One-pot synthesis of a novel magnetic carbon based solid acid for alkylation

Article abstract of DOI:10.1134/S002315841704005X

Magnetic carbon based solid acid has been synthesized via the one-pot hydrothermal carbonization of chitosan, magnetic core and hydroxyethylsulfonic acid at 160°C for 4 h. Chitosan was used as the carbon resource to protect the magnetic core from hydroxyethylsulfonic acid. The magnetic carbon based solid acid owned high BET surface and core shell structure, which provided the easily accessible acid sites on the carbon shell. The novel carbon based solid acid exhibited high activities for the hydrophobic alkylation of 1- dodecene and benzene, which was difficult to activate by traditional carbon based solid acids. The simple magnetic recovery added the advantages of the solid acid. The high activities for hydrophobic reactions, high stability and magnetic recovery were the key properties of the solid acid, which greatly enlarged the application area of the solid acid.

Full text of DOI:10.1134/S002315841704005X

ISSN 0023-1584, Kinetics and Catalysis, 2017, Vol. 58, No. 4, pp. 414–421. © Pleiades Publishing, Ltd., 2017.
Published in Russian in Kinetika i Kataliz, 2017, Vol. 58, No. 4, pp. 429–437.
One-Pot Synthesis of a Novel Magnetic Carbon Based Solid Acid
1
for Alkylation
Siyi Zhang, Junqiao Li, Genzhong Ji, and Xuezheng Liang*
School of Chemistry and Chemical Engineering, Shaoxing University, Shaoxing, 312000, China
*e-mail: liangxuezheng@126.com
Received November 25, 2016
Abstract⎯ Magnetic carbon based solid acid has been synthesized via the one-pot hydrothermal carboniza-
tion of chitosan, magnetic core and hydroxyethylsulfonic acid at 160°C for 4 h. Chitosan was used as the car-
bon resource to protect the magnetic core from hydroxyethylsulfonic acid. The magnetic carbon based solid
acid owned high BET surface and core shell structure, which provided the easily accessible acid sites on the
carbon shell. The novel carbon based solid acid exhibited high activities for the hydrophobic alkylation of 1-
dodecene and benzene, which was difficult to activate by traditional carbon based solid acids. The simple
magnetic recovery added the advantages of the solid acid. The high activities for hydrophobic reactions, high
stability and magnetic recovery were the key properties of the solid acid, which greatly enlarged the applica-
tion area of the solid acid.
Keywords: magnetic carbon based solid acid, catalysts, composite materials, alkylation
DOI: 10.1134/S002315841704005X
1
. INTRODUCTION
For hydrophilic reactants such as organic acids and
alcohols, the polar functionalities increased the affin-
ity, which resulted in high activities. However, the
solid acids showed very low activities for hydrophobic
reactions with the repulsion effect of the hydrophilic
groups [11]. Therefore, the carbon based solid acids
with easily accessible acidic sites for hydrophobic
reactants were highly demanded. The hard template
method was applied to synthesize of the mesoporous
carbon/silica composite based solid acids [12]. But the
use of mesoporous molecule sieves added the produc-
tion cost. The more economical activating methods
were used to increase the surface. The pretreated raw
materials such as impregnating the cellulosic precur-
sor [13] and mesoporous starch [14–16] were applied
for the synthesis of the carbon based solid acids. How-
ever, their applications were still limited in the hydro-
philic reactions. The mild hydrothermal carbonization
was also used to produce the carbon intermediate in our
previous work [17]. The other materials such as corncob
Acid catalysts were very important in chemical
industries for producing various useful chemicals [1, 2].
Sulfuric acid was the widely-used acid catalyst and large
amounts of sulfuric acid were consumed annually
worldwide. However, the liquid acid was difficult in
separation and enormous wastes were formed during
the energy-consuming post-treatment process [3].
Therefore, the solid acids with easy recovery received
wide attention [4]. The carbon based solid acids were
the promising catalysts with high acidity and stability,
which held great potential in substituting the liquid
acids in green chemistry [5–7]. These solid acids were
generally prepared through the carbonization and sul-
fonation. First, the carbohydrate compounds were
incompletely decomposed to form the polycyclic aro-
matic carbon sheets at relatively high temperature
(
400–550°C). The carbonization should be well con-
trolled to confirm sufficient sites for sulfonation.
