A novel route for the synthesis of alkanes from glycerol in a two step process using a Pd/SBA-15 catalyst

Article abstract of DOI:10.1039/c5ra10744j

Glycerol is produced as a valuable by-product in the transesterification of fatty acids, but it cannot be used directly as a fuel additive. In this study, we developed a systematic conversion for glycerol, which proceeds via synthesizing the key intermediate, 1,2,3-tribromopropane and using the Suzuki coupling reaction to introduce the alkyl group. A series of Pd/SBA-15 catalysts with different wt% of Pd (10%, 15% and 20%) was prepared by a one step sol-gel method. The structure and composition of the catalysts were characterized by X-ray diffraction analysis (XRD), N₂ adsorption-desorption isotherms, transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectrometry (ICP-OES). The metallic state of dispersed palladium in SBA-15 is confirmed with X-ray photoelectron spectroscopy (XPS). Pd/SBA-15 with a Pd loading of 20 wt% shows good catalytic activity at 90 °C with methylboronic acid, allowing the complete conversion of 1,2,3-tribromopropane and 64% selectivity of 3-methylpentane. The optimized catalysts were also employed in coupling reactions between various alkylhalides and methylboronic acid, which obtained the desired product with an excellent selectivity. The catalyst can be successfully recycled five times. After the first cycle, we observed a drop in activity with 20% Pd/SBA-15, which was due to the leaching of palladium but in the later cycles, there was no significant decrease in activity.

Full text of DOI:10.1039/c5ra10744j

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Page 1 of 32
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A novel route synthesis of alkanes from glycerol in two step process using
Pd/SBA-15 catalyst
a
V. Udayakumar , A. Pandurangan *
a,
a
Department of Chemistry, Anna University, Guindy, Chennai 600 025, India
Glycerol is produced as a valuable by-product in transesterification of fatty acids but it
cannot be used directly as a fuel additive. In this study, we have developed a systematic
conversion with glycerol, which proceeds via synthesizing the key intermediate, 1,2,3-
tribromopropane and Suzuki coupling reaction is utilized to introduce alkyl group. A series of
Pd/SBA-15 catalyst with different wt% of Pd ranging from 10, 15 and 20 % was prepared by one
step sol-gel method. The structure and composition of the catalysts were characterized with X-
ray diffraction analysis (XRD), N adsorption-desorption isotherm, transmission electron
2
microscope (TEM) and inductively coupled plasma optical emission spectrometry (ICP-OES).
Metallic state of dispersed palladium in SBA-15 is confirmed with X-ray photoelectron
spectroscopy (XPS). Pd/SBA-15 with a Pd loading of 20 wt% expose good catalytic activity at
o
9
0 C with methylboronic acid, allowing a complete conversion of 1,2,3-tribromopropane and a
4 % selectivity of 3-methylpentane. The optimized catalysts were also carried out in coupling
6
reaction between various alkylhalides and methylboronic acid, which gave the desired product
with excellent selectivity. The catalyst can be successfully recycled for five times. After the first
cycle we observed a drop in activity with 20% Pd/SBA-15 which was due to leaching of
palladium but in later cycles there was no significant decrease in activity.
*
Corresponding author at: Department of Chemistry, Anna University, Guindy, Chennai-600 025, India.
Tel.: +91 44 22358653; fax: +91 44 22200660.

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E-mail address: pandurangan_a@yahoo.com (A.Pandurangan).
1
. Introduction
Biodiesel production from vegetable oils is increasing rapidly, hence glycerol is formed
1
as a major by-product in this process. Around 4.53 kg of crude glycerol is produced as a by-
2
,3
product in every 45.3 kg of biodiesel synthesis. It is a triol containing three hydroxyl group,
which is a very important chemical compound for various applications. One mole of glycerol is
4
produced per mole of triglyceride feed in the transesterification of vegetable oil. Cost of
glycerol is expected to diminish significantly from the actual cost as the biodiesel production
5
increases. Value added products such as hydrogen, syngas or liquid chemicals may be produced
from glycerol if the financial supports for biodiesel production are improved. Biodiesel
production increases which results in accumulation of glycerol in the market and also the prices
6
of glycerol may fall to 50 %. Conversion of glycerol to value added chemicals by heterogeneous
catalyst is not new, acrolein and other oxygenated chemicals are produced from glycerol in an
7
,8
autoclave reactor using Pd/Fe O and Ru-Cu/bentonitecatalysts. Yuming Li et al used Pd/SBA-
2
3
9
5 in glycerol hydrogenolysis to obtain 1,2-propanediol, additives to fuel were synthesized by
1
1
actualization of glycerol with butanol over zeolites. Aqueous-phase reforming of glycerol in
0
1
1
the presence of hydrogen over Pt/H-ZSM-5 catalyst has been carried out for propane formation.
Catalytic conversion of glycerol to liquid alkanes with Fischer-Tropsch synthesis in a two-bed
reactor system using Pt-Re/C and Ru/TiO catalysts was reported by James A.Dumesic and co-
2
1
workers. Conversion of glycerol to hydrocarbons has been proven feasible in limited number of
2
literatures and also further research has to be carried out for the enhancement in this area was
13
concluded by Nor AishahSaidina Aminet al.

