Production of γ-Valerolactone from One-Pot Transformation of Biomass-Derived Carbohydrates Over Chitosan-Supported Ruthenium Catalyst Combined with Zeolite ZSM-5

Article abstract of DOI:10.1002/ejoc.201901704

It remains as a challenge to directly transform the biomass-derived C5 carbohydrates, such as furfural (FF) and its upstream product xylose and hemicellulose, to γ-valerolactone (GVL), a versatile renewable chemical platform, due to various restrictions in the current synthetic strategies. Using formic acid as green hydrogen source, we synthesized the recyclable chitosan-Ru/PPh₃ catalyst system, effective for both the hydrogenation of FF to furfuryl alcohol (FAL) and the reduction of levulinic acid (LA) or ethyl levulinate (EL) to GVL, affording up to 99 % product yields. The combination of chitosan-Ru/PPh₃ with ZSM-5 could successfully achieve up to 79 % yield of GVL from one-pot conversion of FF under mild condition. Preliminary studies indicated that this method could also be applied to the direct conversion of biomass-derived C5 carbohydrates such as xylose and hemicellulose to GVL in 37 % or 30 % yield, respectively.

Full text of DOI:10.1002/ejoc.201901704

DOI: 10.1002/ejoc.201901704
Full Paper
Biomass Conversion
Production of γ-Valerolactone from One-Pot Transformation of
Biomass-Derived Carbohydrates Over Chitosan-Supported
Ruthenium Catalyst Combined with Zeolite ZSM-5
Tianlong Wang,[a] Jianghua He,*[a] and Yuetao Zhang*[a]
Abstract: It remains as a challenge to directly transform the linic acid (LA) or ethyl levulinate (EL) to GVL, affording up to
biomass-derived C5 carbohydrates, such as furfural (FF) and its 99 % product yields. The combination of chitosan-Ru/PPh3 with
upstream product xylose and hemicellulose, to γ-valerolactone ZSM-5 could successfully achieve up to 79 % yield of GVL from
(GVL), a versatile renewable chemical platform, due to various one-pot conversion of FF under mild condition. Preliminary
restrictions in the current synthetic strategies. Using formic acid studies indicated that this method could also be applied to the
as green hydrogen source, we synthesized the recyclable chi- direct conversion of biomass-derived C5 carbohydrates such as
tosan-Ru/PPh3 catalyst system, effective for both the hydrogen- xylose and hemicellulose to GVL in 37 % or 30 % yield, respec-
ation of FF to furfuryl alcohol (FAL) and the reduction of levu- tively.
Introduction
from one-pot conversion of the abundant biomass-derived C5
carbohydrates such as furfural, xylose and hemicellulose. How-
ever, only a handful of catalyst systems have been developed
to accomplish this goal so far.[16–20] Such as Román-Leshkov
and co-workers achieved a 78 % yield of GVL from the domino
reaction catalyzed by zeolites with both Brønsted and Lewis
acid catalyst sites in 2013.[16] Later, bifunctional Zr-Al-Beta zeo-
lite prepared through a post-synthetic route obtained GVL in
22.6 % or 34 % yield from one-pot conversion of FF or xylose
in 2-propanol, respectively.[17] The combination of Au/ZrO2 and
ZSM-5 could achieve an 80.4 % yield of GVL from one-pot con-
version of FF.[18] In 2018, hafnium-based metal-organic frame-
works was combined with Brønsted-acidic Al-beta zeolite to fur-
nish a 75 % yield of GVL from one-pot conversion of FF.[19] Het-
eropoly acid supported on Zr-Beta zeolite was also reported to
obtain GVL in 68 % yield from one-pot transformation of FF.[20]
As one of three important components (cellulose, hemicellulose
and lignin) in lignocellulosic biomass,[1] hemicellulose is highly
underutilized.[2] Furfural (FF), the main products obtained from
hemicellulose, is considered as one of the top ten value-added
platform chemicals[3] for production of energy fuels and various
useful chemicals such as furfuryl alcohol (FAL),[4] furoic acid,[5] 2-
methylfuran,[6] maleic anhydride,[7] γ-valerolactone (GVL)[8] etc.
