Effect Of CeO2 Research Articles

The Effect of CeO2 on the Catalytic Activity and SO2 Resistance of the V2O5-MoO3/TiO2 Catalyst Prepared Using the Ball Milling Method for the NH3-SCR of NO

The Effect of CeO2 on the Catalytic Activity and SO2 Resistance of the V2O5-MoO3/TiO2 Catalyst Prepared Using the Ball Milling Method for the NH3-SCR of NO

Effect of CeO2 on the preparation of functional ceramsite and the adsorption effect of ammonia-nitrogen wastewater treatment

This study investigates the effect of rare earth oxide CeO2 on the physical properties of ceramsite and its efficiency in treating ammonia-nitrogen wastewater. Ceramsite was prepared from solid waste with 10 % coal gangue added as a pore-forming agent. Ceramsite sample I with CeO2 and sample II without CeO2 were prepared using pure reagents. The process parameters for both samples were optimized using an orthogonal test. Additionally, the effects of CeO2 on ceramsite performance and the treatment of ammonia-nitrogen wastewater were studied, and the adsorption mechanism of CeO2 on ammonia-nitrogen wastewater was clarified. The process parameters for preparing ceramsite sample Ⅰ were: preheating for 30 min at 600 °C, followed by roasting for 20 min at 1090 °C. The parameters for preparing ceramsite sample Ⅱ were: preheating for 30 min at 600 °C, followed by roasting time for 15 min at 1090 °C. The presence of CeO2 increased the porosity of the ceramsite by 0.89 % and the specific surface area by 0.66 m2/g. Under neutral environmental conditions of water samples, CeO2 increased the removal rate of ammonia nitrogen by 1.85 %. Ceramsite has a high porosity and specific surface area, indicating that it has abundant internal pores, a large contact area with ammonia-nitrogen, a strong ability to remove ammonia nitrogen, and resistance to erosion and water flow shear, which are conducive to the treatment of ammonia-nitrogen wastewater.

Development of calcium phosphate cement composed of silica-modified hydroxyapatite, cerium oxide, and silica as an osteoporotic bone filler

Calcium phosphate cement (CPC), composed of silica-modified hydroxyapatite (HA-SiO2), cerium oxide (CeO2), and silica (SiO2), was developed as an osteoporosis bone filler. The effect of CeO2 and SiO2 content on the CPC's properties, such as crystal parameters, surface properties, antibacterial activity, and toxicity properties, were studied. HA-SiO2 was prepared using the sol-gel method, while CeO2 was prepared using the precipitation method. HA in HA-SiO2 has crystal properties similar to pure HA. Synthesized CeO2 contains Ce3+ and Ce4+ ions with Ce3+/Ce4+ = 0.34. Computational calculation predicted that the CeO2 (111) surface and glycine molecule interaction was categorized as chemisorption. Moreover, CeO2 has antibacterial activity toward Escherichia coli and Staphylococcus aureus. Combining HA-SiO2 and CeO2 did not change the adsorption-desorption isotherm curve type, but slightly decreased the surface area, total pore volume, and average pore. Increasing the percentage of CeO2 and adding 10 % SiO2 (w/w) affected the particle's size and CeO2 distribution. However, CPC lost antibacterial activity toward Staphylococcus aureus but adding 10 % SiO2 (w/w) increases the bacterial activity toward Escherichia coli close to that of pure CeO2. The MTT assay using pre-osteoblast MC3T3E1 cells showed that the CPC has IC50 = 4227 μg/ml or is nontoxic.

