Repositório do LNEG
Repositório Científico do Laboratório Nacional de Energia e Geologia
Entradas recentes
Highly selective valorisation of D-xylose from corncobs hydrolysates catalysed by C-scorpionate gold(III) complexes
Publication . Van-Dúnem, Vanmira; Duarte, Luís; Martins, Pedro L.; Lapa, Hugo; Martins, Luisa Margarida; Carvalheiro, Florbela
ABSTRACT: D-xylonic acid is a multifunctional, environmentally friendly, and versatile platform chemical, and one of the most promising conversion products of D-xylose for replacing several petrochemicals that is still not produced commercially. Although microbial conversion is the most widely studied process, the low efficiency and cost of these methods create opportunities for the development of chemical routes. In this work, we report for the first time the direct chemical conversion of real hemicellulose-derived pentose-rich hydrolysates into D-xylonic acid. Furthermore, a novel chemical oxidation route based on C-scorpionate gold(III) complexes was explored. Two specific complexes are used as model catalysts, the cationic [AuCl2(kappa 2-Tpm)]Cl (1, Tpm = hydrotris(pyrazol-1-yl)methane, HC(C3N2H3)(3)) or the neutral [AuCl2(kappa 2-Tpms)] complex (2, Tpms = tris(1H-pyrazol-1-yl)methane sulfonate, [SO3C(C3H3N2)(3)](-)). The catalytic operational conditions (i.e., reaction time, temperature, type and concentration of alkali and oxidant agent) were initially optimised for D-xylose solutions using cationic complex 1. Under the best conditions (100 degrees C, 2 mmol NaOH and 20 mmol H2O2) nearly 100% conversion of D-xylose and a 94% D-xylonic acid yield were achieved, with minimal formation of secondary products, when using 6 g/L D-xylose as sole carbon substrate. The direct catalytic conversion of real hemicellulosic hydrolysate, without any previous purification was possible and up to 36 g/L of D-xylose, regardless of the presence of other sugars, aliphatic acids, furans and phenolic compounds. Comparing similar catalytic conditions among model D-xylose solutions and real hydrolysates with similar titres, the later presented better performance, even though D-xylose conversion and D-xylonic acid yield decreased slightly for higher D-xylose concentrations. The catalysis was further improved by using the neutral gold(III) C-scorpionate complex 2, which further increased the D-xylose conversion and selectivity.
Strategic pathways for decarbonization: a data-driven typology to strengthen climate policy
Publication . Bento, Nuno; Alves, Tiago; Ribeiro, Ricardo; Fontes, Margarida
ABSTRACT: As global temperatures approach critical thresholds and emissions continue to rise, the urgency for strategic, accelerated decarbonization grows. The climate mitigation literature is vast, but evidence on how mitigation options cluster into overarching decarbonization pathways remains fragmented. Here, we use artificial intelligence–enabled text and citation analysis on an initial corpus of over one million scientific papers (2011–2021) to derive a data-driven typology of six recurrent decarbonization pathways: Technology Breakthrough, Electrification of Uses, Integrated Policy, Decarbonization of Electricity, Demand Reduction & Co-Benefits, and Land Use & Circularity. Rather than proposing new mitigation options, this typology organizes existing work into a small set of archetypal strategies and maps their prevalence across regions, disciplines, and policy orientations. For example, Electrification of Uses is most prominent in the EU27, while Technology Breakthrough dominates in China, the United States, and Japan. The analysis highlights synergies and complementarities between pathways, the scientific competencies that typically underpin them, and persistent gaps – particularly in Land Use & Circularity. We illustrate the policy relevance of the typology by comparing pathway profiles with stated climate policy directions, identifying areas where research and policy emphases are misaligned. This framework can support policymakers and researchers by benchmarking policy portfolios against the typology and highlighting research needs associated with national decarbonization goals.
Mineralogical and Geochemical Characterization of Geological Materials, 2nd Edition
Publication . Silva, Teresa; de Oliveira, Daniel Pipa Soares; Veiga, João Pedro
ABSTRACT: This Special Issue reinforces the strategic role of mineralogical and geochemical characterization in tackling key scientific challenges associated with mineral resources, providing essential insights into ore genesis, mineral processing, environmental performance, and the sustainable supply of raw materials. The topics demonstrate how advanced analytical techniques and multidisciplinary approaches are improving knowledge of geological materials and Earth processes while supporting sustainable resource management, environmental protection, and cultural heritage conservation. Studies on lithium-bearing pegmatites, mining waste, and abandoned mine sites showcase the manner in which detailed mineralogical and geochemical research is able to uncover new resource opportunities, promote circular economy practices, and support responsible resource recovery. Contributions also explore applications in geoheritage and heritage conservation, including the use of geopolymers as sustainable restoration materials and the assessment of natural stones for monument preservation. Furthermore, environmental studies address soil geochemistry, environmental monitoring, and occupational health through innovative mineral and particle characterization methods. Several papers showcase cutting-edge analytical tools, including Raman spectroscopy, SEM-EDS, LA-ICP-MS, and ToF-SIMS, highlighting advances in analytical accuracy, efficiency, and data interpretation. This reprint provides an important reference resource for researchers working across Earth and materials sciences.
