Fe2O3 Catalyst Research Articles

Effect of Fe3O4 nanoparticles on magnetic xerogel composites for enhanced removal of fluoride and arsenic from aqueous solution

Fe3O4 magnetic xerogel composites were prepared by polycondensation of resorcinol (R)–formaldehyde reaction via a sol–gel process in an aqueous solution through varying the molar ratio of Fe3O4 nanoparticles (MNPs), catalyst (C), and water (W) content. MNPs were obtained by co-precipitation (MC), oxidation of iron salts (MO), or solvothermal synthesis (MS). Both MNPs and magnetic xerogels were examined regarding the performance of arsenic and fluoride removal in a batch system. The MC-based MNPs had higher adsorption capacities for both fluoride (202.9 mg/g) and arsenic (3.2 mg/g) than other MNPs in optimum conditions. The X-ray diffraction, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy confirmed that Fe was composed into the polymeric matrix of magnetic xerogels that contained 0.59%–4.42% of Fe with a molar ratio of MNPs (M) to R between 0.01 and 0.10. With low R/C and optimum M/R ratios, an increase in the surface area of magnetic xerogels affected the fluoride and arsenic adsorption capacities. The magnetic xerogel composites with the MC-based MNPs prepared at a fixed R/C ratio (100) and at different R/W (0.05–0.06) and M/R (0.07–0.10) ratios had a high arsenic removal efficiency of 100% at an As(V) concentration of 0.1 mg/L and pH of 3.0. The maximum adsorption capacities of magnetic xerogels were approximately five times higher than those of the xerogels without MNP composites. Therefore, Fe3O4 nanoparticles enhanced the adsorption of arsenate and fluoride. The variations of alkaline catalyst and water content significantly affected the resulting properties of textural and surface chemistry of magnetic xerogel composites.

A simple method to form a forest of carbon nanotube bundles during growth stage

This study reports a novel, cost-effective and reproducible method of densifying carbon nanotubes into bundles during growth stage. This is achieved by utilizing Fe3O4 catalyst nanoparticles and microwave plasma-enhanced chemical vapor deposition. The grown CNTs were characterized using TEM, SEM and Raman spectrometer. The achieved site density of bundles is 5 × 109 m–2, with an inter-bundle distance of 14 μm and bundle height of 17 μm. A qualitative investigation was carried out, and a possible densification mechanism was proposed.Article HighlightsA cost-effective method to form bundles of carbon nanotubes.Densification of carbon nanotubes occurs during growth stage.The resultant structures are desirable for electron field emission applications.

Electronic modulation of InNi3C0.5/Fe3O4 by support precursor toward efficient CO2 hydrogenation to methanol

Carbon neutrality is spurring worldwide impetus on the exploration of CO2 hydrogenation to methanol, but groundbreaking catalyst presents a grand challenge. An outstanding InNi3C0.5/Fe3O4 catalyst is tailored by finely tuning the electronic metal-support interaction (EMSI) that is controlled by Fe3O4 precursor. The one using Fe3O4-N (from ferric nitrate) stands out against the ones using Fe3O4-A (ferrous acetate) and Fe3O4-C (ferric chloride), achieving a turnover frequency (421.6 h−1) 2.3–3.1 times as high as that of the two others. There is a correlation between the oxygen deficiency of Fe3O4 and the EMSI-governed activity. The EMSI effect is enhanced substantially by the highly oxygen-deficient Fe3O4-N. Enhanced EMSI makes InNi3C0.5 electron-enriched and thus enables CO2 to be dissociated easily. The InNi3C0.5/Fe3O4-N achieves a high methanol space time yield of 2.60 gMeOH gcat−1 h−1 with 92.0% methanol selectivity at 325 °C and 6.0 MPa. This catalyst is also highly anti-sintering and anti-sulfur poisoning.

