Sol-gel synthesis of inorganic and hybrid transition metal oxides based materials

The research activity of this PhD project was focused on the preparation by sol-gel synthesis of hybrid (ZrO2-acetylacetonate, HSGZ) and inorganic (Nb2O5∙SiO2 and Ru/RuO2@Nb2O5∙SiO2) mixed-oxide materials. HSGZ was prepared at room temperature by a sol-gel synthesis using suitable process conditions to produce a homogeneous chemical gel. The thermal stability of the material was investigated by thermogravimetry-differential thermal analysis, and Fourier transform infrared spectroscopy. In addition, HSGZ was tested in the oxidative degradation of four different phenoxy herbicides (2-methyl-4-chlorophenoxyacetic acid (MCPA), 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB), 4-chlorophenoxyacetic acid (4-CPA) and 2,4-dichlorophenoxyacetic acid (2,4 D)). For each herbicide, a virtually complete removal in about 3 days without light irradiation at room temperature was achieved. A long-term application of the HSGZ catalyst assessed by repeated-batch tests was achieved, as well. Finally, in order to clarify the mechanism of action of this catalyst, the physico-chemical properties were investigated by using suitable spectroscopic techniques, such as electron paramagnetic resonance. The promising results about the striking capability of this material to catalyze oxidative degradation reactions in absence of light and without any thermal pretreatment lead the path toward further development of HSGZ and related hybrid materials for ROS-based energy and environmental applications. Part of my research activity was devoted to investigate the influence of the preparation procedure on the structure and the properties of Nb2O5•SiO2 materials containing about the same Nb2O5 amount (19 % wt.) but obtained by different synthetic routes with special attention to their catalytic activity in the epoxidation of methyl oleate with hydrogen peroxide. The catalytic performance of the niobium oxide-based materials can be controlled by modulating the acidic properties, by regulating the structure and in turn, the preparation method. In detail, the catalytic activity of the catalyst prepared by impregnation do not differ substantially from that of commercial Nb2O5. The performances of Nb-supported catalysts prepared by sol-gel depend on the synthesis process parameters. The high dispersion of the active NbOx species obtained by this preparation method gives very higher selectivity than in the case of commercial Nb2O5. Morphological and structural characterization of the catalysts helped justifying the obtained catalytic results in terms of activity and selectivity. Ru-based mixed oxide (Ru/RuO2@Nb2O5-SiO2) was obtained by an innovative sol-gel synthesis wholly performed at room temperature and characterized by both easy handling of precursors and the lack of toxic or pollutant reactants. The surface area and the morphological characteristics of the material were controlled adding different amounts (0.04 and 0.16 wt. %) of a nonionic surfactant (polyethylene glycol hexadecyl ether, Brij-C10) directly in the starting solution of precursors. The influence of Brij-C10 incorporation on porous structure, size and dispersion of ruthenium nanoparticles were investigated in detail by structural, morphological and textural characterization. It was demonstrated that the differences in particle size of ruthenium oxide and their dispersion are likely due to the different grain growth rate during the synthesis caused by the addition of surfactant. These results indicate that Brij-C10 actually plays a role of complexing agent of the metallic species and not only as pore directing agent, as proven by textural analysis. The surfactant, indeed, contribute to increase the SSA and PSD and to obtain a high dispersion of metal species. These materials act as bifunctional catalysts thanks to their acidic and redox functionalities in the hydrogenation of levulinc acid to γ-valerolactone. All catalysts showed the same results in both LA conversion and GVL yield, indicating that the presence of surfactant did not influence the catalytic performance. Therefore, reusability tests clearly indicated that the catalyst without Brij-C10 is very stable under the adopted conditions and no activity loss was ascertained. On the contrary, the presence of surfactant induced a significant deactivation already at its second reuse due to the adsorption of organic species

Andic soils and catastrophic mudflows in Italy: morphological and hydropedological evidences

