Efficient conversion of glucosamine to levulinic acid in a sulfamic acid-catalyzed hydrothermal reaction

Article abstract of DOI:10.1039/c7ra12980g

Glucosamine is a monomer of chitosan, which is a biopolymer derived from the exoskeletons of crustaceans. This work investigated the conversion of glucosamine into the platform chemical levulinic acid (LA), in a sulfamic acid-catalyzed hydrothermal reaction. The optimized results of LA production showed that the conditions of 200 °C, 125 g L^-1 glucosamine, 0.3 M sulfamic acid, and 15 min produced a 33.76 ± 0.19 mol% LA yield. The same conditions produced only 0.14 mol% 5-HMF yield. These results show that glucosamine is a potential bioresource to produce platform chemicals. Also, in the field of biofuels and chemical synthesis processes, the catalytic system using sulfamic acid is significant.

Full text of DOI:10.1039/c7ra12980g

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Efficient conversion of glucosamine to levulinic
acid in a sulfamic acid-catalyzed hydrothermal
reaction†
Cite this: RSC Adv., 2018, 8, 3198
Hyo Seon Kim, Sung-Koo Kim and Gwi-Taek Jeong
*
Glucosamine is a monomer of chitosan, which is a biopolymer derived from the exoskeletons of
crustaceans. This work investigated the conversion of glucosamine into the platform chemical levulinic
acid (LA), in a sulfamic acid-catalyzed hydrothermal reaction. The optimized results of LA production
Received 2nd December 2017
Accepted 10th January 2018
ꢁ1
ꢀ
showed that the conditions of 200 C, 125 g L glucosamine, 0.3 M sulfamic acid, and 15 min produced
a 33.76 ꢂ 0.19 mol% LA yield. The same conditions produced only 0.14 mol% 5-HMF yield. These results
show that glucosamine is a potential bioresource to produce platform chemicals. Also, in the field of
biofuels and chemical synthesis processes, the catalytic system using sulfamic acid is significant.
DOI: 10.1039/c7ra12980g
rsc.li/rsc-advances
7
can be converted into a wide and valuable range of chemicals.
Introduction
LA is known as a versatile green chemical, and is now
The depletion of fossil resources, increasing energy demand, commercially produced by a petrochemical route, using the
and changes of global climate are resulting in the active hydrolysis and hydrogenation of maleic anhydride and furfural
1
–3
2,3,6,7
exploration for new energy resources. Bioresources, such as alcohol.
lignocellulosics or macroalgaes, are attractive alternatives to such as environmental problems, and the increase of crude oil
Incidentally, this route has some disadvantages,
2
,3,6,7
fossil resources, due to their renewability and possible conver- price.
sion by appropriate technology to various bio-based products.
To replace the petrochemical route of LA production,
renewable bioresources, such as starch-based and lignocellu-
Bio-based products, such as biofuels and platform chemicals, losic biomass, are being applied to LA production by various
2
–7
2,3,6,7,9,11,14,15
can replace the carbon skeletons derived from fossil chemical processes.
Also, LA and its derivatives can
2,3,6,7
resources.
be used in the eld of pharmaceuticals, fuel extenders, agri-
Among the various platform chemicals that can be synthe- cultural products, dyes & coating materials, solvents & other
sized from various bioresources, 5-hydroxymethylfurfural (5- chemicals, monomers & specialty polymers, food additives, and
6
,7,11
HMF) offers high potential and versatility for the synthesis of others.
2,3,7
fuels and materials.
5-HMF can be obtained from various
In the present work, glucosamine was employed as a poten-
carbohydrates that are derived from sugar, starch, and ligno- tial bioresource for the production of platform chemicals,
2
,3,7
cellulosic biomass.
chitosan have also been introduced to the production of component of chitin/chitosan. Chitin, a copolymer of glucos-
Recently, macro-algae and chitin/ namely 5-HMF and levulinic acid. Glucosamine is a major
8
–15
chemical intermediates.
Since 5-HMF has hydroxymethyl amine and N-acetylglucosamine linked with b-1–4 bond, is
and aldehyde groups, it can be converted into several valuable a natural biopolymer that is biologically generated from many
products, which is of high interest for the production of fuels, aquatic organisms, terrestrial organisms, and some microor-
1
6,17
pharmaceuticals, solvents, resins, fungicides, textiles, and ganisms.
