Thermal behavior of diesel/biodiesel blends of biodiesel obtained from buriti oil/Comportamento termico de blendas de diesel/biodiesel de biodiesel obtido a partir do oleo de buriti

Biodiesel has been obtained from methanolysis of buriti oil. This biodiesel was added in fossil diesel in order to obtain diesel/biodiesel blends. Thermal analysis of blends were carried on 30-600°C range at rate of 10°C [min.sup.-1]. Kinetic parameters such as activation energy (Ea), pre-exponential factor (Gibbs energy ([Δ.sup.#]G), enthalpy ([Δ.sup.#]H) and entropy ([Δ.sup.#]S) of activation were determined by using Coats-Redfern equation. The Ea, [Δ.sup.#]H and [Δ.sup.#]G values presented a linear increase with biodiesel amount added in blends. The heat of combustion of diesel/biodiesel blends was determined, and it was observed that the heat of combustion decreased with the addition of biodiesel in diesel/biodiesel blends. Keywords: transesterification, vegetable oils, thermogravimetric evaluation. O biodiesel foi obtido a partir de metanolise de oleo de buriti. O biodiesel foi adicionado ao diesel fossil a fim de obter misturas de biodiesel/diesel. Analises termica das misturas foram realizadas entre 30-600°C com uma taxa de aquecimento de 10°C [min.sup.-1]. Parametros cineticos como a energia de ativacao (Ea), fator pre-exponencial (A), energia livre de Gibbs (Δ≠G), entalpia (Δ[not equal to]H) e entropia de ativacao (Δ≠S) foram determinadas usando equacao de Coats-Redfern. Os valores de Ea, Δ[not equal to]H and Δ≠G apresentaram aumento linear com a quantidade de biodiesel adicionado na mistura. O calor de combustao de misturas de biodiesel/diesel foi determinada, e foi observado que o calor de combustao diminuiu com a adicao de biodiesel no diesel e nas misturas de biodiesel. Palavras-chave: transesterificacao, oleos vegetais, avaliacao termogravimetrica.