Effect of CeO2 and Pt introduction on the structure and performance of Fe2O3 for Hg0 removal

In this work, the thermal stability and catalytic activity of Fe2O3 catalyst for Hg0 oxidation were improved by the introduction of CeO2 and Pt. During high-temperature calcination at 400 °C, the mesoporous structure of Pt/CeO2/Fe2O3 remained stable, and it also retained higher specific surface area and lower average pore size than Fe2O3. The X-ray diffraction, transmission electron microscopy, and thermal gravimetric-differential scanning calorimetry results revealed that the modification of CeO2 and Pt retarded the crystallization and growth of Fe2O3 grains during high-temperature calcination, limiting Fe2O3 particles to a smaller size. Temperature-programmed desorption experiments showed that Hg0 adsorption of Pt/CeO2/Fe2O3 was promoted. In addition, X-ray photoelectron spectroscopy spectra suggested that adding CeO2 and Pt also increased the content of chemisorbed oxygen and transformed Fe2O3 into an electron-rich state, which consequently improved its catalytic performance for Hg0 oxidation.

Tailoring interfacial electron redistribution of Ni/Fe3O4 electrocatalysts for superior overall water splitting

Exploring highly active earth-abundant bifunctional electrocatalysts for water splitting at a high output is essential for the forthcoming hydrogen economy. Non-noble Fe3O4 catalyst owns outstanding conductivity and its octahedral Fe sites can markedly promote water dissociation. However, it lacks active centers on the surface, resulting in its poor activity when used as a catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, an electron redistribution strategy is proposed by introducing Ni sites onto the surface of Fe3O4 (Ni/Fe3O4). The abundant delocalized electrons, derived from the electronic interaction of Ni and Fe3O4 species, significantly optimize the electronic structure of the Ni/Fe3O4 catalyst, leading to its improved adsorption behavior. This Ni/Fe3O4 catalyst exhibits remarkable bifunctional activity, steadily outputting 1000 mA cm−2 at the low overpotential of 387 mV for HER and 338 mV for OER, respectively. Using Ni/Fe3O4 as a bifunctional catalyst for overall water splitting reaction exhibits the optimal performance with outstanding stability, obtaining a current density of 1000 mA cm−2 at 1.98 V, much superior to a Pt/C||IrO2 cell. Experimental analysis and theoretical calculations collectively corroborate that the electron redistribution of Fe3O4 is activated by coupling Ni species, leading to the promoted HER and OER kinetics. This electron redistribution strategy provides an effective method to activate transition metal-based catalysts which are promising to be utilized as superior electrocatalysts for the industrial overall water splitting reaction.

In situ deposition of 0D CeO2 quantum dots on Fe2O3-containing solid waste NH3-SCR catalyst: Enhancing redox and NH3 adsorption ability

As NOx has been turning into a crucial environmental problem, NH3-SCR technology with relatively simple device, reliable operation and low secondary pollution, has become a widely used commercial and mature de-nitration technology. However, some weaknesses restricted the further application of commercialized V2O5-WO3/TiO2 NH3-SCR catalysts, while Fe2O3-based catalysts have received much attention due to their high thermal stability, passable N2 selectivity and low cost. In this study, Fe2O3-containing solid waste derived from Zn extraction process of electric arc furnace dust was exploited as the base material for catalyst preparing. Owing to the complementary and synergistic effect of CeO2 and Fe2O3, 0D CeO2 quantum dots (CeQDs) with fully-exposed active sites, large specific surface area, and rapid charge transfer have been introduced and deposited onto Fe2O3-containing solid waste nanorods. The in-situ deposition of CeQDs led to the admirable enhancement in NH3-SCR catalytic activity, N2 selectivity and SO2 tolerance of the extremely low-cost Fe2O3 catalyst. Comprehensive characterizations and DFT calculations describing the adsorption of O2 and NH3 were applied to analyze the catalyst structure and further investigate the detailed relationship between structural properties and activity as well as reaction mechanism. This work provides new insights for the high-value utilization of iron-containing solid waste and a practical reference for boosting the performance of NH3-SCR catalysts by introducing quantum dots.

