Furfural can be produced through a one- or two-stage process.14–16
In the one-stage process, pentosan is hydrolyzed to xylose
and dehydrated to furfural within the same reactor. The
disadvantage of this method is that it gives a low furfural yield
(0.7–3.3%, mass fraction).14 In the two-stage process, hydrolysis
and dehydration reactions occur in separate reactors. There are
two advantages of the two-stage process: a higher furfural yield,
and utilization of the solid residue for the production of cellulose,
glucose, and ethanol via fermentation.15 Homogenous acids, such
as sulfuric acid and phosphoric acid, are widely-used catalysts for
the conversion of lignocellulosic materials to furfural.17,18 However,
this results in several problems, including difficulties in acid
recovery, complicated separation of products, and environmental
pollution. Solid superacid is a type of acid with many advantages
over a liquid acid. For example, a solid superacid is easy to separate
from a reaction mixture and easy to regenerate and reutilize. Due
to these advantages, a number of studies have focused on the solid
acid-catalyzed production of furfural from lignocelluloses.19,20 Due
to the high pentosan content of rice husk and the employment of
functionalized solid acid catalysts, this study aimed to optimize
the conditions in both the hydrolysis and dehydration stages for
the efficient production of furfural using SBA-15, a solid superacid
with high catalytic activity, by an orthogonal test design and
response surface methodology (RSM).