Redox Performance Research Articles

Redox Performance and Optimization of the Chemical Composition of Lanthanum–Strontium–Manganese-Based Perovskite Oxide for Two-Step Thermochemical CO2 Splitting

The effects of substitution at the A- and B sites on the redox performance of a series of lanthanum–strontium–manganese (LSM)-based perovskite oxides (Z = Ni, Co, and Mg) were studied for application in a two-step thermochemical CO2 splitting cycle to produce liquid fuel from synthesis gas using concentrated solar radiation as the proposed energy source and CO2 recovered from the atmosphere as the prospective chemical source. The redox reactivity, stoichiometry of oxygen/CO production, and optimum chemical composition of Ni-, Co-, and Mg-substituted LSM perovskites were investigated to enhance oxygen/CO productivity. Furthermore, the long-term thermal stabilities and thermochemical repeatabilities of the oxides were evaluated and compared with previous data. The valence changes in the constituent ionic species of the perovskite oxides were studied and evaluated by X-ray photoelectron spectroscopy (XPS) for each step of the thermochemical cycle. From the perspectives of high redox reactivity, stoichiometric oxygen/CO production, and thermally stable repeatability in long-term thermochemical cycling, Ni0.20-, Co0.35-, and Mg0.125-substituted La0.7Sr0.3Mn perovskite oxides are the most promising materials among the LSM perovskite oxides for two-step thermochemical CO2 splitting, showing CO productivities of 387–533 μmol/g and time-averaged CO productivities of 12.9–18.0 μmol/(min·g) compared with those of LSM perovskites reported in the literature.

Insights into Nb doping effects on the catalytic activity and SO2 tolerance of Mn–Cu/BCN catalyst for low-temperature NH3-SCR reaction

Biochar-based supported denitration catalysts have shown tremendous potential in reducing NOx, while improving low-temperature NH3-SCR catalytic activity and SO2 tolerance still faces great challenges. In this work, Mn7–Cu3/BCN and Mn7–Cu3-Nbx/BCN catalysts were prepared by one-step wet impregnation. The enhanced effect of Nb doping on the catalytic performance and SO2 tolerance over the Mn7–Cu3/BCN catalyst was evaluated in the temperature range of 75–275 °C. The denitrification activity test showed that the introduction of an appropriate amount of Nb increased the catalytic activity and N2 selectivity of the catalyst. The NO conversion of Mn7–Cu3–Nb0.05/BCN with an optimum doping ratio of 0.05 wt% Nb was higher than 94% at 150–275 °C. The characterization results indicated that the introduction of Nb enhanced the interaction between the active components MnOx and CuOx, accelerated the electron transfer between elements, and thus improved the Mn4+/Mnn+ and Oα/(Oα+Oβ+Oγ) proportions and redox performance. On the other hand, Nb modification increased the number of weakly acidic sites, which was beneficial for the adsorption and activation of the reducing agent NH3 under low-temperature conditions. Meanwhile, Nb could significantly improve the SO2 poisoning resistance of the Mn7–Cu3/BCN–S catalyst when SO2 was added to the reaction system. The NO conversion of Mn7–Cu3–Nb0.05/BCN remained above 75% after a 13.5 h reaction under 100 ppm SO2 and 5 vol% H2O at 225 °C. By combining experimental characterization results with DFT calculation results, we effectively confirmed that Mn7–Cu3–Nb0.05/BCN had good sulfur resistance, mainly because Nb could effectively inhibit the formation of manganese sulfate and promote the decomposition of ammonium bisulfate.

Enhanced morphological maintenance and redox stability by dispersing nickel ferrite into silica matrix for chemical looping hydrogen production via water splitting

Chemical looping hydrogen production (CLHP) is widely regarded as a clean and efficient route for high purity hydrogen production. However, a huge barrier is how to avoid serious deactivation caused by sintering and agglomeration of oxygen carriers. A novel fabrication process of highly dispersing NiFe2O4 into silica matrix is proposed. The oxygen carriers of NiFe2O4 completely dispersed over silica matrix (NFSM) are successfully synthesized. The characterizations, hydrogen production capacity and cycle redox performance of oxygen carriers are further investigated. The results illustrate that NiFe2O4 active components are homogeneously dispersed on the silica matrix without any impurities. NFSM demonstrates the highest reactivity with CO as well as the greatest hydrogen production of 296 mL/g due to the strong confinement effect of silica matrix and good particle dispersion. The porous silica matrix offers large amounts of channels for the lattice oxygen transport and effectively prevents Fe and Ni cations outward migration to particle surface, which actually inhibits the larger clusters and sintering. NFSM can keep stable hydrogen production of approximately 290 mL/g during the cyclic experiments. Briefly, the innovation method of embedding active component into well-established silica matrix supports contributes to the enhanced anti-sintering properties and redox stability of oxygen carriers.

