1,720,973 research outputs found
Nanostructured ceria-based catalysts for automotive application - Formulation of nanostructured systems for diesel and gasoline-type engines
Get PDFL'abstract è presente nell'allegato / the abstract is in the attachmen
Catalytic Activity of Nanostructured Ceria-Based Materials Prepared by Different Synthesis Conditions
No full textNatural Zeolites as Sustainable Materials for Environmental Processes
No full textIn this chapter, the application of natural zeolites as sustainable materials for environmental protection is described. In particular, the clinoptilolite was studied for capturing carbon dioxide (CO2) emitted from industrial processes at moderate outlet temperatures and for wastewater remediation. Specifically, for CO2 capture and storage, the clinoptilolite was used as an adsorbent solid and it was tested at 20 and 65 °C. The wastewater treatment was achieved via Fenton-type reactions with a solution of azo-dyes acid orange 7 (AO7), as target molecule for azo dyes. The physico-chemical properties of the clinoptilolite, along with the ion-exchanged materials, were analyzed by means of N2 physisorption at −196 °C, X-Ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM), and Energy Dispersive X-ray spectroscopy analysis (EDX). The results evidenced that the clinoptilolite can be a sustainable material for capturing CO2, because of the interesting adsorption capacity at moderate temperature. On the other hand, remarkable results for the AO7 degradation were obtained with the Fe-clinoptilolite catalyst in the presence of both ascorbic acid and H2O2
Natural Zeolite Clinoptilolite Application in Wastewater Treatment: Methylene Blue, Zinc and Cadmium Abatement Tests and Kinetic Studies
Get PDFIn recent decades, several abatement techniques have been proposed for organic dyes and metal cations. In this scenario, adsorption is the most known and studied. Clinoptilolite was considered, since it is a zeolite with a relatively low cost (200–600 $ tons−1) compared to the most well-known adsorbent used in wastewater treatment. In this work, Clinoptilolite was used for the adsorption of Methylene Blue (MB) at three different concentrations, namely, 100, 200, and 250 ppm. Furthermore, the adsorption capacity of the natural zeolite was compared with that of Activated Charcoal (250 ppm of MB). The two adsorbents were characterized by complementary techniques, such as N2 physisorption at −196 °C, X-ray diffraction, and field emission scanning electron microscopy. During the adsorption tests, Clinoptilolite exhibited the best adsorption capacities at 100 ppm: the abatement reached 98% (t = 15 min). Both Clinoptilolite and Activated Charcoal, at 250 ppm, exhibited the same adsorption capacities, namely, 96%. Finally, at 250 ppm MB, the adsorption capacity of Clinoptilolite was analyzed with the copresence of Zn2+ and Cd2+ (10 ppm), and the adsorption capacities were compared with those of Activated Charcoal. The results showed that both adsorbents achieved 100% MB abatement (t = 40 min). However, cation adsorption reached a plateau after 120 min (Zn2+ = 86% and 57%; Cd2+ = 53% and 50%, for Activated Charcoal and Clinoptilolite, respectively) due to the preferential adsorption of MB molecules. Furthermore, kinetic studies were performed to fully investigate the adsorption mechanism. It was evidenced that the pseudo-second-order kinetic model is effective in describing the adsorption mechanism of both adsorbents, highlighting the chemical interaction between the adsorbent and adsorbate
CO Oxidation Over Ceria-Based Catalysts: Comparison of Single and Binary Metal Oxides
Get PDFWet air oxidation (WAO) of lignocellulosic biomasses is a promising route for the production of renewable and valuable compounds. In this work, acetovanillone (AV) was selected as lignin model molecule in order to investigate its behavior under the WAO reaction conditions. The experiments were carried out in a pressurized 50 ml batch reactor loaded with NaOH 2M as solvent, the reaction takes 1 h with temperatures ranging from 130 to 190 °C and air pressures between 5 and 30 bar. The perovskite-type mixed oxide LaFeO3 was synthetized and used as heterogeneous catalyst in order to improve the activation of molecular oxygen. Vanillin yield resulted to benefit from high reaction temperature showing a maximum carbon yield of 22%, instead the formation of carboxylic acids from the oxidative degradation of AV largely benefits from high pressure of air, exhibiting an overall carbon yield of 35%. The produced compounds include oxalic, glycolic, lactic, malonic, and levulinic acid
Cu(II)-Based Coordination Polymers Containing 1,4-Bis(1H-imidazol-1-yl)benzene and Monovalent Fluorinated Anions