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Over the past decade palladium catalyst has attracted much deliberation for c-c bond
1
4-16
formation.
Suzuki coupling has been implemented using palladium complexes with various
ligands under homogeneous condition, but this will bring the problem of separating the catalyst
1
7,18
from the reaction mixture, recycling of catalyst and also product contamination.
Hence it is
necessary to develop a heterogeneous catalysts to overcome the problem faced in homogeneous
palladium catalysts. Palladium nanoparticles are anchored on various supports such as
mesoporous silica, alumina, zeolites, organic polymer and dendrimers but heterogeneous systems
1
9
are easy to handle, recover and are “green” processes. Anna and co-workers synthesized
palladium nanoparticles supported on alumina-based oxides by sol-gel method but the surface
area of the support was fewer and the recycle of the catalyst were not reported. Palladium
nanoparticles supported on functionalized polymers for the Suzuki reaction was carried out by
many research groups and they acquired high efficiency of homogeneous catalysts but they
2
0,21
observed little obstacles such as reusability and leaching of metal from the support.
Palladium nanoparticles encapsulated inside the dendrimers was carried out in Suzuki reaction
by El-Sayed and co-workers, they obtained a good yield with desired products but the strong
2
2
encapsulation of palladium nanoparticles resulted in the loss of catalytic activity and also to the
formation of palladium black. Mesoporous catalysts is used as a solid support because of its wide
accessibility, excellent stability, porosity and inert environment for the immobilization of
2
3
transition-metal nanoparticles and the catalyst can be recycled by filtration. Numerous methods
are there to anchor palladium nanoparticles in mesoporous silica such as ion exchange, wetness
impregnation, chemical vapour infiltration, in-situ reduction and so on. Gao and co-workers have
reported a simple one-step method to synthesize palladium nanoparticles in SBA-15 by sol-gel

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method, prepared catalyst which has a pore size in the range of 5-10 nm, a large specific area and
2
4
a highly ordered pore structure.
So many researches have been carried out for the production of liquid alkanes from
glycerol as mentioned above, but all of these processes have some drawbacks such as high
energy consumption to break the carbon-carbon bonds. To the best of our knowledge, no
literature has been reported on the production of liquid alkane from glycerol at lower
temperature. However, in the present work, we propose an alternative approach to augment the
carbon chains by converting glycerol to alkane and also to explore the activation of Pd/SBA-15
catalysts in Suzuki coupling reaction with 1,2,3-tribromopropane intermediate and
methylboronic acid for the synthesis of 3-methylpentane.
2. Experimental
2.1Reagents and Materials
Pd/SBA-15 was synthesized using tetraethylorthosilicate (TEOS, Sigma Aldrich, 99%) as
a silica source and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene
glycol) triblock copolymer (EO PO EO , Pluronic P123, M = 5800, Sigma Aldrich) as a
7
0
20
70
av
structure directing agent, Palladium (II) Chloride (PdCl , Sigma Aldrich, 99%) as a palladium
2
precursor. Methylboronic acid (97%), phosphorous tribromide (99%), cyclohexanol (99%), 4-
methyl-2-pentanol (98%), glycerol (99%), cyclopentanol (99%), 2-Pentanol (98%) and
potassium tert-butoxide (99%) were purchased from Sigma-Aldrich Company. K PO and
3
4
Na CO were purchased from Thomas Baker, India. Solvents like 1,4-dioxane, DMF and DMSO
2
3
were purchased from Merck Millipore.
2.2 Characterization techniques

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X-ray diffraction (XRD) patterns were measured using Bruker D8 diffractometer with Cu
K radiation to identify the phase purity of the catalyst and the Bragg’s angle (2θ) scanning from
α
0.5˚ to 5˚ for low angle and 10˚ to 90˚ for wide angle XRD. The surface area, pore volume and
pore diameter were measured from N adsorption-desorption isotherms (Micromeritics ASAP-
2
2020) carried out in liquid N temperature. Before taking the measurement, the surface of the
2
-3
sample was cleaned by evacuation to low pressure of the order of 10 torr and temperature of
about 200 °C for 3 h. The pore size distributions were calculated from the nitrogen adsorption-
desorption isotherm, using the Barret-Joyner-Hallenda (BJH) algorithm (ASAP-2020 built-in
software from Micromeritics). Transmission electron microscope (TEM) was performed on
Philips CM12. The oxidation state of metal present in the samples was determined by using X-
ray photoelectron spectroscopy (Omicron Nanotechnology). The metal content of palladium in
terms of palladium percentage was determined by ICP-OES Perkin Elmer Optima 5300DV
instrument, the catalysts were assimilated with 0.5 ml HF and then make up to 25 ml of distilled
water with wavelength of 340.458 nm for Pd was used. GCMS analysis was conducted on Perkin
1 13
Elmer, Clarus 500 equipped with FID detector. H and C NMR was recorded on Bruker 400
MHz and 100 MHz spectrometer respectively.
2.3 General procedure for synthesis of Pd/SBA-15
2
4,25
Pd/SBA-15 was prepared as reported in the literature.
1.5 g of P123 was added to 11.5
ml of deionized water and stirred for 2 h at room temperature. 24 g of 2 M HCl was added drop
wise and different weight percentage of PdCl (10, 15, 20 wt%) was added at 40 ˚C under
2
stirring for 4 h, then 3.5 g of TEOS was added at once. The mixture was once again stirred for 24
hat 40 ˚C, and it was transferred into Teflon lined autoclave and aged at 100 ˚C for 48 h. The
obtained solid was filtered off, rinsed with deionized water and then dried at 100 ˚C for 12 h. The

