Influencia de la dispersión axial en la transesterificación supercrítica no catalítica

MARIANA M. BUSTO; SILVANA A. D'IPPOLITO; MARISA E. ITURRIA; JUAN C. YORI; CARLOS L. PIECK; JAVIER M. GRAU; CARLOS R. VERA

Gramados, Río Grande do Sul

Simposio; XX Simposio Iberoamericano de Catálisis; 2006

Fisocat/SBCat

Transesterification of fats and oils by methanol is known to proceed by a three-step consecutive reaction mechanism in which the formation of the diglyceride is the rate-limiting step. At low conversion values (< 35%) the system has mass transfer limitations due to the immiscibility of the oil-methanol system. Non-catalytic transesterification in supercritical methanol overcomes this problem by forming a one phase reacting system. The implementation of this reaction mode in continuous tubular reactor needs for the evaluation of the effect of the backmixing that appears when methanol acquires a gas-like mobility in the supercritical state (³ 250 °C). Such a study was performed here and it was found that supercritical transesterification reactors must be operated at axial Péclet number equal or higher than 1000 in order to limit backmixing to a minimum and achieve batch-like conversions at residence times of 1 hour or less. High onversion values in perfectly mixed reactors can only be obtained by working at inconveniently higher temperatures (T ³ 300 °C) and methanol:oil ratios.