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- Preliminary study on the use of biodiesel obtained from waste vegetable oils for blending with hydrotreated kerosene fossil fuel using Calcium Oxide (CaO) from natural waste materials as heterogeneous catalystPublication . Ozkan, Sila; Puna, Jaime; Gomes, João; Cabrita, T.; Palmeira, José; Santos, Maria TeresaIn this experimental work, calcium from natural seafood wastes was used as a heterogeneous catalyst separately or in a blend of "shell mix" for producing biodiesel. Several chemical reaction runs were conducted at varied reaction times ranging from 30 min to 8 h, at 60 degrees C, with a mass content of 5% (W-cat./W-oil) and a methanol/oil molar ratio of 12. After the purification process, the biodiesel with fatty acid methyl ester (FAME) weight content measured was higher than 99%, which indicated that it was a pure biodiesel. This work also showed that the inorganic solid waste shell mixture used as the heterogeneous catalyst can be reused three times and the reused mixture still resulted in a FAME content higher than 99%. After 40 different transesterification reactions were performed using liquid (waste cooking oils) and solid (calcium seafood shells) wastes for producing biodiesel, under the specific conditions stated above, we found a successful, innovative, and promising way to produce biodiesel. In addition, blends prepared with jet fuel A1 and biodiesel were recorded with no invalid results after certain tests, at 25 degrees C. In this case, except for the 10% blend, the added biodiesel had no significant effect on the viscosity (fluidity) of the biojet fuel.
- A brief review of the supercritical antisolvent (SAS) technique for the preparation of nanocatalysts to be used in biodiesel productionPublication . Santos, Samuel; Puna, Jaime; Gomes, João F. P.In an era where sustainability is becoming the main driving force for research and development, supercritical fluids-based techniques are presented as a very efficient alternative technology to conventional extraction, purification, and recrystallization processes. Supercritical antisolvent (SAS) precipitation is a novel technique that can replace liquid antisolvent precipitation techniques. Additionally, through the optimization of precipitation operating conditions, morphology, particle size, and particle size distribution of nanoparticles can be controlled. As an antisolvent, supercritical carbon dioxide (scCO2) is far more sustainable than its conventional liquid counterparts; not only does it have a critical point (304 K and 73.8 bar) on its phase diagram that allows for the precipitation processes to be developed so close to room temperature, but also its recovery and, consequently, the precipitated solute purification stage is considerably simpler. This technique can be used efficiently for preparing nanocatalysts to be used in biodiesel production processes.
- 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.
- Solvent assisted biodiesel production by co-processing beef tallow and soybean oil over calcium catalystsPublication . Dias, Ana Paula Soares; Ramos, Marta; Catarino, Mónica Inês; Puna, Jaime; Gomes, JoãoDue to sustainability issues, biodiesel must be produced from low-grade fats and the conventional homogeneously-catalyzed processes must be replaced by more efficient and more profitable production processes such as heterogeneous ones. Biodiesel (fatty acids methyl esters, FAME) was produced from a mixture (50 wt%) of soybean oil and non-edible beef tallow over heterogeneous calcium-based catalysts obtained by calcination of scallop shells. In order to improve the catalytic performances, solvent assisted methanolysis was conducted using alcohols (ethanol, 1-propanol, isopropanol and isobutanol), acetone, methylcyclohexane, and tetrahydrofuran (THF) with Vmethanol/Vsolvent = 2.8. Catalytic data revealed that alcohol solvents adsorb competitively with methanol on the catalyst active sites reducing the FAME yield due to their slower alcoholysis rates. Hexane and methylcyclohexane are inadequate for methanolysis reactions since they are immiscible with methanol. THF and acetone are immiscible with the co-produced glycerin, which favors methyl esters formation by displacing the chemical equilibrium towards reaction products. Acetone performs better than THF (FAME yield gain of 14% against 3%) because of its higher miscibility with methanol. THF was the most effective solvent to avoid fat adsorption on the catalyst surface, a key factor for catalyst stability, and to improve the glycerin purity.
- 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.
- Methane production by a combined Sabatier reaction/water electrolysis processPublication . Guerra, Luís; Rossi, S.; Rodrigues, J.; Gomes, João; Puna, Jaime; Santos, Maria TeresaThis paper describes production of synthesis gas (syngas) and its optimization through a one-step innovative 1 kW prototype of alkaline water electrolysis (patented), using graphite electrodes and without gas separation (containing CO, CO2, H2 and small amounts of O2). The behavior of the syngas composition and flow rate has been studied and optimized, changing operational parameters such as temperature, pressure and current intensity, and testing two different kinds of electrodes. Afterwards, the best syngas composition has been sent into a catalytic reactor (filled with a bed of Ni/CaO-Al2O3 catalyst) in order to achieve methane production, at 1 bar and different temperatures. The main competitive advantage of this process lies in the built-in of an innovative technology product, from renewable energy (RE) power in remote locations, such as islands, villages in mountains as an alternative for energy storage for mobility constraints. In the catalytic reactor it was possible to achieve a CH4 yield of 25.5 %, a CO2 conversion into CH4 of 44.2% and a CH4 selectivity of 96.5%.
- Clean forest—project concept and early resultsPublication . Gomes, João; Puna, Jaime; Marques, António; Gominho, Jorge; Lourenço, Ana; Galhano dos Santos, Rui; Ozkan, SilaThe Clean Forest project aims to valorize forest biomass wastes (and then prevent their occurrence as a fuel source in forests), converting it to bioenergy, such as the production of 2nd generation synthetic biofuels, like bio-methanol, bio-DME, and biogas, depending on the process operating conditions. Valorization of potential forest waste biomass thus enhances the reduction of the probability of occurrence of forest fires and, therefore, presents a major value for local rural communities. The proposed process is easy to implement, and energetically, it shows significantly reduced costs than the conventional process of gasification. Additionally, the input of energy necessary to promote electrolysis can be achieved with solar energy, using photovoltaic panels. This paper refers to the actual progress of the project, as well as the further steps which consist of a set of measures aimed at the minimization of the occurrence of forest fires by the valorization of forest wastes into energy sources.
- 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.
- 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.
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