An integrated effluent free process for the production of 5-hydroxymethyl furfural (HMF), levulinic acid (LA) and KNS-ML from aqueous seaweed extract

Article abstract of DOI:10.1016/j.carres.2020.107953

This paper demonstrates an integrated zero liquid discharge (ZLD) process for time-dependent recovery of 5-hydroxymethyl furfural (HMF), levulinic acid (LA) and potassium, nitrogen and sulphur rich mother liquor (KNS-ML) - manure from agar/agarose contain

Full text of DOI:10.1016/j.carres.2020.107953

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An integrated effluent free process for the production of 5-hydroxymethyl furfural
(HMF), levulinic acid (LA) and KNS-ML from aqueous seaweed extract
Faisal Kholiya, Meena R. Rathod, Doddabhimappa R. Gangapur, S. Adimurthy,
Ramavatar Meena
PII:
S0008-6215(19)30521-X
DOI:
https://doi.org/10.1016/j.carres.2020.107953
CAR 107953
Reference:
To appear in: Carbohydrate Research
Received Date: 30 August 2019
Revised Date: 5 February 2020
Accepted Date: 11 February 2020
Please cite this article as: F. Kholiya, M.R. Rathod, D.R. Gangapur, S. Adimurthy, R. Meena, An
integrated effluent free process for the production of 5-hydroxymethyl furfural (HMF), levulinic acid
(LA) and KNS-ML from aqueous seaweed extract, Carbohydrate Research (2020), doi: https://
doi.org/10.1016/j.carres.2020.107953.
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GRAPHICAL ABSTRACT:

An integrated effluent free process for the production of 5-hydroxymethyl furfural
(HMF), levulinic acid (LA) and KNS-ML from aqueous seaweed extract
Faisal Kholiya,[a] Meena R. Rathod,[a] Doddabhimappa R Gangapur,[a] S. Adimurthy*[a,b]
Ramavatar Meena, *[a,b]
[a] Natural Products & Green Chemistry Division, CSIR-Central Salt & Marine Chemicals
Research Institute, G. B Marg, Bhavnagar-364002 (Gujarat), India
[b] Academy of Scientific and Innovative Research (AcSIR), CSIR-Central Salt & Marine
Chemicals Research Institute, G. B Marg, Bhavnagar-364002, (Gujarat), India
E-mail: RM: rmeena@csmcri.res.in; SA: adimurthy@csmcri.res.in
Abstract: This paper demonstrates an integrated zero liquid discharge (ZLD) process for
time-dependent recovery of 5-hydroxymethyl furfural (HMF), levulinic acid (LA) and
potassium, nitrogen and sulphur rich mother liquor (KNS-ML) - manure from agar/agarose
containing seaweed aqueous solution using transition metal-free KHSO4 as an eco-friendly
and reusable catalyst. The selectivity of HMF is higher at 115 ˚C in 3 h and favorable to LA
in 6 h in autoclave conditions. The proposed concept could be fine-tuned for the selective
production of 5-HMF (up to 91% yield) or levulinic acid (56% yield) in the presence of the
KHSO4 catalyst. We have also achieved recyclability of KHSO4 up to nine (09) cycles and the
gram-scale reaction has been demonstrated. The (KNS-ML) obtained after nine cycles
followed by neutralization with ammonia solution utilized for manure makes the process
zero-liquid discharge and more cost-effective. The efficacy of the KNS-ML after nine cycles
has been tested on groundnut plants.
Keywords: Seaweed biomass; 5-hydroxymethyl furfural (HMF); levulinic acid (LA);
Selective recovery; Transition metal-free catalyst; Manure.
1

