2,620 research outputs found

    Promoting light hydrocarbons yield by catalytic hydrodechlorination of residual chloromethanes using palladium supported on zeolite catalysts

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    Gas catalytic hydrodechlorination (HDC) of trichloromethane (TCM) and dichloromethane (DCM) was analyzed using Pd (1 wt.%) on different zeolites as catalysts. The aim of this study was to know the surface properties of the catalysts and reaction conditions that promote the yield to light hydrocarbons in this reaction. Five different zeolite supports were used from three commercial zeolites (KL, L-type; NaY, Faujasite; H-MOR, Mordenite). KL and NaY were submitted to ionic exchange treatments in order to increase their acidity and analyze the effect of the acidity in the activity and selectivity of the HDC reaction. Exchanged zeolites (HL and HY) showed the highest Pd dispersion due to their higher surface acidity. The best TCM/DCM conversion and selectivity to light hydrocarbons was obtained using the two non-exchanged zeolite-catalysts, KL and NaY. Low surface acidity seems to be the key aspect to promote the formation of light hydrocarbons. The formation of these products is favored at high reaction temperatures and low H2: chloromethane ratios. KL showed the highest selectivity to olefins (60%), although with a lower dechlorination degree. Non-exchanged NaY catalyst showed high selectivity to paraffins (70% and 95% for the HDC of DCM and TCM, respectively)Authors gratefully acknowledge financial support from FEDER/Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación/ CTM2017-85498-R. C. Fernández Ruiz acknowledges MINECO for his research gran

    Redescription of Liolaemus robertmertensi, Hellmich 1964 (Iguania: Liolaemidae) with description of a new species

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    We redescribe Liolaemus robertmertensi and describe a new species of Liolaemus, the secondmost speciose lizard genus. These species belong to the L. robertmertensi group of the subgenusLiolaemus sensu stricto. In recent years, some newly identified populations were assignedto Liolaemus robertmertensi. We applied an integrative approach using morphological andphylogenetic evidence to determine the relationships among these populations and found oneto belong to a new species described here. We performed statistical analyses to differentiate L.robertmertensi and the new species from other species of the alticolor-bibronii group. The newspecies shows a set of character states that allows it to be distinguished from L. robertmertensiand from all other species of Liolaemus. Despite the description of this new species, the taxonomicstatus of many populations still remain unknown.Fil: Fernandez, Maria Gimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Abdala, Cristian Simón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Ruiz Monachesi, Mario Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Semhan, Romina Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Quinteros, Andres Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin

    Four decades of geophysical research on Iberia and adjacent margins

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    The dimensions, the geographical position and the complex geological history of the Iberian Peninsula makes it a unique and singular target to study its crustal and upper mantle structure and geodynamical evolution using geophysical methods. The lithospheric structure beneath Iberia has been investigated since the 1970’s using deep multichannel seismic reflection and refraction/wide-angle reflection profiling. Gravimetric and magnetic data were acquired following the deployment of permanent and temporary stations, mostly during the 1990’s. Beginning in the late 1990’s, the progressive use of Global Navigation Satellite Systems (GNSS) instruments contributed to monitor the present-day motions. During the last decades, numerous geological and geophysical surveys have investigated the Iberian lithosphere and upper mantle in the onshore and offshore regions, the most recent ones related to the TopoIberia project. The approach developed in this contribution is twofold. Firstly, we summarize the available geophysical information over Iberia, from focusing on the upper crust to the lithosphere-asthenosphere boundary and the transition zone marking the bottom of the upper mantle. Results of GNSS data, potential fields, controlled source seismic profiles, magnetotelluric data, body and surface wave tomography, receiver functions and 2D and 3D lithospheric modeling are reviewed and compared. Secondly, we focus on the areas of greater geodynamic interest and the regions where inconsistencies within the geophysical results, or contradictions in their tectonic interpretation exist, identifying the major questions that are still under debate. Besides shedding light to the state of knowledge and pointing out present-day research challenges, this review provides a tool for the integration of the diverse geophysical datasets with the surface geology and geodynamical processes that are interpreted to have built the complex geology of the Iberian Peninsula.The authors acknowledge funding from the Generalitat de Catalunya, grant/awards number AGAUR 2017SGR1022, and AGAUR 2017SGR847, the Spanish Ministry of Science, Innovation, and Universities grant numbers RTI2018-095594-B-I00, PGC2018-095154-B-100 and PGC2018-094227-B-I00 and the Spanish Ministry of Economy and Competitiveness grant numbers CGL2017-84901-C2 and PIE-CSIC-201830E039. IP is funded by the Spanish Ministry of Science, Innovation, and Universities and University of Salamanca grant BEAGAL18/00090. AV acknowledges funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).Peer reviewe

    Rents, knowledge and neo-structuralism: transforming the productive matrix in Ecuador

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    This paper explores the relationship between ground rent, production and knowledge in Ecuador’s neo-structuralist, state-led project to transform the productive matrix. Based upon insights from the Marxian approach to the critique of political economy, we interrogate how neo-structuralism has conceptualised the relationship between ‘natural resource income’ and ‘knowledge-based’ economic development. The paper argues that a rent-theoretical perspective, which takes seriously the regional unfolding of uneven geographical development in Latin America, can highlight the limits of a national development plan conceived according to the logic of Schumpeterian efficiency. In doing so, the paper identifies the contradictory relationship between natural resource exports, state-led ‘knowledge’-based development and capital accumulation. On this basis the paper offers a historically and empirically informed critical analysis of selective import substitution industrialisation and vanguard science and technology strategies designed to transition Ecuador away from primary resource dependence
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