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- Study on the use of MgAl hydrotalcites as solid heterogeneous catalysts for biodiesel productionPublication . Gomes, João; Puna, Jaime; Gonçalves, Lissa M.; Bordado, JoãoThis paper, reports experimental work on the use of new heterogeneous solid basic catalysts for biodiesel production: double oxides of Mg and Al, produced by calcination, at high temperature, of MgAl lamellar structures, the hydrotalcites (HT). The most suitable catalyst system studied are hydrotalcite Mg:Al 2:1 calcinated at 507 degrees C and 700 degrees C, leading to higher values of FAME also in the second reaction stage. One of the prepared catalysts resulted in 97.1% Fatty acids methyl esters (FAME) in the 1st reaction step, 92.2% FAME in the 2nd reaction step and 34% FAME in the 3rd reaction step. The biodiesel obtained in the transesterification reaction showed composition and quality parameters within the limits specified by the European Standard EN 14214. 2.5% wt catalyst/oil and a molar ratio methanol:oil of 9:1 or 12:1 at 60 -65 degrees C and 4 h of reaction time are the best operating conditions achieved in this study. This study showed the potential of Mg/Al hydrotalcites as heterogeneous catalysts for biodiesel production. (C) 2011 Elsevier Ltd. All rights reserved.
- Synthesis gas production from water electrolysis, using the Electrocracking conceptPublication . Guerra, Luís; Moura, K.; Rodrigues, J.; Gomes, João; Puna, Jaime; Bordado, João; Santos, Maria TeresaThe present research work is focused on the production of synthesis gas by water electrolysis, using renewable electric energy and, further on, liquefied biomass as a carbon source necessary for obtaining carbon monoxide and carbon dioxide. In order to demonstrate and also optimize this process, this study comprised the influence of the electrolyte concentration, liquefied cork concentration, temperature and pressure and the main process outputs, such as: the flow rate of the produced gas, carbon monoxide, carbon dioxide and oxygen composition, as well as the energy consumed in the process. This gas can further on, be used for producing renewable synthetic fuels, such as: methane, methanol, dimethyl ether (DME), diesel, etc. The optimum operational conditions thus determined for this process, at laboratory scale, comprised the use of NaOH 1.2 M mixed with 20% (v/v) liquefied cork, as electrolyte. Applying these operating conditions a synthesis gas composed of 66.67% H2, 25.32% CO, 0.00% CO2 and 8.01% O2 was obtained at a flow rate of 8.31 L/h, consuming a power of 7.75 Wh/L. Also, the analysis of the residual biomass deposited in the electrodes showed some changes in the initial structure, as expected.
- Strontium-doped lime catalysts for biodiesel production: activity and stability during soybean oil methanolysisPublication . Dias, Ana Paula Soares; Puna, Jaime; Neiva Correia, Maria Joana; Gomes, João; Bordado, JoãoBiodiesel produced by alcoholysis of vegetable oils is a low carbon fuel, which can replace the fossil diesel in internal combustion engines. CaO is a cheap and environmentally benign material showing interesting catalytic performances in the methanolysis reaction of vegetable oils. However, the reaction rate is slower than the conventional homogeneous-catalyzed by sodium methoxide. In order to improve the catalytic activity, lime catalyst (commercial) was doped with different amounts of strontium. The catalysts, prepared by wet impregnation using aqueous solutions of nitrate salt, were calcined at 575 °C and 800 °C. The physical-chemical characterization of catalysts showed that the doping element had an apparently null effect on the basicity assessed by Hammett indicators. The Ca(OH)2, with weak basicity, formed in the Sr-modified catalysts eventually masked the Sr effect on the basicity. In the tested conditions, all the prepared catalysts were active allowing fatty acid methyl esters’ (FAME) yields higher than 94%. The catalyst stability tests, performed without intermediate reactivation, showed that Sr dopant promoted accelerated decay due to calcium diglyceroxide formation which is leached into the reaction medium. High temperature calcination had a negative effect on the catalyst stability due to the formation of Ca(OH)2. Such undesired effect was prompted by the Sr dopant.