Among these, GVL is of particular interests since it could serve
as a versatile biomass-derived platform chemical due to its ex-
cellent properties as green solvent[9] and fuel additive as well
as precursor for the synthesis of various liquid alkenes[10] and
renewable biopolymers.[11] Compared with fructose derived
from cellulose, FF originated from hemicellulose is more suit-
able for the production of GVL and exhibits better carbon atom
economy since it does not lose one carbon during the produc-
tion of levulinic acid (LA).[12] In general, several steps are re-
quired for the production of GVL including the hydrogenation
of FF to FAL,[13] the subsequent alcoholysis of FAL to LA or alkyl
levulinate,[14] and then hydrogenation of LA or alkyl levulinate
to corresponding 4-hydroxypentanoates (4-HPs), followed by
the lactonization of 4-HPs to generate GVL.[15] For economic
and cost-saving purpose, it is more desirable to produce GVL
To avoid using high-pressure H2 (> 30 bar) as hydrogen
source like cellulose protocol did,[12a] it is essential to explore
green hydrogen sources for the production of biomass-derived
GVL. In addition to 2-propanol employed in the Meerwein–
Ponndorf–Verley reduction, formic acid (FA) is also considered
to be an alternative and renewable hydrogen source for hyd-
rogenation reaction, such as the reduction of unsaturated C=
C[21] and C=O bond,[22] exhibiting better performance than gas-
eous hydrogen due to its high hydrogen density and easy ac-
cess from the hydrogenolysis of cellulose.[23] Both the homoge-
neous and heterogeneous ruthenium(Ru)-based catalyst could
promote the decomposition of HCOOH for the production of
GVL from LA. Such as a recyclable RuCl3/PPh3/pyridine catalyst
system produced an 95 % yield of GVL from LA[22d] whereas
Ru/C catalyst furnished a 57 % yield of GVL from LA.[24] How-
ever, no bio-derived, recyclable Ru-based catalyst was reported
[a] State Key Laboratory of Supramolecular Structure and Materials, College
of Chemistry, Jilin University,
Changchun, Jilin 130012, China
E-mail: hjh2015@jlu.edu.cn
ytzhang2009@jlu.edu.cn
Yuetao Zhang: http://supramol.jlu.edu.cn/info/1030/1894.htm
Jianghua He: http://chem.jlu.edu.cn/info/1029/3915.htm?admin=admin
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.201901704.
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Scheme 1. One-pot conversion of FF (xylose, hemicellulose) to GVL by chitosan-Ru/PPh3 combined with ZSM-5.
for conversion of the biomass-derived C5 carbohydrates to GVL ing vibration of amino and hydroxyl group in chitosan was
by using HCOOH as green hydrogen source so far.
shifted to the broader peak centered at 3371 cm–1, and the
1420 cm–1 peak in the chitosan[25] belong to the bending vibra-
tion of –OH also weakened, which suggested the coordination
of Ru ions to the N and O atom in the chitosan-Ru. As shown
in XPS characterization of the chitosan-Ru (Figure 1b), energy
peaks at 463.9 and 486.1 eV were attributed to the Ru3+ 3p1/
As a biodegradable and inexpensive amino-polysaccharide
with high binding affinity for transition-metal ions,[25] chitosan
is commonly employed as catalyst support to generate hetero-
geneous chitosan supported metal complexes (chitosan-M) for
various catalytic applications in organic synthesis.[26] We envi-
sioned that the employment of biomass-derived chitosan-M
might enable us to achieve one-pot conversion of FF to GVL by
using HCOOH as hydrogen source. Here we synthesized a series
of chitosan-M (M = Ru, Pd, Co, Ni) and found that chitosan-Ru/
PPh3 system is highly effective for both the hydrogenation of
FF to FAL and reduction of LA/alkyl levulinate to GVL, achieving
up to 99 % product yield by using HCOOH as hydrogen source.