Aer cellulose, it is the second most abundant
1
0
polymer materials by hydrogenation, halogenation, amination, nitrogen-containing organic compounds on earth (from 10 to
1
2
16,18,19
etherication, oxygenation, polymerization, and other chemical 10 tons per year).
Chitosan, polycationic biopolymer, is
a deacetylated form of chitin. Nowadays, a large quantity of
Levulinic acid (LA; 4-oxopentanoic acid), which has two chitin/chitosan can easily be obtained from by-products as food
2,3,7,14,15
reactions.
16
reactive groups, i.e., carbonyl and carboxy groups, has been waste in the shell-crustaceous sh industry. Because of its
selected by the U.S. Department of Energy (DOE) as one of the properties of nontoxicity, biocompatibility, and biodegrad-
3
16,20,21
highest valued bio-based chemicals. These two reactive groups ability,
chitosan has been widely applied in various elds,
including cosmetics, medical treatment, biomedicine, food,
chemical industries, bers, sewage treatment, and environ-
Department of Biotechnology, Pukyong National University, Busan 48513, Republic of
Korea. E-mail: gtjeong@pknu.ac.kr; Fax: +82-51-629-5863; Tel: +82-51-629-5869
8,11,16,22
mental protection.
Sulfamic acid has the properties of being non-volatile,
odorless, non-corrodible, moderately acidic (pK
¼ 1.0), non-
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c7ra12980g
1
a
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hygroscopic, and low cost; and also, it is efficient as a green 0.5 M), and reaction time (0–60 min). Firstly, the effects of
23
catalyst. Sulfamic acid has been focused on to provide alter- biomass concentration were investigated for different glucos-
ꢁ
1
natives to Brønsted- and Lewis acid catalysts, due to its unique amine concentrations in the range of 50–150 g L , under the
ꢀ
catalytic properties and intrinsic zwitterionic nature conditions of 180 C, 0.2 M sulfamic acid, and 30–90 min.
+
3ꢁ
23,25
(H
3
N SO ), which occurs by its tautomer structure.
In a few Secondly, the effect of reaction temperature was investigated for
ꢀ
years, sulfamic acid has been applied as an efficient acidic various temperatures in the range of 150–220 C, under the
catalyst in various acid-catalyzed organic reactions, such as conditions of 125 g L glucosamine, 0.2 M sulfamic acid, and
ꢁ1
acetalization, esterication, acetylation, Biginelli condensation, 30–120 min. Thirdly, the effect of catalyst concentration was
2
3,26
Beckmann rearrangement, and Michael reaction.
investigated for various catalyst concentrations in the range
ꢀ
Many works relating to 5-HMF and LA production from of 0.0375–0.5 M sulfamic acid, under the conditions of 200 C,
ꢁ1
various renewable biomasses, such as mono-sugars, starch, and 125 g L glucosamine, and 15–60 min. Finally, the effect of
2
,3,6,7,9,11,14,15
lignocellulosics, have been reported.
Moreover, reaction time in the range of 0–60 min was investigated under the
ꢀ
ꢁ1
marine macro-algae and chitin/chitosan were recently intro- conditions of 200 C, 125 g L glucosamine, and 0.3 M sulfamic
duced to produce 5-HMF and LA. Recently, the application of acid. All of the experiments were performed with two or more
8
–15
sulfamic acid as catalyst in the 5-HMF and LA production from repetitions, and the data are presented as the mean ꢂ SD.
24
bamboo ber was also reported. However, there has been no
study of the conversion of glucosamine using sulfamic acid as Denition of the combined severity factor
a catalyst for platform chemicals, such as 5-HMF and LA.
The effect of the sulfamic acid-catalyzed hydrothermal reaction
In this study, the sulfamic acid-catalyzed hydrothermal
conversion of glucosamine into the platform chemicals 5-HMF
and LA was investigated, and the reaction factors were opti-
mized. Also, the efficiency of sulfamic acid-catalyzed hydro-
thermal conversion was evaluated with the tool of the combined
severity factor (CSF).
on 5-HMF and LA production was determined and compared
using the combined severity factor (CSF). The CSF indicates the
severity of the reaction, which is a function of the reaction
conditions of reaction temperature, time, and acidity of
14,15,27
solution.