Introduction
Nowadays, most fuels and other commodity chemicals are obtained from non-renewable
resources such as fossil fuels, petroleum, coal, and natural gas. Large utilization of fossil fuel
decreases its availability, which leads to higher prices of the petrochemicals. The search for
alternatives to fossil fuel resources which are renewable is of great importance [1]. The
conversion of the biomass into a range of liquid fuels or commodity chemicals has been
proved as an alternative for declining fossil fuel. As several types of liquid fuels, fine
chemicals, and monomers for polymeric materials could be derived from HMF (5-
hydroxymethyl furfural), it has become a potentially important platform chemical [2-6]. It is
one of the prominent intermediate derived from the biomass in the present study. The good
yield or recovery of HMF is mainly from glucose isomerization to fructose followed by direct
conversion of fructose dehydration [7-11]. Most of the methods use either homogeneous or
heterogeneous catalysts to obtain HMF from glucose [12-14]. Although there are advantages
and disadvantages to these methods, to overcome some disadvantages, reactions have been
performed under biphasic systems using various metal-based catalysts [15, 16]. HMF also
can be produced from cellulose in aqueous solutions, but the main disadvantage is low yields
(less than 8%) due to the formation of humins [17, 18]. The large-scale production of HMF
and its purification may pose difficulties when DMSO is used as a solvent [6]. Although, the
microwave-assisted method for the selective production of 5-hydroxymethyl
furfural/levulinic acid has been reported from seaweed-derived agarose, which may not be
easily scalable for industrial production. Some approach also involved sulphuric acid for LA
recovery under the microwave which is highly toxic and corrosive [19]. The main
disadvantage of microwave technology is perhaps the high investment costs and overheating
of sensitive substances [20]. In addition to above approaches for recovery of HMF, presently
reaction criteria like transition metal-free, eco-friendly, organic-solvent-free and sustainable
2

protocol to recover HMF has become a centre of attraction for the researcher. The biomass
conversion to suitable chemicals, fuels, and fuel intermediates represents a major contest
rather than getting these chemicals from sugars.
The biomass that contains less lignin content is advisable for the recovery of HMF - a
potential intermediate for many useful & important chemicals. The seaweed-based biomass
contains lower amount of lignin [21]. There are two main categories of seaweeds (i) macro
algae and (ii) micro algae. The macro algae are classified as red algae, brown algae, and
green algae. Gracilaria spp. is a red seaweed belongs to agarophytes, which account for half
of the world agar production and cultivated on a commercial scale in Israel, Chile, South
Africa, China and Taiwan [15]. Agar/agarose polysaccharides derived from the Gracilaria
spp. is composed of ᴅ-galactose and 3,6-anhydro-ւ-galactopyranose units. These seaweeds-
based polysaccharides are the best choice to recover HMF [22]. Seaweed biomass production
does not require the aerial land, freshwater, and fertilizers for the mass production of
polysaccharides. In India, our Institute is located in the western parts which have the longest
coastal (ca. 1600 km) area available for seaweed cultivation [23]. Our Institute has been
working on the cultivation of commercially important red seaweeds since its establishment (5
decades). Recently, our group has developed a process to extract agar/agarose from cultivated
red seaweeds [24]. In continuation of our research activities on the functional modification of
seaweed polysaccharides [25], we described a simple approach to recover HMF or LA from
the agar/agarose aqueous extract under transition metal-free and organic solvent-free
conditions by elaborating the duration of an autoclave treatment [26].
Results and Discussion
Based on our expertise on the utility of KHSO4 in organic transformations [27-29], we
hypothesized that it may act as selective and safe acid catalyst for the conversion of
agar/agarose to HMF. To test our hypothesis, we subjected the direct conversion of agarose to
3

