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- 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.
- Co-processing lard soybean oil over Ca-based catalysts to greener biodieselPublication . Soares Dias, A. P.; Catarino, Mónica; Gomes, JoãoFatty Acid Methyl Esters (FAME) were produced from lard/soybean oil (SBO) mixtures using a calcium-based heterogeneous catalyst. The green catalyst was prepared by scallop shell calcination at a relatively low temperature (800 degrees C) to minimize energy consumption. Images from Scanning Electron Microscopy showed agglomerates of a few tens micrometers with rhombohedral calcite crystallites studded with lime. X-ray diffractogram of fresh catalyst presented overlapped patterns of calcite and lime In tested conditions (methanol reflux temperature, 5% (fat mass basis), methanol fat = 12 molar ratio, and 150 min), the FAME yield reached 95% (mass) with SBO. However, only 75% FAME yield was obtained from pure lard since the active sites of the catalyst were partially neutralized by lard acidity. Co-processing lard/SBO mixtures attenuated the undesirable fat acidity drawback allowing FAME yields around 90% for mixtures containing less than 50% (mass) of lard. The low-grade fat content of the processed mixture showed no impact on the glycerin quality. Co-processing lard/SBO is a smart strategy to overcome the low-grade fats acidity in biodiesel production process thus providing a more sustainable biodiesel production route.
- 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.