Efficient CO Oxidation using Co3O4−CeO2 Nanoparticles Supported on Resin–Based Spherical Activated Carbon with Controllable Oxygen Species

AbstractThe oxygen vacancies and surface oxygen species play pivotal roles in CO catalytic oxidation. In this study, Co3O4−CeO2 supported on resin based spherical activated carbon was fabricated and the effect of CeO2 on surface oxygen species was demonstrated through controlling various Ce contents. When Ce content was optimal (nCo : nCe=9), the maximum surface adsorbed oxygen content (60.3 %) is displayed and the catalyst achieved good CO conversion (T100=110 °C), water resistance and robust stability. DFT simulation calculation confirmed that the energy barriers of two transition states significantly decreased to 0.60 eV and 0.37 eV, respectively, with the addition of CeO2. The results indicate that the presence of CeO2 is conducive to the increasement of surface adsorbed oxygen content and optimal Co/Ce ratio is the most favorable for the CO oxidation. It is attributed to the visible decline of the energy barrier between oxygen vacancies and gas–phase oxygen at the Co3O4−CeO2 interface, and the process of oxygen vacancies replenishment could be more prone to occur at the interface. This study may provide a protocol for further improving surface species on supporting catalysts.

Cu/ZnO/CeO2 Supported on MOF-5 as a Novel Catalyst for the CO2 Hydrogenation to Methanol: A Mechanistic Study on the Effect of CeO2 and MOF-5 on Active Sites

Cu/ZnO/CeO2 nanocomposite was supported on metal organic framework (MOF-5) to enhance active sites dispersion and control the nanoparticles agglomeration during synthesis through strong metal-support interactions. The incorporation of MOF-5 alleviated the obstacle facing the commercial ternary Cu/ZnO/Al2O3 regarding low surface area due to nanoparticles agglomeration. In addition, Cu/ZnO/CeO2@MOF-5 gave higher methanol selectivity than the commercial catalyst which can be accounted for by the interfacial sites generated between MOF-5 and Cu/ZnO which favour methanol synthesis over carbon monoxide through regulating the intermediates bonding energies. CeO2 as support for Cu/ZnO nanoparticles was also compared with commercial support and showed to have led to smaller particle size and superior dispersion of Cu active sites as well. Cu/ZnO/CeO2@MOF-5 resulted in methanol STY of 23.3 mg gcat h−1 and selectivity of 79% at mild reaction temperature (260 °C) and pressure (10 bar). Two different MOFs including cerium based MOF and ZIF-8 demonstrated inferior performance compared to MOF-5.Graphical

Effect of CeO2 on the Microstructure and Properties of In Situ Nano-VC Reinforced Sub-micron Fe-Based Laser Cladding Layers

Effect of CeO2 on the Microstructure and Properties of In Situ Nano-VC Reinforced Sub-micron Fe-Based Laser Cladding Layers

Effect of CeO2 on the microstructure and properties of AlCoCrFeNi2.1 laser cladding coatings

In the process of strengthening the substrate’s surface properties, it is easy to produce cracks or air holes and other defects between the coatings and the substrate, and rare earth elements can improve the microstructure and properties of the metal surface coatings. Using laser cladding(LC) technology, the effect of the addition of rare earth oxides CeO2 on the properties of AlCoCrFeNi2.1 coatings is investigated to find the optimal amount of CeO2 added. AlCoCrFeNi2.1 alloy powder doped with Xwt% (X = 0–3) rare-earth oxide CeO2 was clad on the surface of the H13 steel substrate by laser cladding process using RFL-C3000 laser. The macroscopic morphology, microstructure, hardness, and corrosion resistance of specimens were analyzed and studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), hardness tester, and other equipment. The results show that the addition of the appropriate amount of rare earth oxide CeO2 (3 %) can effectively reduce the cracks, air holes, and inclusions in the composite layer, and promote grain refinement. The addition of 3 wt%CeO2 to AlCoCrFeNi2.1 can improve the microstructure uniformity and surface hardness of the coatings, and significantly improve the wear and corrosion resistance of the composite coatings.