The combination of chitosan-Ru/PPh3 with ZSM-5 zeolite
(Scheme 1) successfully achieved one-pot transformation of
biomass-derived carbohydrates such as FF as well as its up-
stream product such as xylose or hemicellulose to GVL in 79 %,
37 %, or 30 % yield, respectively. Corresponding reuse and recy-
cle experiments were also included in this study.
and 3p3/2 bands, which further revealed that Ru species is
2
trivalent.[27] As shown in Figure 1c, powder XRD spectra of chi-
tosan-M and the recovered chitosan-Ru catalyst revealed that
the fresh-prepared is similar with that of the recovered chi-
tosan-Ru. According to ICP measurement (Table S1), the corre-
sponding metal loading in chitosan-M (M = Ru, Pd, Co, Ni) is
6.14 wt.-% for Ru, 5.18 wt.-% for Pd, 5.82 wt.-% for Co and 5.40
wt.-% for Ni, respectively. TG analysis (Figure 1d) revealed that
the framework of both the synthesized chitosan-Ru complex
and chitosan could be maintained up to 200 °C. The CO2 and
NH3-temperatured program desorption (TPD) spectra showed
that the biomass-derived chitosan-Ru had both acidic and basic
catalyst sites (Figure S5), which are significantly important for
the decomposition of FA and the subsequent hydrogenation
reaction.[28]
Results and Discussion
Catalyst Characterization
Catalytic Hydrogenation of the C=O Bonds in FF and
Other Substrates
After the synthesis of chitosan-Ru (check experimental section
for details), we collected filtrate and recrystallized it with acet- Using FF as substrate and HCOOH as hydrogen source, control
one to furnish white solids in 88 % yield. Upon heating the experiments showed that chitosan is completely ineffective for
obtained white solids in NaOH solution, the wet red litmus pa- hydrogenation of FF to FAL (entry 1, Table 1) while chitosan-Ru
per became blue color revealed the existence of ammonium only obtained 33 % yield of FAL at 120 °C for the hydrogenation
ions in the filtrate. Adding white solids to AgNO3 solution acidi- of FF (entry 2, Table 1), which implied that both chitosan and
fied by HNO3 led to the formation of white flocculent precipi- chitosan-Ru are not efficient catalysts for the decomposition
tates immediately, which suggested that the chloride ions of of FA. Therefore, a series of additives were examined for their
RuCl3 was retained in the filtrate rather than on the synthesized effectiveness on the reaction (Table S2). It turned out that the
chitosan-Ru and the obtained white solids should be NH4Cl. It highest FAL yield of 99 % was achieved by the combination of
should be noted that NH4Cl was generated from the neutraliza- triphenylphosphine (PPh3) with chitosan-Ru (entry 1, Table S2).
tion of HCl released from the reaction of chitosan with RuCl3 It is also noted that solvents with medium polarity (i.e. CH2Cl2,
by ammonia (NH3·H2O). FT-IR spectra of the synthesized chi- ethanol, THF) exhibited comparable activity towards the de-
tosan-Ru complex and chitosan (Figure 1a) indicated that chi- composition of formic acid and the subsequent hydrogenation
tosan-Ru maintained the similar framework with that of chi- reaction. However, solvents with the higher or lower polarity
tosan. The peak centered at 3433 cm–1 attributed to the stretch- such as DMF and TOL would drastically slow down the reaction
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Figure 1. (a) FT-IR spectra of chitosan-Ru and chitosan; (b) XPS spectra of chitosan-Ru and recovered chitosan-Ru from the transformation of FF to FAL;
(c) overlay of Powder XRD spectra of chitosan and various chitosan-M complexes; (d) TGA curves of chitosan and chitosan-Ru.
