Journal of the American Oil Chemists' Society

, Volume 81, Issue 1, pp 83–89

In situ alkaline transesterification: An effective method for the production of fatty acid esters from vegetable oils

  • Michael J. Haas
  • Karen M. Scott
  • William N. Marmer
  • Thomas A. Foglia
Article

Abstract

The production of simple alkyl FA esters by direct alkali-catalyzed in situ transesterification of the acylglycerols (AG) in soybeans was examined. Initial experiments demonstrated that the lipid in commercially produced soy flakes was readily transesterified during agitation at 60°C in sealed containers of alcoholic NaOH. Methyl, ethyl, and isopropyl alcohols readily participated in the reaction, suggesting that the phenomenon is a general one. Statistical experimental design methods and response surface regression analysis were used to optimize reaction conditions, using methanol as alcohol. At 60°C, the highest yields of methyl ester with minimal contamination by FFA and AG were predicted at a molar ratio of methanol/AG/NaOH of 226∶1∶1.6 with an approximately 8-h incubation. An increase in the amount of methanol, coupled with a reduced alkali concentration, also gave high ester yields with low FFA and AG contamination. The reaction also proceeded well at 23°C (room temperature), giving higher predicted ester yields than at 60°C. At room temperature, maximal esterification was predicted at a molar ratio of 543∶1∶2.0 for methanol/AG/NaOH, again in 8 h. Of the lipid in soy flakes, 95% was removed under such conditions. The amount of FAME recovered after in situ transesterification corresponded to 84% of this solubilized lipid. Given the 95% removal of lipid from the soy flakes and an 84% efficiency of conversion of this solubilized lipid to FAME, one calculates an overall transesterification efficiency of 80%. The FAME fraction contained only 0.72% (mass basis) FFA and no AG. Of the glycerol released by transesterification, 93% was located in the alcoholic ester phase and 75 was on the post-transesterification flakes.

Key Words

Biodiesel fats and oil utilization fatty acid ester in situ transesterification transesterification 

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Copyright information

© AOCS Press 2004

Authors and Affiliations

  • Michael J. Haas
    • 1
  • Karen M. Scott
    • 1
  • William N. Marmer
    • 1
  • Thomas A. Foglia
    • 1
  1. 1.Agricultural Research Service, Eastern Regional Research CenterU.S. Department of AgricultureWyndmoor

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