National energy and material flows along the building supply chain in the EU
Publication . Barbosa, Juliana Pacheco; Simoes, Sofia; Jordao, Cristine; Mao, Ruichang; Aloini, Davide; Zerbino, Pierluigi; Mabroum, Safaa; Montalbano, Giammarco; Sameer, Husam; Dürr, Hans H.; Jerónimo, B.; Maçãs Lima, Ana Teresa
ABSTRACT: Construction activity is responsible for substantial greenhouse gas (GHG) emissions, but most of these reflect only a single stage of the building construction supply chain. Closing the gap, this work presents a cross-supply-chain perspective on annual material and energy consumption and GHG emissions for the sector on the European scale. These are estimated at the country level, disaggregated for raw material extraction, material manufacturing, demolition, and several intermediary transport stages. The study underscores cement, steel, flat glass, and ceramic bricks as manufactured materials; and sand, limestone, clay, iron ore, and coal as raw materials. Estimates consider both new construction and renovation, across varied typologies of residential and non-residential buildings. The results show that new construction & renovation of the building stock emits 235.31 Mt of CO2 annually, excluding energy consumption for building operations. These are associated with the consumption of circa 1 994.29 Mt raw and construction materials, and circa 1 990.27 PJ of final energy per year. These figures correspond to 4.33% of the total EU values (45 923 PJ). New building construction and renovation account for 63% of the materials used, while the material manufacturing stage accounts for 74% of the final energy consumption. By adopting a full supply chain perspective at the European level, we can support the development of holistic and more targeted public policies to decarbonize the sector.
Geomorphological and sedimentary evolution of the Southwestern sector of the Tagus river [Resumo]
Publication . Dias, Ruben; Ressurreição, Ricardo; Legoinha, Paulo
ABSTRACT: The present-day Tejo River flows within the Lower Tejo Basin, a Cenozoic tectonic depression formed during the Alpine orogeny at the end of the Cretaceous and during the Paleogene under a NNE–SSW compressional stress. Deformation intensified during the Miocene with NNW–SSE compressional stress, reactivating pre-existing faults that controlled the accommodation space and thickness of the basin’s sedimentary fill. Tectonic inversion led to the uplift of the Lusitanian Basin and the Central Cordillera, which supplied sediments laterally to the Tejo Basin. Sedimentation began in the Paleogene with the development of extensive alluvial fan systems, later evolving into fluvial environments. Throughout the Miocene, the southwestern sector of the basin experienced several marine incursions, leading to the formation of reefs and coastal swamp environments that extended inland to the Santarém–Lavre region. Eustatic fluctuations caused repeated shoreline advances and retreats, controlling the position of the fluvial system. The pre-Tejo River developed as an alluvial plain dominated by a meandering system. At the beginning of the Pliocene, the pre-Tejo was characterized by an extensive alluvial plain transporting and depositing mainly medium- to coarse-grained siliciclastic sands. The river likely received contributions from the Alvalade Basin fluvial system and discharged into an estuary north of the Grândola range. The southern margin of the river can be recognized near Melides. Pliocene dating from Galé beach (Melides) and the Setúbal Peninsula indicates ages of ≈ 4.5 Ma (Ressurreição, 2018) and 3.8 Ma (Azevedo, 2006), respectively, showing progressively younger deposits towards the north. These data suggest that during the Pliocene the river gradually migrated northward, eventually reaching the
Setúbal Peninsula. Clay deposits in the Pegões region, with considerable lateral extent and thickness, suggest proximity to the mouth of a major river system. During the Pleistocene, fluvial incision began and terrace levels formed as the valley progressively entrenched. The river continued to migrate northward and eventually established its outlet in the Gargalo do Tejo constriction, possibly due to tectonic activity along its fault and/or river capture. The main clay depocentre shifted to the Mar da Palha. Overall, during the Pliocene and Pleistocene, the estuarine sector of the Tejo fluvial system experienced a
progressive northward migration until it became entrenched and stabilized in its present position.