(Table S3). THF displayed the best catalytic performance among than by the H2 decomposed from FA. With the identification
the investigated solvents. Combined with the screening results of the excellent hydrogenation system of chitosan-Ru/PPh3, we
of the other parameters (Tables S2 and S3), hydrogenation of further expanded the scope of substrates for hydrogenation
FF was carried out with a 3 mol-% catalyst loading, 8 mg of and achieved above 95 % alcohol yields for all substrates with
PPh3 and 5 equiv. HCOOH at 120 °C to examine the effective- a C=O bond (entries 11-16, Table 1). The fact that a 95 % yield
ness of different catalysts in THF. In sharp contrast to chitosan- of cinnamyl alcohol was obtained for the hydrogenation of
Ru, neither chitosan-Co nor chitosan-Ni works for the reaction cinnamaldehyde indicated the excellent selectivity of chitosan-
(entries 4 and 5, Table 1) and chitosan-Pd only obtained 10 % Ru/PPh3 catalyst system for the reduction of aldehyde groups
FAL yield (entry 6, Table 1). The reactivity difference between (C=O) rather than C=C under such condition (entry 13, Table 1).
these chitosan-M (M = Co, Ni, Pd) and chitosan-Ru might be Moreover, chitosan-Ru/PPh3 only obtained in 10 % yield from
attributed to their metallicity differences resulting from the dif- the hydrogenation of acetophenone after heated at 120 °C for
ferent metal centers.[21a,29] The employment of RuCl3 obtained 8 h (entry 15, Table 1). Increasing reaction temperature to
30 % yield of FAL (entry 8, Table 1), which may due to the ab- 160 °C resulted in the significantly enhanced yield of 98% for
sence of base additive. Previous studies indicated the employ- 1-phenylethanol (entry 16, Table 1). These results prompted us
ment of Ru0/C as catalyst achieve 80.7 % GVL yield from LA in to apply the chitosan-Ru/PPh3 catalyst system to the hydrogen-
the presence of FA, but with the requirement of Et3N.[30] In ation of levulinic acid (LA) and ethyl levulinate (EL). Similar to
sharp contrast, only 8 % yield of FAL was obtained by zero- the reduction of acetophenone, hydrogenation of LA with
valent ruthenium support on carbon (Ru/C, entry 7, Table 1), HCOOH performed at 120 °C only afforded GVL in 20 % yield
which might be attributed to the absence of basic sites in (entry 1, Table S4), probably due to the absence of conjugated
Ru/C. It is noted that the hydrogen source is also essentially system and larger steric hindrance of ketone structure in LA
important to the hydrogenation of FF. Replacing HCOOH with than that of aldehyde group in FF.[31] Increasing reaction tem-
HCOONa only furnished 6 % yield of FAL (entry 10, Table 1) perature resulted in the significantly enhanced GVL yield
while using 10 bar H2 as hydrogen source will quench the (140 °C, 56 %, entry 2, Table S4 and 160 °C, 99 %, entry 17,
hydrogenation reaction (entry 9, Table 1), which indicated that Table 1). Switching to EL, a 97 % GVL yield were achieved under
the hydrogenation of FF was through hydrogen transfer rather similar condition (entry 18, Table 1). These results further
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Table 1. Transfer hydrogenation using FA as hydrogen source.[a]
[a] Conditions: 0.5 mmol substrate, 3 mol-% catalyst, 6 mol-% PPh3, 5 equiv. FA in 1 mL THF. [b] Yield was determined by GC analysis using naphthalene as
internal standard. [c] H2 as hydrogen source instead of HCOOH. [d] HCOONa was used as hydrogen source instead of HCOOH.
demonstrated the excellent catalytic performance of chitosan- both the hydrogenation of FF to FAL and reduction of LA (or
Ru/PPh3 system on the hydrogenation of LA or EL to GVL.
