Isomerization of trans-but-2-ene to cis-but-2-ene and double bond migration of trans-but-2-ene to but-1-ene have been investigated by means of density functional theory calculations on a suitable model of H-ZSM-5 surface. The study has been afforded on outer surface sites by considering the hydroxyl group of either a SiO2(OH)2 or a AlO2H(OH)2 moiety. On these outer surface sites, one alkoxide species occurs as a stable intermediate both along the isomerization and double bond migration pathways. The latter process could also occur via a single-step mechanism, which involves a six-center transition state. The energy barriers of the outer surface processes above do not take any advantage by the occurrence of Al↔Si substitutions on the surface, resulting the considered butene transformations negatively affected, indeed. This occurrence can be explained since the reactions on the external surface do not involve acidic hydrogen atoms of the AlO2H(OH)2 moiety.

The isomerization of cis-but-2-ene to trans-but-2-ene within a 22T H-ZSM-5 zeolite model, also in the presence of two adsorbed Pd atoms, has been studied by DFT calculations. The results obtained allow us to state that the cis/trans but-2-ene isomerization can easily proceed inside unsupported zeolite cavities. In this case, differently than in the gas phase reaction, the trans-but-2-ene is less stable than the cis-but-2-ene, when adsorbed on the zeolite inner surface. Excluding the adsorption-desorption steps, the isomerization process involves two intermediates and three transition states, whose energy content is always very low with respect to that of reagents and intermediate species. The reaction is in principle allowed also in the presence of two Pd atoms embedded inside the zeolite cavity. However, strong H-Pd interactions seem to cause higher activation energies along the formation of the involved intermediates and transition states. To evaluate the confining effects of the zeolite room on the cis/trans isomerization process, the latter has been also analyzed on protonated (Pd2H(+)) and unprotonated (Pd2) bare palladium fragments at different multiplicity states. The but-2-ene adsorption on the considered systems and the mutual influence occurring between the metal atoms and the hydrogen acidic sites at different multiplicity states have also been taken into consideration.

A new thermal process for the inactivation of microorganisms in beverages has been studied and is presented in this paper. The treatment, not yet studied in the scientific literature, mainly consists of a thermal shock characterized by temperature increases up to 30°C/s, with final temperatures up to 65°C. This study presents the first experimental results obtained by the application of the new thermal treatment, with different combinations of the process parameters (rate of temperature rise, final temperature and holding time), on separate suspensions of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Listeria innocua and Candida albicans. The required rapid temperature increase has been performed by means of a properly designed test bench. The treatment proved to be effective against all the microorganisms tested, obtaining a load reduction greater than 5 Log units. Compared with the commonly employed thermal treatments for microorganisms inactivation, this new process is characterized by a very interesting combination of a short duration (few seconds) and a low final temperature, which makes it particularly attractive for the application in the beverage industry

Dielectric properties of apple, apricot, peach, and pear nectars were studied in the frequency range from 15 kHz to 30 MHz and the temperature range from 25 to 60°C. Both the relative dielectric constants and the dielectric loss factors decreased by increasing frequency and increased linearly with increasing temperature with values in the order 10 4 -10 2 and 10 5 -10 2 , respectively. The power dissipation densities and the power penetration depths were found to increase linearly with temperature. Power dissipation densities remained essentially constant for all the samples while power penetration depths decreased significantly on increasing frequency. The dependence of each of the two dielectric properties on frequency and temperature has been described by two simple equations that proved to be adequate to describe the trend of the relative dielectric constant and dielectric loss factor for all the frequencies temperatures considered. It has been established that the dominant mechanism for the dielectric loss is ionic conductivity.

This review shortly discusses recent results obtained by the application of density functional theory for the calculations of the adsorption and diffusion properties of small molecules and their reactivity on heterogenous catalytic systems, in the ambit of the Nanocat project. Particular focus has been devoted to palladium catalysts, either in atomic or small cluster form. Some protocols have been tested to obtain efficient ways able to treat the electronic and geometric influence of supports like zeolites and carbon nanotubes on the catalytic properties of palladium. The hydroisomerization of cis-but-2-ene is discussed as model reaction on supported and unsupported Pd clusters. Some preliminary results on the structural investigation of systems formed by a palladium clusters and block copolymers are also presented.