Effect of metal oxides on reaction route and product distribution of catalytic cellulose hydrogenolysis

The effects of CeO2, ZrO2, Nb2O5, and ZnO catalysts supported on carbon nanotubes (CNT) relative to cellulose hydrothermal hydrogenolysis in the presence of Ni/CNT and pressured H2 was studied in this work. The catalysts were characterized by inductively coupled plasma – optical emission spectrometry, X-ray diffraction, X-ray photoelectron spectrometry, transmission electron microscopy, NH3 temperature programmed desorption (TPD), and CO2-TPD. Glucose and its isomers were detected by mass spectrometry. The results showed that redox active CeO2/CNT with strong Lewis acid and strong Lewis base sites was active in C-C bong cracking, isomerization, dehydrogenation, and hydrodeoxygenation reaction, yielding 36.3% ethylene glycol and 17.2% 1,2-propylene glycol. The ZnO/CNT with Bronsted base accelerated isomerization, retro-aldol condensation, and dehydrogenation, yielding 20.7% 1,2-propylene glycol, 17.8% ethylene glycol, and 12.7% tetrahydrofuran dimethanol. The Nb2O5/CNT and ZrO2/CNT were inert to C-C bond cracking, whereas H+ in hot compressed water and the Bronsted acid in Nb2O5/CNT accelerated dehydration, yielding more sorbitol and sorbitans. The results provide reference for catalyst selection and product regulation in cellulose hydrogenolysis.

Effects of CeO2 and Hf as Inoculant on the Microstructure and Impact Properties of Hadfield Austenitic Manganese Steel

Effects of CeO2 and Hf as Inoculant on the Microstructure and Impact Properties of Hadfield Austenitic Manganese Steel

Microstructure and Properties of Direct Laser-Deposited CeO2-Modified Cobalt-Based Composite Coatings

The seawater circulation pump is a significant piece of equipment in coastal nuclear power plants that is susceptible to erosion and corrosion in the seawater. In this work, CeO2-modified cobalt-based composite coatings were prepared on the surface of martensitic stainless steel by direct laser deposition. The effect of CeO2 on the phase composition, microstructure, microhardness, corrosion resistance, and erosion properties of the cobalt-based composite coatings was systematically investigated. While the addition of CeO2 did not affect the phase composition of the coatings that comprised γ-Co, γ-Ni, M7C3, and M23C6 (M = Cr, W, Fe) metallic carbides, the eutectic organization showed an obvious phenomenon of contiguous aggregation. Microscopic pores were found in the coatings with 2 wt.% CeO2, and the number of pores increased with the increase in CeO2 content. Despite the higher self-corrosion potential (−0.27668 V) of cobalt-based alloy coating compared to the substrate (−0.37019 V), indicating enhanced corrosion resistance, the difference in self-corrosion potential among coatings with varying CeO2 addition amounts is small (0.027 V), and the corrosion current densities are within one order of magnitude (10−8 A/cm2). These findings suggest that the addition of CeO2 has no significant impact on the coating’s corrosion resistance.

Insight into the effect of catalytic reactions on correlations of soot oxidation activity and microspatial structures

A catalyst is usually coated on Diesel particulate filter (DPF) for assisted regeneration. In this paper, the oxidation activity and pore structure evolutions of soot under the effect of CeO2 are explored. CeO2 effectively increases the oxidation activity of soot and reduces the initial activation energy; in the meantime, the addition of CeO2 changes the soot oxidation mode. Pure soot particles tend to produce the porous structure in the oxidation process. Mesopores promote the diffusion of oxygen, and macropores contribute to reduce the agglomeration of soot particles. Additionally, CeO2 provides the active oxygen for soot oxidation and promotes the multi-point oxidation at the beginning of soot oxidation. With the oxidation proceeding, catalysis causes the collapsion of soot microspatial structures, in the meantime, the macropores caused by the catalytic oxidation are filled by CeO2. It results in the tight contact between soot and catalyst, further promoting the formation of the available active oxygen for soot oxidation. This paper is meaningful to analyze the oxidation mechanism of soot under catalysis, which lays a foundation for improving the regeneration efficiency of DPF and reducing the particle emission.

