Immobilization of calcium oxide onto chitosan beads as a heterogeneous catalyst for biodiesel production

A biopolymer, chitosan, was used as a novel substrate for the immobilization of calcium oxide (CaO). CaO immobilized onto chitosan beads was employed as a heterogeneous catalyst to produce biodiesel catalytically, through transesterification of soybean oil with methanol. To obtain a stable immobilized catalyst, the chitosan beads with immobilized CaO were cross-linked with glutaraldehyde. Two crosslinking parameters, crosslinking time and glutaraldehyde concentration, were studied to reveal the optimal immobilization conditions, which were 30min and 0.22 mol L-1, respectively. Under those conditions, an immobilized catalyst with a very low degree of CaO leaching could be obtained. The immobilized CaO catalyst obtained was investigated by being used to catalyze the transesterification of soybean oil with methanol. The transesterification rate, which was affected by catalyst loading, molar ratio of methanol to oil and temperature, was investigated by using response surface methodology. A maximum reaction rate of 0.6 h(-1) was obtained at 60 degrees C, methanol to oil molar ratio of 13.4 and catalyst loading of 13.78 wt%. Under these reaction conditions, the equilibrium conversion of soybean oil was 97% after 3 h of reaction time. In addition, the immobilized catalyst could be reused at least five times. This study developed an easy and energy-efficient process for preparing a chitosan-based immobilized CaO catalyst, which is promising for potential applications including biodiesel production. (C) 2011 Society of Chemical Industry