- Biodiesel production from waste frying oils over lime catalystsPublication . Puna, Jaime; Correia, Maria Joana Neiva; Dias, Ana Paula Soares; Gomes, João; Bordado, JoãoBiodiesel production from semi-refined oils (SRO) and waste frying oils (WFO) was studied using commercial CaO as heterogeneous catalyst. The methanolysis tests were carried out in mild reaction conditions (62 A degrees C, atmospheric pressure). With such conditions, SRO (soybean and rapeseed) allowed to produce a biodiesel containing 97-98 % of methyl esters (FAME), whereas WFO only provided 86-87 % of FAME. The lower FAME yield for WFO oil is ascribable to the partial neutralization of the catalyst by free fatty acids. Also, soaps formation from the WFO oil reduced the weight yield of the oil phase (containing FAME) obtained and increased the MONG content of the glycerin phase. The catalysts stability tests showed high stability even when WFO oil was processed. Catalytic tests performed with blends of WFO/semi-refined oils showed blending as a good strategy to process low value raw oils with minor decay of the catalyst performance. Both WFO and semi-refined oils showed S-shape kinetics curves thus discarding significant differences of the reaction mechanisms.
- On the assessment of exposure to airborne ultrafine particles in urban environmentsPublication . Gomes, João; Bordado, João; Albuquerque, PaulaThe aim of this study was to contribute to the assessment of exposure levels of ultrafine particles in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung deposited alveolar surface area (resulting from exposure to ultrafine particles) in a major avenue leading to the town center during late spring, as well as in indoor buildings facing it. Data revealed differentiated patterns for week days and weekends, consistent with PM2.5 and PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels may be directly correlated with fluxes in automobile traffic. During a typical week, amounts of ultrafine particles per alveolar deposited surface area varied between 35 and 89.2 mu m2/cm3, which are comparable with levels reported for other towns in Germany and the United States. The measured values allowed for determination of the number of ultrafine particles per cubic centimeter, which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32 to 63%) outdoors, which is somewhat lower than levels observed in houses in Ontario.
- Biodiesel production processes and sustainable raw materialsPublication . Ramos, Marta; Dias, Ana; Puna, Jaime; Gomes, João; Bordado, JoãoEnergy security and environmental concerns, related to the increasing carbon emissions, have prompted in the last years the search for renewable and sustainable fuels. Biodiesel, a mixture of fatty acids alkyl esters shows properties, which make it a feasible substitute for fossil diesel. Biodiesel can be produced using different processes and different raw materials. The most common, first generation, biodiesel is produced by methanolysis of vegetable oils using basic or acid homogeneous catalysts. The use of vegetable oils for biodiesel production raises serious questions about biodiesel sustainability. Used cooking oils and animal fats can replace the vegetable oils in biodiesel production thus allowing to produce a more sustainable biofuel. Moreover, methanol can be replaced by ethanol being totally renewable since it can be produced by biomass fermentation. The substitution of homogeneous catalyzed processes, nowadays used in the biodiesel industry, by heterogeneous ones can contribute to improve the biodiesel sustainability with simultaneous cost reduction. From the existing literature on biodiesel production, it stands out that several strategies can be adopted to improve the sustainability of biodiesel. A literature review is presented to underline the strategies allowing to improve the biodiesel sustainability.
- Utilização de biomassa liquefeita na produção eletroquímica de gás de síntesePublication . Gonçalves, Ana Luísa; Guerra, Luís Filipe; Rodrigues, J.; Puna, Jaime; Gomes, João; Bordado, JoãoO presente trabalho de investigação visa, precisamente, a utilização de energias renováveis (solar ou eólica) no processo de eletrólise alcalina da água tendo como objetivo a produção de gás de síntese, com recurso a biomassa liquefeita como fonte de carbono, para uma posterior produção de biocombustíveis sintéticos.