Ce-promoted Fe-K-Mg catalyst and its application in dehydrogenation of ethylbenzene

The continuous pursuit of green, low-carbon, and efficient processes in catalysis necessitates a deep understanding of catalytic reaction mechanisms and the structure-performance relationship of catalysts. Styrene, a vital monomer in the chemical industry, is primarily produced through the catalytic dehydrogenation of ethylbenzene over Fe-based catalysts. This study prepared a series of Fe-K-Mg catalysts promoted with different CeO2 contents. Various techniques such as mercury intrusion, particle strength tests, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed techniques were employed to characterize the catalysts' physical properties, surface, and bulk structures. The results indicate that the bulk density and crush strength of the catalyst are closely related to the pore structure and grain size of potassium β-ferrite. The surface of the Ce-promoted catalyst contains potassium β-ferrite KFe11O17, cerium dioxide, and potassium carbonate, while the bulk structure consists of potassium β-ferrite and cerium dioxide. The addition of Ce enhances the catalytic activity of ethylbenzene dehydrogenation, but the selectivity of styrene shows the opposite trend. The Fe-K-Mg catalyst containing 12% CeO2 exhibited the highest single-pass yield of styrene, reaching 70.9%. This study also discusses the possible effect of CeO2 on the performance of the Fe-K-Mg catalyst for ethylbenzene dehydrogenation.

CO2 hydrogenation to methanol over Zr- and Ce-doped indium oxide

In recent decades, climate change has become a major issue that needs to be addressed. Many efforts have been made on the reduction of CO2 emissions and its conversion in energy carriers and high value-added products such as methane, methanol, dimethyl-ether, and hydrocarbons. The present study focuses on the development of catalysts for hydrogenating CO2 to methanol, which is a useful chemical and an alternative liquid fuel. According to the literature, In2O3-based catalysts are particularly selective in the hydrogenation of CO2 to methanol, reducing the production of CO even at high space velocities compared to the more common ternary catalysts such as Cu/ZnO/Al2O3 or Cu/ZnO/ZrO2. Therefore, the effects of CeO2 and ZrO2 on In2O3-based catalysts were investigated in the present study. The InxCe100−x and the InxZr100−x mixed oxides catalysts were synthesized via gel-oxalate coprecipitation by varying the atomic ratios between the elements. Subsequently, they were analysed with several characterisation techniques to rationalise the catalytic performances that were obtained by testing the samples in a fixed bed reactor under different reaction conditions. The addition of different amounts Ce or Zr modified the structure and morphology of the samples and promoted the adsorption of CO2 from 1.8 mmolCO2⋅gcat−1 up to 10.6 mmolCO2⋅gcat−1. ZrO2 stabilises the structure and the results suggests that the greater specific activity (168 mgCH3OH⋅gIn2O3−1⋅h−1 at 300 °C and 2.5 MPa of In40Zr60) could be ascribed to the electronic promotion of Zr. On the contrary, the addition of CeO2 did not reveal a beneficial effect on the activity. Concerning the stability, In2O3-ZrO2 binary oxides seemed to be affected mainly by sintering; whereas In2O3-CeO2 were affected by at least three deactivating phenomena: sintering, reduction of In2O3 to metallic indium and coking. Consequently, the deactivation rate of these binary oxides increased from 1.04 ⋅ 10−2 h−1 of the In100 to 4.13 ⋅ 10−2 h−1 of the In40Ce60.

