Transient Predictive Model for Dynamic Analysis, Kinetic Study, and Reactor Design of Triglycerides Transesterification to Biodiesel

This paper proposes a predictive mechanistic model to describe the classical pseudo-homogeneous second order kinetic law; the objective of the model is to study the transesterification process of any triglycerides feed stock into the synthetized biodiesel in a batch reactor, which contains a jacket heat exchanger system and a stirrer. The developed model consists of a set of ordinary differential equations which represent the mass and the energy balance for each chemical component in the reactor, accomplished by the temperature’s dynamics in the heat exchanger system, as well as, a reaction kinetic scheme, where the apparent rate and activation energies follow the Arrhenius equation (Noureddini and Zhu 1997, 1457), and the physical-chemical properties of oils, biodiesel and products have been considered. The physical-chemical properties required for products, intermediates and reactants were estimated implementing molecular group contribution methods. The constants in the reactions rates were taken directly from relevant works oriented to experimental study of the kinetic triglycerides methanolysis. The model’s usefulness was verified comparing the produced results against experimental results obtained in the biodiesel synthesis from sunflower (Vicente et al. 2005, 5447), Brassica carinata (Vicente et al. 2005, 899) and soybean (Noureddini and Zhu 1997, 1457) oils. In each case, the model matched the experimental results. Using the proposed model, it is possible to evaluate how the operating conditions and variables like the type of feed, the temperatures of the reactor and the jacket, the heat transfer, the stirrer rate and the changes on thermophysical properties of the species affect the conversion and reactor performance.