In Situ Fabrication of an S-Scheme NaNbO3/Bi2O2CO3 Heterojunction for Enhanced Performance in Photocatalytic Nitrogen Fixation.

In this study, NaNbO3 microcubes were introduced during the preparation of Bi2O2CO3 nanosheets to construct a series of NaNbO3/Bi2O2CO3 heterojunctions with varying NaNbO3 content. Their photoactivities for N2 fixation were examined and compared. Results demonstrated that 7.5% NaNbO3/Bi2O2CO3 had the highest photoactivity. The NH3 production rate under simulated solar light is 453.1 μmol L-1 g-1 h-1, representing 2.0 and 3.8-fold increases compared to those of Bi2O2CO3 and NaNbO3, respectively. A comprehensive investigation encompassing the physical and chemical properties of the NaNbO3/Bi2O2CO3 photocatalyst was conducted. Bi2O2CO3 nanosheets were discovered to be distributed on the NaNbO3 microcubes surface. The addition of NaNbO3 exhibited nearly no effect on the photoabsorption performance and specific surface area of the Bi2O2CO3. However, the tight contact between NaNbO3 and Bi2O2CO3 and their appropriate band positions led to the formation of a heterojunction structure between them. The electron drift occurring in the interface region induces the creation of an internal electric field and energy band bending. This facilitates the transfer of photogenerated electrons and holes through an S-scheme mechanism, achieving efficient separation without compromising the redox performance. As a result, the NaNbO3/Bi2O2CO3 composite exhibits exceptional performance in the photocatalytic nitrogen fixation reaction. This study expands the application of S-scheme photocatalysts in the field of N2 reduction and provides insights into the preparation of efficient S-scheme photocatalysts.

Catalytic oxidation of toluene over highly dispersed Mn-Ce solid solutions synthesized with weakly acidic precursors

In this paper, a series of Mn-Ce composite oxide catalysts were prepared by different preparation methods using different Mn and Ce acidic precursors for the catalytic oxidation of toluene. The activity test results revealed that the Mn-Ce composite catalysts, synthesized through the sol-gel method using weakly acidic Mn acetate and Ce acetate as precursors, exhibited the highest performance for the catalytic oxidation of toluene. The T50 and T90 values for this catalyst were measured at 208 °C and 235 °C, respectively. The relatively weak acidity of manganese acetate and cerium acetate facilitates the presence of acidic -OH groups, which interact with the oxygen-negative charge sites on each other. Furthermore, during the calcination process, there was a strong interaction between hydrated Mn and Ce ions, resulting in the formation of highly dispersed metal oxide species. The formation of Mn-Ce solid solution demonstrated by Raman, XRD. The H2-TPR characterization indicated that the superior redox performance of the MnOx species on the catalyst surface played a pivotal role in achieving high activity. Moreover, the catalytic activity of the CeO2 species was further enhanced by employing the sol-gel method. XPS and O2-TPD results revealed a significantly higher amount of reactive oxygen species on the catalyst surface, which was identified as the primary reason for the increased activity. This study provides a new strategy for the selection of the catalyst precursors, thereby enhancing the catalytic activity of Mn-Ce composite oxides.

Blocking Accretion Enables Dimension Reduction of Metal-Organic Framework for Photocatalytic Performance.

The evolution and formation process of two-dimensional metal-organic frameworks (MOFs) primarily arise from the anisotropic growth of crystals, leading to variations in photocatalytic performance. It is crucial to achieve a synergistic combination of anisotropic electron transfer direction and dimension reduction strategies. In this study, a novel approach that effectively blocks crystal growth accretion through the coordination of solvent molecules is presented, achieving the successful synthesis of impurity-free two-dimensional nanosheet Zn-PTC with exceptional hydrogen evolution reaction (HER) performance (15.4mmolg-1 h-1 ). The structural and photophysical characterizations validate the successful prevention of crystal accretion, while establishing correlation between structural anisotropy and intrinsic charge transfer mode through transient spectroscopy. These findings unequivocally demonstrate that electron transfer along the [001] direction plays a pivotal role in the redox performance of nano-Zn-PTC. Subsequently, by coupling the photocatalytic performance and density functional theory (DFT) simulation calculations, the carrier diffusion kinetics is explored, revealing that effective dimension reduction along the ligand-to-metal charge transfer (LMCT) direction is the key to achieving superior photocatalytic performance.