CSF ¼ log[t exp(T ꢁ Tref)/14.75] ꢁ pH
Materials and methods
Materials
ꢀ
where, T(t) is the reaction temperature ( C), Tref is the reference
temperature (i.e., 100), t is the reaction time (min), and 14.75 is
Glucosamine HCl as the substrate was obtained from Sigma the tted value of the arbitrary constant. The pH of solution was
14,15,27
Aldrich Co. Ltd. (USA). The employed sulfamic acid (Ducksan measured at room temperature before the reaction.
Chemicals, Co. Ltd., Korea) was of reagent grade, and 5-HMF,
LA, and all other chemicals were of analytical grade.
Analysis
The concentration of glucosamine was analyzed using modied
DNS method with spectrophotometry (Spekol 1300, Analytik
Experimental procedure
The batch experiment for 5-HMF and LA production from Jena, Germany) at 540 nm and glucosamine as standard. The
glucosamine was performed as follows. In preparatory work, concentrations of 5-HMF and LA were analyzed using an Agilent
setting amounts of glucosamine and sulfamic acid solution as HPLC system (Agilent 1100, USA) combined with refractive
catalyst were introduced into a 2 mL glass vial. Prior to sealing, index detector and Aminex-87H column (Bio-Rad, USA). The
ꢀ
the reactant was sufficiently vortexed for sufficient dissolving HPLC operated in the conditions of 65 C oven temperature,
ꢁ1
and mixing. Aer these glass vials were sealed, they were 5 mM sulfuric acid as mobile phase, and 0.6 mL min ow
11,14,15
inserted into stainless steel reactor for hydrothermal reaction. rate.
For residue (humins) analysis, the product solution
The reaction was initiated at the time of reaching the setting was removed by centrifugation at 17 000 rpm for 10 min, and
temperature of the reactor in the oil bath with monitoring and subsequently remained residues aer washing with distilled
controlling by PID temperature controller. Until reaching the water were dried at vacuum oven for 24 h, and the dried solid
setting temperature, a preheating time of approximately 5 min was considered as insoluble humins. FT-IT spectra of the
ꢁ
1
was required. Upon completion of the reaction, the reactor was humins were analyzed from 649–4000 cm at resolution of
ꢁ
1
quickly cooled to room temperature by dipping into tap water. 4 cm using Fourier Transform Infra Red Spectrometer (Perkin
For HPLC analysis, the product solution was recovered by Elmer (U.S.A), Spectrum X).
centrifugation at 17 000 rpm for 10 min, and subsequently
11

ltered using a 0.2 mm syringe lter.
Determination of the conversion yield
The yield of glucosamine, 5-HMF, FA and LA was calculated by
Sulfamic acid-catalyzed hydrothermal conversion
the following equation: conversion yield (mol%) ¼ mole
The sulfamic acid-catalyzed conversion of glucosamine was concentration of product (M)/mole concentration of initial
performed to optimize the reaction factors for 5-HMF and LA substrate (M) ꢃ 100%. Humins yield (wt%) ¼ dry weight of
ꢁ1
production: glucosamine concentration (50–150 g L ), reaction residue (g)/dry weight of initial substrate (g) ꢃ 100%. The
ꢀ
temperature (150–220 C), sulfamic acid concentration (0.0375– results were recorded as average ꢂ SD.
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decreased LA yields. Also, the increase of reaction time
produced slight increase of LA yield in the tested range. The
Results and discussion
In this study, the sulfamic acid-catalyzed hydrothermal highest LA yield achieved was 35.06 ꢂ 0.47% at the conditions
ꢁ
1
conversion of glucosamine into 5-HMF and LA was investigated. of 50 g L
glucosamine and 30 min. Nevertheless, in the
ꢁ1
To optimize the production of 5-HMF and LA, the effects of conditions of 50–150 g L range of glucosamine and constant
reaction factors of biomass concentration, reaction tempera- reaction time, the difference of LA yield was little. It is suggested
ture, catalyst concentration, and reaction time were investi- that the limitation of contact between biomass and catalyst
gated. Also, the effect of the sulfamic acid-catalyzed resulted in the relatively low LA yield that was achieved at high
11
hydrothermal reaction was compared using the CSF.
