Analysis of the dark-colored impurities in sulfonated fatty acid methyl ester |
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Authors: | Kaoru Yamada Shigeaki Matsutani |
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Affiliation: | (1) Lion Corporation, Tokyo, Japan;(2) 13-12 Hirai 7 Chome, Edogawa-ku, 132 Tokyo, Japan |
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Abstract: | A fractionally distilled C14−C16 fatty acid methyl ester, derived from palm oil, was sulfonated with gaseous SO3 in a falling film reactor to form an α-sulfo fatty acid methyl ester (α-SF; unbleached and unneutralized form). The included
dark-colored impurities were then separated from α-SF as a diethyl ether-insoluble matter. After purification by thin-layer
chromatography, the colored species were analyzed by ion-exchange chromatography, gel-permeation chromatography, and nuclear
magnetic resonance spectrometry. These data suggested that the colored species were polysulfonated compounds with conjugated
double bonds. Minor components in the raw fatty acid methyl ester, found by gas chromatography/mass spectrometry, were spiked
into the purified methyl palmitate and then sulfonated. The unsaturated methyl ester and hydroxy ester showed the worst color
results. The methyl oleate and methyl 12-hydroxystearate were then sulfonated and analyzed. Deep black products were obtained,
which showed the same properties as the colored species in α-SF. It was concluded that low levels of unsaturated fatty acid
methyl esters and hydroxy esters in the fatty acid methyl ester are the main causes of the coloring. |
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Keywords: | Bleach coloring methyl ester palm fatty acid palm oil α -SF α -sulfo fatty acid methyl ester sulfonation |
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