- The role of alkali dopants on the oil methanolysis behavior of lime catalyst: activity & stabilityPublication . Soares Dias, A. P.; Puna, Jaime; Gomes, João; Ramos, Marta; Rijo, Bruna; Bordado, JoãoHeterogeneous basic catalysts, namely calcium oxide, are referred to as promising catalysts for biodiesel (FAME, fatty acid methyl esters) production since they can be easily separated from the reaction medium allowing them to operate in a continuous mode. Despite the relatively high catalytic activity of calcium catalysts, they present slower alcoholysis rates than homogeneous conventional catalysts (sodium or potassium methanoate). In order to improve the catalytic activity, CaO-based catalysts, modified with alkali elements (Li, Cs, Sr, and Mg) were prepared. Dopant element contents of 10% and 30%, as weight basis (5–50% molar), were introduced by wet impregnation using aqueous solutions of nitrate salts. The effect of calcination temperature (575°C and 800°C) on both activity and stability was studied. All the prepared catalysts, raw and alkali modified, showed pKa<15.0 when characterized by Hammett indicators in methanolic solution. Such basicity is characteristic of Ca hydroxide, thus indicating that the catalysts surfaces were covered with Ca-OH species. FAME yield, in soybean oil methanolysis, higher than 96% was obtained for the first batch reaction for all the tested catalysts showing that alkali dopants have an almost nihil effect on the catalysts performances. The deactivation tests performed with catalysts without intermediate reactivation showed that calcination temperature plays a major role in stability as it enhances the formation of calcium diglyceroxide. The presence of Ca hydroxide in fresh catalysts appears to be responsible for fast deactivation. The dopant elements prompt the catalysts deactivation. Catalysts calcined at higher temperatures showed slower deactivation, which can be due to the formation of larger particles, thus reducing the contact with the formed glycerin. Alkali dopants enhanced the CaO sintering for the highest calcination temperature. Calcium diglyceroxide formed during the reaction is responsible for deactivating the catalyst, due to leaching, and such effect is prompted by alkali dopants.
- Biofouling inhibition with grafted econea biocide: toward a nonreleasing eco-friendly multiresistant antifouling coatingPublication . Regina Ferreira, Olga; Rijo, Patrícia; Gomes, João; Santos, Ricardo; Monteiro, Silvia; Vilas-Boas, Cátia; Correia-da-Silva, Marta; Almada, Stephanie; Alves, Luis G.; Bordado, João; Silva, Elisabete R.The most effective strategies to control biofouling release toxic and persistent agents into the aquatic environment causing environmental concerns and leading to the implementation of more strict international legislation. This work presents recent progress on an innovative eco-friendly antifouling approach based on the isocyanate-functionalized Econea biocide allowing its chemical fixation in polymeric frameworks, namely, in a foul-release marine coating. The antifouling potential of the generated nonbiocide release coatings for both antimicrobial and long-term marine anti-biofouling applications is reported here for the first time. Inhibition growth effects against Methicillin-resistant Staphylococcus aureus bacterium obtained for Econea-based coatings reveal a decrease in the number of colony forming units (CFUs) up to 5 orders of magnitude in 6 h of exposure when compared to the free bacteria. The growth and the viability profiles (CFU/mL) revealed also bacteriostatic effects. The nonbiocide release coatings were able to minimize considerably the biocide release, becoming 10-fold lower than in a conventional releasing system and providing long-lasting antifouling effects, more than two years, under real seawater conditions. Both antifouling effects follow a nonbiocide release strategy leading to a minimization of the environmental impact of the biocidal coatings and the selective pressure on the microorganisms that evolve treatment resistance.
- Soybean oil transesterification for biodiesel production with micro-structured calcium oxide (CaO) from natural waste materials as a heterogeneous catalystPublication . Santos, Samuel; Nobre; Gomes, João; Puna, Jaime; Quinta-Ferreira, Rosa; J.C. Bordado, J. Moura Bordado, J.C.M. BordadoIn this study, micro-structured calcium oxide obtained from the calcination (850 degrees C for 3 h) of Gallus gallus domesticus (chicken) eggshells was used as a catalyst in the transesterification of soybean oil. This catalyst was characterized by Scanning Electron Spectroscopy (SEM) methods. The structure of the obtained CaO showed several agglomerates of white granular solids with a non-regular and unsymmetrical shape. In terms of calcium oxide catalytic activity, three different catalyst loadings (1%wt, 3%wt, and 5%wt) were tested for the same reaction conditions, resulting in transesterification yields of 77.27%wt, 84.53%wt, and 85.83%wt respectively. The results were compared to the current literature, and whilst they were lower, they were promising, allowing us to conclude that the tendency of yield improvement for this reaction, when the size range of catalyst particles is to be reduced to a nano scale, can be verified.