biomass concentration. Comparably, increasing the glucos-
amine concentration within the 50–120 g L range in the
ꢁ
1
sulfuric acid-catalyzed hydrothermal reaction slightly decreased
the LA yield. Because the production cost is closely related to
the initial biomass concentration, further experiment with
Effect of biomass concentration
4,11
Fig. 1 shows the effect of biomass concentration in the range of
ꢁ
1
5
1
0–150 g L on 5-HMF and LA yield under the conditions of
regard to the LA yield and biomass concentration was con-
ꢀ
80 C, 0.2 M sulfamic acid, and 30–90 min. Fig. 1(A) shows that
ꢁ1
ducted under the condition of 125 g L
concentration.
glucosamine
in the case of 5-HMF production, increasing biomass concen-
tration in the tested ranges sharply decreased the yield of 5-
HMF. Also, the increase of reaction time caused serious
decrease of the 5-HMF yield. The highest 5-HMF yield obtained Effect of reaction temperature
ꢁ
1
was 2.76 ꢂ 0.01% at 50 g L glucosamine. Overall, the yields of
Fig. 2 shows the effect of reaction temperature on the glucos-
5
-HMF were low in the tested biomass ranges. Fig. 1(B) shows
that in LA production, increasing biomass concentration in the
tested ranges at constant reaction time condition slightly
amine conversion into 5-HMF and LA under the conditions of
ꢀ
ꢁ1
1
3
50–220 C, 125 g L glucosamine, 0.2 M sulfamic acid, and
0–120 min. Fig. 2(A) shows that in the formation of 5-HMF,
Fig.
ymethylfurfural and levulinic acid production from glucosamine by and levulinic acid production from glucosamine by sulfamic acid-
sulfamic acid-catalyzed hydrothermal conversion. catalyzed hydrothermal conversion.
1 Effect of the biomass concentration on 5-hydrox- Fig. 2 Effect of the reaction temperature on 5-hydroxymethylfurfural
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increasing the reaction temperature in the tested ranges sharply
decreased the 5-HMF yield. At all reaction temperature ranges,
passing reaction time sharply decreased the 5-HMF yield. In
ꢀ
particular, the condition of over 180 C resulted in the forma-
tion of 5-HMF being below 1%. High 5-HMF yield was obtained
at the conditions of low temperature and short reaction time.
ꢀ
The highest 5-HMF yield of 6.36 ꢂ 0.01% was obtained at 150 C
and 30 min. This indicates that under the conditions of higher
temperature and longer reaction time, the 5-HMF is easily
8,11
degraded to LA and FA.
In comparison, the hydrothermal
conversion of N-acetyl-D-glucosamine using ionic liquid catalyst
under water-DMSO mixture gradually increased the 5-HMF
ꢀ
13
yield, which peaked at 180 C. Also, in the sulfamic acid-
catalyzed conversion process of bamboo ber with microwave
irradiation in biphasic system, the 5-HMF yield consistently
ꢀ
24
increased, and peaked at 180 C.
Fig. 3 Effect of the catalyst concentration on levulinic acid production
from glucosamine by sulfamic acid-catalyzed hydrothermal
conversion.
Fig. 2(B) shows that in the formation of LA, increasing
reaction temperature linearly increased the LA yields, and then
over 200 C did not show any signicant difference. The highest
ꢀ
ꢀ
ꢀ
yield of 34.7% was achieved at 200 C and 90 min. Below 180 C,
passing reaction time linearly increased the LA yield. In
catalyzed conversion of chitosan and GluNAc, GluNAc showed
more signicant effect in 5-HMF production than that of chi-
tosan, due to the inhibited access of catalyst to chitosan by the
extensive intra- and inter-molecular hydrogen bonds of chito-
ꢀ
particular, the over 200 C condition maintained LA yield at
similar high values of 32.5–34.7%. The conditions of high
temperature and long reaction time formed high LA yield.
