Homogeneous catalytic hydrogenation of free carboxylic acids in the presence of cluster ruthenium carbonyl hydrides

Saturated monocarboxylic acids up to C₆, several bicarboxylic acids and some of the corresponding anhydrides are hydrogenated in the homogeneous phase with H₄Ru₄(CO)₈(PBu₃)₄ as catalyst to give the corresponding alcohols (present among the reaction products as esters) or lactones at 100–200°C under a pressure of 100–200 atm of hydrogen. Anhydrides react at temperatures lower than those needed for acids. Esters are not reduced. Only δ-valerolactone is hydrogenated to 1,5-pentanediol. Ruthenium carbonyl carboxylates have been recovered at the end of the reaction and appear to be catalytically active intermediates.     

Extension of the 2-p-opt and 1-shift algorithms to the heterogeneous probabilistic traveling salesman problem

The probabilistic traveling salesman problem is a well known problem that is quite challenging to solve. It involves finding the tour with the lowest expected cost for customers that will require a visit with a given probability. There are several proposed algorithms for the homogeneous version of the problem, where all customers have identical probability of being realized. From the literature, the most successful approaches involve local search procedures, with the most famous being the 2-p-opt and 1-shift procedures proposed by Bertsimas [D.J. Bertsimas, L. Howell, Further results on the probabilistic traveling salesman problem, European Journal of Operational Research 65 (1) (1993) 68–95]. Recently, however, evidence has emerged that indicates the equations offered for these procedures are not correct, and even when corrected, the translation to the heterogeneous version of the problem is not simple. In this paper we extend the analysis and correction to the heterogeneous case. We derive new expressions for computing the cost of 2-p-opt and 1-shift local search moves, and we show that the neighborhood of a solution may be explored in O(n²) time, the same as for the homogeneous case, instead of O(n³) as first reported in the literature.     

Experimental microkinetic approach of the photocatalytic oxidation of isopropyl alcohol on TiO2. Part 2. from the surface elementary steps to the rates of oxidation of the C3H(x)O species

The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of the PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factors and activation energies). These kinetic parameters are used to evaluate a priori the catalytic activity (turnover frequency, TOF, in s(-1)) of the solid that is compared to the experimental value. The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The microkinetic study shows that only strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The apparent rate constant (1.4 10(-3) s(-1)) of the Langmuir-Hinshelwood elementary step between IPA(sads) and the active oxygen containing species generated by the UV irradiation provides the TOF of the PCO for IPA/O2 gas mixtures. The kinetic parameters of the elementary steps determined by the experimental microkinetic approach allow us to provide a reasonable simulation of the experimental data (coverages of the adsorbed species and partial pressures of the gases of interest) recorded during a static PCO of IPA(sads) species.     

The Mediterranean aromatic plants and their culinary use.

Over the centuries, aromatic plants have acquired both practical relevance and socio-cultural meanings that have influenced the evolution of humanity itself and created relevant economic value. In fact, since a long time ago spices were promoted to a leading economic role, and their profitability has been often comparable to that of other commodities traded in much larger volumes. Many geographical discoveries, explorations, worldwide relationships between populations in different continents, were undertaken in order to meet the quest for new flavours, new tastes, new medicinal plants or to find new markets for those already known. While the use of plants in medicine offers an extensive written documentation produced by most ancient human civilizations, the same can not be said for food herbs and flavouring spices. However, without the adequate selection of edible, reliable and valuable plants from the whole biodiversity pool operated by folk cultures everywhere in the world, their proper combination would have never been elaborated and cuisines, like the Mediterranean ones, would have not attained such unique mix of flavour, taste and nutrient content that has no equal in the world. Therefore, any consideration on herbs and aromatic plants in the kitchen leads inequivocally to a journey into tradition.     

Influence of ultrasound on the preparation of ruthenium catalysts supported on alumina

Ultrasound waves are commonly used to clean or to erode the surface of solid materials thanks to the strength of the jets of solvent, hitting the surface itself, created by the collapse of the liquid phase. In the present work, ultrasound was used to obtain highly dispersed ruthenium on alumina catalysts. The samples were characterized with different techniques to study the influence of the sonication on both the metal crystallites and the support.