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pulverized sample was calcined at 550 ˚C for 6 h. The compositions of the three samples were
labeled as 10% Pd/SBA-15, 15% Pd/SBA-15 and 20% Pd/SBA-15. Then, the labeled samples
were reduced under H atmosphere at 100 ˚C for 1 h.
2
2.4 General procedure for alkylbromide reaction
o
Alcohol (2 g, 1.0 equiv.) was added to a 50 ml round bottomed flask and cooled to 0 C,
after being stirred for 10 min. Phosphorous tribromide (see Table 1 for amount and equiv.) was
added drop wise over a period of 1 h. The reaction mixture was slowly warmed at room
o
temperature, the mixture was further heated at 60 C with stirring for 1 h and the crude was
purified by preparative reverse-phase HPLC using Atlantis dC18 column coupled with
1
evaporative light scattering detector (ELSD). The product was confirmed with GCMS, H NMR
1
and C NMR spectroscopy.
3
1
,2,3-tribromopropane (Table 1, entry 1). Selectivity (61 %), pale yellow liquid. H NMR (400
1
1
3
MHz, CDCl ): 3.86 (4H, d, CH ), 3.98-4.04 (1H, m, CH); C NMR (100 MHz, CDCl ): 34.76,
3
2
3
45.71.
1
-bromo-4-methylpentane (Table 1, entry 2). Selectivity (70 %), pale yellow liquid. H NMR
2
(400 MHz, CDCl ): 1.04 (6H, d, CH ), 1.14-1.23 (3H, m), 2.23 (3H, d, CH ), 4.05-4.27 (1H, m,
3 3 3
1
3
CH); C NMR (100 MHz, CDCl ): 25.78, 28.26, 35.73, 48.31, 55.73.
3
1
Bromocyclohexane (Table 1, entry 3). Selectivity (75 %), pale yellow liquid. H NMR (400
1
MHz, CDCl ): 1.13-1.58 (6H, m, CH ), 1.74-2.24 (4H, m, CH ), 3.79-3.85 (1H, m, CH); C
3
3
2
2
NMR (100 MHz, CDCl ): 24.01, 25.55, 37.90, 53.50.
3

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1
Bromocyclopentane (Table 1, entry 4). Selectivity (74 %), pale yellow liquid. H NMR (400
1
MHz, CDCl ): 1.54-1.74 (4H, m, CH ), 1.81-2.17 (4H, m, CH ), 3.75-3.83 (1H, m, CH); C
3
3
2
2
NMR (100 MHz, CDCl ): 25.16, 36.44, 55.21.
3
1
-bromopentane (Table 1, entry 5). Selectivity (70 %), pale yellow liquid. H NMR (400 MHz,
2
CDCl ): 0.95-1.22 (3H, m, CH ), 1.22-1.50 (4H, m, CH ), 1.63-1.84 (3H, m, CH ), 3.62-3.71
3
3
2
3
1
1H, m, CH); C NMR (100 MHz, CDCl ): 14.03, 26.81, 43.10, 51.20.
3
(
3
2.5 General procedure for Suzuki coupling reaction
The 20 ml sealed tube reactor was charged with alkylhalide (1 g, 1.0 equiv.), 1,4-dioxane
10 ml), KOt-Bu (3 equiv.) and methylboronic acid (see Table 2 for amount and equiv.),
(
degassed for few minutes. 20% Pd/SBA-15 (0.025 mol% Pd) was added and again degassed for
few minutes. The resulting mixture was heated at 90 ˚C with stirring for 3 h, the mixture was
cooled down to room temperature, and the catalyst was removed by filtration. Ethyl acetate
(4x10 ml) and water were added to the reaction mixture and stirred well for few minutes. The
organic layer was dried over Na SO and the product was isolated after distillation and
2
4
1 13
confirmed with GCMS, H NMR and C NMR spectroscopy.
1
-methylpentane (Table2, entry 1). Selectivity (64 %), colorless liquid. H NMR (400 MHz,
3
1
CDCl ): 0.61-0.87 (9H, m, CH ), 0.99 (4H, m, CH ), 1.06-1.09 (1H, m, CH); C NMR (100
3
3
3
2
MHz, CDCl ): 11.26, 20.82, 28.99, 36.30 (Supplementary information; Fig. S1).
3
1
,4-dimethylpentane (Table 2, entry 2). Selectivity (86 %), colorless liquid. H NMR (400 MHz,
2
1
3
CDCl ): 0.86 (12H, d, CH ), 1.13-1.19 (2H, m, CH ), 1.24-1.50 (2H, m, CH); C NMR (100
3
3
2
MHz, CDCl ): 25.35, 27.13, 50.24 (Supplementary information; Fig. S2).
3

