Phosphorus promoted SO42-/TiO2 solid acid catalyst for acetalization reaction

Article abstract of DOI:10.4067/s0717-97072015000300006

A novel phosphorus modifed SO₄^2-/TiO₂ catalyst was synthesized by a facile coprecipitation method, followed by calcination. The catalytic performance of this novel solid acid was evaluated by acetalization. The results showed that the phosphorus was very effcient to enhance the catalytic activity of SO₄^2-/TiO₂. The solid acid owned high activity for the acetalization with the yields over 90%. Moreover, the solid acid could be reused for six times without loss of initial catalytic activities.

Full text of DOI:10.4067/s0717-97072015000300006

J. Chil. Chem. Soc., 60, Nº 3 (2015)
2-
PHOSPHORUS PROMOTED SO /TiO SOLID ACID CATALYST FOR ACETALIZATION REACTION
4
2
1
,21*
2
1
SHAOFENG ZHONG , QIONGRONG OU , LINJUN SHAO
1
Department of Textile, Zhejiang Industry Polytechnic College, Shaoxing 312000, People’s Republic of China;
2
Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433, People’s Republic of China
ABSTRACT
2
-
A novel phosphorus modified SO4 /TiO catalyst was synthesized by a facile coprecipitation method, followed by calcination. The catalytic performance of
2
2
-
this novel solid acid was evaluated by acetalization. The results showed that the phosphorus was very efficient to enhance the catalytic activity of SO4 /TiO . The
2
solid acid owned high activity for the acetalization with the yields over 90%. Moreover, the solid acid could be reused for six times without loss of initial catalytic
activities.
Keywords: solid acid, TiO , acetalization, coprecipitation, phosphorus.
2
INTRODUCTION
of TiO particles was the same as that of TiO -P.
2 2
General procedure for acetalization reaction
Acid catalyzed reactions played an important role in chemical industry
to produce various chemicals. Over 15 million tons of homogeneous acid
sulfuric acid, phosphorus acid, etc) is annually consumed as an unrecyclable
Aldehyde or ketone (20 mmol), diol (24 mmol), 5 mL cyclohexane, and
the catalyst (20 mg) were mixed together in a three necked round bottomed
flask equipped with a magnetic stirrer and a thermometer, and a Dean-Stark
apparatus which was constituted with manifold and condenser to remove the
water continuously from the reaction mixture. The reaction was refluxed for 2
h to complete the reaction.
1
,2
(
catalyst, which requires costly and inefficient separation of the catalyst from
homogeneous reaction mixture. Thus, heterogeneous catalyst has received
tremendous interest because catalyst reuse and recycling can further improve
the overall productivity and cost-effectiveness, thereby minimizing the waste
generation and catalyst contamination, leading to a greener and more sustainable
Characterization
1
2
The acidity was determined according to the literature. The quantitative
analysis was performed on a Shimadzu (GC-14B) gas chromatograph. The
morphologies of electrospun fiber mats were recorded with a scanning electron
microscope (SEM) (Jeol, jsm-6360lv, Japan). Samples for SEM were coated
with a 2-3 nm layer of Au to make them conductive. The elemental analysis
was taken on the EuroEA 3000 from Leeman, USA. FT-IR/ATR spectra
were recorded on a FT-IR spectrometer (Nicolet, Nexus-470, USA) with the
accessories of attenuated total reflection. Phase composition of samples was
determined by means of X-ray powder diffraction (XRD) (Rigaku D, max-
3BX, Japan). Surface area was measured by TriStar II 3020 from Micromeritics,
USA.
3
-5
chemical transformation process. Solid acid could be easily separated from
the reaction mixture by simple filtration or centrifugation and do not require
the neutralization procedure. During the past decades, many solid acids have
6
,7
been developed for the replacement of homogeneous acid catalyst. However,
till now, preparation of a solid acid as active, stable and inexpensive as sulfuric
acid is still great challenging for the researchers.
TiO based solid acid are quite promising because they are environmentally
2
benign, easy to prepare, low cost, excellent thermal stability and strong
8,9
surface acidity. As mixed oxides usually show better physicochemical and
acidic properties than individual component oxides, TiO mixed oxides were
2
1
0,11
synthesized to further increase the catalytic performance of TiO2.
Herein,
phosphorus was firstly incorporated into the TiO particles and its catalytic
performance was evaluated by the acetalization reaction (Schemce 1).
RESULTS AND DISCUSSION
Characterization of the catalyst
2
2
-
The surface morphologies of SO /TiO -P and TiO powder were shown in
4
2
2
2
-
Figure 1. It can be found that the SO4 /TiO catalyst was spherical particle with
2
2
-
diameters about 1 μm, while the SO4 /TiO -P powder was irregular. The BET
2
2
-
measurements also showed that the surface specific area of SO /TiO catalyst
4
2
2
2-
2
(
134 m /g) was a little larger than that of SO /TiO -P (125 m /g).
4 2
Scheme 1. Scheme representation of acetalization reaction.
EXPERIMENTAL
Materials
All organic reagents were commercial products of the highest purity
available (>98%) and were used for the reactions without further purification.
TiO (anatase) particles was purchased from Shanghai Reagent Plant.
2
Catalyst preparation
The phosphorus modified SO4 /TiO2 (SO4 /TiO -P) was prepared as
2
-
2-
2
follows: 2 g titanium butoxide was dissolved in 10 ml anhydrous ethanol
2
-
2-
and 2 g H PO was added to the titanium butoxide/ethanol solution. A white
Figure 1. SEM images of SO4 /TiO -P (a) and SO /TiO (b).
2 4 2
3
4
precipitate was produced and the suspension was stirred at room temperature
for another 3 hrs. The prepared phosphorus modified TiO was separated by
The FT-IR spectra of TiO -P before and after thermal treatment were
2
2
o
centrifugation and then treated at 500 C (TiO -P) in air for 5 hrs.
shown in Figure 2. After thermal treatment, the intensities of absorption at 3300
2
2
-
-
1
-
1
Sulfated TiO -P (SO /TiO -P) was prepared as follows: 2 g TiO -P
cm and 1626 cm assigned to –OH group were significantly decreased. The
-1
2
4
2
2
powder was added into 10 mL of H SO aqueous solution (0.5M) and stirred
strong absorbance band at 1015 cm was attributed to the P-O group. It can
2
4
2
-
magneticallyfor2hrs.TheSO4 /TiO -Pcatalystwasseparatedbycentrifugation
be concluded that the phosphorus has been successfully incorporated into the
2
o
and then treated at calcined at 200 C in air for 2 h before catalysis use.
TiO structure.
2
Sulfated TiO was also prepared for comparison and the sulfation process
2
e-mail address: sfzhong76@163.com
3005

