New ZrO
x
N
y
thin films were deposited
via
reactive RF magnetron sputtering on stainless steel substrate from a Y
2
O
3
-doped ZrO
2
(3YSZ) target. In order to reduce their porosity and increase ...corrosion resistance, the films were annealed at 265 °C in an inert atmosphere at reduced pressure, increasing their density and corrosion resistance in saline solution. The crystal structure of the films was characterized by means of X-ray diffraction, the morphology
via
scanning electron microscopy and atomic force microscopy, and the chemical composition
via
X-ray photoelectron spectroscopy. The corrosion resistance was evaluated using electrochemical techniques based on linear polarization. The results show that the annealing treatment decreases the morphological imperfections of the coatings such as pores and cracks, which allows increasing the corrosion resistance of the substrate-coating system.
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► Partial oxidation of H2S to sulphur is selectively obtained over pure and Na-doped V2O5. ► V4O9 is selectively formed during the selective oxidation of H2S over V2O5. ► Na0.33V2O5 ...is mainly observed in Na-promoted catalysts with Na/V ratio higher than 0.1. ► Na0.33V2O5 bronze is also active and selective in partial oxidation of H2S.
Present paper describes the influence of the incorporation of alkali metal cations (AM=Li, Na, K, Cs; and an AM/V ratio of 0.04) and Na-content (Na/V ratio of 0.02–0.30) in alkali metal promoted V2O5 catalyst on both the catalyst structure and the catalytic performance in H2S partial oxidation reactions. The catalytic activity depends on the alkali metal and the amount of alkali metal added, although Na-containing catalysts seem to be the more active ones. However, selectivity to sulphur higher than 98% is achieved in the main of catalysts when working at reaction temperature lower than 220°C. According to the characterization results of used catalysts, V4O9 is selectively formed during the catalytic tests on catalysts presenting V2O5 crystallites. In catalysts with Na/V ratios higher than 0.04, V4O9 and Na0.33V2O5 are observed, the presence of Na0.33V2O5 increasing when increasing the Na/V ratio. Accordingly, V4O9 and Na0.33V2O5 can be proposed as the active and selective crystalline phase in Na-containing catalysts. The role of the presence of V4+−O–V5+ pairs in partial oxidation of H2S is also discussed.
Designed synthesis of nanostructured ZrO2 as support for glycerol valorization reaction was investigated. The nanocasting route was used to obtain the ZrO2 support possessing well-dispersed Cu and Zn ...nanoparticles. The solids were fully characterized by High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), N2-physisorption isotherms, Temperature-programmed desorption of ammonia (NH3-TPD), Scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared (FTIR) spectroscopy measurements. The resultant CuZn/ZrO2 catalyst presented here was distinguished by its unique mesostructured features and defective sites formation. The promotional effect of Cu nanoparticles on the activity illustrated that the formation of active acid sites of medium to strong strength can be modulated by adding a second metal to the catalyst. All these properties provided active solids for acetalization of glycerol with aldehydes and ketones due to the interaction between the active centers and the nanostructured support. Density functional theory (DFT) calculation showed the most favorable mechanistic route of low energy for biofuel additives production.
