324
HMF along with 5-methoxymethylfurfural (MMF) were obtained with an increase
in the total yield to 65%. Using methanol as solvent, etherification was initiated as
HMF was converted into MMF with 37% yield (Table 7, entry 2) [130]. Commercially
attractive process for the production of HMF from high fructose corn syrup was
developed by Jeong et al. They found 1,4-dioxane to be a promising solvent media
after screening various solvents using Amberlyst-15 a solid acid catalyst. HMF
yield was 80% with the reusability of the catalyst up to five times and solvent recycled after simple distillation (Table 7, entry 3) [131]. Morales group reported high
sulfonic acid-loaded acidic resin as a heterogeneous catalyst for the dehydration of
fructose to HMF in DMSO, yielding 93% of HMF in 1 h (Table 7, entry 4). The
authors also studied this reaction with glucose as a starting material, which yielded
33% HMF in 24 h. In this case, DMSO as a solvent played an important role in
dehydrating glucose to anhydroglucose which facilitated the production of HMF by
reducing side reaction [132].
A study done by our group showed the influence of DMSO and dimethylformamide (DMF) on the recyclability of Amberlyst-15 catalyst for the dehydration of
fructose to HMF. In case of DMSO as a solvent, stable activity of the catalyst is
noted, whereas in DMF, significant loss of activity is observed up on recycling. The
loss of activity in DMF is due to the neutralization of acidic sites by the formation
of ammonium ions which was inferred from FT-IR and CHNS studies. To regenerate the catalytic activity, dilute acid treatment was required (Table 7, entry 5) [133].
Functionalized Carbon Materials
High stability of carbon materials and complementary properties on hydrophobicity
have resulted in the use of mainly sulfonated carbonaceous materials as solid catalysts for fructose dehydration to HMF. Wang group reported a carbon-based solid
acid, prepared from glucose and p-toluenesulfonic acid (TsOH), and used for catalytic dehydration of fructose into HMF (91.2% yield). The catalyst was active in
DMSO at 130 °C for 1.5 h (Table 8, entry 1). Moreover, this catalyst showed a good
reusability for five reaction cycles [134]. Huang et al. reported cellulose-sulphuric
acid as catalyst, prepared from cellulose treated with chlorosulfonic acid. The recyclable solid acid catalyst revealed high yield (93.6%) of HMF in DMSO for 45 min
(Table 8, entry 2) [135].
A series of sulfonic acid-functionalized carbon materials (C-SO 3 H), including
poly(p-styrenesulfonic acid)-grafted carbon nanotubes (CNT-PSSA), poly(pstyrenesulfonic acid)-grafted carbon nanofibers (CNF-PSSA), benzenesulfonic acidgrafted CMK-5 (CMK-5-BSA) and benzenesulfonic acid-grafted carbon nanotubes
(CNT-BSA), was studied for this conversion. Among these functionalized carbons,
CNT-PSSA showed exceptional catalytic activity and afforded 89% HMF yield (Table 8,
entry 3). This excellent catalytic activity is due to the high Bronsted acid strength which
is confirmed by potentiometric acid-base titration and ion chromatography [136].
Russo et al. adopted a simple synthetic procedure for the preparation of carbonsilica composite activated with SO 3 H groups by acid treatment with different acid
S. Gundekari et al.
HMF along with 5-methoxymethylfurfural (MMF) were obtained with an increase
in the total yield to 65%. Using methanol as solvent, etherification was initiated as
HMF was converted into MMF with 37% yield (Table 7, entry 2) [130]. Commercially
attractive process for the production of HMF from high fructose corn syrup was
developed by Jeong et al. They found 1,4-dioxane to be a promising solvent media
after screening various solvents using Amberlyst-15 a solid acid catalyst. HMF
yield was 80% with the reusability of the catalyst up to five times and solvent recycled after simple distillation (Table 7, entry 3) [131]. Morales group reported high
sulfonic acid-loaded acidic resin as a heterogeneous catalyst for the dehydration of
fructose to HMF in DMSO, yielding 93% of HMF in 1 h (Table 7, entry 4). The
authors also studied this reaction with glucose as a starting material, which yielded
33% HMF in 24 h. In this case, DMSO as a solvent played an important role in
dehydrating glucose to anhydroglucose which facilitated the production of HMF by
reducing side reaction [132].
A study done by our group showed the influence of DMSO and dimethylformamide (DMF) on the recyclability of Amberlyst-15 catalyst for the dehydration of
fructose to HMF. In case of DMSO as a solvent, stable activity of the catalyst is
noted, whereas in DMF, significant loss of activity is observed up on recycling. The
loss of activity in DMF is due to the neutralization of acidic sites by the formation
of ammonium ions which was inferred from FT-IR and CHNS studies. To regenerate the catalytic activity, dilute acid treatment was required (Table 7, entry 5) [133].
Functionalized Carbon Materials
High stability of carbon materials and complementary properties on hydrophobicity
have resulted in the use of mainly sulfonated carbonaceous materials as solid catalysts for fructose dehydration to HMF. Wang group reported a carbon-based solid
acid, prepared from glucose and p-toluenesulfonic acid (TsOH), and used for catalytic dehydration of fructose into HMF (91.2% yield). The catalyst was active in
DMSO at 130 °C for 1.5 h (Table 8, entry 1). Moreover, this catalyst showed a good
reusability for five reaction cycles [134]. Huang et al. reported cellulose-sulphuric
acid as catalyst, prepared from cellulose treated with chlorosulfonic acid. The recyclable solid acid catalyst revealed high yield (93.6%) of HMF in DMSO for 45 min
(Table 8, entry 2) [135].
A series of sulfonic acid-functionalized carbon materials (C-SO 3 H), including
poly(p-styrenesulfonic acid)-grafted carbon nanotubes (CNT-PSSA), poly(pstyrenesulfonic acid)-grafted carbon nanofibers (CNF-PSSA), benzenesulfonic acidgrafted CMK-5 (CMK-5-BSA) and benzenesulfonic acid-grafted carbon nanotubes
(CNT-BSA), was studied for this conversion. Among these functionalized carbons,
CNT-PSSA showed exceptional catalytic activity and afforded 89% HMF yield (Table 8,
entry 3). This excellent catalytic activity is due to the high Bronsted acid strength which
is confirmed by potentiometric acid-base titration and ion chromatography [136].
Russo et al. adopted a simple synthetic procedure for the preparation of carbonsilica composite activated with SO 3 H groups by acid treatment with different acid
S. Gundekari et al.