J. Chil. Chem. Soc., 60, Nº 3 (2015)
a
Table 1. The catalytic activity comparison of different catalysts.
Entry
Catalyst
Conversion (%)
Yield (%)
2
-
1
2
3
4
SO4 /TiO2
87
85
86
82
97
99
2
-
b
SO4 /TiO2
2
-
SO4 /TiO -P
99
2
H SO
100
2
4
a:
Catalytic condition: 20 mmol cyclohexanone; 24 mmol 1,2-ethenediol;
0 mg catalyst in 5 mL cyclohexane under reflux for 2 h; with Dean-Stark
apparatus.
1
b:
The synthesis and sulfation processes of TiO were the same with that of
2
2
-
SO4 /TiO -P but with H O as the replacement of H PO .
2
2
3
4
Effect of catalyst amount on the acetalization
Table 2 summarizes the dependence of the acetalization with the catalyst
loading. It can be found that the yields for the acetalization of cyclohexanone
2
-
with 1,2-ethenediol gradually increased with the increment of SO4 /TiO -P
2
Figure 2. FT-IR spectra of TiO , TiO -P befor and after calcination.
2
2
catalyst. Excellent conversion and yield could be obtained even by just using
2
-
1
0 mg catalyst. When the amount of SO4 /TiO -P catalyst increased to 20 mg,
2
The crystal phases of the two catalysts were analyzed by the XRD pattern.
the yield was up to 99% and the further addition of catalyst has no obvious
o
The diffraction peaks at 25 was the characteristic peaks of the (101) planes
2-
effect on the yield of acetalization, indicating that 20 mg SO4 /TiO -P catalyst
2
of anatase phase of TiO , which is known for its high catalytic activities. The
2
was enough for the acetalization.
treatment of sulfuric acid had no influence on the crystal phase of TiO2.
Table 2. Effect of catalyst amount on the conversion and yield of
a
acetalization of cyclohexanone with 1,2-ethenediol.
2
-
Amount of SO4 /TiO -P
2
1
0
20
30
40
50
(mg)
Conversion (%)
98
98
99
99
99
99
99
99
99
99
Yield (%0
a:
Reaction condition: 20 mmol cyclohexanone; 24 mmol 1,2-ethenediol; 5
mL cyclohexane under reflux for 2 h.
2
-
Acetalization catalyzed by SO4 /TiO -P catalyst
2
A series of carbonyl compounds and diols were employed to examine
2
-
the scope of SO4 /TiO -P catalyst (Table 3). Examination of entry 1-8 in
2
table 2 showed that the aliphatic aldehydes were more reactive than the
aromatic aldehydes due to the electronic effect. Due to the steric hindrance,
the cyclohexanone acted more effective than the 2-butanone (Entry 11, 12, 15,
and 16 in Table 3). As the five- and six- membered ring were more stable than
seven-membered ring, 1,2-ethanediol, 1,2-propylenediol and 2,2-dimethyl-1,3-
propanediol worked better with carbonyl compound than 1,4-butanediol.
2
-
2-
4
Figure 3. XRD patterns of TiO , SO /TiO and SO /TiO -P catalysts.
2
4
2
2
2
-
The elemental analysis catalyst showed that the sulfur contents in SO
/
4
2-
TiO2 and SO4 /TiO -P catalysts were 6.51% and 6.72%, respectively. This
2
result demonstrated that the amounts of absorbed H SO in the two catalysts
2
4
2
-
were comparable. The acidity measurement showed that the acidities of SO
TiO and SO4 /TiO -P were 1.95 mmol/g and 2.67 mmol/g, respectively, which
indicated the phosphorus could increased the acid centre in the surface of SO4
/
4
2-
2
2
2
-
/
TiO catalyst.
2
The catalytic activities for the acetalization
A comparative study on the catalytic activities of the SO4 /TiO -P with
2
-
2
heterogeneous and homogeneous acid catalyst was carried out (Table 1). It is
interesting to found that the phosphorus species could significantly increase
2
-
the catalytic activity of SO4 /TiO catalyst (Entry 1-3 in Table 1). Yang et al
2
have reported that the sulfate species and silica species could work together
2
-
13
to increase the acidity and catalytic activity of SO4 /TiO catalyst. Thus, it
2
can be concluded that the sulfate species and phosphorus species may also
have the similar synergetic effects, which is responsible for the high catalytic
2-
activity of SO4 /TiO -P catalyst. Due to the disfavored kinetics of the biphasic
2
catalytic system, the heterogeneous catalyst usually was not as active as the
2
-
homogeneous catalyst. Although the catalytic activity of SO4 /TiO catalyst
2
could be obviously enhanced by incorporation of phosphors, it is still slightly
2
-
lower than that of homogeneous H SO catalyst.
Figure 4. The reuse of the SO4 /TiO -P catalyst.
2
2
4
3
006