Then, sulfonation by concentrated sulfuric acid or
fuming sulfuric acid was taken to introduce the sul- were also used in hydrothermal carbonization and good
fonic acid groups. Besides sugars, various materials results were received [18]. In order to simplify the syn-
such as vegetable oil asphalt [8], petroleum asphalt [9] thetic process, the one-pot hydrothermal carbonization
and glycerol [10] were used as carbon resources. The of sugar and hydroxyethylsulfonic acid was developed
carbon based solid acids owned high acidity, which for the synthesis of carbon based solid acids [19, 20].
showed excellent performances for various reactions. However, these carbon based solid acids still restricted
However, these solid acids owned very low BET sur- in hydrophilic reactions. For the hydrophobic reac-
face (~2 m /g) with abundant polar functionalities.
2
tions, these solid acids showed low activities. Magnetic
materials gained wide applications in various fields such
as data storage, magnetic resonance imaging and bio-
1
The article is published in the original.
414

ONE-POT SYNTHESIS OF A NOVEL MAGNETIC CARBON BASED SOLID ACID
415
medicine, which could be easily functionalized with sites for reactants. In order to avoid the corrosion of the
certain groups to create active surface [21].
magnetic core by hydroxyethylsulfonic acid, chitosan
Here the novel magnetic carbon based solid acid was selected as the carbon resource. The amino-
with core shell structure was presented through the one- groups in chitosan could act as the acid binding agents.
pot hydrothermal carbonization of chitosan, magnetic The magnetic carbon based solid acid showed high
core and hydroxyethylsulfonic acid at 160°C for 4 h activities for the hydrophobic alkylation of benzene
(
Scheme 1). The acid sites were dispersed around the with 1-dodecene, which was hard for traditional carbon
external carbon shell, which greatly reduced the diffu- based solid acids. The results greatly enlarged the appli-
sion difficulty and provided the easily accessible active cation area of the magnetic carbon based solid acid.
The synthesis route of magnetic carbon based solid acid
Сhitosan HOCH CH SO H
2
2
3
SO H
3
HO3S
HO3S
SO3H
Carbon shell
SO H
HTC
HO3S
3
Fe O Core
3
4
Magnetic iron oxide
HO3S
SO H
3
Scheme 1.
2
. EXPERIMENTAL
attraction. The quantitative analysis of the reaction
system was carried out on chromatographic analysis
using Shimadzu gas chromatograph (GC-14C). The
qualitative analysis of products was taken by GC–MS
on Agilent 7890A.
All organic reagents were commercial products of
high purity available and used for the reactions with-
out further purification.
2
.1. Synthesis of the Magnetic Carbon Based Solid Acid
The magnetic core was obtained by coprecipitation
3
. RESULTS AND DISCUSSION
3
.1. Characterization of the Novel Magnetic Carbon
[
22]. The solution of FeCl and FeCl with the molar
3 2
Based Solid Acid
ratio of 2 : 1 was stirred at room temperature (25°C).
Then, NH solution was dropped to adjust the pH
3
Chitosan was dehydrated to form the aromatic
value between 11 and 12. The magnetic core was col- rings and double bonds during the hydrothermal car-
lected by magnet and washed with water.
bonization, which contained various reactions such as
Chitosan (0.5 g) was added to 80 mL water with polymerization, aldolization and Diels–Alder [23].
stirring for 10 min. Then, 0.3 g 2-hydroxyethylsulfonic Hydroxyethylsulfonic acid owned hydroxyl groups,
acid was added to the mixture to form the chitosan which involved in those reactions to introduce sulfonic
solution. Finally, 0.5 g magnetic core was dispersed in acid groups. Here the carbonization should be carried
the solution using ultrasonic vibration. The obtained out around the magnetic core to form the core–shell
mixture was hydrothermal carbonized at 160°C for 4 h structure and the hydroxyethylsulfonic acid also acted
in 100 mL Teflon-lined stainless steel autoclaves. The as the catalyst. However, hydroxyethylsulfonic acid
resulted solid was magnetic attracted and washed with would cause the corrosion of magnetic core. There-
water. The magnetic carbon based solid acid was fore, chitosan with –NH groups was used as the car-
2
obtained after drying at 100°C overnight.
bon resource, which also acted as the acid binding
agent. In order to form the magnetic carbon based
solid acid with core shell structures, the feed composi-
tion of raw materials should be carefully controlled.
2.2. Alkylation of Benzene with 1-Dodecene
The benzene, 1-dodecene and catalyst were placed The magnetic core would be destroyed when
in the flask with mechanically stirring. The alkylation hydroxyethylsulfonic acid amount was too high. On
was carried out at certain temperature. The reaction the other hand, the solid acid with low acidity was
process was monitored by GC analysis. After reac- obtained with low usage. Also, chitosan would involve
tions, the catalyst was recycled by the simple magnetic in self-carbonization when the amount of chitosan
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16
SIYI ZHANG et al.