Characterization and mechanism of red-mud-catalyzed steam gasification of corn stover

Catalytic biomass gasification has received extensive attention from scholars worldwide. This study proposes steam gasification of corn stover using red mud (RM), an industrial solid waste, as a catalyst to produce high-quality reducing gas. Experiments were conducted at different reaction temperatures and gasification times. Characterization of RM and its three main components, Fe2O3, CaCO3, and Al2O3, in the catalytic steam gasification process of corn stover, was performed and its catalytic mechanism was explored by characterizing magnetic separation products. Results show that an increase in reaction temperature significantly promotes the production of CO, CO2, and H2. The promotion of steam to H2 production is caused by the gas-phase reaction and gasification of fixed carbon (FC). Fe2O3 promotes gas-phase reactions, such as the water–gas shift reaction, and effectively catalyzes the steam gasification of FC as an intermediate reactant. The addition of Al2O3 is beneficial for the production of CH4 and H2. The CO2 produced by the decomposition of CaCO3 inhibits the water–gas shift and methane-steam reforming reactions, thus reducing H2 output. The addition of RM is beneficial for the production of H2 and CO2 and inhibits the production of CO. Compared with pure Fe2O3, the superior pore structure and unique solid solution structure of RM provide Fe2O3 with more active surface lattice oxygen, higher redox performance, larger gas–solid contact area, superior ability to prevent carbon deposition, and better catalytic ability.

Commercial SCR catalyst modified with Cu metal to simultaneously efficiently remove NO and toluene in the fuel gas.

Developing an environmentally friendly selective catalytic reduction (SCR) catalyst to effectively eliminate both nitric oxides (NO) and toluene has garnered significant attention for regulating emissions from automobiles and the combustion of fossil fuels. This study synthesized a series of novel commercial V2O5-WO3/TiO2 catalysts modified with Cu through the wet impregnation method, which was employed to simultaneously remove NO and toluene from the fuel gas. The assessment of catalyst removal performance was conducted at a selective catalytic reduction system, and the experimental results showed a significant increase in the catalytic activity due to the modification of the copper metal. The 10% Cu/SCR catalyst showed a superior activity that the NO and toluene conversion reached 100% and 95.56% at 300 °C, respectively. Subsequently, various characterization techniques were employed to investigate the crystal phase, morphology, physical features, chemical states, and surface acidity properties of the synthesis catalysts. According to the characterization results, the presence of Cu metal did not have a noticeable impact on the physical property. However, the redox performance was enhanced, and the number of surface acidic sites was also increased after adding Cu to the SCR catalyst. Furthermore, the redox cycle of Cu metal and V species was facilitated to produce more active oxygen which helped to improve the NO and toluene conversion. This work offered a novel perspective into the synergistic oxidation of both NO and toluene, which was potentially relevant for improving the selective catalytic reduction process in coal-fired power plants.

Promoting effect of Si on MnOx catalysts for low-temperature NH3-SCR of NO: Enhanced N2 selectivity and SO2 resistance

Manganese-based catalysts have excellent catalytic performance for the effective removal of NOx in low-temperature flue gas through selective catalytic reduction with NH3 (NH3-SCR). However, the catalysts suffer from poor SO2 resistance and N2 selectivity in the actual process, which still need to be solved. In this study, MnOx-SiO2 mixed oxide catalysts were designed and prepared by coprecipitation method to improve the SO2 resistance and N2 selectivity in NH3-SCR process. In the presence of 100 ppm SO2, MnOx-SiO2(0.72) catalyst showed excellent sulfur resistance with the conversion of NOx reached 95 % even after introducing SO2 for 8 h. The doping of SiO2 greatly improved the specific surface area and surface acidity of the catalyst, which was conducive to the adsorption of NH3. Meanwhile, the redox performance of the catalyst was decreased, improving the N2 selectivity. The study on the sulfur resistance mechanism revealed that the doping of SiO2 reduced the adsorption of SO2 on the surface of catalyst, protecting the active components and avoiding the accumulation of sulfates, thus achieving good sulfur resistance performance. This work provided an environmentally friendly NH3-SCR catalyst by inhibiting SO2 adsorption to have good catalytic performance and SO2 resistance.