J. Chil. Chem. Soc., 60, Nº 3 (2015)
2
-
a
Table 3. The SO4 /TiO -P catalyst catalyzed acetalization.
2
Yield
Entry
Carbonyl compound
Product
Conversion (%)
(%)
O
Cl
1
2
3
4
5
6
7
8
99
99
99
98
98
98
96
96
99
99
98
98
98
98
96
95
O
O
Cl
O
O
Cl
CHO
Cl
O
O
Cl
O
O
O
O
O
CHO
O
O
O
O
O
9
99
99
O
O
1
0
1
99
99
93
99
97
93
O
O
O
1
O
O
1
2
O
O
O
1
1
1
3
4
5
99
99
99
99
99
98
O
O
O
O
O
O
1
6
99
98
O
a:
Catalytic condition: 20 mmol carbonyl compound; 24 mmol diol; 20 mg catalyst in 5 mL cyclohexane under reflux for 2 h; with Dean-Stark apparatus.
2
4
-
2-
2-
Reuse of SO /TiO -P catalyst
SO4 /TiO2 solid acid. The SO4 /TiO -P catalyst was very efficient for the
2
2
2-
2-
As the SO4 /TiO -P catalyst is immiscibility with organic compound and
acetalization. Moreover, the SO4 /TiO -P solid acid could be recovered
2
2
solvent, the catalyst could be recovered by centrifugation. The reusability of the
conveniently and reused for six times without loss of its initial activity. This
2
-
2-
SO4 /TiO -P catalyst was evaluated by the acetalization of cyclohexanone with
environmentally benign heterogeneous SO4 /TiO -P solid acid will have
2
2
2
-
1
,2-ethanediol. After the reactions, the SO4 /TiO -P catalyst was recovered by
potential for large-scale industrial applications.
2
centrifugation and reused in the second run directly. Figure 4 clearly showed
2
-
that the catalytic activity of the SO4 /TiO -P was unchanged even after six runs.
ACKNOWLEDGEMENT
2
CONCLUSION
The author gratefully acknowledges financial supports from Professional
Leaders Leading Project of Education Department of Zhejiang Province, China
(No. lj2013131) and Science and Technology Project of Education Department
of Zhejiang Province, China (No.Y201432680).
2
-
In summary, a novel phosphorus modified SO4 /TiO2 solid acid was
prepared. The phosphorus species could increase the catalytic activity of
3
007

