Stable complex formation with boric acid in pyrolysis of levoglucosan in acidic media |
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Authors: | H Kawamoto S Saito S Saka |
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Institution: | aGraduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan |
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Abstract: | The influence of boric acid or phenylboronic acid on thermal conversion of levoglucosan in acidic sulfolane was studied. Although levoglucosan was converted to levoglucosenone, furfural and 5-hydroxymethyl furfural (total yield: 40 mol%) at 200 °C in sulfolane containing 0.1 wt% H2SO4, addition of boric acid enormously lowered the yields of these, and instead caused the formation of a stable complex in more than 70 mol% yield. Thus, boric acid substantially suppressed the acid-catalyzed dehydration and formation of furfurals from levoglucosan through complex formation. From the 1H NMR spectrum, the chemical structure of this complex was confirmed as -d-glucofuranose cyclic 1,2:3,5-bisborate, which was readily hydrolyzed quantitatively to glucose by the addition of water. Phenylboronic acid also exhibited similar influences. |
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Keywords: | Levoglucosan Pyrolysis Boric acid Phenylboronic acid Borate Boronate Thermal stability |
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