Thermally Inducing Viscous Fluids to Generate Co-Based Perovskites Enriched with Active Species for the Removal of VOCs.

Various Co-based perovskites are synthesized through thermally driving viscous fluids. In this process, rare earth salts, cobalt salts, and citric acid do not require homogeneous mixing but only need to be heated until they melt into a molten viscous slurry. The physicochemical properties of cobalt-based perovskites were examined using techniques such as X-ray diffraction (XRD), electron paramagnetic resonance (EPR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-Mapping-EDS), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), oxygen temperature-programmed desorption (O2-TPD), and N2 adsorption-desorption. The results indicate that the surface-active species can be controlled by altering the A-site elements of cobalt-based perovskites. All catalysts synthesized through the thermal treatment of viscous mixtures exhibited a low activation temperature and a low apparent activation energy for the catalytic oxidation of toluene. Among all cobalt-based perovskites, LaCoO3 demonstrated the most outstanding catalytic activity, primarily attributed to its capacity to expose a larger number of surface-active sites and oxygen species, as well as its superior reducibility. Furthermore, the formation process of optimal LaCoO3 was monitored using thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), and the byproducts of the low-temperature catalytic oxidation of toluene by the catalyst were identified using gas chromatography-mass spectrometry (GC-MS). The possible mechanism of toluene oxidation was inferred by in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). Moreover, LaCoO3 exhibits a predominant resistance to high-temperature hydrothermal conditions. This work provides a scalable and innovative approach to fabricating exceptionally effective catalysts for the efficient purification of VOCs.

Comparative Study on the Macroscopic Characteristics of Gasoline and Ethanol Spray from a GDI Injector under Injection Pressures of 10 and 60 MPa.

To reduce particulate matter (PM) emissions from vehicles powered by gasoline direct injection (GDI) engines, increasing the fuel injection pressure has been one promising approach. However, a comparison of macroscopic characteristics between gasoline and ethanol from a GDI injector under an ultrahigh injection pressure of more than 50 MPa has not been reported. The experimental study presented in this paper can provide some new and valuable information about comparing and analyzing the macroscopic characteristics of gasoline and ethanol spray from a GDI injector in both front and side views under injection pressures of 10 and 60 MPa. The experimental results show that compared to ethanol, gasoline spray has a slight advantage in L S (penetration of whole spray), L C (penetration of core region of spray), θS (spray cone angle), and R I (irregularity of spray boundary) under both P I (injection pressure) = 10 MPa and P I = 60 MPa, which would promote a more homogeneous mixture of air and fuel. Furthermore, the advantage of gasoline in θS is more pronounced under P I = 60 MPa. At the end of injection, S S (area of whole spray) of gasoline is around 2% larger than ethanol, while its advantage in S C (area of core region of spray) can be around 5%. With the increase of P I from 10 to 60 MPa, a marked increase of R S (the ratio of S C to S S) and R I indicates that atomization and air-fuel mixture homogeneity can be significantly improved for both gasoline and ethanol spray. Besides, a minor revision to the Dent model helps achieve a significant improvement in the prediction accuracy of L S for both gasoline and ethanol spray under injection pressures of 10 and 60 MPa.

In-situ regulation of acid sites on Mn-based perovskite@mullite composite for promoting catalytic oxidation of chlorobenzene.

A series of Sm-Mn perovskite@mullite composites with different amounts of acid sites were successfully synthesized by regulating the level of in situ etched-surface modification. X-ray diffraction (XRD) test showed that the crystal structure of catalyst gradually changed from perovskite to perovskite@mullite composites and mullite. The characterization of temperature programmed desorption with ammonia (NH3-TPD) confirmed the acid sites on the surface of catalyst can be deployed by the in-situ modification. The temperature-programmed reduction with hydrogen (H2-TPR), and N2 adsorption-desorption showed that the surface modification also increased the reducibility, surface area, and mesoporosity of catalyst. The catalytic activities were compared by a long-term catalytic oxidation of chlorobenzene evaluation for 20 h of uninterrupted reaction at a relatively low temperature of 300 °C, and the Sm-Mn perovskite@mullite composite (SMPM-1.2) possessed the best catalytic stability. The X-ray photoelectron spectroscopy (XPS) measurement determined that the high ratios of lattice oxygen and tetravalent manganese did not improve the stability of catalyst in the catalytic oxidation of chlorobenzene, but the activities trends of samples were consistent with the change of surface (Mn4++Mn3+)/Mn2+ ratios. Meanwhile, the catalytic experiments for benzene, toluene, o-xylene and acetone showed that the as-prepared catalyst was also suitable for the efficient removal of the different types of VOCs. This work supplied a method for the further development of high activity catalysts for the removal of VOCs.

In-Depth Understanding of the Morphology Effect of α-Fe2O3 on Catalytic Ethane Destruction.

Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe2O3 oxides with different micromorphologies were rationally synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N2 sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mössbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H2-TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of α-Fe2O3 were explored by DFT calculations. It is shown that nanosphere-like α-Fe2O3 exhibits much higher ethane destruction activity and reaction stability than nanocube-like α-Fe2O3 and nanorod-like α-Fe2O3 due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like α-Fe2O3 has the lowest formation energy of oxygen vacancy on the (110) facet ( Evo (110) = 1.97 eV) and the strongest adsorption energy for ethane (-0.26 eV) and O2 (-1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face-dependent activities of α-Fe2O3 in alkane destruction.

Influence of implant number on the biomechanical behaviour of mandibular implant-retained/supported overdentures: a three-dimensional finite element analysis.

OBJECTIVE: The aim of this study was to evaluate strain distribution in peri-implant bone, stress in the abutments and denture stability of mandibular overdentures anchored by different numbers of implants under different loading conditions, through three-dimensional finite element analysis (3D FEA). METHODS: Four 3D finite element models of mandibular overdentures were established, using between one and four Straumann implants with Locator attachments. Three types of load were applied to the overdenture in each model: 100N vertical and inclined loads on the left first molar and a 100N vertical load on the lower incisors. The biomechanical behaviours of peri-implant bone, implants, abutments and overdentures were recorded. RESULTS: Under vertical load on the lower incisors, the single-implant overdenture rotated over the implant from side to side, and no obvious increase of strain was found in peri-implant bone. Under the same loading conditions, the two-implant-retained overdenture showed more apparent rotation around the fulcrum line passing through the two implants, and the maximum equivalent stress in the abutments was higher than in the other models. In the three-implant-supported overdenture, no strain concentration was found in cortical bone around the middle implant under three loading conditions. CONCLUSIONS AND CLINICAL SIGNIFICANCE: Single-implant-retained mandibular overdentures do not show damaging strain concentration in the bone around the only implant and may be a cost-effective treatment option for edentulous patients. A third implant can be placed between the original two when patients rehabilitated by two-implant overdentures report constant and obvious denture rotation around the fulcrum line.