Effect of CeO2 on Al–Ti–C and matrix conversion between TiC and α-Al orientation relationship

Effect of CeO2 on Al–Ti–C and matrix conversion between TiC and α-Al orientation relationship

Fabrication of carbon nanotube with high purity and crystallinity by methane decomposition over ceria-supported catalysts

Because of its unique properties, CeO2 is a widely used support material in steam reforming and dry reforming reactions conducted using CH4 as a reactant. However, it has been rarely used in the catalytic decomposition of methane (CDM). In a pre-test, a Co/CeO2 catalyst showed higher activity than Ni/Al2O3, Co/Al2O3, and Mo-Ni/MgO catalysts in the CDM conducted via catalytic chemical vapor deposition (CCVD). Therefore, in this study, the CDM for carbon nanotube (CNT) synthesis over CeO2-supported Co, Fe, and Ni catalysts was investigated, while focusing on the effects of CeO2 on the activities of the active metals in the CDM. Among the investigated catalysts, Ni/CeO2 showed a decent catalytic performance at 600 °C, which is a considerably lower temperature than those previously reported. X-ray diffraction, Brunauer–Emmett–Teller surface area, temperature-programmed reduction/desorption (TPR/TPD), and X-ray photoelectron spectroscopy (XPS) analyses were performed to characterize the catalysts. Through these experiments, it was found that Ni/CeO2 had many adsorption sites for CH4 molecules which could react with mobile oxygen existing in CeO2. Furthermore, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric (TG) analyses were performed to examine the morphologies and properties of the carbon material grown on the catalysts.

Using tungstophosphoric acid-modified CeO2, TiO2, and SiO2 catalysts to promote secondary reactions leading to aromatics during waste tire pyrolysis

The synthesis of catalysts for upgrading waste tire pyrolysis oils (TPO) into marketable products such as fuels, solvents or fine chemicals is a major challenge. Herein, the effect of CeO2, SiO2, and TiO2 catalysts containing tunsgtophosphoric acid (TPA) on the selectivity to aromatics (benzene, toluene, and xylenes viz. BTXs) and p-cymene was studied for the first time. Modifying TiO2 with 1% and 10% TPA allowed modulating the oxide's acidity, resulting in a ratio of Lewis acid sites and strong Brønsted acid sites that favored the target compound formation. The 1%TPA catalyst enhanced the p-cymene production (Sp-cymene = 56.3%). In contrast, 10%TPA promoted BTX formation (SBTX= 26%) over p-cymene (Sp-cymene = 6.5%) due to its greater content of Brønsted acid sites. The selectivity of SiO2 and CeO2-based catalysts to these aromatic compounds was in the same order as the uncatalyzed reaction. The p-cymene is mainly formed from secondary reactions of isomerization of limonene to other terpenes (terpinolene, α-terpinene, and γ-terpinene) and the subsequent ring dehydrogenation with an activation energy of 62.3 kJ mol−1. The BTXs were kinetically favored on 10%TPATi catalyst with an Ea = 112 kJ mol−1. The study was performed in a fixed bed Pyr-GC/MS system under kinetically controlled regime.

Effect of CeO2 on Microstructure and Properties of Wear and Corrosion Resistance Martensitic Stainless Steel‐Based Coating on Laser Cladding

The effects of CeO2 on the quantity, morphology, and distribution of carbides, the microhardness, friction and wear properties, and corrosion resistance of 0.3C–16Cr martensitic stainless steel‐based cladding layer are investigated. The results show that the addition of CeO2 inhibits the dendrite growth and improves the morphology, size, and distribution of carbides in the cladding layer. The hardness shows a peak with the increase in CeO2 content, the wear rate of the cladding layer with CeO2 decreases, and the wear resistance increases. In addition, CeO2 significantly improves the corrosion resistance of the cladding layer, causing the pitting potential to increase and the blunt current density to decrease. Compared with the original sample, the wear amount and dimensional blunt current density of the sample with 0.3% CeO2 content are reduced by 55.36% and 35.32%, respectively, and the pitting potential is increased by 2.71 times. The comprehensive performance of the cladding layer is the best. This is mainly because CeO2 can increase the latent heat of crystallization during the cooling process of the cladding layer, reduce the constitutional supercooling, inhibit the directional growth of dendrites, improve the uniformity of the microstructure and composition, and thereby improve the wear resistance and corrosion resistance.

