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Moisture Removal Substantially Improves the Efficiency of in Situ Biodiesel Production from Soybeans
Author(s) -
Haas Michael J.,
Scott Karen M.
Publication year - 2007
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-006-1024-2
Subject(s) - transesterification , methanol , biodiesel production , biodiesel , raw material , moisture , reagent , materials science , pulp and paper industry , chemistry , organic chemistry , catalysis , engineering
In an effort to reduce the production cost of biodiesel, we previously described an approach termed “in situ transesterification” wherein the transesterification of a vegetable oil occurred directly in its raw agricultural material. In that method, substantial quantities of reagents were required to achieve high‐efficiency transesterification. Here we report that by drying the substrate a marked reduction in the reagent requirements was achieved. Reaction conditions for maximum fatty acid methyl ester (FAME) production were identified using statistical experimental design methods. In 16‐h reactions with 5 g of flakes (2.6% moisture) and 18 mL of 0.10 N NaOH in methanol, 97% theoretical maximum transesterification was achieved. For dry flakes, optimal transesterification was achieved in 10 h in reactions containing 5 g of flakes and 12 mL of 0.10 N NaOH in methanol. This represented a 60% reduction in methanol and a 56% reduction in NaOH use compared with the transesterification of full‐moisture flakes. Under these conditions the degree of transesterification was 100% of the theoretical maximum. The transesterification of 20 kg of flakes with a moisture content of 0.8% was conducted under optimal reaction conditions. Both triacylglycerols (TAG) and phosphoacylglycerols (PL) were transesterified to high degrees, with an overall efficiency of 97.3% of the maximum theoretical efficiency. PL were not detected in the flakes following transesterification, and the amount of remaining unreacted TAG was only 1.0% of that input. Following washes with water, 0.5 M NaCl, and dilute NaOH, the recovered FAME met the ASTM specifications for biodiesel. The tocopherol levels of the FAME exceeded by 76% those of a representative commercial biodiesel. Soy flakes retained 97% of their protein following in situ transesterification.