30 kV ×10000
1 μm 0001 08/Jan/14
3500
3000
2500
2000
1500
1000
Wavenumbers, cm–1
Fig. 2. SEM image of the magnetic carbon based solid
acid.
Fig. 1. IR spectrum of the carbonaceous material.
To improve the solid yields, the hydrothermal carbon-
ization was carried out in relatively high concentra-
tion, which caused the reactions between different
particles occurred more frequently and formed some
bulky particles [24]. The magnetic attractions
enhanced the gathered process especially at the first
stage of the reactions. The distances between particles
increased with the reaction for the carbonaceous shell
became thicker, which weakened the magnetic attrac-
tion. Also, the ethyl sulfonic acid groups bonded to the
carbon shell owned certain steric hindrance, which
prevented the gathering. As a result, the solid acid
owned the gathered structures with small particle size.
The TEM image of the solid acid displayed the
sphere structures with the diameter about 10–20 nm
(Fig. 3). The magnetic core was coated by carbon to
form the protective shell from the acidity. The carbon
shell also supplied enough active sites to introduce the
sulfonic acid groups, which made the acidic sites
around the external surface easily accessible to reac-
tants. The high concentration of reactants in hydro-
thermal carbonization caused the uneven dispersion
of the magnetic cores. The high partial concentration
of the chitosan formed the thick carbon shell of 8–
was too high. Also, the chitosan could not be well dis-
solved with little acid amount. The magnetic carbon
based solid acid with the acidity of 1.1 mmol/g was
obtained when 0.5 g chitosan and 0.3 g 2-hydroxyethyl-
sulfonic acid were used. The acidity increased with
hydroxyethylsulfonic acid amount. However, the mag-
netic core was serious corroded when the hydroxyethyl-
sulfonic acid amount increased over 1.0 g. The mag-
netic carbon with low acidity was obtained when the
hydroxyethylsulfonic acid amount was quite low.
The Fourier transform infrared spectroscopy
(
FT-IR) spectrum of the magnetic carbon based solid
acid was displayed in Fig. 1. The strong absorbability
–1
at 1041 cm was assigned to the S=O stretching vibra-
tion, which confirmed the existence of the sulfonic
acid groups. Also, FT-IR showed the strong C–O
–1
stretching vibration peaks in 1100–1250 cm , which
suggested the rich oxygen-containing groups in the
–1
solid acid. The absorbed peak at 1425 cm was
attributed to the C–N stretching vibration, which was
derived from the chitosan. FT-IR spectrum also
–1
showed that the solid contained the C=O (1674 cm )
groups, which existed in the forms of esters or carbonyl
acids. For the high absorption of the hydroxyl groups,
1
0 nm in some particles. On the other hand, the gath-
ered magnetic cores caused the thin shell of 3–5 nm.
Except for the unevenly dispersed particles, all the
magnetic cores were coated by carbon shell, which
formed the good guard against the acid. However, the
–1
the multiple broad peaks from 2700–3500 cm were
found, which also contained other functionalities such
–1
–1
as Ar–H (3020 cm ), C–H groups (2950 cm ).
+
carbon shell was not the dense enough to stop the H
ions permeating into the magnetic core [25].
Hydroxyethylsulfonic acid amount should be carefully
controlled. The acid sites covered on the carbon shell
would greatly decrease the diffusion difficulty, which
benefited the catalytic activities especially for hydro-
phobic reactants.
The scanning electron microscopy (SEM) image of
the solid acid showed the packed structures with the
particle sizes of 10–20 nm as depicted in Fig. 2. The
particles gathered together for the magnetic attraction.
The bulky molecules of chitosan were easy to coat
around the magnetic core. The dehydration reactions
occurred between the hydroxyl groups and the func-
The element analysis of the solid acid showed the
tionalities from different particles could also involved results: C 12.8; H 0.9%; S 3.5%; Fe 54.3%. The S con-
in the reactions, which enhanced the gathering trend. tent agreed well with the acidity, which indicated that
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ONE-POT SYNTHESIS OF A NOVEL MAGNETIC CARBON BASED SOLID ACID
00
417
1
9
5
0
5
0
9
8
8
75
7
6
6
0
5
0
1
00 200 300 400 500 600 700 800 900
T, °C
Fig. 4. TG analysis of the magnetic carbon based solid
acid.
