New catalysts for the water gas shift reaction at middle-temperature

H2 demand is continuously increasing since its many relevant applications, for example, in the ammonia production, refinery processes or fuel cells. The Water Gas Shift (WGS) reaction (CO + H2O = CO2 + H2 DeltaH = -41.1 kJ.mol-1) is a step in the H2 production, reducing significantly the CO content and increasing the H2 one in the gas mixtures obtained from steam reforming. Industrially, the reaction is carried out in two stages with different temperature: the first stage operates at high temperature (350-450 °C) using Fe-based catalysts, while the second one is performed at lower temperature (190-250 °C) over Cu-based catalysts. However, recently, an increasing interest emerges to develop new catalytic formulations, operating in a single-stage at middle temperature (MTS), while maintaining optimum characteristics of activity and stability. These formulations may be obtained by improving activity and selectivity of Fe-based catalysts or increasing thermal stability of Cu-based catalysts. In the present work, Cu-based catalysts (Cu/ZnO/Al2O3) prepared starting from hydrotalcite-type precursors show good homogeneity and very interesting physical properties, which worsen by increasing the Cu content. Among the catalysts with different Cu contents, the catalyst with 20 wt.% of Cu represents the best compromise to obtain high catalytic activity and stability. On these bases, the catalytic performances seem to depend on both metallic Cu surface area and synergetic interactions between Cu and ZnO. The increase of the Al content enhances the homogeneity of the precursors, leading to a higher Cu dispersion and consequent better catalytic performances. The catalyst with 20 wt.% of Cu and a molar ratio M(II)/M(III) of 2 shows a high activity also at 250 °C and a good stability at middle temperature. Thus, it may be considered an optimum catalyst for the WGS reaction at middle temperature (about 300 °C). Finally, by replacing 50 % (as at. ratio) of Zn by Mg (which is not active in the WGS reaction), better physical properties were observed, although associate with poor catalytic performances. This result confirms the important role of ZnO on the catalytic performances, favoring synergetic interactions with metallic Cu.

Nuovi processi catalitici per la produzione di syngas

The study of the combined Steam/Dry Reforming (S/DR) process for the production of syngas (CO + H2) from clean biogas was carried out using Ni/Ir bimetallic catalysts on Mg and Al mixed-oxides, obtained by calcination of hydrotalcite-type precursors (Ht) prepared by co-precipitation. The presence of small amounts of Ir promoted the catalytic activity and limited the deactivation phenomena through the formation of a bimetallic alloy, which does the catalyst very active even at lowest temperature and in lack of steam. By integrating a High Temperature–WGS unit (HTS) after the S/DR reactor it was possible to increase the H2 yield of the process. The performance of the Zn/Al/Cu-based catalyst was improved using a templating agent during the synthesis of the catalyst, which increased the catalyst’s structural properties and activity especially at lowest temperatures and at highest contact times. Finally, starting from the laboratory data, it was possible to simulate the S/DR process on industrial scale, evaluating its scalability and environmental impact. The results showed that, using the S/DR technology instead of the current processes, it was possible to reduce the energy costs and the atmospheric emissions of the plant.

Jeans modeling of massive early-type galaxies with observed stellar kinematic profiles up to 2-3 effective radii

A recent integral-field spectroscopic (IFS) survey, the MASSIVE survey (Ma et al. 2014), observed the 116 most massive (MK < −25.3 mag, stellar mass M∗ > 10^11.6 M⊙) early-type galaxies (ETGs) within 108 Mpc, out to radii as large as 40 kpc, that correspond to ∼ 2 − 3 effective radii (Re). One of the major findings of the MASSIVE survey is that the galaxy sample is split nearly equally among three groups showing three different velocity dispersion profiles σ(R) outer of a radius ∼ 5 kpc (falling, flat and rising with radius). The purpose of this thesis is to model the kinematic profiles of six ETGs included in the MASSIVE survey and representative of the three observed σ(R) shapes, with the aim of investigating their dynamical structure. Models for the chosen galaxies are built using the numerical code JASMINE (Posacki, Pellegrini, and Ciotti 2013). The code produces models of axisymmetric galaxies, based on the solution of the Jeans equations for a multicomponent gravitational potential (supermassive black hole, stars and dark matter halo). With the aim of having a good agreement between the kinematics obtained from the Jeans equations, and the observed σ and rotation velocity V of MASSIVE (Veale et al. 2016, 2018), I derived constraints on the dark matter distribution and orbital anisotropy. This work suggests a trend of the dark matter amount and distribution with the shape of the velocity dispersion profiles in the outer regions: the models of galaxies with flat or rising velocity dispersion profiles show higher dark matter fractions fDM both within 1 Re and 5 Re. Orbital anisotropy alone cannot account for the different observed trends of σ(R) and has a minor effect compared to variations of the mass profile. Galaxies with similar stellar mass M∗ that show different velocity dispersion profiles (from falling to rising) are successfully modelled with a variation of the halo mass Mh.

