Hydrogenolysis of 2-tosyloxy-1,3-propanediol into 1,3-propanediol over Raney Ni catalyst

Article abstract of DOI:10.5935/0103-5053.20130049

2-Tosyloxy-1,3-propanediol (TPD), a potential precursor for 1,3-propanediol (1,3-PD) production, is produced by the tosylation of glycerol with the help of protecting group techniques. In this work, the hydrogenolysis of TPD into 1,3-PD over Raney Ni catalyst is discussed at different reaction parameters to optimize the reaction conditions for selective formation of 1,3-PD. The mechanisms of the hydrogenolysis of TPD and the side reactions were also confirmed by gas chromatography-mass spectrometry (GC-MS) technique.

Full text of DOI:10.5935/0103-5053.20130049

http://dx.doi.org/10.5935/0103-5053.20130049
J. Braz. Chem. Soc., Vol. 24, No. 3, 385-391, 2013.
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Article
A
Hydrogenolysis of 2-Tosyloxy-1,3-propanediol into 1,3-Propanediol over Raney Ni Catalyst
Zhi Zheng, Jianli Wang,* Zhen Lu, Min Luo, Miao Zhang, Lixin Xu and Jianbing Ji
Zhejiang Province Key Laboratory of Biofuel, The State Key Laboratory Breeding Base of Green
Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou 310014, P. R. China
2-Tosiloxi-1,3-propanodiol (TPD), um potencial precursor para produção de
1,3-propanodiol (1,3-PD), é produzido através da tosilação do glicerol com a ajuda de uma
técnica de proteção de grupos. Neste trabalho, discutiu-se a hidrogenólise do TPD em 1,3-PD sobre
catalisador de Raney Ni através de diferentes parâmetros de reação para otimizar as condições
de reação para formação seletiva do 1,3-PD. O mecanismo de hidrogenólise do TPD e reações
laterais também foram confirmados pela técnica de cromatografia em fase gasosa acoplada à
espectrometria de massas (GC-MS).
2-Tosyloxy-1,3-propanediol (TPD), a potential precursor for 1,3-propanediol (1,3-PD)
production, is produced by the tosylation of glycerol with the help of protecting group techniques.
In this work, the hydrogenolysis of TPD into 1,3-PD over Raney Ni catalyst is discussed at different
reaction parameters to optimize the reaction conditions for selective formation of 1,3-PD. The
mechanisms of the hydrogenolysis of TPD and the side reactions were also confirmed by gas
chromatography-mass spectrometry (GC-MS) technique.
Keywords: glycerol, 2-tosyloxy-1,3-propanediol, 1,3-propanediol, hydrogenolysis, Raney Ni
Introduction
selective for 1,3-PD.9-14 Kurosaka et al.11 found that the
yield of 1,3-PD was up to 24% by the hydrogenolysis
of glycerol over Pt/WO3/ZrO2 catalyst. Most recently,
Nakagawa et al.13 made a break through when they
obtained 38% yield of 1,3-PD by running the reaction using
Ir-ReOx/SiO2 as a catalyst.
Glycerol, a promising biomass-derived compound,
is available as a major byproduct (10% in weight) in
the manufacturing of biodiesel.1-3 Because of the recent
escalating production and the utilization of biodiesel
worldwide, large quantities of glycerol have been
produced.4,5 The rich availability makes it an important raw
material for the manufacture of some valuable chemicals
(diols, epoxides, esters, ethers, etc.), thereby facilitating
the replacement of petroleum-based products, and also
benefiting the emerging biodiesel industry.6-8
1,3-Propanediol (1,3-PD), currently produced from
petroleum derivatives, such as ethylene oxide (Shell route) or
acrolein (Degussa-DuPont route), is an important precursor
for the synthesis of polymethylene terephthalate and
polyurethanes.8 Recent advances in the hydrogenolysis of
glycerol into 1,3-PD have produced a range of possible
hydrogenolysis products, such as 1,3-PD, 1,2-propanediol
(1,2-PD), 1-propanol (1-PrOH), 2-propanol (2-PrOH), and
some other degradation products (ethylene glycerol,
ethanol, methanol and methane), but few catalysts are
The hydrogenolysis of glycerol might proceed through
different pathways, depending on whether the primary or
secondary hydroxyl is more easily reduced (Scheme 1).10
Because of the glycerol molecule with hydroxyl groups
of similar reactivity, it is difficult to produce the desired
1,3-PD in a high selectivity. 2-Tosyloxy-1,3-propanediol
(TPD), a potential precursor for the production of 1,3-PD,
is produced by the tosylation of glycerol with the help of
a group protection technique (acetalization).15-17 Compared
with hydroxyl group, the tosyloxyl group is a better living
group, and is easier to be replaced with a hydride ion.
Therefore, 1,3-PD can be obtained in a high selectivity
by the subsequent removal of the tosyloxyl group of TPD
(Scheme 2). In this work, instead of expensive reducing
reagent lithium hydride, the detosyloxylation of TPD
was carried out by catalytic hydrogenolysis over the
non-expensive Raney Ni catalyst, and studied at different
reaction parameters to optimize the reaction conditions for
selective formation of 1,3-PD.
*e-mail: wangjl@zjut.edu.cn

