A DFT Approach for Methanol Synthesis via Hydrogenation of CO on Gallia, Ceria and ZnO surfaces

A systematic theoretical study of the consecutive hydrogenation reactions of the CO molecule for the methanol synthesis catalyzed by different oxides of Zn, Ce and Ga is reported in this work. First, the CO hydrogenation with the formation of formyl species (HCO) was analyzed, followed by the successive hydrogenations that lead to formaldehyde (H2CO), methoxy (H3CO) and, finally, methanol (H3COH). The co-adsorption with H, in almost all the intermediate species, allows the corresponding hydrogenation reaction. Oxygen vacancies promote the reactivity in the generation of both formaldehyde and methoxy species. The formation of these species involves an important geometric difference between the initial and the final states, leading to high activation barriers. Comparing the surfaces studied in this work, we found that ZnO (0001)vacO has shown to be of a greater interest for methanol synthesis. However, the foregoing is not the most relevant of our results, but, instead, that the Brönsted Evans Polanyi (BEP) relationships between the initial or the final states and the transition states (TS) allowed to find a very good correlation between surface structure and reactivity.Fil: Reimers, Walter Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Zubieta, Carolina Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Branda, Maria Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentin

Contribution to the knowledge of continental ostracod from Chile

Our knowledge of continental ostracods in South America is still in its infancy with a total of only 260 species (MARTENS & BEHEN, 1994). Particularly in Chile, it is still scarce and scattered, with large voids in the taxonomy and distribution. In Chile, the first records were reported by DADAY (1902), BREHM (1934) and LÖFFLER (1961a, b). Later, SCHWALB & BURNS (1999) cited species of Limnocytheridae and KARANOVIC (2012) provided new records of Candonidae from Chile. The main objective of this work is to provide a checklist of ostracods in Chile with updated distributional records.Fil: Cardenas, Javiera. Universidad de Concepción; ChileFil: Baltanas, Angel. Universidad Autónoma de Madrid; EspañaFil: Figueroa, Ricardo. Universidad de Concepción; ChileFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; ArgentinaFil: Laprida, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos; ArgentinaFil: Ramon Mercau, Josefina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Alvarez, Denisse. Universidad de Concepción; ChileFil: Urrutia, Roberto. Universidad de Concepción; Chil

From Naples 1963 to Rome 2013 - A brief review of how the international research group on Ostracoda (IRGO) developed as a social communication system

The 1st International Symposiumon Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposiumand the logical outcome of what is nowknown as the International Research Group on Ostracoda (IRGO) are here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963 and 1983, is related to applied research for the oil industry aswell as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was thework by researchers dealing with Palaeozoic ostracods,who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved the communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research "politics" within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003-2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked

Degradation of the Oxirane Ring of Epoxidized Vegetable Oils with Solvated Acetic Acid Using Cation-exchange Resins

Vegetable oil epoxides (oxiranes) are customarily manufactured using acetic acid (AA) as oxygen carrier and reactant source, in aqueous/organic media. Further attack of the oxirane ring by AA proceeds in this acid-catalyzed process, lowering yield. We report a study of the degradation of the ring by water-solvated AA, using Amberlite IR-120 as heterogeneous catalyst. The ring opening with solvated AA was found to be first order with respect to the concentration of epoxide groups and second order with respect to the carboxylic acid, with an activation energy of 58.7 ± 0.42 kJ mol-1. This value is within the range found in liquid-liquid systems (51.3–66.3 kJ mol-1). Yet, using IR-120, the degradation increases identically either by adding more mass of catalyst or by reducing its particle diameter while keeping the total mass constant, as both situations lead to higher external (exposed) area of the acidic catalyst (i.e., free protons associated to the sulfonic group) on the outer surface of the ion exchange resin beads. These free protons, in turn, become available to catalyze the attack on the oxirane groups of the long-chain fatty acids, which cannot enter (diffuse) into the gel phase of the resin. Despite the unavoidable presence of surface-exposed protons, the degradation can be reduced by several orders of magnitude – for similar process conditions – by using this type of heterogeneous catalysts instead of mineral acids.Fil: Campanella, Alejandrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Estructura y organizacion de las comunidades de macroinvertebrados bentonicos del Alto Tajo Escala, patrones aleatorios y perturbacion

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Degradation of the Oxirane Ring of Epoxidized Vegetable Oils in a Liquid-liquid-solid Heterogeneous Reaction System

The main oxirane-ring opening reactions that occur during the manufacture of epoxidized vegetable oils using a strongly acidic, gel-type ionexchange resin (IER) (Amberlite IR-120, 8% crosslinking) were analyzed. By using a heterogeneous liquid–liquid–solid model, the reactivity oneach phase was individually assessed, taking into account each transport step as well as the relevant partition equilibria.The combined results on the attack onto the oxirane ring of epoxidized vegetable oils by either hydrogen peroxide (H2O2) or solvated aceticacid (AA) indicate that under ‘regular’ process conditions these attacks proceed in the kinetic regime; that is, they are not mass-transfer controlled.The study indicated that most of the degradation occurs on the catalyst and, also, confirmed that the external surface protons of the IER are themain responsibles of the deleterious degradation of the oxirane ring as, in both cases, the degradation rate was directly proportional to the availableexternal area of the catalyst.Fil: Campanella, Alejandrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Degradation of the Oxirane Ring of Epoxidized Vegetable Oils with Hydrogen Peroxide Using an Ion Exchange Resin