AL) to GVL (achieving up to 99 % product yield for both case),
we envisioned that an effective, Brønsted acidic alcoholysis rea-
gent might be the missing piece from the chitosan-Ru/PPh3
catalytic system to enable us to accomplish one-pot conversion
of FF to GVL. After digging literature, we found that commer-
Production of GVL from One-Pot Conversion of FF, Xylose
and Hemicellulose to GVL
The successes achieved in the hydrogenation of FF and reduc- cially available, acidic zeolite ZSM-5 is highly effective for the
tion of LA or EL inspired us to examine the effectiveness of transformation of FAL to AL[32] and the mechanism of alcoholy-
chitosan-Ru/PPh3 system for one-pot conversion FF to GVL in sis of FAL to allyl levulinate by Brønsted acid catalyst has also
THF. However, no GVL was produced probably due to the ab- been studied.[33] Therefore, acidic zeolite ZSM-5 was employed
sence of effective reagent for the alcoholysis of FAL to alkyl to combine with chitosan-Ru/PPh3 system and ethanol was
levulinate (AL) during the conversion of FF to GVL. The use of used as both green solvent and alcoholysis reactant for the
ethanol as solvent still did not obtain GVL, producing FAL in tandem conversion of FF to GVL. We systematically investigated
96 % yield instead (entry 1, Table 2). According to the reaction the influences of the dosage of FA, ZSM-5, chitosan-Ru catalyst,
route (Scheme 1), Brønsted acidic catalyst is required to pro- and PPh3 on one-pot conversion of FF heated at 160 °C for 30 h
mote the alcoholysis of FAL to AL in the tandem conversion of (Figure 2). It turned out the optimal results were achieved by
FF to GVL. Since chitosan-Ru/PPh3 system is highly effective for the experiment performed with 3 mol-% catalyst loading of chi-
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Table 2. One-pot conversion of FF, xylose and hemicellulose to GVL.[a]
Entry
Substrate
Catalyst
Other product,
yield[b] [%]
GVL
yield[b] [%]
1
2
3
4
FF
FF
FF
FF
Chitosan-Ru
FAL, 96
EL, < 1
EL, 24
0
Chitosan-Ru/ZSM-5(Si:Al = 25)
Chitosan-Ru/ZSM-5(Si:Al = 80)
Chitosan-Ru/ZSM-5(Si:Al =200)
Chitosan-Ru/ZSM-5(Si:Al = 25)
Chitosan-Ru/ZSM-5(Si:Al = 25)
Chitosan-Ru/ZSM-5(Si:Al = 25)
Chitosan-Ru/ZSM-5(Si:Al = 25)
79
44
34
26
37
23
30
EL, 32
5[c]
6[d]
7[c]
8[d]
xylose
xylose
hemicellulose
hemicellulose
EL, < 1
EL, < 1
EL, < 1
EL, < 1
[a] Conditions: 0.5 mmol FF, 3 mol-% catalyst, 8 mg of PPh3, 200 mg of ZSM-5 (except entry 1) and 5 equiv. FA in 1.2 mL ethanol, heated at 160 °C for 30 h.
[b] Yield were determined by GC analysis using naphthalene as internal standard. [c] Heated at 170 °C for 30 h. [d] Addition of 10 equiv. of H2O and heated
at 170 °C for 30 h.
tosan-Ru, 8 mg of PPh3, 200 mg of ZSM-5 (Si:Al = 25:1) and of FA, thus being beneficial for the hydrogenation.[36] Therefore,
5 equiv. FA, furnishing 79 % GVL yield (Entry 1, Table 2). It the presence of PPh3 is also crucially important for the reaction.
should be noted that in the presence of PPh3, chitosan-Ru could Without PPh3, only 30 % yield of GVL could be produced from
achieve 99 % product yield from the hydrogenation of FF to one-pot conversion of FF. As far as ZSM-5 is concerned, its
FAL at 120 °C and transformation of LA or AL to GVL at 160 °C strong Brønsted acidity enabled us to successfully achieve one-
whereas only 80 % yield of GVL was obtained for one pot con- pot conversion of FF to GVL by connecting the hydrogenation
version of FF at 160 °C, which might be attributed to the forma- of FF to FAL and transformation of AL to GVL. Furthermore, the
tion of humins, resulting from the self-polymerization of furfural employment of ZSM-5 (Si:Al = 25, entry 2, Table 2) with the
at high temperature.[34] Previous studies indicated that PPh3 lower Si/Al ratio exhibited better catalytic performance than
can act as an electron-donor additive[35] and have a weak inter- that by ZSM-5 with higher Si/Al ratio (Si:Al = 80 or 200, entries
action with Ru3+ ions, which can facilitate the decomposition 3 and 4, Table 2), indicating the higher content of Al atom
Figure 2. Effect of the dosage of FA, ZSM-5, chitosan-Ru and PPh3 of the one-pot conversion of FF to GVL at 160 °C for 30 h. Conditions: (a) 0.5 mmol FF in
1 mL ethanol, 3 mol-% chitosan-Ru, 8 mg of PPh3, 200 mg of ZSM-5, 160 °C and 30 h; (b) 0.5 mmol FF in 1 mL ethanol, 3 mol-% chitosan-Ru, 8 mg of PPh3,
5 equiv. 160 °C and 30 h; (c) 0.5 mmol FF in 1 mL ethanol, 3 mol-% chitosan-Ru, 200 mg of ZSM-5, 5 equiv. formic acid, 160 °C and 30 h; (d) 0.5 mmol FF in
1 mL ethanol, 200 mg of ZSM-5, 5 equiv. FA.