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Hydrogenolysis of 2-Tosyloxy-1,3-propanediol into 1,3-Propanediol over Raney Ni Catalyst
J. Braz. Chem. Soc.
OH
Dehydration/Hydrogenation route
HO
O
OH
HO
HO
+OH2
OH
H2O
H2O
HO
H+
OH
HO
+OH2
H+
O
OH
OH
H2
H2
H2
H2
OH
OH
HO
HO
HO
M
OH
M
H2
OH
M
H2
OH
(H)O
O(H)
(H)O
O(H)
M
Chelation/Hydrogenolysis route
Scheme 1. Illustration of the pathways of glycerol hydrogenolysis (adapted from reference 10).
OTs
2H, J 8.1 Hz), 4.56 (p, 1H, J 4.7 Hz), 3.78 (m, 4H), 2.80
(s, 2H, OH), 2.44 (s, 3H); 13C NMR (125 MHz, CDCl3)
d / ppm 145.2, 133.1, 130.0, 127.9, 82.7, 61.1, 21.6.
Raney Ni, H2
-TsOH
HO
OH
HO
OH
1,3-propanediol (1,3-PD)
2-tosyloxy-1,3-propanediol (TPD)
Scheme 2. Illustration of the hydrogenolysis of TPD into 1,3-PD.
Experimental
Hydrogenolysis of TPD
The hydrogenolysis of TPD was carried out in
a 200 mL stainless steel autoclave. The autoclave
was charged with 100 mL TPD dioxane solution
(2 wt.%), 0.32-0.96 g Raney Ni. After being sealed and
purged repeatedly with 2 MPa H2 to eliminate air, the
autoclave was heated to the required temperature and
then pressurized with H2 to a given value. The stirring
speed was set constant at 750 rpm. The reactions were
Reagents and materials
Glycerol (≥ 99%) was supplied by Ningbo Jiesen
Biodiesel Co., Ltd. Benzaldehyde (> 98.5%) and
p-toluenesulfonyl chloride (≥ 98.5%) were brought
from Sinopharm Chemical Reagent Co., Ltd. 1,3-PD
(≥ 99.6%) and 1-PrOH (≥ 99.7%) were purchased
from Sigma-Aldrich Chemical Co. 1,4-Butanediol
(≥ 99.0%) was provided by Shanghai Chemical Reagents
Supply Procurement of Five Chemical Plants. High
purity grade hydrogen was obtained from Hangzhou
Electrochemical Group Co., Ltd. Raney Ni (Ni ≥ 90%,
activity min-1 g-1 ≥ 5 mL H2) was bought from Dalian
General Chemical Industry Co., Ltd.
o
conducted at the following conditions: 110-150 C,
0.4-4 MPa H2, 2-8 h. After reaction, the autoclave was
cooled to room temperature. The products were analyzed
by gas chromatograph, (GC, Shimadzu GC-17A,
HP-FFAP 30 m × 0.25 mm × 0.25 mm, flame ionization
detector), and identified by gas chromatography-mass
spectrometry (GC-MS, Agilent 7890A/5875C, HP-5SM
30 m × 0.25 mm × 0.25 μm). Quantifications were achieved
by using 1,4-butanediol as an internal standard. The
unreacted TPD was confirmed by high performance liquid
chromatography (HPLC, Varian Prostar 210, kromasil
100-5 C18 column: Ф 4.6 mm × 250 mm, UV-Vis detector).
Synthesis of TPD
TPD was prepared from glycerol in a three-step
sequence (acetalisation with benzaldehyde-tosylation-
deacetalisation) (see in the Supplementary Information
(SI) section).15,17,18 The overall yield of TPD was 90%. No
further experiment was performed to maximize the yield
of TPD. The chemical structure of TPD was confirmed by
1H and 13C NMR (nuclear magnetic resonance , Bruker
AVANCE III 500MHz, Switzerland) spectra.1H NMR
(500 MHz, CDCl3) d (ppm) 7.82 (d, 2H, J 8.3 Hz), 7.35 (d,
Results and Discussion
Reaction scheme and product identification
The hydrogenolysis of glycerol is suggested to
proceed via dehydration of glycerol into acetol and
3-hydroxypropanal (3-HPA) intermediate, and followed by

