ZIF-8 films were successfully prepared on a flexible nylon substrate with a contra-diffusion synthesis method, and gas permeation experiments indicated that the films were continuous and compact.
In
this study, the acid-catalyzed conversion of xylose to furfural
was investigated in 20 solvents ranging from water, alcohol, ketones,
furans, ethers, esters, hydrocarbons, and aromatics with the aim to
understand their involvement in each step from xylose to furfural.
Compared with water, alcohols can stabilize the reactive intermediates,
promote the formation of furfural, and slow its degradation with prolonged
reaction times. Iso-propanol and 2-butanol can direct the conversion
of xylose to levulinic esters via transfer hydrogenation catalyzed
by a Brønsted acid catalyst. The other solvents with the carbonyl
groups (i.e., ketones) or conjugated π bonds (e.g., furan) react
with both xylose and furfural. Either xylose cannot make its way to
furfural or furfural cannot survive for long in these solvents. In
ethers, hydrocarbons, and aromatics, the formation of furfural is
quick but so is the degradation of furfural due to the aprotic properties
of these solvents. In an ester like methyl formate, xylose can be
converted to furfural selectively and efficiently. Approximately 70%
yields of furfural were achieved at 150 °C in a very short time,
and more importantly, methyl formate is highly volatile (boiling point:
32 °C). It can be distilled from furfural very easily, making
it a promising solvent for furfural production. The solvents also
interact with the acidic resin catalysts in varied ways due to their
different polarities and molecular size/shape, determining the availability
of the acidic sites on the inner surfaces of the catalysts.
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