ESTiG - Dissertações de Mestrado Alunos
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- Study of the application of choline hydroxide as a catalyst in biodiesel productionPublication . Hachemane, Khadidja; Queiroz, Ana; Ribeiro, António E.; Brito, Paulo; Adjdir, MehdiDue to the finite stock of fossil fuels and its negative impact on the environment, many countries across the world are now leaning toward renewable energy sources like solar energy, wind energy, biofuel, hydropower, geothermal and ocean energy to ensure energy for the society development security. Biodiesel is one type of biofuel that is renewable, biodegradable and has similar properties of fossil diesel fuels. Biodiesel is a mixture of fatty acids methyl esters (FAMEs) and can be produced through esterification of fatty acid mixtures or transesterification of vegetable oils and animal fats, using homogeneous and heterogeneous catalysts. Ionic liquid (IL) based catalysts are more and more used since they can be recovered and reused and can have the ability to catalyze both esterification and transesterification reactions. Thus, these types of catalysts, represent clear environmental and safety advantages in relation to classical catalysts. The present work aims to study the use of choline hydroxide (ChOH) IL as a potentially reusable catalyst for the production of biodiesel. A kinetic study was carried out for the transesterification of a previously characterized vegetable oil sample, with methanol, under the specific conditions: 2 wt.% catalyst dosage, 1:10 oil/methanol molar ratio, for the reaction times of 10, 20, 30, 45, 60 and 120 minutes at 65, 55, 45, and 35 ℃. Transesterification with ChOH provided a 95.7% conversion in FAME content for 30 min of reaction at 65 ℃. The results of the kinetic study demonstrated that the first-order model was generally the best fit for the reaction kinetics considering all the temperatures, with a rate constant (k) estimated as 0.1182 min-1 for 65 ℃, and an estimated activation energy of 13.64 kJ/mol. An activation of LDHs by intercalation was made with 0 (blank test), 1, 2, 4 and 5 wt% of IL (BMIM HSO4). The activation of LDH by intercalation with BMIM HSO4 was not successful, because the conversion values are very low.
- Xylene isomers sorption on zeolite betaPublication . Abdelaziz, Bakhta; Silva, José A.C.; Adjdir, MehdiThe separation of C8 alkylaromatic mixed compounds is an important process in the chemical industry due to its direct connection with the manufacturing of PET (Polyethylene Terephthalate).The separation can be performed by distillation but the similarity of its boiling points increase significantly the cost. Alternatives are the crystallization and adsorption. In this work it is studied the ability of zeolite BETA to adsorb xylene isomers as a possible alternative adsorbent to the commonly used Faujasite zeolite or Y zeolite in the so called adsorptive process. Zeolite BETA is an intergrowth of two or three polymorphs of crystalline microporous materials formed by tetrahedral corner-sharing TO4 (T = Si or Al) in a unique porous structure with fine thermal and chemical stability. They have found wide spread applications in many industrial field such as catalysis, adsorption, separation, and ion exchange. In this work it is studied the application of Zeolite BETA to separate xylene isomers in vapor phase by adsorption, through an experimental study to determine single component adsorption equilibrium isotherms of xylene isomers and ethylbenzene between the temperatures ranges from 125 to 175ºC. The results obtained in this work are important for further studies in multicomponent systems regarding the ability of zeolite BETA to separate xylene isomers. The adsorbed amount is higher at the lower temperature (125 °C) with values around 0.8 g/100gads and decrease with the increase temperature (175 °C).The adsorption hierarchy order is: EB > OX > PX> MX . The selectivity is very low but we could improve it with decrease the temperature.