Similar to glucose, the results of Fig. 2 suggest that 5-HMF
was rst formed by glucosamine conversion by the sequential
reactions of deamination and dehydration. Subsequently, in the
condition of higher temperature, LA and FA was formed by
12
san. In summary, considering the catalyst cost and LA yield,
further experiments in view of the LA yield and catalyst
concentration were therefore carried out under the 0.3 M sul-
famic acid condition.
2,9,11
rehydration from 5-HMF.
In comparison, under the sulfuric
acid-catalyzed hydrothermal conversion of glucosamine, LA
ꢀ
Effect of reaction time
production was linearly increased within the 160–190
C
11
range. These results might reect the LA formation from 5- Fig. 4 shows the effect of the reaction time on LA and other
HMF, because the activation energy for 5-HMF degradation is products formation at different reaction times in the range of
13,28
ꢁ1
ꢀ
lower than that of 5-HMF formation from sugars.
In
0–60 min under the conditions of 200 C, 125 g L glucos-
summary, in this study, higher temperature in the sulfamic amine, and 0.3 M sulfamic acid. The conversion of glucosamine
acid-catalyzed hydrothermal reaction of glucosamine favored sharply increased, and then aer 15 min, steadily maintained.
LA production. Therefore, further works were conducted under The highest glucosamine conversion of 94.5% was obtained at
ꢀ
the reaction temperature of 200 C.
60 min. The 5-HMF yield sharply decreased, and then aer
Effect of catalyst concentration
Fig. 3 shows the effect of catalyst concentration on the forma-
tion of LA in the range of 0.0375–0.5 M sulfamic acid under the
ꢀ
ꢁ1
conditions of 200 C, 125 g L glucosamine, and 15–60 min. In
-HMF production, all tested catalyst concentration ranges
5
provided the obtained 5-HMF yield of below 0.17% (data not
shown). In LA production (Fig. 3), increasing of catalyst
concentration until 0.3 M slightly increased the LA yield, and
then at the 0.5 M catalyst condition was similarly maintained.
The highest LA yield of 33% was obtained under the conditions
of 0.3 M sulfamic acid and 60 min. In spite of that, the range of
over 0.3 M catalyst concentration produced less difference of LA
yield. The increase of access and active sites of catalyst with
12,13
high sulfamic acid concentration increased LA yield.
In
comparison, in the sulfuric acid-catalyzed hydrothermal
conversion of glucosamine, increasing sulfuric acid concentra-
Fig. 4 Effect of the reaction time on 5-hydroxymethylfurfural, levu-
linic acid, formic acid, humins production from glucosamine by sul-
famic acid-catalyzed hydrothermal conversion.
11
tion within 2–4% slightly increased the LA yield. In the FeCl
2
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1
0
0 min, nearly disappeared. The highest 5-HMF yield of 8.82 ꢂ glucosamine (pyranose form with amine group) is rst iso-
.14% was achieved at 0 min. However, increasing the reaction merized to the furanose form with amine group. This furanose
time until 10 min sharply increased the LA yield. Aer 20 min, form was converted into 5-HMF by deamination, dehydration,
1
2,25,35
the LA yield was similarly maintained at approximately 33.8%. and keto–enol tautomerization.
Under acidic conditions,
Unfortunately, the veri-
9
,10,12,36
The pattern of FA formation was similar to LA. At 10 min, FA the deamination is accelerated.
yield was reached to 40.4 ꢂ 0.10%. Aer 30 min, FA yield was cation of deamination during glucosamine conversion has
9
,12,36
decreased. It is indicated that the decomposition of FA to CO
2
,
been failed by this and other works.
Moreover, formed 5-
29
H
2
and H
Moreover, the formation of humins (insoluble dark materials) high acidic condition.
linearly increased, and then aer 15 min, slightly increased with In this study, the glucosamine is converted by sulfamic acid,
increasing time. It is opposite pattern with LA and FA yield. At which owing to its tautomer structure, has dual-catalyst sites of
2
O is occurred under severe harsh conditions.
HMF is rehydrated to LA and FA under high temperature and
11,14
23–25
6
0 min, humins formation was reached to 29.0 ꢂ 0.05%. The both Brønsted acid and Lewis acid sites.