Effect of CeO2 on carbon deposition resistance of Ni/CeO2 catalyst supported on SiC porous ceramic for ethanol steam reforming

Ni/CeO2 catalysts (nCeO2:nNi = 0, 1, 4, 7, 10) supported on SiC porous ceramics for ethanol steam reforming (ESR) were investigated with respect to hydrogen production performance and growth of carbon deposition. The oxygen released from CeO2 enables the oxidation of CHx species to serve as carbon precursors, thus providing Ni/CeO2 catalysts with stronger resistance to carbon deposition compared with Ni catalysts. The Ni/CeO2 catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics. Under 500 °C for 25 h of ESR reaction, the ethanol conversion rate over Ni/CeO2 catalysts (nCeO2:nNi = 7) is sustained up to 100% and H2 selectivity is essentially kept at 74%. The by-product selectivity declines stepwise with increasing content of CeO2, which is attributed to the adsorption and oxidation of CO and of CHx species as CH4 precursor from CeO2. The scanning electron microscopy (SEM) and transform electron microscopy (TEM) results reveal that further loading of CeO2 on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles. Furthermore, carbon deposition on Ni/CeO2 catalysts preferentially outgrow filamentous rather than amorphous carbon, with a tendency for the latter to be more deactivated.

Structure-performance evolution on thermal-oxidative aging of CeO2/SBS co-modified asphalt

ABSTRACT Aging has a significant effect on the performance of asphalt, and the use of modifiers is the key to solving this problem. The mechanism of CeO2 effect on the thermal-oxidative aging resistance of SBS modified asphalt was explored by studying the microstructure and macroscopic properties of asphalt. The melt blending method was used to prepare CeO2/SBS co-modified asphalt, and the short-term thermal-oxidative aging process was demonstrated by a thin film oven test. Then, the effects of CeO2 on the properties of SBS modified asphalt were investigated by using dynamic shear rheometry, nuclear magnetic resonance, and electron paramagnetic resonance spectroscopy tests. The results showed that CeO2 increased the decomposition temperature of SBS modified asphalt and improved its thermal stability. The rheological results showed that the complex shear modulus aging index of CeO2/SBS co-modified asphalt is lower than that of SBS modified asphalt, and the phase angle aging index increases. In addition, CeO2 can make the internal molecular structure of asphalt produce more isomerisation and generate more long chains after aging. EPR results showed that CeO2 can reduce the generation of free radicals during aging, thus slowing down the generation of oxygen-containing functional groups and improving the thermal-oxidative aging resistance of asphalt.

Effects of CeO2 on the phase, microstructure and mechanical properties of Al2O3-ZrO2(CeO2) nanocomposite ceramics (AZC-NCs) by solid solution precipitation

It is one of the most concerning issues to achieve fine nanostructures and a reasonable ZrO2 crystal structure in Al2O3–ZrO2 structural ceramics. Herein, Al2O3–ZrO2(CeO2) nanocomposite ceramics (AZC-NCs) with different CeO2 contents were prepared by sintering Al2O3–ZrO2(CeO2) supersaturated solid solution powders (AZC-SSSPs). The effects of CeO2 on the phase, microstructure, and mechanical properties of AZC-NCs were investigated systematically. During rapid solidification process, three phases of Al2O3, ZrO2 and CeO2 are dissolved together and form AZC-SSSPs with regular spheres. After sintering, the AZC-SSSPs transform into two-phase structure and compact into AZC-NCs. The AZC-NCs show an intragranular/intercrystalline nanoprecipitation structure, and large amounts of ZrO2 in AZC-NCs remain in a tetragonal structure at room temperature because of the addition of CeO2. Among the AZC-NCs, that with 6 mol% CeO2 shows the best mechanical properties with the highest values of strength and toughness: 865 ± 24 MPa and 8.4 ± 0.16 MPa·m1/2. Spark plasma sintering has no obvious influence on the microstructure and phase composition of AZC-NCs. This work provides guidance to optimize the microstructure and ZrO2 crystal structure of AZC-NCs.