Lightweight Internet Traffic Classification - A Subject Based Solution with Word Embeddings

Internet traffic classification is a relevant and mature research field, anyway of growing importance and with still open technical challenges, also due to the pervasive presence of Internet-connected devices into everyday life. We claim the need for innovative traffic classification solutions capable of being lightweight, of adopting a domain-based approach, of not only concentrating on application-level protocol categorization but also classifying Internet traffic by subject. To this purpose, this paper originally proposes a classification solution that leverages domain name information extracted from IPFIX summaries, DNS logs, and DHCP leases, with the possibility to be applied to any kind of traffic. Our proposed solution is based on an extension of Word2vec unsupervised learning techniques running on a specialized Apache Spark cluster. In particular, learning techniques are leveraged to generate word-embeddings from a mixed dataset composed by domain names and natural language corpuses in a lightweight way and with general applicability. The paper also reports lessons learnt from our implementation and deployment experience that demonstrates that our solution can process 5500 IPFIX summaries per second on an Apache Spark cluster with 1 slave instance in Amazon EC2 at a cost of $ 3860 year. Reported experimental results about Precision, Recall, F-Measure, Accuracy, and Cohen's Kappa show the feasibility and effectiveness of the proposal. The experiments prove that words contained in domain names do have a relation with the kind of traffic directed towards them, therefore using specifically trained word embeddings we are able to classify them in customizable categories. We also show that training word embeddings on larger natural language corpuses leads improvements in terms of precision up to 180%.

Synthesis and characterization of heteroleptic Cu(I) complexes based on quinolin-yl-1,2,3-triazole and pyridin-yl-1,2,3 triazole

The present work is part of a research project that involves the study of new copper based complexes to be employed as photosensitizer in carbon dioxide photoreduction reaction. My research project is focused on the synthesis and characterization of 1,2,3 triazoles with a quinoline or pyridine in the lateral chain, which have been successively utilized to synthesize heteroleptic Cu(I) complexes. Redox potential and photophysic properties have been studied.

Synthesis, Characterization, and Applications of a Novel Cu(II)-MOF Based on a Propargylcarbamate-Functionalized Isophthalate Ligand

This work describes the synthesis of a propargylcarbamate-functionalized isophthalate ligand and its use in the solvothermal preparation of a new copper(II)-based metal organic framework named [Cu(1,3-YBDC)]ˑxH2O (also abbreviated as Cu-MOF. The characterization of this compound was performed using several complementary techniques such as infrared (ATR-FTIR) and Raman spectroscopy, X-ray powder diffraction spectroscopy (PXRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS) as well as thermal and surface area measurements. Synchrotron X-ray diffraction analysis revealed that this MOF contains a complex network of 5-substituted isophthalate anions bound to Cu(II) centers, arranged in pairs within paddlewheel (or “Chinese lantern”) structure with a short Cu…Cu distance of 2.633 Å. Quite unexpectedly, the apical atom in the paddlewheel structure belongs to the carbamate carbonyl oxygen atom. Such extra coordination by the propargylcarbamate groups drastically reduces the MOF porosity, a feature that was also confirmed by BET measurements. Indeed, its surface area was determined to be low (14.5 ± 0.8 m2/g) as its total pore volume (46 mm3/g). Successively the Cu-MOF was treated with HAuCl4 with the aim of studying the ability of the propargylcarbamate functionality to capture the Au(III) ion and reduce it to Au(0) to give gold nanoparticles (AuNPs). The overall amount of gold retained by the Cu-MOF/Au was determined by AAS while the amount of gold and its oxidation state on the surface of the MOF was studied by XPS. A glassy carbon (GC) electrode was drop-casted with a Cu-MOF suspension to electrochemically characterize the material through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The performance of the modified electrodes towards nitrite oxidation was tested by CV and chronoamperometry.

Fabrication by magnetron sputtering and characterization of electrodes based on CuIn0.7Ga0.3Se2 (CIGS)

This thesis work aims to produce and test multilayer electrodes for their use as photocathode in a PEC device. The electrode developed is based on CIGS, a I-III-VI2 semiconductor material composed of copper (Cu), indium (In), Gallium (Ga) and selenium (Se). It has a bandgap in the range of 1.0-2.4 eV and an absorption coefficient of about 105cm−1, which makes it a promising photocathode for PEC water splitting. The idea of our multilayer electrode is to deposit a thin layer of CdS on top of CIGS to form a solid-state p–n junction and lead to more efficient charge separation. In addition another thin layer of AZO (Aluminum doped zinc oxide) is deposit on top of CdS since it would form a better alignment between the AZO/CdS/CIGS interfaces, which would help to drive the charge transport further and minimize charge recombination. Finally, a TiO2 layer on top of the electrodes is used as protective layer during the H2 evolution. FTO (Fluorine doped tin oxide) and Molybdenum are used as back-contact. We used the technique of RF magnetron sputtering to deposit the thin layers of material. The structural characterization performed by XDR measurement confirm a polycrystalline chalcopyrite structural with a preferential orientation along the (112) direction for the CIGS. From linear fit of the Tauc plot, we get an energy gap of about 1.16 eV. In addition, from a four points measurements, we get a resistivity of 0.26 Ωcm. We performed an electrochemical characterization in cell of our electrodes. The results show that our samples have a good stability but produce a photocurrent of the order of μA, three orders of magnitude smaller than our targets. The EIS analysis confirm a significant depletion of the species in front of the electrode causing a lower conversion of the species and less current flows.