In Italy rapid landslides are the most frequently occurring natural disasters and, after earthquakes, cause the highest number of victims. In this contribution we attempt to prove that there exist a tight connection between the presence of a specific soil type, namely andic soils, and the occurrence of the main catastrophic mudflows and debris flows occurred in Italy in the last decades. The study was performed by means of an integrated pedological and hydrological analysis on the detachment crowns of some of the most important catastrophic mudflows and debris flows occurred in Italy in the last decades and involving/evolving surface soils. The results at both regional (Campania) and National (Italy) scale clearly show that despite the large variability of the environmental settings of the studied sites there are indeed some striking homogeneous soil features in the detachment crowns including (i) soil morphology, (ii) andic features ranging from high to moderate, (iii) high water retention throughout a large range of pressure heads. Results seem to reveal clear cause-effect evidences between andic soils and the investigated catastrophic mudflows/debrisflows; this must be related to the unique physical properties of these soils inducing high landslide vulnerability

Response of rumen microbial ecosystem to diets integrated with chestnut or quebracho tannins in dairy ewes

The aim of this study was to evaluate the response of rumen microbial ecosystem to diets integrated with chestnut or quebracho tannins in dairy ewes. The experiment was conducted as 3 X 3 Latin square design and the trial was repeated 2 times. Three fistulated ewes fed 3 diets based on chopped grass hay ad libitum administered and on 800 g / head and day of 3 experimental concentrates containing 84.5 g of soybean oil / kg of DM and 52.8 g / kg DM of bentonite (CON) or chestnut tannin extract (CHT) or quebracho tannin extract (QUE). At the end of each experimental period rumen liquor was analysed for fatty acid and microbial profiles. On the basis of the molar stoichiometric relations between rumen volatile fatty acid and CH4 production (CH4=0.45 x acetate-0.275 x propionate + 0.4 x butyrate), the CH4 emission was also predicted for each diet. A canonical correspondence analysis (CCA) was performed in order to find potential connection between microbial community, fatty acid composition of rumen liquor and potential CH4 emission, and how these connections are influenced by the different diets. DGGE bands were used as "species" data, while fatty acids and potential CH4 emission as "environmental" variables. The microbial profile was affected by the presence of tannins. The bacterial community of QUE and CHT samples of rumen liquor was positively correlated to vaccenic acid, conjugated linoleic acid and C18:2 trans-11 cis-15. Moreover, the bacterial communities as affected by CHT resulted mainly positively correlated to butyric acid, acetic acid and with potential CH4 emission. In contrast, the bacterial communities as affected by CON resulted mainly correlated positively to C18:2 cis-9 cis-12 and C18:0 production

An Environmentally Friendly Nb–P–Si Solid Catalyst for Acid-Demanding Reactions

Here, we report the structural characteristics, the surface properties, and the catalytic performances of a Nb–P–Si ternary oxide material (2.5Nb2O5·2.5P2O5·95SiO2, 2.5NbP) in two reactions of importance for biomass valorisation and green industrial production: hydrolysis of inulin and esterification of oleic acid with polyalcohol for biolubricant production. High dispersion of the Nb centers, ascertained by UV–vis–DRS, 29Si, 31P, and 1H solid-state NMR spectroscopy, is the key point for the successful activity of 2.5NbP. Intrinsic and effective acidities of the sample were studied by FT-IR of adsorbed pyridine in the absence and presence of water and by volumetric titrations of the acid sites in cyclohexane and in water, to enlighten the nature and amount of acid sites in different environments. For both studied reactions, 2.5NbP catalyst exhibits water-tolerant acidic sites, mainly Brønsted ones, giving higher activity and better stability in the reaction medium than well-known niobium oxophosphate catalyst, which is considered one of the best water-tolerant acid catalysts

Effect of Dietary Chestnut or Quebracho Tannin Supplementation on Microbial Community and Fatty Acid Profile in the Rumen of Dairy Ewes

Ruminants derived products have a prominent role in diets and economy worldwide; therefore, the capability to control the rumen microbial ecosystem, for ameliorating their quality, is of fundamental importance in the livestock sector. e aim of this study was to evaluate the e ect of dietary supplementation with chestnut and quebracho tannins on microbial community and fatty acid pro le, in the rumen uid of dairy ewes. Multivariate analysis of PCR-DGGE pro les of rumen microbial communities showed a correlation among the presence of chestnut or quebracho in the diet, the speci c Butyrivibrio group DGGE pro les, the increase in 18:3 cis9, cis12, and cis15; 18:2 cis9 and cis12; 18:2 cis9 and trans11; 18:2 trans11 and cis15; and 18:1 trans11 content, and the decrease in 18:0 concentration. Phylogenetic analysis of DGGE band sequences revealed the presence of bacteria representatives related to the genera Hungatella, Ruminococcus, and Eubacterium and unclassi ed Lachnospiraceae family members, suggesting that these taxa could be a ected by tannins presence in the diets. e results of this study showed that tannins from chestnut and quebracho can reduce the biohydrogenation of unsaturated fatty acids through changes in rumen microbial communities

