Kinetic and Equilibrium Studies of Stearic Acid Adsorption in Urea Complexation

摘要

High quality biodiesel needs proper vegetable oil or animal fats as feed stocks. Vegetable oils consist of various fatty acids, including saturated and unsaturated ones. Cloud point and pour point are some of important physical properties which have to be fulfilled for producing high quality biodiesel. The lower cloud and pour point of the biodiesel, the better it is for using in cold weather. These properties are can be achieved by using high concentration unsaturated fatty acids as the feed stock. Urea complexation is a fractionation process to separate saturated fatty acids (SFAs) from vegetable oil or animal fats. Stearic acid is the most saturated fatty acid consisted in vegetable oil. This research studied the kinetics and equilibrium data of the stearic acid complexation using an adsorption process. Batch adsorption process was developed to obtain the experimental data. Experimental sets of data were observed with adsorption kinetics and equilibrium models. High concentration of stearic acid was used to represent adsorption kinetics and equilibrium parameters. Kinetic data were examined with pseudo-first order, pseudo-second order and intra particle diffusion models. Freundlich and Langmuir isotherm were used to study the equilibrium model of this adsorption. The experimental data showed that stearic acid adsorption in urea crystal followed pseudo-second order model. The compatibility of the data with Langmuir isotherm showed that urea complexation was a monolayer adsorption.