No full textThe design of the organic linker is one of the most important steps in driving the formation of the desired crystal structure in coordination polymers. Imidazole derivatives exhibit wide and interesting coordination capabilities. This property makes these π-conjugated ligands suitable linkers in the synthesis of metal–organic frameworks (MOFs). Despite these considerations, few examples of two-dimensional (2D) materials based on the 1,4-bis(1H-imidazol-1-yl)benzene (bib) ligand, which can be seen as a topological analogue of 4,4′-bipyridine, have been reported so far, and there is a lack of literature on the exploration of their gas adsorption properties. The combination of bib ligand with Cu(BF4)2 led us to obtain a doubly interpenetrated three-dimensional (3D) material (UdP-1) of minimal formula [Cu(bib)2.5(BF4)]·(BF4)·1.5H2O that loses 0.5 equiv of bib upon heating and undergoes a phase transition to a new material named UdP-2. UdP-2 was obtained as a microcrystalline powder by direct synthesis, but its crystal structure could not be elucidated. Attempts to obtain single crystals of UdP-2 led us to discover four new compounds, named UdP-3, UdP-3-i, UdP-4, and UdP-5, displaying both 2D and 3D structures. Using Cu(CF3SO3)2 instead of Cu(BF4)2 allowed us to prepare a 2D layered material of the formula [Cu(bib)2(CF3SO3)2]·2MeOH (UdP-6), where the methanol molecules are trapped in the pores of the structure as in the ELM-12 structure, which contains 4,4′-bipyridine as the organic ligand. Different from ELM-12, UdP-6 displays a Type I CO2 adsorption isotherm, with no evidence of a gating phenomenon. This behavior is attributed to the larger number of supramolecular interactions existing between adjacent layers in UdP-6
Novel Mn–Cu-Containing CeO2 Nanopolyhedra for the Oxidation of CO and Diesel Soot: Effect of Dopants on the Nanostructure and Catalytic Activity
No full textPhosphorous-Based Titania Nanoparticles for the Photocatalytic Abatement of VOCs
No full textIn this work, different TiO2-based systems were synthesized. Specifically, phosphorous was considered as nonmetal dopant into TiO2 structure of the photocatalysts. The doped samples were herein labeled as TiO2-P0.6, TiO2-P0.7, and TiO2-P3, where 0.6, 0.7, and 3 indicate the average atomic phosphorus content into each sample.
The physico-chemical properties of the samples were investigated by complementary techniques, including XRD, N2 physisorption at −196 °C, FESEM, EDX, XPS, and (DR)UV-Vis spectroscopies. Then, the samples were tested for the total oxidation of ethylene under two different sources: UVB (wavelength = 312 nm, intensity = 12 W m−2) and UVA (wavelength = 365 nm, intensity = 8 W m−2).
The results under UVB source have shown that the most promising catalyst is TiO2-P3 (TOF = 7.5 μmol h−1 g−1, TOS = 160 min) and a positive reactivity trend was observed: the higher the P-content, the higher the reactivity. On the other hand, under the UVA source, the most promising catalyst is TiO2-P0.6 (TOF = 21.3 μmol h−1 g−1, TOS = 160 min). In fact, the samples with higher P-contents decrease their performances at longer TOS, likely due to the surface deposition of carbon-like molecules
Synthesis and characterization of ordered mesoporous silicas for the immobilization of formate dehydrogenase (FDH)
Get PDFProperties of the Clinoptilolite: Characterization and Adsorption Tests with Methylene Blue
Get PDFAbstract: In this work, the physico-chemical properties of clinoptilolite (a natural zeolite) were analyzed by complementary techniques including X-ray diffractogram, N2 physisorption at -196 °C, FESEM and EDX analysis. Zeolite is classified as a mesoporous material (cavities≈ 15 nm) with a specific surface area of 36 m2g-1. The porous size distribution shows a peak in the mesoporous region. This zeolite is characterized by anhedral particles assembled on top of one another: this is a characteristic of material growth by magma with impurities (Mordenite) in the pores. The presence of impurities was evidenced with EDX analysis (Fe=0.68% at, Mg=0.47% at.). Then, the adsorption tests were performed with two solutions of methylene blue (MB) at different concentrations (namely 250 and 500 mgL-1). The results showed that the adsorption of the dye is more efficient in the case of250 mg L-1concentration, with an abatement of 96% after 2h. The abatement corresponding to the higher concentration of MB is about 92.5% after 2h. The kinetic order of MB on clinoptilolite was calculated. The results suggest a second order reaction. In the future, clinoptilolite will be studied for the abatement of metal ion solutions in order to be used as a molecular sieve in the waste water treatment field
- …
