N. Giordano

Cyclohexane as a liquid phase carrier in hydrogen storage and transport

The availability of large tonnages of hydrogen, as foreseen in “Hydrogen economy” requires the development of a suitable means for handling, storage and transportation of this fuel. Present technology already offers proven ways for handling and storage (cryogenic, pressurized, hydrides, hollow spheres) but lacks suitable means for long-distance transportation. Reversible catalytic (de)hydrogenation reaction appears a possible solution to this problem. Work carried out in this Institute has proven full reversibility for the (de)hydrogenation of cyclohexane, in the presence of a proper catalyst. The round-trip efficiency for a foreseeable closed cycle to store hydrogen amounts to about 98%, provided it is possible to recover the exothermic reaction heat. Economic evaluation shows that in spite of heat penalties and losses, systems based on the reversible cyclohexane (de) hydrogenation process are more advantageous than conventional ones, especially because of the low cost of materials storage and high hydrogen density per unit volume (0.056 g(H2)/cm3(Cy)liq.). Most important, it provides a safe and simple means for H2 transport over any desirable distance, the carrier being in a liquid phase.

Hydrothermal synthesis of zeolites from pumice in alkaline and saline environment

Lipari pumice has selectively been transformed into zeolites in NaOH/NaCl media. The influence of NaCl and retention times on the degree of zeolitization is discussed for different NaOH concentrations. In the absence of NaCl, the high SiO 2 /Al 2 O 3 ratio zeolites ZK-19 and phillipsite appear after long induction periods, whereas the SiO 2 /Al 2 O 3 -rich hydroxysodalite and faujasite are formed exclusively for [NaOH] = 120 g l −1 in the presence of NaCl.

Fast simple and accurate measurement of zeolite thermal conductivity

A simple and fast method to measure the thermal conductivity of zeolite brick is presented. The theory of the measurement and the experimental device are accurately described. Results obtained using zeolite samples produced in the CNR-TAE Institute with a specific and patented procedure confirm the accuracy of the measurement methodology, which is simple and inexpensive and can be used in any laboratory, especially for comparison measurements.

Preparation and analysis of ε-caprolactam and ε-thiocaprolactam platinue(II) and rhodium(III) complexes

Abstract The synthesis and properties of some Pt(II) and Rh(III) complexes with e-caprolactam (L) and e-thiocaprolactam (L′) are reported. The compounds, L 3 RhCl 3 , L 2 PtCl 2 , [L′ 4 RhCl 2 ]Cl and [L′ 4 Pt]Cl 2 , have been characterized by chemical analysis, infra-red, n.m.r. and electronic spectra, X-ray powder diffraction and electrical conductance. Evidence is presented for coordination of the unidentate ligands through the oxygen or sulfur atoms. Configurational assignments indicate trans-coordination in both the square-planar L 2 PtCl 2 and octahedral L 3 RhCl 3 complexes.

Thermodynamic analysis of SOFC fuelled by biomass-derived gas

Abstract A thermodynamic evaluation of an integrated biomass catalytic gasifier-solid oxide fuel cell (SOFC) system has been made, as a preliminary approach to assess the technical feasibility of electrical energy production from a renewable source such as biomass. Equilibrium calculations have been made to predict conversion levels in a chemical reacting system including cellulose as a typical biomass feedstock and water vapor or CO2 as the gasifying agent. The allowable electrical efficiencies of the cellulose product-gas-fuelled SOFC have been calculated for different gasifier operating conditions, namely H2O (CO2)/biomass ratio and gasifier operating temperature. For a gasifier temperature of 700°C, electrical efficiencies in the SOFC are 47% and 51% for steam (steam/biomass = 1.12) and CO2(CO2/biomass = 1.30), respectively.

Solid polymer electrolyte fuel cell (SPEFC) research and development at the institute CNR-TAE of messina

Abstract In the sector of solid polymer electrolyte fuel cells, the CNR-TAE activities have been focused on the development of a fuel cell system based on a proprietary dual-layer electrode preparation procedure. The influence of some characteristic parameters of the electrodes, i.e. hydrophobic agent and Nafion® loadings, on electrochemical performance has been explored. It has been concluded that in the diffusion layer, the amount of hydrophobic agent controls the water transfer into the cell and consequently the mass transport phenomena. In the active layer, the Nafion® content mostly influences the electrocatalytic activity and the ionic resistance of the cell.

Hydrothermal synthesis of zeolites from low-cost natural silica-alumina sources

Abstract Sardinian perlite and Sicilian tuff have been subjected to hydrotermal synthesis in NaOH media. The influence of the nature and chemical composition of the starting material, pH and concentration of the mineralizing agent (NaOH) and reaction temperatures and time on the zeolitization process is discussed and compared to the performance of Lipari pumice. The chemical composition, in particular the SiO 2 Al 2 O 3 ratio, of volcanic glasses is the most important factor in the dissolution process leading to formation of zeolitic products.

Photoassisted decomposition of water over modified rutile electrodes

Abstract The photoelectrolysis of water was investigated on a series of TiO 2 semiconductors prepared by air oxidation of Ti laminae at 700°C, by impregnation with TiCl 3 and metals (as nitrates), and by flame oxidation in air at 1300°C. The photocurrent of the TiO 2 electrodes was modified exclusively by impregnation with cations (of higher and lower valency) with radii close to or lower than that of Ti(IV); other cations had no effect or a slightly negative effect. For the most efficacious cations, the use of chlorides instead of nitrates increased energy efficiency. Impregnation with Pt had the most marked positive influence: up to an energy conversion of 2.7% at 1 sun concentration vs 0.5% for the pure sample. The energy efficiency of the electrodes is strongly influenced by the preparative procedure. The results are interpreted with emphasis on the adsorptive and catalytic properties of the impregnated surfaces. It is suggested that most efficacious cations, and notably Pt, act through reduction of the surface, thereby decreasing its acidity and increasing n -type character. As a result, adsorbed molecular water is assumed to decompose at a faster rate than on pure titania.

Photoelectrochemical behavior of thermally activated natural pyrite-based photoelectrodes

Abstract Natural pyrite-based photoelectrodes have been manufactured by the screen printing technique. Solid state investigation of the starting material, as well as of the thermally activated powders, has been carried out by X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDX). Information on the electrochemical reactivity of the surface has been obtained by cyclic voltammetry in alkaline solution. The air-treated electrodes have been shown to be photoactive when tested as photoanodes in polyiodide — containing photoelectrochemical cells. The maximum obtained efficiency for solar energy conversion was 0.5%. Formation of a heterostructure composed of FeS2 and Fe2O3 phases is considered to be a promising way for the development of low-cost devices in the direct conversion of solar energy.

A spectroscopic investigation of cerium molybdenum oxides

A detailed X-ray photoelectron, i.r., and Raman spectral study has been made of Ce2(MoO4)3 and five novel cerium molybdenum oxides (α- and β-Ce2Mo4O15, β- and γ-Ce2Mo3O13, and Ce8Mo12O49), which are of particular interest as they are closely related to the cerium molybdenum oxide species which are expected to play an active role in an industrial cerium molybdenum tellurium oxide acrylonitrile catalyst. The photoemission results add to the few existing previous data concerning cerium compounds and confirm the valence distribution in the compounds. With the exception of the tetrahedral oxomolybdenum co-ordination in Ce2(MoO4)3 the cerium molybdates consist of highly irregular or mixed polyhedral arrangements with Mo–O bond strengths (in valence units) either below 0.3 v.u or above 1.0 v.u.