Preparation and characterization of TiO2, ZnO,and TiO2/ZnO nanofilms via sol–gel process

The preparation of the TiO₂, ZnO, and TiO₂/ZnO nanofilms was conducted on glass via sol–gel process. The prepared film was detailedly characterized by means of OM, SEM, XRD, and EDS. The results showed that the obtained pure TiO₂ was composed of nanoparticles. For pure ZnO it consisted of nanoparticles and large agglomerates. Both the microstructural morphology and the crystallization of the prepared TiO₂/ZnO composite film were strongly related to the Ti/Zn ratio in the film. With a Ti/Zn ratio less than 1/1, the composite film was absence of cracks. Poor crystallization was definitely observed for the composite film with Ti/Zn ratio of 3/1 and 1/1. The EDS analysis revealed homogeneous distribution of Ti and Zn elements in the film.     

H2 and H2/CO oxidation mechanism on Pt/C, Ru/C and Pt–Ru/C electrocatalysts

The oxidation kinetics of H₂ and H₂ + 100 ppm CO were investigated on Pt, Ru and Pt–Ru electrocatalysts supported on a high-surface area carbon powder. The atomic ratios of Pt to Ru were 3, 1 and 0.33. XRD, TEM, EDS and XPS were used to characterize the electrocatalysts. When alloyed with ruthenium, a decrease in mean particle size and a modification of the platinum electronic structure were identified. Impedance measurements in H₂SO₄, at open circuit potential, indicated different mechanisms for hydrogen oxidation on Pt/C (Tafel–Volmer path) and Pt–Ru/C (Heyrowsky–Volmer path). These mechanisms also occur in the presence of CO. Best performances, both in H₂ and H₂ + CO, were achieved by the catalyst with the ratio Pt/Ru = 1. This is due to a compromise between the number of free sites and the presence of adsorbed water on the catalyst. For CO tolerance, an intrinsic mechanism not involving CO electroxidation was proposed. This mechanism derives from changes in the electronic structure of platinum when alloyed with ruthenium.     

Comparative Study of Reactive Dyes Oxidation by H2O2/UV,H2O2/UV/Fe2+ and H2O2/UV/Fe° Processes

The decolorization and mineralization of two reactive dyes C.I. Reactive Blue 4 (RB 4) and C.I. Reactive Blue 268 (RB 268) were studied using various advanced oxidation processes (AOPs) such as H₂O₂/UV, H₂O₂/UV/Fe²⁺, and the H₂O₂/UV/Fe°. All processes were performed within a laboratory-scale photo-reactor setup. The experimental results were assessed in terms of absorbance (A) and total organic carbon (TOC) reduction. The main degradation products were identified by high resolution gas chromatography/high resolution mass spectrometry analyses. The results of our study demonstrated that the additions of moderate concentrations of H₂O₂ and Fe catalyst during the AOPs evidently increased the decolorization efficiencies within the first few minutes of the processing time (5–10 min) for both tested dyes, and prolonged irradiation does not necessarily significantly improve decolorization. On contrary, TOC removal rate increased with the processing time and with the addition of the catalyst from 40–50% up to 70–80% at defined experimental conditions. All the tested AOPs were very successful methods for RB 268 decolorization, having very complex structure and much higher molecular weight compared to the dye RB 4. This is important from both economic and ecological points of view.     

Ozone formation with (V)UV‐enhanced dielectric barrier discharges in dry and humid gas mixtures of O2, N2/O2, and Ar/O2

The effect of (V)UV illumination at 172 run and 253.7 run on ozone formation with dielectric barrier discharges in air‐like mixtures of nitrogen/oxygen and argon/oxygen as function of the water concentration is presented. Although (V)UV at these wavelengths efficiently cleaves ozone, the ozone concentration in a combined (V)UV/dielectric barrier discharge in oxygen‐containing gases is reduced only very little. This corresponds to an enhanced concentration of atomic singlet oxygen, which, in presence of water, increases the production of hydroxyl radicals. This is confirmed by measurements of the removal rates of 2‐propanol and of its byproducts in dry and humid air in a combined (V)UV/dielectric barrier discharge treatment.     

