Biomedical Engineering Reference
In-Depth Information
Dias et al. [
93
] studied sulfonic acid loaded on the microporous-mesoporous
silica as the catalyst to dehydrate xylose to obtain furfural. The reaction was carried
out in a microreactor and used dimethyl sulfoxide, water, and methyl isopropyl
ketone or toluene as the solvent. In the reactor, 30 mg xylose, 20 mg catalyst, and
1 mL solvent were added, and then the reaction temperature was increased to 140
ı
C
and kept for 24 h. The conversion rate of xylose was 90 % with 82 % selectivity
for furfural. The results proved that the sulfonic acid loaded on microporous-
mesoporous silica materials was an efficient catalyst, but the surface of these silicate
catalysts were prone to coking results in decreased yield.
Kim and Lee [
102
] also performed a study of the supercritical CO
2
extraction
process, in which sulfation titanium oxide and sulfation zirconium oxide were used
as solid catalysts to prepare furfural. In this work, 10 g catalyst and 400 g water were
added to the reactor, CO
2
was aerated to bring the pressure of the system to 8 MPa,
and then the temperature was raised to 180
ı
C. Supercritical CO
2
was pumped to
a pressure of 20 MPa when the temperature was steady, then 100 g of 10 % xylose
aqueous solution were added. Supercritical CO
2
was pumped from the bottom of the
reactor continuously, and samples were obtained from the liquid for analysis during
the reaction. However, the yield of furfural was 60 % using sulfated titania oxide as
a catalyst; the yield was about 50 % using sulfated zirconia as a catalyst. There was
no sintering phenomenon in these two catalysts.
7.6.3
Preparation and Separation of Furfural Using
Hemicellulose from Steam-Exploded Corn Stover
Because of the problems of a limited amount of corncobs, large acid consumption,
and difficulty in comprehensive utilization of furfural slag in current furfural pro-
duction, Chen et al. [
103
,
104
] explored a new process using water extraction from
steam-exploded corn straw to prepare furfural (Fig.
7.3
). First, they used the steam
explosion technology to pretreat cornstalks, in which most of the hemicellulose was
degraded and separated. Xylose from the degraded hemicellulose of steam-exploded
corn straw was extracted by water, and then the xylose is used to produce furfural
under high-temperature and high-pressure conditions. The optical conditions of
steam explosion, water extraction, and furfural production and the phenomenon of
coking were studied.
The results showed that the effect of steam explosion was better when the
pressure was 1.4 MPa and kept for 4 min. The structure of materials obtained under
such conditions was loose, and the xylose dissolution rate could be up to 3.25 %
in water extract. Several components were greatly changed in cornstalks; among
them, the hemicellulose content dropped from 23.7 to 5.55 %. Conditions for water
extraction were also investigated, and the effect of water extraction was better with a
solid-liquid ratio of 1:6 and 80
ı
C hot water. The water extraction time did not show