Vol. 24, No. 3, 2013
Zheng et al.
387
o
the subsequent hydrogenation to produce the corresponding
1,2-PD and 1,3-PD, respectively.9-14,19,20 Hence, as shown
in Scheme 3, the selective transformation of glycerol
to 1,3-PD requires a catalyst system with the ability
to not only promote the coupled glycerol dehydration
(equilibria: Kglycerol dehydration)/3-HPA hydrogenation
(equilibria: Kdiol) reactions, but also minimize the 3-HPA
dehydration (equilibria: Keq). However, as stated by
Taher et al.,19 the activation barrier of initial dehydration
of glycerol was much higher than the dehydration/
hydrogenation of 3-HPA, that is:
3-HPA at low temperature (ca. 100-140 C). This means
that the activation barrier
ΔG‡ (Kglycerol dehydration) » ΔG‡ (Kdetosyloxylation) › ΔG‡ (Kdiol) ›
ΔG‡ (Keq),
thereby minimizing the dehydration route of the 3-HPA
to produce 1-PrOH. The determination of the optimum
reaction conditions of Scheme 3 for selective formation of
1,3-PD, therefore, mainly depends on the adjustment of two
equilibria of 3-HPA/AO (Keq) and 3-HPA/1,3-PD (Kdiol).
Moreover, with the exception of the 1,3-PD and
1-PrOH, about 15 kinds of chemicals were also separated
by GC, and half of them can be possibly identified via
MS by the comparison with the standard mass spectrum
in the NIST data base (see MS spectra comparison in the
SI section). As stated by Huang et al.20 and Schlaf et al.,24
the alcohol and aldehyde can be easily condensed
over acid catalysts in the hydrogenolysis of glycerol;
da Silva et al.25 and Medeiros et al.26 have demonstrated
that the condensation reaction between the glycerol and
assorted alcohols, and the self-condensation of glycerol
can be readily achieved over acid catalyst. Based on these
proposed mechanism of formation, as shown in Scheme 4,
in the present of TsOH, these identified byproducts
can be supposed from the following reactions: (i) the
decomposition of TPD to produce glycerol, and followed
by the subsequent hydrogenolysis reaction, (ii) the
condensation of 1,3-PD and acetaldehyde, and (iii) the
self-condensation of glycerol or 1,2-PD.
ΔG‡ (Kglycerol dehydration) » ΔG‡ (Kdiol) › ΔG‡ (Keq).
To overcome the ΔG‡ (Kglycerol dehydration), the dehydration
of 3-HPA to acrolein (AO) is highly favored at higher
temperature (> 175 oC).
In our investigation, by using GC-MS as a qualitative
assay, the dominative TPD hydrogenolysis products were
1,3-PD and 1-PrOH. Based on these proposed mechanism
of 1,3-PD formation in glycerol hydrogenolysis,19-23 the
hydrogenolysis of TPD might occur as shown in Scheme 3.
TPD undergoes a detosyloxylation to give 3-HPA andTsOH,
the subsequent reaction of 3-HPA proceed via the following
routes: (i) hydrogenation of 3-HPA to produce 1,3-PD, and
(ii) dehydration of 3-HPA to form AO intermediate, and
followed by the subsequent hydrogenation to produce
1-PrOH. Compared with the hydroxyl group of glycerol,
the tosyloxyl group of TPD is a better living group, and
can easily undergo a detosyloxylation to give the exclusive
OH
K'glycerol dehydration
HO
OH
-H2O
glycerol
Kglycerol dehydration
Kdetosyloxylation
-H2O
OTs
Kdiol
HO
OH
O
HO
HO
OH
cat., -TsOH
3-hydroxypropanal (3-HPA)
cat.,+H2
2-tosyloxy-
1,3-propanediol (1,3-PD)
1,3-propanediol (TPD)
Keq=k1/k-1
-H2O
O
O
Kallyl alcohol
cat.,+H2
OH
HO
allyl alcohol
acetol
acrolein (AO)
Kpropanol
cat.,+H2
Kpropanal
cat.,+H2
cat.,+H2
OH
HO
K'propanol
cat.,+H2
OH
O
1-propanal
1-propanol (1-PrOH)
1,2-propanediol (1,2-PD)
Scheme 3. The potential pathways of TPD hydrogenolysis. Adapted from references 9-14,19-23.