100 nm
the proper acid binding agent for the reactions. The
proper composition of raw materials and mild carbon-
ization condition were the key factor to keep the mag-
netic properties of the novel carbon based solid acid.
Fig. 3. TEM image of the magnetic carbon based solid
acid.
the sulfur element existed main in the forms of sulfonic
acid groups. It could be concluded that the magnetic
attached much importance to the solid acid, which
offered the magnetic properties and the accessible
3
.2. Catalytic Activities for Alkylation
of Benzene and 1-Dodecene
The effect of the reaction time on the alkylation
acidic sites in the carbon shell. The high magnetic core was investigated (Fig. 6). The solid acid showed very
content effectively decreased the solid acid cost.
high activities for the reaction with 100% conversion.
About 85% dodecene was transformed to the alky
products within 10 min, which indicated that the solid
acid was very efficient for the reaction. Although the
acidity was not very high for the solid acid, the acidic
sites around the external surface were quite accessible
for reactants, which benefited the mass transfer effi-
ciency and confirmed all the acidic sites fully func-
The thermogravimetry (TG) analysis was carried in
the air atmosphere (Fig. 4). The result showed that the
carbon based solid acid owned high thermal stability
with the weight loss from 200°C, which was very high
for the sulfonic acid groups functionalized solid acid.
The carbon shell was destroyed when the temperature
reached 400°C and the sharp weight lost occurred. The
carbon shell totally decomposed with the process and
the pure magnetic core iron oxide was obtained with
2
5% weight loss, which agreed well with the element
results. The high inexpensive iron oxide content also
reduced the catalyst cost.
The magnetic carbon based solid acid owned the
2
BET area of 116 m /g, which offered high surface for
the reactions. The aggregation of the particles formed
some packed pores, which enlarged the BET surface.
The high BET surface and the acid sites around the
external carbon shell would greatly reduce the diffu-
sion difficulty and confirm the high activities.
1
2
Figure 5 showed the XRD pattern of the magnetic
carbon based solid acid. The diffraction peaks at 30.2°,
3
5.4°, 43.4°, 51.5°, 57.4° and 62.5° were assigned to
20
40
60
80
the (220), (311), (400), (422), (511), and (440) planes
of the magnetic Fe O respectively [25]. The solid acid
2θ, deg
3
4
owned the similar peaks to the magnetic core, which
indicated that the iron oxide structure was well kept
during the carbonization process. The chitosan was
Fig. 5. XRD patterns of the magnetic carbon based solid
acid: 1—magnetic core, 2—carbon based solid acid.
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18
SIYI ZHANG et al.
1
zene molecules attacked the carbenium cations before
1
00
the carbenium was totally formed, which effectively
prevented the cations rearranging. Also, the polar func-
tionalities on the carbon shell caused high steric hin-
drance for hydrophobic dodecene. The conformation
of the bulky carbenium cations from dodecene could
not transform smoothly for the steric hindrance, which
effectively improved the selectivity of 2- or 3-LABs.
Therefore, the high selectivity was obtained for the
solid acid. Furthermore, no branched products were
formed using the solid acid. The reaction was com-
pleted after 60 min with high selectivity of 73.4%. So
8
0
0
0
0
2
6
4
2
60 min was the optimal reaction time.
The effect of molar ratio of benzene and dodecene
on the reaction was also investigated (Table 1). The
benzene amount was very important for the reaction.
The conversion of dodecene increased with adding
benzene amount, which accounted for increasing col-
lision probability of reactants. The total conversion
was reached with the benzene amount of 18.5 g.
10
20
30
40
50
60
70
80
Reaction time, min
Fig. 6. Effect of the reaction time on the reaction. Reaction
conditions: dodecene 4.2 g, benzene 18.5 g, catalyst 0.23 g,
8
0°C. The conversion (1) was calculated on dodecene and
selectivity (2) was based on the 2- or 3-dodecylbenzene.
The selectivity seemed more sensitive to the ben-
zene amount. The multi alkylated products were often
formed during the alkylation for the alkyl groups with
electron donating ability activated aromatic rings.