HMF using KHSO4 as a dehydrating agent under the mild reaction conditions (scheme1,
Table 1). The plausible mechanism for the synthesis of the HMF from the agar/agarose is
depicted in scheme 1.
Scheme 1. A plausible mechanism for the formation of HMF from Agar/Agarose.
Initially, agarose was subjected to dehydrative conversion to HMF and it may be noted
that only 3,6-anhydro-ւ -galactopyranose units convert to HMF [22] and the other unit of
agarose moiety remains as humins and galactose in the aqueous phase [30]. With 5% (w/v) of
aqueous KHSO4, 40% selectivity to HMF was observed with only 23.00% yield at 110°C
conventional heating in an oil bath for nine hours reaction time (Table 1, entry 1). When 10%
(w/v) of aqueous KHSO4 was employed under the same conditions, to our delight over 99%
selectivity (Fig. S1) to HMF was observed with 59.75% yield (Table 1, entry 2). NMR
analysis confirmed the purity of HMF obtained through simple extraction. The NMR
spectrum of the prepared HMF is identical with the pure HMF (Fig. S2).
Table 1. Optimization of conditions for HMF by conversion of agar/agarose [a].
Effect of KHSO4 concentration
Entry KHSO4 Time (h) Selectivity Yield (%) [b]
(% w/v)
(%)
1
2
3
5
9
9
9
40.22
99.65 [c]
91.76
23.00
59.75
61.00
10
20
4

4
5
10
10
6
99.00
92.00
50.0
12
57.00
[a] Conditions: Agarose 2.5 g, aq. KHSO4 solution (50 mL),
conventional heating in an oil bath, selectivity determined by GC-MS.
[b] Isolated yield (based on wt% of starting agarose used)
[c] HMF confirmed by NMR analysis.
After optimization of the conventional heating process (Table 1), autoclave reaction was
conducted for 3 h reaction time at 110 °C under the same reaction conditions, 91% HMF
selectivity was observed with only 30.5% yield (Fig. 1). The reaction parameters were
optimized for the recovery of HMF under an autoclave condition. Firstly, the reaction time
was optimized by keeping the reaction temperature 115 °C and KHSO4 concentration 10%
w/v constant. The yield and selectivity were observed maximum at 3 h, beyond this the yield
and selectivity were decreased. Further, the reaction temperature was optimized by keeping
the KHSO4 concentration 10% w/v and reaction time 3 h constant. The maximum yield and
selectivity were observed at 115°C. For KHSO4 concentration optimization, other reaction
parameters like time and temperature for all the experiments remain same i.e. 3 h and 115 °C
respectively. From all the experiments, the maximum yield 60.18% and selectivity 89% (Fig.
S3) were observed with 10 % w/v KHSO4 at 115 °C temperature for 3 h (Fig. 1). As HMF is
highly useful platform chemical intermediate to check the feasibility for scale-up studies, we
have conducted the reaction at 50.0 g batch for agar under autoclave conditions and observed
64% yield of HMF with 93.1% selectivity even at a gram scale (Fig. S4). This reaction
reveals the large-scale applicability of the method for HMF production.
5

Fig. 1. Optimization of the reaction parameter for the synthesis of HMF. Conditions: Agarose
2.5 g aq. KHSO4 solution (50 mL), autoclave and selectivity determined by GC-MS.
As observed, both conventional and autoclave conditions are favorable for the
conversion of agar or agarose to HMF, only time and temperature are the dependent factors.
Under both conditions, the yield of HMF would be almost identical, but the selectivity is 99%
and 89% with former and later, respectively. From the Table 1 and Fig. 1, it was observed
that as increase in the temperature from 120°C to 130°C levulinic acid (LA) was formed
rather than increase the yield of HMF. The Levulinic acid has been recognized as a platform
chemical for bio-refineries [31] and also an important intermediate for the production of other
useful chemicals such as fuel additives, polymers, and resins [32]. Considering its potential
application, the sustainable recovery or conversion of biomass to LA is the recent focus [33,
34]. Looking to its importance today, the reaction conditions were further optimized to obtain
LA from Agar (Table 2).
6