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1
Methylcyclohexane (Table 2, entry 3). Selectivity (93 %), colorless liquid. H NMR (400 MHz,
1
CDCl ): 0.85 (3H, d, CH ), 1.07-1.69 (10H, m, CH ); C NMR (100 MHz, CDCl ): 23.31,
3
3
3
2
3
26.45, 27.11, 32.74, 35.44 (Supplementary information; Fig. S3).
1
Methylcyclopentane (Table 2, entry 4). Selectivity (85 %), colorless liquid. H NMR (400 MHz,
1
CDCl ): 0.96 (3H, d, CH ), 1.52-1.81 (8H, m, CH ), 1.68-1.80 (1H, m, CH); C NMR (100
3
3
3
2
MHz, CDCl ): 20.13, 25.02, 35.33 (Supplementary information; Fig. S4).
3
1
-methylpentane (Table 2, entry 5). Selectivity (84 %), colorless liquid. H NMR (400 MHz,
2
1
3
CDCl ): 0.57-0.61 (9H, t, CH ), 0.82-0.89 (4H, m, CH ), 0.97-0.99 (1H, m, CH); C NMR (100
3
3
2
MHz, CDCl ): 15.01, 20.74, 23.82, 27.75, 42.70 (Supplementary information; Fig. S5).
3
3. Results and discussion
3.1 Characterization of Pd/SBA-15
Nitrogen adsorption-desorption isotherm of SBA-15 and Pd/ SBA-15 are shown in Fig. 1.
The textural parameters of the samples are summarized in Table 3. Isotherm of all the catalysts
depict an ordered mesoporous nature, type IV isotherm with sharp hysteresis loops observed at
relative pressure p/p = 0.6 to 0.8 corresponds to capillary condensation of N and also which
o
2
indicate well defined cylindrical narrow pore size distribution inserted in Fig. 1. BET surface
2
3
area, BJH pore size and pore volumes of bare SBA-15 are 658 m /g, 5.2 nm and 0.71 cm /g
respectively. Palladium was introduced in SBA-15. The gradual decrease in surface area, pore
size and pore volume are observed which suggests that the palladium nanoparticles are dispersed
2
6
and incorporated into the pore channels of SBA-15 and also the metal is anchored successfully
without disintegrating the structure. The palladium percentage in SBA-15 derived from ICP-OES
is tabulated in Table 3, and the results show that palladium loading decreases from 7.13 wt% to

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16.85 wt% for 10% Pd/SBA-15 and 20% Pd/SBA-15 which is less than the expected palladium
loading i.e. 10, 15 and 20 wt%. These results suggest that Pd precursor does not deposit
completely into the silica matrix.
The crystalline nature and ordered hexagonal mesostructures of parent SBA-15 and
Pd/SBA-15 were determined by XRD, exhibit the three well resolved diffraction peaks in Fig. 2.
One intense peak in the range of 0.9-0.95˚ and two weak peaks in the range of 1.5-1.6˚
corresponds to (100), (110) and (200) planes respectively. These peaks are the characteristic
2
7
patterns of SBA-15, in good correlation with the reported prototype of plain SBA-15.
Therefore, the retention of ordered hexagonal mesostructure of SBA-15 was maintained.
Palladium loading increases, there is a gradual decrease in the intensity of d , d and d200
1
00
110
peaks, this indicating the incorporation and blocking of pores channels in SBA-15 with
palladium crystallites. In addition, diffraction peaks shifted to a higher 2θ values which might be
2
8
due to constriction of framework, similar to the results previously reported in the literature. The
wide angle XRD patterns of SBA-15 and Pd/SBA-15 showed a typical broad diffraction peak at
about 22.64˚ corresponds to amorphous silica was shown in Fig. 3. The four diffraction peaks at
2
θ= 40.08˚, 46.62˚, 68.08˚ and 82.14˚ correspond to the diffraction of (111), (200), (220) and
(311) planes that are assigned to face-centered cubic patterns of crystalline palladium and also it
2
9
reveals that the palladium species remains as metallic state. The average crystalline size
distribution of 10%, 15% and 20% of Pd/SBA-15 can be calculated based on Debye-Scherer
equation and the crystalline size of the samples which are found to be approximately 7.4, 9.4 and
11.9 nm respectively.
TEM images of bare SBA-15 and 20% Pd/SBA-15 samples are illustrated in Fig. 4a, b
and c respectively. A very narrow distribution of palladium particles was observed on the