Insight into highly efficient FeOx catalysts for the selective catalytic reduction of NOx by NH3: Experimental and DFT study

Fe3O4, α-Fe2O3 and γ-Fe2O3 catalysts were synthesized and showed excellent activities for the selective catalytic reduction (SCR) of NOx by NH3 in the temperature range that was between 433 K and 653 K in the presence of excess oxygen. Physical and chemical properties of catalysts were tested to investigate the effect of the iron oxides on the NH3-SCR activities by a series of characterization methods that were XRD, H2-TPR, NH3-TPD, BET and XPS. The related results indicated that the species of iron oxides had significant effects on oxidation–reduction ability, surface acidity distribution, BET surface area and surface adsorbed oxygen. Meanwhile, DRIFTS tests were carried out to further investigate the reduction process over α-Fe2O3, γ-Fe2O3 and Fe3O4 catalysts, supporting the DFT calculations. The adsorption energy of ammonia and nitric oxide on α-Fe2O3 (001), γ-Fe2O3 (001) and Fe3O4 (111) surfaces are calculated by the Density Functional Theory (DFT) calculations, suggesting that ammonia and nitric oxide are easily adsorbed on the Fe3O4 (111) surface. Moreover, it is reasonable to draw a conclusion that more surface chemisorbed oxygen, easier adsorption of reaction gases (NO, NH3 and O2) and more effortless oxidative dehydrogenation process can promote NH3-SCR.

Fast pyrolysis characteristics and its mechanism of corn stover over iron oxide via quick infrared heating

The harm done to the environment by fossil fuels was serious, and it is urgent to find effective methods and adopt carbon–neutral feedstock to prevent further environmental damage. An innovative infrared heating reactor was developed for the generation of high-yield bio-oil and cleaner pyrolysis gases. This work was devoted to exploring the fast pyrolysis characteristics and its mechanism of corn stover over the iron oxide in a novel infrared heating (IH) reactor and a traditional electric heating (EH) reactor. In the IH reactor, the bio-oil yield increased initially and then decreased with increasing pyrolysis temperature, reaching a maximum yield of 29 wt% at 600 °C. The yield of pyrolysis bio-oil and water decreased as the reusability number rose, whereas the char yield increased. Bio-oil yields decreased less from R0 to R3 and the catalyst was more effective in IH. IH produced more char and gas but considerably less water than EH, and its bio-oil had fewer phenols. Raman spectroscopy demonstrated that the aromatic structure of biochar increased as the pyrolysis temperature increased. Cellulose and hemicellulose can be completely cleaved at lower temperatures in IH. In addition, Fe2O3 catalysts have shown the advantages of low cost, efficient cycling, and long action time. Infrared heating coupled with iron oxide catalyst shows the potential to increase bio-oil yield and is more promising for industrial production than EH.

Enhancing catalytic activity of Fe3O4 for electrochemical water oxidation via the coupling of OER-inert Au

Interfacial charge transfer efficiency and electronic states of active sites are two essential issues to restrict catalytic activity of electrocatalysts for oxygen evolution reaction (OER). In this work, we show that although Au is recognized to be inert towards OER, the catalytic activity of Fe3O4 catalyst for OER was highly boosted by coupling Fe3O4 with Au to address these two issues. Here, Au nanoparticles were attached to hierarchical Fe3O4 microsphere through electrochemical deposition, a mild and rapid approach that can be accomplished within 3 min and requires no sophisticated equipment. With the coupling of Au, interfacial charge transfer resistance of Fe3O4 declined remarkably. On the other hand, oxidability of Fe sites and electron accepting capability of Au sites was elevated due to strong interaction between Au and Fe3O4. Owing to these two merits induced by Au, Fe3O4 exhibited enhanced catalytic activity for OER. The potential of Fe3O4 to obtain 10 mA/cm2 decreased by 640 mV, the current density was amplified up to 2.5 fold at the potential of 2 V (vs SCE), and the Tafel slop was reduced by 146 mV/dec.