Besides the relatively low conversion of 85.4%, the
selectivity was quite low with only 15.4% to 2-, 3-LABs,
when 1.85 g benzene was used with the molar ratio of
tioned during the catalytic activities. Dodecene was
completely conversed after 1 h. On the acidic condi-
tion, dodecene could undertake various transforma-
tions including polymerization and alkylation via car-
benium ions mechanism [27]. 1-Dodecene was trans-
formed to 2-carbenium ions, which were easy to
rearrange into 2-, 3-, 4-, 5-, 6-dodecyl carbenium ions
and formed different linear dodecylbenzene products
1
: 1. Benzene amount was not enough attack the car-
benium cations during the formation process. There-
fore, the rearrangement of the cation was heavily
occurred, which formed the 4-, 5- and 6- isomers [28].
The undesired branched products were also formed
via the carbenium cations alkyl migration rearrange-
ment. Furthermore, the multi alkylated products were
formed with little benzene amount, which also
resulted in the low conversion. On the other hand, the
multi alkylated products could be effectively avoided
with more benzene amount. When the benzene
amount was increased to 18.5 g, the multi alkylated
and branched products were disappeared. Further
increasing the benzene amount seemed useless for the
reaction. Therefore, 18.5 g benzene was used for the
reaction with the molar ratio of 10 : 1.
(
LAB). Besides the LABs, the branched products were
also formed via the carbenium cations rearrangement,
which were the undesired products due to the weak
biodegradability. The 2- or 3-LABs were the isomers
desired products, which could be well biodegraded.
The solid acid also achieved the high selectivity of 81%
for the 2- or 3-LABs in first 10 min. The reaction
gradually reached the equilibrium with the time and
the thermodynamic stable products 4-, 5-, 6-LABs
were formed. Therefore, the selectivity was decreased
and the selectivity of 74.4% was achieved when
dodecene was completely conversed. The hydropho-
bic dodecene accessed into the sulfonic acid sites on
the solid surface and formed the carbenium cations.
The reaction temperature was also investigated
Then the cations were attacked by benzene to form the (Table 2). Limited by the boiling point of benzene
LABs. The acid strength of the solid acid was middle (80°C), the alkylation temperature was investigated
and the carbenium cations formed slowly. The ben- below 100°C. The reaction temperature was also
greatly affected reaction. The conversion was low at
low temperature (40°C) and the reaction could not be
Table 1. Effect of the molar ratio on the reactiona, b
effectively activated. On the other hand, the selectivity
was quite high at low temperature. It was generally
known that the reaction occurred at low temperature
was the typical dynamic control process [29]. The car-
benium cations were produce at very low speed and the
benzene attacked cations during the formation pro-
cess, which effectively avoided the cation rearrange-
ment and resulted in the high 2- or 3-LABs selectivity.
With increasing temperature, some carbenium cations
Benzene, g
Conversion, %
Selectivity, %
1.85
9.3
97.5 100
65.6 73.4
18.5
20.3
100
73.2
85.4
25.3
a
Reaction conditions: dodecene 4.2 g, catalyst 0.23 g, 80°C,
0 min.
The conversion was calculated on dodecene, and selectivity was
6
b
based on the 2- or 3-dodecylbenzene.
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ONE-POT SYNTHESIS OF A NOVEL MAGNETIC CARBON BASED SOLID ACID
419
could be produced quickly and the rearrangement also Table 2. Effect of the reaction temperature on the reactiona, b
carried out, which reduced the selectivity for 2- and
T, °C
40
60
86.8 100
75.6 73.4
80
100
3
-LABs. For the 100% conversion was obtained at
8
0°C and the selectivity was decreased when further Conversion, %
66.8
82.1
100
69.3
increasing the reaction temperature. The reaction
Selectivity, %
temperature was chosen as 80°C.
a
Reaction conditions: dodecene 4.2 g, benzene 18.5 g, catalyst
.23 g, 60 min.
The conversion was calculated on dodecene and selectivity was
The catalyst amount was also investigated (Table 3).
0
b
The catalyst was very efficient for the reaction with
the conversion of 91.4% with only 0.1 g solid acid based on the 2- or 3-dodecylbenzene.
(
0.44 wt %). The core shell structure and high BET
surface provide the easily accessible active sites for
reactants. The acidic sites could fully involve in the
catalytic process, which resulted in the high activity of
the novel solid acid. Both the conversion and selectiv-
ity increased when adding the catalyst amount. More
Table 3. Effect of the catalyst amount on the reactiona, b
Catalyst amount, g
0.10
0.16
0.23
100
73.4
0.29
100
72.5
Conversion, %
91.4
71.3
97.1
72.5
catalyst amount provided more active sites, which Selectivitiy, %
promoted the reaction.
a
Reaction conditions: dodecene 4.2 g, benzene 18.5 g, 80°C,
Also, the probability of the isomerization of the 60 min.
b
dodecylbenzenes by the solid acid was also observed.