Electrolyte performance of green synthesized carbon quantum dots from fermented tea for high-speed capacitors

In recent years, obtaining carbon nanomaterials from natural products by natural methods has been among the most popular topics. The materials synthesized by this way have beneficial properties such as biocompatible, photostable and less harmful for environment. In this study, carbon quantum dots (CQDs) were synthesized by using fermented tea as a natural material and carbon source. The capacitor performance as an electrolyte was investigated with high-speed charge-discharge method as unusual in the literature. The characterizations of the CQDs were realized by HRTEM, XRD, XPS, UV–Vis absorption, and fluorescence spectroscopy techniques. The resulting particles have a size of about 10 nm according to HRTEM image. While the structural properties of the CQDs were confirmed by XRD and XPS, and optical behaviors were confirmed by UV–Vis and fluorescence spectroscopies. The electrochemical behavior of the obtained CQDs was tested as electrolyte material for capacitor applications. Experiments were carried out in three different operating potential windows in the 0–2 V range, and CQDs electrolytes exhibited high capacitive effect in symmetrical capacitors. However, the cyclic voltammetry (CV) analyses revealed that the CQDs electrolytes displayed a full supercapacitor electrolyte feature in the 0–0.5 V range. The CQDs electrolytes have a promising material for technological and industrial applications with their unique redox performance and high capacitive effect.

Recyclable NiMnOx/NaF catalysts: Hydrogen generation via steam reforming of formaldehyde

In this paper, a low-cost and efficient NiMnOx/NaF catalyst that can be recycled for re-preparation was developed by sol–gel method for formaldehyde steam reforming to produce hydrogen, aiming at the high cost of commercial reforming catalyst and the difficulty of recycling after deactivation and abandonment. Results showed that the NiMnOx/NaF catalyst could efficiently steam reforming formaldehyde to produce hydrogen. Among them, the catalyst with 5 wt% NiMnOx had better hydrogen production performance, achieving 100% hydrogen yield, 100% formaldehyde conversion and 100% carbon balance from 500 to 600 ℃. Moreover, 5%-NiMnOx/NaF catalyst exhibited excellent stability at 500 ℃ for 28 h and the hydrogen production performance of the recycled catalyst was restored to the level of the initial fresh sample. Combining analysis of FE-SEM, N2 adsorption/desorption, XRD, H2-TPR, in situ DRIFTS, XPS, and DFT calculations, it was found that the surface micro-structure of the NaF carrier was dense, and the specific surface area of the NiMnOx/NaF catalyst was very small, breaking through the limitation of low specific surface area catalysts that cannot obtain high-quality catalytic activity. Its steam reforming of formaldehyde to produce hydrogen was a fast surface reaction process. Ni and Mn species combined with NaF to form the Na0.67Ni0.33Mn0.67O2 phase, and F atom had a strong induction effect on Ni atom, which was conducive to weakening the Ni-O bond, thus improving the low-temperature redox performance of Ni2+. In the process of reforming formaldehyde to produce hydrogen, the NiMnOx/NaF catalyst could quickly adsorb and activate formaldehyde and H2O molecules, and promoted the formation of formate intermediates through the adsorbed hydroxyl groups on the surface, and then rapidly produced H2 and CO2.

Effect of Nickel and Cobalt Doping on the Redox Performance of SrFeO3−δ toward Chemical Looping Dry Reforming of Methane

Effect of Nickel and Cobalt Doping on the Redox Performance of SrFeO_3−δ toward Chemical Looping Dry Reforming of Methane

Heterojunction architecture of Ce2S3 nanocubes with ZnxCd1-xS photocatalyst enables efficient hydrogen evolution

Heterojunction coupling with narrow bandgap semiconductor can effectively promote light absorption, inhibits photoinduced carrier recombination and enhances redox performance. Herein, a novel Ce2S3 nanocube was synthesized via a high-temperature sulfating method, then ZnxCd1-xS (ZCS) was grown on Ce2S3 cube to form a tight junction for the photocatalytic hydrogen evolution (PHE) activity. The experimental results confirm that this novel composite vastly boosts the redox performance due to superior visible light absorbance, narrow bandgap and fast charge carrier separation via a Z-scheme mechanism. Consequently, the optimized Ce2S3/ZCS composite presents the best PHE rate of 35.35 mmol h−1 g−1 without an obvious reduction in efficiency for cycling experiments, which has a 4.8-fold increase over Pt/ZCS. This strategy proposes a novel method for optimizing ZCS-based photocatalysis by introducing Ce2S3 component to improve the property of PHE.