As a previous
24
HPLC chromatogram of product analysis was presented in report, Sun et al. published that dual-catalyst sites of sulfamic
Fig. 1S.† Glucosamine and sulfamic acid did not determined by acid might be promote the polymer hydrolysis and subsequent
our HPLC analysis. FA (13.93 min), LA (15.65 min) and 5-HMF dehydration of glucose to 5-HMF. Although there is no
(29.49 min) were detected. Especially, from the experience of suggestion of detailed mechanism, it is supposed due to the
HPLC analysis, in the range of 8–11 min of retention time, synergetic effect between Lewis acid site of sulfamic acid and
24
monomeric sugars was detected (glucose 9.13 min; fructose (or the hydroxyl group in cellulose. In comparison with this work,
xylose, mannose, galactose) 9.89 min). By the way, some due to similar structure of glucosamine and glucose, sulfamic
unknown peaks were observed at 8–11 min range. Overall, this acid might have converted the glucosamine more by the
23–25
demonstrates the conversion of glucosamine into LA. Glucos- synergetic effect of dual-active sites of catalyst.
Recently,
amine is rst converted to 5-HMF by deamination and dehy- several works reported that the combining Brønsted and Lewis
dration. Further reaction of rehydration and passing time acids have positive synergistic catalytic effects on the produc-
3
6–41
converts the 5-HMF formed from glucosamine into LA and tion of 5-HMF and LA from various carbohydrates.
Zhang
2,9,11
40
41
FA.
Similarly, 5-HMF shows high yield at the initial period of et al., and Acharjee and Lee proposed the glucose conversion
about 3 min, and then decreases with time passing. However, pathway using dual acid catalysts. They referred that the
in the sulfuric acid-catalyzed hydrothermal reaction of glucos- isomerization of glucose was mostly catalyzed by Lewis acid,
amine, under the 175 C and 90 g L glucosamine conditions, whereas, dehydration was catalyzed by Brønsted and Lewis
increasing reaction time linearly increased the LA yield. From acids. Moreover, the rehydration of 5-HMF to LA and FA was
11
ꢀ
ꢁ1
11
40,41
the overall experimental results, in the sulfamic acid-catalyzed catalyzed by Brønsted acid.
hydrothermal reaction of glucosamine, the optimal conditions glucose, the conversion pathway glucosamine with sulfamic
Due to similar structure to
ꢀ
ꢁ1
40,41
of LA production are 200 C, 125 g L glucosamine, 0.3 M acid was proposed and illustrated as Scheme 1.
sulfamic acid, and 20 min. These results show the signicance We compared and analyzed the structures of glucosamine,
and availability of glucosamine and sulfamic acid to the eld of sulfamic acid and residues (humins) using Fourier transform
infrared (FT-IR) (Fig. 5). The peaks at 3345 and 3275 cm were
The several mechanisms of 5-HMF and LA formation by correspond to N–H and O–H stretching vibrations. The peaks
Several at 2997 and 2908 cm were attributed the C–H stretching
reports have been suggested both cyclic and acyclic reaction vibrations. The peak at 1545 cm was attributed –NH
ꢁ
1
platform chemicals production from renewable bioresources.
12
6,11,30
ꢁ1
several carbohydrates and catalysts were proposed.
ꢁ
1
2
bending
1
0,30,31
12
ꢁ1
routes as the conversion mechanism of glucose.
routes occurred through fructose isomerization.
Cyclic vibration. The band of 1200–1000 cm attributed to stretch-
Glucos- ing of the glycosidic linkage (C–O–C) and C–OH in the sugar
1
0,30,31
42,43
ꢁ1
amine is the pyranose form, which is similar structure to ring.
The band of 1350–1000 cm
was corresponded
9–11
ꢁ1
glucose, with amine group (–NH2).
In accordance with amines. The peak at 1274 cm was ascribed sulfonamide. The
previous works, it have been suggested as similar modied band of 1054–867 cm was ascribed to pyranose unit of poly-
ꢁ
1
32–34
12
route to glucose.
Like glucose conversion mechanism, saccharide. Fig. 2S† shows the FT-IR spectra of residues
40,41
Scheme 1 Overall reaction scheme of sulfamic acid catalyzed production of levulinic acid from glucosamine.
