Browsing by Issue Date, starting with "2013"
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- Hydrogenation of rapeseed oil for production of liquid bio-chemicalsPublication . Pinto, Filomena; Martins, Susana; Gonçalves, Maria Margarida; Costa, Paula; Gulyurtlu, Ibrahim; Alves, Andreia; Mendes, BenildeThe main objective of rapeseed oil hydrogenation tests was the production of liquid bio-chemicals to be used as renewable raw material for the production of several chemicals and in chemical synthesis to substitute petroleum derived stuff. As, hydrogenation of vegetable oils is already applied for the production of biofuels, the work done focused in producing aromatic compounds, due to their economic value. The effect of experimental conditions on rapeseed oil hydrogenation was studied, namely, reaction temperature and time with the aim of selecting the most favourable conditions to convert rapeseed oil into liquid valuable bio-chemicals. Rapeseed oil was hydrogenated at a hydrogen initial pressure of 1.10 MPa. Reaction temperature varied in the range from 200 C to 400 C, while reaction times between 6 and 180 min were tested. The performance of a commercial cobalt and molybdenum catalyst was also studied. The highest hydrocarbons yields were obtained at the highest temperature and reaction times tested. At a temperature of 400 C and at the reaction time of 120 min hydrocarbons yield was about 92% in catalyst presence, while in the absence of the catalyst this value decreased to 85%. Hydrocarbons yield was even higher when the reaction time of 180 min was used in the presence of catalyst, as the yield of 97% was observed. At these conditions hydrocarbons formed had a high content of aromatic compounds, around 50%. For this reason, the viscosity values of hydrogenated oils were lower than that established by EN590, which together with hydrogenated liquids composition prevented its use as direct liquid fuel to substitute fossil gas oil for transport sector. However, hydrocarbons analysis showed the presence of several valuable compounds that encourages their use as a raw material for the production of several chemicals and in chemical synthesis.
- Gold deposition from 1-butyl-1-methyl-pyrrolidinium dicyanamide ionic liquid at open-circuit and under potentiostatic controlPublication . Sá, A.I. De; Eugénio, S.; Quaresma, S.; Rangel, C. M.; Vilar, R.In this work, the deposition of gold on copper substrates from solutions of HAuCl4.3H2O in 1-butyl-1-methylpyrrolidinium dicyanamide was studied. Deposition was carried out in open-circuit and under potentiostatic control at temperatures from 293 to 353 K, in normal atmosphere, with deposition conditions allowing water from atmospheric absorption up to 0.8 wt.%. Films of gold were obtained by both methods. Deposition at open-circuit occurs by galvanic displacement mechanism. Involvement of Cu+ species in the electrodeposition process was suggested by cyclic voltammetry. Furthermore, copper incorporation in the gold films was confirmed by X-ray diffraction. SEM observation and XRD analysis show that films are nanocrystalline with a globular morphology except for the films formed under potentiostatic control at 353 K, which show a dendritic structure. The size of the crystallites determined by Scherrer's equation varies in the range from 6 to 25 nm.
- Characterisation and performance studies of a LiFePO4 cathode material synthesized by microwave heatingPublication . Plancha, Maria João; Paiva Luís, Teresa; Rangel, C. M.Lithium iron phosphate with incorporated carbon, LiFePO4-C, was synthesized by the microwave-assisted method. X-ray diffraction analyses showed higher crystallization degrees for samples submitted to higher irradiation times. A particle-agglomerated morphology was associated as revealed by scanning electron microscopy. The electrochemical character-istics of a composite cathode containing the synthesized product were evaluated. The two-phase electrochemical process between FePO4 and LiFePO4 was evidenced in the cycling voltammogram profile and its reversibility and stability were demonstrated. An additional redox reversible reaction was revealed and assigned to another phosphate present in the synthesized product. The charge/discharge performance study indicated a good capacity retention after the initial cy-cles where capacity fading was associated to the resistance of a SEI film that forms and grows on the cathode’s surface. Results obtained by electrochemical impedance analysis before and after cell’s cycling are discussed.
- Methodology to study the life cycle cost of floating offshore wind farmsPublication . Castro-Santos, Laura; Garcia, Geuffer; Diaz-Casas, VicenteThe main objective of this paper is to determine a theoretical methodology process to study the life cycle cost of floating offshore wind farms. The principal purpose is adapting the LCC (Life-Cycle Cost Calculation) from several authors to the offshore wind energy world, providing a new method which will be called LCSFOWF. In this sense, several general steps will be defined: life cycle definition, process breakdown structure, viability study and sensitivity study. Moreover, technical and economic issues and their relations will be considered. On the other hand, six life cycle phases needed to install a floating offshore wind farm will be defined: conception and definition, design and development, manufacturing, installation, exploitation and dismantling. They will be useful to define the majority of the steps in the process. This methodology could be considered to calculate the real cost of constructing floating offshore wind farms.