Pedological (micromorphological and chemical) investigation in an archaeological site of the Early Bronze Age: the case study of Palma Campania (southern Italy): Soil properties of the last 9000 years in a plain close to Vesuvius

Archaeological records from excavations of the last forty years in the Campania region (southern Italy) attest an intense human occupation from the Early Bronze Age (EBA) to the present day. Findings of the cultural sphereof the EBA, known asfacies of Palma Campaniain the southern Italy, have beenwidelyburied by the pyroclastic deposits of the Vesuvius Pomici diAvellino eruption (3945yrcalBP).Because of the exceptional importance and preservation of the relicsfoundin the excavation of the 1995in Balle/Pirucchi locationat Palma Campania (Naples),a detailed (micromorphological and chemical) soil study was carried out oni) avery deepsoil chronosequence (approximately 9 m), composed of soil and pyroclastic deposits dating from the Pomici di Mercato eruption (8890 yrcal BP) until the present day and ii) a wide (4500 m2) paleo-surface belonging to the EBA. As shown by the chemical (i.e. organic matter– OM, cation exchange capacity– CEC, pH, ammonium oxalate extractable Al and Fe–Alo+0.5Feo index, organic and inorganic phosphorous fractions – OP and IOP) and physical (i.e. particle size distribution - PSD) properties, allsoils of the sequence i) formed by weathering of volcanic materials,ii) satisfy the requirements for Andosolclassification,iii) are markedly different in terms ofdepth, degree of andic properties and chemical fertility, iv) show micromorphological features (e.g. clay and silty coatings, laminar features, iron segregations, weathering rims,ecc.) indicatingspecific weathering environments.Moreover, the comparison of selected soil properties, such as Alo+0.5Feo index(essential for Andosols) and OM,andthe estimated pedogenetic times (EPT), calculated on the basis of the volcanological markers,withthe climatic conditions by the literature,highlights a markedrelationship between the degree of development of those properties (i.e. their content) in the soils of Palma Campania and the humidity/aridity of the environment. These resultsencourage furtherapplications aimed to use these soil propertiesas proxy for the reconstruction of past climatic conditions in volcanic environments. The soil properties measured in the different areas of the EBA paleo-surface showed very consistent with both archaeological findings and reconstructed agricultural uses. Indeed, the very high OP content, along with the enrichment of OMin the soils of the North and Central sectors are in accordance with the pasture and agricultural activities, respectively,suggested by the numerous chaotically scattered animal track sand the parallel furrows of “strip” cultivation, while both OP and OM are markedly lower in the coetaneous soil analyzed along the soil chronosequence, where no anthropic or animal traces were found. Regarding to the controversial interpretation about the use of the South area, peculiar pedological features and chemical properties strongly suggest the anthropic genesis for the ancient micro-topography.Indeed, the presence of a broken soil structure, horizontal planar pores and vertical orientated laminar aggregates in a massive structure reveal a process of deeply mixing and strongly compacting soil horizons to form micro-relieves and micro-concavities. High O Pand OM content are found at 7-25 cm below the soil surface, probably as a consequence of manuring and ploughing. Further abandonment and waterlogging of the area are consistent with the presence of Phragmites footprints,previously found during the archaeological survey, and absence of a specific shape of ploughing traces

In-situ sol-gel modification strategies to develop a monolith continuous microreactor for enzymatic green reactions

Two synthetic strategies were developed for in-situ modification of a silica sol gel matrix in a PEEK tubing, to obtain a hybrid monolith with entrapped lipases. A suitable combination of the sol-gel precursors (tetramethoxysilane, methyltrimethoxysilane and n-propyltrimethoxysilane) was found, for the simultaneous improvement of the monolith adhesion to the tubing internal surfaces and of the catalytic properties of the entrapped enzyme. The effects of the immobilization procedure were characterized as regards both the catalytic properties of the enzyme, as well as the secondary structure of lipases by FTIR. The catalytic efficiency of the entrapped enzyme was better preserved in more hydrophobic microenvironment. The improved stability of the biocatalysts allows further industrial applications