388
Hydrogenolysis of 2-Tosyloxy-1,3-propanediol into 1,3-Propanediol over Raney Ni Catalyst
J. Braz. Chem. Soc.
i
OTs
hydrogenolysis
decomposition
OH
OH
HO
HO
OH
OH
HO
OH
OH
OH
propane-1,2-diol
ethanol
ii
O
O
O
2-methyl-1,3-dioxane
iii
OH
OH
HO
OH
O
OH
O
HO
OH
HO
OH
O
OH
O
(1,4-dioxane-2,6-diyl)dimethanol
(1,4-dioxane-2,5-diyl)dimethanol
OH OH
HO
O
OH
3,3'-oxydipropane-1,2-diol
OH
OH
OH
O
O
O
OH
HO
OH
HO
OH
1,1'-(2-methylpropane-1,3-diyl)
bis(oxy)dipropan-2-ol
1,1'-oxydipropan-2-ol
Scheme 4. The potential side reactions ofTPD hydrogenolysis (the products identified via GC-MS were highlighted in bold).Adapted from references 20, 24-26.
Effect of reaction temperature
Figure 1 shows the effect of temperature on TPD
conversion and product selectivity. As the temperature
o
elevated from 110 to 150 C, there was a proportional
increase in TPD conversion from 16.7 to 84.1%. The
selectivity of 1,3-PD increased until 140 oC and began to
decrease from 57.1 to 55.2%, as the temperature further
elevated to 150 oC. Conversely, when the temperature was
above 140 oC, the selectivity of 1-PrOH increased from 24.8
to 42.7%. It is to prove that the dehydration of 3-HPA to
form AO is highly favored at high temperature (> 140 oC)
to drive the reaction towards the side of 1-PrOH formation.
As stated in Huang et al.,20 it was found a similar conclusion
o
that high operating temperature (180-230 C) resulted in
Figure 1. The effect of temperature on TPD hydrogenolysis (2 wt.% of
low selectivity of 1,3-PD (25-13%).
TPD in dioxane, 3 MPa H2, 0.32 g Raney Ni, 4 h).
Effect of catalyst weight
catalyst weight from 0.32 to 0.80 g, and slowly increased
to 74.5% as the catalyst weight further increased to 0.96 g.
Conversely, the selectivity towards 1-PrOH presented a
distinct decrease (25.6-15.0%) within the catalyst weight
range of 0.32-0.80 g. It is to validate the hypothesis that, as
illustrated in Scheme 3, the 1,3-PD and 1-PrOH are formed
in parallel, and the selectivity of 1,3-PD and 1-PrOH can be
controlled by the relative hydrogenation/dehydration rate
of 3-HPA. Thus, increasing Raney Ni weight can fasten
the hydrogenation rate of 3-HPA and the selectivity of
Figure 2 provides the effect of catalyst weight on
TPD hydrogenolysis. The conversion of TPD increased
obviously within the catalyst weight range of 0.32-0.96 g.
In the absence of Raney Ni, TPD was found to be inactive
at 140 oC, indicating that the function of Raney Ni is not
only limited to 3-HPA and AO hydrogenation, but also
involved in detosyloxylation step as well. The selectivity
of 1,3-PD increased from 57.1 to 73.9% with the increasing