J. Chil. Chem. Soc., 60, Nº 3 (2015)
REFERENCES
8. Atghia, S. V.; Beigbaghlou, S. S. J. Organomet. Chem. 2013, 745–746,
2-49.
4
1.
2.
3.
Gupta P.; Paul S. Catal. Today 2014, DOI: 10.1016/j.cattod.2014.04.010.
Okuhara T. Chem. Rev. 2002, 102. 3641-3665.
Gholamzadeh P.; Ziarani G. M.; Lashgari N.; Badiei A.; Asadiatouei P. J.
Mol. Catal. A: Chem. 2014, 391, 208-222.
9. Krishnakumar, B.; Velmurugan, R.; Swaminathan, M. Catal. Commun.
2011, 12, 375-379.
10. Li, H. L.; Deng, A. J.; Ren, J. L.; Liu, C. Y.; Wang, W. J.; Peng, F.; Sun, R.
C. Catal. Today 2014, 234, 251-256.
4
.
.
Parangi T.; Wani B.; Chudasama U. Appl. Catal. A: Gen. 2013, 467, 430-
11. Li, K. -T.; Wang, C. -K.; Wang, I.; Wang, C. -M. Appl. Catal. A: Gen. 2011,
392, 180-183.
12. Wang, Y. M.; Chen, C. J.; Luo, J. H.; Gao, D. S.; Li, D.; Wu, M. X.; Ma, J.
B. Chinese J. Struct. Chem. 1999, 18, 175-181.
4
38.
5
Mohammadi, B.;HosseiniJamkarani, S. M.;A. Kamali,T.;Nasrollahzadeh,
M.; Mohajeri A. Turk. J. Chem. 2010, 34, 613-619.
6
7
.
.
İlgen, O. Z.; Akin, A. N.; Boz, N. Turk. J. Chem. 2009, 33, 289-294.
Du, Y. J.; Shao, L. J.; Luo, L. Y.; Shi, S.; Qi, C. Z. Turk. J. Chem. 2014, 38,
13. Xie, C.; Yang, Q. J.; Xu, Z. L.; Liu, C. J.; Du, Y. G. J. Phys. Chem. B. 2006,
110, 8587-8592.
1
57-163.
3
008