Selective Production of Aromatics Directly from Carbon Dioxide Hydrogenation over nNa–Cu–Fe2O3/HZSM-5

Na and Cu additives have been widely studied for their promotional efficiency of Fe-based catalysts directly converting CO2 to valuable hydrocarbons. Selective hydrogenation of CO2 toward aromatics, however, is still a huge challenge. Herein, we fabricated a bifunctional catalyst comprising Fe2O3 promoted by Na and Cu and hierarchical nanocrystalline HZSM-5, and then the catalytic performance and reaction conditions of CO2 hydrogenation were investigated by coupling nNa–Cu–Fe2O3 catalysts with HZSM-5. The maximum aromatic selectivity achieved 57.74% (including CO) at 33.26% CO2 conversion, and the proportion of aromatics in liquid products reached up to 94.81%. Moreover, the selectivity of light aromatics achieved 30.36%. The subtle synergy between Na and Cu in Fe2O3 contributed to the activation of iron species and the conversion of intermediates. In addition, the enhanced mesoporous and appropriate acidity over HZSM-5 was attributed to the post-treatment modification which facilitated the high aromatic selectivity and outstanding catalytic stability. Significantly, fast diffusion pulled off the synergistic effect on the tandem reaction owing to the presence of hierarchical HZSM-5.

Experimental study on Denitrification and in-situ reduction of NO with Fe2O3 catalyst during coke combustion

ABSTRACT Fe2O3, as a cheap and readily available metal catalyst, can effectively reduce the emission of polluting gases in the combustion process, which is an encouraging way to realize the clean utilization of coke. This work focuses on the effect of Fe2O3 in denitration (deNOX) and in-situ reduction of NO during civil clean coke combustion. The influence of catalyst addition and temperature on char-N migration was discussed. Results showed that the catalytic reduction activity is the best when the addition amount is 3%. The reaction is accelerated and the NO emission time is shortened with an increase of combustion temperature, which is mainly due to the enhanced promotion of Fe2O3. Fe reacted with NO, further reducing its releasing amount. Furthermore, char has more significant effects on the reduction of NO in the presence of CO and Fe2O3, up to 90%. Thus, the effect of Fe2O3 on reaction paths is determined. The reduction effect of Fe2O3 on NO was mainly due to the formation of reduced Fe0 during the pyrolysis process. This study can provide some theoretical guidance for the pollution control of loose coal combustion in rural areas.

Catalytical enhancement on hydrogen production from LiAlH4 by Fe–Fe2O3 addition

Hydrogen storage technology plays an important role on the development of hydrogen fuel cell and lithium aluminum hydride is a powerful candidate for solid-state hydrogen storage materials. However, the high stability and slow dehydrogenation kinetics of LiAlH4 hinder its application. In this paper, the two-step thermal decomposition properties of LiAlH4 with and without Fe–Fe2O3 catalysts are investigated. According to the master plots, the model of mample power law (Pn) and nucleation and growth (An) are the optimal mechanism functions for the two-step decomposition of LiAlH4, respectively. After doping catalysts, the activation energies decrease significantly. The theoretical and optimized kinetic method are consistent with each other on activation energy. And the latter can also yield other kinetic parameters for a more comprehensive kinetic modelling of LiAlH4 decomposition. Furthermore, Fe–Al2O3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH4.