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support and the highly ordered mesoporous structure was preserved in 20% Pd/SBA-15, which
was consistent with the results of XRD and N adsorption-desorption isotherm. The average pore
2
diameter of SBA-15 precursor is about 6.5 nm. The crystalline palladium was not found on the
external surface in Fig. 4c. These findings show that the palladium nanoparticles are dispersed
uniformly inside the pore channels of SBA-15 with an average particle size of about 5 nm.
A typical XPS elemental survey scan of 20% Pd/SBA-15 is depicted in Fig. 5. Palladium
was detected as a minor peak around 335 eV and the other peaks corresponding to silicon and
oxygen were observed as an intense peak. The peaks around 104, 155 and 535 eV are assigned to
3
1
Si2p, Si2s and O1s respectively. XPS spectrum of 20% Pd/SBA-15 is shown in Fig. 6. The
peaks at 335 eV and 340 eV were attributed to Pd 3d5/2 and Pd 3d3/2 respectively. Binding energy
values of Pd 3d5/2 and Pd 3d3/2 ascribed to metallic Pd, suggest that the prepared 20% Pd/SBA-15
catalyst exhibits good catalytic activity in C-C bond formation. This result is in accordance with
3
2,33
XRD observation.
3.2 Impact of various parameters in Suzuki coupling reaction
Suzuki coupling reaction of 1,2,3-tribromopropane with methylboronic acid was chosen
as a model reaction to find out the catalytic activity of (10, 15 and 20 wt%) Pd/SBA-15.
Conversion obtained over different catalyst are presented in Fig. 7a and the order of activity is
20% Pd/SBA-15> 15% Pd/SBA-15> 10% Pd/SBA-15. It is noted that the selectivity increases
with high Pd loading, reaches maximum at 3 h and also attain complete conversion of 1,2,3-
tribromopropane with a TON of 2560 was achieved. For comparison, 10% Pd/SBA-15 and 15%
Pd/SBA-15 were also tested under similar experimental condition but only 34-70 % of 1,2,3-
tribromopropane is consumed with low TON of 760 and 1640 respectively. In contrast with the

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2
4,34
results of previous studies 20% Pd/SBA-15 catalyst provides high TON,
it is suggest that
even though the palladium content is high in 20% Pd/SBA-15 the metal is dispersed uniformly
3
5
over the support and possess higher activity. Besides, the activity of catalysts with different
palladium loading was further examined for the Suzuki coupling reaction of various alkyl
bromides and methylboronic acid. The details are summarized in Table 2.
We have attempted a series of experiments with different temperature, bases and solvents
in Suzuki coupling reaction between 1,2,3-tribromopropane and methylboronic acid (3.5 equiv.)
using 20% Pd/SBA-15 catalyst. TON value calculated for different experimental run is presented
in Table 4. To study the influence of temperature to achieve a reasonable reaction rate, the
o
reaction was carried out at room temperature and 60 C (Fig. 7b). 1,2,3-tribromopropane
o
conversion is initially low but increases rapidly beyond 60 C and complete conversion is
o
attained at 90 C. At lower temperature, presence of other compounds like 1-bromo-2-
o
methylbutane (BMB) and 1,2-dibromobutane (DBB) are high but decrease significantly at 90 C.
The major product of the reaction is 3-methylpentane (MP) at the end of 3 h, however reasonable
amount of BMB and DBB is also present in the reaction mixture suggesting the reaction might
be proceed in the sequence 1,2,3-tribromopropane
1,2-dibromobutane (DBB)
1-bromo-
2-methylbutane (BMB)
3-methylpentane (MP).
The reaction was investigated with different solvents like 1,4-dioxane, DMF and DMSO,
3
6, 37
the choice of solvents made a significant impact on c-c bond formation.
Among the solvents
examined 1,4-dioxane was the most efficient with complete conversion of 1,2,3-tribromopropane
for the formation of alkyl-alkyl Suzuki coupling reaction, DMSO and DMF exhibit 39-79 %
conversion of 1,2,3-tribromopropane and also gave the desired product in slightly less selectivity
(Fig. 7c).