As observed from the data of table 2, the best selectivity (87.68%) for LA was found
with 10% (w/v) aqueous KHSO4, at 115° C temperature, for 6 h reaction time (Table 2, entry
3). At the end of the process the of KHSO4 ends up in aqueous solution, after the extraction
of HMF into an organic solvent. Then we focused on the recyclability of the entire aqueous
KHSO4 solution, which also contains water-soluble humins. We performed recyclability
studies with 2.5 g batch of agar in each cycle after the extraction of HMF with the organic
solvent, and charged the aqueous part with fresh agar and continued the process up to 9
recycles (HPLC shown in ESI, Fig. S13-21).
Table 2. Optimization of conditions for the conversion of agar to LA.a
Selectivity to d
KHSO4
Time LA Yield
Entry Temp
(wt.%) b
LA
HMF Unidentified
(
w/v %)
(h)
(%)
(%)
products (%)
1
2
3
4
5
6
7
115
115
115
115
120
130
130
10
10
10
10
10
10
20
3
4
6
8
3
3
3
6.79
10.64 89.36
26.98 69.91
-
17.37
3.11
2.02
56.48c
39.91
13.78
40.34
39.1
10.29
87.68
62.23 33.09
20.51 79.49
56.73 39.63
60.86 26.11
4.68
-
3.64
13.03
[a] Conditions: Agar 2.5 g, aq. KHSO4 solution (50 mL), autoclave, selectivity determined
by GC-MS. [b] Crude yield (based on mole% of starting agar used). [c] LA confirmed by
NMR analysis (see ESI, Fig. S22). [d] Selectivity calculated by GC-MS (see ESI, Fig. S5-
S12).
The HMF selectivity and yield for the recyclability studies are depicted in Table S1. The
yield of HMF was marginally increased as the number of cycles increased; it may be because
of the residual HMF from the aqueous layer. It could also explain based on the salt out
process during the recycle experiments as agar polymer having potassium, sodium and other
metal ions, which may help to enhance selectivity and the yield of HMF [35, 36]. Despite the
7

humins formation, the Brønsted acidic property of KHSO4 could not change for the
conversion of agar to HMF up to 9 recycles studied (Table S1). It shows not only the
potential nature of KHSO4 but also its resistance to humins. Hence, it is a suitable and
efficient acid under only aqueous conditions for easy recovery of HMF. To check the
physical form of the KHSO4 after the 9th cycle whether it remains in its original form as
KHSO4 or converted to K2SO4, we performed the control experiments using K2SO4 in place
of KHSO4. We observed no conversion with K2SO4 and recovered agar completely. This
experiment suggests that only KHSO4 promotes the conversion but not K2SO4.
As seen from Fig. S2 (a), the proton NMR of HMF, the peak at 4.66 ppm (peak no 4)
singlet corresponds to methylene (-CH2-), and the two singlets at 6.64 and 7.50 ppm
correspond to two aromatic protons of HMF (peak nos. 3 and 2 respectively). The aldehyde
proton appears at 9.42 ppm (peak no. 1). Similarly, from Figure 1(b), the 13C-NMR peaks for
HMF at 59.01 ppm (peak no. 1) correspond to methylene carbon. The four aromatic carbons
at 164.33, 113.97, 129.88, and 154.80 ppm correspond to peak nos. 2-5 respectively. The
1
13
carbonyl carbon peak (no. 6) appeared at 183.45 ppm. Both H and C-NMR spectra were
well matched and are in good agreement with the reported spectra [37].
The total acids mainly play the role of the catalytic activity of the catalyst for the
recovery of the HMF [38-40]. Ammonia-temperature programmed desorption (NH3-TPD)
was used to determin total acidity of the catalyst at the temperature between 100-600°C. Fig.
2 shows the NH3-TPD graph in which we observed two major peaks, first in the range of 200-
250°C and the second one is nearly 410°C. The presence of two peaks shows that the catalyst
has two types of acid sites. The low-temperature peak is for the lower strength of the acid site.
These acid sites may be of Lewis acidic nature. The high-temperature peak attributes towards
the strong strength acid site of the catalyst. The strong acid site must be because of the
Brønsted acidic property of KHSO4 [41-44]. Bronsted and Lewis acid properties of the used
8

