| There is an increasing worldwide concern for environmental protection and for the conservation of non-renewable natural resources. For this reason the possibility of developing alternative neat energy sources to replace tradition fossil fuels has been attracting a great interest. Among the numerous substitute fuels, the biodiesel is very provides a promising alternative because of its excellent performance. Additionally, most of waste cooking oils (WCO) poured into the sewer system. This practice contributes to the pollution which is very harmful for environment and human health. In a word, biodiesel produced from WCO will be of great significance for cost reduction and environmental protecting.Aiming at the problem of traditional technique, we use two-step catalyzed process of esterification and transesterification for producing biodiesel from WCO and menthol. In the first step, the active carbon loaded with ferric sulfate (Fe2(SO4)3 /C) was firstly used as catalyst in the esterification, and it was found that about 98.00% of free fatty acids was transferred to methyl esters at the optimal condition : absorption load of active carbon was 26.8% (w/w) , amount of catalyst was 3.5% (w/w), molar ratio of methanol and FFA was 18:1, reaction time is 3h, and reaction temperature is 95℃. In the second step, potassium hydroxide was used to catalyze transesterification of glycerides in the WCO to methyl esters. 98.83% of WCO were transformed to biodiesel when 1.0% (w/w) of potassium hydroxide was added to the reaction mixtures containing the molar ratio of methanol and oil with 7:1 and reached at 60℃for 60 minutes.In addition, we also discussed the kinetics of esterification and transesterification for biodiesel production in two-step process from waste cooking oil, and the kinetic equations was also established under the experimental condition. The result showed that the kinetic equations of esterification and transesterification can describe their reaction processes very well respectively within the range of the experimental condition. |
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