1978 Research Article Received: 16 November 2012 Revised: 23 January 2013 Accepted article published: 13 February 2013 Published online in Wiley Online Library: 22 March 2013 (wileyonlinelibrary.com) DOI 10.1002/jctb.4054 Refining the glycerin phase from palm-oil biodiesel by ion-exchange with cationic resins Luis Javier Gallego Morales, Fernando Carde ˜ no L ´ opez and Luis Alberto Rios * Abstract BACKGROUND: Glycerin is produced as an 11% by-product in biodiesel manufacturing. Impurities are concentrated in the glycerin phase. High-vacuum distillation of glycerin is an energy-intensive process. A new low-cost purification strategy for glycerin is needed. This paper reports the refining of the glycerin phase obtained from palm-oil biodiesel synthesis by ion-exchange with cationic resins. In the literature and to the best of the authors’ knowledge, the use of a real glycerin phase from biodiesel has not been reported. The ion-exchange equilibrium was determined in a batch process, while variables for the industrial scaling-up were studied in continuous operation. RESULTS: The sodium content obtained with low amounts of resin is lower than that obtained with mineral-acid refining. Almost complete sodium removal could be achieved in continuous operation. Langmuir and Freundlich models give a good fit to the equilibrium data. Amberlyst was the best resin. Breakthrough capacity was 96% of static exchange capacity. 95% of the static ion exchange was recovered by washing with water-soap. CONCLUSION: A 96.6% purification level of glycerol was obtained with the resin Amberlyst 15, using a methanol content of 60%, liquid phase flow of 0.8 mL min -1 and 0.3 g resin g -1 glycerin phase; dynamic exchange capacity was 96% of the static exchange capacity. Exchange capacity is almost completely regenerated by washing with water-soap. c  2013 Society of Chemical Industry Keywords: glycerin; biodiesel; refining; ion exchange; cationic resins; isotherms INTRODUCTION Glycerin is produced as an 11% by-product in the transesterifica- tion of triglycerides, which are the main feedstock for producing biodiesel. The global increase in biodiesel production has led to a marked increase in world glycerin production. Because the demand for biodiesel is projected to increase, the use of glyc- erin becomes a matter of great importance, since this would greatly improve the overall economics of the biodiesel production process. 1 Glycerin is a versatile and valuable chemical and has a wide variety of uses and applications, e.g. in the manufacture of alkyd resins, adhesives, plasticizer and explosives. 2 The added production of glycerin by the biodiesel industry has created an oversupply that has encouraged the development of new indus- trial applications for this material. Glycerin could be used as a raw material for the production of high-volume industrial chem- icals such as propylene glycol, epichlorohydrin, acrylic acid and polyhydroxybutyrate. 1 In biodiesel production plants it is necessary to optimize process conditions to have the best conversion and selectivity. Theoretically, 3 mol of methanol per mol of triglyceride are necessary but in practice a 6:1 ratio is used to ensure high conversion in the transesterification reaction. Typically, conversions around 98–99% are obtained for the majority of oils when homogeneous catalysts, such as sodium methylate, are used at 0.7– 1% wt with respect to oil. The transesterification of triglycerides with methanol generates a methyl-ester phase and a glycerin phase. Impurities such as catalyst, soap, methanol and water are preferentially concentrated in the glycerin phase. The glycerin phase is typically neutralized with an acid and the cationic component of the catalyst is incorporated as a salt; this process leads to a glycerin phase that has a high salt content, typically ranging from 4 to 8%. A purification step is then required to transform crude glycerin to a usable chemical. Heterogeneous catalysts, like enzyme and solid metal-oxides, are promoted as alternatives to homogeneous alkaline catalysts. However, even in these kinds of processes, impurities present in the oil accumulate in the glycerin phase andpurification is not avoidable. 1 The current industrial method for the purification of glycerin consists of high vacuum distillation, which is an established technology that produces high-purity glycerin (grade USP) in high yield. However, the distillation of glycerin is an energy- intensive process because glycerin has a high vaporization temperature, which demands a high-energy input for vaporization. Besides, a high vacuum is required to prevent high-temperature denaturation of the glycerin via oligomers and acrolein formation. This suggests that for future glycerin markets a new low-cost purification strategy for glycerin is needed badly. Amin et al. 3,4 studied ultra-filtration as an alternative glycerin- purification process; they worked with synthetic mixtures of ∗ Correspondence to: Luis Alberto Rios, Grupo Procesos Fisicoqu´ ımicos Aplicados, Sede de Investigaci´ on Universitaria, Universidad de Antioquia, Cra. 53 #61-30, Medell´ ın, Colombia. E-mail: larios@udea.edu.co Grupo Procesos Fisicoqu´ ımicos Aplicados, Sede de Investigaci´ on Universitaria, Universidad de Antioquia, Cra. 53 #61-30, Medell´ ın, Colombia J Chem Technol Biotechnol 2013; 88: 1978–1983 www.soci.org c  2013 Society of Chemical Industry