Comparative study of H2O2/PDS-based advanced oxidation process using Fe3O4 nanoparticles for Rhodamine B degradation: Mechanism, stability and applicability

In this work, we made a comparative study on the differences in the mechanism, stability and applicability of H2O2/Fe3O4 and PDS/Fe3O4 systems for Rhodamine B (RhB) degradation. The RhB degradation rate of H2O2/Fe3O4 system could reach 71.5% at 60 min, and its primary mechanism was regarded as the heterogeneous catalysis occurring on Fe3O4 surface. In this process, the newly formed Fe2O3 covered the active sites on Fe3O4 surface, hindering the continuous interaction between H2O2 and Fe3O4. Alternatively, the RhB degradation rate of PDS/Fe3O4 system could reach 98.5% at 60 min, and the homogeneous and heterogeneous catalysis were equally important. In this process, the formed S2O82‐ promoted the cycle of iron species to produce a lot of OH and SO4−, which significantly improved degradation performance. The RhB degradation pathway of two oxidation systems went through N-de-ethylation, chromophore cleavage, ring-opening and mineralization. After six cycles of degradation experiment, the RhB degradation rate of H2O2/Fe3O4 and PDS/Fe3O4 systems still reached 67.3% and 93.7%, and the corresponding mass loss of Fe3O4 catalyst was only 2.68% and 4.5%, respectively. Next, the alkaline environment greatly hindered the catalytic decomposition of H2O2 by Fe3O4, thus the H2O2/Fe3O4 system had a narrow pH application range (4.0–6.0), but PDS could be activated effectively by Fe3O4 catalyst in a wide pH range (4.0–10.0). In addition, the PDS/Fe3O4 system presented the stronger adaptability to actual water (including Cl‐, CO32-, HCO3-) and multi-pollutant degradation (including methylene blue, acid orange 7, tetracycline and bisphenol A) than the H2O2/Fe3O4 system. Finally, the two oxidation systems both effectively reduced the toxicity of pollutants and presented the exact cost.

Hollow Meso-crystalline Mn-doped Fe3O4 Fenton-like catalysis for ciprofloxacin degradation: Applications in water purification on wide pH range

Herein, an unprecedented heterogeneous Fenton-like catalyst with a hollow meso-crystalline Fe3O4 catalyst doped with Mn was prepared for the first time through a one-pot method, which can effectively activate H2O2 in a wide pH range and has good stability. The results show the catalyst can achieve rapid degradation of ciprofloxacin (CIP) under the conditions of pH = 4.5 to pH = 9.5, which greatly expands the application conditions of Fenton. Sufficient experimental exploration clearly demonstrated that the uniform doping of Mn in Fe3O4 crystal lattice, and the formation process of Mn-doped Fe3O4 hollow meso-crystalline microspheres was reasonably analyzed based on Ostwald curing theory and bubble theory. The dual reaction center theory reasonably explains the reaction mechanism of the catalyst. The H2O2 adsorbed on the electron-rich Fe center is reduced to •OH, while the H2O2 adsorbed on the electron-deficient Mn center is oxidized to •O2–/HO2•, •OH and •O2–/HO2• are further converted to 1O2, which participates in involved in the degradation process of CIP. This research provides new ideas for the rational design of catalysts that can apply the heterogeneous Fenton reaction to actual water purification in a wide pH range.

Electrochemically Reconstructed Cu‐FeOOH/Fe3O4 Catalyst for Efficient Hydrogen Evolution in Alkaline Media

AbstractSurface self‐reconstruction via incorporating an amorphous structure on the surface of a catalyst can induce abundant defects and unsaturated sites for enhanced hydrogen evolution reaction (HER) activity. Herein, an electrochemical activation method is proposed to reconstruct the surface of a Cu‐Fe3O4 catalyst. Following a “dissolution–redeposition” path, the defective FeOOH is formed under potential stimulation on the surface of the Cu‐Fe3O4 precursor during the electrochemical activation process. This Cu‐FeOOH/Fe3O4 catalyst exhibits excellent stability as well as extremely low overpotential toward the alkaline HER (e.g., 129 and 285 mV at the large current densities of −100 and 500 mA cm−2, respectively), much superior to the Pt/C catalyst. The experimental and density functional theory calculation results demonstrate that the Cu‐FeOOH/Fe3O4 catalyst has abundant oxygen vacancies, featuring optimized surface chemical composition and electronic structure for improving the active sites and intrinsic activity. Introducing defective FeOOH on the surface of a Cu‐Fe3O4 catalyst by means of an electrochemical activation method decreases the energy barrier of both H2O dissociation and H2 generation. Such a surface self‐reconstruction strategy provides a new avenue toward the production of efficient non‐noble metal catalysts for the HER.