- End-of-life Zn–MnO2 batteries: electrode materials characterizationPublication . Cabral, Marta; Pedrosa, Fátima; Margarido, F.; Nogueira, CarlosPhysical and chemical characterization of several sizes and shapes of alkaline and saline spent Zn–MnO2 batteries was carried out, aiming at contributing for a better definition of the applicable recycling processes. The characterization essays included the mass balance of the components, cathode and anode elemental analysis, the identification of zinc and manganese bearing phases and the morphology analysis of the electrode particles. The electrode materials correspond to 64–79% of the total weigh of the batteries, with the cathodes having clearly the highest contribution (usually more than 50%). The steel components, mainly from the cases, are also important (17–30%). Elemental analysis showed that the electrodes are highly concentrated in zinc (from 48–87% in anodes) and manganese (from 35–50% in cathodes). X-Ray powder diffraction allowed for identifying several phases in the electrodes, namely zinc oxide, in the anodes of all the types of saline and alkaline batteries tested, while zinc hydroxide chloride and ammine zinc chloride only appear in some types of saline batteries. The manganese found in the cathode materials is present as two main phases, MnO·Mn2O3 and ZnO·Mn2O3, the latter corroborating that zinc migration from anode to cathode occurs during the batteries lifespan. A unreacted MnO2 phase was also found presenting a low crystalline level. Leaching trials with diluted HCl solutions of alkaline and saline battery samples showed that all zinc species are reactive attaining easily over than 90% leaching yields, and about 30% of manganese, present as Mn(ii/iii) forms. The MnO2 phase is less reactive and requires higher temperatures to achieve a more efficient solubilization.
- Simulation of a stand-alone residential PEMFC power system with sodium borohydride as hydrogen sourcePublication . Pinto, P.J.R.; Sousa, T.; Fernandes, Vitor; Pinto, A. M. F. R.; Rangel, C. M.Catalytic hydrolysis of sodium borohydride (NaBH4) has been investigated as a method to generate hydrogen for fuel cell applications. The high purity of the generated hydrogen makes this process a potential source of hydrogen for polymer electrolyte membrane fuel cells (PEMFCs). In this paper, a PEMFC power system employing a NaBH4 hydrogen generator is designed to supply continuous power to residential power applications as stand-alone loads and simulated using Matlab/Simulink software package. The overall system is sized to meet a real end-use load, representative of standard European domestic medium electric energy consumption, over a 1-week period. Supervisory control strategies are proposed to manage the hydrogen generation and storage, and the power flow. Simulation results show that the proposed supervisory control strategies are effective and the NaBH4–PEMFC power system is a technologically feasible solution for stand-alone residential applications.
- CCS infrastructure development scenarios for the integrated Iberian Peninsula and Morocco energy systemPublication . Kanudia, Amit; Berghout, Niels; Boavida, Dulce; Van den Broek, Machteld; Cabal, Helena; Carneiro, Júlio; Fortes, Patricia; Gargiulo, Maurizio; Gouveia, João Pedro; Labriet, Maryse; Lechón, Yolanda; Martinez, Roberto; Mesquita, Paulo; Rimi, Abdelkrim; Seixas, Júlia; Tosato, GianCarloThis paper briefly illustrates a method to represent national energy systems and the geographical details of CCS infrastructures in the same technical-economic model. In the MARKAL-TIMES modeling framework a model of Morocco, Portugal and Spain with both spatial and temporal details has been implemented. As a function of assumptions on the development to 2050 of mitigation levels, economic growth and CO2 capture-transport storage characteristics, dozens of scenarios were prepared with the TIMES-COMET model. A few results on optimal levels of CCS contribution to mitigation compared to other energy system options are presented. The results also indicate the least cost lay out of the main capture, transport and storage infrastructures. It is concluded that the availability of CCS after 2020 will reduce the cost of mitigation in the Iberian Peninsula as soon as the EU GHG emissions reduction targets become more stringent than decided so far.
- Métodos de fraccionamento de biomassa para as biorrefinariasPublication . Carvalheiro, Florbela; Duarte, Luís C.; Lukasik, Rafal M.; Moniz, PatriciaO desenvolvimento de processos que permitam o fraccionamento eficiente da biomassa (tradicionalmente designados por pré-tratamentos) constitui uma parte muito significativa do esforço científico que tem sido feito para a transformação das biorrefinarias numa realidade industrial. Este artigo apresenta uma breve revisão dos processos de fraccionamento, sendo dada particular atenção a processos emergentes, discutindo também as suas possíveis vantagens e limitações.
- Energy requirement and CO2 emissions of bioH2 production from microalgal biomassPublication . Ferreira, Ana F.; Ortigueira, Joana; Alves, Luís; Gouveia, Luisa; Moura, Patrícia; Silva, Carla M.This paper presents the life cycle inventory (LCI) of hydrogen production by Clostridium butyricum fermentation of Scenedesmus obliquus hydrolysate. The main purpose of this work was to evaluate the potential of H2 production from microalgal biomass and the respective energy consumption and CO2 emissions in the bioconversion process considering the microalga production, acid hydrolysis of S. obliquus biomass, preparation of the inoculum and culture media, and fermentation. The scale-up to industrial production was not envisaged. The hydrogen yield obtained in this work was 2.9 ± 0.3 mol H2/mol sugars in S. obliquus hydrolysate. Results show that this process of biological production of hydrogen can achieve 7270 MJ/MJH2 of energy consumption and 670Kg CO2/MJH2. The microalgal culture is the stage responsible for 98% of these total final values due to the use of artificial lighting. All stages and processes with the highest values of energy consumption and CO2 emissions were identified for future energetic and environmental optimisation.
- A Margem Sul Portuguesa profundaPublication . Terrinha, Pedro; Matias, L.; Valadares, Vasco; Roque, Cristina; Duarte, João; Rosas, Filipe M.; Iribarren, L.; Silva, S.; Cunha, Tiago A.; Batista, Luís; Duarte, Henrique; Neves, M. C.; Carrara, Gabriela; Zitellini, Nevio; Gràcia, Eulàlia; Gutscher, Marc-André; Lourenço, Nuno; Abreu, M. P.