catalyst (KHSO4) may be favorable for the formation of HMF with a significant yield.
Brønsted acid leads to break the glycosidic bond and 3,6-anhydrogalactopyronose unit of the
agarose while Lewis acid caused dehydration reaction to form the HMF [45].
Fig. 2. NH3-TPD of KHSO4.
In the present study, potassium, nitrogen, and sulphur-rich mother liquor (KNS-ML)
obtained after 9 cycles followed by neutralization with ammonia solution was tested as
manure for agriculture (agronuetrients) to make the process zero-liquid discharge. The
contents of the potassium, nitrogen and sulphur in the KNS-ML was found to be 10.4%, 9.2%
and 17.4%, respectively. Nitrogen and sulphur are essential elements for the protein and may
increase the yield of crops. Potassium promotes to increase the number of bunches, weight,
fruit number, and size of the fruits [46-49]. Hence, the obtained KNS-ML was tested on the
groundnut (Groundnut Gujarat-20) crop for their efficiency at laboratory scale using 18
groundnut plants. To check the fertilizer efficacy of KNS rich KNS-ML, we used the solution
of 10%, 20% and 30% as a foliar spray in 30 days, 60 days and 90 days after sowing. The
effect of the fertilizer is mentioned in Table 3 and can see the significant changes that
happened to yield better and plant growth. The height of the plant in a control study was 31.5
9

cm while with KNS-ML it was increased to 32.9 cm. It also increases the percentage of the
oil content in groundnut plant after the spraying KNS-ML (Table 3; ESI, Fig. S23). From the
results, we can conclude that the mother liquor obtained after the recycling batch has
significate efficiency for using as fertilizer.
Table 3. Fertilizer efficacy of KNS rich mother liquor on Groundnut plants.
Experiments
Parameters measured
Plant
height
(cm)
Number of
primary
branches
per plant
(NPB)
Number of
Secondary
branches per
plant (NSB)
Pod
yield
per
plant
(gm)
(PYP)
Number
of kernels content
per plant
(NKP)
Oil
(%)
31.5
32.9
2.5
2.7
2.7
2.8
3.5
6.5
7.2
33.20
37.33
Control (spray
with water)
3.6
Mother
liquor/Manure
Conclusions
We have developed an integrated and zero liquid discharge process for the production of
multiple valuable products such as HMF, LA, and potassium, nitrogen and sulphur (KNS)
rich KNS-ML manure from agar/agarose aqueous solutions using transition metal-free
KHSO4 as a promoter. Aqueous solutions of agar/agarose were obtained from the red
seaweed G. dura collected from the west coast, Gujarat, India and subjected to the present
conditions to obtain HMF and LA at 115°C for 3 h and 6 h respectively in an autoclave.
Under conventional heating (oil bath) at 110° C, over 99% selectivity to HMF was observed,
and no conversion to LA on elaboration reaction time. We can recycle the aqueous KHSO4
along with water-soluble humins up to 9 cycles and observed with almost constant selectivity
of HMF with increased yield. We have also checked the feasibility of the present process at a
10

50 g scale. The major advantages of the method are: (i) the process is an organic solvent-free,
(ii) transition metal-free conditions, (iii) recyclability of the aqueous KHSO4, and (iv)
suitability for scale-up preparation of HMF with simple purification system. Another main
advantage is to obtain KNS rich mother liquor (KNS-ML) after 9 cycles, which shows good
efficacy on groundnut plants.
Experimental Section
Chemical
Agar/agarose rich aqueous solutions were prepared in our laboratory from the red
seaweed Gracilaria dura (G. dura) using the previously described method [50, 51].
Potassium hydrogen sulphate was purchased from (KHSO4) Sisco Research Laboratories Pvt.
Ltd. 5- hydroxymethylfurfural was purchased from Spectrochem Pvt. Ltd. Mumbai, levulinic
acid was purchased from TCI Chemicals (India) Pvt. Ltd. Ethyl acetate was purchased from
Fisher Scientific India Pvt. Ltd.
General procedure for the synthesis of HMF and LA
In a typical procedure, 2.5 g of agar/agarose was added into 50 mL water under stirring
followed by the addition of transition metal-free KHSO4 between 5-20% w/v. This reaction
mixture was cooked on the oil bath or in the autoclave as per described conditions in Table 1,
Table 2 and Table 3. After completion of the reaction, the reaction mixture then extracted by
ethyl acetate and collected the organic layer and analysed by GC-MS. The collected organic
aliquot was dried in a vacuum dryer and weight for the calculation of yield using eq. (1)
reported earlier [22]. For the recycle, after the extraction of HMF by ethyl acetate, the
aqueous layer was collected and made up to 50 mL if required. Then 2.5 g of agar/agarose
was added and put into an autoclave at 115 °C for 3 h. After completion of the reaction, HMF
was extracted using ethyl acetate and purity was checked by HPLC. The aqueous layer was
further recycled for the synthesis of HMF. We tested the recycling efficiency of the catalyst
11

