C. Moreau et al., Isomerization of glucose into fructose in the presence of cation-exchangedzeolites and hydrotalcites, APP CATAL A, 193(1-2), 2000, pp. 257-264
Isomerization of glucose into fructose was performed in a batch mode in the
presence of a series of alkaline solid catalysts such as cation-exchanged
A, X, Y zeolites and hydrotalcites.
Under optimized operating conditions, water as the solvent, 95 degrees C, u
p to 250 g/l of initial glucose concentration, up to 20 wt.% of catalyst, 7
00-1200 rpm and 8 bar of nitrogen pressure to avoid oxidation reactions, th
e reaction is not controlled by external or internal diffusional limitation
s. Among the different catalysts used, Li-, Na-, K-, Cs-, Ca- and Ba-exchan
ged A, X and Y zeolites, and hydrotalcites, Ca- and Ba-exchanged A, X and Y
zeolites were found less selective, whereas those with a moderate basicity
such as NaX and KX were found to achieve isomerization of glucose into fru
ctose with a selectivity to fructose of about 90%, but at low glucose conve
rsion, around 10-20%. However, the high selectivity to fructose is only obt
ained at glucose conversions lower than 25%. Furthermore, it was found that
a significant amount of the cation passed into water (around 15% in the ca
se of monovalent cation-exchanged X zeolites). This leaching phenomenon is
no longer observed after a second run. The conversion of glucose is stabili
zed at about 10% without loss of selectivity to fructose, so that a continu
ous process may be considered. (C) 2000 Elsevier Science B.V. All rights re
served.