Oxygen release and reduction kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 as oxygen carriers for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a viable technology by converting CH4 and CO2 to various value-added products to achieve carbon neutrality. However, it is vital for the technology to find suitable oxygen carriers with high oxygen capacity and activity. La0.35Sr0.35Ba0.3Fe1-xCoxO3 perovskite-type oxides were proposed as oxygen carriers for CL-DRM. The oxygen (O2) release property and the kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 reduction by CH4 were investigated via thermogravimetric analysis, O2-temperature programmed desorption and then in a fixed-bed reactor. The O2 release process of La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be divided into two phases. The O2 release process and corresponding rate of OCs were facilitated due to the substitution of Fe with Co in B-site. The total amounts of O2 release for these OCs were enhanced about 1.5 times from 0.445 mmol/gOC to 0.706 mmol/gOC as Co atomic fraction in B-site changes from 0 to 1. The linear correlation for high temperature phase and a volcano-curve for low temperature phase was found for the correlations among total O2 release and Co content during the O2 release process. The reduction kinetics of CH4 over OCs was described using the Avrami–Erofe'ev model (A1.5 or A2). The values of apparent activation energy (Ea) for all OCs were obtained. The results indicated the best substitution proportion of Co in La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be set in the range of 0.2–0.4 to emerge the excellent redox performance. The kinetics models and parameters offer valuable information for CL-DRM reactor design and further development of OCs with different A or/and B-site modifications.

Influences analysis of Sb/Si dopant in TiO2 on NH3-SCR activity and low temperature SO2 resistance of V2O5/TiO2 catalysts

The Sb/Si doped TiO2 prepared by sol–gel method were used as supports of V2O5/TiO2 SCR catalysts in order to improve SCR activity and SO2 resistance. The type of dopant atoms changed catalyst physiochemical properties discriminatively. Surface chemical properties of catalysts played more important role in their catalytic performance. Simultaneous enhanced surface acidity and redox capacity leaded to the better SCR activity for V2O5/Sb-TiO2 compared with other catalysts. The low temperature SO2 resistance was improved for the support doped catalysts. The special electronic charge migration brought by surface sulfate species for V2O5/Sb-TiO2 even elevated its SCR activity during SO2 resistance test, which was due to the formation of new acid sites and enhancement of redox performance. Even though NOx conversion for V2O5/Si-TiO2 decreased, the relative stable efficiency was kept at low temperatures with SO2. The results proved hetero atom doping in TiO2 by sol–gel method was a useful method to improve low temperature SO2 resistance of catalysts. By contrast, Sb is a better choice for the development of support doped V2O5/TiO2 SCR catalyst used in a wide temperature range.

Waste eggshell to valuable Co3O4/eggshell material as an efficient catalyst for catalytic decomposition of N2O under simulated real tail gases

Co3O4 shows excellent catalytic activity for N2O decomposition, in which it is urgently needed to develop novel efficient catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts (Co3O4/eggshell-GR, Co3O4/eggshell-IM, and Co3O4/eggshell-DP) were prepared using simple grinding, impregnation, and deposition-precipitation methods, where waste eggshells were used as an effective support and reaction-promoter. The results indicated that the preparation methods significantly influenced the catalytic activity of Co3O4/eggshell catalysts; the highest activity was obtained over the Co3O4/eggshell-DP. The activity of Co3O4/eggshell-DP was comparable to that of pure Co3O4. More importantly, its specific activity was about 7.3 times that of Co3O4 at 400 °C. The examined Co3O4/eggshell-DP also displayed outstanding stability and anti-poisoning property in NO, O2, and/or H2O-containing atmospheres. It was also verified that the excellent activity of Co3O4/eggshell-DP correlated with the unique structure of the eggshell and the close incorporation between CaCO3 and Co3O4. The Co3O4/eggshell-DP catalyst owned abundant Co3O4 nanoparticles, more Co3+ species, and excellent redox performance, promoting the conversion of N2O at a lower temperature. The presence of abundant surface basic sites and a larger amount of oxygen vacancies also facilitated the catalytic efficiency of Co3O4/eggshell-DP.

