 18 nm for samples annealed at 500°C and 800°C respectively. The grain size effect on optical bandgap is investigated from diffuse reflectance spectroscopy (DRS). The orange and red color emissions of europium doped ceria nanoparticles were investigated by photoluminescence (PL) spectra under excitation of 330 nm. The high intense orange emission peak was found at 591 nm for as-prepared and annealed nanoparticles. This is the characteristic peak of the Eu³⁺ ion corresponding to the parity allowed magnetic dipole transition between the ⁵D₀–⁷F₁ states. Site occupancy of europium ions was estimated by Red (R)/Orange (O) intensity ratio using PL spectrum.

The hybrid nanomaterials of platinum/cerium oxide/multi-walled carbon nanotubes (Pt/CeO₂/MWCNTs) are synthesized successfully via impregnation and polyol processes. MWCNTs serve as an excellent supporter where CeO₂ nanoparticles are decorated with well-distributed Pt nanoparticles. Images show the average particle size of crystalline Pt and CeO₂ on MWCNTs are 3–7 and 20–30 nm, respectively. In electrochemical reaction, the redox peak of Pt/CeO₂-700°C/MWCNTs reveals lower potential and higher current density in methanol electro-oxidation than those of other Pt-based ones. The study indicates that the cerium oxide in Pt/CeO₂-700°C/MWCNTs catalyst will enhance significantly the oxygen ions transportation between the interface of Pt and MWCNTs to eliminate the CO poison effect on Pt catalyst.

The most promising way of CO₂ utilization is its catalytic conversion into valuable products, in particular, the direct hydrogenation of CO₂ on heterogeneous catalysts to obtain such products as synthesis gas, hydrocarbons, alcohols, esters, carboxylic acids, and some other organic molecules. Heterogeneous iron-based catalysts possess a special position among the promising candidates for the synthesis of CO₂-based hydrocarbons. However, individual iron oxide catalysts have a fairly low surface area, which requires their deposition on the support or modification. CeO₂ is rather attractive in catalysis because of its high oxygen storage capacity. The most effective thermal stabilizer of CeO₂ is ZrO₂. In this work, cerium–zirconium systems with various Ce to Zr ratios were synthesized by the method of coprecipitation in the absence and presence of the hexadecyltrimethylammonium bromide template. These systems were characterized by adsorption of N₂, XRD, and DTA-TG-DTG and used as supports for 5% Fe catalysts. The activity of synthesized Fe-containing catalysts was investigated in the reaction of CO₂ hydrogenation. The developed surface and the presence of cerium in the supports are the possible reasons for the high activity of Fe-containing catalysts in the hydrogenation reaction of CO₂.

In this study, the modified polystyrene aldehyde microspheres (PS-CHO) were first prepared via the copolymerization of the styrene and the acrolein, and then PS-CHO@CeO₂ composite microspheres were fabricated through in-situ chemical deposition of CeO₂ nanoparticles. These composite microspheres were used to catalyze the oxidative degradation of methyl orange (MO) by H₂O₂. The morphology of the products was observed by transmission electron microscopy (TEM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the chemical state and structure. Optical absorption and band energy properties were investigated by ultraviolet-visible/near-infrared diffuse reflectance spectra (UV-Vis-NIR). The degradation process was monitored with ultraviolet-visible spectrometer (UV-Vis). The results revealed that when the mass ratio of PS-CHO and cerium nitrate was 1:0.26, highly-uniformed and well-dispersibility PS-CHO@CeO₂ composite microspheres were obtained at pH 8.5 and the concentration of Ce${}^{3+}$ ions was significantly increased compared with commercial CeO₂ NPs. Under ultraviolet light irradiation, the degradation efficiency of MO by PS-CHO@CeO₂ composite microspheres was increased up to 93.03%, which was 1.44 times that of commercial CeO₂ NPs in 120 min. The reiteratively tests further proved that the activity of the composite microspheres maintained unchanged after four cycles. The formation and photocatalytic mechanisms of PS-CHO@CeO₂ composite microspheres were proposed.

Four cerium dioxide (CeO₂) powders with different particle sizes and shapes were prepared via regulating the amount of alkali and hydrothermal temperature. Then twelve 20 wt.% ${\text{CuO}}_x$/${\text{CeO}}_2$ materials were provided by loading the corresponding quantity cupric acetate in the cerium oxide carriers by impregnation method and changing the calcination temperature and atmosphere. These loaded ${\text{CuO}}_x$/${\text{CeO}}_2$ catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), displaying different valence state of copper on the support surface. The catalytic properties of these new materials were examined by using the coupling reaction of cyclohexanone, morpholine and phenylacetylene as a template reaction. It showed that the small-sized rod-like 20wt.% ${\text{CuO}}_x$/${\text{CeO}}_2$-r-8.4-200 material has the best catalytic effect, and the isolation yield of $\alpha$-tert-propargylamine product could reach 75% under the conditions of 10 mg cat, 110${}^{°}$C, 12 h and no solvent. Notably, the catalyst yield was still above 62% after four cycles of experiments, confirming the practical recoverability of the catalyst. Moreover, some examples of $\alpha$-tert-propargylamine derivatives can be obtained in medium isolated yields by replacing morpholine, and/or phenylacetylene. The synthesis mechanisms were discussed. The present results provide a three-component coupling reaction method for synthesizing $\alpha$-tert-propargylamine, which has the advantages of simple post-treatment, solvent-free and reusable catalyst.