Optimization of the Pre-Treatment Process of Cottonseed Oil for Biodiesel Production

Cotton seed has approximately 19 wt% of oil, which can be used for biodiesel production. However current refining processes used industrially for cotton oil production turn the biodiesel production from cotton oil not economically attractive. A batch-wise refining process using sodium hydroxide and clay washing steps is normally employed to remove gossypol and other acid contaminants of the cottonseed oil, under different conditions of temperature and agitation. The objective of the present study is to optimize the variables of this cotton oil pre-treatment process, and evaluate the influence of operations conditions on cottonseed oil quality. A factorial design and response surface methodology was utilized in order to determine the relationship between quality control of oil (color, acidity, amount of soap) and biodiesel molar yield. The results show that the initial and the final temperature operating conditions, and the sodium hydroxide concentration and excess affect significantly the oil quality in the pre-treatment process. Optimal values for these operating variables were used to achieve an oil quality that makes it possible to synthesize biodiesel with a maximum molar yield. Samples of this oil were evaluated according to the parameters of oil characterization (acidity, color, soap content).