Three different mesoporous molecular sieves of MCM-41 type (a pure silica and two aluminum doped silica with Si/Al molar ratios of 10 and 30) were evaluated for adsorption of polycyclic aromatic ...hydrocarbons (PAHs) from an organic solution. The aluminum containing samples were synthesized at room temperature using a sol–gel method with two reaction steps: acid hydrolysis of the metallic alkoxides (pH 2) and alkaline condensation of the hydrolysis products (pH 10). The removal of the organic template (dodecylamine hydrochloride) was performed by solvent extraction (ethanol/HNO
3 0.1
M) followed by calcination at 550
°C for 3
h. Surface chemistry of synthesized samples was analysed by X-ray photoelectronic spectroscopy (XPS). Acidity values (proton concentration) were obtained using thermogravimetric analysis of the adsorbed cyclohexylamine (CHA) at 250
°C on the calcined materials. Equilibrium adsorption properties of naphthalene, anthracene and pyrene (PAHs) in isooctane were measured at 25, 40 and 60
°C by the contact method (finite bath). The Langmuir model correlates well the equilibrium data, indicating decreasing adsorption maximum capacity (
q
m) in the following order: Al-MCM-41(10)
>
Al-MCM-41(30)
>
MCM-41. For all samples, PHA adsorption capacity increased with the number of aromatic rings. The estimated heats of adsorption (−Δ
H) show a regular increase with increasing number of π-electrons in the aromatic structure. These results indicate that electrostatic interactions between the π-electrons of aromatic rings and the acidic centers of the MCM-41 materials, caused by both isomorphic and extra-framework Al, may play a significant role in adsorption of PAHs in addition to van der Waals forces.
The synthesis of PCH from natural bentonite produces a porous heterostructure material effective for the adsorption of glyphosate from water. The adsorption process takes place through an interaction ...between the silanol group of montmorillonite and/or the PCH adsorbent with the functional groups of glyphosate. The glyphosate adsorption isotherms, recorded for all the studied samples, have been established to be of Langmuir type. The kinetic of the herbicide adsorption on the PCH was best described by the pseudo-second-order model. With the increase in temperature from 25 to 50 °C, the sorption capacities of the materials studied towards glyphosate increased. The process of glyphosate adsorption was found to be endothermic and spontaneous in nature, as indicated by positive values of ΔH and negative values of ΔG. According to the results obtained, the herbicide sorption was more effective in a basic environment. The maximum amount of adsorbed glyphosate is almost doubled with PCH from 13.5 mg/g of natural clay to 27.5 mg/g of PCH.
Graphic abstract
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► In this study we examine alumina pillared montmorillonite as catalyst supports of sulfide ruthenium. ► We study the catalytic hydrodesulfurization of dibenzothiophene and we find ...that the prepared catalysts are active. ► We conclude that the dispersion of the active phase determinates the activity and the stability.
Sulfided ruthenium supported catalysts based on an Al pillared montmorillonite, with different Al contents, have been prepared and characterized by XRD, SBET, TEM, XPS, and tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The role of the Al content in the catalytic activity of RuS2 based catalysts was studied. The activity and selectivity of the catalysts studied in the HDS of DBT suggest that Al pillared montmorillonite could be of interest as a low cost support for this reaction.
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•Some interaction metal-Mo controls the acidity, reducibility and dispersion of the resultant sample.•PtMo/SiO2 catalyst is always more effective, all hydrogen consumed leads to ...O-free hydrogenated products.•In both bimetallic catalysts the HDO capability improved if compared to the monometallic ones.•Mo promotes the hydrogenolysis reaction regardless the noble metal.•The results confirmed the presence of an enhancing synergetic effect between noble metal and molybdenum.
Molybdenum was incorporated into catalysts based on noble metals (Pt or Pd) and supported on silica in order to evaluate how its presence can modify the catalytic response of monometallic catalysts for hydrodeoxygenation (HDO). To this end, the catalysts were evaluated in the hydrodeoxygenation (HDO) reaction of dibenzofuran (DBF) and characterized by different experimental techniques to understand its structure, texture and acidic properties. Catalytic results showed that the active phase had much influence on the activity and selectivity to different reaction products, although, in all cases, bicyclohexane (BCH) was the main reaction product observed. Molybdenum played a very important role in the case of bimetallic catalysts, mainly in the case of palladium. Molybdenum species improved the selectivity to O-free products related to its capacity to break the CO bond. However, molybdenum activity was nil in the absence of noble metal. Moreover, regardless of the noble metal employed, the reducibility, acidity and dispersion of the molybdenum species changed and this is possibly associated to a synergism effect between noble metal and Mo.