Fe3O4 catalytic ozonation of iohexol degradation in the presence of 1-hydroxybenzotriazole: Performance, transformation mechanism, and pathways

This study explored the degradation of an iodine X-ray contrast media, iohexol, under heterogeneous ozone-catalyzed oxidation by adding Fe3O4 and 1-hydroxybenzotriazole (HBT). Results show that increasing the dosages of Fe3O4 catalyst and ozone as well as solution pH were beneficial to the degradation of iohexol. The presence of low background humic acid (HA) concentration (≤10 mg/L) promoted iohexol degradation, but high HA concentration (≥20 mg/L) inhibited it. Adding HBT exhibited a similar effect on iohexol degradation as HA. The degradation rate constant of iohexol was calculated as 0.07108 min−1 in the Fe3O4/O3/HBT process ([HBT] = 5 μM) at pH 7.0, which was approximately 1.5 times higher than that in the Fe3O4/O3 process (0.04533 min−1), and 4 times higher than that in the O3 process (0.01742 min−1). Fe3O4/O3/HBT process was pH-dependent with high degradation efficiency of iohexol at pH 5 or 7. Singlet oxygen (1O2), hydroxyl radical (OH∙), and superoxide radical (O2-∙) have been identified in the Fe3O4/O3/HBT process, and the conversion of Fe2+ to Fe3+ was more obvious on the surface of Fe3O4 compared to that in the Fe3O4/O3 process. Transformation intermediates were identified, and the degradation pathways of iohexol were proposed. Overall, Fe3O4/O3 could enhance iohexol degradation compared with ozone-only system, and adding trace HBT in Fe3O4/O3 system can further enhance heterogeneous ozone-catalyzed process for rapid organic matter degradation.

Simultaneous Removal of Hg0 and H2S over a Regenerable Fe2O3/AC Catalyst

Simultaneous removal of Hg0 and H2S over a regenerable activated coke supported Fe2O3 catalyst (Fe2O3/AC) was studied in simulated coal-derived syngas. It was found that the Fe2O3/AC catalyst exhibited high capability for Hg0 and H2S removal, which was attributed to the catalytic oxidation activity of Fe2O3. Its capability for Hg0 and H2S removal increased with an increase of Fe2O3 loading amount, and the highest was at 150 °C for Hg0 removal. CO and H2 showed no obvious effect on Hg0 removal by Fe2O3/AC, while H2S had a promotion effect, which was due to S and FeSx produced by the H2S reaction on Fe2O3/AC. The results of SEM-EDX and the temperature programmed desorption experiment (TPD) revealed that Fe2O3 played a critical role in Hg0 oxidation, and HgS was generated upon the reaction of Hg0 with H2S on Fe2O3/AC. The used Fe2O3/AC catalyst after Hg0 and H2S removal could be effectively regenerated and still had high capability for Hg0 and H2S removal.

Sulphuric acid decomposition using Cr–Fe2O3 catalyst in a tubular Packed Bed Reactor (PBR): Modeling and experimental studies