Vol. 24, No. 3, 2013
Zheng et al.
389
1,3-PD increased correspondingly. Opposite to the work
presented by Dasari et al.,27 the excess catalyst did not
further promote the excessive hydrogenolysis of 1,3-PD
to lower alcohol and gas.
Figure 3. The effect of hydrogen pressure on TPD hydrogenolysis (2 wt.%
of TPD in dioxane, 140 oC, 0.8 g Raney Ni, 0.4-4 MPa H2, 4 h).
81.0%, and the selectivity of 1-PrOH slightly increased
from 14.4 to 16.2%. Opposite observations were reported
in the literature,28-31 it was observed that the low selectivity
of 1,3-PD formation in glycerol hydrogenolysis could be
contributed to the high reactivity of 1,3-PD in water medium
catalyzed by Ru/C +Amberlyst, and most 1,3-PD (77.7%)
was further hydrogenolysed into 1-PrOH and ethanol. In
our experiment, after reaction for 8 h in dioxane, the yield
of 1,3-PD was up to 73.8% without obvious degradation.
Figure 2. The effect of Raney Ni weight on TPD hydrogenolysis (2 wt.%
of TPD in dioxane, 140 oC, 3 MPa H2, 4 h).
Effect of hydrogen pressure
Figure 3 summaries the TPD conversion and product
selectivity at different H2 pressure. The conversion of
TPD was independent with H2 pressure. Enhancing the
H2 pressure from 0.4 to 1.0 MPa lead to an increase in
the selectivity of 1,3-PD from 63.6 to 74.0%, whereas
the selectivity of 1-PrOH declined from 17.8 to 15.0%.
These results imply that the high H2 pressure could fasten
the hydrogenation rate of 3-HPA, and drive the reaction
equilibrium towards 1,3-PD formation. As the H2 pressure
further enhanced from 1.0 to 4.0 MPa, there was no further
increase in the selectivity of 1,3-PD (74.0-73.9%), and the
excess H2 pressure did not cause considerable change in
the selectivity of 1-PrOH either, suggesting that 1-PrOH
is produced through the dehydration of 3-HPA rather than
the excessive hydrogenolysis of 1,3-PD. To validate this
speculation, the hydrogenolysis of 1,3-PD was carried out
in dioxane at 140 oC under 5.0 MPa H2, after reaction for
4 h, the conversion of 1,3-PD was low, no n-PrOH was
produced (Figure S12 in the SI section).
Figure 4. The effect of reaction time on TPD hydrogenolysis (2 wt.% of
TPD in dioxane, 140 oC, 0.8 g Raney Ni, 1 MPa H2).
Effect of TPD concentration
Effect of reaction time
The study was also performed in different TPD
concentrations, and the results are presented in Figure 5.
The conversion of TPD as well as the selectivity of
1,3-PD and 1-PrOH were kept constant within the TPD
concentration range of 2-6 wt.%. As TPD concentration
further raised from 6 to 20 wt.%, the conversion of TPD
increased from 91.2 to 95.0%, while the selectivity of
The effect of reaction time on TPD conversion and
product selectivity was studied, and the results are tabulated
in Figure 4. With the reaction time prolonged from 2 to 8 h,
the conversion of TPD increased from 67.8 to 91.2%,
meanwhile the selectivity of 1,3-PD raised from 76.7 to

390
Hydrogenolysis of 2-Tosyloxy-1,3-propanediol into 1,3-Propanediol over Raney Ni Catalyst
J. Braz. Chem. Soc.
1,3-PD decreased from 81.0 to 64.3%, and the selectivity of
1-PrOH declined from 16.2 to 9.3%.As shown in Scheme 4,
the decline in the selectivity of 1,3-PD and 1-PrOH was
contributed to the TPD decomposition reaction under high
concentration of TsOH, and followed by the subsequent
hydrogenolysis to produce 1,2-PD and ethanol.
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