The mixture of LABs and the solid acid was treated
and stirred at 120°C for 3 h. The composition of the
LABs was analyzed after the treatment and no changes
occurred. This result confirmed that LABs isomers
were produced from the carbenium cations rearrange-
ment instead of dodecylbenzenes. Further increasing
the catalyst amount, the many carbenium cations were
produced at the same time, which caused the rear-
rangement probability and decreased selectivity.
The conversion was calculated on dodecene and selectivity was
based on the 2- or 3-dodecylbenzene.
more, the undesired branched products were also
formed with 15% selectivity, which accounted for the
high activities of the Lewis acid for the rearrange-
ment reactions. For sulfuric acid, the strong acid sites
chelated quickly with 1-dodecene to form carbenium
cations, which were easy to rearrange and formed the
isomers.
For the strong acidity, the carbenium cations could
be totally formed, which would cause the rearrange-
ment to form the thermodynamic stable products. As
3
.3. Recycled Activity
of the Magnetic Carbon Based Solid Acid
Besides the high activities, the magnetic property a result, 4-, 5- or 6-LABs were formed, which reduced
of the solid acid also added the recovery efficiency. the selectivity to the more biodegradable products 2-
After reactions, the solid acid could be easily recovered and 3-LABs.
via magnetic attraction. The recycled catalytic activi-
The traditional carbon based solid acid [5] with low
ties of the solid acid were investigated (Fig. 7). The
2
BET surface (~2 m /g) and the polar functionalities
results showed that the solid acid owned very high sta-
was also investigated here. The catalyst showed poor
bility. The reaction yield remained almost the same
after being recycled for six times with the yield of
3.4% for 2- or 3-LABs. The recycled solid acid still
7
8
0
0
owned the total conversion and selectivity for the
LABs. The recycled magnetic carbon based solid acid
owned the acidity of 1.07 mmol/g after being recycled
for six times, which was almost the same as fresh cata-
lyst. The element analysis of the recycled solid acid
showed little changes, which further confirmed the
high stability of the solid acid. Furthermore, the XRD
pattern showed the magnetic properties were well kept
for the solid acid.
7
60
50
40
30
20
3
.4. Comparative Study on Different Acid Catalysts
1
0
To compare the catalytic activities, the traditional
0
acid catalysts were also investigated (Table 4). For the
traditional alkylation catalyst AlCl , dodecene was
1
2
3
4
5
6
3
completely transformed with 100% conversion. How-
ever, the large catalyst amount caused the serious pol-
lution and difficulty in product purification. Further-
Recycled time
Fig. 7. Recycled activity of the solid acid.
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SIYI ZHANG et al.
Table 4. Alkylation of benzene and dodecenea, b
Catalyst
Catalyst amount, g
Reaction time, min
60
Conversion, %
Selectivity, %
Novel magnetic solid acid
0.20
1
100
4.5
73.4
65.5
67.2
50.9
55.8
400
Sulfonated carbon [5]
Carbon base acid
AlCl3
2
2.8
1.8
360
180
300
35.2
100
98.7
H SO4
2
a
b
The reaction conditions: dodecene 4.2 g, benzene 18.5 g, 80°C.
The conversion was calculated on dodecene and selectivity was based on the 2- or 3-dodecylbenzene.
activities with the conversion below 5%, which netic core showed poor activity for the reaction. The
accounted for the inaccessible active sites to hydro- magnetic property also provided the more simple and
phobic reactants. The novel magnetic carbon based efficient recovery process of the solid acid. The high
solid acid owned high BET surface and the core shell activities, easy accessible acidic sites, high thermal and
structures, which made the hydrophobic reactants chemical stability and the magnetism were the key
quite accessible to acidic sites. Dodecene could reach characteristics of the novel solid acid, which also hold
the acidic sites easily and interact with the active sites great potential in green chemistry.
to form the carbenium ion intermediates, which
resulted in high activity.
ACKNOWLEDGMENTS
Also, the carbon based solid acid was also synthe-
sized under the same reaction condition without using
The work was supported by National Natural Sci-
of the magnetic core. The solid acid owned the acidity ence Foundation of China no. 21103111.
of 1.0 mmol/g and relatively high BET surface of
2
4
5 m /g, which provided some accessible acidic sites
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amount, short reaction and the high selectivity were the
main advantages of the novel carbon based solid acid.
These results indicated that the novel solid acid hold
great potential in the hydrophobic reactions, which
greatly enlarge the application field of the carbon based
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