Estudo da preparação de biodiesel utilizando diferentes compostos de nióbio como catalisadores na transesterificação de óleos vegetais e álcoois de cadeia curta
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Data
2016-03-30
Autores
Arpini, Bruno Henrique
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Universidade Federal do Espírito Santo
Resumo
This study aims to obtain new methods of obtaining ethyl and methyl biodiesel from three different compounds of niobium acting as catalysts in transesterification reactions, they are niobium pentoxide, pentachloride and niobium ammonium oxalate niobium. Various parameters such as temperature, reaction time, mass ratio of the catalyst, the reaction system (refluxing and ultrasound bath) were varied to obtain the best conditions for obtaining biodiesel. It is verified by various studies that niobium compounds exhibit Lewis acidity. Nb2O5 is a white solid, and its hydrate is also known as niobic acid may act as both Bronsted acid as Lewis acid. The NbCl5 is a yellow solid, easily hydrolysable upon contact with water and has high acidity. NH4[NbO(C2O4)2(H2O)].nH2O is a white solid, very soluble in water and is mainly used as a precursor for niobium oxides. The NbCl5 did not obtain satisfactory yields due to its difficult handling and the presence of water as a byproduct in parallel reaction to transesterification, the esterification of free fatty acids. NH4[NbO(C2O4)2(H2O)].nH2O showed good yields mainly at reflux for 48 hours, using ethanol and in particular in a proportion of 100% by weight towards oils. Nb2O5 may act as both Bronsted acid as Lewis acid, but in calcination temperature of 300 ° C it leads to higher yields, related to a rise of Lewis sites and a larger organization of their crystalline structure. The reactions using ultrasound bath has not shown satisfactory results compared to reflux reactions, due to the much lower reaction time and consequently lower energy addition to the reaction system.
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Palavras-chave
Niobium pentoxide , Niobium pentachloride , Ammonium oxalate niobium , Oxalato amoniacal de nióbio , Catalysis , Pentacloreto de nióbio , Biofuel , Pentóxido de nióbio
Citação
ARPINI, Bruno Henrique. Estudo da preparação de biodiesel utilizando diferentes compostos de nióbio como catalisadores na transesterificação de óleos vegetais e álcoois de cadeia curta. 2016. 101 f. Dissertação (Mestrado em Química) – Universidade Federal do Espírito Santo, Centro de Ciências Exatas, Vitória, 2016.