Biomass and Bioenergy ] (]]]]) ]]]–]]] Biodiesel production by esterification of palm fatty acid distillate S. Chongkhong à , C. Tongurai, P. Chetpattananondh, C. Bunyakan Department of Chemical Engineering, Faculty of Engineering, Prince of Songkla University, HatYai, Songkhla 90112, Thailand Received 15 December 2006; received in revised form 30 January 2007; accepted 1 March 2007 Abstract Production of fatty acid methyl ester (FAME) from palm fatty acid distillate (PFAD) having high free fatty acids (FFA) was investigated in this work. Batch esterifications of PFAD were carried out to study the influence of: including reaction temperatures of 70–100 1C, molar ratios of methanol to PFAD of 0.4:1–12:1, quantity of catalysts of 0–5.502% (wt of sulfuric acid/wt of PFAD) and reaction times of 15–240 min. The optimum condition for the continuous esterification process (CSTR) was molar ratio of methanol to PFAD at 8:1 with 1.834 wt% of H 2 SO 4 at 70 1C under its own pressure with a retention time of 60 min. The amount of FFA was reduced from 93 wt% to less than 2 wt% at the end of the esterification process. The FAME was purified by neutralization with 3 M sodium hydroxide in water solution at a reaction temperature of 80 1C for 15 min followed by transesterification process with 0.396 M sodium hydroxide in methanol solution at a reaction temperature of 65 1C for 15 min. The final FAME product met with the Thai biodiesel quality standard, and ASTM D6751-02. r 2007 Elsevier Ltd. All rights reserved. Keywords: Oleic acid; Palmitic acid; Taguchi method; Biodiesel 1. Introduction There is growing interest in biodiesel (fatty acid methyl ester or FAME) because of the similarity in its properties when compared to those of diesel fuels [1]. However, production cost of the biodiesel is not economically competitive with petroleum-based fuel according to rela- tively high cost of the lipid feedstocks, which are usually edible-grade refined oils. With low-cost lipid feedstocks containing high amount of free fatty acids (FFA), conventional biodiesel production by transesterification with alcohol using base catalyst is not appropriated. A two- step process is then proposed [2–7]. The first step of the process is to reduce FFA content in vegetable oil by esterification with methanol and acid catalyst. The second step is transesterification process, in which triglyceride (TG) portion of the oil reacts with methanol and base catalyst to form ester and glycerol. The acid catalyst is generally sulfuric acid [8,9] while the base catalyst is usually sodium or potassium hydroxide [10]. Product from the reactions is separated into two phases by gravity. The FAME portion is then purified by water washing process to meet the biodiesel fuel standards. With tobacco seed oil, the FFA level was reduced from about 17 wt% to less than 2 wt% in 25 min at reaction temperature of 60 1C and molar ratio of 18:1 of methanol to oil in the first step. In the second step, the maximum yield of 91% FAME was obtained in 30 min at molar ratio of methanol to triglycerides of 6:1, KOH amount of 1 wt% and a reaction temperature of 60 1C [4]. FAME production from a high content of FFA waste cooking oil (WCO) catalyzed by sulfuric acid increased rapidly within 1–6 h and then dropped down. When the molar ratio of methanol to oil exceeded 16, WCO conversion increased rapidly. In addition, WCO conversion increased with the amount of sulfuric acid up to 4 wt% [5]. Crude palm oil (CPO) esterification was carried out at temperature of about 80 1C for 30 min in a fixed bed reactor. The esterification reaction products were then transferred to the transesterification section which con- sisted of two stirred tank reactors. In the both reactors, the transesterification reaction was carried out at about 70 1C for 30 min to achieve 498% conversion [11]. ARTICLE IN PRESS www.elsevier.com/locate/biombioe 0961-9534/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biombioe.2007.03.001 à Corresponding author. Tel.: +66 74287055; fax: +66 74212896. E-mail address: c.sininart@yahoo.co.th (S. Chongkhong). Please cite this article as: Chongkhong S, et al. Biodiesel production by esterification of palm fatty acid distillate. Biomass and Bioenergy (2007), doi:10.1016/j.biombioe.2007.03.001