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Fig. 5 FT-IR spectra of glucosamine and the residue.
(humins) during conversion reaction of glucosamine with sul-
famic acid. The FT-IR spectra of residues showed similar
pattern results.
Fig.
7
Effect of the combined severity factor on 5-hydrox-
ymethylfurfural and levulinic acid production from glucosamine by
sulfamic acid-catalyzed hydrothermal conversion.
Mass balance of HMF and LA production
Fig. 6 shows the mass balance diagram of 5-HMF, LA, FA, and
ꢁ
1
ꢁ1
ꢁ1
0.03 mol%) LA, 10.4 g L (39.03 ꢂ 0.06 mol%) FA and 33.1 g L
insoluble matters (humins) under the conditions of 125 g L
ꢀ
(26.49 ꢂ 0.68 wt%) humins. Especially, 5-HMF detected nearly
glucosamine and 0.3 M sulfamic acid at 200 C for 30 min. From
ꢁ1
zero amount under these conditions.
this condition, the results presented that 125 g L glucosamine
ꢁ
1
(
92.9% conversion) could be convert to 22.8 g L (33.83 ꢂ
Fig. 6 Mass balance of formation of levulinic acid, formic acid and humins from glucosamine with sulfamic acid.
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Table 1 Comparison of LA production from chitosan and glucosamine
Materials
Reaction conditions
LA
References
a
ꢀ
ꢀ
ꢀ
ꢀ
Chitosan
MI , 200 C, 0.24 mmol SnCl
4
$5H
$5H
2
2
O, 30 min, 100 mg chitosan with 4 mL water
23.9 wt%
32.0 wt%
25.3 wt%
33.76 mol%
9
9
11
a
Glucosamine
Glucosamine
Glucosamine
MI , 200 C, 0.26 mmol SnCl
4
O, 100 mg glucosamine and 20 mL water
b
ꢁ1
CH , 188 C, 4 wt% sulfuric acid, 49 min, 120 g L glucosamine
b
ꢁ1
CH , 200 C, 125 g L glucosamine, 0.3 M sulfamic acid and 15 min
This work
a
b
MI: microwave irradiation. CH: conventional heating.
Effect of combined severity factor
glucosamine, 0.3 M sulfamic acid, and 15 min achieved a 33.76
ꢂ 0.19 mol% LA yield. The same conditions produced only
The effect of the sulfamic acid-catalyzed hydrothermal reaction
on the 5-HMF and LA yield was evaluated using the CSF. Fig. 7
shows the relationships of CSF value and 5-HMF or LA yield in
the sulfamic acid-catalyzed hydrothermal conversion of
glucosamine. In the 5-HMF case (Fig. 6(A)), increasing CSF
values decreased the 5-HMF yield. This is well tted to the
regression pattern of exponential decay (f ¼ y + a exp(ꢁbx); y ¼
0.14 mol% of 5-HMF yield. These results show the potential and
availability in the eld of biofuels and materials synthesis of
glucosamine as a bioresource, and sulfamic acid as catalyst.
Conflicts of interest
0
0
2
ꢁ
0.350, a ¼ 244.637, b ¼ 1.971), with regression value (R ) of There are no conicts to declare.
2
0
.811 (Adj. R ¼ 0.805). The highest 5-HMF yield was 6.36% at
CSF 1.77. Over CSF 3, the 5-HMF yields were nearly zero. In the
case of LA production, increasing CSF value sharply linearly
increased the LA yield until CSF 3, and then with further
increasing CSF value, steadily maintained it. The highest LA
yield is obtained near the CSF 3 range. It is well tted to the
regression pattern of the sigmoidal model (f ¼ a/(1 + exp(ꢁ(x ꢁ
x )/b)); a ¼ 33.196, x ¼ 2.122, b ¼ 0.233) with high regression
Acknowledgements
This research was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education (NRF-2015R1D1A3A01015882).
0
0
2
2
value (R ) of 0.934 (Adj. R ¼ 0.932). This indicates that in the
sulfamic acid-catalyzed hydrothermal reaction of glucosamine,
a higher CSF, which is a harsh reaction condition, can signi-
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