One-step synthesis of ferrocenyl glycidyl ethers as combustion catalysts for the thermal decomposition of ammonium perchlorate

As an oxidant, the pyrolysis behavior of ammonium perchlorate is the key to the combustion of composite solid propellants. Seeking a suitable catalyst to promote AP decomposition has drawn much attention. Ferrocene-based compounds are often used as burning rate catalysts because of their excellent catalytic effect. However, ferrocene-based burning rate catalysts are prone to migration during storage of propellants. In this study, six ferrocenyl glycidyl ethers were designed and synthesized to improve the anti-migration properties, and the related spectra characterization techniques were adopted to confirm their molecular structures. Furthermore, their related properties and mechanisms were also studied. As a result, they showed good redox performance, positive promotion on AP decomposition, excellent combustion and mechanical performance. Meanwhile, they had a higher anti-migration behavior compared with catocene and ferrocene. This study demonstrates that ferrocenyl glycidyl ethers have great potential to be applied as multifunctional burning rate catalysts in composite solid propellants.

In situ synthesis of silver-decorated defective graphitic carbon nitride for enhanced photocatalytic redox performance

Graphitic carbon nitride (g-C3N4) is known to be a promising visible-light-responsive photocatalyst but suffers from limited visible-light response and fast charge recombination. This study provides a facile, in-situ citric acid/AgNO3-assisted strategy to synthesize ultrasmall silver-decorated carbon-deficient g-C3N4 (Ag/D-UCN). The Ag/D-UCN catalyst exhibits excellent performance in the photocatalytic oxidation of organic pollutants and the photocatalytic reduction for H2 evolution. The experimental results confirms that the synergistic effect of ultrasmall Ag and carbon vacancy not only enlarges the light harvesting capacity but also promotes fast charge separation within g-C3N4 and from g-C3N4 to Ag, which are critical for the excellent photocatalytic redox activity of Ag/D-UCN. Thus, this study provides a promising in-situ strategy for the synthesis of high-quality Ag and defects co-modified g-C3N4 for the degradation of organic pollutants and clean energy production.

An effective strategy to enhance the sulfur resistance of Ce-based catalyst for low temperature SCR reaction

SO2 has a significant impact on SCR reaction, and how to suppress the effect of SO2 on Ce-based catalyst activity has been a goal pursued by the scientific community. In this work, the CeSmFTi catalyst was prepared by one-pot hydrothermal method to study the catalytic activity and SO2 resistance performance in NH3-SCR reaction. The experimental findings suggested that Ce5Sm1FTi94 catalyst had better catalytic performance, with the NO conversion exceeding 90% at 320 °C. After enduring SO2 test, the NO conversion could gradually recover to more than 80%. The results showed that the presence of CeF3 efficiently regulated the proportion of active state Ce3+ and accelerated the “fast SCR” reaction, which significantly enhanced the catalytic performance of the catalyst and inhibited the oxidation of SO2. Notably, doping a certain amount of Sm into Ce5FTi94 catalyst not only improved the surface acidity and redox performance, but also promoted the electron transfer and interaction between Ce and Sm species, thereby inhibiting the combination of SO2 and cerium species. Therefore, the formation of sulfate species on the catalyst was minimized, resulting in a better SO2 tolerance. Simultaneously, the in-situ DRIFTs analysis revealed that both L-H and E-R mechanisms were presented on Ce5Sm1FTi94 catalyst to carry out the NH3-SCR reaction process, with the L-H mechanism being dominant.

Insights into the effect of Cu and Fe dispersion state over Ce0.1Al on the catalytic performance of NO reduction by CO

In this paper, Cu and Fe dispersion states over Ce0.1Al were modified by different doping methods such as impregnation and co-precipitation. Cu and Fe were dispersed on the surface of Ce0.1Al carriers in Cu/Fe/Ce0.1Al sample, while for Cu/FeCe0.1Al catalyst, Fe was doped in the carriers and Cu was uniformly dispersed on the surface. The effects of dispersion states on the catalytic behaviors of NO reduction by CO were investigated. The resistance to O2 and SO2 was also verified. Cu/FeCe0.1Al catalyst owned superior denitrification activity and O2/SO2-tolerance performance than Cu/Fe/Ce0.1Al. For the front one, Fe was introduced by co-precipitation scheme. Small particle size and higher specific surface area was achieved. Thus its redox and adsorption performance were ameliorated. For the latter, more active species were enriched on the surface, which was conductive to the defects formation and the reduction of surface adsorbed oxygen. In combination with microstructure characterizations, the intrinsic mechanism was proposed. In essences, the interaction among Cu, Fe and Ce was modified owing to their different dispersion state of Cu and Fe. As a result, NO+CO reaction followed different mechanism over two catalysts. NO reduction by CO on Cu/Fe/Ce0.1Al catalyst followed E-R mechanism, while L-H mechanism was dominant over Cu/FeCe0.1Al catalyst.