Zhejiang Kaile Chemical Plant. Diesel fuel with 16% aromatics
was kindly provided by the Research Institute of Petroleum
Processing.
Analytical methods
HPLC was performed on an Agilent 1100 (HP1100, Agilent,
USA) liquid chromatography equipped with an autosampler,
a reversed-phase Zorbax SB-C18 column (4.6 mm ¥ 250 mm;
Preparation of ionic liquids
5
mm), and a diode array detector. The mobile phase was 90%
-
1
of methanol in water (v/v,%) with a flow rate of 1.0 mL min .
For the quantification of TS, the external standard method was
used at 230 nm, and for the quantification of BT, DBT and 4,6-
DMDBT, the external standard method was used at 280 nm.
The total sulfur content (by weight) in diesel fuel was mea-
sured in triplicate for each sample by combustion of samples and
measurement of the released sulfur dioxide with a microcoulomb
analyzer (RPA-200, JiangHuan Electroanalysis, China).
The ILs [BMIM][HSO
according to the published literature.
N-methylimidazole (1.0 mol) and 1-chlorobutane (1.0 mol) were
added to a round-bottomed flask (500 mL) fitted with a reflux
condenser and reacted at 70 C for 24 h. The white precipitates
were filtered off and washed three times with ethyl acetate to
get [BMIM][Cl] which was monitored by copper(II) chloride
4
] and [C
4
Py][HSO
4
] were prepared
17,18
Equimolar amounts of
◦
19
in ethanol and no blue colour can be found. [BMIM][HSO ]
4
was obtained by a dropwise addition of one equivalent of
concentrated sulfuric acid (98%, 11.5 g) to a cooled solution
Regeneration of used ionic liquid
of [BMIM][Cl] (20 g) in anhydrous dichloromethane (CH
2
Cl
2
,
The oil phase was separated by decantation from the IL. An
equal volume of water was added to the solution of the IL,
and white precipitate was removed by filtration. The water and
oxidant were evaporated from the IL phase at 100 C for 3 h
by rotary evaporation. The residue was washed with an equal
volume of diethyl ether for three times to recover the IL for reuse.
3
0 mL). The mixture was refluxed for 48 h and the by-product
HCl formed in the reaction was carried out from the condenser
under a stream of dry nitrogen and then dissolved in deionized
◦
◦
water at 0 C. When the formed HCl had been completely
removed, CH
2
Cl
2
was evaporated with a rotary evaporator. The
◦
product was dried under vacuum at 70 C for 6 h and stored in
a desiccator.
[
C
4
Py][HSO
similar to that used for [BMIM][HSO
in the [BMIM][HSO ] and [C Py][HSO
.06 wt% by Karl Fischer titration. The content of chloride
was determined by a chloride-selective electrode, and 0.019 and
4
] was prepared according to a procedure
]. The water content
] was 0.04 wt% and
Results and discussion
4
Influence of different desulfurization systems on DBT removal
4
4
4
0
Two kinds of desulfurization systems were investigated: ex-
traction and extraction combined with catalytic oxidation. In
extraction system, [BMIM][HSO ] and [C Py][HSO ] were used
as extractant, the model oil was 1000 ppm S as DBT in n-octane,
and the model oil/IL volume ratio was set at 2 : 1 (Vmodel oil/VIL
.021 mol kg- of the impurity were observed in [BMIM][HSO
and [C Py][HSO ], respectively. The structure of these ILs, as
shown in Fig. 1, has been identified by H NMR as follows. H
NMR, d (600 MHz, CD CN): [BMIM][HSO ]: 0.922 (t, 3H),
.314 (m, 2H), 1.804 (m, 2H), 3.857 (s, 3H), 4.161 (t, 2H), 7.402
m, 2H), 8.443 (s, 1H), 8.780 (s, 1H). [C Py][HSO ]: 0.933 (t,
H), 1.368 (m, 2H), 1.941 (m, 2H), 4.595 (t, 2H), 8.061 (t, 2H),
.516 (m, 1H), 8.840 (d, 2H), 10.612 (s, 1H)
1
]
0
4
4
4
4
4
4
1
1
=
H
3
4
2 : 1) at room temperature. On the other hand, in the extraction
combined with catalytic oxidation system, [BMIM][HSO ] and
1
4
(
4
4
[C Py][HSO ] were used as extractant and catalyst, the model
4
4
3
8
oil was 1000 ppm S as DBT in n-octane, the model oil/IL
volume ratio was set at 2 : 1 (Vmodel oil/VIL = 2 : 1), and O/S
molar ratio was 5 (O/S = 5) at room temperature. As seen
in Fig. 2, the data at the time 0 min reflected the abilities
of [BMIM][HSO
n-octane. The sulfur removal of DBT by [BMIM][HSO
Py][HSO ] was 17.7% and 28.1%, respectively. The two ILs
4
] and [C
4
Py][HSO
4
] to extract DBT from
4
] and
[
C
4
4
have the same anion but different cations. It can be concluded
that pyridinium cation has better extractive performance than
imidazolium cation, which was also confirmed by our previous
Fig. 1 Chemical structures of the Brønsted acidic ILs.
20,21
research.
With the addition of a certain amount of H
ratio of H
of DBT increased sharply with the time increasing when the
extraction combined with catalytic oxidation was carried out
2
O (the molar
/DBT was 5, O/S = 5), the sulfur removal
2
Oxidative and extractive desulfurization process
2
O
2
Model oil was prepared by dissolving 4,6-DMDBT, DBT, BT,
and TS in n-octane, respectively, giving a corresponding sulfur
content 500, 1000, 1000, and 1000 ppm. All the oxidative
and extractive desulfurization experiments were conducted in
a 50 mL flask containing 3 mL of IL and 6 mL of model oil
using a magnetic stirrer with running speed 900 rpm at room
temperature. During the experiment, the sample was periodi-
cally taken and analyzed by HPLC. The sulfur compound-IL
extraction equilibrium was reached after 15 min when the sulfur
by [BMIM][HSO
by [C Py][HSO ] increased negligibly until 2 h. These results
indicated that [BMIM][HSO ] IL played a significant role in
the desulfurization process. When [BMIM][HSO ] served as
4
]. In contrast, the sulfur removal of DBT
4
4
4
4
extractant and catalyst, the equilibrium was reached after
90 min and the sulfur removal was up to 99.6%. However,
for [C
4
Py][HSO ] the sulfur removal of DBT was less than
4
content is constant. Then a certain amount of oxidant H
30%) was added to the mixture.
2
O
2
32.8% under the present conditions. It may be due to that
22
(
the pyridinium cation was oxidized by H
2
O
2
.
Fig. 2 also
This journal is © The Royal Society of Chemistry 2010
Green Chem., 2010, 12, 1220–1224 | 1221
Gao, Hongshuai