The influence of different process variables (stirring, temperature, hydrogen peroxide concentration, particle diameter and amount of catalyst added) on the oxirane ring-opening reaction caused by hydrogen peroxide (H2O2) during the manufacture of epoxides obtained from triglycerides using a gel-type strong acid ion exchange resin, Amberlite IR-120, is analyzed. The degradation reaction with H2O2 is first-order with respect to the epoxide [kobs(70 ºC) = 3.37 ± 0.606 x 10 -4 min -1; Ea = 99.2 ± 1.3 kJ mol -1] and second-order with respect to H2O2, as expected, but only if moderate concentrations of peroxide are used. Highly concentrated H2O2 attacks the structure of the polymer and exposes free protons from the resin network. Ring opening increases either by adding a higher amount of catalyst to the system or by decreasing the particle size of the catalyst since, in both cases, the external area of the catalyst (i.e., available surface protons) becomes larger.Fil: Campanella, Alejandrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Degradation of the Oxirane Ring of Epoxidized Vegetable Oils in Liquid-liquid Heterogeneous Reaction Systems

The reaction regimes under which proceed some of the relevant and deletereous consecutive reactions that occur during the conventional epoxidation process of vegetable oils were analyzed in detail, considering – separately – each transport and intrinsic kinetic step. Epoxidized soybean oil (ESBO) was used as a model material. In this process, peracetic acid is generated in situ by reacting acetic acid and H2O2 (aq) in a polar phase, so that the (acid catalyzed) reaction system is always heterogeneous. The distribution constants between the organic and the polar phases of soybean oil and ESBO were determined, as well as (in the case of the ring opening with acetic acid) the reaction rate constant in the homogeneous ESBO–glacial acetic acid reaction system. The epoxide ring opening caused by hydrogen peroxide is always slow and, unlike the attack by the acetic acid, progresses only in the polar phase. When no catalyst is added, the attack by acetic acid is also moderate, and the ring-opening reaction proceeds slowly in both phases, albeit slightly above the kinetic regime in the aqueous phase. However, if a homogeneous catalyst (e.g., sulfuric acid) is added, the reaction makes way in the instantaneous (mass-transfer controlled) regime in said phase.Fil: Campanella, Alejandrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Production of natural antioxidants from vegetable oil deodorizer distillates: Effect of catalytic hydrogenation

Natural tocopherols are one of the main types of antioxidants found in living creatures, but they also have other critical biological functions. The biopotency of natural (+)alfa-tocopherol (RRR) is 36% higher than that of the synthetic racemic mixture and 300% higher than the SRR stereoisomer. Vegetable oil deodorizer distillates (DD) are an excellent source of natural tocopherols. Catalytic hydrogenation of DD preconcentrates has been suggested as a feasible route for recovery of tocopherols in high yield. However, it is important to know whether the hydrogenation operation, as applied to these tocopherol-rich mixtures, is capable of preserving the chiral (RRR) character, which is critical to its biopotency.(+)alfa-tocopherol enriched sunflower oil and methyl stearate, as well as sunflower oil DD, were fully hydrogenated using commercial Ni and Pd catalysts (120?180 C; 20?60 psig). Products were analyzed by chiral HPLC. Results show that the desired chiral configuration (RRR) is fully retained. Thus, the hydrogenation route can be safely considered as a valid alternative for increasing the efficiency of tocopherol recovery processes from DDs while preserving their natural characteristics.Fil: Pagani, María Ayelén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Baltanas, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin

Taxonomic diversity of groundwater harpacticoida (Copepoda, crustacea) in southern France. A contribution to characterise Hotspot Diversity Sites

Hotspot Diversity Sites (HDS) are characterised by high taxonomic richness and high numbers of rare (generally endemic) species; for troglobitic fauna the number of stygobitic species is also an important aspect. Additional criteria for definition of HDS are proposed here, based on the taxonomic diversity of entire subterranean faunal assemblages, i.e. the use of the indices of Average Taxonomic Distinctness and the Variation in Taxonomic Distinctness as well as the number of supra-specific taxa such as genera and families. To exemplify our approach we compared assemblages of harpacticoid copepod microcrustaceans as a focal group. We analysed 44 data sets from both groundwater and surface-water sites with special emphasis on 9 sites from southern France (Moulis in Ariège). The origin and development of the taxonomic diversity of the harpacticoid assemblages from Moulis area are analysed using phenetic and cladistic methods. The colonisation process of subsurface habitats within this area is a repetitive process occurring over long periods of time. Four sites in southern France, the Baget and the Goueil di Her (Karstic systems) and the Lachein and the Nert (alluvial interstitial areas) are recognised as HDS; three others are located in non-karstic areas of Central Europe (southern Germany and eastern Austria) and South America (Central Brazil)