Search results for "Heterogeneou"
showing 10 items of 461 documents
Turning lipophilic phthalocyanines/TiO2 composites into efficient photocatalysts for the conversion of CO2 into formic acid under UV–vis light irradi…
2014
Metal-free, Cu(II)- or Zn(II) tetrakis [4-(2,4-bis-(1,1-dimethylpropyl)phenoxy)]phthalocyanines loaded over TiO2 (anatase) proved to be active in the photoreduction of CO2 to formic acid (HCO2H) in water under UV-vis light. CuPc/TiO2 is catalyst of choice, allowing to reach a maximum yield of HCO2H, unequalled by any other similar catalytic systems. Because of their low environmental impact, low potential cost, and efficient power conversion, these multipurpose materials show promise in the setup of sustainable methods for CO2 valorization. (C) 2014 Elsevier B.V. All rights reserved.
Preparation, Characterization, and Photoactivity of Polycrystalline Nanostructured TiO2 Catalysts.
2004
Various preparations of nanostructured TiO2 starting from Ti(iso-OC3H7)4 or TiCl4 are reported. The samples were characterized by X-ray diffractometry, specific surface area and porosity determinations, scanning and transmission electron microscopy, and diffuse reflectance spectroscopy. 4-Nitrophenol photodegradation in aqueous medium was employed as a probe reaction to test the photoactivity of the catalysts. The photoactivity of some samples derived from Ti(iso-OC3H7)4 was found comparable with that of commercial powders. Calcination after the hydrolysis process was necessary to achieve crystallization of the particles before using them as photocatalysts for the reaction studied. The samp…
Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts
2009
[EN] Alkali metal-doped MoVSbO catalysts have been prepared by impregnation of a MoVSbO-mixed oxide (prepared previously by a hydrothermal synthesis) and finally activated at 500 or 600 degrees C in N-2. The catalysts have been characterized and tested for the selective oxidation of propane and propylene. Alkali-doped catalysts improved in general the catalytic performance of MoVSbO, resulting more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free MoVSbO catalysts. However, the specific behaviour strongly depends on both the alkali metal added and/or the final activation temperature. At isoconversion conditions, catalysts activated at 600 degrees…
The influence of ultrasound on the RuI3-catalyzed oxidation of phenol: Catalyst study and experimental design
2009
Abstract The influence of ultrasound at 24 kHz on the heterogeneous aqueous oxidation of phenol over RuI3 with hydrogen peroxide (H2O2) was studied isothermally at 298 K. Effect of ultrasound irradiation on catalytic properties and performance of RuI3 has been studied in details by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), dispersion analyzer and a surface analyzer. Turn over frequency of the catalyst was also calculated. In this work, experimental design methodology was applied to optimize the degradation of phenol in aqueous solution, while minimizing an excessive consumption of chemical reagents. The independent variables considered were the catalyst lo…
Joint Dynamic Resource Allocation for Coupled Heterogeneous Wireless Networks Based on Hopfield Neural Networks
2008
This paper proposes an algorithm to solve the problem of Joint Dynamic Resource Allocation in heterogeneous wireless networks. The algorithm is based on Hopfield Neural Networks to achieve fast and suboptimal solutions. The generic formulation is particularized and evaluated in an HSDPA and 802.11e WLAN coupled networks. Some illustrative simulations results are presented to evaluate the performance of the new algorithm as compared with other strategies. The obtained results confirm the validity of the proposal.
Multi-doped Brookite-Prevalent TiO2 Photocatalyst with Enhanced Activity in the Visible Light
2018
© 2018 Springer Science+Business Media, LLC, part of Springer Nature Abstract: Enabling solar and/or visible light-driven photocatalysis is a crucial step to access innovative applications in environmental science and sustainable energy. Titanium dioxide is the most used photocatalyst because of its low cost and toxicity, however it is also limitedly active under visible light irradiation due to its wide band gap. Among its polymorphs, brookite holds promising optoelectronic properties for visible light photocatalysis, which have to the best of our knowledge been limitedly exploited. Here, a C,S,N-doped brookite-based TiO2has been prepared via a rapid one-pot sol–gel synthesis. Besides subs…
A study of the behaviour of Pt supported on CeO2–ZrO2/Al2O3–BaO as NO storage–reduction catalyst for the treatment of lean burn engine emissions
2002
Abstract The behaviour of a Pt(1 wt.%) supported on CeO2–ZrO2(20 wt.%)/Al2O3(64 wt.%)–BaO(16 wt.%) as a novel NOx storage–reduction catalyst is studied by reactivity tests and DRIFT experiments and compared with that of Pt(1%)–BaO(15 wt.%) on alumina. The former catalyst, designed as a hydrothermally stable sample, is composed of an alumina modified with Ba ions and an overlayer of ceria-zirconia. The results pointed out that during the calcination barium ions migrates over the surface of the catalyst which thus show a good NOx storage–reduction behaviour comparable with that of Pt–BaO on alumina, although Ba ions result much better dispersed.
Cell Association for MTC Devices in 5G Networks: Schemes and Performance Evaluation
2021
Fifth generation (5G) networks offer tremendous opportunities for Internet of things applications by facilitating massive machine-type communications (MTC). As many MTC devices are battery powered and intend to stay often in the sleep or power-saving mode, cell (re)association needs to be performed when a device wakes up. On the other hand, 5G networks are usually deployed as heterogeneous networks consisting of both macro and small cells under which a single device may be covered by multiple radio access technologies (RATs) simultaneously. Therefore, it is imperative to design effective cell association schemes for the purpose of efficient connectivity and resource utilization, especially …
Catalytic transesterification of Pistacia chinensis seed oil using HPW immobilized on magnetic composite graphene oxide/cellulose microspheres
2018
Abstract In the present study, magnetic composite graphene oxide/cellulose (GO/CM@Fe3O4) microspheres were prepared as support material, which are cost-efficient, non-toxic and environmental friendly. The microspheres with higher adsorption capacity were further modified using triethylene tetramine (TETA), and H3PW12O40 (HPW) was immobilized to form GO/CM-NH2@Fe3O4-HPW microspheres as heterogeneous catalyst for biodiesel production. The novel heterogeneous catalyst was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and X-ray diffractometry (XRD). For the first time, GO/CM-NH2@Fe3O4--HPW was applied in the tr…