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might be beneficial for the sufficient alcoholysis of FAL to EL examined the effectiveness of chitosan/PPh3/ZSM-5 system for
due to its higher Brønsted acidity.
the one-pot conversion of xylose and hemicellulose, and fur-
nishing GVL in 26 % and 23 % yield after heated at 170 °C for
30 h, respectively (entries 5 and 7, Table 2). It is reported that
the mixing of water with organic solvents is beneficial for the
degradation of xylose and xylan to furfural.[38] Investigation
towards the effects of water on the reaction showed that the
addition of 10 equiv. of water led to a slightly enhanced GVL
yield of 37 % and 30 % for xylose and hemicellulose, respec-
tively (entries 6 and 8, Table 2). However, further increase of the
amount of water showed no more improvements on the GVL
yield.
Under the optimized conditions, we also investigated the re-
action kinetics of one-pot conversion of FF to GVL (Figure 3). It
should be noted that FAL and 2-(Ethoxymethyl)furan (EMF) ini-
tially generated and then disappeared after being heated at
160 °C in less than 1 h, which indicated both the hydrogenation
of FF to FAL and the alcoholysis of FAL to EL are rapid processes,
consisting with the results as shown in Figure 2. After that, only
EL is shown to be gradually transformed into GVL, this step
proceeded relatively slow, thus being the rate-determining step
of the one-pot conversion FF to GVL.
Proposed Mechanism for the One-Pot Hydrogen Transfer
of Furfural to GVL with Formic Acid (FA)
Based on the experimental details and previous litera-
tures,[29b,29c,39] we proposed a possible reaction mechanism for
the above-mentioned one-pot FF conversion to GVL
(Scheme 2). It is noted that both Ru3+ ions and N atoms in the
chitosan-Ru can serve as the possible active catalyst sites. Dur-
ing chitosan-Ru-catalyzed FF conversion to FAL in the presence
of PPh3, the electronegative N atoms acted as a base to adsorb
FA to the catalyst surface. The H+ of FA was captured and the
HCOO– was coordinated with Ru3+ ions, which led to the gener-
ation of Ru-H– species along with the release of CO2. The reduc-
tion of C=O bonds in FF by both H+ and Ru-H– species resulted
in the formation of FAL. The alcoholysis of FAL to EL catalyzed
by ZSM-5 adopted the similar reaction pathway as reported in
the previous mechanistic studies.[33] With the catalysis of chi-
tosan-Ru, hydrogenation of the produced EL afforded 4-HPs,
which was further converted to GVL through the lactoniza-
tion.[16,40]
Figure 3. Kinetic behaviour of the one-pot production of GVL from FF. Reac-
tion conditions: 0.5 mmol FF, 3 mol-% chitosan-Ru, 8 mg of PPh3, 5 equiv.
HCOOH, 200 mg of ZSM-5, 1 mL ethanol, 160 °C and 30 h.
