Amount Of Cerium Research Articles

Effect of Adding Cerium on Microstructure and Morphology of Ce-Based Inclusions Formed in Low-Carbon Steel

Intra-granular Acicular Ferrite (IAF), as one of the most well-known desirable microstructure of ferrite with a chaotic crystallographic orientation, can not only refine the microstructure and retard the propagation of cleavage crack but also provide excellent combination of strength and toughness in steel. The effect of adding cerium on microstructure and controlling proper cerium-based inclusions in order to improve properties in low-carbon commercial steel (SS400) were investigated. The type of inclusions can be controlled by changing S/O ratio and Ce content. Without Ce modification, MnS is a dominate inclusion. After adding Ce, the stable inclusion phases change from AlCeO3 to Ce2O2S. The optimum amount of cerium, 0.0235 wt.%, lead in proper grain refinement and formation of cerium oxide, oxy-sulfide and sulfide inclusions. Having a high amount of cerium results in increasing the number of inclusions significantly as a result it cannot be effective enough and the inclusions will act like barriers for others. It is found that the inclusions with a size of about 4∼7 μm can serve as heterogeneous nucleation sites for AF formation. Thermodynamic calculations have been applied to predict the inclusion formation in this molten steel as well, which show a good agreement with experimental one.

Ceria-stabilized meso-Al2O3: synthesis, characterization and desorption kinetics

A highly stable mesoporous ceria-doped alumina for steam gasification of biomass was synthesized using a template free method. Aluminum nitrate nonahydrate and cerium nitrate hexahydrate were used as the precursors to synthesize the ceria-doped alumina support by hydrolyzing it with ammonium carbonate. The thermogravimetric analysis indicates that the ceria-doped alumina support was stable up to 750 °C. By varying the amount of Ceria from 0.5 to 1.5 wt%, the structural and physico-chemical properties of the mesoporous support could be tuned. X-ray diffraction patterns showed that the newly prepared stabilized supports (calcined at 750 °C), exhibit γ-phase, while the textural characterization confirmed that all the catalyst supports are indeed mesoporous. The sample containing 1.0 wt% ceria on alumina has the highest post calcination (to 750 °C) surface area of 152 m2/g, pore volume of 0.43 mL/g, total acidity of 6.87 cm3/g, indicating its suitable application in biomass gasification. NH3-desorption kinetics studies revealed that 1.0 wt % Ce containing Ce/Al2O3 sample has higher activation energy for NH3 desorption than bare Al2O3, implying a moderate Ce/Al2O3 matrix interaction and that ceria incorporation will not impair active site availability of the alumina support. Finally, the high oxygen carrying capacity of ceria coupled with the synthesis method, which ensured a high dispersion of ceria in alumina matrix are responsible for the observed thermal stability. The favorable properties of these new alumina supports, can serve them as potential candidates for steam gasification of biomass among other applications, when loaded with the appropriate metal, metal oxide, or an organic functional group.

Activating effect of cerium in hydrotalcite derived Cu\u2013Mg\u2013Al catalysts for selective ammonia oxidation and the selective reduction of NO with ammonia

Hydrotalcite originated mixed metal Cu–Mg–Al oxide system was doped with various amounts of cerium (0.5 or 3.0 wt%) and tested in the role of catalysts for the selective catalytic oxidation of ammonia to dinitrogen (NH3-SCO) and the selective catalytic reduction of NO with ammonia (NH3-SCR). The activating effect of cerium was observed in both studied processes. However, the CeO2 loading is a very important parameter determining catalytic performance of the studied samples. It was shown that an introduction of cerium into Cu–Mg–Al mixed oxide resulted in its significant activation in the low-temperature NH3-SCR process, independently of the CeO2 loading and a decrease in the efficiency of the NO reduction at higher temperatures, which was more significant for the catalyst with the lower cerium content. In the case of the NH3-SCO process, the introduction of cerium into Cu–Mg–Al mixed oxide resulted in the activation of the low temperature reaction, which was more intensive for the catalyst with lower cerium content. These effects were related to the presence of cerium in the form of crystallites of various size and therefore their different reducibility.

Spectrophotometric Microdetermination of Alzheimer’s Drug Memantine HCl in Biological Samples

Three simple, rapid, accurate and precise methods are described for the determination of memantine hydrochloride (MEM) by oxidation with cerium (IV) sulphate. Method (A) is based on the oxidation of the drug by a known excess amount of cerium (IV) sulphate and the unreacted Ce4+ is treated with ammonium ferrous sulphate, and the iron (III) sulphate produced is complexed with thiocyanate and measured at 480 nm. The methods B and C involve the addition of excess Ce4+ and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable λmax 528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable λmax 525 nm for method C. Different variables affecting the reaction between memantine HCl and Ce4+ were studied and optimized. The molar absorptivity and Sandell sensitivity of the procedure were calculated in addition to limits of detection and quantification. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures, which successfully applied to the determination of MEM in bulk drug forms, tablets and spiked human plasma.

RBS Analysis of Down-conversion Layers Comprising Two Rare-Earth Elements

Rutherford Backscattering Spectroscopy (RBS) of samples containing two rare-earth elements is difficult owing to the small mass separation of even the lightest and heaviest members of the group. In studies of the growth of silicon nitride down-conversion layers, compatible with silicon photovoltaic technology, 2-3 MeV RBS has been combined with RBS at 5 MeV and alpha PIXE, to determine the composition of samples grown with different amounts of cerium and ytterbium. The films were produced using reactive magnetron co-sputtering. Conventional RBS at 2.2 MeV is used to determine the nitrogen and oxygen and silicon content of the films. At this energy, elements from carbon upwards have scattering cross-sections determined by the Coulomb potential. However, the cerium and ytterbium peaks at this energy merge into one and make it very difficult to determine the ratio of these elements and the absolute amount of each element. At 5 MeV sufficient separation was achieved between the cerium and ytterbium peaks that their ratio and absolute amount could be measured. At this energy the scattering from these elements is still determined by the Coulomb potential. For all the other elements in the sample the Coulomb barrier has been exceeded such that data from them is unusable. Care also needs to be taken to ensure there is no interference between the rare-earth scattering peaks in the spectrum and products of nuclear reactions from the lower Z-elements.

Rapid synthesis of 2-amino maleonitrile Schiff bases in aqueous media catalyzed by cerium(IV) ammonium nitrate (CAN) and a new method for the one-pot preparation of their dicyano imidazoles (DCI)

A quick and simple method has been developed for the synthesis of 2-amino maleonitrile Schiff bases 3(a–k) through the reaction of 2,3-diaminomaleonitrile (DAMN) and aromatic aldehydes in the presence of catalytic amounts of cerium(IV) ammonium nitrate (CAN) in aqueous media at room temperature. Also, the facile synthesis of 2-aryl-4,5-dicarbonitrile imidazoles 4(a–k) by one-pot condensation of DAMN with various aromatic aldehydes using CAN as efficient reagent in acetonitrile at 50 °C has been described. In this way, the one-pot synthesis of raw materials is presented for the first time. The new synthesized compounds were characterized using IR, 1H NMR, 13C NMR and mass spectroscopy. The present procedure offers several advantages, such as good to excellent yields, the use of an inexpensive and available catalyst, easy and quick isolation of the pure product and short reaction times compared with previous reports.

Investigation on the mechanism of adsorption and desorption behavior in cerium ions modified Y-type zeolite and improved hydrocarbons conversion

AbstractDifferent types of Y zeolites (HY, USY and NaY) containing various amounts of cerium (Ce) were prepared with the method of liquid ion exchange and characterized by X-ray diffraction (XRD), intelligent gravimetric analyzer (IGA), and a molecular simulation technology (grand canonical Monte Carlo simulation, GCMC). A novel calculation method of desorption index (DI) was proposed and the influence of cerium cationic species on the processes of adsorption-desorption of hydrocarbon molecules (n-octane) on the cerium modified Y zeolites (CeY) was studied. The results indicated that Ce ion species played a key role in reducing desorption activation energy of n-octane on Y type zeolites, leading to an improvement of the desorption ability of the CeY and the regulation of the adsorption state of n-octane from aggregation to decentralization. These findings are essential factors for enhancing the product selectivity of light hydrocarbon component and the catalytic activity of rare earth modified Y zeolites (REY) catalysts in fluid catalytic cracking (FCC) process.

3,3-(Butane-1,4-diyl)bis(1,2-dimethyl-1H-imidazole-3-ium)bromide–cerium(IV) ammonium nitrate: A novel reagent for mild synthesis of 12-aryldibenzo[i,b]pyrano[4,3-b]chromenone of benzyl alcohols

A novel and efficient procedure for the synthesis of pyrano[4,3-b]chromene derivatives via three-component condensation reaction of benzyl alcohol, β-naphthol, and 4-hydroxycoumarin using a catalytical amount of cerium(IV) ammonium nitrate (CAN) and a reusable ionic liquid as a catalyst at room temperature is presented. The method provides several advantages such as simple work-up, environmental friendliness and shorter reaction time along with high yields. All synthesized compounds were elucidated by comparison with authentic samples, IR, 1H, and 13C NMR spectroscopy, and elemental analysis.

Application of Cerium (IV) as an Oxidimetric Agent for the Determination of Ethionamide in Pharmaceutical Formulations.

Two simple methods are described for the determination of ethionamide (ETM) in bulk drug and tablets using cerium (IV) sulphate as the oxidimetric agent. In both methods, the sample solution is treated with a measured excess of cerium (IV) solution in H2SO4 medium, and after a fixed standing time, the residual oxidant is determined either by back titration with standard iron (II) solution to a ferroin end point in titrimetry or by reacting with o-dianisidine followed by measurement of the absorbance of the orange-red coloured product at 470 nm in spectrophotometry. In titrimetry, the reaction proceeded with a stoichiometry of 1 : 2 (ETM : Ce (IV)) and the amount of cerium (IV) consumed by ETM was related to the latter's amount, and the method was applicable over 1.0–8.0 mg of drug. In spectrophotometry, Beer's law was obeyed over the concentration range of 0.5–5.0 μg/mL ETM with a molar absorptivity value of 2.66 × 104 L/(mol·cm). The limits of detection (LOD) and quantification (LOQ) calculated according to ICH guidelines were 0.013 and 0.043 μg/mL, respectively. The proposed titrimetric and spectrophotometric methods were found to yield reliable results when applied to bulk drug and tablets analysis, and hence they can be applied in quality control laboratories.

Hydrogen production from steam and oxidative steam reforming of liquefied petroleum gas over cerium and strontium doped LaNiO3 catalysts

This study investigated LaNiO3 doped with small amounts of cerium and strontium as catalyst precursors for LPG steam and oxidative reforming. La1-xCexNiO3 (x=0, 0.05, 0.1) and La1-xSrxNiO3 (x=0, 0.05, 0.1) perovskite-type oxides were prepared by precipitation. The characterization showed that samples doped with cerium had smaller nickel average particle size and higher oxygen storage capacities when compared to the samples containing strontium. All the samples were tested for LPG steam and oxidative steam reforming at 873K. The LPG steam reforming results showed that all catalysts presented strong deactivation. The addition of a small amount of oxygen to the system (oxidative steam reform) leads to better catalytic performance for all samples. The La0.95Ce0.05NiO3 precursor stood out by presenting better performance for hydrogen production in all conditions. These results can be attributed to the presence of ceria and to smaller metallic nickel average crystallite sizes. The results of the in-situ X-ray diffraction analysis indicated that for the sample originated from La0.95Ce0.05NiO3, the reduced form of the material was preserved longer, thus justifying leading to greater stability in reaction conditions. In-situ XANES data collected during steam LPG reforming showed that the samples derived from La0.95Ce0.05NiO3 presented no significant change in the increase of the white line, which, in this case, would characterize the oxidation of the precursors. The same reforming reactions were conducted at higher temperatures using La0.95Ce0.05NiO3 precursor, and the results showed that at higher temperatures it is possible to maintain high activity, with stable hydrogen production.

Characteristics and catalytic behavior of NiAlCe catalysts in the hydrogenation of canola oil: the effect of cerium on cis/trans selectivity

A series of co-precipitated cerium-promoted nickel–aluminum catalysts was prepared. The physicochemical properties of the precursors were analyzed by means of various methods including XRF, HT-XRD, TPR, surface area and thermal decomposition as well as porosity measurements. The activity and selectivity of the NiAlCe catalysts in the hydrogenation reaction of canola oil were investigated and the results compared to those for the cerium-free catalyst. Besides improving some physicochemical properties of the precursors, the addition of cerium significantly improved the cis/trans selectivity, yet at the expense of some loss of the activity in case of larger cerium loadings. Upon addition of a relatively low amount of cerium (0.67 wt%) the content of the C18:1 trans fraction decreased by ca. 35 %. Together with the synergistic effect of the hydrogen pressure a significant decrease of the C18:1 trans fraction by ca. 48 % could be achieved. Furthermore, compared to the cerium-free catalyst, the addition of cerium resulted in a slower drop of the C18:1 cis fraction and a slower increase of the C18:0 fraction in time during the hydrogenation process.

Preferential oxidation of carbon monoxide on Pt/γ-Al2O3 catalyst: Effect of adding ceria and nickel

The effect of adding ceria and nickel to Pt/γ-Al2O3 catalyst was studied for preferential oxidation (PROX) of CO. The catalysts were characterized by XRD, BET, TPR, XRF and H2 chemisorption techniques. An optimum amount of ceria and nickel was required for improving the activity and selectivity. Adding small amount of ceria (1 wt. %) and/or nickel (1 wt. %) improved the activity and selectivity of 1% Pt/γ-Al2O3 catalyst. When 1 wt. % of both the promoters i.e. ceria and nickel were added to 1% Pt/γ-Al2O3 catalyst, a significant improvement was observed in its activity and selectivity. With 1%Pt-1%Ni/1%CeO2/γ-Al2O3 catalyst, complete CO conversion was obtained even at 100 °C for a feed containing 1% CO, 1% O2, 40% H2 and balance N2. This novel catalyst also widened the temperature range of operation for complete CO conversion from 100 to 200 °C and no methanation activity was observed in this temperature range. The high activity and selectivity of this catalyst was most likely due to the formation of bimetallic Pt–Ni phase on the catalyst and higher dispersion of Pt metal on the catalyst as observed from H2 chemisorption.

An efficient multicomponent, one-pot synthesis of Betti bases catalyzed by cerium (IV) ammonium nitrate (CAN) at ambient temperature

Abstract Starting from readily available 2-naphthol, aldehydes, aryl and alkylamines, a variety of Betti bases were efficiently synthesized utilizing a catalytic amount of cerium (IV) ammonium nitrate (CAN) at room temperature. This protocol has advantages of high yield, mild reaction conditions, no environmental pollution, diversity of reactants and simple work up procedure.

Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents.

We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce–Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce–Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns.

Characterization and performance evaluation of Ni-based catalysts with Ce promoter for methane and hydrocarbons steam reforming process

The Ni–Ce/Al steam reforming catalysts with Ni loading 13wt% and Ce loading 0–2.0wt% were prepared to study the effects of cerium addition on the catalytic performance for methane and hydrocarbons steam reforming, combining with characterizations of BET, N2 adsorption/desorption, TPR, H2-chemisorption, XRD, and TEM. The optimal intrinsic activity was achieved over Ni–Ce/Al (1.02wt% Ce) by atmospheric pressure micro-reaction device at steam/methane of 3.0, CH4 space velocity of 10,000h−1 and temperature of 450–750°C. The optimal pressurized activity and stability was also achieved over Ni–Ce/Al (1.02wt% Ce) with the carbon conversion of 75% of the light hydrocarbons at H2O/C of 2.7, carbon space velocity of 6000h−1, the bed temperature of 480–580–850°C (entrance-2/3-export) and the pressure of 3.0MPa, and 100% of hydrocarbons were reformed into CH4, CO, CO2, H2 without C2 or others. It was indicated that the addition of small amount of cerium can improve the dispersion of nickel and inhibit carbon deposition, but more amount of cerium addition was not favorable for nickel dispersion due to the blocking of active sites. Among the catalysts tested, Ni–Ce/Al (1.02wt% Ce) catalyst with the smallest average nickel diameter exhibited the best catalytic performance and the strongest resistance toward carbon deposition maintaining the Ni particle size of 13.0nm after 300h experiment.

Thermal and Chemical Expansion of Proton-Conducting Ceramics BaCexZr0.9-XY0.1O3-d (x=0 and 0.2)

For more than three decades, perovskite materials based on doped barium/strontium cerate/zirconate have been studied as potential hydrogen separation membranes and electrolyte for proton ceramic fuel cells or electrolysis cells. It is well known that cerates are unstable in carbon dioxide and high steam containing atmospheres. Additionally, higher conductivities are obtained with barium instead of strontium on the A-site of the perovskite. Therefore, devices are designed using solid solution of barium cerate-zirconate with low amount of cerium (BaCexZr0.9-xY0.1O3-δ, BCZY). The protonic defects (OHo ·) are incorporated in the material by the hydration equation, also known as the Wagner equation [1] (Eq. 1), in which water dissociates in oxygen vacancies. H2O (g) + Vo ·· + Oo x ↔ 2 OHo · (1) The incorporation and removal of protonic defects create chemical expansion and contraction respectively, which have a tremendous impact on the mechanical strength of the device: the difference of coefficient of thermal expansion (CTE) between the electrolyte and the electrodes increases in the hydration/dehydration region and can cause failure of the device, especially as the trend is to decrease the electrolyte thickness. Therefore, it is imperative that the dehydration temperature and chemical expansion is considered for sealing, startup, and operation of devices based on proton-conducting ceramics. There is limited high temperature X-ray diffraction (HT-XRD) work on BaCexZr0.9-xY0.1O3-δ materials. Hiraiwa et al. [2] studied the chemical expansion/contraction of BaZr0.8Y0.2O3-δ (BZY20) in dry oxidizing atmosphere and reported the presence of chemical expansion in the temperature range of 300-450 °C, due to the dehydration of the sample (water incorporated during fabrication) and also found that the chemical expansion depends on the high temperature thermal history of the part. Andersson et al. [3] recorded HT-XRD on hydrated BZY in flowing synthetic air (1 ppm H2O) and determined a dehydration temperature of about 300 °C. In this work, HT-XRD was used to determine the thermal and chemical expansion of BZY10 (BaZr0.9Y0.1O3-δ) and BCZY27 (BaCe0.2Zr0.7Y0.1O3-δ). Two sets of experiments will be presented and the pros and cons of each will be detailed: in-situ hydration and pre-hydration via autoclave. Figure 1 displays the lattice parameter of BCZY27 recorded while cooling in dry 4% H2 and 4% H2 containing 1 or 3% moisture. The knee in the curve observed in the temperature range 300-500°C in moist conditions is related to hydration of the material. The lower CTE in this temperature range comes from the competition between the contraction due to cooling and the expansion due to protonic defect incorporation. Additionally, an ideal start-up procedure for BCZY based materials will be proposed. [1] V.S. Stotz, C. Wagner, Ber Bunsenges Phys. Chem. 70 (1967) 781 [2] C. Hiraiwa, D. Han, A. Kuramitsu, A. Kuwabara, H. Takeuchi, M. Majima, T. Uda, J. Am. Ceram. Soc. 96 (2013) 879 [3] A.K.E. Andersson, S.M. Selbach, C.S. Knee, T. Grande, J. Am. Ceram. Soc. 97 (2014) 2654 Figure 1