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The main role of base in Suzuki reaction is to increase the reactivity of boronic acid
3
towards the Pd-halide complex. To study the effect of bases, the reaction was explored with
8
different bases such as Na CO , K PO and KOt-Bu. As shown in Fig. 7d, KOt-Bu gave
2
3
3
4
complete conversion of 1,2,3-tribromopropane while examining the other two bases, the
conversion being 7-50 % for Na CO and K PO respectively; however, previous studies in
2
3
3
4
alkyl-alkyl Suzuki coupling reaction showed that KOt-Bu favor the reactivity of alkylhalide and
3
9
alkylboronic acid.
The recyclability and stability of the 20% Pd/SBA-15 catalyst was investigated with
,2,3-tribromopropane and methylboronic acid, the catalyst gave 64 % selectivity for the fresh
1
catalyst. Recyclability was checked by recovering the catalyst after the reaction by filtration,
washed with water and acetone, dried at 100 °C for 12 h. The selectivity was diminished to 60 %
in the first cycle which was due to the loss of palladium in to the reaction medium. The
recovered 20% Pd/SBA-15 catalyst was analyzed by ICP-OES for Pd content and the results
confirmed that 15.20 wt% of Pd is present and the catalyst was reused up to 5 cycles. In later
cycles, there is no significant loss of palladium is noticed thus signifying the stability of the
catalyst up on recycle (Fig. 8).
4
0
Hot filtration test was performed to check the heterogeneity of 20% Pd/SBA-15 catalyst
in 1,2,3-tribromopropane and methylboronic acid (Fig. 9). For this purpose, the catalyst was
removed by filtration from the reaction mixture after 30 minutes in a hot condition and the
mixture was left to react for 5 h. At 30 minutes of run the selectivity of the product is 5 % and
furthers the selectivity decreasing when compared with 20% Pd/SBA-15 catalytic run. But after
5
h the product selectivity is raised only up to8 %, this might be due to Pd leaching which is
confirmed from ICP-OES. Whereas with the catalytic run the selectivity of the product is found

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to increase. These verdicts indicate that the reaction is proceeding truly with heterogeneous
catalyst.
4. Conclusions
The current work reports the successful synthesis of 3-methylpentane from glycerol at
lower temperature. In the first step 1,2,3-tribromopropane is prepared from glycerol with PBr at
3
o
0 C followed by Suzuki reaction to install alkyl group. We have also synthesized three
6
different wt% of Pd/SBA-15 by sol-gel method, and the activity of the catalyst is investigated
individually in the second step for Suzuki coupling reaction with 1,2,3-tribromopropane and
methylboronic acid. The resulting 20% Pd/SBA-15 acts as a highly efficient, low palladium
leaching catalyst and also provides 64 % product selectivity at 90 ˚C for 3 h. The reusability of
the catalyst carried out for 20% Pd/SBA-15 exhibits a better recycling effect and stability for
fifth cycle. In this process, we have developed a new methodology for the production of liquid
alkanes; it has major advantages over the other reported literatures such as low temperature
employed in the reaction. In this work, we prominently utilize the by-product of glycerol and
also it provides an alternative route for the production of fuel additives in a “green” manner.
Acknowledgements
The authors are thankful to the Department of Chemistry, Anna University, Chennai and
Institute of Catalysis and Petroleum Technology, Anna University, Chennai for the instrumental
facilities provided under the DST-FIST programme. The authors would also like to thank Prof.
S. Ramaprabhu, AENL, Indian Institute of Technology, Madras, for the TEM and XPS analysis.

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References
1
2
3
4
5
6
7
8
9
. M. Ayoub and A.Z. Abdullah, Renew. Sust. Energy Rev., 2012, 16, 2671.
. Ma Fangrui and M.A. Hanna, Bioresour. Technol., 1999, 70, 1.
. A. Corma, G.W. Huber, L. Sauvanaud and P. O’Connor, J. Catal., 2008, 257, 163.
. G.W. Huber, S. Iborra, and A. Corma, Chem. Rev., 2006, 106, 4044.
. M. Mc Coy, Chem. Eng. News, 2005, 83, 19.
. K. Pathak, K. M. Reddy, N.N. Bakhshi and A.K. Dalai, ApplCatal. A 2010, 372, 224.
. M. Musolino, L. Scarpino, F. Mauriello and R. Pietropaolo, Green Chem., 2009, 11, 1511.
. T. Jiang, Y. Zhou, S. Liang, H. Liu and B. Han, Green Chem., 2009, 11, 1000.
. Y. Li, H. Liu, L Ma and D He, RSC Adv., 2014, 4, 5503.
10. H. Serafim, I.M. Fonseca, A.M. Ramos, J. Vital and J.E. Castanheiro, Chem. Eng. J., 2011,
178, 291.
11. K. Murata, I. Takahara and M. Inaba, React. Kinet.Catal.Lett., 2008, 93, 59.
12. D. A. Simonetti, J. Rass-Hansen, E.L. Kunkes, R.R. Soares and J.A. Dumesic, Green Chem.,
2007, 9, 1029.
1
1
1
3. Z.Y. Zakaria, N.A. Saidina Amin and J. Linnekoski, Biomass Bioenergy, 2013, 55, 370.
4. I.P. Beletskaya and A.V. Cheprakov, Coord. Chem. Rev., 2004, 248, 2337.
5. W.A. Herrmann, V.P.W. Bohm, C.P. Reisinger and J. Organomet.Chem., 1999, 576, 23.