Current synthetic strategy employs LA or AL as the starting
material for production of GVL, but generally LA needs to be
highly purified. To reduce the production cost, it would be more
desirable to directly synthesize GVL from one-pot transforma-
tion of abundant biomass resources such as xylose (the major
intermediate produced during the hydrolysis of hemicellulose
to FF) or hemicellulose (one of three important components
Recycle and Reuse Experiments
in lignocellulosic biomass). Since the strong acidic ZSM-5 was The recycle and reuse experiments were carried out to examine
previously reported for the degradation of xylan to FF,[37] we the economical and environment-friendly feature of chitosan-
Scheme 2. Proposed mechanism for the one-pot conversion of furfural into GVL with HCOOH as hydrogen source and ZSM-5 as connected catalyst.
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Ru/PPh3 catalyst system. After the completion of the reaction, ation of FF to FAL and reduction of LA or alkyl levulinate to GVL
catalysts were collected by filtration and washed by ethanol. by using formic acid as green hydrogen source, achieving up
After dried at 50 °C under vacuum for 5 h, the recovered cata- to 99 % product yield under mild condition for both cases. The
lysts were used for the next run. XPS spectra revealed that the recycle and reuse experiments demonstrated the good
recovered chitosan-Ru is similar with the fresh-prepared one recyclability of chitosan-Ru/PPh3 system for both hydrogenation
(Figure 1b). In addition, ICP analysis indicated that there was of FF and reduction of LA or alkyl levulinate. Moreover, the
only 0.04 % and 0.64 % metal weight percent decrease for FF combination of acidic zeolite ZSM-5 with chitosan-Ru/PPh3
to FAL and LA to GVL respectively in the recovered catalyst could successfully realize a one-pot conversion of FF to GVL in
compared with the fresh-prepared catalyst (Table S1). Over up to 79 % yield. More importantly, this method enabled us to
90 % yield of FAL could be achieved even after five runs of achieve a 37 % or 30 % yield of GVL from a one-pot catalytic
hydrogenation of FF by chitosan-Ru/PPh3 (Figure 4a) while over transformation of xylose or hemicellulose respectively. These
80 % GVL yield could be obtained after five runs of hydrogen- results should stimulate future efforts in developing highly ef-
ation of LA by chitosan-Ru/PPh3(Figure S2). These results con- fective catalyst system for the tandem conversion of the bio-
firmed the good recyclability of chitosan-Ru/PPh3 catalyst sys- mass-derived carbohydrates to GVL, thereby further expanding
tem for both hydrogenation of FF to FAL and reduction of LA the application of GVL in future.
to GVL. For one-pot conversion of FF to GVL by chitosan-Ru/
PPh3/ZSM-5, GVL yield was drastically decreased to 49 % after
five runs as Figure 4b, which might be ascribed to the gradual
loss of chitosan-Ru catalyst during each recycle.
Experimental Section
Materials
Chitosan (medium viscosity, 98 %), xylose (98 %), ruthenium(III)
chloride (RuCl3, 99 %), palladium chloride (PdCl2, 98 %), cobalt
chloride (CoCl2, 97 %), nickel chloride (NiCl2, 97 %), furfural (FF,
98 %), furfuryl alcohol (FAL, 98 %), levulinic acid (LA, 98 %), ethyl
levulinate (EL, 98 %), γ-valerolactone (GVL, 98 %), benzaldehyde
(99 %), benzyl alcohol (99 %), anisaldehyde (98 %), anisalcohol
(98 %), octanal (98 %), octanol (98 %), cinnamaldehyde (98 %),
acetophenone (98 %), 1-phenylethanol (98 %) were purchased from
Energy Chemical. Hemicellulose (reagent grade, 90 % xylan) was
purchased from Sigma-Aldrich Chemical. Formic acid (HCOOH,
99 %), sodium formate (HCOONa, 98 %) and ammonia (NH3·H2O,
28 %) were purchased from J&K company. H-type ZSM-5 (Si:Al = 25,
80, 200) (surface area: 340 m2/g; pore size: 0.5 nm) were purchased
from Nankai university catalyst Co., Ltd. Ethanol and other solvents
were purchased from Adamas company and directly used without
any purification.