Comparative Study on Partial Oxidation of Methane over Ni/ZrO2, Ni/CeO2 and Ni/Ce–ZrO2 Catalysts

The partial oxidation of methane has been studied by sequential pulse experiments with CH₄ O₂ CH₄ and simultaneous pulse reaction of CH₄/O₂ (2/1) over Ni/CeO₂, Ni/ZrO₂ and Ni/Ce–ZrO₂ catalysts. Over Ni/CeO₂, CH₄ dissociates on Ni and the resultant carbon species quickly migrate to the interface of Ni–CeO₂, and then react with lattice oxygen of CeO₂ to form CO. A synergistic effect between Ni and CeO₂ support contributes to CH₄ conversion. Over Ni/ZrO₂, CH₄ and O₂ are activated on the surface of metallic Ni, and then adsorbed carbon reacts with adsorbed oxygen to produce CO, which is composed of the main path for the partial oxidation of methane. The addition of ceria to zirconia enhances CH₄ dissociation and improves the carbon storage capacity. Moreover, it increases the storage capacity and mobility of oxygen in the catalyst, thus promoting carbon elimination.     

O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解磺基水杨酸

实验利用O3/UV,O3/TiO2/UV,O3/VO2/TiO2降解了磺基水杨酸.结果表明,在这三种高级氧化技术中,O3/VO2/TiO2的氧化效果最好,如在相同的条件下,30 min后取样表明三者COD的去除率分别为47%,55%和70%.在不同pH条件下研究表明O3/TiO2/UV对水体pH的影响较为敏感.通过加入自由基猝灭剂研究表明三者产生羟基自由基的活性顺序是O3/VO2/TiO2＞O3/TiO2/UV＞O3/UV.     

SO2 Reactions over γ-Al2O3,Pt/γ-Al2O3,Sn/γ-Al2O3 and Pt–Sn/γ-Al2O3

Platinum and Platinum–tin bimetallic catalysts supported on alumina were prepared by co-impregnation of both metallic precursors on the support and used as catalysts for the oxidation of SO₂. Platinum dispersion was determined by means of H₂–O₂ titration. Tin addition (1 and 2 wt%) only slightly decreased the exposed platinum atoms suggesting that tin is mainly over the support. At temperatures lower than 300 °C, SO₂ did not react with oxygen. Nevertheless, when the temperature was increased, the SO₂ oxidation began. The ignition temperatures for SO₂ oxidation (taken at 50% conversion) were 345 °C for 1% Pt/Al₂O₃ and 520 °C for 1% Pt–2% Sn/Al₂O₃. The strong displacement on activity suggests that tin plays an important role as inhibitor of the SO₂ oxidation reaction.     

Transesterification of Soybean Oil Over Me/Al2O3 (Me = Na, Ba, Ca, and K) Catalysts and Monolith K/Al2O3-Cordierite

Four different Me/Al₂O₃ (Me = Na, Ba, Ca, and K) powder catalysts prepared by incipient-wetness impregnation, and a K/Al₂O₃-cordierite monolithic catalyst produced by the dipcoating technique were used for biodiesel production. The samples were characterized and studied in the transesterification of soybean oil with methanol at 120 °C and 500 rpm, with a alcohol/oil molar ratio = 32, and a catalyst load = 1 wt% for the powder catalyst and 0.5 wt% for the monolith. The Ca/Al₂O₃, Na/Al₂O₃ and K/Al₂O₃ powder catalysts reported a FAME (fatty acid methyl esters) formation of 94.7, 97.1, and 98.9% respectively after 6 h of reaction. On the other hand, Ba/Al₂O₃ showed little activity (7.6%). The leaching of the alkali and alkaline earth metal species during reaction was important, what indicates that the activity could be explained in terms of a homogeneous–heterogeneous catalyst effect. When the monolithic sample and the powder catalyst were compared (under identical reaction conditions), the production of FAME for the latter was 89.5–59.1% for the monolithic catalyst. After two consecutive runs, the monolithic catalyst presented a partial deactivation of 8% in the FAME yield. The present work shows that the use of monolithic catalysts in the transesterification of vegetable oils is a viable alternative.     

Hydrogenation of Sunflower Oil over M/SiO2 and M/Al2O3 (M = Ni,Pd, Pt,Co, Cu) Catalysts

This work is aimed at evaluating the performance of several catalysts in the partial hydrogenation of sunflower oil. The catalysts are composed of noble (Pd and Pt) and base metals (Ni, Co and Cu), supported on both silica and alumina. The following order can be proposed for the effect of the metal on the hydrogenation activity: Pd > Pt > Ni > Co > Cu. At a target iodine value of 70 (a typical value for oleomargarine), the production of trans isomers is minimum for supported nickel catalysts (25.7–32.4 %, depending on the operating conditions). Regarding the effect of the support, Al₂O₃ allows for more active catalysts based on noble metals (Pd and Pt) and Co, the effect being much more pronounced for Pt. Binary mixtures of catalysts have been studied, in order to strike a balance between catalyst activity and product distribution. The results evidence that Pd/Al₂O₃–Co/SiO₂ mixture has a good balance between activity and selectivity, and leads to a very low production of trans isomers (11.8 %) and a moderate amount of saturated stearic acid (13.5 %). Consequently, the utilization of cobalt‐based catalysts (or the addition of cobalt to other metallic catalysts) could be considered a promising alternative for the hydrogenation of edible oil.     

Catalytic removal of NO in waste incineration processes over Rh/Al2O3 and Rh–Na/Al2O3: Effects of particulates,heavy metals,SO2 and HCl

Two novel catalysts Rh/Al₂O₃ and Rh–Na/Al₂O₃ were prepared for NO removal and tested their practical performances in a laboratory-scale waste incineration system. The effects of particulates, heavy metals, and acid gases on the catalysts were evaluated and investigated through several characterization techniques, such as SEM, EA, XRPD, ESCA, and FTIR. The results indicated that the NO conversions were increased with the accumulation of particulates on the surface of catalysts, which was attributed to the increase in carbon content. However, the increase in heavy metals Cd and Pb contents on the surface of catalysts decreased the activity of catalyst for NO removal but did not change the chemical state of Rh and Na. The Rh/Al₂O₃ catalysts were poisoned when the acid gases SO₂ and HCl were present in the flue gas, because Rh and Al reacted with S and Cl to form inactive products. Adding Na to Rh/Al₂O₃ catalysts produced a promoting effect for SO₂ removal due to the formation of Na₂SO₄. The influence levels of different pollutants on the performances of Rh/Al₂O₃ and Rh–Na/Al₂O₃ catalysts for NO removal followed the sequence of HCl > heavy metals > SO₂ > particles.     

Preparation,characterization, and kinetic evaluation of dendrimer-derived bimetallic Pt–Ru/SiO2 catalysts

A series of silica-supported Pt, Ru, and Pt–Ru catalysts has been synthesized using dendrimer–metal nanocomposite (DMN) precursors prepared by both co- and sequential complexation with metal salts. The catalysts have been characterized by several techniques, including electron microscopy, temperature-programmed titration of adsorbed oxygen, and X-ray diffraction. Liquid-phase selective hydrogenation of 3,4-epoxy-1-butene (EpB) was used as a probe reaction to evaluate their catalytic performance. The bimetallic catalyst prepared by the co-complexation method exhibits a superior catalytic activity compared to the sequential one, and is much more active than a conventional catalyst prepared by incipient wetness. The activity enhancement is attributed to a bifunctional performance of the PtRu alloy sites created, based on a strong correlation between turnover frequencies, and both the alloy compositions and metal surface site distributions. In addition, the co-complexation catalyst is selective toward crotonaldehyde, suggesting that this reaction pathway is favored on the PtRu sites.     

Oxidative Steam Reforming of Ethanol over Ni–Cu/SiO2, Rh/Al2O3 and Ir/CeO2: Effect of Metal and Support on Reaction Mechanism

The effect of metal and support on ethanol oxidative steam reforming (OSR) has been investigated over a series of stable and active catalytic systems with noble (Rh or Ir) and non noble metal (Ni–Cu) supported over neutral (SiO₂), amphoteric (Al₂O₃) or redox (CeO₂) supports. Ethanol decomposition and oxidative steam reforming was investigated by in situ diffuse reflectance infrared spectroscopy under temperature-programmed desorption and surface reaction conditions. Different mechanisms were established for these systems, from the initial steps of ethanol activation to the final equilibration of the decomposition products CO, CO₂, H₂ and H₂O. Various intermediates such as formates, acetates and/or carbonates were found to play different roles depending on the catalyst composition. The stability and activity of the investigated systems were finally assigned to specific features of these mechanisms.     

Synthesis,densification and characterization of TaB2–SiC composites

The TaB₂–27.9 vol% SiC composite was synthesized by self-propagating high-temperature synthesis starting from mechanically activated Ta, B₄C and Si reactants. The obtained powders were spark plasma sintered at 1800 °C and 20 MPa for 30 min total time, thus obtaining a 96% dense product. The latter one was characterized in terms of microstructure, hardness, fracture toughness, and oxidation resistance. The obtained results, particularly the fracture toughness, are promising when compared to those related to analogous materials reported in the literature and fabricated with similar and different processing routes.     

GLP-2 Attenuates LPS-Induced Inflammation in BV-2 Cells by Inhibiting ERK1/2, JNK1/2 and NF-κB Signaling Pathways

The pathogenesis of Parkinson’s disease (PD) often involves the over-activation of microglia. Over-activated microglia could produce several inflammatory mediators, which trigger excessive inflammation and ultimately cause dopaminergic neuron damage. Anti-inflammatory effects of glucagon-like peptide-2 (GLP-2) in the periphery have been shown. Nonetheless, it has not been illustrated in the brain. Thus, in this study, we aimed to understand the role of GLP-2 in microglia activation and to elucidate the underlying mechanisms. BV-2 cells were pretreated with GLP-2 and then stimulated by lipopolysaccharide (LPS). Cells were assessed for the responses of pro-inflammatory enzymes (iNOS and COX-2) and pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α); the related signaling pathways were evaluated by Western blotting. The rescue effect of GLP-2 on microglia-mediated neurotoxicity was also examined. The results showed that GLP-2 significantly reduced LPS-induced production of inducible nitric oxide synthase (iNOS), cyclooxygenase-s (COX-2), IL-1β, IL-6 and TNF-α. Blocking of Gα_s by NF449 resulted in a loss of this anti-inflammatory effect in BV-2 cells. Analyses in signaling pathways demonstrated that GLP-2 reduced LPS-induced phosphorylation of ERK1/2, JNK1/2 and p65, while no effect was observed on p38 phosphorylation. In addition, GLP-2 could suppress microglia-mediated neurotoxicity. All results imply that GLP-2 inhibits LPS-induced microglia activation by collectively regulating ERK1/2, JNK1/2 and p65.     

Exafs investigations of Fe-, Ni-, Co- and Cu- MoS2/γ-Al2O3 hydrodesulphurization catalyst systems

In-situ EXAFS studies have been carried out on several transition metal (T)-MoS₂ (T = Fe, Co, Ni or Cu) catalysts supported on -Al₂O₃. While Mo is present in small crystallites of MoS₂ in all the systems studied, the local sulphidic environment around the transition metal atom varies significantly with the catalytic activity. Short T-S distances (compared to the bulk sulphides) are found in the case of the Ni and Co catalysts due to the formation of the active Ni(Co)-Mo-S state. In the case of Fe, which is not a good promoter, the Fe-S distance in the catalyst is only slightly shorter than in the bulk sulphides. No such short distance is found in the Cu-MoS₂/Al₂O₃ system since Cu acts as a poison; instead only bulk sulphides are formed. Effects of the method of preparation, order of impregnation, metal loading and other factors have been examined to arrive at the conditions favourable for the formation of the active Ni(Co)-Mo-S state.Contribution No. 774 from the Solid State & Structural Chemistry Unit.     

Ablation of C/SiC,C/SiC–ZrO2 and C/SiC–ZrB2 composites in dry air and air mixed with water vapor

C/SiC composites with different additives (ZrO₂ and ZrB₂) were fabricated by CVI and CVD and their oxidation and ablation properties at 1700–1800 °C were investigated. Two different ablation test conditions, dry air and air mixed with water vapor, are compared. The ablation test results are reviewed, the weight loss rates are presented and the corresponding micro-structures are investigated in detail. The results show that in dry air, the weight loss rate of C/SiC composites is greater than those with ZrO₂ and ZrB₂ additives. However, in air mixed with water vapor (5 wt%) to simulate the hygrothermal condition, the weight loss rates of these three composites all become relatively smaller. A model is proposed to predict the weight loss of C/SiC composites and it agrees well with the experimental data.     

Long-term oxidation and ablation behavior of Cf/ZrB2–SiC composites at 1500, 2000, and 2200°C

Although C_f/ZrB₂–SiC composites prepared via direct ink writing combined with low-temperature hot-pressing were shown to exhibit high relative density, high preparation efficiency, and excellent flexural strength and fracture toughness in our previous work, their oxidation and ablation resistance at high and ultrahigh temperatures had not been investigated. In this work, the oxidation and ablation resistance of C_f/ZrB₂–SiC composites were evaluated via static oxidation at high temperature (1500°C) and oxyacetylene ablation at ultrahigh temperatures (2080 and 2270°C), respectively. The thickness of the oxide layer of the C_f/ZrB₂–SiC composites is <40 μm after oxidizing at 1500°C for 1 h. The C_f/ZrB₂–SiC composites exhibit non-ablative properties after oxyacetylene ablation at 2080 and 2270°C for >600 s, with mass ablation rates of 3.77 × 10⁻³ and 5.53 × 10⁻³ mg/(cm² s), and linear ablation rates of −4.5 × 10⁻⁴ and −5.8 × 10⁻⁴ mm/s, respectively. Upon an increase in the ablation temperature from 2080 to 2270°C, the thickness of the total oxide layer increases from 360 to 570 μm, and the carbon fibers remain intact in the unaffected region. Moreover, the oxidation and ablation process of C_f/ZrB₂–SiC at various temperatures was analyzed and discussed.     

Hydrogen production via methanol steam reforming over Au/CuO,Au/CeO2, and Au/CuO–CeO2 catalysts prepared by deposition–precipitation

The production of hydrogen (H₂) with a low concentration of carbon monoxide (CO) via steam reforming of methanol (SRM) over Au/CuO, Au/CeO₂, (50:50)CuO–CeO₂, Au/(50:50)CuO–CeO₂, and commercial MegaMax 700 catalysts were investigated over reaction temperatures between 200 °C and 300 °C at atmospheric pressure. Au loading in the catalysts was maintained at 5 wt%. Supports were prepared by co-precipitation (CP) whilst all prepared catalysts were synthesized by deposition–precipitation (DP). The catalysts were characterized by Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy (SEM). Au/(50:50)CuO–CeO₂ catalysts expressed a higher methanol conversion with negligible amount of CO than the others due to the integration of CuO particles into the CeO₂ lattice, as evidenced by XRD, and a interaction of Au and CuO species, as evidenced by TPR. A 50:50 Cu:Ce atomic ratio was optimal for Au supported on CuO–CeO₂ catalysts which can then promote SRM. Increasing the reaction time, by reducing the liquid feed rate from 3 to 1.5 cm³ h^?1, resulted in a catalytic activity with complete (100%) methanol conversion, and a H₂ and CO selectivity of ～82% and ～1.3%, respectively. From stability testing, Au/(50:50)CuO–CeO₂ catalysts were still active for 540 min use even though the CuO was reduced to metallic Cu, as evidenced by XRD. Therefore, it can be concluded that metallic Cu is one of active components of the catalysts for SRM.     

Synthesis and luminescence properties of Y2O2S:Dy,Mg, Tiphosphors prepared by sol–gel process

Y₂O₂S:Dy³⁺, Mg²⁺, Ti⁴⁺ white-light long-lasting phosphors were synthesized by sol–gel method. Y₂O₂S:Dy³⁺, Mg²⁺, Ti⁴⁺ phosphors were characterized by X-ray diffraction, photoluminescence spectroscopy and thermally stimulated spectrometry. The results showed that the samples calcined at different temperatures from 900 °C to 1200 °C were composed of the pure Y₂O₂S phase. Under 359 nm UV excitation, the phosphor presented white luminescence due to mixing of the dominating emissions centered at 488 nm (blue) and 579 nm (yellow), corresponding to ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺, respectively. Both the fluorescence intensity and afterglow time reached the largest values in the phosphor calcined at 1200 °C and the afterglow time could last for over 65 min (≥1 mcd/m²) when the excited source was cut off.