Number of metallic clusters in Y zeolites obtained from129Xe NMR

We present a simple model which permits to obtain the number of metallic clusters entrapped in Y zeolites from the curves of the chemical shifts of¹²⁹Xe NMR against the pressure of Xe. From the metal loading the average number of atoms per cluster can also be calculated. We apply the model to Pt/NaY and the bimetallic Pt-Cu/NaY.     

Penalized factor mixture analysis for variable selection in clustered data

A model-based clustering approach which contextually performs dimension reduction and variable selection is presented. Dimension reduction is achieved by assuming that the data have been generated by a linear factor model with latent variables modeled as Gaussian mixtures. Variable selection is performed by shrinking the factor loadings though a penalized likelihood method with an L1 penalty. A maximum likelihood estimation procedure via the EM algorithm is developed and a modified BIC criterion to select the penalization parameter is illustrated. The effectiveness of the proposed model is explored in a Monte Carlo simulation study and in a real example.     

Catalytic and sorbent materials based on mayenite for sorption enhanced steam methane reforming with different packed-bed configurations

An experimental study was performed on sorption enhanced steam methane reforming (SESMR) by Ni-mayenite reforming catalyst and CaO-mayenite CO₂-sorbents with several CaO contents. Materials were synthesized, characterized (by XRD, BET and BJH methods, TPR) and tested in a micro-reactor, comparing two configurations: two separated, consequential packed-beds and the more usual raw mixing. Ni-mayenite always allowed a high, stable CH₄ conversion (>93%). A generalized direct effect from CO₂ capture emerged on water gas shift reaction extent, while enhancement of methane conversion took place only in raw mixing.In practical applications, investigated materials are bound to face alternatively reforming and sorbent regeneration conditions: an automated bench-scale system was used to perform 205 SESMR/regeneration cycles, with separate beds of Ni-mayenite and CaO-mayenite (30 wt% free-CaO), proving good activity and stability throughout cycles (stable CH₄ conversion > 95%, pre-breakthrough CO₂ concentration < 3 vol% dry, dilution-free).     

A comparative study of water gas shift reaction over gold and platinum supported on ZrO2 and CeO2–ZrO2

In this study platinum- and gold-based catalysts supported on ZrO₂ and ceria–zirconia solid solution have been characterized by several techniques (TPR, XRD, BET, HRTEM) and tested in the water gas shift (WGS) reaction under feed conditions typical of an autothermal reformer outlet. Platinum and gold catalysts behave differently especially in the range of 423–513 K, with gold being superior than platinum. The possibility of modifying the redox and structural characteristics of zirconia with the insertion of ceria allowed us to conclude that the bulk redox properties of the support play a secondary role, while the key parameter for an active WGS catalyst is the nature of metal support interface. This, in turn, depends on the metal particle distribution and on the structural and morphological properties of support. It has been found that the synergism between precious metals and support can be designed with an appropriate choice of the parameters of synthesis and the characteristics of support.     

Optimal fermentation conditions for maximizing the ethanol production by Kluyveromyces fragilis from cheese whey powder

Cheese whey powder (CWP) is an attractive raw material for ethanol production since it is a dried and concentrated form of CW and contains lactose in addition to nitrogen, phosphate and other essential nutrients. In the present work, deproteinized CWP was utilized as fermentation medium for ethanol production by Kluyveromyces fragilis. The individual and combined effects of initial lactose concentration (50-150 kg m⁻³), temperature (25-35 °C) and inoculum concentration (1-3 kg m⁻³) were investigated through a 2³ full-factorial central composite design, and the optimal conditions for maximizing the ethanol production were determined. According to the statistical analysis, in the studied range of values, only the initial lactose concentration had a significant effect on ethanol production, resulting in higher product formation as the initial substrate concentration was increased. Assays with initial lactose concentration varying from 150 to 250 kg m⁻³ were thus performed and revealed that the use of 200 kg m⁻³ initial lactose concentration, inoculum concentration of 1 kg m⁻³ and temperature of 35 °C were the best conditions for maximizing the ethanol production from CWP solution. Under these conditions, 80.95 kg m⁻³ of ethanol was obtained after 44 h of fermentation.     

The HEPD particle detector of the CSES satellite mission for investigating seismo-associated perturbations of the Van Allen belts

CSES(China Seismo-Electromagnetic Satellite) is a mission developed by CNSA(Chinese National Space Administration) and ASI(Italian Space Agency), to investigate the near-Earth electromagnetic, plasma and particle environment, for studying the seismo-associated disturbances in the ionosphere-magnetosphere transition zone. The anthropogenic and electromagnetic noise,as well as the natural non-seismic electromagnetic emissions is mainly due to tropospheric activity. In particular, the mission aims to confirming the existence of possible temporal correlations between the occurrence of earthquakes for medium and strong magnitude and the observation in space of electromagnetic perturbations, plasma variations and precipitation of bursts with highenergy charged particles from the inner Van Allen belt. In this framework, the high energy particle detector(HEPD) of the CSES mission has been developed by the Italian LIMADOU Collaboration. HEPD is an advanced detector based on a tower of scintillators and a silicon tracker that provides good energy and angular resolution and a wide angular acceptance, for electrons of 3–100 Me V, protons of 30–200 Me V and light nuclei up to the oxygen. CSES satellite has been launched on February 2~(nd), 2018 from the Jiuquan Satellite Launch Center(China).     

On the evaluation of superplastic characteristics using the finite element method

In recent years, there has been a considerable interest in the application of superplastic forming in the aircraft and automotive industries to realize complex parts. This requires a detailed design of the technological process in order to better exploit its peculiar potentialities. Nowadays, the finite element method represents the mainly used technique to plan the sheet metal forming processes whose simulation requires determination of material constants for superplastic materials. The aim of the present work is aimed to show a simple method to characterize superplastic materials. In this study, constant pressure free bulging for superplastic materials is analysed by finite element method and expressions to determine the constants of the superplastic materials have been proposed. In order to support the proposed method, numerical and experimental activities have been carried out which show the good reliability of values obtained from proposed expressions.