Page 15 of 32
RSC Advances
View Article Online
DOI: 10.1039/C5RA10744J
16. M. Albrecht and G.V. Koten, Angew. Chem. Int. Ed., 2001, 40, 3750.
17. K.M. Clapham, A.S. Batsanov, M.R. Bryce and B. Tarbit, Org. Biomol. Chem., 2009, 7,
2155.
1
1
2
8. K.B. Lee, S.M. Lee, and J. Cheon, Adv. Mater., 2001, 13, 517,
9. H. Yang, X. Han, Zhancheng Ma, R. Wang, J. Liu and X. Ji, Green Chem., 2010, 12, 441.
0. A. Fihri, M. Bouhrara, B. Nekoueishahraki, J.M. Basset and V. Polshettiwar, Chem. Soc.
Rev., 2011, 40, 5181
21. A. Gniewek, J.J. Ziolkowski, Anna M. Trzeciak, M. Zawadzki, H. Grabowska and J.
Wrzyszcz, J. Catal., 2008, 254, 121.
2
2
2
2. Y. Li and M.A. El-Sayed, J. Phys. Chem., B 2001, 105, 8938.
3. D.E. De Vos, M. Dams, B.F. Sels, and P.A. Jacobs, Chem. Rev., 2002, 102, 3615.
4. P. Han, X. Wang, X. Qui, X. Ji and L. Gao, J. Mol. Catal. A: Chem., 2007, 272, 136.
25. D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, and G.D. Stucky, J. Am. Chem. Soc., 1998, 120,
6024.
26. P. Wang and X. Zheng, Powder Technol., 2011, 210, 115.
27. J. Jarupatrakorn and T.D. Tilley, J. Am. Chem. Soc., 2002, 124, 8380.
28. F. Zhang, Y. Yan, H. Yang, Y. Meng, C. Yu, B. Tu and D. Zhao, J. Phys. Chem., B 2005,
109, 8723.
29. H. Wang and C.J. Liu, Appl. Catal. B 2011, 106, 672.

RSC Advances
Page 16 of 32
View Article Online
DOI: 10.1039/C5RA10744J
3
3
3
3
3
3
3
0. J. Zhi, D. Song, Z. Li, X. Lei and A. Hu, Chem. Commun., 2011, 47, 10707.
1. K. Belkacemi and S. Hamoudi, Ind. Eng. Chem. Res., 2010, 49, 6878.
2. T.L. Barr, J. Phys. Chem., 1978, 82, 1801.
3. Y. Li and B.W.L. Jang, Appl. Catal. A 2011, 392, 173.
4. K. Karami and N.H. Naeini, Appl. Organometal. Chem., 2015, 29, 33.
5. J.W. Sun, Y.S. Fu, G.Y. He, X.Q. Sun and X. Wang, Catal.Sci. Technol., 2014, 4, 1742.
6. E. Alza, L. Laraia, B.M. Ibbeson, S. Collins, W.R. J. D. Galloway, J.E. Stokes, A.R.
Venkitaraman and D.R. Spring,Chem. Sci., 2015, 6, 390.
37. B. Saito and G.C. Fu, J. Am. Chem. Soc., 2007, 129, 9602.
38. C.F.R.A.C. Lima, A.S.M.C. Rodrigues, V.L.M. Silva, A.M.S. Silva, and L.M.N.B.F. Santos,
Chem. Cat. Chem., 2014, 6, 1291.
39. Z. Lu and G.C. Fu, Angew. Chem. Int. Ed., 2010, 49, 6676.
40. V. Udayakumar and A. Pandurangan, J. Porous. Mater., 2014, 21, 921.
41. J.H. Kirchhoff, M.R. Netherton, I.D. Hills and G.C. Fu, J. Am. Chem. Soc., 2002, 124,
13662.
4
2. J.Terao, Y. Naitoh, H. Kuniyasu and N. Kambe, Chem. Lett., 2003, 32, 890.
3. J. Zhou and G. C. Fu, J. Am. Chem., Soc., 2004, 126, 1340.
4

Page 17 of 32
RSC Advances
View Article Online
DOI: 10.1039/C5RA10744J
44. Y. Yagi, H. Kimura, K. Arimitsu, M. Ono, K. Maeda, H. Kusuhara, T. Kajimoto, Y.
Sugiyama and H. Saji, Org. Biomol. Chem., 2015, 13, 1113.
4
4
4
5. J. Sun, Y. Fu, G. He, X. Sun and X. Wang, Appl. Catal. B 2015, 165, 661.
6. M. Eckhardt and G.C. Fu, J. Am. Chem. Soc., 2003, 125, 13642.
7. A. Bahl, W. Grahn, S. Stadler, F. Feiner, G. Bourhill, C. Brauchle, A. Reisner and P.G.
Jones, Angew. Chem. Int. Ed., 1995, 34, 1485.
48. M. R. Netherton and G. C. Fu, Angew. Chem. Int. Ed., 2002, 114, 4066.
49. M. R. Netherton, C. Dai, K. Neuschutz and G. C. Fu, J. Am. Chem. Soc., 2001, 123, 10099.