Catalytic decomposition of sulphur trioxide (SO3), is the rate-controlling and high temperature-endothermic reaction step in three-step decomposition of sulphuric acid. In this work, formulation of one dimensional (1-D) model, detailed transport modeling and experimental studies have been carried out for a non-isothermal, non-adiabatic, tubular-Packed Bed Reactor (PBR). This is to study the effect of heat and mass transfer resistances, in the catalyst bed and also within the catalyst particle, for the decomposition of SO3. 1-D model consists of set of coupled Differential Algebraic Equations (DAEs), which are numerically solved for axial profiles (Temperature, Flow, Pressure) with plug flow reactor assumption. Further, a double-porosity modeling of the reactor has been carried out for the detailed transport study using COMSOL MULTIPHYSICS® simulation software. Here transport equations with the rate law are solved for two different porosities (domains); micro pores inside the catalyst particle (ε) and macro pores (void fraction-φ) in the packing. Models are validated with experimental studies and the molar conversion of SO3 obtained using the models are compared with conversion of an isothermal PBR. Chromium doped iron oxide (Cr–Fe2O3) catalyst; a ‘pellet’ type catalyst is used in this experimental study. Experiments are carried out at different flow (liquid) rates (160–315 ml h−1), wall temperature (973–1243 K) and with two different catalyst bed lengths (catalyst loading of 555 g and 288 g). Double-porosity (COMSOL) model predictions are better close to the experimental data. A multi-scale analysis of the system has been carried out using the double-porosity model, in order to get an insight of concentration drops in the particle (pore diffusion resistance) and fluid film (film resistance) at various locations inside the reactor. Film resistance is found to be negligible when compared with the pore diffusion resistance, in the studied experimental conditions. Modeling of transport (heat and mass transfer) resistances together with kinetics of SO3-decomposition, in two different porous-domains in a PBR, is the novelty of present work. The developed models are useful for maximizing the conversion of SO3 (by tuning the model parameters) in a PBR by minimizing the heat and mass transfer resistances.

Induction Heating of Magnetically Susceptible Nanoparticles for Enhanced Hydrogenation of Oleic Acid.

Radio frequency (RF) induction heating was compared to conventional thermal heating for the hydrogenation of oleic acid to stearic acid. The RF reaction demonstrated decreased coke accumulation and increased product selectivity at comparable temperatures over mesoporous Fe3O4 catalysts composed of 28–32 nm diameter nanoparticles. The Fe3O4 supports were decorated with Pd and Pt active sites and served as the local heat generators when subjected to an alternating magnetic field. For hydrogenation over Pd/Fe3O4, both heating methods gave similar liquid product selectivities, but thermogravimetric analysis–differential scanning calorimetry measurements showed no coke accumulation for the RF-heated catalyst versus 6.5 wt % for the conventionally heated catalyst. A different trend emerged when hydrogenation over Pt/Fe3O4 was performed. Compared to conventional heating, the RF increased the selectivity to stearic acid by an additional 15%. Based on these results, RF heating acting upon a magnetically susceptible nanoparticle catalyst would also be expected to positively impact systems with high coking rates, for example, nonoxidative dehydrogenations.

Discovering the key role of MnO2 and CeO2 particles in the Fe2O3 catalysts for enhancing the catalytic oxidation of VOC: Synergistic effect of the lattice oxygen species and surface-adsorbed oxygen

Highly active mesoporous Fe–Mn–Ce catalysts with high specific surface area (SBET) were synthesized by a modified precipitation process for catalyzing toluene oxidation. The Fe0.85Mn0.1Ce0.05 catalyst presents richer surface oxygen species (OS), a higher proportion of Mn4+ and Ce4+, a higher concentration of lattice defects and oxygen vacancies, the highest Oads/Olatt ratio, and a superior low-temperature redox property compared with the Fe-Mn binary oxide and Fe2O3 and MnO2 catalysts. The properties contribute to a high catalytic activity to achieve T90% of toluene conversion at 264 °C and 185 °C with a gas hourly space velocity (GHSV) at 180,000 and 20,000 mL/(g∙h), respectively. The introduction of a slight quantity of Ce and Mn onto the Fe2O3 catalyst is the key to enhancing the synergistic effect of the lattice OS and surface-adsorbed oxygen, contributing to the activation oxidation procedure of toluene. In-situ DRIFTS analysis reveals that the rich oxygen vacancy concentration of catalysts accelerates the key steps for the generation and activation of oxidized products. These catalysts with rich oxygen vacancies can efficiently diminish the accumulation of a small number of the intermediary species (phenolate, C6H5–OH) produced during the catalytic oxidation of toluene.