<> Jungshik Kang, Anne Vonderheide
and Vadim V. Guliants Chemical
Engineering, University of Cincinnati, Cincinnati OH 45221 Abstract Two
hemicellulose- and cellulose-derived molecules, 2-methylfuran (2-MF) and 2,5-dimethylfuran
(DMF), respectively, can
be hydrogenated into mixtures of substituted tetrahydrofurans
(THFs), alcohols and ketones with potential applications as specialty solvents,
flavor additives, and alternative fuels. However, the current understanding of reaction
pathways for these transformations over noble metal catalysts is rather
limited. Accordingly, vapor-phase hydrogenation of 2-MF and DMF was carried out
over 5 wt. % Pd/C and Pt/C
catalysts in a deuterium atmosphere. The deuterated
THFs, ketones and alcohols were produced under different reaction conditions
and analyzed by GC-MS employing chemical ionization to avoid fragmentation of
parent ions. It was observed that the furan ring saturation with deuterium over
a Pd/C catalyst occurred at low reaction temperatures
leading to various deuterated THFs, followed by the deuterium
exchange for hydrogen in the THF ring as the temperature increased. Finally, the
H/D exchange occurred in the substituent methyl group on the THF ring. The C-O bond
cleavage also occurred over a Pd/C catalyst at elevated
temperatures resulting in deuterated ketones where
all hydrogen atoms were eventually exchanged for
deuterium. Alcohols
were produced over a Pt/C catalyst at low reaction
temperatures because of the favorable chemical equilibrium with corresponding ketones.
It was found that deuterium was exchanged for hydrogen on all carbon atoms of
the original furan ring and saturated the oxygen and carbon atoms of the broken
C-O bond in both deuterated 2-pentanol and 2-hexanol.
At elevated reaction temperatures, all H atoms in the deuterated
alcohols were exchanged for deuterium except for the last ~2 hydrogens on the methyl groups.
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