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Table captions
a
1. Alkyl bromide reaction of various alcohols with phosphorous tribromide
2. Suzuki coupling reaction of various alkyl bromide with methylboronic acid catalyzed by
a
Pd/SBA-15
3
. BET analysis of SBA-15-Palladium catalyst and its metal content.
. Turn over number value for different experimental run.
4
Figure captions
1
1
. Nitrogen adsorption-desorption isotherms and pore size distribution of Palladium loaded SBA-
5 catalysts.
2. Low angle X-ray diffraction patterns of calcined Palladium loaded SBA-15 catalysts.
(a) SBA-15; (b) 10% Pd/SBA-15; (c) 15% Pd/SBA-15; (d) 20% Pd/SBA-15
3
. Wide angle X-ray diffraction patterns of calcined Palladium loaded SBA-15 catalysts.
a) 20% Pd/SBA-15; (b) 15% Pd/SBA-15; (c) 10% Pd/SBA-15; (d) SBA-15
(
4
5
6
7
. TEM images of SBA-15 (a) and 20 % Pd/SBA-15 (b and c).
. Elemental survey scan XPS spectrum of 20 % Pd/SBA-15.
. XPS spectrum of 20 % Pd/SBA-15.
. Influence of various parameters in Suzuki coupling reaction of 1,2,3-tribromopropane with
methylboronic acid catalyzed by 20 wt% Pd/SBA15.
8
. Recyclability of 20% Pd/SBA-15 in 1,2,3-tribromopropane with methylboronic acid
o
Reaction conditions: Temperature - 90 C; 20 % Pd/SBA-15 (0.025 mol); KOt-Bu (3
(
equivalent); reaction time - 3 h; solvent- 1,4-dioxane)
9. Hot filtration test.

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Table 1
Entry
Compound
PBr3
molar
equiv)
Product
Time
(h)
Product
selectivity (%)
b
(
1
0.5
1
61
2
3
0.12
0.12
1
1
70
75
4
5
0.12
0.12
1
1
74
70
a
Reaction conditions: For entry 1, Glycerol (2 g, 1.0 equiv.), phosphorous tribromide (2.13 g, 0.5
o
euiv.), Temperature = 0-60 C, Time = 1 h. For entries 2-3, Substrate (2 g, 1.0 equiv.),
o
phosphorous tribromide (0.73 g, 0.12 euiv.), Temperature = 0-60 C; Time = 1 h.
Determined by GCMS.
b

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Table 2
1
0% Pd/SBA-15
(0.012 mol% Pd)
15% Pd/SBA-15
(0.018 mol% Pd)
20% Pd/SBA-15
(0.025 mol% Pd)
Entry Compound Product
c
c
c
Product
Selectivity
TON
Product
Selectivity
TON
Product
Selectivity
TON
b
b
b
(%)
(%)
(%)
1
2
19
1583
1916
2083
1833
1666
41
53
56
51
49
2277
2944
3111
2833
2722
64
86
93
85
84
2560
3440
3720
3400
3360
23
25
3
4
2
2
0
5
2
Reaction conditions: For entry 1, 1,2,3-tribromopropane (1 g, 1.0 equiv.), methylboronic acid (0.94 g,
3
o
.5 equiv.), KOt-Bu (3 equivalent), 1,4-dioxane (10 ml) Temperature - 90 C, Time- 3 h. For entries
2
dioxane (10 ml) Temperature - 90 C, Time- 3 h.
-5, Substrate (1 g, 1.0 equiv.), methylboronic acid (0.5 g, 1.5 equiv.), KOt-Bu (3 equivalent), 1,4-
o
b
Determined by GCMS.
TON= mmol of products/mmol of Pd.
c

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Table 3
Entry
a
Catalysts
BET surface Pore size Pore volume Pd loading
2
area (m /g) BJHAds (nm) BJHAds (cc/g) (wt %)
1
2
3
4
SBA-15
658
5.3
5.0
4.9
4.8
0.71
0.69
0.65
0.61
-
10 % Pd/SBA-15
15 % Pd/SBA-15
20 % Pd/SBA-15
614
7.13
11.92
16.85
572
513
a
Determined by ICP-OES measurements.

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Table 4
“Optimized” conditions
b
Entry
Deviation from
optimized” conditions
Pd
(mol% )
Product
selectivity (%)
TON
Ref.
a
“
1
2
3
4
5
6
7
None
0.025
0.025
0.025
0.025
0.025
0.025
0.025
64
10
36
21
42
4
2560
400
[37,39,41]
[41,42]
[43]
room temperature
o
60 C
1440
840
D.MS.O
D.M.F
[44,45]
[45,46]
[47,48]
[49]
1680
160
Na CO
2
3
K PO
3
19
760
4
a
Determined by GCMS.
TON= mmol of products/mmol of Pd.
b

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Fig. 1

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Fig. 2

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Fig. 3

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Fig. 4

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Fig. 5

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Fig. 6

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Fig. 7