Synthesis and Characterization of Chitosan-M Complexes (M =
Ru, Pd, Co, Ni): Chitosan-M complexes were prepared according to
a modified procedure.[26a] Taking chitosan-Ru as an example, chi-
tosan (600 mg) and 100 mg of RuCl3 was suspended in 20 mL of
distilled water and the pH was adjusted and maintained between
9 or 10 by 28 % ammonia. After stirred overnight at room tempera-
ture (RT), the black solids were collected by filtration and washed
by ethanol for three times, and then dried at 50 °C under vacuum
for 5 h. The colourless filtrate indicated that most of ruthenium
should be loaded onto chitosan. The other chitosan-M (M = Pd, Co,
Ni) complexes were synthesized in the same manner as described
for chitosan-Ru. The metal loading of chitosan-M was measured by
ICP (inductively coupled plasma) carried out on a Perkin-Elmer Op-
tima 3300 DV ICP instrument. Powder X-ray diffraction (PXRD) spec-
tra of chitosan-M were examined on a Rigaku D/Max 2550 diffrac-
tometer using Cu-Kα radiation (λ = 1.5418 Å). Fourier transform in-
frared spectrometer spectrum (FT-IR) was recorded on Bruker VER-
TEX 80V in wavenumber range of 400-4000 cm–1 with the resolution
ratio of 4 cm–1. Thermal properties of chitosan and chitosan-M and
the support chitosan were examined by thermogravimetry (TG)
analysis on a TA Q50 instrument under N2 atmosphere at a heating
rate of 10 °C/min from room temperature to 800 °C. The NH3 and
CO2-temperatured program desorption (NH3/CO2-TPD) were con-
ducted on autochem II 2920 and the results was obtained from
Figure 4. Recycle experiments for chitosan-Ru. (a) The catalyst reusability for
the conversion of FF into FAL. Conditions: 0.5 mmol FF, 3 mol-% catalyst,
8 mg of PPh3, 5 equiv. formic acid in 1 mL ethanol, 120 °C and 1.5 h. (b) The
catalyst reusability for the conversion of FF into GVL. Conditions: 0.5 mmol
FF, 3 mol-% catalyst, 8 mg of PPh3, 200 mg of ZSM-5, 5 equiv. formic acid in
1 mL of ethanol, 160 °C and 30 h.
Conclusions
In summary, we developed a biomass-supported chitosan-Ru/
PPh3 catalyst system highly effective for both the hydrogen- 50 °C to 200 °C, which was within the decomposition temperature
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of chitosan-Ru. X-ray Photoelectron Spectroscopy (XPS) characteri-
zation was performed on an ESCALAB 250 spectrometer, and
the binding energies of the XPS spectra was referred to the C 1s
(284.5 eV) as internal reference.
Keywords: Biomass conversion · Furfural · Ruthenium ·
Supported catalysts · γ-Valerolactone
Catalytic Test
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Hydrogenation of FF to FAL or LA to GVL with HCOOH: The
reactions were carried out in a thick wall flask with Teflon-lined
screw cap under air. Typically, 0.5 mmol FF was dissolved in 1 mL
of THF in the flask, then 25 mg (3 mol-% relative to FF determined
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same manner as described for the hydrogenation of FF.
One-Pot Conversion of FF to GVL: Under N2 atmosphere,
0.5 mmol FF was dissolved in ethanol in a thick wall flask, then
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One-Pot Conversion of Xylose or Hemicellulose to GVL: The one-
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Recycle and Reuse Experiments
After the reaction, the catalysts were collected by filtration and
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Product Analysis
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Acknowledgments
This work was supported by the National Natural Science Foun-
dation of China (Grant no. 21975102, 21871107, 21774042,
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Received: November 20, 2019
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Biomass Conversion
T. Wang, J. He,* Y. Zhang* ............ 1–10
Production of γ-Valerolactone from
One-Pot Transformation of Biomass-
Derived Carbohydrates Over Chi-
tosan-Supported Ruthenium Cata-
lyst Combined with Zeolite ZSM-5
In the presence of formic acid, the the direct transformation of biomass
combination of biomass-derived chi- such as furfural, xylose, and hemicellu-
tosan-Ru complex with zeolite ZSM-5 lose into γ-valerolactone.
exhibited good performance towards
DOI: 10.1002/ejoc.201901704
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