Hollow microspheres of silica were synthesized and functionalized with amino groups to enhance carbon dioxide adsorption. Functionalization was intended to provide acid–base interaction between CO2 ...and amine groups. Samples were characterized by N2 adsorption/desorption isotherms at 77 K, X-ray diffraction, scanning electronic microscopy, and Fourier transform infrared spectroscopy. For adsorption experiments, both volumetric and gravimetric devices were used to quantify adsorbed CO2 as a function of pressure and temperature. CO2 adsorption isotherms obtained for the amine grafted silica confirmed the coexistence of chemical and physical adsorption sites within the material, which means that CO2 binding occurs not only by physical mechanisms on micropores but also due to interactions with amino groups. The saturation of the adsorbent with H2S to simulate the purification of natural gas or biogas slightly diminishes CO2 adsorption capacity due to competition between CO2 and H2S for amine sites. Preadsorption of H2O on the H2S saturated adsorbent did not lead to improvements in CO2 uptake. On the contrary, preloaded H2O combined with H2S seems to block some of the chemical sites involved in CO2 adsorption.
CuO supported on CeO2, Ce0.8Zr0.2O2 and Ce0.8Al0.2O2 based catalysts (6%wt Cu) were synthesized and tested in the preferential oxidation of CO in a H2-rich stream (CO-PROX). Nanocrystalline supports, ...CeO2 and solid solutions of modified CeO2 with zirconium and aluminum were prepared by a freeze-drying method. CuO was supported by incipient wetness impregnation and calcination at 400 °C. All catalysts exhibit high activity in the CO-PROX reaction and selectivity to CO2 at low reaction temperature, being the catalyst supported on CeO2 the more active and stable. The influence of the presence of CO2 and H2O was also studied.
•CeO2, Ce0.8Al0.2O2, Ce0.8Zr0.2O2 were synthesized by freeze-drying method.•Freeze-drying method gives rise ceria with low particle size.•Copper oxide supported on ceria-based materials was employed for CO-PROX reaction.•6CUCE exhibits higher stability and tolerance to CO2 and H2O.
An integrated 90° hybrid 2 × 4 coupler based on flexible, thermal stable, and low insertion losses organic–inorganic hybrids thin films was fabricated using direct laser writing, resulting in an ...optical coherent receiver able to extract modulated data IQ components. Its performance was demonstrated for demodulation of 20 Gb/s QPSK transmission (over 40 km), yielding a 2.5 dB power penalty (BER = 3.8 × 10−3) which are the best values known for low-refractive index contrast waveguides. Thus, the presented device is an energy-efficient and low cost alternative to the current coherent receivers, capable of breaking cost-performance barriers and easily incorporated in PICs for the NGOA.
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•We present a QPSK demodulator produced in di-ureasil organic-inorganic hybrid films.•The device was patterned by UV-direct laser writing, which is low-cost methodology.•The 90° hybrid coupler was validated with 20 Gbs QPSK transmission in 40 km of fibre.•The demodulator performance was demonstrated revealing a power penalty of 2.5 dB.•The device performance and low-cost constitutes a breakthrough in the PIC production.
The recent advances in coherent optical systems enable the use of efficient modulation formats, such as quadrature phase shift keying (QPSK). In this framework, we present an integrated 90° hybrid 2 × 4 coupler based on self-patternable organic–inorganic hybrid thin films fabricated using direct laser writing. The device was coupled to balanced photodiodes, resulting in an optical coherent receiver with capacity to extract the modulated data. The device performance was demonstrated for a transmission over 40 km (G.652 fiber) with a 20 Gb/s QPSK, yielding a 2.5 dB power penalty (BER = 3.8 × 10−3), being the best figures of merit for waveguides processed by low-cost patterning techniques. Furthermore, the hybrid materials are thermally and mechanically stable than polymers, with lower fiber-to-device insertion losses. Therefore, the proposed optical coherent receiver is an easy processed and cost-effective approach for the next generation of optical access networks.
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