Sviluppo di materiali nanostrutturati e apparati per applicazioni in catalisi eterogenea.

The doctoral research period was devoted to the development of new ideas in the field of heterogeneous catalysis, involving both the realisation of novel apparatus for the study of catalysts and the synthesis of new catalytic materials. A new apparatus for the study of selectivity in oxidative dehydrogenation reaction was initially setup aiming at studying the performances of new saponite catalysts. These materials have been shown to lead to coke productivity during ODH reaction. These data gave us the idea to use saponite materials as polymer flame retardant. The clay material flame retardant effect is due to two synergic effect: the creation of a protective inorganic layer on the surface of the polymer matrix and the formation of char laminar structures. Our purpose was to increase the catalytic conversion performances of propene to coke by exploiting both acid saponite sites and vanadium species. The catalytic performances of different saponite materials toward propene ODH reaction was studied. Different metal-free acidic saponites (containing different amount of Brønsted acid sites) and V-containing saponite both acidic and non-acidic were investigated. We found that the synergic effect of acidic site and Vanadium presence allow to the system (HV-Sap) to reach the highest low temperature activities and it is the only system that still maintain a positive coke production at 773 K. The second research field is the development of apparatus suitable for planar catalyst libraries tests. A reactor which is able to scan small active catalytic surfaces using very low gas flow was developed and successfully tested in our laboratories. The reactor is designed to allow a continuous scanning test on a reduced circular area without any sealing system. The system consists of two main parts: the sample holder and the reactor head. The sample holder is mounted on a movable XYZ stage to set the relative 3D position with respect the fixed reactor head position. The reactor head features a little open chamber at the bottom; the reactant gas mixture is fed by a hose in the middle of the chamber, whereas the reaction gases are extracted by a side hose. The entire system (reactor head and sample holder) is located in a controlled argon atmosphere chamber. The product gas mixture is confined and diluted in-situ by a flow of inert leakage gas from the controlled external atmosphere. The product gas mixtures are analysed by a downstream quadrupole-based mass spectrometer. Two model reactions were used to develop the scanning reactor: the hydrogenation of 1-3 butadiene over Pd nano-structured and the CO oxidation reaction over gold supported on titania Finally, the possibility to obtain hydrogen from the photoproduction of renewable chemicals is investigated. At present, hydrogen is mainly produced from fossil fuels; a very interesting hydrogen source is water-splitting but, in spite of the intense research activities registered in the last decades, pure water splitting is still far from any technological application due to the complexity of the process and its inherent drawbacks. In particular, the main issue is the fast recombination between H2 and O2 (thermodynamically favourable inverse reaction) or between photogenerated electrons and holes. A different approach to photoproduction is the use of organic compound as sacrificial agent for the hole sequestration: this reaction is accordingly called photoreforming. In particular, the catalytic photoreforming of ethanol and glycerol is investigated in this study. The first is obtained from carbohydrates fermentation and glycerol is the main byproduct of trans-etherification reaction for biodiesel production, being both cheap and widely available chemicals. We want to study bimetallic gold-platinum systems supported over titania; a number of application of monometallic system in photoreforming are known in the literature and bimetallic systems are known to show optimal performances as catalytic system for a large number of reactions but they have never been used as photocatalysts. The bimetallic system showed the highest activity during the photoreforming reaction of ethanol but during the reactions with glycerol solution the presence of both metal didn’t improve the reactivity of the system. Also the activity of photodeposited system were investigated on glycerol photoreforming with UV-A light. The hydrogen production rate of photodeposited gold monometallic system is close to the impregnated bimetallic system; the photodeposited bimetallic system showed a hydrogen production rate of 3400 μmol g-1 h-1 after 6 reaction hours,1000 μmol g-1 h-1 higher than bimetallic impregnated system.