The Effect of the Presence of Ceria on the Character of TiO2 Mesoporous Films Used as Pt Catalyst Support for Methanol Combustion at Low Temperature

A series of ceria-doped mesoporous TiO2 thin films with anatase phase are synthesized and used as the support of platinum catalysts for low-temperature catalytic combustion of methanol. Since the methanol combustion on the catalysts can usually generate local overheating, which unavoidably leads to the structure destruction and catalytic activity loss, the structure thermal stability of catalytic material is very important. Results show that an appropriate amount of ceria can improve the mesoporous order and especially structure thermal stability of TiO2 thin films. For the TiO2 film (calcined at low temperature of 350°C)-supported Pt catalysts, the catalytic activity of ceria-doped catalysts with ceria dosage of 1–2 mol% is comparable to that of the Pt/TiO2 catalyst without ceria doping and the methanol conversion on these kinds of catalysts is about 70% at room temperature. However, for those TiO2 films calcined at 550°C, under the same reaction condition, methanol conversion on Pt/TiO2 drops to 27% but the conversion on Pt/Ceria-TiO2 with the same small ceria dosage of 1–2 mol% can still be kept as 43%. Moreover, after 72 h reaction at room temperature, the catalytic activity has not changed obviously, which means that the stability of the Pt/Ceria-TiO2 catalyst is very high.

Ceria doped titania nano particles: Synthesis and photocatalytic activity

Ceria (0.5, 1 and 2 mol%) doped titania nano catalysts were prepared by combustion synthesis method, using titanium isopropoxide as the starting material. The prepared catalysts were characterized by X-ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Scanning electron microscopy (SEM) and Infra red spectroscopy (FTIR). Total acidity of the prepared catalysts were determined by temperature programmed desorption of ammonia (TPD – NH3). XRD pattern of 1% ceria doped titania obtained by calcinations at 873 K indicated that the samples were crystalline with a mixture of anatase and rutile phase. No peaks corresponding to cerium oxide were observed XRD patterns indicating that the amount of cerium is negligible on the surface of titania catalyst. The photo catalytic activity was evaluated for the degradation of methylene blue (MB) under visible light irradiation. The degradation rates of MB on cerium doped TiO2 samples were higher than that of pure TiO2. The introduction of structural defects (cationic ceria dopant) into the titania crystal lattice leads to the change of band gap energy. As a result, the excitation energy is expanded from UV light of anatase TiO2 to visible light for ceria doped titania.

High performance photoelectrode of dye-sensitised solar cells by Mo-Ce doped TiO<SUB align="right">2 nanoparticles/nanotubes

The one-dimensional structure of TiO2 provides improved photoelectric performance, but it has a small surface area that reduces the adsorption of dye on its surface. Therefore, in this study, TiO2 nanoparticles doped with different amounts of cerium (CeO2) prepared using the sol-gel method and molybdenum (MoO3)-doped TiO2 nanotube photoelectrodes were successfully fabricated via the three-step anodisation of titanium followed by a hydrothermal doping treatment process. The samples were characterised by XRD, SEM, UV-vis, EIS, and I-V curves. The results indicate that metal-doped TiO2 nanoparticles/nanotubes exhibit a broadened absorption in the visible region and a reduced ion recombination as well. The dye-sensitised solar cells (DSSCs) show a maximum conversion efficiency of 6.14% and JSC of 14.80 mA/cm2 under a simulated solar light irradiation of 100 mW/cm2 (AM 1.5).

РАЗРАБОТКА МЕТОДИКИ ОПРЕДЕЛЕНИЯ МАЛЫХ КОЛИЧЕСТВ ЦЕРИЯ В СПЛАВАХ СИСТЕМЫ Co–Cr–W–Ta–Ti–Ce

РАЗРАБОТКА МЕТОДИКИ ОПРЕДЕЛЕНИЯ МАЛЫХ КОЛИЧЕСТВ ЦЕРИЯ В СПЛАВАХ СИСТЕМЫ Co–Cr–W–Ta–Ti–Ce