Barbara Bonelli

Preparation and characterization of mesoporous molecular sieves containing Al, Fe or Zn

Abstract Silica M41S type materials have been prepared starting from the mixture: 0.29 Na 2 O:0.12 CTABr:1 SiO 2 :100 H 2 O using water–glass as silica source. Syntheses were carried out at three different temperatures: 303, 343 and 413 K. The effect of the synthesis temperature on the nature of the products, the presence of Al, Fe or Zn, as well as the properties of the so-obtained materials and their thermal stability were studied. XRD, N 2 adsorption, FTIR and NMR techniques were used for the characterization of the products. The adopted procedure enables the synthesis of thermally stable hexagonal mesoporous materials from hydrogels with Si/Al ratios ⩾10. The Al forms contain both Bronsted and Lewis acid sites, whereas the Fe forms only contain Lewis acidic sites.

Retention properties of mesoporous silica based materials

Abstract The partition and retention properties have been studied of mesoporous silicas prepared using a surfactant-based supramolecular templating approach towards environmental pollutants (trichloroacetic acid and haloderivatives such as chloroform, 1,1,1-trichloroethane, trichloroethylene and tetrachloroethylene). Gas-chromatography and suppressed anion-exchange chromatography have been used to evaluate the amount of retained analytes. The effect of the composition (presence and absence of the surfactant templating agent and of aluminum) and the influence of synthesis procedure of mesoporous silicates on the sorption performances have been considered. Calcined materials do not show affinity for ionic analytes. The same materials show good affinity for non-ionic analytes: different retention properties towards the tested molecules are observed, interpreted in terms of van der Waals and hydrogen bonding interactions between silica surface and analytes. As-prepared materials show excellent retention performances towards TCA, which depend on the conditions used for the synthesis. All this provides the basis for potential applications of these materials as preconcentrators and sorptive chromatographic substrates for selective separation and/or enrichment (removal) of specific classes of analytes.

Solid–Gas Hydrogenation of Hex-3-yne and 1,4-Cyclohexadiene in the Presence of the Clusters Ru3(CO)12, H4Ru4(CO)12, H2Ru4(CO)13, and H2FeRu3(CO)13 Supported on Inorganic Materials. Infrared Evidence for Surface Organometallic Reactions

The clusters Ru3(CO)12 (1), H4Ru4(CO)12 (2), H2Ru4(CO)13 (3), and H2FeRu3(CO)13 (4) supported on pyrex borosilicate glass behave as catalysts for solid–gas hydrogenation reactions of hex-3-yne and 1,4-cyclohexadiene. Their activity and selectivity are discussed. Ru3(CO)12 (1) was also supported on inorganic oxides, normally used as chromatographic materials or supports for heterogeneous catalysis and characterized by different acidities and surface areas. The observed activities depend on the nature of the inorganic supports; the presence of water also has some influence. Some of these materials were characterized by HRTEM microscopy. Organometallic products have been collected after the catalytic runs both when pyrex and inorganic oxides were used as supports. In particular, the “surface organometallic reactions” of Ru3(CO)12 and H4Ru4(CO)12 supported on silica have been followed by IR spectroscopy. The nature and role of the arising organometallic compounds are discussed. Our solid–gas results are in good agreement with the mechanisms previously proposed for the hydrogenation of comparable substrates under homogeneous conditions.

Mesoporous materials for the retention and separation of haloacetic acids

SummaryMesoporous silica-based materials have been synthesized and studied for applications in the environmental field. Haloacetic acids have been chosen as test compounds since they are byproducts of disinfection processes of water for human consumption. For this purpose mesoporous materials have been synthesized in acid, basic or neutral conditions. The effect of composition and synthesis conditions of mesoporous materials on their retention properties have been studied. The retention mechanism has also been elucidated in term of electrostatic interactions and as a function of the residual surfactant content in the materials.

Human Exploration of the Moon: Multi-stage lunar Dust Removal System

International space exploration plans and scenarios are driven by the long-term goal to enable human exploration of Moon and Mars. To prepare for these ambitious goals, robotic and human space missions are required to gradually develop and demonstrate the enabling technologies and capabilities. In the f rame of such scenario, the research program STEPS aims at developing technologies needed for the future exploration missions of the solar system. The perva sive presence of lunar dust could jeopardize the re turn of the man to the Moon, seriously affecting the hea lth of future crews. It is therefore essential to d esign dust abatement systems that are reliable, reusable, and efficient. The present paper describes the desi gn and manufacturing of a dust removal system developed as part of the Environmental Control and Life Support System of a manned rover for the exploration of the lunar surface near the South Pole. The Dus t Removal System proposed has been designed to abate the amount of airborne dust present inside the pressurized volume of the rover due to the External Vehicular Activities of the crew. The proposed syste m consists of three dust-abatement stages arranged in succession in order to increase both the collectio n efficiency and the reliability of the whole system. The first stage, a cyclonic separator coupled with a magnetic collector, has been designed to remove the greater part of airborne particulates without the use of filters, through cyclonic and magnetic separatio n. Taking advantages of the peculiar electro-magneti c properties of the lunar regolith, due to abundant n ano-phase metallic Fe, an electro-active filter sec ond stage has been designed that ionizes and removes smaller-grained particulates. The last stage is a High Efficiency Particulate Air filter able to remove at least 99.97% of airborne particles larger than 0.3 micrometers in diameter. To test (on ground) the Dust Removal System, testing processes and procedures with the use of the enhanced lunar dust simulant ar e under investigation.

Isomerization of K(CO)+ and K(OC)+ carbonyls formed upon CO adsorption on the faujasite-type K-Y zeolite

Abstract When adsorbed on the faujasite-type K-Y zeolite, carbon monoxide forms cationic C-bonded K(CO)+ carbonyls and also O-bonded K(OC)+ isocarbonyls. The carbonyl species gives a characteristic C-O stretching band at 2158 cm−1, while that of the isocarbonyl appears at 2124 cm−1. By means of variable-temperature infrared spectroscopy, these K(CO)+ and K(OC)+ species were found to be in a temperature-dependent isomerization equilibrium, where the relative proportion of the isocarbonyl increases as temperature is raised. The corresponding isomerization enthalpy resulted to be 1.6(±0.5) kJ mol−1. Comparison with data available for other alkali-metal-exchanged zeolites shows that, for most cases, this thermodynamic parameter is an approximately linear function of the electrostatic field at the cation site. Lithium-exchanged zeolites, however, do not seem to conform to this rule; presumably because of the strong polarizing power of the Li+ ion.