up to 9 cycles. The mother liquor obtained after 9 cycles was treated with an ammonia
solution to adjust the pH to neutral and used as KNS rich KNS-ML.
W
× MW
Ag
HMF/LA
ꢀ
ꢁ
% Yield HMF/LA = W
×100
…… eq. (1)
× MW
Ag
HMF/LA
Where, WHMF/LA = weight of the HMF or LA obtained, MWAg = molecular weight of agarose,
WAg = weight of the agarose taken & MWHMF/LA = molecular weight of HMF or LA.
GC-MS analysis
The collected dried HMF sample was diluted with ethyl acetate and analyzed with
Shimadzu Gas Chromatography-Mass Spectrometer (GCMS-TQ8040) equipped with Rtx-
5ms column (30 m × 250 µm × 0.25 µm). The oven temperature was initially 40°C and rose
to 300°C at 15°C/min. The initial temperature was held for 3 min while the final for 10 min.
The flow rate of the carrier gas was 1 mL/min.
HPLC analysis
The collected dried HMF sample was diluted with ethyl acetate using HPLC (Shimadzu
Liquid Chromatography) using SPD Detector SPD M-10A with C18 column (Phenomenex;
50 × 4.6 mm; 5 µm particle size) and acetonitrile and water (30:70 v/v) as a mobile phase in
an Isocratic mode with 0.6 mL/min flow rate.
NMR analysis
The dried optimized HMF sample (Table no. 1 Entry no. 2 and Table no. 3 Entry no. 3)
were solubilized in D2O and 13C (at ~150 MHz) and 1H (at 600 MHz) Spectra were recorded
at ambient temperature using JEOL- (Ec-z600R).
NH3 TPD analysis
Total acidity was measured by NH3-TPD. NH3-TPD measured by Sprint Testing
Solutions using ASAP 2920; M/s Micromeritics Instrument Corp., Norcross GA, USA
analyzer.
Elemental analysis
12

The mother liquor obtained after the recycling batches of HMF synthesis has been
neutralized with ammonia solution followed by freeze drying to obtain the solid dried product
for elemental analysis. The Total Nitrogen content was estimated by Standard Semi-micro-
Kjeldahl method and Potassium was determined using Flame Photometry (Flame Photometer
128, Systronics, India) according to the method prescribed by previous literature [52].
Sulphur was determined by gravimetrically using BaCl2.
Acknowledgments
CSIR-CSMCRI communication No. CSIR-CSMCRI – 177/2017. We thank Science and
Engineering Research Board (SERB), DST, Government of India (EMR/2016/004944) and
CSIR-CSMCRI (OLP-088) and for CSIR-SRF to F. Kholiya for financial support. F. Kholiya
is also thankful to CHARUSAT for his Ph.D. enrollment and the “Analytical Discipline and
Centralized Instrument Facility” for providing instrumentation facilities.
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19

Highlights:
•
•
•
•
Time dependent recovery of HMF and LA directly from seaweed extracts.
Solid acid KHSO4 used as catalyst for the first time in this study.
Recyclability of catalyst up to nine cycles was achieved at gram scale reaction.
Another main advantage is to utilise aqueous phase as manure after successful
recycling up to 9 cycles.

Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: